JP7149079B2 - alkaline secondary battery - Google Patents

Description

TECHNICAL FIELD The present invention relates to an alkaline secondary battery in which a decrease in capacity in the early stages of charge-discharge cycles is suppressed and which has excellent charge-discharge cycle characteristics.

Alkaline batteries having negative electrodes containing zinc or zinc alloys and alkaline electrolytes are commonly used as primary batteries.

On the other hand, the use of the alkaline battery having the above structure as a secondary battery has also been studied. In order to enhance various characteristics of alkaline secondary batteries, for example, a specific amount of dopant is used in the silver material that is the positive electrode active material, or a specific anion conductive film is interposed between the negative electrode and the separator. , techniques for adding additives such as polyalkylene glycol to the alkaline electrolyte have been proposed (Patent Documents 1 and 2, etc.).

Japanese National Publication of International Patent Application No. 2013-541815 (claim 1, paragraph [0173], etc.) WO 2017/047628 (claim 1, paragraph [0105], etc.)

According to the techniques described in Patent Documents 1 and 2, it is possible to improve various characteristics of alkaline secondary batteries. is required to be further improved, and in particular, it is required to suppress a rapid decrease in capacity at the initial stage of charge/discharge cycles (up to about 10 cycles). Therefore, further studies are needed to improve the charge-discharge cycle characteristics of alkaline secondary batteries.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an alkaline secondary battery in which a decrease in capacity in the early stages of charge-discharge cycles is suppressed and which has excellent charge-discharge cycle characteristics.

The alkaline secondary battery of the present invention has a positive electrode, a negative electrode and an alkaline electrolyte, the negative electrode contains zinc-based particles selected from zinc particles and zinc alloy particles, and the alkaline electrolyte is potassium hydroxide. Alternatively, it is characterized by containing sodium hydroxide, lithium hydroxide, and polyalkylene glycols.

ADVANTAGE OF THE INVENTION According to this invention, the capacity|capacitance fall in the early stage of a charge/discharge cycle is suppressed, and the alkaline secondary battery excellent in charge/discharge cycle characteristics can be provided.

1 is a side view schematically showing an example of an alkaline secondary battery of the present invention; FIG. FIG. 2 is a cross-sectional view of the main part of the alkaline secondary battery shown in FIG. 1; 4 is a graph showing the results of a charge-discharge cycle test of alkaline secondary batteries of Examples and Comparative Examples.

In an alkaline secondary battery having a negative electrode containing zinc-based particles selected from zinc particles and zinc alloy particles (hereinafter sometimes simply referred to as "zinc-based particles"), when charging and discharging are repeated, a small number of repetitions The battery capacity may drop suddenly. As a factor on the negative electrode side, zinc dendrite is generated at the negative electrode due to charging and discharging of the battery, and this grows up to the counter electrode to cause an internal short circuit.

Therefore, in the alkaline secondary battery of the present invention, an alkaline electrolyte containing lithium hydroxide and polyalkylene glycols is used. It is possible to ensure excellent charge-discharge cycle characteristics. It is known that lithium hydroxide can be used as an electrolyte salt for alkaline electrolytes in alkaline secondary batteries. Lithium is included in the alkaline electrolyte.

The present inventors presume that the reason why the charge-discharge cycle characteristics of alkaline secondary batteries are improved by using an alkaline electrolyte containing lithium hydroxide and polyalkylene glycols is due to the following mechanism.

When an alkaline secondary battery having a negative electrode containing zinc-based particles is discharged, tetrahydroxozinc(II) ion [Zn(OH) ₄ ^2- ] is produced in the negative electrode and released into the alkaline electrolyte. When the alkaline secondary battery is charged, the tetrahydroxozinc(II) ion returns to the surface of the zinc-based particles of the negative electrode to form zinc dendrites.

However, when the alkaline electrolyte contains polyalkylene glycols, the polyalkylene glycol adheres to the surface of the zinc-based particles of the negative electrode, making it difficult for the tetrahydroxozinc(II) ions to return to the surface of the zinc-based particles. It is considered to be. Also, when the alkaline electrolyte contains lithium hydroxide, the tetrahydroxozinc(II) ion can exist relatively stably in the alkaline electrolyte. It is presumed that these actions suppress the formation of zinc dendrites and make short circuits less likely to occur during charge-discharge cycles.

