Morphological and Phase Characterisation of the Solid Conversion of Sulfur in Highly Concentrated Electrolytes

Lithium-Sulfur (LiS) batteries offer a five-fold increase in energy density compared to commercial lithium-ion cells, but low efficiency and poor long-term cyclability hinders the full potential of this technology. Recently, new electrolyte formulations have been proposed to transition to a ‘solid-solid’ conversion pathway, avoiding the detrimental polysulfide dissolution, and seeing a significant increase in performance. This experiment aims to realise the first combined operando X-ray tomographic microscopy and X-ray diffraction experiment to track the microstructure evolution along the ‘solid-solid’ conversion pathway and identify the formation of phases during cell operation. From the results, we will elucidate the nature of the 'solid-solid' conversion of S8 to Li2S and correlate the morphological and phase changes with electrochemical data, providing insights into the rational design of electrodes and electrolytes for high-performance cells.