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The increased deployment for renewable energy sources to mitigate the climate crisis has accelerated the need to develop efficient energy storage devices. Batteries are at the top of the list of the most in-demand devices in the current decade. Nowadays, research is in full swing to develop a battery that meets the needs of today’s renewable energy systems, which are intermittent by nature. Within the framework of improving the performance of batteries, there are parameters in the composition of the battery that play an important role in its performance: electrode materials, electrolytes, separators, and other factors. The key to battery development is the manufacture of electrode materials with optimal properties. Two-dimensional (2D) materials have led to advances in this field, firstly, using graphite as the anode in lithium-ion batteries (LIBs). However, when using the standard graphite as the anode for sodium-ion batteries (NIBs), the large ionic size and energetic instability of Na+ limit intercalation, resulting in a low storage capacity. Therefore, other 2D materials with large interlayer spacing need to be identified for use as electrodes. In this dissertation, our approach is focus on optimizing anode electrode materials by in situ conversion of 2D materials to obtain hybrid materials. These hybrids materials will synergistically improve the performance of LIBs and NIBs by combining the advantages of individual 2D materials. Starting with converted Ti0.87O2 nanosheets to the TiO2/TiS2 hybrid nanosheets. Then, taking advantage of the properties of MXene, we developed hybrid electrodes based on MXenes by converted V2CTx MXene into V2S3@C@V2S3 heterostructures. Finally, we boosted the redox kinetics and cycling stability of Mo2CTx MXene by using a laser scribing process to construct a multiple-scale Mo2CTx/Mo2C-carbon (LS-Mo2CTx) hybrid material.

This paper examines the possibility of adding a photovoltaic(PV) power station to an already planned wind park in terms of profitability. At this time, southern Sweden’s grid is facing a number of challenges and is hurting economic development. Hybrid parks have showed to be able to tackle some of those challenges. This study has used a two-scaled methodology to analyse which solar PV size is the optimal to be co-located to the wind park of 24MW[Office1] . The results show that the 21MW size is the ideal one. In addition, to complement the findings, an analysis has been conducted to determine which battery size would be the optimal size to be added to the hybrid system. The results showed that a 1MW/1MWh battery storage would be the ideal size, however, it is possible that a 5MW/MWh battery storage might produce better results if peak shaving is included. All the scenarios in this study have been analysed in terms of IRR.

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A process, called carbon nanotube templated microfabrication (CNT-M) makes high aspect ratio microstructures out of a wide variety of materials by growing patterned vertically aligned carbon nanotubes (VACNTs) as a framework and then infiltrating various materials into the frameworks by chemical vapor deposition (CVD). By using the CNT-M procedure, a partial Si infiltration of carbon nanotube frameworks results in porous three dimensional microscale shapes consisting of silicon-carbon nanotube composites. The addition of thin silicon shells to the vertically aligned CNTs (VACNTs) enables the fabrication of robust silicon nanostructures with edibility to design a wide range of geometries. Nanoscale dimensions are determined by the diameter and spacing of the resulting silicon/carbon nanotubes while microscale dimensions are controlled by the lithographic patterning of CNT growth catalyst. The characterization and application of the new silicon nanomaterial, silicon-carbon core-shell nanotube (Si/CNT) composite, is investigated thoroughly in the dissertation.The Si/CNT composite is used as thin layer chromatography (TLC) separations media with precise microscale channels for fluid flow control and nanoscale porosity for high analyte capacity. Chemical separations done on the CNT-M structured media outperform commercial high performance TLC media resulting from separation efficiency and retention factor. The Si/CNT composite is also used as an anode material for lithium ion batteries. The composite is assembled into cells and tested by cycling against a lithium counter electrode. This CNT-M structured composite provides an effective test bed for studying the effects of geometry (e.g. electrode thickness, porosity, and surface area) on capacity and cycling performance. A combination of high gravimetric, volumetric, and areal capacity makes the composite an enabling materials system for high performance Li-ion batteries.Last, a thermal annealing to the Si/CNT composite results in the formation of silicon carbide nanowires (SiCNWs). This combination of annealing and Si/CNTs yields a unique fabrication approach resulting in porous three dimensional silicon carbide structures with precise control over shape and porosity.

