Operando strain analysis of electrodes using internal sensors and holistic electrochemical-microstructural modeling

Embedding fiber Bragg grating (FBG) sensors directly into the graphite anode of lithium-ion battery cells enables operando quantification of in-plane strain. It is a critical factor in electrode design that influences the selection of active material, current collector, and manufacturing conditions. However, predictive modeling for electrode mechanics has been hindered by morphological complexity and the lack of suitable in-situ validation techniques. In this study, we combine FBG sensor measurements with a lithiated gold wire reference electrode and a representative two-dimensional microstructural electrode model to overcome this limitation. The model, which is parameterized with electrode properties, captures expansion across different states of charge and C-rates. The integration of the reference electrode allows the determination of lithiation ranges. This approach enabled the use of a pseudo two-dimensional electrochemical model to determine the spatial distribution of lithium-ion-induced particle swelling. Experimental validation with embedded FBG sensors and literature data confirms that electrode swelling depends strongly on overall electrode lithiation and its distribution within the electrode. To represent the complete in-plane dimension, we model the substantial impact of design features such as the current collector and graphite overhang on electrode swelling. This combined electrochemical and mechanical modeling approach provides a computationally efficient method for assessing electrode mechanics. It offers new insights into the role of electrode design parameters and paves the way for more efficient electrode design optimization. • Operando in-plane electrode strain is measured using embedded FBG sensors. • A holistic electrochemical-microstructural-mechanical model predicts deformation. • FBG and gold-wire references enable precise state-of-charge-mechanics correlation. • Modeling shows electrode swelling strongly depends on design features like overhang. • A robust method is presented for embedding sensors during pouch-cell fabrication.