bluuebunny/crossref_metadata_2025 huggingface dataset:
Novel Highly Conductive Polymer Electrolytes for Li-Ion Batteries Applications
Authors: Leclere Melody , Mendil-Jakani Hakima , Rannou Patrice , Lyonnard Sandrine , Livi Sebastien , Gebel Gerard , Duchet-Rumeau Jannick , Picard Lionel
Published: February 2020

One of the most important research topics in the field of Li-ion batteries is the substitution of the conventional liquid electrolytes by solid polymer electrolytes for increasing both safety and performances. But another approach concerning the conduction mechanisms of the Li+ has to be envisaged to increase the intrinsic performance of the polymer. Recently, a new approach has been developed by Armand & al [1,2]: they immobilize the anion on a block copolymer using STFSI[i]  monomer for one block.  But the conduction mechanism is still ensured by POE blocks.

In this work we developed a novel class of anionic epoxy polymer electrolytes, with noteable properties (thermotropic liquid crystalline), involving a new mode of Li+ mobility. The thermodynamic encryption given by the nature of different segment of the polymer lead to a self-organization of the polymer (columnar, lamellar, gyroid …). We propose that the anionic sites are thus organized for efficient Li-conduction by a hoping mechanism as presented in the figure below. The synthesis and electrochemical properties of this new crystalline polyelectrolyte were investigated. The preliminary results showed a RT conductivity over 0.1 mS.cm-1.

[i] 4-styrenesulfonyl)(trifluoromethanesulfonyl)imide

[1] Meziane, R; Bonnet, J.P; Courty, M; Djellab, K; Armand, M. Electrochimica Acta
, 2011, 57, 14

[2] Bouchet, R; Maria, S; Meziane, R. ; Aboulaich, A ; Lienafa, L ; Bonnet, J.P ; Phan, T. N. T. ; Bertin, D ; Gigmes, D. ; Devaux, D; Denoyel, R ; Armand, M. Nature Materials, 2013,12,452

Figure 1
Progress Towards Magnesium-Ion Batteries
Authors: Marschilok Amy C , Takeuchi Kenneth J , Takeuchi Esther S
Published: February 2020

The efficient management of energy sources is critical to addressing future global energy demands.  For example, the growing electrical energy storage needs of mobile and stationary devices demonstrate the need for rechargeable batteries with a variety of application-based performance capabilities, including sufficient energy density, appropriate voltage and current capabilities.  One of the most successful and broadly implemented rechargeable battery technologies developed to date is lithium ion.  However, questions regarding the future of using lithium ion technology for large scale applications center on the sustainability and high cost of lithium, especially due to the projected increase in demand for lithium based electrodes used in hybrid and plug in electric vehicles and stationary (grid) storage.

Of the possible alternatives to lithium ion, rechargeable magnesium-ion batteries are an intriguing candidate, and research into the technology has accelerated in recent years.  Magnesium ion technology is promising due to divalent nature of Mg ions, presenting a potential advantage in terms of high volumetric capacity, the high natural earth abundance of magnesium, and higher atmospheric and thermal stability for magnesium metal relative to lithium metal.  

One critical issue impeding progress in this area has been development of a suitable electrolyte-anode interphase which will enable reversible release of Mg2+ ions and reversible charge of Mg based anodes.  A second fundamental challenge is the strong polarization of the small divalent Mg2+, requiring mitigation of the inherently slow ion diffusion associated with magnesium-ion cathodes.  Progress toward viable Mg-ion battery systems will be described in this presentation, including recent achievements in the development of anodes, cathodes, and electrolytes.
Tailoring the Desired Surface Chemistry in Silicon-Based Lithium-Ion Batteries with Electrolyte Additives
Authors: Shi Feifei , Zhao Hui , Komvopoulos Kyriakos , Somorjai Gabor , Ross Philip N
Published: February 2020

The design of safe, high-energy batteries exhibiting prolonged lifetime greatly depends on understanding the surface reactions occurring on the electrode surfaces and the role of the solid electrolyte interphase (SEI) film. Most of the naturally forming SEI films demonstrate undesirable characteristics, such as instability and continuous surface reaction that decrease the capacity of Si-based Li-ion batteries (LIBs). An effective and economic way to modify the surface chemistry in LIBs rather than the Si architecture is by electrolyte additives. The objective of the present study is the examination of the concentration dependence of vinylene carbonate (VC) and fluoroethylene carbonate (FEC) additives on the long-term electrochemical performance of LIBs, as well as the dependence of the SEI formation mechanism on the concentration of the VC and FEC additives.

A significant improvement in the cycling performance of Si electrodes can be achieved under operation conditions of optimum VC and FEC concentration. To better understand the additive concentration effect, the reduction mechanisms of VC and FEC were investigated for both Si nanoparticle and Si(100) single crystal working electrodes. Ex-situ ATR-FTIR spectra of Si electrodes for 5% VC additive show a broad peak at a higher wavenumber (1831 cm–1) compared to the EC residual electrolyte (1799 and 1769 cm–1) (Fig. 1). Based on synthesized poly-VC standard spectra, the VC additive reduction compound is assigned to poly-VC or its oligomer, which is consistent with previous reports. However, for Si electrode and FEC additive, the original C=O stretch (1829 and 1802 cm–1) disappears or shifts to a lower wavenumber. The exact reduction product of FEC degradation has not been confirmed yet due to the lack of significant features other than the residual electrolyte. However, it is clear that FEC follows a different reduction path than VC. The reduction path of VC is polymerization with the reduction product remaining a “ring” structure (the C=O peak shifts to a higher wavenumber), whereas the reduction path of FEC is similar to that of ethylene carbonate (EC), leading to a reduction product of open “ring” structure, similar to that produced from EC reduction. More experiments are underway to confirm the different reduction paths of VC and FEC stated above.

