The salt was prepared via a cation exchange reaction, using LiTFSI and guanidium sulphate (Gdm2SO4) as precursors. In a typical batch, equimolar amounts of LiTFSI and Gdm2SO4 were dissolved separately in the minimum volume of water. The Gdm2SO4 solution was added dropwise to the LiTFSI solution, with the immediate formation of a crystalline solid. The solution was dried, obtaining a crude solid containing a mixture of GdmTFSI and Li2SO4. The mixture was extracted twice with dry acetone, the filtrate was collected, and pure GdmTFSI is obtained after removing the solvent under vacuum, with a yield of 97%. Residual lithium content was probed using inductively coupled plasma mass spectrometry (ICP-MS), where only 3.7 µgLi/mg were detected Fig. (left). Dilute equimolar solutions of GdmTFSI and BaCl2 were mixed to probe any residual SO4 2-; the mixed solution remained clear indicating that no detectable SO4 2-is present in the final product. Thermogravimetric analysis (TGA), Fig. (right), showcases that GdmTFSI is free of moisture and has a decomposition temperature of 350 °C. Differential scanning calorimetry (DSC), Fig. (left), showcases the phase transition from solid to a liquid for GdmTFSI occurs at 96 °C, consistent with the previously reported melting point of the compound (98 °C). Suitable crystals for single-crystal X-ray diffraction were obtained by slow evaporation of a GdmTFSI solution in water. GdmTFSI crystallizes in a triclinic P-1 space group with cell parameters: a = 15.9721(9) Å, b = 18.6173(9) Å, and c = 25.1641(5) Å; and angles α = 89.960(3)°, β = 85.636(3) °, and γ = 87.428(4)°. The crystals are composed of Gdm-TFSI layers held together by an HBN between the -NH2 groups of the cations and the -SO2 and -N-atoms of the anion (Fig. ). The TFSI anion alternates between cis and trans conformation along the a axis of the cell in cis-trans-cis configuration (Fig. ). Fig. showcases the infrared spectroscopy (IR) of the GdmTFSI salt, which displays the presence of both the Gdm + and the TFSI -. The different coordination environment of the TFSI -between the precursor LiTFSI salt and the obtained GdmTFSI salt can be observed when comparing the respective IR spectra. Fig. displays the region between 700 -850 cm -1 , where peaks around 740 cm -1 and 800 cm -1 correspond to the symmetric and asymmetric C-S and SNS stretching vibrations (denoted sC-S and aSNS) of the TFSI anion, respectively. A redshift of these bands is observed for GdmTFSI, indicating that, in the crystal, the TFSI anion is more loosely bound compared to LiTFSI. The weaker cation-anion interaction can be explained by the larger size and higher charge delocalization of Gdm + compared to Li + and can be used to explain the lower melting point of 96 °C (GdmTFSI) compared to 234 °C (LiTFSI). The bands in the 3000-3600 cm -1 region correspond to the -NH stretching vibrations of Gdm + , which are influenced by hydrogen bonding interactions between Gdm + and the anion. Fig. illustrates a shift to higher wavenumbers for N-H stretching vibrations in GdmTFSI salt compared to Gdm2SO4 salt. This shift can be attributed to the lower charge density of TFSI -compared to SO4 2-, resulting in weaker hydrogen bonding with Gdm + .