JP2026008382A - Zinc fuel, zinc fuel manufacturing method, zinc fuel cell, and zinc fuel regeneration system - Google Patents

Abstract

The present invention proposes a zinc fuel that can be produced by regenerating zinc oxide, is easy to handle and store, and easily ensures contact with a current collector, as well as a method for producing the same.
[Solution] The zinc fuel 2 has a granular support 3 whose surface is formed by a current collector 5, and an anode active material layer 4 covering the surface of the support 3. The anode active material layer 4 is a zinc layer formed by dendritic crystals of zinc or zinc alloy precipitated on the surface of the support 3, with some of the dendritic crystals crushed and densified, and gaps formed between the crushed dendritic crystals. The zinc fuel 2 is produced by placing the granular support 3, at least the surface of which is formed by a current collector, in a barrel 54, and rotating it in an electrolyte while electrolyzing zinc oxide to precipitate dendritic crystals of zinc or zinc alloy on the surface of the support 3.
[Selected Figure] Figure 3

Description

The present invention relates to a zinc fuel and its manufacturing method, a zinc fuel cell, and a zinc fuel regeneration system.

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 of lithium-ion batteries increases and they become larger in scale, the risk of secondary disasters in the event of a breakdown becomes an issue.

Batteries that generate electricity through chemical reactions of metals in an electrolyte include those that use a variety of metals, but zinc-air batteries are known for their high energy density. Because zinc-air batteries use oxygen from the atmosphere as the positive electrode active material, there is no need to mount the positive electrode active material inside the container. However, the zinc-air batteries commonly available are primary batteries, and no technology has been developed to make them rechargeable. This makes them difficult to use as energy storage systems.

As a method for using air-zinc batteries as batteries in power storage systems, a method has been proposed in which, instead of charging the air-zinc battery, zinc is newly supplied as the negative electrode active material from an external source. 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 the negative electrode is equipped with a storage area for storing metallic zinc powder and a supply port.

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 storage area can be designed to any size, making it possible to miniaturize it and making it practical.

In the following description, a battery that uses a system in which zinc, the negative electrode active material, is not packaged in the battery but can be supplied externally, as in Patent Documents 1 and 2, is referred to as a zinc fuel cell. When using a mechanical charging type zinc fuel cell, from the perspective of utilizing renewable energy, it is expected that the zinc oxide produced by discharging the battery can be regenerated and reused as zinc fuel.

Patent No. 6290509 Patent No. 6716308

One method for utilizing zinc oxide produced by the discharge reaction of batteries using zinc as the negative electrode active material to regenerate zinc fuel is to precipitate zinc through a reduction reaction of zinc oxide by electrolysis. However, dendritic zinc crystals are difficult to handle due to their fragility. Furthermore, because the specific surface area of dendritic crystals is very large, they are prone to spontaneous oxidation when stored in the air, which can pose a risk of fire due to oxidation heat.

Furthermore, in mechanical charging zinc fuel cells, the zinc fuel supplied from an external source must be able to ensure 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 come into contact with the current collector. Therefore, there is a risk of insufficient electrical contact with the current collector.

In light of the above, the objective of the present invention is to provide a zinc fuel that can be efficiently produced from zinc oxide, is easy to handle, store, and refill into batteries, and ensures good contact with the current collector, a method for producing the same, a zinc fuel production device, and a zinc fuel regeneration system.

In order to solve the above problems, one embodiment of the zinc fuel according to the present invention comprises a granular support, at least the surface of which is 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 zinc layer formed from dendritic crystals of zinc or zinc alloy precipitated on the surface of the support, and the zinc layer is characterized in that at least some of the dendritic crystals are crushed and densified, and that voids are present between the crushed dendritic crystals.

Another aspect of the method for producing zinc fuel according to the present invention is a method for producing zinc fuel having a granular support, at least the surface of which is formed by a conductive current collector, and a negative electrode active material layer covering the surface of the support, characterized in that a barrel containing the support is immersed in an electrolyte containing zinc oxide, and while rotating the barrel, the zinc oxide is reduced to precipitate dendritic crystals of zinc or a zinc alloy on the surface of the support, thereby forming a zinc layer, and the support is rolled within the barrel by rotating the barrel, thereby crushing at least a portion of the dendritic crystals and densifying them.

