JP7412143B2 - Negative electrode for zinc batteries - Google Patents

Description

The present invention relates to a negative electrode for zinc batteries.

Known examples of zinc batteries include nickel-zinc batteries, zinc-air batteries, and silver-zinc batteries. For example, a nickel-zinc battery is a water-based battery that uses an aqueous electrolyte such as an aqueous potassium hydroxide solution, so it is highly safe, and the combination of a zinc electrode and a nickel electrode produces a high electromotive force for a water-based battery. It is known to have. Furthermore, in addition to excellent input/output performance, nickel-zinc batteries are low-cost and can be applied to industrial applications (e.g., backup power sources, etc.) and automotive applications (e.g., hybrid vehicles, etc.). gender is being considered. Patent Document 1 discloses a technology related to a zinc electrode plate used as a negative electrode of a sealed nickel-zinc battery. The zinc electrode plate described in Patent Document 1 is a porous mat made of copper or a copper alloy, or a porous mat made of a resin foam plated with copper, and at least one of metallic zinc or zinc oxide and a binder. The active material is filled with the active material.

Japanese Patent Application Publication No. 7-6758

For example, as in the zinc electrode plate described in Patent Document 1, copper is used more often in negative electrode current collectors of zinc batteries than ever before. This is because copper has good electrical conductivity and high corrosion resistance. However, due to various circumstances such as manufacturing costs, there are cases where it is desired to have a negative electrode current collector whose main constituent material is another material that can be substituted for copper. One aspect of the present invention is to provide a negative electrode for a zinc battery that includes a negative electrode current collector whose main constituent material is another material that can be substituted for copper.

A negative electrode for a zinc battery according to one aspect of the present invention is a negative electrode for a zinc battery that includes a current collector, and the current collector includes a base material mainly containing carbon steel and at least a portion of the surface of the base material. and a tin plating film covering the. The volume ratio of carbon steel to the negative electrode for zinc batteries is 8% or more and 18% or less.

The negative electrode for a zinc battery may further include a negative electrode material layer fixed to a current collector, and the current collector may have a plurality of holes penetrating in the thickness direction and filled with the negative electrode material layer.

In the above negative electrode for a zinc battery, the base material of the current collector may be made of carbon steel.

In the above negative electrode for a zinc battery, the carbon content of the carbon steel may be 0.001% by mass or more and 0.15% by mass or less.
In the above negative electrode for zinc batteries, the base material may be a cold rolled steel plate. In that case, the cold rolled steel plate may be SPCC.
In the above negative electrode for a zinc battery, the tin plating film may have a thickness of 0.1 μm or more and 5 μm or less.

According to one aspect of the present invention, it is possible to provide a negative electrode for a zinc battery that includes a negative electrode current collector whose main constituent material is another material that can be substituted for copper.

It is a schematic diagram showing negative electrode 1 for zinc batteries of one embodiment. (a) is a front view showing the negative electrode 1 for a zinc battery, and (b) is a cross-sectional view taken along line Ib-Ib in (a). (a) is a chart showing the discharge capacity for each discharge rate in each of the nickel-zinc batteries of Examples and Comparative Examples. (b) is a chart showing the discharge capacity retention rate for each discharge rate in each of the nickel-zinc batteries of Examples and Comparative Examples. It is a graph showing the relationship between discharge capacity retention rate and discharge rate.

In this specification, a numerical range indicated using "~" indicates a range that includes the numerical values written before and after "~" as the minimum and maximum values, respectively. In the numerical ranges described stepwise in this specification, the upper limit or lower limit of the numerical range of one step can be arbitrarily combined with the upper limit or lower limit of the numerical range of another step. In the numerical ranges described in this specification, the upper limit or lower limit of the numerical range may be replaced with the values shown in the examples. "A or B" may include either A or B, or may include both. The materials exemplified herein can be used alone or in combination of two or more, unless otherwise specified. In the present specification, if there are multiple substances corresponding to each component in the composition, the content of each component in the composition refers to the total amount of the multiple substances present in the composition, unless otherwise specified. means. Furthermore, in this specification, the term "film" or "layer" includes not only a structure formed on the entire surface but also a structure formed in a part when observed as a plan view. be done.

