JP2014127289A - Hybrid zinc battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hybrid zinc battery having a novel configuration, which is excellent in charge/discharge efficiency and output characteristics.SOLUTION: A hybrid zinc battery of the present invention includes: a negative electrode 1 formed of zinc or a zinc alloy; an oxygen reduction electrode 2 arranged on the side of one surface of the negative electrode 1 with a first partition wall 6a interposed therebetween; an oxygen generation electrode 3 arranged on the side of the other surface of the negative electrode 1 with a second partition wall 6b interposed therebetween; an aqueous solution electrolyte 5 containing zinc ions; and a case 4 housing the negative electrode 1, the oxygen reduction electrode 2, the oxygen generation electrode 3, the partition walls and the aqueous solution electrolyte 5. The oxygen generating electrode 3 is formed of nickel, iron or an alloy of nickel or iron.

Description

  The present invention relates to a hybrid zinc battery.

  As storage batteries, various types of batteries such as lead storage batteries, lithium ion secondary batteries, NAS batteries, redox flow batteries have been developed. Depending on applications such as power leveling and load leveling (use of nighttime power), a system with a suitable device configuration and electric capacity has been proposed. Among these storage batteries, zinc-air batteries that use oxygen in the atmosphere as the positive electrode active material have a very high weight energy density and a large theoretical capacity of 1000 Wh / kg. Yes. However, the zinc-air battery has problems such as low charge / discharge efficiency, low current density, corrosion of the air electrode during charging, and deterioration of the electrolytic solution due to CO2, and has not yet been put into practical use.

  Conventionally, as to the problem of corrosion of the positive electrode of a rechargeable battery of a zinc-air battery, a three-electrode air battery that performs oxygen generation (charging) and oxygen reduction (discharging) with different electrodes as described in Patent Document 1 Has been proposed.

JP 2006-93022 A

  The three-electrode zinc-air battery can be expected to suppress the corrosion of the air electrode during charging, but the energy obtained by discharging is less than the energy used for charging (charge / discharge efficiency is low) and the output characteristics are low. Issues remain.

  An object of the present invention is to provide a hybrid zinc battery having a novel configuration with a large capacity and excellent output characteristics.

  In order to solve the above problems, the gist of the present invention is as follows.

  The present invention uses an electrode material having a function of performing a charge reaction of a zinc-air battery and a function of a negative electrode containing zinc and a positive electrode for forming a secondary battery as an oxygen generating electrode of a three-electrode type zinc-air battery. Thus, a hybrid zinc battery in which two types of secondary batteries are combined is used.

  Specifically, the hybrid zinc battery of the present invention includes a negative electrode made of zinc or a zinc alloy, an oxygen reduction electrode disposed on one surface side of the negative electrode via a first partition, and the other of the negative electrode. An oxygen generating electrode disposed on the surface side via a second partition, an aqueous electrolyte containing zinc ions, and a housing for housing the negative electrode, oxygen reducing electrode, oxygen generating electrode, partition, and aqueous electrolyte And the oxygen generating electrode is nickel, iron, or any alloy thereof.

  ADVANTAGE OF THE INVENTION According to this invention, the hybrid zinc battery of the novel structure which was large capacity and excellent in the output characteristic can be provided.

The schematic diagram of the hybrid zinc battery which concerns on 1st Embodiment of this invention. The schematic diagram of the hybrid zinc battery which concerns on 2nd Embodiment of this invention. The schematic diagram of the hybrid zinc battery which concerns on 3rd Embodiment of this invention.

