bluuebunny/crossref_metadata_2025 huggingface dataset:
Water-Activated Graphite Felt As a High-Performance Electrode for Vanadium Redox Flow Batteries
Authors: Wang Chen-Hao , Kabtamu Daniel Manaye , Chen Jian-Yu , Chang Yu-Chung
Published: February 2020

A simple, green, novel, time-efficient, and potentially cost-effective water activation method was employed to enhance the electrochemical activity of graphite felt (GF) electrodes for vanadium redox flow batteries (VRFBs). The GF electrode prepared with a water vapor injection time of 5 min at 700 °C exhibits the highest electrochemical activity for the VO2+/VO2
+ couple among all the tested electrodes. This is attributed to the small, controlled amount of water vapor that was introduced producing high contents of oxygen-containing functional groups, such as –OH groups, on the surface of the GF fibers, which are known to be electrochemically active sites for vanadium redox reactions. Charge–discharge tests further confirm that only 5 min of GF water activation is required to improve the efficiency of the VRFB cell. The average coulombic efficiency, voltage efficiency, and energy efficiency are 95.06%, 87.42%, and 83.10%, respectively, at a current density of 50 mA cm−2. These voltage and energy efficiencies are determined to be considerably higher than those of VRFB cells assembled using heat-treated GF electrodes without water activation and pristine GF electrodes.

Figure 1
Fluid Transport Properties from 3D Tomographic Images of Electrospun Carbon Electrodes for Flow Batteries
Authors: Kok Matthew D. R. , Gostick Jeff T. , Shearing Paul R. , Jervis Rhodri
Published: February 2020

The flow battery remains a cost challenged technology, significant effort has been made into improving performance by way of advanced redox couples, different chemistries, and different electrode materials.[1] One aspect of flow cell performance that has remained relatively overlooked is the effect of different transport properties in the electrode itself. The structure and morphology of the porous media plays an essential role in the electrolyte dispersion and the access the fibers have to the active species.

Custom made porous media was electrospun in house and carbonized for use in as a flow battery electrode. 3D tomography images were taken of both the carbonized and ‘as-spun’ polyacrylonitrile (PAN) mats at a variety of different spinning conditions. Lattice-Boltzmann simulations were performed on the tomographic images to determine the flow distribution through the material as well as the permeability of the electrospun mats. The findings were consistent with previous experimentally measured permeabilities of electrospun PAN materials.[2] 

While the results indicated permeabilities that would be acceptable or even beneficial for a flow battery, the modelling and analysis showed that material inconsistencies in the fibrous mat led to a large variability in local material and transport properties that could have a very negative effect on flow battery performance. There was a small variation in local fiber sizes and a much more significant variation in material porosity. Because these variations only existed in one axis, specifically through the thickness of the material, we were able to determine that the cause must be changing electrospinning conditions as the material was deposited.  

The findings of this study are being used to develop more optimized flow battery electrodes from electrospun materials. While there is tradeoff in terms of ease of production when utilizing electrospun electrodes versus traditional graphite fibrous electrodes, electrospun materials allow for a greater degree of control of fiber size and general morphology allowing the optimization of permeability, surface area as well as mass transfer properties. 

The attached figure demonstrates the detail and the accuracy generated through the Lattice-Boltzmann simulations. The fibers and streamlines shown are actual electrospun carbonized PAN with fibers that have a diameter of approximately 750 nm. 

[1]A. Z. Weber, M. M. Mench, J. P. Meyers, P. N. Ross, J. T. Gostick, and Q. Liu, “Redox flow batteries: a review,” J. Appl. Electrochem., vol. 41, no. 10, pp. 1137–1164, Sep. 2011.

[2]M. D. R. Kok and J. T. Gostick, “Transport properties of electrospun fibrous membranes with controlled anisotropy,” J. Membr. Sci., vol. 473, pp. 237–244, Jan. 2015. 

Figure 1
From the Junkyard to the Power Grid: Ambient Processing of Scrap Metals into Nanostructured Electrodes for Ultrafast Rechargeable Batteries
Authors: Westover Andrew S , Muralidharan Nitin , Sun Haotian , Galioto Nicholas , Carter Rachel E. , Cohn Adam P , Oakes Landon , Pint Cary L.
Published: February 2020

Here we present the first full-cell battery device that is developed entirely from scrap metals of brass and steel – two of the most commonly used and discarded metals. A room temperature chemical process is developed to convert brass and steel into functional electrodes for rechargeable energy storage that transforms these multicomponent alloys into redox-active iron-oxide and copper-oxide materials. The resulting steel-brass battery exhibits cell voltages up to 1.8 V, energy density up to 20 Wh/kg, power density up to 20 kW/kg, and stable cycling over 5000 cycles in alkaline electrolytes. Further, we show the versatility of this technique to enable processing of steel and brass materials of different shapes, sizes, and purity, such as screws and shavings, to produce functional battery components. The simplicity of this approach, building from commonly available chemicals enables a simple pathway to the local recovery, processing, and assembly of storage systems based on materials that would otherwise be discarded.
Cross-Conjugated Oligomer Based Organic Batteries for Energy Storage
Authors: Jing Yan , Liang Yanliang , Gheytani Saman , Yao Yan
Published: February 2020

