Electrolytic solution and battery

The present invention relates to an electrolytic solution containing a solvent and an electrolyte salt, and a battery using the same.

In recent years, portable electronic devices such as camera-integrated VTRs (video tape recorders), mobile phones, and notebook computers have become widespread, and there is a strong demand for their miniaturization, weight reduction, and long life. Along with this, as a power source for portable electronic devices, batteries, especially secondary batteries that are lightweight and capable of obtaining high energy density, are being developed.

Among them, secondary batteries (so-called lithium ion secondary batteries) that utilize the storage and release of lithium for the charge / discharge reaction are highly expected because they can obtain a larger energy density than lead batteries and nickel-cadmium batteries. .. In this secondary battery, a carbon material is widely used as a negative electrode active material, but recently, since further improvement in battery capacity is required, it is considered to use silicon or tin instead of the carbon material. Has been done. This is because the theoretical capacity of silicon (4199mAh / g) and the theoretical capacity of tin (994mAh / g) are much larger than the theoretical capacity of graphite (372mAh / g), so a significant improvement in battery capacity can be expected. It has been reported that for secondary batteries using a thin film of silicon or tin as the negative electrode active material, high discharge capacity can be obtained because the pulverization of the negative electrode active material is suppressed even when lithium is occluded and released. (See, for example, Patent Document 1).<patcit num="1"><text>International release WO 01/03 1724 pamphlet</text></patcit>

However, when silicon or tin is used as the negative electrode active material, the activity becomes high when lithium is occluded. Therefore, as the solvent of the electrolytic solution, a high dielectric constant solvent such as cyclic carbonate and a chain carbonate are used. When used in combination with a low-viscosity solvent, there was a concern that the chain carbonate ester was mainly decomposed and lithium was easily inactivated. In this case, if the pulverization of the negative electrode active material is not sufficiently suppressed in the charge / discharge process, the charge / discharge efficiency is lowered, so that sufficient cycle characteristics and storage characteristics cannot be obtained.

Therefore, as a method for improving the cycle characteristics and the storage characteristics, a method of incorporating a cyclic or chain-like carbonic acid ester having a halogen as a constituent element in the electrolytic solution is known (see, for example, Patent Documents 2 to 6). It is presumed that the reason why the characteristics are improved by this method is that a film having high ion permeability and high stability is formed on the surface of the negative electrode at the time of initial charging, so that the decomposition reaction of the electrolytic solution is suppressed. Will be done.<patcit num="2"><text>Japanese Unexamined Patent Publication No. 10-144346</text></patcit><patcit num="3"><text>Japanese Unexamined Patent Publication No. 10-247519</text></patcit><patcit num="4"><text>Japanese Unexamined Patent Publication No. 2004-014134</text></patcit><patcit num="5"><text>Japanese Unexamined Patent Publication No. 2006-190635</text></patcit><patcit num="6"><text>Japanese Unexamined Patent Publication No. 2006-261092</text></patcit>

<p> In recent electronic devices, the performance and the number of functions tend to increase more and more, and therefore, the cycle characteristics tend to deteriorate due to frequent repetition of charging and discharging of the secondary battery. Moreover, since the amount of heat generated tends to increase more and more due to factors such as higher performance of electronic components represented by the CPU (central processing unit), the storage characteristics are also improved by exposing the secondary battery to a high temperature atmosphere. It tends to decrease. Therefore, further improvement in the cycle characteristics and storage characteristics of the secondary battery is desired.</p><p> The present invention has been made in view of such problems, and an object of the present invention is to provide an electrolytic solution and a battery capable of improving cycle characteristics and storage characteristics.</p>

<p> The electrolytic solution according to the present invention contains a solvent and an electrolyte salt, and the solvent contains a cyclic carbonate ester represented by Chemical formula 1 and a chain carbonate ester represented by Chemical formula 2.<chemistry num="1"><img file="JP2008123714A_D0001.tif" /></chemistry> (R1 to R4 are hydrogen groups, fluorine groups, alkyl groups or fluorinated alkyl groups, which may be the same or different from each other, but at least one of them is a fluorinated group or an alkyl fluorinated group. is there.)<chemistry num="2"><img file="JP2008123714A_D0002.tif" /></chemistry> (R5 and R6 are hydrogen groups, fluorine groups, alkyl groups or fluorinated alkyl groups, which may be the same or different from each other, but at least one of them is a fluorinated group or an alkyl fluorinated group. is there.)</p><p> The battery according to the present invention is provided with an electrolytic solution together with a positive electrode and a negative electrode, the electrolytic solution contains a solvent and an electrolyte salt, and the solvent is represented by a cyclic carbonate ester represented by Chemical formula 3 and Chemical formula 4. It contains a chain carbonate ester to be formed.<chemistry num="3"><img file="JP2008123714A_D0003.tif" /></chemistry> (R1 to R4 are hydrogen groups, fluorine groups, alkyl groups or fluorinated alkyl groups, which may be the same or different from each other, but at least one of them is a fluorinated group or an alkyl fluorinated group. is there.)<chemistry num="4"><img file="JP2008123714A_D0004.tif" /></chemistry> (R5 and R6 are hydrogen groups, fluorine groups, alkyl groups or fluorinated alkyl groups, which may be the same or different from each other, but at least one of them is a fluorinated group or an alkyl fluorinated group. is there.)</p>

<p> According to the electrolytic solution of the present invention, since the solvent contains both the cyclic carbonate ester shown in Chemical formula 1 and the chain carbonate ester shown in Chemical formula 2, it is compared with the case where both of them are not contained. When used in an electrochemical device such as a battery, the decomposition reaction is suppressed. As a result, in the battery using the electrolytic solution of the present invention, the electrolytic solution is electrochemically stabilized, so that the cycle characteristics and the storage characteristics can be improved.</p>

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

The electrolytic solution according to the embodiment of the present invention is used for an electrochemical device such as a battery, and contains a solvent and an electrolyte salt. This solvent contains a cyclic carbonate represented by Chemical formula 5 and a chain carbonate ester represented by Chemical formula 6. The reason why both the cyclic carbonic acid ester shown in Chemical formula 5 and the chain carbonate ester shown in Chemical formula 6 are contained is that the decomposition reaction is suppressed and electrochemically stabilized when used in an electrochemical device. This is because the cycle characteristics and storage characteristics are improved. The carbon number of R5 and R6 shown in Chemical formula 6 is preferably 5, for example. This is to prevent the viscosity of the electrolytic solution from becoming too high and to ensure ionic conductivity.

<chemistry num="5"><img file="JP2008123714A_D0005.tif" /></chemistry> (R1 to R4 are hydrogen groups, fluorine groups, alkyl groups or fluorinated alkyl groups, which may be the same or different from each other, but at least one of them is a fluorinated group or an alkyl fluorinated group. is there.)

<chemistry num="6"><img file="JP2008123714A_D0006.tif" /></chemistry> (R5 and R6 are hydrogen groups, fluorine groups, alkyl groups or fluorinated alkyl groups, which may be the same or different from each other, but at least one of them is a fluorinated group or an alkyl fluorinated group. is there.)

The content of the cyclic carbonic acid ester shown in Chemical formula 5 in the solvent is in the range of 1% by weight or more and 50% by weight or less, and the content of the chain carbonate ester shown in Chemical formula 6 in the solvent is 1% by weight or more and 50% by weight. It is preferably in the range of% by weight or less. This is because a higher effect can be obtained. Specifically, if the content of each is less than 1% by weight, the decomposing inhibitory effect of the electrolytic solution is extremely reduced, so that sufficient cycle characteristics and storage characteristics may not be obtained, while the content is high. If it is more than 50% by weight, the ionic conductivity is extremely lowered, so that sufficient cycle characteristics and storage characteristics may not be obtained.

Examples of the cyclic carbonate shown in Chemical formula 5 include 4-fluoro-1,3-dioxolane-2-one represented by (1) of Chemical formula 7 or 4,5 represented by (2) of Chemical formula 7. -Difluoro-1,3-dioxolan-2-one and the like can be mentioned. Examples of the cyclic carbonate ester described above include tetrafluoro-1,3-dioxolane-2-one, 4,5-bistrifluoromethyl-1,3-dioxolane-2-one, and 4-trifluoromethyl-1. , 3-Dioxolan-2-one, 4,5-difluoro-4,5-dimethyl-1,3-dioxolan-2-one, 4-methyl-5,5-difluoro-1,3-dioxolan-2-one , 4-Ethyl-5,5-difluoro-1,3-dioxolan-2-one, 4-trifluoromethyl-5-fluoro-1,3-dioxolan-2-one, 4-trifluoromethyl-5-methyl -1,3-Dioxolane-2-one, 4-fluoro-4,5-dimethyl-1,3-dioxolan-2-one, 4,4-difluoro-5- (1,1-difluoroethyl) -1, 3-Dioxolane-2-one, 4-ethyl-5-fluoro-1,3-dioxolan-2-one, 4-ethyl-4,5-difluoro-1,3-dioxolan-2-one, 4-ethyl- 4,5,5-Trifluoro-1,3-dioxolan-2-one or 4-fluoro-4-methyl-1,3-dioxolan-2-one may also be mentioned. These may be used alone or in admixture of a plurality of types. Among them, at least one of 4-fluoro-1,3-dioxolane-2-one and 4,5-difluoro-1,3-dioxolan-2-one is preferable as the cyclic carbonic acid ester shown in Chemical formula 5. .. This is because it is easily available and a sufficient effect can be obtained. In particular, as 4,5-difluoro-1,3-dioxolan-2-one, a trans isomer is preferable to a cis isomer in order to obtain a higher effect.

<chemistry num="7"><img file="JP2008123714A_D0007.tif" /></chemistry>

Examples of the chain carbonate ester shown in Chemical formula 6 include fluoromethylmethyl carbonate represented by (1) of Chemical formula 8 and bis (fluoromethyl) carbonate represented by (2) of Chemical formula 8. Further, examples of the above-mentioned chain carbonic acid ester include difluoromethylmethyl carbonate, fluoroethyl ethyl carbonate and bis (fluoroethyl) carbonate. These may be used alone or in admixture of a plurality of types. Among them, at least one of fluoromethylmethyl carbonate and bis (fluoromethyl) carbonate is preferable as the chain carbonate ester shown in Chemical formula 6. This is because it is easily available and a sufficient effect can be obtained.

<chemistry num="8"><img file="JP2008123714A_D0008.tif" /></chemistry>

In particular, the solvent contains 4,5-difluoro-1,3-dioxolan-2-one as the cyclic carbonic acid ester shown in Chemical formula 5, and bis carbonate (fluoromethyl) as the chain carbonate ester shown in Chemical formula 6. It is preferable to include it. This is because a higher effect can be obtained in this combination.

