Primary battery and its manufacturing method

Abstract

To provide a primary battery excellent in load discharge characteristics and a method for manufacturing the same.SOLUTION: A primary battery according to the present invention includes a negative electrode having a negative electrode active material made of zinc or a zinc alloy, a positive electrode, and an electrolytic solution, the electrolytic solution is an aqueous solution having a pH of 10 or less, and in the XPS spectrum of the surface of the negative electrode active material, the peak of Zn2p3 / 2 exists near 1021.0 eV. The primary battery according to the present invention can be manufactured by maintaining the negative electrode having the negative electrode active material made of zinc or a zinc alloy in a temperature environment of 50°C or higher for 10 hours or longer, and then using it to assemble a battery.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a primary battery having excellent heavy load discharge characteristics and a method for manufacturing the same. [Background technology]

[0002] BACKGROUND ART Batteries (primary batteries and secondary batteries) having a negative electrode containing zinc or a zinc alloy and an electrolyte solution made of an aqueous solution, such as air batteries and alkaline batteries, are currently in widespread use.

[0003] Various improvements have been made to such batteries. For example, Patent Document 1 proposes a technology for suppressing internal gas generation in alkaline batteries by partially attaching one or more metals selected from the group consisting of mercury, indium, lead, thallium, gallium, and cadmium to the surfaces of zinc particles, and using zinc oxide on the remaining surfaces of the zinc particles as the negative electrode.

[0004] Furthermore, Patent Document 2 proposes a technology for improving the cycle characteristics of alkaline zinc storage batteries (secondary batteries) by using a surface-modified active material in the negative electrode, in which a zinc oxide layer is formed on the surface of zinc alloy particles containing at least one additive element selected from the group consisting of indium, thallium, gallium, tin, bismuth, and lead.

[0005] The batteries described in Patent Documents 1 and 2 use alkaline electrolytes, but the zinc oxide (zinc oxide layer) on the surfaces of the zinc particles in the negative electrode is easily dissolved in the alkaline electrolyte, and it is presumed that this dissolved zinc oxide contributes to ensuring the effects described in Patent Documents 1 and 2. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 61-109256 [Patent Document 2] Japanese Patent Application Publication No. 2-215048 Summary of the Invention [Problem to be solved by the invention]

[0007] Incidentally, in recent years, primary batteries having an electrolyte solution made of an aqueous solution have been considered for use in applications requiring discharge at a relatively large current value, and as a result, there are cases where improvement in heavy load discharge characteristics is required.

[0008] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a primary battery having excellent heavy load discharge characteristics, and a method for producing the same. [Means for solving the problem]

[0009] The primary battery of the present invention comprises a negative electrode having a negative electrode active material made of zinc or a zinc alloy, a positive electrode, and an electrolyte, the electrolyte being an aqueous solution having a pH of 10 or less, and an XPS spectrum of the surface of the negative electrode active material showing Zn2p 3 / 2 The peak is located near 1021.0 eV.

[0010] The method for producing a primary battery of the present invention is characterized in that the negative electrode is maintained in a temperature environment of 50° C. or higher for 10 hours or more before being used to assemble a battery. [Effects of the Invention]

[0011] According to the present invention, it is possible to provide a primary battery having excellent heavy load discharge characteristics and a method for producing the same. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a plan view schematically illustrating an example of a primary battery of the present invention. [Figure 2] FIG. 2 is a cross-sectional view taken along line II in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0013] The primary battery of the present invention has a negative electrode having a negative electrode active material made of zinc or a zinc alloy, a positive electrode, and an electrolyte, wherein the electrolyte is an aqueous solution having a pH of 10 or less, and an XPS (X-ray photoelectron spectroscopy) spectrum of the surface of the negative electrode active material shows that Zn2p 3 / 2 The peak is present around 1021.0 eV.

[0014] When an oxide layer is formed on the surface of the negative electrode active material, the internal resistance of the negative electrode increases, and the discharge characteristics of the battery are usually impaired. In the case of zinc foil or zinc alloy foil without surface treatment, the XPS spectrum of the surface shows Zn2p around 1021.7 eV. 3 / 2 On the other hand, in the primary battery of the present invention, the Zn2p peak is observed in the XPS spectrum of the surface of the negative electrode active material. 3 / 2 The peak of is present in the vicinity of 1021.0 eV, and the negative electrode active material has a surface state different from that of ordinary zinc foil or zinc alloy foil.

