Two-in-one strategy for optimizing chemical and structural properties of carbon felt electrodes for vanadium redox flow batteries.

Vanadium redox flow batteries (VRFBs) have received significant attention for use in large-scale energy storage systems (ESSs) because of their long cycle life, flexible capacity, power design, and safety. However, the poor electrochemical activity of the conventionally used carbon felt electrode results in low energy efficiency of the VRFBs and consequently impedes their commercialization. In this study, a carbon felt (CF) electrode with numerous nanopores and robust oxygen-containing functional groups at its edge sites is designed to improve the electrochemical activity of a carbon felt electrode. To achieve this, Ni metal nanoparticles were initially precipitated on the surface of the CF electrode, followed by etching of the precipitated Ni nanoparticles on the CF electrode using sulfuric acid. The resulting CF electrode had a specific surface area eight times larger than that of the pristine CF electrode. In addition, the oxygen-containing functional groups anchored at the graphite edge sites of the nanopores can act as robust electrocatalysts for VO2+/VO2+ and V2+/V3+ redox reactions. Consequently, the VRFB cell with the resulting carbon felt electrode can deliver a high energy efficiency of 86.2% at the current density of 60 mA cm-2, which is 20% higher than that of the VRFB cell with the conventionally heat-treated CF electrode. Furthermore, the VRFB cell with the resultant carbon felt electrodes showed stable cycling performance with no considerable energy efficiency loss over 200 charge-discharge cycles. In addition, even at a high current density of 160 mA cm-2 , the developed carbon felt electrode can achieve an energy efficiency of 70.1%.

This work reveals the importance of the robust graphite edge-site oxygen functional group and the holey structure of the ET-CF electrode, emphasizing that high VRFB efficiency can be achieved by engineering both the structure and surface properties of the carbon felt electrode.

Flattening of Lithium Plating in Carbonate Electrolytes Enabled by All-In-One Separator.

The uncontrollable dendritic growth of metallic lithium during repeated cycling in carbonate electrolytes is a crucial obstacle hindering the practical use of Li-metal batteries (LMBs). Among numerous approaches proposed to mitigate the intrinsic constraints of Li metal, the design of a functional separator is an attractive approach to effectively suppress the growth of Li dendrites because direct contact with both the Li metal surface and the electrolyte is maintained. Here, a newly designed all-in-one separator containing bifunctional CaCO3 nanoparticles (CPP separator) is proposed to achieve the flattening of Li deposits on the Li electrode. Strong interactions between the highly polar CaCO3 nanoparticles and the polar solvent reduces the ionic radius of the Li+ -solvent complex, thus increasing the Li+ transference number and leading to a reduced concentration overpotential in the electrolyte-filled separator. Furthermore, the integration of CaCO3 nanoparticles into the separator induces the spontaneous formation of mechanically-strong and lithiophilic CaLi2 at the Li/separator interface, which effectively decreases the nucleation overpotential toward Li plating. As a result, the Li deposits exhibit dendrite-free planar morphologies, thus enabling excellent cycling performance in LMBs configured with a high-Ni cathode in a carbonate electrolyte under practical operating conditions.

Orange G degradation by heterogeneous peroxymonosulfate activation based on magnetic MnFe2O4/α-MnO2 hybrid.

Wastewater containing an azo dye Orange G (OG) causes massive environmental pollution, thus it is critical to develop a highly effective, environmental-friendly, and reusable catalyst in peroxymonosulfate (PMS) activation for OG degradation. In this work, we successfully applied a magnetic MnFe2O4/α-MnO2 hybrid fabricated by a simple hydrothermal method for OG removal in water. The characteristics of the hybrid were investigated by X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, Brunauer-Emmett-Teller method, vibrating sample magnetometry, electron paramagnetic resonance, thermogravimetric analysis, and X-ray photoelectron spectroscopy. The effects of operational parameters (i.e., catalytic system, catalytic dose, solution pH, and temperature) were investigated. The results exhibited that 96.8% of OG degradation was obtained with MnFe2O4/α-MnO2(1:9)/PMS system in 30 min regardless of solution pH changes. Furthermore, the possible reaction mechanism of the coupling system was proposed, and the degradation intermediates of OG were identified by mass spectroscopy. The radical quenching experiments and EPR tests demonstrated that SO4•̶, O2•̶, and 1O2 were the primary reactive oxygen species responsible for the OG degradation. The hybrid also displayed unusual stability with less than 30% loss in the OG removal after four sequential cycles. Overall, magnetic MnFe2O4/α-MnO2 hybrid could be used as a high potential activator of PMS to remove orange G and maybe other dyes from wastewater.

