Multivalent Batteries—Prospects for High Energy Density: Ca Batteries

Batteries based on Ca hold the promise to leapfrog ahead regarding increases in energy densities and are especially attractive as Ca is the 5th most abundant element in the Earth's crust. The viability of Ca metal anodes has recently been shown by approaches that either use wide potential window electrolytes at moderately elevated temperatures or THF-based electrolytes at room temperature. This paper provides realistic estimates of the practical energy densities for Ca-based rechargeable batteries at the cell level, calculated using open source models for several concepts. The results from the Ca metal anode batteries indicate that doubled or even tripled energy density as compared to the state-of-the-art Li-ion batteries is viable if a practical proof-of-concept can be achieved

Synthèse, caractérisation et étude des mécanismes de décharge et d'autodécharge des hydroxydes et oxyhydroxydes de nickel et de cobalt

L'objectif de cette thèse était d'établir une meilleure compréhension du comportement électrochimique de l'électrode à hydroxyde de nickel lors de la décharge, et de mieux cerner les mécanismes d'autodécharge afin de les limiter en vue d'application dans les piles Ni/Zn, parues récemment sur le marché. Les mécanismes de décharge de l'électrode de nickel, et notamment le phénomène du second plateau, ont été étudiés par diffraction de neutrons in situ qui permet de suivre simultanément les modifications structurales et le comportement électrochimique des phases. Une origine chimique au second plateau a ainsi pu être exclue définitivement, l'existence de celui-ci n'étant pas spécifique à une phase identifiée. L'étude plus appliquée portant sur l'autodécharge des oxyhydroxydes de nickel de type gIII en milieu alcalin a été développée selon deux axes de recherche principaux: l'étude du mécanisme à proprement dit, et le développement de solutions visant à minimiser ce phénomèneAMIENS-BU Sciences (800212103) / SudocSudocFranceF

A High-Surface-Area Carbon-Coated 3D Nickel Nanomesh for Li-O-2 Batteries

Nanostructured electrodes show great promises for application in batteries and could improve their energy and power density. Herein, a carbon-coated 3D Ni nanomesh was used as an air cathode for non-aqueous Li-air (O2 ) battery applications. A 3 μm thick 3D Ni nanomesh was fabricated, showing an excellent surface area/footprint area ratio (90 cm2 :1 cm2 ) and uniformly distributed pores, on which a conformal amorphous carbon coating was applied for the first time. This carbon-coated 3D Ni nanomesh showed an approximately 100 times larger charge-footprint capacity than that of the glassy carbon electrode. Owing to its tunable properties, a capacity higher than 6 mAh cm-2 could be achieved for a carbon-coated 3D Ni nanomesh with a thickness of 100 μm, whereas the practical capacities of current air electrodes are in the range of 2 mAh cm-2 .status: publishe

Li-O-2 Battery with a Dimethylformamide Electrolyte

Stability of the electrolyte toward reduced oxygen species generated at the cathode is a crucial challenge for the rechargeable nonaqueous Li-O-2 battery. Here, we investigate dimethylformamide as the basis of an electrolyte. Although reactions at the O-2 cathode on the first discharge charge cycle are dominated by reversible Li2O2 formation/decomposition, there is also electrolyte decomposition, which increases on cycling. The products of decomposition at the. cathode on discharge are Li2O2, Li2CO3, HCO2Li, CH3CO2Li, NO, H2O, and CO2. Li2CO3 accumulates in the electrode with cycling. The stability of dimethylformamide toward reduced oxygen species is insufficient for its use in the rechargeable nonaqueous Li-O-2 battery.</p

Li-O-2 Battery with a Dimethylformamide Electrolyte

Stability of the electrolyte toward reduced oxygen species generated at the cathode is a crucial challenge for the rechargeable nonaqueous Li-O-2 battery. Here, we investigate dimethylformamide as the basis of an electrolyte. Although reactions at the O-2 cathode on the first discharge charge cycle are dominated by reversible Li2O2 formation/decomposition, there is also electrolyte decomposition, which increases on cycling. The products of decomposition at the. cathode on discharge are Li2O2, Li2CO3, HCO2Li, CH3CO2Li, NO, H2O, and CO2. Li2CO3 accumulates in the electrode with cycling. The stability of dimethylformamide toward reduced oxygen species is insufficient for its use in the rechargeable nonaqueous Li-O-2 battery.</p

Sulfone-based electrolytes for nonaqueous Li-O2 batteries

We investigated the use of sulfone-based electrolytes for the Li-O 2 battery. The study compared the behavior of three commercially available sulfones: ethyl vinyl sulfone (EVS), tetramethylene sulfone (TMS), also called sulfolane, and ethyl methyl sulfone (EMS). First, we carried out a preliminary investigation of the oxygen reduction reaction and oxygen evolution reaction (ORR/OER) as a function of solvent type and Li+ concentration. Then, TMS and EMS were tested (LiTFSI salt) in Li-O2 cells. The cells exhibited initial capacities around 1800 and 2000 mAh.g -1carbon, respectively. The capacity retention on cycling was quite low. We analyzed the reaction products during discharge and charge by means of powder X-ray diffraction, infrared spectroscopy, 1H-nuclear magnetic resonance, and mass spectrometry. Although EVS was at first sight the most attractive sulfone, since it is a liquid at room temperature, it was the least stable in the presence of oxygen; its vinyl group was attacked by reduced O2 species. On the other hand, both TMS and EMS performed better during the first five cycles; Li2O2 formation and decomposition was the main reaction, although some byproducts formed during cycling. After five cycles, there was still a considerable amount of Li 2O2 formed, but decomposition to form Li 2CO3 became significant, and it accumulated at the O 2 electrode. This was the likely reason for capacity fading. © 2014 American Chemical Society.status: publishe