bluuebunny/crossref_metadata_2025 huggingface dataset:
Multilayer Hierarchical Nanofibrillar Electrodes with Tuneable Lacunarity with 2D like Pt Deposits for PEMFC
Authors: Ercolano Giorgio , Farina Filippo , Cavaliere Sara , Jones Deborah J. , Rozière Jacques
Published: February 2020

Here we present a novel approach to electrocatalysts layer design for PEMFC. Pt conformally electrodeposited around surface of carbon nanotubes growth on a self-standing nanofibrous electrode (NFE). We found that by combining two cost-effective and up-scalable techniques, electrospinning and electrodeposition it is possible to produce a layered electrode with tuneable lacunarity and engineer the surface area distribution along the electrode thickness and in turn the Pt content distribution.

It is possible to obtain an electrocatalyst with outstanding Pt exploitation and high durability while minimizing fabrication complexity[1]. We produced hierarchical 3D electrocatalyst layers with tuneable morphology that can be used directly in a membrane electrode assembly, allowing the complete exploitation of their highly porous structure, in a similar fashion to NSTF[2] or other 3D macroscopic assembly techniques. These structured electrocatalyst layers have high electrical conductivity for fast charge transport, and engineered density for efficient reactant mass transportation. This method allowed us to obtain self-standing nanofibrous electrodes with ultra-low Pt loading (0.05 mg/cm 2), that show very high activity towards the oxygen reduction reaction and electrochemical surface areas as high as 150 m2/g. A detailed microscopic, structural and electrochemical characterisation of the complete electrodes, including their application as the cathode in a proton exchange membrane fuel cell is presented.

[1] G. Ercolano, F. Farina, S. Cavaliere, D.J. Jones, J. Rozière, J. Mater. Chem. A 5 (2017) 3974-3980.

[2] M.K. Debe, A.K. Schmoeckel, G.D. Vernstrom, R. Atanasoski, J. Power Sources 161 (2006) 1002–1011.

Acknowledgement: This project has received funding from the Fuel Cells and Hydrogen 2 Joint Undertaking under grant agreement No 700127 INSPIRE. This Joint Undertaking receives support from the European Union’s Horizon 2020 research and innovation programme.
Investigating the Durability of Unsupported Pt-Alloy Aerogel Cathode
Authors: Henning Sebastian , Ishikawa Hiroshi , Kühn Laura , Herranz Juan , Eychmüller Alexander , Schmidt Thomas J.
Published: February 2020

State-of-the-art polymer electrolyte fuel cells (PEFCs) require considerate amounts of carbon-supported platinum nanoparticle (Pt/C) catalysts (up to 0.4 mgPt/cm2
MEA) to catalyse the cathodic oxygen reduction reaction (ORR) [1]. To reduce overall PEFC costs, these excessive Pt-loadings must be reduced by enhancing the catalysts’ ORR activity and stability; e.g. by alloying platinum with other metals like Ni, Cu, Co [2] and by replacing or completely removing the carbon support that suffers from significant corrosion during the normal operation of PEFCs [3].

To overcome these activity and stability challenges, unsupported bimetallic Pt-alloy aerogels consisting of a 3D nanochain network (~ 30 m2
ECSA/gPt) were synthesized (see Figure 1 for a TEM image of Pt3Ni aerogel) [4, 5]. Both Pt-Ni and Pt-Cu aerogels meet the US Department of Energy ORR activity target for 2017 of 440 A/gPt at 0.9 VRHE[6] when tested in liquid half cells. Considering that this outstanding performance needs to be demonstrated in an actual PEFC, Pt-Ni and Pt-Cu aerogels were processed into membrane electrode assemblies (MEAs) and characterized in a differential PEFC [7].

In this contribution, we present the MEA optimization process for unsupported Pt-alloy aerogel ORR catalysts and compare cell performance and durability (start-stop cycles, load cycles) to a conventional Pt/C benchmark. To explain the outstanding stability of Pt-alloy aerogel catalysts for start-stop cycling (see Figure 1), catalyst layers were investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDX) at beginning-of-life and end-of-life.

[1] F.T. Wagner, B. Lakshmanan, M.F. Mathias, J. Phys. Chem. Lett. 1 (2010), 2204-2219.

[2] H.H. Wang, Z.Y. Zhou, Q. Yuan, et al., Chem. Commun. 47 (2011), 3407-3409.

[3] C. Hartnig, T. J. Schmidt, J. Pow. Sourc. 196 (2011), 5564-5572.

[4] S. Henning, L. Kühn, J. Herranz, et al., J. Electrochem. Soc. 163 (2016), F998-F1003.

[5] S. Henning, L. Kühn, J. Herranz, et al., Electrochim. Acta 233 (2017), 210-217.

[6] O. Gröger, H.A. Gasteiger, J.P. Suchsland, J. Electrochem. Soc. 162 (2015), A2605-A2622.

[7] P. Oberholzer, P. Boillat, R. Siegrist, et al., Electrochem. Commun. 20 (2012), 67-70.
Assessment of Cathode Catalyst Characteristics to Enhance High Current Density Performance in PEMFCs
Authors: Mani Prasanna , Cimenti Max , Manolescu Dorina , Susac Darija , Jankovic Jasna , Sun Dennis , Habisch Aronne
Published: February 2020

At AFCC continuous effort has been made to improve the power density of fuel cell stack for automotive application in the past decade*. The unique challenges in durability posed by the need for much higher power generation per catalyst loading, kW/mg-Pt is still a major driver and a minimum viable stack functionality for mass production. This presentation will focus on one of the ways to meet the above criterion using mature Pt/C technology (10 to 50 wt% Pt on a high surface area carbon) for oxygen reduction in the cathode. The catalysts were custom made by Tanaka Kikinzoku Kogyo K.K to maximize and stabilize the Pt nanoparticles activity during their life cycle. The graph shows the linear dependency of a mix of the above catalysts characteristics such as Pt surface area (CO Chemisorption), Pt crystallite size (XRD), and catalyst surface area (N2 BET) as a function of Pt wt% on Carbon.

