The medical interest in targeted alpha therapy (TAT) has increased the demand for actinium-225 (225Ac), a promising isotope for cancer treatment. However, the production falls short. One potential route is the generation of 225Ac via proton irradiation of radium-226 (226Ra), introducing the challenge of separating these radionuclides. In this study, lanthanum and barium were used as chemical analogues for actinium and radium, respectively. This study investigates the production and characterisation of α-titanium phosphate (α-Ti(HPO4)2 · H2O, α-TiP) and its feasibility for the separation of lanthanum and barium using ion exchange.

Three synthesis methods were used with different titanium precursors: TiO2, Ti powder and TiOSO4. The resulting α-TiP samples were characterised using X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS), confirming phase purity but showing morphological differences.

The ion exchange behaviour of α-TiP was found to be closely linked to morphology and exchange site accessibility. Batch adsorption experiments demonstrated that α-TiP exhibits strong selectivity for trivalent lanthanum (La3+) over divalent barium (Ba2+) ions at acidic pH and relevant concentration ([La3+] = 2.5 μM and [Ba2+] = 1.0 mM).

The results support the potential of α-TiP as a viable material for lanthanum–barium separation. However, further studies are required to confirm radiation stability, reversibility of ion uptake and performance in column-based separation systems. Additionally, experiments should validate whether similar separation behaviour will be achieved for actinium and radium separation.

The radionuclide technetium-99m (99𝑚Tc) is utilized in 80-85% of in-vivo nuclear medicine diagnostics due to its ideal physical and chemical properties, including a short half-life, gamma emission suitable for imaging, and versatile chemistry. Its production relies on molybdenum-99 (99Mo), traditionally generated through uranium fission. However, the transition to low-enriched uranium (LEU) targets and growing demand for 99𝑚Tc have driven the search for alternative production methods and materials. This study investigates the potential of molybdenum silicide (MoSi2) materials as targets for neutron-activated 99Mo production and as generators for 99𝑚Tc extraction. Three synthesis methods were explored to produce nanoscale molybdenum silicides. A sol-gel carbothermic reduction method failed to produce MoSi2, yielding elemental molybdenum, molybdenum dioxide, and molybdenum carbide due to oxygen contamination. The sol-gel preoxidation method successfully coated commercial MoSi2 with an amorphous silica layer, enhancing the material’s stability. The magnesiothermic reduction method successfully produced an oxide mixture intermediate (SiO2/MoO3) with nanosphere structures, initially containing 0.57 wt% molybdenum. The molybdenum content was later increased to 23.96 wt%. However, synthesis of the Si/MoSi2 nanocomposites from this intermediate was not completed due to time constraints. The chemical stability, extraction and retention behavior of commercial and silica-coated MoSi2 were evaluated in MilliQ and methyl ethyl ketone (MEK). The silica coating reduced molybdenum leaching and exhibited selective 99𝑚Tc extraction. Retention studies highlighted the significant role of solvent interactions in governing radionuclide adsorption. In MEK, the silica-coated material exhibited lower 99𝑚Tc retention, likely due to reduced adsorption sites caused by solvent interactions with silanol groups, while 99Mo retention could not be evaluated due to insufficient extraction data. The results demonstrate the potential of silica-coated MoSi2 in 99Mo/99𝑚Tc generator applications. However, further work is needed to optimize synthesis, increase surface area and evaluate long-term performance under irradiation. This could pave the way for sustainable and efficient isotope production systems.

As climate change concerns increase, the maritime industry faces an urgent need to reduce emissions and adopt sustainable practices. The integration of hybrid systems, particularly those incorporating Battery Energy Storage Systems (BESS), has emerged as a promising solution to enhance energy effi- ciency and lower the environmental impact. This Master Thesis focuses on developing a methodology for determining the most suitable battery size and type for existing vessels to be hybridized, balancing effectiveness and cost-efficiency. This thesis was conducted in collaboration with Jan De Nul Group, a leading global firm in environmental services, engineering, marine construction, and dredging.

The primary goal of this research is to design a methodology that compares different control strate- gies for sizing battery systems and selecting appropriate chemistries. A case study based on a trailing suction hopper dredger vessel was explored.

