Barium-doped dual-pillar-stabilized calcium vanadate hydrate for high-performance aqueous zinc-ion batteries

To meet the stringent requirements for safety, sustainability, and cost-effectiveness in large-scale energy storage systems, aqueous zinc-ion batteries (AZIBs) have attracted considerable attention in recent years. However, layered vanadium oxides, some of the most promising cathode materials, often suffer from structural degradation and sluggish kinetics during cycling, which severely limits the overall performance of the batteries. Herein, we regulate the interlayer architecture of calcium vanadate hydrate (CaV₈O₂₀·4H₂O, CVO) through partial substitution with large-radius Ba²⁺, forming Ca_xBa_1-xV₈O₂₀·4H₂O (CBVO). The incorporation of Ba²⁺ expands the interlayer spacing while preserving the layered framework, establishing a dual-pillar configuration with Ca²⁺ that balances structural rigidity and lattice adaptability. This structural modulation lowers the Zn²⁺ migration barrier and suppresses strain accumulation during repeated insertion/extraction. As a result, the optimized CBVO electrode exhibits fast, reversible Zn²⁺ storage with a high specific capacity of 360.9 mAh g^-1 at 0.1 A g^-1 and maintains 91% capacity retention after 3500 cycles at 5 A g^-1. Kinetic analysis reveals a transition toward pseudocapacitive behavior, while in situ XRD identifies a reversible Zn²⁺/H⁺ co-intercalation mechanism. This work establishes interlayer cation engineering as a general strategy for high-rate and durable multivalent ion storage.