Mechanistic Insights of Zn2+ Storage in Sodium Vanadates

Abstract Rechargeable aqueous zinc‐ion batteries (ZIBs) with high safety and low‐cost are highly desirable for grid‐scale energy storage, yet the energy storage mechanisms in the current cathode materials are still complicated and unclear. Hence, several sodium vanadates with NaV 3 O 8 ‐type layered structure (e.g., Na 5 V 12 O 32 and HNaV 6 O 16 ·4H 2 O) and β‐Na 0.33 V 2 O 5 ‐type tunneled structure (e.g., Na 0.76 V 6 O 15 ) are constructed and the storage/release behaviors of Zn 2+ ions are deeply investigated in these two typical structures. It should be mentioned that the 2D layered Na 5 V 12 O 32 and HNaV 6 O 16 ·4H 2 O with more effective path for Zn 2+ diffusion exhibit higher ion diffusion coefficients than that of tunneled Na 0.76 V 6 O 15 . As a result, Na 5 V 12 O 32 delivers higher capacity than that of Na 0.76 V 6 O 15 , and a long‐term cyclic performance up to 2000 cycles at 4.0 A g −1 in spite of its capacity fading. This work provides a new perspective of Zn 2+ storage mechanism in aqueous ZIB systems.