An Efficient Carbon Coating Process Applied in Different Synthetic Routes of LiFePO4 Cathode Materials

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Four LiFePO 4 /C composites have been successfully synthesized via Fe 2 O 3 route, FeC 2 O 4 route, FePO 4 route in solid-state method and FeSO 4 route in hydrothermal method with an efficient carbon coating process which innovatively employed compound carbon sources that consisted of fructose and calcium lignosulfonate. Kilogram grade pilot samples have been prepared and 2000 mAh pouch cells have been assembled and investigated. Due to the introduction of fructose and calcium lignosulfonate, the as- prepared LiFePO 4 /C composites possess a layer of conductive carbon that contains calcium compound on the surface of LiFePO 4 particles, which are supposed to improve the electronic conductivity and reduce the side reaction between LiFePO 4 and electrolytes. All of the as-prepared LiFePO 4 /C composites show different characteristics in full cells, the capacity retention of Fe 2 O 3 derived LFP-S1 was as high as 92.2% after 400 days storage, the capacity retention of FeC 2 O 4 derived LFP-S2 at 5C rate was 93.0%, the capacity retention of FePO 4 derived LFP-S3 at -20 °C was 66.7%, the capacity retention of FeSO 4 derived LFP-S4 was as high as 90.2% after 3000 cycles at 25 °C.