JP2017120704A - Metal air battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a metal air battery capable of obtaining a stable output for a long time.SOLUTION: The metal-air battery includes: a metal electrode serving as a negative electrode; a separator for eluting metal ions from the metal electrode; a cell unit in which an air electrode serving as a positive electrode is stacked in a first direction, and a casing accommodating the cell unit. The air electrode has an activated carbon sheet, a hydrophobic resin dispersed on at least the separator side of the activated carbon sheet, and a current collector graphene. The hydrophobic resin may contain a fluororesin.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a metal-air battery using a metal as a negative electrode and an air electrode as a positive electrode.

  A metal-air battery using a metal such as a magnesium alloy as a negative electrode and air as a positive electrode has attracted attention as a next-generation energy source because of its high energy density. Patent Document 1 discloses a magnesium battery capable of continuously increasing the capacity of a negative electrode made of magnesium. Patent Document 2 discloses a magnesium fuel cell that uses a magnesium alloy negative electrode material containing aluminum and calcium to prevent self-discharge of the negative electrode material and allows electricity to flow stably over a long period of time. Is done.

  Patent Documents 3 and 4 disclose techniques for imparting hydrophobicity (water repellency) to the positive electrode by including a hydrophobic material in the positive electrode material.

JP 2010-182435 A JP 2012-234799 A JP 2014-197477 A JP 2014-165178 A

  In the metal-air battery, as the material for the positive electrode that is an air electrode, an activated carbon sheet having a high activated carbon ratio is preferable from the viewpoint of conductivity, air permeability, and thickness reduction. However, the higher the proportion of the activated carbon in the activated carbon sheet, the worse the shape retention, and the easier it is to handle or break during assembly. On the other hand, in a positive electrode in which a slurry in which a fluororesin or a binder is mixed with activated carbon is formed and dried after molding, it is difficult to appropriately adjust the amount of water between the adjacent electrolyte layers. Either of these causes a decrease in output voltage and instability of the metal-air battery.

  An object of this invention is to provide the metal air battery which can obtain the stable output for a long time.

  In order to solve the above problems, a metal-air battery of the present invention includes a cell unit in which a metal electrode serving as a negative electrode, a separator that elutes metal ions from the metal electrode, and an air electrode serving as a positive electrode are stacked in a first direction, A housing for housing the unit, and the air electrode includes an activated carbon sheet and a hydrophobic resin dispersed on at least a separator side surface of the activated carbon sheet.

  According to such a configuration, since the hydrophobic resin is scattered on the separator-side surface of the activated carbon sheet in the air electrode, the retainability of the shape of the activated carbon sheet is improved while maintaining conductivity, and the air electrode. The amount of moisture between the separator and the separator is appropriately adjusted.

  In the metal-air battery of the present invention, the hydrophobic resin may contain a fluororesin. Hydrophobic resin improves the hydrophobicity and connectivity of the activated carbon sheet.

  In the metal-air battery of the present invention, the air electrode may contain sodium chloride. By containing sodium chloride in the air electrode, the rate of oxygen reduction reaction in the air electrode is adjusted, and a stable output voltage can be obtained for a long period of time.

  In the metal-air battery of the present invention, the separator may have a sheet-like non-size paper. Thereby, since the water retention power of a separator improves, when the water | moisture content adjustment between a separator and an air electrode is performed, the tolerance | permissible_range of moderate water | moisture content can be expanded.

  In the metal-air battery of the present invention, the separator may contain citric acid. Thereby, the oxidation-reduction reaction in the cell unit can be stabilized, and a stable output voltage can be obtained for a long period of time.

  In the metal-air battery of the present invention, the cell unit further includes a current collector plate in contact with the air electrode on the side opposite to the metal electrode of the air electrode, and the current collector plate may be composed of a carbon-based conductive material containing graphene. Good. Thereby, a stable output voltage can be obtained for a long time.

  The metal-air battery of the present invention further includes a pressing member that is provided in a gap in the first direction between the cell unit and the inner wall of the housing and applies a pressing force to the cell unit, and the pressing member has a first direction when the gap is narrowed. It may be provided so as to extend in a second direction orthogonal to. Thereby, when a cell unit expand | swells and a clearance gap becomes narrow, a press member is extended in a 2nd direction, and moderate press force is given to a cell unit from a press member.

