Molecular Dynamics Study of Ion Transport in Polymer Electrolytes of All-Solid-State Li-Ion Batteries

Abstract

Atomistic analysis of the ion transport in polymer electrolytes for all-solid-state Li-ion batteries was performed using molecular dynamics simulations to investigate the relationship between Li-ion transport and polymer morphology. Polyethylene oxide (PEO) and poly(diethylene oxide-alt-oxymethylene), P(2EO-MO), were used as the electrolyte materials, and the effects of salt concentrations and polymer types on the ion transport properties were explored. The size and number of LiTFSI clusters were found to increase with increasing salt concentrations, leading to a decrease in ion diffusivity at high salt concentrations. The Li-ion transport mechanisms were further analyzed by calculating the inter/intra-hopping rate and distance at various ion concentrations in PEO and P(2EO-MO) polymers. While the balance between the rate and distance of inter-hopping was comparable for both PEO and P(2EO-MO), the intra-hopping rate and distance were found to be higher in PEO than in P(2EO-MO), leading to a higher diffusivity in PEO. The results of this study provide insights into the correlation between the nanoscopic structures of ion solvation and the dynamics of Li-ion transport in polymer electrolytes.

Synergistic theoretical and experimental study on the ion dynamics of bis(trifluoromethanesulfonyl)imide-based alkali metal salts for solid polymer electrolytes

“…The DFT calculations were performed with the Fritz Haber Institute ab initio molecular simulations (FHI-AIMS) software, 47,48 incorporating the Becke's three parameters (B3) exchange functional with the Lee-Yang-Parr (LYP) nonlocal correlation functional (B3LYP) 49,50 adopted with the ''tier2'' standard basis set in the FHI-AIMS code. The partial charges of TFSI À were calculated using the electrostatic potential (ESP) method 26,27,30,34,[51][52][53][54] and scaled to À0.7. The charges of Li + , Na + , K + , and Cs + were also scaled to +0.7 each to maintain charge neutrality.…”

“…Atomistic modelling of polymer electrolytes is an effective approach to accelerate the search towards new alkali metal salts and alkali metal-based electrolyte components, especially considering the recent advances in computing power. 8,[25][26][27][28][29] The growing utilization of modelling techniques is driven by several factors, including reduced environmental impact compared to experimental processes, faster simulation times compared to traditional experimental methods, and the capability to acquire information that may not be readily attainable through experimental characterization techniques. 8,[30][31][32][33][34] Yet, a key element for the successful integration of computational-based methods in materials development is comprehensive model validation against well-defined, high-quality experimental data, which is often lacking but crucially needed in the field.…”

Molecular-Level Insight into Charge Carrier Transport and Speciation in Solid Polymer Electrolytes by Chemically Tuning Both Polymer and Lithium Salt

“…Both Li–O PEO C–O and Li–O Anion RDFs corroborate that complete Li salt dissociation occurs within all the PEO-based SPEs. 12 , 43 − 45 , 47 , 50 Yet, for PEO-based SPEs, RDF analysis conveys a similar degree of association for the lithium–PEO interaction (Li–O PEO C–O ) upon changing the anionic structure, in contrast to the observed experimental trends regarding the different values measured for the lithium transference number ( Figure 2 a). The situation is very different in PCL ( Figure S1b–d ), where Li + preferentially interacts with the configuration Li–O PCL C=O , as reported in the literature 12 and confirmed by the computed RDFs.…”

“…DFT (FHI-AIMS) was used to calculate the partial atomic charges required for the MD simulations using the electrostatic potential (ESP) method. The Li + charge was reduced to +0.7 to equal the scale factor applied to TFSI – and to keep the system neutrally charged. ,,− The cutoff for van der Waals force and the real space of Ewald summation was 10 Å. The fast smooth particle mesh Ewald (PME) electrostatics was used to treat Coulomb interactions in a periodic system.…”

Polymer Electrolytes for Lithium-Ion Batteries Studied by NMR Techniques

“…In addition to the experimental methods of NMR and AC impedance spectroscopy, the method of molecular dynamics (MD) is also used. MD is mainly applied to solid polymer [131] or liquid [132] electrolytes. The gel polymer electrolytes are considered in only one paper [32].…”