Multi-Physics Simulation of Solid-State Batteries with Active Material Coating

Abstract

Surface coating of active material (AM) particles with an oxide-based electrolyte is considered to be one of the most effective ways to reduce the interfacial resistance arising from the direct contact between the AM and sulfide-based solid electrolyte (SE) particles. This work aims to quantitatively discuss the influence of interfacial electron/ion transfer on the discharge characteristics of a solid-state battery cathode using the finite-element method. We used an in-house code to construct a composite cathode microstructure consisting of the coated AM and SE particles. To independently discuss the influence of bulk and interfacial properties, we first best estimated the bulk properties of AM based on single particle simulations and determined the properties of SE by referring to the model experiments. Using those bulk properties, we next investigated the electrochemical resistances arising from the electrochemical processes at the AM/AM, AM/SE, and SE/SE interfaces as well as those related to the buffer layer coating on the AM surface. Various interfacial parameters used in the electrochemical model are determined by validation with the experimental results of LiCoO2 (LCO), LiNbO3, and Li3.25Ge0.25P0.75S4 (LGPS) as the AM, coating material, and SE, respectively. Overall good agreement between the numerical simulation and the experiment is obtained.