JPH11354118A - Nonaqueous secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve cycle life, by using, as a negative electrode material, a compound including silicon atoms which Li can be inserted into or discharged from, and, as a positive electrode active material, a Li-containing transition metal composite oxide including a fixed metal, having an α-NaFeO2 type layered structure, and having specified contents of alkaline earth metal elements and sulfur. SOLUTION: For a negative electrode material, simple silicon, a silicon alloy, or a silicide is used as a compound which Li can be inserted into or discharged from. For a positive electrode active material, a Li-containing transition metal composite oxide including metal of one kind or more selected from Co, Ni, Mn, and Fe, and having a layered structure of LiMnO4 oxide of a spinel structure of an α-NaFeO2 type or an A[B2 ]O4 type, and impurities getting mixed in the positive electrode active material are specified to have an alkaline earth metal element content of 0.1 wt.% or less, a sulfur content of 0.1 wt.% or less, and a percentage water content of about 0.5 or less.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a nonaqueous lithium secondary battery having a high capacity and a long cycle life, using a silicon compound for a negative electrode.

[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. on the other hand,
It is well known that the theoretical capacity of silicon, which forms an intermetallic compound with lithium, exceeds 4000 mAh / g and is larger than that of carbon. For example, JP-A-5-7446
No. 3 discloses single-crystal silicon.
9602 discloses amorphous silicon. In the case of alloys containing silicon, examples of the Li-Al alloy containing silicon are described in JP-A-63-66369 (19% by weight of silicon) and JP-A-63-174275 (silicon is 0.05 to 1.0%).
0% by weight) and 63-285865 (1 to 5% by weight of silicon). 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, silicon is 0.05%.
~ 1.0 wt% alloy is disclosed. JP-A-62-2
226563 discloses a method of mixing a graphite powder with a metal that can be alloyed with lithium. 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. In addition, general-purpose 4V
Lithium-ion secondary battery positive electrode active material is Li
CoO ₂ , LiCo _1-x Ni _x O ₂ , LiNiO ₂ , L
iNi _1-x M _x O ₂ , LiMn ₂ O ₄ , LiMn _2-x M
_x O ₄ (M is one or more metal cations) capable layered compound typified by Li inserted released to the like are used. Among them, LiCoO ₂ disclosed in Japanese Patent Application Laid-Open No. 55-136131 is particularly effective at 3.5 Vvs. It is quickly commercialized in that it provides a high charge / discharge potential equal to or higher than Li and has a long cycle life. On the other hand, the development of secondary batteries using Mn or Ni instead of Co, which has a limited resource supply and is expensive, has been activated. As disclosed in Japanese Unexamined Patent Publications Nos. 6-096969 and 6-276739, Ni-based oxide secondary batteries are characterized by having a higher current capacity than Co-based batteries. In addition, the Mn-based oxide has the features that it is the cheapest of the three metal oxides, and that it has a high average voltage and is excellent in safety. However, since these Ni-based and Mn-based active materials are electrochemically unstable in crystal structure as compared with LiCoO ₂ due to the generation of Jan-Teller distortion, it is practical that the charge / discharge cycle life is inferior. This is a major challenge for the future. In particular, in the case of Ni, since the reduced Ni trivalent is more stable than Co,
In the case of Li _x NiO ₂ (x ≦ 1), the oxidation-reduction potential is low, and the capacity is remarkably deteriorated in a charge repetition cycle exceeding 4 V where the average charge of Ni approaches tetravalent. Therefore, as disclosed in JP-A-63-212565, JP-A-5-242891, and JP-A-8-213015, Co is added to Ni.
A method of stabilizing cycle life and increasing potential by adding other metal cations is generally used. Mn
In addition, in addition to the occurrence of Yang-Teller distortion on the discharge side having a high Li content, the elution of Mn trivalent occurs on the charge side, which deteriorates the cycleability.
In the same manner as described above, a method of stabilizing the cycle life and increasing the potential by adding Co and other metal cations is used. However, even if these metal-doped positive electrode active materials have the same charge composition ratio, the cycle performance and storage stability may fluctuate due to differences in the purity of synthesis raw materials including the raw material of the doping element (D) and the purification conditions. However, there is a need for technology construction for stabilizing performance including control of the purity of the positive electrode active material.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to increase the amount of energy of a lithium secondary battery and to stably maintain charge / discharge characteristics including cycle life.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a positive electrode having a positive electrode active material, a negative electrode having a negative electrode material, and a non-aqueous secondary battery comprising a non-aqueous electrolyte. Wherein the positive electrode active material contains at least one metal selected from Co, Ni, Mn, and Fe and has a lithium content of an α-NaFeO ₂ type or spinel type layered structure. A transition metal composite oxide, wherein the content of the alkaline earth element in the positive electrode composite oxide is 0.1% by weight or less and the content of sulfur is 0.1% by weight or less.
The problem was solved by using a non-aqueous secondary battery characterized by being 1% by weight or less.

[0005]

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) Non-aqueous secondary battery, in a non-aqueous secondary battery comprising a positive electrode having a positive electrode active material, a negative electrode having a negative electrode material and a non-aqueous electrolyte, the negative electrode material can insert and release lithium A compound containing a silicon atom, wherein the positive electrode active material is C
a lithium-containing transition metal composite oxide containing at least one metal selected from the group consisting of o, Ni, Mn, and Fe and having a layered structure of α-NaFeO ₂ (also called rock salt type) or spinel type; The content of alkaline earth element in the oxide is 0.1% by weight or less, and the content of sulfur is 0.1% by weight.
1% by weight or less. (2) The average particle size of the silicon compound in the item (1) is 0.01.
５０50 μm. (3) The silicon compound of item (1) is an alloy. (4) In the alloy of the item (3), at least one kind of metal other than silicon is an alkaline earth metal, a transition metal, or a metalloid. (5) At least one of the metals of paragraphs (3) and (4) is Ge, B
e, Ag, Al, Au, Cd, Ga, In, Sb, S
n and Zn. (6) The weight ratio of the metal to silicon in the items (3) to (5) is 5
~ 90%. (7) The silicon compound of the item (1) is silicon obtained by removing a metal from a metal silicide. (8) The metal silicide of the item (7) is a lithium silicide. (9) The lithium content of the lithium silicide of the item (8) is 100 to 420 atomic% with respect to silicon. (10) The silicon compound of the item (1) is attached to a ceramic that does not react with lithium. (11) The ceramic of item (10) is made of Al ₂ O ₃ , SiO ₂ , Ti
At least one selected from O ₂ , SiC, and Si ₃ N ₄ . (12) The weight ratio of the ceramic to the silicon compound of the items (10) and (11) is 2 to 50%. (13) The method for attaching the ceramic to the silicon compound according to any one of the above items (10) to (12), comprising a step of heating to 300 to 1300 ° C. (14) The silicon compound of the item (1) is coated with at least a metal. (15) The method of coating with the metal of paragraph (14) is an electroless plating method,
These are a vapor deposition method, a sputtering method, and a chemical vapor deposition method. (16) At least one of the metals to be coated according to items (14) and (15) is Ni, Cu, Ag, Co, Fe, Cr, W, Ti, A
u, Pt, Pd, Sn, and Zn. (17) The specific conductivity of the silicon compound coated with the metal of the items (14) to (16) is one of the specific conductivity of the uncoated silicon compound.
0 times or more. (18) The silicon compound of the item (1) is previously coated with a thermoplastic resin. (19) The thermoplastic resin of the item (18) is polyvinylidene fluoride or polytetrafluoroethylene.

