Search

Dion-Jacobson phases, like MLaNb2O7, are an interesting class of ion-exchangeable layered perovskites possessing electronic and photocatalytic properties. Their protonated and organo-modified homologues, in particular, have already been indicated as promising catalysts. However, the structural analysis of these highly tailorable materials is still incomplete, and both the intercalation process and thermal stability of the included organic moieties are far from being completely understood. In this study, we present a thorough solid-state NMR characterization of HLaNb2O7·xH2O intercalated with different amounts of octylamine, or with decylamine. Samples were analyzed as prepared, and after thermal treatment at different temperatures up to 220 °C. The substitution of pristine proton ions was followed via(1)H MAS NMR spectroscopy, whereas the alkyl chains were monitored through (13)C((1)H) CP MAS experiments. The interactions in the interlayer space were explored using (13)C((1)H) 2D heteronuclear correlation experiments. We demonstrate that some of the protons are involved in the functionalization reaction, and some of them are in close proximity to the alkyl ammonium chains. Heating of the hybrid materials leads first to a rearrangement of the alkyl chains and then to their degradation. The spatial arrangement of the chains, their interactions and the thermal behavior of the materials depend on the extent of the functionalization, and on the nature of the intercalated alkyl ammonium ions.

Autonomic self-healing (SH), namely, the ability to repair damages from mechanical stress spontaneously, is polarizing attention in the field of new-generation electrochemical devices. This property is highly attractive to enhance the durability of rechargeable Li-ion batteries (LIBs) or Na-ion batteries (SIBs), where high-performing anode active materials (silicon, phosphorus, etc.) are strongly affected by volume expansion and phase changes upon ion insertion. Here, we applied a SH strategy, based on the dynamic quadruple hydrogen bonding, to nanosized black phosphorus (BP) anodes for Na-ion cells. The goal is to overcome drastic capacity decay and short lifetime, resulting from mechanical damages induced by the volumetric expansion/contraction upon sodiation/desodiation. Specifically, we developed novel ureidopyrimidinone (UPy)-telechelic systems and related blends with poly(ethylene oxide) as novel and green binders alternative to the more conventional ones, such as polyacrylic acid and carboxymethylcellulose, which are typically used in SIBs. BP anodes show impressively improved (more than 6 times) capacity retention when employing the new SH polymeric blend. In particular, the SH electrode still works at a current density higher than 3.5 A g-1, whereas the standard BP electrode exhibits very poor performances already at current densities lower than 0.5 A g-1. This is the result of better adhesion, buffering properties, and spontaneous damage reparation.

The eco-friendly method of kneading was here used to synthesize a cocrystal of probenecid, an uricosuric drug used in treating gout and hyperuricemia, with the aim to improve its pharmaceutical behavior. Benzamide was selected as a co-former showing functional groups favorable to the formation of supramolecular synthons with the active principle. The kneading product was characterized by a range of experimental techniques (microscopic, spectroscopic, thermal and diffractometric) all proving the formation of the new multicomponent crystal. In particular, the FT-IR and NMR techniques showed that an important change of hydrogen bonds network takes place in the kneading product and that the acid–acid interaction in the pristine drug is replaced with the related acid-amide one in the cocrystal. The cocrystal solubility and dissolution rate measured in several biorelevant fluids showed an actual improvement with respect to the pure drug.

The aim of this study was to synthetize cocrystals of nateglinide, an antidiabetic agent of biopharmaceutics classification system Class IIa, as a strategy to improve both the solubility and the dissolution rate of the drug. Benzamide was selected by a screening procedure as a suitable coformer, and binary mixtures with different compositions were prepared and analyzed by differential scanning calorimetry (DSC). An in-depth analysis of DSC data allowed obtaining both the eutectic mixture and cocrystal compositions. The rationale of such an analysis was highlighted and explained. Cocrystals were prepared by kneading and solvent evaporation. Their formation was proved by DSC and confirmed by X-ray powder diffraction, solid-state nuclear magnetic resonance, and Fourier-transform infrared spectroscopy. The functional groups involved in the interaction leading to cocrystals formation were investigated by spectroscopic techniques. The in vitro dissolution profiles show that cocrystals have definite better pharmaceutical performances than the pure drug.

