bluuebunny/crossref_metadata_2025 huggingface dataset:
In Situ Stress Measurements during Electrochemical Cycling of Lithium-Rich Cathodes
Authors: Nation Leah , Li Juchuan , James Christine , Qi Yue , Dudney Nancy J , Sheldon Brian W.
Published: February 2020

Lithium-rich layered oxides (Li1+xM1-xO2, M= Ni, Mn, Co) are attractive cathode materials for lithium ion batteries due to their high reversible capacity originating from their high lithium and manganese content. During cycling, structural changes cause compositional stresses that may lead to mechanical degradation. In this study, we seek to characterize this degradation using Li1.2Mn0.55Ni0.125Co0.125O2 (LR-NMC) thin-films prepared by sputtering on sapphire substrates and characterized using x-ray diffraction (XRD), raman spectroscopy, and scanning electron microscopy (SEM). A multibeam optical stress sensor (MOSS) is used to quantitatively measure the average stress in the cathode film during electrochemical cycling. A unique and unpredicted stress signature is observed during the first charge. Initially, a tensile stress is observed, consistent with volume contraction from lithium removal, however, the stress reverses and becomes compressive with continued charging beyond ~4V vs Li/Li+, indicating volume expansion; this phenomenon is present in the first cycle only. The origin of this irreversible stress during the first charge is not clear; cracking, oxygen loss, and the formation of a surface phase are explored as possible causes. Subsequent cycling is reversible, with volume expansion during lithiation and volume contraction during delithiation. Raman spectroscopy provides evidence of the layered-to-spinel phase transition after cycling. After reannealing in an oxygen environment, the original raman spectra is recovered. Annealed samples show the same first cycle behavior after re-cycling. Atomistic modelling in conjunction with experimental results aids in understanding the effects of stress on kinetics and phase transformations, guiding the development of improved lithium rich cathodes.
(Invited) Differntiating the Behaviour of Electrochemical Capacitor Materials
Authors: Donne Scott W , Dupont Madeleine F
Published: February 2020

Electrochemical capacitors are rapidly emerging as a viable energy storage technology for many different applications, encompassing a wide range of size scales. Their performance is typified by a high power density and excellent cyclability, as well as a relatively low energy density, improving which has been the focus of considerable research activity. Environmental considerations and cost per unit of energy are also important for widespread commercial acceptance.

During the quest for development of an improved electrochemical system many different materials have been examined for electrode use. Most often activated carbon is the material of choice for electrochemical capacitors, in particular when coupled with a non-aqueous electrolyte based on either acetonitrile, propylene carbonate, or perhaps even an ionic liquid. Improving the performance of the activated carbon has been an important avenue of research, in particular optimizing the pore size distribution of the material to enable maximum charge storage in the electrical double layer. Other avenues of research have focused on developing other classes of materials, such as metal oxides and conducting polymers, so as to store charge via pseudo-capacitance, which can be defined as facile, reversible redox reactions occurring at the electrode-electrolyte interface. In this way, the near-surface region of the electrode material can be accessed for what is effectively pseudo-3D charge storage.

The study of materials that exhibit pseudo-capacitance has enabled many materials previously considered as battery materials, to make in-roads into electrochemical capacitor applications. While the concept and study of pseudo-capacitive materials is very worthwhile for electrochemical capacitor applications, there is growing interest in highlighting the differences in charge storage mechanisms that occur in these materials, particularly so since the end electrochemical result is very similar even though the choice of materials and notional charge storage mechanisms are very different.

This presentation will highlight the differences in materials used, as well as differentiate the charge storage mechanisms that various materials undergo. The presentation will also seek to describe how materials can exhibit battery-like behaviour under one set of conditions, and electrochemical capacitor-like behaviour under others.
Mechanism Study on the Asymmetric Behaviors of Carbon/Carbon Supercapacitors
Authors: Hu Lintong , Li Huiqiao
Published: February 2020

Electrical double layer capacitors (EDLCs) have attracted tremendous attention for their high power density, long cycle life, excellent stability and fast charge-discharge rate. Due to the high surface area, good conductivity, and high chemical stability in different solutions, many efforts are devoted to explore carbon-based materials for EDLCs. However, a common phenomenon that the positive and negative electrodes have unequal capacitance in carbon/carbon supercapacitors has not received the deserved attention. [1, 2] The asymmetric capacitance limits the potential window and hence the cell energy density. [3,4] By smart balancing the asymmetric behaviors of the positive and negative electrodes, a higher energy density can be expected for supercapacitors without additional cost. Thus the mechanism study on the asymmetric phenomenon is of great meaning to achieve high performance supercapacitors.

We studied the capacitive behaviors of the positive and negative electrode in a carbon/carbon supercapacitor respectively by using both experimental measurements and molecular dynamics calculations. Two different electrolytes, tetraethylammonium tetrafluoroborate (TEABF4) and lithium hexafluorophosphate (LiPF6) in propylene carbonate (PC), were used for the identical carbon electrodes. Cyclic voltammetry (CV) and galvanostatic charge-discharge (GCD) tests show that the two electrodes in a capacitor not only exhibit different specific capacitance but also work in different width of voltage window. Theoretical calculations give a full explanation of the experiment observations, which indicate that the size of solvated ions, the diffusion property and the solvation energy play important roles in such asymmetric behaviors. The results help to get a deep understanding of factors involved in the charge storage mechanism and can provide guidance for designing appropriate carbon-electrolyte system for EDLCs.

