Ni-MOF composite polypyrrole applied to supercapacitor energy storage

Abstract

Electrodes for supercapacitors made from metal–organic frameworks (MOFs) are still hindered by electron transfer properties. Therefore, an electrode composite material Ni-MOF@PPy was synthesized from a Ni-based metal–organic framework (Ni-MOF) doped with poly-pyrrole (PPy) using a simple chemical oxidation method to improve its electron transfer property. After introducing the electrochemically active substance K₄Fe(CN)₆ into the electrolyte, the composite material had a specific capacitance of 1815.4 F g⁻¹ at a current density of 1 A g⁻¹. Ni-MOF@PPy and active carbon (AC) as the positive and negative electrodes have been used, respectively, to assemble asymmetric supercapacitors (ASCs) in the KOH and K₄Fe(CN)₆ mixed electrolyte. This novel Ni-MOF@PPy//AC ASC energy storage device can provide 38.5 W h kg⁻¹ energy density, 7001 W kg⁻¹ power density, and 90.2% capacitance retention after 3000 cycles. Therefore, Ni-MOF@PPy//AC ASC is an excellent energy storage device with practical and economic value. The synergistic effect strategy proposed in this work can be easily applied to develop other MOFs with unique crystal structures as well as other redox active additives, providing new avenues and research ideas for exploring novel energy storage devices.