bluuebunny/crossref_metadata_2025 huggingface dataset:
Simultaneous Determination of Young’s Modulus and Residual Stress in PECVD a-SiC from Postbuckling Vibration of MEMS Beams
Authors: Pratap Rudra , Behera Amruta Ranjan
Published: February 2020

Silicon carbide is a highly desirable material for MEMS sensor applications due to its robustness against harsh environments, especially high temperature and chemically corrosive environments. It is also an excellent material for high frequency applications due to its high Young’s modulus (E). Unfortunately, it is also a very difficult material to grow on silicon as crystalline SiC. In comparison, it is much easier to grow SiC by PECVD and integrate into a MEMS stack. However, the PECVD grown SiC is amorphous and its material properties vary considerably depending on the process parameters. For example, the Young’s modulus of PECVD grown a-SiC has been reported in the range of 138-196 GPa. This large variation makes it difficult to design MEMS structures with desirable characteristics using a specific value of E. The other significant process induced uncertainty is due to the residual stress (σ) in the structure. In order to have reliable response from the micromechanical structures made of such SiC, it is important to have reliable values of both the residual stress and the Young’s modulus.

In this work, we report a method for simultaneous determination of E and σ by designing the test structures in the form of fixed-fixed beams and using their frequency response in buckled state. We exploit the invariance of even mode frequencies on residual stress to uncouple the effects of E and σ on the frequency, thus making it possible to determine E, along with another possible unknown- the underetch length. We subsequently use this information to find the residual stress from the odd mode frequencies. This evaluation requires a single sweep of frequency response from the buckled beam. The only condition here is that the beams have to be designed such that they result in buckled structures after release. This condition is essential, as only the buckled state guarantees the invariance of even modes on residual stress. Compared to other methods for determination of these properties, the advantage here is that we use a single method of measurement – LDV based frequency response measurement and a single type of test structures. Since the proposed method does not involve electrostatic actuation, in general it is applicable for dielectric thin films.

In order to ensure repeatability, we have used measured results from more than 100 test structures. For the procedure to work, we need at least one of each even and odd mode frequencies to estimate the unknown parameters. Since in our experiment we are able to measure first four frequencies, we have two modes each from odd and even category. Thus there are total four modal combinations of measured data available to proceed with estimation of material properties, i.e. 2nd – 1st, 2nd – 3rd, 4th – 1st, 4th – 3rd. However not all of these combinations are always equally feasible. We have developed a good understanding of the circumstances, which favours use of one combination against the others.
(Invited) Using Airbrushes to Pattern Reagents and Electrical Components on Flexible Substrates
Authors: Fan Hugh , Cassano Christopher , Sondhi Kartik , Nishida Toshi
Published: February 2020

This paper is related to two subject areas. One subject area is point-of-care (POC) testing, which includes lateral flow assays that use paper as the substrate material to carry a sample toward the detection zone. The other subject area is flexible electronics, which could lead to wearable sensors and other devices.

We report using airbrushes to pattern reagents and conductive inks onto a variety of flexible substrates including paper, thermoplastics, and elastomers. On paper substrates, we patterned small molecules, proteins, and DNA for sensing and biomarker detection. A range of operational parameters were used to control the line width and pattern contours. We employed an airbrush to pattern lines and dot arrays from hundreds of µm to tens of mm. Both enzymatic assays and DNA hybridization have been demonstrated in paper devices to show that the airbrushing method is amenable with various reagents and it has a potential to make paper-based devices more accessible.

On both thermoplastics and elastomers, we explored the use of an airbrush to pattern electrical components and compare it with screen-printing. Among these substrates, elastomers such as polydimethylsiloxane (PDMS) are more stretchable than thermoplastics such as thermoplastic polyurethane (TPU). However, commercial conductive materials such as silver inks are not formulated to be adherent to PDMS. As a result, we developed a surface modification method to achieve better adhesion. We compared airbrushed resistors with screen-printed resistors and studied their adhesion and abrasion resistance. Changes in the resistance of resistors fabricated on both PDMS and TPU were investigated after they are stretched numerous times. Other electronic components and circuits have also been fabricated on flexible substrates.
Lithium-Ion Battery State of Charge and Health Estimation – Electrochemical or Equivalent Circuit Model– a Review
Authors: Enoch-Oghene Samuel , Yesufu Thomas Kokumo , Olayiwola Pipeloluwa Samuel , Akhigbe Godswill Ehimengbale
Published: February 2020

With the advent of the fourth (4th) industrial revolution, energy needs are increasing. For this revolution which is expected to improve the quality of human lives to succeed – energy that is reliable, affordable and sustainable is a sine qua non. At the heart of energy storage are electrochemical devices of which batteries are key. However, batteries require monitoring in order to accurately estimate the states of charge (SOC) and health (SOH).

To effectively monitor SOC and SOH – there is a need to develop smart models which can accurately track and capture battery dynamic and static characteristics.

Two main classes of models are used in battery modeling are electrochemical and electrical models (equivalent circuit models, ECMs). The electrochemical models tend to be accurate but computationally expensive. They have also been reported as impractical for online usage. The reverse happens with ECMs but they are much less accurate.