As one class of the most promising organic electrode materials, quinone derivatives have received more and more attentions from energy storage community due to structural diversity and electrochemical reversibility.[1] However, the limited rate capability arising from their electronically insulating nature remains challenging for the use of quinones in rechargeable batteries.[2] Molecular structure and conformation can significantly affect the electronic conductivity of organic compounds. In this work, we report two heteroaromatic-fused quinone oligomers with extended cross-conjugation paths but different conformation. Using benzo[1,2-b:4,5-b']dithiophene-4,8-dione (BDTD) as the building block, cross-conjugated PBDTD (poly(benzo[1,2-b:4,5-b']dithiophene-4,8-dione-2,6-diyl)) with a rigid and planar conformation was constructed. To further investigate the influence of conformation on electrochemical property, we introduced C-S-C single bonds between BDTD units to obtain PBDTDS (poly(benzo[1,2-b:4,5-b']dithiophene-4,8-dione-2,6-diyl sulfide)), which show a helical conformation. The electrochemcial properties of PBDTD(S) are evaluated in lithium cells. Both oligomers demonstrate over 200 mAh g–1 and 2.5 V vs. Li/Li+ at C/10. PBDTD(S) also show over 96% of capacity retention after 250 cycles as well as ~100% of Coulombic efficiencies. Finally we found PBDTD possesses superior rate capability over PBDTDS (as shown in Figure 1). In contrast to the helical structure of PBDTDS, the planar conformation of PBDTD provides more efficient electron transport paths in both inter- and intra-molecular directions, leading to the superior rate capability.

Reference

[1] B. Häupler, A. Wild, U. S. Schubert, Adv. Energy Mater.
2015, 5, 1402034.

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

Figure 1
A High Energy-Density, Low-Cost Hybrid Organic Flow Battery
Authors: Zhang Cheng , Zhao Tianshou , Chen Qing
Published: February 2020

In this work, a novel hybrid flow battery system is proposed. In the negative side, we explore a vitamin-based molecule that has never been tested in a flow battery before. As a quinone derivative, it undergoes a reversible two-electron redox reaction at 0.05 V vs. standard hydrogen electrode. The solubility of the molecule is higher than 4.5 M, leading to a volumetric energy density of 120 Wh/L, when paired with a lead dioxide/lead sulfate electrode [1]. Such a hybrid flow battery achieves a cell voltage of 1.68 V and can be cycled stably for over 50 cycles without significant capacity loss. The adoption of solid-state lead-based electrode eliminates the need of an expensive ion exchange membrane. More importantly, as the molecule has been mass-produced at low cost, the cost of this novel system is much lower than current existing flow battery systems [2-3]. It is a promising candidate for both large scale energy storage usages and mobile applications in both perspectives of cost and energy density.

[1] Leung, P. K., Qian Xu, and T. S. Zhao. "High-potential zinc–lead dioxide rechargeable cells." Electrochimica Acta 79 (2012): 117-125.

[2] Zhang, Mengqi, et al. "Capital cost sensitivity analysis of an all-vanadium redox-flow battery." Journal of The Electrochemical Society 159.8 (2012): A1183-A1188.

[3] Zeng, Y. K., et al. "A comparative study of all-vanadium and iron-chromium redox flow batteries for large-scale energy storage." Journal of Power Sources 300 (2015): 438-443.
High-Performance Flow-Field Structured Iron-Chromium Redox Flow Batteries for Large-Scale Energy Storage
Authors: Zeng Yikai , Zhou Xuelong , Jiang Haoran , Ren Yuxun , Zhao Tianshou
Published: February 2020

The conventional flow-through structured ICRFBs have to employ thick carbon felts (typically 3.0-6.0 mm) as the electrodes to circumvent high pump loss, which inevitably results in high ohmic resistance, low operating current densities (around 80 mA cm-2) as well as cumbersome and costly cell stacks. Increasing the operating current density/power density is an effective strategy to reduce the cell stack size and cost. Recently, a flow-field structured ICRFB with thin carbon paper electrodes demonstrates a significantly increased operating current density of 200 mA cm-2 at the energy efficiency of 79.6% mainly due to the reduced ohmic resistance [1]. Further enhancement of ICRFB performance is achieved by adopting the interdigitated flow fields, which enhances the active species transport at the porous electrode and enables a more uniform catalyst distribution [2]. In addition, the effects of design parameters including electrode compression ratio, electrode pretreatment intensity, membrane thickness and catalyst loading on the ICRFB charge-discharge performance have been are investigated [3]. Results show that: i) with a thin NR-211 membrane and a high electrode compression ratio of 62.5%, the operating current density of the ICRFB can reach as high as 480 mA cm-2 at an energy efficiency of higher than 80%; ii) the bismuth catalyst loading has insignificant effect on the battery performance in the range of 0.52-10.45 mg cm-2; iii) the moderately oxidative thermal pretreatment of the electrode improves the energy efficiency compared to the as-received electrode while the electrode prepared with a harsh pretreatment deteriorates the battery performance; and iv) for the present ICRFBs operating at both 25oC and 65oC, the dominant loss is identified to be ohmic loss rather than kinetics loss.

References

[1] Y.K. Zeng, X.L. Zhou, L. An, L. Wei, T.S. Zhao, A high-performance flow-field structured iron-chromium redox flow battery, J. Power Sources, 324 (2016) 738-744.

[2] Y.K. Zeng, X.L. Zhou, L. Zeng, X.H. Yan, T.S. Zhao, Performance enhancement of iron-chromium redox flow batteries by employing interdigitated flow fields, J. Power Sources, 327 (2016) 258-264.

