JP2016081932A - Magnesium battery system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnesium battery system capable of enhancing power generation efficiency of a magnesium battery.SOLUTION: A magnesium battery system 1 includes a magnesium battery 2, an electrolyte circulation passage 3 having the opposite ends for connection with the magnesium battery, and a circulation pump 4 for circulating the electrolyte of the magnesium battery 2 through the electrolyte circulation passage 3. When the circulation pump 4 is driven, the electrolyte 26 of the magnesium battery 2 is circulated through the electrolyte circulation passage 3. Since the electrolyte 26 is circulated during power generation of the magnesium battery 2, power generation capacity of the magnesium battery 2 can be enhanced.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a magnesium battery system including a magnesium battery.

  Conventionally, a magnesium battery using metal magnesium or an alloy thereof as a negative electrode material is known (see, for example, Patent Document 1).

Special table 2004-537151 gazette

  Recently, magnesium batteries have been put into practical use. However, a high-power magnesium battery has not been provided, and improving the power generation capacity of the magnesium battery is a common issue for those involved in the development of magnesium batteries.

  The objective of this invention is providing the magnesium battery system which can aim at the improvement of the power generation capability of a magnesium battery.

  In order to achieve the above object, a magnesium battery system according to the present invention includes a magnesium battery, an electrolyte circuit that is connected to the magnesium battery at both ends, and a circulation pump that circulates the electrolyte of the magnesium battery through the electrolyte circuit. Including.

  According to this configuration, when the circulation pump is driven, the electrolyte of the magnesium battery circulates through the electrolyte circulation path. The power generation capacity (output) of the magnesium battery can be improved by circulating the electrolyte.

  The mechanism by which the circulation of the electrolyte leads to the improvement of power generation capacity is not clear, but when the electrolyte is circulated, a flow of the electrolyte occurs in the magnesium battery, which causes the electrons generated at the negative electrode to flow into the positive electrode. The arrival rate is expected to increase, and in the experiments by the present inventors, it has been confirmed that the power generation capacity is improved by the circulation of the electrolyte.

  During power generation of the magnesium battery, the circulation pump may be always driven, but may be limitedly driven under a situation where the output of the magnesium battery is reduced.

  For example, when the supply of power from the magnesium battery to the load is started, that is, when the power generation of the magnesium battery is started, the output of the magnesium battery is low, so the circulation pump is driven until a certain time has elapsed since the start of power generation. Also good. Thereby, the output at the time of the power generation start of a magnesium battery can be improved.

  In a magnesium battery, magnesium hydroxide is generated with a power generation reaction. When the amount of magnesium hydroxide in the electrolytic solution increases, the electrical resistivity of the electrolytic solution increases and the output of the magnesium battery decreases. Therefore, when the electrical resistivity of the electrolytic solution is equal to or higher than a predetermined reference resistivity, the circulation pump is driven, and when the electrical resistivity of the electrolytic solution is less than the reference resistivity, the driving of the circulation pump is stopped. May be. In this case, the magnesium battery system controls the driving of the circulation pump based on the resistivity detector that detects the electrical resistivity of the electrolyte solution at the bottom of the magnesium battery and the electrical resistivity detected by the resistivity detector. And a control unit.

  A filter for filtering the electrolytic solution flowing through the electrolytic solution circulation path and removing magnesium hydroxide from the electrolytic solution is interposed in the middle part of the electrolytic solution circulation route or at the connection portion between the electrolytic solution circulation route and the magnesium battery. It is preferable.

  Thereby, the magnesium hydroxide in electrolyte solution can be removed at the time of circulation of electrolyte solution. As a result, the power generation capacity of the magnesium battery can be further improved.

  Further, the magnesium battery system may include an air supply path that is connected at one end to a portion where the electrolyte in the magnesium battery is stored, and an air pump that feeds air from the other end to the air supply path.

  According to this configuration, when the air pump is driven, air is fed into the air supply path, and the air is supplied into the electrolyte in the magnesium battery through the air supply path. Thereby, air can be satisfactorily supplied to the positive electrode, and the power generation reaction at the positive electrode can be promoted. As a result, the power generation capacity of the magnesium battery can be further improved.

  The magnesium battery includes a negative electrode formed by bonding a thin film negative electrode material mainly composed of magnesium on both sides of a conductive plate made of aluminum, and a lead wire for taking out electrons from the negative electrode is connected to the conductive plate. Good.

  Thereby, it can suppress that the local oxidation of magnesium advances in the part to which the lead wire was connected. As a result, it is possible to prevent the lead wire from being detached from the negative electrode after a short period of use, and in turn, it is possible to extend the life of the magnesium battery.

