Due to its high theoretical specific capacity, the lithium/sulfur battery is one of the most promising candidates for replacing current lithium-ion batteries. In this work, we investigate both ...chemical and morphological changes in the electrodes during cycling, by coupling operando spatially resolved X-ray diffraction and absorption tomography to characterize Li/S cells under real working conditions. By combining these tools, the state of the active material in the entire cell was correlated with its electrochemical behavior, leading to a deeper understanding of the performance limiting degradation phenomena in Li/S batteries. Highly heterogeneous behavior of lithium stripping/plating was observed in the anode, while the evolution of sulfur distribution in the cathode depth was followed during cycling.
Lithium/sulfur batteries have been under intense study for the last two decades, due to the high specific capacity promised by elemental sulfur as an active material. Sulfur is also cheap, abundant ...and non-toxic compared to conventional transition metal oxides. The Li/S electrochemical cell is traditionally composed of a sulfur-based electrode, an organic liquid electrolyte and a lithium metal electrode. Lithium metal technologies have received a renewed interest, due to the light weight and low operating voltage of the lithium electrode, which makes it the ultimate choice to be combined with high-energy positive electrode materials. In this paper, operando X-ray absorption and phase contrast tomography were employed to characterize the lithium metal electrode morphology and heterogeneity in a liquid Li/S cell. It was observed that oxidation of the lithium foil occurs in a heterogeneous fashion with pit formation from the beginning of discharge, with the pits growing in diameter, depth and quantity during the discharge. Using Faraday's law, the local current density distribution was calculated to confirm the strongly heterogeneous behavior of the lithium metal electrode. We demonstrate that decreasing the current density leads to lithium stripping/plating occurring more homogenously, with the formation of a smaller number of pits.
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•X-ray absorption tomography is a powerful tool to characterize the lithium.•Presence of large number of pits during lithium oxidation at high current density.•Determination of the local current density distribution.•Lithium heterogeneity starts at the beginning of the cell life.
High capacity sulfur electrodes are expected to be used in the next-generation of high energy density and low cost rechargeable lithium batteries. The positive sulfur electrode undergoes complex ...electrochemical reactions, which cause morphological changes of the composite electrode while cycling. In the course to deeper understand the failures of this rather complex, but promising technology, the operando technics are in the heart of the advanced characterizations. In this study, a new electrochemical cell was designed which allows, for the first time, the combination operando of multimodal X-ray characterizations: the absorption tomography to study the morphological evolution of electrodes, and the X-ray diffraction computed tomography to probe locally the structural modification of the crystalline active materials S8 and Li2S. The combination of these two techniques simultaneously with the electrochemical cycling, allows the production of correlated 3D-maps of quantitative phase distributions and morphology in the electrode, with time resolution on the scale of battery kinetics. It was thus possible to show the heterogeneous behavior in the bulk of the electrode and to propose kinetics law.
•New operando cell designed for coupling XRDCT and X-ray microtomography.•Correlated 3D-maps of phase distributions and morphology in the sulfur electrode.•Evidence of heterogeneous behavior in a 3D-electrode.
L’objectif principal de la thèse était d’identifier les processus limitants et les phénomènes de dégradation intervenant lors du cyclage d’un accumulateur Li/S, et d’expliciter l’évolution des ...performances électrochimiques au cours du temps. Pour ce faire, une cellule électrochimique a été développée permettant de réaliser des caractérisations à l’ESRF par diffraction et absorption des rayons X en mode operando. Ces deux techniques complémentaires ont permis de mettre en évidence des changements morphologiques importants et des cinétiques de réactions limitées par le transport de matière au sein de la structure 3D de l’électrode positive de soufre. L’oxydation/réduction de l’électrode négative de lithium a également été caractérisée, permettant de mettre en évidence une évolution hétérogène de l’interface lithium/électrolyte, fonction de la densité de courant, induisant une diminution des performances électrochimiques en cyclage.
The main objective was to identify the degradations phenomena and the limiting processes occurring while cycling Li/S accumulators to therefore put in relation the electrode morphology, the cell design, the electrochemical performances and the degradations phenomena. A new design of operando cell has been developed to be suitable with ESRF experiments. Operando Absorption and X-ray Diffraction tomography technics were performed. Thanks to both technics, the morphological changes and transport limitation kinetics along the 3D positive electrode have been evidenced. In addition, the lithium electrode/electrolyte interface has been characterized and heterogeneous stripping/plating has been evidenced, leading to low electrochemical performances while cycling.
Carriers of pathogenic variants in both BRCA1 and BRCA2 genes as a double mutation (BRCA1/2 DM) have been rarely reported in women with epithelial ovarian cancer (EOC).
We reviewed the English ...literature and interrogated three repositories reporting EOC patients carrying BRCA1/2 DM. The clinicopathological parameters of 36 EOC patients carrying germline BRCA1/2 DM were compared to high-grade serous EOC women of the COEUR cohort with known germline BRCA1/BRCA2 mutation carrier status (n = 376 non-carriers, n = 65 BRCA1 and n = 38 BRCA2). Clinicopathological parameters evaluated were age at diagnosis, stage of disease, loss of heterozygosity, type of mutation, immunohistochemistry profile, progression occurrence and survival.
Median age at diagnosis of BRCA1/2 DM patients was 51.9 years, similar to BRCA1 mutation carriers (49.7 years, p = .58) and younger than BRCA2 mutation carriers (58.1 years, p = .02). Most patients were diagnosed at advanced stage (III-IV; 82%) and were carriers of founder/frequent mutations (69%). Tissue immunostainings revealed no progesterone receptor expression and low intraepithelial inflammation. The 5-year survival rate (60%) was significantly lower than that of BRCA2 mutation carriers (76%, p = .03) but not of BRCA1 mutation carriers (51%, p = .37).
Our data suggests some co-dominant effect of both mutations but the outcome of these patients more closely resembled that of BRCA1 mutation carriers with poor prognosis factors.
•Double germline mutation (DM) carriers in both BRCA1 and BRCA2 genes are rare among ovarian cancer patients.•Germline BRCA DM is associated with absence of Progesterone Receptor expression.•Outcome of patients harboring BRCA DM more closely resembled that of BRCA1 mutation carriers with a poor prognosis.
We hypothesized that the transcriptome of primary cultures of morphologically normal ovarian surface epithelial cells could be altered by the presence of a heterozygous BRCA1 or BRCA2 mutation. We ...aimed to discover early events associated with ovarian carcinogenesis, which could represent putative targets for preventive strategies of this silent killer tumor. We identified the first molecular signature associated with French Canadian BRCA1 or BRCA2 founder mutations in morphologically normal ovarian epithelial cells. We discovered that wild-type and mutated BRCA2 allelic transcripts were expressed not only in morphologically normal but also in tumor cells from BRCA2-8765delAG carriers. Further analysis of morphologically normal ovarian and tumor cells from BRCA1-4446C>T carriers lead to the same observation. Our data support the idea that one single hit in BRCA1 or BRCA2 is sufficient to alter the transcriptome of phenotypically normal ovarian epithelial cells. The highest level of BRCA2-mutated allele transcript expression was measured in cells originating from the most aggressive ovarian tumor. The penetrance of the mutation and the aggressiveness of the related tumor could depend on a dosage effect of the mutated allele transcript.
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