JP5684929B1 - Metal air battery - Google Patents

Abstract

A metal-air battery that facilitates resuming a battery reaction is provided. In a metal-air battery including a negative electrode composed of a magnesium electrode and a positive electrode composed of an air electrode, an open / close type circuit that selectively forms a closed circuit including the magnesium electrode and the air electrode. A short circuit 31 is provided. [Selection] Figure 1

Description

The present invention relates to a technique for removing a passive film formed on the surface of a negative electrode (metal electrode) of a metal-air battery and restarting the battery reaction after stopping the use of the metal-air battery.

  There are known metal-air batteries that can generate electricity when an electrolyte such as saline is injected in a natural disaster, storm and flood damage, or in an environment where it is difficult to obtain an AC power supply. In this type of metal-air battery, the negative electrode is formed of a metal electrode, the positive electrode is formed of an air electrode, and the metal electrode uses an alloy prepared by mixing other elements in addition to the metal element as the main reactant. (For example, refer to Patent Document 1). This Patent Document 1 describes using a magnesium alloy in which aluminum (Al), zinc (Zn), or the like is added to a metal electrode in order to suppress generation of hydrogen gas due to a self-discharge reaction of the metal electrode. Yes.

JP 2012-234799 A

  It is known that the above additive elements are greatly involved in the formation of a protective film that inhibits self-reaction and suppresses the generation of hydrogen on the surface of the alloy. As a result of investigations by the inventors, the protective coating may inhibit the battery reaction, and it may be difficult to resume the battery reaction when attempting to use the battery again after the battery is stopped and stopped. .

  This invention is made | formed in view of the situation mentioned above, and it aims at providing the metal air battery which made it easy to restart battery reaction.

In order to solve the above-described problems, the present invention includes a negative electrode made of a metal electrode and a positive electrode made of an air electrode, and is used in a metal-air battery that is used by injecting an electrolyte solution. Before, the passive film is not formed on the surface, and it is a metal electrode in which the passive film is formed on the surface by the oxide generated by the battery reaction after the injection of the electrolyte, and the passive film is removed For this purpose, a circuit is provided that selectively forms a closed circuit including the negative electrode and the positive electrode in a state where a load is not connected . According to this configuration, it is possible to form a closed circuit including the negative electrode and the positive electrode, remove the passive film formed on the negative electrode (metal electrode) surface of the metal-air battery, and refresh the negative electrode (metal electrode) surface. This makes it easier to restart the battery reaction.

  The circuit may be an open / close short circuit provided between the negative electrode and the positive electrode. According to this configuration, it is easy to restart the battery reaction with a simple configuration.

Further, the circuit may be an open / close type resistance discharge circuit provided between the negative electrode and the positive electrode. According to this configuration, it is easy to restart the battery reaction with a simple configuration.
In this case, the resistance discharge circuit may be a circuit protector switch that opens when the value of the current flowing through the circuit exceeds a predetermined value. According to this configuration, it becomes easy to protect the circuit and the like, and an operation for opening the switch can be made unnecessary. In addition, the loss of discharge power can be reduced.

  In addition, a plurality of unit cells including the negative electrode and the positive electrode may be connected in series, and the circuit may be provided between the negative electrode and the positive electrode at both ends of the assembled battery including the plurality of unit cells. . According to this configuration, it is easy to flow a large current and the number of parts can be reduced as compared with the case where an open / close short circuit is provided for each unit battery.

Further, a current detection unit that detects a current value flowing through the closed circuit may be provided. According to this configuration, the passive film formed on the negative electrode (metal electrode) surface of the metal-air battery can be removed, and information capable of determining whether the negative electrode (metal electrode) surface has been refreshed can be obtained.
In this case, the current detection unit may open the circuit according to the detected current value. According to this configuration, a user operation for switching to an open circuit can be made unnecessary, and loss of discharge power can be reduced.

Further, an integrated current detection unit that detects an integrated current value flowing through the closed circuit may be provided. According to this configuration, the passive film formed on the negative electrode (metal electrode) surface of the metal-air battery can be removed, and information capable of determining whether the negative electrode (metal electrode) surface has been refreshed can be obtained.
In this case, the integrated current detection unit may open the circuit according to the detected integrated current value. According to this configuration, a user operation for switching to an open circuit can be made unnecessary, and loss of discharge power can be reduced.

Moreover, you may make it provide the time detection part which detects the elapsed time after making the said closed circuit. According to this configuration, the passive film formed on the negative electrode (metal electrode) surface of the metal-air battery can be removed, and information capable of determining whether the negative electrode (metal electrode) surface has been refreshed can be obtained.
In this case, the time detection unit may open the circuit according to the detected elapsed time. According to this configuration, a user operation for switching to an open circuit can be made unnecessary, and loss of discharge power can be reduced.