Issues and Advances in Scaling up Sulfide-Based All-Solid-State Batteries.

ConspectusAll-solid-state batteries (ASSBs) are considered to be a next-generation energy storage concept that offers enhanced safety and potentially high energy density. The identification of solid electrolytes (SEs) with high ionic conductivity was the stepping-stone that enabled the recent surge in activity in this research area. Among the various types of SEs, including those based on oxides, sulfides, polymers, and hybrids thereof, sulfide-based SEs have gained discernible attention owing to their exceptional room temperature ionic conductivity comparable even to those of their liquid electrolyte counterparts. Moreover, the good deformability of sulfide SEs renders them suitable for reducing the interfacial resistance between particles, thereby obviating the need for high-temperature sintering. Nevertheless, sulfide-based ASSB technology still remains at the research stage without any manufacturing schemes having been established. This state of affairs originates from the complex challenges presented by various aspects of these SEs: their weak stability in air, questions surrounding the exact combination of slurry solvent and polymeric binder for solution-based electrode fabrication, their high interfacial resistance resulting from solid particle contacts, and limited scalability with respect to electrode fabrication and cell assembly. In this Account, we review recent developments in which these issues were addressed by starting with the materials and moving on to processing, focusing on new trials. As for enhancing the air stability of sulfide SEs, strengthening the metal-sulfur bond based on the hard-soft acid-base (HSAB) theory has yielded the most notable results, although the resulting sacrificed energy density and weakened anode interface stability would need to be resolved. Novel electrode fabrication techniques that endeavor to overcome the critical issues originating from the use of sulfide SEs are subsequently introduced. The wet chemical coating process can take advantage of the know-how and facilities inherited from the more established lithium-ion batteries (LIBs). However, the dilemmatic matter of contention relating to the polarity mismatch among the slurry solvent, SE, and binder requires attention. Recent solutions to these problems involved the exploration of various emerging concepts, such as polarity switching during electrode fabrication, fine polarity tuning by accurate grafting, and infiltration of the electrode voids by a solution of the SE. The process of using a dry film with a fibrous binder has also raised interest, motivated by lowering the manufacturing cost, maintaining the environment, and boosting the volumetric energy density. Finally, optimization of the cell assembly and operation is reviewed. In particular, the application of external pressure to each unit cell has been universally adopted both in the fabrication step and during cell operation to realize high cell performance. The effect of pressurization is discussed by correlating it with the interface stability and robust interparticle contacts. Based on the significant progress that has been made thus far, we aim to encourage the battery community to engage their wide-ranging expertise toward advancing sulfide-based ASSBs that are practically feasible.

Early Treatment Effects of Nonablative Fractional Lasers (NAFL) on Hypertrophic Scars in an Animal Model.

BACKGROUND AND OBJECTIVES: Recently, there have been several attempts to apply the laser therapy to hypertrophic scars (HTS). In particular, the fractional laser is in the spotlight for its usefulness in rapid wound healing and dermal remodeling. However, most previous studies have focused on the ablative fractional laser (AFL), and there are no studies on the mechanism of the nonablative fractional laser (NAFL) effect in HTS treatment. In this study, we aimed to evaluate the changes in histology and molecular chemistry to provide scientific evidence for the early treatment of HTS with NAFL. STUDY DESIGN/MATERIALS AND METHODS: A total of 40 hypertrophic burn scars were made on the abdomens of two female pigs. After epithelialization, the HTS were randomly subdivided into four groups-control, AFL, NAFL (low energy), and NAFL (high energy). Laser treatment was initiated 1 week after the crust fell and the epithelium became covered, and it was repeated for six sessions over an interval of 2 weeks. Five excisional biopsies were obtained for histologic analysis and biomarker assessment. RESULTS: Histologically, dermal remodeling with thin coil-shaped collagen fibers was observed in the NAFL groups. It also showed a significant increase of matrix metalloproteinase-2 (MMP-2) and Decorin at 16 weeks in an enzyme-linked immunosorbent assay. The reverse-transcription polymerase chain reaction analysis showed a tendency that high-pulse energy of NAFL led to higher messenger RNA expression than did the low-energy group. CONCLUSION: The NAFL-treated groups showed characteristic collagen re-arrangement and a significant increase in MMP-2 and Decorin. These molecular changes suggest that MMP-2 and Decorin play a significant role in dermal remodeling. Early NAFL treatment for HTS could be supported with both histological and molecular evidence. Lasers Surg. Med. © 2020 Wiley Periodicals, Inc.

