Structure Design Of Ni-Co Matrix Composites And Study On Properties Of Supercapacitors

Supercapacitors are common energy storage devices with high power density and excellent cycle stability.They are widely used in portable electronic devices,electric vehicles,backup energy systems and electronic products.The chemical characteristic of electrode material is the decisive factor in the electrochemical characteristics of supercapacitor,so the structural design optimization of electrode material is particularly important.NiCo-based electrode materials have the problems of capacitance decay and poor rate performance under high rate charging and discharging.In order to obtain excellent electrochemical performance,this paper uses cotton as substrate and template,studies the chemical reaction design and synthesis mechanism,and realizes the preparation of nickel-cobalt-oxygen and phosphide with nanometer multilayer and porous structure,and studies the structure-activity relationship between the obtained nanostructures and electrical properties.The details are as follows:（1）NiCo₂O₄ nanowire precursor was uniformly grown on a cotton substrate and template through interface chemical reactions.After calcination in air,NiCo₂O₄NWs@HCMT hollow microtube material was obtained.The uniform growth of NiCo₂O₄ nanowires on carbon microtubes shortened the electron transfer distance between the carbon-based material and the pseudocapacitive material,significantly improving the conductivity and active sites.The specific capacitance of NiCo₂O₄NWs@HCMT electrode material was 1 064 F g^-1 at a current density of 1 A g^-1.The energy density of NiCo₂O₄ NWs@HCMT//AC asymmetric supercapacitor was 58.6Wh kg^-1 at a power density of 375 W kg^-1.（2）NiCo₂O₄ precursor nanosheets were grown on cotton substrate and template using a solvothermal method,and then NiCo₂O₄ NSs@HCMT hollow microtubular material was obtained after calcination in air.At a current density of 1 A g^-1,the NiCo₂O₄ NSs@HCMT composite electrode material exhibited a high specific capacitance of 1 500 F g^-1,and the capacitance retention rate of the electrode material was still 88%after 5000 charge-discharge cycles.At a power density of 375 W kg^-1,the NiCo₂O₄ NSs@HCMT//AC asymmetric supercapacitor exhibited a high energy density of 64.8 Wh kg^-1.（3）Based on the above research,NiCoP NWs@HCMT and NiCoP NSs@HCMT were prepared by phosphorization of nanowires and nanosheets of cobalt-nickel precursors in an argon atmosphere.The electrochemical performance differences of different morphologies of NiCoP as a supercapacitor positive electrode material were investigated.At a current density of 1 A g^-1,the specific capacitances of NiCoP NWs@HCMT electrode and NiCoP NSs@HCMT electrode were 2 256 and 2 404 F g^-1,respectively.After 5 000 cycles,the cycling stability of NiCoP nanowire electrode was 89.45%,and that of NiCoP nanosheet electrode was 87.25%.At a power density of 375 W kg^-1,NiCoP NWs@HCMT//AC asymmetric supercapacitor exhibited a high energy density of 72.8 Wh kg^-1,and NiCo₂O₄ NSs@HCMT//AC asymmetric supercapacitor exhibited a high energy density of 82.9 Wh kg^-1.