bluuebunny/crossref_metadata_2025 huggingface dataset:
Understanding the Electrochemical Performance of SOFC Stacks
Authors: Lang Michael , Auer Corinna , Braniek Gabor , Wenz Franziska , Hauler Felix
Published: February 2020

In the past much effort was spent for the detailed understanding of the electrochemical behavior of SOFC single cells. However, these results can only hardly be transferred to the SOFC stack technology because of huge differences in fuel utilization, in temperature distribution, in gas flow design and in electrical current load. Therefore, proper and detailed understanding of the electrochemical behavior of the SOFC stacks is obligatory for the successful introduction and acceptance of the SOFC technology into the global energy market. The paper presents both experimental and modeling results of the electrochemical behavior of SOFC short stacks with anode supported cells (ASC) in the cassette design at different operating conditions. The focus lies on the investigation of the different resistances and the voltage losses in the stack layers, which can be classified in ohmic, electrode polarization and gas concentration ones. The influence of the different operation conditions, e.g. temperature, current density and fuel utilization is outlined. The stacks were investigated by current-voltage curves, electrochemical impedance spectroscopy (EIS), gas analysis and long term measurements. Results of both integral and locally resolved measurements along the fuel gas flow path are presented. The modeling results were obtained with a two dimensional elementary kinetic model which represents a single cell along the gas channels and through the thickness of the membrane-electrode assembly.
Microstructural Characterization of SrZrO3 Formation and the Influence to SOFC Performance
Authors: Kanae Shu , Toyofuku Yasuhiro , Kawabata Tsutomu , Inoue Yuko , Daio Takeshi , Matsuda Junko , Chou Jyh-Tyng , Shiratori Yusuke , Taniguchi Shunsuke , Sasaki Kazunari
Published: February 2020

One of the major phenomena to shorten SOFC durability is the formation of insulated phases, such as SrZrO3, between the cathode and the electrolyte. It is known that SrZrO3 is formed and grown during sintering processes as well as during long-term operation. A systematical study is therefore desired to clarify the SrZrO3formation mechanisms and their influence on electrochemical properties.

 In this study, four parameters are considered and systematically varied: sintering temperatures of cathode, electrolyte, and buffer layer, and buffer layer thickness. The cells tested consist of yttria stabilized zirconia (YSZ) as the electrolyte, Ni- yttria stabilized zirconia (Ni-YSZ) as the anode, La(Sr)Co(Fe)O3（LSCF）as the cathode, and Ce0.9Gd0.1O2 (GDC) as the buffer layer. The GDC layer was sintered at 1300oC with 5μm in thickness, while the YSZ electrolyte was sintered at 1400oC. Cathode sintering temperature was varied from (1) 1000oC to (2) 1100oC and (3) 1200oC. The electrochemical performance of the cells was tested at 800oC, 0.2A/cm2 for 100h by feeding humidified fuel: H2 (97 cc/min) and H2O (3 cc/min). Microstructure of the three types of model cells after sintering and testing for 100h was observed in details by FE-SEM (Field Emission Scanning Electron Microscope) and STEM (Scanning Transmission Electron Microscope).

 Microstructural observation has been revealed (1) no SrZrO3 formation during sintering LSCF at 1000oC, and (2) a partial formation of SrZrO3 between the cathode and the electrolyte after sintering LSCF at 1100oC. (3) After the sintering of the LSCF cathode at 1200oC, the interface was fully covered by the SrZrO3 layer, clarified by the microstructural observation with EDX elementary mapping. Such SrZrO3 formation led to a decrease in electrochemical performance. These results indicate the importance of the SrZrO3 formation controlling the SOFC performance.
A Case Study Analysis of System Efficiency, Viability and Energy Values of SOFC Based Fuel Cell Micro-CHP for Office Buildings
Authors: Tesfai Alem Teklebrhan , Mylona Anastasia , Connor Paul , Cassidy Mark , Irvine John T. S.
Published: February 2020

A case study analysis of economical and energy values of SOFC based fuel cell micro-CHP for residential homes.

 

Dr Alem Tesfai, Dr Anastasia Mylona and Professor John T S Irvine

KTP Associate Chartered Institution of Building Services Engineers222 Balham High RoadLondonSW12 9BS Tel: +44 (0) 20 8772 3699 at61@st-andrews.ac.uk, ATesfai@cibse.org

Abstract

This work presents the experimental and CFD model analysis of a 1.5 kW prototype SOFC micro-CHP system. The potential application of Fuel cell micro-CHP in a typical office building is investigated experimentally. With the current fuel cell technology the use of such systems in office buildings has the potential to be more efficient and reliable than in a single family home. This study documents the economic and energy related values of the fuel cell micro-CHP. This study will also look at how to optimise the operating conditions of the system in different climate conditions i.e. during the winter, autumn and the summer. To optimise and compere the experimental data a typical single family apartment heated by radiators will be analysed using a three-dimensional CFD model. Different heat transfer coefficients for the outer wall, the window and for the doors were considered. The seasonal heat requirements were also considered and heat recovery of the fuel cell micro CHP system was optimised. Different options i.e. whether to use the hot water supplied by the fuel cell micro CHP for domestic appliances or for space heating possibly by adding a combination boiler as a booster was also considered.
Introducing Anode Fluidization into a Tubular Liquid Antimony Anode Direct Carbon Fuel Cell
Authors: Cao Tianyu , Shi Yixiang , Cai Ningsheng
Published: February 2020

