Towards standard electrolytes for sodium-ion batteries: physical properties, ion solvation and ion-pairing in alkyl carbonate solvents

Monti, Damien; Jónsson, Erlendur; Boschin, Andrea; Ponrouch, Alexandre; Johansson, Patrik

doi:10.1039/d0cp03639k

Cited by 39 publications

(24 citation statements)

References 79 publications

(102 reference statements)

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“…[4][5][6] In this context, alternative technological strategies include the development of Na-ion batteries due to sodium abundance and highperformance aqueous-based supercapacitors which are more environmentally friendly compared to the traditional organicbased devices using toxic solvents. 6,7 In addition, aqueousbased supercapacitors are an attractive technology due to high ionic conductivity, which decreases the equivalent series resistance (R ESR ), and the non-flammability characteristics. 1 The major drawback regarding the use of aqueous-based supercapacitors is the reduced working voltage window (or electrochemical stability window -ESW) that limits the specific energy E = CU 2 /2, where C is the specific capacitance and U = ESW.…”

Section: Introductionmentioning

confidence: 99%

Effect of conductivity, viscosity, and density of water-in-salt electrolytes on the electrochemical behavior of supercapacitors: molecular dynamics simulations and in situ characterization studies

et al. 2022

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Section: Introductionmentioning

confidence: 99%

Effect of conductivity, viscosity, and density of water-in-salt electrolytes on the electrochemical behavior of supercapacitors: molecular dynamics simulations and in situ characterization studies

et al. 2022

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“…Sodium-ion batteries are in many aspects similar to lithium-ion batteries and often stated as the technology that will be used in the large-scale storage segment of the battery market due to their potential to decrease costs. − The abundance and low cost of raw materials are the underlying arguments for such statements, and although it is potentially true for electrode materials based on naturally abundant elements such as iron, manganese, and carbon, it is not as clear cut for electrolytes. , The perceived necessity of common expensive electrolyte salts, such as sodium salts based on hexafluorophosphates (PF 6 – ) or even more costly salts like bis(fluorosulfonyl)imid (FSI – ) or bis trifluoromethanesulfonyl imide (TFSI – ), presents a bottleneck in an attempt to decrease the cost of electrolytes for sodium-ion batteries …”

Section: Introductionmentioning

confidence: 99%

A Wide-Temperature-Range, Low-Cost, Fluorine-Free Battery Electrolyte Based On Sodium Bis(Oxalate)Borate

et al. 2021

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Common battery electrolytes comprise organic carbonate solvents and fluorinated salts based on hexafluorophosphate (PF6 –) anions. However, these electrolytes suffer from high flammability, limited operating temperature window, and high cost. To address those issues, we here propose a fluorine-free electrolyte based on sodium bis(oxalate)borate (NaBOB). Although lithium bis(oxalate)borate (LiBOB) has previously been investigated for lithium-ion batteries, NaBOB was considered too insoluble in organic solvents to be used in practice. Here, we show that NaBOB can be dissolved in mixtures of N-methyl-2-pyrrolidone (NMP) and trimethyl phosphate (TMP) and in each sole solvent. NMP provides higher solubility of NaBOB with a concentration of almost 0.7 M, resulting in an ionic conductivity up to 8.83 mS cm–1 at room temperature. The physical and electrochemical properties of electrolytes based on NaBOB salt dissolved in NMP and TMP solvents and their binary mixtures are here investigated. The results include the thermal behavior of the sole solvents and their mixtures, flammability tests, NaBOB solubility, and ionic conductivity measurements of the electrolyte mixtures. Full-cell sodium-ion batteries based on hard carbon anodes and Prussian white cathodes were evaluated at room temperature and 55 °C using the aforementioned electrolytes. The results show a much improved performance compared to conventional electrolytes of 1 M NaPF6 in carbonate solvents at high currents and elevated temperatures. The proposed electrolytes provide a high ionic conductivity at a wide temperature range from room temperature to −60 °C as NMP–TMP mixtures have low freezing points. The flammability tests indicate that NaBOB in NMP–TMP electrolytes are nonflammable when the electrolyte contains more than 30 vol % TMP.

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“…The total number of coordinating oxygen atoms ( N tot in Table ) decreases with increasing salt concentration. Such an effect was observed for total CNs deduced from Raman spectra of NaTFSI solutions in carbonate solvents or mixed molecular/ionic liquid electrolytes . Steric effects hindering both solvents and TFSI to simultaneously coordinate the Na + ion were the suggested origin of these observations …”

Section: Resultsmentioning

confidence: 79%

NaFSI and NaTFSI Solutions in Ether Solvents from Monoglyme to Poly(ethylene oxide)—A Molecular Dynamics Study

2021

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Classical molecular dynamics simulations have been performed for a series of electrolytes based on sodium bis(fluorosulfonyl)imide or sodium bis(trifluoromethylsulfonyl)imide salts and monoglyme, tetraglyme, and poly(ethylene oxide) as solvents. Structural properties have been assessed through the analysis of coordination numbers and binding patterns. Residence times for Na–O interactions have been used to investigate the stability of solvation shells. Diffusion coefficients of ions and electrical conductivity of the electrolytes have been estimated from molecular dynamics trajectories. Contributions to the total conductivity have been analyzed in order to investigate the role of ion–ion correlations. It has been found that the anion–cation interactions are more probable in the systems with NaTFSI salts. Accordingly, the degree of correlations between ion motions is larger in NaTFSI-based electrolytes.

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Towards standard electrolytes for sodium-ion batteries: physical properties, ion solvation and ion-pairing in alkyl carbonate solvents

Abstract: In-depth physico-chemical and molecular characterization of EC:DMC Na+-electrolytes is provided while we observed several DMC conformers in the solvation shells.

Cited by 39 publications

References 79 publications

Effect of conductivity, viscosity, and density of water-in-salt electrolytes on the electrochemical behavior of supercapacitors: molecular dynamics simulations and in situ characterization studies

Effect of conductivity, viscosity, and density of water-in-salt electrolytes on the electrochemical behavior of supercapacitors: molecular dynamics simulations and in situ characterization studies

A Wide-Temperature-Range, Low-Cost, Fluorine-Free Battery Electrolyte Based On Sodium Bis(Oxalate)Borate

NaFSI and NaTFSI Solutions in Ether Solvents from Monoglyme to Poly(ethylene oxide)—A Molecular Dynamics Study

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