bluuebunny/crossref_metadata_2025 huggingface dataset:
Mathematical Modeling of a Proton-Conducting Solid Oxide Electrolyzer Cell Using Computational Fluid Dynamics Simulation
Authors: Boyer Hailey , Shimpalee Sirivatch , Weidner John W. , Ma Zhiwen
Published: February 2020

The proton-conducting solid oxide electrolyzer cell (H-SOEC) is a novel electrolysis technology, which operates in the intermediate temperature range (500-700°C), as opposed to the high temperature (800-1000°C) operating range of oxygen ion conducting solid oxide electrolysis cells (O-SOECs), or the low temperature (70-80°C) operating range of proton-exchange membrane (PEM) electrolyzers [1]. Proton-conducting electrolyte has high ionic conductivity in this intermediate temperature range, which is not exhibited in O-SOECs; this means that there are fewer material challenges for the development of these devices because they do not need to withstand temperatures up to 1000°C [1,2]. Additionally, this temperature ranges yields the benefits of improved thermodynamics at increased temperature, meaning they require less electrical energy input as compared to PEM electrolyzers [1]. H-SOECs are a promising technology because they retain the thermodynamic benefits of operation at high temperature, without the material complications seen in O-SOECs.

The purpose of this work is to model the 2D current density distribution of an H-SOEC at a applied electrolysis voltage. The model considers overpotential losses that occur due to kinetics of the electrochemical reaction, resistance in the cell components, and mass transport. The mathematical model uses electrochemical parameters fit with experimental data from [3] and is incorporated into the solving routine of computational fluid dynamics (CFD) software, Fluent. Figure 1 shows an example of the current density distribution in a planar H-SOEC cell that was obtained from the model simulation. Such parametric distribution is difficult to be measured, and the outcomes of this work would help the experimental development of this novel electrolyzer technology through optimization of operating conditions like temperature and gas feed compositions. The modeling approach also helps understand the thermal-flow management needs of this device as it is scaled up to the stack level. It will also provide a baseline understanding for more complex models that consider the internal transport phenomena in 3D, as only limited modeling papers on H-SOEC are available now.

References:

Bi et al., Chemical Society Reviews, 43 (24), (2014) 8255-8270.

Namwong et al., Journal of Power Sources, 331, (2016) 515-526.

Wu et al., Advanced Science, 1800360, (2018) 1-9.

Figure 1
Directly Removing of Irreversible Capacity in Lithium Ion Battery By Pre-Lithiation Using through-Holed Cathode and Anode Electrodes in a Laminated Cell
Authors: Watanabe Tatsuya , Tsuda Takashi , Gunji Takao , Ando Nobuo , Nakamura Susumu , Hayashi Narumi , Soma Naohiko , Ohsaka Takeo , Matsumoto Futoshi
Published: February 2020

In order to remove irreversible capacity showed by graphite anodes at first charging process, pre-lithiation was applied to the anodes which were laminated with cathodes and separator sheets. Through-holes were formed in the anodes and cathodes. By contacting the anodes with Li metal which was attached beside the laminated cell, the pre-lithiation process to the graphite anodes was started. After pre-lithiation for a limited period of time, the pre-lithiated capacity was balancing among the pre-lithiated graphite by contacting among the anodes. The cells composed of through-holed anodes and cathodes were tested in charging/discharging cycle and removal of the irreversible capacity which can be observed at the first charging/discharging cycle was confirmed. The anodes which were treated with appropriate pre-lithiation charge and balancing period successfully could decrease irreversible capacity from 7 to 1% and the cells exhibited stable 100% of targeted capacity. In this study, practical pre-lithiation process to decrease the irreversible capacity could be proposed.

Fig. １ Schematic of a series of the process of perpendicular pre-doping, capacity balancing and charging/discharging examined in this study.

Figure 1
Oxygen Reduction Reactions in Low-Viscosity Ionic Liquids Based on Phosphonium Cations
Authors: Higashi Toshikazu , Yamada Hirohisa , Sakguchi Yuki , Nomizu Daiki , Tsunashima Katsuhiko , Sakai Chikako , Katakura Katsumi
Published: February 2020

There is high expectation for the lithium-oxygen (Li-O2) battery due to its high energy density because the cathodic active material is O2 in the air. The oxygen reduction reaction (ORR) at the cathode is of great importance, and it is strongly influenced by types of electrolytes. In particular, mass transport of oxygen molecules and its parameter, i. e. the solubility and the diffusion coefficient, are important for high performance of Li-O2 battery.

Ionic liquids (ILs) have drawn attentions as an electrolyte for Li-O2 battery, because of their unique properties like incombustibility, low vapor pressure, good ionic conductivity and wide electrochemical potential window [1]. Major ILs used for such electrochemical devices include imidazolium, pyridinium, quaternary ammonium, pyrrolidinium and piperidinium derivatives. On the other hand, phosphonium ILs have the remarkable features such as their chemical and thermal stabilities, and lower viscosity, compared to the ammonium counterparts [2]. Therefore, we focused on the phosphonium ILs. Recently, much lower viscosity was reported that based on small phosphonium cation such as triethylalkylphosphonium cation or tri-n-butylalkylphosphonium cation [2,3].

