Void Evolution at the Li/LLZO Interface: Stack Pressure and Operating Temperature-Driven Creep Effect.

Area of Science:

• Materials Science
• Electrochemistry
• Solid-state Batteries

Background:

• All-solid-state lithium metal batteries offer high energy density and safety but suffer from interface voids during cycling.
• Void formation at the lithium metal anode/solid-state electrolyte interface degrades contact and cycle stability.
• Understanding the role of stack pressure and temperature on void evolution via creep is crucial for interface stability.

Purpose of the Study:

• To develop a model for void evolution at the lithium metal anode/solid-state electrolyte interface.
• To investigate the influence of stack pressure and operating temperature on void healing through creep deformation.
• To establish a theoretical basis for optimizing pressure and temperature to ensure interface stability.

Main Methods:

• Developed a coupled electrochemical-diffusion-mechanical (creep)-phase field for void evolution (EDMP-VE) model.
• Modeled lithium stripping/deposition, diffusion, creep, lattice distortion, and vacancy dynamics.
• Utilized normalized geometric parameters and stress/strain evolution to characterize void dynamics.

Main Results:

• The EDMP-VE model accurately captures void evolution during lithium stripping and plating cycles.
• High stack pressure and operating temperature promote lithium metal creep, suppressing void expansion and accelerating void filling.
• A phase diagram identified optimal pressure-temperature windows for void healing and interface stability.

Conclusions:

• Stack pressure and operating temperature-driven creep significantly impact void evolution and interface integrity in solid-state batteries.
• Optimizing these parameters can lead to void annihilation and improved interfacial contact.
• This study provides a theoretical framework and practical guidance for enhancing solid-state battery cycle life.