Fast charging can cause irreversible lithium migration in solid-state batteries

Solid-state batteries are often viewed as a promising path toward safer and more powerful energy storage. However, one key question has remained difficult to answer: How does lithium actually move inside the solid materials during charging and discharging? Unlike liquid batteries, where ions can move more freely, solid-state batteries depend on lithium passing through dense solid particles and across complex interfaces. This makes their internal behavior hard to observe and even harder to control.