Rare Earth Element Aliovalent Doping Substitution and ElectrochemicalPerformance of LiFe_(1-x) Nd_xPO_4Rare Earth Element Aliovalent Doping Substitution and ElectrochemicalPerformance 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. Thestructure and electrochemical performances of LiFe_(1-x)Nd_xPO_4/C(x = 0 - 0.08) have been studiedby XRD, FE-SEM, EIS and galvanostatic charge-discharge. The magnetization curve ofLiFe_(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 ofaliovalent Nd~(3+)-dopant substitution on Fe~(+2)can effectively reduce the particle size of LiFePO_4/C.The cell parameters of LiFe_(1-x)Nd_xPO_4(x = 0.04 - 0.08) are calculated on Si internal standard, andLiFe_(1-x)Nd_xPO_4/C has the same olivine structure as LiFePO_4,and delivers highest dischargecapacity of 165.2 mAh. g~(-1)at 0.2 C rate and the capacity retention is 92.8 % after100cycles.The charge transfer resistance decreases with adding glucose and Nd~(3+)ion. The measuredtheoretical capacity of 168.65 mAh·g~(-1)is obtained. All the results imply that aliovalent dopingsubstitution on Fe site in LiFePO_4is tolerant.