Anion intercalation in the graphite positive electrode of a dual-ion battery requires high potential (> 4.3 V vs Li+/Li), which aggravates parasitic reactions involving electrolyte decomposition and Al corrosion, manifesting in poor coulombic efficiency, cycle life, and quick self-discharge. This study aims to investigate the stability of anion-intercalated graphite electrodes in a 4 M solution of lithium bis(fluorosulfonyl)imide (LiFSI) in ethyl methyl carbonate (EMC) using both in-situ and ex-situ Raman spectroscopy. The concentrated electrolyte is essential as it limits parasitic reactions at the cathode-electrolyte interface (CEI) occurring in parallel to anion intercalation. Using electrochemical methods including cyclic voltammetry, and post-mortem electron microscopy it was confirmed that the Al current collector is largely stable at potentials as high as 5.2 V in the electrolyte under consideration; no dissolved Al species were detected using EDX characterization. Results from the cyclic voltammetry study also indicate that parasitic reactions can be mitigated when the cut-off potential is limited to 5.0 V leading to higher coulombic efficiency (CE = 94 %) and more stable discharge capacity (85.17 mAh g-1). However, extending the potential to 5.1 and 5.2 V results in the discharge capacity increasing by almost 20 mAh g-1, though at the expense of the coulombic efficiency, which decreases from 94 to 76 %. Upon raising the cut-off potential to 5.3 V, the CE significantly decreased (20.62 %) as a result of extensive solvent decomposition ultimately leading to much quicker capacity fading.  Based on SEM images taken after 50 cycles, graphite particles did not sustain any structural or morphological change during cycling regardless of the cut-off potentials applied. Further tests were conducted on Li-graphite DIBs using galvanostatic methods in the range from 3 to 5 V, and at different specific currents (20, 50, and 100 mA g-1). Though the cells exhibited good performance in terms of capacity retention, and cycle life at all currents, the coulombic efficiency tended to decrease as the test currents were lowered. This observation confirms the presence of parasitic reactions which are only visible when the experimental timescale is sufficiently long. At 50 and 100 mA g-1, the CE reached > 98 % which further verifies the kinetic aspect of electrolyte decomposition reactions. It is evident that self-discharge sustained in the course of open-circuit potential (OCP) relaxation of the fully charged cell can reveal the stability of the electrolyte and the anion-intercalated graphite. Raman spectroscopy measurements conducted in-situ and ex-situ on graphite electrodes charged and discharged to a series of potential cut-offs reveal the existence of self-discharge leading to extraction of anions from the graphite particles. This was demonstrated through the spectral appearance of E2g2(i) band next to E2g2(b) band at a fully intercalated state, as opposed to the in-situ spectrum, which only showed one intercalated band (E2g2(b)). It can be concluded that concentrated electrolytes (such as 4 M LiFSI in EMC) only provide kinetic stability and are unable to entirely inhibit parasitic reactions at the interface. This further highlights the need for electrolyte additives that can create a more stable interfacial passivation layer on the positive electrode so that more reversible anion intercalation can be attained.

