Design Insights for Bilayer Electrode Batteries in In-Situ Curvature Measurement Based upon Mechanical-Electrochemical Coupling Simulation

The largely bending bilayer electrode model battery has been widely used to measure the mechanical properties of composite electrode materials. The assumption used in the method that lithium is uniformly distributed in the active layer lacks quantitative evaluation, and the uniformity of concentration distribution is crucial for accurate in-situ measurements of concentration-related material properties and stress in bilayer electrodes. Therefore, this paper proposes a mechanical-electrochemical coupled model to study the lithium concentration distribution in the active layer during lithiation. This model includes lithium concentration diffusion and active layer deformation. By comparing experimental and simulated curvature evolution of the active layer during lithiation and delithiation, the reliability of this simulation model is verified. We then derive the precise concentration distribution inside the active layer and suggest using relative error to quantitatively evaluate the uniformity of lithium concentration in the active layer. Results show that a low relative error in lithium concentration can be achieved in the middle region of the active layer. Additionally, the effects of different rates and geometric parameters on the lithium concentration distribution in the active layer are discussed. Results indicate that reduced rates, thinner active layers, shorter active layer lengths, and increased spacing between the working and counter electrodes can lead to a more uniform distribution of lithium concentration in the active layer. These insights help improve experimental methods and equipment, promoting uniform distribution of lithium in the active layer and enhancing measurement accuracy.