Embodiments of the present invention will be described in detail below. However, the present invention is not limited to the following embodiments, and can be implemented with various modifications within the scope of the gist. The sizes of the components in each figure are conceptual, and the relative size relationships between the components are not limited to those shown in each figure.

FIG. 1 is a schematic diagram showing a negative electrode 1 for a zinc battery according to the present embodiment. FIG. 1(a) is a front view showing the negative electrode 1 for a zinc battery according to the present embodiment, and FIG. 1(b) is a sectional view taken along line Ib-Ib in FIG. 1(a). As shown in FIGS. 1A and 1B, a negative electrode 1 for a zinc battery includes a current collector (negative electrode current collector) 2 and a negative electrode material layer 3. The current collector 2 constitutes a current conduction path from the negative electrode material layer 3 . Current collector 2 has a base material 21 and a tin-plated film 22.

The base material 21 mainly contains carbon steel, and in one example, consists only of carbon steel. The structure of the base material 21 is not particularly limited, and may be, for example, in the shape of a flat plate or sheet, and has a three-dimensional network structure made of foamed metal, expanded metal, felt-like material of metal fibers, etc. You can. As an example, the illustrated base material 21 has a plurality of holes 21a that penetrate the base material 21 in the thickness direction. The plurality of holes 21a are two-dimensionally distributed in a plane perpendicular to the thickness direction of the base material 21. In this case, the base material 21 may be a punched metal made of carbon steel. Carbon steel has electrical conductivity and alkali resistance, and is also stable at the reaction potential of the negative electrode. The carbon (C) content of carbon steel is, for example, 0.001% by mass or more and 0.15% by mass or less. Carbon steel may contain at least one of manganese (Mn), phosphorus (P), and sulfur (S) in addition to carbon (C). In one example, the manganese (Mn) content is 0.001% by mass or more and 0.60% by mass or less, the phosphorus (P) content is 0.001% by mass or more and 0.05% by mass or less, and the sulfur (S ) The content is 0.001% by mass or more and 0.05% by mass or less. The base material 21 may be, for example, a cold rolled steel plate or a processed cold rolled steel plate. The processing includes, for example, bending, pressing, and/or drawing. The cold rolled steel plate is, for example, SPCC. According to the standards, the carbon (C) content of SPCC is 0.15% by mass or less, the manganese (Mn) content is 0.60% by mass or less, and the phosphorus (P) content is 0.100% by mass. The content of sulfur (S) is 0.050% by mass or less. The thickness of the base material 21 may be, for example, 0.01 mm or more and 0.5 mm or less. Further, the shape of the base material 21 when viewed from the front may be various shapes such as a rectangle or a square. The area of the base material 21 viewed from the front may be, for example, 2000 mm ² or more and 20000 mm ² or less.

The tin plating film (tin film) 22 covers all or part of the surface of the base material 21 . When at least a portion of the base material 21 is covered with the tin plating film 22, oxidation of the base material 21 can be suppressed. Further, in the negative electrode, a decomposition reaction of the electrolyte proceeds as a side reaction and hydrogen gas is generated, but when at least a portion of the base material 21 is covered with the tin plating film 22, the progress of such side reactions can be suppressed. . The thickness of the tin plating film 22 may be, for example, 0.1 μm or more and 5 μm or less.

The volume ratio of carbon steel in the zinc battery negative electrode 1 is preferably 8% or more, and preferably 18% or less. In addition, the volume ratio here is a value calculated by the following formula.
Volume ratio = (Volume of current collector in coated part of negative electrode material layer 3) ÷ (Volume of negative electrode material layer 3) x 100
When the volume ratio of carbon steel is 8% or more, diffusion resistance can be kept low and good discharge performance can be obtained. When the volume ratio of carbon steel is 18% or less, the influence of the relatively large electrical resistance of carbon steel can be suppressed, and good discharge performance can be obtained. Note that while the specific electrical resistance of copper (Cu) used in conventional negative electrodes for zinc batteries is 1.7×10 ^-8 (Ω・m), the specific electrical resistance of SPCC is 9.7× 10 ⁻⁸ (Ω·m).

