Nickel-zinc battery

Abstract

To provide a nickel zinc battery including a negative electrode current collector whose main constituent material is another material that can be substituted for copper.SOLUTION: A nickel zinc battery includes a positive electrode and a negative electrode having a current collector. The current collector has a base material mainly containing carbon steel, and a tin plating film that covers at least a portion of the surface of the base material. The thickness of the tin plating film is 0.1 μm or more and 5 μm or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to nickel-zinc batteries. [Background technology]

[0002] Known zinc batteries include nickel-zinc batteries, air-zinc batteries, and silver-zinc batteries. For example, nickel-zinc batteries are aqueous batteries that use an aqueous electrolyte such as a potassium hydroxide solution, and are therefore highly safe. Furthermore, due to the combination of zinc and nickel electrodes, they are known to have a high electromotive force for an aqueous battery. Furthermore, nickel-zinc batteries have excellent input / output performance and low cost, and their applicability to industrial applications (e.g., backup power sources) and automotive applications (e.g., hybrid vehicles) is being considered. Patent Document 1 discloses technology related to zinc electrode plates used as negative electrodes in sealed nickel-zinc batteries. The zinc electrode plate described in Patent Document 1 is constructed by filling a porous mat made of copper or a copper alloy, or a porous mat made by copper-plating a resin foam, with an active material containing at least one of metallic zinc and zinc oxide and a binder. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 7-6758 Summary of the Invention [Problem to be solved by the invention]

[0004] Copper has traditionally been widely used for the negative electrode current collector of zinc batteries, as in the zinc plate described in Patent Document 1. This is because copper has good electrical conductivity and high corrosion resistance. However, due to various factors, such as manufacturing costs, a negative electrode current collector whose main constituent material is another material that can be substituted for copper may be desired. One aspect of the present invention aims to provide a nickel-zinc battery having a negative electrode current collector whose main constituent material is another material that can be substituted for copper. [Means for solving the problem]

[0005] A nickel-zinc battery according to one aspect of the present invention includes a positive electrode and a negative electrode having a current collector. The current collector has a substrate mainly containing carbon steel and a tin-plated film covering at least a portion of the surface of the substrate.

[0006] In the nickel-zinc battery, the thickness of the tin plating film may be 0.1 μm or more and 5 μm or less. [Effects of the Invention]

[0007] According to one aspect of the present invention, a nickel-zinc battery can be provided that includes a negative electrode current collector whose main constituent material is a material that can be substituted for copper. [Brief explanation of the drawings]

[0008] [Figure 1] 1A and 1B are schematic diagrams showing an embodiment of a zinc battery negative electrode 1. FIG. 1A is a front view showing the zinc battery negative electrode 1, and FIG. 1B is a cross-sectional view taken along line Ib-Ib in FIG. 1A. [Figure 2] 1A is a graph showing the discharge capacity at each discharge rate for the nickel-zinc batteries of the Examples and Comparative Examples, and FIG. 1B is a graph showing the discharge capacity retention rate at each discharge rate for the nickel-zinc batteries of the Examples and Comparative Examples. [Figure 3] 1 is a graph showing the relationship between the discharge capacity retention rate and the discharge rate. DETAILED DESCRIPTION OF THE INVENTION

[0009] In this specification, a numerical range indicated with "to" indicates a range that includes the numerical values before and after "to" as the minimum and maximum values, respectively. In the numerical ranges described in stages in this specification, the upper or lower limit of a certain numerical range can be arbitrarily combined with the upper or lower limit of another numerical range. In the numerical ranges described in this specification, the upper or lower limit of the numerical range may be replaced with a value shown in the examples. "A or B" may include either A or B, or both. Unless otherwise specified, the materials exemplified in this specification can be used alone or in combination of two or more. In this specification, when multiple substances corresponding to each component are present in the composition, the content of each component refers to the total amount of the multiple substances present in the composition, unless otherwise specified. Furthermore, in this specification, the terms "film" and "layer" encompass structures that are formed over the entire surface as well as structures that are formed only partially when observed in a plan view.