[3] Y. Zeng, T. Zhao, X. Zhou, L. Zeng, L. Wei, The effects of design parameters on the charge-discharge performance of iron-chromium redox flow batteries, Appl. Energy, 182 (2016) 204-209.
A Stable Aqueous Zinc-Ion Battery with High Energy Density
Authors: Li Bin , Pan Huilin , Nie Zimin , Li Guosheng , Liu Jun , Sprenkle Vincent
Published: February 2020

Electrical energy storage systems have attracted much more attentions as the ideal technology to overcome the drawbacks associated with the storage and use of intermittent renewable energies, such as solar and wind. These systems are not only able to provide energy where and when it is required but also reduce the high capital cost of managing peak demands on the grid as well as large investments in grid infrastructures. Cost, reliability and safety are the most important factors to be considered to develop these systems. Recently, several battery technologies, such as redox flow, sodium sulfur, or lithium ion, have been proposed as possible systems for large-scale stationary energy storage, but they suffer from low charging rates, high operating temperatures, the use of hazardous or flammable materials in their components, and/or high costs. In particular, for traditional Li ion battery, the high cost and poor safety owing to the use of Li and flammable non-aqueous electrolytes limits its application in the field of grid scale energy storage. Therefore, recently, in place of Li ion battery, aqueous rechargeable battery, like zinc ion battery, has become more attractive because of its low cost and high safety. However, the disadvantages, such as the low energy density and poor cycling stability, seem to be the biggest issues to be addressed.

Here, we introduced a kind of cathode material and demonstrated a new zinc-ion battery systems with zinc foil as anode materials. For this system, the open circuit voltage (OCV) was around 1.5 V and the energy density could achieve as high as around 170 mAh/g at 0.5C. Also, no zinc dendrites were found at the anode side, and the coulomb efficiency (CE) was almost close to 100%. No significant capacity fading was observed over 1000 cycles at 5C. The different water-soluble zinc salts were applied to this system, which greatly affected the battery performances. The mechanisms behind that were investigated in detail.
Predicting the Electrochemical Stability of Core-Shell Catalysts from First Principles
Authors: Weitzner Stephen Eric , Dabo Ismaila
Published: February 2020

The rational design of heterogenous electrocatalysts requires a detailed understanding of the physicochemical properties of catalytic surfaces under applied voltage and in contact with a liquid electrolyte. Significant progress has been made recently in part to refined synthetic approaches that provide an unprecedented level of control over the surface chemistry of catalytic electrodes. One such strategy involves the underpotential deposition of a sacrificial component such as copper followed by a surface limited redox replacement reaction with a nobler component such as platinum. These approaches have enabled the design of cost effective core-shell nanostructures with ultrathin films that often exhibit higher performance and higher durability compared to traditional elemental electrocatalysts. Nevertheless, the efficacy of these electrocatalysts for particular reactions can only be determined after performing detailed experimental studies aimed at measuring the activity, selectivity, and durability of the catalyst under a wide range of experimental conditions. In principle, this process can be accelerated by performing virtual experiments on a computer that can reveal the thermodynamic properties of catalytic electrodes in electrochemical environments. The latter relies heavily on the development of predictive models that are capable of describing the complex nature of the electrode-solution interface in an efficient and effective manner. Recently, we have reported a first principles model of electrodeposition phenomena [Weitzner, S. E. and Dabo, I. npj Computational Materials, in press] that incorporates a polarizable continuum dielectric region and a model ionic countercharge to efficiently describe the liquid electrolyte within density-functional calculations of the interface. Electrification of the quantum–continuum interface enables a direct assessment of the stability of electrodeposited species in electrochemical environments. In this talk, we present recent progress on the modeling of underpotential deposition phenomena and surface limited redox replacement reactions under realistic environmental conditions. We additionally discuss the performance of the interfacial model in describing the stability of bimetallic and trimetallic core-shell nanoparticles for catalysis applications.
Multiscale Modeling of Non-Local Damage Evolution in Lithium-Ion Batteries
Authors: Behrou Reza , Maute Kurt
Published: February 2020

We present a multi-scale finite element model to study the evolution of non-local damage in the electrode active materials. The electrochemical and mechanical phenomena in the separator, porous electrode with solid active materials and liquid electrolyte are described through a multi-scale modeling approach. Our multi-scale model accounts for the interactions between different physical phenomena at different computational scales. Three different length scales are distinguished in our multi-scale model: at the macro-scale, the electrochemical and mechanical interactions of the entire battery cell are characterized through the transport of Li+, the electric potential in the solid and liquid phases, and macroscopic mechanical deformation; at the micro-scale, the performance of a single representative active particle is modeled through the concentration of lithium in the electrode active particles, microscopic mechanical deformation, and hydrostatic stress; and at the meso-scale, the homogenization methods are used to relate the interactions between macro- and micro-scales. The evolution of damage in the electrode active materials, caused by the diffusion induced stresses, is described by a non-local damage model that solves the Helmholtz-type differential equation. To trigger the influence of damage evolution on transport properties and the electrochemical performance of the battery, the diffusivity of the electrode is coupled with the damage evolution parameters. The influences of damage evolution on the electrochemical and mechanical performance of the battery are evaluated through numerical examples. Our preliminary results reveal the influence of particle shape and discharge rate on the damage evolution and electrochemical and mechanical performance of the battery. The results also show that there is a significant influences of the damage evolution on capacity fade and reduction in the electrochemical-mechanical performance of the battery.

