Negative electrode for zinc battery, and zinc battery

Abstract

A negative electrode for a zinc battery, comprising: a non-porous current collector; and a negative electrode mixture layer held on the current collector and containing at least one of zinc, a zinc alloy, and a zinc-containing compound. The negative electrode has a current collector exposed portion in which the negative electrode mixture layer is not disposed at a portion located on the outermost peripheral surface when the negative electrode is wound.

Description

Technical Field

[0001] The invention relates to a negative electrode for a zinc battery and a zinc battery. Background Art

[0002] Zinc batteries are batteries that use zinc, zinc alloys, or zinc-containing compounds in the negative electrode active material. Batteries that use zinc or the like in the negative electrode active material include primary batteries and secondary batteries, such as zinc-air batteries that use oxygen in the air in the positive electrode active material, nickel-zinc batteries that use nickel-containing compounds in the positive electrode active material, manganese-zinc batteries and zinc-ion batteries that use manganese-containing compounds in the positive electrode active material, and silver-zinc batteries that use silver-containing compounds in the positive electrode active material.

[0003] Among these, nickel-zinc batteries are aqueous batteries that use aqueous electrolytes, so they are safer than non-aqueous batteries. In addition, the combination of zinc electrodes and nickel electrodes has a high electromotive force as an aqueous battery and is relatively low in cost. Therefore, applications in industrial uses (e.g., backup power supplies) or automotive uses (e.g., hybrid vehicles) are being explored.

[0004] For example, Patent Document 1 discloses an alkaline zinc storage battery comprising: a wound body in which a positive electrode including nickel hydroxide and the like and a negative electrode including zinc oxide and metal zinc and the like are wound in a stacked state with a separator interposed therebetween; and an outer can accommodating the wound body. The negative electrode is disposed on the outermost peripheral surface of the wound body.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Laid-Open No. 53-071234 Summary of the invention

[0008] Problem that the invention aims to solve

[0009] However, in the zinc battery disclosed in Patent Document 1, self-discharge cannot be sufficiently suppressed. That is, the negative electrode active material, namely the metal zinc, of the negative electrode located at the outermost periphery of the winding body comes into contact with the electrolyte and dissolves spontaneously. As a result, the generated electrons move to the outer can, and a local battery reaction occurs between the negative electrode active material and the inner wall surface of the outer can, which makes self-discharge more likely to occur.

[0010] The present invention has been accomplished based on the above circumstances, and an object of the present invention is to provide a negative electrode for a zinc battery and a zinc battery that can suppress self-discharge more than before.

[0011] Solutions to the problem

[0012] According to the present invention, a negative electrode for a zinc battery can be provided, which is wound and contained in an outer can in a state of being stacked with a positive electrode via a separator, and the negative electrode for a zinc battery comprises: a non-porous current collector; and a negative electrode mixture layer retained on the current collector and comprising at least one of zinc, a zinc alloy and a zinc-containing compound, and the negative electrode for a zinc battery has a current collector exposed portion where the negative electrode mixture layer is not configured at the portion located on the outermost peripheral surface when the negative electrode is wound.

[0013] According to the present invention, a zinc battery can be provided, comprising: a wound body in which a negative electrode and a positive electrode are wound in a stacked state with a separator therebetween; and an outer can accommodating the wound body, wherein the negative electrode comprises: a non-porous current collector; and a negative electrode mixture layer retained on the current collector and comprising at least one of zinc, a zinc alloy and a zinc-containing compound, the negative electrode being arranged on the outermost peripheral surface of the wound body, and the negative electrode having a current collector exposed portion at a portion located on the outermost peripheral surface where the negative electrode mixture layer is not arranged.

[0014] Effects of the Invention

[0015] According to the present invention, a negative electrode for a zinc battery and a zinc battery capable of suppressing self-discharge more than ever before can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a perspective view showing a zinc battery according to an embodiment of the present invention in partial cutaway.

[0017] Figure 2A to Figure 2C Yes means Figure 1 Schematic diagram of the composition of the negative electrode used in the zinc battery. DETAILED DESCRIPTION

[0018] 1. Zinc battery

[0019] Hereinafter, a nickel-zinc battery will be described as an example of the zinc battery according to the present embodiment.

[0020] Figure 1 This is a partially cutaway perspective view of a zinc battery 10 according to an embodiment of the present invention. In this figure, a part of the winding body 16 is omitted. In addition, the one-dot chain line portion shows an enlarged view of the cross section at that location.

[0021] like Figure 1 As shown, the zinc battery 10 according to the present embodiment is, for example, a cylindrical battery of FA size, and includes an outer can 12 , a sealing body 14 , a winding body 16 (electrode group), an electrolyte (not shown), an upper insulating member 18 , and a lower insulating member 20 .

