High-Resolution Mapping of Discharge Product in Li─O₂ Batteries

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Lithium-oxygen (Li-O2) batteries offer high theoretical specific energy but suffer from low practical capacity, especially at high discharge rates.
• Key limitations include air electrode surface passivation and restricted O2 mass transport through the porous electrode structure.

Purpose of the Study:

• To spatially determine the relative utilization of different electrode portions in Li-O2 batteries.
• To identify whether air electrode passivation or O2 mass transport is the primary factor limiting discharge capacity.

Main Methods:

• Cross-sectional scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM-EDS) to map discharge product distribution.
• X-ray nano-computed tomography to corroborate SEM-EDS findings and assess sample preparation effects.
• Modeling and simulation of Li-O2 battery performance.

Main Results:

• SEM-EDS mapping revealed significant discharge product accumulation on the O2-side of the air electrode.
• This distribution confirms that pore blockage and oxygen starvation are critical factors causing under-utilization of the air electrode.
• Simulated battery results aligned with experimental discharge product distribution, validating the model.

Conclusions:

• Pore blockage and oxygen starvation are identified as key limitations in Li-O2 battery performance.
• The applied techniques (SEM-EDS, X-ray nano-CT) are effective for diagnosing performance issues in Li-O2 cells.
• These methods can guide improvements in electrode design, electrolyte composition, and operating conditions for enhanced Li-O2 battery performance.