Revealing the spatial distribution of decomposition products upon ageing on Li6PS5Cl solid electrolyte via X-ray diffraction computed tomography

In order to achieve a high energy density and safety promised by all solid-state batteries there remain a number of challenges, in particular relating to the stability of the solid electrolyte during cycling. Thiophosphate solid electrolytes have been intensely studied recently, due to their good conductivity at room temperature, processability and low-cost. Li6PS5Cl (LPSCl) is one of the most promising candidates in this category, however many questions remain about the chemical, electrochemical, structural, and morphological changes experienced during cycling. In this work, we analysed ex situ half cells of LPSCL cycled against Li-In for more than 20 cycles by X-ray diffraction computed tomography (XRD-CT), in order to reconstruct in 3 dimensions, the extent of LPSCL decomposition. We show that decomposition products are localized not only at the electrochemical interfaces and that competition between chemical and electrochemical degradation is occurring, leading to the presence of known decomposition products through the entirety of the electrochemical cell. Using a homemade diffraction peak algorithm, we determine the presence of several other phases not yet reported in the literature. is. Our work highlights the need for advanced 3D characterisation techniques to understand the extent of decomposition phases in LPSCl solid electrolyte and assess properly the ageing of solid-state batteries.