A facile in situ Mg surface chemistry strategy for conditioning-free Mg[AlCl4]2 electrolytes

Developing a simple and reliable strategy for modulating overpotential of Mg plating/stripping is crucial for realizing overall high performance of rechargeable Mg batteries, which have been demonstrated to be rather challenging. Herein, we report a facile LiI-assisted Mg surface chemistry to reduce Mg plating/stripping overpotential via in situ solubilization mechanism and ion conductive surface layer formation mechanism. As a result, we successfully formulate a new conditioning-free Mg[AlCl4]2-based Mg electrolyte system that improves Mg plating/stripping from the very first cycle. The overpotential of Mg plating/stripping of the as-prepared electrolyte with a LiI electrolyte additive is remarkably reduced to 240/240 mV at a current density of 1000 µA cm−2. Using this electrolyte, a rechargeable Mg battery coupled with PANi intercalated V2O5 (V2O5-PANi) cathode and Mg anode delivers a stable discharge specific capacity of nearly 50 mA h g−1 after an impressively prolonged cycle life of 500 cycles. Our finding provides a new inspiration of in situ Mg surface chemistry to activate Mg anode surface with high Mg ion conductivity.