  According to the present invention, the power generation capability (output) of a magnesium battery can be improved.

It is a figure which shows the structure of the magnesium battery system which concerns on one Embodiment of this invention. It is a block diagram which shows the electrical constitution of a magnesium battery system. It is a flowchart which shows the flow of a power generation capability adjustment process.

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

<System configuration>
FIG. 1 is a diagram showing a configuration of a magnesium battery system 1 according to an embodiment of the present invention.

  The magnesium battery system 1 includes a magnesium battery 2.

  The magnesium battery 2 is a fuel cell using magnesium for the negative electrode 21.

  The negative electrode 21 has a configuration in which a thin film negative electrode material 23 is bonded to both surfaces of a thin plate-like conductive plate 22. The conductive plate 22 is made of aluminum, and the negative electrode material 23 is made of magnesium to which 1.5 to 2.5% by weight of calcium is added. The conductive plate 22 and the negative electrode material 23 are joined by, for example, pressure bonding.

  In the magnesium battery 2, the positive electrode 24 is disposed to face the one surface of the negative electrode 21 with a space therebetween. The positive electrode 24 is made of copper or a copper alloy (for example, gun metal).

  The negative electrode 21 and the positive electrode 24 are disposed in the container 25. An electrolytic solution 26 is stored in the container 25, and at least a part of the negative electrode 21 and the positive electrode 24 is immersed in the electrolytic solution 26. The electrolytic solution 26 includes citric acid, sodium chloride, and water. The concentration of citric acid is, for example, 3 to 5% by weight, preferably 5% by weight.

  One end of lead wires 27 and 28 is connected to the conductive plate 22 and the positive electrode 24 of the negative electrode 21 by soldering. The other ends of the lead wires 27 and 28 are connected to an electric load (not shown).

In the magnesium battery 2, a power generation reaction occurs, and an electromotive force is generated by the power generation reaction. Specifically, in the magnesium battery 2, magnesium of the negative electrode material 23 of the negative electrode 21 emits electrons (e ⁻ ), and magnesium ions (Mg ²⁺ ) are eluted into the electrolytic solution. On the other hand, in the positive electrode, oxygen (O ₂ ) and water (H ₂ O) receive electrons and become hydroxide ions. When viewed as a whole of the magnesium battery 2, magnesium hydroxide (Mg (OH) ₂ ) is generated from magnesium, oxygen, and water, and an electromotive force is generated between the negative electrode 21 and the positive electrode 24.

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 ↓

  The magnesium battery system 1 includes an electrolyte circulation path 3, a circulation pump 4, an air supply path 5, an air pump 6, an exhaust gas path 7, an exhaust gas valve 8, and a resistivity detector 9.

  One end of the electrolyte circulation path 3 is connected to the bottom of the container 25 of the magnesium battery 2. The other end of the electrolytic solution circulation path 3 is connected to the upper part of the container 25 of the magnesium battery 2.

  The circulation pump 4 is interposed in the middle of the electrolyte circulation path 3.

  When the circulation pump 4 is driven, the electrolytic solution 26 stored in the container 25 of the magnesium battery 2 is sucked out from the bottom of the container 25 into the electrolytic solution circulation path 3. The electrolytic solution sucked into the electrolytic solution circulation path 3 flows through the electrolytic solution circulation path 3 and is returned from the upper part of the container 25 into the container 25. Thereby, the electrolyte solution 26 circulates through the magnesium battery 2 and the electrolyte circuit 3.

  Further, a filter 10 is interposed in the middle of the electrolytic solution circulation path 3. In the magnesium battery 2, magnesium hydroxide is generated along with the power generation reaction. Magnesium hydroxide does not dissolve in the electrolytic solution, and a part of it precipitates at the bottom of the container 25 of the magnesium battery 2. Therefore, when the circulation pump 4 is driven, magnesium hydroxide flows out together with the electrolytic solution 26 into the electrolytic solution circulation path 3. With the filter 10, the electrolytic solution 26 flowing through the electrolytic solution circulation path 3 can be filtered to remove magnesium hydroxide from the electrolytic solution 26.

  The filter 10 may be interposed upstream of the circulation pump 4 in the flow direction of the electrolyte solution 26 in the electrolyte circulation path 3, or may be interposed downstream. When the filter 10 is interposed on the upstream side of the circulation pump 4, magnesium hydroxide can be prevented from entering the circulation pump 4. Further, the filter 10 may be interposed in a connection portion between the container 25 of the magnesium battery 2 and the electrolyte circulation path 3.

