bluuebunny/crossref_metadata_2025_split huggingface dataset:
Unusual Na Storage Behavior of Ordered Mesoporous Carbon on Ether-Based Electrolyte System
Authors: Kim Yunok , Lew Gil Hwan , Oh Woong , Jeong Mihee , Jin Xing , Kim JI Man , Yoon Won-Sub 
Published: February 2020

The Li-ion battery (LIB) market increases rapidly due to the development of portable electronic devices and energy storage systems (ESSs). By increasing the demand for commercialization of scale-up LIB, large amounts of accumulated lithium resources will be consumed in the near future. Recently, Na-ion battery (NIB) system is considered as an alternative to LIB system because sodium resources are abundant and distributed around the world as well as sodium storage mechanism is similar to that of lithium. In contrast to LIB, graphite is not suitable for NIB anode material due to the small interlayer for large ionic radius of Na+ ion. Therefore, previous studies have investigated that non-graphitic carbon materials can deliver reversible Na+ ion insertion and extraction with initial capacity up to 300mAh g-1, however, the cycle stability of non-graphitic carbon materials is very poor.
Ordered mesoporous carbon (OMC) has the advantage of large surface area due to the development of nano-sized pores inside a micron-sized particle, which results in large electrode/electrolyte interface, easy penetration of electrolyte, and fast diffusion of Li+/Na+ ion. The ordered hexagonal structure of the OMC was formed as an inverse replica of a mesoporous silica SBA-15 structure and started from phenanthrene as a carbon source. In carbonate-based electrolyte system, the first and second discharge capacities of the OMC were 800 mAh g-1 and 350 mAh g-1 at a current density of 100 mA g-1, respectively, which means a large irreversible capacity loss, whereas in ether-based electrolyte system, the first irreversible capacity decreased considerably, implying an enhanced reaction reversibility. Even though the first discharge capacity in the ether-based electrolyte was about 200 mAh g-1, the capacity in the ether-based electrolyte increased during repeated cycling and achieved 350 mAh g-1 after 100 cycles. In contrast, the cycle retention in carbonate-based electrolyte degraded down to 200mAh g-1 consistently during 100 cycles.
To elucidate the electrolyte system-dependent Na+ storage of the OMC, various electrochemical analyses and synchrotron X-ray based techniques were performed using two-type electrolytes of 1 M NaPF6 in EC/DMC=1/1 and 1 M NaPF6 in DEG/DME.
Sulfides Electrolytes for All Solid State Metal Ion Batteries
Authors: Chen Hailong , McDaniel Malte , Xiong Shan , Wang Hai 
Published: February 2020

Replacing the organic, liquid, flammable electrolytes in conventional lithium ion batteries with inorganic, solid, nonflammable electrolytes can potentially eliminate the fire hazard of the batteries. Solid state batteries may also use simpler and lower cost manufacturing methods than what has been used for conventional lithium ion batteries. However, the development of solid state batteries previously has been limited by the low ionic conductivity of the solid electrolytes. Recently discovered superfast ionic conductors such as Li10GeP2S12 (LGPS) and Li10SnP2S12have demonstrated solid state electrolyte can have comparable or even higher Li ion conductivity than commercial liquid electrolyte. All solid state batteries with using sulfide electrolytes has also been reported by Kanno et al. with very high rates at room temperature and elevated temperatures.
Currently many sulfides showed high Li and Na conductivities than their oxides counter parts. However, in general, sulfides are much less explored than oxides. Novel sulfides with good ionic conductivities may exist in the previously unexplored regions in the phase diagrams. We aim to design and discover novel sulfide Li and Na ionic conductors by systematically exploring a number of selected Na(Li)-M1-(M2)-S ternary and quaternary phase diagrams combining conventional solid state synthesis and variable temperature in situ XRD for synthesis. In this work, we report the synthesis, in situ XRD study and electrochemical testing of several sodium tin sulfides as solid electrolyte for sodium ion batteries. Na4SnS4 was synthesized by solid state reactions in pure phase. In situ XRD study on the synthesis process were used to reveal the formation mechanism of this compound. The Na ion conductivity of this compound at various temperatures was measured by using electrochemical impedance spectroscopy (EIS). The relationship between the conductivity and synthesis condition and starting materials are discussed. Several other sulfides were also successfully synthesized in pure phase. Their conductivities were also measured and compared with Na4SnS4. These novel Na ion conductors provide new promise for developing high performance all solid state sodium ion batteries.
Figure caption:
Figure 1. in situ X-ray diffraction patterns of the solid state synthesis process of Na4SnS4sample.
Reference:[1] Y. Kato, S. Hori, T. Saito, K. Suzuki, M. Hirayama, A. Mitsui, M. Yonemura, H. Iba, R. Kanno, High-power all-solid-state batteries using sulfide superionic conductors, Nature Energy, (2016) 16030.

