A surface coating of SiO2 is applied to a Ni rich LiNi0.6Co0.2Mn0.2O2 cathode material in a bid to improve its electrochemical and thermal properties. A uniform coating is achieved through a wet ...process using nano-sized SiO2 powder, and though the coated electrode is found to exhibit a reduced rate capability, its cycle performance at a high temperature of 60 °C is greatly enhanced. The effect of this SiO2 coating is further investigated by electrochemical impedance spectroscopy, which confirms that it suppresses the growth of interfacial impedance during progressive cycles. The SiO2 coating also demonstrates good HF scavenging ability, producing a subsequent reduction in the degradation of the active core material. The thermal properties of LiNi0.6Co0.2Mn0.2O2 are also improved by the SiO2 coating due to a reduction in the direct contact between the electrode and electrolyte. On the basis of these results, SiO2 coating is considered a viable surface modification method for improving the electrochemical and thermal properties of LiNi0.6Co0.2Mn0.2O2.
•Nano-sized SiO2 was uniformly coated on the surface of LiNi0.6Co0.2Mn0.2O2 cathode.•Thermal stability and cycle performance are improved by SiO2 coating.•EIS results suggest that side reaction on interface is suppressed by SiO2 coating.•SiO2 coating shows significant HF scavenging effect.
High‐index dielectric nanostructures offer strong magnetic and electric resonances in the visible range and low optical losses, stimulating research interest in their use for light manipulation ...technologies. Lithographic fabrication of dielectric nanostructures, while providing precise control over the pattern dimensions, limits the scalability of this approach for practical applications due to an inefficient fabrication process and limited production quantity. Here, the colloidal synthesis of high‐index chiral dielectric nanostructures with a broom‐like geometry made from trigonal Se is demonstrated. The anisotropic morphology and crystal structure of Se nanobrooms enable both linearly and circularly polarized scattering, as well as spectrum variation along the particle axis, which is, to the authors’ knowledge, the first observation of such behavior from dielectric colloidal nanostructures. To show the versatility of the highly scattering Se NB suspensions, 2D and 3D printing of Se NB inks are demonstrated as a proof of concept. This approach provides a way to manipulate light using aqueous dispersions of high‐index dielectric nanostructures, unlocking their potential to fit in various morphologies and dimensions in 2D and 3D for broad applications.
This study shows the colloidal synthesis of high‐index chiral dielectric nanostructures with a broom‐like geometry made from trigonal Se. The anisotropic morphology and crystal structure of Se nanobrooms enable both linearly and circularly polarized scattering, as well as color spectrum variation along the broom axis. The versatility of Se nanostructure suspension is demonstrated as 2D and 3D printing inks as proof of concept.
Despite extensive research on flexible/wearable power sources, their structural stability and electrochemical reliability upon mechanical deformation and charge/discharge cycling have not yet been ...completely achieved. A new class of galvanically replaced single‐bodied lithium‐ion battery (LIB) fabric electrodes is demonstrated. As a proof of concept, metallic tin (Sn) is chosen as an electrode active material. Mechanically compliable polyethyleneterephthalate (PET) fabrics are conformally coated with thin metallic nickel (Ni) layers via electroless plating to develop flexible current collectors. Driven by the electrochemical potential difference between Ni and Sn, the thin Ni layers are galvanically replaced with Sn, resulting in the fabrication of a single‐bodied Sn@Ni fabric electrode (Sn is monolithically embedded in the Ni matrix on the PET fabric). Benefiting from the chemical/structural uniqueness and rationally designed bicontinuous ion/electron transport pathways, the single‐bodied Sn@Ni fabric electrode provides exceptional redox reaction kinetics and omnidirectional deformability (notably, origami‐folding boats), which lie far beyond those attainable with conventional LIB electrode technologies.
A galvanically replaced single‐bodied Sn@Ni fabric electrode is presented as a new approach for developing high‐performance lithium‐ion battery (LIB) electrodes with exceptional redox reaction kinetics and omnidirectional deformability. Benefiting from the chemical/structural uniqueness, the single‐bodied Sn@Ni fabric electrode provides significant improvements in electrochemical performance and mechanical flexibility, which lie far beyond those attainable with conventional LIB electrode technologies.
