Добірка наукової літератури з теми "LI2MN03"

Recently, new types of cation disordered rocksalt (DRS) have been reported which show good reversibility. In our study we combined the strategy of using high-valent cations with partial substitution of fluorine for oxygen anions in disordered rocksalt-structure phase to achieve optimal Mn2+/Mn4+ double-redox reaction in the composition system Li2MnxTi1-xO2F (1/3 ≤ x ≤ 1). we synthesized 4 different compositions (Li2MnIIIO2F, Li2MnII 1/3MnIII 1/3TiIV 1/3O2F, Li2MnII 1/2TiIV 1/2O2F and Li2MnII 1/3TiIII 1/3TiIV 1/3O2F). Two of them were synthesized for the first time, Li2MnII 1/3MnIII 1/3TiIV 1/3O2F and Li2Mn II 1/3TiIII 1/3TiIV 1/3O2F. By studying the electrochemical properties of different compounds we found that Ti+4 in the structure keeps Mn at the second state of charge, thus enabling a double redox reaction of Mn2+/Mn4+. By investigating the electrochemical properties of all samples we found that the sample with the composition Li2Mn2/3Ti1/3O2F showed the best electrochemical properties with initial high discharge capacity of 227 mAh g-1 in the voltage window of 1.5-4.3 V and 82% of capacity retentionafter 100 cycles. However, fluorination might lead to several issues such as synthesis limitation, lithium diffusion issues due to preferable strong Li-F bonds, etc. thus, two more different samples based on the Li2Mn2/3Ti1/3O2F composition were synthesized and their properties were investigated (Li1.5MnII 1/3MnIII 1/3TiIV 1/3O2F0.5 and Li1.25MnII 1/3MnIII 1/3TiIV 1/3O2F0.25) in order to find the proper amount of fluorine in the structure which promises the electrochemical behavior. In the following the effect of fluorine on lithium diffusion was investigated by ex-situ Raman studies. These studies shed light on the diffusion pathways of lithium ions during charge and discharge process. The structural characteristics are examined using X-ray diffraction patterns, Rietveld refinement, energy-dispersive X-ray spectroscopy and scanning electron microscopy, transmission electron microscopy and Raman spectroscopy. The oxidation states and charge transfer mechanism are also studied further using extended X-ray absorption fine structure and X-ray photoelectron spectroscopy in which the results approve the double redox mechanism of Mn2+/Mn4+ in agreement with Mn-Ti structural charge compensation. The findings pave the way for designing high capacity electrode materials with multi-electron redox reactions. References: [1]: Chen, R.; Ren, S.; Knapp, M.; Wang, D.; Witter, R.; Fichtner, M.; Hahn, H., Disordered Lithium‐Rich Oxyfluoride as a Stable Host for Enhanced Li+ Intercalation Storage. Advanced Energy Materials 2015, 5, (9), 1401814. [2]: Lee, J.; Kitchaev, D. A.; Kwon, D.-H.; Lee, C.-W.; Papp, J. K.; Liu, Y.-S.; Lun, Z.; Clément, R. J.; Shi, T.; McCloskey, B. D., Reversible Mn 2+/Mn 4+ double redox in lithium-excess cathode materials. Nature 2018, 556, (7700), 185-190.

To make supercapattery devices feasible, there is an urgent need to find electrode materials that exhibit a hybrid mechanism of energy storage. Herein, we provide a first report on the capability of lithium manganese sulfates to be used as supercapattery materials at elevated temperatures. Two compositions are studied: monoclinic Li2Mn(SO4)2 and orthorhombic Li2Mn2(SO4)3, which are prepared by a freeze-drying method followed by heat treatment at 500 °C. The electrochemical performance of sulfate electrodes is evaluated in lithium-ion cells using two types of electrolytes: conventional carbonate-based electrolytes and ionic liquid IL ones. The electrochemical measurements are carried out in the temperature range of 20–60 °C. The stability of sulfate electrodes after cycling is monitored by in-situ Raman spectroscopy and ex-situ XRD and TEM analysis. It is found that sulfate salts store Li+ by a hybrid mechanism that depends on the kind of electrolyte used and the recording temperature. Li2Mn(SO4)2 outperforms Li2Mn2(SO4)3 and displays excellent electrochemical properties at elevated temperatures: at 60 °C, the energy density reaches 280 Wh/kg at a power density of 11,000 W/kg. During cell cycling, there is a transformation of the Li-rich salt, Li2Mn(SO4)2, into a defective Li-poor one, Li2Mn2(SO4)3, which appears to be responsible for the improved storage properties. The data reveals that Li2Mn(SO4)2 is a prospective candidate for supercapacitor electrode materials at elevated temperatures.