All electrochemical measurements such as cyclic voltammetry (CV) and potential-step chronoamperometry (CA) were performed using a three electrode type electrochemical cell at 25oC. A glassy carbon (GC) disk electrode (d = 1 mm) or a carbon fiber (CF) microdisk electrode (d = 33 μm) were used as the working electrode. Counter electrode and reference electrode were Pt wire and Ag+/Ag in 0.1 M Ag-OTf / EMI-TFSA , respectively.

CAs were performed on the CF microdisk electrode to estimate the solubility and the diffusion coefficient of oxygen in the ILs, individually, by the micro-electrode technique [4]. Two typical groups which consisted of triethylalkyl or tri-n-butylalkyl phosphonium cation were observed in the solubility correlated with molar volume. Moreover, two linear relationship between the diffusion coefficient and the viscosity of ILs were observed. In addition, the diffusion coefficients were correlated to occupied molar volumes which were calculated by the oxygen solubility in each IL. These result suggested that diffusion coefficient was not only affected the viscosity but also diffusion path originated from the cation structure.

[1] A. Khan, C. Zhao, ACS sustainable Chem. Eng.
4, 506 (2016)

[2] K. Tsunashima, M. Sugiya, Electrochem. Commun.
9, 2353 (2007)

[3] K. Tsunashima, M. Sugiya, Electrochemistry, (2007), in press.

[4] J. Maruyama, M. Inaba, T. Morita, Z. Ogumi, J. Electroanal. Chem.
504, 208 (2001)
Mathematical Modeling of Lithium Sulfur Batteries
Authors: Kamyab Niloofar , White Ralph E. , Weidner John W.
Published: February 2020

Present day automotive battery packs typically consist of a large number of LIBs (few hundreds to thousands) to meet the required power and capacity needs of an EV. The high cost and limited mileage of present LIB-powered cars are due to the intrinsic limited capacities of the Li-ion insertion cathodes, which are nearing their practical limits and even a two-fold increase in energy density of current LIB cells is insufficient for the long-term demands of transport and electricity storage. Hence, for a wide deployment of EVs and maximizing electrification of the road transportation system, drastic improvements in today’s battery pack performance is needed.

Among new generation of lithium batteries, high theoretical energy density (~600 Wh/Kg) that may be 4-5 times higher compared to that of Li-ion batteries, good low-temperature performance, and abundance of inexpensive nontoxic raw material, make the lithium sulfur batteries (LSB) a promising candidate for major energy applications. However, there are several major issues facing rechargeable LSBs that impede their practical applications. In other words, challenges such as fast capacity loss, limited cycle life, high self-discharge rates, over-heating, and volume change of the cathode have hindered mass commercialization of these cells and limit their current application to UAVs and defense applications where the lightness and high energy is more important than life cycle.

Although a wide range of experimental researches have investigated novel strategies, material and designs for the cells, the mathematical and theoretical studies are scarce. Theoretical modeling plays crucial role in the exploration of the phenomena happening in the LiS cells. A mathematical model is presented to provides a better understanding of the complex multistep electrochemical reactions, side reactions, multiscale and multi component transport phenomena, phase change phenomena and precipitation reaction, and porosity and volume change of the cathode.
Electrochemical Melting of DNA: Optimization and Application
Authors: Madrigal Eddie , West Ryan M
Published: February 2020

A biosensor is an analytical device that can detect, quantitate, and/or characterize biologically-relevant molecules, often utilizing biologically-derived recognition elements, such as DNA oligomers or enzymes. Applications in point-of-care diagnostics, drug development, and forensic toxicology require portable, rapid, reliable, and easy-to-use devices. Electrochemistry provides a promising platform for such devices due to its potential for parallel measurements, its sensitivity, and its ease-of-miniaturization. In this work, gold electrodes modified with self-assembled monolayers of DNA are utilized to study the electric field assisted melting of double-stranded DNA (i.e. “e-melting”). We have previously demonstrated the ability to detect single mismatches in short DNA oligomers using this approach (J. Electrochem. Soc. 2019 volume 166, issue 4, B236-B242). Broadly, this project aims to (1) develop a better understanding of the mechanism of e-melting and (2) correlate e-melting behavior (kinetics, dependence on applied potential, ionic strength, etc.) to DNA structure and stability. Such analysis has the potential to provide fast and portable screening of biological samples for specific sequences, presence of mismatches, and other mutations. In addition, this method could provide a new platform for fundamental biophysical studies aimed at understanding the behavior of DNA in high electric fields.

We will present several key improvements to the procedure for formation of the DNA monolayers using a potential pulse routine during electrode modification. This procedure has now replaced the “passive” method used in previous work and has decreased the amounts of reagents, decreased the reaction time, and increased reproducibility of the DNA surface coverage. This has made possible a correlation between the electrochemical signal (peak height obtained from voltammetric measurements) and the DNA surface coverage (DNA molecules per cm2). Additionally, improvements to the electrochemical melting routine itself will also be presented.These improvements in the methodology allows more controlled and reproducible studies, decreasing the signal-to-noise, and increasing sensitivity to small changes in DNA stability or structure. Results from the application of this method towards the study of interactions between DNA and small molecules, specifically cisplatin, will also be presented. Cisplatin has a strong affinity for DNA: it binds to the N7 of two neighboring purines with preference to neighboring guanines. This binding causes a kink in the DNA which destabilizes it. This research will contribute to a better understanding of the way in which small molecules, like cisplatin, affect the stability of DNA and how such interactions are affected by high electric fields. Ultimately, these studies may provide the foundation upon which future electrochemical biosensors can be developed.
Designing Corrosion Resistant High Entropy Alloys Via Chlorine Susceptibility Index
Authors: Li Sirui , Ke Huibin , Panindre Anup , Taylor Christopher , Frankel Gerald S.
Published: February 2020