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. This ensures electrical contact between the zinc and the current collector. Furthermore, the zinc layer is densified, increasing the crystal density and making it less likely to fall off, making the zinc fuel easy to handle, store, and charge into a zinc fuel cell. Furthermore, because the crystals are densified to the extent that voids remain between them, a sufficient contact area with the electrolyte is ensured, which also has the advantage of high reactivity. Furthermore, the zinc layer can be formed and densified by placing a granular support in a barrel and rotating it in the electrolyte while reducing zinc oxide. Therefore, zinc fuel can be efficiently manufactured using plating techniques and equipment.

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 surface of the base material can be provided with a current collector layer by plating. When using a resin material as the base material, the current collector layer can be provided on the surface by electroless plating.

In the zinc fuel according to the present invention, the current collector is preferably made of at least one of copper, tin, lead, indium, and bismuth. Alternatively, it may be an alloy of these metals. These metals have a high hydrogen generation overvoltage, comparable to that of zinc. Therefore, the hydrogen generation dissolution reaction of zinc at the negative electrode can be suppressed, and the decrease in battery capacity due to the progression of the self-discharge reaction can be suppressed. Furthermore, these metals have high 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.

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.

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

In the zinc fuel of the present invention, the support is preferably a sphere. Furthermore, it is preferable that the longest dimension of the support be 10 mm or less. A sphere rolls easily inside the barrel, allowing the resulting zinc layer to be uniformly densified. Therefore, a homogeneous negative electrode active material layer can be formed over the entire surface of the support. Furthermore, by reducing the size of the support, the weight proportion of the negative electrode active material layer can be increased. Furthermore, since the size of the zinc fuel can be reduced, it is suitable for miniaturizing zinc fuel cells.

In the zinc fuel production method according to the present invention, the electrolyte is preferably an alkaline aqueous solution. Using an alkaline electrolyte can increase the rate at which dendritic crystals are produced by the reduction reaction of zinc oxide.

In the zinc fuel manufacturing method according to the present invention, it is preferable that a leveling material be added to the electrolyte. This can reduce the unevenness of the resulting zinc layer.

In order to use such zinc fuel, one embodiment of the zinc fuel cell according to the present invention has an electrolyte tank, an anode and a cathode placed in the electrolyte tank, and the anode is provided with a zinc fuel storage section for storing zinc fuel in which the surface of a granular support is covered with a layer of anode active material; a support recovery section placed below the zinc fuel storage section; and a partition section separating the zinc fuel storage section from the support recovery section, and the partition section is provided with a passage section through which the support can pass but the zinc fuel cannot.

In this way, when the zinc fuel supplied to the zinc fuel storage section consumes the negative electrode active material layer through discharge, the remaining support passes through the passage section and falls into the support recovery section. Therefore, the support can be efficiently separated and recovered from the zinc fuel, allowing for efficient regeneration of the zinc fuel.

In this case, it is preferable to provide a removal section for removing the support from the support recovery section. This allows for more efficient separation and recovery of the support and regeneration of the zinc fuel. It is also preferable that the positive electrode is an air electrode. This eliminates the need to replenish the positive electrode active material.

Next, one aspect of the zinc fuel regeneration system of 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 has a zinc deposition tank to which an electrolyte containing zinc oxide is supplied, and the zinc deposition tank is provided with an anode and a cathode, and the cathode is provided with a barrel to which a granular support material is supplied, the support material having at least a surface formed by a conductive current collector.

In this way, by combining a mechanical charging zinc fuel cell with a zinc fuel production device that can produce zinc fuel through electrolysis from an electrolyte containing zinc oxide generated by discharge, it is possible to create an energy circulation system that uses zinc as an energy carrier. Furthermore, the produced zinc fuel is easy to handle, store, and add to the zinc fuel cell, ensures contact between the zinc and the current collector, and is highly reactive in the electrolyte. Furthermore, it can be produced efficiently using barrel plating methods and equipment. Therefore, energy circulation using zinc as an energy carrier can be carried out efficiently.

The present invention provides a zinc fuel and a method for producing the same that can be easily produced from zinc oxide, is easy to handle, store, and refill into batteries, and ensures good contact with the current collector. Furthermore, the zinc fuel can be efficiently regenerated, enabling efficient energy circulation using zinc as an energy carrier.

