Non-Faradaic Li⁺ Migration and Chemical Coordination across Solid-State Battery Interfaces

Area of Science:

• Materials Science
• Electrochemistry
• Solid-State Batteries

Background:

• Efficient charge transfer is crucial for high-performance solid-state batteries.
• Interfacial chemistry significantly impacts battery cell function, but remains poorly understood.
• Space-charge layers, involving charge enrichment/depletion, are theorized but experimentally uncharacterized at solid-state interfaces.

Purpose of the Study:

• To elucidate the interfacial chemistry and space-charge effects at the LiCoO2-LIPON solid-state battery interface.
• To experimentally validate the existence and impact of space-charge layers.
• To identify strategies for mitigating interfacial losses and improving battery performance.

Main Methods:

• Combined X-ray photoelectron spectroscopy (XPS) and electrochemical techniques.
• Investigated the LiCoO2-LIPON interface in solid-state batteries.
• Analyzed the effect of a LiNbO3 interlayer.

Main Results:

• Experimental validation of space-charge separation at the LiCoO2-LIPON interface.
• Identified non-Faradaic Li+ ion migration from the electrode to the electrolyte, causing ~15% reversible cathodic capacity loss.
• Demonstrated that a LiNbO3 interlayer reduces space-charge separation and mitigates Li+ loss.

Conclusions:

• Interfacial chemistry, specifically space-charge layer formation and ion migration, critically affects solid-state battery performance.
• The LiNbO3 interlayer effectively suppresses detrimental interfacial effects, restoring theoretical cathodic capacity.
• This study highlights the importance of interfacial engineering for advancing solid-state battery technology.