  In the present invention, the negative electrode may be formed of a magnesium alloy containing at least zinc. According to this configuration, when it becomes difficult to restart the battery reaction after the battery is suspended due to the influence of zinc, the battery reaction is easily restarted.

ADVANTAGE OF THE INVENTION According to this invention, the metal-air battery which removed the passive film formed in the negative electrode surface of a metal-air battery and made it easy to restart a battery reaction can be provided.

It is the figure which showed the structure of the metal air battery system which concerns on 1st Embodiment of this invention. It is the figure which showed the modification of the metal air battery system which concerns on 1st Embodiment. (A) is the figure which showed the structure of the metal air battery system which concerns on 2nd Embodiment, (B) is the figure which showed the modification. It is the figure which showed another modification of the metal air battery system which concerns on 2nd Embodiment. (A) is the figure which showed the structure of the metal air battery system which concerns on 3rd Embodiment, (B) is the figure which showed the structure of the metal air battery system which concerns on 4th Embodiment. It is the figure which showed the structure of the metal air battery system which concerns on 5th Embodiment. It is the figure which showed the structure of the metal air battery system which concerns on 6th Embodiment.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
(First embodiment)
FIG. 1 is a diagram showing a configuration of a metal-air battery system 10 according to the first embodiment of the present invention.
The metal-air battery system 10 includes a plurality (four in the present configuration) of metal-air batteries 21 constituting a unit battery (single cell battery). Each metal-air battery 21 is a primary battery that includes a pair of magnesium electrodes (metal electrodes) 22 and an air electrode 23 and generates electric power using oxygen in the air for an electrochemical reaction. During this electrochemical reaction (battery reaction), the magnesium electrode 22 acts as a negative electrode, and the air electrode 23 acts as a positive electrode.

The plurality of metal-air batteries 21 are connected in series, and a DC-DC converter (power converter) 25 is connected to the magnesium electrode 22 and the air electrode 23 at both ends. When there is no need to distinguish between the plurality of metal-air batteries 21 in particular, they are denoted as an assembled battery 21A.
The DC-DC converter 25 includes a conversion circuit 26 that converts DC power into different DC power. As a result, the DC power output from the assembled battery 21A is converted into DC power suitable for charging a mobile phone and the like, and is output from the metal-air battery system 10.

  That is, the DC-DC conversion device 25 functions as a power conversion device that converts power into power suitable for the use-side device. Therefore, for example, when the device on the use side is a device that requires a higher current value or voltage value than the mobile phone, it can be easily handled by changing the DC-DC converter 25. Moreover, you may comprise this DC-DC converter 25 so that the switching function which switches output electric power to various electric power may be comprised. Moreover, when the electric power obtained by the assembled battery 21 </ b> A is large, a DC-AC conversion device that converts it into AC power may be provided.

When the metal-air battery system 10 is used, an electrolytic solution capable of eluting magnesium ions from the magnesium electrode 22 is filled between the magnesium electrode 22 and the air electrode 23.
Specifically, the electrolytic solution contains chloride ions as anions, alkali metal ions (Li, Na, K, Rb, Cs, Fr) as cations, alkaline earth metal ions (Be, Mg, Ca, Sr, An aqueous solution containing at least one of Ba, Ra) is used. In the present embodiment, a sodium chloride aqueous solution containing sodium ions is used as the electrolytic solution in terms of safety and high conductivity.

  The magnesium electrode 22 is made of ASTM standard AZ31, AZ61, AZ91, or the like, which is 96% magnesium, 3% aluminum, and 1% zinc. In addition, you may use not only what is based on an ASTM specification but a well-known Mg-Al-Zn type alloy. Further, elements other than aluminum and zinc may be added. For example, other elements such as Si, Cu, Li, Na, K, Fe, Ni, Ti, and Zr may be added.

  The air electrode 23 is made of a material obtained by mixing a carbon mesh (copper wire mesh) with carbon and Teflon (registered trademark) into a sheet having a predetermined thickness, and then dried and fired. The sheet is then pressed and clamped from both sides of the copper mesh. As a result, the air electrode 23 allows external air to pass through the inside of the metal-air battery 21, and the internal electrolyte solution has non-water permeability that cannot be transmitted to the outside. A known metal air battery can be widely applied to the metal air battery 21.

  In the metal-air battery 21 having this configuration, the reactions of the air electrode 23 and the magnesium electrode 22 are as follows.