[0015] It is believed that the heavy load discharge characteristics improve due to a change in the oxidation state of zinc on the surface of the negative electrode active material.

[0016] The zinc oxide layer on the surface of the negative electrode active material is easily soluble in the alkaline electrolyte used in general alkaline batteries, but is difficult to dissolve in an aqueous solution (electrolyte) with a pH of 10 or less. Therefore, even if ordinary zinc or a zinc alloy is directly immersed in an aqueous electrolyte with a pH of 10 or less, the oxide layer increases the internal resistance of the negative electrode, causing a deterioration in the discharge characteristics of the battery.

[0017] On the other hand, the primary battery of the present invention can achieve excellent heavy load discharge characteristics even when an aqueous solution with a pH of 10 or less is used as the electrolyte, because the surface state of the negative electrode active material is changed.

[0018] The primary battery of the present invention has an electrolyte solution consisting of an aqueous solution with a pH of 10 or less, and can take the form of, for example, an air battery or a manganese battery.

[0019] For the negative electrode of the primary battery, zinc or a zinc alloy is used as the negative electrode active material.

[0020] Examples of alloy components of zinc alloys include 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.

[0021] In consideration of reducing the environmental impact when the battery is disposed of, it is preferable that the zinc alloy used in the negative electrode contains small amounts of mercury, cadmium, lead, and chromium, and more preferably the specific contents are, by mass, mercury: 0.1% or less, cadmium: 0.01% or less, lead: 0.1% or less, and chromium: 0.1% or less.

[0022] For zinc or zinc alloy, a sheet (zinc foil or zinc alloy foil) can be preferably used, and for example, the negative electrode can be composed of only a zinc or zinc alloy sheet. The thickness of the zinc or zinc alloy sheet is preferably 10 to 500 μm.

[0023] Zinc foil (zinc alloy foil) includes electrolytic zinc foil and rolled zinc foil, but electrolytic zinc foil is preferably used because electrolytic zinc foil is less likely to generate gas due to reaction with the electrolyte in the battery, and electrolytic zinc foil containing bismuth is more preferably used. The preferred range of the bismuth content in electrolytic zinc foil is 0.02% or more and 0.1% or less by mass.

[0024] The negative electrode may also contain zinc or zinc alloy particles. Regarding the particle size of the zinc or zinc alloy particles, for example, the proportion of particles with a particle size of 75 μm or less is preferably 50 mass % or less, more preferably 30 mass % or less, of the total particles, and the proportion of particles with a particle size of 100 to 200 μm is 50 mass % or more, more preferably 90 mass % or more.

[0025] The particle size of zinc or zinc alloy particles referred to in this specification is the particle size at a cumulative frequency of 50% on a volume basis (D ) measured by dispersing these 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.). 50 )

[0026] The zinc or zinc alloy used as the negative electrode active material shows Zn2p in the XPS (X-ray photoelectron spectroscopy) spectrum of its surface. 3 / 2 The peak is around 1021.0 eV to As mentioned above, the surface condition is different from that of ordinary zinc foil or zinc alloy foil.

[0027] The negative electrode active material in this state can be obtained by holding zinc or a zinc alloy at a temperature of, for example, 50°C or higher for a certain period of time. The holding time can be adjusted depending on the temperature, but may be, for example, 100 hours or longer. On the other hand, if the temperature is too high, problems such as deformation of the negative electrode may occur, so the holding temperature may be, for example, 200°C or lower.

[0028] In the case of a negative electrode containing zinc or zinc alloy particles, a gelling agent (such as polyethylene oxide, sodium polyacrylate, or carboxymethyl cellulose) or a binder may be added as needed, and an electrolytic solution may be added to the gelling agent to form a negative electrode material (such as a gelled negative electrode). The amount of gelling agent in the negative electrode is preferably 0.5 to 1.5 mass %, and the amount of binder is preferably 0.5 to 3 mass %.

[0029] The electrolyte for the negative electrode containing zinc or zinc alloy particles can be the same as that injected into the battery.

