bluuebunny/crossref_metadata_2025_split huggingface dataset:
SEI Formation Vs. Lithium Intercalation: In-Situ AFM Experiments on Graphite and Silicon Electrodes
Authors: Benning Svenja , Chen Chunguang , Notten Peter , Hausen Florian 
Published: February 2020

The formation of the solid-electrolyte interphase (SEI) passivation layer on anode materials in lithium ion batteries (LIB) is not yet fully understood at the micro- and nanometer scale. Therefore, experiments under realistic conditions with high spatial resolution are of primary importance. Hence, atomic force microscopy (AFM) is an ideal technique to study in-situ the mechanisms at the electrode-electrolyte interface down to the (sub-) nanometer level.
Within this contribution we present a combined AFM and electrochemical (de-) lithiation study of the electrode-interface for two types of anode materials. Highly oriented pyrolytic graphite (HOPG) as a model system has been investigated in order to observe the topographical and electrochemical properties simultaneously. We find a clear influence of defect structures on the SEI formation process. Furthermore, the structural as well as the mechanical behavior of silicon anodes during (de-) lithiation will be presented. Sputtered silicon thin film electrodes [1] have been used to avoid strain and crack formation [2] on the silicon electrode during lithiation. We will introduce AFM measurements that enable a differentiation between SEI formation and expansion of the silicon electrode upon lithiation. We observed significant variations in the elastic modulus during the (de-) lithiation processes on the silicon electrode that can be directly attributed to the formation of an SEI layer as well as the expansion of the electrode due to the lithium insertion. Additionally, the analysis of the surface roughness will be discussed with respect to (ir-) reversible processes on the electrode surface.

References:

[1] R. Kumar et al., ACS Energy Lett., 2016, 1, 689-697
[2] P. Harks et al., Journal of Power Sources, 2015, 288, 92-105
Synthesis, Characterization and Electrocatalytic Activity for Hydrogen Evolution Reaction of Ternary Transition Metal Borides
Authors: Park Hyounmyung , Fokwa Boniface P.T. 
Published: February 2020

Recently, as the concerns on the global warming and the depletion of fossil fuels, the most immediate scientific challenge is developing clean and renewable energy. Hydrogen has focused as one of the promising alternatives to carbon-based fuels because hydrogen is eco-friendly energy.
There are lots of methods to produce hydrogen. One easy and simple way to produce extremely pure hydrogen is water electrolysis, through hydrogen evolution reaction (HER).
Currently, noble metals such as platinum are generally regarded as the state-of-the-art electrocatalysts for improving the kinetics and efficiency of HER. However, their prohibitive price and scarcity limit their application industrially. It is therefore highly desirable to discover highly active and stable HER electrocatalysts composed of inexpensive and earth abundant elements.
In the last few years, boron based materials have been proposed as low-cost alternative electrocatalysts for HER. Recently, binary molybdenum borides (MoB, Mo2B, MoB2 and Mo2B4), iron boride (FeB2) and amorphous cobalt boride (Co2B) were reported to have outstanding catalytic activities for the HER.
In this work, we have synthesized molybdenum-tungsten diborides using solid solution synthesis. We substituted tungsten for molybdenum. The synthesized materials were characterized by X-ray power diffraction (XRD), X-ray photoelectron spectroscopy (XPS), energy dispersive X-ray analysis (EDX) and scanning electron microscope (SEM). Linear sweep voltammetry (LSV) was performed to determine the electrochemical properties by using a three electrodes system, and cyclic voltammetry (CV) was conducted to measure stability.
In Operando Cell Diagnostic with MRI
Authors: Silletta Emilia Victoria , Mohammadi Mohaddese , Ilott Andrew , Ganter Matthew J. , Schauerman Christopher , Jerschow Alexej 
Published: February 2020

