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Abstract: This thesis contains work related to the sustainable development of an aqueous aluminum ion battery. The battery consists of a titanium dioxide negative electrode and copper hexacynoferrate positive electrode, the electrolyte is 1 M aluminium chloride and 1 M potassium chloride. At the start of the PhD project the reported energy density was 15 Wh kg − 1 and power density of 300 W kg − 1 , with a cycle life of 1750 charge/discharge cycles. Aluminium is a viable option for secondary battery technology, not only is the theoretical energy density high (~8000 W kg − 1 ), but there are already well established mining, production, and recycling industries built around aluminium, making it a sustainable option too. Further, the use of an aqueous electrolyte, while limiting of the voltage range a cell can operate at - due to the electrochemical stability window of water - is an inherently safe option for an electrolyte, which also boasts an ease of manufacture. The core concept throughout this thesis is that of minimising the environmental impacts of the battery as the design develops, and as such, a life-cycle assessment (LCA) is conducted on the current stage of the design, and compared to supercapacitors - this is due to the pseudo-capacitive, high power, nature of the battery. The design, in its current bench-based state, is found to be more environmentally friendly overall than commercial supercapacitors, and capacitors. A practical application of this battery in a dual energy storage system is studied for an EV car and bus, showing that, for a long lifetime of the EV, using dual energy storage systems has reduced environmental impacts. The LCA results were then compared to the market leader in energy storage (Li-ion) for environmental impacts. Based on the comparison to Li-ion, development goals were set based on achieving the same or better lifetime CO 2 emissions, and it was found that by increasing the cycle life of the battery, and increasing the amount of utilised active material within the battery, it would become environmentally competitive with Li-ion. Following this outcome, the focus for the experimental part of the PhD was split into active material increase and lifetime extension. To increase the active material \% within the battery, both increasing the actual amount of active material, and reducing the amount of support material were investigated. Coin-cell development of this battery to reduce support material found that a closed cell would not be appropriate - due to gas production, however 7000 stable cycles were achieved with an uncrimped cell. The loading of active material within the battery was investigated and found that a lower loading lead to increased discharge capacity (287.2 mAh g − 1 for the positive and 205 mAh g − 1 for the negative electrode). The performance of the TiO 2 electrodes were also investigated in terms of temperature. Given the porosity of the carbon felt, the impacts of compression on performance is being investigated in collaboration with Diamond Light Source, and initial findings are presented. For increasing the lifetime of a battery it is prudent to understand the degradation mechanisms that occur over time as the battery loses capacity. Once this is known, design decisions and usage prescriptions can be made to mitigate or minimise these mechanisms and therefore increase the life of the battery. Based on this, a long duration experiment spanning eleven months was run at Diamond Light Source, which performed X-ray diffraction on six cycling coin cells each week. The resulting diffraction patterns, alongside X-ray computed tomography of the final coin cells have uncovered information about how the make up of the electrodes have changed over time. Overall, this thesis shows that by working with the environmental impacts of a battery, we can produce development road-maps that both improve performance and respects the planet.

Open Access

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Abstract: Lead halide perovskites have emerged as promising materials for solar energy conversion and X-ray detection owing to their remarkable optoelectronic properties. However, the microscopic origins of their superior performance remain unclear. Here we show that low-symmetry dynamic nanodomains present in the high-symmetry average cubic phases, whose characteristics are dictated by the A-site cation, govern the macroscopic behaviour. We combine X-ray diffuse scattering, inelastic neutron spectroscopy, hyperspectral photoluminescence microscopy and machine-learning-assisted molecular dynamics simulations to directly correlate local nanoscale dynamics with macroscopic optoelectronic response. Our approach reveals that methylammonium-based perovskites form densely packed, anisotropic dynamic nanodomains with out-of-phase octahedral tilting, whereas formamidinium-based systems develop sparse, isotropic, spherical nanodomains with in-phase tilting, even when crystallography reveals cubic symmetry on average. We demonstrate that these sparsely distributed isotropic nanodomains present in formamidinium-based systems reduce electronic dynamic disorder, resulting in a beneficial optoelectronic response, thereby enhancing the performance of formamidinium-based lead halide perovskite devices. By elucidating the influence of the A-site cation on local dynamic nanodomains, and consequently, on the macroscopic properties, we propose leveraging this relationship to engineer the optoelectronic response of these materials, propelling further advancements in perovskite-based photovoltaics, optoelectronics and X-ray imaging.