  One end of the air supply path 5 is connected to the bottom of the container 25 of the magnesium battery 2. The other end of the air supply path 5 is connected to the discharge port of the air pump 6.

  One end of an air suction pipe 11 is connected to the suction port of the air pump 6. The other end of the air suction pipe 11 is open to the atmosphere via an air filter 12.

  When the air pump 6 is driven, air (atmosphere) is sucked into the air suction pipe 11 through the air filter 12. The air sucked into the air suction pipe 11 is sent from the air pump 6 to the air supply path 5, and supplied through the air supply path 5 from the bottom of the container 25 of the magnesium battery 2 into the electrolytic solution 26 in the container 25.

  One end of the exhaust gas path 7 is connected to an upper portion of the container 25 of the magnesium battery 2, specifically, a portion in the container 25 where the electrolyte solution 26 is not stored. The other end of the exhaust gas passage 7 is open to the atmosphere.

  The exhaust gas valve 8 is interposed in the middle of the exhaust gas passage 7 and opens and closes the exhaust gas passage 7. In the magnesium battery 2, magnesium of the negative electrode material 23 emits electrons and magnesium ions are eluted into the electrolytic solution, but the emitted electrons react with hydrogen ions in the electrolytic solution 26 to generate hydrogen. By opening the exhaust gas valve 8 at an appropriate timing, the hydrogen remaining in the container 25 can be discharged through the exhaust gas passage 7. For example, when the magnesium battery system 1 is applied to a vehicle equipped with a hydrogen fuel engine that is an internal combustion engine using hydrogen as fuel, hydrogen discharged through the exhaust gas passage 7 may be supplied to the hydrogen fuel engine. Thereby, the hydrogen generated in the magnesium battery 2 can be used as the fuel for the hydrogen fuel engine, and the fuel efficiency of the vehicle equipped with the hydrogen fuel engine can be improved.

  The resistivity detector 9 is attached to the bottom of the container 25 of the magnesium battery 2 and detects the electrical resistivity of the electrolyte solution 26 at the bottom of the container 25.

<Electrical configuration>
FIG. 2 is a block diagram showing an electrical configuration of the magnesium battery system 1.

  The magnesium battery system 1 includes a control unit 13 having a configuration including a CPU and a memory.

  A resistivity detector 9 is connected to the control unit 13. A detection signal of the resistivity detector 9 is input. The control unit 13 is connected with a circulation pump 4, an air pump 6, and an exhaust gas valve 8 as control targets.

  The control unit 13 controls the driving of the circulation pump 4 and the air pump 6 based on the detection signal input from the resistivity detector 9 according to the program stored in the memory, and controls the opening / closing of the exhaust gas valve 8.

<Power generation capacity adjustment processing>
FIG. 3 is a flowchart showing the flow of the power generation capacity adjustment process.

  The control unit 13 starts the power generation capacity adjustment process with the start of power generation of the magnesium battery 2. For example, when a power generation request is input to the control unit 13 of the magnesium battery system 1 from a power control device that controls the supply of power to the electric load, power generation of the magnesium battery 2 is started in response to this.

  In the power generation capacity adjustment process, first, the circulation pump 4 is driven (turned on) (step S1). By driving the circulation pump 4, the electrolyte solution 26 circulates through the magnesium battery 2 and the electrolyte solution circulation path 3.

  Further, the air pump 6 is driven (turned on) (step S2). Air is supplied into the electrolyte solution 26 of the magnesium battery 2 by driving the air pump 6.

  Next, it is determined whether or not a fixed time has elapsed since the start of driving of the circulation pump 4 and the air pump 6, that is, the power generation start of the magnesium battery 2 (step S3). The circulation pump 4 and the air pump 6 are continuously driven until a certain time has elapsed from the start of power generation by the magnesium battery 2.

  When a certain time has elapsed from the start of power generation by the magnesium battery 2 (YES in step S3), the detection signal of the resistivity detector 9 is referred to, and the electrical resistivity of the electrolyte 26 detected by the resistivity detector 9 is predetermined. It is determined whether or not the reference resistivity is greater than or equal to (step S4).

  When the electrical resistivity detected by the resistivity detector 9 is equal to or higher than the reference resistivity (YES in step S4), if the circulation pump 4 is stopped, the circulation pump 4 is driven again (ON). If the circulating pump 4 is driven, the driving state is maintained (step S5).

  On the other hand, when the electrical resistivity detected by the resistivity detector 9 is less than the reference resistivity (NO in step S4), if the driving of the circulation pump 4 is stopped, the stopped state is maintained, and the circulation pump If 4 is driven, the drive is stopped (off) (step S6).

