Zinc fuel, method and apparatus for producing zinc fuel, and system for regenerating zinc fuel

Abstract

To provide a zinc fuel which can be manufactured by regeneration of zinc oxide, is easy to handle and store, and is easy to secure contact with a current collector, and to provide its manufacturing method.SOLUTION: The zinc fuel 2 has a support 3 whose surface is formed by a current collector 5, and a negative electrode active material layer 4 covering the surface of the support 3. The negative electrode active material layer 4 is a generated zinc layer formed by dendritic crystals of zinc or a zinc alloy deposited on the surface of the support 3, in which some of the dendritic crystals are crushed and densified, and voids are provided between the crushed dendritic crystals. For example, a long sheet 6 is used as the support 3, and the sheet 6 is immersed in the zinc deposition bath 21 to deposit dendritic crystals on the surface by electrolysis of zinc oxide. The sheet 6 is drawn out from the zinc deposition tank 21, and after a negative electrode active material layer 4 is formed by densifying the generated zinc layer by a press mechanism 23, it is wound in a roll shape to manufacture the zinc fuel 2.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a zinc fuel and a method for producing the same, a zinc fuel production apparatus, and a zinc fuel regeneration system. [Background technology]

[0002] As the use of renewable energy is encouraged, attention is being paid to energy storage technologies that temporarily store unstable renewable energy. For example, lithium-ion batteries are used, but as the distribution volume and scale of lithium-ion batteries increase, the risk of secondary disasters in the event of a breakdown becomes an issue.

[0003] Batteries that extract power through chemical reactions of metals in an electrolyte include those that use various metals, but zinc-air batteries are known as batteries with high energy density. Because zinc-air batteries use oxygen in the air as the positive electrode active material, there is no need to install a positive electrode active material inside the container. However, the zinc-air batteries that are commonly available are primary batteries, and no technology has been developed to make them rechargeable. Therefore, they are difficult to use as energy storage systems.

[0004] As a method for using an air-zinc battery as a battery in a power storage system, a method has been proposed in which, instead of charging the air-zinc battery, zinc, which is a new negative electrode active material, is supplied from the outside. For example, Patent Document 1 describes a flow-type air-zinc battery equipped with a zinc slurry negative electrode system in which a zinc slurry storage tank and a negative electrode current collector are connected by a flow path. Furthermore, Patent Document 2 describes a mechanical charging-type air-zinc battery in which a storage portion for storing metal zinc powder and a supply port are provided in the negative electrode.

[0005] The flow-type zinc-air battery described in Patent Document 1 requires large auxiliary equipment, such as a pump, to supply zinc slurry, making it difficult to miniaturize. On the other hand, the mechanical charging system does not require auxiliary equipment to supply metallic zinc powder, and the size of the storage area can be designed to any size, making it possible to miniaturize and practical.

[0006] In the following description, a zinc fuel cell refers to a battery that does not package zinc, the negative electrode active material, in the battery but can be supplied from the outside, as in Patent Documents 1 and 2. When using a mechanical charging type zinc fuel cell, from the viewpoint of utilizing renewable energy, it is expected that the zinc oxide produced by the discharge of the battery can be regenerated and reused as zinc fuel. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Patent No. 6290509 [Patent Document 2] Patent No. 6716308 Summary of the Invention [Problem to be solved by the invention]

[0008] One method for utilizing zinc oxide produced by the discharge reaction of a battery using zinc as the negative electrode active material for the regeneration of zinc fuel is to precipitate zinc by the reduction reaction of zinc oxide through electrolysis. However, dendritic crystals of zinc are difficult to handle because they are brittle. In addition, dendritic crystals have a specific surface area of Because it is so large, it is prone to spontaneous oxidation when stored in the atmosphere, and there is a risk of fire due to oxidation heat.

[0009] Furthermore, in a mechanical charging zinc fuel cell, it is necessary to ensure that the zinc fuel supplied from the outside can make electrical contact with the current collector placed on the negative electrode. For example, in Patent Document 2, a current collector is placed on the bottom surface of a storage area where metallic zinc powder is placed. However, only the powder in contact with the bottom surface can make contact with the current collector. Therefore, there is a risk that electrical contact with the current collector will be insufficient.

[0010] In view of the above, the object of the present invention is to propose a zinc fuel that can be efficiently produced from zinc oxide, is easy to handle, store, and refill into a battery, and easily ensures contact with the current collector, a method for producing the same, a zinc fuel production apparatus, and a zinc fuel regeneration system. [Means for solving the problem]

[0011] In order to solve the above problem, one aspect of the zinc fuel of the present invention has a support having at least a surface formed from a conductive current collector, and a negative electrode active material layer covering the surface of the support, wherein the negative electrode active material layer is a generated zinc layer formed from dendritic crystals of zinc or zinc alloy precipitated on the surface of the support, and the generated zinc layer is characterized in that at least a portion of the dendritic crystals are crushed and densified, and that there are voids between the crushed dendritic crystals.

