A Binary Ionogel Electrolyte for the Realization of an All Solid-State Electrical Double-Layer Capacitor Performing at Low Temperature.

Over the last years, solid-state electrolytes made of an ionic liquid (IL) confined in a solid (inorganic or polymer) matrix, also known as ionogels, have been proposed to solve the leakage problems occurring at high temperatures in classical electrical double-layer capacitors (EDLCs) with an organic electrolyte, and thereof improve the safety. However, making ionogel-based EDLCs perform with reasonable power at low temperature is still a major challenge due to the high melting point of the confined IL. To overcome these limitations, the present contribution discloses ionogel films prepared in a totally oxygen/moisture-free atmosphere by encapsulating 70 wt % of an equimolar mixture of 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide and 1-ethyl-3-methylimidazolium tetrafluoroborate - [EMIm][BF][FSI] - into a poly(vinylidene fluoride-co-hexafluoropropylene) (PVdF-HFP) network.

Electrical Double-Layer Capacitors Based on a Ternary Ionic Liquid Electrolyte Operating at Low Temperature with Realistic Gravimetric and Volumetric Energy Outputs.

We report on electrical double-layer capacitors (EDLCs) performing effectively at low temperature (down to -40 °C), owing to the tuned characteristics of both the ionic liquid (IL) electrolyte and carbonaceous electrodes. The transport properties of the electrolyte have been enhanced by adding a low-viscosity IL with the tetracyanoborate anion, [EMIm][TCB], to a mixture of [EMIm][FSI] with [EMIm][BF ], which was already successfully applied for this application. The formulated ternary electrolyte, [EMIm][FSI] [BF ] [TCB] , remained in the liquid state until it reached the glass transition at -99 °C and displayed a relatively low viscosity and high conductivity (η=23.

Hydrogel-Polymer Electrolyte for Electrochemical Capacitors with High Volumetric Energy and Life Span.

AC/AC (AC=activated carbon) electrochemical capacitors (ECs) were designed with a 1 mol L lithium sulfate hydrogel- polymer electrolyte (HPE) based on carboxymethyl cellulose sodium salt (CMC). The electrochemical performance of the ECs was compared with that of cells composed of common separators such as a polyolefin membrane (Celgard 3501, polypropylene separator coated by surfactant) and a glass microfiber membrane (Whatman GF/A). The ECs with Celgard 3501 and home-made CMC-HPE demonstrated a higher volumetric energy than that with Whatman GF/A.

Quantification of the Charge Consuming Phenomena under High-Voltage Hold of Carbon/Carbon Supercapacitors by Coupling Operando and Post-Mortem Analyses.

Enhancing the operating voltage of supercapacitors (SCs), hence their specific energy, is important. However, long-term hold at high voltage entails loss of capacitance, increase of resistance and internal pressure. Such detrimental effects could be reduced by obtaining quantitative information on the relative impact of the various mechanisms leading to the worsening of the SCs performance.

Carbons and electrolytes for advanced supercapacitors.

Electrical energy storage (EES) is one of the most critical areas of technological research around the world. Storing and efficiently using electricity generated by intermittent sources and the transition of our transportation fleet to electric drive depend fundamentally on the development of EES systems with high energy and power densities. Supercapacitors are promising devices for highly efficient energy storage and power management, yet they still suffer from moderate energy densities compared to batteries.

Carbon nanofibers grafted on activated carbon as an electrode in high-power supercapacitors.

A hybrid electrode material for high-power supercapacitors was fabricated by grafting carbon nanofibers (CNFs) onto the surface of powdered activated carbon (AC) through catalytic chemical vapor deposition (CCVD). A uniform thin layer of disentangled CNFs with a herringbone structure was deposited on the carbon surface through the decomposition of propane at 450 °C over an AC-supported nickel catalyst. CNF coating was controlled by the reaction time and the nickel content.

Exploring electrolyte organization in supercapacitor electrodes with solid-state NMR.

Supercapacitors are electrochemical energy-storage devices that exploit the electrostatic interaction between high-surface-area nanoporous electrodes and electrolyte ions. Insight into the molecular mechanisms at work inside supercapacitor carbon electrodes is obtained with (13)C and (11)B ex situ magic-angle spinning nuclear magnetic resonance (MAS-NMR). In activated carbons soaked with an electrolyte solution, two distinct adsorption sites are detected by NMR, both undergoing chemical exchange with the free electrolyte molecules.