The solvent may contain, for example, another solvent (for example, a non-aqueous solvent such as an organic solvent) in addition to the cyclic carbonate ester shown in Chemical formula 5 and the chain carbonate ester shown in Chemical formula 6. Other solvents include, for example, ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, γ-butyrolactone, γ-valerolactone, 1,2-dimethoxyethane, tetrahydrofuran, etc. 2-Methyl tetrahydrofuran, tetrahydropyran, 1,3-dioxolane, 4-methyl-1,3-dioxolane, 1,3-dioxane, 1,4-dioxane, methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, Methyl butyrate, methyl isobutyrate, methyl trimethylacetate, ethyl trimethylacetate, acetonitrile, glutaronitrile, adiponitrile, methoxynitrile, 3-methoxypropionitrile, N, N-dimethylformamide, N-methylpyrrolidinone, N-methyloxazolidinone, Examples thereof include N, N'-dimethylimidazolidinone, nitromethane, nitroethane, sulfolane, trimethyl phosphate, dimethyl sulfoxide or dimethyl sulfoxide phosphate. This is because excellent capacitance characteristics, cycle characteristics and storage characteristics can be obtained in an electrochemical device provided with an electrolytic solution. These may be used alone or in admixture of a plurality of types. Among them, the solvent preferably contains at least one of the group consisting of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate. This is because a sufficient effect can be obtained. In this case, in particular, ethylene carbonate or propylene carbonate having a high viscosity (high dielectric constant) solvent (for example, relative permittivity ε 30) and dimethyl carbonate having a low viscosity solvent (for example, viscosity 1 mPa · s) , Diethyl carbonate or ethylmethyl carbonate is preferably mixed and contained. This is because the dissociation of the electrolyte salt and the mobility of ions are improved, so that a higher effect can be obtained.

The electrolyte salt contains, for example, a light metal salt such as a lithium salt. Examples of this lithium salt include lithium hexafluorophosphate (LiPF).₆), Lithium tetrafluorobolate (LiBF)₄), Lithium perchlorate (LiClO)₄), Lithium hexafluoride (LiAsF)₆), Lithium tetraphenylborate (LiB (C)₆H₅)₄), Lithium methanesulfonate (LiCH)₃SO₃), Lithium trifluoromethanesulfonate (LiCF)₃SO₃), Lithium tetrachloroaluminate LiAlCl₄, Lithium hexafluoride silicate (Li₂SiF₆), Lithium chloride (LiCl), Lithium bromide (LiBr), Bis (trifluoromethanesulfonyl) imid lithium (LiN (CF)₃SO₂)₂), Bis (pentafluoroethanesulfonyl) imide lithium (LiN (C)₂ F₅SO₂ )₂), (Trifluoromethanesulfonyl) (pentafluoroethanesulfonyl) imide lithium (LiN (CF)₃SO₂) (C₂F₅SO₂)), (Trifluoromethanesulfonyl) (Heptafluoropropanesulfonyl) Imid Lithium (LiN (CF)₃SO₂) (C₃F₇SO₂)), (Trifluoromethanesulfonyl) (nonafluorobutanesulfonyl) imide lithium (LiN (CF)₃SO₂) (C₄F₉SO₂)), 1,2-Perfluoroethanedisulfonylimide lithium, 1,3-perfluoropropanedisulfonylimide lithium, 1,3-perfluorobutanedisulfonylimide lithium, 1,4-perfluorobutanedisulfonylimide lithium Alternatively, lithium tris (trifluoromethanesulfonyl) methide (LiC (CF))₃SO₂)₃) And so on. This is because excellent capacitance characteristics, cycle characteristics and storage characteristics can be obtained in an electrochemical device provided with an electrolytic solution. These may be used alone or in admixture of a plurality of types. Among them, the electrolyte salt preferably contains at least one of the group consisting of lithium hexafluoride phosphate, lithium tetrafluoroborate, lithium perchlorate and lithium hexafluoride arsenate. This is because a higher effect can be obtained. In particular, when lithium hexafluorophosphate is contained, the internal resistance is lowered and the cycle characteristics and the storage characteristics are further improved, and when lithium tetrafluoroborate is contained, the storage characteristics are further improved.

The electrolyte salt may contain, for example, the compound represented by Chemical formula 9. This is because the storage characteristics are further improved. Among them, as the compound shown in Chemical formula 9, a compound in which the central element M2 is boron is preferable. This is because a sufficient effect can be obtained. In particular, the electrolyte salt comprises at least one of the group consisting of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluorophosphate and the compounds shown in Chemical formula 9. It is preferable to have. This is because a higher effect can be obtained.

<chemistry num="9"><img file="JP2008123714A_D0009.tif" /></chemistry> (R1 is -OC-R3-CO-, -OC-C (R4) (R5)-or -OC-CO-, and R2 is a halogen group, alkyl group, alkyl halide group, aryl group or aryl halide. R3 is an alkylene group, an alkylene halide group, an arylene group or an arylene halide group, and R4 and R5 are an alkyl group, an alkyl halide group, an aryl group or an aryl halide group. X1 and X2 is oxygen or sulfur. M1 is a Group 1A or Group 2A element or aluminum in the short-period periodic table, and M2 is a transition metal element or Group 3B element, Group 4B element or in the short-period periodic table. Group B elements. A is an integer of 1 to 4, b is an integer of 0 or 1 to 8, and c, d, e and f are integers of 1 to 3.)

Examples of the compound shown in Chemical formula 9 include bis [oxorat-O, O'] lithium borate, difluoro [oxorat-O, O'] lithium borate, and difluoro [3,3,3-trifluoro-2-". Oxide-2-trifluoromethylpropionato (2-)-O, O'] Lithium borate, bis [3,3,3-trifluoro-2-oxide-2-trifluoromethylpropionato (2-)- Examples thereof include lithium borate [O, O'], lithium tetrafluoro [oxorat-O, O'] lithium phosphate, and difluorobis [oxorat-O, O'] lithium phosphate. These may be used alone or in admixture of a plurality of types.

The content of the electrolyte salt in the solvent is preferably in the range of 0.3 mol / kg or more and 3.0 mol / kg or less. This is because the ionic conductivity is extremely lowered outside this range, so that the capacitance characteristics and the like may not be sufficiently obtained.

The electrolytic solution may further contain, for example, a compound other than the above as an additive. This is because the storage characteristics are further improved in the electrochemical device provided with the electrolytic solution. Examples of this additive include sultone (cyclic sulfonic acid ester), acid anhydride, cyclic carbonate having an unsaturated bond, and the like. These may be used alone or in admixture of a plurality of types. As an example, the acid anhydride includes succinic anhydride, glutaric anhydride, maleic anhydride and the like. Examples of the sultone include propane sultone and propene sultone. Examples of the cyclic carbonate having an unsaturated bond include vinylene carbonate and vinyl acetate. The content of the additive in the electrolytic solution is preferably in the range of 0.5% by weight or more and 3% by weight or less. This is because a sufficient effect can be obtained.

According to this electrolytic solution, since the solvent contains both the cyclic carbonate ester shown in Chemical formula 5 and the chain carbonate ester shown in Chemical formula 6, the battery and the like are compared with the case where both of them are not contained. Degradation reaction is suppressed when used in the electrochemical device of. As a result, the electrolytic solution is electrochemically stabilized in the electrochemical device, which can contribute to the improvement of cycle characteristics and storage characteristics. In this case, in particular, if the content of the cyclic carbonic acid ester shown in Chemical formula 5 and the chain carbonate ester shown in Chemical formula 6 in the solvent are both within the range of 1% by weight or more and 50% by weight or less. A high effect can be obtained.

Next, an example of using the above-mentioned electrolytic solution will be described. Here, taking a battery as an example of an electrochemical device, the electrolytic solution is used for the battery as follows.

(First Battery) FIG. 1 shows the cross-sectional configuration of the first battery. This battery is a so-called lithium ion secondary battery in which the capacity of the negative electrode is represented by a capacity component based on the occlusion and release of lithium, which is an electrode reactant. FIG. 1 shows a so-called cylindrical battery structure.

In this secondary battery, a wound electrode body 20 in which a positive electrode 21 and a negative electrode 22 are wound via a separator 23 and a pair of insulating plates 12 and 13 are housed inside a battery can 11 having a substantially hollow columnar shape. It was done. The battery can 11 is made of, for example, nickel (Ni) plated iron (Fe), and one end and the other end thereof are closed and open, respectively. The pair of insulating plates 12 and 13 are arranged so as to sandwich the wound electrode body 20 and extend perpendicularly to the winding peripheral surface thereof.

A battery lid 14, a safety valve mechanism 15 provided inside the battery can 11, and a heat-sensitive resistance element (Positive Temperature Coefficient; PTC element) 16 are attached to the open end of the battery can 11 by being crimped via a gasket 17. The inside of the battery can 11 is sealed. The battery lid 14 is made of, for example, the same material as the battery can 11. The safety valve mechanism 15 is electrically connected to the battery lid 14 via the heat-sensitive resistance element 16. In this safety valve mechanism 15, when the internal pressure exceeds a certain level due to an internal short circuit or heating from the outside, the disk plate 15A is inverted to generate electricity between the battery lid 14 and the wound electrode body 20. The target connection is disconnected. The heat-sensitive resistance element 16 limits the current by increasing the resistance as the temperature rises, and prevents abnormal heat generation due to a large current. The gasket 17 is made of, for example, an insulating material, and the surface thereof is coated with asphalt.

For example, a center pin 24 is inserted in the center of the wound electrode body 20. In the wound electrode body 20, the positive electrode lead 25 made of aluminum or the like is connected to the positive electrode 21, and the negative electrode lead 26 made of nickel or the like is connected to the negative electrode 22. The positive electrode lead 25 is electrically connected to the battery lid 14 by being welded to the safety valve mechanism 15, and the negative electrode lead 26 is electrically connected to the battery can 11 by being welded to the battery can 11.

FIG. 2 is an enlarged representation of a part of the wound electrode body 20 shown in FIG. The positive electrode 21 is, for example, one in which positive electrode active material layers 21B are provided on both sides of a positive electrode current collector 21A having a pair of facing surfaces. The positive electrode current collector 21A is made of a metal material such as aluminum, nickel, or stainless steel. The positive electrode active material layer 21B contains, for example, one or more of positive electrode materials capable of occluding and releasing lithium, which is an electrode reactant, as the positive electrode active material. The positive electrode active material layer 21B may contain a conductive agent, a binder, or the like, if necessary.

Examples of the positive electrode material capable of occluding and releasing lithium include lithium cobalt oxide, lithium nickel oxide, and a solid solution containing them (Li (Ni)._xCo_yMn_z) O₂); The values of x, y and z are 0 &lt;x &lt;1,0 &lt;y &lt;1,0 &lt;z &lt;1, x + y + z = 1, respectively. ), Or lithium manganate with a spinel structure (LiMn)₂O₄) Or its solid solution (Li (Mn)_2-vNi_v) O₄The value of; v is v &lt;2. ) And other lithium composite oxides and lithium iron phosphate (LiFePO)₄) And the like, a phosphoric acid compound having an olivine structure is preferable. This is because a high energy density can be obtained. In addition to the above, for example, oxides such as titanium oxide, vanadium oxide or manganese dioxide, disulfides such as iron disulfide, titanium disulfide or molybdenum disulfide, sulfur, polyaniline or polythiophene and the like have high conductivity. Molecules are also mentioned.

The negative electrode 22 is provided with negative electrode active material layers 22B on both sides of a negative electrode current collector 22A having a pair of facing surfaces, for example. The negative electrode current collector 22A is made of a metal material such as copper (Cu), nickel, or stainless steel. The negative electrode active material layer 22B contains any one or more of the negative electrode materials capable of occluding and releasing lithium. The negative electrode active material layer 22B may contain a conductive agent, a binder, or the like, if necessary.

Examples of the negative electrode material capable of occluding and releasing lithium include a material capable of occluding and releasing lithium and containing at least one of a metal element and a metalloid element as a constituent element. .. It is preferable to use such a negative electrode material because a high energy density can be obtained. The negative electrode material may be a simple substance, an alloy, or a compound of a metal element or a metalloid element, or may have one or more phases thereof in at least a part thereof. The alloy in the present invention includes, in addition to those composed of two or more kinds of metal elements, those containing one or more kinds of metal elements and one or more kinds of metalloid elements. The alloy in the present invention may contain a non-metallic element. Some of these structures are solid solutions, eutectic (eutectic mixtures), intermetallic compounds, or two or more of them coexist.