Figure 1
A Photodetector Based on a Conjugated Polymer and PbS Colloidal Quantum Dots
Authors: Ghomian Taher , Choi Jin-Woo 
Published: February 2020

This work presents the development of a light intensity sensor based using colloidal PbS quantum dots. A simple fabrication method at low cost makes the developed sensor suitable for light detection applications. Photodetectors based on quantum dots have various advantages compared to solid-state photodetectors. The reported advantages include ease of fabrication, narrow and tunable spectral response, large sensing area, reduced dark current, and high sensitivity [1, 2]. Solution-based fabrication makes the whole process simple and cost efficient.
The structure of the sensor in this work is shown in the figure having a light sensitive composite sandwiched by two electrodes of which one is usually a transparent electrode made of indium tin oxide (ITO). For validation, we employed PbS colloidal quantum dots and poly(2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene) or MEH-PPV to form the light sensitive composite [3]. In the light sensitive composite, a charge separation occurs by a photon generating a neutral exciton at the interface of the conjugated polymer and the quantum dots.
We started with an ITO coated glass substrate. The light sensitive composite made of MEH-PPV and colloidal quantum dots was then cast on top by spin coating. For the other electric contact, an aluminum layer was deposited by physical vapor deposition. The fabricated photodetector shows a promising sensitivity to incident light, and further characterization is currently underway. Since the entire structure of the photodetector is simple and the entire process can be done with low thermal budget, the photodetector can also be formed on a flexible substrate.
References
[1] P. V. Kamat, “Quantum dot solar cells. Semiconductor nanocrystals as light harvesters,” The Journal of Physical Chemistry C, vol. 112, pp. 18737-18753, 2008.
[2] I. Robel, V. Subramanian, M. Kuno, and P. V. Kamat, “Quantum dot solar cells. Harvesting light energy with CdSe nanocrystals molecularly linked to mesoscopic TiO2 films,” Journal of the American Chemical Society, vol. 128, pp. 2385-2393, 2006.
[3] S. A. Mcdonald, G. Konstantatos, S. Zhang, P. W. Cyr, E. J. Klem, L. Levina, and E. H. Sargent, “Solution-processed PbS quantum dot infrared photodetectors and photovoltaics,” Nature Materials, vol 4, pp.138-142, 2005.

Figure 1
Fabrication of an MWCNT-Reinforced Tin Anode for Use in Lithium Ion Batteries By Electrodeposition in Sulfuric Acid
Authors: Matsunaga Kouki , Shimizu Masahiro , Arai Susumu 
Published: February 2020

Introduction

Lithium ion batteries employing graphite as the anode active material exhibit higher energy densities than conventional rechargeable batteries, although increasing the capacity of these devices will require the use of alternative anode compounds. Since tin (Sn) has a higher theoretical capacity (991 mAh g-1) than graphite (372 mAh g-1), it has been considered for this role. However, Sn tends to fall off the current collector during charge-discharge cycles due to significant volume variations, degrading the battery performance. One approach to avoiding this problem is to anchor the Sn layer to an underlying copper (Cu) layer using fibrous materials. We have already reported the excellent charge-discharge characteristics of a new tin anode reinforced with multiwalled carbon nanotubes (MWCNTs), formed by a combination of Cu/MWCNT composite plating and electroless tin plating.
In this study, we examined a new fabrication process for the MWCNT-reinforced tin anode structure based on tin electrodeposition using a sulfuric acid bath, and explored the correlation between the new negative electrode structure and its electrochemical characteristics.

