  Redox flow batteries (RFBs) have gained popularity as large-scale energy
storage systems for wind and solar powered grids. Modern RFB systems are based
on highly corrosive and/or flammable electrolytes. Organic redox active species
for RFBs are gaining commercial traction, but there is a trade-off in choosing
aqueous or non-aqueous electrolytes in terms of rate capabilities, energy
density, safety and cost. While modification of organic redox molecules to
mitigate these issues is prevalent in the literature, the search for novel
electrolyte systems is scarce. Here we present microemulsion-based electrolytes
as an alternative for the next generation of organic RFBs. Micro-emulsion
electrolytes (MEs) offer the advantages of decoupled solubility and ionic
conductivity, broad electrochemical windows, non-flammability, simple
fabrication modes and low cost of constituent chemicals. The electrochemical
properties of organic redox species in MEs have been investigated for RFB
requirements and a proof-of-concept flow cell with a widely studied redox
system and a commercial membrane is shown. The compositions of MEs can be
tailored to the redox system, making them a platform of electrolytes for all
organic redox systems under consideration and benefit.
