Eutectogels: A New Class of Solid Composite Electrolytes for Li/Li-Ion Batteries

Here, we introduce deep eutectic solvent (DES)–silica composites as a promising candidate for solid composite electrolytes (SCEs). The proposed DES-based gel electrolytes, further referred to as eutectogels (ETGs), are characterized by high ionic conductivity (1.46 mS cm^–1), thermal (up to 130 °C), and electrochemical stability (up to 4.8 V) and are chemically inert to solvents and water. These ETGs can be easily processed and potentially at lower costs compared to ionic-liquid-based composite electrolytes. The good prospects of ETGs for application in Li/Li-ion batteries are demonstrated by stable cycling of Li/ETG/LiFePO₄ cells over 100 cycles at C/10

Reversible Surface Engineering via Nitrone-Mediated Radical Coupling

Efficient and simple polymer conjugation reactions are critical for introducing functionalities on surfaces. For polymer surface grafting, postpolymerization modifications are often required, which can impose a significant synthetic hurdle. Here, we report two strategies that allow for reversible surface engineering via nitrone-mediated radical coupling (NMRC). Macroradicals stemming from the activation of polymers generated by copper-mediated radical polymerization are grafted via radical trapping with a surface-immobilized nitrone or a solution-borne nitrone. Since the product of NMRC coupling features an alkoxyamine linker, the grafting reactions can be reversed or chain insertions can be performed via nitroxide-mediated polymerization (NMP). Poly­(<i>n</i>-butyl acrylate) (<i>M</i>_n = 1570 g·mol^–1, <i>D̵</i> = 1.12) with a bromine terminus was reversibly grafted to planar silicon substrates or silica nanoparticles as successfully evidenced via X-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry, and grazing angle attenuated total reflection Fourier-transform infrared spectroscopy (GAATR-FTIR). NMP chain insertions of styrene are evidenced via GAATR-FTIR. On silica nanoparticles, an NMRC grafting density of close to 0.21 chains per nm² was determined by dynamic light scattering and thermogravimetric analysis. Concomitantly, a simple way to decorate particles with nitroxide radicals with precise control over the radical concentration is introduced. Silica microparticles and zinc oxide, barium titanate, and silicon nanoparticles were successfully functionalized

Chemical Composition of an Aqueous Oxalato-/Citrato-VO²⁺ Solution as Determinant for Vanadium Oxide Phase Formation

Aqueous solutions of oxalato- and citrato-VO²⁺ complexes are prepared, and their ligand exchange reaction is investigated as a function of the amount of citrate present in the aqueous solution via continuous-wave electron paramagnetic resonance (CW EPR) and hyperfine sublevel correlation (HYSCORE) spectroscopy. With a low amount of citrate, monomeric <i>cis</i>-oxalato-VO²⁺ complexes occur with a distorted square-pyramidal geometry. As the amount of citrate increases, oxalate is gradually exchanged for citrate. This leads to (i) an intermediate situation of monomeric VO²⁺ complexes with a mix of oxalate/citrate ligands and (ii) a final situation of both monomeric and dimeric complexes with exclusively citrato ligands. The monomeric citrato-VO²⁺ complexes dominate (abundance > 80%) and are characterized by a 6-fold chelation of the vanadium­(IV) ion by 4 RCO₂^– ligands at the equatorial positions and a H₂O/R–OH ligand at the axial position. The different redox stabilities of these complexes, relative to that of dissolved O₂ in the aqueous solution, is analyzed via ⁵¹V NMR. It is shown that the oxidation rate is the highest for the oxalato-VO²⁺ complexes. In addition, the stability of the VO²⁺ complexes can be drastically improved by evacuation of the dissolved O₂ from the solution and subsequent storage in a N₂ ambient atmosphere. The vanadium oxide phase formation process, starting with the chemical solution deposition of the aqueous solutions and continuing with subsequent processing in an ambient 0.1% O₂ atmosphere, differs for the two complexes. The oxalato-VO²⁺ complexes turn into the oxygen-deficient crystalline VO₂ B at 400 °C, which then turns into crystalline V₆O₁₃ at 500 °C. In contrast, the citrato-VO²⁺ complexes form an amorphous film at 400 °C that crystallizes into VO₂ M1 and V₆O₁₃ at 500 °C

Factors Influencing the Conductivity of Aqueous Sol(ution)–Gel-Processed Al-Doped ZnO Films

Solution processing of Al-doped ZnO (AZO) is interesting from an economical point of view for reducing synthesis and deposition costs in comparison to that for vacuum methods. Several (aqueous) chemical solution deposition routes have been explored for AZO, but the question that has never been answered is how state-of-the-art conductivity is achieved. Here, we fine tune an aqueous solution precursor for AZO, resulting in resistivities within the 10^–3 Ohm cm range after a reductive treatment. Profound insights are gained through the study of the density of the film, the crystal phase, the optimum Al doping, and the effect of Al positioning in the ZnO lattice, as determined by ²⁷Al magic-angle-spinning nuclear magnetic resonance (MAS NMR) spectroscopy in combination with ¹H NMR, in order to understand the conductivity mechanism. As the conductivity of the AZO films drops as a function of time, the position of Al is studied with respect to the observance of charge carriers using Fourier transform infrared spectroscopy. The influences of all of these different factors on conductivity are summarized in a general overview