The requirements for implantable medical batteries include high energy density, reliable performance, and a long service lifetime. These requirements have typically been satisfied by lithium primary cells. However, many new and exciting medical devices are being developed which have energy requirements that cannot be satisfied by a reasonably sized primary cell. For these applications, a secondary cell will be required. Lithium-ion secondary cells are a suitable choice for many applications by virtue of their high energy and power density, low self-discharge, long service lifetimes, excellent safety characteristics, and lack of memory effect.