JPH07114915A - Nonaqueous secondary battery - Google Patents

Abstract

PURPOSE:To stably provide nonaqueous secondary batteries having good coated properties and excellent self-discharge properties. CONSTITUTION:A nonaqueous secondary battery is composed of a negative electrode having a material which can absorb and desorb a light metal or its alloy or lithium ion as a negative electrode active material, a positive electrode having a metal oxide as a positive electrode active material, a nonaqueous electrolytic liquid in which an alkali metal salt is dissolved, and a separator. In the process to sinter the positive electrode active material at the time of preparation, a first sintering is carried out at 450-800 deg.C for 3-100 hours and continuously sintering is carried out at sintering temperature higher than the first sintering temperature by 50-600 deg.C for 0.5-50 hours and then cooling is carried out at 0.1-25 deg.C/min to give the positive electrode active material.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a non-aqueous secondary battery,
In particular, the present invention relates to a non-aqueous secondary battery in which an anode metal is an alkali metal or an alloy thereof, particularly a lithium metal or an alloy thereof, or an active material that absorbs and releases lithium ions.

[0002]

2. Description of the Related Art A non-aqueous battery using a lithium metal or its alloy or an active material which absorbs and releases lithium ions as a negative electrode active material is expected to be put into practical use because it has a high energy density. Among them, as a positive electrode active material, JP-A-55
-136131 LiCoO ₂ , LiNiO ₂
Has a high discharge potential and is expected to have a higher energy density. Since LiCoO ₂ and LiNiO ₂ are powders, they are used by kneading an active material, a conductive agent, a binder, etc. and coating them on a support. In this case, if the active material particles are large, there is a problem that the support may be damaged during coating, or the separator may be damaged when wound with the negative electrode and the separator, causing a short circuit.

In JP-A-1-304664, an average particle size of 1
0 to 150 μm LiCoO ₂ , JP-A-5-15199
In No. 8, Li having a 90% cumulative diameter of 30 to 80 μm
Although a non-aqueous electrolyte battery using CoO ₂ is disclosed,
The coating property was not satisfactory. JP-A-4-3326
No. 0 discloses a method in which a lithium salt having a melting point of 500 ° C. or less is used and LiCoO ₂ having an average particle diameter of 0.5 μm or less is used. Although the coating surface condition is satisfactory, The self-discharge characteristics were inferior. Japanese Patent Laid-Open No. 5-
In 94822, the particle size distribution is D (25%) = 0.5 to 3.
0 μ, D (50%) = 2 to 10 μ, D (75%) = 3.
Although a Li and Co composite oxide having a particle size of 5 to 30 μm is disclosed, it has poor self-discharge characteristics and manufacturing stability.

[0004]

In order to obtain a good performance non-aqueous secondary battery using the positive electrode active material as described above, the positive electrode active material has good coating characteristics and good self-discharge characteristics. Stability is required for manufacturing. An object of the present invention is to obtain an excellent non-aqueous secondary battery by stably providing an active material for a non-aqueous secondary battery having excellent coating properties and self-discharge properties.

[0005]

Means for Solving the Problems The above problems are solved by a light metal or its alloy, or a negative electrode of an active material capable of inserting and extracting lithium ions, a positive electrode of a positive electrode active material made of a metal oxide, and a non-aqueous electrolyte made of a non-aqueous electrolyte. In the next battery, in the process of firing the positive electrode active material during the production thereof, the first firing is performed at a temperature of 450 to 800 ° C. for 3 to 100 hours, and then the second firing is continued to the first firing. A non-aqueous secondary battery characterized by being obtained by performing the treatment at a temperature 50 to 600 ° C. higher than the temperature for 0.5 to 50 hours, and cooling at a cooling rate of 0.1 to 25 ° C./min after firing. Achieved Hereinafter, the present invention will be described in detail.

The positive electrode active material used in the present invention is a metal oxide, preferably a composite metal oxide, more preferably a lithium composite oxide, and particularly preferably an oxide represented by the following general formula A. It is a thing. In the general formula A Li _x M _y1 N _y2 O _z , M represents Co or Ni, and preferably Co. N represents Ni, V, Fe, Mn, Ti, Cu, and is preferably V. y1 is 0.6 to 1.0, preferably 0.7 to 1.0, and more preferably 0.8 to
It is 1.0. y2 is 0 to 0.4, preferably 0
It is 0.3, and more preferably 0 to 0.2. Also
y1 + y2 = 1. Although x varies depending on charge and discharge, the value at the time of firing is preferably 0.8 to 1.0, more preferably 0.85 to 0.98, and particularly preferably 0.8 to 0.97. Is. Further, z is 1.5 to 3.
0 is preferred.

