京都大学 / 0048 / 新制・課程博士 / 博士(人間・環境学) / 甲第19072号 / 人博第725号 / 新制||人||174(附属図書館) / 26||人博||725(吉田南総合図書館) / 32023 / 京都大学大学院人間・環境学研究科相関環境学専攻 / (主査)教授 内本 喜晴, 教授 加藤 立久, 教授 吉田 寿雄 / 学位規則第4条第1項該当 / Doctor of Human and Environmental Studies / Kyoto University / DGAM

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第19739号 / 工博第4194号 / 新制||工||1647(附属図書館) / 32775 / 京都大学大学院工学研究科物質エネルギー化学専攻 / (主査)教授 安部 武志, 教授 陰山 洋, 教授 作花 哲夫 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

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Thesis advisor: Dunwei Wang / Metal organic frameworks (MOFs) are a class of compounds that show promising potential for a variety of applications due to their uniformity, highly porous structure, lack of dead volume, and fine-tunability. One of these significant applications is in selective ion transport, which makes MOF films a uniquely good separatory material for dual-electrolyte setups, such as those being investigated with Mg-Br batteries. This research has important environmental and industrial ramifications, considering the various drawbacks associated with commercially available batteries such as the lithium-ion battery. The MOF investigated was Mg-MOF-74, which showed promising selective Mg2+ transport abilities. Both Mg-MOF-74 powder and films were synthesized via a vapor-assisted conversion process to maximize efficiency. To characterize the MOF, XRD and SEM imaging was used. This allowed us to gain a nuanced understanding of the material and its properties for further applications. / Thesis (BA) — Boston College, 2022. / Submitted to: Boston College. College of Arts and Sciences. / Discipline: Departmental Honors. / Discipline: Chemistry.

Battery electric vehicles (BEV) powered by renewable energy are expected to enable a largedecarbonization of the land-based transport. Recent estimations of the International EnergyAgency suggest that BEVs could grow 20-fold by 2030, reaching 200 to 350 million unitsglobally. However, the environmental impacts of BEVs remains a critical issue to be addressed.Batteries are responsible for 80% of the life cycle environmental impacts of BEVs, mainly dueto the extraction of raw materials, manufacture and charge. A concept that aims at avoiding theexploitation of new materials by extending the lifetime of resources and products is circularity.Among various circular business models, one that so far has not been substantially addressedin the literature is battery leasing.This thesis investigates the economic and environmental impacts of leasing batteries for BEVsas a circular business model and compares them to those of the linear model of selling-buyingbatteries. For doing this, we combine three models, namely a battery fleet model, a net presentvalue (NPV) model and a cradle-to-grave life cycle assessment (LCA). In contrast to commonLCAs, our battery fleet model considers different types of driving profiles instead of the typical‘average’ profile, which offers a more accurate depiction of reality.Results indicate that leasing batteries may be as profitable as selling them, but leasingcompanies may require higher revenues and pay higher taxes to attain the same NPV as selling.To generate more income, companies would need to charge fees to customers that are notalways beneficial for them. In fact, buying the battery remains the cheapest option for usersdriving more than 10 thousand km/year, which is the majority. From an environmentalperspective, LCA results show that environmental benefits of leasing batteries compared toselling them are marginal. This suggests that while leasing batteries offer some advantages(e.g., making BEVs more affordable, facilitating flexibility to users, promote the repairing,repurpose and recycling of batteries, etc.), it is unlikely to improve the cost-effectiveness andenvironmental impact of buying/selling them.