With more in-depth analyses, preliminary optimization of catalyst layer for each of the above catalysts will be performed and the results will be discussed. These activities would facilitate the understanding of the effect of catalyst characteristics, catalyst structure (ionomer, catalyst layer thickness, EPSA, etc.), and electrode Pt loading (0.25 and 0.15 mg-Pt/cm2) on the high current density performance up to 3 A/cm2. Identifying the above parameters would leverage further development in maximizing the fuel cell functionalities and improving the stack durability.

 
*Reference:AFCC accomplishments, http://www.afcc-auto.com/company/about-us/

Figure 1
Anion Conducting Ionomers for Fuel Cell and Electrolyzer Applications
Authors: Huang Garrett , Liu Lisha , Ahlfield John M. , Kim Yunbum , Kaburagi Yuna , Tricker Andrew , Kohl Paul A
Published: February 2020

Electrochemical devices, such as fuel cells and electrolyzers, which operate under alkaline conditions, are of interest because they have reduced platinum usage and certain performance advantages. New and improved anion conducting membranes (AEM) have been developed. It is desirable for AEMs to have high molecular weight and low oxygen or fuel permeability.

The anion conducting ionomers used to make the electrodes for fuel cells and electrolyzers share some properties with the membranes, such as chemical stability and high ionic conductivity. However, they differ from membranes in other areas such as oxygen or fuel permeability and molecular weight.

In this study, the performance of a variety of anion conducting ionomers was tested in alkaline fuel cells and electrolyzers. It was found that low molecular weight ionomers gave higher initial and long-term performance. The performance was correlated with materials properties and results from impedance spectroscopy.

Financial support from US Office of the Deputy Assistant Secretary of the Army for Defense Exports and Cooperation (DASA-DE&C) is gratefully acknowledged.
Investigating Non-Precious Metal Catalyst-Electrolyte Interface in Anodes for Alkaline Fuel Cells
Authors: Narvaez Villarrubia Claudia Wuillma , Serov Alexey , Dumont Joseph H , Atanassov Plamen , Kim Yu Seung
Published: February 2020

Extensive research is being performed in renewable and sustainable energy to satisfy the world’s demand and reduce carbon dioxide emissions. Part of these efforts focuses on the development of energy conversion devices such as fuel cells. Alkaline membrane fuel cells (AMFCs) gained attention due to their good activities for oxygen reduction reaction (ORR) in high pH environments using non-precious metal catalysts.1 However, the hydrogen oxidation reaction (HOR) activities with non-precious metal catalysts are still low and poorly understood. Our previous research3,4 with Pt catalysts in alkyl ammonium and guanidinium alkali organic solvents indicated that the HOR activity of Pt is limited by cationic group adsorption at the surface of the catalyst, showing the performance of fuel cells rapidly degraded. In this presentation, we expand our investigation to the HOR interfacial behavior of non-precious Ni-based catalysts-quaternary ammonium functionalized ionomers using microelectrode set-up. Our data suggests that the time-dependent cationic group adsorption with the non-precious metal catalyst is less than that of the Pt catalysts, in spite of the much lower HOR initial activity of the non-precious metal catalysts. Here we will present the microlectrode and surface-FTIR mechanism studies of the interaction of non-precious metal catalyst and various quaternized alkaline polymer electrolytes and their impact on the kinetics of HOR under high pH conditions.

Acknowledgment

This work is supported by US Department of Energy, Energy Efficiency and Renewable Energy, Fuel Cell Technology Office.

References

[1] H. Meng, P. K. Shen, “Novel Pt-free catalyst for oxygen electroreduction,” Electrochem. Commun.
8, 588–594 (2006).

[2] W.C. Sheng, H.A. Gasteiger, Y. Shao-Horn, “Hydrogen Oxidation and Evolution Reaction Kinetics on Platinum: Acid vs Alkaline Electrolytes,” J. Electrochem. Soc., 157, B1529 (2010).

[3] S.-D. Yim, H. T. Chung, J. Chlistunoff, D.-S. Kim, C. Fujimoto, T.-H. Yang, Y. S. Kim, “A Microelectrode Study of Interfacial Reactions at the Platinum-Alkaline Polymer Interface,” J. Electrochem. Soc., 162, F499 (2015).

[4] H. T. Chung, Y.-K. Choe, U. Martinez, J. H. Dumont, A. Mohanty, C. Bae, I. Matanovic, Y. S. Kim, “Effect of Organic Cations on Hydrogen Oxidatin Reaction of Carbon Supported Platinum,” J. Electrochem. Soc., 163(14), F1-F7 (2016).
(Invited) Electrode Evolution in Solid Oxide Cells
Authors: Irvine John
Published: February 2020

Fuel cells will undoubtedly find widespread use in this new millennium in the conversion of chemical to electrical energy, as they offer very high efficiencies and have unique scalability in electricity generation applications. The solid oxide fuel cell (SOFC) offers certain advantages over lower temperature fuel cells, notably its ability to utilise CO as a fuel rather than being poisoned and the availability of high-grade exhaust heat for combined heat and power or combined cycle gas turbine applications. Although cost is clearly a key barrier to widespread SOFC implementation, perhaps the most important technical barriers currently being addressed relate to the electrodes, particularly the fuel electrode or anode. In terms of mitigating global warming, the ability of the SOFC to utilise commonly available fuels at high efficiency, promises an effective and early reduction in carbon dioxide emissions and hence is one of the lead new technologies to improve the environment.In the longer term the ability to utilise waste derived fuels such as biogas will be of critical importance.

