Revealing the Quantitative Connection between Electrode-level Cracks and Capacity Fading of Silicon Electrodes in Lithium-ion Battery

Abstract

For the coupling problems of lithium-ion batteries, a key issue at hand is that it is still unclear which mechanical failures can cause degradation and how, which is particularly salient at the electrode level. In this work, the correlation between electrode-level cracks and cycling capacity of silicon electrodes is investigated. Unexpectedly, for cracks in active layers, the capacity decreases with the increase of crack width, while the connection of other crack features to the capacity is weaker or even absent. Meanwhile, the modeling results, however, suggest that the increase in crack width cannot directly cause the capacity fading. To explain these results, the relationship between electrode debonding and active layer crack opening is also described quantitatively. By combining the debonding model and the porous electrode model, the connection between crack widths of active layers and capacity fading is clarified, and accurate predictions are obtained. These results indicate that the easily measurable width of active layer cracks is qualified to evaluate degradation, while the electrode debonding is in fact the direct cause of capacity fading. The findings in this work provide a more precise understanding of the degradation mechanism in lithium-ion battery electrodes.