Examples of the metal element or metalloid element constituting the negative electrode material include a metal element or metalloid element capable of forming an alloy with lithium. Specifically, magnesium (Mg), boron, aluminum, gallium (Ga), indium (In), silicon (Si), germanium (Ge), tin (Sn), lead (Pb), bismuth (Bi), cadmium. Examples include (Cd), silver (Ag), zinc (Zn), hafnium (Hf), zirconium (Zr), indium (Y), palladium (Pd) or platinum (Pt). Of these, at least one of silicon and tin is particularly preferred. This is because the ability to occlude and release lithium is particularly large, and a high energy density can be obtained.

The negative electrode material containing at least one of silicon and tin includes, for example, a simple substance, an alloy, or a compound of silicon, or a simple substance, an alloy, or a compound of tin, or at least one or more phases thereof. Some materials are included. These may be used alone or in admixture of a plurality of types.

As an alloy of silicon, for example, as a second constituent element other than silicon, among the group consisting of tin, nickel, copper, iron, cobalt, manganese, zinc, indium, silver, titanium, germanium, bismuth, antimony and chromium. Those containing at least one of the above are mentioned. Examples of tin alloys include silicon, nickel, copper, iron, cobalt (Co), manganese (Mn), zinc, indium, silver, titanium (Ti), germanium, and bismuth as second constituent elements other than tin. , Antimon (Sb) and chromium (Cr), including at least one of the group.

Examples of the silicon compound or the tin compound include those containing oxygen (O) or carbon (C), and may contain the above-mentioned second constituent element in addition to tin or silicon.

In particular, as a material containing at least one of silicon and tin, for example, it is preferable that tin is the first constituent element and the second constituent element and the third constituent element are contained in addition to the tin. .. The second constituent elements are cobalt, iron, magnesium, titanium, vanadium (V), chromium, manganese, nickel, copper, zinc, gallium, zirconium, niobium (Nb), molybdenum (Mo), silver, indium, cerium ( It is at least one of the group consisting of Ce), hafnium, tantalum (Ta), tungsten (W), bismuth and silicon. The third constituent element is at least one of the group consisting of boron, carbon, aluminum and phosphorus. This is because the cycle characteristics are improved by containing the second element and the third element.

Among them, the negative electrode material contains tin, cobalt and carbon as constituent elements, and the carbon content is in the range of 9.9% by mass or more and 29.7% by mass or less, and the ratio of cobalt to the total of tin and cobalt (Co / (Sn +). A CoSnC-containing material in which Co)) is in the range of 30% by mass or more and 70% by mass or less is preferable. This is because, in such a composition range, a high energy density can be obtained and excellent cycle characteristics can be obtained.

This CoSnC-containing material may further contain other constituent elements, if necessary. As other constituent elements, for example, silicon, iron, nickel, chromium, indium, niobium, germanium, titanium, molybdenum, aluminum, phosphorus, gallium, bismuth and the like are preferable, and two or more of them may be contained. This is because the capacitance or cycle characteristics are further improved.

The CoSnC-containing material has a phase containing tin, cobalt and carbon, and this phase preferably has a low crystallinity or an amorphous structure. Further, in the CoSnC-containing material, it is preferable that at least a part of carbon which is a constituent element is bonded to a metal element or a metalloid element which is another constituent element. It is considered that the deterioration of the cycle characteristics is due to the aggregation or crystallization of tin or the like, and the binding of carbon with other elements suppresses such aggregation or crystallization.

Examples of the measurement method for investigating the bonding state of elements include X-ray Photoelectron Spectroscopy (XPS). In this XPS, in a device energy calibrated so that the 4f orbital (Au4f) peak of the gold atom is obtained at 84.0eV, the carbon 1s orbital (C1s) peak appears at 284.5eV for graphite. If it is surface-contaminated carbon, it appears at 284.8 eV. On the other hand, when the charge density of the carbon element is high, for example, when carbon is bonded to a metal element or a metalloid element, the peak of C1s appears in a region lower than 284.5 eV. That is, when the peak of the synthetic wave of C1s obtained for the CoSnC-containing material appears in the region lower than 284.5 eV, at least a part of the carbon contained in the CoSnC-containing material is a metal element or a metalloid which is another constituent element. It is bound to the element.

In XPS, for example, the peak of C1s is used to correct the energy axis of the spectrum. Normally, surface-contaminated carbon is present on the surface, so the peak of C1s of surface-contaminated carbon is set to 284.8 eV, and this is used as the energy standard. In XPS, the waveform of the C1s peak is obtained as a form including the peak of surface-contaminated carbon and the peak of carbon in the CoSnC-containing material. Therefore, for example, surface contamination can be obtained by analyzing using commercially available software. The carbon peak is separated from the carbon peak in the CoSnC-containing material. In the waveform analysis, the position of the main peak existing on the lowest binding energy side is used as the energy reference (284.8 eV).

Examples of the negative electrode material capable of occluding and releasing lithium include carbon materials, metal oxides and polymer compounds. Of course, these negative electrode materials may be used together with the above-mentioned negative electrode materials. Examples of the carbon material include easily graphitized carbon, non-graphitized carbon having a (002) plane spacing of 0.37 nm or more, and graphite having a (002) plane spacing of 0.34 nm or less. More specifically, there are pyrolytic carbons, cokes, graphites, glassy carbon fibers, calcined organic polymer compounds, carbon fibers, activated carbon, carbon blacks and the like. Among these, coke includes pitch coke, needle coke, petroleum coke, etc., and the organic polymer compound fired body refers to a carbonized product obtained by firing phenol resin, furan resin, etc. at an appropriate temperature. .. Since the carbon material has very little change in crystal structure due to occlusion and release of lithium, for example, when used together with other negative electrode materials, high energy density can be obtained and excellent cycle characteristics can be obtained. Moreover, it is preferable because it also functions as a conductive agent. Examples of the metal oxide include iron oxide, ruthenium oxide and molybdenum oxide, and examples of the polymer compound include polyacetylene, polyaniline and polypyrrole.

Examples of the conductive agent include carbon materials such as graphite, carbon black and kechen black. These may be used alone or in admixture of a plurality of types. The conductive agent may be a metal material, a conductive polymer, or the like as long as it is a conductive material.

Examples of the binder include synthetic rubber such as styrene-butadiene rubber, fluorine-based rubber or ethylene propylene diene, and polymer materials such as polyvinylidene fluoride. These may be used alone or in admixture of a plurality of types. However, as shown in FIG. 1, when the positive electrode 21 and the negative electrode 22 are wound, it is preferable to use highly flexible styrene-butadiene rubber, fluorine-based rubber, or the like.

In this secondary battery, by adjusting the amount between the positive electrode active material and the negative electrode active material, the charging capacity of the negative electrode active material becomes larger than the charging capacity of the positive electrode active material, and even when fully charged. Lithium metal does not precipitate on the negative electrode 22.

The separator 23 separates the positive electrode 21 and the negative electrode 22 and allows lithium ions to pass through while preventing a short circuit of current due to contact between the two electrodes. The separator 23 is composed of, for example, a porous film made of a synthetic resin made of polytetrafluoroethylene, polypropylene, polyethylene, or the like, or a multi-hard film made of ceramic, and two or more of these porous films are laminated. The structure may be the same. Above all, the porous film made of polyolefin is preferable because it has an excellent short-circuit prevention effect and can improve the safety of the battery by the shutdown effect. In particular, polyethylene is preferable because it can obtain a shutdown effect in the range of 100 ° C or more and 160 ° C or less and is also excellent in electrochemical stability. In addition, polypropylene is also preferable, and other resins having chemical stability may be copolymerized with polyethylene or polypropylene, or blended.

The separator 23 is impregnated with the above-mentioned electrolytic solution as a liquid electrolyte. This is because excellent cycle characteristics and storage characteristics can be obtained.

This secondary battery is manufactured, for example, as follows.

First, the positive electrode 21 is produced by forming the positive electrode active material layers 21B on both sides of the positive electrode current collector 21A. When forming the positive electrode active material layer 21B, a positive electrode mixture obtained by mixing a positive electrode active material powder, a conductive agent, and a binder is dispersed in a solvent such as N-methyl-2-pyrrolidone. A paste-like positive electrode mixture slurry is prepared, and the positive electrode mixture slurry is applied to the positive electrode current collector 21A, dried, and then compression-molded. Further, the negative electrode 22 is manufactured by forming the negative electrode active material layers 22B on both sides of the negative electrode current collector 22A according to the same procedure as that of the positive electrode 21.

Subsequently, the positive electrode lead 25 is welded and attached to the positive electrode current collector 21A, and the negative electrode lead 26 is welded and attached to the negative electrode current collector 22A. Subsequently, the positive electrode 21 and the negative electrode 22 are wound around the separator 23 to form a wound electrode body 20, the tip of the positive electrode lead 25 is welded to the safety valve mechanism 15, and the tip of the negative electrode lead 26 is a battery. After welding to the can 11, the wound electrode body 20 is housed inside the battery can 11 while being sandwiched between the pair of insulating plates 12 and 13. Subsequently, the electrolytic solution is injected into the battery can 11 to impregnate the separator 23. Finally, the battery lid 14, the safety valve mechanism 15, and the heat-sensitive resistance element 16 are fixed to the open end of the battery can 11 by caulking via the gasket 17. As a result, the secondary batteries shown in FIGS. 1 and 2 are completed.

In this secondary battery, when charging is performed, for example, lithium ions are released from the positive electrode 21 and occluded in the negative electrode 22 via an electrolytic solution. On the other hand, when the electric discharge is performed, for example, lithium ions are released from the negative electrode 22 and occluded in the positive electrode 21 via the electrolytic solution.

According to this secondary battery, when the capacity of the negative electrode 22 is represented by the capacity component based on the occlusion and release of lithium, the above-mentioned electrolytic solution is provided, so that the cycle characteristics and the storage characteristics can be improved. it can.

Next, the second and third batteries will be described, but the components common to the first battery are designated by the same reference numerals and the description thereof will be omitted.

(Second Battery) The second battery has the same configuration, operation and effect as the first battery except that the configuration of the negative electrode 22 is different, and is manufactured by the same procedure.

Like the first battery, the negative electrode 22 is provided with negative electrode active material layers 22B on both sides of the negative electrode current collector 22A. The negative electrode active material layer 22B contains, for example, a negative electrode active material containing silicon or tin as a constituent element. Specifically, for example, it contains a simple substance of silicon, an alloy or a compound, or a simple substance of tin, an alloy or a compound, and may contain two or more of them. Silicon and tin are preferable because they have a large ability to occlude and release lithium and can obtain a high energy density.

The negative electrode active material layer 22B is formed by, for example, a vapor phase method, a liquid phase method, a spraying method or a firing method, or two or more of these methods, and is formed by using the negative electrode active material layer 22B and the negative electrode collection. It is preferable that the electric body 22A is alloyed with at least a part of the interface. Specifically, at the interface, the constituent elements of the negative electrode current collector 22A diffuse into the negative electrode active material layer 22B, or the constituent elements of the negative electrode active material layer 22B diffuse into the negative electrode current collector 22A, or these constituent elements It is preferable that they diffuse each other. This is because it is possible to suppress the destruction of the negative electrode active material layer 22B due to expansion and contraction due to charging and discharging, and to improve the electron conductivity between the negative electrode active material layer 22B and the negative electrode current collector 22A. ..