The negative electrode material layer 3 is a layer formed of negative electrode material. The negative electrode material layer 3 is supported by the current collector 2 by filling the mesh (a plurality of holes 21a) of the current collector 2 with negative electrode material. Negative electrode material layer 3 contains a zinc-containing component. Examples of zinc-containing components include metallic zinc, zinc oxide, and zinc hydroxide. The zinc-containing component functions as a negative electrode active material in a zinc battery, and can also be referred to as a raw material for the negative electrode active material. The content of the zinc-containing component is preferably 50% by mass or more, more preferably 70% by mass or more, and even more preferably It is 75% by mass or more. The content of the zinc-containing component is preferably 95% by mass or less, more preferably 90% by mass or less, and even more preferably It is 85% by mass or less.

The negative electrode material layer 3 may further contain additives such as a binder and a conductive material. Examples of the binder include hydrophilic or hydrophobic polymers. Specifically, for example, polytetrafluoroethylene (PTFE), hydroxyethyl cellulose (HEC), carboxymethyl cellulose (CMC), polyethylene oxide, polyethylene, polypropylene, etc. can be used as the binder. The binder can be used singly or in combination. The viscosity of the binder may be, for example, 3000 to 6000 cp at room temperature (25° C.) in an aqueous solution with a concentration of 2%, and about 25 cp at room temperature (25° C.) in an aqueous solution with a concentration of 60%. The content of the binder is, for example, 0.5 to 10 parts by weight per 100 parts by weight of the zinc-containing component. Examples of the conductive material include indium compounds such as indium oxide. The content of the conductive agent is, for example, 1 to 20 parts by weight per 100 parts by weight of the zinc-containing component.

As a method for producing the negative electrode 1 for a zinc battery, for example, there is a method in which a current collector 2 is prepared, a negative electrode material paste is placed on the current collector 2, and then dried. The negative electrode material paste may be placed on the current collector, for example, by rolling the negative electrode material paste with a roller to form a sheet and pasting the sheet onto the current collector. The negative electrode material paste may be placed on the current collector 2 and/or inside the current collector 2, for example, by applying or filling the current collector 2 with the negative electrode material paste. The method of applying or filling the negative electrode material paste is not particularly limited, and may be appropriately selected depending on the shape of the current collector 2, the shape of the negative electrode material layer, etc. By drying the negative electrode material paste layer made of the negative electrode material paste, a negative electrode material layer made of the negative electrode material is formed. The density of the negative electrode material layer may be increased by pressing or the like, if necessary. The negative electrode material paste contains raw materials for the negative electrode material and a solvent (for example, water). The negative electrode material paste is obtained by adding a solvent (for example, water) to the raw material of the negative electrode material and kneading the mixture. Raw materials for the negative electrode material include zinc-containing components, additives, and the like.

Next, a nickel-zinc battery will be described as an example of the zinc battery of this embodiment in which the above negative electrode 1 for zinc batteries is used. In a nickel-zinc battery, the negative electrode is a zinc (Zn) electrode and the positive electrode is a nickel (Ni) electrode.

The nickel-zinc battery (for example, a nickel-zinc secondary battery) of this embodiment includes, for example, a battery case, an electrode group (for example, an electrode plate group), and an electrolytic solution housed in the battery case. The nickel-zinc battery may be either chemically formed or unformed. If the nickel-zinc battery is an unformed nickel-zinc battery, the electrodes (negative and positive electrodes) are unformed electrodes, and if the nickel-zinc battery is a chemically formed nickel-zinc battery, the electrodes are the chemically formed electrodes. .

The electrode group includes, for example, a negative electrode (for example, a negative electrode plate), a positive electrode (for example, a positive electrode plate), and a separator provided between the two electrodes. The electrode group may include a plurality of negative electrodes, positive electrodes, and separators. The plurality of negative electrodes and the plurality of positive electrodes may be connected, for example, with a strap. The negative electrode has the configuration of the zinc battery negative electrode 1 described above. The separator is, for example, a separator having a flat shape, a sheet shape, or the like. Examples of the separator include microporous polyolefin membranes, microporous nylon membranes, oxidation-resistant ion exchange resin membranes, recycled cellophane resin membranes, inorganic-organic separators, and polyolefin nonwoven fabrics.