Fe2O3 and Fe2O3:Ge nanofibers (NFs) were prepared via electrospinning and thoroughly characterized via several techniques in order to investigate the effects produced by germanium incorporation in the nanostructure and crystalline phase of the oxide. The results indicate that reference Fe2O3 NFs consist of interconnected hematite grains, whereas in Fe2O3:Ge NFs, constituted by finer and elongated nanostructures developing mainly along their axis, an amorphous component coexists with the dominant α-Fe2O3 and γ-Fe2O3 phases. Ge4+ ions, mostly dispersed as dopant impurities, are accommodated in the tetrahedral sites of the maghemite lattice and probably in the defective hematite surface sites. When tested as anode active material for sodium ion batteries, Fe2O3:Ge NFs show good specific capacity (320 mAh g−1 at 50 mA g−1) and excellent rate capability (still delivering 140 mAh g−1 at 2 A g−1). This behavior derives from the synergistic combination of the nanostructured morphology, the electronic transport properties of the complex material, and the pseudo-capacitive nature of the charge storage mechanism.

The safety issues of lithium-ion batteries require the substitution of volatile and flammable organic components of the electrolyte. In this context, deep eutectic solvents (DESs) represent an interesting alternative to conventional ionic liquids as green solvents to dissolve common lithium salts. This paper explores two eutectics: i) ethylene glycol/choline chloride (EG/ChCl, 3:1 mol/mol), and ii) L-(+)-lactic acid/choline chloride (LA/ChCl, 2:1 mol/mol). The lithium salts added in both cases were LiN(CF3SO2)2 and LiPF6, both in concentration of either 0.5 M or 1 M. They still retain their liquid properties despite the addition of relatively high molar contents (up to 1.0 M) of lithium salts. The 0.5 M LiPF6/EG:ChCl electrolyte, in particular, displays ionic conductivity of 7.95 mS cm−1 at room temperature, and is thus very promising as a green and cheap electrolyte.

Since their discovery in 2011, MXene compounds, and in particular the Ti3C2-based phases, have gained increasing interest from researchers leading to over 2000 scientific works in 2020. The peculiar morphological, charge transport, and surface properties make the MXenes ideal materials for energy storage applications such as active material in alkaline ion batteries and supercapacitors, as conductive or buffer agent in composite electrodes for high energy applications, and as electrocatalytic materials for oxygen evolution or redox flow batteries. Among this almost endless literature, this work focuses on 5 recent articles (2019/2020) that summarize the potential of MXenes in different energy storage applications, also resuming the most promising preparatory routes regarding industrial scalability.

Al-ion batteries technology is receiving growing attention thanks to the high natural abundance of aluminum and to the high energy density that can be obtained with a three-electron redox process. In this work, the physicochemical properties of the room temperature ionic liquid composed of aluminum chloride and 1-ethyl-3-methylimidazolium chloride ([EMIm]Cl) were systematically investigated by varying the molar ratio AlCl3/[EMIm]Cl in the range 1.11.7. The combined use of multinuclear (Al-27, C-13, H-1) NMR, electrochemical impedance spectroscopy, and thermal analysis allowed us to shed light on the structureproperties relationships of this complex system, also resolving some controversial conclusions of previous literature. We showed that the 1.2 molar ratio is the best compromise between high ionic conductivity and the use of the highly toxic AlCl3. This electrolyte was tested in a standard Al-ion cell and gave promising results even at very high current densities (i > 200 mA g(-1))

The FA(1-x)MA(x)PbI(3) solid solution has been carefully investigated in terms of the MA/FA stoichiometry, crystal structure, and optical properties. This work allowed for the determination of reliable correlations between the amount of protonated amine and the physicochemical properties. The deleterious effect of aging on the mixed MA/FA. composition was observed by diffraction and optical measurements, showing progressive phase separation within the samples.

