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

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, ΔH, is found to be ≈2 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

Nanoporous carbons from hydrothermally treated biomass as anode materials for lithium ion batteries

Biomass is transformed to carbon nanoparticles with surface-end groups called ‘hydrochar’ (HC) by an efficient and green hydrothermal carbonization (HTC) method. Three different approaches are used to introduce porosity to the HC: sole heat treatment, traditional potassium hydroxide (KOH) activation, and environmentally benign magnesium oxide (MgO) templating. All the resulting microporous materials are tested as Li-ion intercalation hosts in lithium cells by using an 1 M LiPF6 in EC/DMC electrolyte solution. They all show stable reversible capacities at elevated current rates (1C), closely comparable to the maximum theoretical capacity of graphite. Among all the materials studied, the HC-MA with a surface area of 150 m2 g1 and obtained by MgO templating of the hydrochar shows the best cycling performance in lithium cell at room temperature (307 mAh g1 at cycle 100 at 1C). The HC-600 with the highest degree of aromaticity/order, lowest content of oxygen functional groups and surface area of 250 m2 g1, obtained by heating the hydrochar at 600 C under inert atmosphere, shows the best power and overall performance with its ability to sustain high discharge/charge rates (1C, 2C, 5C, 10C, 20C). These electrochemical performances attained with materials of reasonable specific surface areas – obtained by green, low cost and practical strategies – can address the space limitations in Li-ion battery applications by improving volumetric energy densities

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

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)

Lightweight Borohydrides Electro-Activity in Lithium Cells

As a substitute for graphite, the negative electrode material commonly used in Li-ion batteries, hydrides have the theoretical potential to overcome performance limits of the current state-of-the-art Li-ion cells. Hydrides can operate through a conversion process proved for some interstitial hydrides like MgH2: MxAy + n Li = x M + y LimA, where m = n/y. Even if far from optimization, outstanding performances were observed, drawing the attention to the whole hydride family. Looking for high capacity systems, lightweight complex metal hydrides, such as borohydrides, deserve consideration. Capacities in the order of 2000–4000 mAh/g can be theoretically expected thanks to the very low formula unit weight. Although the potential technological impact of these materials can lead to major breakthroughs in Li-ion batteries, this new research field requires the tackling of fundamental issues that are completely unexplored. Here, our recent findings on the incorporation of borohydrides are presented and discusse

Hydrides as high capacity anodes in lithium cells: an Italian “Futuro in Ricerca di Base FIRB-2010” project

Automotive and stationary energy storage are among the most recently-proposed and still unfulfilled applications for lithium ion devices. Higher energy, power and superior safety standards, well beyond the present state of the art, are actually required to extend the Li-ion battery market to these challenging fields, but such a goal can only be achieved by the development of new materials with improved performances. Focusing on the negative electrode materials, alloying and conversion chemistries have been widely explored in the last decade to circumvent the main weakness of the intercalation processes: the limitation in capacity to one or at most two lithium atoms per host formula unit. Among all of the many proposed conversion chemistries, hydrides have been proposed and investigated since 2008. In lithium cells, these materials undergo a conversion reaction that gives metallic nanoparticles surrounded by an amorphous matrix of LiH. Among all of the reported conversion materials, hydrides have outstanding theoretical properties and have been only marginally explored, thus making this class of materials an interesting playground for both fundamental and applied research. In this review, we illustrate the most relevant results achieved in the frame of the Italian National Research Project FIRB 2010 Futuro in Ricerca “Hydrides as high capacity anodes in lithium cells” and possible future perspectives of research for this class of materials in electrochemical energy storage devices

A lithium-ion battery based on a graphene nanoflakes ink anode and a lithium iron phosphate cathode

Li-ion rechargeable batteries have enabled the wireless revolution transforming global communication. Future challenges, however, demands distributed energy supply at a level that is not feasible with the current energy-storage technology. New materials, capable of providing higher energy density are needed. Here we report a new class of lithium-ion batteries based on a graphene ink anode and a lithium iron phosphate cathode. By carefully balancing the cell composition and suppressing the initial irreversible capacity of the anode, we demonstrate an optimal battery performance in terms of specific capacity, i.e. 165 mAhg-1, estimated energy density of about 190 Whkg-1 and life, with a stable operation for over 80 charge-discharge cycles. We link these unique properties to the graphene nanoflake anode displaying crystalline order and high uptake of lithium at the edges, as well as to its structural and morphological optimization in relation to the overall battery composition. Our approach, compatible with any printing technologies, is cheap and scalable and opens up new opportunities for the development of high-capacity Li-ion batteries.Comment: 17 pages, 10 figure

In-situ gelled electrolyte for lithium battery: Electrochemical and Raman characterization

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

A large number of nano-sized oxides have been studied in the literature as fillers for polymeric membranes, such as Nafion®. 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

Nanostructured tin-carbon/ LiNi0.5Mn1.5O4 lithium-ion battery operating at low temperature

An advanced lithium ion battery using nanostructured tinecarbon lithium alloying anode and a high voltage LiNi0.5Mn1.5O4 spinel-type cathode is studied, with particular focus to the low temperature range. The stable behavior of the battery is assured by the use of an electrolyte media based on a LiPF6 salt dissolved in EC-DEC-DMC, i.e. a mixture particularly suitable for the low temperature application. Cycling tests, both in half cells and in full lithium ion battery using the SneC anode and the LiNi0.5Mn1.5O4 cathode, performed in a temperature range extending from room temperature to "30 C, indicate that the electrode/electrolyte configuration here adopted may be suitable for effective application in the lithium ion battery field. The full cell, cycled at -5 °C, shows stable capacity of about 105 mAh g-1 over more than 200 chargee-discharge cycles that is considered a relevant performance considering the low temperature region

Electrochemical synthesis of nanowires electrodes and their application in energy storage devices

In this work, an electrochemical approach to synthesize Metal-MetalOxide/Hydroxide core-shell nanowires electrodes (NWE) is illustrated. NWE electrodes were obtained by electrodeposition of a targeted metal into the nanopores of nanoporous alumina templates generated by one-step anodization of aluminum. Following metal electrodeposition, the alumina template was selectively etched to obtain an array of free-standing metal nanowires. The imposed electrodeposition conditions allowed directly attaining a core-shell nanostructure, with a metal core covered by a thin metal oxide/hydroxide film. NWE electrodes produced by the proposed synthesis route were tested for the application as electrodes in lithium batteries and supercapacitors. To this purpose, an array of cobalt nanowires (CoNWs) supported by a nanostructured copper current collector was produced by sequential electrodeposition of cobalt and copper, and it was employed as anode in a lithium battery, while a NWE based on Ni-NiO/OH2 (NiNWs) was obtained by nickel electrodeposition and tested as electrode in a supercapacitor. A thorough analysis and characterization of the produced electrodes were performed. The experiments with the lithium cell evidenced the positive effect of metallic core on stability, while the electrochemical characterization of the supercapacitor showed the presence of both NiO and NiOH2 leading, when cycled, to a capacity close to the best literature value