References

[1] Chmiola, J.; Largeot, C.; Taberna, P. L.; Simon, P.; Gogotsi, Y.; Angew. Chem. Int. Ed. 2008, 47, 3392.

[2] Wang, H.; Forse, A. C.; Griffin, J. M.; Trease, N. M.; Trognko, L.; Taberna, P. L.; Simon, P.; Grey, C. P.; J. Am. Chem. Soc.
2013, 135, 18968.

[3] Weng, Z.; Li, F.; Wang, D. W.; Wen, L.; Cheng, H. M.; Angew. Chem. Int. Ed.
2013, 52, 3722.

[4] Aken, K. L. V.; Beidaghi, M.; Gogotsi, Y.; Angew. Chem. Int. Ed. 2015, 54, 4806-4809.

Figure 1
Printable Micro-Supercapacitor with Ni@ MnO2 Dendritical Core-Shell Nanostructure and Pattern Design for Flexible Electronic Applications
Authors: Lin Yuanjing , Gao Yuan , Fan Zhiyong
Published: February 2020

The blooming market needs for wearable devices have propelled the research of on-chip flexible micro-supercapacitors. Planar micro-supercapacitors are superior to sandwich structure in terms of device integration compatibility. In this work, a cost -effective inkjet printing method was adopted to fabricate high resolution and flexible interdigitated silver electrode, followed by two-step electrochemical deposition and thus, the unique Nickel (Ni)@ Manganese dioxide (MnO2) dendritical core-shell structure is achieved for pseudocapacitor application. The as-built pseudocapacitor device achieves an areal capacitance of 37.3 mF cm-2
which is among the highest as compared with previously reports for planar devices. In addition, the concept of pseudocapacitor artistic design was demonstrated in this work. Utilizing printing technique, various artistic patterns have been generated followed by supercapacitor device fabrication and performance characterization. It is shown that the devices have respectable performance and good robustness. These results demonstrate the versatility of the device fabrication process developed here, and the viability as supplementary power sources of the printable micro-supercapacitors for flexible and wearable electronics.
Mechanically Stable Carbide Derived Carbon Nanoporous Films for Micro-Supercapacitors
Authors: Taberna Pierre-Louis , Simon Patrice , Lethien Christophe , Huang Peihua , Pinaud Sebastien , Brousse Kevin , Laloo Raphael , Turq Viviane , Respaud Marc , Demortiere Arnaud , Daffos Barbara , Chaudret Bruno , Gogotsi Yury
Published: February 2020

Integration of electrochemical capacitors with silicon-based electronics is a major challenge, limiting energy storage on a chip. Here it will be presented the electrochemical behavior of micro-supercapacitors achieved of strongly adhering carbide-derived carbon films obtained from TiC conversion through a process compatible with current microfabrication and silicon-based device technology. By playing around chloration temperature, electrochemical properties are easily tunable, then capacitance of those films reaches 410 farads per cubic centimeter/200 millifarads per square centimeter in aqueous electrolyte and 170 farads per cubic centimeter/85 millifarads per square centimeter in organic electrolyte. With a maximum areal power and energy of 100 milliwatts per square centimeter and 19 microwatthours per square centimeter, for a 2 micrometers thick film, such achieved carbon layers outperform today's microsupercapacitor state of the art. What's more, those carbon films exhibit an excellent mechanical stability since a Young's modulus of 14.5 gigapascals is measured enabling the preparation of self-supported, mechanically stable, micrometer-thick porous carbon. So further transfer onto flexible substrates is feasible and it is demonstrated that carbon free standing films can exhibit a volumetric capacitance as high as 400 farads per cubic centimeter. These materials are interesting for applications in structural energy storage, tribology, and gas separation.
Silica-Based Ionogel Electrolyte for Electrical Double Layer Capacitors
Authors: Negre Léo , Daffos Barbara , Taberna Pierre-Louis , Simon Patrice
Published: February 2020

Electrochemical Capacitors (ECs), also known as supercapacitors, have now reached the technical maturity for complementing- and sometimes replacing- batteries in a broad range of applications. Conventional electrolytes based on acetonitrile or propylene carbonate solvents have been mainly used in combination with ammonium cations and fluoride anions. Designing solid electrolytes for ECs would be of great interest in the aim of solving packaging issues, corrosion, self-discharge or leaks. Moreover these solid electrolytes could be used for flexible supercapacitors applications.

Ionogels are quasi-solid electrolyte obtained from the trapping of an IL into a silica scaffold using a sol-gel process. The first part of our work has been devoted to a better understanding of the non-hydrolytic sol-gel mechanisms occurring during the formation of ionogels, using electrochemical impedance spectroscopy. Change of the conductivity of the sol-gel mixture (a Formic acid and Tetraethyl orthosilicate mixture) shows two different time domains. The mixture conductivity is first decreasing drastically during the first 25 minutes of the sol-gel process, assuming to originate from the in-situ generation of water through esterification reaction. In the second time range (t>25 min), the conductivity tends to level off, associated with a series of chemical reactions. More details about this study will be added during the presentation.

