JP7802973B2 - Aqueous electrolyte batteries and patches - Google Patents

Description

The present invention relates to an aqueous electrolyte battery with excellent load characteristics and reliability, and a patch equipped with such a battery.

Batteries that use aqueous electrolytes, such as air batteries and alkaline batteries, are generally button-shaped with a metal can as the exterior body, or cylindrical with a cylindrical exterior can.

On the other hand, batteries having the above-mentioned negative electrodes have also been made into sheet-type batteries using an exterior body made of a resin film (see, for example, Patent Document 1).

Taking advantage of their shape and other characteristics, such batteries are being considered for use as power sources for various body sensors, such as temperature patches. To better meet these needs, Patent Document 1 uses a low-pH electrolyte so that the impact on the environment can be minimized when users dispose of replaced batteries.

Note that using an electrolyte with a low pH, such as that described above, tends to reduce the battery's discharge capacity, but the battery described in Patent Document 1 avoids this problem by using a separator made of a semipermeable membrane such as a resin microporous membrane, nonwoven fabric, or cellophane film, with an air permeability limited to a specific value or higher.

International Publication No. 2018/056307

In recent years, the application of batteries containing aqueous electrolytes to applications requiring discharge at relatively large current values has been considered, and as a result, there are cases where improvements in load characteristics are required. However, the technology described in Patent Document 1 still leaves room for improvement in this regard.

On the other hand, it is possible to improve the load characteristics of a battery by using a membrane with very low air permeability and excellent ion permeability, such as a resin nonwoven fabric, as a separator, but batteries using such separators are prone to micro-short circuits, which can reduce their reliability.

The present invention was made in consideration of the above circumstances, and its purpose is to provide an aqueous electrolyte battery with excellent load characteristics and reliability, and a patch equipped with such a battery.

The aqueous electrolyte battery of the present invention comprises a positive electrode, a negative electrode containing a metallic material, a separator, and an aqueous electrolyte housed within an exterior case; the separator is a porous film having a thickness of 5 μm to 100 μm, an air permeability of 10 sec/100 mL to 3000 sec/100 mL, and a contact angle with water of 90° or less; and the negative electrode comprises electrolytic zinc foil.

The patch of the present invention is characterized by being wearable on the body and including the aqueous electrolyte battery of the present invention as a power source.

The present invention provides an aqueous electrolyte battery with excellent load characteristics and reliability, and a patch equipped with the battery.

1 is a plan view schematically illustrating an example of an aqueous electrolyte battery of the present invention. FIG. 2 is a cross-sectional view taken along line II in FIG. 1.

The separator of the aqueous electrolyte battery of the present invention is made of resin and is composed of a porous film with a thickness of 5 μm to 100 μm, an air permeability of 10 sec/100 mL to 3000 sec/100 mL, and a contact angle with water of 90° or less.

As mentioned above, when a semipermeable membrane such as cellophane film is used, a decrease in the battery's discharge capacity can be prevented, even when an electrolyte with a pH of 3 or higher but less than 12 is used. On the other hand, although semipermeable membranes are ion-permeable, they are essentially non-porous membranes with very high air permeability, which limits the amount of ions that drive the battery reaction that can pass through, making them susceptible to a decrease in the battery's load characteristics (discharge characteristics under heavy loads).

On the other hand, nonwoven fabrics made from resins such as polyolefins have an air permeability of less than 5 sec/100 mL and very high ion permeability. While batteries using these as separators can prevent a decline in load characteristics, they are prone to micro-short circuits and have poor reliability and storage capacity. This is thought to be because separators made from nonwoven fabrics typically have large pores (voids), allowing protrusions on the surface of the positive or negative electrode to pass through these pores and come into contact with the counter electrode.

Furthermore, when a microporous membrane made of a resin such as polyolefin, which is commonly used in non-aqueous secondary batteries, is used as the separator, the occurrence of the aforementioned micro-short circuit can be suppressed more effectively than when a nonwoven fabric is used as the separator. However, as with the use of a semipermeable membrane as the separator, the load characteristics of the battery are likely to deteriorate. According to the inventors' investigations, it was found that the microporous membrane made of the resin is difficult to wet with aqueous electrolyte solutions and has poor ion permeability, which is the cause of the deteriorated load characteristics.

In this invention, therefore, a porous resin membrane with a specific thickness, specific air permeability, and a contact angle with water of 90° or less is used as the separator. This porous membrane has a high affinity with water, the solvent that makes up the aqueous electrolyte, and good permeability, allowing a large amount of ions to pass through the separator. Therefore, by using this as a separator, it is possible to extract a large capacity from the battery even during heavy load discharge.

In addition, the porous membrane has high air permeability and limited breathability to a certain extent, and also has a certain thickness, so batteries using it as a separator can suppress the occurrence of the micro-short circuit.

The aqueous electrolyte battery of the present invention achieves both excellent load characteristics and high reliability through the above-mentioned effects.

The porous membrane used as the separator in an aqueous electrolyte battery has a contact angle with water of 90° or less, preferably 70° or less, and particularly preferably 60° or less. If the porous membrane has a contact angle with water that satisfies these values and an air permeability within the range described below, using it as a separator will have high affinity with the aqueous electrolyte and good ion permeability, thereby improving the load characteristics of the battery. There is no particular limit to the lower limit of the contact angle with water of the porous membrane used as a separator, but it is usually 10° or more. To broaden the range of resins that can be used and the conditions for hydrophilization treatment, and to facilitate manufacturing, a contact angle of 20° or more is preferred, and a contact angle of 30° or more is particularly preferred.

