LiTiO was synthesized via a solid state reaction and lithiated at 400 °C in a custom built galvanostatic cell consisting of a molten LiCl-KCl electrolyte and Li-Al alloy wires as counter and reference electrodes. The material exhibits decreased rate capability at 400 °C compared to the room temperature behavior. Electrochemical lithiation at C/20 exhibits a discharge profile with both a sloping curve and flat plateau, which is indicative of a solid solution behavior before reaching a two phase region. This electrochemical behavior is shown to be correlated with reversible formation of the cubic LiTiO phase.

We discuss hydrogen diffusion and solubility in aluminum alloyed Fe-Mn alloys. The systems of interest are subjected to tetragonal and isotropic deformations. Based on ab initio modelling, we calculate solution energies, then employ Oriani's theory which reflects the influence of Al alloying via trap site diffusion. This local equilibrium model is complemented by qualitative considerations of Einstein diffusion. Therefore, we apply the climbing image nudged elastic band method to compute the minimum energy paths and energy barriers for hydrogen diffusion. Both for diffusivity and solubility of hydrogen, we find that the influence of the substitutional Al atom has both local chemical and nonlocal volumetric contributions. arXiv:1605.00084v2 [cond-mat.mtrl-sci]

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Although LixCoO2 has been in use as cathode material in Lithium-ion batteries for quite some time the mechanisms responsible for its cycling behavior are not completely understood. In practice only about 50 % of its theoretical capacity is accessible without rapid deterioration of cathode performance due to changes in the crystal structure. Moreover, its performance as a cathode material is known to be significantly influenced by the metal-insulator transition within a compositional range of x in [0.75; 0.94]. This concentration range marks the 2-phase region within which the cathode potential exhibits a plateau in agreement with the Gibbs’ phase rule. Up to now this transition has never been modeled by ab initio calculations due to the lack of feasible straight-forward methods for strongly correlated materials to account for the interactions of the open-shell d-electrons as they exist in LixCoO2. In this work the ambition is to capture the 2-phase region by running a number of calculation series on various compositions within the 2-phase-region by using the GGA+U approach. The space of magnetic configurations is sampled and results are analyzed with respect to metallic and semiconducting properties. Convex hulls are drawn through the acquired data points in a total energy versus Lithium-concentration plot for the metallic and semiconducting states. The common tangent of both convex hulls will pinpoint the borders of the two-phase region. The successful DFT-modeling of the metal-insulator transition is of particular interest since effects of dopants on this region could be studied. Especially the effect on the potential and the compositional range of the region would be leading aspects to look at since a higher potential and a broader two-phase region are beneficial for the cathode’s overall performance.

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