A Comparison of Aesthetic Outcomes of Umbilicoplasty in Breast Reconstruction with Abdominal Flap: Inverted-U Versus Vertical Oval Incision.

BACKGROUND: The umbilicus is a key aesthetic unit of the abdominal wall. It contributes to the natural curvature of the abdomen and is now considered as one of the most important factors in the overall results and patient satisfaction. In this study, we present an inverted-U incisional technique for umbilicoplasty. This study aims to describe the senior author's approach to umbilicoplasty and compare the aesthetic outcomes of the inverted-U method with those of the vertical oval incisional technique. METHODS: In this retrospective cohort study, we analyzed a total of 109 patients including 51 who underwent umbilicoplasty with the inverted-U incisional technique and 58 who had surgery with the vertical oval incisional method. With the description of our operative technique, the aesthetic outcomes of both techniques were compared by two independent surgeons using a 5-point Likert scale in terms of shape, size, depth, natural appearance and periumbilical scarring. Also, the total scores of the five items were calculated to give a final score for each patient (range, from 5 to 25 points). RESULTS: On all measured parameters, the inverted-U incisional technique produced favorable outcomes compared with the vertical oval incisional technique. Also, the inverted-U incisional technique was given significantly higher total scores than was the vertical oval incisional technique (inverted-U 14.73 ± 2.47 vs. vertical oval 11.26 ± 3.02, p = 0.002). CONCLUSIONS: In this study, an inverted-U incisional technique produced significantly favorable outcomes in terms of shape, size, depth, natural appearance and overall score compared to a vertical oval incision (p < 0.05). We believe that this technique enables surgeons to achieve a better shape, natural retrusive appearance and superior hood. LEVEL OF EVIDENCE III: In this study, an inverted-U incisional technique produced significantly favorable outcomes in terms of shape, size, depth, natural appearance and overall score compared to a vertical oval incision (p < 0.05). We believe that this technique enables surgeons to achieve a better shape, natural retrusive appearance and superior hood.

Reliability of the Patient and Observer Scar Assessment Scale in Evaluating Linear Scars after Thyroidectomy.

OBJECTIVE: To compare the reliability of the Patient and Observer Scar Assessment Scale (POSAS) with the Vancouver Scar Scale (VSS) in evaluating thyroidectomy scars. METHODS: At 6 months after the operation, 112 patients who underwent thyroid surgery via collar neck incision were evaluated by two blinded plastic surgeons and two senior residents using the VSS and the observer component of the POSAS. In addition, the observer-reported VAS score and patient-reported Likert score were evaluated. Internal consistency, interobserver reliability, and correlations between the patient- and observer-reported outcomes were examined. RESULTS: The observer component of POSAS scores demonstrated higher internal consistency and interobserver reliability than the VSS. However, the correlations between the observer-reported VAS score and the patient-reported Likert score (0.450) and between the total sum of patient and observer component scores (0.551) were low to moderate. CONCLUSIONS: The POSAS is more consistent over repeated measurements; accordingly, it may be considered a more objective and reliable scar assessment tool than the VSS. However, a clinician's perspective may not exactly match the patient's perception of the same scar.

Fluorinated Aromatic Diluent for High-Performance Lithium Metal Batteries.

