Scalable Dry Process for Fabricating a Na Superionic Conductor-Type Solid Electrolyte Sheet.

The cost reduction and mass production of oxide-based solid electrolytes are critical for the commercialization of all-solid-state batteries. In this study, an environmentally friendly, low-cost, and high-density oxide-based Na superionic conductor-type solid electrolyte sheet was fabricated via a dry process without the use of any solvent. The polytetrafluoroethylene (PTFE), used as a binder, was transformed into thin thread-like structures via shear force, resulting in a flexible solid electrolyte sheet. The solid electrolyte powder quantity was limited to 50 wt % for fabricating a uniform green sheet via the wet process. However, when the dry process was employed for green sheet fabrication, the solid electrolyte powder quantity could be increased to values exceeding 95 wt %. Therefore, the green sheets produced by using the dry process demonstrated a higher density than those fabricated by using the wet process. The binder content and particle size affected the ionic conductivity of a solid electrolyte sheet fabricated via a dry process. The sheet obtained via the blending of 3 wt % PTFE binder with a solid electrolyte powder, finely ground using a planetary ball mill, which exhibited the highest total ionic conductivity of 1.03 mS cm-1.

Molecular Dipoles as a Surface Flattening and Interface Stabilizing Agent for Lithium-Metal Batteries.

Reaching the border of the capable energy limit in existing battery technology has turned research attention away from the rebirth of unstable Li-metal anode chemistry in order to achieve exceptional performance. Strict regulation of the dendritic Li surface reaction, which results in a short circuit and safety issues, should be achieved to realize Li-metal batteries. Herein, this study reports a surface-flattening and interface product stabilizing agent employing methyl pyrrolidone (MP) molecular dipoles in the electrolyte for cyclable Li-metal batteries. The excellent stability of the Li-metal electrode over 600 cycles at a high current density of 5 mA cm-2 has been demonstrated using an optimal concentration of the MP additive. This study has identified the flattening surface reconstruction and crystal rearrangement behavior along the stable (110) plane assisted by the MP molecular dipoles. The stabilization of the Li-metal anodes using molecular dipole agents has helped develop next-generation energy storage devices using Li-metal anodes, such as Li-air, Li-S, and semi-solid-state batteries.

A Novel High-Performance TiO2-x /TiO1-y Ny Coating Material for Silicon Anode in Lithium-Ion Batteries.

Protective surface coatings on Si anodes are promising for improving the electrochemical performance of lithium-ion batteries (LIBs). Nevertheless, most coating materials have severe issues, including low initial coulombic efficiency, structural fracture, morphology control, and complicated synthetic processing. In this study, a multifunctional TiO2- x /TiO1- y Ny (TTN) formed via a facile and scalable synthetic process is applied as a coating material for Si anodes. A thin layer of amorphous TiO2 is uniformly coated onto Si nanoparticles by a simple sol-gel method and then converted into a two phase TiO2- x /TiO1- y Ny via nitridation. The lithiated TiO2-x provides high ionic and electrical conductivity, while TiO1-y Ny can improve mechanical strength that alleviates volume change of Si to address capacity fading issue. Owing to these synergetic advantages, TiO2- x /TiO1- y Ny -coated Si (Si@TTN) exhibits excellent electrochemical properties, including a high charge capacity of 1650 mA h g-1 at 0.1 A g-1 and 84% capacity retention after 100 cycles at 1 A g-1 . Moreover, a significantly enhanced rate performance can be achieved at a high current density. This investigation presents a facile and effective coating material to use as the high-capacity silicon anode in the emerging Si anode technology in LIBs.

Synthesis of Sodium Cobalt Fluoride/Reduced Graphene Oxide (NaCoF3/rGO) Nanocomposites and Investigation of Their Electrochemical Properties as Cathodes for Li-Ion Batteries.

In this study, sodium cobalt fluoride (NaCoF3)/reduced graphene oxide (NCF/rGO) nanocomposites were fabricated through a simple one-pot solvothermal process and their electrochemical performance as cathodes for Li-ion batteries (LIBs) was investigated. The NCF nanoclusters (NCs) on the composites (300-500 nm in size) were formed by the assembly of primary nanoparticles (~20 nm), which were then incorporated on the surface of rGO. This morphology provided NCF NCs with a large surface area for efficient ion diffusion and also allowed for close contact with the conductive matrix to promote rapid electron transfer. As a cathode for LIBs, the NCF/rGO electrode achieved a high reversible capacity of 465 mAh·g-1 at 20 mA·g-1 via the conversion reaction, and this enhancement represented more than five times the reversible capacity of the bare NCF electrode. Additionally, the NCF/rGO electrode exhibited both better specific capacity and cyclability within the current density testing range (from 20 to 200 mA·g-1), compared with those of the bare NCF electrode.

