A Modeling Framework of Electrochemo-mechanics of Lithium-ion Battery: Part II. Porous Electrodes with Contact Stress Effect

Extended from the electrochemo-mechanical single particle model, an electrochemo-mechanical impedance model for porous electrode in LIB, which consider the effect of the contact stress, is proposed in this work. A modified coefficient ζ which links the mechanical properties of the electrode and particle material is introduced to describe the effect of contact stress. Firstly, we find that the contact stress can weaken the stress-induced semicircle in the low frequency range through analyzing the Faradaic part of the impedance. Secondly, considering the contact stress is determined by the mechanical bonding between electrode layer and the current collector, we introduce a pseudo-elastic boundary condition to analyze the bonding effect. For rigid substrate, namely the in-plane deformation is totally restricted, the effect of the contact stress is strong. For free substrate, namely the in-plane deformation is not restricted, the contact stress is not induced thus its effect on impedance disappears. Lastly, we discuss the interaction effect of stress and the ionic transport in the electrolyte and find that the interaction is strong for silicon-based material, which indicates the stress effect needs to be considered when interpreting the impedance data in this case.