Abstract
Introduction: Sulfolane (SL), having an edge of low melting point over other sulfones, has been adopted as an electrolyte co-solvent for lithium-ion battery (LIB), as it exhibits high stability against oxidation and combustion while not causing much side effects to the battery electrochemistry. It is therefore expected that SL may serve as a safety-enhancing agent in sodium-ion battery (SIB). To evaluate the effect of SL content on the behavior of common carbonate-based sodium electrolytes as well as the compatibility of SL-based electrolytes with NaNi1=3Mn1=3Co1=3O2 (NaNMC) cathode, mixtures of 0, 10, 20, 30 or 50% vol. SL and each of the following, EC:PC 1:1 vol. (EP11), EC:DMC 1:1 vol. (ED11), EC:PC:DMC 1:1:3 vol. (EPD113) and EC:PC:DMC 3:1:1 vol. (EPD311), with or without 1M NaClO4, were studied with regard to both inherent properties and performance in NaNMC half-cells.
 Methods: Solvent flammability was evaluated via the self-extinguishing time (SET) and ignition time indexes. Conductivity and viscosity were respectively measured by Electrochemical Impedance Spectroscopy (EIS) and Ostwald method. Electrochemical techniques, i.e. Cyclic Voltammetry (CV) and Galvanostatic Cycling with Potential Limitation (GCPL), were used to test the sodium-ion battery performance.
 Results: A moderate amount of SL (typically below 30% vol.) proved to enhance both electrolyte non-flammability and self-extinguishing behavior, while maintaining an acceptable compromising rate in viscosity and conductivity. Amongst 30%-SL electrolytes, EPD311-based ones allow the best Na+ diffusion when combined with NaNMC cathode in sodium half-cell configuration. The corresponding system gives satisfactory performance: initial specific capacity of 97 mAh.g-1, 92% capacity retention, and above 90% reversibility after 30 cycles at C/10 rate.
 Conclusion: SL can be used as a stabilizing co-solvent for SIB, but its content should be limited to below 30% vol. to ensure its effectiveness.
Highlights
Sulfolane (SL), having an edge of low melting point over other sulfones, has been adopted as an electrolyte co-solvent for lithium-ion battery (LIB), as it exhibits high stability against oxidation and combustion while not causing much side effects to the battery electrochemistry
To evaluate the effects of SL on the behavior of carbonate-based sodium electrolytes and estimate the appropriate SL content, we investigated the mixtures of 0, 10, 20, 30 or 50% vol SL with each of the four common carbonate combinations, namely ethylene carbonate (EC):propylene carbonate (PC) 1:1 vol (EP11), EC:dimethyl carbonate (DMC) 1:1 vol (ED11), EC:PC:DMC 1:1:3 vol (EPD113) and EC:PC:DMC 3:1:1 vol (EPD311), either in the absence or presence of 1M NaClO4
With the addition of SL, self-extinguishing time (SET) values initially decreased to reach a minimum at around 20% to 30% vol SL, before sharply rising up. This suggests that while SL, at a reasonable content, does exhibit flame-retardant effects, its presence in excessive amount may be detrimental to the solvent self-extinguished behavior
Summary
Sulfolane (SL), having an edge of low melting point over other sulfones, has been adopted as an electrolyte co-solvent for lithium-ion battery (LIB), as it exhibits high stability against oxidation and combustion while not causing much side effects to the battery electrochemistry. It is expected that SL may serve as a safety-enhancing agent in sodium-ion battery (SIB). Results: A moderate amount of SL (typically below 30% vol.) proved to enhance both electrolyte non-flammability and self-extinguishing behavior, while maintaining an acceptable compromising rate in viscosity and conductivity. Similar to its lithium predecessor, SIBs generally suffer from unguaranteed fire safety that arises from high volatility and flammability of the commonly used electrolyte solvents, i.e. organic carbonates 2–4.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
