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 for 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 X 33 mm X 13.5 mm. Later, the Model 8615 was introduced. This cell has a theoretical capacity of 3.0 Ah and dimensions of 52 mm X 21 mm X 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-discharge 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.