[0012] In addition, one aspect of the method for producing zinc fuel according to the present invention is a method for producing zinc fuel having a support having at least a surface formed from a conductive collector and a negative electrode active material layer covering the surface of the support, characterized in that the support is immersed in an electrolyte containing zinc oxide, the zinc oxide is reduced, and dendritic crystals of zinc or a zinc alloy are precipitated on the surface of the support to form a generated zinc layer, and after forming the generated zinc layer, or during the formation of the generated zinc layer, at least a portion of the dendritic crystals are crushed to densify them, and voids are left between the crushed dendritic crystals to form the negative electrode active material layer.

[0013] The zinc fuel and its manufacturing method according to the present invention form a zinc layer by precipitating zinc dendritic crystals on the surface of a current collector. Therefore, electrical contact between the zinc and the current collector can be ensured. Furthermore, the zinc layer is densified, increasing the crystal density and making it less likely to fall off, making it easy to handle and store the zinc fuel and charge it into a zinc fuel cell. Furthermore, because the zinc layer is densified to the extent that voids remain between the crystals, it is possible to ensure a sufficient contact area with the electrolyte, which has the advantage of high reactivity. Furthermore, the zinc layer can be formed using plating techniques and equipment. Therefore, zinc fuel can be manufactured efficiently.

[0014] The current collector only needs to be provided on the surface of the support. Therefore, the support can be manufactured using various metals or resin materials as the base material, and the current collector layer can be provided on the surface of the base material by plating. When a resin material is used as the base material, the current collector layer can be provided on the surface by electroless plating.

[0015] In the zinc fuel according to the present invention, the current collector is preferably made of at least one metal selected from the group consisting of copper, tin, lead, indium, and bismuth. Alternatively, it may be an alloy of these metals. These metals have a high hydrogen generation overvoltage, equivalent to that of zinc. Therefore, it is possible to suppress the hydrogen generation type dissolution reaction of zinc at the negative electrode, and to suppress the decrease in battery capacity due to the progression of the self-discharge reaction. Furthermore, these metals have good corrosion resistance to alkalis. Therefore, when an alkaline electrolyte is used as the electrolyte and the support is made of metal, corrosion of the support can be suppressed.

[0016] In the zinc fuel according to the present invention, the weight ratio of the negative electrode active material layer to the total weight is preferably 10% or more. Here, the weight ratio of the negative electrode active material layer is more preferably 20% or more, and even more preferably 50% or more. By using a manufacturing method that grows dendritic crystals, it is possible to support a large amount of zinc and increase the amount of electricity that can be extracted. Therefore, it is suitable for use as an electricity storage system that stores electrical energy in the form of zinc.

[0017] In the zinc fuel according to the present invention, the negative electrode active material layer is preferably a zinc alloy containing any of copper, tin, indium, and bismuth. As described above, the use of these metals can suppress hydrogen generation and the decrease in battery capacity due to the progression of self-discharge reactions.

[0018] In the zinc fuel according to the present invention, it is preferable that the support is a long sheet, and that the sheet having the negative electrode active material layer formed on its surface is wound into a roll. Also, in the method for producing zinc fuel according to the present invention, it is preferable that the support is a long sheet, and that the sheet is immersed in a zinc deposition tank containing the electrolytic solution to form the zinc layer on the surface of the sheet, and the sheet with the zinc layer laminated on its surface is pulled out from the zinc deposition tank and passed through a press mechanism during transport, and then the sheet is wound up to form a roll.

[0019] In this way, by using a sheet-like support, the surface area of ​​the support can be secured. Therefore, a large amount of zinc can be supported. Furthermore, by rolling it into a roll, handling and storage become easier, and it becomes easier to input into a zinc fuel cell. Furthermore, by using a hoop plating method and equipment, the process from forming the zinc layer to winding can be performed in a continuous, integrated process. In this case, the process can be performed in an integrated manner, including the press mechanism. For example, the zinc layer can be crushed and densified by passing it between rolls after removal from the zinc deposition tank.