This paper reviews models reported in previous works for Lithium-ion battery SOC & SOH estimation in battery management systems (BMS). Comparison is made of ELECTROCHEMICAL models as well as ECMs on the Lithium-ion batteries. This gives a working overview of how practical smart-battery models can be developed. This is in order to track accurately parameters such as film resistance and diffusion coefficients etc which are beneficial for accurate SOC and SOH estimation.
Study of Chronoamperometric Transients Obtained from Stainless Steel A304 in a Solution Type NACE TM 0177
Authors: Quirino Gutiérrez Josephine Inés , Veloz Rodríguez Maria Aurora , Uruchurtu Jorge , Reyes Cruz Victor Esteban , Hernández Ávila Juan , Rodríguez Lugo Ventura
Published: February 2020

Stainless steel is one of the most important materials, because its composition provides it corrosion resistance property, so this material it is known like a multipropose material. That is why A304 stainless steel is the most useful steel in chemical industry. At present, few authors have been interested in the study of corrosion with purpose of using it as a method of obtaining electrochemically active surfaces for technological purposes. In the present work, the results of the study of the energetic conditions for controlled pit production in stainless steel A304 are shown. The study was carried out using corrosive medium rich in chlorides like solution type NACE TM 0177. A flat three-electrode electrochemical cell was assembled using A304 stainless steel samples as working electrodes, saturated calomel (SCE) as reference electrode and a graphite bar as auxiliary electrode. This cell was coupled to a potentiostat-galvanostat GAMRY EIS 300 to perform Potentiodynamic Polarization in from OCP to 0.5 V. From the obtained results there were selected four different potentials for chronoamperometric transients study, which were performed using the electrochemical flat cell coupled to a potenctiostat-galvanostat and Zero Resistance Ammeter ACM Gill AC, at four different time laps. The obtained surface after the experiments was characterized with Scanning Electron Microscopy (SEM) to analyze the pits characteristics morphology and size.
Modification of Graphite Felt Surface for Electrochemical and Magnetic Treatment of Aqueous Contaminants
Authors: Calderon Zavaleta Sandy Luz , Kong Moreno Maynard J.
Published: February 2020

Iron nanoparticles (Fe NPs) are known to be applied efficiently to remove organic and inorganic pollutants from wastewater effluents, particularly by means of advanced oxidation processes (AOPs) such as in Fenton and electro-Fenton treatments.1,2 In these systems, surface-modified graphite felt electrodes were used either as anodes or as cathodes. Among other procedures, the surface modification of graphite felt cathodes has been achieved through the self-assembly of magnetite nanoparticles (Fe3O4 NPs).2 As for the modification of graphite felt anodes, the electrodeposition of gold nanoparticles (Au NPs) has been found to minimize the overall consumption of energy during electro-Fenton treatment operations, as opposed to most wastewater treament methods.3

In our research we are modifying the surface of graphite felt electrodes, by depositing Fe3O4 NPs on the cathode and Au NPs on the anode, in order to achieve high oxidation rates of organic compounds in aqueous systems. According to our calculations, a cell containing these combined electrodes are meant to operate under favourable energetic conditions in a range close to 200 mV and 18.1 mW m-2. These results are currently being optimized by controlling the electric charge distributed on the modified surface of these electrodes. On the other hand, we are also studying the use of magnetic interactions to remove paramagnetic probe species from aqueous phase in contact with graphite felt surfaces containing Fe3O4 NPs. Our preliminary results show that above 60% of such paramagnetic species can be removed by applying this method, which would enhance the efficiency in wastewater treatment processes.

References

Shahwan, T., Sirriah, S. A., Nairat, M., Boyacı, E., Eroğlu, A. E., Scott, T. B., & Hallam, K. R. (2011). Green synthesis of iron nanoparticles and their application as a Fenton-like catalyst for the degradation of aqueous cationic and anionic dyes. Chemical Engineering Journal, 172(1), 258-266.

Do, T. M., Byun, J. Y., & Kim, S. H. (2017). An electro-Fenton system using magnetite coated metallic foams as cathode for dye degradation. Catalysis Today, 295, 48-55.

Le, T. X. H., Esmilaire, R., Drobek, M., Bechelany, M., Vallicari, C., Nguyen, D. L., & Cretin, M. (2016). Design of a novel fuel cell-Fenton system: a smart approach to zero energy depollution. Journal of Materials Chemistry A, 4(45), 17686-17693.

Figure 1
The Hydrogen Peroxide Electrochemical Reduction Mechanism on Silver Nanoparticles
Authors: Cai Xiaosheng
Published: February 2020

The hydrogen peroxide reduction on a silver nanoparticle modified electrode shows a CE mechanism. A diffusion oxygen layer is formed via the disproportionation of hydrogen peroxide on silver nanoparticles, and then reduced to hydrogen peroxide during electrochemistry process. Cyclic voltammetry and simulation are combined to confirm this mechanism, demonstrating the electrochemical reduction signal depends on the interacting time between silver and hydrogen peroxide via the disproportionation step before the voltammetric analysis.
Structural Change of the Discharge Products in Lithium Sulfur Battery during Storage
Authors: Noh Hyungjun , Kim Yun-Jung , Lee Jinhong , Kim Hee-Tak
Published: February 2020

Lithium-Sulfur (Li-S) battery has been regarded as one of the most promising candidates to commercialize electric vehcles (EVs). Compared to Ni-Cd or commercialized Li ion battery, Li-S battery possesses many advantages, including high theoretical capacity (1,675 mAh/g) and low price of active materials. Energy density, rate capability, and cycling stabilities are regarded as key performances of any next generation secondary batteries, however, memory effect, which is history-dependent variation in battery state, is also a highly important battery chacteristic to be considered. As exampled with Ni-Cd battery, memory effect often leads to an accelerated cell deterioration [1]. In recent years, it was also reported that LiFePO4,which is a promising cathode material for EV applications, has memory effect [2] and it could result in a severe error of battery managment system (BMS). In spite of its importance, such memory effect has not been issued for Li-S battery.

