关键词: 锂离子电池, Li₃V₂(BO₃)₃, 负极材料, 电化学性能

Abstract: The Li₃V₂(BO₃)₃/C (LVB/C) composite materials were successfully synthesized in two steps：Firstly, a stoichiomertric mixture of Li₂C₂O₄, V₂O₅, H₃BO₃, H₂C₂O₄•H₂O and ethanol was thoroughly ball-milled to get the precursors. Secondly, the precursors were post-calcinated to get the ultimate products. The calcination temperatures of 750 ℃, 800 ℃ and 850 ℃ were selected based on TG-DTA analyses. The crystal structures, surface morphologies and carbon contents of the samples calcinated at five conditions, namely, a(750 ℃, 10 h), b(800 ℃, 10 h), c(850 ℃, 10 h), d(800 ℃, 5 h) and e(800 ℃, 15 h), were characterized by XRD, SEM and EDS, respectively. The results showed that the dominant phase of all the samples was (Li_0.31V_0.69)₃BO₅ with the impure Li₃VO₄ phase in Samples a, b, c, and LiVO₂ phase in Samples a, b, d and e. All of the samples consisted of many cylindrical particles, polygonal particles and agglomerations, among which Sample b showed better crystallized and less-agglomerated particles. EDS data demonstrated that the carbon, oxygen and vanadium elements were uniformly distributed in Sample b, and the carbon contents in Samples a, b, c, d, e were 2.64 %, 1.17 %, 1.51 %, 1.97 %, 1.30 %, respectively. The electrochemical performances of Samples a, b, c, d and e were compared by obtaining the galvanostatic charge/discharge, cycling ability, cyclic voltammetry curves, and electrochemical impedance spectra. The results revealed that Sample b achieved the optimal electrochemical performance. The initial charge/discharge capacities at a current density of 50 mA•g^-1 were 427.6 mAh•g^-1 and 669.1 mAh•g^-1, respectively. However, after 10 cycles, only 55.4 % and 35.2 % of the initial charge/discharge capacities were retained, which might be related to the phase transformation from crystalline to amorphous during the insertion and extraction of lithium ions.

Key words: lithium-ion batteries, Li₃V₂ (BO₃)₃, anode materials, electrochemical properties