[0022] The outer can 12 is a container for accommodating the wound body 16, and in the present embodiment, is a container in the shape of a bottomed cylinder with an open top. The outer can 12 has conductivity, and its bottom wall 12A functions as a negative electrode terminal.

[0023] The material constituting the outer can 12 can be any material that is conductive and corrosion-resistant to the electrochemical reaction inside the electrolyte and the battery, and generally includes metal materials such as iron and steel. Preferably, plating is implemented on the inner wall surface of the outer can 12. In the present embodiment, a plating film 12B is arranged on the inner wall surface of the outer can 12. The metal constituting the plating film 12B can be any metal with a higher hydrogen overpotential than the metal constituting the main body of the outer can 12, preferably a metal with a higher hydrogen overpotential than iron or steel. Examples of such metals include nickel, tin, copper, indium, bismuth, etc. Among them, tin is preferred from the viewpoint of further reducing self-discharge. It should be noted that although nickel does not show a high hydrogen overpotential as tin, by adopting the structure of the present invention, self-discharge can be well reduced even when nickel is used.

[0024] The sealing body 14 is fixed to the opening of the outer can 12 via the insulating gasket 22, and seals the outer can 12 and provides a positive electrode terminal. The sealing body 14 includes a cover plate 24, a valve body 26, and a positive electrode terminal 28.

[0025] The cover plate 24 is a conductive disc-shaped member having a through hole 24A in the center. The insulating gasket 22 has a ring shape surrounding the cover plate 24 and is sandwiched between the outer can 12 and the sealing body 14. The insulating gasket 22 is fixed to the opening edge 12C of the outer can 12 by caulking the opening edge 12C of the outer can 12. Thus, the cover plate 24 and the insulating gasket 22 cooperate with each other to hermetically seal the opening of the outer can 12.

[0026] The valve body 26 is a rubber member, and is disposed on the outer surface of the cover plate 24 so as to close the through hole 24A.

[0027] The positive terminal 28 is a metal cylindrical member with a flange, and is electrically connected to the outer surface of the cover plate 24 so as to cover the valve body 26. The positive terminal 28 presses the valve body 26 toward the cover plate 24. The positive terminal 28 has an opening for a vent (not shown).

[0028] Furthermore, during normal operation, the through hole 24A is hermetically closed by the valve body 26. On the other hand, when gas is generated in the outer can 12 and the internal pressure thereof increases, the valve body 26 is compressed by the internal pressure and the through hole 24A is opened, and as a result, the gas is discharged from the outer can 12 to the outside through the through hole 24A and the exhaust hole (not shown) of the positive terminal 28. That is, the through hole 24A, the valve body 26 and the positive terminal 28 form a safety valve for the battery.

[0029] The wound body 16 is an electrode group that is contained in the outer can 12 and includes the positive electrode 30, the negative electrode 32, and the separator 34. Specifically, the wound body 16 is an electrode group in which the positive electrode 30 and the negative electrode 32 are wound in a stacked state with the separator 34 interposed therebetween. More specifically, the wound body 16 is a structure in which the separator 34, the positive electrode 30, the separator 34, and the negative electrode 32 are stacked and wound in such a way that the negative electrode 32 is on the outside.

[0030] A negative electrode 32 is disposed on the outermost circumference of the wound body 16, and the negative electrode 32 is in contact with the inner wall surface of the outer can 12. That is, the negative electrode 32 and the outer can 12 serving as a negative electrode terminal are electrically connected to each other. In the present embodiment, the negative electrode 32 (specifically, the negative electrode current collector 38 exposed in the current collector exposed portion 42 described later) located on the outermost circumference of the wound body 16 is in direct contact with the inner wall surface of the outer can 12, but the present invention is not limited thereto, and a conductive member such as a metal sheet may be disposed between the negative electrode 32 located on the outermost circumference and the inner wall surface of the outer can 12. However, from the viewpoint of reducing internal resistance, an insulating coating film and an insulating member are not disposed between the negative electrode 32 located on the outermost circumference and the inner wall surface of the outer can 12.

[0031] On the other hand, a positive electrode lead 36 is connected to the positive electrode 30 of the wound body 16. One end of the positive electrode lead 36 is connected to the positive electrode 30, and the other end is connected to the cover plate 24. Thus, the positive electrode 30 and the positive electrode terminal 28 are electrically connected to each other via the positive electrode lead 36 and the cover plate 24.

[0032] The upper insulating member 18 is disposed between the wound body 16 and the cover plate 24. Thus, the negative electrode 32 of the wound body 16 does not come into contact with the sealing body 14. The upper insulating member 18 has a slit 18A, and the positive electrode lead 36 is passed through the slit 18A.

