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Optimizing electrosynthetic reactions requires fine tuning of a vast chemical space, including charge transfer at electrocatalyst/electrode surfaces, engineering of mass transport limitations, and complex interactions of reactants and products with their environment. Hybrid electrolytes, in which supporting salt ions and substrates are dissolved in a binary mixture of organic solvent and water, represent a new piece of this complex puzzle as they offer a unique opportunity to harness water as the oxygen or proton source in electrosynthesis. In this work, we demonstrate that modulating water–organic solvent interactions drastically impacts the solvation properties of hybrid electrolytes. Combining various spectroscopies with synchrotron small-angle X-ray scattering (SAXS) and force field-based molecular dynamics (MD) simulations, we show that the size and composition of aqueous domains forming in hybrid electrolytes can be controlled. We demonstrate that water is more reactive for the hydrogen evolution reaction (HER) in aqueous domains than when strongly interacting with solvent molecules, which originates from a change in reaction kinetics rather than a thermodynamic effect. We exemplify novel opportunities arising from this new knowledge for optimizing electrosynthetic reactions in hybrid electrolytes. For reactions proceeding first via the activation of water, fine tuning of aqueous domains impacts the kinetics and potentially the selectivity of the reaction. Instead, for organic substrates reacting prior to water, aqueous domains have no impact on the reaction kinetics, while selectivity may be affected. We believe that such a fine comprehension of solvation properties of hybrid electrolytes can be transposed to numerous electrosynthetic reactions.

The adsorption of small ions on the surface of inorganic material has been studied extensively through the lens of nuclear magnetic resonance relaxation enhancements. In mixtures of a commercial titanium dioxide (TiO2) powder with various aqueous electrolytes based on ammonium nitrate (NH4NO3) and alkali (Li, Na, Rb, Cs) bromide, the adsorption of Li+, Na+, Rb+, Cs+, Br–, NH4+, and NO3–onto TiO2was investigated with 14N, 15N, 7Li, 23Na, 87Rb, and 133Cs and 81Br NMR π/2 single-pulse spectra and longitudinal relaxation curves analysis (T1). In the TiO2/NH4NO3slurry, the preferential adsorption of NH4+ions on titania was reflected in the broadening of their 14N peak and the increase of the longitudinal relaxation rates of both 14NH4+and 15NH4+, with a more significant effect for 14N (undergoing surface-induced quadrupolar relaxation, SIQR) than 15N (experiencing dipolar relaxation). To probe alkali ion adsorption on TiO2, single π/2 pulse NMR spectra were first recorded on slurries containing a single alkali ion. Fractions of adsorbed ions and the corresponding density per unit area were derived from the signal losses for 23Na+and 87Rb+. The latter approach was limited to 7Li+and 133Cs+, for which no signal loss was recorded, although SIQR was observed for all ions. To compare the alkali adsorption properties, simultaneous exposures of TiO2surfaces to pairs of cations allowed SIQR to be measured and surface affinities to be ranked in the following order Cs+> Rb+> Na+> Li+, which is strongly correlated to the water structure-breaking properties of both TiO2and ions.

Sodium ion batteries, because of their sustainability attributes, could be an attractive alternative to Li-ion technology for specific applications. However, it remains challenging to design high energy density and moisture stable Na-based positive electrodes. Here, we report an O3-type NaLi1/3Mn2/3O2phase showing anionic redox activity, obtained through a ceramic process by carefully adjusting synthesis conditions and stoichiometry. This phase shows a sustained reversible capacity of 190 mAh g−1that is rooted in cumulative oxygen and manganese redox processes as deduced by combined spectroscopy techniques. Unlike many other anionic redox layered oxides so far reported, O3-NaLi1/3Mn2/3O2electrodes do not show discernible voltage fade on cycling. This finding, rationalized by density functional theory, sheds light on the role of inter- versus intralayer 3dcationic migration in ruling voltage fade in anionic redox electrodes. Another practical asset of this material stems from its moisture stability, hence facilitating its handling and electrode processing. Overall, this work offers future directions towards designing highly performing sodium electrodes for advanced Na-ion batteries.

