Lithium batteries can be dangerous if mistreated or mis-used.
Always use a case for safe storage when not in use. Never in your pocket, purse etc. Keep away from keys, coins and small metallic objects.
Batteries should never be charged in a mod. It’s good practice to charge batteries on an external charger that is correctly rated for Li-Ion cells. Never leave them charging unattended and they should be removed when fully charged.
Batteries should be periodically inspected for tears and rips. Never use a batteries with a damaged PVC wrap, either recycle the cell or repair immediately.
Do not over-stress these batteries. Batteries should be suitable for the application (correct size, amp draw etc).