Construction Of Nickel-based Electrode Based On MOFs And Its Application In Supercapacitor

Supercapacitors have always piqued people’s interest as a viable energy storage device.However,due to its poor energy density,it cannot be employed in novel ways.Developing high-performance electrode materials is crucial for overcoming the aforementioned challenges and meeting the ever-increasing needs of energy sources.Nickel-based compounds have become a hot spot of supercapacitor electrode materials due to their advantages of high theoretical capacity,large reserves,economy,and environmental friendliness.However,nickel-based compounds’weak conductivity and poor structural stability prevent them from being used in supercapacitors in the future.In this paper,MOFs materials are used as the research object,and the low-dimensional nickel-based MOFs composites and MOFs-derived nickel-based composites are bulit by using the structural orientation of low-dimensional substrates,in order to regulate the physical and chemical characteristics of electrode materials,improve the conductivity and cycle stability of nickel-based composites,as well as optimize the electrochemical performance.By using BDC as organic ligands and Ni²⁺as metal centers,the Ni-MOFs was induced growth along the surface of Ti₃C₂T_x MXenes.The existence of MXenes not only improves the conductivity of composites,but also provide additional electric double-layer capacitance and Faraday pseudocapacitance.In addition,with the synergistic effect of Ni-MOFs microbelts and MXenes,Ti₃C₂T_x/Ni-MOFs microbelts provide abundant reaction sites and shorten the ion transfer pathway to promote ion diffusion rate.At the current density of 1 A g^-1,it shows a high specific capacity of 1124 F g^-1,and it still has a specific capacity of 697 F g^-1（capacity retention rate of 62%）at 20 A g^-1.By using 1D Co-CH nanowires as substrate,Ni-MOFs were in-situ grown on its surface,forming uniform 1D core-shell heterostructures.The heterogeneous interface can increase the active sites and improve the electronic structure as well as accelerate the charge transfer rate.In addition,the core-shell heterostructure can increase the adsorption energy of OH^-ions and promote the electrochemical activity,thus enhancing the reaction kinetics of electrode materials.Therefore,the Co-CH@Ni-MOFs electrode showed a high specific capacity of 1246 F g^-1 at 1A g^-1,and the capacity retention rate was still 70.3%at 150 A g^-1.In addition,the energy density of the assembled Co-CH@Ni-MOFs//AC asymmetric supercapacitor can reach 58.0 W h kg^-1at 800 W kg^-1.And kept the energy density of 29.9 W h kg^-1 at 16,000 W kg^-1.Co-dimethylimidazole（Co-Mim）was uniformly grown with Ti₃C₂T_x MXenes structure-oriented substrates followed by self-template transformation strategy,the synthesized NiCo-LDH/Ti₃C₂T_x inherits the morphologies of Co-Mim/Ti₃C₂T_x,forming a entire contact composite.The construction of the composite materials not only improved the electrical conductivity,but also exposed abundant active sites,thus improving the electrochemical performance.In addition,the theoretical calculation shows that the coupling of LDHs and Ti₃C₂T_x MXenes can enhance the electrochemical reaction activity and the improve the adsorption energy of OH^-ions as well as promote the electrochemical activity,thus improving the reversible redox reaction kinetics in the electrode materials.Therefore,the electrode of NiCo-LDH/Ti₃C₂T_x shows a high capacitance of 1030 F g^-1 at 1 A g^-1,and still maintains 61%of the initial specific capacity at 50 A g^-1.The corresponding asymmetric supercapacitor also achieves a high energy density of 59 W h kg^-1 at a power density of 800 W kg^-1.