In a second part of the talk, we will show the electrochemical performance of an supercapacitors cell assembled with activated carbon as active materials and an ionogel electrolyte containing an ionic liquid mixture (1:1 by weight or molar ratio) of N-methyl-N-propylpiperidinium bis(fluorosulfonyl)imide (PIP13FSI) and N-butyl-N-methylpyrrolidinium bis(fluorosulfonyl)imide (PYR14FSI). Cyclic voltammetries and electrochemical impedance spectroscopy plots in a large temperature range (-40°C to +60°C) will be presented and discussed. The ionogel exhibits a high ionic conductivity over a wide temperature range (from 0.2 mS.cm−1 at −40 °C up to 10 mS.cm−1 at 60 °C). The ionogel-based supercapacitor using two activated carbon electrodes can be operated over 3 V cell voltage window. Moreover this all solid-supercapacitor shows a capacitance up to 90 F.g−1 at room temperature. These encouraging results show the interest of developing such devices, including non-toxic and safer electrolytes, packaging issues and flexible devices development.
(Invited) Novel Ti4O7 /MnO2 Pseudocapacitive Composite for High Energy Density and Stability Supercapacitor
Authors: Weng Yu-Ting , Huang Sheng-Siang , Chuang Chung-Hsien , Wu Nae-Lih
Published: February 2020

Titanium dioxide (TiO2)-rutile has been considered as one of the promising candidates in supercapacitors due to its low cost, electrochemical stability, natural abundance, high surface area, low toxicity, and easy preparation in defined nanoscale dimensions. However, its specific capacitance is substantially lower than those of other pseudocapacitive metal oxides. In this study, we have demonstrated that the specific capacitance of TiO2-rutile can be dramatically improved by increasing oxygen deficiency. After phase transition to Magnéli phase, Ti4O7-electrode possesses a high specific capacitance of 168 F/g at 2 mV/sec, which is 10 times that of pristine TiO2-rutile. To further improve the specific capacitance, Ti4O7 is modified with 7 wt% MnO2, showing 345.5 F/g in an aqueous Li2SO4 electrolyte between 1 V and -1 V versus Ag/AgCl/saturated KCl without the problem of Mn ion dissolution. Furthermore, the composite electrode exhibits a high specific capacitance of 225 F/g even at a high scan rate of 400 mV/sec since Ti4O7 shows high conductivity. In addition, the Ti4O7/MnO2 supercapacitor exhibits 81 % capacitance retention with cycling up to 5000 cycles under the large potential range (1.6V). In view of the energy storage capacity, this new composite electrode holds great promise for next-generation high-energy supercapacitors.

Figure 1
Activated Carbon Derived from Tree Bark Biomass for High Performance Electrochemical Capacitors
Authors: Momodu Damilola Yusuf , Madito Moshawe Jack , Barzegar Farshad , Masikhwa Tshifhiwa Moureen , Ugbo Faith , Khaleed Abubakar Abubakar , Bello Abdulhakeem , Dangbegnon Julien Koudio , Manyala Ncholu
Published: February 2020

Activated carbon from tree bark (AC-B) has been synthesized by a facile and environmentally friendly activation and carbonization process at different temperatures (600, 700 and 800⁰ C) using potassium hydroxide (KOH) as an activation agent with different mass loading in an attempt to optimize the activation process in obtaining a uniformly porous material. The physicochemical characteristics of the as-obtained AC-B material were studied using scanning and (SEM), N2-adsorption/desorption measurements, Raman spectroscopy, X-ray photoelectron spectroscopy etc. The microscopy results reveal an interconnected porous architecture with an ion-accessible surface required for fast ion transport. The BET specific surface area (SSA) obtained show an improved SSA with increasing carbonization temperature up to 1018 m2 g-1 and a high pore volume of 0.67 cm3 g-1 in the presence of active micro/mesopores. The electrochemical capability of the AC-B material was investigated as a potential supercapacitor device electrode in different neutral aqueous electrolytes (NaNO3, Na2SO4, and KCl) via different techniques such as cyclic voltammetry, galvanostatic charge/discharge and impedance spectroscopy in a three (3) electrode configuration. The device electrode exhibited the best EDLC behaviour with the Na2SO4 electrolyte working in both positive and negative potential range. A specific capacitance of 155 F/g at a current density of 1 A/g was obtained for the AC-B material in a 0.80 V operating potential window. The cycling stability of the device was depicted in its overall coulombic efficiency which remained relatively stable even after 2,000 cycles. The result obtained provides a means of using cheaper biomass material in the production of high surface area activated carbon with outstanding electrochemical properties for supercapacitor applications.
Synthesized the Nano-Rod Structured Metal Oxide By AAO Template Method Application to Electrochemical Capacitors
Authors: Kim Cheong , Habazaki Hiroki , Park Soo-gil
Published: February 2020

