Lithium/Silver Vanadium Oxide Batteries for Implantable Defibrillators

Lithium/silver vanadium oxide (SVO) batteries have been under development in these laboratories since 1980. The system consists of a lithium anode, a liquid organic electrolyte, a cathode composed of conductive additives, a binder, and silver vanadium oxide, a vanadium oxide bronze produced by the thermal decomposition of vanadium oxide and silver nitrate. High rate batteries/or implantable cardiac defibrillators based on this chemistry have been under development since 1984. The first Li/SVO defibrillator battery introduced was the Model 8512 with a theoretical capacity of 5.5 Ah and dimensions of 52 mm × 33 mm × 13.5 mm. Later, the Model 8615 was introduced. This cell has a theoretical capacity of 3.0 Ah and dimensions of 52 mm × 21 mm × 13.5 mm. Two other cells which are proprietary have also been introduced. All of the cells can deliver pulses of up to 2.0 amps from a microampere background. The self‐d is charge of the cells has been shown to be less than 2% per year. In addition, the silver vanadium oxide chemistry provides a discharge curve whose voltage decreases with depth of discharge. This feature can be used as a state‐of‐charge indicator. The cells have been subjected to rigorous environmental and abuse testing and have been found to have characteristics suitable for implantable applications.