Boeing's mods to the 787 battery system are at least partially successful. On 14 Jan, this year, A JAL 787 started to smoke while standing on the ramp. A single cell in the eight cell main battery got in trouble, heated up, and vented. The main part of the 787 mods was a fireproof metal battery box vented overboard. That part worked fine, the overheated cell did not touch off the rest of the cells in the battery, the ovrheating/fire was contained inside the new battery box. Not clear is the effects of such a failure in flight. Depends upon the flight I suppose. If the engines keep running, the engine driven alternators will supply plenty of juice. If we have first a battery failure, and then total engine failure, will the batteries ( there are two of them) have enough juice to get the gear and flaps down, power the radio, and keep the cockpit instrument lights alive? And keep the fancy fly-by-wire system working?
Anyhow, doesn't look like they have licked the battery bursts into fire problem, but the battery box is strong enough to contain the fire.