In this work, the structural change of discharge products during storage and its influence on the subsequent cycle was studied. Structural changes with different storage time were clearly observed with ex-situ X-ray diffraction (XRD) and X-ray photoeletron spectroscopy (XPS) analysis. The XRD results demonstrated that the discharge products with a low crystallinity is converted to a more crystalline structure during a storage at room temperature. In addition, the XPS spectra collected at different storage time suggest that the structural change observed in XRD originates from a compositional change of the solid discharge products. The structural evolution of the discharge products significantly influence the overpotential of the subsequent charging step. This small perturbation in voltage profile can induce severe error in battery management system in EVs because it can lead to mis-estimate state of charge. The mechanism for the behavior and the impact on the Li-S performances will be presented and discussed.
Developing Graphene-Based Nanocomposites for Energy Conversion and Storage
Authors: Dong Lifeng , Yu Liyan , Pang Beili , Dong Hongzhou , Bao Xichang , Yang Renqiang
Published: February 2020

Due to its unique chemical and physical properties, graphene is a potential candidate for broad applications including energy conversion and storage. During the past several years, we have investigated applications of graphene as counter electrode for dye-sensitized solar cells, electron and hole transport layers in organic solar cells, catalyst and catalyst support for methanol/ethanol oxidation and oxygen reduction, and electrodes for supercapacitors. In this report, we will discuss how to tailor structures of graphene to fit their broad applications. The findings in the study above will provide information for design, synthesis and applications of graphene-based nanocomposites for energy conversion and storage.
Enhancement Supercapacitive Behavior of Electrodeposited Doped Polypyrrole for Supercapacitor Applications
Authors: Abdel-Fattah Tarek M , Ebrahim Shaker , Soliman Moataz , Shehab Mona , Elshaer Ahmed
Published: February 2020

Polypyrrole (PPy) have been extensively studied because of their low cost, easy production, good conductivity and controlled doping/de-doping properties as well as extensive applications in various areas such as energy storage, sensors, and electronic devices 1, 2. A detailed study of the effects of different electropolymerization conditions on the supercapacitive properties of polypyrrole (ppy) films doped using different dopants deposited on stainless steel was reported. The resulting thin films have been characterized by scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR) and transmission electron microscopy (TEM). The electrochemical properties of PPy thin films were investigated by cyclic voltammetry, electorochemical impedance spectroscopy (EIS) and galvanostatic charge/discharge. The results showed that the different electrodeposition operating conditions of synthesis and the type of dopant and the electrolyte used significantly affect the supercapacitive properties of PPy thin films. Thus, these results provide a useful orientation for the use of optimized electrodeposition modes for the growth of PPy thin films to be applied as electrode material in supercapacitors and achieved a specific capacitance of 266 F/g for amperometric deposited PPy thin film doped with 0.03 M dodecylbenzene sulfonic acid (DBSA) and using 0.1 M H2SO4 as an electrolyte.

References

Cai, Z.; Xiong, H.; Zhu, Z.; Huang, H.; Li, L.; Huang, Y.; Yu, X., Electrochemical synthesis of graphene/polypyrrole nanotube composites for multifunctional applications. 2017,
Synthetic Metals 227, 100-105.

Dubal, D. P.; Lee, S. H.; Kim, J. G.; Kim, W. B.; Lokhande, C. D., Porous polypyrrole clusters prepared by electropolymerization for a high performance supercapacitor. 2012,
Journal of Materials Chemistry 22, 3044-3052.

Figure 1: Cyclic voltammetry of PPy doped by DBSA and a schematic diagram of supercapacitor components

Figure 1
Synthesis of Cu Nanowires Using Ascorbic Acid in Aqueous Solution and Their Applications for Flexible Transparent Conductive Films
Authors: Yokoyama Shun , Motomiya Kenichi , Jeyadevan Balachandran , Tohji Kazuyuki
Published: February 2020

Cu nanowires (NWs) have been extensively studied to produce flexible, low-cost and high-conductivity transparent films because of their flexibility, low cost and high conductivity. Most synthetic procedures are based on chemical reduction, which often requires high temperature, organic solvents, and toxic reagents such as N2H4. It is desirable to develop a cost-efficient and environmentally friendly synthetic procedure for practical use. Furthermore, Cu NWs with high aspect ratios are required to improve performances of the transparent conductive films. Previously, we synthesized Cu nanoparticles based on chemical aqueous reduction employing ascorbic acid (vitamin C) as a reducing agent instead of commonly used toxic reducing agents. The key to the wire-like morphologies is the adsorption of surface ligands to metal crystal facets during the nucleation of NWs. Surface ligands selectively adsorbs onto {100} facets and consequently the anisotropic growth along the <110> direction occurs. In addition, reaction speed control and additives are also important for syntheses of NWs with high aspect ratios. In this study, we examined to synthesize Cu NWs by chemically reducing aqueous Cu chloride complexes using ascorbic acid as a mild reducing agent instead of the commonly employed toxic reducing agent. We chose polyvinylpyrrolidone (PVP) and NaCl as a surface ligand and an additive, respectively. In addition, we controlled aspect ratios of Cu NWs by changing type of capping agent, optimizing additives and atmosphere.

