bluuebunny/crossref_metadata_2025 huggingface dataset:
Electrocatalytic Activity and Stability of Supported Palladium Nanoparticles
Authors: Ju Wenbo , Brülle Tine , Favaro Marco , Agnoli Stefano , Granozzi Gaetano , Schneider Oliver , Stimming Ulrich
Published: February 2020

The overall performance of the polymer electrolyte membrane fuel cell (PEMFC) essentially depends on the catalytic activity of its core-part: the membrane electrode assembly (MEA). Palladium (Pd), one of the platinum group elements, is a potential substitute for Pt to be applied as the electrocatalyst, since it has more abundant reserves and a lower price compared to Pt. Pd is stable under extremely corrosive conditions similar to Pt.

Nanosized metal particles perform considerably different as compared to the corresponding bulk materials. Furthermore, some reactions catalyzed by metal particles show a strong particle-size sensitivity. In previous work of our group, particle-size dependent activity of metal particles for electrocatalytic reaction was observed, such as Au nanoparticles supported on HOPG for oxygen reduction reaction (ORR) [1] and Pd nanoislands supported on Au(111) surface for hydrogen evolution reaction (HER) [2]. Beside the particle-size effects, support effects (e.g. ligand effect, strain effect) play important roles on electrocatalytic activity as well [3].

In order to research the particle-size effects and support effects on the activity and stability of Pd nanoparticles, highly oriented pyrolytic graphite (HOPG) and nitrogen doped HOPG (N-HOPG) [4] were used in this work. Due to the weak interaction of HOPG with metal deposits, the substrate-related effects can be eliminated. N-HOPG is rich in electronegative nitrogen functional groups, and the roughness of N-HOPG is much higher than the untreated HOPG before the nitrogen implantation process. Pd nanoparticles were electrochemically deposited by double-pulse electrochemical deposition on both substrates. Pd nanoparticles are located mainly at the defects and step-edges on HOPG surface, but on the N-HOPG particles are distributed homogeneously. For ORR, the smaller particles have a negative particle-size effect. Pd nanoparticles supported on N-HOPG do not show enhanced activity for ORR. For HER, the case is much more difficult for the behavior of hydrogen absorption of Pd. The content of absorbed hydrogen atoms in Pd NPs is influenced by the particle size. The stability of Pd nanoparticles on HOPG is influenced not only by the particle size, but also by the pH value of the electrolyte. Pd particles on N-HOPG show poorer stability as compared to the pure HOPG insofar as they dissolved rapidly in potential cycling measurements.

[1] Brülle, T.; Ju, W.; Niedermayr, P.; Denisenko, A.; Paschos, O.; Schneider, O.; Stimming, U., Molecules 2011, 16 (12), 10059-77.

[2] Pandelov, S.; Stimming, U., Electrochimica Acta 2007, 52 (18), 5548-5555.

[3] T. Bligaard, J.K. Nørskov, Electrochimica Acta, 52 (2007) 5512-5516.

[4] Favaro, M.; Perini, L.; Agnoli, S.; Durante, C.; Granozzi, G.; Gennaro, A., Electrochimica Acta 2013, 88, 477-487.
Study of Corrosion Inhibitors for Mg Alloy AZ31B with Variations of PCO2 and Electrolyte Layer Thickness
Authors: Kaminski Daniel , Buchheit R.
Published: February 2020

Magnesium alloys have been proven as useful, lightweight, engineering materials in several applications such as aerospace transmission casings and enclosure frames for general consumer electronics. Automotive industry has also shown much interest in this material both in the past and recent years. Yet, the full applicability of magnesium alloys has not yet been achieved due to their active corrosion in common media.

One way to act upon the corrosion of magnesium alloys is by corrosion inhibiting chemical compounds. Such compounds, when effective at low concentrations, are ideal candidates for coatings-based inhibitor systems provided that they can be stored and released by ion-exchange pigment additions to the coating. To date, corrosion inhibitor studies for magnesium alloys have almost entirely relied on techniques based on immersion of specimen in bulk solution.

In the present work, it is shown that the corrosion product and effectiveness of several inorganic inhibitor compounds on AZ31B, such as sodium metavandate, vary with both electrolyte layer thickness and partial pressure of CO2. Characterization of corrosion product layers indicates tendency for the formation of magnesium carbonates rather than Mg(OH)2 (brucite) when specimen are exposed to electrolyte layers as thick as 250µm compared to test conditions of the same CO2 partial pressure in bulk solution. Furthermore, it is shown that in some cases inhibitor compounds exhibit change in speciation with the changing parameters. It is well known that corrosion inhibition by inorganic ions is often particular to oxidation state and speciation of the compound such as is the case for tetrahedral coordinated vanadate species. Hence corrosion inhibitor effectiveness is altered by accessibility of CO2 and electrolyte layer thickness.

