Fundamental studies of the structure-performance correlations and interfaces in hard carbon anodes for Na-ion batteries

Na-ion batteries (NIBs) have recently attracted extensive attention from the scientific community, as a cost effective and environmentally friendly alternative to Li-ion batteries (LIBs). Meanwhile, they also share the same working principle with LIBs, which makes the manufacturing of NIBs easy to scale-up to large volumes using the well-established LIBs production knowledge. However, the remaining challenges for NIBs commercialization are the lack of suitable materials for the negative electrode and a realistic focus on exploring electrolytes that bring these NIBs to market. Unfortunately, graphite, which is the most commonly used anode material in LIBs, shows poor electrochemical performance in NIBs. Hard carbon (non-graphizatible carbon), due to its relatively low cost and good electrochemical performance, is the most promising anode material for NIBs. Due to the structural complexity of hard carbons, understanding the correlation between carbon structure and the Na-ion storage mechanism is still a challenge to be overcome for commercialization of hard carbons as anodes in NIBs. There have been reports regarding the Na-ion storage mechanism in hard carbon anodes in NIBs, however discrepancies still exist. Herein, this thesis addresses two main topics. The first focuses on understanding the structure-performance correlations of Na-ion in hard carbons and improving the performance of hard carbon anodes. For this purpose, a series of hard carbons with tuned structure was synthesized by changing the carbonization temperature to vary systematically the porosity, number of defects, and graphitic structure. The microstructure of hard carbon and sodium storage behavior was demonstrated with X-ray and neutron scattering, Raman spectroscopy, transmission electron microscopy (TEM) and corroborated with density functional theory (DFT) calculations. Additionally, in-situ electrochemical dilatometry was also used to examine electrode expansion during cycling; to our knowledge, this is the first time that this procedure has been extended to sodium ion storage system investigations in hard carbons. Combined experimental studies and theoretical calculations reveal that it is the Na-ion storage at defect sites and intercalation in expanded graphene layers that corresponds to the slope capacity, while pore filling is responsible for the low voltage plateau region. It shows that hierarchically structured porous materials with partially large closed (internal) pores could act as active site for electrochemical storage and lead to reversible redox capacity. Therefore, in this thesis, a simple pore forming technique known as soft templating method is applied to synthesize mesoporous carbon with large closed pores to investigate the effect of closed mesopores and the results are compared with the microporous hard carbons. Here, the electrochemical these 7 findings are of interest to the battery community, as they are important for the design of future electrode materials with high capacity and therefore building better batteries. In order to develop high performance anode electrodes, a more integrated and holistic approach to the cell components is required. It should be noted that the performance of anode materials is influenced by the application of electrolytes and counter electrode; therefore, all components need to be investigated simultaneously. It is of crucial importance to understand and eventually control electrode interface and electrolyte chemistry, because the choice of electrolyte and the chemistry of the electrode interface has an important role on the energy density, cycle life, storage performance and reversible capacity of active materials. The second focus topic of this thesis is to study the surface chemistry of the anode electrode and electrolyte interface, which is another key consideration for the development of anode materials. The most commonly used Na salts, namely NaClO4 and NaPF6, were compared in EC: DMC and diglyme solvents. The vital role of the salt anion in the process of electrolyte decomposition at the sodium metal were further demonstrated. Comparison of half-cell configuration with sodium metal and full cell with NVPF/C cathode showed that employing metallic sodium anodes has critical consequences for the long-term cycling performance of batteries.Open Acces

Operando visualisation of battery chemistry in a sodium-ion battery by 23Na magnetic resonance imaging

© 2020, The Author(s). Sodium-ion batteries are a promising battery technology for their cost and sustainability. This has led to increasing interest in the development of new sodium-ion batteries and new analytical methods to non-invasively, directly visualise battery chemistry. Here we report operando 1H and 23Na nuclear magnetic resonance spectroscopy and imaging experiments to observe the speciation and distribution of sodium in the electrode and electrolyte during sodiation and desodiation of hard carbon in a sodium metal cell and a sodium-ion full-cell configuration. The evolution of the hard carbon sodiation and subsequent formation and evolution of sodium dendrites, upon over-sodiation of the hard carbon, are observed and mapped by 23Na nuclear magnetic resonance spectroscopy and imaging, and their three-dimensional microstructure visualised by 1H magnetic resonance imaging. We also observe, for the first time, the formation of metallic sodium species on hard carbon upon first charge (formation) in a full-cell configuration

The sustainable materials roadmap

Over the past 150 years, our ability to produce and transform engineered materials has been responsible for our current high standards of living, especially in developed economies. However, we must carefully think of the effects our addiction to creating and using materials at this fast rate will have on the future generations. The way we currently make and use materials detrimentally affects the planet Earth, creating many severe environmental problems. It affects the next generations by putting in danger the future of the economy, energy, and climate. We are at the point where something must drastically change, and it must change now. We must create more sustainable materials alternatives using natural raw materials and inspiration from nature while making sure not to deplete important resources, i.e. in competition with the food chain supply. We must use less materials, eliminate the use of toxic materials and create a circular materials economy where reuse and recycle are priorities. We must develop sustainable methods for materials recycling and encourage design for disassembly. We must look across the whole materials life cycle from raw resources till end of life and apply thorough life cycle assessments (LCAs) based on reliable and relevant data to quantify sustainability. We need to seriously start thinking of where our future materials will come from and how could we track them, given that we are confronted with resource scarcity and geographical constrains. This is particularly important for the development of new and sustainable energy technologies, key to our transition to net zero. Currently 'critical materials' are central components of sustainable energy systems because they are the best performing. A few examples include the permanent magnets based on rare earth metals (Dy, Nd, Pr) used in wind turbines, Li and Co in Li-ion batteries, Pt and Ir in fuel cells and electrolysers, Si in solar cells just to mention a few. These materials are classified as 'critical' by the European Union and Department of Energy. Except in sustainable energy, materials are also key components in packaging, construction, and textile industry along with many other industrial sectors. This roadmap authored by prominent researchers working across disciplines in the very important field of sustainable materials is intended to highlight the outstanding issues that must be addressed and provide an insight into the pathways towards solving them adopted by the sustainable materials community. In compiling this roadmap, we hope to aid the development of the wider sustainable materials research community, providing a guide for academia, industry, government, and funding agencies in this critically important and rapidly developing research space which is key to future sustainability.journal articl