[0020] In order to carry out such a zinc fuel production method, one aspect of the zinc fuel production apparatus according to the present invention comprises a zinc deposition tank, an anode and a cathode disposed in the zinc deposition tank, a sheet transport mechanism for transporting a support consisting of a long sheet with a conductive current collector on its surface through the zinc deposition tank, a press mechanism disposed downstream of the zinc deposition tank in the sheet transport path, and a winding mechanism disposed downstream of the press mechanism, wherein the press mechanism crushes and flattens the resulting zinc layer composed of dendritic crystals of zinc or zinc alloy deposited on the surface of the sheet in the zinc deposition tank, and the winding mechanism winds up the sheet and the resulting zinc layer that have passed through the press mechanism to form a wound body. It is preferable to provide a rinsing tank between the press mechanism and the winding mechanism, and perform a drying process after removing the sheet from the rinsing tank and before winding.

[0021] In the zinc fuel according to the present invention, the thickness of the sheet is preferably 1 mm or less. By reducing the thickness of the sheet, winding becomes easier, and the wound body can be easily manufactured. Furthermore, the weight ratio of the negative electrode active material can be increased. The thickness of the sheet is more preferably 0.1 mm or less, and even more preferably 0.05 mm or less.

[0022] In the zinc fuel according to the present invention, the sheet is preferably porous. For example, it is preferably a mesh sheet, a lath sheet, or a punched sheet. These have a large surface area, so they can support a large amount of zinc, and the weight of the negative electrode active material is reduced. The amount of zinc can be increased. Also, if the sheet is porous, the resulting zinc layer is less likely to fall off from the sheet. Furthermore, when immersed in an electrolyte bath, a zinc fuel can be produced in which the electrolyte flows through the sheet. Therefore, reactivity is improved.

[0023] In the method for producing zinc fuel according to the present invention, the electrolyte is preferably an alkaline aqueous solution. By using an alkaline electrolyte, the rate of formation of dendrite crystals due to the reduction reaction of zinc oxide can be increased.

[0024] In the method for producing zinc fuel according to the present invention, it is preferable that the electrolyte contains a leveling agent, which can reduce the unevenness of the produced zinc layer.

[0025] Next, one aspect of the zinc fuel regeneration system according to the present invention is a zinc fuel regeneration system comprising a zinc fuel cell having an electrolyte tank and an anode and a cathode placed in the electrolyte tank, and a zinc fuel production device, wherein the zinc fuel cell has a zinc fuel storage section at the anode that can supply zinc fuel produced by the zinc fuel production device from the outside, and the zinc fuel production device comprises a zinc deposition tank to which an electrolyte containing zinc oxide is supplied, and a press mechanism, the zinc deposition tank is provided with an anode and a cathode, and the cathode is supplied with a support formed of a conductive current collector at least on its surface, and at the cathode, a reduction reaction of the zinc oxide by electrolysis precipitates dendritic crystals of zinc or zinc alloy on the surface of the support to form a zinc layer, and the press mechanism crushes at least a portion of the dendritic crystals to densify them when the support with the zinc layer formed on its surface passes through the press mechanism, and leaves gaps between the crushed dendritic crystals.

[0026] In this way, by combining a mechanical charging zinc fuel cell with a zinc fuel production device that produces zinc fuel by electrolysis of an electrolyte containing zinc oxide to precipitate zinc or a zinc alloy, it is possible to construct an energy circulation system using zinc as an energy carrier. Furthermore, zinc fuel is easy to handle, store, and charge into the battery, ensures contact with the current collector, and has a highly reactive structure. It can be efficiently produced using zinc oxide as a raw material through a continuous, integrated process. Therefore, energy circulation using zinc as an energy carrier can be efficiently performed.

[0027] In the zinc fuel regeneration system according to the present invention, it is preferable that the support is a long sheet, the zinc fuel is a rolled body formed by rolling up the sheet with a negative electrode active material layer made of the produced zinc layer on its surface, and the zinc fuel storage unit is capable of accommodating the rolled body. It is also preferable that the positive electrode is an air electrode. This eliminates the need to replenish the positive electrode active material. [Effects of the Invention]

[0028] According to the present invention, it is possible to provide a zinc fuel that can be easily produced from zinc oxide, is easy to handle, store, and refill into a battery, and easily ensures contact with a current collector, and a method for producing the same.Furthermore, it is possible to efficiently regenerate the zinc fuel, and to efficiently circulate energy using zinc as an energy medium. [Brief explanation of the drawings]

[0029] [Figure 1] FIG. 1 is a system configuration diagram that schematically illustrates a zinc fuel regeneration system. [Figure 2] 1A and 1B are a side view and a cross-sectional view schematically showing a zinc fuel; [Figure 3] FIG. 1 is an explanatory diagram schematically showing a zinc fuel production apparatus. [Figure 4] 1 is a scanning electron microscope (SEM) image of the resulting zinc layer after pressing. [Figure 5]1A and 1B are explanatory diagrams of a method for manufacturing a test specimen used in a discharge test and an air battery cell. [Figure 6] 1 is a table showing the configuration of the test specimen and the test results. [Figure 7] 1 is a scanning electron microscope (SEM) image of the zinc slurry of Comparative Example 2. DETAILED DESCRIPTION OF THE INVENTION

[0030] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The embodiment described below is a form in which zinc fuel is input into a zinc-air battery to supply electricity. Note that the zinc fuel cell according to the present invention, which inputs zinc fuel to supply electricity, is not limited to an air zinc battery.

