Decoupling segmental relaxation and ionic conductivity for lithium-ion polymer electrolytes

Bresser, Dominic; Lyonnard, Sandrine; Iojoiu, Cristina; Picard, Lionel; Passerini, Stefano

doi:10.1039/c9me00038k

Cited by 155 publications

(157 citation statements)

References 135 publications

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“…Conventional wisdom suggests that ion diffusion is coupled to segmental motion of polymers on short time scales. [25,[45][46][47] The sub-diffusive mean squared displacement characteristics of the ions are thus assumed to be similar to that of the Rouse regime, as shown in Figure 5. [25] Simulation results [48] are qualitatively consistent with this assumption.…”

Section: Polymer and Ion Dynamical Modes And Experimental Methodsmentioning

confidence: 99%

Diffusion and migration in polymer electrolytes

Choo

Halat

Villaluenga

et al. 2020

Progress in Polymer Science

126

113

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Mixtures of neutral polymers and lithium salts have the potential to serve as electrolytes in next-generation rechargeable Li-ion batteries. The purpose of this review is to expose the delicate interplay between polymer-salt interactions at the segmental level and macroscopic ion transport at the battery level. Since complete characterization of this interplay has only been completed in one system: mixtures of poly(ethylene oxide) and lithium bis(trifluoromethanesulfonyl)imide (PEO/LiTFSI), we focus on data obtained from this system. We begin with a discussion of the activity coefficient, followed by a discussion of six different diffusion coefficients: the Rouse motion of polymer segments is quantified by Dseg, the self-diffusion of cations and anions is quantified by Dself,+ and Dself,-, and the build-up of concentration gradients in electrolytes under an applied potential is quantified by Stefan-Maxwell diffusion coefficients, 0+ , 0− , and +−. The Stefan-Maxwell diffusion coefficients can be used to predict the velocities of the ions at very early times after an electric field is applied across the electrolyte. The surprising result is that 0− is negative in certain concentration windows. A consequence of this finding is that at these concentrations, both cations and anions are predicted to migrate toward the positive electrode at early times. We describe the controversies that surround this result. Knowledge of the Stefan-Maxwell diffusion coefficients enable prediction of the limiting current. We argue that the limiting current is the most important characteristic of an electrolyte. Excellent agreement between theoretical and experimental limiting current is seen in PEO/LiTFSI mixtures. What sequence of monomers that, when polymerized, will lead to the highest limiting current remains an important unanswered question. It is our hope that the approach presented in this review will guide the development of such polymers.

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Section: Polymer and Ion Dynamical Modes And Experimental Methodsmentioning

confidence: 99%

Diffusion and migration in polymer electrolytes

Choo

Halat

Villaluenga

et al. 2020

Progress in Polymer Science

126

113

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“…To achieve the high ionic conduction in amorphous solid electrolytes, one of the prerequisites that the materials should satisfy is the decoupling of ion motion from the structural relaxation [ 22 ] (or the segmental relaxation in polymer electrolytes). [ 23,38 ] The realization of “all solid‐state battery” is an objective in the current research of lithium‐ion batteries, [ 39–41 ] and thereby the understanding of solidification of liquid electrolytes is a subject of considerable interest. According to Angell, [ 22 ] SIC glasses are characterized by a value of the decoupling index R = τ α / τ σ larger than R = 10 12 , where τ α and τ σ are the time constants of the structural relaxation and the electrical conductivity relaxation, respectively.…”

Section: Ac Phenomena In the Structural Relaxation And The Electricalmentioning

confidence: 99%

“…The purpose of the present study is to explore the relation between the AC behaviors of the structural relaxation and the electrical conductivity relaxation, and to deepen the understanding of the decoupling characteristics [ 22 ] which is a crucial mechanism in solid electrolytes. [ 23–26 ] The implication of the AC behaviors to the occurrence of the high ionic conduction via decoupling is discussed in terms of the BSCNF model and the FSE law. As far as the authors are informed, no previous study has focused on this point.…”