Three control strategies were evaluated using numerical modeling: optimal operation of the current scenario without batteries, load smoothing using a moving average approach, and optimal range op- eration of generators. To optimise the number of running generators and reduce maintenance costs, an automatic start-stop logic is implemented as a model initialisation. The optimal operation of the current scenario without batteries highlights the need for battery integration to compensate for the high supply deficit. In addition, the load smoothing strategy creates a more stable demand curve, allowing generators to operate more efficiently, while the optimal range strategy keeps generators near their rated power, maximizing efficiency and minimizing fuel consumption.

The study assesses battery performance under two scenarios: continuous full cycling throughout the year and calendar aging specifically during harbour operations. Battery power is calculated based on demand and generator output, considering state-of-charge constraints. Three types of lithium-ion batteries were evaluated for their suitability in ocean-going hybrid vessels: Lithium Nickel Cobalt Manganese Oxide (NMC), Lithium Iron Phosphate (LFP), and Lithium Titanate Oxide (LTO).

A total of 648 battery solutions under the load smoothing strategy and 216 under the optimal range strategy were assessed. Using four key criteria, the selection of battery options was narrowed down. Given the limitations of the model used in this research, findings suggest that batteries affected primar- ily by calendar aging have shorter lifespans, making cycling behavior preferable for achieving longer battery lifetime and higher Return On Investment (ROI). The optimal range strategy leads to higher fuel savings compared to load smoothing, while load smoothing results in a longer battery lifespan due to fewer equivalent cycles. In summary, selecting the best battery solution hinges on whether the priority is immediate ROI or long-term operational efficiency. This thesis offers a comprehensive methodology for integrating BESS, contributing valuable insights to the advancement of sustainable energy solutions in the maritime sector.

This study explores the electrokinetic properties of zinc-alginate beads in the context of a zinc-air solid- mediated flow battery, as there has been a renewed interest in zinc–air batteries due to their potential for high energy density, safety, and environmental benefits [43]. On the contrary, there are several challenges related to both the anode and the cathode of the Zn-air battery. This research focuses on the challenges related to the anode side which consists of zinc dendrite formation, reducing the battery’s lifetime. Also, Zn passivation increases internal resistance and reduces active capacity. Additionally, hydrogen evolution reaction during charging decreases the coulombic efficiency and leads to safety risks due to gas pressure build-up [40][43]. Trying to solve these issues, a European pathfinder project, ReZilient, has proposed a Zinc-Air Solid Mediated Flow Battery. In the anolyte tank, alginate beads are introduced to encapsulate zinc, aiming to prevent these parasitic reactions. Besides, the encapsulation of solid ZnO microparticles overcomes the limited solubility of ZnO and could significantly enhance the system’s energy density. This study explores the electrokinetic and mechanical properties of Zn/ZnO beads and the capability of preventing these parasitic reactions. Experimental research, including thermogravimetric analysis, scanning elec- tron microscopy, cyclic voltammetry and electrical impedance spectroscopy was used to characterize and evaluate the bead’s electrochemical and mechanical behaviour. After synthesizing the beads it was found that beads consisting of 2.5% and 5% w/v sodium alginate demonstrated a strong structure of which the last one was used for further experimental research. The synthesized beads were uniformly sized, with diameters mainly between 3.3 mm and 3.5 mm. Besides, thermogravimetric analysis was performed on beads produced from a 5% w/v sodium alginate, 3% carbon black and 10% ZnO solution. The analysis revealed that the bead consisted of 82.7% water, 7.4% organic alginate and carbon black, and 9.9% metal oxides including ZnO and CaO, although the specific ratio of calcium remains to be determined. Additionally, the diffusion rates for alkali metal hydroxides like NaOH and KOH were measured at 0.0464 s−1 and 0.0435 s−1, respectively. Conductivity assessments via cyclic voltammetry identified a con- ductivity of 0.01 S/m at a 3% KS4 graphite concentration, which aligned with literature studies. Addi- tionally, hydrogen evolution was observed within the beads during voltammetry experiments conducted between 0 and -1.4 V (vs Ag/AgCl), indicating that the alginate’s carboxylic acid groups do not suffi- ciently increase the overpotential for the reduction of water to mitigate hydrogen evolution. Still, cyclic voltammetry of the bead was performed with a technique, called film voltammetry, inspired by the study of Yoon et al. (2019). The measurement showed that the Zn/ZnO could perform a redox reaction while situating in the bead. it exhibited a redox potential of around -1.4 V (vs Ag/AgCl) at a pH of 12, indicating Zn/Zn(OH)−2 4 . However, it suffered from very low zinc utilization of 0.0007% and limited reversibility as the reduction kinetics were unfavourable. The Zn-Ca-crosslinked bead demonstrated faster reaction kinetics and achieved a redox potential of -1.05 V (vs Ag/AgCl), indicating Zn/Zn+2, yet it also experienced zinc loss and declining efficiency over time as it shifted to similar electrochemical behaviour as the Zn/ZnO bead. To improve zinc utilization, ZnO was encapsulated with a carbon micro-shell before being added to the alginate beads to increase ionic and electronic conductivity. However, it only showed slightly enhanced reduction currents, while zinc utilization remained low. Next to the electrochemical behaviour, were the mechanical properties of the beads tested as well, with a Young’s modulus of 0.58 MPa for the 5% w/v Na-Alg with 3% w/v KS4 graphite bead. These findings show that strong beads were synthesised and Zn/ZnO is electrochemically reactive within the bead. Nevertheless, the low zinc utilization and dogged parasitic reactions require further research. This research provides a foundation for improving the performance of Zn beads in zinc-air solid-mediated flow batteries by addressing their electrochemical behaviour and mechanical properties.