[0010] Hereinafter, an embodiment of the present invention will be described in detail. However, the present invention is not limited to the following embodiment, and various modifications can be made within the scope of the gist of the present invention. 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.

[0011] FIG. 1 is a schematic diagram showing a zinc battery negative electrode 1 of this embodiment. FIG. 1(a) is a front view showing the zinc battery negative electrode 1 of this embodiment, and FIG. 1(b) is a cross-sectional view taken along line Ib-Ib in FIG. 1(a). As shown in FIGS. 1(a) and 1(b), the zinc battery negative electrode 1 includes a current collector (negative electrode current collector) 2 and a negative electrode material layer 3. The current collector 2 forms a conductive path for current from the negative electrode material layer 3. The current collector 2 includes a substrate 21 and a tin-plated film 22.

[0012] The substrate 21 mainly contains carbon steel, and in one example, is made solely of carbon steel. The structure of the substrate 21 is not particularly limited and may be, for example, a flat plate or sheet, or may have a three-dimensional mesh structure made of foam metal, expanded metal, metal fiber felt, or the like. As an example, the substrate 21 shown in the figure has multiple holes 21a penetrating the substrate 21 in the thickness direction. The multiple holes 21a are two-dimensionally dispersed and arranged in a plane perpendicular to the thickness direction of the substrate 21. In this case, the substrate 21 may be a punched metal made of carbon steel. Carbon steel is electrically conductive and alkali-resistant, and is stable even at the reaction potential of the negative electrode. The carbon (C) content of the carbon steel is, for example, 0.001% by mass or more and 0.15% by mass or less. In addition to carbon (C), the carbon steel may contain at least one of manganese (Mn), phosphorus (P), and sulfur (S). For 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) content is 0.001% by mass or more and 0.05% by mass or less. The substrate 21 may be, for example, a cold-rolled steel sheet or a processed cold-rolled steel sheet. The processing may be, for example, bending, pressing, and / or drawing. The cold-rolled steel sheet is, for example, SPCC. According to the standard, the carbon (C) content of SPCC is 0.15% by mass or less, the manganese (Mn) content is 0.60% by mass or less, the phosphorus (P) content is 0.100% by mass or less, and the sulfur (S) content is 0.050% by mass or less. The thickness of the substrate 21 may be, for example, 0.01 mm or more and 0.5 mm or less. The shape of the base material 21 as viewed from the front may be various shapes such as a rectangle or a square. The area of the base material 21 as viewed from the front may be, for example, 2000 mm 2 It may be more than 20,000 mm 2 It may be the following:

[0013] The tin plating film (tin film) 22 covers all or part of the surface of the base material 21. When at least a part of the base material 21 is covered with the tin plating film 22, oxidation of the base material 21 can be suppressed. Furthermore, at the negative electrode, a decomposition reaction of the electrolyte proceeds as a side reaction, generating hydrogen gas, but when at least a part of the base material 21 is covered with the tin plating film 22, the progress of such a side reaction 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.

[0014] The volume ratio of carbon steel in the zinc battery negative electrode 1 is preferably 8% or more and 18% or less. The volume ratio here is a value calculated by the following formula. Volume ratio = (volume of the current collector in the coated portion of the negative electrode material layer 3) ÷ (volume of the negative electrode material layer 3) × 100 When the volume fraction of carbon steel is 8% or more, the diffusion resistance can be kept low, and good discharge performance can be obtained. When the volume fraction 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 the specific electrical resistance of copper (Cu), which is used in conventional zinc battery negative electrodes, is 1.7 x 10 -8 (Ω·m), whereas the specific electrical resistivity of SPCC is 9.7×10 -8 (Ω·m).

