bluuebunny/crossref_metadata_2025 huggingface dataset:
(Invited) FinFET Technology
Authors: Cheng Kangguo
Published: February 2020

FinFET has been emerged as the leading device architecture for continuing CMOS scaling. It has entered mainstream CMOS manufacturing since 22nm node. In this paper, I will provide an overview on the challenges associated with CMOS scaling and articulate how FinFET circumvents those scaling challenges. Meanwhile, FinFET has its own unique issues related to device design and process integration. A detailed discussion on challenges and opportunities of FinFET will be discussed in detail. A general guidance for further scaling FinFET will be provided including channel materials, high-k/metal gate, strain techniques, device isolations. Advanced FinFET manufacturing techniques such as self-aligned multiple patterning and EUV lithography, selective epitaxy, and high-aspect ratio dielectric deposition will also be covered. Some common misconceptions about FinFET technology such as confusing technology node names adopted by different companies will be clarified. Finally, FinFET will be compared with other device architectures such as fully depleted SOI (FDSOI) and nanowire transistors. The advantages and drawbacks of each device architecture will be summarized.
(Invited) SiGe BiCMOS Heterogeneous Integration Using Wafer Bonding Technologies
Authors: Wietstruck Matthias , Kaynak Mehmet , Mai Andreas
Published: February 2020

Heterogeneous integration has been a very attractive research topic for the last decades. Due to the limitations for further device scaling the More-than-Moore approach based on heterogeneous integration has been pointed out as the key integration path for future smart system integration [1]. Temporary and permanent wafer bonding technologies are one of the key enabling technologies for heterogeneous integration. Temporary wafer bonding is a well-established bonding technique to provide a stable handling and fabrication of ultra-thin silicon wafers. Permanent wafer bonding with various electrical isolating or conductive bonding interfaces is applied for wafer-level heterogeneous device integration [2]. Making available both temporary and permanent wafer bonding technologies together with a high performance SiGe BiCMOS technology will pave the way for new applications like millimeter-wave packaging, 3D-integration and smart sensors to realize multi-functional and miniaturized systems.

The potential of temporary and permanent wafer bonding techniques for heterogeneous integration of a high performance SiGe BiCMOS technology with additional devices and technology modules will be presented by three different application examples namely BiCMOS embedded Through-Silicon Vias (TSV), silicon interposer including substrate-integrated waveguides and BiCMOS embedded microfluidics. With respect to the different applications the potential and the main technology obstacles for SiGe BiCMOS temporary and permanent wafer bonding will be highlighted. While the temporary wafer bonding process with subsequent wafer thinning and thin wafer backside fabrication is mainly limited by the robustness of adhesives against high temperature and high vacuum process conditions, the permanent wafer bonding based on SiO2-SiO2 fusion bonding is mainly limited by the demanding surface requirements in terms of roughness and wafer bow which has been optimized to fulfill the requirements. By optimizing the SiGe BiCMOS technology both temporary and permanent wafer bonding together with subsequent semiconductor fabrication becomes feasible.

In summary, the development of wafer bonding application together with an industrial-level BiCMOS process will be presented. By the use of temporary and permanent wafer bonding new applications in the area of heterogeneous integration becomes feasible making SiGe BiCMOS technologies more attractive for future smart system applications.
Air-Stable n-Type Polymers for Thermoelectric Applications
Authors: Menon Akanksha , Wolfe Rylan , Yee Shannon K. , Marder Seth , Reynolds John R
Published: February 2020

Polymer-based thermoelectrics have the potential for waste heat recovery and energy harvesting from temperatures less than 200°C. These devices can be fabricated via printing processes that are low cost from materials that are lightweight and flexible, with applications ranging from self-powered sensors to wearable electronics. In the past decade, significant progress has been made with high performing p-type thermoelectrics such as PEDOT-derivatives, while n-type polymers have lagged behind due to their air sensitivity and low electrical conductivity. In this work, we optimize the thermoelectric properties of metallo-organic polymers with nickel as the metal center. We report the synthesis, characterization and thermoelectric properties of poly(nickel-ethenetetrathiolate) and poly(nickel-tetrathiooxalate) that are intrinsically electrically conducting. We modify the extent of oxidation and study the role of different oxidants and counterions on tuning the electrical conductivity. Interestingly, the Seebeck coefficient (thermopower) remains largely unchanged over the course of oxidation indicating that this may be a viable technique to decouple thermopower and electrical conductivity in such materials. The temperature dependent properties for these polymers show semi-conducting behavior that is consistent with hopping transport. Film measurements by blending with an inert matrix indicate that these polymers maintain their stability in air, making them suitable for energy harvesting devices. To enhance the Seebeck coefficient, we blend the metallo-organic polymers with other materials to form composites. This enables optimization of the power factor to realize high performance n-type polymer thermoelectrics.
(Invited) Molten Semiconductors for High Temperature Thermoelectricity
Authors: Zhao Youyang , Rinzler Charles Cooper , Allanore Antoine
Published: February 2020

