bluuebunny/crossref_metadata_2025 huggingface dataset:
Carbon Nanotube Array Field Effect Transistors with High Current Density and On/Off Ratio
Authors: Brady Gerald J , Way Austin J , Jaccoberger Robert M , Joo Yongho , Gopalan Padma , Arnold Michael S.
Published: February 2020

Single walled carbon nanotubes (SWCNTs) exhibit extraordinarily high current carrying capacity and suitable band gaps for logic and thin film field-effect transistors (FETs). Progress in honing the exceptional properties of SWCNTs at the multi-tube level, however, has been dampened by incremental advances in the materials science of electronic type sorting and assembly of SWCNTs. To address these challenges we leveraged the exceptional semiconducting sorting fidelity of polyfluorene polymers and we pioneered an alignment technique known as Floating Evaporative Self-Assembly (FESA).1 Recently, we demonstrated individually placed and uniformly pitched purely semiconducting SWCNT arrays using these techniques, allowing for negligible current lost to scaling when the arrays were implemented as the channel in FETs. The SWCNT array FETs exhibited the highest on-state conductance of 261 μS/μm with a simultaneous on/off conductance ratio exceeding 105 for a multi-tube SWCNT FET.2 Here we present our recent optimization of the contact resistance at the palladium-SWCNT interface, which enables a substantial increase in device on-current density compared to our previous report.

            For SWCNTs, the quality of the contact-semiconductor interface is highly dependent on the SWCNT packing density, film cleanliness, and surface energy, where any non-idealities may lead to poor palladium film adhesion, or even complete film delamination.3 To address the contact challenge we perform surface treatments on the SWCNT array prior to depositing palladium contacts, which involves rinsing the SWCNT arrays in specific solvents and annealing the films in vacuum. In XPS and optical absorbance spectra, we observe significant mass reduction of the polyfluorene wrapper while maintaining the quality and alignment of the SWCNT array. AFM height maps of the palladium contacts deposited on top of the surface treated SWCNTs demonstrate nearly ideal conformation of the palladium on the SWCNT array. The surface-treated SWCNT array FETs exhibit more than 10-fold improvement in the device on-conductance compared to non-treated samples.

[1]  Y. Joo, G. J. Brady, M. S. Arnold, and P. Gopalan,  Langmuir  30 (12), 3460 (2014).

[2]  G. J. Brady, Y. Joo, M. Y. Wu, M. J. Shea, P. Gopalan, and M. S. Arnold,  ACS Nano 8 (11), 11614 (2014).

[3]  V. Perebeinos and J. Tersoff,  Physical Review Letters 114 (8), 4 (2015).
Stretchable Carbon Nanotube Transistors Enabled By Buckled Carbon Nanotube Thins Films, Ion Gel Gate Dielectrics, and Metal Electrodes
Authors: Wu Meng-Yin , Zhao Juan , Xu Feng , Arnold Michael S.
Published: February 2020

Deformable field-effect transistors (FETs) are expected to facilitate new technologies like stretchable displays, conformal devices, and electronic skins. Thin film percolating networks of electronic-type controlled semiconducting carbon nanotubes are highly intriguing options for the active channel of stretchable FETs due to the excellent mechanical resilience of individual nanotubes, their possibility to accommodate large strain in thin film form via nanotube–nanotube sliding and buckling, and their exceptional charge transport properties. We demonstrate stretchable FETs based on buckled thin films of polyfluorene-wrapped semiconducting single-walled carbon nanotubes as the channel, buckled metal films as electrodes, and unbuckled flexible ion gel films as the dielectric.[1] The buckled thin film morphology is induced by depositing the nanotubes onto a pre-strained polydimethylsiloxane (PDMS) substrate and then releasing it, greatly improving the device stretchability. The FETs are stretchable up to 50% without appreciable degradation in performance before failure of the ion gel film. We furthermore show that by buckling the ion gel, the integrity and performance of the nanotube FETs are extended to nearly 90% elongation, limited by the stretchability of the elastomer substrate.[2] The FETs maintain an on/off ratio of >104 and a field-effect mobility of 5 cm2 V−1 s−1 under elongation and demonstrate invariant performance over 1000 stretching cycles.

[1] Xu F, Wu M-Y, Safron NS, Singha Roy S, Jacobberger RM, Bindl DJ, Seo J-H, Chang T-H, Ma Z, Arnold MS, Highly Stretchable Carbon Nanotube Transistors with Ion Gel Gate Dielectrics, NANO LETTERS, 4 (2), pp 682–686 (2014).

[2] Wu M-Y, Zhao J, Xu F, Chang T-H, Jacobberger RM, Ma Z, Arnold MS, Highly Stretchable Carbon Nanotube Transistors Enabled by Buckled Ion Gel Gate Dielectrics, APPLIED PHYSICS LETTERS, 107, 053301 (2015).
Real-Time Catalytic Activity of Bimetallic Ru-Pt Nanoparticles Attached on Carbon Nanotube Electronic Devices
Authors: Bouilly Delphine , Vanhorenbeke Béatrice , Hon Jason , Nuckolls Colin , Hermans Sophie , Martel Richard
Published: February 2020