[0015] The negative electrode material layer 3 is a layer formed from a negative electrode material. The negative electrode material layer 3 is supported on the current collector 2 by filling the spaces between the meshes (the plurality of holes 21a) of the current collector 2 with the negative electrode material. The negative electrode material layer 3 contains a zinc-containing component. Examples of the zinc-containing component include metallic zinc, zinc oxide, and zinc hydroxide. The zinc-containing component functions as a negative electrode active material in zinc batteries and can also be referred to as a raw material for the negative electrode active material. From the viewpoint of obtaining better life performance, the content of the zinc-containing component is preferably 50 mass% or more, more preferably 70 mass% or more, and even more preferably 75 mass% or more, based on the total mass of the negative electrode material. From the viewpoint of obtaining better life performance, the content of the zinc-containing component is preferably 95 mass% or less, more preferably 90 mass% or less, and even more preferably 85 mass% or less, based on the total mass of the negative electrode material.

[0016] The negative electrode layer 3 may further contain additives such as a binder (binding agent) and a conductive material. Examples of binders include hydrophilic and hydrophobic polymers. Specific examples of binders that can be used include polytetrafluoroethylene (PTFE), hydroxyethyl cellulose (HEC), carboxymethyl cellulose (CMC), polyethylene oxide, polyethylene, and polypropylene. One binder may be used alone, or multiple binders may be used in combination. The viscosity of the binder may be, for example, 3000 to 6000 cp at room temperature (25°C) in a 2% aqueous solution, or about 25 cp at room temperature (25°C) in a 60% aqueous solution. The binder content is, for example, 0.5 to 10 parts by mass relative to 100 parts by mass of the zinc-containing component. Examples of conductive materials include indium compounds such as indium oxide. The conductive material content is, for example, 1 to 20 parts by mass relative to 100 parts by mass of the zinc-containing component.

[0017] The zinc battery negative electrode 1 can be fabricated, for example, by preparing a current collector 2, disposing a negative electrode material paste on the current collector 2, and then drying the paste. The negative electrode material paste may be disposed on the current collector by, for example, rolling the negative electrode material paste with a roller to form a sheet and attaching the sheet to the current collector. The negative electrode material paste may be disposed on the current collector 2 and / or inside the current collector 2 by, for example, applying or filling the negative electrode material paste to the current collector 2. 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. A negative electrode material layer made of a negative electrode material is formed by drying a negative electrode material paste layer. The density of the negative electrode material layer may be increased by pressing, etc., as necessary. The negative electrode material paste contains a raw material for the negative electrode material and a solvent (e.g., water). The negative electrode material paste is obtained by adding a solvent (e.g., water) to the raw material for the negative electrode material and kneading the mixture. The raw materials for the negative electrode material include zinc-containing components, additives, and the like.

[0018] Next, a nickel-zinc battery will be described as an example of the zinc battery of this embodiment that uses the zinc battery negative electrode 1. In the nickel-zinc battery, the negative electrode is a zinc (Zn) electrode and the positive electrode is a nickel (Ni) electrode.

[0019] The nickel-zinc battery (e.g., nickel-zinc secondary battery) of this embodiment includes, for example, a battery case, and an electrode group (e.g., an electrode plate group) and an electrolyte housed in the battery case. The nickel-zinc battery may be either formed or unformed. When the nickel-zinc battery is an unformed nickel-zinc battery, the electrodes (negative and positive electrodes) are unformed electrodes, and when the nickel-zinc battery is a formed nickel-zinc battery, the electrodes are formed electrodes.

[0020] The electrode group includes, for example, a negative electrode (e.g., a negative electrode plate), a positive electrode (e.g., 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 to each other, for example, by straps. 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 plate shape, a sheet shape, or the like. Examples of separators include polyolefin-based microporous membranes, nylon-based microporous membranes, oxidation-resistant ion-exchange resin membranes, cellophane-based recycled resin membranes, inorganic-organic separators, and polyolefin-based nonwoven fabrics.

