Electrolyte additive engineering for enhanced stability of sodium vanadate cathodes in aqueous zinc-ion batteries

Abstract

Tunnel-structured Na_0.33V₂O₅ (NVO) nanobelts have been synthesized via a solid–liquid mixing and calcination method and employed as cathode materials in aqueous zinc-ion batteries (AZIBs). A Na⁺/Zn²⁺ dual-ion co-intercalation mechanism has been successfully established by introducing 1 M NaClO₄ into a 2.5 M Zn(ClO₄)₂ electrolyte. The dissolution and shuttling behavior of NVO, primarily caused by the loss of interlayer Na⁺ during Zn²⁺ insertion/extraction and subsequent disruption of the V–O layered framework, has been effectively suppressed through Na⁺ replenishment from the electrolyte. This strategy stabilized the NVO structure during cycling and expanded the interlayer spacing, allowing more charge carriers to reversibly intercalate and improving capacity retention. In addition, the NaClO₄ additive modulated the Zn anode surface charge, improved interfacial reaction kinetics, and inhibited dendrite formation and parasitic reactions. As a result, the NVO Zn cell employing the Zn(ClO₄)₂/NaClO₄ electrolyte gave a high specific capacity of 301 mA h g⁻¹ after 1200 cycles at 1 A g⁻¹ at 25 °C and retained 87% of its initial capacity after 8200 cycles at −20 °C. The dissolution mechanism of NVO and the functional role of the NaClO₄ additive were identified from these results, which have shown to provide a useful reference for electrolyte additive engineering and the creation of vanadium-based AZIBs with a long cycle life and high capacity.