Boosting Zn²⁺ Diffusion via Tunnel-Type Hydrogen Vanadium Bronze for High-Performance Zinc Ion Batteries

Aqueous zinc ion batteries (ZIBs) are emerging as a promising candidate in the post-lithium ion battery era, while the limited choice of cathode materials plagues their further development, especially the tunnel-type cathode materials with high electrochemical performance. Here, a tunnel-type vanadium-based compound based on hydrogen vanadium bronze (H_xV₂O₅) microspheres has been fabricated and employed as the cathode for fast Zn²⁺ ions' intercalation/deintercalation, which delivers an excellent capacity (425 mAh g^-1 at 0.1 A g^-1), a remarkable cyclability (91.3% after 5000 cycles at 20 A g^-1), and a sufficient energy density (311.5 Wh kg^-1). As revealed by the experimental and theoretical results, such excellent electrochemical performance is confirmed to result from the fast ions/electrons diffusion kinetics promoted by the unique tunnel structure (3.7 × 4.22 Ų, along the c direction), which accomplishes a low Zn²⁺ ion diffusion barrier and the superior electron-transfer capability of H_xV₂O₅. These results shed light on designing tunnel-type vanadium-based compounds to boost the prosperous development of Zn²⁺ ion storage cathodes.