[0021] The positive electrode includes a positive electrode current collector and a positive electrode material supported on the positive electrode current collector. The positive electrode current collector forms a conductive path for current from the positive electrode material. The positive electrode current collector may have a shape such as a flat plate or a sheet. The positive electrode current collector may be a collector with a three-dimensional mesh structure formed from foam metal, expanded metal, punched metal, or metal fiber felt. The positive electrode current collector is made of a material that is conductive and alkali-resistant. Examples of such materials include materials that are stable even at the reaction potential of the positive electrode (e.g., materials with a redox potential higher than the reaction potential of the positive electrode, materials that form a protective coating such as an oxide coating on the substrate surface in an alkaline aqueous solution to stabilize the positive electrode). Furthermore, in the positive electrode, a decomposition reaction of the electrolyte proceeds as a side reaction, generating oxygen gas. Materials with a high oxygen overvoltage are preferred because they can suppress the progression of such side reactions. Specific examples of materials constituting the positive electrode current collector include platinum; nickel (foamed nickel, etc.); and metal materials (copper, brass, steel, etc.) plated with a metal such as nickel. Among these, a positive electrode current collector made of foamed nickel is preferably used. From the viewpoint of further improving high-rate discharge performance, it is preferable that at least the portion of the positive electrode current collector that supports the positive electrode material (positive electrode material support portion) is made of foamed nickel.

[0022] The positive electrode material is, for example, layered. That is, the positive electrode may have a positive electrode material layer. The positive electrode material layer may be formed on a positive electrode current collector. When the positive electrode material support portion of the positive electrode current collector has a three-dimensional mesh structure, the positive electrode material may be filled between the meshes of the current collector to form the 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 an end-of-discharge state. The content of the positive electrode active material may be, for example, 50 to 95 mass% based on the total mass of the positive electrode material.

[0023] The positive electrode material may further contain, as additives, components other than the positive electrode active material. Examples of additives include binders (binding agents), conductive agents, and expansion inhibitors. Examples of binders include hydrophilic or hydrophobic polymers. Specifically, for example, carboxymethyl cellulose (CMC), hydroxyethyl cellulose (HEC), hydroxypropyl methyl cellulose (HPMC), sodium polyacrylate (SPA), and fluorine-based polymers (polytetrafluoroethylene (PTFE) and the like) can be used as binders. The content of the binder is, for example, 0.01 to 5 parts by mass per 100 parts by mass of the positive electrode active material. Examples of conductive agents include cobalt compounds (metallic cobalt, cobalt oxide, cobalt hydroxide and the like). The content of the conductive agent is, for example, 1 to 20 parts by mass per 100 parts by mass of the positive electrode active material. Examples of expansion inhibitors include zinc oxide and the like. The content of the expansion inhibitor is, for example, 0.01 to 5 parts by mass with respect to 100 parts by mass of the positive electrode active material.

[0024] The electrolytic solution contains, for example, a solvent and an electrolyte. Examples of the solvent include water (e.g., ion-exchanged water). 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, a nonionic surfactant, an anionic surfactant, etc.

[0025] The nickel-zinc battery described above can be obtained, for example, by a method including an assembly step in which components including electrodes are assembled to obtain a nickel-zinc battery. In the assembly step, for example, unformed positive electrodes and unformed negative electrodes are first alternately stacked with separators interposed therebetween, and the positive electrodes and negative electrodes are connected with straps to form an electrode group. Next, this electrode group is placed in a battery case, and a lid is attached to the top of the battery case to obtain an unformed nickel-zinc battery. Next, an electrolyte is poured into the battery case of the unformed nickel-zinc battery, and the battery is left for a certain period of time. Next, the battery is charged under specified conditions to form the nickel-zinc battery.

