CoSe2 Nanoparticles as Anode for Lithium Ion Battery

Orthorhombic CoSe2 nanoparticles were synthesized via a facile one-step hydrothermal approach. The size, morphology, as well as phase structure were characterized by scanning electron microscopy (SEM) and powder X-ray diffraction (XRD). It was confirmed that CoSe2/Li battery cycled between 2.5 V and 0 V was more appropriate than between 3.0 V and 0 V. And the initial discharge capacity was 975.9 mAh g(-1) at a current density of 100 mA g(-1), while it increased after about 90 cycles, and even exceeded theoretical discharge capacity (494.4 mAh g(-1)) after about 485 cycles due to the activating reactions and the electric double layer effect. Electrochemical mechanism of CoSe2 as anode for lithium ion battery was verified by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). It showed that solid electrolyte interface (SEI) started to be formed at 1.4 V in the first discharge process. SEI-film resistance (RSEI), electron-transfer resistance (Re), and charge-transfer resistance (Rct) played the key part in the first discharge process of lithium intercalation respectively.