Facile Synthesis of Rod-like Cu2−xSe and Insight into its Improved Lithium-Storage Property

A rod-like Cu2−xSe is synthesized by a facile water evaporation process. The electrochemical reaction mechanism is investigated by ex situ X-ray diffraction (XRD). By adopting an ether-based electrolyte instead of a carbonate-based electrolyte, the electrochemical performance of Cu2−xSe electrodes improved significantly. The Cu2−xSe electrodes exhibit outstanding cycle performance: after 1000 cycles, 160 mA h g−1 can be maintained with a retention of 80.3 %. At current densities of 100, 200, 500, and 1000 mA g−1, the capacity of a Cu2−xSe/Li battery was 208, 202, 200, and 198 mA h g−1, respectively, showing excellent rate capability. The 4-probe conductivity measurements along with electrochemical impendence spectroscopy (EIS) and cyclic voltammetry (CV) tests illustrate that the Cu2−xSe electrodes display high specific conductivity and impressive lithium–ion diffusion rate, which makes the Cu2−xSe a promising anode material for lithium–ion batteries.