Liquid antimony is considered to be a promising anode for direct carbon fuel cell. The pilot system built in this research is made up with fuel supplement unit, cooling sub-system and power generating core block with tubular SOFC (solid oxide fuel cell) planted into liquid antimony bath. The metal bath serves as anode of direct carbon fuel cell and shall be fluidized during fuel cell operation. The fluidize wind acts as a carrier as well as a stirrer, for it carries pulverized coal directly into liquid antimony bath to feed the fuel cell before mixing the coal up with antimony anode. Well-stirred fluidized anode promotes the fuel cell performance, enhancing heat and mass transfer in the anode region, reducing the risk of thermal shock of tubular SOFC as well as accelerating the electrochemical oxidation of carbon fuel at the same time. The system exhibits stable performance during operation, and well-designed setup of liquid metal bath makes it much easier for stack assembly and system scale up, on the other hand, continuous fuel supply procedure employed in this system will also inspire direct carbon fuel cell operation in its future application.

Figure 1
Synthesis, Characterization and Performance of Calcium and Samarium Co- doped Ceria Electrolytes for Low and Intermediate Temperature Solid Oxide Fuel Cells
Authors: Pandey Dyuti , Basu Suddhasatwa
Published: February 2020

Three different compositions of samarium and calcium co-doped ceria were synthesized by cation- complexation process. The calcium content in co-doped Ce0.8Sm0.2-xCaxO2-δ varied from x=0.5 to 0.15. The effects of variation in calcium content on phase, crystallite size and morphology of the synthesized powders were investigated by XRD, SEM and TEM analyses. All synthesized powders were fluorite-type ceria nano-solutions. The particle size of Ce0.8Sm0.15Ca0.05O2-δ was around 10-17 nm as shown in fig.1. To evaluate the electrochemical behaviour the synthesized powders were die-pressed into pellets and sintered at 1450 °C for 10 hours. At 550°C, out of the three synthesized compositions, Ce0.8Sm0.15Ca0.05O2-δ showed the highest conductivity (0.013 S/cm). Anode-supported SOFCs with LSCF/Ce0.8Sm0.2-xCaxO2- δ /NiO-Ce0.8Sm0.2-xCaxO2-δ have been fabricated and tested for the purpose of investigating their potential use in low and intermediate temperature SOFCs.

Key words: Co-doped Ceria, SOFC.

References

[1] M. Sebastian, M. Gazda, P. Jasinski, J. Rare Earths., 2009, 27(4), 655-660.

[2] M. Dudek, J. Eur. Ceram. Soc., 2008, 28, 965-971.

[3] S. Banerjee, P.S. Devi, D. Topwal, S. Mandal, K. Menon, Adv. Funct. Mater., 2007, 17, 2847-2854.

Key words: Co-doped Ceria, SOFC.

Figure 1
Praseodymium Doped Ceria: The Role of 4f-Electrons of Pr Dopant in Doped Ceria
Authors: Alaydrus Musa , Sakaue Mamoru , Linh Nguyen Hoang , Aspera Susan Meñez , Wungu Triati Dewi Kencana , Kasai Hideaki
Published: February 2020

Oxides like ceria (CeO2) are very promising for solid electrolyte materials when doped by suitable aliovalent dopants, as they introduce high oxygen ion conduction leading to intermediate to low temperature operations (T ≤ 800°C ). Over the past decades, engineering new compositions aiming at high ionic conductivity at lower operating temperatures has been a key issue of developing solid oxide fuel cells. However, the understanding over the underlying physics on the oxygen ion conduction in this system remain unclear. In this study, we discuss DFT+U study on the effect of the 4f-electrons on Pr-doped CeO2. We found that, regardless of their localized nature tendency, we found significant contributions from the Pr-dopant 4f-electrons to the oxygen vacancy formation energy as well as the preferential site of the oxygen vacancy formation in comparison with the model of fully localized 4f-electrons, though the geometrical properties for each local minimum structure remain unaffected.
Assessment of Possibilities for Operation of Ni-Catalyst Partial Oxidation Reformers in SOFC Systems after Soot Formation
Authors: Baskakov Albert Pavlovich , Plotnikov Nikita , Wang W. , Peng J. , Volkova Yulia , Dong Z , Lu X , Luo Q
Published: February 2020

Solid oxide fuel cells (SOFCs) allow us to directly convert the chemical energy of fuel into electricity. With their emissions consisting mainly of Н2О and СО2, SOFC-based power generation systems are highly efficient (with efficiency up to 70%) and environmental friendly, which makes them increasingly attractive for the use in stationary power generation systems. The mixture of CO and H2(synthesis gas) supplied to the SOFC anode can be produced from the natural gas using the dry or steam reforming or partial oxidation methods. The partial oxidation of methane, that is typically done with Ni catalysts, seems the best option for start-up systems of power plants with the anode gas recirculation or other applications where no water supply can be possibly organized. In this case, carbon deposition on the parts of reformer can be a problem, particularly, where the air-gas mixture supply system works abnormally.

The simple method of calculation of thermodynamically equilibrium composition of partial fuel oxidation products was used to calculate the degree of air consumption  in a reformer which permits to avoid soot formation. The value  ensuring auto thermal process in CPOX reformer was determined.  Air flow rate used in reaction with synthesis gas and for cooling the reformer, was calculated also.

