Desymmetrization of Viologen Anolytes Empowering Energy Dense, Ultra Stable Flow Batteries toward Long-Duration Energy Storage

摘要

Aqueous organic redox flow batteries (AORFBs) have been recognized as apromising technology for large-scale, long-duration energy storage of renewables(e.g., solar and wind) by overcoming their intermittence and fluctuation.However, simultaneous demonstration of high energy densities and stablecycling are still challenging for AORFBs. Herein, asymmetrically substitutedsulfonate viologen molecular designs, e.g. (1-[3-sulfonatopropyl]-1′-[4-sulfonatobutane]-4,4′-bipyridinium (3,4-S_2V), as capacity dense, chemicallystable anolytes for cation exchange AORFBs are presented. The robust cyclingperformance of 3,4-S2V is confirmed using half-cell and full-cell flow batterystudies at pH neutral conditions. The 3,4-S2V based AORFB is demonstratedwith a discharge capacity of 23.2 Ah L~（?1） for 1700 cycles or 100 days withoutobserving chemical degradation. Furthermore, a 3,4-S_2V/(NH_4)_4[Fe(CN)_6]AORFB with a discharge capacity of 259.9 mAh is demonstrated for 50 daysof authentic energy storage for the first time with a total capacity retention of97.77% or a temporal capacity retention rate of 99.955% per day, representingthe most stable, longest cycled AORFB to date.