Rare Earth Element Aliovalent Doping Substitution and Electrochemical Performance of LiFe1-x NdxPO4
LiFe1-xNdxPO4 /C cathode material has been synthesized by solid-state reaction. The structure and electrochemical performances of LiFe1-xNdxPO4 /C(x = 0 - 0.08) have been studied by XRD, FE-SEM, EIS and galvanostatic charge-discharge. The magnetization curve of LiFe1-xNdxPO4/C sample is measured by SQUID (Superconducting Quantum Interference Device) to examine if Fe3+ ion exists in LiFe1-xNdxPO4/C. The results show that a small amount of aliovalent Nd3+-dopant substitution on Fe+2 can effectively reduce the particle size of LiFePO4/C. The cell parameters of LiFe1-xNdxPO4 (x = 0.04 - 0.08) are calculated on Si internal standard, and LiFe1-xNdxPO4/C has the same olivine structure as LiFePO4, and delivers the highest discharge capacity of 165.2 mAh•g−1 at 0.2 C rate and the capacity retention rate is 92.8 % after 100 cycles. The charge transfer resistance decreases with adding glucose and Nd3+ ion. The measured theoretical capacity of 168.65 mAh∙g-1 is obtained. All the results imply that aliovalent doping substitution on Fe site in LiFePO4 is tolerant.
Jian-Feng Nie and Allan Morton
M. S. Zhao and L. Zhang, "Rare Earth Element Aliovalent Doping Substitution and Electrochemical Performance of LiFe1-x NdxPO4 ", Materials Science Forum, Vols. 654-656, pp. 2883-2886, 2010