Nonaqueous electrolyte battery

The present invention relates to a non-aqueous electrolyte battery including a positive electrode containing a positive electrode active material capable of storing and releasing lithium ions, a negative electrode containing a negative electrode active material capable of storing and releasing lithium ions, and a non-aqueous electrolyte.

In recent years, portable electronic devices such as mobile phones, notebook personal computers, and video cameras have become more sophisticated, smaller and lighter, and high energy density batteries used in these electronic devices include lithium-ion batteries. The use of non-aqueous electrolyte batteries is expanding. In a lithium ion battery, for example, a power generation element and an electrolytic solution in which a sheet-shaped or foil-shaped positive electrode plate and a negative electrode plate are wound around via a separator are housed in a battery case.

In recent years, along with the improvement in performance of small electronic devices or portable electronic devices, the capacity of batteries has been increased. The capacity of the battery is increased, for example, by increasing the proportion of the positive electrode active material contained in the positive electrode mixture layer of the positive electrode plate and increasing the filling rate of the positive electrode mixture layer.

However, due to the high density of the positive electrode plate as described above, there is a problem that the high rate discharge performance or the cycle life performance is lowered. Further, as the filling rate of the positive electrode active material increases, there is a problem that the thermal stability of the battery in a high temperature environment decreases.

To solve such a problem, an electrolytic solution for a lithium secondary battery containing a lithium salt as a solute, a cyclic sulfate ester, and an organic solvent for dissolving the lithium salt has been proposed (see, for example, Patent Document 1). .. In this electrolytic solution for a lithium secondary battery, it is said that the capacity decrease that occurs with the progress of the charge / discharge cycle is small.

Further, a non-aqueous electrolytic solution composed of a non-aqueous solvent containing a fluorine-containing ether compound and a carbonic acid ester and an electrolyte has been proposed (see, for example, Patent Document 2). In this non-aqueous electrolytic solution, the heat generation rate due to the reaction with the positive electrode is low, and it is said that the non-aqueous electrolytic solution is excellent in safety.<patcit num="1"><text>Japanese Unexamined Patent Publication No. 10-189042</text></patcit><patcit num="2"><text>International Publication No. 00/16427 Pamphlet</text></patcit>

<p> However, Patent Document 1 has a problem that the thickness of the battery increases significantly in a high temperature environment. Further, Patent Document 2 has a problem that the self-discharge in a high temperature environment is large and a problem that the discharge performance in a low temperature environment is greatly deteriorated.</p><p> The present invention has been made in view of such circumstances, and by adding a cyclic sulfate ester derivative to an electrolyte, volume reduction in a high temperature environment and a low temperature environment is suppressed, and a fluorinated ether compound is added to the electrolyte. It is an object of the present invention to provide a non-aqueous electrolyte battery capable of suppressing an increase in the thickness of the battery in a high temperature environment.</p>

<p> The non-aqueous electrolyte battery according to the present invention is a non-aqueous electrolyte battery comprising a positive electrode containing a positive electrode active material capable of storing and releasing lithium ions, a negative electrode containing a negative electrode active material capable of storing and releasing lithium ions, and a non-aqueous electrolyte. In the above, the non-aqueous electrolyte is characterized by containing one or more kinds of cyclic sulfuric acid ester derivatives and one or more kinds of fluorinated ether compounds.</p><p> In the present invention, the cyclic sulfate ester derivative added to the electrolyte suppresses the self-discharge of the negative electrode, so that the capacity decrease in a high temperature environment is suppressed. Further, the cyclic sulfuric acid ester derivative added to the electrolyte improves the discharge characteristics of the negative electrode, so that the capacity decrease in a low temperature environment is suppressed. Further, since the fluorinated ether compound added to the electrolyte suppresses the decomposition of the electrolytic solution at the positive electrode in a high temperature environment, the amount of gas generated is reduced and the increase in the thickness of the battery is suppressed.</p>

<p> According to the present invention, it is possible to suppress a decrease in capacity in a high temperature environment and a low temperature environment, and an increase in the thickness of a battery in a high temperature environment.</p>

Hereinafter, the present invention will be specifically described with reference to the drawings showing the embodiments thereof. (Example 1) FIG. 1 is a schematic cross-sectional view of a non-aqueous electrolyte battery (hereinafter referred to as a battery) according to the present invention. The battery 1 is a flat winding in which a negative electrode plate 3 formed by applying a negative electrode mixture to a copper current collector and a positive electrode plate 4 formed by applying a positive electrode mixture to an aluminum current collector are wound via a separator 5. The power generation element 2 and the non-aqueous electrolytic solution (hereinafter referred to as the electrolytic solution) are housed in an aluminum battery case 6. The battery case 6 has a bottom and a side wall, and a case lid 7 having a safety valve 8 and a negative electrode terminal 9 is attached to the opening by laser welding. Further, the negative electrode terminal 9 is connected to the negative electrode plate 3 via the negative electrode lead 10, and the positive electrode plate 4 is electrically connected to the battery case 6.

