High rate capability of LiFePO4 cathodes doped with a high amount of Ti

A Li-ion battery cathode with target stoichiometry LiTi0.08Fe0.92PO4 was prepared by doping a high amount of Ti4+ into the olivine structure using solid-state reaction at 700 °C. Synchrotron X-ray diffraction studies confirmed the presence of a major olivine phase and NASICON-type ion-conducting Li3Fe2(PO)4 and Li2TiFe(PO4)3 impurities. Further, the calculated lattice parameter values appear to confirm Ti-doping in LiFePO4. Electron microscopy and particle distribution studies not only revealed a slightly increased average particle-size and particle fragmentation but also confirmed a fair distribution of Ti4+ ions in the prepared sample. The LiTi0.08Fe0.92PO4 cathode delivered high specific capacities and good capacity retentions (≤2% capacity loss after 50 cycles) for lithium battery applications. Besides, the cathode delivered impressive rate capabilities as specific capacities of 160 and 110 mA h g−1 at 0.2 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.