Experimental

A Cu/MWCNT composite plating bath (0.85 M CuSO4
●5H2O + 0.55 M H2SO4 + MWCNT + polyacrylic acid), and a tin plating bath (0.2 M SnSO4 + 0.5 M H2SO4 + additive) were prepared. Using these baths, a Cu/MWCNT film was applied to a pure copper plate and tin was subsequently electrodeposited on the Cu/MWCNT film, resulting in the MWCNT-reinforced tin anode structure. For comparison purposes, tin was also electrodeposited on a pure copper plate. Electroplating was carried out under galvanostatic conditions at 25 °C.
The microstructure of the new tin anode was examined by field emission scanning electron microscopy (FE-SEM). The phase structure of the deposits was analyzed by X-ray diffraction (XRD).
Electrochemical studies of the tin-based anodes were carried out using coin cells (2032) assembled in an Ar-filled glove box. Each coin cell consisted of a lithium foil counter and reference electrodes and a tin-based anode as the working electrode. The electrolyte was 1 M LiPF6in a mixture of ethylene carbonate (EC) and diethyl carbonate (DEC) (1:1 vol%). Cycling tests were performed at a constant temperature of 25 °C.

Results and Discussion

Figure 1 shows a surface SEM image of the tin anode fabricated by the new process. MWCNTs are seen to be uniformly dispersed over the Sn layer. Figure 2 presents a cross-sectional SEM image of the tin anode. It can be seen that MWCNTs connect the Sn and Cu layers. No defects, such as voids or cracks, are observed between the two layers.
The electrochemical characteristics of the tin anode will be discussed in detail during the presentation.

References

1) S. Arai and R. Fukuoka, J. Appl. Electrochem., 46, 331 (2016).

Figure 1
Fabrication and Characterization of Composite Membranes for Vanadium Redox Flow Batteries
Authors: Park Su Mi , Lee So Hee , Kim Haekyoung 
Published: February 2020

Vanadium redox flow battery (VRFB) is a form of rechargeable battery which converts chemical energy directly to electrical energy. VRFB have been investigated for their potential utility as large energy storage systems due to their advantageous performances in terms of long cycle life, high energy efficiency, low cost, and flexible design. Catholyte and anolyte, in the negative and positive half-cells respectively, containing dissolved electro-active species flows through an electrochemical cell and generate cell potential. During operation of VRFB, ion-exchange membrane separate the catholyte and anolyte for preventing cross contamination which is induced by diffusion of different ions across from one half-cell to the other, will result in self-discharge and thus the loss of the chemical energy. Therefore, the ion-exchange is one of the most important components in the VRFB system and it should have low permeability and high ionic conductivity. A perfluorosulfonic acid (PSFA) membrane, such as Nafion (DuPont) for example, is the most commonly used membrane due to its high chemical-mechanical stability and high ionic conductivity. However, Nafion is permeable to electrolyte and expensive. The major focus is to modify the water-filled channels of the Nafion membrane by introducing non-conducting metal oxides. For example, SiO2 and TiO2 have been used to prepare Nafion-metal oxide composite membranes. The inorganic fillers, such as SiO2, act as a physical barrier for diffusing vanadium cation through the membrane channels, while allowing proton transport.
In this study, composite membranes based on Nafion and nanoclay were fabricated and characterized in terms of ionic conductivity and permeability. The ionic conductivity was measured with four point prove method and the permeability was measured with UV spectroscopy. For fabrication of the composite membranes, nanoclay solution was blended with Nafion solution according to the nanoclay composition in the dry membrane (5, 3 and 1 wt.% : identified as NF-NC 5, 3 or 1 wt.%, respectively). Ionic conductivity and the permeability were decreased with the increasing of the nanoclay composition in the composite membrane. With performances of VRFBs, the energy efficiencies of VRFBs and optimum composition of the composite membrane will be discussed.
Operando Observation of Cobalt Catalysts for Oxygen Evolution By Electrochemical XAFS Technique Using Soft X-Ray
Authors: Mitsutomi Yosuke , Yoshida Masaaki , Nagasaka Masanari , Yuzawa Hayato , Kosugi Nobuhiro , Kondoh Hiroshi 
Published: February 2020

