When you charge your phone or electric car, tiny particles called lithium ions travel through the battery to store energy. Scientists have long wanted to watch this happen inside a new type of battery called a solid-state battery, but the process happens deep inside solid materials where it's hard to see. Now, researchers at National Taiwan University have found a way to peer inside these batteries while they work — and what they discovered could help create batteries that charge faster, last longer, and are safer to use.
In a study published in the journal Angewandte Chemie International Edition, the team developed a practical method to track lithium as it moves through solid electrolytes. Instead of just measuring how well a battery performs overall, they watched what happens inside the battery materials themselves, following how lithium actually changes the structure of the solid electrolyte during operation.
One important discovery: lithium does not spread evenly through the solid electrolyte. Instead, it prefers to travel through more ordered regions — like water flowing through cracks in a rock rather than soaking through solid stone. These preferred pathways help lithium cross the boundary between the electrode and the solid electrolyte more easily.
The researchers also found that some strained regions inside the battery actively resist accepting lithium, which causes uneven distribution. Imagine trying to evenly fill a lumpy balloon with water — some areas get more, others less.
Perhaps the most practical finding concerns how we charge our devices. The study suggests that rapid charging — not simply charging a battery fully — is more likely to cause lithium to move in ways that cannot be undone. This means the speed at which we charge matters more than how much we charge, which could change how manufacturers design charging systems.
"This study provides a clearer picture of how lithium moves inside solid-state batteries and shows that understanding these hidden pathways is essential to designing safer, faster-charging, and more durable next-generation batteries," said Dr. Ru-Shi Liu, a distinguished professor of chemistry at National Taiwan University who led the research.
Solid-state batteries are considered a promising step forward because they can store more energy and are less likely to catch fire than batteries using liquid electrolytes. By finally being able to watch lithium move in real time, scientists now have a clearer roadmap for improving them. The work could eventually lead to electric cars that charge in minutes instead of hours, smartphones with batteries that hold their charge for days, and grid-scale energy storage to power entire cities cleanly.
The research was led by Po-Jui Chu and colleagues, with findings published in 2026.