A long-life aqueous Zn battery enabled by simultaneous suppressing cathode dissolution and Zn dendrites via a novel water-in-deep eutectic solvent electrolyte

Aqueous Zn metal batteries (ZMBs) are promising to provide high energy density and inherent safety at a low cost, which is a candidate for large-scale energy storage. However, the cycle life of ZMBs is challenged by the cathode dissolution and irreversible plating/stripping of Zn metal anode (ZMA). Herein, we report a novel deep eutectic solvent electrolyte, 30 m ZnCl2 + 15 m C5H14ClNO (choline chloride, ChCl), where ChCl restrains water’s activity in both the bulk electrolyte and the Zn2+ solvation sheaths by coordinating with Zn2+. The presence of ChCl mitigates the cathode dissolution problem and eliminates the zinc dendrites of ZMBs. With this electrolyte, the vanadium oxide cathode, V2O5·0.41H2O, maintains a capacity of ∼305 mAh g−1 over 100 cycles at a harsh current density of 50 mA g−1 and ∼180 mAh g−1 over 1500 cycles at 500 mA g−1; the ZMA can be cycled up to 1600 h at a harsh current density of 0.2 mA cm−2, 950 h higher than 30 m ZnCl2, without dendrite formation. This study highlights the function of ChCl as a co-salt for ZnCl2 to facilitate high performance of ZMBs.