Thesis (Ph.D.(Physics)) -- University of Limpopo, 2020 / We employ molecular dynamics simulations, using DL_POLY code, to study the structural behaviour of β-MnO2 cathode material during discharging through lithium-ion intercalation into the bulk, nanoparticle, nanorod, nanosheet, and nanoporous β-MnO2. It is shown that lithium-ions have an average coordination number of about 5.70 and prefer surface sites with high oxygen coordination. The average lattice parameter values at intercalation of 0.85 Li/Mn are found to be under 4% relative to the experimental values obtained at 0.92 Li/Mn. Moreover, all the lithiated β-MnO2 structures did not collapse at 0.85 Li/Mn as observed in the β-MnO2 mesoporous in experimental work. As lithium is limited, sodium is a good alternative charge carrier in lithium-ion batteries. As a result, we have also performed studies on sodium intercalation into bulk, nanoparticle, nanorod, nanosheet and nanoporous β-MnO2. The microstructures and radial distribution functions show that the β-MnO2 structures could be intercalated up to 0.24 Na/Mn without any obvious structural degradation. Beyond this sodium concentration, the microstructure collapses and become amorphous thus predicting a potentially lower capacity for Na-MnO2-β batteries. Also, as the voltage is an important factor in the energy density of lithium-ion batteries, we have studied the trends in the average intercalation potentials in relation to the various nano architectures. The trend, in increasing value of average intercalation potentials, were found to be bulk structure, nanorod, nanosheet, nanoporous and nanoparticle. This suggests that nanostructuring can enhance cell voltage. Mechanical properties studies on the pure and lithiated bulk and nanorod β-MnO2 were also performed through uniaxial compressive and tensile strain application. The results show that under compressive strain the bulk structure and nanorod mitigate stress through the contraction and collapse of the inherent tunnel structures, known to cause electrochemical inactivity, and also through the shifting of the MnO6 octahedral planes. The collapsing of tunnels was found to occur more on the bulk structure and less on the nanorod, while the MnO6 octahedral plane shifts were found to occur more on the nanorod and less on the bulk structure. Unoccupied 1x2 or conjoined 1x2 were found to result in structural collapse irrespective of the host nanoarchitecture. The X-ray diffraction pattern (v) plots suggest that lithium intercalation and compressive stress application have a similar impact on the underlying structure of the various nanostructures. The microstructure analysis for bulk β-MnO2 under tensile strain reveals that fracture occurred in the brookite region and along the dislocation/stacking fault. The nanorod β-MnO2 mitigated stress through a rutile-to-brookite phase transition which occurred in the unstrained Li0.73MnO2-β and under tensile strain in LixMnO2-β for x = 0.00, 0.03, 0.12, and 0.24. In both the bulk and nanorod β-MnO2 the brookite phase was succeeded by structural breakdown leading to fracture and served as an indicator for imminent structural failure upon more tensile strain application. / National Research Foundation (NRF)

