bluuebunny/crossref_metadata_2025 huggingface dataset:
Composite "Layered-Layered-Spinel" Electrodes for High Energy Lithium-Ion Batteries
Authors: Park Joong Sun , Croy Jason R. , Long Brandon R. , Lee Eungje , Thackeray Michael M.
Published: February 2020

The lithium- and manganese-rich class of composite materials, xLi2MnO3•(1-x)LiMO2(M=Ni ,Mn, Co), have attracted  great interest as  next generation cathode materials for advanced lithium ion batteries [1]. Significant capacities of over 250mAh/g can be achieved with x values between 0.3 and 0.5; however these electrodes suffer from severe structural and electrochemical decay related to voltage fade and hysteresis [2].

Recently, structurally compatible spinel components have been incorporated into the ‘layered-layered’ structures, and it has been demonstrated that these new ‘layered-layered-spinel’ composites, with formula y[xLi2MnO3•(1-x)LiMO2]•(1-y)LiM2O4), show enhanced electrochemical properties including high first cycle efficiency and good structural stability through careful control operating voltage and composition [3,4]. In a recent study it was found that the cobalt concentration plays an important role in controlling the cycling stability of ‘layered-layered-spinel’ composites [4].

This presentation will discuss results on electrochemical properties of ‘layered-layered-spinel’ composites obtained by further exploring and optimizing electrode compositions and structures. In particular, the effect of nickel and manganese concentrations on tailoring of structures and electrochemical performance will be reviewed.

References

[1] M. M. Thackeray, C. S. Johnson, J. T. Vaughey, N. Li, and S. A. Hackney, J. Mat. Chem., 15, 2257 (2005).

[2] J. R. Croy, K. G. Gallagher, M. Balasubramanian, B. R. Long, and M. M. Thackeray, J. Electrochem. Soc, 161, A318 (2014).

[3] D. Kim, G. Sandi, J. R. Croy, K. G. Gallagher, S.-H. Kang, E. Lee, M. D. Slater, C. S. Johnson, M. M. Thackeray, J. Electrochem. Soc., 160, A31 (2013).

[4] B. R. Long, J. R. Croy, J. S. Park, J. Wen, D. J. Miller, M. M. Thackeray, J. Electrochem. Soc, 161, A2160 (2014)

 

Acknowledgment

Support from the Vehicle Technologies Program, Hybrid and Electric Systems, in particular, David Howell, Peter Faguy, and Tien Duong at the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, is gratefully acknowledged.  

The submitted document has been created by UChicago Argonne, LLC, Operator of Argonne National Laboratory (“Argonne”). Argonne, a U.S. Department of Energy Office of Science laboratory, is operated under Contract No. DE-AC02-06CH11357. The U.S. Government retains for itself, and others acting on its behalf, a paid-up nonexclusive, irrevocable worldwide license in said article to reproduce, prepare derivative works, distribute copies to the public, and perform publicly and display publicly, by or on behalf of the Government.
Performance Enhancement of Li4Ti5O12 and Si/C Electrodes Using Graphene/CMC Conductive Composite Binder
Authors: Lee Ji-Eun , Choi In-Yeong , Oh Eun-Suok
Published: February 2020

Lithium titanium oxide (Li4Ti5O12, LTO) is a prospective anode material for high-powered and long-lasting Lithium Ion Batteries (LIBs) due to its fast cycle reversibility and zero-strain during charge/discharge processes. Despite these advantages, there is a major drawback that LTO has low electrical conductivity, leading to relatively worse performance at high current rates[1].

Another promising anode material for LIBs is silicon due to its very high capacity of 4200 mAh/g. However, the critical defect of silicon is huge volumetric change during charge/discharge processes, ultimately resulting in the isolation of silicon from conductive materials.

In order to overcome these problems, we try to enhance electrical conductivity of LTO and Si electrodes using a conductive composite binder, graphene/carboxymethyl cellulose (CMC). To evaluate the effect of the conductive composite binder, physical and electrochemical characteristics have been tested by FT-IR, cycle performance, rate capability, Cyclic Voltammetry (CV) and Electrochemical Impedance Spectroscopy (EIS), and so on.

 

Reference

1. Sang-Wook Han, So-Jin Kim, and Eun-Suok Oh, Journal of The Electrochemical Society, 161 (4) A587-A592 (2014)
(Invited) High Electrochemical Performance of High Voltage LiNi0.5Mn1.5O4 By Decoupling the Ni/Mn Disordering from the Presence of Mn3+ ions
Authors: Kang Byoungwoo
Published: February 2020

High energy density of a lithium ion battery (LIB) is an essential requirement for novel applications such as plug-in hybrid electric vehicles and electric vehicles. Increasing the redox potential of cathode materials is an effective way to achieve high energy density in the cell. For this purpose, high-voltage spinel LiNi0.5Mn1.5O4 (LNMO) is a promising cathode material for LIBs because it has a high redox potential of ~ 4.7 V, which makes its energy density (~650 W∙h/kg) 20% higher than that of conventional LiCoO2. However, the electrochemical properties of LNMO spinel depend on several factors such as its structure, the quantity of Mn3+ ions, the particle size, and the morphology of particles.