Eco-friendly and facile synthesis of size-controlled spherical silica particles from rice husk.

The valorization of inorganic silica components from rice husk has been considered an important research topic over the last few decades. However, owing to various problems, such as the difficulty in controlling precise morphological properties, complex extraction and manufacturing processes, and the use of hazardous acids, the technology for producing high value-added silica for industrial applications is still insufficient. In this study, we developed a method for obtaining size-controlled spherical silica from rice husk using an eco-friendly and simplified process that overcomes the above-mentioned limitations. Silica particles were obtained by extraction from rice husk in alkaline media under mild conditions (80 °C) followed by pH adjustment with acetic acid. Therefore, the use of strong acids was excluded, no special equipment was required for the process, and the overall synthetic process was significantly simplified. The silica particles obtained through this method were uniformly spherical in shape, with a surface area of more than 200 m2 g-1. Our results indicate that the preparation of silicate solution under appropriate conditions and the use of polyethylene glycol (PEG) additives during the precipitation step are important for obtaining spherical silica. Moreover, by adjusting the temperature in the precipitation step, the size of the spherical silica particles can be controlled in the range of ∼250 nm to ∼1.4 µm. Our study contributes to the development of rice husk-derived silica that can be applied to practical industrial applications.

ON/OFF Switchable Nanocomposite Membranes for Separations.

Although water, air, and other resources are abundant on earth, they have been subjected to strict environmental regulations. This is because of their limitation of availability for human consumption. In the separation industry, the membrane system was introduced to increase the amount of resources available to mankind. Experts used an easy-to-use polymeric material to design several membranes with porous structures for wastewater treatment, gas separation, and chemical removal; consequently, they succeeded in obtaining positive results. However, past polymeric membranes exhibited a chronic drawback such that it was difficult to simultaneously augment the permeate flux and improve its selectivity toward certain substances. Because of the trade-off relationship that existed between permeability and selectivity, the membrane efficiency was not very good; consequently, the cost-effectiveness was significantly hindered because there was no other alternative than to replace the membrane in order to maintain its initial characteristics steadily. This review begins with the introduction of a polymer nanocomposite (PNC) membrane that has been designed to solve the chronic problem of polymeric membranes; subsequently, the stimuli-responsive PNC membrane is elucidated, which has established itself as a popular topic among researchers in the separation industry for several decades. Furthermore, we have listed the different types and examples of stimuli-responsive PNC membranes, which can be switched by external stimuli, while discussing the future direction of the membrane separation industry.

Mesoporous carbon host material for stable lithium metal anode.

Lithium (Li) metal is a promising anode material for next-generation batteries because of its low standard reduction potential (-3.04 V vs. SHE) and high specific capacity (3860 mA h g-1). However, it is still challenging to directly use Li metal as anode material in commercial batteries because of unstable Li dendrite formation and accumulated solid-electrolyte interphase. Possible methods that can suppress the unwanted formation of Li dendrites are (i) by increasing the electrode surface area and (ii) formation of porosity for confining Li. Here, we tested microporous (<2 nm) carbon and mesoporous (2-50 nm) carbon as host materials for the Li metal anode to avoid their degradation during cycling of lithium metal batteries (LMBs). Mesoporous carbon was more effective than microporous carbon as a host material to confine the Li metal and the lifetime of mesoporous carbon was more than twice as long as those of the Cu foil and microporous carbon. After confirmed better anode performance of mesoporous carbon host material, we applied Li-plated mesoporous carbon as an anode in a lithium-sulfur battery (Li-S) full cell. This research work suggests that mesopores, in spite of their low specific surface area, are better than micropores in stabilizing the Li metal and that a mesoporous host material can be applied to Li metal anodes for use in next-generation battery applications.

Ammonium Fluoride Mediated Synthesis of Anhydrous Metal Fluoride-Mesoporous Carbon Nanocomposites for High-Performance Lithium Ion Battery Cathodes.

Metal fluorides (MFx) are one of the most attractive cathode candidates for Li ion batteries (LIBs) due to their high conversion potentials with large capacities. However, only a limited number of synthetic methods, generally involving highly toxic or inaccessible reagents, currently exist, which has made it difficult to produce well-designed nanostructures suitable for cathodes; consequently, harnessing their potential cathodic properties has been a challenge. Herein, we report a new bottom-up synthetic method utilizing ammonium fluoride (NH4F) for the preparation of anhydrous MFx (CuF2, FeF3, and CoF2)/mesoporous carbon (MSU-F-C) nanocomposites, whereby a series of metal precursor nanoparticles preconfined in mesoporous carbon were readily converted to anhydrous MFx through simple heat treatment with NH4F under solventless conditions. We demonstrate the versatility, lower toxicity, and efficiency of this synthetic method and, using XRD analysis, propose a mechanism for the reaction. All MFx/MSU-F-C prepared in this study exhibited superior electrochemical performances, through conversion reactions, as the cathode for LIBs. In particular, FeF3/MSU-F-C maintained a capacity of 650 mAh g-1FeF3 across 50 cycles, which is ∼90% of its initial capacity. We expect that this facile synthesis method will trigger further research into the development of various nanostructured MFx for use in energy storage and other applications.

