bluuebunny/crossref_metadata_2025 huggingface dataset:
(Invited) Spectroscopy Techniques Applied to Operando Characterization of PGM-Free Catalysts for Fuel Cells
Authors: Jaouen Frederic , Li Jingkun , Sougrati Moulay-Tahar , Stievano Lorenzo , Zitolo Andrea
Published: February 2020

Metal-N-C catalysts (Metal = Fe, Co primarily) are being developed and studied as alternative catalysts to platinum for catalyzing the O2 reduction reaction (ORR), in acidic and alkaline media. The nature of their active sites is still a topic of intense discussions and advanced studies, this class of materials possibly comprising N-doped sites, Metal-Nx moieties and various crystallographic structures. The latter often result from excess metal relative to the number of defect sites in the carbon matrix that may host Metal-Nx moieties.

Improved understanding has been gained first through the combination of controlled synthesis, ex situ spectroscopic characterization and ex-situ structure / activity correlations. More recently, operando and/or in-situ spectroscopic techniques have been applied on novel Metal-NC catalysts to better understand their site formation during pyrolysis, their electronic, spin-state and coordinative environment as a function of electrochemical potential and/or time scales. Operando spectroscopy on such catalysts may also offer a way to distinguish the metal-based sites that are electrochemically accessible from those that aren’t. This is a recognized issue for pyrolysed Metal-N-C materials.

This presentation will focus on the application of X-ray absorption techniques to the operando characterization of Fe and Co in Metal-NC catalysts in various electrochemical conditions, and of what could be learnt additionally to ex situ or post mortem studies. Initial results acquired with operando 57Fe Mössbauer spectroscopy will also be presented and discussed.
Characterization of Surface Adsorption of Engineered Nanoparticles By Collision Electrochemistry
Authors: Hosseini Narouei Farideh , Andreescu Silvana
Published: February 2020

Applications of engineered nanoparticles in many areas, including sensing, water purification, biomedical and environmental fields continue to increase. A key issue in the use of nanoparticles in practical applications is controlling their properties for achieving targeted interactions with the systems of interest. A wide range of nanoparticles such as metal oxide and magnetic nanoparticles are being used and discarded in the environment with little regulations. Although these nanoparticles are found to be relatively non-toxic in their native state, when they are released in the environment they can undergo transformations and interact with small molecules and metal ions which drastically change their properties and toxicity profile. This work will discuss electrochemical studies to investigate the interaction of these particles with heavy metals in the environment. Examples of nanoparticle systems and studies to assess the effect of particle type, surface coatings and environmental composition will be provided along with the parameters controlling adsorption/desorption of toxicants, measured using collision electrochemistry and a suite of spectroscopic procedures. We demonstrate the use of electrochemistry as a powerful tool to quantify heavy metal adsorption and determining mechanisms to predict the interaction of nanoparticles in the environment.
In-Situ Electrochemical Techniques to Determine Ionomer Coverage in PEFC Electrodes
Authors: Van Cleve Timothy , Khandavalli Sunilkumar , Medina Samantha , Pylypenko Svitlana , Mauger Scott A , Neyerlin K.C.
Published: February 2020

Many electrochemical devices such as low temperature fuels utilize ionomers to improve efficiency and overall performance. In polymer electrolyte fuel cells (PEFCs), perflurosulfonic acid ionomers improve ionic (protonic) conductivity and Pt utilization within the catalyst layer. However, the strong interaction between sulfonate (-SO3
-) functional groups and Pt nanoparticles have been linked lower catalytic rates and higher O2 transport resistances.1,2 There have been numerous strategies implemented to control the local distribution of ionomer and Pt/C catalyst particles, but limitations in the resolution of state-of-the-art characterization techniques make it difficult to assess how ink formulations and/or electrode fabrication techniques control ionomer-catalyst interactions and its impact device performance.3–5

Herein, the development and utilization of in situ electrochemical techniques designed to probe the local ionomer interactions will be utilized in conjunction with established testing protocols to relate ionomer coverage (on Pt and/or C support) with kinetic performance and O2 transport resistance of fully-conditioned PEFC electrodes. Specifically, CO displacement chronoamperometry and electrochemical impedance spectroscopy techniques will be described to determine local ionomer coverages across a series of Pt/C MEAs. These results will promote a deeper understanding of ionomer-catalyst interactions which in turn will inform future materials development and integration necessary to achieve high performance PGM (e.g. Pt/C and Pt alloy/C) electrocatalyst-based electrodes.

Schuler, T. et al. Fuel-Cell Catalyst-Layer Resistance via Hydrogen Limiting-Current Measurements. J. Electrochem. Soc.
166, F3020–F3031 (2019).

Subbaraman, R., Strmcnik, D., Paulikas, A. P., Stamenkovic, V. R. & Markovic, N. M. Oxygen Reduction Reaction at Three-Phase Interfaces. ChemPhysChem
11, 2825–2833 (2010).

Berlinger, S. A., McCloskey, B. D. & Weber, A. Z. Inherent Acidity of Perfluorosulfonic Acid Ionomer Dispersions and Implications for Ink Aggregation. J. Phys. Chem. B
122, 7790–7796 (2018).

