bluuebunny/crossref_metadata_2025 huggingface dataset:
Characterization of GaN Switches for Solar Invertors
Authors: Gachovska Tanya , Radimov Nikolay , Gerolami Chris , Orr Ray , Hudgins Jerry L , Shenai Krishna
Published: February 2020

To improve the coefficient of efficiency of a solar cell application two directions are necessary. The first one is to improve the quality of the solar panels and the second direction is to increase the inverter efficiency. The second one can be obtained by using high frequency switches with low on and switching losses. GaN has significantly bigger bandgap compared to Si and SiC materials, resulting in higher breaking voltage. Also the channel lengths of GaN MOSFETs are smaller and therefore having smaller gate to source and drain to source capacitance. In this work, different GaN switches are characterized through their steady state and switching characteristics. Also, using GaN switches in some Solantro Semiconductor Corp. applications and comparing the total power losses of Si and SiC switches are also presented.
Growth of Transition Metal Dichalcogenide Monolayers with Chemical Vapor Deposition
Authors: Li Lain-Jong
Published: February 2020

The direct-gap property of the semiconducting transition metal dichalcogenide monolayers are attractive for optoelectronics and energy harvesting. Here I would like to discuss the synthetic approach to obtain MoS2 (WSe2) monolayer directly on arbitrary substrates using vapor phase reaction between metal oxides and S or Se powders. These layer materials can be transferred to desired substrates, making them suitable building blocks for constructing multilayer stacking structures. The significance of charge movement in the emerging field of 2d heterostructures, and the charge distribution strongly affects the properties of the 2d heterostructures. The interaction between these layer materials are characterized by Raman, PL spectra and Second Harmonic Generation properties. Some possible applications based on these 2d heterostructures including photodetection and DNA detection shall be discussed.
Prolonged Hot Electron Dynamics in Plasmonic-Metal/Semiconductor (Au/TiO2) Heterostructures with Implications for Solar Photocatalysis
Authors: Wei Wei David
Published: February 2020

Ideal solar-to-fuel photocatalysts must effectively harvest sunlight to generate the significant quantities of long-lived charge carriers necessary for chemical reactions. Here we demonstrate the merits of augmenting traditional photoelectrochemical cells with plasmonic nanoparticles to satisfy these daunting photocatalytic requirements. Electrochemical techniques were employed to elucidate the mechanics of plasmon-mediated electron transfer in Au/TiO2 heterostructures in solution under visible-light (λ > 515 nm) irradiation. Significantly, we discovered that these transferred electrons displayed excited-state lifetimes two orders of magnitude longer than those of electrons photogenerated directly within TiO2 via UV excitation. These long-lived electrons further enable visible-light-driven H2 evolution from water, heralding a new photocatalytic paradigm for solar energy conversion.
Large-Area, Cost-Effective Nanoplasmonic Structures and Their Applications
Authors: Choi Dukhyun
Published: February 2020

Nanoscale functional material design and fabrication are essentially fundamental requirement for basic scientific researches and industrial applications of nano-science and engineering. Innovative, effective, reproducible, large-area uniform, tunable and robust nanostructure/material synthesis are still challenging. On the other hand, nanoscale controls of optical effects are a key element in advanced innovative nanophotonics and biophotonics, especially for biological and environmental molecular detection/imaging. Such optical modulation is also the critical technology in many optical devices such as a solar cell and a light-emitting diode (LED). However, optically tunable nanostructures/nanodevices have shown the big problem in the structural stability, thus resulting in a limited life-time under external loads, and moreover, if robust and tunable optical devices can be completed, the effort involved to precisely control the optical effects with structural strength and the reproducibility is so great that commercial-scale manufacture would never be cost-effective. Here, I would like to introduce the novel nanofabrications which rely on template-based nanolithography and present the surface plasmon (SP) which can effectively control the optical effects in nanostructures by simply modulating geometrical properties such as shape, size, and periodicity. Furthermore, in order to provide label-free and non-destructive molecular detection method, Raman scattering will be combined.

Plasmonic nanostructures with a localized surface plasmon resonance (LSPR), which is generated by the coupling of light to the collective oscillation of electrons on the nano-sized metallic surface, have generated considerable interest with the development of nanotechnology due to its ability to enhance the weak physical process such as the absorption of light. By adopting such a plasmonic nanostructure inside/onto/beneath a photoactive layer, a power conversion efficiency of solar cells could be improved because an electromagnetic (EM) field is greatly enhanced by plasmonic “hot spots”. Furthermore, optical biosensors such as surface-enhanced Raman scattering (SERS) could be designed with an ultrahigh sensitivity through a local field enhancement from the “hot spots”. A variety of optoelectronic devices and optical biosensors integrated with plasmonic nanostructures thus have been explosively studied and developed. In this study, we report large-area 3D plasmonic nanostructures though a high-throughput and cost-effective process. The surface morphology and optical properties are characterized by SEM and UV-vis. spectroscopy. Furthermore, their enhancement factor is evaluated by using SERS signals.
Growth of High-Quality Arbitrary-Shape Compound Semiconductors on Non-Epitaxial Substrates for Photovoltaic and Optoelectronic Device Applications
Authors: Kapadia Rehan
Published: February 2020

