A ZnCl water-in-salt electrolyte for a reversible Zn metal anode.

We report a low-cost water-in-salt electrolyte, of 30 m ZnCl2, which enables a dendrite-free Zn metal anode to possess a high coulombic efficiency (CE). In asymmetric Zn‖Zn cells with a limited mass of plated Zn as the working electrode, the ZnCl2 WiSE improves the average CE of the Zn anode to 95.4% from 73.