A quasi-solid-state Li-ion hybrid capacitor based on a colloidal metal–organic framework interwoven by in situ polymerized PANI

Abstract

Metal–organic frameworks (MOFs) have emerged as promising candidates for advanced energy storage systems. However, their practical application is hindered by intrinsic conductivity limitations. This study introduces a novel in situ gel-confined polymerization strategy to fabricate MOF gel/polyaniline (MOG/PANI) composites with precisely tunable architectures. Systematic adjustment of PANI content elucidates critical composition–property relationships, where the optimized MOG/PANI-3 composite exhibits uniform component distribution and enhanced interfacial interactions. The developed electrode exhibits an impressive specific capacitance of 423.8 F g⁻¹ at a current density of 1 A g⁻¹. Electrochemical studies showed that excessive incorporation of PANI induces detrimental aggregation phenomena that degrade impedance characteristics. The study developed a quasi-solid-state Li-ion hybrid capacitor using a MOG/PANI-3 cathode paired with an activated carbon anode. This configuration achieves an exceptional energy density of 41.3 W h kg⁻¹ at 900 W kg⁻¹. Furthermore, it maintains 87.3% capacitance retention after 4000 cycles at 5 A g⁻¹, demonstrating acceptable cycling stability. This gel-confined synthesis method effectively addresses the poor conductivity issues inherent in MOF-based electrode materials. Simultaneously, it creates a flexible platform for developing multifunctional hybrid materials tailored to next-generation energy storage systems.