Battery

Abstract

Provided is a battery having an aqueous electrolyte solution and having excellent safety and discharge characteristics at low temperatures. The battery according to the present invention comprises a positive electrode, a negative electrode, and an electrolyte solution, and is characterized in that the electrolyte solution 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. The amount of LiCl is preferably 50 parts by mass or more when the amount of all electrolyte salts contained in the electrolyte solution is taken as 100 parts by mass.

Description

Technical Field

[0001] This invention relates to a battery with an aqueous electrolyte that exhibits excellent safety and low-temperature discharge characteristics. Background Technology

[0002] Batteries using aqueous electrolytes, such as air batteries and alkaline batteries, have been widely used for a long time, but in recent years, their application in powering various sensors for the body, such as body temperature patches, has been developing rapidly.

[0003] Various improvements have been made to batteries with aqueous electrolytes. For example, Patent Document 1 proposes a technique in which, in a sheet battery with an outer casing composed of polymer compound sheets, the depletion of the electrolyte caused by the evaporation of water from the electrolyte passing through the sheet over time is suppressed by adding a compound different from the electrolyte salt to the electrolyte. The water vapor pressure of the saturated aqueous solution of this compound at the operating temperature is below the atmospheric water vapor partial pressure corresponding to a relative humidity of 40% at that temperature. It should be noted that, in the embodiment of Patent Document 1, lithium chloride (LiCl) and calcium chloride (CaCl2) are used as the compounds added to the electrolyte.

[0004] In addition, improvements have been made to batteries with aqueous electrolytes for the purposes described above. For example, from the viewpoint of minimizing the environmental impact even when the user discards the replaced battery, attempts have been made to use an aqueous solution containing salts of strong acid and weak base as electrolyte salts, thereby lowering its pH while ensuring good properties (Patent Document 2, Patent Document 3, etc.).

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 5-135778

[0008] Patent Document 2: International Publication No. 2018 / 056307

[0009] Patent Document 3: International Publication No. 2020 / 162591 Summary of the Invention

[0010] The problem that the invention aims to solve

[0011] However, in the batteries described in Patent Documents 2 and 3 that use salts containing strong acids such as ammonium chloride and weak bases as electrolyte salts, there is a problem that the discharge characteristics are greatly impaired at low temperatures (below 0°C, especially below -20°C (for example, around -40°C)). There is still room for improvement in this regard.

[0012] On the other hand, in manganese batteries and the like, an aqueous solution of zinc chloride, a salt equivalent to a strong acid and a weak base, is used as the electrolyte, and it has been confirmed that it can discharge well even at low temperatures. However, zinc chloride is a compound designated as a hazardous substance, so it is desirable to minimize the amount of this compound used in the electrolyte.

[0013] The present invention was made in view of the above circumstances, and its object is to provide a battery having an aqueous electrolyte and excellent safety and low-temperature discharge characteristics.

[0014] Methods for solving problems

[0015] The battery of the present invention comprises a positive electrode, a negative electrode and an electrolyte, characterized in that 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% by mass or more.

[0016] Invention Effects

[0017] According to the present invention, a battery with an aqueous electrolyte and excellent safety and low-temperature discharge characteristics can be provided. Attached Figure Description

[0018] Figure 1 This is a top view schematically illustrating an example of the battery of the present invention.

[0019] Figure 2 yes Figure 1 Sectional view of line II.

[0020] Figure 3 This is a graph showing the evaluation results of the discharge characteristics of the batteries in the examples and comparative examples at low temperatures.

[0021] Figure 4 This is a graph showing the evaluation results of the discharge characteristics of the battery in the embodiment at low temperatures. Detailed Implementation

[0022] Batteries using aqueous solutions of strong acid and weak base salts (such as ammonium chloride) as electrolytes have a low pH and exhibit good discharge characteristics. However, even with such batteries, depending on the type of electrolyte salt, adequate discharge characteristics cannot be guaranteed in low-temperature environments below 0°C, especially below -20°C (e.g., around -40°C), due to electrolyte salt precipitation or freezing of the aqueous solution.

[0023] On the other hand, in manganese batteries and the like that use manganese oxide as the positive electrode, an aqueous solution of zinc chloride as the electrolyte salt is used as the electrolyte. In such batteries, discharge can be performed well even under the aforementioned low-temperature conditions. However, zinc chloride is a hazardous substance, so there is room for improvement in terms of safety in cases where the electrolyte leaks and adheres to the body.

[0024] Therefore, in this invention, an aqueous solution containing LiCl as an electrolyte salt at a certain concentration is used as the electrolyte. This ensures certain discharge characteristics at low temperatures, thereby enabling the formation of an electrolyte composition that is free of zinc chloride or has a reduced zinc chloride content, thus improving safety.

[0025] The battery of the present invention can be used in various types of batteries (manganese batteries, silver oxide batteries, air batteries, etc.) that have an aqueous electrolyte, that is, an electrolyte composed of an aqueous solution with water as a solvent.

[0026] (Aqueous electrolyte)

[0027] The battery of the present invention has an aqueous electrolyte containing at least LiCl as an electrolyte salt and having a LiCl concentration of 16% by mass or more.

[0028] The aqueous electrolyte contains a high concentration of LiCl, thus enabling the battery to exhibit good load characteristics even when placed at low temperatures. Furthermore, using an aqueous electrolyte with LiCl as the electrolyte salt effectively suppresses corrosion of the negative electrode caused by the aqueous electrolyte and the associated gas generation within the battery. Therefore, in the battery of the present invention, problems such as leakage caused by internally generated gas are also effectively suppressed.

[0029] The concentration of LiCl in the aqueous electrolyte is 16% by mass or more, preferably 20% by mass or more, and more preferably 25% by mass or more. Furthermore, from the viewpoint of preventing salt precipitation and improving the discharge characteristics (especially load characteristics) of the battery at low temperatures, the concentration of LiCl in the aqueous electrolyte is preferably 45% by mass or less, more preferably 40% by mass or less, and particularly preferably 35% by mass or less.

