JP2020061364A - Magnesium fuel body and magnesium air cell - Google Patents

Abstract

To provide a magnesium fuel body that suppresses a decrease in current due to an oxide film formed on a negative electrode in a magnesium-air battery that uses oxygen in the air as a positive electrode active material and magnesium as a negative electrode active material, and a magnesium air cell including the magnesium fuel body.SOLUTION: A magnesium fuel body 100 is provided with a magnesium plate 101 having notches 102 at two places and a conducting plate 103. The conducting plate 103 is inserted into the notches 102 and bent, and the bent mountain portion and the inside of the notches 102 are strongly crimped.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a magnesium fuel body and a magnesium air battery.

  In a magnesium-air battery using oxygen in the air as a positive electrode active material and magnesium as a negative electrode active material, a magnesium hydroxide film that does not pass electricity or ions is formed on the surface of magnesium as the reaction progresses, and gradually increases from the negative electrode. It becomes difficult to extract the electric current. In the magnesium-air battery described in Patent Document 1, magnesium is deposited on a conductive film to form a roll, and the roll-shaped film is rotated to cooperate with a positive electrode located in the vicinity of the film to unreact one after another. The parts react and generate electricity continuously.

  Further, as in Patent Document 2, the same effect can be obtained by replacing the thin plate-shaped fuel when the reaction is lowered. In Patent Document 2, a thin plate-shaped fuel is installed in a separator folded in a bellows shape, thereby enabling continuous introduction and withdrawal of the fuel from the electrode.

Patent No. 5598883 Patent No. 5891569

  In the mechanism as disclosed in Patent Document 1 or Patent Document 2, it is necessary to efficiently extract electricity from the surface of the fuel to be replaced. Since an oxide film is formed on the surface of magnesium in a short time, it is difficult to efficiently draw electricity by point contact. Further, if the fuel manufacturing process becomes complicated, the fuel price will rise sharply and the production amount will decrease.

The present invention has been made in view of the above points, and a magnesium fuel body that suppresses a decrease in current due to an oxide film formed on a negative electrode by a simple structure, and a magnesium air battery including the magnesium fuel body, The purpose is to provide.

In order to achieve the above object, the magnesium fuel body according to the first aspect of the present invention,
A sheet of metal magnesium with multiple notches,
A conductive plate that takes out electricity by contact with external electrodes,
Equipped with
The inside of the notch and the mountain portion formed when the conducting plate is bent, the conducting plate is inserted into the notch of the magnesium thin plate while contacting each other.
It is characterized by the following.

The magnesium air battery according to the second aspect of the present invention,
A magnesium fuel body according to the first aspect of the present invention,
The cathode,
Electrolyte and
An electrolytic solution holding material formed of a material capable of impregnating the electrolytic solution,
An electrolytic solution tank for storing the electrolytic solution;
Equipped with
The magnesium fuel body wrapped by the electrolyte holding material is inserted between the two cathodes,
The cathode is not immersed in the electrolytic solution, the electrolytic solution holding material is immersed in the electrolytic solution, and the electrolytic solution holding material impregnates the electrolytic solution to start a battery reaction,
It is characterized by the following.

In addition, the magnesium air battery,
The magnesium fuel body may be installed at an angle with respect to the water surface of the electrolytic solution.

  The magnesium-air battery may include a connection terminal including a groove that supports the two cathodes and a circular tube portion that connects a lead wire that is electrically connected to the outside.

A plurality of the magnesium-air batteries,
Each connected in series,
The cathode is not immersed in the electrolytic solution, the electrolytic solution holding portion and the magnesium fuel body is immersed in the electrolytic solution,
The plurality of magnesium-air batteries connected in series share one electrolytic solution tank.

  Further, the magnesium-air battery may be provided with a frame-shaped or girder-shaped spacer near the cathodes, which forms a gap between the adjacent cathodes and takes in air necessary for a cell reaction.

The magnesium air battery is
In the vicinity of the electrolyte holding material,
A container having an air-permeable and water-impermeable film on the inner wall and a vent hole for taking in air on the outer wall,
May be housed in.

  ADVANTAGE OF THE INVENTION According to this invention, the magnesium fuel body which suppressed the fall of the electric current by the oxide film formed in a negative electrode by a simple structure, and the magnesium air cell provided with the magnesium fuel body can be provided.

