The thermodynamic properties of magnesium make it a natural choice for use as an anode material in rechargeable batteries, because it may provide a considerably higher energy density than the commonly used lead-acid and nickel-cadmium systems. Moreover, in contrast to lead and cadmium, magnesium is inexpensive, environmentally friendly and safe to handle. But the development of Mg batteries has been hindered by two problems. First, owing to the chemical activity of Mg, only solutions that neither donate nor accept protons are suitable as electrolytes; but most of these solutions allow the growth of passivating surface films, which inhibit any electrochemical reaction. Second, the choice of cathode materials has been limited by the difficulty of intercalating Mg ions in many hosts. Following previous studies of the electrochemistry of Mg electrodes in various non-aqueous solutions, and of a variety of intercalation electrodes, we have now developed rechargeable Mg battery systems that show promise for applications. The systems comprise electrolyte solutions based on Mg organohaloaluminate salts, and Mg(x)Mo3S4 cathodes, into which Mg ions can be intercalated reversibly, and with relatively fast kinetics. We expect that further improvements in the energy density will make these batteries a viable alternative to existing systems.

Carbon cloth was produced by temperature-programmed pyroloysis of commercial cotton cloth under an argon flow. The temperature program included a slow ramp of 0.5ЊC/min in the 150 to 400ЊC range, and 1ЊC/min from 400 to 600ЊC. These slow ramps cover the temperature range in which the major part of the pyrolitic chemical changes take place. The samples were then heated at a faster rate up

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The morphology of lithium electrodes in a variety of alkyl carbonate solutions was studied using in situ atomic force microscopy (AFM). We made use of a workstation specially built for the study of highly reactive electrochemical systems by AFM and other scanning probe techniques, based on an evacuable, vibration-protected glovebox. The electrolyte solution used was composed of propylene carbonate (PC), mixtures of ethylene carbonate (EC), dimethyl carbonate (DMC), diethyl carbonate (DEC), and Li salts from the following list:  LiPF6, LiClO4, LiAsF6, LiN(SO2CF3)2, LiN(SO2CF2CF3)2, and LiC(SO2CF3)3. We studied the effect of solution composition, prolonged storage, Li deposition, and dissolution at low and high current densities. The AFM imaging of these systems shows the complicated morphology of the Li electrodes that depend on the solution composition. We were able to clearly follow the nonuniform nature of Li deposition and dissolution in these systems. We were also able to follow by in situ AFM imaging critical events such as the onset of dendrite formation and the breakdown and repair of the surface films on lithium during Li dissolution at high current densities. The basic morphology of Li electrodes in alkyl carbonate solutions and the condition for the reversible behavior of Li electrodes is discussed.

Magnesium deposition processes from ethereal solutions of Grignard salts of the RMgX type ͑R ϭ alkyl, aryl groups and X ϭ halide; Cl, Br͒, and complexes of the Mg͑AX 4Ϫn R n Ј R n Љ Ј ) 2 type ͑A ϭ Al, B, X ϭ halide; R,RЈ ϭ alkyl or aryl groups and nЈ ϩ nЉ ϭ n͒ were investigated. These complexes can be considered as interaction products between RЈRMg bases and AX 3Ϫn R n Ј R n Љ Ј Lewis acids. The use of such complexes in ether solvents enables solutions of high anodic stability to be obtained, which can be suitable for rechargeable Mg battery systems. In situ scanning tunneling microscopy, scanning electron microscopy in conjunction with element analysis by dispersive X-ray, electrochemical quartz crystal microbalance, and impedance spectroscopy were used. Mg deposition in all the solutions studied initially form a porous deposit that becomes compact and crystalline as the process continues. It was found that the morphology of Mg deposition is strongly dependent on the solution's composition. This is because these processes are accompanied by adsorption processes. The specific adsorbed species in each solution probably influence the nucleation processes and thus affect the final morphology of Mg deposition in each solution. There is a clear correlation between the morphology of these processes and the cycling efficiency of Mg anodes measured in each solution. The results thus obtained are important for R&D of rechargeable Mg battery systems.

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In this study, surface film formation on nonactive-metal electrodes was analyzed using several in situ spectroelectrochemical techniques. These techniques included in situ Fourier transform infrared spectroscopy in both internal and external reflectance modes, impedance spectroscopy, electrochemical quartz crystal microbalance, and atomic force microscopy. The solutions studied included ethylene carbonate-dimethyl carbonate (EC-DMC) and EC-tetrahydrofurane (EC-THF) mixtures with Li salts, such as LiAsF6, LiPF6, LiClO4, and LiBr, part of which are essential for practical Li ion batteries. This work aimed to determine the onset of surface film formation, the impact of the solvent and salt used, and to compare the stability of the surface films formed in the various systems. The onset of surface film formation in these systems usually approximated 1.5 V (Li/Li + ). EC reduction products, probably (CH2OCO2Li)2, are dominant constituents in the surface films. However, in LiPF6 solutions, Li salt reduction products become dominant in the surface films. The surface film formation is accompanied by an injection of charge which does not form stable surface species and by dissolution processes of surface species (until the solution becomes saturated with them). The coherence of the data obtained from the four techniques mentioned above and the relative stability of the surface films formed in the various solutions are discussed.