Catalysis plays a crucial role in chemical research and industry, yet its dynamics at the nanoscale has been little explored. Here, we use carbon nanotube transistors to measure in real time the catalytic activity of metallic nanoparticles. First, we present a method based on covalent nanotube functionalization to selectively attach a small number of nanoparticles on an individual carbon nanotube device. We demonstrate the covalent attachment of bimetallic Ru-Pt clusters and their aggregation into less than 10 nanoparticles (RuPtNP) on each nanotube device, using a combination of techniques including electrical spectroscopy and atomic force microscopy. Second, we monitor the catalytic transformation of dimethylphenylsilane in dimethylphenylsilanol with water in real-time, through changes in the nanotube electrical conductance. Upon exposure to silane, RuPtNP-decorated carbon nanotube devices show a rapid change in electrical conductance that decays slowly back to its initial state. We present the effect of silane concentration and electrostatic doping of the nanotube, and discuss possible mechanisms for the interaction between the catalytic reaction and the electrical signature. Carbon nanotube electronic sensors form a powerful tool to investigate various catalysis reactions, providing real-time monitoring over a broad range of time scales.
(Invited) Chemistry, Electronic Structure, Properties and Applications of Carbon Nanotubes and Graphene
Authors: Haddon Robert C
Published: February 2020

I will discuss some aspects of our work on the chemistry, properties, and device aspects of single-walled carbon nanotubes and graphene .
(Invited) Fluorescent Quantum Defects in Carbon Nanotubes
Authors: Wang YuHuang
Published: February 2020

Fluorescent quantum defects that can be synthetically incorporated into semiconducting carbon nanotubes have opened up exciting new opportunities to imaging, sensing, and single photon generation. In this talk, we will discuss chemical strategies to create this new class of synthetic quantum structures. We will also present new progress in experimentally probing quantum defects and fundamentally understanding the effects of chemical functionalization on low dimensional carbon materials.
(Invited) Bulk Synthesis of Oxygen-Doped Single-Walled Carbon Nanotubes and Their Application As Fluorescent Probes
Authors: Okazaki Toshiya
Published: February 2020

It has been found that the photoluminescence (PL) efficiency of single-walled carbon nanotubes (SWCNTs) can be enhanced by substituting oxygen atoms to the carbon network of the tube wall [1]. The oxygen-doped SWCNTs (o-SWCNTs) have been mostly prepared by the exposure of ozone to the SWCNTs solution under the light. This method can provide only a small amount of o-SWCNTs, and the surfactants are normally adsorbed on the surface of the obtained o-SWCNTs, which prevents further applications of the material. Recently, we found a very simple method for obtaining o-SWCNTs in bulk. In this meeting, the synthesis method and the characterization of the o-SWCNTs, and their application as in-vivo and in-vitro near-infrared imaging probes will be reported.

 

1. S. Ghosh, S. M. Bachilo, R. A. Simonette, K. M. Beckingham, R. B. Weisman, Science, 330, 1656 (2010).
Impedance-Based Characterization of Functional Carbon Nano-Tube/Cement Composites
Authors: Seo Ki-Won , Choi Yoo-Jin , Kim Jin-Soo , Kim Eui-Hyun , Hwang Jinha
Published: February 2020

Carbon-based materials allows for their derivatives such as fullerenes, carbon nano-tubes (CNTs), and graphenes in addition to the conventional bulk carbon materials. The high conductive feature of carbon-based derivatives can be exploited as the conduction path of the carbon/inorganic mixture. In this work, carbon-based materials are combined with cement-based materials in order to being fabricated as the pressure-sensors under the high-impact condition. In particular, the CNTs are combined with cement-based materials. The corresponding hydration is monitored as a function of time using impedance spectroscopy. The addition of CNTs into the cement matrix system modifies the conventional conduction path, forming a conductive one, leading to the significant change in impedance spectra. The frequency-dependent impedance information allows for an equivalent circuit model which reflects the microstructure composed of CNTs and cement-based products. Based on the microstructural/electrical understanding, a possibility of being a piezoresistive sensor is discussed as a novel application involving the peculiar features of 1-dimensional CNT materials.
Photoluminescence from Thin Carbon Nanotube Films
Authors: Namal Imge , Schoeppler Friedrich , Hertel Tobias
Published: February 2020

Their remarkable light absorption and energy transport characteristics make single-wall carbon nanotubes (SWNTs) intriguing candidates for photovoltaic applications. Here, we study the photophysical properties of polymer wrapped SWNT films with varying thickness, so as to help identify processes which may affect device performance and that may impose limitations on the use of SWNT thin films as active layers in photovoltaic devices.

Non-radiative exciton decay is of particular interest in this context and we have studied its dependence on the thickness of monochiral SWNT films. The films were made of PFOBPy wrapped and  highly (6,5) enriched SWNT suspensions using a modified version of the filtration wet transfer technique reported earlier.1 Non radiative decay was probed by means of photoluminescence (PL) spectroscopy and by comparison of thin film data with data obtained from bulk suspensions. For thicker films we observe a pronounced decrease of the PL quantum yield (QY) for emission from the first subband S1 exciton state. However, the total PL QY is much less strongly affected by interactions within the thin film network because of a considerable shift of PL intensity to lower lying states. Surprisingly, some of the lower energy emission resembles PL phonon-sidebands of the first subband exciton which was previously attributed to the coupling between K-point phonons and dark excitons by Murakami et. al.2

Wu, Z.. Science 305, Nr. 5688 (2004): 1273–76.