Thesis (Ph.D. (Physics)) -- University of Limpopo, 2019 / LiMn2O4 spinel (LMO) is a promising cathode material for secondary lithium-ion batteries which, despite its high average voltage of lithium intercalation, suffers crystal symmetry lowering due to the Jahn-Teller active six-fold Mn3+ cations. Although Ni has been proposed as a suitable substitutional dopant to improve the energy density of LiMn2O4 and enhance the average lithium intercalation voltage, the thermodynamics of Ni incorporation and its effect on the electrochemical properties of this spinel are not fully understood. Firstly, structural, electronic and mechanical properties of spinel LiMn2O4 and LiNixMn2-xO4 have been calculated out using density functional theory employing the pseudo-potential plane-wave approach within the generalised gradient approximation, together with Virtual Cluster Approximation. The structural properties included equilibrium lattice parameters; electronic properties cover both total and partial density of states and mechanical properties investigated elastic properties of all systems. Secondly, the pressure variation of several properties was investigated, from 0 GPa to 50 GPa. Nickel concentration was changed and the systems LiNi0.25Mn1.75O4, LiNi0.5Mn1.5O4 LiNi0.75Mn1.25O4 and LiNi0.875Mn1.125O4 were studied. Calculated lattice parameters for LiMn2O4 and LiNi0.5Mn1.5O4 systems are consistent with the available experimental and literature results. The average Mn(Ni)-O bond length for all systems was found to be 1.9 Å. The bond lengths decreased with an increase in nickel content, except for LiNi0.75Mn1.25O4, which gave the same results as LiNi0.25Mn1.75O4. Generally, analysis of electronic properties predicted the nature of bonding for both pure and doped systems with partial density of states showing the contribution of each metal in our systems. All systems are shown to be metallic as it has been previously observed for pure spinel LiMn2O4, and mechanical properties, as deduced from elastic properties, depicted their stabilities. Furthermore, the cluster expansion formalism was used to investigate the nickel doped LiMn2O4 phase stabilities. The method determines stable multi-component crystal structures and ranks metastable structures by the enthalpy of formation while iv maintaining the predictive power and accuracy of first-principles density functional methods. The ground-state phase diagram with occupancy of Mn 0.81 and Ni 0.31 generated various structures with different concentrations and symmetries. The findings predict that all nickel doped LMO structures on the ground state line are most likely stable. Relevant structures (Li4Ni8O16, Li12MnNi17O48, Li4Mn6Ni2O16, Li4Mn7NiO16 and Li4Mn8O16) were selected on the basis of how well they weighed the cross-validation (CV) score of 1.1 meV, which is a statistical way of describing how good the cluster expansion is at predicting the energy of each stable structure. Although the structures have different symmetries and space groups they were further investigated by calculating the mechanical and vibrational properties, where the elastic constants and phonon vibrations indicated that the structures are stable in accordance with stability conditions of mechanical properties and phonon dispersions. Lastly, a computer program that identifies different site occupancy configurations for any structure with arbitrary supercell size, space group or composition was employed to investigate voltage profiles for LiNixMn2-xO4. The density functional theory calculations, with a Hubbard Hamiltonian (DFT+U), was used to study the thermodynamics of mixing for Li(Mn1-xNix)2O4 solid solution. The results suggested that LiMn1.5Ni0.5O4 is the most stable composition from room temperature up to at least 1000K, which is in excellent agreement with experiments. It was also found that the configurational entropy is much lower than the maximum entropy at 1000K, indicating that higher temperatures are required to reach a fully disordered solid solution. The maximum average lithium intercalation voltage of 4.8 eV was calculated for the LiMn1.5Ni0.5O4 composition which correlates very well with the experimental value. The temperature has a negligible effect on the Li intercalation voltage of the most stable composition. The approach presented here shows that moderate Ni doping of the LiMn2O4 leads to a substantial change in the average voltage of lithium intercalation, suggesting an attractive route for tuning the cathode properties of this spinel. / National Research Foundation (NRF)

The properties of C/SiCN nanocomposites synthesized by thermal decomposition of polymer precursors were studied in this work. The novel polymer-to-ceramic process enables us to tailor the ceramic structure in atomic level by designing the starting chemicals and pyrolysis procedures. It is of both fundamental and practical significance to investigate the properties and structures relationship of the nanocomposites. In this work, we explored their application potential in using as anode of lithium-ion secondary batteries. The structure and structural evolution of C/SiCN nanocomposite were investigated by using XRD, FTIR, SEM, TEM, Solid state NMR and Raman spectroscopy. The results revealed the nanocomposites consisted of amorphous SiCxNx-4 matrix and carbon nanoclusters distributed within it. The size of the carbon was measured by Raman spectroscopy, varied with starting chemicals and pyrolysis temperature. The electronic properties of the C/SiCN nanocomposite were studied by measuring the IV curves and a.c. impedance. The d.c. conductivity increased with carbon content and pyrolysis temperatures. The impedance spectra and fitted equivalent circuit results confirmed the existence of two phases in the nanocomposite. The possibility of using C/SiCN as anode in lithium-ion secondary batteries was investigated by electrochemical measurements, namely cyclic voltammetry, galvanostatic cyclic test and electrochemical impedance spectroscopy. The galvanostatic measurements showed that the nanocomposite with 26% of carbon nanoclusters exhibited a specific capacity of 480 mAh/g, iv which is 30% higher than that of commercial graphite anode. The high capacity of the nanocomposites is attributed to the formation of a novel structure around C/SiCN interface. The excellent electrochemical properties, together with the simple, low-cost processing, make the nanocomposites very promising for Li-ion battery applications

