Untangling a strange phenomenon in lithium-ion batteries

New research offers the first complete picture of why a promising approach of stuffing more lithium into battery cathodes leads to their failure.

A better understanding of this could be the key to smaller phone batteries and electric cars that drive farther between charges.
The lithium-ion batteries that power electric vehicles and phones charge and discharge by ferrying lithium ions back and forth between two electrodes, an anode and a cathode. The more lithium ions the electrodes are able to absorb and release, the more energy the battery can store.
One issue plaguing today’s commercial battery materials is that they are only able to release about half of the lithium ions they contain. A promising solution is to cram cathodes with extra lithium ions, allowing them to store more energy in the same amount of space. But for some reason, every new charge and discharge cycle slowly strips these lithium-rich cathodes of their voltage and capacity.
A new study provides a comprehensive model of this process, identifying what gives rise to it and how it ultimately leads to the battery’s downfall. Led by researchers from Stanford University and the Department of Energy’s SLAC National Accelerator Laboratory and Lawrence Berkeley National Laboratory, it was published today in Nature Materials.

>Read more on the Stanford Synchrotron Radiation Lightsource (SSRL)

Image: A mysterious process called oxygen oxidation strips electrons from oxygen atoms in lithium-rich battery cathodes and degrades their performance, shown at left. Better understanding this property and controlling its effects could lead to better performing electric vehicles.
Credit: Gregory Stewart/SLAC National Accelerator Laboratory)