bluuebunny/crossref_metadata_2025 huggingface dataset:
Improved Anode Catalyst for Formic Acid Fuel Cells
Authors: Pemberton Kailey D , Rice Cynthia A.
Published: February 2020

The use of direct formic acid fuel cells (DFAFCs) in portable electronic devices can improve available power density and convenience, compared to today’s rechargeable batteries. Unfortunately, current DFAFC anode catalysts either have high parasitic overpotentials and/or deactivate over time. This deactivation causes a decrease in sustained performance of the catalyst over time.[1] A typical anode catalyst used in these DFAFC consists of carbon supported platinum nanoparticles with a sub-monolayer of bismuth (Pt/C-Bi).[2] Over time, bismuth is oxidized and lost from surface resulting in deactivation of the catalyst nanoparticles, which leads to the DFAFC losing performance.[3]

Bismuth at moderate Pt surface coverages promotes formic acid adsorption in the CH-down orientation through a combination of the third-body (steric) and electronic effects. When formic acid adsorbs in the CH-down orientation the direct reaction pathway is promoted bypassing the formation of strongly adsorbed reaction intermediates. The overpotentials associated with the direct reaction pathway are minimal, thereby elevating the power output of the DFAFCs.

The goal of this project is to explore stable alternative adsorbates to replace bismuth in order to maximize power density and durability of DFAFCs. Three-electrode electrochemical studies are performed on a polycrystalline Pt disk working electrode in 0.1M HClO4. Initial studies with citrate have demonstrated strong surface adsorption to Pt. The cyclic voltammograms in Figure 1 demonstrate that citrate blocks hydrogen adsorption/desorption sites on Pt and coverage is tailorable to that of a submonolayer of citrate. Linear sweep voltammetry in formic acid shows minimal electro-oxidation performance on pure Pt and a full monolayer of citrate. However, for a submonolayer of citrate the activation overpotential is reduced to 0.2 V vs. RHE due to the significant contribution to the direct reaction pathway.

References:

1. X. Yu and P.G. Pickup, Journal of Power Sources, 182, 124, (2008).

2. A.S. Bauskar and C.A. Rice, Electrochimica Acta, 93, 152, (2013).

3. A.O. Pistono, C.S. Burke, J.W. Cisco, C. Wilson, B.G. Adams, and C.A. Rice, ECS Electrochemistry Letters, 3, F65, (2014).

Figure 1
Electrodeposition of Amorphous Molybdenum Sulfide on Carbon Paper As an Electrocatalyst for Hydrogen Evolution Reaction
Authors: Kim Jung Hwan , Kim Junhyeong , Kim Hyunki , Ahn Sang Hyun
Published: February 2020

Hydrogen is a very versatile element which can be used for many applications such as metallic ore reduction, hydrogen fuel cells, fertilizer and etc. In common, hydrogen can be obtained from fossil fuels with plasma and steam reforming. However, a problem arises in that both methods require high operating temperatures, which leads to use of fossil fuels and ultimately, emission of pollutants. Electrolysis of water is comparatively superior in the aspect that it could be operated at lower temperature range. Thus, the water electrolysis is introduced as a promising method for producing hydrogen. Currently, the most excellent catalyst for water electrolysis is known as platinum. However, the use of this noble metal is still limited, because of its scarcity and excessive cost. Therefore, the pressing issue to resolve this problem is synthesizing an alternative catalyst. Among them, transition metal chalcogenides are typical candidates for replacing noble metals. This work is focused on molybdenum sulfides because it has been reported that the Gibbs free energy of adsorbed atomic hydrogen on molybdenum sulfides is favorable for hydrogen evolution reaction (HER). Recently various groups have revealed that the basal planes of molybdenum sulfide films were inactive to HER, whereas the edges were highly active. In this work molybdenum sulfide precursor in electrolyte was electrochemically reduced to fabricate continuous films on annealed carbon paper via cathodic electrodeposition. The catalyst was synthesized by varying potential, concentration and deposition time. The field emission scanning electron microscope analysis confirmed the formation of molybdenum sulfide thin films on the surface of carbon paper. Through X-ray diffraction and X-ray photoelectron spectroscopy, it was confirmed that the nature of the as deposited catalyst was amorphous. The HER activity was tested by using linear sweep voltammetry in 0.5 M sulfuric acid. Electrochemical surface area was measured by conducting a cyclic voltammetry at different scan rates. The performance of this catalyst was remarkable at highly negative potentials and showed excellent stability after extensive experimentation in a proton exchange membrane water electrolyzer.
Porous Silver/Indium and Gold/Indium Electrocatalysts for Electrochemical Conversion of Carbon Dioxide
Authors: Lee Hyunju , Kim Hyenki , Ahn Sang Hyun
Published: February 2020

As the use of fossil fuels increased, the global warming is becoming much serious problem by huge emission of CO2 to atmosphere. Thus, tremendous efforts have been conducted to reduce the concentration of CO2 in atmosphere. As one of the promising technologies, the electrochemical conversion of CO2 to useful products has been received a great attention because these products are able to be utilized in various industrial fields. Among the products, the production of CO is known to have an economical benefit because the market price of CO is relatively higher than other products. As the electrocatalysts, the silver and gold-based metals are commonly used to produce CO from the electrochemical reduction of CO2. However, the cost is an important criterion for CO2 conversion although these noble metals are highly active and selective for CO production. In this study, the porous copper foam was fabricated by two-step galvanostatic electrodeposition in order to obtain a large electrochemical surface area, and then indium electrodeposition was carried out on the top of copper foam to suppress the hydrogen evolution reaction which is known as competitive reaction with electrochemical CO2 reduction. Then porous indium was immersed in the electrolytes which contained noble metals precursor in order to decrease the amount of noble metal usage. The fabricated porous silver/indium and gold/indium were used as electrocatalysts for the CO2 conversion reaction. The obtained CO Faradaic efficiency was varied by the material properties of silver/indium and gold/indium catalysts such as morphology, roughness and surface composition.
(Invited Plenary) Platinum-Free Fuel Cells for Affordable Zero-Emission Cars
Authors: Yan Yushan
Published: February 2020

