bluuebunny/crossref_metadata_2025 huggingface dataset:
Ni-based Alloys as Protective Layer for a Conventional Solid Oxide Fuel Cell Fed with Biofuels
Authors: Lo Faro Massimiliano , Trocino Stefano , Campagna Zignani Sabrina , Machado Reis Rafael , Monforte Giuseppe , Ticianelli Edson A. , Aricò Antonino S.
Published: February 2020

A possible scenario for the future is the utilization of alternative fuels especially those obtained from renewable sources including those derived from biomass. One of the main implications is regarding the consumer’s ability to use an increasingly diverse selection of energy sources. New business models could be especially important in the stationary power sector as fuel cell-based distributed energy systems become an alternative to backup for centrally generated power. Small fuel cells systems, typically less than 10kW, are under consideration for many applications that traditional electric utilities have not supplied widely. In this area, solid oxide fuel cells (SOFCs) may enable new companies to enter the power-generation business as equipment providers or heat and electricity providers. The most common type of SOFC is composed by cells based on yttrium stabilized zirconia (YSZ) as electrolyte Ni-YSZ as anode and La0.8Sr0.2MnO3 (LSM) or La0.6Sr0.4Fe0.8Co0.2 (LSFCO) as cathode operating at temperatures above 700 °C using H2 or syngas (H2+ CO) produced from a reforming process (internal or external).

Bimetallic Ni-based alloys mixed with gadolinium-doped ceria in order to obtain a composite material with mixed electronic-ionic conductivity utilized as a barrier layer in a conventional anode-supported solid oxide fuel cell may represent a practical solution to provide a mitigation of the degradation reactions occurring during the feeding of biofuels.

In this communication, we report few guidelines for the preparation of catalysts having proper behaviour for the utilization as protective layer. Complete physico-chemical characterization and electrochemical investigation of Ni0.5M0.5(M=Cu, Co, Sn, Zn, Fe) will be discussed.

Acknowledgements

The present work was in part carried out within an Agreement between the Italian Ministry of Economic Development (MSE) and National Research Council (CNR) in the framework of a Research Program for the Electric System (sub-activity: Development of materials and components, design, demonstration and optimization of FC systems for co-generative applications) and in part carried out in the framework of the Research Program promoted by the Brazialian “Conselho Nacional de Desenvolvimento Científico e Tecnológico“ entitled “Ciência sem Fronteiras”  processo nº 402180/2012-7.

S. C. Zignani wants to thank CNPq for the grant n. 238319/2012-1.

R. M. Reis wants to thank FAPESP for the grant n. 2014/04100-2.

The authors also acknowledge the Italian Ministry of Research and Education for the financial support of the BIOITSOFC project within the program "PROGRAMMI DI RICERCA SCIENTIFICA DI RILEVANTE INTERESSE NAZIONALE- PRIN PROGRAMMA DI RICERCA - Anno 2010-2011 - prot. 2010KHLKFC"
Performance of Protonic Ceramic Fuel Cell with Thin Film Yttrium Doped Barium Zirconate Electrolyte
Authors: Bae Kiho , Jang Dong Young , Noh Ho-Sung , Kim Hyun Joong , Hong Jongsup , Yoon Kyung Joong , Kim Byung-Kook , Son Ji-Won , Shim Joon Hyung
Published: February 2020

Perovskite protonic ceramics, or proton-conducting oxides, have attracted much attention in recent decades as alternative electrolytes for conventional solid oxide fuel cells (SOFCs). Protonic ceramics have higher ionic conductivity and lower activation energy in SOFCs’ low operating temperature region (under 600°C) than oxide-ion-conducting oxides. Recently, many attempts have been made to enhance fuel cell performance by adopting thin-film protonic ceramics as electrolytes. In this work, anode-supported thin-film protonic ceramic fuel cells (PCFCs) were fabricated with thin-film yttrium-doped barium zirconate (BZY, BaZr0.85Y0.15O3-δ), which is one of the best-performing protonic ceramics with high bulk ion conductivity and good chemical stability. However, this material possesses poor sinterability, resulting in severe grain separation and a dramatic increase in ohmic overpotential from slow ion transport. In this work, we have applied novel multi-step annealing processes to achieve the densification of the BZY electrolytes, good adhesion between layers, and effective grain growth of the supporting composites. The NiO-BZY composite anode support was fabricated by tape casting and the BZY electrolyte was deposited by pulsed laser deposition (PLD) with a thickness of 2 μm. A perovskite cathode material of La0.6Sr0.4Co3-δ (LSC) was formed porously by PLD with a thickness of 2 μm. The microstructures of the fabricated PCFCs were analyzed using scanning electron microscopy (SEM). The electrochemical performance in terms of current–voltage characteristics was obtained, and the maximum power output of 320‒530 mW/cm2 was measured at 450‒600°C. The alternating current (AC) impedance data were collected under DC bias conditions at each operating temperature and analyzed to determine the resistive factors for the power outputs.
Numerical Simulation of SOFC System Performance at 90% Fuel Utilization with or without Anode Off-Gas Recycle for Enhancing Efficiency
Authors: Tanaka Yohei , Terayama Takeshi , Momma Akihiko , Kato Tohru
Published: February 2020

