bluuebunny/crossref_metadata_2025_split huggingface dataset:
Amorphous Soft Carbon Coated Graphite As Anode Material for Lithium Ion Battery
Authors: Kim Byung-Ryang , Hong Young Kyu , Kang Hye-Joung , Choi Nak-Mo , Shin Sang-Yong , Lee Jong-hyuk , Kim Sun Ah , Lee Ki-Tae , Shin Jin-Koog 
Published: February 2020

The natural graphite was used without a purification process and processing step that results in the folding of the graphite fragments into small spheres. It is well known that spherically shaped anode material is preferable as a means of improving the anode characteristics due to its high tapping density [1]. To reduce movement of impurities and side reaction with electrolyte impurities [2], the amorphous soft carbon was coated on the spherical graphite surface.
In this study, we report the characteristics of anode which is made from the amorphous soft carbon coated natural graphite and charge-discharge behavior of half cells. The electrodes were prepared by pasting an aqueous slurry with styrene butadiene rubber (SBR), and carboxymethyl cellulose (CMC).
The charge–discharge tests were performed in CR2032 coin cell. Half cells consisted of the working electrode to be studied, Li metal as the counter electrode, and Celgard 2400 separator. 1 M LiPF6in ethylene carbonate and dimethyl carbonate (1:1 by volume) was used to electrolyte. Anode half-cells were tested between 1.5 V and 5 mV at a C-rate of 0.1 C. Microstructure of the amorphous soft carbon coating layer on graphite particle was observed using TEM to examine the cycle stability. Fig. 1 shows structural stability of carbon layer after charge-discharge cycles and thickness of carbon layer was about 50nm. Fig. 2 shows the charge(Li insertion)-discharge(Li extraction) curves of the amorphous soft carbon coating sample versus non-coating sample for the first cycle, charged in CC-CV mode and discharged in CC mode. The discharge capacity obtained at carbon coated sample is about 330 mAh/g and the columbic efficiency is about 90 %.
This research was financially supported by the Ministry of Trade, Industry and Energy(MOTIE) and Korea Institute for Advancement of Technology(KIAT) through the Promoting Regional specialized Industry

References

[1] Y. Chen, G.X. Wang, J.P. Tian, K. Konstantinov, H.K. Liu, Electrochim. Acta 50 (2004) 435–441.
[2] C. Wang, X. Zhang, A.J. Appleby, X. Chen, F.E. Little, J. Power Sources 112 (2002) 98-104.
Electrochemical Characteristics of (Li0.33La0.56)1.005Ti0.99Al0.01O3 Ceramic As a Solid Electrolyte for Lithium-Oxygen Batteries
Authors: Le Hang T.T. , Park Chan-Jin 
Published: February 2020

