Co-synthesis and Electrochemical Investigation of the Nitrogen-Doped Carbon Layer with Metallic Nano Beads on the SiOx Anode for Lithium Secondary Batteries

The high theoretical capacity (∼2000 mAh g-1) of silicon suboxide (SiOx, with 1 < x < 2) can solve the energy density issue of the graphite anode in Li-ion batteries. In addition, it has an advantage in terms of volume expansion or side reactions compared to pure Si or Li metals, which are considered as next-generation anode materials. However, the loading content of SiOx is limited in commercial anodes because of its low cycle stability and initial coulombic efficiency. In this study, a nitrogen-doped carbon layer with Cu beads (N-C/Cu) derived from copper phthalocyanine (CuPc) is applied to a SiOx electrode to improve its electrochemical performance. The SiOx electrode is simultaneously coated with a Cu- and N-doped carbon layer using CuPc. N-C/Cu synergistically enhances the electric conductivity of the electrode, thus improving its electrochemical performance. The SiOx/N-C/Cu composite has better cyclability and higher capacity (1095.5 mAh g-1) than the uncoated electrode, even after 200 cycles in the 0.5 C condition. In full-cell cycling with NCM811 cathodes, the SiOx (60 wt % of SiOx, with a n/p ratio of 1.1) and graphite-mixed (7.8 wt % of SiOx, with a n/p ratio of 1.1) anodes also show improved electrochemical performances in the same conditions.

Aqueous Quaternary Polymer Binder Enabling Long-Life Lithium-Sulfur Batteries by Multifunctional Physicochemical Properties

Lithium-sulfur batteries (LSBs) have been considered promising candidates for application in high-density energy storage systems owing to their high gravimetric and volumetric energy densities. However, LSB technology faces many barriers from the intrinsic properties of active materials that need to be solved to realize high-performance LSBs. Herein, an aqueous binder, that is, PPCP, based on polyethyleneimine (PEI), polyvinylpyrrolidone (PVP), citric acid (CA), and polyethylene oxide (PEO), was developed. The synthesized PPCP binder has incredible mechanical properties, suitable viscosity, and essential functional groups for developing an effective and reliable LSB system. This study demonstrates that CA is crucial in cross-linking PEI-PVP polymer molecules, and PEO segments significantly enhance the flexibility of the PPCP binder; thus, the binder can mechanically stabilize the cathode structure over many operating cycles. The redistribution of active materials during the charge-discharge processes and reduction of the shuttle effect originate from the excellent chemical interactions of PPCP with lithium polysulfides, which is confirmed by the density functional theory calculation, enabling an ultra-long electrochemical cycle life of 1800 cycles with a low decay rate of 0.0278% cycle^-1.

Enabling reversible redox reactions in electrochemical cells using protected LiAl intermetallics as lithium metal anodes

Rechargeable electrochemical cells with metallic anodes are of increasing scientific and technological interest. The complex composition, poorly defined morphology, heterogeneous chemistry, and unpredictable mechanics of interphases formed spontaneously on the anodes are often examined but rarely controlled. Here, we couple computational studies with experimental analysis of well-defined LiAl electrodes in realistic electrochemical environments to design anodes and interphases of known composition. We compare phase behavior, Li binding energies, and activation energy barriers for adatom transport and study their effects on the electrochemical reversibility of battery cells. As an illustration of potential practical benefits of our findings, we create cells in which LiAl anodes protected by Langmuir-Blodgett MoS2 interphases are paired with 4.1 mAh cm-2 LiNi0.8Co0.1Mn0.1O2 cathodes. These studies reveal that small- and larger-format (196 mAh, 294 Wh kg-1, and 513 Wh liter-1) cells based on protected LiAl anodes exhibit high reversibility and support stable Li migration during recharge of the cells.

