Preparation of Ga-doped lithium trivanadates as cathode materials for lithium-ion batteries

摘要

A series of gallium-doped lithium trivanadates, LiV_(3-x)Ga_xO_8 (x=0.00, 0.02, 0.04, 0.06, and 0.08), were prepared as cathode materials by a sol-gel method. The characterizations of the crystal structures and microstructures were investigated using X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM) mapping. Charge-discharge cycling performance, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were also used to characterize their electrochemical properties. The charge-discharge tests show that the electrochemical performance of LiV_3O_8 improved with Ga~(3+) doping and that LiV_(2.94)Ga_(0.06)O_8 has the best electrochemical properties, exhibits a high discharge capacity of 277 (±3) mAh g~(-1) and maintains a stable capacity of 226(±3)mAh g~(-1) within 50 cycles at the charge-discharge rate of 0.1 C and in the voltage range of 1.8-4.0 V. The LiV_(2.94)Ga_(0.06)O_8 electrode also shows better electrochemical performances at higher rates. The EIS results show that both the charge-transfer resistance and the resistance of the lithium ion diffusion decreased greatly after doping, which is favorable for fast lithium-ion intercalations/deintercalations in bulk materials.