Battery

Abstract

The present invention provides a battery which has an aqueous electrolyte solution and is excellent in terms of safety and discharge characteristics at low temperatures.　A battery according to the present invention includes a positive electrode, a negative electrode, and an electrolyte solution, and is characterized in that: the electrolyte solution is an aqueous solution that contains at least LiCl as an electrolyte salt; and the concentration of LiCl in the aqueous solution is 16% by mass or more. If the amount of the total electrolyte salt contained in the electrolyte solution is taken as 100 parts by mass, the amount of LiCl is preferably 50 parts by mass or more.

Description

battery

[0001] The present invention relates to a battery having an aqueous electrolyte solution, which is safe and has excellent discharge characteristics at low temperatures.

[0002] Batteries using aqueous electrolytes, such as air batteries and alkaline batteries, have been widely used for a long time, but in recent years they have increasingly been used as power sources for various body sensors, such as temperature patches.

[0003] Various improvements have been made to batteries having aqueous electrolyte solutions. For example, Patent Document 1 proposes a technology for a sheet battery having an exterior body made of a polymer compound sheet, in which a compound, separate from an electrolyte salt, is added to the electrolyte solution, the water vapor pressure of which in saturated aqueous solution at the operating temperature is equal to or less than the partial pressure of water vapor in the atmosphere corresponding to an atmospheric relative humidity of 40% at that temperature, thereby suppressing depletion of the electrolyte solution due to evaporation of water in the electrolyte solution through the sheet over time. In the examples of Patent Document 1, lithium chloride (LiCl) and calcium chloride (CaCl) are added as the compounds to the electrolyte solution. ２ ) is used.

[0004] Furthermore, improvements are being made to batteries having an aqueous electrolyte solution in light of the above-mentioned expansion of applications. For example, from the viewpoint of minimizing the impact on the environment even when a user discards a replaced battery, attempts have been made to ensure good characteristics while lowering the pH of the electrolyte solution by using an aqueous solution containing a salt of a strong acid and a weak base as the electrolyte salt (Patent Documents 2 and 3, etc.).

[0005] Japanese Patent Application Laid-Open No. 5-135778 International Publication No. 2018 / 056307 International Publication No. 2020 / 162591

[0006] However, batteries using an electrolyte solution containing a salt of a strong acid and a weak base as an electrolyte salt, such as ammonium chloride, as described in Patent Document 2 and Patent Document 3, have a problem in that discharge characteristics are significantly impaired at low temperatures (0°C or lower, particularly -20°C or lower (e.g., about -40°C)), and there is still room for improvement in this regard.

[0007] On the other hand, in manganese batteries and the like, an aqueous solution containing zinc chloride, which corresponds to a salt of a strong acid and a weak base, as the electrolyte salt is used, and it has been confirmed that the battery can discharge well even in a low-temperature environment. However, since zinc chloride is a compound designated as a deleterious substance, it is desirable to reduce the amount of such compound used in the electrolyte as much as possible.

[0008] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a battery that contains an aqueous electrolyte solution and has excellent safety and low-temperature discharge characteristics.

[0009] The battery of the present invention is a battery including a positive electrode, a negative electrode, and an electrolyte, wherein the electrolyte is an aqueous solution containing at least LiCl as an electrolyte salt, and the concentration of LiCl in the aqueous solution is 16 mass % or more.

[0010] According to the present invention, it is possible to provide a battery that contains an aqueous electrolyte solution and has excellent safety and low-temperature discharge characteristics.

[0011] 1 is a plan view schematically showing an example of a battery of the present invention. It is a cross-sectional view taken along line II in FIG. 1. It is a graph showing the evaluation results of the discharge characteristics at low temperatures of the batteries of Examples and Comparative Examples. It is a graph showing the evaluation results of the discharge characteristics at low temperatures of the batteries of Examples.

[0012] Batteries that use an aqueous solution of electrolyte salts, such as ammonium chloride, as an electrolyte salt, have a low pH and good discharge characteristics. However, even in such batteries, depending on the type of electrolyte salt, in low-temperature environments below 0°C, particularly below −20°C (for example, about −40°C), the electrolyte salt may precipitate or the aqueous solution may freeze, making it impossible to ensure sufficient discharge characteristics.

[0013] On the other hand, manganese batteries using manganese oxide in the positive electrode use an aqueous solution of zinc chloride as the electrolyte salt, and such batteries can discharge well even in the low-temperature environment. However, because zinc chloride is a deleterious substance, there is room for improvement in terms of safety in the event that the electrolyte leaks and comes into contact with the body.

[0014] Therefore, in the present invention, an aqueous solution containing at least LiCl as an electrolyte salt at a certain concentration or higher is used as the electrolyte, which ensures a certain level of discharge characteristics at low temperatures and also improves safety by providing an electrolyte that does not contain zinc chloride or has a reduced zinc chloride content.

[0015] The battery of the present invention can take the form of various batteries (manganese battery, silver oxide battery, air battery, etc.) having an aqueous electrolyte, that is, an electrolyte consisting of an aqueous solution with water as the solvent.

[0016] (Aqueous Electrolyte) The battery of the present invention has, as the aqueous electrolyte, an aqueous solution containing at least LiCl as an electrolyte salt, with a LiCl concentration of 16 mass % or more.

[0017] The aqueous electrolyte contains a high concentration of LiCl, which allows the battery to exhibit good load characteristics even when placed at low temperatures. Furthermore, when an aqueous electrolyte containing LiCl as the electrolyte salt is used, corrosion of the negative electrode caused by the aqueous electrolyte and the associated gas generation within the battery can be effectively suppressed. Therefore, the battery of the present invention can effectively suppress problems such as leakage that may be caused by gas generated inside the battery.

[0018] The LiCl concentration in the aqueous electrolyte solution is 16% by mass or more, preferably 20% by mass or more, and more preferably 25% by mass or more. From the viewpoint of preventing salt precipitation and improving the discharge characteristics (particularly load characteristics) of the battery at low temperatures, the LiCl concentration in the aqueous electrolyte solution is preferably 45% by mass or less, more preferably 40% by mass or less, and particularly preferably 35% by mass or less.