Orfanidi, A., Rheinländer, P. J., Schulte, N. & Gasteiger, H. A. Ink Solvent Dependence of the Ionomer Distribution in the Catalyst Layer of a PEMFC. J. Electrochem. Soc. (2018). doi:10.1149/2.1251814jes

Khandavalli, S. et al. Rheological Investigation on the Microstructure of Fuel Cell Catalyst Inks. ACS Appl. Mater. Interfaces (2018). doi:10.1021/acsami.8b15039
Probing Sulfur Contamination Mechanisms in Solid Oxide Fuel Cells Using Operando Methods
Authors: Maza William A , Pomeroy Elias D , Steinhurst Daniel A , Tsoi Stanislav , Walker Robert A. , Owrutsky Jeffrey C.
Published: February 2020

Solid oxide fuel cells (SOFCs) are high temperature combined heat and power systems that are fuel flexible and offer an attractive alternative to traditional proton exchange fuel cells. However, sulfur contaminants found in bio-derived and logistics fuels can severely hinder conversion efficiency due to interactions between sulfur and the nickel-based anodes commonly used in SOFCs. Identifying themechanisms responsible for sulfur degradation of SOFCs and their dependence on operating conditions would help in improving device performance and durability. In this study, the effects of sulfur contamination and the subsequent degradation of SOFCs operating on methane between 600° – 800° C are characterized using chronocoulometry, electrochemical impedance spectroscopy, and operando optical methods. The latter include near infrared thermal imaging as well as spectroelectrochemical vibrational Raman and IR emission spectroscopies. The results indicate that sulfur contaminants competitively inhibit methane catalytic and electrocatalytic sites and induce irreversible changes of the Ni-YSZ anode permanently perturbing their catalytic and electrocatalytic function. Studies are performed to determine if sulfur degradation is reversible and how it depends on fuel composition and temperature.
Undergraduate Research Projects As a Prelude to Graduate Research
Authors: Noel James J.
Published: February 2020

An undergraduate research experience might take the form of a summer project, a co-op term, a volunteer internship, or a credit course, such as a senior research thesis project. Designing a research project to be undertaken by an undergraduate student can pay off in numerous ways. Such a project can benefit the undergraduate student by offering valuable research experience and an opportunity for personal development, of course, but there could be many possible benefits to the research supervisor and the research group as well. The project could provide a low-risk means of exploring a potential new avenue of research that, if found to be promising, could then be followed up by a graduate research undertaking, either by that same student or by another graduate, or by a funding proposal if the supervisor seeks to open a new area of research. It might also serve as a recruiting tool to stir interest in an undergraduate student who might then consider returning to the same lab for graduate studies; conversely, it affords the supervisor a preview of student performance that may inform the decision to take that student on for a graduate degree. As undergraduates tend to be hard-working and relatively inexpensive, an undergraduate project could be a cost-effective means of accelerating research progress. Moreover, designing the undergraduate project to involve mentorship from a graduate student can provide an extra dimension of professional training for the graduate student, as he/she learns to take on responsibility for the training and direction of the undergraduate. To achieve these benefits through an undergraduate research experience requires that the project be thoughtfully designed to suit: 1) the education, experience, and abilities of the undergraduate, 2) the facilities, equipment, and other resources available, as well as the project duration, 3) the feasibility of the work, and 4) the ability and availability of the mentor (whether that is a graduate student, PDF, or the professor). In this presentation I discuss my efforts to strategically employ undergraduate projects in my own research group.
Bioelectrochemistry in Undergraduate Curriculum and Research
Authors: Rasmussen Michelle
Published: February 2020

Electrochemistry has a wide range of uses and applications, but undergraduate students do not appreciate this when the topic is first introduced in General Chemistry. Introducing more electrochemical methods in later chemistry courses can encourage interest in the field. In the chemistry department at Lebanon Valley College, the students first encounter electrochemistry through the typical introduction of redox reactions, the Nernst equation, and galvanic cells. The topic is expanded in Analytical Chemistry for juniors during which the students learn about and perform electroanalyltical methods, including potentiometric analysis, coulometry, amperometry, and voltammetry. Students who choose the advanced elective Chemical Sensors and Biosensors learn about electrochemical sensors as one unit of the course. This unit also includes a section on bioelectrochemical sensors. Students develop a hydrogen peroxide biosensor and use amperometry to evaluate its performance, giving them a better understanding of concepts like limit of detection, sensitivity, and dynamic linear range.

In addition to the chemistry curriculum, students can choose to do electrochemical research in the department. Recent projects include fabricating and evaluating enzyme electrodes for a wide range of biologically relevant molecules, designing self-powered biosensors, and designing a biophotovoltaic device for solar energy conversion with plants. Students gain experience with several electrochemical methods, analysis of electrochemical data, and general lab skills. They are also required to present their work, either in posters or oral presentation, skills that will prepare them for their careers after college.

