No abstract

Oxide ion conduction mechanism was clarified by Rietveld and MEM analysis for both RE 9.33 (SiO 4 ) 6 O 2 and Sr 2 RE 8 (SiO 4 ) 6 O 2 (RE = La and Nd) in high purity using neutron powder diffraction data collected at room temperature. All compounds had an apatite type structure in space group P6 3 /m. There was neither site splitting nor interstitial site of oxide ion. RE 9.33 (SiO 4 ) 6 O 2 had cation vacancies only at 4f site. In Sr 2 RE 8 (SiO 4 ) 6 O 2 , the 4f sites were fully occupied by strontium and rare earth with a molar ratio of 1:1. Oxide ion at hexagonal channel site had large displacement along c-axis in RE 9.33 (SiO 4 ) 6 O 2 . The large displacement is induced by cooperative rotation of SiO 4 tetrahedra around rare earth in 4f site through oxide ion polyhedra around another rare earth in 6h site. The displacement, enhanced by a vacancy in the 4f site, is directly related to the oxide ion conduction in RE 9.33 (SiO 4 ) 6 O 2 .2

No abstract

Lithium-ion conductive Li6PS5Br is prepared using ultrasonication of Li2S, P2S5 and LiBr in ethyl propionate-ethanol solution and subsequent heating at 453 K. The main phase of the synthesized product is Li6PS5Br and its lithium ion conductivity is 3.4 × 10 −5 S cm −1 at room temperature. The cathode composite of LiCo1/3Ni1/3Mn1/3O2, Li6PS5Br and vapor grown carbon fiber (VGCF) is prepared via ultrasonication of the Li6PS5Br precursor solution containing LiCo1/3Ni1/3Mn1/3O2 and VGCF, and the all-solid-state lithium battery using this cathode composite is fabricated. The cell exhibits the discharge capacity of 109 mAh g-1 for the first cycle and its capacity of 87 mAh g-1 after 10 cycles.

Electron-beam induced recrystallization of irradiation-induced amorphous Sr2Nd8(SiO4)6O2 is investigated in situ using transmission electron microscopy with 200keV electrons at room temperature. Epitaxial recrystallization is observed from both the amorphous/crystalline interface and the surface, and the recrystallization is more pronounced with increasing electron-beam flux. Since the temperature increase induced by electron-beam irradiation is estimated to be less than 7K and maximum energies transferred to target atoms are below the displacement energies, ionization-induced processes are considered to be the primary mechanisms for the solid-phase epitaxial recrystallization observed in the present study.

In bulk-type all-solid-state lithium batteries with sulfide-based solid electrolytes, composite electrodes, in which an active material, a solid electrolyte, and a conductive additive are mixed, have been used to enhance lithium ion diffusion and electronic conductivity. However, the addition of electrolytes and electron-conductive additives to the composite electrodes decreases the amount of active materials in the batteries. In the present study, FePS3 is employed as the electrode in an all-solid-state lithium secondary battery, without mixing the solid electrolytes and conductive additives. The all-solid-state cell using the FePS3 electrode exhibits reversible charge-discharge behavior for more than 30 cycles under a constant current density of 0.13 mA cm 2 at room temperature. The discharge capacity of the cell is 107 mAh g 1 at the 30th cycle. This behavior is comparable to that of a cell with an electrode including a solid electrolyte and/or a conductive additive, indicating that the FePS3 electrode has sufficient paths of lithium ions and of electron conduction. These results suggest that FePS3 is an attractive iron-based electrode for an all-solid-state battery using a sulfide-based solid electrolyte.

All solid state batteries with cathode composites containing high concentration of active materials are required to achieve higher energy densities. Here, a composite cathode containing up to 89 wt% of high voltage cathode active material (LiNi Mn Co O ) was prepared by covering this with a solution derived solid electrolyte (argyrodite, Li PS Cl) and the incorporation of different content binder (ethyl cellulose). All solid state batteries were fabricated using 80Li S•20P S (mol%) glass and indium metal as a solid electrolyte and anode, respectively. The all solid state battery with a composite cathode containing 0.5 wt% of ethyl cellulose showed an initial discharge capacity of 45 mAhg at 25 °C and maintained 91.7% of the discharge capacity after ten cycles, around 30% higher than that obtained for the battery with the composite cathode without a binder.

Abstract:The catalytic activity of manganese oxynitrides in the oxygen reduction reaction (ORR) was investigated in alkaline solutions to clarify the effect of nitrogen on ORR activity. These oxynitrides, having rocksalt-based structures with different nitrogen content, were synthesized by reactions of MnO, Mn2O3, and MnO2 with molten NaNH2 at 240-280 C. Anion contents and Mn valence states were determined by combustion analysis, powder X-ray diffraction, and X-ray absorption near edge structure analysis. An increase in nitrogen content in rocksaltbased manganese oxynitrides enhanced the valence of manganese and reinforced the catalytic activity for the ORR in 1 M KOH solution. Nearly single-electron occupancy in antibonding eg states and high covalency in Mn-N bonding would enhance the ORR activity of nitrogen-rich manganese oxynitrides.Catalysts for the oxygen reduction reaction (ORR) in alkaline solutions (O2 + 2H2O + 4e -→ 4OH -) are key materials for nextgeneration energy conversion and storage systems, including fuel cells and metal-air batteries, and highly efficient ORR catalysts are highly desirable. [1] A group of well-studied catalysts includes perovskite oxides, such as LaCoO3 and LaMnO3, whose structure-activity correlation has been extensively explored. [1][2] Although the ORR is mechanistically complicated and is influenced by crystal structure, composition, electronic conductivity, surface absorption behavior, and the incorporation of conductive additives, [1a] the structure-activity correlation gives the rational guidelines for designing and understanding ORR catalysts.Nitrides and related compounds have been studied as ORR catalysts. Binary and ternary nitrides, such as AlN, TiN, Cu3N, and Cu3PdN, show catalytic activity for the ORR. [3] Oxynitrides, including ZrOxNy, MoOxNy, TaOxNy and CoMoOxNy, also show the catalytic activity. [4] Nonetheless, the correlation between structure and ORR activity has not been extensively studied, and the role of nitrogen in altering catalytic activity is not completely understood. The challenge would be the difficulty of tuning the amount of incorporated nitrogen, mainly due to the thermodynamic stability of the triple bond in molecular N2. Additionally, the different nitrogen amount often has a significant effect on the crystal structure of synthesized products, [5] thus complicating the interpretation of results.Pervoskite oxides contain metal-oxygen octahedron, whose electronic structure can be schematically depicted as tg and eg states. Suntivich et al. have reported that nearly single-electron occupancy in eg states composed by antibonding metal-oxygen interaction is beneficial for an electron transfer during the ORR cycle. [2d] ; a typical example of a single electron in eg states is LaMnO3 with trivalent manganese. Additionally, more covalency of metal-oxygen bonding in perovskite oxides is favorable for the ORR . [2c, 2d] Since nitrogen has less electron than oxygen and metal-nitrogen bonding is more covalent than metal-oxygen one, the tuning of nit...