Preferred lithium compounds as the firing raw material of the present invention include lithium hydroxide, lithium oxide, lithium carbonate, lithium phosphate, lithium nitrate, lithium sulfite, lithium tetraborate, lithium formate, lithium acetate, lithium oxalate and lithium citrate. , Lithium chlorate, lithium perchlorate, lithium thiocyanate, lithium lactate,
Examples thereof include lithium tartrate, lithium hexafluorophosphate, lithium fluoride, lithium chloride, lithium bromide and lithium iodide. Among them, preferred compounds have a melting point of 200 ° C. or higher, more preferably a melting point of 300 ° C. or higher,
Particularly preferably, the melting point is 400 ° C. or higher.

Preferred compounds for the firing raw material of the present invention are TiO ₂ , lithium titanate, acetylacetonato titanyl, titanium tetrachloride, titanium tetraiodide, titanyl ammonium oxalate, and VO _d (d = 2 to 2.5, d). = 2.5
Compound of vanadium pentoxide), lithium compound of VO _d , vanadium hydroxide, ammonium metavanadate,
Vanadium oxosulfate, vanadium oxytrichloride, vanadium tetrachloride, MnO ₂ , Mn ₂ O ₃ , manganese hydroxide, manganese carbonate, manganese nitrate, manganese sulfate, manganese sulfate ammonium, manganese sulfite, manganese phosphate, manganese borate, perchloric acid Manganese, manganese chlorate, manganese thiocyanate, manganese formate, manganese acetate, manganese oxalate, manganese citrate, manganese lactate,
Manganese tartrate, manganese stearate, manganese fluoride, manganese chloride, manganese bromide, manganese iodide, manganese acetylacetonate, iron oxide (2,3 valent), ferric oxide, iron hydroxide (2,3 valent) , Iron chloride (2, 3 valent),
Iron bromide (2,3 valent), iron iodide (2,3 valent), iron sulfate (2,3 valent), ammonium iron sulfate (2,3 valent), iron nitrate (2,3 valent), iron phosphate (2,3 values), iron perchlorate, iron chlorate, iron acetate (2,3 values), iron citrate (2,3 values)
Valence), ammonium iron citrate (2,3 valence), iron oxalate (2,3 valence), ammonium iron oxalate (2,3 valence).

Further, CoO, Co ₂ O ₃ , Co ₃ O ₄ ,
Cobalt carbonate, basic cobalt carbonate, cobalt hydroxide,
Cobalt sulfate, cobalt nitrate, cobalt sulfite, cobalt perchlorate, cobalt thiocyanate, cobalt oxalate, cobalt acetate, cobalt fluoride, cobalt chloride, cobalt bromide, cobalt iodide, hexaamminecobalt complex salts (sulfuric acid, nitric acid as salts, Perchloric acid, thiocyanic acid, oxalic acid, acetic acid, fluorine, chlorine, bromine, iodine), nickel oxide, nickel hydroxide, nickel carbonate, basic nickel carbonate, nickel sulfate, nickel nitrate, nickel fluoride, nickel chloride, bromide Nickel, nickel iodide, nickel formate, nickel acetate, nickel acetylacetonate, copper oxide (1, 2 valent), copper hydroxide, copper sulfate, copper nitrate, copper phosphate, copper fluoride, copper chloride, ammonium chloride copper, Examples include copper bromide, copper iodide, copper formate, copper acetate, copper oxalate, and copper citrate.

Among them, TiO 2 is particularly preferable.
₂ , titanyl ammonium oxalate, VO _d (d = 2-2.
5, compound of d = 2.5 is vanadium pentoxide), VO _d
Lithium compounds, ammonium metavanadate, Mn
O ₂ , Mn ₂ O ₃ , manganese hydroxide, manganese carbonate, manganese nitrate, ammonium manganese sulfate, manganese acetate, manganese oxalate, manganese citrate, iron oxide (2, 3
Value), triiron tetraoxide, iron hydroxide (2,3 value), iron acetate (2,3 value), iron citrate (2,3 value), ammonium iron citrate (2,3 value), iron oxalate (2,3 valence), ammonium iron oxalate (2,3 valence), CoO, Co ₂ O ₃ , C
o ₃ O ₄ , cobalt carbonate, basic cobalt carbonate, cobalt hydroxide, cobalt oxalate, cobalt acetate, nickel oxide, nickel hydroxide, nickel carbonate, basic nickel carbonate, nickel sulfate, nickel nitrate, nickel acetate, nickel acetylacetate Examples include nato, copper oxide (monovalent and divalent), copper hydroxide, and copper citrate.

As a particularly preferable combination of firing raw materials used in the present invention, lithium hydroxide, lithium carbonate or lithium nitrate, TiO ₂ , VO _d (d = 2 to 2.5, d) are used.
= 2.5 compounds are vanadium pentoxide), VO _d lithium compounds, ammonium metavanadate, MnO ₂ ,
Mn ₂ O ₃ , manganese hydroxide, manganese carbonate, manganese nitrate, iron oxide (2,3 valent), triiron tetraoxide, iron hydroxide (2,3 valent), iron acetate (2,3 valent), citric acid Iron (2,
Trivalent), ammonium iron citrate (2,3 valent), iron oxalate (2,3 valent), ammonium iron oxalate (2,3 valent), Co
O, Co ₂ O ₃ , Co ₃ O ₄ , cobalt carbonate, basic cobalt carbonate, cobalt hydroxide, cobalt oxalate, cobalt acetate, nickel oxide, nickel hydroxide, nickel carbonate,
A combination with at least one of basic nickel carbonate, nickel sulfate, nickel nitrate, nickel acetate, copper oxide (monovalent and divalent), and copper hydroxide can be mentioned.

