High energy density batteries are the power sources of choice for a variety of military and consumer applications. Presently, much of the primary battery needs are met by lithium (Li) systems. A problem with Li batteries has been their tendency to exhibit unsafe behavior due in some part to the low melting point of Li. To overcome this problem, an anode with similar properties to Li but with a higher melting point is worth exploring, for example magnesium (Mg). The overall goal of this study is to develop a high energy density Mg battery which will have the high power capabilities of Li systems such as Li/SOCi2 and Li/SO2 cells, but would be significantly safer, and would not have the startup (voltage delay) problems of aqueous Mg batteries. The key to the successful development of such a battery would be the selection of an electrolyte solution in which Mg will be stable under both open-circuit and discharge conditions. A perceived advantage of sulfur dioxide (SO2) as a solvent is that the protective films formed on Mg from its reaction with SO2 would be insoluble in this solvent making the Mg anode highly stable. Specific uses of the Mg batteries will include communication devices, robotics, hand-held tools, toys, military and space equipment and biomedical devices. This Small Business Innovation Research Phase I will consist of experimental work to test the feasibility of developing high energy density batteries utilizing Mg as the anode. SO2 will be used either as a cathode depolarizer or as an electrolyte solvent. In the latter configuration, the cathode depolarizer will be either CuF2 or NiF2. Two specific tasks will be performed: (1) Electrolyte characterization - electrolytes comprised of Mg(AlCl4)2 or Mg(GaCl4)2 in SO2 will be prepared and their conductivities determined. (2) Fabrication and testing of laboratory Mg cells - The electrochemical tests will include measurement of the open- circuit potential of the cells at different temperatures, for example, -20, 0 and 25oC, determination of their discharge capacities at a variety of current densities and temperatures, and an evaluation of the storage behavior of the cells.