  In the metal-air battery of the present invention, the cell unit may have a configuration in which a plurality of unit cells including metal electrodes, separators, and air electrodes are stacked in the first direction. Since the cell unit has a laminated structure of a plurality of unit cells, a stable output voltage can be obtained for a long period of time.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to provide the metal air battery which can obtain the stable output for a long time.

(A) And (b) is a schematic diagram which illustrates the metal air battery which concerns on this embodiment. It is a disassembled perspective view of a cell and a press member. It is the schematic cross section which expanded a part of air electrode. (A) And (b) is sectional drawing explaining expansion | swelling of a cell unit, and extending | stretching of a press member. (A)-(c) is sectional drawing which shows the example of the cell unit of multiple cells. It is a figure explaining the time change of a drive voltage and a drive current. It is a model perspective view which illustrates the composition of a power generator.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, the same members are denoted by the same reference numerals, and the description of the members once described is omitted as appropriate.

[Structure of metal-air battery]
1A and 1B are schematic views illustrating a metal-air battery according to this embodiment.
FIG. 1A shows a perspective view of the metal-air battery 1 according to this embodiment, and FIG. 1B shows a cross-sectional view taken along line AA of FIG. In FIG. 1A, for convenience of explanation, the housing 20 is indicated by a two-dot chain line.
FIG. 2 is an exploded perspective view of the cell and the pressing member.
FIG. 3 is an enlarged schematic cross-sectional view of a part of the air electrode.

  The metal-air battery 1 includes a cell unit 10, a housing 20, and a pressing member 30. The cell unit 10 has at least one cell C. The cell C includes a metal electrode 11 serving as a negative electrode, a separator 12 that elutes metal ions from the metal electrode 11, and an air electrode 13 serving as an anode. The cell C may have a current collector plate 14. Each of the metal electrode 11, the separator 12, the air electrode 13, and the current collector plate 14 is provided in a thin plate shape, and is laminated in this order. In the present embodiment, the stacking direction is the first direction D1. One of the directions orthogonal to the first direction D1 is the second direction D2, and the direction orthogonal to the first direction D1 and the second direction D2 is the third direction D3. With such a laminated structure, the cell C has a structure in which the separator 12 is sandwiched between the metal electrode 11 and the air electrode 13.

  The metal electrode 11 contains a metal that is an electrode active material. As a material of the metal electrode 11, zinc, aluminum, iron, magnesium, lithium, sodium, calcium, or an alloy containing at least one of them as a main component is used. In this embodiment, a magnesium alloy containing magnesium as a main component is used.

  The separator 12 is disposed between the metal electrode 11 that is the negative electrode and the air electrode 13 that is the positive electrode, and plays a role of separating the two. The separator 12 holds an electrolytic solution. When a magnesium alloy is used as the metal electrode 11, for example, a sodium chloride aqueous solution is used as the electrolytic solution.

  The separator 12 is provided longer in the second direction D2 than the metal electrode 11, the air electrode 13, and the current collector plate 14, and absorbs moisture from the protruding portion. Thereby, the electrolyte solution of the separator 12 is adjusted. The separator 12 does not contain an electrolytic solution and may be in a dry state. In this case, the separator 12 sucks up moisture when used, and can bring an appropriate amount of water to the air electrode 13. That is, the water stored in the separator 12 serves to replenish an appropriate amount of water necessary for the chemical reaction to the air electrode 13 having a high concentration.

  In the present embodiment, paper is used for the separator 12. As a state before use, the separator 12 is made of dry paper containing sodium chloride. As a material used for the separator 12, a sheet-like non-size paper is suitable. Non-size paper refers to paper that has not been subjected to sizing treatment (treatment for fixing a sizing agent, which is rosin, on paper fibers) that suppresses bleeding of the paper. Non-size paper is, for example, blotting paper. By using a sheet-like non-size paper, the water retention of the separator 12 that absorbs moisture during use is improved. For this reason, when the water | moisture content adjustment between the separator 12 and the air electrode 13 is performed, the tolerance | permissible_range of a moderate water | moisture content can be expanded. The separator 12 may be made of a material having the same water absorption and drainage properties as that of the non-size paper, sponge, felt fiber, or the like.