One of the grand challenges facing humanity today is the development of an alternative energy system that is safe, clean, and sustainable and where combustion of fossil fuels no longer dominates. A distributed renewable electrochemical energy and mobility system (DREEMS) could meet this challenge. At the foundation of this new energy system, we have chosen to study a number of electrochemical devices including fuel cells, electrolyzers, and flow batteries. For all these devices electrocatalysis and polymer electrolytes play a critical role in controlling their performance, cost, and durability, and thus their economic viability. In this presentation, I will focus on our recent work on hydroxide exchange membrane fuel cells (HEMFCs) which can work with nonprecious metal catalysts and inexpensive hydrocarbon polymer membranes. More specifically I will show the roadmap we have developed for this technology, the progress we have made in developing the most stable membranes and the most active nonprecious metal catalysts. I will also discuss why hydrogen oxidation reactions are slower in base than in acid for precious metal catalysts.
(Invited) Tuning the Structure and Property of Electrode Materials of Lithium Battery
Authors: Li Jun-Tao , Huang Ling , Sun Shi-Gang
Published: February 2020

Along with fast development of compact mobile electronic devices, electric vehicles and large scale electricity storage for renewable energies, the demand on lithium batteries for increasing their energy, power, safety and lowering their cost of become a focal issue in today’s society and R&D communities. It is well recognized that the performances of lithium battery depend strongly on electrode materials, and the structure, especially the surface structure, of electrode determines the density of active sites for Li conversion reaction and the channels for Li+ intercalation/deintercalation. Therefore, it is of crucial importance in controlling the transport kinetics of lithium ions and promoting the performances of lithium battery through tuning the structure of electrode materials.

This communication reports our recent progresses in tuning the surface structure and property of electrode materials. Different materials including nanostructured metal oxides, habit-tuned LNMO nanoplates, NCM hexagonal nanobricks, graphene-based sulfur and RuO2/MnO2 nanorods were designed and control-synthesized, and served as electrodes in lithium ion battery, lithium-sulfur battery and lithium-air battery. The results demonstrated clearly the significant enhancement of electrochemical performances of specific capacity, cycleability and rate property of the as-prepared electrode materials with well-defined structure. Besides the active materials of electrode, the guar gum binder that is a low-cost, environmentally friendly and multi-functional binder for the next generation lithium-ion batteries with high energy density has been developed and applied in both anode and cathode of lithium ion batteries.

Acknowledgements: This work was supported by NSFC (21621091,1373008).

References:

1. G. Z. Wei, X. Lu, F. S. Ke, L. Huang, J. T. Li, Z. X. Wang, Z. Y. Zhou, S. G. Sun, Adv. Mater., 2010, 22(39), 4364.

2. F. Fu, G.L. Xu, Q. Wang, Y.P. Deng, X. Li, J.T. Li, L. Huang, S.G. Sun, 2013, 1, 3860.

3. G.L. Xu, Y.F. Xu, J.C. Fang, F. Fu, H. Sun, L. Huang, S. Yang, S.G. Sun, ACS Applied Materials & Interface, 2013, 5, 6316-6323

4. G.L. Xu, Q. Wang, J.C. Fang, Y.F. Xu, J.T. Li, L. Huang, S.G. Sun, J. Mater. Chem. A, 2014, 2,19941.

5. J. Liu, Q. Zhang, T Zhang, J.T. Li, L. Huang, S.G. Sun, Adv. Funct. Mater. 2015, 25, 3599.

6. T. Zhang, J.T. Li, J. Liu, Y.P. Deng, Z.G.Wu, Z.W. Yin, D. Guo, L. Huang, S.G. Sun, Chem. Commun. 2016, 52, 4683.

7. Y.Q, Lu, J.T. Li, X.X. Peng, T Zhang, Y.P. Deng, Z.Y. Wu, L. Huang, X.D. Zhou, S.G. Sun, Electrochem. Commun. 2016, 72, 79.

8. Y.F. Xu, Y. Chen, G.L. Xu, X.R. Zhang, Z. Chen, J.T. Li, L. Huang, K. Amine, S.G. Sun, Nano Energy, 2016, 28, 63.
Development of a Portable SOFC System with Internal Partial Oxidation Reforming of Butane and Steam Reforming of Ethanol
Authors: Sumi Hirofumi , Yamaguchi Toshiaki , Shimada Hiroyuki , Fujishiro Yoshinobu , Awano Masanobu
Published: February 2020

Internal partial oxidation reforming of butane and steam reforming of ethanol were investigated using microtubular solid oxide fuel cells (SOFCs) supported on nickel-gadolinia doped ceria (Ni-GDC) anode for portable power sources in an emergency situation and mobilities such as vehicles, robots and drones. At oxygen/carbon (O/C) ratio of 1.0, which is a coking condition in the equilibrium, the Ni-GDC anode deteriorated for 28 h by internal partial oxidation of butane at 650 oC. However, power generation was also impossible after 8 and 79 h at S/C = 1.0 and 1.5, respectively, by internal steam reforming of ethanol in spite of no carbon deposition condition in the equilibrium at 650 oC. Power can be generated over a period of more than 100 h at O/C = 1.5 in butane and at S/C = 2.0 in ethanol. The O/C and S/C ratios are significantly important to prevent carbon deposition on the Ni-GDC anode for internal partial oxidation reforming of methane and steam reforming of ethanol in SOFCs.
Chemical and Electrochemical Properties of La0.58Sr0.4Fe0.8Co0.2O3-
δ (LSCF) Thin Films upon Oxygen Reduction and Evolution Reactions
Authors: Pitscheider Simon , Machala Michael , Guan Zixuan , Chen Di , Hjelm Johan , Jacobsen Torben , Chueh William C , Mogensen Mogens Bjerg , Chatzichristodoulou Christodoulos
Published: February 2020

