JP3481157B2 - Non-aqueous electrolyte battery and method for manufacturing the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-aqueous electrolyte secondary battery that uses a lithium ion conductive non-aqueous electrolyte as a positive and negative electrode active material that can store and release lithium ions, and more particularly, The present invention relates to a novel secondary battery having excellent withstand voltage characteristics or over-discharge characteristics, easily predicting the remaining battery level, and having high reliability.

[0002]

2. Description of the Related Art Non-aqueous electrolyte batteries using lithium as a negative electrode active material have advantages such as high energy density, small self-discharge and excellent long-term reliability. Therefore, primary batteries for memory backup, cameras, etc. It is already widely used as a power source. However, in recent years, with the remarkable development of portable electronic devices, communication devices, and the like, a rechargeable / dischargeable secondary battery has been strongly demanded from the viewpoint of economy and reduction in size and weight of the device. For this reason, research and development for promoting the use of the non-aqueous electrolyte battery as a secondary battery have been actively conducted.

Conventionally, conductive polymer materials such as metal oxides, polyacene and polyacetylene have been used for the positive electrode of non-aqueous electrolyte secondary batteries. In addition, metallic lithium is used for the negative electrode,
Lithium alloys, carbonaceous materials, metal oxides, and conductive polymer materials such as polyacene and polyacetylene are used and put to practical use. An example of using activated carbon for the positive electrode is disclosed in Japanese Patent Laid-Open No.
Although it is disclosed in Japanese Patent Publication No. 9-173979, it is practically used because of its lack of safety because the negative electrode is metallic lithium, and deterioration when the battery is over-discharged to 0 V (hereinafter referred to as over-discharge). It has not been converted. In addition, JP-A-8-1
07048 and Japanese Patent Laid-Open No. 9-55342 disclose that a carbonaceous material is used for the negative electrode, but this also deteriorates when over-discharged and has not been put to practical use. Positive again,
A capacitor using an electric double layer for both the negative electrode and the negative electrode has a drawback that it deteriorates when a high voltage is continuously applied (hereinafter referred to as withstanding voltage).

[0004]

Conventionally, the following four types of positive electrode active materials have been found as the positive electrode active material constituting this type of secondary battery, depending on the form of charge / discharge reaction. First
Types include metal chalcogen compounds such as TiS2, MoS2, NbSe3, MnO2, V2O5, LiCoO.
2, LiNiO2, LiMn2O4, Li1.33Ti1.66
A type in which only lithium ions (cations) move in and out due to intercalation, deintercalation reactions, etc., such as between metal oxides such as O4 and the like, between crystal layers, between lattice positions or lattice gaps. The second type is a type such as a conductive polymer such as polyaniline, polypyrrole, polyparaphenylene, etc. in which mainly anions are stably doped and come in and out by a dedoping reaction. The third type is a type (intercalation, deintercalation or doping, dedoping, etc.) in which both lithium cations and anions can enter and exit, such as graphite intercalation compounds and conductive polymers such as polyacene. Fourth
Type is a type in which lithium ions move to the pore surface of a porous material such as activated carbon to form an electric double layer.

When a metal chalcogen compound or a metal oxide is used as a positive electrode, a large amount of lithium ions can be stored and released compared with other types, so that a secondary battery having a large capacity can be obtained. However, since the discharge voltage hardly changes depending on the remaining capacity, it becomes difficult to predict the remaining capacity of the battery. A conductive polymer material such as polyaniline can easily predict the remaining amount of a battery, but there is a problem that conductivity is deteriorated due to lithium emission.

On the other hand, as the negative electrode active material, (1) the electrode potential is the most base when metal lithium is used alone. Therefore, when it is combined with the positive electrode using the positive electrode active material as described above, the withstand voltage characteristics are improved. It is possible to make a secondary battery with excellent capacity. However, there is a problem that dendrites and passivation compounds are generated on the lithium negative electrode along with charge and discharge, and deterioration due to charge and discharge is large, and cycle life is short. In order to solve this problem, (2) lithium and Al,
It was considered to use alloys with other metals such as Zn, Sn, Pb, Bi and Cd. However, it has been found that there is a problem that the utilization efficiency of lithium during charging / discharging is low, and the cycle life is short because cracks occur in the electrodes due to repeated charging / discharging and the like. Further, when the battery is over-discharged, an excessive amount of lithium ions will be occluded by the counter positive electrode, which causes a problem of deterioration of the positive electrode active material. (3) It has been proposed to use a substance capable of inserting and extracting lithium ions, such as a conductive polymer such as polyacene or polyacetylene doped with lithium ions, but the charge / discharge capacity, especially the charge / discharge capacity per volume is small. There's a problem.