This work continues our systematic study of Li- and Mn- rich cathodes for lithium-ion batteries. We chose Li2MnO3 as a model electrode material with the aim of correlating the improved electrochemical characteristics of these cathodes initially activated at 0 °C with the structural evolution of Li2MnO3, oxygen loss, formation of per-oxo like species (O22−) and the surface chemistry. It was established that performing a few initial charge/discharge (activation) cycles of Li2MnO3 at 0 °C resulted in increased discharge capacity and higher capacity retention, and decreased and substantially stabilized the voltage hysteresis upon subsequent cycling at 30 °C or at 45 °C. In contrast to the activation of Li2MnO3 at these higher temperatures, Li2MnO3 underwent step-by-step activation at 0 °C, providing a stepwise traversing of the voltage plateau at >4.5 V during initial cycling. Importantly, these findings agree well with our previous studies on the activation at 0 °C of 0.35Li2MnO3·0.65Li[Mn0.45Ni0.35Co0.20]O2 materials. The stability of the interface developed at 0 °C can be ascribed to the reduced interactions of the per-oxo-like species formed and the oxygen released from Li2MnO3 with solvents in ethylene carbonate–methyl-ethyl carbonate/LiPF6 solutions. Our TEM studies revealed that typically, upon initial cycling both at 0 °C and 30 °C, Li2MnO3 underwent partial structural layered-to-spinel (Li2Mn2O4) transition.

The drastic changes (Li2MnO3→Li1.67MnO2.1F0.2) in the first cycle of Li2MnO3-like through oxygen release (O2−→O2) and in operando F-doping, activated a two-electron redox of Mn4+/2+ with a capacity of 326 mA h g−1.

The layer-structured monoclinic Li2MnO3 is a key material, mainly due to its role in Li-ion batteries and as a precursor for adsorbent used in lithium recovery from aqueous solutions. In the present work, we used first-principles calculations based on density functional theory (DFT) to study the crystal structure, optical phonon frequencies, infra-red (IR), and Raman active modes and compared the results with experimental data. First, Li2MnO3 powder was synthesized by the hydrothermal method and successively characterized by XRD, TEM, FTIR, and Raman spectroscopy. Secondly, by using Local Density Approximation (LDA), we carried out a DFT study of the crystal structure and electronic properties of Li2MnO3. Finally, we calculated the vibrational properties using Density Functional Perturbation Theory (DFPT). Our results show that simulated IR and Raman spectra agree well with the observed phonon structure. Additionally, the IR and Raman theoretical spectra show similar features compared to the experimental ones. This research is useful in investigations involving the physicochemical characterization of Li2MnO3 material.

Lithium manganite, Li2MnO3, is an attractive cathode material for rechargeable lithium ion batteries due to its large capacity, low cost and low toxicity. We employed well-established atomistic simulation techniques to examine defect processes, favourable dopants on the Mn site and lithium ion diffusion pathways in Li2MnO3. The Li Frenkel, which is necessary for the formation of Li vacancies in vacancy-assisted Li ion diffusion, is calculated to be the most favourable intrinsic defect (1.21 eV/defect). The cation intermixing is calculated to be the second most favourable defect process. High lithium ionic conductivity with a low activation energy of 0.44 eV indicates that a Li ion can be extracted easily in this material. To increase the capacity, trivalent dopants (Al3+, Co3+, Ga3+, Sc3+, In3+, Y3+, Gd3+ and La3+) were considered to create extra Li in Li2MnO3. The present calculations show that Al3+ is an ideal dopant for this strategy and that this is in agreement with the experiential study of Al-doped Li2MnO3. The favourable isovalent dopants are found to be the Si4+ and the Ge4+ on the Mn site.

