Electrolyte compositions for use in a metal-halogen flow battery

1. A flow battery system, comprising:

a stack of flow battery cells that do not contain a separator in reaction zones formed between anode and cathode electrodes of each flow battery cell;

a reservoir connected to the reaction zones of the stack; and

a liquid electrolyte disposed in the reservoir, the electrolyte comprising an aqueous phase comprising:

at least one metal halide;

at least one halogen;

an anti-dendrite agent comprising bisphenol A alkoxylate (BPA);

a metal plating enhancer comprising a bismuth salt.

2. The system of claim 1 , wherein the bismuth salt is bismuth oxide.

3. The system of claim 1 , wherein the halogen is bromine and wherein the electrolyte further comprises an ionic phase comprising a bromine sequestering agent.

4. The system of claim 3 , wherein:

the metal of the metal halide is zinc;

the halide of the metal halide is bromine or chlorine and bromine; and

the sequestering agent is at least one of a morpholinium, pyrrolidinium, imidazolium, picolinium, pyridinium, or ammonium bromide salt (QBr).

5. The system of claim 4 , wherein the sequestering agent is at least one of 1-dodecyl-1-methylmorpholinium bromide, 1-dodecyl-1-methylpyrrolidinium bromide, 1-dodecylpyridinium bromide, dodecyltrimethylammonium bromide, benzyldodecyldimethylammonium bromide, tetrabutylammonium bromide, 1-ethyl-1-methylpyrrolidinium bromide (MEP), and 1-ethyl-1-methyl-morpholinium bromide (MEM).

6. The system of claim 3 , wherein the aqueous phase comprises of about 0.1-68% (w/v) zinc bromide.

7. The system of claim 6 , wherein the aqueous phase further comprises about 0-30% (w/v) zinc chloride.

8. The system of claim 1 , wherein the electrolyte further comprises an anti-corrosion agent.

9. The system of claim 8 , wherein the anti-corrosion agent is a poly(oxy ether) having a molecular weight of at least 4000 Daltons.

10. The system of claim 8 , wherein:

the at least one metal halide comprises zinc bromide and zinc chloride;

the at least one halogen comprises bromine; and

the anti-corrosion agent comprises poly(ethylene oxide) (PEG) having a molecular weight of at least 4000 Daltons.

11. The system of claim 10 , wherein the chelating agent comprises ethylenediaminetetraacetic acid (EDTA) or derivatives thereof.

12. The system of claim 10 , wherein the bismuth salt is at least one of bismuth oxide, bismuth chloride, and bismuth citrate.

13. The system of claim 1 , wherein the electrolyte further comprises a chelating agent.

14. The system of claim 13 , wherein the chelating agent is an aminopolycarboxylic acid.

15. The system of claim 1 , wherein the stack of flow battery cells is located in a cell chamber separate from the reservoir, and wherein the cell chamber is fluidly connected to the reservoir by a plurality of electrolyte conduits.

16. The system of claim 15 , wherein:

the system contains only the single electrolyte reservoir;

the halogen comprises bromine;

the flow battery is a zinc-bromine, zinc-chlorine, or zinc-chlorine-bromine flow battery configured to use a liquid electrolyte;

the aqueous phase comprises at least one of zinc bromide, zinc chloride or a mixture of zinc chloride and zinc bromide; and

the electrolyte further comprises an ionic phase comprising a bromine sequestering agent.

17. A method of operating a flow battery system, comprising circulating a liquid-metal-halide electrolyte between a reservoir and a stack of flow battery cells that do not contain a separator in reaction zones formed between anode and cathode electrodes of each flow battery cell,

wherein the electrolyte comprises a metal-halide, a halogen, a metal plating enhancer comprising a bismuth salt, and an anti-dendrite agent comprising bisphenol A alkoxylate (BPA).

18. The method of claim 17 , wherein the circulating comprises using at least one pump to circulate the electrolyte between a chamber housing the stack of flow battery cells and the reservoir.

19. The method of claim 17 , wherein:

the system contains only the single electrolyte reservoir;

the halogen comprises bromine;

the electrolyte comprises at least one of zinc bromide, zinc chloride or a mixture of zinc chloride and zinc bromide; and

the electrolyte further comprises a bromine sequestering agent.

20. The method of claim 19 , wherein:

the metal plating enhancer comprises at least one of bismuth oxide, bismuth chloride, and bismuth citrate; and

further comprising a chelating agent which comprises ethylenediaminetetraacetic acid (EDTA) or derivatives thereof.