Investigations Of Polypyrrole-coated Textile Substrate As Supercapacitor Electrode

Inherently conducting polymers (ICPs) are particularly interesting materials for wearablecharge storage devices including batteries and supercapacitors due to their relatively hightheoretical capacities, inherent fast redox switching, good conductivity, mechanical flexibilityand low weight. Polypyrrole (PPy) and its derivatives, are most attractive due to their relativelow oxidation potential, high stability, excellent electrical properties and ease of synthise.However, the poor mechanical properties and processing performance limit their application.In this thesis, flexible supercapacitor electrodes that showed possessing excellentelectrochemical properties were obtained by controlling the morphlogy of the PPy on thetextile substrates (including cotton and bacteria cellulose membrane) using cetyl trimethylammonium bromide (CTAB), sodium dodecyl benzene sulfonate (SDBS) and lignin sulfonatesodium (LGS) as templates. The detailed results were included:(1) We used an everyday cotton fabric coated with poly(pyrrole) as flexible electrodes.Poly(pyrrole) nanoparticles were synthesized on the fabrics via a simple chemicalpolymerization process with the mixed surfactants of cetyltrimethylammonium bromide(CTAB) and sodium dodecyl benzene sulfonate (SDBS) as soft template. A highly conductivefabric with surface resistance of14/□could be produced by changing concentration ofsurfactant. Such a conductive textile showed outstanding flexibility and stretchability anddemonstrated strong adhesion between the PPy and the cellulose fiber. The fabric electrodeexhibited a discharge capacity of51.7mAh/g with high cycling stability (negligible decayafter100cycles).(2) Polypyrrole/lignosulfonate (PPy/LGS) coated on cotton fabrics have been preparedvia situ oxidation polymerization of pyrrole in the presence of lignosulfonate as both templateand dopant. The mass loading on the fabric samples decreased dramatically with theincreased LGS content. The electrical conductivity of the coated fabrics achieved3.03S/cmunder the optimized conditions. The electrochemical properties of the coated fabrics were investigated using cyclic voltammetry and galvanostatic charge–discharge measurements.The specific capacitance of the coated fabrics could be as high as304F/g at a current densityof0.1A/g in aqueous electrolyte. These novel fabrics are desirable for applications inwearable supercapacitors.(3) Conductive nanocomposite membranes of polypyrrole/bacterial cellulose (PPy/BC)were fabricated in situ by oxidative polymerization of pyrrole with iron (III) chloride as anoxi-dant and BC as a template. The morphology of the PPy/BC membrane indicated that PPynanoparticles deposited on the BC surface connected to form a continuous nanosheathstructure by taking along the BC nanofiber. The flexible PPy/BC membrane obtained with theoptimized reaction condition exhibited a high electrical conductivity of3.9S/cm, which washardly affected by bending stress. The PPy/BC membrane could be directly used as flexiblesupercapacitor electrodes, with a maximum discharge capacity of101.9mAh/g (459.5F/g) at0.16A/g current density. The capacity decreased with charge/discharge cycling, which isattributed to mechanical degradation of PPy which can be concluded by the results ofscanning electron microscopy (SEM).(4) Cotton fabrics were coated with conducting polypyrrole (PPy) by mistpolymerization derived from aqueous solution of pyrrole (Py) with ferric chloride (FeCl3) asoxidant. The polymerization conditions, such as the reaction time, the concentrations ofmonomer and oxidant, were systematically investigated. The prepared PPy-coated fabricscould keep their temperature at about24°C–44°C with varying a fixed DC voltage of1V–3V. The results indicated that these PPy-coated fabrics can be used potentially as heatingpads and integrated into the apparel to make the wearer warm enough using a portable battery.Furthermore, such fabrics having flexibility and breathability are more comfortable than thefabrics treated through the conventional heating pads.