  Subsequently, it is determined whether or not the output value (output voltage value or output current value) of the magnesium battery 2 is less than a predetermined reference output value (step S7).

  When the output value of the magnesium battery 2 is less than the reference output value (YES in step S7), if the drive of the air pump 6 is stopped, the air pump 6 is driven (turned on) again, and the air pump 6 is driven. If so, the driving state is maintained (step S8).

  On the other hand, when the output value of the magnesium battery 2 is equal to or higher than the reference output value (NO in step S7), if the driving of the air pump 6 is stopped, the stopped state is maintained and the air pump 6 is driven. If so, the driving is stopped (OFF) (step S9).

  Thereafter, it is determined whether or not the output of the magnesium battery 2 is stopped, for example, whether or not the power generation request from the power control device of the electric load to the control unit 13 is stopped (step S10).

  While the output of the magnesium battery 2 continues (NO in step S10), it is repeatedly determined whether or not the electrical resistivity of the electrolytic solution 26 detected by the resistivity detector 9 is equal to or higher than the reference resistivity ( In step S4), the driving of the circulation pump 4 is controlled based on the determination result (steps S5 and S6). Further, it is repeatedly determined whether or not the output value of the magnesium battery 2 is less than the reference output value (step S7), and the drive of the air pump 6 is controlled based on the determination result (steps S8 and S9).

  When the output of the magnesium battery 2 is stopped (YES in step S10), for example, when the power generation request from the power control device of the electric load to the control unit 13 is stopped, the circulation pump 4 and the air pump 6 may be in operation. If so, their driving is stopped (steps S11 and S12), and the power generation capacity adjustment process is terminated.

<Effect>
As described above, the magnesium battery system 1 includes the magnesium battery 2, the electrolyte circuit 3 that is connected to the magnesium battery at both ends, and the circulation pump 4 that circulates the electrolyte of the magnesium battery 2 through the electrolyte circuit 3. including. When the circulation pump 4 is driven, the electrolyte solution 26 of the magnesium battery 2 circulates through the electrolyte circuit 3. The electrolytic solution 26 is circulated during the power generation of the magnesium battery 2, so that the power generation capacity of the magnesium battery 2 can be improved.

  When the supply of power from the magnesium battery 2 to the load is started, that is, when the power generation of the magnesium battery 2 is started, the output of the magnesium battery 2 is low, so that the circulation pump 4 is driven until a certain time elapses from the start of power generation. Is done. Thereby, the power generation capability at the start of power generation of the magnesium battery 2 can be improved.

  In the magnesium battery 2, magnesium hydroxide is generated along with the power generation reaction. When the amount of magnesium hydroxide in the electrolytic solution 26 increases, the electrical resistivity of the electrolytic solution 26 increases and the power generation capacity of the magnesium battery 2 decreases. Therefore, when the electrical resistivity of the electrolytic solution 26 is equal to or higher than a predetermined reference resistivity, the circulation pump 4 is driven, and when the electrical resistivity of the electrolytic solution 26 is less than the reference resistivity, the circulation pump 4 Driving is stopped. Thereby, the power generation capability of the magnesium battery 2 can be improved in a situation where the power generation capability of the magnesium battery 2 is reduced.

  Further, when the electrolytic solution 26 flows through the electrolytic solution circulation path 3, magnesium hydroxide is removed from the electrolytic solution 26 by the filter 10. Therefore, the power generation capability of the magnesium battery 2 can be further improved.

  Further, when the output value of the magnesium battery 2 is less than the reference output value, the air pump 6 is driven, and when the output value of the magnesium battery 2 is equal to or higher than the reference output value, the driving of the air pump 6 is stopped. When the air pump 6 is driven, air is sent into the air supply path 5, and the air is supplied into the electrolyte solution 26 in the magnesium battery 2 through the air supply path 5. Thereby, air can be satisfactorily supplied to the positive electrode 24 and the power generation reaction at the positive electrode 24 can be promoted. As a result, the power generation capacity of the magnesium battery 2 can be further improved.

  The negative electrode 21 of the magnesium battery 2 is formed by bonding a negative electrode material 23 mainly composed of magnesium to both surfaces of a conductive plate 22 made of aluminum. A lead wire 27 for taking out electrons from the negative electrode 21 is connected to the conductive plate 22. Thereby, it can suppress that the local oxidation of the negative electrode material 23 (magnesium) advances in the part to which the lead wire 27 was connected. As a result, it is possible to prevent the lead wire from coming off from the negative electrode 21 after a short period of use, and thus the life of the magnesium battery 2 can be extended.

  As mentioned above, although one Embodiment of this invention was described, this invention can also be implemented with another form.