[0019] The aqueous electrolyte may contain electrolyte salts other than LiCl, but if the concentration of electrolyte salts other than LiCl becomes high, it may be difficult to increase the LiCl concentration, which may make it difficult to improve the low-temperature load characteristics of the battery. Therefore, when the amount of all electrolyte salts in the aqueous electrolyte is 100 parts by mass, the amount of LiCl is preferably 50 parts by mass or more, more preferably 70 parts by mass or more, and particularly preferably 80 parts by mass or more. Since the aqueous electrolyte may contain only LiCl as the electrolyte salt, the upper limit of the amount of LiCl when the amount of all electrolyte salts in the aqueous electrolyte is 100 parts by mass is 100 parts by mass.

[0020] Examples of electrolyte salts other than LiCl that can be used in aqueous electrolyte solutions include chlorides such as sodium chloride, potassium chloride, magnesium chloride, calcium chloride, ammonium chloride, and zinc chloride; hydroxides of alkali metals and alkaline earth metals (sodium hydroxide, potassium hydroxide, magnesium hydroxide, etc.), acetates thereof (sodium acetate, potassium acetate, magnesium acetate, etc.), nitrates thereof (sodium nitrate, potassium nitrate, magnesium nitrate, etc.), sulfates thereof (sodium sulfate, potassium sulfate, magnesium sulfate, etc.), phosphates thereof (sodium phosphate, potassium phosphate, magnesium phosphate, etc.), borates thereof (sodium borate, potassium borate, magnesium borate, etc.), citrates thereof (sodium citrate, potassium citrate, magnesium citrate, etc.), glutamate salts thereof (sodium glutamate, potassium glutamate, magnesium glutamate, etc.); hydrogen carbonates of alkali metals (sodium hydrogen carbonate, potassium hydrogen carbonate, etc.); percarbonates of alkali metals (sodium percarbonate, potassium percarbonate, etc.); compounds containing halogens such as fluorides; polycarboxylic acids; and the like. One or more of these can be used.

[0021] Among the above-mentioned exemplary electrolyte salts, the electrolyte salt used in combination with LiCl is preferably at least one selected from the group consisting of ammonium chloride, zinc chloride, hydroxides of alkali metals, and hydroxides of alkaline earth metals, and more preferably ammonium chloride. By using ammonium chloride together with LiCl as the electrolyte salt, it is expected that the open circuit voltage (OCV) and closed circuit voltage (CCV) will be increased when the battery is used at room temperature. It is also more preferable to use zinc chloride together with LiCl as the electrolyte salt, which is expected to further improve the characteristics at low temperatures.

[0022] When using ammonium chloride and zinc chloride, they may be contained so that the ratio with LiCl falls within the aforementioned range. However, since zinc chloride is a deleterious substance, its content should be as low as possible. While a typical manganese battery uses an electrolyte containing approximately 30% by mass of zinc chloride, in the present invention, from the viewpoint of safety, the concentration of zinc chloride in the aqueous electrolyte is preferably 15% by mass or less, more preferably 10% by mass or less, and more preferably 5% by mass or less, and may not be present at all. Furthermore, from the viewpoint of better ensuring the above-mentioned effects of using ammonium chloride in the aqueous electrolyte, the amount of ammonium chloride is preferably 0.5 parts by mass or more, more preferably 5 parts by mass or more, and even more preferably 10 parts by mass or more, when the amount of all electrolyte salts in the aqueous electrolyte is 100 parts by mass. Furthermore, the amount of ammonium chloride is preferably 20 parts by mass or less, when the amount of all electrolyte salts in the aqueous electrolyte is 100 parts by mass.

[0023] When the battery is an air battery, the water in the aqueous electrolyte solution evaporates and dissipates through the air holes, which can cause fluctuations in the electrolyte solution composition. To avoid this problem, a water-soluble high-boiling solvent with a boiling point of 150° C. or higher (preferably 320° C. or lower) can be used together with water as a solvent for the aqueous electrolyte solution, or a thickener can be added to the aqueous electrolyte solution (more preferably, a gel (gel electrolyte) can be formed).

[0024] Examples of the water-soluble high-boiling point solvent include polyhydric alcohols such as ethylene glycol (boiling point 197°C), propylene glycol (boiling point 188°C), and glycerin (boiling point 290°C); polyalkylene glycols (preferably those having a molecular weight of 600 or less) such as polyethylene glycol (PEG; for example, boiling point 230°C); etc. When a water-soluble high-boiling point solvent is used, its proportion in the total solvent is preferably 3 to 30 mass%.

[0025] Furthermore, in a battery having a negative electrode using a metal sheet (metal foil) that acts as a negative electrode active material as described below, when an aqueous electrolyte solution consisting of an aqueous solution is used, there is a risk that the negative electrode will break due to corrosion by the aqueous electrolyte solution, and problems such as inability to fully utilize capacity may occur. When LiCl is used as the electrolyte salt of the aqueous electrolyte solution, it is possible to suppress corrosion of the negative electrode as described above, but when a thickener is added to the aqueous electrolyte solution, more preferably in a gel form (gel electrolyte), it is possible to avoid the problem of fluctuations in the electrolyte solution composition, and further suppress unnecessary corrosion reactions of the negative electrode, and further suppress the associated gas generation and breakage of the negative electrode. Examples of thickeners that can be incorporated into aqueous electrolyte solutions include cellulose derivatives such as carboxymethyl cellulose (CMC) and carboxyethyl cellulose (CEC); polyalkylene oxides such as polyethylene oxide (PEO) (however, those with a molecular weight of 1,000 or more are desirable, and those with a molecular weight of 10,000 or more are more desirable); polyvinylpyrrolidone; polyvinyl acetate; starch; guar gum; xanthan gum; sodium alginate; hyaluronic acid; gelatin; polyacrylic acid; and acrylamide polymers or copolymers. Furthermore, when using thickeners among the above examples that have a functional group consisting of a carboxyl group or a salt thereof (such as -COOH or -COONa) in the molecule, it is also preferable to incorporate a polyvalent metal salt that acts as a gelation promoter into the aqueous electrolyte solution. The amount of thickener in the aqueous electrolyte solution is preferably 0.1% by mass or more, more preferably 1% by mass or more, and even more preferably 3% by mass or more in order to enhance the above-mentioned effect, and is preferably 20% by mass or less, more preferably 15% by mass or less, and even more preferably 10% by mass or less in order to prevent a decrease in discharge characteristics. Furthermore, when a gelation accelerator is used, the proportion of the gelation accelerator is preferably 1 to 30% by mass when the proportion of the thickener is 100.

