Transport Properties of the Solid Polymer Electrolyte System P(EO)<i><sub>n</sub></i>LiTFSI

Edman, Ludvig; Doeff, Marca M.; Ferry, Anders; Kerr, John B.; DeJonghe, Lutgard C.

doi:10.1021/jp993897z

Cited by 146 publications

(129 citation statements)

References 41 publications

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“…The t + value of this electrolyte was about 0.12 (SI Appendix, Fig. S6), consistent with literature reports that t + values for LiTFSI/PEO electrolytes are between 0.1 and 0.3 (31,32). In the future, we will use more rigorous approaches to measure t + (33).…”

Section: Significancesupporting

confidence: 86%

Nonflammable perfluoropolyether-based electrolytes for lithium batteries

Wong

Thelen

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

204

214

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The flammability of conventional alkyl carbonate electrolytes hinders the integration of large-scale lithium-ion batteries in transportation and grid storage applications. In this study, we have prepared a unique nonflammable electrolyte composed of low molecular weight perfluoropolyethers and bis(trifluoromethane)sulfonimide lithium salt. These electrolytes exhibit thermal stability beyond 200°C and a remarkably high transference number of at least 0.91 (more than double that of conventional electrolytes). Li/LiNi 1/3 Co 1/3 Mn 1/3 O 2 cells made with this electrolyte show good performance in galvanostatic cycling, confirming their potential as rechargeable lithium batteries with enhanced safety and longevity.fluorinated polymers | nonflammable electrolytes L arge-scale rechargeable batteries are expected to play a key role in today's emerging sustainable energy landscape (1, 2). State-of-the-art lithium (Li) batteries not only are used to power zero-emission electric vehicles, but they currently are gaining traction as backup power in aircraft and smart grid applications (3, 4). The electrolyte used in these batteries, however, hinders their use in large-scale applications: it contains a flammable mixture of alkyl carbonate solvents that frequently leads to safety issues. Dimethyl carbonate (DMC), an important component in commercial Li-ion battery electrolytes, has an HMIS (Hazardous Materials Identification System) flammability rating of 3 on a scale of 0-4, indicating a high risk of ignition under most operating conditions. The intrinsic instability of carbonate-based solvents worsens at higher temperatures, at which exothermic electrolyte breakdown often leads to thermal runaway (5, 6), resulting in catastrophic failure of the battery. Although this failure rate stands at about one in ten million systems, it is intolerable for large-scale applications in which cost and user safety might be heavily compromised. This necessitates the development of radically new electrolytes with improved safety.Desirable electrolyte properties include a large window of phase stability (no vaporization or crystallization), complete nonflammability, a wide electrochemical stability window, and suitable ionic transport for the targeted application. There are many approaches to synthesizing materials with these properties, e.g., ionic liquids (7, 8), gel-polymer matrices (9, 10), and small molecule additives (11-13). Systems using poly(ethylene oxide) (PEO) also are well studied (14,15). PEO can solvate high concentrations of lithium salts and is considered nonflammable. Unfortunately, practical conductivity often is limited within a high temperature range (14), and it is well known that in these systems, the motion of the Li ion carries only a small fraction of the overall current (also known as the Li-ion transference number, t + ). PEO-based electrolytes typically exhibit t + values between 0.1 and 0.5 (16-20), leading to strong salt concentration gradients across the electrolytes that limit power density. Recently, we repor...

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Section: Significancesupporting

confidence: 86%

Nonflammable perfluoropolyether-based electrolytes for lithium batteries

Wong

Thelen

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

204

214

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“…This result agrees with the fact that the salt weight % of the maximum ionic conductivity is shifted from the eutectic point to the more concentrated phase, which is also shown in other systems [41]. Figure 4 shows the dependence of the OCV for the concentration cell form Li | PEO n Lithium bis-trifluoromethanesulfonate imide (LiTFSI) | PEO m LiTFSI | Li at 85° [42]. LiTFSI is reported to act as a plasticizer when complexed with PEO [43].…”

Section: The Melting Point Depression Theorysupporting

confidence: 83%

Open circuit voltage for solid polymer electrolyte/salt systems in lithium batteries

Pai

Bae

2005

J Appl Electrochem

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The open circuit voltage (OCV) model of the solid polymer electrolyte (SPE)/salt system in lithium batteries is established by combining concentrated solution theory with the modified double lattice-non-random (MDL-NR) model which describes the non-ideal behavior of the salt activity in the polymer electrolyte. The activity parameters are obtained from the phase diagram for the given systems and used to describe the OCV of the corresponding systems with one additional parameter, transport number, t 0 þ . The proposed model agrees very well with the OCV data for various PEO/salt systems.

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“…• C, 37 Figure 2c. We find that t +,SS decreases monotonically with increasing r, with a maximum value of 0.18 at r = 0.01 and a minimum of 0.06 at r = 0.16.…”

Section: Resultsmentioning

confidence: 99%

“…We also note that the transference number of this system was found to be positive at all salt concentrations. 37 It is not clear if differences in molecular weight are responsible for these differences. Figure 5.…”

Section: Resultsmentioning

confidence: 99%

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

Pesko

Timachova

Bhattacharya

et al. 2017

J. Electrochem. Soc.

191

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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Transport Properties of the Solid Polymer Electrolyte System P(EO)_nLiTFSI

Cited by 146 publications

References 41 publications

Nonflammable perfluoropolyether-based electrolytes for lithium batteries

Nonflammable perfluoropolyether-based electrolytes for lithium batteries

Open circuit voltage for solid polymer electrolyte/salt systems in lithium batteries

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

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Transport Properties of the Solid Polymer Electrolyte System P(EO)nLiTFSI

Cited by 146 publications

References 41 publications

Nonflammable perfluoropolyether-based electrolytes for lithium batteries

Nonflammable perfluoropolyether-based electrolytes for lithium batteries

Open circuit voltage for solid polymer electrolyte/salt systems in lithium batteries

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

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Product

Resources

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Transport Properties of the Solid Polymer Electrolyte System P(EO)_nLiTFSI