@Lyman
The failure mechanism is known.
I am fairly confident about causes of cascading - Secondary and Tertiary - failures. Known?, Not yet. Lets say we are on a good track to understanding.
Can this battery be made safe such that containment is not a requirement?
Yes, upon remedy after gaining understanding of the failure causes.
Containment is just an additional layer and is not critical part of safe operation.
To accomplish this
- Monitor and Manage cells better
- Eliminate cascading failures - Stop secondary and thereby Tertiary failure
Safe means that a cascading failure occurs less frequently than what the regulator specifies.
The grounding is better discussed in the other thread.