To date, lithium lanthanum titanate (LLTO) of the nominal formula Li3xLa2/3-x
1/3-2xTiO3 with perovskite structure have been considered to be promising solid electrolyte materials for lithium batteries due to a numerous outstanding advantages such as: (i) a high lithium conductivity at room temperature, (ii) a high lithium diffusion coefficient, (iii) a low electronic conductivity, (iv) an electrochemical window larger than 4 V. However, the LLTO materials have also suffered from a few disadvantages such as insufficient total conductivity due to the large grain boundary resistance and difficulty in controlling Li+ content and Li+ conductivity of the materials especially after exposure to high annealing temperature. In addition, when LLTO contacts directly with Li metal, Ti4+ in LLTO can be reduced into Ti3+ by metallic Li leading to increase in the electronic conductivity of LLTO.
In this study, we focused on enhancement of the total conductivity of LLTO ceramics by improving the bulk conductivity using Al3+ dopant and the grain boundary conductivity using excess Li2O. Al-doped LLTO powders of (Li0.33La0.56)1.005Ti0.99Al0.01O3 with a various amount of 10-35% excess Li2O in stoichiometry were synthesized using sol-gel modified Pechini method, and then pelletized and sintered at 1350 oC.
The XRD patterns on the synthesized powders were compared and matched with Li0.33La0.56TiO3 (PDF#01-087-0935; Tetragonal) confirming pure tetragonal crystalline structure (P4/mmm space group) of perovskite phase without secondary phases. With the amount of excess Li2O 15%, crystal grains grew significantly. The largest grain size reached 100 m. The grains with typical rectangle shape were connected together closely.
The ionic conductivity of the obtained materials was measured using electrochemical impedance spectroscopy (EIS). Obviously, the bulk and grain boundary conductivities increased with the addition of excess Li2O. A maximum total conductivity of 3.17 10-4 S/cm was achieved for the sample with 20% excess Li2O, which is 4 times higher than that of the sample without excess Li2O. The high conductivity of the sample with 20 % excess Li2O is attributed to the minimum total activation energy of 0.358 eV and the somewhat large crystal grain size, 50 m.
To realize the application of LLTO materials as a solid electrolyte separator in Li-air batteries, a lithium phosphorous oxynitride (LIPON) interlayer fabricated using sputtering method was employed to prevent direct contact between Li metal and LLTO. The Li-O2 cells employing the LLTO ceramic electrolytes were tested in galvanostatic mode. Initial results showed that the Li-O2 cell employing LLTO electrolyte layer exhibited the satisfactory performance.
Diverse Pyrochlore Materials for Oxygen Reduction and Evolution Reaction in Alkaline Medium
Authors: Manivannan A. , Abreu-Sepulveda Maria , Quesnel David J 
Published: February 2020

The oxygen reduction and evolution reactions (ORR and OER) have proven to be the limiting factors on the development of rechargeable metal-air batteries. Numerous research work has been carried out on the improvement of cathode technologies in order to reduce the voltage loss associated with the oxygen reactions. ORR and OER have proven to be a catalytic electrochemical process, and thus, the catalytic material in the cathode plays an important role in the performance of such batteries.
Current catalysts used for air cathodes can be classified into noble metals and metal alloys, carbons, and transition metal oxides. Platinum and platinum-based electrodes such as Pt-nanopartices dispersed on a carbon support have been the primary choice to catalyze the ORR because of their known superior electrocatalytic activity. Other Pt-based alloys, Pt3M (where M can be Fe, Co among others) have also shown superior ORR activities. Carbonaceous materials have also emerged as an alternative for metal-free electrodes. Some of the best performing carbonaceous materials are vertically aligned nitrogen doped carbon nanotubes (VA-NCNT), nitrogen doped porous carbons and graphenes which have exhibit comparable activity to that of the Pt-based electrodes [1]. However, in order to fully develop the applicability of metal-air batteries, bifunctional electrodes are essential.
In the present research, a group of pyrochlore materials, A2B2O7-δOδ, have being synthesized, characterized and studied for bifunctional oxygen electrode applications. Among the characteristics that make pyrochlores attractive for air cathodes, is the unusual framework containing oxygen vacancy ordering. Lanthanum, lead and bismuth-based pyrochlores has been synthesized by the well-known Pechini, solid state, and stearic acid methods.
All the samples were characterized by XRD for phase analysis, and electrochemical performance has been investigated by means of cyclic voltammetry. The effect of dopant concentration on the electronic conductivity as well as oxygen activity will be presented.

Acknowledgements

This work is supported by the IGERT-NSF fellowship and partially funded by the US Dept. of Energy/NETL, Oak Ridge Institute for Science and Education (ORISE) fellowship.

References

[1] Y. Lu, z. Xu, H.A. Gasteiger, S. Chen, K. Hamad-Schifferli, Y. Shao-Horn, J. Am. Chem. Soc. 2010, 132, 12170-12171.
[2] D. Geng, et al. Energy Environ. Sci., 2011, 4, 760-764.
Electrode Materials for Lithium-Ion Batteries with Surface Modification by Advanced Hybrid Polymers
Authors: Bittner Andreas , Guntow Uwe , Schulz Jochen , Olsowski Birke-Elisabeth , Lorrmann Henning , Sextl Gerhard 
Published: February 2020

