Effects of titanium incorporation on phase and electrochemical performance in LiFePO4 cathode material

Ti-incorporated LiFe1−xTixPO4 (0 ≤ x ≤ 0.2) samples have been prepared via a two-step solid-state reaction route. The samples have systematically been investigated with X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, scanning electron microscope (SEM), transmission electron microscope (TEM), cyclic voltammetry (CV) and charge/discharge measurements. The incorporation of Ti in LiFePO4 significantly enhances the electrochemical performance; the carbon-coated LiFe0.9Ti0.1PO4 sample shows the best performance. It is confirmed that LiFe1−xTixPO4 with x ≤ 0.05 are of single phase while those with 0.07 ≤ x ≤ 0.2 contain impurity phases: LiTi2(PO4)3 and TiP2O7. The impurities influence not only the electronic conductivity, but also the total specific capacity. Appropriate amount of titanium incorporation is favorable for the improvement in electrochemical performance.

► Nominal LiFe1−xTixPO4 cathode materials were synthesized via solid-state reaction. ► A clear feature of Ti-doped LiFePO4 has been clarified. ► The formation of impurity phases strongly depends on Ti doping level. ► Appropriate amount of Ti in LiFePO4 can enhance the electrochemical performance.