Murakami, Y., Benjamin L., Said K., Nobutsugu M., Tatsuya O., Shigeo M. Phys. Rev. B 79, Nr. 19 (2009): 195407.
Angular Emission Properties of Single-Wall Carbon Nanotubes and Individual Covalent Dopant Sites
Authors: Hartmann Nicolai F. , Ma Xuedan , Htoon Han , Doorn Stephen K.
Published: February 2020

Controlled low-level covalent functionalization of single-wall carbon nanotubes (SWCNTs) has refocused the attention of the nanophotonics community on the use of SWCNTs as promising building blocks in photonic circuits due to their recently discovered property of room temperature single photon emission.1 Further, these new emitting states introduced through chemically stable oxygen2 and aryl diazonium dopants3 exhibit a significant increase in photoluminescence (PL) quantum yield and sensitivity to their dielectric environment, which enables their use in imaging and sensor applications.4 However, successful integration into waveguide structures and other photonic circuits requires a comprehensive understanding of the angular emission behavior of these dopant sites. One powerful microscopy technique to study the angular emission properties of emitters is Back focal plane (BFP) imaging, which enables to distinguish different radiation channels5, to reveal emitter orientations6 and magnetic light properties7, amongst others.

We present a refinement of the covalent doping procedure2,3 to achieve the control of the doping level and type of dopant down to the introduction of individual dopant sites in a short timescale. At the same time this procedure is compatible with protocols for isolating chirality sorted and rather long SWCNTs8, which enables us to study the length dependence of the angular emission as a function of SWCNT length. In contrast, we also investigate the spatially localized emission from individual dopant sites along the SWCNTs to learn in which angles the emission occurs and to be able to design waveguides tailored specifically to the emission properties. Further we show the significant redirection of emission when placing doped SWCNTs on plasmonic gold thin films. Both, the pristine E
11 and the dopant E
11
*emission can launch different propagating surface plasmons along the metal interface. These plasmons can be coupled into propagating light via leakage radiation and observed in the BFP.

1 X. Ma, et. al., Nat.
Nanotechnol.
2015, 10, 671. 2 S. Ghosh, et al., Science, 2010,
330, 1656. 3 Y. Piao, et al., Nat. Chem., 2013, 5, 840. 4 H. Kwon, et. al., J. Phys. Chem. C
2015, 119, 3733. 5 N. F. Hartmann, et. al., ACS Nano
2013, 7, 10257. 6 A. Lieb, et. al., J. Opt. Soc. Am. B
2004, 21, 1210. 7 T. H. Taminiau et. al., Nat. Commun.
2012, 3, 979. 8 N. F. Hartmann, et. al., Nanoscale
2015, 7, 20521.
(Invited) Physics and Applications of Spontaneously Aligned Macroscopic Nanotube Assemblies
Authors: Gao Weilu , He Xiaowei , Zubair Ahmed , Komatsu Natsumi , Guo Cheng , Xie Lijuan , Kono Junichiro
Published: February 2020

One of the outstanding challenges in nanotechnology is how to assemble individual nano-objects into macroscopic architectures while preserving their extraordinary properties.  For example, the one-dimensional character of electrons in individual carbon nanotubes leads to extremely anisotropic transport, optical, and magnetic phenomena, but their macroscopic manifestations have been limited.  Here, we describe novel methods for preparing macroscopic films, sheets, and fibers of highly aligned carbon nanotubes and their applications to basic and applied studies.  Sufficiently thick films act as ideal terahertz polarizers, and appropriately doped films operate as polarization-sensitive, flexible, powerless, and ultrabroadband photodetectors.  Together with recently developed chirality enrichment methods, these developments will allow us to probe, understand, and control dynamic conductivities of interacting one-dimensional electrons in macroscopic single crystals of single-chirality single-wall carbon nanotubes.
(Invited) Exciton Dissociation and Trion Generation in Individual Carbon Nanotubes
Authors: Kato Yuichiro K.
Published: February 2020

Screening is limited in single-walled carbon nanotubes because of their one-dimensional nature, and the strong Coulomb interactions result in optical spectra dominated by excitons with binding energies lager than half an eV. Also because of the limited screening, a charged carrier can be bound to an exciton to form a trion that is stable at room temperature.

Here we discuss experiments aimed at highlighting the behaviors of excitons and trions under electric fields. Microspectroscopy measurements are performed on individual suspended carbon nanotubes integrated into field-effect devices. Simultaneous photoluminescence and photoconductivity spectroscopy show evidences for spontaneous dissociation [1], despite the expectation that free carrier generation from such a tightly-bound state would be difficult. As the field is increased, we observe an emergence of new absorption peaks in the excitation spectra, which can be explained by electrical activation of dark excited states [2]. Although trion formation has been thought to be difficult in suspended nanotubes due to low exciton-carrier scattering rates, we have succeeded in identifying trion emission under an application of gate voltages [3].

Work supported by KAKENHI, The Canon Foundation, The Asahi Glass Foundation, and the Photon Frontier Network Program of MEXT, Japan.

[1] Y. Kumamoto, M. Yoshida, A. Ishii, A. Yokoyama, T. Shimada, Y. K. Kato, Phys. Rev. Lett. 112, 117401 (2014).

[2] T. Uda, M. Yoshida, A. Ishii, Y. K. Kato, submitted.

[3] M. Yoshida, A. Popert, Y. K. Kato, arXiv:1510.08996.
(Invited) Anisotropic Magnetism of an Endohedral Metallofullerene for Molecular Location Sensor
Authors: Takano Yuta , Tashita Ryo , Suzuki Mitsuaki , Imahori Hiroshi , Nagase Shigeru , Akasaka Takeshi
Published: February 2020

Location recognition in molecular-scale provides valuable information on positional relationship, absolute conformation and dynamics of molecules. They can be used for deep understanding of nature of functional molecular materials or for elucidating biological processes. Therefore, a number of molecular probes have been developed and reported to date for molecular recognition and location determination.

