Spin relaxation studies of Li⁺ ion dynamics in polymer gel electrolytes

Abstract

Two ternary polymer gel electrolyte systems are compared, containing either polyethylene oxide (PEO) or the poly-ionic liquid poly(diallyldimethylammonium) bis(trifluoromethyl sulfonyl)imide (PDADMA-TFSI). Both gel types are based on the ionic liquid 1-butyl-1-methylpyrrolidinium bis(trifluoromethyl sulfonyl)imide (PTFSI) and LiTFSI. We study the influence of the polymers on the local lithium ion dynamics at different polymer concentrations using Li spin-lattice relaxation data in dependence on frequency and temperature. In all cases the relaxation rates are well described by the Cole-Davidson motional model with Arrhenius dependence of the correlation time and a temperature dependent quadrupole coupling constant. For both polymers the correlation times are found to increase with polymer concentration. The activation energy of local motions slightly increases with increasing PEO concentration, and slightly decreases with increasing PDADMA-TFSI concentration. Thus the local Li motion is reduced by the presence of either polymer; however, the reduction is less effective in the PDADMA samples. We thus conclude that mechanical stabilization of a liquid electrolyte by a polymer can be achieved at a lower decrease of Li motion when a cationic polymer is used instead of PEO.

Influence of Cationic Poly(ionic liquid) Architecture on the Ion Dynamics in Polymer Gel Electrolytes

“…In spite of the lower local activation energy, the correlation times are higher for the PIL2–4 ter systems. However, such an opposing trend of correlation time and activation energy is in accordance with previous results for PIL1 …”

“…A strategy to hinder this migration toward the anode is to break the lithium anion cluster. In recent studies, we have shown that these clusters are partially suppressed if the cationic polymer PDADMA + , corresponding to PIL1 in the present study, is used. , …”

“…In recent studies, we have shown that these clusters are partially suppressed if the cationic polymer PDADMA + , corresponding to PIL1 in the present study, is used. 17,54 In Table 3, the highest local activation energy E A,T1 and the lowest correlation time are obtained for the PIL1 ter system. Changes of the local Li dynamics by the presence of a polymer can be induced by alterations in the lithium-TFSA-clusters.…”

Polymer‐Induced Inversion of the Li+ Drift Direction in Ionic Liquid‐Based Ternary Polymer Electrolytes

“…[ 10 ] It was shown that the specific interactions of the functional polymer groups with the ionic constituents can significantly alter ion transport. [ 9b,11 ]…”

Dynamics of binary mixtures of an ionic liquid and ethanol by NMR

“…Regarding their applications in industry, ILs have gained special interest because they are considered as alternative solvents in many applications because of their unique properties such as nonflammability, negligible vapor pressure, and exceptional chemical and thermal stability . These properties make ILs very attractive materials to be used as dye‐sensitized solar cells, green solvents with low environmental impact, the design of IL crystals, and part of electrolytes in lithium‐ion batteries, among many other applications …”