Lithium-ion diffusion path of tetragonal tungsten bronze (TTB) phase Nb18W16O93
(1. State Key Laboratory of Solidification Processing, Center for Nano Energy Materials, School of Materials Science and Engineering, Northwestern Polytechnical University, Xi’an 710072, China;
2. Research & Development Institute of Northwestern Polytechnical University in Shenzhen, Northwestern Polytechnical University, Shenzhen 518057, China;
3. Tianjin Institute of Power Sources, Tianjin 300384, China)
2. Research & Development Institute of Northwestern Polytechnical University in Shenzhen, Northwestern Polytechnical University, Shenzhen 518057, China;
3. Tianjin Institute of Power Sources, Tianjin 300384, China)
Abstract: By taking tetragonal tungsten bronze (TTB) phase Nb18W16O93 as an example, an improved solid-state sintering method at lower temperature of 1000 °C for 36 h was proposed via applying nanoscale raw materials. XRD, SEM and XPS confirm that the expected sample was produced. GITT results show that the lithium-ion diffusion coefficient of Nb18W16O93 (10-12 cm2/s) is higher than that of the conventional titanium-based anode, ensuring a relatively superior electrochemical performance. The lithium-ion diffusion mechanism was thoroughly revealed by using density functional theory simulation. There are three diffusion paths in TTB phase, among which the interlayer diffusion with the smallest diffusion barrier (0.46 eV) has more advantages than other typical anodes (such as graphite, 0.56 eV). The relatively smaller lithium-ion diffusion barrier makes TTB phase Nb18W16O93 become a potential high- specific-power anode material.
Key words: lithium-ion battery; niobium tungsten oxide; tetragonal tungsten bronze (TTB) phase; lithium-ion diffusion mechanism; diffusion path