Preparation Of Lignocellulosic Flexible Electrode And Study Of Its Electrochemical Performance

In r ecent years,with t he r apid de velopment o f p ortable,bendable,w earable and f oldable flexible electronic devices.It is important and urgent to develop a sustainable energy device(such as lit hium-ion batteries,su percapacitors,and so larcel Is)t o meet t he p ower needs o f t hese electronic devices.Among various energy storage devices,flexible supercapacitors are expected to become a promising power source for flexible and lightweight electronic devices due to their advantages such as high power density,high cycle life,fast charge and discharge speed,and safe green.H owever,in t he traditional co ncept,a f lexible su percapacitor electrode achieves its flexibility by compressing an active material on a flexible self-supporting substrate or directly coating t he active material o n a flexible s ubstrate,t hereby obtaining a hi gh s torage c apacity.However,in this composite system,due to the small interface contact area between materials and the weak binding force,the active materials are prone to agglomerate or fall off during the cyclic charging and discharging process,thereby greatly reducing the power density and energy density of supercapacitors,leading to their It still faces great challenges in practical applications.In view of the above problems,this paper uses lignocellulose as a raw material,uses its nanometer size,rich oxygen-containing functional groups on the surface,and softness properties to combine with carboxylated carbon nanotubes to construct a flexible substrate.Based on the principle of interface interaction,a flexible e lectrode w ith reasonable s tructure,strong m echanical properties,hi gh specific capacitance and good cyclic stability was designed to effectively enhance the bonding force between interfaces."Nanocellulose-carboxylated carbon nanotubes-graphite/polypyrrole"and "nanocellulose-carboxylated carbon nanotubes-graphite-copper sulfide/polypyrrole" flexible electrode composites were prepared.Combined with cyclic voltammetry,constant current charge and discharge,and electrochemical impedance spectroscopy,as well as SEM,TEM,FTIR,XPS and other characterization testing methods,the electrochemical performance of the synthesized composite electrode was studied in depth.The specific research contents and conclusions are as follows.1.Nanocellulose and carboxylated carbon nanotubes were prepared by chemical treatment of wood p ulp an d carbon n anotubes.T he two w ere m ixed at a cer tain ratio and su bjected to ultrasonic treatment,and the nanocellulose/carboxylated carbon nanometers were prepared by vacuum filtration.Tube flexible substrate.A suitable amount of pencil graphite was coated on the surface of the substrate by a coating method,and a "nanocellulose-carboxylated carbon nanotube-graphite/polypyrrole" flexible electrode c omposite material was o btained th rough o xidative polymerization under t he h ydrogen bonding i nterface i nteraction.The r esults show t hat t he electrode do es no t br eak w hen f lat,f olded and s tretched,and exhibits s trong m echanical properties,and its tensile strength reaches 28.90 MPa.The porous structure of hydrophilic CNF and CNT s-COOH e nhances the diffusion path of i ons a nd e lectrons.The a ddition o f PGr effectively increases the conductive path of the flexible electrode composite and gives it excellent conductive properties.The electrical conductivity of the CNF-CNTs-COOH-PGr/P Py flexible electrode composite obtained after the oxidative polymerization reached 5.403 S·c m-1.In a 1 mol·L-1 H2SO4 solution at a current density of 0.5 A·g-1,the flexible electrode composite has a high specific capacitance of 521 F·g-1,and its capacitance remains after 1500 charge-discharge cycles.The rate is as high as 68%.Based on the excellent mechanical properties,electrochemical properties and conductive properties of flexible electrodes,CNF-CNTs-COOH-PGr/PPy has the basic characteristics of becoming flexible electrode materials for energy storage devices.2.U sing nanocellulose/carboxylated carbon nanotubes as a flexible substrate,coating an appropriate amount of a graphite layer on the surface,and depositing copper sulfide nanoparticles on the surface of the s ubstrate by an "ion a dsorption" m ethod.F inally,pol ypyrrole w as successfully coated on the substrate surface by oxidative polymerization.The results show that the"nanocellulose-carboxylated c arbon nanotube-graphite-copper s ulfide/polypyrrole" flexible electrode has strong electrical conductivity and excellent mechanical properties,and its electrical conductivity and tensile strength reach 1 8.80 S·cm-1 and 85.45MPa.The addition of copper sulfide si gnificantly i ncreased t he s pecific ca pacitance of the flexible electrode.Under the conditions of 0.5 A·g-1 current density and 1 mol·L-1 H2SO4 solution,the flexible electrode has a high specific capacitance of 775.5 F·g-1 And,after 2000 charge and discharge cycles,its capacitance retention rate is as high as 88%,showing good electrochemical performance.