bluuebunny/crossref_metadata_2025 huggingface dataset:
(Invited) Molecular Engineering on Transition Metal Dichalcogenides
Authors: Kiriya Daisuke
Published: February 2020

Molecular interaction and assembly is an essential process in various fields such as in chemistry, biology and materials science. As one of sophisticated systems, the process is successfully incorporated in biology to construct functional structures, including the membrane of cells. Through the interactions of each molecule, molecules show assembly to form functional patterns and structures. We are trying to extend the molecular interaction/assembly onto inorganic electronic materials/devices. This presentation shows our recent results of molecular interaction on 2D materials, especially the semiconducting 2D material, transition metal dichalcogenides (TMDCs).1,2,3

The TMDC is constructed from atomically thin layers (thickness ~0.7 nm) with van der Waals interaction, and is expected to make tiny optoelectronic devices due to their thin nature. However, the essential requirement for controlling carriers is a problem because the conventional methods, such as ion plantation, are not applicable due to its atomically thin nature. We found that mere contact of a dopant molecule with MoS2, the donor molecule is effective to control the carrier concentration of a TMDC, MoS2.1 They formed an organic-inorganic electron transfer interaction (Fig. 1a). As a result, the doping level of MoS2 can be varied depending on the amount of the donor molecule. We also found that the doping process can make a high-performance MoS2 transistor with subthreshold swings as low as 77 mV/dec. close to the theoretical limit.

We further examined the assembly and pattern formation of molecules on MoS2; MoS2 was used as a new class of substrates for assembling or patterning molecules (Fig. 1b). 2 First, we found that MoS2 is a model substrate for growth of in-plane Au nanowires (NWs). Au NWs show oriented growth despite the nearly 8% lattice mismatch between MoS2 and Au. Au NWs on the MoS2 surface are oriented along three symmetrically equivalent directions within the substrate that arise from the symmetry of MoS2 that templates the oriented growth. In terms of the electronic state point of view, the growth process of Au NWs includes a strong charge transfer process between Au NWs and MoS2, resulting in degenerate p-doping of MoS2.

We also found that a dopant molecule showed a pattern formation on MoS2 as like cellular structure or patterns shown in natural systems. We destabilized an ultrathin molecular film on MoS2 by external perturbation, induced lateral diffusion of molecules on MoS2 surface and showed various patterns such as tiny holes, networks, maze structures. Since the lateral undulation of the pattern was on the 100 nm scales, the pattern was revealed to modify MoS2 characteristics. In the presentation, the details of the above research will be discussed from the structural point of view to the electronic point of view.

References:

1D. Kiriya et al., J. Am. Chem. Soc. 2014, 136, 7853. 2
Adv. Funct. Mater. 2015, 25, 6257. 3M. Amani*, D.H. Lien*, D. Kiriya*
et al., Science, 2015, 350, 1065.

Figure 1
(Invited) Recent Advances in Research and Development of Quantum Dots in Lighting and Displays
Authors: Chen Hsueh-Shih
Published: February 2020

Quantum dots (QDs) are considered a key material in next-generation lighting and displays. They have various application forms such as polymer/QDs thin film, QD light emitting diodes (QD-LEDs), QD color filter photo resist (QD CFPR), light guide panel (LGP), and electroluminescence (EL) devices. Currently, QDs are being widely introduced to enhance the energy efficiency and color quality of the lighting and display in the industries, where QDs are used a wavelength-convertor to increase the color rendering of light sources or the color gamut of displays. However, the material properties and engineering processes are encountering various technical challenges and issues in the industries. For example, quantum yield (QY), emission band width, thermal stability, photo stability, process compatibility, long term reliability, color fluctuation, batch consistency, and so on, still need to be researched and further improved. This report will be focused on the recent advances in research and development of QD materials applications and challenges in lighting and displays.

Keywords: Quantum dots, QD-LED, QD Film, QD PR
(Invited) Molybdenum Disulfide Biosensors
Authors: Wang Hsiang-Chen
Published: February 2020

The two-dimensional layered material MoS2 is the most common transition metal dichalcogenide. The bulk MoS2 is a semiconductor material with an indirect energy gap (about 1.3 eV) with strong sulfur and molybdenum metal in the plane of the monolayer valence bond function, and there is a very weak Van der Waals force between layers. The monolayer MoS2 has a direct energy gap (about 1.9 eV) and an N-type semiconductor material with strong light emission characteristics, high planar electron mobility and tough mechanical properties, making it applicable applies to transistors, gas sensing detector, photodetector, battery, optoelectronic components. In the past, our laboratory successfully used CVD method to grow graphene and molybdenum disulfide films, combined with the hyper-spectral imaging for the optical properties detection of a few layers of thin film. On the other hand, we also have been successfully fabricated some nanostructures of cuprous oxide and zinc oxide. These nanostructures are made of anodized aluminum and two-beam interference technology. We expect to combine two-dimensional materials and semiconductor device fabrication into biochip through the use of biochips. Using biosensors based on semiconductor material synthesis and micro-nanostructure technology, we hope to develop a low-cost and fast response time, simultaneous detection of biosensors simple program. Recent studies have found that the change of surface stress of transition metal dichalcogenide will change its optical properties such as energy gap, absorption spectrum, even the electron mobility and induced magnetic force. The changes of these properties will enhance the optoelectronic performances of the transition metal dichalcogenide device and material properties. In this study, we will design the best transition metal dichalcogenide devices based on the previous research results. We will apply these devices to biological, gas, and photoelectric sensors and discuss the relationship between the photoelectric characteristics and stress distribution of various devices, and through the deep learning technology to enhance the photoelectric efficiency of devices.
(Invited) Wide-Bandgap Semiconductor Based Power Electronic Devices for Energy Efficiency
Authors: Carlson Eric P , Cunningham Daniel W , Kizilyalli Isik C.
Published: February 2020