[0030] It should be noted that aqueous electrolytes can contain electrolyte salts other than LiCl. However, if the concentration of electrolyte salts other than LiCl increases, it may be difficult to increase the concentration of LiCl, thus hindering the improvement of the battery's low-temperature load characteristics. Therefore, when the total amount of electrolyte salts in the aqueous electrolyte is set to 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. Aqueous electrolytes can contain only LiCl as an electrolyte salt; therefore, when the total amount of electrolyte salts in the aqueous electrolyte is set to 100 parts by mass, the upper limit for the amount of LiCl is 100 parts by mass.

[0031] Examples of electrolyte salts other than LiCl that can be used in aqueous electrolytes include chlorides such as sodium chloride, potassium chloride, magnesium chloride, calcium chloride, ammonium chloride, and zinc chloride; hydroxides of alkali metals or alkaline earth metals (sodium hydroxide, potassium hydroxide, magnesium hydroxide, etc.), their acetates (sodium acetate, potassium acetate, magnesium acetate, etc.), their nitrates (sodium nitrate, potassium nitrate, magnesium nitrate, etc.), their sulfates (sodium sulfate, potassium sulfate, magnesium sulfate, etc.), their phosphates (sodium phosphate, potassium phosphate, magnesium phosphate, etc.), their borates (sodium borate, potassium borate, magnesium borate, etc.), their citrates (sodium citrate, potassium citrate, magnesium citrate, etc.), their glutamates (monosodium glutamate, potassium glutamate, magnesium glutamate, etc.); alkali metal bicarbonates (sodium bicarbonate, potassium bicarbonate, etc.); alkali metal percarbonates (sodium percarbonate, potassium percarbonate, etc.); halogen-containing compounds such as fluorides; and polycarboxylic acids, etc. One or more of these can be used.

[0032] Of the electrolyte salts exemplified above, the preferred electrolyte salt for use in combination with LiCl is at least one selected from ammonium chloride, zinc chloride, alkali metal hydroxides, and alkaline earth metal hydroxides, with ammonium chloride being more preferred. By using ammonium chloride as an electrolyte salt in combination with LiCl, it is expected to improve the open-circuit voltage (OCV) and closed-circuit voltage (CCV) of the battery when used at room temperature. Furthermore, zinc chloride is also more preferred as an electrolyte salt in combination with LiCl, thereby further improving the performance at low temperatures.

[0033] When using ammonium chloride and zinc chloride, they can be contained in a ratio to LiCl within the aforementioned range. However, since zinc chloride is a harmful substance, it is preferable to minimize its content as much as possible. In general manganese batteries, an electrolyte containing about 30% by mass of zinc chloride is used. However, in this invention, from a safety perspective, the concentration of zinc chloride in the aqueous electrolyte is preferably 15% by mass or less, preferably 10% by mass or less, more preferably 5% by mass or less, or it may be absent altogether. Furthermore, from the viewpoint of better ensuring the aforementioned effects obtained by using ammonium chloride in the aqueous electrolyte, when the total amount of electrolyte salts in the aqueous electrolyte is set to 100 parts by mass, 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. Moreover, when the total amount of electrolyte salts in the aqueous electrolyte is set to 100 parts by mass, the amount of ammonium chloride is preferably 20 parts by mass or less.

[0034] In the case of an air battery, the following problem can easily occur: water in the aqueous electrolyte evaporates and escapes through the air pores, causing changes in the electrolyte composition. Accordingly, from the viewpoint of avoiding such problems, a water-soluble high-boiling-point solvent with a boiling point of 150°C or higher (preferably 320°C or lower) can be used as a solvent for the aqueous electrolyte, or a thickener can be added to the aqueous electrolyte composed of an aqueous solution (more preferably, it can be made into a gel form (gel electrolyte)).

[0035] Examples of water-soluble high-boiling-point solvents include polyols such as ethylene glycol (boiling point 197°C), propylene glycol (boiling point 188°C), and glycerol (boiling point 290°C); and polyalkylene glycols such as polyethylene glycol (PEG, for example, boiling point 230°C) (preferably polyalkylene glycols with a molecular weight of 600 or less). When using a water-soluble high-boiling-point solvent, its proportion in the total solvent is preferably 3 to 30% by mass.

[0036] Furthermore, in batteries with a negative electrode made of a metal sheet (metal foil) that functions as the negative electrode active material as described later, the use of an aqueous electrolyte composed of an aqueous solution may lead to problems such as negative electrode breakage due to corrosion of the aqueous electrolyte, resulting in insufficient capacity utilization. When using LiCl as the electrolyte salt in an aqueous electrolyte, as mentioned above, negative electrode corrosion can be suppressed. However, by pre-compacting a thickener into the aqueous electrolyte, and more preferably preparing it into a gel-like state (gel electrolyte), not only can the aforementioned problems of electrolyte composition variation be avoided, but unwanted corrosion reactions of the negative electrode can also be further suppressed, as well as the associated gas generation and negative electrode breakage. Examples of thickeners suitable for use in aqueous electrolytes include cellulose derivatives such as carboxymethyl cellulose (CMC) and carboxyethyl cellulose (CEC); polyepoxides such as polyethylene oxide (PEO) (preferably polyepoxides with a molecular weight of 1000 or more, more preferably polyepoxides with a molecular weight of 10000 or more); polyvinylpyrrolidone; polyvinyl acetate; starch; guar gum; xanthan gum; sodium alginate; hyaluronic acid; gelatin; polyacrylic acid; and polymers or copolymers of acrylamide, etc. Furthermore, when using thickeners among the examples described above that have functional groups (-COOH, -COONa, etc.) composed of carboxyl groups or their salts, it is also preferable to incorporate a polyvalent metal salt, which acts as a gelation promoter, into the aqueous electrolyte. To improve the above-mentioned effects, the amount of thickener in the aqueous electrolyte is preferably 0.1% by mass or more, more preferably 1% by mass or more, and even more preferably 3% by mass or more. To prevent a decrease in discharge characteristics, it is preferably 20% by mass or less, more preferably 15% by mass or less, and even more preferably 10% by mass or less. Furthermore, when using a gelation accelerator, if the proportion of the thickener is set to 100 by mass, the proportion of the gelation accelerator is preferably 1 to 30.

