bluuebunny/crossref_metadata_2025 huggingface dataset:
Unveiling Formation Mechanisms of Atomically Dispersed FeN4 Active Sites
Authors: Wu Gang , Wang Guofeng , Feng Zhenxing , Cullen David A.
Published: February 2020

Iron and nitrogen co-doped carbon (Fe-N-C) catalysts are the most promising platinum group metal (PGM) free catalysts for oxygen reduction reaction (ORR) in acid media for proton exchange membrane fuel cell (PEMFC) application. Despite remarkable progresses have been made in the design of new materials and the study of active sites structures for PGM-free catalysts [1-5], the synthetic methods are primarily dependent on the pyrolysis of metal, nitrogen and carbon sources simultaneously. The formation mechanism of Fe-N4 active sites has remained elusive due to the accompanying process involved in decomposition process of nitrogen and carbon precursors and carbon graphitization, therefore hindering to understand the interaction between Fe and N during the high temperature. In this presentation, we report a non-pyrolysis method that enable high-performance by employing a well-defined model system consist of nitrogen doping, iron and carbon. The as prepared Fe-N-C catalysts showed superior activity in both acid solution (E1/2 =0.84 V vs. RHE) and fuel cell test. Correlation between ORR performance (activity, stability) and thermal activation was also established. A low-temperature activation is enough to generate high activity (E1/2 =0.79 V vs. RHE). Importantly, the formation of Fe-N
x

active sites can separate from nitrogen-doping and carbonization process. Comprehensive studies including X-ray absorption spectroscopy and atomic-resolution electron microscopy proved that high-active Fe-N
x
sites can be formed at low temperature. Molecular dynamics simulation and first-principle calculations further proved that the structure evolution and charge redistribution during the formation of FeNx active sites. These findings provide knowledge of Fe-N-C catalysts as well as other electrocatalysts with metal-N
x
active site.

References

Zhang, S. Ding, S. Hwang, X. Zhao, D. Su, H. Xu, H. Yang, G. Wu, Journal of The Electrochemical Society 2019, 166, F3116.

Zhang, S. Hwang, M. Wang, Z. Feng, S. Karakalos, L. Luo, Z. Qiao, X. Xie, C. Wang, D. Su, Y. Shao, G. Wu, Journal of the American Chemical Society 2017, 139, 14143.

Li, M. Chen, D. A. Cullen, S. Hwang, M. Wang, B. Li, K. Liu, S. Karakalos, M. Lucero, H. Zhang, C. Lei, H. Xu, G. E. Sterbinsky, Z. Feng, D. Su, K. L. More, G. Wang, Z. Wang, G. Wu, Nature Catalysis 2018, 1, 935.

He, S. Hwang, D. A. Cullen, M. A. Uddin, L. Langhorst, B. Li, S. Karakalos, A. J. Kropf, E. C. Wegener, J. Sokolowski, M. Chen, D. Myers, D. Su, K. L. More, G. Wang, S. Litster, G. Wu, Energy & Environmental Science 2019, 12, 250.

X. Wang, D. A. Cullen, Y.-T. Pan, S. Hwang, M. Wang, Z. Feng, J. Wang, M. H. Engelhard, H. Zhang, Y. He, Y. Shao, D. Su, K. L. More, J. S. Spendelow, G. Wu, Advanced Materials 2018, 30, 1706758.
Hydrogen Evolution Reaction on Transition Metals: Promoting Water Dissociation By Tuning the Surface Oxophilicity.
Authors: Farinazzo Bergamo Dias Martins Pedro , Strmcnik Dusan , Lopes Pietro Papa , Connell Justin G. , Ticianelli Edson A. , Stamenkovic Vojislav R. , Markovic Nenad M.
Published: February 2020

Hydrogen evolution reaction (HER) has been at the core of the development of fundamentals of electrochemistry and electrocatalysis. In acidic electrolytes, it has been generally accepted that the differences in reaction rates/activity are closely related to the differences in hydrogen adsorption free energy on different materials. In recent years, the fundamental investigation of the HER has been enjoying a renewed vigor, but this time in alkaline electrolytes, where there is much less consensus on the underlying activity descriptors. While some groups insist on the single descriptor of hydrogen binding energy, our group has continuously pointed out to the bifunctional nature of the HER in alkaline environments, i.e. a good catalyst needs both a beneficial OHad energetics and beneficial Had energetics. In most cases, the OHad-metal energetics is by far the more unfavorable of the two and OHad adsorption therefore represents the rate determining step. In some cases (e.g. polycrystalline iridium), the OHad-metal energetics no longer represents a significant obstacle in the HER process; hence the catalyst's rate determining step becomes Had adsorption and the catalyst starts behaving as it would in acid – as a pseudo mono-functional catalyst. For most materials, however, the HER rates in alkaline environments are significantly lower than in acid. One such example is copper (Cu), where reported values for HER activity in alkaline are indeed lower but are interestingly scattered over a wide range of values. In a manuscript recently published [1], we were interested in the underlying cause of these discrepancies. We explore how the different history the polycrystalline copper surfaces experienced changes their electrochemical properties (e.g. the HER activity). By using detailed spectroscopic surface analysis, we were able to find different extents of oxidation on various copper surfaces and link them to different hydrophilicity of the surfaces. With the established trends we propose that the formation of Cu(I)-OHad‐‐‐OH2 activated complex is essential in lowering the energy barrier for water dissociation, which leads to higher activity for the HER in alkali environments.