The electrochemical reactions in fuel cells and electrolysers occur at the interface between electrodes and electrolyte. Here we look at attempts to nanoengineer this interface to enhance performance and also probe the changes in local structure that relate to activation or ageing during operation.

References:

[1] “Switching on electrocatalytic activity in solid oxide cells”, J-H. Myung, D. Neagu, D.N. Miller & J.T.S. Irvine, Nature, 2016, doi:10.1038/nature19090

[2] “Evolution of the electrochemical interface in high-temperature fuel cells and electrolysers”. JTS. Irvine, D. Neagu, MC. Verbraeken, C. Chatzichristodoulou, C. Graves, MB. Mogensen. Nat. Energy. 2016, 1, 15014
(Invited) High Temperature Ionic Ceramics Fuel Cell to Power Unmanned Aerial Systems (UASs)
Authors: Chu Deryn
Published: February 2020

Small unmanned aerial systems (SUASs) have a great potential for numerous applications. The SUASs are light-weight, man-portable, and capable of delivering commercial products. Currently, small UASs are powered by lithium-ion batteries, however, flight endurance is limited and requires frequent charging battery due to low capacity and energy density. Numerous research and development efforts have focused on alternative power sources. These alternative power sources include technologies such as solar cells and hydrogen based polymer electrolyte membrane fuel cells. In this presentation, we address a high temperature ionic ceramics fuel cell to power a ~20lbs unmanned aerial system for 8hrs (4x improvements over the competing battery technology).
(Invited) Design of Porous Si/C-Graphite Electrodes with Long Cycle Stability and Controlled Swelling
Authors: Li Xiaolin , Yan Pengfei , Xiao Xingcheng , Woo Jae Ha , Wang Chongmin , Liu Jun , Zhang Ji-Guang
Published: February 2020

Silicon (Si) is one of the most promising candidates to replace graphite anode in the next generation of Li ion batteries. Although various approaches have been adopted to improve the performance of Si-based anodes during the last decade, a main challenge on the practical application of Si-based anodes, i.e., the thickness swelling of Si based anode has been much less investigated. Here, we use the porous Si/C-graphite electrode as an example to elucidate the design principle for stable Si anodes of controlled thickness swelling. Excellent agreement between the theoretical design and experimental data was demonstrated. The practical electrode (~3 mAh/cm2 loading) with ~650 mAh/g specific capacity has ~82% capacity retention over 450 cycles. The initial electrode swelling upon full lithiation is <20%. The calendered electrodes demonstrated ~56% end-of-life swelling and ~90% capacity retention after 200 cycles. The full-cell of Li(Ni1/3Mn1/3Co1/3)O2 and the pre-lithiated anode demonstrates >84% capacity retention over 300 cycles.
Optimization of Anion Exchange Membranes Derived from Cross-linked Chitosan-Poly (diallyldimethylammonium chloride) for All-solid Electrochemical Capacitors
Authors: Wei Yanan , Ao Bei , Qiao Jinli , Lian Keryn
Published: February 2020

Carbon dioxide can be formed in many ways, especially in combustion, it is one of the most important reasons lead to greenhouse effect and global warming. So many scientists devoted themselves to techniques that can reduce CO2 emissions. Among these promising techniques, electrochemical ways provide a efficient means, as it can convert carbon dioxide into fuels and other useful materials.[1,2] This way has many advantages: (a) the process is controllable by setting the temperature of electrode; (b) the system can take advantage of new energy resources and the production do not contaminate environment; (c) the system is compact and easily operated; (d) the experiment can be operated under normal atmospheric pressure and temperature.[3,4]

In this paper, Tin-Cu alloy was deposited on carbon paper by electrodeposition in aqueous solution, which was employed as a cathode for electrochemical reduction of CO2 to formate, and how to obtain big catalytic current density, high efficiency and high production rate of formate were explored and discussed. Tin-Cu alloys with different compositions were characterized by morphology, structure, and composition. The electrochemical behavior of the alloys was measured by EIS and CV analysis. In addition, FE, partial current density (PCD), and concentration of HCOO− on the alloys were investigated and compared with those on Sn and Cu electrodes.

References

[1] S. Rasul, D.H. Anjum, A. Jedidi, Y. Minenkov, L. Cavallo, K. Takanabe, Angew. Chem. Int. Ed., 54,2146(2015).

[2] Q. Lu, J. Rosen, Y. Zhou, G.S. Hutchings, Y.C. Kimmel, J.G. Chen, F. Jiao, Nat. Commun., 5,4242(2014).

[3] Q. Shen, Z.F. Chen, X.F. Huang, M.C. Liu, G.H. Zhao, Environ. Sci. Technol., 49,5828(2015).

[4] X.Q. Min, M.W. Kanan, J. Am. Chem. Soc., 137, 4701(2015).
Defect Chemistry Analysis of the Nonstoichiometry and Conductivity in Pr1-XNdxO2-D
Authors: Wang Yudong , Dogdibegovic Emir , Koser B , Zhou Xiao-Dong
Published: February 2020

