Stress induced by diffusion, curvature, and reversible electrochemical reaction in bilayer lithium-ion battery electrode plates

Abstract

In this paper, a new reaction-diffusion model, coupling the reversible electrochemical reaction, Lithium (Li) diffusion, and bending, is proposed to investigate the curvature, neutral axis movement, and stress in bilayer electrode. Bending curvature and stress, for the first time, are analytically and numerically investigated relate to both the diffusion and the reversible electrochemical reaction. The results reveal that the reversible electrochemical reaction retards the lithiation process, leading to the slowing down of diffusion process. Two neutral axes exist in the active plate due to a gradient of mechanical properties during lithiation. The reaction makes the stress turn to compressive-state at the side surface of active plate, and more violent reaction aggravates this compressive stress during charging. Moreover, the reaction alleviates the compressive stress at interface, and limits the movement of the maximum tensile stress to the interface or the side surface of the active plate where the manufacturing defects are often present, thus eliminating the surface or interface fracture behaviors. The effect of the backward reaction is found to be ignorable under potentiostatic charging. Finally, the thickness ratio of current collector to active plate should be less than 0.3 on the premise of strength requirement. Current collector should be fabricated as softly as possible to mitigate the adverse stress.