Development of advanced power electronics with increased functionality, efficiency, reliability, and reduced form factor are required in an increasingly electrified world economy. Fast switching power semiconductor devices are key to increasing the efficiency and reducing the size of power electronic systems. However, the prevailing power semiconductor devices, based on silicon, are fast approaching their performance limits. Wide band-gap (WBG) semiconductors, such as gallium nitride (GaN) and silicon carbide (SiC), with their superior electrical properties are enabling a new generation of power semiconductor devices that offer enormous energy efficiency gains in a wide range of applications. The U.S. Department of Energy’s Advanced Research Projects Agency-Energy (ARPA-E) SWITCHES program identified the lack of a viable selective area doping processes as a major barrier to fabricating vertical GaN power electronic devices. The most obvious approaches, such as ion implantation with activation or selective area diffusion of dopants, have not produced p-type regions or satisfactory p-n junctions. Furthermore, selective area etch and regrowth approaches have resulted in poor electrical performance not sufficient for power electronic applications. To address this challenge ARPA-E launched the PNDIODES program to develop transformational advances and mechanistic understanding in the process of selective area doping in the group III-Nitride wide-bandgap semiconductor material systems. The progress and challenges of selective area doping faced by the SWITCHES program is reviewed along with the mechanistic understanding being developed under the PNDIODES program. Material and processing challenges, including reliability concerns, for GaN power devices are also described. A glimpse into the future trends in device development and commercialization is offered.
(Invited) Materials Properties and Their Impact on Beta Gallium Oxide for High Power Electronics Applications
Authors: Goorsky Mark S. , Liao Michael , Li Chao , Hobart Karl D.
Published: February 2020

Beta gallium oxide represents a promising material for high power device applications. However, the incorporation of this material into device structures is not as well understood as materials which have been used previously for high power device applications. Those materials (for example silicon, SiC, and GaN) possess crystal structures with higher symmetry. The monoclinic structure of beta gallium oxide leads to non-uniform thermal stresses in bulk and epitaxial layers and significant differences in reactivity due to surface orientations and doping levels. The low thermal conductivity of beta gallium oxide can be compensated by integrating it with other high conductivity materials. We address the crystalline perfection in state-of-the-art beta gallium oxide using high resolution x-ray scattering and topography techniques, the role of chemical mechanical polishing on sub-surface damage, the impact of the differences in thermal expansion coefficients along different crystallographic directions on gallium oxide structures in epitaxial systems, and initial studies into large scale exfoliation techniques for materials integration of gallium oxide with high thermal conductivity materials.
Evaluation of Model for Determining Nitrogen Doping Concentration from Resultant Strain in Heavily Doped 4H-SiC Crystals
Authors: Ailihumaer Tuerxun , Yang Yu , Guo Jianqiu , Raghothamachar Balaji , Dudley Michael
Published: February 2020

Lattice strain in 4H-SiC substrate wafers can strongly affect the performance of power electronic devices especially under the high temperature operation. The impurity incorporation in highly doped 4H-SiC crystals can result in significant lattice parameter change. Recently we reported [1] the synchrotron X-ray topographic contour mapping [2] technique to deconvolute lattice parameter variations from lattice tilt and thus generate strain maps. These strain maps have been incorporated into an anisotropic elasticity model to derive the nitrogen doping concentration variation in the 4H-SiC wafer. Doping distribution can be derived using a set of anisotropic strain maps detected by recording series of diffraction contours across the same region. The nondestructive contour mapping method we developed is capable of not only determining the concentration but also the distribution of the doping i.e. a doping map. In order to verify the doping level determined by contour mapping, we prepared samples with different N-doping levels. Contacts were created by depositing Ni using e-beam evaporator followed by rapid annealing. Hall effect measurements have been carried out on these samples to measure the carrier concentration in order to determine the doping values. The measured values are found to be in good agreement with the doping map derived using our contour mapping method.

Reference

Yu Yang, Jianqiu Guo, Balaji Raghothamachar, Xiaojun Chan, Taejin Kim, Michael Dudley, J. Electron. Mater. 47(2), 938-943 (2018).

J. Guo, Y. Yang, B. Raghothamachar, M. Dudley, and S. Stoupin, J. Electron. Mater. 47(2), 903-909 (2018).
Study of Baseplate Materials for High-Temperature Operation of SiC Power Modules
Authors: Koui Kenichi , Kato Fumiki , Tanisawa Hidekazu , Sato Shinji , Murakami Yoshinori , Sato Hiroshi
Published: February 2020

We are developing a SiC power module that can operate at high temperatures. The high temperature operation of the power module has advantages such as increase in the output power of the converter and miniaturization. When the power module operates at high temperatures, reliability of large area solder such as ceramic substrate-to-baseplate bonding is decreased due to the thermal stress. Furthermore, to minimize the size of the power module, reduction of the thermal resistance is required for the baseplate. We demonstrated that mechanical specification and thermal specification of baseplate materials applicable to SiC power module that can operated at high temperature up to 250 °C. Figure 1 shows the overview of the test module structure. Table 1 shows the specification of baseplate materials. We investigated shear stress on the substrate-to-baseplate solder (BP-solder) can be suppressed with lower Young's modulus baseplate. Figure 2 shows the shear stresses of the BP-solder with various baseplate materials different in coefficient thermal expansion (CTE) and Young's modulus by finite element method (FEM) simulation. This result revealed the baseplate with copper-molybdenum-copper (CMC) has better thermo-physical properties and also lower Young's modulus than other baseplate materials. Figure 3 shows the transient thermal resistance measurement result according to baseplate materials. The CMC baseplate has been shown to have equivalent thermal resistance to the Cu baseplate. In figure 4, the CMC baseplate shows that the shear stress on the BP-solder was small and the better thermal characteristics than other baseplate materials. As the result, it was shown that by applying the CMC baseplate, it is possible to manufacture a power module with better solder reliability and thermal characteristics than other baseplate materials for the high temperature SiC power module.