Understanding the atomic structure variation at the surface of electrode materials in contact with an electrolyte is an essential step toward achieving better electrochemical performance of ...rechargeable cells. Different types of water‐based aqueous solutions are suggested as alternative electrolytes to the currently used flammable organic solvents in Li‐ion batteries. However, most research on aqueous rechargeable Li‐ion cells has largely focused on the synthetic processing of materials and resulting electrochemical properties rather than in‐depth atomic‐level observation on the electrode surface where the initial charge transfer and the (de)intercalation reaction take place. By using LiFePO4 and LiCoO2 single crystals, serious P and Co dissolution from LiFePO4 and LiCoO2 into aqueous solutions without any electrochemical cycling is identified. Furthermore, both strong temperature‐dependent behavior of P dissolution in LiFePO4 and very unusual occupancy of Co in the tetrahedral interstices in LiCoO2 are directly demonstrated via atomic‐scale (scanning) transmission electron microscopy. Ab initio density functional theory calculations also reveal that this tetrahedral‐site occupation is stabilized when cation vacancies are simultaneously present in both Li and Co sites. The findings in this work emphasize the significance of direct observation on the atomic structure variation and local stability of the cathode materials.
Substantial P and Co dissolution from LiFePO4 and LiCoO2 crystals into aqueous electrolytes without any electrochemical cycling is identified. Furthermore, atomic‐scale scanning transmission electron microscopy analysis shows unusual Co occupancy in the tetrahedral interstices in LiCoO2. The findings emphasize the significance of direct observation on the atomic structure variation and local stability of the cathode materials.
Since the recognition of a significant oxygen‐redox contribution to enhancing the capacity of Li transition‐metal oxide cathodes, the oxygen release and subsequent structural variations together with ...capacity fading are critical issues to achieve better electrochemical performance. As most previous reports dealt with the structural degradation of cathodes after electrochemical cycling, it is fairly difficult to clarify how substantial the effect of lattice strain on the oxygen release will be while exclusively ruling out any electrochemical influences. By utilizing nanoindentation and mechanical surface polishing of single‐crystal LiCoO2 and Li2MnO3, the local variations of both the atomic structure and oxygen content are scrutinized. Atomic‐column‐resolved imaging reveals that local LiM (M = Co and Mn) disordering and further amorphization are induced by mechanical strain. Moreover, substantial oxygen deficiency in the regions with these structural changes is directly identified by spectroscopic analyses. Ab initio density functional theory calculations also demonstrate energetically favorable formation of oxygen vacancies under shear strain. Providing direct evidence of oxygen release as a consequence of lattice strain, the findings in this work suggest that efficient strain relaxation will be of great significance for longevity of the anion framework in layered oxide cathodes.
Atomic‐scale observation directly shows that a significant amount of oxygen loss is induced exclusively by lattice strain in pristine layered oxides without any electrochemical Li extraction under high voltage application. This work offers crucial insight toward the importance of strain relaxation to suppress oxygen loss for better cycling performance of layered oxide cathodes.
A layer-by-layer deposition of two conducting polymers, each layer of which is a few tenths of nanometer thick, has been successfully performed to enhance the thermoelectric power factor of organic ...thin films, which are critical components of flexible thermoelectric energy harvesting devices. The multilayer films were deposited via multiple solution processes, which exhibit enhanced electrical conductivity without any significant degradation of the Seebeck coefficient, in contrast to a coupling behavior between the electrical conductivity and the Seebeck coefficient in bulk materials. The electrical conductivity and power factor-proportional to the electrical conductivity-of 5(PEDOT:PSS/PANI-CSA) multilayer films are 1.3 and 2 times higher than those of a single PEDOT:PSS layer. Transmission electron microscopy (TEM) and electron energy loss spectroscopy (EELS) reveal distinct interfaces through which an enhanced electrical conductivity and power factor have been achieved in our multilayer films. From the TEM, EELS, and Raman analyses, a model for the enhancement of the electrical conductivity has been proposed. The enhancement of electrical conductivity occurs via stretching of PEDOT and PANI chains and hole diffusion from the PANI-CSA layer to the PEDOT:PSS layer. The band alignment in the multilayer structure not only enhances electrical conductivity but also maintains the Seebeck coefficient at an optimum value. Our study suggests that the layer-by-layer deposition of polymer thin films is a promising technique for manipulating the thermoelectric properties of each polymer component to enhance thermoelectric performance.