A method for direct growth of optoelectronic quality III-V semiconductors on non-epitaxial substrates will be discussed. Specifically, structures with geometries ranging from micro/nanostructures to ultra-large grain polycrystalline thin films may be grown via a phase transformation technique where the group III element is first deposited in the desired geometry and subsequently exposed to a vapor of the group V element. By careful control over nucleation and growth of the resulting III-V semiconductor, arbitrarily shaped III-V structures may be grown on non-epitaxial substrates. First, the general method for this growth will be discussed, showing how different structures and geometries may be obtained using InP as a model system. Next characterization of the InP films obtained will be presented, showing that films grown via this method on metal foils exhibit mobilities of ~500 cm^2/V-s, minority carrier lifetimes of >2 ns, and radiative efficiencies comparable to single crystal InP wafers. Additionally, methods for control over nucleation are demonstrated, showing that single crystalline structures >100 um in diameter may be easily obtained and, with proper tuning, mm scale crystals may be grown on non-epitaxial substrates. Furthermore, the use of this nucleation and growth control will be used to demonstrate InP for electronic and optoelectronic applications.
Atomic Scale and Interface Interactions in Redox-Based Resistive Switching Memories
Authors: Valov Ilia , Tappertzhofen Stefan , Linn Eike , Menzel Stephan , van den Hurk Jan , Waser Rainer
Published: February 2020

Controlling electrochemical processes at interfaces or within thin films at the atomic scale is a key factor for further development of future nanoelectronics and information technology. This aspect becomes even more important considering concepts beyond conventional data storage like neuromorphic and memristive systems, demonstrating learning abilities and allowing logic operations.

Redox-based resistive switching memories (ReRAM) are major candidates to fulfil all requirements for low power consumption, ultrafast operation, high information density and non-volatility. Their metal/solid-electrolyte/metal structure makes the preparation process simple and compatible with current CMOS technology. In ReRAMs, the solid electrolyte thickness varies in the range between few nanometers up to some ten nanometers. Due to the small dimensions, the high electric fields in the order of E ~ 108 Vm–
1, and current densities of j ~ 109 Acm–
2, the interface regions are dynamically changing as a function of the thermodynamic and operation conditions. Deposited as nanoscale films, even macroscopic insulating materials like SiO2 and Ta2O5 are able to conduct ions, and electrochemical measurements well known from the liquid electrochemistry can be performed.

The talk gives an overview on the current state-of-the-art knowledge on redox-based resistive switching ReRAMs, focusing on the electrochemical dynamics at the metal/solid-electrolyte interfaces of nanoscaled thin films and quantum effects. The electrochemical kinetics during formation of nanofilaments will be discussed along with influence of the local environment and the generic relevance of the counter charges. The relation of these studies to the more fundamental issue of describing the microscopic electrochemical processes at the atomic scale will be emphasized.
Effect of Selenium Doping on GeSb for Phase Change Memory Applications
Authors: Ko Dae Hong , Kim Jeong Hoon , Byeon Dae-Seoup , Park Jeong hee
Published: February 2020

Phase change memory(PCM) has been focused as the alternative for next generation memory since it shows several advantages such as low fabrication cost, a scalability below 20nm design rule, large endurance cycles, and compatibility with semiconductor process. However, there still exist essential problems that are mainly determined by the properties of a phase change material. For example, the PCM cells composed of GeSbTe alloy relatively show low crystallization temperature, slow operation speed, and narrow resistance margin between reset and set state in respect of commercialization of PCM.

In our study, the GeSb film was selected as phase change material due to its fast crystallization speed and selenium was employed doping element for increasing thermal stability and the margin between high and low resistance. When the selenium was incorporated into GeSb film up to 8 at %, the crystallization temperature increased from 150oC to 225oC and the amorphous sheet resistance was elevated more than 13 times compared with undoped GeSb film. In addition, the resistance margin of the film significantly increased more 2 order of magnitude than that of GeSbTe film. The phase separation was found in the GeSb film doped with selenium over 8 at % and this was proved by XRD and XPS analyses. As a consequence, Selenium doped GeSb film was strongly demonstrated as phase change material of PCM cell due to its thermal stability and large resistance margin including high crystallization speed.
Charge Trapping Properties of Silicon Carbonitride Storage Layers for Nonvolatile Memories
Authors: Kobayashi Kiyoteru , Naito Shinji , Tanaka Shin , Ito Yoshina
Published: February 2020

Charge-trapping nonvolatile memories have received considerable attention as a promising candidate for the future data storages in communication and multimedia applications. In this architecture, electron and hole trapping phenomena by point defects distributed in charge trapping dielectric layers, such as silicon nitrides, are commonly used to memorize data. Recently, we have proposed the application of SiCN films with a low-dielectric constant (low-k) and a narrow band gap to the charge trapping layers [1]. The relative dielectric constant of SiCN films is 4.8-4.9, which is lower than that of silicon nitride films. Charges trapped in the low-k SiCN charge trapping layer induce the larger threshold voltage shift in MISFETs as compared with those trapped in the silicon nitride layer. In addition, the band gap of SiCN films is 3 to 4 eV, which is narrower than that of silicon nitride films (~5 eV). The narrower band gap of the charge trapping layer reduces the energy barrier for carrier injection into the layer. Thus, the low-k and narrow-band gap SiCN films would yield higher programming and erasing speeds and reduced power consumption. In the present study, we conducted a comparative study on charge trapping characteristics of the SiCN and silicon nitride films.

