114 research outputs found

    An infrared spectroscopy study of the conformational evolution of the Bis(trifluoromethanesulfonyl)imide ion in the liquid and in the glass state

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    We measure the far-infrared spectrum of N,N-Dimethyl-N-ethyl-N-benzylammonium (DEBA) bis(trifluoromethanesulfonyl) imide (TFSI) ionic liquid (IL) in the temperature range between 160 and 307 K. Differential scanning calorimetry measurements indicate that such IL undergoes a glass transition around 210K. DFT calculations allow us to assign all the experimental absorptions to specific vibrations of the DEBA cation or of the two conformers of the TFSI anion. We find that the vibration frequencies calculated by means of the PBE0 functional are in better agreement with the experimental ones than those calculated at the B3LYP level, largely used for the attribution of vibration lines of ionic liquids. Experimentally we show that, in the liquid state, the relative concentrations of the two conformers of TFSI depend on temperature through the Boltzmann factor and the energy separation, őĒH, is found to be ‚Čą2 kJ/mol, in agreement with previous calculations and literature. However, in the glassy state, the concentrations of the cis-TFSI and trans-TFSI remain fixed, witnessing the frozen state of this phase

    A high-power and fast charging Li-ion battery with outstanding cycle-life

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    Electrochemical energy storage devices based on Li-ion cells currently power almost all electronic devices and power tools. The development of new Li-ion cell configurations by incorporating innovative functional components (electrode materials and electrolyte formulations) will allow to bring this technology beyond mobile electronics and to boost performance largely beyond the state-of-the-art. Here we demonstrate a new full Li-ion cell constituted by a high-potential cathode material, i.e. LiNi0.5Mn1.5O4, a safe nanostructured anode material, i.e. TiO2, and a composite electrolyte made by a mixture of an ionic liquid suitable for high potential applications, i.e. Pyr1,4PF6, a lithium salt, i.e. LiPF6, and standard organic carbonates. The final cell configuration is able to reversibly cycle lithium for thousands of cycles at 1000 mAg-1 and a capacity retention of 65% at cycle 2000. © 2017 The Author(s)

    Room-temperature synthesis of 2D-Ti3C2Tx nano-sheets by organic base treatment

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    The growing demand for improved electrochemical performance in energy storage systems has stimulated research into advanced two-dimensional (2D) materials for electrodes. In this work, we obtain a layered MXene compound by exfoliating a titanium aluminum carbide precursor using tetramethylammonium hydroxide (TMAOH) ions in a full room temperature process followed by manual shaking. The hexagonal crystal structure and composition of the layered materials are characterized using different techniques. X-Ray diffraction shows the formation of 2D nano-sheets before and after the TMAOH treatment via its characteristic (002) diffraction peak, bringing to light an increase in the interlayer spacing after treatment. Scanning electron microscopy images confirm the layered morphology, whose composition is determined by energy dispersive x-ray analysis for the bulk material and by x-ray photoelectron spectroscopy for the surface of the obtained compounds. This study demonstrates a promising route to enhance delamination of this MXene 2D material in a low-cost room-temperature approach

    Na-seawater battery technology integration with renewable energies: The case study of Sardinia Island

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    Europe has committed to net zero carbon dioxide emissions by 2050 to boost the clean energy transition. Renewable electricity will be the key energy medium for decarbonization and a huge increase in renewable energy sources (RES) exploitation is expected. Due to RES stochastic character, an extensive energy storage integration in the energy system is needed to avoid the mismatch between generation and demand profiles. Reactive metals are promising energy carriers and storage media characterized by high volumetric energy densities and circularity, due to ease of storage and transportation, material availability and low cost. Among them, sodium is a largely available element since it can be extracted from seawater and exploited through the innovative sodium-seawater battery (SWB). Sodium cations are transferred from SWB‚Äôs open cathode to the anode side during charging. Upon discharge, Na metal is oxidized to Na+^+ ions, which are discarded in seawater. This study assesses the impact of SWB technology focusing on Sardinia Island as a case study. For short-term application, SWB integration to wave energy converters allows a potential reduction of greater than 85% of generated power fluctuations, largely improving the quality of power injected into the grid. Regarding the long-term scenario, SWBs implementation in the energy system allows coverage of the Sardinia annual energy demand thanks to the integration of ‚ąľ340,000 cubic meter of Na metal, corresponding to a 12-m height Na reservoir under 4 soccer fields. SWB application to Sardinia also produces CO2_2 sequestration while covering ‚ąľ29% of desalinated water requirements for the Sardinian population

    Understanding the impact of Fe-doping on the structure and battery performance of a Co-free Li-rich layered cathodes