Acknowledgement

This work was supported by the Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Freedom CAR and Vehicle Technologies of the U.S. Department of Energy under contract No. DE-AC02-OSCH11231.

Figure 1
Solvating Additives and Their Role in Increasing the Capacity of Nonaqueous Li-O2 Batteries
Authors: Viswanathan Venkatasubramanian
Published: February 2020

The passivation of Li-O2 battery cathode by the electronically insulating Li2O2 limits the maximum attainable capacity in these batteries.[1] We show that electrolyte additives, such as tiny amounts of water, which activate solution-mediated growth of Li2O2, make it possible to circumvent this fundamental limitation and enable high capacity Li-O2 batteries. Design rules for choosing these solvent additives are presented.[2] 

V. Viswanathan, K. Thygesen, J.S. Hummelshøj, J. K. Nørskov, G. Girishkumar, B.D. McCloskey, A. Luntz,  J. Chem. Phys., 135, 214704 (2011).

N. B. Aetukuri, B. D. McCloskey, Jeannette M. García, L. E. Krupp, V. Viswanathan and A. C. Luntz, Nature Chemistry., DOI: 10.1038/nchem.2132 (2014).

Figure 1: Proposed mechanism for the growth of Li2O2 toroids in the presence of water.The deposition of Li2O2 in a Li-O2 cell is shown, schematically, to proceed via a surface electrochemical growth process. The presence of a additive (water in our experiments) that solvates LiO2
* to Li+ and O2
- triggering a solution mechanism.  Design rules for additive engineering are presented in the contour plot.

Figure 1
An Experimental Investigation - How Much Influence Has the Electrolyte Composition on the Ageing Behaviour of Separators in Lithium-Ion Cells?
Authors: Kraemer Yvonne , Meiler Markus , Hintennach Andreas
Published: February 2020

The most widely used liquid non-aqueous electrolytes for lithium-ion cells used in  HEV (hybrid electric vehicle), PHEV (plug-in-hybrid electric vehicle) and EV (electric vehicle) applications consist of LiPF6 dissolved in carbonates (e.g. EC, DMC and DEC). These electrolytes undergo a variety of hydrolysis and thermal aging mechanisms [1]. Ongoing decomposition reactions lead to further impurities inside the lithium-ion cell which are not well-known. The separator is a second critical component in lithium-ion cells, which can be classified into three groups according to structure and composition: microporous polymer membranes, non-woven fabric mats and inorganic composite membranes [2].

In this contribution, the decomposition reaction mechanisms are evaluated under a number of different thermal conditions for various commercial electrolytes from automotive lithium-ion cells. Furthermore, their influences on the ageing behaviour of different separator types are investigated. Details of the experimental procedure, analytical methods (NMR, GC-MS, SEM/EDX) and first results will be presented. Finally, we will give an overview of our mechanistic interpretation.

References:

 [1]        P. Handel, G. Fauler, K. Kapper, M. Schmuck, C. Stangl, R. Fischer, F. Uhlig, S. Koller, J. of Power Sources
2014,

             doi: 10.1016/j.jpowersour.2014.05.080

 [2]        S. Zhang,J. of Power Sources
2007, 164, 351 – 364

Acknowledgement: 

This research is funded by the German Federal Ministry of Education and Research (BMBF) under the grant number 03X4631E within the cluster “excellence and technological implementation of Battery research (ExcellentBattery).
In-Situ TEM Study of Intercalation- and Conversion-Driven Lithiation in Single Î±-MnO2 Nanowire
Authors: Yuan Yifei , Nie Anmin , Santhanagopalan Sunand , He Kun , Meng Dennis Desheng , Klie Robert F , Shahbzian-Yassar Reza
Published: February 2020

Nano-sized transitional metal oxides (TMOs, M=Fe, Co, Cu, Mn, etc.) have been increasingly recognized as promising candidate anode for lithium ion battery (LIB) with high specific capacity (700–1200 mAh/g). The high capacity is achieved via a so-called reversible “conversion reaction” with Li+, as shown in Equation (1):

                                 MxOy + 2yLi+ + 2ye- = xM + yLi2O                                                 (1)

where TMO, after reaction with Li+, is reduced to metal (M), and Li2O also forms via combination of Li+ and O2-. In spite of their high capacity, most TMOs suffer from poor rate performance, poor cycle performance and low coulombic efficiency in 1st cycle, preventing its commercialization. The origins and mechanisms underlying these problems are still unclear.

        In this study, single crystalline α-MnO2 nanowire is used as a TMO representative to study the electrochemical lithiation mechanism by constructing an all-solid open-cell inside Transmission Electron Microscope (TEM) with MnO2 as the target electrode and Li metal as Li+ source. Morphological evolution, structural change and phase transition are simultaneously characterized inside TEM. A novel two-step expansion behavior of α-MnO2 nanowire is first visually observed during lithiation. These two expansion stages are sharply different in terms of expansion-needed time, propagation speed of each expansion front and volume change during each expansion. High resolution TEM and Selected Area Electron Diffraction analysis confirm that the first expansion stage is lead by 2×2 tunnel-driven lithiation and formation of LixMnO2 solid solution, while the second expansion stage is caused by thorough conversion of LixMnO2 to Mn and Li2O accompanied by fracture formation and electrode pulverization. These findings provide possible origins for electrochemical drawbacks of TMOs as LIB electrode and also cast light on potential electrode improvement by proper structural and compositional modification.
High Density Sodium and Lithium Ion Battery Anodes from Banana Peels
Authors: Mitlin David
Published: February 2020