One of the biggest obstacles in the way of battery technology development is the limited amount of information that one can obtain from the battery mechanism without taking it apart. Here we are presenting a novel non-destructive battery assessment technology that is capable of obtaining crucial information from batteries even when the cells are encased in conductive material. One important application is commercial-type cell-phone batteries, which can be analyzed with this method. The technique is based on measuring the magnetic susceptibility of active ingredients inside an electrochemical cell that is affected by the oxidation state of the materials to give insights into the state of charge (SOC) of the battery, its failure mechanisms and the current distributions. The technique has been demonstrated on various cell types, defects, chemistries, and current level. The measurement is based on Magnetic Resonance Imaging (MRI) techniques, is fast (a couple of seconds), and could be adapted to a range of cell types. The figure shows the schematic setup and examples of images of different cells which are used to diagnose the SOC and the state of health. The technology represents a new opportunity for nondestructive cell diagnostics, and hence could be of great help in the development of next-generation batteries. We demonstrate the identification of defect, state of charge, and classification of cells based on different types of features. The method can also provide localized current distribution measurements.
Figure caption: Magnetic field map measurements for the fully charged cells. (A)-(C) sample placement, and image orientation; (D)-(E) Field maps measured for the cells. Field maps are referenced to the empty holder, giving an absolute field map for the Li-ion cell. (F) Magnetic field maps for the defect cells, with the mean and standard deviation indicated (taken over all of the voxels in each image). The fields are given relative to one of the non-defect cells (not shown).

Figure 1
(Invited) DNA Quadruplex Hydrogels: An Application of Synthetic DNA As Bulk Material
Authors: Kuzuya Akinori 
Published: February 2020

DNA is a water-soluble and biodegradable polymer, which forms right-handed double helices and carries genetic information in life. Because of its high structure regularity and sequence programmability, DNA has been used as a key component in development of functional nanomaterial. Despite such success in nanoscience, reports on application of DNA to typical material, i.e. hydrogels, are very few, except for some excellent achievements, because preparation of DNA in gram scales usually requires unreasonable costs. One solution for this problem is liquid-phase DNA synthesis method developed by Bonora et al. They used monofunctional MeO-PEG as a soluble polymeric support, which enables coupling reaction of phosphoramidite monomers in liquid phase and can be easily precipitated by ether addition for product separation.
We have applied this system to synthesize DNA-PEG-DNA tri-block copolymer in grams, and successfully prepared biodegradable PEG hydrogels by using higher-order DNA structures, such as G-quadruplexes, for cross-linking points. Aqueous solution of a tri-block copolymer bearing multiple guanosines at the ends, for example, immediately turns into gel upon addition of Na+ or K+ ions at reasonable concentration. Various body-related fluids such as PBS, artificial saliva, sweat, or tear can trigger gelation. The resulting hydrogels are self-healable since the crosslinking points are stable but still reversible structure. Moreover, introduction of toehold sequence realized complete control of such sol-gel transition by the addition of complementary DNA strand.
Development of Hydrogel Fatigue Sensor
Authors: Iijima Tetsuro , Inoue Shota , Saito Azusa , Tamate Hideaki , Khosla Ajit , Kawakami Masaru , Murasawa Go , Furukawa Hidemitsu 
Published: February 2020

In recent years, various high-strength gels having strength of several MPa have been developed one after another by devising the internal structure of the gel. They have attracted attention as a new material. High-strength double network gel (DN gel) is a gel consisting of a hard 1st network and a soft 2nd network and have excellent properties such as super low friction, flexibility and biocompatibility. Particle double network gel (P-DN gel) consisting of powdered 1st network and 2nd network is a high strength gel capable of 3D free form fabrication by using 3D gel printer. Utilizing these advantages, there are expectations for soft robot materials and mechanical materials. It is also important to grasp the number of deformation of the gel and how much fatigued it is when the gel material is industrially used. Specifically, by attaching a fatigue sensor to a soft robot, it is possible to predict the optimum time to replace the parts. When it is used for mechanical materials, we need to judge on the necessity of emergency treatment. It will be considered to lead to comfortable use of things.
In this study, we aimed to develop a gel fatigue sensor with reference to the internal structure and destruction phenomenon of P-DN gel. P-DN gels of various compositions were prepared and mechanical tests and evaluation of internal structure by dynamic light scattering were carried out to investigate the physical properties of these gels. As a result, the P-DN gel using super absorbent polymer (SAP) as the 1st gel showed the most suitable physical properties for use as a fatigue sensor.
(Invited) Sliding Dynamics and Mechanical Properties of Slide-Ring Gels
Authors: Mayumi Koichi , Liu Chang , Jiang Lan , Hidaka Yuta , Yokoyama Hideaki , Ito Kohzo 
Published: February 2020