In addition, lithium hydroxide in the alkaline electrolyte has the effect of reducing the charging efficiency of the battery in the initial stage of charging and discharging, but when the alkaline electrolyte further contains polyalkylene glycols, lithium hydroxide is suppressed.

In the present invention, it is considered that the above-mentioned action of polyalkylene glycols and the above-mentioned action of lithium hydroxide are synergistically functioning. It is presumed that this is suppressed and excellent charge/discharge cycle characteristics are ensured.

For the alkaline electrolyte of the alkaline secondary battery of the present invention, for example, an aqueous solution (alkaline electrolyte) of potassium hydroxide or sodium hydroxide, which is an electrolyte salt, can be used. The alkaline electrolyte further contains lithium hydroxide and polyalkylene glycols.

The content (concentration; the same shall apply hereinafter) of lithium hydroxide in the alkaline electrolyte should be 0.1% by mass or more from the viewpoint of better ensuring the above-mentioned effects of containing lithium hydroxide in the alkaline electrolyte. is preferred, and 0.5% by mass or more is more preferred. In addition, since excessive addition of lithium hydroxide leads to an increase in the internal resistance of the battery, the content of lithium hydroxide in the alkaline electrolyte is preferably 5% by mass or less, and preferably 3% by mass or less. more preferred.

Polyalkylene glycols used in the present invention are compounds having a structure in which alkylene glycols such as ethylene glycol, propylene glycol and butylene glycol are polymerized or copolymerized, and may have a crosslinked structure or a branched structure. A compound having a terminal-substituted structure may also be used, and a compound having a weight-average molecular weight of about 200 or more is preferably used. Although the upper limit of the weight average molecular weight is not particularly defined, it is preferable that the compound is water-soluble in order to make it easier to exhibit the effect of addition, and usually 20000 or less is preferably used, and 5000 or less It is used more preferably.

More specifically, polyethylene glycols having a structure in which ethylene glycol is polymerized, polypropylene glycols having a structure in which propylene glycol is polymerized, and the like can be preferably used.

Examples of the polyethylene glycols include polyethylene glycol and polyethylene oxide, and compounds having a straight chain structure include, for example, compounds represented by the following general formula (1).

In general formula (1), X is an alkyl group, hydroxyl group, carboxyl group, amino group, or halogen atom, Y is a hydrogen atom or an alkyl group, and n is 4 or more on average.

Incidentally, n in the general formula (1) corresponds to the average added mole number of ethylene oxide in polyethylene glycols. n is 4 or more on average, and the upper limit of n is not particularly limited, but a compound having a weight average molecular weight of about 200 to 20,000 is preferably used.

As the polypropylene glycols, in addition to polypropylene glycol and polypropylene oxide, as the compound having a linear structure, for example, a compound represented by the following general formula (2) is preferably used.

In general formula (2), Z is an alkyl group, a hydroxyl group, a carboxyl group, an amino group, or a halogen atom, T is a hydrogen atom or an alkyl group, and m represents 3 or more on average.

Note that m in the general formula (2) corresponds to the average added mole number of propylene oxide in the polypropylene glycols. m is 3 or more on average, and the upper limit of m is not particularly limited, but a compound having a weight average molecular weight of about 200 to 20,000 is preferably used.

Polyalkylene glycols may be copolymer compounds (such as polyoxyethylene polyoxypropylene glycol) containing ethylene oxide units and propylene oxide units.

The content (concentration) of the polyalkylene glycols in the alkaline electrolyte. When multiple compounds are used as the polyalkylene glycols, the total amount thereof. The same shall apply hereinafter.) From the viewpoint of better securing the above effects, the content is preferably 0.1% by mass or more, and more preferably 0.5% by mass or more. In addition, if the amount of polyalkylene glycols in the alkaline electrolyte is too large, the discharge characteristics of the battery may be impaired. Therefore, from the viewpoint of limiting the amount of polyalkylene glycol in the alkaline electrolyte and maintaining better discharge characteristics of the battery, the content of polyalkylene glycols in the alkaline electrolyte is preferably 8% by mass or less. It is preferably 4% by mass or less, and more preferably 4% by mass or less.

As described above, the alkaline electrolyte contains potassium hydroxide or sodium hydroxide as an electrolyte salt. The alkaline electrolyte may contain either one of potassium hydroxide and sodium hydroxide, or may contain both.

