Materials with three-dimensional (3D) hierarchical architectures exhibit attractive mechanical, energy conversion and thermal radiative cooling properties not found in their bulk counterparts. However, implementation of hierarchically structured 3D transition metal dichalcogenides (TMDs) is widely deemed not possible, by the lack of manufacturing solutions that overcome the hierarchy, quality, and scalability dilemma. Here we report dewetting-driven destabilization (DDD) process that enables simple, template-free, high throughput printing of 3D architected MoS2 Foam with hierarchy spanning seven orders of magnitude — from angstroms to centimeters. Although extremely simple, our manufacturing process combines electrohydrodynamic printing with dewetting-induced-patterning. This technique can be applied to a range of dissimilar twodimensional (2D) layered materials, including Ti3C2Tx MXene and reduced graphene oxide (rGO). The deposited MoS2 Foam achieves amplification of resilience and conductivity. It constructs hierarchically porous and spatially interconnected networks for both ions and electrons transfer. We further demonstrate the 3D MoS2 architected foam as high-performance anodes with an otherwise unachievable combination of a 99% battery yield, a dynamic recovery (up to 85%) to withstand excessive volume expansion, a strain-induced reduction in diffusion barrier (0.2 eV), and improved electron transport abilities across the entire structure. The result is the high Li-ion charge storage capacity with robust cycling stability at a bulk scale (~3.5 mg/cm2) and under a high current density (10,000 mA/g). The outstanding electrochemical performance arises from the architected structure-induced pseudocapacitive energy storage mechanism based on the redox reaction of Mo, rather than the traditional conversion reaction. Notably, the performance achieved is on par with or surpasses state-of-the-art anodes made of black phosphorus composites, Si-graphene and mesoporous graphene particle anodes, while the technique offers an evaporation-like simplicity for industrial scalability. This work is foundational, and the developed DDD process opens a new sight to manufacture structurally robust, multifunctional hierarchical structures from 2D materials. Given the high adjustability of synthesis conditions and a wide variety of 2D materials, we anticipate previously unattainable possibilities in the energy storage, flexible electronics, catalysis, separation and drug delivery.

Lithium-rich layered transition metal oxide cathode, represented as the chemical formula of xLi₂MnO₃ · (1 - x)LiMO₂(M = Mn, Ni, Co) , retains immense interest as one of the most promising candidates for energy storage system ranging from mobile devices to electric vehicle applications (EV/HEV/PHEV). This battery type benefits from superior theoretical capacity (>250 mAhg^-1), high chemical potential (>4.6 V vs Li⁰), good thermal stability, high discharge capacity and lower cost compared with conventional cathodes (e.g. LiCoO₂, Li(Ni_1/3Mn_1/3Co_1/3)O₂ cathodes). However, there remain major barriers which still need to be improved in order to achieve a successful commercialization for large-scale devices or electric vehicle applications. The irreversible capacity loss of 40-100 mAhg^-1 during the initial electrochemical cycle and the battery fading phenomena (capacity fading/voltage decay) on further cycles are the major problems which have emerged. The Li⁺ ion extraction accompanied by oxygen release from the active material in the form of oxide known as lithia (Li₂O) along with the transition metal migration has been suggested as the dominant processes underlying the capacity fading mechanism. Those processes, in turn, cause a phase transition from a layered structure into a spinel within the electrode material. The interplay of the local atomic environments between Li₂MnO₃ (monoclinic, C2/m) and LiMO₂ (trigonal/hexagonal, R3m) holds the key to developing better cathodes with enhanced stability. In the present thesis, an in operando XAS study using a specially-designed cell of the graphene- coated Li(Li_0.2Mn_0.54Ni_0.13Co_0.13)O₂ cathode is employed to examine the chemical, electronic, and structural states of the transition metals (Mn, Co, and Ni) during electrochemical cycle(s). Precise oxidation states for the transition metals is evaluated by the combined analyses from the XANES and SQUID measurements. The K-edge XANES spectral shift is quantified to investigate the contribution to the charge compensation mechanism by the oxidation change. Absorption features in K-edge XANES are identified. These features describe the electronic state of the individual atoms in the cathode composite, as well as the local distortion from the octahedral structure of MO₆. The Fourier transform of EXAFS offers a satisfactory description of the local structure changes with the connection to the cation arrangement. The description is generally involved with the peak amplitude, position, shape changes (trend), and coordination numbers in the real space. Hence, similarities or discrepancies in the local atomic environments could be compared at different state of charge. Major structural parameters are deduced from the EXAFS fitting process. These parameters can be used to distinguish different atomic environments upon voltage bias levels or investigate the appearance of the Jahn-Teller effect. A new approach to understand the atomic environment upon charge-discharge is demonstrated, namely, a Continuous Cauchy Wavelet Transform (CCWT) which enables the visualization of the EXAFS spectra in three dimensions by decomposing the k-space and R-space (uncorrected for phase shift) signals. The wavelet transform analysis provides possible evidence of the precursor that leads to the spinel phase transition in this battery system.