To overcome the trade-off relationship between stiffness and toughness of conventional polymer gels with covalent cross-links, introducing dynamical cross-links into polymer network is a promising strategy. A typical example of dynamically cross-linked gels is slide-ring gel, in which polymer chains are cross-linked by rings and the cross-linking points can slide along polymer chains. When slide-ring gels are deformed, the network structure of slide-ring gels is homogenized due to the sliding of the ring molecules, which causes their high deformability [1]. We have recently performed crack propagation tests on slide-ring gels and found that their fracture energy is dominated by the sliding distance of the movable cross-links [2].
In this work, we investigate the relationship between the macroscopic fracture toughness of slide-ring gels and nano-scale sliding dynamics of rings on polymer chains. Slide-ring gels are prepared by cross-linking ring molecules of polyrotaxanes, necklace-like supramolecules consisting of cyclodextrins and polyethylene glycol. The fracture energy of slide-ring gels keeps constant at strain rates below a certain value, and decreases at a high strain rate, where the movable cross-linking points cannot slide and behave like covalent cross-links. From the strain rate dependence of the fracture energy, we have estimated the time scale for the sliding dynamics of cross-links in slide-ring gels.
References
[1] Ito, K., Polym. J., 39, 489 (2007).
[2] Liu, C., Kadono, H., Mayumi, K., Kato, K., Yokoyama, H., Ito, K. ACS Macro Letters, 6, 1409　(2017).

Figure 1
Molecular Dynamics Study Investigating the Interface between Nanoparticles and Matrix in Composite Materials
Authors: De Nicola Antonio 
Published: February 2020

Polymer composites attract large attention for their industrial use because of their unique features. The preparation of equilibrated melts of long entangled chains in the presence of a solid
nanoparticle in molecular dynamics simulations is a very difficult task due to the slow relaxation time. We present a coarse-grained (CG) model suitable for polymer nanocomposites which combines Iterative Boltzmann-Inversion derived polymer models, the hybrid particle-field representation of non-bonded interactions, and a convenient description of a solid nanoparticle suitable for hybrid particle-field models. The proposed approach is applied to test simulations of well characterized polystyrene-silica nanocomposites models. Finally, procedures for an efficient relaxation of pure polymer melts and interphase structures of large molecular weight nanocomposites are proposed.
Interface of Hydrated Perfluorosulfonic Acid Electrolyte and Platinum Catalyst: Dissipative Particle Dynamics Simulation Model
Authors: Tajima Nobuo , Nara Jun , Yamasaki Takahiro , Ozawa Taku , Nitta Hiroya , Ohata Kosuke , Ohno Takahisa 
Published: February 2020

Polymer electrolyte fuel cells (PEFC) are expected to be used widely in the future as a non-polluting power source in various applications. PEFC applications are only limited currently however, as PEFCs are still not competitive with existing power sources in energy efficiency and cost. One of the most popular forms of PEFC are composed of an electrolyte of hydrated perfluorosulfonic acid (PFSA), and carbon based electrodes that support small catalyst particles (typically Pt) on the surface. The global performance of PEFC of this type is governed by the rate of red-ox reactions on the catalyst surface, which are affected by molecular level dynamics of fuel, oxidants, and protons in the electrolyte near the catalyst surface. We need deeper understanding on this interfacial structures for new insights into the mechanisms that control the electrochemical surface processes. Several structure models have been proposed for the bulk electrolyte, while only little is understood as to its structure near the catalyst surface so far.
In this study, to investigate the interfacial system of hydrated PFSA and platinum surface, we constructed models of this system for dissipative particle dynamics (DPD) simulations. DPD simulation is a kind of coarse-grained simulation which is used to study mesoscopic systems, typically consisting of macromolecules like polymers and biomolecules. We coarse grained the simulation system with DPD particles corresponding to PFSA segments A-C (see Fig.1), those grouping four water molecules (denoted as W), and those grouping ~8 platinum atoms (Pt). The catalyst surface was represented by a fixed slab of the Pt particles forming a simple lattice. We used soft potentials constructed via quantum chemical calculations by Okuwaki et al. [1] for interactions of DPD particles A-C and W; while we newly constructed soft potentials for the interactions of Pt with other DPD particles by analyzing their affinities via all-atom classical MD simulations for some small systems. For these all-atom MD simulations, we derived some intermolecular potential functions by first principles calculations. Details of our DPD simulations as well as the interaction model constructions will be presented in the conference session (a snapshot is displayed in Fig. 2).
A portion of this research was supported by MEXT within the priority issue 6 of the FLAGSHIP2020 project (Project ID: hp160226, hp170253,hp180187).
[1] K. Okuwaki et al., JSAP spring meeting (2016) 20a-W323-6.

