JP2000012092A - Nonaqueous secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase the amount of energy in a lithium secondary battery and prolong the cycle life by using a lithium-containing transition metal oxide as a positive electrode active material, using a compound containing silicon atoms and capable of inserting/discharging lithium as a negative electrode active material, and causing the weight of the positive electrode active material included in the battery to be larger than that of the negative electrode active material. SOLUTION: The total weight of a positive electrode active material included in a nonaqueous secondary battery is more than two times and less than 50 times the total weight of a negative electrode active material. A wound electrode group 2 made by successively laminating a positive electrode sheet, a microporous polyethylene film separator, a negative electrode sheet, and another separator, and winding these in a spiral manner, is stored in a nickel-plated, bottomed, cylindrical battery can 1 serving both as a negative electrode terminal, and further an upper insulating plate 3 is inserted therein. A cylindrical battery is made by injecting an electrolyte into the battery can 1, inserting therein a layered product comprising a positive-electrode terminal 6, an insulation ring, a PTC element 63, a current interrupt element 62, and a pressure-responsive valve element 61, and caulking the battery can 1 with a gasket 5 in-between.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a non-aqueous secondary battery, and more particularly to a lithium secondary battery having a high capacity and a long cycle life.

[0002]

2. Description of the Related Art In a lithium secondary battery using a negative electrode material containing no lithium metal and a positive electrode active material containing lithium, first, lithium contained in the positive electrode active material is inserted into the negative electrode material to increase the activity of the negative electrode material. . This is the charging reaction, and the reverse reaction of inserting lithium ions from the negative electrode material into the positive electrode active material is the discharging reaction. Carbon is used as this type of lithium battery negative electrode material.
The theoretical capacity of carbon (C ₆ Li) is 372 mAh / g, and an even higher capacity negative electrode material is desired. The theoretical capacity of silicon forming an intermetallic compound with lithium is 400
It is well known that it exceeds 0 mAh / g and is larger than that of carbon. For example, Japanese Patent Application Laid-Open No. Hei 5-74463 discloses single-crystal silicon.
02 discloses amorphous silicon. Examples of alloys containing silicon include Li-Al alloys containing silicon as disclosed in JP-A-63-66369 (19% by weight of silicon),
63-174275 (0.05 to 1.0% by weight of silicon) and 63-285865 (1 to 5% by weight of silicon)
Is disclosed. However, since all of these alloy patent applications mainly use lithium, a compound containing no lithium was used as the positive electrode active material. Also,
In Japanese Patent Application Laid-Open No. 4-109562, 0.05 to 1.
A 0% by weight alloy is disclosed. JP-A-62-226
No. 563 discloses a method of mixing a metal that can be alloyed with lithium and graphite powder. However, none of them has a poor cycle life and has not been put to practical use. It is presumed that the cycle life of silicon is inferior because the electron conductivity is low, the volume is expanded by lithium insertion, and the particles are pulverized.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to increase the energy amount and the cycle life of a lithium secondary battery.

[0004]

An object of the present invention is to provide a non-aqueous secondary battery comprising an electrode sheet containing a positive electrode active material, an electrode sheet containing a negative electrode material, and a non-aqueous electrolyte. Is a lithium-containing transition metal oxide, the anode active material is a compound containing a silicon atom capable of inserting and releasing lithium, and the total weight of the cathode active material contained in the nonaqueous secondary battery is the anode active material. The problem was solved by a non-aqueous secondary battery characterized by being larger than the total weight of the substance.

[0005] It is found that the above-mentioned compound containing silicon has a larger lithium storage capacity per atom than carbon or the like, so that the cycle life greatly differs depending on the balance between the usage of the negative electrode active material and the usage of the positive electrode active material. Was. In general, the amount of use of the positive electrode and the negative electrode is incorporated in a balance of about the same weight. It turned out that the effect appeared.

The thickness of the mixture in the negative electrode sheet is preferably smaller than the thickness of the mixture in the positive electrode sheet. Further, the thickness of the mixture in the negative electrode sheet is 1.2 times the thickness in the positive electrode sheet. It was found that the value is preferably at least 5 times or less. This is thought to be related to the rate of insertion and release of the lithium-containing compound in the positive electrode active material and the silicon-containing compound used in the negative electrode active material. It is worth mentioning that the cycle life is improved.

Further, when the compound containing a silicon atom is used as a negative electrode active material, the compound has a weight of 90% based on the weight of the negative electrode mixture.
% Is preferably used. That is, it is preferable that a conductive agent such as carbon or fine powder metal is contained in addition to the compound containing a silicon atom in the mixture. However, the carbon or the fine powdered metal may function as an active material of the electrode. More preferably, the content of the compound containing a silicon atom is from 8% by weight to 80% by weight based on the weight of the negative electrode mixture. Even in the case of a conventional negative electrode active material other than carbon, such as a Sn-based negative electrode, a conductive agent was necessary, but an unexpected result was found that the use of a relatively large amount of the conductive agent improved cycleability.

[0008] When the mixture of the compound containing a silicon atom is applied to the negative electrode current collector, setting the thickness in a specific range with respect to the thickness of the current collector can specifically improve cycleability. all right. It has been found that some of the compounds containing silicon atoms have a very large volume expansion when lithium is inserted. As a result, it was found that when the thickness of the negative electrode mixture was extremely thin, cracks were formed in the surface direction, the current collector was exposed, and the mixture was peeled off, thereby deteriorating the cyclability. Conversely, it was found that if the thickness of the negative electrode mixture with respect to the current collector was too large, the electrode sheet itself was distorted due to the expansion, or in the worst case, the current collector was cut. Therefore, the thickness of the negative electrode mixture is preferably 0.2 times or more and 20 times or less with respect to the thickness of the current collector.

[0009] Many of the above-mentioned features are particularly advantageous in producing a cylinder battery in which a winding group is formed by sheet-like electrodes.
It was first revealed and unexpected.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below, but the present invention is not limited to these embodiments. (1) In a non-aqueous secondary battery comprising an electrode sheet containing a positive electrode active material, an electrode sheet containing a negative electrode active material, and a non-aqueous electrolyte, the positive electrode active material is a lithium-containing transition metal oxide; The negative electrode active material is a compound containing a silicon atom capable of inserting and releasing lithium, and the total weight of the positive electrode active material contained in the nonaqueous secondary battery is larger than the total weight of the negative electrode active material. Non-aqueous secondary battery. (2) The non-aqueous secondary battery according to item 1, wherein the total weight of the positive electrode active material contained in the non-aqueous secondary battery is 2 to 50 times the total weight of the negative electrode material. . (3) The non-aqueous secondary battery according to item 1, wherein the total weight of the positive electrode active material contained in the non-aqueous secondary battery is 4 to 30 times the total weight of the negative electrode active material. battery. (4) The electrode sheet, wherein a metal foil is used as a current collector and a mixture containing the positive electrode active material or the negative electrode active material is coated on both surfaces thereof, and the mixture of the positive electrode of the electrode sheet is provided. Item 4. The non-aqueous secondary battery according to any one of Items 1 to 3, wherein the film thickness of the portion is larger than the thickness of the mixture portion of the negative electrode. (5) The nonaqueous secondary battery according to item 4, wherein the thickness of the mixture portion of the positive electrode sheet is 1.2 to 5 times the thickness of the mixture portion of the negative electrode sheet. (6) The content of the positive electrode active material in the positive electrode mixture is 60% by weight or more and 99% by weight or less, and the content of the negative electrode active material in the negative electrode mixture is 1% by weight or more and 90% by weight or less. Item 6. The non-aqueous secondary battery according to any one of Items 1 to 5. (7) The content of the positive electrode active material in the positive electrode mixture is 70% by weight or more and 98% by weight or less, and the content of the negative electrode active material in the negative electrode mixture is 8% by weight or more and 80% by weight or less. Item 7. The non-aqueous secondary battery according to Item 6, wherein (8) The non-aqueous secondary according to any one of Items 1 to 7, wherein the thickness of the negative electrode mixture is 0.2 to 20 times the thickness of the negative electrode current collector in the negative electrode sheet. battery. (9) The nonaqueous secondary battery according to item 8, wherein the thickness of the negative electrode mixture is 0.5 to 10 times the thickness of the negative electrode current collector in the negative electrode sheet. (10) A non-aqueous secondary battery in which the compound containing a silicon atom according to any one of (1) to (9) has an average particle size of 0.01 to 100 μm. (11) A non-aqueous secondary battery in which the compound containing a silicon atom according to the item (10) is an alloy containing silicon and a metal other than silicon. (12) The metal other than silicon of the alloy is an alkaline earth metal,
The nonaqueous secondary battery according to item (11), which is at least one selected from transition metals and semimetals. (13) At least one of the metals described in (11) or (12) is Ge, Be, Ag, Al, Au, Cd, Ga, I
A non-aqueous secondary battery comprising n, Sb, Sn, and Zn. (14) A non-aqueous secondary battery in which the compound containing a silicon atom according to any one of (1) to (9) is silicon obtained by removing a metal from a metal silicide. (15) A nonaqueous secondary battery in which the metal silicide according to (14) is a lithium silicide. (16) A nonaqueous secondary battery according to item (15), wherein the lithium silicide has a lithium content of 100 to 420 atomic% with respect to silicon. (17) A nonaqueous secondary battery in which the compound containing a silicon atom according to any one of (1) to (9) is a silicon compound adhered to a ceramic that does not react with lithium. (18) The ceramic described in item (17) is made of Al ₂ O ₃ , SiO
_{2, TiO 2, Si 3 N} 4, at least one ceramic in a non-aqueous secondary battery selected from SiC. (19) A non-aqueous secondary battery in which the compound containing a silicon atom according to any one of (1) to (9) is coated with at least a metal. (20) A method for producing a negative electrode material, wherein the method of coating with a metal according to item (19) is an electroless plating method, a vapor deposition method, a sputtering method, or a chemical vapor deposition method. (21) A non-aqueous secondary battery in which the compound containing a silicon atom according to any one of (1) to (9) is coated with a thermoplastic resin in advance. (22) A non-aqueous secondary battery in which the thermoplastic resin described in (21) is polyvinylidene fluoride or polytetrafluoroethylene. (23) A non-aqueous secondary battery using a negative electrode in which 5 to 1900% by weight of carbon coexists with the silicon atom-containing compound according to any one of the above items (1) to (9). (24) A nonaqueous secondary battery in which the carbon according to item (23) is flaky natural graphite. (25) When the charge / discharge range of the compound containing a silicon atom according to any one of the above items (1) to (9) is expressed by Li _x Si as an equivalent ratio of lithium to be inserted into and released from silicon, x is from 0 to 4.2. Non-aqueous secondary batteries that are within range.

