Anamolously High Lithium Storage in Mesoporous Nanoparticulate Aggregation of Fe3+ Doped Anatase Titania

Abstract

Implications of iron (Fe3+) doping on lithium insertion/de-insertion capacity of anatase TiO2 is discussed here. Iron doped anatase TiO2 mesoporous nanoparticulate aggregated at various Fe3+ doping concentrations was synthesized by an optimized sol-gel method. The electrochemistry and lithium storage capacities of anatase TiO2 exhibited strong function of dopant iron (Fe3+) concentration. A very high first discharge cycle capacity of 704 mAhg−1 corresponding to approximately 2.1 mol of Li was observed for 5% iron (Fe3+) doped TiO2 at a current density of 75 mAg−1. At the 30th discharge cycle, the capacity was remarkably high at 272 mAhg−1 (0.81 mol of Li) with coulombic efficiency greater than 96%. Increase in the iron (Fe3+) concentration beyond 5% resulted in deterioration of lithium storage in TiO2. An improvement in lithium storage of more than 50% is noticed for 5% iron (Fe3+) doped TiO2 compared to pure anatase TiO2 which shows an initial discharge capacity of 279 mAhg−1. The anomalous lithium storage behavior in all the iron (Fe3+) doped TiO2 samples has been accounted, in addition to homogeneous Li insertion in the octahedral sites, via local conversion reaction and heterogeneous interfacial storage at Fe and Li2O.