Topochemical synthesis of Mn 2 O 3 /TiO 2 and MnTiO 3 /TiO 2 nanocomposites as lithium-ion battery anodes with fast Li + migration and giant pseudocapacitance via the mesocrystalline effect.

Transition metal compounds are a promising substitute for graphite as lithium-ion battery (LIB) anodes. In this study, mesocrystalline Mn 2 O 3 /TiO 2 and MnTiO 3 /TiO 2 nanocomposites were synthesized using a layered titanic acid H 1.07 Ti 1.73 O 4 (HTO) precursor. The β-MnOOH layer is intercalated into the interlayer of HTO by Mn 2+ -exchange treatment of H 2 O 2 -intercalated HTO, which includes ion-exchange of Mn 2+ with H + in the interlayer and oxidation of Mn 2+ to the β-MnOOH layer by H 2 O 2 in the interlayer space. Mesocrystalline Mn 2 O 3 /TiO 2 and MnTiO 3 /TiO 2 nanocomposites with a platelike morphology were obtained by heat treatment of a sandwich layered HTO/β-MnOOH under air and H 2 /Ar atmospheres, respectively. The electrochemical results suggest that the mesocrystalline Mn 2 O 3 /TiO 2 and MnTiO 3 /TiO 2 nanocomposites show a synergistic effect for enhanced cycling stability and a mesocrystalline effect for enhanced discharge-charge specific capacity by improving the Li + mobility and enhancing the pseudocapacitance of the mesocrystalline nanocomposites as LIB anode materials. The discharge-charge specific capacity of the mesocrystalline Mn 2 O 3 /TiO 2 nanocomposite is twice as high as that of the polycrystalline one caused by the mesocrystalline effect. Furthermore, the synergistic and mesocrystalline effects led to a stable large discharge-charge specific capacity of 710 mA h g -1 for the mesocrystalline Mn 2 O 3 /TiO 2 nanocomposite. This work proposes a new concept to enhance the performance of anode materials for LIBs using mesocrystalline materials.