bluuebunny/crossref_metadata_2025_split huggingface dataset:
Metal-Organic Framework Derived Carbonaceous Materials As Superior Electrode Catalysts for Quantum Dot Sensitized Solar Cells
Authors: Li Yan , Zhao Lianjing , Zhao Leilei 
Published: February 2020

An efficient electrocatalyst for the reduction of polysulfide electrolyte is vital to the construction of quantum dot sensitized solar cells (QDSCs). Carbonaceous materials would be the promising candidates for the fabrication of counter electrodes (CEs) on account of the competitive prices, good conductivity and corrosion inertness for the reduction of polysulfide electrolyte. Metal-organic frameworks (MOFs), especially N-rich zeolitic imidazolate frameworks (ZIFs), recently have been considered to be versatile precursors/sacrificial templates for the preparation of various homogeneous hetero-doping mesoporous carbons with predetermined functionalities.
In view of the abundant doped active sites and inherent larger surface area of ZIF derived carbon materials, we prepared Co,N-bidoped carbon nanomaterials simply via the pyrolysis of bimetallic (Zn and Co) ZIFs. In light of the inherent characteristics of heteroatom doped carbons and the benign catalytic performance of Cu nanoparticles (NPs), the N-C@Cu composites with 2-4 nm Cu NPs uniformly distributing in mesoporous N doped carbons prepared by carbonization of ZIF-8 were also synthesized. The obtained Co,N-bidoped and N-C@Cu composites were utilized as electrocatalysts to develop CEs for QDSCs. The CEs based on both Co,N-bidoped and N-C@Cu composites exhibit superior catalytic activity for polysulfide reduction in QDSCs, resulting in a low charge transfer resistance at the interface of CE/electrolyte, an improved fill factor (FF) and a high short circuit current density (J
sc). The outstanding performances of the CEs can be ascribed to the uniform distributed catalytic active sites, large hydrophilic surface area, and good conductivity. When Co,N-bidoped carbons deposited on fluorine doped tin oxide (FTO) glass were used as CEs, an impressive power conversion efficiency of 9.12% (V
oc = 0.635 V, J
sc = 26.15 mA·cm-
2, FF = 0.549) under one sun illumination with 100 mW·cm-
2 intensity was observed on QDSCs using Zn-Cu-In-Se QDs as sensitizers. Under the same conditions, the optimized N-C@Cu based QDSCs present a promising power conversion efficiency of 9.23%, significantly superior to those of pristine N-C/FTO (7.20%) and Cu2S/FTO (8.89%) CE based QDSCs. Consequently, there is a good chance to fabricate QDSCs of high efficiency with the CE catalysts derived from MOFs.
Rheological Properties of Dense Suspensions of Thermo-Responsive Microgel Mixtures Undergoing Colloidal Gelation
Authors: Minami Saori , Watanabe Takumi , Suzuki Daisuke , Urayama Kenji 
Published: February 2020