(20) The weight ratio of the thermoplastic resin to the silicon compound in the items (18) and (19) is 2 to 30%. (21) The covering ratio of the thermoplastic resin of the items (18) to (20) is 5 to 100.
%. (22) 5 to 5 weight ratio of carbon to the silicon compound of (1).
1900% coexist. The carbon of the item (23) (22) is flaky natural graphite. In the charge / discharge range of the silicon compound of the item (24) (1), x is in the range of 0 to 4.2 in terms of LixSi as an equivalent ratio of lithium inserted into and released from silicon. (25) The charge / discharge range of the silicon compound of the item (1) is LixSi
X is in the range from 0 to 3.7. (26) The positive electrode active material of the item (1) is an α-NaFeO ₂ type layered compound containing at least one metal selected from Co, Ni, and Fe as a main component, preferably Li _x Ni _1-y D _y O
_ba X _a (D is Mn, Cr, Fe, Co, Cu, Zn,
Mo, Ag, W, B, Al, Ga, In, Sn, Pb,
One or more elements selected from Sb and P, X is a halogen element, and 0.2 <x ≦ 1.2, 0.1 ≦ y ≦ 0.5,
It is a lithium-containing nickel composite oxide represented by the following composition: 1.8 ≦ b ≦ 2.3, 0 ≦ a ≦ 1.0). (27) The positive electrode active material of claim (1) _{Li x Mn 2-y D y} O ba X
_a (D is Cr, Fe, Co, Cu, Zn, Mo, Ag,
One or more elements selected from W, B, Al, Ga, In, Sn, Pb, Sb, and P, X is a halogen element,
0.05 <x ≦ 1.2, 0 ≦ y ≦ 0.5, 3.5 ≦ b ≦
This is a spinel-structured lithium-containing manganese composite oxide having a composition of 4.5, 0 ≦ a ≦ 1.0.

(28) The content of the alkaline earth element in the lithium-containing composite oxide of the positive electrode is 0.04% by weight or less, and the content of sulfur is 0.04% by weight or less. (29) The water content in the lithium-containing composite oxide of the positive electrode is 0.5
% By weight or less. (30) The content of the alkaline earth element in the lithium-containing composite oxide of the positive electrode is 0.02% by weight or less, and the content of sulfur is 0.1% or less.
Not more than 02% by weight. (31) the water content in the lithium-containing composite oxide of the positive electrode is 0.2
% By weight or less. The average particle size of silicon used in the item (32) (3) to (25) is 0.01 to 50 μm. The silicon referred to here is a simple substance of silicon, a silicon alloy, or a silicide that can react with lithium. (33) The ceramics of (7) to (13) are adhered to the alloy of (3) to (6). (34) The alloys of (3) to (6) are coated with the metals of (14) to (17). (35) The material of item (33) is coated with the metal of items (14) to (17). (36) The alloy of (3) to (6) is coated with the thermoplastic resin of (18) to (21). (37) The materials of (33) to (35) are coated with the thermoplastic resin of (18) to (21). (38) The carbon of items (22) and (23) is allowed to coexist in the alloy of items (3) to (6). (39) The carbon of items (22) and (23) coexists in the material of items (33) to (37).

(40) The alloys of items (3) to (6) are used in the charge and discharge ranges of items (24) and (25). Used in the charge / discharge range of (25). (42) The compound of item (26) is used as the positive electrode active material of the alloy negative electrode of items (3) to (6). (43) The compound of item (26) is used as the positive electrode active material of the materials of items (33) to (39). (44) The ceramic of items (7) to (13) is adhered to the silicon of items (7) to (9). (45) The metal of items (14) to (17) is coated on the silicon of items (7) to (9). (46) The material of item (39) is coated with the metal of items (14) to (17). (47) The silicon of items (7) to (9) is coated with the thermoplastic resin of items (18) to (21). (48) The materials of (44) to (46) are coated with the thermoplastic resin of (18) to (21). (49) The carbon of items (22) and (23) is allowed to coexist with the silicon of items (7) to (9). (50) The carbon of items (22) and (23) coexists in the material of items (44) to (48). (51) The silicon of items (7) to (9) is used in the charge / discharge range of items (24) and (25). (52) The materials of (44) to (50) are used in the charge and discharge ranges of (24) and (25). (53) Item (26) as the positive electrode active material of the silicon negative electrode of items (7) to (9)
Is used. (54) The compound of item (26) is used as the positive electrode active material of the negative electrode of items (44) to (50). (55) The silicon compound of (10) to (13) is coated with the metal of (14) to (17). (56) The silicon compound of (10) to (13) is coated with the thermoplastic resin of (18) to (21). (57) The material of item (50) is coated with the thermoplastic resin of items (18) to (21). (58) The carbons of (22) and (23) coexist in the silicon compound of (10) to (13). (59) The carbon of items (22) and (23) coexists in the material of items (55) to (57).

(60) The silicon compound of item (10) to item (13)
Used in the charge / discharge range of 4) and (25). (61) The materials of items (55) to (57) are used in the charge / discharge range of items (24) and (25). (62) The compound of item (26) is used as the positive electrode active material of the silicon compound negative electrode of items (10) to (13). (63) Item (55)-(57)
Is used. (64) The ceramics of (7) to (13) are adhered to the materials of (14) to (17). (65) The materials of (14) to (17) are coated with the thermoplastic resin of (18) to (21). (66) The material of item (64) is coated with the thermoplastic resin of items (18) to (21). (67) The carbon of items (22) and (23) coexists in the materials of items (14) to (17) and (64) to (66). (68) The materials of (14) to (17) and (64) to (67) are used in the charge and discharge ranges of (24) and (25). (69) The compound of item (26) is used as the positive electrode active material of the negative electrode of the materials of items (14) to (17) and (64) to (67).

(70) The ceramics of (7) to (13) are adhered to the materials of (18) to (21). (71) The materials of (18) to (21) and (70) are coated with the metal of (14) to (17). (72) The carbon of items (22) and (23) coexist in the materials of items (18) to (21), (70) and (71). (73) The materials of paragraphs (18) to (21) and (70) to (71) are used in the charge and discharge ranges of paragraphs (24) and (25). (74) The compound of item (26) is used as the positive electrode active material of the negative electrode of the materials of items (18) to (21) and (70) to (71). (75) The compound of item (26) is used as the positive electrode active material of the negative electrode of items (22) and (23).

