A novel hydrophobic-zincophilic bifunctional layer for stable Zn metal anodes

Abstract

Zn metal serving as anode endows aqueous Zn-ion batteries (AZBs) attractive advantages of high energy density, inherent safety and low cost. However, direct contact between electrolytes and Zn metal leads to severe surface corrosion and dendrite growth, which have greatly compromised the calendar life and Coulombic efficiency (CE) of AZBs. Herein, a novel hydrophobic-zincophilic bifunctional layer (HZBL) is introduced on Zn surface (HZBL-Zn) to provide hydrophobic and uniform pathways for zinc ions. In this unique design, hydrophobic framework serves as a buffer layer to isolate active Zn from bulk electrolytes, and meanwhile zincophilic functional groups on sidechains form uniform pathways to regulate Zn deposition behavior. Correspondingly, HZBL can not only inhibit notorious side reaction but promote the uniform deposition on Zn surface. With this synergy effect, HZBL-Zn symmetrical cells stably perform 2500 h with 40 mV polarization voltage at 1 mA cm−2 with a capacity of 1 mAh cm−2. Surprisingly, the average CE of Zn stripping/plating underneath HZBL reach 99.88% after 2700 cycles. This concept of hydrophobic-zincophilic bifunctional molecular reassembly holds great prospects in the development of highly stable Zn metal anodes.