An experiment is carried out to simulate the abnormal operation of the CPOX reformer with further soot formation on the Ni-catalyst and its walls. The results show that even in the event of the abnormal operation and carbon deposition in it, the CPOX reformer can continue working. Specifically, the carbon gasification takes place. The CO-content of the synthesis gas in this case is twice as much, on the average; however, this is not of critical character for SOFC systems.
Effects of SOFC Exhaust Gas Recirculation on Performance of Solid Oxide Fuel Cell-Gas Turbine Hybrid System Utilizing Renewable Fuels
Authors: Saebea Dang , Authayanun Suthida , Patcharavorachot Yaneeporn , Arpornwichanop Amornchai
Published: February 2020

A solid oxide fuel cell-gas turbine (SOFC-GT) hybrid system run on renewable fuels, such as biogas and ethanol, is an interesting power generation technology due to its high efficiency. To avoid a carbon formation on the anode catalyst by the direct feed of hydrocarbon fuels to SOFC, a pre-reformer is needed to integrate with the SOFC system for hydrogen production. As the steam reformer and air preheater are units that require high external energy input, the efficient heat management of the SOFC system is necessary. Regarding the SOFC system, the anode and cathode recirculations are employed to recover high-quality waste heat for reformate gas and gas turbine cycle, affecting the electrical and thermal system efficiency. In this study, a steam reformer and SOFC-GT hybrid system with anode and cathode recirculations is investigated. The aim of this work is to analyze the effects of the anode and cathode recirculations on the performance of SOFC-GT systems. The mathematical model of SOFC, gas turbine, and auxiliary units based on mass and energy balances under steady-state operation is employed for this study. The parametric analysis of key operating parameters, such as fuel utilization, steam to carbon ratio and operating pressure, on the system performance is performed. The results indicate that the SOFC hybrid system with the anode recirculation can reduce the supplied heat for the external steam reformer; on the other hand, it degrades the gas turbine performance due to a decrease in the turbine inlet temperature. When considering the hybrid system with the cathode recirculation, it is found that the efficiency of the SOFC-GT system is higher. However, the turbine inlet temperature is extremely high, leading to the cooling problem of a micro turbine.
Sulfur Poisoning of LSCF Cathode in Single Step Co-fired SOFC
Authors: Mori Naoya , Sato Yosuke , Iha Michiaki , Takada Takahiro , Konoike Takehiro , Kishimoto Haruo , Yamaji Katsuhiko , Yokokawa Harumi
Published: February 2020

Murata Manufacturing Co., Ltd. has been developing planar-type solid oxide fuel cells (SOFCs) based on new design concept.  The cell is fabricated by a single-step co-firing process and consists of an electrolyte, electrodes, current collectors, gas-separators with manifolds, and gas-flow channels. The membrane electrode assembly (MEA) is sandwiched between ceramic gas-separators with via-hole electrodes providing electrical paths between cells. Removing metal interconnects around cathode in the cell enables reducing Cr vapor from metal and achieving high durability. A long-term operation has been carried out at 750°C over 8000h under galvanostatic condition. Single cell voltage degradation rate was less than 0.20%/kh after 2000h operation, and Cr poisoning in the LSCF cathode after long term operation over 8000h was not observed. From these results, the cell structure is effective to reduce Cr vapor in the cathode. But Sulfur distribution in the cathode was observed by analyzing in detail. Larger amount of Sulfur to form SrSO4 was distributed at the air channel on the upstream than that on the downstream. And furthermore, Co segregation was observed in LSCF near the GDC barrier layer at the air channel on the upstream. To study sulfur poisoning mechanism, SO2 poisoning test was carried out with various temperature and current density. Distribution of Sulfur and Co depended on operating temperature and current density.
Role of Strain Ans Sr-Doping for the Anisotropic Oxygen Diffusion in LaMnO3
Authors: Salawu Omotayo akande , Gan Liyong , Schwingenschlogl Udo
Published: February 2020

A high ionic conductivity is desireable property for cathode materials for

solid oxide fuel cells. LaMnO3 is a well studied candidate for this applica-

tion. Hence, it is important to understand the oxygen transport mecha-

nism. We find increase in oxygen vacancy formation energy and diffusion

under compressive and tensile strain as well as under Sr-doping using the

density functional theory and nudged-elastic band calculations. The oxy-

gen vacancy sites and diffusion paths are studied. We investigate the effect

of Sr-doping on the anisotropy of the diffusion. Modified strengths of

the Mn and O bonding as well as volume change are identified as fac-

tors that affect the formation/diffusion of vacancies. Furhermore, tensile

strain facilitates enhanced oxygen vacancy diffusion along the [011]/[0 ̄11] direction. The weakening of the Mn- O bonds as well as the distortion of

the MnO6 octahedra hinder diffusion along the [110]/[1 ̄ 10}direction.
Effect of Nature of the Ceramic Component of the Composite Electrodes Based on La1.7Ca(Sr)0.3NiO4+δ on Their Electrochemical Performance
Authors: Pikalova E. , Bogdanovich N. , Kolchugin A. , Brouzgou A. , Bronin D. , Plaksin Sergey Vladimirovich , Khasanov A. , Tsiakaras P.
Published: February 2020

The development of a cathode that is stable against CO2 present in the atmosphere still remains a challenge. Over the past ten years layered perovskite La2NiO4±δ has been the subject of careful research as far as also concerns their potential use as cathodes in electrochemical devices. So far as La2NiO4±δ is a p-type conductor, appropriate acceptor doping on A-site could improve the electronic conductivity by generating extra electron holes for charge compensation. Experimental results reveal that the electronic conductivity does indeed increase with a certain amount of Sr or Ca-doping. However, the substitution of La by alkali-earth elements deteriorates its electrochemical activity due to a decrease in the sub-stoichiometric oxygen amount in the structure and ionic component of conductivity [1]. One way to increase ionic conductivity is development of composite electrodes with ionic conductor as a second component, usually CeO2-based electrolyte [2]. The composite electrodes with proton-conducting electrolyte, especially in case when such electrodes are proposed to be used in contact with this electrolyte, could provide more extended area of electrochemical reaction.

