In situ encapsulation of V2O5@ZIF-8 nanocomposites as electrode materials for high-performance supercapacitors with long term cycling stability

Abstract

The development of hierarchical metal–organic frameworks (MOFs) consisting of interconnected nanostructures is of great importance for biosensors, gas separation, energy storage, healthcare and catalysis as a consequence of efficient mass transfer kinetics by means of mesopores. We outline a simple strategy to modify zeolitic imidazolate framework-8 (ZIF-8) with porous V₂O₅ to achieve V₂O₅ incorporated ZIF-8 nanocomposites through a simple in situ synthesis method. Powder X-ray diffraction and infrared spectroscopy analyses confirmed the formation of the hybrid nanocomposites. A strong band at 421 cm⁻¹ corresponding to Zn–N stretching has been observed due to the bonding of the zinc atoms in the ZIF-8 structure with the nitrogen atoms of the 2-methylimidazole linker during the formation of V₂O₅@ZIF-8 composites. The nanocomposites have been morphologically characterized using scanning electron microscopy and transmission electron microscopy analyses. The electrochemical performance is evaluated based on high potential redox reactions occurring in a blend of additive redox electrolytes in a potential window of 0.85 V, attaining a capacity of 802.88 F g⁻¹ at 10 A g⁻¹. These hybrid nanocomposites have higher electrochemical capacitance than ZIF-8 nanocrystals as advanced materials for supercapacitor electrodes. This fascinating electrochemical capability is majorly associated with the synergistic effect of the Zn-MOF and vanadia nanoparticles. These characteristics make our V₂O₅@ZIF-8 nanocomposite an ideal MOF-based electrode for high-performance energy storage applications. An asymmetric supercapacitor device fabricated using the redox additive electrolyte shows energy densities and power densities of 8.56 Wh kg⁻¹ and 1923.07 W kg⁻¹, respectively.