A Multi-Colored, Structure-Tolerant Vanadate Cathode for High-Performance Aqueous Zinc-Ion Batteries

Abstract

Vanadium-based cathode materials for aqueous zinc-ion batteries (AZIBs) have attracted much attention in large-scale energy storage devices yet their unsatisfactory cyclic stability and slow diffusion rate of Zn²⁺ ions during insertion and extraction hinder further commercial applications. Therefore, the development of vanadium-based cathode materials with stable crystal structures and fast Zn²⁺ storage remains challenging. Herein, Na₂CaV₄O₁₂ (NCVO) nanowires are reported as a promising cathode of excellent electrochemical performance in AZIBs, simultaneously rendering high specific capacity (443.2 mAh g⁻¹ at 0.1 A g⁻¹) and high average voltage plateau (0.91 V) with impressive energy density (403.3 Wh kg⁻¹) and power density (1533 W kg⁻¹). As NCVO features a unique open crystal structure with alternately arranged inactive layers ([NaO₆] and [CaO₈] polyhedra) and active layers ([VO₄] tetrahedra), the expansion of the [VO₄] tetrahedra during Zn²⁺ insertion is well balanced by the contraction of the inactive layer, thus enabling remarkable long-term cycling stability (91.9% and 80% capacity retention after 5000 and 10 000 cycles at 10 A g⁻¹, respectively). With the electrochromic property of the NCVO cathode, the AZIB can further be used for adaptive camouflage under a range of scenarios, shedding light on the future development of high-performance cathodes for AZIBs.