  Especially, the structure of the spinel has a critical influence on its electrochemical performance. LNMO structure is dictated by the ordering of Ni and Mn at two octahedral sites, which take two forms: disordered and ordered spinel. However, under typical experimental conditions, disordered spinel shows the disordering of Ni/Mn with the presence of Mn3+ ions, whereas ordered spinel shows the ordering of Ni/Mn without Mn3+ ions. As a result, electrochemical properties of the disordered spinel always depend on both the disordering of Ni/Mn and Mn3+ ions. For example, disordered spinel shows an extended solid-solution reaction during phase transformation whereas ordered spinel shows two distinct two-phases reactions. Furthermore, the presence of Mn3+ ions in the disordered spinel increases its electronic conductivity, and thereby improves its electrochemical performance. Therefore, disordered LNMO spinel can have better electrochemical performance than ordered spinel due to high electronic conductivity and facile phase transformation. The origin of the different electrochemical properties in the disordered spinel is not clear because of the coupling of the Ni/Mn disordering with Mn3+ ions. Understanding of this origin could guide improvement of LMNO’s electrochemical properties. However, experimentally understanding the effect of disordering or the effect of Mn3+ ions on the electrochemical properties is not easy because the Ni/Mn disordering is always coupled with the presence of Mn3+ ions.

  In this presentation, we will discuss the effect of the Ni/Mn disordering without the presence of Mn3+ on the electrochemical performance. At first, the Ni/Mn disordering was decoupled from the Mn3+ ions in this study. By using this decoupling, we will show how the Ni/Mn disordering affects electrochemical properties and the phase transformation behavior. Furthermore, we will discuss about key factors affecting superior rate capability in high voltage spinel by decoupling of the disordering from Mn3+ ions.
Low-Temperature Prepared Lithium-Cobalt-Nickel-Oxide Spinels
Authors: Lee Eungje , Croy Jason R. , Park Joong Sun , Johnson Christopher , Thackeray Michael M.
Published: February 2020

LiMn2O4-based spinel materials have been one of the most important types of cathode materials in current lithium-ion batteries since layered LiCoO2 was used in the first commercial products by Sony Corporation in 1991. While LiCoO2 is still the preferred cathode of choice for portable electronic devices such as mobile phones, cameras, and laptop computers, the LiMn2O4-based spinels, which have low price and high power performance, are finding application in batteries for electric vehicles.1

Compared to the extensive understanding of manganese-based spinel materials, relatively little is known about the structural and electrochemical properties of cobalt-nickel-based spinel electrodes, since lithium-cobalt-nickel-oxides stabilize as a layered structure during high-temperature synthesis. However, low-temperature firing of precursor materials during the solid state synthesis of layered oxide compositions, particularly those with high cobalt content, can result in intermediate structures with quasi-spinel character.2,3 A significant advantage of these Li-Co-Ni-O (LCNO-S) spinel structures is that they offer an attractive ~3.6 V vs. lithium, i.e., approximately 600 mV higher than their manganese analogues. Moreover, unlike manganese, cobalt has a lower propensity to migrate during the electrochemical reactions. In this presentation, the low-temperature prepared LCNO-S materials will be revisited to delve into their structural and electrochemical properties.

References

1.   M. M. Thackeray, C. Wolverton and E. D. Isaacs, Energy & Environmental Science, 5, 7854 (2012).

2.   R. J. Gummow, M. M. Thackeray, W. I. F. David and S. Hull, Materials Research Bulletin, 27, 327 (1992).

3.   R. J. Gummow and M. M. Thackeray, Solid State Ionics, 53, 681 (1992).
Use of Swcnts to Increase the Energy Density of Li-Ion Batteries
Authors: Bobrenok Oleg , Kosolapov Andrew , Tikhonov Konstantin , Notman Konstantin
Published: February 2020

New advances in synthesis of single wall carbon nanotubes (SWCNTs) allowed for the first time to produce multi-ton quantities of this unique material while significantly reducing its cost, opening up many commercial applications in energy storage.

One of the applications is the use of SWCNTs as a conductive additive for high energy Li-ion batteries. It was found, that electrical properties of SWCNTs allow to reduce the amount of it in cathode and anode formulations to below 0.1% versus typical 2-5% of carbon black, maximizing the percentage of active materials and increasing the energy density of the Li-ion cells. Investigation of the electrode formulations revealed uniform distribution of SWCNT throughout the electrode structures, reinforcement of the electrode structure resulting in improved mechanical properties and electrochemical performance with both cathode and anode materials. In this presentation we will discuss the properties of commercially made SWCNTs and their comparison to MWCNTs and typical conductive carbons.

Technical challenges facing application of SWCNTs in batteries include preparation of stable dispersions and formulation of electrodes with good electrical and mechanical properties. The results on various polymer dispersants will be presented along with ways of accommodating low concentration dispersions into the material mixing process and battery  manufacturing.

Test data was generated with LCO, LFP and NCM cathode materials and Si anode material will be discussed in detail with short term rate capability and long term cycle life and storage results.
Interrogation of Active Battery Material Intrinsic Properties
Authors: Takeuchi Esther S , Marschilok Amy C , Takeuchi Kenneth J
Published: February 2020

The electrochemistry of an active material in a composite battery electrode may vary significantly depending on the selection of the type and amount of binder and conductive additives, as well as the preparation method used for the electrode.  Only a few studies on the electrochemistry of individual particles have been reported where the lithiation or delithiation of individual particles of the pure active material in the absence of any additives was conducted. These types of studies provide the ability to interrogate the intrinsic properties of an active material directly without the complications of a composite electrode.  