When the battery is over-discharged, that is, when the positive electrode active material occludes an excessive amount of lithium ions and approaches the lithium potential, the crystal structure collapses and an irreversible substance is generated, so that a stable charge / discharge cycle cannot be performed. , Loses its function as a secondary battery. Therefore, the negative electrode active material needs to be controllable so as not to occlude excess lithium ions in the positive electrode even when the battery is overdischarged. Further, the negative electrode active material is required to occlude excess lithium ions in order to improve withstand voltage characteristics and to be able to perform a stable charge / discharge cycle without collapse of the crystal structure or generation of irreversible substances even when approaching the lithium potential. Further, a secondary battery as an electronic component is required to be compatible with an automatic soldering device using infrared reflow when mounted on a printed circuit board or the like. Although it is an instant, in order to make a battery that does not deteriorate even when placed in a high temperature environment, it is necessary to reduce the amount of thermally active lithium as much as possible,
It is preferable to use a negative electrode that can make maximum use of the absorbed lithium, that is, a negative electrode active material that has a small irreversible capacity.

[0008]

In order to solve the above problems, the present inventors have focused on activated carbon as a positive electrode active material,
I investigated its characteristics. A test cell composed of a working electrode having activated carbon, a counter electrode made of lithium metal, and a non-aqueous electrolyte solution was charged and discharged, and the relationship between the working electrode capacity and the lithium potential was investigated. As a result, the potential range that can be repeatedly charged and discharged stably shows charge and discharge that is linearly proportional to the capacity in the range of 2 to 4 V (vs. Li), and is an excellent active material that can easily predict the remaining amount of the battery. We found that (Fig. 2). This charging / discharging mechanism is presumed to be desorption of ions in the electrolyte to the activated carbon. Further, when the potential range was raised to 4.5 V, deterioration due to decomposition of the non-aqueous electrolyte solution was observed, and when it was 2 V or less, the linearity of charge / discharge was lost, and repeated charge / discharge was impossible in both cases.

Under these circumstances, the present inventors arrived at the present invention as a result of earnest research. That is, in order to bring out the excellent characteristics of the activated carbon positive electrode, if there is a negative electrode active material that can be repeatedly charged and discharged in a range of 0 to 2 V (vs. Li) that cannot be achieved with metallic lithium or a lithium alloy negative electrode, the withstand voltage can be increased. The over-discharge characteristic can be improved without deteriorating the characteristics.

First, the present inventors have proposed that the composition formula LixSiOy
(However, the lithium-containing silicon oxide represented by 0 ≦ x, 0 <y <2) is contained in the non-aqueous electrolyte in an electrode potential range of at least 0 to 3 V with respect to the lithium reference electrode (metallic lithium). We have discovered that it can electrochemically and stably repeatedly occlude and release lithium ions, making it an excellent negative electrode active material, and applied for a patent (Japanese Patent Application No. 4-2651).
79, ibid. 5-35851, ibid. 5-162958, etc.). The use of this negative electrode active material can solve the above problems. Further, the present inventors have found that the composition formula LixSnOy (however,
The composite oxide of tin and lithium containing lithium represented by 0 ≦ x) has an electrode potential of 3 V or 4 with respect to the lithium reference electrode (metal lithium) in the non-aqueous electrolyte.
When a positive electrode active material having a high potential of V or more was used, it was found that an extremely stable battery having a long cycle life was obtained, and a patent was filed (JP-A-6-2752684).

Further, in the non-aqueous electrolyte battery using lithium, research on niobium oxide has been actively conducted. For example, Electrochemistry 46 P411 No. 7 197
In No. 8, research was conducted as a primary battery. JP-A-56-
147368, JP-A-57-11476, and JP-A-5-
In 166536, niobium pentoxide is used as the negative electrode of a secondary battery, and an oxide or sulfide is used as the positive electrode, but no study using activated carbon for the positive electrode has been made. Regarding molybdenum oxide, an example of using it as a positive electrode is shown in Japanese Patent Publication No. 63-901, but its use as a negative electrode has not been examined. Regarding titanium oxide, Japanese Patent Publication No. 63-858
8 shows an example of using vanadium oxide for the positive electrode, but no study using activated carbon for the positive electrode has been made.

Using these oxides of Si, Sn, Nb, Mo, and Ti as working electrodes, a test cell composed of a counter electrode made of lithium metal and a non-aqueous electrolyte solution was charged and discharged to give 0-
The relationship between the working electrode capacity and the lithium potential was examined in the range of 2 V (Fig. 3). As a result, it was confirmed that it was possible to repeatedly charge and discharge stably except for Ti, and it was found that when combined with an activated carbon positive electrode, it was a negative electrode active material that could solve the above problems. However, when the Ti oxide absorbs lithium until it reaches 0 V, there is cycle deterioration that is presumed to be a destruction of the crystal structure, and when the potential range is narrowed to 1.5-2 V, charging and discharging can be repeated sufficiently stably, When combined with an activated carbon positive electrode, good over-discharge characteristics can be expected although the withstand voltage characteristics are inferior.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Any known activated carbon may be used as the positive electrode of the battery of the present invention, and examples thereof include powder compacts, fibrous and sheet-like aggregates. Further, the aggregate may substantially contain activated carbon, and other positive electrode constituent materials may be mixed therein.

