Synthesis And Electrochemical Performance Of One-Dimensional Textile Yarn Electrode Materials

With the depletion of fossil fuel energy and the serious environmental pollution issues,developing clean energy sources is very important.In recent years,energy storage devices such as supercapacitors and batteries have drawn more and more attention because they can power various electronic devices.Among various energy storage devices,supercapacitors possess excellent properties including fast charge and discharge rate,high power density,high specific capacitance,light weight,small size,long service life and safety.Recently,one-dimensional flexible supercapacitors have great potential in the fields of wearable electronic devices because they knitted into daily clothing.In this thesis,textile yarns were used as the flexible substrate to prepare high-performance yarn electrode materials.The specific research contents are as follows:(1)A composite yarn electrode was synthesized by coating cotton fiber cores with graphene(G)sheets inside cotton yarns(CT)and followed by further growing polyaniline(PANI)nanowire array layers through in situ polymerization of aniline.The three-dimensional(3D)electrode structure facilitates the electrolyte ion diffusion.The electron transportation is greatly enhanced by the 3D conductive network which is constructed by graphene sheet layers.The PANI nanowires which were bridged by graphene sheets further increase the electrochemically active surface area of PANI and the electron transportation.The unique electrode structure endows the cotton/graphene/polyaniline(CT/G/PANI)yarn electrode with excellent electrochemical performance.The maximum areal capacitance and capacitance retention reached 246 mF/cm~2at5mV/s and 98%after 3800 cycles,respectively.A symmetric solid-state yarn supercapacitor fabricated by the CT/G/PANI electrode achieved a high energy density of 9.7?Wh/cm~2at a power density of 840.9?W/cm~2.(2)A textile yarn electrode material was synthesized by electroless plating Ni with cotton fiber and followed by further growing Co-Ni LDH nanosheet array layers.The cotton/Ni/Co-Ni LDH(CT/Ni/Co-Ni LDH)composite yarn electrode material with 3D porous electrode structure facilitates to promote the electrolyte ion diffusion.The electron transportation is enhanced by the metallic Ni layers.The nanosheet-like Co-Ni LDH provide high electrochemically active surface.The CT/Ni/Co-Ni LDH electrode show an excellent electrochemical performance.The maximum areal capacitance reached 1.26F/cm~2 at scanning rate of 5mV/s.A symmetric solid-state yarn super-capacitor which was fabricated by two CT/Ni/Co-Ni LDH electrodes achieved a high energy density of 9.3?Wh/cm~2at a power density of 43.99?W/cm~2.Its cycle stability was 79%after cycling 2000 times.