bluuebunny/crossref_metadata_2025 huggingface dataset:
Achieving High Unity Li Transference Number Via Single-Ion Conducting Polymer Electrolyte for Li-Ion Batteries
Authors: Liu Kewei , Jiang Sisi , Liao Chen
Published: February 2020

Driven by the fast-growing demand for high energy density and safety of Li-ion batteries, a number of efforts have been applied on developing Li-ion conducting solid electrolyte. Polymer electrolyte with its unique flexibility and low-cost has been regarded as one of the promising candidates. However, the performance of the conventional lithium ion polymer electrolyte is greatly limited due to the low transference number of Li, which is the active species in battery cycling. Gradient concentration of Li+ exists in a conventional Li-ion battery cell, resulting in polarization and impedance from concentration gradients. In this work, a single-ion conducting polymer electrolyte is prepared via an efficient thiol-ene reaction initiated by UV light. A high unity Li transference number of 0.91 is achieved by anchoring anions onto the polymer network. The polymer electrolyte exhibited an ionic conductivity of 10-4 S/cm at 35 ºC. Utilized in a Li//LFP cell set-up, the cells with single-ion conducting electrolyte delivered a promising averaged coulombic efficiency of 99.95% for 175 cycles.
Computational Investigation of the Binding Energy and Electrochemical Stability of Poly(ethylene oxide) with Li-Ion Salts
Authors: Venkatram Shruti , Chen Lihua , Ramprasad Rampi
Published: February 2020

The increasing awareness to maximize the use of energy resources has led to exploration in effective energy storage viz. high energy density batteries which are reliable, cost-effective and have low energy losses. This has spearheaded the development of solid polymer electrolytes for safer lithium-ion batteries with comparable properties to conventional liquid electrolyte-based lithium-ion batteries. Since the polymer functions as the electrolyte as well as the separator, they must possess a number of critical properties to seamlessly function in the battery. The electrochemical stability window (ESW) is a critical consideration which determines the safe operational voltage outside which the electrolyte degrades. Another factor is the Li-binding energy of the ions to the polymer which is a prelude to the Li-ion migration in the electrolyte and provides an estimate of the solubility of the salt in the polymer matrix. An optimal binding energy is desired where it is high enough for the Li-ion to bind to the polymer but not high enough to prevent its migration through the electrolyte. In this work, molecular dynamics (MD) and density functional theory (DFT) calculations are performed to determine the ESW and the binding energy of polyethylene oxide (PEO), an excellent inflammable and stable polymer electrolyte with multiple Li salts namely, LiBr, LiCl, LiI, LiClO4, LiSCN, LiCH3COO, LiNO3, LiBH4, LiCF3SO3 and LiBF4 to ascertain realistic ESW and binding energy values. We establish a relationship between the effects of the salt anion on the ESW and the binding energy. The ESW decreases in the presence of a salt in the polymer host, and we explore the effects of the salt anion size on the ESW. We also determine an optimal binding energy range for PEO with the salts which successfully propagates polymer-salt solvation as well as Li-ion migration. We believe this study should be able to guide the experimental design of stable and safe solid polymer electrolytes in the future.
Study on Phase Evolution and Material Properties of Li10SiP2S12-XOx
Authors: Kim KwangHyun
Published: February 2020

Oxygen substitution was carried out on Li10SiP2S12 (LSiPS) which has the Li10GeP2S12 (LGPS) type crystalline structure. The general formula of Li10SiP2S12-xOx (LSiPSO) where 0 ≤ x ≤ 1.75 was set for solid state reaction to produce oxy-sulfide sites. The phase distribution and local structural units of LSiPSO were determined by powder X-ray diffraction (PXRD), and Raman, FT-IR,29Si and 31P Solid State NMR spectroscopies. The LGPS like LSiPSO phase increased while the impurity phase, β-Li3PS4 was reduced and formed Li3PO4 phase by O substitution. The optimized lithium ionic conductivity was found for x = 0.7 at 3.1 x 10-3 S/cm at 25℃. However, for the higher doped oxygen such as x > 0.9, a degradation of LSiPSO occurs and it is also expected to become the Li3PO4 phase which leads to a decrease in the ionic conductivity. The local structural units was determined by 31P and 29Si NMR and spectrum deconvolution to show sulfide, oxide and mixed oxy-sulfide local units. On the other hand, the doped O was found that only incorporating with phosphate centered tetrahedral unit such as PS4-xOx during no pure orthosilicate SiO4
4- units were observed, even at the highest x examined.
Enhanced Performance and Safety in Intermediate Temperature Lithium-Sulfur Batteries
Authors: Gritton Jack E. , Fu Zhezhen , McOwen Dennis W. , Hitz Gregory T. , Wachsman Eric D.
Published: February 2020

