Synthesis and electrochemical properties of LiFePO₄/C composite cathode material prepared by a new route using supercritical carbon dioxide as a solvent

From the viewpoint of energy efficiency and cost, an intensive search for less energy demanding synthesis methods for LiFePO₄ appears quite attractive and is still in full swing. Here, we report that carbon coated LiFePO₄ (LiFePO₄/C) powders can be successfully synthesized by a new route using supercritical carbon dioxide as a solvent. The obtained high-purity LiFePO₄/C powders are uniform in shape and 0.5 m to 1 m in size. As for the electrochemical performance, at the current density of 0.1 C, the electrode exhibits a discharge capacity of 158 mA h g^-1 as well as good cycling stability - there is no obvious capacity fading after 100 cycles. When the synthesis reaction temperature increases from 50 to 200 °C, the primary particle size grows from approximately 0.5 to 2 m, and the initial discharge capacity decreases from 158 to 41 mA h g^-1, which shows that 50 °C is the optimum temperature to synthesize LiFePO₄ in supercritical carbon dioxide. Needless to say, such a new approach, which is not specific to LiFePO₄, offers great opportunities for the synthesis of new electrode materials.