The Chevrel phase Mo6S8 is prepared by reaction of CuCl2 and (NH4)2MoS4 in DMF (90 °C, 6 h) followed by heating of the precipitate in 5% H2/Ar atmosphere (1000 °C, 7 h).

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Reversible Electrochemical Intercalation of Aluminum in Mo6S8

In this paper a brief survey is given of the properties of non-aqueous electrolyte solutions and their applications in chemistry and technology without going into the details of theory. Specific solvent-solute interactions and the role of the solvent beyond its function as a homogenous isotropic medium are stressed. Taking into account Parker's statement1) “Scientists nowadays are under increasing pressure to consider the relevance of their research, and rightly so” we have included examples showing the increasing industrial interest in non-aqueous electrolyte solutions.

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Non-aqueous electrolyte solutions in chemistry and modern technology

Various lightweight metals such as Li, Na, Mg, etc. are the basis of promising rechargeable batteries, but aluminium has some unique advantages: (i) the most abundant metal in the Earth's crust, (ii) trivalent charge carrier storing three times more charge with each ion transfer in comparison with Li, (iii) the volumetric capacity of the Al anode is four times higher than that of Li while their gravimetric capacities are comparable, (iv) employing a metallic Al anode does not have a major safety risk as is the case for alkali metals. However, there are serious obstacles to the practical development of Al batteries such as the complicated nature of trivalent Al3+ intercalation into the cathode of Al-ion batteries and corrosion of the metallic Al anode in aqueous electrolytes. Owing to the highly charged nature of small Al3+ ions, the diffusing species are indeed the Al complexed ions, which might be the intercalating ions in the solid-state too. The present manuscript reviews the current status of various aluminum batteries to narrate their unique potentials while highlighting the issues that should be addressed at this stage. Although Al–air batteries have a long history going back to the 1960s, the focus of this manuscript is on Al-ion batteries including Al–sulfur batteries, but other possibilities for electrochemical energy storage by Al charge carriers such as Al redox batteries, Al supercapacitors, etc. will be reviewed too. In the latter case, it seems the pseudocapacitance is more practical than intercalation for the case of Al3+ ions. Furthermore, the application of Al anodes in lithium-ion batteries is briefly described as the anode performance is similar to their application in Al batteries.

Electrochemical energy storage by aluminum as a lightweight and cheap anode/charge carrier

Electrolytic conductivities of LiClO4 and LiPF6 have been investigated in the mixed systems of the high permittivity solvents and low viscosity solvents. Propylene carbonate (PC), sulfolane (S), and dimethyl sulfoxide (DMSO) were used as the high permittivity solvents, and 1,2-dimethoxyethane (DME) and tetrahydrofuran (THF) as the low viscosity solvents. The conductivity of 1 mol dm−3 LiClO4 has a miximum in the mixed solvent with 40–80 m/o ether for every system. The conductance improvement by solvent-blending was qualitatively described in terms of a favorable combination of high permittivity and low viscosity of each component. The maximum conductivity of 1 mol dm−3 LiClO4 increased in the order of S<PC<DMSO for the systems containing THF. The difference in the order of maximum conductivity between DME and THF was interpreted by ion-solvent interactions, whose measure is generally expressed by the donor and acceptor properties of the solvent. The LiPF6 solutions had much higher conductance than those o...

Conductivity of lithium salts in the mixed systems of high permittivity solvents and low viscosity solvents.

Rechargeable batteries employing metal negative electrodes (i.e., anodes) are attractive next-generation energy storage devices because of their greater theoretical energy densities compared to intercalation-based anodes. An important consideration for a metal's viability as an anode is the efficiency with which it undergoes electrodeposition and electrodissolution. The present study assesses thermodynamic deposition/dissolution efficiencies and associated nucleation rates for seven metals (Li, Na, K, Mg, Ca, Al, and Zn) of relevance for battery applications. First-principles calculations were used to evaluate thermodynamic overpotentials at terraces and steps on several low-energy surfaces of these metals. In general, overpotentials are observed to be the smallest for plating/stripping at steps and largest at terrace sites. The difference in the coordination number for a surface atom from that in the bulk was found to correlate with the overpotential magnitude. Consequently, because of their low bulk coordination, the body-centered alkali metals (Li, Na, and K) are predicted to be among the most thermodynamically efficient for plating/stripping. In contrast, metals with larger bulk coordination such as Al, Zn, and the alkaline earths (Ca and Mg) generally exhibit higher thermodynamic overpotentials. The rate of steady-state nucleation during electrodeposition was estimated using a classical nucleation model informed by the present first-principles calculations. Nucleation rates are predicted to be several orders of magnitude larger on alkali metal surfaces than on the other metals. This multiscale model highlights the sensitivity of the nucleation behavior on the structure and composition of the electrode surface.

Thermodynamic Overpotentials and Nucleation Rates for Electrodeposition on Metal Anodes

The polarization characteristics of aluminium anodes have been studied in various organic electrolytes containing aluminium chloride. The small amount of oxide present on the metal was dissolved by an anodic pre-treatment. The charge transfer number of the overall reaction was three. The current density supported by the electrolytes decreased in the order nitromethane>acetonitrile >propylene carbonate, formamide>tetrahydrofuran. The rest potential increased in the order formamide<propylene carbonate<tetrahydrofuran<acetonitrile<nitromethane.

Y. ŌOuchi

Papers

Anodic polarization of aluminium in organic electrolytes