Nonaqueous secondary battery

The present invention relates to a non-aqueous secondary battery and a method for manufacturing the same.

Since non-aqueous secondary batteries have high voltage and high capacity, great expectations are placed on their development. In addition to Li (lithium) and Li alloy, natural or artificial graphite-based carbon materials capable of inserting and removing Li ions are applied to the negative electrode material (negative electrode active material) of non-aqueous secondary batteries. ..

Recently, however, there has been a demand for even higher capacities for batteries for portable devices that have become smaller and more multifunctional, and in response to this, low crystalline carbon, Si (silicon), Sn (tin), etc. have been desired. As described above, a material capable of accommodating a larger amount of Li is attracting attention as a negative electrode material (hereinafter, also referred to as high-capacity negative electrode material).

As one of the high-capacity negative electrode materials for such non-aqueous secondary batteries, Si ultrafine particles are SiO₂Compound with dispersed structure (SiO)_x) Is attracting attention. When this material is used as the negative electrode active material, Si that reacts with Li is ultrafine particles, so charging and discharging can be performed smoothly, while SiO having the above structure_xSince the particles themselves have a small surface area, they have good coatability when used as a paint for forming the negative electrode mixture layer and adhesiveness of the negative electrode mixture layer to the current collector.

However, SiO_xIs an oxide having low conductivity. Therefore, when forming a negative electrode using this oxide, it is necessary to sufficiently mix and disperse it with a conductive auxiliary agent. In Patent Document 1 and Patent Document 2, SiO_xDisclosed is a technique for forming a negative electrode after coating the surface of the material with carbon to increase its conductivity.

By the way, SiO_xHas a relatively large so-called irreversible capacity, so SiO_xIn order to further increase the capacity of the battery by using the above as the negative electrode material, it is preferable to introduce a Li source such as Li metal on the negative electrode side.

As a method of introducing Li metal into the negative electrode material, for example, when manufacturing the negative electrode, a Li metal foil is attached to the surface of the negative electrode mixture layer containing the negative electrode material, and the Li metal foil is used as the negative electrode mixture. There is a method of introducing Li metal into the negative electrode material in the agent layer. However, according to the study by the present inventors, SiO_xIs very reactive with Li, so SiO_xWhen the Li metal leaf is provided directly on the negative electrode mixture layer containing, Li becomes SiO just by contacting._xInvades inside and SiO_xIt was found that the negative electrode is curved because the reaction of not only expanding but also converting to Li occurs non-uniformly depending on the location.

As a technique relating to a battery in which Li metal is introduced into a negative electrode material in advance, Patent Document 3 provides an auxiliary layer containing water-insoluble particles between a layer containing a negative electrode material (negative electrode mixture layer) and a Li metal foil. A method of constructing a battery using the provided negative electrode has been proposed. If the technology disclosed in Patent Document 3 can be applied and the introduction rate from the Li metal foil to the negative electrode mixture layer can be controlled by examining the configuration of the auxiliary layer described above, SiO can be used as the negative electrode material._xThere is a possibility that the bending of the negative electrode can be prevented even by using.

<patcit num="1"><text>Japanese Unexamined Patent Publication No. 2004-47404</text></patcit><patcit num="2"><text>Japanese Patent Application Laid-Open No. 2005-259697</text></patcit><patcit num="3"><text>Japanese Unexamined Patent Publication No. 2000-182602</text></patcit>

<p> However, according to the study by the present inventors, when the positive electrode material is a Li-containing transition metal oxide, SiO_xIt has been found that even if a non-aqueous secondary battery is constructed by applying the technique disclosed in Patent Document 3 to the negative electrode using the above, the precipitation of lithium dendrite occurs and the battery characteristics are easily impaired. This is because the Li metal leaf has a certain thickness (several tens of μm) or more, and SiO_xThis is due to the fact that more Li is present in the battery in a metallic state than the amount to be introduced into the battery, and this is due to reprecipitation on the negative electrode as dendrites. Since the Li metal foil is very soft, it is difficult to process it into a thin and uniform thickness, and the amount of Li introduced into the negative electrode material in advance cannot be limited.</p><p> On the other hand, in the configuration disclosed in Patent Document 3, the negative electrode material is Sn oxide having a large irreversible capacity and the like, and SiO_xIn addition to the need to introduce more Li than the above, a metal oxide that does not contain Li in advance is used for the positive electrode material (positive electrode active material), and Li can be incorporated into the positive electrode material, so a Li metal foil is used. However, the precipitation of dendrite can be suppressed. However, from the viewpoint of increasing the capacity of the non-aqueous secondary battery, the Li-containing transition metal oxide is preferable to the Li-free metal oxide as the positive electrode material (positive electrode active material), and SiO is preferable._xIt is desired to further increase the capacity of the battery by combining the above with the negative electrode used as the negative electrode material.</p><p> The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a non-aqueous secondary battery having a high capacity and good battery characteristics, and a method for manufacturing the same.</p>

<p> The non-aqueous secondary battery of the present invention that has achieved the above object is a non-aqueous secondary battery provided with a positive electrode, a negative electrode and a non-aqueous electrolyte, and the positive electrode is a positive electrode containing a Li-containing transition metal oxide. The negative electrode has a mixture layer, and covers the core containing a compound containing Si and O as constituent elements (however, the atomic ratio x of O to Si is 0.5 x 1.5) and its surface. It has a negative electrode mixture layer containing a negative electrode material composed of a carbon coating layer, and a porous layer formed on the negative electrode mixture layer and containing an insulating material that does not react with Li. The compound containing Si and O as constituent elements is characterized by having a peak in the range of at least 1850 to 1860 eV in the structure spectrum near the X-ray absorption end of the K absorption end of Si at the end of discharge of the battery. It is a thing.</p><p> Further, the non-aqueous secondary battery of the present invention is a non-aqueous secondary battery provided with a positive electrode, a negative electrode and a non-aqueous electrolyte, and the positive electrode has a positive electrode mixture layer containing a Li-containing transition metal oxide. The negative electrode is a carbon coating layer that covers a core containing a compound containing Si and O as constituent elements (however, the atomic ratio x of O to Si is 0.5 x 1.5) and its surface. It has a negative electrode mixture layer containing a negative electrode material composed of the above, and a porous layer formed on the negative electrode mixture layer containing an insulating material that does not react with Li. The compound containing O as a constituent element is characterized by containing Li in an atomic ratio of 0.8 to 2.4 times that of Si at the end of discharge of the battery.</p><p> The method for producing a non-aqueous secondary battery of the present invention is a method for producing a non-aqueous secondary battery including a positive electrode having a positive electrode mixture layer containing a Li-containing transition metal oxide, a negative electrode, and a non-aqueous electrolyte. The negative electrode is composed of a core containing a compound containing Si and O as constituent elements (however, the atomic ratio x of O to Si is 0.5 x 1.5) and a carbon coating layer covering the surface thereof. It has a negative electrode mixture layer containing the configured negative electrode material, and suppresses the reaction between the Li-containing layer formed by the vapor phase method on the negative electrode mixture layer and the Li-containing layer and the negative electrode material. It has a step of sequentially laminating the buffer layer so that the buffer layer is arranged on the side of the negative electrode mixture layer, and a step of storing Li of the Li-containing layer in the negative electrode material by an electrochemical reaction. It is characterized by.</p>

