Synthesis and characterization of carbon-coated Li_0.5Ni_0.25TiOPO₄ anode material

Li_0.5Ni_0.25TiOPO₄/C composite was synthesized by the co-precipitation method using polyethylene glycol as carbon source. X-ray diffraction study showed that the as-prepared material crystallizes in the monoclinic system (S.G. P2₁/c). This 3D structure exhibits an open framework favourable to intercalation reactions. The morphology and the microstructure characterisation was performed by scanning electron microscopy (SEM). Small particles (∼1 μm) coated by carbon were observed. Raman study confirms the presence of carbon graphite in the Li_0.5Ni_0.25TiOPO₄/C composite. Cyclic voltammetry (CV) and charge-discharge galvanostatic cycling were used to characterize its electrochemical properties. The Li_0.5Ni_0.25TiOPO₄/C composite exhibits excellent electrochemical performances with good capacity retention for 50 cycles. Approximately 200 mAh/g could be reached at C, C/2, C/5 and C/20 rates in the 0.5-3 V potential range. These results clearly evidenced the positive effect of the carbon coating on the electrochemical properties of the studied phosphate.