Improvement of the electrochemical performance of carbon-coated LiFePO4 modified with reduced graphene oxide

Abstract

In this work, carbon-coated LiFePO₄ was further modified with reduced graphene oxide (RGO) using an ultrasonic-assisted rheological phase method coupled with carbothermal treatment. X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), and electrochemical methods were used to characterize the material's properties. The results showed that the composite material consisting of carbon-coated LiFePO₄ and RGO sheets possesses a unique and effective three-dimensional “sheet-web” structure. In the structure, the LiFePO₄ particle size can be maintained at nanosize to form abundant voids between the nanoparticles while the RGO sheets are significantly beneficial for Li⁺ diffusion. As a result, the electrochemical properties of the composite material have been greatly improved. A sample with 5 wt% RGO exhibited high specific capacity and superior rate performance with the discharge capacities of 160.4 mA h g⁻¹ at 0.2 C and 115.0 mA h g⁻¹ at 20 C. The sample also showed an excellent cycling stability with only about 10% capacity decay at 10 C after 1000 cycles.