  The separator 12 may contain citric acid. Thereby, the sheet-like non-size paper of the separator 12 contains sodium chloride and citric acid, and the oxidation-reduction reaction in the cell unit 10 can be stabilized.

  The air electrode 13 is a porous electrode provided so that water contained in the separator 12 can permeate. In the present embodiment, as the material of the air electrode 13, for example, a carbonaceous material such as activated carbon, carbon fiber, or carbon felt is used. In the present embodiment, an activated carbon sheet 131 obtained by forming activated carbon into a sheet shape is used.

  As shown in FIG. 3, the air electrode 13 includes an activated carbon sheet 131 and a hydrophobic resin 132. The hydrophobic resin 132 is dispersed on at least the surface 131 a on the separator 12 side of the activated carbon sheet 131. As the hydrophobic resin 132, for example, a fluororesin is used. The state in which the hydrophobic resin 132 is sprayed refers to a state in which the hydrophobic resin 132 is not formed in a layered manner on the surface 131a but is discretely attached. For example, the hydrophobic resin 132 is in a granular form and is attached to a part of the activated carbon surface of the activated carbon sheet 131. Therefore, a part of the separator 12 is in contact with the hydrophobic resin 132, and the separator 12 and the activated carbon sheet 131 are in contact with each other.

  An example of a method for manufacturing the air electrode 13 is as follows. First, sodium chloride, trisodium citrate, manganese dioxide, heat-resistant polymer and silicone are mixed with water at appropriate values to form a solution. Next, this solution is absorbed by the activated carbon sheet 131 and then dried. Thereafter, a hydrophobic resin 132 such as a fluororesin is sprayed on the activated carbon sheet 131.

  The hydrophobic resin 132 is sprayed on the surface 131a of the activated carbon sheet 131, for example, in the form of a mist. Since the hydrophobic resin 132 is sprayed on the activated carbon sheet 131, the amount of water between the air electrode 13 and the separator 12 is appropriately adjusted while maintaining the conductivity of the air electrode 13. Thereby, the air electrode 13 is completed.

  As described above, as the material of the positive electrode that is the air electrode 13, the activated carbon sheet 131 having a high activated carbon ratio is preferable from the viewpoint of conductivity, air permeability, and thickness reduction. The higher the activated carbon ratio, the higher the water absorption. As in the present embodiment, the hydrophobic resin 132 is dispersed on the activated carbon sheet 131, so that the activated carbon sheet 131 retains the water retention capability while the hydrophobic resin 132 causes the activated carbon sheet 131 to have more moisture than necessary from the outside. Infiltration can be prevented, and an appropriate amount of water can be maintained for a long time.

  Moreover, the hydrophobic resin 132 serves as a binder for the activated carbon sheet 131. The activated carbon sheet 131 tends to collapse in shape as the ratio of activated carbon increases. Since the hydrophobic resin 132 becomes a binder, the shape retention of the activated carbon sheet 131 is improved as compared with the case where the hydrophobic resin 132 is not sprayed. This facilitates handling of the activated carbon sheet 131 when assembling the cell C.

  The air electrode 13 may contain sodium chloride. Further, the air electrode 13 may contain manganese dioxide. By including these materials in the air electrode 13, the speed of the oxygen reduction reaction in the air electrode 13 is adjusted, and a stable output voltage can be obtained for a long period of time.

  The current collector plate 14 is a conductive plate material and is disposed so as to be in contact with the air electrode 13. A metal plate such as copper or stainless steel is used for the current collector plate 14. As the current collecting plate 14, it is preferable to use an oxidation-resistant material having conductivity. For example, as the current collector plate 14, it is preferable to use a carbon-based conductive material containing graphene. The carbon-based conductive material includes a single layer of graphene and a plurality of layers of graphene. For example, a graphene sheet having a thickness of about 100 μm is suitable as the current collector plate 14.