[0031] (Zinc fuel regeneration system) FIG. 1 is a system configuration diagram that schematically shows a zinc fuel regeneration system 1. The zinc fuel regeneration system 1 includes a zinc fuel cell 10 and a zinc fuel production device 20. In the zinc fuel regeneration system 1, zinc oxide produced by a discharge reaction in the zinc fuel cell 10 is regenerated as zinc fuel 2 by electrolysis in the zinc fuel production device 20. The zinc fuel 2 can be stored in the atmosphere and is supplied to the zinc fuel cell 10 as needed. Therefore, the zinc fuel regeneration system 1 is an energy circulation system that uses zinc as an energy medium.

[0032] (Zinc fuel cell) FIG. 1 shows a schematic diagram of an example of the configuration of a zinc fuel cell 10. The zinc fuel cell 10 includes a zinc fuel storage section 11 that can be replenished with zinc fuel 2 from the outside. The zinc fuel cell 10 includes a negative electrode 12, a positive electrode 13, and an electrolyte tank 14. The positive electrode 13 includes a positive electrode current collector connected to the positive electrode terminal. The negative electrode 12 includes a negative electrode current collector connected to the negative electrode terminal. The positive electrode 13 is an air electrode. The positive electrode 13 can be provided, for example, on the side of the electrolyte tank 14. Note that the zinc fuel cell 10 is not limited to the configuration shown in FIG. 1 as long as it includes a zinc fuel storage section 11.

[0033] The zinc fuel reservoir 11 is provided on the negative electrode 12. The zinc fuel reservoir 11 holds the zinc fuel 2 in contact with the electrolyte. For example, the zinc fuel reservoir 11 has a portion that contacts the electrolyte formed by a mesh-like or punched negative electrode current collector.

[0034] The electrolyte tank 14 contains an electroconductive electrolyte. The electrolyte is not particularly limited, but an organic solvent-based electrolyte, an aqueous electrolyte, or a mixture thereof can be used. For example, as an alkaline aqueous electrolyte, an aqueous potassium hydroxide solution, an aqueous sodium hydroxide solution, an aqueous lithium hydroxide solution, an aqueous zinc sulfate solution, an aqueous zinc nitrate solution, an aqueous zinc phosphate solution, an aqueous zinc acetate solution, or a mixture thereof can be used. The electrolyte may further contain other inorganic and organic additives.

[0035] (Zinc fuel and its manufacturing method) FIG. 2 shows a side view and a cross-sectional view of a zinc fuel 2. The zinc fuel 2 includes a support 3 and an anode active material layer 4 covering the surface of the support 3. As described below, the anode active material layer 4 includes a zinc layer formed from dendritic crystals of zinc or a zinc alloy deposited by electrolysis of zinc oxide. When the zinc layer is formed from a zinc alloy, the zinc alloy preferably contains copper, tin, indium, or bismuth. These metals can suppress the hydrogen-generating dissolution reaction of zinc in an alkaline electrolyte. These metals also have high resistance to corrosion by alkali. Therefore, when the support 3 is formed from a metal and an alkaline electrolyte is used as the electrolyte during discharge, corrosion of the support 3 can be suppressed.

[0036] As will be described later, the resulting zinc layer is densified by crushing some of the dendritic crystals of zinc or zinc alloy. Voids remain between the crushed dendritic crystals. The process of crushing the dendritic crystals may be carried out after the resulting zinc layer is formed, or may be carried out during the formation of the resulting zinc layer.

[0037] At least the surface of the support 3 needs to be formed by the current collector 5. The current collector 5 only needs to be electrically conductive, but is preferably a metal that does not undergo a reaction that generates hydrogen in the electrolyte when in contact with zinc. Examples of such metals that can be used include copper, tin, lead, indium, or bismuth, or alloys of these metals. For example, the current collector 5 may be a layer of a single metal, or may be a laminate of multiple metal layers. When multiple layers are laminated, each layer should be made of one of the above metals (copper, tin, lead, indium, and bismuth).

