Preparation And Electrochemical Performance Of Polyaniline/silicon-oxygen Compound Hybrid Electrodes

Polyaniline?PANI?is one of the important supercapacitor electrodes due to its convenient synthesis,low cost,controllable morphology and environmental friendliness.Unfortunately,there are still many key technologies needed to achieve in industrial application of polyaniline electrode materials,such as low specific capacitance and poor cyclic stability.In this paper,nano electrode materials with different structures were designed based on silicon-oxygen compound and polyaniline.The structure and electrochemical properties of the electrodes were systematically investigated.The results showed that the polyaniline/silicon-oxygen compound have porous structures with different layers;the specific surface area of the composites increased and the structural stability of the composites was improved by innovating the structure design and fabrication process of the composites;the materials obtained displayed high specific capacitance retention,cycling performance stability and comprehensive performance.The detailed specific work was as follows:1.Polyaniline/silicon dioxide composites were synthesized by in-situ polymerization using nano-silica as hard template,and then the template was removed.Porous polyaniline electrode materials with different levels of distribution were prepared after removing the template.The obtained porous polyaniline was tested by FTIR and UV-vis spectrum analysis.The effects of SiO₂ templates on specific surface area of porous materials were investigated.When the mass ratio of aniline/silica was 1:2,the specific surface of the porous material was55.89 m² g^-1.When the content of silica template was within a certain range,the specific surface area of the electrode could be adjusted by the amount of silica.Porous polyaniline provided an effective channel for the diffusion of electrolyte ions due to its large specific surface area and multistage pore channels.The specific capacity of porous polyaniline electrode materials was 397 F g^-1 at 1 A g^-1,which was much higher than that of nonporous polyaniline(182 F g^-1).Moreover,the porous structure could improve the cyclic stability of polyaniline.After 500 cycles of GCD,the porous polyaniline maintained 76%of its initial specific capacity,while the non-porous polyaniline could only maintain 65%of the initial specific capacity.Several reasons could be explained,?i?the construction of the porous structure increased the contact area between the electrolyte and the electrode,providing more electrochemical active sites to participate in the redox reaction;?ii?this structure facilitated the transfer of ions and electrons,improved the mass transfer of ions and electrons,and then improved the electrochemical utilization rate of PANI nanoparticles;?iii?porous structure was conducive to the repeated implantation and release of ions during the redox reaction,thus improving the cyclic stability of electrode materials.2.Nitrogen-doped porous carbon?N-HPC?electrode materials were prepared by carbonization and template removal of the above-mentioned polyaniline/silica composites.Before and after carbonization,the microstructure of the sample was basically maintained,except the particle size,which was mainly caused by the overflow of H,N,O and other elements.The influence of SiO₂ template content on the porous structure of electrode materials was investigated.The N-C material prepared without SiO₂ template had a wide pore size distribution,while the N-HPC prepared with SiO₂ had a relatively narrow pore size distribution.With the increase of SiO₂ template content,the medium hole proportion of the material increases significantly.As an electrode material,macropores could shorten the diffusion path of ions and mesoporous could promote rapid ion transfer.The specific capacitance of N-HPC?1:3?was as high as 218.75 F g^-1 at the current density of 0.5 A g^-1.The N-HPC?1:3?could hold 99%of the initial specific capacitance at the current density of 10 A g^-1,which had good specific capacitance and excellent cycle stability.3.Polyaniline/aniline modified silica composites were prepared by functional modification of silica with silane coupling agent containing aniline group.The surface modification of silica could not only avoid the agglomeration of silica nanoparticles,but also introduce reactive aniline functional groups.Inorganic nanoparticles with stable structure were introduced into the conductive polyaniline skeleton material through chemical bond,which could improve the electrode material's cycle stability.The structure of M-SiO₂ and PANI/M-SiO₂ composite were verified by FTIR and XRD spectra.Under mechanical stirring and ultrasonic dispersing,the surface of the electrode material was regular.The effect of M-SiO₂ dosages on the micro morphology of electrode materials were also investigated.Compared with pure PANI,the fiber diameter of PANI/M-SiO₂ composite was small with the large specific surface area.Among these electrodes,PANI/M-SiO₂?1%?composite had the most regular structure and the maximum specific surface area.The specific capacitance of PANI/M-SiO₂?1%?reached 307.5 F g^-1 at the current density was 1A g^-1.The cyclic life of electrode materials was tested by cyclic GCD method.It was found that the specific capacitance holding rate of PANI/M-SiO₂?1%?was better than that of pure PANI.4.Polyaniline/eight-amino caged silsesquioxane?POSS-NH₂?organic/inorganic hybrids were prepared by hydrogen bond induced force.The structural stability of the composite material was improved and the comprehensive performance of the material was enhanced.Under the condition of alkali catalysis,POSS-NH₂ was prepared efficiently.Its structure was confirmed by nuclear magnetic resonance.The effects of POSS-NH₂ dosage on microstructure and electrochemical properties were investigated.The results of nitrogen adsorption and desorption test showed that the specific surface area of PANI/POSS-NH₂?5%?composite was 28.52 m² g^-1.The specific capacitance of PANI/POSS-NH₂?5%?reached 272.5F g^-11 at 1 A g^-1.PANI/POSS-NH₂?5%?could hold 64.44%of the initial specific capacitance at the current density of 8 A g^-1 after 5000 cycle,which was better than that of PANI?19.58%?.PANI/POSS-NH₂ composite had a good specific capacitance holding rate and excellent cyclic stability due to the synergistic effect between POSS and PANI.