W3Nb14O44 nanowires: Ultrastable lithium storage anode materials for advanced rechargeable batteries

Abstract

Lithium-ion batteries (LIBs) have been extensively explored to meet the needs of current energy applications; nevertheless, the development of high-performance anode materials is a bottleneck for LIBs advancement. Current commercial LIBs based on graphite or Li4Ti5O12 anodes unavoidably possess some problems, such as high safety risk or low energy density. In this work, W3Nb14O44 nanowires are developed via facile electrospinning as an anode material for LIBs. The W3Nb14O44 demonstrates higher capacity, better cycling stability, and better rate performance than Ti-based compounds, such as Li4Ti5O12 and TiO2. The average working voltage plateau of W3Nb14O44 nanowires is similar to those of Li4Ti5O12 (about 1.55 V) and TiO2 (about 1.6 V), which makes it a promising alternative to the Ti-based anode materials. Furthermore, W3Nb14O44 exhibits a relatively large theoretical capacity of 293.56 mA h g−1 (W6+/W5+, Nb5+/Nb4+, and Nb4+/Nb3+). In particular, when cycled at 1000 mA g−1, W3Nb14O44 nanowires can still deliver an initial reversible capacity of 130.6 mAh g−1, while the electrospun Li4Ti5O12 nanofibers and TiO2 nanofibers can only deliver an initial reversible capacity of 95 and 75 mAh g−1, respectively. Furthermore, the in-situ X-ray diffraction, ex-situ X-ray photoelectron spectroscopy, and ex-situ transmission electron microscope results reveal that W3Nb14O44 nanowires undergo a reversible electrochemical reaction. The total volume change during charge/discharge is about 5.9%. In addition, W3Nb14O44 nanowires exhibit a large Li+ diffusion coefficient of up to 8.02 × 10–13 cm2 s−1. Such prominent merits of W3Nb14O44 nanowires make them more likely to replace Ti-based anode materials for LIBs.