FIG. 3 is a side view showing a schematic configuration of a magnesium fuel body 100. It is a top view which shows the schematic structure which looked at the magnesium fuel body 100 from the top. FIG. 3 is a side sectional view showing a schematic configuration of a magnesium air battery 200. It is a perspective view (a) and a side view (b) showing an example of connection terminal 205. 3 is a perspective view showing a schematic configuration of a magnesium air battery 200. FIG. It is the experimental result which recorded the change of the electric current [A] and electric capacity [Wh] in the form (Case 1, 2, 3) of three fuel bodies. It is a perspective view (a) and a side sectional view (b) showing a schematic structure of a magnesium air battery 300. It is a top view which shows the schematic structure which looked at the magnesium air battery 300 from above. It is a perspective view showing a schematic structure of a container 303. It is a side sectional view of a part of the wall surface of the container 303. It is a side sectional view showing a part of magnesium air cell of the present invention. 6 is a schematic perspective view showing the configuration of a magnesium fuel body 100 of Embodiment 3. FIG. 7 is a sectional view of a magnesium fuel body 100 of Embodiment 3. FIG. 7 is a sectional view of a magnesium fuel body 100 of Embodiment 3. FIG.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(Embodiment 1)
1A and 1B are side views showing a schematic configuration of a magnesium fuel body according to the first aspect of the present invention. The magnesium fuel body 100 is composed of a magnesium thin plate 101 and a conducting plate 103, and functions as a fuel for a magnesium air cell.

  As shown in FIG. 1A, the magnesium thin plate 101 is a metal magnesium thin plate having a notch 102. Although there are two cuts 102 in FIG. 1, a plurality of cuts 102 may be provided. This will be described later.

  The conductive plate 103 is formed of a conductive material, has a plate shape, and takes out electricity when an external electrode contacts. The conductive plate 103 is formed of, for example, a copper plate or the like. The conducting plate 103 is bent into the notch 102 while being inserted into the notch 102 as shown in FIG. 1A, and the magnesium thin plate 101 and the conducting plate 103 are inside the notch 102 as shown in FIG. 1B. Crimp it so that it makes good contact. At this time, the conducting plate 103 is applied with pressure from above or from the left and right so that the inside of the notch 102 of the magnesium thin plate 101 and the bent portion of the conducting plate 103 come into contact with each other firmly and without any gap, so that the contact electrode from the outside can also be used. It conducts with almost no resistance due to the oxide film. FIG. 2 is a plan view showing this from above.

  As described above, in the magnesium fuel body 100, the conducting plate 103 is inserted into the notch 102 and strongly pressed, and the conducting plate 103 is brought into contact with an external electrode so that the contact electrode is conducted with almost no resistance due to the oxide film.

  Next, a magnesium air battery 200 using the magnesium fuel body 100 as a fuel will be described.

  The magnesium air battery 200 includes an electrolytic solution holding material 201, a cathode 202, an electrolytic solution 203, an electrolytic solution tank 204, and a connection terminal 205, and produces electromotive force by using the magnesium fuel body 100 as a fuel.

  FIG. 3 is a side sectional view showing a schematic configuration of the magnesium air battery 200. (However, the connection terminal 205 is omitted.) The electrolytic solution holding material 201 is formed of a material that holds liquid and has high water absorption. The electrolytic solution holding material 201 holds the electrolytic solution 203 by containing water. At the same time, the cathode 202 is protected by holding the reaction product (for example, magnesium hydroxide) formed after the cell reaction, inside. Examples of the material forming the electrolyte solution holding material 201 include, but are not limited to, felt, non-woven fabric, carbon felt, gel and the like. The electrolyte solution holding member 201 wraps the magnesium fuel body 100 with the conduction plate 103 exposed.

  The electrolytic solution 203 is an electrolytic solution that enables ion exchange between the magnesium fuel body 100 and the cathode 202. The electrolytic solution 203 is, for example, a sodium hydroxide aqueous solution, but is not limited to this.

