Apr 9, 2025
4:30pm - 4:45pm
Summit, Level 4, Room 428
Chihyun Nam1,Bonho Koo1,Juwon Kim1,Jinkyu Chung1,Jaejung Song1,Namdong Kim2,Markus Weigand3,Jian Wang4,Jongwoo Lim1
Seoul National University1,Pohang University of Science and Technology2,Helmholtz-Zentrum Berlin3,Canadian Light Source4
Chihyun Nam1,Bonho Koo1,Juwon Kim1,Jinkyu Chung1,Jaejung Song1,Namdong Kim2,Markus Weigand3,Jian Wang4,Jongwoo Lim1
Seoul National University1,Pohang University of Science and Technology2,Helmholtz-Zentrum Berlin3,Canadian Light Source4
Lithium transport in battery particles, along with the strain and stress during cycling, plays a key role in the chemo-mechanical degradation of lithium-ion batteries. Non-uniform Li distribution, driven by non-equilibrium (de)insertion processes, causes localized volume expansions, leading to mechanical stress and crack formation. Cracks often develop at interfaces between Li-rich and Li-poor regions in phase-separating electrodes but can also form in solid-solution electrodes due to dynamic Li heterogeneity. Understanding how Li concentration evolves and contributes to crack formation during battery operation is critical for improving battery performance and durability.
Intraparticle cracks in battery particles are categorized as major or minor nanoscale cracks. Major cracks delaminate sections of active material, leading to capacity loss and performance degradation, and are often observed post-mortem. In contrast, minor nano-cracks, though harder to detect, form abundantly during cycling and maintain electrical and ionic connections. These nano-cracks create new electrochemically active surfaces, altering Li (de)insertion pathways and affecting internal strain and stress fields. Over time, they may contribute to larger crack formation. Nano-cracks modify Li transport pathways compared to the original structure, and their widespread presence during operation complicates battery behavior. However, the mechanisms by which cycling induces nano-cracks and alters Li transport, strain, and stress fields, as well as the impact of cycling history, remain poorly understood.
In this study, we utilized
operando scanning transmission X-ray microscopy on individual LiFePO
4 particles to visualize the relationship between lithium (de)insertion pathways and crack formation and propagation
1,2. We first demonstrate the generation mechanism of nano-cracks occurs when the lithium insertion pathway at the edge of fresh LFP particles induces strong tensile stress in the middle of particle. Then, we directly observe the nano-crack propagation mechanism, where the freshly exposed surface near the crack activates a fast Li (de)insertion pathway, completely altering the internal stress fields near the nano-crack. Once the nano-crack transforms the dynamic lithium pathway and distribution, the delithiation process induces crack-opening tensile stress, while the lithiation process generates crack-closing compressive stress. 3D phase-field simulations support these observations, showing how dynamic lithium distribution shapes stress fields. Our findings reveal a recursive chemo-mechanical loop involving Li (de)insertion pathways, internal stress fields, and crack development.
References
1. J. Lim
et al. Science 353, 566-572 (2016).
2. B. Koo
et al. Energy Environ. Sci. 16, 3302-3313 (2023).