Lithium ion batteries can self ignite when charging as seen many times with the Samsung Note and various other appliances such as the electric scooters.

LiFePO4 which are the batteries we use in our vans etc do not self ignite but if you pierce them with a steel bar you can cause a fire which is very difficult to extinguish.  They do not explode either.

https://www.youtube.com/watch?v=07BS6QY3wI8

Do not do this at home