FIG. 1 is a system configuration diagram that schematically illustrates a zinc fuel regeneration system. 1A and 1B are a side view and a cross-sectional view showing a zinc fuel and an explanatory diagram of a method for recovering the support. FIG. 1 is an explanatory diagram schematically showing a zinc fuel production apparatus. 1 is a scanning electron microscope (SEM) image of the resulting densified zinc layer and the zinc slurry. FIG. 2 is an explanatory diagram of an air battery cell used in a discharge test. 1 is a table showing the configuration of the test specimen and the test results.

Embodiments of the present invention will be described below with reference to the drawings. The embodiments described below are in a form in which zinc fuel is fed into a zinc-air battery to supply electricity. Note that the zinc fuel cell according to the present invention, which supplies electricity by feeding zinc fuel into it, is not limited to zinc-air batteries.

(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 comprises a zinc fuel cell 10 and a zinc fuel production device 50. 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 50. 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.

(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.

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 portion of the zinc fuel reservoir 11 that comes into contact with the electrolyte is formed from a mesh-like or punched negative electrode current collector.

In the electrolyte tank 14, a support recovery section 15 is provided below the zinc fuel storage section 11. In the example shown in Figure 1, the bottom of the zinc fuel storage section 11 is a partition section 16 that separates the zinc fuel storage section 11 from the support recovery section 15. The detailed configuration of the support recovery section 15 and the partition section 16 will be described later.

The electrolyte tank 14 contains an electrically conductive electrolyte. The electrolyte is not particularly limited, but an organic solvent-based electrolyte, an aqueous electrolyte, or a mixture of these can be used. For example, alkaline aqueous electrolytes include potassium hydroxide aqueous solution, sodium hydroxide aqueous solution, lithium hydroxide aqueous solution, zinc sulfate aqueous solution, zinc nitrate aqueous solution, zinc phosphate aqueous solution, zinc acetate aqueous solution, and mixtures of these. The electrolyte may further contain other inorganic and organic additives.

(Zinc fuel and its manufacturing method)
FIG. 2 shows a side view and a cross-sectional view of the zinc fuel 2, and an explanatory diagram of a method for recovering the support 3. 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 one of copper, tin, indium, and 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.

As described below, the resulting zinc layer is densified by crushing some of the zinc or zinc alloy dendritic crystals. Voids remain between the crushed dendritic crystals. In this embodiment, the process of crushing the dendritic crystals is carried out simultaneously while the resulting zinc layer is being formed. It is also possible to crush the dendritic crystals after the resulting zinc layer has been formed.

At least the surface of the support 3 needs to be formed by the current collector 5. In the example shown in Figure 2, the surface of the support 3's substrate 7 is covered with a layer of current collector 5. The current collector 5 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 include copper, tin, lead, indium, or bismuth, or alloys of these metals. For example, the current collector 5 layer may be a single metal layer, or may be a laminate of multiple metal layers. When multiple layers are laminated, each layer is made of one of the above metals (copper, tin, lead, indium, or bismuth).

The support 3 may be formed entirely from the current collector 5, or may be a substrate 7 made of a metal different from the current collector 5, or a non-metal such as a resin material, with a current collector 5 layer provided on the surface. For example, the current collector 5 layer can be provided on the surface by plating. Resin materials that can be used include PP (polypropylene), PE (polyethylene), nylon, PPS (polyphenylene sulfide), and ABS (acrylonitrile-butadiene-styrene). If the substrate 7 is made of a resin material, the current collector 5 layer can be provided on the surface by electroless plating.

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, it is 20% or more, and even more preferably, it is 50% or more. The zinc fuel 2 of this embodiment grows dendritic crystals on the surface of the current collector 5, allowing a large amount of zinc to be supported. By supporting a large amount of zinc, the amount of electricity that can be extracted can be increased. Therefore, it is suitable for an energy storage system that stores electrical energy in the form of zinc.

In the example shown in Figure 2, the support 3 is granular. While "granular" generally refers to something round, in this specification, "granule" includes shapes other than spheres. For example, the support 3 is preferably spherical, but may be a shape other than spherical. For example, it may be a three-dimensional shape such as a cube, a prism, a pyramid, an octahedron, or other polyhedron, a cylinder, or a cone, or a small piece of any shape, such as a rod or flake. The surface may also have irregularities or perforations. In the case of a shape other than a sphere, it is preferable that the shape have an aspect ratio close to 1 to facilitate rolling inside the barrel described below during manufacturing.

