The Influence of Open Circuit Potential on Electrode Dynamics

Abstract

Phase separation, inducing a miscibility gap and non-monotonic open-circuit potential (OCP), is typical for widespread Li-ion battery electrodes such as LiFePO4, Li₄Ti₅OPhase separation, inducing a miscibility gap and non-monotonic open-circuit potential (OCP), is typical for widespread Li-ion battery electrodes such as LiFePO4, Li₄Ti₅O12 and Graphite. Although particle-scale effects of phase separation are well documented, its influence on transport-limited, porous electrodes remains largely overlooked. Here we embed physically consistent non-monotonic OCP profiles in a simplified Doyle–Fuller–Newman framework to compare their behavior against that of solid- solution materials with monotonic OCPs. Our findings provide deeper and general understanding of the different electrode ensemble behavior of solid solution (monotonic OCP) and phase separating (non-monotonic OCP) electrode materials, demonstrating why larger miscibility gaps are associated with decreasing rate capabilities and electrode utilization, amplifying local current heterogeneity and electrolyte depletion. By contrast, simulations employing conventional flat, fitted OCPs mask these effects and overpredict performance—particularly under dynamic cycling protocols such as galvanostatic intermittent titration (GITT). Our results reveal why accounting for realistic OCPs is essential for reliable modelling of high-loading electrodes, providing fundamental understanding and guidance for model-driven design and control of next-generation batteries and Graphite. Although particle-scale effects of phase separation are well documented, its influence on transport-limited, porous electrodes remains largely overlooked. Here we embed physically consistent non-monotonic OCP profiles in a simplified Doyle–Fuller–Newman framework to compare their behavior against that of solid- solution materials with monotonic OCPs. Our findings provide deeper and general understanding of the different electrode ensemble behavior of solid solution (monotonic OCP) and phase separating (non-monotonic OCP) electrode materials, demonstrating why larger miscibility gaps are associated with decreasing rate capabilities and electrode utilization, amplifying local current heterogeneity and electrolyte depletion. By contrast, simulations employing conventional flat, fitted OCPs mask these effects and overpredict performance—particularly under dynamic cycling protocols such as galvanostatic intermittent titration (GITT). Our results reveal why accounting for realistic OCPs is essential for reliable modelling of high-loading electrodes, providing fundamental understanding and guidance for model-driven design and control of next-generation batteries..