AbstractNanoparticles of Li2MnO3 were fabricated by sol-gel method using precursors of lithium acetate and manganese acetate, and citric acid as chelating agent in the stoichiometric ratio. TGA/DTA measurements of the sample in the regions of 30 °C to 176 °C, 176 °C to 422 °C and 422 °C to 462 °C were taken to identify the decomposition temperature and weight loss. The XRD analysis of the sample indicates that the synthesized material is monoclinic crystalline in nature and the calculated lattice parameters are 4.928 Å (a), 8.533 Å (b), and 9.604 Å (c). The surface morphology, particle size and elemental analysis of the samples were observed using SEM and EDAX techniques and the results confirmed the agglomeration of nanoparticles and, as expected, Li2MnO3 composition. Half cells of Li2MnO3 were assembled and tested at C/10 rate and the maximum capacity of 27 mAh/g was obtained. Charging and discharging processes that occurred at 3 V and 4 V were clearly observed from the cyclic voltammetric experiments. Stability of the electrodes was confirmed by the perfect reversibility of the anodic and cathodic peak positions observed in the cyclic voltammogram of the sample. The Li2MnO3 nanoparticles exhibit excellent properties and they are suitable for cathode materials in lithium ion batteries.

Capacity degradation and voltage fade of Li2MnO3 during cycling are the limiting factors for its practical use as a high-capacity lithium-ion battery cathode. Here, the simulated amorphisation and recrystallisation (A + R) technique is used, for generating nanoporous Li2MnO3 models of different lattice sizes (73 Å and 75 Å), under molecular dynamics (MD) simulations. Charging was carried out by removing oxygen and lithium ions, with oxygen charge compensated for, to restrain the release of oxygen, resulting in Li2−xMnO3−x composites. Detailed analysis of these composites reveals that the models crystallised into multiple grains, with grain boundaries increasing with decreasing Li/O content, and the complex internal microstructures depicted a wealth of defects, leading to the evolution of distorted cubic spinel LiMn2O4, Li2MnO3, and LiMnO2 polymorphs. The X-ray diffraction (XRD) patterns for the simulated systems revealed peak broadening in comparison with calculated XRD, also, the emergence of peak 2Θ ~ 18–25° and peak 2Θ ~ 29° were associated with the spinel phase. Lithium ions diffuse better on the nanoporous 73 Å structures than on the nanoporous 75 Å structures. Particularly, the Li1.00MnO2.00 shows a high diffusion coefficient value, compared to all concentrations. This study shed insights on the structural behaviour of Li2MnO3 cathodes during the charging mechanism, involving the concurrent removal of lithium and oxygen.

Li2MnO3 nanoparticles were prepared using the Sol-Gel method and characterized by XRD, AFM, SEM, TGA and DSC with major peaks (18.81°), (37.10°) and (44.76°) using AfM, the average diameter of the nanoparticles was (45.71 nm). SEM was used to assess the surface morphology; The micropicture showed homogeneous spherical formations with particle sizes ranging from 2 to 4 meters. Thermal analysis was determined by TGA and DSC results showed a thermal stability from 500 to 750, indicating development of the phase. Li2MnO3 nanoparticles display excellent properties and are suitable as cathode materials in lithium-ion batteries.

The paper presents the results of the study of phase composition and electrochemical performance of lithium­manganese oxide spinel with excess lithium of nominal composition of Li1+xMn2O4 obtained by solidphase method. It was established that samples with x = 0.1 and 0.2 were composite materials with LiMn2O4 being the basic phase and Li2MnO3 being the impurity (3 and 7 mas.%, respectively) also comprising trace amounts of MnO2. The composite material with 3% of Li2MnO3 (x = 0.1) retained 80–90% of the initial specific capacity after 300 charge­discharge cycles at C/2, while single­phase stoichiometric spinel LiMn2O4 retained less than 70–75%.

Nanosized (10~50 nm) cathode material Li2MnO3 was prepared for with MnSO4·H2O，KMnO4 and Li- OH aqueous solution as the precursor via single-step hydrothermal reaction by controlling the reaction time, proportion of processor, and the reagent concentration. The prepared materials were well crystallized and exhibited a monoclinic Li2MnO3 structure with a space group of C2/m phase. The electrochemical performance of the material was tested at current density of 60 mAg-1 (1/4 C) between 4.3V and 2.0 V at room temperature, showing good electrochemical properties with the initial discharge capacity of 243 mAh·g-1, because it was more exposed to the electrolyte due to its nanostructure. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/35190

