Les mécanismes mis en jeu lors du cyclage de batteries au Lithium Li//Li1.20Mn0.54Co0.13Ni0.13O2 ont été étudiés avec l’objectif de déterminer l’origine des capacités très élevées délivrées par les oxydes lamellaires « (1-x)LiMO2.xLi2MnO3 ». La caractérisation par diffraction des RX et des neutrons montre que la structure est maintenue et l’existence de fluctuations de composition qui peuvent être assimilées à l’existence de deux phases de compositions voisines. Les résultats des tests électrochimiques et les analyses menées au cours du cyclage en spectroscopie d’absorption des rayons X ont suggéré la participation de l’oxygène aux processus redox. Celle-ci a été confirmée par la préparation et la caractérisation de matériaux désintercalés et réintercalés chimiquement en lithium. Les analyses en microscopie électronique à transmission (HAADF-STEM) et en nanodiffraction, montrent qu’une densification associée à un dégagement d’oxygène a lieu à la périphérie des particules / The charge and discharge mechanism of Li1.20Mn0.54Co0.13Ni0.13O2 was studied using several characterization tools in order to determine the origin of the high capacity observed for the system (1-x)LiMO2.xLi2MnO3 used as positive electrode for Li-ion batteries. The electrochemical results and in operando XAS analyses performed during the 1st cycle of Li//Li1.20Mn0.54Co0.13Ni0.13O2 cells suggested the possible participation of oxygen anion to the redox processes. It was supported by the in-depth analysis of materials prepared by chemical Li deintercalation and reinsertion. The results of XRD, HAADF-STEM and nanodiffraction analyses, combined with electrochemical experiments performed in different conditions (rate, temperature …), revealed that different types of reactions occur in the particles during the 1st cycle. Within the bulk Ni, Co and O are involved in the redox processes, whereas Mn is not: oxygen ions are oxidized in charge and reduced during the next discharge reversibly. At the surface, the same oxidation processes occur during the first charge, but with the release of oxygen gaz and a densification of the lattice. During the next discharge and subsequent cycles, the redox reaction occurring near the surface after the 1st charge involves thus Co, Ni and Mn.

Transition metals (TMs) are ‘elements whose atoms have partially filled d-shell, or which can give rise to cations with an incomplete d-shell’. In TMs, the d-shell overlaps with next higher s-shell. Most of the TMs exhibit more than one (multiple) oxidation states. Some TMs, such as silver and gold, occur naturally in their metallic state but, most of the TM minerals are generally oxides. Most of the minerals on the planet earth are metal oxides, because of large free energies of formation for the oxides. The thermodynamic stability of the oxides is determined from the Ellingham diagram. Ellingham diagram shows the temperature dependence of the stability (free energy) for binaries such as metal oxides. Ellingham diagram also shows the ease of reducibility of metal oxides. TM oxides of general formulas MO, M2O3, MO2, M2O5, MO3 are known to exist, many of them being the ultimate products of oxidation in air in their highest oxidation states. In addition, TM oxides also exist in lower oxidation states which are prepared under controlled conditions. The nature of bonding in these oxides varies from mainly ionic (e.g. NiO, CoO) to mainly covalent (e.g. OsO4). Simple binary oxides of the compositions, MO, generally possess the rock salt structure (e.g. NiO), while the dioxides, MO2, possess the rutile structure (e.g. TiO2); many sesquioxides, M2O3, possess the corundum structure (e.g. Cr2O3). TMs form important ternary oxides like perovskites (e.g. CaTiO3), spinels (e.g. MgFe2O4) and so on. In TM oxides, the valence (outer) d-shell could be empty, d0 (e. g. TiO2), partially filled, dn (1≤ n≤ 9) (e.g. TiO, VO, NiO etc.) or completely filled, d10 (e.g. ZnO, CdO, Cu2O etc.). The outer d electrons in TM oxides could be localized or delocalized. Localized outer d electrons give insulators/semiconductors, while delocalized/itinerant d electrons make the TM oxide ‘metallic’ (e.g. ReO3, RuO2). Partially filled dn states are normally expected to give rise to itinerant (metallic) electron behaviour. But most of TM oxides with partially filled d shell are insulators because of special electronic energy (correlation energy) involved in d electron transfer to adjacent