Pr1-xNdxO2-d is a potential compound to add into (Pr,Nd)2NiO4 (PNNO) to further improve the activity and phase stability of PNNO used as the cathode for solid oxide fuel cells. In this work, we employ defect chemistry to investigate the nonstoichiometry and electrical conductivity of Pr1-xNdxO2-d (0 <x < 1). The powders of Pr1-xNdxO2-d are synthesized from a glycine-nitrate combustion method, followed by high temperature calcination. The Pr1-xNdxO2-d bars are sintered at various temperatures to obtain a dense ceramic. Electronic and ionic conductivities are measured from 650 to 850 °C by using a blocking electrode based on Hebb-Wagner method. In Pr rich compounds, the electronic conductance dominates. This is consistent with the DFT calculation showing a higher density of states (DOS) at the Fermi level with a richer Pr; while the extracted DOS at the Fermi level sharply decreases in Nd-rich compounds.
Simultaneous Function of Gd2O3 As Solid Dopant and Sintering Aid for Anode Support Type Solid Oxide Fuel Cells
Authors: Kim Chanho , Jang Inyoung , Kim Sungmin , Yoon Heesung , Paik Ungyu
Published: February 2020

For anode support-type solid oxide fuel cell (SOFC), the mechanical strength of anode layer is important factor for commercialization and scale-up. The high sinterability of anode support increase the strength of the cell. NiO/Gd-doped ceria(GDC) cermet is commonly used material for anode support. However, in this study NiO/undoped-ceria(CeO2) was employed as starting material due to the purpose of adopting Gd2O3 as a sintering aid and a dopant. Gd2O3 was uniformly formed on the surface of NiO/CeO2 anode particles. During the sintering procedure, the Gd-ion migrate from Gd2O3 which was formed on the pre-sintered anode support to CeO2 due to similar atomic radius between Gd and Ce. In addition, sinterability of anode support was improved since Gd2O3 functioned as sintering aids. Finally, open-circuit voltage (OCV) was enhanced by less electrical loss and gas separation in soild electrolyte.
Mechanical Characterization of SOFC Anode Support Materials at Operating Conditions
Authors: Stanley Patrick , Hays Thomas H , Wachsman Eric D.
Published: February 2020

Solid-oxide fuel cells (SOFCs) rely on a good seal between the anode and cathode sides of the cell to function properly. This means that cells must be manufactured, assembled, and sealed in a manner that does not compromise the gas-tight separation of anode and cathode. The mechanical properties of the cell, specifically the anode support layer, must be able to withstand the stresses it is subjected to without cracking. While the specific material and processing conditions can affect the mechanical properties, so can the temperature and oxygen concentration, thus it is of interest to characterize the mechanical properties not only at ambient conditions, but also at elevated temperatures and under reducing environments.

To study these properties, flexural bend tests were performed on gadolinium doped ceria samples at various temperatures and oxygen partial pressures to study their flexural modulus and flexural strength. This was then compared with other characterization and mechanical testing techniques, such as scanning electron microscopy, X-ray diffraction, indentation and impulse excitation techniques, to evaluate what phenomenon are occurring under what conditions. From this work, it can be better understood how a SOFC must be designed and manufactured to be able to withstand stresses while under operating conditions.
Development of Stabilized Bismuth Oxide Based Composite Cathodes for Low Temperature SOFCs
Authors: Pesaran Alireza , Jaiswal Abhishek , Wachsman Eric D.
Published: February 2020

Commercialization of SOFCs will be advanced by the development of cell materials and components which operate well at lower temperatures. Lower operating temperatures allow the use of inexpensive ferritic stainless steels as interconnect, improve the chemical and mechanical stability of the cells, and increase stack lifetime. However, oxygen reduction reaction (ORR) kinetics at cathode of the cell is slower at lower temperatures, which significantly reduces the maximum power density of the cell. Electrochemical impedance spectroscopy (EIS) measurements on anode supported bilayer electrolyte SOFCs at 600oC with stabilized bismuth oxide based composite cathode indicated that the non-ohmic polarization accounted for half to two-third of the total cell area specific resistance (ASR). In this work, composite cathodes of various compositions, i.e. weight ratio of electron conducting phase (LSM or BRO) to stabilized bismuth oxide, were fabricated and tested on symmetrical cells using EIS. The starting powder was made by solid-state and wet-chemical methods followed by ball milling to achieve different particle size distributions. Reactivity of stabilized bismuth oxide and electron conducting phase at high temperatures was studied using XRD. EIS spectrum was studied to deconvolute the kinetics of ORR and the performance of the composite cathode as a function of weight ratio and particle size distribution of the two phases was looked at. Lastly, long term performance stability of selected cathode compositions was determined.
Development of High Performance Intermediate Temperature Proton-Conducting Solid Oxide Electrolysis Cells
Authors: Wu Wei , Ding Dong , He Ting
Published: February 2020

Steam electrolysis by solid oxide fuel cell technology, known as SOEC, is considered the most efficient and cost effective option for hydrogen production from renewable sources. By using proton-conducting electrolyte, the SOEC operating temperature can be reduced from over 800oC to below 600oC. Technical barriers associated with the conventional oxygen-ion conducting SOECs, such as hydrogen separation from water, oxidation of steam electrode, and instability of oxygen electrode, can be largely mitigated. In this report, an intermediate temperature (400-600°C) electrolysis technology was developed where a novel proton-conductor and a triple-conducting oxide were used as the electrolyte and anode, respectively. The electrolysis cell demonstrated excellent performance and durability at intermediate temperatures, promising a new prospective for next-generation steam electrolysis.
Features of Molten Oxide Fuel Cells and Molten Oxide Membranes for Electrochemical Energy Conversion and Oxygen Separation
Authors: Belousov Valery
Published: February 2020

Recently, the molten oxide fuel cell (MOFC) and molten oxide membrane (MOM) concepts have been proposed.1-4 MOFCs are a new class of intermediate temperature fuel cells combined the advantages of both solid oxide fuel cells, SOFCs (air as a cathode gas) and molten carbonate fuel cells, MCFCs (a highly conductive molten electrolyte) and could be used for electric power generation. MOMs are a new type of ion transport membranes which demonstrate competitive oxygen permeability and highest oxygen selectivity and could be used for ultrahigh purity oxygen separation from air. However, before MOFC and MOM technologies can gain a share of the energy market, important issues have to be addressed. These issues include the development of innovative molten oxide materials with enhanced performance and establishment of oxygen ion transport mechanisms in these materials. Understanding the oxygen ion transport mechanisms in molten oxides is important for the discovery of next-generation electrochemical materials that can enable the operation of MOFCs and MOMs efficiently. In this paper, we highlight the progress made in developing this understanding as well as the advances made in searching innovative electrochemical materials for MOFCs and MOMs.