[0030] The content of zinc or zinc alloy 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.

[0031] The negative electrode containing zinc or zinc alloy particles preferably contains an indium compound, which can more effectively prevent hydrogen gas generation due to a corrosion reaction between the zinc or zinc alloy particles and the electrolyte.

[0032] Examples of the indium compound include indium oxide and indium hydroxide.

[0033] The amount of indium compound used in the negative electrode is preferably 0.003 to 1 in terms of mass ratio to 100 particles of zinc or zinc alloy.

[0034] The negative electrode may also include a current collector as needed. Examples of the current collector for the negative electrode include a mesh, foil, expanded metal, or punched metal made of metal such as nickel, copper, or stainless steel; or a carbon sheet or mesh. The thickness of the negative electrode current collector is preferably 10 μm or more and 300 μm or less.

[0035] When a sheet-like outer casing described below is used as the outer casing of a battery, the negative electrode current collector can be used by applying a carbon paste to the surface that is to become the inner surface of the sheet-like outer casing. The thickness of the carbon paste layer is preferably 50 to 200 μm.

[0036] The electrolyte in a primary battery is an aqueous solution with a pH of 10 or less.

[0037] Compared to batteries using alkaline electrolytes with high pH, ​​batteries using aqueous electrolytes with a pH of 10 or less generally have poor heavy load discharge characteristics. However, in the primary battery of the present invention, the Zn2p 3 / 2 The negative electrode active material has a peak at around 1021.0 eV, i.e., a negative electrode active material with a surface state different from that of ordinary zinc foil or zinc alloy foil, so that excellent heavy load discharge characteristics can be ensured even when an aqueous solution with a pH of 10 or less is used as the electrolyte.

[0038] From the viewpoints of reducing the environmental load at the time of disposal, ensuring safety in the event of leakage of the electrolyte due to damage to the exterior body, and inhibiting corrosion of the negative electrode active material, the pH of the electrolyte is preferably weakly acidic or as close to neutral as possible, and the pH is preferably 10 or less, more preferably 3 or more, and more preferably 5 or more. Furthermore, in the case of an air battery, the pH is preferably less than 7 to avoid the influence of carbon dioxide.

[0039] For example, when the primary battery is an air battery, examples of the electrolyte salt to be dissolved in 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, Examples of electrolyte salts include magnesium phosphate, 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.

[0040] 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. - , SO4 2- , HSO4 - and NO3 -and at least one ion selected from Al ions, Mg ions, Fe ions, and ammonium ions. Examples of suitable ions include ammonium salts such as ammonium sulfate, ammonium hydrogen sulfate [(NH4)HSO4], 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 [(NH4)2Fe(SO4)2], iron(III), iron(II) chloride, and iron(II) nitrate.

[0041] As mentioned above, zinc or a zinc alloy is used as the negative electrode active material for the negative electrode of a primary battery. However, an electrolyte consisting of an aqueous solution containing a salt of a strong acid and a weak base as exemplified above has a relatively weaker effect of corroding the negative electrode active material than an electrolyte containing a salt of a strong acid and a strong base such as sodium chloride. Furthermore, among salts of strong acids, an electrolyte containing a salt of a metal element selected from Al, Mg, and Fe or an ammonium salt has a relatively higher conductivity than, for example, an aqueous zinc chloride solution. Therefore, as a salt of a strong acid and a weak base, Cl - , SO4 2- , HSO4 - and NO3 - When an electrolyte solution consisting of an aqueous solution containing a salt of at least one ion selected from the group consisting of Al ions, Mg ions, Fe ions, and ammonium ions is used, the discharge characteristics of the primary battery can be further improved.

[0042] However, Cl - ions and Fe 3+ Regarding the salt with an ion [iron(III) chloride], it is preferable to use a salt other than iron(III) chloride because it has a stronger corrosive effect on the negative electrode active material than salts with other ion combinations, and it is more preferable to use an ammonium salt, and it is particularly preferable to use ammonium chloride, because it has a weaker corrosive effect on the negative electrode active material.

