Electrochemical characterization for lithium vanadium phosphate with different calcination temperatures prepared by the sol–gel method
Li{sub 3}V{sub 2}(PO{sub 4}){sub 3}/C (LVP/C) composite materials were synthesized via a sol–gel method with oxalic acid as the chelating agent and polyethylene glycol (PEG) as the supplementary carbon source. The oxalic acid and PEG serve as double carbon sources. This study focused on the effect of different calcination temperatures on the electrochemical properties of Li{sub 3}V{sub 2}(PO{sub 4}){sub 3}. The diffraction peaks for all of the samples are well indexed to monoclinic Li{sub 3}V{sub 2}(PO{sub 4}){sub 3} with a P2{sub 1}/n space group. The TGA data indicate that the residual carbon content of LVP/C-700 is the highest (i.e., 2.31 wt.%), and as the calcination temperature increased, the residual carbon content of the material gradually decreased. SEM and TEM analyses indicated that the LVP particles that were calcined at 700 °C exhibit a uniform particle size distribution and the carbon coating exhibited a complete and orderly moderate thickness. The LVP/C-700 material exhibits the best electrochemical performance in the voltage range of 3.0 to 4.3 V and 0.1 C where the initial discharge capacity can reach 128.98 mAh g{sup −} {sup 1}. Even after 200 cycles, the discharge capacity was 119.31 mAh g{sup −} {sup 1}, and the capacity retention rate was 92.49%. - Highlights: • Li{sub 3}V{sub 2}(PO{sub 4}){sub 3}/C composite materials have been synthesized via a sol–gel method with double carbon sources. • The different calcination temperatures affect the grain growth and crystallinity of the Li{sub 3}V{sub 2}(PO{sub 4}){sub 3}/C materials. • The LVP/C-700 material exhibites the largest lithium ion diffusivity and electronic conductivity.