Figure 1: The influences of damage evolution and electrode shape on capacity fade and the electrochemical performance of the battery.

Figure 1
(Invited) Opportunities for Additive Manufacturing of Membraneless Electrolysis Devices
Authors: Davis Jonathan T , Esposito Daniel V
Published: February 2020

3D printing technology has a tremendous potential to transform how electrochemical devices and products are manufactured. This opportunity is particularly rich for water electrolysis devices, or electrolyzers, which are used to produce hydrogen (H2) fuel from water and electricity. In this work, we explore how 3D printing can simplify the fabrication of low-cost electrolysis devices by significantly reducing the number of parts and associated device assembly. These efforts are focused on membraneless electrolyzers based on angled mesh flow-through electrodes, which are a substantial departure from conventional membrane-electrode assembly (MEA) and alkaline electrolyzer architectures. Membranes and dividers can be costly, prone to fouling and mechanical failure, and constrain the pH range of operation. Recently, our group has demonstrated 3D printed membraneless electrolyzers that separate the O2 and H2 product species using flowing electrolyte and contain as few as three parts. [1] In this presentation, we present new 3D printed electrolyzer and photovoltaic (PV)-electrolyzer designs that achieve high product purity using buoyancy-induced product separation that obviates the need for actively pumped electrolyte. As a part of this talk, we highlight challenges and opportunities for commercially viable 3D printed membraneless electrolyzers.

[1] O’Neil G. D., Christian C. D., Brown D. E. and Esposito D. V. 2016 Hydrogen Production with a Simple and Scalable Membraneless Electrolyzer J. Electrochem. Soc.
163 3012–9
Fluidic Force Microscope for Electrochemical Additive Manifacturing of Metal Microstructures
Authors: Zambelli Tomaso , Hirt Luca , Vörös János
Published: February 2020

FluidFM is a force-controlled nanopipette [1], combining AFM technology and microfluidics. A fluidic channel is incorporated directly in a hollow AFM cantilever. This channel ends in a nanosized aperture at the apex of the AFM pyramidal tip, allowing for local dispensing of soluble molecules in air and in liquid, while retaining the inherent imaging capabilities and force feedback of an AFM system.

Recently, we have achieved 2D electrochemical patterning with sub-micron precision by reduction of copper as well as diazonium salts filled in the microchannel with subsequent in-situ AFM imaging [2]. Furthermore, we recognized that this method offered an access to the 3rd dimension.

Micro- and nanometer-scale patterning of functional materials is of great interest in various fields such as microelectronics or micro-electromechanical systems (MEMS) design [3], but also for biosensing and biomedical applications, where manipulation techniques often have to be suitable for use in a liquid environment. In this context, we currently explore the use of FluidFM as a tool for both fabrication and subsequent imaging of microstructures in liquid using the same probe.

Indeed, we succeeded in using the system in the same configuration for 3D additive manufacturing of copper on the micrometer scale [4]. In the proposed protocol, we take advantage of the FluidFM probes as a local source of Cu2+ in a macro electrochemical cell. The nanopipette is approached to the working electrode and metal ions are provided by inducing a liquid flow. Thus, metal can be reduced locally under the FluidFM probe. Conveniently, the inherent force sensing capability of the cantilever provides a means to automate this process: Whenever the growing metal deposit touches the cantilever, the cantilever bends, and its deflection is registered so that the probe may be positioned to the next place, where the process continues. Therefore, our protocol enables true voxel-by-voxel (i.e. layer-by-layer) printing with consequent almost complete geometry freedom (see the three interwined helixes).

Upon introducing the microprinting protocol with copper, we discuss our current efforts to adapt it to other metals.

[1] A. Meister et al. (T. Zambelli), Nano Lett.
2009
9:2501

[2] L. Hirt et al. (T. Zambelli), RSC Adv.
2015
5:84517

[3] L. Hirt et al. (T. Zambelli), Adv. Mater.
2016
DOI: 10.1002/adma201604211

[4] L. Hirt et al. (T. Zambelli), Adv. Mater.
2016
28:2311

Figure 1
(Invited) Study on Electro-Polishing of Nb Surface By Periodic Reverse Current Method with Sodium Hydroxide Solution for Particle Accelerator Application
Authors: Saeki Takayuki , Hayano Hitoshi , Taguchi Junji , Reece Charlie E , Tian Hui
Published: February 2020

Superconducting Radio-Frequency (SRF) cavities are used to accelerate particles in particle accelerators. In this application, the cavity is made of niobium (Nb) material and the inner surface of cavity should be polished so as to obtain the high performance of particle accelerator. The Electro-Polishing (EP) process is one of the best methods to polish the inner-surface of Nb cavity where the electrolyte is the mixture of sulfuric and hydrofluoric acids. However, this EP electrolyte is very dangerous in the operation and thus the operators need rigorous protection. Furthermore, all parts of instrument for the EP process must be made of high density polyethylene or fluorocarbon resin because the corrosion of metal occurs by hydrofluoric acid. These are the reasons why the cost of EP process becomes very expensive. In addition, the EP process produces sulfur compound on the Nb surface as a by-product. This sulfur compound can be the sources of field-emission on the inner surface of cavity and degrades the accelerating performance. In this article, we report a novel EP method using periodic reverse current and sodium hydroxide solution. The reaction produces no sulfur content and the instrument is less expensive because it is made of usual plastic material. As the result of experiments with Nb-coupon samples, we found that the surface roughness is equivalent to the conventional EP method. And some experiments with a Nb single-cell cavity will be reported.
(Invited) Chiroplasmonic and Chiroexcitonic Assemblies of Nanoparticles
Authors: Kotov Nicholas , Feng Wenchun
Published: February 2020