The Oxygen Evolution and Oxygen Reduction Reactions (OER/ORR), occurring at the oxygen electrode of Solid Oxide Cells (SOCs) in the two possible ways of operation, require substantial overpotentials, therefore lowering the operating efficiency of the cells. The reaction mechanisms occurring at these electrodesare still not completely understood due to their complexity and localized character at the interfaces between different materials or between the gas atmosphere and the electrocatalyst, and need in situ techniques with very high chemical sensitivity, with the additional difficulty of probing the materials as close as possible to their realistic operating conditions.

In addition, the properties of LSCF are, despite numerous studies, still unclear in many aspects, despite LSCF being one of the state-of-the-art electrocatalysts used for SOCs. It is understood that the surface chemical composition deviates from the nominal bulk composition, and that secondary phases can segregate at the surfaces and interfaces during operation. Furthermore, the electrochemical properties such as Area Specific Resistance (ASR), oxygen exchange coefficient (kex), ASR activation energy (Ea) and pO2exponents for LSCF reported in the literature vary considerably.

This study aims to better understand the properties of LSCF, by combining the results of Electrochemical Impedance Spectroscopy (EIS) and Near-Ambient Pressure X-ray Photoelectron Spectroscopy (NAP-XPS) on model electrodes, both in polarized and unpolarized conditions. In particular, NAP-XPS studies of the surface chemistry evolution under operation, as well as the correlation between surface potential changes in relation to the applied overpotential are addressed, in an attempt to determine the real driving force for the oxygen reactions.

For this purpose, thin films of LSCF are deposited by Pulsed Laser Deposition (PLD) through shadow masks, in order to obtain well-defined electrode geometries with low risk of contamination, and subsequently tested both in highly clean EIS measuring setups and at the synchrotron beamline. The results of both kinds of experiments are correlated, the goal being a better understanding of the material’s properties under operation, as well as possible degradation phenomena.

Acknowledgements:

We gratefully acknowledge financial support from ECoProbe (DFF – 4005-00129) funded by the Danish Independent Research Council, Otto Mønsteds Fond (17-70-0196) and SUNCAT in collaboration with the Danish Agency for Science and Higher Education (7032-00001B)
Nanostructured Electrodes for Low-Temperature Operating SOFCs
Authors: Abdul Jabbar Mohammed Hussain , Huang Yi-Lin , Pellegrinelli Christopher , Robinson Ian , Pan Ke-Ji , Wachsman Eric D.
Published: February 2020

Production of electricity by directly utilizing abundantly available fuels such as natural gas can meet the energy demands in various sectors. To make a robust, reliable and cost effective SOFC technology, the operating temperature of SOFCs has to be lowered down to 500°C. Albeit low ionic conductivity of electrolytes and hampered electrode kinetics at such low temperatures significantly affect the efficiency. Reducing the thickness of fast oxide-ion conducting electrolytes (e.g. Ce0.9Gd0.1O2-
δ) and by using highly electrically conducing electrodes can lower the ohmic losses; however sluggish electrode reaction rates at low-temperatures remains a difficult problem causing huge non-ohmic losses. Nanostructuring of electrocatalyst on an electrically conducting electrode can significantly improve the reaction rate for hydrogen oxidation and oxygen reduction, thereby enhancing the efficiency of SOFCs. Additionally, operating SOFCs at a low temperature range would reduce particle growth and extend cell life-time compared to high-temperature SOFCs. In this study, the effect of nanostructured infiltrates on both catalytically active and inactive porous electrodes will be analyzed in detail. Improvement in electrode reaction rate will be quantified using electrochemical impedance spectroscopy (EIS). The main focus of the study will be on understanding how nanostructured electrodes could improve the efficiency and long-term stability of LT-SOFCs.
Fabrication and Testing of Anode Supported Protonic Ceramic Fuel Cells in Biogas
Authors: Nasani Narendar , Pukazh Selvan D , Fagg Duncan Paul
Published: February 2020

Protonic Ceramic fuel cells (PCFCs) offer a low-pollution technology to generate electricity electrochemically with high efficiency when compared to that of combustion engines [1]. PCFCs also offer the advantage of keeping fuel electrode (anode) undiluted, with the water formation taking place at the air electrode (cathode) side. Thin electrolyte membranes are preferred, to reduce the ohmic losses during the fuel cell test [2], with the most common electrolyte materials being alkaline earth doped cerates, zirconates and their solid solutions, due to high proton conductivity and low activation energy. Nonetheless, the chemical instability of BaCeO3 in acidic atmospheres and the high sintering temperature and resistive grain boundaries of BaZrO3 are the main problems currently limiting their application in PCFCs [3]. As a compromise, the composition 40% Ce substituted Ba (Zr, Y) O3-δ, lying in the solid solution between the zirconate and cerate materials, has been received great attention due to improving the chemical stability of the cerate, while maintaining high total protonic conductivity[4][5].

In the present work, anode (Ni-BaCe(1-x)Zr(x-y)Y(1-x-y)O3-δ) supported thin electrolyte membrane (~6µm thickness) protonic cells were developed by a spin coating technique, with a triple conducting cathode (H+/O2-/e-) is deposited on this electrolyte/anode half-cell, figure 1. The performance of the complete PCFC cell is tested in biogas, an important feedstock from bio-waste mainly consisting of CH4 and CO2. The behavior of the triple conducting cathode, fuel utilization, carbon deposition and overall performance (I-V-P) comparison results will be discussed in detail.