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    A series of Co-free Li-rich layered oxides, Li1.24Mn0.62-xNi0.14FexO2 (x=0, 0.01, 0.02 and 0.03) has been synthetized by a self-combustion reaction. Fe doping affects either lattice structure and bonding as shown by the changes in the size of unit cell calculated from diffraction patterns and in the vibrational frequencies observed in Raman spectra. The electrochemical performance has been evaluated in a lithium cell by galvanostatic cycling: Doped samples show better capacity retention and minor decreases in the specific capacity (i. e., Li1.24Mn0.60Ni0.14Fe0.02O2 can supply a specific capacity of 235 mAhg‚ąí1 with 94 % of capacity retention after 150 cycles). These positive effects originated by alterations in the point defectivity (Ni3+ concentration, anionic and cationic vacancies), changes in the transport properties, as showed by Cyclic Voltammetry; as well as an improved structural resilience compared to the un-doped material in postmortem analyses. ¬© 2023 The Authors. ChemElectroChem published by Wiley-VCH GmbH

    Electrolyte Measures to Prevent Polysulfide Shuttle in Lithium‚ÄźSulfur Batteries

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    Lithium-sulfur (Li‚ąíS) batteries are recognized as one of the most promising technologies with the potential to become the next-generation batteries. However, to ensure Li‚ąíS batteries reach commercialization, complex challenges remain, among which the tailoring of an appropriate electrolyte is the most important. This review discusses the role of electrolytes in Li‚ąíS batteries, focusing on the main issues and solutions for the shuttle mechanism of polysulfides and the instability of the interface with lithium metal. Herein, we present a background on Li‚ąíS chemistry followed by the state-of-the-art electrolytes highlighting the different strategies undertaken with liquid and solid electrolytes

    Structural and spectroscopic characterization of A nanosized sulfated TiO2 filler and of nanocomposite nafion membranes

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    A large number of nano-sized oxides have been studied in the literature as fillers for polymeric membranes, such as Nafion¬ģ. Superacidic sulfated oxides have been proposed and characterized. Once incorporated into polymer matrices, their beneficial effect on peculiar membrane properties has been demonstrated. The alteration of physical-chemical properties of composite membranes has roots in the intermolecular interaction between the inorganic filler surface groups and the polymer chains. In the attempt to tackle this fundamental issue, here we discuss, by a multi-technique approach, the properties of a nanosized sulfated titania material as a candidate filler for Nafion membranes. The results of a systematic study carried out by synchrotron X-ray diffraction, transmission electron microscopy, thermogravimetry, Raman and infrared spectroscopies are presented and discussed to get novel insights about the structural features, molecular properties, and morphological characteristics of sulphated TiO2 nanopowders and composite Nafion membranes containing different amount of sulfated TiO2 nanoparticles (2%, 5%, 7% w/w

    Production of nanostructured electrodes from spent Lithium ion batteries and their application in new energy storage devices

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    The present work is aimed at demonstrating the potentiality of lithium ion batteries recycling through the production of high added value nanostructured material. Nanostructured electrodic materials were synthesized starting from waste lithium ion batteries (LIBs). Firstly, the metals contained in the electrodic powder of exhausted LIBs were extracted by acid-reducing leaching. After filtration, metals rich solution was separated from graphite. Nanoparticles- based electrodes were produced by controlled precipitation and subsequent calcination of metals in order to obtain nanoparticles of LiNi1/3Co1/3Mn1/3O2, one of the most employed LIBs cathodic material. Cathodic materials synthesized starting from waste LIBs and from high grade synthetic reagents were compared after their characterization by SEM, EDX and XRD. The electrochemical performance of the electrodes was evaluated by galvanostatic cycling the electrodes in a lithium half-cell. Remarkably, the electrochemical performances obtained with the electrodes produced by the recovery of metals are close to those recorded using electrodes produced by synthetic reagents. © 2020 Author(s)

    Chemically stabilised extruded and recast short side chain Aquivion proton exchange membranes for high current density operation in water electrolysis

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    Membrane-electrode assemblies based on chemically stabilised short-side-chain proton exchange Aquivion¬ģ membranes, prepared by extrusion or recast methods, have been investigated for operation at high current density (3-4 A cm -2 ) in water electrolysis cells. A thickness of 90 ¬Ķm was selected for these perfluorosulfonic acid membranes in order to provide proper resilience to hydrogen crossover under differential pressure operation while allowing operation at high currents. The membranes showed proper mechanical strength for high-pressure operation and suitable conductivity to reduce ohmic losses at high current densities. Both membranes showed excellent performance in electrolysis cells by achieving a voltage efficiency better than 85% and 80% (1.85 V) at 3 and 4 A cm -2 , respectively, in polarisation curves at 90 ¬įC. A smaller surface roughness was observed from atomic force microscopy for the recast membrane compared to the extruded one. This may affect the intimate contact between the ionic clusters of the membrane and the catalyst agglomerate at the interface producing a catalytic enhancement in the activation region of the polarisation curves in the case of the recast membrane. At high cell voltages, the polarisation resistance was instead slightly lower for the cell based on the extruded membrane. Interestingly, the different characteristics of the membrane-electrodes interface produced lower recoverable losses in durability studies for the recast membrane-based electrolyser allowing stable operation at both 3 and 4 A cm -2 . Hydrogen crossover analysis at a differential pressure of 20 bar showed low gas permeation through both membranes allowing for a wide load range (15-100 %) and high faradaic efficiency >99% at practical current densities (1-4 A cm -2 )
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