The size of the support 3 is preferably 10 mm or less at its largest dimension, more preferably 5 mm or less, and even more preferably 1 mm or less. For shapes other than spheres, it is preferable that the longest side be this dimension. For spheres, it is preferably 10 mm or less, more preferably 5 mm or less, and even more preferably 1 mm or less. To prevent the support 3 from falling out of the barrel described below during manufacturing, it is preferable that the smallest dimension be 1 μm or more. For spheres, the diameter is preferably 1 μm or more. By reducing the size of the support 3, the weight ratio of the negative electrode active material layer 4 to the total weight of the zinc fuel 2 can be increased.

Now, with reference to the lower diagram of Figure 2, we will explain the support recovery section 15 provided in the zinc fuel cell 10. The zinc fuel cell 10 is designed to be able to recover the remaining support 3 when the negative electrode active material layer 4 of the zinc fuel 2 is depleted due to discharge. As described above, a partition section 16 is provided between the zinc fuel storage section 11 and the support recovery section 15, and the partition section 16 is provided with a penetration section that functions as a passage section 17 of a size that allows the support 3 to pass through but does not allow the zinc fuel 2 to pass through. Therefore, the support 3 can be dropped into the support recovery section 15 and recovered.

In the example shown in Figure 2, the support recovery section 15 is provided with a removal section 18 for removing the recovered support 3 to the outside. For example, a drain is provided as the removal section 18. This allows the support 3 that has fallen into the support recovery section 15 to be removed to the outside through the drain. Note that the passing section 17 and removal section 18 are not shown in Figure 1.

In the zinc fuel cell 10, solid zinc oxide is precipitated during the discharge process. In the zinc fuel cell 10 shown in Figure 2, the zinc oxide precipitated on the surface of the support 3 that falls into the support recovery section 15 can be recovered together with the support 3.

(Zinc fuel production equipment)
3 is an explanatory diagram showing a schematic diagram of a zinc fuel production apparatus 50. The zinc fuel production apparatus 50 includes a zinc deposition tank 51 containing an electrolytic solution containing zinc oxide, an anode 52 and a cathode 53 immersed in the electrolytic solution, and a barrel 54 immersed in the electrolytic solution. The cathode 53 is disposed inside the barrel 54. A barrel plating machine can be used as this zinc fuel production apparatus 50.

In the zinc fuel production device 50, granular support 3 is placed in a barrel 54 and rotated, while a reduction reaction of zinc oxide is carried out by electrolysis at a cathode 53. The support 3 rolls inside the barrel 54 and comes into contact with the cathode 53. As a result, dendritic crystals of zinc or a zinc alloy are precipitated on the surface of the support 3, forming a zinc layer.

As the zinc layer is formed while rolling inside the barrel 54, the dendrite-like crystals grow on the surface of the support 3 while being crushed, forming a dense zinc layer. Once the amount of precipitated zinc reaches the target amount, the electrolysis and rotation of the barrel 54 are stopped, and the zinc fuel 2 is removed from the barrel 54. The removed zinc fuel 2 is immersed in a rinse tank (not shown), subjected to a drying process, and then stored in the atmosphere.

When performing the reduction reaction of zinc oxide through electrolysis in the zinc deposition tank 51, either an acid or alkaline electrolyte can be used, and there are no particular restrictions as long as it can dissolve zinc as ions. However, using an alkaline electrolyte can speed up the rate at which zinc is produced by the reduction reaction of zinc oxide. Therefore, it is preferable that the electrolyte be an alkaline aqueous solution. It is also preferable to add a leveling material to the electrolyte to smooth out any unevenness in the zinc.

The left image in Figure 4 is a scanning electron microscope (SEM) image of the densified zinc layer. As can be seen from this image, the densified zinc layer has crushed dendrite-like crystals, with voids remaining between the crushed dendrite-like crystals.

The image on the right of Figure 4 is a scanning electron microscope (SEM) image of zinc slurry. In conventional batteries that use zinc as the negative electrode active material, the zinc slurry applied to the negative electrode is made by mixing zinc powder (fine zinc particles) with a binder.