sites. Such insulating TM oxides are known as Mott insulators (e. g. NiO, CoO etc.). Certain TM oxides are known to exhibit both localized (insulating) and itinerant (metallic) behaviour as a function of temperature or pressure. For example, VO2 shows a insulator–metal transition at ~340K. Similar transitions are also known for V2O3, metal-rich EuO and so on. The chemical composition and bonding of TM oxides, which determine the crystal and electronic structures, give rise to functional properties. Table 1 gives representative examples. Properties like ionic conductivity and diffusion are governed by both the crystal structure and the defect structure (point defects), whereas properties such as magnetism and electron transport mainly arise from the electronic structures of the materials. Accordingly, TM oxides provide a platform for exploring functional materials properties. Among the various functional materials properties exhibited by transition metal oxides, the present thesis is devoted to investigations of lithium ion battery cathodes, inorganic pigments and magnetic perovskites. Over the years, most of the lithium containing first row transition metal oxides of rock salt derived structure have been investigated for possible application as cathode materials in lithium ion batteries (LIBs). First major breakthrough in LIBs research was achieved by electrochemically deinserting and inserting lithium in LiCoO2. A new series of cathode materials for LIBs were prepared by incorporating excess lithium into the transition metal containing layered lithium oxides through solid solution formation between Li2MnO3–LiMO2 (M = Cr, Mn, Fe, Co, Ni), known as lithium-rich layered oxides (LLOs). LLOs exhibit improved electrochemical performance as compared to the corresponding end members and hence received significant attention as a potential next generation cathode materials for LIBs in recent times. LiCoO2 (R-3m) crystallizes in the layered α-NaFeO2 structure with the oxygens in a ccp arrangement. Li+ and Co3+ ions almost perfectly order in the octahedral sites (3a and 3b) to give alternating (111) planes of LiO6 and CoO6 octahedra. Table 1. Materials properties exhibited by representative TM oxides. Property Example(s) Ferroelectricity BaTiO3, PbTiO3, Bi4Ti3O12 Nonlinear Optical Response LiNbO3 Multiferroic response BiFeO3, TbMnO3 Microwave dielectric properties Ba3ZnTa2O9 Relaxor Dielectric Properties Pb3MgNb2O9, Colossal Magnetoresistance Tl2Mn2O7 Metallic ‘Ferroelectricity’ Cd2Re2O7 Superconductivity AOs2O6(A = K, Rb, Cs) Redox deinsertion/insertion of LiCoO2 lithium Photocatalysis/water splitting TiO2 Pigment Ca(1-x)LaxTaO(2-x)N1+x (yellow-red), YIn1-xMnxO3 (blue) Metallic Ferromagnetism CrO2 Antiferromagnetism NiO, LaFeO3 Zero thermal expansion ZrW2O8 The reversible capacity of LiCoO2 in common LIBs is relatively low at around 140 mA h g-1 (half of theoretical capacity), corresponding to: LiCo3+O2 → Li0.5Co3+0.5Co4+0.5O2 + 0.5Li+ + 0.5e– . Substitution of one or more transition metal ions in LiCOO2 has been explored to improve the electrochemical performance. The structure of LLOs is described as a solid solution or nano composite of Li2MnO3 (C2/m) and LiMO2 (R-3m). The electrochemical deinsertion/insertion behaviour of LLOs is complex and also not yet understood completely. The present thesis consists of four parts. After a brief introduction (Part 1), Part 2 is devoted to materials for Li-ion battery cathode, consisting of three Chapters 2.1, 2.2 and 2.3. In Chapter 2.1, we describe the synthesis, crystal structure, magnetic and electrochemical characterization of new LiCoO2 type rock salt oxides of formula, Li3M2RuO6 (M = Co, Ni). The M =Co oxide adopts the LiCoO2 (R-3m) structure, whereas the M = Ni oxide also adopts a similar layered structure related to Li2TiO3. Magnetic susceptibility measurements reveal that in Li3Co2RuO6, the oxidation states of transition metal ions are Co3+, Co2+ and Ru4+, whereas in Li3Ni2RuO6, the oxidation states are Ni2+ and Ru5+. Li3Co2RuO6 orders antiferromagnetically at ~10K. On the other hand, Li3Ni2RuO6 presents a ferrimagnetic behaviour with a Curie temperature of ~100K. Electrochemical Li-deinsertion/insertion studies show that high first charge capacities (between ca.160 and 180 mA h g−1) corresponding to ca.2/3 of theoretical capacity are reached albeit, in both cases, capacity retention and cyclability are not satisfactory. Chapter 2.2 presents