Design And Performance Of A Novel Polymer Gel-based Flexible Supercapacitor

With the rapid development of portable,smart and wearable electronics,new challenges are imposed on their energy storage devices,which require such energy storage devices to have good mechanical properties such as good tensile,bending,and compression,and second,good stability and high safety,light weight and excellent electrochemical performance.Due to the high power density,long cycle life and fast charge and discharge rate,supercapacitors become an indispensable new energy storage device in the field of energy at present and in the future.Especially,the flexible supercapacitor prepared by using a gel as an electrolyte has high tensile,bending,and compression mechanical properties,high power density,energy density and long cycle stability.At the same time,by modifying the gel electrolyte to make it self-healing,it has become one of the hotspots in current supercapacitor research.Therefore,in this paper,new polymer gel electrolytes are synthesized by selecting different polymers through doping,cross-linking and other methods,and then the self-healing,integrated and self-healing integrated flexible supercapacitors were designed and assembled with novel polymer gels as electrolytes.The effects of polymer structure and composition on the mechanical properties,electrochemical properties,and self-healing properties of gel electrolytes and supercapacitor devices were studied.The main contents are as follows:1.A novel self-healing B-PVA/KCl/GO gel with boron cross-linking was synthesized in polyvinyl alcohol?PVA?aqueous solution by doping graphene oxide?GO?,KCl and borax solution.The results showed that the GO doping significantly increased the ionic conductivity of the gel.When the addition amount was 2.3 wt%,the ionic conductivity of the B-PVA/KCl/GO gel could reach 47.5 mS/cm.Simultaneously,the B-PVA/KCl/GO gel exhibits excellent self-healing capability that can repair its original configuration with 5 min when it is cut.The self-healing flexible supercapacitor assembled with B-PVA/KCl/GO gel as the electrolyte and separator and activated carbon as the electrode material can achieve an energy density of 5 Wh kg^-1 and a power density of 492.7 W kg^-1 at 1 A g^-1.The specific capacitance is still maintained at about92%of the initial capacitance,and its capacitance performance can still be restored through 7 self-healing cycles.2.Using acrylamide?AAm?as monomer,a ultra-flexible PAM/LiCl gel is prepared by radical polymerization in LiCl aqueous solution.subsequently,using PAM/LiCl gel as a substrate,PPy nanoparticles were deposited on the surface of the gel by in-situ polymerization to form PPy/PAM/LiCl composite film.It is found that the PPy/PAM/LiCl hydrogel can be stretched up to 650%,and tied a knot,twisted,folded,bended and compressed without fracturing.An all-in-one flexible supercapacitor with PPy?electrode?-PAM/LiCl?gel electrolyte?-PPy?electrode?configuration is obtained by cutting off the edge of the gel film.which can obtain a large areal capacitance of 229.8mF/cm² at a current density of 0.8 mA/cm².The capacitance can remain 80%of initial capacitance after 5000 cycles.3.A highly ionic conductive self-healing PVP/PAM/LiCl gel is synthesized bydissolving acrylamide?AAm?monomer powder and LiCl into PVP aqueous solution through chemical and physical crosslinking,the ionic conductivity can reach 84 mS/cm.The excellent self-healing ability of the gel is mainly derived from hydrogen bonding between PVP and PAM molecules.A novel self-healing DA-PPy/PVP/PAM/LiCl gel film is formed by in situ polymerization and deposition of dopamine decorated PPy nanocomposites electrode materials onto the two-sided faces of the self-healing PVP/PAM/LiCl hydrogel support.Which can stretch up to 750%,Simultaneously,the self-healing integrated flexible supercapacitor constructed based on this gel film,can obtain large areal capacitance 308 mF/cm² at 1.0 mA/cm²,achieve repeated healable 5cycles without extra addition and bend different angles?0^o,30°,90°and 180°?with slight performance decay,which suggests that integrated supercapacitor has excellent flexibility.