Preparation Of Novel Carbon Based Flexible Film And Research On Its Supercapacitor Performance

With the emergence of wearable electronics,much attention has been paid on flexible energy storage devices.Owing to the rapid charge/discharge ability,long cycling life,safety etc,flexible supercapacitor is recognized as one of the ideal flexible energy storage devices.For flexible supercapacitor,as one of the core components,flexible electrode material has a decisive influence on its capacitive property,bending performance and cycling stability.Due to the high electrical conductivity,abundant morphologies,high stability etc,carbon based flexible film electrode becomes a research hotspot in recent years and achieves significant progress.However,usually,there still remains some issues for these electrodes,such as:low material utilization rate,relative low rate capability and low specific capacitance?especially for the electrode with high mass loading?.Therefore,it is of great significance to develop high mass loading carbon based flexible electrode with good rate performance and high specific capacitance.Based on these,this dissertation focuses on porous carbon and graphene materials and a number of studies are carried out to improve the charge transfer speed and storage performance of film electrodes.The specific researches are as follows:?1?Binder-free porous carbon film with outstanding rate capability is prepared by solute and solvent phase separation method.The morphologies and pore structure of the porous carbon films can be tailored by the solvents and the amount of catalyst,which can be used to further optimize the capacitive properties.Research results show that,when dipropylene glycol is adopted as the solvent and the amount of HI acid catalyst is 0.5 g?account for 12.5 wt%of the total mass of solvent and solute?,the prepared porous carbon film is composed by interconnected carbon sphere?CS?.Moreover,it is not only with hierarchically structure,but also with high specific surface area.Attributed to the favorable morphology and structure,the film is with excellent rate performance:When the current density improves from 1 A g^-1 to 100 A g^-1,the capacitance retention is as high as 83.1%.Besides,the flexible supercapacitor displays a capacitance retention of 97.5%under bending state,showing good electrochemical stability.?2?Owing to Cl atom is with high electronegativity,the strategy of doping Cl atom into graphene is proposed to induce electron withdrawing effect to obtain Cl-doped reduced graphene oxide film?Cl-RGOF?with significant enhanced conductivity.Owing to this feature,the electron transfer performance of Cl-RGOF improves dramatically when compared with undoped reduced graphene oxide film.Results show that when the mass loading of Cl-RGOF increases from 1 mg cm^-2 to commercial-level of 10 mg cm^-2,the specific areal capacitance grows near-linearly.The Cl-RGOF with high mass loading shows a high specific areal capacitance of 2312 mF cm^-2 in flexible supercapacitor,and can remain 78.7%capacitance when the current density increases 20-fold.Additional,the flexible supercapacitor can deliver a high areal energy density of 160.6?Wh cm^-2.Besides,the capacitance retention of the flexible supercapacitor under different bending angles is as high as 99%,and can also remain 98%capacitance after 500-time bending.?3?Based on the above two researches,solute and solvent phase separation method is adopted to prepare self-assembled micro CSs with large amount of pores.Then the CSs are added into Cl-RGOF to increase the porosity,which leads to there being more ion transportation paths in composite film.Results show that,when compared with Cl-RGOF,CS/Cl-RGOF shows better capacitive performance.When the mass loading of CS/Cl-RGOF is low,the specific gravimetric capacitance at 1 A g^-1 is 213.5 F g^-1.When the mass loading improves to 18 mg cm^-2,the specific areal capacitance at 1 mA cm^-2 is as high as4232 mF cm^-2,and remains 70.6%capacitance when the current density increases 50-fold.Accordingly,the energy density of the corresponding supercapacitor is as high as293.89?Wh cm^-2 at the power density of 0.5 mW cm^-2.Additional,the flexible supercapacitor based on the films shows capacitance retention of 94%after 500-time bending and can also remain>97.3%capacitance under various bending angles,showing good electrochemical stability under bending states.?4?By utilizing the microscopic force in graphene oxide film,fluffy porous graphene hydrogel framework is constructed,and 2,6-diaminoanthraquinone?DAA?molecule with multiple redox ability is introduced into the above framework simultaneously.Finally,hierarchically DAA-graphene hydrogel film?DAA-GHF?is prepared.Benefited from the excellent porous structure and high pseudocapacitance of DAA,DAA-GHF is endowed with excellent charge transfer and charge storage property.Results show that the specific gravimetric capacitance at 1 A g^-1 of DAA-GHF with low mass loading is as high as 394.3 F g^-1,which is 2-times higher than the pure GHF.When at 100 A g^-1,the specific gravimetric capacitance is 273.2 F g^-1,remaining 69.3%,comparable to that of GHF.Moreover,DAA-GHF with mass loading close to commercial-level shows 335F g^-1 at 1 A g^-1,3076.5 mF cm^-2 at 1 mA cm^-2 and 73.1%capacitance retention at 50mA cm^-2.Additional,the DAA-GHF based flexible supercapacitor shows a capacitance retention higher than 93.5%under various bending angles and can maintain 94%capacitance after 500-time bending,displaying good electrochemical stability.