BiNb5.4O15: A new Li+-storage material with a tetragonal tungsten bronze crystal structure

Abstract

Niobates with tungsten bronze crystal structures are regarded as prospective Li[Formula: see text]-storage anode candidates due to the rich chemistry of niobium and structural openness. However, the exploration of this type of materials is still insufficient. Here, BiNb[Formula: see text]O[Formula: see text] with a tetragonal tungsten bronze crystal structure (Cmmm space group) is explored. Abundant large-sized tunnels and a large interlayer spacing of [Formula: see text]3.97 Å are found in this open structure, enabling fast Li[Formula: see text] diffusivity (3.25 × 10[Formula: see text]/1.68 × 10[Formula: see text] cm2 ⋅ s[Formula: see text] during lithiation/delithiation). Additionally, this structure is very stable after the first lithiation process, resulting in excellent cyclability (95.4%/[Formula: see text]100% capacity retention after 100/1000 cycles at 1C/10C). BiNb[Formula: see text]O[Formula: see text] further exhibits a safe Li[Formula: see text]-storage potential ([Formula: see text]1.55 V) and a large reversible capacity (309.7 mAh ⋅ g[Formula: see text]@ 0.1C). Therefore, BiNb[Formula: see text]O[Formula: see text] can be a practical Li[Formula: see text]-stora ge anode compound for large-scale energy-storage applications.