Determination of Diffusion Mechanisms in Battery Materials using Quasi-Elastic Neutron Scattering Techniques. / Willis, Toby.

2017. 211 p.

Research output: ThesisDoctoral Thesis

Unpublished

Standard

Harvard

APA

Vancouver

Author

BibTeX

@phdthesis{dfe6a3eda1f540ceb1b7fb83ae65e276,
title = "Determination of Diffusion Mechanisms in Battery Materials using Quasi-Elastic Neutron Scattering Techniques",
abstract = "The diffusion of ions within a battery material is inherently important toits capacity to charge and discharge electrons through a circuit during its normal operation. Understanding the pathways ions use to diffuse within a crystalstructure, identifying where the barrier to movement is small, can inform thedirection of future battery research. Two crystalline materials, Na0.8CoO2 andLi0.29La0.57TiO3, have been studied using a combination of experimental andcomputational techniques due to their promising characteristics.NaxCoO2 is closely related to the commercially dominant LixCoO2 cathodematerial. They are intercalation materials with rigid CoO2 layers that the Na orLi ions can diffuse between. The effect of ordering of the Na ions within a layeron the diffusion rate has been studied with molecular dynamics simulations byfirst principles density functional theory calculations using CASTEP. Clusteringof ions is observed to enhance the diffusion rate by opening up short range pathways with a greatly reduced energy barrier to diffusion. The diffusion rate ofNa0.8CoO2 was measured using quasi-elastic neutron scattering with the signalvarying according to the self-correlation function, effectively providing a value for the average time an ion stays in one site between 'hops'.Li0.29La0.57TiO3 is a solid electrolyte with ionic conduction rates equivalent toliquid and polymer based systems. The use of a solid electrolyte has significantadvantages, particularly its improved stability and safety. Using single crystalX-ray diffraction, structures of several crystals have been identified, including acompletely novel Ruddlesden-Popper structure previously unreported in literature. Quasi-elastic neutron scattering over a large temperature range is used to measure the diffusion rate and activation energy. The hopping geometry is found to be consistent with the predictions of molecular dynamics simulations.",
keywords = "Battery, Diffusion, density functional theory (DFT), NaCoO2, LiLaTiO3, neutron diffraction, Neutron spectroscopy, Neutron scattering, crystal",
author = "Toby Willis",
year = "2017",
language = "English",
school = "Royal Holloway, University of London",

}

RIS

TY - THES

T1 - Determination of Diffusion Mechanisms in Battery Materials using Quasi-Elastic Neutron Scattering Techniques

AU - Willis, Toby

PY - 2017

Y1 - 2017

N2 - The diffusion of ions within a battery material is inherently important toits capacity to charge and discharge electrons through a circuit during its normal operation. Understanding the pathways ions use to diffuse within a crystalstructure, identifying where the barrier to movement is small, can inform thedirection of future battery research. Two crystalline materials, Na0.8CoO2 andLi0.29La0.57TiO3, have been studied using a combination of experimental andcomputational techniques due to their promising characteristics.NaxCoO2 is closely related to the commercially dominant LixCoO2 cathodematerial. They are intercalation materials with rigid CoO2 layers that the Na orLi ions can diffuse between. The effect of ordering of the Na ions within a layeron the diffusion rate has been studied with molecular dynamics simulations byfirst principles density functional theory calculations using CASTEP. Clusteringof ions is observed to enhance the diffusion rate by opening up short range pathways with a greatly reduced energy barrier to diffusion. The diffusion rate ofNa0.8CoO2 was measured using quasi-elastic neutron scattering with the signalvarying according to the self-correlation function, effectively providing a value for the average time an ion stays in one site between 'hops'.Li0.29La0.57TiO3 is a solid electrolyte with ionic conduction rates equivalent toliquid and polymer based systems. The use of a solid electrolyte has significantadvantages, particularly its improved stability and safety. Using single crystalX-ray diffraction, structures of several crystals have been identified, including acompletely novel Ruddlesden-Popper structure previously unreported in literature. Quasi-elastic neutron scattering over a large temperature range is used to measure the diffusion rate and activation energy. The hopping geometry is found to be consistent with the predictions of molecular dynamics simulations.

AB - The diffusion of ions within a battery material is inherently important toits capacity to charge and discharge electrons through a circuit during its normal operation. Understanding the pathways ions use to diffuse within a crystalstructure, identifying where the barrier to movement is small, can inform thedirection of future battery research. Two crystalline materials, Na0.8CoO2 andLi0.29La0.57TiO3, have been studied using a combination of experimental andcomputational techniques due to their promising characteristics.NaxCoO2 is closely related to the commercially dominant LixCoO2 cathodematerial. They are intercalation materials with rigid CoO2 layers that the Na orLi ions can diffuse between. The effect of ordering of the Na ions within a layeron the diffusion rate has been studied with molecular dynamics simulations byfirst principles density functional theory calculations using CASTEP. Clusteringof ions is observed to enhance the diffusion rate by opening up short range pathways with a greatly reduced energy barrier to diffusion. The diffusion rate ofNa0.8CoO2 was measured using quasi-elastic neutron scattering with the signalvarying according to the self-correlation function, effectively providing a value for the average time an ion stays in one site between 'hops'.Li0.29La0.57TiO3 is a solid electrolyte with ionic conduction rates equivalent toliquid and polymer based systems. The use of a solid electrolyte has significantadvantages, particularly its improved stability and safety. Using single crystalX-ray diffraction, structures of several crystals have been identified, including acompletely novel Ruddlesden-Popper structure previously unreported in literature. Quasi-elastic neutron scattering over a large temperature range is used to measure the diffusion rate and activation energy. The hopping geometry is found to be consistent with the predictions of molecular dynamics simulations.

KW - Battery

KW - Diffusion

KW - density functional theory (DFT)

KW - NaCoO2

KW - LiLaTiO3

KW - neutron diffraction

KW - Neutron spectroscopy

KW - Neutron scattering

KW - crystal

M3 - Doctoral Thesis

ER -