The positive electrode paste is a lithium cobalt composite oxide LiCoO as a positive electrode active material.₂, Acetylene black as a conductive auxiliary agent, and polyvinylidene fluoride (PVDF) as a binder are mixed so as to have a mass ratio of 95: 2: 3, and N-methyl-2-, which is a solvent, is mixed therewith. It was obtained by adding an appropriate amount of pyrrolidene (NMP) and stirring. The positive electrode plate 4 was produced by uniformly applying the positive electrode paste to an aluminum foil current collector having a thickness of 15 μm, drying the mixture, and then compression molding with a roll press.

For the negative electrode paste, add an appropriate amount of N-methyl-2-pyrrolidone (NMP) to a negative electrode mixture containing graphite and polyvinylidene fluoride (PVDF) as a binder at a mass ratio of 90:10. I got it. The negative electrode plate 3 was produced by applying the negative electrode paste on both sides of a copper foil current collector having a thickness of 10 μm, drying the mixture, and pressing the negative electrode plate 3.

A polyethylene microporous membrane was used for the separator 5. The electrolyte is a mixed solvent of ethylene carbonate (EC), diethyl carbonate (DEC) and ethyl methyl carbonate (EMC) with a volume ratio of 3: 5: 2 and LiPF.₆Was dissolved in 1 mol / l. In addition, CH is added to the electrolytic solution as a fluorinated ether compound.₃OCH₂CH₂OCH₂CF₃Was added in an amount of 2% by mass, and GLST shown in Table 1 was added in an amount of 1% by mass as a cyclic sulfate ester derivative.

<tables num="1"><img file="JP2005293920A_D0001.tif" /></tables>

Battery 1 has a thickness of 4.2 mm, a width of 34 mm, a height of 50 mm, and a rated capacity of 800 mAh.

(Example 2) CH as a fluorinated ether compound in the electrolytic solution₃OCH₂CH₂OCH₂CF₃A battery was prepared in the same manner as in Example 1 except that 2% by mass was added and 1% by mass of PGLST shown in Table 1 was added as a cyclic sulfate ester derivative.

(Example 3) CH as a fluorinated ether compound in the electrolytic solution₃OCH₂CH₂OCH₂CF₃A battery was prepared in the same manner as in Example 1 except that 2% by mass was added and 1% by mass of BGLST shown in Table 1 was added as a cyclic sulfate ester derivative.

(Example 4) CH as a fluorinated ether compound in the electrolytic solution₃OCH₂CH₂OCH₂CF₃A battery was prepared in the same manner as in Example 1 except that 2% by mass was added and 1% by mass of DMGLST shown in Table 1 was added as a cyclic sulfate ester derivative.

(Example 5) CH as a fluorinated ether compound in the electrolytic solution₃OCH₂CH₂OCH₂CF₃A battery was prepared in the same manner as in Example 1 except that 2% by mass was added and 1% by mass of VST shown in Table 1 was added as a cyclic sulfate ester derivative.

(Example 6) CH as a fluorinated ether compound in the electrolytic solution₃OCH₂CH₂OCH₂CF₃A battery was prepared in the same manner as in Example 1 except that 2% by mass was added and 1% by mass of VEST shown in Table 1 was added as a cyclic sulfate ester derivative.

(Example 7) CH as a fluorinated ether compound in the electrolytic solution₃OCH₂CH₂OCH₂CF₃A battery was prepared in the same manner as in Example 1 except that 2% by mass was added and 1% by mass of PLST shown in Table 1 was added as a cyclic sulfate ester derivative.

(Example 8) CH as a fluorinated ether compound in the electrolytic solution₃OCH₂CH₂OCH₂CF₃A battery was prepared in the same manner as in Example 1 except that 2% by mass was added and 1% by mass of 2MPLST shown in Table 1 was added as a cyclic sulfate ester derivative.

(Example 9) CH as a fluorinated ether compound in the electrolytic solution₃OCH₂CH₂OCH₂CF₃A battery was prepared in the same manner as in Example 1 except that 2% by mass was added and 1% by mass of 3MPLST shown in Table 1 was added as a cyclic sulfate ester derivative.