[0043] Furthermore, among the salts of the strong acid and the weak base, perchlorates pose a risk of combustion or explosion when heated or impacted. Therefore, from the viewpoint of environmental load and safety during disposal, it is preferable that the aqueous solution does not contain perchlorate ions, or if it does contain perchlorate ions, the amount thereof is small (preferably less than 100 ppm, more preferably less than 10 ppm).

[0044] Furthermore, among the salts of strong acids and weak bases, many heavy metal salts (excluding iron salts), such as copper sulfate, are harmful. Therefore, from the viewpoint of environmental load and safety during disposal, it is preferable that the aqueous solution does not contain such salts, or, if it does contain such salts, the amount of heavy metal ions excluding iron ions is small (preferably less than 100 ppm, more preferably less than 10 ppm).

[0045] Furthermore, when the primary battery is an air battery, the aqueous solution usable 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 capacity decreases during discharge, the voltage decreases accordingly. However, in the later stages of discharge when the capacity decreases, not only does the voltage decrease but the voltage fluctuations tend to become large. However, when the aqueous solution contains a water-soluble high-boiling-point solvent, the voltage fluctuations 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 usually 320°C.

[0046] The water-soluble high-boiling-point solvent preferably has a 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); and 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). The electrolyte may contain only one of these water-soluble high-boiling-point solvents, or two or more of them may be used in combination. However, it is more preferable to use glycerin.

[0047] When a water-soluble high-boiling solvent is used, in order to ensure the desired effect of its use, the content of the water-soluble high-boiling solvent in the total solvent of the aqueous solution constituting the electrolyte solution is preferably 1% by mass or more, more preferably 3% by mass or more. However, if the amount of the water-soluble high-boiling 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 solvent in the total solvent of the aqueous solution is preferably 30% by mass or less, more preferably 20% by mass or less.

[0048] When the primary battery is an air battery, the concentration of the electrolyte salt in the aqueous solution may be such that the conductivity of the aqueous solution can be adjusted to about 80 to 700 mS / cm, and is usually 5 to 50 mass %.

[0049] 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, the generation of hydrogen gas in the battery can be effectively suppressed.

[0050] Examples of the indium compound to be dissolved in the aqueous solution include indium hydroxide, indium oxide, indium sulfate, indium sulfide, indium nitrate, indium bromide, and indium chloride.

[0051] The concentration of the indium compound in the aqueous solution is preferably 0.005% or more, more preferably 0.01% or more, and particularly preferably 0.05% or more, by mass, and is preferably 1% or less, more preferably 0.5% or less, and particularly preferably 0.1% or less.

[0052] In addition to the above components, various known additives may be added to the aqueous solution as needed, provided that the effects of the present invention are not impaired. For example, zinc oxide may be added to prevent corrosion (oxidation) of the metal material used in the negative electrode.

[0053] When the primary battery is a manganese battery, the electrolyte preferably contains an aqueous solution of zinc chloride, with the zinc chloride concentration preferably being 10 to 40% by mass. When the primary battery is a manganese battery, the aqueous solution of zinc chloride preferably contains ammonium chloride dissolved therein, with the ammonium chloride concentration preferably being 2 to 10% by mass.

[0054] In either case where the primary battery is an air battery or a manganese battery, the aqueous solution that serves as the electrolyte may be thickened or made into a gel using a known thickener (cellulose derivatives such as carboxymethyl cellulose, synthetic polymers such as polyacrylamide and polyalkylene glycols such as polyethylene glycol, natural polymers such as guar gum and xanthan gum, etc.).

[0055] When the primary battery is a manganese battery, the positive electrode may be, for example, one having a layer of a positive electrode mixture (positive electrode mixture layer) containing a positive electrode active material, a conductive additive, and a binder on one or both sides of a current collector, or a molded body of the positive electrode mixture.

[0056] When the primary battery is a manganese battery, a manganese oxide such as manganese dioxide is used as the positive electrode active material.

[0057] Examples of the conductive additive for the positive electrode mixture that can be used include carbon materials such as acetylene black; ketjen black; carbon blacks such as channel black, furnace black, lamp black, and thermal black; and carbon fibers; as well as conductive fibers such as metal fibers; carbon fluoride; metal powders such as copper and nickel; and organic conductive materials such as polyphenylene derivatives.