Here we report the electrochemistry, conductivity, and visual changes associated with the electrochemical reduction of small individual particles of electrochemically active material.   Our examination of individual small particles involves aggregates of several crystallites where the influence of grain boundaries must be considered.  In addition to quantitative electrochemistry, the particles were characterized as a function of state of charge.   For example, a nanoprobe system was utilized to determine the resistance of the particle.  Different locations within an individual particle were measured and probed the local resistance changes as a function of particle reduction.   Finally, correlation of the behavior of the individual particle was reconciled relative to bulk material electrochemical performance.  This study will help elucidate the behavior of mesoscale energy storage systems.
In Situ solvothermal synthesis of High-Energy Cathodes for Lithium-Ion Batteries
Authors: Bai Jianming , Wang Liping , Wang Feng
Published: February 2020

For the large-scale application of lithium-ion batteries in electric vehicles and grid-scale storage, it has been of great interest to develop cost-efficient solvothermal methods to synthesize high-energy electrodes. As synthesis is generally carried out in a sealed reactor, like a black box where the inputs and outputs are known, little is known about the intermediate phases and the overall reaction pathway. In addition, the synthesis condition is far from thermodynamic equilibrium, implying that the reactions and induced phase transformations often proceed along a kinetics-controlled pathway that excludes the feasibility of following synthesis reactions using ex-situ methods.  Herein, we report our latest results from development and application of in-situ techniques and capabilities for studying synthesis reaction in real time during preparing cathode materials (Fig. 1). Specific examples will be given on time-resolved XRD studies of solvothermal synthesis of high-energy polyanioic cathodes (i.e. LiFexMn1-xPO4, Li-V-PO4),1, 2to show how insights gained from these studies can be applied to gain precise control of the phase, stoichiometry and morphology. This research was supported by DOE-EERE under the Advanced Battery Materials Research (BMR) program, under Contract No. DE-SC0012704.

[1] J. Bai, J. Hong, H. Chen, J. Graetz and F. Wang, J. Phys. Chem. C.119, 2266 (2015).

[2] L. Wang, J. Bai, P. Gao, X. Wang, and F. Wang, Structure tracking aided design and synthesis of Li3V2(PO4)3 nanocrystals as high-power cathodes for lithium-ion batteries (submitted).

Figure 1
Dimensionally Stable and Fast-Charging Graphite-Silicon Planar Composite Anode for Li-Ion Batteries
Authors: Wu Nae-Lih , Yang Nai-Hsuan , Wu Yu-Shiang , Chou Jackey
Published: February 2020

Advanced Li-ion batteries (LIBs) have been developed to have high capacity density, long cycle life, and high-rate performance for portable electronics, electric vehicles (EVs), and renewable energy storage. Graphite is currently the predominant anode material for commercial LIBs because it has a low cost, low charge/discharge plateau potential, satisfactory specific capacity (372 mAh/g), and substantially high dimensional stability; its essential role in high-energy LIBs is expected to continue. Si is a potential Li-insertion anode material that has a substantially higher capacity than graphite but is susceptible to large (>300% when fully lithiated) volume expansion. The cyclic dimensional variations during charge/discharge cycles result in pulverization and electrical disconnection from the conductive paths of the Si active materials, leading to rapid capacity reduction during the cycles. In spite of a large amount of literature devoted to solving this issue in the past years, long-lasting Si anode up to now remains as a formidable challenge. On the other hand, composite anodes comprising graphite and limited amount of Si or Si oxide may be attractive transient products for advanced high-energy LIBs before viable Si-dominant anodes are realized. Moreover, improvement in the rate capability of Si-based anodes is needed for meeting the power requirements of various applications.

In this presentation, a planar graphite-silicon composite Li-ion battery anode showing substantially higher capacities than graphite, fast-charging capability, and exceptional cycle stability will be described. The Si oxide-coated graphite flake (SGF) composite anode for Li-ion batteries (LIBs) synthesized by a unique microwave-heating process of graphite flakes (GFs) in a solution made of liquid polysiloxanes as the Si-containing precursor. Microwave-heating of the GFs induces the deposition of a conformal Si-containing conformal layer on the GF surfaces, which subsequently turns into oxide-graphite-oxide sandwiched planar composite structure. The resulting SGF exhibits a reversible specific capacity of nearly 480 mAh/g, 97% capacity retention at the current density of 2.5 A/g (~5C-rate), and 95% capacity retention after 400 cycles with an average Coulombic efficiency > 99.9%. The data suggest new strategies for both designing and synthesizing high-performance anode materials for LIB applications.

Figure 1
Pulsed Laser Deposited Sns-Snse Composite Thin Film As a New Anode Material for Lithium Storage
Authors: Liu Xiaojiang , Liu Jiabing , Cui Yanhua
Published: February 2020

In recent years tin-based materials has been subjected as promising anode materials due to a high theoretical capacity of Li4.4Sn (994mAh g-1). However, tin-based materials is still far away from practical use since it suffers from significant volume change. It has been demonstrated that nano-thin film have its unique characteristics than bulk materials.

