Lithium salt-added ionic liquid mixtures have shown promise as alternate electrolyte media for Li-ion batteries. Densities and dynamic viscosities of lithium bis(trifluoromethylsulfonyl) imide (LiTf2N) mixed with 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide ([emim][Tf2N]) for 0 <= x(LiTf2N) <= 0.4 in the temperature range (298.15-358.15) K are presented. Decrease in density with increasing temperature is found to follow a simple linear expression. The density of ([emim][Tf2N] + LiTf2N) mixtures increases with increasing x(LiTf2N) quadratically. The temperature dependence of the dynamic viscosity of the ([emim][Tf2N] + LiTf2N) mixtures follows Vogel-Fulcher-Tamman (VFT) model as opposed to an Arrhenius expression. The dynamic viscosity of ([emim][Tf2N] + LiTf2N) mixture at a given temperature increases exponentially with x(LiTf2N); the exponential increase being more prominent at lower temperatures (T <= 328.15 K). The exponential increase in dynamic viscosity with x(LiTf2N) is attributed to the well-documented formation of [Li(Tf2N)(2)](-) anionic aggregates that are less favored at higher temperatures. (C) 2017 Elsevier Ltd.