Chiral inorganic nanostructures discovered over the last two decades include individual nanoparticles (NPs), their assemblies in dispersions and surfaces, as well as 2D/3D lithographic patterns. For many of them exceptionally strong polarization rotation was observed. In this talk, I will address, the (1) origin of enhanced polarization rotation; (2) methods of enantioselective assembly of nanostructures; and (3) their fundamental relevance to life homochirality on Earth, Special effort will be placed on the translation of enhanced chiroptical properties of plasmonic and excitonic NPs to applications. It will be exemplified by the bioanalytical applications for detection of DNA oligomers using CD spectroscopy that enables 1-3 order of magnitude improvement of detection of protein, DNA oligomers, and small chiral molecules. Other technological applications in chiral catalysis and polarization-based optical devices. Should time permit, recent data on the preparation and properties of chiral graphene quantum dots and chiral ceramic nanoparticles relevant to the chiroplasmonc and chiroexcitonic technologies will be presented.

Figure 1
(Invited) Scalable Nanostructure Integration for Multi-Mode Chemical Sensing
Authors: Gao Pu-Xian
Published: February 2020

Using a combination of vapor and solution phase deposition methods, scalable heterostrutured nanowire arrays have been successfully fabricated composed of metal oxide nanowire cores ~100-300 nm in diameter, ~1-30 nm thick shells of perovskite, metal oxide and noble metal nanoparticles on ceramic substrates. The nanowire structure features tuned composition, density, geometry, and dimensions through varying the deposition temperature, concentration, pH, substrate temperature, time, etc.. Multi-mode chemical sensing platform has been achieved at both room temperature and elevated temperature to include photocurrent, electrical resistance and electrochemical impedance modes. Depending on the selections of comprising materials, dimensions and post-treatment processes, trace amount decoration of perovskite, metal oxide and noble metal nanoparticle shells may enable formations of catalytic filters, sensitizers and hetero-junctions that can drastically enhance nanosensor performance in both oxidative and reductive gas atmospheres. Specifically the materials-synergy effect in metal oxide/perovskite, and metal oxide/noble metal nanowire array sensors are discussed toward sensing of various gaseous species such as O2, CO, HCs, SOx, and NOx. Toward mixture gas conditions, this new type of multi-mode nanowire array sensors allows selective and sensitive detection of multiple chemical species in a single-device platform.
(Invited) Dynamic Bandgap Engineering in 2D Materials for Beyond Boltzmann Devices
Authors: Das Saptarshi
Published: February 2020

In this talk I will discuss a disruptive device concept based on dynamic bandgap engineering in two dimensional layered seminconductors in order to achieve sub-60mV/decade subthrshold swing [1]. 
This device is refer to as two-dimensional electrostrictive field effect transistor or 2D-EFET and it works on the principle of voltage induced stress transduction. It uses an electrostrictive material as gate insulator which expands when a gate bias is applied and thereby transduces an out-of-plane stress on the 2D semiconducting channel. The stress decreases the inter-layer distance between the consecutive layers of the 2D material and dynamically reduces its bandgap. Thus the device operates with a large bandgap in the OFF state and a small or zero bandgap in the ON state. As a consequence of this transduction mechanism, internal voltage amplification takes place which results in sub-60mV/decade subthreshold swing (SS). 

1. Das, S. "Two Dimensional Electrostrictive Field Effect Transistor (2D-EFET): A sub-60mV/decade Steep Slope Device with High ON current", Scientific Reports 2016,
6 (34811).
Mechanisms of Hysteresis Generation in Multi-Layered MoS2 Field Effect Transistor
Authors: Kim Juhyung , Seo Byungchan , Lee Sanghyun , Jeong Seokwon , Roh Yonghan
Published: February 2020

Recently, two-dimensional transition metal dichalcogenides (2D TMDs) with layered structure have attracted much attention due to their unique electrical and optical properties. In particular, they exhibit a great potential for realizing the field effect transistors (FETs) which can apply for low power applications. Among them, molybdenum based 2D TMD (i.e., MoS2) is one of the most studied compounds. However, FETs with multi-layered MoS2 employed as a semiconductor layer must tackle many practical problems. For example, it has been speculated that either adsorbed molecules (e.g., water molecule) on the top of exposed MoS2 channel layer or traps at the MoS2-insulator interface causes the device instability such as the hysteresis generation in MoS2 FETs. Until now, research on the hysteresis phenomenon of FETs with multi-layered MoS2 has been focused on finding the origin of the hysteresis. However, the underlying mechanism(s) for this phenomenon has not yet been clearly clarified. Although recent several studies have suggested that the charge trapping and de-trapping processes at the MoS2-insulator interface cause the device instabilities including hysteresis, it is not sufficient to explain the origin of traps giving rise to the hysteresis phenomenon of the MoS2 FETs. In this work, we analyzed the hysteresis characteristics of the MoS2 capacitors, using high frequency capacitance-voltage (C-V) measurements. Based on this analysis, we will demonstrate the roles of the interface traps originated from sulfur vacancy defects on the hysteresis generation in MoS2 FETs. Based on these experimental results, we will propose a model to explain the hysteresis phenomenon observed in multi-layered MoS2 FETs.
Reversing the Properties of 2D Black Phosphorus through Water Rinsing
Authors: Kim Suhyun
Published: February 2020

