JPS5983366A - Electrolyte for zinc-bromine battery - Google Patents

Abstract

PURPOSE:To prevent any decrease in the efficiency of a liquid-circulation-type zinc-bromine battery as well as any breakage of the battery by adding a specified organic bromide used as a dendrite suppressing agent to prepare electrolyte for the battery. CONSTITUTION:In electrolyte for a liquid-circulation-type zinc-bromine battery prepared by using ZnBr2 as an active material and adding a bromine-complex forming agent and a dendrite suppressing agent, one compound selected from among the following organic bromides is used as the dendrite suppressing agent: methyl dodecyl, methyl decyl morpholinium bromide, trimethyl dodecyl, trimethyl decyl, dimethyl benzyl dodecyl, dimethyl benzyl decyl, tetrabutyl, tributyl benzyl ammonium bromide, dodecyl, decyl pyridium bromide, dodecyl methyl or decyl methyl pyrrolidinium bromide.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention tit 'f1. f, 'ppj'/+Circulating Paris Zinc-Bromide Electrolyte A for secondary batteries etc. In detail, how to suppress the generation of zinc dendrites? This relates to the composition of the catholyte.

Recently, zinc-bromine secondary batteries have been attracting attention and being developed from the viewpoint of effective energy utilization. For example, for purposes such as effective use of nighttime electricity, electrolyte circulation type zinc-
Bromine secondary batteries are used. Figure 1 shows its basic configuration. In the figure, 1 is a battery reaction tank, 2 is an anode chamber, a melting cathode chamber, and 4 diaphragms (ion exchange membranes or multi-layer separators with a single thin film).

5 anodes, 6 cathodes, 7 anode electrolyte reservoirs, 8 cathode electrolyte reservoirs, 9 and 10 pumps, 11 and 1'tk electrodes, 2 dendrites.

In these electrolyte circulation type zinc-bromine secondary batteries, t,
During J charging, the zinc deposited on the cathode surface, indicated by Ω in the diagram, cannot become smooth due to the non-uniform electric field distribution near the cathode surface and the disturbance of the flow of the catholyte, and forms open dendrites in dendrites. This becomes a problem especially when the number of charge/discharge cycles increases. This dendrite zinc is a very brittle metal.
It easily separates from the electrode, reducing battery efficiency. Even if it does not detach from the electrode, the dendrite grows like a resin 12 and breaks the diaphragm 4. 1. There was a risk of short circuit between the battery and the anode, leading to damage to the battery.

Therefore, in order to prevent the conventional generation of dendrites, various dendrite inhibitors such as nonionic surfactants and 1F lead plating brighteners are added to the catholyte.

However, non-ionic surfactants, dendrite inhibitors such as lead plating brighteners, + lead odor, etc. When a porous (1q) thin film is used, bromine molecules Br2 generated at the anode 5 during charging and permeated and diffused into the cathode chamber through the diaphragm 4 gradually decompose during long-term cycle use. Stable 1. Therefore, it is impossible to maintain a zinc-bromine secondary battery. Furthermore, even those with bromine resistance often develop dendrites due to the formation of an oxidized film of unrestricted zinc on the surface of the zinc deposited on the cathode surface during repeated charge/discharge cycles.

The object of the present invention is to develop a catholyte solution that solves the problems of dendrite generation and growth that occur during charging of the electrolyte circulation type zinc-bromine secondary battery 412 as described above.

Based on this, the inventors added various dendrite inhibitors to a specific amount of zinc bromide, which is the active material of the negative electrode electrolyte, and a bromine complex forming agent at the r; As a result of conducting charge/discharge tests, we discovered a cathode electrolyte storage tank that solves the problems that occur when using a circulating electrolyte zinc-bromine secondary battery.7
This led to the invention.

The main purpose of the present invention is to use zinc bromide as the active material in the cathode electrolyte composition of the electrolyte circulation (type 1 zinc-bromine secondary 71), and to add a bromine complex to the zinc bromide as the active material. It is made by adding and mixing a forming agent and a dendrite inhibitor, and the amounts of each are specified.

That is, the present invention combines zinc bromide (Z) with the active material of the catholyte.
Based on n+1r2) 3 mot/l,
In addition, as a bromine complex forming agent, the following ↑〃
Methyl ethyl pyrrolidium bromide and methyl ethyl pyrrolidium bromide, which are monocyclic quaternary ammonium salts, were each mixed with 0.0.
The composition of the electrolytic solution is obtained by adding one of the 12 additives a) to e) as a dendrite inhibitor having the structure shown below to the electrolyte containing 5 mol/z.

In addition, each of the above two types of bromine complex forming agents is used in an amount of 1 mol/
It has been confirmed through experiments that even if bromine is added, the effect of trapping bromine molecules that have penetrated and diffused from the anode chamber and mixed into the catholyte is sufficient, and that it is also possible to add a dendrite inhibitor to this. However, add 0.5mat/to each of the two types to make a total of 1
mot//j gave slightly better results (1+).