<p> In the present invention, a compound containing Si and O as constituent elements contained in the negative electrode mixture layer (however, the atomic ratio x of O to Si is 0.5 x 1.5. Hereinafter, the compound is referred to as SiO._xMay be abbreviated as. ), And a buffer layer (for example, with Li) capable of suppressing the reaction in which Li is incorporated into the negative electrode material when the negative electrode material composed of the core containing) and the carbon coating layer covering the surface thereof is occluded in advance. By providing a porous layer containing a non-reactive insulating material) on the negative electrode mixture layer, SiO_xIt is possible to prevent a rapid and non-uniform reaction between Li and Li, and to prevent bending of the negative electrode due to expansion of the negative electrode mixture layer. Further, by occluding the required amount of Li in the negative electrode material by an electrochemical reaction, it is possible to prevent the formation of dendrite due to the presence of excess Li, and it is possible to prevent the deterioration of battery characteristics due to this. .. Therefore, according to the present invention, a Li-containing transition metal oxide can be used as a positive electrode material, and a non-aqueous secondary battery having a high capacity and good battery characteristics can be provided.</p>

The negative electrode according to the non-aqueous secondary battery of the present invention can be produced, for example, by the following method. First, a negative electrode composed of a core containing a compound containing Si and O as constituent elements (however, the atomic ratio x of O to Si is 0.5 x 1.5) and a carbon coating layer covering the surface thereof. On the negative electrode mixture layer containing the material, SiO_xA buffer layer for controlling the reactivity with Li is laminated, and a Li-containing layer containing Li to be occluded in the negative electrode material is formed on the buffer layer by the vapor phase method to form a negative electrode precursor. Next, Li is moved from the Li-containing layer of the negative electrode precursor into the negative electrode mixture layer by an electrochemical reaction, and SiO in the negative electrode material is transferred._xThe Li is occluded to form a negative electrode.

FIG. 1 shows an example of a negative electrode precursor for obtaining a negative electrode according to the non-aqueous secondary battery of the present invention, and FIG. 2 shows an example of a negative electrode according to the non-aqueous secondary battery of the present invention. The negative electrode precursor 1 in FIG. 1 is a coating of a core containing a compound containing Si and O as constituent elements (where, the atomic ratio x of O to Si is 0.5 x 1.5) and a carbon coating on the surface thereof. Negative electrode mixture layer 4, SiO containing a negative electrode material composed of layers_xThe buffer layer 3 for controlling the reactivity with Li and the Li-containing layer 2 formed by the vapor phase method are sequentially laminated. Note that 5 is a current collector. Then, Li in the Li-containing layer 2 in the negative electrode precursor 1 of FIG. 1 is subjected to an electrochemical reaction with the injection of the electrolytic solution, and the SiO in the negative electrode mixture layer 4 is passed through the buffer layer 3._xIt becomes the negative electrode 1a of the configuration shown in FIG.

The core compound in the negative electrode material, that is, the compound containing Si and O as constituent elements may contain a microcrystalline phase or an amorphous phase of Si, and in this case, the atomic ratio of Si and O is Si. The ratio including the microcrystalline or amorphous phase Si of the above may be considered.

That is, the above compounds include not only simple Si oxides but also amorphous SiO.₂The matrix contains a structure in which Si (for example, microcrystalline Si) is dispersed, and in this case, an amorphous SiO.₂And Si dispersed therein may be combined, and the above atomic ratio x may satisfy 0.5 x 1.5. For example, amorphous SiO₂Si is dispersed in the matrix, and SiO₂In the case of a compound having a molar ratio of and Si of 1: 1, x = 1, so the composition formula is expressed as SiO. In the case of a compound having such a structure, for example, in X-ray diffraction analysis, a peak due to the presence of Si (microcrystalline Si) may not be observed, but when observed with a transmission electron microscope, the presence of fine Si is observed. Can be confirmed.

Then, the above compound SiO_xThe surface of is coated with carbon. As mentioned above, SiO_xHas poor conductivity, so when using this as a negative electrode active material, a conductive auxiliary agent is used from the viewpoint of ensuring good battery characteristics, and SiO in the negative electrode is used._xIt is necessary to improve the mixing and dispersion of the conductive auxiliary agent and the conductive auxiliary agent to form an excellent conductive network. However, in the negative electrode material of the present invention, SiO_xBecause it has a carbon coating layer on its surface, for example, simply SiO_xA conductive network at the negative electrode is formed better than when a material obtained by mixing and a conductive auxiliary agent made of a carbon material is used.

Further, when the negative electrode material is further compounded with a carbon material that functions as a conductive auxiliary agent and used as a composite, a better conductive network can be formed at the negative electrode, so that the negative electrode material has a higher capacity and battery characteristics ( For example, it is possible to realize a non-aqueous secondary battery having excellent charge / discharge cycle characteristics). Carbon-coated SiO_xAs a composite of carbon material and carbon material, for example, SiO coated with carbon_xAnd a granulated material obtained by granulating carbon material.

The core material of the negative electrode material is SiO._xIt may be a composite of a conductive material having a specific resistance value smaller than that of the composite material, for example, a granulated body, and a negative electrode material in which such a composite material is coated with carbon has good conductivity inside the material. Since a network can be formed, battery characteristics such as heavy load discharge characteristics can be further improved, which is preferable.

SiO_xAs the conductive material that can be used for forming the granulated body, for example, carbon materials such as graphite, low crystalline carbon, carbon nanotubes, and vapor-grown carbon fibers are preferable.

Details of the conductive material include fibrous or coiled carbon material, fibrous or coiled metal, carbon black (including acetylene black and Ketjen black), artificial graphite, graphitized carbon and graphitized. At least one material selected from the group consisting of carbon is preferred. A fibrous or coiled carbon material or a fibrous or coiled metal is preferable because it easily forms a conductive network and has a large surface area. Carbon black (including acetylene black and Ketjen black), artificial graphite, graphitized carbon and non-graphitized carbon have high electrical conductivity and high liquid retention properties, and further, SiO is obtained by charging and discharging the battery._xIt is preferable in that it has a property of easily maintaining contact with the particles even if the particles expand and contract.

