No abstract

The application of machine learning models to predict material properties is determined by the availability of high-quality data. We present an expert-curated dataset of lithium ion conductors and associated lithium ion conductivities measured by a.c. impedance spectroscopy. This dataset has 820 entries collected from 214 sources; entries contain a chemical composition, an expert-assigned structural label, and ionic conductivity at a specific temperature (from 5 to 873 °C). There are 403 unique chemical compositions with an associated ionic conductivity near room temperature (15–35 °C). The materials contained in this dataset are placed in the context of compounds reported in the Inorganic Crystal Structure Database with unsupervised machine learning and the Element Movers Distance. This dataset is used to train a CrabNet-based classifier to estimate whether a chemical composition has high or low ionic conductivity. This classifier is a practical tool to aid experimentalists in prioritizing candidates for further investigation as lithium ion conductors.

Argyrodite is a key structure type for ion-transporting materials. Oxide argyrodites are largely unexplored despite sulfide argyrodites being a leading family of solid-state lithium-ion conductors, in which the control of lithium distribution over a wide range of available sites strongly influences the conductivity. We present a new cubic Li-rich (>6 Li + per formula unit) oxide argyrodite Li 7 SiO 5 Cl that crystallizes with an ordered cubic (P2 1 3) structure at room temperature, undergoing a transition at 473 K to a Li + site disordered F4̅ 3m structure, consistent with the symmetry adopted by superionic sulfide argyrodites. Four different Li + sites are occupied in Li 7 SiO 5 Cl (T5, T5a, T3, and T4), the combination of which is previously unreported for Li-containing argyrodites. The disordered F4̅ 3m structure is stabilized to room temperature via substitution of Si 4+ with P 5+ in Li 6+x P 1−x Si x O 5 Cl (0.3 < x < 0.85) solid solution. The resulting delocalization of Li + sites leads to a maximum ionic conductivity of 1.82(1) × 10 −6 S cm −1 at x = 0.75, which is 3 orders of magnitude higher than the conductivities reported previously for oxide argyrodites. The variation of ionic conductivity with composition in Li 6+x P 1−x Si x O 5 Cl is directly connected to structural changes occurring within the Li + sublattice. These materials present superior atmospheric stability over analogous sulfide argyrodites and are stable against Li metal. The ability to control the ionic conductivity through structure and composition emphasizes the advances that can be made with further research in the open field of oxide argyrodites.

This alluaudite-type structure is constituted of infinite layers formed by links between M 2O10 (M = Cr1/Na1) dimers and MoO4 tetra­hedra. The Na+ and Cr3+ cations are located in the same genel site with, respectively, 0.25 and 0.75 occupancies. The layers are related by sharing corners with MoO4 tetra­hedra, resulting an in open three-dimensional framework with hexa­gonal-form cavities occupied by Na+ cations.