2021 roadmap for sodium-ion batteries

Abstract: Increasing concerns regarding the sustainability of lithium sources, due to their limited availability and consequent expected price increase, have raised awareness of the importance of developing alternative energy-storage candidates that can sustain the ever-growing energy demand. Furthermore, limitations on the availability of the transition metals used in the manufacturing of cathode materials, together with questionable mining practices, are driving development towards more sustainable elements. Given the uniformly high abundance and cost-effectiveness of sodium, as well as its very suitable redox potential (close to that of lithium), sodium-ion battery technology offers tremendous potential to be a counterpart to lithium-ion batteries (LIBs) in different application scenarios, such as stationary energy storage and low-cost vehicles. This potential is reflected by the major investments that are being made by industry in a wide variety of markets and in diverse material combinations. Despite the associated advantages of being a drop-in replacement for LIBs, there are remarkable differences in the physicochemical properties between sodium and lithium that give rise to different behaviours, for example, different coordination preferences in compounds, desolvation energies, or solubility of the solid–electrolyte interphase inorganic salt components. This demands a more detailed study of the underlying physical and chemical processes occurring in sodium-ion batteries and allows great scope for groundbreaking advances in the field, from lab-scale to scale-up. This roadmap provides an extensive review by experts in academia and industry of the current state of the art in 2021 and the different research directions and strategies currently underway to improve the performance of sodium-ion batteries. The aim is to provide an opinion with respect to the current challenges and opportunities, from the fundamental properties to the practical applications of this technology

Investigation of tunable wetting properties of modified natural mineral powders = Modifiye edilmiş doğal mineral tozların ayarlanabilir ıslanma özelliklerinin incelenmesi

MODİFİYE EDİLMİŞ DOĞAL MİNERAL TOZLARIN AYARLANABİLİR ISLANMA ÖZELLİKLERİNİN İNCELENMESİ ÖZET Bu tezde doğal mineral tozlarından (diatomit ve talk) su tutmayan yüzeylerin hazırlanması için uygulanabilir yöntemler sunulmuştur. Yüzey aşılaması için farklı silan çeşitleri kullanılmış ve en iyi sonuç mono klorosilan ile alınmıştır. Yüzey modifikasyonu yapılmış diatomitlerin su hassasiyet analizleri, parçacık yüzeyi üzerindeki ayarlanabilir ıslanma özelliklerinin incelenmesi için önemli bir çalışmadır. Mineral toz üzerine yapılan aşılanma sonrasında yüzeydeki kovalent bağlanma X-ışını fotoelektron spektroskopisi (XPS) ile teyit edilmiştir. Termogravimetrik analiz, azot adsorpsiyon izotermleri ve temas açısı ölçümleri, aşılama yoğunluğu ve hidrofobik partiküllerin diğer temel özelliklerinin değerlendirilmesinde kullanılmıştır. Diatomit minerali yüzey modifikasyonunda etkili bir strateji geliştirmek için prototip olarak seçilmiş ve yapılan çalışmalar suya karşı iki yönlü davranışta bulunan diğer bir doğal mineral olan talk üzerine uygulanmıştır. Bu tez çalışması uygun doğal minerallerden süperhidrofobik tozların üretilmesi için yeni bir yaklaşıma yol gösterici olmuştur

Characteristics of fired clay bricks with waste marble powder addition as building materials

Fired clay bricks lightened by adding up to 35 wt.\% waste marble powder have been produced by semidry pressing process. Chemical composition, phase identification, thermal behavior and microstructure of the raw materials were analyzed by XRF, XRD, TGA and SEM, respectively. The brick mixtures containing waste marble powder at different proportions were formed, dried and then fired at 950 and 1050 degrees C for 2 h. Properties such as drying and firing shrinkages, loss on ignition, bulk density, porosity, water absorption, compressive strength, thermal conductivity, microstructure and phase content of the fired brick samples were determined. It was found that the use of waste marble powder addition reduced the bulk density of the samples. It was observed that their porosity ratios up to about 40\% improved with increasing of waste marble powder addition up to 30 wt.\% for all samples, whereas their compressive strengths decreased until 8.2 MPa. However, their strengths were enough according to the values required by the standards. Thermal conductivity of the samples decreased from 0.97 to 0.40 W/mK. Increasing of the firing temperature also affected their mechanical and physical properties. This study showed that the waste marble powders could be used as a pore maker and contributing to the formation of crystalline phases in brick production at certain ratios. (C) 2015 Elsevier Ltd. All rights reserved