Lithium Ion Batteries tend to explode do to the battery creating a spark when it gets moved around.
The components in lithium Ion Batteries are designed to be lightweight, which translates into thin partitions between cells and a thin outer covering.
When the Lithium Ion batteries get moved around those thin partitions can lead to slight sparking which can cause the batteries to explode or catch fire.
Lithium Ion batteries are pretty safe though but it's best to store the spare lithium ion batteries somewhere secure where they cannot be moved around too much during transportation.
Another cause of Lithium Ion batteries catching fire or exploding is due to overcharging of the battery because the battery starts to heat up and when the battery gets too hot a fire or explosion can happen.
So if you're charging something with a lithium Ion battery make sure to unplug the charger when it's fully charged to prevent a fire or explosion due to overcharging the battery.