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A simple, experiment-based model of the initial self-discharge of lithium-sulphur batteries

A simple, experiment-based model of the initial self-discharge of lithium-sulphur batteries
A simple, experiment-based model of the initial self-discharge of lithium-sulphur batteries
One of the main challenges in the development of lithium-sulphur batteries is the so called “shuttle mechanism”, which involves the diffusion of sulphur and polysulphides from the sulphur electrode to the lithium electrode, where they get reduced via chemical reactions with lithium. The shuttle mechanism decreases the capacity delivered by the battery, hampers its rechargeability, and promotes battery self-discharge. We have developed a simple model of the shuttle mechanism that reproduces quantitatively the rate of the initial self discharge of lithium-sulphur batteries. The rate of sulphur and polysulphide diffusion has been quantified by studying cells with varying number of separators between the electrodes. We have found that it is essential that the model incorporates the presence of carbon additive in the sulphur electrode, which slows down the decrease of the open circuit potential with time. The model also reproduces well the rate of self-discharge of lithium-sulphur cells containing sulphur dissolved in the electrolyte. In conclusion, the present model provides a basic understanding of the mechanism of self-discharge of lithium-sulphur cells, and allows quantifying the two main causes of sulphur loss at the sulphur electrode: sulphur diffusion across a concentration gradient and sulphur reaction with polysulphides formed at the lithium electrode.
lithium-sulphur batteries, shuttle mechanism, model, diffusion
0378-7753
323-328
Al-Mahmoud, Saddam M.
c44b3401-34c4-41a1-8502-36e6e39382d1
Dibden, James W.
0a189dfc-bdec-48fa-ba0f-c1d8dcaddcc2
Owen, John R.
067986ea-f3f3-4a83-bc87-7387cc5ac85d
Denuault, Guy
5c76e69f-e04e-4be5-83c5-e729887ffd4e
Garcia-Araez, Nuria
9358a0f9-309c-495e-b6bf-da985ad81c37
Al-Mahmoud, Saddam M.
c44b3401-34c4-41a1-8502-36e6e39382d1
Dibden, James W.
0a189dfc-bdec-48fa-ba0f-c1d8dcaddcc2
Owen, John R.
067986ea-f3f3-4a83-bc87-7387cc5ac85d
Denuault, Guy
5c76e69f-e04e-4be5-83c5-e729887ffd4e
Garcia-Araez, Nuria
9358a0f9-309c-495e-b6bf-da985ad81c37

Al-Mahmoud, Saddam M., Dibden, James W., Owen, John R., Denuault, Guy and Garcia-Araez, Nuria (2016) A simple, experiment-based model of the initial self-discharge of lithium-sulphur batteries. Journal of Power Sources, 306, 323-328. (doi:10.1016/j.jpowsour.2015.12.031).

Record type: Article

Abstract

One of the main challenges in the development of lithium-sulphur batteries is the so called “shuttle mechanism”, which involves the diffusion of sulphur and polysulphides from the sulphur electrode to the lithium electrode, where they get reduced via chemical reactions with lithium. The shuttle mechanism decreases the capacity delivered by the battery, hampers its rechargeability, and promotes battery self-discharge. We have developed a simple model of the shuttle mechanism that reproduces quantitatively the rate of the initial self discharge of lithium-sulphur batteries. The rate of sulphur and polysulphide diffusion has been quantified by studying cells with varying number of separators between the electrodes. We have found that it is essential that the model incorporates the presence of carbon additive in the sulphur electrode, which slows down the decrease of the open circuit potential with time. The model also reproduces well the rate of self-discharge of lithium-sulphur cells containing sulphur dissolved in the electrolyte. In conclusion, the present model provides a basic understanding of the mechanism of self-discharge of lithium-sulphur cells, and allows quantifying the two main causes of sulphur loss at the sulphur electrode: sulphur diffusion across a concentration gradient and sulphur reaction with polysulphides formed at the lithium electrode.

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Accepted/In Press date: 8 December 2015
e-pub ahead of print date: 21 December 2015
Published date: 29 February 2016
Keywords: lithium-sulphur batteries, shuttle mechanism, model, diffusion
Organisations: Electrochemistry

Identifiers

Local EPrints ID: 385825
URI: http://eprints.soton.ac.uk/id/eprint/385825
ISSN: 0378-7753
PURE UUID: 43ea8d07-7364-4535-ac4e-1986e72571ce
ORCID for John R. Owen: ORCID iD orcid.org/0000-0002-4938-3693
ORCID for Guy Denuault: ORCID iD orcid.org/0000-0002-8630-9492
ORCID for Nuria Garcia-Araez: ORCID iD orcid.org/0000-0001-9095-2379

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Date deposited: 25 Jan 2016 10:20
Last modified: 17 Dec 2019 02:01

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