Lithium Metal Batteries (LMB) require solid or quasi-solid electrolytes able to block dendrites formation during cell cycling. Polymer-in-ceramic nanocomposites with the ceramic fraction exceeding the one normally used as the filler (>10 ÷ 15 wt%) are among the most interesting options on the table. Here, we report on a new hybrid material encompassing brush-like TiO2 nanocrystals functionalized with low molecular weight poly(ethylene oxide) (PEO). The nanocomposite electrolyte membranes are then obtained by blending the brush-like nanocrystals with high molecular weight PEO and LiTFSI. The intrinsic chemical compatibility among the PEO moieties allows a TiO2 content as high as ∼39 wt% (90:10 w/w functionalized nanocrystals/PEO-LiTFSI), while maintaining good processability and mechanical resistance. The 50:50 w/w nanocomposite electrolyte (18.8 wt% functionalized TiO2) displays ionic conductivity of 3 × 10−4 S cm−1 at 70 °C. Stripping/plating experiments show an excellent long-term behavior even at relatively high currents of 200 μA cm−2. Upon testing in a lab-scale Li/electrolyte/LiFePO4 cell, the material delivers 130 mAh g−1 and 120 mAh g−1 after 40 and 50 cycles at 0.05 and 0.1 mA, respectively, with Coulombic efficiency exceeding 99.5%, which demonstrates the very promising prospects of these newly developed nanocomposite solid electrolyte for future development of LMBs.

We report a thorough, multitechnique investigation of the structure and transport properties of a UV-cross-linked polymer electrolyte based on poly(ethylene oxide), tetra(ethylene glycol)dimethyl ether (G4), and lithium bis-(trifluoromethane)sulfonimide. The properties of the cross linked polymer electrolyte are compared to those of a non cross-linked sample of same composition. The effect of UV induced cross-linking on the physico/chemical characteristics is evaluated by X-ray diffraction, differential scanning calorimetry, shear rheology, and Li-7 magic angle spinning nuclear magnetic resonance (NMR) spectroscopy, F-19 and Li-7 pulsed field gradient stimulated echo NMR analyses, electrochemical impedance spectroscopy, and Fourier transform Raman spectroscopy. Comprehensive analysis confirms that UV-induced cross-linking is an effective technique to suppress the crystallinity of the polymer matrix and reduce ion aggregation, yielding improved Li+ transport number (>0.5) and ionic conductivity (>0.1 mS cm(-1)) at ambient temperature, by tailoring the structural/morphological characteristics of the polymer matrix. Finally, the polymer electrolyte allows reversible operation with stable profile for hundreds of cycles upon galvanostatic test at ambient temperature of LiFePO4-based lithium-metal cells, which deliver full capacity at 0.05 or 0.1C current rate and keep high rate capabilities up to 1C. This enforces the role of UV-induced cross-linking in achieving excellent electrochemical characteristics, exploiting a practical, easy up-scalable process.

Hybrid polymer–ceramic electrolytes with high ceramic loading are currently investigated as a promising solution to achieve high safety and optimal mechanical properties in all-solid-state rechargeable batteries. In this study composite poly(ethylene oxide)/Li1.3Al0.3Ti1.7(PO4)3 (PEO/LATP) electrolytes, with and without lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) as the Li+ salt, were investigated through a combination of physicochemical and electrochemical techniques, including X-ray diffraction, scanning electron microscopy, thermal analysis, solid-state MAS-NMR and impedance spectroscopy. We were able to shed light on the interactions between the ceramic and the polymer phases, and on the mechanisms for Li+ transport. Membranes containing 70 wt% of LATP and 30 wt% of P(EO)15LiTFSI exhibit conductivity values of 4 × 10−5 Ω−1 cm−1 at 25 °C and in excess of 10−4 Ω−1 cm−1 at 45 °C. These promising results, obtained on a quasi-ceramic electrolyte through room temperature processing, suggest that further improvements in the transport properties of “polymer-in-ceramic” systems may be sought by increasing the amorphous polymer content, and by carefully investigating the role of the ceramic particles’ composition, dimensions and dispersion on the transport properties of the hybrid system.

