Preconditioned Current to Activate Reaction Sites for Uniform Stripping/Plating toward Long-Life Magnesium Metal...

Magnesium (Mg) batteries are promising next-generation energy storage systems, while the Mg metal anode suffers from uneven stripping and plating, resulting in a poor cycle life. The origin of nonuniformity needs to be intensively explored. Herein, we systematically investigate the stripping/plating behaviors of the Mg anode under various current densities in both chloride-containing and chloride-free electrolyte systems. We find that, within the range of 0.5-5 mA cm^-2, an increase in current density leads to enhanced morphological uniformity, which challenges the conventional viewpoint that the uneven stripping/plating is caused by the corrosion from chloride. The Mg anode exhibits a uniform potential distribution at a higher current density but shows pronounced potential differences at a low current density. The uniform potential distribution facilitates a homogeneous electrochemical reaction. We propose a preconditioned current (PCC) strategy to preactivate electrochemical reaction sites. This PCC treatment markedly enhances surface uniformity and enables the Mg anode to deliver stable cycling performance for more than 2500 h at 1 mA cm^-2. Furthermore, the Mg//Mo₆S₈ full cell with a PCC-treated anode demonstrates a capacity retention of 97% over 1000 cycles. This study provides a comprehensive understanding of current density-dependent surface behavior on the Mg metal anode and introduces a practical strategy for enhancing its electrochemical performance.