a study of new ruthenium containing LLOs, Li3MRuO5 (M = Co and Ni). Both the oxides crystallize in the layered LLO type LiCoO2 (α-NaFeO2) structure consisting of Li[Li0.2M0.4Ru0.4]O2 layers. Magnetic susceptibility data suggest that the oxidation states of transition metals are Li3Co3+Ru4+O5 for the M = Co compound and Li3Ni2+Ru5+O5 for the M = Ni compound. Electrochemical investigations of lithium deintercalation–intercalation behaviour reveal that both Co and Ni phases exhibit attractive specific capacities of ca. 200 mA h g-1 at an average voltage of 4 V, that has been interpreted as due to the oxidation of Co3+ and Ru4+ in Li3CoRuO5 and Ni2+ to Ni4+ in the case of Li3NiRuO5. Thus, we find that ruthenium plays a favourable role in LLOs than in non-LLOs in stabilizing higher reversible electrochemical capacities. In Chapter 2.3, we describe the synthesis, crystal structure and lithium deinsertion–insertion electrochemistry of two new LLOs, Li3MRuO5 (M=Mn, Fe) which are analogs of the oxides described in Chapter 2.2. The Li3MnRuO5 oxide adopts a structure related to Li2MnO3 (C2/m), while the Li3FeRuO5 oxide adopts a near-perfect LiCoO2 (R-3m) structure. Lithium electrochemistry shows typical behaviour of LLOs for both oxides, where participation of oxide ions in the electrochemical processes is observed. A long first charge process with capacities of 240 mA h g-1 (2.3 Li per f.u.) and 144 mA h g-1 (1.38 Li per f.u.) is observed for Li3MnRuO5 and Li3FeRuO5, respectively. Further discharge–charge cycling points to partial reversibility. X-ray photoelectron spectroscopy (XPS) characterisation of both pristine and electrochemically oxidized Li3MRuO5 reveals that in the Li3MnRuO5 oxide, Mn3+ and Ru4+ are partially oxidized to Mn4+ and Ru5+ in the sloping region at low voltage, while in the long plateau, O2- is also oxidized. In the Li3FeRuO5 oxide, the oxidation process appears to affect only Ru (4+ to 5+ in the sloping region) and O2- (plateau), while Fe seems to retain its 3+ state. Another characteristic feature of TMs is formation of several coloured solid materials where d–d transitions, band gap transitions and charge transfer transitions are involved in the colouration mechanism. Coloured TM oxides absorbing visible light find important applications as visible light photocatalyst (for example, yellow BiVO4 for solar water splitting and red Sr1-xNbO3 for oxidation of methylene blue) and inorganic pigments [for example, Egyptian blue (CaCuSi4O10), Malachite green (Cu2CO3(OH)2), Ochre red (Fe2O3)]. Pigments are applied as colouring materials in inks, dyes, paints, plastics, ceramic glazers, enamels and textiles. In this thesis, we have focused on the coloured TM oxides for possible application as inorganic pigments. Generally, colours arise from electronic transitions that absorb visible light. Colours of the inorganic pigments arise mainly from electronic transitions involving TM ions in various ligand fields and charge transfer transitions governed by different selection rules. The ligand field d–d transitions are parity forbidden but are relaxed due to various reasons, such as distortion (absence of center of inversion) and vibronic coupling. The d-electrons can be excited by light absorption in the visible region of the spectrum imparting colour to the material. Charge transfer transitions in the visible region are not restricted by the parity selection rules and therefore give intense colours. Here we have investigated the colours of manganese in unusual oxidation state (Mn5+) as well as the colours of different 3d-TM ions in distorted octahedral and trigonal prismatic sites in appropriate colourless crystalline host oxides. These results are discussed in Part 3 of the thesis. In Chapter 3.1, we describe a blue/green inorganic material, Ba3(P1−xMnxO4)2 (I) based on tetrahedral Mn5+O4 :3d2 chromophore. The solid solutions (I) which are sky-blue and turquoise-blue for x ≤ 0•25 and dark green for x ≥ 0•50, are readily synthesized in air from commonly available starting materials, stabilizing the Mn5+O4 chromophore in an isostructural phosphate host. We suggest that the covalency/ionicity of P–O/Mn–O bonds in the solid solutions tunes the crystal field strength around Mn(V) such that a blue colour results for materials with small values of x. The material could serve as a nontoxic blue/green inorganic pigment. In Chapter 3.2, an experimental investigation of the stabilization