An “immobilizing and relocating” strategy for a highly reversible metallic zinc anode

Abstract

Over the last decade, aqueous metallic zinc batteries have aroused broad attention as a complementary alternative to lithium-ion batteries due to their safe and eco-friendly characteristics. However, the parasitic reactions (i.e., dendrite growth, by-product formation, and hydrogen evolution) during zinc plating/stripping severely impair the electrochemical stability and reversibility of the metallic zinc anode. Herein, we proposed an “immobilizing and relocating” strategy for managing the electrode–electrolyte interface by introducing bifunctional betaine zwitterions into the baseline electrolyte. We found that the cation end of the zwitterions can be adsorbed onto metallic zinc and homogenize zinc plating/stripping by adjusting the electric field distribution. Meanwhile, the anion end of the zwitterions can interact with the water molecules around the electrode/electrolyte interface through hydrogen bonds and promote the zinc plating/stripping kinetics. Based on this “immobilizing and relocating” strategy, the initial coulombic efficiency (CE) of the zinc plating/stripping in Zn‖Cu half-cells exceeds 94.99% at a current density of 1 mA cm⁻², and the average CE reaches 99.93%. A Zn‖MnO₂ full cell adopting 20 μm thick zinc stably runs for 500 cycles with a capacity retention of 86.4%. This work provides a new insight into realizing highly reversible metallic zinc anode.