The main discharge products formed at the cathode of nonaqueous Li−air batteries are known to be Li 2 O 2 and residual Li 2 CO 3 . Recent experiments indicate that the charge transport through these materials is the main limiting factor for the battery performance. It has been also shown that the performance of the battery decreases drastically when the amount of Li 2 CO 3 at the cathode increases with respect to Li 2 O 2 . In this work, we study the formation and transport of hole and electron polarons in Li 2 O 2 and Li 2 CO 3 using density functional theory (DFT) within the PBE+U approximation. For both materials, we find that the formation of polarons (both hole and electron) is stabilized with respect to the delocalized states for all physically relevant values of U. We find a much higher mobility for hole polarons than for the electron polarons, and we show that the poor charge transport in Li 2 CO 3 compared to Li 2 O 2 can be understood through a polaronic model for the conduction. Furthermore, the hole polaronic model in Li 2 O 2 provides a possible explanation for the experimentally observed preferential growth direction of the films. Our results also suggest that doping is unlikely to be a viable route for improving the transport properties of Li 2 O 2 or Li 2 CO 3 .

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The LiBH 4 −LiI solid solution is a good Li + conductor and a promising crystalline electrolyte for all-solid-state lithium based batteries. The focus of the present work is on the effect of heat treatment on the Li + conduction. Solid solutions with a LiI content of 6.25−50% were synthesized by high-energy ball milling and annealed at 140 °C. Powder X-ray diffraction and scanning electron microscopy were used for characterizing the samples and for comparing their crystallite sizes and the density of defects before and after the annealing. The Li + conductivity was measured using impedance spectroscopy, resulting in conductivities exceeding 0.1 mS/cm at 30 °C and 10 mS/cm at 140 °C. It was found that the formation of defect-rich microstructures during ball milling increased the specific conductivities of these compounds significantly. The phase transition temperatures between the orthorhombic and hexagonal structures of LiBH 4 were measured using differential scanning calorimetry (DSC). The measured transition temperatures range from 100 to −70 °C and show a linear decrease of 70 °C for every 10% of LiI addition up to a LiI content of 25%. The relative stability of the two structures was calculated using density functional theory, and together with the DSC measurements, the calculations were used to evaluate the change in entropic difference between the structures with LiI content.

Using a DFT-based genetic algorithm (GA) approach, we have determined the most stable structure and stoichiometry of a 309-atom icosahedral AuCu nanoalloy, for potential use as an electrocatalyst for CO2 reduction. The identified core-shell nano-particle consists of a copper core interspersed with gold atoms having only copper neighbors and a gold surface with a few copper atoms in the terraces. We also present an adsorbate-dependent correction scheme, which enables an accurate determination of adsorption energies using a computationally fast, localized LCAO-basis set. These show that it is possible to use the LCAO mode to obtain a realistic estimate of the molecular chemisorption energy for systems where the computation in normal grid mode is not computationally feasible. These corrections are employed when calculating adsorption energies on the Cu, Au and most stable mixed particles. This shows that the mixed Cu135@Au174 core-shell nanoalloy has a similar adsorption energy, for the most favorable site, as a pure gold nano-particle. Cu, however, has the effect of stabilizing the icosahedral structure because Au particles are easily distorted when adding adsorbates.