A detailed characterization of the polymorphs constituting cathode materials, both before and after cell cycling, is mandatory to develop more stable and powerful lithium batteries. In many cases, e.g., for transition metal lithium silicates, standard diffraction techniques cannot give a clear-cut response. Here we show that broadband adiabatic fast MAS NMR can give unique information in the case of model Li2(Mn,Fe)SiO4 high-capacity cathode materials. By coupling 7Li and 29Si 1D and 2D spectra, we are able to address polymorphs speciation also in the mixed Mn/Fe compositions, which is a nearly impossible task for X-rays and neutrons diffraction. We finally discuss the conditions under which this approach is useful when applied to rare nuclei such as 29Si.

One of the primary targets of current research in the field of energy storage and conversion is the identification of easy, low-cost approaches for synthesizing cell active materials. Herein, we present a novel method for preparing nanometric slabs of Na 0.44 MnO 2 , making use of the eco-friendly urea within a solution synthesis approach. This kind of preparation greatly reduces the time of reaction, decreases the thermal treatment temperature, and allows the obtaining of particles with smaller dimensions compared with those obtained through conventional solid-state synthesis. Such a decrease in particle size guarantees improved electrochemical performance, particularly at high current densities, where kinetic limitations become relevant. Indeed, the materials produced via solution synthesis outperform those prepared via solid-state synthesis both at 2 C, (95 mA h g −1 vs. 85 mA h g −1 , respectively) and 5 C, (78 mA h g −1 vs. 68.5 mA h g −1 , respectively). Additionally, the former material is rather stable over 200 cycles, with a high capacity retention of 75.7%.

Objective: To improve the pharmaceutical behavior of the oral antidiabetic agent gliclazide through the synthesis of multicomponent crystals with tromethamine. Methods: Multicomponent crystals were prepared by solvent evaporation method, kneading, and combining mechanical and thermal activation. DSC, FT-IR spectroscopy, X-ray diffraction, SEM-EDS, and SSNMR were used to investigate their formation. Measurements of solubility and dissolution rate were carried out for the pharmaceutical characterization. Results: The formation of multicomponent crystals of gliclazide and tromethamine was confirmed by all the techniques. In particular, FT-IR and NMR measurements revealed that the interaction between drug and coformer leads to significant changes of the hydrogen bond scheme, and that almost all the functional groups of the two molecules are involved. The dissolution profile of the new phase is significantly better than that of both pure gliclazide and of the reference commercial product Diabrezide®. Conclusions: The new system shows an improved pharmaceutical behavior and could be formulated in a dosage form to obtain a rapid and complete release of the drug available for absorption

The use of lithium metal as the anode for Lithium Metal Batteries (LMB) requires having solid or quasi-solid electrolytes able to block dendrites formation during cell cycling. Here we reported on a hybrid electrolyte membrane based on nanostructured yttria-stabilized-zirconia, sintered by means of High Pressure-Field Assisted Sintering Technique (HP-FAST) in order to retain proper nano-porosity, and activated with a standard LiPF6-EC-DMC solution. By a thorough physico-chemical and functional characterization, we demonstrated that the liquid is effectively nano-confined in the ceramic membrane, and the resulting quasi-solid electrolyte is non-flammable. A remarkable conductivity value of 0.91 mS cm−1 was observed at room temperature, with activation energy of 0.2 eV, and cation transference number, t+ = 0.55, substantially higher than that of the pure liquid electrolyte. The hybrid electrolyte showed electrochemical stability up to 5.5 V vs. Li+/Li, and excellent resistance to dendrite formation for more than 350 cycles in a Li/electrolyte/Li symmetrical cell. A full cell Li/electrolyte/LiMn2O4 showed more than 90 mAh g−1 at 2C for more than 120 cycles. These very promising results indicated that nano-porous ceramic hybrid electrolytes may be conveniently used in LMB.

