Battery-powered medical devices have been surgically implanted into the bodies of several million persons during the past one-third of a century. Implantable devices have been used to treat an increasingly diverse number of conditions including cardiac arrhythmias, chronic pain, epilepsy, hearing loss, obesity, vision loss, and scoliosis. It is estimated that in the year 2004 over 500,000 heart pacemakers were implanted.

A lithium primary battery powers the typical cardiac pacemaker. The reliability and the longevity of the pacemaker are determined by its design and manufacturing parameters, as well as therapy-related variables. As battery failure results in a cessation of pacemaker output, the selection of the appropriate battery is an important step in the product development. A large number of battery designs have been developed to meet the unique requirements of implantable medical devices, ranging from the very-low-rate batteries that can power a pacemaker for many years, to the high-rate batteries required for cardiac defibrillators.