Tailoring Mg<sup>2+</sup> Solvation Structure in a Facile All‐Inorganic [Mg<sub>x</sub>Li<sub>y</sub>Cl<sub>2x+y</sub>·<i>n</i>THF] Complex Electrolyte for High Rate and Long Cycle‐Life Mg Battery
Haiyan Fan, Xinxin Zhang, Yuxing Zhao, Jianhua Xiao, Hua Yuan, Wang Guang, Yitao Lin, Jifang Zhang, Ludi Pan, Ting Pan, Yang Liu, Yuegang Zhang
Abstract
A high‐performance all‐inorganic magnesium–lithium chloride complex (MLCC) electrolyte is synthesized by a simple room‐temperature reaction of LiCl with MgCl 2 in tetrahydrofuran (THF) solvent. Molecular dynamics simulation, density functional theory calculation, Raman spectroscopy, and nuclear magnetic resonance spectroscopy reveal that the formation of [Mg x Li y Cl 2x+y · n THF] complex solvation structure significantly lowers the coordination number of THF in the first solvation sheath of Mg 2+ , which significantly enhances its de‐solvation kinetics. The MLCC electrolyte presents a stable electrochemical window up to 3.1 V (vs Mg/Mg 2+ ) and enables reversible cycling of Mg metal deposition/stripping with an outstanding Coulombic efficiency up to 99% at current densities as high as 10 mA cm −2 . Utilizing the MLCC electrolyte, a Mg/Mo 6 S 8 full cell can be cycled for over 10 000 cycles with a superior capacity retention of 85 mA h g −1 under an ultrahigh rate of 50 C (1 C = 128.8 mA g −1 ). The facile synthesis of high‐performance MLCC electrolyte provides a promising solution for future practical magnesium batteries.