In lithium metal batteries, electrolytes containing a high concentration of salts have demonstrated promising cyclability, but their practicality with respect to the cost of materials is yet to be proved. Here we report a fluorinated aromatic compound, namely 1,2-difluorobenzene, for use as a diluent solvent in the electrolyte to realize the "high-concentration effect". The low energy level of the lowest unoccupied molecular orbital (LUMO), weak binding affinity for lithium ions, and high fluorine-donating power of 1,2-difluorobenzene jointly give rise to the high-concentration effect at a bulk salt concentration near 2 m, while modifying the composition of the solid-electrolyte-interphase (SEI) layer to be rich in lithium fluoride (LiF). The employment of triple salts to prevent corrosion of the aluminum current collector further improves cycling performance. This study offers a design principle for achieving a local high-concentration effect with reasonably low bulk concentrations of salts.

Solution-Processed Metal Coating to Nonwoven Fabrics for Wearable Rechargeable Batteries.

Wearable rechargeable batteries require electrode platforms that can withstand various physical motions, such as bending, folding, and twisting. To this end, conductive textiles and paper have been highlighted, as their porous structures can accommodate the stress built during various physical motions. However, fabrics with plain weaves or knit structures have been mostly adopted without exploration of nonwoven counterparts. Also, the integration of conductive materials, such as carbon or metal nanomaterials, to achieve sufficient conductivity as current collectors is not well-aligned with large-scale processing in terms of cost and quality control. Here, the superiority of nonwoven fabrics is reported in electrochemical performance and bending capability compared to currently dominant woven counterparts, due to smooth morphology near the fiber intersections and the homogeneous distribution of fibers. Moreover, solution-processed electroless deposition of aluminum and nickel-copper composite is adopted for cathodes and anodes, respectively, demonstrating the large-scale feasibility of conductive nonwoven platforms for wearable rechargeable batteries.

Self-Extinguishing Lithium Ion Batteries Based on Internally Embedded Fire-Extinguishing Microcapsules with Temperature-Responsiveness.

User safety is one of the most critical issues for the successful implementation of lithium ion batteries (LIBs) in electric vehicles and their further expansion in large-scale energy storage systems. Herein, we propose a novel approach to realize self-extinguishing capability of LIBs for effective safety improvement by integrating temperature-responsive microcapsules containing a fire-extinguishing agent. The microcapsules are designed to release an extinguisher agent upon increased internal temperature of an LIB, resulting in rapid heat absorption through an in situ endothermic reaction and suppression of further temperature rise and undesirable thermal runaway. In a standard nail penetration test, the temperature rise is reduced by 74% without compromising electrochemical performances. It is anticipated that on the strengths of excellent scalability, simplicity, and cost-effectiveness, this novel strategy can be extensively applied to various high energy-density devices to ensure human safety.

Porous nanoarchitectures of spinel-type transition metal oxides for electrochemical energy storage systems.

Transition metal oxides possessing two kinds of metals (denoted as AxB3-xO4, which is generally defined as a spinel structure; A, B = Co, Ni, Zn, Mn, Fe, etc.), with stoichiometric or even non-stoichiometric compositions, have recently attracted great interest in electrochemical energy storage systems (ESSs). The spinel-type transition metal oxides exhibit outstanding electrochemical activity and stability, and thus, they can play a key role in realising cost-effective and environmentally friendly ESSs. Moreover, porous nanoarchitectures can offer a large number of electrochemically active sites and, at the same time, facilitate transport of charge carriers (electrons and ions) during energy storage reactions. In the design of spinel-type transition metal oxides for energy storage applications, therefore, nanostructural engineering is one of the most essential approaches to achieving high electrochemical performance in ESSs. In this perspective, we introduce spinel-type transition metal oxides with various transition metals and present recent research advances in material design of spinel-type transition metal oxides with tunable architectures (shape, porosity, and size) and compositions on the micro- and nano-scale. Furthermore, their technological applications as electrode materials for next-generation ESSs, including metal-air batteries, lithium-ion batteries, and supercapacitors, are discussed.

Depth profile studies on nickel rich cathode material surfaces after cycling with an electrolyte containing vinylene carbonate at elevated temperature.

