bluuebunny/crossref_metadata_2025_split huggingface dataset:
Invited: Microplasma Spray Deposition of Nanostructured Films for Catalytic, Magnetic, and Photonic Applications
Authors: Koh Travis , Pebley Andrew , Mackie Katie , Gordon Michael 
Published: February 2020

We present a hybrid plasma spray deposition technique, based on geometrically-confined, supersonic microplasma jets, which can realize a wide range of metal oxide/sulfide nanoparticles and nanostructured thin film materials (e.g., CuO/CuS, ZnO, SnO2, NiO/NiFe2O4) on virtually any surface. Organometallic precursors are dissociated in a hollow cathode microplasma jet under different reducing/oxidizing atmospheres at high pressure (10-100 torr), creating a directed flux of active metal and oxide species for the subsequent growth of nanostructured films. Interaction of the jet afterglow with the background gas can create additional species (e.g., excited neutrals, radicals, etc.) which participate in film growth. By varying supersonic jet flow characteristics, plasma current, precursor flux, source distance, and deposition time, deposits ranging from isolated nanoparticles to films of fibers, aggregates, nanowires, and dense columns can be realized. The talk will highlight our recent efforts [1-5] in oxide/sulfide nanomaterial synthesis via microplasmas with emphasis on the physics of the jet source, dynamics of the growth process, and applications such as solar cell electrodes, photo(electro)catalysis, and nanogranular films for magnetic exchange bias applications.
[1] T. Koh and M.J Gordon, J. Phys. D: App. Phys.
46, 495204 (2013).
[2] T. Koh, I. Chiles, and M.J Gordon, Appl. Phys. Lett.
103, 163115 (2013).
[3] T. Koh and M.J Gordon, JVST A
31, 061312 (2013).
[4] T. Koh and M.J. Gordon, J. Crystal Growth
363, 69 (2012).
[5] T. Koh, E. O'Hara, and M.J. Gordon, Nanotechnology
23, 425603 (2012).
Invited: Continuum Modeling of Interfacial and Transport Phenomena in Electrochemical Capacitors
Authors: Pilon Laurent , d'Entremont Anna , Girard Henri-Louis 
Published: February 2020

Electrochemical capacitors are promising electrical energy storage devices bridging the gap between batteries and conventional dielectric capacitors. They can be divided in two categories: electric double layer capacitors (EDLCs) and pseudocapacitors. EDLCs store electric charge physically in the electric double layer forming at the interfaces between the electrolyte and nanoporous electrodes. During charging or discharging, ions are transported in the electrolyte under the combined influence of diffusion and electrostatic forces as well as steric effects. On the other hand, pseudocapacitors store energy not only via the electric double layer but also via fast surface redox reactions and possibly ion intercalation within the redox-active electrode.
This talk will present physical modeling of interfacial phenomena, transport phenomena, and redox reactions in electrochemical capacitors under charging and discharging conditions. The model accounts for finite ion size, asymmetric electrolytes, and three-dimensional electrode morphology. It also considers faradaic reactions and ion intercalation when simulating pseudocapacitors. Typical cyclic voltammetry measurements will be reproduced numerically for various electrolyte and electrode materials and different scan rates. The results will be used to provide detailed physical interpretation of experimental measurements. Special effort will be made to systematically compare model predictions with experimental data.
MnO2 Inks for the Fabrication of Supercapacitor Electrodes
Authors: Coustan Laura , Ould Amara Salem , Favier Frederic 
Published: February 2020

The gap between electronics and users is becoming narrower as the portable electronics comes to wearable. As such, power supply, including storage devices, comes to wearable too. In addition to power and energy, specific characteristics are required for integration: lightweight, thickness, safety, washability, flexibility... and eventually hypoallergenic or biocompatibility. Facing these specifications, integration of storage devices such as Li-ion batteries or supercapacitors in clothes remains an exiting challenge. Supercapacitors based on pseudocapacitive metal oxide -based electrodes operated in neutral aqueous electrolytes could fit most of these requirements. The context of this study is the development of supercapacitor electrodes based on the deposition of MnO2 onto flexible current collectors. Although various approaches have been investigated for the fabrication of high-performance flexible supercapacitors, they have to consider various material/device characteristics including intrinsic flexibility, mechanical integrity of the current collector/electroactive material assemble and retention of the electrochemical performances under stress. The material deposition onto flexible substrates can be carried out by electrodeposition, spin coating, spray or inkjet deposition [1]. Many surfactants have been used such as sodium dodecyl sulfate, Triton X100 or Caffeic acid, for the formulation of the complex MnO2 particle suspensions required for the fabrication of homogeneous and performing electrodes by these latter techniques.