To investigate possibility to enhance electrical efficiency, performance of methane-fueled 10 kW SOFC systems was numerically simulated with calculated voltage-current-density curves at 750ºC of a single cell with a bipolar plate, which approximated a stack performance. Operation at 90% fuel utilization (U
f) with anode off-gas recycle (AGR) and with steam reforming (no recycle) led to 75-67%-LHV and 72-66%-LHV DC electrical efficiency at 0.05-0.40 A/cm2, respectively. System simulations considering heat loss from a cell stack clarified that 750ºC stack temperature can be maintained at 0.12-0.40 A/cm2 and 64-58% and 63-59% net AC electrical efficiency will be attainable at U
f = 90% with and without AGR, respectively. Furthermore, enhancement of net AC efficiencies was found to be 11-10 percentage points at those current densities against ones of a Ene-farm-like conventional system using steam reforming at U
f = 73%.
Influence of Ni-YSZ Electrode Thickness on the Behaviour of Commercial Solid Oxide Electrolysis Cells by Mean of Electrochemical Impedance Spectroscopy
Authors: Nechache Aziz , Cassir Michel , Ringuede Armelle
Published: February 2020

Our world is facing energy needs always growing, the mid-term disappearance of important energy resources such as fossil fuels and global warming issues consecutive to massive greenhouse gas production. A possible answer to produce renewable and clean energy consists in combining promising technologies such as solar photovoltaic, wind turbine and fuel cell, thus making an energy mix. Hydrogen is an energy carrier which can be part of this energy mix. High temperature electrolysis (HTE) using a solid oxide electrolyte is a clean way to produce, from water and electricity, hydrogen. However, many studies showed that the electrochemical phenomena related to the Ni-YSZ electrode have a strong influence on cell performances, including the ones associated to gas transport [1-3]. Further investigations on the hydrogen side of the cell are hence needed. In the following work, two commercial cells with different Ni-YSZ thicknesses are considered. A deep analysis is performed in a two-electrode configuration by mean of electrochemical impedance spectroscopy (EIS) with the use of electrical equivalent circuits (EEC), showing that all the main phenomena governing SOEC functioning are related to the Ni-YSZ electrode for both cells, each one characterized by a specific relaxation frequency and capacitance. Indeed, the impedance diagrams measured were deconvoluted, from the highest to the lowest frequencies, into four arcs: a high frequency arc (HF arc), a first middle frequency arc (MF1 arc), a second middle frequency arc (MF2 arc) and a low frequency arc (LF arc). These arcs were respectively associated to charge transfer at the Ni-YSZ electrode, a first H2O diffusion phenomenon, gas conversion at the Ni-YSZ electrode and a second H2O diffusion phenomenon. Thus, changing Ni-YSZ electrode thickness appears to mainly influence the H2O diffusion phenomenon associated to MF1 arc and the H2O gas conversion related to MF2 arc, while phenomena associated to HF and LF arcs are poorly sensitive to this thickness change. This result suggests that the phenomena associated to MF1 and MF2 arcs occur mainly in the volume of Ni-YSZ electrode, contrary to phenomena related to HF and LF arcs. This in the same time allows distinguishing the two H2O diffusion phenomena identified.

[1] A. Nechache, M. Cassir, A. Ringuedé, J. Power Sources 258 164 (2014).

[2] P. Kim-Lohsoontorn, J. Bae, J. Power Sources, 196, 7161(2011).

[3] PK. Patro PK, T. Delahaye T, E. Bouyer E, PK Sinha, Int. J. Hydrogen Energy, 37, 3865 (2012).
Sensitivity Analysis for the Efficiency Improvement of a Light Integrated Gasification Fuel Cell Power Plant
Authors: Taufiq Bin Nur , Kikuchi Yasunori , Ishimoto Takayoshi , Honda Kuniaki , Koyama Michihisa
Published: February 2020

The solid oxide fuel cell (SOFC) is recognized as one of high efficiency plants of electricity generation for a sustainable future system with low environmental effects. In term of fuel flexibility, SOFC is suitable for direct use of syngas from a coal gasification plant.  The application of integrated SOFC in coal gasification based power plant, such as a light integrated gasification fuel cell (L-IGFC) power plant, could be one of the most promising coal energy conversions system providing high electrical efficiency with low CO2 emitted to the atmosphere. The system consists of a coal gasifier and intermediate temperature SOFC module on the top of a steam turbine. The syngas produced by pressurized coal gasifier is used in SOFC module after heat recovery units and cleaning processes. To minimize exergy loses in the plant, the dry gas desulfurization (DGD) unit which can operate at elevated operating temperature and pressure are adopted. The heat generated by SOFC module can be utilized by the heat recovery steam generator providing high quality steam for a steam turbine. In this work, thermodynamic analysis is carried out to develop process integration of the L-IGFC plant. The overall plant analysis of a baseline system design is performed by identifying the major factors effecting plant performance by using the Aspen Plus simulation. The Aspen plus simulation is then used to perform parametric analysis to identify optimum values for the maximum system efficiency. Modifications to the baseline system design are made in order to determine the most viable system designs based on maximizing total system efficiency.
Fabrication and Performance Evaluation of Solid Oxide Electrolysis Cell Integrated with Metal Interconnect by Joining Process
Authors: Yoo Young-Sung , Choi Mihwa , Yang Seugran , Jin Hyun-Jin , Park Min-Ah , Kim Eui-Hyun
Published: February 2020