Banana peel pseudographite (BPPG) offers superb dual functionality for sodium ion battery (NIB) and lithium ion battery (LIB) anodes. The materials possess low surface areas (19 - 217 m2 g-1) and a relatively high electrode packing density (0.75 g cm-3
vs. ~ 1 g cm-3 for graphite). Tested against Na, BPPG delivers a gravimetric (and volumetric) capacity of 355 mAhg-1 (by active material ~ 700 mAh cm-3, by electrode volume ~ 270 mAh cm-3) after 10 cycles at 50 mAg-1. A nearly flat ~ 200 mAhg-1 plateau that is below 0.1 V, and a minimal charge/discharge voltage hysteresis, makes BPPG a direct electrochemical analogue to graphite but with Na. A charge capacity of 221 mAhg-1 at 500 mAg-1 is degraded by 7% after 600 cycles, while a capacity of 336 mAhg-1 at 100 mAg-1 is degraded by 11% after 300 cycles, in both cases with ~ 100% cycling coulombic efficiency. For LIB applications BPPG offers a gravimetric (volumetric) capacity of 1090 mAhg-1 (by material ~ 2200 mAh cm-3, by electrode ~ 900 mAh cm-3) at 50 mAg-1. The reason that BPPG works so well for both NIBs and LIBs is that it uniquely contains three essential features: a) dilated intergraphene spacing for Na intercalation at low voltages; b) highly accessible near-surface nanopores for Li metal filling at low voltages; and c) substantial defect content in the graphene planes for Li adsorption at higher voltages. The < 0.1 V charge storage mechanism is fundamentally different for Na versus for Li. A combination of XRD and XPS demonstrates highly reversible Na intercalation rather than metal underpotential deposition. By contrast, the same analysis proves the presence of metallic Li in the pores, with intercalation being much less pronounced.
Synthesis and Effect of Heat Treatment on LiCo0.3Ni0.3Mn0.3Ti0.1O2
Authors: Elong Kelimah , Kamarulzaman Norlida , Rusdi Roshidah , Jaafar Mohd Hilmi
Published: February 2020

In the synthesis process of cathode materials, the synthesis method as well as synthesis route is important because cathode materials are very sensitive to the preparation process. Thermal behaviour of the precursors obtained during the synthesis process will indicate if pure and single products can be obtained after annealing. The synthesis method used here is the self-propagating combustion (spc). LiMn1/3Co1/3Ni1/3O2 and LiMn0.3Co0.3Ni0.3Ti0.1O2 are two types of cathode materials synthesized using this method. The TG/DSC of the materials indicates that the LiMn0.3Co0.3Ni0.3Ti0.1O2 is formed at a lower temperature than LiMn1/3Co1/3Ni1/3O2 material. Therefore, annealing the materials at different temperatures and durations will result in differences of the materials’ characteristics that will affect their electrochemical behaviour. These materials’ characteristics will affect the electrochemical performance of the cathodes. The reasons for the differences in electrochemical performances can be attributable to the phases, purity, crystallite size and the crystallinity of the materials.
Growth of LiCoO2 and Li4Ti5O12 Crystals in Lithium Ion Conductive Li2.2C0.75B0.25O3 glass for All-Solid-State Libs
Authors: Teshima Katsuya , Miyakoshi Tatsuya , Onodera Hitoshi , Matsumoto Mitsuhiro , Zettsu Nobuyuki
Published: February 2020

All-solid-state lithium ion rechargeable batteries (LIBs) consisting of solid electrolytes have been desired for higher energy density, long term durability and safety. A great challenge of all-solid-state LIBs for practical use is reduction of the interfacial resistance. Effective interface modification techniques have been proposed, however, the interfacial resistance is still large because the charge transfer resistance at the active material/ solid electrolyte interface would be strongly affected by interfacial contact condition. Herein, we propose a new route to prepare smart interfaces for all-solid-state lithium ion batteries via the direct growth of electrode active material crystals in Li ion conductive glass.

Co3O4, Li2CO3, and Li3BO3 were used as a starting materials for LiCoO2 crystal growth in Li2-xC1-x+yBxO3+2y glass matrix. The volume fraction of LiCoO2 crystal was controlled to be >80% toward the glass matrix. The mixed powders was heated at designated temperature for 1 min to 5 h. Subsequently the powders were cooled to 500°C under temperature controlled conditions. The as obtained composites were structurally characterized by XRD, SEM-EDS, XRD, and TEM. All diffraction lines were in agreement with the ICDD data for LiCoO2. Since the diffraction lines of Li2CO3, and Li3BO3 were not observed, Li2-xC1-x+yBxO3+2y formed amorphous. SEM revealed the idiomorphic LiCoO2 crystal having barreled shape were homogeneously dispersed in the glass flax. Furthermore, the interface was atomically connected without any sub-phases formation, evaluated by TEM, suggesting that the interfaces provide seamless Li+ transportation pathways. Growth of Li4Ti5O12 crystals and futher electrochemical characteristics of these active material crystals will present in the ECS 227th Meeting.
Development of Ceramic-Polymer Composite Electrolyte for All-Solid Lithium Ion Batteries
Authors: Penumaka Rani V , Murakami Sho , Kim Youngsik , Zhu Likun
Published: February 2020

In recent years, research on all-solid lithium ion batteries (LIBs) has increased considerably due to raised concerns relating to safety hazards such as the solvent leakage and flammability of liquid electrolytes used in commercial LIBs. All-solid LIBs use fast Li ion conducting solid electrolytes that do not carry the safety burdens of liquid electrolytes and are more effective. In addition, all-solid LIBs can increase the energy density of the entire battery pack by reducing the need for auxiliary systems such as safety monitoring systems. However, even with the highly ionic conductive solid electrolytes, it has been a struggle for a solid electrolyte LIBs to obtain similar specific capacity, rate capability, and cycle life to those of a liquid electrolyte LIBs. Studies conclude that these issues arise from the solid electrolyte’s inability to interface with the solid electrodes mainly due to the volume change of electrode materials during charge and discharge processes (1). In addition, it is difficult to manufacture on large scale the ceramic solid electrolyte LIBs, because the ceramic type solid electrolyte materials are hard and brittle.  