Two-dimensional (2D) materials have gained a significant attention due to their unique properties. Among various 2D materials, black phosphorus is known for its excellent electrical and optical properties. Not only does its mobility can reach as high as 1000 cm2/V·s, the on/off current ratio has the maximum value of 105
. BP is also remarkable in the fact that it has direct bandgap regardless of number of layers and the bandgap can be controlled from 0.3 eV in bulk to 2.0 eV in monolayer BP. Despite all these advantageous properties, the instability of BP under air condition is critical in studying BP and applying to various fields. It has been already revealed by previous researches that BP readily degrades through oxidation process of phosphorus atoms reacting with oxygen chemisorbed on the surface. Once oxygen molecules chemisorb, BP surface becomes hydrophilic and water molecules physisorb, forming large bubble on the surface. These bubbles on thin BP flake are initially small and great in number, however, they coalesce as the exposure time in air condition increases and eventually become one large bubble, which can be even thicker than 500 nm, covering the whole surface. This bubble is the result of reaction between phosphorus and water molecules and it was found out that phosphoric acids are the product components of the reaction. This fact has been confirmed once more when the bubble was successfully rinsed with deionized (DI) water; phosphoric acid is known to be very soluble in water. Thus the bubble is very likely to be consisted of phosphoric acid components dissolved in water. We have investigated the effect of DI rinsing and employed this method plus further treatments to recover the pristine surface of BP. After intentionally causing degradation on the surface using UV lamp, the samples were immersed in DI water and annealed under vacuum condition. Field effect transistors were also fabricated using BP as the channel material in order to analyze the change in electrical properties using semiconductor parameter analyzer. In addition, the morphology and optical properties were observed using atomic force microscopy and Raman spectroscopy, respectively. In conclusion, the pristine properties could be obtained even after degradation that is rather inevitable during characterizations and fabrication processes, meaning BP-based devices with higher performance can still be fabricated without strictly controlled vacuum system. Further results and discussion will be presented in detail.
Slurry-Processed Glass-Ceramic LI2S-P2S5-LiI Electrolyte for All-Solid-State Li-Ion Batteries
Authors: Choi Seon-joo , Lee Sang-hun , Yu Ji-hyun , Doh Chil-Hoon , Ha Yoon-Cheol
Published: February 2020

Lithium-ion batteries (LIBs) have widely been used as power sources for from small electronic devices to large-scale systems such as electric and plug-in hybrid electric vehicles, mostly due to their high power and high energy density. However, the organic electrolyte in commercial LIBs has evoked safety issues, making all-solid-state LIBs with inorganic solid electrolyte an alternative of conventional organic electrolyte batteries. Solid electrolytes are not only safer and more reliable than liquid electrolytes in thermochemical point of view but also more compatible with Li metal anode and high voltage cathode materials. Among solid electrolytes, sulfide-based electrolytes have received great attention because of their high lithium ion conductivities of 10-4 to 10-2 S cm-1 at room temperature, comparable to organic electrolytes. In most studies, however, the solid electrolytes were pressed into a pellet under extremely high pressure to increase the ionic conductivity by minimizing the void and interface between electrolyte particles. This method is not suitable for the practical cell fabrication considering the scale-up manufacture. Moreover, although the electrochemical stability of sulfide-based solid electrolytes with cathode materials was improved by an interphase coating such as LiNbO3, the stability with the anode, especially with Li metal, has not been fully studied yet, mostly reporting a short-term stability evaluated by cyclic voltammetry. In this study, we evaluate long-term electrochemical stabilities of sulfide-based solid electrolytes, LGPS (Li10GeP2S12), LPS (Li7P3S11), and LPSI (Li2S-P2S5-LiI glass-ceramic and Li7P2S8I) with respect to Li metal. Area specific interfacial resistances of the solid electrolytes were characterized by using a DC cycling method, i.e., a repeated long-term charge/discharge over 100 hours with the current density of 0.1 mA/cm2 and the duty cycle of 1 hour. Then, we demonstrate a slurry-processed all-solid-state cell with Li metal anode, LPSI glass-ceramic electrolyte, and a composite cathode, where a mixture of LiNbO3-coated LiNi0.6Mn0.2Co0.2O2, LPSI solid electrolyte, carbon black, and binder dissolved in an appropriate solvent was slurry-coated and, after drying and pressing, LPSI electrolyte slurry was coated on top of the cathode layer. The cell performances of the slurry-processed all solid-state LIB cells are evaluated in comparison with pellet-type cells.
Stabilizing High-Voltage Cathode-Electrolyte Interface Using High-Voltage Additive
Authors: Pham Hieu Quang , Kwon Young-Gil , Hwang Eui-Hyung , Lee Jung-Gyu , Song Seung-Wan
Published: February 2020

