Igor Mele currently works at the Faculty of Mechanical Engineering, University of Ljubljana. Igor does research in modelling of Li-ion batteries and discussed his role at the NEXTCELL project.
What is UL’s role in developing the phase-field-based model for the silicon anode and its interface with the electrolyte? How do these models help understand the electrochemical performance of the cathode material?
Phase-field models have become an important tool for studying silicon anodes in lithium-ion batteries, particularly in understanding the complex interactions at the silicon-electrolyte interface. The use of these models is crucial due to the intricate mechanical, chemical, and electrochemical processes that occur during battery operation. It is known that the Silicon undergoes significant volumetric expansion (up to ~300%) during lithiation (when lithium ions are inserted) and contraction during delithiation (when lithium ions are removed). This volume change causes mechanical stresses that lead to cracking, pulverization, and ultimately, degradation of the silicon anode. Phase-field models are particularly useful for prediction of the interplay between concentration and stress fields inside silicon during battery cycling. This is important for predicting the long-term mechanical integrity of silicon anodes.
UL will contribute its advanced expertise in phase-field methods by simulating the microstructural evolution during electrochemical cycling. Phase-field models will provide us a powerful framework for simulating the complex, coupled phenomena that occur inside the material, including mechanical degradation and ion transport. By leveraging these models, we will be able to better predict and mitigate the challenges associated with inherent phenomena of the electrode materials, ultimately leading to more durable and efficient battery systems.
How does UL contribute to integrating the chemo-mechanical and microstructure models into the multiscale simulation software for the bi-cell level model?
Phase field models enable the coupling of different physical phenomena, such as mechanics, electrochemistry and diffusion. This multi-physics approach is essential for the accurate simulation of the behaviour of silicon anodes under real operating conditions. For example, mechanical stresses due to lithiation-induced expansion can influence ion transport, which in turn affects the rate of cracking. Phase field modelling captures these feedback loops and provides a more comprehensive understanding of how different factors contribute to silicon anode performance and failure. Phase field models are usually too computationally intensive to be integrated into the multiscale simulations. Therefore, we will apply an upscaling strategy from the microscale to the continuum scale while preserving the most important phenomena.
What are some key features of the TEMHD (Transport, Electrochemical, Mechanical, Heat generation, and Degradation) model being developed?
At the silicon-electrolyte interface, electrochemical reactions occur where lithium ions move between the electrolyte and silicon. These reactions are critical to battery performance, but they also contribute to side reactions and the formation of the solid electrolyte interphase (SEI) layer. The SEI layer, a passivation layer that forms at the silicon-electrolyte interface, plays a critical role in preventing further side reactions and improving battery cycle life. However, the SEI is fragile and can break down due to the mechanical stresses caused by silicon’s volume changes. Phase-field models can simulate the nucleation and growth of the SEI layer, as well as its mechanical and chemical degradation. By modelling the interactions between the SEI and anode material, we will be able to provide insights into how ion transport, interfacial reactions, and phase transformations affect battery efficiency and stability.