In this work, SnS-SnSe composite thin films are synthesized by plused laser deposition. Its first discharge capacity was 1225.8 mAh g-1 and capacity after three cycles maintained about 650 mAh g-1. SnS-SnSe composite thin film firstly reacted with Li during discharge to form Li2SALi2Se and Sn, then Sn reacted with Li to form LixSn alloy. During the charge, LixSn firstly decomposed to form elementary Sn, then Sn catalyzed Li2S and Li2Se to decompose to rebuild SnS-SnSe composite thin film. Li2S and Li2Se produced during discharge can suffer a certain amount of volume change which enhanced the cycle performance. SnS-SnSe composite thin film had more grain boundary than SnS or SnSe thin film which could effectively enhance electrochemical activity and increase capacity.

Fig.1 The first three CVs of SnS-SnSe composite thin film

Fig.2 Galvanostatic charge-discharge curve of SnS-SnSe composite thin film electrodes

Fig.3 Cycling performance of SnS-SnSe, SnS and SnSe thin films with 20 cycles

Acknowledgements

The authors appreciate the financial support of LPMT, CAEP (ZZ13007), Project 2013A030214 supported by CAEP.

Figure 1
3D Paper-Based Lithium-Ion Batteries Using Origami Folding Principles
Authors: Cheng Qian , Chan Candace K.
Published: February 2020

Recently, there has been much interest in the development of energy storage and electronic devices using paper and textile components. The low cost, roll-to-roll fabrication methods, flexibility, and bendability of these substrates are attractive for high-performance devices. Many flexible devices demonstrated using paper or cellulose components include organic field effect transistors, RF devices, sensors, microfluidics, displays, transparent conducting films, and light-emitting diodes and 3D antennas. Specifically for energy storage and conversion applications, the ability for the power source to be intimately integrated to unconventional substrates has motivated research in flexible devices such as batteries, supercapacitors, nanogenerators, solar cells, and fuel cells.

For applications such as MEMS, smart dust motes, and on-chip power, there is an increasing need for batteries with high energy areal energy due to the limited area available in the device. However, it is difficult to increase the energy per footprint area in 2D, planar devices since increasing the thickness of the active material layers also leads to a corresponding increase in resistivity and decrease in electrochemical performance.

To address these issues, we have taken an approach that uses the conventional 2D planar battery platform but applies origami folding concepts typically used to fold paper into more compact shapes in order to realize a Li-ion battery with higher areal charge storage capacity. Origami paper folding techniques, namely the Miura-ori pattern, were used to compact a Li-ion battery and increase its energy per footprint area. Full cells were prepared using Li4Ti5O12 and LiCoO2 powders deposited onto paper coated with carbon nanotubes as current collectors. Our 5 x 5 folded cell was found to display a ~14X increase in areal energy density compared to the planar version. 

 References:

Q. Cheng, Z. Song, T. Ma, B.B. Smith, R. Tang, H. Yu, H. Jiang, C.K. Chan, Nano Lett., 13, 4969-4974 (2013).

Z. Song, T. Ma, R. Tang, Q. Cheng, X. Wang, D. Krishnaraju, R. Panat, C.K. Chan, H. Yu, H. Jiang, Nature Commun., 5, 3140 (2013).
Synthesis of MoO2 and Nitrogen-Doped Carbon Nanotubes Composite Materials By Electrodeposition As Binder-Free Electrode for Lithium-Ion Batteries
Authors: Cui Yanhua , Zhang Hui
Published: February 2020

Molybdenum dioxide (MoO2) have attracted much attention as an electrode material for lithium ion batteries because of  high theoretical capacity. But bulk MoO2 exhibits low specific capacity and poor cycle stability because of the inert kinetics and significant structure change during the insertion/deinsertion of lithium ions. To address these problems, different nano-morphologies  MoO2 is prepared to improve the specific capacity and enhance the cycle performance. Despite the superior specific capacity is obtained, the cycle performance of pure MoO2 is still not satisfactory. Another effective strategy to address these problems is to composite MoO2with high electro-conducting carbon materials.

In this work, MoO2 and N-CNTs nanocomposite have been successfully synthesized by a facile electrodepositon method followed by thermal annealing in argon atmosphere. As an anode material for lithium ion batteries, electrochemical behavior of the nanocomposite has been studied. The as-prepared nanocomposite with desirable structural features exhibits significantly improved electrochemical performance compared to pure MoO2 or N-CNTs, resulting from that the conductive and elastic carbon nanotube can effectively mitigate the strain caused by structural and volume change and prevent the aggregation of active materials during cycling. This novel architecture of the nanocomposite has the advantage of the high inherently higher capacity of the MoO2as well as the good cycle performance of the N-CNTs, feature which make the nanocomposite a promising anode material for lithium ion batteries.

Acknowledgements

The authors appreciate the financial support of LPMT, CAEP (ZZ13007), Project 2013A030214 supported by CAEP.

Figure 1
Design and Performances of Three-Dimensional Lithium-Ion Battery
Authors: Yang Ho-Jung , Park Hwi-Yeol , Cho Kyung-Hoon , Heo Jin S. , Nam Seunghoon , Jeong Huisu
Published: February 2020

High-power and high-energy densities of lithium ion batteries are required, whereas there has been much less progress in the improvement of the conventional lithium ion batteries.  Three-dimensional (3D) concept of batteries has been suggested to improve performances of batteries. A number of 3D architectures, such as 3D interdigitated rods, 3D interdigitated plates, concentric tube, and 3D aperiodic sponge structures, have been proposed in order to increase the areal energy density [1]. The 3D cells showed higher energy and power compared to the conventional structure of cells; however, their energy was limited due to the limitation of the manufacturing process.[2]

In this paper, the novel design and the performances of 3D lithium ion battery were suggested. First, the 3D trench cathode structure was rendered without a conducting agent or a binder. The cathode has an internal current collector for the electronic conduction and was controlled as a thick-film. Lipon and Li metal were applied as the electrolyte and the anode, respectively. Expansion buffers were located in the anode to stable the cell structure under the anode expansion during the charge. The design of the 3D cell increased the energy density considerably, depending on the dimension of the electrode.