Due to the high theoretical capacity and energy density, lithium-sulfur is considered one of the most promising battery chemistries. Difficulties with passivation and polysulfide shuttle have traditionally plagued the lithium anode and sulfur cathode, respectively, in conventional liquid electrolyte batteries. Solid-state electrolytes, such as lithium garnets, can largely address these issues as the dense ceramic layer helps block polysulfide shuttle and are stable to metallic lithium. However, poor electron transfer kinetics resulting from high electronic resistance and large volumetric changes of sulfur limit the development of solid-state Li-S batteries. At intermediate temperatures, the diffusivity of sulfur is thermally activated, facilitating electron transfer. Here we mimic encapsulated sulfur through infiltration of sulfur, carbon, and a series of binders into one side of a porous-dense-porous garnet structure. The garnet provides ionic conduction through the cell while helping to entrap sulfur with aid of binder. Cell cycling was performed to determine the effect of binder on specific capacity and capacity fade. Electrochemical impedance spectroscopy was used to elucidate the changes occurring within the cathode. While the pore size is larger than what is used for most encapsulated sulfur cathodes, thermal activation allows certain binder systems enhanced performance. In addition to conductive benefits, this large-scale enclosure of sulfur helps avoid corrosion issues possible with sulfur at elevated temperature.
Mitigating Li-Loss during Processing of Thin-Film Li6.22Al0.26La3Zr2O12 Solid Electrolytes
Authors: Parejiya Anand , Li Jianlin , Wood David L.
Published: February 2020

LLZO (Li7La3Zr2O12) garnets are one of the most promising solid electrolytes for All Solid-State Batteries (ASSBs) owing to their high Li-ion conductivity and electrochemical stability against Lithium metal anode[1]. Processability is the greatest challenge with these electrolytes since it requires very thin and highly dense solid electrolytes for better performance of Li-ion batteries. ASSBs will require less than a 20-μm electrolyte to match the cycle rate performance of conventional Li-ion batteries [2]. Currently, most of the research is being carried out on compressed LLZO pellets, which are sintered in dry air at elevated temperatures to achieve higher bulk ionic conductivity. Since lithium is volatile at such high temperatures, Li-loss adversely affects performance of LLZO. Addition of 10 wt% excess lithium while synthesis of LLZO powders and covering the compressed pellets with mother-powder is often adopted to compensate Li-loss [3].

This work has resulted in the development of strategies for processing very thin film electrolytes via slurry processing. Green films as thin as 20 μm were prepared with optimized composition of binder-solvent-plasticizer system to achieve homogeneous coating. It was seen that the Li-loss is significant in thin-green-film sintering compared to compressed pellets. This phenomenon was attributed to higher surface to volume ration compared to compressed pellets, which are generally 1 mm thick. We have taken an approach of non-mother-powder based sintering for ease of post processing, which has never been reported for thin film electrolyte processing. As shown in the left figure, 75 wt% excess Li was required to compensate for Li-loss while sintering 50 μm green film. Excess Li percentages were optimized to get a pure cubic phase of LALZO after sintering green film thicknesses ranging from 20 to 100 μm. Atomic ratios of all the elements were analyzed with inductively coupled plasma - optical emission spectrometry (ICP-OES), and a compound stoichiometry of Li6.22Al0.26La3Zr2O12 was measured after sintering. The results from this work will provide a wealth of information for the first step in development of high performance inorganic solid-state electrolytes.

References:

[1] Yizhou Z,; Xingfeng H.; Yifei M.; First Principles Study on Electrochemical and Chemical Stability of Solid Electrolyte-electrode Interfaces in All-solid-state Li-ion Batteries. J. Mater. Chem. A, 2016, 4, 3253, DOI: 10.1039/C5TA08574H

[2] Advanced Research Projects Agency-Energy (ARPA-E), U.S. Department of Energy. DE-FOA-0001478. Integration and optimization of novel ion conducting solids (IONICS). 2016, (https://arpa-e-foa.energy.gov/)

[3] Inada, R.; Yasuda, S.; Tojo, M.; Tsuritani, K.; Tojo, T.; Sakurai, Y. Development of Lithium-Stuffed Garnet-Type Oxide Solid Electrolytes with High Ionic Conductivity for Application to All-Solid-State Batteries. Front. Energy Res. 2016, DOI: 10.3389/fenrg.2016.00028.

Figure 1
(Invited) Beyond Dendrites, Cycling Li-Metal across Garnet at High Current Densities
Authors: Wachsman Eric D.
Published: February 2020

Solid-state Li-batteries (SSLiBs) have the potential to be a transformational and intrinsically safe energy storage solution. However, their progress has been limited by high solid-solid interfacial impedance and numerous reports of Li-dendrites and a corresponding “critical current density”. By first modifying the garnet surface to enable Li-metal to wet it and then fabricating garnet-electrolytes into tailored tri-layer microstructuresto form electrode supported dense thin-film (~10μm) solid-state electrolytes we have been able to overcome these limitations. The microstrucurally tailored porous garnet scaffold support increases electrode/electrolyte interfacial area, overcoming the high impedance typical of planar geometry SSLiBs resulting in an area specific resistance (ASR) of only ~2 to 7 Ωcm-2at room temperature. The unique garnet scaffold/electrolyte/scaffold structure further allows for charge/discharge of the Li-metal anode and cathode scaffolds by pore-filling, thus providing high depth of discharge ability without mechanical cycling fatigue seen with typical electrodes. Moreover, these scalable multilayer ceramic fabrication techniques, without need for dry rooms or vacuum equipment, provide for dramatically reduced manufacturing cost.