References

V.V. Belousov. Next-Generation Electrochemical Energy Materials for Intermediate Temperature Molten Oxide Fuel Cells and Ion Transport Molten Oxide Membranes, Acc. Chem. Res., 2017, 50, 273.

V.V. Belousov, S.V. Fedorov. A Novel Molten Oxide Fuel Cell Concept, Fuel Cells, 2016, 16, 401.

V.V. Belousov, S.V. Fedorov. A Highly Conductive Electrolyte for Molten Oxide Fuel Cells, Chem. Commun., 2017, 53, 565.

V.V. Belousov, I.V. Kulbakin, S.V. Fedorov, A.A. Klimashin. Novel Molten Oxide Membrane for Ultrahigh Purity Oxygen Separation from Air, ACS Appl. Mater. Interfaces, 2016, 8, 22324.
Stabilization of Electrode-Electrolyte Interface By Conformal Passivating Layers on the Surface of Spinel Nanocrystals
Authors: Kwon Bob Jin , Key Baris , Dogan Fulya , Jokisaari Jacob , Kim Chunjoong , Klie Robert F , Cabana Jordi
Published: February 2020

Stable cycling performance with high power density in lithium ion battery (LIBs) is required to meet the criteria for the power source such as electric vehicles. But generally, high power density is hindered by slow diffusion of lithium ions in micrometric electrode materials. [1] From this perspective, nanoparticle electrode materials can enhance the rate of lithium ions because of shortened diffusion pathway of lithium ion. Besides, high surface area of electrode induces facile access of charge via large contact area with electrolyte and conducting additives like carbon. In contrast, chemical degradation at electrode-electrolyte interface is also facilitated by large contact area with nanoparticle electrode. Unfavorable interfacial reactions such as dissolution of cathode species and decomposition of electrolyte mainly occur through energetically unstable surfaces of the active material. [2] In order to minimize side reactions that can negatively affect electrochemical performance, introducing electrochemically inactive ions on the surface of active materials can improve the interfacial stability. However, this substitution should take place as thin passivating layers on individual particles to preserve storage capacity. [3] A strategy toward the stabilization of electrode-electrolyte interfaces has been devised by introducing core-shell nanocrystals, consisting of electroactive lithium transition metal oxide cores and ultra-thin inactive epitaxial oxide shells on the surface. Spinel Li1+xMn2-xO4 nanocrystals were used as a core component, with an Al-rich shell as passivation layers to minimize unfavorable reaction on the surface of cathode particles. The electrochemical performance shows that Spinel Li1+xMn2-xO4 nanoparticle with conformal shell reveals improved capacity retention and rate capability even at elevated temperature, compared to a bare counterpart.

Reference

1. Isaac D. Scott, Yoon Seok Jung, Andrew S. Cavanagh, Yanfa Yan, Anne C. Dillon, Steven M. George, and Se-Hee Lee, Nano Letters, 414–418, 11 (2011).

2. Peter G. Bruce, Bruno Scrosati, and Jean-Marie Tarascon, Angew. Chem. Int. Ed, 2930-2946, 47 (2008).

3. Chunjoong Kim, Patrick J. Phillips, Linping Xu, Angang Dong, Raffaella Buonsanti, Robert F. Klie, and Jordi Cabana, Chem. Matter, 394-399, 27 (2014).
Enhanced Electrochemical Performance of Mechano-Activated Nanoparticles of the Low Temperature Orthorhombic Phase of Li2FeSiO4
Authors: Rasool Majid , Lu Xia , Chiu Hsien-Chieh , Voisard Frédéric , Gauvin Raynald , Jiang De-Tong , Zaghib Karim , Demopoulos George P.
Published: February 2020

Lithium transition metal silicates Li2

M
SiO4 (
M
 = Fe, Mn, Co, etc.) have been under intense research due to their high theoretical capacity of 330 mAh/g. However, most of the present work have been focused on the electrochemistry of the high temperature monoclinic phase (m-LFS), which shows clear phase transition to a thermodynamically stable low-temperature orthorhombic phase (o-LFS) during cycling. In this context we thought of interest to investigate the cycling behavior of the low-temperature o-LFS that we synthesized via hydrothermal processing. However, as synthesized o-LFS crystals have large ~1.5 µm size, which is undesirable for li-ion intercalation. Therefore, for particle size reduction, we used high energy planetary ball milling and obtained nanoparticles of ~50 nm. Interestingly, XRD results showed improved crystallinity during ball milling. Moreover, electrochemical performance of such mechanically activated nanoparticles showed improved capacity with increasing milling time. This intriguing (unusual) behavior could have significant implications to the development of high capacity LIB materials.