Acknowledgement

This work was supported by Council for Science, Technology and Innovation (CSTI), Cross-ministerial Strategic Innovation Promotion Program (SIP), "Next-generation power electronics / Consistent R&D of next-generation SiC power electronics" (funding agency: NEDO).

Figure 1
Electrolysis Pumping on Centrifugal Microfluidic Platforms for Automation of Bioanalytical Assays
Authors: Romero Soto Fabian Oswaldo , Aeinehvand MohammadMahdi , Jimenez Moreno Martin Francisco , Mager Dario , Madou Marc J , Martínez-Chapa Sergio Omar
Published: February 2020

One of the advantages of Lab on a Disc (LoD), compared to Lab on a Chip (LoC), is the use of centrifugal forces to move liquids within the chambers and microchannels; eliminating the need of external mechanical pumps (e.g., syringe pump) and piping networks for the automatization of bioanalytical assays. However, the centrifugal force is unidirectional and therefore liquids can only be displaced from the center to the edge of the disc. This prevents the possibility of utilizing all the available space in the disc for the implementation of a complex microfluidic process. To overcome this limitation, we developed an electrolysis system to induce a pneumatic force to move liquids towards the center of a spinning disc or against the direction of centrifugal force. We developed a microfluidic disc that contains a series of electrolysis pumps and peptide microarrays to automate a multiplexed immunoassay for the detection of different antibodies e.g., Ha and anti-flag antibodies. The pumps on this centrifugal microfluidic platform are powered and controlled wirelessly using the electronics-LoD [1]. In general, the develop pumping system allows for the best use of the limited space of microfluidic disc and the automation of complex bioanalytical process for point of care applications.

[1] S.M.T. Delgado, D.J. Kinahan, F.S. Sandoval, L.A.N. Julius, N.A. Kilcawley, J. Ducrée, D. Mager, Fully automated chemiluminescence detection using an electrified-Lab-on-a-Disc (eLoaD) platform, Lab Chip. 16 (2016) 4002–4011. doi:10.1039/C6LC00973E.
Characterization of Lithium in Batteries with EDS and EELS
Authors: Gauvin Raynald , Brodusch Nicolas , Voisard Frédéric , Demopoulos George P. , Trudeau Michel , Zaghib Karim
Published: February 2020

This paper will present start of the art characterization of Lithium in battery materials using energy dispersive spectroscopy (EDS) and electron energy loss spectroscopy (EELS) at 30 keV with the state of the art field emission scanning transmission electron microscope (FE-STEM) Hitachi SU-9000EA. This microscope has a resolution of 0,22 nm in bright field imaging at 30 keV. It has the extreme EDS detector from Oxford that allows the detection of the Ka line of Lithium. It has a EELS system with 0.5 eV resolution that allows to map the chemical state of Li in various materials. Examples of applications of these techniques will be presented as well as the challenges and limitations for Lithium characterization.
(Invited) A Route to High Energy Density Co-free Cathode Materials
Authors: Ceder Gerbrand
Published: February 2020

Cobalt resources may not be able to keep up with the rapidly growing demand for Li-ion energy storage. Disordered rocksalt cathodes present a Co-free alternative to the layered NMC-style cathode materials, used today in much of Li-ion technology. The flexibility of working with a cation-disordered structure creates the option to use a much broader set elements, many of which are abundant and inexpensive. More than a dozen novel cation-disordered cathode materials have been synthesized and tested, most of which contain one or more of either Ti4+, Nb5+, Zr4+, Mo6+ and a redox active elements from the group of Mn, Fe, V, Ni. In addition, these materials can be fluorinated through simple solid state reactions for enhanced safety and stability at high potential. Bu substituting a large amount of F substitution for O the metal valence can be lowered enough to activate unconventional redox couples, such as Mn2+/Mn4+ leading to very high capacities. Besides the large chemical freedom one has in designing and optimizing these materials, structural features can also be used to optimize the materials. I will show that short-range cation order, which can be influenced by the composition as well as the heat treatment can have a profound influence on performance.
Disordered Rocksalt Type Li-Rich Manganese Oxyfluoride As High-Capacity Cathode Material for Rechargeable Lithium Ion Batteries
Authors: Natsui Ryuichi , Ikeuchi Issei , Ohuchi Satoru , Nakura Kensuke
Published: February 2020

For the coming full-fledged xEV era, rechargeable lithium ion batteries with higher capacities are strongly desired. However, the current commercial cathode materials, such as layered-rocksalt oxide, are reaching the limit of their theoretical capacities.

Li-rich oxide cathode materials, which can access not only to transition metal redox reactions but also to redox reactions during the Li insertion/de-insertion, are expected as candidates for the next generation high capacity cathode materials as they can store much more Li ions than the current commercial cathode materials. However, one of the main drawback of these materials are voltage-fading with structural transition upon electrochemical cycling. It is considered due to oxygen loss at surface and transition metal rearrangement [1][2].