The following two methods can be mentioned as preferred methods for producing the lithium-containing silicon oxide LixSiOy used as the negative electrode active material of the battery of the present invention.
It is not limited to these. The first method is to mix or mix each element of silicon and lithium or a compound thereof in a predetermined molar ratio, and in a non-oxidizing atmosphere such as an inert atmosphere or in a vacuum, or when the silicon and lithium are in a predetermined amount. In this method, a composite oxide of silicon and lithium is formed by heat treatment in an atmosphere in which the amount of oxygen is controlled so that the oxidation number is reached.
The respective compounds of silicon and lithium as starting materials are oxides, hydroxides, or carbonates,
A compound such as a salt such as a nitrate or an organic compound which forms each oxide by heat treatment in a non-oxidizing atmosphere is preferable. As a method of mixing these starting materials, in addition to a method of directly dry mixing powders of the respective materials, these materials are dissolved or dispersed in water, alcohol or other solvent, and uniformly mixed or reacted in the solution. After that, various methods such as a method of drying and a method of atomizing or ionizing these raw materials by heating, electromagnetic waves, light, etc. and simultaneously or alternately depositing or precipitating are possible. The temperature of the heat treatment carried out after or while mixing the raw materials in this manner varies depending on the starting raw materials and the heat treatment atmosphere, but the synthesis can be carried out at 400 ° C or higher, preferably 600 ° C or higher. Good. On the other hand, in an inert atmosphere or in a vacuum, a disproportionation reaction of silicon and tetravalent silicon oxide may occur at a temperature of 800 ° C. or higher. In such a case, the temperature of 600 to 800 ° C. preferable.

Among these combinations of starting materials, lithium oxide is produced by heat treatment such as lithium oxide Li2O, lithium hydroxide LiOH, salts such as Li2CO3 or LiNO3 and their hydrates as a lithium feed material. A lithium compound is used, and as a supply source of silicon, simple substance silicon or a lower oxide of silicon SiOy ′ (provided that
When 0 <y '<2) is used, the mixture can be synthesized by heat-treating the mixture in an atmosphere in which oxygen is cut off, such as in an inert atmosphere or in a vacuum, and the oxygen content in the heat-treatment atmosphere can be increased. Alternatively, the oxygen partial pressure is easily controlled, and the production is easy, which is particularly preferable.

Further, when various silicic acids having hydrogen as a silicon compound are used as the starting material or when lithium hydroxide or the like is used as a lithium compound, hydrogen is not completely desorbed by the heat treatment, It is possible that a part of the product remains after the heat treatment and lithium and hydrogen coexist.
Included in the present invention. Further, together with lithium or a compound thereof and silicon or a compound thereof, another alkali metal such as sodium, potassium, rubidium, an alkaline earth metal such as magnesium or calcium and / or iron,
Nickel, cobalt, manganese, vanadium, titanium,
Niobium, tungsten, molybdenum, copper, zinc, tin,
Lead, aluminum, indium, bismuth, gallium,
Other metals or non-metal elements such as germanium, carbon, boron, nitrogen, phosphorus, etc., or their compounds, etc. are also added and mixed, and the mixture is heat-treated. Can also coexist with, and these cases are also included in the present invention.

The lithium-containing silicon oxide thus obtained can be used as a negative electrode active material as it is or after being optionally subjected to processing such as pulverizing and granulating and granulating. Further, similar to the second method described below, depending on an electrochemical reaction between the lithium-containing silicon oxide and a substance containing lithium or lithium, the lithium-containing silicon oxide is further occluded with lithium ions,
Alternatively, on the contrary, a compound in which lithium content is increased or decreased by releasing lithium ions from this composite oxide may be used as the negative electrode active material.

In the second method, a silicon-containing lower oxide SiOy (2>y> 0) containing no lithium is synthesized in advance, and the obtained silicon lower oxide SiOy and lithium or lithium are contained. This is a method in which lithium ions are occluded in the lower oxide SiOy of silicon by an electrochemical reaction with a substance to obtain a lower oxide LixSiOy of silicon containing lithium. As such a lower oxide SiOy of silicon, SiO1.5 (Si2O3), S
iO1.33 (Si3O4), SiO and SiO0.5 (Si2
In addition to stoichiometric compositions such as O), y may be of any composition in which y is greater than 0 and less than 2. Further, these lower oxides of silicon SiOy can be produced by various known methods as described below. That is, (1) a method of mixing silicon dioxide SiO2 and silicon Si in a predetermined molar ratio and heating the mixture in a non-oxidizing atmosphere or in vacuum, (2)
A method of heating silicon dioxide SiO2 in a reducing gas such as hydrogen H2 to reduce a predetermined amount, (3) silicon dioxide SiO2
Is mixed with a predetermined amount of carbon C, a metal, etc., and heated to reduce a predetermined amount, (4) a method of heating silicon Si with oxygen gas or an oxide to oxidize a predetermined amount, (5) silane SiH4
A CVD method or a plasma CVD method in which a mixed gas of a silicon compound gas such as oxygen and oxygen O2 is heated or plasma-decomposed.

Further, the lower oxide SiOy of silicon contains, together with silicon, an alkali metal such as hydrogen, sodium, potassium and rubidium, an alkaline earth metal such as magnesium and calcium, and / or iron, nickel, cobalt, manganese, Vanadium, titanium, niobium, tungsten, molybdenum, copper, zinc, tin, lead, aluminum, indium, bismuth, gallium, germanium,
Other metal or non-metal elements such as carbon, boron, nitrogen, phosphorus, etc. may be included and these are also included in the present invention.