  According to the experiment of the present inventor, it was found that the driving time can be greatly extended when a graphene sheet is used as compared with the case where a copper foil plate is used as the current collector plate 14. This is because the copper foil plate in the salt water easily becomes copper chloride or copper oxide and is easily corroded, and the corrosion is accelerated by applying a voltage in the positive direction. On the other hand, in the case of a graphene sheet, it is considered that carbon is strong against corrosion and the rate of corrosion is slow even when a voltage is applied in the positive direction. Therefore, a graphene sheet is mentioned as one of the optimal materials for the current collector plate 14.

  A laminated body of the metal electrode 11, the separator 12, the air electrode 13, and the current collector plate 14 is housed in the housing 20 as a cell C. The casing 20 is made of a highly insulating material. Examples of the material of the housing 20 include polyvinyl chloride (PVC), polyvinyl alcohol (PVA), polyphenylene ether (PPE), polyvinyl acetate, ABS, vinylidene chloride, polyacetal, polyethylene, polypropylene, polyisobutylene, fluororesin, Epoxy resin is used.

  An opening is provided in a part of the housing 20, and the cell unit 10 including the cell C can be accommodated in the housing 20 from the opening. A lid 25 which is a part of the housing 20 is provided in the opening. Extraction electrodes 51 and 52 are provided on the outer wall of the lid 25. The extraction electrode 51 is a positive electrode, and the extraction electrode 52 is a negative electrode. The extraction electrodes 51 and 52 have a key shape bent from the outer wall of the lid 25 to the inside of the housing 20. Thereby, each of the extraction electrodes 51 and 52 is fixed so as to be hooked on the edge of the lid 25.

  A hole h is provided in the bottom wall 26 opposite to the lid 25 of the housing 20. When not in use (when power is not generated), the hole h may be covered with the sealing material 27. In this case, when used (when generating electric power), the sealing material 27 is peeled off or broken, so that moisture enters the housing 20 from the hole h and is absorbed by the separator 12 of the cell C. Thereby, power generation is performed.

  In a state where the cell unit 10 including the cell C is housed in the housing 20, the gap G is provided between the cell unit 10 and the inner wall 21 of the housing 20 in the first direction D <b> 1. In the present embodiment, the pressing member 30 is provided in the gap G. In the example shown in FIG. 1, the pressing member 30 includes a first pressing member 31 and a second pressing member 32. The first pressing member 31 is provided in the gap G <b> 1 between the cell unit 10 and one inner wall 211 of the housing 20. The second pressing member 32 is provided in the gap G <b> 2 between the cell unit 10 and the other inner wall 212 of the housing 20. The pressing member 30 applies a pressing force to the cell unit 10 by being provided in the gap G.

  The pressing member 30 is provided to be stretchable in the second direction D2. In the example shown in FIG. 1, the pressing member 30 is provided in a corrugated shape extending in the second direction D2. By providing the pressing member 30 in a corrugated shape, it is possible to secure an amount extending in the second direction D2 while applying an appropriate elastic force to the pressing member 30 in the first direction D1. The elastic force can be set not only by the elastic coefficient of the material of the pressing member 30, but also by the wave shape size (pitch, height) and number.

  In the example shown in FIG. 1, the cell unit 10 is sandwiched between the first pressing member 31 and the second pressing member 32. The first pressing member 31 presses the air electrode 13 side of the cell unit 10 in the first direction D1, and the second pressing member 32 presses the metal electrode 11 side of the cell unit 10 in the first direction D1. An appropriate pressing force is applied to the cell unit 10 by the elastic force of the first pressing member 31 and the second pressing member 32.

  The pressing member 30 extends in the second direction D2 when the gap G becomes narrower. Thereby, even when the cell unit 10 expands and the gap G becomes narrow, the pressing member 30 extends in the second direction D2, and an appropriate pressing force from the pressing member 30 to the cell unit 10 can be maintained. . The stretching of the pressing member 30 will be described later.

  One end 30a of the pressing member 30 is a fixed end fixed to the housing 20, and the other end 30b is a free end. In the present embodiment, a conductive material (for example, stainless steel) is used as the pressing member 30. One end 30 a of the first pressing member 31 is electrically connected to the extraction electrode 51. The first pressing member 31 functions as an anode that is the air electrode 13 by being in contact with the current collector plate 14. The first pressing member 31 may be formed integrally with the extraction electrode 51. Thereby, for example, the corrugated first pressing member 31 and the extraction electrode 51 can be formed by pressing a stainless steel plate.