Effects of 3-Dimensional Lumbar Stabilization Training for Balance in Chronic Hemiplegic Stroke Patients: A Randomized Controlled Trial.

OBJECTIVE: To investigate the effects of the newly developed Spine Balance 3D system on the balance and gait abilities of hemiplegic stroke patients. METHODS: Twenty-eight hemiplegic patients with chronic stroke were randomly assigned to an experimental (n=14) or control group (n=14). The experimental and control groups performed balance training by using the newly developed Spine Balance 3D system and the well-known Biodex Balance System 30 minutes per day, three times a week for 7 weeks. The Berg Balance Scale (BBS), 10-m walking test (10mWT), Timed Up and Go Test (TUG), Functional Reach Test (FRT), the Korean version of the Fall Efficacy Scale-International (KFES-I), trunk muscle strength and stability were evaluated before and after 7 weeks of intervention. RESULTS: The 10mWT improved significantly (p=0.001) in the experimental group (using the Spine Balance 3D system) but not in the control group, and core muscle strength, which we checked using Spine Balance 3D system evaluation program, improved more in the experimental group as well. The results of the BBS, FRT, TUG, KFES-I, and Biodex Balance System evaluation program improved in both groups after 7 weeks of balance training. CONCLUSION: We suggest that the newly-developed Spine Balance 3D system can be a more useful therapeutic tool for gait and dynamic balance rehabilitation in hemiplegic patients than a conventional 2D-based balance training system. A large-scale randomized controlled study is needed to prove the effect of this system.

Facile Synthesis of Nb2O5@Carbon Core-Shell Nanocrystals with Controlled Crystalline Structure for High-Power Anodes in Hybrid Supercapacitors.

Hybrid supercapacitors (battery-supercapacitor hybrid devices, HSCs) deliver high energy within seconds (excellent rate capability) with stable cyclability. One of the key limitations in developing high-performance HSCs is imbalance in power capability between the sluggish Faradaic lithium-intercalation anode and rapid non-Faradaic capacitive cathode. To solve this problem, we synthesize Nb2O5@carbon core-shell nanocyrstals (Nb2O5@C NCs) as high-power anode materials with controlled crystalline phases (orthorhombic (T) and pseudohexagonal (TT)) via a facile one-pot synthesis method based on a water-in-oil microemulsion system. The synthesis of ideal T-Nb2O5 for fast Li(+) diffusion is simply achieved by controlling the microemulsion parameter (e.g., pH control). The T-Nb2O5@C NCs shows a reversible specific capacity of ∼180 mA h g(-1) at 0.05 A g(-1) (1.1-3.0 V vs Li/Li(+)) with rapid rate capability compared to that of TT-Nb2O5@C and carbon shell-free Nb2O5 NCs, mainly due to synergistic effects of (i) the structural merit of T-Nb2O5 and (ii) the conductive carbon shell for high electron mobility. The highest energy (∼63 W h kg(-1)) and power (16 528 W kg(-1) achieved at ∼5 W h kg(-1)) densities within the voltage range of 1.0-3.5 V of the HSC using T-Nb2O5@C anode and MSP-20 cathode are remarkable.

Mesoporous Ge/GeO2/Carbon Lithium-Ion Battery Anodes with High Capacity and High Reversibility.

We report mesoporous composite materials (m-GeO2, m-GeO2/C, and m-Ge-GeO2/C) with large pore size which are synthesized by a simple block copolymer directed self-assembly. m-Ge/GeO2/C shows greatly enhanced Coulombic efficiency, high reversible capacity (1631 mA h g(-1)), and stable cycle life compared with the other mesoporous and bulk GeO2 electrodes. m-Ge/GeO2/C exhibits one of the highest areal capacities (1.65 mA h cm(-2)) among previously reported Ge- and GeO2-based anodes. The superior electrochemical performance in m-Ge/GeO2/C arises from the highly improved kinetics of conversion reaction due to the synergistic effects of the mesoporous structures and the conductive carbon and metallic Ge.

Advanced hybrid supercapacitor based on a mesoporous niobium pentoxide/carbon as high-performance anode.