The storage of lithium ions by the electrochemical reaction of the silicon to the lower oxide SiOy can be carried out in the battery after the battery is assembled, or inside or outside the battery during the battery manufacturing process. Specifically, it can be performed as follows. That is, (1) one of the electrodes (working electrode) is formed of a lower oxide of silicon or a mixture of the lower oxide of silicon and a conductive agent, a binder or the like into a predetermined shape, and contains metallic lithium or lithium. The other electrode (counter electrode) is used as the other electrode (counter electrode) to come into contact with the lithium ion conductive non-aqueous electrolyte so that both electrodes face each other to form an electrochemical cell, and the working electrode is energized with an appropriate current in the direction of cathode reaction Lithium ions are chemically absorbed in the lower oxide of silicon. A non-aqueous electrolyte secondary battery is constructed by using the obtained working electrode as it is as a negative electrode or as a negative electrode active material constituting the negative electrode. (2) The low-grade oxide of silicon or a mixture of the low-grade oxide of silicon and a conductive agent, a binder or the like is molded into a predetermined shape, and lithium or an alloy of lithium or the like is pressure-bonded or brought into contact with the laminated electrode. The obtained product is incorporated into a non-aqueous electrolyte secondary battery as a negative electrode. A method of forming a kind of local battery by exposing the laminated electrode to the electrolyte in the battery, and self-discharging to electrochemically occlude lithium in the lower oxide of silicon.
(3) A non-aqueous electrolyte secondary battery is constructed using the lower oxide of silicon as a negative electrode active material and a material containing lithium and capable of inserting and extracting lithium ions as a positive electrode active material. A method in which lithium ions released from the positive electrode by being charged when used as a battery are occluded in the lower oxide of silicon.

Examples of the substance for occluding lithium in the silicon oxide of the present invention include lithium metal, lithium alloy and the like, and calcined carbonaceous compounds capable of occluding and releasing lithium ion or lithium metal. The particle size of the silicon oxide or lithium-containing silicon oxide is preferably 500 μm or less, more preferably 100 μm or less, and especially 5 μm or less.
0 to 0.1 μm is preferable. Specific surface area is 0.05-100m
3 / g is preferable, and more preferably 0.1-50 m3 /
g, especially 0.1 to 30 m3 / g is good.

The lithium-containing silicon oxide LixSiOy thus obtained is used as a negative electrode active material. Although the lithium-containing silicon oxide is shown above, Sn, N containing lithium, which is another negative electrode active material in the present invention, is used.
The oxides of b, Mo, and Ti can be produced by the same knowledge. Further, a composite oxide using a substance prepared by mixing two or more thereof as an active material can also be applied to the present invention.

The shape of the electrode can be various shapes such as a plate shape, a film shape, a column shape, or a shape formed on a metal foil depending on the intended battery. When the shape of the battery is a coin or a button, the mixture of the positive electrode active material and the negative electrode active material is used by being compressed into a pellet shape. Further, in the case of a thin coin or button, a sheet-shaped electrode may be punched and used. The thickness and diameter of the pellet are determined by the size of the battery. Further, when the battery has a sheet, cylinder, or square shape, the mixture of the positive electrode active material and the negative electrode active material is mainly used after being coated, dried, and compressed on the current collector. The coat thickness, length and width are
The thickness of the coat, which is determined by the size of the battery, is particularly preferably 1 to 2000 μm in the compressed state after drying. As a pellet or sheet pressing method, a generally adopted method can be used, but a die pressing method or a calendar pressing method is particularly preferable. The pressing pressure is not particularly limited, but is preferably 0.2 to 3 t / cm @ 2. The press speed of the calendar press method is preferably 0.1 to 50 m / min. The pressing temperature is preferably room temperature to 200 ° C.
A conductive agent, a binder, a filler, or the like can be added to the electrode mixture. The type of the conductive agent is not particularly limited and may be a metal powder, but a carbon-based one is particularly preferable. The most common carbon materials are natural graphite (scaly graphite, flake graphite, earth graphite, etc.), artificial graphite, carbon black, channel black, thermal black, furnace black, acetylene black, carbon fiber, etc. . Further, as the metal, metal powder such as copper, nickel, silver or the like, or metal fiber is used. Conducting polymers are also used. The amount of carbon added varies depending on the electrical conductivity of the active material, the electrode shape, etc., and is not particularly limited, but in the case of the negative electrode, it is 1 to 90 wt%
Is preferred.

The average particle size of carbon is 0.5 to 50 μm.
, Preferably in the range of 0.5 to 15 μm, and more preferably in the range of 0.5 to 6 μm, the contact between the active materials becomes good, and the electron conduction network formation is improved,
The active material that does not participate in the electrochemical reaction is reduced. The binder is preferably insoluble in the electrolytic solution, but is not particularly limited. Usually, polyacrylic acid and neutralized polyacrylic acid, polyvinyl alcohol, carboxymethyl cellulose, starch, hydroxypropyl cellulose,
Regenerated cellulose, diacetyl cellulose, polyvinyl chloride, polyvinylpyrrolidone, tetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPD
M), sulfonated EPDM, styrene-butadiene rubber,
Polybutadiene, fluororubber, polyethylene oxide,
Polyimide, an epoxy resin, a polysaccharide such as a phenol resin, a thermoplastic resin, a thermosetting resin, a polymer having rubber elasticity and the like are used alone or as a mixture thereof. The amount of the binder added is not particularly limited, but is 1 to 5
0% by weight is preferred.