Figure: Cyclic voltammograms of Mn-oxide/free (a), Mn-oxide/SDS (b), Mn-oxide/CA (c), and Mn-oxide/TX100 (d) at a scan rate of 5 mV.s-1 in 1M Na2SO4 aqueous electrolyte.
To enhance the rheological characteristics of the prepared inks, we have considered the use of these surfactants at the preliminary stages of the synthesis of MnO2 particles by wet chemistry. The present study focuses on the impact of three different surfactants used for the synthesis by co-precipitation of MnO2 on the (electro)chemical characteristics of the prepared powders. It also describes various approaches for the fabrication of supercapacitor electrodes based on these MnO2 powders.
[1] J. Keskinen, E. Sivonen, S. Jussila, M. Bergelin, M. Johansson, A. Vaari, M. Smolander, Electrochimica Acta 85 (2012) 302-306
Synthesis of Ni-Co Oxides/Sulfides Nanowire Arrays for Ultrahigh Electrochemical Capacitors
Authors: Xiao Peng , Li Yan Hong , Zhang Yunhuai , Yang Yang 
Published: February 2020

Electrochemical capacitors (supercapacitors) have attracted intense attention due to their high power density, fast charge-discharge process, long cycle life and used in many practical applications. Ni-Co composites, also known as ternary metal composites, have excited great interest in recent years because of their high-performance in supercapacitors. Owing to the coupling of two metal species, these materials could render the composites with rich redox reactions and improved electronic conductivity, which are beneficial to electrochemical applications. In particular, the tunable compositions in the Ni-Co oxides provide vast opportunities to manipulate the crystal structure and its physical/chemical properties. During the past years, different shapes and structures of Ni-Co oxides/sulfides were investigated and most of the researches were focused on NiCo2X4 (X=O, S). Very few works investigated Ni-Co composites with different Ni-Co molar ratio and its fabrication of free standing electrode structure.
Here we report the interesting formation of Ni-Co oxides and Ni-Co sulfide nanowire arrys (NWAs) with Ni/Co molar ratio at 1: 1 and their derived free standing structure on different substrates for ECs. Ni-Co oxides NWAs were synthesized on ordered TiO2 nanotubes and Ni foam respectively by a facile hydrothermal method. Ni-Co sulfides NWAs were fabricated through S2- ion exchange using synthesized Ni-Co oxides nanowires as precursor. The electrochemistry testes showed that this self-supported electrode is able to deliver ultrahigh specific capacitance. To raise the cell voltage and thereby boost the energy density more effectively, we use the Ni-Co sulfides NWAs for the battery-like Faradic electrode and activated carbon for the capacitive electrode to compose an asymmetric cell, and this has extended the cell voltage to 1.8V in an aqueous electrolyte, resulting in high energy density, high power density and good cycling stability all together. To the best of our knowledge, such a prototype device has not been fabricated and explored before.
One-Step Synthesis of Carbon Supported Nb2O5 Particles for Electrochemical Capacitor Applications by Oxidation of Layered Nb2C
Authors: Beidaghi Majid , Zhang Chuanfang , Lukatskaya Maria , Maloney Ryan , Dunn Bruce , Gogotsi Yury 
Published: February 2020

