N-doped carbon encapsulated CoMoO nanorods as long-cycle life anode for sodium-ion batteries.

Volume expansion and poor conductivity result in poor cyclability and low rate capability, which are the major challenges of transition-metal oxide as anode materials for sodium-ion batteries (SIBs). Herein, N-doped carbon encapsulated CoMoO (CoMoO@NC) nanorods are developed as excellent anode materials for SIBs with long-cycle life. The N-doped carbon shells serve as buffer to accommodate severe volume changes during sodiation/desodiation, and at the same time improve electronic conductivity and activate surface sites of CoMoO. The optimized composite presents rapid reaction kinetics and excellent cycle stability. Even at a high current density of 1 A g, it still shows long-cycle life and maintains specific capacity of 190 mAh g after 3200 cycles. Furthermore, CoMoO@NC anode is applied to match with NaV(PO) cathode to assemble full-cells, in which it accomplishes reversible capacity of 152 mAh g after 100 cycles, with capacity retention of 75% at a current density of 1 A g, highlighting the practical application for SIBs.