Preparation And Their Capacitance Properties Of Micro-nano Structure Polyaniline Composites

Conductive polymer materials,due to their low cost,simple synthesis method and large theoretical specific capacitance,have been regarded as the most promising commercial electrode materials in supercapacitors.However,polyaniline itself is difficult to melt and processability is poor.And it is easy to cause large volume shrinkage and expansion during charging and discharging,which limits the improvement of electrochemical performance.By preparing the composite material from conductive polymer and carbon material in a certain manner,the synergistic effect of the two materials can be maximized,thereby improving the electrochemical performance of the composite material.In this paper,conductive polymer polyaniline(PANI)and carbon materials(resorcinol resin-based carbon spheres and polyacrylonitrile-based carbon fibers)are combined into a composite of yolk-shell structure and core-sheath structure respectively.The regulation of composition,structure,size and morphology are controlled by changing the experimental conditions.Furthermore,the electrochemical performance are also studied.Firstly,a thermosetting resorcinol resin was used as a precursor by a polycondensation reaction method.Then the surface of the precursor was coated with silica by a sol-gel method,and then the product was carbonized to obtain a C@SiO2 microsphere.The yolk-shell structure of C@PANI composite was obtained by in-situ polymerization of aniline and strong alkali etching.The structure and morphology of the composites were controlled by changing the amount of aniline monomer.The SEM,TEM,FT-IR,XRD and BET were used to characterize and test.The electrochemical properties of the composites were also studied.The results show that the yolk-shell C@PANI(1:1.5)composite has a fine spherical shape and a rough surface with a large number of fiber protrusions.The specific surface area is 105 m2/g,which helps the electrolyte to fully infiltrate and exhibits the best capacitance performance.At a current density of 0.2A/g,the composites' specific capacitance is as high as 242 F/g.After charging and discharging 5000 times at a current density of 10 A/g,the specific capacitance retention rate is still as high as 83.56%,which is much larger than pure polyaniline and carbon material.It shows that the composite material has outstanding electrochemical performance.The polyacrylonitrile was spun into a fiber of uniform diameter by electrospinning,followed by pre-oxidation and high-temperature carbonization to obtain a polyacrylonitrile-based carbon fiber.Then,the activated carbon fiber was obtained by secondary activation with KOH,and finally the PANI was coated on the activated carbon fiber by in-situ polymerization of the aniline monomer to obtain a core-sheath structure composite material.The composites were characterized by SEM,TEM,FT-IR,XRD and BET.At the same time,the composites'electrochemical properties were tested.The structure and morphology of the composites were controlled by changing the amount of aniline monomer,and the influence of different aniline monomer dosages on the electrochemical properties of the composites was investigated.The results show that when the mass ratio of aniline monomer to carbon fiber is 1:1,the obtained composite material ACF@PANI(1:1)has the best electrochemical performance.Its specific capacitance is as high as 537 F/g at 0.2A/g current density.After charging and discharging 5000 times at a current density of 10 A/g,the specific capacitance is only attenuated by 23.74%,which shows excellent capacitance performance.