In this poster presentation, first principle density functional theory (DFT) implemented in the Vienna Ab-initio Simulation Package (VASP) is coupled with Chlorine Susceptibility Index (CSI) to guide the design of high entropy alloys (HEA) for materials employed in marine environment. On the atomic scale, elements within HEAs are randomly distributed throughout the alloy. This disordered crystalline state renders the investigation of all possible combinations impossible for DFT calculations. The CSI methodology developed by Dr. Huibin Ke in the Taylor group can be applied here to circumvent this issue [1]. The first successful CSI model for alloy systems was derived based on the special quasi-random structure approach[2] utilized for the study of Ni-Cr 22 alloy[3] and uses the first-principles thermodynamics approximation that allows the prediction of preferred chemisorption states in mixed media as a function of pH, electrochemical potential and chloride concentration[4]. Herein, we apply this method in search for combinations of elements that can provide the best corrosion resistance, under constraints of satisfying the high entropy alloy predictors of configurational entropy, valence electron concentration, atomic size difference[5] as well as cost efficiency (cost should be on par with Stainless Steel 304). Performance predictions will be compared with a parallel experimental program involving alloy synthesis, structural characterization and electrochemical characterization of the corrosion performance [6].

Reference:

[1] H. Ke and C.D. Taylor, Chloride Susceptibility Index (CSI): An ab initio based corrosion resistance indicator, Research in Progress, NACE (2019), Nashville, TN

[2] S. Wei, L.G. Ferreira, J.E. Bernard, A. Zunger, Electronic properties of random alloys: Special quasirandom structures, 42 (1990).

[3] A.J. Samin, C.D. Taylor, First-principles investigation of surface properties and adsorption of oxygen on Ni-22Cr and the role of molybdenum, Corros. Sci. 134 (2018) 103–111. doi:10.1016/j.corsci.2018.02.017.

[4] C.D. Taylor, S. Li, A. Samin, S. Li, A. Samin, Oxidation versus salt-film formation: Competitive adsorption on a series of metals from first-principles, Electrochim. Acta. (2018). doi:10.1016/j.electacta.2018.02.150.This.

[5] M.C. Gao, J.-W. Yeh, P.K. Liaw, Y. Zhang, eds., High-Entropy Alloys: Fundamentals and Applications, Springer, 2016. doi:10.1007/978-3-319-27013-5_12.

[6] A. Panindre, G.B. Viswanathan, S. Li, C. D. Taylor, G.S. Frankel, The effect of intermediate temperature anneal on the corrosion properties of a High Entropy Alloy, NACE Conference 2019, Nashville, TN, USA.
Ultrasmall Metal Nanoclusters As Bifuntional Electrocatalysts for Overall Water Splitting
Authors: Choi Woojun , Kwak Kyuju , Lee Dongil
Published: February 2020

Splitting water into hydrogen and oxygen is one of the key processes for renewable energy production. Electrocatalytic water splitting composed of hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is considered to be a viable method due to its high efficiency and strong connectivity to energy-related electrodevices. Consequently, development of water splitting electrocatalysts is emerging field spanning from traditional Pt group metals to non-precious metal based catalysts. Ligand-protected metal nanoclusters could be one of the candidates because of their uniformity, stability and distinctive catalytic activity. Here we report electrocatalytic activity of atomically precise Mx(SR)y (M = metal, SR = thiolate) nanoclusters for water splitting reactions. HER activities were investigated by linear sweep voltammetry (LSV) and constant potential electrolysis (CPE). Metal nanoclusters exhibited distinctive HER activity with low Tafel slopes for universal pH range (pH 1 – 14). The activity could be modified by controlling the number of metals and ligands with atomic precision. OER activities of metal nanoclusters were examined by LSV and showed higher catalytic current than commercial IrO2 in alkaline media. Furthermore, metal nanoclusters were used as bifunctional water splitting (HER/OER) catalysts that showed high current density (100 mA cm-2) at a low electrochemical cell potential (2.5 V).
(Invited) National Science Foundation Innovation Programs
Authors: Soriano Molla Jesus
Published: February 2020

This presentation will discuss the challenges faced by academic institutions when trying to commercialize the output of federally funded research. Through the Partnerships for Innovation (PFI) program, the National Science Foundation (NSF) offers researchers from all disciplines of science and engineering the opportunity to perform translational research and technology development, catalyze partnerships and accelerate the transition of discoveries from the laboratory to the marketplace for societal benefit.

PFI has five broad goals, as set forth by the American Innovation and Competitiveness Act of 2017 (“the Act”, S.3084— 114th Congress; Sec. 602. Translational Research Grants): (1) identifying and supporting NSF-sponsored research and technologies that have the potential for accelerated commercialization; (2) supporting prior or current NSF-sponsored investigators, institutions of higher education, and non-profit organizations that partner with an institution of higher education in undertaking proof-of-concept work, including the development of technology prototypes that are derived from NSF-sponsored research and have potential market value; (3) promoting sustainable partnerships between NSF-funded institutions, industry, and other organizations within academia and the private sector with the purpose of accelerating the transfer of technology; (4) developing multi-disciplinary innovation ecosystems which involve and are responsive to the specific needs of academia and industry; (5) providing professional development, mentoring, and advice in entrepreneurship, project management, and technology and business development to innovators.

