Effects of pre-existing interfacial defects on the structural evolution of alumina coated Si electrode during delithiation

• Published in: Applied surface science 2020-08, Vol.520, p.146366, Article 146366
• Main Authors: Feng, Chen, Shi, Tielin, Li, Junjie, Cheng, Siyi, Liao, Guanglan, Tang, Zirong
• Format: Article
• Language: English
• Subjects: Capacity loss; Interfacial delamination; Molecular dynamics; Nanoporosity; Silicon electrode
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/j.apsusc.2020.146366

[Display omitted] •Effective coverage ratio (ECR) were introduced to mimic the different degrees of pre-existing interface defects.•Battery capacity would have a rapider loss when the ECR reduced below a threshold (about 55%).•Pre-existing defects would “boost” interfacial delamination during subsequent cycles in full discharge condition. Interfacial degradation is one of the root causes of the poor performance of Si-based lithium-ion batteries. Only figure out the role of interfacial degradation in cycling can we optimize electrodes to improve the battery robustness and durability. Here, we performed reactive force field (ReaxFF) atomistic simulations to investigate the “natural” delithiation responses of a-Si-core/a-Al2O3-coating electrode with different degrees of pre-existing interfacial defects. Effective coverage ratio (ECR) was introduced to mimic different degrees of the pre-existing defects on the a-LixSi/a-LixAl2O3 interface. The simulation quantitatively showed that, in any ECR samples, the delithiation could be characterized as two stages: a steady stage with a higher discharge rate and a lower nanoporosity, and an unsteady stage with a lower discharge rate and a larger aggregates of nanopores. The deterioration of ECR caused the steady stage shortened and unsteady stage prolonged. Consequently, further interfacial delamination was easier to form in lower ECR samples in full discharge condition, and the pre-existing defects would “boost” interfacial delamination during subsequent cycles. Besides, the battery capacity would have a rapid loss when the ECR reduced below a threshold (about 55%). This work provides a fundamental understanding of delithiation-induced interfacial degradation mechanism of Si electrodes at atomic-level.