of the turquoise-coloured Mn5+O4 chromophore in various oxide hosts, viz., A3(VO4)2 (A = Ba, Sr, Ca), YVO4, and Ba2MO4 (M = Ti, Si), has been carried out. The results reveal that substitution of Mn5+O4 occurs in Ba3(VO4)2 forming the entire solid solution series Ba3(V1−xMnxO4)2 (0 < x ≤ 1.0), while, with the corresponding strontium derivative, only up to about 10% of Mn5+O4 substitution is possible. Ca3(VO4)2 and YVO4 do not stabilize Mn5+O4 at all. With Ba2MO4 (M = Ti, Si), we could prepare only partially substituted materials, Ba2M1−xMn5+xO4+x/2 for x up to 0.15, that are turquoise-coloured. We rationalize the results that a large stabilization of the O 2p-valence band states occurs in the presence of the electropositive barium that renders the Mn5+ oxidation state accessible in oxoanion compounds containing PO43−, VO43−, etc. By way of proof-of-concept, we synthesized new turquoise-coloured Mn5+O4 materials, Ba5(BO3)(MnO4)2Cl and Ba5(BO3)(PO4)(MnO4)Cl, based on the apatite – Ba5(PO4)3Cl – structure. Chapter 3.3 discusses crystal structures, and optical absorption spectra/colours of 3d-transition metal substituted lyonsite type oxides, Li3Al1-xMIIIx(MoO4)3 (0< x ≤1.0) (MIII = Cr, Fe) and Li3-xAl1-xMII2x(MoO4)3 (0< x ≤1.0) (MII = Co, Ni, Cu). Crystal structures determined from Rietveld refinement of PXRD data reveal that in the smaller trivalent metal substituted lyonsite oxides, MIII ions occupy the octahedral (8d, 4c) sites and the lithium ions exclusively occur at the trigonal prismatic (4c) site in the orthorhombic (Pnma) structure; on the other hand, larger divalent cations (CoII/CuII) substituted derivatives show occupancy of CoII/CuII ions at both the octahedral and trigonal prismatic sites. We have investigated the colours and optical absorption spectra of Li3Al1-xMIIIx(MoO4)3 (MIII = Cr, Fe) and Li3-xAl1-xMII2x(MoO4)3 (MII = Co, Ni, Cu) and interpreted the results in terms of average crystal field strengths experienced by MIII/MII ions at multiple coordination geometries. We have also identified the role of metal-to-metal charge transfer (MMCT) from the partially filled transition metal 3d orbitals to the empty Mo – 4d orbitals in the resulting colours of these oxides. B The ABO3 perovskite structure consists of a three dimensional framework of corner shared BO6 octahedra in which large A cation occupies dodecahedral site, surrounded by twelve oxide ions. The ideal cubic structure occurs when the Goldschmidt’s tolerance factor, t = (rA + rO)/{√2(rB + rO)}, adopts a value of unity and the A–O and B–O bond distances are perfectly matched. The BO6 octahedra tilt and bend the B – O – B bridges co-operatively to adjust for the non-ideal size of A cations, resulting deviation from ideal cubic structure to lower symmetries. Ordering of cations at the A and B sites of perovskite structure is an important phenomenon. Ordering of site cations in double (A2BB'O6) and multiple (A3BB'2O9) perovskites give rise to newer and interesting materials properties. Depending upon the constituent transition metals and ordering, double perovskite oxides exhibit a variety of magnetic behaviour such as ferromagnetism, ferrimagnetism, antiferromagnetism, spin-glass magnetism and so on. We also have coupled magnetic properties such as magnetoresistance (Sr2FeMoO6), magnetodielectric (La2NiMnO6) and magnetooptic (Sr2CrWO6) behaviour. Here we have investigated new magnetically frustrated double perovskite oxides of the formula Ln3B2RuO9(B = Co, Ni and Ln = La, Nd). The Chapter 4.1 describes Ln3B2RuO9 (B = Co, Ni and Ln = La, Nd) oxides (prepared by a solid state metathesis route) which adopt a monoclinic (P21/n) A2BB'O6 double perovskite structure, wherein the two independent octahedral 2c and 2d sites are occupied by B2+ and (B2+1/3Ru5+2/3) atoms, respectively. Temperature dependence of the molar magnetic susceptibility plots obtained under zero field cooled (ZFC) condition exhibit maxima in the temperature range 25–35K, suggesting an antiferromagnetic interaction in all these oxides. Ln3B2RuO9 oxides show spin-glass behavior and no long-range magnetic order is found down to 2 K. The results reveal the importance of competing nearest neighbour (NN), next nearest neighbor (NNN) and third nearest neighbour (third NN) interactions between the magnetic Ni2+/Co2+ and Ru5+ atoms in the partially ordered double perovskite structure that conspire to thwart the expected ferromagnetic order in these materials.

