New tool maps battery damage patterns to prevent sudden failure
Researchers have developed a rapid diagnostic technique that reveals where lithium-ion batteries degrade unevenly—a leading cause of sudden breakdowns in large cells. The method could help manufacturers catch defects earlier and improve battery reliability for electric vehicles and grid storage, potentially reducing warranty costs and safety risks.
Originaltitel: High-throughput tools for spatially resolved assessment of heterogeneous degradation
Large-format Li-ion battery cells tend to exhibit spatial heterogeneity in terms of material degradation, which in extreme cases can contribute to the initiation and propagation of severe degradation mechanisms such as Li plating. Studying large cells poses a challenge in terms of sample statistics and effort required for an analysis which covers a large fraction of the electrode surface area. This necessitates high-throughput, quantitative techniques capable of increased surface coverage and in a time-efficient manner. In this study we present a novel method we refer to as “OLSA” (Open-circuit potential based Local State of health Assessment), that maps the local state of health (SoH) within the cell by measurement of local electrode potential combined with a fitting procedure to estimate states of charge and subsequently offsets in lithium inventory, which enables an estimation of SoH. The technique is validated and then demonstrated by mapping aged electrodes from large format prismatic cell. The results show heterogeneous distribution of local SoH and increased LLI in areas of Li plating. We also present image analysis as a complementary method for conveniently evaluating and quantifying visible degradation on the negative electrode with 100% surface coverage. In this work, we show that the regions of lithium plating coincide with lower local SoH and higher LLI. We find that although image analysis provides limited predictive capacity to predict SoH, it is a convenient and powerful tool to assist in understanding the root causes of heterogeneous degradation.