The water contact angle of a porous membrane referred to in this specification is the value measured from the side after 1 minute after 50 μL of ion-exchanged water is dropped onto the surface of the porous membrane. Contact angles can be measured using a common measuring device, such as the dynamic contact angle meter "1100DAT" (product name) manufactured by Fibro.

The air permeability of a porous membrane used as a separator in an aqueous electrolyte battery is 3000 sec/100 mL or less, preferably 1000 sec/100 mL or less, and particularly preferably 600 sec/100 mL or less. If the air permeability of the porous membrane satisfies these values and the contact angle with water satisfies the above values, using it as a separator can improve the load characteristics of the battery, as described above. However, if a porous membrane with too low an air permeability is used as a separator, micro-short circuits in the battery are more likely to occur. Therefore, from the perspective of suppressing the occurrence of micro-short circuits and improving battery reliability, the air permeability of a porous membrane used as a separator is 10 sec/100 mL or more, preferably 20 sec/100 mL or more, and particularly preferably 50 sec/100 mL or more. Note that if the separator is composed of multiple layers, each layer may be configured so that the air permeability of the separator as a whole is within the above range.

The air permeability of a porous membrane referred to in this specification is the value determined by the Gurley method specified in JIS P 8117.

In addition, the porous membrane used as the separator in an aqueous electrolyte battery is 5 μm or more in order to effectively prevent the occurrence of micro-short circuits in the battery, and is 100 μm or less, preferably 30 μm or less, in order to prevent a decrease in the volumetric capacity density of the battery due to an increase in the separator thickness.

The porous membrane used as the separator is made of resin. The resin that makes up the porous membrane can be either one with high or low affinity for water, but it is preferable to use polyolefins (polyethylene (PE), polypropylene (PP), ethylene-propylene copolymers, etc.) that are commonly used in battery separators.

The porous membrane can be a microporous membrane made of the resin described above (a porous membrane commonly used as a battery separator and known as a "microporous membrane").

The porous membrane may be selected from porous membranes such as microporous membranes made of the resins described above, so long as they satisfy the above-mentioned air permeability and thickness requirements. In the case of microporous membranes made of resin, the air permeability can be adjusted by adjusting the porosity and tortuosity of the pores.

In addition, polyolefins and other resins suitable for use as constituent resins of porous membranes have low affinity for water, and porous membranes formed from these have a contact angle with water that exceeds the upper limit mentioned above. However, porous membranes made from such resins can be used as separators if they are subjected to a hydrophilization treatment so that the contact angle with water satisfies the above-mentioned value.

Examples of hydrophilic treatments for porous membranes include a method of introducing sulfonic acid groups into the constituent resin of the porous membrane by sulfuric acid treatment, and a method of treatment with fluorine gas and a reactive gas containing oxygen atoms and/or sulfur atoms (both of these methods are disclosed in, for example, JP 2000-355633 A). Porous membranes can also be hydrophilized using common methods for hydrophilizing resin films, such as corona discharge treatment and atmospheric pressure plasma treatment.

The aqueous electrolyte battery of the present invention is not particularly limited in its configuration, as long as it uses an aqueous electrolyte and has the porous membrane as a separator. In other words, the aqueous electrolyte battery of the present invention can take the form of various batteries that use an aqueous electrolyte, such as alkaline batteries (alkaline primary batteries, alkaline secondary batteries); manganese batteries; and air batteries. Examples of such alkaline batteries include nickel-zinc batteries that use nickel oxyhydroxide as the positive electrode active material and a zinc-based material (a term that collectively refers to zinc materials and zinc alloy materials) as the negative electrode active material; and silver-zinc batteries that use silver oxide as the positive electrode active material and a zinc-based material as the negative electrode active material.

The electrolyte in an aqueous electrolyte battery is an aqueous solution in which an electrolyte salt is dissolved in water as a solvent. There are no particular limitations on the aqueous solution used as the electrolyte, and it is possible to use a high-concentration alkaline electrolyte (pH: approximately 14) used in alkaline dry batteries. However, from the standpoint of reducing the environmental impact during disposal and ensuring safety in the event of electrolyte leakage due to damage to the exterior, it is preferable that the pH of the electrolyte be as close to neutral as possible. The pH is preferably 3 or higher, more preferably 5 or higher, and preferably less than 12, more preferably 10 or lower. From the standpoint of inhibiting corrosion of the negative electrode active material, a pH of less than 7 is even more preferable.

The electrolyte salts of the aqueous solution used as the electrolyte 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 (lithium hydroxide, sodium hydroxide, potassium hydroxide, magnesium hydroxide, etc.); acetates (sodium acetate, potassium acetate, magnesium acetate, etc.); nitrates (sodium nitrate, potassium nitrate, magnesium nitrate, etc.); sulfates (sodium sulfate, potassium sulfate, magnesium sulfate, etc.); phosphates (sodium phosphate, potassium phosphate, magnesium phosphate, etc.); ), borates (sodium borate, potassium borate, magnesium borate, etc.), citrates (sodium citrate, potassium citrate, magnesium citrate, etc.), glutamates (sodium 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; polycarboxylic acids; and the aqueous solution may contain one or more of these electrolyte salts.

The electrolyte salt is preferably a salt of a strong acid selected from hydrochloric acid, sulfuric acid, and nitric acid with a weak base such as ammonia or a hydroxide of a metal element such as aluminum hydroxide or magnesium hydroxide, and more preferably an ammonium salt or a salt of a specific metal element. Specific examples include a salt of at least one ion selected from Cl ^- , SO ₄ ^2- , HSO ₄ ^- , and NO ₃ ^- with at least one ion selected from Al ion, Mg ion, Fe ion, and ammonium ion. Examples include ammonium salts such as ammonium sulfate, ammonium hydrogen sulfate [(NH ₄ )HSO ₄ ], ammonium chloride, and ammonium nitrate; aluminum salts such as aluminum sulfate, aluminum chloride, and aluminum nitrate; magnesium salts such as magnesium sulfate, magnesium chloride, magnesium chloride hydroxide [MgCl(OH)], and magnesium nitrate; and iron salts such as iron(II) sulfate, ammonium iron(II) sulfate [(NH ₄ ) ₂ Fe(SO ₄ ) ₂ ], iron(III) sulfate, iron(II) chloride, and iron(II) nitrate.