In addition, PFI responds to the mandate set by Congress in Section 601(c)(3) of the Act (Follow-on Grants), to support prototype or proof-of-concept development work by participants, including I-Corps participants, with innovations that because of the early stage of development are not eligible to participate in a Small Business Innovation Research Program or a Small Business Technology Transfer Program.

Finally, PFI seeks to implement the mandate set by Congress in Section 102(c)(a) of the Act (Broader Impacts Review Criterion Update) by enhancing partnerships between academia and industry in the United States and expanding the participation of women and individuals from underrepresented groups in innovation, technology translation, and entrepreneurship.

The presentation will describe other entrepreneurship, innovation and industrial partnerships programs offered by the NSF to catalyze the commercialization of high-risk, high-impact technologies.
(Invited) Batteries to Power Implantable Medical Devices: Development and Inspiration
Authors: Takeuchi Esther S , Takeuchi Kenneth J , Marschilok Amy C.
Published: February 2020

Batteries for implantable medical devices have requirements specific to each device. However, some characteristics are demanded by all implantable applications including high energy density both volumetrically and gravimetrically, exceptional reliability, predictable behavior, and ability to determine state of charge. The lithium/iodine (Li/I2) solid electrolyte battery system has been used successfully for decades as a high energy density primary battery to power implantable cardiac pacemakers delivering microampere level currents with an exceptional record of predictability and reliability. In contrast, high power cells capable of delivering ampere level pulses based on the lithium/silver vanadium oxide chemistry power implantable cardiac defibrillators.

Case studies will be provided to illustrate that understanding the batteries systems used under the rigorous requirements demanded by implantable medical devices can provide inspiration for addressing issues in battery systems intended for a wide variety of applications. Strategies to extend the life time of lithium batteries comparing cathode materials based on transition metal oxides with transition metal phosphates will be described. Known failure modes are explored along with their impact on interfacial phenomena. The lithium/iodine pacemaker battery is used as inspiration for demonstration of a rechargeable solid state battery based on the use of LiI rich lithium iodide-(3-hydroxyproprionitrile)2 solid state electrolyte. The battery is assembled fully discharged using only the solid state electrolyte. On charge, lithium metal forms at the negative side of the battery and iodine forms at the positive side. Finally, strategies to successfully increase power of high energy density batteries will be described.
Optimizing Electrochemical Thermal Control Devices: Investigating the Effect of Water Contamination on Reversible Silver Thin-Film Plating
Authors: Ganley Emily Nicole , Plumley John Bryan , Tsui Lok-kun , Peng Thomas , Garzon Fernando H
Published: February 2020

Reversible Electrochemical Mirror (REM) technology describes a variable emissivity system that can switch between reflective and transmissive states through the application of a voltage to electrodeposit and remove a reflective mirror film. Such a system is an ideal replacement for traditional thermal control methods in space (louvres and radiators), because it is lighter, has no moving parts, and offers a finer degree of tunability.

We have investigated various silver-plating systems that achieve this switching effect, including (1) AgNO3 in DMSO solvent, as well as (2) AgI and LiBr salts in γ-Butyrolactone. The effect of water contamination on these systems was determined, and the subsequent enhancement or degradation of the system quantified. While silver nucleation occurs more readily in water-contaminated systems, the presence of water may be detrimental to the stability and reversibility of the system such as more ready oxidation of the deposited film. For the DMSO/AgNO3 system, the addition of water also results in an increase in current during deposition (Figure 1). This is hypothesized to be a result of easier dissociation of AgNO3 in the presence of water which leads to greater silver ion conductivity.

Thin film growth will be carried out on various substrates (indium tin oxide (ITO), silver, and gold) to determine the ways in which small amounts of water contamination affect the microstructure, optical reflectivity, reversibility, and stability of the system.

Figure 1: Silver plating at -0.05 V in DMSO/AgNO3 systems (WE: ITO, CE: ITO, RE: Ag/AgNO3/0.1M AgNO3 in DMSO) with various amounts of water-doping. As the concentration of water increases, current increases.

Figure 1
Printed Gas Sensors for Crew Cabin Air Quality Monitoring
Authors: Kim Beomseok , Moon Dong-il , Meyyappan M. , Han Jin-woo
Published: February 2020

Air quality monitoring in the crew cabin is important for crew health and safety. In the past, bulky instruments such as mass spectrometer have been used but simple sensors, which are small and consume low power can be used to get variation of gas concentrations across the cabin. Availability of such sensor chips would be useful for planetary exploration that involves mapping the atmosphere. We have been developing printed sensors that can be printed on demand using the future “ Fablab “ facilities being planned for the International Space Station. We use single-walled carbon nanotubes as the primary sensing material and use variations such as doping, functionalization etc. to incorporate multiple sensors in a sensor array. Since commercial nanomaterials lack consistency in quality, we have also developed a multielectrode system that gives N(N-1)/2 data points for N number of electrodes to provide a stochastic system instead of a single deterministic data point from a two-electrode system. This “ Single Input Multiple Output (SIMO)” system provides a better sensor-to-sensor variation and results for sensing CO2 and ammonia will be presented. This work was supported by the NASA In Space Manufacturing program.
Pulsed Electrophoretic Deposition of Carbon Nanotubes for Anti-Reflective Coatings
Authors: Wang Dan , Hall Timothy D. , Inman Maria , Taylor E. J. , Skinn Brian , Snyder Stephen
Published: February 2020

