Gold-Nanolayer-Derived Zincophilicity Suppressing Metallic Zinc Dendrites and Its Efficacy in Improving Electrochemical Stability of Aqueous Zinc-Ion Batteries.

Herein, an Au-coating layer adjusted on the surface of a Zn metal electrode that effectively suppresses the dendrite growth as well as the mechanisms underlying the dendrite suppression as a result of the zincophilic character of Au is introduced. For the Au-coated Zn metal symmetric cell, uniform deposition of Zn-derived compounds was revealed by operando synchrotron tomography. Microscopic studies demonstrate that the Au-coating layer is induced to form a new Zn-Au alloy during the initial Zn deposition, resulting in stabilized long-term stripping/plating of Zn via the 'embracing effect' that intimately accommodates Zn deposition for further cycles. This property supports the successful operation of symmetrical cells up to 50 mA cm-2 . According to Zn electrodeposition simulation, it is verified that the suppression of dendrite growth is responsible for the electro-conducting Au nanolayer that uniformly distributes the electric field and protects the Zn electrode from corrosion, ultimately promoting uniform Zn growth. The compatibility of the Au-coating layer for full cell configuration is verified using NaV3 O8 as a cathode material over 1 000 cycles. This finding provides a new pathway for the enhancement of the electrochemical performance of ZIBs by suppressing the dendritic growth of Zn by means of a zincophilic Au nanolayer.

Bio-Derived Surface Layer Suitable for Long Term Cycling Ni-Rich Cathode for Lithium-Ion Batteries.

Since Ni-rich cathode material is very sensitive to moisture and easily forms residual lithium compounds that degrade cell performance, it is very important to pay attention to the selection of the surface modifying media. Accordingly, hydroxyapatite (Ca5 (PO4 )3 (OH)), a tooth-derived material showing excellent mechanical and thermodynamic stabilities, is selected. To verify the availability of hydroxyapatite as a surface protection material, lithium-doped hydroxyapatite, Ca4.67 Li0.33 (PO4 )3 (OH), is formed with ≈10-nm layer after reacting with residual lithium compounds on Li[Ni0.8 Co0.15 Al0.05 ]O2 , which spontaneously results in dramatic reduction of surface lithium residues to 2879 ppm from 22364 ppm. The Ca4.67 Li0.33 (PO4 )3 (OH)-modified Li[Ni0.8 Co0.15 Al0.05 ]O2 electrode provides ultra-long term cycling stability, enabling 1000 cycles retaining 66.3% of its initial capacity. Also, morphological degradations such as micro-cracking or amorphization of surface are significantly suppressed by the presence of Ca4.67 Li0.33 (PO4 )3 (OH) layer on the Li[Ni0.8 Co0.15 Al0.05 ]O2 , of which the Ca4.67 Li0.33 (PO4 )3 (OH) is transformed to CaF2 via Ca4.67 Li0.33 (PO4 )3 F during the long term cycles reacting with HF in electrolyte. In addition, the authors' density function theory (DFT) results explain the reason of instability of NCA and why CaF2 layers can delay the micro-cracking during electrochemical reaction. Therefore, the stable Ca4.67 Li0.33 (PO4 )3 F and CaF2 layers play a pivotal role to protect the Li[Ni0.8 Co0.15 Al0.05 ]O2 with ultra-long cycling stability.

High-Voltage Stability in KFSI Nonaqueous Carbonate Solutions for Potassium-Ion Batteries: Current Collectors and Coin-Cell Components.

Cu, Al, and 316L stainless steel are the main components of the current collectors and coin-type cells used in the characterization of potassium-ion battery (KIB) materials and are expected to be electrochemically inactive. Herein, their electrochemical stabilities in a nonaqueous potassium-bis(fluorosulfonyl)imide (KFSI)-based electrolyte are investigated. In dynamic- and transient-mode polarization, passivation of each metal is observed to occur below 3.9, 3.8, and 4.05 V versus K+/K for Cu, Al, and 316L stainless steel, respectively, which are considered the threshold potentials. The composition of the passive layers of each metal is determined using time-of-flight secondary-ion mass spectrometry. The passive layers of Cu and Al consist of Cu-O (CuO or Cu2O) and Al-O (Al2O3), respectively, and 316L stainless steel is passivated with an outermost Cr-F (CrF3) layer and an inner Cr-O (Cr2O3) layer. Above the threshold potentials, however, severe corrosion of each metal occurs accompanied by the dissolution of metal ions, which could affect the reliability of experimental results for KIBs using KFSI-based electrolytes.