[0037] In addition, aqueous electrolytes can be made into gel-like electrolytes (gel electrolytes) using known gelling agents such as polymers.

[0038] The pH of the aqueous electrolyte is not particularly limited, but to prevent corrosion of the negative electrode active material, it is preferably 3 or higher, more preferably 4 or higher. On the other hand, in the case of an air battery, to prevent carbon dioxide from the air from being introduced into the electrolyte, it is preferable to set the pH of the aqueous electrolyte to 8 or lower, more preferably 7 or lower, and even more preferably 6 or lower. The pH of the aqueous electrolyte can be adjusted by using salts of weak acids and strong bases, or salts of strong acids and weak bases. In addition, by including weak acids such as carboxylic acids, carbonic acid, and phosphoric acid in the electrolyte, the pH of the aqueous electrolyte can also be adjusted to a lower value.

[0039] (negative electrode)

[0040] The negative electrode may use at least one metal selected from zinc, aluminum, magnesium and their alloys as the active material.

[0041] As a specific example of such a negative electrode, a metal sheet (zinc foil, zinc alloy foil, magnesium foil, magnesium alloy foil, aluminum foil, aluminum alloy foil) made of the above-mentioned materials is preferably used. The thickness of the metal sheet is preferably 5 to 1000 μm.

[0042] Alternatively, metal particles composed of the above materials (zinc particles, zinc alloy particles, magnesium particles, magnesium alloy particles, aluminum particles, aluminum alloy particles) can also be used.

[0043] As alloying components of zinc alloys, examples include indium, bismuth, and aluminum, and one or more of the above elements may be contained.

[0044] The content of each alloying element in the zinc alloy is as follows: The indium content is, for example, 0.005% or more by mass, and less than 0.1%. The bismuth content is, for example, 0.002% or more by mass, and less than 0.2%. The aluminum content is, for example, 0.0001% or more by mass, and less than 0.15%.

[0045] It should be noted that zinc foil and zinc alloy foil include electrolytic foil and rolled foil. However, since electrolytic foil does not easily generate gas in the battery due to reaction with the electrolyte, it is preferred to use electrolytic foil, and more preferably, electrolytic zinc alloy foil containing bismuth. The preferred bismuth content in the electrolytic zinc alloy foil is 0.02% or more and 0.1% or less by mass.

[0046] In addition, as alloying components of magnesium alloys, for example, calcium, manganese, zinc, aluminum, etc., one or more of the above elements may be contained.

[0047] The content of each alloying element in the magnesium alloy is as follows: Calcium content, for example, is 1% or more by mass, and less than 3% by mass. Manganese content, for example, is 0.1% or more by mass, and less than 0.5% by mass. Zinc content, for example, is 0.4% or more by mass, and less than 1% by mass. Aluminum content, for example, is 8% or more by mass, and less than 10% by mass.

[0048] Furthermore, as an alloying component of aluminum alloys, for example, zinc, tin, gallium, silicon, iron, magnesium, manganese, etc., one or more of the above elements may be contained.

[0049] The content of each alloying element in the aluminum alloy is as follows: Zinc content is, for example, 0.5% or more by mass, and less than 10%. Tin content is, for example, 0.04% or more by mass, and less than 1.0%. Gallium content is, for example, 0.003% or more by mass, and less than 1.0%. Silicon content is, for example, less than 0.05% by mass. Iron content is, for example, less than 0.1% by mass. Magnesium content is, for example, 0.1% or more by mass, and less than 2.0%. Manganese content is, for example, 0.01% or more by mass, and less than 0.5%.

[0050] In the case of a negative electrode containing metal particles, one type of metal particle can be used alone, or two or more types can be used.

[0051] It should be noted that, in order to reduce the environmental impact of battery disposal, the metal materials used in the negative electrode preferably have low contents of mercury, cadmium, lead and chromium. Specifically, the contents, based on mass, are preferably mercury: less than 0.1%, cadmium: less than 0.01%, lead: less than 0.1% and chromium: less than 0.1%.

[0052] As for the particle size of zinc particles and zinc alloy particles, for example, the proportion of particles with a diameter of 75 μm or less in all particles is 50% by mass or less, more preferably 30% by mass or less. In addition, the proportion of particles with a diameter of 100 to 200 μm is 50% by mass or more, more preferably 90% by mass or more.

[0053] Furthermore, regarding the particle size of magnesium particles, magnesium alloy particles, aluminum particles, and aluminum alloy particles, examples include particles with a diameter of 30 μm or less having a mass percentage of 50% or less, more preferably 30% or less, and particles with a diameter of 50 to 200 μm having a mass percentage of 50% or more, more preferably 90% or more.

[0054] The particle size of the metal particles mentioned in this specification is the particle size (D50) at 50% of the cumulative frequency, measured on a volume basis, by dispersing these particles in a medium that does not dissolve particles using a laser scattering particle size analyzer (e.g., the "LA-920" manufactured by Horiba Corporation).

[0055] In the case of a negative electrode containing the aforementioned metal particles, when forming the mixture, a gelling agent (sodium polyacrylate, carboxymethyl cellulose, etc.) and a binder may be added as needed. A negative electrode mixture (gel-like negative electrode, etc.) formed by adding an electrolyte can be used. The amount of gelling agent in the negative electrode is preferably set to, for example, 0.5 to 1.5% by mass, and the amount of binder is preferably set to 0.5 to 3% by mass.

