Degradation of a water-in-salt electrolyte at graphite and Na metal electrodes from first principles

By preventing water decomposition on the electrode surface, the solid-electrolyte interphase (SEI) plays a crucial role in enhancing the electrochemical stability of water-in-salt electrolytes, thereby facilitating their commercialization. In this study, we employ density functional theory calculations to explore the initial stages of SEI formation within a sodium triflate water-in-salt electrolyte on two types of electrodes: graphite, known for its inert characteristics, and a highly reactive sodium metal surface, both commonly used in sodium-ion batteries. The insights gained from our calculations offer predictive information on the potential composition of the interfacial layer forming on these surface models, shedding light on the electrochemical performance of the system as a battery feature.