JP4075866B2 - Flat organic electrolyte battery - Google Patents

Description

  The present invention relates to a flat organic electrolyte battery that can withstand use in a high-temperature and high-humidity environment and has excellent low-temperature discharge characteristics.

  Recently, a battery has been demanded as a power source for equipment used in severe environments such as a high temperature atmosphere exceeding 100 ° C. such as a pressure sensor inside a tire, a humid environment, and a low temperature atmosphere such as −40 ° C. Yes. Candidates satisfying the specifications are promising organic electrolyte batteries such as lithium primary batteries and lithium secondary batteries that use organic electrolytes with a low freezing point of 0 ° C or lower and a high boiling point of 100 ° C or higher. Has been actively conducted.

  As the shape of the organic electrolyte battery, a flat type (button type, coin type, flat rectangular type) is optimal in view of necessary discharge capacity, size, mountability, cost, and the like.

  Japanese Patent Application Laid-Open No. H10-228707 discloses changing the gasket, separator, electrolytic solution, and the like of conventional battery constituent materials with respect to the required characteristics in the above temperature range. According to this, since the conventionally used polypropylene (PP) is softened at a temperature of 100 ° C. or higher and sufficient strength cannot be obtained, engineering plastics such as polyphenylene sulfide (PPS), polyetheretherketone Resins such as (PEEK) and tetrafluoroethylene-perfluoroalkoxyethylene copolymer (PFA) are considered optimal because they can maintain strength even in a high temperature atmosphere of 100 ° C. or higher, Similarly, it has been proposed to use polybutylene terephthalate (PBT), polyphenylene sulfide (PPS) or the like instead of low melting point polyethylene (PE) or polypropylene (PP) for the separator. Proposal to use a solvent with high boiling point and low freezing point It has been.

Patent Document 2 proposes a separator material made of glass fiber as a separator material having excellent ion permeability, high strength, thinness, excellent insulating properties, and excellent heat resistance, compared to other separators. As a result, the resistance component is reduced and the discharge characteristics under various conditions are improved.
JP-A-8-32287 JP-A-10-270088

  However, electrolytes using a solvent with a high boiling point and a low freezing point generally have very high viscosity, so the impregnation into the separator is very low, the resistance component in the separator is high, and the load characteristics are very poor. There is a fear.

In addition, lithium hexafluorophosphate (LiPF ₆ ) and lithium tetrafluoroborate (LiBF ₄ ), which are solutes commonly used in organic electrolytes, easily react with moisture to form hydrofluoric acid, It adversely affects battery components. For this reason, efforts are being made to improve sealing performance against strict moisture monitoring during battery manufacture and moisture intrusion into the battery. However, the flat organic electrolyte battery is sealed with a caulking seal, which is less airtight than other laser seals or glass hermetic seals. In addition, when a flat battery is exposed to a hot and humid atmosphere as a power source such as a pressure sensor inside the tire, it is difficult to prevent moisture from entering from the outside of the battery.

Under such circumstances, a separator made of glass fiber becomes a fluoride glass (SiF ₄ ) due to a rapid reaction with hydrofluoric acid (HF) as a problem peculiar to glass, and the function as a separator is extremely lowered. Resulting in. That is, the colorless and transparent or white glass separator becomes a black fluoride glass due to the reaction with hydrofluoric acid, and the discharge performance may be remarkably lowered as the separator function is lowered.

  An object of the present invention is to provide a flat organic electrolyte battery that is excellent in ensuring reliability in a high-temperature and high-humidity environment and having high-load discharge characteristics in a low-temperature atmosphere.

In order to solve the above problems, the flat organic electrolyte battery of the present invention has an annular gasket interposed between a negative electrode can formed into a bottomed cylindrical shape and a positive electrode can formed into a bottomed cylindrical shape, A flat organic electrolyte battery in which a positive electrode, a negative electrode, a separator, and a power generation element composed of an organic electrolyte are sealed by caulking the opening of the positive electrode can, wherein the separator is mainly composed of glass fiber, and the organic The electrolytic solution contains lithium bisperfluoromethylsulfonylimide (LiN (CF ₃ SO ₂ ) ₂ ) and imidazole , and the content of the imidazole is lithium bisperfluoromethylsulfonylimide (LiN (CF ₃ SO ₂ ) ₂ ) and imidazole. It is characterized by being 5-35 mol% with respect to the total amount.

