Development of a Mg/O ReaxFF Potential to describe the Passivation Processes in Magnesium‐Ion Batteries**

Abstract

One of the key challenges preventing the breakthrough of magnesium‐ion batteries (MIB) is the formation of a passivating boundary layer at the Mg anode. To describe the initial steps of Mg anode degradation by O2 impurities, a Mg/O ReaxFF (force field for reactive systems) parameter set was developed capable of accurately modeling the bulk, surface, adsorption, and diffusion properties of metallic Mg and the salt MgO. It is shown that O2 immediately dissociates upon first contact with the Mg anode (modeled as Mg(0001), Mg(10 1‾ $\bar 1$ 0)A, and Mg(10 1‾ $\bar 1$ 1)), heating the surface to several 1000 K. The high temperature assists the further oxidation and forms a rock salt interphase intersected by several grain boundaries. Among the Mg surface terminations, Mg(10 1‾ $\bar 1$ 0)A is the most reactive, forming an MgO layer with a thickness of up to 25 Å. The trained force field can be used to model the ongoing reactions in Mg–air batteries but also to study the oxidation of magnesium metal in general.

Enhancing ReaxFF for Molecular Dynamics Simulations of Lithium-Ion Batteries: An interactive reparameterization protocol

“…In addition to the sensitivity of the ReaxFF to the training set used, the difficulty in accurately describing the system studied in this work may also be attributed to an intrinsic bias of the force field. In particular, it is worth noting that the original formulation of the ReaxFF potentials proposed by Van Duin in 2001 was validated primarily on organic systems [39], and various new functionals have been added to improve the accuracy and applicability of ReaxFF in other systems over the past few decades [89][90][91]. These include the "lone-pair" energy term (V lp in Eq.…”

Study of Solid-State Diffusion Impedance in Li-Ion Batteries Using Parallel-Diffusion Warburg Model

“…Within these MD simulations, we implemented the canonical ensemble (NVT) coupled with a Nose-Hoover (NHC) thermostat and Martyna-Tobis-Klein (MTK) barostat to ensure stable temperature and pressure throughout. 48 The simulations are carried out using a time-step (Δt) of 1 fs. In this context, the MD simulations consist of three primary phases for the GB simulations: an annealing stage set at T = 800 K for 10 ps, succeeded by a constant temperature of 800 K for 10 ps and followed by stepwise quenching from 800 K to 0 K at a rate of 8 × 10 14 Ks −1 .…”

Reaction Dynamics of CO2 Hydrogenation on Iron Catalysts Using ReaxFF Molecular Dynamics Simulation

“…Among the theoretical methods, reactive molecular dynamics simulation using the ReaxFF force field (ReaxFF-MD) is a promising approach, allowing for the simulation of chemical reactions up to larger time scales and length scales, − enabling the study of both reaction dynamics and molecular transport properties. The ReaxFF-MD simulations have been successfully applied to various systems such as HC combustions, , reactive processes in batteries, − and surface reactions on nanoparticles. , …”