To suppress the oxygen loss without decreasing capacity, we focused on the oxyfluoride cathode material. Especially, we confirmed that disordered Rocksalt type-Li2MnO2F synthesized by mechanochemical process exhibit a discharge capacity of 330mAh/g with both transition metal and oxygen redox reaction, which is much higher than conventional cathode materials (200mAh/g) [3]. Recently, Bruce et al, disclosed that the Li1.9Mn0.95O2.05F0.95 does not exhibit oxygen loss from the lattice. This indicates that the Li-rich oxyfluoride is one of the noteworthy material for the high capacity cathode materials.

In this study, we will discuss the possibility of the oxyfluoride materials for the next-generation high capacity cathode material from the view point of structures and compositions by comparing with some other oxide cathode materials without fluorine doping.

[1] N. Yabuuchi et al, J. Am. Chem. Soc. 133 (2011) 4404

[2] Y. S. Meng et al, Energy Environ. Sci., 4 (2011) 2223

[3] R. Natsui, K Nakura, POSITIVE ELECTRODE ACTIVE MATERIAL AND BATTERY, WO2017/013848

[4] P. G. Bruce et al, Energy Environ. Sci., (2018) Advanced Article
Advanced Impedance Analysis of Calendar and Cycle Aged NCA-LCO/Graphite Lithium-Ion Batteries
Authors: Dippon Michael , Weiss Michael , Gantenbein Sophia , Ivers-Tiffée Ellen
Published: February 2020

Lithium-ion batteries deteriorate in energy and power density over lifetime. Power density fades away with increasing internal resistance (Ri) and is generally monitored by pulse measurements, which do not describe details of the underlying loss contributions.

Loss contributions as (i) ohmic resistance R0, (ii) contact resistance RCC and (iii) charge transfer resistance RCT are separated by electrochemical impedance spectroscopy (EIS) combined with the distribution of relaxation times method (DRT), and quantified using a simple equivalent-circuit model (Figure 1). This approach allows the systematic investigation of Li-ion batteries over lifetime, and gives more insight into the effect of temperature, cycling profiles and discharge/charge rates.

We present a lifetime analysis of a high-energy pouch cell (KOKAM 560 mAh), using a wide set of procedures during cycling and calendar aging. The investigated cell consists of a NCA-LCO blend cathode and a graphite anode. The relationship between numerous test profiles (variation of temperature, charge/discharge rate and depth of discharge) and predominant aging mechanism of the cell resistance is quantified versus begin of life (BOL) and its origin is discussed in great detail.

Figure 1
(Invited) Screening Plus Testing of Cathode Materials for Ca and Mg Batteries
Authors: Arroyo-de Dompablo M. Elena , Torres Arturo , Padilla M. Pilar , Luque Javier , Bardé Fanny , Tchitchekova Deyana , Black Ashley , Ponrouch Alexandre , Palacin M Rosa
Published: February 2020

While the current state-of-the-art in rechargeable batteries is the Li-ion technology, research efforts are intensified towards the development of alternative technologies to satisfy the ever-increasing demand for enhanced energy density. The development of rechargeable batteries based on the intercalation reaction of multivalent cations (Ca2+, Mg2+, Al3+) is a current challenge for electrochemical energy storage. Designing such batteries demands the identification of competitive electrode materials and electrolytes for each particular active ion. In the last years, we have combined computational and experimental techniques in the search of potential cathode materials that could reversibly insert Mg/Ca ions [1-4].

First principles calculations are used to predict three fundamental electrochemical properties of materials: average intercalation voltage, specific capacity and ionic mobility. Benchmarking the computational results with experimental evidences is a necessary step to accelerate reliable materials design based on DFT calculations. Therefore, our experimental investigations comprise the synthesis, characterization and electrochemical testing of materials. In this work, we confront computational and experimental results for selected oxides, nitrides, sulphides and silicate materials. We will show that the combined computational/experimental approaches lead to proof of concept and rationalization for the reversible electrochemical intercalation and deintercalation of calcium in TiS2 [4].

Acknowledgments: Authors are grateful for financial support from Ministerio de Ciencia e Innovación (grant MAT2014-53500-R), the European Union H2020-FETOPEN funded project CARBAT-766617 and Toyota Motor Europe.

References:

[1]. M.E. Arroyo-de Dompablo, C. Krich, J. Nava-Avendaño, M.R. Palacin, F. Barde. Phys. Chem. Chem. Phys. 18 (2016) 19966.

[2]. M.E. Arroyo-de Dompablo, C. Krich, J. Nava-Avendaño, N. Biskup, M.R. Palacin, F. Barde. Chem. Mater. 28 (2016) 6886.

[3] R. Verrelli, M.E. Arroyo-de Dompablo, D. Tchitchekova, A.P. Black, C. Frontera, A. Fuertes, M.R. Palacin. Phys. Chem. Chem. Phys., 19 (2017) 26435

[4]. D. Tchitchekova, A. Ponrouch, R. Verrelli, T. Broux, C. Frontera, A. Sorrentino, F. Barde, N. Biskup, M.E. Arroyo-de Dompablo, M.R. Palacin. Chem. Mater. 30 (2018) 847
LiNi0.6Mn0.2Co0.2O2 Dry-Coated with Nano- Alumina As Positive Electrode Material
Authors: Zheng Lituo , Obrovac M. N.
Published: February 2020

Applications of lithium ion batteries in grid storage and electric vehicle require long lifetime. Surface coating of active material is an effective way to improve the long-term cycling of lithium ion batteries.1 Most of the coating methods reported so far are wet-coating method, which produces waste liquid and requires additional drying process. In this study, LiNi0.6Mn0.2Co0.2O2 was coated with nano-alumina using a convenient dry-coating method and characterized in Li cells.