Photoelectrochemical water splitting using solar energy is an attractive candidate to produce hydrogen gas from water. This system consists of two half reactions of hydrogen and oxygen evolutions. Among them, the rate of oxygen evolution is generally slower than that of hydrogen evolution. Thus, the development of efficient oxygen evolution catalyst has been required toward highly active energy conversion system. Recently, a cobalt-borate electrodeposited from a dilute Co2+ solution in a borate-buffered electrolyte (Co-Bi) was reported to function as an efficient electrocatalyst for oxygen evolution reaction [1]. The structural information was investigated by X-ray pair distribution function (PDF), which indicates that Co-Bi catalyst is formed by coherent domains consisting of 3−4 nm cobaltate clusters with up to three layers [1]. However, the correlation between structure and activity is still unclear. Therefore, in this study, the Co-Bi catalyst was investigated by in-situ O K-edge XAFS measurements under potential control conditions.
Electrochemical XAFS measurements with transmission mode using soft X-rays were performed at BL3U in the UVSOR Synchrotron, according to the previous works [2]. A home-made electrochemical cell was used with Au/Cr/SiC thin film substrates as working electrodes, a Pt mesh counter electrode, and a Ag/AgCl (saturated KCl) reference electrode. Co-Bi catalyst was prepared on the Au/Cr/SiC working electrode at 1.0 V in 0.1 M potassium borate (K-Bi) electrolyte containing 0.5 mM Co(NO3)2.
Figure 1 shows the linear sweep voltammograms of bare and Co-Bi-modified Au electrodes in 0.1 M K-Bi electrolyte. The current density of oxygen evolution reaction for Co-Bi-modified electrode was higher than that for bare Au electrode, which exhibits that Co-Bi can function as an efficient oxygen evolution catalyst. Figure 2 shows the O K-edge XAFS spectra for Co-Bi catalyst at 0.9 and 0.0 V in 0.1 M K-Bi. Two absorption peaks assigned to the oxygen species in the CoOOH were observed around 530 and 531 eV. Meanwhile, an absorption peak of the lower energy was detected around 529 eV for the spectrum of Co-Bi at 0.9 V. Empirically, the O K-edge absorption peak position shifts to lower energies with increasing the formal oxidation state. Thus, the lowest energy absorption peak for Co-Bi sample at 0.9 V is probably attributed to Co4+ species, and the formation of the Co4+ is likely to contribute to oxygen evolution reaction. In this presentation, we will discuss more detailed assignment for the XAFS spectra and relationship with the activity of oxygen evolution reaction.
[1] D. G. Nocera et al., J. Am. Chem. Soc. 135 (2013) 6403.
[2] M. Nagasaka et al., J. Electron. Spectrosc. Relat. Phenom. 177 (2010) 130., J. Phys. Chem. C 117 (2013) 16343., Rev. Sci. Instrum. 85 (2014) 104105.

Figure 1
Effect of Dispersion Methods on Oxygen Reduction and Ammonia Oxidation Reactions for Multiwall Carbon Nanotube Supported Pt
Authors: Harada Yuya , Ooya Kayato , Shirasaka Ryo , Shiroishi Hidenobu , Nishitani-Gamo Mikka , Nagai Keiji 
Published: February 2020

When the activity of a catalyst was estimated by a rotating ring disk electrode (RRDE) method, the modified glassy carbon (GC) electrode was generally fabricated by casting catalyst suspension prepared by various methods, followed by drying under various conditions. There are many preparation methods for catalyst suspension. And it is known that the dispersivity of the catalyst on the GC electrode, which affects collection efficiency of H2O2as well as current density, depends on the above methods and conditions. Since an optimum method and condition often varies with the kinds of catalysts, researchers have to find them. However, it is difficult to evaluate the dispersivity on the electrode and reproducibility quantitatively. In this study, the dispersivity of multi wall carbon nanotube supported Pt catalyst (Pt/MWCNT) on the modified electrode prepared by various methods was estimated by digitizing height data of the electrode using a laser surface roughness meter.
30 wt% Pt/MWCNT (Pt particle size: 4.26 ± 0.09 nm) catalyst was synthesized by a microwave polyol process. 2 mg/mL of 30 wt% Pt/MWCNT-0.1 wt% various alcohol (MeOH, EtOH, and 2-PrOH) suspensions were prepared by ultrasonication for 10 min. 10 μL of the suspensions cast on a GC electrode, and the electrode allowed to dry by three method: 1) in air for 1 h (abbreviated as Air), 2) in saturated ethanol vapor pressure for 1 h (EV), and 3) in air with infrared irradiation for 10 min at 60 °C (IR). The samples were named as [solvent] – [drying method]. The modified electrodes were observed with a digital microscope (MSP-3080, PANRICO). And the surface height data of the modified electrodes were digitized with a laser surface roughness meter (SV-C4500 CNC, Mitutoyo), and the data were analyzed by a software "Roughness Analyzer" developed by our laboratory. The software detects secondary particles of the catalyst (clusters) on the electrode and the user can obtain the volumes, the average height, and the area of the clusters as well as the distribution of the catalysts from the center of the electrode.
Fig. 1 (a) shows cumulative cluster volume distribution for MeOH–Air, 2-PrOH-Air and EtOH–EV. The electrode surface prepared by the EtOH-EV method had the clusters up to 1.9×10-3
mm3, whereas those prepared by MeOH-Air and EtOH-EV had the clusters up to 6.7×10-4 mm3 and 1.9×10-3
mm3, respectively, suggesting that the EtOH-EV method tend to be aggregated to produce large secondary particles.
Fig. 1 (b) shows the average cluster heights of the samples. The standard deviation of the average cluster height for 2-PrOH-Air was the smallest of the three methods, indicating that the 2-PrOH-Air method is the most reproducible casting method of the three methods. Some quantification methods will be reported in the meeting.

