Stress-regulated pulse charging protocols via coupled electrochemical-mechanical model for the mechanical stability of electrode materials in lithium-ion batteries

The effects of microstructural geometries and C-rates (charge and discharge rates) on mechanical failure have been widely studied to reduce the side reaction and capacity fade in Li-ion batteries. Recently, to achieve the maximum state of charge with least mechanical failure, stress-regulated charging protocols have been considered an emerging strategy. However, the theoretical studies of the charging protocols are limited to either using the equivalent circuit models, or considering only the active material phase. In this paper, we predict the pulse charging profiles by simultaneously controlling the stress level of the active particle and binder, to avoid mechanical failure of the particle, binder, and particle-binder interface. The charging protocol profiles are decided by controlling the stresses within a safe range. The simulations show that both the stress in the active particle and the binder stress and interfacial tractions play important roles in deciding the characteristics of pulse charging profiles, such as duty cycles and pulse frequencies. In addition, the binder constraint significantly affects the use of the pulse charging method. As the particle size and binder stiffness increase, and the binder contact angle decreases, binder stress plays a dominant role in controlling pulse charging. These new insights provide better understanding towards designing fast-charging protocols for Li-ion batteries.