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Towards safer electrolytes: comparing the air stability and electrochemical properties of NaPF6, NaTFSI and Na[B(hfip)4]·DME for sodium-ion batteries

Darren Ould, James Courtney Orcid Logo, David J. Morgan Orcid Logo, Daniel Curtis Orcid Logo, Marcin Orzech Orcid Logo, Sajad Kiani Orcid Logo, Brent de Boode, Clare P. Grey Orcid Logo, Dominic S. Wright Orcid Logo, Serena Margadonna Orcid Logo

EES Batteries, Volume: 2, Issue: 2, Pages: 475 - 489

Swansea University Authors: Darren Ould, James Courtney Orcid Logo, Daniel Curtis Orcid Logo, Marcin Orzech Orcid Logo, Sajad Kiani Orcid Logo, Serena Margadonna Orcid Logo

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DOI (Published version): 10.1039/d6eb00011h

Abstract

Sodium-ion batteries (SIBs) are a promising post lithium-ion battery (LIB) technology, which offer advantages in improved sustainability. This work investigates using NaTFSI [TFSI = bis(trifluoromethylsulfonyl)imide] and Na[B(hfip)4]·DME [hfip = OCH(CF3)2 (OiPrF), DME = 1,2-dimethoxyethane] as alter...

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Published in: EES Batteries
ISSN: 3033-4071
Published: Royal Society of Chemistry (RSC) 2026
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URI: https://cronfa.swan.ac.uk/Record/cronfa71325
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This work investigates using NaTFSI [TFSI = bis(trifluoromethylsulfonyl)imide] and Na[B(hfip)4]&#xB7;DME [hfip = OCH(CF3)2 (OiPrF), DME = 1,2-dimethoxyethane] as alternative electrolyte salts to the current benchmark standard NaPF6 and compares their air stability, electrochemical properties and performance in sodium-ion coin cells. Multinuclear NMR spectroscopic experiments found that NaPF6 and NaTFSI were stable to atmospheric air after one month, whereas Na[B(hfip)4]&#xB7;DME showed signs of degradation. The air stability of NaPF6 was compared to LiPF6, where the latter underwent complete decomposition after 24 hours. Electrochemical investigations in 1 M solutions of ethylene carbonate: diethyl carbonate (EC:DEC) solvent revealed 1 M NaPF6 has the highest bulk conductivity. Cyclic voltammetry experiments showed 1 M NaPF6 and 1 M Na[B(hfip)4]&#xB7;DME are compatible with aluminium foils up to 4.2 V vs. Na/Na+, whereas 1 M NaTFSI underwent aluminium corrosion. Corrosion could be supressed by either limiting cut-off voltage or by the addition of 2 wt% NaPF6 as an additive, both applicable mitigation strategies. Stable long-term cycling at 1C rate in cells using a Prussian white cathode and hard carbon anode occured with both 1 M NaPF6 and 1 M NaTFSI electrolytes. Thus, 1 M NaTFSI is a viable alternative to 1 M NaPF6 in SIBs with a Prussian white cathode, offering a potentially safer electrolyte choice by limiting HF generation on account of the strong C&#x2013;F bonds in NaTFSI.</abstract><type>Journal Article</type><journal>EES Batteries</journal><volume>2</volume><journalNumber>2</journalNumber><paginationStart>475</paginationStart><paginationEnd>489</paginationEnd><publisher>Royal Society of Chemistry (RSC)</publisher><placeOfPublication/><isbnPrint/><isbnElectronic/><issnPrint/><issnElectronic>3033-4071</issnElectronic><keywords/><publishedDay>1</publishedDay><publishedMonth>4</publishedMonth><publishedYear>2026</publishedYear><publishedDate>2026-04-01</publishedDate><doi>10.1039/d6eb00011h</doi><url/><notes/><college>COLLEGE NANME</college><department>Engineering and Applied Sciences School</department><CollegeCode>COLLEGE CODE</CollegeCode><DepartmentCode>EAAS</DepartmentCode><institution>Swansea University</institution><apcterm>Not Required</apcterm><funders>SM