Preparation And Performance Study Of All-solid Flexible Asymmetric Supercapacitor Based On Flexible Substrate

Flexible wearable devices are lightweight,flexible,intelligent and efficient,and can bring transformative development to the wearable field.Compared with traditional lithium batteries,flexible supercapacitors（FSC）have high safety,higher theoretical capacity,and fast charge and discharge characteristics,making them an ideal energy storage device for wearable devices.To meet application requirements,FSC needs to have excellent capacitance,high mechanical durability,and long cycle life,which poses challenges to the design of electrode materials and devices.This paper focuses on the development of high-capacity and high-stability FSC devices,with a focus on the selection and preparation of flexible conductive substrates.A series of methods based on electrodeposition and hydrothermal synthesis were established to construct flexible electrodes.The composition-structure-performance relationship of positive and negative electrode materials such as polypyrrole,manganese oxide,molybdenum sulfide,and hydroxylated iron oxide in FSC was investigated.The prepared FSC not only has the characteristic of high energy density but also has excellent structural stability of FSC devices.The specific research contents are as follows:1.A method of electrodeposition was used to construct polypyrrole nanoparticles on carbon cloth as the positive electrode of the FSC.Tungsten oxide nanowires were synthesized via a hydrothermal method and coated onto conductive titanium foil to serve as the negative electrode.The FSC device was constructed using sulfuric acid/polyvinyl alcohol hydrogel as the gel electrolyte and encapsulated with a polyethylene terephthalate（PET）film.The large surface area of the tungsten oxide nanowire structure provided sufficient active sites for the required electrochemical reactions at the titanium foil/tungsten oxide interface.The constructed FSC device can reach an area capacitance of 570.0 m F cm^-2 at a current density of 1 m A cm^-2,and the obtained power density and energy density are 0.5 m W cm^-2 and 79.2μWh cm^-2,exhibiting excellent electrochemical properties and good mechanical stability.2.In this study,the in-situ loading of electrode materials on flexible conductive substrates was employed to prepare the positive and negative electrodes of the FSC device.The surface electrochemical deposition method was used to deposit manganese dioxide nanosheets on conductive carbon cloth as the positive electrode material,while a composite material consisting of ultra-thin molybdenum sulfide nanosheets and iron oxide nanoparticles was constructed on a molybdenum mesh as the negative electrode material.The FSC device was assembled using a lithium chloride/polyvinyl alcohol gel electrolyte and encapsulated with PET film.The assembled FSC displayed a wide operating voltage window of 2.0 V and exhibited a high specific capacitance of 727.1m F cm^-2 at a current density of 1 m A cm^-2,which resulted in a high energy density of101.0μWh cm^-2 and a power density of 0.5 m W cm^-2.Even under mechanical bending,the FSC showed good cycling stability and excellent electrochemical integrity.3.A new metal-graphene-fabric composite flexible conductive substrate for FSC was prepared.The composite conductive substrate was prepared by depositing metal nickel on the surface of a reduced graphene oxide-fabric coating,and further electrodepositing hydrogen cobalt and hydroxylated iron oxide nanorod arrays to make flexible positive and negative electrodes,respectively.The flexible device was composed of potassium hydroxide/polyvinyl alcohol as the gel electrolyte and further encapsulated with a PET film.In the charge-discharge test,the FSC obtained a capacitance of 155.7 m F cm^-2,a power density of 0.8 m W cm^-2,and an energy density of 36.5μWh cm^-2 at a current density of 1 m A cm^-2.The conductive substrate prepared by this method has the characteristics of lightweight,high flexibility,and excellent conductivity.