Doctor of Philosophy / Department of Mechanical and Nuclear Engineering / Gurpreet Singh / Molecular precursor derived ceramics (also known as polymer-derived ceramics or PDCs) are high temperature glasses that have been studied for applications involving operation at elevated temperatures. Prepared from controlled thermal degradation of liquid-phase organosilicon precursors, these ceramics offer remarkable engineering properties such as resistance to crystallization up to 1400 °C, semiconductor behavior at high temperatures and intense photoluminescence. These properties are a direct result of their covalent bonded amorphous network and free (-sp2) carbon along with mixed Si/B/C/N/O bonds, which otherwise can not be obtained through conventional ceramic processing techniques. This thesis demonstrates synthesis of a unique core/shell type nanowire structure involving either siliconboroncarbonitride (SiBCN) or siliconoxycarbide (SiOC) as the shell with carbon nanotube (CNT) acting as the core. This was made possible by liquid phase functionalization of CNT surfaces with respective polymeric precursor (e.g., home-made boron-modified polyureamethylvinylsilazane for SiBCN/CNT and commercially obtained polysiloxane for SiOC/CNT), followed by controlled pyrolysis in inert conditions. This unique architecture has several benefits such as high temperature oxidation resistance (provided by the ceramic shell), improved electrical conductivity and mechanical toughness (attributed to the CNT core) that allowed us to explore its use in energy conversion and storage devices. The first application involved use of SiBCN/CNT composite as a high temperature radiation absorbant material for laser thermal calorimeter. SiBCN/CNT spray coatings on copper substrate were exposed to high energy laser beams (continuous wave at 10.6 μm, 2.5 kW CO2 laser, 10 seconds) and resulting change in its microstructure was studied ex-situ. With the aid of multiple techniques we ascertained the thermal damage resistance to be 15 kW/cm2 with optical absorbance exceeding 97 %. This represents one order of magnitude improvement over bare CNTs (1.4 kW/cm2) coatings and two orders of magnitude over the conventional carbon paint (0.1 kW/cm2) currently in use. The second application involved use of SiBCN/CNT and SiOC/CNT composite coatings as energy storage (anode) material in a Li-ion rechargeable battery. Anode coatings (~1mg/cm2) prepared using SiBCN/CNT synthesized at 1100 °C exhibited high reversible (useable) capacity of 412 mAh/g even after 30 cycles. Further improvement in reversible capacity was obtained for SiOC/CNT coatings with 686 mAh/g at 40 cycles and approximately 99.6 % cyclic efficiency. Further, post cycling imaging of dissembled cells indicated good mechanical stability of these anodes and formation of a stable passivating layer necessary for long term cycling of the cell. This improved performance was collectively attributed to the amorphous ceramic shell that offered Li storage sites and the CNT core that provided the required mechanical strength against volume changes associated with repeated Li-cycling. This novel approach for synthesis of PDC nanocomposites and its application based testing offers a starting point to carry out further research with a variety of PDC chemistries at both fundamental and applied levels.