Nature-Derived Cellulose-Based Composite Separator for Sodium-Ion Batteries.

Sodium-ion batteries (SIBs) are emerging power sources for the replacement of lithium-ion batteries. Recent studies have focused on the development of electrodes and electrolytes, with thick glass fiber separators (~380 µm) generally adopted. In this work, we introduce a new thin (~50 µm) cellulose-polyacrylonitrile-alumina composite as a separator for SIBs. The separator exhibits excellent thermal stability with no shrinkage up to 300°C and electrolyte uptake with a contact angle of 0°. The sodium ion transference number, t Na + , of the separator is measured to be 0.78, which is higher than that of bare cellulose ( t Na + : 0.31). These outstanding physical properties of the separator enable the long-term operation of NaCrO2 cathode/hard carbon anode full cells in a conventional carbonate electrolyte, with capacity retention of 82% for 500 cycles. Time-of-flight secondary-ion mass spectroscopy analysis reveals the additional role of the Al2O3 coating, which is transformed into AlF3 upon long-term cycling owing to HF scavenging. Our findings will open the door to the use of cellulose-based functional separators for high-performance SIBs.

The Conversion Chemistry for High-Energy Cathodes of Rechargeable Sodium Batteries.

Herein, the Cu2P2O7/carbon-nanotube nanocomposite is reported as a cathode material based on a conversion reaction for rechargeable sodium batteries (RSBs). The nanocomposite electrode exhibits the large capacity of 355 mAh g-1, which is consistent with the 4 mol Na+ storage per formula unit determined by first-principles calculation. Its average operation voltage is approximately 2.4 V (vs Na+/Na). Even at 1800 mA g-1, a capacity of 223 mAh g-1 is maintained. Moreover, the composite electrode exhibits acceptable capacity retention of over 75% of the initial capacity for 300 cycles at 360 mA g-1. The overall conversion reaction mechanism on the Cu2P2O7/carbon-nanotube nanocomposite is determined to be Cu2P2O7 + 4Na+ + 4e- → 2Cu + Na4P2O7 based on operando/ex situ structural and physicochemical analyses. The high energy density of the Cu2P2O7/carbon-nanotube nanocomposite (720 Wh kg-1) supported by this conversion chemistry indicates a high possibility of application of this material as a promising cathode candidate for RSBs.

New Insight into Ethylenediaminetetraacetic Acid Tetrasodium Salt as a Sacrificing Sodium Ion Source for Sodium-Deficient Cathode Materials for Full Cells.

Sacrificing sodium supply sources is needed for sodium-deficient cathode materials to achieve commercialization of sodium-ion full cells using sodium-ion intercalation anode materials. Herein, the potential of ethylenediaminetetraacetic acid tetrasodium salt (EDTA-4Na) as a sacrificing sodium supply source was investigated by intimately blending it with sodium-deficient P2-type Na0.67[Al0.05Mn0.95]O2. The EDTA-4Na/Na0.67[Al0.05Mn0.95]O2 composite electrode unexpectedly exhibited an improved charge capacity of 177 mA h (g-oxide)-1 compared with the low charge capacity of 83 mA h (g-oxide)-1 for bare Na0.67[Al0.05Mn0.95]O2. The reversible capacity of an EDTA-4Na/Na0.67[Al0.05Mn0.95]O2//hard carbon full-cell system increased to 152 mA h (g-oxide)-1 at the first discharge with a Coulombic efficiency of 89%, whereas the Na0.67[Al0.05Mn0.95]O2 without EDTA-4Na delivered a discharge capacity 51 mA h g-1 because of the small charge capacity. The EDTA-4Na sacrificed itself to generate Na+ ions via oxidative decomposition by releasing four sodium ions and producing C3N as a decomposition resultant on charge. It is thought that the slight increase in discharge capacity is associated with the electroconducting nature of the C3N deposits formed on the surface of the Na0.67[Al0.05Mn0.95]O2 electrode. We elucidated the reaction mechanism and sacrificial activity of EDTA-4Na, and our findings suggest that the addition of EDTA-4Na is beneficial as an additional source of Na+ ions that contribute to the charge capacity.

Conversion Chemistry of Cobalt Oxalate for Sodium Storage.

