Study On The Electrode Structure Design Of Cellulose-based Flexible Electrodes With High Mass Loading And Their Application In Supercapacitors

Recently,flexible electronics have shown great promise in wearable electronics,display,sensing,healthcare,and etc.The development and application of flexible electronics rely on the development of suitable flexible energy storage devices that can withstand mechanical deformation.Flexible supercapacitors stand out from numerous electrochemical energy storage devices due to their low-cost,high safety,long lifespan,and high power density,making them ideal energy storage devices for flexible electronics.In addition,replacing traditional fossil resources with green biomass for the development of flexible supercapacitor materials can not only realize high-value utilization of biomass and solve the problem of resources shortage,but also has an important significance for the sustainable development of the environment and energy in the context of energy crisis,environmental pollution,and resource shortage.Among numerous biomass resources,cellulose derived cellulose textiles have been regarded as an ideal substrate for flexible supercapacitors owing to their unique three-dimensional network structure,sustainable nature,mature textile processes,excellent flexibility and wearability.However,the mass loading of active materials on textile substrates is generally very low due to the smooth surface and low specific surface area,while increasing the mass loading of active materials always brings difficulty for electron/ion transport and uncontrolled aggregation of nano-scaled electrochemically active materials,resulting in low energy density.This dissertation explored the cellulose textile as a flexible substrate and studied the loading and efficient utilization of active materials from the perspectives of structure-performance relationship of substrate,interface modification,electrode structure design,and active materials development.Based on these efforts,high mass loading cellulose textile-based flexible electrodes with high energy density were obtained.The main research contents are shown as follows:（1）Structure-performance relationship of cellulose textile and cellulose paper as a flexible substrate was studied based on the characteristics of raw materials and materials structure.Compared to cellulose paper,cellulose textile is convenient to be converted to a highly conductive flexible substrate with excellent mechanical properties through simple carbonization due to its unique textile structure and high crystallinity cellulose fibers.The loading of Mn O₂ pseudocapacitive nanomaterials was studied using carbonized cellulose textile as a flexible substrate.The fabricated Mn O₂/cellulose textile electrode exhibits a high areal capacitance of 1713.5 m F cm^-2,indicating that cellulose textile shows great promise in flexible substrates of supercapacitors.（2）In order to address the aforementioned limitations,a multifunctional interface modification method for active material loading was proposed using cellulose textile as a flexible substrate.An adhesive polydopamine interface was in-situ constructed on cellulose textile through oxidative polymerization of dopamine.The loading of graphene oxide on the adhesive polydopamine interface was studied.The adhesive polydopamine interface can enhance the adhesion and compatibility between nanomaterials and cellulose substrates.After pyrolysis,the polydopamine interface is transformed into a porous nitrogen-doped carbon interface,which can significantly increase the specific surface area of electrode(347.6 m² g^-1),while improving the interfacial conductivity and enhancing the electrochemical activity of the electrode.Based on this multifunctional interface modification,cellulose textile-based flexible electrodes with dramatically improved electrochemical performance were achieved.（3）One-dimensional carbon nanomaterials were deposited on the above multifunctional interface modified cellulose textile to prepare high performance double-layer flexible electrodes with high mass loading.The loading and dispersion of carbon nanotubes and carbon nanofibers on the modified textile were studied by electrophoretic deposition.The modified textile with high specific surface area provides sufficient space for the loading and dispersion of carbon nanomaterials,which is beneficial for improving the stacking state of carbon nanomaterials and maintaining electrode porosity at high mass loading.Thus,rapid electron/ion transfer kinetics of the electrode can be achieved even under high mass loading(30.1 mg cm^-2),resulting in high performance cellulose textile-based flexible electrodes.（4）Conductive polymers were deposited on the above multifunctional interface modified cellulose textile to prepare high performance psuedocapacitive flexible electrodes with high mass loading.The loading and dispersion of polypyrrole nanotubes and polyaniline nanomaterials on the modified textile were studied through electrophoretic deposition and in-situ polymerization.The modified textile with high specific surface area provides sufficient space for the loading and dispersion of conductive polymers,while the nitrogen-doped carbon matrix promotes interfacial electron transport and the stability of conductive polymers.Based on this structure design,high performance cellulose textile-based flexible electrodes with high mass loading were achieved.（5）Further,an efficient synergetic strategy of active material development coupled with electrode structure design was proposed based on the above structure design.Firstly,N/S co-doped graphene-like carbon nanomaterials were prepared using low-cost urea and renewable lignosulfonate as raw materials via a one-step sacrificial template method.Then,a unique pomegranate-like structure was obtained by in-situ growth of N/S co-doped graphene-like carbon in the modified textile framework.N/S co-doped graphene-like carbon networks provide continuous highly conductive pathway for electron transport.The porous framework provides sufficient space to accommodate the N/S co-doped graphene-like carbon,which can maintain electrode porosity at high mass loading.Thus,rapid electron/ion transfer kinetics of the electrode can be achieved even under high mass loading(19.5 mg cm^-2),resulting in high performance cellulose textile-based flexible electrodes.