Recently, we have succeeded in the development of new tight-binding quantum chemical molecular dynamics code "Colors", based on our original tight-binding theory. It realizes 5000 times acceleration compared to the conventional first-principles molecular dynamics method and enables us to simulate huge simulation models. Hence, in the present study we applied our new tight-binding quantum chemical molecular dynamics method to the investigation of the electronic structure of the interface of the Li0.5CoO2 electrode and the ethylene carbonate (EC) electrolyte along with LiPF6. Our electronic structure calculations for the Li0.5CoO2/EC+LiPF6 interface suggest that the EC+LiPF6 electrolyte significantly stabilizes the instability of the Li0.5CoO2 surface. Moreover, the detailed analyses for the electronic structure of the electrode/electrolyte interface were also performed. These analyses cannot be realized by the conventional first-principles approach, since it requests huge computational time for such large and complicated system. Hence, we confirmed the effectiveness of our tight-binding quantum chemical molecular dynamics approach to the investigation of the electrode/electrolyte interface on electronic- and atomic-level. (C) 2004 Elsevier B.V. All rights reserved.