Research On Structure Regulation And Electrochemical Performance Of Positive Electrode Of Carbon Nanofiber-based Zinc Ion Batter

In recent years,the large demand for portable rechargeable devices has promoted the rapid development of energy storage devices.Lithium-ion batteries（LIBs）are widely used in a variety of devices because of their high energy density and long life.However,flammable organic electrolytes,rising costs,and lack of lithium resources hinder further large-scale applications.Aqueous zinc-ion batteries（ZIBs）have attracted much attention because of high safety,low cost,and environmental friendliness.The design of its cathode structure to improve the specific capacity and cycle life has become a research hotspot in the field of ZIBs.Carbon nanofibers（CNFs）have the advantages of large specific surface area,high aspect ratio,easy to adjust structure and performance,mass production and so on,so it is widely used in the diaphragm,intermediate layer,positive and negative current collector of electrochemical energy storage devices.In this paper,based on electrospinning technology,using polyacrylonitrile（PAN）as substrate,combined with structural design and performance control,composite materials for the cathode of ZIBs were prepared.The main research contents are as follows:（1）Mn O₂@CNFs composites were prepared by electrospinning,high-temperature annealing,and electrochemical deposition,which have excellent three-dimensional structural stability and provide a structural basis for the long-term stability of the cathode.With Mn O₂@CNFs as the cathode,the ZIBs is obtained a specific capacity of647.9 m Ah/g at a current density of 0.1 A/g.After 1000 cycles at a current density of0.5 A/g,the specific capacity remains above 100 m Ah/g.And has good rate performance.（2）Using PAN solution as skin layer and the solution containing Mn（NO₃）₂·x H₂O as a core layer,the Mn O₂@MCNFs composites with the sebaceous gland-like protruding structure on the surface were prepared by coaxial electrospinning combined with electrochemical deposition.The sebaceous gland-like protruding structure plays the role of riveting,which improves the interface binding between Mn O₂ active material and MCNFs substrate obviously,and reduces the interface resistance between them.The capacity of ZIBs with Mn O₂@MCNFs as cathode can reach 581.16 m Ah/g,and the specific capacity of 300.4 m Ah/g can be maintained after 100 cycles,under 0.1 A/g current density.And the specific capacity of 120 m Ah/g can be maintained after 1000cycles under 1 A/g current density,and the AC impedance performance is greatly improved.（3）Using the mixture of Super-P/PAN and CNTs/PVP as the spinning solution,Mn O₂@CSCNFs composites with the protruding structure on the surface were prepared by biaxially electrospun.The incorporation of CNTs and Super-P improves the electrical conductivity of the carbon nanofiber film;Super-P is partly embedded in the fiber and partly exposed on the fiber surface to form a raised structure,which plays a riveting role,and it enhances the interface bonding between the substrate and the active material,and reduces the interface resistance between the two;CNTs builds a conductive channel between the granular Super-P,which improves the conductivity between the Super-P particles and the particles.The stability of ZIBs with Mn O₂@CSCNFs as the cathode is obviously improved,and the discharge specific capacity of 500 m Ah/g is still maintained after 100 cycles;the AC impedance performance is further improved,and the semicircle diameter of Nyquist curve is greatly reduced;the rate performance is excellent,and the discharge specific capacity of 290.37 m Ah/g is maintained under a high current density of 2 A/g,and the capacity recovery rate is as high as 96.33%when the current density is restored to 0.1 A/g.