Simulating the Impact of Particle Size Distribution on the Performance of Graphite Electrodes in Lithium-Ion Batteries

• Published in: Energy technology (Weinheim, Germany) Vol. 4; no. 12; pp. 1588 - 1597
• Main Authors: Röder, Fridolin, Sonntag, Sören, Schröder, Daniel, Krewer, Ulrike
• Format: Journal Article
• Language: English
• Published: Weinheim Blackwell Publishing Ltd 01-12-2016; Wiley Subscription Services, Inc
• Subjects: Agglomeration; Atoms & subatomic particles; batteries; Degradation; Diffusion rate; electrochemistry; Electrodes; Graphite; Heterogeneity; Impact analysis; Lithium; Lithium-ion batteries; Local current; Mathematical models; Particle size; Particle size distribution; Performance degradation; Rechargeable batteries
• ISSN: 2194-4288; 2194-4296
• DOI: 10.1002/ente.201600232

In this work we present a fundamental model‐based analysis of the effect of active material particle size distribution (PSD) on graphite electrodes and their performance. We focused on the determination of the impact of differently shaped and scaled PSDs on the electrode performance, which is mainly influenced by the performance of the individual particles and their interaction. A mathematical electrode model with a distributed particle size is used for analysis to identify the different local current densities and the charging behavior of the particles. The heterogeneity provokes uneven surface overpotentials and reaction rates. Their identification facilitates the investigation of the degradation of such heterogeneous systems. In addition, we present an approach that accounts for the change of a PSD because of the restructuring of the electrode morphology during battery usage into the mathematical model and identify the general impact of particle cracking and agglomeration on the battery performance. Moreover, the importance of PSD in Li‐ion batteries is shown by comparing the results obtained with a single particle model used commonly. This comparison shows that in case of narrow distributions surface‐area‐ and volume‐based mean approximations are sufficient to predict overpotentials and electrode capacity if kinetic losses are dominated either by reaction at the surface or diffusion processes, respectively. This work indicates that the PSD and its change impact the performance and degradation of Li‐ion batteries considerably. We suggest that the PSD and its evolution should be of particular interest in the study of the degradation of particle‐based electrodes.
Modeling of particle size distribution: An electrode model with multiple particle sizes is used to determine the impact of particle size distribution on the performance of graphite electrodes. The model is compared with homogeneous mean approximations to identify their accuracy. Furthermore, the effect of degradation is investigated through the analysis of the local current density and distribution evolution caused by particle cracking and agglomeration.