Electrochemical capacitors have been interested to various industrial fields like medical tools, sport equipment and electric vehicles to support the lithium-ion battery due to their high power density and cycle stability. However, it has not enough rate capability for application of large scale device. To solve these problems, many studies of synthesized the nano-sized materials have many attentions because nano-sized materials have large surface area, which can lead to increasing the reaction surface. In addition, the symmetric technology is also applied to the arrangement where both composite electrodes are made of metal oxides and carbon materials. This new technology demonstrates superior performance compared to the conventional electrochemical capacitors: improved safety, higher specific energy, more stable operating voltage and voltage self-balancing in high-voltage strings of capacitor cells. In this study, we tried to synthesize the nano-rod structured of metal oxide by anodic alumina oxide (AAO) template for application of electrochemical capacitors electrode material. Among the numerous methods of the synthesized nano-fiber or nano-rod, anodic alumina oxide (AAO) templates have been received considerable attention for the growth of adjustable self-organized, highly ordered nano-fibers owing to easily control of the orientation of nano-rods. To observe the morphology and electrochemical performance of metal oxide, field emission scanning electron microscopy (FE-SEM), impedance, cyclic voltammetry and cycle performance were carried out.
The Effects of Duty Cycle on the Step Potential Electrochemical Spectroscopy (SPECS) and Electrochemical Impedance Spectroscopy (EIS) Analysis of Manganese Oxides for Electrochemical Capacitors
Authors: Donne Scott W , Forghiani Marveh
Published: February 2020

Step potential electrochemical Spectroscopy (SPECS) and electrochemical impedance spectroscopy (EIS) have been developed for characterising the performance of electrochemical capacitors. However the effects of the different duty cycle on the behaviour and analysis of electrochemical methods still need to be investigated. In SPECS method a small potential step is applied with a sufficient rest time to allow equilibrium between each step throughout an applied potential window. This small scan rate enables an electrode to reach to its maximum charge storage capabilities. More importantly, it allows separation of the charge storage mechanisms such as electrical double layer charge storage and diffusional processes. EIS method also can provide the different information about the electrochemical cell such as double layer capacitance, series resistance, charge transfer resistance and mass transport using a small AC excitation signal. However, the AC excitation signal can be large in magnitude for the electrochemical capacitors due to the cyclability over a large potential window. In this work, the combined SPECS and EIS methods have been applied to electrolytic manganese dioxide (EMD) in 0.5 M Na2SO4 between 0.0 – 0.8 V (vs SCE) at different duty cycles to examine the changes in charge storage mechanisms. Hence, the different scan rates and equilibrium times have been applied for the same electrode ink and electrolyte. Firstly, the same duty cycle with the same effective scan rate has been examined with increasing the step size and equilibrium time which is constituted of the scan rate of 10 mV in 120 s, 25 mV in 300 s and 50 mV in 600 s. Then, the longer duty cycle with slower discharge rate such as 25 mV in 10 min has been applied to compare the results of different duty cycles. So, nine different experiments have been run using the different step size of 10 mV, 25 mV and 50 mV and different equilibrium times ranging of 120 s, 300 s and 600 s. The outcome of this work indicates the systematic effects of different scan rate on the charge storage mechanisms. Also, it can be seen that, the average capacitance of the electrochemical cell from cycling voltammetry (CV), increased with decreasing the scan rate of the duty cycle.
Graphene Oxide Self-Assembled with a Cationic Fullerene for High Performance Supercapacitor Applications
Authors: Senthilkumar Krishnan
Published: February 2020

Supercapacitors, with promising high power densities and long cycle life, have attracted considerable attention due to their widespread applications in electric vehicles and high power appliances. Currently, carbon based porous materials such as activated carbon, activated carbon fibers, carbon aerogels, graphene, etc., are popularly used as electrode materials for supercapacitor applications. Graphene oxide (GO), an intermediate in the graphene synthesis from graphite, laden with oxygen functionalities behaves much like the quinone/hydroquinone redox switching process and has been exploited as a pseudocapacitor. However, the inevitable partial stacking occurring in GO, reduce surface area exposure to the electrolyte, thus substantially affecting the pseudocapacitive response. In the present work, we present a new strategy to prepare a cationic fullerene (CFU) intercalated graphene oxide (GO-CFU) composite. In an aqueous solution, positively charged CFU was electrostatically aligned with oppositely charged GO. The CFU behaving as a spacer between GO layers, suppress the GO stacking and expose basal plane oxygen functionalities with electrolyte more effectively. XRD analysis of GO-CFU shows that the (001) and (002) plane of GO is shifted negatively (by 2q of 1 and 1.2o, respectively) which validates the intercalation of CFU into GO layers. The prepared composite was subjected to supercapacitor performance evaluation studies. It was found that specific capacitance of the composite reached 357 F g-1 at 0.4 A g-1 current density in 1 M H2SO4. During 5000 charge/discharge cycles at 5 A g-1, the capacitance of the GO-CFU composite increases slightly (4% increase in GO-CFU vs. 4% decrease in GO), which validates the effectiveness of a self-assembly strategy for high performance supercapacitor applications.
Functionalization of Graphene Sheets By the Diazonium Chemistry during the Electrochemical Exfoliation of Graphite
Authors: Ossonon Benjamin Diby , Bélanger Daniel
Published: February 2020

Graphene is undoubtedly one of the most attractive material for researchers and new technologies due to its potential applications in several different areas.Various approaches are being developed for its large-scale preparation by green and cost-effective method. One of the best methods is the electrochemical exfoliation of graphite in an aqueous solution. However, for several applications graphene must be functionalized either non-covalently or covalently. In this work, graphene sheets produced electrochemically were functionalized during the exfoliation process by using appropriate reagents and experimental conditions. The resulting materials were characterized by several techniques such as X-ray photoelectron, Raman spectroscopy, thermogravimetric analysis, TEM, SEM, electronic conductivity measurements and electrochemical techniques.
Gallium Catalysed Direct Growth of Graphene Epitaxial Layer on SiC Substrates By Chemical Vapor Deposition
Authors: Jeganathan Kulandaivel , Dharmaraj Periyanagounder
Published: February 2020

