Decoupling of Ionic Transport from Segmental Relaxation in Polymer Electrolytes

Wang, Yangyang; Agapov, Alexander L.; Fan, Fei; Hong, Kunlun; Yu, Xiang; Mays, Jimmy W.; Sokolov, Alexei P.

doi:10.1103/physrevlett.108.088303

Cited by 162 publications

(188 citation statements)

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“…Sokolov et al recently reported a strong correlation between the fragility parameter m of polymers and the decoupling of ionic transport from segmental motion in PEs [47,48]. It was suggested that ionic transport is strongly coupled to the segmental relaxation of less fragile polymers with well-packed structures, whereas ions may diffuse more freely through loosely packed chains of fragile polymers.…”

Section: Ionic Transport Propertiesmentioning

confidence: 95%

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

Kido

Ueno

Iwata

et al. 2015

Electrochimica Acta

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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.

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Section: Ionic Transport Propertiesmentioning

confidence: 95%

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

Kido

Ueno

Iwata

et al. 2015

Electrochimica Acta

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“…Contrary to the case of materials with flexible chains (for example, PEO and its derivatives), in which ionic diffusion is strongly coupled to structural relaxation, the analysis of broadband dielectric spectra presented by Agapov and Sokolov [31][32][33] demonstrated that it is the sluggish segmental dynamics of polyethers that causes low conductivity in polymer electrolytes at ambient temperatures. They also showed that the loose structure of the rigid chains leads to significant ionic diffusion even when segmental relaxation is very slow.…”

Section: Solid Polymer Electrolytes-structure and Mechanism Of Ion Trmentioning

confidence: 99%

Review—On Order and Disorder in Polymer Electrolytes

Golodnitsky

Strauss

Greenbaum

2015

J. Electrochem. Soc.

206

135

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This contribution presents an overview of more than three-decades-long studies of the structure and mechanism of ion conduction in polyethylene-oxide-based solid polymer electrolytes. Conductivity in polymer electrolytes has long been viewed as confined to the amorphous phase above the glass-transition temperature (Tg). Above Tg, polymer chain motion creates a dynamic, disordered environment that was thought to play a critical role in facilitating ion transport. Difficulty of finding the amorphous polymer with sufficient ionic conductivity has raised the fundamental question of whether polymer electrolytes are intrinsically inferior to other electrolytes in terms of their charge-transport capability. Recently, enhanced ionic conductivity has been detected in ordered (longitudinally stretched and cast under gradient magnetic field) polymer electrolytes, in crystalline ion-polyether 1:6 complexes and polymer-in-salt electrolytes. These results have opened a new trend in the search for ion transport in solid polymer electrolytes. The very latest publications present new hybrid-and block-co-polymers, a new class of functional materials (polymerized ionic liquids), and new promising approaches aimed at the development of polymer-based superionic conductors with rigid nanochannel architectures that enable rapid ion transport decoupled from segmental relaxation. Solid Polymer Electrolytes-Structure and Mechanism of Ion TransportMuch research deals with high-ionic-conductive polymer electrolytes because of their current and potential applications as electrochromic and temperature-sensitive printed electronics devices, biomedical sensors, supercapacitors, solar cells and batteries. Polymer electrolytes offer pronounced advantages over conventional liquid electrolytes. These include: a versatile shape, mechanical strength and stable contact between the electrode and electrolyte interfaces. In addition, solid electrolytes are safer than liquid electrolytes as they do not have a leakage problem and because of their nontoxic, low-vaporpressure, and non-flammable properties. [1][2][3][4][5][6][7] Ion-polyether complexes (or polymer electrolytes) were first discovered by Fenton, Parker and Wright in 1973. 8 Since then, such complexes have been prepared with many different monatomic ions and indeed many different polymeric ligands. Armand in 1979 recognized that Li + -polyether complexes could be used as solid electrolytes in electrochemical devices. 9The classic polymer electrolyte comprises organic macromolecules (usually polyether polymer) that are complexed with inorganic salts. The polymer matrix must contain a Lewis base (e.g. ethylene-oxide unit, -OCH 2 CH 2 -) to solvate the lithium salt. The salt-solvent mixing entropy consists mainly of two components: translational and configurational. Contrary to the case of water, the mixing entropy for the formation of polymer electrolytes is small or even positive. The incorporation of salts into the polymer inevitably reduces the freedom of polymer-chain motion, thus causing ...

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“…Intercept of the curve at Z′ axis shifts towards lower value, with increasing salt concentration, indicating that impedance of the material is decreasing. This decrease can be correlated with increase of number of charge carriers and/or salt plasticization effect [19].…”

Section: Impedance Analysismentioning

confidence: 99%

“…They can be obtained from dielectric spectra. The ion diffusivity is calculated from tan δ vs. log ω curve [17][18][19] using the following relation:…”

Section: Analysis Techniquesmentioning

confidence: 99%

Ion dynamics and relaxation behavior of NaPF6-doped polymer electrolyte systems

Srivastava

Kumar

2016

J Solid State Electrochem

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The present paper discusses the ion dynamics of a novel polymeric system prepared by doping of NaPF 6 in a labprepared polymer matrix. Ion dynamics of the system is analyzed by presenting the impedance data in different formalisms. Mobility (and hence the conductivity) continuously increases with salt concentration, and the phenomenon is correlated with salt's plasticization nature, which is reconfirmed by the shifting of minima in ∂logε′/∂logω vs. logω curve towards high frequency. It has been observed that number of charge carriers (N′) estimated from conductivity data do not represent the real charge concentration in the system. Within the experimental frequency (∼MHz) range, three different regions are identified in ∂logσ vs. ∂logω curves namely (i) dc conductivity/free hopping, (ii) correlated ion hopping, and (iii) caged movement of ions. In the present case, also a scaled master conductivity curve is obtained by estimating the σ 0 and ω p (exclusively in Jonscher Power Law or JPL region) according to our previously proposed method. Scaling is realized with respect to salt concentration and temperature, which is an indication that salt concentration and temperature are only governing the number of charge carriers and mobility without affecting the underlying ion transport mechanism. NonDebye-type relaxation phenomenon is indicated by KWW exponent β (<1). Relaxation times, obtained from tanδ vs. logω curves, inversely follow the conductivity, indicating strongly correlated ion-polymer segmental motions.

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Decoupling of Ionic Transport from Segmental Relaxation in Polymer Electrolytes

Cited by 162 publications

References 34 publications

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

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

Review—On Order and Disorder in Polymer Electrolytes

Ion dynamics and relaxation behavior of NaPF6-doped polymer electrolyte systems

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