To lower these discrepancies, we had started a series of combined experimental and theoretical model studies. Aiming at a molecular-/atomic-level understanding of the processes at the electrode|electrolyte interface of Li-ion batteries, we had explored the chemical interaction between the battery-relevant ionic liquid (IL) 1-butyl-1methylpyrrolidinium bis(trifluoromethylsulfonyl)imide (BMP-TFSI) as solvent, Li + as charge carrying shuttle ion and structurally well defined, single-crystalline model electrodes of varying chemical activity such as Ag(111) or Au(111), , Cu(111), graphite (0001) and oxide surfaces such as TiO2(110) or Co oxides. Experimentally, this mainly involved a combination of scanning tunneling microscopy (STM) imaging and photoelectron spectroscopy (PES) measurements of the different adsorbate covered surfaces resulting after vapor deposition of either Li and / or BMP-TFSI under different conditions and quantitative evaluation of the resulting surface structures and surface compositions. Theoretically, we determined energetically favorable decomposition products resulting from the interaction between surface and deposits, in some cases also reaction barriers, their apparent structure in STM images, and most recently, also the binding energies of the core level peaks resulting from possible reaction intermediates. Finally, we also compared the composition of BMP-TFSI decomposition layers resulting from reaction with Li under vacuum conditions and upon electrochemical cycling in Li containing BMP-TFSI electrolyte in a combined electrochemical and surface science-type model study, using HOPG and a binder-free graphite powder material as substrate / electrode. In a recent combined experimental and theoretical study we had determined the decomposition products resulting from the room temperature (RT) interaction of postdeposited Li and a thick BMP-TFSI film, where the Li is expected to directly interact with the BMP-TFSI without preceding adsorption on the underlying graphite (0001) substrate. In that study, also the core level binding energies had been determined for a large number of possible reaction products. Experimentally, this involved a comprehensive X-ray photoelectron spectroscopy (XPS) characterization of the surface composition resulting after reaction the BMP-TFSI film and post-deposited Li 0 . Theoretically, this reaction was described as reaction between a BMP-TFSI ion pair and one or more Li 0 atoms. In the present work, we will extend this approach to the reaction between a BMP-TFSI monolayer film adsorbed on graphite (0001) and post-deposited Li, in a similar combined experimental and theoretical approach as described above. To assess the role and impact of kinetic barriers in the various reaction and desorption steps, we furthermore investigated the impact of thermal annealing steps to temperatures up to 700 K, both for the BMP-TFSI + Li monolayer system and the thick BMP-TFSI multilayer films. Theoretically, we identified the most stable reaction products resulting from the interaction of adsorbed BMP-TFSI and one or more co-adsorbed Li atoms, which were relaxed in the unit cell before reaction, and their respective reaction energies. Subsequently, we calculated the core level binding energies (BEs) for comparison with experimental XP spectra, using an approach that been described in detail recently. This allows a direct comparison between experimental XP spectra and characteristic binding energies of possible interaction or reaction products.