Dopant-Mediated Tunable Polarization in a MOF Structure with Co-Doped NiN2O4 Octahedra Enables High-Performance Supercapacitor

Addressing the challenge of rapid electrolyte ion diffusion in supercapacitors is of paramount importance. The key lies in the meticulous design of electrode materials featuring tailored built-in electric fields to optimize ion diffusion and transfer kinetics. In this study, we embarked on the synthesis of a series of Co-doped Ni-metal–organic frameworks (Co:Ni-MOFs) with varying Co doping ratios, enabling us to regulate the inherent polarization electric field. By manipulating the Co dopant levels, we effectively induced the [NiN2O4] octahedral distortion in interlayers. This allowed for precise control of the polarization electric field, ultimately promoting the diffusion and transfer kinetics of electrolyte ions. Notably, in the case of Co:Ni-MOF-3 (with a molar ratio of approximately Ni/Co = 3:1), the cumulative built-in polarization electric field proved most conducive to the diffusion of electrolyte ions into the interior and pores of the material. This refined design resulted in a remarkable specific capacitance of 1515 F/g at a current density of 1 A/g for Co:Ni-MOF-3, surpassing the performance of most MOFs-based electrode materials reported to date. Our current approach unveils interesting insights into structural tuning and the enhancement of energy storage properties through MOFs, harnessing the potential of controlled doping and built-in electric field modifications.