Although metallic materials such as metals and alloys are typically used as the negative electrode active material for the negative electrode of aqueous electrolyte batteries, electrolytes consisting of aqueous solutions containing salts of strong acids and weak bases, such as those exemplified above, have a relatively weaker corrosive effect on the metallic material serving as the negative electrode active material than electrolytes containing salts of strong acids and strong bases, such as sodium chloride. Furthermore, electrolytes containing salts of metal elements selected from Al, Mg, and Fe, or ammonium salts, among salts of strong acids, have relatively higher electrical conductivity than, for example, aqueous zinc chloride solutions. Therefore, when an electrolyte consisting of an aqueous solution containing, as the salt of a strong acid and a weak base, at least one ion selected from Cl ⁻ , SO ₄ ²⁻ , HSO ₄ ⁻ , and NO ₃ ⁻ and at least one ion selected from Al ions, Mg ions, Fe ions, and ammonium ions is used, the discharge characteristics of aqueous electrolyte batteries can be further improved.

However, a salt of Cl ⁻ ions and Fe ^ions [iron (III) chloride] has a stronger corrosive effect on the metal material that is the negative electrode active material than salts made from other ion combinations, so it is preferable to use a salt other than iron (III) chloride, and it is more preferable to use an ammonium salt because it has a weaker corrosive effect on the metal material that is the negative electrode active material.

Furthermore, among the salts of strong acids and weak bases, perchlorates pose a risk of combustion or explosion when heated or impacted. Therefore, from the standpoint of environmental impact and safety during disposal, it is preferable that they are not contained in the aqueous solution, or that, if they are contained, the amount of perchlorate ions be very small (preferably less than 100 ppm, and more preferably less than 10 ppm).

Furthermore, among the salts of strong acids and weak bases, heavy metal salts (excluding iron salts), such as zinc chloride and copper sulfate, are often harmful. Therefore, from the standpoint of environmental impact and safety during disposal, it is preferable that they not be included in the aqueous solution, or that, if they are included, the amount of heavy metal ions excluding iron ions be very small (preferably less than 100 ppm, and more preferably less than 10 ppm).

Furthermore, when the aqueous electrolyte battery is an air battery, the aqueous solution that can be used as the electrolyte preferably contains a water-soluble high-boiling-point solvent with a boiling point of 150°C or higher as a solvent together with water. In an air battery, as the remaining capacity of the negative electrode decreases during discharge, the voltage decreases accordingly. However, in the latter stages of discharge when the remaining capacity becomes low, not only does the voltage decrease but the voltage fluctuations tend to become greater. However, if the aqueous solution contains a water-soluble high-boiling-point solvent, this voltage fluctuation in the later stages of discharge can be suppressed, resulting in an air battery with better discharge characteristics. The upper limit of the boiling point of the water-soluble high-boiling-point solvent is typically 320°C.

It is desirable for the water-soluble high-boiling-point solvent to have high surface tension and dielectric constant. Specific examples include polyhydric alcohols such as ethylene glycol (boiling point 197°C, surface tension 48 mN/m, dielectric constant 39), propylene glycol (boiling point 188°C, surface tension 36 mN/m, dielectric constant 32), and glycerin (boiling point 290°C, surface tension 63 mN/m, dielectric constant 43); polyalkylene glycols (preferably with a molecular weight of 600 or less) such as PEG (e.g., boiling point 230°C, surface tension 43 mN/m, dielectric constant 35); and the like. The electrolyte solution may contain only one of these water-soluble high-boiling-point solvents, or two or more may be used in combination; however, it is more preferable to use glycerin.

When a water-soluble high-boiling-point solvent is used, in order to ensure the desired effects of its use, the content of the water-soluble high-boiling-point solvent in the total solvent of the aqueous solution is preferably 1% by mass or more, and more preferably 3% by mass or more. However, if the amount of water-soluble high-boiling-point solvent in the aqueous solution is too large, the ionic conductivity of the aqueous solution may become too low, which may result in a deterioration in battery characteristics. Therefore, the content of the water-soluble high-boiling-point solvent in the total solvent of the aqueous solution is preferably 30% by mass or less, and more preferably 20% by mass or less.

The concentration of the electrolyte salt in the aqueous solution may be, for example, a concentration that can adjust the conductivity of the aqueous solution to approximately 80 to 700 mS/cm, and is typically 5 to 50% by mass.

The aqueous solution used as the electrolyte preferably contains an indium compound dissolved in its solvent (water or a mixed solvent of water and a water-soluble high-boiling-point solvent). When an indium compound is dissolved in the aqueous solution, hydrogen gas generation within the battery can be effectively suppressed.

Examples of indium compounds that can be dissolved in the aqueous solution include indium hydroxide, indium oxide, indium sulfate, indium sulfide, indium nitrate, indium bromide, and indium chloride.

The concentration of the indium compound in the aqueous solution is preferably 0.005% or more by mass, more preferably 0.01% or more, and particularly preferably 0.05% or more, and is preferably 1% or less, more preferably 0.5% or less, and particularly preferably 0.1% or less.