acknowledges support from the Royal Society through an Industry Fellowship (IF\R2\23200112). DMCO and SM also acknowledge funding from the Faraday Institution through the Industry SPRINT programme (grant number FIRG074) and Batri Ltd for supply of hard carbon. DMCO, CPG and DSW would like to thank the Faraday Institution FIRG064 and FIRG089 for supporting this work. XPS data collection was performed at the Cardiff hub of the EPSRC National Facility for X-ray photoelectron spectroscopy, the EPSRC National Facility for XPS (&#x201C;HarwellXPS&#x201D;, EP/Y023587/1, EP/Y023609/1, EP/Y023536/1, EP/Y023552/1 and EP/Y023544/1).</funders><projectreference/><lastEdited>2026-05-21T14:35:03.0761019</lastEdited><Created>2026-01-27T20:19:33.3167895</Created><path><level id="1">Faculty of Science and Engineering</level><level id="2">School of Engineering and Applied Sciences - Chemical Engineering</level></path><authors><author><firstname>Darren</firstname><surname>Ould</surname><orcid/><order>1</order></author><author><firstname>James</firstname><surname>Courtney</surname><orcid>0000-0003-2944-3393</orcid><order>2</order></author><author><firstname>David J.</firstname><surname>Morgan</surname><orcid>0000-0002-6571-5731</orcid><order>3</order></author><author><firstname>Daniel</firstname><surname>Curtis</surname><orcid>0000-0002-6955-0524</orcid><order>4</order></author><author><firstname>Marcin</firstname><surname>Orzech</surname><orcid>0000-0002-1086-4481</orcid><order>5</order></author><author><firstname>Sajad</firstname><surname>Kiani</surname><orcid>0000-0003-1609-6855</orcid><order>6</order></author><author><firstname>Brent de</firstname><surname>Boode</surname><order>7</order></author><author><firstname>Clare P.</firstname><surname>Grey</surname><orcid>0000-0001-5572-192x</orcid><order>8</order></author><author><firstname>Dominic S.</firstname><surname>Wright</surname><orcid>0000-0002-9952-3877</orcid><order>9</order></author><author><firstname>Serena</firstname><surname>Margadonna</surname><orcid>0000-0002-6996-6562</orcid><order>10</order></author></authors><documents><document><filename>71325__36165__b1a2ddfc96cc4b968664227087d61baa.pdf</filename><originalFilename>71325.VoR.pdf</originalFilename><uploaded>2026-02-02T14:55:47.4863389</uploaded><type>Output</type><contentLength>2379182</contentLength><contentType>application/pdf</contentType><version>Version of Record</version><cronfaStatus>true</cronfaStatus><documentNotes>&#xA9;2026The Author(s). 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spelling 2026-05-21T14:35:03.0761019 v2 71325 2026-01-27 Towards safer electrolytes: comparing the air stability and electrochemical properties of NaPF6, NaTFSI and Na[B(hfip)4]·DME for sodium-ion batteries 6abdf0ba47ad51e529f810b24a67bc19 Darren Ould Darren Ould true false 919d02ade339d2aff29e96445039211b 0000-0003-2944-3393 James Courtney James Courtney true false e76ff28a23af2fe37099c4e9a24c1e58 0000-0002-6955-0524 Daniel Curtis Daniel Curtis true false d47b0185188280619c0d61f40ea98a9a 0000-0002-1086-4481 Marcin Orzech Marcin Orzech true false fe9ec46699e095368faf2a0465b598c5 0000-0003-1609-6855 Sajad Kiani Sajad Kiani true false e31904a10b1b1240b98ab52d9977dfbe 0000-0002-6996-6562 Serena Margadonna Serena Margadonna true false 2026-01-27 EAAS Sodium-ion batteries (SIBs) are a promising post lithium-ion battery (LIB) technology, which offer advantages in improved sustainability. This work investigates using NaTFSI [TFSI = bis(trifluoromethylsulfonyl)imide] and Na[B(hfip)4]·DME [hfip = OCH(CF3)2 (OiPrF), DME = 1,2-dimethoxyethane] as alternative electrolyte salts to the current benchmark standard NaPF6 and compares their air stability, electrochemical