Cu chloride complexes were reduced to Cu metal through CuCl by ascorbic acid. The shape of the Cu metal particles highly depended on pH in the presence of PVP. Cu NWs were synthesized in the pH range of 3 to 4 while Cu nanoparticles were synthesized above pH 4. The reduction speed accelerated with increasing pH because the reduction capability of ascorbic acid increased with increasing pH. In fast reduction, all Cu chloride complexes were reduced to Cu particles before the anisotropic growth. In slow reduction, PVP effectively stabilized {110} facets of Cu rather than {111} facets, resulting in Cu NWs. The length and diameter of the Cu NWs were affected by atmosphere rather than additives and type of PVP. In the case of using ascorbic acid in aqueous solution, dissolved oxygen reacted with ascorbic acid to form hydrogen peroxide. Subsequently, hydrogen peroxide oxidized Cu metal surface and consequently prevented the anisotropic growth, resulting in Cu NWs with low aspect rations. By changing atmosphere from air to N2, we synthesized Cu NWs (length: 36 µm, diameter: 124 nm) from the reaction using ascorbic acid in aqueous solution. In our presentation, detailed results and discussion about the synthesis mechanism and performances as transparent conductive films will be introduced.
Effect of Electrolyte Composition on the Solid Electrolyte Interface (SEI) and Electrochemical Cycling of Lithium Metal Anodes
Authors: Lucht Brett L. , Brown Zachary Lee , Jurng Sunhyung
Published: February 2020

The role of the electrolyte composition in the formation and evolution of the solid electrolyte interface (SEI) on lithium metal anodes will be reported. A systematic investigation of the effect of composition of carbonate based electrolytes (salt, solvent, and additive) on the electrochemical performance of lithium metal anodes has been conducted. Electrolytes have been investigated in both Li/Li symmetrical cells and in Cu/LiFePO4 cells. The electrochemical performance of the cells is highly dependent upon the composition of the electrolyte. Optimization of the electrolyte composition results in dramatic improvement of the cycling performance of the lithium metal anodes. The structure and composition of the SEI for different electrolyte compositions has been investigated via a combination of Infrared spectroscopy with attenuated total reflectance (IR-ATR), X-ray photoelectron spectroscopy (XPS), and Transmission Electron Microscopy (TEM). The ex-situ surface analysis suggests a strong correlation between SEI structure and electrochemical performance.
(Invited) Effect of Electrolyte Electrode Interface Design on Lto Cell Performance
Authors: Ma Chengsong
Published: February 2020

Li plating on graphite electrode is a well-known issue which consumes active li and cause capacity loss and increase cell impedance. It also triggers degradation of active material and electrode conductive network. Cold temperature and high rate charge on graphite electrode can easily cause Li plating. The carbon anode is coated on Cu current collector and Cu will be oxidized at 0V cell potential. LTO is 1.5V separated from Li plating so it can be used for very fast charge and cold temperature charge. Al foil can be used as current collector for LTO electrode thus makes 0V cell storage feasible. Using LTO anode in Li ion cell can reduce or eliminate battery thermal management for weight reduction.

Saft has been studying LTO since 2010 and developed different LTO based cells for DOD, Rail, USABC. Recently Saft started to develop LTO cells for space application. The high DOD discharge capability make LTO cell have similar or higher usable energy than graphite cells in some space missions. Details of the cells and cell performance data will be presented.
First-Principles Modeling Study of Transition-Metal Dissolution from LiNi0.5Mn1.5O4 Spinel Surfaces
Authors: Alexandrov Vitaly , Intan Nadia N , Klyukin Konstantin
Published: February 2020

Mixed spinel materials such as LiM0.5Mn1.5O4 (M=Ni, Fe, Co) have emerged as a promising class of high-voltage cathodes for Li-ion batteries (LIB). These materials, however, suffer from transition metal dissolution that leads to the loss of active electrode species causing capacity fading and the formation of passivating solid electrolyte interphase (SEI). Herein, we employ a combination of static DFT, ab initio molecular dynamics and accelerated free energy sampling simulations to investigate adsorption/decomposition of electrolyte species, the mechanism and kinetics of Mn and Ni dissolution into the electrolyte. We especially analyze how dissolution pathways and rates are affected by oxidation states of transition metals on the surface, lithiation/delithiation state and the presence of surface protons and oxygen vacancies. This mechanistic study enables a better understanding of LIB interfacial chemistry and factors controlling dissolution process of redox active metals from spinel-type cathodes.
Sulfide Based Solid Electrolyte for Lithium-Sulfur Batteries
Authors: Lu Dongping , Wang Yuxing , Xiao Jie , Zhang Ji-Guang , Liu Jun
Published: February 2020