Figure 1
Dynamic Transformations of Layered Compounds at Full Delithiation Due to Surface Triggered Reactions
Authors: Faenza Nicholas , Mukherjee Pinaki , Sallis Shawn , Pereira Nathalie , Das Hena , Ceder Gerbrand , Piper Louis F.J. , Cosandey Frederic , Amatucci Glenn G 
Published: February 2020

Modern lithium-ion batteries using layered R-3m intercalation positive electrodes have insufficient practical capacity and energy density to meet the future demands of portable electronics, and electric vehicles. If the complete, reversible, theoretical capacity upon full delithiation of these materials could be accessed while retaining high voltages and a narrow voltage swing, a significant advancement in energy density could be achieved. Although, full delithiation of most layered compounds has been known for decades, the failure modes that prevent practical cycle life are still in question.

This paper focuses on a model R-3m layered compound of Li[Ni0.8Co0.15Al0.05]O2 (NCA) and explores the failure modes at the surface and subsurface utilizing a unique combination of operando microcalorimetry / electrochemical impedance spectroscopy , high resolution transmission electron microscopy, electron energy loss spectroscopy, x-ray photo electron microscopy, x-ray absorption spectroscopy, hard x-ray photoelectron spectroscopy, and x-ray diffraction. The development of operando microcalorimetry (isothermal and DSC mode) enables simultaneous measurement of the heat flux, current, and impedance, while controlling the environmental temperature and the electrochemical testing parameters. Although surface changes are known in NCA, we explore the evolution of the surface and subsurface at extreme levels of delithiation and take efforts to isolate the failure modes induced by cycling vs. static transitions. The progression of the surface and subsurface structure and chemistry is found to be much more complex than previously identified and has direct implications to impedance development throughout the electrochemical cell. Specific attention was given to surface catalyzed triggers of the surface and subsurface failure modes, evolution of surface and subsurface phase transformations, and comments on the broad applicability of our findings to other layered compounds.
Metal-Free Nanocomposite Materials Based on Carbon Nitride Nanofibers and Graphene Oxide for Electrochemical Applications: Supercapacitors & Catalysts for Oxygen Reduction Reaction (ORR)
Authors: Movil-Cabrera Omar , Staser John A , Rodriguez-Silva Allen Armando 
Published: February 2020

Electrochemical devices such as fuel cells and supercapacitors have recently been proposed as alternatives to remedy issues related to the scarcity of fossil fuels and climate change. However, it is necessary to reduce the costs and enhance the performance of these devices to compete economically with fossil fuel-based technology. This work is mainly focused on the development of new metal-free nanomaterials based on carbon nitride nanofibers (CNNF) and reduced graphene oxide (RGO) for the application mentioned above. More specifically, RGO sheets were decorated with CNNF in order to create 3-D porous materials with enhanced redox ability, charge transfer and chemical stability. RGO was obtained by the reduction of graphene oxide (GO) with hydrazine, whereas CNNF was obtained via polymerization of modified melamine. The fabricated materials were characterized via XRD, FTIR, UV-vis, TGA, XPS, SEM, TEM, cyclic voltammetry and galvanostatic charge/discharge. In addition, the effects of RGO/CNNF ratio and electrolyte nature on the electrochemical performance of these nanocomposite materials was evaluated.
[Office1]Should this be “reduced”?