As the filler, any fibrous material which does not cause a chemical change in the constructed battery can be used. Generally, 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 0
-30% by weight is preferred. The electrolytic solution is not particularly limited, and an organic solvent used in conventional non-aqueous secondary batteries is used. As the organic solvent, cyclic esters, chain esters, cyclic ethers, chain ethers and the like are used, and specifically, propylene carbonate (PC),
Ethylene carbonate (EC), butylene carbonate (BC), vinylene carbonate, dimethyl carbonate (DMC), diethyl carbonate (DEC), γ-
Butyrolactone (γBL), 2-methyl-γ-butyrolactone, acetyl-γ-butyrolactone, γ-valerolactone, 1,2-dimethoxyethane (DME), 1,2-
Ethoxyethane, diethyl ether, ethylene glycol dialkyl ether, diethylene glycol dialkyl ether, triethylene glycol dialkyl ether, tetraethylene glycol dialkyl ether, dipropyl carbonate, methyl ethyl carbonate, methyl butyl carbonate, methyl propyl carbonate, ethyl butyl carbonate, ethyl propyl carbonate , Butyl propyl carbonate, propionic acid alkyl ester, malonic acid dialkyl ester, acetic acid alkyl ester, tetrahydrofuran (THF), alkyl tetrahydrofuran, dialkylalkyltetrahydrofuran, alkoxytetrahydrofuran, dialkoxytetrahydrofuran, 1,3-dioxolane, alkyl-1,3- Geo SORUN, 1,4-dioxolane,
2-methyltetrahydrofuran, dimethylsulfoxide, 1,3-dioxolane, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane, methyl formate, methyl acetate, methyl propionate,
Organic solvents such as ethyl propionate and phosphoric acid triester, and derivatives and mixtures thereof are preferably used. From the viewpoint of suppressing the reductive decomposition reaction of the solvent, use of an electrolytic solution in which carbon dioxide gas (CO2) is dissolved is effective in improving the capacity and the cycle life. Main impurities present in the mixed solvent (non-aqueous solvent) include water and organic peroxides (eg glycols, alcohols, carboxylic acids) and the like. It is considered that each of the impurities forms an insulating film on the surface of the graphitized product and increases the interfacial resistance of the electrode. Therefore, the cycle life and the capacity may be reduced. High temperature (60 ℃
Above) self-discharge during storage may increase. Therefore, it is preferable that the impurities are reduced as much as possible in the electrolytic solution containing the non-aqueous solvent. Specifically, the water content is 50 ppm or less, and the organic peroxide is 1000 p
It is preferably pm or less. As the supporting salt, lithium perchlorate (LiClO4), lithium hexafluorophosphate (LiPF6), lithium borofluoride (LiBF4),
Lithium arsenide hexafluoride (LiAsF6), lithium trifluorometasulfonate (LiCF3 SO3), lithium bistrifluoromethylsulfonylimide [LiN
(CF3 SO2) 2], one or more salts such as a lithium salt (electrolyte) such as a thiocyanate salt and an aluminum fluoride salt can be used. The amount dissolved in a non-aqueous solvent is
It is desirable to set it to 0.5 to 3.0 mol / 1.

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. Li-nitrides, halides, oxyacid salts, and the like are well known as inorganic solid electrolytes. For 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 phosphoric acid ester polymer and the like are effective. A method of using an inorganic and organic solid electrolyte in combination is also known.

Additives may be added for the purpose of improving discharge and charge / discharge characteristics. Although it may be added directly to the active material, the most common method is to add it to the electrolytic solution.
For example, there are toluene, pyridine 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.

Further, the mixture of the positive electrode and the negative electrode may 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. As the collector of the electrode active material, a metal plate or metal foil having a low electric resistance is preferred.
For example, for the positive electrode, materials such as stainless steel, nickel, aluminum, titanium, tungsten, gold, platinum,
In addition to calcined carbon, aluminum or stainless steel whose surface is treated with carbon, nickel, titanium or silver is used. Duplex stainless steel is effective for corrosion. In the case of coin and button batteries, nickel plating is performed on the outside of the battery. Treatment methods include wet plating, dry plating, C
There are VD, PVD, clad formation by pressure bonding, coating, and the like.

For the negative electrode, as materials, stainless steel, nickel, copper, titanium, aluminum, tungsten, gold,
In addition to platinum and calcined carbon, copper or stainless steel whose surface is treated with carbon, nickel, titanium or silver, or an Al—Cd alloy is used. Examples of the treatment method include wet plating, dry plating, CVD, PVD, cladding by pressure bonding, coating and the like.

