Ethylene carbonate as an organic electrolyte additive for high-performance aqueous rechargeable zinc-ion batteries

Rechargeable zinc-ion batteries (ZIBs) have recently received tremendous attention for large-scale electrochemical energy storage, but their poor cyclic stability and reversibility and low coulombic efficiency, which are mainly caused by dendrite issues and parasitic reactions of zinc (Zn) anode, prevent them from achieving their full potential. Herein, we investigated the use of ethylene carbonate (EC) as an electrolyte additive to improve the performance of ZIBs. The addition of 6% (w/v) EC substantially enhanced the first-cycle discharge capacity from 115 to 203 mAh g−1 at 0.1 A g−1, while retaining this high discharge capacity (102% retention of the initial capacity) after 200 cycles, and from 43 to 54 mAh g−1 at 1 A g−1 with 85% capacity retention after 1,000 cycles. The ex-situ characterizations and electrochemical impedance spectroscopy analysis before and after Zn–MnO2 and Zn–Zn battery cycling suggested that the addition of EC could effectively suppress dendrite formation and parasitic reactions on the Zn anode, possibly via electrolyte/Zn anode interface film formation in the presence of EC. Moreover, the presence of EC made the MnO2 morphology more open and accessible. These led to substantial improvements in the rate performance and cyclability compared to the additive-free electrolyte.