Controllable Preparation And Electrochemical Performance Study Of Multi-shell Electrospun Carbon Fiber Matrix Composites

One-dimensional electrospun carbon nanofibers(CNFs)have the characteristics of high specific surface area,unidirectional high-efficiency transmission of electrons,and easy surface functionalization,so it becomes a popular choice for supercapacitor electrode materials.However,one-dimensional CNFs have low specific capacity and low conductivity.This paper uses electrospinning technology combined with pre-oxidation,carbonization,and other means to obtain graphene-coated carbon nanofibers(GCNF).Polyaniline(PANI)is coated by in-situ polymerization to obtain GCNF/PANI composite material.Basic nickel carbonate(Ni₂(CO₃)(OH)₂),nickel-cobalt bimetallic layered hydroxide(Ni Co-LDH),and nickel-cobalt bimetallic sulfide(Co Ni₂S₄)are coated by hydrothermal treatment,and finally obtained multi-shell layer electrospun carbon fiber-based composite material,respectively.Through the control of the active components,morphology,and structure of the material,its electrochemical performance is improved.A multi-shell electrospun carbon fiber-based composite material is used as positive electrodes to assemble asymmetric supercapacitors,and the practical application of the materials is explored.The specific content is as follows:1.Constructing multi-shell GCNF/PANI/Ni₂(CO₃)(OH)₂ composite electrode materials,exploring the influence of each component on the material properties.The study found that Ni₂(CO₃)(OH)₂ provides capacity contribution to composite materials;PANI increases capacity and conductivity at the same time;GCNF provides base material and composite material framework.The composite material has low crystallinity and the Ni₂(CO₃)(OH)₂ on the surface is flexible sheet layers,the specific capacitance of the material at 1 A g^-1 is as high as 1565 F g^-1;the capacitance retention rate at 20 A g^-1is 46.4%.Assembling an asymmetric capacitor,the energy density reaches 35.4 Wh kg^-1when the power density is 750W kg^-1.2.Constructing multi-shell GCNF/PANI/Ni Co-LDH composite materials and exploring the influence of different hydrothermal time on the electrochemical performance of electrode materials.The composite material has high crystallinity and many Ni Co-LDH nano-hexagonal sheets gather neatly into clusters and grow uniformly on the surface of GCNF/PANI to form a stable composite structure.When the hydrothermal reaction time is 8 h,the material has the best specific capacitance and rate performance and is better than the GCNF/PANI/Ni₂(CO₃)(OH)₂ composite material.3.Constructing multi-shell GCNF/PANI/Co Ni₂S₄ composite electrode materials and exploring the influence of the precursor solution concentration on the material properties.The results show that the material has the best specific capacitance and rate performance and is better than the above-mentioned GCNF/PANI/Ni Co-LDH and GCNF/PANI/Ni₂(CO₃)(OH)₂ composite materials when the concentration is moderate.Assembling an asymmetric capacitor,the energy density is 57.28 Wh kg^-1when the power density is 800 W kg^-1.Compare to the GCNF/PANI/Ni₂(CO₃)(OH)₂//AC and GCNF/PANI/Ni Co-LDH//AC ASC,the energy density of GCNF/PANI/Co Ni₂S₄//AC ASC is greatly improved and higher than that of many other Co Ni₂S₄-based ASC device.