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High Rate Performance of Ti Doped LiFePO4 Cathodes for Lithium Ion Battery

Monday, 20 June 2016
Riverside Center (Hyatt Regency)
S. Kim, V. Mathew, J. Gim, J. Song, J. Jo, T. Vu Thi, S. Kim, and J. Kim (Chonnam National University)
A Li-ion battery cathode with target stoichiometry LiTi0.08Fe0.92PO4 was prepared by doping excess amount of Ti4+ into the olivine structure using solid-state reaction at 700 °C. X-ray diffraction (XRD) results of the prepared sample confirmed the presence of a major olivine phase in addition to few impurity phases including the ion-conducting NASICON-type Li3Fe2(PO)4 and Li2TiFe(PO4)3 phases. Further, the calculated lattice parameter values appear to confirm Ti-doping in LiFePO4. Electron microscopy and particle distribution studies revealed a slight increase in the average particle-sizes in addition to fragmented particles and the presence of surface carbon coating on the sample particles. EDX mapping studies revealed a fair distribution of Ti4+ ions in the prepared sample. When examined as a cathode in a non-aqueous lithium cell at room temperature, LiTi0.08Fe0.92PO4 delivered high specific capacities and good capacity retentions (≤ 2% capacity loss after 50 cycles). Besides, the cathode delivered impressive rate capabilities as specific capacities of 160 and 110 mAhg-1 at 0.1 and 11.4 C, respectively, were retained. Although the average particle-size was slightly higher, the presence of ion-conducting NASICON-type species appear to contribute to the enhanced electrical conductivity and hence to the cathode performance of LiTi0.08Fe0.92PO4.