SPIN RELAXATION STUDY OF 7LI DYNAMICS IN POLYMER GEL ELECTROLYTES

M. BRINKKOTER; M. GOUVERNEUR; F. VACA CHAVEZ; P. SEBASTIAO; M. SCHOENHOFF

Congreso; Euromar 2015; 2015

In order to analyse the mobility of the ions in electrolyte systems, the local ion dynamics can be studied byusing spinlatticeNMR relaxation measurements (T1) and by describing the temperature and frequencydependent data by different models. Ternary polymer gel electrolytes consisting of an ionic liquid, a polymerand a lithium salt are promising materials for a compromise between sufficient conductivity and mechanicalstability in lithium ion conducting battery electrolytes. In particular, poly(ionic liquids) such as for examplepoly(diallyldimethylammonium) bis(trifluoromethanesulfonyl) imide (PDADMATFSI) were recently introduced asthe polymeric component .Here, we compare two ternary polymer electrolyte systems, containing either PDADMATFSI or polyethyleneoxide (PEO), which are based on the ionic liquid 1butyl1methylpyrrolidiniumbis(trifluoromethyl sulfonyl)imide(P14TFSI) and LiTFSI. We study the influence of the polymers on the local lithium ion dynamic at a constantlithium ion concentration using T1 relaxation measurements which were performed at different frequencies andat different temperatures. From the relaxation experiments we can conclude that the local lithium mobility andthe local lithium environment is influenced by the type of polymer and by the polymer concentration. It ispossible to describe the data by a motional model of the Li dynamics: We fit the lithium data assuming the ColeDavidsonmodel with Arrhenius behavior and a temperature dependent prefactor. The local activation energy isslightly increasing for higher amount of PEO and slightly decreasing for higher amount of PDADMATFSI. Theresults show that PDADMATFSI has a more beneficial effect on the local Li dynamics in comparison to PEO,as it hinders Li motion to a lesser extent.