Defect chemistry and lithium transport in Li₃OCl anti-perovskite superionic conductors

Abstract

Lithium-rich anti-perovskites (LiRAPs) are a promising family of solid electrolytes, which exhibit ionic conductivities above 10(-3) S cm(-1) at room temperature, among the highest reported values to date. In this work, we investigate the defect chemistry and the associated lithium transport in Li3OCl, a prototypical LiRAP, using ab initio density functional theory (DFT) calculations and classical molecular dynamics (MD) simulations. We studied three types of charge neutral defect pairs, namely the LiCl Schottky pair, the Li2O Schottky pair, and the Li interstitial with a substitutional defect of O on the Cl site. Among them the LiCl Schottky pair has the lowest binding energy and is the most energetically favorable for diffusion as computed by DFT. This is confirmed by classical MD simulations, where the computed Li ion diffusion coefficients for LiCl Schottky systems are significantly higher than those for the other two defects considered and the activation energy in LiCl deficient Li3OCl is comparable to experimental values. The high conductivities and low activation energies of LiCl Schottky systems are explained by the low energy pathways of Li between the Cl vacancies. We propose that Li vacancy hopping is the main diffusion mechanism in highly conductive Li3OCl.

Vibrational contributions to intrinsic friction in charged transition metal dichalcogenides

“…The M-X pair cophonicity is a measure of how the M and X atomic species contribute to form the phonon states in the considered range, and has been applied to the study of the electro-structural coupling in distinct classes of materials. [35][36][37] We observe that the variation range of q B is wider in WX systems, and can be put in correspondance with a larger variation of the structural distortions with the charge content ( Figure 6). Bond covalency is slightly decreasing upon charge injection, displaying a general linear trend with the system charge; however, by comparing Figure 8b) and c), it is immediately apparent that the covalent character of the bond is not strictly related to the q B charge difference, nor directly connected with the structural distortions δ (Figure 6).…”

Data mining of molecular dynamics data reveals Li diffusion characteristics in garnet Li7La3Zr2O12

“…if the simulation is characterized by N atoms and T snapshots then it requires ( NT )2 operations), DCT relies on the computation of density and the neighboring search is done by indexing, requiring M calculations for a density map with M voxels. In addition, the nuclear density computation is ubiquitous in molecular dynamics simulations as a way to assist the interpretation of particle transport mechanism3738394041. The proposed method therefore can be used in conjunction with the exploratory data analysis of the nuclear density pattern.…”

Protons Enhance Conductivities in Lithium Halide Hydroxide/Lithium Oxyhalide Solid Electrolytes by Forming Rotating Hydroxy Groups

“…These observations may suggest that LiX-deficient SSE structures are formed and no decomposition reactions (e.g., decomposition of Li 2 OHCl to LiOH and LiCl or to Li 2 O and HCl or decomposition of Li 2 OHBr to LiOH and LiBr) could be detected. [12] [12] …”