Li+ Ion Transport in Polymer Electrolytes Based on a Glyme-Li Salt Solvate Ionic Liquid

Abstract

Keywords: solvate ionic liquid polymer electrolyte polymer-in-salt ionicity glyme A B S T R A C T Polymer electrolytes (PEs) have served as the focus of intensive research as new ion-conducting materials, especially for lithium battery applications. A new strategy to develop fast lithium-conducting PEs is reported here. The thermal, ionic transport, and electrochemical properties of polymer solutions in a glyme-Li salt solvate ionic liquid, [Li(G4) 1 ][TFSA], composed of an equimolar mixture of lithium bis (trifluoromethanesulfonyl) amide (Li[TFSA]) and tetraglyme (G4), were characterized. Poly(ethylene oxide) (PEO), poly(methyl methacrylate) (PMMA), and poly(butyl acrylate) (PBA) were combined with [Li(G4) 1 ][TFSA] in order to explore the effects of polymer structure on the properties. The self-diffusion coefficient ratio of the glyme and Li + ions (D G /D Li ) was investigated to evaluate the stability of the complex (solvate) cations. The D G /D Li values suggested that the [Li(G4) 1 ] + complex cations underwent a ligand exchange reaction between G4 and PEO in the PEO-based solution, whereas the cations remained stable (D G /D Li = 1) in the PMMA-and PBA-based solutions. The robustness of the [Li(G4) 1 ] + complex cations in the PMMA-and PBA-based solutions was reflected in high weight-loss temperature, greater Li transference number, and high oxidative stability.Owing to the lower glass transition temperature and low affinity towards Li + ions, the PBA-based solutions yielded superior lithium transport properties (ionic conductivity of 10 À4 $10 À3 Scm À1 and Li transference number as high as 0.5) among the investigated polymer solutions.

A review of NMR methods used in the study of the structure and dynamics of ionic liquids

“…This suggests that the diffusional activation energy of Li + cation is not influenced by the addition of polymer to the IL mixtures . The diffusional motion of polymeric solutions of glyme‐Li + salt mixtures has been studied by taking an equimolar mixtures of LiTFSI in tetraglyme ([Li(G4) 1 ][TFSI]) known as the solvated IL (SILs) . Various polymers such as PEO, PMMA, and PBA and its effects on the stability of complex lithium cation ([Li(G4) 1 ] + ) have been studied from the ratio of the self‐diffusion coefficients of glyme and Li + cation (D G /D Li ).…”

“…Various polymers such as PEO, PMMA, and PBA and its effects on the stability of complex lithium cation ([Li(G4) 1 ] + ) have been studied from the ratio of the self‐diffusion coefficients of glyme and Li + cation (D G /D Li ). The ratio indicates that a ligand exchange reaction has been taken place between the G4 and PEO in the PEO‐based mixture; however, the complex cation is stable in the PMMA‐ and PBA‐based solutions with D G /D Li = 1 . In another report, the effect of various solvents on the stability of two SILs, namely, [Li(G3)][TFSA] and [Li(G4)][TFSA] has been studied through the self‐diffusion measurements .…”

Polymer Electrolytes Containing Solvate Ionic Liquids: A New Approach To Achieve High Ionic Conductivity, Thermal Stability, and a Wide Potential Window

“…PMMA, PBA, and PEO are compatible with SILs, as we have reported previously. 24 The stabilities of the complex cation structure of [Li(glyme)] + in the gels were evaluated based on the ratio of self-diffusion coefficients of Li + and glyme and molecular dynamics (MD) simulations. In addition, thermogravimetric measurements were carried out to evaluate the thermal stability of the gels.…”

“…Previously, it has been reported that Li + ligand exchange took place in a mixture of PEO and SIL and the uncoordinated glyme was liberated from [Li(glyme)] + . 24 Polyethers form complexes with alkali metal cations, 33 electrolytes are also shown in Table 3. The conductivity of the SMS-based electrolyte declined to nearly one-tenth of that of [Li(G4)][TFSA] on the addition of the triblock copolymer.…”

Solid terpolymer electrolyte based on poly(vinyl butyral‐co‐vinyl alcohol‐co‐vinyl acetate) incorporated with lithium salt and tetraglyme for EDLCs

“…Based on the graph, the highest ionic conductivity was found to be 21.9 µS cm −1 for G20. The significant increase of ionic conductivity with the addition of tetraglyme is due to the presence of abundant oxygen‐containing functional group in tetraglyme, which provides more charge carrier mobility . Besides, tetraglyme has glyme molecules which can solvate Li‐salt to form Li complex form, [Li(glyme) 1 ] + .…”