[0026] The aqueous electrolyte may be made into a gel (gel electrolyte) by using a gelling agent such as a known polymer.

[0027] The pH of the aqueous electrolyte solution is not particularly limited, but is preferably 3 or higher, more preferably 4 or higher, in order to prevent corrosion of the negative electrode active material. On the other hand, when constructing an air battery, the pH of the aqueous electrolyte solution is preferably 8 or lower, more preferably 7 or lower, and even more preferably 6 or lower, in order to prevent carbon dioxide in the air from being absorbed into the electrolyte solution. The pH of the aqueous electrolyte solution can be adjusted by using a salt of a weak acid and a strong base or a salt of a strong acid and a weak base in combination. Furthermore, the pH of the aqueous electrolyte solution can also be adjusted to a lower value by adding a weak acid such as carboxylic acid, carbonic acid, or phosphoric acid to the electrolyte solution.

[0028] (Negative Electrode) For the negative electrode, for example, one containing at least one metal selected from the group consisting of zinc, aluminum, magnesium, and alloys thereof as an active material is used.

[0029] Specific examples of such negative electrodes that are preferably used include metal sheets made of the above-mentioned materials (zinc foil, zinc alloy foil, magnesium foil, magnesium alloy foil, aluminum foil, and aluminum alloy foil). The thickness of the metal sheet is preferably 5 to 1000 μm.

[0030] Metal particles made of the above materials (zinc particles, zinc alloy particles, magnesium particles, magnesium alloy particles, aluminum particles, aluminum alloy particles) can also be used.

[0031] Examples of alloying components of the zinc alloy include indium, bismuth, and aluminum, and one or more of these elements may be contained.

[0032] The contents of the alloy components in the zinc alloy are, for example, as follows: The indium content is, for example, 0.005% or more and 0.1% or less by mass; The bismuth content is, for example, 0.002% or more and 0.2% or less by mass; and The aluminum content is, for example, 0.0001% or more and 0.15% or less by mass.

[0033] Zinc foil and zinc alloy foil include electrolytic foil and rolled foil, but electrolytic foil is preferred because electrolytic foil is less likely to generate gas due to reaction with the electrolyte in the battery, and electrolytic zinc alloy foil containing bismuth is more preferred. The preferred range of bismuth content in electrolytic zinc alloy foil is 0.02% or more and 0.1% or less by mass.

[0034] Furthermore, examples of alloying components of magnesium alloys include calcium, manganese, zinc, and aluminum, and one or more of these elements may be contained.

[0035] The contents of the alloy components in the magnesium alloy are, for example, as follows: The calcium content is, for example, 1% or more and 3% or less by mass; The manganese content is, for example, 0.1% or more and 0.5% or less by mass; The zinc content is, for example, 0.4% or more and 1% or less by mass; and The aluminum content is, for example, 8% or more and 10% or less by mass.

[0036] Furthermore, examples of alloying components of the aluminum alloy include zinc, tin, gallium, silicon, iron, magnesium, and manganese, and one or more of these elements may be contained.

[0037] The contents of each alloy component in the aluminum alloy are, for example, as follows: The zinc content is, for example, 0.5% or more and 10% or less by mass. The tin content is, for example, 0.04% or more and 1.0% or less by mass. The gallium content is, for example, 0.003% or more and 1.0% or less by mass. The silicon content is, for example, 0.05% or less by mass. The iron content is, for example, 0.1% or less by mass. The magnesium content is, for example, 0.1% or more and 2.0% or less by mass. The manganese content is, for example, 0.01% or more and 0.5% or less by mass.

[0038] In the case of a negative electrode containing metal particles, the metal particles may be of one type alone or two or more types.

[0039] In consideration of reducing the environmental load when discarding batteries, it is preferable that the metal material used for the negative electrode contains small amounts of mercury, cadmium, lead, and chromium, and more preferably the specific contents are, on a mass basis, mercury: 0.1% or less, cadmium: 0.01% or less, lead: 0.1% or less, and chromium: 0.1% or less.

[0040] Regarding the particle size of the zinc particles and zinc alloy particles, for example, the proportion of particles having a particle size of 75 μm or less among all particles is preferably 50 mass% or less, more preferably 30 mass% or less, and the proportion of particles having a particle size of 100 to 200 μm is 50 mass% or more, more preferably 90 mass% or more.

[0041] Regarding the particle size of the magnesium particles, magnesium alloy particles, aluminum particles, and aluminum alloy particles, for example, the proportion of particles having a particle size of 30 μm or less among all particles is preferably 50 mass% or less, more preferably 30 mass% or less, and the proportion of particles having a particle size of 50 to 200 μm is 50 mass% or more, more preferably 90 mass% or more.

[0042] The particle size of metal particles referred to in this specification is the particle size (D50) at a cumulative frequency of 50% on a volume basis, measured by dispersing the particles in a medium that does not dissolve the particles using a laser scattering particle size distribution analyzer (for example, "LA-920" manufactured by Horiba, Ltd.).

[0043] In the case of a negative electrode containing the above-mentioned metal particles, a gelling agent (such as sodium polyacrylate or carboxymethyl cellulose) or a binder may be added as needed to form the mixture, and a negative electrode mixture (such as a gelled negative electrode) can be used by adding an electrolytic solution to this. The amount of gelling agent in the negative electrode is preferably 0.5 to 1.5 mass %, and the amount of binder is preferably 0.5 to 3 mass %.

[0044] The electrolyte for the negative electrode containing metal particles can be the same as that injected into the battery.

