Studying batteries… in vivo

What parameters play a role in the batteries operation? To try to improve their performances, material sciences experiments are carried out on ODE beamline…

STUDYING BATTERIES… IN VIVO

The lithium-ion batteries found in our cell phones, laptops and electric cars must demonstrate their efficiency before they are put on the market. 
They must be able to handle thousands of charge/discharge cycles without losing their capacity. 
At the SOLEIL synchrotron, scientists hope to understand why some batteries perform better than others by investigating the structure of their materials. 
 
Guy Ouvrard, PULSSE project manager IMN-CNRS-University of Nantes 
Until now, most material characterizations have been conducted on batteries at rest. 
It is possible to operate a battery, take it apart and see what happened to the material after its operation, but in this case we are trying to find out what goes on while the battery is operating – not when it is at rest. 
 
The researchers therefore decided to make use of the synchrotron’s X-rays, which are intense enough to track transformations of matter while a battery is operating. 
One of the goals is to observe the ‘dance’ of ions and electrons as they attach and detach themselves from iron atoms.
 
Guy Ouvrard 
We watch what is going on around the iron atom in particular; we know this atom is the active principle in the battery’s operation. 

 
François Baudelet, ODE beamline manager 
We select these atoms and then look at their environment, how many neighbouring atoms they have, at what distance, with what angles and so on. 
This tells us whether these atoms are going lose one, two or three electrons during the chemical or electrochemical process. 
Another advantage is that this setup is very rapid: it can display spectra in just a few milliseconds, so we can see transformations of matter quite quickly. 

 
To view the inner workings of matter, the team developed a battery that is transparent to X-rays. 
The components are assembled in an inert atmosphere because the lithium in the battery reacts strongly with the air’s humidity. 
It’s ready! 
While the charging or discharging battery is subjected to X-rays, spectra are drawn every 300 milliseconds on the screen in the control room. 
Each of them represents a true photograph of the matter’s state. 
By repeating these experiments, scientists hope to determine which parameters influence the battery’s performance. 

 
Guy Ouvrard 
If we know that reducing particle size improves the battery’s operation, that means we need to explore that avenue. 
And tells us how far we can go with that approach. 

 
In the long run, this research method based on synchrotron radiation could help identify the materials that will be used in the batteries of the future.