Carbon Nitride Phosphorus as an Effective Lithium Polysulfide Adsorbent for Lithium-Sulfur Batteries

Lithium-sulfur (Li-S) batteries are attracting substantial attention because of their high-energy densities and potential applications in portable electronics. However, an intrinsic property of Li-S systems, that is, the solubility of lithium polysulfides (LiPSs), hinders the commercialization of Li-S batteries. Herein, a new material, that is, carbon nitride phosphorus (CNP), is designed and synthesized as a superior LiPS adsorbent to overcome the issues of Li-S batteries. Both the experimental results and the density functional theory (DFT) calculations confirm that CNP possesses the highest binding energy with LiPS at a P concentration of ∼22% (CNP22). The DFT calculations explain the simultaneous existence of Li-N bonding and P-S coordination in the sulfur cathode when CNP22 interacts with LiPS. By introducing CNP22 into the Li-S systems, a sufficient charging capacity at a low cutoff voltage, that is, 2.45 V, is effectively implemented, to minimize the side reactions, and therefore, to prolong the cycling life of Li-S systems. After 700 cycles, a Li-S cell with CNP22 gives a high discharge capacity of 850 mA h g^-1 and a cycling stability with a decay rate of 0.041% cycle^-1. The incorporation of CNP22 can achieve high performance in Li-S batteries without concerns regarding the LiPS shuttling phenomenon.

Two-Dimensional WS2@Nitrogen-Doped Graphite for High-Performance Lithium Ion Batteries: Experiments and Molecular Dynamics Simulations

As promising candidates for anode materials in lithium ion batteries (LIB), two-dimensional tungsten disulfide (WS₂) and WS₂@(N-doped) graphite composites were synthesized, and their electrochemical properties were comprehensibly studied in conjunction with calculations. The WS₂ nanosheets, WS₂@graphite, and WS₂@N-doped graphite (N-graphite) exhibit outstanding cycling performance with capacities of 633, 780, and 963 mA h g^-1, respectively. To understand their lithium storage mechanism, first-principles calculations involving a series of ab initio NVT- NPT molecular dynamics simulations were conducted. The calculated discharge curves for amorphous phase are well matched with the experimental ones, and the capacities reach 620, 743, and 915 mA h g^-1 for WS₂, WS₂@graphite, and WS₂@N-graphite, respectively. The large capacities of the two composites can be attributed to the tendency of W and Li atoms to interact with graphite, suppressing the formation of W metal clusters. In the case of WS₂@N-graphite, vigorous amorphization of the N-graphite enhances the interaction of W and Li atoms with the fragmented N-graphite in such a way that unfavorable Li-W repulsion is avoided at very early stage of lithiation. As a result, the volume expansion in WS₂@graphite and WS₂@N-graphite is calculated to be remarkably small (only 6 and 44%, respectively, versus 150% for WS₂). Therefore WS₂@(N-)graphite composites are expected to be almost free of mechanical pulverization after repeated cycles, which makes them promising and excellent candidates for high-performance LIBs.

Arsenic for high-capacity lithium- and sodium-ion batteries

We report arsenic (As) as a promising alternative to graphite anode materials in lithium- and sodium-ion batteries (LIBs and SIBs). The electrochemical properties of the As/carbon nanocomposite for both LIBs and SIBs were investigated using experimental and theoretical approaches. The LIBs showed excellent cycling performance, with a reversible capacity of 1306 mA h g-1 (after 100 cycles), which is much higher than that of Li3As (1072 mA h g-1). In the corresponding SIBs, the measured reversible capacity was 750 mA h g-1 (after 200 cycles), which is lower than that of Na3As. Extensive first-principles calculations were performed employing a structure prediction method for crystalline LixAs and NaxAs (x = 1-6) phases, as well as ab initio molecular dynamics simulations for their amorphous phases. In good agreement with the experimental LIB data, our calculations successfully predict the discharge capacity versus voltage curves, showing that the capacity of the amorphous phase reaches up to that of Li4As. In contrast, the SIB exhibited difficulty in reaching the predicted capacity (x = 3.5), probably due to significant volume expansion. Comparison of the theoretical discharge curves with the experimental data provides valuable information for the development of high-performance LIBs and SIBs.

Synthesis of graphitic ordered mesoporous carbon with cubic symmetry and its application in lithium-sulfur batteries

The lithium-sulfur (Li-S) battery faces a couple of major problems in practical applications, including the low conductivity of sulfur and the dissolution of polysulfides. A cathode constructed using a composite of sulfur and ordered mesoporous carbon (OMC) is a promising solution to both problems, as OMCs can have high conductivity and a complex pore structure to trap polysulfides. In this work, we demonstrate that performance of the Li-S battery can be significantly enhanced by using an OMC with a high degree of graphitization and a pore network with cubic symmetry. This graphitic OMC (GOMC) can be produced in a single step using iron phthalocyanine precursor and a silica template with cubic Ia3d symmetry. The GOMC-sulfur (GOMC/S) composite is 175% higher in electrical conductivity compared to the typical OMC-sulfur (OMC/S) composite. In addition, the three-dimensional pore network in GOMC prevents the migration of dissolved polysulfides. These characteristics of GOMC contribute to the improved rate capability and cyclability of the corresponding Li-S battery.

