Multivariate Method-Assisted Ab Initio Study of Olivine-Type LiMXO₄ (Main Group M²⁺–X⁵⁺ and M³⁺–X⁴⁺) Compositions as Potential Solid Electrolytes

Abstract

Lithium-ion conductive solid oxide electrolytes are receiving increasing attention for the development of highperformance all-solid state rechargeable Li-ion batteries. In this study, we report an effective search method that uses a combination of ab initio calculations and multivariate analysis to find potential solid oxide electrolyte materials with low Li-ion hopping energies (EAs) among 66 olivine-type oxides with an ordered structure LiMXO 4 (main group M 2+ −X 5+ , M 3+ −X 4+ ). The ionic size of M, with its associated octahedral distortion leading to the appreciable local lattice distortion during the actual Li ion hop, made the most significant contribution to the variation in EA values. Promising M−X pairs (<0.30 eV) with experimental data in the Inorganic Crystal Structure Database include Mg−As (0.17 eV), Sc−Ge (0.22 eV), In−Ge (0.28 eV), and Mg−P (0.30 eV); Mg−As and Sc−Ge are reported here for the first time as battery materials. Promising theoretical compositions are also determined for Group 13 Al−X, Ga−X, and In−X pairs, and for Ca−X pairs.

A Critical Review of Machine Learning of Energy Materials

“…Using high‐throughput computations and ML, Jalem et al have studied vacancy‐mediated Li ion migration and the Li hopping energies in olivine LiMXO 4 (main group M 2+ –X 5+ , M 3+ –X 4+ ) and tavorite LiMTO 4 F (M 3+ –T 5+ , M 2+ –T 6+ ) cathodes. In olivine LiMXO 4 , the authors revealed that the degree of M octahedron distortion increases with ionic size of the M cation, which in turn results in an energy‐penalizing local lattice distortion around the migration pathway and a higher migration barrier (see Figure 5 a).…”

“…The blue data points represent experimental data in ICSD. Reproduced with permission . Copyright 2012, American Chemical Society.…”

“…Copyright 2015, American Chemical Society. Reproduced with permission . Copyright 2012 American Chemical Society and 2015 American Chemical Society.…”

Alkali Ion Transport in Tavorite-Type ABTO4X (A: Li, Na; B-T: Al-P, Mg-S; X: F)

“…Also, this path dimensionality has been observed in Li-based olivine frameworks although there is a difference in terms of the intermediate position between two adjacent crystallographic sites. [28][29][30][31] In the tavorite structure, the intermediate position it is located at an octahedral site while in the olivine structure, is located at a tetrahedral site. In the next sections, the different factors that affect ME will be discussed.…”

“…However, T-O bonding is determined to be strongly covalent as indicated by the relatively lower values of the Born charges than the nominal ones. 28 This T-O covalency should allow for a reduced interaction between the mobile A cation and the lattice along paths 2 and 3, and should lead to a lower ME; the electron cloud from the oxide ion in BO 4 F 2 is drawn away towards TO 4 (Figs. 2b-2d), thus effectively minimizing the energy penalty for electron cloud overlap at the transition site for paths 2 and 3.…”