Polyethylene Oxide (PEO)-based Polymer Electrolytes And Its Application In Flexible Supercapacitors

In recent years,with the progress of society and the rapid development of electronic technology,numerous electronic devices are developing toward miniaturization,portability and flexibility.One of the challenges in developing flexible electronic devices is to lighten and flex energy storage devices that match them.Flexible supercapacitors,as a new type of energy storage device,exhibit higher power density,faster charge and discharge speed,and longer cycle life than lithium-ion batteries,has become a research hotspot in the field of energy storage devices.Flexible supercapacitors usually consist of flexible electrodes,polymer electrolytes,current collectors,and flexible packaging materials.Among them,polymer electrolytes,as an essential part of flexible supercapacitors,have an important impact on the overall performance of supercapacitors.Therefore,designing and constructing new high-performance polymer electrolytes have become a top priority.Polyethylene oxide（PEO）-based polymer electrolytes,which are prepared by mixing the PEO with several lithium salts,have been extensively studied in recent years.The dissociation and migration of the Li cation is related to the ether oxygen atoms（-CH₂-CH₂-O-）on the amorphous segments of the PEO chain with the breaking/forming lithium-oxygen（Li-O）bonds.However,the regularity of the molecular chain of the PEO polymer itself makes it relatively high crystallinity at room temperature,which results in the low room temperature ionic conductivity of the PEO based polymer electrolyte;meanwhile,the lower melting point of PEO makes it poor thermal stability and mechanical properties,which limits its practical application in the field of polymer electrolyte matrix.As an important part of solid-state supercapacitors,the polymer electrolyte not only plays a role of ions transportation,but also plays a role of isolating the electrode to prevent its short circuit.Therefore,the good polymer electrolyte candidate should have strong mechanical properties.Moreover,supercapacitors have been gradually applied in extreme environments such as military weapons,aerospace and borehole operation,thus the requirements of polymer electrolytes used in high temperature have also increased.To solve the problems of current PEO-based polymer electrolytes,i.e.,low ionic conductivity at room temperature,poor mechanical properties and thermal stability,and large contact resistance between the electrolyte-electrode interface,we combined poly（aryl ether ketone）s special engineering plastics and other molecules with a benzene ring rigid structure with the lithium ion-conducting PEO based polymers through chemically copolymerization,physically blending or chemical crosslinking.Then a series of novel polymer electrolytes（main-chain type,grafted side chain type,cross-linking type）with excellent comprehensive properties were fabricated and used in flexible supercapacitors.The relationship between the micro-structure of the novel PEO based polymer electrolytes and its functional properties were explored in detail,and the empirical regularity of design and preparation of polymer electrolytes and its application in flexible supercapacitors were obtained.The research in this paper provides new approaches for the design and construction of new polymer electrolytes and flexible supercapacitors.