In addition to the above-mentioned components, various known additives may be added to the aqueous solution as needed, as long as they do not impair the effects of the present invention. For example, zinc oxide may be added to prevent corrosion (oxidation) of the metal material used in the negative electrode.

The aqueous solution that constitutes the electrolyte may be gelled. It is also preferable to use a gelled electrolyte (gelled electrolyte) composed of an aqueous solution containing an electrolyte salt and having a pH of 3 or greater but less than 12, combined with a thickener (such as sodium polyacrylate or carboxymethyl cellulose) as the electrolyte for an aqueous electrolyte battery. In this case, voltage fluctuations during the later stages of discharge can be suppressed, further improving the discharge characteristics of the aqueous electrolyte battery. Furthermore, because water evaporation from the gelled electrolyte is suppressed, deterioration in discharge characteristics due to fluctuations in the electrolyte composition can be suppressed, particularly in air batteries that have air holes in the exterior, and the storage characteristics of the battery can also be further improved.

When the aqueous electrolyte battery is an alkaline battery or a manganese battery, the positive electrode can have a structure in which, for example, 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.

When the aqueous electrolyte is an alkaline battery, usable positive electrode active materials include silver oxide (silver (I) oxide, silver (II) oxide, etc.); manganese oxides such as manganese dioxide; nickel oxyhydroxide; and composite oxides of silver with cobalt, nickel, or bismuth. Furthermore, when the sheet-type battery is a manganese battery, manganese oxides such as manganese dioxide are used as the positive electrode active material.

Conductive additives for the positive electrode mixture layer can include, for example, carbon materials such as acetylene black; ketjen black; carbon blacks such as channel black, furnace black, lamp black, and thermal black; carbon fibers; conductive fibers such as metal fibers; carbon fluoride; metal powders such as copper and nickel; and organic conductive materials such as polyphenylene derivatives.

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

The positive electrode mixture layer preferably contains 80 to 98% by mass of positive electrode active material, 1.5 to 10% by mass of conductive additive, and 0.5 to 10% by mass of binder. The thickness of the positive electrode mixture layer (thickness per side of the current collector) is preferably 30 to 300 μm.

A positive electrode having a positive electrode mixture layer can be manufactured, for example, by dispersing the positive electrode active material, conductive additive, binder, etc. in water or an organic solvent such as 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, when the aqueous electrolyte battery is an air battery, the positive electrode can have a catalyst layer, for example, a structure in which a catalyst layer and a current collector are stacked.

The catalyst layer can contain catalysts, binders, etc.

Examples of the catalyst for the catalyst layer include silver, platinum group metals or alloys thereof, transition metals, platinum/metal oxides such as Pt/ _IrO2 , perovskite oxides such as _{La1- xCaxCoO3} , carbides such as WC, nitrides such as _Mn4N , manganese oxides such as manganese dioxide, and carbon ₍ graphite, carbon black (acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black, etc.), charcoal, activated carbon, etc.), and one or more of these may be used.

It is preferable that the catalyst layer contain no more than 1% by mass of heavy metals, excluding components of the electrolyte solution. A positive electrode having a catalyst layer with such a low heavy metal content can be disposed of without any special treatment, resulting in a battery with a low environmental impact.

The heavy metal content in the catalyst layer referred to in this specification can be measured by X-ray fluorescence analysis. For example, it can be measured using a Rigaku Corporation "ZSX100e" under the following conditions: excitation source: Rh 50 kV, analysis area: φ10 mm.

For this reason, it is recommended that the catalyst used in the catalyst layer does not contain heavy metals, and it is more preferable to use the various carbons mentioned above.

Furthermore, from the viewpoint of further enhancing the reactivity of the positive electrode, the specific surface area of the carbon used as a catalyst is preferably 200 m ² /g or more, more preferably 300 m ² /g or more, and even more preferably 500 m ² /g or more. The specific surface area of carbon referred to in this specification is a value determined by the BET method in accordance with JIS K 6217, and can be measured, for example, using a specific surface area measuring device ("Macsorb HM model-1201" manufactured by Mountech) using a nitrogen adsorption method. The upper limit of the specific surface area of carbon is usually about 2000 m ² /g.

The catalyst content in the catalyst layer is preferably 20 to 70% by mass.

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.

A positive electrode with a catalyst layer can be manufactured, for example, by mixing the catalyst, binder, etc. with water, rolling the mixture with a roll, and then adhering it to a current collector. Alternatively, the catalyst and optional binder, etc., can be dispersed in water or an organic solvent to prepare a catalyst layer-forming composition (slurry, paste, etc.), which is then applied to the surface of the current collector, dried, and then optionally subjected to a pressing process such as calendaring.

Current collectors for positive electrodes having a positive electrode mixture layer or a positive electrode having a catalyst layer can be made of, for example, metal mesh, foil, expanded metal, or punched metal such as titanium, nickel, stainless steel, or copper; or carbon mesh or sheet. The thickness of the current collector for the positive electrode is preferably 10 μm or more and 300 μm or less.

Furthermore, when a resin film sheet-like exterior (described in detail below) is used as the exterior of the battery, the resin film that constitutes the sheet-like exterior can also 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 exterior to form a current collector, and a positive electrode mixture layer and catalyst layer can be formed on this surface using the same method as above to form a positive electrode. The thickness of the carbon paste layer is preferably 30 to 300 μm.

Aqueous electrolyte batteries use negative electrodes containing metal materials such as zinc-based materials (zinc or zinc alloys), magnesium-based materials (magnesium or magnesium alloys), and aluminum-based materials (aluminum or aluminum alloys). In such negative electrodes, metals such as zinc, magnesium, and aluminum act as the active material.

