High-performance LiFePO4/C materials: Effect of carbon source on microstructure and performance

Abstract

In this work, high-performance LiFePO4/C materials are successfully prepared by a spray drying-carbothermal method. The effect of the carbon source (viz. inorganic, organic and their hybrid) is extensively investigated on the microstructure and electrochemical property of the composite materials. Vulcan XC-72, an inorganic carbon additive, can remarkably improve the electronic conductivity of the composite material; however, the resultant large crystallite size and low specific surface area limit the Li ion diffusion and thereby lower the electrochemical performance. As a typical organic carbon additive, glucose yields mesoporous LiFePO4/C particles with a much higher specific surface area and smaller crystallite size; however, the electronic conductivity of the pyrolyzed carbon is insufficiently high for the real applications. By using the dual hybrid carbon sources, the synthesized LiFePO4/C material features a high electronic conductivity, large specific surface area, small grain size, and the formation of mesopores. In line with these advantages, the composite yields the best electrochemical performance with the discharge capacity of 168.1 mAh g−1 at 0.1 C, which is approximate to the theoretical capacity. This material also performs well at high rates with discharge capacities of 122.0 and 93.0 mAh g−1 at 5.0 and 10.0 C, respectively.