The negative electrode active material layer 4 (produced zinc layer) in this embodiment has a structure in which dendritic crystals have been crushed and densified, whereas zinc slurry has a structure in which zinc powder is dispersed among binders, and can be clearly distinguished from the shapes of the crystals and zinc powder. The produced zinc layer can also be distinguished from the fact that it does not have binders and the voids are not filled.

(Discharge experiment)
Test specimens were produced by regenerating zinc oxide and providing a negative electrode active material layer on the surface of a current collector. These were placed in air battery cells and discharge tests were conducted to verify the difference in discharge capacity compared to the comparative example. Storage stability in the atmosphere was also verified. 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 specimens and the test results.

Examples 1 to 8 shown in Figure 6 were produced as test specimens for the discharge test. For Comparative Example 1, commercially available zinc particles were used. For Comparative Example 2, produced zinc consisting of dendritic crystals that had not been subjected to densification treatment was used. Using the same method as for Examples 1 to 8, attempts were made to produce Comparative Examples 3 and 4. Comparative Example 3 was successfully produced, but for Comparative Example 4, a produced zinc layer could not be formed.

The test specimens for Examples 1 to 8 were manufactured using the method described below. A potassium hydroxide solution was introduced into a 1000 mL acrylic tank as the electrolyte, and 15 g of zinc oxide was added. The potassium hydroxide solution concentration was 30 wt%. A nickel mesh was placed along the outer wall of the acrylic tank as the counter electrode. A cylindrical barrel with a diameter of 25 mm was placed inside the tank. 100 spheres with a diameter of 1 mm were placed inside the barrel and placed so that they came into contact with the working electrode while rotating. A current of 100 mA was applied between the counter electrode and working electrode, and zinc was deposited on the sphere surface while the barrel was rotated at a speed of 5 rotations per minute, forming a zinc layer. The total amount of zinc produced was set to 1 g.

6, in Examples 1 to 8, the spheres (i.e., supports 3) to be placed in the barrel had at least the surface formed of copper, tin, or brass, i.e., at least the surface formed of a current collector. As a result, in all of Examples 1 to 8, a densified zinc layer was formed on the surface of the sphere.

As shown in Figure 6, in Comparative Examples 3 and 4, the spheres added consisted of only a substrate, and no surface treatment was performed to provide a current collector on the surface. In Comparative Example 3, steel spheres without surface treatment were added. In Comparative Example 4, PP (polypropylene) spheres without surface treatment were added. As a result, a zinc layer was formed in Comparative Example 3, but not in Comparative Example 4.

The above Examples 1 to 8 and Comparative Examples 1 and 3 were each mounted on the negative electrode 62 of the air battery cell shown in Figure 5, and a discharge test was conducted. The air battery cell had an air electrode 61 made of conductive carbon at the bottom of an electrolyte tank 63. A potassium hydroxide aqueous solution with a concentration of 30 wt% was used as the electrolyte. A test specimen of zinc fuel 2 was placed in the electrolyte and discharged, and the capacity obtained per gram of zinc in the test specimen was evaluated.

From the results shown in Figure 6, it was verified that the test specimens of Examples 1 to 8 had higher capacity efficiency than the test specimens of Comparative Examples 1 and 3. Furthermore, with regard to storage stability in the atmosphere, it was verified that Comparative Example 2, which was not subjected to densification treatment, burned due to ignition caused by oxidation heat, whereas Examples 1 to 8 did not burn and maintained storage stability. From the above, it was verified that Examples 1 to 8 were able to achieve both improved discharge capacity and storage stability.

(Main effects of this embodiment)
As described above, the zinc fuel 2 of this embodiment has a granular 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.

In addition, the method for producing zinc fuel 2 in this embodiment involves immersing a barrel 54 containing granular support 3, at least the surface of which is formed from a conductive current collector 5, in an electrolyte containing zinc oxide, and rotating the barrel 54 to reduce the zinc oxide and precipitate dendritic crystals of zinc or a zinc alloy on the surface of the support 3, thereby forming a zinc layer. By rotating the barrel 54 and rolling the support 3 within the barrel, at least some of the dendritic crystals are crushed and densified, and voids are left between the crushed dendritic crystals, thereby forming a negative electrode active material layer 4.