Conversion electrodes, which can realize high capacities by employing the wider valence states of transition metals, are investigated for sodium storage and applied for rechargeable sodium-ion batteries (SIBs). Importantly, this work is a first report for the sodium storage ability and related storage mechanism in oxalate compounds, specifically cobalt oxalate (CoC2O4) nanorods. The nanorods are intimately blended with acetylene black powders to achieve sufficient electrical conductivity (∼10-3 S cm-1). The resulting C-CoC2O4 electrode delivers an initial capacity of about 330 mA h (g-CoC2O4)-1 at a rate of 0.2 C (60 mA g-1) and preserves 75% of the initial capacity over 200 cycles. A high charge (oxidation) capacity, ∼111 mA h g-1, was achieved even at 30 C (9000 mA g-1). This remarkable electrode performance is reported for the first time for metal oxalate compounds tested for Na cells, to the best of our knowledge. X-ray diffraction, transmission electron microscopy, and time-of-flight secondary-ion mass spectroscopy analyses lead to the proposal of a new sodium storage mechanism. For this mechanism, CoC2O4 is converted into Co metal involving with the creation of Na2C2O4 on discharge (reduction), and the Co metal is recovered to CoC2O4 on charge. The employed electroconducting carbon is likely to provide good electron conduction paths, which enables fast conversion on both discharge and charge. A full cell comprised of the C-CoC2O4 anode and carbon-coated NaCrO2 cathode exhibits good retention capacity over prolonged cycling, with retention of about 84.7% of the first capacity [107 mA h (g-NaCrO2)-1] for 300 cycles, and is active at a rate of 5 C (550 mA g-1), with a capacity of 79.5 mA h g-1. This result demonstrates the potential of applying C-CoC2O4 as an anode material for rechargeable SIBs.

Synthesis and Electrochemical Reaction of Tin Oxalate-Reduced Graphene Oxide Composite Anode for Rechargeable Lithium Batteries.

Unlike for SnO2, few studies have reported on the use of SnC2O4 as an anode material for rechargeable lithium batteries. Here, we first introduce a SnC2O4-reduced graphene oxide composite produced via hydrothermal reactions followed by a layer-by-layer self-assembly process. The addition of rGO increased the electric conductivity up to ∼10-3 S cm-1. As a result, the SnC2O4-reduced graphene oxide electrode exhibited a high charge (oxidation) capacity of ∼1166 mAh g-1 at a current of 100 mA g-1 (0.1 C-rate) with a good retention delivering approximately 620 mAh g-1 at the 200th cycle. Even at a rate of 10 C (10 A g-1), the composite electrode was able to obtain a charge capacity of 467 mAh g-1. In contrast, the bare SnC2O4 had inferior electrochemical properties relative to those of the SnC2O4-reduced graphene oxide composite: ∼643 mAh g-1 at the first charge, retaining 192 mAh g-1 at the 200th cycle and 289 mAh g-1 at 10 C. This improvement in electrochemical properties is most likely due to the improvement in electric conductivity, which enables facile electron transfer via simultaneous conversion above 0.75 V and de/alloy reactions below 0.75 V: SnC2O4 + 2Li+ + 2e- → Sn + Li2C2O4 + xLi+ + xe- → LixSn on discharge (reduction) and vice versa on charge. This was confirmed by systematic studies of ex situ X-ray diffraction, transmission electron microscopy, and time-of-flight secondary-ion mass spectroscopy.

Synthesis of LiVOPO4 by Emulsion Drying Method for Use as an Anode Material for Rechargeable Lithium Batteries.

Highly crystalline ß-LiVOPO4 was synthesized from a water-in-oil emulsion. At 400 °C in ambient air, removal of the oil phase from the emulsion precipitates resulted in a poorly crystalline intermediate compound. On increasing the temperature to 750 °C under Ar, a single phase was formed. Rietveld refinement of the X-ray diffraction (XRD) data obtained from the product heated at 750 °C indicated that the product has an orthorhombic ß-LiVOPO4 olivine structure with no impurities. Although the ß-LiVOPO4 had an irreversible capacity in the first cycle, the electrode exhibited stable cyclability for 100 cycles, maintaining approximately 85.5% (573 mAh g-1) of the first charge capacity (670 mAh g-1). In addition, the ß-LiVOPO4 electrode had a high capacity even at high rates: 601 mAh g-1 at 1C rate (670 mA g-1) and 373 mAh g-1 at 30C rates (20.1 A g-1). Consolidating the results from XRD, X-ray photoelectron spectroscopy, and time-of-flight secondary mass spectroscopy, we suggest that the electrochemical activity of the ß-LiVOPO4 arises from the conversion reaction accompanied by the formation of Li2O and Li3PO4. In addition, the ion-conducting Li3PO4 contributes to high capacity delivery at high rates up to a C-rate of 30.

