From Atomistic to Continuum Models of Interfaces in Lithium-Ion Batteries

A fully-funded 4 year PhD studentship in theoretical / computational chemistry is available in the Department of Chemistry at the University of Bath. The project is supervised by Dr Benjamin Morgan and Prof Saiful Islam with collaboration from Dr Eike Müller (Department of Mathematical Sciences) and is suitable for students with an interest in solid state computational chemistry, materials science, scientific software, and / or numerical methods.

Context:

The ongoing transition to low carbon energy sources means new energy storage technologies are urgently needed. Lithium-ion batteries are all around us, but present day technologies suffer from limitations that prevent their commercial use in applications such as electric vehicles and grid-scale storage.

All solid-state lithium-ion batteries are one "next-generation" battery technology with the potential to address these problems. In conventional lithium-ion batteries, the electrolyte, which transports lithium between the two electrodes, is typically a (flammable) organic liquid or polymer. These electrolytes have limited electrochemical stabilities, which prevents their use with high voltage electrodes, makes them susceptible to degradation, and introduces a fire risk. All-solid-state batteries instead use an electrochemically inert ceramic as the electrolyte, which has the potential to produce batteries with greatly improved energy densities, operating lifetimes, and safety profiles. A number of promising candidate materials have been identified, and are the subject of great deal of ongoing research, but none yet meets all the criteria for commercial use. Trying to understand the factors that determine the performance of solid electrolyte materials, and using this information to design and optimise new batteries, is an active area of research.

One of the key factors that determines the ability of a solid electrolyte to transport lithium ions is microstructure. Solid electrolytes are usually polycrystalline, and contain grain boundaries, where the local atomic structure differs from the crystalline bulk. Lithium ions may be trapped by, or repelled from, these grain boundaries, producing inhomogeneous distributions of lithium through the electrolyte, and affecting the ionic conductivity. Understanding this behaviour is a key challenge in describing the properties of solid electrolytes.

Experimental studies of lithium distribution and motion at grain boundaries are highly challenging. Computational modelling provides a more tractable approach, but the accuracy of any predictions depends critically on the quality of the underlying physical models. The current state-of-the-art approach is to solve the Poisson-Boltzmann equation for the mobile lithium ions, which assumes that the ions exist in a featureless continuous medium, and only interact through mean-field electrostatics.

This project:

The goal of this PhD project is to develop new physical models that go beyond conventional Poisson-Boltzmann theory, focussing on improved descriptions of the interactions between mobile ions in solid electrolytes. These models will be implemented in our groups’ existing Poisson-Boltzmann simulation code, and used to simulate grain boundary behaviour in solid state battery electrolyte materials.

The project will involve first-principles and classical atomistic modelling, theory and method development, and programming. The project will have strong interactions with the Faraday Challenge projects (particularly the multiscale modelling project) and will include opportunities for training across a range of areas related to battery science.

Informal enquiries should be directed to Dr Benjamin Morgan on [Email Address Removed]

Formal applications should be made via the University of Bath’s online application form for a PhD in Chemistry:
https://www.bath.ac.uk/samis/urd/sits.urd/run/siw_ipp_lgn.login?process=siw_ipp_app&code1=RDUCH-FP01&code2=0012

More information about applying for a PhD at Bath may be found here:
http://www.bath.ac.uk/guides/how-to-apply-for-doctoral-study/

Anticipated start date: 1 October 2018.