A metastable β-sulfur phase stabilized at room temperature during cycling of high efficiency carbon fibre-sulfur composites for Li-S batteries

Due to the insulating behavior of sulfur particles, the development of a suitable conductive matrix becomes a real challenge. Here, we present new composites obtained by mixing sulfur with carbon fibres. These composites possess a specific charge higher than 1200 mA h g(-1) of sulfur, and exhibit hardly any fading during cycling. We performed for the first time high resolution in situ X-ray diffraction to understand the role of the composite template. Surprisingly after 1 cycle the beta-sulfur phase was formed, stable normally only above 96 degrees C. A post-mortem analysis was also performed to show the impact of cycling as well as the storage of the powder.