In addition to the above lithium compound and metal compound,
Generally, compounds that enhance ionic conductivity, such as Ca ²⁺ ,
(For example, calcium carbonate, calcium acetate, calcium oxalate, calcium citrate, calcium phosphate, calcium stearate) or an amorphous forming agent containing P, B, Si (for example, P ₂ O ₅ , H ₃ BO ₃ , SiO
₂ etc.) and may be baked. The addition amount is not particularly limited, but 0.2 to 10 mol% is preferable.

When the compound of the present invention is obtained by calcination, first, the first calcination is carried out at a temperature of 450 to 800 ° C. for 3 to 10
After 0 hour, 50 ~ 50% from the first firing temperature.
Baking is performed at a high temperature of 600 ° C. for 0.5 to 50 hours. It is preferable that the first firing is performed at a temperature of 500 to 800 ° C. for 3 to 50 hours, and then the firing is performed at a temperature 50 to 500 ° C. higher than the first firing temperature for 0.5 to 25 hours, and particularly preferably. Is the first firing 600 ~ 7
After 5 to 15 hours at a temperature of 50 ° C., 0.5 to 0.5 at a temperature 100 to 300 ° C. higher than the first firing temperature.
It is to fire for 5 hours.

The cooling rate is preferably 0.1 to 2
5 ° C / min, more preferably 0.5-10 ° C /
min, and particularly preferably 0.5 to 5 ° C./min. Moreover, the density of the raw material mixture to be baked is 0.1 to 5.
It is preferably 0 g / cm ³ , more preferably 0.1 to 3.5 g / cm ³ , and most preferably 0.1.
It is 5 to 1.5 g / cm ³ . In addition, the rate of temperature rise during the firing is preferably 5 to 50 ° C / min.
And more preferably 10 to 50 ° C./min,
Particularly preferably, it is 10 to 30 ° C./min.

The calcined product of the present invention is first roughly crushed. The average particle size of the roughly crushed product is preferably 10 to 80 μm, more preferably 10 to 50 μm, and particularly preferably 10 to 30 μm. is there. Furthermore, this coarsely pulverized product is further pulverized once more, with an average particle size of 0.5 to 9 μm, and 75% or more of the total volume is 3 to 15
The average particle size is preferably 1 to 9 μm, and 80% or more of the total volume is 3 to 1
The average particle size is 3 to 8 μm, and 80% or more of the total volume is 3 to 15 μm.
It is to be μm. The average particle diameter referred to here is a median diameter, and is measured by a laser diffraction type particle size distribution measuring device.

As a method of coarse pulverization, a generally used method, for example, the method described in “Particle Handbook” (Jinbo et al., Asakura Shoten), page 227 can be used.
For example, a mortar, a ball mill, a vibrating ball mill, a satellite ball mill, a tube mill, a pebble mill, a conical mill, a rod mill, a vibrating mill, a vibracon and the like can be used. It is possible to use the same method as the coarse pulverization for the second pulverization, but it is preferable to pulverize while classifying so that excessive pulverization does not occur.
A high-speed air current impact method (jet mill) and the like are preferable.

In the above pulverization, wet pulverization or dry pulverization may be used as the pulverization method. Then, after crushing, normal classification is performed. The classification method may be wet type or dry type, and as the classifying device, a sieving shaker, a sonic sieving machine, an electromagnetic sieving machine, a centrifugal sieving machine, an inertial classifying machine, a thickener, a cyclone, a centrifugal classifying machine or the like can be used. The powder obtained by this pulverization may be washed with water, methanol, ethanol or the like and used. The powder obtained by this pulverization has a specific surface area of 0.1 m.
Is preferably ² / ^{g~10m 2} / g, more preferably 0.1m ² / g~5m ² / g, particularly preferably 0.2m ² / g~2m ² / g. The measurement of this specific surface area was performed by the BET method. In the present invention, the grain size and the surface area can be controlled by appropriately setting those conditions by changing the firing temperature and pulverizing in two stages so that the grain size does not become too fine.
In particular, when the pulverization is carried out in one stage, many of the particles have a fine particle size and the particle size distribution becomes non-uniform.