Examples of the vapor phase method include a physical deposition method or a chemical deposition method, specifically, a vacuum deposition method, a sputtering method, an ion plating method, a laser ablation method, and a thermochemical vapor deposition (CVD). Examples thereof include a method or a plasma chemical vapor deposition method. As the liquid phase method, a known method such as electroplating or electroless plating can be used. The firing method is, for example, a method in which a particulate negative electrode active material is mixed with a binder or the like and dispersed in a solvent to apply the mixture, and then heat-treated at a temperature higher than the melting point of the binder or the like. As for the firing method, a known method can be used, and examples thereof include an atmosphere firing method, a reaction firing method, and a hot press firing method.

(Third Battery) The third battery is a so-called lithium metal secondary battery in which the capacity of the negative electrode 22 is represented by a capacity component based on the precipitation and dissolution of lithium. This secondary battery has the same configuration as the first battery except that the negative electrode active material layer 22B is composed of lithium metal, and is manufactured by the same procedure.

In this secondary battery, lithium metal is used as the negative electrode active material, which makes it possible to obtain a high energy density. The negative electrode active material layer 22B may already be present from the time of assembly, but may be composed of a lithium metal that does not exist at the time of assembly and is precipitated at the time of charging. Further, the negative electrode current collector 22A may be omitted by using the negative electrode active material layer 22B as a current collector.

In this secondary battery, when charging is performed, for example, lithium ions are released from the positive electrode 21 and are deposited as lithium metal on the surface of the negative electrode current collector 22A via the electrolytic solution. On the other hand, when the electric discharge is performed, for example, the lithium metal is eluted from the negative electrode active material layer 22B as lithium ions, and is occluded in the positive electrode 21 via the electrolytic solution.

According to this secondary battery, when the capacity of the negative electrode 22 is represented by a capacity component based on the precipitation and dissolution of lithium, the above-mentioned electrolytic solution is provided, so that the cycle characteristics and the storage characteristics can be improved. it can.

(Fourth Battery) FIG. 3 shows the disassembled perspective configuration of the fourth battery. This battery contains a wound electrode body 30 to which a positive electrode lead 31 and a negative electrode lead 32 are attached inside a film-shaped exterior member 40, and this battery structure is a so-called laminated type.

The positive electrode lead 31 and the negative electrode lead 32 are, for example, led out in the same direction from the inside to the outside of the exterior member 40, respectively. The positive electrode lead 31 is made of a metal material such as aluminum, and the negative electrode lead 32 is made of a metal material such as copper, nickel or stainless steel. Each of the metal materials constituting the positive electrode lead 31 and the negative electrode lead 32 has a thin plate shape or a mesh shape.

The exterior member 40 is made of, for example, a rectangular aluminum laminate film in which a nylon film, an aluminum foil, and a polyethylene film are bonded in this order. In the exterior member 40, for example, the polyethylene film faces the wound electrode body 30, and the outer edges thereof are brought into close contact with each other by fusion or adhesive. An adhesive film 41 for preventing the intrusion of outside air is inserted between the exterior member 40 and the positive electrode lead 31 and the negative electrode lead 32. The adhesion film 41 is made of a material having adhesion to the positive electrode lead 31 and the negative electrode lead 32, for example, a polyolefin resin such as polyethylene, polypropylene, modified polyethylene, or modified polypropylene.

The exterior member 40 may be made of a laminated film having another structure instead of the above-mentioned three-layer aluminum laminated film, or may be made of a polymer film such as polypropylene or a metal film. You may.

FIG. 4 shows the cross-sectional configuration of the wound electrode body 30 shown in FIG. 3 along the IV-IV line. The electrode winding body 30 is formed by laminating a positive electrode 33 and a negative electrode 34 via a separator 35 and an electrolyte 36 and then winding the electrode winding body 30, and the outermost peripheral portion thereof is protected by a protective tape 37.

The positive electrode 33 is, for example, one in which positive electrode active material layers 33B are provided on both sides of the positive electrode current collector 33A. The negative electrode 34 is provided with negative electrode active material layers 34B on both sides of the negative electrode current collector 34A, and the negative electrode active material layer 34B is arranged so as to face the positive electrode active material layer 33B. The configurations of the positive electrode current collector 33A, the positive electrode active material layer 33B, the negative electrode current collector 34A, the negative electrode active material layer 34B, and the separator 35 are the positive electrode current collector 21A and the positive electrode active material layer in the first or second battery, respectively. The configuration is the same as that of 21B, the negative electrode current collector 22A, the negative electrode active material layer 22B, and the separator 23.

The electrolyte 36 contains the above-mentioned electrolytic solution and a polymer compound that retains the above-mentioned electrolytic solution, and is in a so-called gel form. A gel-like electrolyte is preferable because it provides high ionic conductivity (for example, 1 mS / cm or more at room temperature) and prevents liquid leakage.

Examples of the polymer compound include polyacrylonitrile, polyvinylidene fluoride, a copolymer of vinylidene fluoride and polyhexafluoropyrene, polytetrafluoroethylene, polyhexafluoropropylene, polyethylene oxide, polypropylene oxide, polyphosphazene, and poly. Examples thereof include siloxane, polyvinylidene acetate, polyvinyl alcohol, polymethylmethacrylate, polyacrylic acid, polymethacrylic acid, styrene-butadiene rubber, nitrile-butadiene rubber, polystyrene and polycarbonate. These may be used alone or in admixture of a plurality of types. In particular, from the viewpoint of electrochemical stability, it is preferable to use polyacrylonitrile, polyvinylidene fluoride, polyhexafluoropropylene, polyethylene oxide or the like. The amount of the polymer compound added to the electrolytic solution varies depending on the compatibility between the two, but is preferably in the range of, for example, 5% by mass or more and 50% by mass or less.

The content of the electrolyte salt is the same as in the case described above for the electrolytic solution. However, the solvent in this case is a broad concept including not only a liquid solvent but also a solvent having ionic conductivity capable of dissociating an electrolyte salt. Therefore, when a polymer compound having ionic conductivity is used, the polymer compound is also included in the solvent.

As the electrolyte 36, the electrolytic solution may be used as it is instead of the one in which the electrolytic solution is held by the polymer compound. In this case, the electrolyte is impregnated in the separator 35.

This secondary battery is manufactured, for example, as follows.

First, a precursor solution containing an electrolytic solution, a polymer compound, and a mixed solvent is prepared, applied to each of the positive electrode 33 and the negative electrode 34, and then the mixed solvent is volatilized to form the electrolyte 36. Subsequently, the positive electrode lead 31 is attached to the positive electrode current collector 33A, and the negative electrode lead 32 is attached to the negative electrode current collector 34A. Subsequently, the positive electrode 33 and the negative electrode 34 on which the electrolyte 36 is formed are laminated via the separator 35, and then wound in the longitudinal direction and the protective tape 37 is adhered to the outermost peripheral portion to adhere the wound electrode body 30. To form. Subsequently, for example, the wound electrode body 30 is sandwiched between the exterior members 40, and the outer edges of the exterior members 40 are brought into close contact with each other by heat fusion or the like to enclose the wound electrode body 30. At that time, the adhesion film 41 is inserted between the positive electrode lead 31 and the negative electrode lead 32 and the exterior member 40. As a result, the secondary batteries shown in FIGS. 3 and 4 are completed.

The secondary battery may be manufactured as follows. First, the positive electrode lead 31 and the negative electrode lead 32 are attached to the positive electrode 33 and the negative electrode 34, respectively, and then the positive electrode 33 and the negative electrode 34 are laminated and wound via the separator 35, and the protective tape 37 is adhered to the outermost peripheral portion. As a result, a wound body which is a precursor of the wound electrode body 30 is formed. Subsequently, the winding body is sandwiched between the exterior members 40, and the remaining outer peripheral edges other than the outer peripheral edge on one side are brought into close contact with each other by heat fusion or the like, so that the wound body is housed inside the bag-shaped exterior member 40. Subsequently, an electrolyte composition containing an electrolytic solution, a monomer as a raw material for a polymer compound, a polymerization initiator, and other materials such as a polymerization inhibitor, if necessary, is prepared, and a bag-shaped exterior member is prepared. After injecting into the inside of 40, the opening of the exterior member 40 is sealed by heat fusion or the like. Finally, the monomer is thermally polymerized to form a polymer compound to form a gel-like electrolyte 36. As a result, the secondary batteries shown in FIGS. 3 and 4 are completed.

The action and effect of this secondary battery are the same as those of the first or second secondary battery described above.

Specific examples of the present invention will be described in detail.

(1) Metalloid negative electrode (electron beam vapor deposition method) Silicon was used as the negative electrode active material to manufacture the cylindrical secondary batteries shown in FIGS. 1 and 2. At this time, the capacity of the negative electrode 22 is set to be a lithium ion secondary battery represented by a capacity component based on the occlusion and release of lithium.

(Example 1) First, a positive electrode 21 was produced. That is, lithium carbonate (Li₂CO₃) And cobalt carbonate (CoCO)₃) At a molar ratio of 0.5: 1 and then calcined in air at 900 ° C for 5 hours to obtain a lithium-cobalt composite oxide (LiCoO).₂) Was obtained. Subsequently, 91 parts by mass of lithium-cobalt composite oxide as a positive electrode active material, 6 parts by mass of graphite as a conductive agent, and 3 parts by mass of polyvinylidene fluoride as a binder were mixed to prepare a positive electrode mixture. By dispersing in N-methyl-2-pyrrolidone, a paste-like positive electrode mixture slurry was obtained. Finally, the positive electrode mixture slurry is applied to both sides of the positive electrode current collector 21A made of strip-shaped aluminum foil (12 μm thick), dried, and then compression-molded with a roll press to form the positive electrode active material layer 21B. Formed. After that, an aluminum positive electrode lead 25 was welded and attached to one end of the positive electrode current collector 21A.

Further, the negative electrode 22 was produced by forming a negative electrode active material layer 22B made of silicon on both sides of a negative electrode current collector 22A made of copper foil (thickness of 15 μm) by an electron beam vapor deposition method. After that, a nickel negative electrode lead 26 was attached to one end of the negative electrode current collector 22A.

Subsequently, the positive electrode 21, the separator 23 made of a microporous polypropylene film (25 μm thickness), and the negative electrode 22 are laminated in this order, wound many times in a spiral shape, and then the end portion of the winding is covered with adhesive tape. By fixing, the wound electrode body 20 was formed. Subsequently, after preparing the nickel-plated iron battery can 11, the wound electrode body 20 is sandwiched between the pair of insulating plates 12 and 13, the negative electrode lead 26 is welded to the battery can 11, and the positive electrode lead 25 is attached. Welded to the safety valve mechanism 15, and the wound electrode body 20 was housed inside the battery can 11. Subsequently, the electrolytic solution was injected into the inside of the battery can 11 by a decompression method.

As the solvent of this electrolytic solution, ethylene carbonate (EC), diethyl carbonate (DEC), 4-fluoro-1,3-dioxolan-2-one (FEC), which is a cyclic carbonic acid ester shown in Chemical formula 5, and Using a mixture of fluoromethylmethyl carbonate (FDMC), which is the chain carbonate ester shown in Chemical formula 6, the composition of the solvent was changed to EC: DEC: FEC: FDMC = 20: 60: 10: 10 by weight. did. The electrolyte salt is lithium hexafluorophosphate (LiPF).₆) Was used to set the concentration of the electrolyte salt in the electrolytic solution to 1 mol / kg.

