I have been flying model airplanes for roughly 40 years, the last 20 of those it has all been electric. With the introduction of brushless motors and lithium batteries electric flying has really taken off.....get it.....oh well....anyhoo.
No one on the planet is more mean to batteries then toy airplane flyers, we want as light as possible for pretty clear reasons, and it is really common to pull well over 100A out of these little things for 5 minutes straight. They can be a bit toasty when they come down.
In the RC world they have things like this to store and charge the batteries in, these bags are to contain the fire.
Personally I have lost one plane in the air to a lipo fire, a fairly nice F9F Panther EDF jet. Looked like it got hit by flak or something, started smoking like crazy....if you have ever seen a lipo fire you know what I am talking about. I got it "almost" on the ground before it burned in two, starting a fire in the middle of the grass runway. These fires do not go out, the extinguishers are to keep the surrounding grass from catching fire. You just need to let them burn out.
Second one was during charging. It was just sitting there and I ran upstairs for just "a minute", come back down to flames. Move everything out of the way, get a large pair of channel locks pick the battery up trying not to breathe that junk, it is VERY bad for you, and got it into the driveway. Again just let it burn.
Now I charge all the "hobby" batteries in ammo cans. This was what people did before these bags came on scene. It works for me....at least so far.
Now tool batteries, I should know better having first hand experience with this, but I do just charge them all on a long shelf. I think I should re think that, but really I am just lazy. I like having the ability to just grab the tool and battery when I need it. They are all right there and easy to get.
But yes you should charge them all in something.
That all said however....
Tool, phone, laptop, whatever batteries are really very safe. They are generally over sized for their application, so you are not really working the batteries hard. This is key to making them happy. You will likely notice there is usually a third connection on most batteries, sometime more. This is USUALLY for some form of charging sensor, a temp sensor, voltage or amperage....something that will go back to the "smart" charger. The charger is to look at that and say NOPE I don't like what I am seeing here and will shut down the charge. Again I am sure most have put a tool battery on a charger and seen it come up with an error. Could be a great deal of things, but it could also be, expecially when being charged for a while, it went into something that the charger did not like.
You are pumping HUGE amounts of energy into these batteries, think of your battery tools and you are really amazed at just how powerful they are....they might rival your plug in tools in some cases, or at least run even with them for a while. All due to the battery. This is also why you see some high draw tools not run on the "smaller" batteries. It is just too much for the "little' battery and will damage it.
If you have read this far, then I feel the need to comment on electric cars. This falls into the area of our RC toys. Weight is the enemy here in a major way. So you are going to use the smallest battery with the lowest C rating you can to get the job done, just like in RC planes. That means that the battery is worked just that much harder, and that is not good on it. Same reason we see so many EV fires as we see RC fires, we are pushing the batteries very hard.
And how often here am I going to get a chance to post some pics of my planes, you can see the little Panther in the back of the pic. The Phantom will clock in at just over 90mph in level flight, and well over 100mph in a shallow dive. Checked on real cop radar gun.