[1] Farinazzo Bergamo Dias Martins, P. et al. Hydrogen evolution reaction on copper: Promoting water dissociation by tuning the surface oxophilicity. Electrochem. commun.
100, 30-33 (2019).
Modeling the Mesoscopic Influence of SEI Mechanical Response to Electrode Swelling
Authors: Hooper Justin B.
Published: February 2020

This work focuses on investigating the role that mesoscopic configuration plays in dictating the solid-electrolyte interface (SEI) mechanical durability on lithiation in silicon (Si) anodes. Due to the large expansion of Si upon lithiation, SEI formation and cohesion at the electrolyte interface of Si based anodes is a principle concern in performance of the overall cell, and enabling a more durable SEI would lead to the ability to employ higher Si percentages in anodes, increasing capacity. However, we are still building fundamental understanding of SEI formation and the resultant meso- and microscopic structure evolved due to this formation. This work seeks not to understand the formation itself, but instead to establish intuition about what type of resultant structure we should target as we learn to control the SEI formation process, by investigating the effect that non-homogenous SEI configurations have upon the overall SEI response when subjected to large strain due to the swelling of the underlying Si anode.

Utilizing the material point method (MPM), a continuum mechanics approach akin to the finite element method, but particularly well suited for investigation of materials subjected to large deformation, we model the intrinsic swelling of Silicon under lithiation when coupled to a model SEI. This model SEI, in turn, is constructed of multiple different phases with mesoscopic variability and realistic material response parameterized from atomistic simulation of the mesoscopic phases including both crystalline and glassy inner SEI compounds and ordered/disordered outer SEI compounds derived from liquid carbonate decomposition products. Model mesostructures are constructed and fed into the MPM framework, from which an overall SEI mechanical response may be extracted via numerical simulation. By varying the mesostructures, sensitivity of the mechanical response to the mesostructural features is quantified, providing guidance to possible experimental approaches at improving the SEI capability of protecting the anode during multiple charge/discharge cycles.
Synchrotron-Based Characterization of Perfluorinated Sulfonic-Acid Ionomers
Authors: Dudenas Peter J , Weber Adam Z. , Kusoglu Ahmet
Published: February 2020

Perfluorinated sulfonic-acid (PFSA) ion-conducting polymers (ionomers) serve as both a binder and active ion-transport material in electrochemical energy-conversion electrodes including fuel cells, electrolyzers, and redox-flow batteries. Within the catalyst layer of these devices, ionomer shuttles ionic and liquid or gaseous species to/from catalytic sites.1-2 Optimizing the multi-functional role that PFSA ionomers play is crucial to developing next generation devices, and, to do so, the underlying fundamental structure-property relationships of these materials must first be established. Reducing the complex heterogeneous environment of catalyst layers down to representative model systems enables probing these relationships in a systematic and fundamental manner. To accomplish this effort, we spin-cast thin films of Nafion and 3M ionomer chemistries, including multi-acid side chains, across a range of thicknesses and processing conditions. Synchrotron-based x-ray scattering and spectroscopy, and advanced analysis of the collected data, is employed to characterize the phase-separated nano-structure of PFSA thin films. Results show the universality of confinement effects across chemistries, and how processing conditions modify the chemistry-confinement interplay and impact structure-function relationships. X-ray characterization is carried out in both ambient and humidified environment, in-situ, to determine the nanostructural changes in ionomer film in response to environment. These structural investigations are correlated to thermodynamic swelling properties using ellipsometry to identify factors controlling ionomer transport functionality in electrode structure of energy conversion devices.

Acknowledgments

We thank Mike Yandrasits and Andrew Haug of 3M for providing ionomers and helpful discussions. This research used beamline 7.3.3 of the Advanced Light Source, which is a DOE Office of Science User Facility under contract no. DE-AC02-05CH11231.3 The study was funded under the Fuel Cell Performance and Durability Consortium (FC-PAD) funded by the Energy Efficiency and Renewable Energy, Fuel Cell Technologies Office, of the U.S. Department of Energy under contract number DE-AC02- 05CH11231.

References

Mauritz, K. A.; Moore, R. B., State of understanding of Nafion. Chemical reviews
2004,
104 (10), 4535-4586.

Kusoglu, A.; Weber, A. Z., New Insights into Perfluorinated Sulfonic-Acid Ionomers. Chemical Reviews
2017,
117 (3), 987-1104.

Alexander, H.; Wim, B.; James, G.; Eric, S.; Eliot, G.; Rick, K.; Alastair, M.; Matthew, C.; Bruce, R.; Howard, P., A SAXS/WAXS/GISAXS Beamline with Multilayer Monochromator. Journal of Physics: Conference Series
2010,
247 (1), 012007.
(Invited) Successes and Challenges of Teaching and Conducting Electrochemistry-Based Research at an Undergraduate Institution
Authors: Kariuki James
Published: February 2020

Undergraduate research, which is considered a high-impact practice in higher education, has been shown to provide an enriching educational experience to students. Undergraduate research provides students with an opportunity to engage in hands-on activities and allows them to develop potential solutions to real-world problems. It has been demonstrated that students who participate in undergraduate research significantly improve their critical thinking and communication skills and are more satisfied with their overall educational experience.