Graphene, fascinates with its relativistic linear dispersion relation at low energies and the chiral nature of charge carriers, has garnered tremendous interest due to its unusual properties including high electron mobility with low electronic scattering which makes it as a potential candidate in nanoelectronics and photonic devices. Several outstanding advancements in graphene fabrication technology have been explored including research grade mechanical exfoliation of graphite, chemical vapor deposition (CVD), and thermal decomposition of SiC and chemical methods. In particular, the thermal decomposition of SiC surfaces is presently being a very promising approach since it offers wafer scale growth of graphene layers and a promise for high speed nanoelectronics devices. This method utilizes thermal energy to sublimate the topmost Si atoms from the SiC and carbon atoms bond together to form epitaxial graphene.

At present, ever growing effort is centered on the direct growth of graphene on SiC substrates by external carbon feedstock using CVD as it would offer several benefits toward the development of wafer scale industrial production of graphene technology on SiC. Moreover, this method facilitates the controlled monolayer growth on the flat SiC surface with high mobility and desirable band gap by varying the mass transport of the carbon precursor. However, a catalytic material must entail to soluble the decomposed carbon atoms on SiC surface to form carbon layers since the underlying SiC shown to have very weak catalytic activity. In this work, we employ a novel approach by utilizing metal gallium vapors as a catalyst and exposing it onto the SiC substrates along the carbon precursor to promote the catalytic activity for the direct fabrication of graphene. At elevated temperatures on the SiC surface, the gallium vapors assist to decompose the acetylene gases and nucleate the carbon atoms to form graphene layers over the substrate scale. The growth mechanism of epitaxial graphene on SiC substrate and the results will be presented in detail.

References:

P. Dharmaraj et al, J. Phys. Chem. C, 117, 19195 (2013)

P. Dharmaraj et al, Appl. Phys. Lett. 108, 051605 (2016).

K. Murakami et al, Appl. Phys. Lett.106, 093112 (2015).

W. Strupinski et al, Nano Lett. 11, 1786 (2011).
Improving Gas Barrier Performance of Polymer Nanocomposites with Carbon Nanotube Nanofillers
Authors: Cui Yanbin , Kumar S
Published: February 2020

Conventional materials such as metals and ceramics have been replaced by polymers over the last two decades in packaging applications due to their functionality, lightweight, ease of manufacturing and low cost. However, a limiting property of polymeric materials in food packaging is their inherent permeability to gases, including oxygen, carbon dioxide and organic vapors. This has boosted interest in developing new strategies to enhance the barrier properties of polymers. The barrier properties of polymers can be significantly enhanced by inclusion of fillers, such as clay and graphene. These nanofillers make the diffusing molecules follow tortuous pathways to pass through the nanocomposite film. As a result, a decline in permeability is obtained. In this study, polyethylene (PE) filled with carbon nanotube was synthesized via a liquid mixing process. It was found that the gas barrier properties of the composites filled with carbon nanotube are improved by 40% compared with pure polymer.
Development of Low-Temperature Methane Gas Sensors By Using Cup-Stacked Carbon Nanofilament-Supported Pd Catalyst
Authors: Koyama Kenta , Oda Hirokazu , Nakagawa Kiyoharu , Ando Toshihiro
Published: February 2020

Methane gas is found in environment, industrial and domestic areas. On the other hand, methane can cause explosions due to its inflammability. Thus, detection of methane gas in the environment is very important to avoid any accidental explosion. Catalytic combustion-type methane gas sensors can detect methane gas immediately. This type of methane gas sensors utilizes heat from catalytic combustion of methane by Pd-loaded catalysts. To indicate high catalytic activity, it is necessary for catalyst to heat around 250 ~ 600 °C because of thermochemical stability of methane. Consequently, electrical power consumption on the sensors is large. Hence development of efficient methane sensors that could work even at low temperatures is required.

In this work, cup-stacked carbon nanofilament (CSCNF) was used for Pd support material. γ-Al2O3 was used for general catalytic combustion-type methane gas sensors. Relatively large amount of Pd is required to indicate catalytic activity in using γ-Al2O3 support. On the other hand, CSCNF has functional groups such as C=O carbonyl-type structures and C-O-C ether-type structures on its edge surface regularly. These functional groups interact with metallic ion in preparing catalysts by impregnating method. Therefore, Pd can be discretely distributed in small particles on the surface of CSCNF. CSCNF supported catalysts are considered to indicated high activity with even small amount of Pd. Therefore, low-temperature combustion of methane is expected. Moreover, sensors can detect heat of methane combustion immediately because CSCNF has good thermal conductivity.