High temperature (>900°C) industrial waste heat recovery remains at the frontier in thermoelectric materials. The high temperature (greater than 1200°C), low heat-flux, and large surface area encountered in high temperature industrial reactors imply that materials cost dictates deployment. Molten semiconductors are one cost-effective material option that remains understudied. Here we report the performance of a laboratory-scale device based on molten SnS, in particular the Figure of Merit (ZT) and the conversion efficiency of this first generation of material. Furthermore, a discussion of the Seebeck and transport properties of molten SnS is proposed [1]. It is found that electronic properties of molten semiconductors are promising, and that the remaining question lies in the thermal transport properties. Recent experimental results show that thermal transport in molten SnS involves drastically different mechanisms than in the solid-state , and it calls for advances in the prediction and evaluation of physical properties of molten materials. The results with SnS highlight the materials and engineering challenges that will allow the next generation of molten semiconductors to be developed.

[1] Youyang Zhao, Charles Rinzler, and Antoine Allanore, Molten Semiconductors for High Temperature Thermoelectricity, ECS J. Solid State Sci. Technol. 2017 6(3): N3010-N3016; doi:10.1149/2.0031703jss
Skutterudite-Based Thermoelectric Technology for Integration into a Proposed Emmrtg for Space Power Applications
Authors: Caillat Thierry , Chi Ike Suchih , Firdosy Samad , Huang Chen-Kuo , Smith Kevin , Yu Kevin , Ni Jennifer , Paik Jong-Ah , Gogna Pawan , Fleurial Jean-Pierre
Published: February 2020

The overall objective of the Skutterudite Technology Maturation (STM) project at NASA’s Jet Propulsion Laboratory (JPL) is to advance JPL-developed skutterudite (SKD) technology to a point where it can be considered for use in a proposed enhanced Multi-Mission Radioisotope Thermoelectric Generator (eMMRTG). The goal is to be prepared for potential flight unit development readiness by end of FY2018. Conversion efficiency values on the order of 9% have been demonstrated for SKD-based un-segmented couples when operating at a hot junction of 600C and a cold junction of 200C. This represents ~ a 25% improvement over the conversion efficiency of PbTe/TAGS MMRTG couples at beginning-of-life (BOL). The STM project entered its third year at the beginning of FY2016. This talk will highlight the material and device challenges associated with the maturation of this technology. During the first two years of the project, JPL and Teledyne Energy Systems Inc. (TESI) have collaborated to complete the initial technical technology transfer to TESI. Manufacturing capabilities for SKD TE materials have been established at TESI. TESI has also established the manufacturing capabilities for couples and module thermal insulation. First iteration SKD couples have been fabricated and tested at TESI. Key findings from this initial Phase of the technology maturation project will be summarized. TESI and JPL are currently developing a second iteration of couples and module thermal insulation, incorporating lessons learned from the development and testing of the first iteration of couples and insulation. Progress to date on the development of this second iteration of couples will be presented and discussed. The eMMRTG life performance prediction approach and development status will also be presented.
(Invited) Template Assisted Electrochemical Deposition and High Power Factor Materials for Integrated Thermoelectric Devices
Authors: Schierning Gabi , Li Guodong , Barati Vida , Lara Ramos David Alberto , Sieger Tom , Garcia Javier , Perez Rodriguez Nicolas , Mohn Melanie , Schlörb Heike , Freudenberger Jens , Reith Heiko , Nielsch Kornelius
Published: February 2020

Next generation integrated micro-scale thermoelectric devices are envisioned for spot cooling of active electronic parts or as independent power supply units to exploit small hot spots within electronic circuits. In the first case, a thermoelectric cooler is added to manage the temperature stability of sensitive electronic or photonic devices, hence to remove high density heat fluxes from these critical parts. In the second case, a thermoelectric generator is intended to recover a proportion of waste heat of a hot spot, i.e. a small, but otherwise unlimited heat source, in the electronic circuits. Both cases are technologically challenging since they request for a fabrication route that is compatible with a CMOS back-end processing. But especially the latter application provides also novel requirements to the thermoelectric material. The typical paradigm of thermoelectric material's development aims towards low thermal conductivity. This is not necessarily helpful for the given example of application where the heat has to be efficiently removed from the active electronic part, utilizing a proportion of this heat for thermoelectric power generation. Hence, this paradigm has to shift towards the development of high power factor materials, rather than low thermal conductivity materials.

A processing that, at least in principle, can be fully compatible with CMOS back-end technology is given by the combination of lithographic structuring and the electrochemical deposition of the functional thick films into pre-structured cavities. A material class that provides both, high power factors and sufficiently high thermal conductivity for the removal of waste heat, is given by metallic alloys. This paper will therefore provide experimental details of the processing technology of integrated micro-scale thermoelectric devices and a discussion of high power factor materials for thermoelectric devices.
(Invited) IV-VI Monochalcogenide Nanostructures: Synthesis, Doping and Thermoelectric Properties
Authors: Gao Xuan
Published: February 2020