The crystalline network of orthorhombic niobium oxide (T-Nb2O5) offers two-dimensional transport pathways for fast intercalation of lithium ions, leading to its high and rate independent intercalation pseudocapacitance. Unlike many other lithium intercalation metal oxides, T-Nb2O5 can be charged in short periods of time, making it suitable as a supercapacitor electrode material. This is due to the fast solid-state diffusion and no structural change of T-Nb2O5 upon intercalation of Li ions. For practical applications of Nb2O5 and other metal oxides in supercapacitors, thick electrodes with large mass loadings are necessary. This, however, will result in ohmic losses and ion transport limitations due the relatively low electrical conductivity of the oxide and limited ion diffusion through the electrode thickness. To address these limitations, we have successfully prepared the layered Nb2O5/carbon hybrid materials through controlled oxidation of layered Nb2C (also called Nb2C-MXene). As-prepared Nb2O5/C well inherited the two dimensional structure of the precursor with Nb2O5 nanocrystals formed between the MXene layers. A detailed study of oxidation temperatures and durations was conducted to achieve nanostructured of T- Nb2O5 and XRD, SEM and TEM studies show the uniform formation T-phase of Nb2O5 on carbon sheets after oxidation at 850℃. The electrochemical characterization of thick electrodes of synthesized material show very promising performance, with specific capacitance of about 350 F/g in 1M LiClO4 /EC/DMC (1:1 in volume ratio) electrolyte. The performance of developed electrodes is believed to be highly dependent of layered two-dimensional structure of Nb2O5/carbon hybrid materials.
Acknowledgements: Authors acknowledge Dr. Mengqiang Zhao for his help with TEM studies. Support from DOE via Sandia National Laboratory is appreciated.
High-Voltage, High-Frequency Electrochemical Capacitor
Authors: Miller John R. , Outlaw Ronald A , Butler Sue M. 
Published: February 2020

Electric double layer capacitors (EDLCs) with electrical performance like aluminum electrolytic capacitors have been developed.(1) They can be smaller in size and offer higher reliability. Operation of such devices relies on charge stored on vertically oriented graphene nanosheet (VOGN) carbon. Vertically oriented graphene nanosheets are prepared using RF plasma enhanced chemical deposition of a hydrocarbon feed gas.(2) Under proper growth conditions, VOGN are ohmically connected to the metal current collector on which they grow, offer high electronic conductivity, and have an “open” structure totally free of porous electrode behavior. Each of these characteristics is necessary for efficient operation at frequencies of 1 kHz and higher.
EDLC cells, like battery cells, operate at low voltage. Thus cells must be series connected to operate at high-voltage. Figure 1 shows an approach devised for interconnecting the EDLC cells to create a high-voltage, high-frequency EDLC. It involves interconnecting planar EDLC cells using the substrate metallization. As shown, interdigitated gaps are created in the VOGN that has been grown on a thin metal layer covering an insulating substrate, for instance, nickel on alumina. The gap is created using a laser to cut through the VOGN and metal down to the insulating substrate. This then creates multiple electrically-isolated regions (six are shown in the figure). Two adjacent regions become a single EDLC after electrolyte is applied over the gap and the surface of that region. To make a series connection of cells, each gap must be individually covered with an electrolyte, making sure that the electrolyte band does not touch the neighboring bands. This is a “bipolar” design in two dimensions, the substrate metallization serving as the bipolar plate.
Connecting M cells in series each rated at voltage Vo with capacitance Co and series resistance Ro yields a capacitor with a voltage rating M·Vo, capacitance Co/M, and series resistance M·Ro. The frequency response of this high-voltage capacitor is nearly identical to that of one of its cells because the interconnects add minimal resistance. Voltage-balance resistors can be added using, for instance, thick-film printing processes. Details of the fabrication process are described and electrical performance data on these high-voltage, high-frequency electric double layer capacitors is presented.

References

1J.R. Miller el al, “Graphene Double-Layer Capacitor with ac Line-Filtering Performance”, Science 329
, 1637 (2010).

2Cai M, Outlaw RA, Butler SM, and Miller JR, “A High Density of Vertically-Oriented Graphenes for Use in Electric Double Layer Capacitors”, Carbon
50, 5481–5488 (2012).
.
Aqueous Hybrid Supercapacitor Using Protected Pre-Lithiated Carbon Anode
Authors: Sugimoto Wataru , Makino Sho , Shimizu Wataru 
Published: February 2020