[0033] The lower insulating member 20 is disposed between the wound body 16 and the bottom of the outer can 12 . Thus, the positive electrode 30 of the wound body 16 does not come into contact with the inner wall surface of the outer can 12 .

[0034] The electrolyte (not shown) is an alkaline electrolyte, and is sealed in the outer can 12 . The wound body 16 is impregnated with the alkaline electrolyte, and the alkaline electrolyte is mainly retained in the separator 34 .

[0035] The alkaline electrolyte is preferably an aqueous solution containing at least one of KOH, NaOH and LiOH as a solute. The concentration (solute concentration) of the alkaline electrolyte is not particularly limited, and can be set to about 7N (about 30% by mass), for example. In addition, in the present embodiment, the alkaline electrolyte is preferably an electrolyte in which zinc oxide is dissolved to a saturated concentration. This is to suppress the dissolution of zinc ions from the negative electrode to the electrolyte as much as possible.

[0036] Next, each member constituting the wound body 16 will be described.

[0037] (positive electrode)

[0038] The positive electrode 30 includes a positive electrode current collector and a positive electrode mixture.

[0039] The positive electrode current collector can be a non-porous current collector or a porous current collector. The porous current collector is, for example, a current collector having a porous structure, preferably a metal body having a three-dimensional mesh skeleton. The skeleton of the metal body extends throughout the entirety of the positive electrode current collector, and interconnecting holes are formed by the gaps in the skeleton. Furthermore, the interconnecting holes are filled with a positive electrode mixture. The material constituting the positive electrode current collector can be any metal material that is conductive and stable even at the reaction potential of the positive electrode, preferably nickel. That is, the positive electrode current collector can be a mesh, sponge or fibrous metal body made of nickel foam or nickel-plated.

[0040] The positive electrode mixture is held on the positive electrode current collector and contains a positive electrode active material.

[0041] Examples of the positive electrode active material include nickel hydroxide. The nickel hydroxide is in the form of a powder, for example. The nickel hydroxide particles are preferably high-valent nickel hydroxide particles. Preferably, the nickel hydroxide particles contain Co, Zn, Cd, etc. in a solid solution.

[0042] In addition, the nickel hydroxide particles are preferably covered with a surface layer containing a cobalt compound. The surface layer is preferably a high-valent cobalt compound layer containing a cobalt compound that is valenced to be trivalent or higher. As the cobalt compound that is valenced to be trivalent or higher, cobalt oxyhydroxide (CoOOH) that is valenced to be trivalent or higher is included. This is because the high-valent cobalt compound layer containing such a high-valent cobalt compound has excellent conductivity and forms a conductive network.

[0043] The positive electrode mixture may contain a positive electrode additive and a binder in addition to the positive electrode active material.

[0044] Examples of the positive electrode additive include yttrium oxide; cobalt compounds such as cobalt oxide, metallic cobalt, and cobalt hydroxide; zinc compounds such as metallic zinc, zinc oxide, and zinc hydroxide; rare earth compounds such as erbium oxide; and niobium oxide.

[0045] The binder plays the following role: the positive electrode active material and the positive electrode additive are bonded to each other, and the positive electrode active material and the positive electrode additive are bonded to the positive electrode current collector. As the binder, for example, hydrophilic or hydrophobic polymers can be listed, for example, hydroxypropyl cellulose and carboxymethyl cellulose, sodium polyacrylate, fluorine polymers (polytetrafluoroethylene (PTFE) and the like).

[0046] (negative electrode)

[0047] Figure 2A to Figure 2C Yes means Figure 1FIG. 3 is a diagram of a strip-shaped negative electrode 32 used in a wound body 16. Figure 2A is a top view of the negative electrode 32, Figure 2B is a bottom view of the negative electrode 32, Figure 2C It is a cross-sectional view of the negative electrode 32 taken along line 2C-2C.

[0048] like Figure 2A to Figure 2C As shown, the negative electrode 32 includes a negative electrode current collector 38 and a negative electrode mixture layer 40 .

[0049] The negative electrode current collector 38 is a non-porous current collector, preferably a non-porous sheet-shaped metal conductor, that is, a non-porous foil. In this specification, non-porous means that there is no hole between the front and back of the sheet, specifically, it means that there is no hole in the entire sheet. The material constituting the negative electrode current collector 38 can be any metal material that is conductive and stable even at the reaction potential of the negative electrode, and copper and copper alloys (such as brass, etc.) and iron can be listed, preferably copper. That is, the negative electrode current collector 38 is preferably copper foil.

