Nano-sized transition metal oxide negative electrode materials for lithium-ion batteries

• Main Author: Lubke, Mechthild
• Published: University College London (University of London) 2018
• Subjects: 540
• Online Access: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.747406

This thesis focuses on the synthesis, characterization and electrochemical evaluation of various nano-sized materials for use in high power and high energy lithium-ion batteries. The materials were synthesised via a continuous hydrothermal flow synthesis (CHFS) process, which is a single step synthesis method with many advantages including screening processes (chapter 5). Electrochemical energy storage is introduced in chapter 1, with a focus on high power and high energy negative electrode materials for lithium-ion batteries (and capacitors). Many different classes of materials are discussed with associated advantages and disadvantages. This is followed by an experimental section in chapter 2. Chapter 3 deals with the main question regarding why some high power insertion materials show a wider operational potential window than expected. The nature of this electrochemical performance is discussed and classified towards battery-like and supercapacitor-like behaviour. Chapter 4 deals with Nb-doped anatase TiO2, which was tested for high power insertion materials. The role of the dopant was discussed in a comprehensive study. Chapter 5 gives an excellent example how CHFS processes can help accurately answer a scientific question. In this case the question dealt with the impact of transition metal dopants on the electrochemical performance of SnO2. Since CHFS enables similar materials properties despite doping, the real impact could be investigated in a fair manner. Finally, chapter 6 shows a strategy of achieving higher energy simultaneously with high cycle life. Insertion materials are combined with alloying materials in a simple, single step synthesis and this showed increased capacity, which is essential for high energy.