  The second pressing member 32 has the same configuration as the first pressing member 31. That is, one end 30 a of the second pressing member 32 is electrically connected to the extraction electrode 52. The second pressing member 32 functions as a cathode by contacting the metal electrode 11. The second pressing member 32 may have the same shape as the first pressing member 31. In the case of the same shape, it can be used as the second pressing member 32 by reversing the front and back of the first pressing member 31.

  The width of the pressing member 30 (the length in the third direction D3) is substantially equal to the width of the cell unit 10. Thereby, the cell unit 10 can be uniformly pressed in the width direction by the pressing member 30. The length of the pressing member 30 in the second direction D2 is shorter than the length of the cell unit 10 in the second direction D2. Thereby, the area | region for the press member 30 to extend to the 2nd direction D2 is securable.

  When one end 30a of the pressing member 30 is a fixed end and the other end 30b is a free end, a movable region S of the other end 30b (free end) is provided in an area adjacent to the pressing member 30 in the gap G. The movable region S is a space generated by making the length of the pressing member 30 in the second direction D2 shorter than the length of the cell unit 10 in the second direction D2. A movable region S1 is secured at the tip of the other end 30b (free end) of the first pressing member 31, and a movable region S2 is secured at the tip of the other end 30b (free end) of the second pressing member 32. .

In the metal-air battery 1 having the above-described configuration, when a magnesium alloy is used as the metal electrode 11, the following reaction occurs in the cell C, and an electromotive force is generated between both electrodes.
Positive electrode: O ₂ + 2H ₂ O + 4e ⁻ → 4OH ⁻
Negative electrode: 2Mg → 2Mg ²⁺ + 4e ⁻
Overall: 2Mg + O ₂ + 2H ₂ O → 2Mg (OH) ₂ ↓
By this reaction, a metal oxide or a metal hydroxide is deposited in the cell C. Therefore, as the reaction proceeds, the amount of the deposited substance increases, and the volume of the cell C increases (expands).

  Due to the expansion of the cell C (cell unit 10), the adhesion of each of the metal electrode 11, the separator 12 and the air electrode 13 is lowered, and the output voltage is lowered or unstable. In the metal-air battery 1 according to the present embodiment, in order to obtain a stable output by suppressing a decrease in the adhesion of each of the metal electrode 11, the separator 12 and the air electrode 13 accompanying the expansion of the cell C (cell unit 10). The pressing member 30 is provided.

4A and 4B are cross-sectional views illustrating the expansion of the cell unit and the extension of the pressing member.
FIG. 4A shows a state before the cell unit 10 is expanded, and FIG. 4B shows a state where the cell unit 10 is expanded.
As shown in FIG. 4A, the gap G between the cell unit 10 and the inner wall 21 of the housing 20 is relatively wide before the cell unit 10 expands. The pressing member 30 is fitted in the gap G and appropriately presses the cell unit 10 by the elastic force of the corrugated plate material. The cell unit 10 is pressed so as to be sandwiched between the first pressing member 31 and the second pressing member 32. In a state where the cell unit 10 is not expanded, the length of the pressing member 30 in the second direction D2 is L1.

  As shown in FIG. 4B, when the reaction proceeds and the cell unit 10 expands, the gap G between the cell unit 10 and the inner wall 21 of the housing 20 becomes narrower. The pressing member 30 is crushed in the first direction D1 when the gap G is narrowed, and extends in the second direction D2 in accordance with the crushed portion. As the cell unit 10 expands, the length of the pressing member 30 extends from L1 to L2. Even if the gap G becomes narrow and the pressing member 30 extends, the pressing force from the pressing member 30 to the cell unit 10 is maintained.

  Here, if an excessive pressing force is applied from the pressing member 30, the cell unit 10 cannot expand, and the reaction may be hindered. In the metal-air battery 1 of the present embodiment, the pressing member 30 extends in the second direction D2, so that it is possible to avoid applying excessive pressing force to the cell unit 10 even when the gap G is narrowed. Thereby, while allowing the cell unit 10 to expand, a decrease in the adhesion of each of the metal electrode 11, the separator 12, and the air electrode 13 due to the expansion is suppressed, and a stable output voltage can be obtained.

