Today, the increased concern about the future of the world reserve of fossil fuels and the general request for a global reduction of green-house gases emission make the electric traction technology (EV) the most promising alternative to the internal combustion engine one. It must be noted, however, that a strong improvement of the power sources characteristics is needed so that the EV can reach the internal combustion engine performances. A possible alternative to the state-of-the-art lithium/ion batteries is that of using at the positive electrode an oxygen reduction electrode (lithium/air cell). This would allow to greatly increase the positive electrode capacity, as the active material would not be stored in the battery but would come from the air. It is possible to foresee that Li/air batteries can lead to the possibility of fully electric vehicles, which would be a strong simplification with respect to the current hybrid vehicles. The development of Li/air batteries is actually a hot spot of the top applied research. Just as simple examples, recently IBM strongly invested on the development of Li/air batteries for a lightweight 500-miles family car (www.technologyreview.com/energy/22780). The DOE announced that 24 million hours of supercomputing time out of a total of 1.6 billion available at Argonne and Oak Ridge National Labs have been awarded to investigate materials for developing lithium-air batteries, in cooperation with IBM (Ceramic Tech Today, February 1, 2010).
The lithium/air cell with organic electrolyte behaves differently from the already known metal/O2 systems in that the reduction products during discharge (Li2O2 and Li2O) cannot dissolve in the electrolyte. In principle, the cell consists of a thin lithium foil as the anode, an organic or hybrid Li ions conducting membrane as the electrolyte, and a carbon thin film of high surface area, supporting a suitable catalyst, as the cathode. Here oxygen, the cathodic active material, is reduced during the discharge of the battery. The electrolyte has the multiple task of driving Li ions and isolating the anode from the cathode, open to the outer ambient, so preventing the incoming of moisture and carbon dioxide present in the air. Beside a notable value of the theoretical specific energy, this power source shows two positive aspects: the oxygen reaction can be promoted also by catalyst material not containing noble metals, a necessity in the case of fuel cells that is delaying their full development. Moreover, differently from others Me/air systems, this is perspectively a real rechargeable system.
The proposed research project aims at the development of new nanostructured materials for the electrolyte and cathodic compartments of an innovative lithium/air battery, to be applied in the electric vehicle field, capable of forwarding a specific energy about one order of magnitude higher than that obtained by the actual lithium/ion batteries. The main focus of the project will be centred on the cathode compartment, although a not secondary point will be given by the electrolyte, which will contain new generation ionic liquids (ILs). Here, the major challenge will be to lower the ILs intrinsic high viscosity. Being this system oriented to the electric vehicle, which is a foreseen large production item in the future, the materials constituting the battery should be ecologically friend, safe and, in the case of an industrial standard production, low cost. The end point of the project is the fabrication of a demonstrator.
The project will be carried out by two partners from University of Pavia (R.U. 1, project leader), and University of Milano (R.U. 2). The R.U. of Pavia will be involved in: i) preparation and characterization of the materials for the electrolyte, consisting of a composite or nanocomposite polymeric membrane in which a ionic liquid is incorporated as the electrolyte; ii) characterization the Li metal anode/electrolyte interface; iii) cell assembling and testing. The activity of the R.U. of Milano is focused on the synthesis and characterization, both from the electrochemical and the spectroscopic points of view, of nanostructured multiphase materials, metal or metal oxide based, presenting electrocatalytic properties for the cathodic Li/air batteries. In particular, starting from the already tested EMD (Electrolytic Manganese Dioxide), as reference material for the optimization of the experimental set up, the R.U. of Milano will synthesize, via sol-gel route, new mixed oxide nanoparticles to improve the charge/discharge cycles, and possibly to reduce the charge potential. These multiphase materials will be used in carbon based matrices, provided by an external research group acting as a subcontractor, for the preparation of the positive electrode. A substantial effort will be devoted to the formation, in an interdisciplinary environment, of PhD students and post-docs. The project is two years long, an the overall people engagement is 95 person/months, 77 of which will be given by temporary staff (YR) hired on the project. The project overall cost is 400000 Euro, and the grant requested to CARIPLO Foundation is 200000 Euro.