(Air electrode) O ₂ + 2H ₂ O + 4e− → 4OH−
(Magnesium electrode)
Power generation reaction of magnesium: Mg + 2OH− → Mg (OH) ₂ + 2e−
Magnesium self-discharge: Mg + 2H ₂ O → Mg (OH) ₂ + H ₂
Power generation reaction of zinc: Zn + 4OH− → Zn (OH) ₄ ²⁻ + 2e−
In the electrolyte: Zn (OH) ₄ ²⁻ → ZnO + H ₂ O + 2OH−
Power generation reaction of aluminum: Al + 3OH− → Al (OH) ₃ + 3e−

In general, since magnesium is a highly reactive material, self-discharge tends to occur as described above.
In this configuration, by using the magnesium alloy, a protective film (passivation) that suppresses the generation of hydrogen by inhibiting self-discharge on the surface of the magnesium electrode 22 by the oxide (for example, zinc oxide) generated by the battery reaction. ) And the self-discharge reaction can be suppressed.

  However, according to the study by the inventors, the protective coating may also inhibit the battery reaction (power generation reaction), and when the battery is stopped and stopped, the battery reaction is sufficient when trying to use the battery again. It was found that the necessary current could not be taken out. In particular, when zinc was added, a situation where current could not be taken out easily occurred.

Therefore, in this embodiment, an open / close short circuit 31 is provided between the magnesium electrode 22 and the air electrode 23 of the metal-air battery 21. This open / close short circuit 31 is connected between the magnesium electrode 22 and the air electrode 23 at both ends of the metal-air batteries 21 connected in series, and can be manually opened and closed by the user (so-called manual switch). It is configured.
Then, by switching the open / close type short circuit 31 from open to closed, the closed circuit including the electrode plates 22 and 23 of all the metal-air batteries 21, that is, the closed circuit that short-circuits all the metal-air batteries 21. A circuit is formed. As a result, a relatively large current is forced to temporarily flow through each metal-air battery 21, and the protective film (corresponding to the passive film layer) formed on the surface of the magnesium electrode 22 is dissolved in the electrolytic solution. The exposed metal surface.

Therefore, after the battery is suspended, the metal-air battery 21 can be easily refreshed by temporarily switching the open / close type short circuit 31 from open to closed, and the battery reaction is easily resumed. be able to.
For this reason, the battery reaction can be restarted by returning the short circuit 31 from the closed state to the open state after the refresh, and a sufficient current can be immediately output. Accordingly, if a usage-side device is connected to the output side of the metal-air battery system 10, it is possible to immediately supply power suitable for driving and charging the usage-side device.
In addition, since all the metal air batteries 21 are short-circuited in a state where they are connected in series, it is easier to flow a large current and the number of parts compared to the case where an open / close-type short circuit 31 is provided for each metal air battery. Can be reduced.

Furthermore, the open / close short circuit 31 is provided in the DC-DC converter 25 as shown in FIG. For this reason, the short circuit 31 can be accommodated using the exterior body of the DC-DC converter 25, and the exterior body only for the short circuit 31 can be made unnecessary. In addition, since the short circuit 31 is configured to be interposed between the magnesium electrode 22 and the air electrode 23 of the assembled battery 21A, the short circuit 31 can be easily added to a conventional metal-air battery system that does not include the short circuit 31. It can be added.
Moreover, as shown in FIG. 1, since the short circuit 31 is provided on the input side (metal-air battery side) of the conversion circuit 26, the conversion circuit is formed on the closed circuit that can be formed when the short circuit 31 is switched to the closed state. Therefore, the resistance in the closed circuit can be reduced accordingly. Therefore, a large current (short-circuit current) can be passed efficiently, and the metal-air battery 21 can be easily refreshed.

  Moreover, since the short circuit 31 is provided in the DC-DC converter 25, if the DC-DC converter 25 is removed, the short circuit 31 can also be removed, and the short circuit 31 is easily attached and detached. Therefore, maintenance work such as replacement and inspection of the short circuit 31 can be easily performed.

As described above, the metal-air battery system 10 of the present embodiment is an open / closed short circuit that is a circuit that selectively forms a closed circuit including the magnesium electrode 22 constituting the negative electrode and the air electrode 23 constituting the positive electrode. Since the circuit 31 is provided, it is easy to restart the battery reaction even when it is difficult to restart the battery reaction after the battery is stopped due to the influence of the protective coating ( passive coating) of the magnesium electrode 22.
Moreover, the short circuit 31 may be provided between the magnesium electrode 22 and the air electrode 23 of the assembled battery 21A, and can be provided simply. Therefore, an increase in the number of parts and an increase in the size of the apparatus can be suppressed, and an increase in cost can be easily suppressed.
In addition, since the open / close-type short circuit 31 includes a manual switch, it can be easily configured and is easy for the user to operate.