The high theoretical volumetric capacity, abundance of magnesium in the earth’s crust, and the relatively good safety features of Mg metal, have drawn great attention to developing Magnesium batteries as a follow-up to the success of Li-ion battery technology. However, the magnesium metal is incompatible with most electrolyte solvents and salts, which passivates the surface of magnesium and causes the battery failure. One of the crucial approaches to address this problem is to seek novel electrolytes which have good metallic Mg compatibility and subsequently improve the cycling performance.

In this research, the feasibility of combing PEO, Mg-alginate and MgCl2 to design a solid polymer electrolyte (SPE) for Mg-ion batteries has been assessed. The SPE membrane shows a conductivity of ~10-5 S·cm-1 at 60 °C and an increased value up to ~10-4 S·cm-1 at 80 °C and above. The XRD results have suggested there is no real interaction in between the two polymers which can cause reconstruction of the polymer structure. Moreover, this electrolyte material is highlighted with an excellent cycling stability of up to 150 hours. At last, a possible model which could explain the Arrhenius behavior of temperature-dependent ion conduction is proposed for this SPE material. Overall, this research demonstrates the potential application of Mg-alginate for Mg energy storage in terms of developing a polymer electrolyte, despite further modification in the future is needed.

In the coming energy transition, the availability of reliable and affordable energy storage will be of vital importance. Battery storage is a large factor in the energy storage sector, and current battery storage is dominated by lithium-based batteries. However, lately, alternatives to lithium have been given renewed attention, due to the insufficient abundance of lithium in the earth’s crust and the promising theoretical aspects of these other types of batteries. Fluoride-based batteries, for example, have high theoretical capacities and are theorized to be very suitable for application in solid-state battery technology. Fluoride-based batteries have only been produced on a lab-scale relatively recently, with the first reversible solid-state fluoride-ion battery produced in 2011, and the first room temperature reversible fluoride-ion battery produced in 2018, yet interest in this technology has drastically increased over the past few years. The current main issues fluoride- ion batteries are running into are its poor cyclability, its low current densities, and its inability to meet the theoretical capacities. In this report, multiple facets of fluoride-ion batteries have been analyzed in an effort to improve on these characteristics. In particular a focus has been placed on two commonly used materials in fluoride-ion batteries: electrolyte BaSnF4 and cathode material BiF3. The ionic conductivity dependence on pressure was deduced for each material, with BaSnF4 having its highest ionic conductivity at ∼280 MPa and BiF3 having its highest ionic conductivity at ∼680 MPa. To test the effect of oxides in BiF3, which form spontaneously when BiF3 is exposed to air or humidity, various Bi-O-F compounds were synthesized and had their ionic conductivity measured. It was found that each of the compounds that contained oxygen had a drastically lower (factor 1,000-10,000) ionic conductivity than pure BiF3. An attempt was also made to improve the ionic conductivity of BiF3 by doping that material with SnF2. BiF3 doped with SnF2 concentrations of 5-20% were synthesized, and had their ionic conductivity measured. It was found that the ionic conductivity was increased by dopant concentrations of 5% and 10%, with the material with 10% SnF2 having the highest ionic conductivity, while the materials with 15% and 20% SnF2 had a similar ionic conductivity to pure BiF3. Symmetric fluoride-ion batteries were also produced, with BiF3 as an electrode material and BaSnF4 as an electrolyte material. The produced batteries reached charge and discharge capacities with values of at most only 30% of the values reported in literature. The batteries also had poor capacity retention over multiple charge-discharge cycles. Batteries were also produced using BiF3 doped with 5% and 10% SnF2 as an electrode material. These batteries had higher initial capacities but had even poorer capacity retention over subsequent cycles. It was however also found that the critical current density for the batteries had increased as a result of doping with SnF2, allowing higher current densities to be applied to the batteries.

