The improvement of the high-rate charge/discharge performances of LiFePO4 cathode material by Sn doping

Nanocrystalline LiFePO4 and LiFe0.97Sn0.03PO4 cathode materials were synthesized by an inorganic-based sol-gel route. The physicochemical properties of samples were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy, and elemental mapping. The doping effect of Sn on the electrochemical performance of LiFePO4 cathode material was extensively investigated. The results showed that the doping of tin was beneficial to refine the particle size, increase the electrical conductivity, and facilitate the lithium-ion diffusion, which contributed to the improvement of the electrochemical properties of LiFePO4, especially the high-rate charge/discharge performance. At the low discharge rate of 0.5 C, the LiFe0.97Sn0.03PO4 sample delivered a specific capacity of 158 mAh g(-1), as compared with 147 mAh g(-1) of the pristine LiFePO4. At higher C-rate, the doping sample exhibited more excellent discharge performance. LiFe0.97Sn0.03PO4 delivered specific capacity of 146 and 128 mAh g(-1) at 5 C and 10 C, respectively, in comparison with 119 and 107 mAh g(-1) for LiFePO4. Moreover, the doping of Sn did not influence the cycle capability, even at 10 C.