Nitrogen-doped carbonized polyimide microsphere as a novel anode material for high performance lithium ion capacitors

Lithium ion capacitors (LICs), which bridge the gap between lithium ion battery and electric double layer capacitor, have recently attracted considerable attention. Herein, we first propose the possible utilization of nitrogen-doped carbonized polyimide microsphere (CPIMS) as a novel anode material of LICs. The structures and lithium intercalation properties of CPIMS treated at different temperatures are investigated. It is demonstrated that some of nitrogen atoms are kept in the CPIMS, which is helpful for improving the electrochemical performances. The CPIMS900 (900 is the carbonization temperature) can deliver specific capacities of 328.3 and 48.2 mAh g−1 at 10 mA g−1 and 10 A g−1, respectively. When the pre-lithiated CPIMS900 is coupled with an activated carbon cathode, an energy density of 28.5 Wh kg−1 at 348 W kg−1 is obtained based on the weight of both electrode materials. Even at 6940 W kg−1, the energy density still remains 13.1 Wh kg−1. After 5000 cycles at 500 mA g−1, the capacity retention ratio is as high as 97.1%. The present work offers an opportunity to utilize the CPIMS material in LIC with high energy density, high power density and promising cycle life.