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 Zn3V3O8 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 Zn3(OH)2V2O7·2H2O in the initial charging at 1.3 V, and this phase transition is nonreversible. After the second cycle, the intercalation/extraction of Zn2+ in Zn3(OH)2V2O7·2H2O supplies the reversible capacity. Besides, to solve the rapid capacity delay caused by dendrite growth at low current density on the Zn anodes, the C3N4 coating Zn is prepared to modify the separator (Zn@C3N4@GF). It has effectively relieved the negative effect of Zn dendrite with highly improved stability. When the ZVO@CN and Zn@C3N4@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.