Water-in-salt electrolytes (WiSE), are especially relevant to batteries due to their percolating nanodomains in bulk. However, these types of electrolytes are still poorly understood and characterized at interfaces. This article addresses that gap, characterizing LiTFSI electrolytes and their formation of a double layer, on a charged electrode surface. For a better understanding of WiSE, different techniques were used, including infrared spectroscopy with IRUBIS silicon ATR crystals.