Achieving Ultra-Long Cycle Life of Zn Anode Using ZnSn(OH)6 Coating Layer via Desolvation Effect and Uniform Zn2+ Flux.

Aqueous zinc-ion batteries (AZIBs) are considered as a promising energy storage system because of good safety, low cost, abundant resources, and environmental friendliness. However, the bottlenecks including dendrite growth, hydrogen evolution, and corrosion seriously limit their practical application. Herein, a novel ZnSn(OH)₆ coating layer with rich hydroxyl groups is employed to achieve highly stable Zn anode. The hydroxyl groups can feasibly interact with H₂O molecules, contributing to the desolvation of hydrated Zn²⁺ and the inhibition of side reactions on Zn anode surface. Furthermore, according to the DFT calculation, the adsorption energy of Zn²⁺ among various sites on the surface of ZnSn(OH)₆ coating layer is relatively large, which helps the uniform distribution of Zn²⁺ flux and the prevention of dendrite growth. Consequently, the ZnSn(OH)₆@Zn anode delivers ultra-long cycle life (6770 h), low polarization voltage (27 mV), and high Coulombic efficiency (99.2% over 800 cycles) at 1 mA cm^-2, 1 mAh cm^-2. Besides, the assembled NaV₃O₈·xH₂O//ZnSn(OH)₆@Zn full cell can operate stably for 1500 cycles at 2 A g^-1 with a high specific capacity of 144.9 mAh g^-1, demonstrating an excellent application potential. This simple and effective coating layer with high electrochemical performance provides an appealing strategy for the development of rechargeable AZIBs.