Free-Standing Hydrated Sodium Vanadate Papers for High-Stability Zinc-Ion Batteries

Making batteries more sustainable and affordable is seen as fundamental for enabling the electric grid to depend on power generated from renewable sources. In this context, zinc-ion batteries (ZIBs) are seen as promising candidates to suit the niche application stemming from the appealing properties of Zn, but their advancement is plagued by a limited choice of cathode and a better understanding of structure-property relationships that underpin the electrochemistry. Here, we demonstrate a hydrothermal method to prepare Na₂V₆O₁₆ ⋅ 3H₂O nanobelts with high degree of homogeneity and preferred orientation, enabling the construction of free-standing paper electrode for ZIBs. By virtue of the favorable structural features of the Na₂V₆O₁₆ ⋅ 3H₂O nanobelts that arise from the pillaring effect of interlayer metal ions/structural water and nanoscale morphology, the electrode displays good cycling performance (281 and 142 mAh g⁻¹ is achieved at 2.0 and 5.0 A g⁻¹ after 5000 cycles, respectively) with nearly 100 % Coulombic efficiency and impressive rate capability (216 and 167 mAh g⁻¹ are achieved at 3.0 and 5.0 A g⁻¹ respectively). Mechanistic study on the intercalation reaction of the Na₂V₆O₁₆ ⋅ 3H₂O nanobelts using ex situ XRD and HRTEM reveals their good structural and electrochemical reversibility, which enlightens the material advantages as promising cathode for ZIBs.