Effect of Ce3+ doping on the properties of LiFePO4 cathode material

LiFe1-xCexPO4/C cathode materials were synthesized by solid-state reaction method. The effects of various Ce-doping amounts on the microstructure and electrochemical performance of LiFePO4/C cathode material were intensively investigated. The samples were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), galvanostatic charge-discharge measurements and electrochemical impedance spectroscopy (EIS). The results indicated that Ce-doping did not destroy the lattice structure of LiFePO4/C, while enlarged the lattice volume tailored the particle size, decreased charge transfer resistance, increased electrical conductivity and Li-ion diffusion rate of LiFePO4/C, and thus markedly enhanced the electrochemical performance of the LiFePO4/C. Electrochemical test results showed that the LiFe0.9Ce0.1PO4/C sample exhibited the best electrochemical performance with initial specific capacity of 155.4 mAh/g at 0.2 C, the capacity retention ratios of 99.6% at 100 cycles at 1 C and delivered a discharge capacity of 160.1 (0.1 C), 156.6 (0.2 C), 151.2 (0.5 C), 147.6 (1 C), 140.7 (2 C) and 136.7 mAh/g (5 C), respectively, presented the best rate capacity among all the samples. EIS results demonstrated that the transfer resistance of the sample decreased greatly by doping an appropriate amount of Ce.

Graphical Abstract(a) Nyquist plots from the EIS measurements and (b) electronic conductivity (σ) for LiFe1–xCexPO4/C compositesFigure optionsDownload as PowerPoint slide