Fe-V redox flow batteries
A redox flow battery having a supporting solution that includes Cl − anions is characterized by an anolyte having V 2+ and V 3+ in the supporting solution, a catholyte having Fe 2+ and Fe 3+ in the supporting solution, and a membrane separating the anolyte and the catholyte. The anolyte and catholyte can have V cations and Fe cations, respectively, or the anolyte and catholyte can each contain both V and Fe cations in a mixture. Furthermore, the supporting solution can contain a mixture of SO 4 2− and Cl − anions.
1. A redox flow battery system having:
A membrane separating an anolyte and a catholyte;
the anolyte comprising V 2+ and V 3+ in a negative supporting solution comprising an initial concentration of at least 0.5M Fe cations and Cl− anions;
the catholyte comprising Fe 2+ and Fe 3+ in a positive supporting solution comprising an initial concentration of at least 0.5M V cations and Cl− anions;
wherein the initial concentration of Fe cations in the negative supporting solution is substantially equal to the initial concentration of V cations in the positive supporting solution.
2. The system of claim 1 , wherein the Fe 2+ and Fe 3+ concentrations are greater than 0.5 M.
3. The system of claim 1 , wherein the V 2+ and V 3+ concentrations are greater than 0.5M.
4. The system of claim 1 , wherein the membrane is a hydrocarbon-based membrane.
5. The system of claim 1 , wherein the membrane is a micro-porous separator.
6. The system of claim 1 , wherein the membrane is not a sulfonated tetrafluoroethylene based fluoropolymer-copolymer.
7. The system of claim 1 , further comprising negative and positive electrodes in contact with the anolyte and the catholyte, respectively, wherein the electrodes do not contain a redox catalyst.
8. The system of claim 1 , having a cell temperature less than 60° C. during operation.
9. The system of claim 1 , having a cell temperature between −20° C. and 50° C. during operation.
10. The system of claim 1 , wherein the positive supporting solution, the negative supporting solution, or both further comprises SO 4 2− anions.
11. The system of claim 10 , wherein the Cl − to SO 4 2− concentration ratio is between 1:100 and 100:1.
12. The system of claim 10 , wherein the Cl − to SO 4 2− concentration ratio is between 1:10 and 10:1.
13. The system of claim 10 , wherein the Cl− and SO 4 2− concentration ratio is between 1:3 and 3:1.
14. The system of claim 12 , wherein concentrations of V 2+ , V 3+ , Fe 2+ , and Fe 3+ are greater than 1M in the anolyte and in the catholyte.
15. The system of claim 10 , wherein concentrations of V 2+ and V 3+ are greater than 1.5M in the anolyte and concentrations of Fe 2+ and Fe 3+ are greater than 1.5M in the catholyte.
16. The system of claim 1 , wherein said cations of V have a concentration greater than 0.5 M in the positive supporting solution and said cations of Fe have a concentration greater than 0.5 M in the negative supporting solution.
17. The system of claim 1 , having a catholyte side of the membrane and an anolyte side of the membrane, wherein the catholyte side of the membrane has a total concentration of Fe and V that is substantially equal to that of the anolyte side of the membrane.
18. A redox flow battery system comprising:
A membrane separating an anolyte and a catholyte
the anolyte comprising a total concentration of V2+ and V3+ cations greater than 0.5 M in a an initial negative supporting solution comprising Cl− anions and greater than a 0.5 M concentration of Fe cations;
the catholyte comprising a total concentration of Fe2+ and Fe3+ cations greater than 0.5 M in a an initial positive supporting solution comprising Cl− anions and greater than a 0.5 M concentration of V cations.