properties and performance in sodium-ion coin cells. Multinuclear NMR spectroscopic experiments found that NaPF6 and NaTFSI were stable to atmospheric air after one month, whereas Na[B(hfip)4]·DME showed signs of degradation. The air stability of NaPF6 was compared to LiPF6, where the latter underwent complete decomposition after 24 hours. Electrochemical investigations in 1 M solutions of ethylene carbonate: diethyl carbonate (EC:DEC) solvent revealed 1 M NaPF6 has the highest bulk conductivity. Cyclic voltammetry experiments showed 1 M NaPF6 and 1 M Na[B(hfip)4]·DME are compatible with aluminium foils up to 4.2 V vs. Na/Na+, whereas 1 M NaTFSI underwent aluminium corrosion. Corrosion could be supressed by either limiting cut-off voltage or by the addition of 2 wt% NaPF6 as an additive, both applicable mitigation strategies. Stable long-term cycling at 1C rate in cells using a Prussian white cathode and hard carbon anode occured with both 1 M NaPF6 and 1 M NaTFSI electrolytes. Thus, 1 M NaTFSI is a viable alternative to 1 M NaPF6 in SIBs with a Prussian white cathode, offering a potentially safer electrolyte choice by limiting HF generation on account of the strong C–F bonds in NaTFSI. Journal Article EES Batteries 2 2 475 489 Royal Society of Chemistry (RSC) 3033-4071 1 4 2026 2026-04-01 10.1039/d6eb00011h COLLEGE NANME Engineering and Applied Sciences School COLLEGE CODE EAAS Swansea University Not Required SM acknowledges support from the Royal Society through an Industry Fellowship (IF\R2\23200112). DMCO and SM also acknowledge funding from the Faraday Institution through the Industry SPRINT programme (grant number FIRG074) and Batri Ltd for supply of hard carbon. DMCO, CPG and DSW would like to thank the Faraday Institution FIRG064 and FIRG089 for supporting this work. XPS data collection was performed at the Cardiff hub of the EPSRC National Facility for X-ray photoelectron spectroscopy, the EPSRC National Facility for XPS (“HarwellXPS”, EP/Y023587/1, EP/Y023609/1, EP/Y023536/1, EP/Y023552/1 and EP/Y023544/1). 2026-05-21T14:35:03.0761019 2026-01-27T20:19:33.3167895 Faculty of Science and Engineering School of Engineering and Applied Sciences - Chemical Engineering Darren Ould 1 James Courtney 0000-0003-2944-3393 2 David J. Morgan 0000-0002-6571-5731 3 Daniel Curtis 0000-0002-6955-0524 4 Marcin Orzech 0000-0002-1086-4481 5 Sajad Kiani 0000-0003-1609-6855 6 Brent de Boode 7 Clare P. Grey 0000-0001-5572-192x 8 Dominic S. Wright 0000-0002-9952-3877 9 Serena Margadonna 0000-0002-6996-6562 10 71325__36165__b1a2ddfc96cc4b968664227087d61baa.pdf 71325.VoR.pdf 2026-02-02T14:55:47.4863389 Output 2379182 application/pdf Version of Record true ©2026The Author(s). This article is licensed under a Creative Commons Attribution 3.0 Unported Licence. true eng http://creativecommons.org/licenses/by/3.0/
title Towards safer electrolytes: comparing the air stability and electrochemical properties of NaPF6, NaTFSI and Na[B(hfip)4]·DME for sodium-ion batteries
spellingShingle Towards safer electrolytes: comparing the air stability and electrochemical properties of NaPF6, NaTFSI and Na[B(hfip)4]·DME for sodium-ion batteries
Darren Ould
James Courtney
Daniel Curtis
Marcin Orzech
Sajad Kiani
Serena Margadonna
title_short Towards safer electrolytes: comparing the air stability and electrochemical properties of NaPF6, NaTFSI and Na[B(hfip)4]·DME for sodium-ion batteries
title_full Towards safer electrolytes: comparing the air stability and electrochemical properties of NaPF6, NaTFSI and Na[B(hfip)4]·DME for sodium-ion batteries
title_fullStr Towards safer electrolytes: comparing the air stability and electrochemical properties of NaPF6, NaTFSI and Na[B(hfip)4]·DME for sodium-ion batteries