Lastly, synergistic effects of exposure cnditions with corrosion inhibitor compounds is discussed and examples given. These conclusions highlight the importance of replication of likely field exposure environment in design of lab experiments for magnesium alloys. Such information is crucial to the future development of coatings-based inhibitor systems.
Thermal Conductivity Measurements of Bi2Te3 Nanostructure By Raman Thermography
Authors: Park Dambi , Park Sungjin , Jeong Kwaungsik , Yoo Bongyoung , Cho Mann-Ho
Published: February 2020

Single-crystal Bi2Te3 nanowire and nanoribbon were synthesized by using a vapor-liquid-solid method with Bi2Te3 powder. The composition and crystalline structure of nanowires were confirmed by energy-dispersive spectroscopy (EDS) and high resolution transmission electron microscopy (HRTEM), respectively. To investigate the thermal properties of Bi2Te3 nanostructure, a nondestructive technique based on Raman temperature mapping was carried out. The red shift of Raman peaks and peak broadening observed as temperature increased. In addition, the fraction of the laser power absorbed inside the Bi2Te3 nanostructure was estimated by optical simulation for calculation of thermal conductivity value (κ). The obtained thermal conductivity value of Bi2Te3 nanowire and nanoribbon is 2.67 Wm-1K-1 and 2.81 Wm-1K-1, respectively. The difference in thermal conductivity value between nanowire and nanoribbon is caused by the dimension difference.
Quantitative Characterization of SEIs and Lithiation/Delithiation Processes in Electrolytes with Additives Using In Situ Electrochemical Quartz Crystal Microbalance-Dissipation (EQCM-D)
Authors: Yang Zhenzhen , Trahey Lynn , Thackeray Michael M.
Published: February 2020

In recent years, the crucial role of solid electrolyte interphases (SEIs) in Li-ion batteries (LIBs) has been well recognized by extensive studies. In spite of all available information, there are still issues relevant to the SEI formation, composition, and mechanical properties that have to be addressed. We have recently utilized Electrochemical Quartz Crystal Microbalance with Dissipation (EQCM-D) to study how SEI develops on tin thin film electrodes and probed the mass gain/loss in electrolytes with different amounts of fluoroethylene carbonate (FEC) additives upon electrochemical cycling. As shown in Figure 1, the detailed processes of the decomposition of the electrolyte on the electrode surface and Li alloying/dealloying with Sn were characterized quantitatively by measuring the decrease/increase of the resonance frequency in the cell. The effects of FEC on SEI formation and lithiation/delithiation cycles are also carefully studied and presented. The results suggest that varying the concentration of FEC is important for adjusting the SEI mass and thickness on the anodes.

The key points of employing EQCM-D in this work are the extension of measurements to higher harmonics and incorporation of dissipation (D). The capabilities enable the detection of the properties of interfacial films such as rigidity and viscoelasticity. The final modeling results from EQCM-D demonstrate that the SEI layer is dynamically shifting in the mass, thickness and viscoelastic properties during every cycle. Therefore, given the unique advantage of EQCM-D, it is expected that the full picture of SEI formation, including mechanic properties and compositional change, can be reflected.
In-Depth Investigation on Electrochemical Behaviors of Next Generation Cathode Materials for Lithium-Ion Batteries
Authors: Kim Young Jin , Shi Zhong , Sheargold Stephen
Published: February 2020

The transportation landscape is changing and vehicle electrification continues to gain traction in the market. The trend towards electric mobility (e-mobility) has shown a significant rise in recent years along with advances in technology and government subsidies, but there is still a long way to go for the future of e-mobility to be realized. The heart of e-mobility is the battery and its performance is fundamental to the success of e-mobility.

The cathode has a large stake in the key characteristics of the battery, such as energy density, power capability, safety, and cost. Advancements of cathode materials directly result in the improved battery performance with higher significance. BASF has focused on the development of next generation cathode materials (high energy Li-Mn-rich NCM and high voltage spinel) as well as advanced surface modification techniques.

In this presentation, we will report the electrochemical behaviors of a few of our latest cathode materials for advanced lithium-ion batteries. Three-electrode cell testing results will reveal in-depth information regarding early stage electrochemical formation process as well as cycling performance. Subsequently performed post-mortem investigation will provide analysis of capacity fade and failure mechanism during/after cycling procedure. Also, insights on the path forwards to further improve battery performance will be shared.
Effect of Metal Composition on the Electrochemical Properties of Lithium-Rich Positive Electrode Materials
Authors: Shunmugasundaram Ramesh , Dahn Jeff
Published: February 2020

Introduction

Lithium-rich mixed transition metal (TM) oxide positive electrode materials such as Li[Li0.2Ni0.2Mn0.6]O2 and Li[Li0.2Mn0.54Ni0.13Co0.13]O2 are attractive due to their high reversible capacities. However, they suffer from some problems such as high irreversible capacity loss1, poor rate capability2 and voltage fade3. There is no clear understanding in the literature how the overall metal composition of the Li-rich material affects their electrochemical properties including the above mentioned issues. Hence we embark, in this study, on studying the effect of metal composition on the electrochemical properties of the Li-rich positive electrode materials.

Experiment

A series of Ni(II)aMn(II)bCo(II)cCO3 precursors where a + b + c = 1 were made with co-precipitation synthesis using a continuously-stirring tank reactor (CSTR). Ni(II)aMn(II)bCo(II)cCO3 precursors were mixed with required amounts of Li2CO3and made into Li-rich positive electrode materials of the desired composition using solid-state synthesis at 900ᵒC in air. All the prepared materials were characterized by X-ray diffraction and their true densities were measured using a helium pycnometer. Coin-type cells were made from the synthesized positive electrode materials and Li metal anodes, which were then electrochemically tested under galvanostatic conditions at constant temperature, and their electrochemical properties were compared.