Dans les batteries ion lithium, la présence d’électrolytes organiques volatiles et inflammables engendre des problèmes récurrents de sécurité. Une possible solution consiste à les remplacer par des sels fondus liquides à température ambiante, les liquides ioniques (LI), présentant une tension de vapeur négligeable et sont considérés comme flamme retardant. Leur utilisation avec des électrodes carbone (les plus usitées dans les batteries commerciales) nécessitent la présence d’un additif pour améliorer les performances des batteries.Le but de cette thèse était de déterminer le rôle de cet additif par des méthodes analytiques et de la modélisation. Tout d’abord, l’impact de cet additif sur la solvatation et la diffusion des sels de lithium a été étudié par RMN 2-D [NOE et HOESY {1H-7Li}, {1H-19F}, et la sphère de coordination du cation lithium a été simulée par dynamique moléculaire. Puis des études électrochimiques ont été développées notamment le cyclage galvanostatique à potentiel sélectionné et le cyclage voltamétrique afin de déterminer la capacité de la batterie et d’étudier les étapes d‘insertion du cation lithium au cours de la première étape de réduction. Cette étape a également été analysée par impédance électrochimique. En complément, une analyse par XPS (spectrométrie photoélectronique X) sur les électrodes post-mortem de piles arrêtées aux potentiels déterminés par impédance, a permis de caractériser les composés chimiques formés à la surface des électrodes au cours de la première réduction, mais également après plusieurs cycles de charge/décharge / In lithium ion batteries, the commercial organic electrolytes induce difficulties in the manufacturing and the use of the battery (volatile and flammable components). There are active research to eliminate these safety problems, one of the approach is the replacement of conventional battery electrolytes with room temperature ionic liquids (RTILs), which exhibit negligible vapor pressure, low flammability, high flash point. The use of ILs based electrolytes for carbon based electrodes requires presence of organic additive for improving the cyclic performance. The aim of this thesis was to determine the exact role of the organic additive through experimental and computer simulation methodologies. Its impact onto the solvation and transportation of lithium cation was investigated through {1H-7Li}, {1H-19F} NOE correlations (HOESY), and pulsed field gradient spin-echo (PGSE) NMR experiences and Molecular Dynamic simulation. The electrochemical studies were developed such as electrochemical window, galvanostatic cycling with potential limitation and cycling voltammetry showing the obtained capacity of the cell and [Li+] insertion stages during the first reduction step. Moreover, the electrochemical impedance spectroscopy (EIS) during the first reduction process, and XPS analysis of post mortem Gr electrodes stopped at chosen potential during the first reduction process, as well as, after the several charge/discharge cycles were used

Mgr. Martina Nádherná PhD. Thesis Applications of ionic liquids in electrolytes for amperometric gas sensors and Li-ion batteries SUMMARY The dissertation presents the results of preparation and characterisation of new aprotic electrolytes based on ionic liquids for the solid-state electrochemical gas sensors and for the electrochemical energy storage devices - secondary lithium-ion batteries. In the part dealing with the solid-state amperometric sensor for NO2 research was aimed at development of new solid electrolyte. This electrolyte is developed as a system of ionic liquid embedded in the structure of a polymer, when the ionic liquid joints the properties of a solvent and a dissolved salt. The electrolyte therefore does not contain any volatile component and is long-term chemically and electrochemically stable. Several series of electrolytes were prepared with different polymers or macromonomers and imidazolium-based ionic liquids. The composition, especially the polymer-IL ratio was optimized. The electrolytes were successfully tested in a solid-state NO2 sensor with a gold minigrid serving as the indicating electrode. The research included the determination of basic electrochemical parameters and study of the sensor behaviour under different conditions. The influence of atmosphere humidity,...

