Effect of Dy3+-doping on Electrochemical Properties of LiFePO4/C Cathode for Lithium-Ion Batteries

Dy doping and carbon coating are adopted to synthesize a LiFePO4 cathode material in a simple solution environment. The samples were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Their electrochemical properties were investigated by cyclic voltammetry (CV) and galvanostatic charge-discharge tests. An initial discharge capacity of 153 mAh/g was achieved for the LiDy0.02Fe0.98PO4/C composite cathode with a rate of 0.1 C. In addition the electronic conductivity of Dy doped LiFePO4/C was enhanced to 1.9 x 10(-2) Scm(-1). The results suggest that the improvement of the electrochemical properties are attributed to the dysprosium doping and carbon coating which facilitates the phase transformation between triphylite and heterosite during cycling. XRD data indicate that doping did not destroy the lattice structure of LiFePO4. To evaluate the effect of Dy substitution, cyclic voltammetry was used at room temperature. prepared. From Cv measurement a more symmetric curve with smaller interval between the cathodic and anodic peak current was obtained by Dy substitution. This denoted a decreasing of polarization with Dy substitution, which illustrated an enhancement of electrochemical performances.