The positive electrode (or negative electrode) used in the present invention
Applies the positive electrode mixture (or the negative electrode mixture) on the current collector,
It can be made by molding. The positive electrode mixture (or negative electrode mixture) may include a conductive agent, a binder, a dispersant, a filler, an ionic conductive agent, a pressure enhancer, and various additives in addition to the positive electrode active material (or the negative electrode material). it can. These electrodes may be disk-shaped or plate-shaped, but are preferably in the form of a flexible sheet.

Hereinafter, the constitution and material of the present invention will be described in detail. The compound containing a silicon atom capable of inserting and releasing lithium used in the negative electrode material of the present invention means a simple substance of silicon, a silicon alloy, or a silicide. As silicon alone,
Any of single crystal, polycrystal, and amorphous can be used. The purity of the single crystal is preferably 85% by weight or more.
It is preferably at least 95% by weight. Furthermore, 99% by weight or more is particularly preferable. In the case of polycrystal and non-crystal, the purity as a silicon atom is preferably 99% or less, more preferably 95% or less, most preferably 90% or less and 60% or more.
The average particle size is preferably from 0.01 to 20 μm. In particular, 0.02 to 15 μm is preferable. In addition, 0.05
-10 μm is preferred.

The silicon alloy suppresses pulverization due to expansion and contraction of silicon generated when lithium is inserted and released,
It is considered to be effective in improving the low conductivity of silicon. As the alloy, an alloy with an alkaline earth metal, a transition metal or a metalloid is preferable. Particularly, a solid solution alloy or a eutectic alloy is preferable. A solid solution alloy is an alloy that forms a solid solution. For example, a Ge alloy is a solid solution alloy. A eutectic alloy is an alloy that eutectic in any proportion with silicon, but the solid obtained upon cooling is a mixture of silicon and metal. Be, Ag, Al, Au, Cd, Ga, In,
Sb, Sn, and Zn form a eutectic alloy. Among these, Ge, Be, Ag, Al, Au, Cd, Ga, I
An alloy of n, Sb, Sn, and Zn is more preferable. Also, two or more of these alloys are preferable. In particular, Ge, Ag,
An alloy containing Al, Cd, In, Sb, Sn, and Zn is preferable. The mixing ratio of these alloys is 5 to silicon.
70% by weight is preferred. In particular, 10 to 60% by weight is preferable. In this case, the electric conductivity is improved, but the battery performance,
In particular, in terms of discharge capacity, high rate characteristics, and cycle life, it is preferable that the specific conductivity be 10 times or more the specific conductivity of silicon or a silicon compound before alloying. The average particle size of the alloy is preferably 0.01 to 40 μm. In particular,
0.03-5 μm is preferred.

[0014] Silicide refers to a compound of silicon and a metal. As silicides, CaSi, CaSi ₂ , Mg ₂ S
i, BaSi ₂ , SrSi ₂ , Cu ₅ Si, FeSi, F
eSi ₂ , CoSi ₂ , Ni ₂ Si, NiSi ₂ , MnS
i, MnSi ₂ , MoSi ₂ , CrSi ₂ , TiSi ₂ , T
i ₅ Si ₃ , Cr ₃ Si, NbSi ₂ , NdSi ₂ , CeS
i ₂ , SmSi ₂ , DySi ₂ , ZrSi ₂ , WSi ₂ , W _{5
Si 3, TaSi 2, Ta 5} Si 3, TmSi 2, TbS
i ₂ , YbSi ₂ , YSi ₂ , YSi ₂ , ErSi, ErS
i ₂ , GdSi _2, PtSi, V ₃ Si, VSi ₂ , HfS
i ₂ , PdSi, PrSi ₂ , HoSi ₂ , EuSi ₂ , L
aSi, RuSi, ReSi, RhSi and the like are used.

As the silicon compound, silicon obtained by removing a metal from a metal silicide can be used. Examples of the shape of the silicon include porous particles having a particle size of 1 μm or less, and particles having fine secondary particles aggregated to form porous secondary particles. The reason that the cycle life is improved by using silicon is considered to be that it is difficult to pulverize. The metal of the metal silicide is preferably an alkali metal or an alkaline earth metal. Above all, L
Preferably, i, Ca, and Mg are used. In particular, Li is preferable. The lithium content of the lithium silicide is preferably 100 to 420 mol% based on silicon. In particular,
200 to 420 are preferred. The method of removing an alkali metal or an alkaline earth metal from a silicide of an alkali metal or an alkaline earth metal is preferably performed by reacting with an alkali metal or an alkaline earth metal, and using a solvent in which a reaction product is dissolved. . As the solvent, water and alcohols are preferable. In particular, degassed and dehydrated alcohols are preferred. As alcohols, methyl alcohol, ethyl alcohol, 1-propyl alcohol, 2-
Preferred are propyl alcohol, 1-butyl alcohol, 2-butyl alcohol, t-butyl alcohol, 1-pentyl alcohol, 2-pentyl alcohol, and 3-pentyl alcohol. In particular, 1-propyl alcohol,
2-propyl alcohol, 1-butyl alcohol, 2-
Butyl alcohol and t-butyl alcohol are preferred.
For removing Ca and Mg, water is preferable. It is more preferable to use a pH buffer that keeps the pH around neutral.

It is considered that the ceramic adhered to the silicon compound is effective in suppressing the pulverization of silicon. As the ceramic, a compound that does not basically react with lithium is preferable. In particular, Al ₂ O ₃ , SiO ₂ , TiO ₂ , Si
C and Si ₃ N ₄ are preferred. As a method for attaching silicon and ceramic, mixing, heating, vapor deposition, and CVD are used, and particularly, a combination of mixing and heating is preferable. In particular, after the Al ₂ O ₃ or SiO ₂ sol and silicon are dispersed and mixed, the mixture is heated and the solid solution is pulverized to form silicon and Al _2.
Deposits of O ₃ and SiO ₂ can be obtained. in this case,
The Al ₂ O ₃ and SiO ₂ deposits, or as Al ₂ O ₃ and the surface of SiO ₂ or the like is covered with the silicon powder, as Al ₂ O ₃ or Si
It refers to a state in which the particles are trapped inside a mass of O ₂ or the like, or the surface of silicon is covered with them. Mixing and dispersion can be achieved by mechanical stirring, ultrasonic waves, and kneading.
The heating is preferably performed in an inert gas at a temperature in the range of 300 to 1300 ° C, and particularly preferably 500 to 1200 ° C. Inert gases include argon, nitrogen and hydrogen. These mixed gases are also used. As the pulverizing method, a well-known method such as a ball mill, a vibration mill, a planetary ball mill, and a jet mill is used. This pulverization is also preferably performed in an inert gas. The mixing ratio of the ceramic to silicon is preferably in the range of 2 to 50% by weight, and particularly preferably 3 to 40%. The average particle size of the silicon determined by observation with an electron microscope is preferably 0.01 to 40 μm. In particular, it is preferably from 0.03 to 5 μm.

As the metal coating of the silicon compound of the present invention, there are electroplating, displacement plating, electroless plating, resistance heating evaporation, electron beam evaporation, cluster ion evaporation, etc., sputtering, chemical vapor deposition, and the like. This can be achieved by a phase growth method (CVD method). In particular, an electroless plating method, a resistance heating evaporation method, an electron beam evaporation method, an evaporation method such as a cluster ion evaporation method, a sputtering method, and a CVD method are preferable. Further, an electroless plating method is particularly preferable.
The electroless plating method is described in “Electroless Plating Basics and Applications”, edited by Electroplating Research Group, published by Nikkan Kogyo Shimbun (1994). The reducing agents are phosphinates, phosphonates,
Preferred are borohydrides, aldehydes, sugars, amines and metal salts. Preferred are sodium hydrogen phosphinate, sodium hydrogen phosphonate, sodium borohydride, dimethylamine borane, formaldehyde, sucrose, dextrin, hydroxylamine, hydrazine, ascorbic acid, and titanium chloride. The plating solution preferably contains a pH adjuster and a complexing agent in addition to the reducing agent. For these, the compounds described in the above “Electroless Plating Basics and Applications” are used. The pH of the plating solution is not particularly limited, but is preferably 4 to 13. The temperature of the solution is preferably from 10 ° C to 100 ° C,
C. to 95.degree. C. is preferred. In addition to the plating bath, an activation bath composed of an aqueous solution of SnCl ₂ hydrochloric acid, a nucleation bath composed of an aqueous solution of PdCl ₂ hydrochloric acid, a filtration step, a washing step,
A pulverizing step and a drying step are used.