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 simple substance is preferably 85% by weight or more,
It is preferably at least 5% by weight. Furthermore, 99% by weight or more is particularly preferable. Its average particle size is 0.01-50 μm
Is preferred. In particular, 0.02 to 30 μm is preferable. Further, the thickness is preferably 0.05 to 5 μm.

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. Especially,
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 a porous fine particle having a particle size of 1 μm or less and a fine silicon particle formed by agglomeration of fine particles to form a porous secondary particle. 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. Especially,
200 to 420 are preferred. A method for 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 treating with 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 ,
SiC 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 dispersing and mixing Al ₂ O ₃ or SiO ₂ sol and silicon, the mixture is heated, and the solid solution is pulverized to form silicon and Al.
Deposits of ₂ O ₃ and SiO ₂ can be obtained. In this case, the deposit of Al ₂ O ₃ or SiO ₂ means Al ₂ O ₃ or Si ₂
The surface of O ₂ or the like is covered with silicon powder, or Al ₂ O ₃
Or it is confined to the inside of and SiO ₂ or the like of the masses,
The state where the silicon surface is covered with them. Mixing and dispersion can be achieved by mechanical stirring, ultrasonic waves, and kneading. Heating is preferably performed in an inert gas at a temperature in the range of 300 ° C to 1300 ° C.
0 ° C. is preferred. 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 determined from electron microscopic observation of silicon is 0.01 to 40 μm
Is preferred. In particular, it is preferably from 0.03 to 5 μm.

The metal coating of the silicon compound of the present invention may be performed by electroplating, displacement plating, electroless plating, resistance heating evaporation, electron beam evaporation, cluster ion evaporation, etc., sputtering, chemical vapor deposition, etc. 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 preferred.
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 agent is preferably a phosphinate, phosphonate, borohydride, aldehyde, saccharide, amine, or metal salt. Sodium hydrogen phosphinate,
Sodium hydrogen phosphonate, sodium borohydride,
Dimethylamine borane, formaldehyde, sucrose, dextrin, hydroxylamine, hydrazine, ascorbic acid, and titanium chloride are preferred. 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,
0 ° C to 95 ° C is preferred. In addition to the plating bath, SnCl ₂
An activation bath composed of an aqueous hydrochloric acid solution and a nucleation bath composed of an aqueous PdCl ₂ hydrochloric acid solution are used. Further, 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 water-soluble polymers such as polyacrylic acid, sodium polyacrylate, polyvinylphenol, polyvinylmethylether, polyvinyl alcohol, polyvinylpyrrolidone, polyacrylamide, polyhydroxy (meth) acrylate, and styrene-maleic acid copolymer; Polyvinyl chloride, polytetrafluoroethylene, polyvinylidene fluoride, tetrafluoroethylene-hexafluoropropylene copolymer, vinylidene fluoride-tetrafluoroethylene-hexafluoropropylene copolymer, polyethylene, polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, polyvinyl acetal resin, (meth) acrylates such as methyl methacrylate and 2-ethylhexyl acrylate. To (meth) acrylic acid ester copolymer,
(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, carbon black such as acetylene black, furnace black, ketjen black, channel black, lamp black, and thermal black, 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 anode material is determined by the ratio of lithium and silicon atoms that can be inserted and released by Lix
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 around 0.5 V (body lithium metal) is obtained 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 improved is also found.

Although the method having the effect of improving the cycle life while maintaining the high capacity of the silicon compound has been individually described, a more preferred embodiment is that a further improvement effect is obtained by combining the above methods. I found something to gain. In the present invention, as the negative electrode material, a compound capable of inserting and releasing lithium such as carbonaceous material, oxide material, nitride material, sulfide material, lithium metal, and lithium alloy with respect to the silicon compound of the present invention. Can be combined.

The cathode material used in the present invention is Co, N
α- containing at least one metal selected from i, Mn, and Fe
NaFeO_TwoLayered structure or spinel type layered structure
It is a transition metal composite oxide containing lithium. This
Among them, the preferred composition of the positive electrode active material is Li_xM_1-yD
_yO_baX_a(M is Ni or Co, D is M
n, Cr, Fe, Co, Cu, Zn, Mo, Ag, W,
Selected from B, Al, Ga, In, Sn, Pb, Sb, P
One or more elements, X is a halogen element;
<X ≦ 1.2, 0 ≦ y ≦ 0.5, 1.8 ≦ b ≦ 2.3,
Lithium-containing cobalt having a composition of 0 ≦ a ≦ 1.0)
Composite oxide or lithium-containing nickel composite oxide
It is. Among them, particularly preferred is Li_xNi
_1-yD_yO_{b- a}X_a(D is Mn, Cr, Fe, Co, C
u, Zn, Mo, Ag, W, B, Al, Ga, In, S
X is one or more elements selected from n, Pb, Sb, and P;
A halogen element, 0.2 <x ≦ 1.2, 0.1 ≦ y
≤0.5, 1.8≤b≤2.3, 0≤a≤1.0)
This is a lithium-containing nickel composite oxide shown in FIG.
Further, another preferred composition of the positive electrode active material is Li_xMn
_2-yD_yO_baX_a(D is Cr, Fe, Co, Cu, Z
n, Mo, Ag, W, B, Al, Ga, In, Sn, P
X is one or more elements selected from b, Sb, and P;
Element, and 0.05 <x ≦ 1.2, 0 ≦ y ≦ 0.
5, 3.5 ≦ b ≦ 4.5, 0 ≦ a ≦ 1.0)
Lithium-containing manganese composite oxidation with spinel structure
Things. In the above general formula of the positive electrode active material, D represents a central metal.
Of transition elements (Co, Ni, Mn) or part of Li
One or more metal or metalloid elements to be substituted
Increase in the average discharge voltage or cycle
Factors that contribute to improved battery performance, such as improved battery life
You. Specific examples of the positive electrode active material include Li_xCoO_Two, L
i_xNiO_Two, Li_xMnO_Two, Li_xCo_1-yNi_y
O_Two, Li_xCo_1-yV_yO_z, Li_xCo_1-yFe_y
O_Two, Li_xMn_TwoO_Four, Li_xMn_2-yCo_yO_Four,
Li_xMn_2-yNi _yO_Four, Li_xMn_2-yV_yO_Four,
Li_xMn_2-yFe_yO_Four(Where x = 0.2-1.
2, y = 0.1 to 0.9, z = 2.01 to 2.3), etc.
Is raised. Examples of particularly preferred compositions include L
i_xNi_1-yCo_yO_Two, Li_xNi_{1- y}Al_yO_Two,
Li_xNi_1-yCo_yO_2-bF_b, Li_xNi_1-yB_y
O_Two, Li_xMn_TwoO_Four, Li_xMn_2-yAl_yO_Four,
Li_xMn_2-yCo_yO_Four, Li _xMn_2-yFe_yO_Four
(X = 0.2-1.2, y = 0.1-0.3, b = 0-
0.3). Here, the value of x is
Value, which increases and decreases beyond the above range by charging and discharging.

