Scientists at a Basque university have been the first to use neutron radiography to track the inner workings of a custom-designed neutron friendly lead-acid cell and casing.
The work by the Universidad del País Vasco highlights the potential of neutron imaging for tracking battery function and outlines opportunities for further development.
The team studied the technology in-operando during electrochemical cycling in order to observe the activity within the electrolyte and at the electrodes.
The researchers noted that neutron transmittance of electrodes either increases or decreases during cycling. The findings confirm experimental simulation work of neutron transmittance using the Monte Carlo method.
Neutron spectroscopy was developed as a tool for spotting defects in metals, predominantly military applications.
Neutrons can deliver a ‘cleaner’ image because they have no charge, and do not interact with higher atomic weight elements, such as metals— although, because of their size, do not give the same resolution that x-rays or electrons can provide.
BEST insight by our technical editor Dr Mike McDonagh
The attraction for use in lead-acid batteries (LABs) is that it will give images of the internal processes of the lead-based electrodes in real time.
You could have a video of the charge and discharge processes inside the active material as it happens. There is also the possibility that the electrolyte/metal interface reactions, which are critical to the performance of lead-acid could be mapped in real time.
If the resolution were good enough it could be very useful, particularly if we are looking at the effect of additives and the speed of material conversion and deterioration processes such as sulfation and PCL in dilute solutions.
All that said, the usefulness of this paper is quite limited. Its main objective and conclusions are to pave the way for use of this technique on LABs. In this respect it fell a bit short in my opinion. It found difficulties with identifying the SoC because of its limitations in dealing with the electrolyte. Its inability to get accurate voltage figures that matched the galvanic measurements are quite concerning.
The main pitfall of this paper was the decision made by the researchers to remove the separators and increase the distance between the plates. This completely removes the effect of the separator on the interface reactions and changes the whole dynamic of the concentration gradients that drive the reaction speeds of the crucial electrolyte/metal interface reactions. Think Gouey-Chapman and double layers.
My comments on this would be that the concept of real-time monitoring of charge-discharge reactions in the lead-acid system is of great benefit. This research was designed to demonstrate the feasibility of using neutron radiography for this purpose but it encountered some difficulties particularly for the electrolyte. The findings for the processes occurring in the plates were not new and already well understood.
A lot more work is required to demonstrate the usefulness of this technique as well as to iron out the experimental difficulties in reconstructing real battery conditions during the test.
If these issues can be resolved then it could be of real benefit in understanding LAB’s real-time operational characteristics and the effect of AM utilisation improvement methods.
This would lead to prediction of what further methods could be employed and to quantify the effects of those methods. That could be ground-breaking.