[0038] The support 3 may be entirely made of the current collector 5, or may be made of a metal different from the current collector 5, or a non-metallic substrate such as a resin material, with a current collector 5 layer formed on the surface. For example, the current collector 5 layer can be formed on the surface by plating. Examples of resin materials that can be used include PP (polypropylene), PE (polyethylene), nylon, PPS (polyphenylene sulfide), and ABS (acrylonitrile butadiene styrene). When the substrate is made of a resin material, the current collector 5 layer can be formed on the surface by electroless plating.

[0039] The weight ratio of the negative electrode active material layer 4 to the total weight of the zinc fuel 2 is 10% or more, more preferably 20% or more, and even more preferably 50% or more. The zinc fuel 2 of this embodiment grows dendritic crystals on the surface of the current collector 5, so a large amount of zinc can be supported. Supporting a large amount of zinc increases the amount of electricity that can be extracted. Therefore, it is suitable for an electricity storage system that stores electrical energy in the form of zinc.

[0040] In the example shown in Fig. 2, the support 3 is a long strip-shaped sheet 6. At least one surface of the sheet 6 is formed by a current collector 5. The zinc fuel 2 is a rolled body obtained by winding a laminate in which a negative electrode active material layer 4 made of a produced zinc layer is laminated on at least one surface of the sheet 6.

[0041] By using the sheet 6 as the support 3, it is possible to secure a surface area and support a large amount of zinc. The size of the wound body can be determined appropriately taking into consideration handling, storage, and the size of the zinc fuel reservoir 11 to be loaded.

[0042] For winding into a roll, the thickness of the sheet 6 is preferably thin. By making the sheet 6 thin, winding becomes easier, and the wound body can be easily manufactured. Furthermore, if the sheet 6 is thin, the weight ratio of the negative electrode active material layer 4 to the total weight of the zinc fuel 2 can be increased. The thickness of the sheet 6 is preferably 1 mm or less, more preferably 0.1 mm or less, and even more preferably 0.05 mm or less.

[0043] The width of the sheet 6 is not particularly limited, but is preferably 2 cm or less, since if the width is too wide, unevenness may occur in the negative electrode active material layer 4 and uniformity may not be ensured. The length of the sheet 6 can be set to a length corresponding to the size (diameter of the wound body) of the zinc fuel 2 to be produced.

[0044] The sheet 6 may be a sheet without holes, but is preferably porous. For example, a mesh sheet, a lath sheet, or a punched sheet can be used. This increases the surface area and allows a large amount of zinc to be supported. Furthermore, holes are also formed in the zinc layer at the positions of the holes in the sheet, so when the sheet is immersed in the electrolyte, the electrolyte flows in a direction penetrating the zinc fuel 2. This allows the electrolyte to pass through the inside of the zinc fuel 2, improving reactivity.

[0045] (Zinc fuel production equipment) FIG. 3 is an explanatory diagram schematically showing a zinc fuel manufacturing apparatus 20. The zinc fuel manufacturing apparatus 20 includes a zinc deposition tank 21 that receives an electrolyte containing zinc oxide, and a sheet conveying mechanism 22 that conveys a sheet 6 through the zinc deposition tank 21. In the conveying path of the sheet conveying mechanism 22, a press mechanism 23, a rinse tank 24, a drying mechanism 25, and a winding mechanism 26 are arranged in this order downstream of the zinc deposition tank 21. The press mechanism 23 is composed of, for example, rollers that sandwich and convey the sheet 6. In this case, a part of the sheet conveying mechanism 22 doubles as the press mechanism 23. However, the press mechanism 23 is not limited to this configuration.

[0046] The zinc fuel production device 20 produces zinc fuel 2 by a RtoR method in which a sheet 6 is unwound from a roll of sheet material in the upstream stage of the zinc deposition tank 21, and in the final process is wound up by a winding mechanism 26. Therefore, zinc fuel 2 can be produced by a continuous, integrated process.

[0047] An anode and a cathode (not shown) are placed in the zinc deposition tank 21, and a reduction reaction of zinc oxide is carried out at the cathode by electrolysis. As a result, dendritic crystals of zinc or zinc alloy are precipitated on the surface of the sheet 6 supplied to the cathode, forming a zinc layer. After the sheet 6 with the zinc layer formed thereon is removed from the zinc deposition tank 21, it passes through a pressing mechanism 23. During this process, the zinc layer is mechanically flattened, and some of the dendritic crystals are crushed and densified. This forms the negative electrode active material layer 4.

