Enhancing electrochemical performances of small quinone toward lithium and sodium energy storage

Further application of organic quinone cathodes is restricted because they are inherent in poor conductivity and tend to dissolve in aprotic electrolytes. Salinization can work on the strong solubility of quinones. Herein, the ortho-disodium salt of tetrahydroxyquinone (o-Na2THBQ) was selected to promote the electrochemical properties of tetrahydroxyquinone (THBQ). Reduced dissolution of o-Na2THBQ in electrolyte after salinization (replacement of two H with two Na) contributed to enhanced electrochemical performance. In sodium-ion batteries (SIBs) in ester-based electrolyte, o-Na2THBQ cathodes at 50 mA·g−1 exhibited a reversible discharge capacity of 107 mAh·g−1 after 200 cycles. Ulteriorly, in ether-based electrolyte, reversible discharge capacities of 200.4, 102.2, 99.5 and 88 mAh·g−1 were obtained at 800, 1600, 3200 and 4800 mA·g−1 after 1000, 2000, 5000 and 8000 cycles, respectively. The ultraviolet absorption spectra and ex situ dissolution experiments of THBQ and o-Na2THBQ showed that o-Na2THBQ hardly dissolved in ether-based electrolyte. In lithium-ion batteries (LIBs), graphene was selected to further enhance the conductivity of o-Na2THBQ. At 50 mA·g−1, o-Na2THBQ and o-Na2THBQ/Gr cathodes exhibited reversible discharge capacities of 124 and 131.5 mAh·g−1 after 200 cycles in ester-based electrolyte, respectively. At 50 mA·g−1, PTPAn/o-Na2THBQ electrodes in an all-organic Na/Li-ion battery showed reversible charge/discharge capacities of 51/50.3 and 33.8/33.1 mAh·g−1 after 200 cycles.