The fabrication of supported dense thin-film garnet electrolytes, their ability to cycle Li-metal at high current densities with no dendrite formation, and results for Li-metal anode/garnet-electrolyte based batteries with a number of different cathode chemistries will be presented.
Atomic-Scale Simulations of Grain Boundary Mechanical Properties in the Solid Electrolyte Li7La3Zr2O12
Authors: Yu Seungho , Park Haesun , Siegel Donald J
Published: February 2020

The garnet oxide Li7La3Zr2O12 (LLZO) is a promising solid electrolyte due to its high ionic conductivity, favorable elastic properties, and chemical stability against Li metal. Nevertheless, despite its high shear modulus, recent studies have shown that metallic Li ‘dendrites’ can penetrate LLZO through its grain boundary (GB) network, resulting in a short-circuit. This behavior suggests that microstructural features (such as GB) will play an important role in suppressing this failure mode. The present study examines the possibility for nanoscale softening (i.e., reduced elastic moduli) and reduced strength in the vicinity of GBs in LLZO. Molecular dynamics simulations were performed to predict the Young’s and shear modulus near two prototypical grain boundaries. The ideal shear strength and fracture toughness was also calculated for bulk and GB-containing systems to determine the impact of GBs on plastic deformation and the potential for Li penetration along GBs. Our calculations reveal that all three of these mechanical properties (elastic modulus, ideal strength, and fracture toughness) are reduced in the vicinity of GBs relative to the bulk. This behavior could potentially contribute to the observed penetration of Li along GBs in LLZO at high current densities. Similar behavior is anticipated at defects such as surface cracks or pores.
A Double-Layered Solid Polymer Composite Separator with Improved Electrode/Separator Interfacial Stability
Authors: Lv Weiqiang
Published: February 2020

Solid-state lithium-ion batteries (LIBs) show significantly improved safety since they avoid the use of flammable liquid organic electrolytes in traditional LIBs. However, one of the most challenge issues for all solid state LIBs is the effective solid-solid interfacial contact and stability with repeated charges/discharges at electrode/separator interfaces. Ceramic separators are mechanically brittle and hard to process. The volume change of electrode materials during charges/discharges causes serious crack at electrode/separator interfaces. In comparison, polymer electrolyte membranes are flexible and easy to process, and are more feasible to solve the interfacial problem. In this work, a double-layered solid polymer separator is prepared to improve the stability of Li metal/solid separator interface. In the separator, one layer contacted with cathode is poly(vinylidene fluoride) (PVDF)/ Li6.75La3Zr1.75Ta0.25O12 (LLZTO)/LiTFSI, which exhibits a room-temperature Li+ conductivity of 5 × 10−4 S cm−1. The other layer close to Li metal is much thinner as compared with the first layer, which contains PVDF/LLZO/LiTFSI/graphene. Our results show that adding graphene into the separator can suppress Li dendrite and improve coulombic efficiency. Conductive graphene sheets in the separator not just stop mechanically the Li dendrite growth, but also allow the dendrite Li charge/discharge and avoid the presence of dead Li. By optimize the separator composition and parameters, the performance of Li metal based cells are improved significantly due to the improve electrode/separator interfacial stability.
Direct Conversion of Natural Date Pulp to Hierarchically Porous Carbon Spheres As Efficient and Stable Oxygen-Reduction Electrocatalysts
Authors: Su Chao , Shao Zongping
Published: February 2020

The impending global energy crisis and environmental concerns associated with the excessive use of fossil fuels have prompted us to explore highly sustainable alternative energy sources as well as highly efficient eco-friendly energy conversion and storage technologies. Fuel cells are electrochemical energy conversion devices with energy conversion efficiencies two times greater than those of conventional fire powered plants. Such electrochemical devices normally involve an oxygen reduction reaction (ORR) over their positive electrode; unfortunately, the sluggish ORR kinetics at room temperature significantly limit their efficiency and performance, and thus have become a major obstacle towards their practical applications. The development of efficient electrocatalysts for promoting the ORR is the key to realize the practical use of such advanced technologie. Carbon materials are promising alternatives to noble metal catalysts for oxygen reduction reactions (ORR) in energy conversion devices. Here we report hierarchically porous carbon spheres with a trace amount of encapsulated cobalt as highly active and stable electrocatalysts for the ORR under both alkaline and acidic conditions. We use renewable natural date pulp as the carbon precursor and a facile hydrothermal carbonization method with in situ formed cobalt as a template for the synthesis. These catalysts yield competitive catalytic activity (a small Tafel slope of 53 mV dec-1) and superb durability and methanol tolerance compared to the benchmark Pt/C catalyst in alkaline electrolyte. Even under harsh acidic conditions, the catalysts deliver a satisfactory catalytic performance and good stability, indicating their extensive applicability. This performance is mainly attributed to the rich surface defects and the hierarchically porous structure that provide abundant active sites for the ORR. In situ formed cobalt nanoparticles are critical to the creation of the abundant mesopores, high specific surface area, and catalytically active defect sites over the carbon material. The encapsulated cobalt residual further enhances the ORR activity of the catalysts, while having a negligible effect on the cost due to its trace level (0.2 at.%).
Study of Anodic Electrochemical Exfoliation of Graphite Under Acidic Electrolyte for Scalable Production of Graphene
Authors: Lee Hoyoung , Choi Ji Il , Jang Seung Soon , Lee Seung Woo
Published: February 2020

