Rechargeable sodium-ion batteries may be considered key contenders of the replacement of lithium-ion batteries, with future research, due to their natural abundance and low cost of the raw materials. An increased focus on the reduction of global carbon emissions and the transition to net zero has placed a greater emphasis on the development of energy storage systems. Gaps in the research of sodium-ion based batteries means more studies must be conducted before they can be confirmed as a successful substitution for the well-known lithium-ion based batteries. The optimisation of their cathode materials is a starting point.
The aim of this project was to provide an overview of the current batteries available alongside the research that has gone into sodium-ion based batteries. This research was used in synthesising cathode materials doped with varying ratios of transition metals. The approach taken was to produce Na(NiMnCo)O2 (Na-NMC) buckyballs by sodiating (NiMnCo)CO3 (NMC) precursors that were initially synthesised via a hydrothermal method. The first goal was to investigate the ratios of nickel and cobalt by changing their ratios during synthesis of the precursors. The second goal involved altering the ratios of sodium incorporated into the precursor [Ni0.13Mn0.54Co0.13]CO3. The chemical structure of the precursors and products were explored using XRD, SEM, EDX, ICP-OES, IR and Raman spectroscopy. Coin-cell batteries were then fabricated with four of the synthesised NMC cathode materials and their galvanostatic recharge performance recorded.
This project provides an initial study into varying the elements within a cathode material for application in sodium-ion batteries with a focus on the impacts on material structure and battery performance. XRD inferred lower amounts of cobalt are insufficient in directing the formation of a stable P2-NMC structure. SEM images conveyed that small, non-uniform crystalline structures were produced with sizes of 2-10 μm and featured some sphere-like particles. EDX and ICP-OES conveyed the ratios of elements within the structure were not as expected with the measured ratios of sodium generally being higher than expected and the ratios of nickel and cobalt being lower than expect. IR spectroscopy confirmed the transition in the presence of carbonate to carbonyl functional groups when analysing precursors and products respectively. During galvanostatic charge, a wide range of capacities were recorded varying between 2 and 700 mAh g-1. Higher cobalt amounts increased the conductivity of the material whilst low cobalt amounts conveyed very poor battery performances.
The initial research and results of this project confirmed the prospects for further experimentation concerning high-performance sodium-ion battery cathode materials.
PLEASE NOTE: You must be a member of the University of Lincoln to be able to view this dissertation. Please log in here.