Synthesis of poly(triethylene oxide glycidyl ether)s for solid polymer electrolytes

Abstract

Well controlled synthesis of Poly[2-(2-(2-methoxyethoxy)ethoxy)ethyl glycidyl ether] (PTG), poly(allyl glycidyl ether)-b-PTG-b-poly(allyl glycidyl ether) (PAGE-b-PTG-b-PAGE) were reported. The triethylene oxide methyl ether side chain is expected to improve the dissociation of the lithium salt, reduce the crystallinity of the polymer backbone and improve the ionic conductivity. PTG was end capped with acrylate forming PTG-diacrylate. Crosslinked solid polymer electrolytes (SPEs) based on PTG-diacrylate, PAGE-b-PTG-b-PAGE polymers are formed via thiol-acrylate linkage and thiol-ene click reactions under UV irradiation. The ionic conductivities obtained with these materials are >10-4 S/cm at 30℃. The Li ion transference number (tLi+) of 0.1–0.3 is the highest for the conventional liquid electrolytes. tLi+>0.3 is achieved in all the cases of the SPEs. Moreover, the lithium plating/stripping tests showed a stable performance for more than 100 h in all the SPEs fabricated. Chapter 1 deals with the general trends and review of the SPEs based on poly(ethylene oxide). Chapter 2 deals with the SPEs formed from end to end crosslinked PTG-diacrylate/poly(ethylene glycol)-diacrylate mixtures with thiol-acrylate crosslinking. SPEs made showed tLi+ of 0.6 and ionic conductivity 4.67 X 10-3 S/cm at 30℃. Lithium stripping/plating tests showed stable performance of more than 150 h without any additives for Li/SPE interfacial stability. The electrochemical stability window is up to 4.8 V which is good for most of the applications. Chapter 3 deals with crosslinked PAGE-b-PTG-b-PAGE with the allyl side chains functionalized by the dimethyl amine. Here, the effect of the side chain and crosslinking has been studied. Crosslinking was achieved by thiol-ene click reaction. tLi+ of 0.48 was achieved, with >100 h Li Stripping/plating stability without any additives. SPEs showed a maximum ionic conductivity of 0.84 X 10-3 S/cm at 30℃. Chapter 4 deals with crosslinked PAGE-b-PTG-b-PAGE with side chains functionalized by cysteine via thiol-ene click reaction. The amine functional group is used for crosslinking using the poly(ethylene oxide) diglycidyl ether. The carboxylic group present acts as a single Li ion conductor. The crosslinker chain length is varied and optimized for conductivity with 0.6 X 10-3 S/cm at 30℃ and tLi+ of 0.78. the Li stripping/plating stability of more than 80 h is achieved without additives.