Solvate Ionic Liquids (SILs) are a novel class of liquids composed of a salt and a solvent capable of forming stoichimetric complexes with the salt. The concept of SILs was introduced by the Watanabe group in 2010. Here, a stable chelate complex is built, leading to properties comparable with classic ionic liquids (ILs). These include high thermal and electrochemical stability as well as low inflammability. However, despite their favorable thermal and electrochemical properties, SILs often possess high viscosities and low ionic conductivities. Depending on the composition of the SIL, these properties can be tuned, making them suitable electrolytes for more environmentally friendly and safer batteries. Their possibilities for application as electrolytes for lithium-ion batteries have been explored intensively, with SILs being considered instrumental for achieving highly reversible charge-discharge of Li electrodes in Li metal batteries. The electrolyte properties of glyme-based SILs have recently been reviewed by However, there is a need to differentiate between highly concentrated electrolyte solutions and SILS. Both can have similar compositions, but only in SILs, long-lived solvate-cation complexes are built. Therefore, Ueno et al. suggested criteria for distinguishing between the two liquid types. In both cases, Coulomb interactions occur between the lithium cations and their counterions. Additionally, ion-dipole interactions are present between the cations and the solvate molecules. The competition between Coulomb interactions and ion-dipole interactions plays a crucial role in determining the character of the ionic system. Stable cation-solvate complex structures can only be formed if the ion-dipole interaction overcomes the attractive interaction between cations and anions. To further explore this, they suggest investigating the self-diffusion coefficients of the lithium cation and the complex-forming solvent as a reliable criterion. If the ratio of the two diffusion coefficients equals unity, it is expected that long-lived complex cations are formed, and the mixture is proposed to be a SIL. However, if the ratio differs significantly from unity, a concentrated solution is formed rather than a SIL. This implies either rapidly exchanging ligands in the cationic complex or the existence of free, uncoordinated solvate molecules. In addition, Ueno showed that the formation of SILs strongly depends on the ionicity of the system and the interaction strength of the counterions. The lower the ionicity, the higher the SIL character. As another criterion, the amount of free solvate molecules can be taken into account: Here, the amount should not exceed 20 % because the presence of free solvent molecules strongly correlates with the thermal and electrochemical properties of the electrolyte. Ueno observed that for glyme-based SILs, both the thermal stability and the oxidative stability of glymes are increased compared to systems they classified as concentrated solutions. In addition, the character of the anion needs to be taken into account. Here, weakly coordinating, bulky anions should be considered. This way, the dipole-ion interaction can compete with the Coulomb interactions more easily. In summary, the composition of the mixture of salt and the solvate molecules has to be chosen carefully to obtain SILs. The most promising and highly investigated candidates for possible SILs are lithium salts dissolved in ethereal solvents. For certain mixing ratios, the binary systems form stable molten complexes, resulting in a liquid at ambient conditions. Due to the liquid state, they are also often referred to as molten salts. Therefore, mixtures of lithium salts with weakly-coordinating anions such as the bis(trifluoro-methanesulfonyl)imide anion ( [Li][NTf 2 ]) have been studied intensively in combination with glyme solvents ((H-(CH 2 -O-CH 2 ) n -H)) such as monoglyme (G1, n = 2), diglyme (G2, n = 3), triglyme (G3, n = 4) and tetraglyme (G4, n = 5). Recent studies showed that the number of coordination sites on the glyme molecule, namely their oxygen atoms, have a strong impact on the stability of the cationic complexes formed within these systems. Zhang et al. proved that the lithium cations prefer an oxygen coordination number of 4 to 5 independent of the glyme solvent used. Hence, mixtures with G3 or G4 as a ligand yielded more stable complex cations as compared to mixtures employing monoglyme or diglyme as solvent due to the chelate effect of the complexating solvent.