Hard to believe that a small LI battery can cause this type of damage. It is possible this battery was smoldering for some time as the aircraft was unattended for several hours. Still this gives us an idea the heat generated by these LI batteries when they go off. Think about the heat from the larger LI Cobalt battery, which is considered the most volatile of all the LI batteries. This calls into question the choice of LI battery for the Main and APU location. This problem will not go away. Every time B787 meets with an incident, the question will pop 'Is it that battery again?'. This is unfortunate.
The choice of composite materials would not have changed the out come here. Aluminum also can melt in a fire situation. Only difference could be metal conduct heat faster, so fire may not make a burn through easily. This damage occurred mainly due to the unattended nature of the aircraft on ground. If this incident had taken place in flight, the fire would be detected quickly and extinguished. ELTs are located inside the overhead storage bin and easily removed. These bins have blankets and pillows stored on most aircraft. May be they contributed to propagate the initial combustion. ELTs are in use on all modern aircraft, and cannot remember having a previous fire incident on this item. Correct me if I am wrong.