Hereinafter, the hybrid zinc battery according to the present embodiment will be described with reference to the drawings as appropriate.
[1. First Embodiment]
FIG. 1 is a diagram schematically showing the configuration of the hybrid zinc battery according to the first embodiment of the present invention. The hybrid zinc battery of the present embodiment includes a charge / discharge cell unit, an oxygen pipe 8, an oxygen pressure adjusting valve 9, and an oxygen chamber 7. The charge / discharge cell part is composed of a zinc negative electrode 1, an oxygen reduction electrode 2, an oxygen generation electrode 3, an aqueous electrolyte 5 and a partition wall 6, and a housing 4 for housing them. The oxygen reduction electrode 2 is disposed on one surface side of the zinc negative electrode 1 via the partition wall 6a, and the oxygen generation electrode 3 is disposed on the other surface side of the zinc negative electrode 1 via the partition wall 6b. The zinc negative electrode 1 and the oxygen generating electrode 3 are connected to a power source 10, and the zinc negative electrode 1 and the oxygen reducing electrode 2 and the zinc negative electrode 1 and the oxygen generating electrode 3 are connected to output terminals 11 and 12, respectively. The oxygen generation electrode 3 has a function as a positive electrode for forming a secondary battery with the zinc negative electrode 1 as well as a function of performing a charging reaction of the zinc-air battery. For this reason, in the hybrid zinc battery of this embodiment, the positive electrode is only the oxygen generating electrode 3 during charging, but both the oxygen reducing electrode 2 and the oxygen generating electrode 3 can be used as positive electrodes during discharging.

  Below, each structure of the hybrid zinc battery of this embodiment is demonstrated.

  First, in the air battery, zinc, aluminum, magnesium, iron, lead, lithium, and the like have been proposed as the negative electrode active material, but it can be charged and discharged with an aqueous electrolyte, and the overvoltage of water electrolysis is high. Zinc is most preferable as a material having a high energy density. Since an aqueous electrolyte can be applied, there are advantages that safety is improved and handling and transportation are facilitated. The zinc negative electrode 1 used in the present embodiment is made of zinc or a zinc alloy, and preferably has a high specific surface area. Examples of the high specific surface area shape include a shape of a porous body, a mesh, a punching metal, an expanded metal, a non-woven fabric, a shape roughened by high specific surface area plating, machining, or the like. Moreover, the zinc negative electrode 1 is good also as a structure which formed zinc or zinc alloy in the surface of support base materials, such as copper, aluminum, and iron.

  For the oxygen reduction electrode 2, platinum, silver, palladium, rhodium, iron, nickel, cobalt, iridium oxide, ruthenium oxide, manganese dioxide, nitrogen-containing carbon, phthalocyanine complex, and the like, which are catalysts having oxygen reduction activity, are used. Can do. From the viewpoint of equipment cost, it is preferable to use a composite material of nickel, manganese dioxide, cobalt, and carbon. Since the oxygen reduction electrode 2 has a low density of gaseous oxygen, the oxygen reduction electrode 2 preferably has an area of about 10 to 1000 times the apparent surface area. Therefore, it is preferable that a conductive carrier such as carbon black or metal powder having a high specific surface area carrying the catalyst is bound with a binder. In addition, if the catalyst surface is covered with the aqueous electrolyte 5, contact with oxygen is hindered and the reactivity is lowered. Therefore, the surface of the oxygen reduction electrode 2 is preferably made water-repellent.

  The oxygen generation electrode 3 is preferably a material having a low oxygen generation overvoltage in water electrolysis and high corrosion resistance. Furthermore, the electrode material which has a function as an electrode which forms the zinc negative electrode 2 and a secondary battery is used. Specific examples of such an electrode material include nickel and iron. Nickel and iron may be alloys. Among these, nickel or a nickel alloy, which has been put into practical use as a positive electrode material for charge / discharge reaction of a battery and has a low oxygen generation overvoltage, is most preferable. In order to improve the reaction area as with the zinc negative electrode 1, it is preferable to have a shape with a high specific surface area.

  The aqueous electrolyte 5 contains zinc ions, and any one of potassium hydroxide, sodium hydroxide and lithium hydroxide is used alone or in combination as an electrolyte. The concentration of zinc ions is preferably a saturated concentration. The supply source of zinc ions is not particularly limited, and examples thereof include a method of adding a zinc compound such as zinc oxide and zinc sulfate to the aqueous electrolyte. Moreover, the method of making it melt | dissolve in aqueous solution electrolyte after installing the zinc negative electrode 1 may be used. The aqueous electrolyte 5 is filled in the housing 4 so as to exist at least on the surfaces of the zinc negative electrode 1 and the oxygen generating electrode 3.

  During charging, zinc ions in the aqueous electrolyte are deposited on the zinc negative electrode 1, and oxygen is generated at the oxygen generation electrode 3. The generated oxygen moves to the oxygen chamber 7 through the oxygen pipe 8. On the other hand, at the time of discharge, in the air battery reaction system, zinc is dissolved at the zinc negative electrode 1, and oxygen is reduced at the oxygen reducing electrode 3. When nickel is used for the oxygen generating electrode 3, a zinc-nickel battery can be formed. Therefore, zinc is dissolved at the zinc negative electrode 1 at the time of discharge, and dehydrogenation of nickel hydroxide proceeds at the oxygen generating electrode 3. It can be used.