Catalytic activity of Pd/CSCNF was evaluated by temperature programmed reaction (TPR). This catalyst combusted 1 % methane in air at relatively low temperature 270 °C. Pd/γ-Al2O3, which was reference, combusted methane at 330 °C. CSCNF support was able to upgrade catalytic activity of Pd nanoparticles. Pd/CSCNF could reduce methane combustion temperature 60 °C lower than that of Pd/γ-Al2O3. It seems that CSCNF supported catalysts are attractive for methane combustion at low temperatures. CSCNF-loaded catalysts are more efficient for catalytic combustion-type methane gas sensors than the conventional sensors.
The Redox Reaction of Triiodide Ions/Iodide at Various Carbon Nanohorn Films-Modified Electrodes Prepared By the Electrophoretic Deposition Will be Discussed
Authors: Matsunaga Mariko , Suda Kento
Published: February 2020

Various types of nano carbon film-modified electrodes have been investigated for the application to a catalyst or catalyst support as an alternative to platinum electrodes because of their large specific surface area, high porosity, excellent electron conductivity, and the relative chemical stability. However, in our recent studies, the peeling resistance of these electrodes in solutions was confirmed to be weak in many cases. Then, we developed an electrophoretic deposition method to increase the pealing resistance using silane coupling agents(1). As a result, a film is successfully deposited homogeneously on the entire transparent electrodes (Figure) with strong pealing resistance against an acidic solution, even with nanohorns, which is known to show high water solubility. In addition, the film thickness is demonstrated to be controllable by the deposition time and voltage. The redox reaction of triiodide ions/iodide couples are confirmed to take place at these electrodes depending on the thickness of the film. The redox reaction of triiodide ions/iodide couple at various carbon nanohorn films-modified electrodes prepared by the electrophoretic deposition will be discussed on the day.

(1) “Preparation of Carbon Nanohorn Films by Electrophoretic Deposition with Silane Molecules for Application to Counter Electrodes of Dye-Sensitized Solar Cell,” Kento Suda, Rikiya Karasuno, Mariko Matsunaga, The 83th Annual Meeting of Japan Electrochemical Society, Osaka, Japan, Mar. (2016).

Figure 1
Electrochemical Corrosion Behaviors of 304 Stainless Steel with the Bimodal Grain Size Distribution
Authors: Gao Yan
Published: February 2020

Electrochemical corrosion behaviors of the bimodal microstructured (BMS) stainless steel (SS) were investigated by comparing with the coarse crystalline (CC) SS and the nanocrystalline (NC) SS. The BMS SS, consisting of the ultrafine grained matrix with an average gain size 350 nm (62 % (v/v)) and the micrometer embedded body with an average grain size 1.4 µm (38 % (v/v)), was obtained by post-ECAP heat treatment. Electrochemical corrosion properties of the BMS SS is found to be medium between the CC SS and NC SS from the results of the electrochemical tests, which is attributed to the “compound” microstructure including the relatively compact inner layer and the relatively porous outer layer in the passive film on the BMS SS according to the results of the equivalent electrical circuit (EEC) simulation and atomic force spectroscopy (AFM) analysis.

Figure 1
Correlation Between Free Volume and Ionic Conductivity of Non-Aqueous Lithium Battery Electrolyte Solutions over a Wide Concentration Range
Authors: Abu-Lebdeh Yaser , Tam Jasper , Soboleski Hayden
Published: February 2020

There is little known about the transport behavior of ions in electrolyte solutions at very high concentration and there is currently no satisfactory theory/equation to describe it [1,2]. In this work electrolyte solutions of lithium salts of various anions: [(CF3SO2)2N]°¥, (TFSI), [PF6]°¥ and [BF4]°¥ dissolved in polar solvents and solvent mixtures up to saturation have been prepared. The solvents are propylene carbonate (PC), acetonitrile (ACN), adiponitrile (ADN) and ethylene carbonate:dimethyl carbonate (1:1 v/v) (EC:DMC). The Ionic conductivity and density of the electrolyte solutions have been  measured over a wide concentration range (up to 5.4 M).

The specific ionic conductivity (κ) vs. C plots show a non-ideal behavior with very strong dependence on concentration (a typical Gaussian-like function) while the molar conductivity (Λ) vs. C plots show an exponential decrease similar to the behavior of weak electrolyte solutions. The conductivity vs. concentration data were fitted to various equations of known models (Debye-Hückel-Onsager’s square-rate law: Λ vs. C^1/2, Cubic-root law: Λ vs. C^3, Casteel-Amis equation: κ/κmax vs. C/Cmax , or the corresponding state-law equation based on the pseudo-lattice theory: κ/κmax vs. C/Cmax .The models show good fit only in the low concentration, with the last two models fail to show universal behavior beyond the  concentration of maximum conductivity, Cmax. However, we have derived a new, semi-empirical equation that shows a very good fit over the whole concentration range and can correlate molar ionic conductivity to changes in free volume within the liquid solution:

Λ = A' exp [-B C], B =-γ Vo/Vf, and  Vf = V-Vo

Where Vƒ is the free volume which can be calculated from the difference between the measured volume, V, of the liquid (from density measurements) and the Van der Waal “molecular “volume, Vo, which can be obtained from XRD data at low temperatures or calculated using chemical models. C is concentration, A’ is a pre-exponential factor that can be related to limiting molar conductivity and square root of temerature. γ is a correction factor for overlapping holes with a value between 0.5 and 1.

These preliminary results are encouraging in bringing us closer to a free volume-based approach to explain the behavior of ionic conductivity of electrolyte solutions at very high concentrations. However, more work is underway to study more solutions with different chemical and physical properties, including aqueous solutions, to test the validity of this approach.

