IONIC CONDUCTIVITY AND LITHIUM TRANSFERENCE NUMBER OF POLY(ETHYLENE OXIDE):LiTFSI SYSTEM

Pożyczka, Karol; Marzantowicz, M.; Dygas, J.R.; Krok, F.

doi:10.1016/j.electacta.2016.12.172

Cited by 192 publications

(175 citation statements)

References 45 publications

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“…41−43 A simple measure of the efficacy of a polymer electrolyte is the product σt +,ss . This metric has been reported previously for PEO 78 as well as newly designed polymer electrolyte systems.…”

Section: ■ Experimental Sectionsupporting

confidence: 71%

Optimizing Ion Transport in Polyether-Based Electrolytes for Lithium Batteries

et al. 2018

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ABSTRACT:We report on the synthesis of poly(diethylene oxidealt-oxymethylene), P(2EO-MO), via cationic ring-opening polymerization of the cyclic ether monomer, 1,3,6-trioxocane. We use a combined experimental and computational approach to study ion transport in electrolytes comprising mixtures of P(2EO-MO) and lithium bis(trifluoromethanesulfonyl) imide (LiTFSI) salt. Mixtures of poly(ethylene oxide) (PEO) and LiTFSI are used as a baseline. The maximum ionic conductivities, σ, of P(2EO-MO) and PEO electrolytes at 90°C are 1.1 × 10 −3 and 1.5 × 10 −3 S/cm, respectively. This difference is attributed to the T g of P(2EO-MO)/ LiTFSI (−12°C), which is significantly higher than that of PEO/LiTFSI (−44°C) at the same salt concentration. Self-diffusion coefficients measured using pulsed-field gradient NMR (PFG-NMR) show that both Li + and TFSI − ions diffuse more rapidly in PEO than in P(2EO-MO). However, the NMR-based cation transference number in P(2EO-MO) (0.36) is approximately twice that in PEO (0.19). The transference number measured by the steady-state current technique, t +,ss , in P(2EO-MO) (0.20) is higher than in PEO (0.08) by a similar factor. We find that the product σt +,ss is greater in P(2-EO-MO) electrolytes; thus, P(2EO-MO) is expected to sustain higher steady-state currents under dc polarization, making it a more efficacious electrolyte for battery applications. Molecular-level insight into the factors that govern ion transport in our electrolytes was obtained using MD simulations. These simulations show that the solvation structures around Li + are similar in both polymers. The same is true for TFSI − . However, the density of Li + solvation sites in P(2EO-MO) is double that in PEO. We posit that this is responsible for the observed differences in the experimentally determined transport properties of P(2EO-MO) and PEO electrolytes.

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Section: ■ Experimental Sectionsupporting

confidence: 71%

Optimizing Ion Transport in Polyether-Based Electrolytes for Lithium Batteries

et al. 2018

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“…[17][18][19] While these electrolytes exhibit reasonable conductivity at room temperature and lithium salts can be dissolved at high concentrations, the transference number based on the steady-state current method can be as low as 0.05. 20 This is due to specific interactions between the solvent and the cation. A consequence of our hypothesis that the properties of PFE electrolytes are governed by interactions between the solvent and the anion is the expectation that these systems should exhibit significantly higher transference numbers.…”

mentioning

confidence: 99%

Effect of Anion Size on Conductivity and Transference Number of Perfluoroether Electrolytes with Lithium Salts

