Solid Electrolyte Bimodal Grain Structures for Improved Cycling Performance.

Area of Science:

• Materials Science
• Electrochemistry
• Solid-State Chemistry

Background:

• Lithium dendrite formation causes short circuits in solid-state electrolytes, limiting battery performance.
• Controlling grain size and pore distribution in ceramic electrolytes like Li$_{7}$La$_{3}$Zr$_{2}$O$_{12}$ is crucial for mitigating dendrite growth.

Purpose of the Study:

• To propose and validate a "detour and buffer" strategy for solid-state electrolytes.
• To optimize microstructure for enhanced lithium battery performance by combining coarse and fine grains.

Main Methods:

• Fabrication of a coarse/fine bimodal grain microstructure by seeding unpulverized particles.
• Tuning grain and pore rearrangement by varying powder ratios.
• Postmortem analysis to confirm "detour and buffer" mechanisms.

Main Results:

• An optimized bimodal microstructure (equal mix of coarse and fine powders) was achieved.
• The optimized electrolyte cycled for over 2000 hours at increased current densities (1.0 to 2.0 mA·cm$^{-2}$).
• Fine grains created complex boundaries hindering Li infiltration; coarse grains increased Li path tortuosity.

Conclusions:

• The "detour and buffer" strategy effectively suppresses lithium dendrites in polycrystalline solid-state electrolytes.
• Microstructure optimization is key to enhancing the performance and safety of solid-state lithium batteries.