Synthesis and optimization of three-dimensional lamellar LiFePO4 and nanocarbon composite cathode materials by polyol process

Three-dimensional lamellar LiFePO4 composite cathode materials (with nanocarbon of carbon nanotube and graphene) have been synthesized by an in-situ polyol process. A series of experiments have been conducted to optimize the content of nanocarbon, and the temperature and duration of the post heat treatment. The morphologies and microstructures of the composites were characterized by scanning electron microscopy, X-ray diffraction, transmission electron microscopy, energy dispersive spectroscopy and X-ray photoelectron spectroscopy. The electrochemical properties were investigated by constant current charge/discharge tests, cyclic voltammetry and electrochemical impedance techniques. It's found that the morphology and crystal structure could be optimized to improve the electrochemical performance of LiFePO4 by the appropriate experimental conditions. The optimized composite materials present greatly enhanced specific discharge capacities of 163 and 127 mAh g−1 at 0.1 and 1 C, along with excellent capacity retention close to 99% after 100 cycles at 1 C, which are promising for applications in lithium-ion power batteries.