References

[1] Stefania Ferrari et al, J. Power Sources, 286 (2015) 25-46

[1] Matthew Roberts et al, J. Mater. Chem, 21 (2011) 9876-90
Improving Lto Performance: Gassing, Impedance and Cycling Study
Authors: Margez Carine L , Tan Bing , Tokuoka Saori , Greszler Thomas A
Published: February 2020

SAFT’s goal is to study and understand the source of the gas being generated in LTO-LMO cells:

What are the design factors that impact the gassing?

What are the process factors that impact the gassing?

What is the relative importance of the factors?

What is the gassing mechanism?

Different electrode formulations were tested showing dramatically different gassing rates (see figures below). In addition, SAFT will share the outcome of recent electrolyte screening, cycle life improvement and impedance growth reduction experiments. From the results the mechanism of LTO gassing can be inferred and will be discussed.

Figure 1
A Study on the Conductivity and Selectivity of Lithiated Nafion Membranes in Non-Aqueous Electrolytes
Authors: Su Liang , Darling Robert M. , Gallagher Kevin G. , Xie Wei , Thelen Jacob L. , Balsara Nitash P. , Brushett Fikile R.
Published: February 2020

ABSTRACT 

In a range of electrical energy storage technologies, redox flow batteries (RFBs), which reversibly convert chemical energy to electrical energy, have shown a favorable balance of cost, safety, and performance for stationary applications. Shifting from aqueous to non-aqueous electrolytes may promise a higher cell voltage due to the extended electrochemically stable window (~ 4 V) and an enriched selection of redox materials due to the broader variety of organic solvents [1]. As a key component in RFBs, an ideal membrane should have negligible electronic conductivity, high ionic conductivity, good chemical stability and mechanical strength, and low active species crossover. However, to date, no non-aqueous membrane has been identified that simultaneously fulfills these requirements, especially high ionic conductivity and low crossover rate.

To meet aggressive established cost targets ($120/kWh), our recent work suggests the maximum area-specific resistance for non-aqueous RFBs is 2.3 Ω ∙ cm2, which corresponds to the ionic conductivity of 1.1 mS/cm and 7.7 mS/cm for a membrane with a thickness of 25.4 µm (such as Nafion® 211) and 177.8 µm (such as Nafion® 117), respectively [2].  However, there is little data on the effectiveness of successful aqueous membranes under non-aqueous conditions.  To this end, we explore the performance of lithiated Nafion 117 (Li N117) in non-aqueous electrolytes with a focus on the relationships between ionic conductivity, species selectivity, and membrane microstructure.  Key membrane properties and performance metrics are quantified in electrolytes consisting of different salt and solvent combinations.  Species crossover is studied using model compounds with positive, neutral, and negative charge.  Membrane microstructure is probed using Small Angle X-ray Scattering and solvent permeability measurements.  Results indicate a critical relationship between pore size, ionic conductivity and species selectivity and provide guidance for future research directions in non-aqueous separations.

ACKNOWLEDGEMENTS

This work was supported as part of the Joint Center for Energy Storage Research, an Energy Innovation Hub funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences.

REFERENCES

[1]. R. Darling, K. Gallagher, J. Kowalski, S. Ha and F. Brushett. Energy & Environmental Science, vol. 7, no. 11, pp. 3459-3477, 2014.

[2]. R. Darling, K. Gallagher, W. Xie, L. Su and F. Brushett. submitted manuscript
Pseudocapacitive Carbon Nanofibers Using Sodium Chloride (a.k.a common salt)
Authors: Singhal Richa , Kalra Vibha
Published: February 2020

Pseudocapacitors have gained attention due to their higher achievable energy densities than electric double layer capacitors. The most studied pseudocapacitive materials are transition metal oxides such as RuO2, MnO2, etc. and conducting polymers such as polyaniline and polypyrrole. However, these materials present some important drawbacks such as they are expensive, operate in a low voltage window, cause decomposition of the electrolyte, or have poor stability. An alternative approach is the surface modification of carbon materials to include functional groups, which can participate in pseudofaradaic charge transfer reactions and maintain the high cyclability of supercapacitors.

A novel and simple method of incorporating pseudocapacitive surface functionalities on free-standing carbon nanofibers using common salt (sodium chloride (NaCl)) is presented. NaCl enhances capacitance by modifying carbon surface functionalities, while still keeping intact the free-standing matrix of carbon nanofibers. The blend of sodium chloride and polyacrylonitrile is electrospun together, followed by pyrolysis and mild acid treatment to obtain functionalized free-standing (binder-free) carbon nanofibers. The synthesized materials have a low surface area of only 24 m2 g-1, however the electrochemical studies show a five-fold increase in specific capacitance on incorporation of NaCl (CNF-13) compared to that without NaCl (CNF-0) (Fig.1). The XPS characterization demonstrates that the presence of NaCl leads to enhanced oxygen on the surface of carbon nanofibers, particularly in the form of carboxyl groups. These carboxyl groups then facilitate the adsorption of sulfur functional groups on acid treatment. A high specific capacitance of 204 F g-1, areal capacitance of 1.15 F cm-2, and volumetric capacitance of 63 F cm-3 in 1 M H2SO4 are obtained, which are attributed to the surface functional groups participating in the pseudocapacitive redox reactions. The fabricated nanofibers demonstrate good capacitance retention at high current densities (57% at 20 A g-1) and high cyclability.

