Silicon-Based Solid-State Batteries: Electrochemistry and Mechanics to Guide Design and Operation

Area of Science:

• Materials Science
• Electrochemistry
• Mechanical Engineering

Background:

• Solid-state batteries (SSBs) offer an alternative to lithium-ion technology but face challenges like resistive interfaces and void formation.
• These interfacial issues lead to reduced cycle life due to fracture and delamination, hindering widespread adoption.

Purpose of the Study:

• To investigate stress evolution at solid electrolyte (SE) and electrode interfaces in silicon-based SSBs.
• To link chemo-mechanical properties and electrochemical response for optimized SSB design and manufacturing.
• To understand the impact of applied pressure and C-rate on stress, strain, and capacity in thin-film SSBs.

Main Methods:

• A 2D chemo-mechanical model was developed for continuum-scale simulations.
• Simulations analyzed the stress-strain response of a thin-film SSB with an amorphous silicon negative electrode.
• The model incorporated lithiation-induced expansion, Li diffusion, and concentration gradients within the silicon electrode.

Main Results:

• Lithium-ion diffusion in silicon creates concentration gradients, leading to localized strains and interfacial stress.
• Operating at moderate C-rates with low applied pressure reduces interfacial stress and strain at 100% state of charge (SOC).
• Tailoring SE mechanical properties, such as Young's modulus and yield strength, can mitigate silicon stress and optimize cell performance.

Conclusions:

• SE material selection is critical for optimizing thin-film SSB performance.
• Consideration of mechanical properties and operating conditions is essential for enhancing SSB cycle life and preventing interfacial degradation.
• This modeling approach provides guidance for designing robust and efficient silicon-based solid-state batteries.