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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
EES Batteries
Swansea University Authors:
Darren Ould, James Courtney , Daniel Curtis
, Marcin Orzech
, Sajad Kiani
, Serena Margadonna
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©2026The Author(s). This article is licensed under a Creative Commons Attribution 3.0 Unported Licence.
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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...
| 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 |
| first_indexed |
2026-01-27T22:01:49Z |
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| last_indexed |
2026-02-03T05:33:08Z |
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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. 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2026-02-02T15:05:29.7069628 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 0 Royal Society of Chemistry (RSC) 3033-4071 21 1 2026 2026-01-21 10.1039/d6eb00011h COLLEGE NANME Engineering and Applied Sciences School COLLEGE CODE EAAS Swansea University Other Faraday Institution (SPR_100064) 2026-02-02T15:05:29.7069628 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 |
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| container_title |
EES Batteries |
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2026 |
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Swansea University |
| issn |
3033-4071 |
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10.1039/d6eb00011h |
| publisher |
Royal Society of Chemistry (RSC) |
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Faculty of Science and Engineering |
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| 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 |
2026-01-21T05:35:02Z |
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1856987099727659008 |
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11.096068 |

