Preparation Of Ni-based Electrode Materials And Study On The Performance Of Supercapacitors

At present,the energy crisis and environmental pollution caused by the rapid consumption of traditional fossil energy have seriously affected people's daily lives.Humans urgently need to develop green and efficient energy storage devices to solve this problem.Supercapacitors?SCS?has focused by researchers because of its long service life,good storage performance,good temperature characteristics,fast energy release speed,green environmental protection and other advantages.Generally speaking,the electrochemical performance of SCS depends on its electrode material.The limited active sites and slow reaction kinetics of electrode materials make its real electrochemical performance such as specific capacitance,rate performance and cycle stability decline in the practical application.Therefore,the development and application of high efficiency electrode materials is the key to improve the electrochemical performance of SCS.Nickel-based electrode materials have the characteristics of excellent electrochemical performance,good chemical stability,well thermal stability and high theoretical specific capacitance,which make them become the research hotspot in the field of electrode materials.In addition,the unique 4f electron orbit of Ni atom is easy to form Ni²⁺and Ni³⁺electron pairs in the process of redox reaction.NiCo₂O₄ and Ni₂P₂O₇ are widely used in the preparation of electrode materials,which have the advantages of non-toxic,good electrochemical performance and thermal stability.NiCo₂O₄ and Ni₂P₂O₇ are easy to agglomerate and have small specific surface area,which is not conducive to the electrochemical reaction.In this paper,the specific surface area of nano-electrode materials is increased to expose more active sites.Furthermore,porous structure materials are introduced to construct composite electrode materials,so as to improve its electrochemical performance and cycle stability.In this paper,a 3D porous carnation like N-C/NiCo₂O₄ composite material is designed by using the advantage of electron pair in 3D porous multi-channel structure,which can effectively promote the electrochemical performance of SCS;one-dimensional?1D?Ni₂P₂O₇ nanowire and two-dimensional?2D?Ni₂P₂O₇ nanoflake are designed by using the synergistic effect between multi-dimensional structures,and then on the Ni₂P₂O₇nanoflake table surface modified with Co₃O₄-C derived from ZIF-67 was used to construct 2D/3D composite electrode.This paper mainly includes the following three contents:?1?3D porous flower ball type N-C/NiCo₂O₄ was prepared by high temperature calcination with nitrogen and air with2-methylimidazole as substrate,Co?NO₃?₂·6H₂O and Ni?CH₃COO?₂ as reductant.The morphology and structure of N-C/NiCo₂O₄composite were characterized by SEM,TEM,XRD and so on.The electrochemical characterization of the N-C/NiCo₂O₄ composite was carried out on the surface of the nickel foam and tested by three electrode system.The electrochemical experiment results show that the N-C/NiCo₂O₄ composite has excellent electrochemical performance and cycle stability.The specific capacitance at 1 A/g is about 1263.75 F/g,and the capacitance retention rate is 87.56%at 3000 cycles.The improvement of the electrochemical performance and stability of the electrode materials can be attributed to the fact that flower ball type N-C/NiCo₂O₄ has a 3D porous layered structure to provide an open space and rich active sites.?2?NiNH₄PO₄·H₂O nanowires?NWs?were prepared with Ni?NO₃?₂·6H₂O as nickel source,K₂CO₃ as precipitant,KH₂PO₄ as phosphorus source,C₂H₅OH,NH₃·H₂O and H₂O as solvent by controlling the solvent concentration.Then the electrode material Ni₂P₂O₇ NWs was prepared by calcining NiNH₄PO₄·H₂O at high temperature.The morphology,structure and electrochemical properties of Ni₂P₂O₇NWs were characterized by SEM,TEM,XRD,electrochemical workstation and so on.The results show that Ni₂P₂O₇ NWs has excellent electrochemical properties in the three-electrode test,and the porous Ni₂P₂O₇ NWs electrode material can achieve a high specific capacitance of 772.5 F/g at 1 A/g.Furthermore,this paper use Ni₂P₂O₇ NWs as the positive electrode material and CNT as the negative electrode material to assemble the asymmetric supercapacitor,which is used to evaluate the feasibility of the nanocomposite in practical application.The maximum area capacitance of the porous Ni₂P₂O₇ NWs//CNT hybrid supercapacitor?ASC?is 37.5 F/cm² at 0.5 mA/cm².In addition,the porous Ni₂P₂O₇ NWs//CNT ASC also has a stable cycle life,with a capacitance retention rate of 94%in 3000 cycle tests.?3?2D NiNH₄PO₄·H₂O nanosheets were synthesized by precipitation and mixed solvent thermal method.ZIF-67 was grown in 2D Ni₂P₂O₇ by precipitation method to prepare Co₃O₄-C/Ni₂P₂O₇ composite electrode material.The morphology and structure of Co₃O₄-C/Ni₂P₂O₇ were characterized by SEM,TEM,XRD and other instruments.The electrochemical characterization of Co₃O₄-C/Ni₂P₂O₇ composite electrode material is loaded onto the surface of the nickel foam by smearing.Then the electrochemical performance of the Co₃O₄-C/Ni₂P₂O₇ electrode material was tested by three electrode system.The results show that the electrochemical properties of the Ni₂P₂O₇ electrode can be effectively improved by adding ZIF-67 derived Co₃O₄-C,and the mass ratio of the Co₃O₄-C/Ni₂P₂O₇ composite electrode is much higher than that of Ni₂P₂O₇.The capacitance is 2537.8 F/g and the cycle stability is 88.5% after 3000 cycles.