Exo-atmospheric optical sensors, seeker telescopes, and some other space-borne instruments require low reflectivity surfaces to minimize stray and reflected light across the visible and infrared wavebands. For example, in order to improve the sensitivity of missile-defense sensors and seekers, baffles are used within optical telescopes to reduce stray light. Some materials (e.g., aluminum, beryllium, etc.) are too reflective to use as absorptive baffles without surface processing, although they have lightweight and good thermo-structural properties, and survive harsh environments. Black surface coating treatments have been demonstrated as effective approaches to obtain low reflective surfaces. The surface features and intrinsic properties of the coating materials play an important role for scattering, absorbing, or trapping light. The excellent optical absorption performance and light weight of carbon nanotubes (CNTs) make them as ideal coating materials for obtaining low reflectivity surfaces.

Within this context, Faraday Technology demonstrated the feasibility of a low-cost, efficient and scalable manufacturing process for the deposition of durable, low reflectivity carbon nanotube black coatings based on the use of pulse and pulse reverse electrophoretic deposition. As shown in Figure 1 A, the uniform CNT coatings are formed on stainless steel substrate (Figure 1 A, Inset), and the diffuse reflectance of the CNT coatings is ~ 1% over the visible range. We also demonstrated the potential to apply CNT coating on the internal diameter of cylinders at room temperature (Figure 1 B). Faraday are currently working on developing CNT coatings on the surface of absorptive baffle materials, such as beryllium and aluminum. The economic and scalable technology for producing CNT black coatings on desired substrates can not only be used for minimizing stray and reflected light for space-borne instruments, but also offer potential applications in other optical related devices which request low reflective surfaces, such as solar cells.

Acknowledgements: The financial support of NASA Contract No. 80NNSC18P2062 and DOD MDA Contract No. HQ0147-19-C-7065 are acknowledged.

Figure 1
Paving the Way for K-Ion Batteries: Role of the Electrolyte Reactivity
Authors: Caracciolo Laure , Gachot Grégory , Gabaudan Vincent , Petit Emmanuel , Stievano Lorenzo , Monconduit Laure , Martinez Hervé , Madec Lénaïc
Published: February 2020

Developing batteries based on Earth abundant elements such as sodium, magnesium or more recently potassium has become a mandatory challenge in the context of renewable energy growth that requires large-scale storage systems for which cost is the dominant factor and lithium supply a possible issue. Due to the beneficial potassium abundance (2.09 wt.% of the Earth’s crust), low standard potential of K+/K,1 weaker K+ Lewis acidity,2 K-ion batteries (KIBs) are expected to greatly favor both the energy and power density compared to NIB. Numerous new materials for KIBs have thus rapidly been proposed3 but their performance evaluation still remains greatly limited by the lack of efficient electrolytes and the high reactivity of K metal in half cells.4 Indeed, the use of KN(SO2F)2 (KFSI) instead of KPF6 have been reported to be beneficial to most of the anode materials5 while detrimental to some cathode materials,6 probably due to the corrosion of Al current collector by KFSI at high potential.

In this presentation, the impact of KPF6 and KFSI salts in carbonate- and glyme-based electrolytes is investigated. The reactivity of K metal is first evaluated by its immersion in the different electrolytes. The soluble/gaseous and solid electrolyte degradation species are analyzed using GC/MS and XPS, respectively. A comparison with the reactivity of Li metal in the equivalent Li salts based electrolyte is also performed. Moreover, K//graphite and K//KVPO4F half-cells have also been prepared and stored (no cycling) to investigate interactions between electrodes (i.e. migration of electrolyte degradation species from the K metal to the working electrode) and their impact in solid electrolyte interphases formation and resulting electrochemical performance.

References

N. Matsuura, K. Umemoto, and Z. Takeuchi, Bull. Chem. Soc. Jpn., 47, 813–817 (1974).

M. Okoshi, Y. Yamada, S. Komaba, A. Yamada, and H. Nakai, J. Electrochem. Soc., 164, A54–A60 (2017).

K. Kubota, M. Dahbi, T. Hosaka, S. Kumakura, and S. Komaba, Chem. Rec., 18, 1–22 (2018).

L. Madec, V. Gabaudan, G. Gachot, L. Stievano, L. Monconduit, and H. Martinez, ACS Appl. Mater. Interfaces, 10, 34116–34122 (2018).

N. Xiao, W. D. McCulloch, and Y. Wu, J. Am. Chem. Soc., 139, 9475–9478 (2017).

X. Jiang, T. Zhang, L. Yang, G. Li, and J. Y. Lee, ChemElectroChem, 4, 2237–2242 (2017).
Designing in-Situ Formed Interphases Enables Highly Reversible Cobalt-Free LiNiO2 Cathode for Lithium Metal/Ion Batteries
Authors: Deng Tao , Wang Chunsheng
Published: February 2020

Cathode materials control both the energy density and cost of lithium metal/ion batteries. The cobalt-free LiNiO2 with relatively low cost and extremely high theoretical energy density (~ 1050 Wh kg-1) is one of the most promising cathode materials for high-energy batteries. However, the continuous Ni dissolution, structural disordering, particle cracking and unstable cathode-electrolyte interphase (CEI) during cycling hinder its practical applications. Herein, we surmount these challenges by forming a robust F- and B-rich CEI on LiNiO2 using a high-fluorinated electrolyte with LiDFOB additive. The optimized CEI is able to protect the integrity of particle structure, decrease the dissolution of Ni and suppress the irreversible structure transformation. The LiNiO2 cathode maintains an unprecedentedly high capacity retention of >80% after 400 deep cycles at a high charge cut-off voltage of 4.4 V (vs. Li/Li+). In addition, the reduction of fluorinated electrolytes with LiDFOB additive forms an F, B-rich solid electrolyte interphase (SEI) on the Li metal/graphite anodes, enhancing the Coulombic efficiency to >99% for Li plating/stripping and >99.99 % for the lithiation/delithiation of graphite. This work sheds light on the designing interfacial chemistry for high-energy cathodes, and the design principle is also applicable for other alkali metal ion cathodes.

