Mg–Zn–Cl-integrated functional interface for enhancing the cycle life of Mg electrodes

Abstract

The instability of the Mg-electrolyte interface in nonaqueous electrolytes hinders the realization of rechargeable Mg batteries (RMBs). Herein, we adopted surface engineering to address this issue by alleviating the passivation characteristics of reductive Mg electrodes. Among a series of artificial interfaces derived from different elements, the Mg–Zn–Cl-integrated artificial interface imparted outstanding Mg deposition–dissolution cycling performance upon combination with a halide-free weakly coordinated anion-based electrolyte. The artificial interface allowed Mg deposition–dissolution reactions beneath the interface, as evidenced by systematic scanning electron microscopy observations combined with electron backscatter diffraction analyses, and such interfacial characteristics suppressed the intrusion of Mg deposits into microporous separators, leading to remarkably stable cycling even under exceptionally high utilization conditions (>30 %). The amorphous nature induced by Cl integration improved interfacial stability during the successive morphological changes of Mg electrodes owing to electrochemical deposition–dissolution cycling. In addition, the artificial interface enabled the employment of a thin PTFE-based separator, which was unattainable using unmodified Mg. The developed techniques can pave the way for assessing the interfacial behavior under harsh, lean electrolyte conditions, which is an extremely important but unexplored research area of RMB chemistry.