Continuum transport laws for locally non-neutral concentrated electrolytes

Solid Polymer Electrolytes from Crosslinked PEG and Dilithium N,N'-Bis(trifluoromethanesulfonyl)perfluoroalkane-1,ω-disulfonamide and Lithium Bis(trifluoromethanesulfonyl)imide Salts

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc20081777 ◽

2008 ◽

Vol 73 (12) ◽

pp. 1777-1798 ◽

Cited By ~ 1

Author(s):

Olt E. Geiculescu ◽

Rama V. Rajagopal ◽

Emilia C. Mladin ◽

Stephen E. Creager ◽

Darryl D. Desmarteau

Keyword(s):

Ionic Conductivity ◽

Polymer Electrolytes ◽

Minimum Energy ◽

Ionic Conductivities ◽

Solid Polymer Electrolytes ◽

Solid Polymer ◽

Segmental Motion ◽

Concentrated Electrolytes ◽

Two Factors ◽

Poly Ethylene

The present work consists of a series of studies with regard to the structure and charge transport in solid polymer electrolytes (SPE) prepared using various new bis(trifluoromethanesulfonyl)imide (TFSI)-based dianionic dilithium salts in crosslinked low-molecular-weight poly(ethylene glycol). Some of the thermal properties (glass transition temperature, differential molar heat capacity) and ionic conductivities were determined for both diluted (EO/Li = 30:1) and concentrated (EO/Li = 10:1) SPEs. Trends in ionic conductivity of the new SPEs with respect to anion structure revealed that while for the dilute electrolytes ionic conductivity is generally rising with increased length of the perfluoroalkylene linking group in the dianions, for the concentrated electrolytes the trend is reversed with respect to dianion length. This behavior could be the result of a combination of two factors: on one hand a decrease in dianion basicity that results in diminished ion pairing and an enhancement in the number of charge carriers with increasing fluorine anion content, thereby increasing ionic conductivity while on the other hand the increasing anion size and concentration produce an increase in the friction/entanglements of the polymeric segments which lowers even more the reduced segmental motion of the crosslinked polymer and decrease the dianion contribution to the overall ionic conductivity. DFT modeling of the same TFSI-based dianionic dilithium salts reveals that the reason for the trend observed is due to the variation in ion dissociation enthalpy, derived from minimum-energy structures, with respect to perfluoroalkylene chain length.

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Concentrated electrolytes unlock the full energy potential of potassium-sulfur battery chemistry

Energy Storage Materials ◽

10.1016/j.ensm.2018.10.004 ◽

2019 ◽

Vol 18 ◽

pp. 470-475 ◽

Cited By ~ 25

Author(s):

Lu Wang ◽

Jingze Bao ◽

Qin Liu ◽

Chuan-Fu Sun

Keyword(s):

Energy Potential ◽

Full Energy ◽

Concentrated Electrolytes ◽

Sulfur Battery

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Conservation Laws and Transport Laws

The Newman Lectures on Transport Phenomena ◽

10.1201/9781315108292-2 ◽

2020 ◽

pp. 3-4

Author(s):

John Newman ◽

Vincent Battaglia

Keyword(s):

Conservation Laws ◽

Transport Laws

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Towards the Understanding of Water-in-Salt Electrolytes: Individual Ion Activities and Liquid Junction Potentials in Highly Concentrated Aqueous Solutions

10.26434/chemrxiv.14695674 ◽

2021 ◽

Author(s):

Damien Degoulange ◽

Nicolas Dubouis ◽

Alexis Grimaud

Keyword(s):

Activity Coefficients ◽

Operating Voltage ◽

Redox Potentials ◽

Liquid Junction ◽

Nernst Potential ◽

Concentrated Electrolytes ◽

Ion Activity ◽

Ion Activities ◽

Single Ion Activity ◽

Increased Activity

Highly concentrated electrolytes were recently proposed to improve the performances of aqueous electrochemical systems by delaying the water splitting and increasing the operating voltage for battery applications. While advances were made regarding their implementation in practical devices, debate exists regarding the physical origin for the delayed water reduction occurring at the electrode/electrolyte interface. Evidently, one difficulty resides in our lack of knowledge regarding ions activity arising from this novel class of electrolyte, it being necessary to estimate the Nernst potential of associated redox reactions such as Li+ intercalation or the hydrogen evolution reaction. In this work, we first measured the potential shift of electrodes selective to either Li+, H+ or Zn2+ ions from diluted to highly concentrated regimes in LiCl or LiTFSI solutions. Observing similar shifts for these different cations and environments, we establish that shifts in redox potentials from diluted to highly concentrated regime originates in large from an increase junction potential, it being dependent on the ions activity coefficients that increase with concentration. While our study shows that single ion activity coefficients, unlike mean ion activity coefficients, cannot be captured by any electrochemical means, we demonstrate that protons concentration increases by approximatively two orders of magnitude from 1 mol.kg-1 to 15-20 mol.kg-1 solutions. Combined with the increased activity coefficients, this increases the activity of protons and thus the pH of highly concentrated solutions which appears acidic.

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