Abstract
Rechargeable Mg batteries are one of the emerging next-generation battery systems. The anode-free configuration further enhances the energy density of rechargeable Mg batteries, and the microstructure of electrodeposited Mg layers on current collectors during the first charge cycle plays a crucial role in the cell performance. LiCl is an additive to boost the electrochemical performance of all phenyl complex (APC) electrolytes for rechargeable Mg batteries. However, the effect of LiCl addition in APC electrolyte on the microstructure of electrodeposited Mg layers has not been systematically studied. Combining electrochemical measurements and microstructure characterizations, effects of electrodeposition conditions and LiCl addition in the APC electrolyte on the microstructure of electrodeposited Mg layers on Cu current collectors were investigated. Electrochemical measurements revealed that LiCl addition enhanced the reaction kinetics of the APC electrolyte by facilitating faster interfacial reactions and increasing the mobility of Mg complex ions, which suppressed dendritic Mg growth under high current densities. The enhanced reaction kinetics after LiCl addition resulted in smaller overpotentials and less nucleation driving forces under the same electrodeposition conditions, leading to reduced nucleation rates and larger electrodeposited Mg grains. Furthermore, the preferred crystallographic orientations of electrodeposited Mg layers in the APC + LiCl electrolyte were less sensitive to the applied current density, and the (102) and (103) orientations were preferred after LiCl addition.
•LiCl addition enhances APC electrolyte reaction kinetics and complex ions mobility.•Enhanced kinetics lead to reduced nucleation rates and larger Mg grains.•Added LiCl effectively suppresses dendritic Mg growth at high current densities.•Mg in APC + LiCl electrolyte show (102) and (103) preferred crystal orientations.•APT confirms that no Li co-deposition occurs with Mg after LiCl addition.