Revealing Cycling-Induced Evolution of Intact Sodium Metal Battery Interfaces Using Cryo-Focused Ion Beam...

Area of Science:

• Materials Science
• Electrochemistry
• Nanotechnology

Background:

• Battery performance relies on understanding complex anode and cathode interfaces.
• Analyzing these interfaces in liquid-electrolyte batteries is challenging due to handling and size limitations.
• Cryogenic focused ion beam (cryo-FIB) milling has been limited to single electrodes.

Purpose of the Study:

• To present a full-cell cryo-FIB milling process for realistic battery architectures.
• To compare degradation mechanisms in sodium-ion batteries using different electrolyte solvents.
• To enable nanoscale structural analysis of anode, cathode, and separator interfaces simultaneously.

Main Methods:

• Developed a full-cell cryo-FIB milling technique for liquid electrolyte cells.
• Investigated sodium metal anode and Na0.44MnO2 cathode interfaces.
• Compared ethylene carbonate/diethyl carbonate and diglyme solvents with NaPF6 salt.

Main Results:

• Full-cell cryo-milling visualized interfaces at both electrodes.
• Degradation pathways differed significantly between carbonate- and ether-based electrolytes after 10-50 cycles.
• Carbonate electrolytes showed rapid degradation due to anode SEI formation; diglyme electrolytes degraded at the cathode.

Conclusions:

• Full-cell cryo-FIB milling provides critical insights into solvent-specific battery degradation.
• Understanding these mechanisms is vital for developing more stable and long-lasting sodium-ion batteries.
• Findings guide future electrolyte and battery design for improved performance.