The implementation of aqueous electrode processing of cathode materials is a key for the development of greener Na-ion batteries. Herein, the development and optimization of the aqueous electrode processing for the ecofriendly Na0.44MnO2 (NMO) cathode material, employing carboxymethyl cellulose (CMC) as binder, are reported for the first time. The characterization of such an electrode reveals that the performances are strongly affected by the employed electrolyte solution, especially, the sodium salt and the use of electrolyte's additives. In particular, the best results are obtained using the 1 M solution of NaPF6 in EC/DEC (ethylene carbonate/diethyl carbonate) 3:7 (v/v) + 2 wt % FEC (fluoroethylene carbonate). With this electrolyte, the outstanding capacity of 99.7 mA h g-1 is delivered by the CMC-NMO cathode after 800 cycles at a 1C charge/discharge rate. On the basis of this excellent long-Term performance, a full sodium cell, composed of a CMC-based NMO cathode and hard carbon from biowaste (corn cob), has been assembled and tested. The cell delivers excellent performances in terms of specific capacity, capacity retention, and long-Term cycling stability. After 75 cycles at a C/5 rate, the capacity of the NMO in the full-cell approaches 109 mA h g-1 with a Coulombic efficiency of 99.9%.

LaW x Nb 1−x O 4+x/2 ceramics (x = 0.16) were prepared via a solid state route and studied with respect to phase stability and mixed ionic and electronic conductivity under conditions of technological relevance for fuel cell applications. The chemical compatibility against standard cathode materials revealed that Sr-doped LaMnO 3 could be used without detectable chemical interaction up to at least 1000 °C. Impedance spectroscopy measurements performed in the range 400–850 °C, using different atmospheres (air and N 2 +H 2 , both dry and water vapour saturated), suggest oxygen transport numbers equal to 1 under oxidising conditions, and decreasing when exposed to extreme reducing conditions. The total conductivity at 800 °C increases from 1.4·10 −3 S cm −1 in air to 2.5·10 −3 S cm −1 in wet hydrogen and 6.1·10 −3 S cm −1 in dry hydrogen, but the observed onset of n-type conductivity has little practical impact under typical fuel cell operating conditions.

Lattice strain is considered a promising approach to modulate the structural and functional properties of oxide materials. In this study we investigate the effect of lattice strain on doping, hydration and proton transport for the family of scheelite-type proton conductors using both atomistic and DFT computational methods. The results suggest that tensile strain improves the dopant solubility and proton uptake of the material. The anisotropic proton pathways change from being within the a-b plane to being in the a-c plane. However, the predicted reduction in the migration barrier suggests that improvements in ionic conductivity due to lattice strain effects will be limited, in contrast with the work on oxide ion conduction. Such results are rationalized in terms of structural changes and differences in migration steps between oxide ions and protonic species.

Sodium-ion batteries (SIBs) are considered a good choice for post-lithium devices. Transition metal sodium pyrophosphates are among the most interesting cathode materials for SIBs. Here we study the electrochemical properties of the system Na 2 Fe 1´x Mn x P 2 O 7 (x = 0, 0.25, 0.5, 0.75, 1). By means of cyclic voltammetry (CV) and galvanostatic experiments, we confirm that pure Fe and Fe-rich compounds are promising for application in sodium batteries, whereas Mn-rich samples are less satisfactory, at least in case of solid-state reaction recipes and standard slurry preparations. Proper carbon coating is likely needed to improve the electrochemical behavior of Mn-rich samples.