The content of the electrolyte salt in the alkaline electrolyte may be within a range that ensures good conductivity in the alkaline electrolyte. For example, when potassium hydroxide is used, the content (concentration) of potassium hydroxide is , preferably 20% by mass or more, more preferably 30% by mass or more, and preferably 40% by mass or less, more preferably 38% by mass or less.

In addition to the components described above, various known additives may be added to the alkaline electrolyte as necessary within a range that does not impair the effects of the present invention. For example, zinc oxide may be added to prevent corrosion (oxidation) of zinc-based particles used in the negative electrode of alkaline secondary batteries. Note that zinc oxide can also be added to the negative electrode.

When silver oxide is used as the positive electrode active material (details will be described later), one or more selected from the group consisting of manganese compounds, tin compounds and indium compounds is dissolved in the alkaline electrolyte. preferable.

When an alkaline secondary battery containing silver oxide in the positive electrode is discharged, silver is produced from the silver oxide, but when this battery is charged, silver oxide crystals are formed around the silver, inhibiting subsequent battery reactions. There is fear. When manganese compounds, tin compounds, or indium compounds are dissolved in the alkaline electrolyte, ions derived from these compounds (manganese ions, tin ions, and indium ions) adsorb to the positive electrode, forming silver oxide crystals. It suppresses the growth and refines the silver oxide crystals to be formed. Therefore, it is possible to suppress the occurrence of the problem that the silver oxide crystals generated during charging of the battery impede the battery reaction, and further improve the charge-discharge cycle characteristics of the battery.

Manganese compounds dissolved in the alkaline electrolyte include manganese chloride, manganese acetate, manganese sulfide, manganese sulfate, and manganese hydroxide. Tin compounds dissolved in alkaline electrolytes include tin chloride, tin acetate, tin sulfide, tin bromide, tin oxide, tin hydroxide, and tin sulfate. Indium compounds dissolved in the alkaline electrolyte include indium hydroxide, indium oxide, indium sulfate, indium sulfide, indium nitrate, indium bromide, and indium chloride.

The concentration of the indium compound, manganese compound and tin compound in the alkaline electrolyte (the concentration when only one of these is dissolved, and the total concentration when two or more of them are dissolved) , From the viewpoint of ensuring the above effects better, it is preferably 50 ppm or more, more preferably 500 ppm or more, and preferably 10000 ppm or less, preferably 5000 ppm or less on a mass basis. more preferred.

A negative electrode of an alkaline secondary battery contains zinc-based particles selected from zinc particles and zinc alloy particles. In such a negative electrode, zinc in the particles acts as an active material. Examples of the alloy component of the zinc alloy particles include indium (for example, the content is 50 to 500 ppm based on mass), bismuth (for example, the content is 50 to 500 ppm based on mass), etc. (The balance is zinc and inevitable impurities. be). The zinc-based particles contained in the negative electrode may be of one kind alone, or may be of two or more kinds.

However, it is preferable to use zinc-based particles that do not contain mercury as an alloy component. A battery using such zinc-based particles can suppress environmental pollution caused by disposal of the battery. For the same reason as mercury, it is preferable to use zinc-based particles that do not contain lead as an alloying component.

As for the particle size of the zinc-based particles, for example, the proportion of particles having a particle size of 75 μm or less in the total powder is preferably 50% by mass or less, more preferably 30% by mass or less, and the particle size is 100 to 100. The ratio of 200 μm powder is 50% by mass or more, more preferably 90% by mass or more. The particle size of the zinc-based particles as used herein is a value obtained by the same measuring method as the method for measuring the average particle size of silver oxide, which will be described later.

The negative electrode may contain, for example, a gelling agent (sodium polyacrylate, carboxymethyl cellulose, etc.) added as necessary in addition to the zinc-based particles described above, and is formed by adding an alkaline electrolyte thereto. A negative electrode agent (gelled negative electrode) may be used. The amount of gelling agent in the negative electrode is preferably 0.5 to 1.5% by mass, for example.

The negative electrode can also be a non-gelled negative electrode that does not substantially contain a gelling agent as described above (in the case of a non-gelled negative electrode, the alkaline electrolyte present in the vicinity of the zinc-based particles increases the viscosity). Since it does not matter if the gelling agent is not included, "substantially does not contain a gelling agent" means that it may be contained to the extent that the viscosity of the alkaline electrolyte is not affected. be). In the case of a gelled negative electrode, an alkaline electrolyte is present together with a gelling agent in the vicinity of the zinc-based particles. Movement of ions in the electrolyte is suppressed. For this reason, the reaction rate at the negative electrode is suppressed, and this is considered to hinder the improvement of battery load characteristics (particularly heavy load characteristics). On the other hand, by making the negative electrode non-gelled and keeping the migration rate of ions in the alkaline electrolyte high without increasing the viscosity of the alkaline electrolyte present in the vicinity of the zinc-based particles, the reaction rate at the negative electrode is increased, Load characteristics (particularly heavy load characteristics) can be further improved.