Enabling the high energy density Li-ion batteries requires the use of high-capacity cathode material such as Li-rich layered oxide cathode (xLi2MnO3·(1-x)LiMO2 (M=Mn,Ni,Co)) that can be charged to high-voltage above 4.4 V vs. Li/Li+. The development of new electrolyte components with high anodic stability above 4.4 V vs. Li/Li+ is thus the necessity of high-voltage charging of Li-rich layered oxide cathode. Our recent research results have shown that the use of high-voltage electrolyte additives is effective in charging the Li-ion cell with Li-rich layered oxide cathode above 4.6 V vs. Li/Li+ and even at elevated temperatures, which enables high-energy density Li-ion cells. Systematic surface analyses of the cathodes revealed that the formation of surface protective film by the use of high-voltage additives led to interfacial stabilization of both cathode and anode and significantly improved cycling performance, compared to the case of conventional electrolyte. In this presentation, we report the stabilization of high-voltage interface of Li-rich layered oxide cathode under a harsh condition of high charge cut-off voltage above 4.6 V vs. Li/Li+ using fluorinated carbonates as high-voltage electrolyte additives. The results of mechanistic studies of high-voltage surface film formation and composition, and interfacial stability of Li-rich layered oxide cathode using surface sensitive spectroscopy combined with electrochemical impedance spectroscopy would be discussed.

Acknowledgements: This research was supported by the Korean Ministry of Trade, Industry & Energy (R0004645) and Chungnam National University.
(Invited) Ion-Transport in Polymer-in-Ceramic Electrolytes
Authors: Golodnitsky Diana , Blanga Raymond , Berman Marc Brian , Biton Moshiel , Tariq Farid , Yufit Vladimir , Brandon Nigel P. , Greenbaum Steven
Published: February 2020

Solid electrolytes could revolutionize battery and supercapacitor technology because of their nontoxicity, stability during operation and enhanced safety. The major limitation of solid electrolytes is their low ionic conductivity at room temperature, and intricate ion transport complicated by grain-boundary phenomena. We have developed, and present here, novel polymer-in-ceramic composite electrolytes with high ion-conduction properties, prepared by electrophoretic deposition. Nanoparticles of LiAlO2, Li10SnP2S12, and some ion-conducting glasses were used as ceramic matrices. Polyethyleneimine (PEI) and polyethylene oxide (PEO) were tested as binders and lithium-ion-conducting media. Our recently developed simplified Poisson-Boltzmann model reveals that the adsorption of PEI on the surface of ceramic particles increases zeta potential, repulsion forces between the particles and their deposition rate. The electrophoretic deposition of PEO and nanoceramic powders occurs from the individual entities. We have succeeded in depositing films containing 5 to 40% PEO which are homogeneous in composition and uniform in thickness. XRD and DSC tests showed that the crystallinity of the polymer confined in the pores of ceramics, is suppressed. This was expected to improve the ionic conductivity of composite electrolytes saturated with LiI salt. However, on the basis of AC-impedance, NMR and high-resolution X-ray tomography data, we suggest that the high ionic conductivity (0.5mS/cm) at room temperature and low activation energy (2.3kJ/mole) are brought about by the grain-boundaries current path between the excess of LiI and ceramic nanoparticles, and not by the confined-in-ceramic polymer. The nanoarchitecturing of ordered, fast-ion-conduction paths and the elimination of perpendicular blocking grain boundaries is expected to reduce the effect of high-resistant grains.
Large Enhancement of Ionic Conductivity in Composite Polymer Electrolyte with Well-Aligned Ceramic Nanowires
Authors: Liu Wei , Cui Yi
Published: February 2020

Solid Li-ion electrolytes are considered as an alternative to replace conventional liquid electrolytes for next-generation high-energy and safe batteries. However, the low ionic conductivities of solid electrolytes limit their applications. Inorganic nanoparticles have been widely used to incorporate into host polymers to obtain solid composite polymer electrolytes with improved electrochemical performance and mechanical strength. Here for the first time, we demonstrated composite polymer electrolytes with well-aligned inorganic nanowires. The results show that random nanowires in composite polymer electrolyte introduce larger enhancement of ionic conductivity than nanoparticles. The most exciting result is that the ionic conductivity of composite polymer electrolyte with aligned nanowires is about 10 times higher than that with randomly dispersed nanowires. This is because that an aligned nanowire offers a continuous fast ion pathway without crossing junctions like those between nanoparticles or between random nanowires. The nanowire interfacial conductivity has an impressive liquid-like conductivity of 1.26×10-2 S cm-1 at 30 °C.
Solid Electrolytes for Thin Film Li-Ion Batteries with Novel Si and SiC Based Anodes
Authors: Mentbayeva Almagul , Kurmanbayeva Indira , Kulametov Zhalgas , Batyrbekuly Dauren , Umirov Nurzhan , Bakenov Zhumabay
Published: February 2020

Recent advances in microelectromechanical systems technology have led to development of diverse small-scale devices that include microsensors, micromachines and devices for medical application. For these devices, there is an urgent need of new micro lithium-ion batteries (MLIBs) with high energy density and low cost. To avoid the leakage problems which could worsen both the operation and safety of microdevices powered powered by MLIB the use of solid electrolyte is highly desirable.

In this work, ceramic solid state and polymer solid electrolytes were prepared and deposited on the surface of SiC thin film anode by various techniques: in situ polymerization, drop coating technique, electropolymerization, magnetron spattering etc.

