Non-Grignard and Lewis Acid-Free Sulfone Electrolytes for Rechargeable Magnesium Batteries

A major challenge for developing rechargeable Mg-ion batteries (MIB) is the lack of suitable electrolytes. We report herein dialkyl sulfones as non-Grignard and Lewis acid-free MIB electrolytes. In particular, a dipropyl sulfone (DPSO)/tetrahydrofuran (THF) (1/1, v/v) solution with MgCl₂ salt exhibits high ionic conductivity (1.1 mS cm^–1 at 30 °C), Mg cycling efficiency (>90%), and anodic stability (ca. 3.0 V vs Mg). As evidenced by single crystal X-ray diffraction analysis, a novel [Mg­(DPSO)₆]²⁺ cation complex balanced by two [MgCl₃(THF)]⁻ anions is identified in the DPSO/THF solution. The DPSO/THF electrolyte also enables excellent cycle performance (>300 cycles) of a Chevrel phase Mo₆S₈ cathode and displays a decent compatibility with an organic cathode (3,4,9,10-perylenetetracarboxylic dianhydride, PTCDA). Along with the superior electrochemical properties of the DPSO/THF electrolyte, its innate chemical stability and eco-friendly nature make it a promising MIB electrolyte

Two-Dimensional Phosphorene-Derived Protective Layers on a Lithium Metal Anode for Lithium-Oxygen Batteries

Lithium-oxygen (Li-O₂) batteries are desirable for electric vehicles because of their high energy density. Li dendrite growth and severe electrolyte decomposition on Li metal are, however, challenging issues for the practical application of these batteries. In this connection, an electrochemically active two-dimensional phosphorene-derived lithium phosphide is introduced as a Li metal protective layer, where the nanosized protective layer on Li metal suppresses electrolyte decomposition and Li dendrite growth. This suppression is attributed to thermodynamic properties of the electrochemically active lithium phosphide protective layer. The electrolyte decomposition is suppressed on the protective layer because the redox potential of lithium phosphide layer is higher than that of electrolyte decomposition. Li plating is thermodynamically unfavorable on lithium phosphide layers, which hinders Li dendrite growth during cycling. As a result, the nanosized lithium phosphide protective layer improves the cycle performance of Li symmetric cells and Li-O₂ batteries with various electrolytes including lithium bis­(trifluoromethanesulfonyl)­imide in <i>N,N</i>-dimethylacetamide. A variety of <i>ex situ</i> analyses and theoretical calculations support these behaviors of the phosphorene-derived lithium phosphide protective layer