Figure 1
(Invited) Ordering and Structural Transformations upon Li, Na, K and Mg Intercalation in Transition Metal Oxides and Sulfides
Authors: Van der Ven Anton , Kaufman Jonas , Kolli Sanjeev Krishna , Vinckeviciute Julija
Published: February 2020

Variations in size and electropositivity among Li, Na, K and Mg can lead to very different electrochemical behavior when these species intercalate into transition metal oxides and sulfides. First-principles statistical mechanics approaches are capable of predicting a wide variety of thermodynamic and kinetic properties associated with intercalation processes. We have performed a systematic first-principles study of the electrochemical properties of AxMO2 and AxMS2 where A = Li, Na, K, Mg and where M are different transition metals such as Co, Ti, Ni and Mn. Many differences in the predicted electrochemical properties of these compounds can be attributed to variations in the size of the A cation. Larger cations tend to induce a multitude of stacking sequence change phase transformations. They also lead to stronger ordering tendencies in the layered compounds as the larger separation between MO2 and MS2 slabs results in a reduction of screening between positive cations. We find a rich hierarchy of ordered phases in Na and K containing intercalation compounds that are made up of well-ordered domains separated by anti-phase boundaries. These ordered phases have important consequences for diffusion mechanisms in layered intercalation compounds. The multitude of stacking sequence change transformations also have consequences for cycle life performance.
Understanding Chemo-Mechanical Degradation in High-Capacity Electrode Materials for Beyond-Lithium-Ion Batteries
Authors: Boebinger Matthew G , Wang Baolin , Papakyriakou Marc , Yarema Maksym , Wood Vanessa , Xia Shuman , Zhu Ting , McDowell Matthew T
Published: February 2020

In recent years there has been growing interest in the development of large-volume-change electrode materials for use in lithium-, sodium- and potassium-ion based systems to satisfy the demand for batteries with low cost and/or high energy density. Conversion and alloying battery materials are attractive options for such systems due to their high specific capacity. The conventional thought is that the larger volume changes due to reaction with larger ions (e.g., Na+ and K+) cause significant mechanical degradation. However, the mechanisms by which these ions react with high-capacity materials are largely unknown. In this work, in situ transmission electron microscopy (TEM) experiments are used to examine the nanoscale transformation mechanisms of two different high-capacity nanocrystal materials during reaction with various alkali ions. In both cases, we find that unexpected changes in morphology during reaction arise due to significant mechanical stress evolution within the nanocrystals. Overall, these results are important because they provide guidance for engineering high-capacity electrode materials with improved durability and cyclability.

In the first set of experiments, cubic FeS2 nanocrystals were examined with in situ TEM as they underwent reaction with Li+, Na+, and K+. In all cases, the FeS2 nanocrystals exhibited a conversion-type reaction, but mechanical fracture during reaction was only observed during lithiation (which caused the smallest volumetric changes). This non-intuitive behavior was found to be due to differently-shaped reaction fronts that formed during reaction with Li+ compared to Na+ and K+. Specifically, lithiation induced a reaction front with sharp corners, while sodiation and potassiation resulted in fronts with blunted corners. Chemomechanical modeling of the reaction-induced expansion showed that the sharp corners during lithiation led to higher tensile stress concentrations and thus particle fracture. These results indicate that previously-dismissed high-capacity materials may in fact exhibit good chemo-mechanical stability during reaction and cycling with Na+ and K+. Next, other in situ TEM experiments were performed to investigate reaction mechanisms of Sb nanocrystals. These experiments showed that Sb nanocrystals naturally evolve to form hollow structures during ion removal. This finding indicates that electrochemically optimized nanoscale structures can evolve naturally in certain alloying anode materials, which may obviate the need for complex and expensive synthesis of hollow nanostructures for maximizing cyclability and Coulombic efficiency in battery anodes.

Figure 1
Potential-Dependent Oxidation Mechanism of Li2O2 and Its Application in Li-O2 Batteries
Authors: Wang Yu , Lu Yi-Chun
Published: February 2020

Non-aqueous lithium-oxygen (Li-O2) batteries have attracted intensive research attentions owing to their potential to provide gravimetric energy density 3–5 times that of conventional Li-ion batteries. In-depth understandings of the reaction mechanisms during discharge and charge are the prerequisites for further advancement of the Li-O2 technology. The ORR has been widely established to generate Li2O2 by surface (electrochemical) or solution (chemical) pathway via manipulating the fate of superoxide intermediate (LiO2). However, the reaction mechanism of the charging reaction in Li-O2 batteries (OER, or Li2O2
oxidation) is still under debates.

