Structural water and composing with graphene synergistically boosting electrochemical lithium-storage performance of hydrated tungsten oxides.

Transition metal oxide materials have received widespread attention as high-performance anode materials for lithium-ion batteries. However, serious issues including poor electrical conductivity, significant volume change, and low cycling stability limit their wide implementation. Herein, both bare hydrated tungsten oxides (WO·nHO, n = 0, 0.33 and 1) and their composites with reduced graphene oxide (rGO) were successfully synthesized by regulating solvent ratio through a facile one-step solvothermal method using tungsten chloride and graphene oxide (GO) as raw materials. The phase components, microstructures, interface interaction effects, electrochemical properties and reaction mechanism and kinetics were investigated in detail by both physical and electrochemical characterizations and theoretical calculations. It was demonstrated that, moderate amount of structural water molecule in WO·nHO can greatly boost lithium-ion migration and provide additional active sites for lithium storage. Attributed to the synergistic effect of moderate structural water, conductive rGO and its strong electrostatic interactions with WO·0.33HO, the as-synthesized WO·0.33HO/rGO composite delivered superior electrochemical performance for lithium storage, including an ultrahigh reversible capacity of 916.4 mAh/g at 200 mA g and extraordinary capacity retention of 82 % after 200 cycles (750.2 mAh/g), showing promising alternative anode material for LIBs. These findings provide a novel strategy to improve electrochemical performance of electrode materials for reversible batteries.