[1] S. I. Smedley, The Interpretation of Ionic Conductivity in Liquids, Springer, 1980

[2] C.A. Angell, J. Phys. Chem., 70, 1966, 3988
Superconcentrated Electrolytes for a High-Voltage Lithium-Ion Battery
Authors: Wang Jianhui , Yamada Yuki , Sodeyama Keitaro , Chiang Ching Hua , Tateyama Yoshitaka , Yamada Atsuo
Published: February 2020

Finding a viable electrolyte for next-generation 5 V-class lithium-ion batteries is of primary importance. A long-standing obstacle has been metal ion dissolution at high voltages. The LiPF6 salt in conventional electrolytes is chemically unstable, which accelerates transition metal (TM) dissolution of the electrode material, yet beneficially suppresses oxidative dissolution of the aluminium current collector; replacing LiPF6 with more stable lithium salts may diminish TM dissolution but unfortunately encounters severe aluminium oxidation. Here we report a new electrolyte design that can solve this dilemma. By mixing a higly stable lithium salt with a solvent at extremely high concentrations, we obtain an unsual liquid showing a three-dimension network of anions and solvent molecules that coordinate strongly to Li+ ions. This new class of electrolytes inhibits the dissolution of both aluminium and TM at around 5 V, and realizes a high-voltage LiNi0.5Mn1.5O4/graphite battery that exhibits excellent cycling durability and high rate capability. Additionally, the electrolytes show superior thermal stability and flame retardant ability. Therefore, the superconcentrated electrolytes might offer many new opportunities in building safe and stable high-voltage batteries not limited to the lithium-ion.

Figure 1 Discharge capacity retention of high-voltage LiNi0.5Mn1.5O4/natural graphite batteries using lab-made superconcentrated and commercial dilute electrolytes. The inset shows EDS spectra on the graphite electrode surface after the cycling test. Charge and discharge were conducted at 40 °C with a current rate of 29.4 mA g−1 (C/5) on the weight basis of the LiNi0.5Mn1.5O4 electrode.

Figure 1
Effect of Calcination Temperature on the Characterizations of P-Type Na0.6Mn0.65Ni0.25Co0.10O2 Cathode Materials in Sodium-Ion Batteries
Authors: Nguyen Ngoc Anh , Kim Kyuman , Kim Yong Joo , Kim Sang Hern , Ryou Myung-Hyun , Lee Yong Min
Published: February 2020

Recently, the demand for energy storage devices for electricity supply has been increasing remarkably. Lithium-ion batteries have already been popular power supplies for devices such as mobile phones, notebooks, digital devices and hybrid vehicles and so on. This increases the rate of lithium consumption; therefore, its cost has risen because of lithium source problem. Owing to abundant sodium resource and its low cost in comparison with lithium, sodium-ion batteries are promising for energy storage devices. Concerning cathode materials, layered NaxMO2 are classified into two main groups (O3 type or P2 type) in which the sodium ions are accommodated at octahedral and prismatic sites, respectively. Many works reported that P2-type structure exhibits a higher capacity and cyclability than O3-type structure. In this work, P-type Na0.6Mn0.65Ni0.25Co0.10O2 cathode materials were synthesized by a co-precipitation method. Effect of calcination temperature on the morphology, crystalline structure and electrochemical properties were investigated. Both P3-type (700 oC) and P2-type (800-1000 oC) structures were obtained at different calcination temperatures. In the cycling process, the P3-type material revealed a high discharge capacity of 136 mAh g-1 but a poor cycling performance. In contrast, the P2-type synthesized at 900 oC gave a highest specific discharge capacity of 148 mAh g-1and a more stable cycling performance and a good rate capability between 2.1 and 4.3 V.

Acknowledgement 

 This work was supported by the Human Resource Training Program for Regional Innovation and Creativity through the Ministry of Education and National Research Foundation of Korea (NRF-2014H1C1A1066977).

References

[1]     C. Delmas, J. Braconnier, C. Fouassier, and P. Hagenmuller,  Solid State Ionics, vol. 3–4, pp. 165–169, 1981.

[2]      J. M. Paulsen and J. R. Dahn,   Solid State Ionics, vol. 126, pp. 3–24, 1999.

[3]      N. Yabuuchi, M. Kajiyama, J. Iwatate, H. Nishikawa, S. Hitomi, R. Okuyama, R. Usui, Y. Yamada, and S. Komaba,   Nat. Mater., vol. 11, no. 6, pp. 512–517, 2012.

Figure 1
Low-Cost Sodium-Ion Batteries (LOCO-NIBs Project)
Authors: Salcianu Carmen , Titirici Maria-Magdalena
Published: February 2020

The LOCO-NIBs (Low-cost Na-ion Batteries) Project funded by Innovate UK aims to investigate novel anode and cathode materials with compositions and morphologies which allow stable insertion and removal of sodium ions for a long number of cycles. This would facilitate the creation of energy storage systems of significantly lower cost due to the abundance of the sodium resources and materials implemented. This collaboration between School of Materials Science and Engineering at Queen Mary University of London (QMUL) and Johnson Matthey (JM) aims to develop low cost and highly performing electrode materials for sodium-ion electrodes based on abundant sodium resources and biomass derived low cost carbon electrodes. This will accelerate the development of sodium ion batteries which could be then integrated into battery modules, creating a new generation of competitive stationary battery systems increasing thus the security of supply, and the use of clean and locally generated energy sources such as solar and wind.   