Dense suspensions of thermo-responsive poly(N-isopropyl acrylamide) (N) microgels exhibit a characteristic temperature (T)-dependent viscoelasticity at characteristic temperature (T
c) due to T-induced changes in the type of interparticle interaction as well as the volume fraction of microgels[1]. In the range of T < T
c
N, where the swollen microgels with repulsive interparticle interactions are densely packed, the equilibrium modulus (G) decreases upon heating due entirely to the packing effect, i.e., a reduction in the volume fraction of the microgels (φ). At T > T
c
N where the attractive interparticle interactions between dehydrated and hydrophobic microgels emerge, the suspensions show solid-like elastic properties due to the network-like flocculation of the shrunken microgels (colloidal gelation), even when φ becomes considerably lower than the threshold for randomly close packing. The T-dependence of G shows minimum at a characteristic temperature (T
B; T
B > T
c
N) due to the competition between the repulsive interparticle interactions from the packing effect and electrostatic force, and the attractive interactions from the hydrophobicity.
The present study focuses on the mixtures of thermo-responsive N and poly(N-isopropyl methacrylamide) (NM) microgels with different volume transition temperatures (T
c
N = 31oC and T
c
NM = 39 oC, respectively)[2]. The temperature T
B in N/NM mixture suspensions shifts to a higher value with a decrease in N content in the mixtures (X
N), accompanied by a discontinuous-like change at a specific value of X
N. We analyze the T-dependent viscoelasticity of the mixture suspensions with various X
N on the basis of the volume fractions of the total microgels (φ
m) as well as the hydrophobic microgels (Φ
m
a). This analysis indicates that (1) the crossover of the φ
m dependence of G occurs at a value of φ
m at T
c
N and/or T
c
NM, and that (2) the values of Φ
m
a at T
B are about 0.3 independently of X
N.
We also demonstrate the significant impacts of electrostatic repulsive interaction on the colloidal gelation using the NIPAm-co-fumaric acid microgels. At pH 11, the attractive interparticle force through hydrophobic interactions is fully suppressed due to the highly charges surface of the microgels, with the result that neither colloidal gelation nor the crossover of the φ
m-dependence of G at T
c
NF occur. This result indicates that the repulsive electrostatic force with an appropriate strength requires for the stability of the network-like flocculation.
[1] S. Minami, T. Watanabe, D. Suzuki, K. Urayama, Polymer Journal, 48, 1079-1086, 2016
[2] S. Minami, T. Watanabe, D. Suzuki, K. Urayama, Soft Matter, 14, 1596-1607, 2018

Figure 1
(Invited) Formation Process and Structure of Poly (acrylonitrile) Gels
Authors: Matsuba Go 
Published: February 2020

We carried out small angle neutron scattering measurements to clarify the gelation processes of 10 wt% polyacrylonitrile solutions in various water contents. The water in the mixed solvent was accelerated with the phase separation and gelation because of poor solubility of poly(acrylo-nitrile) (PAN) in water.
The solute is amorphous PAN with weight-average molecular weight of Mw = 250,000 and a molecular weight distribution Mw / Mn = 1.8. Mixed solvent is DMF / H2O (0 ~ 9 wt%). amorphous PAN was dissolved in mixed solvent at 90 ºC (PAN : mixed solvent = 10 : 90) after quenching at room temperature. In order to observe the structure and formation process of PAN gels, we used various kinds of scattering methods, e.g. light scattering, small angle X-ray scattering (SAXS). These measurements conducted at room temperature. Time-resolved SAXS was performed using an apparatus installed at beamline BL10C, Photon Factory, KEK (Tsukuba, Japan). The wavelength of X-ray beam was 1.488 Å. The camera length was 2.0 m for SAXS measurements.
The inhomogeneities of polymer chains grow just after quenching then the correlation length increases with time at first. In the opaque gel case, we found the growth of crosslinking points with smooth surfaces. Around the gel point, the crosslinking points emerge and then, the correlation length decreases with time since increasing the crosslinking points. On the other hand, in the transparent gel, we did not observe scattering from surface of crosslinking points but only the correlation length. The correlation length increases during gelation process, then the entanglements of polymer chains play a role of crosslinking points.
Photolithographic Fabrication of Pocket-like Hydrogel Microstructures for Novel Cell Culture System
Authors: Tsukyukubo Atsushi , Sumaru Kimio , Kanamori Toshiyuki 
Published: February 2020

Various functional hydrogels have been developed, and can be applied to the fields of bioengineering, such as cell culture substrates and microfluidic systems. It is very important to provide these materials with some functional shapes in a scale of micrometers when these applications are examined. In this study, we proposed the fabrication of unique hydrogel microstructures through photolithography, and examined its application to novel cell culture system. They are expected to be applied to compose novel cell culture system which can maintain physiological activity of living cells, and to contribute to increasing precision of drug screening through providing totally different culture environment from conventional systems composed of rigid materials.
First, we coated a solution containing a UV responsive photo acid generator (PAG) on polystylene (PS) surface, and then coated a methanol solution containing poly (acrylic acid) (PAAc). The micro-patterned light irradiation (wavelength: 365nm) was carried out to induce area-selective cross-linking. After flushing with water, ethanol and 1M NaOH aqueous solution, a micro-patterned cross-linked PAAc layer was obtained.
Next, we prepared a pre-gel layer by coating a solution containing hydroxypropyl cellulose (HPC) 1,3,4,6-tetrakis (methoxymethyl) glycoluril, an acid catalyzed cross-linker, and PAG, on the cross-linked PAAc layer. The pre-gel layer was irradiated with the light in a different micro-pattern, and was baked at 85 ˚C to promote acid-catalyzed cross-linking of HPC.
After flushing with water, a micro-patterned cross-linked HPC layer was obtained on the cross-linked PAAc layer. By soaking the patterned bilayer in 1M NaOH aqueous solution, HPC gel sheet lifted off of the substrate and swelled in the areas where the cross-linked PAAc had remained while the sheet was immobilized on the PS surface in the other areas. As a result, pocket-like semi-3D microstructures were obtained. To provided the hydrogel with the property of cell adhesion, we examined the coating of several polymer materials on HPC.
Friction Properties of Gel Rings and Plates
Authors: Yahagi Hikaru , Yoshida Kazunari , Wada Masato , Khosla Ajit , Kawakami Masaru , Furukawa Hidemitsu 
Published: February 2020