The zinc fuel 2 and its manufacturing method of this embodiment deposits and densifies dendritic crystals of zinc or zinc alloy on the surface of the current collector 5, ensuring electrical contact between the zinc and the current collector 5. It can also be manufactured efficiently using barrel 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.

The zinc fuel cell 10 of this embodiment, into which zinc fuel 2 is input, has an electrolyte tank 14, and an anode 12 and a cathode 13 placed in the electrolyte tank 14. The anode 12 is provided with a zinc fuel storage section 11 for storing zinc fuel 2, in which the surface of a granular support 3 is covered with an anode active material layer 4. The device is also equipped with a support recovery section 15 placed below the zinc fuel storage section 11 and a partition section 16 separating the zinc fuel storage section 11 and the support recovery section 15, and the partition section 16 is provided with a passage section 17 through which the support 3 can pass but the zinc fuel 2 cannot.

In this embodiment of the zinc fuel cell 10, the support after the negative electrode active material layer 4 has been consumed can be efficiently separated and recovered from the zinc fuel. Furthermore, the support 3 recovered in the support recovery section 15 can be removed from the cell through the removal section 18. Therefore, the zinc fuel 2 can be efficiently regenerated using the recovered support 3. Furthermore, because the positive electrode 13 is an air electrode, there is no need to supply positive electrode active material.

By combining the zinc fuel cell 10 of this embodiment with the zinc fuel production device 50, a zinc fuel regeneration system 1 can be constructed. This allows for efficient energy circulation using zinc as the energy medium.

1...zinc fuel regeneration system, 2...zinc fuel, 3...support, 4...negative electrode active material layer, 5...current collector, 7...substrate, 10...zinc fuel cell, 11...zinc fuel storage section, 12...negative electrode, 13...positive electrode, 14...electrolyte tank, 15...support recovery section, 16...partition section, 17...passage section, 18...removal section, 50...zinc fuel production device, 51...zinc deposition tank, 52...anode electrode, 53...cathode electrode, 54...barrel, 61...air electrode, 62...negative electrode, 63...electrolyte tank

Claims (13)

The negative electrode comprises a granular support, at least the surface of which is 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. The zinc fuel described in claim 1, characterized in that the current collector is made of at least one of the following metals: copper, tin, lead, indium, and bismuth. The zinc fuel described in claim 1, characterized in that the weight ratio of the negative electrode active material layer to the total weight is 10% or more. The zinc fuel described in claim 1, characterized in that the negative electrode active material layer is a zinc alloy containing one of copper, tin, indium, and bismuth. The zinc fuel described in claim 1, characterized in that the support is a sphere. The zinc fuel described in claim 1, characterized in that the support has a longest dimension of 10 mm or less. A method for producing zinc fuel, comprising: a granular support, at least the surface of which is formed by a conductive current collector; and a negative electrode active material layer covering the surface of the support,
a barrel containing the support is immersed in an electrolyte containing zinc oxide, and while rotating the barrel, the zinc oxide is reduced to 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 the support is rolled within the barrel by rotating the barrel, thereby crushing and densifying at least a portion of the dendritic crystals. The method for producing zinc fuel described in claim 7, characterized in that the electrolyte is an alkaline aqueous solution. The method for producing zinc fuel described in claim 7, characterized in that the electrolyte contains a leveling agent. an electrolytic solution tank; and a negative electrode and a positive electrode disposed in the electrolytic solution tank;
The negative electrode is provided with a zinc fuel reservoir for storing zinc fuel, the surface of which is a granular support covered with a negative electrode active material layer,
A support recovery section disposed below the zinc fuel storage section;
A partition section that separates the zinc fuel storage section from the support recovery section,
A zinc fuel cell characterized in that the partition section is provided with a passage section through which the support can pass but the zinc fuel cannot pass. A zinc fuel cell as described in claim 10, characterized in that it is provided with an extraction section for extracting the support from the support recovery section. The zinc fuel cell described in claim 10, characterized in that the positive electrode is an air electrode. 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 device is equipped with a zinc deposition tank to which an electrolyte containing zinc oxide is supplied, the zinc deposition tank is provided with an anode and a cathode, and the cathode is provided with a barrel to which a granular support formed of a conductive current collector is supplied, at least the surface of which is disposed.This zinc fuel regeneration system is characterized by the above.