[0048] In the zinc deposition tank 21, when the reduction reaction of zinc oxide is carried out by electrolysis, either an acid or an alkali electrolyte can be used as the electrolyte, and there is no particular limitation as long as it can dissolve zinc as ions. However, the use of an alkaline electrolyte can speed up the rate at which zinc is produced by the reduction reaction of zinc oxide. Therefore, the electrolyte is preferably an alkaline aqueous solution. It is also preferable to add a leveling agent to the electrolyte to smooth out any unevenness in the zinc.

[0049] Figure 4 is a scanning electron microscope (SEM) image of the resulting zinc layer after pressing. As shown in the enlarged image of Figure 4, the resulting zinc layer after pressing is entirely flattened, and the dendrite-like crystals are crushed and densified. Voids remain between the crushed dendrite-like crystals.

[0050] The negative electrode active material layer 4 of this embodiment is a zinc layer formed from crystals precipitated by electrolysis. Therefore, as can be seen from FIG. 4, unlike zinc slurry (see FIG. 7 described later), which is made by mixing zinc powder (zinc fine particles) with a binder and applying it to an electrode, this layer does not contain a binder, and the voids are not filled with the binder. Furthermore, the dendritic crystals have a different shape from zinc powder. Therefore, the zinc layer and zinc slurry can be clearly distinguished.

[0051] (Discharge experiment) A test specimen with a negative electrode active material layer formed on the surface of a current collector by regenerating zinc oxide was placed in an air battery cell and a discharge test was conducted to verify the difference in discharge capacity compared to the comparative example. Storage stability in the atmosphere was also verified. The upper diagram in Figure 5 is an explanatory diagram of the manufacturing method for the test specimen used in the discharge test. The lower diagram in Figure 5 is an explanatory diagram of the air battery cell used in the discharge test. Figure 6 is a table showing the configuration of the test specimen and the test results. Figure 7 is a scanning electron microscope (SEM) image of the zinc slurry of Comparative Example 2.

[0052] Examples 1 to 10 and Comparative Examples 1 to 3 shown in FIG. 6 were prepared as specimens for the discharge test. Examples 1 to 10 are specimens in which a zinc layer is formed on the surface of a current collector, which is then densified by a pressing process and used as the negative electrode active material. Comparative Example 1 is a specimen in which a commercially available zinc plate is used as the negative electrode active material. Comparative Example 2 is a specimen in which a zinc slurry in which zinc powder and a binder are mixed in a ratio of 5:2 is used. The test specimen used was a zinc layer that had not been densified by a pressing process.

[0053] The specimens of Examples 1 to 10 and Comparative Example 3 were produced by the method described below. As shown in the upper diagram of FIG. 5, a 200 mL beaker 31 was used as a zinc deposition bath. An aqueous potassium hydroxide solution was introduced into the beaker 31 as an electrolyte, and 15 g of zinc oxide, the raw material for zinc, was then introduced thereto. A nickel mesh was arranged circumferentially along the outer wall of the beaker 31 as the counter electrode 32. A copper mesh with a lead wire attached was placed at the center of the counter electrode 32 as the working electrode 33. The copper mesh had a wire diameter of 100 μm and a size of 2 cm × 2 cm. A graphite rod was placed as the reference electrode 34, away from the counter electrode 32 and the working electrode 33. In this state, a zinc layer was formed on the surface of the copper mesh placed on the working electrode 33 by electrolysis.

[0054] At this time, in the zinc deposition tank, the zinc generation rate is set to 20 mA / cm 2 , 50mA / cm 2 , 200mA / cm 2 The zinc layer was formed under the same conditions as in Example 1. The zinc layers of the specimens of Examples 1 to 10 were subjected to a press treatment. The zinc layer of the specimen of Comparative Example 3 was not subjected to a press treatment.

[0055] Fig. 7 is a scanning electron microscope (SEM) image of the zinc slurry of Comparative Example 2. As shown in Fig. 7, Comparative Example 2 has a structure in which gaps between zinc powder particles are filled with a binder, and has no voids.

[0056] Each of the above Examples 1 to 10 and Comparative Examples 1 to 3 was mounted on the negative electrode 42 of an air battery cell 40, and a discharge test was conducted. As shown in the lower diagram of FIG. 5, the air battery cell 40 used in the discharge test had an air electrode 41 made of conductive carbon. A potassium hydroxide aqueous solution with a concentration of 30 wt % was used as the electrolyte. With the negative electrode 42 immersed in the electrolyte, the battery was discharged until the terminal tube voltage between the negative and positive terminals reached 0.5 V, and the discharge capacity was measured.

