A friend who runs R&D at a major Indian cell manufacturer told me recently about a warranty problem. Their cells were failing in the field at rates substantially higher than the equivalent imported product. The chemistry was the same. The form factor was the same. The production line was new. They had spent eight months and a great deal of money on X-ray CT, electrochemical impedance, and accelerated cycling, and they still did not know why the failures were happening.
Their problem was that the failure was almost certainly hidden inside the sealed cell can — a gas pocket, perhaps, or a region where the electrolyte had not wet the separator uniformly, or a local lithium plating event during fast charging. A determined X-ray physicist will tell you that phase-contrast and high-resolution micro-CT can sometimes coax these features out under ideal geometry and unlimited time. But the lithium, the electrolyte, and the gas are nearly invisible to electron-density imaging, and the steel-and-aluminium can is exactly what X-rays do see. The contrast you need is buried in the noise. You can occasionally win that fight on a single cell in a research lab; you cannot win it on a sampling cadence that keeps up with a production line. Neutrons give you the same answer in one exposure, with stark and unambiguous contrast, because the physics is working for you instead of against you.
Thirty years of neutron radiography literature would have given them the answer in a day. They knew this. They could not access it. The nearest commercial neutron-imaging facility was in Switzerland.