Carbon-coated nonstoichiometric TiOx for application of Li-ion battery anodes in fast charging-in situ XRD study

Lithium-ion batteries have emerged as a promising solution for electric vehicles, owing to their high specific capacity. However, the commonly used carbon anodes suffer from poor high-rate capability, which restricts their wider application. In this work carbon-coated nonstoichiometric TiO_x (C@TiO₁.₉₄₄) nanopowder was synthesized using a two-step annealing method. The performances of batteries show that the C@TiO_1.944 electrode has a remarkable initial capacity of 246.3 mAh/g with 71.5 % ICE and retains 166.2 mAh/g at a rate of 0.2C with 100 % CE and 109.0 mAh/g at 5C after formation. In contrast, the TiOx battery's initial capacity is 264.3 mAh/g with a 67.4 % ICE with a retention of 156.6 mAh/g at the same rate and 79.2 mAh/g at a discharge rate of 5C. Additionally, in situ X-ray diffraction (XRD) experiments was conducted with a potentiostat for elucidating the reaction mechanism which enables to track the phase transition in real-time during charge and discharge. The carbon coating protects the inner TiOx core from phase transition and lattice distortion occurs when Li ions are intercalated in the rutile TiO₂ matrix. The Li storage mechanism of rutile TiO₂ indicates it is not phase-transformed that can be taken as extra evidence for the high Coulombic efficiency. Further, the carbon coating enhanced the Coulombic efficiency by preventing dead Li ions while retaining in the anatase phase. The results shows that carbon-coated nonstoichiometric TiO₂ (C@TiOx) used in LIBs will be a solution for rapid charge application.