I’m going to go against what you just said, even though you might be a firefighter.
Take that battery OUTSIDE AWAY FROM ANY TREES OR YOUR HOME and put it in salt water to kill it completely. The water should have so much salt in it that the salt refuses to stir in and you can see the salt at the bottom after heavy stirring meaning the water cant dilute the salt anymore. .
The salt water bath over the next two days will completely drain the battery to 0 volts at which point it is no longer dangerous.
The salt water method is the only fully safe way to handle that battery.