Working mechanism of chemically self-charging ZIBs during a chemical charging and b galvanostatic discharging process. c The galvanostatic discharge curves of Zn/CaZn3.6−xVO batteries at 0.1 A g−1 after the CaZn3.6VO electrodes were oxidized for different times. d Effect of the oxidation time on OCV and discharge capacity of Zn/CaZn3.6−xVO batteries. e Voltage–time curves of the Zn/CaZn3.6−xVO batteries after being chemically charged to different states (dotted lines: chemical charging for different times. Solid lines: galvanostatic discharging at 0.1 A g−1). f Chemical charging/galvanostatic discharging cycling stability of the Zn/CaZn3.6−xVO battery in a voltage window from 0.3 to ~1.05 V.