Ultrahigh capacity and cyclability of dual-phase TiO2 nanowires with low working potential at room and subzero temperatures

Abstract

The commercialization of TiO₂ materials for lithium-ion battery (LIB) anodes has been seriously limited due to unsatisfactory capacities and high voltage plateaus vs. Li/Li⁺ (∼1.75 V). In this work, we synthesized unique dual-phase TiO₂ nanowires composed of anatase and TiO₂–B phases with tunable phase ratios and studied their electrochemical performance in the extended potential range of 0.01–3.0 V. It was found that the dual-phase nanowire with a phase ratio of ∼1.0, named TiO₂-350, possesses the best rate and cyclic performance. More importantly, lowering the discharge cut-off voltage from 1.0 V to 0.01 V significantly increases the capacities, and moreover results in a decreased average discharge voltage of ∼0.58 V vs. Li/Li⁺. At the rates of 0.5C and 1C, TiO₂-350 delivers the ultrahigh capacities of 518.0 and 444.5 mA h g⁻¹ and remarkable long-term cyclic stability, which are strikingly higher than those reported in the literature and the theoretical capacity of TiO₂. Cyclic voltammetry results indicated that the ultrahigh capacity of the TiO₂ nanowire is the main reason that the capacitive contribution is below 1.0 V. Structural analyses indicated the solid solution reaction of TiO₂-350 nanowires with Li⁺ and the excellent structure stability during cycling, which contributes to the excellent cyclic performance of nanowires. Furthermore, the TiO₂-350 anode exhibits superb low-temperature performance between 0.01 V and 3.0 V at 273 K and 248 K. This work demonstrates a TiO₂-based anode with ultrahigh capacity and low working potential, and will promote the practical application of TiO₂-based materials for all-climate LIB anodes.