Despite the advantages of high capacity and low voltage of Si anode, its practical application restricted by severe volume expansion and mechanical degradation upon lithium alloying and de-alloying processes. In this term flexible thin polymer electrolyte could be a promising solution. A combination of nanoparticulate and thin film structure can provide significant mechanical stability to Si and mitigate its limitations.

Physical properties of the obtained samples were characterized by Raman spectroscopy, X-ray diffraction, atomic force microscopy and scanning/transmission electron microscopy techniques. Further, assembling CR2032 coin type cell, the electrochemical properties of the cell with obtained samples were evaluated as a part of all solid-state thin film battery.

Acknowledgements

This research was funded by the target program №0115РК03029 "NU­ Berkeley strategic initiative in warm ­dense matter, advanced materials and energy sources for 2014­-2018" from the Ministry of Education and Science of the Republic of Kazakhstan.
(Invited) Overcoming Catalytic Material Challenges for Advanced Water Splitting Technologies
Authors: Peterson David , Miller Eric L. , Randolph Katie , Vickers James
Published: February 2020

The emergence of hydrogen and fuel cell technologies offers the world important and potentially transformative environmental and energy security benefits. In recent years, research sponsored by the US Department of Energy’s (DOE) Fuel Cell Technologies Office (FCTO) has made significant contributions to the development of these technologies. With major automotive manufacturers rolling out commercial fuel-cell electric vehicles, enabling technologies for the widespread production of affordable hydrogen are becoming increasingly important. FCTO’s Hydrogen Production Program supports a broad range of hydrogen production pathways using diverse feedstocks, ranging from nearer-term to longer term technologies. One of the more versatile pathways is based on splitting water via either electrolytic, photoelectrochemical, or thermochemical routes. For these advanced water splitting (AWS) technologies, there are tradeoffs amongst efficiency, durability, and cost at the materials, device, and system levels that need to be balanced for low cost hydrogen production. Recent advances have been made in catalytic materials for AWS to improve these attributes; however, further developments, from new materials to scale-up of state-of-the-art (SOA) materials, are required to reach large scale technoeconomic viability. Research innovations to advance the SOA in AWS materials are being facilitated by the DOE “HydroGEN” Energy Materials Network (EMN) consortium. An overview of FCTO’s Hydrogen Production Program activities with a focus on catalysts for advanced water splitting technologies and the HydroGEN consortium will be provided.
An Electrochemistry in Situ TEM Study on the Shape Evolution of Octahedral Pt-Ni Nanoparticles
Authors: Beermann Vera , Holtz Megan E , Muller David A. , Strasser Peter
Published: February 2020

In polymer electrolyte membrane fuel cell research, shaped nanoparticles have attracted much attention in the last years. For the cathode, octahedral PtNi nanoparticles show promise in their high oxygen reduction reaction (ORR) activities due to their extended availability of (111) facets. This group of materials has been studied extensively including methods like XPS, TEM, EDX and EELS to understand their growth and degradation1-4. However, nanoscale analysis of their degradation has not been observed in real time.

Here, we present a novel in situ TEM electrochemistry study in acidic media on octahedral Pt-Ni nanoparticles synthesized via a solvo-thermal route. With real time imaging we were able to track and observe changes in the catalyst structure and particle shape during different electrochemical treatments5. For each electrochemical treatment, various potential sequences were applied in the TEM cell. We were able to confirm strong corrosive consequences on the catalyst structure and particle shape of an uncontrolled high open circuit potential (~ 1.6 V vs. RHE) after controlled electrochemical cycling. Additionally the impact on the material of stepwise increase of the upper potential (≤ 1.4 V vs. RHE) during electrochemical cycling in comparison with equivalent chronoamperometric profile was studied, showing increased degradation rates when high potentials were held. Furthermore we were able to observe the dissolution of nickel catalyst particles, even with relatively cautious electrochemical treatment (0.0 – 1.0 V vs. RHE). While electrochemical cycling up to 1.2 V vs. RHE is not harmful to the octahedral particle shape, it was still possible to observe limitations of catalyst stability by motion on the catalyst support.

Our study allows us to gain deeper insight of the real time behavior and degradation of shaped PtNi electrocatalysts, and develop understanding of the parameters that will optimize the lifetime of the catalyst.

1. Arán-Ais, R. M.; Yu, Y.; Hovden, R.; Solla-Gullón, J.; Herrero, E.; Feliu, J. M.; Abruña, H. D. Journal of the American Chemical Society
2015,137, (47), 14992-14998.

2. Choi, S.-I.; Xie, S.; Shao, M.; Odell, J. H.; Lu, N.; Peng, H.-C.; Protsailo, L.; Guerrero, S.; Park, J.; Xia, X.; Wang, J.; Kim, M. J.; Xia, Y. Nano Letters
2013,13, (7), 3420-3425.

3. Gan, L.; Cui, C.; Heggen, M.; Dionigi, F.; Rudi, S.; Strasser, P. Science
2014,346, (6216), 1502-1506.

4. Beermann, V.; Gocyla, M.; Willinger, E.; Rudi, S.; Heggen, M.; Dunin-Borkowski, R. E.; Willinger, M.-G.; Strasser, P. Nano Letters
2016, 16, (3), 1719-1725.

5. Holtz, M. E.; Yu, Y.; Gunceler, D.; Gao, J.; Sundararaman, R.; Schwarz, K. A.; Arias, T. A.; Abruña, H. D.; Muller, D. A. Nano Letters
2014, 14, (3), 1453-1459.