CuP2 as high-capacity and long-cycle-life anode for potassium-ion batteries

Metal phosphides have shown great potential for potassium-ion batteries because of their high theoretical specific capacity. Nevertheless, most of the metal phosphide anodes are plagued by rapid capacity decay (caused by the large volume changes during the discharge/charge process), which would restrict their further practical application. Herein, a chemically bonded CuP 2 /C composite was prepared by a facile high-energy ball milling method. A potassium bis(trifluoromethanesulfonyl)imide (KFSI)-based electrolyte was adopted instead of a conventional KPF 6 -based electrolyte for the CuP 2 /C composite anode. Benefiting from the synergistic effects of the formation of strong P–O–C chemical bonds and the KFSI-based electrolyte, the CuP 2 /C composite anode exhibited high reversible capacity (451.4 mAh g −1 at 50 mA g −1 ), excellent rate performance (123.5 mAh g −1 at 1000 mA g −1 ), and superior cycling stability (300 mAh g −1 after 100 cycles). This work paves the way for the development of high-performance CuP 2 anode for potassium-ion batteries.