Fabrication of a heterovalent dual-cation pre-embedded hydrated vanadium oxide cathode for high-performance zinc ion storage

Abstract

Vanadium-based oxides are considered desirable cathode materials for aqueous zinc ion batteries owing to their high theoretical specific capacity and open crystal structure. However, the comparatively insufficient capacity and poor stability of vanadium-based oxides restrict their potential applications for the further development of aqueous zinc ion batteries. Herein, K⁺ and Al³⁺ were simultaneously pre-inserted into vanadium oxide through a facile hydrothermal process to construct a robust K_0.098Al_0.12V₂O₅·0.86H₂O (denoted as KAlVOH) nano-microsphere with a large interlayer spacing of 13.26 Å. The obtained results showed that pre-embedded K⁺ plays a vital role in maintaining the structural stability of the layered framework upon cycling. Meanwhile, the pre-insertion of Al³⁺ widened the interlayer spacing, which promoted zinc transport kinetics and increased the specific capacity. Consequently, the proposed KAlVOH cathode material showed high-performance zinc ion storage with a significant specific capacity of up to 424 mA h g⁻¹ at 0.05 A g⁻¹. This was further accompanied by an excellent rate capability (up to 210 mA h g⁻¹ at 10 A g⁻¹) and impressive long cycling stability (96% capacity retention after 3000 cycles at 5 A g⁻¹). Moreover, distinctive K⁺/Al³⁺ ratios and alkali metal analogues were also investigated for this heterovalent dual-cation pre-insertion strategy. The novel design of the K⁺ and Al³⁺ co-inserted vanadium oxide cathode is envisaged as a promising alternative for the construction of robust layered vanadium-based cathodes for rapid and stable zinc ion storage.