Construction And Electrical Properties Of A New Polyacrylonitrile Aerogel Electrode

Entering the 21st century,a variety of intelligent devices such as smart phones,smartwatches and electric cars have gradually entered people's lives and changed people's entertainment,social and travel.To satisfy the diversity of these intelligent equipment,electrode materials as important part of energy storage devices should own special feathers such as flexibility,wearable,simple preparation,fast charge-discharge characteristics,high energy density,etc.To meet various of demands,it is very important to develop a method and technology for preparing electrodes.Fiber template method is a promising strategy to prepare functional fiber or film materials.Thanks to the feather of highly conductity,high porosity,high mass loading,fiber templates with different characteristics combain various materials through in-situ polymerization,electrodeposition,hydrothermal,sacrificial template,dip method can be applied in the field of electromagnetic shielding and supercapacitors.Traditional fiber templates contain carbon nanotube yarn,carbon fiber yarn,natural or synthetic fiber yarn,metal fiber yarns,porous metal wires,etc.Film-based fiber templates include carbon nanotube films,carbon paper,metal fiber mesh,natural or synthetic fiber fabrics,etc.Although templates have their pros and cons in different fields,it is still challenging to develop special functional fiber templates to produce fiber electrodes or thin films with high capacity,high rate performance or multifunctional applications.In this paper,glycerol-engineered polyacrylonitrile(PAN)nanofibers are prepared by electrospun.According to the characteristics of the fibers,glycerol-engineered PAN nanofibers can be used as hydrophilic removable fiber aerogel template,macroscale amphiphilic aerogel fibers template,hydrophilic shrinkable fiber membrane template.Fiber-shaped electrodes and highly crosslinked conductive fiber network were fabricated through these fiber templates,and their applications in high-rate fiber-shaped supercapacitor,high-capacity supercapacitor,high rate film supercapacitor,highperformance electromagnetic shielding are studied as follows:1.Hydrophilically engineered polyacrylonitrile nanofiber aerogel as a soft template for high-rate wire-shaped supercapacitors:Hydrophilically engineered PAN nanofibers by adding glycerol were electrospun on a Ti metal wire to form the sacrificial aerogel template with a huge void volume,in which poly(3,4ethylenedioxythiophene):poly(styrenesulfonate)(PEDOT:PSS)solution was dip coated to achieve a large mass loading.The capillary effect in the subsequent natural drying process,slow dissolution of the template in DMF,and PSS etching in H2SO4,together lead to a high thick mesoporous PEDOT coating network formed on the metal wire with a high conductivity,strong mechanical strength and intimate interface adhesion.The resulted solid-state supercapacitor based on Ti/PEDOT electrodes exhibited a high potential window,large specific capacitance,ultrahigh rate capability and energy/power densities.2.Macroscale amphiphilic aerogel fibers made from nonwoven nanofibers for large active mass loading:Macroscale amphiphilic aerogel-like fibers made from electrospun glycerol-functionalized PAN nanofibers(GPN)on a centering metal wire.The addition of glycerol for nanofiber electrospinning plays a key role in the amphiphilic property of the fiber and its aerogel-like structure.The function of glycerol is to induce electrostatic charges,which will align the nanofibers along the vertical electric field direction and balance the gravity field,and thus much easier to be collected by the rotating wire.And the the rotating rate of the collector is one of the factors in determining its porosity.This unique highly porous structure is very effective for solution absorption and serve as a high mass loading electrode base.Through facile dip coating,a series of PEDOT:PSS(PP)@GPN/Ti aerogel fibers with an macroscopic-thickness were fabricated,to serve as a porous current collector for loading PANI by electrodeposition.The as prepared PANI@PP@GPN/Ti displays a fiber-length-specific capacitance in yarn-shaped solid-state supercapacitors(YSCs).Colza oil was further selected as oily solvent to investigate the high load capacity of GPN aerogel fiber.3.Macroscale aerogel fibers compounded with CNTs or Ti3C2Tx:Macroscale aerogel fibers are used as templates to load one-dimensional materials CNTs or two-dimensional materials Ti3C2Tx through dip coating and freeze drying process.The composite aerogel fiber based on CNTs has a unique roll-up structure,high CNTs mass loading based on per unit length and high conductivity which result into potential applications in many fields such as fiber current collector,heating unit.The composite aerogel fiber based on Ti3C2Tx has a high capacity as the fiber electrode.4.Scalable fabrication of highly crosslinked conductive nanofibrous films based on fabric-shrinking strategy and their applications in energy storage and electromagnetic interference shielding:We designed a fabric-shrinking strategy based on electrospinning to prepare nanofiber with water swellable ability.Hydrophilicity-engineered PAN-based nanofibers were electrospun from a solution of PAN and glycerol in dimethylfrmamide(DMF),denoted as glycerol-PAN-based nanofibers or GPN,which were then dip-coated with PEDOT:PSS(PP)in its aqueous solution,forming a highly interconnected 3D PP/GPN film(PP/GPNF)network with controllable and uniform thickness.They are applied as electrodes to fabricate supercapacitors for high-rate charging and discharging.The PANI based electrode exhibits a high rate performance,which confirms highly crosslinked structure could bring high rate character for pseudocapacitive material with high specific capacitance.Their mechanical and electrical properties were further studied toward applications as high-performance flexible films for EMI shielding.