Detection of load orientation effects in Lithium-ion batteries via electrochemical impedance spectroscopy

This study investigates the influence of load orientation effects on the impedance response of commercial lithium-ion prismatic cells. Electrochemical impedance spectroscopy (EIS) was performed during stepwise deformation using a cylindrical impactor oriented along the cell's X-direction (length) and Y-direction (width). The results reveal a direction-dependent behavior. The greatest relative changes of ΔZ and ΔPhase occur in the mid- to low-frequency range (6382.80 Hz to 0.01 Hz), suggesting significant impacts on charge transfer, interfacial, and diffusion processes. Deformation in the X-direction causes changes that are up to 50% larger than those in the Y-direction. The differences are attributed to the anisotropic separator structure, as well as the direction-dependent distortion of electronic current paths. Further parameter analysis shows that ΔL 0 , ΔR 0 , ΔR 1 , and ΔCPE 0 exhibit stronger variation in the X-direction, particularly at high deformation levels. This demonstrates the coupling between mechanical stress, cell microstructure and electrochemical response. The findings demonstrate that load orientation strongly affects impedance behavior and provide valuable insight into the coupling between mechanical deformation and electrochemical response. These results may support the future development of EIS-based diagnostic approaches for identifying mechanically induced changes in lithium-ion batteries.