Poly(benzoquinonyl sulfide) as a High-Energy Organic Cathode for Rechargeable Li and Na Batteries

In concern of resource sustainability and environmental friendliness, organic electrode materials for rechargeable batteries have attracted increasing attentions in recent years. However, for many researchers, the primary impression on organic cathode materials is the poor cycling stability and low energy density, mainly due to the unfavorable dissolution and low redox potential, respectively. Herein, a novel polymer cathode material, namely poly(benzoquinonyl sulfide) (PBQS) is reported, for either rechargeable Li or Na battery. Remarkably, PBQS shows a high energy density of 734 W h kg^-1 (2.67 V × 275 mA h g^-1) in Li battery, or 557 W h kg^-1 (2.08 V × 268 mA h g^-1) in Na battery, which exceeds those of most inorganic Li or Na intercalation cathodes. Moreover, PBQS also demonstrates excellent long-term cycling stability (1000 cycles, 86%) and superior rate capability (5000 mA g^-1, 72%) in Li battery. Besides the exciting battery performance, investigations on the structure-property relationship between benzoquinone (BQ) and PBQS, and electrochemical behavior difference between Li-PBQS battery and Na-PBQS battery, also provide significant insights into developing better Li-organic and Na-organic batteries beyond conventional Li-ion batteries.