   Recently, our group has reported anisotropic magnetism of an endohedral metallofullerene (EMF) Ce@C82 both in a pristine form and chemically functionalized form.1,2 Remarkably, the anisotropy of the magnetism which is led by the encapsulated Ce atom was slightly influenced by the carbene addition reaction. In addition, absolute position of the hydrogen atoms of the addend were assigned by the difference in the effective distance of the anisotropic magnetism, which is decreased with the cube of distance between the Ce and hydrogen atoms. 

   In this study, we have developed Ce@C82 derivatives that demonstrate a potential of EMFs for location recognition in molecular-scale. Five derivatives of Ce@C82 were successfully synthesized and isolated by a similar radical reaction that we reported recently.3 Addition position of the two isomers of them were unambiguously determined by a single crystal structure and/or characteristic absorption spectra. DFT calculations provide reasonable criteria to predict the addition position by the radical coupling reaction. The carbon atoms that have high SOMO density and positive charge are preferable for the addition position.

   Temperature-dependent 1H-NMR measurements demonstrated unique paramagnetic shifts that are derived by the anisotropic magnetism of the Ce atom. And further analysis of the shifts revealed the dependency of the shift based on the distance and relative position from the Ce atom. This result indicates that the paramagnetic shifts provide location information of the addend. Therefore, Ce@C82 is capable to act as an molecular probe for location recognition of atoms by utilizing anisotropic magnetism of an EMF.

Reference:

1. T. Wakahara et al. J. Am. Chem. Soc.
2004, 126, 4883-4887.

2. Y. Takano et al. J. Am. Chem. Soc. 2009, 131, 9340-9346.

3. Y. Takano et al. J. Am. Chem. Soc. 2008, 130, 16224-16230.
(Invited) Chemical Purification of M3N Clusters in the Larger C88-C102 Cage
Authors: Stevenson Steven
Published: February 2020

Since the discovery of Sc3N@C80 in 1999, much literature has focused on isolating metallic nitride clusters (M3N) entrapped within the smaller C80 cage.  Over time, scientists (e.g., Echegoyen) have explored the same M3N clusters, but with bigger cage sizes, to expand the family of M3N@C2n.  While HPLC has been the dominant method to isolate the larger M3N@C88-112, our research group is investigating non-chromatographic methods to purify M3N@C88-112
 with the goal of disseminating these larger species to the scientific community.  In this presentation, we demonstrate selective reactions of metallic nitride endohedrals present in soot extracts.  Successful reagents include electron-poor Lewis acids and electron-rich amines.  Combining these two reaction classes now permits the chemical purification of mixed-metal CeLu2N@C80 as an example of a C80 cage.  Our most recent example of chemically isolating a metallic nitride in a larger cage is Gd3N@C88.  Currently, we are spreading this purification method to transition metal and other rare-earth M3N clusterfullerenes.
(Invited) Controlling the Dipolar Coupling in Endohedral Fullerene-Phthalocyanine Dyads
Authors: Porfyrakis Kyriakos
Published: February 2020

Paramagnetic endohedral fullerenes and phthalocyanine (Pc) complexes can be electron spin-active molecules. Hence they hold promise in applications where control of the electron spin properties is important such as spintronics and quantum information processing.

An important step towards these applications is the ability to tune the coupling between adjacent molecules. In this talk, I shall present our recent progress in the chemical functionalization of N@C60. I shall demonstrate how we have linked N@C60 and copper-phthalocyanine (CuPc) together, and characterized the resulting electron paramagnetic resonance properties, including the spin dipolar coupling between the fullerene spin and the CuPc spin. We were able to vary the distance between the two spin-active molecules and to interpret the distance-dependent coupling strength quantitatively. We then went one step further. We discovered an antiferromagnetic aggregation effect of the CuPc moieties and we demonstrated an extra facile method of tuning the dipolar coupling in such dyad systems: simply by adjusting the solution concentration. The solution concentration dependency opens a new way of tuning the dipolar coupling strength. We can turn on the dipolar coupling by diluting the sample, and turn off the dipolar coupling by concentrating the sample. I believe this to be the first step towards achieving exquisite spin-coupling control in future device architectures.
(Invited) Aligning Organic Dipolar Molecules in Carbon Nanotubes for Nonlinear Optics
Authors: Cambre Sofie , Campo Jochen , Beirnaert Charlie , Verlackt Christof C. , Wenseleers Wim
Published: February 2020

The 1D character of single-walled carbon nanotubes (SWCNT) combined with their mechanical robustness, chemical inertness and wide range of diameters makes them ideal nanocontainers for various molecules. Here we show that by encapsulating elongated dipolar molecules in the 1D internal channel of SWCNTs, Coulomb interactions naturally favour a polar head-to-tail alignment of the molecular dipoles, resulting in a cooperative enhancement of directional properties, such as the dipole moment and the second-order nonlinear optical (NLO) response.[1]  This principle is demonstrated for a prototypical dipolar molecule encapsulated in various SWCNT samples. The encapsulation is evidenced by extensive wavelength-dependent fluorescence-excitation and resonant Raman experiments on bile-salt solubilised dye-filled SWCNTs[2], revealing the effect of encapsulation on the vibrational and electronic properties of the SWCNTs and the encapsulated molecules.[3-6] The polar alignment is demonstrated by wavelength-dependent hyper Rayleigh scattering experiments (HRS)[7-9] (i.e. second harmonic light scattering). The newly synthesized organic nanohybrids possess a giant total dipole moment and NLO response, corresponding to ~70 identically aligned molecules (HRS intensity scaling quadratically with this number). These nanohybrids form solution processible building blocks highly interesting for the development of electro-optic modulators and switches.