Overall this combination of curriculum and research leads to more students being interested in electrochemistry. They learn that these methods can be used for every area of chemistry, not just analytical. It has lead to an increase in the number of graduating students who continue working in the field, whether in industry or academia.
Aqueous Exfoliation of Nife LDH/CB to Boost Its Oxygen Evolution Reaction Activity in Alkaline Solutions
Authors: Munonde Tshimangadzo Saddam , Zheng Haitao , Nomngongo Philiswa Nosizo
Published: February 2020

Water electrolysis has recently progressed as the most efficient and attractive way of producing hydrogen and oxygen gasses [1]. However, to ensure the effective production of hydrogen and oxygen yielding high current densities at a low overpotential, a catalyst is needed. Present advancements in the water electrolysis process have opened pathways leading to the synthesis of a variety of non-precious materials as electrocatalysts in place of precious materials [2,3]. In this work, we present the hydrothermal synthesis of the non-precious NiFe2O4/MoS2/C nanocomposites to be used as a bifunctional electrocatalysts for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) for water electrolysis in both alkaline and acidic electrolytes. To increase the conductivity of the NiFe2O4/MoS2/C composite, the material was supported on carbon black. Sonochemistry application was employed as a Post-treatment technique to boost the catalytic activity for NiFe2O4/MoS2/C nanocomposites. The post-treated material showed an intense increase in the catalytic activity of NiFe2O4/MoS2/C nanocomposites. The composites also show comparable activity and durability with commercial Pt/C for HER and RuO2/C for OER.

Keywords: water electrolysis, NiFe2O4/MoS2, post-treatment, catalytic activity.

References

[1] Shi, Y., Zhang, B. (2016).. Chem. Soc. Rev, 45(6), 1529-1541.

[2] Lv, H., Xi, Z., Chen, Z., Guo, S., Yu, Y., Zhu, W., Mu, S. (2015). J. Am. Chem.Soc, 137(18), 5859-5862.

[3] Xu, X., Sun, Y., Qiao, W., Zhang, X., Chen, X., Song, X., Du, Y. (2017). Appl. Surf. Sci., 396, 1520-1527.
Sonoelectrochemical CO2 Reduction on Polycrystalline Copper Electrodes
Authors: Mehrabi Hamed , Islam Md Hujjatul , Erades De Quevedo Raul , Pollet Bruno G. , Coridan Robert
Published: February 2020

Electrochemical CO2 reduction targets the electrolytic conversion of carbon dioxide to more useful fuels and chemicals. Most metal electrocatalysts produce two-electron reduced products from CO2 reduction (CO, COOH-) with some selectivity over the reduction of protons to H2 in water. Cu is a unique electrocatalyst in that it can produce a range of multi-electron products, including C2 (ethylene, ethanol, acetaldehyde) and C3 (ethylene glycol, propanol) molecules. The broad range of products formed on Cu present a different challenge, namely in tailoring the selectivity of products by modifying the reaction conditions or electrode structure. Sonoelectrochemical electrolysis offers opportunities for improving the selectivity of CO2 reduction. Ultrasonic agitation of the electrolyte can improve mass transport to the electrode interface compared to stagnant solutions and generate radicals that contribute to the electrochemical transformations. Here, we describe experiments to understand the effects of sonoelectrochemical reactors for the selectivity of carbon dioxide reduction on polycrystalline Cu electrodes. We explore the multiple effects that sonication can have on the reaction, including improved mass transport and thermal effects on the electrolyte. In temperature-controlled sonoelectrochemical experiments we observe a change in the electrolytic CO2 branching ratios, with a particular shift towards the formation of liquid-phase products. Finally, we detail the potential for combining sonoelectrochemical CO2 reduction to other strategies for targeted selectivity on Cu in new reaction schemes.
Stabilizing Silicon Anode Chemistry for Long Cycle and Calendar Life Electrodes
Authors: Han Binghong , Liao Chen , Dogan Fulya , Trask Stephen E. , Lapidus Saul , Vaughey John T. , Key Baris
Published: February 2020

Replacing traditional graphite anode by Si anode can greatly improve the energy density of lithium-ion batteries. However, the large volume expansion and the formation of highly reactive lithium silicides during charging cause the continuous lithium and electrolyte consumption as well as the fast decay of Si anodes. In this work, by formulating new electrolytes and additives, we demonstrate lifetime stabilization of the anode chemistry during the initial lithiation process. Using solid-state nuclear magnetic resonance spectroscopy, we show that stabilization suppresses the detrimental chemical reactions between the lithium silicides and common electrolyte solvents as well as binders. Formulated electrolytes were tested in commercially relevant electrodes, which show higher capacity, superior cyclability, and higher coulombic efficiencies in both half-cell and full-cell configurations when compared with standard electrolytes. We show an improvement in capacity retention from ~25% after 270 cycles to ~60% and a consistent 0.2%+ improvement in coulombic efficiencies in full cells when compared to state of the art baselines with silicon anodes. Post-electrochemistry characterizations demonstrate the mechanistic details silicon anion stabilization. This study opens a new and simple way to stabilize silicon anodes to enable widespread application of Si anodes for lithium-ion batteries.
In-Situ Study of Multistep Lithium-Bismuth Alloying Mechanisms
Authors: Yuan Yifei , Yao Wentao , Yurkiv Vitaliy , Ma Lu , Liu Tongchao , Mashayek Farzad , Lu Jun , Amine Khalil , Shahbazian-Yassar Reza
Published: February 2020

