Samsung (Japan)

Almost all mobile communication systems today use spectrum in the range of 300 MHz-3 GHz. In this article, we reason why the wireless community should start looking at the 3-300 GHz spectrum for mobile broadband applications. We discuss propagation and device technology challenges associated with this band as well as its unique advantages for mobile communication. We introduce a millimeter-wave mobile broadband (MMB) system as a candidate next generation mobile communication system. We demonstrate the feasibility for MMB to achieve gigabit-per-second data rates at a distance up to 1 km in an urban mobile environment. A few key concepts in MMB network architecture such as the MMB base station grid, MMB interBS backhaul link, and a hybrid MMB + 4G system are described. We also discuss beamforming techniques and the frame structure of the MMB air interface.

Sodium-ion batteries are emerging as candidates for large-scale energy storage due to their low cost and the wide variety of cathode materials available. As battery size and adoption in critical applications increases, safety concerns are resurfacing due to the inherent flammability of organic electrolytes currently in use in both lithium and sodium battery chemistries. Development of solid-state batteries with ionic electrolytes eliminates this concern, while also allowing novel device architectures and potentially improving cycle life. Here we report the computation-assisted discovery and synthesis of a high-performance solid-state electrolyte material: Na10SnP2S12, with room temperature ionic conductivity of 0.4 mS cm(-1) rivalling the conductivity of the best sodium sulfide solid electrolytes to date. We also computationally investigate the variants of this compound where tin is substituted by germanium or silicon and find that the latter may achieve even higher conductivity.

This paper examines patterns of cellular phone adoption and usage in an urban setting. One hundred and seventy-six cellular telephone users were surveyed about their patterns of usage, demographic and socio-economic characteristics, perceptions about the technology, and their motivations to use cellular services. The results of this study confirm that users' perceptions are significantly associated with their motivation to use cellular phones. Specifically, perceived ease of use was found to have significant effects on users' extrinsic and intrinsic motivations; apprehensiveness about cellular technology had a negative effect on intrinsic motivations. Implications of these findings for practice and research are examined.

Lithium-sulfur (Li-S) batteries are promising candidates for next generation electrical energy storage devices due to their high specific energy. Despite intense research, there are still a number of technical challenges in developing a high performance Li-S battery. To elucidate the issues, an all solid-state Li-S battery was fabricated using Li3PS4 solid electrolyte. Most of the theoretical capacity of sulfur, 1600 mAhg−1 was attained in the initial discharge-charge cycles with a high coulombic efficiency approaching 99%. To verify the benefit of the solid state electrolyte, galvanostatic stripping-deposition tests were also carried out on a symmetrical Li/Li cell and compared with those of a liquid electrolyte (1M- lithium bis(trifluoromethane sulfonyl) imide (LiTFSI) in a mixture of 1,3-dioxolane (DOL)-diethoxyethane (DEE)). The kinetics and thermodynamics of the solid-state cell are discussed from the viewpoint of the charge transfer processes. This study demonstrates both the merits and drawbacks of using the solid sulfide electrolyte in a Li-S battery and facilitates the further improvement of this important high energy storage device.

Driven by a paradigm shift from conventional liquid-based systems to all-solid-state batteries (ASSBs), the chemo-mechanical behavior of the solid–solid interface is of growing importance for understanding the intricate interfacial phenomena of ASSBs.

Abstract Lithium metal batteries (LMBs) with inorganic solid-state electrolytes are considered promising secondary battery systems because of their higher energy content than their Li-ion counterpart. However, the LMB performance remains unsatisfactory for commercialization, primarily owing to the inability of the inorganic solid-state electrolytes to hinder lithium dendrite propagation. Here, using an Ag-coated Li 6.4 La 3 Zr 1.7 Ta 0.3 O 12 (LLZTO) inorganic solid electrolyte in combination with a silver-carbon interlayer, we demonstrate the production of stable interfacially engineered lab-scale LMBs. Via experimental measurements and computational modelling, we prove that the interlayers strategy effectively regulates lithium stripping/plating and prevents dendrite penetration in the solid-state electrolyte pellet. By coupling the surface-engineered LLZTO with a lithium metal negative electrode, a high-voltage positive electrode with an ionic liquid-based liquid electrolyte solution in pouch cell configuration, we report 800 cycles at 1.6 mA/cm 2 and 25 °C without applying external pressure. This cell enables an initial discharge capacity of about 3 mAh/cm 2 and a discharge capacity retention of about 85%.