Two types of film structures were fabricated on p-type (100) silicon substrates: (A) a SiOX-SiCN-SiO2 film and (B) a SiOX-SiNX-SiO2 film. In the both types of films, a tunnel oxide film of 2.4 nm in thickness was first formed using rapid thermal oxidation. A 31.5-nm-thick SiCN film with the relative dielectric constant of 4.8-4.9 was grown at 400 °C using a PECVD technique. A 30.4-nm-thick SiNX film was grown at 600 °C using a LPCVD technique. A blocking oxide film of 17.3 nm was grown using a PECVD technique. Finally, an aluminum film was deposited to form the gate electrode. After electrons or holes were injected into the charge trapping layers, the flat-band voltage shifts ΔVFBwere measured.

Figure 1 shows the programming and erasing characteristics under the gate biases of +14.3 V and -15.1 V. The programming and erasing speeds in the SiOX-SiCN-SiO2 structure were obviously higher than those in the SiOX-SiNX-SiO2 structure. In the programming operation, the higher programming speed in the SiCN sample was mainly attributed to the low-dielectric constant of the SiCN film. In the erasing operation, the hole trapping speed in the SiCN sample was higher than that in the SiNX sample. The higher erasing speed in the SiCN sample arose from the higher hole trapping speed and the low-dielectric constant of the SiCN film. Figure 2 shows the retention characteristics of the SiOX-SiCN-SiO2 and SiOX-SiNX-SiO2 structures. The extrapolated 10-year memory window of the SiCN sample was wider than that of the SiNXsample. The SiCN films can be employed as the charge trapping layer of advanced nonvolatile memories.

References: [1] K. Kobayashi, S. Naito, S. Nakiri and Y. Ito, ECS Trans. 58(5) (2013) 81.
Electron Device Potential of 2D Crystal Semiconductors
Authors: Jena Debdeep
Published: February 2020

2D crystal semiconductors such as graphene and transition metal dichalcogenide are emerging as potentially attractive candidates for extending existing electronic device paradigms. More importantly, in the attempt to replicate existing electronic devices, the structural and electronic properties of these materials point towards potentially novel devices [1]. In this contribution, FOUR aspects of this emerging story will be presented, combining theory and experimental demonstrations.

FIRST, the physical properties of 2D crystal materials such as graphene, MoS2, etc will be compared with conventional semiconductors such as Si, Ge, GaAs, GaN, etc. Structural properties, energy bandgaps, electron/hole transport properties, etc pertinent to electronic devices will be compared, and contrasted specifically as the dimensions are scaled down to nanoscale thicknesses.

SECOND, the novel transport properties of 2D crystal semiconductors will be discussed. In particular, the mobilities of these materials within a band are affected by the coupling to surrounding dielectrics and by the presence of d-orbital band-edge states. The effect of out-of plane phonon vibrations and charged impurity scattering currently limits the mobilities severely in the MoS2 family of 2D semiconductors. Methods to boost the transport properties as predicted by the theoretical analysis will be presented. In addition, interband tunneling transport in both graphene and gapped MoS2-type chalcogenide semiconductors will be presented, with an eye towards novel electron device applications.

THIRD, conventional FET-type devices using these materials will be discussed and contrasted with existing state-of-the-art performance with Si and III-V semiconductor devices. Challenges and opportunities in this arena for 2D crystal semiconductors such as advantages of electrostatic scaling advantages, and ohmic contact challenges will be discussed. Experimental results on 2D crystal semiconductor FETs with high on/off ratios, respectable mobilities, and robust current saturation will be presented.

FOURTH, novel nanoelectronic devices that depend on tunneling transport will be presented. Specifically device proposals that exploit the intrinsic properties of 2D crystal semiconductors, such as graphene nanoribbon tunnel-FETs (TFET), Symmetric FET (SymFET), and TFETs with transition metal dichalcogenides will be presented. Finally, the very recent experimental demonstrations of some of these proposed devices will be discussed, and the challenges in realizing these devices, and their promise will be discussed.

[1] D. Jena, Proceedings of the IEEE, 101, 1705 (2013).
Unipolar CMOS Logic for Thin-Film Transistor Technology
Authors: Ma T.P.
Published: February 2020

For most thin-film transistors, it is very difficult, if not impossible, to fabricate CMOS circuits because of the difficulty in realizing both p-type and n-type channels in the same thin-film semiconductor, despite the well-known advantage of CMOS circuits’ lower stand-by power.

The operating principle of the proposed unipolar logic circuits will be described in the context of both the double-gate transistor architecture and the single-gate transistor architecture.

Figure 1 shows a circuit diagram for a two-input unipolar NOR and OR logic gates based on all n-channel MOSFETs, and Fig. 2 shows a circuit diagram for a two-input unipolar NAND and AND logic gates, also based on all n-channel MOSFETs.

Figure 3 shows a schematic diagram of the possible implementation of a unipolar NAND and AND circuits based on the IGZO thin-film transistor double-gate architecture, and Fig.4 shows its counterpart based on single-gate architecture.

The unipolar logic circuits typically suffers from the “threshold voltage loss” problem at the “HIGH” output, and we have developed a novel bootstrapping block to restore the voltage for the “HIGH” output. Examples will be presented to show the effectiveness of the bootstrapping circuits.

The power savings resulting from the unipolar approach as compared to its conventional counterparts will be shown by the use of simulation.