Batteries are increasingly seen as an indispensable element in the rapid progress of the energy transition. With forecasts for global demand set to reach 2 TWh by 2030 and increasing policy support for battery manufacturers, many questions arise on whether the current rapid expansion of battery manufacturing industry is sustainable. Issues regarding the stability of the supply chain and rising energy security concerns has led to an expanded focus on alternate battery technologies. Sodium ion cells are commonly cited as a potential solution to many of the current issues facing the lithium-ion battery industry. With sodium ion cells reaching commercialization, this thesis would like to explore the viability of commercial sodium ion cells through a bottom-up manufacturing and regional cost analysis of Sodium Prussian Blue Analogues and Sodium Layered Oxides. To account for the more qualitative aspects of regional battery manufacturing, the current policy framework and supply chain are briefly explored. To study the current commercial sodium ion cells, the report considers Na0.9[Cu0.22Fe0.30Mn0.48] O2 (Na Oxide) and Na2MnFe(CN)6 (Na PBA) cathode chemistries which are similar to the cells manufactured by HiNa and Novasis Energies respectively. These cells are compared to two of the most common Lithium chemistries on the market, LiFePO4 (LFP) and LiNi0.3Mn0.3Co0.3 (Li NMC111). Various manufacturing scales of the model plant are explored for each chemistry, and the changes in manufacturing costs for the US, China, India, Sweden and Chile are explored. Considering a baseline plant of 1500 MWh/yr, the base case results show that from the cost perspective the sodium ion cells are not too different from that of the lithium-ion cells. The cost of the lithium ion cells NMC111 and LFP (2019 US$) are at 126 $/kWh and 113$/kWh while the Na Oxide and Na PBA cell costs are at 125 $/kWh and 148 $/kWh. While the costs are comparable, the volumetric energy density of the sodium cells is almost half that of their lithium counterparts, which hampers the overall cost advantage from the cheaper materials. Compared to the lithium cells where the cathode and anode are on average the most expensive components, the separator and the hard carbon anode become the most expensive cost components in the sodium ion cells studied. In the regional analysis, China and Chile have the cheapest cell costs for both sodium and lithium, while the US and India are the most expensive within the countries studied with the maximum cost difference in the range of 15 $/kWh. While most countries have differing approaches in terms of policy support, the trend towards domestic sourcing of supplies can clearly be seen in most of the countries studied. The past three years has seen interest in battery manufacturing escalate significantly, with slow policy support in the 2010s from most countries. Chile is a notable exception with a lack of strong policy support. For the manufacturing scale, it was found that the minimum effective scale was 1500 MWh annually. The capital costs for the sodium ion cell plants were 16% more expensive than the lithium cell plants due to increased production rates to meet the same annual production. With cathode thickness, it was found that the Na PBA cell benefited the most with the increase in thickness, as it had the highest CAM capacity. The cost advantages of the sodium ion cells start to materialise when considering the increase in price of materials in 2022. When considering increased metal costs in 2022, the price of the Li NMC and LFP cells increase to around 186 $/kWh, while sodium ion cells don’t display an appreciable change in cost. Furthermore, when considering a higher power rate of 5C, the lithium cells perform poorly with Li NMC increasing to 188 $/kWh and LFP to 148 $/kWh while the sodium cells remain close to their 