bluuebunny/crossref_metadata_2025 huggingface dataset:
Reaction and Mass Transport Simulation of 3-Dimensional All-Solid-State Lithium-Ion Batteries for the Optimum Structural Design
Authors: Itoh Fumiya , Inoue Gen , Kawase Motoaki
Published: February 2020

In order to increase energy density and enhance safety, all-solid-sate lithium-ion batteries have been developed as a storage battery for electric vehicle (EV). However, it is necessary to decrease a mass transfer resistance and a reaction resistance because its power density is too low to be applied for EV. In recent years, 3-dimensional (3D) electrode such as an interdigitated electrode is proposed, which can increase power density without losing high energy density [1, 2]. The purpose of this study is to simulate the electrochemical reaction and lithium-ion transport phenomena of 3D all-solid-state batteries for the optimum design of 3D structure which can fully charge within 5 minutes.

Based on the porous electrode theory, reaction and mass transport at the galvanostatic discharge were simulated [3, 4]. In this work, the solid-solid interface resistance and the volume change of active materials were neglected. The temperature distribution in the cell was presumed to be uniform. Assuming that active materials are nano-scale particles, lithium diffuses rapidly enough in an active material particle. Therefore, the lithium concentration distribution in the particles was also supposed to be uniform. Figure 1shows some examples of 2D and 3D structures for simulation. These structures are symmetry and the cell is the same size in all structures. In addition, all volume of cathode, solid electrolyte (SE) and anode layer is equal. LiCoO2 and graphite were employed as cathode and anode active materials, respectively. Each structure was simulated at a rate of 1-10C and an SE ionic conductivity of 1-0.01 S/m. And discharge properties of 2D and 3D structures were investigated.

Figure 2shows the galvanostatic discharge curve obtained from the simulation at a rate of 10C and an ionic conductivity of 1 S/m. There was no big difference between the discharge curves of Str.1-13 at a rate of 1C. However, discharge properties of some structures at 10C were degraded because a voltage drop occurred before depth of discharge reaches 1.0. As shown in Figure 2, Str.2 and Str.3 displayed high discharge property at 10C as well as at 1C. This result indicates that discharge property was improved by complicating 3D structures. Furthermore, a cell design parameter was proposed and investigated for the optimum structural design.

References

[1] R.W. Hart, H. White, B. Dunn, D. Rolison, Electrochem. Commun.
5 (2003), 120-123.

[2] Y. Suzuki, H. Munakata, K. Kajihara, K. Kanamura, Y. Sato, K. Yamamoto, T. Yoshida, ECS Transactions, 16 (26) (2009), 37-43.

[3] M. Doyle, T. F. Fuller, J. Newman, J. Electrochem. Soc., 140(1993), 1526-1533.

[4] G. M. Goldin, A. M. Colclasure, A. H. Wiedemann, R. J. Kee, Electrochimica Acta, 64 (2012), 118-129.

Figure 1
Electrolyte Properties of Li4P2S6 -- Simulations and Comparison with Experiment
Authors: Holzwarth Natalie A. W. , Hood Zachary D. , Kirkham Melanie J.
Published: February 2020

Structural and electrolyte properties of Li4P2S6 have been investigated with computer simulations and with a variety of experiments including X-ray and neutron diffraction, electrochemical measurements, and thermal response. Compared with other thiophosphate materials, Li4P2S6 is quite stable; maintaining the same crystal structure up to temperatures as high as 950 degrees C in vacuum and up to 280 degrees C in air. While its ionic conductivity is relatively small, its Arrhenius activation energy of 0.29 eV is similar to technologically viable electrolytes. Computer simulations  provide insight into the causes and effects of disorder in this material and indicate that the mechanism of the ion conductivity is dominated by interstitial sites.  Simulations of idealized interfaces of a Li4P2S6 electrolyte with a  Li metal anode are also analyzed.

Acknowledgements:

The computational portion of this work was supported by NSF grant DMR-1105485. Z. D. Hood was supported by the Higher Education Research Experiences (HERE) program at Oak Ridge National Laboratory. The experimental portion of this work was primarily conducted at the Center for Nanophase Materials Sciences and  ORNL’s Spallation Neutron Source , which are DOE Office of Science User Facilities.  Cameron Kates, Shiba Adhikari, and Chengdu Liang also contributed to this project.  Assistance from Jong Keum, Andrew Payzant, Gayatri Sahu,  Hui Wang,  Keerthi Senevirathne, Cynthia Day, and Abdessadek Lachgar are also gratefully acknowledged.
Mg Desolvation and Intercalation Mechanism at the Mo6S8 Chevrel Phase Surface
Authors: Wan Liwen , Perdue Brian Robert , Apblett Christopher A. , Prendergast David
Published: February 2020

In recent years, there are strong interests to develop new divalent electrochemical systems that can potentially provide higher energy density compared with current Li-ion batteries, but with lowered cost and improved cycle stability. Mg-ion battery technology, first established in 2000 [Aurbach et al., Nature 407, 724 (2000)], proves the cyclability of such divalent battery cell. In this manuscript, we examine Mg-ion desolvation and intercalation process at the Chevrel phase Mo6S8 cathode surface using first-principles based methods. It is known that in chloride based electrolytes, Mg2+ is strongly coordinated by the counterion Cl- with a binding energy on the order of 3 eV. During cell discharge, this Mg-Cl bond is broken and Mg is intercalated into the cathode material. Our simulation indicates the broken of such strong ionic bond can only be possible if another electrophilic agent, such as Mo, exists on the cathode surface to attract Cl- away from Mg2+. Once Mg is intercalated, the Chevrel phase surface becomes chlorinated, i.e. all open Mo sites are attached with Cl-. Further simulations show that this chlorinated surface can continue to interact with incoming MgCl+ species and form various MgCly adsorbates. These surface adsorbates can then release neutral MgCl2 back into the electrolyte and reopen Mo sites to the electrolyte to permit continuous Mg intercalation. The newly release MgCl2 species will likely increase salt concentration near the cathode surface and initiate MgxCly oligomerization and precipitation, which are characterized by full-cell experiments.