[0058] Examples of binders for the positive electrode mixture include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), styrene butadiene rubber (SBR), carboxymethyl cellulose (CMC), and polyvinylpyrrolidone (PVP).

[0059] The positive electrode mixture 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. In the case of a positive electrode having a positive electrode mixture layer and a current collector, the thickness of the positive electrode mixture layer (thickness per surface of the current collector) is preferably 30 to 300 μm. In the case of a positive electrode made of a compact of the positive electrode mixture, the thickness of the compact of the positive electrode mixture is preferably 0.15 to 4 mm.

[0060] In the case of a molded body of a positive electrode mixture, the positive electrode can be manufactured, for example, by press-molding a positive electrode mixture prepared by mixing a positive electrode active material, a conductive additive, a binder, etc. into a predetermined shape.

[0061] Furthermore, in the case of a positive electrode having a positive electrode mixture layer and a current collector, for example, a positive electrode active material, a conductive additive, a binder, and the like are dispersed in water or an organic solvent such as N-methyl-2-pyrrolidone (NMP) to prepare a positive electrode mixture-containing composition (slurry, paste, etc.), which is then applied to a current collector, dried, and, if necessary, subjected to a pressing process such as a calendaring process, thereby producing the positive electrode.

[0062] However, the positive electrode is not limited to those produced by the above methods, and may be produced by other methods.

[0063] When the primary battery is an air battery, the positive electrode can be an air electrode having a catalyst layer, for example, an air electrode having a structure in which a catalyst layer and a current collector are laminated.

[0064] The catalyst layer may contain a catalyst, a binder, and the like.

[0065] 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, La 1-x Ca x Examples include perovskite oxides such as CoO3, 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.

[0066] The catalyst layer preferably contains 1% by mass or less of heavy metals, excluding components of the electrolyte solution. In the case of a positive electrode having a catalyst layer with such a low heavy metal content, the battery can be disposed of without any special treatment, resulting in a low environmental impact.

[0067] The content of heavy metals in the catalyst layer referred to in this specification can be measured by fluorescent X-ray analysis. For example, it can be measured using a Rigaku "ZSX100e" under the conditions of an excitation source of Rh 50 kV and an analysis area of ​​φ10 mm.

[0068] Therefore, it is recommended that the catalyst for the catalyst layer does not contain heavy metals, and it is more preferable to use the various carbons mentioned above.

[0069] In addition, from the viewpoint of further increasing the reactivity of the positive electrode, the specific surface area of ​​the carbon used as a catalyst is set to 200 m 2 / g or more is preferable, and 300m 2 / g or more is more preferable, and 500m 2 / g or more is more preferable. The specific surface area of ​​carbon referred to in this specification is a value determined by the BET method in accordance with Japanese Industrial Standards (JIS) K 6217, and can be measured, for example, using a specific surface area measuring device ("Macsorb HM model e-1201" manufactured by Mountech Co., Ltd.) using the nitrogen adsorption method. The upper limit of the specific surface area of ​​carbon is usually 2000 m 2 / g.

[0070] The catalyst content in the catalyst layer is preferably 20 to 70 mass %.

[0071] Examples of binders for the catalyst layer include fluororesin binders such as PVDF, polytetrafluoroethylene (PTFE), vinylidene fluoride copolymers, and tetrafluoroethylene copolymers (e.g., 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.

[0072] A positive electrode having a catalyst layer can be produced, 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 positive electrode can be produced by dispersing the catalyst and optionally a binder, etc., in water or an organic solvent to prepare a catalyst layer-forming composition (slurry, paste, etc.), applying the composition to the surface of the current collector, drying it, and then optionally performing a pressing process such as calendering.

[0073] The catalyst layer may also be a porous carbon sheet made of fibrous carbon, such as carbon paper, carbon cloth, or carbon felt. The carbon sheet may also be used as a current collector for the positive electrode, which will be described later, or may serve as both.

[0074] The current collector for a positive electrode having a positive electrode mixture layer or a positive electrode having a catalyst layer can be made of, for example, a mesh, foil, expanded metal, or punched metal made of metal such as titanium, nickel, stainless steel, or copper; a carbon mesh or sheet; etc. The thickness of the current collector for the positive electrode is preferably 10 μm or more and 300 μm or less.

