Metal-organic materials as electrode precursors and hosts for lithium-ion and lithium-sulfur batteries

This thesis describes the development of a range of metal oxide, metal chalcogenide and metal alloy composites, using metal-organic materials (MOMs) as sacrificial precursors and their application as electrode materials in next generation Li-ion batteries. A porous MOM was also implemented as a potential sulfur host in Lithium Sulfur (LiS) batteries. The phase-controlled synthesis of MOM (HKUST-1) derived copper sulfide (CuxS)/C (x = 1, 1.8, 2) composites, via sulfurisation, for the application as cathode materials in Li-ion batteries is described in Chapter 3. This study demonstrates the link between the sulfurisation temperature of the HKUST-1 and the resultant CuxS phase formed with Cu-rich phases formed at higher temperatures. The results indicate the cathode performance is dependent on both the phase of the CuxS and the crystal morphology with the Cu1.8S/C-500 composite with nanowires exhibited the best performance with a specific capacity of 200 mAh/g). Chapter 4 details the synthesis of a new bimetallic 2D interpenetrated MOM and its use as a sacrificial template for the formation of Cu2SnS3/SnS2/C composite and its application as an anode material in Li-ion batteries. The lithiation/delithiation mechanisms of the Cu2SnS3/SnS2/C material were explored as well as the optimisation of the anode testing conditions, leading to the use of a 1 V upper cycling cut-off rather than the conventional voltage limit of 3 V. Cu2SnS3/SnS2/C anodes retained 84 % of their specific capacity after 100 cycles. Chapter 5 explores the synthesis of a range of metal oxide, selenide and alloy composite materials derived from the same MOM precursor demonstrating the versatility of the starting template. This represents the first metal alloy-in-carbon composite from a MOM starting material. Their electrochemical performances are compared with the metal alloy exhibiting the best performance. Chapter 6 details the encapsulation of sulfur within a porous MOM, TIFSIX-1-Cu, for use as a cathode material in LiS batteries. Importantly, the results from the initial electrochemical testing indicate that the interaction between the host material and the electrolyte is very important and demonstrates that a thorough screening process is needed to ensure the stability of the host material prior to sulfur encapsulation and electrochemical testing. TIFSIX-1-Cu interacts with the salts in the electrolyte causing it to be destroyed and meaning that it can no longer act as an effective sulfur host.