Rare Earth Element Aliovalent Doping Substitution and Electrochemical Performance of LiFe_(1-x) Nd_xPO_4

摘要

LiFe_(1-x)Nd_xPO_4/C cathode material has been synthesized by solid-state reaction. The structure and electrochemical performances of LiFe_(1-x)Nd_xPO_4/C(x = 0 - 0.08) have been studied by XRD, FE-SEM, EIS and galvanostatic charge-discharge. The magnetization curve of LiFe_(1-x)Nd_xPO_4/C sample is measured by SQUID (Superconducting Quantum Interference Device) to examine if Fe~(3+) ion exists in LiFe_(1-x)Nd_xPO_4/C. The results show that a small amount of aliovalent Nd~(3+)-dopant substitution on Fe~(+2) can effectively reduce the particle size of LiFePCVC. The cell parameters of LiFe_(1-x)Nd_xPO_4 (x = 0.04 - 0.08) are calculated on Si internal standard, and LiFe_(1-x)Nd_xPO_4/C has the same olivine structure as LiFePO_4, 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 Nd~(3+) 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 LiFePO_4 is tolerant.