Regulating Interfacial Kinetics of Mg Metal Anode by Introducing Thiourea Additives to Halogen-Free Electrolyte

Regulating interfacial kinetics at the Mg metal anode is crucial to advancing the performance of magnesium–sulfur (Mg–S) batteries. In this study, we present a novel strategy by introducing thiourea (TU) additives to a halogen-free electrolyte (HFE), aiming to stabilize the Mg–electrolyte interface and enhance Mg2+ transport. The optimized TU content (0.05–0.2 g) added to 1.5 g of Mg(NO3)2·6H2O improves ion mobility, increases the transference number to 0.81, and enhances ionic conductivity. Coin cells assembled with TU-modified electrolytes exhibit an initial discharge capacity of 880 mAh g–1 and more stable electrochemical behavior over the early cycles, along with reduced polysulfide diffusion compared to that of the pristine system. Comprehensive characterizations (X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS)) confirm that the TU additive facilitates the formation of a more uniform and stable interfacial layer on the Mg anode surface. These findings demonstrate that interfacial kinetics can be effectively regulated through simple electrolyte engineering, offering a promising route to enhance the electrochemical performance of Mg–S batteries.