Physical properties of solid polymer electrolyte PEO(LiTFSI) complexes

Gorecki, W.; Jeannin, Mathieu; Bélorizky, E.; Roux, Christel; Armand, Michel

doi:10.1088/0953-8984/7/34/007

Cited by 289 publications

(331 citation statements)

References 26 publications

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“…71 This differs substantially from the value that we report (3.3 at r = 0.08). We also note that the transference number of this system was found to be positive at all salt concentrations.…”

Section: Resultscontrasting

confidence: 95%

Negative Transference Numbers in Poly(ethylene oxide)-Based Electrolytes

Pesko

Timachova

Bhattacharya

et al. 2017

J. Electrochem. Soc.

186

367

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The performance of battery electrolytes depends on three independent transport properties: ionic conductivity, diffusion coefficient, and transference number. While rigorous experimental techniques for measuring conductivity and diffusion coefficients are well-established, popular techniques for measuring the transference number rely on the assumption of ideal solutions. We employ three independent techniques for measuring transference number, t + , in mixtures of polyethylene oxide (PEO) and lithium bis(trifluoromethanesulfonyl) imide (LiTFSI) salt. Transference numbers obtained using the steady-state current method pioneered by Bruce and Vincent, t +,SS , and those obtained by pulsed-field gradient NMR, t +,NMR , are compared against a new approach detailed by Newman and coworkers, t +,Ne , for a range of salt concentrations. The latter approach is rigorous and based on concentrated solution theory, while the other two approaches only yield the true transference number in ideal solutions. Not surprisingly, we find that t +,SS and t +,NMR are positive throughout the entire salt concentration range, and decrease monotonically with increasing salt concentration. In contrast, t +,Ne has a non-monotonic dependence on salt concentration and is negative in the highly-concentrated regime. Our work implies that ion transport in PEO/LiTFSI electrolytes at high salt concentrations is dominated by the transport of ionic clusters. Energy density and safety of conventional lithium-ion batteries is limited by the use of liquid electrolytes comprising mixtures of flammable organic solvents and lithium salts. Polymer electrolytes have the potential to address both limitations. However, the power and lifetime of batteries containing solvent-free polymer electrolytes remain inadequate for most applications. The performance of electrolytes in batteries depends on three independent transport properties: ionic conductivity, σ, salt diffusion coefficient, D, and cation transference number, t + .1 The poor performance of batteries with polymer electrolytes is generally attributed to low conductivity, which is on the order of 10 −3 S/cm at 90• C for mixtures of polyethylene oxide (PEO) and lithium bis(trifluoromethanesulfonyl) imide (LiTFSI) salt, 2,3 compared to that of liquid electrolytes which is 10 −2 S/cm at ambient temperatures. 4 Much of the literature in this field has been devoted to increasing the ionic conductivity of these materials.5-32 The purpose of our work is to shed light on another transport property of polymer electrolytes, the transference number.In a pioneering study, Ma and coworkers showed that the transference number of a mixture of PEO and a sodium salt is negative. 33Following this approach, others have obtained t + <0 in polymers containing lithium or sodium salts. [34][35][36] Nevertheless, the majority of reports for t + in polymer electrolytes fall between zero and one. [37][38][39][40][41][42][43][44][45][46][47][48][49][50][51] In contrast, all reports of t + in non-aqueous liquid electrolytes containi...

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Section: Resultscontrasting

confidence: 95%

Negative Transference Numbers in Poly(ethylene oxide)-Based Electrolytes

Pesko

Timachova

Bhattacharya

et al. 2017

J. Electrochem. Soc.

186

367

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“…Detailed characterizations were carried out by methods like infrared spectroscopy [29][30][31], nuclear magnetic resonance (NMR) [32][33][34][35][36][37][38][39][40] and viscosimetry [41][42][43][44] in order to clarify the interaction of the cations with a polymer network and their associated transport dynamics.…”

Section: Introductionmentioning

confidence: 99%

Transport Mechanisms of Ions in Graft-Copolymer Based Salt-in-Polymer Electrolytes