My presentation will focus on recruitment strategies for undergraduate researchers, different categories of research projects, and the successes and challenges associated with undergraduate research. Specifically, my talk will focus on the teaching of electrochemistry and discuss the scope of possible electrochemistry-based research at a primarily undergraduate institution.
Deconvoluting Li-Ion Battery Electrode Crosstalk with Electrochemical Generator-Collector Measurements
Authors: Harris Oliver Clyde , Tang Maureen H
Published: February 2020

Accelerated capacity fade in high-voltage Li-ion batteries is attributed to crosstalk between the positive and negative electrodes. During low potential operation of the negative electrode and high potential operation of the positive electrode, the nonaqueous electrolyte is reduced and oxidized, respectively, forming soluble, insoluble, and gaseous byproducts. Additionally, during electrolyte oxidation transition metals dissolve from active material of the cathode. After cycling, soluble species from the positive electrode are detectable at the negative electrode and are suspected to play an important role in disrupting the formation, growth, and performance of the solid-electrolyte interphase (SEI), leading to unmitigated capacity fade. In full-cell studies the effects of electrolyte decomposition and metal dissolution on battery lifetime and coulombic efficiency are well-documented, however the precise nature of crosstalk species and the mechanism of capacity fade remain to be understood.

Here we present two applications of our generator-collector approach to understanding battery crosstalk. First, we employ rotating-ring disk electrode (RRDE) voltammetry to study the effects of metal dissolution from LNMO (LiNi0.5Mn1.5O4) on SEI performance. By cycling an LNMO-coated glassy carbon disk to high operating potentials, we stimulate metal dissolution and collect these soluble species on the downstream glassy carbon ring electrode, which is cycling to low potentials to form and grow an SEI. The effects of metal contamination on SEI passivation are characterized via a redox mediator method and quantified using finite element simulations. We find that metal dissolution has a more profound impact on electronic than morphological SEI properties. Interpreting these results with physics-based models of SEI passivation imply that the inorganic layer is critical to passivation, while organic layers are inert at best.

In the second application, we demonstrate an improved method for performing generator-collector measurements on composite electrodes via the development of a microfluidic electrochemical cell. Our design incorporates commercial high-voltage positive electrodes, a graphite negative electrode, and commercial Li-ion battery electrolyte. Forced convection from electrolyte flow isolates the upstream electrode from crosstalk species generated at the downstream electrode, and deconvolutes the role of electrolyte oxidation and reduction on capacity fade. We study the effects of flow rate and flow direction on charge/discharge behavior for each electrode, and correlate coulombic efficiencies to the extent of crosstalk. These electrochemical generator-collector studies provide a greater understanding of the mechanism behind transition metal travel from the positive to negative electrode in a full-cell, as well as the importance of electrolyte decomposition in this transport mechanism.
Development of Novel Binders for Silicon Anodes for Lithium Ion Batteries
Authors: Lucht Brett , Chandrasiri Kaveendi
Published: February 2020

High capacity electrode material has been studied over the years due to the constant demand for high energy density applications in li ion batteries. Among others, silicon has been considered a more promising candidate for its high theoretical capacity of ~ 3600 mAh/g, abundant resources, low cost and low toxicity. However, silicon-based electrodes face rapid degradation due to the extensive volume variation (~300%) in the charge discharge process. Binders used in the electrode fabrication plays a crucial role in these high-performance electrodes since it can reduce the mechanical fracture in the cycling process.

Utilization of polymeric material as binders to hold the active material has been the most common approach used in the li ion battery electrode preparation. Recent studies have shown the use of small molecular carboxylic acids as binders which showed an improvement in the cell performance for silicon electrodes. We will review various non-polymeric binder for silicon electrodes. Many of these alternative binders afford electrode preparation in water which reduces the introduction of toxic organic solvents such as NMP to the environment. The novel non-polymeric binders have better performance compared to PVDF. Surface morphology and Solid electrolyte interface was analyzed using electron microscopy techniques and spectroscopic methods and the results will be discussed.
Rational Design of Bian Based Anode Binder/Additive for High Performance Li Ion Secondary Batteries
Authors: Matsumi Noriyoshi , Patnaik Sai Gourang , Vedarajan Raman
Published: February 2020

Bisiminoacenaphthene (BIAN) has been an important ligand structure for a variety of metal complex and widely employed as a ligand for olefin polymerization catalysts. However, in spite of their unique electrochemistry, it has not been widely utilized for energy devices. In the present work, firstly BIAN based novel conjugated polymer was prepared by Sonogashira-coupling polymerization and the obtained polymer (P-BIAN) was employed as anode binder in Li/EC:DEC/C type anodic half cells. Second, novel additive material bearing BIAN structure (BIANODA) was synthesized, which was used as additive to improve the characteristics of MNC cathode material (LiMn1/3Ni1/3Co1/3O2).

Electrochemistry of these materials along with characteristics of fabricated Li ion battery cells under these design protocol will be presented in detail.

The BIAN based polymer, P-BIAN shows lower LUMO level in comparison with ethylene carbonate (EC). This means reductive doping of P-BIAN takes place prior to reductive decomposition of EC at anode surface, which will restrict thick SEI formation at anode. When cyclic voltammetry measurements were carried out for coin cell with P-BIAN, peak due to reductive decomposition of EC was not observed, unlike the case of PVDF. Further, after charge-discharge cycles, coin cell with P-BIAN exhibited much smaller internal resistance when compared with PVDF. This indicates that reductive doping of P-BIAN and restriction of SEI decomposition had synergistically decreased internal resistance of battery cells. As a result, coin cell with P-BIAN showed 1.5 times higher discharging capacity in comparison with coin cell with PVDF.

