High rate capabilities Fe3O4-based Cu nano-architectured electrodes for lithium-ion battery applications

All battery technologies are known to suffer from kinetic problems linked to the solid-state diffusion of Li in intercalation electrodes, the conductivity of the electrolyte in some cases and the quality of interfaces. For Li-ion technology the latter effect is especially acute when conversion rather than intercalation electrodes are used. Nano-architectured electrodes are usually suggested to enhance kinetics, although their realization is cumbersome. To tackle this issue for the conversion electrode material Fe3O4, we have used a two-step electrode design consisting of the electrochemically assisted template growth of Cu nanorods onto a current collector followed by electrochemical plating of Fe3O4. Using such electrodes, we demonstrate a factor of six improvement in power density over planar electrodes while maintaining the same total discharge time. The capacity at the 8C rate was 80% of the total capacity and was sustained over 100 cycles. The origin of the large hysteresis between charge and discharge, intrinsic to conversion reactions, is discussed and approaches to reduce it are proposed. We hope that such findings will help pave the way for the use of conversion reaction electrodes in future-generation Li-ion batteries

Recent developments in borohydride fuel cell cells

Developments in direct borohydride fuel cells (DBFC) are considered together with electrolyte stability and the choice of membrane and electrode materials. The cyclic voltammetry of borohydride oxidation was studied at three electrodes: a) gold on carbon, Au/C, b) gold on titanate nanotubes, Au/TiN and (c) gold foil. Similar currents were observed from the three electrodes. A DBFC in a single, 2- and 4-bipolar cell configuration with Au/C anode and Pt/C cathode produced 2.2, 3.2 and 9.6 W showed cell voltages of 1.06, 0.81 and 3 V, respectively. In another single cell, the reduction of peroxide on a Pd/Ir coated microfibrous carbon cathode was catalytically more active than a platinised-carbon one. The maximum power density achieved was 78 mW cm-2 at a cell voltage of 1.09 V. The need for further research is highlighted, particularly into new electrocatalyst material

Ecosystem modelling of the Eastern Corsican Coast (ECC): Case study of one of the least trawled shelves of the Mediterranean Sea

International audienceThe Eastern Corsican Coast (ECC) is distinguished by its shallow sandy shelf, extensive Posidonia seagrass meadows, and the relatively limited exploitation of fish in this region. To understand ECC trophic functioning and the effects of fishing in this region of the Mediterranean Sea, we applied the Ecopath and EcoTroph approaches. Our model encompassed 5 groups of primary producers and detritus, 14 invertebrate groups, two groups of Chondrichthyes, 16 teleost groups, one seabird group, and one group of cetaceans. The ECC ecosystem was structured into five trophic levels, regulated top-down by Sphyraenidae, Epinephelus marginatus, and Dentex dentex. The ecosystem displayed a high degree of benthic-pelagic coupling, confirmed by keystone groups/species located at intermediate trophic levels (planktivorous teleosts, benthic cephalopods, shrimps, zooplankton). The ECC demonstrated the lowest exploitation rate (F/Z) of all exploited Mediterranean ecosystems, with trawling representing 55% of catches, followed by the lobster net (27%) and fish net (18%) fisheries. Catches often included untargeted groups-often discarded dead-in particular sharks and rays, and several protected species. Moreover, Palinurus elephas, Scorpaena scrofa, and Dentex dentex had elevated F/Z values, highlighting their vulnerabilities to fishing. Although the fishing simulations suggested that the ECC could support a greater exploitation, they also revealed that these fisheries have a marked impact on upper trophic levels. Our study draws attention to the critical habitat the ECC provides for Chondrichthyes, evidenced by the significant biomass for these taxa and the low fishing pressure relative to other exploited Mediterranean systems. This first modelling of the ECC is an initial step towards modelling all Corsican marine ecosystems to serve as a guide for preserving these ecosystems through appropriate management measures

A novel approach for real mass transformation from V2O5 particles to nanorods

A solid-state, mass-quantity transformation from V2O5 powders to nanorods has been realized via a two-step approach. The nanorods were formed through a controlled nanoscale growth from the nanocrystalline V2O5 phase created by a ball milling treatment. The nanorods grow along the [010] direction and are dominated by {001} surfaces. Surface energy minimization and surface diffusion play important roles in their growth mechanism. Real large quantity production can be achieved when the annealing process is conducted in a fluidized bed which can treat large quantities of the milled materials at once. The crystal orientation of nanorods provides an improved cycling stability for lithium intercalation.<br /