[0056] The electrolyte for the negative electrode containing metal particles can be the same electrolyte injected into the battery.

[0057] The content of metal particles in the negative electrode is 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.

[0058] The negative electrode containing metal particles preferably contains an indium compound. By containing an indium compound in the negative electrode, it is possible to more effectively prevent the generation of hydrogen gas due to the corrosion reaction between the metal particles and the electrolyte.

[0059] Examples of indium compounds include indium oxide and indium hydroxide.

[0060] The amount of indium compound used in the negative electrode is preferably 0.003 to 1 by mass relative to the metal particles 100.

[0061] In addition, a current collector can be used in negative electrodes containing metallic materials, as needed. Examples of current collectors for negative electrodes containing metallic materials include meshes, foils, expanded alloys, and perforated metals made of metals such as nickel, copper, and stainless steel; and sheets and meshes made of carbon. The thickness of the current collector for the negative electrode is preferably 10 μm or more and 300 μm or less.

[0062] Furthermore, for the current collector of the negative electrode, similarly to the case of the positive electrode, a carbon paste can be coated onto the inner surface of the intended sheet-like outer casing. The thickness of the carbon paste layer is preferably 50 to 200 μm.

[0063] As the terminal portion for connecting to the battery in an application device, for example, a foil (plate, sheet), wire, or the like made of metal or carbon, which are materials that can constitute a negative electrode current collector, can be used. When the terminal portion of the negative electrode is a foil (plate, sheet), its thickness is preferably 20 μm or more and 500 μm or less. Furthermore, when the terminal portion of the negative electrode is a wire, its diameter is preferably 50 μm or more and 1500 μm or less.

[0064] Alternatively, a portion 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, by cutting the metal sheet into a shape having a main body portion and a terminal portion that function as a negative electrode active material layer, it is also possible to form a negative electrode with a main body portion and a terminal portion from a single metal sheet.

[0065] (positive electrode)

[0066] In the case of manganese batteries or silver oxide batteries, the positive electrode can be, for example, a positive electrode with a structure having a positive electrode compound layer containing positive electrode active material, conductive additive and binder on one or both sides of the current collector, or a molded body formed by molding a positive electrode compound containing positive electrode active material, conductive additive and binder.

[0067] In the case of a manganese battery, manganese oxides such as manganese dioxide are used as the positive electrode active material. Additionally, in the case of a silver oxide battery, silver oxide (silver oxide, silver monoxide, etc.), silver-nickel composite oxides, or other silver-containing oxides are used as the positive electrode active material. It should be noted that, to improve the battery's load characteristics, the silver-containing oxides are preferably in particulate form. Conductive additives for the positive electrode mixture can include, for example, carbon blacks such as acetylene black, Ketjen black, channel black, furnace black, lamp black, and thermally cracked carbon black; carbon materials such as carbon fibers; conductive fibers such as metal fibers; fluorinated carbon; metal powders such as copper and nickel; and organic conductive materials such as polyphenylene derivatives.

[0068] Examples of binders used as positive electrode binders include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), styrene-butadiene rubber (SBR), CMC, and polyvinylpyrrolidone (PVP).

[0069] As components of the positive electrode binder, the amount of positive electrode active material is preferably 80-98% by mass, the content of conductive additive is preferably 1.5-10% by mass, and the content of binder is preferably 0.5-10% by mass. Furthermore, in the case of a positive electrode having a positive electrode binder layer and a current collector, the thickness of the positive electrode binder layer (the thickness of each side of the current collector) is preferably 30-300 μm. Moreover, in the case of a positive electrode having a molded positive electrode binder, the thickness of the molded positive electrode binder is preferably 0.2-0.25 mm.

[0070] A positive electrode having a positive electrode binder layer can be manufactured, for example, by dispersing a positive electrode active material, a conductive additive, and a binder in water or an organic solvent such as N-methyl-2-pyrrolidone (NMP) to prepare a positive electrode binder-containing composition (slurry, paste, etc.) (the binder can be dissolved in the solvent), coating it onto a current collector and drying it, and performing a pressing process such as calendering as needed. Alternatively, in the case of a positive electrode having a molded body with a positive electrode binder, it can be manufactured, for example, by pressing the positive electrode binder into a mold, or by pressing the molded body of such a positive electrode binder onto a current collector.

[0071] In addition, in the case of an air battery, a positive electrode (air electrode) with a catalyst layer can be used, such as a positive electrode with a structure that stacks a catalyst layer and a current collector.

[0072] The catalyst layer may contain catalysts, binders, etc.

[0073] Catalysts used as catalyst layers include, for example, phthalocyanine metal complexes; silver, platinum group metals or their alloys; transition metals; platinum / metal oxides such as Pt / IrO2; and La. 1-x Cax CoO3 and other perovskite oxides; WC and other carbides; Mn4N and other nitrides; manganese oxides such as manganese dioxide; carbon (graphite, carbon black (acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal cracking black, etc.), charcoal, activated carbon, etc.), etc., using one or more of them.

[0074] It should be noted that the heavy metal content of the catalyst layer is preferably less than 1% by mass. While batteries, depending on their shape, can be easily destroyed by tearing with hands or the like when discarded, a positive electrode with a catalyst layer containing low heavy metal content, as described above, can produce a battery with a low environmental impact even when discarded without special treatment.

[0075] The content of heavy metals in the catalyst layer described in this specification can be determined by fluorescence X-ray analysis. For example, it can be determined using a fluorescence X-ray analysis device "ZSX 100e" manufactured by Rigaku Corporation, under the conditions of excitation source Rh, 50 kV, and analysis area φ10 mm.

[0076] Accordingly, the catalyst for the catalyst layer is recommended to be free of heavy metals, and more preferably, the various types of carbon mentioned above are used.