References

[1] S. Cambré et al. Nature Nanotechnol. 10, 248 (2015)

[2] W. Wenseleers et al. Adv. Funct. Mater. 14, 1105 (2004)

[3] W. Wenseleers et al. Adv. Mater. 19, 2274 (2007)

[4] S. Cambré et al. Phys. Rev. Lett. 104, 207401 (2010)

[5] S. Cambré et al, ACS nano 6, 2649 (2012)

[6] S. Cambré et al. Angew. Chem. Int. Ed. 50, 2764 (2011)

[7] E. Goovaerts et al. In Handbook of advanced electronic and photonic Materials and Devices, Vol. 7: Nonlinear optical materials, Academic Press, San Diego, 127-191 (2001)

[8] J. Campo et al. Optics Express 17, 4587 (2009)

[9] J. Campo et al. J. Phys. Chem. Lett. .3, 2248 (2012)
Real-Time Observations of Electrochemical Reactions in Rechargeable Energy Storage Systems
Authors: Shahbazian-Yassar Reza
Published: February 2020

Electrodes in rechargeable batteries undergo complex electrochemically-driven phase transformations upon driving Li ions into their structure. Such phase transitions in turn affect the reversibility and stability of the battery. This presentation gives an overview of the PI’s research program on in-situ transmission electron microscopy (TEM) of battery materials. In-situ TEM has been shown to be a very powerful technique in shedding light to some of the mysteries in electrochemical performance of new materials. Various anode materials including SnO2, MnO2, ZnSb were subjected to lithiation process and the transport of Li ions was visualized within their atomic structure. For SnO2 nanowires, it was observed that the Li ion transport results in local strain development preferably along (200) or (020) plans and [001] crystallographic directions. The lithiation behavior in the presence of twin boundary defects was completely different compared to pristine state with no twin boundary defect. We showed that twin boundaries in general provide a more accessible pathway for Li ion transport. Anisotropic plastic deformation was also observed along [010] directions of MnO2 nanowires. Sb-based intermetallics, such as Zn-Sb system, which have been proved to be promising anode materials for Li-ion batteries, are also capable of storing of sodium ions. We investigated the microstructural changes and phase evolution of the Zn-Sb intermetallic nanowires using in-situ TEM. Zn-Sb alloys also exhibit a new cubic alloying phase Li2ZnSb that form by intermixing of the ABAB atomic ordering in hexagonal LiZnSb due to Li inclusion in their lattices. Our results indicate that the reaction between Zn-Sb and sodium proceeds through a different pathway during the first compared to the subsequent cycles. Atomic resolution imaging shows that NaZnSb has a layered structure, which provides channels for fast Na+ diffusion.
A Simple and Low-Cost Method to Fabricate Beta-Alumina Solid Electrolyte (BASE) for Na Battery Applications
Authors: Lu Xiaochuan , Li Guosheng , Meinhardt Kerry , Sprenkle Vincent
Published: February 2020

βʺ-Al2O3 has been the dominated choice for the electrolyte materials of sodium batteries because of its high ionic conductivity, excellent stability with the electrode materials, satisfactory mechanical strength, and low material cost. To achieve adequate electrical and mechanical performance, sintering of βʺ-Al2O3 is typically carried out at temperatures above 1600°C with deliberate efforts on controlling the phase, composition, and microstructure. Here, we reported a simple method to fabricate βʺ-Al2O3 /YSZ electrolyte at relatively lower temperatures. With the starting material of boehmite, single phase of βʺ-Al2O3 can be achieved at as low as 1200°C. It was found that TiO2 was extremely effective as a sintering aid for the densification of βʺ-Al2O3 and similar behavior was observed with MnO2 for YSZ. With the addition of 2 mol% TiO2 and 5 mol% MnO2, the βʺ-Al2O3 /YSZ composite was able to be densified at as low as 1400°C with a fine microstructure and good electrical/mechanical performance. This study demonstrated a new approach of synthesis and sintering of βʺ-Al2O3 /YSZ composite, which represented a simple and low-cost method for fabrication of high-performance βʺ-Al2O3 /YSZ electrolyte.
Doped Lithium Orthosilicates - Promising High Rate Lithium-Ion Conductors for Li-S Batteries
Authors: Murugavel Shanthi Pavithra , Jampani Hanumantha Prashanth , Gattu Bharat , Velikokhatnyi Oleg I , Kumta Prashant N
Published: February 2020

There is an increased demand for portable energy storage systems that demonstrate high efficiency. The current Li – ion battery system based on Li – graphite insertion chemistry has a theoretical capacity of 372 mAh/g. For Li – ion batteries to be implemented in portable energy devices, specific capacities twice than that of the current system is necessary.

Sulfur demonstrates a high theoretical specific capacity of 1672 mAh/g1
,
2, and is hence a promising candidate for high energy density lithium batteries. Moreover, sulfur is a low cost material and is easily available. Sulfur has very low conductivity (- 10-15 S/cm) which restricts the complete utilization of active material. Sulfur forms non – intercalation based polysulfide intermediates (Li2Sn ; n = 2 – 8)3which are soluble in liquid electrolyte resulting in loss of active material. In addition, the dissolved polysulfide gets coated onto the anode resulting in gradual cell voltage drop ultimately resulting in failure. These problems prevent the technology from being commercialized. Jampani et al. demonstrated reduced polysulfide dissolution and improved cycling stability by coating the sulfur cathodes with a lithium-ion conductor (LIC)4. The study identified Li4SiO4as a stable LIC. However, the application of this coating strategy is limited by the ionic conductivity of the LIC. In this work, the Li4SiO4 LIC was doped with dopants identified using first principles calculations by a high temperature solid state approach. The LIC was doped up to 5% without phase separation as represented in Figure 1. The doped LIC demonstrates a threefold increase in ionic conductivity as shown in Figure 2. This enhanced ionic conductivity is expected to improve the cycling stability of lithium-sulfur cathodes which will be discussed and presented in detail.