On the other hand, BIANODA has higher HOMO level than that of EC, which enables oxidative polymerization of BIANODA prior to oxidative decomposition of EC. This will restrict thick SEI formation at MNC cathode surface. Use of Schiff base can trap HF generated during the cycling, and strong binding property of BIAN can stabilize MNC cathode for long term use. Consequently, BIANODA additive had enhanced the discharging performance of MNC/EC:DC/Li cathodic half cells.

Both P-BIAN as anodic binder material and BIANODA as MNC cathode additive were found to be remarkably effective to improve the performance of Li ion battery cells.
(Invited) Beyond Si and SiO
x
: SiN
x
and SiC
x
Anode Materials for Lithium-Ion Batteries
Authors: Cho Jaephil , Sung Jaekyung
Published: February 2020

The research of silicon (Si) anode with commercial feasibility for high energy lithium ion batteries continues to accelerate because of its high specific capacity of 3592 mAh g-1. Since the massive volume change upon repeated charging-dischrage process turned out as the main origin of insufficient cycling stability, the various material designs has recently been proposed. Nanostructure engineering has been spotlighted because the stress is highly mitigated during lithiation when its size decreases to the nano level. However, although theoretical simulation results have concluded that the size of silicon with quantum level (1~5 nm) shows extremely low stress evolution during (de)lithiation process, previously reported Si-based anodes have been too much focusing on void space or morphological properties with the size of over 10 nm. Alternatively, phase control of active-inacitve matrix has received considerable attention because the nano-engineering advantages (low stress intensification) are strenthened and the nano-property weakenesses (low tap density, high surface area and poor elecrical properties) are compensated simultaneously. For example, micron-sized SiO
x
consisting of nano-Si (active matrix) with the size of the under 5 nm and SiO1-2 (inactive matrix) has been highlighted owing to its high cycling performance and tap density. Nevertheless, its utilization as a commercial anodes are still hindered by its inferior battery performance including low coulombic efficiency of < 85% caused by intrinsic characteristics of inactive matrix (irreversible formation of Li2O and Li4SiO4). As a result, there is strong motivation to develop the technology realizing the silicon size up to the quantum dot level (1~5 nm) in addition to the phase control of fascinating inacitve matrix. In this aspect, the SiNx and SiCx anodes will be proposed as alternative high capacity anodes with commercial feasibility for high energy lithium ion batteries. In addition to its fundamental features and variety of strategies according to the synthetic method, the critical factors affecting the electrochemical performances of SiN
x
and SiC
x
anodes will be covered. Furthermore, these anodes will be compared with the state of the art benchmarking samples including SiOx and Si-carbon composites under the industrial standard conditions.
1D Buliding Block Strategies for High Energy Density Li-Ion Batteries
Authors: Kim Ju-Myung , Lee Sang-Young
Published: February 2020

Ever-increasing demand for high-performance portable electronics, electric vehicles (EVs) and grid-scale energy storage systems (ESSs) has been in relentless pursuit of advanced energy storage systems with reliable electrochemical properties. Among a vast variety of rechargeable power sources, undoubtedly, lithium-ion batteries have been most widespread and still garnered considerable attention due to their well-customized battery characteristics. From the electrode architecture point of view, most conventional electrodes are characterized with simple and random pile-up of electrode active materials, carbon powder conductive additives and polymer binders on top of metallic foil current collectors. Unfortunately, such a stereotyped electrode architecture often gives rise to non-uniform and sluggish electron/ion transport particularly in their through-thickness direction and is also vulnerable to structural disruption upon mechanical deformation. In particular, the poorly-developed electron/ion conduction pathways of the electrodes eventually provoke unwanted electrochemical polarization, which becomes more serious at harsh operating conditions such as high-mass loading electrodes and fast charge/discharge current densities that are urgently needed for high-energy EV batteries. Due to these unavoidable limitations, the conventional electrode architecture has posed a formidable challenge to sustainable progress of battery performance, thus pushing us to search for alternative solutions. Here, we demonstrate a new class of all-nanomat lithium-ion batteries (LIBs) based on one-dimensional (1D) building elements interweaved into heteronanomat skeletons. Among various electrode materials, silicon (Si), over-lithiated layered oxide (OLO) materials and redox-active organic materials are chosen as model systems to explore the feasibility of this new cell architecture and achieve unprecedented cell capacity. Nanomat electrodes, which are completely different from conventional slurry-cast electrodes, are fabricated through concurrent electrospinning (for polymeric nanofibers) and electrospraying (for electrode materials/carbon nanotubes (CNTs)). Electrode active material powders are compactly embedded in the spatially interweaved polymeric nanofiber/CNT heteromat skeletons, which play a crucial role in constructing three-dimensional (3D)-bicontinuous ion/electron transport pathways and in removing metallic foil current collectors. Driven by the aforementioned structural/chemical uniqueness, the all-nanomat electrodes show exceptional improvement in electrochemical performance as well as mechanical deformability, which lie far beyond the values achievable with conventional LIB technologies.
Reduced Surface Area Cathode Particles By Mechanofusion Processing
Authors: Zheng Lituo , Obrovac M. N.
Published: February 2020

Polycrystalline layered-type cathode materials are usually in the form of spherical secondary particles consisting of an aggregate of primary particles. The surface of polycrystalline cathode particles contains features in the form of pits and valleys, leading to a high surface area. As the parasitic reactions with electrolyte occur at cathode surfaces, it is important to reduce the surface area in order to obtain long cycle life. Here, we present a study of using a mechanofusion method to reduce the surface area and improve the cycling performance of LiNi0.6Mn0.2Co0.2O2 (NMC622).