The positive electrode includes a positive electrode current collector and a positive electrode material supported by the positive electrode current collector. The positive electrode current collector constitutes a current conduction path from the positive electrode material. The positive electrode current collector has a shape such as a flat plate or a sheet. The positive electrode current collector may be a three-dimensional network structure current collector made of foamed metal, expanded metal, punched metal, metal fiber felt, or the like. The positive electrode current collector is made of a material having conductivity and alkali resistance. Such materials include, for example, materials that are stable even at the reaction potential of the positive electrode (materials that have a redox potential that is more noble than the reaction potential of the positive electrode, and materials that form a protective film such as an oxide film on the surface of the substrate in an alkaline aqueous solution). (e.g., materials that are stabilized by Further, in the positive electrode, a decomposition reaction of the electrolytic solution proceeds as a side reaction and oxygen gas is generated, but a material with a high oxygen overvoltage is preferable in that it can suppress the progress of such side reactions. Specific examples of materials constituting the positive electrode current collector include platinum; nickel (foamed nickel, etc.); and metal materials plated with metal such as nickel (copper, brass, steel, etc.). Among these, a positive electrode current collector made of foamed nickel is preferably used. From the viewpoint of further improving the high rate discharge performance, it is preferable that at least a portion of the positive electrode current collector that supports the positive electrode material (positive electrode material support portion) is made of foamed nickel.

For example, the positive electrode material has a layered shape. That is, the positive electrode may have a positive electrode material layer. The positive electrode material layer may be formed on the positive electrode current collector. When the positive electrode material supporting portion of the positive electrode current collector has a three-dimensional network structure, the positive electrode material may be filled between the meshes of the current collector to form a positive electrode material layer. The positive electrode material contains a positive electrode active material containing nickel. Examples of the positive electrode active material include nickel oxyhydroxide (NiOOH) and nickel hydroxide. The positive electrode material contains, for example, nickel oxyhydroxide in a fully charged state, and nickel hydroxide in a fully discharged state. The content of the positive electrode active material may be, for example, 50 to 95% by mass based on the total mass of the positive electrode material.

The positive electrode material may further contain components other than the positive electrode active material as additives. Examples of additives include binders, conductive agents, and expansion inhibitors. Examples of the binder include hydrophilic or hydrophobic polymers. Specifically, for example, carboxymethyl cellulose (CMC), hydroxyethyl cellulose (HEC), hydroxypropyl methyl cellulose (HPMC), sodium polyacrylate (SPA), fluorine-based polymers (polytetrafluoroethylene (PTFE), etc.) are used as binders. It can be used as The content of the binder is, for example, 0.01 to 5 parts by weight based on 100 parts by weight of the positive electrode active material. Examples of the conductive agent include cobalt compounds (cobalt metal, cobalt oxide, cobalt hydroxide, etc.). The content of the conductive agent is, for example, 1 to 20 parts by weight based on 100 parts by weight of the positive electrode active material. Examples of the expansion inhibitor include zinc oxide and the like. The content of the expansion inhibitor is, for example, 0.01 to 5 parts by mass based on 100 parts by mass of the positive electrode active material.

The electrolytic solution contains, for example, a solvent and an electrolyte. Examples of the solvent include water (eg, ion-exchanged water) and the like. Examples of the electrolyte include basic compounds, such as alkali metal hydroxides such as potassium hydroxide (KOH), sodium hydroxide (NaOH), and lithium hydroxide (LiOH). The electrolytic solution may contain components other than the solvent and electrolyte, such as potassium phosphate, potassium fluoride, potassium carbonate, sodium phosphate, sodium fluoride, zinc oxide, antimony oxide, titanium dioxide, nonionic It may contain a surfactant, an anionic surfactant, etc.

The nickel-zinc battery described above can be obtained, for example, by a method including an assembly step of assembling constituent members including electrodes to obtain a nickel-zinc battery. In the assembly process, for example, first, unformed positive electrodes and unformed negative electrodes are alternately stacked with separators interposed therebetween, and the positive electrodes and the negative electrodes are connected with straps to produce an electrode group. Next, after placing this electrode group in a battery case, a lid is adhered to the top surface of the battery case to obtain an unformed nickel-zinc battery. Next, the electrolytic solution is injected into the container of the unformed nickel-zinc battery, and then left for a certain period of time. Next, a nickel-zinc battery is obtained by performing chemical conversion by charging under predetermined conditions.

