High-Power and Large-Area Anodes for Safe Lithium-Metal Batteries.

The lithium deposited via the complex electrochemical heterogeneous lithium deposition reaction (LDR) process on a lithium foil-based anode (LFA) forms a high-aspect-ratio shape whenever the reaction kinetics reach its limit, threatening battery safety. Thereby, a research strategy that boosts the LDR kinetics is needed to construct a high-power and safe lithium metal anode. In this study, the kinetic limitations of the LDR process on LFA are elucidated through operando and ex situ observations using in-depth electrochemical analyses. In addition, ultra-thin (≈0.5 µm) and high modulus (≥19 GPa) double-walled carbon nanotube (DWNT) membranes with different surface properties are designed to catalyze high-safety LDRs. The oxygen-functionalized DWNT membranes introduced on the LFA top surface simultaneously induce multitudinous lithium nuclei, leading to film-like lithium deposition even at a high current density of 20 mA cm-2. More importantly, the layer-by-layer assembly of the oxygen-functionalized and pristine DWNT membranes results in different surface energies between the top and bottom surfaces, enabling selective surface LDRs underneath the high-modulus bilayer membranes. The protective LDR on the bilayer-covered LFA guarantees an invulnerable cycling process in large-area pouch cells at high current densities for more than 1000 cycles, demonstrating the practicability of LFA in a conventional liquid electrolyte system.

Electrolyte-Dependent Sodium Ion Transport Behaviors in Hard Carbon Anode.

A comprehensive study is conducted on hard carbon (HC) series samples by tuning the graphitic local microstructures systematically as an anode for SIBs in both carbonate- (CBE) and glyme-based electrolytes (GBE). The results reveal more detailed charge storage characters of HCs on the LVP section. 1) The LVP capacity is closely related to the prismatic surface area to the basal plane as well as the bulk density, regardless of electrolyte systems. 2) The glyme-sodium ion complex can facilitate sodium ion delivery into the internal closed pores of the HCs along with not well-ordered graphitic structures. 3) The glyme-mediated sodium ion-storage behavior causes significant decreases in both surface film resistance and charge transfer resistance, leading to enhanced rate capability. 4) The LVP originates from the formation of pseudo-metallic sodium nanoclusters, which are the same in a CBE and GBE. These results provide insight into the sodium ion-storage behaviors of HCs, particularly on the interrelationship between graphitic local microstructures and electrolyte systems. In addition, a high-performance HC anode with a plateau capacity of ≈300 mA h g-1 is designed based on the information, and its workability is demonstrated in a full-cell SIB device.

Atomic-Distributed Coordination State of Metal-Phenolic Compounds Enabled Low Temperature Graphitization for High-Performance Multioriented Graphite Anode.

Continuous efforts have been made to achieve nanostructured carbon materials with highly ordered graphitic structures using facile synthetic methods. 3D graphite nanoballs (GNBs) are synthesized by the low-temperature pyrolysis of a non-graphitizable precursor, tannic acid (TA). Abundant phenol groups on TA bind to Ni2+ to form metal-phenolic coordination, which renders each Ni cation to be atomically distributed by the TA ligands. Even at low temperatures (1000 °C), highly ordered graphitic structure is promoted by the distributed Ni nanoparticles that act as a graphitization catalyzer. The crystallinity of the GNB is fully corroborated by the intense 2D peak observed in Raman spectroscopy. In particular, the graphitic layers have orientations pointing toward multidirections, which are beneficial for the rapid transport of Li-ions into graphite grains. The resulting materials exhibit outstanding electrochemical performance (120 mAh g-1 at 5 C and 282 mAh g-1 at 0.5 C after 500 cycles) when evaluated as a fast-chargeable negative electrode for lithium ion batteries.

Anode-Free Sodium Metal Batteries Based on Nanohybrid Core-Shell Templates.

Anode-free sodium metal batteries (AF-SMBs) can deliver high energy and enormous power, but their cycle lives are still insufficient for them to be practical as a power source in modern electronic devices and/or grid systems. In this study, a nanohybrid template based on high aspect-ratio silver nanofibers and nitrogen-rich carbon thin layers as a core-shell structure is designed to improve the Coulombic efficiency (CE) and cycling performance of AF-SMBs. The catalytic nanohybrid templates dramatically reduce the voltage overshooting caused by metal nucleation to one-fifth that of a bare Al foil electrode (≈6 mV vs ≈30 mV), and high average CE values of >99% are achieved over a wide range of current rates from 0.2 to 8 mA cm-2 . Moreover, exceptionally long cycle lives for more than 1600 cycles and an additional 1500 cycles are achieved with a highly stable CE of >99.9%. These results show that AF-SMBs are feasible with the nanohybrid electrode system.

