Influence of lanthanum doping on performance of LiFePO4 cathode materials for lithium-ion batteries

Using solid-state synthesis method,a series of samples of lanthanum doped Li1-xLaxFePO4(x=0.0025,0.005,0.0075,0.01) were prepared.Each cathode structural and electrochemical properties were investigated using X-ray diffractometry(XRD),scanning electron microscopy(SEM),electrochemical impedance spectroscopy(EIS) and charge/discharge cycling.Nanopowders material with single-phase could be obtained.The reversible capacity could be drastically improved by the introduction of La.The optimum cells with Li0.99La0.01FePO4 cathode showed relatively high capacity of 123 mAh/g close to 73% of the theoretical capacity for C/2 discharge rate.Upon further cycling,the maintenance of the capacity was observed in the Li1-xLaxFePO4/1 mol/L LiPF6+ EC/DMC(1:1 vol)/Li cells during cycling studies.The effect of La was to form lattice doping,reduce crystal size to nanoscale,increase conductivity and enhance diffusion rate of lithium ion.The results confirmed that rare earth doping is an effective method for improving electrochemical properties of the promising alternative cathode.