Potassium-intervened copper–nickel bimetallic organic framework with a potassium hydrogen phthalate ligand for high-performance aqueous potassium-ion hybrid supercapacitors

Abstract

To develop high-performance electrode materials for aqueous potassium-ion hybrid supercapacitors (APICs), a bimetallic metal–organic framework (MOF), CuNi–KHP (KHP = potassium hydrogen phthalate), was prepared via a solvothermal method. The material features a 3D architecture constructed by stacking 2D nanosheets, with Cu/Ni bimetallic nodes and a multi-layered structure. Potassium ions were pre-inserted into the MOF using potassium hydrogen phthalate as the ligand, which regulates interlayer interactions and creates hierarchical pores for ion transport. Electrochemical characterization studies show that CuNi–KHP exhibits a high specific capacitance of 1568.58 F g⁻¹ at 0.5 A g⁻¹, accompanied by an energy density of 50.52 Wh kg⁻¹ and a power density of 676.12 W kg⁻¹. It also maintains 90.1% capacity retention after 10 000 cycles. The assembled CuNi–KHP//AC hybrid PIC delivers an energy density of 76 Wh kg⁻¹ and a power density of 812 W kg⁻¹ at 0.5 A g⁻¹, with a capacity retention efficiency of 75% after 10 000 cycles at 1 A g⁻¹. These results demonstrate that CuNi–KHP is a promising cathode material for high-performance PICs, owing to its synergistic bimetallic effect and K⁺-regulated porous structure.