Recently IV-VI monochalcogenide SnSe or SnS has been proposed as a promising two-dimensional (2D) material for valleytronics and thermoelectrics. Despite much theoretical interest and many experimental reports on the thermoelectric characterizations of SnSe single crystals, experimental studies on SnSe and SnS in the nanostructured form are still limited. We report the synthesis of SnSe nanoflakes and thin films with chemical vapor deposition (CVD) and their thermoelectric properties. As grown SnSe nanostructures are found to be intrinsically p-type and different types of dopants (In, Pb and Ag) were explored to control the carrier density. We will present the electrical transport property of SnSe nanoflake field effect transistor devices and the effects of doping on the electrical conductivity, Seebeck coefficient, power factor and anisotropy in SnSe films. By doping, the power factor of SnSe films can be improved by at least one order of magnitude compared to the "intrinsic" as grown materials. If time permits, we will also discuss the transport properties of SnS nanoflakes obtained by mechanical exfoliation to compare with the chemically grown SnSe nanostructures. Our work provides an initial step in the pursuit of IV-VI monochalcogenide nanostructures as novel 2D semiconductors for electronics and thermoelectrics.
(Invited) Formation of Conducting Filaments in TaOx-Based Resistive Switching Devices
Authors: Ma Yuanzhi , Herzing Andrew , Li Dasheng , Nuhfer Noel T. , Bain James A. , Skowronski Marek
Published: February 2020

Resistive switching phenomenon and resistive switching devices could form the basis for the next generation non-volatile solid state memories. Particularly promising are structures based on dielectric oxides such as TaOx and HfOx which have been demonstrated to large OFF/ON ratio, low energy dissipation per switching cycle, long endurance, and sub-nanosecond switching times. It is widely accepted that the first switching cycle, referred to as electroforming, results in formation of a conducting small diameter filament within the highly resistive matrix. This is due to the electric field which induces the transfer of oxygen ions across the interfaces and into the metal electrodes producing locally oxygen-deficient conducting oxide. Most of the structural changes induced during electroforming and switching have been reported in devices that experienced high current levels during switching cycle.

The devices used in this study were 500×500 nm2 crossbar structures with 20 nm thick TiN electrodes and 100 nm of reactively sputtered amorphous TaOx. The devices were electroformed and electroformed/switched with the current compliance of 10-20 μA. The data have been gathered in several imaging modes of electron microscopy including bright field, High Angle Annular Dark Field (HAADF), Energy Dispersive X-ray Spectroscopy, and low loss and core regions of Electron Energy Loss Spectroscopy (EELS). The entire volume of the functional layer remained amorphous with no signs of crystallization. It contained only one area of bright contrast in HAADF images corresponding to the conductive filament with the diameter of approximately 50 nm. The maps produced by all techniques clearly indicate an increase of [Ta]/[O] ratio within the filament. In addition to overall change of the composition, the core of the filament shows a fine structure of the composition on the scale of 5-10 nm. We interpret the changes in distribution as due to thermodiffusion in the temperature gradient induced by current constriction when the device enters the negative differential resistance region of its I-V. The temperature distribution during this process has been estimated using a self-consistent finite element model.
(Invited) Unconventional Computing with Memristors
Authors: Strukov Dmitri
Published: February 2020

By now, there have been many demonstrations of resistive switching (“memristive”) devices based on organic, chalcogenide, transition metal-oxide and silicon materials and involving different physical switching mechanisms, such as phase-change transitions and modulation of the ionic concentration profiles by electrical and/or thermal forces. The conductance of some properly engineered memristors can be continuously tuned with relatively large electrical bias, and retained, effectively indefinitely, when small stress is applied. Such analog nonvolatile memory functionality combined with potentially very high device density, achieved by lateral scaling and/or monolithical vertical integration, enable many new exciting applications of memristors in neuromorphic and other types of computing.

In my talk, I will review several such applications based on metal-oxide memristors which were a recent focus of my group. I will start with stateful material implication logic, which was originally suggested by HPL group. In our work, we showed that 3D version of this logic allows resolving Feynman grand challenge of implementing 8-bit adder in a volume smaller than 50-nm cube. I will then review our experimental work on memristor-based security primitives, in which we utilized device variations and their nonlinear I-Vs to demonstrate functionality and physical performance superior to those of conventional approaches. Finally, I will discuss Race Logic, a novel computing paradigm in which information is encoded in timing of the signals, so that a particular problem is mapped to a circuit with controllable memristor-based delay elements, and the solution is provided by measuring the time for the injected signals to propagate via circuit. Due to direct encoding of the computation to the underlying physics, Race Logic is extremely energy efficient for a variety of problems, such as bioinformatics and neurocomputing. I will conclude my talk with a summary on the device/material challenges, and potential future work, specific to the discussed applications.
Investigation of Ingaas-Based Pin Photodiode for High Quantum Efficiency
Authors: Oh Hwa Sub , Park Jong Min , Jung Sung Hoon , Lee Dong Wook , Lee Kang Seok
Published: February 2020

Photodetectors are key components in every photonic sensors like photonics, bio-signal detection in health care and internet of things, etc.1-3To serve as the converter from the optical to the electrical signal, the photodetector should offer high responsivity and sensitivity. Avalanche photodiodes are widely used as opto-electronic converter for highly-sensitive optical receivers. For covering the spectral range from 800 nm to 1600 nm wavelength, the avalanche photodiodes are needed sophisticated layer structures and supply voltage values in excess of 20 V. Particularly, the avalanche photodiodes are not appropriate to apply in comfortable applications like wearable devices and smart phones. In addition, the operation of the photodetector should be facilitated by a compact size, a low power supply voltage and temperature insensitivity. To overcome this problem, InGaAs-baed PIN photodiodes are investigated to obtain a high quantum efficiency and low leakage current.

