Local electronic structure variation resulting in Li 'filament' formation within solid electrolytes.

Area of Science:

• Materials Science
• Electrochemistry
• Solid-State Batteries

Background:

• Solid electrolytes are crucial for safe lithium metal anodes.
• Lithium infiltration along grain boundaries causes short circuits and battery failure.
• The mechanism of lithium infiltration in solid electrolytes is poorly understood.

Purpose of the Study:

• To investigate the phenomenon of lithium infiltration in solid oxide electrolytes.
• To understand the role of electronic band structure in lithium infiltration.
• To identify strategies for preventing short circuits in solid-state batteries.

Main Methods:

• Electron microscopy measurements.
• Analysis of the electronic band structure of grain boundaries.
• Study of a representative solid oxide electrolyte system, Li$_{7}$La$_{3}$Zr$_{2}$O$_{12}$.

Main Results:

• Approximately 50% of grain boundaries in Li$_{7}$La$_{3}$Zr$_{2}$O$_{12}$ exhibit a reduced bandgap (1-3 eV).
• Reduced bandgaps create pathways for leakage current and premature lithium-ion reduction.
• Local lithium filaments form at grain boundaries, leading to short circuits.

Conclusions:

• Grain boundary electronic conductivity is a critical factor in solid-state battery performance.
• Optimizing grain boundary electronic properties is essential for preventing lithium infiltration.
• This research provides insights into designing more stable and reliable solid-state batteries.