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Abstract: Niobium–based Wadsley–Roth oxides have recently attracted attention as promising anode materials for lithium-ion batteries, providing high charging and discharging rates and cycling stability. The higher operating potential of Wadsley–Roth oxide anodes, while impacting the overall energy density, reduces the risk of dendrite formation, making them safer at high power densities. We present the rapid preparation of two Wadsley–Roth oxide compounds, AlNb11O29 and Ti2Nb10O29, by a microwave-assisted preparation method in under 10 min starting from oxide materials, and heating in open crucibles. No further processing is required to make effective electrode materials from these compounds other than grinding with the usual conducting carbon and binder. High-resolution synchrotron X-ray diffraction and scanning electron microscopy are employed to understand the impact of rapid preparation on the structure and morphology. Excellent electrochemical performance is achieved, with reversible capacities of up to 250 mAh g–1 with high capacity retention over 100 cycles and fast-charging rates up to 10C without much loss of capacity. The materials reported here are compared to reports from the literature. Despite the very similar structures and compositions, AlNb11O29 is found to be less effective as an anode material than Ti2Nb10O29, and in this work, we delve into possible reasons for this.

Open Access

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Abstract: The real-time interface chemistry between the lithium cobalt oxide (LCO) working electrode and the LiClO4/propylene carbonate (PC) electrolyte is investigated during lithiation/delithiation using dip-and-pull ambient pressure photoelectron spectroscopy (APXPS). The APXPS results appear to exhibit the seldom discussed Co2+ state in the LCO structure, where the operando measurements indicate electron transfer among Co2+, Co3+, and Co4+ states. Specifically, the lithiation of LCO reduces the Co4+ state to both Co3+ and Co2+ states, where, as a function of voltage, reduction to Co2+ state is initially more pronounced followed by Co3+ formation. In addition, a delay in surface delithiation is observed during the reverse potential steps. This is discussed in terms of overpotential at the interface measurement position as a consequence of the dip-and-pull setup for this experiment. Finally, the shifts in the apparent binding energies of the spectral features corresponding to the electrolyte and LCO at their interface shows that the electrochemical potentials at delithiation voltage steps are different from the lithiation steps at the same applied voltages. This further explains the non-responsive delithiation. The BE shift observed from the LCO surface is argued to be dominantly due to the semi-conductive nature of the sample. Overall, this article shows the importance of operando APXPS for probing non-equilibrium states in battery electrodes for understanding electron transfer in the reactions.

Open Access

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Abstract: Solid-state lithium batteries are developing rapidly as a promising next-generation battery, while challenges still persist in understanding their degradation processes during cycling due to the difficulties in characterization. In this study, the 3D morphological evolution of the Li3PS4 solid electrolyte was tracked during electrochemical cycles (plating and stripping) until short circuit by utilizing in situ synchrotron X-ray computed tomography with sufficient spatial and temporal resolution. During the degradation process, cracks in the electrolyte alternately generated from the two electrode/electrolyte interfaces and propagated until shorting. The lithium dendrites filled in the electrolyte cracks but had a greatly reduced filling ratio after the first plating stage; therefore, the cell could continue working for some time after the solid electrolyte was fully fractured by cracks. The compression of the two lithium electrodes mainly occurred in initial cycles where a ca. 4–7 μm reduction in thickness was observed. The mechanical force and electric potential fields were modeled to visualize their redistributions in different stages of cycling. The release of strain energy after the first penetration and thereafter the subsequent driving forces are discussed. These results reveal a fast degradation of solid electrolyte in the initial cycles, providing insights for further modifications and improvements in solid-state batteries.