The oxide of the positive electrode active material used in the present invention may be crystalline or amorphous, but a crystalline compound is preferred. The light metal or its alloy used in the present invention, or the negative electrode of an active material capable of inserting and extracting lithium ions,
Alkali metal or alloy thereof, carbonaceous material, or Lip ZOR (wherein Z is a transition metal at least one of which contains Ti, V, Mn, Co, Fe, Nb, Mo, p = 0 to 3.1) , R = 1.6 to 4.1), and a lithium-containing transition metal oxide represented by the formula (1), r = 1.6 to 4.1).
l alloy, Li-Mg alloy, Li-Al-Ni alloy, Li
-Al-Mn alloy, especially Li metal, Li-Al
It is effective to use an alloy. As the carbonaceous material, graphite, natural graphite, artificial graphite or the like can be used.

Preferred lithium-containing transition metal oxides used in the present invention include Li _p Z _1q1 Z _2q2 ... Z.
_nqn O _r (where Z is at least one of Ti, V, M
The transition metal containing n, Co, Ni, and Fe p = 0 to 3.
1, q1 + q2 + ... + qn = 1, n = 1 to 10, r
= 1.6 to 4.1). As a further most preferred lithium-containing transition metal oxides used in the present _{invention, Li p Co q V 1-} q O r, Li p Ni q V 1-q O r
(Here, p = 0.3 to 2.2, q = 0.02 to 0.7,
r = 1.5 to 2.5). The most preferable lithium-containing transition metal oxide used in the present invention is Li _p CoVO ₄ or Li _p NiVO ₄ (where p =
0.3-2.2).

In the present invention, it is preferable that the positive electrode active material and the negative electrode active material have different composition formulas. The positive electrode active material and the negative electrode active material used in the present invention can be achieved by combining compounds having different standard redox potentials. The firing temperature of the negative electrode active material precursor used in the present invention may be a temperature at which a part of the mixed compound used in the present invention is decomposed and melted, and is preferably 250 to 2000 ° C., particularly 3
50-1500 degreeC is preferable. The firing gas atmosphere used in the present invention is not particularly limited, but the positive electrode active material is in air or in a gas having a large proportion of oxygen (for example, about 30).
% Or more), and the negative electrode active material is preferably in the air or in a gas having a small oxygen content (for example, about 10% or less) or in an inert gas (nitrogen gas, argon gas).

The average particle size of the negative electrode active material precursor used in the present invention is not particularly limited, but is preferably 0.2 to 50 μm. The chemical formula of the compound obtained by firing by the method of the present invention was calculated by an inductively coupled plasma (ICP) emission spectroscopic analysis method as a measurement method, and as a simple method from the weight difference between the powder before and after firing. The light metal or its alloy, which is one of the negative electrode active materials used in the present invention, is preferably an alkali metal or its alloy, and more preferably lithium or its alloy.

As the negative electrode active material that can be used in combination with the present invention, lithium metal, lithium alloy (Al, A
1-Mn (US Pat. No. 4,820,599), Al-M
g (JP-A-57-98977), Al-Sn (JP-A-Sho 6)
3-6, 742), Al-In, Al-Cd (Japanese Unexamined Patent Publication No.
-144,573) or the like, or a calcined carbonaceous compound capable of inserting and extracting lithium ions or lithium metal (for example,
JP-A-58-209,864 and 61-214,41.
7, 62-88, 269, 62-216, 62-
170, 63-3, 282, 63-24, 55
5, same 63-121,247, same 63-121,25
7, 63-155,568, 63-276,87
3, same 63-314, 821, JP-A-1-204, 36.
1, the same 1-221, 859, the same 1-274, 360). The purpose of using the lithium metal or lithium alloy together is to insert lithium ions into the battery, and does not utilize the dissolution / precipitation reaction of lithium metal or the like as the battery reaction.

A conductive agent, a binder, a filler and the like can be added to the electrode mixture. The conductive agent may be any electron-conductive material that does not cause a chemical change in the constructed battery. Usually, natural graphite (scaly graphite, flake graphite, earthy graphite, etc.), artificial graphite, carbon black, acetylene black, Ketjen black, carbon fibers and metals (copper, nickel, aluminum, silver (JP-A-63) -1
48, 554), powders, metal fibers, or polyphenylene derivatives (Japanese Patent Laid-Open No. 59-20971) can be included as one kind or a mixture thereof. The combined use of graphite and acetylene black is particularly preferred. The amount added is not particularly limited, but is preferably 1 to 50% by weight, and particularly preferably 2 to 30% by weight. For carbon and graphite, 2 to 15% by weight is particularly preferable.

The binder is usually starch, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, regenerated cellulose, diacetyl cellulose, polyvinyl chloride, polyvinylpyrrolidone,
Polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, ethylene-propylene-
Diene terpolymer (EPDM), sulfonated EPD
M, styrene-butadiene rubber, polybutadiene, fluororubber, polysaccharides such as polyethylene oxide, thermoplastic resins, polymers having rubber elasticity and the like are used alone or as a mixture thereof. When a compound containing a functional group that reacts with lithium, such as a polysaccharide, is used, it is preferable to add a compound such as an isocyanate group to deactivate the functional group. The amount of the binder added is not particularly limited, but is preferably 1 to 50% by weight, and particularly preferably 2 to 30% by weight. The filler is
Any fibrous material that does not undergo a chemical change can be used in the constructed battery. Usually, olefin polymers such as polypropylene and polyethylene,
Fibers such as glass and carbon are used. The amount of the filler added is not particularly limited, but is preferably 0 to 30% by weight.