In consideration of reducing the environmental impact when batteries are disposed of, it is preferable that the metal material used for the negative electrode contains low amounts of mercury, cadmium, lead, and chromium, and more preferably the specific contents, by mass, are mercury: 0.1% or less, cadmium: 0.01% or less, lead: 0.1% or less, and chromium: 0.1% or less.

Specific examples of negative electrodes containing metal materials include metal sheets made of the above materials (zinc foil, zinc alloy foil, magnesium foil, magnesium alloy foil, aluminum foil, aluminum alloy foil, etc.). The thickness of such negative electrodes is preferably 10 to 500 μm.

Alloying components of zinc alloys include, for example, indium, bismuth, and aluminum, and alloys containing one or more of these elements are used.

The indium content in the zinc alloy 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. The aluminum content is, for example, 0.001% or more and 0.15% or less by mass.

Zinc foil (zinc alloy foil) can be electrolytic zinc foil or rolled zinc foil. Electrolytic zinc foil is preferred because it is less likely to produce gas due to reaction with the electrolyte inside the battery, and electrolytic zinc foil containing bismuth is particularly preferred. The preferred range of bismuth content in electrolytic zinc foil is 0.02% to 0.1% by mass.

Also, alloy components of magnesium alloys include, for example, calcium, manganese, zinc, and aluminum, and alloys containing one or more of these elements are used.

The calcium content in the magnesium alloy 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. The aluminum content is, for example, 8% or more and 10% or less by mass.

Furthermore, alloying components of aluminum alloys include, for example, zinc, tin, gallium, silicon, iron, magnesium, manganese, etc., and alloys containing one or more of the above elements are used.

The zinc content in the aluminum alloy 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.

Another example of a negative electrode containing a metal material is a negative electrode containing metal particles, such as particles made of the above-mentioned material.

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

As for the particle size of the zinc-based material, for example, the proportion of particles with a particle size of 75 μm or less among all particles is preferably 50% by mass or less, more preferably 30% by mass or less, and the proportion of particles with a particle size of 100 to 200 μm is 50% by mass or more, more preferably 90% by mass or more.

Furthermore, with regard to the particle size of the magnesium-based material particles and aluminum-based material particles, for example, the proportion of particles with 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 with a particle size of 50 to 200 μm is 50 mass% or more, more preferably 90 mass% or more.

The particle size of metal particles referred to in this specification is the particle size (D 50 ) 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.).

Anodes containing the aforementioned metal particles may contain a gelling agent (such as polyethylene oxide, sodium polyacrylate, or carboxymethyl cellulose) or binder, which may be added as needed, and an anode material (such as a gelled anode) can be used by adding an electrolyte solution to this. The amount of gelling agent in the anode is preferably 0.5 to 1.5% by mass, and the amount of binder is preferably 0.5 to 3% by mass.

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

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.

A negative electrode containing metal particles preferably contains an indium compound. By containing an indium compound in the negative electrode, hydrogen gas generation due to a corrosion reaction between the metal particles and the electrolyte can be more effectively prevented.

Examples of the indium compound include indium oxide and indium hydroxide.

The amount of indium compound used in the negative electrode is preferably 0.003 to 1 part by mass of metal particles per 100 parts by mass.

A current collector may also be used, if necessary, for negative electrodes containing metallic materials. Examples of current collectors for negative electrodes containing metallic materials include mesh, foil, expanded metal, and punched metal made of metals such as nickel, copper, and stainless steel; and carbon sheets and mesh. The thickness of the negative electrode current collector is preferably 10 μm or more and 300 μm or less.

Furthermore, when a sheet-like outer casing made of a resin film is used as the battery outer casing, the negative electrode current collector can be used by applying carbon paste to the surface intended to become the inner surface of the sheet-like outer casing, as in the case of the positive electrode. The thickness of the carbon paste layer is preferably 50 to 200 μm.

There are no particular restrictions on the shape of the aqueous electrolyte battery, and it can be any shape, such as a flat type (including coin and button types) with a battery case in which the outer can and sealing plate are crimped together via a gasket or sealed by welding; a sheet type with a sheet-like outer casing made of resin film; or a cylindrical type (cylindrical or prismatic (rectangular cylindrical)) with a battery case in which the outer can and sealing plate are crimped together via a gasket or sealed by welding.

When using an aqueous electrolyte battery as a power source for medical and health-related equipment, such as a patch that can be worn on the body, particularly a patch worn on the surface of the skin to measure body conditions such as body temperature, pulse rate, and sweat rate, it is preferable to make it a sheet-type battery with a sheet-type outer casing made of resin film.

The sheet-like outer packaging is made of a resin film, such as nylon film (such as nylon 66 film) or polyester film (such as polyethylene terephthalate (PET) film).

The sheet-like outer packaging is generally sealed by heat-sealing the edges of the upper and lower resin films of the sheet-like outer packaging. However, to facilitate this heat-sealing, a heat-sealing resin layer may be laminated onto the resin film exemplified above and used for the sheet-like outer packaging. The separator may also be sandwiched between the upper and lower heat-sealing resin layers and heat-sealed. Examples of heat-sealing resins that make up the heat-sealing resin layer include modified polyolefin films (such as modified polyolefin ionomer films), polypropylene, and copolymers thereof. The thickness of the heat-sealing resin layer is preferably 20 to 200 μm.

A metal layer may also be laminated onto the resin film. The metal layer can be made 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 to 150 μm.

Furthermore, the resin film constituting the sheet-like outer packaging may be a film having a laminated structure of the heat-sealable resin layer and the metal layer.

It is also preferable that the resin film constituting the sheet-like outer packaging 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 functions as a water vapor barrier layer, or a multi-layer structure in which it has multiple layers of electrically insulating resin film, at least one of which functions as a water vapor barrier layer, or a multi-layer structure in which an electrically insulating water vapor barrier layer is formed on the surface of a base layer made of resin film.

