Polar Organic Cations at Electrified Metal with Superconcentrated Ionic Liquid Electrolyte and Implications for Sodium Metal Batteries

Dmitrii A. Rakov; Ju Sun; Shammi A. Ferdousi; Patrick C. Howlett; Alexandr N. Simonov; Fangfang Chen; Maria Forsyth

doi:10.1021/acsmaterialslett.2c00496

Polar Organic Cations at Electrified Metal with Superconcentrated Ionic Liquid Electrolyte and Implications for Sodium Metal Batteries

Dmitrii A. Rakov
, Ju Sun
, Shammi A. Ferdousi
, Patrick C. Howlett
, Alexandr N. Simonov
, Fangfang Chen
, Maria Forsyth

School of Chemistry

Research output: Contribution to journal › Article › Research › peer-review

22 Citations (Scopus)

Abstract

Understanding the potential-induced changes across the electrode/electrolyte interface, the so-called electric double layer (EDL), is essential to adjust the working properties of energy-storage devices. Electrolytes with a high molar ratio of metal salt to solvent (1:1 salt:solvent), e.g., superconcentrated ionic liquids (ILs), enable uniform metal deposition, formation of stable solid-electrolyte interphase (SEI), and higher redox stability, which make them attractive for battery applications. However, the presence of an organic IL cation and its interactions with metal salt complexes can significantly impact the mechanism of charge transfer at an electrode compared with conventional ether/ester-based electrolytes. The competition between IL and metal cations to enter the electrified interface affects interfacial chemistry, a key determinant of metal deposition potential and the nature of the SEI. This, in turn, is also affected by IL cation and anion chemistries, which are not yet fully understood. This letter demonstrates that the polarity of an organic IL cation, which is expressed through its dipole moment (μ), and its redox stability can serve as a predictive descriptor for EDL structure in superconcentrated IL electrolytes and the implications for charge transfer. We showed that, in the family of pyrrolidinium cations, a less polar organic cation with a small μ, e.g. N-methyl-N-ethylpyrrolidinium [C2mpyr]+, packs tighter and in a greater number at a negatively charged electrode/electrolyte interface in comparison to more polar IL cations with greater μ, e.g. N-methyl-N-propylpyrrolidinium [C3mpyr]+ and N-methyl-N-methoxymethylpyrrolidinium [C2O1mpyr]+. This IL cation-rich interface results in a greater overpotential for Na deposition, whereas the nature of the SEI and sodium anode cycling behavior correlate with both the dipole moment and the reductive stability of the IL cation.

Original language	English
Pages (from-to)	1984-1990
Number of pages	7
Journal	ACS Materials Letters
Volume	4
Issue number	10
DOIs	https://doi.org/10.1021/acsmaterialslett.2c00496
Publication status	Published - 9 Sept 2022

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10.1021/acsmaterialslett.2c00496

404223584-oaAccepted author manuscript, 1.02 MBLicence: Unspecified

Cite this

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title = "Polar Organic Cations at Electrified Metal with Superconcentrated Ionic Liquid Electrolyte and Implications for Sodium Metal Batteries",

abstract = "Understanding the potential-induced changes across the electrode/electrolyte interface, the so-called electric double layer (EDL), is essential to adjust the working properties of energy-storage devices. Electrolytes with a high molar ratio of metal salt to solvent (1:1 salt:solvent), e.g., superconcentrated ionic liquids (ILs), enable uniform metal deposition, formation of stable solid-electrolyte interphase (SEI), and higher redox stability, which make them attractive for battery applications. However, the presence of an organic IL cation and its interactions with metal salt complexes can significantly impact the mechanism of charge transfer at an electrode compared with conventional ether/ester-based electrolytes. The competition between IL and metal cations to enter the electrified interface affects interfacial chemistry, a key determinant of metal deposition potential and the nature of the SEI. This, in turn, is also affected by IL cation and anion chemistries, which are not yet fully understood. This letter demonstrates that the polarity of an organic IL cation, which is expressed through its dipole moment (μ), and its redox stability can serve as a predictive descriptor for EDL structure in superconcentrated IL electrolytes and the implications for charge transfer. We showed that, in the family of pyrrolidinium cations, a less polar organic cation with a small μ, e.g. N-methyl-N-ethylpyrrolidinium [C2mpyr]+, packs tighter and in a greater number at a negatively charged electrode/electrolyte interface in comparison to more polar IL cations with greater μ, e.g. N-methyl-N-propylpyrrolidinium [C3mpyr]+ and N-methyl-N-methoxymethylpyrrolidinium [C2O1mpyr]+. This IL cation-rich interface results in a greater overpotential for Na deposition, whereas the nature of the SEI and sodium anode cycling behavior correlate with both the dipole moment and the reductive stability of the IL cation. ",

author = "Rakov, \{Dmitrii A.\} and Ju Sun and Ferdousi, \{Shammi A.\} and Howlett, \{Patrick C.\} and Simonov, \{Alexandr N.\} and Fangfang Chen and Maria Forsyth",

note = "Funding Information: D.R., F.C., M.F., and P.C.H. acknowledge the Australian Research Council (ARC) for funding via the Australian Centre for Electromaterials Science, grant CE140100012. M.F., F.C., and P.C.H. acknowledge ARC grant DP210101172. A.N.S. acknowledges ARC funding through Future Fellowship (FT200100317). The simulation work was undertaken with the assistance of resources provided at the NCI National Facility systems at the Australian National University through the National Computational Merit Allocation Scheme supported by the Australian Government. Publisher Copyright: {\textcopyright} 2022 American Chemical Society.",

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T1 - Polar Organic Cations at Electrified Metal with Superconcentrated Ionic Liquid Electrolyte and Implications for Sodium Metal Batteries

AU - Rakov, Dmitrii A.