Lithium-sulfur (Li-S) batteries have the potential to deliver higher energy at lower cost compared to state-of-the-art Li-ion batteries. Greatest obstacles for deployment of Li-S batteries lie in polysulfide dissolution/shuttle and high Electrolyte/sulfur ratio required for stable long term cycling. In all-solid-state Li-S batteries (ASSLiS), S conversion undergoes the solid-state route therefore excludes the problems of polysulfide dissolution and high E/S ratio. Sulfide-based solid electrolytes are most suitable for ASSLiS and excellent performance of S cathode has been demonstrated.1

Due to the insulating nature of S particles, short diffusion length is needed to realize high S utilization. Liquid phase synthesis of sulfide-based solid electrolyte has advantages of easy preparation of nanosized particle, great flexibility and tunability, better scalability, and thus is desired for sulfur electrode preparation. It was found in our study the crystalline Li7P3S11 forms through a two-step reaction: 1) formation of solid Li3PS4∙ACN and amorphous ‘Li2S∙P2S5’ phases in the liquid phase; 2) solid-state conversion of the two phases.2 The other significant obstacle of ASSLiS is lack of solid state electrolytes that support stable Li metal cycling at relevant current density and cycling depth. We developed a sulfide-based solid electrolyte that has extremely high ionic conductivity of 4.7 mS/cm and kinetically stable, low-impedance interface (< 10 Ω cm2) with Li metal anode. Long term Li/Li symmetric cell cycling was achieved at 0.5 mA/cm2. In addition, the material remains stable in structure and ionic conductivity within two hours exposure in the dry room environment. In this talk, we present our progress on the sulfide-based solid electrolytes for ASSLiS.

References

H. Nagata, Y. Chikusa. Journal of Power Sources 264 (2014) 206-210

Y. Wang, D. Lu, Z Deng, J Xiao, J. Zhang and J. Liu. Chemistry of Materials 30 (3):990-997. doi:10.1021/acs.chemmater.7b04842
In-Situ Formation of Poly (Vinylene Carbonate) Based Gel Polymer Electrolyte for High Rate Cycling of Lithium Metal
Authors: Zhou Hongyao , Liu Haodong , Yue Xiujun , Liu Ping
Published: February 2020

Lithium metal based battery has high theoretical capacity and high energy density, ideal for large-scale energy storages such as in electric vehicles. However, dendritic deposition of lithium metal, which is especially severe at high current charging, causes serious safety problems. Previously, we reported in-situ formation of a single-component coating of crystalline lithium methyl carbonate (LMC) and stable cycling of lithium metals (ACS App. Mater. Interface, 2017, 30635). Here we extend the methodology and report a polymer gel coating on lithium metal surface formed in-situ from a pure vinylene carbonate (VC) solution . The polymerization rate of VC can be controlled by time, temperature, and the initiator, which resulted in a stable polymer gel. The mechanically robust gel can be used directly as an electrolyte layer in battery cells. Remarkably, the Li/Li cell cycled for 1000 hours without increase of resistance at a current density of 5 mA cm−2. A dense layer of lithium metal was observed at the interface of lithium and the gel, which indicated the stabilization of lithium metal by the polymer gel. The chemical structure of the polymer was analyzed by infrared spectroscopy and 1H NMR and evaluated as poly (vinylene carbonate) (polyVC) with a partially branched structure. The polymerization step is proposed to occur in a living radical fashion. The formation of electrolyte layers through in-situ polymerization is a promising approach to stabilize lithium metal electrodes.
Analysis of Interfacial Processes at Tin Anodes Using in situ Enhanced Raman Spectroscopy (SHINERS) and Advanced Electrochemical Techniques
Authors: Torres Bautista Blanca Estela , Bignaud Charles , Fillaud Laure , Perrot Hubert , Sel Ozlem , Lucas Ivan
Published: February 2020

As Li-ion batteries (LiBs) have become on one of the most reliable power sources, new electrode materials with higher lithium-retention capacity such as tin and silicon-based anodes as well as high voltage oxide or polyanion-type cathodes materials already stand as promising candidates to address the growing need of inexpensive, efficient energy storage systems for the forthcoming energy transition. Despite their initial promising capacity, continuous cycling ineluctably leads to a fading of their performances. The comprehension of failure mechanisms during operation will pave new routes for the design of battery electrode and electrolytes.

This work focusses on the study of interfacial processes at tin anodes, specifically on the dynamics of formation and composition of the solid electrolyte interphase upon cycling. The strategy proposed herein consists in associating enhanced Raman spectroscopy and advanced electrochemistry techniques derived from electrochemical impedance techniques (Quart crystal microbalance and AC electrogravimetry).

We report the compositional study of the SEI (1) by SHINERS using the plasmon resonance of gold nanoparticles which enhances the Raman signal of the compounds in close vicinity and compensates for the low Raman scattering cross section of the compounds forming the SEI (2). Using SHINs on tin electrodes, Raman signature of the SEI were successfully extracted ex-situ but also in situ through the electrolyte. Composition data are compared to structural information of the SEI extracted by EQCM (3,4). Influence of the electrolyte composition on the SEI properties will be detailed during the presentation.

References:

[1] F. Shi, et al, J. Phys. Chem., vol 118, 2014, 14732.