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

Examples of inorganic oxides that make up the water vapor barrier layer include aluminum oxide and silicon oxide. Note that water vapor barrier layers made up of silicon oxide tend to have a stronger ability to inhibit the permeation of moisture in the electrolyte inside the battery than water vapor barrier layers made up of aluminum oxide. Therefore, it is more preferable to use silicon oxide as the inorganic oxide that makes up the water vapor barrier layer.

A water vapor barrier layer made of an inorganic oxide 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.

The substrate layer of the resin film having a water vapor barrier layer can be made of the aforementioned nylon film or polyester film, as well as polyolefin film, polyimide film, polycarbonate film, etc. The thickness of the substrate layer is preferably 5 to 100 μm.

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 side opposite the substrate layer).

In addition, 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.

The overall thickness of the resin film is preferably 10 μm or more to ensure sufficient strength for the battery, and is preferably 200 μm or less to prevent an increase in battery thickness or a decrease in energy density.

The water vapor permeability of the resin film constituting the sheet-like outer packaging body is preferably 10 g/ ^m² ·24 h or less. Note that it is desirable for the resin film to be as impermeable to water vapor as possible, i.e., its water vapor permeability is preferably as small as possible, and may be 0 g/ ^m² ·24 h.

The water vapor permeability of resin films referred to in this specification is a value measured in accordance with JIS K 7129B.

When the aqueous electrolyte battery is an air battery, it is preferable that the resin film constituting the sheet-like outer casing have a certain degree of oxygen permeability. Air batteries discharge by supplying air (oxygen) to the positive electrode, so air holes are formed in the sheet-like outer casing to introduce oxygen into the battery. However, if the resin film constituting the sheet-like outer casing is oxygen permeable, oxygen can be introduced into the battery through the outer casing at 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.

When the aqueous electrolyte battery is an air battery, the specific oxygen permeability of the resin film constituting the sheet-like outer casing is preferably 0.02 cm ³ /m ² 24h MPa or more, and more preferably 0.2 cm ³ /m ² 24h MPa or more. However, when the battery is an air battery, if the resin film constituting the sheet-like outer casing allows too much oxygen to pass through, self-discharge may occur and the capacity may be lost, so the oxygen permeability of the resin film is preferably 100 cm ³ /m ² 24h MPa or less, and more preferably 50 cm ³ /m ² 24h MPa or less.

On the other hand, when the aqueous electrolyte battery is a battery other than an air battery, there are no particular restrictions on the oxygen permeability of the resin film constituting the sheet-like outer casing, but 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, and specifically, the oxygen permeability of the resin film is preferably 10 cm ³ /m ² ·24 h ·MPa or less.

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

In addition, when using an exterior body that is crimp-sealed, the material for the gasket placed between the exterior can and the sealing plate can be polypropylene, nylon, or other materials used in alkaline batteries.

In addition, to prevent elements such as iron that make up the outer can from leaching out during charging, it is desirable to plate the inside of the outer can with a corrosion-resistant metal such as tin, zinc, or indium.

Figures 1 and 2 show a schematic diagram of an example of an aqueous electrolyte battery of the present invention. Figures 1 and 2 show an example of an aqueous electrolyte battery that is an air battery (sheet-type air battery) with a sheet-like outer casing. Figure 1 shows a plan view of the battery, and Figure 2 shows a cross-sectional view taken along line I-I in Figure 1.

As shown in Figure 2, in the aqueous electrolyte battery 1, the positive electrode 10, separator 30, negative electrode 20, and electrolyte (not shown) are contained within a sheet-like outer casing 50. Note that the dotted line in Figure 1 represents the size of the positive electrode 10 contained within the sheet-like outer casing 50 (the size of the wide main body excluding the terminal portion, which corresponds to the size of the positive electrode's catalyst layer).

The terminal portion 10a of the positive electrode 10 and the terminal portion 20a of the negative electrode 20 protrude from the upper edge of the sheet-like outer casing 50 in the figure. These terminal portions 10a, 20a are used as external terminals for electrically connecting the aqueous electrolyte battery 1 to an applicable device.

The sheet-like outer casing 50 has multiple air holes 51 on one side where the positive electrode 10 is placed, allowing air to enter the positive electrode. A water-repellent film 40 is placed on the sheet-like outer casing 50 side of the positive electrode 10 to prevent leakage of the electrolyte through the air holes 51.

The positive electrode 10 has a catalyst layer, and as described above, for example, has a structure in which the catalyst layer is laminated with a current collector. However, in Figure 2, to avoid cluttering the drawing, the individual layers of the positive electrode 10 are not shown separately. Also, in Figure 2, the sheet-like outer casing 50 (the resin film that constitutes it) is shown as having a single-layer structure, but as described above, the resin film that constitutes the sheet-like outer casing can also have a multi-layer structure.

The positive electrode terminal portion may be provided by a positive electrode current collector shaped to have a main portion where the positive electrode mixture layer and catalyst layer are formed, and an exposed portion where no positive electrode mixture layer or catalyst layer is formed, or by attaching a separate lead body to the positive electrode current collector by welding or the like.

Furthermore, in the case of a negative electrode having a negative electrode current collector, the negative electrode terminal portion can be formed by shaping the negative electrode current collector to have a main portion where a layer containing the negative electrode active material etc. is formed, and an exposed portion where this layer is not formed, and providing the terminal portion on this exposed portion, or by attaching a separate lead body to the negative electrode current collector by welding, etc.

