In-situ Spectroscopic Investigations of High Energy Li-S Batteries Based on New Carbon Cathodes

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The successful design of Li-S batteries with high energy density has the challenging perspective to significantly improve existing battery technology and to boost the development of environmentally friendly automotive development. Li-S batteries could triple the energy density of existing Li-ion batteries combined with high reversibility of fast charging-discharging cycles and lifetime of thousands of cycles. Recently, based on novel approaches for battery design we have been able to develop Li-S test cells with relatively high energy density and stability over 50 cycles. There are, however still problems to be solved related to the insulating nature of active sulfur, polysulfide dissolution and redox shuttle phenomena, volume expansion, electrode passivation by sulfides etc. that limits the performance of Li-S batteries. In this project we will develop novel composite cathodes, protective membranes and new electrolytes which will allow improvement of the performance of Li-S batteries. Due to the complex nature of ongoing processes we believe that systematic and basic studies of charging and discharging processes are necessary. Therefore, we propose to use sophisticated characterisation techniques, i.e. near edge X-ray absorption fine structure (NEXAFS) spectroscopy, Raman spectroscopy and electron spin resonance, where chemical modifications at different locations inside the cell during charging and discharging may be followed in situ and radical formation is detected. Thus, elemental sulfur and in particular polysulfide distribution and kinetics will be determined, allowing specific optimisation of the cells. In our multidisciplinary consortium, development of new polymer-based porous cathode materials, formulation of advanced electrolytes and optimisation electrochemical performance at experimental and theoretical levels will be realised by the combined efforts of the three partners. Application aspects will be discussed in close contact with a leading battery producing company.