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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
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David J. Morgan ,
Daniel Curtis ,
Marcin Orzech ,
Sajad Kiani ,
Brent de Boode,
Clare P. Grey ,
Dominic S. Wright ,
Serena Margadonna
EES Batteries, Volume: 2, Issue: 2, Pages: 475 - 489
Swansea University Authors:
Darren Ould, James Courtney , Daniel Curtis , Marcin Orzech , Sajad Kiani , Serena Margadonna
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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 |
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| ISSN: | 3033-4071 |
| Published: |
Royal Society of Chemistry (RSC)
2026
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| Online Access: |
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| URI: | https://cronfa.swan.ac.uk/Record/cronfa71325 |
| 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 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. |
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| College: |
Faculty of Science and Engineering |
| 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 (“HarwellXPS”, EP/Y023587/1, EP/Y023609/1, EP/Y023536/1, EP/Y023552/1 and EP/Y023544/1). |
| Issue: |
2 |
| Start Page: |
475 |
| End Page: |
489 |