In addition, when the negative electrode is composed of a metal sheet, the metal sheet can be cut into a shape having a main body portion that functions as the negative electrode active material layer and a terminal portion, thereby forming a negative electrode having a main body portion and a terminal portion from a single metal sheet.

The shape of the sheet-like outer casing may be polygonal in plan view (triangle, quadrangle, pentagon, hexagon, heptagon, octagon), 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 extended to the outside from the same side, or may be extended to the outside from different sides.

When the aqueous electrolyte battery is an air battery, as shown in Figure 2, a water-repellent film is typically placed between the positive electrode and the exterior body. This water-repellent film 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.

If the aqueous electrolyte battery is an air battery, an air diffusion membrane may be placed 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 can be made of 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.

When the aqueous electrolyte battery is a sheet-type battery, there are no particular restrictions on its thickness (the length of a in Figure 2), and it can be changed as appropriate depending on the battery's intended use. One advantage of sheet-type batteries is that they can be made thin, and from this perspective, it is preferable that their thickness be, for example, 1 mm or less. When the aqueous electrolyte battery is a sheet-type air battery, it is particularly easy to provide such a thin battery.

There is also no particular lower limit on the thickness of sheet-type batteries, but to ensure a certain capacity, it is usually preferable to make it 0.2 mm or more.

The present invention will be described in detail below based on examples. However, the following examples do not limit the present invention.

Example 1
<Positive electrode>
A composition for forming a catalyst layer was prepared by mixing 30 parts by mass of carbon (Ketjenblack EC600JD (Lion Specialty Chemicals)) with a DBP oil absorption of 495 cm ³ /100 g and a specific surface area of 1270 m ² /g, 15 parts by mass of an acrylic dispersant, 60 parts by mass of SBR, and 500 parts by mass of water.

A porous carbon paper (thickness: 0.25 mm, porosity: 75%) was used as a current collector, and the catalyst layer-forming composition was applied in stripes to the surface of the substrate so that the coating amount after drying was 10 mg/ ^cm2 , followed by drying to obtain a current collector having a region where a catalyst layer was formed and a region where no catalyst layer was formed. This current collector was punched out into a shape with a catalyst layer size of 15 mm x 15 mm and a lead portion with a size of 5 mm x 15 mm at one end where no catalyst layer was formed, to produce a positive electrode (air electrode) with an overall thickness of 0.27 mm.

<Negative electrode>
A zinc alloy foil (thickness: 0.05 mm) containing 0.05% In, 0.04% Bi, and 0.001% Al as additive elements was punched out into a shape having a 15 mm × 15 mm portion that would function as an active material and a 5 mm × 15 mm portion at one end that would serve as a lead portion, to prepare a negative electrode.

<Electrolyte>
Glycerin was added to a 20% by mass aqueous solution of ammonium sulfate in an amount that would result in a 10% by mass total with water to prepare an electrolyte solution (pH was 5.3 as measured at 25°C using a HORIBA, Ltd. LAQUA Twin Compact pH Meter. The pH values determined by the same measurement method for the electrolyte solutions of the sheet-type air batteries of all Examples and Comparative Examples described below were the same). The concentrations of perchlorate ions and heavy metal ions excluding iron ions in the electrolyte solution were each less than 100 ppm. The same was true for the electrolyte solutions of the sheet-type air batteries of Examples 2 and 3 and Comparative Examples 1 to 3 described below.

<Separator>
The separator used was a hydrophilized PE microporous membrane (thickness: 16 μm, air permeability: 45 sec/100 mL, contact angle with water: 65°). The hydrophilization of the PE microporous membrane was carried out by treating it with sulfuric acid to introduce sulfonic acid groups into the PE constituting the microporous membrane, and then treating it with a mixed gas containing fluorine gas, oxygen, sulfur dioxide, and nitrogen.

<Water-repellent film>
The water-repellent film was a PTFE sheet having a thickness of 200 μm.

<Battery assembly>
Two sheets of 25 mm x 25 mm aluminum laminate film (thickness: 65 μm) having a PET film on the outer surface of the aluminum foil and a PP film as a heat-sealable resin layer on the inner surface were used as the exterior body.

One of the exterior bodies, located on the positive electrode side, had nine 0.2 mm diameter air holes formed in a regular pattern of three holes spaced equally apart (5 mm center-to-center distance between air holes) measuring 4.8 mm vertically and 4.8 mm horizontally, and the water-repellent film was heat-sealed to the inner surface using hot-melt resin. Furthermore, on the other exterior body, located on the negative electrode side, a modified polyolefin ionomer film was attached parallel to the sides of the exterior body to the area where the positive and negative electrode leads are located, in order to improve the sealing of the heat-sealed joints between the leads and the exterior body.

The sheet-like outer casing with the water-repellent film was placed face down, and the positive electrode, separator, and negative electrode were layered in that order on top of the water-repellent film on that outer casing. Another outer casing was then placed on top of it, with the modified polyolefin ionomer film positioned on top of the leads of the positive and negative electrodes. Next, the three sides of the two outer casings were heat-sealed together to form a bag. The electrolyte was poured into the opening, and the opening was then heat-sealed to form a sheet-like air battery (aqueous electrolyte battery).

Example 2
A sheet-type air battery was produced in the same manner as in Example 1, except that the separator was changed to a PE microporous membrane having a thickness of 20 μm, an air permeability of 150 sec/100 mL, and a contact angle with water of 63°, which had been hydrophilized in the same manner as in Example 1.

Example 3
A sheet-type air battery was fabricated in the same manner as in Example 1, except that the separator was changed to a PE/PP/PE microporous membrane (a microporous membrane with a three-layer structure having a PE layer on both sides of a PP layer) that had been hydrophilized in the same manner as in Example 1, and had a thickness of 25 μm, an air permeability of 550 sec/100 mL, and a contact angle with water of 63°.