This work has been partially supported by the

Sandia National Laboratory PO#1383897.
Niobium Phosphate Glass Thin Film As an Intermediate-Temperature Proton Conductor
Authors: Kim Dae Ho , Park Sung Bum , Park Yong-il
Published: February 2020

Fuel cells operating at intermediate temperatures between 200°C and 400°C have attracted much attention because of the advantages such as enhanced reaction kinetics, resistance to CO poisoning, potential use of renewable fuels, reducing or eventually eliminating the noble metal catalysts. At intermediate temperature, phosphate glasses are suited to new solid state electrolytes. Phosphate glasses containing alkali ion have a structure in which protons have higher mobility and have been shown to possess high ionic conductivities because the hydrogen bonding network maintains between the adjacent oxide ions in the structures allowing for proton mobility by the hopping mechanism. However, the materials based on phosphate glasses have some problems. Contents of phosphorus can change due to volatilization during heat treatment and the glass structure can even break down through hydrolysis. Therefore, one of the solutions for the problem is improving the chemical and mechanical stability of phosphate glasses. Niobium ions in phosphate glass network have been reported as to increase the proton conductivity of the phosphate glasses, effectively preserving P content from severe volatilization. In this study, we report the chemical stability and the electrical properties at intermediate temperature of niobium phosphate glass thin films fabricated through sol-gel processing.
Robust Microbial Carbon Based Electrode System for Ureolysis of Urine
Authors: Morales-Cruz Myreisa , Morales Roberto , Martínez-Rodríguez Roberto A. , Gonzalez-Gonzalez Ileana , Toranzos Gary A. , Cabrera Carlos R
Published: February 2020

There still exists an indisputable growing demand for water around the world, therefore is of major interest to recycle and reuse water. One of the effective measures to help solve the water shortage problem involves recycling of urine. Urea is one of the most common compounds found in urine, and its degradation has been a matter of study for several years. Although the use of urease for urea decomposition is well known, none of the previously published reports involved the complete oxidation of urea to nitrogen. This work presents an innovative technique that integrates the use of a urease-positive bacteria, Proteus vulgaris, for such purposes. In addition platinum will be used as catalyst for the ammonium oxidation in order to obtain energy in the process. In this work the bacterial oxidation of urea to ammonia was chronoamperometrically detected by a polycrystalline platinum disk electrode. The ureolysis of the urea solution was done at several alkaline levels to find the compromising conditions for the bacterial and electrochemical reactions in synthetic urine.
Structural and Electrochemical Performance of Ternary Type-I Clathrate As Anode Materials for Lithium-Ion Batteries
Authors: Li Ying , Raghavan Rahul , Wagner Nicholas , Chan Candace
Published: February 2020

Due to its high theoretical specific capacity, silicon has been the subject of intense interest and research as a high energy density anode for lithium-ion batteries. In the last several years, nanostructured silicon has been shown to be very effective for relieving lithiation induced strain and avoiding pulverization, which can lead to capacities > 3000 mAh/g, a 10X improvement over the commercially used graphite anode. However, despite this impressive proof-of-principle, nanostructured silicon can still suffer from degradation over long cycling times due to several reasons such as collapse of the nanostructure, increased porosity, structural instability, and insufficient surface passivation. The work to be presented here will introduce our investigations into the lithiation of silicon clathrates, (fullerene-like materials where silicon atoms are arranged in cage-like structures) that have been shown, through first principles calculations, to be able to allow lithium insertion without a large volume change or pulverization [1].

In our group, we have investigated silicon clathrate materials, which have cage-like structures, as an anode material of Li-ion battery. Our studies on type II clathrate based on Na24Si136 show that lithium insertion is energetically feasible inside silicon cages that are fully occupied by other guest atoms. However, large amounts of lithium insertion cause a transformation between from the clathrate structure to an amorphous silicide and eventually Li15Si4 [2].

This presentation discusses the structure and electrochemical performance of ternary Ba-X-Si type-I clathrate (where X = Cu, Al). Polycrystalline silicon clathrate materials are synthesized using thermal annealing and arc-melting methods. Electrochemical and structural analysis show these cage-like silicon structures have the ability to allow lithium insertion and removal without a large volume change or pulverization. Lithiation/delithiation of silicon clathrate anodes will be presented comparing to that of diamond cubic and amorphous silicon. Ex-situ X-ray diffraction, X-ray photoelectron spectroscopy, and nuclear magnetic resonance are also employed to understand the structural changes upon lithiation and delithiation.

References:

[1] K.S. Chan, C.K. Chan, W. Liang, Silicon clathrate anodes for lithium ion batteries. U.S. Patent Application no. 12/842,224 (2010)

[2] N.A. Wagner, R. Raghavan, R. Zhao, Q. Wei, X. Peng, C.K. Chan. Electrochemical cycling of sodium-filled silicon clathrate. ChemElectroChem. 1, 347-353 (2014).
Electrochemical Characterization of Si Alloy Anodes for Libs Synthesized By Mechanical Ball Milling
Authors: Cho Jong-Soo , Ahn Hyeong-Gi , Suh Soon sung , Kim Jae hyuk , Kwon Seung uk , Oh Kyu Hwan
Published: February 2020