Our results suggest that when designing new divalent battery systems, one should consider the compatibility issue between the electrolyte and the cathode material that has often been overlooked. For example, with the potential of increasing cell voltage, transition metal oxides, such as V2O5 and MoO3 are proposed as the Mg intercalation cathode. However, these layered oxide structures usually do not present open metal sites, but rather oxygen at their surfaces, which is less likely to attract any strongly coordinated counterions away from Mg2+ to assist its desolvation and intercalation. Therefore, such oxide cathodes usually require weakly coordinated anions to be used in the electrolyte, which may no longer be compatible with Mg metal as the anode material.

This work is supported as part of the Joint Center for Energy Storage Research (JCESR), an Energy Innovation Hub funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences.
Synthesis of II-VI Semiconductors Thin Films By Ecald from Citric Buffer
Authors: Kowalik Remigiusz
Published: February 2020

Electrochemical Atomic Layer Deposition (ECALD) was proposed by Stickney and coworkers[1] to obtain low-cost production of structurally well-ordered II-VI compound semiconductors, such as transition metal chalcogenides, on polycrystalline as well as on single-crystal electrodes. The method is based on the alternate underpotential deposition (UPD) of atomic layers of the elements that form the compound. Underpotential deposition is the well-known phenomenon whereby the potential necessary to deposit one element onto a second element occurs before that necessary to deposit the element on itself. The phenomenon is surface limited, so that the resulting deposit is generally limited to one atomic layer.  Moreover, when the UPD is performed on a single crystal face the resulting deposit is epitaxial.

The free energy change involved in the compound formation is generally negative enough to produce the underpotential deposition of the metallic element on a layer of the previously deposited nonmetallic element, and vice versa. The number of cycles, which determines the thickness of the deposits, can be repeated as many times as desired to obtain deposits of practical importance. By limiting depositions to single atomic layers, no three dimensional growth is promoted and epitaxy should result.

Once the deposit is formed, the amount of the elements deposited is determined from the charge involved in their stripping. Such investigations always confirmed the stoichiometric ratio of the elements forming the compound.

The fundamental object to the method is the necessity of singling out the proper electrochemical conditions to be used, i.e. potentials, reactants, electrolytes and pH. Moreover, being the method based on surface phenomena, the electrochemical conditions are also dependent on the substrate used. Here, the first results of the electrodeposition of CdSe and ZnSe on polycrystalline gold from citric buffer are reported.

Acknowledgments

This work was supported by the Polish National Center of Science under grant 2011/01/D/ST5/05743.

1.             Gregory, B.W. and J.L. Stickney, Electrochemical atomic layer epitaxy (ECALE). Journal of Electroanalytical Chemistry, 1991. 300(1-2): p. 543-561.
Nanostructured, Bimetallic, Noble Metal Powders Prepared By Atomic Layer Electroless Deposition for Applications in Sensing and Catalysis
Authors: Cappillino Patrick J , Sugar Joshua D , El Gabaly Farid , Cai Trevor , Liu Zhi , Stickney John Lewellen , Robinson David B.
Published: February 2020

Bimetallic materials exhibit properties that are superior to their constituents in many applications. Examples include alkyne hydrogenation catalysts (selectivity), fuel cell cathodes (higher activity), formic acid oxidation catalysts (resistance to poisoning) and hydrogen storage materials (faster kinetics). A key to improving our understanding of these phenomena is preparation of these materials with nanoscale control of composition. Although recent efforts have focused on controlled synthesis of bimetallic particles, there remains a strong need for a synthetic strategy combining the properties of (i) scalability on high-surface-area substrates, (ii) uniform deposition and (iii) low-temperature processing conditions that preserve nanostructures.

Presented herein are details of an Atomic Layer Electroless Deposition (ALED) technique that meets these criteria. By exposing Pd powder to dilute hydrogen in nitrogen gas, sacrificial surface PdH is formed along with dilute interstitial hydride. Once the flow of reagent is terminated, addition of metal salts facilitates galvanic displacement of the hydride, and controlled deposition of an overlayer having sub-nanometer thickness. This process can be cycled to create mesoscale layers. The electroless nature of ALED and its ambient processing conditions, make it an excellent complement to existing strategies of noble metal ALD.

We will present high-resolution scanning electron microscopy demonstrating that conformal layers can be formed, and that the degree to which three-dimensional growth occurs is dependent upon deposition conditions. In addition, depth-profiles of bimetallic powders of varying adlayer thickness, generated using energy-resolved X-ray photoelectron spectroscopy, will be presented. We will also show evidence for fractional adlayer coverage based on the infrared spectra of adsorbed organic molecules. These data provide a proof of concept for using materials prepared by ALED as high-selectivity, high-dynamic-range sensors for various target molecules. Finally, we will demonstrate the ability of materials prepared in this manner to act as bi-functional catalysts.

Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-AC04-94AL85000. The Advanced Light Source is supported by the Director, Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231. Support for JLS was in part provided by the National Science Foundation, Division of Materials Research, grant #1006747. The authors also thank Mark Homer for STEM sample preparation.

Figure 1
Towards a Mechanistic Understanding of Platinum Thin Film Deposition on Au(111)
Authors: Schwarz Kathleen , Moffat Thomas
Published: February 2020

Pt group metals and alloys thereof have important application as magnetic thin film materials and catalysts for fuel cell applications. The production of ultrathin Pt group metals thin films currently relies on surface-limited place-exchange, requiring the time-consuming exchange of electrolyte, and resulting in films with a possibility of metallic impurities. A new method was recently reported for the production of thin films through the use of large overpotential deposition of Pt on Au(111) using Pt(II) electrolytes with a high halide concentration. Under these conditions, two-dimensional islands form, and three-dimensional growth is inhibited. The mechanisms of this two-dimensional deposition and the self-termination are not completely understood, although experimental evidence suggests that the self-termination is due to underpotential deposited hydrogen blocking the surface of the newly-formed platinum film, preventing additional layers from growing. We use computational techniques coupled with electrochemical experiments to probe the reaction pathway and associated barriers to gain more insight into the growth process and its extendability to other metals.
Electropolymerization of Poly(phenylene oxide) Films with Variable Thickness
Authors: Timmermans Marina , Deheryan Stella , Mattelaer Felix , Detavernier Christophe , Vereecken Philippe M.
Published: February 2020

Electrochemical polymerization is a useful method for polymer coating formation that allows room temperature processing, selectivity in electrode modification and conformal deposition on high aspect ratio structures. This work is focused on the electropolymerization of phenol to prepare pinhole free poly(phenylene oxide) (PPO) films. PPO films have been shown promising for various applications including protective coatings of the battery electrode from electrochemical dissolution [1], blocking layers for reducing the leakage current in supercapacitors [2] or gate dielectric in field effect transistors [3]. Our interest in this study is to examine the electrodeposition of PPO on various conductive surfaces by cyclic voltammetry leading to its rapid passivation. We show that a thin PPO film that conformally coats porous MnO2 electrode can act as a lithium ion conductor with electronically insulating properties, interesting for battery applications. The thickness of the PPO film was altered by controlling the potential applied between the working and reference electrodes of an electrochemical cell (see Figure). Electronically insulating PPO films with the thickness of 10-50 nm were deposited on TiN substrates. Thermal stability of the PPO films of various thickness was investigated in various environments by in-situ spectroscopic ellipsometry in the temperature range of 0-400oC. The ellipsometric results of the PPO thickness lay in the same range as the AFM measurements. It was found that thicker films withstand the annealing temperature up to 250oC prior to the onset of the PPO thickness decrease. This insight is important for the optimization of the  PPO anneal conditions in order to remove the residual solvent and potentially improve the polymer chains stacking.

[1] Rhodes C.P., et al, J. Non-Cryst. Solids, 350 (2004)

[2] Tevi T., et al., J. Power Sources, 241 (2013)

[3] Lipatov A., et al., Chem. Mater., 27 (2015)

Figure 1
Removal of Cyanide in Solution Using Electrodeionization
Authors: Tian Yun , Yang Yang , Fan Zheng , Wu Xingxing , Wu Zucheng
Published: February 2020

Toxic and harmful gases such as HCN are emitted during the polyacrylonitrile-based carbon fiber production process. Electrodeionization(EDI) was applied to remove the CN-in the solution which obtained after the absorption by NaOH from the waste gas stream, meanwhile regenerate NaOH solution back to the absorption process.

A modified three-chambers EDI device was applied. There were three chambers from the cathode to the anode in proper order: negative electrode chamber 1 which was fed in the CN- solution from the bottom to the top, resin chamber 2 filled up with anion exchange resin, and the positive electrode chamber 3 flowing NaCl solution. There were anion-exchange membranes dividing the chambers between the chambers. CN- in chamber1 transferred into the resin chamber, and part of OH- produced by ionization under the DC power would regenerate the resin and make the CN- going through into chamber 3 continuously. Also, Cl2 was produced on the anode electrode in chamber 3 by electrolytic action which would oxidize the CN- to harmless substance. And, the main OH- stayed in chamber 1 so thatNaOH was regenerated. Effects of the configurations like the sizes, and operation conditions such as the current density and the flow rate were investigated to examine the feasibility of device. With the optimization of operation conditions, the effluent water of chamber 3 can reach below 0.5mg/L which meets the requirement of cyanide discharge standard.
Synthesis of Noble Metal Nanoparticles By Atomic Layer Deposition Utilizing Self-Assembled Monolayers Templates
Authors: Zhu Qianqian , Cao Kun , Shan Bin , Chen Rong
Published: February 2020

Self-assembled monolayers (SAMs) are widely used as surface modification structures for thin films synthesis and designed nanostructures fabrication1. Alkyltrichlorosilanes is a group of SAMs widely applied in the field of area-selective atomic layer deposition (AS-ALD). The closely packed octadecyltrichlorosilane (ODTS) SAMs could act as monolayer resist to prohibit ALD2, while the pinholes on unsaturated ODTS SAMs could act as nucleation sites to initiate ALD growth. Thus the distribution and structure of pinholes, including its size and density, are important factors for utilizing SAMs template to fabricate nanoparticles via ALD. Many studies characterize SAMs and pinholes by atomic force microscopy (AFM), scanning electron microscopy (SEM), scanning tunneling microscope (STM), etc3. Most of these methods could provide the microscopic information on the pinhole structures, yet the information from these methods is quite localized and hard to obtain statistical average and full-scale information about the pinhole size and distribution density.        