[0045] The content of metal particles in the negative electrode is, for example, preferably 60% by mass or more, more preferably 65% ​​by mass or more, and preferably 95% by mass or less, more preferably 90% by mass or less.

[0046] The negative electrode containing metal particles preferably contains an indium compound, which can more effectively prevent hydrogen gas generation due to a corrosion reaction between the metal particles and the electrolyte.

[0047] Examples of the indium compound include indium oxide and indium hydroxide.

[0048] The amount of the indium compound used in the negative electrode is preferably 0.003 to 1 in terms of mass ratio to 100 metal particles.

[0049] Furthermore, a current collector may be used for the negative electrode containing a metal material, if necessary. Examples of the current collector for the negative electrode containing a metal material include a mesh, foil, expanded metal, and punched metal made of metal such as nickel, copper, and stainless steel; and a carbon sheet or mesh. The thickness of the negative electrode current collector is preferably 10 μm or more and 300 μm or less.

[0050] As in the case of the positive electrode, the negative electrode current collector can be used by applying a carbon paste to the surface of the sheet-like outer casing that is to become the inner surface. The thickness of the carbon paste layer is preferably 50 to 200 μm.

[0051] The negative electrode terminal for connecting the battery to an application device can be, for example, a foil (plate, sheet), wire, or the like made of the metal or carbon exemplified above as a possible negative electrode current collector. When the negative electrode terminal is a foil (plate, sheet), the thickness is preferably 20 μm or more and 500 μm or less. When the negative electrode terminal is a wire, the diameter is preferably 50 μm or more and 1500 μm or less.

[0052] In addition, a part of the current collector of the negative electrode can be used as a terminal portion. Furthermore, when the negative electrode is made of a metal sheet, the metal sheet can be cut into a shape having a main portion that functions as a negative electrode active material layer and a terminal portion, thereby forming a negative electrode having a main portion and a terminal portion from a single metal sheet.

[0053] (Positive Electrode) When the battery is a manganese battery or a silver oxide battery, the positive electrode may have a structure in which a positive electrode mixture layer containing a positive electrode active material, a conductive additive, and a binder is provided on one or both sides of a current collector, or a molded body obtained by molding a positive electrode mixture containing a positive electrode active material, a conductive additive, and a binder.

[0054] When the battery is a manganese battery, a manganese oxide such as manganese dioxide is used as the positive electrode active material. When the battery is a silver oxide battery, a silver-containing oxide such as silver oxide (silver(I) oxide, silver(II) oxide, etc.) or a silver-nickel composite oxide is used as the positive electrode active material. To improve the load characteristics of the battery, the silver-containing oxide is preferably granular. Examples of conductive additives for the positive electrode mixture include carbon materials such as carbon blacks (acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black, etc.); carbon fibers; conductive fibers (metal fibers, etc.); carbon fluoride; metal powders (e.g., copper, nickel, etc.); and organic conductive materials (e.g., polyphenylene derivatives).

[0055] Examples of binders for the positive electrode mixture include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), styrene butadiene rubber (SBR), CMC, and polyvinylpyrrolidone (PVP).

[0056] The composition of the positive electrode mixture is preferably such that the amount of positive electrode active material is 80 to 98% by mass, the content of the conductive additive is preferably 1.5 to 10% by mass, and the content of the binder is preferably 0.5 to 10% by mass. Furthermore, in the case of a positive electrode having a positive electrode mixture layer and a current collector, the thickness of the positive electrode mixture layer (thickness per side of the current collector) is preferably 30 to 300 μm. Furthermore, in the case of a positive electrode having a molded body of the positive electrode mixture, the thickness of the molded body of the positive electrode mixture is preferably 0.2 to 0.25 mm.

[0057] A positive electrode having a positive electrode mixture layer can be produced, for example, by dispersing a positive electrode active material, a conductive additive, a binder, etc. in an organic solvent such as water or N-methyl-2-pyrrolidone (NMP) to prepare a positive electrode mixture-containing composition (slurry, paste, etc.) (the binder may be dissolved in the solvent), applying this to a current collector, drying it, and, if necessary, performing a pressing process such as calendaring. Furthermore, in the case of a positive electrode having a molded body of a positive electrode mixture, for example, it can be produced by pressure molding the positive electrode mixture, or by pressing the molded body of the positive electrode mixture obtained in this way onto a current collector.

[0058] When the battery is an air battery, the positive electrode (air electrode) may have a catalyst layer, for example, a structure in which a catalyst layer and a current collector are laminated.

[0059] The catalyst layer may contain a catalyst, a binder, and the like.

[0060] Examples of catalysts for the catalyst layer include phthalocyanine-based metal complexes; silver, platinum group metals or alloys thereof; transition metals; and Pt / IrO. ２ Platinum / metal oxides such as La １－ｘ Ca ｘ CoO ３ Perovskite oxides such as WC; carbides such as Mn ４ manganese oxides such as manganese dioxide; carbon (graphite, carbon black (acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black, etc.), charcoal, activated carbon, etc.), and the like, and one or more of these may be used.

[0061] The catalyst layer preferably has a heavy metal content of 1% by mass or less. Depending on the form of the battery, it can be easily torn apart by hand or the like when disposed of, but in the case of a positive electrode having a catalyst layer with a low heavy metal content as described above, the battery can be disposed of without any special treatment, resulting in a low environmental impact.

[0062] The content of heavy metals in the catalyst layer referred to in this specification can be measured by X-ray fluorescence analysis. For example, the measurement can be performed using an X-ray fluorescence analyzer "ZSX100e" manufactured by Rigaku Corporation under the conditions of an excitation source of Rh 50 kV and an analysis area of ​​φ10 mm.

[0063] Therefore, it is recommended that the catalyst for the catalyst layer does not contain heavy metals, and it is more preferable to use the various carbons mentioned above.