Commercial LiNi0.6Mn0.2Co0.2O2 powders (obtained from Umicore) were mixed with 3% Al2O3 (13 nm, from Sigma-Aldrich) using a dry-coating method. For comparison, LiNi0.6Mn0.2Co0.2O2 powders were also mixed with 3% Al2O3 by hand-grinding. Electrodes were made with active material, PVDF binder, carbon black at a ratio of 86:7:7 and dried under vacuum at 120 ℃ overnight. 1M LiPF6 in a solution of EC and DEC (volume ratio 1:2) was used as electrolyte and Li foil was used as counter/reference electrode.

Figure 1(a) shows the SEM image of LiNi0.6Mn0.2Co0.2O2 powders. Secondary particles with spherical morphology were observed. The average particle size is ~1 μm for primary particle and ~10 μm for secondary particle. Figure 1(b) shows the SEM image of LiNi0.6Mn0.2Co0.2O2 powders coated with 3% Al2O3 using the dry coating method. Figure 1(c) shows the SEM image of LiNi0.6Mn0.2Co0.2O2 powders mixed with 3% Al2O3 by hand-grinding. The dry coating method produced a more homogeneous and dense coating, compared to materials produced by hand-grinding.

Figure 2 shows the cycling performance at C/2 for all the materials cycled between 3 V – 4.4 V. Compared to pristine NMC 622, the materials processed with 3% Al2O3 displayed lower reversible capacity. However, the cycling performance was improved for both materials. Notably, materials dry-coated with 3% Al2O3 showed little capacity fade in 50 cycles. This study gives an example of using dry coating method for improving the cycling performance of positive electrode materials for lithium ion batteries.

References

Z. Chen et al., J. Mater. Chem.,
20, 7606-7612 (2010)

Figure 1
Stress and Electrochemical Analyses of LiNixMnyCo1-x-YO2(NMC)/Graphite Lithium-Ion Battery with Real 3D Microstructures
Authors: Kim Sangwook , Huang Hsiao-Ying Shadow
Published: February 2020

LiNixMnyCo1-x-yO2 (NMC) is one of promising cathode materials in lithium-ion batteries (LIBs) for power tools and electric vehicles due to their higher specific capacity and energy density. However, it is observed that repeated cycling leads to micro-scale fracture along the grain boundaries in the secondary particles of NMC, and it could eventually cause low cycling stability and irreversible capacity retention.

The aim of this study is to investigate the correlation of mechanical stresses and electrochemical battery degradation. Specifically, mechanical stress and strain caused by lithium intercalation and diffusion in both cathode and anode were calculated and crack initiation in particles was predicted. Furthermore, a modified Butler-Volmer equation, which accounts for the influence of mechanical stress on electrochemical reactions, is considered. In this study, we adopted real 3D microstructures of both anode (graphite) and cathode (NMC) based on over 100 images from a synchrotron radiation X-ray tomographic microscopy (SRXTM). The 3D finite element model (FEM) was developed by COMOSL Multiphysics 5.2a and followed by coupled electrochemical and mechanical analyses of a whole cell, including cathode, anode, and electrolyte.

As the first step, the electrochemical model based on the microstructure was compared with results from the previous study with a simple geometry (e.g. spherical particles). Specifically, the real 3D microstructure model, concentration, polarization, over potential, and von-Mises stress distribution across both electrodes (e.g. graphite and NMC) were computed under different C-rates. We observed that effects of phase transformation of NMC on mechanical stress was significant during discharging processes. Moreover, the model revealed that at particle connections where exhibit complicated geometries and the bulged regimes of smaller curvature showed higher stress and were vulnerable to particle cracking. Finally, it is confirmed that mechanical stress plays important role in electrochemical performance.

This computational model can make a solid foundation to understand the relationship between mechanical stress and electrochemical performance in NMC/graphite battery chemistry. It might be helpful to understand key factors in the deterioration of Lithium-ion batteries with higher C-rates and longer cycle life.
Study of the Influence of Carbon Additive Content in LiMn0.5Ni1.5O2 Cathodes in Lithium Ion Batteries
Authors: Guzmán Gregorio , Diaz-Chavez L , Ramos-Sánchez Guadalupe , González I
Published: February 2020

LiMn0.5Ni1.5O2 is one of the most important materials for high voltage Lithium Ion batteries. Due to the high operation voltage, the LiMn0.5Ni1.5O2 – electrolyte interphase suffers high reactivity which limits the cyclability of the electrodes. Several modifications to the electrolyte, cathode material, and inclusion of additives in both phases have been investigated, however although they have provided slight improvements, the reasons behind the stability enhancement still are not fully understood [1]. Additionally, the presence of carbon additives has also been reported to influence the initial capacity and cyclability of the cathodes; however, the great variety of cathode composite compositions, type of carbon additives and experimental conditions makes difficult a fair comparison between them. In this work the influence of carbon additives at two compositions (2 and 10%) is studied by cyclic voltammetry charge and discharge curves and Electrochemical Impedance spectroscopy (EIS), the cyclability in both cases resulted very high with high coulombic efficiency close to 100% with Li anodes. The EIS spectra were adjusted to several equivalent electric circuits, while most of them results in a fair agreement, the explications derived from them are not applicable to all cases, moreover, a phenomenological interpretation was proposing which resulted in excellent xi2 adjustment (10-5) which overpasses by far state of the art results (10-3) with limited phenomenological information. In this work the EIS was applied at several conditions of the electrode and in general it was observed an enormous increase of charge transfer resistance as cycling goes on. However, the lower carbon content results in an even faster degradation process which is also accelerated by longer times at higher voltages. Therefore, the carbon additive also has a big influence on the reactivity of the electrode-electrolyte interphase and can serve as additional tool to increase the cyclability of the electrodes.