Enhanced electrochemical performance of a ZnO–MnO composite as an anode material for lithium ion batteries

A reduced ZnO–MnO composite electrode exhibits improved electrochemical performance as an anode material for lithium ion batteries.

Composition-tuned SnxGe1−xS nanocrystals for enhanced-performance lithium ion batteries

Complete composition-tuned Sn_xGe_1−xS alloy nanocrystals exhibit excellent cycling performances in lithium ion batteries, with the greatest rate capability for Sn-rich compositions.

Tetragonal phase germanium nanocrystals in lithium ion batteries

Various germanium-based nanostructures have recently demonstrated outstanding lithium ion storage ability and are being considered as the most promising candidates to substitute current carbonaceous anodes of lithium ion batteries. However, there is limited understanding of their structure and phase evolution during discharge/charge cycles. Furthermore, the theoretical model of lithium insertion still remains a challenging issue. Herein, we performed comparative studies on the cycle-dependent lithiation/delithiation processes of germanium (Ge), germanium sulfide (GeS), and germanium oxide (GeO2) nanocrystals (NCs). We synthesized the NCs using a convenient gas phase laser photolysis reaction and attained an excellent reversible capacity: 1100-1220 mAh/g after 100 cycles. Remarkably, metastable tetragonal (ST12) phase Ge NCs were constantly produced upon lithiation and became the dominant phase after a few cycles, completely replacing the original phase. The crystalline ST12 phase persisted through 100 cycles. First-principles calculations on polymorphic lithium-intercalated structures proposed that the ST12 phase Ge12Lix structures at x ≥ 4 become more thermodynamically stable than the cubic phase Ge8Lix structures with the same stoichiometry. The production and persistence of the ST12 phase can be attributed to a stronger binding interaction of the lithium atoms compared to the cubic phase, which enhanced the cycling performance.

Sulfur/graphitic hollow carbon sphere nano-composite as a cathode material for high-power lithium-sulfur battery

The intrinsic low conductivity of sulfur which leads to a low performance at a high current rate is one of the most limiting factors for the commercialization of lithium-sulfur battery. Here, we present an easy and convenient method to synthesize a mono-dispersed hollow carbon sphere with a thin graphitic wall which can be utilized as a support with a good electrical conductivity for the preparation of sulfur/carbon nano-composite cathode. The hollow carbon sphere was prepared from the pyrolysis of the homogenous mixture of the mono-dispersed spherical silica and Fe-phthalocyanine powder in elevated temperature. The composite cathode was manufactured by infiltrating sulfur melt into the inner side of the graphitic wall. The electrochemical cycling shows a capacity of 425 mAh g-1 at 3 C current rate which is more than five times larger than that for the sulfur/carbon black nano-composite prepared by simple ball milling.

Assessment of nurses' nutritional knowledge regarding therapeutic diet regimens

Metabolic diseases and cardiovascular disease (CVD), the incidence of which is currently increasing in Korea, can be managed well with dietary education and modification. However, it has yet to be established whether nurses have sufficient knowledge to impart appropriate nutritional counseling to patients with these diseases. Our study involved 506 nurses working at Asan Medical Center, Samsung Medical Center, and Seoul National University Hospital between March and May, 2006. The questionnaire was comprised of 42 diet-related questions pertaining to diabetes, obesity, and CVD. Nurses' correct-response rate for overall nutritional knowledge was worse than reported in Western countries (58.4%), and particularly so with regard to obesity and CVD. Although many nurses were aware of the therapeutic aspects of nutrients in relation to CVD, most of them had limited knowledge about low-cholesterol diets and sources of water-soluble fiber, fatty acids and the specific food items that prevent CVD. Our results suggest that there is an urgent need to update the contents of nutrition education for nurses to reflect the current changes in the Korean diet and the increasing incidence of metabolic diseases and CVD.