Fig. 1 Cyclic voltammograms of the treated carbon nanofibers in 1 M H2SO4 using a two-electrode test cell at a scan rate of 5 mV s-1.

References:

R. Singhal and V. Kalra, J. Mater. Chem. A, 2015, 3, 377–385.

Figure 1
Probing the Mechanical Deformation of 2D Titanium Carbide (MXene) upon Cation Intercalation at the Nanoscale
Authors: Come Jeremy , Black Jennifer , Naguib Michael , Lukatskaya Maria R. , Beidaghi Majid , Gogotsi Yury , Kalinin Sergei V. , Balke Nina
Published: February 2020

The titanium carbide Ti3C2
Tx
(where Tx
stands for termination functions at the surface such as –OH, =O, and –F) is a member of the recently discovered family of two-dimensional (2D) materials known as MXenes. This material demonstrates a high intercalation capacitance related to the rapid transport of ions within the structure, making this a promising electrode material for supercapacitors.[1] To date however, the intercalation mechanism is poorly understood and other techniques able to probe the dynamics are required. In this work, in-situ Atomic Force Microscopy is used to monitor the strain developed in a Ti3C2
Tx
electrode during intercalation/extraction of monovalent and divalent cations in a variety of aqueous electrolytes. Interestingly, the electrode undergoes a large contraction during Li+, Na+ or Mg2+ intercalation, differentiating the MXene paper from conventional electrodes where redox intercalation of ions (e.g. Li+) into the bulk phase (e.g. graphite, silicon) results in volumetric expansion. The relative deformation amplitude strongly depends on the cation radius and electric charge ranging from almost no change to over 15% of shrinkage.[2] This feature may explain the excellent rate performance and cyclability reported for MXenes.The unique mechanical changes induced by the presence of cations between the layers were investigated by Contact Resonance Piezoresponse Force Microscopy. Spatial mapping of the resonance frequency with high resolution showed that the elastic modulus of the carbide increases when Li+ ions are intercalated, in good agreement with the strong interactions between MXene sheets that leads to contraction. Furthermore, it revealed that the cation intercalation preferentially occurs at the shallow sites of the MXene flakes.

These results are exciting because they shed light on the intricate interplay of the MXene mechanical properties with the electrochemical performance. Moreover, they show that the cation dynamics in the confined 2D spaces can be efficiently probed with in-situ AFM techniques.

References

[1] M. Ghidiu et al., Conductive Two-Dimensional Titanium Carbide ‘Clay’ with High Volumetric Capacitance, Nature, 2014, 516, 78-82

[2] J. Come et al., Controlling the Actuation Properties of MXene Paper Electrodes upon Cation Intercalation, Nano Energy, under review.
Unveiling the Pseudocapacitance of Ti2C Monolayer for High Performance Electrochemical Capacitor: a First-Principles Study
Authors: Ji Xiao , Jiang Jianjun
Published: February 2020

Two-dimensional (2D) transition-metal (TM) compound nanomaterials have been widely investigated for electrochemical capacitor due to their high-surface-area and large potential of providing pseudocapacitance. Very recently, a new family of 2D materials called MXenes were synthesized and have been considered as one of the most promising pseudocapacitor electrode materials with respect to both power density and energy density. In this work, we employ first-principles calculations to study the electronic structures and redox potential and diffusion of Li on Ti2C monolayer, a representative MXene, based on density functional theory (DFT). The electronic structures indicate a significant redox pseudocapacitance characteristics as an anode with the redox potential at about 0.25 V and 0.75 V refer to the standard hydrogen electrode. Moreover, the calculated metallic behavior and low Li ions diffusion barriers suggest that Ti2C monolayer would manifest a low resistance in charging/discharging process. Our findings provide an evidence that the Ti2C monolayer is a promising electrochemical capacitor electrode material.

Figure a shows the crystal structure of Ti2C monolayer in the top view and side view. The Ti and C are revealed by yellow and blue spheres, respectively. On the top view, the lighter yellow spheres consist of the first layer with the third layer formed by dim ones. Relative dispositions of PDOS and Integral DOS of d-orbitals of Ti atoms in Ti2C monolayers are shown in Figure b both on the vacuum scale and with respect to the SHE reference. The dot dashed red lines indicate the Fermi level positions of Ti2C monolayer. The light blue region represents the electrolyte window. To deliberate the diffusion of Ti2C monolayer, three pathways (Figure c) and corresponding energy barriers (Figure d) are considered.

Figure 1
Facile Hydrothermal Synthesis of Feather-like Nickel Phosphite As Cathode Materials for Supercapacitors
Authors: Ruan Yunjun , Jiang Jianjun , Wan Houzhao
Published: February 2020

Recently, supercapacitors have attracted plenty of attentions, due to its high power density, long cycling lifespan and excellent stability. According to the charge storage mechanism, supercapacitors can be divided into double layer capacitors and pseudocapacitors. Moreover, the pseudocapacitors depend on faradic reaction and can result in much higher specific capacitance than double layer capacitors. For instance, nickel-based compounds exhibit outstanding performance reported in many literatures.

