Host-Guest Interactions Enhance The Performance Of Viologen Electrolytes For Aqueous Organic Redox Flow Batteries

Host-guest interactions are an attractive approach to design redox electrolytes, enabling to precisely tune the key properties for redox flow batteries such as half-cell redox potential, solubility, and stability. Herein we report a host-guest complex of highly water soluble (2-hydroxypropyl)-beta-cyclodextrin with 1-decyl-1 '-ethyl-4,4 '-bipyridinium dibromide as anolyte in a new aqueous organic redox flow battery (AORFB). The supramolecular anolyte ensured the total RFB voltage increase of approximate to 9 % up to 0.97 V and provided a stable capacity delivery for more than 500 cycles with a capacity fade rate of 0.037 %/cycle (2.84 %/day) at high Coulombic (>99.5 %) and energy (>62 %) efficiencies. The results highlight host-guest interactions as promising strategy towards more effective storage of renewable energy within AORFBs.