Advanced electrochemical performance of ZnMn2O4/N-doped graphene hybrid as cathode material for zinc ion battery

Rechargeable aqueous zinc ion batteries are considered as a good substitute for large-scale energy storage due to their cost-effectiveness, materials abundance and safety. However, suitable cathode materials with high capacity and long cycling stability are still rare. Herein, we propose the first use of ZnMn2O4/N-doped graphene nanocomposite as cathode material, which exhibits a maximum discharge capacity of 221 mAh g−1 at 100 mA g−1, and ultralong cycle life with 97.4% capacity retention after 2500 cycles at 1000 mA g−1. The outstanding performance is attributed to the synergistic effect of superfine ZnMn2O4 nanoparticles (21 nm) that provide rapid surface capacitive reaction and short electronic/ion transport path lengths, as well as the highly conductive N-doped graphene medium that could facilities the fast electronic transport and stabilizes the composite structure to tolerate volume expansion during charge/discharge process. Significant insight into the zinc ion storage mechanism is confirmed by galvanostatic intermittent titration technique, ex-situ X-ray diffraction, and X-ray photoelectron spectroscopy characterizations. The long-term stability, high specific capacity together with the facile preparation method propose the ZnMn2O4/N-doped graphene hybrid a new class of competitive cathode material for zinc ion battery.