Using an organic electrolytic solution containing a separator mainly composed of glass fiber and lithium bisperfluoromethylsulfonylimide (LiN (CF ₃ SO ₂ ) ₂ ) as a lithium salt , imidazo
By containing an appropriate amount of the steel, it is possible to provide a flat organic electrolyte battery excellent in reliability under a high-temperature and high-humidity environment and high load discharge characteristics under a low-temperature atmosphere.

  Hereinafter, preferred embodiments of the present invention will be described.

In the present invention, an annular gasket is interposed between a negative electrode can formed in a bottomed cylindrical shape and a positive electrode can formed in a bottomed cylindrical shape, and an opening of the positive electrode can is caulked inward to form a positive electrode and a negative electrode , A separator, and a flat organic electrolyte battery in which a power generation element composed of an organic electrolyte is sealed, wherein the separator is mainly composed of glass fiber, and the organic electrolyte is lithium bisperfluoromethylsulfonylimide (LiN (CF ₃ SO ₂ ) ₂ ) and imidazole , and the content of imidazole is 5 to 35 mol% with respect to the total amount of lithium bisperfluoromethylsulfonylimide (LiN (CF ₃ SO ₂ ) ₂ ) and imidazole. And

In a flat organic electrolyte battery, by combining a separator mainly composed of glass fibers, imidazole, and LiN (CF ₃ SO ₂ ) ₂ , the degradation reaction of the glass separator is suppressed even in a high temperature and high humidity environment. It is possible to ensure excellent reliability and discharge performance.

Although the detailed mechanism is not clear, imidazole is adsorbed on the SiO ₂ surface of the glass fiber due to chemical affinity (hydrogen bond between oxygen of the glass fiber and hydrogen of NH group of imidazole), and LiN (CF ₃ SO ₂ ) ₂ and imidazole form a product that is close to an ionic liquid to suppress the movement of moisture to the vicinity of the separator mainly composed of glass fiber, and to suppress the generation of hydrofluoric acid It seems that imidazole traps the hydrofluoric acid produced or produced to inhibit the reaction.

The organic electrolyte containing LiN (CF ₃ SO _{2) 2} as a lithium salt, the clear color of the liquid upon addition of imidazole was changed to pale pink transparent, and the like any reaction or complex ions formed It is. Details are unknown.

In addition, an ionic liquid composed of N (CF ₃ SO ₂ ) ₂ ^— or the like, which is an anion having a sulfone group and an imide bond, generally exhibits hydrophobicity. Therefore, the above imidazole and LiN (CF ₃ SO ₂ ) ₂ the product associated with is also inferred that express similar hydrophobicity.

When both of the above are not combined with a separator mainly composed of glass fiber, the separator deteriorates severely in a high-temperature and high-humidity environment. Therefore, a separator mainly composed of glass fiber, imidazole, LiN (CF ₃ SO _{2 2} ) The combination of 3 is very important.

  As a method for adding imidazole to the inside of the battery, there is an addition to the electrolytic solution or the positive electrode / negative electrode, and the more effective addition is to the electrolytic solution. The added imidazole is diffused and present in any part of the power generation element of the electrolytic solution, the positive electrode, the negative electrode, and the separator by dissolving in the electrolytic solution.

When the amount of imidazole added is less than 5 mol% with respect to the total amount of LiN (CF ₃ SO ₂ ) ₂ and imidazole, the effect of the interaction is weakened, and the glass separator is likely to be deteriorated in a high-temperature and high-humidity environment. On the other hand, if it exceeds 35 mol%, the lithium ion conductivity of the electrolytic solution is reduced, and the discharge performance is degraded.

Lithium bisperfluoromethylsulfonylimide (LiN (CF ₃ SO ₂ ) ₂ ) is less reactive to moisture and excellent in heat resistance than LiPF ₆ and LiBF ₄ salts containing fluorine. The concentration of lithium bisperfluoromethylsulfonylimide (LiN (CF ₃ SO ₂ ) ₂ ) is preferably 0.75 to 1.5 mol / l .

  The organic solvent constituting the electrolyte includes γ-butyrolactone, ethylene carbonate, propylene carbonate, butylene carbonate, sulfolane, 3-methylsulfolane, tetraglyme and other high-boiling / high-viscosity solvents, or monoglyme and diglyme. A mixture of a low-viscosity solvent such as glymes such as triglyme and a chain carbonate such as dimethyl carbonate, ethyl methyl carbonate, and diethyl carbonate is preferred.

