Structure evolution of azo-fused conjugated microporous polymers for high performance lithium-ion batteries anodes

Redox polymers as electrodes for rechargeable batteries have gained much attention because of their tunable chemical structures and designable electrochemical performance. Herein, a class of azo-fused conjugated microporous polymers with distinct electronic structures is reported as anode materials of rechargeable lithiumion batteries. The structure-performance correlation revealed by the comparative study in this work demonstrates that the lowest unoccupied molecular orbital energy level and the band gap play significant roles in enhancing the capability of Li ions storage for the azo-fused conjugated microporous polymer electrodes. The polymer of AzoBT comprising azo and benzothiadiazole units delivers a high reversible capacity up to 1543 mAh g(-1) at 50 mA g(-1), outstanding rate capability (366 mAh g(-1) at 3 A g(-1)) and stable cycling performance of 1000 cycles at 2 A g(-1), demonstrating that the newly developed azo-fused conjugated microporous polymers are potential candidate anodes for energy storage. The result underlines the key role of electronic structures in the structure design of high-performance organic electrodes for rechargeable lithium-ion batteries.