1. Introduction
Pseudocapacitive oxide electrodes generally perform best in aqueous electrolytes. The use of aqueous electrolytes unfortunately limits the maximum cell voltage to no more than 2 V, which is a disadvantage for energy density (E=0.5 CV2). This disadvantage can be overcome by using a water-stable solid electrolyte [1-3]. The new cell configuration is based on the use of a protected Li anode, which consists of a water stable Li-conducting solid electrolyte, a Li-conducting gel electrolyte buffer layer, and Li foil as the negative electrode. The application of the water stable anode allows the implement of aqueous electrolytes at the pseudocapacitive positive electrode. The cell voltage can reach as high as 4.3 V when MnO2 is used as the positive electrode [1,3]. In this study, we pre-lithiated carbon (LixC6) was adopted as the negative electrode instead of Li.
2. Experimental
Li doping into graphite was conducted with a three-electrode cell at constant current (0.2C) in 1.0 M LiPF6/EC:DEC. After the pre-doping procedure, the cell was disassembled and reassembled into a pouched cell. The multi-layered anode consists of a LISICON-type solid glass ceramic (Li1+x+y(Ti,Ge)2-xAlxSiyP3-yO12 (Ohara Inc., Japan, hereafter denoted as LTAP) as the water-stable solid electrolyte, and a buffer layer consisting of polyethylene oxide with Li(CF3SO2)2N polymer electrolyte (PEO-LiTFSI) between the lithium metal or pre-lithiated carbon and the solid electrolyte. These 3 layers were sealed into a laminated pouched cell leaving a 5 mm x 5 mm window cut out for the solid electrolyte (LTAP) to come into contact with the aqueous electrolyte.
Results and discussion
After Li-doping of graphite in the pre-doping cell, the potential of the negative electrode was 57 mV vs. Li/Li+. The color pf graphite changed from black to gold with Li doping. Taking into consideration the irreversible capacity, it can be assumed that pre-doping at 0.2C is sufficient to achieve close to fully doped state. Figure 1 shows the charge/discharge curves using activated carbon positive electrode (LiC6 | PEO-LiTFSI | LTAP | 1.0 M Li2SO4aq. | AC). Maximum cell voltage of 3.7 V was obtained. The AC positive electrode showed capacitive behavior with the potential varying linearly with time between 0.33 and 1.29 V vs RHE. The potential of the negative electrode was -0.24 V vs RHE, and exhibited typical battery-like behavior. The overall cell performance is similar to lithium-ion capacitors. The specific capacitance of the AC positive electrode was 135 F/g.
1) S. Makino, Y. Shinohara, T. Ban, W. Shimizu, K. Takahashi, N. Imanishi and W. Sugimoto, RSC Adv., 2, 12144 (2012).
2) S. Makino, T. Ban and W. Sugimoto, Electrochemistry, 81, 795 (2013).
3) W. Shimizu, S. Makino, K. Takahashi, N. Imanishi, W. Sugimoto, J. Power Sources, 241, 572-577 (2013).
Figure 1. Galvanostatic charge/discharge curves of aqueous hybrid capacitor (LiC6 | PEO-LiTFSI | LTAP | 1.0 M Li2SO4 aq. | AC) at 0.102 mA cm-2.
Development of a Coupled Electrical, Thermal and Degradation Supercapacitor Model for Automotive Applications
Authors: Sarwar Wasim , Marinescu Monica , Taylor Nigel , Offer Greg 
Published: February 2020

Despite the fact that supercapacitors are less complex than lithium ion batteries, they are less well understood. Although supercapacitors do not possess sufficient energy density to make them suitable as the only source of energy storage in the majority of applications, they are ideal as a buffer for the primary energy source. Applied to hybrid and electric cars, supercapacitors can be used to reduce the degradation and power requirements of the primary energy source, typically lithium ion batteries.
To the best of the author’s knowledge, currently, no unified, high fidelity, electrical, thermal and degradation model exists of a supercapacitor that meets automotive requirements. This is because the electrical and thermal models must re-create both short term and long term cell behavior over a large range of temperatures, frequencies, and currents. They must also include degradation models that are valid under complex cycling conditions and not simply under constant current cycling.
The state-of-the-art electrical models of a supercapacitor are equivalent circuit models, which utilize a de-Levie transmission line. The length of the transmission line is analogous to the path length of an ion from its initial location to forming part of the electrical double layer, or pore depth penetration. Thus, the transmission line can be utilised to either model the available electrode surface for ion adsorption, and hence capacitance variation with frequency, or model the charge distribution throughout the porous structure, and hence determine voltage hysteresis as a result of charge re-distribution. The standard de-Levie transmission line cannot be used to characterize both of these effects simultaneously, (which is necessary for automotive requirements) without being adapted.
The majority of supercapacitor thermal models are either lumped models or axi-symmetric models utilizing an assumption of uniform heat generation. Although these models are suitable for determining thermal management strategies, and degradation under steady state conditions, they are unsuitable for determining degradation in highly dynamic systems. They are unable to predict localized hotspots at the electrode/electrolyte interface, which are caused by the entropy effects of the generation or breakdown of the electrical double layer. Furthermore, they are unable to predict the temperature difference between the positive and negative terminals.
This talk will outline the development and validation of a new equivalent circuit model of a supercapacitor for automotive use. The electrical model is capable of reproducing cell behavior, including power limits, variation of capacitance and resistance with operating temperature and frequency, charge re-distribution and self-discharge. The coupled thermal model is capable of predicting reversible and irreversible heat generation and its spatial distribution throughout the cell, and the resultant degradation.
Enabling Sub-10nm Lithography with Atomic Layer Deposition and Block Copolymer Self Assembly
Authors: Ruiz Ricardo , Chapuis Yves-Andre , Wan Lei , Xiong Shisheng , Gao He , Patel Kanayialal , Dobisz Elizabeth , Bogdanov Alexei , Nealey Paul , Albrecht Thomas 
Published: February 2020

