Research Update: Ca doping effect on the Li-ion conductivity in NASICON-type solid electrolyte LiZr2(PO4)3: A first-principles molecular dynamics study

Abstract

In this work, we used a density functional theory-based molecular dynamics simulation to investigate the Ca content-dependent Li-ion conductivity of NASICON-type Li1+2xCaxZr2-x(PO4)3 (LCZP) solid electrolytes (0.063 ≤ x ≤ 0.375) which exhibit a Li-excess chemical composition. The LCZP systems show a higher room temperature Li-ion conductivity and a lower activation energy than pristine LiZr2(PO4)3 (LZP), and the tendencies of those properties agree with the experimental results. In addition, the Li-ion conduction mechanisms in LCZP were clarified by analyzing the radial distribution functions and site displacement functions obtained from our molecular dynamics simulations. For minimal Ca substitution for LZP, the Li-ion conductivity is enhanced because of the creation of interstitial Li ions by Ca doping in the LCZP systems; the frequency of collisions with Li ions dramatically increases. For substantial Ca substitution for LZP, the Li-ion conductivity gradually worsened because some Li ions were trapped at the M1 (most stable) and M2 (metastable) sites near Ca atoms.

Computational investigation of the Mg-ion conductivity and phase stability of MgZr4(PO4)6

“…Therefore, low temperature conductivities are extrapolated from high temperature data as reported in our previous FPMD calculations. 10,11,37 The Arrhenius plots for the NASICON-type and the b-iron sulfate-type structures is shown in Fig. 4, and the migration energies of Mg were evaluated by a simple linear tting scheme.…”

“…Above FPMD studies have been performed in our previous studies, showing reasonable accordance between the experimental and the computational results. 10,11,37 We evaluated the thermodynamic stability of the MZP polymorphs by rst principles DFT calculations. Temperature-and/ or pressure-dependent phase stability was also evaluated using DFT-based phonon calculations or cell-volume constraint calculations, respectively.…”

Na superionic conductor-type LiZr2(PO4)3 as a promising solid electrolyte for use in all-solid-state Li metal batteries

“…92 Ionic conductivity may be increased by introducing low-valence ions, such as Ca 2+ and Y 3+ , at the Zr ion sites of LZP and inducing a state of excess Li. 33,41,42,49,72 However, only single-element doping has been used in most studies to date, with few examples wherein two elements have been doped simultaneously (i.e. co-doping).…”

Data‐Driven Materials Exploration for Li‐Ion Conductive Ceramics by Exhaustive and Informatics‐Aided Computations

“…We also evaluate the Li migration energies for all 400 compounds (Dataset 1) by using fast force‐field (FF) calculations. As mentioned before, first‐principles DFT approaches can precisely evaluate the Li migration energies for various inorganic solid‐state compounds by nudged elastic band (NEB) and/or first‐principles molecular dynamics (FPMD) techniques . However, these techniques have large computational demands, and the exhaustive evaluation of materials properties is thus technically difficult.…”