Although the surface of these materials may be oxidized, benzotriazole, triazine thiol, alkyl thiol, fluorine-based water-generating agent, silicon-based water-generating agent or the like may be used for rust-preventing treatment. As the shape, in addition to the foil, a coin button battery can, a film, a sheet, a net, a punched product, a lath body, a porous body, a foamed body, a molded body of fibers, and the like are used. The thickness is not particularly limited. In the case of a coin button battery can, in order to mount it on a substrate, the terminal may be attached by resistance welding, laser welding, or the like. The material of the terminal includes stainless steel, stainless-nickel clad material, stainless steel plated with nickel or gold, and the like, and is not particularly limited as long as it is a metal.

The separator is a porous body which has continuous ventilation holes and is durable against an electrolytic solution or an electrode active material and has no electron conductivity, and is usually a cloth, a non-woven cloth or a non-woven cloth made of glass fiber, polyethylene or polypropylene. Is a porous body. The pore size of the separator is in the range generally used for batteries. For example, 0.01 to 10 μm
Is used. The thickness of the separator is, for example, 5 to 300 μm, which is generally used in the range for batteries. The separator is fixed in the battery case so that there is no practical problem. Also, as a safety measure, it is effective to use a separator that changes the ion permeability depending on the temperature.

It is also possible to fix the electrode active material and the current collector with a conductive adhesive. As the conductive adhesive, a resin obtained by adding powder or fibers of carbon or metal to a resin dissolved in a solvent, a solution obtained by dissolving a conductive polymer, or the like is used. In the case of a pellet-shaped electrode, it is applied between the current collector and the electrode pellet to fix the electrode. The conductive adhesive in this case often contains a thermosetting resin. In the case of an electrode in the case of a sheet, it is used for the purpose of electrically connecting the current collector and the electrode rather than physically adhering them.

When used as a coin or button battery,
As the gasket, polypropylene, polyethylene, polyamide resin, various engineering plastics are used. Usually, polypropylene is generally used, but a material such as engineering plastic having a high heat resistant temperature may be used in order to cope with the reflow temperature when the battery is mounted on the substrate.

In the case of coin and button batteries, a sealant of one kind or a mixture of asphalt pitch, butyl rubber, fluorinated oil, chlorosulfonated polyethylene, epoxy resin and the like is used between the gasket and the positive and negative electrode cans. When the sealant is transparent, it is also colored to clarify the presence or absence of application. Examples of the method for applying the sealing agent include injecting the sealing agent into the gasket, applying it to the positive and negative electrode cans, and dipping the gasket into the sealing agent solution.

The shape of the battery can be any of coins, buttons, sheets, cylinders, corners and the like. Applications of the non-aqueous electrolyte secondary battery of the present invention are not particularly limited, but include, for example, backup power supplies for mobile phones, pagers, and the like, power supplies for wristwatches having a power generation function, and the like.

The battery of the present invention is preferably assembled in a dehumidifying atmosphere or an inert gas atmosphere. It is also preferable that the parts to be assembled are also dried in advance. As a method of drying or dehydrating the pellets, sheets and other parts, a generally adopted method can be used. In particular, it is preferable to use hot air, vacuum, infrared rays, far infrared rays, electron beams, and low humidity air alone or in combination. The temperature is preferably in the range of 80 to 350 ° C, particularly 10
The range of 0 to 250 ° C. is preferable. The water content of the whole battery is preferably 2000 ppm or less, and each of the positive electrode mixture, the negative electrode mixture and the electrolyte is preferably 50 ppm or less from the viewpoint of cycleability.

[0037]

EXAMPLES The present invention will be described in more detail below with reference to examples. (Example 1) In this example, activated carbon was used as the positive electrode active material and SiO was used as the negative electrode active material. A cross-sectional view of the battery is shown in FIG. The size of the battery is 6.8m in outer diameter.
m and thickness 2.1 mm.

The positive electrode was manufactured as follows. Carbon black was mixed with commercially available activated carbon as a conductive agent and fluorine resin as a binder at a weight ratio of 80: 12: 8 to obtain a positive electrode mixture, which was pressure-molded into a sheet and had a thickness of 0. It was 8 mm. The volume density of this sheet was 0.4 g / cm 3. This sheet was punched out with a diameter of 4 mm. Thereafter, the positive electrode pellet 101 thus obtained is used as an electrode current collector 1 made of a conductive resin adhesive containing carbon as a conductive filler.
After being bonded and integrated with the positive electrode case 103 using 02,
It was dried under reduced pressure at 150 ° C. for 8 hours.

The negative electrode was manufactured as follows. Commercially available silicon monoxide (SiO) was pulverized and sized to a particle size of 44 μm or less by an automatic mortar and used as the active material of the working electrode.
Graphite as a conductive agent and polyacrylic acid as a binder were mixed with this active material at a weight ratio of 45:40:15 to prepare a negative electrode mixture. 2 ton / cm
2 was pressed into pellets having a diameter of 4 mm and a thickness of 0.19 mm. The pellet weight was 4.2 mg. Thereafter, the negative electrode pellet 104 thus obtained is used as an electrode current collector 10 made of a conductive resin adhesive containing carbon as a conductive filler.
After using 2 to adhere to and integrate with the negative electrode case 105, 1
It was dried under reduced pressure at 00 ° C. for 8 hours. Further, a lithium foil 106 having a diameter of 4 mm and a thickness of 0.16 is placed on the pellet.
What was punched out in mm was pressure-bonded to obtain a lithium-negative electrode pellet laminated electrode.

