Operando investigation of polysulfide speciation on carbon fibre electrodes

Li-S batteries are a promising alternative to Li-ion, but uncontrolled diffusion and side reactions of soluble polysulfide (PS) intermediates (Li2Sn, 2≤n≤8) result in reduced Coulombic efficiency and rapid degradation. We use free-standing carbon fibres with tuneable surface chemistry and porosity to control nucleation, growth and retention of PSs at the cathode. This experiment uses the tender emission spectrometer on beamline ID26 to follow S Kβ emission during battery cycling. A combination of Kβ detected high energy resolution fluorescence detection (HERFD) X-ray absorption spectroscopy and X-ray emission spectroscopy (XES) will be used to follow formation and speciation of PSs during cycling on carbon fibre mats with different porosity and surface functionality. This information will enable us to understand the effect of carbon fibre structural properties on their ability to regulate S species conversion and deposition, allowing us to design materials with improved performance.