Results and Discussion

A Li-rich positive electrode material comprised of Li, Ni2+, Mn4+ and Co3+ can be made from a Ni(II)aMn(II)bCo(II)cCO3 precursor. By knowing the exact composition of Ni(II)aMn(II)bCo(II)cCO3 precursor, the theoretical formula of a Li-rich material can be calculated. For example, the Ni0.25Mn0.75 composition can be used to make Li1.2Ni0.2Mn0.6O2. Thus, the Ni-Mn-Co compositions that can be used to make all the possible Li-rich positive electrode materials were determined. Details results showing how the electrochemical behavior varies with overall metal composition will be presented.

References

1. J. H. Kim, C. W. Park, and Y. K. Sun, Solid State Ionics, 164, 43 (2003).

2. B. Xu , C. R. Fell , M. Chi , Y. S. Meng, Energy Environ. Sci.2011, 4 , 2223

3. Debasish Mohanty, Athena S. Sefat, Jianlin Li, Roberta A. Meisner, Adam J. Rondinone, E. Andrew Payzant, Daniel P. Abraham, David L. Wood, Claus Daniel, Phys.Chem.Chem.Phys., 2013, 15, 19496--19509
Li3V2(PO4)3 As a Positive Electrode Material for Rechargeable Lithium Batteries
Authors: Park Jae Sang , Myung Seung-Taek
Published: February 2020

Nowadays, demands lithium ion batteries which are mounted in portable devices increase day by day. As a result, research towards positive and negative electrode materials being intensively progressed.

Most commonly used positive electrode is LiCoO2 because it has good electrochemical property. However, Co is rare material and it is placed in limited area. Therefore, price of Co increases more and more. To substitute Co, plenty of transition metal material is studied such as Fe, Ni, Mn and V. Among them polyanion phosphate material such as LiMPO4 (M = Fe, Co, Mn and etc) and Li3V2(PO4)3 are considered as possible candidate materials because of their structure, thermal stabilities and low price. However, those polyanion material, LiMPO4 (M = Fe, Co, Mn) has low energy density, causing low energy density. Li3V2(PO4)3 has good safety as LiFePO4 but higher energy density than LiFePO4 because of its high redox potential, V2+/5+. Also, Li3V2(PO4)3 has high reversible capacity and high theoretical capacity (197 mAh g-1). In this paper, physical and electrochemical properties of Li3V2(PO4)3 is investigated.

Li3V2(PO4)3 is synthesized by solid state method. Stoichiometric amount of Li2CO3, NH4H2PO4, and V2O5 powders were grind and mixed by ball mill. The mixed powders were calcined at 500 oC in air atmosphere. The calcined powders were pelletized and sintered at 800 oC for 5 h in reduction atmosphere again. The calcinations, heated pellets were grind in Ar filled glove box to avoid air exposure. The synthesized Li3V2(PO4)3 powders were identified by X-ray diffraction (XRD) with Cu Kα radiation and analyzed by Rietveld refinement. Electrochemical test were carried out in coin type cell. Galvanostatic electrochemical charge and discharge test were made between 3.0 V and 4.8 V at 10 mA g-1 current at room temperature.

The XRD pattern of the product shows single phase Li3V2(PO4)3 were obtained without impurity. The galvanostatic charge and discharge performances of Li3V2(PO4)3 as an positive electrode are tested in voltage range of 3.0 V and 4.8 V. Also to understand the mechanism during charge and discharge, ex-situ XRD, XPS and ToF-SIMS measurement were carried out at the first cycle. Furthermore to understand the affect the thermal stability high temperature XRD and TGA were carried out. Details will be discussed in the conference site.
Healthcare for Lithium-Ion Battery By Multi-in-Situ Electrochemical Impedance Spectroscopy Measurement System
Authors: Shitanda Isao , Hoshi Yoshinao , Honda Keiichiro , Kawado Taiki , Itagaki Masayuki , Aoyagi Shigeo , Fukuizumi Atsuhisa
Published: February 2020

Electrochemical impedance spectroscopy (EIS) is powerful tool to evaluate a performance of lithium-ion battery because time constants in electrochemical signals can be distinguished with no damage to the electrode. 1,2

Separation of time constants of anode and cathode is desired in the interpretation of impedance spectra of a lithium-ion battery. Multi -EIS measurement is an analysis method in which simultaneous measurements of three impedance spectra (cathode-reference electrode, anode-reference electrode and anode-cathode) are carried out using a suitable reference electrode. The time-constants of anode and cathode from full cell impedance spectra can be separated by using Multi-EIS measurement.

On the other hand, in the case of in-situ EIS measurements for lithium-ion battery, impedance spectra were measured successively during charge or discharge sequence. The in-situ EIS measurement is very useful for monitoring the degradation process of lithium-ion battery during the charge-discharge cycles. 3

In the present study, we developed a multi-in-situ EIS measurement system in which simultaneous measurements of three impedance spectra were carried out during the charge-discharge cycle. The system is based on a newly developed potentiostat which has an integrated high-performance frequency response analyser and data processing software.

