In the introduction of this thesis thermodynamic and electrochemical studies on macrocyclic ligands related to those ligands investigated in this thesis are reviewed. A brief account on the progress made and the problems encountered in lithium battery technology are also presented. Thermodynamic parameters of complexation (Gibbs energies, DeltacG°, enthalpies, DeltacH°, and entropies, DeltacS° of lithium (hexafluoroarsenate, tetrafluoroborate and trifluoromethanesulfonate) and crown ethers (1-aza-12-crown-4 and 15-crown-5) in acetonitrile and propylene carbonate and (4'-aminobenzo-15-crown-5 and 4'-nitrobenzo-15-crown-5) in acetonitrile at 298.15 K derived from calorimetric studies are presented. As far as 1-aza-12-crown-4 and 15-crown-5 are concerned the complexation processes are found to be enthalpy controlled. However, the stability (in enthalpic terms) of 15-crown-5 and lithium is slightly higher than that observed for the same cation and 1-aza-12-crown-4 in both solvents. Based on the stability of lithium-crown ether complexes, six lithium coronand salts were isolated and their thermochemical behaviour in dipolar aprotic media investigated. Comparison of solution enthalpies of these salts relative to those containing the free cation shows that while the former are endothermic, the latter are exothermic. This was taken as an indication that the lithium coronand cation is less solvated than the free cation. This statement was corroborated by the significant increase on the conductivity observed by the addition of crown ethers to lithium salts in propylene carbonate. From complexation and solution data for 15-crown-5 and 1-aza-12-crown-4 and lithium, enthalpies for the coordination, process in which the reactants and the product are in their pure physical state were calculated. These data combined with solution enthalpies for 15-crown-5, the un-complexed and complexed lithium salts were used to derive the enthalpy of complexation of 15-crown-5 and lithium in tetrahydrofuran, a solvent of low permittivity.

No description available.

No description available.

No / Polymer gel electrolytes (PGE) based on polyvinylidene fluoride (PVDF), lithium salts and appropriate solvent systems, developed at Leeds University, have been shown to form tough rigid films with conductivities approaching 10¿2 S cm¿1. A continuous process has now been developed for the construction of rechargeable lithium cells by extruding the PGE as a melt and directly laminating between the anode and cathode electrodes. On cooling, the solid PGE acts as electrolyte and separator and binds the cell laminate together from within requiring no external case. This process has been successfully applied for the fabrication of cells with electrodes developed by SpectraPower Inc. in a commercial process enabling cell laminates with PGE thickness less than 0.1 mm and with energy densities approaching 170 Wh kg¿1. A prototype manufacturing facility has been set up to produce rechargeable cells of high specific capacity and high energy density. Future developments will enable rechargeable lithium ion cells to be produced on a continuous process as flat sheets opening the way for novel battery geometries.

Lithium batteries have revolutionized emerging electronic applications and will play more important roles in the future. Unfortunately, the energy density of commercial lithium-ion batteries (100-265 Wh kg-1) cannot satisfy the fast-growing demand for energy storage technologies. Lithium-sulfur (Li-S) batteries stand out for high energy density (2567 Wh kg-1), low-cost, and environmentally benign attributes. However, the development of Li-S full-batteries is still hindered by the dissolution of polysulfides into the organic electrolytes and poor ions transfer at the interfaces of electrolytes and lithium-intercalated electrodes (e.g., lithiated graphite). Improving the electrolytes is a crucial aspect for the development of battery technologies, but the knowledge concerning the electrolyte microstructures remains elusive. This dissertation unravels the microstructures of organic electrolytes and paves the way to the development of Li-S batteries. Firstly, we demonstrate the key role of electrolyte chemistry in the battery performances by showing a synergetic effect of electrolytes coupled with designed sulfur cathodes. Secondly, we investigate the microstructure of electrolytes and discover previously unexplored solvent-solvent and solvent-anion interactions. We show that the interactions are useful to elucidate important battery operations, such as ions transfer at electrolyte-electrode interfaces, and reveal a potential probe for developing battery electrolytes. Thirdly, we optimize the electrolyte composition to obtain a highly reversible Li+ intercalation/deintercalation at the graphite anode, giving high performances of Li-S full-batteries in a dilute electrolyte concentration. Finally, we unravel the key role of additives in suppressing Li+ solvation in the electrolytes. Nitrate (NO3-) anions are observed to incorporate into the solvation shells, change the local environment of Li+ cations, and then lead to an effective Li+ desolvation followed by improved battery performances. Key significances of this dissertation are (i) observation of detailed electrolyte microstructures showing a potential probe for developing battery electrolytes; (ii) evidences of the electrolyte chemistry plays a predominant role in the electrolyte-electrode interfacial reactions, which prevails over the role of commonly believed solid electrolyte interphase (SEI); and (iii) new mechanistic insights into the key role of additives in the electrolyte microstructures. Furthermore, the presented methodology paves the way for developing electrolytes for broad electrochemical applications.