Triethylammonium bis(tetrafluoromethylsulfonyl)amide protic ionic liquid as an electrolyte for electrical double-layer capacitors.

This study describes the preparation, characterization and application of [Et(3)NH][TFSA], either neat or mixed with acetonitrile, as an electrolyte for supercapacitors. Thermal and transport properties were evaluated for the neat [Et(3)NH][TFSA], and the temperature dependence of viscosity and conductivity can be described by the VTF equation. The evolution of conductivity with the addition of acetonitrile rendered it possible to determine the optimal mixture at 25 °C, with a weight fraction of acetonitrile of 0.

A solid-state NMR study of C(70): a model molecule for amorphous carbons.

We show that natural abundance, solid-state MAS-NMR (13)C INADEQUATE spectra can be recorded for crystallized C(70), using the through-bond J-coupling for the magnetization transfer. The effect of strong J-coupling can be lessened at high magnetic fields, allowing the observation of cross-peaks between close resonances. DFT calculations of the chemical shifts show an excellent agreement with the experimental values.

Highly electroconductive multiwalled carbon nanotubes as potentially useful tools for modulating calcium balancing in biological environments.

Aiming to explore the mechanisms modulating cell-carbon nanotube interactions, we investigated whether Ca(2+) ion balancing between intra- and extracellular environments could be affected by multiwalled carbon nanotubes (MWCNTs). We analyzed the effects induced by two different kinds of MWCNTs (as prepared and annealed at 2400°C) on the intracellular Ca(2+) ion levels in rat electrically sensitive cells and on the intercellular junction integrity of rat adenocarcinoma colon cells and platelet aggregation ability, which depend on the Ca(2+) concentration in the medium. MWCNTs, purified by annealing and more electroconductive as compared to nonannealed MWCNTs, affected Ca(2+) ion balancing between extra- and intracellular environments and induced changes on Ca(2+) ion-dependent cellular junctions and platelet aggregation, behaving as the calcium chelator ethylene glycol tetraacetic acid.

Carbon nanotubes as nanotexturing agents for high power supercapacitors based on seaweed carbons.

The advantages provided by multiwalled carbon nanotubes (CNTs) as backbones for composite supercapacitor electrodes are discussed. This paper particularly highlights the electrochemical properties of carbon composites obtained by pyrolysis of seaweed/CNTs blends. Due to the nanotexturing effect of CNTs, supercapacitors fabricated with electrodes from these composites exhibit enhanced electrochemical performances compared with CNT-free carbons.

Electrochemical regeneration of activated carbon cloth exhausted with bentazone.

The electrochemical regeneration of an activated carbon cloth exhausted with a common herbicide (bentazone) was investigated under different operating conditions. The reversibility of the desorption process was confirmed by monitoring the UV spectra of the solution while cathodic polarization is being applied. Neither nanotextural nor chemical changes are produced in the carbon cloth upon polarization in the absence of the adsorbate.

Mechanism of adsorption and electrosorption of bentazone on activated carbon cloth in aqueous solutions.

An electrochemical technique has been applied to enhance the removal of a common herbicide (bentazone) from aqueous solutions using an activated carbon cloth as electrode. A pH increase from acidic to basic reduces the uptake, with capacities going from 127 down to 80 mg/g at pH 2 and 7, respectively. Increasing the oxygen content of the carbon cloth causes a decrease in the bentazone loading capacity at all pH values.

Catalytically grown carbon nanotubes of small diameter have a high Young's modulus.

Experimental studies of carbon nanotubes (CNTs) obtained through different synthesis routes show considerable variability in their mechanical properties. The strongest CNTs obtained so far had a high Young's modulus of 1 TPa but could only be produced in gram scale quantities. The synthesis by catalytic chemical vapor deposition, a method that holds the greatest potential for large-scale production, gives CNTs with a high defect density.

High yield of pure multiwalled carbon nanotubes from the catalytic decomposition of acetylene on in-situ formed cobalt nanoparticles.

For the first time, multiwalled carbon nanotubes (MWNTs) could be formed selectively in a high yield, free of any disordered carbon by-product, from the catalytic decomposition of acetylene at 600 degrees C on a CoxMg(1-x)O solid solution. Starting from 1 g of catalytic substrate, 4 g of pure MWNTs were obtained after its dissolution in boiling concentrated HCl, without any additional purification in strongly oxidizing medium, as is required for other methods of nanotube production. In situ reduction of CoO by dihydrogen liberated from acetylene decomposition allows highly divided metal particles to be continuously produced as synthesis proceeds.