An analytical impedance model and a small-signal equivalent circuit are derived for the impedance spectra of Li-air batteries with porous cathodes. The model takes into consideration the effects of the oxygen diffusion, double layer, and faradaic processes in the cathode and can be applied to Li-air batteries with organic and aqueous electrolytes operating under d.c. discharge. It is shown that the cathode of Li-air batteries can create two slightly asymmetrical semicircles on the Nyquist diagram: one at low frequencies, where the oxygen diffusion dominates the operation of the cell and one at medium frequencies due to the combined effects of the double-layer capacitance and faradaic processes. The second semicircle becomes negligibly small at low values of the cathode width or oxygen concentration. Both semicircles can degenerate into one large semicircle when the double layer capacitance is large enough and masks the effects of the faradaic processes, which happens at large values of the specific area of the cathode and double layer capacitance, or when the oxygen diffusion coefficient in the electrolyte is relatively large. They also degenerate into one semicircle when the porosity is decreased, for instance during the final period of the discharge of Li-air batteries with organic

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The adoption of management ideas requires substantial resources. Most research focuses on a single adoption of ideas, how they come into use and fall out of use. Although some new management ideas ‘come back’, and have a ‘second life’ or even a ‘third life’, how and why they are re-adopted needs further exploration. This chapter explores the re-adoption of self-organization and identifies four drivers of re-adoption, explaining how external and internal conditions, technological change, and employee experience can shape the (re)action to management ideas. It concludes by outlining opportunities for future research avenues.

Conventional classical force fields by construction do not explicitly partition intermolecular interactions to include polarization and charge transfer effects, whereas fully quantum mechanical treatments allow a means to effect this dissection (although not uniquely due to the lack of a charge transfer operator). Considering the importance of polarization in a variety of systems, a particular class of classical models, charge equilibration models, have been extensively developed to study those systems; since these types of interaction models are inherently based on movement of charge throughout a system, they are natural platform for including polarization and charge transfer effects within the context of molecular simulations. Here, we present two bond-space charge equilibration models we term as QE2 and mixed QE2 treat charge transfer in classical molecular mechanical calculations those provide practical solutions to two major drawbacks of charge equilibration models: (a) a nonvanishing amount of charge transfer between two heteroatoms at large separations, and (b) superlinear polarizability scaling during bond dissociation due to charge transfer over unphysical, large distances. To control charge transfer during dissociation of a bond in a molecular system, we introduce a distance-dependent scaling function (QE2 model) which, controls and recovers physical behavior of the homonuclear and heteronuclear charge transfer between two atoms at small and large values of internuclear separation; and the mixed QE2 model in which we combine the QE2 model under allow and disallow charge transfer situations that describe both charge transfer and polarizability in a distance-dependent manner. We demonstrate the utility of both models in the case of a water dimer, and compare the results with other existing models, and further, we perform short molecular dynamics simulations for few water clusters with the QE2 model to show the charge transfer and internuclear separation are correlated in dynamics. © 2017 Wiley Periodicals, Inc.

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In this article we compare the impedance spectra of Li-air batteries using two models: one based on the analytical solution of the oxygen diffusion equation in the cathode and the other one based on finite element simulations. The first model was recently introduced by us to compute the impedance of lithium-air batteries with organic electrolyte and, here, is presented in slightly different form. The second model is based on the solution of the transport equations in concentrated solutions; the complex impedance is computed by the linearizing the partial differential equations that describe the mass and charge transport in Li-air batteries and includes the effects of the oxygen and lithium diffusion, finite electrolyte conductivities of the electrolyte and electrons, and Butler-Volmer kinetics at the anode and cathode.

In this article we develop a mathematical model and analyze the variability of discharge characteristics and impedance spectra in Li-air batteries with organic electrolyte. These batteries are well known to display a large variability of their characteristics from battery to battery (particularly of their specific capacity, energy and power densities), however, the exact reasons of this variability are still under investigation. Our model shows that the intrinsic variability of the pore microstructure which include the variability of the porosity and specific area from one macroscopic location to another macroscopic location inside the same battery and from one battery to another battery can be, at least in part, responsible for the large discrepancy of the results reported in the literature for the discharge characteristics and impedance spectra. It is shown that, while the variance of the specific capacity decreases slightly when the discharge current of the cell is increasing, the relative varianceto-mean ratio increases dramatically.