Long-lifespan benzoquinone-intercalated vanadium oxide with vacancies and disorders on the (00l) facets for efficient sodium-ion battery: A facile approach to Na⁺ capture and pre-sodiation

Via a facile one-step hydrothermal method, it was synthesized (m-BQ)(0.15)V2O5 center dot 0.5H(2)O (m-BQ = m-benzoquinone) (denoted as (m-BQ)-VO) three-dimensional (3D) porous hierarchical microflowers, which possesses a large (0 0 1) lattice spacing of 13.7 angstrom with crystalline vacancies and disorders on the (00l) facets. Rietveld refinement and high-angle annular dark field-scanning transmission election microscopy (HAADF-STEM) of (m-BQ)-VO unveil that the successful intercalation of m-BQ into layered V2O5 leads to the elongation of V-O bonds. As a result, the V centers of the sample are unsaturated with structural oxygen vacancies, and the V-O-V bilayer is split into two V-O-V monolayers with the (001) facet as the division plane. Consequently, upon lower-temperature annealing, the dehydrated sample can deliver a high initial capacity of 252 mAh/g at 0.05 A/g with excellent capacity retentions of 90 % over 210 cycles at 0.1 A/g, and 87 % over 2100 cycles at 2 A/g, respectively, in which no apparent phase change is observed. It is associated with the large interlayer channel with a lower Na+ migration barrier of 0.48 eV. And the anchoring effect of layered V-O-V framework can prevent the leaching of m-BQ into electrolyte. Furthermore, the redox-active m-BQ can provide extra capacity, whose affinity towards Na+ can induce the partial inclusion of Na+ ions in the sample even only immersion in Na+ solution undisturbed under room temperature, giving rise to improved electron conductivity and a facile approach to pre-sodiation, as evidenced by density functional theory (DFT) calculations.