Preparation of carbon and oxide co-modified LiFePO4 cathode material for high performance lithium-ion battery

Abstract

In this study, a LiFePO4/C (LFP/C) material was prepared using a spray dry method. The Li4Ti5O12 (LTO) surface modification on LFP/C composite was performed by a sol–gel method. The characteristic properties were examined using X-ray diffraction, micro-Raman spectroscopy, scanning electron microscopy/energy-dispersive X-ray spectroscopy, transmission electron microscopy, an AC impedance method, and the galvanostatic charge/discharge method. Pristine LFP/C powder and the 1–5 wt.% LTO-coated LFP/C composites were compared. The results revealed that the 3 wt.% LTO-coated LFP/C composite showed the best performance among LFP composite samples. It was found that the 3 wt.% LTO-coated LFP/C composite showed discharge capacities of 159 mAh g−1, 157 mAh g−1, 154 mAh g−1, 148 mAh g−1, 145 mAh g−1, and 138 mAh g−1 at rates of 0.2C, 0.5C, 1C, 3C, 5C, and 10C, respectively at 55 °C. The long-term cycling performance of the LFP/C composite was greatly improved when the dual hybrid coating (carbon and oxide) was carried out. Moreover, the 3 wt.% LTO-coated LFP/C composite with the lowest fading rate maintained cycling stability at 3C rate at 55 °C after 300 cycles; by contrast, the bare LFP/C sample with the highest fading rate had an unfavorable lifecycle, and its discharge capacity decreased rapidly. A hybrid coating is a feasible method for improving the high temperature performance of LFP/C composites.