Types, structural formulas, and specific additions of dendrite inhibitors (1) Methyl e-dodecyl morporium promidro)
Methyl decyl morporium promite) trimethyl dodecyl ammonium bromide =)) IJ
Methyl decyl ammonium bromide) dimethyl φbenzyl dodecyl ammonium bromide) dimethyl benzyl 9 decyl ammonium promite) ) ') methyl benzyl ammonium promitri) dodecyl pyridinium - bromide) decyl・Pyridinium Φpromidol) dodecyl methyl pyrrolidinium bromide 11 ・bromide zinc-bromine cathode acid IL for secondary batteries・M- of ethyl morporium bromide and methyl ethyl pyrrolidium bromide is kept constant, and the above-mentioned quaternary ammonium bromide additives (a) to (e) are added as a dendrite inhibitor in proportions of Iff. After preparing the sample, conduct a charge/discharge test, and evaluate the dendrite generation status on the cathode and the normal temperature status of the electrodeposited surface at f + t7. This is based on an example in which a performance test of 6-hour charging and 6-hour discharging was conducted for 20 cycles.The results were as follows: a) The electrode with methyl dodecyl morpholinium bromide added had the best electrode smoothness at 20 8) Methyl decyl morpholinyl bromide, which could be maintained even after the cycle performance test.
2) Ammonium bromide of l.limedyl decyl was also excellent, and electrolytes containing other types of dendrite inhibitors did not fall below B in all 11 performance tests. The best suppression fltll 7'il is one in which the total number of carbons bonded to the four nitrogen bonds is 12 to 10, and those with less than 8 carbon atoms and those with 20 or more carbon atoms are the best. Even electrodeposition did not give very good results.

The catholyte according to the present invention is used in a liquid circulating type zinc-bromine secondary space.
When used in rTl+, V can sufficiently suppress dendrites from forming on the cathode during multiple charge/discharge cycles]
Not only that, but since it is fPj quaternary ammonium salt, there is no fear of decomposition due to the strong oxidizing properties of bromine that permeates and diffuses into the cathode chamber through the porous membrane during charging, and it can be mixed and added with a complexing agent. Combined, 1! ″!,!,ne molecule (
It is hoped that the efficiency of the battery will be improved as a result of the drop (polyhalide).

Next, examples of the present invention will be described below.

EXAMPLE The cathode electrolyte of a liquid circulation type zinc-bromine secondary battery as shown in FIG. Add 0-5 mol/pyrrolidinium bromide and keep it constant and 1
7. To this, add and blend the dendrite inhibitor of 12 weights to 1 of the above-mentioned a) to e), mix this with the electrolyte, and use a carbon black plus deck electrode as an electric shock absorber at 40 mA/c.
) at a current density of J for 6 hours.

6 hours later, t1'c 4Tfi, the dendrite formation above and the smoothness of the deposited surface were observed and evaluated based on the following criteria. The surface is smooth.

B, De/drye appears in width, but the electrodeposited surface is relatively smooth.

c: A large number of y'ndrites occur (1 to 1), and the Tlf deposition surface is uneven.

Note that "-" on the right shoulder of AB and C is better.

- is a slightly inferior symbol.

Of these evaluated items, 61 had a strong WY value of A.
Performance tests were performed on the seeds at a current density of 30 mA/.4 for 20 cycles of 6-hour charging and 6-hour discharging, and evaluation was performed.

The test results above are shown in the table below.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing the basic configuration of an electrolyte circulation type zinc-bromine secondary battery. 1: battery reaction tank, 2: anode, 3: cathode, 4: diaphragm (separator) 5: positive, iI? i, 6: cathode, 7: anode electrolyte storage tank, 8: cathode electrolyte storage tank, 11: dendrite. Attorney Patent Attorney Sanro Kimura Figure 1

Claims (1)

[Scope of Claims] 1) A liquid circulation type zinc bromine secondary compound made of zinc bromide as an active material and a bromine complex forming agent and a dendrite inhibitor added thereto.
1'■τ, In the pond electrolyte, as a dendrite inhibitor, morpholinium bromide in methyl dodecyl, methyl decyl morpholinium bromide, trimethyl dodecyl ammonium bromide, trimethyl e decyl ammonium bromide, dimethyl・Benzyl eyelid dodecyl ammonium bromide,
Dimethyl benzyl chloride fluorite. Tetra-butyl ammonia bromide, tI
jphthyl benzyl ammonium bromide. Dodecyl pyridium bromide, decyl-pyridium bromide, dodecyl methyl Φpyrrolidinium
・Bromide, decyl Φ methyl virolidinium... It is recommended to add and mix one type of bromide.
2) As the bromine complex forming agent, methyl ethyl molporium
Bromide and methyl ethyl pyrrolidium bromide, Claim 1 x
14 N+-: 'f1 solution of zinc-bromine battery.