Graphene has attracted many attentions due to its exceptional mechanical, thermal, electrical, and chemical properties. There has been active research for scalable production of high-quality graphene from graphite. Anodic electrochemical exfoliation of graphite is one of the promising methods for fast and simple production of graphene at low cost with moderate quality. Sulfate containing electrolytes are known for highest exfoliation efficiency among anions, however mechanistic details of exfoliation process remain poorly understood. Here, the role of sulfate anion during the exfoliation process is studied by comparing with other anions under acid conditions. We reveal that water molecules are the main source of gaseous species that exfoliates graphite via mass spectroscopy. The formation and binding energy of anions between graphene layers are also calculated by DFT computations. The fundamental understanding of the exfoliation mechanism of graphite can be applicable to the electrochemical production of other 2D materials.
(Invited) Near-Field Optical Microscopy and Spectroscopy of Nanocarbon Hybrid Materials
Authors: Ignatova Tetyana , Rotkin Slava V.
Published: February 2020

Plasmonic properties of novel low-dimensional materials (LDMs) are promising for a range of biosensing and information technology applications. Since optical properties of LDMs can be modulated at the ultimate scale of (a few) nanometers, the characterization of these materials requires a similar spatial resolution, not available with regular tools.

Scattering-type scanning near-field optical microscope (sSNOM) allowed us to reveal such plasmonic properties of LDMs. For example, both single-wavelength and hyperspectral sSNOM imaging of graphene enables study of phonon-plasmon polariton coupling in this atomically thin layer of carbon.

Here we cover several hybrid structures based on nanocarbon materials, such as graphene and single-wall nanotubes.

SVR acknowledges help of Mr. M. Blades (Lehigh University) and Dr. T. Gokus (Neaspec). This research was partially supported by the UNCG Faculty First Award, the NSF ECCS-1509786, and Penn State Quantum Characterization Infrastructure initiative.
Control of the Anisotropic Conductivity of Carbon Nanotube Sheet and Their Thermoelectric Properties
Authors: Fujigaya Tsuyohiko , Matsumoto Masamichi , Shima Keisuke , Mukaida Masakazu , Ishida Takao , Watanabe Takanobu
Published: February 2020

Large anisotropy of thermal and electric conductions of the carbon nanotubes (CNTs) paper between in-plane and through-plane direction due to the one-dimensional fibrous structure of CNTs is problematic when the temperature gradient are required for applications such as thermoelectric conversion using Seebeck effect. To control the orientation of the CNT direction, polymer particles are introduced upon paper formation via vacuum filtration method. Thermal and electric conductivity in in-plane direction are decreased as increase the amount of the polymer particles used for the paper formation, while those in through-plane direction are increased. Heat diffusion in the paper are monitored by IR camera and it is found that the larger temperature gradient are observed for the CNT paper with anisotropy control compared to the original paper without anisotropy control.
Optical Rectenna Arrays Using Carbon Nanotubes: From Fundamental Understanding to Next Generation Devices
Authors: Anderson Erik C.
Published: February 2020

Optical rectennas have emerged as promising devices for high frequency optoelectronic applications such as infrared and optical sensing and energy conversion. We achieve optical rectification using vertical multiwall carbon nanotube (CNT) arrays. The CNT nanoantennas absorb electromagnetic waves and ultrafast metal-insulator-metal tunnel diodes fabricated at the CNT tips convert the resulting terahertz AC current into DC electricity.

Since the first demonstration in 2015, considerable progress to CNT optical rectennas has been made. The latest generation of CNT rectenna uses an innovative multi-insulator structure to provide exceptional diode properties and enable air stable materials. We applied photon-assisted tunneling theory to model our device’s optical-frequency behavior. Comparing the rectenna model to our optical experiments through a range of wavelengths (404–1064 nm) has yielded a better fundamental understanding that will guide future device design. The model provides strong evidence that the CNT antennas behave as dipole antennas and implicates a 780 THz diode cutoff frequency that reveals room for performance improvement.

We report ongoing research developing a novel flexible CNT rectenna device structure. We use polydimethylsiloxane (PDMS) to infiltrate the CNT array and create a mechanically flexible substrate and planarized diode surface. This structure enables transparent, conductive top electrodes with PEDOT:PSS. Our recent efforts greatly enhance the commercial development of efficient, low cost, and application tunable CNT rectennas.
Photo-Activated Carbon Dots for Combating Drug Resistant Bacteria
Authors: Yang Liju
Published: February 2020

Bacterial infections are the major cause of infectious diseases and mortality. Antibiotics have been used as an effective treatment method because of the cost and their powerful effects. However, the widespread and the abuse of antibiotics have led to the emergence of many drug resistant bacterial strains. The crisis of bacterial resistance has promoted the global search for novel and effective alternative therapies to complement or replace existing antibiotics/antimicrobial treatments. This research focused on the assessment of the newly explored carbon dots (CDots) as a class of visible light activated antimicrobial agents against multidrug-resistant (MDR) bacteria, using different strains of MDR Enterococci (BM 46, BM 29, and 9756) and non drug-resistant strain (9144) as models, the antimicrobial activity of different concentrations of CDots were evaluated using the log reduction in viable cell number compared to the untreated controls. Several factors including treatment time, buffer, and light intensity were also investigated to examine their effects on the antimicrobial effectiveness of CDots. The study also explored the mechanism of action of CDots’ antimicrobial activity. The results indicated the intracellular reactive oxygen species (ROS) levels in bacteria increased dramatically upon CDots treatment, with ~290% to ~400% increases in tested Enterococcus strains. The addition of radical scavengers, L-Histidine, significantly protected cells from the antimicrobial activity of CDots, while tert-Butanol did not perceivably protect cells from inactivation by CDots, indicating that singlet oxygen is the primary ROS species generated by CDots treatment. The generation of ROS also caused lipid peroxidation in bacteria cells. Live and Dead staining assay and TEM imaging indicated increased cell membrane permeability and cytoplasmic disruption upon CDots treatment.

