Space-Charge Effects at the Li₇La₃Zr₂O₁₂/Poly(ethylene oxide) Interface

Area of Science:

• Materials Science
• Electrochemistry
• Solid-State Chemistry

Background:

• Solid-state lithium-ion batteries utilize composite electrolytes, such as garnet-type lithium lanthanum zirconium oxide (LLZO) ceramic particles in poly(ethylene oxide) (PEO) polymer electrolytes.
• The interface between LLZO and PEO is critical for lithium-ion transport but has been identified as a significant source of resistance.
• Achieving high ionic conductivity in these composite electrolytes requires efficient lithium-ion passage across the LLZO/PEO interface.

Purpose of the Study:

• To investigate the resistive nature of the interface between Al-substituted LLZO and PEO-LiClO4 solid polymer electrolytes.
• To theoretically describe the LLZO/PEO interface using space-charge layer models.
• To experimentally validate theoretical findings regarding the origin of interfacial resistance.

Main Methods:

• Theoretical modeling based on space-charge layers.
• Experimental validation of theoretical predictions.
• Analysis of interfacial resistance in Al-substituted LLZO/PEO-LiClO4 composite electrolytes.

Main Results:

• The interface between Al-substituted LLZO and PEO-LiClO4 is confirmed to be highly resistive.
• Theoretical calculations and experimental data align in identifying the interface's resistive properties.
• The dominant factor contributing to the interfacial resistance is a high activation energy for ion transport.

Conclusions:

• The high resistance at the LLZO/PEO interface is primarily due to elevated activation energy, not electrostatic repulsion of lithium ions.
• Understanding and mitigating this activation energy barrier is crucial for developing high-performance solid-state lithium-ion batteries.
• Further research should focus on strategies to reduce activation energy at the ceramic-polymer electrolyte interface.