Reduction-Tolerance Electrolyte Design for High-Energy Lithium Batteries.

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Lithium and silicon anodes are crucial for next-generation batteries but suffer capacity degradation due to unstable solid electrolyte interphases (SEIs).
• Current anion-derived SEIs are limited by solvent reduction, causing SEI heterogeneity and fractures during battery cycling.

Purpose of the Study:

• To elucidate the relationship between solvent reductive stability and SEI formation on lithium and silicon anodes.
• To identify key solvent properties, namely electrophilicity (EPT) and coordination ability (CDA), that govern SEI characteristics.
• To design and synthesize novel solvents that promote stable, inorganic-rich SEIs for improved battery performance.

Main Methods:

• Investigated solvent decomposition mechanisms based on electrophilicity (EPT) and coordination ability (CDA).
• Synthesized three novel solvents tailored for lithium and silicon anodes.
• Evaluated electrolyte performance using silicon anodes and anode-free pouch cells (Cu||NCM523).

Main Results:

• Solvents with lower EPT and CDA exhibited enhanced reductive stability, forming homogeneous, inorganic-rich SEIs.
• The optimized electrolyte (1M LiFSI in TFSPY) enabled silicon anodes to achieve 81% capacity retention over 600 cycles.
• Anode-free pouch cells demonstrated over 100 cycles with 82% capacity retention using the optimized electrolyte.

Conclusions:

• Reducing solvent decomposition is critical for forming stable SEIs in high-energy lithium batteries.
• Solvent EPT and CDA are key descriptors for designing electrolytes with improved SEI properties.
• This work provides a pathway for developing advanced electrolytes for next-generation lithium battery technologies.