Metal-supported solid oxide electrolysis cell integrated with metal interconnect by joining process (so-called, with fuel electrode(cathode)-supported electrolysis cell) was fabricated and its electrical performance are investigated under both operation mode of fuel cell(hydrogen) and co-electrolysis(steam and CO2) mode at the intermediate temperature of 750 oC~850 oC. The fuel(or steam) electrode layers are prepared using NiO and YSZ(8 mol% Y2O3-doped ZrO2) at the ratio of 1:1. In order to obtain pores in the cathode, graphite powders of 24 volume % with average particle size of 44 mm are added. In the case of a metal-supported solid oxide  electrolysis cell(SOEC) with heat-treated cathode support, 10 mol % Sm2O3-doped CeO2 (SDC) paste is screen-printed on the surface of YSZ and subsequently (La0.6Sr0.4) (Co0.2Fe0.8)O3 (LSCF) paste mixed with SDC at 1:1 weight ratio as anode(air electrode) is screen-printed on the SDC layer and heat-treated for desirable adhesion. The single electrolysis cell performances are compared by analyzing AC impedance spectra and product gas composition by GC(gas chromatography)of metal-supported electrolysis cell integrated with metal interconnect and cathode-supported electrolysis cell, and the current-voltage characteristics and cross-sectional microstructure of cathode-supported cell integrated with metal interconnect are tested. The stable long-term performance with co-electrolysis of carbon dioxide (CO2)and steam(H2O) is shown for about 800 h at 800 oC under the constant current density of 300 mA/cm2, 600 mA/cm2, 800 mA/cm2, and 1000 mA/cm2. In the fuel cell mode operation of metal-supported SOEC cell, the maximum power density of 0.8W/cm2 is indicated with hydrogen fuel. The microstructures are analyzed using optical microscope for observing a diffusion of metal ions at the cathode, adhesion layer and metal support(ferritic stainless steel, STS430) with EDAX analysis. In the present work, we have investigated the performance and microstructures of metal-supported SOEC for the co-electrolysis of CO2 and H2O steam. The exemplary works with AC impedance and the composition of product gas are analyzed in the operation of metal-supported co-electrolysis cell.
An Interfacial Nanospike-Structured Cathode for Low Temperature Solid Oxide Fuel Cells
Authors: Ding Hanping , Xue Xingjian
Published: February 2020

Lowering operating temperatures is a promising strategy to improve the durability and reduce the cost of solid oxide fuel cell (SOFC) systems. However, the ohmic and polarization resistance would increase significantly at low temperatures (500-700 oC), particularly that of cathode electrode due to sluggish oxygen reduction reactions (ORRs). To reduce polarization loss at low temperatures, cathode materials have been studied extensively. The high performance cathode electrodes were also obtained through nano-scale engineering enabled by infiltration technique. Essentially the infiltration is an additive approach to add catalytically active materials into porous cathode to enhance the ORRs. Here we report the fabrication and evaluation of a novel interfacial nanospike-structured cathode. The growth of interfacial nanospikes on the pore walls of the cathode was enabled by a discharge treatment under low-temperature sintering process. The electrochemical performance of the corresponding button cells was well demonstrated at low operating temperatures of 350-550 oC. The stability of interfacial nanospikes was also examined under thermal-cycling conditions.
Microstructure and Polarization characteristics of LSCF-GDC Composite Cathode with Different Volume Fractions
Authors: Kim Y. T. , Ohi Akihiro , He An , Jiao Zhenjun , Shimura Takaaki , Klotz Dino , Hara Shotaro , Shikazono Naoki
Published: February 2020

In the present study, La0.6Sr0.4Co0.2Fe0.8O3(LSCF)-Gd0.1Ce0.9O1.95(GDC) composite cathodes with different volume fractions were fabricated by the screen printing method, and their polarization characteristic and microstructure parameters are evaluated. Cathode overpotentials were evaluated at 700 oC and 100% O2. Microstructures were reconstructed by focused ion beam-scanning electron microscope (FIB-SEM). In addition, current and potential distributions inside the reconstructed microstructures were calculated by a Lattice Boltzmann method. The relationship between polarization characteristics and microstructure is quantitatively investigated.
Development of Solid Oxide Fuel Cells at Versa Power Systems and FuelCell Energy
Authors: Borglum Brian P , Ghezel-Ayagh Hossein
Published: February 2020

Versa Power Systems (VPS) is a developer of solid oxide fuel cells (SOFCs) for clean power generation and is a wholly owned subsidiary of  FuelCell Energy (FCE).  FCE is a global leader in the design, manufacture and distribution of Molten Carbonate Fuel Cell (MCFC) power plants.  From an economic perspective, MCFCs scale-up very well and as a result FCE’s MCFC products are in the multi-megawatt size range.  SOFCs are complementary because they scale-down well and hence are well suited to sub-megawatt applications.  This paper highlights the status of VPS and FCE’s SOFC technology in the areas of cell, stack and system development.
Influence of Cathode Polarization Change on Chromium Deposited on Electrolyte Surface Near Cathode Reaction Sites of SOFC
Authors: Ishibashi Daiki , Park Eunjoo , Taniguchi Shunsuke , Inoue Yuko , Chou Jyh-Tyng , Sasaki Kazunari
Published: February 2020

It has been clarified that chromium deposition occurs significantly onthe electrolyte surface near the cathode reaction sites in consequence of cathode polarization. The deposited chromium probably remains on the surface, not diffusing into the electrolyte. Therefore, focusing on the behavior of the deposited chromium, such as crystal growth or dissipation by cathode polarization change is suitable for clarification of the deposition mechanism in detail.

   In this study, we investigated influence of cathode polarization change on the deposited chromium on the electrolyte surface by using NiO/YSZ or NiO/GDC for the cathode material. We used NiO for the cathode material because of the following two reasons. 1) Effect of cathode polarization can easily be studied because the predetermined cathode polarization is generated at the cathode reaction sites with smaller current flow. 2) Lower reactivity of NiO with chromium vapor than conventional cathode materials (e.g. LSCF, LSM) can make the analysis simpler.