Li electroactivity of iron (II) tungstate nanorods

We herein report the first application of a divalent iron tungstate (FeWO(4)) nanostructured material, with a wolframite structure, to a Li-ion battery anode. The FeWO(4) nanospheres and nanorods were synthesized at 180 °C without any surfactants or templates via a facile hydrothermal process by simply adjusting the pH. The resulting nanopowders were characterized using x-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM), and Brunauer-Emmett-Teller (BET) measurements. Furthermore, we evaluated the Li electroactivity of the FeWO(4) nanorods using cyclic voltammetry and observed that their reversible capacity was over 500 mAh g(-1) after 20 cycles, which proved much higher than that of graphite-based anodes.

Enhanced cycling performance of an Fe0/Fe3O4 nanocomposite electrode for lithium-ion batteries

We demonstrate the formation of a highly conductive, Fe0/Fe3O4 nanocomposite electrode by the hydrogen reduction process. Fe2O3 nanobundles composed of one-dimensional nanowires were initially prepared through thermal dehydrogenation of hydrothermally synthesized FeOOH. The systematic phase and morphological evolutions from Fe2O3 to Fe2O3/Fe3O4, Fe3O4, and finally to Fe/Fe3O4 by the controlled thermochemical reduction at 300 degrees C in H2 were characterized using x-ray diffraction (XRD) and transmission electron microscopy (TEM). The Fe/Fe3O4 nanocomposite electrode shows excellent capacity retention ( approximately 540 mA h g(-1) after 100 cycles at a rate of 185 mA g(-1)), compared to that of Fe2O3 nanobundles. This enhanced electrochemical performance in Fe/Fe3O4 composites was attributed to the formation of unique, core-shell nanostructures offering an efficient electron transport path to the current collector.

Effect of pregnancy on food consumption and consciousness factors associated with food satisfaction

To examine the effect of pregnancy on food consumption, we surveyed the recall of past experience of two groups of women, those who had been pregnant (PY, n=188) and those who never had (PN, n=111), regarding their food consumption and related dietary behaviors. The questionnaire, answered with regard to potato chips, contained 135 objective components expressing sensorial stimuli and 103 subjective consciousness components, including knowledge, education, faith, memory, experience, lifestyle, family values, imagination, and mental state. In the PY group, 86% of the women change in food consumption and preference during pregnancy, and 60% experienced decreased food consumption during emesis gravidarum (EG). The change in food consumption during and after periods of EG was influenced by the number of previous births for the women in the PY group; in women pregnant for a second or third time, the change in food intake was less than during the previous pregnancy. The difference in food satisfaction with regard to potato chips between the PY and PN groups showed that overall food satisfaction could not be explained by a combination of objective sensorial components; the only objective components that were directly related to overall satisfaction were taste and texture. Multidimensional analysis with strength of sensorial stimulus, preference, and overall satisfaction revealed differences in patterns between the PN and PY groups. The effect of the consciousness components on food preference and satisfaction was comparable to that of the sensorial components.

Glucosylceramide: a marker for multiple-drug resistant cancers

BACKGROUND

Multiple-drug resistance (MDR) is a major reason for chemotherapy failure. Herein we describe glucosylceramide, a new marker for MDR.

METHODS

Cellular lipids were analyzed in three human MDR cancer cell lines and their drug-sensitive counterparts. Analysis of glucosylceramide was also performed in six melanoma specimens and one breast tumor specimen obtained from patients who had undergone chemotherapy. Glucosylceramide, analyzed by mass and by cellular utilization of radiolabeled precursor ([3Hpalmitic acid), was isolated by lipid extraction techniques and resolved from other components by thin-layer chromatography.

RESULTS

Glucosylceramide was present consistently in all MDR cell lines and was absent, or present only at very low levels, in the corresponding drug-sensitive cells. Examination of human tumor specimens documented presence of the marker in all patients who had failed chemotherapy, and absence of the marker in each of the patients with known clinical response to chemotherapy. The response to chemotherapy was followed for a median of 8 months in melanoma patients and for 22 months in the breast cancer patient.

CONCLUSION

These findings suggest that glucosylceramide may hold clinical significance for the early identification of drug-resistant tumors.