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

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 Li 2-2 x Zn x MgCl 4 ( x  = 0–0.3) and their application in ASSLBs. By Zn substitution into the Li site of Li 2 MgCl 4 , the Li  +  conductivities of Li 1.6 Zn 0.2 MgCl 4 (1.2 × 10 −5  S/cm) at room temperature is two orders higher than that of Li 2 MgCl 4 (1.9 × 10 −7  S/cm). The activation energy is reduced to 0.28 eV for Li 1.6 Zn 0.2 MgCl 4 (Li 2 MgCl 4 is 0.47 eV). We attributed the enhanced electrochemical performance to Li vacancies generated from the Zn substitution. In addition, we fabricated a Li | Li 1.6 Zn 0.2 MgCl 4 | Li cell to appraise the electrochemical performance in the lithiation and stripping. It is demonstrated that Li 1.6 Zn 0.2 MgCl 4 can cycle for 100 h under a current density of 0.07 mA/cm 2 . This study demonstrates that introducing Li vacancy into Li 2 MgCl 4 may be a valid way to promote the electrochemical properties of the halides.