  As described above, in the metal-air battery 1 according to the present embodiment, the metal electrode 11, the separator 12, and the air electrode 13 as described above can be maintained with appropriate adhesion, the separator 12 can absorb water, and the separator 12 can be formed with the hydrophobic resin 132. Adjustment of the amount of moisture with the air electrode 13 interacts, and a stable output voltage can be obtained over a long period of time.

  That is, when power generation is performed, the water necessary for power generation is sufficiently absorbed and retained by the non-size paper of the separator 12, and the separator 12 and the air electrode 13 are stably adhered between the separator 12 and the air electrode 13. The amount of moisture (degree of humidity) between the two can be maintained at an amount suitable for the power generation reaction for a long time.

  Further, by using non-size paper for the separator 12 and using the activated carbon sheet 131 for the air electrode 13, each water absorption can be increased. On the other hand, since the hydrophobic resin 132 is dispersed on the activated carbon sheet 131 of the air electrode 13, it is possible to prevent excessive moisture from entering the air electrode 13 from the separator 12. That is, the separator 12 serves as a buffer capable of holding a large amount of moisture, and the allowable range of the amount of moisture given when generating power with the metal-air battery 1 can be expanded.

  Furthermore, since sufficient water | moisture content can be hold | maintained at the separator 12 when generating electric power, it can suppress that the water | moisture content of the air electrode 13 or the metal electrode 11 is absorbed by the separator 12 side in the process of electric power generation. This is also a factor for obtaining a stable output for a long time.

FIGS. 5A to 5C are cross-sectional views showing examples of cell units of a plurality of cells.
FIGS. 5B and 5C are enlarged cross-sectional views of a portion B in FIG.
The cell unit 10 may have a configuration in which a plurality of cells C are stacked. In the example illustrated in FIG. 5, the cell unit 10 is configured by stacking four cells C1 to C4 in the first direction D1.

  In the example shown in FIG. 5B, each of the cells C1 to C4 includes a metal electrode 11, a separator 12, an air electrode 13, and a current collector plate 14. In addition, when laminating | stacking several cell C1-C4, it is not necessary to provide the current collecting plate 14 between adjacent cells. That is, the current collector plate 14 may be provided only on the uppermost layer. By stacking a plurality of cells C1 to C4 and connecting them in series, the output voltage can be increased.

  As an example, the size of the metal electrode 11 made of a magnesium alloy, width 25 mm × length 50 mm × thickness 0.3 mm, separator 12 size, width 25 mm × length 50 mm × thickness 0.1 mm, air made of activated carbon sheet 131 One cell C was configured as the size of the pole 13, width 25 mm × length 50 mm × thickness 0.6 mm, size of the current collector plate 14 made of copper foil, width 25 mm × length 50 mm × thickness 0.03 mm. In this case, the cell unit 10 of one cell C is approximately 3V, the cell unit 10 in which the three cells C are stacked is approximately 5V, the cell unit 10 in which the four cells C are stacked is approximately 12V, and the cell in which the seven cells C are stacked. A voltage of about 24V is obtained in the unit 10. Power generation is started by supplying approximately 2 cc of water to one cell C.

  The volume increase amount of the cell unit 10 due to the reaction increases as the number of stacked cells C increases. Therefore, as the number of stacked cells C increases, the effect of obtaining a stable output voltage by providing the pressing member 30 increases.

  As shown in FIG.5 (c), when laminating | stacking several cell C1-C4, you may interpose the electroconductive tape 15 between adjacent cells. As the conductive tape 15, a conductive tape provided with a conductive adhesive on both front and back surfaces of a thin metal plate such as Cu is used. By interposing the conductive tape 15 between adjacent cells, when the plurality of cells C1 to C4 are stacked and connected in series, the conductive tape 15 functions as a connection stable conductive material. That is, the adhesiveness between the adjacent cells and the contact area are increased by the conductive tape 15, and power generation by electrical series connection can be stabilized.

  In stacking the plurality of cells C1 to C4, the generated voltage per cell may be averaged to 1.5V. For example, the generated voltage is averaged to 1.5 V by appropriately setting the internal resistance of a component such as the separator 12. Accordingly, various voltage standards such as 3V for 2 cells, 4.5V for 3 cells, 6V for 4 cells, and 7.5V for 5 cells can be set. Furthermore, if two sets of four cells are connected in series, a voltage of 12V can be obtained if four sets of four cells are connected in series, and voltage setting corresponding to an existing product can be easily performed.