Lithium-ion batteries with vinylene carbonate (VC) in the electrolyte exhibit superior electrochemical and thermal behavior at elevated temperature, especially with a high Ni content in the cathode material. When VC is added to the electrolyte, polymeric species are formed on the cathode surface by a ring-opening reaction of ethylene carbonate (EC) in the electrolyte and VC, respectively. Through X-ray photoelectron spectroscopy (XPS) depth profiling, we have confirmed that these polymer layers are porous and complementary to each other. XPS results of C1s and O1s show that the outer surface and the inner layer consist of different components. Based on the XPS depth profiling results, we have suggested a reaction mechanism for the formation of a thermally stable layer on the cathode when vinylene carbonate is added to the electrolyte.

Ceramic composite separators coated with moisturized ZrO(2) nanoparticles for improving the electrochemical performance and thermal stability of lithium ion batteries.

We introduce a ceramic composite separator prepared by coating moisturized ZrO2 nanoparticles with a poly(vinylidene fluoride-co-hexafluoropropylene) (PVdF-12wt%HFP) copolymer on a polyethylene separator. The effect of moisturized ZrO2 nanoparticles on the morphology and the microstructure of the polymeric coating layer is investigated. A large number of micropores formed around the embedded ZrO2 nanoparticles in the coating layer as a result of the phase inversion caused by the adsorbed moisture. The formation of micropores highly affects the ionic conductivity and electrolyte uptake of the ceramic composite separator and, by extension, the rate discharge properties of lithium ion batteries. In particular, thermal stability of the ceramic composite separators coated with the highly moisturized ZrO2 nanoparticles (a moisture content of 16 000 ppm) is dramatically improved without any degradation in electrochemical performance compared to the performance of pristine polyethylene separators.

Fluoride scavengeable Sb2O3-functionalized poly(imide) separators for prolonged cycling of lithium-ion batteries.

Nanosize-controlled antimony oxides (Sb2O3) that can effectively scavenge fluoride species in a cell are incorporated into a PI separator to regulate its porous structure. The incorporation of the Sb2O3 layer onto the PI separator surface prevents the internal short circuit and efficiently removes fluoride species via chemical scavenging reactions, thereby resulting in stable cycling behaviors upon cycling.

Morphological modification of alpha-MnO2 catalyst for use in Li/air batteries.

Single crystal alpha-MnO2 nanowires and nanopowders have been successfully synthesized in order to facilitate a comparison of their catalytic activity for use in Li-air batteries. The importance of the morphological modification of the alpha-MnO2 catalyst for facilitating electrochemical reactions between Li and O2 is addressed. Distinctive catalytic activity of alpha-MnO2 is observed, which is in line with its different morphologies. The catalytic activity significantly affects the reversible capacity of Li-air batteries. A high aspect ratio, large surface area and good dispersibility of alpha-MnO2 in the nanowire form are advantageous providing larger active surfaces for promoting the fundamental reactions in Li-air batteries. We also introduce a robustly designed air-electrode composed of highly porous carbon and nanostructured alpha-MnO2 catalysts, with employs a metal foam current collector to ensure sufficient air-permeability and to maximize electronic conduction during cycles. Our suggestions should prove helpful in forming a basis for further investigations in developing advanced Li-air batteries.

Naked metallic skin for homo-epitaxial deposition in lithium metal batteries.

Regulating the morphology of lithium plating is the key to extending the cycle life of lithium metal batteries. Fatal dendritic growth is closely related to out-of-plane nucleation on the lithium metal surface. Herein, we report a nearly perfect lattice match between the lithium metal foil and lithium deposits by removing the native oxide layer using simple bromine-based acid-base chemistry. The naked lithium surface induces homo-epitaxial lithium plating with columnar morphologies and lower overpotentials. Using the naked lithium foil, the lithium-lithium symmetric cell maintains stable cycling at 10 mA cm-2 for more than 10,000 cycles, and the full-cell paired with LiFePO4 with high areal capacity of 3.3 mAh cm-2 and practical N/P ratio of 2.5 exhibits 86% capacity retention after 300 cycles. This study elucidates the usefulness of controlling the initial surface state to facilitate homo-epitaxial lithium plating for sustainable cycling of lithium metal batteries.