Submarines face an ongoing (technical) battle to improve the operational effectiveness by increasing the submerged endurance and range. Installing lithium-ion batteries on new or refitted diesel-electric submarines has become increasingly interesting based on their relatively high energy density and specific energy. The characteristics compared to the currently implemented lead-acid batteries are known, meaning that the implementation of lithium-ion batteries on submarines can increase the submerged range and endurance based on their better specifications. Additionally, lithium-ion batteries require less maintenance and provide a relatively longer life expectancy compared to lead-acid batteries. However, lithium-ion batteries can develop a thermal runaway: a process which exponentially generates heat, leading to the risk of an explosion and fire. A thermal runaway can be initiated based on internal failure mechanisms and external causes, such as exceeding critical temperature limits. Understanding of the thermal behaviour of lithium-ion batteries is essential to reduce the probability of a thermal runaway. The probability of initiating a thermal runaway can be further reduced by auxiliary systems such as a cooling system and a battery management system. The main objective of this research is therefore to investigate the implications on preliminary submarine system design based on the thermal behaviour of lithium-ion batteries and to quantify the thermal behaviour and design implications. The relevance is that by quantifying the thermal behaviour, the cell temperatures can be estimated. As a consequence, awareness of the risk of a thermal runaway is established, while at the same time input for the dimensioning of a cooling system is provided. An analysis has been performed concerning the safety of lithium-ion batteries. The causes, the characteristics and the prevention methods regarding a thermal runaway have been studied in this research. The four stages of a thermal runaway are discussed, as well as the generation of toxic and flammable gasses. Moreover, the sources of heat generation in a lithium-ion cell have been described. The heat generation typically consists of reversible and irreversible heat components, of which the relative contributions have been described based on the charge or discharge rate. To support preliminary submarine design, a thermal model of a lithium-ion battery module has been created. The first model that has been created describes the electric behaviour of a lithium-ion battery cell that is typically implemented in marine applications. EST-Floattech has provided technical specifications of the lithium-ion pouch cell that is implemented in their modules. The second model determines the generated heat based on the electrical model and cell specific properties. The third model simulates a lithium-ion battery module, where heat is generated by multiple cells and heat transfer rates with the surroundings are modelled. A lumped thermal capacity approach has been implemented and cooling is modelled to provide insight in typical cooling rates regarding thermal management. Conclusions have been drawn regarding the temperatures of the cells in the module based on three operational profiles. Based on a submerged sprint, C-rates up to 1.0C can be sustained without cooling while remaining below the critical temperature limit of 55°C. For consecutive cycles during a covert transit or covert surveillance, cooling is typically necessary. Only at C-rates below 0.3C a covert transit can be sustained. Typical cooling rates vary between 60 W and 185 W, where the effects of cooling are most significant for covert transit and covert surveillance. Module optimisation provides increased cooling rates while increasing the energy density and specific energy. This results in a decreased mass and volume of the module, resulting in a significant amount of extra space in the entire battery system on board of a submarine. The largest improvement in thermal management can be realised by choosing the right conductive filler. Moreover, the cooling capacity has a significant influence on the cell temperatures. Cell temperatures remain relatively constant after the fourth cell in a row, meaning that modules are typically not limited by the number of cells.