Pyrolytic Carbon Nanosheets for Ultrafast and Ultrastable Sodium-Ion Storage.

Na-ion cointercalation in the graphite host structure in a glyme-based electrolyte represents a new possibility for using carbon-based materials (CMs) as anodes for Na-ion storage. However, local microstructures and nanoscale morphological features in CMs affect their electrochemical performances; they require intensive studies to achieve high levels of Na-ion storage performances. Here, pyrolytic carbon nanosheets (PCNs) composed of multitudinous graphitic nanocrystals are prepared from renewable bioresources by heating. In particular, PCN-2800 prepared by heating at 2800 °C has a distinctive sp2 carbon bonding nature, crystalline domain size of ≈44.2 Å, and high electrical conductivity of ≈320 S cm-1 , presenting significantly high rate capability at 600 C (60 A g-1 ) and stable cycling behaviors over 40 000 cycles as an anode for Na-ion storage. The results of this study show the unusual graphitization behaviors of a char-type carbon precursor and exceptionally high rate and cycling performances of the resulting graphitic material, PCN-2800, even surpassing those of supercapacitors.

Tin Sulfide-Based Nanohybrid for High-Performance Anode of Sodium-Ion Batteries.

Nanohybrid anode materials for Na-ion batteries (NIBs) based on conversion and/or alloying reactions can provide significantly improved energy and power characteristics, while suffering from low Coulombic efficiency and unfavorable voltage properties. An NIB paper-type nanohybrid anode (PNA) based on tin sulfide nanoparticles and acid-treated multiwalled carbon nanotubes is reported. In 1 m NaPF6 dissolved in diethylene glycol dimethyl ether as an electrolyte, the above PNA shows a high reversible capacity of ≈1200 mAh g-1 and a large voltage plateau corresponding to a capacity of ≈550 mAh g-1 in the low-voltage region of ≈0.1 V versus Na+ /Na, exhibiting high rate capabilities at a current rate of 1 A g-1 and good cycling performance over 250 cycles. In addition, the PNA exhibits a high first Coulombic efficiency of ≈90%, achieving values above 99% during subsequent cycles. Furthermore, the feasibility of PNA usage is demonstrated by full-cell tests with a reported cathode, which results in high specific energy and power values of ≈256 Wh kg-1 and 471 W kg-1 , respectively, with stable cycling.

Polymeric Binder Design for Sustainable Lithium-Ion Battery Chemistry.

The design of binders plays a pivotal role in achieving enduring high power in lithium-ion batteries (LIBs) and extending their overall lifespan. This review underscores the indispensable characteristics that a binder must possess when utilized in LIBs, considering factors such as electrochemical, thermal, and dispersion stability, compatibility with electrolytes, solubility in solvents, mechanical properties, and conductivity. In the case of anode materials, binders with robust mechanical properties and elasticity are imperative to uphold electrode integrity, particularly in materials subjected to substantial volume changes. For cathode materials, the selection of a binder hinges on the crystal structure of the cathode material. Other vital considerations in binder design encompass cost effectiveness, adhesion, processability, and environmental friendliness. Incorporating low-cost, eco-friendly, and biodegradable polymers can significantly contribute to sustainable battery development. This review serves as an invaluable resource for comprehending the prerequisites of binder design in high-performance LIBs and offers insights into binder selection for diverse electrode materials. The findings and principles articulated in this review can be extrapolated to other advanced battery systems, charting a course for developing next-generation batteries characterized by enhanced performance and sustainability.

Amorphous carbon nanotube/MnO2/graphene oxide ternary composite electrodes for electrochemical capacitors.

Ternary composites of amorphous carbon nanotube/MnO2/graphene oxide (a-CNT/MnO2/GO) were synthesized by a facile direct redox reaction between potassium permanganate and a-CNT, which was prepared by anodic aluminum oxide template method following co-filtration with GO. Needle-like, 100-nm-thick, MnO2 crystals were homogeneously coated on the a-CNT surface, which was then covered with GO. The electrochemical performance of the resulting MnO2-coated a-CNTs exhibited a specific capacitance of 473 F/g at a scan rate of 5 mV/s, and excellent charge/discharge stability after 500 cycles.