AU - Sun, Ju

AU - Ferdousi, Shammi A.

AU - Howlett, Patrick C.

AU - Simonov, Alexandr N.

AU - Chen, Fangfang

AU - Forsyth, Maria

N1 - Funding Information: D.R., F.C., M.F., and P.C.H. acknowledge the Australian Research Council (ARC) for funding via the Australian Centre for Electromaterials Science, grant CE140100012. M.F., F.C., and P.C.H. acknowledge ARC grant DP210101172. A.N.S. acknowledges ARC funding through Future Fellowship (FT200100317). The simulation work was undertaken with the assistance of resources provided at the NCI National Facility systems at the Australian National University through the National Computational Merit Allocation Scheme supported by the Australian Government. Publisher Copyright: © 2022 American Chemical Society.

PY - 2022/9/9

Y1 - 2022/9/9

N2 - Understanding the potential-induced changes across the electrode/electrolyte interface, the so-called electric double layer (EDL), is essential to adjust the working properties of energy-storage devices. Electrolytes with a high molar ratio of metal salt to solvent (1:1 salt:solvent), e.g., superconcentrated ionic liquids (ILs), enable uniform metal deposition, formation of stable solid-electrolyte interphase (SEI), and higher redox stability, which make them attractive for battery applications. However, the presence of an organic IL cation and its interactions with metal salt complexes can significantly impact the mechanism of charge transfer at an electrode compared with conventional ether/ester-based electrolytes. The competition between IL and metal cations to enter the electrified interface affects interfacial chemistry, a key determinant of metal deposition potential and the nature of the SEI. This, in turn, is also affected by IL cation and anion chemistries, which are not yet fully understood. This letter demonstrates that the polarity of an organic IL cation, which is expressed through its dipole moment (μ), and its redox stability can serve as a predictive descriptor for EDL structure in superconcentrated IL electrolytes and the implications for charge transfer. We showed that, in the family of pyrrolidinium cations, a less polar organic cation with a small μ, e.g. N-methyl-N-ethylpyrrolidinium [C2mpyr]+, packs tighter and in a greater number at a negatively charged electrode/electrolyte interface in comparison to more polar IL cations with greater μ, e.g. N-methyl-N-propylpyrrolidinium [C3mpyr]+ and N-methyl-N-methoxymethylpyrrolidinium [C2O1mpyr]+. This IL cation-rich interface results in a greater overpotential for Na deposition, whereas the nature of the SEI and sodium anode cycling behavior correlate with both the dipole moment and the reductive stability of the IL cation.

AB - Understanding the potential-induced changes across the electrode/electrolyte interface, the so-called electric double layer (EDL), is essential to adjust the working properties of energy-storage devices. Electrolytes with a high molar ratio of metal salt to solvent (1:1 salt:solvent), e.g., superconcentrated ionic liquids (ILs), enable uniform metal deposition, formation of stable solid-electrolyte interphase (SEI), and higher redox stability, which make them attractive for battery applications. However, the presence of an organic IL cation and its interactions with metal salt complexes can significantly impact the mechanism of charge transfer at an electrode compared with conventional ether/ester-based electrolytes. The competition between IL and metal cations to enter the electrified interface affects interfacial chemistry, a key determinant of metal deposition potential and the nature of the SEI. This, in turn, is also affected by IL cation and anion chemistries, which are not yet fully understood. This letter demonstrates that the polarity of an organic IL cation, which is expressed through its dipole moment (μ), and its redox stability can serve as a predictive descriptor for EDL structure in superconcentrated IL electrolytes and the implications for charge transfer. We showed that, in the family of pyrrolidinium cations, a less polar organic cation with a small μ, e.g. N-methyl-N-ethylpyrrolidinium [C2mpyr]+, packs tighter and in a greater number at a negatively charged electrode/electrolyte interface in comparison to more polar IL cations with greater μ, e.g. N-methyl-N-propylpyrrolidinium [C3mpyr]+ and N-methyl-N-methoxymethylpyrrolidinium [C2O1mpyr]+. This IL cation-rich interface results in a greater overpotential for Na deposition, whereas the nature of the SEI and sodium anode cycling behavior correlate with both the dipole moment and the reductive stability of the IL cation.

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U2 - 10.1021/acsmaterialslett.2c00496

DO - 10.1021/acsmaterialslett.2c00496

M3 - Article

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JO - ACS Materials Letters

JF - ACS Materials Letters

IS - 10

ER -

Polar Organic Cations at Electrified Metal with Superconcentrated Ionic Liquid Electrolyte and Implications for Sodium Metal Batteries

Abstract

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New dimensions of electrocatalyst design for sustainable energy future

ARC Centre of Excellence for Electromaterials Science

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Polar Organic Cations at Electrified Metal with Superconcentrated Ionic Liquid Electrolyte and Implications for Sodium Metal Batteries

Abstract

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New dimensions of electrocatalyst design for sustainable energy future

ARC Centre of Excellence for Electromaterials Science

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