With the high energy density, anode materials storing energy based on alloying mechanisms are promising anode candidate in rechargeable lithium ion batteries. Here, we target bismuth (Bi) nanostructures (theoretical volumetric capacity ~3800mAh/cm−3 with formation of Li3Bi) and explore the (de)alloying mechanisms upon insertion/extractiong of Li+. Real-time synchrotron XRD and in situ TEM of the (de)alloying kinetics of Bi working as a LIB anode are carried out, which reveals the reaction mechanism at both bulk level and at single-nanoparticle level. As analyzed by both two methods, the Li-Bi (de)alloying proceeds via a reversible two-step mechanmism featuring two two-phase reactions, where Li1Bi is identified as the intermediate phase. A preferred alloying pathway along Bi-(012) lattice during the Bi-Li1Bi transitioning stage is revealed and further studied by DFT. We expect such fundamentals discussed here to direct the design of alloying electrode materials with enhanced battery performance.
Temporal Mapping of NMC-Graphite Cells during Fast Charging
Authors: Charalambous Harry , Wiaderek Kamila M , Ren Yang
Published: February 2020

Wide scale adoption of electric vehicles has been hampered by the dual challenge of energy density limited range and power density limited long charge time. Nickel-rich NMC cathode, graphite anode cells offer an economical approach to provide high power density using a well characterized cathode chemistry and reliable, widely adopted technology. In order to perform accurate life cycle prediction, the degradation mechanisms during fast cycling must first be characterized. Ex-situ studies often omit key characteristics of cell behavior during the charge discharge cycle including temporal lithiation characteristics, formation of metastable phases, and correlation of component variations in the battery stack. In this study in situ, operando cycling characterization was achieved at the Advanced Photon Source at Argonne National Laboratory. Changes in the crystal structure of both cathode and anode are characterized over multiple fast charge cycles, with 6C charge rate and C/2 discharge rate, and related to electrochemical changes in the cell.
Determination of Transference Number and Thermodynamic Factor By Use of Anion-Exchange Concentration Cells and Concentration Cells
Authors: Craig Nathan , Mullin Scott , Pratt Russell , Crane Gabriel
Published: February 2020

A method is described for the measurement of lithium ion transference number and thermodynamic factor of a binary electrolyte by the combined use of anion-exchange concentration cell measurements and concentration cell measurements. The measurements were carried out using cells consisting of LiTFSI salt, a poly(ethylene oxide) solvent, a polydiallyldimethylammonium bis(trifluoromethanesulfonyl)imide anion-exchange layer, and lithium foil electrodes. The transference number and thermodynamic factor were fit using expansions suggested by electrolyte theory. The thermodynamic factor was measured to lie within the range of 0.3 to 6 at 80 °C. The lithium ion transference number was measured to be 0.18 at infinite dilution and decrease with increasing concentration. Under ideal operation, the anion-exchange concentration cell directly measures the difference in the chemical potential of salt at two different concentrations. The accuracy of the approximation of ideal operation was estimated, showing that the method is more accurate when the salt has low partitioning into the anion-exchange layer and when the salt diffusivity in the anion-exchange layer is lower than in the solvent.

Figure 1
Nickel-Rich Layered Oxide Cathodes for Next Generation Lithium Ion Battery
Authors: Aryal Shankar , Durham Jessica L , Lipson Albert L. , Kahvecioglu Feridun Ozgenur
Published: February 2020

Nickel-rich layered oxide cathodes are getting significant attention because of the attractive initial cycle electrochemical performance, lower cost, and reduced toxicity of lithium ion batteries (LIB). There are factors hindering the stable performance of Ni rich cathodes which include cation mixing after synthesis and/or during electrochemical cycling, oxygen activity at high voltage (≥ 4.3 V), reduced thermal stability and structural distortion during cycling. Stoichiometric LiNiO2 is difficult to synthesize and transforms to multiple crystallographic phases on cycling. The layered oxides of nickel, manganese and cobalt (NMC) are found to be structurally compatible to provide elastic network for lithium deintercalation/intercalation, however the exact role of Mn and Co in NMC cathodes is still not clear. Generally, the change in oxidation state of Ni determines the reversible electrochemical capacity, Co and Mn ions are believed to provide structural stability. Therefore, Ni rich composition with suitable Mn and/or Co doping would be a preferred choice. A series of Ni rich layered oxide cathodes with similar morphology and physical properties have been synthesized to study the effects of Mn and Co doping on the structure and electrochemical performance.

The oxidation state and local environment (bond length, coordination number, thermal disorder) of transition metal ions get changed during charge/discharge cycling. In-situ and ex-situ X-ray absorption spectroscopy (XAS) in which individual elements (Ni, Mn, Co) are probed to scrutinize the electronic state and local geometry. Determining these properties will give insight into the degradation/aging mechanism of Ni rich cathodes.
(Invited) Searching for High Potential Organic Cathode Materials for High Energy Green and Sustainable Batteries
Authors: Jouhara Alia , Dolhem Franck , Guyomard Dominique , Dupré Nicolas , Poizot Philippe
Published: February 2020

Thanks to the use of abundant chemical elements, organic chemistry provides great opportunities for discovering innovative electrode materials, which could be prepared (i) from renewable resources (biomass) and (ii) via eco-efficient processes, making the concept of greener and sustainable batteries possible [1].

