The formation process is a crucial and costly final step in manufacturing battery cells, accounting for up to 33% [1] of production cost. During this stage, a protective interphase layers are stablished at the electrochemically active interfaces that enable a stable operation of the cell outside the electrolyte’s electrochemical stability window.
The formation process, in particular, must be conducted with care, as it plays a crucial role in determining key electrochemical and safety properties of LIBs. However, an overly cautious approach to formation is time-consuming, which conflicts with efforts to speed up battery production and reduce costs.
This study introduces a semi-empirical model designed to enhance the understanding of Solid Electrolyte Interphase (SEI) layer growth during the early stages of cell formation, with the goal of streamlining the experimental workflow. The model is based on a set of coupled ordinary differential equations that simulate SEI growth dynamics and includes a cell thickness expansion model, which is partially driven by SEI development. Additionally, a variable solvent diffusion model has been integrated to track the consumption of different electrolyte solvents during the formation process, providing insights into electrolyte behavior under various conditions.
The model has been validated using both experimental data and findings from the literature, specifically for 2.5 Ah pouch cells, ensuring its accuracy and reliability. Results demonstrate that the model can effectively predict the effects of different formation protocols and electrolyte systems on SEI passivation, a key factor in determining the cell’s longevity and overall stability. Ultimately, this model offers a valuable framework for optimizing formation procedures, with predictive capabilities that can help improve battery performance and extend the operational lifespan of electrochemical cells.