The Research On Redox Electroactive Organic Polymers Modified Carbon Based Flexible Supercapacitors

Flexible supercapacitor have the advantages of high power density,long cycle life,excellent flexibility,light weight,small size,and convenient integration into electronic devices,making it the most promising choice for future energy storage.To better meet its practical application in portable/wearable electronic devices,low cost,environmental friendly and electrochemical stability under different stress and low temperature are also important factors that cannot be ignored.However,building a new type of flexible supercapacitor that simultaneously possesses these excellent characteristics still remain huge challenges.To address these issues,robust 3D porous hydrogel electrode,highly integrated electrode with efficient and stable mass loading,and porous thin film electrode with high stacking density are reasonabl y designed and fabricated by electroactive materials and carbon materials with high mechanical strength and electrochemical stability.The electroactive materials include lignosulfonate（Lig）,tannin（TA）and polyaniline（PANI）,which containing high pseudocapacitance.The formation mechanism,chemical structure,mechanical properties,reinforcement and toughening mechanism,as well as their applications in flexible supercapacitors were studied.（1）The fabrication of robust Lig/PANI hydrogel with 3D porous structure.Lig/PANI hydrogel was obtained through the oxidative polymerization of aniline using electroactive biomass lignosulfonate（Lig）as template and dopant.The hydrogen quinone interconversion of Lig provides additional pseudocapacitance,while the-SO₃^-can stably dope PANI and promote its redox reaction,thereby achieving high electrochemical performance and good compression strength（30.4 k Pa）in Lig/PANI hydrogel.The solid-state supercapacitor based on Lig/PANI hydrogel shows superior capacitance(849 F g^-1),energy density(18.9 Wh kg^-1),and high stability under bending state（no capacitance decay after bending 1000 times）.（2）The construction of a highly integrated electrode with efficient and stable mass loading.Firstly,the functionalized graphene/functionalized carbon cloth（FGH/FCC）hydrogel was formed through one-step hydrothermal treatment of oxidized CC submerged in a mixture of graphene oxide（GO）and p-phenylenediamine（PPD）.Then,FGH/FCC was adopted as a scaffold to load a Lig/PANI hydrogel via in situ polymerization of aniline in the presence of lignosulfonate,and finally obtain the integrated Lig/PANI/FGH/FCC textile.Due to the co-doping effect of GO and CC by PPD,the FGH was firmly fixed in the CC framework through conjugated and covalent bonds,and filled the gaps and large pores in CC,ultimately achieving low interfacial resistance and high mass loading in the corrspongding electrode.The flexible all-solid-state supercapacitor assembled with Lig/PANI/FGH/FCC shows outstanding areal capacitance(1156 m F cm^-2),excellent energy density(160.6μWh cm^-2 at 1000μWh cm^-2),excellent cycling stability and flexibility.（3）The biomimetic desigh of carbon nanotube@polyaniline/reduced graphene oxide（CNT@PANI/rGO）film with high strength and toughness.First,a core-shell structured CNT@PANI nanowire was prepared through an in-situ polymerization of aniline in the presence of CNT.Then the CNT@PANI was assembled with rGO through vacuum filtration followed by hydrothermal treatment,finally formed a lamellar porous structure of CNT@PANI/rGO thin film.Due to the thin layer of PANI coated on CNT,CNT@PANI nanowires intercalate into the rGO interlayers to interlock the nanosheets,result in high tensile strength（123.2 MPa）and significantly enhanced toughness(7.6MJ m^-3)of CNT@PANI/rGO.The supercapacitor based on CNT@PANI/rGO shows outstanding volumetric capacitance(419.2 F cm^-3),energy density(14.6 Wh L^-1)and bending stability.（4）The design and constraction of a porous CNT@PANI/rGO/TA film with high strength,toughness,and high packing density.Electroactive biomass TA was used as glue to further stick CNT@PANI and rGO together via vacuum filtration and hydrothermal treatment,thus result in a porous CNT@PANI/rGO/TA with high packing density.The abundant interface interactions between TA,rGO,and PANI@CNT endow the CNT@PANI/rGO/TA enhanced strength（174.6 MPa）and toughness(9.17 MJ m^-3).The all-solid-state flexible supercapacitor assembled with CNT@PANI/rGO/TA has excellent volumetric capacitance(548.6 F cm^-3)and low temperature tolerance(the specific capacitance of 454.9 F cm^-3 at-40℃).