Commercial lithium ion batteries use liquid electrolytes because of their high ionic conductivity (>10-3 S/cm) over a broad range of temperatures, high dielectric constant, and good electrochemical stability with the electrodes (mainly the cathode cathode). The disadvantages of their use in lithium ion batteries are that they react violently with lithium metal, have special packing needs, and have low lithium ion transference numbers (tLi+ = 0.2-0.3). These limitations prevent them from being used in high energy and power applications such as in hybrid electric vehicles (HEVs), plug in electric vehicles (EVs) and energy storage on the grid. Solid polymer electrolytes (SPEs) will be good choice for replacing liquid electrolytes in lithium/lithium ion batteries because of their increased safety and ease of processability. However, SPEs suffer from RT low ionic conductivity and transference numbers. There have been many approaches to increase the ionic conductivity in solid polymer electrolytes. These have focused on decreasing the crystallinity in the most studied polymer electrolyte, polyethylene oxide (PEO), on finding methods to promote directed ion transport, and on the development of single ion conductors, where the anions are immobile and only the Li+ ions migrate (i.e. tLi+ = 1). But these attempts have not yet achieved the goal of replacing liquid electrolytes with solid polymer electrolytes in lithium ion batteries. In order to increase ionic conductivity and lithium ion transference numbers in solid polymer electrolytes, I have focused on the development of multi-ionic lithium salts. These salts have very large anions, and thus are expected to have low tanion- and high tLi+ transference numbers. In order to make the anions dissociative, structures similar to those formed for mono-ionic salts, e.g. LiBF4 and lithium imides have been synthesized. Some of the multi-ionic salts have Janus-like structures and therefore can self-assemble in polar media. Further, it is possible that these salts may not form non-conductive ion pairs and less conductive ion triplets. First, we have prepared nanocomposite electrolytes from mixtures of two polyoctahedral silsesquioxanes (POSS) nanomaterials, each with a SiO1.5 core and eight side groups. POSS-PEG8 has eight polyethylene glycol side chains that have low glass transition (Tg) and melt (Tm) temperatures and POSS-phenyl7(BF3Li)3 is a Janus-like POSS with hydrophobic phenyl groups and -Si-O-BF3Li ionic groups clustered on one side of the SiO1.5 cube. The electron-withdrawing POSS cage and BF3 groups enable easy dissociation of the Li+. In the presence of polar POSS-PEG8, the hydrophobic phenyl rings of POSS-phenyl7(BF3Li)3 aggregate and crystallize, forming a biphasic morphology, in which the phenyl rings form the structural phase and the POSS-PEG8 forms the conductive phase. The -Si-O-BF3- Li+ groups of POSS-phenyl7(BF3Li)3 are oriented towards the polar POSS-PEG8 phase and dissociate so that the Li+ cations are solvated by the POSS-PEG8. The nonvolatile nanocomposite electrolytes are viscous liquids that do not flow under their own weight. POSS-PEG8/POSS-phenyl7(BF3Li)3 at O/Li = 16/1 has a conductivity, σ = 2.5 x 10-4 S/cm at 30°C, 17 x greater than POSS-PEG8/LiBF4, and a low activation energy (Ea ~ 3-4 kJ/mol); σ = 1.6 x 10-3 S/cm at 90°C and 1.5 x 10-5 S/cm at 10°C. The lithium ion transference number was tLi+ = 0.50 ± 0.01, due to reduced mobility of the large, bulky anion and the system exhibited low interfacial resistance that stabilized after 3 days (both at 80°C). Secondly, solid polymer electrolytes have been prepared from the same salt, POSS-phenyl7(BF3Li)3 and polyethylene oxide (PEO). These exhibit high ambient temperature conductivity, 4 x 10-4 S/cm, and transference number, tLi+ = 0.6. A two-phase morphology is proposed in which the hydrophobic phenyl groups cluster and crystallize, and the three -BF3- form an anionic pocket, with the Li+ ions solvated by the PEO phase. The high ionic conductivity results from interfacial migration of Li+ ions loosely bonded to three -BF3- anions and the ether oxygens of PEO. Physical crosslinks formed between PEO/Li+ chains and the POSS clusters account for the solid structure of the amorphous PEO matrix. The solid polymer electrolyte has an electrochemical stability window of 4.6 V and excellent interfacial stability with lithium metal. In order to further enhance the ionic conductivity of solid polymer electrolytes, we have made two improvements. First, we have used so called half cube structures, T4-POSS, that contain 4 phenyl groups on one side of a Si-O- ring, and 4 ionic groups on the other side, and so are true Janus structures. They contain a 4/4 ratio of phenyl/ionic groups, unlike the previous structures that contain 7 phenyl groups/3 ionic groups. At the same O/Li ratio, the ionic conductivity of [PhOSi(OLi)]4 with POSS-PEG8 is higher than POSS-phenyl7Li3 because of more Li+ dissociation in the former case. Second, we have increased the dissociation of the lithium salts by replacing the Si-O-BF3Li groups with Si-(C3H4NLiSO2CF3)4. Both T4-POSS-(C3H4NLiSO2CF3)4 and POSS-(C3H4NLiSO2CF3)8 have been synthesized and characterized, with some preliminary conductivity data obtained. / Chemistry