Kunze

Schulz

Wiemhöfer

et al. 2010

Zeitschrift Für Physikalische Chemie

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Polymer Electrolyte / Nuclear Magnetic Resonance / Spin Relaxation / Pulsed Field Gradient NMR / ConductivitySalt-in-polymer electrolytes based on graft copolymers with oligoether side chains and added LiCF 3 SO 3 (LiTf) are investigated concerning the transport and dynamics of the ionic species with respect to applications as Li ion conductors. Polymer architectures are based on polysiloxane or polyphosphazene backbones with one or two side chains per monomer, respectively. NMR methods provide information about molecular dynamics on different length scales: The mechanisms governing local dynamics and long range mass transport are studied on the basis of temperature dependent spin-lattice relaxation rates and pulsed field gradient diffusion measurements for 7 Li, 19 F and 1 H, respectively. The correlation times characterizing local ion dynamics reflect the complexation of the cations by the oligoether side chains of the polymer.7 Li and 19 F diffusion coefficients and their activation energies are rather similar, suggesting the formation of ion pairs and clusters with similar activation barriers for cation and/or anion long-range transport. Activation energies of local reorientations are generally significantly smaller than activation energies of long range diffusion. Long range transport is affected by (1) the coupling of conformational side chain reorientations to the cation movement, and (2) the correlated diffusion of cations and anions within ion pairs. Ion pairs and their dissociation play a major role in controlling the resulting conductivity of the material. Guidelines for material optimization in terms of a maximized conductivity can thus be derived by identifying a compromise between high ionic mobility and good Li complexation by the coordinating side chains.

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“…28 In this case, the hygroscopic character of the materials is also reduced due to the bulkiness, flexibility, and charge delocalization of the anion. For lanthanide-based polymer electrolytes the luminescence features of the EuTFSI 3 salt incorporated in poly͑propylene glycol͒, PPG, and in low-molecular-weight POE oligomers have been recently reported.…”

Section: Introductionmentioning

confidence: 99%

White light emission ofEu3+-based hybrid xerogels

et al. 1999

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The luminescence spectra and extended x-ray-absorption fine-structure ͑EXAFS͒ measurements of a series of Eu 3ϩ -based organic/inorganic xerogels were reported and related to the local coordination of the lanthanide cations. The hybrid matrix of these organically modified silicates, classed as U (2000) ureasils, is a siliceous network to which short organic chains containing oxyethylene units are covalently grafted by means of urea bridges. The luminescent centers were incorporated as europium triflate, Eu͑CF 3 SO 3 ͒ 3 , and europium bromide, EuBr 3 , with concentrations 200уnу20 and nϭ80, 40, and 30, respectively-where n is the number of ether oxygens in the polymer chains per Eu 3ϩ cation. EXAFS measurements were carried out in some of the U (2000) n Eu͑CF 3 SO 3 ͒ 3 xerogels ͑nϭ200, 80, 60, and 40͒. The obtained coordination numbers N ranging from 12.8, nϭ200, to 9.7, nϭ40, whereas the average Eu 3ϩ first neighbors distance R is 2.48-2.49 Å. The emission spectra of these multiwavelength phosphors superpose a broad green-blue band to a series of yellow-red narrow 5 D 0 → 7 F 0 -4 Eu 3ϩ lines and to the eye the hybrids appeared to be white, even at room temperature. The ability to tune the emission of the xerogels to colors across the chromaticity diagram is achieved by changing the excitation wavelength and the amount of salt incorporated in the hybrid host. The local environment of Eu 3ϩ is described as a continuous distribution of closely similar low-symmetry network sites. The cations are coordinated by the carbonyl groups of the urea moieties, water molecules, and, for U (2000) n Eu͑CF 3 SO 3 ͒ 3 , by the SO 3 end groups of the triflate anions. No spectral evidences have been found for the coordination by the ether oxygens of the polyether chains. A mean radius for the first coordination shell of Eu 3ϩ is calculated on the basis of the emission energy assignments. The results obtained for U (2000) n Eu͑CF 3 SO 3 ͒ 3 , 2.4 Å for 90 уnу40 and 2.6 and 2.5 Å for nϭ30 and 20, respectively, are in good agreement with the values calculated from EXAFS measurements. The energy of the intraconfigurational charge-transfer transitions, the redshift of the 5 D 0 → 7 F 0 line, with respect to the value calculated for gaseous Eu 3ϩ , and the hypersensitive ratio between the 5 D 0 → 7 F 2 and 5 D 0 → 7 F 1 transitions, point out a rather low covalency nature of the Eu 3ϩ first coordination shell in these xerogels, comparing to the case of analogous polymer electrolytes modified by europium bromide. ͓S0163-1829͑99͒03138-0͔

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Physical properties of solid polymer electrolyte PEO(LiTFSI) complexes

Cited by 289 publications

References 26 publications

Negative Transference Numbers in Poly(ethylene oxide)-Based Electrolytes

Negative Transference Numbers in Poly(ethylene oxide)-Based Electrolytes

Transport Mechanisms of Ions in Graft-Copolymer Based Salt-in-Polymer Electrolytes

White light emission ofEu3+-based hybrid xerogels

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