Research On Supercapacitor Electrode Based On Polypyrrole/carbon Nanotube/cotton Yarn

Flexible yarn-type supercapacitors not only have the inherent advantages of supercapacitors such as fast charge and discharge rate,environmentally friendly,but also meet the wearable requirements of miniaturization,integration and flexibility,and have a wide application prospect in the energy storage of wearable electronic products.Electrodes,as a key part of supercapacitors,have important research value,but their low capacitance and cyclic stability limit their development.Textile yarns are considered to be good flexible substrates for electrodes due to their advantages of porosity,flexibility and strength.In this paper,cotton yarn?CY?is used as a flexible substrate,multi-walled carbon nanotubes?MWCNTs?and polypyrrole?PPy?are used as active materials,and yarn electrodes with better cycle stability and higher capacitance are prepared by using the synergistic effect of MWCNTs and PPy to increase the capacitance of the electrode,using oxygen plasma modification to improve the bonding force between materials and the cycle stability of the electrode.The main contents of this article are as follows:?1?MWCNTs were coated on the surface of CY by immersion-drying method to prepare MWCNTs/CY yarn electrodes.The effects of immersion times on its morphology,conductivity,and capacitance were studied.The results show that when immersed three times,the specific capacitance of the electrode reaches the maximum,and its surface is basically covered with MWCNTs,and there is no serious stacking,and the conductivity of cotton yarn is significantly improved.?2?In order to further increase the capacitance of the electrode,a chemical oxidation method was used to deposit PPy on the surface of MWCNTs/CY to prepare PPy/MWCNTs/CY yarn electrodes.The effects of PPy polymerization conditions on its morphology and capacitance performance were studied.The results show that the maximum capacitance of the PPy/MWCNTs/CY electrode is 870.52 m F/cm²and PPy is evenly coated on the surface of the yarn when the polymerization time is 2 h,the concentration of pyrrole?Py?is 0.3 mol/L,the amount ratio of Fe Cl₃to Py is 3:2,and the concentration of p-toluenesulfonic acid?Ts OH?is 0.5 mol/L.The capacitance of PPy/MWCNTs/CY electrode is the largest?870.52 m F/cm²?.Then,the PPy/CY electrode was prepared under the optimal process.The results show that compared with PPy/CY electrodes,PPy coating on the surface of PPy/MWCNTs/CY is more uniform,and capacitance and cycle stability are significantly improved.PPy/MWCNTs/CY was used as an electrode to assemble a flexible all-solid-state symmetrical yarn-type supercapacitor?YSC?.Tests showed that YSC has a high energy density?at a charge and discharge current of 1 m A,the energy density is 34.35?Wh/cm²?.?3?In order to further improve the cycling stability of the electrode,oxygen plasma was used to modify MWCNTs/CY,and then PPy was coated with chemical oxidation to prepare polypyrrole/modified multi-wall carbon nanotubes/cotton yarn?PPy/m-MWCNTs/CY?yarn electrode.Then,the morphology,structure and electrochemical performance of yarn electrode were tested.The morphology,structure and electrochemical performance were tested.The electrode was assembled with a modified-flexible solid-state symmetric yarn-type supercapacitor?m-YSC?,and the electrochemical performance of m-YSC was tested.The results show that the modification of oxygen plasma improves the binding force between PPy and MWCNTs,the electrode cycling stability is significantly improved?3000 cycles,the capacitance retention rate is 96.1%?,and m-YSC has a higher energy density?charge and discharge at a current of 1 m A,the energy density is 39.70?Wh/cm²?.