[0050] The negative electrode current collector 38 may also be plated on the surface. In this embodiment, the negative electrode current collector 38 has a plated film 38A on the surface (see Figure 1 ). The metal constituting the plating film 38A is a metal having a higher hydrogen overpotential than the metal constituting the main body of the negative electrode current collector 38, preferably a metal having a higher hydrogen overpotential, and more preferably a metal having a higher hydrogen overpotential than copper, such as tin. Due to the presence of the plating film 38A, even if the electrolyte detours to the outermost periphery of the winding body 16 or detours caused by zinc dissolution, the local battery reaction between the negative electrode current collector 38 and the outer can 12 can be suppressed, and self-discharge can be further suppressed.

[0051] The thickness of the negative electrode current collector 38 is not particularly limited, and is, for example, 20 μm to 65 μm. By setting the thickness of the negative electrode current collector 38 to be 20 μm or more, it is possible to further suppress the malfunction caused by deformation of the negative electrode mixture layer 40 disposed on the surface of the negative electrode current collector 38 opposite to the inner wall surface of the outer can 12 during charging and discharging, for example, at the outermost periphery. By setting the thickness of the negative electrode current collector 38 to be 65 μm or less, the amount of negative electrode mixture filled in the outer can 12 is not easily damaged.

[0052] The negative electrode mixture layer 40 is disposed on both the one side and the other side of the negative electrode current collector 38 (see Figure 2C As described above, the negative electrode 32 is disposed on the outermost surface when the winding body 16 is formed. Furthermore, the negative electrode 32 has a current collector exposed portion 42 where the negative electrode mixture layer 40 is not disposed at the portion located on the outermost surface (see Figure 2A ).

[0053] The current collector exposed portion 42 is a portion where the surface of the negative electrode current collector 38 (the surface of the plating film 38A in this embodiment) is peeled off, and refers to a portion where no resin coating film or the like is configured. The current collector exposed portion 42 only needs to be provided at the portion located at the outermost peripheral surface when winding, and can be provided only on a portion of the outermost peripheral surface of the winding body 16, or can be provided on the entire surface. From the viewpoint of further reducing self-discharge, the current collector exposed portion 42 is provided on at least a portion (e.g., more than 50%) of the outermost peripheral surface of the winding body 16, and preferably, is provided on the entire surface. In this embodiment, the negative electrode current collector 38 exposed at the current collector exposed portion 42 is in direct contact with the inner wall surface of the outer can 12.

[0054] The negative electrode mixture constituting the negative electrode mixture layer 40 contains a negative electrode active material.

[0055] As the negative electrode active material, at least one of zinc, zinc alloy and zinc-containing compound is included. As metals constituting the zinc alloy, in addition to zinc, bismuth, aluminum, indium and the like can also be listed. As zinc-containing compounds, for example, zinc oxide (grade 1 / grade 2 / grade 3), zinc hydroxide, zinc sulfide, tetrahydroxy zinc ion salt, zinc halide, zinc acetate and zinc tartrate, zinc oxalate represented by carboxylic acid zinc compounds, magnesium zincate, calcium zincate, barium zincate, zinc borate, zinc silicate, zinc aluminate, zinc fluoride, zinc carbonate, zinc bicarbonate, zinc nitrate, zinc sulfate and the like can be listed. Among them, preferably, the negative electrode active material contains zinc oxide, and more preferably, contains zinc oxide and zinc. In this way, by including zinc, for example, it can not only function as a discharge reserve, but also because the resistance value is lower, the internal resistance of the zinc battery can be further reduced.

[0056] The form of the negative electrode active material is, for example, powder. The particle size of the particles of the negative electrode active material is not particularly limited. When zinc or a zinc alloy is used, the average particle size is preferably 10 μm to 1000 μm, and when a zinc-containing compound is used, it is preferably 0.1 μm to 100 μm. The average particle size refers to the average particle size of 50% cumulatively based on the mass basis, which can be obtained by a laser diffraction / scattering method using a particle size distribution measuring device.

[0057] The negative electrode mixture may contain a negative electrode additive and a binder in addition to the negative electrode active material.

[0058] The negative electrode additive improves the characteristics of the negative electrode, specifically, reduces the dissolution of the negative electrode active material into the electrolyte, for example, bismuth oxide, bismuth hydroxide, indium oxide, indium hydroxide, potassium oxalate and their hydrates. For example, if potassium oxalate and its hydrates are dissolved in the electrolyte, they dissociate into oxalate ions. As a result, the zinc ions dissolved into the electrolyte form a poorly soluble salt with the oxalate ions, covering the surface of the negative electrode active material, thereby reducing the contact between the metal zinc of the negative electrode active material and the electrolyte. As a result, self-discharge is not likely to occur.