We are putting a lot of efforts on greener and sustainable organic non-aqueous and aqueous batteries at the IMN. In this communication, we report on novel crystallized organic positive electrode materials for the non-aqueous application of organic batteries. However the synthesis of high-voltage lithiated materials is rather challenging, so very few examples of all-organic Li-ion cells currently exist.

Compounds of the Mn+
2/n-p-DHT (with Mn+ = Li+, Mg2+, Ca2+ and Ba2+) family were studied to better understand the effect of substitution chemistry on the redox properties of the Li-diphenolate cycle of p-DHT. This innovative chemical approach makes it possible to tune the redox potential of lithiated organic electrode materials, by playing on the nature and the ionic potential of a spectator cation in the host structure. Indeed, by adjusting the attractor/donor electron effects in the organic redox-active backbone, it is possible to modify the redox potential of the molecule by inductive effect.

We show that substituting magnesium (2,5-dilithium-oxy)-terephthalate for lithium (2,5-dilithium-oxy)-terephthalate enables an outstanding voltage gain of 800 mV, leading to a high operating voltage of 3.4V vs. Li+/Li [2]. This Mg(Li2)-p-DHT compound is the first lithiated organic positive electrode material with an operating potential as high as that of LiFePO4. Based on this finding, full organic Li-ion cells with an output voltage of 2.5V and long cycle life have been achieved, thus making a big step forward the design of high energy green and sustainable organic batteries.

References

[1] P. Poizot, F. Dolhem, Energy Environ. Sci. 4, 2003 (2011).

[2] A. Jouhara, N. Dupré, A.C. Gaillot, D. Guyomard, F. Dolhem, P. Poizot, Nature Commun., 9, 4401 (2018).
Dual Salt Electrolyte of Lifsi and LiPF6 for Fast-Charging Lithium Ion Battery
Authors: Liu Tianyi , Wu Xianyang , Lin Feng , Wood David L. , Belharouak Ilias , Du Zhijia
Published: February 2020

Electric vehicles (EVs) have been go from prosperity in the early 20th century to decline. One of the reasons is the charging rate --- it takes over 30 minutes for a Tesla to get 80% charged, but only a few minutes to get a gas-powered vehicle refilled. Therefore, developing extreme fast-charging battery is desirable for EV to occupy the market share in the new round of competition.

Li-Ion batteries (LIBs) have recently been used as power supply for electric vehicles (EVs), and electrolyte plays an important role in the batteries. Here, we report a dual salt electrolyte consisting of LiPF6 and LiFSI for fast charging lithium ion battery. Compared to other commercially available electrolytes, this dual salt electrolyte shows superior performance under fast charging condition (4C) for NMC622//graphite full pouch cell. A systematic research based on this dual salt electrolyte is being built. Electrochemical chemical performance, viscosity, interaction between electrode and electrolyte, and the synergistic effect, etc. of the dual salt has been studied.
Synthesis of Single Crystalline Ni-Rich NMC811 Cathode Materials and Improved Performance Enabled By Ultrathin Surface Coating Layer
Authors: Liu Haidong , Younesi Reza , Edström Kristina
Published: February 2020

Ni-rich LiNi
x
Mn
y
Co1-x-y
O2 (NMC, x ≥ 0.5) cathode materials have attracted intensive attention in developing high energy-density lithium ion batteries, owing to their high capacity and relatively low cost. Among them, LiNi0.8Mn0.1Co0.1O2 (NMC811) is one of the most promising candidates to realize higher energy density, particularly operating at high cut-off voltage (e.g. 4.5 V vs. Li/Li+). However, the limited cycle life is becoming the plague for its practical application due to the structural instability, microcracks formation, and electrolyte decomposition at the electrode/electrolyte interface.[1,2]

As well known, single crystal NMC materials have more stable surface activity because of the low surface area and better mechanical stability than conventional polycrystalline materials. Moreover, single crystalline NMC materials can provide not only high gravimetric energy density, but also high volumetric energy density due to the increased tap density compared to the conventional polycrystalline NMC materials.[2-4]

In this study, a single crystalline NMC811 sample with a large particle size of around 5 μm and polyhedral shape was synthesized by sol-gel method. Furthermore, a homogeneous ultrathin surface coating layer (~2 nm) was built on the surface of the single crystalline NMC811 particles to act as protective layer to prevent the direct contact between electrolyte and active particles. As a result, the coating layer effectively enhances an overall electrochemical performance of single crystalline NMC811 materials and especially leads to a higher reversible capacity as well as a remarkable improvement of the capacity retention (90% after 200 cycles between 3 and 4.5 V vs. Li/Li+). The influences of the coating layer on the structure and interfacial stability and electrochemical properties will be presented in details later.

References:

[1] H. Y. Li, J. Li, X. W. Ma.J. R. Dahn.
J. Electrochem. Soc.

2018,
165, A1038-A1045.

[2] J. Kim, H. Lee, H. Cha, M. Yoon, M. Park, J. Cho.
Adv. Energy Mater
. 2018, 8, 1702028.

[3] H. D. Liu, R. Kloepsch, J. Wang, M. Winter.J. Li.
J. Power Sources

2015,
300, 430-437.