In this work, we successfully synthesize the feather-like nickel phosphite via a facile hydrothermal route at 200 ℃ for 24 h, employing Ni(NO3)2 as nickel source, sodium pyrophosphate as phosphorus source and the mixture of deionized water and glycol as solvent. The diffraction peaks of the product are well matched with the standard diffraction patterns of the orthorhombic Ni(HPO3) (H2O) (JCPDS NO. 01-082-0075) as shown in Figure 1a. The SEM image in Figure 1b reveals the morphology of the sample is feather-like structure.

Figure 2a exhibits cyclic voltammetry curves of the nickel phosphite in 6 M KOH electrolyte at different scan rate from 1 to 50 mV s-1, which indicates the electrode is highly reversible with excellent electrochemical capability and redox processes. The galvanostatic charge-discharge curves measured at different current densities are shown in Figure 2b. The corresponding specific capacitance values of the nickel phosphite are calculated from the discharge curves as shown in Figure 2c. Figure 2d shows the Nyquist plots of the nickel phosphite. Therefore, the nickel phosphite were good candidates for high performance energy storage.

Figure 1
Possibility of Methane Production from Steam and Carbon Dioxide by Using Solid Oxide Electrolysis Cells
Authors: Kato Tohru , Nagata Susumu , Honda Takeo , Negishi Akira , Tanaka Yohei , Momma Akihiko
Published: February 2020

To overcome global warming issue and energy shortage problem, economical hydrogen production technologies from renewable energy or unused fossil fuel with carbon capture technology are being developed all over the world. However it becomes the large problem that it is necessary to reconstruct energy infrastructures for production, transportation and usage of hydrogen and to entail a vast cost.

Against this problem, for effectively utilizing existing energy infrastructures, we are developing a methane producing technique from water and carbon dioxide by using renewable electricity instead of hydrogen production. Specifically, solid oxide electrolysis cell (SOEC) technology for producing syn-gas with high efficiency has been developed and we have succeeded in trial manufacture tubular SOECs whose sin-gas production rate is more than 3.5 sccm/cm2 at the operating temperature of 750 oC and electrolytic voltage of 1.35V.

Therefore, in this paper, the numerical models of an SOEC methane production system and a conventional methane production system were made in reference to performance of the tubular SOECs and dependence of performance of the each system on operating conditions, such as operating temperature, feed gas composition, is analyzed and compared with each other.

The methane producing system which combined a water electrolysis system with a high temperature water-gas shift reactor was considered as a conventional system.

From the result of the analysis, advantage of SOEC methane production system is clarified.
Influence of La/Pr Ratio on the Ageing Properties of La2-X
Pr
x
NiO4+δ as Cathodes in IT-SOFCs
Authors: Vibhu Vaibhav , Bassat Jean-Marc , Flura Aurélien , Nicollet Clément , Grenier Jean-Claude , Rougier Aline
Published: February 2020

The present study is focused on alternative oxygen electrodes for Intermediate Temperature Solid Oxide Fuel Cells (IT-SOFCs) using Metal Supported Cells (MSCs) conditions. To prevent detrimental oxidation of the metal support, sintering of the cell components at high temperature under low pO2 is required. Ln2NiO4+δ (Ln = La, Pr) compounds with the K2NiF4-type structure act as cathode materials for IT-SOFC due to their mixed ionic and electronic conductivity (i.e. MIEC properties). Pr2NiO4+δ shows excellent electrochemical properties at intermediate temperature (i.e. low polarization resistance Rp
value, Rp
= 0.03 Ω.cm² at 700 °C), while La2NiO4+δ exhibits higher chemical stability. Thus, the properties of La2
-x
Pr
x
NiO4+δ mixed nickelates were investigated with the aim to find best compromise between chemical stability and electrochemical performances.

Herein, the chemical stability of the nickelates under air at operating temperatures as well as the evolution of the polarization resistances during ageing (recorded under air at idc
= 0 and idc
≠ 0 conditions) were studied for duration up to one month. La2NiO4+δ is chemically stable whereas Pr2NiO4+δ dissociates after 1 month at 600, 700 and 800 °C. At idc
= 0 condition, the ageing of the half cells during 1 month under air shows no change in Rp
, despite their various degrees of chemical stability. A different behavior is observed under idc
≠ 0 conditions with a large increase in Rp
for Pr-rich phases in SOFC mode while interestingly, Rp
remain stable in SOEC mode. In this presentation, the electrochemical properties of La2
-x
Pr
x
NiO4+δ under ageing and postmortem analysis will be discussed in details.
Microtubular SOFC (mSOFC) System in Truck APU Application
Authors: Kendall Kevin , Newton Jill , Kendall Michaela
Published: February 2020

One of the most sought after applications for small-scale SOFCs has been the Auxiliary Power Unit (APU) for trucks. A mSOFC could provide heat for the cab whilst powering the electrical loads required when the engine is shut down. Significant development efforts have been made by several large companies including Delphi, AVL and Volvo, all using planar configurations with diesel as the fuel. However the planar construction is prone to damage via cracking and use of diesel fuel is known to require problematic reforming. Despite large research funding from SECA and other sources, directed especially toward the 5kWe unit since 2000, there is still no commercial product in the market. The purpose of this paper is to discuss three novel ideas applied to this attractive market area:-