References

1. J. R. Akridge, Y. V. Mikhaylik and N. White, Solid State Ionics, 2004, 175, 243-245.

2. X. Ji and L. F. Nazar, Journal of Materials Chemistry, 2010, 20, 9821-9826.

3. C.-N. Lin, W.-C. Chen, Y.-F. Song, C.-C. Wang, L.-D. Tsai and N.-L. Wu, Journal of Power Sources, 2014, 263, 98-103.

4. P. J. Hanumantha, B. Gattu, O. Velikokhatnyi, M. K. Datta, S. S. Damle and P. N. Kumta, Journal of The Electrochemical Society, 2014, 161, A1173-A1180.

Figure 1
Activated Carbon Modified Electrodes for Soluble Lead-Acid Flow Batteries
Authors: Tang Hao-Lun , Chen Hsun-Yi
Published: February 2020

A soluble lead-acid flow battery (SLFB) system is a promising energy storage technology for its several economic advantages such as free of ion exchange membranes and inexpensive active materials. However, state-of-the-art SLFBs have limited cycle life, which hampers their commercialization. Shedding of lead dioxide (PbO2) at the graphite anode during charging/discharging cycles has been identified as one of the primary reasons for the degradation of SLFBs, since the shed lead dioxide could not be reversed for current extraction. In addition, oxygen evolution or other side reactions can occur when the SLFB is charged at higher rates, which in turn leads to lower coulombic efficiency and limits the flow battery for higher power applications.

This study aims to extend the cyclability and increase the output power of SLFBs through modification of the graphite-based anode with activated-carbon addition. Activated carbon (AC) is known to have a high surface area and can perform capacitive behaviors when presents at the surface of an electrode during charge/discharge. Instantaneous current surge could thus be buffered when capacitive AC additives are employed in SLFBs. Moreover, addition of AC powders to a graphite electrode results in a higher total surface area per volume and will reduce local current densities. Since electroplating could induce dendrite formation because of surface instability, lower local current density could mitigate such instability and reduce shedding of PbO2 particles. Hence, the life time of SLFBs can be prolonged and the output power can be raised under the effects of AC additives.

To determine the most effective portion of AC additives, long-term charge/discharge experiments are conducted. We find the addition of 0.5wt% activated carbon to the graphite anode extends the cycle life of our SLFB system up to over 300 times, as shown in Figure1. However, the columbic efficiency is obsevered to be reduced by around 5% in comparison to the electrode with no additives. In addition to the lower conductivity resulted from the residual metal and impurities, this reduced voltage efficiency of SLFBs may result from the hydrophobic nature of activated carbon materials. This issue could be compensated by increasing the hydrophilicity of activated carbon through pretreatment. Several strategies of pretreatments are taken to remove the impurities and enhance hydrophilicity. Our work demonstrates that longer cycle life and higher power output are possibile to be achived in SLFBs.

Figure1. The charge/discharge efficiency of SLFBs with 0.5wt% activated carbon additive

Figure 1
Novel Vanadium Based Cation-Disordered Lithium Transition Metal Oxides for Li-Ion Batteries
Authors: Cambaz Musa Ali , Fichtner Maximilian
Published: February 2020

Secondary lithium batteries are considered as a fundamental device for green and sustainable energy development and are now used as power sources for EV’s. However, the demand for higher energy density LIB’s necessitates the search for new materials and new systems.

Compounds with the ability to reversibly exchange more than 1 Li+ per formula unit are of great importance in order to achieve high specific capacities without undergoing severe chemical and structural changes. Prominent examples for multiple-electron transfer cathodes are Li2MSiO4 silicates, Li2M(PO4)F fluorophosphates[1] and Li2MTiO4 titanates.[2] The latter belongs to the class of cation-disordered rocksalt structure (spacegroup Fm-3m) with all cations disordered in the Wyckoff 4a site in the cationic sublattice. Up to now the practical capacities of disordered rocksalt titanates were restricted to 1e- transfer to about 150 mAhg-1. Vanadium-based positive materials are well known to possess a high capacity due to the ability of multiple redox-electron transfer. By the introduction of vanadium into the Li2MTiO4 Dominko et al [3] achieved reversible lithium intercalation-deintercalation beyond 1 Li+. Thus it appears, introducing vanadium into Li2M2O4 rock salt compounds is a promising approach in the search for new materials with high reversible capacity.

In this respect we synthesized a novel positive cathode material with disordered rock salt structure. The overall formula is Li2M2O4
with vanadium as one of the redox active transition metals within the structure. To the best of knowledge this compound has not been reported so far.

The XRD pattern of the as-prepared compound is shown in figure a) and can be indexed to cation-disordered cubic rock salt structure (space group Fm-3m) with the lattice parameter of a = 4.129 Å.

Figure b) is showing the charge-discharge profile for two different voltage windows. A narrow window between 3.5-1.0 V showing a reversible capacity of 170 mAhg-1. For an extended cycling window between 4.5-1.3 V a first discharge of around 245 mAhg-1is achieved. Figure c) shows the respective cycling performance. The OCV is around ~ 2.5 V vs Li/Li+. Various characterization techniques were applied to verify the redox process and reversible structural change upon electrochemical cycling.

