A unified and consistent electrical double layer model for the treatment of core and space charge layers in solid electrolytes

Abstract

The electrical double layer (EDL) is critical to the operation of devices for electrochemical energy storage and conversion. Existing EDL models in solid electrolytes simulate the space charge layer and lack a complete treatment of the interfacial core region. The core layer exhibits significant variations in defect properties, such as defect formation energy (DFE), which influence the ionic charge carrier distribution in the space charge layer. We present a general framework for treating both the core and space charge layer in solid electrolytes under dilute and concentrated regimes. This model incorporates DFE variation and defect–defect interactions, consistent with first-principles simulations of solid electrolyte interfaces. Simulations demonstrate that the core layer significantly affects potential and defect concentration profiles and contributes substantially to the conductivity when the interfacial DFE is lower than the bulk DFE. This framework enables accurate predictions of capacitance and ionic conductivity, essential for the design of solid-state electrochemical devices.