  Moreover, an anion exchange membrane is used for the partition 6a, and a porous membrane or a porous ion exchange membrane is used for the partition 6b.

An example of the battery reaction of the hybrid zinc battery of this embodiment when nickel is used for the oxygen generating electrode 3 will be described below. At the time of charging, the charging reaction of the zinc oxygen battery shown in Formulas 1 and 2 and the charging reaction of the zinc-nickel battery shown in Formulas 3 and 4 are performed between the negative electrode 1 and the oxygen generating electrode 3.

(Zinc-air battery charging reaction)
Negative electrode 1: Zn ²⁺ + 2e → Zn (Formula 1)
Oxygen generation electrode 3: 4OH ⁻ → O ₂ + 2H ₂ O + 4e (Formula 2)
(Charging reaction of zinc-nickel battery)
Negative electrode 1: Zn + 2OH ⁻ → Zn (OH) ₂ + 2e (Formula 3)
Oxygen generation electrode 3: NiOOH + 2H ₂ O + e → Ni (OH) ₂ + OH ⁻ (Formula 4)

On the other hand, when the negative electrode 1 and the oxygen reduction electrode 2 are connected to a load at the time of discharge, the discharge reaction of the zinc oxygen battery shown in Formulas 5 and 6 is performed.

(Discharge reaction of zinc-air battery)
Negative electrode 1: Zn → Zn ²⁺ + 2e (Formula 5)
Oxygen reduction electrode 2: O ₂ + 2H ₂ O + 4e → 4OH ⁻ (formula 6)

Further, when the negative electrode 1 and the oxygen generation electrode 3 are connected to a load, the discharge reaction of the zinc oxygen battery shown in equations 7 and 8 is performed.
(Discharge reaction of zinc-nickel battery)
Negative electrode 1: Zn + 4OH ⁻ → Zn (OH) ₄ ² + 2e (formula 7)
Oxygen generation electrode 3: Ni (OH) ₂ + OH ⁻ → NiOOH + 2H ₂ O + e (formula 8)

In the hybrid zinc battery of this embodiment, the oxygen reduction electrode 2 and the oxygen generation electrode 3 are provided, and the air electrode is charged and discharged by a three-electrode type air battery composed of different electrodes, so that Deterioration is suppressed. Moreover, at the time of charge, two charge reactions of the charge reaction of a zinc oxygen battery and the charge reaction of a zinc nickel battery occur. The charge / discharge efficiency of the zinc-nickel battery is significantly higher than the charge / discharge efficiency of the zinc-oxygen battery. Therefore, the charge / discharge efficiency of the entire hybrid zinc battery can be improved as compared with the zinc-air battery alone. Furthermore, the zinc-nickel battery has a feature that discharge with high output is possible although the discharge capacity is inferior to that of the zinc-air battery. In a conventional air battery, when a high output is required, a plurality of unit power generation cells must be connected, and it is difficult to make the battery compact. On the other hand, in the hybrid zinc battery of this embodiment, even when high output power is required by supplying power by discharging from a zinc-nickel battery composed of the zinc negative electrode 1 and the oxygen generating electrode 3. Correspondence becomes possible. In addition, when low power and long-time power supply is required, it is possible to respond by discharging power from a zinc-air battery composed of the zinc negative electrode 1 and the oxygen reduction electrode 2 and supplying power. In this case, it is preferable to perform control so that the output terminal is switched according to the current density during discharge. For example, when the current density during discharge is from 0.1 mA / cm ² to 50 mA / cm ² , zinc is deposited at the zinc negative electrode and oxygen is generated at the oxygen generating electrode during charging, and zinc is dissolved and oxygen reduced at the zinc negative electrode during discharging. When the current density during discharge is from 50 mA / cm ² to 1 A / cm ² , zinc is deposited at the zinc negative electrode and nickel hydroxide is formed at the oxygen generating electrode, and zinc is discharged during discharge. The terminal is switched depending on the current density so as to utilize a charge / discharge reaction in which zinc is dissolved at the negative electrode and decomposition of nickel hydroxide proceeds at the oxygen generating electrode.