The silicon compound to be coated may be in any form such as powder, lump, and plate.
The metal to be coated is not particularly limited as long as it is a metal having high conductivity. In particular, Ni, Cu, Ag, Co, Fe, Cr,
W, Ti, Au, Pt, Pd, Sn and Zn are preferred.
In particular, Ni, Cu, Ag, Co, Fe, Cr, Au,
Pt, Pd, Sn, and Zn are preferable, and Ni, C
u, Ag, Pd, Sn, and Zn are particularly preferred. The amount of the metal to be coated is not particularly limited, but it is preferable that the metal is coated so that the specific conductivity is at least 10 times the specific conductivity of the silicon compound as the base.

It is preferable to coat the silicon compound used in the present invention with a thermoplastic resin. Thermoplastic resin is a fluorine-containing polymer compound, imide polymer, vinyl polymer,
An acrylate polymer, an ester polymer, polyacrylonitrile, or the like is used. In particular, the thermoplastic resin is preferably a resin that does not easily swell in the electrolytic solution. Specific examples include polyacrylic acid, polyacrylic acid Na, polyvinyl phenol, polyvinyl methyl ether, polyvinyl alcohol, polyvinyl pyrrolidone, polyacrylamide, polyhydroxy (meth) acrylate, and styrene-
Water-soluble polymers such as maleic acid copolymer, polyvinyl chloride, polytetrafluoroethylene, polyvinylidene fluoride, tetrafluoroethylene-hexafluoropropylene copolymer, vinylidene fluoride-tetrafluoroethylene-hexafluoropropylene copolymer, (Meth) acrylic acid ester containing (meth) acrylic acid ester such as polyethylene, polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, polyvinyl acetal resin, methyl methacrylate, and 2-ethylhexyl acrylate Coalescing,
(Meth) acrylate-acrylonitrile copolymer, polyvinyl ester copolymer containing vinyl ester such as vinyl acetate, styrene-butadiene copolymer, acrylonitrile-butadiene copolymer, polybutadiene, neoprene rubber, fluorine rubber, poly Emulsions (latex) or suspensions of ethylene oxide, polyester polyurethane resin, polyether polyurethane resin, polycarbonate polyurethane resin, polyester resin, phenol resin, epoxy resin and the like can be given. In particular, polyacrylate latex, carboxymethylcellulose, polytetrafluoroethylene, and polyvinylidene fluoride are exemplified. These compounds can be used alone or as a mixture. Particularly, a fluorine-containing polymer compound is preferable.
Among them, polytetrafluoroethylene and polyvinylidene fluoride are preferable. As a method of coating in advance,
A thermoplastic resin is dissolved in a solvent, and a silicon compound is mixed and kneaded in the solution. A method of drying the solution and pulverizing the obtained solid is preferable. The use amount of the thermoplastic resin to the silicon compound is preferably 2 to 30% by weight. Particularly, 3 to 20% by weight is preferable. The coverage is preferably from 5 to 100%, and particularly preferably from 5 to 90%. The average size of the coated particles is 0.01 μm
４０40 μm is preferred. In particular, it is preferably from 0.03 to 5 μm.

In the present invention, it is preferable to use a mixture of a silicon compound and a carbonaceous compound. As the carbonaceous material, a material used as a conductive agent or a negative electrode material is used. Examples of the carbonaceous material include a non-graphitizable carbon material and a graphite-based carbon material. Specifically, Japanese Patent Application Laid-Open No. 62-122066
, Japanese Unexamined Patent Publications Nos. 2-66856 and 3-245473, and carbon materials having plane spacing, density, and crystallite size, and natural graphite and artificial materials described in Japanese Patent Laid-Open No. 5-290844. A mixture of graphite, JP-A-63-24555,
JP-A-63-13282, JP-A-63-58763, and the vapor-grown carbon material described in JP-A-6-212617, and the non-graphitizable carbon described in JP-A-5-182664 were used.
A material which is heated and fired at a temperature exceeding 400 ° C. and has X-ray diffraction peaks corresponding to a plurality of 002 planes, JP-A-5-307957 and JP-A-5-307958.
, A mesophase carbon material synthesized by pitch firing described in JP-A-7-85862 and JP-A-8-315820, a graphite having a coating layer described in JP-A-6-84516, and various granular materials And carbon materials such as microspheres, flat bodies, microfibers, whisker-shaped carbon materials, phenol resins, acrylonitrile resins, fired products of furfuryl alcohol resins, and polyacene materials containing hydrogen atoms. Further, specific examples of the conductive agent include flake graphite, flake graphite, natural graphite such as earth graphite, petroleum coke, coal coke, celluloses, sugars, high-temperature fired bodies such as mesophase pitch, vapor-grown graphite, etc. Carbon materials such as graphite such as artificial graphite, acetylene black, furnace black, Ketjen black, channel black, lamp black, thermal black, etc., and carbon materials such as asphalt pitch, coal tar, activated carbon, meso fuse pitch and polyacene. preferable. These may be used alone,
It may be used as a mixture.

[0021] In particular, carbon materials and various granular materials, microspheres, flat plates, and the like described in JP-A-5-182664 are disclosed.
A carbon material in the form of a fiber or whisker, a mesophase pitch, a fired body of a phenol resin or an acrylonitrile resin, and a polyacene material containing a hydrogen atom are preferable. Above all, flaky natural graphite is preferable because it strengthens the mixture film. The mixing ratio is 5 to silicon compound.
1900% by weight is preferred. In particular, 20 to 500% by weight is preferable. Furthermore, 30 to 400% by weight is preferable.

As the conductive agent, other metals than carbon can be used. Ni, Cu, Ag, and Fe are preferred.

The charge / discharge range of the silicon compound negative electrode material is defined by the ratio of lithium and silicon atoms that can be inserted and released by Li _x
When represented by Si, x = 0 to 4.2 is preferable. As a result of intensive studies on the improvement of the cycle life of silicon, x = 0 to 3.7.
It has been found that the cycle life is greatly improved when it is within the range. The charging potential was 0.0 V including the overvoltage at x = 4.2 with respect to the lithium metal counter electrode, whereas the charging potential was about 0.05 V at x = 3.7. At this time, the shape of the discharge curve changes, and a flat discharge curve is obtained around 0.5 V (vs. lithium metal) at the return of 0.0 V charge, whereas it is 0.05 V or more, in particular, 0.0 V or more.
At 8 V or more (x = 3.6), a smooth curve having an average voltage at about 0.4 V is obtained. In other words, it is found that a specific phenomenon in which the discharge potential decreases as the charging end voltage is increased is found, and a phenomenon in which the reversibility of the charge / discharge reaction is also increased.

Although a method having the effect of improving the cycle life while maintaining a high capacity of the silicon compound has been individually described, a more preferred embodiment has been found to achieve a higher improvement effect by a combination of the above methods. .

In the present invention, as the negative electrode material, in addition to the silicon compound of the present invention, a carbonaceous material, an oxide material, a nitride material,
It can be combined with a compound capable of inserting and releasing lithium, such as a sulfide material, lithium metal, and lithium alloy.

The cathode material used in the present invention is a lithium-containing transition metal oxide. Preferably Ti, V, Cr,
An oxide mainly containing lithium and at least one transition metal element selected from Mn, Fe, Co, Ni, Mo and W, and having a molar ratio of lithium to transition metal of 0.1.
3 to 2.2. More preferably, V, C
at least one selected from r, Mn, Fe, Co, and Ni
An oxide mainly containing various kinds of transition metal elements and lithium, and a compound in which the molar ratio of lithium to the transition metal is 0.3 to 2.2. It should be noted that Al, Ga, and I are present in a range of less than 30 mole percent based on the transition metal mainly present.
It may contain n, Ge, Sn, Pb, Sb, Bi, Si, P, B, and the like. Among the positive electrode active materials described above, a general formula Li _x MO ₂ (M is at least one of Co, Ni, Fe, and Mn, x = 0 to 1.2), or Li _y N ₂ O ₄ (N is at least It is preferable to use at least one kind of material having a spinel structure represented by y = 0 to 2).

Further, the positive electrode active material is Li_yM_aD_1-aO_Two
(M is at least one of Co, Ni, Fe, and Mn.
Co, Ni, Fe, Mn, Al, Zn, Cu, Mo, A
g, W, Ga, In, Sn, Pb, Sb, Sr, B, P
At least one other than M y = 0 to 1.2, a =
0.5-1), or Li_z(N_bE_1-b) _Two
O_Four(N is Mn E is Co, Ni, Fe, Mn, Al,
Zn, Cu, Mo, Ag, W, Ga, In, Sn, P
at least one of b, Sb, Sr, B, and P, b = 1 to
0.2 having a spinel structure represented by z = 0 to 2)
It is particularly preferred to use at least one of the materials.

