Cation-Vacancy Ordered Superstructure Enhanced Cycling Stability in Tungsten Bronze Anode

Niobium-based tungsten bronze oxides have recently emerged as attractive fast-charging anodes for lithium-ion batteries (LIBs), owing to their structural openings and adjustability. However, electrodes with tungsten bronze structures usually suffer from structural variability induced by Li+ intercalation/de-intercalation, leading to unsatisfactory cycling performance. To circumvent this limitation, a novel tetragonal tungsten bronze (TTB) structure, Ba3.4Nb10O28.4 (BNO), is developed as an anode material for LIBs with prominent cycling performance. An unprecedented cation-vacancy ordered superstructure with a periodic distribution of active and inactive sites is revealed inside the BNO. Through multiple characterizations and theoretical studies, it is demonstrated that this superstructure can improve the lithium-ion diffusion and disperse the structural strain induced by Li+-intercalation to enable stable Li+-storage. Benefiting from the superstructure-induced local structural stability, both the BNO bulk and Ba3.4Nb10O28.4@C (BNO@C) microspheres can deliver >90% capacity retention after 250 cycles at 2 C and close to 90% capacity retention after 2000 cycles at 10 C. These results are of significant importance for establishing the structure-property relationship between the cation-vacancy ordered superstructure and Li+-storage performance, facilitating the rational design of stable tungsten bronze anodes.

Automated summary

A novel tetragonal tungsten bronze structure with an unprecedented cation-vacancy ordered superstructure is developed, which improves the cycling performance of lithium-ion batteries by enhancing lithium-ion diffusion and reducing structural strain induced by lithium-ion intercalation.