Acknowledgments

The authors gratefully acknowledge funding from the FCT, POPH, PTDC/CTM/100412/2008, FCT Investigator Programme, IF/01344/2014/CP1222/CT0001, PTDC/CTM-ENE/6319/2014, QREN, FEDER and COMPETE Portugal and the European Social Fund, European Union.

References

[1] W.G. Coors, J. Power Sources. 118 (2003) 150–156.

[2] E.D. Wachsman, K.T. Lee, Science. 334 (2011) 935–9..

[3] E. Fabbri, D. Pergolesi, E. Traversa, Chem. Soc. Rev. 39 (2010) 4355–69.

[4] L. Bi, E. Fabbri, E. Traversa, Electrochem. Commun. 16 (2012) 37–40.

[5] N. Narendar, P.A.N. Dias, J.A. Saraiva, D.P. Fagg, Int. J. Hydrogen Energy. 38 (2013) 8461.

Figure 1
Materials Design and Synthetic Strategies to Enhance Electron Transport in Composite Materials
Authors: Takeuchi Kenneth J , Takeuchi Esther S , Marschilok Amy C
Published: February 2020

Electroactive materials are typically incorporated into batteries through the fabrication of composite electrodes including additives to enhance conductivity and to mechanically bind the components. These structures provide an opportunity to decrease inert material content if multifunctional materials can be designed and employed. For example, redox active materials that incorporate silver cation (Ag+) demonstrate the possibility for in-situ generation of an electrically conductive percolation network of Ag0 metallic nanoparticles through a reduction displacement reaction. This paradigm has been demonstrated with silver vanadium phosphorous oxide (Ag2VO2PO4) where the electrical conductivity increased 15,000-fold upon lithiation.

This presentation provides new strategies for the deliberate design of composite materials taking advantage of the opportunity for in-situ reduction displacement to form conductive networks. Several new approaches will be described. These include a one pot synthetic approach for the direct formation of a composite where one component is silver ion containing and the second is not. Additionally, surface modification approaches to generate conductive surface coatings will be introduced. These methods can significantly benefit the electrochemistry compared to composites formed by mechanical mixing alone, as will be illustrated in this presentation.
HQ - US Army Development of High Voltage Olivine Cathode
Authors: Allen Jan L. , Delp Samuel A. , Wolfenstine Jeff , Jow T Richard , Liu Dong , Kim Chi-Su , Cho Myunghun , Guerfi Abdelbast , Zaghib Karim
Published: February 2020

The need for environmentally friendly, safe, stable, and low cost materials for application in lithium-ion batteries has led to strong interest in developing olivine-type LiMPO4 (M = Fe, Mn, Co, Ni) cathode materials. Among them, LiFePO4 (LFP) has been extensively studied and commercialized. However, LFP has some special shortcomings in practical applications, such as low potential plateau (3.4 V vs. Li/Li+) and small packing density (due to the inclusion of large-volume carbon), which lead to relatively low specific energy density (580 Wh kg-1). Whereas LiCoPO4 (LCP) in the olivine family has been considered as an attractive cathode candidate due to the large theoretical capacity (167 mAh g-1), high operating voltage (4.8 V vs. Li/Li+) and high specific energy density (800 Wh kg-1).

However, LCP suffers from severe capacity fade due to the low intrinsic electronic/ionic conductivity, structure deterioration and electrolyte decomposition [1]. In this work, Hydro Quebec and US Army Research Laboratory dedicated to develop the high voltage olivine cathode. Specifically, partially Co-substitution strategy with a carbon coating was successfully used to improve the cycling stability of LCP cathode [2]. FIG. 1 shows the cyclability of substituted-LCP olivine cathode at room temperature under C/3 rate, from which no obvious capacity loss was observed in 100 cycles. Moreover, phosphate based cathodes may provide higher abuse tolerance than oxides at a given voltage due the strong covalent band of P-O. Therefore, the substituted high voltage LCP olivine cathode has the apparent potential to be a next decade success story in lithium-ion technologies and to find large application in the next generation lithium-ion batteries.

References

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

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

Figure 1
Studying Electrolyte Limiting Scenarios on Lithium Deposition in Li-Ion Batteries
Authors: P. Rangarajan Sobana , Mukherjee Partha P.
Published: February 2020

Li-ion batteries are the primary choice for energy storage in energy and power intensive applications. However, the performance of Li-ion batteries can be crippled due to the detrimental effect of lithium deposition that may take place during certain operating conditions. Lithium deposition on the electrode surface can lead to issues such as loss of active material or internal short circuit, which may result in performance and safety concerns. A deeper understanding of the lithium deposition phenomena is needed. In this study, the influence of limiting scenarios related to electrolyte transport on lithium plating is explored. The interfacial impedance and morphological implications due to lithium deposition are studied ranging from electrolyte starvation to electrolyte flooding conditions based on electrochemical modeling and experimental analysis.
Interfacial Control at Lithium-Ion Electrodes Using Ultrathin Polymer Coatings Generated By Initiated Chemical Vapor Deposition
Authors: Long Jeffrey W. , Love Corey T
Published: February 2020