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(Invited) 2D Materials: Large Scale Synthesis, Doping, and Transport
Authors: Robinson Joshua A
Published: February 2020

The last decade has seen nearly exponential growth in the science and technology of two-dimensional materials. The evoltion of 2D materials has gone from understanding basic properties in mechanically exfoliated to concerted efforts in synthesizing these layers over arge areas via chemical and physical deposition routes. Furthermore, we have demonstrated that direct synthesis of 2D heterostructure layers also allows for additional “dimensionality” for band structure engineering. In this talk, I will discuss recent breakthroughs in two-dimensional atomic layer synthesis and properties, including novel 2D heterostructures and novel 2D nitrides. Our recent works include development of an understanding of substrate impact on 2D layer growth and properties, doping of 2D materials to tune their elecrtronic properties from p- to n-type, selective area synthesis of 2D materials, and the first demonstration of 2D gallium nitride (2D-GaN). Our work and the work of our collaborators has lead to a better understanding of how substrate not only impacts 2D crystal quality, but also doping efficiency in 2D materials, and stabalization of nitrides at their quantum limit.
An Improved Li-Ion Battery Model to Study the Effect of Electrode Thickness
Authors: Xu Meng , Wang Xia
Published: February 2020

Battery modeling and simulation are efficient tools for optimizing cell design parameters and aiding in material selection. Researchers studied how design parameters affect battery performance by conducting parametric studies using physics-based models. Meanwhile some internal parameters such as the lithium-ion concentration and the local electrical potential can also be predicted through the simulation, while it is near-impossible to measure these variables.

One challenge of battery model development is that many parameters necessary for the battery model are difficult to measure or quantify. For example, the effective diffusion coefficient of lithium ions within the cell is affected by the electrode thickness. This diffusion coefficient, however, was usually treated as a constant in previous work.

This work develops an improved physics-based battery model. The model is developed based on the principles of mass and charge conservation, as well as the electrochemical kinetics for an NCM111 half-cell. The model treats the lithium ion diffusion coefficient as a function of the electrode thickness. The relationship between the lithium ion diffusion coefficient and the electrode thickness is determined by fitting the model with the experimental data. Four half cells are fabricated and tested, and the positive electrode for each cell has a thickness of 46um, 64um, 73um, and 130um, respectively. The lithium diffusion coefficient is found to increase linearly with the electrode thickness. The model is validated at various discharge rates for the cells with different positive electrode thicknesses. It is found that, the utilization of the cell capacity decreases slowly with the increase of the electrode thickness at a low discharge rate. At high discharge rates, the cell with a thick electrode has much poorer rate capability than that with the thin electrode. The physics-based model proposed in the research can be extended to include more cell design parameters. Thus it allows for a better understanding of the influence of cell design parameters on battery performance, and will enable the engineer to more easily design a cell with optimal performance.
Improved Performance of Silicon Anodes Using Copper Nanoparticle Additive
Authors: Bachand Gabrielle , Chidambaram Dev
Published: February 2020

Silicon continues to be an attractive anode material for use in lithium-based battery systems due to its high theoretical capacity and natural abundance. However, the widespread application of the silicon anode remains impeded due to notable, unfavorable characteristics observed during charge/discharge cycling. One such hindrance is the relatively poor electrical conductivity of silicon. Approaches to mitigating this issue often involve increasing the amount of conductive additive, but the additives are usually carbon-based or process-intensive. The focus of this research is the improvement of the electrical conductivity of the anode active layer by introducing nanoscale copper additive to the silicon structure. The fabrication of these anodes involved a simple, cost-effective procedure where the copper nanoparticle additive was homogeneously dispersed within the silicon active layer, and the anodes were tested using CR2032 type coin cells. The results of this research indicate excellent stability and improvements in the charge capacity of the cells with additive as a function of cycle testing. Surface characterization was performed using spectroscopy and imaging methods for comparison of anodes before and after charge/discharge cycling tests. SEM images show the successful integration of the copper nanoparticles within the silicon layer. Acknowledgement: This research was supported by the Office of Vice President for Research Innovation at the University of Nevada, Reno via an AIRE grant. Characterization of electrodes was conducted by Materials Characterization Nevada.
Graphene Coated Ni Foam As a Current Collector for N-Type Doped Si Thin Film Anode for Li-Ion Batteries
Authors: Zharbossyn Assem , Mukanova Aliya , Nurpeissova Arailym , Urazbayev Arshat , Kim Sung-Soo , Bakenov Zhumabay
Published: February 2020

Thin film silicon (Si) has gained a significant attention as an anode material for Li-ion batteries (LIBs), since its nanostructure retains structural integrity through minimizing the volume variation. However, 2D Si thin film experiences delamination from the current collector, and loss of electrical contact leads to further capacity fading. To overcome this issue, recent scientific investigations have shown that the 3D structure of electrodes (porous, rough-surface, etc.) is capable of suppressing volume changes upon lithiation/delithiation and providing large contact area between active material and current collector.