[0026] Although an example of a nickel-zinc battery (e.g., a nickel-zinc secondary battery) in which the positive electrode is a nickel electrode has been described above, the zinc battery may also be an air-zinc battery (e.g., an air-zinc secondary battery) in which the positive electrode is an air electrode, or a silver-zinc battery (e.g., a silver-zinc secondary battery) in which the positive electrode is a silver oxide electrode. A known silver oxide electrode used in a silver-zinc battery can be used as the silver oxide electrode of a silver-zinc battery. The silver oxide electrode contains, for example, silver (I) oxide. Furthermore, a known air electrode used in an air-zinc battery can be used as the air electrode of an air-zinc battery. The air electrode contains, for example, an air electrode catalyst, an electron conductive material, etc. An air electrode catalyst that also functions as an electron conductive material can be used as the air electrode catalyst.

[0027] The air electrode catalyst can be one that functions as a positive electrode in an air-zinc battery, and various air electrode catalysts that can utilize oxygen as a positive electrode active material can be used. Examples of air electrode catalysts include carbon-based materials (such as graphite) that have redox catalytic functions, metal materials (such as platinum and nickel) that have redox catalytic functions, and inorganic oxide materials (such as perovskite-type oxides, manganese dioxide, nickel oxide, cobalt oxide, and spinel oxide) that have redox catalytic functions. The shape of the air electrode catalyst is not particularly limited, and may be, for example, particulate. The amount of the air electrode catalyst used in the air electrode may be 5 to 70 volume % of the total volume of the air electrode, 5 to 60 volume %, or 5 to 50 volume %.

[0028] The electron-conductive material may be electrically conductive and capable of conducting electrons between the air electrode catalyst and the separator. Examples of electron-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 (e.g., flake graphite), artificial graphite, and expanded graphite; conductive fibers such as carbon fiber and metal fiber; metal powders such as copper, silver, nickel, and aluminum; organic electron-conductive materials such as polyphenylene derivatives; and mixtures of any of these. The electron-conductive material may be in particulate form or other shapes. It is preferable that the electron-conductive material be used in a form that provides a continuous phase in the thickness direction of the air electrode. For example, the electron-conductive material may be a porous material. The electron-conductive material may also be in the form of a mixture or composite with the air electrode catalyst, or, as described above, may be an air electrode catalyst that also functions as an 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 relative to the total volume of the air electrode.

[0029] The effects obtained by the zinc battery negative electrode 1 according to the present embodiment described above will be described. As described above, in the zinc battery negative electrode 1 according to the present embodiment, the current collector 2 includes a substrate 21 primarily containing carbon steel and a tin-plated film 22 covering at least a portion of the surface of the substrate 21. Experiments conducted by the inventors have shown that the electrical resistivity of carbon steel is higher than that of copper. However, when a tin-plated film is provided on the surface of carbon steel, the current collector for a zinc battery negative electrode can exhibit electrical performance equal to or superior to that of copper. Therefore, the zinc battery negative electrode 1 according to the present embodiment can provide a zinc battery negative electrode having a current collector primarily composed of a material that can be substituted for copper. In particular, carbon steel, such as cold-rolled steel sheet (e.g., SPCC), is widely distributed and abundantly available, making it less expensive than copper. Therefore, the zinc battery negative electrode 1 can be manufactured at lower cost than when the substrate is made of copper. Furthermore, by providing a tin-plated film 22 on the surface of the substrate 21, which mainly contains carbon steel, oxidation of the carbon steel can be prevented, thereby extending the life of the current collector 2 and reducing the generation of hydrogen on the surface of the current collector 2.

[0030] The zinc battery negative electrode 1 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 that penetrate through the current collector 2 in the thickness direction and are filled with the negative electrode material layer 3. This allows the negative electrode material layer 3 to be firmly fixed to the current collector 2.

[0031] As described above, the substrate 21 may be made of carbon steel. In other words, the substrate 21 may be made of only carbon steel. In this case, the effect of this embodiment can be more pronounced.

