Eco-Friendly Synthesis of Hierarchical Heterostructured CsV3O8/V2O5 Composite Cathode: Lattice Stabilization and Vanadium Dissolution Resistance for Long-Life Aqueous Zinc-Ion Batteries

Developing durable and high-capacity cathode materials is key to advancing aqueous zinc-ion batteries (ZIBs). Herein, we propose a hierarchical heterostructured CsV ₃ O ₈ /V ₂ O ₅ composite (HH–CsVO/VO) cathode synthesized via a simple, cost-effective, and eco-friendly ambient-temperature stirring method. The incorporation of Cs ⁺ ions into the VO framework induces significant lattice compression, compressive strain, and new V coordination environments, leading to mixed-valence V states (V ⁵⁺ /V ⁴⁺ /V ³⁺ ), as confirmed by solid-state ⁵¹ V nuclear magnetic resonance (NMR) spectroscopy and ex-situ X-ray photoelectron spectroscopy (XPS) analyses. This structural modulation is accompanied by band gap narrowing (2.71 → 2.19 eV) and a reduced work function (5.00 → 4.14 eV), enhancing redox kinetics and Zn²⁺ intercalation pathways. Raman and Fourier-transform infrared spectroscopy analyses reveal Cs-induced lattice distortion and compressive strain, while ultraviolet photoelectron spectroscopy confirms interfacial electronic modulation. Ex-situ X-ray diffraction and XPS demonstrate highly reversible phase evolution and structural stability during cycling. The HH–CsVO/VO electrode delivers a high reversible capacity of 482.7 mAh g ^-1 after 200 cycles at 0.3 A g ^-1 and maintains 240.63 mAh g ^-1 after 3000 cycles at 3 A g ^-1 , outperforming pristine VO. Notably, the composite exhibits suppressed voltage polarization and significantly reduced V dissolution, supported by immersion tests and stable cycling. Although Cs–O bonding is not vibrationally active, it is proposed to stabilize vanadyl surface groups and limit dissolution. This study introduces a previously unreported vanadate heterostructure and demonstrates how interfacial engineering and electronic structure modulation can enable high-performance, sustainable aqueous ZIB cathodes.