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

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.