Epitaxially growing multilayer CoNi-MOFs nanosheets on activated carbon cloth for high-performance asymmetric supercapacitors

Supercapacitors (SCs) are promising energy storage technology but suffer from the lack of high energy and scalable electrode materials. Metal-organic frameworks (MOFs) with highly porous structures and reversible redox centers appeal to their application as pseudocapacitive electrodes in SCs. Still, polymetallic MOFs with high redox capacity and specific capacitance are rarely approached. Herein, we imitate the MOF-on-MOF synthesis strategy and synthesize the same type of MOF on MOF using the same preparation method. A self-supported electrode is prepared by anchoring multilayered CoNi-MOF nanosheets (m-CNMs) on activated carbon cloth (AC) via in situ epitaxial growth. The m-CNM/AC, with its multi-layer nanosheet structure and bimetallic synergy, offers more electrochemically active sites and a shorter charge transfer distance, resulting in enhanced kinetics and superior electrochemical performance, with an excellent specific capacitance of 43.58 F/cm² at 5 mA/cm². Nitrogen-doped activated carbon cloth (NAC) is used as the negative electrode to assemble m-CNM//NAC asymmetric supercapacitors with an energy density of 1.25 mWh/cm² at a power density of 4 mW/cm². After 10,000 cycles, 98.9 % of the initial specific capacitance is retained, indicating exceptional long-term cycle stability. These MOF-based electrode materials provide new insights and a theoretical foundation for the application of MOFs in energy storage.