The electrolyte is generally composed of a solvent and a lithium salt (anion and lithium cation) which is soluble in the solvent. As the solvent, propylene carbonate,
Ethylene carbonate, 1,2-dimethoxyethane, diethyl carbonate, dimethyl carbonate, butylene carbonate, γ-butyrolactone, methyl formate, methyl acetate, tetrahydrofuran, dimethyl sulfoxide,
Aprotic solvents such as 1,3-dioxolane, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane, ethyl monoglyme, phosphoric acid triester, trimethoxymethane, sulfolane, 1,3-propanesartone, and ethyl ether are mentioned. It is possible to use one kind or a mixture of two or more kinds.

The lithium salt that can be dissolved in this solvent is L
iClO ₄ , LiBF ₄ , LiPF ₆ , LiCF ₃ SO
_{3, LiCF 3 CO 2, LiAsF} 6, LiSbF 6,
LiB ₁₀ Cl ₁₀ (JP-A-57-74,974), lower aliphatic lithium carboxylate (JP-A-60-41,77)
3), LiAlCl ₄ , LiCl, LiBr, LiI
(JP-A 60-247,265), lithium chloroborane (JP-A 61-165,957), lithium tetraphenylborate (JP-A 61-214,376), and the like are preferable, and LiCF ₃ SO ₃ is more preferable. , LiClO ₄ ,
LiBF ₄ and LiPF ₆ , particularly preferably LiB
F _4, is LiPF _6. The amount of these electrolytes added to the battery is not particularly limited, but a necessary amount can be used depending on the amount of the positive electrode active material or the negative electrode active material and the size of the battery. In particular, a mixture of propylene carbonate or ethylene carbonate with 1,2-dimethoxyethane and / or diethyl carbonate is mixed with LiClO ₄ , L
iBF ₆ , LiCF ₃ SO ₃ and / or LiPF
_An electrolyte containing ₆ is preferred.

The amount of these electrolytes added to the battery is not particularly limited, but a necessary amount can be used depending on the amount of the positive electrode active material or the negative electrode active material and the size of the battery. The volume ratio of the solvent is not particularly limited, but in the case of a mixed solution of propylene carbonate or ethylene carbonate and 1,2-dimethoxyethane and / or diethyl carbonate,
0.4 / 0.6 to 0.6 / 0.4 (the mixing ratio when using 1,2-dimethoxyethane and diethyl carbonate is 0.3 / 0.7 to 0.7 / 0.3) preferable. The concentration of the supporting electrolyte is not particularly limited, but is preferably 0.2 to 3 mol per liter of the electrolytic solution.

In addition to the electrolytic solution, the following solid electrolytes can be used. Solid electrolytes are classified into inorganic solid electrolytes and organic solid electrolytes. As the inorganic solid electrolyte, Li nitride, halide, oxyacid salt and the like are well known. Among them, Li ₃ N, LiI,
_{Li 5 NI 2, Li 3 N} -LiI-LiOH, LiSi
O ₄ , LiSiO ₄ -LiI-LiOH (JP-A-49-
_{81,899), xLi 3 PO 4 -} (1-x) Li 4 S
iO ₄ (JP 59-60,866), Li ₂ SiS ₃
(JP-A-60-501,731) and phosphorus sulfide compounds (JP-A-62-82,665) are effective.

In the organic solid electrolyte, a polyethylene oxide derivative or a polymer containing the derivative (JP-A-63-1)
35, 447), polypropylene oxide derivatives or polymers containing these derivatives, and polymers containing ionic dissociative groups.
(JP-A-62-254, 302, JP-A-62-254, 30
3, 63-193,954), a mixture of a polymer containing an ionic dissociative group and the aprotic electrolyte (US Pat. Nos. 4,792,504, 4,830,939, JP-A-6-93).
2-22, 375, 62-2, 376, 63-2
2,375, 63,22,776, JP-A-1-95,
117), a phosphoric acid ester polymer (JP-A-61-25)
6,573) is effective. Furthermore, there is also a method of adding polyacrylonitrile to the electrolytic solution (JP-A-62-27).
8,774). Further, a method of using an inorganic solid electrolyte and an organic solid electrolyte in combination (Japanese Patent Laid-Open No. 60-1,768) is also known.

As the separator, an insulating thin film having a large ion permeability and a predetermined mechanical strength is used. A sheet or non-woven fabric made of olefin polymer such as polypropylene or glass fiber or polyethylene is used because of its resistance to organic solvent and hydrophobicity. The pore size of the separator is in the range generally used for batteries. For example, 0.01 to 10 μ
m is used. The thickness of the separator is, for example, 5 to 300 μm, which is generally used in the range for batteries.