Nanocomposites of polystyrene/polystyrene-grafted graphene oxides synthesized by in-situ bulk polymerization.

In this study, polystyrene-grafted graphene oxide (GO-g-PS) nanocomposites with different PS chain lengths were prepared by in-situ polymerization, and their reinforcing effect on the PS matrix was investigated. The glass transition (T(g)) and the thermal degradation (T(d)) temperatures of the PS/GO-g-PS nanocomposites were increased up to 2.8 degrees C and 23.9 degrees C, respectively. The addition of only 0.1 wt% of the GO-g-PS to the PS/GO-g-PS nanocomposites increased the tensile strength and Young's modulus by around 20.5% and 71.4%, respectively. These results showed that the thermal and mechanical properties of the PS/GO-g-PS nanocomposites gradually improved with increasing length of the PS chain grafted onto the GO surface. These differences in reinforcing effects were attributed to differences in interfacial interaction between the graphene and PS matrix.

Synergistic effects of alkylated graphene oxide on the properties of polypropylene-based carbon nanocomposites.

Polypropylene (PP)/carbon black (CB)-alkylated graphene oxide (AGO) hybrid nanocomposites were prepared via solution process and the synergistic effects of AGO on the properties of the PP/CB nanocomposites were investigated. AGO at a content of only 0.2 wt% formed an overlapped network structure in the PP matrix and affected the electrical, thermal and mechanical properties of the PP/CB nanocomposites. Specifically, PP/CB (5 wt%)-AGO (0.2 wt%) nanocomposites exhibited an electrical percolation threshold at lower CB contents than the PP/CB nanocomposites did, and the sheet resistance was decreased to 2.3 x 10(7) omega/sq. The thermal degradation temperature and recrystallization temperature of the PP/CB (10 wt%) nanocomposites were increased by 11.3 and 1.6 degrees C, respectively, by the addition of 0.2 wt% AGO. In addition, the Young's modulus of the PP/CB (10 wt%) nanocomposite was increased from 438.1 to 540.1 MPa.

Silver nanowire catalysts on carbon nanotubes-incorporated bacterial cellulose membrane electrodes for oxygen reduction reaction.

Silver nanowires have unique electrical, thermal and optical properties, which support their potential application in numerous fields including catalysis, electronics, optoelectronics, sensing, and surface-enhanced spectroscopy. Especially, their application such as catalysts for alkaline fuel cells (AFCs) have attracted much interest because of their superior electrical conductivity over that of any metal and their lower cost compared to Pt. In this study, multiwalled carbon nanotubes (MWCNTs)-incorporated bacterial cellulose (BC) membrane electrode with silver nanowire catalyst was prepared. First, acid-treated MWCNTs were incorporated into BC membranes and then freeze-dried after solvent exchange to tert-butanol in order to maintain the 3D-network macroporous structure. Second, silver nanowires synthesized by polyol process were introduced onto the surface of the MWCNTs-incorporated BC membrane through easy vacuum filtration. Finally, thermal treatment was carried out to confirm the effect of the PVP on the silver nanowire catalysts toward oxygen reduction reaction. The electrode with thermally treated silver nanowire had great electrocatalytic activity compared with non-treated one. These results suggest that the MWCNTs-incorporated BC electrode with silver nanowire catalysts after thermal treatment could be potentially used in cathodes of AFCs.

Free-standing nitrogen-doped reduced graphene oxide anode for lithium-ion batteries.

Graphenes have been considered suitable candidate materials for electrodes of energy storage devices such as lithium-ion batteries (LIBs) because of their outstanding mechanical, thermal and electrical properties. However, there are problems when using these carbon materials for electrodes because of their low electrochemical performance. In this work, to improve the electrochemical performances of graphenes, free-standing nitrogen-doped reduced graphene oxides (FNRGOs) were prepared as an anode for LIBs using a facile vacuum filtration method and thermal annealing at different temperatures. X-ray diffraction and X-ray photoelectron spectroscopy were employed to characterize the prepared samples, and then their electrochemical performance was investigated by galvanostatic charge/discharge (GCD) tests. GCD tests revealed that FNRGO prepared from thermal annealing at 500 degrees C exhibited good initial reversible capacity (502 mA h/g at 50 mA/g (0.14 C)) and enhanced cycle stability (capacity retention of 90.5% after 50th cycles at 100 mA/g (0.27 C), which demonstrated that FNRGOs were suitable candidates as anodes for LIBs.

