Eco-Efficient Synthesis of LiFePO4 with Different Morphologies for Li-Ion Batteries

LiFePO4 is presently the most studied electrode material for battery applications. It can be prepared via solution, although it requires well-controlled pH conditions to master the iron valence state in the newly created material. Here we report its synthesis via the use of "latent bases" capable of releasing a nitrogen base upon heating. This way of controlling the reaction pH enables, in the absence of excess Li, the preparation of Fe+3-free LiFePO4 powders having various morphologies and showing good electrochemical performance. This approach is shown to offer great opportunities for the low-temperature synthesis of various electrode materials

Geometry-based finite-element modeling of the electrical contact between a cultured neuron and a microelectrode

The electrical contact between a substrate embedded microelectrode and a cultured neuron depends on the geometry of the neuron-electrode interface. Interpretation and improvement of these contacts requires proper modeling of all coupling mechanisms. In literature, it is common practice to model the neuron-electrode contact using lumped circuits in which large simplifications are made in the representation of the interface geometry. In this paper, the finite-element method is used to model the neuron-electrode interface, which permits numerical solutions for a variety of interface geometries. The simulation results offer detailed spatial and temporal information about the combined electrical behavior of extracellular volume, electrode-electrolyte interface and neuronal membrane

Advanced screening of electrode couples

The chromium (Cr(3+)/Cr(2+)) redox couple (electrolyte and electrode) was investigated to determine its suitability as negative electrode for the iron (Fe(3+)/Fe(2+))-chromium (Cr(3+)/Cr(2+)) redox flow battery. Literature search and laboratory investigation established that the solubility and stability of aqueous acidic solutions of chromium(3) chloride and chromium(2) chloride are sufficient for redox battery application. Four categories of electrode materials were tested; namely, metals and metalloid materials (elements and compounds), alloys, plated materials, and Teflon-bonded materials. In all, the relative performance of 26 candidate electrode materials was evaluated on the basis of slow scan rate linear sweep voltammetry in stirred solution. No single material tested gave both acceptable anodic an acceptable cathodic performance. However, the identification of lead as a good cathodic electrocatalyst and gold as a good anodic electrocatalyst led to the invention of the lead/gold combination electrocatalyst. This type of catalyst can be fabricated in several ways and appears to offer the advantages of each metal without the disadvantages associated with their use as single materials. This lead/gold electrocatalyst was tested by NASA-Lewis Research Center in complete, flowing, redox batteries comprising a stack of several cells. A large improvement in the battery's coulombic and energy efficiency was observed

Additive manufacturing for solid oxide cell electrode fabrication

© The Electrochemical Society.Additive manufacturing can potentially offer a highly-defined electrode microstructure, as well as fast and reproducible electrode fabrication. Selective laser sintering is an additive manufacturing technique in which three-dimensional structures are created by bonding subsequent layers of powder using a laser. Although selective laser sintering can be applied to a wide range of materials, including metals and ceramics, the scientific and technical aspects of the manufacturing parameters and their impact on microstructural evolution during the process are not well understood. In the present study, a novel approach for electrode fabrication using selective laser sintering was evaluated by conducting a proof of concept study. A Ni-patterned fuel electrode was laser sintered on an yttria-stabilized zirconia substrate. The optimization process of laser parameters (laser sintering rate and laser power) and the electrochemical results of a full cell with a laser sintered electrode are presented. The challenges and prospects of using selective laser sintering for solid oxide cell fabrication are discussed

Electrochemical Polymerization of PPy-MWCNT composite as a Counter Electrode for Dye-sensitized Solar Cells

Polypyrrole (PPy) - multi wall carbon nanotube (MWCNT) nanocomposites were synthesized by using in situ electrochemical polymerization with different COOH-functionalized MWCNTs. The PPY-MWCNT composites were used as counter electrode in the fabrication of dye sensitized solar cells (DSCs). Compared to the DSC device with PPy counter electrode, the devices with PPY/MWCNT composite electrode offer much higher total photovoltaic conversion efficiency due to the reduced series resistance. These PPY/MWCNT nanocomposite materials proved to be a good alternate to the expensive Pt as counter electrode in DSC

Printable magnesium ion quasi-solid-state asymmetric supercapacitors for flexible solar-charging integrated units.

Wearable and portable self-powered units have stimulated considerable attention in both the scientific and technological realms. However, their innovative development is still limited by inefficient bulky connections between functional modules, incompatible energy storage systems with poor cycling stability, and real safety concerns. Herein, we demonstrate a flexible solar-charging integrated unit based on the design of printed magnesium ion aqueous asymmetric supercapacitors. This power unit exhibits excellent mechanical robustness, high photo-charging cycling stability (98.7% capacitance retention after 100 cycles), excellent overall energy conversion and storage efficiency (ηoverall = 17.57%), and outstanding input current tolerance. In addition, the Mg ion quasi-solid-state asymmetric supercapacitors show high energy density up to 13.1 mWh cm-3 via pseudocapacitive ion storage as investigated by an operando X-ray diffraction technique. The findings pave a practical route toward the design of future self-powered systems affording favorable safety, long life, and high energy

Fabrication of Switches on Polymer-Based by Hot Embossing

In MEMS technology, most of the devices are fabricated on glass or silicon substrate. However, this research presents a novel manufacture method that is derived from conventional hot embossing technology to fabricate the electrostatic switches on polymer material. The procedures of fabrication involve the metal deposition, photolithography, electroplating, hot embossing and hot embed techniques. The fundamental concept of the hot embed technology is that the temperature should be increased above Tg of polymer, and the polymer becomes plastic and viscous and could be molded. According to the fundamental concept, the metal layer on the silicon/glass substrate could be embedded into polymer material during the hot embossing process. Afterward, the metal layer is bonded together with the polymer after removing the substrate in the de-embossing step. Finally, the electrostatic switch is fabricated on polymethylmethacrylate(PMMA) material to demonstrate the novel method.Comment: Submitted on behalf of TIMA Editions (http://irevues.inist.fr/tima-editions