So the new work is based on a hypothetical question: what if we just throw silicon particles in, let them fragment, and then fix them?
As mentioned, the reason fragmentation is a problem is that it leads to small pieces of silicon that have essentially disappeared from the grid; they are no longer in contact with the system that transports charges in and out of the electrode. In many cases, these particles are also partially filled with lithium, removing it from circulation and reducing battery capacity, even when there is sufficient electrode material nearby.
The researchers involved, all at Stanford University, decided there was a way to put these fragments back in touch with the electrical system and showed that this could restore a lot of capacity to a seriously damaged battery.
Bringing things together
The idea behind the new work was that it might be possible to attract the fragments of silicon to an electrode, or at least to another material connected to the charge-handling network. By themselves, the fragments in the anode should have no net charge; if the lithium loses an electron there, it must go back into solution. But the lithium is unlikely to be evenly distributed throughout the fragment, making it a polar material: net neutral, but with regions of higher and lower electron densities. And polar materials will move in an uneven electric field.
And because of the uneven, chaotic structure of a nanoscale electrode, any voltage applied to it will create an uneven electric field. Depending on the local structure, this can attract or repel some of the particles. But because these are largely contained within the electrode structure, it is likely that most silicon fragments will collide with another part of the electrode in the short term. And that could potentially restore a connection to the electrode's current processing system.
To demonstrate that what should happen in theory actually happens in an electrode, the researchers started by taking a used electrode and brushing part of its surface in a solution. They then applied a voltage through the solution and confirmed that the small pieces of material from the battery began to move toward one of the electrodes that they used to apply a voltage to the solution. So everything worked as expected.