     The actual work focuses on the electrochemical performance of the La1.7Ca(Sr)0.3NiO4-based composite cathode materials with Ce0.8Sm0.2O1.9 (SDC) and BaCe0.89Gd0.1Cu0.01O3 (BCGC) ceramic component (in wight ratio 1:1) which were applied as a functional layer in two-layered electrodes with 98 wt.% LаNi0.6Fe0.4O3 + 2 wt.% CuO LаNi0.6Fe0.4O3 and 99.4 wt. % La0.6Sr0.4MnO3 + 0.6 wt.% CuO as a collector layer. Studies by impedance spectroscopy were performed in contact with BCGC and BaCe0.5Zr0.3Y0.2O3 + 1 wt.% CuO (BCZY) proton-conducting electrolytes in comparison with traditionally used 50 wt.% La0.6Sr0.4Fe0.8Co0.2O3 + 50 wt.% SDC and 50 wt.% La0.75Sr0.2MnO3 + 50 wt.% SSZ composite electrodes.

Keywords: La1.7Ca0.3NiO4, cathode, electronic conductivity, proton-conducting electrolyte

Acknowledgments

The authors are grateful for the financial support to: the Ministry of Education and Science of the Russian Federation (Mega-grand contract no. 14.Z50.31.0001), the Russian Foundation for Basic Research (grants no. 13-03-00065, 14-03-00414) and the Russian Foundation for Basic Research (grants no. 13-03 96098 and 14-03-00414).

 References

[1] E.Yu. Pikalova, N.M. Bogdanovich, A.А. Kolchugin, D.A. Osinkin, D.I. Bronin, Electrical and electrochemical properties of La2NiO4+
δ-based cathodes in contact with Ce0.8Sm0.2O2-
δelectrolyte, accepted in Procedia Engineering

[2] B.L. Kuzin, N.M. Bogdanovich, D.I. Bronin et al, Elecrochemical Properties of Cathodes Made of (La,Sr)(Fe,Co)O3Containing Admixtures of Nanoparticles of Cupric Oxide and Intended for Fuel Cells with A Solid Electrolyte Based on Ceric Oxide, Rus. J. Electrochem. 43 (2007) 920.
Materials Search of Perovskite Cathode in SOFC by Statistical Analysis
Authors: Hwang Jaekyun , Ando Yasunobu , Watanabe Satoshi
Published: February 2020

Solid oxide fuel cell (SOFC) technology requires further maturations to become commercialized broadly. Many existing problems are expected to be solved by intermediate temperature SOFC (IT-SOFC). On the other hand, electrochemical resistances of cathode materials increase rapidly at lower temperature. So it is necessary to understand the underlying mechanisms of oxygen reduction reaction and develop new materials. Although many experimental and theoretical researches for this purpose are in progress, traditional trial-and-error materials search must be inefficient and take too long time.

 Considering the above situation, we explore critical factors that can explain the oxygen exchange rate of perovskite oxide cathode in SOFCs. It has been said that the bulk ionic conductivity is strongly related to the oxygen exchange rate, while the electronic conductivity is not as far as it is high enough. However, we found that the combination of ionic and electronic conductivities shows much stronger correlation than ionic conductivity alone while analyzing reported experimental data on 18 materials in figure 1. Materials which have high oxygen exchange rate can be explained by the multiplication of bulk ionic conductivity and electronic conductivity while others explained by the ionic conductivity.

Fig. 1 Relationship between oxygen exchange rate and bulk electronic conductivity, ionic conductivity, and the model function with both conductivities.

Figure 1
Electrical and Oxidation Resistance of Surface Oxide of Porous Fe-Cr-Al Alloy for the Application of Metal Supported SOFCs
Authors: Pham Hung-Cuong , Taniguchi Shunsuke , Inoue Yuko , Chou Jyh-Tyng , Izumi Toru , Matsuoka Koji , Sasaki Kazunari
Published: February 2020

We investigated property of a FeCrAl type stainless steel as a porous alloy substrate of metal supported SOFCs especially on the cathode side. We confirmed not only good heat resistance but also low electrical resistance at the interface between the porous substrate and La0.6Sr0.4Co0.2Fe0.8O3 (LSCF) coating at 700oC in air. Morphology and crystal structure of the surface oxide layer of the FeCrAl alloy was analyzed by STEM-EDS and TEM in detail to clarify the cause of such a low electrical resistance. Long-term stability of the oxidation resistance of the porous FeCrAl alloy substrate was investigated by increasing operating temperature up to 900oC. Oxidation rate of the alloy at 700oC in air was estimated by the increase in weight, thickness of the surface oxide and electrical resistance.
Electrochemical Characterization of Ni/Y2O3-ZrO2 Hydrogen Electrode for Water Splitting in Solid Oxide Electrolysis Cells
Authors: Pan Weiping , Chen Kongfa , Ai Na , Lü Zhe , Jiang San Ping
Published: February 2020