[0077] Furthermore, from the viewpoint of further improving the reactivity of the cathode, the specific surface area of ​​the carbon used as a catalyst is preferably 200 m². 2 / g or more, preferably 300m 2 / g or more, further preferably 500m 2 / g or higher. The specific surface area of ​​carbon mentioned in this specification is the value obtained by the BET method according to Japanese Industrial Standard (JIS) K 6217. For example, it can be measured using a specific surface area measuring device based on nitrogen adsorption (Mountech "Macsorb HM modele-1201"). It should be noted that the upper limit of the specific surface area of ​​carbon is usually 2000 mm². 2 Approximately / g.

[0078] The catalyst content in the catalyst layer is preferably 20-70% by mass.

[0079] Examples of binders for the catalyst layer include fluoropolymers such as PVDF, PTFE, copolymers of vinylidene fluoride, and copolymers of tetrafluoroethylene (PVDF-HFP, PVDF-CTFE, PVDF-TFE, PVDF-HFP-TFE, etc.). Among these, polymers or copolymers of tetrafluoroethylene are preferred, and PTFE is more preferred. The binder content in the catalyst layer is preferably 3-50% by mass.

[0080] In the case of a positive electrode with a catalyst layer, it can be manufactured, for example, by mixing the aforementioned catalyst, binder, etc. with water and rolling it with rollers to make it tightly bonded to the current collector. Alternatively, it can be manufactured by the following steps: dispersing the aforementioned catalyst, binder, etc., as needed, in water and an organic solvent to prepare a catalyst layer forming composition (slurry, paste, etc.), coating it on the surface of the current collector and drying it, and then performing a pressing process such as calendering as needed.

[0081] Alternatively, porous carbon sheets composed of fibrous carbon such as carbon paper, carbon cloth, or carbon felt can be used as the catalyst layer. These carbon sheets can also be used as the current collector for the positive electrode described later, or they can serve both purposes.

[0082] In current collectors for positive electrodes with positive flux layers and positive electrodes with catalyst layers, materials such as meshes, foils, expanded alloys, and perforated metals made of titanium, nickel, stainless steel, copper, etc., or meshes and sheets of carbon can be used. It should be noted that when using current collectors with pores, the components of the positive flux layer and the catalyst layer can be contained within the pores of the current collector, thereby integrating the positive flux layer, catalyst layer, and current collector. The thickness of the current collector for the positive electrode is preferably 10 μm or more and 300 μm or less.

[0083] Furthermore, when the battery has a sheet-like outer casing made of a resin film, a portion of the aforementioned resin film can also be used in the current collector of the positive electrode. In this case, for example, a carbon paste can be coated onto the inner surface of the resin film, which is intended to be a sheet-like outer casing, to form the current collector. Alternatively, the metal layer of the resin film with a metal layer can be used as the current collector, and a positive electrode additive layer and a catalyst layer can be formed on the surface of the current collector using the same method as described above, thereby forming the positive electrode. The thickness of the aforementioned carbon paste layer is preferably 30 to 300 μm.

[0084] The positive electrode typically has a terminal portion for connection to an application device. The terminal portion of the positive electrode can be formed by connecting aluminum foil (plate), wire, nickel foil (plate), or other materials to the current collector of the positive electrode via a lead body, or by directly connecting them to the current collector of the positive electrode. When the terminal portion of the positive electrode is a foil (plate), its thickness is preferably 50 μm or more and 500 μm or less. Furthermore, when the terminal portion of the positive electrode is a wire, its diameter is preferably 100 μm or more and 1500 μm or less. Alternatively, the terminal portion of the positive electrode can be formed by exposing a portion of the current collector to the outside.

[0085] (Diaphragm)

[0086] In a battery, a separator is positioned between the positive and negative electrodes. For manganese batteries and air batteries, separators can be made of nonwoven fabrics primarily composed of vinylon and rayon, vinylon-rayon nonwoven fabrics (vinylon-rayon blended paper), polyamide nonwoven fabrics, polyolefin-rayon nonwoven fabrics, vinylon paper, vinylon-cotton pulp paper, vinylon-mercerized pulp paper, etc. Alternatively, microporous membranes can be used, specifically microporous polyolefin membranes (microporous polyethylene membranes, microporous polypropylene membranes, etc.). To improve wettability with aqueous electrolytes, their surfaces can be hydrophilically treated.

[0087] Alternatively, a membrane formed by stacking the aforementioned microporous membrane, celluloid membrane, and vinylon-rayon blended paper as an absorbent layer (electrolyte retention layer) can also be used as a separator. The thickness of the separator is preferably 10 to 500 μm, for example, 10 to 50 μm in the case of a microporous membrane, and 20 to 500 μm in the case of a nonwoven fabric.

[0088] (Battery form, etc.)

[0089] There are no particular restrictions on the shape of the battery, and it can be any shape, including the following: flat (including coin-shaped and button-shaped), which has a battery casing that is sealed by seaming the outer can and the sealing plate through a gasket or by welding the outer can and the sealing plate together; sheet-shaped, which has a sheet-like outer casing made of resin film; cylindrical (cylindrical, square (square cylindrical)), which has a battery casing that is sealed by seaming the bottomed cylindrical outer can and the sealing plate through a gasket or by welding the outer can and the sealing plate together.

[0090] When the battery is used as a power source for medical and health devices, such as patches that can be worn on the body, especially patches worn on the surface of the skin for measuring physical conditions related to body temperature, pulse, and perspiration, it is preferable to use a sheet battery with a sheet-shaped outer casing made of resin film.

[0091] The sheet-like outer casing is made of a resin film, such as nylon film (nylon 66 film, etc.) and polyester film (polyethylene terephthalate (PET) film, etc.).

