Boletín GEC 28

ABSTRACT: In recent years, the improvement of the energy density of nano-composite battery materials has been object of great study. Hybridizing battery and capacitor materials overcome the energy density limitation of existing generation-I capacitors without much sacrificing the cycling performances. Normal battery-capacitor hybrids employ high-energy & sluggish redox electrode and low-energy & fast double-layer electrodes, possibly producing a larger working voltage and higher over-all capacitance. In order to smoothly operate such asymmetric systems, however, the rates of the two different electrodes must be highly balanced. Especially, the redox rates of the battery electrodes must be substantially increased to the levels of double-layer process. In this report, we attempt to identify the essential issues for the realizable hybrids and suggest ways to overcome the rate enhancement by exemplifying ultrafast performance of the Li₄Ti₅O₁₂ nanocrystal prepared via a unique in-situ material processing technology under ultra-centrifuging.

R. Berenguer, E. Morallón, D. Cazorla-Amorós, H. Nishihara, H. Itoi, T. Ishii, T. Kyotani

ABSTRACT: One option to optimize carbon materials for supercapacitor applications is the generation of surface functional groups that contribute to the pseudocapacitance without losing the designed physical properties. This requires suitable functionalization techniques able to selectively introduce a given amount of electroactive oxygen groups. In this work, the influence of the chemical and electrochemical oxidation methods, on the chemical and physical properties of a zeolite templated carbon (ZTC), as a model carbon material, have been studied and compared. Although both oxidation methods generally produce a loss of the original ZTC physical properties with increasing amount of oxidation, the electrochemical method shows much better controllability and, unlike chemical treatments, enables the generation of a large number of oxygen groups (O = 11000- 3300 μmol/g), with a higher proportion of active functionalities, while retaining a high surface area (ranging between 1900-3500 m²/g), a high microporosity and an ordered 3-D structure.

pp. 15-17

Yasushi Soneda and Masaya Kodama

ABSTRACT: Mesoporous carbons (MPCs) with large specific surface area are synthesized by the heat-treatment and subsequent acid treatment of magnesium citrate.
The MPCs obtained are examined as electrode materials for electric double layer capacitor and show the huge gravimetric capacitance with superior rate performance in sulphuric acid electrolyte. The MPCs also realize the larger capacitance than conventional activated carbon in organic electrolyte and extraordinary high retention of capacitance at very low temperature, such as 80% of room temperature value at -60 °C.

ABSTRACT: The electric double layer capacitor (EDLC) is an electrochemical capacitor storing electric energy by charging the electric double layer on the micropores of a nanoporous carbon electrode such as activated carbon. The EDLC has a fast charge-discharge property and excellent cycle life, but its energy density is lower than other electrochemical energy storage devices such as the rechargeable battery. The energy density of the EDLC can be improved by increasing the double layer capacitance and the maximum charging voltage. In this review, the author describes the activated carbon electrodes for use in a durable EDLC for high voltage charging.

OBJECTIVES AND NOVELTY: Industrial and commercial growth in many countries around the world in the past decades has been accompanied by rapid generation of municipal and industrial solid waste, which creates the most serious environmental problems related to landfill such as the generation of leachates during the decomposition process. Among the emerging contaminants that have been detected in landfill leachates, wastewater, ground water and surface water are plastic additives and herbicides with range 0.01 μg/L to 30 mg/L...