[0032] As described above, the carbon content of the carbon steel may be 0.001% by mass or more and 0.15% by mass or less, in which case the substrate 21 can be obtained with good workability and relatively good electrical conductivity.

[0033] As described above, the substrate 21 may be a cold-rolled steel sheet. The electrical conductivity of cold-rolled steel sheets is relatively good among carbon steels, making them suitable as materials for zinc-coated battery negative electrodes. In this case, the cold-rolled steel sheet may be SPCC. SPCC is one of the cold-rolled steel sheets that is in extremely high circulation and is easy to obtain. [Example]

[0034] The present invention will be described in more detail below using examples, but the present invention is not limited to the following examples.

[0035] (Example) [Preparation of negative electrode] A tin-plated SPCC punched metal with 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 mixture was stirred to prepare a negative electrode material paste. The mass ratio of the solids was adjusted to "zinc oxide: metallic zinc: HEC: surfactant = 84.5:11.5:3.5:0.5." The moisture content of the negative electrode material paste was adjusted to 32.5 mass% based on the total mass of the negative electrode material paste. The negative electrode material paste was then applied to a negative electrode current collector and dried at 80°C for 30 minutes. It was then pressure-molded using a roll press to obtain an unformed negative electrode having a negative electrode material layer.

[0036] [Preparation of electrolyte] Potassium hydroxide (KOH) and lithium hydroxide (LiOH) were added to ion-exchanged water and mixed to prepare an electrolyte solution (potassium hydroxide concentration: 30 mass %, lithium hydroxide concentration: 1 mass %).

[0037] [Preparation of positive electrode] A grid made of foamed nickel with a porosity of 95% was prepared and pressure-molded to obtain a positive electrode current collector. Next, predetermined amounts of cobalt-coated nickel hydroxide powder, metallic cobalt, cobalt hydroxide, yttrium oxide, CMC, PTFE, and ion-exchanged water were weighed and mixed, and the mixture was stirred to produce a positive electrode material paste. The mass ratio of the solids was adjusted to "nickel hydroxide: metallic cobalt: yttrium oxide: cobalt hydroxide: CMC: PTFE = 88:10.3:1:0.3:0.3:0.1." The moisture content of the positive electrode material paste was adjusted to 27.5 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 support portion of the positive electrode current collector and then dried at 80°C for 30 minutes. The mixture was then pressure-molded using a roll press to obtain an unformed positive electrode having a positive electrode material layer.

[0038] [Preparing the separator] For the separator, Celgard® 2500 was used as the microporous membrane, and VL100 (manufactured by Nippon Kodoshi Kogyo Co., Ltd.) was used as the nonwoven fabric. The microporous membrane was hydrophilized using the surfactant Triton®-X100 (manufactured by The Dow Chemical Company) before battery assembly. The hydrophilization was performed by immersing the microporous membrane in an aqueous solution containing 1% by mass of Triton-X100 for 24 hours, followed by drying at room temperature for 1 hour. The microporous membrane was then cut to a predetermined size, folded in half, and processed into a bag shape by heat welding the sides. One positive electrode (unformed positive electrode) and one negative electrode (unformed negative electrode) were housed in the bag-shaped microporous membrane. The nonwoven fabric used was cut to a predetermined size.

[0039] [Preparation of nickel-zinc battery] Two positive electrodes, each housed in a microporous membrane pouch, and three negative electrodes, each housed in a microporous membrane pouch, were alternately stacked, a nonwoven fabric was sandwiched between the positive and negative electrodes, and plates of the same polarity were connected with a strap to form an electrode assembly (plate assembly). This electrode assembly was placed in a battery case, and a lid was attached to the top of the battery case to obtain an unformed nickel-zinc battery. Next, electrolyte was poured into the battery case and left for 24 hours. The battery was then charged at 25 mA for 15 hours to produce a nickel-zinc battery with a nominal capacity of 350 mAh.

