JPH0821415B2 - Fuel cell for rebalancing device for secondary battery - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a fuel cell of a rebalance device for a secondary battery, and more specifically, to a rechargeable battery for a redox flow type secondary battery capable of stable high current density operation. The present invention relates to a fuel cell of a balance device.

[Conventional technology]

Taking an iron-chromium secondary battery as an example, the redox flow secondary battery distributes an aqueous solution of chromium ions (Cr ²⁺ ) and an aqueous solution of trivalent iron ions (Fe ³⁺ ) in a discharged state. By flowing into the positive electrode chamber and the negative electrode chamber of the electrolytic cell,
At the positive electrode, Fe ³⁺ receives one electron and becomes divalent Fe ²⁺ , and at the negative electrode, Cr ²⁺ loses one electron and becomes trivalent Cr ³⁺ .
The electrons transferred between the negative electrode and the positive electrode work through an external circuit to release electric power, and on the other hand, if the reverse operation is performed, charging is performed, and thus the transfer of electrons (oxidation in a broad sense and Reduction) is performed at a separate electrode, the electrons of which flow through an external circuit to release electric energy, and chemical energy is converted into electric energy.

In the redox flow type secondary battery, a small amount of hydrogen gas is produced as a by-product from the negative electrode (chromium) side in the redox flow secondary battery, so that a difference occurs in the charge and discharge depths of the positive electrode liquid and the negative electrode liquid. This difference widens as the charge and discharge are repeated, and the overcharged state of the positive electrode liquid progresses and the capacity of the battery decreases. In order to avoid this, a rebalance device must be provided to eliminate the overcharged state of the positive electrode liquid.

For the redox flow secondary battery revanlance device, a fuel cell that returns hydrogen, which is a side reaction product of the negative electrode, to the original H ⁺ can be used. As such a fuel electric field, Fe ^{3+ −} H ₂ system, Ti ⁴⁺ −
There are H ₂ system, Sn ⁴⁺ -H ₂ system, Br ₂ -H ₂ system, Cl ₂ -H ₂ system and so on.

FIG. 2 is a schematic view of a conventional rebalancing fuel cell body.

This device comprises a hydrogen electrode chamber A composed of a hydrogen electrode electrolyte 2 and a hydrogen electrode 4, a counter electrode chamber B composed of a counter electrode electrolyte 3 and a counter electrode 5, and an ion exchange membrane for partitioning the hydrogen electrode chamber A and the counter electrode chamber B. 1 and current collectors 6A and 6B provided to make the current distribution of both electrodes uniform. In such a configuration, the hydrogen gas by-produced in the secondary battery (not shown) is supplied to the hydrogen electrode chamber A and is oxidized at the hydrogen electrode 4 to become a proton (H ⁺ ). With water, it exists as H ₃ O ⁺ as shown in the following formula.

H ₂ + 2H ₂ O → 2H ₃ O ⁺ + 2e The H ₃ O ⁺ is electrophoresed from the hydrogen electrode chamber A through the ion exchange membrane 1 into the counter electrolyte solution 3 of the counter electrode chamber B, and at the counter electrode 5, for example, the counter electrode active material. When Ti (Ti ⁴⁺ / Ti ³⁺ ) is used for, Ti ⁴⁺ e → Ti ³⁺ is reduced and a current flows.

However, in the above-described conventional fuel cell, H ₃ O ⁺ generated in the hydrogen electrode reaction due to energization passes through the ion exchange membrane 1 and moves to the counter electrode chamber B, so that the water in the hydrogen electrode electrolyte solution 2 is insufficient. However, the hydrogen electrode chamber A becomes dry and the cell resistance increases. On the other hand, in the counter electrode chamber B, the water content in the counter electrode electrolyte 3 increases, so stable high current density operation cannot be performed and rebalancing is not performed. The closed system operation of the device becomes difficult.

[Problems to be solved by the invention]

An object of the present invention is to prevent the movement of water in the electrolyte of the fuel cell used in the rebalance device for the redox flow secondary battery, to maintain stable high current density operation, and to enable closed system operation. It is to provide a fuel cell for a rebalance device for a secondary battery.

[Means for solving problems]

The present invention provides a hydrogen electrode chamber including a hydrogen electrode electrolyte and a hydrogen electrode for hydrogen oxidation, into which hydrogen gas by-produced on the negative electrode side of a redox flow type secondary battery is introduced, and a counter electrode active material capable of oxidizing hydrogen. A counter electrode chamber composed of a counter electrode electrolytic solution containing a counter electrode and a counter electrode for reducing a counter electrode active material is adjacent to each other via an ion exchange membrane, and a fuel for a rebalance device for a secondary battery, each of which is provided with a current collector. In a battery, a hydrogen electrode for hydrogen oxidation in the hydrogen electrode chamber is formed by attaching an electrode catalyst to the ion exchange membrane, and a conductive member is impregnated with a hydrogen electrode electrolyte adjacent to the hydrogen electrode for hydrogen oxidation. A hydrogen diffusion layer,
It is characterized in that the by-product hydrogen gas is introduced into the hydrogen diffusion layer.

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

〔Example〕

FIG. 1 is a schematic view of the inside of a fuel cell according to the present invention.

