Hierarchical LiFePO4/C microspheres with high tap density assembled by nanosheets as cathode materials for high-performance Li-ion batteries

Abstract

In this paper, LiFePO4/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 LiFePO4/C microspheres are uniform with a particle size of 8–10 μm. The microspheres are composed of densely compacted nanosheets with a thickness of 20–30 nm. The gaps between the nanosheets are estimated to be 10–50 nm; a carbon layer with a thickness of ∼4 nm is coated on the surface of the LiFePO4 spheres. The tap density of the LiFePO4/C composite reaches up to 1.5 g cm−3. As cathode material for Li-ion batteries, the composite exhibits a high capacity: 155 mAh g−1, 144 mAh g−1, 129 mAh g−1, and 104 mAh g−1 at 0.1 C, 1 C, 5 C and 10 C, 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.