Subsequently, the safety valve mechanism 15, the heat-sensitive resistance element 16, and the battery lid 14 were fixed by crimping the battery can 11 via a gasket 17 coated with asphalt on the surface. As a result, the airtightness inside the battery can 11 was ensured, and a cylindrical secondary battery was completed.

(Comparative Example 1-1) The procedure was the same as in Example 1-1, except that only EC and DEC were used as solvents. At that time, the composition of the solvent was set to EC: DEC = 30: 70 by weight.

(Comparative Examples 1-2 to 1-4) The same procedure as in Example 1-1 was carried out except that a cyclic carbonate having a halogen as a constituent element was used together with EC and DEC as a solvent. At that time, as the above-mentioned cyclic carbonic acid ester, FEC (Comparative Example 1-2) and 4-chloro-1,3-dioxolane-2-one (ClEC; Comparative Example 1-3), which are the cyclic carbonic acid esters shown in Chemical formula 5, ) And 4-Bromo-1,3-dioxolane-2-one (BrEC; Comparative Example 1-4), and the composition of the solvent by weight ratio was EC: DEC: FEC (or ClEC, BrEC) = 20: 70: It was set to 10.

(Comparative Examples 1-5 to 1-8) The same procedure as in Example 1-1 was carried out except that a chain carbonate having a halogen as a constituent element was used together with EC and DEC as a solvent. At that time, as the above-mentioned chain carbonates, fluoromethylmethyl carbonate (FDMC; Comparative Example 1-5), chloromethylmethyl carbonate (ClDMC; Comparative Example 1-6), which are the chain carbonates shown in Chemical formula 6, Using bromomethylmethyl carbonate (BrDMC; Comparative Example 1-7) and (1-chloroethyl) ethyl carbonate (ClDEC; Comparative Example 1-8), the composition of the solvent by weight ratio was EC: DEC: FDMC (or ClDMC, BrDMC). , ClDEC) = 30: 60: 10.

(Comparative example 1-9 ~ 1-13)

The same procedure as in Example 1-1 was carried out except that a cyclic carbonate having halogen as a constituent element and a chain carbonate having halogen as a constituent element were used as the solvent together with EC and DEC. At that time, as the above-mentioned cyclic carbonate and chain carbonate, FEC and ClDMC (Comparative Example 1-9), FEC and ClDEC (Comparative Example 1-10), ClEC and FDMC (Comparative Example 1-11), ClEC and Using ClDMC (Comparative Example 1-12), and ClEC and ClDEC (Comparative Example 1-13), the composition of the solvent was changed to EC: DEC: FEC (or ClEC): FDMC (or ClDMC, ClDEC) = 20: by weight ratio. It was set to 60:10:10.

When the cycle characteristics and storage characteristics of the secondary batteries of Example 1 and Comparative Examples 1-1 to 1-13 were examined, the results shown in Table 1 were obtained.

When investigating the cycle characteristics, the secondary battery was repeatedly charged and discharged according to the following procedure, and then the discharge capacity retention rate was calculated. First, the discharge capacity of the second cycle was determined by charging and discharging for two cycles in an atmosphere of 23 ° C. Subsequently, the discharge capacity at the 102nd cycle was determined by charging and discharging for 100 cycles in the same atmosphere. Finally, the discharge capacity retention rate (%) = (discharge capacity at the 102nd cycle / discharge capacity at the 2nd cycle) × 100 was calculated. As the charging / discharging conditions for one cycle, after charging with a constant current constant voltage up to an upper limit voltage of 4.2 V with a charging current of 0.2 C, a constant current discharge was performed with a discharge current of 0.2 C to a final voltage of 2.5 V. This "0.2C" is the current value at which the theoretical capacity can be completely discharged in 5 hours.

When investigating the storage characteristics, the discharge capacity retention rate was calculated after storing the secondary battery according to the following procedure. First, the discharge capacity (discharge capacity before storage) of the second cycle was determined by charging and discharging for two cycles in an atmosphere of 23 ° C. Subsequently, the battery was stored in a constant temperature bath at 80 ° C. for 10 days in a recharged state, and then discharged in an atmosphere at 23 ° C. to determine the discharge capacity (discharge capacity after storage). Finally, the discharge capacity retention rate (%) = (discharge capacity after storage / discharge capacity before storage) × 100 was calculated. The charge / discharge conditions for one cycle were the same as when the normal temperature cycle characteristics were examined.

The procedure and conditions for investigating the cycle characteristics and the storage characteristics are the same for the evaluation of the same characteristics in the subsequent series of Examples and Comparative Examples.

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As shown in Table 1, in Example 1-1, in which the solvent contained both FEC and FDMC, the cycle characteristics and cycle characteristics were compared with Comparative Examples 1-1 to 1-13, which did not contain both of them. The discharge capacity retention rate of storage characteristics has increased.

More specifically, when the solvent does not contain both a cyclic carbonate having halogen as a constituent element and a chain carbonate having halogen as a constituent element (Comparative Example 1-1), the cycle characteristics and the storage characteristics are compared. The discharge capacity retention rate was higher than that of Comparative Example 1-1 (26% and 64%) containing neither FEC nor FDMC in Example 1 (78% and 80%) containing both FEC and FDMC. Also became expensive.

Comparing the case where the solvent contains only cyclic carbonate having halogen as a constituent element (Comparative Examples 1-2 to 1-4), the discharge capacity retention rate of the cycle characteristic and the storage characteristic is FEC in Example 1. It was higher than Comparative Example 1-2 (48% and 60%) containing only. In Comparative Examples 1-3 (35% and 62%) and 1-4 (25% and 59%) containing ClEC and BrEC instead of FEC, they were stored as Comparative Example 1-2 containing FEC. The discharge capacity retention rate of the characteristics was almost the same, but the discharge capacity retention rate of the cycle characteristics was significantly lower than that of Comparative Example 1-2. This result shows that when comparing the types of halogens contained in the cyclic carbonate, fluorine is preferable to chlorine and bromine in order to improve the cycle characteristics.

Comparing the case where the solvent contains only a chain carbonate having halogen as a constituent element (Comparative Examples 1-5 to 1-8), the discharge capacity retention rate of the cycle characteristic and the storage characteristic is in Example 1. It was higher than Comparative Example 1-5 (36% and 70%) containing only FDMC. In Comparative Examples 1-6 (27% and 67%), 1-7 (23% and 60%), and 1-8 (28% and 69%) containing ClDMC, BrDMC and ClDEC instead of FDMC. , The discharge capacity retention rate of the storage characteristics was almost the same as that of Comparative Example 1-5 containing FDMC, but the discharge capacity retention rate of the cycle characteristics was significantly lower than that of Comparative Example 1-5. This result shows that when comparing the types of halogens contained in the chain carbonate, fluorine is preferable to chlorine and bromine in order to improve the cycle characteristics.

Comparing the case where the solvent contains both a cyclic carbonate having halogen as a constituent element and a chain carbonate having halogen as a constituent element (Comparative Examples 1-9 to 1-13), the cycle characteristics and the storage characteristics are compared. The discharge capacity retention rate was determined in Comparative Example 1-9 (48% and 62%) containing FEC and ClDMC, and Comparative Example 1-10 (47% and 63%) containing FEC and ClDEC in Example 1. , Comparative Examples 1-11 (43% and 67%) containing ClEC and FDMC, Comparative Examples 1-12 (39% and 64%) containing ClEC and ClDMC, and Comparisons containing ClEC and ClDEC. It was higher than Example 1-13 (41% and 65%). As described above, the fact that fluorine is preferable to chlorine and bromine as the type of halogen means that the discharge capacity retention rate of the cycle characteristics contains FEC rather than Comparative Examples 1-12 and 1-13, which do not contain FEC. It is higher in Comparative Examples 1-9 and 1-10, respectively, or higher in Comparative Examples 1-11 containing FDMC than in Comparative Examples 1-12 and 1-13 not containing FDMC. Is also clear.

From this, in the secondary battery in which the negative electrode 22 contains silicon (electron beam vapor deposition method) as the negative electrode active material and the solvent of the electrolytic solution contains EC and DEC, the solvent is the cyclic carbonate and the chemical carbonate shown in Chemical formula 5. It was confirmed that the cycle characteristics and the storage characteristics were improved by containing both of the chain carbonates shown in.

(Examples 2-1 to 2-12) As solvents, FEC, which is a cyclic carbonic acid ester shown in Chemical formula 5, and FDMC, which is a chain carbonate ester shown in Chemical formula 6, are used together with EC and DEC, and the composition of the solvent is used. EC: DEC: FEC: FDMC = 0: 0: 50: 50 (Example 2-1), 25:25: 25: 25 (Example 2-2), 0:50:30:20 (Example 2-2) Example 2-3), 20:50:10:20 (Example 2-4), 20:65:10: 5 (Example 2-5), 25:50: 5:20 (Example 2-6) ), 25:60: 5:10 (Example 2-7), 25: 65: 5: 5 (Example 2-8), 29:50: 1: 20 (Example 2-9), 29:60 Example 1 except that 1:10 (Example 2-10), 29:65: 1: 5 (Example 2-11) and 29:69: 1: 1 (Example 2-12). I went through the same procedure as -1.

(Comparative Examples 2-1 to 2-4) EC: DEC: FEC: FDMC = 0: 50: 50: 0 (Comparative Example 2-1), 50: 0: 0: 50 (Comparison) Examples 2-1 to 2-12, except for Examples 2-2), 29: 70: 1: 0 (Comparative Example 2-3) and 30: 69: 0: 1 (Comparative Example 2-4). Followed the same procedure as.

When the cycle characteristics and storage characteristics of the secondary batteries of Examples 2-1 to 2-12 and Comparative Examples 2-1 to 2-4 were examined, the results shown in Table 2 were obtained. Table 2 also shows the characteristics of Example 1-1 and Comparative Examples 1-1, 1-2, 1-5.

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As shown in Table 2, the discharge capacity retention rate of the cycle characteristics and the storage characteristics was determined in Examples 1-1, 2-1 to 2-12 in which the solvent contained both FEC and FDMC. It was higher than Comparative Examples 1-1, 1-2, 1-5, 2-1 ~ 2-4 which did not include. Specifically, the discharge capacity retention rates are either in Examples 1-1,2-1 to 2-12 (30% to 79% and 65% to 82%), which include both FEC and FDMC. It was higher than Comparative Example 1-1 (26% and 64%) which did not include. In addition, Examples 2-1 (78% and 65%) and Comparative Examples 2-1 (74% and 54%), 2-2 (44% and 64%) having a FEC and FDMC content of 50% by weight. Examples 1-1 (78% and 80%) and Comparative Examples 1-2 (48% and 60%), 1-5 (36% and 70%), and 1% by weight. Comparing Example 2-12 (30% and 70%) with Comparative Examples 2-3 (27% and 62%) and 2-4 (26% and 69%), respectively, the discharge capacity retention rate is in each case. Was also higher in the examples than in the comparative examples. In particular, when the above results are obtained for Examples 1-1, 2-1 to 2-12, the lower and upper limits of the contents of FEC and FDMC are 1 % by weight and 50, respectively, which are common to FEC and FDMC. It was% by weight. From this, in a secondary battery in which the negative electrode 22 contains silicon (electron beam vapor deposition method) as the negative electrode active material and the solvent of the electrolytic solution contains EC and DEC, the solvent is FEC as the cyclic carbonic acid ester shown in Chemical formula 5. It was confirmed that the inclusion and inclusion of FDMC as the chain carbonate ester shown in Chemical formula 6 improved the cycle characteristics and storage characteristics. In this case, it was also confirmed that the content of FEC and FDMC in the electrolytic solution is preferably in the range of 1% by weight or more and 50% by weight or less.