Next, each of Ni-based oxides and Mn-based oxides which are preferably used as a positive electrode active material will be described. A preferred composition of the Ni oxide-based positive electrode active material is
Represented by _{Li x Ni 1-y D y} O ba X a. Where D
Is usually one or more elements selected from Group 13 and Group 14 elements and transition metal elements of the periodic table, and preferably D is Co, Cr, Fe, Cu, Zn, M
o, Ag, W, B, Al, Ga, In, Sn, Pb, S
At least one element selected from b and P. X is a halogen element. The amount of these elements in the composition is 0.2 <
x ≦ 1.2, 0.1 ≦ y ≦ 0.5, 1.8 ≦ b ≦ 2.
3, 0 ≦ a ≦ 1.0. One of the preferred compositions is Li _x Ni _{1 -y My} O _b (M is Mn,
Cr, Fe, Co, Cu, Zn, Mo, Ag, W, B,
One or more elements selected from Al, Ga, In, Sn, Pb, Sb, and P, 0.2 <x ≦ 1.2, 0.1 ≦ y ≦
0.5, 1.8 ≦ b ≦ 2.3). Further, another preferable composition of the Ni oxide-based positive electrode active material is a composition in which X is substituted with fluorine, and Li _x Ni _{1- y My}
O _ba F _a (M is Mn, Cr, Fe, Co, Cu, Z
n, Mo, Ag, W, B, Al, Ga, In, Sn, P
at least one element selected from b, Sb, and P, 0.2 <x
≦ 1.2, 0.1 ≦ y ≦ 0.5, 1.8 ≦ b ≦ 2.3,
0 <a ≦ 1.0). Particularly preferred as the composition of the positive electrode active material of the present invention is a structure containing M, which is effective for improving the discharge potential as M, and further containing a group M of elements, which are effective as structural reinforcing elements,
_{Li x Ni 1-yz Co y} M z O ba F a (M is, Mn,
Cr, Fe, Cu, Zn, Mo, Ag, W, B, Al,
One or more elements selected from Ga, In, Sn, Pb, Sb and P, 0.2 <x ≦ 1.2, 0.05 ≦ y ≦ 0.
5, 0.01 ≦ z ≦ 0.3, 0 ≦ a ≦ 1.0, 1.8 ≦
It is a nickel-containing lithium composite oxide represented by the composition of b ≦ 2.3).

Mn-based positive electrode active material Preferred as a positive electrode active material
The new thing is A [B_Two O_Four Li with spinel structure
Mn_Two O_Four It is a system oxide. The oxides of this system include LiM
n_TwoO_FourBesides the general formula Li_{1 + x}[Mn_2-y]
O_Four (0 <x <1.7, 0 ≦ y <0.7)
Compounds with non-stoichiometric compositions and defects
included. An example of this is Li_Four Mn_Five O₁₂Or
In the spinel structure display, Li [Li_1/3Mn_5/3O_Four Is raised
I can do it. Other preferred examples include those of the general formula Li _1-x[M
n_2-yO_Four (0 <x <1.0, 0 ≦ y <0.5)
Is done. An example of this is disclosed in, for example, Japanese Patent Application Laid-Open No. Hei 4-2401.
Non-stoichiometric spinel compound shown in 17
Li_Two Mn_Five O₁₁Or Li in spinel structure display_1-x
[Mn_{2- y}O_Four (X = 0.273, y = 0.182)
Is mentioned. Another preferred structure has the general formula Li
_1-x[Mn_2-yO_Four(0 <x ≦ 0.20, 0 <y <
0.4), for example, Li_Two Mn_Four O₉ But
It is. As with Ni-based oxides, the purpose of improving cycle performance
And other metals or semi-metallic cations other than Mn
A Mn-based composite oxide having a solid solution composition is also preferable. Other origin
The element is a trivalent metal element such as Co, Al, Cr, Fe, etc.
Is most preferred, and examples of active material compositions containing these are disclosed in
9-245896.

The other metal element-added type LiNiO ₂ or LiMn ₂ O ₄ is a compound (oxide or oxide) containing various metals to be added in addition to the compound as the Ni or Mn raw material and the Li compound as the Li raw material. Salt) as a raw material, and is synthesized by heat treatment. However, since various metal compounds are used, it is generally difficult to produce a final active material with high purity, and Na, derived from these metal compound raw materials, K, Mg, Ca, Al, sulfur, Cu, F
Different elements such as e and Si are likely to be mixed into the positive electrode active material as impurities. These impurities may cause deterioration of the cycle life of the battery and deterioration of the high-temperature storage property due to the effect of elution into the non-aqueous electrolyte during charge and discharge. Therefore, it is preferable to reduce these impurities to a certain level or less in order to stabilize performance.

The present inventor has found that, among the above-mentioned impurity elements, in particular, alkaline earth metals and sulfur, it is possible to improve the storage characteristics of the battery by limiting the level of contamination to within a specified amount. did. That is,
In the active material containing these elements as impurities simultaneously, for example, there is a problem that the acidity is locally reduced on the surface of the active material in contact with the electrolyte, and the metal element is eluted into the electrolyte to cause a change in the performance of the positive electrode or the negative electrode. Occurs. This phenomenon poses a serious problem particularly in a situation where water is present in the active material or the electrolytic solution, because the acidity is accelerated to decrease. Specifically, the content of the alkaline earth element in the positive electrode active material is 0.1%.
It is effective to improve storage characteristics and cycle life when the content is not more than 0.5% by weight, the content of sulfur is not more than 0.1% by weight, and the water content is not more than 0.5. Effective contents for improving performance include an alkaline earth element content of 0.04% by weight or less, a sulfur content of 0.04% by weight or less, and a water content of 0.2% by weight or less. Further, the content of the alkaline earth element is set to 0.1.
02% by weight or less, sulfur content is 0.02% by weight or less,
The effect is greater when the water content is 0.1% by weight or less. Most preferably, the content of alkaline earth element is 0.1.
The conditions are as follows: 02% by weight or less, sulfur content by weight of 80 ppm or less (0.008% or less), and water content of 0.1% by weight or less.

Among the alkaline earth elements referred to in the present invention, those whose content management is important for improving battery performance include magnesium (Mg), calcium (Ca), strontium (Sr), and barium (Ba). Among them, magnesium (Mg), calcium (Ca), and barium (Ba) are particularly important, and calcium (Ca) is particularly important.

