The Effect of Low-Molecular-Weight Poly(ethylene glycol) (PEG) Plasticizers on the Transport Properties of Lithium Fluorosulfonimide Ionic Melt Electrolytes

Abstract

The influence of low-molecular-weight poly(ethylene glycol) (PEG, Mw ≈ 550 Da) plasticizers on the rheology and ion-transport properties of fluorosulfonimide-based polyether ionic melt (IM) electrolytes has been investigated experimentally and via molecular dynamics (MD) simulations. Addition of PEG plasticizer to samples of IM electrolytes caused a decrease in electrolyte viscosity coupled to an increase in ionic conductivity. MD simulations revealed that addition of plasticizer increased self-diffusion coefficients for both cations and anions with the plasticizer being the fastest diffusing species. Application of a VTF model to fit variable-temperature conductivity and fluidity data shows that plasticization decreases the apparent activation energy (Ea) and pre-exponential factor A for ion transport and also for viscous flow. Increased ionic conductivity with plasticization is thought to reflect a combination of factors including lower viscosity and faster polyether chain segmental dynamics in the electrolyte, coupled with a change in the ion transport mechanism to favor ion solvation and transport by polyethers derived from the plasticizer. Current interrupt experiments with Li/electrolyte/Li cells revealed evidence for salt concentration polarization in electrolytes containing large amounts of plasticizer but not in electrolytes without added plasticizer.

In situpolymerization process: an essential design tool for lithium polymer batteries

“…63,[257][258][259] Carbonate solvents, glymes, low molecular weight poly(ethylene glycol), etc., are used for the activation/plasticization of the polymer matrix. [260][261][262] Besides, room-temperature ionic liquids (RTILs) are used as a safe alternative to low boiling point plasticizers, and several studies have been carried out in this direction. [263][264][265][266][267] RTILs as a plasticizer is an interesting case due to several reasons.…”

Elastic Capacitor Electrode Based on Carbon‐embedded Polymer Matrix

“…Combined with the other constituents, it counters the viscous, liquid phasing of PEG. PEG is added as the plasticizer – it participates in the cation mobility (ionic conduction of the electrolyte), coordinating via the oxygen constituent of the PEG chain . Increasing the PEG content ratio will increase the liquidity of the material, and assist in ion transfer – however it must be balanced as too much will weaken and jellify the material to an incontinent level.…”

Evolution of Ion–Ion Interactions and Structures in Smectic Ionic Liquid Crystals

“…Moreover, the [Li[MPEGP] 3 (TFSI) 1 ] 3− cluster formation is in agreement with the trend of the variation of the oxygen coordination number due to the presence of multiple oxygen sources in the mixtures. 15,37 For example, the numbers of oxygen atoms surrounding a Li + cation are ∼2.5 and ∼1.8 from the fluorosulfonimide anion and the polymer plasticizer, respectively, when a polymer plasticizer is added to a fluorosulfonimide-based polyether ionic melt. 37 The ternary mixed polymer electrolyte of low-molecular-weight poly(ethylene oxide) (PEO), LiTFSI, and N-methyl-N-propylpyrrolidinium bis-(trifluoromethanesulfonyl)imide also showed the oxygen coordination number as 4−5 using a PEO molecule containing two to three oxygen atoms, indicating that two PEO molecules are involved in the formation of clusters.…”