2021/03/26 by Toby Kirk, Toby L. Kirk, Colin P. Please +4
Engineering · Physics and Astronomy · #Advanced Battery Materials and Technologies #Advanced Battery Technologies Research #Advancements in Battery Materials #Applied Physics (physics.app-ph) #Chemical Physics (physics.chem-ph) #FOS: Physical sciences #physics.app-ph #physics.chem-ph
paper · pdf · doi:10.48550/arxiv.2104.12626
32 pages, 9 figures, submitted to Journal of the Electrochemical Society (10/03/2021)
arxiv created 2021/03/26 · openalex publication_date 2021/03/26 · arxiv updated 2021/04/27 · openalex created_date 2022/07/25 · openalex updated_date 2026/07/28
In the lithium-ion battery literature, discharges followed by a relaxation to equilibrium are frequently used to validate models and their parametrizations. Good agreement with experiment during discharge is easily attained with a pseudo-two-dimensional model such as the Doyle-Fuller-Newman (DFN) model. The relaxation portion, however, is typically not well-reproduced, with the relaxation in experiments occurring much more slowly than in models. In this study, using a model that includes a size distribution of the active material particles, we give a physical explanation for the slow relaxation phenomenon. This model, the Many-Particle-DFN (MP-DFN), is compared against discharge and relaxation data from the literature, and optimal fits of the size distribution parameters (mean and variance), as well as solid-state diffusivities, are found using numerical optimization. The voltage after relaxation is captured by careful choice of the current cut-off time, allowing a single set of physical parameters to be used for all C-rates, in contrast to previous studies. We find that the MP-DFN can accurately reproduce the slow relaxation, across a range of C-rates, whereas the DFN cannot. Size distributions allow for greater internal heterogeneities, giving a natural origin of slower relaxation timescales that may be relevant in other, as yet explained, battery behavior.