Among the above-exemplified conductive materials, a fibrous carbon material is particularly preferably used. Since the fibrous carbon material has a thin thread-like shape and high flexibility, SiO is associated with the charging and discharging of the battery._xIt can follow the expansion and contraction of, and because of its high bulk density, SiO_xThis is because it can have many junctions with particles. Examples of the fibrous carbon include polyacrylonitrile (PAN) -based carbon fiber, pitch-based carbon fiber, vapor-grown carbon fiber, carbon nanotube, and any of these may be used.

For fibrous carbon materials and fibrous metals, for example, SiO is used by the vapor phase method._xIt can also be formed on the surface of particles.

SiO_xThe specific resistance value of is usually 10.³~10⁷The specific resistance value of the above-exemplified conductive material is usually 10 while it is kΩcm.^-5It is ~ 10kΩcm.

Among the above-exemplified conductive materials, various carbon materials are the above-mentioned carbon-coated SiO._xIt can also be used as a carbon material for forming a composite with.

Further, the negative electrode material according to the present invention may further have a material layer (material layer containing non-graphitized carbon) that covers the carbon coating layer on the particle surface.

The negative electrode material according to the present invention can be obtained, for example, by the following method.

First, SiO_xThe production method in the case of combining the above will be described. SiO_xPrepares a dispersion liquid dispersed in a dispersion medium, sprays it and dries it to prepare composite particles containing a plurality of particles. As the dispersion medium, for example, ethanol or the like can be used. It is usually appropriate to spray the dispersion in an atmosphere of 50-300 ° C. In addition to the above methods, similar composite particles can also be produced by a granulation method using a mechanical method such as a vibration type or planetary type ball mill or rod mill.

In addition, SiO_xAnd SiO_xWhen producing a granule with a conductive material having a lower resistivity value than_xThe above conductive material is added to the dispersion liquid dispersed in the dispersion medium, and using this dispersion liquid, SiO_xCan be made into composite particles (granular materials) by the same method as in the case of compounding. In addition, SiO is also used by the granulation method by the same mechanical method as described above._xAnd a conductive material can be produced.

Next, SiO_xParticles (SiO)_xComposite particles, or SiO_x(Granular material of and conductive material) and the hydrocarbon gas are heated in the gas phase, and carbon generated by the thermal decomposition of the hydrocarbon gas is deposited on the surface of the particles. In this way, according to the vapor deposition (CVD) method, the hydrocarbon gas spreads to every corner of the composite particle, and the surface of the particle and the pores on the surface are thin and uniform containing conductive carbon. Since a flexible film (carbon coating layer) can be formed, SiO is used with a small amount of carbon._xConductivity can be imparted to the particles with good uniformity.

Carbon-coated SiO_xThe processing temperature (atmospheric temperature) of the vapor phase growth (CVD) method differs depending on the type of hydrocarbon gas, but usually 600 to 1200 ° C is appropriate, especially 700 ° C or higher. It is preferably 800 ° C. or higher, and more preferably 800 ° C. or higher. This is because the higher the treatment temperature, the less impurities remain, and the coating layer containing carbon having high conductivity can be formed.

As the liquid source of the hydrocarbon gas, toluene, benzene, xylene, mesitylene and the like can be used, but toluene, which is easy to handle, is particularly preferable. Hydrocarbon-based gases can be obtained by vaporizing these (for example, bubbling with nitrogen gas). Further, methane gas, acetylene gas and the like can also be used.

Also, SiO by vapor deposition (CVD) method_xParticles (SiO)_xComposite particles, or SiO_xAfter covering the surface of the granule with the conductive material with carbon, select from the group consisting of petroleum-based pitch, coal-based pitch, thermosetting resin, and condensate of naphthalene sulfonate and aldehydes. After adhering at least one organic compound to the coating layer containing carbon, the particles to which the organic compound is attached may be fired.

Specifically, carbon-coated SiO_xParticles (SiO)_xComposite particles, or SiO_xA granulated material of and a conductive material) and the above organic compound are dispersed in a dispersion medium, and the dispersion is sprayed and dried to form particles coated with the organic compound. The particles coated with the organic compound are fired.

An isotropic pitch can be used as the pitch, and a phenol resin, a furan resin, a furfural resin, or the like can be used as the thermosetting resin. As the condensate of naphthalene sulfonate and aldehydes, a naphthalene sulfonic acid formaldehyde condensate can be used.

Carbon-coated SiO_xAs the dispersion medium for dispersing the particles and the organic compound, for example, water or alcohols (ethanol or the like) can be used. It is usually appropriate to spray the dispersion in an atmosphere of 50-300 ° C. The firing temperature is usually preferably 600 to 1200 ° C, but more preferably 700 ° C or higher, and even more preferably 800 ° C or higher. This is because the higher the treatment temperature, the less impurities remain, and the coating layer containing a high-quality carbon material having high conductivity can be formed. However, the processing temperature is SiO_xMust be below the melting point of.

The negative electrode mixture layer is a paste obtained by adding an appropriate solvent (dispersion medium) to a mixture (negative electrode mixture) containing the above negative electrode material and a binder (binding agent) and kneading the mixture sufficiently. A slurry-like composition (paint) can be applied to a current collector, and the solvent (dispersion medium) can be removed by drying or the like to form a slurry having a predetermined thickness and density. The negative electrode mixture layer may be formed by a method other than the above.

Binders are usually polysaccharides such as starch, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, regenerated cellulose, diacetyl cellulose and their variants; polyvinyl chloride, polyvinylpyrrolidone, polytetrafluoroethylene, polyfluorinated vinylidene, polyethylene. , Thermoplastic resins such as polypropylene and their variants; Polymers with rubbery elasticity such as ethylene-propylene-dienter polymer (EPDM), sulfonated EPDM, styrene butadiene rubber, butadiene rubber, polybutadiene, fluororubber, polyethylene oxide, etc. And their variants; etc., and one or more of these can be used.

A conductive auxiliary agent may be further added to the negative electrode mixture. The conductive auxiliary agent is not particularly limited as long as it is an electronically conductive material that does not cause a chemical change in a non-aqueous secondary battery. Usually, natural graphite (scaly graphite, scaly graphite, earthy graphite, etc.), artificial graphite, carbon black, acetylene black, ketjen black, carbon fiber, metal powder (copper, nickel, aluminum, silver, etc.), metal fiber, One or more materials such as a polyphenylene derivative can be used.

