Batteries for implantable medical devices have requirements specific to each device. However, some characteristics are demanded by all implantable applications including high energy density both volumetrically and gravimetrically, exceptional reliability, predictable behavior, and ability to determine state of charge. The lithium/iodine (Li/I₂) solid electrolyte battery system has been used successfully for decades as a high energy density primary battery to power implantable cardiac pacemakers delivering microampere level currents with an exceptional record of predictability and reliability. In contrast, high power cells capable of delivering ampere level pulses based on the lithium/silver vanadium oxide chemistry power implantable cardiac defibrillators.

Case studies will be provided to illustrate that understanding the batteries systems used under the rigorous requirements demanded by implantable medical devices can provide inspiration for addressing issues in battery systems intended for a wide variety of applications. Strategies to extend the life time of lithium batteries comparing cathode materials based on transition metal oxides with transition metal phosphates will be described. Known failure modes are explored along with their impact on interfacial phenomena. The lithium/iodine pacemaker battery is used as inspiration for demonstration of a rechargeable solid state battery based on the use of LiI rich lithium iodide-(3-hydroxyproprionitrile)₂ solid state electrolyte. The battery is assembled fully discharged using only the solid state electrolyte. On charge, lithium metal forms at the negative side of the battery and iodine forms at the positive side. Finally, strategies to successfully increase power of high energy density batteries will be described.