As the alkaline electrolyte contained in the negative electrode, the same alkaline electrolyte as that injected into the battery can be used.

The content of the zinc-based particles in the negative electrode is, for example, preferably 60% by mass or more, more preferably 65% by mass or more, and preferably 75% by mass or less, and 70% by mass or less. It is more preferable to have

The negative electrode preferably contains an indium compound. By containing an indium compound in the negative electrode, it is possible to more effectively prevent gas generation due to a corrosion reaction between the zinc-based particles and the alkaline electrolyte.

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

The mass ratio of the indium compound used in the negative electrode is preferably 0.003 to 1 with respect to zinc-based particles: 100.

For the positive electrode of the alkaline secondary battery, in addition to silver oxide, a compound such as nickel oxyhydroxide that can be used as a positive electrode active material for an alkaline secondary battery can be used. A structure consisting only of a positive electrode mixture layer containing an auxiliary agent (positive electrode mixture molded body), or a structure in which a positive electrode mixture layer containing a positive electrode active material and a conductive auxiliary agent is formed on one or both sides of a current collector. and the like.

AgO and Ag ₂ O can be used when silver oxide is used as the positive electrode active material.

The particle size of the silver oxide is not particularly limited, but the average particle size is preferably 10 μm or less, more preferably 2 μm or less. When the silver oxide of such a size is used, the utilization factor during charging is improved, and a large charge capacity can be obtained even if the final charge voltage is relatively low. In addition, for example, it is possible to suppress swelling of the battery that may be caused by increasing the end-of-charge voltage.

However, the average particle size of the silver oxide is preferably 0.01 μm or more, more preferably 0.03 μm or more, because production and subsequent handling of silver oxides with too small a particle size are difficult. more preferred.

The average particle size of the silver oxide and other particles (insulating inorganic particles and graphite particles described later) referred to in this specification is determined using a laser scattering particle size distribution meter (for example, "LA-920" manufactured by Horiba, Ltd.). is the particle diameter (D ₅₀ ) at 50% cumulative frequency on a volume basis, measured by dispersing these particles in a medium that does not dissolve .

Particles of a carbonaceous material such as carbon black particles and graphite particles can be used as the conductive aid for the positive electrode mixture layer. In addition, it is more preferable to use carbon black particles and graphite particles in combination for the conductive aid.

By using carbon black particles, it is easy to form a good conductive network in the positive electrode mixture layer. increases, the electrical resistance in the positive electrode mixture layer can be effectively reduced, and thus the reaction efficiency of the positive electrode active material can be improved during charging.

On the other hand, when only carbon black particles are used, depending on the thickness of the positive electrode mixture layer, it is necessary to use a binder to improve the moldability. Since the moldability of the layer is improved, even if the positive electrode mixture molded body or the positive electrode mixture layer is as thin as 0.4 mm or less, more preferably 0.3 mm or less, for example, the moldability is good, and the binder can be used. Even if it is not used, it becomes easy to prevent the occurrence of manufacturing defects.

The graphite particles in the positive electrode mixture layer may be either particles of natural graphite (such as flake graphite) or particles of artificial graphite, and one or more of these may be used.

As described above, the graphite particles have the function of enhancing the formability of the positive electrode mixture layer. From the viewpoint of better exhibiting this function, the graphite particles preferably have an average particle size of 1 μm or more. It is more preferably 2 μm or more, and from the viewpoint of improving conductivity, it is preferably 7 μm or less, and more preferably 5 μm or less.

Furnace black, channel black, acetylene black, thermal black and the like are exemplified as the carbon black particles for the positive electrode mixture layer, and one or more of these can be used. Among these carbon black particles, acetylene black, which has high conductivity and contains few impurities, is preferably used.