It is also known to add the compounds shown below to the electrolyte for the purpose of improving discharge and charge / discharge characteristics. For example, pyridine (JP-A-49-108,52)
5), triethylphosphite (JP-A-47-4,3)
76), triethanolamine (JP-A-52-72,4).
25), cyclic ether (JP-A-57-152,68)
4), ethylenediamine (JP-A-58-87,77)
7), n-glyme (JP-A-58-87,778), hexaphosphoric acid triamide (JP-A-58-87,779),
Nitrobenzene derivative (JP-A-58-214, 28)
1), sulfur (JP-A-59-8,280), quinoneimine dye (JP-A-59-68,184), N-substituted oxazolidinone and N, N'-substituted imidazolidinone (JP-A-5-280).
9-154,778), ethylene glycol dialkyl ether (JP-A-59-205,167), quaternary ammonium salt (JP-A-60-30,065), polyethylene glycol (JP-A-60-41). , 773), pyrrole (JP-A-60-79,677), 2-methoxyethanol-
Le (JP 60-89,075), AlCl ₃ (JP-61-88,466), conductive polymer - monomer of the electrode active material - (JP 61-161,673), triethylene phosphoramide Amide (JP-A-61-208,758), trialkylphosphine (JP-A-62-80,976), morpholine (JP-A-62-80,977), aryl compound having a carbonyl group 62-86, 67
3), hexamethylphosphoric triamide and 4-alkylmorpholine (JP 62-217,575), bicyclic tertiary amine (JP 62-217,578), oil (JP 62 -287,580), a quaternary phosphonium salt (JP-A-63-121268), a tertiary sulfonium salt (JP-A-63-121269), and the like.

Further, in order to make the electrolytic solution nonflammable, a halogen-containing solvent such as carbon tetrachloride or ethylene trifluoride chloride can be contained in the electrolytic solution (Japanese Patent Laid-Open No. 48-36,6).
32). Further, the electrolytic solution may contain carbon dioxide gas in order to have suitability for high temperature storage (JP-A-59-13).
4,567). Further, the mixture of the positive electrode and the negative electrode can contain an electrolytic solution or an electrolyte. For example, the ion conductive polymer or nitromethane (Japanese Patent Laid-Open No. 48-36,6).
33), a method of adding an electrolytic solution (JP-A-57-124,870) is known.

Further, the surface of the positive electrode active material can be modified. For example, the surface of the metal oxide may be treated with an esterifying agent (JP-A-55-163,779),
Treatment with a photocatalyst (JP-A-55-163,780), conductive polymers (JP-A-58-163,188, 59-14).
274), polyethylene oxide, etc. (JP-A-60-
97, 561). Also, the surface of the negative electrode active material can be modified. For example, an ion conductive polymer or polyacetylene layer is provided (JP-A-58-111276), or LiCl
(JP-A-58-142,771) and the like.

The collector of the electrode active material may be any electron conductor as long as it does not undergo a chemical change in the constructed battery. For example, for the positive electrode, in addition to stainless steel, nickel, aluminum, titanium, calcined carbon, etc. as the material, carbon on the surface of aluminum or stainless steel,
Those treated with nickel, titanium or silver, and the negative electrode are made of stainless steel, nickel, copper, titanium,
In addition to aluminum and calcined carbon, copper, stainless steel whose surface is treated with carbon, nickel, titanium, or silver), an Al-Cd alloy, or the like is used. It is also used to oxidize the surface of these materials. The shape is
In addition to the foil, a film, a sheet, a net, a punched product, a lath body, a porous body, a foamed body, a molded body of a fiber group and the like are used. The thickness is not particularly limited, but is 1 to 5
Those having a diameter of 00 μm are used.

The shape of the battery can be any of coins, buttons, sheets, cylinders, corners and the like. In coins and buttons, the mixture of the positive electrode active material and the negative electrode active material is used after being pressed into a pellet shape. The thickness and diameter of the pellet are determined by the size of the battery. In the case of sheets, cylinders and prismatic batteries, the mixture of the positive electrode active material and the negative electrode active material is used after being coated, dried, dehydrated and pressed on the current collector. The coating thickness, length and width are determined by the size of the battery, but the coating thickness is particularly preferably 1 to 2000 μm in the compressed state after drying.

The pellets or sheets may be dried or dehydrated by any of the commonly used methods. In particular, vacuum, infrared rays, far infrared rays, electron beams, low humidity air, etc. may be used alone or in combination. The temperature is 80
The temperature is preferably 350 ° C. Particularly, 100 to 250 ° C. is preferable. The water content is preferably 2000 ppm or less for the entire battery, and 500 p for each of the positive electrode mixture, the negative electrode mixture and the electrolytic solution.
It is preferably pm or less from the viewpoint of cycleability. The pellet or sheet may be pressed by a generally used method, but a die pressing method or a calendar pressing method is particularly preferable. The pressing pressure is not particularly limited, but is 0.2 to 3 t
/ Cm ² is preferred. The press speed of the calendar press method is preferably 1 to 50 m / min. The pressing temperature is preferably room temperature to 200 ° C.

