Devisable three-dimensional Cu2Se nanoarrays boosts high rate Na-Ion storage

Because of its low cost and abundant sodium resource, sodium ion batteries (SIBs) are regarded as an excellent substitute for lithium-ion batteries (LIBs). However, due to the slow sodium kinetics and serious volume expansion of the anode material, the high power density and stability of the anode material are unsatisfactory. Here we demonstrate Cu2Se nanoarrays with three-dimensional (3D) skeleton structure that grow on the surface of copper foam (pretreated at different pressures) by in situ selenization, used as high-performance binder-free anodes for sodium ion batteries. The results show that Cu2Se-1 nanoarrays can deliver a reversible capacity of 679 mAh/g and remarkable rate capability: 85 % capacity retention when the current density increases from 0.1 to 2 A/g. Specifically, after 600 cycles at a high current of 5 A/g, the capacity remains as high as 368 mAh/g. Finally, the assembled Cu2Se-1//Na3V2(PO4)3 full battery shows a stable storage capacity of 270 mAh/g at 0.1 A/g. The design of 3D nanoarrays in Cu2Se-1 greatly increases electrochemical active sites, accelerates the diffusion and insertion of sodium ions, increases the contribution of pseudocapacitance, enhances the storage kinetics of sodium ions.