(Examples 3-1 to 3-13) The procedure is the same as in Examples 2-1 to 2-4, 1-1, 2-5 to 2-12, except that DFEC is used instead of FEC as a solvent. Got through.

(Comparative Examples 3-1 to 3-3) The procedure was the same as that of Comparative Examples 2-1, 1-2, 2-3, except that DFEC was used instead of FEC as the solvent.

When the cycle characteristics and storage characteristics of the secondary batteries of Examples 3-1 to 3-13 and Comparative Examples 3-1 to 3-3 were examined, the results shown in Table 3 were obtained. Table 3 also shows the characteristics of Comparative Examples 1-1, 1-5, 2-2, 2-4.

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As shown in Table 3, the discharge capacity retention rates of the cycle characteristics and storage characteristics were compared in Examples 3-1 to 3-13 in which the solvent contained both DFEC and FDMC, and both of them were not contained. It was higher than Example 1-1,1-5,2-2,2-4,3-1 ~ 3-3. Specifically, the discharge capacity retention rate does not include either of them in Examples 3-1 to 3-13 (42% to 82% and 68% to 82%), which includes both DFEC and FDMC. It was higher than Comparative Example 1-1 (26% and 64%). In addition, Examples 3-1 (80% and 70%) and Comparative Examples 3-1 (78% and 56%), 2-2 (44% and 64%) having a content of DFEC and FDMC of 50% by weight. Examples 3-5 (80% and 79%) and Comparative Examples 3-2 (72% and 62%), 1-5 (36% and 70%), and 1% by weight. Comparing Example 3-13 (42% and 70%) with Comparative Examples 3-3 (35% and 63%) and 2-4 (26% and 69%), respectively, the discharge capacity retention rate is in each case. Was also higher in the examples than in the comparative examples. In particular, the lower and upper limits of the contents of DFEC and FDMC when the above results are obtained for Examples 3-1 to 3-13 are 1% by weight and 50% by weight, respectively, which are common to DFEC and FDMC. It was. From this, in a secondary battery in which the negative electrode 22 contains silicon (electron beam vapor deposition method) as the negative electrode active material and the solvent of the electrolytic solution contains EC and DEC, the solvent is DFEC as the cyclic carbonic acid ester shown in Chemical formula 5. It was confirmed that the inclusion and inclusion of FDMC as the chain carbonate ester shown in Chemical formula 6 improved the cycle characteristics and storage characteristics. In this case, it was also confirmed that the content of DFEC and FDMC in the electrolytic solution is preferably in the range of 1% by weight or more and 50% by weight or less.

(Examples 4-1 to 4-13) The procedure is the same as in Examples 2-1 to 2-4, 1-1, 2-5 to 2-12, except that DFDMC is used instead of FDMC as a solvent. Got through.

(Comparative Examples 4-1 to 4-3) The procedure was the same as that of Comparative Examples 2-2, 1-5, 2-4, except that DFDMC was used instead of FDMC as a solvent.

When the cycle characteristics and storage characteristics of the secondary batteries of Examples 4-1 to 4-13 and Comparative Examples 4-1 to 4-3 were examined, the results shown in Table 4 were obtained. Table 4 also shows the characteristics of Comparative Examples 1-1, 1-2, 2-1 and 2-3.

<tables num="4"><img file="JP2008123714A_D0013.tif" /></tables>

As shown in Table 4, the discharge capacity retention rates of the cycle characteristics and storage characteristics were compared in Examples 4-1 to 4-13 in which the solvent contained both FEC and DFDMC, and both of them were not contained. It was higher than Example 1-1,1-2,2-1,2-3,4-1 ~ 4-3. Specifically, the discharge capacity retention rate does not include either of them in Examples 4-1 to 4-13 (32% to 79% and 65% to 82%), which include both FEC and DFDMC. It was higher than Comparative Example 1-1 (26% and 64%). In addition, Examples 4-1 (79% and 68%) and Comparative Examples 2-1 (74% and 54%), 4-1 (49% and 67%) having FEC and DFDMC contents of 50% by weight. , 10% by weight, Examples 4-5 (79% and 80%) and Comparative Examples 1-2 (48% and 60%), 4-2 (43% and 70%), and 1% by weight. Comparing Example 4-13 (32% and 70%) with Comparative Examples 2-3 (27% and 62%) and 4-3 (27% and 69%), the discharge capacity retention rate is in each case. It was higher in the examples than in the comparative examples. In particular, the lower and upper limits of the contents of FEC and DFDMC when the above results are obtained for Examples 4-1 to 4-13 are 1% by weight and 50% by weight, respectively, which are common to FEC and DFDMC. It was. From this, in a secondary battery in which the negative electrode 22 contains silicon (electron beam vapor deposition method) as the negative electrode active material and the solvent of the electrolytic solution contains EC and DEC, the solvent is FEC as the cyclic carbonic acid ester shown in Chemical formula 5. It was confirmed that the inclusion and inclusion of DFDMC as the chain carbonate ester shown in Chemical formula 6 improved the cycle characteristics and storage characteristics. In this case, it was also confirmed that the content of FEC and DFDMC in the electrolytic solution is preferably in the range of 1% by weight or more and 50% by weight or less.

(Examples 5-1 to 5-13) Examples 2-1 to 2-4, 1-1, 2-5 to 2-, except that DFEC and DFDMC were used as solvents instead of FEC and FDMC, respectively. The procedure was the same as in 12.

When the cycle characteristics and storage characteristics of the secondary batteries of Examples 5-1 to 5-13 were examined, the results shown in Table 5 were obtained. Table 5 also shows the characteristics of Comparative Examples 1-1, 3-1 to 3-3, 4-1 to 4-3.

<tables num="5"><img file="JP2008123714A_D0014.tif" /></tables>

As shown in Table 5, the discharge capacity retention rates of the cycle characteristics and storage characteristics were compared in Examples 5-1 to 5-13 in which the solvent contained both DFEC and DFDMC, and both of them were not contained. It was higher than Example 1-1,3-1 ~ 3-3,4-1 ~ 4-3. Specifically, the discharge capacity retention rates do not include either of them in Examples 5-1 to 5-13 (48% to 85% and 68% to 83%), which include both DFEC and DFDMC. It was higher than Comparative Example 1-1 (26% and 64%). In addition, Examples 5-1 (82% and 70%) and Comparative Examples 3-1 (78% and 56%), 4-1 (49% and 67%) having a content of DFEC and DFDMC of 50% by weight. 5-5 (84% and 80%) and Comparative Examples 3-2 (72% and 62%), 4-2 (43% and 70%), and 1% by weight. Comparing Example 5-13 (48% and 71%) with Comparative Examples 3-3 (35% and 63%) and 4-3 (27% and 69%), respectively, the discharge capacity retention rate is in each case. Was also higher in the examples than in the comparative examples. In particular, the lower and upper limits of the contents of DFEC and DFDMC when the above results are obtained for Examples 5-1 to 5-13 are 1% by weight and 50% by weight, respectively, which are common to DFEC and DFDMC. It was. From this, in a secondary battery in which the negative electrode 22 contains silicon (electron beam vapor deposition method) as the negative electrode active material and the solvent of the electrolytic solution contains EC and DEC, the solvent is DFEC as the cyclic carbonic acid ester shown in Chemical formula 5. It was confirmed that the inclusion and inclusion of DFDMC as the chain carbonate ester shown in Chemical formula 6 improved the cycle characteristics and storage characteristics. In this case, it was also confirmed that the content of DFEC and DFDMC in the electrolytic solution is preferably in the range of 1% by weight or more and 50% by weight or less.

Further, from the results shown in Tables 2 to 5, Examples 1-1, which have a common composition except that the types of the cyclic carbonic acid ester shown in Chemical formula 5 and the chain carbonate ester shown in Chemical formula 6 are different. Comparing 3-5,4-5,5-5, the discharge capacity retention of cycle characteristics includes DFEC instead of FEC than Example 1-1 (78%), which contains FEC and FDMC. High in Example 3-5 (80%) and Example 4-5 (79%) containing DFDMC instead of FDMC, and further in Example 5-5 (84%) containing DFEC and DFDMC. ) Was higher. From this, it was confirmed that DFEC and DFDMC are preferable to FEC and FDDC, respectively, and a combination of DFEC and DFDMC is particularly preferable in order to improve the cycle characteristics.

(Examples 6-1 to 6-11) The procedure was the same as in Examples 5-2,5-4 to 5-13, except that propylene carbonate (PC) was used instead of EC as the solvent.

(Comparative Examples 6-1 to 6-6) Comparative Examples 1-1,4-1,3-2,4-2,3-3,4-3, except that PC was used instead of EC as the solvent. Followed the same procedure as.

When the cycle characteristics and storage characteristics of the secondary batteries of Examples 6-1 to 6-11 and Comparative Examples 6-1 to 6-6 were examined, the results shown in Table 6 were obtained. Table 6 also shows the characteristics of Comparative Example 3-1.

<tables num="6"><img file="JP2008123714A_D0015.tif" /></tables>

As shown in Table 6, the discharge capacity retention rates of the cycle characteristics and storage characteristics were compared in Examples 6 to 6-11 in which the solvent contained both DFEC and DFDMC, and both of them were not contained. It was higher than Example 3-1, 6-1 ~ 6-6. Specifically, the discharge capacity retention rate does not include either of them in Examples 6-1 to 6-11 (49% to 84% and 72% to 83%), which include both DFEC and DFDMC. It was higher than Comparative Example 6-1 (25% and 69%). Also, Examples 6-3 (83% and 81%) and Comparative Examples 6-3 (73% and 63%), 6-4 (42% and 71%) in which the contents of DFEC and DFDMC were 10% by weight. , And 1% by weight of Examples 6-11 (49% and 72%) and Comparative Examples 6-5 (34% and 68%), 6-6 (26% and 70%). In each case, the rate was higher in the examples than in the comparative examples. From this, the negative electrode 22 contains silicon (electron beam vapor deposition method) as the negative electrode active material, and the solvent of the electrolytic solution contains both the cyclic carbonate ester shown in Chemical formula 5 and the chain carbonate ester shown in Chemical formula 6. In the battery, it was confirmed that the cycle characteristics and the storage characteristics were improved even when the types of solvents other than the above-mentioned cyclic carbonate and chain carbonate were changed. Although only the case where the solvent contains DFEC and DFDMC is described here, even when the solvent contains PC and DEC, the solvent contains FEC and FDCC, DFEC and FDDC, or FEC and DFDMC. Needless to say, the same results as those shown in Tables 2 to 4 can be obtained.

(Examples 7-1 to 7-5) 2-Propene sultone (PRS; Example 7-1), succinic anhydride (SCAH; Example 7-2), vinylene carbonate (VC; Example 7) in an electrolytic solution. -3), Lithium tetrafluoroborate (LiBF)₄The procedure was the same as in Example 5-5, except that Example 7-4) and lithium bis [oxorat-O, O'] lithium borate (LiBOB; Example 7-5) were added, respectively. At that time, the content of the additive in the electrolytic solution was set to 1% by weight.