Recently, the development of high strength gel has advanced, and it is at the stage of application to mechanical parts utilizing the low friction properties of gel. It is expected that the low friction gel has an ability to increase the energy efficiency in various fields.
In this study, we evaluated the friction properties of DN gel ring-shaped sealant by using unique friction measurement apparatus and investigated the effect of cross-linker ratio on friction properties of gel plates to apply the gel materials to mechanical parts. In the case of ring gel, we measured the frictions of rotational direction and vertical direction (see figure). We revealed that friction force along vertical direction was decreased with increase in rotational speed, and the friction force along rotational direction was increased with rotational speed. In addition, we measured the friction force of gel plates with various concentration of cross-linker. The hardness of gel is strongly influenced by the concentration of cross-linker. The results indicate that the friction forced of the soft gel is larger than that of hard gel. The cause of this behavior is difference of contact situations such as contact area.

Figure 1
Proton-Conducting Ceramics for Metal-Supported Solid Oxide Fuel Cells and Electrolysis Cells
Authors: Wang Ruofan , Byrne Conor , Lau Grace , Tucker Michael C 
Published: February 2020

Proton conducting oxide electrolyte materials could potentially lower the operating temperature of metal-supported solid oxide cells (MS-SOCs) to the intermediate range 400 to 600 °C. The porous metal substrate provides the advantages of MS-SOCs such as high thermal and redox cycling tolerance, low-cost of structural materials, and mechanical ruggedness. The cell structure for fuel cell and electrolysis operation is shown in Figure 1. To incorporate proton-conductors into metal-supported cell configuration through co-sintering fabrication, a key factor is that the proton conductors must be compatible with reducing atmosphere sintering, as the porous metal substrate can not be fired in oxidizing atmosphere.
In this work, viability of co-sintering fabrication of metal-supported proton conducting solid oxide cells is investigated. Candidate proton-conducting ceramics including perovskite-type oxides BaZr0.7Ce0.2Y0.1O3-δ (BZCY), SrZr0.5Ce0.4Y0.1O3-δ (SZCY), and Ba3Ca1.18Nb1.82O9-δ (BCN), pyrochlore-type oxides La1.95Ca0.05Zr2O7-δ (LCZ) and La2Ce2O7 (LCO), and acceptor doped rare-earth ortho-niobates La0.99Ca0.01NbO4 (LCN) were synthesized via solid state reactive synthesis or sol-gel synthesis. These ceramics are sintered at 1450°C in reducing environment alone and supported on Fe-Cr alloy metal support, and their key characteristics such as phase formation, sintering property, and chemical compatibility with metal support are determined. Most electrolyte candidates suffer from one or more challenges identified for this fabrication approach, including: phase decomposition in reducing atmosphere, evaporation of electrolyte constituents, contamination of the electrolyte with Si and Cr from the metal support, and incomplete electrolyte sintering. BZCY is particularly interesting because of its high proton conductivity, but it is found to suffer from reaction with Si and Cr present in the metal support, and loss of Ba via evaporation during sintering. Various approaches to overcome these limitations are proposed, and preliminary assessment indicates that the use of barrier layers, low-Si-content stainless steel, and sintering aids warrant further development.
In contrast, La0.99Ca0.01NbO4 is found to be highly compatible with the metal support and co-sintering processing in reducing atmosphere, allowing dense electrolyte and porous electrode made of LCN to be co-sintered on porous stainless steel, Figure 2. A metal-supported cell is fabricated with La0.99Ca0.01NbO4 electrolyte, ferritic stainless steel support, Pt air electrode and nanoparticulate ceria-Ni hydrogen electrocatalyst. The total resistance is 50 Ω∙cm2 at 600 °C.
This work clearly demonstrates the challenges, opportunities, and breakthrough of metal-supported proton-conducting solid oxide cells by co-sintering fabrication.