 To overcome this problem, a composite electrolyte was designed and fabricated using the combination of ceramic solid electrolyte and Li ion conducting organic polymer. The flexible polymer electrolyte can improve the interface stability and processibility for large cells. In this study, NASICON-type Li1.3Al0.3Ti1.7 (PO4)3 (LATP) was used as the solid electrolyte, which offers chemical stability and high conductivity at room temperature (2). Poly(ethylene oxide) (PEO) was used as the Li ion conducting polymer. The composite electrolyte was prepared by mixing LATP powders and the PEO binder with lithium salt (lithium bis(trifluoromethanesulfonyl)imide) (LITFSI). The conductivity of the composite electrolyte was studied by varying the composition at different temperatures. As shown in Fig.1, a stable composite film with good conductivity and flexibility was achieved with an optimum ratio of 75:25 of the LATP and the PEO binder. By using the composite electrolyte, all-solid LIBs were fabricated and studied. An initial discharge capacity of 92 mAh/g was achieved with 0.1 C rate at 60 °C. The detailed fabrication processes and charge-discharge characteristics of the all-solid LIBs will be reported.

Acknowledgments: This work was supported by US National Science Foundation under Grant No. 1335850.

References:

1.             N. M. Asl, J. Keith, C. Lim, L. K. Zhu and Y. Kim, Electrochimica Acta, 79, 8 (2012).

2.             H. Aono, E. Sugimoto, Y. Sadaoka, N. Imanaka and G. Adachi, Journal of the Electrochemical Society, 137, 1023 (1990).

Figure 1
Study on the Charging Behaviors of Lithium-Ion Batteries By the Simulation of Li Distribution in the Electrode Particles
Authors: Yang Naixing , Zhang Xiongwen , Li Guojun , Hua Dong
Published: February 2020

The charging behaviors of lithium-ion batteries are closely related with the charging current and temperature. Generally, the constant current-constant voltage (CC-CV) mode is the most widely applied charging protocol for lithium-ion batteries. This paper establishes a multi-scale thermal-electrochemical model with considering the Li diffusion process in the electrode particles to investigate the battery charging performances. The change rules of the charging capacity and charging time are separately discussed based on the analysis of the transient characteristics of Li concentration inside the electrode particles when charging with the CC-CV mode.

It is known that the charged capacity is determined by the amount of the transferred Li between the negative and positive electrodes [1, 2]. The experimental and numerical results are compared in Fig.1. Fig.2 shows the distributions of Li concentration inside a carbon particle when battery is in charging with the CC-CV mode (4C→3.6V→0.02C) at 25°C. As the charging time increases, the gradient of Li concentration during the CC charging stage slightly decreases, while it decreases markedly during the CV stage.

The results show that the charged capacity in the CC stage decreases with the increase of the charging current when the current is lower than 4C, whereas it changes slightly in case of the charging current is higher than 4C; the CC charging time decreases with the increase of the charge current, while the change of the CV charging time is slight. For EVs application, the battery is recommended to only charge 90% of the total capacity, which can shorten the charging time significantly.

References

1. L.-x. Li, X.-c. Tang, Y. Qu and H.-t. Liu, Journal of Central South University of Technology, 18, 319 (2011).

2. N. Yang, X. Zhang and G. Li, Journal of Power Sources, 272, 68 (2014).

Figure 1
Iron(III) Oxalate Tetrahydrate: A New Positive Electrode for Li Batteries
Authors: Ahouari Hania , Tarascon Jean Marie , Recham Nadir , Rousse Gwenealle , Rodriguez-Carvaja Juan , Sougrati Moulay-Tahar , Courty Matthieu , Saubanere Matthieu
Published: February 2020

Over the last two decades, energy storage devices and in particular lithium-ion batteries, have been the object of a steady growing demand due to their feasible implementation for automotive electric transportation (PHEV and HEV)[
1
]. However, this market requires the research of new electrode materials with higher energy density and greater power rate. When one looks back on history, the early nineties were solely devoted to oxide-based 3d-metal electrodes[
2
] and in the last 15 years three-dimensional frameworks built on transition metals and polyanions (XO4)n- have become subject of very intensive research[
3
].  

LiFePO4 polyaionic compound offers low cost, environmental compatibility, high theoretical specific capacity (170 mAh/g) and has become the most praised material for the next generation of Li-ion batteries for EV’s [
3-4
].

 Aside from the inorganics polyanionic compounds, we have recently shown the cost-wise attractiveness of some Fe-based phases having organic polyanions such as carbonates, oxalates, malonates, etc. These materials could be attractive electrodes due to their cost, low molecular weight and electronegativity. Herein, we report a new synthesis route to prepare Fe2(C2O4)3·4H2O and determine its crystal structure through X-ray powder diffraction coupled with neutron powder diffraction (Figure 1). We also show for the first time that iron(III) oxalate compound is electrochemical active versus lithium as it can reversibly insert 1.6 Li atom per formula unit at 3.35 V versus Li+/Li0 (Figure 2). 

 Beside reporting the synthesis and the crystal structure of Fe2(C2O4)3·4H2O phase, we will determine the structural changes driven by Li insertion using both in situ XRD and Operando Mössbauer measurements as will be discussed.

References

[1] M. Ati, M. T. Sougrati, G. Rousse, N. Recham, M. L. Doublet, J. C. Jumas and J. M. Tarascon, Chemistry of Materials
2012, 24, 1472-1485.

[2] J. M. Tarascon, W. R. McKinnon, F. Coowar, T. N. Bowmer, G. Amatucci and D. Guyomard, Journal Electrochemical Society
1994, 141, 1421-1431.

