Cascade Solvation Refinement for High-Voltage Lithium Metal Batteries

Area of Science:

• Materials Science
• Electrochemistry
• Battery Technology

Background:

• Unstable interfacial chemistry hinders Li metal battery performance due to limited anion accessibility.
• Existing electrolytes struggle to provide sufficient anion access even with designed solvation structures.

Purpose of the Study:

• To develop a cascade solvation refinement (CSR) strategy for molecular-level control of anion-coordinated Li+ clusters.
• To enhance anion accessibility and stability at electrode interfaces in Li metal batteries.

Main Methods:

• Sequential incorporation of bis(oxalate)borate (BOB-) and bis(trifluoromethanesulphonyl)imide (TFSI-) into a bis(fluorosulfonyl)imide (FSI-) saturated electrolyte.
• Investigating the synergy between anion-anion repulsion and average polarizability for cluster control.
• Analyzing the impact of refined solvation on electric double layer compression and interphase formation.

Main Results:

• Achieved compact, highly dynamic Li+-anion clusters with accelerated anion-exchange kinetics.
• Facilitated formation of robust inorganic-rich interphases and suppressed solvent side reactions.
• Demonstrated significantly extended cycling stability and high gravimetric energy density (>540 Wh kg-1) in 4.4 V and 20 Ah Li-metal pouch cells.

Conclusions:

• The CSR approach offers molecular-level control over solvation structures for improved Li metal battery performance.
• Enhanced anion availability and interphase stability are key to achieving practical, high-energy Li metal batteries.
• This strategy provides a powerful platform for advancing next-generation battery technologies.