Stress-Driven Whisker Formation in Lithium Metal Batteries

Area of Science:

• Materials Science
• Electrochemistry
• Computational Modeling

Background:

• Lithium metal batteries offer high energy density for next-generation applications.
• Lithium whisker formation during electroplating reduces Coulombic efficiency.
• The precise mechanism of lithium whisker growth remains unclear.

Purpose of the Study:

• To computationally investigate the mechanism of lithium whisker formation.
• To explain the observed root growth of lithium whiskers.
• To identify strategies for preventing whisker formation in lithium metal batteries.

Main Methods:

• Modeling lithium extrusion as a power-law Herschel-Bulkley fluid.
• Parameterizing the model using experimental power-law creep data of lithium.
• Analyzing the role of solid-electrolyte-interphase (SEI) cracking versus self-healing.

Main Results:

• A stress-driven extrusion mechanism through SEI cracks explains whisker root growth.
• The model reproduces the characteristic one-dimensional shape of lithium whiskers.
• SEI cracking, rather than self-healing, dictates whisker emergence.

Conclusions:

• SEI cracking is the primary driver for lithium whisker formation.
• Preventing SEI cracking offers a direct strategy to avoid whiskers.
• This provides a simple guideline for enhancing lithium metal battery performance.