where X or XTFSI denote the N1s, C1s, F1s, O1s or S2p levels in the respective adsorbate (X) or in TFSI (XTFSI). We also tested whether the size of the unit cell has an impact on the calculated BE and found that doubling the surface unit cell along the shortest lattice vector (lattice vector a) only leads to small changes in the calculated BEs. For example, the BE(N 1s) of the decomposition product of TFSI with a broken N-S bond changes only by about 0.1 eV if the surface unit cell doubled.