Synthesis and electrochemical performance of La-doped Li3V2−xLax(PO4)3 cathode materials for lithium batteries

La-doped Li3V2−xLax(PO4)3 (x = 0.01, 0.02, and 0.03) cathode materials for lithium ion batteries were synthesized by the microwave-assisted carbothermal reduction method (MW-CTR). The structures and properties of the prepared samples were investigated by X-ray diffraction (XRD) and electrochemical measurements. The results showed that all the three Li3V2−xLax(PO4)3 samples had the same monoclinic structures and sharper diffraction peaks of the crystal plane compared with those of the undoped Li3V2(PO4)3. The initial charge/discharge specific capacity, coulomb efficiency, and discharge decay rate of all the three Li3V2−xLax(PO4)3 samples were superior to those of the undoped Li3V2(PO4)3 sample, and the Li3V1.98La0.02(PO4)3 sample exhibited the best features among the three La-doped Li3V2−xLax(PO4)3 samples. Electrochemical impedance spectroscopy (EIS) demonstrated that the Li3V1.98La0.02(PO4)3 sample had a lower charge transfer resistance and a higher Li ion diffusion coefficient compared with the undoped Li3V2 (PO4)3 sample.