Abstract As the theoretical limit of intercalation material‐based lithium‐ion batteries is approached, alternative chemistries based on conversion reactions are presently considered. The conversion of sulfur is particularly appealing as it is associated with a theoretical gravimetric energy density up to 2510 Wh kg −1 . In this paper, three different carbon‐iron disulfide‐sulfur (C‐FeS 2 ‐S) composites are proposed as alternative positive electrode materials for all‐solid‐state lithium‐sulfur batteries. These are synthesized through a facile, low‐cost, single‐step ball‐milling procedure. It is found that the crystalline structure (evaluated by X‐ray diffraction) and the morphology of the composites (evaluated by scanning electron microscopy) are greatly influenced by the FeS 2 :S ratio. Li/LiI‐Li 3 PS 4 /C‐FeS 2 ‐S solid‐state cells are tested under galvanostatic conditions, while differential capacity plots are used to discuss the peculiar electrochemical features of these novel materials. These cells deliver capacities as high as 1200 mAh g (FeS2+S) −1 at the intermediate loading of 1 mg cm −2 (1.2 mAh cm −2 ), and up to 3.55 mAh cm −2 for active material loadings as high as 5 mg cm −2 at 20 °C. Such an excellent performance, rarely reported for (sulfur/metal sulfide)‐based, all solid‐state cells, makes these composites highly promising for real application where high positive electrode loadings are required.

Abstract The interfacial instability between a thiophosphate solid electrolyte and oxide cathodes results in rapid capacity fade and has driven the need for cathode coatings. In this work, the stability, evolution, and performance of uncoated, Li 2 ZrO 3 ‐coated, and Li 3 B 11 O 18 ‐coated LiNi 0.5 Co 0.2 Mn 0.3 O 2 cathodes are compared using first‐principles computations and electron microscopy characterization. Li 3 B 11 O 18 is identified as a superior coating that exhibits excellent oxidation/chemical stability, leading to substantially improved performance over cells with Li 2 ZrO 3 ‐coated or uncoated cathodes. The chemical and structural origin of the different performance is interpreted using different microscopy techniques which enable the direct observation of the phase decomposition of the Li 2 ZrO 3 coating. It is observed that Li is already extracted from the Li 2 ZrO 3 in the first charge, leading to the formation of ZrO 2 nanocrystallites with loss of protection of the cathode. After 50 cycles separated (Co, Ni)‐sulfides and Mn‐sulfides can be observed within the Li 2 ZrO 3 ‐coated material. This work illustrates the severity of the interfacial reactions between a thiophosphate electrolyte and oxide cathode and shows the importance of using coating materials that are absolutely stable at high voltage.

Nano-structured silicon is an attractive alternative anode material to conventional graphite in lithium-ion batteries. However, the anode designs with higher silicon concentrations remain to be commercialized despite recent remarkable progress. One of the most critical issues is the fundamental understanding of the lithium-silicon Coulombic efficiency. Particularly, this is the key to resolve subtle yet accumulatively significant alterations of Coulombic efficiency by various paths of lithium-silicon processes over cycles. Here, we provide quantitative and qualitative insight into how the irreversible behaviors are altered by the processes under amorphous volume changes and hysteretic amorphous-crystalline phase transformations. Repeated latter transformations over cycles, typically featured as a degradation factor, can govern the reversibility behaviors, improving the irreversibility and eventually minimizing cumulative irreversible lithium consumption. This is clearly different from repeated amorphous volume changes with different lithiation depths. The mechanism behind the correlations is elucidated by electrochemical and structural probing.

Transition metal sulfides have shown to improve the performance of lithium-sulfur batteries both with liquid and solid electrolytes. In this work, the beneficial effect of copper sulfide for enabling high areal capacity lithium-sulfur all-solid-state batteries is shown. Copper sulfide-carbon (CuSC) and three different copper sulfide-sulfur-carbon (CuSS) composites are investigated as positive electrodes in all-solid-state lithium-sulfur batteries. The composites are prepared via facile and low-cost mechanochemical ball-milling. It is found that the CuS/C ratio greatly influences the redox properties of the CuSC cathode. Scanning electron microscopy, ex-situ X-ray diffraction, and galvanostatic cycling were also conducted to evaluate the CuSS composite electrodes in Li|LiI–Li3PS4|CuS–S–C solid-state cells. High mass loading cells made using these composite electrodes deliver capacities as high as 1600 mAh g−1(CuS+S) and 7 mAh cm−2 at 20 ​°C. The higher density of CuS also leads to larger volumetric capacities, up to 3900 mAh cm−3(CuS+S), thus enabling a potential energy density gain up to 15% with respect to a conventional Carbon–Sulfur cathode.

