Mechanism of Dissolution of a Lithium Salt in an Electrolytic Solvent in a Lithium Ion Secondary Battery: A Direct Ab Initio Molecular Dynamics (AIMD) Study

Abstract

The mechanism of dissolution of the Li+ ion in an electrolytic solvent is investigated by the direct ab initio molecular dynamics (AIMD) method. Lithium fluoroborate (Li+BF4−) and ethylene carbonate (EC) are examined as the origin of the Li+ ion and the solvent molecule, respectively. This salt is widely utilized as the electrolyte in the lithium ion secondary battery. The binding of EC to the Li+ moiety of the Li+BF4− salt is exothermic, and the binding energies at the CAM–B3LYP/6‐311++G(d,p) level for n=1, 2, 3, and 4, where n is the number of EC molecules binding to the Li+ ion, (EC)n(Li+BF4−), are calculated to be 91.5, 89.8, 87.2, and 84.0 kcal mol−1 (per EC molecule), respectively. The intermolecular distances between Li+ and the F atom of BF4− are elongated: 1.773 Å (n=0), 1.820 Å (n=1), 1.974 Å (n=2), 1.942 Å (n=3), and 4.156 Å (n=4). The atomic bond populations between Li+ and the F atom for n=0, 1, 2, 3, and 4 are 0.202, 0.186, 0.150, 0.038, and 0.0, respectively. These results indicate that the interaction of Li+ with BF4− becomes weaker as the number of EC molecules is increased. The direct AIMD calculation for n=4 shows that EC reacts spontaneously with (EC)3(Li+BF4−) and the Li+ ion is stripped from the salt. The following substitution reaction takes place: EC+(EC)3(Li+BF4−)→(EC)4Li+−(BF4−). The reaction mechanism is discussed on the basis of the theoretical results.

Boosting Rechargeable Batteries R&D by Multiscale Modeling: Myth or Reality?

“…This can aid interpretation of experimental data from a range of spectroscopic techniques. For example, Tachikawa simulated LiBF 4 in EC applying static and dynamic ab initio calculations of small clusters 176 and found EC to very strongly solvate Li + by creating a [(EC) 3 (Li + BF 4 – )] complex. The calculations also showed that the complex easily dissociates by substitution of the BF 4 – anion by another EC molecule.…”

“…This can aid interpretation of experimental data from a range of spectroscopic techniques. For example, Tachikawa simulated LiBF 4 in EC applying static and dynamic ab initio calculations of small clusters 177 and found EC to very strongly solvate Li + by creating a [(EC) 3 (Li + BF 4…”

Direct ab‐initio molecular dynamics study on the radiation effects on catalytic triad composed of Ser‐His‐Glu residues

“…First, we assumed the CAS‐SCF/6‐31G(d) potential energy surface for the direct AIMD trajectory calculations. In previous papers, we investigated the reaction dynamics of several reaction systems using MP2 wave function. However, the MP2 wave function needs high cost, and was impossible to calculate the present catalytic triad because the present reaction system is very large for the MP2‐dynamics calculation.…”

“…The structure of the catalytic triad was optimized at the MP2/ 6-31111G(d,p) level of theory. The direct AIMD calculation [25][26][27] was carried out from the optimized structure of Ser-His-Glu. We used complete active space-self consistent field theory (CAS-SCF) to calculate electronic structures and multidimensional potential energy surface for the cation and anion systems.…”

Ionization dynamics of the branched water cluster: A long-lived non-proton-transferred intermediate

“…In the direct AIMD calculation [31][32][33][34][35][36], the geometry of the neutral cluster (H 2 O) 4 was fully optimized at the MP2/6-311++G (d,p) level. The trajectory on the ionic state potential energy surface was started from the equilibrium point of the parent neutral (H 2 O) 4 cluster.…”