The electrolyte comprising more robust water and superhalides transforms Zn‐metal anode reversibly and dendrite‐free

Abstract

A great challenge for all aqueous batteries, including Zn‐metal batteries, is the parasitic hydrogen evolution reaction on the low‐potential anode. Herein, we report the formula of a highly concentrated aqueous electrolyte that mitigates hydrogen evolution by transforming water molecules more inert. The electrolyte comprises primarily ZnCl 2 and LiCl as an additive, both of which are inexpensive salts. The O–H covalent bonds in water get strengthened in a chemical environment that has fewer hydrogen bonding interactions and a greater number of Zn–Cl superhalides, as suggested by integrated characterization and simulation. As a result, the average Coulombic efficiency of zinc‐metal anode is raised to an unprecedented >99.7% at 1 mA cm−2. In the new electrolyte, the plating/stripping processes leave the zinc‐metal anode dendrite‐free, and the zinc‐metal anode delivers stable plating/stripping cycles for 4000 hours with an areal capacity of 4 mAh cm−2 at 2 mA cm−2. Furthermore, the high Coulombic efficiency of zinc‐metal anode in the ZnCl 2‐LiCl mixture electrolyte is demonstrated in full cells with a limited anode. The V 2 O 5·H 2 O||Zn full cell with an N/P mass ratio of 1.2 delivers a stable life of more than 2500 cycles, and the LiMn 2 O 4||Zn hybrid cell with an N/P mass ratio of 0.6 exhibits 1500 cycles in its stable life.