The University of Southampton
University of Southampton Institutional Repository

Lithium iron sulphide as a positive electrode material for rechargeable lithium batteries

Lithium iron sulphide as a positive electrode material for rechargeable lithium batteries
Lithium iron sulphide as a positive electrode material for rechargeable lithium batteries
Lithium iron sulphide has been investigated as a low-cost, high energy density and relatively safe positive electrode material for secondary lithium batteries. Lithium iron sulphide was synthesised, characterised and compared with natural pyrite samples and was shown to have a capacity of 350 mAh.g-1 upon cycling between 1.45 and 2.80 V vs. Li. The capacity was attributed to the Fe2+/Fe3+ redox couple at potentials up to 2.55 V, and oxidation of sulphur sites from Fe3+(S2-)2 to Fe3+S2-(S2)2-0.5 up to 2.80 V. The cycle life performance of lithium iron sulphide is poor when the cell is cycled between 1.45 and 2.80 V, with the cell loosing approximately 1.4 mAh.g-1 per cycle, although this performance is superior to comparable pyrite electrodes. Calcium doped samples of lithium iron sulphide were synthesised. Calcium doping was shown to impact upon lithium transport properties of the bulk lithium iron sulphide, improving the rate performance of the material. Improvements in cycle life performance of the calcium doped samples were offset by decreased specific capacity due to lithium substitution. The poor cycle life performance of lithium iron sulphide cells was attributed to the utilisation of the high voltage plateau corresponding to sulphur site oxidation/reduction. Experiments utilising a variety of negative electrode materials has identified the formation of soluble polysulphide species upon cycling of the cell, which reduce irreversibly at the negative electrode, contributing to active mass loss and poor cycle life performance. In-situ XRD studies have highlighted the structural decomposition that occurs upon utilisation of the sulphide, which results in irreversible amorphisation of the lithium iron sulphide crystal structure. Lithium iron sulphide was treated via coating with lithium boron oxide glass and a novel carbon coating method via thermal decomposition of butyl-methyl-pyrrolydinium-dicyanimide. Both treatments were shown to increase the cycle life performance of lithium iron sulphide, due to decreased dissolution of polysulphide upon cycling. The choice of binder, electrode formulation and electrolyte was also shown to impact upon the cycle life performance of lithium iron sulphide cells.
Madsen, Alex
1d4678e9-0d8d-4d87-ba22-7fcc109570ce
Madsen, Alex
1d4678e9-0d8d-4d87-ba22-7fcc109570ce
Owen, John
067986ea-f3f3-4a83-bc87-7387cc5ac85d

(2013) Lithium iron sulphide as a positive electrode material for rechargeable lithium batteries. University of Southampton, Chemistry, Doctoral Thesis, 239pp.

Record type: Thesis (Doctoral)

Abstract

Lithium iron sulphide has been investigated as a low-cost, high energy density and relatively safe positive electrode material for secondary lithium batteries. Lithium iron sulphide was synthesised, characterised and compared with natural pyrite samples and was shown to have a capacity of 350 mAh.g-1 upon cycling between 1.45 and 2.80 V vs. Li. The capacity was attributed to the Fe2+/Fe3+ redox couple at potentials up to 2.55 V, and oxidation of sulphur sites from Fe3+(S2-)2 to Fe3+S2-(S2)2-0.5 up to 2.80 V. The cycle life performance of lithium iron sulphide is poor when the cell is cycled between 1.45 and 2.80 V, with the cell loosing approximately 1.4 mAh.g-1 per cycle, although this performance is superior to comparable pyrite electrodes. Calcium doped samples of lithium iron sulphide were synthesised. Calcium doping was shown to impact upon lithium transport properties of the bulk lithium iron sulphide, improving the rate performance of the material. Improvements in cycle life performance of the calcium doped samples were offset by decreased specific capacity due to lithium substitution. The poor cycle life performance of lithium iron sulphide cells was attributed to the utilisation of the high voltage plateau corresponding to sulphur site oxidation/reduction. Experiments utilising a variety of negative electrode materials has identified the formation of soluble polysulphide species upon cycling of the cell, which reduce irreversibly at the negative electrode, contributing to active mass loss and poor cycle life performance. In-situ XRD studies have highlighted the structural decomposition that occurs upon utilisation of the sulphide, which results in irreversible amorphisation of the lithium iron sulphide crystal structure. Lithium iron sulphide was treated via coating with lithium boron oxide glass and a novel carbon coating method via thermal decomposition of butyl-methyl-pyrrolydinium-dicyanimide. Both treatments were shown to increase the cycle life performance of lithium iron sulphide, due to decreased dissolution of polysulphide upon cycling. The choice of binder, electrode formulation and electrolyte was also shown to impact upon the cycle life performance of lithium iron sulphide cells.

PDF
__soton.ac.uk_ude_PersonalFiles_Users_lp5_mydocuments_Theses PDF files_Thesis_AlexMadsen_final_240713.pdf - Other
Download (6MB)

More information

Published date: 31 July 2013
Organisations: University of Southampton, Chemistry

Identifiers

Local EPrints ID: 355748
URI: http://eprints.soton.ac.uk/id/eprint/355748
PURE UUID: 3720f367-d616-4c81-8529-0b8f8b667e04
ORCID for John Owen: ORCID iD orcid.org/0000-0002-4938-3693

Catalogue record

Date deposited: 18 Nov 2013 11:13
Last modified: 14 Jul 2018 00:37

Export record

Contributors

Author: Alex Madsen
Thesis advisor: John Owen ORCID iD

University divisions

Download statistics

Downloads from ePrints over the past year. Other digital versions may also be available to download e.g. from the publisher's website.

View more statistics

Atom RSS 1.0 RSS 2.0

Contact ePrints Soton: eprints@soton.ac.uk

ePrints Soton supports OAI 2.0 with a base URL of http://eprints.soton.ac.uk/cgi/oai2

This repository has been built using EPrints software, developed at the University of Southampton, but available to everyone to use.

We use cookies to ensure that we give you the best experience on our website. If you continue without changing your settings, we will assume that you are happy to receive cookies on the University of Southampton website.

×