[0075] In primary batteries, a separator is interposed between the positive and negative electrodes. Specific examples of separators include nonwoven fabrics primarily made of vinylon and rayon, vinylon-rayon nonwoven fabrics (vinylon-rayon mixed paper), polyamide nonwoven fabrics, polyolefin-rayon nonwoven fabrics, vinylon paper, vinylon-linter pulp paper, and vinylon-mercerized pulp paper. Microporous films can also be used as separators, specifically microporous polyolefin films (such as microporous polyethylene film and microporous polypropylene film). The surface may be hydrophilized to improve wettability with the aqueous electrolyte.

[0076] Alternatively, the separator may be a stack of the microporous film, a cellophane film, and a liquid-absorbing layer (electrolyte solution holding layer) such as vinylon-rayon mixed paper. The thickness of the separator is preferably, for example, 10 to 500 μm, and in the case of a microporous film, it is preferably 10 to 50 μm, and in the case of a nonwoven fabric, it is preferably 20 to 500 μm.

[0077] The shape of the primary battery is not particularly limited, and various shapes are possible, such as flat (including coin and button shapes), sheet (laminate), and cylindrical (cylindrical and prismatic (rectangular tubular) shapes. Furthermore, the exterior body (battery case) that houses the negative electrode, positive electrode, separator, and nonaqueous electrolyte can be a combination of a metal can (exterior can) with an opening and a lid (sealed can), or a sheet-like exterior body made of a resin film such as a metal laminate film. Specifically, flat or cylindrical batteries can be fabricated by crimping the exterior can and the sealed can with a gasket or by welding them together. Sheet-like batteries can be fabricated by stacking two metal laminate films or by folding one metal laminate film and pasting the edges together to seal the opening.

[0078] An example of a primary battery of the present invention is shown schematically in Figures 1 and 2. Figures 1 and 2 show an example in which the primary battery is a sheet-shaped air battery, with Figure 1 showing a plan view thereof and Figure 2 showing a cross-sectional view taken along line II in Figure 1.

[0079] As shown in Fig. 2, in the primary battery 1, the positive electrode 20, the separator 40, the negative electrode 30, and an electrolyte (not shown) are housed in a sheet-like outer casing 60. The dotted line in Fig. 1 indicates the size of the positive electrode 20 housed in the sheet-like outer casing 60 (the size of the wide main body excluding the terminal portion, which corresponds to the size of the catalyst layer of the positive electrode).

[0080] A terminal portion 20a of the positive electrode 20 and a terminal portion 30a of the negative electrode 30 protrude from the upper side of the sheet-like exterior body 60 in the figure. These terminal portions 20a, 30a are used as external terminals for electrically connecting the primary battery 1 to an applicable device.

[0081] The sheet-like outer casing 60 has a plurality of air holes 61 on one side where the positive electrode 20 is placed, for taking in air into the positive electrode, and a water-repellent film 50 is placed on the sheet-like outer casing 60 side of the positive electrode 20 to prevent leakage of electrolyte from the air holes 61.

[0082] The positive electrode 20 has a catalyst layer, and as described above, for example, has a structure in which the catalyst layer is laminated with a current collector, but in order to avoid cluttering the drawing, the layers of the positive electrode 20 are not shown separately in Fig. 2. Furthermore, in order to avoid cluttering the drawing, the layers of the sheet-like outer casing 60 (the resin film such as a metal laminate film that constitutes it) are not shown separately in Fig. 2.

[0083] The shape of the sheet-like outer casing may be polygonal in plan view (triangle, quadrangle, pentagon, hexagon, heptagon, octagon, etc.), or may be circular or elliptical in plan view. In the case of a sheet-like outer casing that is polygonal in plan view, the positive electrode terminal and the negative electrode terminal may be led out from the same side or from different sides.

[0084] When the primary battery is an air battery, a water-repellent film is usually disposed between the positive electrode and the exterior body, as shown in Fig. 2. The water-repellent film is a film that is water-repellent but air-permeable. Specific examples of such water-repellent films include films made of resins such as fluororesins such as PTFE; and polyolefins such as polypropylene and polyethylene. The thickness of the water-repellent film is preferably 50 to 250 µm.

