Structural Control And Functionalization Of Polyaniline Based Solid State Supercapacitors

As a rapidly developing energy storage device,supercapacitor plays an important role in many special fields because of its fast and efficient charging and discharging characteristics,high power density and excellent cycle stability.Therefore,the research and application of supercapacitor has gradually become a hot spot.For supercapacitor,electrode material is the key factor to determine the electrochemical performance of supercapacitor,so the problem of low energy density can be solved by developing electrode materials with excellent performance.In the process of repeated charge and discharge,conductive polymer materials will cause the expansion and contraction of the electrode material structure,damage the structure of the material,lead to the attenuation of capacitance performance and the deterioration of cycle stability.At the same time,the contact between the traditional solid electrode material and electrolyte is not enough,the solid-liquid interface between the electrode material and electrolyte is not close enough,and there is no stable and continuous ion diffusion and transmission channel,resulting in the actual specific capacitance of the electrode material is far less than its theoretical value.Therefore,the synthesis of electrode materials with excellent electrochemical performance and the improvement of the interface between electrode materials and electrolyte are the focus of current research.Starting from controlling the structure of electrode materials for supercapacitors,a polyaniline(PANI)polyvinyl alcohol(PVA)gel composite electrode material with three-dimensional fibrous network structure was first synthesized.The electrode material and electrolyte reached contact at the molecular level,which improved the combination of electrode materials and electrolytes,thereby enhancing the specific capacitance and cycling stability of electrode materials.Furthermore,polyaniline based solid-state supercapacitor was assembled by using the composite material,and its functionality(tailoring,self-healing,sewing)was studied.Finally,the PANI-PVA gel composite and gel electrolyte were integrated to prepare self supporting integrated gel supercapacitors with no fluid collection and flexible and tensile properties.The results are as follows:(1)PANI-PVA gel composite was synthesized by in-situ polymerization of PANI in PVA hydrogel,and a three-dimensional network structure of the gel composite material was constructed.The electrolyte can penetrate into the whole body of the electrode material through the developed pores in the structure,thus achieving full contact between the electrode material and the electrolyte in three-dimensional space,giving the electrode material a higher specific capacitance(545 F g^-1).The capacitance retention is 80%after3000 cycles.(2)Based on PANI-PVA gel composite materials,the solid state supercapacitors were assembled by using carbon nanotube macro film(CMF)as the collector and H₂SO₄-PVA hydrogel as electrolyte.It is found that the ultra-solid state supercapacitor can still work normally after cutting;the capacitor is cut and self-healing experiment,and the capacitance retention rate of the self-healing supercapacitor is 80%;finally,the capacitor is sewed with needle and thread,and the electrochemical performance of the capacitor is basically unchanged before and after sewing.(3)Using PANI-PVA gel composite as positive and negative electrode materials on both sides of H₂SO₄-PVA hydrogel,a self supporting gel supercapacitor was constructed.The gel supercapacitor is lighter and thinner than the traditional supercapacitor.It has excellent flexibility and tensile properties,and also shows excellent capacitance performance.At 0.2 m A cm^-2current density,the gel integrated supercapacitor volume capacitance is as high as 19000 F cm^-3.