Abstract: TEM is one of the most powerful technologies for material research. In-situ TEM is a TEM technique that allows us to study samples in real-time. Researchers can focus on one area and change the conditions under the electron beam to acquire much more data from the material than conventional TEM techniques. In this research, we use the in-situ TEM technique to observe the rechargeable aqueous zinc-ion batteries which have been considered as a promising candidate for next-generation batteries. We established the platform for the aqueous battery system and studied the charge and discharge processes for both cathode and anode materials in rechargeable aqueous zinc-ion batteries for the first time. Besides, we also combined low-dose TEM techniques to observe the HRTEM images of the electrode materials to probe the change on the surface of the cathode materials and the mechanism of dendrite growth in rechargeable aqueous zinc-ion batteries.

The need for renewable energy is increasing as a result of global warming and other environmental challenges. Renewable energy systems are intermittent in nature and require energy storage solutions. Lithium-ion batteries are the first choice for storing electrical energy due to their high energy density, long cycle life, and small size. However, their widespread use in grid-scale applications is limited by high cost, low lithium resources, and security issues. Among the various options, the rechargeable zinc ion water battery has the advantages of high economic efficiency, high safety, and environmental friendliness, and there are great expectations for energy storage on a network scale. Inspired by these benefits, people have put a lot of effort into developing and manufacturing zinc-based energy storage devices. As the main component of zinc ion battery, the cathode material plays an important role in the storage / release of zinc ions during insertion and extraction. Vanadium-based materials are attracting attention due to their various oxidation states, diverse structures, and abundant natural resources. However, the details of suitable cathode materials and Zn2+ storage mechanism for rechargeable zinc ion battery are not yet fully understood. In this thesis, firstly, the prepared zinc pyrovanadate delivers good zinc ion storage properties owing to its open-framework crystal structure and multiple oxidation states. Mechanistic details of the Zn-storage mechanism in zinc pyrovanadate were also elucidated. Then, a calcium vanadium oxide bronze with expanding cavity size, smaller molecular weight, and higher electrical conductivity are proposed to deeply understand the impact of the crystal structure on battery performance. To improve the stability of the cathode in rechargeable zinc ion battery, an artificial solid electrolyte interphase strategy has been proposed by inducing an ultrathin HfO2 layer via the Atomic layer deposition method, which effectively alleviates the dissolution of active material. Finally, a nitrogen-doped 3D laser scribed graphene with a large surface area and uniform distribution of nucleation sites has been used as the interlayer to control Zn nucleation behavior and suppress Zn dendrite growth, which brings new possibilities for the practical rechargeable zinc ion battery.

Recently, 3D printing has received increasing attention for the fabrication and assembly of electrodes for batteries due to the freedom of creating structures in any shape or size, porosity, flexibility, stretchability, and chemistry. Particularly, zinc ion batteries (ZIBs) are favored due to high safety, cheap materials cost, and high volumetric capacity (5,849 mAh/cm3), however, rapid evaporation of Zn due to low melting temperature has limited its 3D printability via conventional laser-based additive manufacturing technique. Here, we develop a printable ink for the fabrication of flexible and 3D printed Zn anode with varied surface areas using the direct ink writing (DIW) method. Our 3D printed porous and high surface area Zn anode structures effectively suppressed the dendrite growth while providing high Zn ion diffusion towards the cathode to significantly enhance the performance of ZIB. By varying filament distancing and path, we 3D printed zinc anode structures with different active surface areas, surface area to volume ratio, porosity, flexible and multiple layer structures that can be incorporated on any device. Carbon in the composite improved conductivity, and mechanical stability of 3D printed zinc anode. Our 3D printed composite anodes allowed flexible designing of batteries surpassing conventional battery designs such as coin cells or pouch cells and can be used to design printed energy storage systems.