Ni-Y2O3 stabilized ZrO2 (Ni-YSZ) cermet is a widely used hydrogen electrode for solid oxide fuel cells (SOECs), but detailed studies regarding the water splitting processes are scarce. Here we report the preliminary results on the electrocatalytic activity of Ni-YSZ hydrogen electrode in the SOEC mode as a function of operating temperature and water concentration. The electrode activity for the water splitting reaction is strongly influenced by the water concentration and dc bias. The electrochemical performance for the water splitting reaction increases with the increase of water concentration. On the other hand, the electrode polarization resistance increases gradually with the increase of dc bias regardless of the H2O content, which is particularly pronounced in the low frequency impedance process related to the H2O dissociative adsorption and diffusion processes. The reaction mechanism and kinetics of the H2O dissociation reaction on Ni-YSZ hydrogen electrodes are discussed.
LiCoO2 -Based Composite Cathode with PO4-O2 Hybrid Framework for Lithium Ion Batteries
Authors: Min Sul Hee , Jo Mi Ru , Kang Yong-Mook
Published: February 2020

In recent decades, lithium-ion batteries have become the most widely used power source for portable electronic devices and hybrid electric vehicles (HEVs) and plug-in HEVs because it can offer high energy and power density. The most representative cathode material for commercial Li-ion batteries is LiCoO2 due to its high capacity and excellent cycle life. LiCoO2 has the hexagonal α-NaFeO2 phase consisting of the layered rock-salt structure with the order of Li+ and Co3+ on alternating (111) planes in its cubic structure. When a Li/Li1-xCoxO2 cell is typically charged within limited composition range (0 < x < 0.5, 4.2V), it shows reasonably good capacity retention. However, the discharge capacity under the cut-off voltage of 4.2 V is around only 140 mAh/g, which is much lower than the theoretical value (274 mAh/g) of LiCoO2. Unfortunately, the practical use of LiCoO2 has been limited because its stability could be rapidly deteriorated at potentials higher than 4.2 V. Some research groups have reported that the poor cycling performance above 4.2 V is caused by structural instability induced by a phase transition from hexagonal phase to a monoclinic phase, which accompanies a volume change of ~2.6 % along the c-axis. To overcome the above problems, many researchers have developed lots of surface modifications that can improve the structural stability of LiCoO2.

 In this study, we tried to control the interlayer distance variation (lattice parameter c) though the substitution of phosphorus for Li+ sites by a phosphidation process. As a result, the unwanted phase transition could be suppressed by the existence of PO4 framework formed on the surface of LiCoO2 dramatically improving the cycleability and rate capability of LiCoO2 even above 4.5 V. Using this approach, we could easily change the surface O2-framework of LiCoO2 to PO4-framework. Consequently, phosphidated LiCoO2 came to retain very high structural stability and a stable surface film was formed in contact with electrolyte during charging/discharging. Phosphidated LiCoO2 exhibited greater bulk and surface stability compared to pristine LiCoO2 even in high voltage range, suggesting that this methodology will be also promising for other high-voltage cathode materials in lithium ion batteries.
In-Operando Electrochemical-Surface Plasma Resonance (EC-SPR) Observation to the Kinetic Study of Solid Electrolyte Interface (SEI) Formation on Lithium Ion Battery
Authors: Wang Fu-Ming
Published: February 2020

A novel in-operando observation to the formation of solid electrolyte interface (SEI) has been developed. This research demonstrates that the electrochemical-surface plasma resonance (EC-SPR) is able to evaluate the step-by-step kinetic molecule interaction between the electrolyte and the surface of electrode material. In this study, a commercial electrolyte (1M LiPF6 into EC/EMC) has been used to define the SEI formation on gold (Au) electrode. Fig. 1a shows the linear sweep voltammogram (LSV) spectrum was operated at the scanning rate of 0.83 mV/s and in the operation window of 0~(-3) V. This result confirms that the SEI was formed at -1.24V and the lithium ion was going to reduce at -3V, indicating there are at least two passivation processes on this system. Fig. 1b shows a decreasing behavior of intensity difference of SPR, indicating the substances gradually covered for the Au electrode’s surface. In accordance with Fig. 1b, this spectrum can be simply separated by two slopes. The two slopes cross a point at 21.5 min, representing the reduction time of SEI. Fig. 1c also illustrate a decreasing behavior of the angle difference of incidence, indicating a continually dissociation process was taking place. However, three different slopes were discovered and strongly correlated to the result in Fig. 1b. The first slope in Figs. 1b and 1c indicate the lithium ions dissociate from ethylene carbonate (EC) molecules and moves to the Au surface when the electrochemical driving force was triggered. The second slope in Figs. 1b and 1c implies an association process (a stable intensity in Fig. 1b and a lower slope in Fig. 1c), indicating that the lithium ion joins the SEI formation at typical reduction potential on Au surface. However, Fig. 1c reveals that the Au electrode is not able to correlate the SEI formation due to the slope changes into higher value (third slope), which represents the intrinsic property of Au is different to graphite [1], implying the SEI is further dissociated from Au surface. The SEI formation on typical electrode materials such as graphite, graphene, and silicone are under researching. The EC-SPR is a powerful instrument for studying the SEI in order to character an in-operando interaction mechanism between the electrolyte molecules and electrode materials.

Fig. 1 In-operando EC-SPR observations of (a) the LSV, the sensograms of (b) the intensity difference of SPR, and (c) the angle difference of incidence.

Reference

[1] S. S. Zhang, J. Power Sources 162 (2006) 1379.