Si alloy anodes were produced by mechanical milling in this study. They were prepared by ball milling the pieces of pre-alloyed melt spun ribbon. Our study was focused on the effect of a milling time on the electrochemical performance of Si alloys and microstructural evolution. As a result, it appears that the longer milling time, more cycle stability, the finer crystal size. In addition, we performed XRD, TEM analysis to characterize microstructure and intermetallic phases. This study leads to the best understanding to date of the electrochemistry of a Si alloy anode with an inactive matrix
Simplifying Electrothermal Dynamics of 15-Ah Prismatic Li-Ion Batteries
Authors: Secondo Lynn , Kim Sun Ung , Siegel Jason , Stefanopoulou Anna , Monroe Charles W
Published: February 2020

A simply coupled electrochemical and thermal model is validated and presented for a 15 Ah large format prismatic lithium iron phosphate cell. Understanding the thermal response of lithium-ion cells is essential because it would allow the batteries to be operated more efficiently. Two important issues regarding the thermal response are "cold start" and "thermal runaway."[1] Use of a validated simulation can aid in enhancing the performance and safety of these batteries.

To minimize the number of essential parameters, the simplest models are carefully chosen to depict the battery responses. At least two physical models are necessary for describing an electrochemical system: an electrochemical model and a local energy balance. For the electrochemical model, we select the Newman and Tobias model, which provides an analytic solution with an assumption that the ion concentration gradient is negligible.[2] For the energy balance [3,4], three different heat sources are necessary to match our experimental data: (1) Joule heating of the cell materials (simple IR heating), (2) an additional Joule heating generated by the interfacial resistance between electrode and electrolyte, and (3) the reaction heating from reversible entropy change. Joule heating is always exothermic; however, the reversible heat depends on the electrochemical reaction and can be endothermic or exothermic.

Even though the minimal physics are chosen for simplicity, the number of physicochemical parameters in the completed model was more than ten; however, the number could be decreased to five after rigorous dimensional analysis. Therefore, not only do these parameters suggest important factors for the battery response, but they also help to control the battery in efficient ways, since this test shows that many parameters have the same effect in the electrical/thermal response. Comparison to target experimental data characteristics of the battery (Fig. 1) allows iterations of the dimensionless parameters to increase accuracy through multidimensional Newton-Raphson method. Finalized parameters will guide simulations to help control the battery in efficient ways.

[1] T. M. Bandhauer, S. Garimella, and T. F. Fuller, Journal of The Electrochemical Society 158, R1 (2011).

[2] J. S. Newman and C. W. Tobias, 109(12), 1183 (1962).

[3] D. Bernardi, E. Pawlikowski, and J. Newman, J. Electrochem. Soc. 132, 5 (1985).

[4] J. Newman and K. E. Thomas-Alyea, Electrochemical Systems, 3rd ed. Wiley, 2004.
Electrochemical and Structural Characteristics of Type I and Type II Silicon Clathrate Anodes
Authors: Li Ying , Raghavan Rahul , Wagner Nicholas , Chan Candace K.
Published: February 2020

Lithium-ion batteries are one of the most promising energy storage devices due to their high energy density, long cycle life, high voltage, and excellent rate capability. Si is a promising anode material due to its extremely large theoretical capacity of 3579 mAh/g at room temperature. However, the practical use of Si anodes is hindered by the structural failure upon lithium insertion/extraction processes and the low intrinsic electric conductivity.

In our group, we have investigated several different silicon clathrate materials, which have cage-like structures, as anode materials of Li-ion battery. The work to be presented here will discuss the electrochemical and structure characteristics of both type-I and type-II silicon clathrate anodes.

Type-I clathrates, which are synthesized using thermal annealing and arc-melting methods, are made of two pentagonal dodecahedra (Si20) cages and six tet-rakaidecahedra (Si24 cages) per unit cell and crystallize in the Pm3n space group. Results show that ternary type-I clathrates have the ability to allow lithium insertion and removal without a large volume change or pulverization. Type-II clathrates, which are synthesized by thermal decomposition of the Zintl compound, are made of sixteen pentagonal dodecahedra plus eight hexakaidecahedra (Si28 cages) per unit cell and crystallize in the Fd3m space group. Results show that upon electrochemical lithiation the type-II clathrates become amorphous and transform into c-Li15Si4 at low potentials, then remain an amorphous silicide after delithiation. Ex-situ X-ray diffraction, X-ray photoelectron spectroscopy and nuclear magnetic resonance are also employed to understand the structural changes upon lithiation, delithiation and prolonged cycling.
Measurements of SOH Using Stack Stress
Authors: Cannarella John , Arnold Craig B.
Published: February 2020

In previous ageing studies in which the stack stress of commercially available lithium-ion (LCO/C) pouch cells is monitored during cycling [1], we observe that stack stress (Figs 1a and 2a) is linearly related to cell SOH (Figs 1b and 2b) as shown in Figs 1c and 2c [2]. The increase in stack stress is attributed to irreversible volumetric expansion of the anode which we assume to be related to SOH. This suggests the possibility of using stress to measure SOH, a method whose simplicity provides a distinct advantage to conventional computationally intense methods which rely on complex physical models of the underlying cells. Stack stress could be used as a standalone SOH monitoring system, or integrated into existing battery management systems to increase management fidelity. In this talk we investigate the origins of the stress-SOH relationship.

