Synthesis of LiFePO4/C as the positive material for LiFePO4/GRAPHITE Lithium‒Ion batteries

This paper presented the synthesis of carbon coated LiFePO4 (LFP/C) materials by hydrothermal method with glucose as a carbon source at two temperatures of 700oC (LFP700/C) and 800oC (LFP800/C). According to X-ray diffraction analysis, the material's structure was monophasic and devoid of impurities. The scanning electron microscopy revealed that the morphology of the composites at 700oC and 800oC was elongated and irregularly shaped-crystal with the particle size of 100‒500 nm. The Cycling Voltammetry and Galvanostatic Cycling with Potential Limitation were used to examine the electrochemical characteristics of LFP/C materials. After 50 cycles, the specific capacities of the LFP700/C and LFP800/C in 1.0 M LiPF6 EC: DMC: DEC (1: 1: 1, v: v: v) were 115 mAh. g-1 and 136 mAh. g-1, respectively, and the Coulombic efficiency was around 97%. The diffusion coefficient of Li+ reached 7.161. 10-12 cm2. s-1 (LFP700/C) and 2.489. 10-10 cm2. s-1 (LFP800/C) which was higher than that of the raw LFP sample (10-14‒10-13 cm2. s-1). The Full-cell LFP800/Graphite was investigated with four N/P ratios of 1.0, 1.1, 1.2, and 1.3. The charge‒discharge results showed that the full-cell of LFP800/Graphite with N/P ratio of 1.2 in 1.0 M LiPF6 EC: DMC: DEC (1: 1: 1, v: v: v) exhibited an excellent cyclability at C/10. The capacity of this full cell reached 112 mAh. g-1 in the first cycle and remained at 80% capacity after 50 cycles.