The weight of the separator mainly composed of glass fibers is generally 60 to 80 g / m ² and the thickness is generally 0.3 mm or more. In order to improve the discharge characteristics, it is necessary to reduce the thickness as a low weight per unit area. If the weight per unit weight of glass fiber is 60 g / m ² or less, the strength decreases, and there is a risk of internal short circuit without being able to cope with the stress change accompanying the expansion and contraction of the positive and negative electrodes inside the battery. By blending 3 to 25% by weight of acrylic fiber of polyacrylonitrile polymer, polymethyl methacrylate, polyacrylic acid, etc. with glass fiber as the main binder, sufficient strength can be secured in the separator, and the basis weight is 30 to 50 g / m ^2. Thus, a thickness of 0.1 to 0.2 mm can be used.

The positive electrode materials include active materials for primary batteries such as graphite fluoride, copper oxide, copper sulfide, iron sulfide, manganese dioxide, vanadium pentoxide, titanium disulfide, niobium pentoxide, molybdenum trioxide, iron oxyhydroxide, oxy Active materials for 3V class secondary batteries such as nickel hydroxide and lithium manganese composite oxide, and actives for 4V class secondary batteries such as lithium cobaltate, lithium nickelate and spinel type lithium manganate containing lithium Substances.

  Negative electrode materials include lithium alloys such as metallic lithium, Si-Li, Sn-Li, Ge-Li, and Al-Li, carbon-based materials such as graphite and non-graphitizable carbon, silicon monoxide, tin monoxide, and cobalt monoxide. Examples thereof include oxides that react at less than 1 V with lithium mainly composed of, and the like, oxides that react with lithium at 1 V or more, such as spinel lithium titanium oxide, niobium pentoxide, and tungsten dioxide.

  Various combinations of the positive electrode and the negative electrode are possible, and the present invention can be used for both primary batteries and secondary batteries.

  The gasket is preferably a resin such as polyphenylene sulfide (PPS), polyether ether ketone (PEEK), tetrafluoroethylene / perfluoroalkoxyethylene copolymer (PFA), and the resin is used as a filler for the purpose of further improving the strength. Those using glass or inorganic fibers such as calcium titanate are also preferred.

  By adopting the above configuration, it is possible to provide a flat organic electrolyte battery that ensures reliability in a high-temperature and high-humidity environment and is excellent in high-load discharge characteristics in a low-temperature atmosphere.

  Hereinafter, the flat organic electrolyte battery of the present invention will be specifically described based on examples.

Example 1
FIG. 1 is a cross-sectional view of a flat organic electrolyte battery according to an embodiment of the present invention, and has a thickness of 5 mm and a diameter of 24 mm. In FIG. 1, a coin-type battery container that houses a power generation element includes a positive electrode can 5 made of stainless steel having excellent corrosion resistance, a stainless steel negative electrode can 1, and a gasket 6. The power generating element is sealed inside by caulking the part inward. In addition to the function of insulating the positive electrode can 5 and the negative electrode can 1, the gasket 6 has a function of physically sealing the power generation element in a battery container in a liquid-tight manner. A gasket 6 made of polyphenylene sulfide (PPS) resin was used. A solution obtained by diluting butyl rubber with toluene was applied between the gasket 6 and the positive electrode can 5 and between the negative electrode can 1 and the gasket 6, and the toluene was evaporated to obtain a sealant 8 made of a butyl rubber film.

The positive electrode 3 is obtained by mixing electrolytic manganese dioxide (EMD) as an active material, carbon black as a conductive agent, and fluororesin powder as a binder at a mass ratio of 90: 5: 5, and molding the mixture into a pellet shape. It was dried in C for 12 hours. The obtained pellet-like positive electrode material is in contact with the positive electrode current collector 7 formed by applying a carbon paint on the inner surface of the positive electrode can 5. On the other hand, the negative electrode 2 was pressure-bonded to the negative electrode can 1 using a lithium aluminum (Al—Li) alloy. The separator 4 disposed between the positive electrode 3 and the negative electrode 2 has a basis weight of 45 g / m ² , a fiber diameter of 0.3 to 1 μm, a fiber length of 300 to 1000 μm, and is mainly made of glass fiber. A binder containing 15% by weight of acrylic fiber was used. The electrolytic solution was prepared by dissolving 1.0 mol / l of LiN (CF ₃ SO ₂ ) ₂ in a 1: 1 mixed solvent of propylene carbonate and diglyme, imidazole and imidazole and LiN (CF ₃ SO ₂ ). What was added so that it might contain 25 mol% with respect to the total amount of ₂ was used. The battery thus obtained was designated as battery A.