Anatase titania nanorods as an intercalation anode material for rechargeable sodium batteries.

For the first time, we report the electrochemical activity of anatase TiO2 nanorods in a Na cell. The anatase TiO2 nanorods were synthesized by a hydrothermal method, and their surfaces were coated by carbon to improve the electric conductivity through carbonization of pitch at 700 °C for 2 h in Ar flow. The resulting structure does not change before and after the carbon coating, as confirmed by X-ray diffraction (XRD). Transmission electron microscopic images confirm the presence of a carbon coating on the anatase TiO2 nanorods. In cell tests, anodes of bare and carbon-coated anatase TiO2 nanorods exhibit stable cycling performance and attain a capacity of about 172 and 193 mAh g(-1) on the first charge, respectively, in the voltage range of 3-0 V. With the help of the conductive carbon layers, the carbon-coated anatase TiO2 delivers more capacity at high rates, 104 mAh g(-1) at the 10 C-rate (3.3 A g(-1)), 82 mAh g(-1) at the 30 C-rate (10 A g(-1)), and 53 mAh g(-1) at the 100 C-rate (33 A g(-1)). By contrast, the anode of bare anatase TiO2 nanorods delivers only about 38 mAh g(-1) at the 10 C-rate (3.3 A g(-1)). The excellent cyclability and high-rate capability are the result of a Na(+) insertion and extraction reaction into the host structure coupled with Ti(4+/3+) redox reaction, as revealed by X-ray absorption spectroscopy.

Diagnosis of a case of ectopic parathyroid adenoma on the early image of 99mTc-MIBI scintigram.

We report the case of a 64-year-old woman who had a severe hypercalcemia. Serum calcium, intact parathyroid hormone (PTH), 1alpha, 25 (OH)(2 )vitamin D(3) levels were all elevated, and serum phosphorus level was decreased, which were all consistent with primary hyperparathyroidism (PHPT). (201)Tl/(99m)Tc subtraction scintigraphy failed to detect any abnormal accumulation in the neck and chest, while (99m)Tc-MIBI scintigraphy demonstrated the focal accumulation of increased radiotracer uptake in the mediastinum only on the early image, but not on the delayed image. Neck and chest computerized tomography scanning showed a small nodule at the retrosternal region, and a selective venous sampling study of the intact PTH suggested PTH production from the nodule. Together with the observation of the early image of (99m)Tc-MIBI scintigraphy, it was diagnosed that the patient had an ectopic parathyroid adenoma. Video-assisted thoracic surgery was performed. A 15-mm diameter mass, visualized by an intravenous infusion of methylene blue, was excited. The histopathology was consistent with the parathyroid adenoma. The adenoma was composed of mainly chief cells and rarely oxyphil cells. The absence of oxyphil cells would explain the lack of (99m)Tc-MIBI retention on late-phase imaging in our case. Even without uptake on the delayed image of (99m)Tc-MIBI scintigram, the early image was available for the localization of an ectopic parathyroid adenoma.

Purification and characterization of paralytic shellfish toxin transforming enzyme from Mactra chinensis.

A carbamoylase, which catalyzes hydrolysis of the carbamoyl (or N-sulfocarbamoyl) moiety of paralytic shellfish toxins, was purified from the digestive glands of the Japanese clam Mactra chinensis. Using five steps of column chromatography, 290 microg of Carbamoylase I showing homogeneity on SDS-PAGE was obtained. Carbamoylase I was revealed to be a glycoprotein, having estimated molecular weight of 190 kDa. Observation of single band equivalent to 94 kDa on SDS-PAGE under reducing conditions suggested it to be a homodimer. The optimal temperature and pH were 20 degrees C and 7.0. Carbamoylase I did not require a divalent cation and its activity was inhibited by the serine proteinase inhibitors, benzenesulfonyl fluoride and 4-(2-aminoethyl)-benzenesulfonyl fluoride. Carbamoylase I hydrolyzed both carbamate and N-sulfocarbamate toxins. The presence or absence of a hydroxyl moiety at the N-1 position of the substrate toxins did not significantly alter the reaction rate, but the stereochemistry of sulfate esters at C-11 greatly affected it. The K(m) was 3.02 microM for saxitoxin as a substrate. Nineteen amino acids of the N-terminal sequence were identified by the Edman method. MALDI-TOF-MS/MS spectra of (18)O-labeled tryptic peptides indicated the possible internal amino acid sequences of five peptides.