Above, an example of a nickel-zinc battery (for example, a nickel-zinc secondary battery) in which the positive electrode is a nickel electrode has been explained, but a zinc battery is also a zinc-air battery (for example, a zinc-air secondary battery) in which the positive electrode is an air electrode. Alternatively, the battery may be a silver-zinc battery (for example, a silver-zinc secondary battery) in which the positive electrode is a silver oxide electrode. As the silver oxide electrode for the silver-zinc battery, a known silver oxide electrode used for silver-zinc batteries can be used. The silver oxide electrode contains, for example, silver (I) oxide. Further, as the air electrode of the zinc-air battery, a known air electrode used for zinc-air batteries can be used. The air electrode includes, for example, an air electrode catalyst, an electron conductive material, and the like. As the air electrode catalyst, an air electrode catalyst that also functions as an electron conductive material can be used.

As the air electrode catalyst, one that functions as a positive electrode in a zinc-air battery can be used, and various air electrode catalysts that can use oxygen as a positive electrode active material can be used. Air electrode catalysts include carbon-based materials with redox catalytic functions (graphite, etc.), metal materials with redox catalytic functions (platinum, nickel, etc.), and inorganic oxide materials with redox catalytic functions (perovskite-type oxides). , manganese dioxide, nickel oxide, cobalt oxide, spinel oxide, etc.). The shape of the air electrode catalyst is not particularly limited, but may be, for example, particulate. The amount of the air electrode catalyst used in the air electrode may be 5 to 70% by volume, may be 5 to 60% by volume, or may be 5 to 50% by volume, based on the total amount of the air electrode. Good too.

As the electron conductive material, a material that has conductivity and enables electron conduction between the air electrode catalyst and the separator can be used. Examples of electronically conductive materials include carbon blacks such as Ketjen black, acetylene black, channel black, furnace black, lamp black, and thermal black; graphites such as natural graphite such as flaky graphite, artificial graphite, and expanded graphite; Examples include conductive fibers such as carbon fibers and metal fibers; metal powders such as copper, silver, nickel, and aluminum; organic electronic conductive materials such as polyphenylene derivatives; and arbitrary mixtures thereof. The shape of the electron conductive material may be particulate or other shapes. The electron conductive material is preferably used in a form that provides a continuous phase in the thickness direction in the air electrode. For example, the electronically conductive material may be a porous material. Further, the electron conductive material may be in the form of a mixture or composite with the air electrode catalyst, and as described above, the air electrode catalyst may also function as the electron conductive material. The amount of the electron conductive material used in the air electrode may be 10 to 80% by volume, 15 to 80% by volume, or 20 to 80% by volume based on the total amount of the air electrode. You can.

The effects obtained by the zinc battery negative electrode 1 according to the present embodiment described above will be explained. As described above, in the zinc battery negative electrode 1 of the present embodiment, the current collector 2 includes a base material 21 mainly containing carbon steel, and a tin plating film 22 that covers at least a portion of the surface of the base material 21. and has. According to the inventor's experiments, the electrical resistivity of carbon steel is higher than that of copper, but when a tin plating film is provided on the surface of carbon steel, it can be used as a current collector for negative electrodes for zinc batteries. It can demonstrate electrical performance equivalent to or better than copper. Therefore, according to the zinc battery negative electrode 1 of the present embodiment, it is possible to provide a zinc battery negative electrode including a current collector whose main constituent material is another material that can be substituted for copper. In particular, carbon steel such as cold-rolled steel sheets (for example, SPCC) is in extremely large quantities and has abundant resources, so it is less expensive than copper. Therefore, compared to the case where the base material is made of copper, the zinc battery negative electrode 1 can be manufactured at lower cost. Further, by providing the tin plating film 22 on the surface of the base material 21 mainly containing carbon steel, it is possible to prevent oxidation of the carbon steel and extend the life of the current collector 2. can reduce hydrogen generation.

The negative electrode 1 for a zinc battery of this embodiment includes a negative electrode material layer 3 fixed to a current collector 2. In this case, the current collector 2 may have a plurality of holes 21a penetrating in the thickness direction and filled with the negative electrode material layer 3. Thereby, the negative electrode material layer 3 can be firmly fixed to the current collector 2.

As mentioned above, the base material 21 may be made of carbon steel. In other words, the base material 21 may be composed only of carbon steel. In this case, the effects of this embodiment can be more pronounced.