[0057] From the measurement results shown in Figure 6, it was verified that the specimens of Examples 1 to 10 had higher discharge capacities than the specimens of Comparative Examples 1 and 2. Furthermore, regarding storage stability in the atmosphere, it was verified that Comparative Example 3, which was not subjected to pressing treatment, burned due to ignition caused by oxidation heat, whereas Examples 1 to 10 did not burn and were able to ensure storage stability. From the above, it was verified that Examples 1 to 10 were able to achieve both improved discharge capacity and storage stability.

[0058] (Main effects of this embodiment) As described above, the zinc fuel 2 of this embodiment has a support 3, at least the surface of which is formed by a conductive current collector 5, and a negative electrode active material layer 4 covering the surface of the support 3, and the negative electrode active material layer 4 is a generated zinc layer formed by dendritic crystals of zinc or zinc alloy precipitated on the surface of the support 3, and the generated zinc layer has at least some of the dendritic crystals crushed to densify, and has voids between the crushed dendritic crystals.

[0059] In addition, the method for manufacturing zinc fuel 2 in this embodiment involves immersing a support 3 formed of a collector 5 having at least a conductive surface in an electrolyte containing zinc oxide, reducing the zinc oxide and precipitating dendritic crystals of zinc or a zinc alloy on the surface of the support 3, thereby forming a zinc layer, and after forming the zinc layer or during the formation of the zinc layer, crushing at least a portion of the dendritic crystals to densify them, and leaving voids between the crushed dendritic crystals, thereby forming a negative electrode active material layer 4.

[0060] In the zinc fuel 2 and its manufacturing method of this embodiment, densified dendritic crystals of zinc or zinc alloy are precipitated on the surface of the current collector 5, ensuring electrical contact between the zinc and the current collector 5. Furthermore, it can be manufactured efficiently using plating techniques and equipment. Furthermore, the densification increases the density of the crystals, making them less likely to fall off, making them easy to handle, store, and introduce into the zinc fuel cell 10. Furthermore, because voids are left between the crushed crystals, a sufficient contact area with the electrolyte is ensured, resulting in high reactivity.

[0061] A specific example of the zinc fuel 2 is a wound body, in which a long sheet 6 is used as the support 3 and the sheet 6 is wound into a roll with a negative electrode active material layer 4 formed on its surface. This zinc fuel 2 can be produced by immersing the sheet 6 in a zinc deposition bath containing an electrolyte to form a zinc layer on the surface of the sheet 6, withdrawing the sheet 6 with the zinc layer laminated on its surface from the zinc deposition bath and passing it through a press mechanism 23 during transport, and then winding the sheet 6 to form a wound body. Therefore, using hoop plating techniques and equipment, the zinc fuel 2 can be efficiently produced through a continuous, integrated process. Furthermore, the produced zinc fuel 2 supports a large amount of zinc, has a shape that is easy to handle, and is easy to adjust in size.

[0062] A specific form of zinc fuel manufacturing apparatus 20 using the hoop plating technique is preferably an apparatus having a zinc deposition tank 21, an anode and a cathode placed in the zinc deposition tank 21, a sheet conveying mechanism 22 that conveys a support 3 consisting of a long sheet 6 with a conductive current collector 5 on its surface through the zinc deposition tank 21, a press mechanism 23 placed downstream of the zinc deposition tank 21 on the conveying path of the sheet 6, and a winding mechanism 26 placed downstream of the press mechanism 23.

[0063] A zinc fuel regeneration system 1 can be constructed by combining a mechanical charging type zinc fuel cell 10 equipped with a zinc fuel storage section 11 capable of supplying the zinc fuel 2 of this embodiment from the outside with the zinc fuel production device 20. This allows for efficient energy circulation using zinc as an energy medium.

[0064] (Other embodiments) In the present invention, the shapes of the support 3 and zinc fuel 2 shown in FIG. 2 are merely examples, and the support 3 is not limited to a sheet shape. For example, a metal or resin of any shape with a current collector 5 layer formed on its surface can be used as the support 3. Even if the support 3 is in a shape other than a sheet, the zinc layer formed on the surface of the current collector 5 can be crushed and densified. Furthermore, when the support 3 is in a sheet shape, the shape of the zinc fuel 2 is not limited to a wound body. For example, a laminate in which a negative electrode active material layer 4 made of a zinc layer is laminated on the surface of a sheet 6 can be cut or processed into a predetermined shape and used as the zinc fuel 2. [Explanation of symbols]

[0065] 1...zinc fuel regeneration system, 2...zinc fuel, 3...support, 4...negative electrode active material layer, 5...current collector, 6...sheet, 10...zinc fuel cell, 11...zinc fuel storage section, 12...negative electrode, 13...positive electrode, 14...electrolyte tank, 20...zinc fuel production device, 21...zinc deposition tank, 22...sheet conveying mechanism, 23...press mechanism, 24...rinsing tank, 25...drying mechanism, 26...winding mechanism, 31...beaker, 32...counter electrode, 33...working electrode, 34...reference electrode, 40...air battery cell, 41...air electrode, 42...negative electrode

Claims

1. a support having at least a surface formed of a conductive current collector, and a negative electrode active material layer covering the surface of the support, the negative electrode active material layer is a zinc layer formed by dendritic crystals of zinc or a zinc alloy precipitated on the surface of the support, A zinc fuel characterized in that the produced zinc layer is densified by at least some of the dendritic crystals being crushed, and has voids between the crushed dendritic crystals.

