Preparation And Superelectric Properties Of Ni-MOF Derivative Nanomaterials

Supercapacitor?SCs?is a new kind of electrochemical energy storage equipment,which has the advantages of fast charging and discharging rate,long cycling life and high energy density.Electrode materials as the core of SCs,it has an important influence on the performance.Recently,nickel base compounds have attracted wide attention due to their high theoretical capacitance,but their poor electrical conductivity has hindered their large-scale application.In this paper,Ni-MOF was used as the precursor to prepare two different composite materials for SCs,and the structures and components of the two materials were characterized.Through electrochemical testing,the relationship between properties and composition/structure was explored.The asymmetric supercapacitor?ASC?was assembled with suitable negative carbon materials to effectively improve the energy density.Ni-MOF precursor was synthesized by solvent thermal method.NiO/Ni/NCNTs composites with hollow column structure and carbon nanotube network were prepared by two-step calcining method.The influence of calcination temperature on the morphology of the materials was investigated and the structure-activity relationship between the special morphology and the electrochemical properties of the materials was explained.The formation mechanism of the special morphologies formed during calcination is explained by the Kendall effect.In the electrochemical test,it was found that the specific capacitance was 777.5 F g^-11 at 1 A g^-1,and the capacitance retention was up to 63%after 10000 cycles at 10 A g^-1.The porous carbon material was prepared by the ZIF-67 which was selected to assemble the ASC,the energy density of the ASC reached 33.3 Wh kg^-1.The capacitance retention of ASC is nearly 90%after 40000cycles at 1 A g^-1.The experimental results show that the unique hollow structure and carbon nanotube network can benefit the stability and conductivity of the material,which is beneficial to fully exert NiO's high specific capacitance.Ni₂P/Ni/C composite materials were prepared by using the same Ni-MOF as precursor,and the the experimental methods and conditions were simplified.Ni₂P/Ni/C composite were prepared by one-step high-temperature phosphating method,the composite material inherited the column structure of Ni-MOF and contained Ni₂P as the reactive site.Through electrochemical tests,it is found that the Ni₂P/Ni/C?NP-150?with phosphating by adding 150 mg sodium hypophosphite has the best electrochemical performance,it exhibits a specific capacitance of 642.5F g^-11 at 1 A g^-1,the specific capacitance retention is 63.1%after 5000 cycles.The porous carbon material was prepared by the ZIF-8 which was selected to assemble the ASC,the energy density of the ASC reached 25.4 Wh kg^-1,and the capacitance retention rate is 98.14%after 4000 cycles at 1A g^-1.The experimental results show that adding appropriate amount of sodium hypophosphite can regulate the content of Ni₂P in the composite,so as to change the ratio of Ni₂P/Ni,and the appropriate ratio is conducive to the improvement of material properties.