Specifically, Li _x CoO ₂ , Li _x NiO
₂ , Li _x MnO ₂ , Li _x Co _a Ni _{1 -a} O ₂ , Li _x Co _b
V _1-b O _z , Li _x Co _b Fe _1-b O ₂ , Li _x Mn
_{2 O 4, Li x Mn c} Co 2-c O 4, Li x Mn c Ni
_{2-c O 4, Li x} Mn c V 2-c O 4, Li x Mn c Fe 2-c O
₄ (where x = 0.02 to 1.2, a = 0.1 to 0.
9, b = 0.8 to 0.98, c = 1.6 to 1.96, z
= 2.01-2.3). Most preferred lithium-containing transition metal oxides include Li _x CoO ₂ , Li
_x NiO ₂ , Li _x MnO ₂ , Li _x Co _a Ni _1-a O ₂ , L
_{i x Mn 2 O 4, Li} x Co b V 1 -b O z (x = 0.02~
1.2, a = 0.1 to 0.9, b = 0.9 to 0.98,
z = 2.01 to 2.3). The value of x is a value before the start of charge / discharge, and increases / decreases due to charge / discharge.

The positive electrode active material used in the present invention can be synthesized by a method in which a lithium compound and a transition metal compound are mixed and fired, or a solution reaction, but a firing method is particularly preferable. Details of the firing are described in paragraph 35 of JP-A-6-60,867, JP-A-7-14,579 and the like, and these methods can be used. The positive electrode active material obtained by firing may be used after being washed with water, an acidic aqueous solution, an alkaline aqueous solution, or an organic solvent. Further, as a method of chemically inserting lithium ions into the transition metal oxide, a method of synthesizing lithium metal, a lithium alloy, or butyllithium by reaction with the transition metal oxide may be used.

The average particle size of the positive electrode active material used in the present invention is not particularly limited, but is preferably 0.1 to 50 μm. It is preferable that the volume of the particles of 0.5 to 30 μm is 95% or more. The volume occupied by the particle group having a particle size of 3 μm or less is 18% or less of the total volume, and 15 μm or more and 25 μm or more
More preferably, the volume occupied by the particle group of m or less is 18% or less of the total volume. No particular limitation is imposed on the specific surface area is preferably 0.01 to 50 m ² / g by the BET method, particularly preferably 0.2m ² / g~1m ² / g. Further, when 5 g of the positive electrode active material is dissolved in 100 ml of distilled water, the pH of the supernatant is preferably 7 or more and 12 or less.

When the positive electrode active material of the present invention is obtained by firing, the firing temperature is preferably from 500 to 1500 ° C., more preferably from 700 to 1200 ° C., and particularly preferably from 750 to 1000 ° C. The firing time is preferably 4 to 30 hours, more preferably 6 to 20 hours, and particularly preferably 6 to 15 hours.

The conductive agent used in the mixture of the present invention may be any electronic conductive material which does not cause a chemical change in the constructed battery. Specific examples include flake graphite, flake graphite, natural graphite such as earth graphite, petroleum coke, coal coke, celluloses, sugars, high-temperature fired bodies such as mesophase pitch, and graphite such as artificial graphite such as vapor-grown graphite. , Carbon blacks such as acetylene black, furnace black, ketjen black, channel black, lamp black, and thermal black, asphalt pitch, coal tar, activated carbon, meso fuse pitch, carbon materials such as polyacene, and conductive materials such as metal fibers. Fibers, metal powders such as copper, nickel, aluminum, silver, etc.
Conductive whiskers such as zinc oxide and potassium titanate;
Examples thereof include conductive metal oxides such as titanium oxide. In the case of graphite, it is preferable to use a plate-like graphite having an aspect ratio of 5 or more. Among these, graphite and carbon black are preferable, and the particle size is 0.01%.
The particle size is preferably not less than μm and not more than 20 μm, more preferably not less than 0.02 μm and not more than 10 μm. These may be used alone or in combination of two or more. When used together, it is preferable to use carbon blacks such as acetylene black and graphite particles of 1 to 15 μm in combination. The amount of the conductive agent added to the mixture layer is preferably 1 to 50% by weight based on the negative electrode material or the positive electrode material, and more preferably 2 to 3% by weight.
It is preferably 0% by weight. For carbon black and graphite, the content is particularly preferably 3 to 20% by weight.

In the present invention, a binder is used to hold the electrode mixture. Examples of the binder include polysaccharides, thermoplastic resins, and polymers having rubber elasticity. Preferred binders include starch, carboxymethyl cellulose, cellulose, diacetyl cellulose, methyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, sodium alginate, polyacrylic acid,
Water-soluble polymers such as sodium polyacrylate, polyvinylphenol, polyvinylmethylether, polyvinylalcohol, polyvinylpyrrolidone, polyacrylamide, polyhydroxy (meth) acrylate, styrene-maleic acid copolymer, polyvinyl chloride, polytetrafluoroethylene, Polyvinylidene fluoride, tetrafluoroethylene-hexafluoropropylene copolymer, vinylidene fluoride-tetrafluoroethylene-hexafluoropropylene copolymer, polyethylene, polypropylene, ethylene-propylene-diene terpolymer (EPDM),
(Meth) acrylate copolymer containing (meth) acrylate such as sulfonated EPDM, polyvinyl acetal resin, methyl methacrylate, 2-ethylhexyl acrylate, etc., (meth) acrylate-acrylonitrile copolymer, vinyl Polyvinyl ester copolymer containing vinyl ester such as acetate, styrene-butadiene copolymer, acrylonitrile-butadiene copolymer, polybutadiene, neoprene rubber, fluorine rubber, polyethylene oxide, polyester polyurethane resin, polyether polyurethane resin, polycarbonate polyurethane Resin, polyester resin,
An emulsion (latex) such as a phenol resin or an epoxy resin or a suspension can be used. In particular, polyacrylate latex, carboxymethylcellulose, polytetrafluoroethylene, and polyvinylidene fluoride are exemplified. As these binders, it is preferable to use those obtained by dispersing fine powder in water, and it is more preferable to use those in which the average size of the particles in the dispersion is 0.01 to 5 μm, and 0.05 to 1 μm. It is particularly preferred to use one. These binders can be used alone or as a mixture. If the amount of the binder is small, the holding power and cohesive strength of the electrode mixture are weak. If it is too large, the electrode volume increases and the capacity per unit volume or unit weight of the electrode decreases. For these reasons, the amount of binder added is 1
It is preferably from 30 to 30% by weight, particularly preferably from 2 to 10% by weight.

As the filler, any fibrous material that does not cause a chemical change in the constructed battery can be used. Usually, fibers such as olefin-based polymers such as polypropylene and polyethylene, glass, and carbon are used. Although the amount of the filler is not particularly limited,
30% by weight is preferred. As the ionic conductive agent, those known as inorganic and organic solid electrolytes can be used, and the details are described in the section of the electrolytic solution. The pressure booster is a compound for raising the internal pressure of the battery, and a carbonate such as lithium carbonate is a typical example.

In the current collector which can be used in the present invention, the positive electrode is aluminum, stainless steel, nickel, titanium or an alloy thereof, and the negative electrode is copper, stainless steel, nickel,
Titanium or their alloys. The form of the current collector is foil, expanded metal, punched metal, or wire mesh. In particular, an aluminum foil is preferable for the positive electrode, and a copper foil is preferable for the negative electrode.

The thickness of the foil is preferably from 7 μm to 100 μm, more preferably from 7 μm to 50 μm, particularly preferably from 7 μm to 20 μm. Expanded metal, punching metal, wire mesh thickness is 7μm ~
200 μm is preferred, and more preferably 7 μm to 15 μm.
0 μm, particularly preferably 7 μm to 100 μm. The purity of the current collector is preferably 98% or more, more preferably 99% or more, and particularly preferably 99.
3% or more. The surface of the current collector may be washed with an acid, an alkali, an organic solvent, or the like.

The current collector is more preferably formed by forming a metal layer on both sides of a plastic sheet in order to reduce the thickness. The plastic is preferably excellent in stretchability and heat resistance, and is, for example, polyethylene terephthalate. Metals alone have little elasticity and are vulnerable to external forces. If a metal layer is formed on plastic, it will be resistant to impact. More specifically, the current collector may be a composite current collector in which a base material such as a synthetic resin film or paper is coated with an electron conductive material. As a synthetic resin film as a base material,
Examples include fluororesin, polyethylene terephthalate, polycarbonate, polyvinyl chloride, polystyrene, polyethylene, polypropylene, polyimide, polyamide, cellulose dielectric, and polysulfone. Examples of the electron conductive material that coats the base material include carbonaceous materials such as graphite and carbon black, metal elements such as aluminum, copper, nickel, chromium, iron, molybdenum, gold, and silver and alloys thereof. it can. Particularly preferred electron conductive materials are metals, such as aluminum, copper, nickel and stainless steel. The composite current collector may be in a form in which a base sheet and a metal sheet are laminated, or a metal layer may be formed by vapor deposition or the like.

