Investigation of the Na Storage Property of One-Dimensional Cu2- xSe Nanorods.

In this study, one-dimensional Cu2- xSe nanorods synthesized by a simple water evaporation-induced self-assembly approach are served as the anode material for Na-ion batteries for the first time. Cu2- xSe electrodes express outstanding electrochemical properties. The initial discharge capacity is 149.3 mA h g-1 at a current density of 100 mA g-1, and the discharge capacity can remain at 106.2 mA h g-1 after 400 cycles. Even at a high current density of 2000 mA g-1, the discharge capacity of the Cu2- xSe electrode still remains at 62.8 mA h g-1, showing excellent rate performance. Owing to the excellent electronic conductivity and one-dimensional structure of Cu2- xSe, the Cu2- xSe electrodes manifest fast Na+ ion diffusion rate. Moreover, detailed Na+ insertion/extraction mechanism is further investigated by ex situ measurements and theoretical calculations.