Here we report utilizing electrochemical impedance spectroscopy (EIS) to study the size distribution and loading of initial nanoparticles grown in those pinhole sites.  EIS is a powerful and surface sensitive characterization technique to obtain the average and global characters of the detected surfaces4,5. In this study, the properties of unsaturated ODTS SAMs are characterized with EIS methods. The relationship between SAMs growth time and the pinholes properties has been established. With the SAMs immersing time increasing, the sizes and density distribution are both reduced. For SAMs sample immersed over long time, at least 24 hours, negligible pinholes are observed. Furthermore, Pd ALD process has been carried on those SAMs modified substrates. The distribution of Pd nanoparticles corresponds well with the pinholes. The results show that the nanoparticles grown on SAMs modified substrates depend on the pinholes properties. With SAMs modified substrate, ALD grown noble metal nanoparticles with uniform size and controlled loading density can be achieved.  

 References:

J. Christopher Love, Lara A. Estroff, Jennah K. Kriebel, Ralph G. Nuzzo, George M. Whitesides, Chem. Rev. 2005, 105, 1103−1169

Rong Chen, Hyoungsub Kim, Paul C. McIntyre, Stacey F. Bent, Chem. Mater. 2005, 17, 536-544

Han-Bo-Ram Lee, Marja N. Mullings, Xirong Jiang, Bruce M. Clemens, Stacey F. Bent Chem. Mater. 2012, 24, 4051–4059

Byung-Wook Park, Do-Young Yoon, Dong-Shik Kim, Journal of Electroanalytical Chemistry 2011, 661, 329–335

Xiaoquan Lu, Huiqing Yuan, Guofang Zuo, Jiandong Yang, Thin Solid Films 2008, 516, 6476–6482
Surface Chemistry of III-V Semiconductors After Wet Etching with HCl and H2O2
Authors: Mancheno-Posso Pablo , Muscat Anthony J.
Published: February 2020

The introduction of III-V semiconductors in MOSFET technology has been hindered by the lack of good quality III-V oxides. These oxides are a source of surface states at the band edges or within the band gap that are a detriment to electronic performance. The removal of these oxides is typically accomplished by immersion in acid or basic aqueous solutions. The continuous etching of the substrate is achieved by adding an oxidizing agent. After etching, a smooth oxide-free surface is desired. HCl and H2O2 mixtures have been used for the etching of III-V materials.

In this work, we perform a comparative study of the etching of the (100) crystal plane of GaAs, InAs, InP, GaSb, and InSb. The selective etching of these materials was studied as a function of H2O2 concentration (0.0001-5 M) and at a fixed HCl concentration (0.01 M). The etching rate was determined by profilometry measurements made on wafers patterned with conventional photolithography. The chemical composition of the surfaces after etching was studied with X-ray photoelectron spectroscopy (XPS) and the final roughness was characterized with atomic force microscopy (AFM). The etching rate of GaAs and InAs (same group V atom) showed a volcano-shaped dependence on H2O2 concentration (0.01 to 1 M). A maximum etching rate was observed at 0.1 M with a value of 1.1±0.1 nm/s for GaAs and 0.9±0.3 nm/s for InAs. For 1 M H2O2, the etching rate decreased to 0.035±0.010 nm/s for GaAs and 0.26±0.13 nm/s for InAs. The etching rate of InP increased when the H2O2 concentration was changed from 0.01 to 0.1 M, and showed no significant increase for higher concentrations within the error of the measurements. The etching selectivity of GaAs to InP increased from about 55 at 0.01 M H2O2 to 137 at 0.1 M H2O2, and then decreased to 4 at 1 M H2O2. The etching rate of GaSb and InSb (same group V atom) increased linearly between 0.0001 and 0.001 M H2O2, but dropped significantly at higher concentrations. These substrates were visibly oxidized at high H2O2 concentrations and HCl etching was unable to keep up with the rate of oxidation. Substrates with the same group V atom exhibited similar etching trends in the range of H2O2 and HCl concentrations studied. This suggests that the removal of the group V atom is the rate limiting step in the etching of these materials. Temperature programmed desorption (TPD) of a GaAs sample after immersion in HCl showed that the surface was terminated by As-Cl bonds. These results along with the chemical composition of the samples after etching will be used to propose reaction mechanisms of III-V semiconductors in HCl and H2O2 mixtures.
(Invited) Characterization of Individual Si/SiO2 Interface Traps: Direct Observation of Single P
b0 Centers by the Charge Pumping (CP) Method and Correction of the Conventional CP Theory
Authors: Tsuchiya Toshiaki
Published: February 2020

It is considered that interface traps will cause various reliability and variability problems in future nanoscale MOS devices, such as fluctuations in threshold voltage due to the variation in the number of interface traps involved, and the random position of the traps. Therefore, characterization of individual traps will be considered to become increasingly important.

   Charge pumping (CP) technique is known to be a highly-precise method for evaluating the density of interface traps, therefore, the method has been widely used for the last 30 years. The CP current I
CP can be simply described by I
CP=fqN, where f is the gate pulse frequency, q is the electron charge, N is the total number of traps contributing to the CP current. Therefore, the conventional belief is that the density of interface traps N
it can be derived from N
it=I
CP/(fqA
G), where A
G is gate area of MOSFETs, and the CP current per trap should be fq. Actually, observation of single interface traps has been demonstrated by the CP method.