[0059] The binder plays the following role: the negative electrode active material and the negative electrode additive are bonded to each other, and the negative electrode active material and the negative electrode additive are bonded to the negative electrode current collector. Examples of the binder include hydroxypropyl cellulose, carboxymethyl cellulose, polyvinyl alcohol, polyvinyl pyrrolidone, polyacrylic acid, sodium polyacrylate, polyimide, polyamideimide, polyamide, styrene butadiene rubber, polyethylene oxide, polytetrafluoroethylene, polyvinylidene fluoride, perfluoroalkoxy fluorine resin, tetrafluoroethylene-hexafluoropropylene copolymer, etc.

[0060] Among them, styrene butadiene rubber is preferred from the viewpoints of high bonding effect and alkali resistance. In the present invention, a non-porous current collector is particularly used as the negative electrode current collector 38, so it is difficult to obtain bonding between the negative electrode mixture and the current collector compared to a porous current collector. Even in such a case, by using styrene butadiene rubber as a binder, sufficient bonding is easily obtained for the non-porous current collector.

[0061] The content of the binder may be such that the negative electrode mixture layer 40 and the negative electrode current collector 38 are sufficiently bonded to each other. In the case of styrene butadiene rubber, the content of the binder may be, for example, 1 to 5% by mass, preferably 1 to 3% by mass, relative to the total amount of the negative electrode mixture.

[0062] (Diaphragm)

[0063] As described above, the separator 34 is disposed between the positive electrode 30 and the negative electrode 32 (see Figure 1 ). As the separator 34, a nonwoven fabric separator or a dendrite-resistant separator can be cited.

[0064] As non-woven fabric separators, for example, non-woven fabric separators in which hydrophilic functional groups are imparted to non-woven fabrics made of polyamide fibers, non-woven fabric separators in which hydrophilic functional groups are imparted to non-woven fabrics made of polyolefin fibers such as polyethylene and polypropylene, etc. are listed. Among them, non-woven fabrics made of polyolefin fibers that have been subjected to sulfonation treatment and have sulfonic groups are preferred. Sulfonic groups are imparted by treating non-woven fabrics with an acid containing a sulfate group such as sulfuric acid or fuming sulfuric acid. Batteries using separators containing such fibers having sulfonic groups are more likely to reduce self-discharge.

[0065] Examples of the dendrite-resistant separator include polyolefin-based microporous films such as polyethylene and polypropylene.

[0066] The separator 34 may be one or more. For example, a nonwoven separator and a dendrite-resistant separator (preferably a dendrite-resistant separator obtained by hydrophilizing a polyolefin-based microporous membrane) may be laminated.

[0067] Next, the operation of the zinc battery 10 according to the present embodiment will be described.

[0068] The zinc battery 10 includes a wound body 16 as an electrode group in which a positive electrode 30 and a negative electrode 32 are wound in a stacked state with a separator 34 interposed therebetween. Furthermore, the negative electrode 32 is disposed on the outermost peripheral surface of the wound body 16, and the negative electrode 32 has a current collector exposed portion 42 where the negative electrode mixture layer 40 is not disposed and the negative electrode current collector 38 is exposed at a portion located on the outermost peripheral surface.

[0069] This can reduce the dissolution of zinc ions from the negative electrode mixture layer 40 in contact with the inner wall surface of the outer can 12, and can reduce the local battery reaction between the negative electrode 32 and the inner wall surface of the outer can 12. This can suppress self-discharge.

[0070] In particular, in the above embodiment, a predetermined plating film 12B is disposed on the inner wall surface of the outer can 12. Even when the plating film 12B includes a metal with a not-so-high hydrogen overpotential such as nickel, the self-discharge can be highly suppressed by providing the current collector exposed portion 42.

[0071] Furthermore, a plating film 38A made of a metal having a relatively high hydrogen overpotential is disposed on the surface of the negative electrode current collector 38. This can further reduce local battery reactions even near the negative electrode current collector 38, thereby further suppressing self-discharge.

[0072] 2. Manufacturing method of zinc battery

[0073] The zinc battery can be manufactured by any method. For example, the zinc battery can be manufactured through 1) the step of preparing electrodes (positive electrode and negative electrode) and 2) the step of obtaining a zinc battery using the prepared electrodes.

[0074] Regarding the process 1)

[0075] In this step, electrodes (positive electrode and negative electrode) are obtained.

[0076] Specifically, the active material, any additives and a binder are mixed or kneaded with a solvent (e.g., water) to obtain a mixture slurry. Next, the mixture slurry is applied or filled into a current collector, dried, and pressed as needed to form a mixture layer. By pressing, the packing density of the active material in the mixture layer is increased.

[0077] The positive electrode 30 can be produced, for example, by the following steps.