FIG. 6 is a diagram for explaining temporal changes in the output voltage and output current of the metal-air battery.
In FIG. 6, the horizontal axis represents time, and the vertical axis represents output voltage (V) and output current (mA). Data DT1 to DT3 in FIG. 6 are examples of the metal-air battery 1 according to the present embodiment. In the metal-air battery 1 according to this embodiment, non-size paper that does not contain an electrolyte is used as the separator 12, and a graphene sheet is used as the current collector plate 14.

  Data DT4 to DT6 are examples of the metal-air battery according to the reference example. In the metal-air battery according to the reference example, size paper is used as the separator, and the hydrophobic resin is not sprayed on the activated carbon sheet of the air electrode.

  Data DT1 and data DT4 are driving voltages when LEDs are connected and lit (load connection), data DT2 and data DT5 are driving currents when the load is connected, and data DT3 and data DT6 are when no load is applied. Voltage.

  As shown in data DT4 to DT6, in the metal-air battery according to the reference example, when power generation is started by absorption of moisture, the drive voltage when the load is connected is about 2.6 V, and the drive current when the load is connected is about 5. The voltage at 3 mA, no load is about 4.6V. The driving voltage and the driving voltage suddenly decrease in about 3 hours from the start of power generation. This is because the voltage and current cannot be obtained because excessive moisture is absorbed by the separator. Thereafter, the drive voltage and the drive current are both zero from about 5 hours to about 20 hours. After about 20 hours, both the driving voltage and the driving current are recovered, because the moisture absorbed by the separator is dried and the water content is appropriate enough to obtain an electromotive force. After about 41 hours, the electromotive force is lost.

  on the other hand. As shown in the data DT1 to DT3 of FIG. 6, in the metal-air battery 1 according to the present embodiment, when power generation is started by moisture absorption, the drive voltage when the load is connected is about 2.8V, and the drive when the load is connected. The current is about 8 mA and the no-load voltage is about 5.5V. In the metal-air battery 1 according to the present embodiment, a stable drive voltage is obtained even after 147 hours have elapsed from the start of power generation. That is, the drive voltage at the time of load connection is about 2.7 V after 147 hours have elapsed, and is stable with little decrease from the start of power generation. Here, as indicated by the data DT2, the reason why the drive current at the time of connecting the load decreases and increases in the middle is because of water supply at this timing for the convenience of the experiment. The driving current that has decreased due to the replenishment of water will increase again.

  Although not shown, when Cu or stainless steel is used instead of the graphene sheet as the current collecting plate 14 of the metal-air battery 1 according to the present embodiment, a stable driving voltage is obtained until about 72 hours have elapsed from the start of power generation. It has gained.

  As described above, in the metal-air battery 1 according to the present embodiment, the water retention capacity can be increased by using a sheet-like non-size paper as the separator 12. For this reason, even when a large amount of water is supplied by the user when power generation of the metal-air battery 1 is performed, the separator 12 and the air electrode 13 have a saturated water content (a water content that hinders power generation) in a short time. Can be suppressed. Further, since the moisture in the air can be absorbed by the non-size paper of the separator 12, no power generation reaction occurs. Therefore, in the distribution and storage of the metal-air battery 1, it is not necessary to pack the metal-air battery 1 with a vacuum pack, and it is possible to cope with even normal packing.

[Power generation equipment]
FIG. 7 is a schematic perspective view illustrating the configuration of the power generation device.
For convenience of explanation, the case 110 is indicated by a two-dot chain line.
A power generation apparatus 100 shown in FIG. 7 is obtained by storing a plurality of metal-air batteries 1 according to this embodiment in a case 110. Each metal-air battery 1 is housed so that the extraction electrodes 51 and 52 are arranged on the upper side. In the example shown in FIG. 7, a total of 25 metal-air batteries 1 of 5 × 5 are stored in one case 110. Since the casing 20 of the metal-air battery 1 has a box shape, the plurality of metal-air batteries 1 can be efficiently stored in the case 110 in the vertical and horizontal directions.

