Take a look at cement board and the codes for your area for a wood stove.
There’s certain gap requirements for heat etc but you could rig up something fairly simply whether a box or more open enclosure.
There are also fire extinguishers that are activated by heat and sit above a potential fire source. People use them in 3D printer enclosures fairly often. Batteries burn for a long long time depending on how charged they are so it would have limited effectiveness.
This could actually be a really interesting and useful product idea. Maybe a kit with GFCI outlet, surge protector bar with fused outlets, huge spacing between outlets to allow for large plugs, metal/cement board case, wire shelving, ventilation fans to keep batteries cool but have louvre shut to cut oxygen for fires. Hmmm I want this for my garage.
Well, if we’re dreaming big …… my gas water heater has a metal cage surrounding the burner section that is supposed to suppress the flame. Supposedly the cage removed heat or something so any flame didn’t extend beyond. I wonder if something like that would keep a battery fire caged