The electrolytic solution 107 was prepared by adding LiBF to a mixed solvent of γ-butyrolactone and ethylene carbonate in a volume ratio of 1: 1.
What melt | dissolved 1 mol / l of 4 was used. The battery thus produced was subjected to an over-discharge cycle under the conditions of 50 μA constant current, over-discharge at a final voltage of 0 V and 50 μA constant current, and charging up to 3.3 V. The charge / discharge characteristics at this time are shown in FIG.

Example 2 In this example, activated carbon is used as the positive electrode active material and SnO is used as the negative electrode active material.
The same procedure was performed as in Example 1 except for the method for producing the lithium-negative electrode pellet laminated electrode. The negative electrode was manufactured as follows. Commercially available tin monoxide (SnO) with automatic mortar, particle size 44μ
What was pulverized and sized to m or less was used as the active material of the working electrode. Graphite as a conductive agent and polyacrylic acid as a binder were added to the active material in a weight ratio of 70.5: 2, respectively.
The mixture was mixed at a ratio of 1.8: 8 to obtain a negative electrode mixture. Mix 2
It was pressure molded into pellets having a diameter of 4 mm and a thickness of 0.23 mm at ton / cm 2. The pellet weight was 10 mg. After that, the negative electrode pellets 104 thus obtained are bonded and integrated with the negative electrode case 105 using the electrode current collector 102 made of a conductive resin adhesive containing carbon as a conductive filler, and then integrated at 100 ° C. for 8 hours. It was dried under reduced pressure for an hour. further,
Lithium foil 106 having a diameter of 3 mm and a thickness of 0.35 mm was punched on the pellet and pressure-bonded to form a lithium-
A negative electrode pellet laminated electrode was used.

(Example 3) In this example, activated carbon was used as the positive electrode active material and Nb2O5 was used as the negative electrode active material. The same procedure was performed as in Example 1 except for the method for producing the lithium-negative electrode pellet laminated electrode. The negative electrode was manufactured as follows. Add commercially available niobium hydroxide (Nb2O5 ・ nH2O) to 5
Niobium pentoxide (Nb2O) was burned in the air at a temperature of 00 ° C.
5) was obtained. After that, the one pulverized and sized to a particle size of 44 μm or less by an automatic mortar was used as the active material of the working electrode. Graphite as a conductive agent and polyacrylic acid as a binder were mixed with this active material at a weight ratio of 58: 40: 2 to prepare a negative electrode mixture. The mixture was pressed at 4 ton / cm 2 into pellets having a diameter of 4 mm and a thickness of 0.36 mm.
The pellet weight was 11.1 mg. Thereafter, the negative electrode pellets 104 thus obtained are bonded and integrated with the negative electrode case 105 using the electrode current collector 102 made of a conductive resin adhesive containing carbon as a conductive filler, and then 100
It was dried under reduced pressure at 8 ° C. for 8 hours. Further, a lithium foil 106 having a diameter of 3 mm and a thickness of 0.18 mm is formed on the pellet.
What was punched out was pressed to obtain a lithium-negative electrode pellet laminated electrode.

Example 4 In this example, activated carbon was used as the positive electrode active material and MoO 2 was used as the negative electrode active material. The same procedure was performed as in Example 1 except for the method for producing the lithium-negative electrode pellet laminated electrode. The negative electrode was manufactured as follows. Commercially available molybdenum dioxide (MoO2) was crushed and sized by an automatic mortar to have a particle size of 44 μm or less, and used as the active material of the working electrode. Graphite as a conductive agent and polyacrylic acid as a binder were mixed with this active material at a weight ratio of 45:40:15 to prepare a negative electrode mixture. The mixture was pressed at 4 ton / cm @ 2 into pellets having a diameter of 4 mm and a thickness of 0.42 mm. Pellet weight is 13.6 mg
And Then, the negative electrode pellet 1 thus obtained was obtained.
04 was adhered to and integrated with the negative electrode case 105 using the electrode current collector 102 made of a conductive resin adhesive containing carbon as a conductive filler, and dried under reduced pressure at 100 ° C. for 8 hours. Further, a lithium foil 106 having a diameter of 3 mm and a thickness of 0.12 mm punched out on the pellet was pressure-bonded to obtain a lithium-negative electrode pellet laminated electrode.

Example 5 In this example, activated carbon was used as the positive electrode active material and TiO 2 was used as the negative electrode active material. The same procedure as in Example 1 was carried out except for the method for producing the lithium-anode pellet laminated electrode and the charging / discharging conditions. The negative electrode was manufactured as follows. Commercially available anatase type titanium dioxide (T
iO2) was pulverized and sized to a particle size of 44 μm or less with an automatic mortar and used as the active material of the working electrode. Graphite as a conductive agent and polyacrylic acid as a binder were mixed with this active material at a weight ratio of 82: 10: 8 to obtain a negative electrode mixture. Mixture is 4 ton / cm2 and diameter is 4mm
It was pressed into pellets having a thickness of 0.54 mm. The pellet weight was 13.6 mg. After that, the negative electrode pellets 104 thus obtained are bonded and integrated with the negative electrode case 105 using the electrode current collector 102 made of a conductive resin adhesive containing carbon as a conductive filler, and then integrated at 100 ° C. for 8 hours. It was dried under reduced pressure for an hour. Further, a lithium foil 106 having a diameter of 4 mm and a thickness of 0.1 mm was punched out on the pellets and pressed to obtain a lithium-negative electrode pellet laminated electrode. This amount of lithium is the amount of lithium at which the potential does not become 1.5 V or less (vs. Li) when all are stored in the negative electrode active material.