Here, we propose a novel electrode material for LIBs that comprises of Si on graphene coated Ni foam (G-Ni). Porous Ni foam serves as 3D structured highly electroconductive network, and graphene layer was employed with the purpose of improving adhesion and electrochemical stability of Si thin film electrode. Magnetron sputtering was used to deposit n-type doped amorphous Si thin film on G-Ni. Chemical vapor deposition (CVD) was applied to obtain a few layer graphene (FLG) on catalytic Ni foam. The as-grown anode material was tested in a half-cell configuration with metallic lithium as a counter and reference electrode. The results were compared with n-type doped amorphous Si thin film on pristine Ni foam. Galvanostatic cycling performance was evaluated in the voltage range from 0.1 to 1.5 V at a current density of ~ 32 µA cm-2. Si-G-Ni anode exhibited the initial areal capacity of around 141 µA cm-2 and the stable reversible areal capacity of around 80 µA cm-2 over 100 cycles. Si-Ni anode shows an initial capacity of 91 µA/cm-2 with a rapid capacity fading to approximately 30 µA cm-2 at 100th cycle. The results of characterization and electrochemical tests will be presented at the conference.

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Modified Electrodes for Improved Performance of Redox Flow Batteries
Authors: Emmett Robert Keathley , Roberts Mark E.
Published: February 2020

Redox Flow Batteries (RFBs) are an emerging electrochemical energy storage technology well-suited for intermittent energy sources, such as wind and solar. Integrated RFBs into grid-level energy systems would provide the storage necessary for alternative energy with only slight infrastructure changes. Currently, RFBs are limited by high material costs – from the use of precious metals – and/or low electrochemical activity. This work aims at improving power and energy of low-cost RFB electrolyte systems by doping carbon electrodes to facilitate Faradaic charge transfer at the interface, thereby decreasing costs and increasing accessibility of RFB systems. Carbon electrodes are modified with redox mediators to decrease the voltage drop and to increase charge transfer. Simulated half-cell experiments are conducted using carbon modified electrodes soaked with redox electrolytes s that are separated from pure base electrolytes by alkaline modified Nafion. Full cell testing is performed with modified Nafion separating the catholyte (0.7M Fe(CN)6 •3H2O and 1M NaOH) and the anolyte (0.35M Fe2SO4, 0.4M NaCl, Triethanolamine, and 3M NaOH). These electrolytes provide a test bed for evaluating all Iron RFBs as a cheaper alternative to Vanadium, therefore decreasing raw material cost and environmental impact.

Incorporating redox mediators into carbon electrodes improves kinetics elevating voltage efficiency and allowing higher current densities without ebbing discharge voltage. Power is modeled with current and voltage by Ohm’s Law (P=IE). Electrolytes with low inherit voltage efficiency display increased energy density due to fully capturing the redox behavior at raised current densities. Our alkaline discharge voltage difference has a maximum of 1.5 V with our modified electrodes. These electrodes showed a ~10x increase in power with catholyte half-cell testing (305 to 32W/Kg) and a ~4x increase in power with the anolyte (990 to 227Wh/Kg). Energy density improvements were observed for the catholyte (232%) and the anolyte (41%), lowering the volume of electrolyte needed. Long term stability experimentation revealed consistent, coulombic and voltage efficiencies for 1400 cycles (~4 years of daily use). These adaptations to RFB electrodes could also be applied to current RFBs to increase their performance, thereby decreasing material costs and improving cheaper alternatives.

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Novel Electrode Materials By Modification Route of Negative Thermal Expansion Materials
Authors: Liu Junnan , Schulz Bernd , Sharma Neeraj
Published: February 2020

Until now and most likely for the next few decades, lithium-ion batteries (LIBs) are likely to remain as one of the best energy storage devices. However, the price of lithium metal is increasing dramatically and some safety issues have been reported, which leads research towards alternative battery chemistries like sodium-ion and potassium-ion batteries to potentially alleviate some of these issues. Unfortunately, due to the larger size of sodium and potassium ions compared with lithium ion, they typically require electrode materials with larger voids to allow reversible insertion. In this project, we illustrate how some negative thermal expansion (NTE) materials fit these requirements and thus may be a candidate electrode for next-generation batteries. At the same time, we find that cation insertion into the voids changes the properties of the NTE materials. Modified NTE materials that tend towards zero thermal expansion (ZTE) materials could have significant advantages in use for industrial applications, for example, in fibre optic systems and as packaging materials for refractive index gratings or in high-value engineering industries. So in this research, we have investigated a new electrode material for next-generation batteries and manipulated their properties for applications in other fields.