[2] S. Hy, et al, J. Pow. Sour., vol 256, 2014, 324.

[3] J.-T. Li, et al, Langmuir, vol 23, 2007, 13174

[4] Z. Yang, et al, Appl. Mater. Interfaces, vol 7, 2015, 26585

Figure 1
(Invited) Material Criticality and Energy Storage Materials
Authors: Eggert Roderick
Published: February 2020

A critical raw material provides essential properties to an engineered material or system, has few if any easy substitutes and is subject to supply-chain risks or concerns about long-term availability. In lithium-ion batteries, cobalt, lithium and graphite frequently are cited as possible critical materials. In addition, for emerging energy storage technologies, manganese, magnesium, vanadium and others are possible critical materials. In some cases, supply-chain risks relate to geopolitical concerns about nations mining or processing a raw material. In other cases, risks are due to a material's being produced largely as a by-product or companion to other major or host materials - in which case, a material's availability depends on developments in the markets for both the companion and host materials. Over the longer term, society is not in danger of running out of any single raw material. Rather, it faces the prospect of mining lower quality mineral resources, implying higher costs and greater environmental disturbances unless offset by process innovations. This talk reviews the nature and degree of 'criticality' for those raw materials with actual or possible important roles in energy storage.
Enabling a Safe Metallic Sodium Anode Using Chemically-Engineered Porous Copper Matrix with Cylindrical Core-Shell Skeleton
Authors: Li Weiyang , Wang Chuanlong , Wang Huan
Published: February 2020

Sodium (Na) metal is the most promising alternative for lithium metal as an anode material for the next-generation energy storage systems due to its high theoretical capacity, low cost and high natural abundance. However, huge volume change and severe dendrite growth of Na metal anode during repeated electrochemical stripping/plating result in rapid electrode degradation, low Coulombic efficiency, and even the risk of explosion caused by short circuit of the batteries. Because of its very soft nature, Na metal is susceptible to deform and degrade during both battery assembly process and electrochemical cycling. The volume and morphology change of the “hostless” Na severely aggravates the growth of Na dendrites. Thus, it is essential to seek an ideal host to support Na metal so as to maintain the high integrity of the electrode. Here we present the employment of a chemically engineered 3D porous copper (Cu) matrix with a cylindrical core-shell skeleton structure as a highly stable host for metallic Na anode, enabling a high Na areal mass loading of 70 mg cm-2, through a facile and cost-effective surface treatment on commercially available Cu foam in forming high performance composite anode for Na-based batteries. We find that the unique surface characteristics of the as-obtained matrix can not only facilitate uniform impregnation and confinement of Na within the matrix pores promoted by the chemical interaction between Na and the matrix, but also can divert the Na plating from the matrix skeleton towards the Na reservoirs within the pores upon cycling. Benefiting from our delicately surface-engineered matrix as a host for Na, we demonstrate an excellent Na anode cycling stability in carbonate electrolyte without any additives over 100 cycles (300 hours) at a current density up to 2 mA cm-2 with a high cycling capacity up to 3 mAh cm-2. A stable rate performance up to 3 mA cm-2 is also demonstrated. A full cell made of Na3V2(PO4)3 as cathode and the as-prepared surface-treated Na composite as anode is further tested, showing superior cycling performance and high rate capability (at 5C) compared with that using bare Na metal as anode. In addition to performance improvement, we systematically investigate the interfacial interactions between treated/untreated Cu matrixes and metallic Na to reveal how the surface property of the matrix skeleton greatly influences the electrochemical stability of Na anode.
(Invited) Safety Enhancements for Large Format, High Power, Lithium-Ion Cells and Batteries
Authors: Gitzendanner Rob , Puglia Frank , Ravdel Boris , Trebukhova Svetlana , Santee Stuart
Published: February 2020

Batteries are inherently a complex electrical, chemical and mechanical system. For such systems, safety can not be a single-point problem; and addressing safety requires a semi-holistic approach to provide a meaningful advancement of system-level safety. The Yardney Technology Center of EaglePicher Technologies is focused on the advancement of large Lithium-ion systems for high power applications such as aircraft and Directed Energy systems; which requires a targeted approach to system-level safety. The effort has focused on cell chemistry and design aspects, battery/module mechanical and thermal designs, and other design features to enhance overall tolerance to abuse, limit cell-to-cell propagation, and mitigate impact to other systems. Cell-level chemical and physical design enhancements help reduce both the likelihood and severity of a safety event. Reduced flammability electrolytes and proper material selection help to reduce the secondary impacts of a thermal runaway event in a cell or battery. Mechanical design of the cells improve thermal management of any heat generation. Thermal management of these systems is required not only for safety enhancements, but the ability to quickly and uniformly heat cells provides for better operation in very low temperature environments (as low as -40⁰C), and rapid cooling of cells during high rate discharges allows for multiple pulses or quick recharges for the next pulse. Thus, designing cells with high surface area to volume ratios assist in transferring heat both into and out of the cells for improved performance and safety. Analyzing the thermal design aspects of modules and batteries has led to designs that can manage the thermal load from a single cell thermal runaway event and prevent propagation to nearest neighbors in a battery pack. Other battery-level design features, such as flame suppression materials and proper thermal venting of gasses provide an additional level of safety enhancements for high power batteries. The overarching goal of all of these enhancements is to mitigate the effects of an abuse event within the battery and control impact to exterior systems and personnel. Demonstration test results for all of these design enhancements in large-format cells and batteries will be presented.
(Invited) Kinetics-Controlled Degradation Reactionsat Lipon/Li(x)CoO(2) and LiPON/Li-Metal Interfaces
Authors: Leung Kevin , Pearse Alexander J , Talin Albert Alec , Fuller Elliot James , Rubloff Gary W , Modine Normand A.
Published: February 2020