[0092] It should be noted that the sealing of sheet-like outer casings is generally achieved by heat-fusion bonding the ends of the upper and lower resin films of the sheet-like outer casing. However, to facilitate this heat-fusion bonding, a heat-fused resin layer can also be laminated onto the resin film exemplified above for use in sheet-like outer casings. Examples of heat-fused resins constituting the heat-fused resin layer include modified polyolefin films (such as modified polyolefin ionomer films), polypropylene, and copolymers thereof. The thickness of the heat-fused resin layer is preferably 20 to 200 μm.

[0093] Alternatively, a metal layer can be laminated onto the resin film. The metal layer can be composed of aluminum film (aluminum foil, including aluminum alloy foil), stainless steel film (stainless steel foil), etc. The thickness of the metal layer is preferably 10~150μm.

[0094] Furthermore, the resin film constituting the sheet-like outer casing can be a film with a structure consisting of the aforementioned hot-melt resin layer and the aforementioned metal layer stacked together.

[0095] Furthermore, the resin film constituting the sheet-like outer casing preferably has an electrically insulating water vapor barrier layer. In this case, it can be a single-layer structure in which the electrically insulating resin film itself also functions as a water vapor barrier layer, or a multilayer structure in which multiple layers of electrically insulating resin films are formed, with at least one layer functioning as a water vapor barrier layer. Alternatively, it can be a multilayer structure in which an electrically insulating water vapor barrier layer is formed on the surface of a substrate layer composed of resin films.

[0096] In such resin film formation, it is preferable to use a resin film in which a water vapor barrier layer composed of at least inorganic oxides is formed on the surface of a substrate layer composed of resin film.

[0097] Examples of inorganic oxides constituting the water vapor barrier layer include aluminum oxide and silicon oxide. It should be noted that, compared to a water vapor barrier layer composed of aluminum oxide, a water vapor barrier layer composed of silicon oxide tends to have a higher tendency to suppress the permeation of moisture from the electrolyte within the battery. Therefore, silicon oxide is more preferably used as the inorganic oxide constituting the water vapor barrier layer.

[0098] A water vapor barrier layer composed of inorganic oxides can be formed on the surface of the substrate layer, for example, by vapor deposition. The thickness of the water vapor barrier layer is preferably 10 to 300 nm.

[0099] In the substrate layer of a resin film with a water vapor barrier layer, in addition to the nylon film and polyester film mentioned above, polyolefin film, polyimide film, polycarbonate film, etc. can also be used. The thickness of the substrate layer is preferably 5~100μm.

[0100] 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 can be formed on the surface of the water vapor barrier layer (the side opposite to the substrate layer).

[0101] In addition, in the case of a resin film having a water vapor barrier layer and a substrate layer, the above-mentioned hot-melt resin layer can be further laminated.

[0102] From the viewpoint of ensuring sufficient strength of the battery, the overall thickness of the resin film is preferably 10 μm or more, and from the viewpoint of suppressing the increase in battery thickness and the decrease in energy density, it is preferably 200 μm or less.

[0103] The water vapor transmission rate of the resin film constituting the sheet-like outer casing is preferably 10 g / m³. 2 • Less than 24 hours. It should be noted that the resin film is preferably as impermeable to water vapor as possible; that is, its water vapor transmission rate is preferably as low as possible, or even 0 g / m³. 2 ·24h.

[0104] The water vapor transmission rate of the resin film mentioned in this specification is the value determined according to the JIS K 7129B method.

[0105] It should be noted that, in the case of an air battery, the resin film constituting the sheet-like outer casing preferably has a certain degree of oxygen permeability. For air batteries, in order to supply air (oxygen) to the positive electrode for discharge, air holes for introducing oxygen into the battery must be formed on the sheet-like outer casing. However, when the resin film constituting the sheet-like outer casing has oxygen permeability, oxygen can also be introduced into the battery through the outer casing from areas other than the air holes. Therefore, oxygen can be supplied more uniformly throughout the positive electrode, improving the battery's discharge characteristics or extending its discharge time. Furthermore, it is also possible to realize a sheet-like air battery without air holes in the sheet-like outer casing.

[0106] When the battery is an air battery, the oxygen permeability of the resin film constituting the sheet-like outer casing is preferably 0.02 cm⁻¹. 3 / m 2 • 24h • MPa or higher, more preferably 0.2cm 3 / m 2• 24h • MPa or higher. However, in the case of an air battery, if the resin film constituting the sheet-like outer casing is too permeable to oxygen, self-discharge may occur, damaging the capacity. Therefore, the oxygen permeability of the resin film is preferably 100 cm⁻¹. 3 / m 2 • 24h • MPa or less, preferably 50cm 3 / m 2 • 24h • below MPa

[0107] On the other hand, when the battery is not an air battery, there is no particular limitation on the oxygen permeability of the resin film constituting the sheet-like outer casing. However, from the viewpoint of improving battery storage performance, a resin film with low oxygen permeability is preferred. Specifically, the oxygen permeability of the resin film is preferably 10 cm⁻¹. 3 / m 2 • 24h • below MPa

[0108] The oxygen permeability of the resin film mentioned in this specification is the value determined according to the JIS K 7126-2 method.

[0109] In addition, when using an outer casing with a slit-sealed opening, the gasket between the outer casing and the sealing plate can be made of materials such as polypropylene and nylon used in alkaline batteries.

[0110] In addition, to prevent elements such as iron that make up the outer can from dissolving during charging, it is preferable to plate the inner surface of the outer can with corrosion-resistant metals such as tin, zinc, and indium.

[0111] In the case of an air-filled battery, a waterproof membrane is typically placed between the positive electrode and the outer casing. This waterproof membrane is made of a material that is both waterproof and permeable to air. Specific examples of such a waterproof membrane include membranes made of fluoropolymers such as PTFE, or polyolefins such as polypropylene and polyethylene. The thickness of the waterproof membrane is preferably 50 to 250 μm.