Figure 1
Study of Solid Polymer Electrolytes for Room Temperature All-Solid-State Lithium Ion Batteries
Authors: Liu Jin , Lin Yue , Zhang Cheng , Liu Yexiang
Published: February 2020

All-solid-state lithium ion batteries based on solid polymer electrolytes (SPEs) have shown high commercialization and technical values. However, severe capacity decay of the batteries occurs as a decrease of working temperature. This is mainly due to low lithium ionic conductivity of SPEs at room temperature. Hence, preparation of SPEs with high ionic conductivities for wide temperature applications of all-solid-state lithium ion batteries remains a challenge. In this study, preparation, structure and electrochemical properties of SPEs as well as fabrication of all-solid-state lithium ion batteries using the SPEs are investigated. Results show that lithium ionic conductivity and electrochemical stability of the SPEs can be adjusted by simultaneously grafting cyclic carbonate and combed poly(ethyleneoxide) on polysiloxane. The LiFePO4/Li batteries with the SPEs present excellent cycling performance in the temperature range from 25 to 100 oC.
Application of Graphene-Based Electrodes in Lithium-Ion Battery
Authors: Agostini Marco , Hassoun Jusef
Published: February 2020

The recent widespread of electric (EVs) and hybrid vehicles (HEVs), with the final goal of reducing the greenhouse gas emission and atmosphere pollution, required efficient and clean power sources. Due to their high energy density, lithium-ion batteries are an ideal candidate as side system to store energy from renewable sources and power electric vehicles
1
. Although appropriate for the consumer electronic market, the present lithium-ion battery technology is still inadequate for the electric motion. The large diffusion of LIBs is still prevented by issues, including poor safety, high cost, restrict operating temperature range and materials availability. Improvements in energy density and safety, as well as reduction in cost, are mandatory steps to meet the EVs and HEVs severe targets
2
. Among the issues of LIBs technology, low theoretical capacity of the graphite anode, i.e. 372 mAh g-1, represents a limiting parameter. Indeed, great attention is now focusing on the study of alternative anode material such as Sn (994 mAh g-1), Si (4200 mAh g-1) or SnO2 (782 mAh g-1), however their application is still limited by the large volume changes upon lithium alloying-de-alloying processes. Recently, the suitability of the graphene as negative electrode in replacement of the commercial graphite anode has been demonstrated. Graphene-based electrodes have the possibility to accommodate increased amount of Li-ions in respect to common graphite
3
, thus allowing a capacity value two to three times higher in respect to graphite. Herein, we report the use of different types of graphene-based electrodes in lithium-ion cell.

[1] M. Armand and J.M. Tarascon, Nat. 2008, 451, 652.

[2] B. Scrosati, J. Garche, J. Power Sources 2010, 195, 2419.

[3] J. Hassoun, F. Bonaccorso, M. Agostini, M. Angelucci, M.G. Betti, R. Cingolani, M. Gemmi, C. Mariani, S. Panero, V. Pellegrini, B. Scrosati, Nano Letters 2014, 14, 4901.

Figure 1
Magnesium Ion Behavior in Ionic Liquids for Mg-Ion Power
Authors: Sutto Thomas Edward
Published: February 2020

Our work here has focused on the behavior of Mg2+
in bis(trifluoromethane)sulfonyl imide based ionic liquids.  Charge discharge behavior of both amorphous carbon and graphene have been studied vs. Mg metal as potential anode materials for a rechargeable Mg-ion based battery.  Additional work has looked into oxide nanoparticles of the general format of Mg(M1M2)O2 prepared via a novel, flash solution oxidation process.  Results will be presented focusing on the primary effort to develop cathode materials for Mg ion systems with high reversibility and capacity.

Figure 1
Optimization of Process Parameters during Solid State Synthesis of LiMn2O4 as Cathode Material for Lithium-Ion Batteries
Authors: van Holt Désirée , Sun Ruoheng , Hoffmann Anja , Eurich Svitlana , Jakes Peter , Schierholz Roland , Granwehr Josef , Kungl Hans , Eichel Rüdiger-Albrecht , de Haart L.G.J.
Published: February 2020

One focus of the present research of Lithium-Ion Batteries is the development of higher energy and higher power density materials. Spinels like LiMn2O4 exhibit a potential of 4.1 V v.s. Li/Li+ that can be further increased by substitution of Mn by transition metals like Ni. Those substituted spinels like LiMn1.5Ni0.5O4 are highly interesting cathode-materials for the high-energy range up to 5 V. The synthesis of spinels via a solid state route enables the production of high amounts up to 100 g with inexpensive starting materials and a combined step for milling and homogeni­zation of the raw materials. However, the solid state synthesis is a challenging approach regarding an adequate homogenization and a potential eva­po­ra­tion of Li during calcination[1].

The present work aims the characterization of calcined cathode-materials to control the processing parameters in order to prepare single-phase spinel materials. Therefore, different compositions of LixMn2O4 have been synthesized from Li2CO3 and MnO2 as starting materials, applying different milling parameters and calcination conditions. The calcined powders were then characterized by powder diffraction (XRD) and electron-paramagnetic-resonance spectroscopy (EPR). It is known that Li2MnO3 might be formed during the calcination process as an undesirable lithium-rich secondary phase[2]. Thus, particular attention has been paid on this phase. The formation of Li2MnO3 may occur by non-homogeneous mixing or remaining coarse particles of Li2CO3 in the powder mixture. The EPR is a highly sensitive method to obtain even small amounts of Li2MnO3 besides LiMn2O4in the calcined product and is therefore highly interesting for this application.

[1] Y. Lee, The Effects of Lithium and Oxygen Contents Inducing Capacity Loss of the LiMn2O4    Obtained at High Synthetic Temperature, Journal of Electroceramics, 9, 209 – 214, 2002.

