Two‐Step Oxidation of Mxene in the Synthesis of Layer‐Stacked Anatase Titania with Enhanced Lithium‐Storage Performance

Layer‐stacked anatase titania (a‐TiO 2 ) was synthesized with two‐step oxidation of MXene (Ti 3 C 2 T x , T=O, OH, or F). Compared with direct oxidation of MXene in air, the two‐step oxidation process involving additional hydrothermal pre‐oxidation could alleviate the anomalous grain growth of TiO 2 , and largely keep the fine structure of MXene. The layered structure derived from MXene enabled the synthesized a‐TiO 2 to exhibit superior electrochemical properties. Its discharge capacities reached 241.9 and 131.1 mA h g −1 at the current rates of 0.3 and 12 C, respectively. Even after 10 000 cycles at 6 C, its capacity remained at 107.1 mA h g −1 , which is approximately 70 % of the initial capacity. Cyclic voltammetry analysis showed that both diffusive lithium storage in the bulk and interfacial (pseudocapacitive) lithium storage at the surface of layer‐stacked a‐TiO 2 contributed to its electrochemical properties.