Acknowledgements This work was supported, GR thanks (project seciti/080/2017) IG thanks CONACYT (proyect 237343) for financial support. G. Guzman is grateful to CONACYT for the scholarship granted to pursue his doctoral studies.

[1] Kang-Joon Park,a Byung-Beom Lim,a Moon-Ho Choi,a Hun-Gi Jung, Yang-Kook Sun, Marta Haro, Nuria Vicente, Juan Bisquert and Germá Garcia-Belmonte, J. Mater. Chem. A, 2015, 3, 22183
Strategic Architecture of Silicon Nanolayer-Embedded Graphite Hybrid for High Energy Lithium-Ion Battery Anodes
Authors: Ko Minseong , Oh Pilgun , Jung Jae-il
Published: February 2020

As the widespread emergence of modern technologies combined with human life, lithium ion battery (LIBs) has become one of the most important power supplier for mobile electronic devices, electric vehicles and stationary applications. However, the current LIBs provide a low energy density with approaching to the capacity limits, which emphasize the urgent need for high energy density battery systems.

Herein, we have prepared the amorphous silicon nanolayer-embedded graphite/carbon (SGC) hybrids by chemical vapor deposition (CVD) method with developing the cost-effective and scalable pyrolysis system. With developing an industrial-relevant modified CVD process, sophisticated structure of optimum SGC hybrids achieved high reversible capacity (523 mAh g-1) and unprecedented coloumbic efficiency (92%) at a 1st cycle in the industrial standard electrode density (> 1.6 g cc-1) and areal capacity loading of > 3.3 mAh cm-2. Moreover, fabricated SGC electrode confirmed rapid increase of cycling efficiency upward of 99.5% over only 6th cycles and exactly allowed favorable cyclability of 96% capacity retention after 100 cycles and high rate capability comparable to the industrial graphite anode. In addition, the electrode composed of SGC hybrids entirely overcame the detrimental effects of the volume variation problems, exhibiting 23% of additional expansion excepting for graphite counterpart. This, in turn, completely preserved the electrical interconnectivity and mechanical integrity without any cracks and contact losses. Finally, a prototype full cell device is demonstrated with high voltage lithium cobalt oxide (LCO) cathode through the coin cell configuration, which achieved 92% of capacity retention after 100 cycles with considerable potential toward next generation target as practical devices. Consequently, this successful SGC hybrid anodes could be proposed for commercial extension to the next generation high-energy battery systems as a major breakthrough for electric vehicle or grid energy storage applications.

Scheme 1. Schematic of fabrication process for SGC hybrids. Gas phase of Silane (SiH4) can easily adsorb and penetrate on a pristine graphite (PG), which leads to homogeneous and highly pure amorphous silicon nanolayer coating on both inner and outer surface of PG as silicon graphite (SG) hybrids. In the end, SGC hybrids are invented from SG through carbon coating with acetylene (C2H2) gas by CVD method.

Figure 1
Novel Battery Design Principles for Highly Safe, High Energy Density Lithium Ion Battery Using Less Volatile Electrolyte
Authors: Unemoto Atsushi , Seki Eiji , Konishi Hiroaki , Nishimura Katsunori , Kawaji Jun , Okumura Takefumi
Published: February 2020

Enhancing battery energy density is of particular importance for distributing electric vehicles and stationary uses. For EV uses, high energy density battery allows for longer driving distance per a charge, and cycle life, while it leads to an enlarged risk on safety. Hence, it exists a trade-off relationship between energy density and safety for battery packs developed for EVs.

Safety failure in the current lithium ion battery is often related to an explosion of a volatile and flammable electrolyte liquid. Once internal short takes place irregularly, joule heat generation takes place and thereby it leads to the explosion of volatile and flammable electrolyte as this called thermal runaway. In addition, fields of the battery used is limited, namely, the battery use in the enclosed space is likely to be prohibited to prevent the leakage of toxic and volatile electrolyte liquid into the space.

To overcome the issues related to the battery safety, we recently developed a novel electrolyte having a lower vapor pressure electrolyte than the conventional organic liquid electrolyte, and applied the electrolyte to lithium ion battery with a high energy density. A repeated operation of the battery was successfully demonstrated.

In this presentation, the concept our electrolyte, and evaluated results on electrolyte volatility and charge-discharge property of the battery will be reported.
Effect of LiNO3 Electrolyte Additives for Improved the Rate Capability of Micro-Patterened Lithium Metal Anode
Authors: Jin Dahee , Oh Jeonghun , Yoon Byeolhee , Park Jinkyu , Lee Yong Min , Ryou Myung-Hyun
Published: February 2020

The commercialization of Li metal electrodes is a long-standing objective in the battery community for electric vehicles (EVs) and energy storage systems (ESSs) due to its high theoretical specific capacity of 3,860 mAh g-1 and lowest potential of -3.040 V vs. SHE. To achieve this goal, the formation of Li dendrites and mossy Li deposition, which cause poor cycle performance and safety issues, must be resolved.