[0040] (Comparative Example) A nickel-zinc battery was fabricated in the same manner as in the above example, except that a tin-plated copper punched metal with a porosity of 50% was used as the negative electrode current collector when fabricating the negative electrode.

[0041] <Discharge performance evaluation> The nickel-zinc batteries of the Examples and Comparative Examples were charged under constant voltage conditions of 25°C, an initial current of 350 mA (1 C), and a voltage of 1.9 V until the current decayed to 17.5 mA (0.05 C), and then discharged at a constant current of 17.5 mA (0.05 C) until the battery voltage reached 1.1 V. Low-rate discharge performance was determined by this. The nickel-zinc batteries of the Examples and Comparative Examples were charged under the same conditions as above, and then discharged at a constant current of 3500 mA (10.0 C) until the battery voltage reached 1.1 V. The "C" above represents the relative magnitude of the current when the rated capacity is discharged at a constant current from a fully charged state. The "C" above refers to "discharge current value (A) / battery capacity (Ah)." For example, a current that can discharge the rated capacity in 1 hour is expressed as "1 C," and a current that can discharge the rated capacity in 2 hours is expressed as "0.5 C."

[0042] FIG. 2(a) is a graph showing the discharge capacity (unit: Ah) for each discharge rate (0.05 C, 0.2 C, 1.0 C, 3.0 C, 5.0 C, and 10.0 C) for each of the nickel-zinc batteries of the Examples and Comparative Examples. FIG. 2(b) is a graph showing the discharge capacity retention rate (percentage relative to 0.05 C, unit: %) for each discharge rate for each of the nickel-zinc batteries of the Examples and Comparative Examples. FIG. 3 is a graph showing the relationship between the discharge capacity retention rate and the discharge rate. In FIG. 3, graph G1 shows the Examples, and graph G2 shows the Comparative Examples.

[0043] As shown in Figures 2 and 3, when tin-plated SPCC was used as the current collector for the negative electrode of a zinc battery, electrical performance equivalent to or better than that achieved when tin-plated copper was used was achieved. It is presumed that similar results would be achieved if carbon steel with a composition similar to or close to that of SPCC was used. This example confirmed the effects of the above-mentioned embodiment. The maximum temperature actually measured 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 achieved inside 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. Furthermore, when the DC resistance was measured 10 seconds after the start of discharge at a 50% charge state, it was 2.39 (Ω·cm) in the example. 2 ) in the comparative example, and 2.35 (Ω cm 2 ) This confirmed that the DC resistance was also approximately the same between the example and the comparative example.

[0044] [Note] The above-mentioned zinc battery negative electrode is a zinc battery negative electrode including a current collector, and the current collector has a substrate mainly containing carbon steel and a tin-plated film covering at least a portion of the surface of the substrate. The zinc battery negative electrode may further include a negative electrode material layer fixed to a current collector, and the current collector may have a plurality of holes that penetrate through the thickness direction and are filled with the negative electrode material layer. In the above-mentioned negative electrode for a zinc battery, the substrate of the current collector may be made of carbon steel. In the above zinc battery negative electrode, 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 zinc battery negative electrode, the substrate may be a cold-rolled steel sheet, and in that case, the cold-rolled steel sheet may be SPCC. [Explanation of symbols]

[0045] 1...zinc battery negative electrode, 2...current collector, 3...negative electrode material layer, 21...substrate, 21a...hole, 22...tin-plated film

Claims

1. A positive electrode and a negative electrode having a current collector and a negative electrode material layer fixed to the current collector, The current collector is a substrate consisting solely of carbon steel; a tin plating film covering at least a portion of the surface of the base material; and A nickel-zinc battery, wherein the carbon content of the carbon steel is 0.001% by mass or more and 0.15% by mass or less.

2. 2. The nickel-zinc battery according to claim 1, wherein the thickness of the tin plating film is 0.1 μm or more and 5 μm or less.

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