Hierarchically organized CNT@TiO2@Mn3O4 nanostructures for enhanced lithium storage performance

Abstract

Here a new concept is conceived to design CNT@TiO₂@Mn₃O₄ nanostructures, in which CNTs, TiO₂ nanosheets and Mn₃O₄ nanoparticles are hierarchically organized in a three-stage order. In this concept, each component plays a unique, indispensable role. In the first stage, 1D CNTs serve not only as a backbone to accommodate mechanical stress, but also as a conductive dopant to facilitate electron transport. In the second stage, 2D TiO₂ nanosheets act as a major active material to ensure high safety and a long cycle life. In the third stage, 0D Mn₃O₄ nanoparticles function as an auxiliary active material to contribute an extraordinarily high theoretical capacity. Besides, the CNTs can minimize the restacking of the TiO₂ nanosheets, thus guaranteeing good structural integrity. TiO₂ nanosheets, being flexible and elastic in nature, are able to inhibit the aggregation of Mn₃O₄ nanoparticles, as well as buffer the volume variation suffered during repeated lithiation/delithiation. Mn₃O₄ nanoparticles, in turn, are capable of physically isolating the TiO₂ nanosheets to enlarge their interlayer distances for easy lithium and electron access. Thanks to the significant synergy, CNT@TiO₂@Mn₃O₄ nanostructures exhibit enhanced cycle and rate performances and represent a new step towards high-performance anode candidates of lithium-ion batteries.