Dual phase Li4Ti5O12–TiO2 nanowire arrays as integrated anodes for high-rate lithium-ion batteries

Abstract

Lithium titanate (Li4Ti5O12) is well known as a zero strain material inherently, which provides excellent long cycle stability as a negative electrode for lithium ion batteries. However, the low specific capacity (175mAhg−1) limits it to power batteries although the low electrical conductivity is another intrinsic issue need to be solved. In this work, we developed a facile hydrothermal and ion-exchange route to synthesize the self-supported dual-phase Li4Ti5O12–TiO2 nanowire arrays to further improve its capacity as well as rate capability. The ratio of Li4Ti5O12 to TiO2 in the dual phase Li4Ti5O12–TiO2 nanowire is around 2:1. The introduction of TiO2 into Li4Ti5O12 increases the specific capacity. More importantly, by interface design, it creates a dual-phase nanostructure with high grain boundary density that facilitates both electron and Li ion transport. Compared with phase-pure nanowire Li4Ti5O12 and TiO2 nanaowire arrays, the dual-phase nanowire electrode yielded superior rate capability (135.5 at 5C, 129.4 at 10C, 120.2 at 20C and 115.5mAhg−1 at 30C). In-situ transmission electron microscope clearly shows the near zero deformation of the dual phase structure, which explains its excellent cycle stability.