Interfacial processes at the surfaces of charge-storing materials in Li-ion batteries have a great impact on such critical operational characteristics as rate capabilities, cycle and calendar life, and safety. Solid-electrolyte interfaces (SEIs) that form spontaneously in situ serve to control surface reactivity in most Li-ion systems, yet may not yield optimized electrode and battery performance. Recent advancements in deposition protocols for nanoscale coatings open new opportunities to pursue deliberately designed & applied surface coatings at Li-ion electrodes. Initiated chemical vapor deposition (iCVD) has emerged as a promising route to generate ultrathin polymer coatings with thickness control at the nanoscale [1], even on complex, porous substrates [2], while also being readily adaptable to scaled manufacturing. As a further benefit for electrochemical applications, the siloxane-based polymers most commonly generated by iCVD contain ether-like functionalities that support the solvation and transport of Li+ salts, transforming them into Li-ion conductors [3]. We are exploring iCVD protocols as a means to apply nanometers-thick polysiloxanes at the surfaces of commercially available powder-composite electrodes, including graphite-based anodes and metal oxide/phosphate-containing cathodes. The performance of polymer-modified electrodes is assessed in conventional Li-ion coin cells, in which we assess such properties as specific power, irreversible capacity (e.g., due to SEI formation), coulombic efficiency and cycle life, as we vary the thickness of the polymer coating from 5–50 nm. Test cells containing these electrodes are also subjected to more extreme operating conditions (overcharge and overdischarge; high-rate charging at low temperatures) to assess the benefits of the nanoscale polymer coating for suppressing undesirable reactions at the electrode/electrolyte interface.

Tenhaeff, W.E.; Gleason, K.K. Adv. Func. Mater. 2010, 18, 979.

Sassin, M.B.; Long, J.W.; Wallace, J.M.; Rolison, D.R. Mater. Horizons
2015, 2, 502.

B. Reeja-Jayan, N. Chen, J. Lau, J. A. Kattirtzi, P. Moni, A. Liu, I. G. Miller, R. Kayser, A. P. Williard, B. Dunn, and K. Gleason, Macromolecules
48, 5222 (2015)
An Orthogonal Investigation in Structures and Performances of Vanadium Modified Li2FeSiO4
Authors: Wei Xuexia , Huang Jiaqi , Liu Shiyang , Cheng Xuan , Zhang Ying
Published: February 2020

A series of vanadium modified carbon coated lithium iron silicate (Li2Fe1-xVxSiO4/C) composites were prepared by sol-gel precursor and solid-state reaction using ammonium metavanadate (NH4VO3) as a vanadium source material. The effects of vanadium content (x), sucrose amount (y), sol-gel time (t) and type of carboxylate acid on crystal structure, surface morphology, elemental composition and electrochemical performance of Li2Fe1-xVxSiO4/C composites were investigated through orthogonal design experiments. The preparation parameters were optimized to be x=35%, y=80%, t=2 h and use of citric acid as a pH regulator. The initial discharge capacity of 216.7 mAh/g (corresponding to 1.30 moles per formula unit) was achieved at 0.1C and room temperature with the Li2Fe0.65V0.35SiO4/C composite synthesized under the abovementioned optimized condition. A mixed Pmn21 and P21 phase was identified as the main structure, while metallic iron and lithium silicate (Li2SiO3) as the impure phases. The elemental analysis result revealed that 10.7% carbon was introduced. The elemental vanadium was detected by performing energy dispersive X-ray spectroscopic (EDX) analysis.
Graphene and Disulfide-Based Framework As a Transition Metal-Free Electrode Material for Li-Ion Battery
Authors: Yoo Young Geun , Park Soomin , Bae Seongjun , Park Jongseok , Nam Inho , Lee Su Young , Kim Yong Hwa , Yi Jongheop
Published: February 2020

For a brand-new electrode material with transition metal-free and high electrochemical performance for Li-ion battery (LIB), graphene and disulfide-based framework was designed and synthesized by hybridizing graphene and organic compounds. For the designing of the material, we focused on the four important electrochemical properties: specific capacity, potential sensitiveness, cyclic stability and high Li+/e- mobility. As a result, graphene framework with a layered structure constructed by the formation of disulfide bonds between terminal dithiol organic linker molecules and thiol-functionalized graphene sheets. The organic linker molecules play a role as pillars which maintains the framework structure and prevents restacking of graphene sheets. Various types of dithiol organics were investigated as linker components in GSF for evaluating the effect of its length or structure on electrochemical properties. As a result, distinctive electrochemical performance among the synthesized materials was observed depending on current density, implies the involvement of multiple Li-incorporation mechanisms. Based on the differential analyses and electrochemical impedance spectroscopy (EIS), the linker-dependent Li storage mechanism in GSFs was suggested. Also, reversible breakage-formation of disulfide bond within GSF was proved by ex-situ XPS analysis with varied state of charge (SOC), which represents self-healing functionality of the material. The GSF proposed in this study could be a promising electrode material for transition metal-free, low cost and high performance energy storage system.
Effect of NaCl Impurity in TiO2 on Li4Ti5O12 Formation
Authors: Wen Lei , Wu Zeyi , Luo Hongze
Published: February 2020

Li4Ti5O12 with high purity and high crystallinity is essential as anode for lithium ion battery. The unwanted impurity of rutile TiO2 in Li4Ti5O12 which results a reduced electrochemical performance as anode material for lithium ion battery. The solid-state synthesis is the most favorable to produce the large scale Li4Ti5O12 for lithium ion battery due to low-cost and environmental friendly. However, the rutile TiO2 often exists in Li4Ti5O12 prepared via the solid-state synthesis route using TiO2 and Li2CO3. The impurity in the starting reagents effects on purity and crystallinity of Li4Ti5O12 formation which has been not reported yet. In this work, it was found that NaCl impurity induced the formation of unwanted rutile TiO2 phase for the first time. The crystal structures and electrochemical properties were compared for the Li4Ti5O12 prepared from pure TiO2 and TiO2 with NaCl impurity. The high purity and high crystallinity of Li4Ti5O12 prepared from the TiO2 without NaCl impurity, which displayed high capacity, excellent cyclic performance and good rate capability compared that of Li4Ti5O12 prepared from TiO2 with NaCl impurity.
Direct Visualization of Li Dendrite Growth Process at Short-Circuit Condition Via Transmission X-Ray Microscopy
Authors: Park Jeung Hun , Raj Abhishek , Steingart Daniel A
Published: February 2020