As mentioned above, the carbon content of the carbon steel may be 0.001% by mass or more and 0.15% by mass or less. In this case, it is possible to obtain a base material 21 that has good workability and relatively good electrical conductivity.

As mentioned above, the base material 21 may be a cold rolled steel plate. Cold-rolled steel sheets have relatively good electrical conductivity among carbon steels, so they are suitable as a material for negative electrodes for zinc batteries. In that case, the cold rolled steel plate may be SPCC. SPCC has extremely large distribution volume among cold-rolled steel sheets and is easy to obtain.

Hereinafter, the content of the present invention will be explained in more detail using examples, but the present invention is not limited to the following examples.

(Example)
[Preparation of negative electrode]
A SPCC punched metal plated with tin and having a porosity of 50% was prepared as a negative electrode current collector. Next, predetermined amounts of zinc oxide, metallic zinc, surfactant, HEC, and ion-exchanged water were weighed and mixed, and the resulting mixed solution was stirred to prepare a negative electrode material paste. At this time, the mass ratio of the solid content was adjusted to "zinc oxide: zinc metal: HEC: surfactant = 84.5:11.5:3.5:0.5". The water content of the negative electrode material paste was adjusted to 32.5% by mass based on the total mass of the negative electrode material paste. Next, the negative electrode material paste was applied onto the negative electrode current collector, and then dried at 80° C. for 30 minutes. Thereafter, pressure molding was performed using a roll press to obtain an unformed negative electrode having a negative electrode material layer.

[Preparation of electrolyte]
Potassium hydroxide (KOH) and lithium hydroxide (LiOH) were added to ion-exchanged water and mixed to prepare an electrolytic solution (potassium hydroxide concentration: 30% by mass, lithium hydroxide concentration: 1% by mass).

[Preparation of positive electrode]
A lattice made of nickel foam with a porosity of 95% was prepared, and the lattice was pressure-molded to obtain a positive electrode current collector. Next, predetermined amounts of cobalt-coated nickel hydroxide powder, cobalt metal, cobalt hydroxide, yttrium oxide, CMC, PTFE, and ion-exchanged water were weighed and mixed, and the mixed solution was stirred to prepare a positive electrode material paste. At this time, the solid content mass ratio was set to "nickel hydroxide: metallic cobalt: yttrium oxide: cobalt hydroxide: CMC: PTFE = 88:10.3:1:0.3:0.3:0.1". It was adjusted. The water content of the positive electrode material paste was adjusted to 27.5% by mass based on the total mass of the positive electrode material paste. Next, the positive electrode material paste was applied to the positive electrode material supporting portion of the positive electrode current collector, and then dried at 80° C. for 30 minutes. Thereafter, pressure molding was performed using a roll press to obtain an unformed positive electrode having a positive electrode material layer.

[Separator preparation]
For the separator, Celgard (registered trademark) 2500 was used as a microporous membrane, and VL100 (manufactured by Nippon Kokoshi Kogyo) was used as a nonwoven fabric. The microporous membrane was subjected to hydrophilic treatment using a surfactant Triton (registered trademark)-X100 (manufactured by Dow Chemical Co., Ltd.) before battery assembly. The hydrophilization treatment was performed by immersing the microporous membrane in an aqueous solution containing 1% by mass of Triton-X100 for 24 hours, and then drying it at room temperature for 1 hour. Furthermore, the microporous membrane was cut into a predetermined size, folded in half, and processed into a bag by thermally welding the sides. One positive electrode (unformed positive electrode) and one negative electrode (unformed negative electrode) were housed in a bag-shaped microporous membrane. The nonwoven fabric used was one cut to a predetermined size.

[Fabrication of nickel-zinc battery]
Two positive electrodes, each housed in a bag-shaped microporous membrane, and three negative electrodes, each housed in a bag-shaped microporous membrane, are alternately stacked, and a nonwoven fabric is sandwiched between the positive electrode and the negative electrode. An electrode group (electrode plate group) was produced by connecting electrode plates of the same polarity with each other with a strap. After placing this electrode group in a battery case, a lid was adhered to the top surface of the battery case to obtain an unformed nickel-zinc battery. Next, the electrolytic solution was injected into the container of an unformed nickel-zinc battery, and then left for 24 hours. Thereafter, charging was performed at 25 mA for 15 hours to produce a nickel-zinc battery with a nominal capacity of 350 mAh.

