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

In this study, one-dimensional Cu_{2- x}Se 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. Cu_{2- x}Se 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 Cu_{2- x}Se 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 Cu_{2- x}Se, the Cu_{2- x}Se electrodes manifest fast Na⁺ ion diffusion rate. Moreover, detailed Na⁺ insertion/extraction mechanism is further investigated by ex situ measurements and theoretical calculations.