There was recently 2 articles in the Medical Journal Pediatrics documenting the increased dangers from lithium cell batteries for young children. Lithium cells batteries are the small round silver "button" batteries used for remote controls, toys and electronics. Ingestion of the batteries is a surprisingly common problem, and could be serious for small children, who can put almost anything in their mouth. In recent years there has been a sevenfold increase in severe complications from button cell ingestions.
Federal safety rules require toys that use batteries to have battery compartments that screw shut, but devices for adults do not have that restriction. The batteries that pose the greatest risk are those that begin with the number 20 which stands for 20 millimeters. They are newer and stronger than older models.