  Thus, the hybrid zinc battery of the present embodiment has the oxygen generating electrode 3 as the third electrode and is used as the positive electrode for the charging reaction of the air battery and has a high current density with the zinc negative electrode 1. It is characterized by being used as a compatible battery.

Moreover, the hybrid zinc battery of this embodiment is provided with the following characteristics. As shown in Equations 2 and 6, the oxygen generation electrode 3 generates the same amount of oxygen as consumed by the oxygen reduction electrode 2. Therefore, in the hybrid zinc battery of the present embodiment, an oxygen pipe 8 for supplying oxygen generated by the charging reaction of the oxygen generating electrode 3 to the oxygen chamber 7 of the oxygen reducing electrode 2 is provided, and oxygen circulates in the battery. It is said. Charging and discharging can be repeated by filling the oxygen chamber 7 with oxygen in advance at the time of battery production or the like. In a conventional air battery that discharges by supplying external air to the oxygen reduction electrode, the air contains only about 20% of the oxygen required for the discharge reaction, so that the reaction efficiency can be increased. It was difficult. On the other hand, in this embodiment, since high concentration oxygen can be supplied to the oxygen reduction electrode, the discharge efficiency can be improved. Further, when external air is supplied to the oxygen electrode, there is a problem that carbon dioxide contained in the air reacts with the electrolytic solution, and carbonates are precipitated in the electrolytic solution, thereby deteriorating characteristics. As a result of supplying a high concentration of oxygen as in this embodiment, deterioration due to carbon dioxide can also be prevented. Here, it is preferable to install a pressure regulating valve 9 in the oxygen pipe 8. The reason is that a pressure difference is necessary for oxygen generated in the oxygen generating electrode 3 to move to the oxygen chamber. Therefore, the pressure adjusting valve 9 controls the oxygen generated in the oxygen generating electrode 3 until it reaches a predetermined pressure. In the case where the oxygen chamber 7 is at normal pressure, oxygen moves to the oxygen chamber 7 if there is a pressure difference higher than that, but it may be supplied at a higher pressure in order to improve the reactivity. However, if the pressure exceeds 10 atmospheres, the pressure of the high-pressure gas method is restricted, so the oxygen chamber pressure is preferably 10 atmospheres or less.
[2. Second Embodiment]
FIG. 2 shows a schematic diagram of a hybrid zinc battery according to a second embodiment of the present invention. In FIG. 2, the power supply, power wiring, and terminals are omitted for simplification of the drawing. The connection configuration of the power supply, power wiring, and terminals is the same as in FIG.

  In the hybrid zinc battery of this embodiment, the aqueous solution electrolyte tank 21, the pipe 25 connecting the aqueous solution electrolyte tank 21 and the housing 4 to the outside of the charge / discharge cell unit, and the aqueous solution electrolyte tank 21 provided in the pipe 25. It is characterized in that a liquid feed pump 23 for feeding the aqueous electrolyte of the above to the charge / discharge cell portion and an oxygen tank 22 connected to the oxygen pipe 8 are provided.

The amount of electricity per unit volume of metallic zinc is 5.84 Ah / cm ² , which corresponds to, for example, about 100 cm ³ in an electrolytic solution in which 1 mol / L of zinc ions are dissolved. Although depending on the solubility of zinc ions, the aqueous electrolyte 5 having a volume of several tens to several hundreds of times is required to store large electric power in the zinc negative electrode. Since it is difficult to hold this inside the storage battery, when a large amount of electricity needs to be stored, the aqueous electrolyte is stored in the external aqueous electrolyte tank 21 as in this embodiment, and the zinc negative electrode is supplied by the liquid feed pump 23. 1 is preferably circulated and fed. Thereby, even if it does not change the size of a charging / discharging cell part, a large capacity | capacitance electric power storage is attained by changing the size of the aqueous solution system electrolyte tank 21. FIG. In the aqueous electrolyte tank 21, metallic zinc or a zinc compound may be stored together with the aqueous electrolyte 5 containing zinc ions. When metallic zinc exists only in the zinc negative electrode 1, the power storage amount is limited by the total volume of the zinc negative electrode 1, but by storing the metallic zinc or zinc compound in the aqueous electrolyte tank 21 in a colloidal state, Power storage can be determined by tank size.