The main challenges in the development of lithium-ion batteries for automotive applications are the improvement of energy density and cycling stability. For this purpose the electrodes have to be protected from irreversible reactions with the electrolyte which occur especially at high operating voltages.
A very promising approach to prevent this degradation process is the surface coating of electrode materials with protective layers. To achieve these protective layers a new nanosized multifunctional coating was designed. The coating (shown in Fig. 1) consists of an inorganic-organic hybrid polymer, named ORMOCER® (trademark of Fraunhofer ISC). Due to its specific design of inorganic and organic networks on the molecular level, several remarkable material properties could be generated. These properties include an electrochemical stability up to at least 5.0 V. This enables the stabilization of high-voltage materials like LiMn1.6Ni0.4O4. The hybrid polymer also displays a high elasticity, which provides a long-term mechanical stability of the coating during cycling. Moreover, the coating material has a good ionic conductivity of 10-4 S/cm to facilitate the ion transport into the electrode material.
Based on these properties, the new core-shell nanocomposite approach can be applied to various electrode materials to improve their cycling performance, especially on materials with high operating voltages to achieve a high energy density of the batteries. Fig. 2 shows such an improvement, expressed in a significantly reduced capacity fade of coated LiMn1.6Ni0.4O4 electrodes during cycling.
This work was supported by the Bavarian State Ministry of Economics, Infrastructure, Traffic and Technology.
Investigation of the Active Thickness of Solid Oxide Fuel Cell Cathode
Authors: Zheng Keqing , Ni Meng 
Published: February 2020

In solid oxide fuel cell (SOFC) electrode, electrochemical reaction only occurs in a narrow region near the interface of electrode and electrolyte, which is regarded as the “active thickness”. However, as a key parameter for SOFC electrode microstructure design and optimization, the active thickness of SOFC cathode reported by different research groups vary significantly (from 13 μm [1] to 253 μm [2]) due to different measuring conditions or simulation assumptions.
In this study, a detailed SOFC model is developed, in which the dusty gas model (DGM), Ohm’s law and the concentration related Butler-Volmer equation are used to describe the gas diffusion in pores, ion and electron conduction in electrolyte and electrodes, and electrochemical reaction kinetics, respectively. The effective ionic conductivity, electronic conductivity and the TPB length are calculated with the percolation theory and coordinate number theory [3]. Current density distribution in cathode is investigated under various operating conditions and 99% total current density is used as the indicator of the active thickness. This work could provide useful information for SOFC cathode microstructure optimization and for performance enhancement.

Keywords: Solid oxide fuel cell; Cathode thickness; Triple phase boundary length
[1] Lu, Z., Hardy, J. S., Templeton, J. W., & Stevenson, J. W. (2012).Extended reaction zone of La0.6Sr0. 4Co0.2Fe0. 8O3 cathode for solid oxide fuel cell. Journal of Power Sources, 198: 90-94.
[2] Jiang, Z. Y., Xia, C. R., & Chen, F. L. (2010). Efficient thickness of solid oxide fuel cell composite electrode. Chinese Journal of Chemical Physics, 23(2), 217.
[3] Chen, D., Bi, W., Kong, W., & Lin, Z. (2010). Combined micro-scale and macro-scale modeling of the composite electrode of a solid oxide fuel cell. Journal of Power Sources, 195(19), 6598-6610.
Infrared Spectroscopy of Thin Organic Films Adsorbed at a Gold Electrode Surface
Authors: Lipkowski Jacek 
Published: February 2020

