Tuning Li₂O₂ Formation Routes by Facet Engineering of MnO₂ Cathode Catalysts.

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Lithium-oxygen batteries offer high energy density but face challenges in cycle life and capacity.
• The formation route of the lithium peroxide (Li₂O₂) discharge product is crucial for battery performance.
• Electrolyte properties, particularly Li₂O₂ solubility, influence Li₂O₂ formation pathways.

Purpose of the Study:

• To investigate the effect of cathode catalyst facet engineering on Li₂O₂ formation routes in lithium-oxygen batteries.
• To explore an alternative strategy to electrolyte design for controlling Li₂O₂ deposition.
• To correlate catalyst facet properties with Li₂O₂ formation mechanisms and battery performance.

Main Methods:

• Synthesis of β-MnO₂ crystals with controlled {111} and {100} facet exposure.
• Electrochemical testing of Li-O₂ batteries using engineered β-MnO₂ cathodes.
• Analysis of Li₂O₂ morphology and deposition pathways.
• Computational studies to understand LiO₂ adsorption on different facets.

Main Results:

• {111}-dominated β-MnO₂ facilitated Li₂O₂ formation via solution routes, yielding large toroidal particles.
• {100}-dominated β-MnO₂ promoted Li₂O₂ formation via surface routes, resulting in thin films.
• Computational analysis suggested differences in LiO₂ adsorption energies on {111} and {100} facets.
• Facet engineering offers a method to tune Li₂O₂ formation in low-donor-number electrolytes.

Conclusions:

• Catalyst facet engineering is a viable strategy to control Li₂O₂ formation routes in lithium-oxygen batteries.
• This approach provides new avenues for designing high-capacity, long-cycle-life lithium-oxygen batteries.
• Tailoring catalyst surface properties can overcome limitations associated with electrolyte-dependent Li₂O₂ deposition.