According to the Seattle Times, the fix also involves using a system of venting tubes that in case of an incident would channel any flammable vapours or liquids directly out of the plane, and continuous monitoring of the temperature and voltage of individual cells within the battery.
The stuff is put through a strainer to remove random debris, then sucked via tubes into a vacuum system that blends it with other polyurethane scraps recovered from car dashboards and shipping materials.