Electrolyte engineering via non-fluorinated solvent for high-performance lithium metal batteries

Area of Science:

• Materials Science
• Electrochemistry
• Chemical Engineering

Background:

• Lithium metal batteries (LMBs) offer high energy density but face challenges like dendrite growth and electrolyte instability.
• Conventional electrolytes based on 1,2-dimethoxyethane (DME) have limited oxidative stability, hindering high-voltage cathode compatibility.

Purpose of the Study:

• To design a novel siloxane-based electrolyte system for high-voltage LMBs with enhanced oxidative stability and improved interfacial properties.
• To investigate the molecular mechanisms behind the electrolyte's performance using advanced characterization and simulation techniques.

Main Methods:

• Solvent molecular engineering to create siloxane-based electrolytes with strong Si-O bonds.
• In-operando Raman spectroscopy to study electrolyte behavior during battery operation.
• Molecular dynamics simulations to analyze ion coordination and solvation sheath structure.
• Electrochemical testing of Li||Cu and Li||LiNi0.8Co0.1Mn0.1O2 cells to evaluate performance.

Main Results:

• The siloxane electrolyte exhibits superior oxidative stability due to high Si-O bond energy compared to C-O bonds in DME.
• Enhanced Li+ coordination with FSI- anions in the siloxane electrolyte promotes the formation of a stable, inorganic-rich solid-electrolyte interphase (SEI).
• Optimized electrolyte (DMS-3) demonstrates excellent cycling stability (e.g., 99.4% CE for 1000 cycles at 0.5 mA cm-2) and high capacity retention in full cells (92.26% after 110 cycles).

Conclusions:

• Siloxane-based electrolytes represent a promising strategy for developing stable and high-performance high-voltage LMBs.
• Molecular design of electrolytes, focusing on solvent structure and ion coordination, is crucial for overcoming key challenges in LMB technology.
• This work provides a new paradigm for electrolyte engineering, paving the way for next-generation energy storage systems.