   We made systematic measurements of CP current from single Si/SiO2 interface traps, and successfully observed for the first time that their current range is 0<I
CP≤2fq, but not a fixed value of fq. In order to judge if CP characteristics are due to single interface traps, we need to separate the CP characteristics into components from individual traps. For this purpose, we utilized some effective procedures, i.e., observation of the differences in threshold voltage in the local area where each trap is located, the dependences of CP characteristics upon on-time and off-time of the gate pulse. From the on-time and off-time dependences, we can observe electron capture processes and electron emission (i.e., hole capture) processes in individual traps, respectively.

   Using these procedures, we confirmed if CP characteristics are due to single interface traps. We measured seventy samples, and among them, twenty-seven samples showed single trap properties. Thus, we concluded that CP current from single Si/SiO2 interface traps is indeed in the range of 0<I
CP≤2fq, but not a fixed value of fq, and the conventional CP theory is basically wrong. Moreover, using the procedures, we demonstrated fundamental trap-counting by the CP method. The current range 0<I
CP≤2fq can be expected from the nature of the P
b0 centers, therefore, the obtained results mean that we succeeded to directly and electrically observe single P
b0 centers, for the first time.
A Modified Electrolyte for a Rechargeable Manganese-Zinc Alkaline Cell
Authors: Hertzberg Benjamin Joseph , Steingart Daniel A , Chamoun Mylad , Hsieh Andrew , Davies Greg , Huang An , Meng Shirley
Published: February 2020

There is a need for reliable, low-cost energy storage for electric vehicle applications. While advanced Li-ion batteries may possess sufficient power and energy density to be useful for electric vehicles, their high manufacturing and materials costs make them unsuitable outside of a relatively small market niche. Alkaline batteries, one of the most common modern forms of primary battery, are potentially ideal for electric vehicles. These cells depend on a reaction between zinc (Zn) and manganese dioxide (MnO2) to generate energy. This reaction gives alkaline batteries a relatively high energy density and a low cost per kilowatt-hour, but phase transformations occurring during deep discharge, particularly the formation of the electrochemically inactive ZnMn2O4 phase, prevent recharge. In a typical alkaline battery, useful rechargeability with minimal capacity losses can only be achieved if no more than 10% of the cathode’s capacity is used. [1]

We have developed a new, low-cost electrolyte which prevents the formation of electrochemically inactive phases, even during deep discharge. A capacity of 360 mAh/g on a cathode basis has been achieved cycling against zinc for more than 60 stable cycles, without evidence of ZnMn2O4 formation. We have also characterized the effects of this electrolyte as well as more conventional alkaline battery electrolytes using both conventional and in-operando synchrotron XRD techniques. We will discuss the impact of electrolyte formulation, charging and discharging protocols, and conductive additives on the performance of the system, and hypothesize on the mechanism by which this electrolyte prevents formation of electrochemically inactive phases.

References:

1. Shen, Yuwei, and Karl Kordesch. "The mechanism of capacity fade of rechargeable alkaline manganese dioxide zinc cells." Journal of power sources 87.1 (2000): 162-166
Electrochemical Behavior of Some Sodium Nickel Oxides for a Sodium-Ion Battery
Authors: Park Kyusung , Yu Byeong-Chul , Goodenough John B.
Published: February 2020

Sodium-ion batteries have been considered as a cheap alternative to lithium-ion batteries. Electrode materials for a sodium-ion battery and a lithium-ion battery have interesting similarities and differences in materials characteristics and electrochemical properties. Layered lithium nickel oxide, LiNiO2 has been developed to achieve a high capacity battery, but it shows interslab cation mixing and poor thermal stability. Li2NiO2 has also been studied mainly as a cathode additive to compensate the lithium loss at the anode side owing to the SEI formation. It can provide a large irreversible charging capacity at the first cycle, but it exhibits a significant oxygen evolution upon charging. In this study, we report electrochemical properties of their sodium analogues for a sodium-ion battery. The materials were prepared via solid state reactions and characterized with powder XRD and SEM. Electrochemical properties of them are examined with coin half- and full-cells, and further characterized with ex-situ electrode XRD analysis. The experimental data was correlated to DFT+U calculations. Details on the materials and electrochemical properties will be presented at the meeting.
Amorphous Iron Phosphate : Potential Host for Various Charge Carrier Ions
Authors: Kim Sungjin , Gim Jihyeon , Song Jinju , Baboo Joseph Paul , Alfaruqi Muhammad Hilmy , Jo Jeonggeun , Kim Dongyun , Kim Yeoeun , Kim Jaekook
Published: February 2020

Since 1990, the global demand for electricity has increased twice as much as the demand for energy overall, and the demand for electricity is expected to further increase by more than two-thirds over the next 20 years. Energy storage/conversion technologies have therefore become a crucial research topic as we seek to make society sustainable. In particular, electrical energy storage is critical not only for supporting electronic, vehicular and load-leveling applications but also for efficiently commercializing renewable solar and wind power. In response to the ever-increasing global demand for viable energy-storage systems, sodium and potassium batteries appear to be promising alternatives to lithium ion batteries because of the abundance, low cost and environmental benignity of sodium/potassium. Electrical energy storage via ion-intercalation reactions in crystalline electrodes is critically dependent on the sizes of the guest ions. Herein, we report on the use of a porous amorphous iron phosphate synthesized using ambient temperature strategies as a potential host that stores electrical energy through the feasible insertion of mono-/di-/tri-valent ions. A combination of ex situ studies reveals the existence of a reversible amorphous-to-crystalline transition in this versatile electrode during electrochemical reactions with monovalent sodium, potassium and lithium. This reconstitutive reaction contributes to realizing specific capacities of 179 and 156 mAh/g versus sodium and potassium at current densities of 10 and 5 mA/g, respectively. This finding facilitates the feasible development of several amorphous electrodes with similar phase behavior for energy-storage applications.