[0112] Alternatively, in the case of an air battery, an air diffusion membrane can be disposed between the outer casing and the waterproof membrane to supply air taken into the outer casing to the positive electrode. The air diffusion membrane can be a nonwoven fabric made of resins such as cellulose, polyvinyl alcohol, polypropylene, or nylon. The thickness of the air diffusion membrane is preferably 100-250 μm.

[0113] Figure 1 and Figure 2 An example of a battery is shown schematically. Figure 1 and Figure 2 This is an example of a battery that has a negative electrode with a metal sheet and a sheet-like outer casing (the case of a sheet-like battery). Figure 1 Showing its top view, Figure 2 Show Figure 1 Sectional view of line II.

[0114] like Figure 2 As shown, in battery 10, the positive electrode 20, the separator 40, the negative electrode 30, and the aqueous electrolyte (not shown) are housed in a sheet-like outer casing 50.

[0115] The terminal portion 21 of the positive electrode 20 and the terminal portion 31 of the negative electrode 30 protrude from the upper part of the sheet-like outer casing 50 in the figure. For example... Figure 2 As shown, the positive terminal 21 is connected to the positive terminal 20 inside the battery 10. Additionally, although not shown, the negative terminal 31 is also connected to the negative terminal 30 inside the battery 10. These terminals 21 and 31 serve as external terminals for electrically connecting the battery 10 to an application device.

[0116] It should be noted that, in Figure 2 In this text, the sheet-like outer casing 50 (constituting a resin film therein) is represented as a single-layer structure; however, as mentioned above, the resin film constituting the sheet-like outer casing can also be a multi-layer structure. Furthermore, in... Figure 2 In the figure, the positive electrode 10 and the negative electrode 20 are also shown as single-layer structures, but as mentioned above, the positive electrode and the negative electrode can also be multi-layer structures. Furthermore, the negative electrode can also contain metal particles such as zinc particles.

[0117] The shape of the sheet-like outer casing can be polygonal (triangle, quadrilateral, pentagon, hexagon, heptagon, octagon, etc.) when viewed from above, or it can be circular or elliptical. It should be noted that when the sheet-like outer casing is polygonal when viewed from above, the positive terminal and the negative terminal can be led outward from the same side, or they can be led outward from different sides.

[0118] When the battery is a sheet-like cell, its thickness ( Figure 2 The length of 'a' is not particularly limited and can be varied appropriately depending on the application of the battery. It should be noted that one of the advantages of sheet batteries is their ability to be made thin; from this perspective, their thickness is preferably, for example, 1 mm or less. Such thin batteries are particularly easy to provide when the battery is a sheet-type air battery.

[0119] In addition, there is no particular limit to the lower limit of the battery thickness, but in order to ensure a certain capacity, it is usually preferred to be 0.2mm or more.

[0120] Example

[0121] The present invention will now be described in detail based on embodiments. However, the following embodiments do not limit the present invention.

[0122] (Example 1)

[0123] Positive electrode

[0124] A positive electrode-containing compound was prepared by mixing 87.5 parts by weight of electrolytic manganese dioxide (SP-A manufactured by Tosoh Corporation, with an average particle size of 0.5 μm), 10 parts by weight of graphite (SP-20 manufactured by Nippon Graphite Corporation, with an average particle size of 30 μm), 2.5 parts by weight of ammonium polyacrylate, and 150 parts by weight of water.

[0125] By strip-coating the above-mentioned positive electrode mixture composition onto porous carbon paper (thickness: approximately 0.2 mm, porosity: 75%, air permeability (Gurley): 70 seconds / 100 ml) and drying it, a carbon paper is obtained having a region (hereinafter referred to as "Region A") in which the positive electrode active material (positive electrode mixture) is retained in the pores and the surface is covered by a layer containing the positive electrode active material (positive electrode mixture layer), and a region of carbon paper only (hereinafter referred to as "Region B") in which the positive electrode active material is not retained in the pores and no layer containing the positive electrode active material is formed on the surface. This carbon paper is then punched into a shape having a main body consisting of Region A (15 mm × 15 mm) containing the positive electrode active material and a positive electrode consisting of Region B (10 mm × 20 mm), thus producing a positive electrode with a theoretical capacity of 36 mAh.

[0126] <Negative electrode>

[0127] The negative electrode is made by punching an electrolytic zinc alloy foil (thickness: 0.03 mm) composed of a zinc alloy containing 0.05% by mass of Bi as an additive element and no In. The foil is punched into a shape with a main body of 15 mm × 15 mm and a negative electrode of 10 mm × 20 mm.

[0128] Electrolyte

[0129] The electrolyte used is an aqueous solution containing LiCl at a concentration of 16.7% by mass.

[0130] <Septum>

[0131] The diaphragm uses a polypropylene nonwoven membrane with a hydrophilic treatment on its surface (thickness: 50μm, weight per unit area: 12g / m²). 2 ).

[0132] <Sheet-shaped exterior body>

[0133] Two 25mm×30mm aluminum laminates (thickness: 65μm) are used as sheet-like outer packaging. The aluminum laminates have a PET film on the outer surface of the aluminum foil and a polypropylene film on the inner surface as a heat-melting resin layer.

[0134] <Battery Assembly>

[0135] The positive electrode, the separator, and the negative electrode are sequentially stacked on an aluminum laminate, and then another aluminum laminate is overlapped. Next, the three edges of the two aluminum laminates are heat-fused together to form a bag shape. 0.12 ml of the electrolyte is then injected through the opening, and the opening is heat-fused to seal it, thus creating a bag that... Figure 1 and Figure 2 The sheet battery shown has the same structure as the one shown.

[0136] Examples 2-5

[0137] Except for changing the concentration of LiCl in the electrolyte to 23.1% by mass, 28.6% by mass, 33.3% by mass and 37.5% by mass respectively, the sheet batteries of Examples 2 to 5 were produced in the same manner as in Example 1.