Figure 1
(Invited) Proton Conductivity Enhancement in Polymer Thin Films By Molecular Orientation and Organized Structure
Authors: Nagao Yuki 
Published: February 2020

Highly proton-conductive polymers have long attracted the attention of researchers for use in energy conversion, sensors, catalysts, and other applications. From the viewpoint of scientific history of creating highly proton-conductive polymers, one fundamental approach is based on the strategy of phase-segregated structures with strong acid groups.[1-3] Protons are considered to be transported through the hydrophilic parts.
In the recent polymer research fields, taking advantage of the interface extends the molecular design such as the oriented structure and organized structure for the highly proton conductive materials. Matsui et al. showed anisotropic proton conductivity in Langmuir–Blodgett thin films with well-defined lamellar structures [4]. Proton conductivity is enhanced by the formation of 2D hydrogen-bonding networks in multilayer nanosheets [5, 6].
In this presentation, the author demonstrates a new approach to enhance the proton conductivity of the polymer thin films using an interface that can modify the degrees of freedom for a polymer structure through interaction between the substrate surface and polymers.[7-12] The interface can modify the degrees of freedom for polymer structures through interaction for functional groups, wettability, and surface charge between the substrate surface and polymers. Some proton-conductive polymers exhibit an oriented structure determined by an IR p-polarized multiple angle incidence resolution spectrometry (pMAIRS) [13]. Their oriented thin films show unique proton transport properties compared to those of non-oriented samples.

References

[1] K.D. Kreuer, J. Membr. Sci., 185 (2001) 29-39.
[2] M.A. Hickner, H. Ghassemi, Y.S. Kim, B.R. Einsla, J.E. McGrath, Chem. Rev., 104 (2004) 4587-4611.
[3] T.J. Peckham, S. Holdcroft, Adv. Mater., 22 (2010) 4667-4690.
[4] T. Sato, Y. Hayasaka, M. Mitsuishi, T. Miyashita, S. Nagano, J. Matsui, Langmuir, 31 (2015) 5174-5180.
[5] T. Sato, M. Tsukamoto, S. Yamamoto, M. Mitsuishi, T. Miyashita, S. Nagano, J. Matsui, Langmuir, 33 (2017) 12897-12902.
[6] J. Matsui, H. Miyata, Y. Hanaoka, T. Miyashita, ACS Appl. Mater. Inter., 3 (2011) 1394-1397.
[7] Y. Nagao, Langmuir, 33 (2017) 12547-12558.
[8] Y. Ono, R. Goto, M. Hara, S. Nagano, T. Abe, Y. Nagao, Macromolecules, 51 (2018) 3351-3359.
[9] K. Krishnan, H. Iwatsuki, M. Hara, S. Nagano, Y. Nagao, J. Mater. Chem. A, 2 (2014) 6895-6903.
[10] K. Krishnan, H. Iwatsuki, M. Hara, S. Nagano, Y. Nagao, J. Phys. Chem. C, 119 (2015) 21767-21774.
[11] Y. Nagao, J. Phys. Chem. C, 117 (2013) 3294-3297.
[12] Y. Nagao, J. Matsui, T. Abe, H. Hiramatsu, H. Yamamoto, T. Miyashita, N. Sata, H. Yugami, Langmuir, 29 (2013) 6798-6804.
[13] T. Hasegawa, Anal. Chem., 79 (2007) 4385-4389.
Molecular Dynamics Simulations of Li+ Desolvation in Electric Double Layer at the Lithium Ion Battery Graphitic Anode Interface
Authors: Aoyagi Koutarou , Otani Minoru 
Published: February 2020