   Although ohmic resistances of these cathodes using NiO are higher than usual, they showed enough performance to control cathode polarization. Chromium poisoning tests were conducted at 700 oC for 100 hours keeping cathode polarization constant at 200 mV. At the end of the chromium poisoning tests, several different procedures to stop the cell tests were executed concerning the timing to remove the cathode polarization

   After the chromium poisoning tests at 200 mV, chromium deposition was observed on the surface of the electrolyte near the cathode/electrolyte interface as observed in LSM cathode. The deposited chromium segregated at the interface of NiO and YSZ for the NiO/YSZ cathode by decreasing cathode polarization, which suggests nucleation under cathode polarization at 200 mV and growth of chromium compounds after decreasing the cathode polarization. On the other hand, the deposited chromium decreased for the NiO/GDC cathode after decreasing cathode polarization.
Degradation of LSCF Cathode Induced by SO2 in Air
Authors: Kishimoto Haruo , Wang Fangfang , Cho Do-Hyung , Lv Peiling , Bagarinao Katherine Develos- , Yamaji Katsuhiko , Horita Teruhisa , Yokokawa Harumi
Published: February 2020

SO2 is one of the most major impurities in air and it induces a performance degradation of SOFC cathodes.  Our group has investigated the enforced degradation behaviors of LSCF cathodes by SO2 containing air.  It has been clearly observed that SO2 induced degradation is affected by the SO2 concentration in air, the operating temperature, the Sr content in LSCF cathode, the flowrate of air, the humidity of air as well as cell operation.  We also find out that sulfur is a tendency to preferentially exist in the vicinity of the cathode/electrolyte interface.  In this presentation, we try to provide a comprehensive description of SO2 induced degradation of LSCF cathode from a thermodynamical perspective.  In progress of degradation, sulfur reacts with Sr component in LSCF and forms SrSO4.  As a result, both conductivity and oxygen reduction reaction activity of LSCF decrease.  There seems to be a relationship between increments of ohmic resistance and reaction resistance in each degradation step
Interaction between Crofer 22 APU Current Collector and LSCF Cathode Contacting Layer under Cell Operation
Authors: Spotorno Roberto , Piccardo Paolo , Perrozzi Francesco
Published: February 2020

The metal interconnect oxidation and interaction with the cell are issues limiting the performances and the durability of the SOFC stacks. Despite the application of additional surface treatments or protective coatings such problematic are still affecting the system reliability because of hardly avoidable interactions since the operating conditions to which such material are exposed. Beside the high temperatures and oxygen partial pressures one should consider also the presence of a current load which acts locally changing the working conditions and the kinetic aspect of the  oxidation processes. In this work the current density effect has been investigated on Crofer 22 APU in air at 750°C. The same material has been pre-oxidized and coated with a state-of-the-art Co1.5Mn1.5O4 spinel coating to test the effect of such treatments on the interaction with a La0.6Sr0.4Co0.2Fe0.8O3 contacting layer simulating the interconnect interface at the cathode compartment. The behavior of such samples has been compared with the results on a working reproduction of a stack cathode compartment.
Development of a Tubular Solid Oxide Cell for Co-Electrolysis of H2O and CO2 for Syngas Production
Authors: Tanaka Yohei , Kato Tohru , Nagata Susumu , Negishi Akira
Published: February 2020

A tubular Ni-8YSZ/SSZ/GDC/SSC (Strontium-doped Samarium Cobaltite) cell was prepared for high temperature co-electrolysis of H2O and CO2. This cell enhanced a current density at750ºC and 1.28 V by two-fold compared to a previous type of our cell. Measurements of voltage-current density (V-J) curves revealed that 0.55 A/cm2 was attained at 750ºC and a thermoneutral voltage (1.33 V). The V-J curves were not influenced by change of H2/C (= 2-4) and flow-rate ratio (= 1-4) of positive electrode to negative one. In addition, V-J curve measurement at constant 80% utilization of H2O and CO2 clarified that the cell was stable at the high utilization and 0.41 A/cm2 was achieved at the thermoneutral voltage.
Addressing the Instability of High Capacity Lithium Battery Cathodes
Authors: Thackeray Michael M. , Long Brandon , Croy Jason R. , Lee Eungje , Park Joong Sun , Shin Youngho , Krumdick Gregory , Wen Jianguo , Miller Dean
Published: February 2020

Layered lithium- and manganese-rich mixed metal oxides are receiving worldwide attention as cathode materials for lithium-ion batteries because, once activated above 4.5 V, they can provide the theoretical capacity of a typical LiMO2 (M=Mn, Ni, Co) electrode (250-260 mAh/g) [1-3].  These Li- and Mn-rich materials can be represented in their initial state by the two-component formula xLi2MnO3·(1-x)LiMO2 or, in normalized layered notation, Li1+xM1-xO2.

Although xLi2MnO3·(1-x)LiMO2 electrodes maintain their capacity when repeatedly charged to high potetials (>4.5 V), structural changes result in voltage decay and hysteresis during repeated charge/discharge cycles, repressing their use in commercial battery products.   The structural decay has been attributed to the irreversible migration of transition metal ions (predominantly Mn) into the lithium-depleted layers.  This disadvantage is being addressed by slightly reducing the lithium content in parent xLi2MnO3·(1-x)LiMO2materials to introduce ‘pillaring’ transition metal ions in the lithium layers of the composite structure.

This presentation will discuss the background and versatility of composite electrode structures and highlight the opportunity that these materials present for overcoming voltage fade, with a specific focus on composite ‘layered-spinel’ electrode structures.

References

Z. Lu and J. R. Dahn, J. Electrochem. Soc., 149,A778 (2002).

J-S. Kim, C. S. Johnson, J. T. Vaughey, M. M. Thackeray, S. A. Hackney, W. Yoon and C. P. Grey, Chem Mater. 16, 1996 (2004).