Electrode power performance is tied with electrode design that influences particularly the electronic wiring of the active mass and the speed of lithium salt diffusion in the pores. Improved capacity delivery, especially at 0 and 40°C was seen for NMC532 electrodes containing carbon nanotubes (CNT) comparatively to carbon black (CB). At low temperature CNT significantly increase the electrode conductivity as seen from the decrease of the polarization resistance. Furthermore, the analysis of the current density dependence of the discharge capacity with the Penetration Depth Model (PDM) reveal that the CNT improve the ionic transport at high temperature because they would minimize the effect of the PVdF swelling by the electrolyte and the resulting increase of the electrode tortuosity.

Solid polymer electrolytes (SPEs) have emerged as promising candidates for sodium-based batteries due to their cost-effectiveness and excellent flexibility. However, achieving high ionic conductivity and desirable mechanical properties in SPEs remains a challenge. In this study, we investigated an AB diblock copolymer, PS–PEA(BuImTFSI), as a potential SPE for sodium batteries. We explored binary and ternary electrolyte systems by combining the polymer with salt and [C3mpyr][FSI] ionic liquid (IL) and analyzed their thermal and electrochemical properties. Differential scanning calorimetry revealed phase separation in the polymer systems. The addition of salt exhibited a plasticizing effect localized to the polyionic liquid (PIL) phase, resulting in an increased ionic conductivity in the binary electrolytes. Introducing the IL further enhanced the plasticizing effect, elevating the ionic conductivity in the ternary system. Spectroscopic analysis, for the first time, revealed that the incorporation of NaFSI and IL influences the conformation of TFSI–and weakens the interaction between TFSI–and the polymer. This establishes correlations between anions and Na+, ultimately enhancing the diffusivity of Na ions. The electrochemical properties of an optimized SPE in Na/Na symmetrical cells were investigated, showcasing stable Na plating/stripping at high current densities up to 0.7 mA cm–2, maintaining its integrity at 70 °C. Furthermore, we evaluated the performance of a Na|NaFePO4cell cycled at different rates (C/10 and C/5) and temperatures (50 and 70 °C), revealing remarkable high-capacity retention and Coulombic efficiency. This study highlights the potential of solvent-free diblock copolymer electrolytes for high-performance sodium-based energy storage systems, contributing to advanced electrolyte materials.

Nuclear magnetic resonance is one of the rare techniques able to probe selectively the ions inside the nanoporous network in supercapacitor devices. With a magnetic resonance imaging method able to detect all ions (adsorbed and nonadsorbed), we record one-dimensional concentration profiles of the active ions in supercapacitors with an electrode configuration close to that used in industry. Larger anionic concentration changes are probed upon charge and discharge in a carbide-derived carbon (CDC) with micropores smaller than 1 nm compared to a conventional nanoporous carbon (CC) with a larger distribution of pore sizes, up to 2 nm. They highlight the increased interaction of the anions with CDC and provide a better understanding of the enhanced capacitance in CDC-based supercapacitors.

Aqueous biphasic systems (ABSs), in which two aqueous phases with different compositions coexist as separate liquids, were first reported more than a century ago with polymer solutions. Recent observations of ABS forming from concentrated mixtures of inorganic salts and ionic liquids raise the fundamental question of how “different” the components of such mixtures should be for a liquid–liquid phase separation to occur. Here we show that even two monovalent salts sharing a common cation (lithium) but with different anions, namely, LiCl and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), may result in the formation of ABSs over a wide range of compositions at room temperature. Using a combination of experimental techniques and molecular simulations, we analyze the coexistence diagram and the mechanism driving the phase separation, arising from the different anion sizes. The understanding and control of ABS may provide new avenues for aqueous-based battery systems.

Hybrid solid electrolytes (HSEs) aim to combine the superior ionic conductivity of inorganic fillers with the scalable process of polymer electrolytes in a unique material for solid-state batteries. Pursuing the goal of optimizing the key metrics (σion≥ 10–4S·cm–1at 25 °C and self-standing property), we successfully developed an HSE based on a modified poly(ethylene oxide):LiTFSI organic matrix, which binds together a high loading (75 wt %) of Li6PS5Cl particles, following a solvent-free route. A rational study of available formulation parameters has enabled us to understand the role of each component in conductivity, mixing, and mechanical cohesion. Especially, the type of activation mechanism (Arrhenius or Vogel–Fulcher–Tammann (VFT)) and its associated energy are proposed as a new metric to unravel the ionic pathway inside the HSE. We showed that a polymer-in-ceramic approach is mandatory to obtain enhanced conduction through the HSE ceramic network, as well as superior mechanical properties, revealed by the tensile test. Probing the compatibility of phases, using electrochemical impedance spectroscopy (EIS) alongside 7Li nuclear magnetic resonance (NMR), reveals the formation of an interphase, the quantity and resistivity of which grow with time and temperature. Finally, electrochemical performances are evaluated by assembling an HSE-based battery, which displays comparable stability as pure ceramic ones but still suffers from higher polarization and thus lower capacity. Altogether, we hope these findings provide valuable knowledge to develop a successful HSE, by placing the optimization of the right metrics at the core of the formulation.