[3] C. Masquelier and L. Croguennec, Chemical  Reviews
2013, 113, 6552-6591.

[4] N. Recham, J. Oró-Solé, K. Djellab, M. R. Palacín, C. Masquelier and J. M. Tarascon, Solid State Ionics
2012, 220, 47-52.

Figure 1
First Principles Study on Phase Stability in Li-Rich Layered Li2MnO3-LiMO2 (M=Mn, Ni, Co)
Authors: Lu Zhi , Morgan Dane , Wolverton Chris
Published: February 2020

Lithium–rich layered oxides Li2MnO3-LiMO2 have attracted much attention as cathode materials in Li-ion battery recently because of their higher capacity (larger than 250 mAh/g), increased energy density and structural stability at high voltage. However, in order to be commercialized, there are still some unclear issues (structure complexity and reaction mechanisms) and challenges (first-cycle irreversible capacity loss, poor rate performance and voltage fade with cycling which is related to structural evolution).

Regarding their structure complexity, there is significant debate in the literature so far on whether these Lithium–rich layered cathode material form homogeneous solid solutions or Li2MnO3 nano-composite within a LiMO2matrix. It is important to get a clear picture of the actual detail structure, to understand and control their electrochemical performance. And without a detailed knowledge of the structure, it will be problematic to further explore failure mechanisms with cycling.

Recently in our research, the atomic order in Li-rich layered composites with composition xLi2MnO3-(1-x)LiMO2 is investigated with first-principles calculations using Generalized Gradient Approximation (GGA) +U method. The random solid solution structure model between Li2MnO3 and LiMO2 are created by Special Quasirandom Structures (SQSs) theory. After calculating the mixing energy, the miscibility gap is achieved and phase separation between Li2MnO3 and LiMO2 are predicted. Further study on the coherency strain energy shows that the strain energy is relatively small compared to mixing energy. Phase separation cannot be inhibited by strain.

Figure 1
Dilute Hydrogen Sulfide Sensing Characteristics of a Pt/GaN Schottky Diode
Authors: Xiao Jian-Feng , Hsu Chen-Pin , Wang Yu-Lin
Published: February 2020

Hydrogen sulfide is a colorless, flammable and highly toxic gas with the characteristic foul odor of rotten eggs, often results from the bacterial breakdown of organic matters. Because of its toxicity, many personal safety gas detectors are set to alarm at 10ppm[i]. A number of sensors based on Schottky diode have been investigated as gas sensors since 1980s. In 2011, Professor Liu studied a Pt/AlGaN/GaN Schottky diode, which can exhibit ammonia detection limit lower than 35ppm NH3/air[ii]. There are also many papers research in H2S sensing with Schottky diode or metal oxide, most of their detection limit is higher than 10 ppm, expect one sensor made by thin film of CuO-SnO2, which can reach to 0.02ppm[iii].

The sensor studied in this paper contains four layers, which is showed in Figure 1 in detail. The Ohmic contact was formed by lift-off of e-beam evaporated Ti(200 Å)/Al(800Å)/ Ni(400Å)/Au(1000Å) and annealed at 850°C for 42 s under a flowing N2 ambient in a Premtek / ARTs 150. 100Å of Pt was deposited by e-beam evaporation to form Schottky contact as well as used as catalytic metal. Figure 2 shows three sets of Pt/GaN Schottky diode in different size and the size for the whole device is about 2×2mm. As the result of experiment, all of these three diodes are sensitive to H2S. Figure 3 shows real-time detection of 0.7ppm H2S in air. Figure 4 shows the relation between current change and concentration of H2S from 0.1-1ppm. All of the devices are tested in 200℃ and applied with 0.5ms width 1.5V pulse every second. With this Pt/GaN Schottky diode we can detect H2S down to 0.05pp.

[i] Agency for Toxic Substances and Disease Registry (July 2006)."Toxicological Profile For Hydrogen Sulfide". p. 154. Retrieved 2012-06-20.

[ii] T. Y. Chen, H. I. Chen, Y. J. Liu, C. C. Huang, C. S. Hsu, C. F. Chang, and W. C. Liu, “Ammonia sensing properties of a Pt/AlGaN/GaN Schottky diode,” IEEE Trans. Electron Devices, vol. 58, no. 5, pp. 1541–1547, May 2011.

[iii] Jun Tamaki , Kengo Shimanoe, Yoshihiro Yamada, Yoshifumi Yamamoto, Morio Miura, and Noboru Yamazoe,” Dilute Hydrogen Sulfide Sensing Properties of Copper Oxide-Tin Oxide Thin Film Prepared by Low-Pressure Evaporation” Solid State Sensors and Actuators, 1997 International Conference  

Figure 1
Fabrication and Characterization of Well-Tunable and Titanium Thin-Film Liquid/Gas Diffusion Layers
Authors: Steen Stuart M. , Mo Jingke , Retterer Scott , Terekhov Alexander , Zhang Feng-Yuan
Published: February 2020

A liquid/gas diffusion layer (LGDL) is located between the catalyst layer and current collecting flow field in proton exchange membrane (PEM) devices. Typically composed of carbon-based materials for PEM fuel cells (PEMFCs), this is unsuitable for PEM water electrolyzers (PEMWEs) due to the high anodic potential of the oxygen electrode that occurs during electrolysis, which creates a highly corrosive environment. Titanium has received considerable attention as a promising material to replace carbon LGDLs due to its high corrosion resistance at high positive overpotential, even in highly acidic and humid conditions. In addition, titanium provides high thermal/electrical conductivities and excellent mechanical properties. Current titanium LGDLs may be woven mesh, foams, and sintered fiber felt. Woven mesh are difficult to machine, and do not have the pore size controlled due to limitations of the material and available fabrication methods. Titanium felt on the other hand is similar in random structure to carbon paper, where shaved fibers of metal are sintered together to form a non-ordered porous material. In addition, their extra thickness increases significant electrical conductive path and fluidic resistance. Because of these challenges with the LGDLs, a thin-film LGDL with well-controllable pore morphology  is  highly desired  in both PEMFCs and PEMWEs.