In the negative electrode mixture layer related to the negative electrode precursor, the content of the negative electrode material is, for example, 10 to 90% by mass, and the content of the binder is, for example, 1 to 20% by mass. preferable. When a conductive auxiliary agent is used, the content of the conductive auxiliary agent in the negative electrode mixture layer is preferably, for example, 1 to 90% by mass.

The thickness of the negative electrode mixture layer is preferably, for example, 10 to 100 μm.

The buffer layer related to the negative electrode precursor has an action of controlling the reactivity of the above compound in the negative electrode mixture layer with Li in the Li-containing layer, suppressing these rapid reactions, and preventing the bending of the negative electrode. It is a layer having.

That is, in the negative electrode precursor, due to the presence of the buffer layer, SiO in the negative electrode mixture layer is present in an environment in which the non-aqueous electrolyte (electrolyte solution) of the battery is present (for example, inside the battery)._xIn addition, Li in the Li-containing layer is electrochemically introduced, but in an environment where a non-aqueous electrolyte is absent, SiO_xAlmost no Li introduction reaction occurs. As described above, the buffer layer has a function of supplying Li in the Li-containing layer to the negative electrode mixture layer via the non-aqueous electrolyte, and thereby SiO._xThe reactivity between and Li can be controlled.

The buffer layer is preferably a layer (porous layer) containing, for example, an insulating material that does not react with Li and having pores to the extent that a non-aqueous electrolyte (electrolyte solution) can pass through.

Examples of the insulating material for forming the buffer layer include various inorganic fine particles and organic fine particles. As the inorganic fine particles, chalcogenite (oxide, sulfide, etc.), hydroxide, nitride, carbide, silicide, etc., which is a metal element or a non-metal element, is preferable.

As the above-mentioned metal element or non-metal element chalcogenite, an oxide is preferable, and an oxide that is difficult to reduce is more preferable. Examples of such oxides include MgO, CaO, SrO, BaO, and ZrO.₂, ZnO, B₂O₃, Al₂O₃, Ga₂O₃, In₂O₃, SiO₂, As₄O₆, Sb₂O₅And so on. Further, the hydroxide of the metal element constituting the oxide may be used, and AlOOH (boehmite) or the like can also be used. Among these, ZnO, Al₂O₃, AlOOH, Ga₂O₃, SiO₂, ZrO₂Is particularly preferable. The oxide or hydroxide may be a single compound or a composite compound.

Examples of the above-mentioned nitrides of metal elements or non-metal elements include aluminum nitride (AlN) and BN, and examples of carbides and silicates of metal elements or non-metal elements include SiC, which have high insulating properties and are chemically used. It is preferable in that it is stable.

Among the above-mentioned insulating materials for forming the buffer layer, the organic fine particles preferably flow at a temperature of 300 ° C. or lower and do not form a film or decompose. For example, polytetrafluoroethylene. Fine particles of fluororesin such as (PTFE), crosslinked products of latex, and the like can be used.

The particle size of the insulating material is, for example, 0.1 μm or more, more preferably 0.2 μm or more, and preferably 10 μm or less, more preferably 5 μm or less.

Further, it is desirable that the buffer layer contains an electron conductive material in addition to an insulating material that does not react with Li. This is because the diffusion of Li proceeds smoothly by lowering the electrical resistance between the negative electrode mixture layer and the Li-containing layer. Examples of the electron-conducting material for forming the buffer layer include carbon materials such as carbon particles and carbon fibers; metal materials such as metal particles and metal fibers; and metal oxides. Among these, carbon particles and metal particles having low reactivity with Li are preferable.

As the carbon material contained in the buffer layer, for example, a known carbon material used as a conductive auxiliary agent in an electrode constituting a battery can be used. Specifically, carbon such as carbon black (thermal black, furnace black, channel black, lamp black, ketjen black, acetylene black, etc.) and graphite (natural graphite such as flake graphite, earthy graphite, artificial graphite), etc. Examples include particles and carbon fibers.

Among the above carbon materials, it is particularly preferable to use carbon black and graphite in combination from the viewpoint of dispersibility with the binder described later. Further, as the carbon black, Ketjen black and acetylene black are particularly preferable.

The particle size of the carbon particles is, for example, 0.01 μm or more, more preferably 0.02 μm or more, and preferably 10 μm or less, more preferably 5 μm or less.

Among the electronically conductive materials for forming the buffer layer, those metal particles and metal fibers preferably made of a metal element having low reactivity with Li and difficult to form an alloy with Li. Specific metal elements constituting the metal particles and metal fibers include, for example, Ti, Fe, Ni, Cu, Mo, Ta, W and the like.

In the case of metal particles, the shape is not particularly limited, and any shape such as a lump, a needle, a columnar, or a plate may be used. Further, the surface of the metal particles and metal fibers is preferably not oxidized so much, and those that are excessively oxidized are preferably heat-treated in a reducing atmosphere in advance and then used for forming a buffer layer. ..

The particle size of the metal particles is, for example, 0.02 μm or more, more preferably 0.1 μm or more, and preferably 10 μm or less, more preferably 5 μm or less.

As a combination of an insulating material that does not react with Li and an electron conductive material, for example, aluminum oxide (Al)₂O₃) Or a combination of boehmite and carbon material is particularly preferred.

In forming the buffer layer, it is preferable to use a binder for the purpose of binding an insulating material or an electron conductive material that does not react with Li. As the binder, for example, various materials exemplified as a binder for the negative electrode mixture layer can be used.

In the buffer layer, when the total of the insulating material that does not react with Li and the material having electron conductivity is 100% by mass, the ratio of the material having electron conductivity is, for example, 2.5% by mass or more, more preferably. Is preferably 5% by mass or more, 96% by mass or less, more preferably 95% by mass or less, in other words, the ratio of the insulating material that does not react with Li is, for example, 4% by mass or more. It is preferably 5% by mass or more, 97.5% by mass or less, and more preferably 95% by mass or less.

When a binder is used to form the buffer layer, an insulating material that does not react with Li, a material having electron conductivity, and a binder that does not react with Li when the total of the binder is 100% by mass. The ratio of the total amount of the material to the material having electron conductivity is 40% by mass or more, more preferably 50% by mass or more, and 96% by mass or less, more preferably 94% by mass or less. In other words, it is desirable that the binder ratio is, for example, 4% by mass or more, more preferably 6% by mass or more, and 60% by mass or less, more preferably 50% by mass or less.

