Advanced Materials for High-Energy Rechargeable Batteries: Borate Polyanion Cathodes and Silicon Anodes
type: CreativeWork
description: This thesis explores advanced electrode materials designed to enhance the energy density of next-generation rechargeable batteries, with a dual focus on cathode materials for rechargeable magnesium-ion batteries (RMBs) and anode materials for lithium-ion batteries (LIBs). The work is divided into two major parts: the development and evaluation of borate-based cathodes for RMBs, and the investigation of mechanical degradation in silicon anodes for LIBs. The first part presents a comprehensive study on borate polyanions as potential cathode materials for RMBs. Three structural families were systematically explored: orthoborates (M₃(BO₃)₂), pyroborates (M₂B₂O₅), and ludwigites (M₃BO₅). In Chapter 3, a detailed overview of the solid-state synthesis approaches is presented, including ball-milling, thermal treatment strategies, and the challenges encountered in achieving phase-pure samples. Structural characterisation using X-ray diffraction and neutron powder diffraction was employed to investigate the metal ion disorder in the synthesised compounds and confirm phase purity. Chapter 4 focuses on an in-depth electrochemical investigation of a pyroborate compound (MgFeB₂O₅), initially synthesised with a small weight percentage of Fe metal impurity. Despite encouraging first-charge capacities of up to 200 mAh g⁻¹ between 3.0–4.2 V (vs Li/Li⁺) at 55°C, advanced post-cycling analyses, including X-ray absorption near-edge spectroscopy, Mössbauer spectroscopy, and energy-dispersive X-ray analysis, revealed that the observed capacity stemmed from a faradaic side reaction involving hydrofluoric acid in the electrolyte and the Fe impurity, rather than true Mg²⁺ intercalation. In Chapter 5, the electrochemical properties of all five synthesised borates are evaluated, with a particular focus on the phase-pure orthoborate Mg₂Mn(BO₃)₂. All materials displayed similar voltage profiles and capacity behaviour, prompting a post-mortem study of Mg₂Mn(BO₃)₂ to understand the underlying mech…
abstract: This thesis explores advanced electrode materials designed to enhance the energy density of next-generation rechargeable batteries, with a dual focus on cathode materials for rechargeable magnesium-ion batteries (RMBs) and anode materials for lithium-ion batteries (LIBs). The work is divided into two major parts: the development and evaluation of borate-based cathodes for RMBs, and the investigation of mechanical degradation in silicon anodes for LIBs. The first part presents a comprehensive study on borate polyanions as potential cathode materials for RMBs. Three structural families were systematically explored: orthoborates (M₃(BO₃)₂), pyroborates (M₂B₂O₅), and ludwigites (M₃BO₅). In Chapter 3, a detailed overview of the solid-state synthesis approaches is presented, including ball-milling, thermal treatment strategies, and the challenges encountered in achieving phase-pure samples. Structural characterisation using X-ray diffraction and neutron powder diffraction was employed to investigate the metal ion disorder in the synthesised compounds and confirm phase purity. Chapter 4 focuses on an in-depth electrochemical investigation of a pyroborate compound (MgFeB₂O₅), initially synthesised with a small weight percentage of Fe metal impurity. Despite encouraging first-charge capacities of up to 200 mAh g⁻¹ between 3.0–4.2 V (vs Li/Li⁺) at 55°C, advanced post-cycling analyses, including X-ray absorption near-edge spectroscopy, Mössbauer spectroscopy, and energy-dispersive X-ray analysis, revealed that the observed capacity stemmed from a faradaic side reaction involving hydrofluoric acid in the electrolyte and the Fe impurity, rather than true Mg²⁺ intercalation. In Chapter 5, the electrochemical properties of all five synthesised borates are evaluated, with a particular focus on the phase-pure orthoborate Mg₂Mn(BO₃)₂. All materials displayed similar voltage profiles and capacity behaviour, prompting a post-mortem study of Mg₂Mn(BO₃)₂ to understand the underlying mech…
author: Tacconis, Camilla
language: eng
keywords: Li-ion, Mg-ion, Cathode Materials, Volume Expansion, RMBs, Rechargeable Mg-ion Batteries, Si, High Energy Density Batteries
license: https://www.repository.cam.ac.uk/bitstreams/40afae88-cd74-4f3b-8aa8-906371e0a18b/download
license: https://creativecommons.org/licenses/by/4.0/
date published: 2025-07-04
date modified: 2026-07-22T22:24:13Z
provider: Cambridge University
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: University of Cambridge

PropertyValue
property ID: DOI
value: 10.17863/CAM.127561