Materials modelling of layered crystals for energy storage
File(s)
Author(s)
Huang, Ju
Type
Thesis
Abstract
Energy storage systems are vital for managing the energy grid and the distribution of different renewable energy resources. They are beneficial to the development of advanced electronic devices, such as smart electronics and electric vehicles. Lithium-ion (Li-ion) batteries are one of the most promising energy storage systems due to their high energy storage densities and capacities. However, traditional Li-ion batteries suffer from short lifetimes and safety concerns. These issues have motivated research into the exploration and discovery of novel materials for energy storage.
In this thesis, computational materials science is used to investigate the structures and properties of layered materials for their potential applications in energy storage systems. Computational methods are effective for predicting the performance of these materials, as it allows for modelling of structures and their working mechanisms at a low cost and in a short time, compared to experimental methods in a laboratory. This approach can provide valuable insight into the potential of these materials for energy storage applications. In the first results chapter, a density functional theory (DFT) investigation of eight layered van der Waals (vdWs) pnictide crystals is reported. LiFeP and LiCoAs are found to be promising electrode candidates, as they exhibit low volume change, high electronic conductivity, and reasonable theoretical capacity in the cation de-intercalation process.
To complement the study of traditional inorganic layered electrodes, I also consider porous organic crystals in the form of two-dimensional covalent-organic frameworks (2D-COFs), which are known to show high energy storage capacity, good cycling performance, and stability when used as battery electrodes. However, the performance of COFs is highly dependent on their crystal structures, and disorder is present in their layered structures which can lead to a loss of crystallinity and porosity. These adverse effects are not well understood and have to be studied in order to investigate the energy storage performance of COFs used as energy storage materials. The second and third results chapters of the thesis focus on studying stacking disorder using DFT calculations and molecular dynamics (MD) simulations. These studies reveal that layered COFs feature a disordered stacking sequence between layers, rather than the previously reported perfectly eclipsed stacking. This affects the crystalline and electronic structure of the materials. Further research is needed to understand how these disordered structures affect the energy storage capacities of COFs when used in Li-ion batteries, but an accurate representation of their crystal structures is found to be important.
In this thesis, computational materials science is used to investigate the structures and properties of layered materials for their potential applications in energy storage systems. Computational methods are effective for predicting the performance of these materials, as it allows for modelling of structures and their working mechanisms at a low cost and in a short time, compared to experimental methods in a laboratory. This approach can provide valuable insight into the potential of these materials for energy storage applications. In the first results chapter, a density functional theory (DFT) investigation of eight layered van der Waals (vdWs) pnictide crystals is reported. LiFeP and LiCoAs are found to be promising electrode candidates, as they exhibit low volume change, high electronic conductivity, and reasonable theoretical capacity in the cation de-intercalation process.
To complement the study of traditional inorganic layered electrodes, I also consider porous organic crystals in the form of two-dimensional covalent-organic frameworks (2D-COFs), which are known to show high energy storage capacity, good cycling performance, and stability when used as battery electrodes. However, the performance of COFs is highly dependent on their crystal structures, and disorder is present in their layered structures which can lead to a loss of crystallinity and porosity. These adverse effects are not well understood and have to be studied in order to investigate the energy storage performance of COFs used as energy storage materials. The second and third results chapters of the thesis focus on studying stacking disorder using DFT calculations and molecular dynamics (MD) simulations. These studies reveal that layered COFs feature a disordered stacking sequence between layers, rather than the previously reported perfectly eclipsed stacking. This affects the crystalline and electronic structure of the materials. Further research is needed to understand how these disordered structures affect the energy storage capacities of COFs when used in Li-ion batteries, but an accurate representation of their crystal structures is found to be important.
Version
Open Access
Date Issued
2022-12-31
Date Awarded
01/06/2023
License URL
Advisor
Walsh, Aron
Sponsor
Imperial College London
Publisher Department
Materials
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)