Tremella-like (NH₄)₂V₁₀O₂₅·8H₂O nanosheets boosting 3D diffusion and reversible storage for superior aqueous zinc-ion batteries

The combination of high safety, cost-effectiveness, and environmental sustainability renders aqueous zinc-ion batteries (AZIBs) a compelling option for large-scale energy storage technologies. However, achieving practical application is still hampered by the deficiency of cathode materials that can concurrently provide fast Zn²⁺ diffusion, efficient charge transport, and structural resilience during prolonged cycling. In this work, we report a defect-engineered tremella-like (NH₄)₂V₁₀O₂₅·8H₂O (T-NVO), synthesized via a one-step hydrothermal route using L-cysteine as a reductant and structural modulator. Benefiting from its tremella-like morphology derived from ultrathin nanosheets, T-NVO possesses an expanded interlayer gap of 12.7 Å, considerably larger than the 9.5 Å in pristine NVO. This structural feature effectively promotes Zn²⁺ diffusion kinetics, endowing the material with excellent rate capability. Simultaneously, the partial reduction of V⁵⁺ to V⁴⁺ and the formation of abundant oxygen vacancies induced by L-cysteine enhance electronic conductivity and interfacial charge transfer. Density functional theory calculations further reveal that oxygen vacancies facilitate electron redistribution within the lattice, optimize Zn²⁺ adsorption/desorption kinetics, and create additional electron pathways, collectively boosting zinc storage capability. Leveraging its favorable structural and electronic configuration, T-NVO delivers a remarkable capacity of 397.3 mAh g⁻¹ at 0.1 A g⁻¹, maintains 214.8 mAh g⁻¹ under 7 A g⁻¹, and retains 91.2% capacity after 2000 cycles at 10 A g⁻¹. The proposed approach, which integrates interlayer engineering with defect modulation, provides a generalizable framework for the rational development of next-generation vanadium-based cathodes in AZIBs.