bluuebunny/crossref_metadata_2025 huggingface dataset:
Non-Stoichiometric Titanium Dioxide Incorporation Onto Reduced Graphene Oxide By Atomic Layer Deposition for Oxygen Reduction Catalysis
Authors: Macedo Andrade Angela , Karimaghaloo Alireza , Grewal Simranjit , Lee Min Hwan
Published: February 2020

Renewable energy devices such as fuel cells and metal air batteries harness their energy via lethargic oxygen reduction reactions (ORR) whose catalysis is largely relying on expensive and scarce noble metals. To address this issue, in particular, non-precious metal incorporated in carbon nanostructures have been widely explored. In this study, we focus on synthesizing inexpensive and efficient electrode material for ORR catalysis and energy storage using reduced graphene oxide (rGO) incorporated with non-stoichoimetric titanium dioxide by atomic layer deposition (ALD). Although stoichiometric TiO2 has been rarely considered as an effective ORR electrocatalyst, oxygen-deficient TiO2-x recently showed surprisingly competitive ORR activity and excellent durability[1]. The work was performed on a single crystalline TiO2. Motivated by the recent report and the advantages of TiO2 due to its abundance, safety and cost effectiveness, we probed the feasibility of applying this oxygen-deficient TiO2-x to the widely employed oxide nanoparticle-incorporated carbon nanostructures. This is to leverage extremely high surface area and excellent electronic conductivity of carbon-based 3D structures, which is highly advantageous for maximized catalytically active sites per mass.

We used electrophoretically deposited rGO as the matrix structure. Graphene oxides prepared by the modified Hummer’s method are first deposited onto a stainless steel by electrophoresis. The resulting structure was deposited by highly dispersed nanoparticles or ultrathin films of TiO2-x via ALD. The degree of non-stoichiometry is controlled by either changes in ALD temperature or a separate post-thermal process. ALD is a newer variant of chemical vapor deposition in which materials are deposited on a surface by a multiple sequence of ‘self-limiting’ chemical reactions. This unique sequential process enables a highly uniform deposition of dots/films and accurate control over not only the size/thickness at the atomic scale but also chemical composition and location of deposition.

In this presentation, we will present 1) the feasibility of using TiO2-x incorporated rGO as ORR electrode in terms of catalytic activity and cyclability and 2) the correlation among the ALD process parameters, resulting chemical composition/structure and ORR catalytic activity.

This project is funded by the NASA MUREP Institutional Research Opportunity (MIRO) Program (Grant No. NNX15AQ01A). S.G. is supported by NASA Advanced STEM Training and Research (ASTAR) Fellowship.

Figure 1
Stability and Application of LiBH4-LiNH2 and LiNH2-LiI Compounds in All-Solid-State Libs
Authors: DAO Anh Ha
Published: February 2020

Lithium borohydride and substitutional derivatives with other compounds, such as LiI and LiNH2, are attractive due to their promising properties for hydrogen storage. Recently, it has been reported that they exhibit super ionic conductivity toward lithium ion, which makes them attractive candidates for solid electrolytes in all-solid-state Lithium Ion Batteries (LIBs). In this study, LiBH4 - LiNH2 and LiNH2-LiI mixed compounds have been synthesized by mechanical ball milling. Their ionic conductivities have been studied. Their thermal stabilities and chemical stabilities (towards Li metal and C) are analyzed by DSC measurement. Full cells are built with graphite as positive electrode and Li as contra electrode and LiBH4, LiBH4 - LiNH2 and LiNH2-LiI as solid electrolyte. Their electrochemical stabilities are studied by cyclic voltammetry. This research provides deeper understanding for LiBH4-LiNH2-LiI ternary system and the possibility as solid electrolyte for all-solid-state LIBs.
Studies on Capacity Fading of Lvo Cathode for Li-Metal Batteries
Authors: Kim Byung Hyuk , Yoon Woo Young
Published: February 2020