(Example 10) CH as a fluorinated ether compound in the electrolytic solution₂OCH₂CH₂OCH₂CH₂A battery was prepared in the same manner as in Example 1 except that 2% by mass of F was added and 1% by mass of PGLST shown in Table 1 was added as a cyclic sulfate ester derivative.

(Example 11) CH as a fluorinated ether compound in the electrolytic solution₃CH₂OCH₂CH₂OCH₂CH₂A battery was prepared in the same manner as in Example 1 except that 2% by mass of F was added and 1% by mass of PGLST shown in Table 1 was added as a cyclic sulfate ester derivative.

(Example 12) CH as a fluorinated ether compound in the electrolytic solution₃CH₂OCH₂CH₂OCH₂CF₃A battery was prepared in the same manner as in Example 1 except that 2% by mass was added and 1% by mass of PGLST shown in Table 1 was added as a cyclic sulfate ester derivative.

(Example 13) CF as a fluorinated ether compound in an electrolytic solution₃OCH₂CH₂OCH₂CF₃A battery was prepared in the same manner as in Example 1 except that 2% by mass was added and 1% by mass of PGLST shown in Table 1 was added as a cyclic sulfate ester derivative.

(Example 14) CF as a fluorinated ether compound in an electrolytic solution₃CH₂OCH₂CH₂OCH₂CF₃A battery was prepared in the same manner as in Example 1 except that 2% by mass was added and 1% by mass of PGLST shown in Table 1 was added as a cyclic sulfate ester derivative.

(Example 15) CH as a fluorinated ether compound in the electrolytic solution₃OCH₂CH₂OCH₂CF₃A battery was prepared in the same manner as in Example 1 except that 1% by mass was added and 1% by mass of PGLST shown in Table 1 was added as a cyclic sulfate ester derivative.

(Example 16) CH as a fluorinated ether compound in the electrolytic solution₃OCH₂CH₂OCH₂CF₃A battery was prepared in the same manner as in Example 1 except that 3% by mass was added and 1% by mass of PGLST shown in Table 1 was added as a cyclic sulfate ester derivative.

(Example 17) CH as a fluorinated ether compound in the electrolytic solution₃OCH₂CH₂OCH₂CF₃A battery was prepared in the same manner as in Example 1 except that 2% by mass was added and 0.5% by mass of PGLST shown in Table 1 was added as a cyclic sulfate ester derivative.

(Example 18) CH as a fluorinated ether compound in an electrolytic solution₃OCH₂CH₂OCH₂CF₃A battery was prepared in the same manner as in Example 1 except that 2% by mass was added and 2% by mass of PGLST shown in Table 1 was added as a cyclic sulfate ester derivative.

(Comparative Example 1) CH as a fluorinated ether compound in the electrolytic solution₃OCH₂CH₂OCH₂CF₃Was added in an amount of 2% by mass, but a cyclic sulfuric acid ester derivative was not added, but a battery was prepared in the same manner as in Example 1.

(Comparative Example 2) A battery was prepared in the same manner as in Example 1 except that 1% by mass of PGLST shown in Table 1 was added to the electrolytic solution as a cyclic sulfate ester derivative, but no fluorinated ether compound was added. did.

(Comparative Example 3) A battery was produced in the same manner as in Example 1 except that the fluorinated ether compound was not added to the electrolytic solution and the cyclic sulfate ester derivative was not added.

For the non-aqueous electrolyte batteries of each of these Examples and Comparative Examples, the capacity retention rate and thickness increase rate in a high temperature environment and the capacity retention rate in a low temperature environment were measured. The capacity retention rate and thickness increase rate in a high temperature environment are constant voltage and constant current charging for 3 hours up to a voltage of 4.2 V at a current of 800 mA in an environment of 25 ° C, and 30 days in an environment of 60 ° C after charging. After leaving it to stand, discharge it to a voltage of 3V with a current of 800mA and measure the discharge capacity and the thickness of the battery. The rate of increase) was calculated. The discharge capacity and the thickness of the battery before being left unattended are measured by performing constant voltage / constant current charging up to a voltage of 4.2 V at a current of 800 mA for 3 hours and then discharging to a voltage of 3 V at a current of 800 m after charging. The capacity retention rate in a high temperature environment is good when it is 70% or more, and the thickness increase rate is good when it is 120% or less.

