Monodisperse LiFePO4 microspheres embedded with well-dispersed nitrogen-doped carbon nanotubes as high-performance positive electrode material for lithium-ion batteries

Monodisperse LiFePO4 microspheres embedded with well dispersed nitrogen doped carbon nanotubes (N-CNTs) are synthesized by chemical lithiation of the pre-synthesized FePO4/N-CNTs precursor. The morphology and structure of the composite microspheres are characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), and the electrochemical performances are evaluated using constant current charge/discharge tests, cyclic voltammetry and electrochemical impedance spectroscopy. The nitrogen-doped carbon nanotubes are uniformly dispersed inside the LiFePO4 microsphere to construct a superior three-dimensional conductive network, which allows for efficient charge transfer, ensures short lithium-ion diffusion distance, and facilitates the ion and electron transport throughout the active materials. The LiFePO4/N-CNTs microsphere composites display a reversible discharge capacity of 153 mAh g−1 at 0.1C, a rate capability of 106 mAh g−1 at a high rate of 10C, and an excellent cycling stability (>97% capacity retention after 500 cycles), which are promising positive electrode materials for application in high-performance lithium-ion batteries.