[4] H. D. Liu, J. Wang, X. F. Zhang, D. Zhou, X. Qi, B. Qiu, J. H. Fang, R. Kloepsch, G. Schumacher, Z. P. Liu et al.
ACS Appl. Mater. Interfaces

2016,
8 (7), 4661-4675.

Figure 1
Electrochemical Performance and Rate Capability Studies of Li-Ion Battery Separators for Fast Charging Applications
Authors: Parikh Dhrupad , Li Jianlin , Hsieh Chien-TE
Published: February 2020

Fast charging of batteries is the key to increase the adoption of electric vehicles. All the components of a battery: anode, cathode, electrolyte and separator, contribute to the limiting factors of fast charging. Separators are an important part of Li-ion batteries that allows lithium ions to shuttle between the electrodes and isolates the electronic flow. While majority of the efforts are focused on novel electrode architecture and electrolyte formulation for high rate capabilities, studies on separators are mostly pertaining to their mechanical and physical properties, and little attention has been paid to their effect on rate performance. To achieve the DOE goal of fast charging time of less than 10 minutes and maintaining a cell energy density >180 Wh/kg, it requires improvement in every cell component including separator.

In this study, we report a comprehensive analysis of the physical properties, electrochemical performance, and high rate capabilities of the widely used battery separator Celgard 2325 and Celgard 2500. It is shown in figure 1-a that Celgard 2500 performs better than Celgard 2325 at higher c-rates (1-5C) during both constant charge and constant discharge protocol. This can be attributed to the fast ion diffusion through the Celgard 2500 due to its more porous structure and better electrolyte uptake capability. Figure 1-b shows that Celgard 2500 has lower contact angle compared to 2325 in water and electrolyte, indicating it has higher surface tension, which leads to better electrolyte wettability. It is demonstrated that increasing porosity in separator can improve rate performance and facilitate fast charging.

Figure 1
Enhanced Cycling Stability of Microstructure-Modified Li[Ni0.90Co0.05Mn0.05]O2 Cathode Via Microscale Compositional Partitioning for Next-Generation Electric Vehicles
Authors: Ryu Hoon-Hee , Nam Gyeong Won , Sun Yang-Kook
Published: February 2020

Lithium-ion batteries (LIBs) are considered to be the most promising power sources for electric vehicles (EVs) because of their high energy densities and long cycle lives. However, major impediments for general public acceptance of EVs are their cost, durability, and driving range.1 Therefore, significant improvements in the energy density, cycle life, and safety of the current state-of-the-art LIBs are necessary. Compared to the anode, cathode design is more challenging because the cathode performance is typically limited by low capacity, poor cycle life, safety problems, high cost, and the degradation of the active material resulting from parasitic reactions with the electrolyte, especially hydrogen fluoride (HF). These limitations have provided the impetus for the development of new cathodes that could reduce the weight, volume, and cost of next-generation LIBs while increasing the driving range of EVs by increasing the capacity.

In this study, we have revisited the core–shell structure that we proposed previously to develop a multi-compositional NCM cathode material (CSG90) in which LiNiO2 is placed at the particle core and encapsulated by the well-tested Ni-rich NCM cathode material Li[Ni0.8Co0.1Mn0.1]O2.2,3,4 After lithiation, the final composition of the core is Li[Ni0.94Co0.038Mn0.022] O2, providing a high capacity, while this core is surrounded by a 1.5 μm thick concentration gradient shell with an outermost surface composition of Li[Ni0.841Co0.077Mn0.082]O2. In order to benchmark the effectiveness of the micrometer-scale compositional partitioning of the CSG90 cathode against a conventional single-composition cathode, the structural stability and electrochemical properties of the CSG90 cathode were intensively studied and compared with those of a conventional cathode with a similar average chemical composition.

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.

Y.-K. Sun, S.-T. Myung, B.-C. Park, J. Prakash, I. Belharouak, K. Amine, Nat. Mater.
2009, 8, 320.

D.-W. Jun, C. S. Yoon, U.-H. Kim, Y.-K. Sun, Chem. Mater.
2017, 29, 5048.

U.-H. Kim, H.-H. Ryu, J.-H. Kim, R. Mücke, P. Kaghazchi, C. S. Yoon, Y.-K. Sun, Adv, Energy Mater.
2019, 1803902.
Conductive Metal-Organic Framework Coated Silicon Nanoparticles As an Anode Material for High Power Lithium-Ion Batteries
Authors: Nazir Aqsa , Park Chan-Jin
Published: February 2020

The development of rechargeable lithium-ion batteries (LIBs) with higher capacity and longer cycle life is still in progress. LIBs are the ideal choice as power sources for portable electronic devices and electric vehicles (EVs). However, recent LIBs are not satisfactory for the consumer’s demands due to the inherent capacity restriction of conventional electrode materials such as a graphite. Si, which can be alloyed with Li at lower potential, is a potential alternative to the conventional graphite, due to its high theoretical specific capacity (4200 mAh g-1), natural abundance, and environmental friendliness. However, for Si, the poor Li diffusivity, intrinsic low electrical conductivity, and large volume variation (>300%) during lithiation reduce the practical application of Si as an anode material. Thus far, to overcome these issues, researchers have used strategies such as using Si nanostructures (nanowires, nanorods, nanotubes, and nanoparticles) and employing conductive carbon coatings. Nevertheless, to prevent the capacity fading and exhibit longer cycle life comparable to that of graphite, a breakthrough is needed.

