Construction of highly coarse-grained molecular models for aqueous electrolytes
Molecular modelling of electrochemical systems at larger than atomic scales poses particular challenges, not least the ability to represent correct thermodynamic, hydrodynamic and dielectric properties while still being computationally viable for large scale applications. In the case of aqueous electrolytes such as those used in vanadium-based batteries with oxidation-reduction (redox) reactions, both a background medium that can respond to localised electric fields due to high-valence ions and control over ion transport properties are crucial to embed consistently in the model. To this end, we propose the use of Dissipative Particle Dynamics (DPD) combined with a newly-devised highly coarse-grained polarisable water model with pairwise interactions designed to produce realistic thermodynamic behaviour as the basis for the aqueous electrolytes found in vanadium redox flow batteries (VRFB). We consider how the core water model can be modified to incorporate the ionic species found in VRFB catholytes and anolytes, as well as how the DPD pairwise thermostat forces can be parameterised to attain realistic diffusivities for those species.