In this study, we report a potential-dependent oxidation mechanism of Li2O2 (charging mechanism) by examining the reaction intermediate species at a wide range of charging overpotential via thin-film rotating–ring disk electrode (RRDE) and synchrotron-based X-ray absorption near edge structure (XANES). To investigate the oxidation behavior of Li2O2 at lower overpotential, we used ruthenium (Ru) as the model catalyst to control the charging potential. To make the amount of reactant comparable to that in regular Li-O2 cells, we here employ thin-film RRDE by drop casting Valcun Carbon (VC) or VC supported Ru (Ru/VC) particles onto the glass carbon electrode (disk) to increase the total surface area, as shown in Figure 1. XANES further provides the chemical information of reaction intermediates and parasitic product that caused by the intermediates/discharge product. We will discuss potential-dependent charging reaction pathways and provide insights in the design strategy to achieve efficient Li-O2 batteries.

Acknowledgement

This work is supported by two grants from Research Grants Council (RGC) of the Hong Kong Special Administrative Region, China, under No. C7051-17G and CUHK 14207517.

Figure 1
MgCr2-XVxO4 High Voltage Spinel Oxide Cathodes for Mg-Ion Batteries
Authors: Kwon Bob Jin , Hawthorne Krista L , Lau Ka-Cheong , Kim Soojeong , Wu Yimin , Fister Timothy T , Liao Chen , Klie Robert F , Lapidus Saul , Key Baris , Vaughey John T.
Published: February 2020

Theoretical and experimental evidences have revealed that Cr-spinel oxides fulfill the cationic mobility requirements of Mg-ion cathode with a suitable activation energy, while V-spinel oxides with lower redox potentials are moderate to the operating potentials of current candidates of non-aqueous high voltage electrolyte. By controlling structure, composition and complexity, a largely solid-solution MgCrVO4 spinel was synthesized which unlike nanocomposites can bring together the advantages of each transition metal. The spinel was successfully prepared by a simple solid-state reaction with minor inactive Cr or V rich components which was confirmed via 25Mg MAS NMR and high resolution X-ray diffraction analyses. A thermally stable Mg(TPFA)2/triglyme electrolyte was utilized for high temperature electrochemistry, lowering kinetic barriers at and across interfaces so as to observe reversible intercalation in the designed oxide. Multimodal characterization confirmed an apparent bulk demagnesiation from MgCrVO4 with partial reversibility, by probing evolution of the local and long range structure as well as vanadium and chromium electronic states within the lattice. Characterization experiments also provided direct evidence of (de)intercalation reactions that occurred without any major competitive conversion reactions or insertion of protons into the lattice. These findings expand materials composition and complexity design opportunities for Mg-ion cathodes while highlighting the need to identify the origins of reversibility challenges due to but not limited to phase stability particularly for the charged states, barriers at the interface, electrolyte stability and desolvation phenomena.
Na2MPO4f (M: Fe, Mn, Co): Bifunctional Electrocatalysts for Na-Air Batteries
Authors: Sharma Lalit , Barpanda Prabeer
Published: February 2020

The ever-growing energy demand of the world demands for high energy density storage systems. In this pursuit, metal-air batteries with high-energy density (~5200 Wh kg-1) based on O2-H2O based chemistry have been studied extensively. Though they are marked with high safety, low cost and enhanced ionic conductivity, the performance is still largely affected due to the formation of insoluble discharge product. Hence, hybrid aqueous air batteries can be a good alternative as the discharge product is soluble. Air batteries run on two key processes namely oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), kinetics of which are too slow hence, they require a catalyst to increase the rate of reaction. Existing catalysts are costly and lacks bifunctionality. Motivated by recent reports of various phosphate based materials having bifunctional activity, we studied the electrocatalytic activity of Na2MPO4F (M: Fe, Mn, Co) family. Solution-combustion method was used for the synthesis of all materials giving rise to carbon-coated grains. Presence of carbon not only helps in enhancing the electrical conductivity of the material but also improves the catalytic properties. Catalytic properties of all three materials were studied in alkaline medium and Na2CoPO4F was found to give the best results. The onset potential of Na2CoPO4F was found to be 0.854 V vs. RHE for ORR process, which is comparable to 20% Pt/C while an onset potential of 1.591 V vs. RHE was recorded for OER process. A hybrid Na-air battery was fabricated using Na2CoPO4F as an air-cathode and a roundtrip efficiency of 88% was recorded for over 30 cycles. The catalytic properties of all three materials were also studied by means of density functional theory (DFT) analysis. A detailed structural and catalytic analysis of the family will be presented.

Figure 1: Linear sweep voltammetry plots of Fe, Mn and Co-based fluorophosphtes recorded at 1600 rpm in 0.1 M NaOH electrolyte showing their bifunctional nature.

Figure 1
Novel Sulfonated Aromatic Polymer Membranes for Breaking the Coulombic and Voltage Efficiency Trade-Off Limitation in Vanadium Redox Flow Battery
Authors: Kim Sangil , Wang Tongshuai , Han Junyoung , Kim Kihyun , Munchinger Andreas , Kreuer Klaus-Dieter , Bae Chulsung
Published: February 2020

Vanadium redox flow batteries (VRFBs) have received extensive attention due to its attractive features for the large-scale energy storage because of their design flexibility, absence of intercalation/deintercalation and stress build-up in electrodes, and safe operation. One of the most critical components in VRFB is an ion exchange membrane which can prevent cross mixing of the multivalence vanadium ions, while it still allows the transport of protons (or anions) to complete the circuit. However, the trade-off relationship of proton exchange membrane limits the energy efficiency (EE) of the VRFB due to low coulombic efficiency (CE) caused by vanadium ion cross over through the membrane or high membrane resistances. Anion exchange membrane suffers from poor chemical stability and low voltage efficiency due to low ion conductivity.