Next, the structure of the positive and negative electrodes in the present invention will be described. The positive and negative electrodes preferably have a form in which an electrode mixture is applied to both surfaces of a current collector. In this case, the number of layers per side may be one or two or more. When the number of layers per side is two or more, the number of layers containing the positive electrode active material (or the negative electrode material) may be two or more. More preferably, the layer containing the positive electrode active material (or the negative electrode material) and the positive electrode active material (or the negative electrode material)
This is a case where it is composed of a layer containing no. The layer containing no positive electrode active material (or negative electrode material) includes a protective layer for protecting the layer containing the positive electrode active material (or negative electrode material), and a layer between the divided positive electrode active material (or negative electrode material) containing layer. Layer, positive electrode active material (or negative electrode material)
There is an undercoat layer between the containing layer and the current collector, and these are collectively referred to as an auxiliary layer in the present invention.

The protective layer in the auxiliary layer is preferably provided on at least one of the positive and negative electrodes. When lithium is inserted into a negative electrode material in a battery, it is particularly preferable to provide a protective layer on the negative electrode. When the positive electrode is used in a state where the amount of lithium released from the positive electrode active material is large and the potential is relatively high, it is preferable to provide a protective layer. The protective layer is composed of at least one layer and may be composed of the same or different layers. Further, a form in which a protective layer is provided only on one side of the mixture layer disposed on both sides of the current collector may be used.
These protective layers are composed of particles insoluble in water and a non-aqueous electrolyte, a binder, a dispersant, and the like. As the particles insoluble in water and the non-aqueous electrolyte, various conductive particles or organic and inorganic particles having substantially no conductivity can be used. Examples of the conductive particles include metals, metal oxides, metal fibers, carbon fibers, and carbon particles such as carbon black and graphite. Preferably, those having low reactivity with alkali metals, particularly lithium, are good, and metal powder,
Carbon particles are good. 20 ° C of the element formed by these particles
Is preferably 5 × 10 ⁹ Ω · m or less.

The metal powder is preferably a metal which does not easily form an alloy with lithium, specifically, copper, nickel,
Iron, chromium, molybdenum, titanium, tungsten and tantalum are preferred. The shape of these metal powders may be any of a needle shape, a column shape, a plate shape, and a lump shape, and the maximum diameter is 0.02 μm.
m to 20 μm, preferably 0.1 μm to 10 μm
m or less is more preferable. It is preferable that the surface of these metal powders is not excessively oxidized. When the surfaces are oxidized, it is preferable to perform heat treatment in a reducing atmosphere. As the carbon particles, arable carbon materials used as a conductive material to be used when the electrode active material is not substantially conductive can be used. Specifically, a conductive agent used when preparing an electrode mixture is used. The solubility of these particles in water is 100 ppm or less, more preferably 10 ppm or less. The proportion of particles contained in the protective layer is at least 2.5% by weight,
It is preferably 6% by weight or less, more preferably 5% by weight or more and 95% by weight or less, particularly preferably 10% by weight or more and 93% by weight or less.

Next, examples of organic and inorganic particles having substantially no conductivity include fine powder of Teflon, SiC, aluminum nitride, alumina, zirconia, magnesia, mullite, forsterite, and steatite. I can do it. These particles may be used in combination with the conductive particles. In this case, it is preferable to use the conductive particles in an amount of 0.01 times or more and 50 times or less.

Next, the intermediate layer in the auxiliary layer is preferably arranged in the middle of the case where the positive electrode or the negative electrode has a multilayer structure. The active material containing layer of the electrode is composed of at least two layers, and the type of each active material may be different,
Further, the average particle size of the active materials may be different, and the active material content in the electrode mixture may be different. When the active material-containing layer is divided into a layer close to the current collector and a layer far from the current collector, it is preferable to use the layer according to the purpose. In particular, the layer near the current collector has a smaller active material particle diameter than the layer far away,
It is preferable to arrange one having a large specific surface area. Or,
It is preferable to dispose a layer containing a large amount of the active material or a layer containing the active material having a relatively fast electrode reaction with lithium near the current collector.

The intermediate layer disposed between the two or more active material-containing layers adjusts the amount of retained electrolyte, functions as a buffer for the expansion and contraction of the electrode due to charge / discharge, and controls overcharge and overcharge. It has a function to improve the safety at the time of pressure breakdown of the battery.

The intermediate layer is composed of the same particles as those used for the protective layer, which are insoluble in water and non-aqueous electrolyte, and a binder and a dispersant, or a conductive agent. Particularly, use of carbon or metal powder having high electron conductivity is preferable. In addition, it is also preferable to include a polymer material having a function of retaining the electrolytic solution. Specifically, polyethylene oxide,
Polypropylene oxide and their copolymers, polyvinylidene fluoride, polysiloxane, polyphosphazene and their copolymers.

The undercoat layer in the auxiliary layer is a layer provided between the current collector of the positive electrode or the negative electrode and the respective electrode mixture layers, and is particularly preferably applied directly to the current collector. The undercoat layer has the purpose of improving the adhesion between the electrode mixture layer and the current collector, stably maintaining the electrical resistance between the current collector and the electrode mixture layer, and has the above-mentioned protective layer. May be the same composition, preferably a layer of a thin film of carboxymethylcellulose alone, or a layer mixed with a conductive agent or a binder thereto,
Alternatively, it is a thin film of a polymer compound used for the intermediate layer. These thin films need not have conductivity. In such a case, the thinness provides the necessary conductivity when the upper mixture layer is applied and then pressed and formed, or does not hinder electron conduction. It is preferable to apply it to such a small thickness.

The positive (negative) electrode sheet can be prepared by applying a positive (negative) electrode mixture on a current collector, drying and compressing. For the preparation of the mixture, a positive electrode active material (or a negative electrode material) and a conductive agent are mixed, a binder (a suspension or emulsion of resin powder), and a dispersion medium are added and kneaded and mixed. The dispersion can be carried out by a stirring mixer such as a mixer, a homogenizer, a dissolver, a planetary mixer, a paint shaker, a sand mill, or a disperser. Water or an organic solvent is used as the dispersion medium, but water is preferred. In addition, additives such as a filler, an ion conductive agent, and a pressure enhancer may be appropriately added. The pH of the dispersion is 5 to 10 for the negative electrode and 7 to 10 for the positive electrode.
12 is preferred.

The coating can be performed by various methods.
Examples of the method include a reverse roll method, a direct roll method, a blade method, a knife method, an extrusion method, a slide method, a curtain method, a gravure method, a bar method, a dip method, and a squeeze method. A method using an extrusion die and a method using a slide coater are particularly preferable. The coating is preferably performed at a speed of 0.1 to 100 m / min. At this time, by selecting the above-mentioned coating method in accordance with the liquid physical properties and drying properties of the mixture paste, a good surface state of the coating layer can be obtained.
When the electrode layer has a plurality of layers, it is preferable to apply the plurality of layers simultaneously from the viewpoint of uniform electrode production, production cost, and the like. The thickness, length and width of the coating layer are determined by the size of the battery. A typical thickness of the coating layer is 10 to 1000 μm in a compressed state after drying. The electrode sheet after application is hot air, vacuum, infrared, far infrared,
It is dried and dehydrated by the action of electron beams and low humidity air. These methods can be used alone or in combination. The drying temperature is preferably in the range of 80 to 350C, particularly preferably in the range of 100 to 260C. The water content after drying is preferably 2000 ppm or less, more preferably 500 ppm or less. The compression of the electrode sheet can be performed by a commonly used pressing method, but a die pressing method and a calendar pressing method are particularly preferable. The press pressure is not particularly limited, but is preferably 10 kg / cm ^{2 to 3} t / cm ² . The press speed of the calendar press method is 0.1 ~
50 m / min is preferred. Press temperature is from room temperature to 200 ℃
Is preferred.

The separator which can be used in the present invention may be any thin film having a high ion permeability, a predetermined mechanical strength and an insulating thin film.
Fluorine polymer, cellulose polymer, polyimide, nylon, glass fiber, alumina fiber is used,
As the form, a nonwoven fabric, a woven fabric, or a microporous film is used. In particular, the material is preferably polypropylene, polyethylene, a mixture of polypropylene and polyethylene, a mixture of polypropylene and Teflon, a mixture of polyethylene and Teflon, and the form is preferably a microporous film. In particular, a microporous film having a pore size of 0.01 to 1 μm and a thickness of 5 to 50 μm is preferable. These microporous films may be a single film or a composite film composed of two or more layers having different properties such as the shape, density, and material of the micropores. For example, a composite film obtained by laminating a polyethylene film and a polypropylene film can be used.

The electrolytic solution generally comprises a supporting salt and a solvent. As a supporting salt in a lithium secondary battery, a lithium salt is mainly used. Examples of the lithium salt that can be used in the present invention include LiClO ₄ , LiBF ₄ , LiPF ₆ ,
_{LiCF 3 CO 2, LiAsF 6,} LiSbF 6, LiB 10
Cl ₁₀ , a fluorosulfonic acid represented by LiOSO ₂ C _n F _{2n + 1} (n is a positive integer of 6 or less), LiN (SO ₂ C _n F
_{2n + 1} ) (SO ₂ C _m F _{2m + 1} ) (m, n
Is a positive integer of 6 or less), LiC (SO ₂ C _p F
_{2p + 1) (SO 2 C} q F 2q + 1) (SO 2 C r F 2r + 1 methide salts (p represented by), q, r are each 6 or less positive integer), lower aliphatic carboxylic Lithium oxide, LiAlCl
₄ , Li salts such as LiCl, LiBr, LiI, lithium chloroborane and lithium tetraphenylborate can be used, and one or more of these can be used in combination. Among them, those in which LiBF ₄ and / or LiPF ₆ are dissolved are preferable. The concentration of the supporting salt is not particularly limited, but may be 0.1 to 1 liter of the electrolytic solution.
2-3 moles are preferred.