[2] V. Massarotti et al., Stoichiometry of Li2MnO3 and LiMn2O4 Coexisting Phases: XRD and EPR Characterization, Journal of Solid State Chemistry, 128, 80 – 86, 1997.
Fully-Reversible Solid-State Li-Ion Rechargeable Battery Composed of Positive and Negative Electrodes with the Same Active Material
Authors: Baba Mamoru , Ye Rongbin , Ohta Koji
Published: February 2020

In this paper, we found out for the first time that the fully-reversible solid-state Li-ion rechargeable battery composed of positive and negative electrodes with the same active material Li2Mn2O4.  It should be noted that the present novel reversible operation is observed because of the solid-state Li-ion battery.  It will be expected that such a reversible battery is expected to be refreshed on the backward stage, when the RiLiB battery has run down at last on the forward stage,
Investigating the Surface Segregation of Perovskite Thin Films to Optimise the Redox Behaviour for Application in Metal-Air Batteries
Authors: van den Bosch Celeste Anna Maria , Harrington George Frederick , Skinner Stephen J. , Aguadero Ainara
Published: February 2020

It is essential to improve energy storage in tandem with developing renewable energy alternatives as an intrinsic challenge of renewable energy sources is irregular power production. Currently oxygen evolution and oxygen reduction are two key electrochemical reactions which limit the efficiency of energy storage devices including metal-air batteries. Hence, improving these reactions would greatly benefit the development of a renewable energy economy.

It has previously been demonstrated that the perovskite La0.5Sr0.5Co0.5Mn0.5O3-
δ (LSCM) [1] can reversibly accommodate both a fully oxidised phase (δ = 0) and a reduced phase (δ = 0.62), making this the most hypo-stoichiometric simple perovskite reported to date (Figure 1). The oxygen vacancies introduced as a result of this variable stoichiometry as well as the potential range of transition metal oxidation states make this material an ideal candidate to investigate as a redox mediator for oxygen reduction and evolution reactions.

The ability to tune and control the defect structure of this system will allow optimisation of the electrochemical behaviour. With this is mind, LSCM thin films of 10 – 75 nm thick have been prepared by pulsed laser deposition with initial x-ray diffraction results indicating a change in lattice structure depending on the substrate the films are deposited on likely due to strain effects [2].

Since the surface characteristics are fundamental factors that governs the activity of these materials, further characterisation of the films included low energy ion scattering (LEIS) to consider segregation effects (Figure 2) [3], atomic force microscopy and x-ray photoelectron spectroscopy to determine changes in transition metal oxidation state. The redox activity of LSCM under different polarisation conditions has been investigated with isotopic labelling through secondary ion mass spectroscopy [4].

A systematic study of the La0.5Sr0.5Co0.5Mn0.5O3-
δ thin films has shown that we can control the cell parameters of LSCM by growing thin films on different substrates. The LEIS measurement revealed that the induced strain may be affecting the surface termination and hence, may be instrumental in optimising the electrochemical behaviour of the perovskite.

Figure
1 – Thermogravimetric analysis of La0.5Sr0.5Co0.5Mn0.5O3-δ

Figure 2 – Comparison of the elemental composition of La0.5Sr0.5Co0.5Mn0.5O3-δ thin films on lanthanum aluminate (LAO, left) where in-plane compressive strain is expected and magnesium oxides (MgO, right) substrates where tensile strain of the thin films is expected

[1] A. Aguadero, et. al., Angew. Chem. Int. Ed. Engl., 2011, 50, 6557–61.

[2] M. Kubicek, et. al., ACS Nano, 2013, 7, 3276–86.

[3] J. Druce, et. al., Solid State Ionics, 2014, 262, 893–896.

[4] J. A. Kilner, et. al., J. Solid State Electrochem., 2011, 15, 861–876.

Figure 1
New Generation High Performance Lithium-Ion Capacitor Laminate Cells
Authors: Cao Wanjun , Chen Xujie , Shih Jonathan , Zheng Jim P.
Published: February 2020

In recent years considerable research has been focused on the development of high energy density EC capacitors. Among all the energy storage systems that have been investigated and developed in the last few years, Lithium-ion Capacitors (LICs) have emerged to be one of the most promising because LICs achieve higher energy density than conventional Electric Double-Layer Capacitors (EDLCs), and better power performance than Li-ion batteries (LIBs) as well being capable of long cycle life which is shown in Fig. 1. LICs contain a pre-lithiated LIB anode electrode and an EDLC cathode electrode. Previously, we have reported a LIC with activated carbon (AC) cathode and hard carbon (HC)/stabilized lithium metal powder (SLMP) anode electrodes with high energy density, high power density and long cycle life1-7. From all the study before, we have achieved a high energy density LIC pouch cell4 with an energy density as high as 30 Wh kg-1 but only with a usable specific power of about 1.0 kW kg-1 and a maximum specific power of 2.0 kW kg-1. Therefore in this paper, we wish to report new generation high performance LIC laminate cells with higher power density and longer cycle life by sacrificing the energy density of the cells. The low temperature performance of the LIC laminate cells is also included in this paper. It can be concluded from the following data figures (from Fig. 2 to Fig. 4) that the specific energy and energy density as high as 20 Wh kg-1 and 38 Wh L-1 have been achieved, respectively. The laminate cells obtained a maximum specific power of 7.8 kW kg-1, respectively. The developed LICs can operate in a temperature as wide as from -40 degree C to +70 degree C. After 50,000 cycles, the LIC laminate cells still have 92% of the initial discharge capacity.