Acknowledgement: The research was supported by NSF grants DMR# 1701399 and the NIH grant R15GM114752.
First-Principles Investigation of Pt-Graphene Hybrid System
Authors: Choi Ji Il , Alamgir Faisal M. , Jang Seung Soon
Published: February 2020

Pt is a face centered cubic structured crystal that has been widely known as a superior catalyst for various chemical reactions, while low-dimensional structures, such as mono- or bi-layer platinum, have attracted less attention due to experimental difficulties in synthesizing such 2D structures. In this study, we present a computational research on the unique architecture of epitaxial platinum (mono/multi) layers grown on graphene (Pt_ML/GR), in support of remarkable recent progress in the synthesis of these architectures in simple cubic-like (SC-L) and face-centered cubic-like (FCC-L) phases on the graphene. Recently proposed strongly constrained and appropriately normed (SCAN) density function study (DFT) is employed to investigate the structural and electronic properties of the epitaxial SC-L Pt layered graphene. In these architectures, Pt exhibits registry with the C-C bridge sites along the armchair and zigzag directions. Here, the details of the atomistic/electronic structures and binding energies are discussed. Further, the detailed band structure and the partial/total densities of state (DOS) of the Pt_ML/GR architectures, with Pt in an SC-L registry, are presented. Interestingly, it is found that electrochemical reactions such as oxygen reduction reaction can occur on graphene side as well as Pt side. This would provide a good strategy for 1) the protection of metallic catalyst and 2) tune the electronic structure of catalyst.
Pyrolytic Carbon Films with Tunable Electronic Structure and Surface Functionality: A Planar Stand-in for Electroanalysis of Energy-Relevant Reactions
Authors: Chervin Christopher N. , Long Jeffrey W. , Sassin Megan B. , Parker Joseph F. , So Christopher R , Jeon Seokmin , Rolison Debra R.
Published: February 2020

Nanostructured carbons are critical components within many of the electrodes used for energy-storage and –conversion systems, where they can provide pathways for electron conduction to enable high-rate operation, act as supports for other active materials (e.g., electrocatalytic metals and oxides), and contribute to the mechanical properties of the electrode. Yet often overlooked when selecting a particular carbon is the nature of electronic/chemical/physical interactions at the junction of carbon with nanoscale phases that impart desired storage or electrocatalytic functionality. Our own research with otherwise high-performing carbon-based electrode architectures suggests that sub-optimal interface design ultimately hinders energy and power capability. In order to address fundamental questions regarding interfacial processes, we step back from the complex structure of practical carbon-containing electrodes to a planar electrode configuration designed to mimic those same interfaces. For example, pyrolytic carbon (pyC) films prepared by chemical vapor deposition are planar analogs of the disordered carbon blacks used in many battery and fuel-cell electrodes, and thus serve as an electroanalytical substrate on which we deposit charge-storing metal oxides (e.g., MnO2), electroactive polymers, and metal colloids [1]. We use classical electroanalytical methods to determine fundamental properties such as electron-transfer rate constants and impedance-derived response times, absent the complexities imposed by 3D electrodes. By moving to 2D model surfaces we are also able to interrogate interfacial processes by scanning probe microscopy, including in situ monitoring of conductivity and surface morphology under potential/current control. Lessons learned from these model 2D interfaces are readily applied to the redesign of practical 3D electrode structures to improve next-generation electrochemical capacitors and batteries.

[1] J. F. Parker, G. E. Kamm, A. D. McGovern, P. A. DeSario, D. R. Rolison, and J. W. Long, Languir, 33 (2017) 9415–9425.
Corrosion Susceptibility of Austenitic Stainless Steels in Direct Carbon Fuel Cell
Authors: Mathan Bobby , Islam Monirul , Glenn Michael , Beyad Yaser , Allen Jessica A , Donne Scott W
Published: February 2020

The direct carbon fuel cell (DCFC) is a future energy technology which is an efficient process for electrical energy generation from carbon-based sources. This technology has an extremely high theoretical efficiency due to favourable thermodynamics of the electro-oxidation reactions in the process. However, several technical challenges exist which must be addressed before the technology can be commercialized. One of the challenges is the corrosion of metal parts in the cell which limits the service life of the unit. In recent year, research on the development of new alloys and surface engineering have been done to address the corrosion issues in molten carbonate fuel cells. However, the literature on the corrosion behaviour of metals in a slurry system (coal + carbonate) is limited.

