Realizing horizontal magnesium platelet deposition and suppressed surface passivation for high-performance magnesium metal batteries

Abstract

Rechargeable magnesium batteries (RMBs) are emerging as promising alternatives to lithium-ion batteries due to their high volumetric capacity and natural abundance. However, challenges arising from severe passivation and uneven deposition in conventional electrolytes persist, resulting in poor reversibility and cycling stability. Herein, a covalent molecule of 1-chloropropane (CP) is introduced into conventional electrolytes to manipulate the kinetics and surface chemistry of Mg anodes. Stemming from the reduced surface energy of the Mg (002) crystal plane from CP–Mg interactions, a horizontally arranged platelet morphology with enhanced (002) orientations is preferentially formed during the electrodeposition process. Moreover, the appropriate lowest unoccupied molecular orbital energy level of CP enables a robust Cl-rich interphase in situ formed on the Mg electrode surface. The planar deposition morphology coupled with the protective interphase can effectively suppress parasitic reactions between Mg electrodes and electrolytes and facilitate the electrochemical reaction kinetics. The as-designed electrolyte achieves reversible Mg plating/stripping with a high coulombic efficiency of 99.79% in asymmetric cells and maintains stable cycling for over 215 h in symmetric cells at an ultrahigh current density of 25 mA cm⁻², outperforming previously reported results. This engineered electrolyte also exhibits excellent compatibility with different inorganic/organic cathode materials, offering promising opportunities for RMB applications.