Figure 1
A Structurally Stable α-MnO2 nanorod Cathode for Enhanced Reversible Divalent Zinc Storage
Authors: Mathew Vinod , Xiu Zhiliang , Alfaruqi Muhammad Hilmy , Gim Jihyeon , Kim Sungjin , Song Jinju , Vu Thi Trang , Tung Duong Pham , Baboo Joseph Paul , Kim Jaekook
Published: February 2020

In this study, a nanorod-type α-MnO2 cathode prepared by a facile hydrothermal reaction was utilized for rechargeable aqueous zinc-ion battery (ZIB) applications. Electron microscopy studies revealed rod-type particles with approximately 20 and 200 nm of width and length, respectively. When tested for zinc storage properties, the nanorod cathode exhibited an initial discharge capacity of 176.8 mAh/g at a current density of 83 mA/g and demonstrated nearly 100% Coulombic efficiencies under prolonged cycling. Further, rate performance measurements revealed that specific capacities of 43.33 and 31.48 mAh/g were attained at current densities as high as 1333 and 1666 mA/g. Ex-situ XAS investigations confirmed the reversibility of electrochemical Zn-insertion into the a-MnO2 electrode. Moreover, a combination of ex-situ synchrotron XRD studies, visualization and pattern-fitting software programs not only established the electrochemical Zn-insertion into the host a-MnO2 structure but also indicated that the unit cell volume of the [2x2] tunnels in the a-MnO2 host expands by approximately 3.12% during Zn-insertion. The present study thus paves the way for further development of aqueous ZIB as an ideal energy storage system due to its excellent safety and reliability.
High Performance TiP2O7 Based Intercalation Negative Electrode for Aqueous Lithium-Ion Batteries Via a Facile Synthetic Route
Authors: Whitacre Jay , Wu Wei , Shanbhag Sneha , Chang Jiang , Rutt Ann
Published: February 2020

Combining high energy mechanical alloying with intimate carbon coating has proven effective in improving electrochemical performance of polyanion-based materials (1, 2). Ball milling with intimate carbon helps to prepare a homogenous mixture of precursors and reduce particle size during following thermal treatment (3, 4). In addition, this combination can decrease the thermal treatment time needed (5). In this study, we demonstrated TiP2O7/graphite prepared by high energy mechanical alloying combined with intimate carbon coating has superior cycling performance in aqueous lithium-ion electrolyte.

The TiP2O7/graphite composite material was prepared by an intensive mechanical mixing solid state synthesis method at 700°C. Physical properties were characterized via powder X-ray diffraction, Rietveld refinement, SEM, BET and TGA. Electrochemical performance was evaluated in both a three electrode test setup and two electrode coin cells via cyclic voltammetry and galvanostatic cycling tests. The TiP2O7/Graphite composite demonstrates excellent cycling performance in 1M Li2SO4 when matched with LiMn2O4 as a positive electrode: when cycled at C/2 for 150 cycles, the capacity retention is over 91% with coulombic efficiencies exceeding 99%. The initial discharge capacity obtained at a C/10 rate is 91mAh/g which was about 75% of theoretical capacity 121mAh/g.

Reference:

1.            W. Wu, A. Mohamed and J. F. Whitacre, Journal of The Electrochemical Society, 160, A497 (2013).

2.            W. Wu, J. Yan, A. Wise, A. Rutt and J. F. Whitacre, Journal of The Electrochemical Society, 161, A561 (2014).

3.            J.-K. Kim, G. Cheruvally, J.-W. Choi, J.-U. Kim, J.-H. Ahn, G.-B. Cho, K.-W. Kim and H.-J. Ahn, Journal of Power Sources, 166, 211 (2007).

4.            J.-K. Kim, J.-W. Choi, G. Cheruvally, J.-U. Kim, J.-H. Ahn, G.-B. Cho, K.-W. Kim and H.-J. Ahn, Materials Letters, 61, 3822 (2007).

5.            L.-X. Yuan, Z.-H. Wang, W.-X. Zhang, X.-L. Hu, J.-T. Chen, Y.-H. Huang and J. B. Goodenough, Energy & Environmental Science, 4, 269 (2011).

Figure 1
Effect of Pth-Coated Li Powder Anode in Lithium Metal Batteries System
Authors: Lee Jae Won , Hwang Sun Woo , Yoon Woo Young
Published: February 2020

The Li metal anode is one of interested electrode which applied on the post-LIB (Li ion battery) system. However the dendrite growth on the Li surface made hard to commercialized Li metal anode battery. In this reason, we fabricated Li powder by Droplet Emulsion Technique (DET) and coated polythiophene (Pth) on the Li powder by polymerization method.[1] The thiophene monomer and FeCl3 was stirred in CHCl3 solution and polymerized by in situ on the surface of lithium powder.[2] This experiment formatted uniformly PTh layer on the Li powder surface. This Pth layer was helpful to suppressed the lithium dendrite growth when Li ion deposited on the Li powder (charge process). To fabricate the electrode Pth-coated lithium powder was placed on the stainless steel (SUS) mesh (15 Φ) and pressed 20 kg cm-2 regularly. Also the LiV3O8 (LVO) was used as cathode electrode because it is non-lithiated material. The cell was assembled in the coin type cell (CR2032) in Dry room.