The electrode reactions in rechargeable batteries do not satisfy the time stability during the charge–discharge cycles and the low frequency components of the impedance might contain significant errors due to the time variation. In order to compensate the impedance spectrum deviated by the variation of reaction resistance in the charge or discharge, the impedance spectra were measured successively and plotted on the three-dimensional (3D) complex diagram, which has a time axis. The plots were connected by the spline under tension function at each frequency. The cross-section of 3D impedance shell perpendicular to the time axis gives the instantaneous impedance at an arbitrary time, which can be given automatically by using the software. We investigated the influence of SOC and C-rate on impedance spectra of both cathode and anode.

Acknowledgement

This work was supported by JST A-STEP (AS2421666K).

References

1. M. Itagaki, in Nanoscale Technology for Advanced Lithium Batteries, T. Osaka and Z. Ogumi, Editor, p.123, Springer Science+Business Media, New York (2014).

2. T. Osaka, T. Momma, D. Mukoyama, H. Nara, J. Power Souces 205 (2012) 483.

3. M. Itagaki, N. Kobari, S. Yotsuda, K. Watanabe, S. Kinoshita, M. Ue, J. Power Souces 148 (2005) 78.
Ex Situ Activation of Li-Excess Layered Cathode Materials for High-Capacity Lithium Ion Batteries
Authors: Zhao Jianqing , Wang Ying
Published: February 2020

Ex situ activation of Li-excess layered cathode material (Li[Li0.2Mn0.54Ni0.13Co0.13]O2) has been carried out via proton exchange in hydrochloric acid (HCl), followed by chemical exfoliation in tetrabutylammonium hydroxide (TBA·OH) solution and post-heat treatment, in which morphologic and structural reconstructions of pristine cathode material simultaneously take place. Exquisite nanoflower-shaped derivative is achieved with significant increased surface area and uniform pore size distribution after protonation and TBA·OH exfoliation. Sintering nanoflower-structured derivative contributes to hierarchical mesoporous structure and cubic spinel phase within final converted cathode material. The chemical activation of Li-excess layered cathode material results in phase transition from original layered to refactored spinel structure. The activated cathode material in spinel phase and hierarchical porous structure shows significantly improved electrochemical performance, which reveals Coulombic efficiency of 99.93% in the initial cycle at 1C (1C=250 mA/g) and retains high specific capacity of 200.8 mAh/g after 100 cycles, in comparison with 59.16% and 58.1 mAh/g of pristine Li-excess layered cathode materials, respectively. Remarkable enhanced rate capability has also been accomplished in activated cathode, delivering initial discharge capacities of 313.6, 267.2, and 126.3 mAh/g at 0.1, 0.5, and 5C, respectively. Such considerably enhanced cycleabilitiy and rate capability can be attributed to ex situ activation of Li2MnO3 component, phase transition, and/or morphologic and structural reconstructions of Li[Li0.2Mn0.54Ni0.13Co0.13]O2. This work opens up various routes to achieve excellent electrochemical performance from high-capacity Li-excess layered cathode materials.
Ultra-Long-Term Cyclability of Ge/C Nanocomposite Anode for Li-Ion Batteries
Authors: Ngo Duc Tung , Kim Sang-Wan , Park Chan-Jin
Published: February 2020

Germanium (Ge) is the potential candidate to replace graphite anode material for lithium ion batteries (LIB). Graphite has been used until now as a main anode material in LIB. However, its limited specific capacity cannot meet the world’s growing demand for energy. The volumetric capacity of Ge (7366 Ah/l) is relatively smaller than that of Si (8344 Ahl-1), but Ge has more advantage over Si: the diffusion coefficient of Li in Ge is approximately two orders of magnitude greater than that in Si, intrinsically electrical conductivity of Ge is four order higher than that of Si due to its smaller band gap, and the volume expansion during lithium insertion-deinsertion into Ge is smaller compared with Si. Despite these of promising characteristic, the capacity fading of Ge after some charge/discharge cycles is main problem to be addressed. To improve the cyclability of Ge most studies so far have focused on the use of buffer layer or reducing particle size of Ge. The use of buffer layer has negligible effect on specific capacity of Ge but it will improve significantly the performance of Ge at high rate of charge-discharge owing to improvement in mechanical properties, contact between active material with electrode, and diffusivity of Li.

In this study, we introduced a simple method for synthesis of Ge nano particles interconnected by carbon (GEC). The GEC electrode showed a high specific capacity up to 1339 mAh/g at the rate of C/2, after 50 cycles the specific capacity retained at value of 1321 mA h/g. Even with increasing the charge-discharge rate up to 10C, the specific capacity only decreased about 30 % compared with that at the rate of C/10. The excellent electrochemical performance of GEC electrode was not only due to the buffer layer of carbon but also the interface layer of Ge-carbon. The formation of Ge-C bonding at interface layer is believed to improve the contact between Ge and C, increase the stability during charge-discharge process and reduce stress tension during volume expansion.

The cyclic life of GEC electrode is under-investigation and it can be observed from its initial data that the electrode shows steady performance till the obtained data. However, further cycling data is necessary for making any stamen about the stability in its performance. The initial results demonstrate that the synthesized GEC can be used as an active Li storage material for lithium ion batteries.
High-Energy and High-Power Electrochemical Energy Storage Based on Dual Intercalation/Radical Electrodes
Authors: Wohlmuth Dominik , Fontaine Olivier , Wilkening Martin , Freunberger Stefan A
Published: February 2020

Li-ion and related battery technologies will be important for years to come. However, society needs energy storage that exceeds the energy and power of common Li-ion batteries.1,2 Many prospective applications of batteries require improving both energy density and rate capability. The simultaneous improvement of these two parameters is not sufficiently addressed by state-of-the-art approaches. High capacity lithium intercalation materials often exhibit poor ionic and electronic conductivity which limit rate capability. Battery electrodes based on polymers bearing organic free radicals allow for exceptionally high rates but fall short in meeting energy density requirements.3,4

Here, we combine the advantages of both storage principles, to form battery electrodes capable of delivering the capacity of the high-energy intercalation material and intermittently the high rate capability of the radical material. First, we must understand the processes that occur in the cell on discharge and charge to fully take advantage of the potential of the concept.