This lecture will review our research involving IR spectroscopy at the solid –liquid interface. After a brief review of basic principles of IR spectroscopy and the laws of reflection of light at interfaces, three methods of Infrared Reflection Absorption Spectroscopy (IRRAS) will be described. The first is subtractively normalized interfacial Fourier transform infrared spectroscopy (SNIFTIRS) or in short potential difference IR spectroscopy. This technique finds application to study reversible adsorption of soluble molecules at electrode surfaces. The methods of optimisation of the SNIFTIRS experiment will be discussed. Its application will be illustrated by the case of adsorption of a soluble surfactant such as sodium dodecyl sulphate (SDS) at a gold electrode surface.1 The second technique to measure IR spectra at interfaces is the photon polarization modulation infrared reflection absorption spectroscopy (PM IRRAS). This technique is used to study films of insoluble molecules a various interfaces. I will discuss application of this technique to study model biological membranes supported at a gold electrode surface.2 The third technique is the surface enhanced infrared reflection absorption spectroscopy (SEIRAS). It is performed using attenuated total internal reflection (ATR) element covered by nanoparticles of gold. The intensity of the IR signal is then enhanced by a factor of 100. In addition, since the film of metal nanoparticles is conductive it is used to study phenomena at electrified interfaces. I will describe application of this technique to study structure of water in model biological membrane supported at a gold electrode surface.3 I will emphasize complementarity of SEIRAS and PMIRRAS in application to bio-electrochemical research.
Literature
1.Jay Leitch, John Collins, K. Andreas Friedrich, Ulrich Stimming, John R. Dutcher, Jacek Lipkowski “Infrared Studies of the Potential Controlled Adsorption of Sodium Dodecyl Sulfate at the Au(111) Electrode Surface”, Langmuir,
2012,28,2455-2464.
2. Jacek Lipkowski, “Building model biomimetic membrane at a gold electrode surface”, Phys. Chem. Chem. Phys., 2010,12,13874-13887.
3. Taro Uchida, Masatoshi Osawa and Jacek Lipkowski, “SEIRAS studies of water structure at the gold electrode surface in the presence of supported lipid bilayer”, J.Electroanal.Chem. DOI:10.1016/j.jelechem.2013.10.015
In-Situ Surface-Enhanced Raman Scattering Observation of Intermediate Species at Plasmon-Induced Water Oxidation Process Using Au Nanostructures on Titanium Oxide Single Crystal
Authors: Suzuki Kentaro , Nagasawa Fumika , Yasuda Satoshi , Murakoshi Kei 
Published: February 2020

Recent attempts to use localized surface plasmon resonance (LSPR) for photoexcitation of molecules suggests the possibility to modify the excitation processes and the selection rule of electrons [1, 2]. Among several choices of the applications of LSPR, the system of Au-nanostructured titanium dioxide (TiO2) is one of promising approaches for plasmon-enhanced photoenergy conversion under illumination of visible and near infrared light . It has been suggested that photo-induced electron injection from the Au structure into the TiO2 conduction band occurs by localized surface plasmons excitation. In this system, Au-nanostructured TiO2 enabled efficient water oxidation owing to the excitation of multiple electrons and holes generated by near-infrared light, and the evolution of O2 via four-electron oxidation of water. In this work, size-controlled Au-nanostructures was fabricated on a TiO2 single crystalline by means of angle-resolved nanosphere lithography (AR-NSL) to measure surface-enhanced Raman scattering (SERS) from the intermediate species at water oxidation process at the electrode-electrolyte interface under near-infrared light irradiation. SERS spectra were obtained from the size-controlled Au nano-dimer (Au-NSL) arrays on a single crystalline TiO2 immersed in 0.1 M NaF solution. For comparison, we also measured SERS spectra from Au-NSL on indium tin oxide (ITO). Observed spectral feature at ~580 cm-1 can be attributed to Au-O stretching vibrations of adsorbates. This wavenumber suggests that adsorbed hydroxide anion with Au-O bonding are produced as intermediate of water oxidation reaction at Au/TiO2. It should be noteworthy that Au-O vibration was observed at more negative potential on Au/TiO2 than that of Au/ITO. Negative shift is attributed to the water oxidation on Au/TiO2 is assisted by electrons and holes generated by plasmon-induced excitation.