Objective
Exposure to ultraviolet (UV) radiation from sunlight induces the production of essential vitamin D, whereas overexposure to sunlight leads to skin cancer. Sunlight exposure has been ...measured using questionnaires, dosimeters, and vitamin D levels. Several studies have measured vitamin D in the working population; however, these studies were limited to certain occupations such as farmers and construction workers. In the present study, we evaluated sunlight exposure using blood vitamin D as an exposure surrogate across industries and occupations.
Methods
The Korea National Health and Nutrition Examination Survey (KNHANES) is a nationwide study representing the Korean population. We analyzed data from KNHANES between 2008 and 2009. We examined the association between vitamin D levels and pertinent personal, seasonal, residential, and occupational factors. Furthermore, we developed a multiple regression model with factors other than occupational factors (industry and occupation) and obtained residual values. We computed the third quartile (Q3) of the residuals and then calculated the fractions exceeding the Q3 level for each combination of industry and occupation.
Results
Age, sex, body mass index, year, season, latitude, living area, living in an apartment, industry, and occupation were significantly associated with vitamin D levels. Based on the exceeding fraction, the armed forces showed the highest exceeding fraction level of 0.71.
Conclusions
Our results present the high exposure groups to sunlight across industries and occupations. Our results may provide a source for prioritizing occupational groups with a high risk of adverse health effects from sunlight exposure.
•S. serratifolium contain a high level of meroterpenoids as antioxidant compounds.•Ethyl acetate, ethanol, and methanol extracts showed high TPC and antioxidant capacity.•SHQA, SCM and SQA are main ...antioxidant components in S. serratifolium.
Sargassum serratifolium has been known to contain a high level of meroterpenoids as antioxidant components. We investigated antioxidant activities and active components in various solvent extracts from S. serratifolium. Ethyl acetate, ethanol, and methanol extracts showed relatively strong DPPH, ABTs, and superoxide radical scavenging activities. Hexane and ethyl acetate extract showed the strongest hydroxyl radical and reactive oxygen species (ROS), respectively, scavenging activities. Sargahydroquinoic acid (SHQA), sargachromanol (SCM) and sargaquinoic acid (SQA) were main antioxidant components in S. serratifolium. Ethanol extract showed the highest levels of SHQA, SCM, and SQA which comprised to be 227 ± 6.31 mg/g. SHQA and SCM exhibited stronger antioxidant capacities than SQA based on lower IC50 values in ROS, DPPH, ABTs, and superoxide radical scavenging assays. The result showed that ethanol is the most efficient extracting solvent for the active components from S. serratifolium and the plant has the potential as a natural antioxidant.
With the prevalence of connected TV, streaming is replacing linear TV while expanding its functionality. To structurally explain this replacement based on functional similarity, we applied two-way ...fixed-effects regression to log data from 197,273 smart TVs in Japan from July 2019 to June 2022. Results showed that professional videos on demand primarily substituted linear TV's recorded viewing, dramas, and movies, whereas substitution by YouTube was broader. Catch-up streaming substituted recorded viewing while complementing viewing without recording. These multiple relationships support the applicability of media substitution theory and foreshadow that functional expansion of streaming would further contribute to linear TV's replacement.
Porous carbon is considered an attractive host material for high‐energy sulfur electrodes. This study concerns the design of a porous carbon‐based sulfur electrode for the formulation of high‐energy ...Li−S batteries. The porous carbon is impregnated with up to 80 vol.% of sulfur and a reduction in both the conductive agent and binder content. Therefore, less solvent can be used during slurry casting to inhibit crack formation following electrode drying. In addition, the utilization of two distinct electrically conducting networks enables reduced battery polarization, resulting in a battery with a capacity of 690 mAh g−1 (even after 100 cycles). Finally, pouch cells are prepared to characterize the practical performance of the optimized cathode. This yields a capacity of 741 mAh and a cathode energy density of 1001 Wh kg−1. These findings are expected to guide the further development of high‐energy‐density cathode materials for Li−S batteries.
Get in the C: A micro‐scale active material is prepared by infiltrating sulfur into porous carbon material, and by combining carbon nanotubes and carbon black to increase sulfur content. The active material is incorporated into a lithium−sulfur battery with high‐energy and enhanced electron conductivity.
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