M. M. Thackeray, C. S. Johnson, J. T. Vaughey, N. Li and S. A. Hackney, J. Mater. Chem. 15, 2257 (2005).
Visualisation and Quantification of Microstructural Change in Battery Electrodes
Authors: Brandon Nigel P. , Tariq Farid , Biton Moshiel , Yufit Vladimir , Wu Billy
Published: February 2020

The paper will present recent results in which 3D imaging and analysis is used to explore the microstructure of electrodes used within lithium batteries, zinc-air batteries and redox flow batteries. In particular, case studies will be presented observing in-operando delamination in silicon based lithium battery anodes, and zinc dendrite formation in zinc-air batteries. These studies offer insight into associated degradation and failure mechanisms, and inform work aimed at engineering improved microstructures for energy storage applications.
Magnetic Resonance Imaging of Batteries
Authors: Britton Melanie , Bayley Paul , Davenport Alison J , Forsyth Maria
Published: February 2020

The design and development of improved batteries and energy storage devices requires understanding of the electrochemical reactions, transport and concentration gradients within these devices during operation. However, there are few methods that are able to visualise and quantify these spatially, in situ and in real time. Magnetic resonance imaging (MRI), a technique typically associated with medical research and diagnosis, has proven to be an excellent tool for non-invasively studying complex, spatially heterogeneous chemical systems in materials, engineering and chemical research1. While MRI has enormous potential for in situ investigation of the spatial distribution, speciation, and mobility of molecules and ions in electrochemical devices, there are currently very few examples of MRI being used to probe such systems. This is largely due to the experimental challenges associated with setting up an electrochemical cell inside a strong magnetic field and the imaging artefacts caused by the presence of metals that lead to undesirable variations in the radiofrequency (RF) and magnetic fields across the sample2. However, recent work3 has shown that such issues can be overcome and that it is possible to collect viable, quantitative, in situ data for the electrolyte near metal electrodes.

Using MRI, the molecular transport and zinc and oxygen electrochemistry in an alkaline electrolyte have been investigated in a model Zn-air battery. Magnetic resonance relaxation maps of the electrolyte are used to visualise the chemical composition and electrochemical processes occurring during discharge. This paper will also review the challenges and opportunities MRI offers for the investigation of batteries and other energy storage devices.

References

[1]       M. M. Britton, Chem. Soc. Rev.
2010, 39, 4036-4043.

[2]       M. M. Britton, Chemphyschem
2015, 15, 1731-36.

[3]       M. M. Britton, P. M. Bayley, P. C. Howlett, A. J. Davenport, M. Forsyth, J. Phys. Chem. Lett.
2013, 4, 3019–3023.; A. J. Davenport, M. Forsyth, M. M. Britton, Electrochem. Comm.
2010, 12, 44-47.

.

Figure 1
High-Rate Electrochemistry in Bulk (um) Particles: NMR Insights into Nb2O5
Authors: Griffith Kent J. , Forse Alexander C. , Griffin John M. , Grey Clare P
Published: February 2020

Recent studies have shown that Nb2O5 can act as a high-rate cathode material in lithium-ion batteries; mesoporous, orthorhombic T-Nb2O5 has demonstrated reversible capacity of 130 mA∙h∙g-1 at a 10C rate and over 100 mA∙h∙g-1 even at a 100C rate.1,2  Intercalation in this material therefore occurs at noticeably higher rates than in a standard lithium-ion battery.  Inspired by work3,4 on the relationship between structure and electrochemical performance in Nb2O5polymorphs, an investigation was opened into the mechanisms responsible for the rapid lithium-ion intercalation in niobium(V) oxides. 

TT (pseudohexagonal), T (orthorhombic), B (monoclinic), and H (monoclinic) polymorphs of Nb2O5 were synthesised by calcining NbO2 for 24 hours over a range of temperatures.  In addition to low cost and ease of synthesis, solid state preparative methods were selected in an effort to characterise inherent properties of the bulk crystal structure of the various polymorphs, as it is well known that nanostructuring can fundamentally change the kinetics and thermodynamics of intercalation reactions.  Samples were prepared at every 50 °C interval from 200 °C to 1100 °C and analysed by x-ray diffraction (XRD). Electrochemically, the Wadsley–Roth type shear structure of H-Nb2O5 exhibited the highest capacity, reversibly intercalating more than one electron per transition metal ion.  Akin to the nanostructured mesoporous oxides, TT-Nb2O5 and T-Nb2O5 from NbO2displayed impressive intercalation kinetics and no phase change upon discharge-charge cycling; this result is somewhat unexpected considering the large (μm) scale of the particles in this investigation.

Solid state NMR was employed to examine lithiation mechanisms and energy barriers within the high-rate (T) and high-capacity (H) phases.  Results will be presented from ex situ magic angle spinning (MAS) 93Nb, 17O, and 7Li solid state NMR experiments, which were performed on pristine niobia samples and cycled coin cell cathodes to examine the different local atomic environments within each structural moiety and to correlate local and long range structural changes and lithium transport with rate performance for the different polymorphs.  Changes in NMR chemical shift, peak shape, intensity, and relaxation parameters were observed as a function of degree of lithiation and in variable temperature experiments.