Shah

Olson

Karny

et al. 2017

J. Electrochem. Soc.

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Mixtures of perfluoropolyethers (PFPE) and lithium salts with fluorinated anions are a new class of electrolytes for lithium batteries. Unlike conventional electrolytes wherein electron-donating oxygen groups interact primarily with the lithium cations, the properties of PFPE-based electrolytes appear to be dependent on interactions between the fluorinated anions and the fluorinated backbones. We study these interactions by examining a family of lithium salts wherein the size of the fluorinated anion is systematically increased: lithium bis(fluorosulfonyl)imide (LiFSI), bis(trifluoromethanesulfonyl)imide (LiTFSI) salts and lithium bis(pentafluoroethanesulfonyl)imide (LiBETI). Two short chain perfluoroethers (PFE), one with three repeat units, C6-DMC, and another with four repeat units, C8-DMC were studied; both systems have dimethyl carbonate end groups. We find that LiFSI provides the highest conductivity in both C6-DMC and C8-DMC. These systems also present the lowest interfacial resistance against lithium metal electrodes. The steady-state transference number (t + ss ) was above 0.6 for all of the electrolytes and was an increasing function of anion size. The product of conductivity and the steady-state transference number, a convenient measure of the efficacy of the electrolytes for lithium battery applications, exhibited a maximum at about 20 wt% salt in all electrolytes. Amongst the systems studied, LiFSI/PFE mixtures were the most efficacious electrolytes.

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“…[36] As far as ion complexations are involved, the theory of hard/softa cids and bases by Pearson shed some insighta st ow hy cations,i np articular lithium, are held onto strongly.Acombination of both hard components (ethereal oxygenso fP EO and Li + cations) constitute av ery strong interaction that can limit cation movement. ion pairs, doublets and triplets) that misleads conductivity resultsoft he material [43] Ion transport is widely believed to occur in the amorphous region of the polymer, where its segmented movement creates vacancies or free volumes fori ons to move about.R elying alone on this motion does not contribute to ionic conductivity significantly because of sluggishi on transport. [37] One way to lessen anion impact on polymer electrolytes is to choose conductive salts with bulkier anions, such as lithium bis(fluorosulfonyl)imide(LiFSI) or its analogue, lithium bis(trifluoromethanesulfonyl)imide(LiTFSI).…”

Section: Factors Affecting Ion Transport In Polymer Electrolytesmentioning

confidence: 99%

“…[43,62] In the context of this paper,t he transferencen umber is attained using the easiest and most accessible polarisation technique as explained below. Methods of analysing and obtaining transferencen umbersa re subjectt od ebates as of presents ince simplea pproximations are not ideal to describe the true phenomenono ccurring in the system.T hen again, other techniques require complex equipmenta nd uncertainties following additional experimental assumptions.…”

Section: Electrochemical Propertiesmentioning

confidence: 99%

Hybrid Solid Polymer Electrolytes with Two‐Dimensional Inorganic Nanofillers

Chua

Fang

Sun

et al. 2018

Chemistry A European J

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Solidp olymer electrolytes are of rapidly increasing importance for the research andd evelopment of future safe batteries with high energy density.T he diversified chemistry and structures of polymers allow the utilization of aw ide range of soft structures for all-polymers olid-state electrolytes. With equal importance is the hybrid solid-state electrolytes consisting of both "soft" polymeric structure and "hard" inorganic nanofillers.T he recent emergence of the re-discovery of many two-dimensional layered materials hass timulated the booming of advanced research in energy storage fields, such as batteries, supercapacitors, and fuel cells. Of special interesti st he mass transport properties of these 2D nanostructures for water,g as, or ions. This review aims at the current progress and prospective development of hybrid polymer-inorganic solid electrolytes based on important 2D materials, including natural clay and synthetic lamellar structures. The ion conduction mechanism and the fabrication, property and device performance of these hybrid solid electrolyteswill be discussed.

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IONIC CONDUCTIVITY AND LITHIUM TRANSFERENCE NUMBER OF POLY(ETHYLENE OXIDE):LiTFSI SYSTEM

Cited by 192 publications

References 45 publications

Optimizing Ion Transport in Polyether-Based Electrolytes for Lithium Batteries

Optimizing Ion Transport in Polyether-Based Electrolytes for Lithium Batteries

Effect of Anion Size on Conductivity and Transference Number of Perfluoroether Electrolytes with Lithium Salts

Hybrid Solid Polymer Electrolytes with Two‐Dimensional Inorganic Nanofillers

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