<div>Potassium-ion batteries (PIBs) recently emerged as a next-generation energy storage technology, utilizing abundant and inexpensive potassium as the charge carrier cation. PIBs operate by an analogous mechanism to lithium-ion batteries (LIBs), with reversible potassium intercalation in anode and cathode through an inorganic salt - organic solvent electrolyte medium. Despite its larger size, potassium exhibits several electrochemical advantages over sodium, including a higher affinity for intercalation into graphitic (carbonaceous) anodes, forming a stage-one KC₈ structure in graphite for a specific capacity of 279 mAh g^-1. This thesis aims to provide a thorough foundation for PIB carbon anodes, through a comprehensive experimental approach combining electrode synthesis, advanced material characterization and electrochemical-analytical techniques.</div><div><br></div><div>Safety concerns have consistently plagued LIBs despite almost three decades of widespread commercialization. Thermal runaway of LIBs can initiate as early as 80°C from exothermic breakdown of the solid electrolyte interphase (SEI) layer that covers the carbon anode surface. The subsequent reaction of lithiated carbon with electrolyte solvent leads to cathode decomposition and oxygen release for cell gassing and combustion. This thesis investigates the thermal runaway behavior of graphite anode for PIBs via differential scanning calorimetry analysis, determining the effect of electrode material, state-of-charge, and cycling history on heat generation. Notably, the PIB system emits significantly less heat overall than for LIBs, albeit an earlier and more intense onset reaction at 100°C raises safety concerns. Strategies to mitigate this exothermic reaction are presented, including electrode binder manipulation to improve graphite particle coverage and enhance SEI layer stability.</div><div><br></div><div>To further evaluate the practicality of PIBs, the electrochemical behavior of graphite anode was investigated from 0 - 40°C operating temperature, in comparison to standard LIBs. The poor rate capability of potassium is attributed to sluggish solid-state diffusion and augmented cell impedance, where 3-electrode studies revealed dramatic polarization of the potassium metal counter electrode at low temperatures. Accelerated cell aging at elevated temperatures is attributed to SEI layer growth induced by the 61% volumetric expansion of graphite during potassiation, as well as the extreme reactivity of potassium metal. A full-cell system with a Prussian blue nanoparticle cathode and graphite anode showed enhanced rate performance at low temperatures by removing potassium metal counter electrode. These results provide valuable mechanistic insight for potassium intercalation in graphite and offer a practical evaluation of temperature dependent electrochemical performance for PIBs.</div><div><br></div><div>Supplementary research includes the exploration of carbon nanofibers electrospun from polyacrylonitrile precursor with subsequent pyrolysis as PIB anode. The design of an amorphous, low density carbon with a nanoscale one dimensional morphology enables mitigation of the 61% volumetric expansion of graphite during potassiation. Remarkable stability (2000 charge-discharge cycles) is thus achieved by preventing electrode pulverization, SEI layer growth, and impedance rise during cycling. Electrochemical analysis revealed a pseudo-capacitance mechanism, enabling rapid charging through surface storage of potassium that could be enhanced by surface functionalization via plasma oxidation treatment. Moreover, two dimensional MXene transition carbonitride sheets were explored as PIB anode with X-ray diffraction and X-ray photoelectron spectroscopy used to study structural changes during potassium insertion.</div><div><br></div><div>Finally, the effect of particle morphology was investigated for LIB carbon anodes, wherein commercial graphite is compared with synthesized spherical and spiky carbons. Intercalation dynamics, side reaction rates (e.g. SEI growth), self-heating, and thermal runaway behavior were studied through a combination of electrochemical analysis and modeling by a finite volume method. Spherical particles outperform irregular commercial graphite by eliminating unstructured inhomogeneities that lead to non-uniform current distributions. Interestingly, spiky particles offer a nontrivial response, where the ordered irregularities enhance intercalation dynamics to prevent degradation at extreme operating conditions. These findings emphasize the importance of tailoring particle morphology and structure in promoting desired LIB behavior and suppressing unwanted problems.</div>

This thesis develops an advanced battery monitoring and control system based on the electrochemical principles that govern lithium-ion battery dynamics. This work is motivated by the need of having safer and better energy storage systems for all kind of applications, from small scale portable electronics to large scale renewable energy storage. In this context, lithium-ion batteries have become the enabling technology for energy autonomy in appliances (e.g. mobile phone, electric vehicle) and energy self-consumption in households. However, batteries are oversized and pricey, might be unsafe, are slow to charge and may not equalize the lifetime of the application they are intended to power. This work tackles these different issues.This document first introduces the general context of the battery management problem, as well as the particular issues that arise when modeling, supervising and controlling the battery short-term and long-term operation. Different solutions coming from the literature are reviewed, and several standard tools borrowed from control theory are exposed. Then, starting by well-known contributions in electrochemical modeling, we proceed to develop reduced-order models for the battery operation including degradation mechanisms, that are highly descriptive of the real phenomena taking place. This modeling framework is the cornerstone of all the monitoring and control development that follows.Next, we derive a battery diagnosis system with a twofold objective. First, indicators for internal faults affecting the battery state-of-health are obtained. Secondly, detection and isolation of sensor faults is achieved. Both tasks rely on state observers designed from electrochemical models to perform state estimation and residual generation. Whereas the former solution resorts to system identification techniques for health monitoring, the latter solution exploits fault diagnosis for instrumentation assessment.We then develop a feedback battery charge strategy able to push in performance while accounting for constraints associated to battery degradation. The fast and safe charging capabilities of the proposed approach are ultimately validated through long-term cycling experiments. This approach outperforms widely used commercial charging strategies in terms of both charging speed and degradation.The main contribution of this thesis is the exploitation of first principles models to develop battery management strategies towards improving safety, charging time and lifetime of battery systems without jeopardizing performance. The obtained results show that system and control theory offer opportunities to improve battery operation, aside from the material sciences contributions to this field. / Doctorat en Sciences de l'ingénieur et technologie / info:eu-repo/semantics/nonPublished