In this study, we synthesized a series of novel sulfonated aromatic polymer membranes having high proton conductivity as well as selectivity which surpass the proton conductivity-selectivity trade-off relationship. The effect of the pendent group structure on the membrane ion selectivity and battery performance was investigated. It was found that the incorporation of aromatic structures on the pendent groups effectively improved the proton conductivity and selectivity. The membrane with aromatic pendent groups (BPAr-F4) shows 3 times higher vanadium/proton ion selectivity than Nafion 212. As a result, the VRFB single cell equipped with the 80um-thick BPAr-F4 membrane shows significantly better performance in comparison to the cell with Nafion membranes, as high as 97.18% CE, 95.91% VE and 93.20% EE (vs. 75.14% CE, 96.12% VE and 72.22% EE of Nafion 212; 91.30% CE, 95.63% VE and 87.62% EE of Nafion 117) at 20 mA/cm2. Small-angle X-ray scattering (SAXS) studies indicates that their unique morphologies with narrow aqueous ionic domains which are well organized with acidic -SO3H groups results in the high proton selectivity and VRFB performance.
Dicyanobenzoquinone Functionalized Carbon Nanotubes As Cathode Materials for Rechargeable Lithium and Sodium Ion Batteries
Authors: Lyu Hailong , Jafta Charl J , Popovs Ilja , Huang Jingsong , Sumpter Bobby G. , Dai Sheng , Sun Xiao-Guang
Published: February 2020

Currently, lithium ion batteries (LIBs) and sodium ion batteries (SIBs) mainly depend on inorganic cathode materials, which are still plagued by several issues restricting their advancement such as power density, sustainability, and safety. As alternatives, organic electrode materials have been intensively investigated for both LIBs and SIBs due to their advantages of sustainability, flexibility of structure design and environmental friendliness. Among them, organic quinone materials offer a sustainable approach for electric energy storage, however, their intrinsic electrical insulation and dissolution into the electrolyte during cycling have hampered their wide application. To tackle these two issues, we have synthesized novel organic cathode materials by anchoring a quinone compound, 2,3-dicyano-p-benzoquinone (DCBQ) with a high redox potential of 3.37 V vs. Li/Li+, onto carbon nanotubes (CNTs) (CNTs-DCBQ) through a facile ‘‘grafting to’’ method. The elaborate combination of excellent electron conductivity and large surface area of CNTs and stable and reversible redox reaction of DCBQ enables CNTs-DCBQ delivering high reversible capacities of 206.9 and 175.8 mA h g-1 at a current density of 10 mA g-1 and also remarkable capacities of 110.2 and 82.1 mA h g-1 at a higher current density of 200 mA g-1 with a capacity retention approaching 100 % after 1000 cycles for lithium and sodium ion batteries, respectively.
Stabilizing NaCrO2 By Sodium Site Doping with Calcium
Authors: Zheng Lituo , Bennett J. Craig , Obrovac M. N.
Published: February 2020

O3-type NaCrO2 is a promising cathode material as it offers decent energy density and is easy to synthesize from abundant elements. A capacity fade of ~20% in 50 cycles is usually observed for NaCrO2 in organic solvents [1–3]. Research regarding improving the capacity retention of NaCrO2 includes coating the NaCrO2 particle with carbon [1,2], or increasing grain boundary content by nanosizing the grains [3]. In this study, NaCrO2 was Na-site doped with calcium to improve cycling retention in Na cells.

A series of [Na1-2xCax]CrO2 materials were synthesized using a solid state method. Figure 1(a) shows the XRD pattern and Rietveld refinement of [Na0.9Ca0.05]CrO2. A single O3 phase was obtained with no observable impurity. Figure 1(b) shows the capacity and coulombic efficiency versus cycle number for NaCrO2 and [Na0.9Ca0.05]CrO2 when cycled in the voltage range of 2 V – 3.6 V. Both materials have similar initial capacity, However the capacity retention of Na0.9Ca0.05CrO2 is significantly improved, compared to NaCrO2. The coulombic efficiency of Na0.9Ca0.05CrO2 is also constantly higher than NaCrO2. It is speculated that calcium substitution results in a more stable structure during sodium (de)intercalation. The effect of calcium substitution on structural changes during cycling and air-stability will be discussed.

[1] J.J. Ding, Y.N. Zhou, Q. Sun, Z.W. Fu, Cycle Performance Improvement of NaCrO2 Cathode by Carbon Coating for Sodium Ion Batteries, Electrochem. Commun. 22 (2012) 85–88.

[2] C.Y. Yu, J.S. Park, H.G. Jung, K.Y. Chung, D. Aurbach, Y.K. Sun, S.T. Myung, NaCrO2 Cathode for High-Rate Sodium-Ion Batteries, Energy Environ. Sci. 8 (2015) 2019–2026.

[3] Y. Tsuchiya, A.M. Glushenkov, N. Yabuuchi, Effect of Nanosizing on Reversible Sodium Storage in a NaCrO2 Electrode, ACS Appl. Nano Mater. 1 (2018) 364–370.

Figure 1