2. The zinc fuel according to claim 1, characterized in that the current collector is made of at least one metal selected from the group consisting of copper, tin, lead, indium, and bismuth.

3. 2. The zinc fuel according to claim 1, wherein the weight ratio of the negative electrode active material layer to the total weight is 10% or more.

4. 2. The zinc fuel according to claim 1, wherein the negative electrode active material layer is a zinc alloy containing any of copper, tin, indium, and bismuth.

5. the support is a long sheet, 2. The zinc fuel according to claim 1, wherein the sheet having the negative electrode active material layer formed on its surface is wound into a roll.

6. 6. The zinc fuel according to claim 5, wherein the thickness of the sheet is 1 mm or less.

7. 6. The zinc fuel of claim 5, wherein the sheet is porous.

8. A method for producing zinc fuel, comprising: a support having at least a surface formed of a conductive current collector; and a negative electrode active material layer covering the surface of the support; immersing the support in an electrolyte containing zinc oxide to reduce the zinc oxide and precipitate dendritic crystals of zinc or a zinc alloy on the surface of the support, thereby forming a zinc layer; A method for producing zinc fuel, characterized in that after forming the generated zinc layer or during forming the generated zinc layer, at least a portion of the dendritic crystals are crushed to densify them, and voids are left between the crushed dendritic crystals, thereby forming the negative electrode active material layer.

9. 9. The method for producing zinc fuel according to claim 8, wherein the electrolyte is an alkaline electrolyte.

10. The method for producing zinc fuel according to claim 8, characterized in that the electrolyte contains a leveling agent.

11. the support is a long sheet, The sheet is immersed in a zinc deposition bath containing the electrolytic solution to form the zinc layer on the surface of the sheet; A method for producing zinc fuel as described in claim 8, characterized in that a sheet having the produced zinc layer laminated on its surface is pulled out of the zinc deposition tank and passed through a press mechanism while being transported, and then the sheet is wound up to form a wound body.

12. a zinc deposition tank; an anode and a cathode disposed in the zinc deposition tank; a sheet transport mechanism that transports a support made of a long sheet having a conductive current collector provided on its surface through the zinc deposition tank; a press mechanism disposed downstream of the zinc deposition tank in a conveyance path of the sheet; a winding mechanism disposed downstream of the press mechanism, the press mechanism crushes and flattens a produced zinc layer composed of dendritic crystals of zinc or zinc alloy precipitated on the surface of the sheet in the zinc deposition bath; The zinc fuel production apparatus is characterized in that the winding mechanism winds up the sheet and the produced zinc layer that have passed through the press mechanism to form a wound body.

13. A zinc fuel regeneration system comprising: a zinc fuel cell having an electrolyte tank and an anode and a cathode disposed in the electrolyte tank; and a zinc fuel production device, The zinc fuel cell is provided with a zinc fuel storage section at the negative electrode that can externally supply zinc fuel produced by the zinc fuel production device, The zinc fuel production apparatus includes a zinc deposition tank to which an electrolytic solution containing zinc oxide is supplied, and a press mechanism; The zinc deposition tank is provided with an anode and a cathode, a support having at least a surface formed of a conductive current collector is supplied to the cathode, and a zinc layer is formed by precipitating dendritic crystals of zinc or a zinc alloy on the surface of the support through a reduction reaction of the zinc oxide caused by electrolysis at the cathode, The zinc fuel regeneration system is characterized in that when the support having the generated zinc layer formed on its surface passes through the press mechanism, it crushes and densifies at least some of the dendritic crystals, leaving voids between the crushed dendritic crystals.

14. the support is a long sheet, and the zinc fuel is a roll of the sheet having a negative electrode active material layer made of the produced zinc layer formed on the surface thereof, the sheet being wound into a roll, The zinc fuel regeneration system according to claim 13, characterized in that the zinc fuel storage section is capable of accommodating the wound body.

15. 14. The zinc fuel regeneration system of claim 13, wherein the positive electrode is an air electrode.

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