Figure 1(a) shows an SEM image of a pristine NMC622 particle. Primary particles can be seen clearly on the surface of a pristine NMC622 particle, resulting in a rough surface. Figure 1(b) shows an SEM image of an NMC622 particle processed with the mechanofusion method. After the mechanofusion process, the secondary particle size does not change. However, it is apparent that the surface has been smoothed compared to pristine NMC622. Figure 1(c) shows the voltage curve of materials processed using the mechanofusion method for varying times. Figure 1(d) shows the capacity retention rate of all the materials. NMC622 processed with mechanofusion method has better capacity retention than pristine NMC622, which is ascribed to its reduced surface area, resulting in reduced parasitic reactions with electrolyte.

Figure 1
Bulk / Surface Stabilized Tungsten Doped Ni-Rich Li[NixCoyMn(1-x-y)]O2 Layered Cathode Material for High-Energy-Density Lithium-Ion Batteries
Authors: Park Geon-Tae , Nam Gyeong Won , Sun Yang-Kook
Published: February 2020

With electric vehicles (EVs) industry growing at an alarming rate, many kinds of cathode materials were developed so far to satisfy increasing needs for more energy density and cycling lifespan.[1] Regarding structural stability, nothing but layered transition-metal (TM) oxide cathode materials especially Li[NixCoyMn(1-x-y)]O2 and Li[NixCoyAl(1-x-y)]O2 (0.5 < x < 0.8) so called NCM and NCA are used as a practical lithium ion batteries (LIBs) cathodes for EV applications.[2] Especially, NCM and NCA with even higher nickel contents (x > 0.8) are getting much attention in these days. At the end of Ni-rich cathode material lies pure LiNiO2 (LNO), however, the intrinsic structural instability, poor thermal property and complexity on synthesis highly limits its practical application.[3] By referring to J.-H. Kim et al., in order to increase the energy density of Ni-rich cathode material, it may be advantageous to raise the potential rather than increase the nickel contents further.[4] In this study, a series of tungsten (0.5 and 1.0 mol%) were incorporated in Ni-rich layered Li[Ni0.90Co0.05Mn0.05]O2 cathode material to investigate the stabilization role of tungsten especially on higher voltage and thermally aged condition. In situ X-ray diffraction analysis linked with cross-sectional visual imaging were done to demonstrate the effect of tungsten on bulk lattice stabilization. Surface protectivity at upper potential of disordered spinel-like phases which come from tungsten doping was proved through impedance spectroscopy and post-mortem TEM analysis.

References

S.-T. Myung, F. Maglia, K.-J. Park, C. S. Yoon, P. Lamp, S.-J. Kim, Y.-K. Sun, ACS Energy Lett.
2017, 2, 196.

Teslar Motors, http://www.teslamotors.com/ (accessed: December 2017).

C. S. Yoon, D.-W. Jun, S.-T. Myung, Y.-K. Sun, ACS Energy Lett.
2017, 2, 1150.

J.-H. Kim, K.-J. Park, S. J. Kim, C. S. Yoon, Y.-K. Sun, J. Mater. Chem. A, 2019, 7, 2694
Highly Safe and High Energy Density Lithium-Ion Battery Using Less Volatile Electrolyte
Authors: Unemoto Atsushi , Konishi Hiroaki , Nishimura Katsunori , Seki Eiji , Kawaji Jun , Okumura Takefumi
Published: February 2020

Lithium-ion batteries (LIBs) are now used in the variety of fields including vehicles, and industrial and portable uses. Since the current LIBs use volatile and flammable electrolyte liquid, they have a risk on safety, e.g. explosion owing to an unexpected short. For ensuring the LIB safety, the cooling and safety mechanisms need to be installed in battery packs used for large scale applications, i.e. electric vehicles (EVs), and they compromise battery energy density and cost competitiveness.

To overcome the issue related to the LIB safety, we recently developed a novel electrolyte having the lower vapor pressure than the conventional organic liquid electrolyte, and incorporated it into LIB. High energy density of over 300 Wh/kg and high output power of over 1,600 W/kg were successfully demonstrated.

In the presention, the concept of our less volatile electrolyte, and evaluated results on performance of our highly safe, high energy density and high power LIB will be reported.

