Preparation of LiFePO4/Carbon/PANI-CSA Composite and Its Properties as High-Capacity Cathodes for Lithium Ion Batteries

In this work, the spindle-shaped LiFePO4 coating with carbon layer (C-LFP) was successfully synthesized in glycerol solvent assisted by a mild heat-treatment at 600°C for 2 h. Then camphorsulfonic acid doped polyaniline (PANI-CSA) as the conductive polymer was compound with C-LFP to prepare C-LFP/PANI-CSA composite. The morphology, crystal structure and charge-discharge performance of the prepared samples were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and galvanostatic charge-discharge testing. The results showed that the reactant concentration seriously affected the microstructure and electrochemical properties of the resulting LiFePO4 cathodes in lithium ion batteries. And a spindle-shaped LiFePO4 with suitable size has been successfully synthesized at the moderate reactant concentration of 0.5 M. After modified with PANI-CSA, the resulted C-LFP2/PANI-CSA composite cathodes displayed a significantly improved specific capacity and rate capability. And specially, that the C-LFP/10%PANI-CSA composite exhibited the best performance with an initial discharge capacity of 165.3 mAh·g−1 at a constant current of 0.1 C. Electrochemical impedance measurements also demonstrated that the coating of polyaniline significantly decreased the charge-transfer resistance of C-LiFePO4 electrodes.