title_full_unstemmed Towards safer electrolytes: comparing the air stability and electrochemical properties of NaPF6, NaTFSI and Na[B(hfip)4]·DME for sodium-ion batteries
title_sort Towards safer electrolytes: comparing the air stability and electrochemical properties of NaPF6, NaTFSI and Na[B(hfip)4]·DME for sodium-ion batteries
author_id_str_mv 6abdf0ba47ad51e529f810b24a67bc19
919d02ade339d2aff29e96445039211b
e76ff28a23af2fe37099c4e9a24c1e58
d47b0185188280619c0d61f40ea98a9a
fe9ec46699e095368faf2a0465b598c5
e31904a10b1b1240b98ab52d9977dfbe
author_id_fullname_str_mv 6abdf0ba47ad51e529f810b24a67bc19_***_Darren Ould
919d02ade339d2aff29e96445039211b_***_James Courtney
e76ff28a23af2fe37099c4e9a24c1e58_***_Daniel Curtis
d47b0185188280619c0d61f40ea98a9a_***_Marcin Orzech
fe9ec46699e095368faf2a0465b598c5_***_Sajad Kiani
e31904a10b1b1240b98ab52d9977dfbe_***_Serena Margadonna
author Darren Ould
James Courtney
Daniel Curtis
Marcin Orzech
Sajad Kiani
Serena Margadonna
author2 Darren Ould
James Courtney
David J. Morgan
Daniel Curtis
Marcin Orzech
Sajad Kiani
Brent de Boode
Clare P. Grey
Dominic S. Wright
Serena Margadonna
format Journal article
container_title EES Batteries
container_volume 2
container_issue 2
container_start_page 475
publishDate 2026
institution Swansea University
issn 3033-4071
doi_str_mv 10.1039/d6eb00011h
publisher Royal Society of Chemistry (RSC)
college_str Faculty of Science and Engineering
hierarchytype
hierarchy_top_id facultyofscienceandengineering
hierarchy_top_title Faculty of Science and Engineering
hierarchy_parent_id facultyofscienceandengineering
hierarchy_parent_title Faculty of Science and Engineering
department_str School of Engineering and Applied Sciences - Chemical Engineering{{{_:::_}}}Faculty of Science and Engineering{{{_:::_}}}School of Engineering and Applied Sciences - Chemical Engineering
document_store_str 1
active_str 0
description Sodium-ion batteries (SIBs) are a promising post lithium-ion battery (LIB) technology, which offer advantages in improved sustainability. This work investigates using NaTFSI [TFSI = bis(trifluoromethylsulfonyl)imide] and Na[B(hfip)4]·DME [hfip = OCH(CF3)2 (OiPrF), DME = 1,2-dimethoxyethane] as alternative electrolyte salts to the current benchmark standard NaPF6 and compares their air stability, electrochemical properties and performance in sodium-ion coin cells. Multinuclear NMR spectroscopic experiments found that NaPF6 and NaTFSI were stable to atmospheric air after one month, whereas Na[B(hfip)4]·DME showed signs of degradation. The air stability of NaPF6 was compared to LiPF6, where the latter underwent complete decomposition after 24 hours. Electrochemical investigations in 1 M solutions of ethylene carbonate: diethyl carbonate (EC:DEC) solvent revealed 1 M NaPF6 has the highest bulk conductivity. Cyclic voltammetry experiments showed 1 M NaPF6 and 1 M Na[B(hfip)4]·DME are compatible with aluminium foils up to 4.2 V vs. Na/Na+, whereas 1 M NaTFSI underwent aluminium corrosion. Corrosion could be supressed by either limiting cut-off voltage or by the addition of 2 wt% NaPF6 as an additive, both applicable mitigation strategies. Stable long-term cycling at 1C rate in cells using a Prussian white cathode and hard carbon anode occured with both 1 M NaPF6 and 1 M NaTFSI electrolytes. Thus, 1 M NaTFSI is a viable alternative to 1 M NaPF6 in SIBs with a Prussian white cathode, offering a potentially safer electrolyte choice by limiting HF generation on account of the strong C–F bonds in NaTFSI.
published_date 2026-04-01T14:19:29Z
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score 11.108671

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