<p> <p>&nbsp / </p> </p> <p align="left">Retinoblastoma binding protein 6 (RBBP6) is a 250 kDa human splicing-associated protein that is also known to interact with tumour suppressor proteins p53 and pRb and to mediate ubiquitination of p53 via its interaction with Hdm2. RBBP6 is highly up regulated in oesophageal cancer, and has been shown to be a promising target for immunotherapy against the disease. RBBP6 is also known to play a role in mRNA splicing, cell cycle control and apoptosis.</p>

<p> <p>&nbsp / </p> </p> <p align="left">Retinoblastoma binding protein 6 (RBBP6) is a 250 kDa human splicing-associated protein that is also known to interact with tumour suppressor proteins p53 and pRb and to mediate ubiquitination of p53 via its interaction with Hdm2. RBBP6 is highly up regulated in oesophageal cancer, and has been shown to be a promising target for immunotherapy against the disease. RBBP6 is also known to play a role in mRNA splicing, cell cycle control and apoptosis.</p>

Magister Scientiae - MSc / Retinoblastoma binding prot ein 6 (RBBP6) is a 250 kDa human splicing-associated protein that is also known to interact with tumour suppresso r proteins p53 and pRb and to mediate ubiquitination of p53 via its intera ction with Hdm2. RBBP6 is highly up regulated in oesophageal cancer, and has been shown to be a promising target for immunotherapy against the disease. RBBP6 is also known to play a role in mRNA splicing, cell cycle control and apoptosis. / South Africa

The growing renewable energy consumption has stimulated the rapid development of diverse energy storage systems (ESSs) in our electronic society. As a successful representative, lithium-ion batteries (LIBs) play a vital role in meeting today's energy storage demand. However, LIBs are plagued by intrinsic unsafety and detrimental environmental contamination. In this respect, rechargeable aqueous zinc-ion batteries (ZIBs) and supercapacitors (SCs) as potential alternatives have attracted considerable attention due to their characteristics such as innate safety, environmental friendliness, cost-effectiveness, competitive gravimetric energy density, and loose fabrication process. Inspired by these merits, massive efforts have been devoted to designing and exploring high-performance aqueous Zn-based energy storage devices. The key for advanced Zn-based energy storage devices is to exploit high-performance cathode materials. Covalent organic frameworks (COFs) are an emerging class of organic polymer with periodic skeletons showing attractive properties in structural tunability, well-defined porosity, functional versatility, and high chemical stability. The distinguishing features of COFs make them promising electrode materials for electrochemical energy storage applications. However, the electrochemical storage capability and charge storage mechanism of COF materials have been rarely investigated, and their potential applications have not been evaluated yet so far. In this thesis, COFs are proposed as cathode materials for rechargeable aqueous Zn-ion energy storage. Initially, a new phenanthroline COF (PA-COF) material was synthesized and used as an electrode for Zn-ion supercapatteries (ZISs) for the first time. The as-synthesized PA-COF shows abundant nucleophilic sites and suitable pore structure, demonstrating the efficient storage capability of Zn2+ and H+. Further, hexaazatriphenylene-based COF (HA-COF) material with and without precisely grafted quinone functional groups has been proposed to understand structure-activity relationships. In this chapter, the influence of quinone groups on the electrochemical performance of HA-COF has been systematically studied, disclosing an enhancement coordination capability of Zn ions against protons in the quinone-functionalized HA-COF. Lastly, we synthesized a radical benzobisthiazole COF (BBT-COF) and deeply investigated the electrochemical performance. As expected, this COF electrode shows an ultrastable cycling performance and demonstrates a radical reaction pathway.

