Scientists Discover How Oxygen Loss Saps a Lithium-Ion Battery’s Voltage
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.
Now, in a study published in Nature Energy, a research team co-led by SLAC National Accelerator Laboratory, Stanford University, and Berkeley Lab has measured this 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.
Using COSMIC, a multipurpose X-ray instrument at Berkeley Lab’s Advanced Light Source (ALS), the research team scanned across samples of electrode nanoparticles, making high-res images and probing the chemical makeup of each tiny spot. This information was combined with a computational technique called ptychography to reveal nanoscale details, measured in billionths of a meter.
At SLAC’s Stanford Synchrotron Lightsource, the team shot X-rays through entire electrodes to confirm that what they were seeing at the nanoscale level was also true at a much larger scale.