Interface equilibrium modeling of all-solid-state lithium-ion thin film batteries

Abstract

Dynamic modeling of all-solid-state batteries (SSBs) has gained strong research interest in recent years. However, the intrinsic equilibrium state, important for the exchange current calculation and the interface resistance analysis is hardly addressed. For the first time, we introduce an advanced MPNP-FBV model which takes the electrical double layer (EDL) structure and the unoccupied regular lattice sites (vacancies) into account to illustrate the fundamental phenomena at the equilibrium state. This general model is verified from the chemical perspective and the interface experimental results in our previous investigations, which indicates that the model is able to calculate the exchange current and the charge transfer resistance from fundamental material properties. The influence on concentration and electrostatic potential by the different EDL structures, the state of charge (SOC) and the diffusivity are also investigated. Results show that the total electrostatic potential drop at the equilibrium state is related to the free enthalpy difference between the two materials. Furthermore, the charge transfer resistance with the diffuse double layer structure is higher than that with the compact double layer.