The advancements in the field of e-mobility today far outpace all prior projections, and the rate of progress is quick. Due to their high power density and energy density, Lithium-Ion Batteries (LIBs) have grown to be an increasingly appealing alternative for use in electric vehicles. However, over extended use, these batteries frequently experience problems with capacity loss. Additionally, the battery’s current collectors are challenging to scrape off from the cathode, which results in erroneous measurement results under spectroscopic observation. Furthermore, current collectors have a propensity to corrode with repeated use, which reduces the battery’s power output.

In this study, the cathodes are manufactured without a current collector, i.e. a Free-Standing (FS) cathode, to prevent the issues brought on by the current collector. To assess how well these cathodes function in comparison to cathodes with an aluminium current collector, they are cycled both for long term and at different charging rates. In this investigation, the cathode materials examined include NMC 532, NMC 811, and LCO. The cycling behaviour of the FS cathodes was found to be quite comparable to that of the cathodes on current collectors. Using Electrochemical Impedance Spectroscopy (EIS), X-Ray Diffraction (XRD), and X-Ray Photon Spectroscopy (XPS), their cycling behaviour was further assessed in order to ascertain the chemical changes that occurred while cycling. The findings showed that an unstable cathode-electrolyte interface layer caused the cathodes to develop cracks on their surface during long-term cycling. Consequently, the electrolyte started to decompose, depositing impurities on the cathode surfaces. This behaviour produced a high impedance and prevented charge transfer over the cathode surface, leading to quick capacity fading and a subpar electrochemical performance.

To address the issue of capacity loss, the cathodes under investigation are coated with Al2O3 using Atomic Layer Deposition (ALD). Investigation of these cathodes after cycling revealed that the electrolyte decomposition had been greatly decreased, resulting in a virtually impurity-free surface. Additionally, it was discovered that the thicker the ALD coated layer is, the lower its cycle performance is likely to be, due to the increased charge transfer resistance caused by the thick layer. As a result, it is suggested to keep the coating as thin as possible to gain superior performances. The chemical differences between the coated and uncoated cathodes in this work were examined through EIS, Scanning Electron Microscopy coupled with Energy Dispersive X-Ray Spectroscopy (SEM-EDS), XRD, XPS and Nuclear Magnetic Resonance Spectroscopy (NMR). In order to examine the chemistry of the coating layer more effectively, it is recommended to carry out NMR measurements at high magnetic fields. Overall, this thesis effectively illustrated the benefits of coating the cathodes with Al2O3. Additionally, it offered a fascinating route for FS electrode-specific research.

Li-ion batteries have major disadvantages. One of which is the growth of dendrites (in case Li metal based batteries), a major safety issue. In addition to that, Li-ion batteries also use elements such as Co, and Li, which are regionally scarce. Mg-ion batteries are one of the alternatives for Li-ion batteries. However, the electrolyte and cathode materials for Mg-ion batteries, are still in developmental stages.
In this study, the use of a sulphur-based spinel (also known as thiospinel) material as a cathode is explored. After literature review, MgMn2S4 and MgTi2S4 were identified as suitable cathode materials. Following which, the MgMn2S4 spinel is doped with Ti in the place of Mn at different doping ratios and the resulting combinations are evaluated for their stability, average intercalation voltage, volume change, spinel inversion and migration barriers. Two combinations MgMnTiS4 and MgMn0.75Ti1.25S4 are found to be stable with respect to the end members i.e. MgMn2S4 and MgTi2S4. Average voltages of 1.702 and 1.527 V (vs. Mg/Mg2+) are observed for MgMnTiS4 and MgMn0.75Ti1.25S4. However, spinel inversion is observed in MgMnTiS4. A volume change of 21.2, and 20% is observed in MgMnTiS4 and MgMn0.75Ti1.25S4, respectively.