  The cathode 202 is made of a conductive material and supplies electrons to oxygen in the air, which is the positive electrode active material of the magnesium-air battery 200. As a material for forming the cathode 202, for example, carbon, a metal, a manganese compound, and a combination thereof can be considered, but the material is not limited thereto. In order to promote the reaction of reducing oxygen, it is desirable that it has a large surface area and easily adsorbs oxygen. The cathode 202 is arranged so as to sandwich the magnesium fuel body 100 from both sides.

  The electrolytic solution tank 204 has a tank-like shape that holds the electrolytic solution 203 therein and supplies the electrolytic solution to the electrolytic solution holding material 201. The electrolytic solution is automatically supplied by the water absorption of the electrolytic solution holding material 201. The electrolytic solution 203 is held below the electrolytic solution holding member 201 inside the electrolytic solution tank 204.

  Next, the connection terminal 205 will be described. The connection terminal 205 is formed of a conductive material, supports and connects the two cathodes 202, and electrically connects to the outside. As an example of the shape of the connection terminal 205, the perspective view (a) and the side view (b) of FIG. 4 can be considered. The connection terminal 205 of FIG. 4 includes a circular pipe portion 205a in the upper portion and two grooves 205b in the lower portion. A conductor wire is put in the circular tube portion 205a and crimped and fixed from the periphery, and the conductor wire is electrically connected to the outside. The conductor is used for connection to the outside to ensure flexibility, which will be described later. The cathode 202 is sandwiched in the lower groove 205b, and this is also fixed by pressure. As a material for forming the connection terminal 205, a soft and highly conductive metal such as tin can be considered.

  Next, with reference to FIG. 5, a method of using the magnesium fuel body 100 as a fuel for the magnesium air battery 200 will be described. FIG. 5 is a perspective view showing a part of elements constituting the magnesium-air battery 200 in an exploded manner.

  The magnesium fuel body 100 wrapped with the electrolyte holding material 201 leaving the conduction plate 103 is inserted between the two cathodes 202 supported by the connection terminals 205. The electrolytic solution holding member 201 and the magnesium fuel element 100 are immersed in the electrolytic solution 203 in the electrolytic solution tank 204 installed below. On the other hand, the cathode 202 does not come into contact with the electrolytic solution 203. The electrolytic solution holding material 201 is impregnated with the electrolytic solution 203, and the electrolytic solution is slowly and automatically supplied continuously due to a capillary phenomenon. At this time, the electrolytic solution holding material 201 functions as a separator, and ion exchange is performed with the impregnated electrolytic solution 203 to use oxygen in the air as a positive electrode active material and magnesium contained in the magnesium fuel body 100 as a negative electrode active material. A redox reaction as a substance occurs to generate an electromotive force. Electricity is taken out by the conductor wire crimped to the connection terminal 205 and the electrode connected to the conducting plate 103 provided in the magnesium fuel body 100. Since the magnesium fuel body 100 has a structure that can be easily attached to and detached from the magnesium air battery 200, the fuel can be exchanged without a decrease in current due to the oxide film formed on the negative electrode.

  Here, the effect of the magnesium fuel element 100 of the present embodiment will be shown by experimental results. FIG. 6 records changes in current [A] and electric capacity [Wh] with respect to elapsed time [minutes] when a constant voltage of 1 [V] is set for three types of fuel bodies (Case 1, 2, 3). The results of the experiments are shown. In each case, the graph on the lower right shows the current value, and the graph on the upper right shows the electric capacity.

  Case 1 is a fuel body in which electricity is taken out by directly contacting an electrode from the outside with a magnesium thin plate 101 having no notch. Case 2 is a fuel body in which electricity is taken out by making a hole in a magnesium thin plate and tightening a conducting wire with a bolt. Case 3 is the magnesium fuel body 100 of the first embodiment.

Table 1 summarizes these results. Table 1 shows the current [A] 10 minutes after the start of the experiment and the electric capacity [Wh] achieved after 2 hours for each of Case 1 to Case 3. Case 3 showing the experimental result of the present invention shows a higher current value and higher electric capacity than other cases. In the case of Case 1, the result fluctuated for each experiment and almost no current could be obtained, but Table 1 shows the best result. Even in Case 2, although the conductor wire is strongly tightened with the bolt, it cannot be easily attached and detached by fixing with the bolt. In this experiment, since magnesium having a reaction area of 25 cm ² and a thickness of 1 mm was used, the weight of magnesium in this portion was 4.35 g. In Case 3, the current density is 0.18 [A / cm ² ] and the electric capacity is 1.38 [Wh / g].

