The goal of limiting global warming to 1.5 °C requires a drastic reduction in CO2 emissions across many sectors of the world economy. Batteries are vital to this endeavor, whether used in electric vehicles, to store renewable electricity, or in aviation. Present lithium-ion technologies are preparing the public for this inevitable change, but their maximum theoretical specific capacity presents a limitation. Their high cost is another concern for commercial viability. Metal-air batteries have the highest theoretical energy density of all possible secondary battery technologies and could yield step changes in energy storage, if their practical difficulties could be overcome. The scope of this review is to provide an objective, comprehensive, and authoritative assessment of the intensive work invested in nonaqueous rechargeable metal-air batteries over the past few years, which identified the key problems and guides directions to solve them. We focus primarily on the challenges and outlook for Li-O2 cells but include Na-O2, K-O2, and Mg-O2 cells for comparison. Our review highlights the interdisciplinary nature of this field that involves a combination of materials chemistry, electrochemistry, computation, microscopy, spectroscopy, and surface science. The mechanisms of O2 reduction and evolution are considered in the light of recent findings, along with developments in positive and negative electrodes, electrolytes, electrocatalysis on surfaces and in solution, and the degradative effect of singlet oxygen, which is typically formed in Li-O2 cells.

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Lithium-Oxygen Batteries and Related Systems: Potential, Status, and Future

Rechargeable Zn-air batteries: Progress in electrolyte development and cell configuration advancement

The Gibbs energy of solvation of several ions in water and dimethyl sulfoxide (DMSO) solutions was obtained through the use of thermodynamic equations relating ΔGsolv* of the ion with gas phase basicity, pKa, ΔGsolv* of neutral species and the Gibbs energy of solvation of the proton. We have used the most accurate and recent values for these properties, and this report provides 56 Gibbs energy of solvation values in aqueous solution and 30 in DMSO solution. Our results support the general view that anions are much better solvated in aqueous solution than in DMSO. An important example is the hydroxide ion for which the Gibbs energy of transfer from water to DMSO is 26 kcal mol−1. The majority of anions have a Gibbs energy of transfer in the range 10 to 15 kcal mol−1. In the case of cations, DMSO has a larger solvation ability but the difference in the Gibbs
energy of solvation between water and DMSO is not greater than 5 kcal mol−1. The present data can be very useful for the development of continuum solvation models.

Gibbs energy of solvation of organic ions in aqueous and dimethyl sulfoxide solutions

The inter- and intra-molecular dynamics of aqueous dimethyl sulfoxide (DMSO) solutions have been measured using optical heterodyne-detected Raman-induced Kerr effect spectroscopy. Solutions were studied over the entire range of composition at 294 K. The Kerr transients characterize both the underdamped inter- and intra-molecular vibrational motions, as well as the overdamped, diffusive orientational motions. The longer diffusive relaxation time constant τ2 is assigned to DMSO reorientation, and varies strongly with mole fraction of DMSO. The shorter time constant τ1 is assigned to water reorientation, and the value of 1.0 ps is nearly invariant across the range of solution composition. The solutions deviate substantially from hydrodynamic scaling behavior, since the ratio of DMSO reorientation time constant normalized by shear viscosity τ2/η is not a linear function of mole fraction. The peak frequencies for three of five low frequency intramolecular vibrations decrease with increasing water content. Both anisotropic and isotropic Kerr transients are recorded. The isotropic Kerr transient is dominated by the partially depolarized ν10 symmetric C–S–C stretching vibration at 670 cm−1. Electronic structure calculations for isolated DMSO, perdeuterated DMSO (d6-DMSO), and water are carried out using semi-empirical (PM3), density functional (B3LYP), and MP2 methods. Basis sets up to 6-311++G(d,p) are used and vibrational frequencies are calculated within the harmonic approximation. An unusual hemispherical shape is obtained for the electrostatic potential (ESP) about the DMSO oxygen. This hemispherical ESP was consistently observed for all levels of electronic structure theory and all basis sets that were used. Calculated polarizabilities permit us to estimate the anisotropic Kerr signal for an isolated DMSO molecule to be 79 times greater than for an isolated water molecule.

Aqueous dimethyl sulfoxide solutions: Inter- and intra-molecular dynamics

Surface vibrational sum frequency generation (VSFG) spectroscopy complemented with surface tension measurements has been utilized to probe the air/ dimethyl sulfoxide (DMSO) interface as a function of DMSO concentration in water. For the neat DMSO surface, the DMSO methyl groups extend away from the liquid phase and VSFG polarization studies show that the methyl transition dipole moments of pure DMSO are on average oriented a maximum of 55° from the surface normal. A blue shift of the methyl symmetric stretch is observed with decreasing DMSO concentration and attributed to an electronic interaction between the sulfur and the methyl groups of DMSO. From surface tension data of the aqueous DMSO system, it is shown that DMSO number densities are higher at the surface of DMSO−water solutions relative to bulk DMSO concentrations revealing surface partitioning effects. Structural changes of surface DMSO are discussed in terms of monomers, dimers, and clusters which could account for the large differences in VSF...

Molecular structure and adsorption of dimethyl sulfoxide at the surface of aqueous solutions

The total vapor pressures of dimethyl sulfoxide (DMSO) and water mixtures have been measured at 15, 20, 25 and 30°C. The activity coefficients and molar excess Gibbs energies of the system have been calculated. Possible association interaction in the system are discussed.

Xiaoqing Qian

Papers

Vapor pressure of dimethyl sulfoxide and water binary system