Austenitic stainless steels are known for their high temperature corrosion resistance and excellent mechanical properties. In this work, the corrosion susceptibility of two types of austenitic stainless steels, i.e. 316L (16 wt.% Cr and 10wt. % Ni) and 235 MA (21 wt.% Cr and 11 wt.% Ni) were compared for fuel cell tank body application. The corrosion behaviour of the two stainless steels were evaluated in a slurry, which contained 20 wt% coal and 80 wt% ternary-eutectic (Li2CO3: 43.5 mol%, Na2CO3: 31.5 mol%, and K2CO3: 25.0 mol%), with nitrogen as a sweep gas at 800⁰C was examined for a 30-day period. The results indicate that the weight gain (due to corrosion product build-up) for both the stainless steels was marginal after 7 day exposure, i.e., 0.4% and 0.5% for 316L and 253 MA, respectively. However, after 30 days exposure, the weight gain increased to 0.98% for 316L, whereas for 253MA the weight gain remained at ~ 0.5%. Thus, the study suggest that 235 MA stainless steel is superior to 316L stainless steel in the coal-carbonate slurry environment. The corrosion mechanisms of the stainless steels will be discussed in the presentation.
Inhibition of Hydrogen Entry into Pure Iron By Formation of Nitrogen Solid Solution Layer in the Surface
Authors: Sugawara Yu , Sawai Takuya , Hayashi Tomoki , Muto Izumi
Published: February 2020

Hydrogen embrittlement is a serious problem for steels such as high strength steels. In order to prevent hydrogen embrittlement, the inhibition of hydrogen entry into the steel matrix is one of important subjects. The formation of surface layers with low hydrogen diffusivity is thought to be effective in inhibiting the hydrogen entry into the steel matrix. In this study, we formed nitrogen solid solution layers containing iron-nitrogen martensite and retained austenite phases on the surface of pure iron specimens by plasma-nitriding and subsequent quenching, and investigated the hydrogen permeation behavior.

Pure iron sheets of 1 mm in thickness were used as the specimens. Prior to the nitriding treatment, the specimen surfaces were polished using a diamond past down to 1 μm. The plasma nitriding treatments were carried out in a nitrogen-hydrogen atmosphere at 370 Pa for 600 s. The temperature of the specimen surface was kept at 873 K by controlling the supplied DC voltage. After the plasma nitriding, the specimens were quenched from 1073 or 1273 K for 180 s. In the case of the quenching from 1273 K, an iron-nitrogen martensite phase was formed in the surface. The thickness of the surface layer was over 100 µm. Iron-nitrogen martensite and retained austenite phases were formed in the surface of the specimen quenched from 1073 K. The thickness was ca. 50 µm.

To investigate the effect of the nitrogen solid solution layers on the hydrogen permeation behavior through the specimens, a hydrogen permeation test using a conventional Devanathan-Stachurski cell was carried out for 3.6 ks. The nitrided surface was arranged in the hydrogen entry side. Pd of 200 nm in thickness was deposited on the specimen in the hydrogen detection side. The hydrogen detection side was polarized at 0.2 V vs. SHE in 0.1 M NaOH fully deaerated by pure Ar gas. The specimen in the hydrogen entry side was polarized at −0.8 V vs. SHE in 0.1 M H2SO4. The hydrogen permeation tests reveal that the permeation current of the specimen quenched from 1273 K was smaller than that of as-polished one. The surface martensite phase seems to suppress the hydrogen permeation. In addition, no permeation current of the specimen quenched at 1073 K was detected. This is because the hydrogen diffusivity in the austenite phase is much lower than the ferrite phase due to high solubility limit in the austenite phase. The surface layer containing the austenite phase is found to be effective in inhibiting the hydrogen entry into the matrix.
Localized Corrosion Analysis Using Complex Potential Distribution Ratio as a New Transfer Function
Authors: Furukawa Noriyuki , Hoshi Yoshinao , Shitanda Isao , Itagaki Masayuki
Published: February 2020

An electrochemical impedance spectroscopy (EIS) is powerful technique that has been used for the understanding of the corrosion mechanisms. In order to investigate the surface heterogeneities attributed to the localized corrosion, Lillard et al.1) have developed a local electrochemical impedance spectroscopy (LEIS). Because the potential differences related to the iR drop in vertical direction to the working electrode (WE) can be measured with dual microprobes in this method, the local impedance on WE can be calculated.

In the present study, our group developed a Complex Potential Distribution Ratio (CPDR) as a new transfer function to investigate the potential distributions in parallel direction to the WE. Assuming that the surface is composed of the dissolution site and oxide film site, namely, an interfacial impedance at dissolution site is lower than that at oxide film site, the current density of each site is different. In this case, the potential differences were observed in parallel direction to the WE near these sites, indicating that the iR drop of each site is different. The CPDR, Ξ, is expressed by the following equation.

Ξ = ΔV
p / ΔV
applied (1)

In this equation, the ΔV
p is the ac-potential differences between the potentials above the dissolution site, V
1, and oxide film site, V
2, in parallel direction to WE and the ΔV
applied is the ac-potential differences between WE and reference electrode in the bulk solution. In this case, the dual probes are set above the dissolution site and oxide film site to measure the ΔV
p. The impedance (Z) is expressed by the following equation.

Z = ΔV
applied / ΔI
CE (2)

In this equation, the ΔI
CE is the ac-current flowing into CE from WE.

In the present study, the Ξ and Z simulations were performed by using the equivalent circuit based on the concept. The interpretation of calculated spectra was discussed, and we applied the proposed method to the dissolution of metals.

.