The research presented in this thesis focuses on developing new functional polymeric materials that can conduct ions, H+, or OH- or Li+. The motivation behind this work was to understand the similarities and/or differences in the structure property relationships between polymer membranes and the conductivity of H+ and OH- ions, and between polymer membranes and the anhydrous conductivity of H+ and Li+ ions. This understanding is critical to developing durable polymer membranes with high H+, OH- and Li+ ion conductivity for proton exchange membrane fuel cells (PEMFCs), alkaline anion exchange membrane fuel cells (AAEMFCs) and lithium ion batteries respectively. Chapter 1 describes the basic functioning of PEMFCs, AAEMFCs and lithium ion batteries, the challenges associated with each research topic, and the fundamental mechanisms of ion transport. The proton conducting properties of poly(4-vinyl-1H-1,2,3-triazole) were investigated on a macroscopic scale by impedance spectroscopy and microscopic scale by solid state MAS NMR. It was found that proton conductivity is independent of molecular weight of the polymer, but influenced by orders of magnitude by the presence of residual dimethylformamide. To improve the mechanical properties of otherwise liquid-like 1H-1,2,3-triazole functionalized polysiloxane homopolymers, hybrid inorganic-organic proton exchange membranes (PEMs) containing 1H-viii 1,2,3-triazole grafted alkoxy silanes were synthesized, using sol-gel chemistry. This method enabled self-supporting membranes having proton conductivity comparable to uncrosslinked homopolymers. One of the biggest challenges with AEMs for use in AAEMFCs is finding a cationic polyelectrolyte that is chemically stable at elevated temperatures in high pH environment. Novel triazolium ionic salts were developed, having greater chemical stability under alkaline conditions compared to existing imidazolium ionic salts. However, the chemical stability of triazolium cations was not sufficient for AAEMFC applications. Excellent chemical stability of (C5H5)2Co+ in 2 M NaOH at 80°C over 30 days was demonstrated and polymerizable vinyl functionalized cobaltocenium monomers were synthesized. This work paves the way for future development of AEMs containing cobaltocenium moieties to facilitate hydroxide ion transport. Polymers containing covalently attached cyclic carbonates were synthesized and doped with lithium triflate and their lithium ion conductivities were investigated. The findings highlight the importance of high charge carrier density and flexibility of the polymer matrix to achieve high lithium ion conductivity. These results are similar to the key factors influencing anhydrous proton transport.