  In the present embodiment, the case where the short circuit 31 is provided on the assembled battery 21A side of the DC-DC converter 25 has been described, but the short circuit 31 is provided on the output side of the DC-DC converter 25 as shown in FIG. Or may be provided outside the DC-DC converter 25. That is, the position of the short circuit 31 may be changed as appropriate.

(Second Embodiment)
FIG. 3A is a diagram illustrating a configuration of the metal-air battery system 10 according to the second embodiment. In the following description, the same components as those in the first embodiment are denoted by the same reference numerals, and redundant descriptions are omitted.
In the second embodiment, an open / close type resistance discharge circuit 33 is provided between the magnesium electrode 22 and the air electrode 23 of the assembled battery 21 </ b> A. The resistance discharge circuit 33 includes a resistor and a switch. This resistance discharge circuit 33 can also form a closed circuit including the assembled battery 21A by temporarily switching the switch from open to closed. Therefore, similarly to the first embodiment, with a simple configuration, it is possible to forcibly flow a large current temporarily after the battery is suspended and to refresh the battery. As a result, various effects similar to those of the first embodiment, such as easy resumption of the battery reaction, can be obtained with a simple configuration.

FIG. 3B shows a specific example in which a circuit protector switch 33 </ b> S is applied to the resistance discharge circuit 33. The circuit protector switch 33S is a switch that opens when the value of the current flowing through the closed circuit generated when the switch 33S is switched from open to closed exceeds a predetermined threshold, and is also referred to as a circuit protector.
By using the circuit protector switch 33S, the switch can be automatically opened before the current value exceeds a predetermined value set to be equal to or lower than the allowable current, and it becomes easy to protect the circuit. In addition, the operation of opening the switch can be made unnecessary, and since it is not necessary to discharge without permission, the loss of discharge power can also be reduced. Further, since the circuit protector switch 33S is a widely distributed component, it is advantageous for reducing the cost.

  3A and 3B, the case where the resistance discharge circuit 33 (including the circuit protector switch 33S) is provided on the assembled battery 21A side of the DC-DC converter 25 has been described. As shown in FIG. 4, the resistance discharge circuit 33 may be provided on the output side of the DC-DC converter 25 or may be provided outside the DC-DC converter 25. That is, the position of the resistance discharge circuit 33 may be changed as appropriate.

(Third embodiment)
FIG. 5A is a diagram showing a configuration of the metal-air battery system 10 according to the third embodiment. The third embodiment shows a metal-air battery system 10 that does not include the DC-DC converter 25. Also in this metal-air battery system 10, the battery reaction can be easily restarted by providing an open / close type short circuit 31 between the magnesium electrode 22 and the air electrode 23 of the assembled battery 21A. Various similar effects can be obtained.

(Fourth embodiment)
FIG. 5B is a diagram illustrating a configuration of the metal-air battery system 10 according to the fourth embodiment. In the fourth embodiment, a resistance discharge circuit 33 is provided instead of the short circuit 31 of FIG. With this configuration, various effects similar to those of the second embodiment can be obtained. Further, the circuit protector switch 33S may be applied to the resistance discharge circuit 33.

(Fifth embodiment)
FIG. 6 is a diagram illustrating a configuration of the metal-air battery system 10 according to the fifth embodiment.
In the fifth embodiment, an integrated current detector 35 is provided. The integrated current detection unit 35 integrates the current values flowing through the closed circuit including the metal-air battery 21 to detect the integrated current value, and the automatic switch function switches the short-circuit circuit 31 to open according to the integrated current value. And.

  By detecting the integrated current value, information capable of determining whether or not the metal-air battery 21 has been refreshed can be obtained. In the automatic switch function, for example, when an integrated current value sufficient to refresh the metal-air battery 21 is reached, a threshold value is set in advance so that the short circuit 31 is switched to the switch open. Thus, when the integrated current value reaches the threshold value, the circuit is automatically switched to an open circuit, and the refresh operation can be terminated. Therefore, a user operation for switching to an open circuit can be made unnecessary, and loss of discharge power can be reduced.

A well-known configuration can be widely applied to the integrated current detection unit 35.
As a modification, the automatic switch function may be omitted. In this case, the integrated current detector 35 preferably notifies the user when the detected integrated current value reaches a predetermined value. Thereby, it is possible to notify the user of the switch operation timing. Therefore, the user can operate the switch at an appropriate timing. Note that a known notification device such as a display device that transmits information by lighting or display or a voice output device that transmits information by sound can be widely applied as a device that notifies the user. Further, a resistance discharge circuit 33 may be provided in place of the short circuit 31.
In this embodiment, the integrated current value is detected, and the switching operation of the switch of the short circuit 31 is performed according to the detected value. However, the current value is detected instead of the integrated current value, and the short circuit is detected according to the detected value. The switching operation of 31 switches may be performed.