Current value and capacitance in Case 1 to Case 3

  As described above, it is possible to provide a magnesium fuel body in which a decrease in current due to an oxide film formed on the negative electrode is suppressed by a simple structure, and a magnesium air battery including the magnesium fuel body.

(Embodiment 2)
In the second embodiment, many magnesium air batteries 200 of the first embodiment are connected.

  When many magnesium air batteries are connected in parallel or in series, the magnesium air batteries of the second embodiment are connected in series. The output voltage of one battery is often around 1 [V], and the current may be several tens [A]. In such a case, if 10 pieces are connected in parallel, an output of 1 [V] will be output at several hundred [A], and the resistance of the portion connecting these is much smaller than several hundredths of ohms. Therefore, it is difficult to get electricity by contact. By connecting in series, the number of 10 pieces becomes 10 [V], and if it is several tens [A], the condition of contact resistance can be relaxed to a fraction of ohm.

    A schematic configuration of the magnesium-air battery 300 of Embodiment 2 is shown in a perspective view (a) and a side sectional view (b) of FIG. 7. (However, the connection terminal 205 is omitted because the details will be described later.) Each component is the same as that in the first embodiment, and thus the detailed description is omitted. In the magnesium air battery 300, many magnesium air batteries 200 are arranged side by side. At this time, since each magnesium-air battery 200 requires air for the cell reaction, a spacer 301 is provided to form a gap on the air side of the cathode 202.

  The spacer 301 has a frame shape or a girder shape with a certain thickness, and even if the cathodes 202 are placed close to each other, a space for taking in air necessary for a battery reaction can be secured. As a width of the gap obtained by the spacer 301, it is known by experiments that 2-3 mm is sufficient in the case of several amperes. The spacer 301 shown in FIG. 7 has a frame-like shape with a rectangular space in some places, but this is an example, and the present invention is not limited to this.

  As shown in FIG. 7B, the electrolytic solution tank 204 includes one shared by a large number of magnesium-air batteries 200 connected in series. By the way, the electrolytic solution 203 is electrically conductive, and when adjacent batteries contact each other in the electrolytic solution 203, current leakage occurs, and it seems that series connection cannot be realized. In the magnesium-air battery 300, as in the first embodiment, the electrolytic solution 203 does not contact the cathode 202, and only the electrolytic solution holding material 201 is allowed to contain water. The inventor of the present invention has experimentally found that even if only the electrolyte solution holding material 201 and the magnesium fuel body 100 wrapped therein are immersed in the same electrolyte solution 203, no electric leakage occurs. From this, even if a large number of fuels are connected in series, a simple structure in which only one common electrolytic solution tank is arranged does not require a structure for electrically shielding each fuel.

  At this time, the series connection by the connection terminal 205 may be as shown in FIG. FIG. 8 is a plan view showing a schematic configuration of a large number of magnesium-air batteries connected in series and seen from above. The connection terminal 205 and the conducting plate 103 of the magnesium-air battery 200 arranged next to each other are connected by the conductor wire 302 and connected in series. The connection terminals 205 and the conduction plate 103 of the magnesium-air battery arranged at both ends are connected to the outside to take out electricity. By using the conductive wire, the batteries can be arranged in close contact with each other, and the whole can be made compact.

  In addition, the magnesium-air battery 300 can be used by housing it in a container 303 as shown in the schematic perspective view of FIG. 9 to prevent leakage of the electrolytic solution 203 disposed in the lower portion of the battery.

