We report here a detailed impedance analysis of the interface between a selected IL electrolyte, i.e. a solution of lithium N, N-bis(trifluoromethane sulfon) imide in N-n-butyl-N-ethyl pyrrolidinium and a N, N-bis(trifluoromethane sulfon) imide, LiTFSI-Py24TFSI, and two electrodes, namely a conventional lithium metal and an advanced nanostructured Sn-C alloy, respectively. We show that the Sn-C alloy, in virtue of a specific formation of a surface protecting film, has an interface much more stable than that of the Li electrode. This favourable property is exploited for using Sn-C as a new anode for the development of an advanced lithium-ion battery based on LiTFSI-Py24TFSI as the electrolyte and on olivine LiFePO4 as the cathode. The results demonstrated that this battery has very promising performances in terms of cycle life and rate capability. (C) 2009 Elsevier B. V. All rights reserved.