Synthèses et étude de la coordination à des métaux de nouveaux ligand électroactifs (les tétrathiafulvalènythioalkylphosphines mono ou polydentates)

L objectif de ce travail est l étude de nouveaux tétrathiafulvalène-thioalkylphosphines et leur utilisation en tant que ligands électroactifs pour l élaboration de molécules hybride organique-inorganiques. Nous décrivons les synthèses de TTF mono, di et tétrasubstitués possédant des espaceurs alkylthio entre le cœur TTF et la fonction phosphine, ainsi que leur coordination à des complexes métalliques. Nous avons mis en évidence la versatilité du ligand TTF thioalkylmonophosphine qui peut agir comme un ligand mono (P) ou bidentate (P,S). Des TTF cyclophanes comportant un métal par cycle ont également été préparés à partir des TTF diphosphines. Des essais de formation de complexes par transfert de charge à partir de ces mêmes TTF cyclophanes sont décris. Nous présentons également la synthèse de TTF biscyclophanes dont il a été possible de contrôler la formation de chaque cycle soit latérale au cœur TTF soit à chaque extrémité des dithioles.RENNES1-BU Sciences Philo (352382102) / SudocSudocFranceF

Impact of the Salt Anion on K Metal Reactivity in EC/DEC Studied Using GC and XPS Analysis

International audienceTo develop K-ion batteries, the potassium metal reactivity in a half-cells must be understood. Here, it is shown first that the K metal leads to the migration of the electrode degradation species to the working electrode surface so that half-cells' solid electrolyte interphase (SEI) studies cannot be trusted. Then, the K metal reactivity was studied by combining gas chromatography (GC)-mass spectrometry, GC/Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy analysis after storage in ethylene carbonate/diethylene carbonate (EC/DEC) wo/w 0.8 M KPF6 or KFSI. A comparison with Li stored in EC/DEC wo/w 0.8 M LiPF6 was also performed. Overall, full electrolyte degradation pathways were obtained. The results showed a similar alkali reactivity when stored in EC/DEC with the formation of a CH3CH2OCO2M-rich SEI. For a MPF6-based electrolyte, the reactivity was driven by the PF6- anion (i) forming mostly LiF (Li metal) or (ii) catalyzing the solvent degradation into (CH2CH2OCOOK)2 and CH3CH2OCOOK as main SEI products with additional C2H6 release (K metal). This highlights the higher reactivity of the K system. With KFSI, the reactivity was driven by the FSI- anion degradation, leading to an inorganic-rich SEI. These results thus explain the better electrochemical performance often reported in half-cells with KFSI compared to that with KPF6. Finally, the understanding of these chemically driven electrolyte degradation mechanisms should help researchers to design robust carbonate-based electrolyte formulations for KIB

Toward efficient Li-ion cells at high temperatures: Example of TiSnSb material

International audienceDeveloping efficient Li-ion cells with long lifetime for high temperature applications remains a challenging problem due to severe electrolyte degradation. Here, it is showed that superior lifetime, CE and polarization could be obtained at 60 °C compared to 25 °C when TiSnSb/Li coin cells filled with 1 M LiPF6 EC:PC:3DMC +5% FEC +1% VC electrolyte were used. To understand such unexpected phenomenon, a thorough correlation of the electrochemical performance with complementary gas chromatography coupled with electron impact mass spectrometry (GC/MS) and X-ray photoelectron spectroscopy (XPS) analysis was performed. XPS results showed the formation of a more stable and passivating SEI film at the TiSnSb electrode surface at 60 °C due to a specific reactivity of the electrolyte. In good agreement, the GC/MS analysis showed only a partial consumption/reactivity of the FEC/VC additives at 60 °C while a full consumption of the additives and a further degradation of the EC solvent were observed at 25 °C. As a whole, the XPS and GC/MS results allowed to identify the origin of the superior electrochemical performance of the TiSnSb/coin cells at 60 °C

Use of a li-ion battery comprising an anode which contains an alloy based on tin and antimony

The present invention relates to the use of a Li-ion battery comprising an anode which contains an alloy based on tin andantimony, at a high temp., in order to reduce the loss of capacity during cycling of said battery

Use of a li-ion battery comprising an anode which contains an alloy based on tin and antimony

The present invention relates to the use of a Li-ion battery comprising an anode which contains an alloy based on tin andantimony, at a high temp., in order to reduce the loss of capacity during cycling of said battery

Ethylene bis-carbonates as telltales of SEI and electrolyte health,role of carbonate type and new additives

International audienceThe ethylene bis-carbonate compounds formation is responsible for the earliest change in electrolytecomposition which can be one of the reasons for battery performance decay. In this study, liquid GC/MStechnique is used to detect their formation in electrolytes based on solvent mixtures of EC and differentlinear carbonates (DMC, DEC and EMC), after the first cycle in full cells composed of synthetic graphitepowder/commercial positive films. These compounds stem from linear carbonate electrochemical reduc-tion leading to alkoxide compounds and can be quantified using a selective bicyclic boron ester Lewisacid as an electrolyte additive. Moreover, a quantitative study on ethylene bis-carbonate compounds forwhich the generation profile is different depending on the linear carbonate type, shows that either inbatteries or in a simple chemical mixture of electrolyte and lithium alkoxide, their formation stops whenit reaches a threshold concentration due to the thermodynamic equilibrium. The overall informationis useful for investigating the passivation ability and the dissolution of the Solid Electrolyte Interphase(SEI) that is formed on the negative electrode material. Finally, the passivation property of the SEI freshlyformed with four additives - Vinylene Carbonate (VC), Vinyl Ethylene Carbonate (VEC), Fluoro EthyleneCarbonate (FEC) and 1,3-Propane Sultone (1,3-PS)- is studied