Replacing the planar stacks with mSOFCs to give greater robustness

Downsizing to 100We to allow more rapid evolution

Focusing on dual fuel trucks using LNG as clean fuel for the SOFC

An EU project was initiated in 2014 to develop these ideas under the heading SAFARI (SOFC APUs For Auxiliary Road-truck Installations) funded by FCH-JU with 6 partners in the UK, Spain, Poland and Switzerland.  This paper describes results from the first 18 months of the project and shows that mSOFCs operating on LNG can give significant impact in the marketplace.
Modeling of Ni Diffusion Induced Austenite Formation in Ferritic Stainless Steel Interconnects
Authors: Chen Ming , Molin Sebastian , Zhang Lijun , Ta Na , Hendriksen Peter Vang , Kiebach Wolff-Ragnar , Du Yong
Published: February 2020

Interconnect plates, made of ferritic type stainless steel, are widely used in planar solid oxide fuel cell (SOFC) or electrolysis cell (SOEC) stacks. These interconnect plates serve as current collector and separator for the neighboring fuel and oxygen electrode compartments of two adjacent cells. An intimate contact between the cell component and the interconnect (IC) plate is therefore essential to ensure optimum cell and stack performance. During stack production and operation, inter-diffusion across the cell – IC interface takes place, which under certain circumstances introduces adverse effects on the electrical, mechanical, and corrosion properties of the IC plates. One representative example is diffusion of nickel from the Ni/YSZ fuel electrode or from the Ni contact component into the IC plate, while iron and chromium from the steel diffuse in the reverse direction. Diffusion of Ni into the steel causes transformation of the ferritic BCC phase into the austenitic FCC phase in the interface region, accompanied with changes in volume and in mechanical and corrosion properties of the IC plates. Very few studies have been devoted to investigate this process experimentally. In this work, kinetic modeling of the inter-diffusion between Ni and FeCr based ferritic stainless steel was conducted, using the CALPHAD (CALculation of PHAse Diagrams) approach with the DICTRA software. The kinetics of inter-diffusion and austenite formation was explored in full detail, as functions of steel composition, thickness of Ni contact component or IC plate, temperature and time. The simulation was further validated by comparing with previously obtained experimental results. Growth of the austenite phase in commercial interconnect materials such as Crofer 22 APU and Crofer 22H was predicted under practical SOFC and SOEC operation conditions. The present work provides a proper account of the thermodynamics and kinetics of Ni-IC inter-diffusion and in addition provides input to further analysis of associated changes in the mechanical and corrosion properties of the IC plates.
Direct Ethanol Anode-Supported Solid Oxide Fuel Cell
Authors: Nóbrega Shayenne D. , Steil M. C. , Georges Samuel , Uhlenbruck Sven , Fonseca Fabio C.
Published: February 2020

Long term durability was demonstrated on high-performance direct ethanol solid oxide fuel cell operating in gradual internal reforming. Anode supported single cells, fabricated at Forschungszentrum Jülich, composed of (La,Sr)MnO3 cathode, 8 mol% yttria-stabilized zirconia (YSZ) electrolyte, and YSZ-Ni anode were used for long term testing on anhydrous (direct) ethanol. Gadolinia-doped ceria (CGO), with 0.1 wt.% of Ir, catalyst was produced by the impregnation of Ir salt in commercial CGO (Praxair) and mixed with organic additives. The CGO-Ir suspension was deposited onto the surface of the YSZ-Ni anode support with an air brush. Such a catalytic layer acts both as a physical barrier to avoid direct contact of the fuel with Ni-based anode and to promote the gradual internal reforming of ethanol. The CGO-Ir catalyst was designed for the reforming of the main compounds resulting from the thermal decomposition of ethanol at high temperature and to inhibit the formation of ethylene, which is a known source of carbon deposits. After deposition the sample was heated at 850ºC in inert atmosphere to ensure good adhesion between the catalytic layer and the anode. Gold grid and paint were used as current collectors in both cathode and anode sides. The single fuel cells were mounted in the test apparatus, sealed with gold rings and alumina cement and heated to the measuring temperature (850°C) under inert atmosphere. After gas tightness was checked by flowing air on the cathode side and argon on the anode side, the anode was reduced under hydrogen. The fuel cell was kept at 0.6 V while monitoring the current drained from the cell at 850 °C. Samples were initially operated in hydrogen for a few hours and fuel was switched to dry ethanol, carried by nitrogen. It is important to mention that no oxidizing agent was added to the fuel and that water produced by the electrochemical reaction of hydrogen at the anode promoted the reforming of the ethanol in the CGO-based layer, in the so-called gradual internal reforming. In such conditions the current output was recorded and observed to not be significantly different form that under hydrogen. Moreover, the direct ethanol fuel cell was continuously operated for 650 hours without major losses due to carbon formation. The experimental results demonstrate that the water released by the electrochemical oxidation of reformate hydrogen at the electrolyte/anode active interfaces is sufficient for the reforming of the primary fuel in the catalytic layer, provided that a minimum fuel utilization is respected. After the durability tests, energy dispersive X-ray spectroscopy and scanning electron microscopy analyses of the samples revealed no carbon deposit formation in the anode. The experimental results provided compelling evidence for the viability of gradual internal reforming of ethanol in high performance solid oxide fuel cells.