The thickness of the buffer layer is, for example, 2 μm or more, more preferably 3 μm or more, and preferably 10 μm or less, more preferably 8 μm or less. If the buffer layer has such a thickness, the SiO of the negative electrode mixture layer_xThe direct reaction of the Li-containing layer with Li can be controlled more efficiently, and the capacity of the battery can be increased and the battery characteristics can be improved more reliably. That is, if the thickness of the buffer layer is too thin with respect to the surface roughness of the negative electrode mixture layer, for example, it becomes difficult to cover the entire surface of the negative electrode mixture layer without pinholes, and the buffer layer is formed. On the other hand, if the buffer layer is too thick, the effect may be reduced, which leads to a decrease in the capacity of the battery. Therefore, it is preferable to form the buffer layer as thin and uniform as possible.

By providing the buffer layer, the affinity between the negative electrode and the non-aqueous electrolyte is improved, so that the effect of facilitating the introduction of the non-aqueous electrolyte into the battery can be expected.

The buffer layer is in the form of a paste obtained by adding an appropriate solvent (dispersion medium) to a mixture containing, for example, an insulating material that does not react with Li, an electron conductive material, and a binder, and kneading the mixture sufficiently. Or a slurry-like composition (paint) can be applied onto the negative electrode mixture layer, and the solvent (dispersion medium) can be removed by drying or the like to form a predetermined thickness. The buffer layer may be formed by a method other than the above. For example, after the composition for forming the negative electrode mixture layer is applied onto the current collector, the composition for forming the buffer layer is applied and dried before the coating film is completely dried, and the negative electrode mixture is formed. The layer and the buffer layer may be formed at the same time. Further, in addition to the sequential method in which the composition for forming the negative electrode mixture layer and the composition for forming the buffer layer are sequentially applied as described above, the composition for forming the negative electrode mixture layer and the buffer layer are formed. The negative electrode mixture layer and the buffer layer may be formed at the same time by a simultaneous coating method in which the above compositions are applied at the same time.

The Li-containing layer related to the negative electrode precursor is formed by a general gas phase method (gas phase deposition method) such as resistance heating or sputtering, that is, a thin-film deposition film. The Li-containing layer can be formed by facing the vapor deposition source and the buffer layer related to the negative electrode precursor in a vacuum chamber and vapor-depositing until a layer having a predetermined thickness is obtained.

As described above, in the present invention, the negative electrode material is coated with carbon._xThe positive electrode material is a Li-containing transition metal oxide to increase the capacity of the battery. Therefore, SiO_xIt is necessary to control the amount of Li to be introduced into the required range to prevent the precipitation of lithium dendrite due to the excessive amount of Li. However, since the Li metal leaf known as a Li source for the negative electrode material has low strength, it is extremely difficult to form a very thin film (for example, 10 μm or less). Even if it is obtained, cracks and tears are likely to occur at the time of attachment to the buffer layer, and the thickness unevenness is relatively large. Therefore, in a battery having a negative electrode material and a positive electrode material as in the present invention, even if it is used as a Li source of the negative electrode material, SiO_xIn addition, it is not possible to introduce a uniform and appropriate amount of Li over the entire negative electrode, and the amount of Li to be introduced is insufficient or excessive, achieving both high capacity and deterioration of battery characteristics due to precipitation of lithium dendrite. It's difficult to do.

On the other hand, if the method of forming a Li-containing layer on the buffer layer as a vapor deposition film by the vapor phase method, it is easy to form a uniform layer over the entire surface of the buffer layer with a desired thickness. , SiO_xLi required to offset the irreversible capacity of the above can be introduced without excess or deficiency, and high capacity and improvement of battery characteristics can be achieved.

The method of forming a Li-containing layer by the vapor phase method is disadvantageous in terms of productivity and poorly practical when the formation of a thick layer is required, but the battery according to the present invention has no practicality. Carbon-coated SiO with relatively small irreversible capacitance_xIs used as the negative electrode material, and the Li-containing transition metal oxide containing Li in advance is used as the positive electrode material. Therefore, the amount of Li to be supplied is relatively small, and it is sufficient to form the Li-containing layer thinly. Even if the Li-containing layer is formed by the vapor phase method, there is no problem of productivity.

The Li-containing layer may be composed of only Li, for example, Li-Al, Li-Al-Mn, Li-Al-Mg, Li-Al-Sn, Li-Al-In, Li-Al-Cd. It may be composed of a Li alloy such as. When the Li-containing layer is composed of a Li alloy, the Li content ratio in the Li-containing layer is preferably, for example, 50 to 90 mol%.

The thickness of the Li-containing layer is, for example, preferably 2 μm or more, more preferably 4 μm or more, while it is preferably 10 μm or less, more preferably 8 μm or less. By forming the Li-containing layer with such a thickness, Li can be made into SiO._xIt can be introduced without excess or deficiency for the irreversible capacity of. That is, if the Li-containing layer is too thin, SiO existing in the negative electrode mixture layer_xThe amount of Li relative to the amount may decrease, and the capacity improvement effect may decrease. Further, if the Li-containing layer is too thick, the amount of Li may become excessive and the effect of improving the battery characteristics may be reduced, and the amount of vapor deposition increases, so that the productivity also decreases.

A Li-containing transition metal oxide is used as the positive electrode material (positive electrode active material) for the positive electrode in the battery according to the present invention. Specific examples of Li transition metal oxides include, for example, Li._xCoO₂, Li_xNiO₂, Li_xMnO₂, Li_xCo_yNi_1-yO₂, Li_xCo_yM_1-yO₂, Li_xNi_1-yM_yO₂, Li_xMn_yNi_zCo_1-yzO₂, Li_xMn₂O₄, Li_xMn_2-yM_yO₄(In each of the above structural formulas, M is at least one metal element selected from the group consisting of Mg, Mn, Fe, Co, Ni, Cu, Zn, Al, Ti, Ge and Cr, and 0 x. 1.1, 0 &lt;y &lt;1.0, 2.0 &lt;z &lt;1.0) and so on.

The positive electrode is a paste-like or slurry-like positive electrode mixture obtained by adding an appropriate solvent (dispersion medium) to a mixture (positive electrode mixture) containing the above positive electrode material, a conductive auxiliary agent, and a binder and sufficiently kneading the mixture. It can be obtained by applying the contained composition to a current collector to form a positive electrode mixture layer having a predetermined thickness and density. The positive electrode is not limited to the one obtained by the above-mentioned manufacturing method, and may be manufactured by another manufacturing method.

As the binder related to the positive electrode, each of the above-mentioned binders exemplified as those for the negative electrode can be used. Further, as the conductive auxiliary agent related to the positive electrode, each of the above-mentioned conductive auxiliary agents exemplified as those for the negative electrode can be used.