1 is different from FIG. 2 in that a hydrogen electrode, for example, a platinum group metal is closely bonded to an ion exchange membrane (PEM (Polymer Electrolyte Membrane) material) by electroless plating or another method. Pole C is provided and the PEM
A hydrogen diffusion layer 7 is provided outside the hydrogen electrode 8 of the hydrogen electrode C, and
The counter electrode chamber B was provided outside the ion exchange membrane of the PEM hydrogen electrode C.

In such a configuration, hydrogen produced as a by-product on the negative electrode side of the redox flow type secondary battery (not shown) is introduced into the hydrogen diffusion layer 7 and is oxidized by the PEM hydrogen electrode C integrated with the ion exchange membrane. , The generated H ⁺ becomes H ₃ O ⁺ generated along with the water retained in the ion exchange membrane 1 and is directly electrophoresed in the counter electrode chamber B, and further, at the counter electrode 5, reduction of T ⁴⁺ + e → Ti ³⁺ . The reaction takes place and electricity flows. At this time, the movement of H ₃ O ⁺ is in equilibrium with the diffusion movement of electrically neutral water from the counter electrolyte 3 to the ion exchange membrane 1. For this reason, the increase in resistance due to the decrease in water in the hydrogen electrode chamber is eliminated, and stable high current density operation can be maintained and the rebalancing device can be operated in a closed system.

(Experimental Results) As an example, Nafion 117 (registered trademark manufactured by Du Pout) is used as an ion exchange membrane, and one side of this is 100 mm in length × 1 side.
An SPE electrode was prepared by plating platinum in a 0 mm rectangular shape.
The plating was carried out by bringing 1% H ₂ PtO ₆ aqueous solution into contact with one surface of the film and alkaline 2M NaBH ₄ on the other surface for about 3 hours to reduce and precipitate platinum by permeating NaBH _{4 into} the film. The amount of platinum deposited was about 0.2 mgcm ^-2 . The thickness of the anode (platinum deposition surface) collector and H ₂ gas diffusion layer
Graphite cloth with 1 mm and basis weight of 300 gm ^-2 was cut into the same shape as the plated surface. For the cathode, a chemically activated carbon chamber felt with a thickness of 3 mm and a basis weight of 400 gm ^-2 was cut into the same shape as the plated surface.

These were sandwiched between two leaded graphite plates, pressure-bonded, and the periphery was packed with EPDM to form a small fuel cell.

0.5M Ti ³⁺ / Ti ⁴⁺ (basic solution is 2M F
A mixed solution of eCl ₂ , 3NHBr, and 1NHCl) was fed vertically at a rate of 4 mlmin ⁻¹ . H ₂ gas was passed through the anode at a rate of 10 mlmin ⁻¹ .

At 40 ℃, the open circuit voltage of this battery is about 0.1V, the short-circuit current is 170mA (17mAcm ^-2 ), and the overall cell resistance is about 6Ωc.
It was m ² . This cell resistance did not change at all after generating 20,000 coulombs.

(Control experiment) The same experiment was performed using an electrode in which 1 mgcm ^-2 platinum was supported on solid porous carbon having a thickness of 2.5 mm and a basis weight of 200 gm ^-2 as an anode. The initial overall cell resistance was about 20 Ωcm ² , but this increased with power generation, and the current value became almost zero when 2000 Coulomb was energized.

It is needless to say that the fuel cell of the present invention is generally applied to other rebalancing methods for secondary cells that generate hydrogen.

〔The invention's effect〕

According to the present invention, by integrating the hydrogen electrode of the fuel cell as a PEM hydrogen electrode with the ion exchange membrane, the movement of water accompanying the movement of hydrogen ions is eliminated, and stable high current density operation and rebalancing device closure are achieved. System operation has become possible.

[Brief description of drawings]

FIG. 1 is a schematic view of a rebalancing fuel cell body according to the present invention, and FIG. 2 is a schematic view of a conventional rebalancing fuel cell body. 1 ... Ion exchange membrane, 2 ... Hydrogen electrolyte, 3 ... Counter electrolyte, 4, 8 ... Hydrogen electrode, 5 ... Counter electrode, 6A, 6B ... Current collector, 7 ... Hydrogen diffusion layer , A ... Hydrogen electrode chamber, B ... Counter electrode chamber, C ... PEM hydrogen electrode.

Claims (1)

[Claims] 1. A hydrogen electrode chamber comprising a hydrogen electrode electrolyte and a hydrogen electrode for hydrogen oxidation, into which hydrogen gas by-produced on the negative electrode side of a redox flow secondary battery is introduced, and a counter electrode active for oxidizing hydrogen. A counter electrode chamber comprising a counter electrode electrolytic solution containing a substance and a counter electrode for reducing a counter electrode active material is adjacent to each other via an ion exchange membrane, and a rebalance device for a secondary battery is provided with a current collector in each of these two electrode chambers. In a fuel cell, a hydrogen electrode for hydrogen oxidation in the hydrogen electrode chamber is formed by attaching an electrode catalyst to the ion exchange membrane, and a conductive member is impregnated with a hydrogen electrode electrolyte adjacent to the hydrogen electrode for hydrogen oxidation. Arrange the hydrogen diffusion layer,
A fuel cell for a rebalance device for a secondary battery, wherein the by-product hydrogen gas is introduced into the hydrogen diffusion layer.