Figure 1
(Invited) Surface Modified Polypropylene Membrane for High Performance Lithium Metal Coin and Pouch Cell Batteries
Authors: Pol Vilas G. , Kim Patrick , Manikandan P. 
Published: February 2020

For the advanced Li metal batteries, lithium (Li) metal is considered as anode electrode because of its lowest redox potential (–3.04 V vs. standard hydrogen electrode), highest theoretical specific capacity (3,860 mAh g-1), and the low density (0.59 g cm-3). Nevertheless, Li metal anode seriously impede its practical use for viable market because of short-circuit based safety risk associated to dendrite growth and low Coulombic efficiency. Understanding those fundamental challenges, we designed a multifunctional tri-layer membrane by percolating a layer of a polydopamine (PDA) followed by depositing graphene-carboxymethyl cellulose (Gr-CMC) on the top of polypropylene (PP) separator, hypothesizing to improve the cycle stability and performance of Li metal electrodes. The novel, new trilayer comprising Gr-CMC layer of the designed separator depicted an excellent electrolyte wettability, an additional capacity of Li storage and an enhanced electrical conductivity.
In Li/Cu half-cell the Coulombic efficiency was significantly enhanced over 200 cycles after implementing PDA/Gr-CMC separator. LiFePO4 cathode vs Li full cell with trilayer separator directed to long term cycle retention (1000 cycles) with enhanced rate capability. Apart from room temperature, electrochemical stability at 0 oC demonstrated the sanguine potential of PDA/Gr-CMC separator for practical Li-metal batteries. Beyond coin cells, pouch cell studies and cycling abilities will be demonstrated.
High Precision Characterization of Li-Ion Batteries during Extreme Fast Charging
Authors: Karulkar Mohan , Torres-Castro Loraine , Lamb Joshua 
Published: February 2020

With current lithium ion batteries optimized for performance under relatively low charge rate conditions, implementation of Extreme Fast Charging (XFC, 6C charging and above) has been hindered by drawbacks including Li plating, kinetic polarization, and heat dissipation. Novel electrode designs, including anodes optimized for rapid lithium diffusion, show promise in alleviating these drawbacks.[1] However, in order to assess potential anode improvements, materials must be characterized in relevant settings, with tools that can discern critical metrics. This submission will detail efforts at Sandia National Lab to assess battery performance under XFC conditions using ultra high precision coulometry to track cycle-to-cycle efficiency and in-cycle dQdV. Efficiency deviations can reveal lithium plating or cathode breakdown, while dQdV measurements can reveal unintended side processes like lithium stripping during discharge. This submission will also describe the need for quick-response temperature control during XFC testing to minimize the effect of cell heating on characterization.
Figure 1 shows dQdV vs V on a 5Ah NMC/graphite COTS pouch cell, for charge rates of 0.5C (cycle 3), 1C (cycle 6), and 6C (cycle 24) during a rate capability test. It also shows subsequent 1C discharge cycles, and a 1C/1C cycle after the rate capability (cycle 25). Of note is the particular clarity of the dQdV curves, enabled by high precision coulometry performed on a high precision Arbin battery cycler. Charge curves shift right and peaks become more spread out, which is a consequence of cell polarization at higher charge rates. Discharge curves, however, remain nearly identical throughout cycling, indicating that no lithium stripping processes are seen after increasing charge rates.
Figure 2 shows cycling and temperature data for 6C charging / 2C discharge, on the same 5Ah pouch cell type. In this case, rapid response cooling plates are fitted around the cell to reduce cell heating during the high charge rate. The temperature data shows a worst-case temperature rise of only 3oC at the peak of charging along the cell’s edge, which minimizes heating artifacts during cell characterization.
[1] S. Ahmed et al, J. Power Sources, 367, 250-262 (2017).