To overcome this problem, many efforts have been devoted to suppress lithium dendrite growth. Recently, we demonstrated the possibility of using mechanically surface-patterned Li-metal for Li secondary batteries. In our previous work (J. N. Park et. Al), patterned Li-metal anode showed good cycle life at low current density cycling. However, during the repeated Li plating processes with high current density, the controlled surface is filled by granular forms of Li metal, which relatively increases the possibility of side reactions caused by decomposition of electrolyte as well as reduces suppressing effect of dendrite growth.

In this study, we applied a LiNO3 as an electrolyte additives on micro-patterned lithium metal to suppress the dendrite growth and mossy Li deposition. The effect of LiNO3 was studied by using galvanostatic cycling test, scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS) and their electrochemical properties are investigated in detail.
Study on Dead Li Suppression Mechanism of Li Hosting Carbon-Based Protective Layer for Li Metal Anodes
Authors: Jo Hearin , Kim Seokwoo , Jin Dahee , Oh Jeonghun , Choi Junyoung , Yoon Byeolhee , Park Jinkyu , Ryou Myung-Hyun
Published: February 2020

Since Li metal exhibits considerable morphological changes during Li plating/stripping, the use of Li metal as a secondary battery anode material has been limited. Recently, in order to suppress dead Li formation during Li plating, a method of hosting Li metal in a stable structure in plating process has attracted attention. Although many types of conductive Li host materials have been introduced to improve the electrochemical properties of Li metal anodes, the mechanism by which conductive Li hosting materials inhibit dead Li in each system has not been precisely investigated. In this study, we introduce a Carbon-based protective layer on the Li metal surface and investigate the effect of the protective layer on the formation of dead Li. To this end, the adhesion properties of the plated Li and the morphological changes of the Li metal anodes during plating are investigated according to the presence of the protective layer. Furthermore, the effect of protective layer on the electrochemical properties of Li metal anodes is investigated. The protective layer holds plated Li over entire area firmly, resulting in reduced dead Li during repeated cycling. Therefore, a unit cell composed of a Li metal anode having a protective layer exhibits remarkably improved cycle performance (99.4 mAh g-1 after 250 cycles at 1C-rate), which was more than a factor of 3 compared to that of the Li metal w/o protective layer (31.3 mAh g-1 after 250 cycles at 1C-rate). Furthermore, the former showed improved rate capability (63.5 mAh g-1 after 35 cycles at 10C-rate), which was improved by more than a factor of 1.4 compared to that of the Li metal w/o protective layer (45.8 mAh g-1 after 35 cycles at 10C-rate).
New Routes Towards High Energy, Low Cost and Fast-Charging Energy Storage Systems
Authors: Agostini Marco , Matic Aleksandar
Published: February 2020

The rapid growing of electronic technologies as well as electric vehicles requires the development of new, higher energy and environmental friendly storage systems. In this scenario ideal candidates are the batteries systems and in particular those based on the electrochemical process of lithium, thanks to long calendar-life and to favorable design. However, although this technology is adequate for the consumer electronics market, it has some serious shortcomings when considering implementation in electric vehicles or in grid energy storage applications. In particular limiting factors are related to the low energy density of LiCoO2 cathodes and graphite anodes. Additionally, the use of Cu as current collector at the anode and also the increasing cost and reducing availability of Co push the research to the development of alternative chemistries exploiting materials environmental friendly, with higher energy density and reduced cost
1-3
.

In this contribution, we present new strategies to improve the energy density, increase the safety level and reduce the cost of energy storage systems based on Li process.

References

(1) B. Scrosati, J. Garche, J. Power Sources.
195, 2419-2430, (2010).

(2) Y. Yang, G. Zheng, Y. Cui, Energy Environ. Sci.
6, 1552-1558, (2013).

(3) Whittingham, M. Chem. Rev.
104, 4271-4302, (2004).
Charge Transport, Conductivity, and Carrier Density in Tcnq Loaded MOF Films
Authors: Chen Xin , Truong Bobo , Hassan Zeinab Mohamed , Redel Engelbert , Zhang Kai , Zhao Guomeng , Baumgart Helmut
Published: February 2020

Bulk Metal-organic-framework (MOF) films are designed scaffold-like compounds that consist of metal ions connected by organic ligands in the form of crystalline powders, while Surface Anchored Metal-organic-framework (SURMOF) films consist of quasi-liquid phase epitaxially grown highly ordered crystalline films. The ability to conduct electrical charge is one of the most important but least understood properties of MOF films and coordination network materials. Very little work exists on electrical characterization of MOF films, because the early synthesized pristine MOF films exhibited mostly insulating characteristics. Recently, it has been reported that the electrical properties of bulk host MOF films can be modulated by infiltrating guest molecules (metal clusters) inside the porous MOF framework. This renders MOF materials a novel and potentially promising material for microelectronic devices, sensors, and thermoelectrics. For this case study we used MOF Cu3(BTC)2 (BTC: benzene tricarboxylate) films, also known as HKUST-1 (Hong Kong University of Science and Technology-1), which were infiltrated with tetracyano-quinodimethane (TCNQ) guest molecules to modulate the charge transport characteristics. HKUST-1 MOF thin films have been grown using a liquid phase epitaxy (LPE) spray method in which the metal-containing solution [1 mmol Cu(OAc)2] and the linker solution [0.1 mmol BTC] are sprayed alternately on modified silicon substrates. Subsequently, the samples were immersed into an ethanoic TCNQ solution. For benchmarking we have investigated the electrical characteristics of pristine HKUST-1 and TCNQ loaded compact HKUST-1 SURMOF films by Hall-Effect measurements and Seebeck measurements. Both Hall Effect and Seebeck coefficient measurements indicate that electrical conduction in dense compact MOF films involves positive charge carriers. The Hall coefficient, mobility as well as the charge carrier density, the electrical conductivity and the sheet resistance for HKUST-1 MOF films will be discussed.
Water-Gas Shift Reaction Activity of Pt Nanoparticles Hybridized with Metal-Organic Frameworks
Authors: Ogiwara Naoki , Kobayashi Hirokazu , Kitagawa Hiroshi
Published: February 2020

