Hierarchical LiFePO ₄/C microspheres with high tap density assembled by nanosheets as cathode materials for high-performance Li-ion batteries

In this paper, LiFePO ₄/C microspheres consisting of closely packed nanosheets have been synthesized via a simple solvothermal method and a subsequent carbon coating procedure. In order to clarify the microstructure of the product, the as-prepared composite has been characterized by various techniques, such as powder x-ray diffraction, scanning electron microscopy, energy dispersive spectrum, Raman spectroscopy and high-resolution transmission microscopy. Results show that the LiFePO ₄/C microspheres are uniform with a particle size of 8-10μm. The microspheres are composed of densely compacted nanosheets with a thickness of 20-30nm. The gaps between the nanosheets are estimated to be 10-50nm; a carbon layer with a thickness of 4nm is coated on the surface of the LiFePO ₄ spheres. The tap density of the LiFePO ₄/C composite reaches up to 1.5gcm ³. As cathode material for Li-ion batteries, the composite exhibits a high capacity: 155mAhg ¹, 144mAhg ¹, 129mAhg ¹, and 104mAhg ¹ at 0.1C, 1C, 5C and 10C, respectively. Furthermore, the material also shows good cycling stability at both low and high current rates. The unique nanostructure of the material promises its excellent electrochemical properties as a cathode material for lithium batteries.