Lithium is one of the most favorable materials for next-generation secondary energy storage devices due to its low redox potential, high gravimetric/volumetric capacities, and fast reaction kinetics [1]. However, the use of metallic lithium as the anode has been largely limited by the inherent safety concerns with lithium dendrite growth - causing short-circuits, leading to thermal runaway reactions, and fires/explosions [2]. Many efforts have been devoted to understanding dendrite morphologies with the influencing factors - temperature, electrolyte composition, current density and over-potentials [3]. However, the studies are limited to the nucleation and growth of Li dendrite at early stages [1,2]. At present, the growth mechanism and morphological changes taking place in Li dendrite formation near/after short-circuit condition, which presumably form the basis for its improved performance and safety, are not well understood.

Recent advances in in situ electrochemical transmission X-ray microscopy (EC-TXM), with its unique ability to provide simultaneous temporally and spatially resolved information as well as electrochemical parameters, enable exploration of the underlying physics of the electrochemical reactions that occur at the surface and inside of secondary energy storage devices during cycling [4,5]. Here, we focus the direct visualization of the propagation of Li dendrites at short-circuit condition using in situ EC-TXM. After the short-circuit, we follow three-dimensional morphological and microstructural changes of Li dendrites to explore relationships between electrochemical parameters and failure mechanisms during cycling. We further characterize the structural evolution of Li dendrites using in situ X-ray diffraction.

References:

[1] D. Lin, Y. Liu, & Y. Cui. Nat. Nanotechnol. 12, 194−206 (2017).

[2] W. Xu, J. Wang, F. Ding, X. Chen, E. Nasybulin, Y. Zhang, & J.-G. Zhang. Energy Environ. Sci. 7, 513−537 (2014).

[3] D. X. Liu, S. Frisco, P. Mandal, J. Whitacre, S. Litster, C. T. Love, & K. Swider-Lyons. ECS Meeting Abstracts MA2016-01 213.

[4] P. R. Shearing, D. S. Eastwood, R. S. Bradley, J. Gelb, S. J. Cooper, F. Tariq, D. J. L. Brett, N. P. Brandon, P. J. Withers, & P. D. Lee. Microsc. Microanal. 27, 19−22 (2013).

[5] J. Nelson, S. Misra, Y. Yang, A. Jackson, Y. Liu, H. Wang, H. Dai, J. C. Andrews, Y. Cui, & M. F. Toney. J. Am. Chem. Soc. 134, 6337−6343 (2012).

[6] We gratefully acknowledge funding supports from the BP Carbon Mitigation Initiative.
Capturing Solid Solutions during a First-Order Phase Transition of Li1+XMn2O4
Authors: Song Bohang , Veith Gabriel M , Whitfield Pamela , Schmidt Robert , Kirkham Melanie J. , Huq Ashfia
Published: February 2020

Lithium-ion batteries (LIBs) offering the highest energy density among the known battery chemistries are the major contenders for both transportation and stationary storage applications. In order to satisfy the demands of energy density for these applications, new full cell configuration with either improved working voltage or specific capacity is needed to further enlarge its energy density. One candidate that has received a great deal of attention is the spinel cathode LiMn2O4, which offers the advantages of a high operating voltage (4.0 V vs. Li+/Li) and an excellent rate capability. Nonetheless, the relatively low specific capacity of 125 mAh·g-1 is mainly due to the restricted operating voltage between 3 and 4.5 V. In theory, LiMn2O4 cathode can deliver a capacity of ∼297 mAh·g-1 when 2 mole of lithium ions are inserted/extracted into/from both 8a tetrahedral and 16c octahedral sites of the spinel lattice at the voltages of, respectively, ∼4.0 and ∼2.7 V.1 Phase transition related to 4.0 V plateau is highly reversible, involving only two similar cubic spinel phases. However, phase transition related to 2.7 V plateau is partly reversible because a cubic spinel transforms to a tetragonal spinel with Jahn-Teller distortion occurring as a result of Mn3+ formation. The increase in the axial ratio from c/a = 1.0 in the cubic phase to c/a = 1.6 in the tetragonal phase due to the cooperative Jahn-Teller distortion leads to a fracture of large particles, which induces a loss of electrical contact with the current collector upon cycles.2 These effects cause serious capacity fading. However, the dynamic process of this phase transition has never been fully understood due to a lack of characterization techniques.

Based on the above considerations, we report an in operando neutron diffraction study to fully understand the ~2.7 V related phase transition in the Li1+xMn2O4 spinel upon electrochemical cycling. We found solid solution formation upon reversible discharge and charge process, although a first-order phase transition is widely believed. The solid solution formation is possibly due to a thick electrode configuration that we applied and a large overpotential it could generate, which is cosistent with the phenomenon that observed under high-rate charging/discharging of LiFePO4 using in situ synchrotron XRD.3

J. B. Goodenough, M. M. Thackeray, W. I. F. David, P. G. Bruce, Rev. Chim. Miner., 1984, 21, 435.

S.-H. Kang, J. B. Goodenough, and L. K. Rabenberg, Chemistry of Materials, 2001, 13, 1758-1764.