Figure 1
Aging and Electrode Inhomogeneity in Commercial 18650 Lithium-Ion Cells during Long-Term Cycling
Authors: Wang Han , Whitacre Jay 
Published: February 2020

Li-ion battery production has increased dramatically in the past decade. The concerns over the limited source and environmental impact suggest the recycling of Li-ion battery after usage, especially the functional ceramic oxide cathode materials. Recently, a new approach to recycling cathode materials has been investigated: direct recycling method. The key concept of this method is that the aged cathode materials are chemically and/or thermally re functionalized, and we have previously reported that the properties of the aged cathode materials, including level of lithiation,1 SEI layer,2 and surface reconstruction layer,3 can have an effect on the direct-recycled cathode materials.
As such, in this work, we characterized the aging level, in terms of chemical, physical and electrochemical properties, of cathode materials (NCA) harvested from 18650 cells after long-term cycling under different conditions. Specifically, different charge protocols and testing temperatures were used. Different failure mechanisms and rates capacity loss were observed, which we document and explain using a phenomenological model
Additionally, we observed significant area-specific inhomogeneities in the cycled electrodes; certain patterned regions of were found to have different degrees of SEI formation as well as different degrees of lithiation. The potential mechanism behind this phenomenon will be discussed.
Reference:

Wang, Han, and Jay F. Whitacre. "Direct Recycling of Aged LiMn2O4 Cathode Materials used in Aqueous Lithium‐ion Batteries: Processes and Sensitivities." Energy Technology.

Xiong, Xunhui, et al. "Washing effects on electrochemical performance and storage characteristics of LiNi8Co0.1Mn0.1O2 as cathode material for lithium-ion batteries." Journal of Power Sources 222 (2013): 318-325.

Jung, Sung‐Kyun, et al. "Understanding the degradation mechanisms of LiNi5Co0.2Mn0.3O2 cathode material in lithium ion batteries." Advanced Energy Materials4.1 (2014): 1300787.

Figure 1
A Solvent-Free Approach to Lithium-Ion Battery Electrodes Using Melt-Processable Elastomeric Binders
Authors: El Khakani Soumia , Verdier Nina , Rynne Olivier , Ciszewski Dorian , Lepage David , Prébé Arnaud , Ayme-Perrot David , Badia Antonella , Dollé Mickael , Rochefort Dominic 
Published: February 2020

Lithium-ion is currently the leading technology for electrochemical energy storage, especially in the transportation sector. The electrification of vehicles through the use of lithium-ion batteries (LiBs) is at the center of the world efforts to decrease atmospheric pollution by reducing CO2 emission. Due to the high efficiency of electrical motors, a net reduction in greenhouse gases is achieved upon electrification of vehicles even in areas where electricity is generated from fossil fuels. Yet, the rapidly growing production of LiB brings new concerns on the environmental cost of the technology. The analysis of a complete their life cycle, from mining precursors to recycling batteries at the end of their life, reveals that several steps of the cycle can be improved to further reduce the environmental footprint of lithium-ion batteries. It is in this context that our group got interested in developing alternative approached to electrode fabrication, a key aspect of LiB manufacturing. Currently, most of the electrode fabrication processes involves the use of organic solvents, typically N-methyl-2-pyrrolidone (or NMP), which is toxic and costly. As such, a considerable effort is spent during electrode fabrication to recuperate NMP vapors and prevent exposure to the workers and environment. Avoiding the use of any solvents during electrode fabrication would not only minimize the environmental impact but would also result into lower energy consumption.
This contribution presents a study of a new solvent-free melt process technique to LiB electrode fabrication through the use of elastomeric binders. The impact of formulation on active material dispersion, microscopic morphology, electronic percolation and porosity will be discussed. With such parameters optimized, the electrochemical response of composite electrodes based on LiFePO4 and Li4Ti5O12 active materials were characterized both individually and as full cells. The battery performance will be compared with PVDF-based electrodes made with a conventional approach.