Hierarchical polypyrrole-pillared Na₂V₆O₁₆ architectures enabling high-rate and stable aqueous zinc storage

While aqueous Zn-ion batteries represent highly attractive technologies for large-scale grid storage, their practical implementation remains bottlenecked by severe structural degradation and sluggish ion diffusion kinetics in transition-metal oxide cathodes. Herein, a structural buffering hierarchical assembly strategy is proposed to construct a polypyrrole-pillared Na₂V₆O₁₆ (PPy-NaVO) 3D nanoflower cathode. Structural and morphological analyses reveal that in-situ intercalated PPy molecules act as soft pillars to significantly expand the interlayer spacing, which lowers the steric hindrance for ion diffusion and concurrently drives the anisotropic assembly of 1D nanorods into a 3D interconnected porous architecture. This cross-scale structural engineering endows the cathode with intrinsic a structural buffering properties to buffer volumetric strain during continuous cycling. Furthermore, the strong interfacial charge transfer between the PPy network and the V-O framework induces a mixed V⁴⁺/V⁵⁺ valence state. This optimized electronic structure is favorable for interfacial charge transfer and Zn²⁺ diffusion, minimizing the interfacial resistance and enabling ultrafast Zn²⁺/H⁺ co-intercalation kinetics. Consequently, the PPy-NaVO electrode exhibits an impressive reversible capacity (382.2 mAh g^-1). This structural engineering approach enables highly stable and kinetically accelerated cathodes for aqueous zinc batteries.