We report the following data from ageing studies of cells cycled under different conditions: temporal stack stress evolution, capacity evolution, non-destructive differential voltage spectroscopy analysis, and destructive post-mortem analysis. All of the temporal stress and capacity data show a t1/2 dependence suggestive of a diffusion limited mechanism such as SEI growth, as seen in Figs. 1d and 2d. This assertion is corroborated by the differential voltage spectroscopy measurements and destructive post mortem analysis, which also show evidence of a SEI growth mechanism. Stack stress is also observed to increase in cells held at 4.2V in the absence of cycling as shown in Fig. 2a, supporting the notion of a chemical mechanism. Based on the assumptions of an SEI growth mechanism, we present simple scaling arguments which predict a linear relationship between stack stress and SOH. We discuss the implications for this method and model as it applies to battery management systems and fundamental ageing studies.

REFERENCES

[1]. J. Cannarella, C. B. Arnold, “Stress evolution and capacity fade in constrained lithium-ion pouch cells,” J. Power Sources
245 (2014) 745-751.

[2]. J. Cannarella, C. B. Arnold, "State of health and charge measurements in lithium-ion batteries using mechanical stress," submitted.

FIGURE CAPTIONS

Figure 1. Data from a cell aged by cycling under a C/2 CCCV scheme showing (a) stack stress as a function of cycle, (b) C/10 capacity as a function of accumulated cycles, (c) stack stress as a function of SOH, and (d) t1/2 dependence of the C/10 capacity data.

Figure 2. Data from a cell aged by holding at 4.2V at room temperature and periodic cycling at C/10 to measure capacity showing (a) stack stress as a function of time, (b) C/10 capacity as a function of time, (c) stack stress as a function of SOH, and (d) t1/2 dependence of the C/10 capacity data.

ACKNOWLEDGEMENTS

Support was provided by the DoD through the NDSEG Program and by the Siebel Energy Challenge. J. C. also acknowledges the Rutgers-Princeton IGERT in Nanotechnology for Clean Energy.
In-Situ Nanomechanical Measurement of High-Capacity Battery Materials Using MEMS Cantilevers
Authors: Cheng Mark Ming-Cheng
Published: February 2020

This paper investigates a bilayer cantilever for a sensitive and quantitative measurement of the mechanical stress of high-capacity battery materials during electrochemical cycles. Silicon is a promising candidate for anode materials thanks to its high specific capacity (4200 mAh/g). One of the main challenges for silicon anode is the large volume expansion (~400%), causing material degradation and pulverization of the electrode [1-2]. In-situ characterization of stress evolution is critical because it enables the development of nanostructures and nanocomposites in order to enhance mechanical integrity [3-4].

As shown in Fig 1, the bilayer cantilever consists of an active material and copper. Copper is used as a mechanical structure because of its good mechanical properties as well as its popular use as a current collector in anode. During lithiation, where lithium ions are inserted in silicon, the anode is subjected to compressive stress and the cantilever curls up. Similarly, the anode experiences tensile stress during delithiation and the cantilever curls down. The bending of a bilayer cantilever is described by a Timoshenko beam theory. The active material (250nm α-Si) was used as a working electrode, and faced lithium metal (as a counter and a reference electrode). A separator was placed between two electrodes in order to prevent an electrically short circuit. Electrolytes (1 mol LiPF6in ethylene carbonate and dimethyl carbonate with 1:1 ratio) were filled in the chamber. A white light interferometry was used to determine the deformation of the cantilever during electrochemical cycles that was controlled by a potentiostat. Figure 2 shows the voltage vs. time and a corresponding stress profile during the first five cycles. Interestingly, during the first lithiation, the stress did not increase rapidly when the voltage was larger than 300mV, indicating the formation of solid-electrolyte interfaces (SEI). SEI was a result of the decomposition of electrolytes. When the voltage was smaller than 300mV, compressive stress reached -0.3GPa. Then the compressive stress slightly decreased at a lower voltage, probably due to the material cracking. The tensile stress appeared during delithiation. As we observed, the anode material experienced a dynamic change of stress during the first five cycles. Figure 3 shows the surface morphology of silicon anode before and after cycling. Silicon was initially uniformly coated, but many cracks were generated during electrochemical cycles due to mechanical stress.

REFERENCES:

[1] A. Magasinski, et al., Nat
.
Mater
., vol. 9, pp. 353-358, 2010.

[2] R. Teki, et al., Small, vol. 5, pp. 2236-2242, 2009.

[3] S.J. Lee, et al., J. Power Sources, vol. 97-8, pp. 191-193, 2001.

[4] V.A. Sethuraman, et al, J. Power Sources, vol. 195, pp. 5062-5066, 2010.
Single-Crystalline LiFePO4 Nanosheets for High-Rate Lithium Batteries
Authors: Yu Guihua , Zhao Yu , Peng Lele
Published: February 2020

The lithiation/delithiation in LiFePO4 is highly anisotropic with lithium ion diffusion being mainly confined to channels along the b-axis. Controlling the morphology and crystal orientation of LiFePO4 material therefore plays an important role for efficient mass and change transport within this material. We will present our recent effort on the preparation of single crystalline LiFePO4 nanosheets with a large percentage of highly oriented {010} facets, which provide the highest pore density for lithium ion insertion/extraction. The LiFePO4 nanosheets show a high specific capacity at low charge/discharge rates, and retain significant capacities at high C-rates, which may benefit the development of lithium batteries with both favorable energy and power density.
Ordered Distribution of S in a Multi Walled Carbon Nanotubes/Sulfur Composite Cathodes for Li/S Batteries
Authors: Hernandez-Maya Roberto , Castaneda Homero
Published: February 2020

