Spectroscopic investigations of solvent assisted Li-ion transport decoupled from polymer in a gel polymer electrolyte

Abstract

We present here a gel polymer electrolyte, where the Li+-ion transport is completely decoupled from the polymer host solvation and dynamics. A free-standing gel polymer electrolyte with a high volume content (nearly 60%) of xM LiTFSI in G4 (tetraglyme) ( x = 1–7; Li+:G4 = 0.2–1.5) liquid electrolyte confined inside the PAN (polyacrylonitrile)-PEGMEMA [poly (ethylene glycol) methyl ether methacrylate oligomer] based polymer matrix is synthesized using a one-pot free radical polymerization process. For LiTFSI concentrations, x = 1–7 (Li+:G4 = 0.2–1.5), Raman and vibrational spectroscopies reveal that like in the liquid electrolyte, the designed gel polymer electrolytes (GPEs) also show direct coordination of Li+-ions with the tetraglyme leading to the formation of [Li(G4)]+. Coupled with the spectroscopic studies, impedance and nuclear magnetic resonance investigations also show that the ion transport is independent of the polymer segmental motion and is governed by the solvated species {[Li(G4)]+}, very similar to the scenario in ionic liquids. As a result, the magnitude of ionic conductivity and activation energies of the gel polymer electrolyte are very similar to that of the liquid electrolyte. The Li+-ion transport number for the GPE varied from 0.44 ( x = 1) to 0.5 ( x = 7) with the maximum being 0.52 at x = 5.

Recent Advances in Rechargeable Metal–CO2 Batteries with Nonaqueous Electrolytes

“…41 The disorders like amorphousness to the polymer enhance the segmental motion of the polymer chains, causing the ions to move faster than ordered (crystalline phase) above the polymer's glass transition temperature (T g ). 42 Scientists strive to develop polymeric systems that enable high ionic conductivity by establishing a percolation network with a substantial portion of the disordered phase, even under typical ambient temperatures. Decoupling the ionic transport from the polymer host, which includes the addition of plasticizers, metal oxide, and ionic liquids, could be an effective strategy to enhance ionic conductivity.…”

“…Ion transport takes place through intrachain or interchain hopping in the PEO-based electrolyte by breaking and forming lithium–oxygen (Li···O) bonds . The disorders like amorphousness to the polymer enhance the segmental motion of the polymer chains, causing the ions to move faster than ordered (crystalline phase) above the polymer’s glass transition temperature ( T g ) . Scientists strive to develop polymeric systems that enable high ionic conductivity by establishing a percolation network with a substantial portion of the disordered phase, even under typical ambient temperatures.…”

“…Scientists strive to develop polymeric systems that enable high ionic conductivity by establishing a percolation network with a substantial portion of the disordered phase, even under typical ambient temperatures. Decoupling the ionic transport from the polymer host, which includes the addition of plasticizers, metal oxide, and ionic liquids, could be an effective strategy to enhance ionic conductivity . Plastic crystalline material succinonitrile (SN)is often dissolved into the polymer matrix as a high dielectric constant solid-state nonionic plasticizer, which brings amorphousness to the polymer matrix, flexibility and helps in better dissolution of various salts for ionic conduction .…”

“…Decoupling the ionic transport from the polymer host, which includes the addition of plasticizers, metal oxide, and ionic liquids, could be an effective strategy to enhance ionic conductivity. 42 Plastic crystalline material� succinonitrile (SN)�is often dissolved into the polymer matrix as a high dielectric constant solid-state nonionic plasticizer, which brings amorphousness to the polymer matrix, flexibility and helps in better dissolution of various salts for ionic conduction. 29 Many polymer hosts (such as PEO, poly(vinylidene fluoride-cohexafluoropropylene (PVDF-HFP)) act as the Lewis base and strongly interact with the metal ions (Lewis acid), decreasing cationic mobility and conductivity.…”