[0050] Solvents usable in the present invention include propylene.
Lencarbonate, ethylene carbonate, butyleneca
-Carbonate, chloroethylene carbonate, trifcarbonate
Fluoromethylethylene, difluoromethylethylene carbonate
, Monofluoromethyl ethylene carbonate, methyl hexafluoride
Acetate, methyl trifluoride acetate, dimethyl car
Carbonate, diethyl carbonate, methyl ethyl carbonate
, Gamma-butyrolactone, methyl formate, methyl acetate
1,2-dimethoxyethane, tetrahydrofuran,
2-methyltetrahydrofuran, dimethylsulfoxy
Do, 1,3-dioxolan, 2,2-bis (trifluoro
Romethyl) -1,3-dioxolan, formamide, di
Methylformamide, dioxolan, dioxane, ace
Tonitrile, nitromethane, ethyl monoglyme, phosphorus
Acid triester, boric acid triester, trimethoxymeth
Tan, dioxolane derivative, sulfolane, 3-methyl-
2-oxazolidinone, 3-alkylsydnone (alk
Propyl, isopropyl, butyl, etc.), propyl
Lencarbonate derivative, tetrahydrofuran derivative,
Non-prototypes such as ethyl ether and 1,3-propane sultone
And rotonic organic solvents.
Or a mixture of two or more. Among these,
Carbonate solvents are preferred, and cyclic carbonates and
It is particularly preferable to use a mixture of acyclic carbonates.
No. Ethylene carbonate as a cyclic carbonate,
Propylene carbonate is preferred. Also, non-annular cars
As carbonates, diethyl carbonate, dimethyl carbonate
Carbonate and methyl ethyl carbonate are preferred.
As the electrolytic solution that can be used in the present invention, ethylene carbonate
Salt, propylene carbonate, 1,2-dimethoxyethyl
Tan, dimethyl carbonate or diethyl carbonate
LiCF is added to the electrolyte solution_ThreeSO_Three, LiCl
O_Four, LiBF_FourAnd / or LiPF₆Electrolyte containing
Is preferred. Especially propylene carbonate or ethyl
At least one of lencarbonate and dimethyl carbonate
And / or diethyl carbonate
LiCF in the mixed solvent_ThreeSO_Three, LiClO_FourOr
LiBF_FourLi and at least one salt selected from
PF ₆An electrolytic solution containing Put these electrolytes in the battery
The amount added to the material is not particularly limited.
It can be used depending on the amount and the size of the battery.

In addition to the electrolytic solution, the following solid electrolyte can be used in combination. Solid electrolytes are classified into inorganic solid electrolytes and organic solid electrolytes. Well-known inorganic solid electrolytes include nitrides, halides, and oxyacid salts of Li. Among them, Li ₃ N, LiI, Li ₅ N
_{I2, Li 3 N-LiI-} LiOH, Li 4 SiO 4, Li 4
_{SiO 4 -LiI-LiOH, x Li} 3 PO 4 - (1-x) Li
₄ SiO ₄ , Li ₂ SiS ₃ , phosphorus sulfide compounds and the like are effective.

As the organic solid electrolyte, a polyethylene oxide derivative or a polymer containing the derivative, a polypropylene oxide derivative or a polymer containing the derivative, a polymer containing an ion dissociating group, a mixture of the polymer containing an ion dissociating group and the above aprotic electrolyte , A phosphate matrix polymer, and a polymer matrix material containing an aprotic polar solvent are effective. Furthermore, there is a method of adding polyacrylonitrile to the electrolytic solution. In addition, a method of using an inorganic and an organic solid electrolyte in combination is also known.

Also, the purpose of improving discharge and charge / discharge characteristics
Then, another compound may be added to the electrolyte. For example,
Lysine, pyrroline, pyrrole, triphenylamine,
Phenyl carbazole, triethyl phosphite, tri
Ethanolamine, cyclic ether, ethylenediamine,
n-glyme, hexaphosphoric triamide, nitrobenze
Derivatives, sulfur, quinone imine dyes, N-substituted oxazones
Lizinone and N, N'-substituted imidaridinone, ethylene glycol
Recall dialkyl ether, quaternary ammonium salt,
Polyethylene glycol, pyrrole, 2-methoxy eta
Knoll, AlCl _Three, Conductive polymer electrode active material
Mer, triethylene phosphoramide, trialkyl phos
Aryl compounds having fin, morpholine and carbonyl groups
, Crown ethers such as 12-crown-4,
Hexamethylphosphoric triamide and 4-alkylmo
Ruphorin, bicyclic tertiary amine, oil, quaternary phosphoni
And tertiary sulfonium salts.
You. Particularly preferred are triphenylamine, phenylca
When using rubazole alone or in combination
You.

In order to make the electrolyte nonflammable, a halogen-containing solvent such as carbon tetrachloride or ethylene trifluoride chloride can be contained in the electrolyte. In addition, carbon dioxide gas can be included in the electrolytic solution in order to provide suitability for high-temperature storage.

It is desirable that the electrolyte contains as little water and free acid as possible. For this reason, it is preferable that the raw material of the electrolytic solution is sufficiently dehydrated and purified. The adjustment of the electrolytic solution is preferably performed in dry air or an inert gas having a dew point of −30 ° C. or less. The amount of water and free acid in the electrolytic solution is 0.1 to 500 ppm, more preferably 0.2 to 100 ppm.

The entire amount of the electrolytic solution may be injected at one time, but it is preferable to inject it in two or more portions. In the case of injecting two or more times, each liquid may have the same composition but different compositions (for example, after injecting a non-aqueous solvent or a solution in which a lithium salt is dissolved in a non-aqueous solvent, a non-aqueous solution having a higher viscosity than the solvent may be used). A solution in which a lithium salt is dissolved in a solvent or a non-aqueous solvent is injected). Further, in order to shorten the injection time of the electrolyte solution, the pressure of the battery can may be reduced, or a centrifugal force or an ultrasonic wave may be applied to the battery can.

The battery can and the battery lid that can be used in the present invention are made of nickel-plated iron steel plate or stainless steel plate (SUS304, SUS304L, SUS304).
N, SUS316, SUS316L, SUS430, S
US444, etc.), nickel-plated stainless steel plate (same as above), aluminum or its alloy, nickel,
They are titanium and copper, and have a shape of a perfect circular cylinder, an elliptical cylinder, a square cylinder, or a rectangular cylinder. In particular, when the outer can also serves as the negative electrode terminal, a stainless steel plate or a nickel-plated iron steel plate is preferable, and when the outer can also serves as the positive electrode terminal, a stainless steel plate, aluminum or an alloy thereof is preferable. The shape of the battery can may be any of buttons, coins, sheets, cylinders, corners, and the like. A safety valve can be used for the sealing plate as a measure against the rise in the internal pressure of the battery can. In addition, a method of cutting a member such as a battery can or a gasket can also be used. In addition, various conventionally known safety elements (for example, a fuse, a bimetal, a PTC element, or the like as an overcurrent prevention element) may be provided.

For the lead plate used in the present invention, a metal having electrical conductivity (for example, iron, nickel, titanium, chromium, molybdenum, copper, aluminum, etc.) or an alloy thereof can be used. Battery lid, battery can, electrode sheet,
As a method for welding the lead plate, a known method (eg, DC or AC electric welding, laser welding, ultrasonic welding) can be used. A conventionally known compound or mixture such as asphalt can be used as the sealing agent for sealing.

The gaskets usable in the present invention are olefin polymers, fluorine polymers, cellulosic polymers, polyimides and polyamides, and olefin polymers are preferred in view of organic solvent resistance and low moisture permeability. Propylene-based polymers are preferred. Further, it is preferably a block copolymer of propylene and ethylene.

The battery assembled as described above is
It is preferable to perform an aging treatment. The aging treatment includes a pretreatment, an activation treatment, and a post-treatment, whereby a battery having high charge / discharge capacity and excellent cycleability can be manufactured. The pre-treatment is a treatment for making the distribution of lithium in the electrode uniform, such as a control of dissolution of lithium, a temperature control for making the distribution of lithium uniform, a swing and / or rotation treatment, and an optional charge and discharge. Are performed. The activation process is a process for inserting lithium into the negative electrode of the battery body, and it is preferable to insert 50 to 120% of the amount of lithium inserted when the battery is actually used and charged.
The post-processing is a process for sufficiently activating the activation process,
There are a preservation process for making the battery reaction uniform and a charge / discharge process for determination, and these can be arbitrarily combined.

Preferred aging conditions (pretreatment conditions) before activation of the present invention are as follows. The temperature is preferably from 30 ° C. to 70 ° C., more preferably from 30 ° C. to 60 ° C., and even more preferably from 40 ° C. to 60 ° C. The open circuit voltage is preferably 2.5 V or more and 3.8 V or less,
2.5 V or more and 3.5 V or less are more preferable, and 2.8 V or more and 3.3 V or less are more preferable. Aging period is 1
It is preferably from 20 days to 20 days, particularly preferably from 1 day to 15 days. The charging voltage for activation is preferably 4.0 V or more, more preferably 4.05 V or more and 4.3 V or less, and 4.0 V or more.
The voltage is more preferably from 1 V to 4.2 V. As the aging condition after activation, the open circuit voltage is 3.9 V or more and 4.3 V.
The temperature is preferably from 4.0 V to 4.2 V, and the temperature is preferably from 30 ° C. to 70 ° C.
A temperature of at least 60 ° C is particularly preferred. The aging period is 0.
It is preferably from 2 days to 20 days, particularly preferably from 0.5 days to 5 days.