[0064] In addition, from the viewpoint of further increasing the reactivity of the positive electrode, the specific surface area of ​​the carbon used as a catalyst is set to 200 m ２ / g or more, and ２ / g or more is more preferable, and 500m ２ / g or more is more preferable. The specific surface area of ​​carbon referred to in this specification is a value determined by the BET method in accordance with Japanese Industrial Standards (JIS) K 6217, and can be measured, for example, using a specific surface area measuring device ("Macsorb HM model-1201" manufactured by Mountech Co.) using the nitrogen adsorption method. The upper limit of the specific surface area of ​​carbon is usually 2000 mm ２ / g.

[0065] The catalyst content in the catalyst layer is preferably 20 to 70 mass %.

[0066] Examples of binders for the catalyst layer include fluororesin binders such as PVDF, PTFE, vinylidene fluoride copolymers, and tetrafluoroethylene copolymers [such as vinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP), vinylidene fluoride-chlorotrifluoroethylene copolymer (PVDF-CTFE), vinylidene fluoride-tetrafluoroethylene copolymer (PVDF-TFE), and vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymer (PVDF-HFP-TFE)]. Among these, tetrafluoroethylene polymer (PTFE) or copolymers are preferred, with PTFE being more preferred. The binder content in the catalyst layer is preferably 3 to 50% by mass.

[0067] In the case of a positive electrode having a catalyst layer, for example, it can be produced by mixing the catalyst, binder, etc. with water, rolling it with a roll, and bringing it into close contact with a current collector. Alternatively, it can be produced by applying a catalyst layer-forming composition (slurry, paste, etc.) prepared by dispersing the catalyst and a binder, etc. used as needed, in water or an organic solvent to the surface of the current collector, drying it, and then subjecting it to a pressing process such as calendering, as needed.

[0068] The catalyst layer may also be a porous carbon sheet made of fibrous carbon, such as carbon paper, carbon cloth, or carbon felt. The carbon sheet may also be used as a current collector for the positive electrode, which will be described later, or may serve as both.

[0069] For example, a metal mesh, foil, expanded metal, or punched metal such as titanium, nickel, stainless steel, or copper; or a carbon mesh or sheet; can be used as the current collector for a positive electrode having a positive electrode mixture layer or a positive electrode having a catalyst layer. When a current collector having pores is used, the components of the positive electrode mixture layer or the catalyst layer may be held in the pores of the current collector, thereby integrating the positive electrode mixture layer or the catalyst layer with the current collector. The thickness of the current collector for the positive electrode is preferably 10 μm or more and 300 μm or less.

[0070] Furthermore, when a battery has a sheet-like outer casing made of a resin film, a portion of the resin film can be used as the positive electrode current collector. In this case, for example, a carbon paste can be applied to the surface of the resin film that is intended to become the inner surface of the sheet-like outer casing to form a current collector, or a metal layer of a resin film having a metal layer can be used as a current collector, and a positive electrode mixture layer and a catalyst layer can be formed on the surface of this current collector in the same manner as described above to form a positive electrode. The thickness of the carbon paste layer is preferably 30 to 300 μm.

[0071] The positive electrode usually has a terminal portion for connection to an application device. The terminal portion of the positive electrode can be formed by connecting an aluminum foil (plate) or wire, a nickel foil (plate) or wire, or the like to the positive electrode current collector via a lead body, or by directly connecting to the positive electrode current collector. When the terminal portion of the positive electrode is a foil (plate), the thickness is preferably 50 μm or more and 500 μm or less. When the terminal portion of the positive electrode is a wire, the diameter is preferably 100 μm or more and 1500 μm or less. Furthermore, the terminal portion of the positive electrode may be formed by exposing a portion of the current collector to the outside.

[0072] (Separator) In a battery, a separator is interposed between the positive electrode and the negative electrode. When the battery is a manganese battery or an air battery, the separator can be made of a nonwoven fabric mainly made of vinylon and rayon, a vinylon-rayon nonwoven fabric (vinylon-rayon mixed paper), a polyamide nonwoven fabric, a polyolefin-rayon nonwoven fabric, vinylon paper, vinylon-linter pulp paper, vinylon-mercerized pulp paper, or the like. In addition, a microporous film can also be used, and specific examples thereof include a microporous polyolefin film (such as a microporous polyethylene film or a microporous polypropylene film), and the surface of the film may be hydrophilized to improve wettability with an aqueous electrolyte.

[0073] Alternatively, the separator may be a stack of the microporous film, a cellophane film, and a liquid-absorbing layer (electrolyte solution holding layer) such as vinylon-rayon mixed paper. The thickness of the separator is preferably, for example, 10 to 500 μm, and in the case of a microporous film, it is preferably 10 to 50 μm, and in the case of a nonwoven fabric, it is preferably 20 to 500 μm.

[0074] (Battery Shape, etc.) There are no particular limitations on the shape of the battery, and the battery may be any of the following: a flat type (including a coin type and a button type) having a battery case in which the outer can and the sealing plate are crimped and sealed via a gasket, or the outer can and the sealing plate are sealed by welding; a sheet type having a sheet-like outer body made of a resin film; and a cylindrical type (cylindrical, square (rectangular cylindrical)) having a battery case in which the outer can and the sealing plate are crimped and sealed via a gasket, or the outer can and the sealing plate are sealed by welding.

[0075] When the battery is used as a power source for medical and health equipment, such as a patch that can be attached to the body, particularly a patch that is attached to the surface of the skin to measure body conditions such as body temperature, pulse rate, and sweat rate, it is preferable to use a sheet-type battery with a sheet-type outer casing made of a resin film.

[0076] The sheet-like outer packaging body is made of a resin film, and examples of such a resin film include nylon film (such as nylon 66 film) and polyester film (such as polyethylene terephthalate (PET) film).

[0077] In addition, the sheet-like outer packaging body is generally sealed by heat sealing the end of the upper resin film of the sheet-like outer packaging body to the end of the lower resin film, but in order to make this heat sealing easier, a heat-sealing resin layer may be laminated on the resin film exemplified above and used for the sheet-like outer packaging body. Examples of heat-sealing resins that constitute the heat-sealing resin layer include modified polyolefin films (such as modified polyolefin ionomer films), polypropylene and copolymers thereof, etc. The thickness of the heat-sealing resin layer is preferably 20 to 200 μm.

