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

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.

针对锂离子电池的耦合问题，当前的关键在于尚不明确哪些机械故障能够导致性能退化以及其具体机制，尤其在电极层面这一问题尤为突出。本研究中，我们探讨了电极层面裂纹与硅电极循环容量之间的关联。令人惊讶的是，对于活性层中的裂纹，随着裂纹宽度的增加，容量逐渐降低，而其他裂纹特征与容量的关联较弱，甚至不存在。然而，建模结果表明，裂纹宽度的增加并不能直接导致容量衰减。为了解释这些结果，我们还定量描述了电极脱粘与活性层裂纹张开之间的关系。通过结合脱粘模型和多孔电极模型，我们阐明了活性层裂纹宽度与容量衰减之间的联系，并获得了精确的预测。这些结果表明，易于测量的活性层裂纹宽度足以评估退化程度，而电极脱粘实际上才是容量衰减的直接原因。本研究中的发现为锂离子电池电极退化机制提供了更为精确的理解。