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Impedance characterization of the transport properties of electrolytes contained within porous electrodes and separators useful for Li-S batteries

Impedance characterization of the transport properties of electrolytes contained within porous electrodes and separators useful for Li-S batteries
Impedance characterization of the transport properties of electrolytes contained within porous electrodes and separators useful for Li-S batteries
Impedance spectroscopy is used to characterize the key transport properties (effective conductivity, MacMullin number, porosity and tortuosity) of electrolyte solutions confined in porous separators and carbon-sulfur composite electrodes useful for application in Li-S batteries. Three relevant electrolyte concentrations, ranging between 1 and 5 molal, are studied. Impedance measurements are performed in symmetrical cells with two identical electrodes, which overcome complications associated with the contributions of the counter-reference electrode. The electrolyte-filled carbon-sulfur composite electrodes can be represented by an “open” Warburg element, modelling the finite-diffusion of ions through the pores coupled to the double-layer charging of the electrode-electrolyte interface. The carbon-sulfur composite electrodes are at a high enough potential (ca. 3 V vs. Li+/Li) so that charge-transfer reactions of sulfur reduction to polysulfide species are absent during the impedance measurements, and hence capacitive-like behavior is observed at low frequencies. The analysis of the results shows that the rate of transport of ions through porous structures is markedly dependent on the electrode's structure and composition as well as the electrolyte concentration. Synergistic effects, able to enhance the effective conductivity of the electrolyte inside porous composite electrodes, are observed for particular electrode/electrolyte combinations, which are correlated to enhanced performance in Li-S cells.
0013-4651
2741-2749
Raccichini, Rinaldo
7f943ecf-6b1b-4e4a-b222-8f3c27e679df
Furness, Liam
2c50e6af-80f2-40d4-8aca-59843b79b6c1
Dibden, James
0a189dfc-bdec-48fa-ba0f-c1d8dcaddcc2
Owen, John R.
067986ea-f3f3-4a83-bc87-7387cc5ac85d
Garcia-Araez, Nuria
9358a0f9-309c-495e-b6bf-da985ad81c37
Raccichini, Rinaldo
7f943ecf-6b1b-4e4a-b222-8f3c27e679df
Furness, Liam
2c50e6af-80f2-40d4-8aca-59843b79b6c1
Dibden, James
0a189dfc-bdec-48fa-ba0f-c1d8dcaddcc2
Owen, John R.
067986ea-f3f3-4a83-bc87-7387cc5ac85d
Garcia-Araez, Nuria
9358a0f9-309c-495e-b6bf-da985ad81c37

Raccichini, Rinaldo, Furness, Liam, Dibden, James, Owen, John R. and Garcia-Araez, Nuria (2018) Impedance characterization of the transport properties of electrolytes contained within porous electrodes and separators useful for Li-S batteries. Journal of the Electrochemical Society, 165 (11), 2741-2749. (doi:10.1149/2.0631811jes).

Record type: Article

Abstract

Impedance spectroscopy is used to characterize the key transport properties (effective conductivity, MacMullin number, porosity and tortuosity) of electrolyte solutions confined in porous separators and carbon-sulfur composite electrodes useful for application in Li-S batteries. Three relevant electrolyte concentrations, ranging between 1 and 5 molal, are studied. Impedance measurements are performed in symmetrical cells with two identical electrodes, which overcome complications associated with the contributions of the counter-reference electrode. The electrolyte-filled carbon-sulfur composite electrodes can be represented by an “open” Warburg element, modelling the finite-diffusion of ions through the pores coupled to the double-layer charging of the electrode-electrolyte interface. The carbon-sulfur composite electrodes are at a high enough potential (ca. 3 V vs. Li+/Li) so that charge-transfer reactions of sulfur reduction to polysulfide species are absent during the impedance measurements, and hence capacitive-like behavior is observed at low frequencies. The analysis of the results shows that the rate of transport of ions through porous structures is markedly dependent on the electrode's structure and composition as well as the electrolyte concentration. Synergistic effects, able to enhance the effective conductivity of the electrolyte inside porous composite electrodes, are observed for particular electrode/electrolyte combinations, which are correlated to enhanced performance in Li-S cells.

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J. Electrochem. Soc.-2018-Raccichini-A2741-9 - Version of Record
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Submitted date: 22 May 2018
Accepted/In Press date: 23 July 2018
e-pub ahead of print date: 24 August 2018
Published date: August 2018

Identifiers

Local EPrints ID: 424241
URI: http://eprints.soton.ac.uk/id/eprint/424241
ISSN: 0013-4651
PURE UUID: b93ea8d7-78a6-4e8a-b337-28b35ba64cc1
ORCID for John R. Owen: ORCID iD orcid.org/0000-0002-4938-3693
ORCID for Nuria Garcia-Araez: ORCID iD orcid.org/0000-0001-9095-2379

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Date deposited: 05 Oct 2018 11:35
Last modified: 15 Sep 2021 02:00

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Contributors

Author: Rinaldo Raccichini
Author: Liam Furness
Author: James Dibden
Author: John R. Owen ORCID iD

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