In addition, sulfur is often mixed as an impurity from a sulfate group (SO ₄ ) or the like contained in the raw material for firing, and its content of 0.1% or less is effective for improving storage stability. Preferably, the effect is large when the content is preferably 0.04% or less, more preferably 0.02% or less. The most effective improvement in performance is when the sulfur content is 80 ppm or less.

The synthesis of the composite oxide for a positive electrode of the present invention is carried out by
Lithium compound, which is a raw material of titanium, and Co, Ni or
Is a metal compound which is a raw material of Mn and, if necessary, B,
Typified by Al, Cr, Sn, Si, Fe, Ti, etc.
Mixing compound containing other element D
Powder sintering, or sol-gel method
It is performed by a chemical reaction in a liquid state. Lithium raw material
LiOH, Li_Two CO_Three , Li_Two O, LiN
O_Three , Li_Two SO_Four , LiHCO_Three , Li (CH_Three CO
O), alkyl lithium, etc. are used as Ni raw materials
Is NiO, NiCO_Three , Ni (NO_Three )_Two , Ni powder
Powder, NiCl_Two , NiSO_Four , Ni_Three (PO_Four )_Two , N
i (CH_Three COO)_Two , Ni (OH)_Two, NiOOH,
Ni alkoxide and the like are useful. In addition, the other element M
As a raw material, Co_Two O_Three , Co_Three O_Four , CoCO_Three ,
Co (NO_Three )_Two , CoCl_Two , MnCO_Three , MnO
_Two , Mn (NO)_Three , B_Two O_Three , B (OH)_Three , Al_Two 
O_Three , Al (NO_Three )_Three , Al (OH)_Three , SnO_Two ,
SnO, SnCl_Two, Sn alkoxide, SiO_Two , S
iO, alkoxysilane, Fe_Two O_Three , FeCl_Three , F
eOOH, Fe (NO_Three )_Three , TiO_Two , GeO_Two , Z
rO_Two , Nd _Two O_Three , La_Two O_Three , La_Two O_Three , Zn
(NO_Three )_Two , WO_Three , Ga (NO_Three ) _Two , CuO, V
_Two O_Five , Sm_Two O_Three , Y_Two O_Three , AlF_Three , LiF, L
aF_Three , SnF_Two , Li_Three PO_Four , AlPO_Four Use
Can be. Mixing of these raw materials
The raw materials may be mixed as they are, or multiple raw materials may be dissolved in a solvent and mixed.
Into a solid solution and mix it as a dry solid or slurry.
Good as a compound. When synthesizing by firing,
The powder or slurry mixture of the raw materials of
From 1000 to 1000 ° C, preferably from 600 to 900 ° C
In the presence of oxygen or an oxygen partial pressure of 0.2 atm or more
Or in an atmosphere with an oxygen partial pressure of 0.5 or more, from 4 hours
The synthesis is carried out by reacting for 48 hours. Firing as required
It is repeated a plurality of times under the same or different conditions.
The raw material mixture was previously filled into pellets and molded.
May be used. The firing method is described in, for example,
-264560, JP-A-2-40861, 6-267
538, 6-231767, JP-A-6-231767,
4-4-23953, 5-325966, 6-20
3834, a solution mixing method described in JP-A-63-21156.
5. Synthesis method by coprecipitation described in JP-A-5-19830
1. Those who quench the fired product described in 5-2055741
Method described in JP-A-5-283076 and JP-A-6-310145.
Baking method by pellet molding described in JP-A-5-3259
Firing in the molten state using the LiOH hydrate described in 69 as a raw material
Oxygen partial pressure control described in JP-A-6-60887
The method described in JP-A-6-243871
Fluorine doping method, particles described in JP-A-8-138670
For synthesizing active materials with different internal and surface compositions
Is valid.

In the case of Ni oxide or Mn oxide, it is preferable that the particles of the positive electrode active material have the shape of secondary particles formed by agglomeration of primary particles from the viewpoint of improving cycle life and storage stability. The preferred particle size at this time is such that the particle size of the secondary particles is 1 to 30 μm and the particle size of the primary particles is 0.01 to 1 μm.
μm or less, and more preferably the secondary particles have a particle size of 3
２０20 μm, and the particle size of the primary particles is 0.05-0.5 μm. Here, the secondary particles mean particles formed by agglomeration of fine primary particles, and usually correspond to a particle size measured by a laser scattering type particle size distribution measurement or the like, and correspond to a normally defined particle size. As for the shape of the particles, it is particularly preferable that the secondary particles are spherical. The surface of the secondary particles is preferably porous.

The specific surface area of the positive electrode active material corresponds to the above particle morphology, and is from 0.1 to 10 m ² / g as measured by the BET method.
, And more preferably 0.3 to ³ m ² / g.

The positive electrode active material particles used in the present invention may be crystalline or may have an amorphous structure inside or on the surface of the particles, but are preferably crystalline.

The conductive agent used in the mixture of the present invention may be any conductive material which does not cause a chemical change in the battery constructed. Specific examples include flake graphite, flake graphite, natural graphite such as earthy 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, and 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 polyacrylic acid Na, 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, those having an average particle size of 0.01 to 5 μm are more preferably used, and those having an average particle size of 0.05 to 1 μm are particularly preferable. 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 the binder added is preferably 1 to 30% by weight, particularly preferably 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.

The current collector that can be used in the present invention has a positive electrode made of aluminum, stainless steel, nickel, titanium, or an alloy thereof, and a negative electrode made of copper, stainless steel, nickel, or the like.
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. 7 μm to 100 μm as foil thickness
Is preferably, more preferably 7 μm to 50 μm, and particularly preferably 7 μm to 20 μm. Expanded metal, punching metal, wire mesh thickness is 7
μm to 200 μm, more preferably 7 μm
To 150 μm, particularly preferably 7 μm to 100 μm.
m. 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.

Next, the structure of the positive and negative electrodes according to 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.

Preferably, the protective layer is on both the positive and negative electrodes or on either the positive or negative electrode. In the negative electrode, when lithium is inserted into the negative electrode material in the battery, the negative electrode preferably has a form having a protective layer. The protective layer is composed of at least one layer, and may be composed of a plurality of layers of the same type or different types. Further, the current collector may have a form in which the protective layer is provided only on one side of the mixture layer on both sides. These protective layers are composed of water-insoluble particles, a binder and the like. As the binder, the binder used when forming the above-mentioned electrode mixture can be used. As the water-insoluble particles, various kinds of conductive particles, organic and inorganic particles having substantially no conductivity can be used. The solubility of the water-insoluble particles in water is 100 ppm or less, and preferably the insoluble particles are insoluble. 2.5% by weight of particles contained in the protective layer
Not less than 96% by weight, preferably not less than 5% by weight and 95% by weight.
% By weight or less, more preferably 10% by weight or more and 93% by weight or less.

