Microspherical LiFePO 3.98 F 0.02 /3DG/C as an advanced cathode material for high-energy lithium-ion battery with a superior rate capability and long-term cyclability

Regular spherical FePO4/3DG precursor with good dispersion, uniform morphology, and diameters of 2~3 μm was hydrothermally synthesized, followed by synthesizing LiFePO3.98F0.02/3DG/C material via a two-step carbothermal reduction technology with ascorbic acid and glucose as carbon sources. The morphology, structure, and carbon content of the material were characterized by SEM, XRD, XPS, TEM, and thermogravimetric analyzer (TGA). The electrochemical properties of material were systematically studied by means of constant current charge and discharge, electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV). The results revealed that the initial discharge specific capacity of LiFePO0.98F0.02/3DG/C material was 158.7, 144.5, 130.4, 114.8, 96.8, and 80.3 mAh/g at 0.2 C, 0.5 C, 1 C, 2 C, 5 C, and 10 C, respectively, and the capacity retention rate still remained 98.9% after 100 cycles at 0.2 C, indicating excellent rate performance and cycle stability. Obviously, LiFePO3.98F0.02/3DG/C material exhibited remarkable improvement in comparison with the pristine LiFePO4 material. Therefore, the synergy of F− doping and 3DG coating was an effective method in synthesis of high electrochemical performance LiFePO4 composite material.