Keywords: Li2FeSiO4; Orthorhombic; Low temperature; Electrochemical performance; Li-ion battery
(Invited) Cation-Disordered Rocksalt Oxides for High-Capacity Positive Electrodes of Rechargeable Lithium/Sodium Batteries
Authors: Yabuuchi Naoaki
Published: February 2020

In the past decade, lithium-enriched compounds, Li2MeO3 (Me = Mn4+, Ru4+ etc.), have been extensively studied for high-capacity positive electrode materials of lithium batteries. Although the origin of high reversible capacities was a debatable subject for a long time, recently it has been evidenced that charge compensation is partly achieved by solid-state redox of non-metal anions, i.e., oxide ions (anionic redox),[1] coupled with solid-state redox of transition metal ions (cationic redox), which is the basic theory used for classical lithium/sodium insertion materials. Competition between cationic and anionic redox reactions is often evidenced for the lithium-enriched materials because the energy level of oxygen 2p band is lowered by the presence of excess lithium ions with high ionic characters in the crystal lattice. Reversibility of anionic redox reactions is also influenced by ionic and covalent characters for chemical bonds of transition metal ions.[2, 3] In contrast, when the energy of metal 3d band is low enough than that of oxygen 2p, pure cationic redox is realized even for lithium-excess system.[4] In this presentation, we discuss the material design strategy with the concept of cationic and anionic redox reactions to develop new high-capacity lithium/sodium insertion materials for battery applications.

References

[1] M. Sathiya et al, and J.-M. Tarascon, Nature Materials, 12, 827 (2013).

[2] N. Yabuuchi et al., PNAS, 112, 7650 (2015).

[3] N. Yabuuchi et al., Nature Communications, 7, 13814 (2016).

[4] S. Hoshino, et al., and N. Yabuuchi, ACS Energy Letters, 2, 733 (2017).
A Reduced Order Model Derived from DFT with Uncertainty Estimation for the Understanding of Magnetic Cathodes
Authors: Houchins Gregory , Viswanathan Venkatasubramanian
Published: February 2020

Li-ion cathode materials containing magnetic transition metals (Fe, Ni, Co, Mn, Ti) are the most promising materials for rechargeable batteries. The magnetic interactions of the transition metal ions play a significant role in determining the lithium intercalation-deintercalation process, capacity loss, and therefore are crucial for the optimization of cathodes materials and for the discovery of new candidate materials. A large body of work has been dedicated to the study of these materials through ab initio electronic structure calculations using density functional theory (DFT).

The Heisenberg Hamiltonian has previously been used in conjunction with DFT calculations to correctly find the magnetic ground states of materials for complicated structures with large number of possible spin configurations.[1] The mapping of a few DFT calculations to reduced-order models allows for the exploration of a much larger subset of parameter space with much more computational efficiency than DFT alone. We expand this spin Hamiltonian with other energetic contributions including an occupation and nearest neighbor electronic interaction terms. The parameters of this model can be tuned to high fidelity and therefore can accurately extend to high throughput. This reduced order model can then be used with Monte Carlo simulations to generate relevant phase spaces with high resolution and less compute power than comparable collection of DFT only calculations.

A unique aspect of this work is the incorporation of error estimation through the use of the Bayesian Error Estimation Functional (BEEF)[2] and apply that to the prediction of magnetic ground states [3]. This allows us to predict c-values related to the reliability of the prediction of magnetic states identified through the DFT calculations. We use this approach to systematically understand the magnetic properties of various Li-ion cathodes. We then apply that method to predict precisely the Li-NMC (Ni-Mn-Co) phase-diagram and calculate their corresponding voltages. We will report on a robust approach to carry out high-throughput screening of cathode materials using the developed method for uncertainty estimation.

[1] D. Morgan, B. Wang, G. Ceder, and A. van de Walle, Phys. Rev. B 67, 134404 (2003).

[2] J. Wellendorff, K. T. Lundgaard, A. Møgelhøj, V. Petzold, D. D. Landis, J. K. Nørskov, T. Bligaard, and K. W. Jacobsen, Phys. Rev. B 85, 235149 (2012).

[3] G. Houchins and V. Viswanathan to be submitted

Figure 1
Synthesis of MnO Nano-Particle@Flourine Doped Carbon and Its Application in Hybrid Supercapacitor
Authors: Feng Xiaoke , Qu Deyu , Xie Zhizhong , Wei Xi
Published: February 2020

In order to meet the increasing demand for the high energy and high power in the same time, while neither secondary batteries nor double-layer supercapacitors cannot satisfy, a new energy storage device, hybrid supercapacitor, attracked lots of attentions in recent days. The new device hybrid the double layer capacitor electrode, which provides the high power density, with the secondary battery electrode, which supplys the high energy density. Various of lithium ion batteries(LIBs) electrodes are introduced into this hybrid system. As the alternative materials to the carbonaceous anode in commercial LIBs, numerous of transition metals have been studied as the anode of LIBs due to their high theoretical capacity, high safety and environmental benignity. Here, a transition metal MnO, a promising material used as anode in LIBs, worked with porous carbon materials to form a new lithium ion hybrid supercapacitor. In this device, MnO is used as negative electrode. Meantime the porous active carbon electrode serves as positive electrode. Similar with other transition metal materials, the intrinsic high resistance, large volume variation during the charge and discharge will still impede the MnO involving into the hybrid system. Especially the late one will cause the pulverization of the MnO materials and then the loosing contact between active materials and current collector. This will cause a significantly capacity fading and bad cycling stability. Since the high energy capacity, excellent cycle-ability and good rate performance are the major merits of hybrid supercapacitor, therefore those problems of MnO should be solved first.

To solve those problems, covering nano-sized MnO materials with conductive carbon layer is a proper approach. Furthermore, It is widely recognized that doping hetero-atom onto the carbon can change their electronic configuration and then improve the electrochemical performances of the carbon materials. Therefore, in this study, a fluorine-doped carbon encapsulated MnO nano-particle (MnONP@FC) was fabricated through a novel process. In this synthesis process, Nafion ionomers was used as the fluorine doped carbon precursor. As shown in Scheme 1, Mn ions are first self-assembly trapped within the Nafion matrix through the electrostatic interaction between positive charged Mn ion and negative charged sulfonate end groups in Nafion ionomer. Then after pyrolysis under nitrogen atmosphere, the Nafion ionomers was transformed into carbon frameworks and MnO nano-particles was formed and highly dispersed within them. The formed MnONP@FC was characterized through SEM, TEM and XPS and the electrochemical performances of the hybrid device, which composited MnONP@FC with the porous carbon materials, were also investigated. The results exhibited that this new hybrid supercapacitor showed a high energy density up to 40 mAh g-1, long cycle stability and good rate performance.

