We evaluated the charge−discharge performance of a Sn 4 P 3 negative electrode in an ionic liquid electrolyte comprised of Nmethyl-N-propylpyrrolidinium bis(fluorosulfonyl)amide (Py13-FSA) and NaFSA. We also conducted cyclic voltammetry and transmission electron microscopy for the Sn 4 P 3 electrode to reveal the reaction mechanism. It was suggested that Na 15 Sn 4 and Na 3 P are formed via phase separation in the first sodiation and that elemental Sn and elemental P formed by following a desodiation reaction with Na ions in the subsequent cycles. The Sn 4 P 3 electrode exhibited a high Coulombic efficiency of 99.1% at the fourth cycle and an excellent cycling performance with a high reversible capacity of 750 mA h g −1 even at the 200th cycle. We demonstrated that there are two important factors to improve the performance: (i) higher volume fraction of Sn than P and (ii) uniform dispersion of Sn nanoparticles in a P matrix. The ionic liquid electrolyte showed good applicability to the Sn 4 P 3 negative electrode due to its superior electrochemical stability.

The physicochemical and electrochemical properties of the binary ionic liquid, K­[FSA]–[C3C1pyrr]­[FSA] (FSA = bis­(fluorosulfonyl)­amide; C3C1pyrr = N-methyl-N-propylpyrrolidinium), were investigated at 253–393 K, with the aim of developing a new electrolyte for potassium-ion batteries (K-ion batteries; KIBs). A phase diagram was constructed from the results of differential scanning calorimetry measurements and revealed that the melting point of this ionic liquid is below room temperature for compositions of x(K­[FSA]) = 0–0.25 (x(K­[FSA]) = molar fraction of K­[FSA]). The viscosity, ionic conductivity, and density were measured for x(K­[FSA]) = 0–0.25. The ionic conductivity when x(K­[FSA]) = 0.20 was 4.8 mS cm–1 at 298 K, which is higher than that for the equivalent sodium and lithium ionic liquids. Cyclic voltammetry measurements of M­[FSA]–[C3C1pyrr]­[FSA] ionic liquids (x(M­[FSA]) = 0.20; M = K, Na, or Li) indicated that potassium metal deposition/dissolution occurs at a more negative potential than that for lithium and sodium deposition/dissolution, suggesting that KIBs with a high operating voltage can be constructed using K­[FSA]–[C3C1pyrr]­[FSA] as an ionic liquid electrolyte.

No abstract

We present the catalog of high Galactic-latitude (|b| > 10 • ) X-ray sources detected in the first 37-month data of Monitor of All-sky X-ray Image (MAXI) / Gas Slit Camera (GSC). To achieve the best sensitivity, we develop a background model of the GSC that well reproduces the data based on the detailed on-board calibration. Source detection is performed through image fit with the Poisson likelihood algorithm. The catalog contains 500 objects detected in the 4-10 keV band with significance of s D,4−10keV ≥ 7. The limiting sensitivity is ≈ 7.5 × 10 −12 ergs cm −2 s −1 (≈ 0.6 mCrab) in the 4-10 keV band for 50% of the survey area, which is the highest ever achieved as an all-sky survey mission covering this energy band. We summarize the statistical properties of the catalog and results from cross matching with the Swift/BAT 70-month catalog, the metacatalog of X-ray detected clusters of galaxies, and the MAXI/GSC 7-month catalog. Our catalog lists the source name (2MAXI), position and its error, detection significances and fluxes in the 4-10 keV and 3-4 keV bands, their hardness ratio, and basic information of the likely counterpart available for 296 sources.

We report on the in-orbit performance of the Gas Slit Camera (GSC) on the MAXI (Monitor of All-sky X-ray Image) mission carried on the International Space Station (ISS). Its commissioning operation, which started on 2009 August 8, confirmed the basic performances of the effective area in the energy band of 2–30 keV, the spatial resolution of the slit-and-slat collimator and detector with 1 $^\circ\!\!\!.$ 5 FWHM, the source visibility of 40–150 seconds for each scan cycle, and the sky coverage of 85% per 92-minute orbital period and 95% per day. The gas gains and read-out amplifier gains have been stable within 1%. The background rate is consistent with the past X-ray experiments operated at a similar low-earth orbit if its relation with the geomagnetic cutoff rigidity is extrapolated to high latitude. We also present the status of the in-orbit operation and a calibration of the effective area and the energy response matrix using Crab-nebula data.

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We have presented a novel design of a photonic crystal slab (PCS) nanocavity, in which the electric field of the cavity mode is strongly localized in free space. The feature of the cavity is a linear air slot introduced to the center of the mode-gap confined PCS cavity. Owing to the discontinuity of the dielectric constant, the electric field of the cavity mode is strongly enhanced inside the slot, allowing strong matter-field coupling and large interaction volume in free space. Using finite-difference time-domain method, we calculate the properties of the cavity mode as a function of the slot width. The calculated quality factor is still as high as 2 x 10(5) and the mode volume is as small as 0.14 of a cubic wavelength in a vacuum, even if 200-nm-wide slot is introduced to the PCS.

A binary ionic liquid of K­[FSA]-[C3C1pyrr]­[FSA] (2:8 in molar ratio) in which N-methyl-N-propylpyrrolidinium and bis­(fluorosulfonyl)­amide are abbreviated as [C3C1pyrr] and [FSA], respectively, is applied as an electrolyte of K-ion batteries for the first time. A graphite composite electrode with sodium carboxymethylcellulose as the binder undergoes reversible potassium intercalation, forming a KC8 compound in a K half-cell filled with the binary ionic liquid as electrolyte. Because the K­[FSA]-[C3C1pyrr]­[FSA] does not corrode an Al foil current collector even with polarization of up to 6 V versus K+/K, a K2Mn­[Fe­(CN)6] positive electrode yields a highly reversible capacity of 134 mAh g–1 at ca. 4.0 V. We demonstrate a K-ion battery of graphite//K2Mn­[Fe­(CN)6] configuration with an ionic liquid electrolyte that exhibits stable charge and discharge properties over 200 cycles at room temperature. The redox performance is significantly improved by replacing the conventional KPF6 carbonate ester solution with the ionic liquid.