A 2CR5 battery is a lithium-ion battery commonly used in film and digital cameras. Electrical output of this battery type is 6 volts. It is identical to the battery types by the name DL245, EL2CR5, RL2CR5.
It is shaped such that it can be inserted into a battery compartment only one way. Rechargeable versions of the 2CR5 are now available, but at a higher price.