Paving the Way for K-Ion Batteries: Role of Electrolyte Reactivity through the Example of Sb-Based Electrodes

International audienceDeveloping potassium-ion batteries remains a challenge so far due to the lack of efficient electrolytes. Moreover, the high reactivity of K metal and the use of half-cells may greatly alter both the electrochemical performance and the solid electrolyte interphase formation. Here, it is shown that in K metal/Sb half-cells, Coulombic efficiency improvement is achieved by the addition of fluoroethylene carbonate + vinylene carbonate to propylene carbonate (PC), the replacement of PC by ethylene carbonate/diethyl carbonate, and the replacement of KPF6 by potassium bis(fluorosulfonyl)imide. Surprisingly, however, storage of cells containing K metal leads to the coloration of K metal, separators, and Sb electrodes, whereas no change occurs for cells prepared without K metal. These results demonstrate that for all electrolytes, the high electrolyte reactivity with K metal also influences the Sb/electrolyte interface via a cross-talk mechanism. This observation is supported by gas chromatography/mass spectrometry analysis of electrolytes and X-ray photoelectron spectroscopy analysis of Sb electrodes. In summary, these results indicate that the search for efficient electrolytes for potassium-ion batteries must be carried out in full cells if one wants to obtain meaningful correlations between electrochemical performance and electrode/electrolyte interfacial properties. Overall, the results presented here are also likely to benefit the development of other emerging Na- and Mg-ion cell chemistries

Ethylene bis-carbonates as telltales of SEI and electrolyte health,role of carbonate type and new additives

International audienceThe ethylene bis-carbonate compounds formation is responsible for the earliest change in electrolytecomposition which can be one of the reasons for battery performance decay. In this study, liquid GC/MStechnique is used to detect their formation in electrolytes based on solvent mixtures of EC and differentlinear carbonates (DMC, DEC and EMC), after the first cycle in full cells composed of synthetic graphitepowder/commercial positive films. These compounds stem from linear carbonate electrochemical reduc-tion leading to alkoxide compounds and can be quantified using a selective bicyclic boron ester Lewisacid as an electrolyte additive. Moreover, a quantitative study on ethylene bis-carbonate compounds forwhich the generation profile is different depending on the linear carbonate type, shows that either inbatteries or in a simple chemical mixture of electrolyte and lithium alkoxide, their formation stops whenit reaches a threshold concentration due to the thermodynamic equilibrium. The overall informationis useful for investigating the passivation ability and the dissolution of the Solid Electrolyte Interphase(SEI) that is formed on the negative electrode material. Finally, the passivation property of the SEI freshlyformed with four additives - Vinylene Carbonate (VC), Vinyl Ethylene Carbonate (VEC), Fluoro EthyleneCarbonate (FEC) and 1,3-Propane Sultone (1,3-PS)- is studied

Ethylene bis-carbonates as telltales of SEI and electrolyte health,role of carbonate type and new additives

International audienceThe ethylene bis-carbonate compounds formation is responsible for the earliest change in electrolytecomposition which can be one of the reasons for battery performance decay. In this study, liquid GC/MStechnique is used to detect their formation in electrolytes based on solvent mixtures of EC and differentlinear carbonates (DMC, DEC and EMC), after the first cycle in full cells composed of synthetic graphitepowder/commercial positive films. These compounds stem from linear carbonate electrochemical reduc-tion leading to alkoxide compounds and can be quantified using a selective bicyclic boron ester Lewisacid as an electrolyte additive. Moreover, a quantitative study on ethylene bis-carbonate compounds forwhich the generation profile is different depending on the linear carbonate type, shows that either inbatteries or in a simple chemical mixture of electrolyte and lithium alkoxide, their formation stops whenit reaches a threshold concentration due to the thermodynamic equilibrium. The overall informationis useful for investigating the passivation ability and the dissolution of the Solid Electrolyte Interphase(SEI) that is formed on the negative electrode material. Finally, the passivation property of the SEI freshlyformed with four additives - Vinylene Carbonate (VC), Vinyl Ethylene Carbonate (VEC), Fluoro EthyleneCarbonate (FEC) and 1,3-Propane Sultone (1,3-PS)- is studied

How the Binder/Solvent Formulation Impacts the Electrolyte Reactivity/Solid Electrolyte Interphase Formation and Cycling Stability of Conversion Type Electrodes

International audienceConversion/alloying type materials are of great interests in term of electrochemical performance for Li-ion batteries and beyond. To address their large volume change (typically >200%) during cycling, tailoring the binder/solvent system used for the electrode formulation together with the use of electrolyte additives are the most used and efficient approaches. However, only few studies have investigated the role of the binder/solvent formulation on the electrolyte reactivity/solid electrolyte interphase (SEI) formation and its composition. To tackle this issue, gas chromatography coupled with electron impact mass spectrometry and X-ray photoelectron spectroscopy analysis were used to understand the long term cycling stability (100 cycles) of NbSnSb-based electrodes. It is showed that CMC-H2O and PAA-H2O formulations favored the formation of a more homogeneous SEI while maintaining efficient active/conducting particles bridging, which results in high cycling stability. PVDF-NMP and PAA-NMP led, however, to much lower coulombic efficiency and higher irreversible capacity correlated with the formation of thick SEI with a concomitant disconnection of active particles. These results highlight that CMC and PAA act as artificial SEI and/or as SEI stabilizers. Overall, this work should benefit to all researchers working on improving, through electrode formulation, the lifetime of Li-ion batteries and beyond