Up-scalable synthesis, structure and charge storage properties of porous microspheres of LiFePO4@C nanocomposites

Abstract

Novel porous micro-spherical aggregates of LiFePO₄@C nanocomposites have been synthesized in large quantities via an improved sol–gel method combined with spray drying technology (sol–gel-SD method), which required no surfactants or templates. With this new procedure, a precursor was prepared through the process of sol–gel and subsequent spray drying. A series of analyses, including X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), energy dispersive X-ray (EDX), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM) and a combined system focused ion beam (FIB)/SEM were performed after the as-obtained LiFePO₄@C was heat-treated at 700 °C for 12 h. The as-obtained LiFePO₄@C had a large specific surface area (20.2 m²g⁻¹), with an average nano-size of 32 nm and a main pore diameter of 45 nm. Contact with electrolyte occurred easily, which facilitated the electrical and lithium ion diffusion. In comparison with nano-sized LiFePO₄@C particles prepared by a sol–gel method, the current product presented a high coulombic efficiency of 97.2%, a large reversible capacity of 133.8 mAh/g and an excellent capacity retention rate close to 100% after 50 cycles. The sol–gel-SD method provides an additional strategy to easily deal with gelatin and shows potential for use in the preparation of similar superstructures of other composites.