Here we present the results on Sc2-xAlxW3-yMoyO12 as electrodes in Li, Na and K-ion batteries and the change in properties post ion-insertion.
Magnesium-Ion Battery-Relevant Electrochemistry of MgMn2O4: Crystallite Size Effects and the Notable Role of Electrolyte Water Content
Authors: Yin Jiefu , Brady Alexander B , Takeuchi Esther S , Marschilok Amy C , Takeuchi Kenneth J
Published: February 2020

Magnesium-ion (Mg2+) batteries (MIB) can be desirable relative to lithium ion batteries (LIB) as they offer the opportunity for high volumetric capacity due to the divalent nature of Mg2+ (3832 mAh/cm3 of Mg) and enhanced safety due to unlikely dendrite formation on Mg anodes. Spinel magnesium manganese oxide (MgMn2O4) has a tetragonal structure different from the typical cubic structure of spinels, due to distortion induced by the strong Jahn-Teller effect of Mn3+. In this work we present the first systematic study of MgMn2O4 as a cathode material in MIB. The materials were synthesized by a modified Pechini method, and annealing temperature was used to control the crystallite size of the products. The electrochemistry of two different sized samples was studied in magnesium based electrolyte with and without added water in the electrolyte. The MgMn2O4 samples were characterized by synchrotron X-ray powder diffraction (XPD), Transmission electron microscopy (TEM) data was collected and the BET surface area was determined. Capacity retention and rate capability was determined in the presence and absence of water in the electrolyte for both samples. Results with respect to crystallite size and water content will be discussed.
Thermodynamics and Kinetics of Lithium Dendrite Growth
Authors: Jana Aniruddha , Woo Sang Inn , Vikrant Karra Suryanaryana , García R. Edwin
Published: February 2020

Lithium metal anodes are a promising choice to achieve high energy density compared to current graphite anodes. However, lithium whisker growth (dendrites) during battery charging poses a major safety and performance concern for both lithium metal batteries, and overcharging of presently used graphite anodes in lithium-ion batteries. The present understanding of lithium electrodeposit growth is largely based on the Diffusion Limited Aggregation theory that results in a tip-controlled growth of fractal or dendritic structures. However, lithium electrodeposits have been reported in scientific literature to grow from the base at low current densities [1,2,3], that cannot be explained solely by electrodeposition kinetics. In this work, the mechanisms of lithium growth on anodes are analyzed assessing the combined contribution of electrochemical and mechanical driving forces. Physical mechanisms for tip-controlled and base-controlled growth modes are developed based on a thermodynamically consistent formulation, and have been validated based on the available scientific literature. Analytical and numerical solutions are discussed.

References:

[1] F. Orsini, A. D. Pasquier, B. Beaudouin, J. M. Tarascon, M. Trentin, N. Langenhuizen, E. D. Beer, and P. Notten. "In situ SEM study of the interfaces in plastic lithium cells." J. Power Sources 81 (1999) 918-921.

[2] O. Crowther, A.C. West, “Effect of Electrolyte Composition on Lithium Dendrite Growth.” J. Electrochem. Soc., 155 (2008) 806-811

[3] P. Bai, J. Li, F. R. Brushett, M. Z. Bazant. “Transition of lithium growth mechanisms in liquid electrolytes.” Energy Environ. Sci. 9 (2016) 3221-3229
Intercalation Cathodes for Rechargeable Aluminum-Ion Batteries
Authors: Jadhav Ankur , Messinger Robert J.
Published: February 2020

Rechargeable aluminum batteries have been a topic of great interest as aluminum metal has a high volumetric capacity and is the most abundant metal in the earth’s crust. However, few crystalline materials have been shown to reversibly intercalate aluminum ions into their structures. Recently, it has been shown that aluminum ions can reversibly intercalate/de-intercalate into the Chevrel Mo6S8 phase and the spinel Mn2O4 compound. However, the intercalation mechanisms are not well understood, particularly for the spinel Mn2O4, in part due to poor capacity retention and slow solid-state diffusion of the highly charged tri-valent aluminum ions within these crystalline structures. Better understanding of the intercalation mechanism of aluminum ions into these materials, including the dynamics and populations of aluminum ions, is important for the design and optimization of next-generation intercalation electrodes for aluminum batteries.

Our research has focused on these intercalation electrode materials for use in aluminum batteries with AlCl3/[EMIm]Cl ionic liquid electrolyte to study the intercalation process of aluminum ions into crystalline host structures. Cyclic voltammetry was performed at low scan rates to identify oxidation and reduction peaks corresponding to different intercalation sites during the charge-discharge process. Galvanostatic cycling was performed to observe capacity retention at different current densities. Ex situ multi-dimensional solid-state 27Al magic-angle-spinning (MAS) NMR spectroscopy was used to observe changes in the populations and local environments of the aluminum ions, as well as their dynamics. X-ray diffraction and electron microscopy were also used to analyze structural changes in the cathode materials as a function of state-of-charge. Our studies shed light on the intercalation mechanisms of aluminum ions in crystalline transition metal oxide and sulfide host structures.
Novel Carbon-Based Intercalation Structures for Rechargeable Aluminum Batteries
Authors: Xu Jeffrey , Messinger Robert J.
Published: February 2020