References:

1. J.P. Zheng and W.J. Cao, The 20th International Seminar on Double Layer Capacitors and Similar Energy Storage Devices, Florida Educational Seminars Inc. (2010).

2. W.J. Cao, J.P. Zheng, J. Power Sources, 213, (2012) 180.

3. W.J. Cao and J.P. Zheng, J. Electrochem. Soc. 160, (2013) A1572.

4. W.J. Cao, J. Shih, J.P. Zheng, T. Doung, J. Power Sources, 257, (2014) 388-393.

5. W.J. Cao, Y.X. Li, B. Fitch, J. Shih, J.P. Zheng, J. Power Sources, 268, (2014) 841-847.

6. W.J. Cao, J.S. Zheng, D. Adams, T. Doung and J.P. Zheng, J. Electrochem. Soc., 161(14), (2014) A2087-A2092.

7. W.J. Cao, M. Greenleaf, Y.X. Li, D. Adams, M. Hagen, T. Doung, J.P. Zheng, J. Power Sources, 280, (2015) 600-605.

Figure 1
Using Nanostructured Materials to Develop Anodes for Lithium -Ion Batteries and Increase the Efficiency of Photovoltaic Cells
Authors: Stewart Jimmel
Published: February 2020

Renewable energy resources have become one of the most important challenges of the 21st century. One way to tackle the problem of the growing need for a low cost and environmentally friendly storage system is to invest and develop in new research. One solution is to build on the advancements of silicon solar cells and silicon electrode materials for lithium-ion batteries and to consider using nanostructured materials to develop hybrid functional energy materials. This research looks at the use of atomistic simulations to design silicon nanotubes and particles with an enhanced energy harvesting and storage properties. As for carbon, nanotubes with different structures and properties can be created by rolling a layer of graphene in different directions. For silicon, it is found that independent of the way the tubes are created they show metallic behaviour, as opposed to carbon nanotubes which demonstrate both semi-conducting as well as metallic properties. Contrary silicon nanoparticles are insulating in agreement with previous studies. This finding is important for applications in high energy density energy storage applications, where metallic silicon can be employed both as the anode and the cathode material, but it would also improve the efficiency of photovoltaic cells.
Electrode Engineering: Impact of Processing and Design Towards Performance of Nano-Silicon Anodes
Authors: Peters Fabian , Fenske Daniela , Schmerling Marcus , Kohl Mario , Schwenzel Julian
Published: February 2020

Silicon based materials show highest capacity among state-of-the art anode materials for LIBs and next generation batteries. Silicon anodes attract wide attention due to high specific capacity of Si, i.e. 3590mAh/g for Li15Si4 phase at room temperature.

As known, large volume changes and subsequent pulverization of brittle Si during cycling can be alleviated by using nano-sized Si particles [1]. However, the surrounding binder matrix still has to compensate large stress and strain induced by accumulated volume changes of the single particles.

The works presented here focus on the challenges on the electrode level. Choice of binder is crucial to create a matrix that can accommodate mechanical stress and strain during prolonged charge/discharge cycles. For reliable comparison of the impact of active material/binder ensembles, equal properties of electrodes (loading, porosity) are very important and hence receive special attention.

To investigate the impact of processing and electrode matrix in more detail, electrodes with high Si contents (60 to 80wt.%) and controlled, application-related loadings are produced. Characterization is carried out in laboratory sized pouch bag cells. Crucial parameters such as binder, processing, loading and voltage regime on available capacity and cycle life are discussed. Remaining reversible capacity of more than 1500mAh/gcoating (1875mAh/gSi) after 100 cycles at 0.5C is reported. Remaining electrode capacity is approx. 1.5mAh/cm² at this point.

[1]: H. Wu, Y. Cui, Nano Today (2012)

Figure 1
Storage Fading Mechanism of a Commercial 18650 Cell Comprised with Composite NMC/LMO Cathode and Graphite Anode
Authors: Wu She-huang , Lee Po-Han
Published: February 2020

In this study, the capacities and electrochemical impedances at various states of charge (SOC) are measured after the screened commercial 18650 lithium ion cells assembled with composite cathode of layered mixed oxide (NMC) and spinel lithium manganite (LMO) and graphite anode were stored at various states of depth-of-discharge (DOD) at various temperatures for various durations. The results manifest that the capacity fading is strongly affected by the storage temperature and becomes prominent at temperatures higher than 45oC. Incremental capacity analyses (ICA) for the charge/discharge curves before and after storage were performed for the qualitative mechanism study. It demonstrates that the capacity fade of the cell stored at 60oC and 0% DOD can be attributed to the loss of active materials, and the loss of graphite anode is higher than that of composite cathode. The capacity fade of the cell stored at 60oC and 25% DOD can be caused by the lithium inventory loss, the loss of NMC, and the loss due to the morphology change of LMO. Cell stored at 50% DOD manifests similar fading behavior as that of the cell stored at 0% DOD, however, the ICA plots demonstrate that the capacity loss of the cell comes from losses of lithium inventory and NMC caused by the dissolution of transition metals with additional losses of LMO and graphite anode occur after 10 months of accumulated storage. For cell stored at 75% DOD, most the capacity loss can be due to the loss of NMC with minor contribution of lithium inventory loss, while cell stored at 100% DOD shows almost no change after storage for 12 accumulated months. These results revealed from the ICA study are consistent with those determined from the post mortem study of the electrodes obtained from cells before and after storage.