The capacity retention rate in a low temperature environment is such that a constant voltage / constant current charge is performed for 3 hours at a current of 800 mA and a voltage of 4.2 V in an environment of 25 ° C. Discharge to a voltage of 3 V with a current of 800 m, measure the discharge capacity, and determine the ratio of the discharge capacity after leaving to stand (capacity retention rate). The discharge capacity before being left unattended is measured by performing constant voltage / constant current charging up to a voltage of 4.2 V at a current of 800 mA for 3 hours, and then discharging to a voltage of 3 V at a current of 800 mA after charging. The capacity retention rate in a low temperature environment is good if it is 90% or more. The results of each measurement are shown in Table 2.

<tables num="2"><img file="JP2005293920A_D0002.tif" /></tables>

As shown in Examples 1 to 18, the batteries in which the fluorinated ether compound and the cyclic sulfate ester derivative are added to the electrolytic solution have a high capacity retention rate in a high temperature environment and a low temperature environment, and the thickness increases in a high temperature environment. The rate is low and all measurement results are good. These batteries are suitable for personal computer applications used at relatively high temperatures, or for digital camera applications in which an increase in battery thickness is particularly problematic because they are used in slot-in.

When the amount of the fluorinated ether compound and the cyclic sulfate ester derivative is increased, the concentration of the electrolyte in the electrolytic solution is lowered and the battery performance is lowered. Therefore, the amount of the fluorinated ether compound added is 3% by mass or less, cyclic. The sulfate ester derivative is preferably 2% by mass or less, and the total of both is preferably 5% by mass or less. However, when the amount of the fluorinated ether compound added is less than 1% by mass, the effect is insufficient, such as the thickness increase rate in a high temperature environment exceeding 120%. Further, when the addition amount of the cyclic sulfate ester derivative is less than 0.5% by mass, the effect is insufficient such that the capacity retention rate in a low temperature environment becomes less than 90%.

As shown in Comparative Example 1, when the fluorinated ether compound is contained but the cyclic sulfate ester derivative is not contained, the thickness increase rate of the battery in a high temperature environment is good, but the capacity is maintained in a high temperature environment. It has a problem that the rate and the capacity retention rate in a low temperature environment are low.

As shown in Comparative Example 2, when the cyclic sulfate ester derivative is contained but the fluorinated ether compound is not contained, the capacity retention rate in a high temperature environment and the capacity retention rate in a low temperature environment are good, but in a high temperature environment. There is a problem that the thickness increase rate of the battery is high.

As shown in Comparative Example 3, when neither the fluorinated ether compound nor the cyclic sulfate ester derivative is contained, the capacity retention rate in a high temperature environment, the thickness increase rate in a high temperature environment, and the capacity retention rate in a high temperature environment. I have a problem with all of them.

Here, the cyclic sulfuric acid ester derivative to be added to the electrolytic solution is not limited to the above-mentioned examples, and for example, at least one cyclic sulfuric acid ester derivative represented by the following general formulas (1), (2) or (3). It is possible to include any one or more kinds of cyclic sulfuric acid ester derivatives in the electrolytic solution (non-aqueous electrolyte), for example, by adding the above to the electrolytic solution.

<chemistry num="1"><img file="JP2005293920A_D0003.tif" /></chemistry>

<chemistry num="2"><img file="JP2005293920A_D0004.tif" /></chemistry>

<chemistry num="3"><img file="JP2005293920A_D0005.tif" /></chemistry>

However, in the formula, R1 to R6 are independently hydrogen atoms, the same or different alkyl groups, the same or different vinyl groups, the same or different alkoxy groups, the same or different allyl groups, and the same. Represents one or a different type of aryl group, the same type or a different kind of halogen, an alkyl group having a halogen, an allyl group having a halogen, or an aryl group having a halogen.

The fluorinated ether compound to be added to the electrolytic solution is not limited to the above-mentioned examples, and for example, at least one fluorinated ether compound represented by the following general formula (4) or (5) is added to the electrolytic solution. It is possible to include any one or more kinds of fluorinated ether compounds in the electrolytic solution (non-aqueous electrolyte). R7-O- (AO)_n-CH₂-X (4) X-CH₂-(AO)_n-CH₂-X (5) However, in the formula, R7 represents a hydrocarbon group having 1 to 20 carbon atoms, X represents a fluorine atom-substituted hydrocarbon group having 1 to 10 carbon atoms, and A represents an alkylene group having 2 to 4 carbon atoms. Also, n is an integer from 1 to 30.

<figref num="1">It is the schematic sectional drawing of the non-aqueous electrolyte battery which concerns on this invention.</figref>

Code description

1 Battery (non-aqueous electrolyte battery) 2 Power generation element 3 Negative electrode plate 4 Positive electrode plate 5 Separator 6 Battery case 7 Case lid 8 Safety valve 9 Negative electrode terminal 10 Negative electrode lead