This presentation will highlight recent efforts to design and fabricate well-tunable and titanium thin film LGDLs using photolithography and etching techniques. The effect of mask size as well as different etchants on the etch rate  and pore size of titanium is investigated. After fabrication, both performance & efficiency as well as electrochemical impedance spectroscopy is performed on the metallic LGDLs in order to evaluate their effectiveness in the anode side of a PEMWE. Ex-situ analysis is also performed before and after testing in order to characterize the morphological features of the LGDLs post etching and post testing. From the results of the fabrication and testing, new methods for the fabrication of well-tunable thin film LGDLs and the effect of controlling their parameters on the performance and efficiency of PEMWEs will be detailed.
Phase Field Simulation Coupling Microstructural Evolution and Crack Propagation during Performance Degradation of Solid Oxide Fuel Cells
Authors: Abdullah Taufiq , Liu Lin
Published: February 2020

Both microstructural evolution and crack nucleation occur in Solid Oxide Fuel Cells (SOFCs) at elevated operation temperature (above 600°C), which cause severe performance degradation in electrochemical activity as well as structural integrity during their lifetime application. Nickel (Ni) coarsening of Ni-yttria stabilized zirconia (YSZ) in the anode of SOFCs is believed to lead to the microstructural evolution. In the meanwhile, severe thermal stress due to high operation temperature is one of the main factors responsible for crack propagation in the microstructure. Both microstructural evolution and crack nucleation have a significant impact on both electrochemical activity and structural integrity of SOFCs during operation. Based on theories of diffuse-interface and linear elastic fracture mechanics (LEFM), an integrated phase field model is established to couple electrode microstructural evolution and crack nucleation in SOFCs. Then, the model is applied to SOFCs with nonlinearly graded microstructures, which is proposed in our previous work (1), to explore the couple effects on SOFCs performance degradation. The preliminary results show that particle size and ratio, which dictates the triple phase boundaries (TPBs) contact angle, are ones of the most influential microstructural parameters in the microstructural evolution that affects SOFCs’ electrochemical activity. Different crack shapes are considered to reveal the effect of crack nucleation on SOFCs’ structural integrity. With combining the analysis of coupling effect of microstructural evolution and crack propagation on SOFCs’ performance degradation, it is expected the understanding of SOFCs’ performance degradation could be advanced. This work will provide one comprehensive evaluation computational tool for SOFC’s long-term degradation analysis and novel electrode design.

1.             L. Liu, R. Flesner, G. Y. Kim and A. Chandra, Fuel Cells, 12, 97 (2012).
Alkene Difunctionalization Via b-Haloalkoxysulfonium Ions
Authors: Hayashi Ryutaro , Ashikari Yosuke , Nokami Toshiki , Shimizu Akihiro , Yoshida Jun-ichi
Published: February 2020

Alkene difunctionalization via three-membered ring halonium ion intermediates is an important transformation in organic synthesis. The most straightforward method to generate the halonium intermediates is to use halogen cations, which are usually too unstable to accumulate in solution.

 Recently, we reported that halogen cations stabilized by dimethyl sulfoxide (DMSO) were successfully generated and accumulated in solution by low-temperature electrochemical oxidation. Reactions of DMSO-stabilized halogen cations such as Br+ and I+ with alkenes gave b-haloalkoxysulfonium ions. Subsequent treatment of the b-haloalkoxysulfonium ions with triethylamine gave α-halocarbonyl compounds via Swern−Moffatt type oxidation. Here, we report that treatment of the b-haloalkoxysulfonium ions with different bases gives different products, i.e. the use of sodium hydroxide and sodium methoxide gives halohydrins and epoxides, respectively.
Electrosynthesis of Heterocyclic Compounds By Radical Cyclization in Environmentally Friendly Media
Authors: Mendes J.P. , Esperança J.M. S.S. , Esteves A. P. , Silva M. M. , Medeiros M.J.
Published: February 2020

The formation of carbon-carbon bonds by radical cyclisation has become an important tool for the synthesis of natural products containing heterocyclic rings [1].  The majority of radical cyclisations in heterocyclic chemistry are still carried out using tributyltin hydride as the reducing agent. This has disadvantages, as the tributylin hydride is toxic and it is difficult to completely remove the tin species from the reaction mixture.

The electrochemical version of similar intramolecular processes - in reactions involving aryl or vinyl bromides [2], bromoacetals [2], or α-bromoamides [2] with double or triple bonds in the presence of nickel(II) complexes as catalysts - has been shown to be highly efficient.  The reaction can be performed under mild conditions using relatively simple equipment. It also avoids the hazardous or toxic reagents used in the tributyltin hydride method.

Although most of the reactions have been reported in aprotic solvents, their toxicity, hazards and cost make them unattractive.  This makes the search for non-toxic fluid alternatives highly desirable.  

Ionic liquids (ILs) represent a class of alternative solvents currently receiving serious consideration, as they have environmental and technological benefits [3].   Their characteristics render them promising replacements for volatile organic solvents (VOCs).

As an extension of our previous research, we undertake further studies on analogs/derivatives of bromopropargyl esters as substrates. In the present work, we investigate the reductive intramolecular cyclization of bromopropargyl ethers derivatives,  catalysed by electrogenerated (1,4,8,11-tetramethyl-1,4,8,11-tetraaza-cyclotetradecane)nickel(I), [Ni(tmc)]+ as the catalysts in N,N,N-trimethyl-N-(2-hydroxyethyl)ammonium bis(trifluoromethylsulfonyl)imide,[N1 1 1 2(OH)][NTf2] and 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, [C2mim][NTf2] by cyclic voltammetry and controlled-potential electrolysis.  The results show that the reaction leads to the formation of the expected cyclic compounds, which are important intermediates in the synthesis of natural products with possible biological activities [4]. 