Moreover, when silver oxide is used as the positive electrode active material, it is preferable that the positive electrode mixture layer further contains insulating inorganic particles, whereby the charge-discharge cycle characteristics of the battery can be further improved. Moreover, when insulating inorganic particles are used, the charge-discharge cycle characteristics of the battery can be further improved by further containing carbon black particles and graphite particles in the positive electrode mixture layer.

Examples of the insulating inorganic particles for the positive electrode mixture layer include particles such as oxides of at least one element selected from Si, Zr, Ti, Al, Mg and Ca. Further, specific examples of the oxides include Al ₂ O ₃ , TiO ₂ , SiO ₂ , ZrO ₂ , MgO, CaO, AlOOH, Al(OH) ₃ and the like. Particles that do not dissolve or are poorly soluble are preferably used. These insulating inorganic particles may be used alone or in combination of two or more.

If the particle diameter of the insulating inorganic particles is too large, the effect of improving the charge-discharge cycle characteristics of the battery may be reduced. Therefore, from the viewpoint of improving the charge-discharge cycle characteristics of the battery, the average particle size of the insulating inorganic particles is preferably 0.5 μm or less, more preferably 0.3 μm or less.

On the other hand, if the particle size of the insulating inorganic particles is too small, the effect of improving the charging efficiency (initial capacity) of the battery may be reduced. Therefore, from the viewpoint of better charging efficiency of the battery, the average particle size of the insulating inorganic particles is preferably 0.01 μm or more, more preferably 0.05 μm or more.

As for the composition of the positive electrode mixture layer (the positive electrode mixture molded body, the positive electrode mixture coating layer formed on the current collector, etc.), in order to secure the capacity, when silver oxide is used as the positive electrode active material, , the content is, for example, preferably 60% by mass or more, more preferably 80% by mass or more, and 90% by mass or more, based on 100% by mass of the total solid content constituting the positive electrode mixture layer. It is particularly preferred to have

In addition, the content of the conductive aid in the positive electrode mixture layer is preferably 0.2% by mass or more, preferably 0.5% by mass or more, and 1% by mass or more from the viewpoint of conductivity. On the other hand, in order to prevent capacity reduction and gas generation during charging, the content is preferably 8% by mass or less, more preferably 7% by mass or less, and even more preferably 5% by mass or less. , 3% by mass or less.

When carbon black particles and graphite particles are contained in the positive electrode mixture layer, the content of graphite particles is such that the effect of improving the charging efficiency and charge-discharge cycle characteristics of the battery due to the combined use of carbon black particles is well ensured. From a viewpoint, it is preferably 1% by mass or more, and more preferably 2% by mass or more. When carbon black particles and graphite particles are contained in the positive electrode mixture layer, the content of the graphite particles is such that, for example, the amount of silver oxide in the positive electrode mixture layer becomes too small, resulting in a decrease in battery capacity. is preferably 7% by mass or less, more preferably 4% by mass or less, from the viewpoint of suppressing

In addition, when carbon black particles and graphite particles are contained in the positive electrode mixture layer, the content of carbon black particles is such that the effect of improving the charging efficiency and charge-discharge cycle characteristics of the battery due to the combined use of graphite particles is well ensured. From a viewpoint, it is preferably 0.1% by mass or more, and more preferably 0.5% by mass or more. However, if the amount of carbon black particles in the positive electrode mixture layer is too large, for example, when the battery is stored at high temperatures, the positive electrode may swell to a large extent. Therefore, from the viewpoint of suppressing swelling of the positive electrode during storage of the battery (especially storage at a high temperature of about 60° C.) and improving the storage characteristics of the battery, carbon black particles and graphite particles are added to the positive electrode mixture layer. When included, the content of carbon black particles is preferably 1.5% by mass or less, more preferably 1% by mass or less.

In addition, when insulating inorganic particles are contained in the positive electrode mixture layer, the content is 0.1% by mass or more from the viewpoint of satisfactorily ensuring the effect of using the particles (especially the effect of improving the charge-discharge cycle characteristics of the battery). and more preferably 3% by mass or more. However, if the amount of insulating inorganic particles in the positive electrode mixture layer is too large, the filling amount of the positive electrode active material will decrease, leading to a decrease in battery capacity. If this progresses, the discharge capacity may suddenly decrease, so the content of the insulating inorganic particles in the positive electrode mixture layer is preferably 7% by mass or less, and is 5% by mass or less. is more preferable.

