Teoretična študija procesov na medfazni površini med elektrolitom in elektrodo v magnezijevih akumulatorjih

The research of battery materials is becoming an increasingly important scientific field due to the growing demand for the electric energy. Magnesium batteries represent one of the promising multivalent battery architectures. To optimize the Mg battery for commercial use, a potential dependent interfacial processes should be understood. Yet, due to great complexity of the interface, there is a lack of theoretical approaches that would enable facing this challenge. A computationally affordable, fully unparameterized, and widely applicable theoretical methodology based on density functional theory and grand canonical approach is extended to investigate the electrochemical stability of Mg-metal/electrolyte interfaces, and to predict their thermodynamic behaviour. The calculated Mg$^{2+}$/Mg$^{0}$ redox potential differs by less than 3% from the experimental value, demonstrating that the methodology provides physically meaningful and reliable results. The methodology is used to study two different Mg electrolytes, based on ethylene carbonate (EC) and dimethylether (DME) solvents. Experiments have shown that the Mg battery fails with the EC electrolyte, while it works fairly well with the DME electrolyte. Our results successfully elucidate atomistic mechanisms that explain the experimental observations. Moreover, our theoretical insights provides valuable guidelines for designing electrolytes with favourable properties. To broaden the theoretical understanding from atomistic to meso-scale, the dependence of morphology evolution on surface orientation is investigated. We found that the surface with the highest area fraction is not necessarily the one with the lowest surface energy, which is usually the only one considered in literature. Morphology evolution should thus be studied on all commonly present surface orientations. Our results show that diffusion of Mg atoms on the Mg anode is slow on some commonly present Mg surface orientations, indicating that Mg could exhibit uneven deposition.Zaradi naraščajoče potrebe po električni energiji postaja raziskovanje baterijskih materialov vedno bolj pomembno znanstveno področje. Magnezijevi akumulatorji predstavljajo obetaven sistem na področju multivalentnih akumulatorjev, vendar je za njihovo optimizacijo in komercializacijo potrebno razumeti procese na medfazni površini elektroda/elektrolit v odvisnosti od napetosti. Kompleksnost teh procesov je privedla v pomanjkanje teoretičnih pristopov, ki bi omogočili njihovo razumevanje. Računsko dostopno, popolnoma neparametrizirano in široko uporabno teoretično metodologijo, ki temelji na teoriji gostotnega funkcionala in velekanonskem ansamblu, smo razširili z namenom raziskovanja elektrokemijske stabilnosti in termodinamskega obnašanja medfazne površine med elektrolitom in Mg elektrodo. Izračunani Mg$^{2+}$/Mg$^0$ redoks potentical se razlikuje za manj kot 3% od eksperimentalne vrednosti, kar dokazuje, da metodologija zagotavlja fizikalno smiselne in zanesljive rezultate. Metodologija je uporabljena za študij dveh različnih elektrolitov baziranih na etilen karbonatu (EC) in dimetil etru (DME). Eksperimenti so pokazali, da Mg akumulator z EC elektrolitom ne deluje, med tem ko z DME elektrolitom deluje dokaj dobro. Naši rezultati pojasnijo atomistične mehanizme, ki teoretično razložijo eksperimentalno opaženo razliko v obnašanju sistemov. Pridobljeni teoretični vpogledi prispevajo tudi smernice za načrtovanje elektrolitov z optimiziranimi lastnostmi. Da bi razširili razumevanje iz atomistične na mezo-skalo, smo raziskali spreminjanje morfologije različnih Mg površin. Pokazali smo, da najbolj zastopana površina ni nujno najbolj stabilna, čeprav je ponavadi edina obravnavana v literaturi. Spreminjanje morfologije mora zato biti raziskano na vseh pogosto prisotnih orientacijah površine. Naši rezultati so pokazali, da je difuzija Mg atomov na Mg anodi počasna na nekaterih pogosto prisotnih orientacijah površine, kar kaže na možnost neenakomernega odlaganja magnezija

Touch in sculpture and in society

Why to use touch? Because it is one of our senses. As such, it contributes to the holistic perception and optimal development of intellectual, emotional and creative skills. More important question is: why not to use touch? What and when happened that we decided to systematically repress and neglect primal sense of touch, which is important and responsible for the formation and development of a series of intellectual and emotional concepts, not only in the domain of art, but at every aspect of our life? Scale and complexity of the issue revealed themselves in the search for the answer. Physiology of perception, history of art, sculpture, sociology, anthropology and psychology began to intertwine with each other and complement each other. In the first chapter of master the thesis I introduce the process of perception that is unique for each individual and which is imperatively subjected to society, culture and education. In the second chapter I present the development of sculpture, from Egypt until today, and its relation to social development. The entanglement of sculpture, history, anthropology and sociology is presented according to the style of specific period and not chronologically. In subsequent two chapters I demonstrate the use of touch in art through my own artistic expression and by practical work in classroom. I introduce, study and analyze some of the possibilities of including touch in art as well as ways in which we can encourage the use of touch in schools. This would serve as a tool for relaxation, for development of imagination and for raising awareness of the importance of using all our senses

Morphology evolution and dendrite growth in Li- and Mg-metal batteries: A potential dependent thermodynamic and kinetic multiscale ab initio study

International audienc

Modeling interfacial electrochemistry: concepts and tools

International audienc

Electrolyte Reactivity in the Double Layer in Mg Batteries: An Interface Potential-Dependent DFT Study

International audienceThe electrochemical degradation of two solvent-based electrolytes for Mg-metal batteries is investigated through a Grand canonical DFT approach. Both electrolytes are highly reactive in the double layer region where the solvated species have no direct contact with the Mg-surface, hence emphasising that surface reactions are not the only phenomena responsible for electrolyte degradation. Applied to dimethoxyethane (DME) and ethylene carbonate (EC), the present methodology shows that both solvents should thermodynamically decompose in the double layer prior to the Mg 2+ /Mg 0 reduction, leading to electrochemically inactive reaction products. Based on thermodynamic considerations, Mg 0 deposition should not be possible, which is not in agreement with experiments, at least for DME-based electrolytes. This apparent contradiction is here addressed through the rationalization of the electrochemical mechanism underlying solvent electro-activation. An extended operation potential window (OPW) is defined, in which the Mg 2+ /Mg 0 reduction can compete with electrolyte decomposition, thus enabling battery operation beyond the solvated species thermodynamic stability. The chemical study of the degradation products is in excellent agreement with experiments and it offer rationale for the Mg-battery failure in EC electrolyte and 2 capacity fade in DME electrolyte. Potential-dependent approach proposed herein is thus able to successfully tackle the challenging problem of interface electrochemistry. Being fully transferable to any other electrochemical systems, this methodology should provide rational guidelines for the development of viable electrolytes for multivalent batteries, and more generally, energy conversion and storage devices