In the positive electrode mixture layer related to the positive electrode, the content of the positive electrode material (positive electrode active material) is, for example, 79.5 to 99% by mass, and the content of the binder is, for example, 0.5 to 20% by mass. The content of the conductive auxiliary agent is preferably, for example, 0.5 to 20% by mass.

Examples of the non-aqueous electrolyte used in the battery according to the present invention include an electrolytic solution prepared by dissolving the following inorganic ion salts in the following solvent.

Examples of the solvent include ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), dimethyl carbonate, diethyl carbonate (DEC), methyl ethyl carbonate (MEC), γ-butyrolactone, and 1,2-dimethoxyethane. , Tetrahydrofuran, 2-methyltetrahydrofuran, dimethylsulfoxide, 1,3-dioxolane, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane, methyl formate, methyl acetate, phosphate triester, trimethoxymethane, dioxolane derivative, sulfolane, 3 -Aprotonic organic solvents such as methyl-2-oxazolidinone, propylene carbonate derivatives, tetrahydrofuran derivatives, diethyl ether, and 1,3-propanesalton can be used alone or in combination of two or more.

As the inorganic ion salt, Li salt, for example, LiClO₄, LiBF₄, LiPF₆, LiCF₃SO₃, LiCF₃CO₂, LiAsF₆, LiSbF₆, LiB₁₀Cl₁₀, Lower Aliphatic Carboxylic Acid Li, LiAlCl₄, LiCl, LiBr, LiI, chloroborane Li, Li tetraphenylborate and the like can be used alone or in combination of two or more.

A solvent containing at least one selected from the group consisting of 1,2-dimethoxyethane, diethyl carbonate and methyl ethyl carbonate, and ethylene carbonate or propylene carbonate, among the electrolytic solutions in which the inorganic ion salts are dissolved in the solvent. To LiClO₄, LiBF₄, LiPF₆, And LiCF₃SO₃An electrolytic solution in which at least one inorganic ion salt selected from the above group is dissolved is preferable. The concentration of the inorganic ion salt in the electrolytic solution is, for example, 0.2 to 3.0 mol / dm.³Is appropriate.

The non-aqueous secondary battery of the present invention contains the above-mentioned positive electrode, the above-mentioned negative electrode precursor, the above-mentioned non-aqueous electrolyte, and the like in a battery container, and in this battery container, SiO in the negative electrode mixture layer._xIt can be obtained by introducing Li supplied from the Li-containing layer by an electrochemical reaction.

In the non-aqueous secondary battery of the present invention thus obtained, SiO is obtained at the end of battery discharge._xThe thickness of the Li-containing layer may be adjusted so that the amount of Li contained in is in the range of 0.8 to 2.4 times the atomic ratio with respect to Si. When the battery is discharged, SiO_xBy containing Li in the above content, SiO_xThe irreversible capacity of the battery is sufficiently offset, and a part of the capacity of the positive electrode material is offset by the irreversible capacity, so that it is possible to prevent a substantial decrease in the capacity, and an increase in the capacity of the battery can be achieved. Further, if the amount of Li is in the above range, a non-aqueous secondary battery having good battery characteristics can be constructed without causing precipitation of lithium dendrite.

At the end of battery discharge, SiO_xThe amount of Li contained in is more preferably 1.2 times or more, and more preferably 2.0 times or less in terms of the atomic ratio with respect to Si.

SiO introduced with the required amount of Li_xThen, at the end of battery discharge, a peak is observed in the range of at least 1850 to 1860 eV in the structure spectrum near the X-ray absorption edge of the K absorption edge of Si, so this can also be used as a guideline for the amount of Li introduced. .. The peak of the structure spectrum near the X-ray absorption edge is considered to be a peak caused by the formation of lithium silicate by the introduction of Li.

The non-aqueous secondary battery of the present invention may include the above-mentioned negative electrode, the above-mentioned positive electrode, and the above-mentioned non-aqueous electrolyte, and there are no particular restrictions on other components and structures, and the conventionally known non-aqueous secondary battery is not particularly limited. Various components and structures used in the next battery can be applied.

For example, the separator preferably has sufficient strength and can hold a large amount of electrolytic solution. From such a viewpoint, polyethylene, polypropylene, or ethylene-, which has a thickness of 10 to 50 μm and an aperture ratio of 30 to 70%. A microporous film or non-woven fabric containing a propylene copolymer is preferable.

Further, the non-aqueous secondary battery of the present invention is not particularly limited in its shape and the like. For example, it may be any of a coin type, a button type, a sheet type, a laminated type, a cylindrical type, a flat type, a square type, a large type used for an electric vehicle, and the like.

The non-water secondary battery of the present invention has a high capacity and excellent battery characteristics, and by utilizing these characteristics, a conventionally known non-water secondary battery including a power source for a small and multifunctional portable device It can be preferably used in various applications to which a secondary battery is applied.

Hereinafter, the present invention will be described in detail based on Examples. However, the following examples do not limit the present invention, and it is all included in the technical scope of the present invention to carry out modifications without departing from the spirits of the preceding and the following. In the following examples, the average particle size of the composite particles, α-alumina, and graphite is measured by a laser diffraction type particle size distribution measurement method using MICROTRAC HRA (Model: 9320-X100) manufactured by Microtrac. It is a volume average value measured by.

(Example 1) SiO particles (average particle size 5.0 μm) are heated to about 1000 ° C in a boiling bed reactor, and the heated particles are brought into contact with a mixed gas of 25 ° C consisting of benzene and nitrogen gas. Benzene treatment was performed at 1000 ° C for 60 minutes. In this way, carbon (hereinafter, also referred to as CVD carbon) generated by thermal decomposition of the mixed gas was deposited on the surface of SiO particles to form a coating layer, and a negative electrode material was obtained.

When the composition of the negative electrode material was calculated from the mass change before and after the formation of the coating layer, it was SiO: CVD carbon = 85: 15 (mass ratio).

Next, a negative electrode precursor sheet was prepared using the above negative electrode material. 50% by mass of the negative electrode material (content in the total solid content, the same applies hereinafter), 40% by mass of graphite, 2% by mass of Ketjenblack (average particle size 0.05 μm) as a conductive auxiliary agent, and polyvinylidene fluoride as a binder. 8% by mass and dehydrated N-methylpyrrolidone (NMP) were mixed to prepare a slurry containing a negative electrode mixture. In addition, α-alumina (average particle size 1 μm) 80% by mass (content in total solid content, the same applies hereinafter), graphite (average particle size 2 μm) 14% by mass, and polyvinylidene fluoride (PVDF) 6% by mass. , Dehydrated NMP was mixed to prepare a slurry for forming a buffer layer.