References

[1] M. Takase et al., Nature Photonics, 7, 550 (2013).
[2] F. Nagasawa, M. Takase, H. Nabika, K. Murakoshi, "Depolarization of Surface-Enhanced Raman Scattering Photons from a Small Number of Molecules on Metal Surfaces", in Vibrational Spectroscopy at Electrified Interfaces, Eds. C. Korzeniewski, B. Braunschweig and A. Wieckowski: Wiley, NY (2013).
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Oxygen Reduction at Model Pt Single Crystal Surfaces
Authors: Gomez-Marin Ana María , Rizo Ruben , Herrero Enrique , Feliu Juan 
Published: February 2020

Oxygen reduction reaction ORR is the main cathodic problem in electrochemistry and has a deep influence in the development of technologically relevant applications such as fuel cells. It is a complex reaction involving a nonpolar molecule with double bond breaking, 4 electron transfer and 4 O-H bond formation in different scenarios. In the reaction mechanism a possible important role can be played by intermediate peroxo species, after the exchange of only 2 electrons. To enhance reactivity, the understanding of the reaction mechanism at the Pt surfaces is necessary. Models can be used to simplify the complex reaction and from the experimental point of view such models are related to the use of single crystal surfaces with well defined orientations. For Pt(111) electrodes, the activation region is quite narrow despite the high overpotential and the process readily becomes transport controlled. Moreover, in the activation region the platinum electrode is covered by oxygenated species and it is well known the influence that these species can play in the electrode surface order, the surface stability being dependent a structure sensitive process. Possible influence of the surface oxygen-containing species, particularly as intermediates in the ORR is not clearly understood and only has been addressed at Pt(111), which likely is the most stable surface upon oxidation . On the other hand the ORR is structure sensitive, the Pt(111) being the most active in alkaline media [1] in contrast to that observed in acidic solution in which Pt(110) and Pt(hkl) surfaces with small two-dimensional domains are able to reduce oxygen at lower potentials. It is obvious that surface effects play an important role in the activation region as deduced from the marked anion effect that should be less important in alkaline solutions due to the shift in the surface charge on the metal. Another aspect that should be considered is the reactivity of hydrogen peroxide at these platinum surfaces, because its possible role as reaction intermediate [2]. In this respect if the ORR necessarily took place through the peroxo intermediate, a possible strategy would be based in the inhibition of peroxide oxidation while keeping constant ORR.

Acknowledgements

Financial support from MICINN (Spain) through project CTQ2010-16271 and Generalitat Valenciana (PROMETEO/2009/045, FEDER) are greatly acknowledged.

References

1. Rizo R, Herrero E, Feliu JM (2013) Phys Chem Chem Phys 15:15416-15425
2. Gomez-Marin AM, Feliu JM (2013) Chemsuschem 6:1091-1100
Cytochrome C Mutants with Enhanced Capabilities in Multi Layer Arrangements
Authors: Weber Dennis , Turano Paola , Allegrozzi Marco , Lisdat Fred 
Published: February 2020

In the field of biosensors it is important to increase the surface concentration of the selected biological recognition elements for a higher sensitivity. Based on cytochrome c, a small heme containing electron carrier protein from the respiratory chain, fully redox active multi layer assemblies have been developed by using the layer by layer technique, where every immobilized protein contributes to the electron transfer with the electrode. This provides the basis for integrating catalytically active enzymes into the layers, giving the opportunity of tuning the sensitivity by the number of layers deposited. This was shown already e.g. for bilirubin oxidase (BOD) and sulfite oxidase (SOX). However, one limiting factor for the effective coupling of proteins in those multi layer systems is the electron self-exchange rate of the cytochrome c molecules. In order to follow the applied potential but also the enhanced conversion at the embedded enzymes, a rather high exchange rate between the immobilized proteins is necessary.
Based on the hypothesis, that the electron transfer happens via hopping between the heme-centers which are embedded in a protein-pocket that is mainly positively charged at neutral pH, we tried to engineer human cytochrome c mutants with increased electron self exchange rates. By replacing some of the positively charged surface lysines around the heme pocket with uncharged alanines via site directed mutagenesis, repulsion between cytochrome c molecules should be decreased and ease the charge transfer.
Six different mutants have been designed, expressed and evaluated. The electrochemical properties of the cytochrome c mutants have been analyzed by cyclic voltammetry at self assembling mono layers (SAMs) of 11-mercapto-1-undecanol (MU) and 11-mercapto-1-undecanoic acid (MUA) on gold. In a second step cytochrome c mutant multi layers have been prepared and analyzed with respect to different rates of the potential sweep in order to elucidate how the systems can follow the driving force.