LiFePo4[1] is not 100% safe but it's a much safer chemistry compared to the other common alternatives. This is because LiFePo4 chemistry isn't prone to thermal runaway.
Thermal runaway is really bad. Typical lithium rechargeable batteries can't handle overheating without starting a chain reaction: an uncontrollable thermal runaway followed by a literally inextinguishable inferno.
If you short circuit the LiFePo battery it still is going to turn into a welder. It can still start a fire. If you don't short circuit it, under normal conditions it shouldn't spontaneously combust.
1. Note: Confusingly LiFePo4 (Lithium Iron Phosphate) looks a lot like LiPo (Lithium Polymer), however, LiPo batteries are some of the most prone to fire while LiFe batteries are the least prone to fire.
Thermal runaway is really bad. Typical lithium rechargeable batteries can't handle overheating without starting a chain reaction: an uncontrollable thermal runaway followed by a literally inextinguishable inferno.
If you short circuit the LiFePo battery it still is going to turn into a welder. It can still start a fire. If you don't short circuit it, under normal conditions it shouldn't spontaneously combust.
1. Note: Confusingly LiFePo4 (Lithium Iron Phosphate) looks a lot like LiPo (Lithium Polymer), however, LiPo batteries are some of the most prone to fire while LiFe batteries are the least prone to fire.