Organosulfonic modified SBA-15 silicas are promising catalysts for a wide spectrum of organic reactions. In particular, their catalytic activity seems to be effective only when large amounts of functional groups are anchored to the silica skeleton. However, there is evidence that the ordered mesostructure is retained only for contents of sulfonic units not exceeding 20 mol%. In this paper, for the first time to our knowledge, we fully address the gradual structural disordering mechanisms of the SBA-15 silica functionalised with increasing amounts of propylsulfonic groups in the compositional range 0-70 mol%. This investigation was carried out by means of a multi-technique wide approach including thermal analysis, TEM, XRD, N2 adsorption, FTIR/Raman and solid-state multinuclear NMR. We obtained detailed information on the structural modifications of these hybrid systems as a consequence of the sulfonation process. In particular, we showed that high functionalization degrees lead to inhomogeneous materials made of inorganic or low-functionalized clusters where the SBA-15 structure is likely retained, and hybrid clusters where the hexagonal mesoporous structure is destroyed. Moreover, full conversion of -SH into -SO3H groups is efficient until 20 mol% functionalization. In fact for higher sulfonation degrees, the formation of S-S bridges becomes a competitive mechanism, which is predominant in the sample SO3H70%, where only about 20% of the introduced organic moieties are actually oxidized. Therefore, to push sulfonic functionalization above 20 mol% is not necessarily useful, at least for applications where ordered mesoporous structure is mandatory, such as in catalysis or in membranes for polymer fuel cells.

Pyrophosphate-based materials, in particular Na2FeP2O7, constitute an interesting class of cathode compounds for rechargeable Na-ion batteries. In this work we investigate the effect of different synthetic procedures, namely: (i) glucose-assisted solid-state synthesis, and (ii) Pechini-based wet chemistry approach, on the electrochemical performances of Na2FeP2O7. Both the methods allow good specific gravimetric capacity during charge/discharge, with values close to the theoretical one at low current rates, good capacity retention and coulombic efficiency to be obtained. These results, which are better than those obtained from solid-state synthesis without added glucose, are quite independent on the different microstructures originating from the synthesis approaches, and can be attributed to the residuals of the organic fractions added during the synthesis. In addition we show that the glucose-assisted solid-state synthesis assures electrochemical stability even at relatively high currents rates (100 cycles at 1C rate).

International audience; Transition metal-based lithium orthosilicates (Li2MSiO4, M=Fe, Ni, Co, Mn) are gaining a wide interest as cathode materials for lithium-ion batteries. These materials present a very complex polymorphism that could affect their physical properties. In this work, we synthesized the Li2FeSiO4 and Li2MnSiO4 compounds by a sol-gel method at different temperatures. The samples were investigated by XRPD, TEM, Li-7 MAS NMR, and magnetization measurements, in order to characterize the relationships between crystal structure and magnetic properties. High-quality Li-7 MAS NMR spectra were used to determine the silicate structure, which can otherwise be hard to study due to possible mixtures of different polymorphs. The magnetization study revealed that the Neel temperature does not depend on the polymorph structure for both iron and manganese lithium orthosilicates.

International audience; LaSrAl3O7 belongs to the family of (M2T(1)T(2)O7)-T-1-O-2 compounds with tetragonal melilite-like layered structure. In such compounds the local structure and properties may be very different from the average ones, mainly due to cationic disorder on the M site. In this work, solid-state Al-27 NMR spectroscopy and periodic density functional theory calculations were used to highlight the differences between local and average order in the LaSrAl3O7 crystal. The Al-27 isotropic chemical shifts and quadrupolar coupling constants were computed by employing the gauge including projector augmented wave (GIPAW) and PAW formalisms, respectively. An impressive linear relationship between the computed quadrupolar coupling constant C-Q and the Al tetrahedra (T-1, T-2) distortion was observed. In particular, our calculations showed that the distortion of the T-2 environment is determined by the La/Sr speciation around the apical nonbridging oxygen.

The long-range ordering of a crystalline material can be accurately determined by analyzing the Bragg intensities and positions. In contrast, direct observation of short-range ordering in crystalline materials, which is increasingly considered of fundamental importance to unravel the structure-property relationships that underpin their technological applications, is a challenging task. In this study we have investigated the structure of LaSrAlO4, a representative example of compounds with the K2NiF4-type structure. By the combined use of synchrotron and neutron diffraction, pair distribution function analysis, Al-27 MQMAS NMR and atomistic simulations we have highlighted differences between the average and local structure of this material, directly determining the existence of at least two distinct Al sites. The results presented in this study confirm that La and Sr are, on average, randomly distributed throughout the structure, but demonstrate that the situation is considerably more complex at the short range