Silicon anodes can boost the energy density of lithium-ion batteries due to its high theoretical capacity up to ~3600 mAh/g. However, a challenge of the use of silicon anode is 300% swelling/shrink upon lithiation/delithiation, which is a major cause of battery failure. A lithium-ion battery with silicon anode requires the formation of a flexible and stable solid electrolyte interphase (SEI) on the anode’s surface to prevent continuous electrolyte decomposition, to mitigate the volume changes and to enable good Li­-ion transportation. It is still a challenge to develop new electrolyte compositions to mitigate the continuous SEI formation and, consequently, enhance the cycle life. In this thesis, a 100% pure amorphous silicon anode is investigated in lithium-ion battery cells with an energy density up to 1350 Wh/L. The effect of different electrolyte compositions on the electrochemical behaviour and cycle life is studied. The results show that the addition of fluoroethylene carbonate (FEC) and vinylene carbonate (VC) to an electrolyte mixture of LiPF6 and a pure linear carbonate solvent improves the capacity retention for over 100 cycles. The addition of co-solvents, propylene carbonate(PC) or ethylene carbonate (EC), improves the silicon utilisation level from ~1500 to ~1700 mAh/g. The diallyl pyrocarbonate (DAPC) additive in the electrolyte improves the capacity retention at 100 cycles from 67.7% to 72.2% in a full NMC­622/Si coin cell and from 84.2% to 90.8% in a full pouch cell. This study demonstrates that the electrolyte composition has an effect on the cycle life of lithium-ion batteries with silicon anode, likely by SEI formation from preferable decomposition products and from a complementary mixture of electrolyte components.

Solid state lithium ion batteries are generally safer than liquid electrolytes. Li6PS5Cl is a promising electrolyte with an instability in the active material and electrolyte interphase which causes an increase in impedance and capacity loss.
Doping with stable salts of LiCl and LiF could affect the stability. It is found that doping LiCl reduces the specific capacity retention despite having higher ionic conductivity from EIS. With the ex-situ XRD analysis, it is found that the decomposition is less than of pristine argyrodite. This could be due to poor interphase contact. In the case of dopant LiF, small doping of the argyrodite decreases the specific capacity retention of the active material which may be due to lowered ionic conductivity. The higher amount of LiF doped argyrodite improves the specific capacity retention despite the lower ionic conductivities. This could be due high decomposition rate. Alternatively, another doping method was used, but it was found to have higher chemical decomposition despite having good specific capacity retention. To improve the quality of this research, better synthesis of the argyrodite is preferred as this research has side phases. Further analysis that could be included are: TEM, XRD in-operando mode, and EDS.

Lithium ion batteries are currently the most attractive choice for mobile energy storage and power sources [4] in terms of energy density. However, it is unlikely that current battery chemistries will reach the energy density desired for future applications [8]. Li-metal, which has the highest reduction potential of all metals and the highest achievable capacity per weight unit, could significantly increase the energy density when used as an Anode. Unfortunately, the dendritic growth of Li-metal is a safety hazard, and the low electrochemical potential of Li-metal
is outside the stability window of many electrolytes leading to capacity degradation.
It has been suggested that safe Li-metal Anodes may be possible in combination with solid electrolytes, as the higher shear modulo of solid over liquid electrolytes may be able to suppress dendrite formation [21].
To study the stability of the interface between Li-metal and the solid electrolyte Li6PS5Cl, electrochemical measurements of the cells, ex-situ x-ray diffraction, and solid state Nuclear Magnetic Resonance measurements were made. It was not possible to confirm the decomposition products that were proposed in literature by density functional theory calculations and in-situ XPS. The XRD-pattern of the cycled electrolyte did not show additional phases. The NMR spectra developed broader peaks and one additional phosphorous environment upon cycling. As a tool to study dendritic growth through Li-ion concentration profiles, a cell for in-situ neutron depth profiling (NDP) was developed. The electrochemical performance is comparable to regular cells, except for a voltage drop due to contact problems during the break after Li-metal stripping. A thin layer of Li-metal between the window and the electrolyte pellet, as well as a collimator plate to put some pressure on the window, could be the solution
to go towards operando measurements.
The current standard data analysis method was implemented and its sensitivity towards gaussian broadening, due to energy straggling (from small angle scattering in the material and the stochastic nature of energy loss), was
investigated. It is shown that the standard deviation of energy straggling is larger than that of energy broadening due to the detector resolution, and that the error on the depth scale is in the order of micrometers.