Preparation And Performance Investigation Of Singleion Conducting Polymer/PEO Composite Solid Electrolytes

Lithium batteries are considered to be a clean and environmentally friendly energy storage device,they will play a significant role in electric vehicles,smart grids and other fields.Compared with liquid electrolytes used in traditional lithium batteries,solid polymer electrolytes have attracted wide attention as electrolytes for their machinability,high flexibility,light weight and changeable shape.Polyethylene oxide(PEO)is used as a substrate for polymer-based solid electrolytes owing to its low glass transition temperature Tg,melting temperature Tm,as well as its superior ability to dissolve lithium salts.However,the semi-crystalline state of PEO at room temperature inhibits its conductivity to lithium ions(around 10-6 s cm-1 at room temperature),which greatly restricts its application in solid state lithium batteries.Therefore,this research intends to introduce active organic-inorganic hybrid nano-filler and active organic polymer filler into PEO to prepare composite solid electrolytes(CSEs),in order to reduce the crystallinity of PEO matrix and promote the uniform dispersion of filler in PEO,so as to improve the ion conductivity and mechanical strength of solid electrolyte membrane.The main research contents are as follows:(1)The pyridyl disulfide terminated single-ion conducting polymer(py-ss-PLiSSPSI)was synthesized through RAFT(Reversible AdditionFragmentation Chain Transfer)polymerization firstly,then grated onto SiO2 via a thiol-disulfide exchange reaction between SiO2-SH and py-ssPLiSSPSI.The chemical structure,surface morphology and elemental distribution of the prepared polymers and PLiSSPSI-g-SiO2 nanoparticles were analyzed.Then,using PEO/LiTFSI system as the substrate and comparison,the composite solid electrolytes with 2,6 and 10 wt%PLiSSPSI-g-SiO2 nanoparticles(named PLi-g-SiCSE-x,x as the additive amount)were prepared and characterized.The effect of polymer-modified nanoparticle addition content on the electrochemical properties of polymer films was investigated.(2)Two series single-ion conducting star block copolymers with the opposite structure,PLi-(PPM-T)and PPM-(PLi-T),were prepared through RAFT polymerization of LiSSPSI(lithium-ion donator)and PEGMA(EO group container),then the chemical structures of the prepared polymers were analyzed.Subsequently,they were used as active organic fillers and blended with PEO/LiTFSI to prepare CSEs containing 10,20 and 30 wt%copolymers(named PLi(PPM)-CSE-x and PPM(PLi)-CSE-x,x being the additive amount).The effect of the structure and addition of star block copolymers on the electrochemical properties of polymer films was investigated.