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Theory

The Helmholtz Institute Münster forms an interdisciplinary team for theoretical investigations in the area of electrolyte research. Strong synergy effects with the WWU group of Physical Chemistry are present.

Methods

The methods of the theory group comprise classical molecular dynamics (MD) simulations, quantum chemical calculations (mainly DFT), ab initio MD simulations, as well as Monte Carlo (MC) approaches. MD simulations are used to study the structure and transport in large electrolyte systems with atomistic resolution. Quantum chemical approaches enable the characterization of electrochemical properties of individual molecular components. By ab initio MD calculations, for example, reaction rates can be estimated. MC simulations are, among others, used for a coarse-grained representation of batteries.

A recently developed MD/MC hybrid scheme enables the treatment of chemical reactions in classical MD simulations. Additionally, machine learning concepts are developed and applied for the generation of quantum-mechanically (DFT) based force fields.

Harmonious Systems for More Functionality

The systems of interest involve polymer electrolytes, liquid electrolytes including (multifunctional) additives and more complex hybrid systems, tuned to enable advanced electrolyte functionalities. Systems are studied either in the bulk or close to electrode interfaces. Furthermore, anodes such as metallic lithium, involving possible dendrite formation, as well as polymeric cathode systems are studied.

Comprehensive Characterisation

Several conceptual developments by the theory group are of major relevance for an improved understanding of the microscopic mechanisms:

TheoryMolecular dynamics simulation of a block copolymer
Copyright: HI MS / Diddens

(1) For the ionic transport in polymeric electrolytes a transport model based on polymer physics, which captures the different mechanisms of cation dynamics, was developed.

(2) The impact of momentum conservation and hydrodynamic interaction on the ion transport and, in particular, the consequences for the resulting conductivity are explored. This also involves new approaches to characterize the relevance of vehicular vs. hopping transport.

(3) In specific situations strong electric fields may give rise to nonlinear ion transport. Via its appropriate characterization new pieces of information about transport properties can be extracted.

Interdisciplinary Collaborations

On the one hand, collaborations involve the interaction with experimental groups, yielding an improved understanding of the experimental results and helping to improve the theoretical basis. On the other hand, the interaction with modelling groups from the more macroscopic side allows the establishment of true multiscale approaches to understand the detailed mechanisms of a battery, based on microscopic input.


Publications:

Physical Chemistry Chemical Physics 2020, 22, 525, DOI: 10.1039/C9CP04947A

Applied Materials & Interfaces 2020, 12, 567, DOI: 10.1021/acsami.9b16348

ChemElectroChem 2020, 7(6), 1499-1508, DOI: 10.1002/celc.202000386

Chemistry of Materials 2019, 31(9), 3118-3133, DOI: 10.1021/acs.chemmater.8b04172

Journal of Physical Chemistry C 2018, 122(38), 21770-21783, DOI: 10.1021/acs.jpcc.8b06560

Batteries 2018, 4(4), 62, DOI: 10.3390/batteries4040062

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