[0078] A metal layer may be laminated on the resin film. The metal layer may be composed of an aluminum film (aluminum foil, including aluminum alloy foil), a stainless steel film (stainless steel foil), or the like. The thickness of the metal layer is preferably 10 to 150 μm.

[0079] Furthermore, the resin film constituting the sheet-like outer packaging body may be a film having a configuration in which the above-mentioned heat-sealable resin layer and the above-mentioned metal layer are laminated together.

[0080] It is also preferable that the resin film constituting the sheet-like exterior body has an electrically insulating water vapor barrier layer. In this case, the electrically insulating resin film may have a single-layer structure in which it itself also serves as a water vapor barrier layer, or a multilayer structure in which it has multiple electrically insulating resin film layers, at least one of which serves as a water vapor barrier layer, or a multilayer structure in which an electrically insulating water vapor barrier layer is provided on the surface of a base layer made of a resin film.

[0081] Among these resin films, those in which a water vapor barrier layer made of at least an inorganic oxide is formed on the surface of a base layer made of a resin film are preferably used.

[0082] Examples of inorganic oxides constituting the water vapor barrier layer include aluminum oxide and silicon oxide. Note that a water vapor barrier layer made of silicon oxide tends to have a higher function of suppressing the permeation of moisture in the electrolyte solution in the battery than a water vapor barrier layer made of aluminum oxide. Therefore, it is more preferable to use silicon oxide as the inorganic oxide constituting the water vapor barrier layer.

[0083] The water vapor barrier layer made of an inorganic oxide can be formed on the surface of the substrate layer by, for example, a vapor deposition method. The thickness of the water vapor barrier layer is preferably 10 to 300 nm.

[0084] Examples of the substrate layer of the resin film having a water vapor barrier layer include the above-mentioned nylon film and polyester film, as well as polyolefin film, polyimide film, polycarbonate film, etc. The thickness of the substrate layer is preferably 5 to 100 μm.

[0085] In the case of a resin film having a water vapor barrier layer and a substrate layer, a protective layer for protecting the water vapor barrier layer may be formed on the surface of the water vapor barrier layer (the surface opposite to the substrate layer).

[0086] Furthermore, in the case of a resin film having a water vapor barrier layer and a substrate layer, the above-mentioned heat-sealable resin layer may be further laminated thereon.

[0087] The overall thickness of the resin film is preferably 10 μm or more from the viewpoint of providing sufficient strength to the battery, and is preferably 200 μm or less from the viewpoint of preventing an increase in the battery thickness and a decrease in energy density.

[0088] The water vapor permeability of the resin film constituting the sheet-like outer packaging body is 10 g / m ２ It is preferable that the resin film does not transmit water vapor as much as possible, that is, the water vapor transmission rate is preferably as low as possible, and is preferably 0 g / m ２ ・It may be 24 hours.

[0089] The water vapor permeability of the resin film referred to in this specification is a value measured in accordance with JIS K 7129B method.

[0090] In addition, when the battery is an air battery, it is preferable that the resin film constituting the sheet-like outer casing has a certain degree of oxygen permeability. Air batteries discharge by supplying air (oxygen) to the positive electrode, so air holes for introducing oxygen into the battery are formed in the sheet-like outer casing. However, if the resin film constituting the sheet-like outer casing has oxygen permeability, oxygen can be introduced into the battery through the outer casing from locations other than the air holes in the sheet-like outer casing. This allows oxygen to be supplied more uniformly throughout the positive electrode, improving the battery's discharge characteristics and extending its discharge time. It is also possible to realize a sheet-like air battery that does not have air holes in the sheet-like outer casing.

[0091] When the battery is an air battery, the specific oxygen permeability of the resin film constituting the sheet-like outer casing is 0.02 cm ３ / m ２ ・24h ・MPa or more is preferable, 0.2 cm ３ / m ２ However, if the battery is an air battery, if the resin film constituting the sheet-like outer casing is permeable to too much oxygen, self-discharge may occur and the capacity may be lost. Therefore, the oxygen permeability of the resin film is set to 100 cm ３ / m ２ ・24h ・MPa or less is preferable, 50 cm ３ / m ２ It is more preferable that the pressure is 24h·MPa or less.

[0092] On the other hand, when the battery is a battery other than an air battery, there is no particular restriction on the oxygen permeability of the resin film constituting the sheet-like outer casing. However, from the viewpoint of improving the storage stability of the battery, it is preferable that the resin film does not allow much oxygen to permeate. ３ / m ２ It is preferable that the pressure is 24h·MPa or less.

[0093] The oxygen permeability of the resin film referred to in this specification is a value measured in accordance with JIS K 7126-2 method.

[0094] Furthermore, when using an exterior body that is crimp-sealed, the material of the gasket interposed between the exterior can and the sealing plate can be a material that is used for alkaline batteries, such as polypropylene or nylon.

[0095] Furthermore, to prevent elements such as iron that make up the outer can from eluting during charging, it is desirable to plate the inner surface of the outer can with a corrosion-resistant metal such as tin, zinc, or indium.

[0096] When the battery is an air battery, a water-repellent film is usually disposed between the positive electrode and the exterior body. The water-repellent film is a film that is water-repellent but air-permeable. Specific examples of such water-repellent films include films made of resins such as fluororesins such as PTFE; and polyolefins such as polypropylene and polyethylene. The thickness of the water-repellent film is preferably 50 to 250 μm.

[0097] Furthermore, when the battery is an air battery, an air diffusion membrane may be disposed between the exterior body and the water-repellent film to supply air taken into the exterior body to the positive electrode. The air diffusion membrane may be a nonwoven fabric made of a resin such as cellulose, polyvinyl alcohol, polypropylene, or nylon. The thickness of the air diffusion membrane is preferably 100 to 250 μm.

[0098] An example of a battery is shown schematically in Figures 1 and 2. Figures 1 and 2 show an example of a battery equipped with a negative electrode having a metal sheet and a sheet-like outer casing (a sheet-like battery), where Figure 1 shows a plan view and Figure 2 shows a cross-sectional view taken along line II of Figure 1.