Regarding the battery thus manufactured, 50
μA constant current, over discharge of 0V end voltage and 50μA constant current,
A charging / discharging cycle was performed under the condition of charging up to 2V.
The overdischarge characteristics at this time are shown in FIG. Comparative Example This comparative example is a case where activated carbon is used as the positive electrode active material and metallic lithium is used as the negative electrode active material. The procedure was the same as in Example 1 except for the method for producing the lithium-anode laminated electrode.

The negative electrode was manufactured as follows. Negative electrode case 104 without using negative electrode pellet 104 in FIG.
Lithium foil 106 with a diameter of 4 mm and a thickness of 0.8
What was punched out in mm was directly pressure-bonded to obtain a lithium negative electrode. 50 μA for batteries manufactured in this way
2. Constant current, over-discharge of 0V final voltage and 50μA constant current, 3.
The charging / discharging cycle was performed under the condition of charging up to 3V.
The overdischarge characteristics at this time are shown in FIG.

These batteries were subjected to an overdischarge cycle of 1000 cycles to obtain the capacity retention rate. In addition, the initial internal resistance (measured by the alternating current impedance method of 1 mA and 1 kHz) and a voltage of 3.3 V in an environment of 60 ° C.
Changes in internal resistance after a withstand voltage test applied for 0 days were measured, and these results are shown in Table 1. It can be seen that all the secondary batteries of Examples 1-6 using the present invention are excellent in over-discharge characteristics up to 0V. Further, it is understood that the batteries are excellent in withstand voltage characteristics other than batteries using titanium oxide for the negative electrode.

[0048]

[Table 1]

[0049]

As described above in detail, according to the present invention, in order to bring out the excellent characteristics of the positive electrode of the non-aqueous electrolyte secondary battery, 0 to 2 V which cannot be achieved with the metallic lithium or lithium alloy negative electrode.
Li, which is a negative electrode active material that can be repeatedly charged and discharged in a stable manner in the range of (vs.Li), Si, Sn, N
When combined with any of the metal oxides of b, Mo, and Ti, the overdischarge characteristics can be improved, and the ones other than Ti can have excellent withstand voltage characteristics.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a coin-type lithium secondary battery of the present invention.

FIG. 2 is a charging / discharging curve of a test cell made of a working electrode of the present invention, activated carbon, and counter electrode metallic lithium.

FIG. 3 is a working electrode of the present invention, SiO, SnO, and Nb2O.
5 is a charge / discharge characteristic diagram of a test cell made of MoO2, TiO2, and counter electrode lithium.

FIG. 4 uses activated carbon as the positive electrode active material and Si as the negative electrode active material.
The charge / discharge characteristic figure of the lithium secondary battery of this invention which used O, SnO, Nb2O5, and MoO2.

FIG. 5: Activated carbon is used as the positive electrode active material, and Ti is used as the negative electrode active material.
The charge / discharge characteristic figure of the lithium secondary battery of this invention using O2.

FIG. 6 is a charge / discharge characteristic diagram of a lithium secondary battery that is a comparative example with the present invention in which activated carbon is used as a positive electrode active material and metallic lithium is used as a negative electrode active material.

[Explanation of symbols]

101 Positive electrode pellet 102 electrode collector 103 Positive case 104 negative electrode pellet 105 Negative electrode case 106 lithium foil 107 Electrolyte 108 gasket 109 separator

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toyoro Harada 1-8 Nakase, Mihama-ku, Chiba, Chiba Seiko Instruments Inc. (72) Shinichi Takasugi 1-8 Nakase, Mihama-ku, Chiba Seiko Instruments Inc. (56) Reference JP 10-83807 (JP, A) JP 3-95856 (JP, A) JP 6-338325 (JP, A) (58) Fields investigated ( Int.Cl. ⁷ , DB name) H01M 4/02 H01M 10/40 H01M 4/36-4/62

Claims (2)

(57) [Claims] With a 1. A positive electrode using the polarizable electrode material made mainly of activated carbon, a negative electrode employing a lithium metallic oxide is occluded, and a nonaqueous electrolyte containing a lithium salt, the gold
The group oxide contains Si, Sn, Nb, Mo, or Ti
A non-aqueous electrolyte secondary battery characterized by being an oxide containing . 2. A positive electrode using a polarizable electrode material mainly composed of activated carbon, and Si, Sn, which absorbs lithium and
Two or more oxides containing Nb, Mo, or Ti
A non-aqueous electrolyte secondary battery comprising a negative electrode using the above-mixed substance as an active material and a non-aqueous electrolyte containing a lithium salt.