Study On The Microstructure Control And Electrochemical Properties Of Nanostructured Nickel-based Electrode Materials

Supercapacitors（SCs）are an important category of electrochemical energy storage device,having advantages of high-power density,fast charge and discharge speed and long cycle life.Based on energy storage mechanisms,SCs can be divided into double layer capacitors,faradaic capacitors and hybrid capacitors.Nickel-based materials are typical battery type electrode materials for faradaic capacitors,which have the characteristics of high theoretical specific capacity,good electrochemical activity,and low cost.However,nickel-based materials still have the diadvantages of poor rate performance,low conductivity,and poor stability.In this paper,nickel-based materials with excellent electrochemical properties were obtained by controlling microstructure and optimizing composition.The asymmetric supercapacitors assembled with these materials as cathod materials presented high energy density and power density.The main results of this thesis are as follows:（1）The preparation of Ni（OH）₂ with hierarchical nanostructure and investigation on its electrochemical performance:the Ni₃（NO₃）₂（OH）₄ with branched nanosheet-interlaced nanostructure as the precursor was converted to Ni（OH）₂ with the homologous hierarchical nanostructure in alkline electrolyte solution.The two-dimensional nanosheet-interlaced structure o can increase the specific surface area,promote the migration rate of electrolyte ions,improve the structure stability and alleviate the volume shrinkage effect of material.As a result,the Ni（OH）₂ presented high electrochemical performance.（2）The preparation of Co²⁺/Co³⁺-doped Ni（OH）₂ with hierarchical nanostructure and investigation on its electrochemical performance:cobalt ions-doped Ni₃（NO₃）₂（OH）₄ with the similar nanosheet-interlaced nanostructure to Ni₃（NO₃）₂（OH）₄ was prepared by microwave hydrothermal method.The cobalt ions-doped Ni₃（NO₃）₂（OH）₄ was convered to Ni（OH）₂ with the homologous hierarchical nanostructures in alkline electrolyte solution.The synergistic effect of cobalt ions doping and nanostructure are favorable to the increase of stability and electrical conductivity,which greatly improved the rate performance and cycle stability of electrode material.（3）The preparation of Co²⁺/Co³⁺-doped Ni₂P with hierarchical nanostructure and investigation on its electrochemical performance:the Co²⁺/Co³⁺-doped Ni₂P with the nanosheet-interlaced nanostructure was prepared by the low temperature gas-solid phosphating of cobalt ions-doped Ni₃（NO₃）₂（OH）₄.Due to the doped cobalt ions and hierarchical nanostructure,the nickel phosphide showed excellent electrochemical performance.