Examples of the water-insoluble conductive particles include metals, metal oxides, metal fibers, carbon fibers, and carbon particles such as carbon black and graphite. Among these water-insoluble conductive particles, those having low reactivity with alkali metals, particularly lithium, are preferable, and metal powder and carbon particles are more preferable. The electric resistivity at 20 ° C. of the elements constituting the particles is preferably 5 × 10 ⁹ Ω · m or less.

As the metal powder, a metal having low reactivity with lithium, that is, a metal which is unlikely to form a lithium alloy is preferable, and specifically, copper, nickel, iron, chromium, molybdenum, titanium, tungsten, and tantalum are preferable. 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 preferably 0.02 μm or more and 20 μm or less, more preferably 0.1 μm or more and 10 μm or less. 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, there can be used known carbon materials which are conventionally used as a conductive material when the electrode active material is not conductive. Specifically, a conductive agent used when preparing an electrode mixture is used.

Examples of the water-insoluble particles having substantially no conductivity include fine powder of Teflon, SiC, aluminum nitride, alumina, zirconia, magnesia, mullite, forsterite, and steatite.
These particles may be used in combination with the conductive particles, and are preferably used in an amount of 0.01 to 10 times the conductive particles.

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 that 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 electrolyte generally comprises a supporting salt and a solvent.
You. Lithium salt is the main supporting salt in lithium secondary batteries.
Used as As a lithium salt that can be used in the present invention,
For example, LiClO_Four, LiBF_Four, LiP
F₆, LiCF_ThreeCO_Two, LiAsF₆, LiSb
F₆, LiB_TenCl _Ten, LiOSO_TwoC_nF_{2n + 1}Represented by
(N is a positive integer of 6 or less),
iN (SO_TwoC_nF_{2n + 1}) (SO_TwoC_mF_{2m + 1})
Imide salt (m and n are each a positive integer of 6 or less),
LiC (SO_TwoC_pF_{2p * 1}) (SO_TwoC_qF_{2q + 1}) (SO
_TwoC_rF_{2r + 1}) Represented by the methide salt (p, q, r
Each a positive integer of 6 or less), lower aliphatic carboxylic acid lithium
System, LiAlCl_Four, LiCl, LiBr, LiI,
Such as lithium roroborane and lithium tetraphenylborate
Li salt can be raised, one or more of these
The above can be mixed and used. Above all, LiBF
_FourAnd / or LiPF₆Dissolved is preferred
No. The concentration of the supporting salt is not particularly limited.
0.2 to 3 moles per title is preferred.

[0049] Solvents that can be used 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
, Propylene carbonate, 1,2-dimethoxyethyl
Tan, dimethyl carbonate or diethyl carbonate
LiCF is added to the electrolyte solution_ThreeSO_Three, LiC
10_Four, LiBF_FourAnd / or LiPF₆Including
Lysis is preferred. Especially propylene carbonate or
At least one of ethylene carbonate and dimethyl carbonate
At least one of carbonate and diethyl carbonate
LiCF in one of the mixed solvents_ThreeSO _Three, LiClO_Four,Also
Or LiBF_FourAt least one salt selected from
And LiPF₆An electrolytic solution containing These electrolytes
The amount added in the battery is not particularly limited.
It can be used depending on the amount of the material 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
NI 2, Li 3 N-LiI} -LiOH, Li 4 Si
O ₄ , Li ₄ SiO ₄ -LiI-LiOH, xLi ₃ P
_{O 4 - (1-x)} Li 4 SiO 4, Li 2 SiS 3, it is effective and phosphorus sulfide compounds.

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

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.
The temperature is preferably at least 60 ° C. The aging period is 0.
It is preferably from 2 days to 20 days, particularly preferably from 0.5 days to 5 days.

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.

[0058]

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 [Preparation of Negative Electrode Material] The following various solid compounds mainly composed of silicon were used as negative electrode materials in the state of mechanically pulverized powder. Polycrystalline silicon simple substance (compound-1),
The following metallurgically synthesized alloy compounds include Si-A
g 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 40-60), Si-Ag-Sn (compound-
9 weight ratio 40-50-10), Si-Ag-Sb (compound-10 weight ratio 40-50-10), silicon from which Li was eluted from metallurgically synthesized Li ₄ Si using isopropyl alcohol was used. Silicon (compound-11) obtained by pulverizing in argon gas, polycrystalline silicon and colloidal silica fine particles are mixed, and the solid obtained by heating at 1000 ° C. is powdered with a vibration mill in argon gas. Si—SiO ₂ (compound-12 weight ratio 90-10),
Si-Al ₂ O ₃ (compound-13) obtained by the same method
Weight ratio 90-10), Ag-plated Si (compound-14 Si-Ag weight ratio 40-60) as a compound plated on the surface of polycrystalline silicon by electroless plating, and Ni-plated silicon (compound-15) Si-Ni weight ratio 20-80), Zn-plated silicon (compound-16 Si-Zn weight ratio 70-30),
3 g of polyvinylidene fluoride was added to N-methylpyrrolidone 50
30 g of silicon was added to the solution dissolved in g, mixed and kneaded, dried, and pulverized in an automatic mortar (compound-1).
7) was used. Further, a compound obtained by coating compound-11 with Ag by an electroless plating method (weight ratio 65-35 of compound-18 Si-Ag), and a compound obtained by coating compound-12 with Ag by an electroless plating method (compound-19) Si-Si
O ₂ -Ag weight ratio 65-5-30), and a compound (compound-20 Si-SiO ₂ -polyvinylidene fluoride weight ratio 80-10-10) coated with polyvinylidene fluoride using compound 12 as well. Using. The average particle size of the powder of the negative electrode material (compounds 1 to 20) was in the range of 0.05 to 4 μm. Next, 190 g of a powder obtained by sufficiently mixing the above silicon material and an equal weight of flaky natural graphite, and polyvinylidene fluoride 1 as a binder were used.
0 g was dispersed in 500 ml of N-methyl 2-pyrrolidone and uniformly mixed with a homogenizer to prepare a negative electrode paste.

