Well, the battery was completely redesigned. The battery charging system was completely redesigned.
Then, because the damage to the event batteries was so severe they were unable to conclusively determine root cause, as a failsafe they put the battery inside a steel box that would contain any possible battery failure.
Appears to have worked - prior to the redesign there were two failures on 50 aircraft in a few months. Seven years later, with about 600 aircraft in service, there has been a grand total of one battery failure - which due to the battery redesign was contained to a single cell.
So yes, they fixed the 787 battery problem by putting a box over the battery
Constantly repeating the myth that
all Boeing did was put the battery in a box doesn't make the myth true.