Using a blade coater, the above negative electrode mixture-containing slurry is applied to a current collector made of copper foil with a thickness of 8 μm as a lower layer and a buffer layer forming slurry as an upper layer, dried at 120 ° C, and then a roller press machine. A negative electrode mixture layer having a thickness of 35 μm and a buffer layer having a thickness of 7 μm were formed on one surface of the current collector to form a laminated body. The laminate in which the negative electrode mixture layer and the buffer layer were formed on the current collector was dried in vacuum at 100 ° C. for 10 hours.

The dried laminate was further heat-treated at 160 ° C. for 10 hours using a far-infrared heater. In the above-mentioned laminated body after the heat treatment, the adhesiveness between the negative electrode mixture layer and the current collector and the adhesiveness between the negative electrode mixture layer and the buffer layer are good, and the negative electrode mixture layer is collected even by cutting or bending. It did not peel off from the electric body, and the buffer layer did not peel off from the negative electrode mixture layer.

The heat-treated laminate is loaded into a vacuum chamber, a Li foil (purity 99.8%) is attached to a resistance-heated vapor deposition source, and vapor deposition is performed to obtain a Li-containing layer having a thickness of 8 μm (8 μm thick) on the buffer layer of the laminate. Li metal layer) was formed. Subsequent work related to the negative electrode precursor was performed in an argon atmosphere. The laminate on which the Li-containing layer was formed was punched to a diameter of 16 mm to obtain a disk-shaped negative electrode precursor.

Moreover, the positive electrode was produced as follows. First, LiCoO as the positive electrode material₂96% by mass (content in total solid content, the same applies hereinafter), 2% by mass of Ketjen Black (average particle size 0.05 μm) as a conductive auxiliary agent, 2% by mass of PVDF as a binder, and dehydrated NMP. The obtained positive electrode mixture-containing slurry was applied to a current collector made of an aluminum foil having a thickness of 15 μm, dried, and pressed to form a positive electrode mixture layer having a thickness of 85 μm on one surface of the current collector.

Next, the negative electrode precursor was adhered to a storage container made of stainless steel using a conductive adhesive, and a separator made of microporous polyethylene film and a positive electrode were arranged in this order on the negative electrode precursor. After that, 1 mol of LiPF in a solvent of EC: DEC = 1: 2 (volume ratio)₆0.3 ml of an electrolytic solution (non-aqueous electrolyte) prepared by dissolving the above was injected into the storage container, and the inside of the storage container was sealed with a sealing body with a gasket. In the sealed container, Li in the Li-containing layer was electrochemically occluded in SiO in the negative electrode mixture layer to obtain a coin-type non-aqueous secondary battery.

(Example 2) SiO (average particle size 1 μm), fibrous carbon (average length 2 μm, average diameter 0.08 μm) and polyvinylpyrrolidone 10 g are mixed in 1 L of ethanol, and these are further wet jet. The mixture was mixed in a mill to obtain a slurry. The total mass of SiO and fibrous carbon (CF) used for preparing this slurry was 100 g, and the mass ratio was SiO: CF = 80: 20. Next, using the above slurry, composite particles of SiO and CF were prepared by a spray-drying method (atmospheric temperature 200 ° C.). The average particle size of the composite particles was 10 μm. Subsequently, 10 g of the composite particles is heated to about 1000 ° C in a boiling bed reactor, and the heated composite particles are brought into contact with a mixed gas of 25 ° C consisting of benzene and nitrogen gas to make 1000 ° C. The CVD treatment was carried out for 60 minutes. In this way, carbon generated by thermal decomposition of the mixed gas was deposited on the surface of the composite particles to form a coating layer, and a negative electrode material was obtained.

When the composition of the negative electrode material was calculated from the mass change before and after the formation of the coating layer, it was SiO: CF: CVD carbon = 68: 17: 15 (mass ratio).

Next, 75% by mass of the negative electrode material (content in the total solid content, the same applies hereinafter), 15% by mass of graphite, 2% by mass of Ketjen black (average particle size 0.05 μm) as a conductive auxiliary agent, and as a binder. 8% by mass of PVDF and dehydrated NMP were mixed to prepare a slurry containing a negative electrode mixture. A negative electrode precursor was prepared in the same manner as in Example 1 except that the negative electrode mixture-containing slurry was used for forming the negative electrode mixture layer related to the negative electrode precursor, and the negative electrode precursor was used in Examples. A coin-shaped non-aqueous secondary battery was produced in the same manner as in 1.

(Example 3) SiO (average particle size 1 μm), graphite (average particle size 3 μm), and 10 g of polyvinylpyrrolidone are mixed in 1 L of ethanol, and these are further mixed by a wet jet mill to form a slurry. Got The total mass of SiO and graphite used to prepare this slurry was 100 g, and the mass ratio was SiO: graphite = 70:30. Next, using the above slurry, composite particles of SiO and graphite were prepared by a spray-drying method (atmospheric temperature 200 ° C.). The average particle size of the composite particles was 15 μm. Subsequently, 10 g of the composite particles is heated to about 1000 ° C in a boiling bed reactor, and the heated composite particles are brought into contact with a mixed gas of 25 ° C consisting of benzene and nitrogen gas to make 1000 ° C. The CVD treatment was carried out for 60 minutes. In this way, carbon generated by thermal decomposition of the mixed gas was deposited on the surface of the composite particles to form a coating layer, and composite particles covered with the carbon coating layer were obtained.

Subsequently, 100 g of the composite particles having the carbon coating layer and 40 g of the phenol resin are dispersed in 1 L of ethanol, and the dispersion is sprayed and dried (atmospheric temperature 200 ° C.), and the surface of the carbon coating layer is surfaced. Was coated with a phenol resin. Then, the coated particles were calcined at 1000 ° C. to form a material layer containing non-graphitized carbon covering the surface of the carbon coating layer to obtain a negative electrode material.

When the composition of the above negative electrode material was calculated from the mass changes before and after the formation of the carbon coating layer and before and after the formation of the material layer containing non-graphitized carbon, SiO: graphite: CVD carbon: non-graphitized carbon = 50: 20: 15: 15 It was (mass ratio).

Next, 90% by mass of the negative electrode material (content in the total solid content, the same applies hereinafter), 2% by mass of Ketjen Black (average particle size 0.05 μm) as a conductive auxiliary agent, 8% by mass of PVDF as a binder, and dehydration. A slurry containing a negative electrode mixture was prepared by mixing with NMP. A negative electrode precursor was prepared in the same manner as in Example 1 except that the negative electrode mixture-containing slurry was used for forming the negative electrode mixture layer related to the negative electrode precursor, and the negative electrode precursor was used in Examples. A coin-shaped non-aqueous secondary battery was produced in the same manner as in 1.