  The aqueous electrolyte 5 fed from the aqueous electrolyte tank 21 is preferably injected in the vicinity of the zinc negative electrode 1. It has been reported in the literature that zinc changes its electrode shape due to dissolution precipitation or short-circuits due to dendritic growth during deposition. Therefore, zinc deposition can be controlled by circulating zinc electrolyte and always supplying zinc ions.

  Moreover, in the hybrid zinc battery of the first embodiment, the oxygen chamber 7 is integrated in the casing 4 of the charge / discharge cell unit. However, as in the present embodiment shown in FIG. An oxygen tank 22 may be provided. Thereby, the capacity | capacitance of a zinc air battery can be enlarged, without enlarging the size of a charging / discharging cell part.

In the present embodiment, an aqueous electrolyte tank 21 and an oxygen tank 22 are provided outside the housing 4 to increase the amount of zinc, which is a negative electrode active material of a zinc-air battery, and oxygen, which is a positive electrode active material. A storage battery with a capacity can be realized.
[3. Third Embodiment]
FIG. 3 shows a schematic diagram of a hybrid zinc battery according to a second embodiment of the present invention. The power supply, power wiring, and terminals are omitted as in FIG. The connection configuration of the power supply, power wiring, and terminals is the same as in FIG.

  The hybrid zinc battery of this embodiment is characterized in that a heat exchanger 24 is installed between the external tank and the power storage device with respect to the hybrid zinc battery shown in FIG. In the zinc-air battery, the slow generation of oxygen and the progress of reduction are one of the factors for suppressing the performance of the air battery. On the other hand, each reaction can be accelerated | stimulated by raising the reaction temperature at the time of charge and discharge of a zinc air battery. Therefore, by installing the heat exchanger 24 in a pipe for sending the aqueous electrolyte from the aqueous electrolyte tank 21 to the charge / discharge cell unit as in this embodiment, and heating the aqueous electrolyte with the heat exchanger 24, It is preferable to increase the reaction temperature during charging and discharging of the zinc-air battery. As for the heat source of the heat exchanger 24 for heating the aqueous electrolyte, since the use efficiency of electric power is reduced if an electric heater is used, for example, exhaust heat of an external device such as a generator or factory exhaust heat, or It is preferable to use a heat source derived from renewable energy such as solar heat or geothermal heat.

In addition, since natural dissolution of zinc in the zinc negative electrode 1 is promoted at a high temperature, the temperature of the storage battery is kept high during charging and discharging of the zinc-air battery, and when the zinc-nickel battery is discharged and when the battery reaction is not performed, It is desirable to control the amount of heat exchange in the heat exchanger 24 so that the temperature is lowered. Further, when the battery reaction is not performed, the aqueous electrolyte 5 may be removed from the storage battery.
Example 1
A hybrid zinc battery having the configuration shown in FIG. 1 was prepared and evaluated for characteristics. The zinc negative electrode 1 was a copper expanded metal plated with zinc, the oxygen reducing electrode 2 was a thin film electrode formed of carbon black carrying cobalt with a binder, and the oxygen generating electrode 3 was a nickel expanded metal. These electrode areas were all 9 cm ² . For the aqueous electrolyte 5, an aqueous potassium hydroxide solution in which zinc sulfate was dissolved was used. Further, an ion exchange membrane was used for the partition wall 6a, and a porous polyethylene thin film was used for the partition wall 6b. The aqueous electrolyte was built in the case, and the oxygen chamber was integrated inside the case. Oxygen generated by the charging reaction by the resin tube as the oxygen pipe 8 was stored in the oxygen chamber.