References:

(1) Masquelier, C.; Croguennec, L. Chem. Rev.
2013, 113(8), 6552–6591.

(2) Sebastian, L.; Gopalakrishnan, J. J. Solid State Chem.
2003, 172(1), 171–177.

(3) Dominko, R.; Garrido, C. V. A.; Bele, M.; Kuezma, M.; Arcon, I.; Gaberscek, M. J. Power Sources
2011, 196 (16), 6856–6862.

Figure 1
Organic Redox Flow Batteries for Large-Scale Energy Storage
Authors: Hoober-Burkhardt Lena , Yang Bo , Krishnamoorthy Sankarganesh , Murali Advaith , Prakash G. K. Surya , Narayanan S. R.
Published: February 2020

Energy storage is of paramount importance for integrating renewable energy sources into the grid. With energy storage systems, we can manage the intermittency that is inherent in solar photovoltaic and wind-based energy generation. To this end, we are studying an organic redox flow battery (ORBAT), based on water-soluble quinone and anthraquinone derivatives. ORBAT is a promising solution, as it has the potential to meet the demanding requirements for large-scale energy storage [1,2]. ORBAT is environmentally friendly, easily scalable, highly efficient, and has the potential to be inexpensive.

Quinones are ideal for an aqueous redox flow battery system not only because of their fast kinetics and high capacity, but also because they can be tuned for solubility and electrode potential. Addition of substituent groups affects not only solubility and electrode potential but also the kinetics and mechanism of the redox reactions. We will present the chemical and electrochemical properties of various molecules that were studied to understand the effect of substituents. We have studied these effects using electrochemical and spectroscopic techniques.

We will also present the most recent advances in performance resulting from improvements to the cell design that includes the flow field and electrode structure. We have been able to demonstrate current densities of nearly 300 mA/cm2 operating at 0.5 V (see Figure 1). Combining the understanding of the reaction kinetics of the redox molecules with the improved cell design provides a pathway to realizing the chemical reversibility, high efficiency and high power density needed for an ORBAT system to be useful for large-scale energy storage.

Acknowledgement:

The work presented here was funded by ARPA-E Open FOA (DE-AR0000353) and the University of Southern California, Los Angeles, CA.

References:

1) Yang, B.; Hoober-Burkhardt, L.E.; Wang, F.; Prakash, G.K.S.; Narayanan, S.R. J. Electrochem. Soc.
2014, 161, A1371

2) Yang, B.; Hoober-Burkhardt, L.E.; Prakash, G.K.S.; Narayanan, S.R. 227th ECS Conference, Chicago, Il (2015)

Figure 1
Highly-Active, Durable and Inexpensive Iron-Based Electrocatalyst for Oxygen Evolution
Authors: Mitra Debanjan , Yang Chenguang , Manohar Aswin K , Trinh Phong , Narayanan S. R.
Published: February 2020

Development of inexpensive, efficient and robust electrocatalyst for oxygen evolution reaction (OER) is an essential requirement for various large scale energy storage and conversion applications, such as, metal-air rechargeable batteries and regenerative fuel cell. [1] Ru and Ir precious metal-based electrocatalysts are well-known to exhibit good catalytic activity towards OER but high cost and rare abundance of these materials preclude their wide-scale deployment in industrial energy storage applications. In the quest for finding inexpensive as well as active catalysts for OER, we have been investigating perovskites and spinel structures containing transition metals, such as, iron, nickel, cobalt, manganese recently. [2,3,4] Despite these efforts, finding an inexpensive elecrocatalyst for OER with a lower overpotential and high durability comparable with precious metal based catalysts has still remained a challenge to the scientific community.

Here, we report a cost-effective electrocatalyst based on a sintered iron (NSI) electrode modified by thermal decomposition of nickel. We have found such an electrode to be an active and robust electrocataylyst for oxygen evolution in aqueous alkaline medium. To the best of our knowledge this is the first time that iron is used as a substrate to yield a highly robust and durable structure with an exceptionally high electrocatalytic activity. We have obtained 230 mV overpotential at 10 mA/cm2 (Figure 1 a). The same electrode exhibits a highly stable overpotential for 230 hours (Figure 1 b). We have also studied the effects of decomposition temperature of preparation of the NSI catalysts on their activity towards OER. Our study shows that the NSI electrode prepared at 2000 C exhibits a different surface than prepared at 4000 C and is more favorable for OER. We have investigated surface composition using physical characterization methods such as XRD and XPS. We have also investigated the electrochemical kinetics for oxygen evolution through steady-state voltammetry.

References:

S. R. Narayan, A. K. Manohar and S. Mukerjee, Electrochem. Soc. Interface, 24.2 (2015): 65-69.

S. Malkhandi, B. Yang, A. K. Manohar, A. Manivannan, G. K. S. Prakash and S. R. Narayanan, J. Phys. Chem. Lett., 3, 967 (2012).

S. Malkhandi, P. Trinh, A. K. Manohar, A. Manivannan, M. Balasubramanian, G. K. S. Prakash and S. R. Narayanan, J. Phys. Chem. C, 119(15), 8004-8013 (2015).

P. Trinh, S. Malkhandi, A. K. Manohar, A. Manivannan and S. R. Narayanan, ECS., (2015, July) In Meeting Abstracts (No. 1, pp. 25-25).