Section: Introductionmentioning

confidence: 99%

Arrhenius Crossover Phenomena and Ionic Conductivity in Ionic Glass‐Forming Liquids

Aniya

Ikeda

2020

Physica Status Solidi (b)

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Herein, the relation between the Arrhenius crossover (AC) behaviors in the structural relaxation and the electrical conductivity relaxation is explored in terms of the Bond Strength–Coordination Number Fluctuation (BSCNF) model developed by the authors. For the ionic glass‐forming liquids and solution examined, Ca2K3(NO3)7, Ca2Rb3(NO3)7, ZBLAN20 and (LiCl)0.16(H2O)0.84, the electric conductivity at high temperature resembles the behavior of the high‐temperature structural relaxation. This mutual relationship suggests a similar origin of the AC behaviors for both, structural and electrical relaxation. The difference between them is reflected in the different temperatures that demarcate the AC behaviors. The implication of this difference to the occurrence of the high ionic conduction via the decoupling mechanism is discussed in terms of the BSCNF model and the fractional Stokes–Einstein law.

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“…42 The conductivity of PEO complex composites obtained in this work is essentially determined via the conduction process through the network of K 2 PtCl 6 ionic interconnections which suggests that the hopping conduction is the dominant mechanism and gradually increases at the same concentration ( Figure 7) above glass temperature. 43 The ion conduction in dry PEs such as PEO/K 2 PtCl 6 , occurs fundamentally in the amorphous phase via the segmental motion of the cations (Pt + in the case of this study) through the chains of the polymer. 44 Typically, in dry polymer electrode using Li + as a cation, the conductivity is ≥10 −3 S cm −1 .…”

Section: Electrical Conductivity (σ)mentioning

confidence: 91%

Studies of composite films of polyethylene oxide doped with potassium hexachloroplatinate

Al-Akhras

Alzoubi

Ababneh

et al. 2020

J of Applied Polymer Sci

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The permittivity and conductivity relaxation processes of polyethylene oxide (PEO) composite along with potassium hexachloroplatinate (K 2 PtCl 6) electrolytes additive forming PEO/K 2 PtCl 6 complex composite have been investigated. The complex composite has been used as a model for dry-polymer electrolytes (PEs) due to the fact that, the anion is large enough for mimicking the immobilized anion in real dry-polymer electrolytes. Stand-free composite films with 0%, 1%, 3%, and 5% concentrations of K 2 PtCl 6 have been studied using broadband dielectric spectroscopy in the temperatures range from 150 K until 345 K. The microstructural dynamics revealed the α-, β-, and σ-relaxations and their salient spectral characteristics at various concentrations of K 2 PtCl 6 in PEO. The experimental ε" master curves were fitted to HN function for one and/or two relaxation peaks with and without the electrical conductivity contribution in order to investigate the relaxation time (τ), dielectric strengths (Δε), modulus formalism (M") and the electrical conductivitie (σ). The translational and reorientational degrees of freedom of PEO/K 2 PtCl 6 complex composites are responsible for the relaxation behavior which is predicted to be correlated to the relaxation behavior of the polymer electrolyte below and above the glass transition temperature (T g). The relaxation time (τ) deduced from β-relaxation follows Arrhenius-like behavior while that deduced from α-relaxation process follows Vogel-Tamman-Fulcher (VTF) behavior.

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Decoupling segmental relaxation and ionic conductivity for lithium-ion polymer electrolytes

Abstract: This perspective reviews current strategies to decouple segmental motion and ionic conductivity for lithium polymer battery electrolytes, including an outlook for potential future improvements.

Cited by 155 publications

References 135 publications

Diffusion and migration in polymer electrolytes

Diffusion and migration in polymer electrolytes

Arrhenius Crossover Phenomena and Ionic Conductivity in Ionic Glass‐Forming Liquids

Studies of composite films of polyethylene oxide doped with potassium hexachloroplatinate

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