Five homogeneous arsenic selenide glasses with target compositions As2Se3, AsSe2, AsSe3, AsSe4.5, and AsSe6were studied quantitatively by 77Se Carr–Purcell–Meiboom–Gill magic-angle spinning NMR and transmission electron microscopy–energy-dispersive X-ray spectroscopy. The entire set of NMR spectra is simultaneously fitted with six distinct environments taking into account the effect of first and second neighbors on the position of the 77Se resonance. The selenium chains are bound at each end to trivalent arsenic atoms, and the chain length distribution can be modeled with the Flory theory, which is well-known in polymer science and is used here for the first time to model the probability of finding each selenium environment in a selenide glass. No arsenic homopolar bond is detected in our experiments.

An yttria-alumina glass incorporating 4 wt % of SiO2was prepared by the use of an aerodynamic levitator equipped with a laser heating device. Upon post synthesis annealing, the glass is observed to exhibit crystallization below the glass transition temperature. In the current study, this unusual behavior is examined using powder X-ray diffraction and infrared spectroscopy to follow crystallinity and optical absorbance as a function of annealing treatment. Double-resonance 27Al/29Si NMR spectroscopy and synchrotron diffraction experiments demonstrate that Si cations are incorporated in the formed Y3Al5O12(YAG) crystals on the 4-fold coordination Al site during crystallization. This has important consequences on the resulting microstructure of the YAG glass-ceramics.

Transparent nanostructured glasses show interesting properties for optical fibers or laser beam applications. Binary calcium silicate glasses are known to undergo phase separation in silica-rich compositions. However, adding up to a few mole percent of alumina seems to inhibit the phase separation. By adjusting the amount of alumina added to demixing calcium silicate glasses, we managed to obtain transparent, but nanostructured, glasses with either silica-rich or calcium aluminosilicate-rich nanodomains of a controlled size down to 5 nm for compositions beyond the limits of the immiscibility domain. Therefore, the limits of the immiscibility domain of the SiO2–Al2O3–CaO ternary diagram must be extended to consider the presence of nanosized domains. An atomic-scale analysis of these glasses was performed using 29Si and 27Al nuclear magnetic resonance (NMR) experiments, showing that, as the size of the domains decreased, repolymerization of the silicon network and formation of aluminum-rich clusters were observed.

This paper describes the simple, highly reproducible, and robust synthesis of a new solid organic/inorganic electrolyte based on the ionic liquid (IL) 1-butyl-3-(carboxyundecyl)imidazolium bis(trifluoromethylsulfonyl)imide tethered to zirconia nanoparticles (15–25 nm) by coordination and named ZrO2@IL. The IL monolayer formation, ensured by two-dimensional solid-state NMR, at the nanoparticles’ surface considerably reduces both the IL’s consumption and the IL amount at the ZrO2surface compared to the IL-based hybrid electrolytes reported in the literature. After LiTFSI, used as a lithium source, content optimization (26 wt %), the hybrid exhibits unprecedented stable conductivity passing from 0.6 × 10–4S.cm–1to 0.15 × 10–4S.cm–1, respectively, from 85 °C to room temperature (25 °C). Unlike silica which is commonly adopted for this type of hybrid material, zirconia makes it possible to produce more impact-resistant pellets that are easier to compact, thus being favorable for accurate conductivity studies and battery development by electrode/composite/solid electrolyte layer stacking. The ZrO2@IL/LiTFSI solid hybrid electrolyte’s thermal stability (up to 300 °C) and performance make this electrolyte suitable for lithium conduction in all-solid-state batteries.

Through-bond homonuclear correlation experiments can be realised in solids between spins of type X, separated by four chemical bonds, in X–O–Y–O–X motifs, provided a Jcoupling between X and Y exists: central transitions of quadrupolar 27Al spins can be correlated viathe J2scalar coupling between 27Al (X) and 31P (Y) in materials featuring Al–O–P–O–Al motifs.