Figure 1
Clarifying Anionic Redox Chemistry in LiCoO2 By Direct Detection of O-O Bond Length and First-Principle Investigations
Authors: Hu Enyuan , Wang Xuelong , Zhang Jie-Nan , Liu Jue , Bak Seong-Min , Lin Ruoqian , Page Katharine , Xiao Ruijuan , Yu Xiqian , Li Hong , Yang Xiao-Qing
Published: February 2020

Developing high energy density lithium ion battery cathode materials requires exploring novel chemistries that go beyond the conventional redox couple which is solely based on transition metal. Anionic redox reaction that activates lattice oxygen anions during charging and discharging can almost double the capacity of conventional cathode and thereby significantly increases the energy density. The nature of chemical bonding, in particular whether or not oxygen anions can bond in forming dimers or peroxo-like species, is critical to the reversibility of anionic redox couple and consequent cyclability of the material. Unfortunately, because oxygen scatters X-ray weakly and dimers may form locally rather than globally, it is very challenging to characterize the oxygen-oxygen bond unambiguously using conventional structural study tools like XRD. Here it is shown that neutron pair distribution function (NPDF) analysis is an effective tool in probing the existence of oxygen dimers without limitation to long range order. This technique is applied to LiCoO2 which still attracts lots of attention due to its high packing density and potential high energy density (delivers around 220 mAh/g when charged to 4.6 V). Through combining experimental results with theoretical calculations, the nature of anionic redox reaction is unraveled and it is shown that the structure of LiCoO2 can be fairly robust against oxygen release, suggesting the relative stability of the bulk structure and the possibility of fulfilling its potential of high energy density.

Acknowledgement

The work done at Brookhaven National Laboratory were supported by the Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Vehicle Technologies of the U.S. Department of Energy through the Advanced Battery Materials Research (BMR) Program, including Battery500 Consortium under contract DE-SC0012704. Research conducted at ORNL's Spallation Neutron Source was sponsored by the Scientific User Facilities Division, Office of Basic Energy Sciences, U.S. Department of Energy.
Synthesis of α-Mns Hierarchical Architectures By Chemical Vapor Deposition and Its Application As Anode Electrode for Li-Ion Batteries
Authors: Luis Matos Angela , Dorvilien Valerio , Rodriguez Sandra , Mendoza Frank , Weiner Brad R. , Morell Gerardo
Published: February 2020

MnS is a wide band gap (3.1 - 3.7 eV) p-type direct semiconductor that exists in three crystallographic polymorphs; the green α-MnS is the most stable with a rock-salt crystal structure, and the two metastables zincblende (β-MnS) and wurzite (γ-MnS) crystal structures. In particular, α-MnS have been reported to provide very good electrochemical performance for alternative anode electrodes to fabricate flexible all-solid state supercapacitors and electrodes for Li-ion batteries. α, γ, or β-MnS materials are usually synthesized by the chemical solution methods, such as solvothermal and hydrothermal techniques. However, our method in this work consists in the synthesis of free standing α-MnS hierarchical architectures by Chemical Vapor Deposition technique, which is suitable to prepare electrodes for Li-ion batteries. In this presentation, we discuss: a) the growth mechanism of α-MnS by Chemical Vapor Deposition technique; b) its structural, morphological, and compositional characterization; and c) the cyclic voltammetry, charge-discharge behavior, and cycling capacity of coin cells using α-MnS as the anode electrode.
Oxysulfide Lialso: A Lithium Superionic Conductor from First Principles
Authors: WANG Xuelong , Xiao Ruijuan , Li Hong , Chen Liquan
Published: February 2020

Searching for lithium superionic conductors attracts a lot of attention over the past few decades, especially for the development of all-solid-state lithium batterie. So far, the only kinds of solid material with ionic conductivity over 10-2 S/cm at room temperature are among sulfide materials (Li10GeP2S12 and its derivative, Li7P3S11 glass-ceramic, and Li9.54Si1.74P1.44S11.7Cl0.3). However, sulfides generally suffer from high sensitive to moisture and poor stability of solid electrolyte/oxide cathode interfaces. Compared with sulfides, the oxide SEs have significantly better chemical and electrochemical stability, whereas the highest ionic conductivity achieved in them is still one order of magnitude lower than those of liquid electrolytes. To combine the advantages of sulfides and oxides, anion mixing is expected to be a promising strategy to design the lithium superionic conductors with improved stabilities and high ionic conductivity. To the best of our knowledge, there is still no discovery of crystalline oxysulfide for SEs used in lithium batteries.

In this work for the first time we identify a new layered oxysulfide LiAlSO in orthorhombic structure as a novel lithium superionic conductor through first-principles calculations and crystal structure prediction techniques. Two kinds of stacking sequences of AlS2O2 layer are found in different temperature ranges. Phonon and molecular dynamics simulations verify their dynamic stabilities, and wide band gaps up to 5.6 eV are found by electronic structure calculations. The lithium migration energy barrier simulations reveal the collective interstitial-host ion “kick-off” hopping mode with barriers lower than 50 meV as the dominating conduction mechanism for LiAlSO, making it a promising solid state electrolyte in lithium secondary batteries with fast ionic conductivity and wide electrochemical window. This is a first attempt that the lithium superionic conductors are designed by crystal structure prediction method and may help explore other mixed-anion battery materials.

