Atomic-scale mechanisms of sliding along an interdiffused Li-Si-Cu interface

Area of Science:

• Materials Science
• Electrochemistry
• Computational Materials Science

Background:

• Silicon anodes are promising for high-capacity lithium-ion batteries.
• Interfacial reactions between silicon electrodes and copper current collectors can limit battery performance.
• Understanding these interfacial phenomena is crucial for developing durable next-generation batteries.

Purpose of the Study:

• To investigate the shear deformation mechanisms of the lithiated silicon-copper interphase.
• To identify the structural features that govern interface sliding and electrode failure.
• To elucidate the role of specific compounds in capacity fade during battery cycling.

Main Methods:

• Ab initio calculations were employed to simulate the shear deformation response.
• The study focused on the interdiffused Li-Si-Cu phase structure.
• Analysis included the identification of atomic layer bonding and compound formation.

Main Results:

• Well-delineated and weakly bonded Si-Cu and Li-Cu crystalline atomic layers were observed.
• These layers facilitate interface sliding, contributing to electrode flexibility.
• The formation of LiSi3 compounds across these layers was identified as a termination point for sliding.

Conclusions:

• Weakly bonded atomic layers at the Si-Cu interface enable initial sliding.
• The precipitation of LiSi3 is a key factor causing abrupt capacity fade in silicon electrodes.
• Controlling interfacial compound formation is essential for improving the cycling stability of silicon anodes.