To combat climate change, governments have pledged to become more dependent on renewable electricity production. However, the intermittency of renewable power generation requires modern grid-scale energy storage systems, which are currently being explored with lithium-ion batteries (LIBs). However, this technology faces significant safety, social, and financial concerns. As an alternative chemistry, aqueous zinc-ion batteries (ZIBs) show much promise for grid-scale energy storage with their safe, inexpensive design. Major bottlenecks of ZIB performance include their limited practical specific capacity, and low capacity retention. Organic cathodes, specifically the use of redox-active quinone molecules, are an upcoming contender for customizable and simple ZIB cathode design that can be optimized for good performance. However, these cathodes are often plagued by capacity fade caused by quinone dissolution and inactivation. Grafting these quinone molecules to the supporting conductive carbon substrate via covalent bonding had been previously explored in LIB and supercapacitor electrode design as an effective way to mitigate capacity fade. In this work, the development of aqueous ZIB cathodes with 9,10-phenanthrenequinone (PQ) molecules grafted to carbon black substrates was done via a facile in-situ generated diazonium salt reaction synthesis technique. Electrochemical and material analysis confirmed the presence of covalent grafting. This grafting modification was compared to the standard cathode design of adsorbing the quinones on carbon substrates like Ketjenblack (KB) and Vulcan Black (VB). Battery cycling tests were performed and the grafted PQ-KB cells achieved a discharge capacity of 99 mAh g-1 after 1000 charge-discharge cycles with accelerated testing at a charge/discharge rate of 200 mA g-1 and 10 mA g-1. These cells maintained 67% of their initial capacity compared to the 55% for the adsorbed PQ on KB cells. This approach highlights the promise of grafting organic material as a technique to support organic cathodes for next-generation ZIB design. / Thesis / Master of Applied Science (MASc) / Renewable electricity production is necessary to mitigate climate change but the production of electricity through many renewables like wind and solar can vary significantly on any given day. Lithium-ion batteries are being explored for storing electricity for use on the grid, but they have many downsides including being flammable and expensive. Zinc-ion batteries are non-flammable and cost-effective alternatives to lithium-ion batteries. They are currently not as widely used as lithium-ion batteries because of their poorer performance. However, for storing electricity for power grids, with the correct selection of materials to make the battery, zinc-ion batteries can perform well enough to compete with lithium-ion batteries. This work investigates a modification of a material used in zinc-ion batteries, that allows the battery to maintain a higher capacity after many charge and discharge cycles.

With the rapid growth of the world population and the process of industrialization of modern society, the demand for energy continues to rise sharply. There is a pessimistic prediction that a peak of consumption primarily fossil fuels will happen in the 2020s to 2030s, hence it is urgent to develop alternative renewable clean energy sources before this coming energy crisis. But the availability of renewable clean energy always is discontinuous, uncontrollable, and unstable. Besides, the generated renewable energy cannot be used directly. Therefore, an energy storage system is urgently needed as the medium to harvest and store the energy generated from the intermittent renewable resource, and also to regulate the electricity output, and improve the tolerance ability of the power grid to renewable energy. Rechargeable aqueous zinc-ion battery, especially those that use mild electrolytes, is drawing more and more attention in the past decades and is regarded as the most promising candidate for large-scale energy storage systems. Compared with the widely used lithium-ion battery which dominated the commercial energy market now, the aqueous zinc-ion battery holds the merits of high theoretical capacity (820 mAh/g gravimetric capacity and 5855 mAh/m3 volumetric capacity), low electrochemical potential (-0.763 V vs. SHE) and high energy density due to the two-electron redox reaction, high abundance in the earth crust and high mass production, low toxicity, and environmental benignity, and the most valuable advantage intrinsic safety in aqueous electrolyte. In this dissertation, the first part focuses on the preliminary application of an aqueous zinc-ion battery. One kind of planar on-chip aqueous zinc-ion micro-battery with high-rate performance was designed and fabricated. The PEDOT and MnO2 cathode can suppress the dissolution of electrode material which can highly improve the cycling performance of the micro-battery. The as-prepared micro-battery displays a high specific capacity of 25.8 μAh/cm2 after 25 activation cycles at a current density of 1 mA/cm2. A reversible specific capacity of 6.2 μAh/cm2 is achieved after 200 cycles, with 55.4 % of the initial discharge capacity retention. To improve the cycling performance of the aqueous zinc-ion battery, the second part of this thesis is preparing a highly enhanced reversibility Zn anode by in-situ texturing. The crystal plane (002)-textured Zn anode with an ultrathin passivation layer suppressed the Zn corrosion and enhanced the full battery performance. Based on these merits, the cycling stability of the Zn anode is enhanced from 791 hours to more than 1500 hours. The coulombic efficiency (CE) of a Zn||Ti asymmetric cell is greater than 90% over 500-hour cycles. For the Zn||MnO2 full cell, the addition of H3PO4 into the electrolyte improves both the rate capability and cycling stability of Zn||MnO2 cells. More importantly, a highly reversible Zn||O2 full cell is demonstrated at a large depth of discharge of Zn (DODZn > 10%), projecting the lower bounds of the cell-level specific energy of lithium-ion batteries.:Abstract I Kurzfassung III List of Abbreviations IX Chapter 1 Background and motivation 1 1.1 Research motivation 1 1.2 Aim of this dissertation 2 1.3 Dissertation structure 3 Chapter 2 Introduction of aqueous zinc-ion battery and anode protection strategies 5 2.1 Introduction of aqueous zinc-ion battery 5 2.2 The challenges of zinc anode 8 2.2.1 Dendrites and protrusion 9 2.2.2 Hydrogen evolution reaction 10 2.2.3 Passivation layer 10 2.3 The strategies of zinc anode protection 11 2.3.1 Surface engineering 11 2.3.2 Electrolyte modification 15 2.3.3 3D structural skeleton and alloy strategies 22 Chapter 3 Experiment characterizations and calculations 25 3.1 Electrochemical methods 25 3.1.1 Chronoamperometry 25 3.1.2 Chronopotentiometry 26 3.1.3 Cyclic voltammetry 27 3.1.4 Galvanostatic charge/discharge 28 3.1.5 Electrochemical impedance spectroscopy 29 3.1.6 Tafel measurement 30 3.2 Characterization methods 31 3.2.1 X-ray diffraction 31 3.2.2 Scanning electron microscope 32 3.2.3 X-ray photoelectron spectroscopy 32 3.2.4 Raman spectroscopy 33 3.3 Experimental calculations 34 3.3.1 b value calculation 34 3.3.2 CE calculation 34 3.3.3 RTC calculation 35 3.3.4 DFT calculation 36 3.3.5 DOD calculation 37 3.3.6 Corrosion rate calculation 38 Chapter 4 A planar on-chip aqueous zinc-ion micro-battery with high-rate performance 41 4.1 Introduction 41 4.2 Experimental section 43 4.2.1 Interdigitated electrodes 43 4.2.2 Preparation of micro-battery 44 4.2.3 Microstructural properties characterization 45 4.2.4 Electrochemical characterization 45 4.3 Results and discussion 46 4.3.1 Characterization of micro-battery 46 4.3.2 Electrochemical performance measurement 49 4.4 Conclusions 56 Chapter 5 Highly enhanced reversibility of a Zn anode by in-situ texturing 57 5.1 Introduction 57 5.2 Experimental section 63 5.2.1 Preparation of the textured Zn anode 63 5.2.2 Synthesis of cathode materials 63 5.2.3 Electrochemical and material characterizations 64 5.3 Results and discussions 64 5.3.1 Nonuniform Zn deposition on an epitaxial substrate 65 5.3.2 In-situ texturing and SEI formation during the cycling 72 5.3.3 Full-cell performance 77 5.4 Conclusions 81 Chapter 6 Summary and outlook 83 6.1 Summary 83 6.2 Outlook 84 References： 87 Acknowledgment 99 Publications 101 Curriculum Vitae 103 Selbstständigkeitserklärung 105