This study is an investigation if a recurrent long short-term memory (LSTM) based neural network can be used to estimate the battery capacity in electrical cars. There is an enormous interest in finding the underlying reasons why and how Lithium-ion batteries ages and this study is a part of this broader question. The research questions that have been answered are how well a LSTM model estimates the battery capacity, how the LSTM model is performing compared to a linear model and what parameters that are important when estimating the capacity. There have been other studies covering similar topics but only a few that has been performed on a real data set from real cars driving. With a data science approach, it was discovered that the LSTM model indeed is a powerful model to use for estimation the capacity. It had better accuracy than a linear regression model, but the linear regression model still gave good results. The parameters that implied to be important when estimating the capacity were logically related to the properties of a Lithium-ion battery.En studie över hur väl ett återkommande neuralt nätverk kan estimera kapaciteten hos Litium-ion batteri hos elektroniska fordon, när en en datavetenskaplig strategi har använts.

Die wachsende Weltbevölkerung und die stetigen Entwicklungen in der Industrie benötigen einerseits immer größere Mengen an Grundchemikalien und führen andererseits zu einem ständig steigenden Energiebedarf. Die Dissertation behandelt daher die Themen Zeolithe und Kathodenmaterialien, welche zwei aktuelle Forschungsschwerpunkte der chemischen Industrie darstellen. Der Fokus der Arbeit lag in der Steuerung der Partikelgröße durch die hydrothermale und mikrowellenunterstützte Kristallisation.

Electrochemical copolymerizations of thiophene (Th) and 3,4-ethylenedioxythiophene (EDOT) was performed in this study. Incorporation of Th with EDOT units have accelerated deposition rate in relative to the simple polymerization behavior of EDOT. The electrochemical properties of poly(thiophene-co-3,4-ethylenedioxythiophene) (PTh-EDOT) are different from the homopolymers of polythiophene (PTh) and poly(3,4-ethylenedioxythiophene) (PEDOT). PTh-EDOT were then served as cathode materials of lithium-ion (Li-ion) batteries to test their capability to transfer lithium ion in 1.0 M LiPF6/ethylene carbonate/dimethyl carbonate solution. PTh-EDOT copolymer prepared from the monomer ratio of 1/1 (Th/EDOT) shows better stability than PEDOT and PTh homopolymers, polymer property enhancement by copolymerization is thus demonstrated. A composite electrode material PEDOT/LiCoO2 was prepared from the electrochemical polymerization of EDOT on LiCoO2 electrode was primarily prepared to inspect the influence of PEDOT on the electrochemical features of LiCoO2. Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) show the successful deposition of PEDOT over LiCoO2 particles. Compared to the simple LiCoO2 electrode, PEDOT/LiCoO2 composite cathode shows enhanced properties including rate capability and cycle stability for potential Li-ion battery application. Nevertheless, differential scanning calorimetry (DSC) scans on the fully charged cathodes imply that PEDOT may reduce the thermal stability of LiCoO2. Two carbon materials, vapor grown carbon fibers (VGCF) and nano-scaled Ketjen black EC (KB), were implemented into LiCoO2 electrode. The influence of different carbon additive and their content on the performance of LiCoO2 such as rate capability and cycle ability has been evaluated. KB shows more positive effects than VGCF even in the case of a low 1 wt% content. Furthermore, incorporation of PEDOT was made by electrochemical deposition of EDOT on the preformed LiCoO2-VGCF and LiCoO2-KB composite electrodes. The influence of the carbon additives and the conductive PEDOT polymer on LiCoO2 was then investigated. Compared to the electrodes without PEDOT coating, PEDOT-incorporated composite electrodes show larger capacity, better transfer rate of lithium ions in electrolytes, and enhanced cycle ability. The electrochemical deposition of PEDOT on the LiCoO2/nano-carbon cathodes provides a new approach to implement the conducting polymers in Li-ion batteries.