  The container 303 has a box shape with a lid. Since air is required for the battery reaction, the vicinity of the electrolytic solution holding material in the container 303 needs to be provided with a structure having air permeability and water impermeable. FIG. 10 shows a cross-sectional view of the wall surface of the container 303 near the electrolytic solution holding material 201. The container 303 is provided with a film 304 formed of a material having air permeability and water impermeable on an inner wall near the electrolytic solution holding material 201, and an air vent 305 for taking in air on an outer wall. The film 304 may be made of a material such as fluorocarbon resin. The ventilation hole 305 is a hole that serves as a passage for air that sends or sucks air that cools the heat generated by the battery reaction. In FIG. 9, a plurality of small holes are shown as the ventilation hole 305, but the shape is an example, and the invention is not limited to this. The cell reaction of magnesium is exothermic, and about 20 [kJ] is generated per 1 g of magnesium fuel. When the electrolyte evaporates due to this heat, the latent heat of water evaporation is 2.4 [kJ / g], so if this heat is used for water evaporation, 8 g of water will be evaporated per 1 g of magnesium. . This requires a great deal of water. Furthermore, since the electrolytic solution is usually salt water, 0.8 g of salt is deposited by evaporation even with salt water having a concentration of 10%. To prevent this, it is necessary to cool by air cooling. By providing the vent holes 304, heat generated when a large number of batteries are densely connected can be air-cooled from the outside. Air cooling can be performed by sending air through a hole using a fan or the like.

In order to consider the performance required for the device required for air cooling, description will be given using specific numbers. Assuming that the heat generation due to the battery reaction is 20 [kJ / g], if 2000 kJ is generated at 100 g in 2 hours, it is 1000 [kJ / h]. In the case where 12 1 mm-thick magnesium plates are connected in series and weigh 100 g, assuming that the density of magnesium is 1.74 [g / cm ³ ], since each sheet has an area of 48 cm ² , At .18 [A / cm ² ], the output of the battery is 0.18 [A / cm ² ] × 48 [cm ² ] × 12 [V], which corresponds to about 103 [W]. On the other hand, since air has a specific heat of 1 [kJ / kg / K] and a density of approximately 1 [kg / m ³ ], assuming a temperature difference of 50 degrees, it has a cooling capacity of 50 [kJ / m ³ ]. . Here, if the air flow rate is X [m ³ / h],
50X [kJ / h] = 1000 [kJ / h] (1)
That is, X = 20 [m ³ / h] is required to discharge heat of 1000 [kJ / h]. A commercially available small fan has an opening of about 8 cm × 8 cm, has a capacity of 32 CFM (Cubic Feet per min) = 55 [m ³ / h], and consumes 12 [V] × 0.1 [A] = 1. Since it is about 0.2 W, it is sufficient for such a system.

  As described above, it is possible to provide a magnesium fuel body in which a decrease in current due to an oxide film formed on the negative electrode is suppressed by a simple structure, and a magnesium air battery including the magnesium fuel body.

  Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments.

  Although the number of notches 102 in the magnesium fuel body 100 is two in the first embodiment, by providing a plurality of notches 102, even if the size of the magnesium thin plate 101 is increased, the influence of the decrease in the current value due to the resistance of the magnesium thin plate 101 itself is affected. Can be reduced.

  Further, FIG. 11 is a side sectional view showing a part of the magnesium fuel cell 100 and the cathode 202 in the magnesium air battery of the present invention. In the first and second embodiments, the magnesium fuel body 100 has been described as being installed vertically to the electrolytic solution tank 204, but the magnesium fuel body 100 and the cathode 202 are horizontal or tilted with respect to the water surface of the electrolytic solution 203. May be. FIG. 11A shows a case where the magnesium fuel body 100 and the cathode 202 are vertically installed, and FIG. 11B shows a case where the magnesium fuel body 100 and the cathode 202 are inclined. In FIG. 11 (a), water is sucked up by the capillarity, but gravity acts downward, so the height at which water reaches within a certain time is limited. This height is 5-6 cm in a practical battery. Therefore, since the height of the reaction area that can be used is limited, the lateral direction inevitably becomes long. By inclining the magnesium fuel body 100 and the cathode 202 horizontally or with respect to the water surface of the electrolytic solution 203 (see FIG. 11 (b)), the distance at which water is sucked up even if the height of water suction due to the capillary phenomenon remains unchanged. And the reaction area in the magnesium fuel body 100 can be increased. It is known from experiments that, for example, if the height direction is 6 cm, the reaction portion has a length of 12 cm and a double output is obtained when the angle is 30 degrees from the horizontal.

