Preparation And Electrochemical Properties Of Crystal Shell Polypyrrole Hydrogel And Porous Polyaniline Microsphere

Supercapacitors as a type of novel energy storage devices present promising combination of features such as fast charge/discharge rate,high power density and excellent cycling stability,which have great potential for application in field of electric vehicle,electronic information,national defense,military industry and aerospace.The key of developing supercapacitors is to design high performance electrode materials.Conductive polymers such as polyaniline and polypyrrole have merits of high electroactivity,high conductivity,facile preparation and low price,which are very promising electrode materials for supercapacitors.Moreover,conductivity polymer hydrogels that combine advantages of excellent electrochemical performance of conductivity polymer and good flexibility and biocompatibility of hydrogels,can be used as electrode materials to assemble flexible supercapacitors for flexible/wearable electronic device applications.Whereas,conductive polymers experience volume change during repeated charge/discharge process,which severely decrease their cycling life.Moreover,synthesis methods and reaction conditions have great influence on microstructure and morphology of conductive polymers.Therefore,realizing controllable synthesis of conductive polymers and construct stable structure are very important to achieve high performance conductive polymer-based electrode materials.In this work,polyaniline and polypyrrole are employed as electrode materials,2-methylimidazole and NaCl are utilized to manipulate their microstructure and morphology,and synthesis nanocrystal reinforced polypyrrole hydrogel and porous polyaniline microspheres.Systematically and thoroughly investigate the mechanical and electrochemical performance of asprepared materials.Specific research content is described as follows:(1)PPy-MeIm copolymer hydrogels(m-PPy)are prepared in ice-bath condition through simple oxidative polymerization using pyrrole(Py)and 2methylimidazole(MeIm)as raw materials and FeCl₃ as oxidant.m-PPy hpydrogels possess 3D porous network crosslinked by nanoparticles.These nanoparticles present a core-shell structure,in which the amorphous core is consisted of PPy-MeIm copolymers and nanocrystal shell is consisted of MeIm oligomers.The effect of proportion of raw materials,concentration of pyrrole and 2-methylimidazole and the reaction temperature on the microstructure,morphology,mechanical and electrochemical performance of as-prepared hydrogels are systematically investigated.m-PPy_3:3 hydrogel shows excellent comprehensive performance.The m-PPy_3:3 hydrogel can sustain 21.1 kPa compressive strength under 50%strain,and even sustain 200 kPa compressive strength under 80%strain,due to the formation of nanocrystal shell that provide good support and dissipate energy.m-PPy_3:3 hydrogel exhibits a gravimetric specific capacitance of 536 F g^-1 and a rate capability of 51%in a current range of 1-20 A g^-1.Flexible solid-state supercapacitor(FSC)has been assembled using m-PPy_3:3 hydrogels as electrodes and PVA-H₂SO₄ as gel electrolyte.The FSC possesses an areal specific capacitance of 603 mF cm^-2 at a current density of 1 mA cm-1 and energy density of 53.6 ?Wh cm^-2 at a power density of 396?W cm^-2.The FSC shows stable electrochemical properties under different bending operations,and can maintain almost 100%of capacitance after 2000 cycles of 90° bending operation and maintain 91%of capacitance after 10000 cycles of 90° bending operation.The as-prepared FSC shows outstanding mechanical and electrochemical performance,which is promising candidate in flexible supercapacitor applications.(2)Porous polyaniline microspheres are prepared in ice salt bath condition,by using high concentration NaCl solution as template and ammonium persulfate as oxidant to polymerize polyaniline.The high concentration NaCl solution will be over saturated in low temperature to separate out some NaCl crystals.As Clanions are gathering on the surface of NaCl crystals,it can be used as“crosslinkers”to attract positively charges polyaniline chains.As a result,polyaniline nanowires would nuclei and grow on the surface of NaCl crystal to form porous polyaniline microspheres when the NaCl crystals are removed.PANI_Na-32 possesses a specific capacitance of 360 F g^-1 at a current density of 1 A g^-1 and a rate capability of 42%in a current density range of 1-20 A g^-1.The supercapacitor assembled by PANI_Na-32 exhibits a specific capacitance of 300 F g^-1 at a current density of 1 A g^-1 and energy density of 6.67 W h kg^-1.The asprepared porous polyaniline microspheres very meaningful as a guidance for the controllable preparation of polyaniline.