Bi-Morphological Form of SiO2 on a Separator for Modulating Li-Ion Solvation and Self-Scavenging of Li Dendrites in Li Metal Batteries.

The lithium (Li) metal anode is highly desirable for high-energy density batteries. During prolonged Li plating-stripping, however, dendritic Li formation and growth are probabilistically high, allowing physical contact between the two electrodes, which results in a cell short-circuit. Engineering the separator is a promising and facile way to suppress dendritic growth. When a conventional coating approach is applied, it usually sacrifices the bare separator structure and severely increases the thickness, ultimately decreasing the volumetric density. Herein, we introduce dielectric silicon oxide with the feature of bi-morphological form, i.e., backbone-covered and backbone-anchored, onto the conventional polyethylene separator without any volumetric change. These functionally vary the Li+ transference number and the ionic conductivity so as to modulate Li-ion solvation and self-scavenging of Li dendrites. The proposed separator paves the way to maximizing the full cell performance of Li/NCM622 toward practical application.

One-step synthesis of a sulfur-impregnated graphene cathode for lithium-sulfur batteries.

A practical route is introduced for synthesizing a sulfur-impregnated graphene composite as a promising cathode material for lithium-sulfur batteries. Sulfur particles with a size of a few microns are successfully grown in the interior spaces between randomly dispersed graphene sheets through a heterogeneous crystal growth mechanism. The proposed route not only enables the control of the particle size of active sulfur but also affords quantitative yields of composite powder in large quantities. We investigate the potential use of the sulfur-impregnated graphene composite as a cathode material owing to its advantages of confining active sulfur, preventing the dissolution of soluble polysulfides, and providing sufficient electrical conduction. A high discharge capacity of 1237 mA h g(-1) during the first cycle and a good cyclic retention of 67% after 50 cycles are attained in a voltage range of 1.8-2.6 V vs. Li/Li(+). These results emphasize the importance of tailoring cathode materials for improving the electrochemical properties of lithium-sulfur batteries. Our results provide a basis for further investigations on advanced lithium batteries.

Corrosion as the origin of limited lifetime of vanadium oxide-based aqueous zinc ion batteries.

Aqueous zinc ion batteries are receiving increasing attention for large-scale energy storage systems owing to their attractive features with respect to safety, cost, and scalability. Although vanadium oxides with various compositions have been demonstrated to store zinc ions reversibly, their limited cyclability especially at low current densities and their poor calendar life impede their widespread practical adoption. Herein, we reveal that the electrochemically inactive zinc pyrovanadate (ZVO) phase formed on the cathode surface is the main cause of the limited sustainability. Moreover, the formation of ZVO is closely related to the corrosion of the zinc metal counter electrode by perturbing the pH of the electrolyte. Thus, the dissolution of VO2(OH)2-, the source of the vanadium in the ZVO, is no longer prevented. The proposed amalgamated Zn anode improves the cyclability drastically by blocking the corrosion at the anode, verifying the importance of pH control and the interplay between both electrodes.

Hierarchically Porous Ferroelectric Layer with the Aligned Dipole Moment for a High-Performance Aqueous Zn Metal Battery.

Rechargeable aqueous Zn metal batteries (AZMBs) are desirable because of the advantages of metallic Zn and aqueous media. However, AZMBs suffer from limited cyclability and low Coulombic efficiency, originating from uncontrolled dendrite growth and side reactions such as hydrogen gas evolution and corrosion. A hierarchically porous poly(vinylidene difluoride) (PVDF) protection layer with ferroelectric ß-phases is formed on the Zn metal using a simple electrospinning method. This suppresses Zn metal failure modes such as side reactions and dendrite growth and supports rapid electrolyte accessibility. The synergetic effect of hierarchically porous structures and ferroelectricity not only facilitates a supporting matrix to form uniform nucleation sites for Zn deposition but also inhibits corrosion, allowing dendrite-free Zn deposition. This multifunctional PVDF film significantly improves the cyclability of Zn symmetric cells, allowing for up to 850 h of repeated plating/stripping cycles. Moreover, it exhibits an excellent cycle life of 1000 cycles under harsh conditions and high current densities of 4.0-10.0 mA cm-2, which are 62-fold higher than those that the bare Zn electrode tolerates.