In-situ grown hydrophilic-zinophilic ZnCr2O4 protective layer to guide horizontal Zn2+deposition for dendrite-free Zn anodes for aqueous Zn-ion batteries

Aqueous rechargeable Zn-ion batteries (ARZIBs) have attracted much attention owing to their safety, high energy density and environmental friendliness. However, zinc dendrites and corrosive reactions during platting/strip-ping on the surface of Zn anodes limit the practical applications of ARZIBs. Herein, the hydrophilic and zinophilic ZnCr2O4 interface layer is grown in situ on the surface of Zn metal to stabilize Zn anode. The in-situ grown ZnCr2O4 interface protective layer constrains the 2D diffusion of Zn2+and homogenizes the surface electric field, guiding preferentially horizontal deposition of Zn2+ along the Zn foil surface. In addition, the in situ ZnCr2O4 interface layer possesses strong hydrophilicity and zinophilicity to enable rapid desolvation of Zn(H2O)62+ and improve Zn2+ platting/stripping kinetics for dense Zn deposition without dendrite Zn growth. Consequently, the symmetric cell with ZnCr2O4-protected Zn anode can stably operate more than 1500 h at 1 mA cm-2 with 1 mAh cm-2, while the Cu||ZCO@Zn half-cell presents a high average Coulombic efficiency of over 99.7 % during cycling for more than 100 cycles. In addition, the NH4V4O10||ZCO@Zn full cell exhibits the capacity retention of 83.3 % at 3 A g-1 after 1000 cycles. This investigation provides a feasible strategy to efficiently inhibit zinc dendrites by in-situ constructing hydrophilic-zinophilic artificial protective coating on the surface of Zn anodes.