[0062] The battery of the present invention is covered with an exterior material if necessary. Examples of the exterior material include a heat-shrinkable tube, an adhesive tape, a metal film, paper, cloth, paint, a plastic case, and the like. Further, at least a part of the exterior may be provided with a portion that changes color by heat so that the heat history during use can be recognized.

The batteries of the present invention are assembled in series and / or in parallel as necessary and stored in a battery pack. In addition to safety elements such as positive temperature coefficient resistors, thermal fuses, fuses and / or current interrupting elements, battery packs have safety circuits (voltage, temperature, current, etc. of each battery and / or assembled battery as a whole, Then, a circuit having a function of interrupting the current may be provided. In addition to the positive and negative terminals of the whole battery pack, the positive and negative terminals of each battery, the temperature detection terminals of the whole battery pack and each battery, the current detection terminals of the whole battery pack, etc. shall be provided as external terminals on the battery pack. Can also. The battery pack may have a built-in voltage conversion circuit (such as a DC-DC converter). In addition, connection of each battery
The lead plate may be fixed by welding, or may be fixed with a socket or the like so as to be easily detachable. Further, the battery pack may be provided with a display function of the remaining battery capacity, the presence or absence of charging, the number of times of use, and the like.

The battery of the present invention is used for various devices.
In particular, video movies, portable VCRs with built-in monitors, movie cameras with built-in monitors, digital cameras, compact cameras, SLR cameras, film with lenses, notebook computers, notebook word processors, electronic organizers,
It is preferably used for mobile phones, cordless phones, razors, electric tools, electric mixers, automobiles and the like.

[0065]

The present invention will be described in more detail with reference to specific examples, but the present invention is not limited to the examples unless it exceeds the gist of the invention.

Example 1 Polycrystalline silicon alone (compound 1) as a negative electrode material, Si-Ag alloy (compound 2 weight ratio 40-60), Si-Al (compound 3) Weight ratio 40-60), Si-Ag-Cd (compound 4
Weight ratio 40-50-10), Si-Zn (compound 5
Weight 40-60), Si-Au (compound 6 weight ratio 20)
-80), Si-Ag-In (compound 7 weight ratio 40-
50-10), Si-Ge (compound 8 weight ratio 40-6)
0), Si-Ag-Sn (compound 9 at a weight ratio of 40-50)
-10), Si-Ag-Sb (compound 10 at a weight ratio of 40)
-50-10), silicon obtained by pulverizing silicon in which Li was eluted from metallurgically synthesized Li ₄ Si using isopropyl alcohol in argon gas (Compound 1).
1) mixing polycrystalline silicon and colloidal silica,
Si-SiO ₂ (compound 12 weight ratio 90-10) was obtained by heating a solid obtained by heating at 00 ° C. in a vibrating mill in an argon gas, and Si-Al ₂ obtained by the same method.
O ₃ (compound 13 weight ratio 90-10), compound plated on polycrystalline silicon surface by electroless plating method, Ag-plated Si (compound 14 Si-Ag weight ratio 40-
60), also Ni-plated silicon (compound 15 S
i-Ni weight ratio 20-80) was prepared. The average particle size of each of the negative electrode materials (compounds 1 to 15) used was in the range of 0.05 to 4 μm. 200 g of a powder obtained by mixing silicon and flaky natural graphite in a weight ratio of 40-60, and 10 g of polyvinylidene fluoride as a binder were added to carboxymethyl cellulose (C).
MC) was dispersed in 100 g of a 2% aqueous solution, and 600 g of the dispersion was mixed with the above powder, and the mixture was stirred and dispersed while slowly adding water until the viscosity of the resulting paste became suitable for coating. To prepare a coating solution.

Similarly, as a comparative compound, first, SnO was added to 6
7.4 g, and B ₂ O ₃ 17.4g, the Sn ₂ P ₂ O ₇ 10
2.8 g of the three types were mixed, sufficiently crushed in an automatic mortar, set in an alumina crucible, and placed in an argon gas atmosphere under an argon gas atmosphere.
Baking was performed at 00 ° C. for 10 hours. 100 ° C / 10 after firing
Quenched at a speed of 1 min, and a transparent glassy negative electrode material Sn
B _0.5 P _0.5 O ₃ was obtained. (This is referred to as Comparative Compound 1.) 200 g of a powder obtained by mixing Comparative Compound 1 and scaly natural graphite in a weight ratio of 40-60 in the same manner as described above, 10 g of vinylidene fluoride in 2% aqueous solution of carboxymethylcellulose (CMC) 1
Using a dispersion prepared by dispersing the dispersion in an amount of 00 g, 600 g of the dispersion was mixed with the above powder, and the mixture was stirred and dispersed while slowly adding water until the viscosity of the resulting paste became suitable for coating to prepare a coating liquid. did.

200 g of the positive electrode active material LiCoO ₂ and 10 g of acetylene black were mixed with a homogenizer, followed by 5 g of polyvinylidene fluoride as a binder.
-Methyl-2-pyrrolidone (500 ml) was added and kneaded and mixed to prepare a positive electrode mixture paste.

The positive electrode mixture paste prepared above was applied to both sides of a 30 μm-thick aluminum foil current collector with a blade coater, dried at 150 ° C., compression-molded with a roller press, cut into a predetermined size, and strip-shaped. A positive electrode sheet was prepared. Further, in a dry box (dew point; dry air having a temperature of -50 ° C. or lower), dehydration and drying were sufficiently performed with a far-infrared heater to prepare a positive electrode sheet. Similarly, paste the negative electrode mixture
m of the copper foil current collector, and a negative electrode sheet was prepared in the same manner as in the preparation of the positive electrode sheet. At this time, the coating amounts of the positive electrode and the negative electrode were changed according to Table 1, and the pairing of the positive electrode and the negative electrode was determined for each combination. The length of each electrode is
In accordance with the inner diameter of a cylindrical battery having a diameter of 18 mm and a maximum height of 65 mm, the volume ratio of the electrode group occupying the space inside the battery can was made the same for all the electrode groups. The amount of the positive electrode active material used and the negative electrode active material (Compounds 1 to 15 and Comparative Compound 1)
Was changed as shown in Table 1 based on the weight of the negative electrode.

Next, an electrolytic solution was prepared as follows. In an argon atmosphere, 65.3 g of diethyl carbonate was placed in a 200 cc narrow-neck polypropylene container, and the liquid temperature was reduced to 30%.
22.2 g of ethylene carbonate were dissolved in small portions, taking care not to exceed ℃. Next, 0.4 g of LiBF
₄ and 12.1 g of LiPF ₆ were sequentially dissolved in the above polypropylene container in small amounts, each being careful not to exceed a liquid temperature of 30 ° C. The obtained electrolyte was a colorless and transparent liquid having a specific gravity of 1.135. 18 pp water
m (measured with a Karl Fischer moisture meter, product name: MKC-210, manufactured by Kyoto Electronics Co., Ltd.), and the free acid content is 24 ppm (using bromthymol blue as an indicator, 0.1 N NaOH
Neutralization titration using an aqueous solution and measured).

A cylinder battery was prepared as follows. A method of manufacturing a battery will be described with reference to FIG. The positive electrode sheet, the microporous polyethylene film separator, the negative electrode sheet, and the separator prepared above were sequentially laminated, and the resultant was spirally wound. The wound electrode group (2) was housed in a nickel-plated iron bottomed cylindrical battery can (1) also serving as a negative electrode terminal, and an upper insulating plate (3) was further inserted. After injecting the electrolytic solution into the battery can, a positive electrode terminal (6), an insulating ring, a PTC element (63), a current interrupter (62), and a pressure-sensitive valve (61) are laminated on a gasket (5). ) To form a cylindrical battery.

The above cylindrical battery was set in a charging / discharging machine,
The charging voltage was determined in accordance with the battery voltage when the positive electrode potential in the electrode group filled in each battery was charged to an amount of electricity at which the potential with respect to lithium became 4.2 V, and charging was started at 1.5 A. In this case, the charging was performed at a constant current up to the predetermined voltage, and the charging current was controlled so that the voltage was kept constant until 2.5 hours had elapsed from the start of charging. Discharging was performed at a constant current up to 3.0 V with a 0.2 C current. This charge / discharge is 50
Iterative repetition was performed, and the maintenance ratio of the 50th discharge capacity to the discharge capacity at the time of the first discharge was calculated. The results are shown in Table 1.