 

ACKNOWLEDGEMENTS

 We are grateful to the Fundação para a Ciência e Tecnologia (PestC/QUI/UI0686/2013 and FCOMP-01-0124-FEDER-037302) for financial support of this work.

REFERENCES

1. B. Giese, “Radicals in Organic Synthesis: Formation of Carbon-Carbon Bonds”, Pergamon Press, Oxford (1986).

2. E. Dunach, M.J. Medeiros, S. Olivero, New J. Chem., 30, 1534 (2006).

3. Ionic liquids IIIB: Fundamentals, Process, Challenges, and Opportunities, ACS Symp. Ser. (Eds.: R. D. Rogers and K. R. Seddon), ACS, Washington DC, 2005.

4. P.K. Mandal, G. Maiti, S.C. Roy, J. Org.
Chem., 63, 2829 (1998).
Electrochemically-Induced Radical Cation Diels-Alder Reactions Assisted By "Redox Tag Strategy"
Authors: Yamaguchi Yusuke , Okada Yohei , Chiba Kazuhiro
Published: February 2020

Diels-Alder (DA) reaction is among the most important reaction for constructing carbon-carbon bond in organic chemistry. The mechanisms into it are well understood; diene and dienophile should have complementary electronic characters for smooth reaction. In the situation where both substrates are electron-rich, significantly higher temperature or longer time are required.

One of the most effective solution for such electronically-mismatched DA is umpolung process, which can give highly electrophilic radical cation from otherwise nucleophilic electron-rich starting substrates by one electron oxidation. Namely, the radical cations generated from electron-rich olefins can readily afford the DA adduct with nucleophilic electron rich dienes.1 Since electrochemical method has proven to be the simplest approach for the umpolung reaction, anodic method has been developed for the radical cation-mediated DA (rDA).2

Our group have been focused on the anodically-induced C-C bond forming reactions using lithium perchlorate nitromethane electrolyte solution system.3 In particular, [2 + 2] cycloaddition reaction4 between enol ether and unactivated terminal olefin is initiated by one electron oxidation of enol ether to give corresponding radical cation. The reaction allow for the mechanistic study of radical cation species, providing information, for example, intramolecular electron transfer properties5 and functionality of aromatic radical cation intermediates.6

In the talk to be presented, anodically-induced rDA (Scheme 1) will be reported especially to electrochemical condition, scope and limitations, and new design of the rDA based on the previous study of radical cation properties.

References: 

Bellville, D. J.; Wirth, D. D.; Bauld, N. L. J. Am. Chem. Soc.
1981, 103, 718.

Mlcoch, J.; Steckhan, E. Tetrahedron Lett.
1987, 28, 1081.

Chiba, K.; Tada, M. J. Chem. Soc., Chem. Commun.
1994, 2485.

Chiba, K.; Miura, T.; Kim, S.; Kitano, Y.; Tada, M. J. Am. Chem. Soc.
2001, 123, 11314.

Yamaguchi, Y.; Okada, Y.; Chiba, K. J. Org. Chem.
2013, 78, 2626.

Okada, Y.; Nishimoto, A.; Akaba, R.; Chiba, K. J. Org. Chem.
2011, 76, 3470.

Figure 1
All Vanadium Redox Flow Battery Development for Stationary Energy Storage Applications
Authors: Sprenkle Vincent , Reed David , Thomsen Ed , Wang Wei , Li Bin , Nie Zimin , Koeppel Brian J , Recknagle Kurt P , Viswanathan Vilayanur , Crawford Alasdair
Published: February 2020

The DOE Office of Electricity’s – Energy Storage program at Pacific Northwest National Laboratory (PNNL) has been focused on the development of cost effective energy storage technologies to improve the grid reliability, power quality, and adoption of the intermittent renewable energy. Among the most promising large-scale energy storage technologies are redox flow batteries (RFBs). RFB’s are electrochemical devices capable of storing up to multi-megawatt-hours (MWhs) of electrical energy via a reversible electrochemical energy conversion. Unlike traditional batteries in which the electrodes serve as the supply/sink of ionic charge, RFB’s store electricity in liquid electrolytes that flow on either side of a membrane. As such, the power and energy of a RFB can be separately designed, offering greater flexibility for a greater selection of stationary applications.

All-vanadium RFB system enlists the same element, vanadium, in both the catholyte and anolyte. Researchers at PNNL have revisited the standard vanadium sulfate electrolyte chemistry used in this system and developed an novel mixed acid electrolyte (sulfate and chloride) that can stabilize all four vanadium cations at concentrations ≥ 2.5M within a temperature range of 5~50oC. Recently, PNNL recently demonstrated a kW/kWh scale prototype battery utilizing this electrolyte system in order to better understand the system benefits of the mixed acid electrolyte.  The system consisted of ~ 20 cell stack with 780cm2 of active area/cell, ~ 30 liter electrolyte tanks, pumps and associated piping. The stack incorporated new interdigitated flow fields for reduced pressure drop and thinner Nafion membranes for improved performance. Results of stack testing under a wide range of current densities and temperature conditions will be reported along with resulting energy efficiencies.
Building a Better Redox Flow Battery - Innovative Diagnostics to Visualise Reactant Transport
Authors: Rubio-Garcia Javier , Kucernak Anthony R. J.
Published: February 2020

While the optimization of PEMFCs and RFBs require addressing multiple issues, both systems share an operation mechanism based on pumping a fluid (a gas or a liquid) containing chemically reactive species across the face of an electrode. As a consequence of this characteristic, a significant source of inefficiency is linked to mass transport limitations including high pressure drop or inhomogeneous reactant flow distribution across the electrode. Previously, strategies including infrared mapping, (1) magnetic resonance imaging (2) or neutron radiography (3) were employed in an attempt to investigate fluid transport phenomena (predominantly for fuel cells). However, although those studies rendered valuable results, the measuring procedures can be considered as expensive and require delicate equipment.

