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Title: Multiscale simulation of transport phenomena in semi-solid flow batteries
Author: Burrows, Stephen Anthony
ISNI:       0000 0004 7657 9960
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2018
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Semi-solid electrodes are suspensions of high energy density anode and cathode materials in ionic electrolytes. The addition of conductive carbon black particles creates a multi scale system with complex rheology. Here it is investigated how two important simulation methods-molecular dynamics and lattice Boltzmann-can be applied to this technology. Firstly we review some commonly used force fields for molecular simulation of the pure solvents, observing highly variable results. We select TraPPE as the most consistent model, and develop a series of optimizations to the intramolecular terms in the potential in order to improve the prediction of the relative permittivity of alkyl ethers such as 1,2-Dimethoxyethane (DMEt). The new dihedral potentials, generated by fitting two dimensional potential energy surfaces from dispersion-corrected density functional theory, were successful in reproducing the experimentally observed conformer populations of DMEt, and its relative permittivity. We then generate an atomistic model of carbon black (CB) particles using reactive force fields and a quenching simulation. Fictitious repulsive particles are used to generate a specified porosity. The resulting structure is converted into a molecular connectivity format compatible with the GROMACS software, allowing two CB nanoparticles to be simulated using a classical force field, again based on TraPPE. A potential of mean force was calculated for their interaction in an explicit solvent. Finally the development of an OpenCL lattice Boltzmann code is discussed, which makes simultaneous use of CPU and GPU compute hardware. It can simulate spherical particles suspended in a variety of non-Newtonian fluids. It is used to investigate how the dependence of viscosity on the suspension volume fraction differs between Newtonian and non-Newtonian fluids.
Supervisor: Bresme, Fernando ; Haynes, Peter Sponsor: Engineering and Physical Sciences Research Council
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral