As I mentioned, that's a lot of why we have Lithium-Iron batteries for the house instead of Lithium-Cobalt. I think this is a problem particular to Lithium-Cobalt (or at least particularly acute in Li-Co batteries), which is what you have in power tools, laptops, phones and all Tesla products, including the Powerwall.
Not that hydrogen is not flammable/explosive though. Hydrogen fires tend to be less destructive than gasoline fires though - the Hindenberg hydrogen burned out in 90 seconds. One engineer said that if the planes that hit the Twin Towers had been hydrogen-fueled, the towers likely would not have come down.