Sturdier and vented (to outside) case.
Not a "vent" in the traditional sense. The EE Bay is pressurized, so the jettison tube needs to be controlled. The Battery enclosure is in no need of "ventilation" save in the instance of a thermal runaway within. There would need to be a backflow preventer (check valve) that prohibited loss of pressure in normal ops.
Sensors of temperature and pressure would activate the dump duct only in an emergency. The outflow would need to be managed to prevent any sudden changes in pressure, when the contents are being evacuated. An external shield would be necessary to protect the CFRP fuselage from heat and corrosives. The staining of the Main battery dump scupper (ANA) shows why this is required.
The battery enclosure would have to be of sufficient strength to resist crumpling in the interior as the pressure dropped within. If the case crushed the connectors or hots, the situation could get very intense.
Problem is much more serious than just a battery burning. An "electric" plane (we can say that on the 787) made using flammable parts is a new issue.
Not a "new" issue, really. Engineers have studied CFRP behaviour in burning for decades. What is new is installing a volatile new type of battery in proximity to CFRP structures... There will have been mountains of data generated in the 787 development that address this issue. Part of NTSB's concern in the certification process will be this marriage of possible fire and flammable structures. It is inconceivable this issue was not addressed, and then
satisfied.
In the development of this project, there is one consideration that must be observed. Critical Path. Everything that moves along with this path is collateral, to the point where it must be decided which direction to go. Past a certain "jumping off" point, it makes no sense to continue a collateral and replaceable scheme, eg NiCad.
This point can be in design or any time up to the inexorable progress of the path
critical... Dance with the one you brought to the dance.
"This technology suits the demands of the airframe"...At that point, the NiCad alternative is terminated, in design, development, engineering, and production.
Airbus will still have a time of it. None of these systems can be made modular past this committed decision point.
The LiIon system is deeply integrated into 787's electrical distribution complex (sic!).....