The Li- S batteries has pronounced as an excellent alternative in Li batteries, mainly due to its high theoretical specific capacity and energy density. However, the practical application of rechargeable Li/S batteries has several problems due to the low utilization of the active material and low efficiency during charge and discharge cycles. This work proposes the use of MWCNT as support material for the S in this type of batteries. Among the advantages offered by the use of MWCNT like more specific area, there is the prevention of the dissolution of polisufides with long chain, which can cause passivation of the anode and reduce the life cycle of the battery. Functionalization of MWCNT improves the amount of active sites on their surface, therefore, deposition of S in the MWCNT is homogeneous and controlled, allowing increasing of its electrochemical properties. In this work a characterization of this distribution is effectuated using electrochemical techniques, EIS (Electrochemical Impedance Spectroscopy), CV (Cyclic Voltammetry), in organic electrolyte. The surface characterization was made with AFM (Atomic Force Microscopy). Techniques of superficial characterization as LEIS (Localized Electrochemical Impedance Spectroscopy) and SECM (Scanning Electrochemical Microscopy) helps to relate the electrochemical behavior and, the superficial arrangement in this materials.
Electrolytes and Interphases for Beyond Li-Ion Chemistries
Authors: Xu Kang
Published: February 2020

With the intrinsic limit of energy density being approached in Li ion chemistry, there have been extensive efforts aiming at breaking out this limit set by the storage mechanism where only one Li+ could be accommodated per transition metal element. Among the so-called “beyond Li ion” chemistries, in which inert masses are kept at minimum, the electrode integrity is often sacrificed for high specific capacities, which presents severe challenge to the electrode/electrolyte interphases. Understanding the interactions between these new materials and electrolytes and the concomitant interphases would play significant roles in determining their future successes.

This presentation will overview the electrolyte and interphase in these nascent battery chemistries, while emphasizing the most recent breakthroughs achieved in electrolytes and interphasial chemistry in Li/S system..
A Technical and Operational Perspective on the DOE Energy Innovation Hub in Fuels from Sunlight, the Joint Center for Artificial Photosynthesis
Authors: Lewis Nathan S.
Published: February 2020

The design of highly efficient, non‐biological, molecular‐level energy conversion “machines” that generate fuels directly from sunlight, water, and carbon dioxide is both a formidable challenge and an opportunity that, if realized, could have a revolutionary impact on our energy system. Basic research has already provided enormous advances in our understanding of the subtle and complex photochemistry behind the natural photosynthetic system, and in the use of inorganic photo‐catalytic methods to split water or reduce carbon dioxide–key steps in photosynthesis. Yet we still lack sufficient knowledge to design solar fuel generation systems with the required efficiency, scalability, and sustainability to be economically viable.

In the DOE Energy Innovation Hub, the Joint Center for Artificial Photosynthesis, we are developing an artificial photosynthetic system that will only utilize sunlight and water as the inputs and will produce hydrogen and oxygen as the outputs. We are taking a modular, parallel development approach in which the three distinct primary components-the photoanode, the photocathode, and the product-separating but ion-conducting membrane-are fabricated and optimized separately before assembly into a complete water-splitting system. The design principles incorporate two separate, photosensitive semiconductor/liquid junctions that will collectively generate the 1.7-1.9 V at open circuit necessary to support both the oxidation of H2O (or OH-) and the reduction of H+ (or H2O). The photoanode and photocathode will consist of rod-like semiconductor components, with attached heterogeneous multi-electron transfer catalysts, which are needed to drive the oxidation or reduction reactions at low overpotentials. This talk will discuss a feasible and functional prototype and blueprint for an artificial photosynthetic system, composed of only inexpensive, earth-abundant materials, that is simultaneously efficient, durable, scalably manufacturable, and readily upgradeable, including both the operational and technical scope of the JCAP Hub, as well as technical results towards this goal that has recently been developed at Caltech.
Removal of Heavy Metal Ions by Photoelectrodeposition in Aqueous Solutions
Authors: Sato Kazunori , Hoshi Yuhei , Ayawanna Jirachaya , WahTzu Teoh , Saito Nobuo , Inoue Yasunobu , Nishiyama Hiroshi
Published: February 2020

In order to remove hazardous heavy metal ions dissolved in an aqueous environment, the photoelectrodeposition effect on the removal of Pb(II), Cu(II), Cd(II), and Zn(II) ions has been investigated for the (CeO2)1-X(Ln2O3)X (Ln = La, Sm, Gd) photocatalyst oxide particles combined with fine α-FeOOH particles. This effect is also compared with titanium-based oxides. The mixture of 1 mol%α-FeOOH and these photocatalyst oxides showed a high photoelectrodeposition ability particularly for Pb(II) ions under photo irradiation. The removal efficiency of Pb(II) ions was high under the UV irradiation and it decrased with increasing the wavelength of light toward the visible region. This result indicates that the coexistence of fine α-FeOOH particles with (CeO2)1-X(Ln2O3)X particles contributes to an efficient separation of holes and electrons generated by the photo irradiation. The high-resolution scanning electron microscopic observation of the samples revaled that fine α-FeOOH particles supported on the surface of the photocatalyst oxide particles are effective for the charge separation between holes and electrons. This effect is caused by the redox reaction occurring for the transfer of electrons to the surface of α-FeOOH-(CeO2)1-X(Ln2O3)X particles. These composite particles were also found to be effective for the removal of other heavy ions at low concentrations. The removal efficiency of the heavy metal ions is determined by the standard electrode potential of elements involved.
Keynote Presentation: Lithium Solvate Ionic Liquids for Advanced Lithium Secondary Batteries
Authors: Watanabe Masayoshi
Published: February 2020