  Batteries B to D were produced in the same manner as the battery A except that the imidazole content of the battery A was changed from 25 mol% to a content of 5 mol% to 35 mol%.

A battery E was prepared in the same manner as battery A except that LiN (C ₂ F ₅ SO ₂ ) ₂ was used instead of LiN (CF ₃ SO ₂ ) _{2 as} the solute of battery A.

Battery F was prepared in the same manner as Battery A except that LiN (C ₄ F ₉ SO ₂ ) (CF ₃ SO ₂ ) was used instead of LiN (CF ₃ SO ₂ ) _{2 as} the solute of battery A. .

  The batteries produced in the same manner as battery A were designated as batteries 1, 2, and 3 except that the content of imidazole in battery A was 25 mol% without addition (0 mol%), the content was 3 mol%, and the content was 40 mol%. .

A battery produced in the same manner as battery A except that LiPF ₆ was used in place of the solute lithium salt LiN (CF ₃ SO ₂ ) ₂ of battery A was designated as battery 4.

  The batteries A to F according to the present invention and the batteries 1 to 4 as comparative examples were subjected to a constant current discharge of 5 mA at a capacity of 10% with respect to the theoretical capacity of manganese dioxide of the positive electrode, and then stored at 100 ° C. for 240 hours. A high-temperature storage test to be performed and a high-temperature and high-humidity storage test to be stored at 85 ° C. and 90% for 240 hours are performed, and before and after each storage test, discharge is performed at a current value of 3 mA in an environment of −40 ° C. The closed circuit voltage (CCV) after 2 seconds was measured. The results are shown in (Table 1).

Regarding the batteries A to F according to the present invention, the closed circuit voltage (CCV) at a low temperature was not drastically decreased even after the high temperature storage test and the high temperature and humidity storage test, and excellent low temperature discharge characteristics could be maintained. . In battery 1 to which imidazole was not added, battery 2 having a low content, and battery 4 using LiPF ₆ as a solute, the closed circuit voltage (CCV) at a low temperature after the high-temperature and high-humidity storage test was significantly reduced. In the battery 3 having a high imidazole content, the closed circuit voltage (CCV) at a low temperature before the test was at a low level compared to other batteries.

In the embodiments, a lithium manganese dioxide primary battery has been described. However, the present invention is not limited to this, but a primary battery such as a lithium fluoride graphite primary battery or a lithium ion secondary battery in which 4V-class lithium cobaltate and graphite are combined. Or a combination of vanadium pentoxide and a lithium aluminum alloy, a lithium secondary manganese battery containing a lithium-containing manganese oxide or a lithium aluminum alloy, a combination of lithium cobalt oxide and lithium titanium oxide,
The same effect can be obtained with a 2.5 V class lithium secondary battery in which niobium pentoxide and a lithium aluminum alloy are combined.

In the present invention, an annular gasket is interposed between a negative electrode can formed in a bottomed cylindrical shape and a positive electrode can formed in a bottomed cylindrical shape, and an opening of the positive electrode can is caulked inward to form a positive electrode and a negative electrode In a flat organic electrolyte battery in which a power generation element composed of a separator and an organic electrolyte is sealed, a separator mainly composed of glass fiber and lithium bisperfluoromethylsulfonylimide (LiN (CF ₃ SO ₂ ) as a lithium salt By combining the organic electrolyte containing ₂ ) with imidazole, it is possible to provide a flat organic electrolyte battery excellent in reliability under a high temperature and humidity environment and high load discharge characteristics in a low temperature atmosphere.

  In addition, it can be deployed as a power source for tire pressure sensors to ensure the safety of future automobiles, which is extremely useful.

Sectional drawing of the flat organic electrolyte battery which concerns on the Example of this invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Negative electrode can 2 Negative electrode 3 Positive electrode 4 Separator 5 Positive electrode can 6 Gasket

Claims (1)

An annular gasket is interposed between the negative electrode can formed into a bottomed cylindrical shape and the positive electrode can formed into a bottomed cylindrical shape, and the positive electrode, negative electrode, separator, and A flat organic electrolyte battery in which a power generation element made of an organic electrolyte is sealed, wherein the separator is mainly composed of glass fiber, and the organic electrolyte is lithium bisperfluoromethylsulfonylimide (LiN (CF ₃ SO ₂ ) ₂ ) and imidazole , wherein the imidazole content is 5 to 35 mol% with respect to the total amount of lithium bisperfluoromethylsulfonylimide (LiN (CF ₃ SO ₂ ) ₂ ) and imidazole, Organic electrolyte battery.

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