A 45.6 <i>m</i> NaCTFSI/NaFSI hybrid electrolyte for high-voltage aqueous sodium-ion batteries operable at subzero temperatures.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 42139342.
- Also identified by DOI 10.1126/sciadv.aef0138 and PMC identifier 13178543.
- Licence recorded as CC BY-NC.
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Abstract
Aqueous sodium-ion batteries (SIBs) offer a safe and sustainable energy storage option, but their performance is restricted by the narrow electrochemical stability window (ESW) of water and poor low-temperature operability of conventional water-in-salt electrolytes (WISEs). Here, we show that sodium cyano(trifluoromethanesulfonyl)imide (NaCTFSI) addresses these issues. A 17.6 <i>m</i> NaCTFSI solution forms a true WISE, providing an ESW of 2.78 volts and high-voltage compatibility, but crystallizes below room temperature, severely degrading performance. To overcome this, we systematically explore a eutectic-like hybrid electrolyte by mixing NaCTFSI (14.1 <i>m</i>) with sodium bis(fluorosulfonyl)imide (NaFSI; 31.5 <i>m</i>), representing the most concentrated Na<sup>+</sup>-based WISE to date, which remains liquid down to -20°C and extends the ESW to 3.07 volts. Incorporating CTFSI<sup>-</sup> anions mitigates FSI<sup>-</sup>-induced anodic corrosion, ensuring long-term cyclability. Electrochemical tests confirm that KMnC | hybrid | NaMnF full cells sustain over 500 charge-discharge cycles across a wide temperature range, maintaining high capacity even at -20°C, demonstrating a promising platform for safe and wide-climate aqueous SIBs.