We will discuss recent results on the detailed elucidation of the charge transfer mechanism in the so formed dual radical/intercalation electrodes, materials aspects, thermodynamic and kinetic considerations. We combine synthetic, spectroscopic and advanced electroanalytical methods to gain insight into the governing processes.

1. B. Scrosati, J. Hassoun, Y.-K. Sun, Energy Environ. Sci., 4, 3287 (2011).

2. M.M. Thackeray, C. Wolverton, E.D. Isaacs, Energy Environ. Sci., 5, 7854 (2012).

3. K. Oyaizu, H. Nishide, Adv. Mat., 21, 2339 (2009).

4. T. Janoschka, M.D. Hager, U.S. Schubert, Adv. Mat., 24, 6397 (2012).
Lithium-Ion Batteries Assembled with Electrospun Hybrid Polymer Membrane Containing Reactive Silica Nanoparticles
Authors: Park Sae Rom , Shin Won-Kyung , Kim Dong-Won
Published: February 2020

Lithium-ion batteries have been rapidly expanding in portable electronic devices, electric vehicles (EVs) and energy storage systems. In lithium-ion batteries, a separator is a critical component which prevents physical contact of the positive and negative electrodes while permitting free ionic transport within the cell. Most of the separators currently used in lithium-ion batteries are based on microporous polyolefin membranes. Although these separators offer excellent mechanical strength and chemical stability, they shrink, soften and even melt at high temperature, which cause short circuiting between electrodes. Furthermore, the large difference in polarity between the non-polar polyolefin separator and the polar organic electrolyte leads to poor wettability. As a result, there is a high resistance when the pores in the separator are not completely filled with liquid electrolyte. In our previous studies, we synthesized silica nanoparticles with vinyl groups, which permitted the surface reaction with vinyl monomers by radical polymerization [1-3]. With the goal of developing high performance separators with high thermal stability, good transport properties and enhanced wettability for non-aqueous liquid electrolytes, we prepared electrospun hybrid polymer membrane based on polyacrylonitrile (PAN) and reactive SiO2 nanoparticles. Due to the presence of reactive silica particles, it could be thermally cross-linked, resulting in good thermal stability and improved wettability for liquid electrolyte. Using the cross-linked electrospun hybrid polymer membranes, we assembled lithium-ion cell composed of carbon anode and LiNi0.6Co0.2Mn0.2O2 cathode. The cycling performances of the cells with cross-linked hybrid polymer membrane were evaluated, and the results were compared to those obtained with a pristine PE separator.

References

1. Y.S.Lee, S.H.Ju, J.H.Kim, S.S.Hwang, J.M.Choi, Y.K.Sun, H.Kim, B.Scrosati, D.W.Kim, Electrochem. Commun., 17, 18, 2012.

2. S.H.Ju, Y.S.Lee, Y.K.Sun, D.W. Kim, J. Mater. Chem. A, 1, 395, 2013.

3. Y.S.Lee, J.H.Lee, J.A.Choi, W.Y.Yoon, D.W.Kim, Adv. Funct. Mater., 23, 1019, 2013.
Investigation of Solid State Diffusion Coefficient Dependency in Lithium Ion Battery
Authors: Ma Miaomiao , Sisk Brian C
Published: February 2020

The market for electrified vehicles, particularly for low voltage applications, is expected to witness robust growth during the next decade. The emergence of these vehicles will result in the increasing demand of high-power lithium ion batteries. Understanding battery performance over varying temperatures and current pulses plays an important role in battery design, manufacture, and application. In the lithium ion battery performance simulation, the solid state diffusion coefficient is one of the most significant parameters that affect the battery performance.

Solid state diffusion has been previously demonstrated to vary with temperature and state of charge (SOC) [1-2]. Our simulation shows that it also changes with the current density. While the cell ages, the diffusion coefficient decreases as well. With HPPC (hybrid pulse power characterization) data of power cell at different temperatures and different pulse rates, we estimated the diffusion coefficient dependency on current, as seen in Figure1. Using HPPC data from fresh and aged cell, the diffusion coefficient change with time is also summarized.