H. Liu, F. C. Strobridge, O. J. Borkiewicz, K. M. Wiaderek, K. W. Chapman, P. J. Chupas, C. P. Grey, Science 344, 7 (2014).
New Lithium-Excess High-Capacity Positive Electrode Materials with Reversible Three-Electron Redox Reaction of Mo3+/Mo6+
Authors: Hoshino Satoshi , Ichikawa Shinnosuke , Ozaki Tetsuya , Inamasu Tokuo , Yabuuchi Naoaki
Published: February 2020

The demand for the increase in energy density of lithium batteries is steadily growing. The use of three-electron redox of transition metals is expected to be an important strategy to further increase the energy density of positive electrode materials with less transition metal ions. Recently, our group has reported that Mo3+ ions are diluted in lithium-excess oxides, Li2Ti4+O3, Li3Nb5+O4, and Li4Mo6+O5, which have higher lithium contents, and proposed as a new series of high-capacity electrode materials.[1] For instance, Li9/7Nb2/7Mo3/7O2 delivers a large reversible capacity of ca. 280 mAh g-1, which nearly corresponds to the theoretical capacity based on Mo3+/Mo6+.

In this study, this concept is extended into other lithium-excess compounds, and the use of Li3PO4 is targeted. A new binary system with Mo3+ is prepared according to the chemical formula of x Li3PO4 – (1 – x) LiMoO2. Since the molar mass of P is much smaller than that of Nb, the P-based samples are expected to deliver higher reversible capacity. Crystal structures and electrode performance in this binary system are systematically examined. A mixture of Li3PO4 and LiMoO2 was mechanically ball milled at room temperature with a ZrO2 container and balls. The samples of x = 0.4 (Li9/7P2/7Mo3/7O2) and 0.6 (Li11/8P3/8Mo1/4O2) show a relatively small reversible capacities in Li cells (Figure 1). In contrast, the sample of x = 0.2 (Li7/6P1/6Mo2/3O2) delivers the highest reversible capacity of ca. 330 mAh g-1with relatively higher operating voltage compared with the samples without P ions.[1]

From these results, we will discuss the possibility of a new series of high-capacity positive electrode materials with Mo3+ions for rechargeable lithium batteries.

Reference

[1] S. Hoshino, et al., and N. Yabuuchi, ACS Energy Letters, 2, 733 (2017).

Figure 1
Improved High-Voltage Stability of NCM523 Cathode Using Functional Electrolyte Additive
Authors: Kim Jae-Hee , Pham Hieu Quang , Lee Hee-Yeol , Hwang Eui-Hyung , Kwon Young-Gil , Song Seung-Wan
Published: February 2020

Advanced portable electronics, electric vehicles and grid-based energy storage systems demand higher energy density Li-ion batteries than conventional ones as power sources. The energy density of Li-ion batteries can increase by increasing the specific capacity of cathode material, which can increase by raising the charge cut-off voltage. Among various cathode materials, nickel-rich three-components layered oxides of Li(Ni1-x-yCoxMny)O2 (NCM, 1-x-y ≥ 0.5) have been considered as prospective candidates for high-energy density Li-ion batteries because of higher capacity and lower cost than Ni-lean oxides. However, their high-voltage performance is difficult to achieve due to limited anodic stability of conventional electrolyte above 4.2 V vs. Li/Li+ and instability of cathode material at highly charged state. Under such an aggressive charge condition, cathode-electrolyte interfacial reactions often cause a degradation of cathode material and electrolyte consumption by oxidative decomposition of electrolyte, resulting in a rapid performance fade.1-3 We have demonstrated that the use of high-voltage electrolyte additive(s) is efficient and economic because they in situ form a surface protective layer at the cathode during high-voltage cycling, and improve the interfacial stability and cycling performance.1-3

Here we report the development of phosphorus-based additive for the NCM523 cathode to the charge cut-off voltage of 4.6 V. X-ray photoelectron spectroscopic and infrared spectroscopic studies on cathode-electrolyte interfacial phenomena and their correlation to cycling performance would be discussed in the meeting.

Acknowledgements

This research was supported by Ministry of Trade, Industry & Energy (R0004645) and Creative Human Resource Development Consortium for Fusion Technology of Functional Chemical/Bio Materials of BK Plus program by Ministry of Education of Korea.

References

1. Y.-M. Lee, K.-M. Nam, E.-H. Hwang, Y.-G. Kwon , S.-W. Song, J. Phys. Chem.
C, 118, 10631 (2014).

2. D. T. Nguyen, J. Kang, K.-M. Nam, Y. Paik, S.-W. Song, J. Power Sources,
303
, 150 (2016).

3. J. Kang, H. Q. Pham, D.-H. Kang, H.-Y. Park, S.-W. Song, J. Alloys & Compds, 657, 464 (2016).
Effect of Sorted Single-Walled Carbon Nanotubes on Rate Capability of Lithium-Ion Battery Cathodes
Authors: Adepoju Adewale A. , Searles Thomas A. , Fagan Jeffrey A. , Williams Quinton L.
Published: February 2020

Lithium iron phosphate (LFP) is a promising cathode material for Lithium-ion batteries. LFP has many unique properties including great thermal stability, high energy density, and excellent cycle life. However, one disadvantage to LFP is its poor electrical conductivity which leads to low rate capability (C-rate). To overcome this disadvantage, we have incorporated single-walled carbon nanotubes (SWCNTs) into the electrodes of LFP batteries. SWCNTs have emerged as one of the leading additives for LFP batteries due to their ability to enhance electrode conductivity and mechanical stability. The incorporation of SWCNTs create a better electrical percolation network thereby enhancing the C-rate. To this end, LFP coin-cell batteries were fabricated with the addition of sorted metallic and semiconducting SWCNTs. C-rate and cycle stability measurements were made for comparison studies. Test showed that LFP with SWCNTs incorporated into the cathode material led to a modest improvement to the C-rate while good cycle stability was maintained.
Study of the Effect of Lithium Precursor Choice on Performance of Nickel-Rich NMC
Authors: Fitch Brian , Yakovleva Marina
Published: February 2020

According to market research, use of NMC cathode materials for electric vehicle applications will increase dramatically over the next decade. Specifically, migration toward nickel rich NMC532, NMC622 and NMC811 appears likely in all major xEV markets (1).

