Reductive electron redistribution enables ultrafast charging in magnesium batteries

Abstract

Solvation sheath rearrangement is recognized as a key strategy for modifying electrolytes to enhance the kinetics of magnesium batteries. However, its fundamental mechanism diverges significantly from that in Li-ion batteries and remains inadequately understood. Herein, we elucidate the principle that solvation tuning essentially determines the distribution of reductive electrons, whose accumulation on ether molecules directly leads to challenging reorganization and severe solvent decomposition. To address this, a series of organic monoamine salts are designed as additives to capture and stabilize the reductive electrons in the solvation sheath, and screening guidelines are proposed to promote the kinetics and reversibility of Mg plating/stripping. Accordingly, we demonstrate an Mg pouch cell with ultrahigh power density (50C, 13 mA cm⁻², 16.02 kW kg⁻¹ based on the cathode), surpassing the power densities reported in all previous studies. This work offers new insights into solvation tuning strategies that are crucial in designing high-power-density Mg batteries.