Recently, hybrid supercapacitors (HSCs), which combine the use of battery and supercapacitor, have been extensively studied in order to satisfy increasing demands for large energy density and high power capability in energy-storage devices. For this purpose, the requirement for anode materials that provide enhanced charge storage sites (high capacity) and accommodate fast charge transport (high rate capability) has increased. Herein, therefore, a preparation of nanocomposite as anode material is presented and an advanced HSC using it is thoroughly analyzed. The HSC comprises a mesoporous Nb2O5/carbon (m-Nb2O5-C) nanocomposite anode synthesized by a simple one-pot method using a block copolymer assisted self-assembly and commercial activated carbon (MSP-20) cathode under organic electrolyte. The m-Nb2O5-C anode provides high specific capacity with outstanding rate performance and cyclability, mainly stemming from its enhanced pseudocapacitive behavior through introduction of a carbon-coated mesostructure within a voltage range from 3.0 to 1.1 V (vs Li/Li(+)). The HSC using the m-Nb2O5-C anode and MSP-20 cathode exhibits excellent energy and power densities (74 W h kg(-1) and 18,510 W kg(-1)), with advanced cycle life (capacity retention: ∼90% at 1000 mA g(-1) after 1000 cycles) within potential range from 1.0 to 3.5 V. In particular, we note that the highest power density (18,510 W kg(-1)) of HSC is achieved at 15 W h kg(-1), which is the highest level among similar HSC systems previously reported. With further study, the HSCs developed in this work could be a next-generation energy-storage device, bridging the performance gap between conventional batteries and supercapacitors.

Using waste Li ion batteries as cathodes in rechargeable Li-liquid batteries.

The rechargeable Li-liquid battery was developed using waste Li ion battery materials immersed in water and used as the liquid cathode. Either the Li metal or Li ions (by the formation LixC6 or Li(4+x)Ti5O12) was harvested from waste Li ion source materials such as a waste anode (LixC6), cathode (LixFePO4), and electrolyte (LiPF6 in EC:DEC) by charging the cell, which then discharged with the waste products in the liquid cathode solution to produce electric energy. When the Li4Ti5O12 was used as the anode with the waste products as the cathode in the proposed battery system, a good cycle-life with high coulombic efficiency was observed.

Sorption of Pb(II) and Cu(II) onto multi-amine grafted mesoporous silica embedded with nano-magnetite: effects of steric factors.

Steric factors affecting the mass transfer of Pb(II) and Cu(II) in mesocellular silica foams (MSU-F-S) functionalized with multi- (mono-, di-, tri-) amine groups and nano-magnetite were investigated through batch experiments. We observed that neither the sorption capacities nor the sorption rates were linearly proportional to the number of amine groups introduced to a ligand. Unexpectedly, the tri-amine grafted samples exhibited lower affinity for both metal cations. These results are mainly attributed to two important steric factors, pore blockage and a conformational change of available amine groups. The relatively large pore size (∼30 nm) of MSU-F-S could enable various functional molecules such as amines and nano-magnetite to be effectively loaded within the pores. However, their excessive densities in the limited pore structure could have adverse effects on the transport of metal ions into the mesopores. An intraparticle diffusion model was applied to elucidate the mechanisms involved in the sorption process. Our results showed that the diffusional mass transfer into the mesopores was significantly inhibited in tri-amine grafted samples. The present findings further the understanding of steric effects on the transport of cationic metals into functionalized mesoporous silica and designing efficient sorbents.

Magnetite/mesocellular carbon foam as a magnetically recoverable fenton catalyst for removal of phenol and arsenic.

A magnetite-loaded mesocellular carbonaceous material, Fe(3)O(4)/MSU-F-C, exhibited superior activity as both a Fenton catalyst and an adsorbent for removal of phenol and arsenic, and strong magnetic property rendering it separable by simply applying magnetic field. In the presence of hydrogen peroxide, the catalytic process by Fe(3)O(4)/MSU-F-C completely oxidized phenol and As(III) under the conditions where commercial iron oxides showed negligible effects. Notably, the decomposition of H(2)O(2) by Fe(3)O(4)/MSU-F-C was not faster than those by commercial iron oxides, indicating that hydroxyl radical produced via the catalytic process by Fe(3)O(4)/MSU-F-C was used more efficiently for the oxidation of target contaminants compared to the other iron oxides. The homogeneous Fenton reaction by the dissolved iron species eluted from Fe(3)O(4)/MSU-F-C was insignificant. At relatively high doses of Fe(3)O(4)/MSU-F-C, total concentration of arsenic decreased to a significant extent due to the adsorption of arsenic on the catalyst surface. The removal of arsenic by adsorption was found to proceed via preoxidation of As(III) into As(V) and the subsequent adsorption of As(V) onto the catalyst.