Nickel-rich layered cathode materials such as LiNi0.8Co0.15Al0.05O2 (NCA) and nickel-rich LiNi1-x-yCoxMnyO2 (NMC), where Ni content is ≥0.6 moles can deliver high specific capacities of over 200 mAh g-1. However, the challenges surrounding synthesis of these materials are well documented (2), (3), (4). As nickel content increases the choice of lithium precursor, LiOH.H2O or Li2CO3, can have a dramatic effect on the performance of these cathode materials.

Here we report the advantages of using lithium hydroxide as the lithium precursor on the performance of nickel-rich NMC cathode materials. Specifically we will show that using lithium hydroxide as the lithium precursor results in:

Superior physical properties, such as higher tap and packing density, can be achieved at lower synthesis temperatures for nickel-rich NMC materials.

Improved material crystallinity as observed by x-ray diffraction, greater structural purity and less mixing of Ni2+ in the lithium layer determined by Rietveld refinement, leading to improved power performance.

Significant cost reduction due to increased process through-put.

Higher energy density materials at lower production energy consumption.

Also in this study statistical design of experiments has been used to evaluate the effect of temperature, nickel content and synthesis temperature on NMC discharge rate capability and lithium content in the lithium layer. The results show statistically significant interaction between temperature, nickel content and lithium precursor. Linear regression modeling of the DOE data predicts as nickel content in NMC increases, synthesis temperature has a dramatic effect on high rate discharge capacity. The model predicts that the optimum synthesis temperature for NMC622 is 850oC. At this temperature material synthesized using LiOH
.
H2O as the lithium precursor performs significantly better under high rate discharge conditions compared to material synthesized using Li2CO3.

References

Avicenne Energy, International Battery Seminar and Exhibit, March 20th, 2017.

B. H. Kim, et al., The effect of oxygen pressure on the synthesis of LiNiO2. Solid State Phenomena, Vols. 124-126, (2007), p. 1043-1046

P. Kalyani, N. Kalaiselvi, Various aspects of LiNiO2 chemistry: A Review. Science and Technology of Advanced Materials, 6, (2005), p. 689–703

Kim, M.-H., Shin, H.-S., Shin, D. & Sun, Y.-K., Synthesis and electrochemical properties of Li[Ni0.8Co0.1Mn0.1]O2 and Li[Ni0.8Co0.2]O2 via co-precipitation. Journal of Power Sources, (2006), 159, p. 1328-1333

Figure 1
Synthesis and Electrochemistry of High Energy LiVOPO4 with Enhanced Electronic and Ionic Conductivity
Authors: Shi Yong , Zhou Hui , Omenya Fredrick , Whittingham M. Stanley
Published: February 2020

Lithium ion batteries (LIBs) have been widely used in many fields as power suppliers for mobile equipments. Recently, ε-LiVOPO4 has been regarded as a promising multi-electron cathode material that is capable to intercalate two Li per vanadium to achieve a very high theoretical capacity of 318 mAh/g, which exceeds any cathode material in the market today. However, the experimental capacity at useful current densities currently falls short of the theoretical one, and there is no data on long-term cycling behavior. In this study, pure ε-LiVOPO4 was successfully synthesized by an optimized solid-state reaction. This material demonstrates capacities close to the theoretical at moderate current densities. The long-term cycling data was obtained over various voltage windows. The electrochemical results demonstrate that this material suffers capacity loss upon long-term cycling. It is found the phase transformation from LiVOPO4 to VOPO4 is not completely reversible after several cycles, which is likely driven by low electronic and Li ionic conductivity. In this work, different carbon additives were applied to increase electronic conductivity; and surface modification was conducted to improve ionic conductivity. The results demonstrate that the optimized ε-LiVOPO4 has achieved great improvements of electrochemical performance in terms of capacity, rate capability, reversibility and cyclibilty.

This project is supported by the U.S. Department of Energy’s Office of Energy Efficiency and Renewable Energy (EERE) program under Award No. DE-EE0006852.
Li-Storage Performances of Liquid-Phase Exfoliated Two-Dimensional Gallium Sulfide Nanosheets/Single-Walled Carbon Nanotubes Composite
Authors: Park Sang-Hoon , Zhang Chuanfang , Ronan Oskar , Seral-Ascaso Andrés , Coleman Jonathan N , Nicolosi Valeria
Published: February 2020

The two-dimensional nanosheets (2D NS) of layered metal chalcogenide (MC) evoke huge research attention in lithium-ion battery (LiB). Nevertheless, their undesirable electrical conductivity and complicated synthesis procedures negatively the prospects of these NS as a competive LiB electrode material. To this end, we have developed facile, scalable approach, liquid-phase exfoliation (LPE)/filtration, to produce binder-free GaS NS/SWCNT flexible conductive composite for LiB. The uniform GaS NS/SWCNT composite possesses several advantages at the same time: (i) The open channels in the nanostructure result in faster Li+ diffusion. (ii) The entangled SWCNT network forms developed electron transport paths, lowering the junction resistance. (iii) SWCNT could function as the “conductive binder”, maintaining the structural integrity of the thick electrode without losing electrical contact with the current collector. The resultant GaS NS/SWCNT composite exhibited excellent rate capability, high specific capacity (838 mAh g-1) and a remarkably high utilization of GaS NS (1161 mAh g-1), demonstrating electrochemical performances competitive with those of other reported 2D MC-based electrode systems. This work opens up vast opportunities for other families of MC NS to be scalably processed into porous, binder-free, flexible conductive thin films and composites with a broad range of applications.