Salt-added ionic liquid media have emerged as a versatile alternative to the conventional electrolytes in several applications. A lithium bis(trifluoromethylsulfonyl)imide (LiTf2N)-added ionic liquid l-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([emim][Tf2N]) system up to a LiTf2N mole fraction (x(LiXf2N)) of 0.40 is investigated using a fluorophore-quencher pair of pyrene- nitromethane in the 298.15-358.15 K temperature range. Excited-state intensity decay of pyrene fits best to a single-exponential decay function irrespective of the concentration of nitromethane, x(LiTf2N), and the temperature. Pyrene lifetimes decrease with increasing temperature at a given x(LiTf2N) with lifetime becoming more sensitive to temperature at higher LiTf2N concentration. The pyrene-nitromethane fluorophore- quencher pair follows a simplistic Stem-Volmer formulation, indicating the quenching to be purely dynamic in nature affording dynamic quenching constants (K-D) in the process. K-D along with the estimated bimolecular quenching rate constant (K-q) within LiTf2N-added [emim][Tf2N] first increases with increasing LiTf2N until x(LiTf2N) similar to 0.10, decreasing monotonically thereafter until x(LiTf2N) (=) 0.40. The decrease in K-q and k(q) with increasing x(LiTf2N) is attributed to the exponentially increased dynamic viscosity with increasing x(LiTf2N) of the ([emim][Tf2N] + LiTf2N) system. The initial increase in K-D and k(q) is controlled by the structural changes within the system as LiTf2N is added to [emim][Tf2N]. It is proposed that the presence of [Li(Tf2N)(2)](-) anionic clusters stabilizes the partial positive charge that develops on excited pyrene during the electron/charge transfer to nitromethane during the quenching process. While the Stokes-Einstein formulation is not followed by the ([emim][Tf2N] + LiTf2N) system in general, it is found to be obeyed at fixed x(LiTf2N). The role of structural changes within the system beyond viscosity increase on the quenching process is amply highlighted.