Acknowledgment

We acknowledge the National Natural Science Foundation of China (Grant No. 11234013), ‘‘863’’ Project (Grant No. 2015AA034201), and the Beijing S&T Project (Grant No. D161100002416003) for financial support and the Shanghai Supercomputer Center for providing computing resources. We would like to express our thanks to Prof. Jiawang Hong (Beijing Institute of Technology) for his fruitful discussion.
High Energy Lithium-Ion Battery Using Substituted LiCoPO4
Authors: Liu Dongqiang , Kim Chisu , Cho Myunghun , Guerfi Abdelbast , Zaghib Karim , Delp Samuel A. , Allen Jan L. , Jow T Richard
Published: February 2020

There is a constant drive to improve the specific energy and energy density of the state-of-the-art lithium-ion battery. High energy can be achieved by either choosing a cathode material that operates at a higher potential or has a higher specific capacity. Compared with the conventional 4-V cathodes such as LiCoO2 (LCO), LiNi
x
Co
y
Al
z
O2 (NCA), LiMn2O4 (LMO) and 3.5-V LiFePO4 (LFP), LiCoPO4 (LCP) operates at 4.8 V (vs. Li/Li+) with a theoretic capacity of 167 mAh g-1, resulting in a specific energy of ~800 Wh kg-1, which is about 25% higher than those of the conventional LFP and LMO lithium-ion batteries. Although Co is more expensive than the other transition metals, the energy cost of LCP is expected to be cheaper than all commercialized lithium-ion batteries on the market [1] due to the improved energy density (FIG.1).

However, LCP suffers from severe capacity fade due to the low intrinsic electronic/ionic conductivity, structure deterioration and electrolyte decomposition [2]. In order to improve the cyclability and reduce the cost of LCP, Co ions were partially substituted by cheaper elements such as Fe, Cr and Si etc [3]. Meanwhile, a carbon-coating was used to improve the electronic conductivity of LCP. Electrochemical tests showed that both carbon-coating and substitution greatly improved the cycling performance of LCP, which suggests that the substituted LCP is a very promising cathode candidate for high energy lithium-ion battery.

References

[1] S. Brutti, S. Panero, ACS Symposium Series, 1140, Chapter 4, 69 (2013).

[2] K. Tadanaga, F. Mizuno, A. Hayashi, T. Minami, M. Tatsumisago, Electrochemistry
71, 1192 (2003).

[3] J. L. Allen, J. L. Allen, T. Thompson, S. A. Delp, J. Wolfenstine, T. Richard Jow, J. Power Sources, 327, 229 (2016).

FIG. 1. Energy density and energy cost of LCP compared with other cathode materials currently used in lithium-ion batteries.

Figure 1
Effects of Irradiation Induced Defects on TiO2 Electrodes for Lithium Ion Batteries
Authors: Smith Kassiopeia , Savva Andreas , Deng Changjian , Wharry Janelle , Hwang Sooyeon , Su Dong , Wang Yongqiang , Xu Tao , Butt Darryl , Hwang Sooyeon , Xiong Hui (Claire)
Published: February 2020

We are living in a time of growing concerns over population growth, energy consumption, and climate change. These issues are driving the need for advanced electrochemical energy storage (EES) technologies, such as batteries, to support a shift to renewable energy sources. After their commercialization in the 1990’s LIBs have dominated the field of portable electronics, and have become one of the most promising EES systems for renewable energy systems. Even so, the future demands of EES technology will require LIBs to offer increased energy and power density, improved safety, and longer cycle life. As such, recent studies have investigated enhanced electrochemical charge storage in electrodes that contain intentional structural defects.

A new approach to introduce defects in electrode materials is to use ion irradiation to produce damage cascades which result in point defects in the target material. The objective of this work is to investigate the fundamental effects of irradiation on nanostructured TiO2, and to understand how these effects can alter the electrochemical charge behavior when the oxide is used as an electrode in Li-ion batteries. Our work suggests that tailoring the defect generation through ion irradiation within metal oxide electrodes could present a new avenue for design of advanced electrode materials.

In this study, we first focus on separating the effects of irradiating species on defect production by conducting proton, niobium, and nickel irradiations on [100] and [110] rutile TiO2 single crystals. We then extend our study to nanostructured TiO2, irradiated with protons. After room temperature irradiation the nanotubes undergo an irradiation-induced phase transformation accompanied by a 35% reduction in capacity compared to anatase TiO2. On the other hand, proton irradiation at 250 °C induced a disordered rutile phase which along with a 20% increase in capacity. Voltammetric sweep data was used to determine the contributions from diffusion-limited intercalation and capacitive processes and it was found that the electrodes after irradiation has more contributions from diffusion in lithium charge storage. Our work suggests that tailoring the defect generation through ion irradiation within metal oxide electrodes could present a new avenue for design of advanced electrode materials.

Figure 1
(Invited) Spectrally Narrow Quantum Dots and Red Phosphor in White LEDs for Display Applications
Authors: Gangwal Sumit , Chamberlin Danielle , Shimizu Ken , Bechtel Hans-Helmut , Diederich Thomas , Grabowski Stefan , Estrada Daniel , Bohmer Marcel , Bhardwaj Jyoti
Published: February 2020

The total available market size for high color gamut in display applications including TVs, smart phones, and tablets is rapidly growing and expected to exceed $1 billion by 2020. It is highly desirable to use quantum dots (QD), with narrow emission line widths, and narrow band red phosphors (e.g., SLA) materials to achieve high color gamut. An on-chip converter application is preferred over remote configurations because this provides lower cost and lower complexity for LED use in all sizes of displays. We discuss development of on-chip QD LEDs and narrow band phosphor LED solutions for display applications.