Inorganic-Dominated Interphase Enabled by Tuning Solvation Configuration for 4.8 V Lithium-Ion Batteries

Area of Science:

• Electrochemistry
• Materials Science
• Energy Storage

Background:

• Achieving stable, inorganic-dominated cathode electrolyte interphase (CEI) layers is critical for long-term cycling of ultrahigh-voltage cathodes.
• Traditional electrolytes with organic solvents decompose, hindering the formation of robust CEI layers and limiting battery performance.
• Lithium-rich manganese-based oxide (LLMO) cathodes face challenges with phase transitions during cycling, impacting their capacity retention.

Purpose of the Study:

• To overcome the limitations of traditional electrolytes in forming dense, inorganic CEI layers for high-voltage applications.
• To investigate a novel electrolyte system that promotes the formation of an anion-rich Li+ solvation structure.
• To enhance the cycling stability and performance of lithium-rich manganese-based oxide (LLMO) cathodes.

Main Methods:

• Utilized a localized anion mismatch between hexafluorophosphate (PF6-) and 1,1,1-trifluoro-N,N-dimethylmethanesulfonamide (TFDMSA) solvent.
• Employed a specific electrolyte composition: 1 m lithium bis(fluorosulfonyl)imide (LiFSI) + 0.1 m LiPF6 in TFDMSA.
• Fabricated and tested LLMO||Li half-cells to evaluate CEI formation and electrochemical performance.

Main Results:

• Anion-rich Li+ solvation structures were successfully formed, leading to abundant aggregates (AGGs).
• An inorganic-dominated, LiF-rich CEI layer was constructed, effectively suppressing LLMO phase transitions.
• The prepared LLMO||Li half-cells exhibited excellent capacity retention of 80.7% after 350 cycles at 4.8 V.

Conclusions:

• The proposed electrolyte system enables the construction of anion-dominated Li+ solvation structures in local environments.
• This approach facilitates the formation of a stable, inorganic-rich CEI, crucial for ultrahigh-voltage cathode operation.
• The findings offer a new strategy for developing advanced electrolyte systems for next-generation high-energy-density batteries.