As described above, the positive electrode mixture layer can be formed without using a binder. good too. Examples of binders for the positive electrode material mixture layer include fluororesins such as polytetrafluoroethylene (PTFE). When using a binder, the content of the binder in the positive electrode mixture layer is preferably 0.1 to 20% by mass.

When the positive electrode is a positive electrode mixture molded body, for example, a positive electrode active material, a conductive agent, and, if necessary, an alkaline electrolyte (the same alkaline electrolyte that is injected into a battery can be used) are mixed. It can be manufactured by pressure-molding the positive electrode mixture prepared in the above step into a predetermined shape.

In the case of a positive electrode having a positive electrode mixture layer and a current collector, for example, the positive electrode active material and the conductive aid 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.), apply it on a current collector, dry it, and if necessary, perform a press treatment such as calendering. .

However, the positive electrode is not limited to those produced by each of the methods described above, and may be produced by other methods.

When the molded positive electrode mixture is used as the positive electrode, the thickness is preferably 0.15 to 4 mm. On the other hand, in the case of a positive electrode having a positive electrode mixture layer and a current collector, the thickness of the positive electrode mixture layer (thickness per side of the current collector) is preferably 30 to 300 μm.

When a current collector is used for the positive electrode, examples of the current collector include those made of stainless steel such as SUS316, SUS430, and SUS444; aluminum and aluminum alloy; Wire mesh, expanded metal, lath mesh, punching metal, metal foam, foil (plate) and the like can be exemplified. The thickness of the current collector is preferably 0.05 to 0.2 mm, for example. It is also desirable to apply a paste-like conductive material such as carbon paste or silver paste to the surface of such a current collector.

In alkaline secondary batteries, a separator is usually interposed between the positive electrode and the negative electrode. Separators that can be used for alkaline secondary batteries include non-woven fabrics mainly composed of vinylon and rayon, vinylon-rayon non-woven fabrics (vinylon-rayon mixed paper), polyamide non-woven fabrics, polyolefin-rayon non-woven fabrics, vinylon paper, vinylon linter pulp paper, Vinylon mercerized pulp paper and the like can be used. Also, a laminate of hydrophilically treated microporous polyolefin film (microporous polyethylene film, microporous polypropylene film, etc.), cellophane film, and liquid absorbing layer (electrolyte retention layer) such as vinylon/rayon mixed paper. may be used as a separator. The thickness of the separator is preferably 20-500 μm.

In addition, between the positive electrode and the negative electrode, a polymer is used as a matrix, and the matrix contains metal oxides, hydroxides, carbonates, sulfates, phosphates, borates and silicates. It is preferable to dispose an anion-conducting membrane in which particles of at least one metal compound selected from are dispersed.

There are no particular restrictions on the form of the alkaline secondary battery, and it may be a flat type ( (including coin-shaped and button-shaped); Laminated type having an exterior body made of a metal laminate film; Caulking the bottomed cylindrical outer can and the sealing plate via a gasket, or welding the outer can and the sealing plate Any form such as a cylindrical shape [cylindrical shape, prismatic shape (rectangular cylinder shape)] having a battery case that is sealed by pressing can be used.

When using a crimp-sealed outer case, polypropylene, nylon, etc. can be used for the gasket material interposed between the outer can and the sealing plate. is required, fluorine resins such as tetrafluoroethylene-perfluoroalkoxyethylene copolymer (PFA), polyphenylene ether (PEE), polysulfone (PSF), polyarylate (PAR), polyethersulfone (PES ), polyphenylene sulfide (PPS), polyetheretherketone (PEEK), and other heat-resistant resins with a melting point exceeding 240°C can also be used. Moreover, when the battery is applied to applications requiring heat resistance, a glass hermetic seal can be used for the sealing.

In addition, in order to prevent elements such as iron constituting the outer can from eluting during charging, it is desirable to plate the inner surface of the outer can with a corrosion-resistant metal such as gold.

The alkaline secondary battery of the present invention can be used for applications where alkaline primary batteries (silver oxide primary batteries, etc.) are employed, and conventionally known alkaline secondary batteries and non-aqueous electrolyte secondary batteries are also employed. It can also be applied to applications where

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

Example 1
Silver oxide (Ag ₂ O) having an average particle size of 5 μm is used as the positive electrode active material, and graphite particles (BET specific surface area is 20 m ² /g, average particle size is 3.7 μm), carbon black particles (BET ratio Acetylene black having a surface area of 68 m ² /g and an average primary particle size of 35 nm) and TiO ₂ particles (average particle size: 250 nm) were used to form a positive electrode mixture layer.