[Preparation of positive electrode active material] The basic composition is LiNi
A cathode active material (C-1) of _0.8 Co _0.2 O ₂ was synthesized by the following various methods. LiOH · H ₂ as Li material
O (purity 99.9% or more), Ni (NO
₃ ) ₂ · 1.5H ₂ O (purity 99.9% or more) and Co (OH) ₂ (purity 99.9% or more) powder as a Co raw material in a molar ratio of 1: 0.8: 0.2 , And heat-treated at 180 ° C for 2 hours in an oxygen atmosphere, and then calcined at 650 ° C for 6 hours. The fired product
Re-mix and calcinate at 850 ° C. for 8 hours.
The mixture was gradually cooled to room temperature at a rate of
Compound 1 was synthesized. The resulting particles have a nearly spherical shape,
The average particle size of the primary particles was 0.1 μm, and the average particle size of the secondary particles was 7 μm. The specific surface area measured by the BET method was 1.7 m ² / g. The peak ratio of the (104) plane / (003) plane obtained by X-ray diffraction is 0.6, the lattice constant of the a-axis is 2.83, and the lattice constant of the c-axis is 13.
89. An active material having the same basic composition is used as a Ni raw material and a Co raw material, respectively, as Ni (NO ₃ ) ₂ .6H ₂ O.
(Purity 99.9% or more) and high-purity cobalt oxide (purity 99.95% or more) were synthesized to obtain compound C-2. These compounds are completely dissolved in an aqueous nitric acid solution, and Li, C
As a result of quantifying the impurity content of metals other than o and Ni by the ICP method, the content of calcium (Ca) was 0.03% by weight and the content of magnesium (Mg) was 0.1% for alkaline earth elements. 02% by weight or less, individual contents of strontium (Sr) and barium (Ba) are 0.02% by weight or less, the total content of alkaline earth elements is 0.1% or less, and the content of sulfur is The amount is 0.
It was confirmed that the level was 1% or less. In addition, as a result of measuring the water content of the active material powder by the Karl Fischer method, it was confirmed that all were at a level of less than 5% by weight.

As a comparative experiment, batches of nickel oxide (such as NiO) and nickel nitrate, which are ranked as low-purity (purity 99.5% or less) as Ni raw materials, and low-purity (purity 99.5% or less) as Co raw materials. The basic composition is L using each of the batches of cobalt oxide
iNi _0.8 Co _0.2 O ₂ positive electrode active material (compound C-
3, C-4) was synthesized. As shown in Table 1 below, the active materials for these comparisons had levels of either or both of the alkaline earth element and the sulfur content exceeding 0.1% by weight, or the active material powders At a level exceeding 0.5%.

In addition, LiOH.H
Ni (NO ₃ ) ₂ .6H ₂ O as raw material for ₂ O and Ni, Co
In addition to Co (NO ₃ ) ₂ .6H ₂ O as a raw material, Al (OH) ₃ as an Al raw material, manganese nitrate as a Mn raw material,
Using boric acid as a boron raw material and LiF as a fluorine raw material, active materials (C-5, C-6) having the following composition were synthesized. As shown in Table 1 below, the purity of the alkaline earth element and the impurity element of sulfur in these active materials was as described above.
1, It was confirmed that the content of calcium (Ca) was within the range of the present invention as in C-2, and the content of calcium (Ca) was 0.05% by weight or less. LiNi _0.8 Co _0.15 B _0.05 O _2.1 (Compound C-5) LiNi _0.8 Co _0.15 Al _0.05 O _1.9 F _0.1 (Compound C)
-6)

Further, lithium manganese was used as the positive electrode active material.
Li of cobalt composite oxide_1.05Mn _1.95Co_0.05O_4.05
(C-7) was synthesized by the following method. Particle size 0.5-30
μm (including primary particles and secondary particles), BET surface area 40
~ 70m^Two / G of chemically synthesized manganese dioxide (CMD, non-
1% by weight or less of Mn as pure substances_Two O_Three And Mn_Three 
O_Four And less than 0.1% by weight of sulfate, respectively.
0.05% by weight or less of Na, K, and Ca) and the average particle size.
Lithium hydroxide pulverized to 1 to 10 μm,
Baltic (purity 99.9%) is the stoichiometric ratio of the above formula
And heat-treated the mixture at 600 ° C. for 4 hours.
In addition, changing the temperature condition in the range of 650 ° C. to 750 ° C.
Calcination was performed in air for 8 hours. Slowly cool the final fired product to room temperature
The particles obtained as a result of grinding with a laser
According to the measurement, the average median diameter of the primary particles is 0.5 μm.
The secondary particles had a particle size of 10 μm. BET method surface
The product is 2m^Two / G range. Structure and composition with ICP
As a result of identification by X-ray diffraction, the fired product has a spinel crystal structure
Li_1.05Mn_1.95Co_{0. 05}O_4.05And the Cu-α ray
Half of the diffraction peak at 2θ = 36 in X-ray diffraction using
The value range is approximately 0.3, and the intensity is 2θ = 18.6.
27% of the peak. Also the a-axis of the crystal
Had a lattice constant of 8.22A. Also, in the fired product
Traces of LiMnO_Two It was also found that was mixed.
5 g of this calcined product was dispersed in 100 cc of pure water and the pH was measured.
As a result, it was 8.0. Synthetic compound C-7 in aqueous nitric acid
Fully dissolved in the solution and contains impurities of metals other than Li, Co, and Mn.
As a result of determining the amount by the ICP method,
About 0.03 weight of calcium (Ca)
%, Magnesium (Mg) content is 0.02% by weight or less
Below, each of strontium (Sr) and barium (Ba)
Content of not more than 0.02% by weight and an alkaline earth element
The total content of sulfur is 0.1% or less.
It was confirmed that the amount was 0.1% or less.
As a comparison, BET surface area 30-50m^Two / G low purity
Chemically synthesized manganese dioxide (CMD, Mn as impurity)
_Two O_Three And Mn_Three O_Four And less than 0.5% by weight of sulfate
Containing not more than 0.3% by weight of Na, K, and Ca, respectively.
G) and the average particle size is 1 to 10 μm as in the case of C-7.
Crushed lithium hydroxide and cobalt carbonate (purity
99.9%) as a raw material, and mixed under the same conditions as above.
Baking in air with Li_1.05Mn_1.95Co_0.05O
_3.95(C-8) was obtained. This comparative active material is shown in the table below.
As shown in the figure, the content of alkaline earth
Either or both of the contents of the au exceeds 0.1% by weight
Or the water content of the active material powder is 0.5
%.

The above-mentioned various positive electrode active materials (200 g) and acetylene black (10 g) were mixed with a homogenizer, followed by mixing with polyvinylidene fluoride (5 g) as a binder.
Add 500 ml of methyl 2-pyrrolidone, knead and mix,
A positive electrode mixture paste was prepared. The positive electrode mixture paste 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, and cut into a predetermined size to form a belt-shaped positive electrode sheet. 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. The coating amount of the positive and negative electrodes is adjusted so that the charge capacity in the first cycle when the positive electrode active material is 4.2 V with respect to lithium metal and the charge capacity in the first cycle when the negative electrode material is 0.0 V are matched. The amount of the mixture applied was adjusted.

Next, the electrolyte 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 3
22.2 g of ethylene carbonate were dissolved in small portions, taking care not to exceed 0 ° C. Next, 0.4 g of LiB
F _4, taking care of LiPF ₆ 12.1g so as not to exceed the liquid temperature is 30 ° C., each in turn, and dissolved little by little in the polypropylene container. 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).

The 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. Batteries 1 to 44 were prepared by combining the positive electrode active material and the negative electrode material as shown in Table 1.