  A plurality of metal-air batteries 1 are stored in the case 110 by covering the case 110 with a lid (not shown). In addition, an electrode may be provided on the back of the lid, and the metal-air battery 1 may be electrically connected by covering the lid. The electrical connection of each metal-air battery 1 may be in series, in parallel, or a combination thereof.

  The case 110 can be supplied with water. If there is no water supply, no power is generated. When power generation is performed, a predetermined amount of water is supplied to the case 110 and the bottom of the case 110 is immersed in water. This water enters the case 20 from the hole h provided in the case 20 of the metal-air battery 1, and power is generated in the cell unit 10 of each metal-air battery 1.

  The power generation apparatus 100 using the metal-air battery 1 can be stored for a long time unless water is supplied. In addition, power can be generated simply by supplying water, making it ideal as a power source for emergencies such as disasters. In the power generation device 100 according to the present embodiment, the size of the case 110 is about 94 mm long × 172 mm wide × 76 mm high, which is smaller than the engine generator. Moreover, since the weight is light compared with a lead acid battery, it is suitable as a power supply prepared for emergency use.

  Moreover, after it has been used up, the used metal-air battery 1 may be replaced with a new metal-air battery 1, which is economical.

  As described above, according to the metal-air battery 1 according to the embodiment, it is possible to maintain a sufficient amount of water between the separator 12 and the air electrode 13 while improving the water absorption capability of the separator 12. It becomes possible to obtain a stable output over time.

  In addition, although this embodiment and its specific example were demonstrated above, this invention is not limited to these examples. For example, in this embodiment, although the example provided with the press member 30 was shown, even if it is the metal air battery 1 which is not provided with the press member 30, it is applicable. Further, those in which those skilled in the art appropriately added, deleted, and changed the design of the above-described embodiments or specific examples thereof, and combinations of the features of each embodiment as appropriate are also included in the present invention. As long as the gist is provided, it is included in the scope of the present invention.

DESCRIPTION OF SYMBOLS 1 ... Metal-air battery 10 ... Cell unit 11 ... Metal electrode 12 ... Separator 13 ... Air electrode 14 ... Current collecting plate 15 ... Conductive tape 20 ... Housing 21 ... Inner wall 25 ... Lid 26 ... Bottom wall 27 ... Sealing material 30 ... Press member 30a ... one end 30b ... other end 31 ... first press member 32 ... second press member 51 ... take-out electrode 52 ... take-out electrode 100 ... power generation device 110 ... case 131 ... activated carbon sheet 131a ... surface 132 ... hydrophobic resin 211 ... Inner wall 212 ... Inner wall C ... Cell G ... Gap G1 ... Gap G2 ... Gap S ... Movable region S1 ... Movable region S2 ... Movable region h ... Hole

Claims (8)

A cell unit in which a metal electrode serving as a negative electrode, a separator for eluting metal ions from the metal electrode, and an air electrode serving as a positive electrode are laminated in a first direction;
A housing for accommodating the cell unit;
With
The air electrode is a metal-air battery having an activated carbon sheet and a hydrophobic resin dispersed on at least the separator-side surface of the activated carbon sheet.   The metal-air battery according to claim 1, wherein the hydrophobic resin includes a fluororesin.   The metal air battery according to claim 1, wherein the air electrode includes sodium chloride.   The metal-air battery according to claim 1, wherein the separator has a sheet-like non-size paper.   The metal-air battery according to claim 1, wherein the separator contains citric acid. The cell unit further includes a current collector plate in contact with the air electrode on the opposite side of the air electrode from the metal electrode,
6. The metal-air battery according to claim 1, wherein the current collector plate is made of a carbon-based conductive material containing graphene. A pressing member that is provided in a gap in the first direction between the cell unit and the inner wall of the housing, and further applies a pressing force to the cell unit;
The metal-air battery according to any one of claims 1 to 6, wherein the pressing member is provided so as to extend in a second direction orthogonal to the first direction when the gap is narrowed. The metal air battery according to any one of claims 1 to 7, wherein the cell unit has a configuration in which a plurality of unit cells including the metal electrode, the separator, and the air electrode are stacked in the first direction.