Afin de mieux comprendre les évolutions structurales mises en évidence dans les oxydes lamellaires de formule générale Li1+x(Ni0.425Mn0.425Co0.15)O2 utilisés comme électrode positive pour batterie lithium-ion, la structure du composé Li2MnO3 a été étudiée en détail. Obtenu selon différentes voies de synthèses, réalisées à différentes températures, ce matériau qui peut être considéré comme un matériau model à fait l’objet d’une étude cristallographique où l’utilisation de la microscopie électronique a été privilégiée. Deux types de défauts ont été identifiés. D’une part, l’existence de fautes d’empilement au sein du matériau a été démontrée. Leurs conséquences sur les clichés de diffraction électronique et les diagrammes de diffraction des rayons-X ont étés expliquées permettant d’unifier les controverses présentent à ce sujet dans la littérature. D’autre part, l’étude de la stabilité thermique du composé Li2MnO3 a mis en évidence l’apparition de défauts de type « phase spinelle » en surface des grains lorsque la température de traitement thermique devient supérieure ou égale à 900°C. Le traitement du matériau par la voie acide a pu être étudié et le mécanisme de désintercalation chimique du lithium par la voie acide a finalement pu être précisé. Il est montré que ce mécanisme est le même quelle que soit la taille des particules
In order to get a better understanding of the complex structural evolutions occurring in the layered oxides like Li1+x(Ni0.425Mn0.425Co0.15)O2 materials when they are used as positive electrodes in lithium batteries, the structure of Li2MnO3 has been studied in detail. Obtained from several synthesis ways, annealed at various temperatures, this compound that can be considered as a model one regarding these complex materials has been the object of a crystallographic study where the use of electron microscopy was privileged. Two kinds of defects could be identified. From one part, the existence of stacking faults in the Li2MnO3 material has been proved and they have been visualized for the first time. Their consequences on X ray and electron diffraction patterns are explained allowing the unification of discrepancies existing in the bibliography. For other part, the study of the thermal stability of Li2MnO3 evidenced the appearance of spinel type defects when the annealing treatment is performed above 900°C. Finally the delithiation by acid leaching is studied and the lithium extraction mechanism is clarified. It is shown that this mechanism is the same whatever the particle size is

Lithium ion batteries provides un-matched blend of high capacity and energy density, that is why this technology is highly portable for compact gadgets, power devices, control apparatuses, and electric vehicles(full/hybrid). There are vital improvements in latest positive terminal electrode (cathode) materials to substitute the well developed LiCoO2 as cathode material for using in lithium-ion battery (LIBs). In this research work alternative cathode material Li2MnO3 (LMO) nano fibers has been investigated by electro- spinning technique. Physiochemical characterization of LMO nano fibers are performed by XRD (X-rays diffraction), scanning electron microscope (SEM). Electrochemical performance of LMO nano fibers will be investigated to check the capacity, cyclic performance, power density and energy density of the sample which definitely will be used in the lithium-ion batteries in the near future.

碩士
大同大學
材料工程學系(所)
102
Monoclinic Li2MnO3 cathode materials were prepared via Pechini method followed by heat treatment at temperatures between 600 and 900 oC. The effects of heat-treatment temperature and Cr substitution on the physical and the electrochemical properties of Li2MnO3 were investigated. The crystalline structure, composition, and morphology of the prepared samples were studied by XRD, ICP-OES, and FE-SEM, the average valence and of Cr in the prepared samples were estimated by XPS, and the electrochemical properties were analyzed by capacity retention study with Li2MnO3/Li coin-type cells. The reasons of capacity fade upon cycling investigated by TEM. The results of XRD study indicated that the Li2MnO3 prepared at temperatures between 600 and 900 oC crystalize into monoclinic with space group C2/m. From the results of XPS, it can be fiund that the content of Cr6+ increases with increasing Cr substitution for Mn. Among the samples prepared at temperatures between 600 and 900 °C, 600 oC sample shows the highest initial discharge capacity. Furthermore, it is also manifested that be initial discharge capacity is lowered by Cr substitution for Mn shows poor initial discharge capacity