References:

1. J.N. Reimers, M. Shoesmith, Y.S. Lin, and L.O. Valoen, 160, A1870-A1884, (2013)

2. P.Albertus, J. Christensen, and J. Newman, 156, A606-A618, (2009)
Preparation of NMC622 Cathode Materials Using a Cost Effective Circular Type Reactor for Li-Ion Battery Application
Authors: Song Jung-Hoon , Jeon Dong-Hyup , Hong Jong-Pal
Published: February 2020

Li(Ni0.6Mn0.2Co0.2)O2 (NMC622) cathode materials have been recognized as the next generation cathode materials due to its higher capacity and lower raw material cost than commercialized cathode materials such as NMC532. Thus, many industrial companies have been made every effort to commercialize and apply the NMC622 to lithium ion battery system such as energy storage system (ESS). However, production cost of NMC622 still has been recognized as expensive material to be applied in the industrial field and it becomes main issues to be overcome. CSTR (Continuous Stirred Tank Reactor) has been widely applied in the industrial field to produce the NMC622 precursor but it has initial long stabilization time as well as low production efficiency. This is caused by the original limitation of CSTR such as the low mass transfer rate and required complete mixing zone to stabilize the system. Thus, in this study, we suggest the novel reactor system that shows the higher mass transfer rate as well as higher production rate than those of CSTR. Developed novel reactor system uses the taylor-couette flows to induce higher mass transfer rate and production efficiency with uniform particle size distribution.

In this study, we synthesized NMC622 using taylor-couette reactor to understand the function and mechanism of the operation. The effect of operating parameters, i.e. pH, operating rpm, and feed retention time, in the taylor-couette reactor, was investigated thoroughly to evaluate the feasibility to produce NMC622 precursor. Produced precursors are characterized using SEM, XRD, ICP, FIB, PSA. Then, cathode materials are prepared and tested using a galvanostatic intermittent titration method (GITT) to understand the electrochemical properties. This study verified that taylor couette reactor is feasible process to be applied to the commercial NMC622 production.

Acknowledgement - This work was supported by the Korea Institute of Energy Technology Evaluation and Planning under the Energy Technology Development Program (20132020101750)
Electrical Property of Nasicon (Na3Zr2Si2PO12) as Solid-Electrolyte for Na/S Battery
Authors: Park Heetaek , Kang Byoungwoo
Published: February 2020

Na/S battery attracts a lot of attention due to low cost and high energy density for burgeoning large-scale energy storage system. The battery operates at elevated temperature (~300oC), so solid electrolyte which separates molten electrodes is used.1 Beta alumina is widely used as solid electrolyte but it has anisotropic electrical properties and complicated synthesis. In this point of view, Nasicon (Na super ionic Conductor) can be a promising alternative because it has 3-dimensional Na conducting channels and can be obtained by a facile synthesis.

Nasicon (Na1+xZr2SixP3-xO12) has wide composition range (0<x<3) and ionic conductivity of the materials is highest when x equals to 2. However, Nasicon structure goes through transformation from monoclinic phase (Low T) to rhombohedral phase (high T). This phase transformation really affects durability of the solid electrolyte because volumetric change during thermal cycles happens. Thus, the depression of phase transformation is important for high durability.

In this presentation, we will discuss about experimental parameters that influence on the phase transformation and will discuss electrical properties of Nasicon phase using EIS (Electrochemical impedance spectroscopy) measurement

Reference

V. Palomares et al., Energy & Environmetal Science, 5, 5884-5901, 2012
Facile and Scalable Synthesis of 3.9V LiFeSO4F
Authors: Kim Minkyu , Jung Yongjo , Kang Byoungwoo
Published: February 2020

Cathode materials of Li-ion batteries have been developing to achieve high energy density with superior safety for powering novel applications such as electric vehicles and enegy storage systems. With respect to this consideration, polyanion compounds such as phosphates, fluorophosphates, fluorosulfates have attracted a lot of attention because of their superior safety and high energy density. Among these F-containing compounds, LiFeSO4F compound has been paid much attention as a promising candidate for cathode material in Li ion battery because it shows high energy density with high potential and 151 mAh/g. Especially, tripilite LiFeSO4F phase, one of polymorphs, shows much higher voltage (3.9V Vs. Li+/Li) compared to tavorite LiFePO4F phase (3.6V Vs. Li+/Li) leading to higher energy density. However, the utilization of triplite LiFeSO4F phase has been limited because of complicated synthetic process. Typically, the triplite phase is synthesized by transforming tavorite phase which is formed through topotatic process.[2] Therefore, the key point of challenge is direct synthetic process without tavorite phase transformation. Triplite phase is also more stable than tavorite phase with respect to themodynamic condisderation.[3]

In this presentation, we will discuss the key experimental parameters to obtain triplite phase without going through the phase transfroamtion of tavorite phase and will present the electrochemical properties of the triplite phase obtained by fascile and scalable process.

References

[1] N. Recham &Tarascon, Nature Material 9 (2010) 68 - 74

[2] P. Barpanda &Tarascon, Nature Material 10 (2011) 772-779

[3] A. V. Radha & A. Navrotsky, J. Mater. Chem, (2012), 22, 24446 - 24452
Characterization and Electrochemical Properties of Graphene / Silicon Grafted Composite Materials for Applications in Lithium-Ion Battery
Authors: Weissmann Martin , Crosnier Olivier , Lestriez Bernard , Humbert Bernard , Guyomard Dominique , Agnes Charles , Duclairoir Florence , Bidan Gerard , Brousse Thierry
Published: February 2020

Density and energy performance of Li -ion batteries are highly dependent on the physical and chemical properties of the electrode materials. The negative electrode materials still offer a large area to explore to improve both capacity and reversibility for lithium storage. In this context, the development of negative electrodes based on silicon has led to numerous researches (1). The high specific capacitance of silicon (3850 mAh.g-1) is the main asset for the use of this material. However, silicon has major drawbacks (volume expansion, irreversible formation of LixSiy alloys,... ) that cause early degradation of the electrodes.

