Nitrogen-doped graphene guided formation of monodisperse microspheres of LiFePO4 nanoplates as the positive electrode material of lithium-ion batteries

Abstract

Three-dimensional porous composite microspheres of LiFePO₄ and nitrogen-doped graphene have been synthesized by a solvothermal process coupled with subsequent calcination. The morphology and microstructure of the composites were investigated by scanning electron microscopy, X-ray diffraction, transmission electron microscopy and X-ray photoelectron spectroscopy. The electrochemical properties were evaluated by constant current charge/discharge tests, cyclic voltammetry and electrochemical impedance spectroscopy. The unique porous structure of the microspheres was constructed by the assembly of nitrogen-doped graphene and LiFePO₄ nanoplates and can remarkably enlarge the electrode/electrolyte interface area, facilitate the electron transfer process, shorten the ionic diffusion path and accelerate the ionic transport throughout the electrode. In electrochemical measurements of the specific charge capacity, rate capability and cycling stability, the obtained porous composite microsphere materials offer remarkably promising results for applications in high-performance lithium-ion power batteries.