Li-ion batteries have become indispensable in our modern, technology-driven world, powering a wide array of devices. As the demand for high-energy-density batteries continues to surge, there is a need to explore advanced cathode materials. In this regard, Li2MnO3 has emerged as a highly promising contender for high-voltage (>4.5 V) cathodes in Li-ion batteries. Li2MnO3 offers several advantages over conventional cathode materials such as LiCoO2 and intercalation-type compounds. Notably, Li2MnO3 possesses a remarkable high-voltage capability, which is crucial for achieving enhanced energy density in batteries. Furthermore, it exhibits favourable characteristics, including non-toxicity and ease of synthesis, making it an attractive alternative for Li-ion battery technology. In this study, Li2MnO3 was synthesized using a solid-state route, enabling its detailed characterization. X-ray Diffraction (XRD) analysis was employed to investigate the crystallographic properties of the synthesized material. The obtained XRD patterns were subjected to rigorous structural analysis using the Rietveld refinement technique. By applying Scherrer's formula to the XRD peaks, the crystallite size of Li2MnO3 was determined to be approximately 37.05 nm. To evaluate the electrochemical performance of Li2MnO3 as a cathode material, Electrochemical Impedance Spectroscopy (EIS) and Cyclic Voltammetry (CV) analyses were performed. EIS measurements provided valuable insights into charge transfer resistance and ion diffusion behavior, while CV analysis revealed distinct high-voltage peaks around 4.5 V, accompanied by supplementary low-voltage peaks at approximately 3.7 V. These electrochemical findings affirm the potential of Li2MnO3 as a high-voltage cathode material for Li-ion batteries. This study presents a comprehensive exploration of the synthesis, characterization, and electrochemical analysis of Li2MnO3 as a high-voltage cathode material for Li-ion batteries. Its exceptional attributes make it a promising candidate for next-generation battery technology. Ongoing research and development efforts in this area will undoubtedly contribute to the advancement of Li-ion batteries, enabling the creation of more efficient and high-performance energy storage solutions.

碩士
國立清華大學
材料科學工程學系
101
Both Li2MnO3 and LiNi1/3Co1/3Mn1/3O2 are layered structure, and they can be mixed to form a solid solution Li2MnO3．LiNi1/3Co1/3Mn1/3O2, which its charge-discharge region between 2 and 4.8 V. This material will release Li2O due to Li2MnO3 irreversible decomposition when voltage are above 4.5 V in the first charge cycle, and that’s the reson for loss of capacity in the first cycle. This experiment is composed by three part. First, I will discuss how the pH value affect the electrochemical performances when preparing Li2MnO3．LiNi1/3Co1/3Mn1/3O2 precursor through co-precipitation method. The second and the third parts will take apart Li2MnO3．LiNi1/3Co1/3Mn1/3O2 into Li2MnO3 and LiNi1/3Co1/3Mn1/3O2. We try to prepare Li2MnO3 and LiNi1/3Co1/3Mn1/3O2 through hydrothermal and co-precipitatio method, respectively, and observe how the order of these two step processes affect the electrochemical performances. In my report,process that using hydrothermal method to prepare Li2MnO3 first then co-precipitaion method to prepare LiNi1/3Co1/3Mn1/3O2 thereafter can lower the capacity loss in the first cycle, and even have higher capacity and better cycle ability comparing to Li2MnO3．LiNi1/3Co1/3Mn1/3O2 prepared by co-precipitation method.

Lithium ion batteries have been regarded as one of the most promising and intriguing energy storage devices in modern society since 1990s. A lithium ion battery contains three main components, cathode, anode, and electrolyte, and the performance of battery depends on each component and the compatibility between them. Electrolyte acts as a lithium ions conduction medium and two electrodes contribute mainly to the electrochemical performance. Generally, cathode is the limiting factor in terms of capacity and cell potential, which attracts significant research interests in this field.Different from conventional slurry thick film cathodes with additional electrochemically inactive additives, binder-free thin film cathode has become a promising candidate for advanced high-performance lithium ion batteries towards applications such as all-solid-state battery, portable electronics, and microelectronics. However, these electrodes generally require modifications to improve the performance due to intrinsically slow kinetics of cathode materials.

In this thesis work, pulsed laser deposition has been applied to design thin film cathode electrodes with advanced nanostructures and improved electrochemical performance. Both single-phase nanostructure designs and multi-phase nanocomposite designs are explored. In terms of materials, the thesis focuses on manganese based layered oxides because of their high electrochemical performance. In Chapter 3 of the nanocomposite cathode work, well dispersed Au nanoparticles were introduced into highly textured LiNi_0.5Mn_0.3Co_0.2O₂ (NMC532) matrix to act as localized current collectors and decrease the charge transfer resistance. To further develop this design, in Chapter 4, tilted Au pillars were incorporated into Li₂MnO₃ with more effective conductive Au distribution using simple one-step oblique angle pulsed laser deposition. In Chapter 5, the same methodology was also applied to grow 3D Li₂MnO₃ with tilted and isolated columnar morphology, which largely increase the lithium ion intercalation and the resulted rate capability. Finally, in Chapter 6, direct cathode integration of NMC532 was attempted on glass substrates for potential industrial applications.