 

Figure 1
Anthraquinone Functionalized Reduced Graphene Oxide As Electrode Material for Rechargeable Batteries
Authors: Esat Burak , Bahceci Sumeyye , Momchilov Anton Angelov
Published: February 2020

The ever-increasing demand for high-performing, light weight, economical, and safe power storage for high–tech portable devices and electric vehicles leads to augmented research efforts in the field of organic or organic/hybrid materials to be used as electrodes in energy storage devices [1-14]. An anode material based on anthraquinone-functionalized reduced graphene oxide (AQ-RGO) is synthesized and its electrochemical properties have been investigated. The initial studies against Li metal revealed that a quite reversible capacity of 200 mAh/g was obtained based on the weight of electro-active anthraquinone moieties when cycled between 1.8and 3.2  V at 0.3C rate. The energy density was found to be around 450 mWh/g. The AQ-RGO  has been used also as an anode material against in an aqueous battery against NiOOH (AQ-rGO | 30% NaOH | NiOOH). This battery provided a capacity of 140 mA/h at 0.83V.

 [1]Liang ,Y. ; Tao, Z.;  Chen, J. Adv. Energy Mater. 2012, 2, 742–769.

[2] Novák, P.; Müller, K. ; Santhanam , K. S. V. ; Haas , O.  Chem. Rev. 1997 , 97 , 207.

[3]  Cheng , F. Y. ; Tang , W. ; Li , C. S. ; Chen , J. ; Liu , H. K. ; Shen , P. W. ; Dou , S. X. Chem. Eur. J.  2006, 12 , 3082.

[4]  Neves , S. ; Polo Fonseca , C. J. Power Sources
2002 , 107 , 13 .

[5]  Janoschka, T. ; Hager, M. D. ; Schubert, U. S. Adv. Mater. 2012, 24, 6397–6409

[6]  Sukegawa, T. ; Kai, A. ; Oyaizu, K. ; Nishide, H. Macromolecules
2013, 46, 1361−1367

[7]  Choi, W. ; Harada, D. ; Oyaizu, K. ; Nishide, H. J. Am. Chem. Soc.
2011, 133, 19839–19843

[8]  Suga T., Ohshiro H., Sugita S., Oyaizu K., Nishide H., Adv. Mater.
2009 , 21 , 1627

[9] Tang Z. Y., Xu G. X., Acta Phys. -Chim. Sin.
2003 19 , 307 .

[10 Yao M., Senoh H., Sakai T., Kiyobayashi T., , Int. J. Electrochem. Sci
2011. 6 , 2905 .

[11] Yao M., Senoh H., Sakai T., Kiyobayashi T., J. Power Sources
2012,202, 364.

[12] Song Z., Zhan H., Zhou Y., , Chem. Commun. 2009, 448 .

[13] Song Z., Zhan H., Zhou Y., Angew. Chem. Int. Ed. 2010 , 49 , 8444 .

[14] Himadri Chakraborti, Suman Kalyan Pal, Chem. Phys. Lett.
2014,600 , 118–122.

Figure 1
Modeling of a Hollow-in Lithium-Ion Battery for Thermal Design
Authors: Koo Boram , Yi Jaeshin , Shin Chee Burm , Lee Yeongjae , Hong YeongJin
Published: February 2020

The lithium-ion battery (LIB) is one of the preferred candidates for grid-scale energy storage systems due to its outstanding characteristics such as high energy density, modular scalability, long cycle life, and low self-discharge rate among others.In a batterymodule forgrid-scale energy storage applications, an uneven temperature distribution in thecell can be created depending on theoperating conditions and the types ofthermal management. Uneven temperature distribution in amodule couldcauseanelectricalimbalance and thus lead tothelower performance and shorter life of battery. It is, therefore, important to calculate accurately the uneven temperature distribution in a batterycell in order to achieve the optimum performanceand long lifeof the batterycell.

In this work,amodelingis performed toinvestigate the effects of thermal design on the thermal behavior of ahollow-in lithium-ion battery.The modeling of the potential and current density distributions on the electrodes is validated by the comparison between experimental and modeling discharge curves at various discharge rates from 0.5 C rate to 4 C rate. Then, the thermal modeling of the lithium-ion battery is carried out, which accounts for the ohmic heating and the heat generated due to charge transfer at the electrode/electrolyte interface. The heat generation rate is calculated using the results of the modeling of potential and current density distributions.

Fig.1 shows the schematic diagrams of hollow-in lithium-ion battery. The temperature distribution in hollow-in lithium-ion battery with 4 C rate constant current discharge is shown in Fig. 2.

Figure 1
(Invited) STEM / EELS Characterization of Passive Films Formed on Stainless Steels
Authors: Fujimoto Shinji , Kawano Akihiko , Tsuchiya Hiroaki , Saito Minoru
Published: February 2020

Passive films formed on stainless steel were characterized using STEM / EELS and XPS. The Fe22Cr alloy was potenitostatically passivated in a pH 8.4 borate buffer solution and 0.5 M sulphuric acid solution. As usually observed Cr enriched passive film was formed in both solutions. The passive film formed in borate buffer solution was slightly ticker, and exhibit lower Cr concentration, compared to that formed in sulphuric acid solution. The EELS with using a position sensitive detector exhibited very detailed chemical sates across the cross section of the passive film. It is revealed that passive film is composed of Cr2O3 and Fe3O4 with small amount of γ-Fe2O3 located at the outer layer. These results did not necessarily coincide with the observation by XPS, that is, inner oxide layer rich in Cr and covering hydroxide of mainly Cr or Fe depending on solution pH are usually obtained by XPS. This inconsistency might be explained by the difficulty to keep top surface non-crystalline hydroxide layer during sample preparation using a FIB (focused ion beam) technique. The observation of passive film formed in ionic liquid using STEM / EELS will be also presented comparing the observation by AES with sputtering.