Synergistic effect of multi-electron conversion and anion redox media chemistry for high-performance rechargeable aqueous Zn ion batteries

A conversion-type BiOI cathode coupled with ZnI2 additive as a redox medium is proposed to electrochemically store charge. By integrating the redox-targeting reactions interrelated with I- and Bi3+ redox reactions, a volumetric capacity of 3589 mA h cm-3 and cycling life of 16 000 cycles with a capacity decay of 0.006 mA h g-1 per cycle were reached. In-depth electrochemical mechanism research demonstrates that the high electrochemical performance results from the mutual reinforcing effects between Bi0/Bi3+ and I-/I3- conversion reactions.