Rechargeable aluminum-metal batteries promise low cost and and high energy density, as aluminum metal has a theoretical volumetric capacity (8040 mAh/cm3) that is almost four times higher than lithium metal. Various cathode materials (e.g., V2O5 nanowires, Mo6S8, etc.) have been shown to reversibly intercalate aluminum ions, but obstacles such as low working voltages, self-discharge, and low mobilities of intercalated ions are typically observed. Novel graphite-based cathodes have recently been developed that exhibit high cyclability, good discharge voltage plateaus (ca. 2 V), and high rate performances when paired with aluminum anodes and a AlCl3/[EMIm]Cl ionic liquid electrolyte. However, the relationship between the local carbon structure and electrochemical properties of the electrodes is not well understood. Here, we report novel graphene-based electrodes that exhibit high specific capacity (e.g., >100 mAh/g at a current density of 66 mA/g) and discuss how the structural features of various carbon-based cathodes (e.g. synthetic, natural, and exfoliated graphite compounds) correlate with the electrode’s electrochemical properties and cell performance. Galvanostatic cycling and cyclic voltammetry analyses were performed to track electrode performance at various current densities, cycle numbers, and states-of-charge. Ex situ solid-state magic-angle-spinning (MAS) NMR spectroscopy was used to probe the local environments, relative populations, and dynamics of chloroaluminate and solvent species within the carbon electrodes, while X-ray diffraction and electron microscopy were conducted to analyze how the intercalation processes affected their local structures, periodic layering, and morphologies. These studies seek to unveil correlations of local carbon structure with electrochemical performance to aid the development of rechargeable aluminum-carbon batteries.
Evaluation on Catalytic Activity of Bi2-XRu2O7-Z Nano-Particles for Oxygen Reduction and Evolution By Titanium Disk Method
Authors: Sakurai Yuki , Kawaguchi Kenji , Hirose Yutaka , Nishiyama Hiroshi , Nakanishi Shinji , Iba Hideki , Morimitsu Masatsugu
Published: February 2020

A metal hydride (MH)/air secondary battery uses oxygen in air as the active mass of the positive electrode, and the positive electrode’s reactions are oxygen reduction during discharge and oxygen evolution during charge. We have been developing the bi-functional catalysts for these reactions, one of which is a pyrochlore type oxide, Bi2-xRu2O7-z nano-particles, obtained by co-precipitation method. The catalytic activity of such bi-functional catalysts for the oxygen reactions has been investigated with rotating disk electrode (RDE) method and the substrate of the RDE electrode used in alkaline solutions is normally graphite or glassy carbon disk on which the catalyst particles are loaded with ionomers or PTFE. However, such conditions are difficult to eliminate the influence of the carbon substrate, ionomers, or PTFE on the catalytic activity. In this paper, we present a novel method to evaluate the catalytic activity of Bi2-xRu2O7-z nano-particles using RDE method in which the substrate was a titanium disk and the results on the specific activity of Bi2-xRu2O7-z catalysts for ORR and OER at different oxide amount on titanium disk.

Bi2-xRu2O7-z particles were prepared by co-precipitation method which was carried out by the calcination of the precipitates obtained by adding excess NaOH solutions into the metal salt solution containing Bi(III) and Ru(III). The obtained particles were loaded on a titanium disk by dropping the solution prepared by dispersing the oxide particles in distilled water under ultrasonic agitation. No binder and no ion exchange resin were used for this preparation. The oxide loaded titanium disk was analyzed by SEM and used as the working electrode for oxygen reduction and evolution. The concentration of KOH solution at 0.1 mol/L was used at 25 oC. The electrolyte was bubbled with oxygen or nitrogen to measure the net oxygen reduction current. The specific activity of the oxide catalyst was evaluated by the currents normalized with the amount of the loaded catalyst, i
w, or the double layer charge, i
c.

The polarization curves with the oxide loaded titanium disk at different amounts of oxide were measured, and the results indicated that oxygen evolution current increased with increasing the weight of catalyst, while the specific activities, iC and iW, was unchanged with the loaded oxide amount, suggesting that the double layer charge and the catalyst’s amount are linear to the active surface area for oxygen evolution. Although the oxygen reduction current also increased with increasing the weight of catalyst, the specific activity, iW, decreased with increasing catalyst’s weight, which implies that the inner site of catalyst’s layer hardly works for the sites of oxygen reduction under the condition that the active species is only dissolved O2. More detail results will be presented in this paper.
High-Power, Low-Corrosion Aluminum-Air Battery
Authors: Hopkins Brandon James , Hart Douglas P.
Published: February 2020

Aluminum-air (Al-air) batteries are promising candidates for use in electric vehicles due to their high pack-level energy densities and to the abundance, recyclability, lightweight, low cost, and three-electron-redox properties of aluminum. Severe capacity fade during open-circuit conditions, however, has limited Al-air commercialization for over 50 years. Open-circuit capacity fade is caused by corrosion wherein the aluminum anode reacts with water from the aqueous electrolyte. Existing strategies to mitigate open-circuit corrosion, however, generally lead to reduced powers and energy densities. Optimized aqueous systems that use anode alloying and or electrolyte additives achieve high powers (500 mW cm-2) and energy densities (4 kWh kg-Al-1) but suffer from unacceptably high open-circuit corrosion currents (10 mA cm-2). In contrast, gel electrolyte systems yield low powers (91.1 mW cm-2) and energy densities (1.2 kWh kg-Al-1) but achieve no long-term open-circuit corrosion. Here we present a high-power (433 mW cm-2), energy-dense (3.9 kWh kg-Al-1) Al-air battery that experiences no long-term open-circuit corrosion.