When the cycle characteristics and storage characteristics of the secondary batteries of Examples 7-1 to 7-5 were examined, the results shown in Table 7 were obtained. Table 7 also shows the characteristics of Examples 5-5.

<tables num="7"><img file="JP2008123714A_D0016.tif" /></tables>

As shown in Table 7, the discharge capacity retention rate of the storage characteristics is PRS, SCAH, VC, LiBF.₄And in Examples 7-1 to 7-5 (82% to 85%) containing LiBOB, it was higher than in Examples 5-5 (80%) containing them. The discharge capacity retention rate of the cycle characteristics was almost the same in Examples 7-1 to 7-5 (83% to 84%) as in Example 5-5 (84%). From this, when the solvent of the electrolytic solution contains both the cyclic carbonate ester shown in Chemical formula 5 and the chain carbonate ester shown in Chemical formula 6, the electrolytic solution has sulton, acid anhydride, and unsaturated bond. It was confirmed that the storage characteristics were further improved by adding the cyclic carbonate or other lithium salts.

(2) Semimetal-based negative electrode (sintering method) (Examples 8-1 to 8-13) Same as Examples 5-1 to 5-13 except that the negative electrode active material layer 22B was formed by the sintering method. I went through the procedure of. When producing the negative electrode 22, first, 90 parts by mass of silicon powder having an average particle size of 2 μm as a negative electrode active material and 10 parts by mass of polyvinylidene fluoride powder as a binder are mixed to form N-methyl-2-pyrrolidone. Then, it was applied to both sides of the negative electrode current collector 22A made of copper foil (thickness of 20 μm) and dried. Subsequently, compression molding was performed so that the thickness of the negative electrode active material layer 22B on one side of the negative electrode current collector 22A was 15 μm. Finally, it was heated at 350 ° C for 3 hours, cooled, and then cut into strips.

(Comparative Examples 8-1 to 8-7) Comparative Examples 1-1, 3-1 and 4 except that the negative electrode active material layer 22B was formed by the sintering method in the same manner as in Examples 8-1 to 8-13. The procedure was the same as for -1,3-2,4-2,3-3,4-3.

When the cycle characteristics and storage characteristics of the secondary batteries of Examples 8-1 to 8-13 and Comparative Examples 8-1 to 8-7 were examined, the results shown in Table 8 were obtained.

<tables num="8"><img file="JP2008123714A_D0017.tif" /></tables>

As shown in Table 8, the discharge capacity retention rates of the cycle characteristics and storage characteristics were compared in Examples 8-1 to 8-13 in which the solvent contained both DFEC and DFDMC, and both of them were not contained. It was higher than Example 8-1 ~ 8-7. Specifically, the discharge capacity retention rate was higher in Examples 8-1 to 8-13 (48% to 82% and 68% to 83%) than in Comparative Example 8-1 (25% and 67%). .. Also, for each DFEC and DFDMC content, Examples 8-1 (73% and 74%) and Comparative Examples 8-2 (68% and 54%), 8-3 (42% and 73%), Examples. 8-5 (82% and 80%) and Comparative Examples 8-4 (65 and 60%), 8-5 (38% and 72%), and Examples 8-13 (48% and 72%) and Comparative Examples. Comparing 8-6 (30% and 65%) and 8-7 (26% and 71%), the discharge capacity retention rate was higher in each example than in the comparative example. In particular, the lower and upper limits of the contents of DFEC and DFDMC in Examples 8-1 to 8-13 were 1% by weight and 50% by weight, respectively. From this, in the secondary battery in which the negative electrode 22 contains silicon (sinter) as the negative electrode active material and the solvent of the electrolytic solution contains EC and DEC, the solvent contains DFEC as the cyclic carbonic acid ester shown in Chemical formula 5. By including DFDMC as the chain carbonate as shown in Chemical formula 6, the cycle characteristics and storage characteristics are improved, and in particular, the content of DFEC and DFDMC in the electrolytic solution is within the range of 1% by weight or more and 50% by weight or less. Was confirmed to be preferable.

(3) Alloy-based negative electrode A tin alloy was used as the negative electrode active material, and the cylindrical secondary batteries shown in FIGS. 1 and 2 were manufactured so as to be lithium ion secondary batteries.

(Examples 9-1 to 9-13) The procedure was the same as that of Examples 2-1 to 2-4, 1-1, 2-5 to 2-12, except for the procedure for manufacturing the negative electrode 22. When producing the negative electrode 22, first, a tin-cobalt-indium-titanium alloy powder and a carbon powder were mixed, and then a CoSnC-containing material was synthesized by using a mechanochemical reaction. When the composition of this CoSnC-containing material was analyzed, the tin content was 48% by mass, the cobalt content was 23% by mass, and the carbon content was 20% by mass. Co / (Sn + Co) was 32% by mass. Subsequently, 80 parts by mass of CoSnC-containing material powder as a negative electrode active material, 12 parts by mass of graphite as a conductive agent, and 8 parts by mass of polyvinylidene fluoride as a binder were mixed and dispersed in N-methyl-2-pyrrolidone. It was. Finally, the negative electrode active material layer 22B was formed by applying the negative electrode current collector 22A made of copper foil (thickness of 15 μm) to both surfaces, drying the mixture, and then compression molding the negative electrode current collector 22A.

(Comparative Examples 9-1 to 9-7) Comparative Example 1-1, except that the negative electrode active material layer 22B was formed by using a CoSnC-containing material as the negative electrode active material in the same manner as in Examples 9-1 to 9-13. , 2-1, 2-2, 1-2, 1-5, 2-3, 2-4.

When the cycle characteristics and storage characteristics of the secondary batteries of Examples 9-1 to 9-13 and Comparative Examples 9-1 to 9-7 were examined, the results shown in Table 9 were obtained.

<tables num="9"><img file="JP2008123714A_D0018.tif" /></tables>

As shown in Table 9, the discharge capacity retention rate of the cycle characteristic and the storage characteristic was similar to the result of Table 2 in Examples 9-1 to 9-13 in which the solvent contained both FEC and FDMC. It was higher than Comparative Examples 9-1 to 9-7, which did not include both of them. Specifically, the discharge capacity retention rate was higher in Examples 9-1 to 9-13 (52% to 77% and 63% to 82%) than in Comparative Example 9-1 (50% and 62%). .. Also, for each FEC and FDMC content, Examples 9-1 (77% and 63%) and Comparative Examples 9-2 (76% and 52%), 9-3 (52% and 62%), Examples. 9-5 (71% and 80%) and Comparative Examples 9-4 (68% and 55%), 9-5 (56% and 77%), and Examples 9-13 (52% and 72%) and comparison Comparing Examples 9-6 (51% and 60%) and 9-7 (50% and 71%), the discharge capacity retention rate was higher in each case than in Comparative Examples. In particular, the lower and upper limits of the FEC and FDMC contents in Examples 9-1 to 9-13 were 1% by weight and 50% by weight, respectively. From this, in a secondary battery in which the negative electrode 22 contains a CoSnC-containing material as the negative electrode active material and the solvent of the electrolytic solution contains EC and DEC, the solvent contains FEC as the cyclic carbonate shown in Chemical formula 5 and chemicals 6 By including FDMC as the chain carbonic acid ester shown in the above, cycle characteristics and storage characteristics are improved, and in particular, the content of FEC and FDMC in the electrolytic solution is preferably in the range of 1% by weight or more and 50% by weight or less. Was confirmed.

(Examples 10-1 to 10-13) Example 3-1 except that the negative electrode active material layer 22B was formed by using a CoSnC-containing material as the negative electrode active material as in Examples 9-1 to 9-13. The procedure was the same as for ~ 3-13.

(Comparative Examples 10-1 to 10-3) The same procedure as in Comparative Examples 3-1 to 3-3 was performed except that the negative electrode active material layer 22B was formed in the same manner as in Examples 9-1 to 9-13. ..

When the cycle characteristics and storage characteristics of the secondary batteries of Examples 10-1 to 10-13 and Comparative Examples 10-1 to 10-3 were examined, the results shown in Table 10 were obtained. Table 10 also shows the characteristics of Comparative Examples 9-1, 9-3, 9-5, 9-7.

<tables num="10"><img file="JP2008123714A_D0019.tif" /></tables>

As shown in Table 10, the discharge capacity retention rates of the cycle characteristics and storage characteristics were similar to the results in Table 3 in Examples 10-1 to 10-13 in which the solvent contained both DFEC and FDMC. It was higher than Comparative Examples 9-1, 9-3, 9-5, 9-7, 10-1 to 10-3, which did not contain both of them. Specifically, the discharge capacity retention rate was higher in Examples 10-1 to 10-13 (56% to 82% and 73% to 82%) than in Comparative Example 9-1 (50% and 62%). .. Also, for each DFEC and FDMC content, Examples 10-1 (82% and 75%) and Comparative Examples 10-1 (80% and 55%), 9-3 (52% and 62%), Examples. 10-5 (80% and 79%) and Comparative Examples 10-2 (76% and 57%), 9-5 (56% and 77%), and Examples 10-13 (56% and 74%) and comparison Comparing Examples 10-3 (55% and 61%) and 9-7 (50% and 71%), the discharge capacity retention rate was higher in each case than in Comparative Examples. In particular, the lower and upper limits of the DFEC and FDMC contents in Examples 10-1 to 10-13 were 1% by weight and 50% by weight, respectively. From this, in the secondary battery in which the negative electrode 22 contains a CoSnC-containing material as the negative electrode active material and the solvent of the electrolytic solution contains EC and DEC, the solvent of the electrolytic solution contains DFEC as the cyclic carbonate shown in Chemical formula 5. By including FDMC as the chain carbonic acid ester shown in Chemical formula 6, the cycle characteristics and storage characteristics are improved, and in particular, the content of DFEC and FDMC in the electrolytic solution is in the range of 1% by weight or more and 50% by weight or less. It was confirmed that it was preferable.

(Examples 11-1 to 11-13) Example 4-1 except that the negative electrode active material layer 22B was formed by using a CoSnC-containing material as the negative electrode active material as in Examples 9-1 to 9-13. The procedure was the same as for ~ 4-13.

(Comparative Examples 11-1 to 11-3) The same procedure as in Comparative Examples 4-1 to 4-3 was performed except that the negative electrode active material layer 22B was formed in the same manner as in Examples 9-1 to 9-13. ..

When the cycle characteristics and storage characteristics of the secondary batteries of Examples 11-1 to 11-13 and Comparative Examples 11-1 to 11-3 were examined, the results shown in Table 11 were obtained. Table 11 also shows the characteristics of Comparative Examples 9-1, 9-2, 9-4, 9-6.

<tables num="11"><img file="JP2008123714A_D0020.tif" /></tables>

As shown in Table 11, the discharge capacity retention rate of the cycle characteristic and the storage characteristic was similar to the result of Table 4 in Examples 11-1 to 11-13 in which the solvent contained both FEC and DFDMC. It was higher than Comparative Examples 9-1, 9-2, 9-4, 9-6, 11-1 to 11-3, which did not contain both of them. Specifically, the discharge capacity retention rate was higher in Examples 11-1 to 11-13 (53% to 78% and 65% to 85%) than in Comparative Example 9-1 (50% and 62%). .. Also, for each FEC and DFDMC content, Examples 11-1 (78% and 65%) and Comparative Examples 9-2 (76% and 52%), 11-1 (57% and 64%), Examples. 11-5 (72% and 80%) and Comparative Examples 9-4 (68% and 55%), 11-2 (56% and 77%), and Examples 11-13 (53% and 74%) and comparison Comparing Examples 9-6 (51% and 60%) and 11-3 (50% and 73%), the discharge capacity retention rate was higher in each case than in Comparative Examples. In particular, the lower and upper limits of the FEC and DFDMC contents in Examples 11-1 to 11-13 were 1% by weight and 50% by weight, respectively. From this, in the secondary battery in which the negative electrode 22 contains a CoSnC-containing material as the negative electrode active material and the solvent of the electrolytic solution contains EC and DEC, the solvent of the electrolytic solution contains FEC as the cyclic carbonic acid ester shown in Chemical formula 5. By including DFDMC as the chain carbonic acid ester shown in Chemical formula 6, the cycle characteristics and storage characteristics are improved, and in particular, the content of FEC and DFDMC in the electrolytic solution is in the range of 1% by weight or more and 50% by weight or less. It was confirmed that it was preferable.

