A core-shell LiFePO₄/C nanocomposite prepared via a sol-gel method assisted by citric acid

Nanosized LiFePO₄ particles, each covered with a complete but thin carbon shell, are synthesized via a sol-gel process using citric acid (CA) as both chelating agent and organic carbon source in this study. Several precursors are prepared with various mole ratio of CA to total metal ions (n_CA/n_m) first. Then the prepared precursors are investigated by thermogravimetry and derivate thermal analysis. The LiFePO4/C samples obtained via calcining the precursors at different temperatures are characterized by X-ray diffraction, field emission scanning electron microscope, transmission electron microscope and galvanostatic charge/discharge test. The systematic study shows that the LiFePO₄/C nanocomposite, calcined from the precursor with a composition of nCA/nm equal to 1:3 at 650 °C, delivers discharge capacities of 166 and 153 mA h g_-1 at 0.1 and 1C, respectively, and exhibits almost no capacity fade up to 50 cycles.