Influence of Solvating Plasticizer on Ion Conduction of Polysiloxane Single-Ion Conductors

Abstract

Lithium ion conduction is investigated for a polysiloxane-based single-ion conductor containing weak-binding borates and cyclic carbonate side chains, plasticized with poly(ethylene glycol) (PEG). The addition of PEG increases the conductivity by up to 3 orders of magnitude compared to the host ionomer. A physical model of electrode polarization is used to separate ionic conductivity of the ionomers into number density of simultaneously conducting ions and their mobility. A reduction in T g with increasing PEG content boosts ion mobility owing to an increase in polymer chain flexibility. Further, the PEG ether oxygens lower the activation energy of simultaneously conducting ions (from 14 to 8 kJ/mol), significantly increasing conducting ion content by 100X, suggesting that ion aggregates observed in the host ionomer are solvated by PEG. This directly reflects the disappearance of an ion aggregation peak observed in X-ray scattering, and an initial large increase in static dielectric constant (ε s ), upon addition of PEG, suggesting that ionic aggregation is significantly reduced by a small amount of PEG. Further dilution with lower dielectric constant PEG gradually reduces ε s .

A Single‐Ion Conducting Borate Network Polymer as a Viable Quasi‐Solid Electrolyte for Lithium Metal Batteries

“…At 40 °C, the ionic conductivity of the polymer is 8.5 × 10 −5 S cm −1 in the presence of only 10 wt% plasticizer, and this value increases to 4.8 × 10 −4 S cm −1 with 70 wt% plasticizer (Figure S2, Supporting Information). Polar solvating plasticizers such as propylene carbonate have been shown to facilitate ion dissociation in solid electrolytes, and indeed the fraction of mobile charge carriers in ANP‐5 increases with the plasticizer concentration (Figure S3, Supporting Information), helping to rationalize the observed high ionic conductivity. The polymer exhibits low activation energies in the range of 0.16–0.29 eV (Figure 2a, inset) and can therefore be classified as a superionic conductor—defined as an electrolyte with an ionic conductivity >10 −4 S cm −1 and an activation energy <0.4 eV …”

Recent Research on Strategies to Improve Ion Conduction in Alkali Metal‐Ion Batteries

“…The activation energy of LiBH 4 ‐fumed silica mixture (LF 55 vol% composite) reached 0.43 eV (Figure a), which is much lower than the activation energy of pure LiBH 4 , reflecting the faster Li ion conduction through the interface layer. Choi et al . investigated morphology, ion conduction, and dielectric response of polysiloxane‐based single‐ion conductors containing weak‐binding borates and cyclic carbonate side chains mixed with plasticizing PEG600.…”

“…Copyright (2016) Royal Society of Chemistry. (b) Temperature dependence of ionic conductivity for LiPSBC and its blends with PEG600 (and vs DRS in the inset) . Reprinted (adapted) with permission from ref.…”

Expanding the chemistry of single‐ion conducting poly(ionic liquid)s with polyhedral boron anions

“…However, only a few examples of SICs having anions other than sulfonate derivatives have been studied (Scheme , 13 – 19 ). Among them are the polyelectrolytes with complex aluminate ([Al(OR) 4 ] − ) and thioaluminate ([Al(SR) 4 ] − ) anions (Scheme , 13 , 14 ), 1,2,3‐triazolate anions (Scheme 1, 15 ), various borate anions (Scheme 1, 16 , 17 , 18 ) and phosphate anions (Scheme 1, 19 ). These PILs can be represented as the macromolecular analogues of ILs with [{(CF 3 ) 3 CO} 3 AlFAl{OC(CF 3 ) 3 } 3 ] − , triazolate, BF 4 − , BPh 4 − , bis(salicyl)borate, PO 2 (CF 3 ) 2 and PO 4 (CH 3 ) 2 − anions (Scheme ).…”