(Example 4) Put 200 g of SiO (average particle size 1 μm), 60 g of graphite (average particle size 3 μm), and 30 g of polyethylene resin particles of binder in a 4 L stainless steel container, and further put a stainless steel ball. Mixing, pulverization, and granulation were performed for 3 hours in a vibrating mill. As a result, composite particles (composite of SiO and graphite) with an average particle size of 20 μm could be produced. Subsequently, 10 g of the complex particles is heated to about 950 ° C in a boiling bed reactor, and the heated complex particles are brought into contact with a mixed gas of 25 ° C consisting of toluene and nitrogen gas to bring them into contact with each other at 950 ° C. The CVD treatment was carried out for 60 minutes. In this way, carbon generated by thermal decomposition of the mixed gas was deposited on the composite particles to form a coating layer, and a negative electrode material was obtained.

When the composition of the negative electrode material was calculated from the mass change before and after the formation of the carbon coating layer, it was SiO: graphite: CVD carbon = 60: 25: 15 (mass ratio).

Next, 80% by mass of the negative electrode material (content in the total solid content, the same applies hereinafter), 10% by mass of graphite, 2% by mass of Ketjen black (average particle size 0.05 μm) as a conductive auxiliary agent, and as a binder. 8% by mass of PVDF and dehydrated NMP were mixed to prepare a slurry containing a negative electrode mixture. A negative electrode precursor was prepared in the same manner as in Example 1 except that the negative electrode mixture-containing slurry was used for forming the negative electrode mixture layer related to the negative electrode precursor, and the negative electrode precursor was used in Examples. A coin-shaped non-aqueous secondary battery was produced in the same manner as in 1.

(Example 5) A negative electrode precursor was prepared in the same manner as in Example 1 except that the thickness of the Li-containing layer was changed to 4 μm, and coins were prepared in the same manner as in Example 1 except that this negative electrode precursor was used. A non-aqueous secondary battery was manufactured.

(Comparative Example 1) In the same manner as in Example 4, a laminate in which a negative electrode mixture layer and a buffer layer were formed on a current collector was produced. A coin-type non-aqueous secondary battery was produced in the same manner as in Example 4 except that this laminate was used as a negative electrode precursor without forming a Li-containing layer.

(Comparative Example 2) A negative electrode precursor was prepared in the same manner as in Example 4 except that the buffer layer was not formed, and coin-shaped non-water was prepared in the same manner as in Example 4 except that this negative electrode precursor was used. A secondary battery was manufactured.

(Comparative Example 3) In the same manner as in Example 4, a negative electrode mixture layer was formed on the current collector, and a negative electrode precursor was used without forming a buffer layer or a Li-containing layer. A coin-type non-aqueous secondary battery was produced in the same manner as in Example 4 except that this negative electrode precursor was used.

The batteries of Examples 1 to 5 and Comparative Examples 1 to 3 described above were evaluated as follows.

&lt;Analysis of Negative Electrode Material&gt; For the battery in the discharge end state, the structural spectrum near the X-ray absorption edge of SiO was measured and the amount of Li in SiO was analyzed by the following method. The negative electrode was taken out from the discharged battery, and the adhering electrolytic solution was thoroughly washed with a solvent (DEC) and dried. After that, the negative electrode was attached to a special jig, and the fine structure of the K absorption edge was investigated by X-ray absorption measurement by the electron yield method using synchrotron radiation. In addition, the negative electrode that was also washed and dried was quantitatively analyzed for Li and Si by the ICP (Inductive Coupled Plasma) method, and the amount of Li in SiO was calculated.

&lt;Appearance inspection of the negative electrode&gt; For the negative electrode 48 hours after the deposition of the Li-containing layer, the presence or absence of warpage of the negative electrode was visually confirmed.

&lt;Evaluation of battery characteristics&gt; The assembled battery was charged and discharged under the following conditions. Charging has a current density of 0.5mA / cm²It was carried out at a constant current, and after the charging voltage reached 4.2 V, it was carried out at a constant voltage until the current density became 1/10. Discharge has a current density of 0.5mA / cm²The current was constant, and the final discharge voltage was 2.5V. For this first charge / discharge cycle, the ratio of the discharge capacity to the charge capacity was calculated as the initial charge / discharge efficiency. Further, the above charge / discharge cycle is repeated, the discharge capacity (C1) of the second cycle is set as the standard capacity of the battery, and the capacity retention rate is calculated from the standard capacity and the discharge capacity (C2) of the 200th cycle by the following formula. It was calculated and the battery characteristics were evaluated. The results of each of the above evaluations are shown in Table 1.

Capacity retention rate (%) = (C2 / C1) x 100

<tables num="1"><img file="JP2007242590A_D0001.tif" /></tables>

Further, with respect to the negative electrode material of Example 1, the structure spectra near the X-ray absorption edge of the K absorption edge of Si before and after the first charge / discharge are shown in FIG. It was confirmed that Li in the Li-containing layer was occluded in SiO as the negative electrode material, and a new peak appeared in the spectrum in the range of 1850 to 1860 eV.

As is clear from the results shown in Table 1, in the coin-type non-aqueous secondary batteries of Examples 1 to 5, Li in the Li-containing layer was occluded in SiO in the negative electrode mixture layer to compensate for the irreversible capacity. As a result, the capacity of the positive electrode material can be used as it is for charging / discharging the battery, and the capacity of the battery is increased and the initial charge / discharging efficiency is improved as compared with the batteries of Comparative Examples 1 and 3 in which the Li-containing layer is not provided. I was able to plan. Further, by forming the Li-containing layer by the vapor phase method and providing a buffer layer between the Li-containing layer and the negative electrode mixture layer, the amount of Li to be occluded in SiO is controlled within an appropriate range. In addition, since SiO and Li could be reacted gradually and uniformly, it was possible to prevent the negative electrode from warping and to construct a battery having a high capacity retention rate even after repeating the charge / discharge cycle.

<figref num="1">It is sectional drawing which shows an example of the negative electrode precursor for manufacturing the non-aqueous secondary battery of this invention.</figref><figref num="2">It is sectional drawing which shows the negative electrode which concerns on the non-aqueous secondary battery of this invention obtained from the negative electrode precursor shown in FIG.</figref><figref num="3">It is a figure which shows the structure spectrum near the X-ray absorption end of the K absorption end of Si before and after the first charge and discharge about the negative electrode material of Example 1. FIG.</figref>

Code description

1 Negative electrode precursor 1a Negative electrode 2 Li-containing layer 3 Buffer layer 4 Negative electrode mixture layer 5 Current collector