Insights into the Effects of Electrolyte Composition on the Performance and Stability of FeF 2 Conversion-Type Cathodes

As an alternative to commercial Ni- and Co-based intercalation-type cathode materials, conversion-type metal fluoride (MF x ) cathodes are attracting more interest due to their promises to increase cell-level energy density when coupled with lithium (Li) or silicon (Si)-based anodes. Among metal fluorides, iron fluorides (FeF 2 and FeF 3 ) are regarded as some of the most promising candidates due to their high capacity, moderately high potential and the very low cost of Fe. In this study, the impacts of electrolyte composition on the performance and stability of nanostructured FeF 2 cathodes are systematically investigated. Dramatic impacts of Li salt composition, Li salt concentration, solvent composition, and cycling potential range on the cathode's most critical performance parameters-stability, capacity, rate, and voltage hysteresis are discovered. In contrast to previous beliefs, it is observed that even if the Fe 2+ cation dissolution could be avoided, the dissolution of F ? anions may still negatively affect cathode performance. Formation of the more favorable cathode solid electrolyte interface (CEI) is found to minimize both processes.Different aspects of this work were supported by the Army Research Office (ARO grant number W911NF-12-1-0259) and by the Qatar National Research Fund under its National Priorities Research Program (grantnumber NPRP7-567-2-216). The authors also acknowledge fellowship support of Q.H. and X.R. by the China Scholarship Council.Scopu

Assessment of TiO2 nanoparticles accumulation in organs and their effect on cognitive abilities of mice

Because of good optical and electrical properties, TiO2 nanoparticles are widely used in many fields of industry and medicine. To assess the effect of TiO2 nanoparticles on mice cognitive abilities and their accumulation in different organs, daily, up to 2-month period, experimental mice were administrated with TiO2 nanoparticles solution. Accumulation of titanium in blood, brain, liver, kidney, lungs and feces was assessed by neutron activation analysis. Cognitive abilities in mice before and after TiO2 nanoparticles administration were evaluated in the Morris water maze behavioral test. The amount of titanium in all organs was below the limits of detection of the method and in feces it constituted 74 +/- 7 mu g/g. In the main Morris water maze behavioral test at the control points statistically significant differences were found in the parameters of treks between capable experimental and control animals.Web of Science18338437

Angewandte Chemie

Renewable energy sources (solar, wind etc.) can provide a substantial amount of energy, their intermittent nature requires low cost, safe and highly efficient electrochemical energy storage systems (EESs). Tremendous efforts to improve EESs like batteries and supercapacitors have been reported but they mainly address small scale storage (e. g. portable electronics) and grid-scale energy storage still remains a challenging To address this challenge, recently, a novel concept to store grid-scale electrical energy called the electrochemical flow capacitor (EFC) has been reported by our group The fundamental goal of this work is to optimize the electrochemical performance of the flowable electrode. Here, we addressed two different approaches to optimize the electrode; activation of active material (carbon spheres) and the nature of electrolyte (aqueous, nonaqueous etc.). We performed series of physical activations on carbon spheres having diameters between 250-350 µm using CO 2 as an activation agent at four different temperatures 800, 900, 950 and 1000 ˚C for duration of 1hour. The resultant activated carbons were characterized using N 2 adsorption, scanning electron microscope (SEM), cyclic voltammetry, galvanostatic charge/discharge cycling and impedance spectroscopy. Changes in the surface area and pore distribution were observed at different activation temperatures. Between 950 and 1000 ˚C the pore distribution appeared to become more uniform In general, the higher the activation temperature the greater was the capacitance across all rates studie