The above cylindrical battery is charged at 1.5 A.
In this case, charging was performed at a constant current up to 4.1 V, and the charging current was controlled so as to be kept constant at 4.2 V 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. Table 1 shows the discharge capacity, average discharge voltage, energy amount (discharge capacity × average discharge voltage) in the first cycle, and the capacity retention ratio in the 30th cycle of repeated charging and discharging.

(Table 1) Battery Positive electrode Negative electrode Battery No. Active material Alkaline earth Sulfur material Discharge capacity Cycle life Element content Content No. (Weight%) after 30 cycles (Weight%) (Ah) Capacity retention rate (Ah) %) 1 C-1 0.01 0.015 Compound-2 2.30 78 2 C-2 0.05 0.09 Compound-2 2.30 77 3 C-5 0.01 0.015 Compound-2 2.35 804C-6 0.03 0.035 Compound-2 2.35 825 (comparative) C-3 0.12 0.05 compound-2 2.30 756 (comparative) C-4 0.12 0.11 compound-2 2.27 727 C-7 0.015 0.01 compound-2 2.05 82 8 C-8 0.08 0.08 Compound-2 2.05 809 C-1 0.01 0.015 Compound-9 2.32 7910 C-2 0.05 0.09 Compound-9 2.31 7811 C-50.01 0.015 Compound-9 2.37 82 12 C-6 0.03 0.035 Compound Compound-9 2.37 83 13 (comparison) C-3 0.12 0.05 Compound-9 2.31 76 14 (comparison) C-4 0.12 0.11 Compound-9 2.29 7415 C-7 0.015 0.01 Compound-9 2. 15 84 16 C-8 0.08 0.08 Compound-9 2.25 83 17 C-1 0.01 0.015 Compound-12 2.32 82 18 C-2 0.05 0.09 Compound-12 2.30 81 19 C-50.01 0.015 Compound-12 2.35 85 20 C-6 0.03 0.035 Compound-12 2.35 8621 (Comparative) C-3 0.12 0.05 Compound-12 2.31 7922 (Comparative) C-4 0.12 0.11 Compound-12 2.29 7823 C-7 0.015 0.01 compound-12 2.15 8724 C-8 0.08 0.08 compound-12 2.285 85 C-1 0.01 0.015 compound-14 2.35 8526 C-2 0.05 0.09 compound-14 2.34 83 27 (comparison) C-3 0.12 0 .05 Compound-14 2.3327928 (Comparative) C-4 0.12 0.11 Compound-14 2.29 7629 C-1 0.01 0.015 Compound-1 2.5006830 C-1 0.01 0.015 Compound-3 2.40 76 31 C-1 0.01 0.015 Compound-4 2.30 81 32 C-1 0.01 0.015 Compound-5 2.30 80 33 C-1 0.01 0.015 Compound-6 2.20 78 34 C-1 0.01 0.015 Compound-7 2 .30 78 35 C-1 0.01 0.015 Compound-8 2.30 80 36 C-1 0.01 0.015 Compound-10 2.30 80 37 C-7 0.01 0.015 Compound-11 2.10 78 38 C-70.01 0.015 Compound- 13 1.90 75 39 C-7 0.01 0.015 Compound-15 2.00 80 40 C-7 0.01 0.015 Compound-16 2.00 80 41 C-7 0.01 0.015 Compound-17 2.10 82 42 C-7 0.01 0.015 Compound -18 1.95 82 43 C-7 0.01 0.015 Compound -19 2.00 87 44 C-7 0.01 0.015 Compound -20 2.00 86

Example 2 A negative electrode mixture paste was prepared in the same manner as described above except that polycrystalline silicon having an average particle size of 10 μm was used as a negative electrode material for comparison, a negative electrode sheet (Comparative Example-1) was prepared, and a battery 45 was prepared. And A negative electrode sheet (Comparative Example-2) was prepared in the same manner as above except that polycrystalline silicon having a particle size of 2 µm was used, and the addition weight ratio of the silicon and the flaky graphite in the negative electrode mixture was set to 80:20.
Was manufactured to obtain a battery 46. Further, a negative electrode sheet (Comparative Example-3) was prepared in the same manner except that mesophase pitch coke was used as a negative electrode material and 2% by weight of acetylene black was added as a conductive auxiliary agent, and a battery 47 was obtained. Using these batteries, tests similar to those of the batteries 1 to 44 were performed.
Table 2 shows the results of the charge / discharge performance obtained for these comparative batteries.

(Table 2) Battery Positive electrode Negative electrode No. Active material Alkaline earth Sulfur material Cycle life of battery Element content Content No. Discharge capacity After 30 cycles of discharge capacity (% by weight) (% by weight) (% by weight) 45 C-1 0.01 0.015 Comparative Example-1 2.10 63 46 C-10.05 0.09 Comparative Example-2 1.95 52 47 C-10.01 0.015 Comparative Example-3 1.50 91

When comparing the battery of Example 1 using the compound of the present invention, the cycle life was longer when the amount of alkaline earth element or sulfur contained as an impurity in the positive electrode active material exceeded the range of the present invention. It is clear that the performance is deteriorated and the performance is accelerated. Comparing the battery performance of the battery of Example-1 and the battery performance of Comparative Example-1, it is found that the compound having a small average particle size of the negative electrode material has excellent cycle life. Furthermore, when compared with Example-1, the alloy, silicon from which lithium was removed from lithium silicide, silicon to which colloidal silica was adhered, silicon coated with metal by plating, and silicon coated with polyvinylidene fluoride were not treated at all. The cycle life is improved over silicon not subjected to the heat treatment. Further, by combining the treatment of the present invention in the negative electrode material, the cycle life is improved as compared with the case of the negative electrode material treated alone. Further, from Comparative Example-3, the battery using the negative electrode material of the present invention has a higher discharge capacity than the battery using the carbonaceous material for the negative electrode. The above results indicate that LiCoO ₂ and LiCo _1.92 Sn _0.08 were used instead of LiNiO ₂ -based oxide or LiMn ₂ O ₄ -based oxide as the positive electrode active material.
Similar effects were obtained when O ₂ was used.

[0072]

According to the present invention, it is possible to obtain a non-aqueous secondary battery having an improved discharge capacity and energy amount and an improved cycle life.

[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

Claims (1)

[Claims] 1. A non-aqueous secondary battery comprising a positive electrode having a positive electrode active material, a negative electrode having a negative electrode material, and a non-aqueous electrolyte, wherein the negative electrode material contains a silicon atom capable of inserting and releasing lithium. Wherein the positive electrode active material is Co, N
containing one or more metals selected from i, Mn, and Fe
A lithium-containing transition metal composite oxide having a layered structure of NaFeO ₂ type or spinel type, wherein the content of alkaline earth element in the positive electrode composite oxide is 0.1% by weight or less and the content of sulfur is 0.1% by weight or less. A non-aqueous secondary battery characterized by being 1% by weight or less.