[0085] Furthermore, when the primary battery is an air battery, an air diffusion membrane may be disposed between the exterior body and the water-repellent film to supply air taken into the exterior body to the positive electrode. The air diffusion membrane may be a nonwoven fabric made of a resin such as cellulose, polyvinyl alcohol, polypropylene, or nylon. The thickness of the air diffusion membrane is preferably 100 to 250 μm.

[0086] When the primary battery is a sheet-type battery, there is no particular limitation on its thickness (the length of a in FIG. 2), and it can be changed appropriately depending on the intended use of the sheet-type battery. One of the advantages of sheet-type batteries is that they can be made thin, and from this perspective, it is preferable that the thickness is, for example, 1 mm or less. When the primary battery is a sheet-type air battery, it is particularly easy to provide such a thin battery.

[0087] Furthermore, when the primary battery is a sheet-type battery, there is no particular lower limit to the thickness, but in order to ensure a certain capacity, it is usually preferable to make it 0.2 mm or more.

[0088] The primary battery of the present invention uses an aqueous solution with a pH of 10 or less as its electrolyte, which has a small environmental impact and is unlikely to cause problems even if the electrolyte leaks due to breakage and comes into contact with the body. Therefore, the primary battery of the present invention is suitable as a power source for medical and health-related devices, such as patches that can be worn on the body, particularly patches that are worn on the surface of the skin to measure body conditions such as body temperature, pulse rate, and sweat rate, and can also be used in the same applications as those in which conventionally known primary batteries having an aqueous electrolyte, such as air batteries and manganese batteries, are used. [Example]

[0089] The present invention will be described in detail below based on examples, but the present invention is not limited to these examples.

[0090] Example 1 <Positive electrode> DBP oil absorption 495cm 3 / 100g, specific surface area 1270m 2 A catalyst layer-forming composition was prepared by mixing 100 parts by mass of 1 / g of carbon (Ketjenblack EC600JD (manufactured by Lion Specialty Chemicals)), 25 parts by mass of an acrylic dispersant, and 5,000 parts by mass of ethanol.

[0091] A porous carbon paper [thickness: 0.25 mm, porosity: 75%, air permeability (Gurley): 70 sec / 100 ml] was used as the porous conductive substrate, and the catalyst layer-forming composition was applied in a coating amount of 10 mg / cm after drying. 2 The substrate surface was coated with the solution in stripes so that the shape was as shown in Fig. 1, and then dried to obtain a porous conductive substrate (current collector) having a portion with a catalyst layer formed thereon and a portion without the catalyst layer formed thereon. This porous conductive substrate was punched out into a shape having a main body portion measuring 15 mm x 15 mm with the catalyst layer formed thereon and a terminal portion measuring 5 mm x 15 mm with no catalyst-containing layer formed thereon, to produce a positive electrode (air electrode) with an overall thickness of 0.27 mm.

[0092] <Negative electrode> An electrolytic zinc alloy foil (thickness: 0.05 mm) containing 0.022% by mass of Bi as an additive element was punched into a shape having a main body of 15 mm × 15 mm and a terminal of 5 mm × 15 mm, and stored in air at 80 °C for 400 hours to prepare a negative electrode with a theoretical capacity of approximately 65 mAh. X-ray photoelectron spectroscopy (XPS) of the surface of the negative electrode revealed Zn2p 3 / 2 It was confirmed that the peak was present at 1021.0 eV.

[0093] <Electrolyte> The electrolyte used was an aqueous solution of ammonium chloride with a concentration of 20% by mass (pH of 4.3 measured at 25°C using a "LAQUAtwin Compact pH Meter" manufactured by Horiba, Ltd.).

[0094] <Separator> The separator used was made of two graft films (thickness per film: 15 μm) composed of a graft copolymer having a structure in which acrylic acid is graft copolymerized onto a polyethylene main chain, placed on both sides of a cellophane film (thickness: 20 μm) (total thickness: 50 μm).

[0095] <Water-repellent film> The water-repellent film used was a microporous polyethylene film with a thickness of 75 μm.

[0096] <Battery assembly> Two sheets of a commercially available barrier film ("GL FILM (product name)" manufactured by Toppan Printing Co., Ltd., thickness: 67 μm) were cut into a size of 25 mm × 30 mm and used as the exterior body.