Open-circuit corrosion can be stopped with no discernible effect to closed-circuit performance by displacing the aqueous electrolyte with a non-conducting liquid oil. When the battery is in closed-circuit conditions, the aqueous electrolyte can effectively displace the oil due to the natural and designed underwater oleophobic properties of the anode and cathode—the oil beads up and is flushed out by the electrolyte. The figure shows measured anode corrosion via hydrogen collection before and after the electrolyte has been displaced by oil and suggests that long-term open-circuit corrosion is completely stopped. We estimate that an Al-air vehicle battery pack with the proposed corrosion mitigation system could achieve energy densities of 222 Wh-kg-1 (2x that of Li-ion vehicle packs) and 183 Wh-L-1 (comparable to Li-ion vehicle packs) at costs as low as 18 US$-kWh-1 (33x less than Li-ion packs). We anticipate that our findings will further enable the use of aluminum as a critical element for energy storage.

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(Invited) Towards the Realization of Bulk Dynamic Strain By Vertically Aligned VO2 Nanowire Hybrid Arrays
Authors: Wang Yiping , Shi Jian
Published: February 2020

Significant epitaxial strain (~1%) is conventionally believed to exist only below the critical thickness limit at tens of nanometer scale, which greatly hinders the possible applications of strain engineering. The development of nanocomposite materials recently attempts to overcome the barrier by the inclusion of instantaneous phase separation between two materials during growth that ends up with a larger surface area, thus promoting large-scale strain. Here as a step forward, we report the growth of vertically aligned VO2 hybrid nanowire arrays that circumvents the pairing requirements for common nanocomposite and at the same time introduces the dynamic bulk strain by triggering the VO2 phase transformation. By controlling the growth temperature and oxygen vapor pressure, dense arrays of VO2 nanowires are obtained via a Chemical Vapor Deposition method. The ZnO/VO2 and BaTiO3/VO2 nanohybrid was then obtained by radio frequency sputtering. By varying the temperature to trigger the VO2 metal-insulator transition (MIT), we were able to dynamically strain the semiconductor overlayer. By studying both the single core-shell nanowire and the VO2 hybrid by photoluminescence and Raman spectroscopy, we show sound evidence of the dynamical strain from MIT. The utilization of phase transition from strongly correlated oxides thus provides a very promising approach for the realization of strain at bulk.
(Invited) Multi-Shelled V2O5 Hollow Microspheres Synthesized through Anions-Adsorption for High-Rate Lithium-Ion Batteries
Authors: Wang Jiangyan , Wang Dan
Published: February 2020

The future development of lithium-ion batteries (LIBs) is largely hindered by the lower capacity of cathode material. Owning to its high theoretical capacity, V2O5 has been widely considered as an attractive cathode material candidate for LIBs. However, its poor structural stability induced by irreversible phase transitions upon deep discharge limited its application in LIBs. In this article, through an innovative synthetic approach that combines the competitive anions-adsorption with a Trojan catalytic combustion process, multi-shelled V2O5 hollow microsphere (MS-V2O5-HMS) and other metal oxide MS-HMSs were achieved, greatly enriching the variety of multi-shelled oxide family. Moreover, benefited from its structural superiorities, MS-V2O5-HMS exhibited record-high specific capacities, remarkable rate capability and excellent cycling stability (447.9 and 402.4 mAh/g for the 1st and 100th cycle at 1000 mA/g, respectively). Such performance improvements significantly amend the wide capacity gap between the cathode and anode, opening up a new avenue for new generation LIBs development.

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(Invited) Eco-Friendly Nanogenerator and Active Sensor
Authors: Wu Jyh Ming
Published: February 2020

This work, we are the first to discover a high short-circuit current density of triboelectric nanogenerator using recycling rice husks as a source material. On the basis of our FTIR spectra, the nanoporous RHSiO2 fragments offers highly dense Si-O-Si, Si-OH, and OH stretching bonds compare to commercial SiO2 nanoparticles. The RHSiO2 film therefore exhibits strongly tendency to repel the electron because the H atoms have an extremely low electron affinity compared to the PTFE film. The highly positively charged surfaces of the nanoporous RHSiO2 film is five times higher than that of commercially non-porous SiO2 film based on our theoretical calculation results. Rice husk possess many advantageous traits such as their light weight, low cost, being environmentally friendly, high porosity, excellent robustness, exceptionally chemical and thermal stability for superior corrosion resistance, makes it a valuable material for industrial applications. Besides, the active sensor made by lead-free piezoelectric materials and triboelectric materials will also being discussed.

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