Scientists took a unique and detailed nanoscale look at how oxygen seeps out of lithium-ion battery electrodes, sapping their energy over time. The results could suggest a fix.

Now researchers have measured this super-slow process with unprecedented detail, showing how the holes, or vacancies, left by escaping oxygen atoms change the electrode’s structure and chemistry and gradually reduce how much energy it can store.

The results contradict some of the assumptions scientists had made about this process and could suggest new ways of engineering electrodes to prevent it.

The research team from the Department of Energy’s SLAC National Accelerator Laboratory and Stanford University described their work in Nature Energy today.

«We were able to measure a very tiny degree of oxygen trickling out, ever so slowly, over hundreds of cycles,» said Peter Csernica, a Stanford PhD student who worked on the experiments with Associate Professor Will Chueh. «The fact that it’s so slow is also what made it hard to detect.»

A two-way rocking chair

Lithium-ion batteries work like a rocking chair, moving lithium ions back and forth between two electrodes that temporarily store charge. Ideally, those ions are the only things moving in and out of the billions of nanoparticles that make up each electrode. But researchers have known for some time that oxygen atoms leak out of the particles as lithium moves back and forth. The details have been hard to pin down because the signals from these leaks are too small to measure directly.

Story Source: Materials provided by DOE/SLAC National Accelerator Laboratory. Original written by Glennda Chui. Note: Content may be edited for style and length.