Comparative Example 1
A sheet-form air battery was fabricated in the same manner as in Example 1, except that the separator was changed to a PP nonwoven fabric having a thickness of 100 μm and an air permeability of 2 sec/100 mL, which had been hydrophilized in the same manner as in Example 1. The contact angle of this hydrophilized PP nonwoven fabric with water could not be measured because the dropped ion-exchanged water immediately soaked into the nonwoven fabric.

Comparative Example 2
A sheet-type air battery was fabricated in the same manner as in Example 1, except that the separator was changed to two graft films (thickness per film: 15 μm) composed of a graft copolymer having a structure in which acrylic acid was graft-copolymerized onto a PE main chain, arranged on both sides of a cellophane film (thickness: 20 μm) (total thickness: 50 μm). The air permeability of the entire separator exceeded the upper limit of measurement (>3000 sec/100 mL).

Comparative Example 3
A sheet-type air battery was fabricated in the same manner as in Example 1, except that the separator was changed to a PE microporous membrane (thickness: 16 μm, air permeability: 150 sec/100 mL, contact angle with water: 102°) that had not been hydrophilized.

The sheet-shaped air batteries of the examples and comparative examples were evaluated as follows:

[Pulse discharge test (load characteristic evaluation)]
For each of the sheet-shaped air batteries of the Examples and Comparative Examples, a pulse discharge test was carried out 50 times under the conditions of a current value of 30 mA, a pulse width of 10 msec, and a pulse interval of 3 sec, and the closed circuit voltage (CCV) was measured.

[OCV measurement before and after load test (reliability evaluation)]
A 5 kg weight was placed on each of the sheet-air batteries of the Examples and Comparative Examples whose open circuit voltages (OCVs) had been measured, and a load test was carried out at 20° C. for 30 days. Then, the OCV of each battery after the load test was measured.

The configuration of the separators used in the sheet-type air batteries of the Examples and Comparative Examples is shown in Table 1, and the evaluation results are shown in Table 2. In Table 1, a "-" in the "Contact angle with water" column indicates that the contact angle with water could not be measured.

As shown in Tables 1 and 2, the sheet-type air batteries of Examples 1 to 3, which used a porous resin membrane with suitable thickness, air permeability, and water contact angle as a separator, had a high CCV during pulse discharge and good load characteristics. Furthermore, the change in OCV before and after the load test was small, the occurrence of micro-short circuits due to the application of load was suppressed, and they also had excellent reliability.

In contrast, the battery of Comparative Example 1, which used a separator made of a porous membrane (a hydrophilically treated PP nonwoven fabric) with too little air permeability, showed a large drop in OCV during the load test and had poor reliability. Furthermore, the battery of Comparative Example 2, which used a separator made of a laminated graft film and a cellophane film (neither of which has pores) with too much air permeability, and the battery of Comparative Example 3, which used a separator made of a porous membrane with too large a contact angle with water, showed low CCV during pulse discharge and poor load characteristics.

The present invention may be implemented in forms other than those described above without departing from its spirit. 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 above specification, and all modifications within the scope of the claims are included within their scope.

The aqueous electrolyte battery of the present invention uses an aqueous electrolyte, particularly one with a preferred pH of 3 or more but less than 12. This reduces the environmental impact, and even if the electrolyte leaks due to breakage and comes into contact with the body, problems are unlikely to occur. Therefore, the aqueous electrolyte battery of the present invention is suitable as a power source for medical and healthcare devices, such as patches that can be worn on the body, particularly patches worn on the skin to measure body conditions such as body temperature, pulse rate, and sweat rate. It can also be used in the same applications as conventionally known batteries (primary batteries) that use aqueous electrolytes, such as air batteries and alkaline batteries.

1 aqueous electrolyte battery 10 positive electrode (air electrode)
10a: Positive electrode terminal portion 20: Negative electrode 20a: Negative electrode terminal portion 30: Separator 40: Water-repellent film 50: Sheet-like outer casing 51: Air hole

Claims (10)

A battery comprising a positive electrode, a negative electrode containing a metal material, a separator, and an aqueous electrolyte solution housed in an exterior body,
the separator is a porous film made of resin, having a thickness of 5 μm or more and 100 μm or less, an air permeability of 10 sec/100 mL or more and 3000 sec/100 mL or less, and a contact angle with water of 90° or less,
The aqueous electrolyte battery is characterized in that the negative electrode has an electrolytic zinc foil made of a zinc alloy containing 0.02 mass % or more and 0.1 mass % or less of bismuth . The aqueous electrolyte battery according to claim 1, wherein the separator has a contact angle with water of 70° or less. The aqueous electrolyte battery according to claim 1 or 2, wherein the separator has an air permeability of 10 sec/100 mL or more and 1000 sec/100 mL or less. An aqueous electrolyte battery according to any one of claims 1 to 3, wherein the separator has a thickness of 5 μm or more and 30 μm or less. The aqueous electrolyte battery according to any one of claims 1 to 4, wherein the porous membrane is made of polyolefin. The aqueous electrolyte battery according to claim 5, wherein the porous membrane is made of polyethylene or polypropylene. The aqueous electrolyte battery according to any one of claims 1 to 6 is an air battery. The aqueous electrolyte battery according to any one of claims 1 to 7 is a sheet-type battery with a resin film as an exterior. An aqueous electrolyte battery according to any one of claims 1 to 8, wherein the aqueous electrolyte has a pH of 3 or higher and lower than 12. A patch that can be worn on the body, characterized in that it comprises the aqueous electrolyte battery described in any one of claims 1 to 9 as a power source.