Superior sodium storage performance of additive-free V2O5 thin film electrodes

A binder- and conductive-agent-free V2O5 thin film electrode was fabricated by a facile and cost- efficient cathodic deposition method directly on stainless steel substrates followed by annealing at 300 degrees C in air for 1 h. The V2O5 film is approximately 1 mm in thickness and consists of layer- by- layer stacked nanosheets. When used as a cathode for sodium ion batteries, the V2O5 thin film electrode exhibits a high reversible discharge capacity (174 mA h g(-1) at 200 mA g(-1)), excellent cycling stability (almost 100% capacity retention over 200 cycles at 1 A g(-1)), and outstanding rate capability (retaining a capacity of 124 mA h g(-1) at 5 A g(-1)). Cyclic voltammetric analyses reveal that pseudocapacity- dominated charge storage of sodium ions accounts for the superior performance.