[0099] As shown in FIG. 2, in the battery 10, the positive electrode 20, the separator 40, the negative electrode 30, and an aqueous electrolyte (not shown) are housed in a sheet-like outer casing 50.

[0100] A terminal portion 21 of the positive electrode 20 and a terminal portion 31 of the negative electrode 30 protrude from the upper edge of the sheet-like outer casing 50 in the figure. As shown in Figure 2, the terminal portion 21 of the positive electrode is connected to the positive electrode 20 inside the battery 10, and although not shown, the terminal portion 31 of the negative electrode is also connected to the negative electrode 30 inside the battery 10. These terminal portions 21, 31 are used as external terminals for electrically connecting the battery 10 to an applicable device.

[0101] 2, the sheet-like outer casing 50 (the resin film constituting it) is shown as a single layer structure, but as described above, the resin film constituting the sheet-like outer casing can also be a multilayer structure. Also, in FIG. 2, the positive electrode 10 and the negative electrode 20 are shown as single layer structures, but as described above, the positive electrode and the negative electrode can also be a multilayer structure, and further, the negative electrode can contain metal particles such as zinc particles.

[0102] The shape of the sheet-like outer casing may be polygonal in plan view (triangle, quadrangle, pentagon, hexagon, heptagon, octagon, etc.), or may be circular or elliptical in plan view. In the case of a sheet-like outer casing that is polygonal in plan view, the positive electrode terminal and the negative electrode terminal may be led out from the same side or from different sides.

[0103] When the battery is a sheet-type battery, there is no particular limitation on its thickness (the length of a in FIG. 2 ), and it can be changed appropriately depending on the application of the battery. One of the advantages of a sheet-type battery is that it can be made thin, and from this perspective, it is preferable that the thickness is, for example, 1 mm or less. When the battery is a sheet-type air battery, it is particularly easy to provide such a thin battery.

[0104] There is no particular lower limit to the thickness of the battery, but in order to ensure a certain capacity, it is usually preferable to set the thickness to 0.2 mm or more.

[0105] The present invention will be described in detail below based on examples, but the present invention is not limited to these examples.

[0106] Example 1 <Positive Electrode> A positive electrode mixture-containing composition was prepared by mixing 87.5 parts by mass of electrolytic manganese dioxide ("SP-A" manufactured by Tosoh Corporation, average particle size 0.5 μm), 10 parts by mass of graphite ("SP-20" manufactured by Nippon Graphite Co., Ltd., average particle size 30 μm), 2.5 parts by mass of ammonium polyacrylate, and 150 parts by mass of water.

[0107] The positive electrode mixture-containing composition was applied in stripes to porous carbon paper (thickness: approximately 0.2 mm, porosity: 75%, air permeability (Gurley): 70 seconds / 100 ml) and dried to obtain a carbon paper having a region (hereinafter referred to as "Region A") in which the positive electrode active material (positive electrode mixture) was held in the voids and the surface was covered with a layer containing the positive electrode active material (positive electrode mixture layer), and a region (hereinafter referred to as "Region B") in which the positive electrode active material was not held in the voids and the surface was free of a layer containing the positive electrode active material. This was then punched into a shape having a main body holding the positive electrode active material, consisting of Region A measuring 15 mm x 15 mm, and a positive electrode terminal, consisting of Region B measuring 10 mm x 20 mm, to produce a positive electrode with a theoretical capacity of 36 mAh.

[0108] <Negative Electrode> An electrolytic zinc alloy foil (thickness: 0.03 mm) made of a zinc alloy containing 0.05 mass % Bi as an additive element and no In was punched into a shape having a main body measuring 15 mm × 15 mm and a negative electrode terminal measuring 10 mm × 20 mm to prepare a negative electrode.

[0109] <Electrolyte> An aqueous solution containing LiCl at a concentration of 16.7 mass % was used as the electrolyte.

[0110] <Separator> The separator is a polypropylene nonwoven film (thickness: 50 μm, basis weight: 12 g / m) whose surface has been treated to make it hydrophilic. ２ ) was used.

[0111] <Sheet-like outer packaging> A sheet-like outer packaging was prepared using two 25 mm x 30 mm aluminum laminate films (thickness: 65 μm) each having a PET film on the outer surface of an aluminum foil and a polypropylene film as a heat-sealable resin layer on the inner surface.

[0112] <Battery Assembly> The positive electrode, the separator, and the negative electrode were stacked in this order on one aluminum laminate film, and then the other aluminum laminate film was placed on top of it. Next, the three peripheral sides of the two aluminum laminate films were heat-sealed to form a bag, and 0.12 ml of the electrolyte solution was poured into the opening, which was then heat-sealed to seal the opening, to produce a sheet-like battery having the same structure as that shown in Figures 1 and 2.

[0113] Examples 2 to 5 Sheet-type batteries of Examples 2 to 5 were fabricated in the same manner as in Example 1, except that the LiCl concentrations in the electrolyte were changed to 23.1 mass%, 28.6 mass%, 33.3 mass%, and 37.5 mass%, respectively.

[0114] Comparative Example 1 A sheet-type battery was fabricated in the same manner as in Example 1, except that the concentration of LiCl in the electrolyte was changed to 9.1 mass %.

[0115] Comparative Example 2 A sheet-type battery was fabricated in the same manner as in Example 1, except that an aqueous solution containing ammonium chloride at a concentration of 25% by mass was used as the electrolyte.

[0116] Comparative Example 3 A sheet-type battery was fabricated in the same manner as in Example 1, except that an aqueous solution containing zinc chloride at a concentration of 25% by mass was used as the electrolyte.

[0117] Table 1 shows the composition of the aqueous electrolyte used in the sheet-type batteries of the Examples and Comparative Examples.

[0118]

[0119] The sheet-type batteries of Example 1, Examples 3 to 5, and Comparative Examples 1 to 3 were left in a thermostatic chamber at −40° C. for 2 hours, and then a pulse discharge test was performed under the following conditions to evaluate the discharge characteristics of the initial batteries at −40° C.