(Embodiment 3)
FIG. 12 is a schematic perspective view showing the configuration of the magnesium fuel body 100 according to the third embodiment. The magnesium fuel body 100 is composed of a magnesium thin plate 101 and a conducting plate 103, as in the first embodiment, and functions as a fuel for a magnesium air cell. The conducting plate 103 is inserted into the notch 102 provided in the magnesium thin plate 101 as shown by the arrow in FIG.

  As shown in FIG. 12, the magnesium thin plate 101 is a metal magnesium thin plate having perforations 102. The notch 102 is a perforation penetrating the magnesium thin plate 101 and has a circular shape in FIG. 2, but may have any shape.

  The conduction plate 103 is formed of a conductive material and has a columnar shape. The columnar shape may be hollow or tubular.

  The conducting plate 103 is used by being compressed while being inserted into the notch 102. 13 and 14 are cross-sectional views of the magnesium fuel body 100 showing this state, showing a state in which the conduction plate 103 is inserted (FIG. 13) and a state after compression (FIG. 14). At this time, the inner wall of the notch 102 and the conducting plate 103 are firmly and closely contacted with each other by compressing and expanding the columnar shape of the conducting plate 103. Due to this close contact, the magnesium fuel body 100 of the present embodiment conducts with almost no resistance due to the oxide film.

  The magnesium fuel element 100 of the present embodiment can be used as a fuel for a magnesium air cell by the same method as shown in the first and second embodiments. Since this is a duplicate, it is omitted.

  The experimental results of examining the electric current [A] and the electric capacity [Wh] achieved after 2 hours using the magnesium fuel body 100 of the third embodiment are as follows: That is, it was the same as in Table 1.

  As described above, it is possible to provide a magnesium fuel body in which a decrease in current due to an oxide film formed on the negative electrode is suppressed by a simple structure, and a magnesium air battery including the magnesium fuel body.

100 Magnesium fuel body 101 Magnesium thin plate 102 Cut 103 Conductive plate 200, 300 Magnesium air battery 201 Electrolyte holding material 202 Cathode 203 Electrolyte 204 Electrolyte tank 205 Connection terminal 205a Circular tube 205b Groove 301 Spacer 302 Conductor 303 Container 304 Film 305 Vent

Claims (7)

A sheet of metal magnesium with multiple notches,
A conductive plate that takes out electricity by contact with external electrodes,
Equipped with
The inside of the notch and the mountain portion formed when the conducting plate is bent, the conducting plate is inserted into the notch of the magnesium thin plate while contacting each other.
A magnesium fuel body characterized by the following. The magnesium fuel body according to claim 1,
An electrolyte holding material formed of a material that can be impregnated with a liquid,
A cathode sandwiched from both sides of the electrolyte holding material,
An electrolytic solution tank installed below the magnesium fuel body,
An electrolytic solution stored in the electrolytic solution tank,
Equipped with
The magnesium fuel body wrapped by the electrolyte holding material is inserted between the two cathodes,
The cathode is not immersed in the electrolytic solution, the electrolytic solution holding material is immersed in the electrolytic solution, and the electrolytic solution holding material impregnates the electrolytic solution to start a battery reaction,
A magnesium air battery characterized by the above. The magnesium-air battery according to claim 2, wherein the magnesium fuel body is installed at an angle with respect to the water surface of the electrolytic solution.
Magnesium-air battery characterized in that.   The magnesium-air battery according to claim 2 or 3, further comprising a connection terminal including a groove for supporting the two cathodes and a circular tube portion for connecting a conductor wire electrically connected to the outside. And A plurality of magnesium air batteries according to any one of claims 2 to 4,
Connect each in series,
The cathode is not immersed in the electrolytic solution, the electrolytic solution holding portion and the magnesium fuel body is immersed in the electrolytic solution,
A plurality of the magnesium-air batteries connected in series share one electrolyte bath,
It is characterized by the following.   The magnesium-air battery according to claim 5, further comprising a frame-shaped or girder-shaped spacer that forms a gap between the adjacent cathodes and takes in air necessary for a battery reaction, in the vicinity of the cathode. And The magnesium-air battery according to any one of claims 2 to 6,
In the vicinity of the electrolyte holding material, the inner wall is provided with a film having air permeability and water impermeable properties, and the outer wall is provided with a vent hole for taking in air, a container,
May be housed in.

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