All-solid-state batteries are safe and viable approaches to energy storage. Detailed understanding of solid-solid interface structure-function relations is critical for the improvement and wide deployment of such batteries. The interfaces between lithium phosphorous oxynitride ("LiPON") solid electrolyte material, and lithium metal anode and Li(x)CoO(2) cathode surfaces, have been reported to generate solid electrolyte interphase ("SEI")-like products and/or disordered regions. Using electronic structure calculations, we predict that "defective" P-O-P sequences in disordered LiPON regions react with Li metal in battery operational timescales, but in general LiPON is kinetically inert towards lithium at room temperature. In contrast, transfer of oxygen atoms from low-energy Li(x)CoO(2) (104) surfaces to LiPON is much faster under ambient conditions. The mechanisms of the primary reaction steps, experimental results to partially corroborate these predictions, and possible mitigation strategies to reduce degradations are discussed. LiPON interfaces are found to be useful case studies in terms of addressing challenges in modeling redox-active oxide interfaces; differentiating electrochemical from interfacial chemical reactions; and highlighting the importance of kinetics-controlled processes during battery assembly, which often involves moderate processing temperatures.

This work was supported by Nanostructures for Electrical Energy Storage (NEES), an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Award Number DESC0001160. Sandia National Laboratories is a multimission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of EnergyâNational Nuclear Security Administration under contract DE-NA0003525.
(Invited) Evaluating Strategies for Dendrite Prevention in Li Metal Anodes
Authors: Srinivasan Venkat , Barai Pallab , Higa Kenneth
Published: February 2020

With the resurgence of interest in lithium metal anodes, the long-standing problem of dendrite prevention has once again gained popularity as a research focus. There is significant debate as to the actual cause of dendrite growth with different mechanisms observed in polymer and ceramic cells, and different morphologies observed when changing operating conditions.

Over the last year, we have been developing mathematical methods that combine electrochemical effects (kinetics, mass transfer and ohmic) with mechanical interactions (elastic deformation, plastic deformation, and fracture) to understanding the role of material properties and operating conditions on dendrite growth. We have used this model to examine dendrite formation in polymer electrolytes, both single-ion conducting and non-single-ion conducting. In addition, we have been examining the formation of dendrites in ceramic materials.

This talk will use this combined electrochemical/mechanical approach to provide insights into the cause of dendrite formation in polymer electrolytes, the effect of changing operating conditions like current density, the effect of pressure, and the effect of changing material mechanical and transport properties. We also examine the impact of grain boundaries on dendrite formation in ceramics and provide insights into the challenges that need to be solved to enable this system.
(Invited) Multiscale Modeling of Uptake and Transport in Redox-Flow-Battery Separators
Authors: Crothers Andrew Robert , Darling Robert M. , Radke Clayton J. , Weber Adam Z.
Published: February 2020

Understanding transport phenomena is a critical component of electrochemical engineering in terms of optimizing energy-conversion and -storage devices including fuel cells and flow batteries. In these systems, transport through the ion-conducting electrolytes including both polymer (e.g., perflurosulfonic-acid (PFSA) membranes) and liquid electrolyte control the overall device performance. In this talk, recent work on the multiscale modeling of ionomers will be discussed including thermodynamic and multiscale continuum treatments of multi-ion transport through the ionomer nanodomains and the relevant changes to the chemical potential resulting in selective ion and water uptake. This treatment involves a simple accounting for polymer backbone deformation, donnan equilibrium, solvation, and interactions with external electrolyte. The continuum modeling at the nanodomain uses a mean-field local-density theory that accounts for ion/ion, ion/water, and ion/polymer effects. In addition, upscaling methodologies using resistor-network approaches informed by experiment that explore phenomenon-dependent transport pathways for ions and electrolyte will be introduced and demonstrated to yield nonlinear and nonintuitive results. The overall modeling results will be compared to experimental property and uptake data and used to explain the nature of observed phenomena including electro-osmosis, ion conduction, and ion transference.

