Mg(TFSI)2-Based Solid-State Eutectic Electrolyte Towards Safer Magnesium Batteries

Abstract

Magnesium (Mg) batteries are regarded as safer alternatives for Li+-dominated batteries by virtue of the unique dendrite-free property of Mg element. However, traditional liquid electrolytes applied in Mg batteries are mainly based on chloride salts and highly flammable organic solvents, which might cause numerous safety issues such as fire, electrochemical corrosion, and leakage of hazardous chemicals. These kinds of electrolytes seriously violate the original purpose of developing Mg-based batteries. Therefore, exploring non-flammable chloride-free solid-state electrolytes is of significant importance for realizing safer Mg batteries. Here in this work, a novel non-flammable eutectic electrolyte based on chloride-free Mg(TFSI)2 salt is first proposed as a solid electrolyte for safer Mg metal batteries. Our recent results demonstrate that compared with traditional Mg(TFSI)2-based electrolytes which dissolve in flammable organic solvents such as EC, PC, and THF solvent, this Mg(TFSI)2-based eutectic solid electrolyte is non-flammable with robust mechanical structures. When applied in Mg//Mg symmetric batteries, this novel eutectic solid electrolyte could greatly suppress the overpotential phenomenon that occurs in traditional Mg-based electrolytes and achieves stable Mg plating/stripping reversibility with more than 150 h. Furthermore, the practical feasibility of this eutectic solid electrolyte is also demonstrated in Mg//V2O5 full cell, which shows competitive electrochemical performance. We believe that the research on such new electrolytes could provide a new strategy for developing safe and sustainable Mg-based batteries.