Electrode-decoupled RFBs are hampered by the need to separate the cations. This issue was faced by NASA when they first tested the Fe—Cr RFB (L. H. Thaller, U.S. Pat. No. 3,996,064, 1976 and reports cited therein). A Fe—V system proposed by PNNL (Energy Environ. Sci., 2011, 4, 4068) also suffers from the same issue which they circumvent by using a mixed cation electrolyte, which has a significant impact on the performance of the RFB. Others have proposed V—Br, Br—S, Zn—Br, V—Ce, Fe—Br, Mn—Br, Ti—Mn, Fe—Ti systems. An extensive review of RFBs with both elemental and non-elemental actives may be found in Chem. Rev. 2015, 115, 11533-11558. Described herein is an RFB that overcomes and resolves many of the difficulties previously found in these systems. Thus, in one aspect, a Ti—Ce electrode-decoupled RFB is described herein. The following sections describe the electrolyte selection process, the specific economics of the Ti—Ce electrolytes compared to some common combinations in various stages of commercialization, and finally the RFB system and its performance.

In one aspect, disclosed herein is a redox flow battery. The (RFB) generally comprises: a positive electrolyte comprising a first metal ion, a negative electrolyte comprising a second metal ion, an ion exchange membrane positioned between the positive electrolyte and the negative electrolyte, wherein said membrane is configured to restrict and/or prevent the passage of the first metal ion and/or the second metal ion therethrough, and said membrane is configured to maintain ionic conductivity between the positive electrolyte and the negative electrolyte.