Ternary Zn3V3O8 superstructure and synergistic modification of separator promote high performance and stable zinc ion battery

Aqueous zinc-ion batteries have attracted much attention from researchers owing to their safety and eminent energy density. However, the exploration of an appropriate cathode with high reversible capacity is still a huge challenge. In this manuscript, the ternary Zn 3 V 3 O 8 superstructure with an energy density of 317 Wh kg −1 was successfully prepared with a micro-nano ternary hierarchical structure and the incorporation doping of nitrogen and carbon (ZVO@CN). Thanks to the multilevel morphology and high conductivity of carbon and nitrogen, the novel ZVO@CN cathode delivers the eminent reversible capacity of 192 mAh/g at 5 A/g after 2200 cycles for aqueous zinc ion battery. Importantly, the ex-situ XRD and XPS were adopted to explore the energy storage kinetics. Consequently, the pristine material is been transformed to Zn 3 (OH) 2 V 2 O 7 ·2H 2 O in the initial charging at 1.3 V, and this phase transition is nonreversible. After the second cycle, the intercalation/extraction of Zn 2+ in Zn 3 (OH) 2 V 2 O 7 ·2H 2 O supplies the reversible capacity. Besides, to solve the rapid capacity delay caused by dendrite growth at low current density on the Zn anodes, the C 3 N 4 coating Zn is prepared to modify the separator (Zn@C 3 N 4 @GF). It has effectively relieved the negative effect of Zn dendrite with highly improved stability. When the ZVO@CN and Zn@C 3 N 4 @GF were used as cathode and separator, the batteries exhibited a dominant discharge capacity of 235 mAh/g at 0.1 A/g after 380 cycles, only reducing the 50 mAh/g compared to the initial capacity. This means it only decreases the discharge capacity of 0.13 mA g −1 per cycle.