1. Augustyn, V. et al.
Nat. Mater.
12, 518–522 (2013).

2. Brezesinski, K. et al.
J. Am. Chem. Soc.
132, 6982–6990 (2010).

3. Kumagai, N. et al.
J. Electrochem. Soc.
146, 3203–3210 (1999).

4. Rosario, A. V. & Pereira, E. C. J. Solid State Electrochem.
9, 665–673 (2005).

Figure 1
P2- Type NaNi1/3Mn2/3-XZnxO2: As a Cathode Material for Na-Ion Cells
Authors: Venkata Rami Reddy Boddu , Gopukumar Sukumaran
Published: February 2020

Since 1990s Li-ion batteries (LIBs) are playing a vital role in portable electronic devices (1-2) such as mobiles, laptops, tablets, and electric vehicles etc., owing to its compact size and high energy density. However, the main problem of lithium is its abundance and cost deters it from making cost-effective battery. Therefore, researchers (3 – 5) are considering alternatives like Na-ion battery chemistry as sodium is the one of most abundant element in the earth crust and its redox potential close to lithium. In the present work, we report the synthesis and characterization of NaNi1/3Mn2/3-xZnxO2, by using citric acid assisted sol-gel method for use as cathode material in Na-ion battery. Here, citric acid acts both as a fuel and chelating agent. XRD analysis reveals that the P2 type layered structure as depicted in Fig.1 for NaNi1
/3Mn2/3O2, NaNi1
/3Mn2/3-xZnxO2. SEM studies of NaNi1
/3Mn2/3O2, NaNi1
/3Mn2/3-xZnxO2 are confirms that, particle size range is about 1-2 m with different shapes which is shown in Fig., 2 (a, b). Electro chemical studies have been performed between 2.0 - 4.3 V for a Na/ NaNi1/3Mn2/3-xZnxO2   system, here sodium is reference as well as counter electrode assembled in CR-2032 type coin cells using 1M NaClO4 EC: DEC (1:1 V/V) electrolyte medium. 

References:

(1) I. Belharouak, Lithium ion batteries – new developments, p. 1. (2012).                                                                           

(2) D. Linden and T. B. Reddy, Hand Book of Batteries, 3rd. ed., p34.1, (2002).

(3) Z. Lu, J. R. Dahn, J. Electroche. Soc., 148(11), A1225, (2001).

(4) H. Yoshida,  N. Yabuuchi, K. Kubota,  I. Ikeuchi, A. Garsuch, M. S. Dobrick and S. Komaba,  Chem commu., 50, 3677(2014).

(5) B.V. R. Reddy and S. Gopukumar, ECS tranactions, 53(30), 499, (2013).

Figure 1
Drift Effect of Li Ions in Electrolytes on Dendritic Morphology
Authors: Park Min-Sik , Im Dongmin
Published: February 2020

In Li-metal and Li-air batteries, anodic materials are Li metals. In contrast to the intercalation materials such as the graphite, however, the morphology of the Li metal anode surface is not uniform, i.e., dendritic growth, during battery charging. In this study, dendritic growth was simulated by using the diffusion-limited aggregation (DLA) model, where we found the movement of Li ions in electrolytes is critical to change the morphology of dendrites. Especially, the directional drift of Li ions affects the dimension and height of dendrites. It is suggested that less viscous electrolytes can mitigate the dendritic growth on the Li metal anode surface.
Advanced 3D Imaging, Analysis and Characterisation of Zn Dendrite Formation in a Zn-Air Battery
Authors: Biton Moshiel , Tariq Farid , Yufit Vladimir , Wu Billy , Brandon Nigel P.
Published: February 2020

Rising global demand for energy supply, storage and portability in a sustainable manner needs significant improvements to be made in the next generation of batteries, both in terms of performance and lifetime. However, despite their importance, battery electrode microstructures remain relatively poorly understood. 

The performance of the battery is dependent on the nano and micro-structure achieved during manufacture.  Furthermore microstructural evolution during operation may degrade electrochemical performance. The growth of dendrites represents a limiting failure mechanism in some battery systems; in particular this can be a challenge in zinc-air batteries. Tomographic techniques allow the direct 3D imaging and characterisation of complex microstructures, including the observation and quantification of dendrite growth.

Here we present results from 3D x-ray and FIB-SEM tomography of Zn dendrite formation in a zinc-air battery, down to resolutions of tens of nanometers, enabling analysis of dendrite micro-structure.

This approach is shown to be effective in understanding how dendrites grow, and demonstrates that tomography coupled with modeling can provide new insights into degradation mechanisms associated with dendrite growth.
A Study of Current Collectors for Magnesium Batteries in Mg(AlCl2EtBu)2/THF Electrolyte Using the Scanning Vibrating Electrode Technique
Authors: Glover Carol Frances , Williams Geraint
Published: February 2020

Magnesium-based secondary batteries provide a non-toxic, earth-abundant alternative to the Li-ion systems for stationary applications. The appeal of such systems has been recognised after a volumetric capacity that outperforms that of Li-ion systems was demonstrated (3833 mA h/cc compared to 2046 mA h/cc)1. In any battery system, the compatibility of the current collector and the electrolyte is of high importance and for achieving good reversibility in rechargeable systems and a long cycle life. Aurbach et al demonstrated the reversible deposition and dissolution of the Grignard reagent, a tetrahydrofuran (THF) solution of magnesium organohalo-aluminate salt (Mg(AlCl2EtBu)2/THF), with a columbic efficiency of ∼100%2. This electrolyte has been vastly studied since its identification and, subsequently, increased the level of interest in reversible Mg batteries.

The instability of a range of current collectors, when exposed to Grignard reagents, with the exception of Nickel, has been highlighted previously3. In the current study the scanning vibrating electrode technique (SVET) is used to map the current density over the surface of a selection of metals when polarised to an applied potential. The technique can then be used to spatially resolve anodic and cathodic activity. SVET has been used extensively in corrosion research where a wealth of literature is available. Figure 1 shows a typical SVET-derived current density surface map, obtained by scanning a metallic surface when fully immersed in electrolyte; the red peaks denote the anodic regions. The aim of the current study is to further understand the instability of certain metals, that are often considered as suitable current-collectors in Mg-based battery systems, when exposed to (Mg(AlCl2EtBu)2/THF). Copper, nickel, stainless steel and silver will be studied.