Biodegradation in Composting Conditions of PBEAS Monofilaments for the Sustainable End-Use of Fishing Nets.

The development and utilization of biodegradable plastics is an effective way to overcome environmental pollution caused by the disposal of non-degradable plastics. Recently, polybutylene succinate co-butylene adipate co-ethylene succinate co-ethylene adipate, (PBEAS) a biodegradable polymer with excellent strength and elongation, was developed to replace conventional nylon-based non-degradable fishing nets. The biodegradable fishing gear developed in this way can greatly contribute to inhibiting ghost fishing that may occur at the fishing site. In addition, by collecting the products after use and disposing of them in composting conditions, the environmental problem such as the leakage of microplastics strongly can be prevented. In this study, the aerobic biodegradation of PBEAS fishing nets under composting conditions is evaluated and the resulting changes in physicochemical properties are analyzed. The PBEAS fishing gear exhibits a mineralization rate of 82% in a compost environment for 45 days. As a result of physicochemical analysis, PBEAS fibers show a representative decrease in molecular weight and mechanical properties under composting conditions. PBEAS fibers can be used as eco-friendly biodegradable fishing gear that can replace existing non-degradable nylon fibers, and in particular, fishing gear collected after use can be returned to nature through biodegradation under composting conditions.

Biodegradable and hydrophobic nanofibrous membranes produced by solution blow spinning for efficient oil/water separation.

The development of nanofibrous oil-water separation materials is explosively progressing, but the remarkably low productivity is the main factor hindering their practical application. In this study, biodegradable polybutylene succinate (PBS) nanofibers with excellent productivity (27.0 g/h per nozzle) were successfully fabricated using the solution blow spinning (SBS) process, breaking away from the conventional electrospinning method. The prepared PBS nanofibers exhibited extremely thin fiber diameters (130 nm) with high porosity (97.4%). Without any chemical modification or inorganic/organic hybrid materialization, the PBS nanofibrous membrane showed excellent oil adsorption capacity (minimum: 18.7 g/g and maximum: 38.5 g/g) and separation efficiency; water and oil mixtures (99.4-99.98%) and emulsions (98.1-99.5%) compared to conventional organic polymer-based nanofibers. In terms of disposal after use, this biodegradable nanofibrous membrane was able to return to nature through hydrolysis and biodegradation processes.

Revisiting Lithium- and Sodium-Ion Storage in Hard Carbon Anodes.

The galvanostatic lithiation/sodiation voltage profiles of hard carbon anodes are simple, with a sloping drop followed by a plateau. However, a precise understanding of the corresponding redox sites and storage mechanisms is still elusive, which hinders further development in commercial applications. Here, a comprehensive comparison of the lithium- and sodium-ion storage behaviors of hard carbon is conducted, yielding the following key findings: 1) the sloping voltage section is presented by the lithium-ion intercalation in the graphitic lattices of hard carbons, whereas it mainly arises from the chemisorption of sodium ions on their inner surfaces constituting closed pores, even if the graphitic lattices are unoccupied; 2) the redox sites for the plateau capacities are the same as those for the closed pores regardless of the alkali ions; 3) the sodiation plateau capacities are mostly determined by the volume of the available closed pore, whereas the lithiation plateau capacities are primarily affected by the intercalation propensity; and 4) the intercalation preference and the plateau capacity have an inverse correlation. These findings from extensive characterizations and theoretical investigations provide a relatively clear elucidation of the electrochemical footprint of hard carbon anodes in relation to the redox mechanisms and storage sites for lithium and sodium ions, thereby providing a more rational design strategy for constructing better hard carbon anodes.

Controlling microstructure of three-dimensional scaffolds from regenerated silk fibroin by adjusting pH.

