JPH02242570A - Storage of zinc-bromine battery - Google Patents

Abstract

PURPOSE:To prevent the lowering of battery efficiency even for long time storage by removing bromine with zinc electrodeposited to a cathode and anode through a process of forcing an electric current to flow in a discharge direction under a condition where the supply of bromine is stopped after a battery is charged. CONSTITUTION:A zinc-bromine battery 1 to be transported or stored for a long time is charged, the bromine having large specific gravity generated and collected in the bottom part of an anode tank is removed and then the battery is discharged. Then after battery voltage becomes 0V, electric current is forced to flow continuously in a discharge direction, and after the zinc is sufficiently electrically deposited on an anode 11, electrolytic solution is circulated, the bromine is removed in such a way that the zinc and bromine on the anode 11 are made to make direct mutual reaction, and the battery 1 from which the bromine is removed is transported or stored for a long time. This enables the bromine to be unresidual in the battery 1, the deterioration of an electrode or separator due to a bromine attack to be prevented, and the battery to be stored for a long time in its good condition.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Industrial Field of Application The present invention relates to a method for storing zinc-bromine batteries over long periods of time without reducing efficiency.

L3 Summary of the Invention The present invention provides a method for storing a zinc bromine battery using a circulating electrolyte by passing a current in the discharge direction with the supply of bromine cut off after charging the battery to remove bromine. This prevents electrode warpage and deterioration caused by bromine attack,
It allows for good long-term storage.

BACKGROUND OF THE INVENTION Recently, the development of battery power storage systems 18 has been promoted, and electrolyte circulation type zinc-bromine laminated secondary batteries have been developed as a part of this system, as illustrated in FIGS. 2 to 4. There is.

As shown in the structural principle diagram in Fig. 2, this
is divided into an anode chamber 3 and a cathode chamber 4 by a separator 2 made of an ion exchange membrane or a porous membrane, and a liquid sending tube 5.6 and a liquid return tube 7 for circulating the electrolyte in these two electrode chambers, respectively.
8 and electrolyte tank 9. IO is connected and provided, and an electrolytic solution of zinc bromide (7, n f', r 2) is circulated to each electrode chamber. In addition, 11
is an anode, I2 is a cathode, 13.14 are both liquid pumps, 1
5 is a valve.

Therefore, during charging, the electrolyte circulates in the direction of the arrow in the figure, and the cathode 12 has Zn''+2e->Zn,
At the anode II, a reaction of 2Br-→Br2+2e occurs, and the bromine generated at the anode 11 becomes a molecule, mixes in the electrolyte, partially dissolves, and mostly becomes a complex with the complexing agent in the anolyte, and the bromine produced at the anode 11 becomes a molecule. Precipitates and accumulates in the electrolyte tank ① on the room side. Further, during discharge, a reaction opposite to the above reaction formula occurs at each electrode 11 and 12 with the electrolyte circulating, and precipitates (Zn, Br,) or each electrode I+, 12
It is designed so that the upper air energy is consumed (oxidized, reduced) and released.

In addition, the zinc-bromine battery with the construction principle as described above has
A stack of a large number of cell laminated structures is used as a practical laminated battery body as illustrated in FIG. A pair of tightening end plates 16 are used to sandwich and hold the entire cell stack by fitting nuts 29 into a plurality of bolts 28 that penetrate the entire stack from one side to the other.
For example, 30 cells are stacked 1. Configure.

As shown in Fig. 3, this stack has positive electrode manifolds 2, which are liquid flow holes, at its four corners.
4 and the negative electrode manifold 25 are bored.

Further, each separator plate 2I is formed by installing microchannels 26 in a symmetrical shape on the front and back under both vehicle surface portions 1 of a frame body 21a that also functions as a parakin around the separator plate 2I,
The microchannels 26 shown by solid lines on the negative side of the microchannels 26 uniformly spread the electrolytic solution introduced from the positive electrode manifold 24 on the diagonal line and flow it over the entire surface of the separator 2, or collect the solution therefrom. In addition, the microphone [J channel 26 shown by the broken line on the other side is for introducing and recovering the electrolyte from the negative electrode manifold 25.

In this way, between the electrodes arranged on both side surfaces of each separator plate 21, cells that become the unit battery illustrated in FIG. 2 are constructed, and 30 of these cells are connected in series to form a stack. It is configured so that

Conventionally, such a zinc-bromine battery has been stored as follows, depending on whether the battery has been charged or completely discharged.

First, when storing the battery after charging, the storage time is 10
If the time is exceeded, all the electrolyte in the stack is returned to the electrolyte tank 9.10 and stored.

This means that when the battery is charged, zinc is electrodeposited on the cathode 12 surface, and bromine is deposited on the anode 11 surface. Therefore, if the battery is stored with the electrolyte filled in the stack, bromine in the anolyte will cause self-discharge with the zinc on the cathode 12, and furthermore, during storage, this bromine will corrode the electrodes and separators. This is to prevent battery efficiency from decreasing.

In addition, to store the battery after it has been completely discharged, please use the
- The stack was stored with the electrolyte still filled. This means that after the battery is fully discharged, the cathode 12
This is because the upper zinc is completely dissolved and the surface of the cathode 12 is exposed, so there is no fear of self-discharge.

Note that bromine is layered on the surface of the anode 11.

■) Problems to be Solved by the Invention In each of the storage methods described above after charging or completely discharging a battery, as shown in FIG.
Since 111 bromine is attached to L, there is a problem in that during storage, the carbon plastic electrode and separator may corrode, deteriorate them, and reduce battery efficiency.

