DFT-based grand canonical study of the stability of crystalline battery materials under operating conditions

High-throughput computational studies can significantly aid in the identification of crystalline battery materials with improved properties. Here, we present a density functional theory (DFT)-based numerical study addressing the stability of crystalline materials for chloride ion batteries under operating conditions using a grand canonical approach. Cl-ion batteries have emerged at the science stage as a possible energy storage technology promising enhanced energy density based on safe and environmentally benign chemistries. Although significant progress has been achieved in this field recently, the discovery of potential materials is only in its infancy. In the present work, we computationally address the materials class of chloride perovskites for the development of chloride-ion battery materials. Here, 18 782 intercalation configurations for 205 different compounds are evaluated employing a state-of-the-art machine-learning interatomic potential and periodic DFT calculations. For the analysis, focus is put on the comprehensive investigation with grand canonical diagrams. As this method inclusively covers the thermodynamic relations between the pristine compounds, its intercalation configurations, and possible conversion products under varying electrochemical conditions, we believe this approach is of great aid in the theoretical description and identification of potential materials. Our investigation resulted in the proposal of 23 solid electrolyte materials for further investigation. Six compounds exhibit reversible Cl intercalation/deintercalation, i.e., they are, in principle, suitable as cathode materials; however, reversible cycling should only be possible in a rather narrow potential window.