[0078] First, positive electrode active material powder, positive electrode additive, binder and water are added and kneaded to prepare positive electrode mixture slurry. Next, the obtained positive electrode mixture slurry is filled into nickel foam (current collector), for example, and then dried and roll-pressed to form a positive electrode mixture layer. Then, the obtained positive electrode sheet is cut into a specified size to obtain a positive electrode 30.

[0079] The negative electrode 32 can be produced, for example, by the following steps.

[0080] First, the negative electrode active material powder, negative electrode additive, binder and water are kneaded to prepare a negative electrode mixture slurry. The obtained negative electrode mixture slurry is applied to one surface and the other surface of the negative electrode collector respectively. At this time, the negative electrode mixture slurry is not applied to the part (of the negative electrode collector) located on the outermost peripheral surface when the winding body is made. Next, the negative electrode mixture slurry applied on the negative electrode collector is dried and then pressed to form a negative electrode mixture layer. Then, the obtained negative electrode sheet is cut into a specified size to obtain a negative electrode 32.

[0081] Regarding the process of 2)

[0082] In this step, the prepared electrodes are used to prepare zinc batteries.

[0083] Specifically, a wound body is prepared in which the prepared positive electrode 30 and negative electrode 32 are wound in a stacked state with the separator 34 interposed therebetween. The positive electrode lead 36 is welded to one end in the longitudinal direction of the positive electrode 30. Then, for example, the separator 34, the positive electrode 30, the separator 34, and the negative electrode 32 are stacked in sequence, and then wound in the longitudinal direction so that the negative electrode 32 is on the outside, thereby obtaining the wound body 16.

[0084] The obtained wound body 16 is housed in the outer can 12 , and after the electrolyte is injected, the opening of the outer can 12 is sealed with the sealing body 14 .

[0085] After being left for a certain period of time, the battery is charged under predetermined conditions to perform activation treatment. The activation conditions can be adjusted according to the properties of the electrode active material (positive electrode active material and negative electrode active material). In this way, the zinc battery 10 can be obtained.

[0086] 3. Modifications

[0087] In addition, in the above-mentioned embodiment, the example in which the shape of the outer can 12 is cylindrical is shown, but it is not limited to this, and it may be a square shape.

[0088] Furthermore, in the above embodiment, an example is shown in which the plated film 12B is arranged on the inner wall surface of the outer can 12 and the plated film 38A is arranged on the surface of the negative electrode current collector 38 , but these examples may be omitted.

[0089] In the above embodiment, a nickel-zinc battery (eg, a nickel-zinc secondary battery) is shown as an example of a zinc battery, but the present invention is not limited thereto and may be a zinc-air battery (eg, an air-zinc secondary battery), a silver-zinc battery (eg, a silver-zinc secondary battery), or the like.

[0090] Example

[0091] Hereinafter, the present invention will be described with reference to Examples, but the scope of the present invention is not limited to the Examples.

[0092] 1. Battery production and evaluation

[0093] <Example 1>

[0094] (Production of positive electrode)

[0095] (1) Preparation of positive electrode active material

[0096] Nickel sulfate, zinc sulfate and cobalt sulfate were measured in a manner such that 4.0 parts by mass of zinc and 1.0 parts by mass of cobalt were used relative to 100 parts by mass of nickel hydroxide, and these compounds were added to a 1 mol / L sodium hydroxide aqueous solution containing ammonium ions to prepare a mixed aqueous solution. While stirring the obtained mixed aqueous solution, a 1 mol / L sodium hydroxide aqueous solution was slowly added to the mixed aqueous solution to react, and the pH in the reaction was stabilized at 11, thereby generating matrix particles with nickel hydroxide as the main body and Zn and Co dissolved therein.

[0097] The obtained matrix particles were washed three times with 10 times amount of pure water, dehydrated and dried, and the particle size of the obtained matrix particles was measured using a laser diffraction / scattering particle size distribution measuring device. The result showed that the average particle size of the matrix particles based on the mass basis and the cumulative 50% average particle size was 8 μm.

[0098] Next, the obtained base particles are put into a cobalt sulfate aqueous solution, and while stirring the cobalt sulfate aqueous solution, a 1 mol / L sodium hydroxide aqueous solution is slowly added dropwise to react, and a precipitate is generated while the pH in the reaction is maintained at 11. Then, the generated precipitate is filtered and separated, washed with pure water, and then vacuum dried. Thus, intermediate product particles having a layer containing 5% by mass of cobalt hydroxide on the surface of the base particles are obtained. It should be noted that the thickness of the cobalt hydroxide layer is about 0.1 μm.

