This thesis examines parts of the kinetics and performance in Li-battery cells using lithium titanate anodes and lithium manganese oxide cathodes. Lithium titanate (Li4Ti5O12) is a candidate for battery applications in automotive vehicles due to its long lifetime and its suggested zero-strain ability. The zero-strain ability, meaning no volume changes in the material during cycling, would allow for the high charge/discharge rates required in electric vehicles. Two approaches of analysis have been performed. In situ XRD-analysis was used to verify the zero-strain ability of lithium titanate and XPS studies were used to analyze the surface chemistry of lithium titanate after cycling. It is known that lithium titanate/lithium manganeseoxide battery cells suffer from abnormal gas evolution and power degradation, and it is therefore of interest to find ways to prevent this. To be able to find methods of preventing the performance degradation deeper understanding of the kinetics are needed, since the mechanism behind this is not fully understood. The results in this thesis strengthen the understanding of lithium titanate as a zero-strain material. Furthermore, it is seen that the performance degradation possibly can be avoided or postponed by ALD deposition of aluminium oxide on the surface of the lithium manganese oxide electrode.

Recent development in portable electronics and electric vehicles have increased the demand for high performance lithium ion batteries. However, it is still challenging to produce high energy and high power lithium ion batteries. The major objective of this research is to fabricate advanced electrode materials with enhanced power density and energy density. Porous Li4Ti5O12 (LTO) and its nanocomposites (with Si and reduced graphene oxide (rGO)) synthesized by electrostatic spray deposition (ESD) technique were mainly studied and promising electrochemical performance was achieved. In chapter 3, porous LTO thin film electrode was synthesized by ESD to solve the low energy density and low power density issues by providing good ionic and electronic conductivities. Electrochemical test results showed that it had a large specific capacity of 357 mAh g-1 at 0.15 A g-1, which was even higher than its theoretical capacity. It also exhibited very high rate capability of 98 mAh g-1 at 6 A g-1. The improved electrochemical performance was due to the advantage of ESD generated porous structures. In order to further enhance the power density of LTO, ESD derived LTO/rGO composite electrodes were studied in chapter 4. In chapter 5, high energy density component Si was introduced viii into LTO composite. The synergistic effect between commercial LTO and Si powder was studied. Then, ESD derived LTO/Si/rGO composite was prepared and evaluated. At 0.15 A g-1, a stable capacity of 624 mAh g-1 was observed, which was much higher than the capacities of LTO and LTO/rGO electrodes. In addition, effect of activation process on electrochemical performance of carbon nanofibers (ACNFs) and feasibility of ion intercalation into 2D MMT montmorillonite clay (MMT) were studied and discussed in chapter 6. In summary, we have successfully synthesized various LTO based electrodes by ESD. Both high energy and high power density were achieved as compared to commercial LTO electrode. Through electrochemical characterization and charge storage distribution analysis, origins of the high rate capability were proposed. This work demonstrates ESD as a powerful tool for fabricating high performance porous structures and nanocomposite electrode materials.

Les accumulateurs LiNi0.4Mn1.6O4 (LNMO)/Li4Ti5O12 (LTO), permettent d’atteindre théoriquement les densités de puissance et d’énergie fournissant une autonomie suffisante aux véhicules électriques. Cependant, deux problèmes majeurs liés à LNMO limitent leurs performances : l’oxydation prononcée des électrolytes à base de carbonates d’alkyles et la dissolution d’ions de métaux de transition (Mn2+, Ni2+). Les formulations à base de carbonate d’éthylène (EC) ont une aptitude à former des films polymères couvrant la matière active. Les cyclages galvanostatiques, faisant suite ou non à un stockage, confirment la supériorité de ces électrolytes, conduisant à des pertes de capacité réduites de l’électrode LNMO. D’autre part, les sulfones sont des composés prometteurs pour une utilisation dans les batteries LNMO/LTO. L’emploi de cellules symétriques et asymétriques démontre que les sulfones sont non-réactives vis-à-vis des interfaces LNMO/électrolyte et LTO/électrolyte. Cependant, cette non-réactivité ne permet pas le dépôt de films polymères qui auraient permis de stopper la dissolution d’ions Mn2+ et Ni2+ à partir de l’électrode positive. Ceci résulte en des performances dégradées à 30°C des accumulateurs par rapport à ceux employant EC dans les électrolytes. / LiNi0.4Mn1.6O4 (LNMO)/Li4Ti5O12 (LTO) accumulators should theoretically achieve the power and energy densities that provide sufficient autonomy to electric vehicles. However, two major issues related to the use of LNMO limit their performances: the pronounced oxidation of the alkylcarbonate-based electrolytes and the transition metal ion (Mn2+, Ni2+) dissolution. The ethylene carbonate (EC)-based formulations get an ability to form polymer-covering films onto the active material. The galvanostatic cycling tests, after storage or not, confirm the superiority of these electrolytes, leading to reduced capacity losses of the LNMO electrode. Furthermore, sulfones are promising compounds to be applied to LNMO/LTO batteries. The use of symmetric and asymmetric cells demonstrates that sulfones are non-reactive towards the LNMO/electrolyte and LTO/electrolyte interfaces. However, this non-reactivity does not allow the deposition of polymer films, which would have enabled to stop the Mn2+ and Ni2+ dissolution from the positive electrode. This results in degraded performances of batteries at 30°C compared to those using EC in electrolytes.

The dissertation thesis deals with electrode materials and components for lithium-ion power sources. The thesis works with two different kinds of materials, concretely nanostructured Li4Ti5O12 with spinel basis and LiCoO2 with layered structure. The electrochemical properties, structure and element analysis and utilization possibilities in electrochemical industry of new technological electrode material Li4Ti5O12 were investigated. The influences of admixtures and electrolytes on characteristics of electrode materials with aforesaid active masses were also examined. Low cost price, environmental safety and obtained results of electrochemical measurements and structure analysis refer to wide possibilities of usage electrode material Li4Ti5O12 in the field of electrochemistry.

The aim of this work is to describe the influence of temperature on the structure and chemical composition of electrode materials for Li-ion accumulators. Theoretical part of this thesis contains described terminology and general issues of batteries and their division. Every kind of battery is provided with a closer description of a specific battery type. A separate chapter is dedicated to lithium cells, mainly Li-ion batteries. Considering various composition of Li-ion batteries, the next subchapters deeply analyzes the most used cathode (with an emphasis on the LiFePO4, LiMn1/3Ni1/3Co1/3O2) and anode materials (with an emphasis on the Li4Ti5O12). The next chapters describe the used analytical methods: electron microscopy, energy dispersion spectroscopy and thermomechanical analysis. The practical part is devoted to the description of the individual experiments and the achieved results.