Investigating Degradation Mechanisms in Sodium Solid-State Batteries

Abstract

Solid-state sodium batteries are promising candidates for next-generation electro chemical energy storage, with improved sustainability and safety compared to cur rent lithium-ion technologies. In addition, solid electrolytes could potentially en able the use of sodium metal anodes for increased energy density. However, these electrodes currently have short lifetime due to electro-chemo-mechanically coupled degradation mechanisms, which must be well understood in order to mitigate the problems and extend the lifetime of solid-state sodium batteries. This thesis investi gates a sulfide solid electrolyte, with a particular focus on processes at the interface with sodium metal. The study involves electrochemical characterization techniques and imaging with X-ray tomographic microscopy, in order to gain insights into the processes that limit cell lifetime and efficiency. The results show rapid polarization of the cells, attributed to chemical degradation at the interface between sodium metal and the electrolyte. The resulting interphase layer fails to passivate the elec trode, leading to capacity loss from the irreversible side reactions that continuously consume sodium metal and solid electrolyte. The use of chlorine-doped electrolytes and protective interlayers presents promising strategies to improve the interfacial stability and extend the lifetime of sodium metal electrodes.