(Table 1) Battery Negative electrode active material Positive electrode / negative electrode Initial capacity Discharge capacity Remark No. No. Weight ratio Retention 1 Compound 1 6.0 1800 mAh 75% Invention 2 Compound 2 6.0 1700 mAh 78% Invention 3 Compound 3 6.0 1900 mAh 79% Invention 4 Compound 4 6.0 1800 mAh 80% Invention 5 Compound 5 6.0 1700 mAh 77% Invention 6 Compound 1 20 2300 mAh 80% Invention 7 Compound 2 20 2250 mAh 82% Invention 8 Compound 3 20 2300 mAh 81% Invention 9 Compound 1 40 1820 mAh 77% Invention 10 Compound 2 40 1750 mAh 78% Invention 11 Compound 3 40 1850 mAh 77% Invention 12 Compound 160 60 1650 mAh 72% Invention 13 Compound 2 60 1680 mAh 71% Invention 14 Compound 3 60 1690 mAh 70% Invention 15 Compound 1 0.8 1200 mAh 54% Comparative Example 16 Compound 2 0.8 1000 mAh 52 Comparative Example 17 Compound 3 0.8 1000 mAh 50% Comparative Example 18 Comparative Compound 1 0.8 980 mAh 60% Comparative Example 19 Same as above 6.0 1200 mAh 90% Comparative Example 20 Same as above 20 1000 mAh 80% Comparative Example 21 Same as above 40 880 mAh 58% Compare Example 22 Compound 6 15 2100 mAh 82% Invention 23 Compound 7 15 2200 mAh 81% Invention 24 Compound 8 15 2300 mAh 83% Invention 25 Compound 9 15 2000 mAh 82% Invention 26 Compound 10 15 2100 mAh 83% Invention 27 Compound 11 15 2200 mAh 79% Invention 28 Compound 12 15 2000 mAh 80% Invention 29 Compound 13 15 1980 mAh 84% Invention 30 Compound 14 15 2000 mAh 81% Invention 31 Compound 15 15 2100 mAh 80% Invention

As is clear from Table 1, a sufficient battery capacity can be obtained only when the negative electrode material of the present invention is used and the charge and discharge are performed with the balance between the usage of the positive electrode and the negative electrode within the range of the present invention. It can be seen that good cyclability can be obtained while having.

Example 2 Compounds 1, 2, 3, 4, 11, 12, 14,
For No. 15, the active material in the negative electrode mixture and the flake graphite were such that the ratio of the weight of the positive electrode active material to the weight of the negative electrode active material and the ratio of the thickness of the positive electrode mixture to the thickness of the negative electrode mixture were as shown in Table 2. Or the amounts of the active material and acetylene black in the positive electrode mixture were changed. Otherwise, a cylinder battery was produced in the same manner as in Example 1. Table 2 shows the results.

(Table 2) Battery Negative electrode active material Positive electrode active material Negative electrode active material Thickness ratio Weight ratio Discharge capacity Remark No. Quality number Quality content Quality content Positive / negative Positive / negative Maintenance rate 1 Compound 1 90% 20% 1 5.5 3.8 79% Invention 2 Compound 2 90% 20% 1.5 3.8 80% Invention 3 Compound 3 90% 20% 1.6 3.8 80% Invention 4 Compound 1 90% 60% 2.3 7.0 83% Invention 5 Compound 2 90% 60% 2.4 7.0 83% Invention 6 Compound 3 90% 60% 2.3 7.0 82% Invention 7 Compound 1 90% 80 % 3.8 8.5 81% Invention 8 Compound 2 90% 80% 3.5 8.5 80% Invention 9 Compound 3 90% 80% 3.6 8.5 83% Invention 10 Compound 1 90% 0.8% 0.5 1.2 67% The present invention 11 Compound 2 90% 0.8% 1.4 1.3 68% The present invention 12 Compound 1 90% 93% 5.1 8.4 70% The present invention 13 Compound 2 90% 93% 5.1 8.4 70% The present invention 14 Compound 1 60% 60% 0.8 0.9 51% Comparative Example 15 Compound 1 60% 85% 0.8 0.8 50% Comparative Example 16 Compound 1 55% 85% 1.2 0.9 60% Comparative Example 17 Compound 1 75% 75 % 3.5 5.8 81% The present invention 18 compound 1 65% 75% 4.5 5.5 73% The present invention 19 Compound 1 75% 91% 5.5 6.6 70% The present invention 20 Compound 4 80% 60% 1.3 5.5 82% Invention 21 Compound 11 80% 60% 1.3 5.5 81% Invention 22 Compound 12 80% 60% 1.3 5.5 82% Invention 23 Compound 14 80 % 60% 1.3 5.5 80% The present invention 2 Compound 15 80% 60% 1.3 5.5 82% present invention

As can be seen from Table 2, good results are obtained according to the embodiments of the present invention. Particularly, a preferable result is obtained when the thickness of the positive electrode mixture layer is larger than the thickness of the negative electrode mixture layer. Further, it can be seen that more preferable results are obtained when the active material content in the positive electrode mixture and the active material content in the negative electrode mixture are in the ranges shown in claims 6 and 7 of the present invention.

Example 3 In the compounds 1 to 5 and the comparative compound 1 used in Example 1, the film thickness of the mixture applied to the current collector (18 μm thick) of the negative electrode was changed as shown in Table 3 A battery was prepared in the same manner as described above, and charged and discharged up to 50 cycles to calculate a capacity retention ratio. Table 3 shows the results. The thickness of the mixture is the total thickness of both surfaces of the current collector.

(Table 3) Battery Negative electrode active material mixture / copper foil Initial capacity Discharge capacity Remark No. No. Thickness ratio Retention 1 Compound 1 0.4 1750 mAh 77% Invention 2 Compound 2 0.4 1720 mAh 74% Invention 3 Compound 9 0.4 1710 mAh 75% Invention 4 Compound 1 2.0 1920 mAh 85% Invention 5 Compound 2 2.0 1950 mAh 86% Invention 6 Compound 9 2.0 1950 mAh 83% Invention 7 Compound 1 10 2100 mAh 84% The present invention 8 Compound 2 10 2200 mAh 84% The present invention 9 Compound 9 10 2000 mAh 83% The present invention 10 Compound 1 25 2500 mAh 75% The present invention 11 Compound 2 25 2300 mAh 73% The present invention 12 Compound 9 25 2300 mAh 72% The present invention 13 Compound 1 0.1 1000 mAh 71% invention 14 compound 2 0.1 1150 mAh 70% invention 15 compound 9 0.1 1100 mAh 70% invention

As can be seen from Table 3, according to the contents of claims 8 and 9 of the present invention, when the compound containing a silicon atom of the present invention is used as an active material, the capacity is increased. It can be seen that the result is higher than that of the comparative compound, and the cycle performance is specifically dependent on the results.

[0081]

According to the present invention, a non-aqueous secondary battery having a high capacity and an improved cycle life can be obtained.

[Brief description of the drawings]

FIG. 1 is a sectional view of a cylinder battery used in Examples.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Battery can also serve as a negative electrode 2 Wound electrode group 3 Upper insulating plate 4 Positive electrode lead 5 Gasket 6 Battery lid also serving as a positive electrode terminal 61 Pressure sensitive valve element 62 Current cutoff element (switch) 63 PTC element

 ──────────────────────────────────────────────────続 き Continued on the front page F-term (reference)

Claims (9)

[Claims] In a non-aqueous secondary battery comprising an electrode sheet containing a positive electrode active material, an electrode sheet containing a negative electrode active material, and a non-aqueous electrolyte, the positive electrode active material is a lithium-containing transition metal oxide. The negative electrode active material is a compound containing a silicon atom capable of inserting and releasing lithium, and the total weight of the positive electrode active material contained in the nonaqueous secondary battery is larger than the total weight of the negative electrode active material. Non-aqueous secondary battery characterized by the following. 2. The non-aqueous non-aqueous battery according to claim 1, wherein the total weight of the positive electrode active material contained in the non-aqueous secondary battery is at least twice and at most 50 times the total weight of the negative electrode material. Rechargeable battery. 3. The non-aqueous secondary battery according to claim 1, wherein the total weight of the positive electrode active material contained in the non-aqueous secondary battery is 4 to 30 times the total weight of the negative electrode active material. Water secondary battery. 4. The electrode sheet, wherein a metal foil is used as a current collector and a mixture containing the positive electrode active material or the negative electrode active material is coated on both surfaces thereof, and the positive electrode of the electrode sheet is The non-aqueous secondary battery according to claim 1, wherein the film thickness of the mixture portion is larger than the thickness of the mixture portion of the negative electrode. 5. The non-aqueous secondary battery according to claim 1, wherein the thickness of the mixture portion of the positive electrode sheet is 1.2 to 5 times the thickness of the mixture portion of the negative electrode sheet. . 6. The content of the positive electrode active material in the positive electrode mixture is 60% by weight or more and 99% by weight or less, and the content of the negative electrode active material in the negative electrode mixture is 1% by weight or more and 90% by weight or less. The non-aqueous secondary battery according to claim 2, wherein: 7. The content of the positive electrode active material in the positive electrode mixture is 70% by weight or more and 98% by weight or less, and the content of the negative electrode active material in the negative electrode mixture is 8% by weight or more and 80% by weight or less. The non-aqueous secondary battery according to claim 2, wherein: 8. The non-aqueous secondary battery according to claim 1, wherein the thickness of the negative electrode mixture is 0.2 to 20 times the thickness of the negative electrode current collector in the negative electrode sheet. 9. The non-aqueous secondary battery according to claim 1, wherein the thickness of the negative electrode mixture is at least 0.5 and at most 10 times the thickness of the negative electrode current collector in the negative electrode sheet.