Advances in sodium vanadate-based cathodes for practical aqueous zinc-ion batteries: crystal chemistry, electrochemical mechanisms, challenges, and materials engineering strategies

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Aqueous zinc-ion batteries (AZIBs) are promising large-scale energy-storage systems owing to their intrinsic safety, low cost, environmental compatibility, and high theoretical zinc capacity. Among the various cathode materials explored, sodium vanadate's (NaVOs) have emerged as leading candidates due to their diverse crystal structures, multivalent vanadium redox chemistry, open ion-transport channels, and pre-intercalated Na + pillars that facilitate Zn 2+ storage while enhancing ion diffusion and structural stability. Nevertheless, their electrochemical performance is governed by complex Zn 2+ /H + co-storage mechanisms and remains limited by sluggish Zn 2+ diffusion, poor electronic conductivity, vanadium dissolution, interfacial side reactions, proton participation, structural degradation, and the capacity–stability trade-off. Despite extensive efforts to overcome these challenges through materials engineering, a comprehensive review dedicated exclusively to sodium vanadates as a distinct cathode family for AZIBs is still lacking. This review provides the first dedicated and comprehensive assessment of sodium vanadate's (NaVOs) as an independent cathode family for aqueous zinc-ion batteries. We critically examine their structure–mechanism–performance relationships, highlighting key challenges including sluggish Zn 2+ diffusion, poor electronic conductivity, vanadium dissolution, proton participation, interfacial side reactions and structural degradation. Recent advances in ion pre-intercalation, heteroatom doping, defect engineering, conductive-polymer integration, interlayer regulation, surface/interface modification, and composite design are critically analysed to establish clear structure–performance correlations. By elucidating the interplay between ion transport, charge-transfer kinetics, structural evolution, and electrode–electrolyte interactions, this review provides new insights, identifies unresolved challenges, and outlines future design principles for developing high-energy, high-rate, and ultra-stable NaVO cathodes for practical AZIB applications.