It's my opinion, having been using and reviewing Li-ion flashlights for several years now that single Li-ion cells are very easy to handle safely provided they

It's my opinion, having been using and reviewing Li-ion flashlights for several years now that single Li-ion cells are very easy to handle safely provided they and the devices you use them in are of reasonable quality. It's mostly a matter of avoiding short circuits and mechanical damage. Multi-cell devices require a little more knowledge and care, but the main thing is just to make sure the cells match. Being the same model and charged to full before installation will do for new cells, but salvaged ones need to be tested and binned.