In this contribution, a simple and low cost methodology to study the mass transport processes in RFBs is presented. This approach relies on the instantaneous electrochemiluminescence of Luminol. By simply recording the emitted light with a low cost camera,(4) concentration profiles at the surface of the electrode were obtained presenting high temporal and spatial resolutions. In addition, modifications on the electrolyte formulation and flow rate permitted identifying turbulent flow areas located at the turn of the flow field (Fig. 1) as well as leading to the design of improved components.

References:

(1) Wang et al., Journal of Power Sources, 157, 181–187 (2006).

(2) Tsushima et al., Magnetic Resonance Imaging, 23, 255-258 (2005).

(3) Trabold et al., International Journal of Heat and Mass Transfer, 49, 4712–4720 (2006).

(4) Lopes et al., Journal of Power Sources, 274, 382–392 (2015).

Figure 1
Determination of Inorganic Arsenic As(III) in Water By Anodic Stripping Linear Sweep Voltammetry Using Gold Ultra-Microelectrode Array
Authors: Duong Quyet Nguyen , Le Nghiem Van , Le Thuong Dinh , Nguyen Hoang Thai , Tong Hien Duy , Nguyen Thoa Thi Phuong
Published: February 2020

A sensitive electrode has been developed for the determination of arsenic As(III) ions by anodic stripping linear sweep voltammetry (ASLSV). The method shown in this work  for  the  electroanalytical  speciation  of  inorganic As(III) in water used a gold ultra-microelectrode array, consisted of 100 gold wires; each sized of 1 µm width and 1000 µm long. The sensor from gold band microelectrode arrays was made on a silicon wafer by the deposition and etching under angles (DEA) technique.

The parameters of ASLSV, such as deposition potential (Edep) and time (tdep) and potential scan rate, were investigated. Different acidic solutions (HNO3, H2SO4, HClO4, H3PO4, HNO3/KCl, H2SO4/KCl and HClO4/KCl) with various concentrations were tested as a supporting electrolyte for arsenic analysis, from which the 0.1 M H3PO4 solution was chosen due to its medium acidity and being environmental friendly. Well defined voltammetric waves at Edep = -0.450 V (vs. Ag/AgCl reference electrode), tdep = 100 s and 1.000 V/s scan rate are found with peak currents proportional to the concentration of As(III) in the range of 10 to 100 ng.L-1. The limit of detection was 2 ng.L-1(signal-to-noise ratio = 3). These results well satisfy the requirements given by the World Health Organization (WHO). The repeatability, linearity and accuracy of the proposed method were evaluated. This method was applied for analysis of As(III) in natural water samples and the obtained results suggested that the fabricated gold chip would facilitate monitoring of As(III) in water.

This research was part of the project ĐTĐL.2011-G/76, granted by the Ministry of Science and Technology (MOST) Vietnam.

Keywords: anodic stripping voltammetry, arsenic, gold, ultra-microelectrode.
Non-Precious Metal Catalysts for the Oxygen Reduction Reaction
Authors: Varnell Jason A. , Tse Edmund C. M. , Gewirth Andrew A.
Published: February 2020

We report on our efforts to characterize the active site of Fe-based non-precious metal (NPM) catalysts for the oxygen reduction reaction (ORR). Acid leaching using aqua regia significantly decreases the amount of Fe present in the catalyst material to levels below 1 wt% with the lowest Fe content observed at 0.34 wt%. However, no change in the ORR onset is observed following catalyst treatment with acid when tested in acidic media. This indicates that some Fe centers are buried within the carbon material making then inaccessible to the acid treatment. These remaining Fe sites are accessible to oxygen and are catalytically active to the ORR.

To further remove Fe from NPM ORR catalysts we exposed them to chlorine gas at high temperature (600- 1000 °C). Through this treatment Fe content as low as 0.16 wt% is achieved. After the demetalation with chlorine gas the ORR onset is seen to shift to more negative potentials by as much as 250 mV when tested in acidic media. Remetalation by exposure to FeCl3 results in partial recovery of ORR activity.

We also summarize our efforts examining multinuclear copper complexes inspired by laccase, a class of blue copper oxidases that efficiently mediate the four-electron four-proton reduction of dioxygen to water.(1) We first prepare Cu complexes of 2,2'-dipicolylamine (DPA) and test its electrocatalytic activity towards the ORR. To investigate the effect of multinuclearity on the ORR, we connect two DPA units together with a flexible linker and installed a third metal-binding pocket in the ligand framework (Figure 1).

The ORR onset potentials and the diffusion-limited current densities of [Cu(1)]2+ are comparable to that of [Cu(TPA)(H2O)]2+ previously reported by our group. However, the electron transfer rate between [Cu(1)]2+ and carbon electrode surface is low, indicating that more intimate coupling to the electrode may be required for efficient ORR. Covalently linking two [Cu(DPA)]2+ cores together results in ORR activities no better than [Cu(1)]2+ alone.

This study highlights the viability of Cu complexes of DPA to mimic the T3-site of laccase and serves as a guide for designing future laccase models. The relationship between inter-site flexibility and cooperativity is long recognized; it is insufficient to simply connect reactive Cu sites. To ensure cooperativity comparable to that of metalloproteins, future catalysts will require more sophisticated designs.

Reference

1.             E. C. M. Tse, D. Schilter, D. L. Gray, T. B. Rauchfuss and A. A. Gewirth, Inorg. Chem., 53, 8505 (2014).

Figure 1