Materials chemistry basically deals with rational design and synthesis of new solids exhibiting various functional properties. A sound knowledge of crystal structures and chemical bonding is needed to understand the properties of materials. Space group, cell parameters and atomic positions provide a basic crystallographic description of the structure. Crystal structure could be described in a detailed way in terms of close packing of anions and occupancy of cations in different coordination sites. The coordination polyhedra and their interconnectivity bring out the interrelationships between different structures and the properties exhibited. Transition metals (TMs) are d-block elements which occupy groups 3-12 in Periodic Table. IUPAC defines a TM as ‘an element whose atoms have partially filled d-shell, or which can give rise to cations with an incomplete d-shell’. The partially filled d-shell in TMs plays an important role in various chemical and physical properties of TMs. Although TM cations can form compounds with different anions, most of the TM containing compounds are metal oxides due to the large free energies for formation of oxides. Binary TM oxides adopt different kinds of structures among which rock salt (e.g. NiO), rutile (e.g. TiO2), and corundum (e.g. Cr2O3) are most common. Ternary TM oxides are also known to form in variety of structures with the perovskite (e.g. BaTiO3), and the spinel (e.g. MgFe2O4) structures being well known. TM oxides exhibit a broad range of electronic and magnetic properties. TM oxides, at one end, display metallic behavior (e.g. ReO3, RuO2, LaNiO3) due to the delocalized electrons and at other end, show insulating behavior (e.g. NiO) due to the localized electrons. In between, TM oxides have semiconducting properties involving either the hopping of carriers (e.g. partially reduced TiO2, Nb2O5, WO3 and so on) or the electron excitation from the valence band to the conduction band (e.g. SnO2). TM oxides are known to have diverse magnetic properties: diamagnetic (e.g. TiO2, ZrO2), paramagnetic (e.g. VO2, NbO2), ferromagnetic (e.g. CrO2, La0.67Ca0.33MnO3), ferrimagnetic (e.g. Fe3O4, MnFe2O4) and antiferromagnetic (e.g. NiO, LaCrO3). TM oxides with partially filled 3d-shell are expected to be ‘metallic’ according to Bloch-Wilson theory, but in practice they are Mott insulators (localized 3d electrons) because of correlation energy (U) involved in the transfer of d-electrons between adjacent sites. Certain TM oxides also show insulator-metal (I-M) transitions induced by change of temperature, pressure or composition. For example, VO2 and Ba2IrO4 are known for their temperature and pressure induced I-M transitions, respectively. La1-xSrxCoO3 becomes metal at a particular Sr concentration being one of the examples for composition-dependent I-M transition. TM oxides are usually synthesized by conventional ceramic method in which stoichiometric mixture of starting materials is reacted at elevated temperatures. Multiple prolonged heating with intermittent grindings in ceramic method generally results in thermodynamically controlled products. The metastable phases which are of interest may not be obtained by ceramic method. Chimie douce/soft chemistry methods are generally adopted to stabilize the metastable phases. The guiding principle behind the chimie douce is to have kinetic control (rather than thermodynamic control) to realize metastable phases. Accordingly, metastable derivatives are obtained by choosing appropriate precursors, or adopting sol-gel and molten flux or ion exchange/intercalation methods. The present thesis is devoted to an investigation of transition metal oxides towards development of functional materials exhibiting visible light absorption/emission and lithium insertion/extraction for cathode materials in lithium ion battery. TM oxides find application as photovoltaic materials, luminescent emission materials, photocatalysts, light absorption/pigment materials and so on, based on their optical properties. Ferroelectric TM oxides with perovskite structure [Green coloured (KNbO3)1-x (BaNi1/2Nb1/2O3-δ)x] are studied currently as photovoltaic materials which show high open circuit voltage (Voc = 3.5 V) despite very low short circuit current (Vsc = 40 nA cm-2). TM oxides are also known to exhibit photoluminescent emission which could be due to the doping activator ions (e.g. MnII doped Zn2GeO4) or TM oxide (e.g. CaWO4) itself being self-activator. While