The approach developed in our laboratory is to link the two components by a chemical bond (covalent) between the two materials. This covalent bond, resulting from a chemical grafting of a diazonium salt (4-aminoaniline) allows linking the carbon particles to silicon nanoparticles via a phenyl bridge.

This technique has been used to bond silicon nanoparticles to carbon nanotubes (2) which helped to improve the stability of the electrodes during galvanostatic cycling. The work presented here focuses on a coupling between silicon nanoparticles and graphene sheets.

Graphene is potentially interesting for Li-ion batteries applications, it has good electronic conductivity and its layered structure could promote an increase in the strength of the electrodes. The sheets can act as a buffer when the silicon particles volume increases, thereby helping to maintain the cohesion of the electrode during different cycles of charge and discharge (3). The graphene synthesis was performed according to the Hummers method and leads to particles whose specific surface area is about 200 m² /g (Figure 1).

Electrode materials were characterized by different techniques (TGA-MS, BET, SEM, IR / Raman spectroscopy, cyclic voltammetry, galvanostatic cycles ...) at different stages (graphene modification, graphene / silicon coupling) to show the presence of molecular bridges and determine their influence on the electrochemical behavior of a Li-ion battery. Performance measured 0.16A.g-1 (Figure 2) clearly show a significant improvement in grafted materials compared to a simple mixture of graphene / Silicon materials.

Acknowledgments: The authors thank the French National Research Agency (Graf'N'Stock project) for financial support.

References

(1) M. N. Obrovac, L. Christensen, Electrochem. Solid-State Lett. 7 (2004) A93

(2) C. Martin., O. Crosnier, R. Retoux, D. Bélanger, D. M. Schleich, T. Brousse, Advanced Functional Material 21 (2011) 3524

(3) B. Nguyen, N. Kumar, J. Gaubicher, F. Duclairoir, T. Brousse, O. Crosnier, L. Dubos, G. Bidan, D. Guyomard, B. Lestriez, Adv. Energy, Materials, (2013)3, 1351
Understanding the Surface Structure of LiNi0.45Mn1.55O4 Spinel Cathodes with Aberration-Corrected HAADF STEM
Authors: Amos Charles Dallas , Song Jie , Ferreira Paulo Jorge , Goodenough John Bannister
Published: February 2020

In order for Li-ion batteries to mature to a level useful for integration into the current or future energy infrastructure, basic problems such as cyclability, cost and rate capability must be overcome. LiNi0.5Mn1.5O4 (LNM), a spinel cathode material, has the advantage of being both cost-effective and a high-rate capable material, but it is plagued with cyclability problems. In the LNM system the main contributor to cycling degradation is the high operating voltage which leads to solid-electrolyte interphase (SEI) formation. We find that excess-Mn doping of this material (LiNi0.5-XMn1.5+XO4where x=0.05) leads to increased cyclability through natural passivation [1]. To understand the exact role that excess Mn plays in the passivation of this cathode material, it is crucial to determine the surface’s atomic structure. This is because the surface structure determines how reactive the cathode will be with the electrolyte during oxidation and reduction cycles.

In order to understand how excess-Mn LNM reacts with the electrolyte, it is critical to understand the different phases that form in this system. In this regard, aberration-corrected high-angle annular dark-field (HAADF) scanning transmission electron microscopy (STEM) was used to identify the surface and bulk structures in the excess-Mn LNM system. A HAADF STEM image of LiNi0.45Mn1.55O4along the [110] zone axis is shown in Figure 1. The image has been deconvoluted for clarity. This confirms the spinel structure (blue) and shows good agreement with STEM simulations in the bulk. Near the surface however, other phases are observed which include the rock-salt phase (green) and an unexpected phase defined here as “ring-type” (red). The rock-salt structure is expected from x-ray diffraction (XRD) results but the ring-type phase; so-called because of the characteristic rings that are formed within the first few atomic surface layers, is not. All three phases are observed near the surface, however only the spinel is found within the bulk of the particles. HAADF STEM enables a detailed characterization of these phases and has led to an important understanding of the cycling degradation mechanisms in the excess-Mn LNM system. In turn, this work enables us to develop a well-suited cathode material for future energy storage that will potentially spur the evolution of the future sustainable energy landscape.

References:

[1] J. Song et al., Chem. Mater. 24 (2012), 3101.

Figure 1
Addressing Energy-Water Challenges Through Transformative Research
Authors: Klausner James
Published: February 2020

The total annual freshwater withdrawal in the U.S. is 483 billion m3, and 41% (198 billion m3) is used for cooling thermoelectric power plants. Of that, 5 billion m3 is dissipated annually to the atmosphere. Currently, regional fresh water shortages exist in the Southwestern and Southeastern U.S. Considering population growth and climate change models, extreme and severe water shortages are projected in a large portion of the U.S. by 2050, which places at least 4 quadrillion BTUs of annual electricity production at risk. Regions facing freshwater shortages typically have access to brackish or seawater, which can be desalted to produce fresh water. The main hurdles to the adoption of large scale desalination are the large energy consumption and environmental concerns due to concentrated brine discharge back to the source. This talk will examine the applied research interests at the U.S. Department of Energy Advanced Research Projects Agency-Energy (ARPA-E) for addressing future energy-water challenges. The identification of transformative technology for the elimination of power plant water consumption without a penalty on power plant efficiency will be discussed. New technologies that will enable distributed desalination with low energy consumption will be considered. Different geographical regions face different challenges, which will require the development of a variety of technologies to address unique regional energy-water challenges.
Electrochemistry and Co-Generation in Arid Regions
Authors: Aljaberi Ahmed Daghash
Published: February 2020