Acknowledgements

This work was funded under the Fuel Cell Performance and Durability Consortium (FC PAD) funded by the Energy Efficiency and Renewable Energy, Fuel Cell Technologies Office, of the U.S. Department of Energy as well as by the ARPA-E IONICS program under contract DE-AC02-05CH11231.
Predicting and Optimizing the Performance of Thick Battery Electrodes
Authors: Tang Ming , Wang Fan
Published: February 2020

The use of thick electrodes in Li-ion batteries has received widespread interest in recent year as a promising way for energy densisty enhancement and cost reduction, but it faces the instrinsic challenge of slow transport kinetics due to the increased ion diffusion distance between cathode and anode. It is thus important to carefully optimize the microstructure of thick electrodes to improve their rate performance for specific applications. Here we report an efficient computational approach to predict and optimize the performance of thick electrodes as an alternative to the pseudo-2D simulation technique, which is the de-facto modeling method for battery design at the cell-level. We derived an analytical model for predicting the charge/dicharge capacity of the battery cells based on the observations that a pseudo-steady state of ion transport in electrolyte is typically established in thick electrodes during discharge/charge process. As shown in Figure 1a, the model provides predictions on the depth of discharge of battery cells within a range of discharge rate and cell configuration that are in very good agreement with the psedudo-2D battery simulations, but only consumes a negligible amount of computational cost. As a demonstration of its utility, the model is used to efficiently predict the dependence of a cell's specific energy on the cathode porosity and thickness given a required specific power and identify the optimal parameter values (Figure 1b). Our method makes it feasible to design and optimize non-uniform electrode structures that involves a large number of parameters in the design space.

Figure 1 (a) Comparison of depth of discharge (DoD) predicted by pseudo-2D simulation and our analytical model for various electrode thickness in half or full cell configurations. (b) Contour plot of cell-level specific energy of a full cell as a function of cathode porosity and thickness at a given power density. The thick line represents the maximal specific energy at different cathode thicknesses.

Figure 1
Mathematical Modeling of Electron and Hole Tunneling through the Deposit Layers in Li-Oxygen and Li-Sulfur Batteries
Authors: Andrei Petru
Published: February 2020

The main discharge products in Li-oxygen and Li-sulfur batteries, as evidenced by x-ray microscopy, are predominantly crystalline lithium peroxide, lithium superoxide, and lithium sulfide [1, 2]. These products have a high electric resistivity and, practically, the only conduction mechanism in these materials is electron and hole tunneling. In this presentation we develop a mathematical model to describe the tunneling current density in Li-oxygen and Li-sulfur batteries. The model is based on the WKB approximation, which is used to model the electron and hole tunneling probability through the insulating layer. The derivation of the tunneling current is relatively similar to the derivation by Simmons [3], which analyzed metal-insulator-metal systems (MIM) but, in our case, the mathematical derivation is carefully modified to describe metal-insulating-electrolyte systems (instead of MIM systems). More importantly, we derive closed-form equations for the tunneling current density that can be readily used in finite element simulations or in the mathematical modeling of the ohmic losses across the discharge layer in Li-oxygen and Li-sulfur batteries. As we expect the tunneling current density depends on the shape of the conduction and valence bands, applied voltage, and permittivity (because of the image charges created in the carbon). At normal applied voltages (below 0.5 V) the tunneling currents are negligibly small, however, they can become large enough to affect the discharge characteristics of the batteries for low discharge rates (e.g. below 0.1 C) if the barrier heights of the valance band in the case of holes and conduction band in the case of electrons are small. More details about the mathematical derivation, the approximations used in the derivation, the closed-form equations, and a comparison with current models in the literature will be presented at the meeting.

[1] N. Cañas, S. wolff, N. Wagner, K. Andreas Friedrich, In-situ X-ray diffraction studies of lithium-sulfur batteries, 2012.

[2] K.R. Ryan, L. Trahey, J.S. Okasinski, A.K. Burrell, B.J. Ingram, In situ synchrotron X-ray diffraction studies of lithium oxygen batteries, Journal of Materials Chemistry A, 1 (2013) 6915-6919.

[3] J.G. Simmons, Generalized Formula for the Electric Tunnel Effect between Similar Electrodes Separated by a Thin Insulating Film, Journal of Applied Physics, 34 (1963) 1793-1803.

Figure 1
Carbon Nano-Onions Synthesized By Laser Pyrolysis As Catalyst Support in Proton Exchange Membrane Fuel Cells
Authors: Yeon JeHyeon , Choi Indae , Choi Mansoo
Published: February 2020

Proton exchange membrane fuel cells (PEMFC) typically utilize nanostructured carbon (such as carbon black, carbon nanotubes, graphene and porous carbon) as the support material for catalysts. The durability and electrical conductivity of the material are important contributors to the fuel cell performance, as well as the structural design to maximize the triple phase boundary between the fuel, the catalyst and the electrolyte membrane. In view of engineering the structure and composition of the carbon catalyst support, a versatile manufacturing method with flexibility in size, shape, structure, and properties (such as electrical conductivity) of the carbon material would open up a chance to investigate an expansive composition matrix for potential improvements of the cell performance. In addition, for potential commercialization, processes that are clean and high-throughput are desired.

Laser pyrolysis of hydrocarbons has been established as a widely adopted gas phase production of carbon nanoparticles. In particular, multilayered particles with concentric graphitic shells, commonly called carbon nano-onions, are of interest as the size, shape and the number of graphitic shells are easily tuned by adjusting the experimental parameters. In this work, we present a CO2 laser induced pyrolysis of gaseous hydrocarbons (such as acetylene and ethylene) that generates various types of carbon nanoparticles, and demonstrate that these carbon nano-onions have superior durability and electrical conductivity to commonly used commercial carbon materials such as Vulcan XC-72. Platinum-decorated carbon nano-onions have been used to fabricate PEMFCs and they are shown to have comparable performance to conventional cells, and the accelerated stress test reveals that the durability of the cells have improved.