Enhanced electrochemical properties of Li2MgCl4 by Zn substitution for all-solid-state batteries

Abstract

Halides have currently been discovered to be ideal electrolytes for all-solid-state Li batteries (ASSLBs) due to their variability, splendid electrochemical stability, and high Li+ conductivities. Here, we studied the electrochemical properties of Li2-2xZnxMgCl4 (x = 0–0.3) and their application in ASSLBs. By Zn substitution into the Li site of Li2MgCl4, the Li + conductivities of Li1.6Zn0.2MgCl4 (1.2 × 10−5 S/cm) at room temperature is two orders higher than that of Li2MgCl4 (1.9 × 10−7 S/cm). The activation energy is reduced to 0.28 eV for Li1.6Zn0.2MgCl4 (Li2MgCl4 is 0.47 eV). We attributed the enhanced electrochemical performance to Li vacancies generated from the Zn substitution. In addition, we fabricated a Li | Li1.6Zn0.2MgCl4 | Li cell to appraise the electrochemical performance in the lithiation and stripping. It is demonstrated that Li1.6Zn0.2MgCl4 can cycle for 100 h under a current density of 0.07 mA/cm2. This study demonstrates that introducing Li vacancy into Li2MgCl4 may be a valid way to promote the electrochemical properties of the halides.