Rationally Designed Spherical V2O5 Encapsulated by 2d-VS2 as High Capacity Insertion Cathode for Mg-Ion Battery

Abstract

Owing to high energy density and economic viability, rechargeable Mg-ion batteries (MIB) are considered as alternative to lithium-ion batteries. However, beside chevrel phase, none of conventional inorganic cathode materials demonstrate reversible intercalation/deintercalation of Mg+2 ions in anhydrous electrolyte system. The lack of high voltage and high-capacity cathode frustrates the realization of MIB. Previous studies indicated that vanadium pentoxide (V2O5) has potential to reversibly insert\\extract Mg ions. However, many attempts to utilize V2O5 demonstrated limited electrochemical response, due to hindered Mg ion mobility in solid. Herein, we demonstrated a tailored approach to synthesize uniformly dispersed spherical V2O5 homogeneously coated with 2D VS2 through a facile in-situ chemical method and study the electrochemical activity in 0.2 M Mg(TFSI)2 + MgCl2 in DME electrolyte system and Mg metal anode. The V2O5@VS2 cathode exhibit the highest reported 1st discharge capacity of ~ 260 mA.h.g-1, excellent stability, retention and restricted capacity fading after 100 cycles which witness the prominence of VS2 coating in rationally designed V2O5 as a cathode material in non-aqueous electrolyte system for next generation high capacity MIB. Most interestingly, exact phase and morphology is completely retained even after repeated Mg+2 ion intercalation/deintercalation at different current rates, demonstrating pronounced electrochemical activity in anhydrous magnesium electrolyte and realization of a practical MIB.