the green and red emissions are common for TM oxides, blue emission is rare (e.g. Ar+ irradiated SrTiO3 is a blue emitter). Coloured TM oxides with band gap in visible region are employed as photocatalysts for solar water splitting (e.g. yellow BiVO4, yellow Ag3PO4, yellow TaON, red Fe2O3) and photo-oxidation of organic pollutants (e.g. TiO2-xNx and CaCu3Ti4O12). The coloured TM oxides also find application as pigments from early times, for example, Egyptian blue (CaCuSi4O10), Han blue (BaCuSi4O10), Han purple (BaCuSi2O6), Malachite green (Cu2CO3(OH)2), Ochre red (Fe2O3) and many others. A list of pigments based on TM oxides is given in Table 1. Pigment materials are applied as colouring materials in inks, dyes, paints, plastics, ceramics glazers, enamels and textiles. Table 1. List of TM oxide based pigments and their colours Pigment colour Compound White Titanium dioxide (TiO2) Black Iron oxide black (Fe3O4) Red Iron oxide red (Fe2O3), Ca1-xLaxTaO2-xN1+x (yellow-red) Orange Iron oxide orange (Fe2O3) Yellow Yellow ochre [FeO(OH)·H2O] Green Malachite green [Cu2CO3(OH)2], Viridian (Cr2O3. 2H2O), Y2BaCuO5 Blue Egyptian blue (CaCuSi4O10),Cobalt aluminate (CoAl2O4), YIn1-xMnxO3 Purple Han purple (BaCuSi2O6) Violet Cobalt phosphate [Co3(PO4)2] Colours of the TM oxides arise from visible light absorption due to the ligand field d-d electronic transitions. Though d-d transitions are parity forbidden, the selection rules get relaxed due to different reasons such as symmetry reduction (due to distortion) and vibronic couplings. The colour of the TM oxides is influenced mainly by two factors (i) oxidation state of TM ion present and (ii) ligand field around the TM ion produced by anion geometry. In order to develop new pigment oxides, our strategy was to choose colourless metal oxides having unusual (five coordinated geometry) or irregular/distorted (distorted octahedral/tetrahedral) coordination geometries around metal ion and produce coloured oxides by substituting 3d-TM ions at the metal ion site. We made a detailed study on the origin of the colour and pigment quality of the resulting coloured oxides. In the present thesis, which has two parts, the first part (Part 1) discusses the development of 3d-TM ion substituted coloured oxides with potential for pigment applications. Chapter 1.1 describes the purple inorganic pigment, YGa1-xMnxO3 (0 < x ≤ 0.10), based on the hexagonal YGaO3. The metastable series of oxides were prepared by a sol-gel technique where the dried gels, obtained from aqueous solutions of metal nitrates-citric acid mixtures, were calcined for a short duration in preheated furnace around 850°C/10 mins. The purple colour of the oxides arises from the specific trigonal bipyramidal ligand field around MnIII that obtains in the YGaO3 host. Other hexagonal RGaO3 hosts for R = Lu, Tm and Ho substituted with MnIII also produce similar purple coloured materials. In Chapter 1.2, we present a study on substitution of 3d-TM ions in LiMgBO3 host [where Mg(II) has a trigonal bipyramidal (TBP) oxygen coordination)]. We find that single-phase materials are formed for LiMg1-xCo(II)xBO3 (0 < x ≤ 1.0), LiMg1-xNi(II)xBO3 (0 < x ≤ 0.1), LiMg1-xCu(II)xBO3 (0 < x ≤ 0.1) and also Li1-xMg1-xFe(III)xBO3 (0 < x ≤ 0.1) of which the Co(II) and Ni(II) derivatives are strongly coloured, purple-blue and beige-red respectively, thus identifying TBP CoO5 and NiO5 as the new chromophores for these colours. Chapter 1.3 describes the synthesis, crystal structures and optical absorption spectra/colours of 3d-TM substituted α-LiZnBO3 derivatives: α-LiZn1-xMIIxBO3 [MII = CoII (0 < x < 0.50), NiII (0 < x ≤ 0.05) and CuII (0 < x 0.10)] and α-Li1+xZn1-2xMIIIxBO3 [MIII = MnIII (0 < x ≤ 0.10) and FeIII (0 < x 0.25)]. The crystal structure of the host α-LiZnBO3, which is both disordered and distorted with respect to Li and Zn occupancies and coordination geometries, is largely retained in the derivatives, giving rise to unique colours [blue for CoII, magenta for NiII and violet for CuII], that could be of significance for the development of new, inexpensive and environmentally-benevolent pigment materials, especially for the blue colour. Accordingly, the work indentifies distorted tetrahedral MO4 (M = Co, Ni, Cu) (together with a long M-O bond that gives a trigonal bipyramidal geometry) structural units as the new chromophores for the blue, magenta and violet colours respectively, in the α-LiZnBO3 host. In Chapter 1.4, we