[0099] Next, the intermediate product particles were placed in a 25% by mass sodium hydroxide aqueous solution. Here, when the mass of the aggregate of the intermediate product particles was set to P and the mass of the sodium hydroxide aqueous solution was set to Q, the mass ratio of the two was set to P:Q=1:10. Furthermore, a heating treatment was performed while the sodium hydroxide aqueous solution to which the intermediate product powder was added was fixed at 85°C and maintained for 8 hours while stirring.

[0100] The heat-treated intermediate particles were washed with pure water and dried with hot air at 65° C. Thus, an aggregate of positive electrode active material particles (positive electrode active material powder) having a surface layer containing a high-valent cobalt oxide on the surface of the base particles containing Zn and Co in a solid solution was obtained.

[0101] (2) Preparation of positive electrode mixture slurry

[0102] To 100 parts by mass of the obtained positive electrode active material powder, 0.5 parts by mass of yttrium oxide powder, 0.3 parts by mass of niobium oxide powder, 0.5 parts by mass of zinc oxide powder and 30.0 parts by mass of water containing 0.2% by mass of hydroxypropylcellulose powder as a binder were added and kneaded to prepare a slurry of a positive electrode mixture.

[0103] (3) Preparation of positive electrode

[0104] The positive electrode active material slurry was filled to a surface density (weight per unit area) of about 350 g / m 2 After being dried and pressed, the nickel foam (current collector) with a porosity of 95% and a thickness of 1.3 mm is cut into the specified size to make a nickel positive electrode plate with a capacity of 2000 mAh per piece.

[0105] (Production of negative electrode)

[0106] 100 parts by mass of zinc oxide powder, 25 parts by mass of zinc alloy powder, 3 parts by mass of bismuth oxide powder, 0.1 parts by mass of indium oxide powder, 2 parts by mass of potassium oxalate monohydrate powder, 1 part by mass of hydroxypropyl cellulose powder, 8 parts by mass of styrene butadiene rubber aqueous dispersion (50% liquid) and 100 parts by mass of water were mixed to prepare a negative electrode active material slurry.

[0107] The negative electrode active material slurry is applied on both sides of a 38μm thick non-porous copper foil (current collector) with a tin-plated surface. When applying the slurry, the slurry is applied on the entire surface of the non-porous foil on one side, and only on the part facing the positive electrode on the other side. The slurry is not applied on the part located on the outermost peripheral surface of the winding body (the outermost peripheral surface in contact with the inner wall surface of the outer can) to expose the negative electrode collector. After the plate is dried, it is pressed with a pressing roller. It is cut into a specified size to prepare a zinc negative plate with a capacity of 4500mAh per piece.

[0108] (Preparation of electrolyte)

[0109] An aqueous solution containing an alkali metal hydroxide as a solute and saturated with zinc oxide is prepared as an alkaline electrolyte. The alkaline electrolyte is a mixed solution of KOH and LiOH, with a mass ratio of KOH:LiOH=6:0.5 and a specific gravity of 1.31.

[0110] (Battery production)

[0111] The positive electrode plate and the negative electrode plate prepared as above are wound together with a non-woven fabric separator and a dendrite-resistant separator (polyolefin-based microporous film). Specifically, the winding is a structure stacked in the order of non-woven fabric separator and dendrite-resistant separator / positive electrode plate / non-woven fabric separator and dendrite-resistant separator / negative electrode plate. Thus, a winding body is obtained in which the positive electrode plate and the negative electrode plate are wound in a stacked state with the above-mentioned separator interposed therebetween and the negative electrode plate is arranged on the outermost peripheral surface.

[0112] The wound body was placed in a cylindrical outer can (made of iron) with nickel plated inner wall surface. Next, a predetermined amount of the electrolyte prepared above was injected into the outer can to prepare a cylindrical nickel-zinc battery with a nominal capacity of 2000 mAh.

[0113] Furthermore, the obtained battery was activated by performing one cycle of charging to 100% of the nominal capacity and then discharging to 1.3 V.

[0114] <Comparative Example 1>

[0115] (Production of negative electrode)

[0116] A zinc negative electrode plate was prepared in the same manner as in Example 1 except that the slurry was applied to the entire surface of the non-porous foil on one side and the slurry was applied to the entire surface of the non-porous foil on the other side.

[0117] (Battery production)

[0118] A cylindrical nickel-zinc battery was produced in the same manner as in Example 1 except that the negative electrode plate produced above was used.

[0119] <Evaluation>

[0120] The residual rate of discharge capacity of the battery produced above was measured by the following method.

[0121] (Residual rate of discharge capacity)

[0122] The nickel-zinc battery prepared above was charged to 100% of the nominal capacity and then discharged to 1.3 V. This cycle was repeated three times, and the third discharge capacity was taken as the initial discharge capacity [A].