This work was supported by Innovative Science and Technology Initiative for Security, ATLA, Japan.
Insight into Performance Degradation of Ni-Rich Layered Cathode Materials
Authors: Zhang Sheng S.
Published: February 2020

As a promising cathode material for high-energy-density lithium-ion batteries, Ni-rich lithium transition metal oxides, LiNi1-x-yMnxCoyO2, suffer from a number of problems, such as inferior cycling stability, poor safety, and gas generation, which greatly hinder their application in practical batteries. Despite much effort made previously, the mechanism for the above problems is still not well understood. Selecting LiNi0.80Co0.10Mn0.10O2 (NCM811) as an example, in this work we studied performance degradation of the Ni-rich layered cathode materials by cycling and float-charging Li/NCM811 cells in high voltage range (4.5 V and 4.7 V, respectively). It is found that nearly all the above problems can be linked to the oxidation of lattice oxygen occurring in the capacity region with respect to the H2→H3 phase transition. In addition to contributing to overall capacity, the oxidation of lattice oxygen results in irreversible loss of oxygen from the cathode material by means of oxygen evolution and relative reactions between the active oxygen evolution intermediates and electrolyte solvents. It is the loss of oxygen that results in irreversible layered-spinel-rocksalt phase transition, secondary particle crack, and capacity loss. The oxidation of lattice oxygen is an intrinsic property of the Ni-rich layered cathode materials at high state-of-charge states (corresponding to high potentials), which takes place not only on the surface but also in the bulk of the NCM materials. It is suggested that the priority for future research on such cathode materials should give to suppression of the oxygen evolution, and development of the anti-oxygen electrolytes that are chemically stable against the active oxygen evolution intermediates.

Figure 1
The Influence of Polyvinylidene Fluoride (PVDF) Binder Properties on LiNi0.33Co0.33Mn0.33O2 (NMC) Electrodes Made By a Dry-Powder-Coating Process
Authors: Wang Ming , Hu Jiazhi , Wang Yikai , Cheng Yang-Tse
Published: February 2020

A typical electrode fabrication process starts with mixing active materials, conductive agents, polymeric binders, and solvents to form a slurry. Polyvinylidene fluoride (PVDF) is a commonly used binder, which requires N-Methyl-2-pyrrolidone (NMP) as the solvent. The usage of NMP increases the material and manufacturing cost of the electrode because NMP is expensive, toxic, and flammable, as well as requiring energy to dry and capture. Electrostatic spray deposition (ESD), a dry-powder-coating process, is one of the promising methods to eliminate the usage of organic solvents. The influence of PVDF properties on wet-slurry-coated electrodes has been investigated extensively, their effects on the electrodes made by the dry-powder-coating process are still unknown.

In this presentation, we report the effects of the molecular weight of the PVDF binder on the electrochemical performance and mechanical integrity of the NMC electrodes made by a dry-powder-coating process. The microstructure, binding strength, and electrochemical behavior of the electrodes made with two types of PVDF polymers were compared. The results show that a thin layer of PVDF formed on NMC surface after the thermal activation process, acting as both binding points and lithium intercalation/deintercalation barriers in the dry-powder-coated electrode. The microstructure and porosity of the PVDF layer depend strongly on the molecular weight of the PVDF. By increasing the molecular weight of the PVDF, the layer becomes more porous, and capacity retention can be improved without decreasing the binding strength and long-term cycling performance.
Experimental Study on the Fabrication of Metal Oxide Anodes By Hydrochloric Leaching of Ferro-Chrome Alloys
Authors: Gülcan Feryat , Karahan Billur Deniz
Published: February 2020

A new rapid and cheap process has been designed to fabricate composite powders containing iron and chromium. In this concept, first ferro chrome alloys being used as raw material has been leached out with hydrochloric acid solution (5M at room temperature). The acid leaching rates of iron and chromium have been systematically studied based on atomic absorption spectroscopy results. Then, the leachate with metal ions has been transferred into an autoclave and hydrothermally treated (at 1800C for 90 min.) to fabricate composite powders. The morphology and the structure of this powder has been characterized by scanning electron microscopy and x-ray diffraction method. Its possible use as anode material in lithium ion batteries has been evaluated based on electrochemical and galvanostatic test results.
(Invited) Investigation of Megahertz Frequency Modulation Effects on Charge and Discharge Behavior of Lithium Ion Batteries
Authors: Wen Bohua , Tsai Ping-chun , Chiang Yet-Ming
Published: February 2020

Over the past several years, reports have emerged of ultrafast charging algorithms for lithium ion batteries [1,2] that in at least one instance [3] is attributed to megahertz frequency modulation of charging/discharging currents. Such algorithms are claimed to dramatically improve active material utilization as well as cycle life, but no mechanisms have been proposed in published work, nor, to our knowledge, have mechanistic studies have been conducted. In this work, we use a recently developed technique [4] in which single electrode particles having capacities of a few nAh can be interrogated with electrodynamic measurements (EIS, GITT, polarization-depolarization) while varying the state-of-charge. This capability allows clean separation of interfacial vs bulk transport limitations at the individual particle level, without complicating factors from typical composite electrode microstructures. To this capability, we have added AC pulse charging and discharging at ultra-low currents (down to picoA) with high-frequency waveforms (up to ~ MHz).

With this capability, we aim to answer a number of questions such as: Are these effects real? Are they significant? And, what are possible mechanisms by which ion transport kinetics in a lithium ion battery are responsive to megahertz frequency excitation?

This work was supported as part of the NorthEast Center for Chemical Energy Storage (NECCES), an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences under Award # DE-SC0012583.

References:

https://techcrunch.com/2015/05/05/nucleus-scientific-launches-to-revolutionize-batteries/

https://www.greencarreports.com/news/1121116_company-claims-to-harness-ai-for-quicker-electric-car-dc-fast-charging

Sherstyuk et al., Extended life battery, US Patent No. 9,966,780B2, May 2018.

