Layered Structure Regulation for Zinc-Ion Batteries: Rate Capability and Cyclability Enhancement by Rotatable Pillars

Regulating the interlayer spacing of vanadium oxides by various pillars has commonly been used for improving zinc-ion storage performance. However, most of the reported pillars are large and rigid, which sacrifices interlayer free volume, increases the steric hindrance, and results in large volume change. Herein, a layered vanadium oxide with –OH pillars by controllable heat treatment of layered vanadium oxide with rigid NH₄⁺ pillars is prepared. Although the –OH pillars are small-sized, they can firmly support the interlayers through the covalent bond. In addition, the rotatable –OH pillars can promote Zn-ion diffusion and accommodate lattice deformation. Compared to the layered vanadium oxide with rigid pillars, the one with rotatable pillars shows a higher rate capability (321 mAh g⁻¹ at 0.5 A g⁻¹ and 83 mAh g⁻¹ at 20 A g⁻¹) and a better cyclability (93% capacity retention over 2000 cycles at 5 A g⁻¹). Further mechanism studies demonstrate that the rotatable pillars show low-hindrance and high-stability to regulate the interlayer structure. It is emphasized that the interlayer microenvironment can not be neglected, but is crucial for advanced electrodes of aqueous zinc-ion batteries, rather than pursuing larger interlayer spacing.