It has been found recently that low-energy helium (He) plasma irradiation to tungsten (W) leads to the growth of W nanostructures on the surface. The process to grow the nanostructure is identified as a self-growth process of He bubbles and has a potential to open up a new plasma processing method. Here, we show that the metallic nanostructure formation process by the exposure to He plasma can occur in various metals such as, titanium, nickel, iron, and so on. When the irradiation conditions alter, the metallic cone arrays including nanobubbles inside are formed on the surface. Different from W cases, other processes than growth of fiberform structure, i.e., physical sputtering and the growth of large He bubbles, can be dominant on other metals during irradiation; various surface morphology changes can occur. The nanostructured W, part of which was oxidized, has revealed a significant photocatalytic activity under visible light (wavelength >700 nm) in decolorization of methylene blue without any co-catalyst.

Bacterial cellulose nanofiber (BCNF) with high thermal stability produced by an ecofriendly process has emerged as a promising solution to realize safe and sustainable materials in the large-scale battery. However, an understanding of the actual thermal behavior of the BCNF in the full-cell battery has been lacking, and the yield is still limited for commercialization. Here, we report the entire process of BCNF production and battery manufacture. We systematically constructed a strain with the highest yield (31.5%) by increasing metabolic flux and improved safety by introducing a Lewis base to overcome thermochemical degradation in the battery. This report will open ways of exploiting the BCNF as a "single-layer" separator, a good alternative to the existing chemical-derived one, and thus can greatly contribute to solving the environmental and safety issues.

To understand the behaviors of phosphoric acids in fuel cells, the ion conduction mechanisms of phosphoric acids in condensed states without free water and in a monomer state with water were studied by measuring the ionic conductivity (sigma) using AC impedance, thermal properties, and self-diffusion coefficients (D) and spin-lattice relaxation times (T1) with multinuclear NMR. The self-diffusion coefficient of the protons (H+ or H3O+), H2O, and H located around the phosphate were always larger than the diffusion coefficients of the phosphates and the disparity increased with increasing phosphate concentration. The diffusion coefficients of the samples containing D2O paralleled those in the protonated samples. Since the 1H NMR T1 values exhibited a minimum with temperature, it was possible to determine the correlation times and they were found to be of nanosecond order for a distance of nanometer order for a flip. The agreement of the ionic conductivities measured directly and those calculated from the diffusion coefficients indicates that the ion conduction obeys the Nernst-Einstein equation in the condensed phosphoric acids. The proton diffusion plays a dominant role in the ion conduction, especially in the condensed phosphoric acids.

A thin carbon black (CB) layer on a metal current collector is used as a substrate of a deposition‐type Li metal anode for a sulfide‐based all‐solid‐state battery (ASSB). In this ASSB, the capacity of the CB layer is set to ≈5–10% of the cathode. Therefore, the anode soon overcharges and a large proportion of the Li ions precipitate as Li metal on the anode during the charging process, thus this precipitated Li works as a Li metal anode. This CB‐based anode effectively suppresses short circuit of the cell, and an ASSB with this anode has shown an excellent cycle property of over 150 cycles with good capacity retention. From measurements involving cross‐sectional scanning electron microscopy, deposited Li metal layer at the CB/Ni interface is observed. It is also found that the addition of metal particles in the CB‐based anode drastically improves cell performance by extending the cycle life. An ASSB with an Ag/CB‐based anode is operated over 700 cycles at 3 mA cm −2 current density (0.5 C) with a capacity retention of ≈86% after 700 cycles.

Sulfur-based polymeric materials were obtained from surplus feedstock; elemental sulfur; and sustainable algae oil, Botryococcene, via inverse vulcanization. Reactions of elemental sulfur and Botryococcene at 185 °C produce polymeric materials with various weight ratios of sulfur and Botryococcene (5:5 to 9:1), depending on the feed ratio. In this study, these polymers have been characterized from several aspects using spectral analysis, thermoanalysis, and electrochemical analysis. When the composition of sulfur is more than 70 wt %, the polymer contains a residual sulfur element not incorporated in the polymer chains. The sulfur-based polymers can be pressed into intended shapes when heated at 120 °C. The polymers could serve as active materials for Li–S batteries. This investigation of structure and properties provides basic information for future applications.

