Electrochemical performance of Yb-doped LiFePO4/C composites as cathode materials for lithium-ion batteries

Abstract

LiFePO4/C and LiYb0.02Fe0.98PO 4/C composite cathode materials were synthesized by simple solution technique. The samples were characterized by X-ray diffraction, scanning electron microscope, and thermogravimetric-differential thermal analysis. Their electrochemical properties were investigated by cyclic voltammetry, four-point probe conductivity measurements, and galvanostatic charge and discharge tests. The carbon-coated and Yb3+-doped LiFePO4 sample exhibited an enhanced electronic conductivity of 1.9 × 10-3 Scm-1, and a specific discharge capacity of 146 mAhg-1 at 0.1 C. The results suggest that the improvement of the electrochemical performance can be attributed to the ytterbium doping, which facilitates the phase transformation between triphylite and heterosite during cycling, and the conductivity improvement by carbon coating. © 2012 The Author(s).