0.2C costs at 148$/kWh for Na PBA and 127 $/kWh for Na Oxide. / Batterier betraktas i allt högre grad som en oumbärlig komponent i den snabba utvecklingen av energiomställningen. Med prognoser som visar att den globala efterfrågan kommer att nå 2 TWh år 2030, och med ökat stöd från myndigheter till batteritillverkare, uppstår många frågor om huruvida den nuvarande snabba expansionen av batteritillverkningsindustrin är hållbar. Frågor om stabiliteten i leveranskedjan och ökad oro för energisäkerheten har lett till ett ökat fokus på alternativa batteriteknologier. Natriumjonceller nämns ofta som en potentiell lösning på många av de aktuella problemen som litiumjonbatteriindustrin står inför. Denna avhandling syftar till att undersöka livsdugligheten hos kommersiella natriumjonceller genom en bottom-up-tillverkning och regional kostnadsanalys av natriumpreussiska blåanaloger och natriumskiktade oxider. För att belysa de mer kvalitativa aspekterna av regional batteritillverkning undersöks även den nuvarande politiska ramen och leveranskedjan kortfattat. För att studera de nuvarande kommersiella natriumjoncellerna överväger rapporten katodkemin Na0.9[Cu0.22Fe0.30Mn0.48]O2 (Na Oxide) och Na2MnFe(CN)6 (Na PBA), som liknar celler som tillverkas av HiNa respektive Novasis Energies. Dessa celler jämförs med två av de vanligaste litiumkemikalierna på marknaden, LiFePO4 (LFP) och LiNi0.3Mn0.3Co0.3 (Li NMC111). Olika tillverkningsskalor i modellfabriker undersöks för varje kemikalie, och förändringarna i tillverkningskostnaderna i USA, Kina, Indien, Sverige och Chile analyseras. Med en baslinjeanläggning på 1500 MWh/år visar basfallsresultaten att natriumjoncellerna inte skiljer sig alltför mycket kostnadsmässigt från litiumjoncellerna. Kostnaden för litiumjoncellerna NMC111 och LFP är 126 $/kWh respektive 113 $/kWh, medan kostnaderna för Na Oxide och Na PBA-celler ligger på 125 $/kWh respektive 148 $/kWh. Trots att kostnaderna är jämförbara är natriumcellernas volymetriska energitäthet nästan hälften så stor som deras litiumequivalenter, vilket minskar den totala kostnadsfördelen av de billigare materialen. Jämfört med litiumcellerna, där katoden och anoden i genomsnitt utgör de dyraste komponenterna, är separatorn och hårdkolanoden de dyraste kostnadskomponenterna i de undersökta natriumjoncellerna. I den regionala analysen har Kina och Chile de lägsta cellkostnaderna för både natrium och litium, medan USA och Indien är dyrast bland de undersökta länderna med en maximal kostnadsskillnad på 15 $/kWh. Även om de flesta länder har olika tillvägagångssätt när det gäller politiskt stöd, kan trenden mot inhemska inköp av material tydligt ses i de flesta av de undersökta länderna. Under de senaste tre åren har intresset för batteritillverkning ökat betydligt, efter ett långsamt politiskt stöd under 2010-talet från de flesta länder. Chile utgör ett anmärkningsvärt undantag med brist på starkt politiskt stöd. Vid tillverkningsskalan fann man att den lägsta effektiva skalan var 1500 MWh årligen. Kapitalkostnaderna för natriumjoncellsanläggningar var 16 % dyrare än för litiumjoncellsanläggningar på grund av ökade produktionshastigheter för att uppnå samma årsproduktion. När det gäller katoddjocklek så gynnades Na PBA-cellen mest av en ökning i tjocklek, eftersom den hade den högsta CAM-kapaciteten. Fördelarna med natriumjonceller börjar realiseras när man beaktar prisökningen på material år 2022. Vid en ökning av metallkostnaderna 2022 ökar priset på Li NMC- och LFP-cellerna till cirka 186 $/kWh, medan kostnaden för natriumjoncellerna inte uppvisar någon märkbar förändring. Dessutom, vid en högre effekt på 5C, presterar litiumcellerna dåligt med en kostnad på 188 $/kWh för Li NMC och 148 $/kWh för LFP, medan kostnaden för natriumcellerna förblir nära deras kostnader vid 0,2C, nämligen 148 $/kWh för Na PBA och 127 $/kWh för Na Oxide.

