Preparation And Application Of Prussian Blue Analogs And Derivatives Nanomaterials In Supercapacitors

Nowadays,affected by global warming and the gradual depletion of fossil energy,more and more people are beginning to pay attention to the development and utilization of clean and efficient energy,such as secondary batteries,supercapacitors,etc.Among them,supercapacitors are widely used in hybrid electric vehicles and other fields due to their high power density,long cycle life and instantaneous charging and discharging advantages,but their lower energy density also limits their further development.From the energy density calculation formula E=1/2CV² of the supercapacitor,it can be seen that the specific capacitance C and the potential window V of the electrode restrict the improvement of the energy density,and the choice of electrode material is very important to these two factors.Therefore,this paper uses Prussian blue analogues(PBAs)with a three-dimensional porous structure as the precursor,and prepares supercapacitor electrode materials with high specific capacity and wide potential window through element doping,high temperature heat treatment,and composite materials.The energy density of supercapacitors is improved,which provides a basis for the further development of supercapacitor devices with PBAs as the precursor.The main research contents of this paper are as follows:1.Research on the cathode material of supercapacitor based on Ni Co HCFNi_xCo_yHCF with different ratios of nickel and cobalt was prepared by a simple co-precipitation method.Compared with Co HCF,the incorporation of Ni can reduce the lattice change of the PBA framework during the electrochemical cycle,and stabilize the structure,thereby improving the material Rate performance and specific capacity retention rate.At the same time,the charge-discharge curves of different ratios of Ni_xCo_yHCF are calculated.It is found that the Ni Co HCF electrode obtained when Ni:Co is 1:1 can achieve the best electrochemical performance,and achieve a ratio of 255 Fg^-1at a current density of 0.5 Ag^-1.It has high capacity and can work stably under a wide potential window of 0-1 V.This is also due to the open framework structure of Ni Co HCF that allows alkali metal ions to be deintercalated in the metal framework,thereby carrying out charge transfer and storage.At the same time,it is assembled with AC into an asymmetrical water-based supercapacitor,which can achieve an energy density of27.8Wh kg^-1 at a power density of 1 k W kg^-1.2.The preparation and electrochemical performance of Ni O/Co₃O₄/Fe₃O₄ metal oxideIn order to solve the problem of poor conductivity and low capacity of Ni Co HCF nanocubes,Ni Co HCF nanocubes are subjected to high temperature heat treatment to convert them into porous Ni O/Co₃O₄/Fe₃O₄ metal oxides,which improves the conductivity of the material and improves the electrical conductivity of the electrode material.Chemical properties.The cyclic voltammetry scan of the prepared Ni O/Co₃O₄/Fe₃O₄ metal oxide found that there is a current response caused by the oxidation-reduction reaction of nickel ions and cobalt ions with hydroxide in the range of0.2-0.4 V,and with The position of the oxidation peak and the reduction peak of the scan rate increased only in a small range,indicating the material's smaller electrochemical polarization and good reversibility,which benefited from the porous structure of the material and the improvement of the conductivity of Fe₃O₄.At the same time,electrochemical tests of Ni O/Co₃O₄/Fe₃O₄ metal oxides obtained at different calcination temperatures found that NCF-470 obtained at a calcination temperature of 470?has the most beneficial electrochemical performance.Under the current density of 0.5 A g-1It can reach a specific capacity of 437.5 Fg^-1,which is a big improvement compared to the Ni Co HCF in the previous chapter.3.Preparation and electrochemical performance of Ni Co HCF/GH composite materialThe Ni Co HCF precursor was compounded with graphene by a simple hydrothermal method to prepare an NCFG composite with a three-dimensional network structure.The graphene sheet provides an anchoring and dispersed framework for Ni Co HCF,and the presence of Ni Co HCF can prevent graphene Stack between slices.It is proved that this self-supporting package structure helps to improve the conductivity and overall stability of the electrode material.The prepared NCFG composite material has a 3D three-dimensional structure and can be directly sliced on it as an electrode material for supercapacitors,without further adding conductive agents and adhesives.This integrated structure prevents the addition of adhesives from blocking the pores The structure affects the experimental results,and the electrode manufacturing process has been improved.At the same time,NCFG is used as both positive and negative electrodes to assemble a water-based symmetrical supercapacitor with a wide potential window of 2V.The constant current charge and discharge test calculates that the NCFG//NCFG device can achieve 42Wh kg^-1 at a power density of 1k W kg^-1.The energy density of 1 shows the excellent energy storage performance of NCFG materials,and provides a basis for the further development of high energy density supercapacitors.