Silver oxide, graphite particles, carbon black (CB) particles, and _TiO2 particles were mixed in proportions of 85.6% by mass, 3.8% by mass, 0.6% by mass, and 10% by mass, respectively, to form a positive electrode mixture. 80 mg of this positive electrode mixture was filled in a mold and pressure-molded into a disc having a diameter of 5.17 mm and a height of 0.6 mm at a packing density of 5.7 g/cm ³ . An agent molded body (positive electrode mixture layer) was produced.

Aqueous dispersion of PTFE (solid content: 60% by mass): 5 g, aqueous solution of sodium polyacrylate (concentration: 2% by mass): 2.5 g, hydrotalcite particles (average particle size: 0.4 μm): 2.5 g of the mixture was kneaded and rolled to form a membrane with a thickness of 100 μm, which was punched out into a circle with a diameter of 5.7 mm and used as an anion conductive membrane to assemble a battery.

Mercury-free zinc alloy particles commonly used in alkaline primary batteries containing 500 ppm of In, 400 ppm of Bi and 10 ppm of Al as additive elements were used as the negative electrode active material. Regarding the particle size of the zinc alloy particles obtained by the method described above, the average particle size (D ₅₀ ) was 120 μm, and the proportion of particles having a particle size of 75 μm or less was 25% by mass or less.

The zinc alloy particles and ZnO were mixed at a ratio (mass ratio) of 97:3 to obtain a composition for forming a negative electrode (composition for negative electrode). This composition: 19 mg was weighed out and used to prepare a negative electrode.

The alkaline electrolyte is an aqueous solution of potassium hydroxide dissolved at a concentration of 35% by mass, and further zinc oxide, lithium hydroxide (LiOH) and polyethylene glycol (PEG) are added at 3% by mass and 0.5% by mass, respectively. Aqueous solutions with concentrations of % and 1% by weight were used.

For the separator, two graft films (thickness: 30 μm) composed of a graft copolymer having a structure in which acrylic acid is graft-copolymerized to a polyethylene main chain are placed on both sides of a cellophane film (thickness: 20 μm). Then, vinylon-rayon mixed paper (thickness: 100 μm) was further laminated and used by punching out into a circle with a diameter of 5.7 mm.

The positive electrode (positive electrode mixture molded body), the negative electrode (negative electrode composition), the alkaline electrolyte, the anion conductive membrane and the separator are combined with an outer can made of a steel plate whose inner surface is gold-plated, and a copper-stainless steel (SUS304 ) - Sealed in a battery container composed of a sealing plate made of a nickel clad plate and an annular gasket made of nylon 66, having the appearance shown in FIG. 1, the structure shown in FIG. , an alkaline secondary battery having a thickness of 2.7 mm was produced. The anion conductive membrane was arranged so as to face the negative electrode, and the separator was arranged on the positive electrode side.

In the alkaline secondary battery 1 shown in FIGS. 1 and 2, a sealing plate 3 containing a negative electrode 5 is placed in the opening of an outer can 2 containing a positive electrode 4, a separator 6 and an anion conductive membrane 7. The outer can 2 is fitted through an annular gasket (resin gasket) 8, and the open end of the outer can 2 is tightened inward, whereby the resin gasket 8 comes into contact with the sealing plate 3. , the opening of the exterior can 2 is sealed to form a sealed structure inside the battery. 1 and 2, the positive electrode 4, the negative electrode 5, the separator 6 and the anion conductive membrane are placed in the space (sealed space) within the battery container composed of the outer can 2, the sealing plate 3 and the resin gasket 8. A power generation element including 7 is loaded, and an alkaline electrolyte (not shown) is injected and held in a separator. The outer can 2 also serves as a positive electrode terminal, and the sealing plate 3 also serves as a negative electrode terminal. The positive electrode 4 is, as described above, a compact of positive electrode mixture containing silver oxide, graphite particles, carbon black particles and TiO ₂ particles.

Example 2
An alkaline secondary battery was produced in the same manner as in Example 1, except that the concentration of lithium hydroxide dissolved in the alkaline electrolyte was 1% by mass.

Example 3
An alkaline secondary battery was produced in the same manner as in Example 1, except that the concentration of lithium hydroxide dissolved in the alkaline electrolyte was 2% by mass.