Metal-organic frameworks (MOFs) with nanopores have been attracted much attention as a platform for absorbing guest molecules and the absorbed molecules in MOFs exhibit the unique physicochemical properties different from those of free gaseous molecules.1 However, there is poor understanding of how the confined guest molecules affect chemical reactions. To uncover the insight, we designed a hybrid material based on MOFs and metal nanoparticles (NPs), where MOFs provide absorbed molecule as a reactant and metal NPs work as a catalyst.

At first, we prepared 9 nm Pt NPs using a liquid phase reduction method.2 Then, the obtained Pt NPs were coated with a thermally stable Zr-based MOF (UiO-66)3 by a solvothermal method in the presence of ZrCl4 and terephthalic acid. Transmission electron microscopy (TEM) image revealed that the UiO-66 completely covers the Pt surface (Pt@UiO-66). For comparison, we also prepared Pt on UiO-66, where Pt NPs are located on the surface of UiO-66, by mixing Pt NPs and pristine UiO-66 in DMF and centrifuging them. We investigated water-gas shift reaction4 activity of Pt@UiO-66 and Pt on UiO-66 by using a fixed bed flow reactor. Both Pt@UiO-66 and Pt on UiO-66 exhibited higher CO conversion than Pt on ZrO2, demonstrating that the presence of the UiO-66 hybridizing causes an enhancement in the catalytic activity. Interestingly, the activity of Pt@UiO-66 was much higher than that of Pt on UiO-66, demonstrating that the UiO-66 coating enhanced the activity. The detail mechanism on the enhanced activity is also discussed.

References

X. Kong, J. R. Long, J. A. Reimer et al., J. Am. Chem. Soc., 2012, 134, 14341.

C. Tsung, G. A. Somorjai, P. Yang et al., J. Am. Chem. Soc., 2009, 131, 5816.

L. H. Cavka, K. P. Lillerud et al., J. Am. Chem. Soc., 2008, 130, 13850.

H2O + CO → H2 + CO2

Figure 1
A Dipolar Surface Mounted Metal-Organic Framework (SURMOF): Basis for Sensor Applications
Authors: Gies Joshua , Füser Matthias , Bolte Michael , Terfort Andreas , Kind Martin
Published: February 2020

In a cooperation within the COORNETs SPP, we aim to develop novel sensor systems based on dielectric and ferroelectric surface-mounted metal-organic frameworks (SURMOFs). To this end, we synthesize Kitagawa-type metal-organic frameworks, M2L2P (M= metal, L= linker, P= pillar) [1]. For our project, either the linker or the pillar molecules need to comprise a rotatable dipole moment perpendicular to the molecular axis.

We will report on our recent results on the system [Cu2(bdc)2(dpym_btd)] (bdc2- = 1,4-benzenedicarboxylate, dpym_btd = 4,7-di(pyridine-4-yl)-2,1,3-benzothiadiazole). We have synthesized bulk MOF material using a solvothermal procedure, followed by characterization via X-ray crystallography.

A layer-by-layer (LbL) approach was applied to deposit [Cu2(bdc)2(dpym_btd)] as a SURMOF on a functionalized Au(111) model surface. Several LbL parameters were optimized, such as template chemistry, deposition temperature and concentration of the precursors.

Reference:

[1] Kondo, T. Okubo, A. Asami, S. Noro, T. Yoshitomi, S. Kitagawa, T. Ishii, H. Matsuzaka, K. Seki, Angew. Chem. Int. Ed.
1999, 38, 140-143.

Figure 1
SURMOF/Cnc Based "Designer Solids" for Photonic, Optical and Energy Applications
Authors: Redel Engelbert , Walheim Stefan , Schimmel Thomas H. , Liu Jinxuan , Wöll Christof
Published: February 2020

SURMOFs and CCNCs applications well be presented; in the Applications field of low-k and dielectric materials, optoelectronic propeties, novel photonic band gap naterials as well as for PV applications.
(Invited) Fabrication of MOFs Membranes for Molecular Separation
Authors: Qiu Shilun , Xue Ming
Published: February 2020

Metal–organic framework (MOF) materials, which are constructed from metal ions or metal ion clusters and bridging organic linkers, exhibit regular crystalline lattices with relatively well-defined pore structures and interesting properties. As emerging inorganic and organic hybrid materials, MOF materials are very appealing to be assembled into MOF membranes for separation and catalysis applications because their pores can be rationally controlled by the interplay of both inorganic metal ions and organic linkers, and their pore surfaces can be readily functionalised through a variety of approaches.[1,2] The ability to rationally tune the structure of the materials may create unique interactions with guest molecules and thus achieve unusual chemicophysical properties in adsorption and separation.

Reference:

L. Qiu, M. Xue and G. S. Zhu, Chem. Soc. Rev., 2014, 43, 6116.

X. Kang, M. Xue, L. L. Fan, L. Huang, L. J. Guo, B. L. Chen, S. L. Qiu, Energy Environ. Sci, 2014, 7, 4053.