next gen: he implementation of inexpensive and reliable energy storage technologies is crucial for the decarbonisation of energy intensive industry branches and energy supply. Sensible thermal energy storage (TES) in molten salts is a key technology for storage of heat in the scale of gigawatt hours but currently limited to operating temperatures of 560 °C. Increasing the maximum operating temperature while maintaining thermal stability of the storage medium is one of the main challenges next-Generation TES systems are facing. Extending the upper temperature limit by only 40 °C increases the storage capacity by more than 16% allowing for more compact storage designs and cost savings in the $ million-range for large scale storage units. Here we propose a novel storage technology from a materials point of view that pushes the thermal stability limit of Solar Salt up to 600 °C by simply but effectively sealing the storage unit including the gas system. The concentration of the...