Initiating Jahn–Teller Effect in Vanadium Diselenide for High Performance Magnesium-Based Batteries Operated at ?40 ℃

摘要

Poor electronic and ionic conductivity of electrode materials at low temperaturesof ?20℃ and below has significantly impeded development of batteriesfor cold conditions. However, for the first time, layer-structured metallicvanadium diselenide (1T-Vse_2) is reported as a cathode material for lowtemperatureMg~（2+）/Li~+ hybrid batteries. A high electronic conductivity and fastion diffusion kinetics for 1T-Vse_2 are demonstrated at selected temperatures,and a very safe 1T-VSe2/Mg battery for operation at temperatures to ?40℃.The battery exhibits 97% capacity retention over 500 cycles, which is betterperformance than reported Mg-based batteries. The Jahn–Teller effect incompressed configuration is initiated in 1T-Vse_2 with the change of electronicstate occurring on electrochemical intercalation of alkali metal ions. Usingcombined experiment and theory via operando synchrotron X-ray diffraction,ex situ X-ray absorption spectroscopy and DFT computation, it is confirmedthat the weak Jahn–Teller distortion contributes significantly to fast-overallkinetics, structural stability, and high electronic conductivity of the electrode.Understanding at an atomic level of the mechanism is demonstrated, thatprovides valuable guidance in designing high-performance electrode materialsfor low-temperature batteries.