The results presented in this thesis demonstrate the first synthesis of several nanostructured transition metal oxides and lithium containing transition metal oxides. Their uses in lithium-ion batteries and/or as magnetic materials have been investigated. The first example of two and three dimensional mesoporous Fe₂O₃ has been prepared by using the soft templating (surfactant) method. The materials have amorphous walls and exhibit superparamagnetic behaviour. By using a hard template route, a mesoporous α-Fe₂O₃ with highly crystalline walls has been synthesized. Its unique magnetic behaviour, distinct from bulk α-Fe₂O₃, nanoparticulate α-Fe₂O₃, and mesoporous Fe₂O₃ with disordered walls, has been demonstrated. The hard template method was also used to prepare nanowire and mesoporous Co₃O₄, β-MnO₂ and MnO₃ with crystalline walls. Their electrochemical properties as electrodes in Li-ion batteries have been investigated. Mesoporous β-MnO₂ can accommodate 0.9 Li/Mn in stark contrast to bulk β-MnO₂ which cannot accommodate Li. To prepare mesoporous materials which cannot be obtained directly by the hard template method, a post-templating route has been developed. Mesoporous Fe₃O₄, γ-Fe₂O₃, and Mn3O4 with ordered mesostructures and highly crystalline walls have been obtained by post-synthesis reduction/oxidation treatments. All the materials show unique magnetic properties compared with nanoparticulate and bulk materials. Also, the first example of lithium containing mesoporous material, LT-LiCoO₂, was synthesized by first preparing mesoporous Co₃O₄, then reacting this with LiOH to form LT-LiCoO₂, with retention of the ordered nanostructure. The nanostructured LT-LiCoO₂ compounds demonstrate superior performance compared with normal or nanoparticulate LT-LiCoO₂, when used as intercalation electrodes in lithium batteries. Finally, monodispersed Mn₃O₄ nanoparticles (diameter ~ 8 nm) with a core-shell structure (a highly crystalline Mn₃O₄ core encased in a thin MnO₂ shell) have been prepared for the first time. Ordered three-dimensional arrays form by spontaneous self-assembly. Magnetic measurements demonstrated that the self-assembled three-dimensional arrays exhibit spin-glass behaviour, rather than the anticipated superparamagnetic behaviour for isolated nanoparticles. Such behaviour is interpreted as arising from strong interactions between the core (crystallized Mn₃O₄) and shell (MnO₂).

In this thesis, photocrosslinked ferrocene-based methacrylate polymers for thin-film cathodes in lithium batteries have been synthesized. Patterned thin-film electrodes of the ferrocene-based methacrylate polymers are fabricated by photocrosslinking. The structure and composition of the photocrosslinkable polymers are characterized by infrared spectra, nuclear magnetic resonances, and gel permeation chromatography. The result of quartz crystal microbalance shows that the crosslinked polymers prevent the polymers from dissolving into organic electrolytes. The cyclic voltammogram shows the photocrosslinked ferrocene-based methacrylate polymers have a redox couple. The energy capacity of the polymer for lithium batteries is about 40-50 mAh g-1 at a discharge rate of 10 C. The results show that the photocrosslinked ferrocene-based methacrylate polymers also improve the batteries.

Indiana University-Purdue University Indianapolis (IUPUI) / Developing alternative cathodes with high capacity is critical for the next generation rechargeable batteries to meet the ever-increasing desires of global energy storage market. This thesis is focused on two sulfur-based cathode materials ranging from inorganic lithium sulfide to organotrisulfide. For lithium sulfide cathode, we developed a nano-Li2S/MWCNT paper electrode through solution filtration method, which involved a low temperature of 100 °C. The Li2S nanocrystals with a size less than 10 nm were formed uniformly in the pores of carbon paper network. These electrodes show an unprecedented low overpotential (0.1 V) in the first charges, also show high discharge capacities, good rate capability, and excellent cycling performance. This superior electrochemical performance makes them promising for use with lithium metal-free anodes in rechargeable Li–S batteries for practical applications. For organotrisulfide cathode, we use a small organotrisulfide compound, e.g. dimethyl trisulfide, to be a high capacity and high specific energy organosulfide cathode material for rechargeable lithium batteries. Based on XRD, XPS, SEM, and GC-MS analysis, we investigated the cell reaction mechanism. The redox reaction of DMTS is a 4e- process and the major discharge products are LiSCH3 and Li2S. The following cell reaction becomes quite complicated, apart from the major product DMTS, the high order organic polysulfide dimethyl tetrasulfide (DMTtS) and low order organic polysulfide dimethyl disulfide (DMDS) are also formed and charged/discharged in the following cycles. With a LiNO3 containing ether-based electrolyte, DMTS cell delivers an initial discharge capacity of 720 mAh g-1 and retains 74% of the initial capacity over 70 cycles with high DMTS loading of 6.7 mg cm-2 at C/10 rate. When the DMTS loading is increased to 11.3 mg cm-2, the specific energy is 1025 Wh kg-1 for the active materials (DMTS and lithium) and the specific energy is 229 Wh kg-1 for the cell including electrolyte. Adjusting on the organic group R in the organotrisulfide can achieve a group of high capacity cathode materials for rechargeable lithium batteries.

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.