Modelling pulse discharge of hybrid cathode Li/CF_x-SVO batteries using Multiphase Porous Electrode Theory

Power sources of implantable cardioverter-defibrillators (ICD) require high energy density to ensure longevity and sufficient rate capability to provide high power pulses for treating abnormal heart rhythms. Such demands have led to the design of Li/CF_x-SVO battery, which leverages the excellent energy density of carbon monofluoride (CF_x) and power density of silver vanadium oxide (SVO) through the use of a CF_x-SVO hybrid cathode. A single particle model based on porous electrode theory was previously developed for Li/CF_x-SVO. However, it overlooked phase separation in SVO and reaction heterogeneity across particles, and was unable to accurately predict the transient voltage response during transitions from high to low currents. In this work, we present a computational model of Li/CF_x-SVO battery based on Multiphase Porous Electrode Theory for Hybrid Electrodes (Hybrid-MPET). Hybrid-MPET allows us to model the phase separation in SVO particles and predict the evolution of reaction heterogeneities across an ensemble of particles under different current rates. Validated against experimental data, our Li/CF_x-SVO model not only excels at predicting voltage-capacity behavior under constant current or constant load discharge, but also now captures and explains voltage over-recovery phenomenon observed after high power pulses. In addition, we discuss how Hybrid-MPET framework opens up opportunities to study the performance of hybrid electrodes in rechargeable batteries.