Carbon nanotube/Co3O4 composite for air electrode of lithium-air battery

A carbon nanotube [CNT]/Co3O4 composite is introduced as a catalyst for the air electrode of lithium-air [Li/air] batteries. Co3O4 nanoparticles are successfully attached to the sidewall of the CNT by a hydrothermal method. A high discharge capacity and a low overvoltage indicate that the CNT/Co3O4 composite is a very promising catalyst for the air electrode of Li/air batteries

Hierarchical urchin-shaped alpha-MnO2 on graphene-coated carbon microfibers: a binder-free electrode for rechargeable aqueous Na-air battery

With the increasing demand of cost-effective and high-energy devices, sodium-air (Na-air) batteries have attracted immense interest due to the natural abundance of sodium in contrast to lithium. In particular, an aqueous Na-air battery has fundamental advantage over non-aqueous batteries due to the formation of highly water-soluble discharge product, which improve the overall performance of the system in terms of energy density, cyclic stability and round-trip efficiency. Despite these advantages, the rechargeability of aqueous Na-air batteries has not yet been demonstrated when using non-precious metal catalysts. In this work, we rationally synthesized a binder-free and robust electrode by directly growing urchin-shaped MnO2 nanowires on porous reduced graphene oxide-coated carbon microfiber (MGC) mats and fabricated an aqueous Na-air cell using the MGC as an air electrode to demonstrate the rechargeability of an aqueous Na-air battery. The fabricated aqueous Na-air cell exhibited excellent rechargeability and rate capability with a low overpotential gap (0.7 V) and high round-trip efficiency (81%). We believe that our approach opens a new avenue for synthesizing robust and binder-free electrodes that can be utilized to build not only metal-air batteries but also other energy systems such as supercapacitors, metal-ion batteries and fuel cells.ope

Comparisons of heat treatment on the electrochemical performance of different carbons for lithium-oxygen cells

Lithium-oxygen (Li-O2) cells are a promising power source, and carbons are an attractive non-metal catalyst for air electrodes. To improve the electrochemical performance, various carbons are heated in an inert atmosphere. It is found that heat treatment at 900 C can differently improve the electrochemical performance of multiwalled carbon nanotubes (CNTs), acetylene carbon black (AB) and activated carbon (AC), but the improvement of CNTs is the most obvious. After heat treatment, the peak current density of the oxygen reduction reaction (ORR) and the 1st discharge capacity of CNTs increase ∼30% and ∼125%, respectively, while the charge transfer reaction resistance and the Warburg diffusion resistance decrease ∼7.0% and ∼11.1%, respectively. AC has the highest charge capacities and capacity retention ratio in spite of little influence by heat treatment. The possible mechanism and reasons are analyzed using different techniques. Microstructure is superior to conductivity for enhancing the rechargeability and the cyclability, and heat treatment is effective for some carbon materials in improving the electrochemical performance of Li-O2 cells. © 2014 Elsevier Ltd

Le musée forum, un difficile consensus : l'exemple du Muséum National d'Histoire Naturelle

Girault Yves, Débart Cécile. Le musée forum, un difficile consensus : l'exemple du Muséum National d'Histoire Naturelle. In: Quaderni, n°46, Hiver 2001-2002. La Science dans la cité. pp. 147-162

Investigation of the O2 Electrochemistry in a Polymer Electrolyte Solid-State Cell

The oxygen electrode has been the subject of intense activity for more than 150 years, since the report of the first fuel cell in 1842 by Grove. Recently, there had been a revived interest in the utilization of air as oxidizer in the positive electrode of air secondary batteries, for example, lithium–air batteries. Very high specific energies can be obtained from these systems (at 2 kWhkg-1 of reactant for lithium), and these high numbers justify the present excitement for the lithium–air battery

Reactivity of transition metal (Co, Ni, Cu) sulphides versus lithium: The intriguing case of the copper sulphide

Transmission electron microscopy (TEM), in situ X-ray diffraction (XRD) and electrochemical techniques have been used to study the electrochemical reactivity of transition metal (cobalt, nickel, and copper) sulphides. We show that cobalt and nickel sulphides react versus lithium through conversion reactions similarly to their homologous oxides with during the discharge step the formation of metallic nano-particles embedded in Li2S that on the following charge convert back into sulphides. In contrast, the electrochemical reactivity of CuS towards Li was shown to follow a displacement reaction leading to the growth and disappearance of large copper dendrites with a concomitant reversible decomposition/re-crystallization of the initial electrode material. We show from structural considerations that this mechanism is nested in the creation of Cu2-xS phases, since intermediary phases during cycling have both high copper mobility and a sulphur network close to that of Li2S. In spite of their attractive capacity, none of these compounds show good capacity retention over the studied voltage range (0 to 2.5 V); the main reason being rooted in the partial solubility of Li2S into the electrolyte. © 2006 Elsevier SAS. All rights reserved