Root cause analysis important
I am disappointed that no root cause has been discovered and I think that raises concerns even with other mitigating factors in place. The safety analysis should assume that there is a high probability of battery failure until we have substantial experience to the contrary and this necessarily means that the mitigiation and control measures have to be looked at very carefully. At the end of the day it does sometimes happen that it is impossible to identify cause(s) although I am suprised given the effort thrown at this.
I have an ulterior motive because I may be designing a non-aerospace safety critical lithium application and I very much wanted to learn what the cause was. Normally the aircraft industry are very good at identifying and publicising root causes and I follow accident and incident reports for this reason even though I do not work on aircraft.