A series of quaternary nitride solid solutions with a general formula of Sr1−xCaxYSi4N7:Eu2+ (1 atom%) were synthesized by the carbothermal reduction and nitridation (CRN) method. The XRD patterns confirm the formation of a solid solution of Sr1−xCaxYSi4N7:Eu2+ (0 ≤ x ≤ 0.5). With an increase in x, the emission spectra shift from 540 nm to 564 nm under n-UV excitation. In addition, the temperature dependence of the PL intensity was investigated. The thermal stability is comparable to that of the commercial (Ba,Sr)2SiO4:Eu2+ phosphor. All the results indicate that the solid solution Sr1−xCaxYSi4N7:Eu2+ can be a good candidate of phosphor applicable to n-UV LEDs for solid-state lighting.

Block-based image or video coding standards (e.g. JPEG) compress an image lossily by quantizing transform coefficients of non-overlapping pixel blocks. If the chosen quantization parameters (QP) are large, then hard decoding of a compressed image—using indexed quantization bin centers as reconstructed transform coefficients—can lead to unpleasant blocking artifacts. Leveraging on recent advances in graph signal processing (GSP), we propose a dequantization scheme specifically for piecewise smooth (PWS) images: images with sharp object boundaries and smooth interior surfaces. We first mathematically define a PWS image as a low-frequency signal with respect to an inter-pixel similarity graph with edges of weights 1 or 0. Using quantization bin boundaries as constraints, we then jointly optimize the desired graph-signal and the similarity graph in a unified framework. A generalization to consider generalized piecewise smooth (GPWS) images—where sharp object boundaries are replaced by transition regions—is also proposed. Experimental results show that our proposed scheme outperforms a state-of-the-art dequantization method by 1 dB on average in PSNR.

Sulfide based solid electrolytes are of considerable practical interest for all solid-state batteries due to their high ionic conductivity and softness at room temperature. In particular, iodine containing lithium thiophosphate is known to exhibit high ionic conductivity but its applicability in solid-state battery remains to be examined. To demonstrate the possibility of the iodine doped solid electrolyte (SE), LiI-Li3PS4 was used to construct two different types of test cells were prepared, Li/SE/S and Li/SE/LiNi0.80Co0.15Al0.05 cells. The solid electrolyte, LiI-Li3PS4 showed a high ionic conductivity approximately 1.2 mScm-1 at 25 ℃. Within 100 cycles, the capacity retention was better in Li/SE/S cell, and the red-ox shuttle was not observed due to physical blockage of SE layer. The capacity fade was approximately 4% from the maximum capacity observed at 10th cycle, after 100 cycles in Li/SE/S cell. On the contrary, the capacity fade was much larger in Li/SE/LiNi0.80Co0.15Al0.05 cell, probably due to the decomposition of the electrolyte at the operating potential range. Nevertheless, both the Li/SE/LiNi0.80Co0.15Al0.05 and Li/SE/S cells exhibited the high coulombic efficiencies above 99.6% and 99.9% during charge-discharge cycle test, respectively. This fact indicates that a high energy density can be possible without an excess lithium metal anode. In addition, it was particularly interesting that the SE showed a reversible capacity about 260 mAhg-1-SE. This electrolyte may have not only as a role of the ion conduction, but also as a catholite.

The morphology of gold nanoparticles was controlled with hydrogentetrachloroaurate (HAuCl4) and polyvinylpyrrolidon (PVP) through a polyol process using ethyleneglycol as solvent and reducing agent. The polyol process gave various particle morphologies: trihedron, tetrahedron, hexahedron, and sphere in the size range of 100−1000 nm. The polyhedral nanoplate fraction (PNF) was increased by injection of HAuCl4 and PVP to preheated ethyleneglycol. The synthesis method, so-called rapid heating process, provided a suitable crystal growth condition for formation of nanoplates because of rapid reduction of HAuCl4 to form gold nuclei and their oriented crystal growth under the affection of PVP at high temperature. The rapid heating process was found to straightforwardly obtain polyhedral gold nanoplates with an extremely small fraction of spherical particles. Particularly, trihedral gold nanoplates were obtained selectively in a short reaction time.

An inverted-FL antenna is proposal with a self-complementary structure. This unique design is realized by integrating an inverted-F antenna with a self-complementary structure and an inverted-L element. The proposed antenna with a volume of 10 times 10 times 45 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> achieves a constant impedance of 188 Omega without attaching a matching load required since a self-complementary antenna of an axially symmetric type has constant impedance. This antenna acquired broadband and multiband characteristics covering the GSM850/GSM900/DCS/ PCS/UMTS2100/UMTS2600 bands and the 2.5G/3.5G bands for Mobile-WiMAX by simulation and measurement.