Modeling and Characterization of the Resistance of Lithium/SVO Batteries for Implantable Cardioverter Defibrillators

Implantable cardioverter-defibrillators place stringent demands on the lithium/silver vanadium oxide batteries that power them. The batteries run constantly at low power and then occasionally deliver one or more high-power pulses. The ability of lithium/silver vanadium oxide batteries to deliver high-power pulses was characterized over a wide range of conditions. The power was mapped as a function of current density, pulse duration, and depth of discharge. This work defines the conditions under which the batteries can operate at high power; if current density and pulse duration are too high, concentration polarization predominates, especially at high depths of discharge. A time- and temperature-dependent increase in battery resistance was observed starting at a cathode composition of Li 2.8 Ag 2 V 4 O 11 . The added resistance appears mostly on the cathode, and grows at an approximately twofold faster rate when the cathode is synthesized from a decomposition process rather than a combination process. A model was developed to predict discharge behavior of a wide variety of battery designs. This model incorporates time- and temperature-dependent resistance increase using first-order kinetics. The model predicts the behavior of new battery designs very accurately for an application up to five years, but slightly underestimates performance at seven years.