The morphology of lithium dendrite was observed by the FE-SEM, TEM and the coating layer was investigated by NMR and FT-IR. The conductivity of lithium powder anode and polythiophene-coated lithium powder was also measured by impedance analysis. All the cell were charged and discharged to 25% of the theoretical lithium capacity (965 mAhg-1) at 0.2 0.5, 1, 2 C-rate respectively. The result was analyzed EIS and CV.

[1] Shin-Kook Kong, Bok-Ki Kim, Woo-Young Yoon, J. Electrochem. Soc, 159 9) A1551-A1553 (2012)

[2] Haipeng Guo, Li Liu, Hong, Hong Shu, Xiukang Yang, Zhenhua Yang, Meng Zhou, Jinli Tan, Zichao Yan, Hai Hu, Xianyou Wang, J. Power Sources, 247 (2014) 117-126
Advanced Characterization of Materials Electronic Structure with High Energy-Resolution X-Ray Spectroscopy
Authors: Sokaras Dimosthenis , Weng Tsu-Chien , Nordlund Dennis
Published: February 2020

High-resolution hard x-ray spectroscopies (XES, HERFD, RIXS, XRS) are  well-established characterization tools for providing insights of material’s electronic and geometric structure. At SLAC National Accelerator Laboratory we have developed recently a set of high-resolution x-ray spectroscopic capabilities with oustanding throughput and efficiency. These developments have made feasible the routine study of the electronic structure and the ligand environment of metal coordination compounds and active centers in metalloproteins, electrochemical process under in-situ conditions, PV's, as well as studies on catalytic systems under ambient conditions.Representative examples of in-situ application in batteries, electrocatalysis, hydrogen storage, etc. will be presented and discussed from the ongoing spectroscopy programs of Stanford Synchrotron Radiation Lightsource.
Flexible Graphene Electrode-Based Organic Photovoltaics with Record-High Efficiency
Authors: Park Hyesung , Chang Sehoon , Zhou Xiang , Kong Jing , Palacios Tomas , Gradecak Silvija
Published: February 2020

Flexible organic and hybrid organic-inorganic solar cells require both the flexible photoactive media and flexible electrodes with good conductivity and transparency. Graphene has been proposed as a promising flexible electrode due to its mechanical and chemical robustness, excellent electrical and optical properties, and potentially low-cost processing.  We have designed graphene electrode-based flexible polymer solar cells with thieno[3,4-b]thiophene/benzodithiophene (PTB7) and [6,6]-phenyl C71-butyric acid methyl ester (PC71BM) by resolving the issues occurring at the interface between graphene and charge transporting semiconducting materials.  We demonstrate highly efficient flexible devices with power conversion efficiencies of 6.1% (anode) and 7.1% (cathode) achieved via thermal treatment of molybdenum trioxide (MoO3) electron blocking layer, direct deposition of ZnO electron transporting layer on graphene. The advances in this work demonstrate graphene has great potential as a promising transparent electrode in a variety of flexible optoelectronic devices.
Thermal Engineering of GaN Semiconductor Devices
Authors: Graham Samuel
Published: February 2020

The development of gallium nitride (GaN) on a variety of substrates from Si to diamond has been used to create a variety of devices for both RF and power electronics technologies.   In general, GaN devices can accommodate faster switching speeds, higher junction temperatures, and high voltages, allowing for devices operating at higher power with increased efficiency in smaller form factors. However, the lattice mismatch between c-axis hexagonal GaN and other non-native substrates requires the use of buffer layers in order to grow high quality, relaxed GaN required for advanced devices.  Such layers can add to the thermal resistance which impacts to overall device thermal performance and thus, device reliability. In addition, these interfacial layers impact the growth and residual stress in the GaN epitaxial layers that can limit the overall voltage limits of lateral HEMT devices.

In this work we use a variety of experimental techniques to measure the thermal boundary resistance (TBR) for GaN on Si, SiC, and diamond substrates.  The impact of the structure of the interface on the overall TBR and thermal conductivity of the GaN layers grown by MOCVD will be discussed.  In addition to the TBR, the overall stress in the devices caused by growth on the differing substrates, measured by Raman spectroscopy, will be presented.  A unique superlattice structure used to reduce the stress in GaN layers on Si will also be highlighted.  Finally, the electro-thermomechanical performance of GaN devices under DC and pulsed operation will be presented where the temperature of the devices was measured using Raman Spectroscopy while the mechanical deformation was measured by Scanning Joule Expansion Microscopy.   Data will show that rapid heating and high tensile stresses near the drain side edge of the gate during pulsed operation is dependent on the bias conditions, the TBR, substrate material, and the mechanical properties of the device.  Overall, challenges associated with the structure of GaN devices that must be overcome for effective thermally management will be presented.
Catalytic Design through Computational Modeling: Exploring the Electrochemical Oxidation of Glycerol By Nitroxyl Radical
Authors: Hickey David P , Matanovic Ivana , Schiedler David , Atanassov Plamen , Sigman Matthew S , Minteer Shelley D.
Published: February 2020

Recently there has been an increased interest in the development of small molecule electrooxidation catalysts such as (2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO), for use in the anodic compartment of a biofuel cell. Some TEMPO derivatives are capable of electrochemically oxidizing short chain alcohols and various sugars to the corresponding aldehydes and carboxylic acids under physiological aqueous conditions. However, building libraries of such a catalyst is difficult due to the limited number of commercially available TEMPO derivatives and the lack of modular synthetic pathways to more complicated TEMPO structures. A promising alternative to the physical preparation of such libraries is the use of computational modeling to allow for in silico catalytic screening of a much wider range of TEMPO compounds.