  For example, the configuration in which the resistivity detector 9 is provided and the electrical resistivity of the electrolytic solution 26 is detected has been taken up. However, instead of the resistivity detector 9, a conductivity detector is provided and the electrolytic solution 26 is provided. The electrical conductivity (electrical conductivity) may be detected. Electrical conductivity is the reciprocal of electrical resistivity. Therefore, in the configuration in which the conductivity detector is provided, it is determined whether or not the conductivity of the electrolyte solution 26 detected by the conductivity detector is less than a predetermined reference conductivity, and the conductivity of the electrolyte solution 26 is determined. Is lower than the reference conductivity, the circulation pump 4 is driven (turned on) again if the drive of the circulation pump 4 is stopped, and the drive state is maintained if the circulation pump 4 is driven. Good. On the other hand, when the conductivity of the electrolytic solution 26 is equal to or higher than the reference conductivity, the stopped state is maintained if the driving of the circulation pump 4 is stopped, and the driving is performed if the circulation pump 4 is driven. May be stopped (off).

  Further, the material of the conductive plate 22 of the negative electrode 21 is not limited to aluminum, and any material having conductivity may be used. The material of the conductive plate 22 of the negative electrode 21 may be copper, for example. However, the configuration in which the conductive plate 22 is made of aluminum can exhibit better adhesion between the conductive plate 22 and the negative electrode material 23 than the configuration made of copper, and the negative electrode material 23 is peeled off from the conductive plate 22. Can be suppressed.

  The electrolyte solution 26 contains citric acid, sodium chloride, and water. However, the electrolytic solution 26 may be a citric acid aqueous solution that does not contain sodium chloride, or a solution that does not contain citric acid as an electrolyte, such as a copper sulfate aqueous solution, a copper acetate aqueous solution, a copper chloride aqueous solution, or an ammonium chloride aqueous solution. There may be.

  In the above embodiment, when the electrical resistivity detected by the resistivity detector 9 is equal to or higher than the reference resistivity, the circulation pump 4 is driven (turned on), and the electrical resistivity is less than the reference resistivity. In addition, the driving of the circulation pump 4 is stopped (turned off). Not limited to this, when the electrical resistivity detected by the resistivity detector 9 is equal to or higher than the first reference resistivity, the circulation pump 4 is driven (turned on), and the electrical resistivity is equal to the first reference resistivity. The driving of the circulation pump 4 may be stopped (turned off) when they are equal to or less than the different second reference resistivity.

  In the above-described embodiment, when the output value of the magnesium battery 2 is less than the reference output value, the air pump 6 is driven (turned on), and when the output value of the magnesium battery 2 is equal to or greater than the reference output value, the air pump 6 is stopped (turned off). Not limited to this, when the output value of the magnesium battery 2 is less than or equal to the first reference output value, the air pump 6 is driven (turned on), and the output value of the magnesium battery 2 is different from the first reference output value. When the output value is greater than or equal to the output value, the driving of the air pump 6 may be stopped (off).

  In addition, various design changes can be made to the above-described configuration within the scope of the matters described in the claims.

DESCRIPTION OF SYMBOLS 1 Magnesium battery system 2 Magnesium battery 3 Electrolyte circulation path 4 Circulation pump 5 Air supply path 6 Air pump 9 Resistivity detector 10 Filter 13 Control part 21 Negative electrode 22 Conductive plate 23 Negative electrode material 26 Electrolyte 27 Lead wire

Claims (5)

Magnesium battery,
An electrolyte circuit in which both ends are connected to the magnesium battery;
A magnesium battery system comprising: a circulation pump for circulating the electrolyte of the magnesium battery through the electrolyte circuit. A resistivity detector for detecting the electrical resistivity of the electrolyte at the bottom of the magnesium battery;
The magnesium battery system according to claim 1, further comprising a control unit that controls driving of the circulation pump based on an electrical resistivity detected by the resistivity detector. An air supply path having one end connected to a portion where the electrolyte in the magnesium battery is stored;
The magnesium battery system according to claim 1, further comprising an air pump that feeds air into the air supply path from the other end.   The magnesium battery system as described in any one of Claims 1-3 which further includes the filter which filters the electrolyte solution which distribute | circulates the said electrolyte solution circulation path, and removes magnesium hydroxide from electrolyte solution. The magnesium battery includes a negative electrode formed by bonding a thin film negative electrode material mainly composed of magnesium on both surfaces of a conductive plate made of aluminum,
The magnesium battery system according to any one of claims 1 to 4, wherein a lead wire for extracting electrons from the negative electrode is connected to the conductive plate.

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