Characterization and quantification of multi-field coupling in lithium-ion batteries under mechanical constraints

The safety and durability of lithium-ion batteries under mechanical constraints depend significantly on electrochemical, thermal, and mechanical fields in applications. Characterizing and quantifying the multi-field coupling behaviors requires interdisciplinary efforts. Here, we design experiments under mechanical constraints and introduce an in-situ analytical framework to clarify the complex interaction mechanisms and coupling degrees among multi-physics fields. The proposed analytical framework integrates the parameterization of equivalent models, in-situ mechanical analysis, and quantitative assessment of coupling behavior. The results indicate that the significant impact of pressure on impedance at low temperatures results from the diffusion-controlled step, enhancing kinetics when external pressure, like 180 to 240 kPa at 10 °C, is applied. The diversity in control steps for the electrochemical reaction accounts for the varying impact of pressure on battery performance across different temperatures. The thermal expansion rate suggests that the swelling force varies by less than 1.60% per unit of elevated temperature during the lithiation process. By introducing a composite metric, we quantify the coupling correlation and intensity between characteristic parameters and physical fields, uncovering the highest coupling degree in electrochemical-thermal fields. These results underscore the potential of analytical approaches in revealing the mechanisms of interaction among multi-fields, with the goal of enhancing battery performance and advancing battery management.