Modelling of Ion Transport in Solids with a General Bond Valence Based Force-Field

Abstract

Electrode Lithium ion battery Lithium ion pathways Molecular dynamic method Solid electrolyteEmpirical bond length -bond valence relations provide insight into the link between structure of and ion transport in solid electrolytes. Building on our earlier systematic adjustment of bond valence (BV) parameters to the bond softness, here we discuss how the squared BV mismatch can be linked to the absolute energy scale and used as a general Morse-type interaction potential for analyzing low-energy pathways in ion conducting solid or mixed conductors either by an energy landscape approach or by molecular dynamics (MD) simulations. For a wide range of Lithium oxides we could thus model ion transport revealing significant differences to an earlier geometric approach. Our novel BV-based force-field has also been applied to investigate a range of mixed conductors, focusing on cathode materials for lithium ion battery (LIB) applications to promote a systematic design of LIB cathodes that combine high energy density with high power density. To demonstrate the versatility of the new BV-based force-field it is applied in exploring various strategies to enhance the power performance of safe low cost LIB materials (LiFePO 4 , LiVPO 4 F, LiFeSO 4 F, etc.).

Structural Changes in Li2CoPO4F during Lithium-Ion Battery Reactions

“…44 The potential parameters were taken from the BV Web site and related papers. 45,46 The screened Coulomb repulsions were calculated using the Wolf summation technique. 47 The simulations under the periodic boundary condition were implemented using the LAMMPS CMD package.…”

Formulation of a Statistical Mechanical Theory To Understand the Li Ion Conduction in Crystalline Electrolytes: A Case Study on Li-Stuffed Garnets

“…It has been postulated that the lithium ion pathway is the locus of points r Li,c . 15,17 Adams and Rao 17 define the pathways as follows: "These pathways are visualized as regions enclosed by isosurfaces, ..." which in this case are the points that are enclosed in surfaces where ΔV = ΔV c . Within each pathway, the lithium ion interacts with the other ions and, in particular, the negatively charged oxygen ions, which constitute their first coordination layer.…”

“…To consider these near-equilibrium points in a quantitative manner, a small arbitrary cutoff or threshold values Δ V c of Δ V was selected such that any point r Li that possesses a mismatch Δ V ≤ Δ V c will be considered to be close to equilibrium. It has been postulated that the lithium ion pathway is the locus of points r Li,c . , Adams and Rao define the pathways as follows: “These pathways are visualized as regions enclosed by iso-surfaces, ...” which in this case are the points that are enclosed in surfaces where Δ V = Δ V c . Within each pathway, the lithium ion interacts with the other ions and, in particular, the negatively charged oxygen ions, which constitute their first coordination layer.…”

Phosphorus Based Ceramics for Positive Electrode Synthesis and Characterization

“…It is noted that the thermal expansion is a quadratic function of the temperature for this range (before the shrinkage). This relation can be written as: 1.9 10 K − − × [6]. This low thermal expansion coefficient, compared to LiFePO 4 , is an advantage for using this material under extrem conditions.…”

“…The thermal expansion coefficient is determined for the temperature range between 30 and 150˚C at the heating rate and is equal to is 10 2 times more important compared to values often found in the literature ( )6 1…”