N-doped carbon encapsulated CoMoO4 nanorods as long-cycle life anode for sodium-ion batteries.

Abstract 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 CoMoO4 (CoMoO4@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 CoMoO4. The optimized composite presents rapid reaction kinetics and excellent cycle stability. Even at a high current density of 1 A g-1, it still shows long-cycle life and maintains specific capacity of 190 mAh g-1 after 3200 cycles. Furthermore, CoMoO4@NC anode is applied to match with Na3V2(PO4)3 cathode to assemble full-cells, in which it accomplishes reversible capacity of 152 mAh g-1 after 100 cycles, with capacity retention of 75% at a current density of 1 A g-1, highlighting the practical application for SIBs.