We have developed a computational model based on simple geometry optimization and population analysis to probe the catalytic activity and oxidation potential of TEMPO-derived species. Redox potentials were calculated from the free energy cycle of TEMPO oxidation while the relative catalytic activity was modeled using multidimensional analysis involving the computed pKas of various protonation states of the hydroxylamine form of TEMPO along with the corresponding redox potentials. We will also discuss how analysis of the atomic polar tensor (APT) charge of TEMPO can provide insight into the factors that affect its redox potential.
Hydrogen Generation from the Hydrolysis of Sodium Hypophosphite Using CoB2O4 Catalyst for Fuel Cell Operation
Authors: Gorelishvili Giorgi , Nikoleishvili Paata , Tsutsumia Gigla , Kveselava Valentina , Kurtanidze Rusudan , Koiava Nana , Sharabidze Daviti
Published: February 2020

The goal of the work involves a radically new approach – establishment of possibility of the use of sodium hypophosphite (NaH2PO2) as hydrogen source or the study of the process of its reforming; synthesis of corresponding catalysts and their testing for generation of hydrogen. It is well known that in the process of chemical nickel plating at 80-95 0C, in the course of an interaction between sodium hypophosphite and water the formed atomic hydrogen reduces nickel on the surface of the plated metal. Nickel plating with the participation of sodium hypophosphite is self-catalytic. Overall catalytic reaction of the interaction between hypophosphite and water may be presented as follows:

H2PO 2‾ + H2O → H2PO 3‾ + H2

We have established that in the absence of nickel-ions in the hypophosphite solution, and with the use of so-called Raney nickel catalyst, an intensive separation of hydrogen is possible at high temperatures (80-95 0C), but at room temperature the process practically stops. Hence, by selection of corresponding catalyst the hydrogen production from hypophosphite solution and its use in fuel cell are possible. In the work the hydrogen evolution from aqueous solution of sodium hypophosphite was studied at 10-30 0C by CoB2O4 catalyst. In case of 2M NaH2PO2 solution hydrogen evolution rate was 3.4-3.6 ml sec-1 g-1, which was enough for 0.6 W H2–O2 fuel cell operation.

The designate project has been fulfilled by the support of Georgia National Science Foundation. Any idea in this publication is possessed by the authors and may not represent the opinion of “Georgia National Science Foundation"
Synthesis of VC-C Nanocomposite for Electrochemical Applications
Authors: Mahajan Mani , Singh K. , Pandey O. P.
Published: February 2020

Carbon-coated vanadium carbide (VC-C) nanocomposite were synthesized by single-step chemical-reduction route in an autoclave at the temperature of 600oC. In this experiment, vanadium pentode (V2O5) was used as precursor, magnesium as reducing agent (Mg) and acetone as carbon source. The gases produced by the decomposition of acetone generate carbon and H2/CO2 gases at high temperature which further creates high pressure inside the autoclave.  The processing parameters were optimized for the formation of single phase vanadium carbide (VC). The structure, morphology, and thermal stability of the obtained product were studied by XRD, TEM and TGA/DTA techniques, respectively. The N2 adsorption-desorption isotherm indicated the mesoporous structure of the VC. The electrochemical properties of the obtained C@VC were studied by the cyclic voltammetric studies.
Electrochemical Analysis for the Identification of Electrode Reaction in Ni-YSZ Anode as for Solid Oxide Fuel Cell
Authors: Im Ha-Ni , Lim Dae-Kwang , Lee Tae-Ryong , Yoo Young-Sung , Choi Mihwa , Song Sun-Ju
Published: February 2020

The most widely studied anode for oxidation of hydrogen in solid oxide fuel cells (SOFCs) is the Ni/YSZ cermet. A detailed understanding of the rate-limiting steps in Ni-YSZ anodes is highly desirable from an optimization point of view. One of the most promising way of complex system is to define the reaction by impedance spectroscopy.

In principal, impedance measurement is comprised of electrolyte response, electrode response, and transport limitations for supply of reactants and removal of products. The electrolyte response is readily separated out as a series resistance, in simple geometries it can even be used to indicate the magnitude of the microscopic electrode contact area. For high temperature impedance model, transport restriction are believed to be negligible in typical setups. But anode with low resistance transport restrictions may contributes significantly.

The electrode reactions like charge-transfer reaction are suggested to occur in the vicinity of the active triple-phase boundary (TPB) line. The active TPB is defined as the line where the Ni network, the YSZ network, and open pores meet to form percolation paths for transport of electrons, oxide ions, and gas respectively. The reaction resistance related to any process occurring across the active TPB is coupled in parallel between Ni and YSZ.

This paper (i) brings forth a method of rationalizing impedance data and (ii) presents relevant data for the oxidation of hydrogen on Ni/YSZ cermet anodes produced by tape casting. In the analysis of the obtained impedance spectra, the distribution of relaxation times (DRT) was calculated in order to perform a pre-identification of the physico-chemical processes occurring in the cell. The impedance data are rationalized by fitting to a representative equivalent circuit, thus allowing the dependency of three processes on typical parameters to be derived.