Tetraglyme−Li<sup>+</sup> Cation Solvate Structures:  Models for Amorphous Concentrated Liquid and Polymer Electrolytes (II)

Henderson, Wesley A.; Brooks, Neil R.; Young, Victor G.

doi:10.1021/cm034352r

Cited by 113 publications

(134 citation statements)

References 27 publications

(34 reference statements)

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“…Li + cation coordination modes found in the crystalline solvates (G2) 1/3 :LiCF 3 SO 3 and (G4) 2/5 :LiCF 3 CO 2 (Li-purple, O-red, F-light green). 24,25 vates are unsolvated (i.e., the cations are coordinated solely by four CF 3 CO 2 − anions) (Fig. 4).…”

Section: Resultsmentioning

confidence: 99%

Electrolyte Solvation and Ionic Association

Borodin

Han

Daubert

et al. 2015

J. Electrochem. Soc.

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Molecular dynamics (MD) simulations of acetonitrile (AN) mixtures with LiBF 4 , LiCF 3 SO 3 and LiCF 3 CO 2 provide extensive details about the molecular-and mesoscale-level solution interactions and thus explanations as to why these electrolytes have very different thermal phase behavior and electrochemical/physicochemical properties. The simulation results are in full accord with a previous experimental study of these (AN) n -LiX electrolytes. This computational study reveals how the structure of the anions strongly influences the ionic association tendency of the ions, the manner in which the aggregate solvates assemble in solution and the length of time in which the anions remain coordinated to the Li + cations in the solvates which result in dramatic variations in the transport properties of the electrolytes. Understanding the origin of the widely varying transport properties (e.g., viscosity, ionic conductivity and diffusion coefficients) of battery electrolytes remains a key challenge. The present work continues a detailed study into the solution structure of electrolytes-ion solvation and ionic association interactions-to provide mechanistic explanations for electrolyte properties. Previous manuscripts have examined in detail acetonitrile electrolytes with numerous lithium salts: (AN) n -LiX. [1][2][3][4][5][6] Electrolytes with the most strongly associated anions studied (i.e., CF 3 SO 3 − and CF 3 CO 2 − ), in which anion. . . Li + cation coordination (i.e., ionic association interactions) is a prominent feature of solvate formation, were found to have a much lower ionic conductivity than electrolytes with more weakly coordinating anions (e.g., PF 6 − and ClO 4 − ). 3 This is as one might expect once the ionic association tendency of the salts is well understood, but the details of why the conductivity values are low are missing.Two particularly notable points from the previous studies are that:(1) The average solvation numbers, obtained from a Raman spectroscopic analysis, for the (AN) n -LiCF 3 CO 2 solutions were found to be almost constant near a value of 1 (i.e., one AN molecule per Li + cation) over a wide concentration range, even for very dilute solutions. It remains unclear, however, as to why such electrolytes have such a low degree of solvation and why highly concentrated (>5 M) liquid electrolytes-perhaps contrary to expectations-can be prepared with LiCF 3 CO 2 with this being the case.(2) Experimental measurements of the solution structure and transport properties of (AN) n -LiCF 3 SO 3 mixtures were unobtainable due to the rapid crystallization of a solid solvate phase (i.e., (AN) 1 :LiCF 3 SO 3 ) from the electrolytes. 1 Liquid electrolytes with this salt can, however, be readily studied using molecular dynamics (MD) simulations to better understand how and why solution interactions differ for differing anions.The present work therefore delves deeper into the molecular-and mesoscale-level interactions using MD simulations applied to the characterization of (AN) n -LiCF 3 SO 3 and -LiCF ...

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Section: Resultsmentioning

confidence: 99%

Electrolyte Solvation and Ionic Association

Borodin

Han

Daubert

et al. 2015

J. Electrochem. Soc.

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“…Glyme-Li salt complexes are equimolar mixtures consisting of a glyme and a Li salt [35][36][37]. In suitable combinations, the oxygen atoms in a glyme coordinate with Li + to form a complex cation, as observed in crown ether complexes, in which the Li + cation and the ligand (glyme) serve as Lewis acid and Lewis base, respectively.…”

Section: Introductionmentioning

confidence: 99%

New glyme–cyclic imide lithium salt complexes as thermally stable electrolytes for lithium batteries

Tamura

Hachida

Yoshida

et al. 2010

Journal of Power Sources

152

139

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“…[68][69][70] The simulated effective sizes of these solvated complexes were determined by the radii of gyration (R g ) of the solute and the first solvation shell. These shells were typically composed of two solvent molecules, as 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 6 exemplified by the average snapshots shown in Figure 2a.…”

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Polysulfide-Blocking Microporous Polymer Membrane Tailored for Hybrid Li-Sulfur Flow Batteries

et al. 2015

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Redox flow batteries (RFBs) present unique opportunities for multi-hour electrochemical energy storage (EES) at low cost. Too often, the barrier for implementing them in large-scale EES is the unfettered migration of redox active species across the membrane, which shortens battery life and reduces Coulombic efficiency. To advance RFBs for reliable EES, a new paradigm for controlling membrane transport selectivity is needed. We show here that size- and ion-selective transport can be achieved using membranes fabricated from polymers of intrinsic microporosity (PIMs). As a proof-of-concept demonstration, a first-generation PIM membrane dramatically reduced polysulfide crossover (and shuttling at the anode) in lithium-sulfur batteries, even when sulfur cathodes were prepared as flowable energy-dense fluids. The design of our membrane platform was informed by molecular dynamics simulations of the solvated structures of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) vs lithiated polysulfides (Li2Sx, where x = 8, 6, and 4) in glyme-based electrolytes of different oligomer length. These simulations suggested polymer films with pore dimensions less than 1.2-1.7 nm might incur the desired ion-selectivity. Indeed, the polysulfide blocking ability of the PIM-1 membrane (∼0.8 nm pores) was improved 500-fold over mesoporous Celgard separators (∼17 nm pores). As a result, significantly improved battery performance was demonstrated, even in the absence of LiNO3 anode-protecting additives.

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Tetraglyme−Li⁺ Cation Solvate Structures: Models for Amorphous Concentrated Liquid and Polymer Electrolytes (II)

Cited by 113 publications

References 27 publications

Electrolyte Solvation and Ionic Association

Electrolyte Solvation and Ionic Association

New glyme–cyclic imide lithium salt complexes as thermally stable electrolytes for lithium batteries

Polysulfide-Blocking Microporous Polymer Membrane Tailored for Hybrid Li-Sulfur Flow Batteries

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Tetraglyme−Li+ Cation Solvate Structures: Models for Amorphous Concentrated Liquid and Polymer Electrolytes (II)

Cited by 113 publications

References 27 publications

Electrolyte Solvation and Ionic Association

Electrolyte Solvation and Ionic Association

New glyme–cyclic imide lithium salt complexes as thermally stable electrolytes for lithium batteries

Polysulfide-Blocking Microporous Polymer Membrane Tailored for Hybrid Li-Sulfur Flow Batteries

Contact Info

Product

Resources

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Tetraglyme−Li⁺ Cation Solvate Structures: Models for Amorphous Concentrated Liquid and Polymer Electrolytes (II)