P.-C. Tsai, B. Wen, M. Wolfman, M.-J. Choe, M. S. Pan, L. Su, K. Thornton, J. Cabana, Y.-M. Chiang, Single-particle measurements of electrochemical kinetics in NMC and NCA cathodes for Li-ion batteries. Energy Environ. Sci., 2018, 11, 860-871.
Electrochemical Modeling and Experimental Investigation of Aging Mechanisms on NCA and Graphite Electrodes Harvested from Off-Grid PV Lithium-Ion Cells
Authors: Benavente Fabian Andres , Ko Jing Ying , Lundblad Anders Olof , Ekström Henrik , Lindbergh Göran
Published: February 2020

Modelling of electrochemical impedance spectroscopy (EIS) to predict aging in lithium ion batteries is a useful tool when performing a diagnosis of the state of health (SOH) of the battery. Aging of lithium ion batteries happens in applications from electric vehicles to stationary systems and is associated to capacity fade and impedance increase [1]. By predicting the aging parameters through modeling of EIS from separated electrodes, it is possible to estimate the SOH of the full cell and therefore improve its performance. In this work NCA and graphite electrodes were harvested from cylindrical cells aged under an off-grid PV/Battery system conditions and analyzed by means of EIS to determine the causes of electrode deterioration.

The NCA/graphite cylindrical cells were calendar aged and cycle-aged between SOC 20-50 %, 35-65 %, 60-90 % and 20-95 % until end of test (EOT) is reached (e.g. 1000 cycles). The impedance behavior of the calendar and cycle aged cells were measured. Each electrode is carefully harvested once reached the EOT and electrochemically characterized using symmetric cells by means of EIS.

A physics-based impedance model is employed to fit the experimental EIS of symmetrical cells using a least square fitting tool in COMSOL® Multiphysics 5.4. It is based on the pseudo two-dimensional (P2D) model [2] incorporating intercalation kinetics, mass and charge transport based on concentrated solution porous electrode theory. The model additionally accounts for double layer effect and aging mechanisms. Using the model, useful aging parameters were parameterized, and the variation of the aging parameters with different aging history was validated with the support of scattered electron microscopy (SEM) technique. Among the aging mechanisms described, an increase in the local contact resistance between the active material and the conductive carbon, and decrease in particle size due to particle cracking and further film formation due to SEI are considered. The impedance model parameters from both electrodes are then linked to the aging process observed on experimental full cell.

Figure 1 shows the fitting and experimental curves for graphite Nyquist plot, in which we observe a good fitting specifically at low frequencies. Although the model predicts a second semicircle in the middle requency range, the experimental curve also shows a time constant element which can be considered as a truncated semicircle in the same region.

[1] T. G. Zavalis, M. Klett, M. H. Kjell, M. Behm, R. W. Lindström, G. Lindbergh, Electrochemica Acta, 110 (2013) 335-348.

[2] J. Newman and W. Tiedemann, AIChE J., 21, 25–41 (1975).

Figure 1
Life Prediction of Lithium Ion Battery for Grid Scale Energy Storage System
Authors: Hashimoto Tsutomu , Kanamura Kiyoshi
Published: February 2020

As renewable energy with large output fluctuation increases, adoption of a large power storage system in which lithium ion secondary batteries are series-parallelized has been started for stabilization of grid power. However, stationary storage systems may be charged and discharged under more severe conditions than batteries for electric vehicles, and may deteriorate in a short period of time. In this research, while analyzing the change of capacity and internal resistance of the lithium ion secondary battery which uses LFP for the cathode and carbon anode. We estimated the life when charging and discharging under the conditions of ancillary service*, and considered the proposed measures for prolonging the life.

* ancillary service; A power adjustment method for stabilizing grid transmission

Experiment

A sample cell using an electrode (57 mm × 40 mm) including LiFePO4 for the positive electrode and carbon for the negative electrode was used. As evaluation methods, temperature and charge / discharge cycle tests with different charge / discharge rates and calendar life tests were conducted to analyze cycle characteristics and time characteristics of capacity and internal resistance.

Results and Discussion

2.1 Cell performance

The LFP cell produced in this study had an average voltage of 3.05 V (during 1 C discharge), an initial capacity of 1.0 Ah (during 1 C discharge), and a DC resistance of 16 mΩ (SOC 50%). When 1 C charge and discharge were repeated in the initial cell, the temperature rose to 31.1 °C. under natural cooling conditions of 24.9 ° C. outside temperature.

2.2 Degradation characteristics

The capacity decrease is highly dependent on SOC, and in the state of 90% of SOC, the capacity decrease was about twice as fast as 50% of SOC. On the other hand, the increase in resistance was highly temperature-dependent, and the capacity decrease was about twice as fast as at 25 ° C. at 45 ° C. conditions. Also, multiple degradation mechanisms exist because at least two or more inflection points exist, not following the 1/2 power of time, which is the degradation tendency of a general lithium ion secondary battery.

2.3 Life prediction of LIB for grid scale energy storage system

There are many ways to operate the stationary storage system, but as a power adjustment method to stabilize power transmission of the system, the result of predicting the degradation behavior when the battery is operated under the test condition of ancillary service reported by PJM. It has been found that if the number of cells in parallel is reduced to increase the output power per unit cell, the deterioration is accelerated due to the influence of the temperature rise of the cells.