Figure 1 A
typical SVET-derived current density surface map obtained by scanning a metallic surface when fully immersed in electrolyte.

References

1         P. Saha, M. K. Datta, O. I. Velikokhatnyi, A. Manivannan, D. Alman, and P. N. Kumta, Prog. Mater. Sci., 2014, 66, 1–86.

2         D. Aurbach, Z. Lu, A. Schechter, Y. Gofer, H. Gizbar, R. Turgeman, Y. Cohen, M. Moshkovich, and E. Levi, Nature, 2000, 407, 724–7.

3         D. Lv, T. Xu, P. Saha, M. K. Datta, M. L. Gordin, a. Manivannan, P. N. Kumta, and D. Wang, J. Electrochem. Soc, 2012, 160, A351–A355.

Figure 1
A Study on the Electrochemical Characteristics of Kerosene Derived Carbon Nanospheres As Anode Materials of Lithium Secondary Batteries
Authors: Arie Arenst Andreas , Lee Joong-Kee
Published: February 2020

Spherically shaped carbon materials have been explored for decades, and their characteristics have been applied for instance in the various energy-related industries  such as batteries, capacitors or fuel cells. It can be said that the term of carbon spheres refers to all carbon materials that possess a spherical or near spherical shape but do not include the fullerene family of carbons. In general, spherical carbons have been prepared by various methods such as arc discharge, chemical vapor deposition, laser ablation, autoclave process, shockwave process and catalytic pyrolysis process. It can be observed that the different methods can produce carbon spheres with quite different structural and electrical characteristics. In this study, carbon nanospheres (CNSs) were synthesized by the nebulyzed pyrolysis process using kerosene as carbon precursors, ferrocene catalyst and activated carbon support at elevated temperature under an nitrogen atmosphere. Morphology and structure of as grown CNSs were characterized by Scanning Electron Microscope (SEM), High-Resolution Transmission Electron Microscope (HRTEM), Raman and X-ray photo electron spectroscopy. It was found that the carbon products had a turbostratic structures and high degree of disorder carbon structures. Preliminary electrochemical measurements of kerosene derived CNSs as anode materials of lithium secondary batteries were carried out using cyclic voltammetry and charge –discharge tests. Experimental results showed that a stable cycle performances until the 100th cycles was obtained with specific capacity of 400 mAh/g.  However, the main problem is the high irreversible capacity at the first cycle due to the low purity and non uniform carbon nano-spheres.
Gas Diffusion Electrodes for Li/O2 Batteries: Impact of Porosity, Wettabiliy and Electrode Design
Authors: Bardenhagen Ingo , Fenske Daniela , Westphal Anne
Published: February 2020

Beyond lithium ion batteries the metal air technology is considered to be very promising for various energy storage applications in a long-term view. Due to its very high theoretical energy density the aprotic Li/O2 system in particular has attracted broad attention during the recent years. Here molecular oxygen O2 is reduced at a gas diffusion electrode (GDE) upon discharge forming Li2O2 as a solid discharge product which precipitates within the electrode to be reoxidized under the release of oxygen upon recharge. The performance of a Li/O2cell is therefore critically influenced by the structural properties of the used GDE. Based on carbon, especially the porosity, the wetting behavior and the general design of the GDE has a huge impact on the capacity and efficiency of the cell.

Regarding the wettability of a GDE, a thin electrolyte film within the inner pore structure is considered to be ideal to provide efficient oxygen transport through open gas channels as well as improved diffusion properties towards the active surface. Using mesoporous carbon xerogels which exhibit defined open pore structures, large inner surfaces and pore volumes we were able to investigate the pore wettability with different solvents by using 1H relaxation MRT techniques. To investigate them as active material in the Li/O2 system they were synthesized directly into a woven carbon paper to create ready-to-use electrodes without any binder. Here, the discharge reaction was studied by electrical impedance spectroscopy (EIS) using 1M LiTFSI/DMSO as electrolyte and Li metal as reference electrode in a three electrode setup. A model for the interpretation of the limiting factors regarding the GDE performance due to the formation and deposition of the discharge product could be developed. For further investigation of these factors the chemical and morphological characterization of the discharge products in dependence on the GDE design was addressed by XPS analyses. Besides looking at the electrolyte facing side the deposition of discharge product in the bulk of the active layer in the GDE and at the oxygen facing side were investigated. For information about the bulk of the GDE cross-section measurements as well as depth profiling by argon ion sputtering were conducted.
Implications of Metal-Site Vacancies on Li-Ni-Mn-Co Based Positive Electrode Materials
Authors: Shunmugasundaram Ramesh , Senthil Arumugam Rajalakshmi , Dahn Jeff R
Published: February 2020

One of the key issues with Li-excess positive electrode materials is their high irreversible capacity loss (IRC), which is usually ~ 20 % of their first charge capacity. Li-excess materials with IRC as low as 4% have been recently reported by us1. Those materials were intentionally synthesized with less Li than the stoichiometric amount, based on oxidation state rules, and as a result, metal-site vacancies were found in their single-phase, layered, pristine structures. With metal-site vacancies, the structure can be written as Li[ΔqM(1-q)]O2, where Δ is a metal site vacancy and the transition metal layer has no Li atoms.  An elemental analysis of metals only on such materials would conclude they were Li rich because when q > 0, the number of moles of Li is greater than the number of moles of transition metal atoms, even though there are no Li atoms in the transition metal layer.  The small IRC was found to be related to the presence of metal site vacancies.

