From Atomistic to Continuum Models of Interfaces in Lithium-Ion Batteries
Lead Research Organisation:
University of Bath
Department Name: Chemistry
Abstract
Modelling Li transport through Li-ion solid-state electrolytes is important for predicting their performances. These materials are often polycrystalline and have interfaces which significantly affect Li transport through the material. Therefore, it is vital to be able to model the effect of these grain batteries in order to fully explore potential new materials to be used in Li-ion batteries.
The conventional method of modelling ionic transport across grain boundaries involves solving the Poisson-Boltzmann equation to find the equilibrium distri- bution of point defects (e.g. Li interstitials and vacancies) in a 1D continuum model. This approach assumes defects interact only through mean-field electro- statics, and corresponds to modelling the dilute limit of defect concentrations. Where here, structural defects include ion vacancies and dopant ions. In bat- tery materials, where defect concentrations can be high, interactions between these defects are more complex than the dilute limit mean-field description. To develop accurate models of the effects of grain boundaries on lithium-ion trans- port in these materials, it is therefore necessary to go beyond the dilute limit approximation.
The project will involve investigating the thermodynamics of the problem in order to try to incorporate an additional concentration dependent term to the chemical potential. Attempts of producing a model that incorporates the inter- actions between structural defects in solid state electrolytes have been made, however these methods are not widely accepted at the present time, due to the lack of a method for calculating the key parameters for these models [1]. After the form of this additional term is determined, methods of calculating coefficients for such a term for individual grain boundaries and materials will be required. This will require investigating the fundamental thermodynamics of the problem further and determining which calculations are required in order to obtain the values of these parameters a priori. An alternative approach whereby chemical activities are used in order to minimise the free energy of the entire system will also be explored.
Throughout the project, the existing code (written and developed by the pre- vious PhD candidate, Georgina Wellock) will be improved and altered to meet the requirements of the new thermodynamics of the problem or to improve efficiency.
References
[1] Mebane D. S. and De Souza R. A.; Energy Environ. Sci. 2015, 8, 2935-2940.
The conventional method of modelling ionic transport across grain boundaries involves solving the Poisson-Boltzmann equation to find the equilibrium distri- bution of point defects (e.g. Li interstitials and vacancies) in a 1D continuum model. This approach assumes defects interact only through mean-field electro- statics, and corresponds to modelling the dilute limit of defect concentrations. Where here, structural defects include ion vacancies and dopant ions. In bat- tery materials, where defect concentrations can be high, interactions between these defects are more complex than the dilute limit mean-field description. To develop accurate models of the effects of grain boundaries on lithium-ion trans- port in these materials, it is therefore necessary to go beyond the dilute limit approximation.
The project will involve investigating the thermodynamics of the problem in order to try to incorporate an additional concentration dependent term to the chemical potential. Attempts of producing a model that incorporates the inter- actions between structural defects in solid state electrolytes have been made, however these methods are not widely accepted at the present time, due to the lack of a method for calculating the key parameters for these models [1]. After the form of this additional term is determined, methods of calculating coefficients for such a term for individual grain boundaries and materials will be required. This will require investigating the fundamental thermodynamics of the problem further and determining which calculations are required in order to obtain the values of these parameters a priori. An alternative approach whereby chemical activities are used in order to minimise the free energy of the entire system will also be explored.
Throughout the project, the existing code (written and developed by the pre- vious PhD candidate, Georgina Wellock) will be improved and altered to meet the requirements of the new thermodynamics of the problem or to improve efficiency.
References
[1] Mebane D. S. and De Souza R. A.; Energy Environ. Sci. 2015, 8, 2935-2940.
Organisations
People |
ORCID iD |
| Jacob Matthew Dean (Student) |
Studentship Projects
| Project Reference | Relationship | Related To | Start | End | Student Name |
|---|---|---|---|---|---|
| EP/S514901/1 | 01/07/2018 | 31/03/2025 | |||
| 2119790 | Studentship | EP/S514901/1 | 01/10/2018 | 31/03/2023 | Jacob Matthew Dean |
| Description | Solid electrolytes are a promising next generation technology, however their interfacial properties hinder their performance. One phenomenon that reduces interfacial performance is the presence of double / space-charge layers where the concentration of charge carriers are reduced. This reduction in charge carriers at interfaces reduces overall performance. Current models of space-charge layers in solid electrolytes are restricted to systems within the dilute limit where the magnitude of interactions between charged species is low. Using computational models, systems with strong interactions between charge carriers were investigated. These investigations showed the emergence of new phenomena that are the subject of further study. |
| Exploitation Route | Charged interfaces are ubiquitous in modern technology. Advances in technologies require a fundamental understanding of natural phenomena present in such systems. The work carried out in this project adds to the growing body of work in solid electrolytes and other fields of research on interfaces. Collectively, this improved understanding of charged interfaces will aid in the accelerated development of future technologies. |
| Sectors | Energy |