[0120] The pulse discharge conditions were a pulse width of 10 msec, a pulse interval of 3 sec, and a pulse current value of 1 mA. Ten pulse discharges were performed, and the closed circuit voltage (CCV) was measured. The results are shown in Figure 3.

[0121] Separately from the above, the sheet-type batteries of Examples 1 to 5 were discharged at a constant current of 0.5 mA for 60 hours at a temperature of 20°C until the depth of discharge reached 83%. Each of the discharged sheet-type batteries was left in a thermostatic chamber at -40°C for 2 hours, and then subjected to a pulse discharge test under the following conditions.

[0122] The pulse discharge conditions were a pulse width of 10 msec, a pulse interval of 3 sec, and a pulse current value of 10 mA. Ten pulse discharges were performed, and the closed circuit voltage (CCV) was measured. The results are shown in Figure 4.

[0123] As shown in Fig. 3, the sheet batteries of Examples 1 and 3 to 5, which had aqueous electrolyte solutions containing LiCl at a certain concentration or higher, had high CCVs during the evaluation of discharge characteristics at low temperatures, and had excellent low-temperature characteristics similar to those of the sheet battery of Comparative Example 3, which had an aqueous electrolyte solution using zinc chloride. In particular, as shown in Fig. 4, it can be seen that when the LiCl concentration in the aqueous electrolyte solution was in the range of 20 mass % or more and 35 mass % or less, better low-temperature characteristics were obtained.

[0124] Example 6 A sheet-type battery was produced in the same manner as in Example 1, except that the concentration of LiCl in the electrolyte was changed to 33.6% by mass, the positive electrode was changed to a shape having a main body portion for holding the positive electrode active material, which was composed of an area A measuring 15 mm × 15 mm, and a positive electrode terminal, which was composed of an area B measuring 5 mm × 12 mm, and the negative electrode was changed to one prepared by punching out an electrolytic zinc alloy foil (thickness: 0.05 mm) made of a zinc alloy containing 0.05% by mass of Bi as an additive element and no In, into a shape having a main body portion measuring 15 mm × 15 mm and a negative electrode terminal measuring 5 mm × 12 mm.

[0125] Example 7 A sheet-type battery was fabricated in the same manner as in Example 6, except that the electrolyte solution was changed to an aqueous solution containing LiCl at a concentration of 33.6 mass % and ammonium chloride at a concentration of 2.7 mass %.

[0126] Example 8 A sheet-type battery was fabricated in the same manner as in Example 6, except that the electrolyte solution was changed to an aqueous solution containing LiCl at a concentration of 33.6 mass % and ammonium chloride at a concentration of 5.3 mass %.

[0127] The sheet-type batteries of Examples 6 to 8 were subjected to a pulse discharge test under the following conditions. The pulse discharge conditions were room temperature (25°C), pulse width: 10 msec, pulse interval: 3 sec, and pulse current value: 40 mA. Ten pulse discharges were performed, and the closed circuit voltage (CCV) and open circuit voltage (OCV) were measured. The results are shown in Table 2.

[0128]

[0129] As shown in Table 2, the sheet-type batteries of Examples 7 and 8, in which the aqueous electrolyte solution contained ammonium chloride together with LiCl, had higher OCV and CCV values ​​than the sheet-type battery of Example 6, which used an aqueous electrolyte solution containing only LiCl as the electrolyte salt, and had better discharge characteristics at room temperature.

[0130] The present invention can be implemented in other forms without departing from the spirit of the present invention. The embodiments disclosed in this application are merely examples, and the present invention is not limited to these embodiments. The scope of the present invention shall be interpreted in accordance with the appended claims rather than the description in the above specification, and all modifications within the scope of the claims are included in the scope of the claims.

[0131] The battery of the present invention has an aqueous electrolyte solution that is substantially free of heavy metal elements, which reduces the environmental impact and reduces the risk of problems even if the electrolyte leaks and comes into contact with the body due to breakage, etc. Therefore, the battery of the present invention is suitable as a power source for medical and health-related devices, such as patches that can be worn on the body, particularly patches that are worn on the surface of the skin to measure body conditions such as body temperature, pulse rate, and sweat rate, and can also be used in the same applications as conventionally known batteries with aqueous electrolytes, such as air batteries and manganese batteries.

[0132] REFERENCE SIGNS LIST 10 Battery 20 Positive electrode 21 Positive electrode terminal portion 30 Negative electrode 31 Negative electrode terminal portion 40 Separator 50 Sheet-like outer casing

Claims

1. A battery comprising a positive electrode, a negative electrode and an electrolyte, wherein the electrolyte is an aqueous solution containing at least LiCl as an electrolyte salt, and the concentration of LiCl in the aqueous solution is 16 mass % or more.

2. The battery according to claim 1, wherein the concentration of LiCl in the electrolyte is 35 mass % or less.

3. The battery according to claim 1, wherein the electrolyte further contains an electrolyte salt other than LiCl.

4. The battery according to claim 3, which contains, as the electrolyte salt other than LiCl, at least one electrolyte salt selected from the group consisting of ammonium chloride, zinc chloride, hydroxides of alkali metals and hydroxides of alkaline earth metals.

5. The battery according to claim 1, wherein the amount of LiCl is 50 parts by mass or more when the amount of all electrolyte salts contained in the electrolyte is 100 parts by mass.

6. The battery according to claim 5, wherein the electrolyte further contains ammonium chloride as an electrolyte salt other than LiCl, and the amount of ammonium chloride is 0.5 parts by mass or more when the amount of all electrolyte salts contained in the electrolyte is 100 parts by mass.

7. The battery according to claim 6, wherein the amount of ammonium chloride is 20 parts by mass or less when the amount of all electrolyte salts contained in the electrolyte is 100 parts by mass.

8. The battery according to claim 1, wherein the negative electrode has as its active material at least one metal selected from the group consisting of zinc, aluminum, magnesium and alloys thereof.

9. The battery of claim 8, wherein the negative electrode comprises zinc or zinc alloy foil.

10. The battery according to claim 1, wherein the positive electrode has manganese dioxide or silver oxide as an active material.

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