Furthermore, the carbon plastic electrode undergoes warpage (deflection) due to swelling due to bromine, and its smoothness is impaired.

As described above, when worming occurs in the electrodes, the flow distribution of the electrolyte within the stack is disturbed, which causes a decrease in efficiency due to the formation of zinc dendrites (a phenomenon in which zinc is deposited in the form of whiskers). Ta.

Furthermore, in order to prevent such bromine attack on the electrodes, attempts have been made to clean the inside of the stack with ion-exchanged water, but it has been difficult to remove bromine from within the battery body.

In particular, in batteries that use carbon fiber as the material for the anode 11, bromine is adsorbed, so even if washed with ion-exchanged water for several days, bromine cannot be removed, causing this problem. There is no way to solve this problem.

In view of the above points, it is an object of the present invention to provide a new storage method that can prevent the battery efficiency from decreasing even if a zinc bromine battery is stored for a long period of time.

D] Means for Solving the Problems The method for storing a zinc-bromine battery of the present invention includes: after charging the battery,
The present invention is characterized in that, while the supply of bromine is cut off, current is passed in the direction of discharge to cause zinc to be electrodeposited on the cathode and anode, thereby removing bromine.

By applying a method such as "F9 action" in two series, bromine is removed so that it does not remain in the battery, preventing deterioration of the electrodes and separators due to bromine attack, preventing warpage of the electrodes, and keeping the battery in good condition. This has the effect of allowing batteries to be stored for a long period of time.

G. Examples Hereinafter, examples of the method for storing zinc-bromine batteries of the present invention will be described.
This will be explained with reference to FIG. In addition, in this Figure 1,
The same reference numerals are given to the parts corresponding to the conventional example shown in FIGS. 2 to 4 for convenience of explanation.

The means of the present example is an electrochemical treatment method for completely removing bromine in a battery stack, in particular zinc-
This is suitable for transporting bromine batteries and storing them for long periods of time.

First, a zinc-bromine battery to be transported or stored for a long time is charged.

This charging amount of electricity sufficiently exceeds the amount of bromine in the electrolyte during charging and the amount of bromine deposited in the stack, and even when zinc electrodeposition begins on the anode 11, the amount of electricity on the cathode I2 is It shall be possible to secure an appropriate amount of zinc so that there is enough remaining in the zinc. The amount of charged electricity depends on the structure of each individual battery, but if there is a shortage of zinc on the cathode 12, zinc will be deposited on the anode II, but bromine will be generated on the cathode. A sufficient amount is necessary because it will not be possible to remove bromine from the stack.

In this example, a bipolar battery with an electrode area of 1600 c1N2.30 cells was used and was charged at 2OA for 5 hours.

Second, since bromine with a high specific gravity generated during charging in the first step is accumulated at the bottom of the anode tank, this is removed.

Third, discharge the battery. In this example, the battery voltage reached 0■ after discharging for 1 hour at 20Δ.

This discharge occurs while bromine dissolved in the electrolyte and bromine adhered to the anode are consumed.

Fourth, after the battery voltage reaches OV, the current continues to flow in the discharge direction.

As a result, zinc electrodeposition (Z n”-
7, n+ 2 e) and the reduction of bromine (Br, -Br
+ 2 e) reaction occurs at the same time, and by applying current as it is, bromine in the electrolyte is removed 3. In this example,
Electricity was applied in the same direction as the discharge for 2 hours, and the anolyte became colorless and transparent, confirming that bromine had been removed.

Fifth, after sufficiently depositing zinc on the anode 11F] using the above method, the electrolytic solution is circulated to cause the zinc on the anode 11 to react directly with bromine, so that (Z n +B r, + Z
n''÷2Br-) Remove bromine.

As mentioned above, the battery from which bromine has been removed is transported or stored for a long period of time.

In this example, it was left for three months.

After this, in order to see the effects of long-term battery storage methods,
After applying electricity to the charging side and confirming that bromine was generated in the anolyte, the bromine removed in the second step was returned to the tank, and complete discharge was performed. After this, the battery stack was disassembled and investigated, and the electrodes showed no warpage or deterioration, confirming that they were sufficiently effective.

For comparison, the conventional complete discharge described above was performed.
．． When the battery that had been left unattended was dismantled, the electrodes were found to have warpage (about the size of two-page Cl0m scraps) due to bromine deterioration. Even when compared with this, it can be seen that the method of this example is effective.

tr Effects of the Invention As detailed above, according to the method for storing a zinc-bromine battery of the present invention, after charging a zinc-bromine battery, a current is applied in the discharge direction while the supply of bromine to the battery is cut off. Since the batteries are transported and stored for long periods of time after being subjected to a treatment in which zinc is electrodeposited on the cathode and anode to remove bromine, no bromine remains inside the batteries. Therefore, it is possible to prevent deterioration of the electrodes and separators due to bromine attack, prevent warpage of the electrodes, and enable the battery to be stored in good condition for a long period of time.

[Brief explanation of drawings]

Fig. 1 is a diagram illustrating the main parts of a unit cell model explaining an embodiment of the method for storing zinc-bromine batteries according to the present invention, and Fig. 2 is a diagram schematically explaining the principle of a conventional zinc-bromine battery. , FIG. 3 is an enlarged exploded perspective view of the main part of the battery, and FIG. 4 is an explanatory diagram of the main parts showing the unit cell model. 1- Battery body, 11 Anode, 12 Cathode, 18 End plate electrode, 23 Intermediate electrode. pregnancy

Claims (1)

[Claims] (1) Zinc-bromine, characterized in that the battery is charged to a required amount, and then the battery is stored after being energized in the discharge direction with bromine supply cut off to remove bromine. How to store batteries.