In the present work, the Si nanoparticles (SiNPs) was coated with the two-dimensional conductive Cu-ion containing metal-organic framework (Cu-MOF) for the LIBs with high capacity and longer cycle life LIBs. The Cu-MOF grew directly on the highly porous SiNPs. The highly porous Cu-MOF alleviated the stress resulting from volume expansion and acted as a connected channel for the transport of Li-ion and electron. As a result, the SiNPs coated with Cu-MOF (Si@Cu-MOF) could exhibit high capacity, rate capability, and cyclability. In particular, the Si@5Cu-MOF electrode delivered an initial discharge and charge capacities of 3201 and 2511 mAh g-1, respectively, which corresponded to a Coulombic efficiency of 78.5%, at a rate of 0.1C. The reversible capacity retention after 100 cycles was 2529 mAh g-1, which was even higher than that of the first reversible capacity due to the activation effect. In addition, the Si@5Cu-MOF electrode exhibited an excellent rate capability: 2621, 2486, 2096, and 468 mAh g-1 at the rates of 0.2C, 0.5C, 2C, and 20C, respectively. These encouraging properties will assure use of the Si@Cu-MOF as a potential anode material for LIBs.
Study on Anion Doped Polypyrrole As Anode Material for Aqueous Sodium Ion Battery
Authors: Cao Dianxue , Wang Pengfei
Published: February 2020

In order to meet the growing demand for large-scale energy storage, low-cost sodium-based aqueous capacitor battery has received people's attention. Polypyrrole is an inexpensive conductive polymer. In this paper, polypyrrole nanowires with anionic structure were prepared by chemical oxidation and doping ions during the preparation. They could be used as negative electrode material for sodium ion capacitor cells.The sodium ion storage mechanism of polypyrrole doped with anions was studied by cyclic voltammetry, AC impedance method and constant current charge-discharge method. Morphology and structure were analyzed by X-ray diffraction, infrared spectroscopy and scanning electron microscopy. Anions doped polypyrrole can reach a steady capacity of 200 mAh / g in 1 mol / L NaNO3 solution. After 500 cycles, the capacity retention is 70% at a current density of 0.1 A / g.The specific capacity of 120 mAh / g can still be achieved at a current density of 5 A / g. The polypyrrole doped with ions has two kinds of sodium ion intercalation mechanism, has the advantages of batteries and capacitors, has a larger capacity and excellent rate performance, good cycle performance.

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(Invited) Atomistic Insights into Cathode Dissolution and Ion Transport in Li-Ion Batteries
Authors: Narayanan Badri
Published: February 2020

Fundamental understanding of inter-connected electrochemical phenomena, including chemical reactions, charge/ion transport, defect evolution, and solvation dynamics) is crucial to accelerate development of low-cost, safe, and high-performance Li-ion battery architectures. In particular, molecular mechanisms underlying (a) dissolution of cathode into liquid electrolyte; and (b) fast Li-ion transport in novel solid-electrolytes, need to be clearly identified to design Li-ion batteries with exceptional capacity, rate-capability, and cycle life; however, such knowledge remains in its infancy. In this talk, we will first address the key mechanisms governing dissolution of a commercially promising LiMn2O4 (LMO) cathode. Using a combination of ab initio molecular dynamics simulations (AIMD) and quantum-chemical calculations, we demonstrate that dissolved Mn ions exist in 2+ oxidation state in carbonate based electrolytes. This finding resolves the debate raised by recent electron paramagnetic resonance and X-ray absorption near edge structure experiments suggesting that Mn could preferentially exist in 3+ state within solution; and provides evidence supporting the long-standing belief that Hunter’s disproportionation mechanism (2 Mn3+ --> Mn4+ + Mn2+) precedes Mn dissolution. Furthermore, we employed AIMD and density functional theory (DFT) calculations to probe formation of Mn2+ on stable LMO (511) surfaces via surface Hunter charge disproportionation mechanisms, as well as chemical mechanisms involving hydrofluoric acid (HF) electrolyte impurities and oxidation of ethylene carbonate (EC) electrolyte molecules. These studies would guide future strategies to suppress Mn dissolution, and in turn, combat capacity fading in LiBs based on LMO cathodes. Next, we will demonstrate that strongly-correlated rare-earth perovskite nickelates exhibit fast Li-ion conduction with simultaneous suppression of electronic transport via Mott transition. The pronounced Li-ion conduction is facilitated by electron injection into Ni orbitals, and concomitant lattice expansion when the Li ions are inserted from a reservoir. These results will be discussed in the context of developing next-generation lithium ion batteries with exceptional performance.
Electrochemical Impedance Spectroscopy Analysis of Carbon Deposition in an Anode-Supported Planar Solid Oxide Fuel Cell By Segmented Electrodes
Authors: Sasaki Kohei , Nakajima Hironori , Kitahara Tatsumi
Published: February 2020