Block copolymer lithography, an alternative lithographic technique by which self-assembled patterns made from block copolymer thin films are used as lithographic masks, has achieved a high enough level of maturity to be considered for nanofabrication in magnetic recording bit patterned media and in some applications in the semiconductor industry. As the demand for lithographic dimensions squeezes into the single-digit nm scale, pairing block copolymer materials that segregate at these dimensions with adequate pattern transfer techniques is increasingly difficult. For example, PS-b-PMMA, the most mature block copolymer system can only form line/space patterns with pattern transfer above 10 nm. Other promising materials like P2VP-PS-P2VP triblocks, however, lack sufficient etch contrast for reactive ion etching. Here, we present a nanofabrication strategy that integrates atomic layer deposition, ALD, with block copolymer lithography to enable fabrication of sub-10nm features for high density magnetic storage.
The selective, cyclic and self-terminating nature of the materials synthesis within ALD reactors provides powerful nanofabrication tools. In particular, two of these tools stand out as enablers for high density patterning: First, the chemical selectivity of the organometallic precursors has facilitated selective synthesis inside porous polymeric materials. Second, the conformality afforded by the self-terminating nature of the ALD reactions has proven to be ideally suited for feature doubling in self-aligned double patterning, SADP. Integrating these powerful tools with block copolymer lithography opens new possibilities in two fronts: On the one hand, it is possible to generate hybrid nanocomposites with nanometer-scale resolution and high etching contrast. This is particularly useful for high resolution block copolymer materials for which no natural etch contrast exists such as P2VP-PS-P2VP triblocks. On the other hand, it is possible to use the already sub-lithographic features obtained by standard PS-b-PMMA block copolymer lithography as the starting point for an additional density multiplication using spacer lines grown by ALD for SADP.
Be it for selective infiltration synthesis in block copolymer patterns or for the precise conformal growth in nanostructures made from block copolymers, ALD is likely to emerge as an ideal complimentary technique to block copolymer self assembly to enable sub-10nm lithography.
Heteroleptic Precursors for Atomic Layer Deposition
Authors: Niinistö Jaakko , Blanquart Timothee , Seppälä Sanni , Ritala Mikko , Leskelä Markku 
Published: February 2020

As the atomic layer deposition (ALD) method is based on sequential, self-limiting surface reactions the precursor chemistry is the key to a successful processing of conformal high quality thin films. ALD precursor chemistry has traditionally been based on homoleptic compounds such as, but not limited to, metal halides, alkylamides and alkoxides. However, these precursors may have drawbacks such as possible halide contamination and low thermal stabilities in the case of the alkylamides and alkoxides. Consequently, heteroleptic precursors have been investigated as alternatives to the existing homoleptic counterparts, leading to the development of several advantageous processes.
In the recent years, increasing research effort has been dedicated in development of novel ALD processes focusing especially on transition metals and their oxides using heteroleptic precursors. Interestingly, heteroleptic compounds often show different properties than their homoleptic counterparts. One type of ligand can provide reactivity and another stability, thus widening the process window with comparable film growth rate.
In this presentation heteroleptic precursors for ALD processes of transition metals and their oxides will be reviewed. Special focus is given to oxides of the rare earths and groups 4 and 5. Trends in the properties of heteroleptic precursors are discussed. Several examples of our recent results are shown, including introduction of novel processes based on amidinate-cyclopentadienyl complexes for ALD of rare earth oxides.