L'énergie produite par des matières fossiles, pétrole et charbon, va se raréfier de manière inéluctable et couter de plus en plus cher à moyen terme. Pour pallier à la fin des matières fossiles, le développement d'énergies alternatives est indispensable. Parmi celles-ci, la production d'électricité et de chaleur à partir d'hydrogène commence à se développer grâce aux piles à combustible (PAC) depuis les très faibles puissances (des microwatts pour alimenter les capteurs) jusqu'aux fortes puissances (des Mégawatts pour l'industrie) en passant par des puissances moyennes (des kilowatts pour le résidentiel). Une PAC est constituée de 3 éléments : 2 électrodes (anode et cathode) séparées par un électrolyte. Dans cette thèse, ces 3 éléments sont constitués d'oxydes solides et la pile est appelée SOFC (Solid Oxide Fuel Cell). Les piles SOFC actuellement commercialisées fonctionnent à de très hautes températures, typiquement supérieures à 800°C. L'objectif du travail a été d'élaborer des oxydes pour diminuer cette température vers 600°C ce qui permet d'utiliser de l'acier pour contenir ces piles. Pour que la pile SOFC fonctionne à cette température, il est impératif de diminuer la résistance électrique des 2 électrodes et de l'électrolyte de manière à récupérer une tension électrique continue maximale aux bornes de la pile et aussi à faire passer un courant électrique élevé dans celle-ci. La cathode, en contact avec l'oxygène de l'air, est l'élément le plus critique à optimiser. Nous avons choisi comme matériau de cathode un matériau déjà étudié, La₀.₆Sr₀.₄Co₀.₈Fe₀.₂O₃ (LSCF) et comme électrolyte Ce₀.₉Gd₀.₁O₂ (CGO) connu comme performant en dessous de 650 °C. Nous avons élaboré ces matériaux par une méthode de chimie douce, la méthode sol-gel Péchini, et caractérisé ceuxi-ci par diffraction de rayons X et microscopie électronique à balayage. Une part importante du travail a été la caractérisation électrique à l'aide de mesures d'impédance complexe dans une large gamme de fréquence (0,05 Hz à 2 MHz) et de température (300°C à 700 °C). Le meilleur résultat a été obtenu avec une cathode composite poreuse d'épaisseur 40 µm constituée à masses égales de LSCF et de CGO déposée par sérigraphie sur une céramique dense de CGO d'épaisseur 1,5 mm. De plus, un film mince dense de LSCF d'épaisseur 0,1 µm environ a été déposé par centrifugation pour améliorer l'interface entre la cathode et l'électrolyte. À 600 °C la résistance de cette cathode a été mesurée à 0,13 Ω pour 1 cm² de cathode : cette valeur est à l'état de l'art. Une étude du vieillissement de cette cathode et de l'électrolyte a été effectuée à 600 °C pendant 1000 h en continu sous air : cela s'est traduit par une augmentation de la résistance de la cathode de 32%. Ceci peut être lié à la différence de valeurs des coefficients d'expansion thermique des matériaux de cathode et d'électrolyte. / Energy made from fossil fuels, oil or coal, is becoming increasingly rare and its price will increase in the near future. Developing alternative energy sources could compensate the use of fossil fuel. Particularly, an alternative form of energy is being developed through fuel cells, through the production of electricity and heat from hydrogen. Fuel cells can provide low wattage (microwatts for sensor applications), medium wattage (kilowatts for residential applications) and high wattage (megawatts for the industry). A fuel cell consists of 3 components : 2 electrodes (anode and cathode) separated by an electrolyte. In my work, I use solid pxide materials for these three elements in order to expand on the literature of Solid Oxide Fuel Cell (SOFC). Commercialized SOFCs currently operate at very high temperatures, typically above 800°C. The objective of this study was to develop oxides that could decrease the working temperature of the cell to 600°C, which would allow the use of steel to contain these fuel cells. In order to enable the SOFC to operate at this temperature, it is imperative to decrease the electrical resistances of the two electrodes and electrolyte in order to collect a continuous voltage which is maximal at the terminals of the fuel cell, and also to have a high electric current going through the fuel cell. The cathode, in contact with the oxygen present in the atmosphere, is the most critical element to be optimized. I close as a cathode material La₀.₆Sr₀.₄Co₀.₈Fe₀.₂O₃ (LSCF), which has already been studied. As electrolyte, I used Ce₀.₉Gd₀.₁O₂ (CGO) which is known to work below 650°C. I synthesized these materials through the Pechini method, a soft chemistry sol-gel method. The materials were characterized by X-ray diffraction and scanning electron microscopy. An important aspect of this work was the electrical characterization using complex impedance measurements in a wide frequency range (0,05 Hz to 2 MHz) and temperature (300°C to 700°C). The best result was obtained with a 40 µm thick, porous, composite cathode (LSCF/CGO 50/50 wt%) was deposited by screen printing on a 1,5 mm thick and dense CGO ceramic. In addition, a dense thin film of LSCF with a thickness of about 0,1 µm was spin-coated between the cathode and the electrolyte to improve the interface. At 600°C the measured resistance of the cathode was 0,13 Ω for 1 cm² : this value is similar to the results found in the state of the art. An aging study of the cathode and the electrolyte was carried out at 600 °C for 1000 h in air : the resistance of the cathode increased of 32%. This may be related to the different values of the thermal expansion coefficients of the cathode and electrolyte materials.