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Investigation of fluorinated amides for solid-electrolyte interphase stabilization in Li–O₂ batteries using amide-based electrolytes

Evidence and attribution

Authority of statements

Sections below summarize the publication identified by doi, title, and pdf_path in the front matter.

Summary

N,N-dialkyl amides such as DMA are attractive solvents for Li–O₂ cathode chemistry relative to carbonates/glymes, but they do not inherently passivate Li metal against sustained electrolyte reaction. This study benchmarks fluorinated amide formulations (notably N,N-dimethyltrifluoroacetamide, DMTFA) using symmetric Li/electrolyte/Li cells, EIS, and cycling, combined with QM arguments and XPS. α-Fluorinated amides are argued to reduce toward LiF-rich SEI components; XPS supports LiF after DMTFA exposure. A 2% DMTFA additive in LiTFSI/DMA is reported to improve Li anode behavior in a rechargeable Li–O₂ demonstration context.

Methods

  • Electrochemistry: symmetric Li / electrolyte / Li cells with electrochemical impedance spectroscopy (EIS) and galvanostatic Li stripping–plating to compare interfacial impedance and polarization across fluorinated N,N-dialkyl amide solvents relative to N,N-dimethylacetamide (DMA) baselines; electrolytes use LiTFSI (and LiClO₄ where noted in the Experimental section) at concentrations stated in the article.
  • Electronic structure: quantum chemistry calculations of reduction pathways for α-fluorinated amides on Li surfaces to identify low-barrier routes to LiF-forming chemistry.
  • Surface analysis: X-ray photoelectron spectroscopy (XPS) of Li foils exposed to selected amide electrolytes to probe F-containing SEI components.

Static QM / DFT (reduction of fluorinated amides)

Functional: N/A — explicit DFT functional not stated in normalized/extracts/2013bryantsev-venue-jp402844r_p1-2.txt; see Computational details in pdf_path.

Dispersion: N/A — not stated in the excerpt.

Basis: N/A — basis / plane-wave settings not stated in the excerpt.

k-sampling: N/A — k-point / k-mesh / Brillouin sampling not stated in the excerpt.

Structures / pathways: Quantum chemical models address reduction of α-fluorinated amides on Li surfaces along pathways that form LiF with little or no activation energy (abstract).

Properties computed: Reaction energetics / barrier estimates for initial decomposition leading to LiF (abstract).

MD application

N/A — this work is not centered on production AIMD trajectories in the abstract/excerpt; any finite-temperature MD mention in pdf_path should be read there.

Findings

  • Among the fluorinated amides examined, LiTFSI in N,N-dimethyltrifluoroacetamide (DMTFA) shows the smallest interfacial impedance and the lowest polarization for Li dissolution/deposition in the symmetric-cell screening.
  • α-Fluorinated amides are computed to reduce on Li with little or no activation barrier toward LiF, and XPS on DMTFA-exposed Li supports fluoride-rich interfacial composition consistent with that pathway.
  • A practical additive formulation (0.5 M LiTFSI in 98% DMA / 2% DMTFA) is reported to stabilize Li cycling in a rechargeable Li–O₂ demonstration relative to DMA alone, while retaining an amide-based catholyte choice.

The combined electrochemical and spectroscopic thread supports a practical design rule: low concentrations of α-fluorinated amide can steer SEI chemistry toward fluoride-rich films without abandoning amide solvents chosen for cathode oxygen electrochemistry.

Limitations

  • Cell chemistries and interfacial evolution are complex; long-cycle statistics and full gas-phase cathode chemistry are broader than any single interfacial study.

Relevance to group

Adri C. T. van Duin is a co-author; the work couples electrolyte/SEI chemistry with QM reasoning familiar to reactive force-field development contexts.

Citations and evidence anchors

  • Abstract and experimental sections: EIS/XPS/QM claims (J. Phys. Chem. C; DOI above).

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