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Operando characterization of active surface area and passivation effects on sulfur-carbon composites for lithium-sulfur batteries

Operando characterization of active surface area and passivation effects on sulfur-carbon composites for lithium-sulfur batteries
Operando characterization of active surface area and passivation effects on sulfur-carbon composites for lithium-sulfur batteries
Sulfur electrodes for lithium-sulfur batteries necessarily contain a conductive additive, typically carbon, to enable the electrochemical reactions, since sulfur and the discharge product, Li2S, are insulators. Consequently, the full passivation of carbon, by deposition of sulfur and/or Li2S, would necessarily produce the death of the battery. However, here we demonstrate that for high-performance lithium-sulfur batteries operated under lean electrolyte conditions (electrolyte to sulfur ratio of 6 µL mgS−1 in Li-S coin cells), the extent of passivation of carbon is not severe enough to limit performance. This is shown by performing impedance measurements of fully charged lithium-sulfur batteries, from which we demonstrate that we can evaluate the specific surface area of carbon, and we find that the capacity fade with cycling is not due to a decrease in the electrochemically active surface area of carbon. These results show that introducing a higher surface area carbon in the sulfur electrode formulation is not needed to prevent passivation, and that the focus of lithium-sulfur development should be directed towards other issues, such as mitigating undesirable reactions at the lithium electrode and achieving robust sulfur electrode structures enabling fast transport of electrolyte species and, thus, more homogeneous reactions.
Capacity fade, Cathode, Electrochemical impedance spectroscopy, Lithium-sulfur batteries, Mass transport, Passivation
0013-4686
Li, He
1d46f87c-8509-43b9-9ee5-eb1065c4de0f
Lampkin, John
509a899a-1400-46e8-becd-4af728704bcf
Chien, Yu-Chuan
6db11fcd-bb39-4404-8613-e49177154596
Furness, Liam
146129ff-d855-4d8f-a098-34e178fba676
Brandell, Daniel
eafbc5bf-17cf-436a-a2b3-9b2973bbd7c8
Lacey, Matthew
569e58aa-cf7b-4ff2-9ae5-8dd36d045055
Garcia-Araez, Nuria
9358a0f9-309c-495e-b6bf-da985ad81c37
Li, He
1d46f87c-8509-43b9-9ee5-eb1065c4de0f
Lampkin, John
509a899a-1400-46e8-becd-4af728704bcf
Chien, Yu-Chuan
6db11fcd-bb39-4404-8613-e49177154596
Furness, Liam
146129ff-d855-4d8f-a098-34e178fba676
Brandell, Daniel
eafbc5bf-17cf-436a-a2b3-9b2973bbd7c8
Lacey, Matthew
569e58aa-cf7b-4ff2-9ae5-8dd36d045055
Garcia-Araez, Nuria
9358a0f9-309c-495e-b6bf-da985ad81c37

Li, He, Lampkin, John, Chien, Yu-Chuan, Furness, Liam, Brandell, Daniel, Lacey, Matthew and Garcia-Araez, Nuria (2022) Operando characterization of active surface area and passivation effects on sulfur-carbon composites for lithium-sulfur batteries. Electrochimica Acta, 403, [139572]. (doi:10.1016/j.electacta.2021.139572).

Record type: Article

Abstract

Sulfur electrodes for lithium-sulfur batteries necessarily contain a conductive additive, typically carbon, to enable the electrochemical reactions, since sulfur and the discharge product, Li2S, are insulators. Consequently, the full passivation of carbon, by deposition of sulfur and/or Li2S, would necessarily produce the death of the battery. However, here we demonstrate that for high-performance lithium-sulfur batteries operated under lean electrolyte conditions (electrolyte to sulfur ratio of 6 µL mgS−1 in Li-S coin cells), the extent of passivation of carbon is not severe enough to limit performance. This is shown by performing impedance measurements of fully charged lithium-sulfur batteries, from which we demonstrate that we can evaluate the specific surface area of carbon, and we find that the capacity fade with cycling is not due to a decrease in the electrochemically active surface area of carbon. These results show that introducing a higher surface area carbon in the sulfur electrode formulation is not needed to prevent passivation, and that the focus of lithium-sulfur development should be directed towards other issues, such as mitigating undesirable reactions at the lithium electrode and achieving robust sulfur electrode structures enabling fast transport of electrolyte species and, thus, more homogeneous reactions.

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More information

Accepted/In Press date: 9 November 2021
e-pub ahead of print date: 16 November 2021
Published date: 20 January 2022
Keywords: Capacity fade, Cathode, Electrochemical impedance spectroscopy, Lithium-sulfur batteries, Mass transport, Passivation

Identifiers

Local EPrints ID: 452240
URI: http://eprints.soton.ac.uk/id/eprint/452240
ISSN: 0013-4686
PURE UUID: a6a7ba33-037d-4c18-8c7b-28c9925af7f9
ORCID for Nuria Garcia-Araez: ORCID iD orcid.org/0000-0001-9095-2379

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Date deposited: 01 Dec 2021 17:34
Last modified: 17 Mar 2024 06:57

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Contributors

Author: He Li ORCID iD
Author: John Lampkin
Author: Yu-Chuan Chien
Author: Liam Furness
Author: Daniel Brandell
Author: Matthew Lacey

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