Ce travail de thèse présente l’étude du diagramme de phase des oxydes lamellaires NaxMoO2dans le cadre de la recherche de nouveaux matériaux. L’identification des transitionsstructurales au cours de l’intercalation et désintercalation électrochimique du sodium dans lesdomaines de composition ½ ≤ x ≤ 1 et ¼ < x ≤ ½ a été faite par électrochimie combinée à ladiffraction des rayons X in situ. Il a été montré que le profil très accidenté de la courbegalvanostatique résulte de multiples réarrangements structuraux au cours du cyclage.Notamment l’existence de nombreuses phases NaxMoO2 particulières a été mise en évidence,pour lesquelles des mises en ordre des ions sodium et des atomes de molybdène sont attendues.Des composés Na~1/2MoO2, Na~2/3MoO2 et NaMoO2 ont été synthétisés ex situ par voieélectrochimique ou chimique et leur caractérisation révèle des arrangements structurauxcomplexes, tel que des chaînes de clusters de molybdène dans les feuillets [MoO2] de NaMoO2. / This work concerns the investigation of the phase diagram of sodium layered oxides NaxMoO2in the search of new materials. Structural transitions upon sodium electrochemical(de)intercalation were studied by electrochemistry combined with in situ X-ray diffraction forcompositions ½ ≤ x ≤ 1 et ¼ < x ≤ ½. It was shown that the very undulating aspect of theelectrochemical curve results from multiple structural rerarrangements upon cycling. Especiallynumerous NaxMoO2 specific phases have been evidenced, for which sodium/vacancy orderingsas well as the formation of Mo-Mo bonds are expected. Na~1/2MoO2, Na~2/3MoO2 et NaMoO2compounds have been (electro)chemically synthesized and their structural characterizationreveals complex structures, such as chains of diamond-like molybdenum clusters in NaMoO2.

Selon le taux de sodium, par exemple de bonnes caractéristiques thermoélectriques pour les phases riches en sodium, ainsi que la supraconductivité pour certaines compositions (x ~ 0.3) hydratées, en font un exemple de choix pour étudier les corrélations entre la structure et les propriétés. La première partie de ce travail utilise l’électrochimie et la technique de batteries au sodium pour explorer en détail et de manière continue le diagramme de phase de ce système (pour x ≥ 0.5), en particulier avec un suivi in situ par diffraction des rayons X de l’intercalation d’ions sodium. Les compositions monophasées sont caractérisées par un potentiel électrochimique propre, et leur stabilité thermique relative est étudiée lors de cyclages à différentes températures.Dérivant de P2-NaxCoO2, le système ordonné OP4-(Li/Na)CoO2 se caractérise également par des propriétés thermoélectriques remarquables. La seconde partie de ce travail approfondit la connaissance de ce système caractérisé par une intercalation alternée des ions lithium et sodium. A partir de cet empilement, par des échanges ioniques topotactiques, trois nouveaux empilements théoriquement simulés sont expérimentalement mis en évidence et caractérisés. Il s’agit des polytypes inédits O4-LiCoO2 et D4-AgCoO2, ainsi que de l’empilement OD4-(Li/Ag)CoO2, premier exemple d’une intercroissance NaCl / delafossite au sein d’une même structure lamellaire. / The P2-NaxCoO system exhibits various outstanding physical phenomena such as promising thermoelectric properties (for x ~ 0.7) and superconductivity for hydrated compositions. The first part of the present study uses electrochemistry through sodium batteries to deeply explore the P2-NaxCoO2 phase diagram (for x ≥ 0.5) in a continuous way, with especially an in situ XRD experiment that follows sodium ions intercalation. Peculiar single-phase compositions are characterized by a specific electrochemical voltage, and their relative thermal stability is studied through electrochemical cycling at various temperatures.The second part of this project deals with the ordered OP4-(Li/Na)CoO2 system which also exhibits promising thermoelectric features. Its structure is characterized by an alternate intercalation of lithium and sodium ions. Using this system, topotactic ionic exchanges enable to obtain three new stackings, O4-LiCoO2, D4-AgCoO2, and the OD4-(Li/Ag)CoO2 which are first simulated, experimentally evidenced and then characterized. The OD4 stacking is thefirst example of a NaCl / delafossite intergrowth in the same layered structure.