Gelation of Solvate Ionic Liquid by Self-Assembly of Block Copolymer and Characterization as Polymer Electrolyte

Abstract

We report a new class of polymer electrolytes that exhibit high Li + -ionic conductivity and thermal stability up to 200 °C. The polymer electrolyte consists of a solvate ionic liquid ([Li(G4)][TFSA]), comprising an equimolar mixture of lithium bis(trifluoromethanesulfonyl)amide (Li[TFSA]) and tetraglyme (G4), and a well-defined ABA-triblock copolymer, polystyrene-b-poly(methyl methacrylate)-b-polystyrene (PStb-PMMA-b-PSt, SMS). The electrolyte is formed by the selfassembly of SMS, where the solvatophobic PSt segments serves as physical cross-linking points, and the solvatophilic PMMA segment with preferentially dissolved [Li(G4)][TFSA] forms ion-conduction paths. In the electrolyte, the preservation of the complex cation [Li(G4)] + in the PMMA phase was demonstrated by pulsed-field gradient spin−echo (PGSE) NMR, Raman spectra, and thermogravimetric analysis. Because of the preservation of [Li(G4)] + , which hinders the direct interaction of Li + with the polymer segment and the coupling of the ionic transport from the segmental motion, the room temperature ionic conductivity of the electrolyte reached an appreciable level (10 −4 −10 −3 S cm −1 ).

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

“…Actually, we reported self-standing membranes made up of [Li(G4)][TFSA] and polystyrene-PMMA-polystyrene ABA tri-block copolymer (20-30 wt%). That membrane showed conductivity of 0.2 mScm À1 at 30 C [36], which is comparable to that of the PMMA-polymer solution studied here.…”

“…A self-standing PE membrane can be readily obtained by introducing either physical or chemical crosslinking points on the polymers. A polymer gel membrane swollen with ILs (called ion gels) was prepared by the in situ polymerization of vinyl monomers [31,32], by the cross-end coupling reaction of tetra-arm poly(ethylene glycol) [33], or by the self-assembly of ABA-type triblock copolymers where A and B are insoluble and soluble sequences, respectively [33][34][35][36].…”

Design and Materialization of Ionic Liquids Based on an Understanding of Their Fundamental Properties

“…33,126 We reported for the first time the upper critical solution temperature (UCST) phase behavior (low-temperature-insoluble and high-temperaturesoluble behavior) 127 and lower critical solution temperature (LCST) phase behavior (low-temperature-soluble and high-temperatureinsoluble behavior) [128][129][130][131][132][133][134] for certain polymers in ILs (Fig. 11).…”

“…32 Later, we extended out studies of Electrochemistry, 84 (9), 642-653 (2016) polymer electrolytes further to include the combination of taskspecific ILs such as protic ionic liquids (vide infra) and Li + -solvate ionic liquids. 33 The most striking differences of polymer electrolytes of ILs ("ion gels") from polyether electrolytes are the plasticizing effect of the ILs on the polymers and the decoupling of ion transport from the segmental motion of the polymer, enabling fast ion transport that is close to that of ILs themselves. 34 In addition, the useful properties of ILs, non-volatility and thermal stability, are preserved.…”

“…33 Herein, I discuss the application of an ion gel to ionic polymer actuators. [38][39][40][41][42] As a material for manufacturing polymer actuators with bio-mimetic soft motion, electronic and ionic polymer actuators have been proposed and applied to manipulators and robotic devices.…”