Abstract not Available.
All Solid-State Fexible Supercapacitors Based on Titanium Dioxide@Polypyrrole Core–shell Nanowires
Authors: Yu Minghao , Lu Xihong , Tong Yexiang
Published: February 2020

Abstract not Available.
Influence of Li Fast Ion Conductive La0.56Li0.33TiO3 Modification on Morphology and Electrochemical Performance of LiFePO4/C Microspheres
Authors: Shu Hongbo , Chen Mangfan , Wang Aiwen , Yang Xiukang , Bai Yansong , Shen Yongqiang , Wang Xianyou
Published: February 2020

Abstract not Available.
Room-Temperature Synthesis of PtPd Nanochains with Self-Assembled Three-Dimensional Porous Networks for Oxygen Reduction Reaction
Authors: Shen Pei Kang
Published: February 2020

Abstract not Available.
Li-Intercalation of Graphite Anode in Lithium Solvate Ionic Liquids
Authors: Moon HeeJoon
Published: February 2020

Abstract not Available.
Improving the Performance of MnO2
/Acnts Material for Supercapacitors By Plasma Treatment
Authors: Li Huilin , Gao Hongquan , Yang Jianhong
Published: February 2020

Abstract not Available.
Synthesis Of Iron Series Phosphate Micro-Nano-Materials and Their Potential Applications For Electrochemical Energy Storage
Authors: Pang Huan
Published: February 2020

Abstract not Available.
Preparation of Spherical Hierarchical LiNi0.5Mn1.5O4 with High Electrochemical Performances By a Novel Composite Co-Precipitation Method for 5 V Lithium Ion Secondary Batteries
Authors: Zhu Zhi , Lu Qi
Published: February 2020

Abstract not Available.
Insight into the Electrode Mechanism of Microporous Carbon/Sulfur Composite Cathode
Authors: Li Zhen , Yuan Lixia , Huang Yunhui
Published: February 2020

Abstract not Available.
The Preparation of Perovskite Oxide Powders Adopted in Itsofcs Via Inductively Coupled Plasma Technique
Authors: Chang Chun Liang , Hwang Chang Sing , Tsai Chun Huang , Chuang Shie Zong Yang , Chuang Chih Ming , Yang Sheng Fu
Published: February 2020

Abstract not Available.
Nitrated Hydrophilic (NO2-C) Anode Diffusion Layer for DMFC
Authors: Wang Yituo , Wang Meng , Zheng Le , Wang Xindong
Published: February 2020

Abstract not Available.
Nitrogen-Doped Activated Carbon Supporting Pd Nanoparticles for Methanol Electrooxidation
Authors: Qian Huayu , Zhang Wenyao , Wang Xin
Published: February 2020

Abstract not Available.
CaV0,5Mo0,5O3 -Based SOFC Anode Material
Authors: Tolkacheva Anna Sergeevna , Shkerin Sergey Nikolaevich , Belyakov Semen Aleksandrovich
Published: February 2020

Abstract not Available.
Thermoelectric Composite of Bismuth-Telluride Nanoparticles and Si Nanowires for Solar Heat Energy Harvesting
Authors: Yu-Ting Liu , Yue-Yun Tsai , Hsin Cheng-Lun
Published: February 2020

Abstract not Available.
Amphiphilic Block Copolymer Containing Quaternary Ammonium Cation for Anion Exchange Membrane
Authors: Li Yifan , Herring Andrew M , Knauss Daniel M
Published: February 2020

Abstract not Available.
Electrochemical Synthesis of Cuprous Oxide on High Conducting Metal Micro-Pillar Arrays for Water Splitting
Authors: Yoon Sanghwa , Yoo Bongyoung , Lim Jae-Hong
Published: February 2020

Abstract not Available.
Synthesis of Macroporous Si/Al2O3 Composite Anodes for High-Performance Lithium-Ion Batteries
Authors: Choi Sinho , Bok Taesoo , Ryu Jaegeon , Park Soojin
Published: February 2020

Despite the significant advances of carbon-based materials in lithium ion batteries (LIBs), new anode materials exhibiting higher energy density are needed. Among them, silicon (Si) exhibits highest theoretical capacity (4200 mAh/g with a formation of Li4.4Si). However, the major problem is their significant volume changes (over 300%), which occurs during the alloying and dealloying process, leading to pulverization of the active materials and the consequent loss of electrical contacts between particles, resulting in capacity loss and poor cycling performance. In this study, nanoporous silicon and Alumina composite materials were synthesized to overcome several problems mentioned above by combining various porous silica materials and metallothermic reduction reaction(MRR). The porous Si composit materials having a particle size of 1–10um and pores of 10~500 nm were obtained, and subsequently, Alumina major layers were on the surface of porous Si with Alumina contents of 10–50 wt%, have capacities of 3000~600 mAh/g,respectively. It means that if we control contents of silicon, have synthesized anode materials of various capacities. The having 20wt% alumina porous Si showed a highly stable cycling retention over 100 cycles at a high specific capacity of 1000 mAh/g.