This dissertation describes a new vinyl-acrylic copolymer that displays great potential for applications in lithium ion batteries by enabling processes that are novel, faster, safer, and less costly than existing manufacturing methods. Overall, the works presented are based on tailored chemical synthesis directly applied to lithium ion battery manufacturing. Current manufacturing methods still have many flaws such as toxic processes and other time consuming if not costly steps. Understanding the chemistry of materials and processes related to battery manufacturing allows the design of techniques and methods that can ultimately improve the performance of existing batteries while reducing the cost. Chapter 1 provides an introduction to lithium batteries in terms of energy output, standard electrode and electrolyte materials, and processes for fabricating battery components. In this chapter, slightly more emphasis is placed on the electrolyte aspects of lithium battery technology, namely the plasticization of gel polymer hosts by liquid electrolyte and the standalone solid polymer electrolytes. Chapter 2 focuses on the free radical polymerization of poly(ethylene glycol) methyl ether methacrylate (PEGMA), methyl methacrylate (MMA), and isobutyl vinyl ether (IBVE) monomers to afford a vinyl-acrylic poly(PEGMA-co-MMA-co-IBVE) random copolymer and its detailed properties as a soluble, amorphous, and adhesive electrolyte that is able to permanently hold 800 times its own weight. Such material properties envision a printable battery manufacturing procedure, since existing electrolytes lack adhesion at a single macromolecular level. Without adhesion, the cathode and anode layers easily delaminate from the cell assembly, not to mention weak interfacial contact and poor mass transfer with the electrolyte. Many soft matter type electrolytes have been reported, but they lack either adhesive strength or ease of solubility. Obtaining both properties in iv a single material is a rarity. Chapter 3 aims at improving the ionic conductivity of the poly(PEGMA-co-MMA-co-IBVE) copolymer electrolyte by studying the effect of internal and external plasticizers, molecular weight of PEGMA monomer, and addition of inorganic solid state electrolytes. The inorganic electrolyte additives include Li(1+x+y)AlxTi(2-x)SiyP(3-y)O12, LiILi2WO4 mixture, Li7La3Zr2O12, and Li2S-P2S5 as part of an organic-inorganic hybrid approach. Electrolytes can also be used as an electrode binder so long as it has structural integrity and allows ion transfer to and from the active electrode material during insertion/extraction processes. In Chapter 4, the use of this electrolyte as a water-soluble binder for the aqueous fabrication of LiCoO2 cathodes is presented. Results of this study demonstrated the first aqueous process fabrication of thick, flexible, and fully compressed lithium ion battery electrodes by using commercial nickel foam as a supporting current collector. This feat is rather impressive because these properties are far superior to other aqueous binders in terms of material loading per electrode, specific area capacity, durability, and cell resistance. Finally, Chapter 5 expands on this concept by using the poly(PEGMA-co-MMA-co-IBVE) copolymer for the aqueous fabrication of a low voltage Li4Ti5O12 anode type electrode. Each component of a lithium ion battery serves a distinct role and undergoes unique electrochemical processes during cycling. The fact that this poly(PEGMA-co-MMA-co-IBVE) copolymer can be used in all three components, albeit for only about 50 cycles in a liquid half cell setup, demonstrates as a proof of concept that switching the current toxic manufacturing of lithium-ion batteries to an aqueous process is highly feasible. Furthermore, new electrode manufacturing techniques are also deemed possible. A conclusive summary along with directions for future work concerning the v novelties of this unique multifunctional vinyl-acrylic copolymer as an electrolyte, a cathode binder, and an anode binder are discussed in Chapter 6.