Most of the ongoing research in sodium-ion batteries relates to the development of cathodes where replacement of lithium by sodium has been a common route for finding good and low cost electrodes. Thus, a wide range of compounds are being currently studied as cathode materials from oxides to phosphates, fluorophosphates or pyrophosphates. Within this project we aim to investigate cathode candidate materials obtained by replacement or reduction in higher cost metal elements such as Co and Ni, with higher abundance, lower cost elements such as Fe and Mn, while improving cell voltage, capacity and cycling stability through accommodation of volume changes.

Much less research has been dedicated in the field to the anode material due to the inability of sodium to insert into graphite along with the formation of a stable solid electrolyte interface layer. Most of the proposed carbon materials as anodes in sodium ion batteries in the literature are expensive and derived from fossil-fuel precursors, using high-energy production techniques.

Following successful completion of the project, further development up the supply chain into cells and finally into sodium-ion battery based modules and systems is foreseen. The stationary market is predicted to grow in the near future. It is predicted that over 50,000 modules will be required by 2020. If this was the case then this would require 500 tonnes of combined anode and cathode materials. Interactions with energy companies, OEMS and other end users would also be anticipated, promoting the creation of a supply chain for electrical energy storage that would make an important contribution to economic growth and employment in the UK.
SnO2 nanocrystals into Three Dimensional Graphene Architectures for Lithium Ion Batteries
Authors: Kim Hyun-Kyung
Published: February 2020

Li ion batteries (LIBs) are important for energy storage in portable electronic devices, power tools, and electrical vehicles, all of which require high energy density. In order to meet the increasing demand for high energy density batteries, it is essential to develop high-capacity electrode materials. Recently, metal- and metal oxide-based anode materials have been reported to exhibit higher Li storage capacities than commercial graphite anode. However, the reversible charging and discharging process is accompanied by large volume variation, which can result in the pulverization of high capacity anodes and loss of electrical contact, causing rapid capacity decay upon extended cycling. The most promising approach is the integration of metal oxides with carbonaceous materials. Inspired by this approach, we demonstrate a facile strategy for fabricating a 3D reduced graphene oxide (RGO)-SnO2 architecture that encompasses the merits of both SnO2 nanostructures and carbonaceous materials with the aim of improving energy storage in LIBs, especially in terms of cycling performances. The hierarchical SnO2-RGO aerogel shows excellent electrochemical performance, with a high reversible capacity, a high rate capacity and good cycleability. This performance is attributed to the uniform dispersion of SnO2 nanoparticles and the 3D macroporous continuity, which provide a large accessible area, easy ion accessibility, short ion diffusion length, and rapid charge and mass transport. More details will be discussed at the meeting.
Mesoporous Lithium Titanate-Carbon Composite (Li4Ti5O12-Carbon) with Controlled Microstructure As Anode in Lithium Ion Batteries for Low Temperature
Authors: Ho Ching-Kit , Li Chi-Ying Vanessa , Chan Kwong-Yu
Published: February 2020

The high discharge rate performance of lithium titanate (Li4Ti5O12) is limited by the low electronic conductivity of the material (<10-11 Sm-1), addition of carbon is one of the effective way in enhancing the rate performance. [1-3]

In this study, carbons with a hollow core and mesoporous shells of controlled dimensions (in terms of diameter of core, thickness of the shell and diameter of the mesopores) were synthesized via silica hard-template method. Li4Ti5O12-carbon composites were built through impregnation of Li4Ti5O12 into the core-shell carbon. These Li4Ti5O12-carbon composites exhibit higher electronic conductivity, and enhanced electrochemical behavior for prolonged cycles at high discharge rate due to increased surface area of the active material, and improved ion transport pathways from possibly the length scale effect. Cross-section TEM studies have been performed and proved that Li4Ti5O12 particles are impregnated within the mesoporous carbon shell structure. This Li4Ti5O12-carbon composite can achieve superb coulobmic efficiency of 98% and 96%, and superior long-cycling life with remarkably high capacity retention of 99% and 85% over 2,000 cycles at 10C (2.2 Ag-1) and 20C (4.4 Ag-1), respectively. Similar electrochemical behavior is observed for low temperature condition.

References

1. C.K. Ho, H. Yung, M. Zhou, C.Y.V. Li, K.Y. Chan, “Mesoporous Lithium Titanate-Carbon Composite with Controlled Microstructure”, Abstract #1148, 224th ECS Meeting, October 2013, San Francisco, U.S.A.

2. S.W. Ting, C.Y.V. Li, H. Yung. C.K. Ho and K.Y. Chan, “Structural and Electrochemical Studies of Mesoporous Li4Ti5O12-TiO2 Composite Spheres as Anode Material for Lithium ion Batteries”, 222nd ECS Meeting, October 2012, Honolulu, Hawaii, U.S.A.

3. C.Y.V. Li, S.W. Ting, Z. Yang, W. Zhuang, X. Lu, H. Yung and K.Y. Chan, “Lithium Titanate Prepared from Mesoporous TiO2 Fiber as Anode Material for Lithium Ion Batteries”; 222nd ECS Meeting, October 2012, Honolulu, Hawaii, U.S.A.

Acknowledgements

This work was supported by Hong Kong Research Grants Council General Research Fund (HKU 700209P), Strategic Research Theme on Clean Energy, University Development Fund on Initiative on Clean Energy, and Innovation and Technology Fund of the Hong Kong SAR (ITS/076/11).