Ultrahigh capacity due to multi-electron conversion reaction in reduced graphene oxide-wrapped MoO₂ porous nanobelts

Multivalent transition metal oxides (MO_x) containing redox centers which can theoretically accept more than one electron have been suggested as promising anode materials for high-performance lithium ion batteries (LIBs). The Li-storage mechanism of these oxides is suggested to involve an unusual conversion reaction leading to the formation of metallic nanograins and Li₂O; however, a full-scale conversion reaction is seldom observed in molybdenum dioxide (MoO₂) at room temperature due to slow kinetics. Herein, a full-scale multi-electron conversion reaction, leading to a high reversible capacity (974 mA h g^-1 charging capacity at 60 mA g^-1) in LIBs, is realized in a hybrid consisting of reduced graphene oxide (rGO) sheet-wrapped MoO₂ porous nanobelts (rGO/MoO₂ NBs). The rGO wrapping layers stabilize the nanophase transition in MoO₂ and alleviate volume swing effects during lithiation/delithiation processes. This enables the hybrid to exhibit great cycle stability (tested to around 1900 cycles) and ultrafast rate capability (tested up to 50 A g^-1).