This thesis focuses on the development of oxidatively stable cathode and electrolyte materials for sodium-based battery systems. This is primarily achieved through the use of solid-state nuclear magnetic resonance (ssNMR) and pulsed-field gradient (PFG) NMR spectroscopy. ssNMR is used to diagnose the primarily failure mode of the NaOB. It is found through a combined 23Na and 19F study that the main discharge product of the cell, NaO2, oxidizes both the carbon and polyvinylidene fluoride (PVDF) binder of the cathode to produce parasitic Na2CO3 and NaF. In a subsequent study, Ti4O7-coated carbon paper cathodes are implemented in an attempt to stabilize NaO2. The 23Na triple quantum magic angle spinning (3QMAS) and 1H to 23Na dipolar heteronuclear multiple quantum correlation (23Na{1H} D-HMQC) experiments are used to diagnose the failure modes of carbon-coated, and Ti4O7-coated cathodes. It is found that electrochemically formed NaO2 is significantly more stable in Ti4O7-coated cathodes, leading to longer lifetime NaOBs. Oxidatively stable electrolyte materials are also examined. Lithium and sodium bis(trifluoromethansulfonyl)imide (TFSI) in adiponitrile (ADN) electrolytes exhibit extreme oxidative resistance, but are unusable in modern cells due to Al corrosion by TFSI, and spontaneous ADN degradation by Li and Na metal. PFG NMR is used to investigate the transport properties of LiTFSI in ADN as a function of LiTFSI concentration. By measuring the diffusion coefficient of Li+ and TFSI as a function of diffusion time (Δ), diffusional behaviour is encoded as a function of length scale to study the short- and long-range solution structure of the electrolyte. It is found that at high concentrations, LiTFSI in ADN transports Li+ primarily through an ion-hopping mechanism, in contrast to the typical vehicular mechanism observed at low concentrations. This suggests significant structural changes in solution at high concentrations. The NaTFSI in ADN analogue is examined for its electrochemical properties in Na-ion and Na-O2 batteries. It is found that the oxidative resistance of ADN to Na metal is significantly increased at high concentrations, leading to reversible Na deposition and dissolution in cyclic voltammetry (CV) experiments. Linear sweep voltammetry (LSV) and chronoamperometry (CA) experiments on Al current collectors show that Al corrosion by TFSI is similarly suppressed at high concentration. This culminates in high concentration NaTFSI in ADN being able to reversibly intercalate Na3V2(PO4)2F3 (NVPF) cathodes in SIB half-cells for multiple cycles. The knowledge gained from exploring oxidatively stable cathode and electrolyte materials can be used in tandem for the development of a longer lifetime, more oxidatively stable, NaOB in the future. / Thesis / Doctor of Philosophy (PhD) / The continued development of rechargeable batteries is paramount in reducing the world’s reliance on fossil fuels, as they allow for the storage of electrical energy produced by renewable sources. This work primarily examines sodium-based batteries systems, such as the sodium-oxygen battery (NaOB) and sodium-ion battery (SIB), which are possible alternatives to the currently used lithium-ion battery (LIB) system. In order to produce energy, NaOBs produce sodium superoxide (NaO2) during the discharge process, which is formed on the carbon cathode. However, NaO2 is inherently unstable to carbon materials, causing degradation of the battery overtime. Ti4O7 is investigated as a stable coating material in NaOBs, used to coat the carbon cathode to make the system more stable to NaO2 degradation. The degradation processes in NaOBs are characterized by solid state nuclear magnetic resonance (ssNMR) spectroscopy, which uses strong superconducting magnets to probe the magnetic properties of, and consequently identify, the chemical species formed within the battery. It is found that the addition of the Ti4O7 coating inhibits NaO2 degradation, producing longer lifetime NaOBs. Subsequently, both Li-bis(trifluoromethansulfonyl)imide (LiTFSI), and NaTFSI, in adiponitrile (ADN) electrolytes are examined for their use in LIBs and SIBs, respectively. Electrolytes facilitate stable ion transport within the cell, and ADN electrolytes specifically allow for the use of higher voltage cathode materials, which can result in a higher energy density battery. The transport properties of LiTFSI in ADN electrolytes are studied by a pulsed-field gradient (PFG) NMR technique, that allows for the measurement of the rate of ion transport in the electrolyte. It is found that the mechanism of ion transport significantly depends on electrolyte concentration, which suggests significant changes to the electrolyte solution structure at high concentration. The electrochemical ramifications of this are studied for the NaTFSI in ADN electrolyte in SIBs. It is found that the electrolyte becomes substantially more stable at high concentrations, leading to more favourable charging and discharging behaviours when tested in SIBs. The work presented in this thesis illustrates the development of more stable, longer lifetime, batteries over a number of cell chemistries, using a variety of NMR and electrochemical characterization techniques.

The research described here encompasses several different aspects of lithium ion battery operation including deep eutectic electrolytes, manganese trapping evaluation, silicon monoxide anodes, and in-situ NMR development under both static and spinning conditions. Individually, the results of these investigations as contained within the corresponding chapters contribute valuable insight. Collectively, they represent a snapshot into the numerous different ways in which nuclear magnetic resonance spectroscopy is applicable to lithium ion battery characterization. For instance, the deep eutectic electrolytes thus studied were amenable to diffusion coefficient characterization via the 1H, 7Li and 19F nuclei. This provided dynamical information on the anion, cation and neutral component and lent itself well towards parameterization of molecular dynamics simulations. The results thus obtained were useful in describing this relatively understudied class of electrolytes. Another example is that of the evaluation of manganese trapping. In this context 7Li NMR measurements were used to investigate the competitive inhibition of manganese trapping in crown ethers by lithium. Candidate crown ethers were thus evaluated for their ability to trap Mn2+ and Mn3+ in a lithium rich environment. Given the detrimental effects that manganese dissolution from cathode materials has on cycle life performance, the NMR enabled assessment of the appropriate chelating agents had identifiable importance. Additionally described was the progress made with silicon monoxide anodes supported on cellulosic substrates. The high active material loadings achieved, while also intriguing from a performance perspective, enabled 29Si MAS-NMR and 7Li static in-situ NMR measurements. For the in-situ measurements in particular, a novel cell design was constructed to utilize the advantages of a cellulosic substrate in this context. This has also enabled preliminary work on a spinning in-situ design. / Thesis / Doctor of Philosophy (PhD)