. Modified coin cells to evaluate the electrochemical properties of solid-state fluoride-ion batteries at 150°C. Journal of Fluorine Chemistry, Elsevier, 2016, 191, pp.23 -28. 10 AbstractIn the scope of developing new chemistries for electrochemical energy systems, rechargeable solid-state fluoride-ion batteries are attractive devices owing to their high theoretical energy density. State of the art of fluoride ion conductors require the use of high temperature electrochemical cells to overcome the low ionic conductivity of the electrolyte at room temperature. In this work, we modify a coin cell to evaluate the electrochemical properties of fluoride-ion batteries at elevated temperature, over long periods of time and outside a glovebox.The coin cell is covered by a high-temperature epoxy resin that enables efficient sealing and therefore protection against air atmosphere at 150 °C. The suitability of the setup is confirmed by electrochemical investigation performed on a symmetrical cell assembled with composite electrodes made of Bi and BiF3. Notably, a reversible capacity of around 190 mAh/g after 3 cycles is reached with the modified coin cell setup.2

The coordination properties of the biomimetic complex [Cu(TMPA)(H2O)](CF3SO3)2 (TMPA = tris(2-pyridylmethyl)amine) have been investigated by electrochemistry combined with UV-Vis and EPR spectroscopy in different non-coordinating media including imidazolium-based room-temperature ionic liquids, for different water contents. The solid-state X-ray diffraction analysis of the complex shows that the cupric centre lies in a N4O coordination environment with a nearly perfect trigonal bipyramidal geometry (TBP), the water ligand being axially coordinated to Cu(II). In solution, the coordination geometry of the complex remains TBP in all media. Neither the triflate ion nor the anions of the ionic liquids were found to coordinate the copper centre. Cyclic voltammetry in all media shows that the decoordination of the water molecule occurs upon monoelectronic reduction of the Cu(II) complex. Back-coordination of the water ligand at the cuprous state can be detected by increasing the water content and/or decreasing the timescale of the experiment. Numerical simulations of the voltammograms allow the determination of kinetics and thermodynamics for the water association-dissociation mechanism. The resulting data suggest that (i) the binding/unbinding of water at the Cu(I) redox state is relatively slow and equilibrated in all media, and (ii) the binding of water at Cu(I) is somewhat faster in the ionic liquids than in the non-coordinating solvents, while the decoordination process is weakly sensitive to the nature of the solvents. These results suggest that ionic liquids favour water exchange without interfering with the coordination sphere of the metal centre. This makes them promising media for studying host-guest reactions with biomimetic complexes.

We demonstrated that the chemical intercalation of Zn2+ ions within the interlayer space of the structure of a disordered layered titanate results in a drastic increase of the room-temperature bulk proton conductivity from 8.11 × 10–5 S m–1 for the pristine to 3.7 × 10–2 S m–1 for Zn-titanate. Because of the crystallographic disordered nature of these compounds, we combined different techniques to establish the structural-transport relationships. The pair distribution function revealed that upon chemical insertion of Zn2+, the local lepidocrocite arrangement is maintained, providing a suitable model to investigate the effect of chemically intercalated ions on the transport properties and dynamics within the interlayer space. Broadband dielectric spectroscopy (50 to 1010 Hz) enabled establishing that Zn2+ inclusion promotes proton-hopping by self-dissociation of H2O molecules yielding high proton mobility. Using Zn–K edge extended X-ray absorption fine structure and chemical analyses (EDX, TGA, 1H NMR), Zn2+ ions were shown to be stabilized by ZnCl2(H2O) complexes within the interlayer space. Such complexes induce an increase of the H-bonding strength as evidenced by 1H NMR, yielding a fast proton motion. Molecular dynamics simulations highlighted proton transfer between water molecules from the structural interlayer and bonded to Zn2+ ions. The increasing interactions between these water molecules favor proton transfer at the origin of the fast bulk proton conductivity, which was assigned to a Grotthuss-type mechanism taking place at a long-range order. This work provides a better understanding of how ion–water interactions mediated ionic transport and opens perspectives into the design of ionic conductors that can be used in energy-storage applications.

Sn‐based alloys are increasingly investigated owing to possible electronic/structural modulations of interest for electrocatalysis and energy storage applications. Here, we report on the use of a chemical system consisting of an ionic liquid (1‐ethyl‐3‐ methylimidazolium bis(trifluoromethanesulfonyl)imide: [EMIm+][TFSI−]) and Sn‐based precursor Sn(TFSI)2 both featuring similar anionic groups. This strategy increases the solubility of the cationic precursor in the IL and avoids the formation of side‐products during the precipitation of Sn‐nanoparticles formed upon reaction with a reducing agent (NaBH4). Using NMR relaxometry, we further established that these nanoparticles are stabilized by specific interactions with the cationic group of the IL. Targeting the composition Cu6Sn5, we further demonstrated that this approach can be used to prepare Sn‐based alloys which could not be prepared using conventional chloride‐based precursors.

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