Study On The Modification And Supercapacitor Energy Storage Performance Of Nickel-based Phosphides

Super capacitor has the advantages of high power density,fast charge and discharge and long cycle life,which has become a major demand in modern society.Electrode material is the most important part of supercapacitor.Among them,nickel-based phosphide has the advantages of high electrochemical activity and low cost.It is a very ideal electrode material,but it still has the problems of poor magnification and low cycle stability.In view of the above problems,this paper has carried out the following work through structural design,component regulation and structural compound modification:（1）Preparation and electrochemical properties of bimetallic phosphide strengthened by metal nickel（Ni-Co-P@Ni）:In order to improve the electronic conductivity of Ni-Co-P,high-performance core-shell electrode materials（Ni-Co-P@Ni）were prepared by hydrothermal and chemical deposition processes.The as-fabricated electrode shows superior electrochemical performance and delivers a high specific capacity of 510 C g^-1at 1 A g^-1.The asymmetric supercapacitor device（Ni-Co-P@Ni//AC）is composed of Ni-Co-P@Ni as the positive electrode and AC as the negative electrode.The as-obtained device shows a high specific energy of 39.6 W h kg^-1 and a high specific power of 11.9 k W kg^-1,and excellent cycling stability（98.6%capacity retention after 1,000 cycles）.The excellent electrochemical properties of the materials benefit from the rich chemical valence states of bimetallic Ni and co provide more redox reactions and active sites.The metal nickel layer of the shell accelerates the electron transport rate.The core-shell structure can increase the diffusion path of electrolyte ions and improve the utilization and cycle stability of materials.（2）Study on the effect mechanism of phosphorus content on the electrochemical properties of Ni-Co-P:The Ni-Co-P/Ni material was modified by hydrothermal method by adjusting the proportion of phosphorus source to study the effect of phosphorus content on the conductivity of the material.On this basis,the effects of different phosphorus source dosage on the phase,physicochemical properties and electrochemical properties of the products were studied.The results showed that the different amount of phosphorus will directly lead to the existence of Ni metal particles which play the role of electronic conductive agent and phosphate by-products.We assembled supercapacitor device by applying Ni-Co-P as anode and hydrophilic pomelo peel carbon（OPC）as cathode.The Ni-Co-P-2//OPC ASC device utilized in a two-electrode system shows a high specific energy of 34W h kg^-1 and a high specific power of 5.2 k W kg^-1,and excellent cycling stability（98.6%capacity retention after 3,000cycles）.（3）Study on modification of Ni₂P with Ni₂P₄O₁₂ and its electrochemical properties:Ni₂P has high theoretical capacity,but it has the problem of poor cyclicity.In this part,metaphosphate with stable structure is used as the mechanical layer to protect Ni₂P,and improve its electrochemical performance.Samples with different phase ratios of Ni₂P-Ni₂P₄O₁₂ were obtained by adjusting the phosphating time and phosphorus source dosage were regulated by low temperature solid state method.Their growth mechanism was studied and their electrochemical properties were tested.The Ni₂P-Ni₂P₄O₁₂//OPC ASC device utilized in a two-electrode system shows an excellent cycling stability（90%capacity retention after 2,000 cycles）.