Reference:

1) R. S. Lillard, P. J. Moran, H. S. Isaacs, J. Electrochem. Soc., 139 (1992) 1007-1012.
Application of Multipoint Impedence Spectroscopy to Corrosion Monitoring on Shape Memory Alloys in Smart Building Materials.
Authors: Kim Jaehwan , Lee Hyunbae , Hwang Heesu , Oh Jiwon , Choi Eunsoo , Hwang Jin-Ha
Published: February 2020

Impedance spectroscopy has been widely employed in order to monitor the hydration phenomena which reflect the electrical conduction along the porous paths whose ionic features are easily discerned from the electrode polarization. The microstructural changes influence the impedance features composed of resistors, capacitors, and inductors, through their intermixed connections involving series, parallel or, both. Unlike the application of impedance spectroscopy to the bulk phenomena, the three-point impedance spectroscopy can be exploited towards the rational separation of a specific electrode from the remaining system through the multipoint electrode configuration in order to localize the corrosion responses of the electrode under interest. The effects of the electrode configuration are investigated in order to establish the methodology on the corrosion monitoring in reinforcement materials in building materials. The current work chooses Ni/Ti-Based and Fe-Based shape memory alloys as model systems in monitoring the corrosion phenomena encountered in construction applications. The shape memory alloys are mixed with the cement-based materials with the aim to providing self-healing functions in association with the detrimental cracks in smart composite materials. In particular, the Ni-Ti and Fe-Si shape memory alloys are subjected to corrosion environments in everyday and hostile conditions. The conventional potentiostat approaches are performed in parallel, in order to prove the applicability of the multipoint impedance spectroscopy in the electrochemical applications involving nano-materials. The ramifications of multi-point impedance spectroscopy are discussed towards corrosion-specific monitoring in functional shape memory alloys which is recommended as one of powerful next-generation building materials.
(Invited) Application of High Throughput Experimentation to Machine Learning Algorithms for the Development of Lithium Ion Battery Materials
Authors: Strand Dee , Bailey Mark
Published: February 2020

Electrolytes for lithium ion batteries are complex formulations of solvents, salts, and additives. The formulation components affect properties of both the bulk solution and the solid electrolyte interphases on the cathode and the anode. Bulk properties, such as ionic conductivity and viscosity, are typically dominated by solvents and salts and can be predicted by models, such as the Advanced Electrolyte Model developed by Idaho National Lab. However, contributions to electrolyte performance due to additives are much more difficult to predict.

Systematic studies of electrolyte additives require evaluation of those additives in combination with a variety of solvents, salts, and other additives. The additive performance will also depend upon the active materials in the cell as well as the potentials at the anode and cathode. This presentation summarizes a practical approach to effective data gathering in such systems for use in establishing machine learning algorithms to predict performance of new formulations.
(Invited) Progress Toward Large-Format Solid-State Cells Using Sulfide Solid Electrolytes
Authors: Buettner-Garrett Josh , Becker Collin , Huang Haitao , Francisco Brian , Roberts Jason , Kelly Brandon
Published: February 2020

Solid-state batteries are widely considered the most promising candidate to begin displacing conventional lithium ion batteries for electric vehicles and consumer electronics in the next decade, but several challenges remain. High energy density and long cycle must still be demonstrated in large automotive-relevant cells. Low cost and scalable production also need to be proven. Solid Power is working to meet these challenges by combining a sulfide-based solid electrolyte, a nickel-rich NMC cathode, and a lithium metal anode in cells that surpass conventional lithium ion in energy density and safety.

Solid Power and its collaborators have developed a suite of solid electrolytes, cathode materials, Nb-free surface treatments and production processes that deliver excellent energy density and cycle life in laboratory-scale cells. The attached figure shows early cycling performance for a recent 2 cm2 laboratory type lithium metal cell at 70°C and C/10 rate with a 4.3V charge voltage. This cell delivers 193 mAh/g based on surface-treated LiNi0.6Mn0.2Co0.2O2 (NMC622) mass and retains 191 mAh/g after 80 cycles at 100% depth-of-discharge. The excellent cycling stability of this composite cathode comes from improved electrochemical stability at the cathode-electrolyte interfaces as well as the ability to accommodate the volume changes of the NMC during cycling.

Now focus is on scaling of both cell capacity and production throughput. Cells are currently produced up to 250 mAh, and larger cells up to 20 Ah in capacity with improved performance are planned for the next year as Solid Power’s pilot scale production line is completed in early 2019. This production line is built on low-cost processes and equipment that mirror lithium ion production and will be capable of producing up to 1 MWh per month when fully operational. Remaining challenges for Solid Power include demonstrating long life with lithium metal anodes in full-scale cells and working toward low-temperature operation.

Figure 1
(Keynote) All-Solid-State Lithium Battery Based on Sulfidic Electrolytes
Authors: Varzi Alberto , Passerini Stefano , Ates Tugce , Hosseini Seyed Milad
Published: February 2020

Electric vehicles allow emission-free transportation but offer only limited driving range. A technological jump to all-solid-state batteries (ASSBs) that safely implement a lithium metal anode, enabling high energy densities, would dramatically boost the battery performance.

Recent research efforts have yield to a variety of inorganic solid electrolytes with extremely high ionic conductivity at room temperature. In particular, low density sulfidic electrolytes are attractive candidates for high-energy ASSBs. However, many issues still need to be addressed[1]. Herein, we focus on the limited electrochemical stability of sulfidic electrolytes that results in decomposition reactions accompanied by increasing resistances at the electrode/electrolyte-interface.

