Fast Simulations of Lithium-Ion Battery Degradation

Abstract

We propose an algorithm to speed up physics-based battery lifetime simulations by one to two orders of magnitude compared to the state-of-the-art. This algorithm makes use of the difference between the “fast” timescale of battery cycling and the “slow” timescale of battery degradation by adaptively selecting and simulating representative cycles, and hence requires fewer cycle simulations to simulate the entire lifetime. This enables interactions with the simulations on a human timescale [1], and therefore opens the possibility for much faster and more accurate model development, testing, and comparison with experimental data.Physics-based electrochemical models, based on porous electrode theory [2], are very useful for understanding battery degradation, and hence predicting lifetime, since they can directly simulate a wide range of degradation mechanisms at various scales. Many modeling studies investigate the degradation for a single cycle, and there have been significant advances in making simulations of individual cycles as efficient as possible [3,4,5]. However, relatively few simulations of the entire battery life have been conducted. This may be due to the complexity of these models, both in terms of implementation effort and computational time. Previous work has addressed the implementation challenges [6], and this work addresses the computational time.Our proposed multiple scale algorithm simulates degradation over the entire lifetime of a battery in just a few seconds. The algorithm is implemented in the open-source battery modeling package PyBaMM [6] and thus can easily be used to simulate any (current or future) aging model implemented there. Alternatively, it can easily be incorporated in other simulation frameworks. We demonstrate the algorithm in a few case studies, including degradation mechanisms such as SEI formation, lithium plating, and loss of active material. In each case we achieve one to two order of magnitude speed-ups compared to the baseline. Since the speed-up combines multiplicatively with speed-ups in simulation of a single cycle, the entire lifetime of the battery can be simulated in just a few seconds.