Measurement of transference numbers for lithium ion electrolytes via four different methods, a comparative study

Zugmann, Sandra; Fleischmann, Matthias; Amereller, Marius; Gschwind, Ruth M.; Wiemhöfer, Hans‐Dieter; Gores, H. J.

doi:10.1016/j.electacta.2011.02.025

Cited by 390 publications

(362 citation statements)

References 51 publications

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“…[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 containing lithium salts fall between zero and one, including those that followed the techniques outlined by Ma and coworkers. [52][53][54][55][56] Zugmann and coworkers presented a comparative study using four different methods for measuring t + in nonaqueous liquid electrolytes. In all cases, t + fell in the range of 0.25 to 0.35.…”

mentioning

confidence: 99%

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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mentioning

confidence: 99%

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 benefits of LiDFOB based electrolytes include a cationic transference number of 1 M LiDFOB in EC:DEC (3:7, by wt.) that is significantly higher than that of 1 M LiPF 6 in this solvent mixture (0.33 vs. 0.24) [33,34] and the ability to form a very stable and protecting SEI [35,36] on graphite electrodes, just like LiBOB [29,30,37]. Beyond that, the SEI built in an LiDFOB-based electrolyte is also a very good lithium ion conductor, comparable with the SEIs of LiBF 4 -based electrolytes [29,30].…”

Section: Introductionmentioning

confidence: 62%

Results from a Novel Method for Corrosion Studies of Electroplated Lithium Metal Based on Measurements with an Impedance Scanning Electrochemical Quartz Crystal Microbalance

et al. 2013

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Abstract:A new approach to study the chemical stability of electrodeposited lithium on a copper metal substrate via measurements with a fast impedance scanning electrochemical quartz crystal microbalance is presented. The corrosion of electrochemically deposited lithium was compared in two different electrolytes, based on lithium difluoro(oxalato) borate (LiDFOB) and lithium hexafluorophosphate, both salts being dissolved in solvent blends of ethylene carbonate and diethyl carbonate. For a better understanding of the corrosion mechanisms, scanning electron microscopy images of electrodeposited lithium were also consulted. The results of the EQCM experiments were supported by AC impedance measurements and clearly showed two different corrosion mechanisms caused by the different salts and the formed SEIs. The observed mass decrease of the quartz sensor of the LiDFOB-based electrolyte is not smooth, but rather composed of a series of abrupt mass fluctuations in contrast to that of the lithium hexafluorophosphate-based electrolyte. After each slow decrease of mass a rather fast increase of mass is observed several times. The slow mass decrease can be attributed to a consolidation process of the SEI or to the partial dissolution of the SEI leaving finally lithium metal unprotected so that a fast film formation sets in entailing the observed fast mass increases.

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“…This method is no electrochemical method and cannot distinguish free ions from ion pairs. In concentrated solutions this transference number can differ dramatically from transference numbers obtained by electrochemical methods and may even show erroneous concentration dependence [25].…”

Section: Introductionmentioning

confidence: 99%

“…The transference number can also be determined by measuring the diffusion coefficient with nuclear magnetic resonance (NMR) spectroscopy if some precautions are taken into account [25,41,42]. This method is no electrochemical method and cannot distinguish free ions from ion pairs.…”

Section: Introductionmentioning

confidence: 99%

“…It represents the fraction of current carried by lithium ions and it should be as high as possible. Zugmann et al [4,25] have published a survey of various methods for determination of transference numbers based on various electrochemical methods, including the potentiostatic polarization method established by Bruce and Vincent [26], the galvanostatic polarization method according to Ma et al [27], and the electromotive force method proposed by MacInnes and Beattie [28].…”

Section: Introductionmentioning

confidence: 99%

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A Liquid Inorganic Electrolyte Showing an Unusually High Lithium Ion Transference Number: A Concentrated Solution of LiAlCl4 in Sulfur Dioxide

et al. 2013

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Abstract:We report on studies of an inorganic electrolyte: LiAlCl 4 in liquid sulfur dioxide. Concentrated solutions show a very high conductivity when compared with typical electrolytes for lithium ion batteries that are based on organic solvents. Our investigations include conductivity measurements and measurements of transference numbers via nuclear magnetic resonance (NMR) and by a classical direct method, Hittorf's method. For the use of Hittorf's method, it is necessary to measure the concentration of the electrolyte in a selected cell compartment before and after electrochemical polarization very precisely. This task was finally performed by potentiometric titration after hydrolysis of the salt. The Haven ratio was determined to estimate the association behavior of this very concentrated electrolyte solution. The measured unusually high transference number of the lithium cation of the studied most concentrated solution, a molten solvate LiAlCl 4 × 1.6SO 2 , makes this electrolyte a promising alternative for lithium ion cells with high power ability. OPEN ACCESSEnergies 2013, 6 4449

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Measurement of transference numbers for lithium ion electrolytes via four different methods, a comparative study

Cited by 390 publications

References 51 publications

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

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

Results from a Novel Method for Corrosion Studies of Electroplated Lithium Metal Based on Measurements with an Impedance Scanning Electrochemical Quartz Crystal Microbalance

A Liquid Inorganic Electrolyte Showing an Unusually High Lithium Ion Transference Number: A Concentrated Solution of LiAlCl4 in Sulfur Dioxide

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