(Comparative example)
A nickel-zinc battery was fabricated in the same manner as in the above example except that a tin-plated copper punching metal with a porosity of 50% was used as the negative electrode current collector during fabrication of the negative electrode.

<Discharge performance evaluation>
Using the nickel-zinc batteries of Examples and Comparative Examples, the current value attenuated to 17.5 mA (0.05 C) under constant voltage conditions of a temperature of 25°C, an initial current value of 350 mA (1 C), and a voltage of 1.9 V. After charging until the battery voltage reached 1.1V, low rate discharge performance was determined by discharging at a constant current of 17.5mA (0.05C) until the battery voltage reached 1.1V. In addition, after charging the nickel-zinc batteries of Examples and Comparative Examples under the same conditions as above, the nickel-zinc batteries were charged at a constant current of 3500 mA (10.0 C) until the battery voltage reached 1.1 V. High rate discharge performance was determined by discharging. Note that the above "C" is a relative expression of the magnitude of the current when discharging the rated capacity from a fully charged state at a constant current. The above "C" means "discharge current value (A)/battery capacity (Ah)". For example, a current that can discharge the rated capacity in one hour is expressed as "1C", and a current that can discharge the rated capacity in two hours is expressed as "0.5C".

Figure 2(a) shows the discharge at each discharge rate (0.05C, 0.2C, 1.0C, 3.0C, 5.0C, and 10.0C) in the nickel-zinc batteries of the example and comparative example. It is a chart showing capacity (unit: Ah). FIG. 2(b) is a chart showing the discharge capacity retention rate (ratio to 0.05C, unit: %) for each discharge rate in the nickel-zinc batteries of the example and the comparative example. FIG. 3 is a graph showing the relationship between discharge capacity retention rate and discharge rate. In FIG. 3, graph G1 shows an example, and graph G2 shows a comparative example.

As shown in Figures 2 and 3, when tin-plated SPCC is used as the current collector of the negative electrode for zinc batteries, it can exhibit electrical performance equivalent to or better than when tin-plated copper is used. Ta. Note that it is presumed that similar results can be obtained if carbon steel has a composition similar to or close to SPCC. This example confirmed the effects of the above embodiment. Note that the actual measured value of the maximum temperature reached on the outside of the battery case of the nickel-zinc battery at a discharge rate of 5.0 C was 26.1° C. in the example and 25.9° C. in the comparative example. From these values, the maximum temperatures reached within the battery were estimated to be 43.3° C. and 42.9° C., respectively, and it was confirmed that the temperature rise was approximately the same in the Example and the Comparative Example. In addition, when the DC resistance was measured 10 seconds after the start of discharge in a 50% charged state, it was 2.39 (Ω・cm ² ) in the example, and 2.35 (Ω・cm ² ) in the comparative example. there were. From this, it was confirmed that the direct current resistance was also approximately the same between the example and the comparative example.

DESCRIPTION OF SYMBOLS 1... Negative electrode for zinc batteries, 2... Current collector, 3... Negative electrode material layer, 21... Base material, 21a... Hole, 22... Tin plating film.

Claims (7)

A negative electrode for a zinc battery comprising a current collector,
The current collector is
A base material mainly containing carbon steel,
a tin plating film covering at least a portion of the surface of the base material;
has
A negative electrode for a zinc battery, wherein a volume ratio of the carbon steel to the negative electrode for a zinc battery is 8% or more and 18% or less . further comprising a negative electrode material layer fixed to the current collector,
The negative electrode for a zinc battery according to claim 1, wherein the current collector has a plurality of holes penetrating in the thickness direction and filled with the negative electrode material layer. The negative electrode for a zinc battery according to claim 1 or 2, wherein the base material of the current collector is made of carbon steel. The negative electrode for a zinc battery according to any one of claims 1 to 3, wherein the carbon steel has a carbon content of 0.001% by mass or more and 0.15% by mass or less. The negative electrode for a zinc battery according to any one of claims 1 to 3, wherein the base material is a cold rolled steel plate. The negative electrode for a zinc battery according to claim 5, wherein the cold rolled steel plate is SPCC. The negative electrode for a zinc battery according to any one of claims 1 to 6, wherein the tin plating film has a thickness of 0.1 μm or more and 5 μm or less.

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