Influence of PAN/PANI polymer on low-temperature rate performance of LiFePO4

In order to improve the charge transfer rate and Li+ diffusion coefficient of LiFePO4 (LFP), the material was surface treated with polyacrylonitrile/polyaniline (PAN/PANI). PAN/PANI polymers were synthesized by a self-assembly process, and LFP@PAN/PANI were prepared by a wet-coating process. LFP@PAN/PANI exhibits superior electrochemical performance compared to bare LFP, with a discharge capacity of 3088.97 mAh at low temperature and high rate condition (−20 °C, 26650-type cylindrical battery, 5 C rate), and a relatively high low-temperature discharge plateau (2.68 V). Electrochemical impedance spectroscopy (EIS) proves that the Li+ diffusion coefficient of LFP@PAN/PANI is an order of magnitude higher than that of bare LFP. The above performance is improved because the polar cyano group of the polymer can interact with the electrolyte and Li+, and the polyaniline makes the polymer have high conductivity. Therefore, the composite of the two polymers endows LFP with excellent Li+ activity and high conductivity.