Effective Medium Theory of Conduction in Stretched Polymer Electrolytes

Dürr, Oliver; Dieterich, W.; Maass, Philipp; Nitzan, Abraham

doi:10.1021/jp013373a

Cited by 28 publications

(14 citation statements)

References 18 publications

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“…92 This model is based on the idea that a highly conducting phase is associated with oriented molecular structures which are surrounded by poorly conducting boundary regions. The model is evaluated within the framework of the differential effective medium theory (DEMT).…”

Section: 91mentioning

confidence: 99%

Review—On Order and Disorder in Polymer Electrolytes

Golodnitsky

Strauss

Greenbaum

2015

J. Electrochem. Soc.

203

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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Section: 91mentioning

confidence: 99%

Review—On Order and Disorder in Polymer Electrolytes

Golodnitsky

Strauss

Greenbaum

2015

J. Electrochem. Soc.

203

135

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“…It was found that the more amorphous the PE, the less its lengthwise conductivity is influenced by stretching. A model that accounts for stretching-induced structural anisotropy accompanied by ion conduction enhancement was introduced in [9]. It addresses a transition from spherical to spheroidal shapes of the high conduction regions as a result of alignment.…”

Section: Introductionmentioning

confidence: 99%

Polymer geometry and Li+ conduction in poly(ethylene oxide)

Gitelman¹,

Israeli²,

Averbuch³

et al. 2008

Journal of Computational Physics

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We study the effect of molecular shape on Li + conduction in dilute and concentrated polymer electrolytes (LiI : P (EO) n (3 ≤ n ≤ 100)). We model the migration-diffusion of interacting Li + ions in the helical PEO molecule as Brownian motion in a field of electrical force. Our model demonstrates that ionic conductivity of the amorphous PE structure is increased by mechanical stretching due to the unraveling of loops in the polymer molecule and to increased order. The enhancement of the ionic conductivity in the stretch direction, observed in our Brownian simulations, is in agreement with experimental results. We find an up to 40-fold increase in the LiIP (EO) 7 conductivity, which is also in agreement with experimental results. The good agreement with experiment lends much credibility to our physical model of conductivity.

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“…12 is less impressive, with the correct trend seen only at low n values (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20). Given the simplified model used in the simulation, obtaining the correct trend as well as absolute ratio value over the entire n range (as in Fig.…”

Section: Temperature Effectmentioning

confidence: 94%

“…Therefore inter-chain transport is essential for long-range conduction. It has recently been found [5]- [8] that intra-chain transport is far more efficient than inter-chain hopping, making the latter process rate-limiting. The inter-chain ion hopping is assisted by a polymer segmental motion that controls the instantaneous distance between adjacent chains.…”

Section: Introductionmentioning

confidence: 99%

“…It was suggested that stretched polymers adopt a modified helical structure, similar to that of an extended salt-free PEO helix. In [5] the authors presented a model that accounts for stretching-induced structural anisotropy accompanied by ion conduction enhancement. The authors addressed a transition from spherical to spheroidal shapes of the high conduction regions as a result of alignment.…”

Section: Introductionmentioning

confidence: 99%

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Modeling and simulation of Li-ion conduction in poly(ethylene oxide)

Gitelman

Israeli

Averbuch

et al. 2007

Journal of Computational Physics

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Polyethylene oxide (PEO) containing a lithium salt (e.g. LiI) serves as a solid polymer electrolyte (SPE) in thin-film batteries and its ionic conductivity is a key parameter of their performance. We model and simulate Li + ion conduction in a single PEO molecule.Our simplified stochastic model of ionic motion is based on an analogy between protein channels of biological membranes that conduct Na + , K + , and other ions, and the PEO helical chain that conducts Li + ions. In contrast with protein channels and salt solutions, the PEO is both the channel and the solvent for the lithium salt (e.g., LiI). The mobile ions are treated as charged spherical Brownian particles. We simulate Smoluchowski dynamics in channels with a radius of ca 0.1nm and study the effect of stretching and temperature on ion conductivity. We assume that each helix (molecule) forms a random angle with the axis between these electrodes and the polymeric film is composed of many uniformly distributed oriented boxes that include molecules with the same direction. We further assume that mechanical stretching aligns the molecular structures in each box along the axis of stretching (intra-box alignment). Our model thus predicts the PEO conductivity as a function of the stretching, the salt concentration and the temperature. The computed enhancement of the ionic conductivity in the stretch direction is in good agreement with experimental results. The simulation results are also in qualitative agreement with recent theoretical and experimental results.

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Effective Medium Theory of Conduction in Stretched Polymer Electrolytes

Cited by 28 publications

References 18 publications

Review—On Order and Disorder in Polymer Electrolytes

Review—On Order and Disorder in Polymer Electrolytes

Polymer geometry and Li+ conduction in poly(ethylene oxide)

Modeling and simulation of Li-ion conduction in poly(ethylene oxide)

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