(Examples 12-1 to 12-13) Example 5-1 except that the negative electrode active material layer 22B was formed by using a CoSnC-containing material as the negative electrode active material as in Examples 9-1 to 9-13. The procedure was the same as for ~ 5-13.

When the cycle characteristics and storage characteristics of the secondary batteries of Examples 12-1 to 12-13 were examined, the results shown in Table 12 were obtained. Table 12 also shows the characteristics of Comparative Examples 9-1, 10-1 to 10-3, 11-1 to 11-3.

<tables num="12"><img file="JP2008123714A_D0021.tif" /></tables>

As shown in Table 12, the discharge capacity retention rate of the cycle characteristic and the storage characteristic was similar to the result of Table 5 in Examples 12-1 to 12-13 in which the solvent contained both DFEC and DFDMC. It was higher than Comparative Examples 9-1, 10-1 to 10-3, 11-1 to 11-3, which did not contain both of them. Specifically, the discharge capacity retention rate was higher in Examples 12-1 to 12-13 (58% to 82% and 74% to 83%) than in Comparative Example 9-1 (50% and 62%). .. Also, for each DFEC and DFDMC content, Examples 12-1 (82% and 76%) and Comparative Examples 10-1 (80% and 55%), 11-1 (57% and 64%), Examples. 12-5 (81% and 81%) and Comparative Examples 10-2 (76% and 57%), 11-2 (56% and 77%), and Examples 12-13 (58% and 75%) and comparison Comparing Examples 10-3 (55% and 61%) and 11-3 (50% and 73%), the discharge capacity retention rate was higher in each case than in Comparative Examples. In particular, the lower and upper limits of the contents of DFEC and DFDMC in Examples 12-1 to 12-13 were 1% by weight and 50% by weight, respectively. From this, in the secondary battery in which the negative electrode 22 contains a CoSnC-containing material as the negative electrode active material and the solvent of the electrolytic solution contains EC and DEC, the solvent of the electrolytic solution contains DFEC as the cyclic carbonate shown in Chemical formula 5. By including DFDMC as the chain carbonic acid ester shown in Chemical formula 6, the cycle characteristics and storage characteristics are improved, and in particular, the content of DFEC and DFDMC in the electrolytic solution is in the range of 1% by weight or more and 50% by weight or less. It was confirmed that it was preferable.

Further, from the results shown in Tables 9 to 12, Examples 9-5, which have a common composition except that the types of the cyclic carbonic acid ester shown in Chemical formula 5 and the chain carbonate ester shown in Chemical formula 6 are different. Comparing 10-5,11-5,12-5, the discharge capacity retention rate of the cycle characteristics was higher than that of Example 9-5 (71%), similar to the results shown in Tables 2 to 5. It was higher in 10-5 (80%) and 11-5 (72%) of Examples, and further increased in 12-5 (81%) of Examples. From this, it was confirmed that DFEC and DFDMC are preferable to FEC and FDDC, respectively, and a combination of DFEC and DFDMC is particularly preferable in order to improve the cycle characteristics.

(4) Carbon-based negative electrode Using graphite as the negative electrode active material, the cylindrical secondary batteries shown in FIGS. 1 and 2 were manufactured so as to be lithium ion secondary batteries.

(Example 13-1) The same procedure as in Example 1-1 was performed except for the procedure for manufacturing the negative electrode 22. When producing the negative electrode 22, 90 parts by mass of artificial graphite powder as a negative electrode active material and 10 parts by mass of polyvinylidene fluoride as a binder are mixed to prepare a negative electrode mixture, and then N-methyl-2-pyrrolidone is prepared. Dispersed in. Then, the negative electrode active material layer 22B was formed by applying the negative electrode current collector 22A made of a strip-shaped copper foil (thickness of 15 μm) to both sides, drying the negative electrode current collector 22A, and then compression molding the negative electrode current collector 22A.

(Examples 13-2 to 13-4) The same procedure as in Examples 3-5, 4-5, 5-5 was performed except that the negative electrode active material layer 22B was formed in the same manner as in Example 13-1. ..

(Comparative Examples 13-1 to 13-5) Comparative Examples 1-1,1-2,3-2,1-5,4 except that the negative electrode active material layer 22B was formed in the same manner as in Example 13-1. Followed the same procedure as -2.

When the cycle characteristics and storage characteristics of the secondary batteries of Examples 13-1 to 13-4 and Comparative Examples 13-1 to 13-5 were examined, the results shown in Table 13 were obtained.

<tables num="13"><img file="JP2008123714A_D0022.tif" /></tables>

As shown in Table 13, the discharge capacity retention rate of the cycle characteristic and the storage characteristic is the same as the results shown in Tables 2 to 6 and Tables 8 to 12, and the cyclic carbonate (FEC or) shown in Chemical formula 5 is obtained. In Examples 13-1 to 13-4 (94% and 81% to 85%) containing both DFEC) and the chain carbonate (FDMC or DFDMC) shown in Chemical formula 6, both of them were included. Not higher than Comparative Example 13-1 (90% and 75%) and containing only one of them than Comparative Examples 13-2 to 13-4 (91% to 93% and 72% to 79%) It got higher. From this, in the secondary battery in which the negative electrode 22 contains artificial graphite as the negative electrode active material and the solvent of the electrolytic solution contains EC and DEC, the solvent is the cyclic carbonate shown in Chemical formula 5 and the chain shape shown in Chemical formula 6. It was confirmed that the inclusion of both carbonic acid esters improved the cycle characteristics and storage characteristics. Further, as is clear from the comparison of Examples 13-1 to 13-4, in order to improve the storage characteristics, DFEC and DFDMC are preferable to FEC and FDMC, respectively, and a combination of DFEC and DFDMC is particularly preferable. confirmed.

As is clear from the results in Tables 1 to 13 above, the solvent of the electrolytic solution is the cyclic carbonate and the chemical ester shown in Chemical formula 5 regardless of the material used as the negative electrode active material and the method of forming the negative electrode active material layer 22B. It was confirmed that the cycle characteristics and the storage characteristics were improved by containing both of the chain carbonic acid esters shown in. In particular, when a material containing silicon or tin, which can obtain a high energy density, is used as the negative electrode active material, a higher effect can be obtained because the rate of increase in the discharge capacity retention rate has increased in terms of both cycle characteristics and storage characteristics. It turned out to be. This result shows that when a semi-metal material having a high energy density is used as the negative electrode active material, the decomposition reaction of the electrolytic solution at the negative electrode 22 is more likely to occur than when a carbon material is used. It is considered that the effect of suppressing the decomposition of the electrolytic solution by the chain carbonic acid ester shown in Chemical formula 6 was remarkably exhibited.

Although the present invention has been described above with reference to the embodiments and examples, the present invention is not limited to the embodiments described in the above-described embodiments and examples, and various modifications can be made. For example, the application of the electrolytic solution of the present invention is not necessarily limited to a battery, and may be an electrochemical device other than a battery. Other uses include, for example, capacitors.

Further, in the above-described embodiments and examples, the case where an electrolytic solution or a gel-like electrolyte in which the electrolytic solution is held by a polymer compound is used as the electrolyte of the battery of the present invention has been described, but other types of electrolytes may be used. You may use it. Other electrolytes include, for example, a mixture of an ionic conductive inorganic compound such as ionic conductive ceramics, ionic conductive glass or an ionic crystal and an electrolytic solution, or a mixture of another inorganic compound and an electrolytic solution. Or, a mixture of these inorganic compounds and a gel-like electrolyte can be mentioned.

Further, in the above-described embodiments and examples, as the battery of the present invention, a lithium ion secondary battery in which the capacity of the negative electrode is represented by a capacity component based on the occlusion and release of lithium, or a lithium metal is used as the negative electrode active material. Although the lithium metal secondary battery in which the capacity of the negative electrode is represented by the capacity component based on the precipitation and dissolution of lithium has been described, the present invention is not necessarily limited to this. In the battery of the present invention, the charge capacity of the negative electrode material capable of storing and releasing lithium is made smaller than the charge capacity of the positive electrode, so that the capacity of the negative electrode is based on the storage and release of lithium. The same applies to a secondary battery including and a capacity component based on dissolution and represented by the sum of the capacity components.

Further, in the above-described embodiments and examples, the case where lithium is used as the electrode reactant has been described, but other Group 1A elements such as sodium (Na) and potassium (K), magnesium, calcium (Ca) and the like have been described. Group 2A elements and other light metals such as aluminum may be used. Also in this case, the negative electrode material described in the above embodiment can be used as the negative electrode active material.

Further, in the above-described embodiment or embodiment, as the battery structure of the battery of the present invention, a cylindrical type or a laminated film type has been described as an example, but the battery of the present invention has a coin type, a button type, a square type, or the like. The same applies to a secondary battery having another shape, or a secondary battery having another structure such as a laminated structure. Further, the present invention is not limited to the secondary battery, and can be similarly applied to other batteries such as a primary battery.

Further, in the above-described embodiments and examples, the content of the cyclic carbonic acid ester shown in Chemical formula 5 and the chain carbonate ester shown in Chemical formula 6 in the electrolytic solution of the present invention was appropriately derived from the results of Examples. Although the range is explained, the description does not completely rule out the possibility that the content is outside the above range. That is, the above-mentioned appropriate range is a particularly preferable range for obtaining the effect of the present invention, and the content may be slightly out of the above-mentioned range as long as the effect of the present invention can be obtained.

<figref num="1">It is sectional drawing which shows the structure of the 1st battery using the electrolytic solution which concerns on one Embodiment of this invention.</figref><figref num="2">It is sectional drawing which shows the part of the wound electrode body shown in FIG. 1 enlarged.</figref><figref num="3">It is an exploded perspective view which shows the structure of the 3rd battery using the electrolytic solution which concerns on one Embodiment of this invention.</figref><figref num="4">It is sectional drawing which shows the structure along the IV-IV line of the wound electrode body shown in FIG.</figref>

Code description

11 ... Battery can, 12, 13 ... Insulation plate, 14 ... Battery lid, 15 ... Safety valve mechanism, 15A ... Disc plate, 16 ... Thermal resistance element, 17 ... Gasket, 20,30 ... wound electrode body, 21,33 ... positive electrode, 21A, 33A ... positive electrode current collector, 21B, 33B ... positive electrode active material layer, 22,34 ... negative electrode , 22A, 34A ... Negative current collector, 22B, 34B ... Negative active material layer, 23,35 ... Separator, 24 ... Center pin, 25,31 ... Positive lead, 26,32 ... Negative lead, 36 ... Electrolyte, 37 ... Protective tape, 40 ... Exterior component, 41 ... Adhesive film.