Defect-rich and prismatic-shaped vanadium oxynitride nanohybrids cathodes for high-rate aqueous zinc ion batteries

The development of appropriate cathode materials with stable structures and fast diffusion kinetics of zinc ions is crucial for aqueous zinc-ion batteries (AZIBs) but remains significantly challenging. Herein, the design and synthesis of defect-rich and prismatic-shaped nanohybrids composed of vanadium oxynitride nanoparticles confined in the porous nitrogen-doped carbon framework (VN_xO_y@NC) are reported. Its unique structural advantages, including enriched defect sites that effectively enhance electrical conductivity, accelerate charge transfer kinetics, and improve structural stability. Additionally, the introduction of structural defects in VN_xO_y@NC increases the adsorption energy and reduces the hopping barrier of Zn ion, as evidenced by density functional theory (DFT) calculations. The H⁺ and Zn²⁺ co-insertion/extraction mechanism was systematically validated by ex-situ X-ray diffraction and ex-situ X-ray photoelectron spectroscopy tests. Consequently, the VN_xO_y@NC//Zn batteries exhibit an exceptional capacity of 570.9 mAh·g⁻¹ at 0.2 A·g⁻¹, a superior rate capability of 446.7 mAh·g⁻¹ at 20 A·g⁻¹, and long cycling life. Furthermore, the corresponding quasi-solid-state battery delivers an ultra-high energy density of 271.9 Wh·kg⁻¹, demonstrating potential for practical applications. This work presents an effective structural and defect engineering strategy for designing advanced electrode materials with promising applications in AZIBs.

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