The United Arab Emirates (UAE) is actively exploring the spectrum of renewable energy technologies for maintaining its growth while lowering the impact on both the environment and the economy. The scarcity of fresh water supply in the UAE requires a deeper and more evolved planning for combining different technologies for power generation and water production. Hence, the plan proposed, here, combines different renewable energy technologies, with an emphasis on fuel cell related aspects. This plan serves as a basis for more efficient methods to use local resources for co-generation of power and water in the future, and also gives a very clear perspective and justification for the continuous efforts that are made to find new materials for solid oxide fuel cells, that improve flexibility and applicability.
Microbial Fuel Cell for Energy Generation and Wastewater Treatment
Authors: Ulyanova Yevgenia , Singhal Sameer
Published: February 2020

According to a number of reports about 90% of “used” water or wastewater remains untreated, and is pumped back into the environment, causing global pollution. Proper treatment is needed prior to releasing this water back into the ecosystem or re-purposing it for alternate uses.

To meet the above-described need, a microbial fuel cell (MFC) has been developed, that can simultaneously generate energy from wastewater while also removing contaminants and allowing for its reuse, thereby greatly offsetting the net energy costs of water treatment. A MFC is a device that directly converts chemical energy, derived through microbial metabolism, to electrical energy. Specifically for this system the organic contaminants are processed at the anode, while heavy metal (ex. hexavalent chromium) contamination is removed at the cathode. This configuration of the MFC presents the novelty in the system’s design as compared to existing MFC technologies.

The method for bioremediation of organic and heavy metal contaminants in wastewater is different. Organic contaminants are oxidized during wastewater treatment to carbon dioxide, whereas heavy metals are typically reduced to a safe metallic form. Therefore, separate types of bacteria are employed for anode and cathode fabrication. The bioanode bacteria, Shewanella
oneidensis strain MR-1
[
1
], has been widely studied[
2
] for the use in MFC. Bacterial attachment is facilitated by entrapment in biopolymers with carbon nanomaterials (including high surface area porous carbons and graphene) followed by incubation to allow for biofilm growth. Previous work has shown that these composite electrodes form very stable bioelectrodes that can be used for months without degradation[
3
]. Spectroscopic activity assays (Figure 1) along with amperometric activity assays for oxidation of organic substrates are employed to study the effects of bacterial immobilization and catalytic performance at modified bioelectrodes.
Low Energy High Rate Anaerobic – Aerobic Digestion (HRAAD) and Applications
Authors: Cooney Michael John
Published: February 2020

Conventional aerobic technologies based on activated sludge processes have been widely applied for the treatment of domestic wastewater due the high efficiency realized, the possibility for nutrient removal, and high operational flexibility [1]. Unfortunately, the high capital and operation costs that coincide with the introduction of aeration-based technologies likewise impose significant financial constraints upon city and county that process large amounts of dilute wastewater [2]. The dissolution of oxygen is energy intensive, and results in the growth of significant quantities of biomass known as sludge, which requires further treatment/stabilization prior to disposal [3]. As such; reliable, unsophisticated, and cost effective treatment technologies have been proposed, including anaerobic treatment under anoxic conditions, as well as combined forms of anoxic with anaerobic treatment [4]. Of these, anaerobic pretreatment is perhaps the simplest and most conceptually attractive approach for domestic wastewater due to its relatively low construction and operational cost, operational simplicity, low production of excess sludge, production of energy in the form of biogas and applicability in small or large scale [5].

Anaerobic digestion can also be used as a pretreatment step prior to facilitate the use of low energy aerobic treatments used as a polishing step - reducing the organic load flowing into the aeration treatment basins can result in the production of less sludge that will, in turn, will reduce the amount of energy used in sludge handling (e.g., pumping, dewatering through belt presses, drying, trucking, and placing in landfills) [6]. In this presentation on-going research to design high rate anaerobic –aerobic digestion (HRAAD) reactors will be presented, as will results from their deployment in industry at demonstration scale. Commentary on how the HRAAD can be integrated into businesses to achieve sustainable use of fresh water supplies in isolated city communities will also be presented along with the application of sand filtration to this system to produce an R1 effluent for agriculture. Finally, the design of a novel unit operation that combines the elements of both a sand filter and a microbial fuel cell will also be discussed.

________________________________________________________________________________________

1. Gavrilescue, M., et al., Acta Biotechnology, 19(2), 111-145 (1999).

2. Kassab, G., et al., Bioresource Technology, 101(10), 3299-310 (2010).

3. Dufresne, L., et al., Evaluation of Energy Conservation Measures for Wastewater Treatment Facilities. 2010, Environmental Protection Agency: Washington D.C.

4. Chan, Y.J., et al., Chemical Engineering Journal, 1(55), 1-18 (2009).

5. Lettinga, G., Antonie van Leeuwenhoek, 67, 3-28 (1995).

6. Gohil, A., et al., Bioresource Technology, 97, 2141-2152 (2006).