(Sixth embodiment)
FIG. 7 is a diagram showing the configuration of the metal-air battery system 10 according to the sixth embodiment.
In the sixth embodiment, a time detection unit 37 is provided. The time detection unit 37 has a function of detecting (measuring) an elapsed time since the closed circuit and an automatic switch function of switching the short circuit 31 to the switch open according to the detected elapsed time.

  By detecting the elapsed time, information capable of determining whether or not the metal-air battery 21 has been refreshed can be obtained. In the automatic switch function, for example, a threshold value is set in advance so as to switch the short circuit 31 to the switch open when an elapsed time sufficient to refresh the metal-air battery 21 is reached. Thus, when the elapsed time reaches the threshold value, the circuit is automatically switched to an open circuit, and the refresh operation can be terminated at an appropriate timing. Therefore, a user operation for switching to an open circuit can be made unnecessary, and loss of discharge power can be reduced.

As the time detection unit 37, a known configuration can be widely applied.
As a modification, the automatic switch function may be omitted. In this case, when the detected elapsed time reaches a predetermined value, the time detection unit 37 preferably notifies the user to that effect. Accordingly, the switch operation timing can be notified to the user, and the user can perform the switch operation at an appropriate timing. Instead of the short circuit 31, a resistance discharge circuit 33 may be provided.

As mentioned above, although the form for implementing this invention was described, this invention is not limited to the above-mentioned embodiment, Based on the technical idea of this invention, various deformation | transformation and change are possible. For example, in the above-described embodiment, the case where the present invention is applied to the metal-air battery 21 including the magnesium electrode 22 added with aluminum and zinc has been described. The present invention may be applied to the metal-air battery.
Furthermore, the present invention may be applied to a metal-air battery including a magnesium electrode not containing zinc or a metal-air battery including a metal electrode other than magnesium. In short, the present invention can be widely applied to metal-air batteries in which it is difficult to restart the battery reaction after a pause due to the material of the metal electrode or the like.

10 Metal-air battery system 21 Metal-air battery 21A Assembly battery 22 Magnesium electrode (metal electrode)
23 Air electrode 25 DC-DC converter (power converter)
31 Short circuit 33 Resistance discharge circuit 33S Circuit protector switch 35 Accumulated current detector 37 Time detector

Claims (12)

In a metal-air battery comprising a negative electrode made of a metal electrode and a positive electrode made of an air electrode and used by being injected with an electrolyte,
The negative electrode is
Before the electrolyte injection, no passive film is formed on the surface,
It is a metal electrode in which a passive film is formed on the surface by the oxide generated by the battery reaction after the injection of the electrolyte,
A metal-air battery comprising a circuit that selectively forms a closed circuit including the negative electrode and the positive electrode in a state where a load is not connected to remove the passive film .   2. The metal-air battery according to claim 1, wherein the circuit is an open / close short circuit provided between the negative electrode and the positive electrode.   2. The metal-air battery according to claim 1, wherein the circuit is an open / close type resistance discharge circuit provided between the negative electrode and the positive electrode.   The metal-air battery according to claim 3, wherein the resistance discharge circuit is a circuit protector switch that is opened when a current value flowing through the circuit exceeds a predetermined value. A plurality of unit cells including the negative electrode and the positive electrode are connected in series,
5. The metal-air battery according to claim 1, wherein the circuit is provided between the negative electrode and the positive electrode at both ends of the assembled battery including the plurality of unit batteries. 6.   6. The metal-air battery according to claim 1, further comprising a current detection unit that detects a value of a current flowing through the closed circuit.   The metal-air battery according to claim 6, wherein the current detection unit opens the circuit according to the detected current value.   The metal-air battery according to any one of claims 1 to 5, further comprising an integrated current detection unit that detects an integrated current value flowing through the closed circuit.   The metal-air battery according to claim 8, wherein the integrated current detection unit opens the circuit according to the detected integrated current value.   The metal-air battery according to any one of claims 1 to 5, further comprising a time detection unit that detects an elapsed time since the closed circuit. The metal-air battery according to claim 10 , wherein the time detection unit opens the circuit according to the detected elapsed time.   The metal-air battery according to any one of claims 1 to 11, wherein the negative electrode is formed of a magnesium alloy containing at least zinc.

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