We performed electronic structure calculations and long time quantum molecular dynamics simulations of the ionic liquid N-Methyl-N-propylpiperidinium bis trifluoromethanesulfonyl imide (PP13-TFSI) by the charge self-consistent tight-binding method. The adjustment processes of tight-binding parameters are explained briefly. The calculated electronic states well reproduce those by the density functional theory calculation, e.g. the density of states, HOMO and LUMO wavefunctions, and the charge transfer between a cation and an anion. The quantum molecular dynamics simulation is achieved for four ion-pairs of PP13-TFSI at 303 K through 100 ps. A spontaneous dissociation of the ion-pair into the cation and the anion is not observed under the simulation condition, so that we conclude that the ions diffuse as the ion-pair. (C) 2012 Elsevier B.V. All rights reserved.