Investigation of the Na Storage Property of One-Dimensional Cu_2–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.