[0123] Next, the battery was charged again to 100% of the nominal capacity and left at 35°C for one month before being discharged to 1.3 V. The residual capacity [B] was taken as the discharge capacity.

[0124] The measured initial discharge capacity [A] and residual capacity [B] were applied to the following formula to calculate the residual rate.

[0125] Formula (1): Residual rate (%) = (residual capacity [B] / initial capacity [A]) × 100

[0126] The evaluation results are shown in Table 1.

[0127] Table 1

[0128]

[0129] As shown in Table 1, it can be seen that the battery of Example 1 having the current collector exposed portion has a significantly higher residual rate of discharge capacity than that of Comparative Example 1 having no current collector exposed portion. This shows that the self-discharge is reduced by providing the current collector exposed portion.

[0130] <Example 2>

[0131] A cylindrical nickel-zinc battery was prepared in the same manner as in Example 1 except that the obtained wound body was housed in a cylindrical outer can having an inner wall surface plated with tin.

[0132] <Comparative Example 2>

[0133] A cylindrical nickel-zinc battery was prepared in the same manner as in Comparative Example 1 except that the obtained wound body was housed in a cylindrical outer can having an inner wall surface plated with tin.

[0134] <Evaluation>

[0135] The residual rate of discharge capacity of the battery produced above was evaluated by the same method as above. The evaluation results are shown in Table 2.

[0136] Table 2

[0137]

[0138] As shown in Table 2, it can be seen that the battery of Example 2 in which the current collector exposed portion was provided had a higher residual rate of discharge capacity than that of Comparative Example 2 in which the current collector exposed portion was not provided.

[0139] In addition, it can be seen that by setting the metal type of the plating film on the inner wall surface of the outer can to tin, the residual rate is further improved compared to the case where it is nickel (comparison between Example 1 and Example 2). It can be seen that by setting the metal type of the plating film on the inner wall surface of the outer can to tin, self-discharge can be further suppressed.

[0140] Industrial Applicability

[0141] According to the present invention, a negative electrode for a zinc battery and a zinc battery capable of suppressing self-discharge more than ever before can be provided.

[0142] Description of Reference Numerals

[0143] 10: Zinc battery;

[0144] 12: outer can;

[0145] 12A: bottom wall;

[0146] 12B: coating film;

[0147] 12C: opening edge;

[0148] 14: Sealing body;

[0149] 16: winding body (electrode group);

[0150] 18: upper insulating part;

[0151] 20: lower insulating part;

[0152] 22: Insulation pad;

[0153] 24: Cover plate;

[0154] 26: Valve body;

[0155] 28: Positive terminal;

[0156] 30: positive electrode;

[0157] 32: negative electrode;

[0158] 34: diaphragm;

[0159] 36: positive lead;

[0160] 38: negative electrode current collector;

[0161] 38A: coating film;

[0162] 40: negative electrode mixture layer;

[0163] 42: Current collector exposed portion.

Claims

1. A negative electrode for a zinc battery, which is wound in a state of being laminated with a positive electrode via a separator and housed in an outer can, The negative electrode for zinc battery comprises: a non-porous current collector; and a negative electrode mixture layer held on the current collector and comprising at least one of zinc, a zinc alloy and a zinc-containing compound, The zinc battery negative electrode has a current collector exposed portion where the negative electrode mixture layer is not arranged and the current collector is exposed at a portion located on the outermost peripheral surface when the negative electrode is wound.

2. The negative electrode for zinc battery according to claim 1, wherein The negative electrode mixture layer further comprises a binder. The binder includes styrene butadiene rubber.

3. A zinc battery comprising: A wound body is formed by winding the negative electrode and the positive electrode in a stacked state with a separator interposed therebetween; and an outer can accommodating the wound body, In the zinc battery, the negative electrode comprises: a non-porous current collector; and a negative electrode mixture layer held on the current collector and comprising at least one of zinc, a zinc alloy and a zinc-containing compound, The negative electrode is arranged on the outermost peripheral surface of the wound body, The negative electrode has a current collector exposed portion at a portion located on the outermost peripheral surface where the negative electrode mixture layer is not arranged and the current collector is exposed.

4. The zinc battery according to claim 3, wherein: The negative electrode mixture layer further comprises a binder. The binder includes styrene butadiene rubber.

5. The zinc battery according to claim 3, wherein: The current collector exposed at the current collector exposed portion is in direct contact with the inner wall surface of the outer can.

6. The zinc battery according to claim 3, wherein: The outer can has a metal plating film, the metal plating film is arranged on the inner wall surface of the outer can, and the hydrogen overpotential of the metal is higher than that of a metal constituting a main body of the outer can.

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