For tissue engineering, it is very important to design and control the pore architecture of three-dimensional (3D) polymeric scaffolds, which plays an important role in directing tissue formation and function. In this study, 3D porous silk fibroin scaffolds produced using a freeze drying technique were prepared at pHs ranging from 5 to 9. The effects of pH on the pore microstructure of the silk fibroin scaffold were examined by rheometry, FESEM and FTIR. Different pore structures were formed according to the pH of silk fibroin because silk fibroin exhibits water-like behavior under basic conditions and gel-like behavior under acidic conditions.

Enhanced thermal properties of graphene oxide-incorporated polymeric microspheres.

Polystyrene (PS) microspheres coated with graphene oxide (GO) were prepared and the variation of their thermal properties according to the GO loading was examined. The GO content in the PS-GO nanocomposites was controlled by the GO dispersions at various concentrations. The GO was coated onto the surface of the PS microspheres through the strong ionic interaction between polyvinylpyrrolidone and the GO sheet. The thermal properties of the GO incorporated PS microspheres were affected by the GO, which disturbed the chain activity and exhibited effective heat shielding. It also delayed the permeation of oxygen and hindered the escape of volatile degradation products from the PS-GO nanocomposites. In addition, the thermal degradation temperature of the nanocomposites was increased above 15 degrees C and their T(g) was also increased above 4.0 degrees C. PS-GO exhibited higher thermal conductivity (0.173 W/mK) than that of pure PS (0.117 W/mK).

Flexible bio-composites based on silks and celluloses.

Biomaterials have attracted worldwide attention due to the concerns regarding health and the environment. Silk, a natural protein produced by several species of insects, has been examined as a potential material for applications in many biotechnological and biomedical fields. However, regenerated silk fibroin has poor ductility and mechanical properties. Therefore, in this study, silk fibroin-cellulose composite films were prepared in an aqueous system to increase the ductility of regenerated silk fibroin. The morphology of the silk fibroin-cellulose composite film was observed by field emission scanning electron microscopy. The structure of the silk fibroin-cellulose composite films was examined by Fourier transform-infrared spectroscopy. The flexibility was analyzed using a bending test.

Improved thermal properties of graphene oxide-incorporated poly(methyl methacrylate) microspheres.

Graphene, a single layer of carbon atoms in a two-dimensional lattice, has attracted considerable attention owing to its unique physical, chemical and mechanical properties. In particular, because of its excellent thermal properties such as high thermal conductivity and good thermal stability, graphene has been regarded as a one of the promising candidates for the reinforcing fillers on the polymer composites field. In this study, we prepared the poly(methyl methacrylate) (PMMA)/graphene oxide (GO) nanocomposite by a simple solution mixing process, and examined the thermal reinforcing effects of GO on a PMMA matrix. Using thermogravimetric analysis, differential scanning calorimeter, and thermal conductivity meter, we investigated the effects of GO on the thermal properties of PMMA/GO nanocomposites. With 3 wt% of GO loading, the glass transition temperature (Tg) of the PMMA/GO nanocomposite were increased by more than 7 degrees C and the thermal conductivity of which also improved 1.8 times compared to pure PMMA.

Dual Electrorheological and Magnetorheological Behaviors of Poly(N-methyl aniline) Coated ZnFe2O4 Composite Particles.

Magnetic/conducting polymeric hybrid core-shell typed zinc ferrite (ZnFe2O4)/poly(N-methyl aniline) (PMA) particles were fabricated and adopted as electrorheological (ER) and magnetorheological (MR) fluids, and their rheological properties were examined. Solvo-thermally synthesized ZnFe2O4 was coated with a conducting PMA through chemical oxidation polymerization. The size, shape, and chemical composition of the final core-shell shaped particles were scrutinized by scanning electron microscopy, transmission electron microscopy, and Fourier transform-infrared spectroscopy. The crystal faces of the particles before and after coating with PMA were analyzed by X-ray diffraction. The ZnFe2O4/PMA products were suspended in silicone oil to investigate the rheological response to electro- or magnetic stimuli using a rotating rheometer. The shear stresses were analyzed using the CCJ equation. The dynamic yield stress curve was suitable for the conductivity mechanism with a slope of 1.5. When magnetic fields of various intensities were applied, the flow curve was analyzed using the Hershel-Bulkley equation, and the yield stresses had a slope of 1.5. Optical microscopy further showed that the particles dispersed in insulating medium form chain structures under electric and magnetic fields. Via this core-shell fabrication process, not only spherical conducting particles were obtained but also their dual ER and MR responses were demonstrated for their wide potential applications.