Role of SEI layer growth in fracture probability in lithium‐ion battery electrodes

Abstract

Understanding of degradation mechanisms in batteries is essential for the widespread use of eco-friendly vehicles. Degradation mechanisms affect battery performance not only individually but also in a coupled manner. Solid electrolyte interface (SEI) formation deteriorates battery capacity through consuming available lithium ions. On the other hand, as the SEI layer grows over multiple cycles, the level of mechanical constraints is changed, which can affect the fracture behavior of the active particles. We investigate the effect of the SEI layer growth on the fracture probability of the electrode particles. The simulations show that as the SEI layer grows, tensile stress inside the active particles turns into compressive stress, reducing the probability of particle fracture. Once the SEI layer is fractured, the particle fracture is sequentially more likely to happen because the SEI constraint is removed. The study emphasizes that the stability of SEI layers is important because it helps in alleviating electrochemical performance fade as well as mechanical failure probability. In addition, the SEI layer on small particles tends to be more fractured than that on large particles, suggesting that the particle size uniformity is essential for reducing the fracture probability of the SEI layers at the electrode.

Analysis of Lithium‐Ion Battery State and Degradation via Physicochemical Cell and SEI Modeling

“…A possible explanation for a higher surface site density is an increased surface roughness: Due to the multi‐component nature of the SEI, it is likely that a partial decomposition of less stable components could alter its structure and create a rougher surface with more available surface sites. Furthermore, the mechanical stress on the SEI due to the volume expansion of the anode active material during cycling can induce cracks in the surface film [12,75] . Although these cracks would heal by a rapid formation of new SEI, this would alter its surface structure.…”

“…Furthermore, the mechanical stress on the SEI due to the volume expansion of the anode active material during cycling can induce cracks in the surface film. [12,75] Although these cracks would heal by a rapid formation of new SEI, this would alter its surface structure. Alternatively, the observed improvement of kinetics could also relate to a change in interfacial species that may fascilitate, e. g., electrolyte stripping.…”

“…[11] In addition, the breathing of the active material during cycling can trigger fractures in the SEI, promoting additional SEI growth. [12] As a result, the formation of an initial SEI with favorable mechanical, chemical, interfacial, and conductive properties is of significant interest. The substantial process duration for its initial formation during battery production [13] is another strong incentive for a detailed SEI characterization to enable knowledge-based process optimizations.…”

“…When electrochemically less stable SEI components degrade or when soluble components dissolve in the electrolyte, interfacial and bulk properties of the SEI can change [11] . In addition, the breathing of the active material during cycling can trigger fractures in the SEI, promoting additional SEI growth [12] . As a result, the formation of an initial SEI with favorable mechanical, chemical, interfacial, and conductive properties is of significant interest.…”

Anodic Interfacial Evolution in Extremely Fast Charged Lithium-Ion Batteries

“…Some of the plated lithium may get covered entirely with passivation layers on reaction with the electrolyte and be reversibly isolated, resulting in a loss of the active material. − Apart from capacity loss, uncontrolled dendritic lithium growth during plating could eventually perforate the separator membrane and short-circuit the electrodes, leading to thermal runaway. Significant efforts have been made to understand the mechanisms of SEI formation, ,− lithium plating, ,− interfacial film fracture, − and evolution of interfacial impedance after a single-cycle fast charging . However, a detailed experimental analysis of the conjugated interactions between aging mechanisms over multiple cycles has not been performed.…”