The mixture sheet is rolled or folded and inserted into a can, the can and the sheet are electrically connected, an electrolytic solution is injected, and a sealing plate is used to form a battery can. At this time, the safety valve can be used as a sealing plate. For the can and the lead plate, a metal or alloy having electrical conductivity can be used. For example, metals such as iron, nickel, titanium, chromium, molybdenum, copper and aluminum or alloys thereof are used. As the sealing agent for sealing, a conventionally known compound or mixture such as asphalt can be used.

[0038]

EXAMPLES The present invention will be described in more detail with reference to specific examples below, but the present invention is not limited to the examples as long as the gist of the invention is not exceeded. Example 1

(Example of synthesizing positive electrode active material) Lithium carbonate and cobalt carbonate having an atomic ratio of lithium to cobalt of 0.98: 1.
Mixed so that The average particle size of this mixture is 0.0
5 to 2 μm, the density of the mixture is 0.75 g / cm ³ , the temperature is 20 ° C./min in air, the temperature is 675 ° C. for 10 hours, and the temperature is 20 ° C./min. Burned for hours. It was cooled at 3 ° C./min to obtain LiCoO ₂ . When this LiCoO ₂ was roughly pulverized with a vibracon, the average particle size was 12.7 μm. Then, it was pulverized by the high-speed airflow impact method. The average particle size was 4.9 μm, the volume occupied by particles having a particle size of 3 to 15 μm in the total volume was 84%, and the specific surface area was 0.58 m ² / g. The particle size and volume are measured by the diffraction type particle size distribution measuring device (Horiba LA5
00). The compound obtained in this synthesis example is referred to as Compound N
o. Let C-1.

Regarding the above-mentioned synthesis examples, the firing temperature was changed, the compounding ratio of the raw materials was changed, and V and N were used as the raw materials.
The experiment was conducted under the condition that the atomic ratio was changed by adding i, Mn, etc. and the firing temperature was also changed. The compound (positive electrode active material) thus obtained was designated as Compound No. C-2 or less. Tables 1 to 10 show the atomic ratio of the positive electrode active material obtained by firing, the firing conditions, the specific surface area, and the particle size. In the table, “particle size 3 to 15 μm occupied volume%” means particle size 3 to 3 in the total volume.
It represents the volume% occupied by those having a thickness of 15 μm.

[0041]

[Table 1]

[0042]

[Table 2]

[0043]

[Table 3]

[0044]

[Table 4]

[0045]

[Table 5]

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[Table 6]

[0047]

[Table 7]

[0048]

[Table 8]

[0049]

[Table 9]

[0050]

[Table 10]

Comparative Example 1 An experiment was conducted on the above synthesis example under the conditions that the firing temperature was changed and the compounding ratio of the raw materials was changed. The compound (positive electrode active material) thus obtained was designated as Compound No. R-1 to R-1
Set to 4. However, compound No. R-10 to R-14
Corresponds to a comparative example in the case of using the compound of the general formula A of the present invention. First firing method and grain size
The results are shown in Tables 1 to 12.

[0052]

[Table 11]

[0053]

[Table 12]

Example 2 (Preparation of Electrode Mixture and Test Sample) As a method for preparing the mixture, in the positive electrode material, 82% by weight of the positive electrode active material C-1 and 12% by weight of scaly graphite as the conductive agent were mixed. As a binder, a positive electrode pellet (13 mmΦ, obtained by compression-molding a mixture of polytetrafluoroethylene mixed at a mixing ratio of 6% by weight)
0.35 g) in a dry box (dew point -40 to -70
It was used after being sufficiently dehydrated with a far infrared heater in a dry air). As the negative electrode material, a 600 μm thick LiAl alloy punched out with 13 mmΦ was used. 80 μm thick stainless steel SUS316 for both positive and negative electrode cans is used as the current collector.
The net was welded to a coin can and used. 1 as electrolyte
250 μl of mol / liter LiPF ₆ (equal volume mixture of ethylene carbonate and diethyl carbonate) was used, and a microporous polypropylene sheet and polypropylene non-woven fabric were used as a separator to impregnate the non-woven fabric with the electrolytic solution. Using. Then, a coin type lithium battery was manufactured in the same dry box as above.

This lithium battery was charged at a constant current of 1.0 mA for 45 mAh and then stored for 10 days at a constant temperature and humidity of 60 ° C. and a humidity of 90%. The capacity retention rate after storage was 77%. In addition, the capacity retention rate after 200 cycles at 3.0 V to 4.2 V was 90%. Similar experiments were conducted for other compounds. The results are shown in Tables 13 to 16.
Shown in the table. In Tables 13 to 16, ◯ ... No coating unevenness and no damage to the film. △: Part of the film was damaged. X: Many coating irregularities and film damages are seen.