In academic research, mostly pellet-type cells are used to investigate the electrochemical performance. However, this type of cell set-up is far from being practical for large scale battery production and application. A key advantage of sulfidic electrolytes is their ductility permitting this class of materials to be simply cold pressed. Thus, herein, slurry-based procedure is presented that easily allows to process a composite cathode. The cells demonstrate good electrochemical performance, although the type and amount of conductive carbon as well as the active material particles size, are crucial parameters.

Reference

[1] J. Janek, W. G. Zeier, Nat.
Energy 2016, 1, 16141.

Acknowledgment

The research leading to these results has received funding from the German Federal Ministry of Education and Research under grant agreement no. 03XP0026F.
(Invited) Structure-Function Studies of the Effects of F and Cr Doping on the Performance of Lithium-Rich Li1+ XMO2 (M= Ni, Mn, Co) Positive Electrodes
Authors: Peterson Vanessa Kate , Pang Wei Kong , Lin Hsiu-Fen , Lu Cheng Zhang , Liu Chia-Erh , Liao Shih-Chieh , Chen Jin Ming
Published: February 2020

This work will present the results of studies aimed at understanding the chemistry− and structure−function relation of the lithium-rich layered metal oxide material Li1.2Ni0.23Co0.12Mn0.5O2 doped with F and Cr [1].

The electrode material is found to consist of a mixture of R
m and C2/m space-group symmetry components in a weight ration of approximately 4:1. Doping with ~ 2% Cr and 5% F was successful in the main layered phase with R
m space-group, with Cr residing at the 3a transition-metal site and F residing at the 6c oxygen site, as supported by neutron and X-ray powder diffraction as well as electron microscopy.

The electrochemical performance of the doped and undoped materials were compared in coin cells against lithium metal, allowing the comparison of capacity and rate performance, as well as lithium ion diffusion constants within the material as derived from cyclic voltammetry. These differences in measured electrochemical performance were reconciled with the results of structural studies of the electrode powders, as well as differences in the change of these structures that occurred during operation in full 18650 cells against Li4Ti5O12, as measured using in operando neutron powder diffraction.

[1] W.K. Pang, H.F. Lin, V.K. Peterson, C.Z. Lu, C.E. Liu, S.C. Liao, J.M. Chen “Effects of fluorine and chromium doping on the performance of lithium-rich Li1+ xMO2 (M= Ni, Mn, Co) positive electrodes” Chem. Mater. 2017.
(Invited) In Quest of High Voltage Insertion Compounds for Li-Ion and Na-Ion Batteries
Authors: Reynaud Marine , Wizner Agnieszka , Katcho Nebil , Rodríguez-Carvajal Juan , Carrasco Javier , Rousse Gwenaelle , Galceran Montserrat , Rojo Teófilo , Armand Michel , Casas-Cabanas Montse
Published: February 2020

A salient aspect of research in batteries is the discovery of new materials or novel properties of existing compounds. In this quest, the traditional approach is to focus on archetype compounds in which a desirable property was first observed, stimulating further investigations. This has been the innovation pathway of many battery materials (e.g., LiCoO2, LiFePO4) which are found in commercial Li-ion batteries. Indeed, most Li-ion cathode materials belong to a handful of structural families: layered oxides, spinel, and olivine. Similarly, many good Li-ion solid electrolytes crystalize in a few crystal structures: perovskites, NASICON-like, LISICON-like, garnets, and argyrodite. Yet this trial-and-error exploratory research based on extrapolating known solutions to new compositional spaces has high demands in terms of synthesis and characterization times that hinder the emergence of new, disruptive compounds.

In this contribution we will present the strategies, using high-throughput bond-valence calculations and machine learning, that have allowed us to develop new high-voltage materials for the Li-ion and Na-ion batteries. Following this approach our recent results related to the nitridophosphate family (Na3TM(PO3)3N), where N assists an inductively induced high redox potential, will be shown. Within this family, Na3V(PO3)3N has been found to be the Na-ion cathode material with the highest operation voltage for the VIV+/VIII+ redox couple together with Na7V3(P2O7)4. Strategies to further lower the cost and improve the safety of these systems will be shown.
(Invited) A New Model for Investigating Li Nucleation and Growth in Various Electrolytes
Authors: Hwang Bing-Joe
Published: February 2020

The lithium nucleation and growth on a substrate during electroplating is a crucial phenomenon for the cycle life and safety of Li ion batteries (LIBs) or Li metal batteries (LMBs), in particular the interfacial instability of Li metal anode. Hence, understanding the nucleation and growth mechanism of Li metal deposition is an essential key for providing a long cycle life and safe LIBs or LMBs. However, no quantitative report on Li metal deposition is found to the best of our knowledge. In this study, we proposed for the first time a model for nucleation and growth mechanism of Li metal associated with SEI formation by a chronoamperometry method. The current transients at different applied potentials initiate the nucleation and growth of Li metal on Cu substrate. A model considering 3D diffusion-controlled instantaneous process with the simultaneous reduction of electrolyte decomposition due to the SEI fracture is first employed for investigating the nucleation and growth of Li metal. This proposed model opens a new way to quantitatively understand the nucleation and growth of Li metal and electrolyte decomposition in different electrolytes.