The use of lithium-ion (Li-ion) batteries to power hybrid, plug-in hybrid, and electrical vehicles in recent years calls for greater battery charge/discharge rate and cycle life than their applications in electric devices. These properties are largely caused by the phenomenon in the interphase of electrode and electrolyte. For the battery charge/discharge rate, the process of Li+ desolvation in the interphase and intercalation to graphitic anode are key factors. However, there are various hypotheses about Li+ desolvation and it has still not been clarified. Detailed understanding of the interphase can accelerate the development of Li-ion battery. In this work, to gain an understanding of the electrolyte structure in the interphase, atomistic molecular dynamics simulations of the electrode/electrolyte interphase at a constant voltage were performed and Li+ desolvation process were observed.
We utilize a modified version LAMMPS code implemented the novel computational approach to carry out the simulation of the electrolyte in the presence of electrodes and applied voltage. The approach for treating the model of battery interface held at a constant potential, which has necessity to calculate the nonperiodic cell in the surface normal direction, is based on effective screening medium (ESM) method [Otani and Sugino, Phys. Rev. B 73, 115407 (2006)]. The Poisson equation is solved with the help of the green’s function technique. The electrostatic potential V(z) was solved as following equation, V(z) = -∑q
i|z
i-z|/2ε
0
S
0, where ε
0 is the permittivity of vacuum, S
0 is electrode’s surface area, and q
i is the charge of ith atom. If a potential difference V is applied across the two electrodes, then the charges are induced on each electrode surface to be V(z
le) - V(z
re) = V, where z
le is the z of left side electrode surface and z
re is right one.
Prepared simulation model is the box with two edge plane of graphitic electrodes separated by an electrolyte which consists of 1M LiPF6 / ethylene carbonate (EC) / ethyl methyl carbonate (EMC) 30:70. The interelectrode spacing is 8nm. We confirmed it is enough to describe the Electric double layer (EDL) of each electrodes with utilizing ESM-RISM method [Nishihara and Otani, Phys. Rev. B 96, 115429 (2017)].
The simulation of 2ns at 298K was carried out in the constant NVT ensemble with applied voltage of constant 20V. The reason why excess voltage was applied is to get the interphase structure with EDL in short timescale simulation. We observed the dynamics of electrolyte in the interphase of graphitic anode. Then we found that EMC solvate Li+ until the end, and desolvation of EC occur by force of the own dipole facing to the electric field. It was suggested that the desolvation of EC is faster than that of EMC in the EDL. We also calculated dielectric spectrums of solvents on the surface for confirming existence of solvent’s dynamics in EDL by experiment.

Figure 1
The Electrochemical Conversion of Carbon Dioxide on Cu−Ni Stacked Bilayer Electrodes
Authors: Yoshihara Naoki , Saito Hiroki , Noda Masaru 
Published: February 2020

The electrochemical reduction of carbon dioxide (CO2) has gained popularity as a novel technique to realize a sustainable carbon cycle owing to improvements in power generation using renewable energy sources, such as solar and wind energy [1−2]. Recent progress of CO2 conversion utilizing the crystalline copper surfaces offers a promising approach to produce the useful hydrocarbon products.
In our previous works, we demonstrated the fabrication of the single-crystal copper membranes by sputtering copper onto the specific support substrates, such as c-plane sapphire (Al2O3) and magnesium oxide (MgO). The electrochemical reduction of CO2 on these copper surfaces was produced selective hydrocarbons as compared with the commercially available copper plates [3]. In addition, these sputtered single-crystal copper membranes have been successfully peeled away from the support substrates, and thus it is able to fabricate repeatedly onto the identical support substrate [4]. The electrochemical reduction of CO2 on these crystalline copper electrodes is an effective route toward the practical use of the CO2 conversion process, however this methodology of homogeneous copper membrane deposition is essential to the complicated process.
On the other hand, it has been demonstrated that the electrochemical reduction of CO2 to hydrocarbon on a copper surface is due to moderate surface adsorption of a carbonate intermediate by theoretically calculations [5]. Binary metal electrodes, such as copper and another metal, are expected to allow to the carbonate intermediate to adsorb to the appropriate surface and achieve the more effective CO2 conversion to hydrocarbon production as compared with pristine copper electrodes. In this work, we study the electrochemical conversion of CO2 on Cu−Ni stacked bilayer electrodes. Hydrocarbon emissions for the electrochemical reduction of CO2 were strongly dependent on the amount of nickel deposited on the copper electrodes. However, excess deposition of nickel on the copper electrodes suppressed the CO2 conversion. This is suggested that the surface adsorption of the carbonate intermediate is improved on the Cu−Ni stacked bilayer electrodes, compared with pristine copper electrodes, due to the interactions between copper and nickel. Additionally, we also show the selectivity of the hydrocarbon products formed via CO2 conversion on the Cu−Ni stacked bilayer electrodes in terms of the crystal structure underneath the copper electrodes.
Reference
[1] Y. Hori et al., J. Mol. Catal. A Chem., 199, 39–47 (2003).
[2] K. J. P. Schouten et al., ACS Catal., 3(6), 1292–1295 (2013).
[3] N. Yoshihara et al., ECS Trans., 66(24), 83-89 (2015).
[4] N. Yoshihara et al., ECS Trans., 75(43), 33-38 (2017).
[5] A. A. Peterson et al., J. Phys. Chem. Lett., 3, 251−258 (2012).