describe the synthesis, crystal structures and optical absorption spectra of 3d-TM substituted spiroffite derivatives, Zn2-xMxTe3O8 (MII = Co, Ni, Cu; 0 < x ≤ 1.0). The oxides are readily synthesized by solid state reaction of stoichiometric mixtures of the constituent binaries at 620°C/12h. Rietveld refinement of the crystal structures from powder XRD data shows that the Zn/MO6 octahedra are strongly distorted, as in the parent Zn2Te3O8 structure, consisting of five relatively short Zn/MII – O bonds (1.898 – 2.236 Å) and one longer Zn/MII– O bond (2.356 – 2.519 Å). We have interpreted the unique colors and the optical absorption/diffuse reflectance spectra of Zn2-xMxTe3O8 in the visible, in terms of the observed/irregular coordination geometry of the Zn/MII – O chromophores. We could not however prepare the fully-substituted M2Te3O8 (MII = Co, Ni, Cu) by the direct solid state reaction method. Density Functional Theory (DFT) modeling of the electronic structure of both the parent and the transition metal substituted derivatives provides new insights into the bonding and the role of transition metals toward the origin of color in these materials. We believe that transition metal substituted spiroffites Zn2-xMxTe3O8 reported here suggest new directions for the development of colored inorganic materials/pigments featuring irregular/distorted oxygen coordination polyhedra around transition metal ions. Red coloured materials are rare in nature. Li2MnO3 is a unique oxide with an unusual red colour imparted by MnIV ions. Chapter 1.5 describes a detailed experimental investigation of Li2MnO3 together with other related MnIV oxides that probes the red colour of Li2MnO3 as well as its photoluminescence. Optical absorption spectra reveal a strong band gap absorption with a sharp edge at ~ 610 nm and a transparent region between ~ 610 and ~ 650 nm that causes the red colour of Li2MnO3 samples. Octahedral MnIV ligand field transitions, corresponding to both MnIV at ideal sites and MnIV displaced to Li sites in the rock salt based layered structure of Li2MnO3, are observed in the excitation spectra of Li2MnO3 samples. Optical excitation at the ligand field transition energies produces tunable emission in the red-yellow-green region, rendering Li2MnO3 a unique MnIV oxide. The honeycomb ordered [LiMn6] units in the structure likely causes both the absorption and photoluminescence properties of Li2MnO3. Lithium containing TM oxides with rock salt related structure are being investigated extensively for application as next generation cathode materials for Lithium ion batteries (LIBs). Recent research is focused on lithium-rich layered oxides (LLOs) which are solid solutions between Li2MO3 (where M = Ti, Mn and Ru) and LiMO2 (where M = Cr, Mn, Fe, Co, Ni). LLOs have excess lithium in the TM layer in addition to lithium in lithium layer of rock salt derived structure. LLOs have gained attention because of their higher discharge capacity in the range of ~ 250 mAhg-1. While most of the LLOs investigated so far contain 3d-TM ions (Mn, Fe, Co, Ni), recently there has been an interest in the study of the role of ruthenium in addition to 3d-TM ions. We have investigated ruthenium containing LLOs with a view to probe (i) the role of ruthenium and (ii) the concentration of excess lithium in the TM layers in producing higher discharge capacities. The results are discussed in the Part 2 of the thesis.Li5NiMnRuO8(Li[Li0.25Ni0.25Mn0.25Ru0.25]O2) form in the Li2RuO3 crystal structure. Electrochemical studies indicate that the Co-containing oxides exhibit a higher initial discharge capacity (for e.g. ~ 180 mAhg-1 for Li4CoRuO6) as well as a higher reversible discharge capacity (~130 mAhg-1 for Li4CoRuO6) compared to the corresponding Ni-analogs. Participation of oxide ions (higher oxidation state of Ru) in the redox process could explain the higher discharge capacity during the first cycle. Reduced capacity (capacity fade) during the subsequent cycles could arise from the oxygen evolution due to the redox process (2O2- → 2O- → O2), which is not reversible. The present work shows that ruthenium incorporation in rock salt layered oxides along with Co/Ni appears to give a beneficial effect in producing a higher discharge capacity. In addition, the compounds crystallizing with the R-3m structure (related to LiCoO2) appear to give a better reversible capacity than the compounds crystallizing in the C2/c structures (Li2TiO3 and Li2RuO3).