            Following that work, a comprehensive search for materials that contain metal-site vacancies was performed in the Li-Ni-Mn-Co pseudo-ternary system. An array of materials with deliberate Li-deficiency and a wide-range of Ni, Mn, and Co compositions was synthesized and their properties were investigated.  It was found that, in the Li-Ni-Mn-Co pseudo-ternary system, materials with metal-site vacancies can be synthesized at many Ni-Mn-Co combinations by forcing Li deficiency. Most of the materials were layered single-phase materials but increasing Li deficiency eventually caused the evolution of a spinel phase. The presence of metal-site vacancies were verified by density measurements made with a He-pycnometer. Figure 1 shows the XRD patterns of several single-phase materials (a to f), which have considerable amount of metal-site vacancies, in the range of 20° to 34° representing superlattice ordering between TM ions and vacancies in the TM layer similar to that reported by McCalla et al2. The relative intensity of superlattice peaks varied with overall metal composition (not shown here) suggesting different degrees of ordering. For example, the absence of superlattice peaks in samples e and f suggests that only a negligible amount of vacancies reside in the TM layer whereas the prominent superlattice peaks in samples a and b suggests a significant amount of vacancies in the TM layer.  Thus the nature and the relative intensity of the superlattice peaks can be used as a first approximation to predict the location and distribution of vacancies between TM and Li layers. Detailed results on the implications of metal-site vacancies on the properties of Li-Ni-Mn-Co based positive electrode materials will be presented.

References:

Shunmugasundaram, R.; Senthil Arumugam, R.; Dahn, J. R. Chem. Mater.
2015,27, 757–767

McCalla, E.; Rowe, A. W.; Camardese, J.; Dahn, J. R. Chem. Mater.
2013, 25, 2716–2721

Figure 1
A Novel Preparation Procedure of Poly(vinylidenedifluoride)-Based Gel Polymer Electrolyte for Application in Lithium-Ion Batteries
Authors: Fasciani Chiara , Panero Stefania , Hassoun Jusef , Scrosati Bruno
Published: February 2020

Gel-type polymer membrane electrolytes, GPEs, have attracted particular attention thanks to their low volatility, high thermal stability and safety, which make them suitable for use in lithium ion battery (LIB) technology.1

In this work we present a convenient preparation procedure of poly(vinylidene difluoride) (PVdF)-based gel polymer electrolyte. The novelty of the procedure reported is that the electrolyte is prepared under air as a dry, flexible film and directly gelled during LIB assembly. Therefore, the GPE obtained is easy to handle and suitable for roll-to-roll scaling-up and it can be efficiently used for application in LIB. The morphology and electrochemical interphase properties of the electrolyte have been investigated by scanning electron microscopy and impedance spectroscopy, respectively. Moreover, galvanostatic tests suggested good stability of the lithium electrode/gel electrolyte interface and a high lithium transference number. Finally, cycling tests of full lithium ion cell, employing the GPE, a lithium iron phosphate cathode and a graphite anode confirm the suitability of the GPE for application in stable, low cost and environmentally friendly energy storage systems.2

[1]  Croce, F.; Focarete, M. L.; Hassoun, J.; Meschini, I.; Scrosati, B. A Safe, High-Rate and High-Energy Polymer Lithium-Ion Battery Based on Gelled Membranes Prepared by Electrospinning. Energ.
Environ. Sci.2011, 4, 921-927.

[2] Fasciani, C.; Panero, S.; Hassoun, J.; Scrosati, B.  (submitted) 2015.

Figure: Scanning Electron Microscopy pictures (background image) of the PVdF-gel membrane and voltage profile at 25°C of a C/GPE/LFP LIB using an activated, pre-lithiated graphite anode. Current rate: C/5; Voltage limits: 3.8 V - 2 V.

Figure 1
Mechanism Scan in Li-O2 Batteries By Impedance Spectroscopy
Authors: Haro Marta , Vicente Nuria , Garcia-Belmonte Germa
Published: February 2020

Li-O2 batteries are claimed to be the batteries of the future because they can provide the highest energy density among any other type of batteries since Li+ ions and O2 directly react with each other and, in practice, oxygen is not stored in the battery (1). Despite the great deal of attention in this technology currently there exists a great gap between the theoretically achievable energy density and the provided by Li-O2 batteries in practice (2). Therefore, to fully exploit the capacity of Li-O2 batteries, the thermodynamic mechanisms and kinetics that rule and limit their functioning must be understood. In this context, electrochemical impedance spectroscopy (EIS) is a unique technique that allows in-situ monitoring the charge-discharge processes in batteries obtaining kinetic information of the mechanisms developed with different time constant (3). In the present study, the impedance spectra of Li-O2 batteries have been registered at different voltages of the charge and discharge processes. With the obtained data a novel equivalent circuit model is proposed, where interfacial charge transfer, adsorption and diffusion phenomena have been identified as well as the voltages where oxygen reactions (ORR and OER) appear. For each step is associated a resistance what allows to determine the bottleneck process. Furthermore, different parameters (composition and structure) of the cathode have been methodologically modified and the effect on the mechanism step analyzed. The proposed equivalent circuit model is a relevant tool for the rational design of Li-O2 batteries.

References:

(1)   N. Imanishi, A. C. Luntz, P. Bruce The Lithium Air Battery: Fundamentals Springer (2013)

(2)   N-S. Choi, Z. Chen, S. A. Freunberger, X. Li, Y-K. Sun, K. Amine, G. Yushin, L. F. Nazar, J. Cho, P. G. Bruce Angew. Chem. Int. Ed. 51, 9994 (2012)

(3)   F. Martinez-Julian, A. Guerrero, M. Haro, J. Bisquert, D. Bresser, E. Paillard, S. Parrerini, G. Garcia-Belmonte J. Phys. Chem. C 118, 6069 (2014)