Growth of dendrites, limited coulombic efficiency (CE), and the lack of high-voltage electrolytes restrict the commercialization of zinc batteries and capacitors. These issues are resolved by a new electrolyte, based on the zinc(II)–betaine complex [Zn(bet)2][NTf2]2. Solutions in acetonitrile (AN) avoid dendrite formation. A Zn||Zn cell operates stably over 10 110 h (5055 cycles) at 0.2 mA cm−2 or 110 h at 50 mA cm−2, and has an area capacity of 113 mAh cm−2 at 80% depth of discharge. A zinc–graphite battery performs at 2.6 V with a midpoint discharge-voltage of 2.4 V. The capacity-retention at 3 A g−1 (150 C) is 97% after 1000 cycles and 68% after 10 000 cycles. The charge/discharge time is about 24 s at 3.0 A g−1 with an energy density of 49 Wh kg−1 at a power density of 6864 W kg−1 based on the cathode. A zinc||activated-carbon ion-capacitor (coin cell) exhibits an operating-voltage window of 2.5 V, an energy density of 96 Wh kg−1 with a power density of 610 W kg−1 at 0.5 A g−1. At 12 A g−1, 36 Wh kg−1, and 13 600 W kg−1 are achieved with 90% capacity-retention and an average CE of 96% over 10 000 cycles. Quantum-chemical methods and vibrational spectroscopy reveal [Zn(bet)2(AN)2]2+ as the dominant complex in the electrolyte.