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[Table 13]

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[Table 14]

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[Table 15]

[0059]

[Table 16]

Example 3 85% by weight of graphite manufactured by Wako Pure Chemical Industries, Ltd. as a negative electrode, 10% by weight of acetylene black as a conductive agent, and a binder.
A negative electrode pellet (13 mmΦ, obtained by compression-molding a mixture prepared by mixing polytetrafluoroethylene at a mixing ratio of 5% by weight).
The same test as in Example 2 was performed except that 0.35 g) was used. The cycle property was evaluated at 3.0V to 4.2V. The results are shown in Table 17. Example 4 As a negative electrode, a mixture of lithium-containing transition metal oxide in an amount of 82% by weight, flake graphite in an amount of 12% by weight as a conductive agent, and polyvinylidene fluoride in an amount of 6% by weight as a binder was prepared. Compression molded negative electrode pellets (13 mmΦ, 0.
The same test as in Example 2 was conducted except that 35 g) was used. The cycle property was evaluated at 3.0V to 4.2V.
The results are shown in Table 17.

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[Table 17]

Comparative Example 2 The same test as in Example 2 was carried out on the comparative compound.
The results are shown in Table 18. Example 5 Toluene was added to compound C-1, 88 parts by weight, acetylene black, 9 parts by weight, polytetrafluoroethylene, 3 parts by weight, and kneaded. This mixture was applied on both sides of an aluminum foil having a thickness of 20 μm by the doctor blade method, dried and then compression-molded by a roller press machine to obtain an applied thickness of 10
A 0 μm positive electrode sheet was prepared. The coated surface was all uniform and had no damaged parts. There was also no corrosion of the support. Similar experiments were conducted for other compounds.
The results are shown in Tables 13 to 16. In Tables 13 to 16, ◯ ... No coating unevenness and no damage to the film. △: Part of the film was damaged. X: Many coating irregularities and film damages are seen.

Comparative Example 3 The same test as in Example 5 was carried out on the comparative compound.
The results are shown in Table 18.

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[Table 18]

[0065]

As in the present invention, the positive electrode of the positive electrode active material,
In a secondary battery comprising a negative electrode of a light metal or its alloy or an active material capable of occluding and releasing lithium ions, and a non-aqueous electrolyte solution, in the process of firing the positive electrode active material, the first firing is performed at 450 to 800 ° C. for 3 to 100. By using the positive electrode active material obtained by firing for 0.5 to 50 hours at a temperature 50 to 600 ° C. higher than the first firing temperature after cooling for 0.1 to 25 ° C./min. It is possible to obtain a non-aqueous secondary battery that gives good coating characteristics, good charge / discharge cycle characteristics, and good self-discharge characteristics. In the present invention, by performing the firing in two steps, the particle size is not made fine, the particle size and surface area are controlled, and the battery characteristics are improved. Further, the thus obtained product has good coatability when a positive electrode is formed by coating, and the battery obtained also has good battery characteristics.

Claims (5)

[Claims] 1. A nonaqueous secondary battery comprising a light metal or its alloy, or a negative electrode of an active material capable of inserting and extracting lithium ions, a positive electrode of a positive electrode active material composed of a metal oxide, and a nonaqueous electrolytic solution, wherein the positive electrode active material is a positive electrode active material. In the process of firing during its manufacture, the first firing is performed at a temperature of 450 to 800 ° C. for 3 to 100 hours, and then the second firing is performed at a temperature 50 to 600 ° C. higher than the first firing temperature. For 0.5 to 50 hours, and 0.1 to 25 ° C / mi after firing.
A non-aqueous secondary battery, which is obtained by cooling at a cooling rate of n. 2. The positive electrode active material is pulverized into coarse powder having an average particle size of 10 to 80 μm after the firing process and the cooling process,
The non-aqueous secondary battery according to claim 1, which is further pulverized into fine powder having an average particle diameter of 0.5 to 9.0 µm. 3. The positive electrode active material has an average particle size of 0.5 to 0.5.
9.0 μm, and 75% or more of the total volume has a particle size of 3
The non-aqueous secondary battery according to claim 1 or 2, wherein the non-aqueous secondary battery has a thickness of -15 m. 4. The specific surface area of the positive electrode active material is 0.1 m ^2.
/ G to 10 m ² / g.
The non-aqueous secondary battery according to any one of 3 above. 5. The non-aqueous secondary battery according to claim 1, wherein the positive electrode active material is an active material that is fired as a compound represented by the following general formula A. . In the general formula _{A Li x M y1 N y2 O} z ( wherein, M: Co or Ni N: Ni, V, Fe , Mn, Ti, elements .M and N chosen from among Cu varies y1:. 0. 6-1.0 y2: 0-0.4 y1 + y2 = 1 x = 0.8-1.0 z = 1.5-3.0)