Physical-Chemical Characterization of Binary Mixtures of 1-Butyl-1-methylpyrrolidinium Bis{(trifluoromethyl)sulfonyl}imide and Aliphatic Nitrile Solvents as Potential Electrolytes for Electrochemical Energy Storage Applications

In the scope of improving the energy and power densities of electrochemical double layer capacitors (EDLCs), the development of high performance electrolytes with enhanced operative voltages is imperative. The formulation of mixtures containing ionic liquids with organic molecular solvents is an important strategy in the pursuit of developing highly electrochemically stable and safe materials while retaining fast transport properties for high power applications. In this work, we report on the physical–chemical investigations into binary mixtures containing the ionic liquid 1-butyl-1-methylpyrrolidinium bis{(trifluoromethyl)sulfonyl}imide with one mononitrile solvent, butyronitrile, and two dinitrile solvents, glutaronitrile and adiponitrile, as potential electrolytes for EDLCs. The thermal, volumetric, and transport properties of the binary mixtures are investigated as functions of the electrolyte composition and temperature. Furthermore, the electrolyte composition which exhibits the highest conductivity for each of the binary mixtures was determined, and its electrochemical stability is reported using a glassy carbon macrodisk electrode

Direct observation of ion dynamics in supercapacitor electrodes using in situ diffusion NMR spectroscopy

Ionic transport inside porous carbon electrodes underpins the storage of energy in supercapacitors and the rate at which they can charge and discharge, yet few studies have elucidated the materials properties that influence ion dynamics. Here we use in situ pulsed field gradient NMR spectroscopy to measure ionic diffusion in supercapacitors directly. We find that confinement in the nanoporous electrode structures decreases the effective self-diffusion coefficients of ions by over two orders of magnitude compared with neat electrolyte, and in-pore diffusion is modulated by changes in ion populations at the electrode/electrolyte interface during charging. Electrolyte concentration and carbon pore size distributions also affect in-pore diffusion and the movement of ions in and out of the nanopores. In light of our findings we propose that controlling the charging mechanism may allow the tuning of the energy and power performances of supercapacitors for a range of different applications

Carbon blacks as active materials for electrochemical double layer capacitors

Carbon blacks (CBs) are nowadays the most used conductive additives in electrochemical double layer capacitors (EDLCs) and lithium-ion batteries. Nevertheless, taking into account the appealing properties of CBs, e.g. high conductivity and relatively low cost, also their use as active materials for EDLCs appears of high interest. In this work we present a comparison between the electrochemical behavior of EDLCs containing CBs and the conventional activated carbons (AC) as the active materials. The aim of this investigation is to contribute to the assessment of the advantages and limits related to the use of carbon blacks as alternative active carbonaceous materials for EDLCs.Actualmente los negros de carbón son los aditivos promotores de conductividad más utilizados en condensadores electroquímicos de doble capa (EDLCs) y baterías de ión-litio. No obstante, teniendo en cuenta las propiedades atractivas de los negros de carbón, tales como una elevada conductividad eléctrica y un coste relativamente bajo, su utilización como materiales activos para EDLCs presenta gran interés. En este trabajo, presentamos una comparación entre el comportamiento electroquímico de EDLCs basados en negro de carbón y el de los basados en carbones activados convencionales. El objetivo de esta investigación es contribuir a la evaluación de las ventajas y limitaciones relacionadas con el uso de los negros de carbón como materiales activos alternativos para EDLCs