Hierarchical carambola-like Li4Ti5O12-TiO2 composites as advanced anode materials for lithium-ion batteries

Abstract

Hierarchically structured Li4Ti5O12-TiO2 (LTO-TiO2) composites are synthesized using a facile hydrothermal approach upon reaction time control. With control over the time of hydrothermal reaction at 18h, a hierarchical dual-phase LTO-TiO2 composite with appropriate amount of anatase TiO2 can be obtained, and it possesses a uniform carambola-like framework assembled by numerous ultrathin nanosheets, which enable a relatively large specific surface area, along with abundant interlayer channels to favor electrolyte penetration. When used as anode materials for lithium-ion batteries, such carambola-like LTO-TiO2 composite exhibits remarkably improved capacity, high-rate capability, and cycling stability over other LTO-TiO2 samples, which are synthesized at different time of hydrothermal reaction. Specifically, it deliveries a discharge capacity as high as 115.1 and 91.2mAhg−1at a very high current rate of 20 and 40C, respectively, while a stable reversible capacity of 171.7mAhg−1 can be retained after 200 charge-discharge cycles at 1C, corresponding to 88.6% capacity retention. The excellent electrochemical performances benefit from the unique hierarchical carambola-like structure together with the mutually complementary intrinsic advantages between LTO and TiO2. The robust and porous nanosheets-assembled LTO-TiO2 framework not only offers a shorter transport pathway for electron and Li-ion migration within this composite material, but also is able to alleviate the structure distortion during the fast Li-ion insertion/extraction process. The work described here shows that the hierarchical carambola-like LTO-TiO2 composite is a promising anode material for high-power and long-life lithium-ion batteries.