Nonaqueous arylated quinone catholytes for lithium–organic flow batteries†
Chemically modified organic redox couples have the advantages of tunable redox properties, high solubility, environmental benignity, and cost effectiveness. Inspired by nature, a series of quinone derivatives bearing electron-donating methoxy or electron-withdrawing trifluoromethyl groups are synthesized in moderate to high yields by Pd-catalyzed Suzuki cross-coupling reactions. This study utilizes the synthetic quinones as redox-active organic molecules for nonaqueous lithium–organic flow batteries. The aryl moiety incorporated quinone scaffolds show enhanced electrochemical stability and rate capability. The nonaqueous catholyte, 2-phenyl-1,4-naphthoquinone, reaches a cell voltage of ∼2.6 V and a specific capacity of 196 mA h g−1, while the discharge capacity is retained at ∼92% for 150 cycles. Moreover, the tubular lithium–organic flow battery system features stable cycle performance under a continuous circulation without clogging-associated intermittency flow.