Solid oxide fuel cells (SOFCs) have been of practical concern for high efficiency power generation and fuel flexibility. In the planar SOFCs, current and temperature distributions due to fuel consumption and steam generation occur from the upstream to the downstream part along the anode flow channels, causing problems such as lower efficiency and durability. Furthermore, durability to carbon deposition is a common problem with hydrocarbon fuels derived from natural gas and biogas. Identification of degradation factors and locations leads to development of diagnosis method and optimized operation control for prevention of failure and accident. In-situ electrochemical data by the degradation give useful parameters for health diagnosis of SOFCs. In this study, we aim to clarify the spatial degradation behavior using an anode-supported planar cell with a cathode layer segmented into three parts. We fed dry methane gas to the anode as accelerated aging tests and measured the current distribution directly among the upstream, midstream and downstream parts along the anode flow channels. Electrochemical impedance spectroscopy analysis was carried out for each segment as well. For the obtained impedance spectra, curve fitting by nonlinear least squares method was carried out to separate each resistance for the analyses. Upstream part of the cell exhibited larger resistance with more enhanced carbon deposition than the other parts with the dry methane fuel.
Pressure Responsive Multi-Layered Composite Nanoparticles for through Silicon Via (TSV) Chemical Mechanical Planarization (CMP) Applications
Authors: Salinas Maria G , Mikos Allie M , Hill Madison , Mlynarski Amy , Keleher Jason J.
Published: February 2020

Through silicon vias (TSV) have gained much attention due to the emergence of the vertical alignment necessary to produce 3D integrated circuit devices. Due to the large overburden caused by the electroplating process in TSV, high removal rate of copper (Cu) is essential for producing highly planar and defect free substrates. Therefore, focus has shifted to the development of processes and chemistries that produce highly planar and defect free Cu surfaces. In order to obtain this planarity, a process known as chemical mechanical planarization (CMP) is implemented in which a silica nanoparticle dispersion coupled with a mechanical force synergistically removes excess topography. The demands on TSV CMP have become stringent in order to meet the following criteria: very high removal rates, low dishing, high selectivity to nitride after barrier clear, low defectivity, and uniform surface topography. This work focuses on the development of a pressure responsive, multi-layer composite nanoparticle to provide a process driven synergy with the slurry formulation. These composites can be held together either covalently or non-covalently to the nanoparticle core using additives with amine, amino acid, and surfactant functionalities. The additives respond to an applied force and shear at the slurry-pad interface, resulting in controlled release of the slurry chemistry. Initial results show that at downforces ranging between 2.5-5 psi removal rates are at an excess of 1 micron per minute, while at below 1 psi removal rates are below 0.2 micron per minute and produce uniform surface quality at low surface roughness.
Relationship between Oxygen Reduction / Evolution Reaction Activity and Oxygen Non-Stoichiometry of LaNiO3−δ
Authors: Tanaka Hiroyuki , Asakura Hiroyuki , Hosokawa Saburo , Teramura Kentaro , Tanaka Tsunehiro
Published: February 2020

The complicated mechanisms and sluggish kinetics of oxygen reduction reaction (ORR) and evolution reaction (OER) are important issues to be overcome for the popularizations of next-generation technologies such as fuel cell and water splitting. The noble-metal catalysts such as Pt, Pd (for ORR), Ir, Ru (for OER) are considered as promising materials to facilitate the oxygen-related catalysis, while their cost and scarcity can also prevent the devices from wide use. Therefore, non-noble metal catalysts have received much attention as candidates of an air-electrode material to realize the popularizations of next-generation energy devices. Among various materials investigated so far, perovskite-type mixed oxides are known as bifunctional catalysts which shows both of ORR and OER activities. In previous reports, several factors have been proposed as the descriptor of their activities (e.g. the occupancy of the eg electronic states1,2.)

In this work, we focused on the oxygen vacancy and non-stoichiometry of the metal-oxides. We chose LaNiO3-δ as the model of perovskite-type mixed oxide, which is known as one of the most active bifunctional electrocatalysts among perovskite-type oxides, and investigated the influence of the amount of oxygen vacancies on ORR and OER activities. We prepared nonstoichiometric LaNiO3-δ (δ=0.06, 0.11, 0.25, 0.48) by hydrogen reduction process, and compared their activities using linear sweep voltammetry (LSV).

The results showed their ORR activity decreased as the amount of oxygen vacancy sites increased, which agree with the previous report by Suntivich et al1. that demonstrated the perovskite oxides with B site cation possessing one eg electron showed the best ORR activity. We conducted further experiments using similar La-Ni mixed oxides such as Ruddlesden-Popper type La2NiO4 to clarify the role of oxygen vacancies, and the results indicated the oxygen vacancy sites could also contribute to ORR processes.

On the other hand, we found no relationship between non-stoichiometry and the OER activities of LaNiO3-δ, suggesting other factors affecting the activity. From the results of CV and TEM analysis, we found that Ni hydroxide species existed on the surface of the catalysts. Ni hydroxide is a well-known electrochemical catalyst for OER, and these results indicated the amount of hydroxide species had a significant effect on OER activity of perovskite-type metal oxides.

1) J. Suntivich et al., Nat. Chem., 2011, 3, 546−550.

2) J, Suntivich. et al., Science, 2011, 334,1383-1385.

3) O. Diaz-Morales. et al., ACS. Catal., 2015, 5, 5380-5387

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