| Flexible solid-state supercapacitors are frontrunners in energy storage device technology and have attracted extensive attention owing to recent significant breakthroughs in modern wearable electronics.Polyaniline（PANI）has been widely used for the energy storage applications either as a conducting agent or directly as an electroactive material due to the tunable pseudocapacitive performance owing to its various oxidation states.However,the rigid molecular chain of PANI prevents it from being used as a component of a flexible supercapacitor alone,and it also has problems such as poor rate performance and poor stability due to volume expansion and contraction accompanying the cycling process.Therefore,in this thesis,graphene prepared by different methods is selected as the flexible matrix,and rigid polyaniline is introduced into the graphene layer by different methods to prepare a flexible supercapacitor with excellent stability.Firstly,slightly crumpled graphene nanosheets were prepared via the mild surface modification of the graphene oxide（GO）nanosheets with p-phenylenediamine（PPD）at room temperature to inhibit the restacking of graphene.Owing to the slightly crumpled morphology and plentiful surface functional groups after modification with PPD,the PANI nanorods could be well dispersed in the PGO nanosheets,showing a honeycomb-like network structure with hierarchically porous structure,after vacuum filtration and reduction.The proposed PANI@rPGO composite film electrode showed a high specific capacitance of 734.4 F g-1 at 0.5 A g-11 and a high retention of 110%after5000 cycles.The assembled SSCs possessed high mass and areal specific capacitance of 564.5 F g-1 and 2015.2 mF cm-2 respectively,at the current of 0.5 A g-1,with energy density of 12.5 Wh kg-1(39.4 mWh cm-2)at the power density of 199.3 W kg-1(627.6mW cm-2).Furthermore,the assembled SSCs showed satisfactory cycling stability and excellent flexibility.Secondly,the flexible,bendable and knittable PANI@rEGO/GP electrode with PANI in the honeycomb-like rEGO/GP fiber was fabricated for high performance fiber-shaped solid state supercapacitors,via the in-situ electro-polymerization of the aniline monomer adsorbed in the honeycomb-like rEGO/GP fiber,which was prepared by the wet spinning of the expandable graphene oxide（EGO）with graphite powder as spacer,followed with reduction.Compared with the rEGO/GP@PANI electrode with PANI on the surface,the structural and electrochemical stability have been obviously enhanced for the solid state fiber-shaped symmetric supercapacitor of the proposed PANI@rEGO/GP fiber electrode,demonstrating the promising potential for practical application in the high performance fiber-shaped solid state supercapacitors.Thirdly,the influence of different size“spacing”on the structure and the electrochemical performance of the graphene fiber electrode was studied.The PANI was introduced into graphene fibers with honeycomb-like structure and assemble high-performance flexible solid-state symmetric supercapacitors.The proposed rEGO/CB-30%and rEGO/NC-30%showed a high specific capacitance of 75.7 and 113.0 F cm-3at 0.5 A cm-3.The capacitance of PANI@rEGO/CB and PANI@rEGO/NC is 130.5 and177.5 F cm-33 at 0.5 A cm-3,respectively.The assembled SCs possessed high specific capacitance of 40.7 mF cm-11 at 0.103 mA cm-1.The results show that the graphene fiber with more abundant pore structure has excellent energy storage performance,and the honeycomb rEGO/NC-PANI fiber electrode has a broad application prospect in the field of flexible symmetric solid supercapacitor. |
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