Synthesis and electrochemical properties of LiFePO4 cathode material by ionic thermal method using eutectic mixture of tetramethyl ammonium chloride–urea

In this study, the LiFePO 4 cathode was synthesized by the ionic thermal method using the deep eutectic mixture of tetramethyl ammonium chloride and urea. The synthetic conditions were systematically investigated by orthogonal experiments, which indicate that the optimal reaction time, reaction temperature, molar ratio of Li to DES and rotate speed are 96 h, 220 °C, 1:14 and 20 r·min −1 , respectively. X-ray diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscope (TEM) were characterized to investigate the crystalline structure and morphology of the obtained materials, indicating well-crystallized LiFePO 4 with olivine structure. And the physical properties of LiFePO 4 were explored through Fourier transform infrared spectroscopy (FTIR), 57 Fe Mössbauer absorption spectra and Raman spectra. An initial discharge capacity can reach 151 mAh·g −1 at 0.1C rate for LiFePO 4 following by calcining at 600 °C under the optimal conditions, and it retains 125.1 mAh·g −1 after 100 cycles. These results demonstrated that the addition of ionic liquids can improve the rate performance, cycle performance and ion diffusion rate of LiFePO 4 . Graphical abstract