Comparative example 1
The same as Example 1 except that silver oxide, graphite particles, and carbon black particles were mixed in proportions of 95.6% by mass, 3.8% by mass, and 0.6% by mass, respectively, to form a positive electrode mixture. Then, a molded positive electrode mixture was produced.

Except that the positive electrode mixture molded body was used as the positive electrode, and an aqueous solution in which potassium hydroxide was dissolved at a concentration of 35% by mass and zinc oxide was further dissolved at a concentration of 3% by mass was used as the alkaline electrolyte. , an alkaline secondary battery was produced in the same manner as in Example 1.

Comparative example 2
Except for using an aqueous solution in which potassium hydroxide was dissolved at a concentration of 35% by mass as the alkaline electrolyte, and an aqueous solution in which zinc oxide and lithium hydroxide were further dissolved at concentrations of 3% by mass and 2% by mass, respectively. prepared an alkaline secondary battery in the same manner as in Example 1.

Comparative example 3
As the alkaline electrolyte, an aqueous solution in which potassium hydroxide was dissolved at a concentration of 35% by mass, and further an aqueous solution in which zinc oxide and polyethylene glycol were dissolved at concentrations of 3% by mass and 1% by mass, respectively, were used. , an alkaline secondary battery was produced in the same manner as in Example 1.

Comparative example 4
An alkaline electrolyte was prepared in the same manner as in Example 1, except that an aqueous solution in which potassium hydroxide was dissolved at a concentration of 35% by mass and an aqueous solution in which zinc oxide was dissolved at a concentration of 3% by mass was used as the alkaline electrolyte. A following battery was produced.

The charge-discharge cycle characteristics of the alkaline secondary batteries of Examples and Comparative Examples were evaluated by the following method. Constant current-constant voltage charge (CC: 2 mA, CV: 1.8 V, end current: 0.2 mA) and constant current discharge (current value: 2 mA, end voltage: 1.0 V) was repeated 140 times, and the discharge capacity was measured for each cycle. FIG. 3 shows a graph of the measurement results, with the number of cycles on the horizontal axis and the discharge capacity (mAh) on the vertical axis.

Table 1 shows the composition of the positive electrode mixture and the composition of the additive of the alkaline electrolyte in the alkaline secondary batteries of Examples and Comparative Examples.

As shown in FIG. 3, the alkaline secondary batteries of Examples 1 to 3 using an alkaline electrolyte containing lithium hydroxide and polyalkylene glycol (PEG) did not contain both of them. Compared to the batteries of Comparative Examples 1 and 4, the battery of Comparative Example 2 using an alkaline electrolyte that does not contain PEG, and the battery of Comparative Example 3 that uses an alkaline electrolyte that does not contain lithium hydroxide , the decrease in capacity was well suppressed even when the number of cycles progressed, and the battery had excellent charge-discharge cycle characteristics.

In addition, in the battery of Comparative Example 2 using an alkaline electrolyte containing lithium hydroxide but not PEG, the charging efficiency in the initial stage of the charge-discharge cycle was poor, and the discharge capacity was extremely low. In the batteries of Examples 1 to 3 using the alkaline electrolyte containing PEG together with lithium, the charging efficiency in the early stage of the charge-discharge cycle can be improved, and the above-mentioned problems caused by lithium hydroxide can be suppressed. rice field.

REFERENCE SIGNS LIST 1 alkaline secondary battery 2 outer can 3 sealing plate 4 positive electrode (molded body of positive electrode mixture)
5 Negative Electrode 6 Separator 7 Anion Conductive Membrane 8 Gasket

Claims (4)

An alkaline secondary battery having a positive electrode, a negative electrode and an alkaline electrolyte,
The positive electrode has a positive electrode mixture layer containing silver oxide,
The negative electrode contains zinc-based particles selected from zinc particles and zinc alloy particles,
The alkaline secondary battery, wherein the alkaline electrolyte contains potassium hydroxide or sodium hydroxide, lithium hydroxide, and polyalkylene glycols. 2. The alkaline secondary battery in accordance with claim 1, wherein the content of lithium hydroxide in said alkaline electrolyte is 0.1 to 5% by mass. 3. The alkaline secondary battery according to claim 1, wherein the content of polyalkylene glycols in said alkaline electrolyte is 0.1 to 8% by mass. The alkaline secondary battery according to any one of claims 1 to 3 , wherein the positive electrode mixture layer further contains insulating inorganic particles.

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