Batteries power modern life, from smartphones and wireless earbuds to electric vehicles, but anyone who has owned a phone for a few years knows that batteries do not last forever.
Now, researchers have uncovered a key reason why batteries gradually lose their ability to hold a charge: every time they charge and discharge, they physically “breathe.”
A research team from The University of Texas at Austin, Northeastern University, Stanford University, and Argonne National Laboratory has shown that batteries subtly expand and contract during normal use.
This repeated motion puts stress on the battery’s internal materials, slowly weakening them over time.
The findings, published in the journal Science, help explain a long-standing mystery in battery science and could lead to longer-lasting and more reliable batteries in the future.
When a battery charges, lithium ions move into the electrode materials. When it discharges, those ions move back out.
This constant back-and-forth causes the battery’s internal structure to swell and shrink, much like lungs filling with air and then releasing it.
Although the movement is tiny, it happens thousands of times over a battery’s life. Over time, this repeated motion causes permanent damage, a process known as chemomechanical degradation.
According to lead researcher Yijin Liu, every “breath” leaves behind a small, irreversible change. While each individual change is minor, they accumulate with continued use, eventually leading to reduced performance or complete battery failure.
One of the team’s most important discoveries was a process they call “strain cascades.” Inside a battery electrode are hundreds of thousands of microscopic particles, and each one responds differently to charging stress.
Some particles shift rapidly, while others barely move at all. This uneven behaviour causes stress to build up in certain regions, which can then spread to nearby areas. Over time, this can lead to cracks, warping, and other structural damage within the battery.
To observe this process directly, the researchers used advanced X-ray imaging techniques that allowed them to watch battery materials in action as the battery charged and discharged.
Using powerful tools such as transmission X-ray microscopy and 3D X-ray laminography, they were able to capture detailed, real-time images of how individual particles move and interact under stress.
Interestingly, the team first noticed this behaviour while studying a much smaller device: commercial wireless earbuds. The same processes affecting tiny batteries in earbuds also apply to much larger systems, such as electric vehicle batteries.
Understanding how and where strain develops opens the door to better battery design. The researchers suggest that changes such as redesigning electrode structures or applying controlled pressure to battery cells could reduce damage and slow degradation.
The team’s next step is to develop theoretical models that combine chemistry and mechanics, helping engineers predict battery wear and design future batteries that last longer, charge faster, and perform more reliably over many years of use.
Source: KSR.
