Structural Integrity of Prismatic Li-Ion Batteries Under Indentation: Influence of Aging and Mechanical Constraints

Abstract The structural integrity of lithium-ion batteries (LIBs) under mechanical loading is critical for ensuring safe operation in electric vehicle applications. This study investigates the influence of electrochemical aging and mechanical constraints on the structural response of prismatic LIBs under indentation loading. Commercial LIBs were subjected to controlled aging protocols under both constrained and unconstrained conditions, followed by quasi-static and dynamic indentation tests. Results demonstrate that mechanical constraint during cycling significantly preserves structural integrity by limiting internal gas generation and preventing electrode delamination. Cells aged without constraint exhibited reduced stiffness and different failure characteristics after 100 cycles, while mechanically constrained cells maintained nearly identical force–displacement responses up to 200 cycles. X-ray computed tomography revealed that unconstrained aging led to substantial casing deformation and electrode-separator delamination, whereas constrained cells showed minimal structural changes. The findings provide crucial insights for battery pack design and safety assessment, highlighting the importance of appropriate mechanical constraints in maintaining both electrochemical performance and structural integrity throughout battery lifetime.