[0138] Comparative Example 1

[0139] Except for changing the concentration of LiCl in the electrolyte to 9.1% by mass, the same procedure as in Example 1 was followed to fabricate the sheet battery.

[0140] Comparative Example 2

[0141] Except that an aqueous solution containing ammonium chloride at a concentration of 25% by mass was used as the electrolyte, the sheet battery was fabricated in the same manner as in Example 1.

[0142] Comparative Example 3

[0143] Except that an aqueous solution containing zinc chloride at a concentration of 25% by mass was used as the electrolyte, the sheet battery was fabricated in the same manner as in Example 1.

[0144] The composition of the aqueous electrolyte used in the sheet batteries of the examples and comparative examples is shown in Table 1.

[0145] [Table 1]

[0146]

[0147] For the sheet batteries of Examples 1, 3-5 and Comparative Examples 1-3, after being placed in a constant temperature bath at -40°C for 2 hours, a pulse discharge test was performed under the following conditions to evaluate the discharge characteristics of the batteries in their initial state at -40°C.

[0148] The pulse discharge conditions were set as follows: pulse width: 10 msec, pulse interval: 3 sec. Ten pulse discharges were performed with a pulse current of 1 mA, and the closed-circuit voltage (CCV) was measured. The results are presented below. Figure 3 .

[0149] In addition, unlike the above, the sheet 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 to achieve a depth of discharge of 83%. After placing each sheet battery in the above-discharged state in a constant temperature bath at -40°C for 2 hours, a pulse discharge test was conducted under the following conditions.

[0150] The pulse discharge conditions were set as follows: pulse width: 10 msec, pulse interval: 3 sec. Ten pulse discharges were performed with a pulse current of 10 mA, and the closed-circuit voltage (CCV) was measured. The results are presented below. Figure 4 .

[0151] like Figure 3 As shown, the sheet batteries of Examples 1 and 3-5, which have an aqueous electrolyte containing LiCl at a certain concentration or higher, exhibit high CCVs in their low-temperature discharge characteristic evaluation, and possess excellent low-temperature characteristics close to those of the sheet battery of Comparative Example 3, which uses an aqueous electrolyte containing zinc chloride. In particular, as... Figure 4 As shown, it can be seen that in aqueous electrolytes, the concentration of LiCl is above 20% by mass and below 35% by mass, resulting in superior low-temperature characteristics.

[0152] Example 6

[0153] 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 consisting of a 15mm × 15mm region A containing the positive electrode active material and a positive terminal consisting of a 5mm × 12mm region B. The negative electrode was changed to an electrolytic zinc alloy foil (thickness: 0.03mm) consisting of a zinc alloy containing 0.05% by mass of Bi as an additive element and no In, which was punched into a shape having a 15mm × 15mm main body and a 5mm × 12mm negative terminal. Otherwise, the same procedure as in Example 1 was followed to produce a sheet battery.

[0154] Example 7

[0155] Except for changing the electrolyte to an aqueous solution containing LiCl at a concentration of 33.6% by mass and ammonium chloride at a concentration of 2.7% by mass, the sheet battery was fabricated in the same manner as in Example 6.

[0156] Example 8

[0157] Except for changing the electrolyte to an aqueous solution containing LiCl at a concentration of 33.6% by mass and ammonium chloride at a concentration of 5.3% by mass, the same procedure was followed to fabricate the sheet battery as in Example 6.

[0158] For the sheet batteries of Examples 6-8, pulse discharge tests were conducted under the following conditions. The pulse discharge conditions were set as follows: pulse width: 10 msec, pulse interval: 3 sec, pulse current: 40 mA, and 10 pulse discharges were performed. The closed-circuit voltage (CCV) and open-circuit voltage (OCV) were measured. These results are shown in Table 2.

[0159] [Table 2]

[0160]

[0161] As shown in Table 2, the OCV and CCV values ​​of the sheet batteries in Examples 7 and 8, which contain ammonium chloride along with LiCl in an aqueous electrolyte, are higher than those of the sheet battery in Example 6, which uses an aqueous electrolyte with LiCl as the electrolyte salt alone, and exhibit superior discharge characteristics at room temperature.

[0162] This invention can also be implemented in ways other than those described above without departing from its spirit. The embodiments disclosed in this application are merely examples, and the invention is not limited to these embodiments. Compared with the description in the foregoing specification, the scope of the invention is preferably interpreted according to the description in the appended claims, and all modifications within the scope of the claims are included in the claims.

[0163] Industrial availability

[0164] In the battery of the present invention, the electrolyte is an aqueous solution, which is substantially free of heavy metal elements, thus having a low environmental impact. Furthermore, even if the electrolyte leaks out due to breakage and adheres to the body, it is unlikely to cause problems. Accordingly, the battery of the present invention is suitable as a power source for devices used in medical / health applications, such as patches worn on the body, particularly patches worn on the skin surface for measuring body conditions related to temperature, pulse, and perspiration. It can also be used for the same purposes as batteries using conventionally known aqueous electrolytes such as air batteries and manganese batteries.

[0165] Explanation of reference numerals in the attached figures

[0166] 10: Battery, 20: Positive electrode, 21: Positive electrode terminal, 30: Negative electrode, 31: Negative electrode terminal, 40: Separator, 50: Sheet-shaped outer casing.

Claims

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

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

3. The battery according to claim 1, wherein, The electrolyte also contains electrolyte salts other than LiCl.

4. The battery according to claim 3, wherein, As an electrolyte salt other than LiCl, it contains at least one electrolyte salt selected from ammonium chloride, zinc chloride, alkali metal hydroxides and alkaline earth metal hydroxides.

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

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

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

8. The battery according to claim 1, wherein, The negative electrode uses at least one metal selected from zinc, aluminum, magnesium, and their alloys as the active material.

9. The battery according to claim 8, wherein, The negative electrode has zinc foil or zinc alloy foil.

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

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