Figure 1
(Invited) On Interpreting Polarization Curves for Microbial Fuel Cells – How Standard Fuel Cell Interpretations Do Not Apply
Authors: Popat Sudeep
Published: February 2020

Microbial electrochemical technologies (METs) represent a new class of electrochemical technologies in which one or more electrode reactions are catalyzed by microorganisms. The most common example of an MET is the microbial fuel cell (MFC). In MFCs, anode-respiring bacteria (ARB) catalyze the oxidation of simple organic molecules such as acetate, and respire to an anode, thus producing an electrical current. The electrons thus respired move through an external circuit to the cathode, where oxygen is reduced (non-biologically) to water. In this presentation, I will demonstrate through a decade of research I have been involved in how traditional interpretations of a typical fuel cell polarization curve do not apply to MFCs. For example, anodic polarization curves on ARB biofilms show that maximum current in produced with an overpotential of about 0.2 to 0.3 V. Any further increases in anode potential do not result in higher current densities, and the anodic polarization curve looks like it is dominated by a “mass transport limitation”; yet, no amount of higher substrate or buffer (to transport out the protons as a product of anode respiration) results in alleviation of this limitation. The limitation in current production is instead due to intracellular machinery in ARB that is optimized to respire to electron acceptors within a narrow range of redox potentials. On the other hand, cathode polarization curves show a large overpotential at low current densities, representative of “activation losses” as per standard fuel cell interpretations; yet these overpotentials, even for platinum-group metals when used in MFC cathodes, are larger than 0.5 V, which is unrealistic. The large cathodic overpotentials at low current densities are instead mass transport related losses that affect the cathode pH and thus the overall thermodynamics of the oxygen reduction reaction. Through a comprehensive understanding of the differences in overpotentials in MFCs in relation of typical fuel cell overpotentials, we can now begin to apply methods through which these could be overcome to design systems that would perform well as they are scaled up.
(Amazon Catalyst at ECS Grant Winner) Enhancing the Rate of Electrocatalytic Conversion of N2 to NH3 Using Bimetallic Au-Pd Nanoparticles
Authors: Nazemi Mohammadreza , El-Sayed Mostafa
Published: February 2020

Ammonia is one of the widely produced chemicals in the world, with broad applications in producing nitrogen-based fertilizer, energy, and in the pharmaceutical industry. The current industrial method for ammonia production is energy intensive and heavily relies on fossil fuels, which are responsible for environmental pollution. To meet ammonia demands, it is necessary to develop sustainable and environmentally friendly production methods that consume significantly less energy than the current methods. Here, the use of hollow gold nanocages (AuHNCs) as an effective electrocatalyst is evaluated for electrochemical nitrogen reduction reaction (NRR) under ambient conditions. The electrochemical experiments are carried out at various potentials in 0.5M LiClO4 aqueous solution using AuHNCs, and their catalytic efficiency is determined for the conversion of nitrogen to ammonia [1, 2]. The highest ammonia Faradaic efficiency (30.2%) is achieved at−0.4 V vs. RHE while the highest ammonia yield (3.9 μg cm-2 h-1) is obtained at −0.5 V vs. RHE. The electrocatalytic activity of NRR using AuHNCs is further compared with that of solid Au nanoparticles of various shapes (i.e., rods, spheres or cubes) to elucidate the enhanced rate of the reaction resulting from the increase in surface area and confinement effects. The three-fold enhancement in ammonia Faradaic efficiency is achieved by using the AuHNCs (30.2%) compared to the solid Au nanocubes (11.4%) [1]. It has been demonstrated that electrochemical N2 reduction for NH3 production using Pd nanoparticles requires lower overpotential and results in higher electrocatalytic efficiency for NH3 compared with Au nanoparticles. The use of Pd and hybrid Au-Pd nanoparticles is evaluated for electrochemical nitrogen reduction reaction (NRR) under ambient conditions. The results are further complemented by in-situ surface-enhanced Raman spectroscopy (SERS) and ex-situ
1H NMR to monitor the trace amount of NH3 over the course of the experiment and elucidate the possible differences in the reaction mechanism for electrosynthesis of NH3 on Pd and Au surfaces.

References

[1] Nazemi, M., Panikkanvalappil, S.R. and El-Sayed, M.A., 2018. Enhancing the rate of electrochemical nitrogen reduction reaction for ammonia synthesis under ambient conditions using hollow gold nanocages. Nano Energy, 49, pp.316-323.

[2] Nazemi, M. and El-Sayed, M.A., 2018. Electrochemical Synthesis of Ammonia from N2 and H2O under Ambient Conditions Using Pore-Size-Controlled Hollow Gold Nanocatalysts with Tunable Plasmonic Properties. The journal of physical chemistry letters, 9(17), pp.5160-5166.
3D Printable PVDF/Dmaam Based Gel Polymer Electrolyte for Lithium Ion Batteries
Authors: Rahman Md Sazzadur , Khosla Ajit , Kawakami Masaru , Furukawa Hidemitsu
Published: February 2020

A novel 3D printable gel polymer electrolyte (GPE) based on N,N-dimethylacrylamide (DMAAm) and polyvinylidene fluoride (PVDF) are prepared and characterized. 3D printing of DMAAm containing PVDF and ethylene glycol (EG) based liquid electrolyte yields chemically cross-linked PVDF/DMAAm gel polymer electrolyte. A customized 3D gel printer named “Soft and Wet Intelligent Matter-Easy Realizer” (SWIM-ER) is used to fabricate PVDF/DMAAm based GPE via optical method of stereo-lithography. This gel polymer electrolyte exhibits a good ionic conductivity and mechanical properties. Meanwhile, the gel polymer electrolyte shows very good thermal stability.