Surface phase composition of nanosized LiFePO4 and their enhanced electrochemical properties

Abstract

Despite the great achievement in understanding the materials properties of LiFePO₄, the surface phase composition of nanosized LiFePO₄ has been almost ignored. The present study reports the synthesis of nanosized core–shell LiFePO₄ with size of about 50 nm by one step solvothermal route using Polyethylene glycol 600 as solvent. The structural characterization of the surface of nanosized core–shell LiFePO₄ particles has been investigated using soft X-ray absorption spectroscopy, X-ray photoelectron spectroscopy, Raman spectroscopy and transmission electron microscopy. The nanosized LiFePO₄ is well-covered by an amorphous LiFeP₂O₇ layer containing trace carbon. Density functional theory (DFT) calculation is used to illustrate the origin of amorphous LiFeP₂O₇ layer. The nanosized core–shell LiFePO₄ exhibits excellent charge transfer kinetics and charge/discharge performance. These new investigations shed new insight into the surface phase composition of nano-particles. The synthesis of the nanosized core–shell LiFePO₄ paves an effective way to develop cathode materials with high rate capabilities for use in Li-ion batteries.