[0097] Nine air holes with a diameter of approximately 0.2 mm were formed regularly in one of the exterior bodies placed on the positive electrode side, at equal intervals of 9 mm vertically and 9 mm horizontally (the center-to-center distance between air holes was 5 mm), and the water-repellent film was heat-welded to the inner surface using hot-melt resin.

[0098] A sheet-like outer casing having a water-repellent film was placed on the positive electrode side, and the positive electrode, the separator, and the negative electrode were stacked in that order on top of the water-repellent film of the outer casing. Another outer casing was then placed on top of the two outer casings, and the three peripheral sides of the two outer casings were heat-sealed to form a bag. An electrolyte was poured into the opening, and the opening was then heat-sealed to seal, thereby producing a sheet-like primary battery (air battery).

[0099] Comparative Example 1 A sheet-shaped primary battery was fabricated in the same manner as in Example 1, except that the same electrolytic zinc alloy foil as used in Example 1 was punched into a shape having a main body portion measuring 15 mm × 15 mm and a terminal portion measuring 5 mm × 15 mm, and used as such as a negative electrode for assembling a battery. X-ray photoelectron spectroscopy (XPS) of the surface of the negative electrode revealed Zn2p 3 / 2 It was confirmed that the peak was present at 1021.7 eV.

[0100] Comparative Example 2 A sheet-form primary battery was fabricated in the same manner as in Example 1, except that a 30 mass % aqueous potassium hydroxide solution (pH: about 14) was used as the electrolyte.

[0101] Comparative Example 3 A sheet-form primary battery was fabricated in the same manner as in Comparative Example 1, except that a 30 mass % potassium hydroxide aqueous solution (pH: about 14) was used as the electrolyte.

[0102] An AC voltage of 1 kHz was applied to each sheet-type primary battery at room temperature to measure its internal resistance. Next, a 3.9 kΩ resistor was connected to each sheet-type primary battery, and the closed circuit voltage (CCV) was measured after discharging 10 mAh from the start of discharge. The measurement results are shown in Table 1.

[0103] [Table 1]

[0104] As shown in Table 1, in the primary battery of Example 1, the XPS spectrum of the surface of the negative electrode active material shows that Zn2p 3 / 2 Since the peak of α-doped SiO2 is present in the vicinity of 1021.0 eV, the internal resistance is reduced and the heavy load characteristics are improved even when an aqueous solution with a pH of 10 or less is used as the electrolyte.

[0105] On the other hand, as is clear from a comparison between Comparative Examples 2 and 3, in the batteries using alkaline electrolyte, the internal resistance was almost the same regardless of the difference in the surface state of the negative electrode active material, and the heavy load characteristics were also almost the same. [Explanation of symbols]

[0106] 1 Primary battery 20 Positive electrode (air electrode) 20a Positive terminal 30 negative electrode 30a Negative electrode terminal 40 Separator 50 Water-repellent film 60 Sheet-shaped outer packaging 61 Air vent

Claims

1. A primary battery having a negative electrode having a negative electrode active material made of zinc or a zinc alloy, a positive electrode, and an electrolyte, the electrolytic solution is an aqueous solution having a pH of 3 or more and 10 or less, The negative electrode active material has an oxide layer formed on the surface thereof, and zinc element derived from zinc or a zinc alloy in the oxide layer is in an oxidation state that satisfies the following (a): (a) In the XPS spectrum of the surface of the negative electrode active material, Zn2p ３／２ The peak is at 1021.0 eV.

2. 2. The primary battery according to claim 1, wherein the electrolyte contains zinc chloride or ammonium chloride.

3. 3. The primary battery according to claim 1, wherein the negative electrode is made of electrolytic zinc foil or electrolytic zinc alloy foil.

4. 4. The primary battery according to claim 1, wherein the positive electrode is an air electrode.

5. A method for producing a primary battery according to any one of claims 1 to 4, A method for producing a primary battery, comprising maintaining a negative electrode having a negative electrode active material made of zinc or a zinc alloy in a temperature environment of 50°C or higher for 10 hours or more, and then using the negative electrode to assemble a battery.

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