Comparison of electrochemical performances of LiFePO4/C composite materials by two preparation routes

This study reports on the preparation of LiFePO4/C composite materials prepared by the hydrothermal and sol–gel processes for comparison. The synthesis condition on the hydrothermal process was performed at 170 °C for 19 h. The polystyrene (PS) polymer was used as a carbon source; the PS was added at a range of 0–5 wt.%. The temperature of the post-thermal process was set at 750–850 °C. The citric acid (denoted as CA) was used as the reducing agent and the carbon source in the sol–gel process. The temperatures of the sintering process were set at a range of 650–850 °C. The optimal sintering temperature was at 850 °C for 12 h in the hydrothermal process; the optimal carbon residue content was approximately 3.20 wt.%. It was revealed that the highest discharge capacity of LiFePO4/C composites by the hydrothermal process at 0.1 C is 163 mAh g−1. The optimal sintering temperature was found to be at 750 °C for the sol–gel process. The highest carbon content was approximately 11.94 wt.% as the molar ratio of CA is 1.0. The highest discharge capacity of LiFePO4/C composites by the sol–gel process at 0.1 C was approximately 130.35 mAh g−1.

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► Two different synthesis routes for LiFePO4/C materials with different carbon sources were compared.
► The rate capability of the LiFePO4/C materials by a polystyrene carbon source was greatly improved.
► The good electrochemical performance of LiFePO4/C composites by a hydrothermal route was found.
► It is due to the good quality carbon layer (ID/IG = 0.94), uniform and optimal thickness of carbon layer (3–4 nm).