After the zinc negative electrode 1 and the oxygen generating electrode 3 were connected to a power source and charged at 1.9 V for 10 minutes, the open circuit voltage was measured to find that the zinc negative electrode 1 and the oxygen generating electrode 3 were 1.57 V, the zinc negative electrode and oxygen A voltage of 1.44 V was detected between the reducing electrodes, and it was confirmed that charging was possible. Further, when the current density was measured by connecting the terminal 11 to a load, it was confirmed that a current of 100 mA / cm ² was applied in the zinc-nickel system of the zinc negative electrode and the oxygen generating electrode. Further, when the current density was measured by connecting the terminal 12 to a load, it was confirmed that a current of 10 mA / cm ² was applied in the zinc-air system of the zinc negative electrode and the oxygen reduction electrode.
(Example 2)
A hybrid zinc battery having the configuration shown in FIG. 2 was prepared and evaluated for characteristics. The same zinc negative electrode 1 and oxygen generating electrode 3 as in Example 1 were used. The oxygen reduction electrode 2 was a thin film electrode in which carbon black carrying platinum was formed into a film with a binder. The electrode area, aqueous electrolyte composition, and partition walls were the same as in Example 1. The aqueous electrolyte was built in the external aqueous electrolyte tank 21 and the oxygen chamber was integrated inside the casing.

After connecting the zinc negative electrode 1 and the oxygen generating electrode 3 to a power source and charging them at 1.9 V for 10 minutes, the open circuit voltage was measured to find 1.55 V for the zinc negative electrode and the oxygen generating electrode, and the zinc negative electrode and the oxygen reducing electrode. In the meantime, a voltage of 1.54 V was detected, and it was confirmed that charging was possible. Further, when the current density was measured by connecting the terminal 11 to a load, it was confirmed that a current of 100 mA / cm ² was applied in the zinc-nickel system of the zinc negative electrode and the oxygen generating electrode. Further, when the current density was measured by connecting the terminal 12 to a load, it was confirmed that a current of 10 mA / cm ² was applied in the zinc-air system of the zinc negative electrode and the oxygen reduction electrode.
(Example 3)
A hybrid zinc battery having the configuration shown in FIG. 3 was prepared and evaluated for characteristics. Example 2 is the same as Example 2 except that a heat exchanger 24 is provided between the hybrid zinc battery and the external tank.

In Example 3, the effect of heating the aqueous electrolyte was verified. The aqueous electrolyte was heated by a heat exchanger and controlled so that the temperature inside the casing was 120 ° C. At this time, the internal pressure was 1.25 atm. When the oxygen generation voltage was evaluated, it was confirmed that the oxygen generation voltage of the oxygen generation electrode 3 could be reduced by 0.3 V compared to Example 2.

DESCRIPTION OF SYMBOLS 1 ... Zinc negative electrode 2 ... Oxygen reduction electrode 3 ... Oxygen generation electrode 4 ... Case 5 ... Aqueous electrolyte 6a, 6b ... Partition 7 ... Oxygen chamber 8 ... Wiring 9 ... Pressure regulating valve 10 ... Power source 11, 12 ... Output terminal 21 ... Aqueous electrolyte tank 22 ... Oxygen tank 23 ... Liquid feed pump 24 ... Heat exchanger

Claims (7)

A negative electrode made of zinc or a zinc alloy;
An oxygen reduction electrode disposed on one surface side of the negative electrode via a first partition;
An oxygen generating electrode disposed on the other surface side of the negative electrode via a second partition;
An aqueous electrolyte containing zinc ions;
A housing containing the negative electrode, oxygen reduction electrode, oxygen generation electrode, partition wall and aqueous electrolyte,
The hybrid zinc battery, wherein the oxygen generating electrode is nickel, iron, or any alloy thereof.   The hybrid zinc battery according to claim 1, further comprising a first pipe for supplying oxygen generated at the oxygen generation electrode to the oxygen reduction electrode.   4. The hybrid zinc battery according to claim 3, wherein the first pipe has a pressure regulating valve.   The charge terminal for inputting power is connected to the negative electrode and the oxygen generation electrode, and the discharge terminal for outputting power is connected to each of the negative electrode, the oxygen generation electrode, the negative electrode, and the oxygen reduction electrode. A hybrid zinc battery characterized by comprising:   2. The aqueous solution electrolyte tank for storing the aqueous solution electrolyte, the second pipe connected to the aqueous solution electrolyte tank and the casing and through which the aqueous electrolyte flows, and the second pipe according to claim 1. A hybrid zinc battery characterized by having a liquid feed pump.   6. The hybrid zinc battery according to claim 5, wherein metallic zinc or a zinc compound is stored inside the aqueous electrolyte tank.   The hybrid zinc battery according to claim 6, further comprising a heat exchanger for heating the aqueous electrolyte in the second pipe.