Journal of Solid State Electrochemistry

Skundin, Alexander; Tsirlina, Galina

doi: 10.1007/s10008-014-2480-5pmid: N/A

Biesheuvel, P.; Porada, S.; Levi, M.; Bazant, M.

doi: 10.1007/s10008-014-2383-5pmid: N/A

The recently developed modified Donnan (mD) model provides a simple and useful description of the electrical double layer in microporous carbon electrodes, suitable for incorporation in porous electrode theory. By postulating an attractive excess chemical potential for each ion in the micropores that is inversely proportional to the total ion concentration, we show that experimental data for capacitive deionization (CDI) can be accurately predicted over a wide range of applied voltages and salt concentrations. Since the ion spacing and Bjerrum length are each comparable to the micropore size (few nanometers), we postulate that the attraction results from fluctuating bare Coulomb interactions between individual ions and the metallic pore surfaces (image forces) that are not captured by mean-field theories, such as the Poisson-Boltzmann-Stern model or its mathematical limit for overlapping double layers, the Donnan model. Using reasonable estimates of the micropore permittivity and mean size (and no other fitting parameters), we propose a simple theory that predicts the attractive chemical potential inferred from experiments. As additional evidence for attractive forces, we present data for salt adsorption in uncharged microporous carbons, also predicted by the theory.

Visco, Steven; Nimon, Vitaliy; Petrov, Alexei; Pridatko, Kirill; Goncharenko, Nikolay; Nimon, Eugene; Jonghe, Lutgard; Volfkovich, Yury; Bograchev, Daniil

doi: 10.1007/s10008-014-2427-xpmid: N/A

The extremely high theoretical energy density of the lithium-oxygen couple makes it very attractive for next-generation battery development. However, there are a number of challenging technical hurdles that must be addressed for Li-Air batteries to become a commercial reality. In this article, we demonstrate how the invention of water-stable, solid electrolyte-protected lithium electrodes solves many of these issues and paves the way for the development of aqueous and nonaqueous Li-Air batteries with unprecedented energy densities. We also show data for fully packaged Li-Air cells that achieve more than 800 Wh/kg.

Ellerbrock, David; Macdonald, Digby

doi: 10.1007/s10008-013-2334-6pmid: N/A

Diagnostic criteria for the growth of the anodic oxide film on titanium in H2SO4 are reported. The criteria apply to the generalized high field model, which postulates that the electric field within the film is dependent upon the film thickness, and the point defect model, which describes the electric field as being constant during film growth. The diagnostic criteria show that the PDM more realistically models film growth than does the HFM, and we conclude that in this system the electric field strength is invariant with applied voltage and film thickness. The constancy of the electric field in the passive film on titanium, as demonstrated in this work, is attributed to band-to-band Esaki tunneling, which buffers the electric field against changes in the applied voltage and film thickness.