Lithium Trivanadate(LVO) cathode has a theoretically high specific capacity of 280 mAh/g, which one of higher energy capacity batteries than commercial LCO battery. However, Li-LVO batteries have problems resulting from the vanadium dissolution into the electrolyte, volumetric extension of LVO. We are planning an experiment to clear relationship between vanadium dissolution and volumetric extension in charge/discharge process.  To analyze the main reason of LVO fading, Lithiation amount was different during cell test. Cells were tested at the current densities of 0.2 C-rate and 2 C-rate with 1.8V to 4.0V. And we were a time cut in cell test to control the lithiation amount. The interfacial characteristics and electrolyte after cycles were examined by SEM, EDS, ICP-mass and FT-IR. The results surely confirm that main reason of LVO fading between vanadium dissolution and volumetric extension.
Advances in Metal Fluoride Conversion Materials for High Energy Density Batteries
Authors: O'Neill Cory , Li Bin , Kaye Steven S.
Published: February 2020

State-of-the-art lithium-ion technology is based upon the shuttling of lithium ions between graphite and layered oxides, a process that limits the amount of Li to <1 per metal site and the volumetric energy density of the cathode to ~3,500 Wh/L.  An alternative to intercalation-based electrodes are the so-called "conversion" electrodes, in which lithium reacts with an unstable host that undergoes significant (reversible) atomic rearrangement on charging and discharging. Of the known metal fluoride conversion electrodes, the best balance of operating voltage, energy density, and cost is CuF2, which has a theoretical capacity of 466 mAh/g (based on Cu + 2LiF) and a theoretical voltage plateau around 3.5V.

Recently, Wildcat has addressed several challenges currently prevent use of these materials: 1) poor rate capability due to low electronic/ionic conductivity, 2) low energy efficiency, likely from polarization and non-symmetric charge and discharge mechanisms, and 3) limited cycle life caused by sintering of metal nanoparticles and mechanical stress induced by volume expansion.  To overcome these difficulties, Wildcat developed CuF2-based cathodes with conductive and protective coatings to enable high power and stability. Using Wildcat’s proprietary non-graphitic conductive coating, the cathode exhibits 1st cycle capacities of >380 mAh/g at a 1C rate.

Wildcat has also investigated alternative compositions that demonstrate improved conductivity and higher voltage.  A second coating is used to prevent copper dissolution and metal agglomeration, leading to a self-discharge rate of 0.2%/day (vs. 2.0%/day for control) and cyclability. To our knowledge, this was the first reported demonstration of rechargeable CuF2.  Moreover, the CuF2 material has voltage hysteresis of only 0.1-0.3V, compared with ~0.7-1V for FeF3 or BiF3.
Evaporation Rate Effect on the Sicu Helical Shaped Thin Films™ Morphologies and Their Uses As Anodes for Rechargeable Libs
Authors: Polat Deniz Billur , Keles Ozgul
Published: February 2020

Structured silicon based anodes are promising for their high cycleability and rate performance. Because, the nanostructures can provide facile relaxation to prevent electrode pulverization. Plus, they maintain effective electrical contacts in cycling and provide short Li diffusion distances improving their electrochemical performances. Among alternative production methods, glancing angle evaporation becomes prominent since it enables to deposit SiCu films with various structures without a need of binder or any conductive additives. By optimizing the evaporation rate of sources materials (Si and Cu in that case), the incident angle and the azimuthal rotation rate of the substrate nanocolumns, chevrons and helices might be deposit directly on the current collector.

In this work, we keep the incident angle and the azimuthal rotation rate as 85o and 0.02 rpm, respectively. We produce two Si based structured thin films with 10% at. Cu, with different evaporation rates. The quartz crystal microbalances of Cu and Si show 0.4-4.4 Ǻ/s and 0.9-10 Ǻ/s for Samples 1 and 2, during evapoaration. The morphological test results show that the interaction between the evaporation and the azimuthal rotation rates change the structure of the film. Following the morphological and structural characterizations, their potential uses as anodes in lithium ion batteries are evaluated by means of electrochemical tests.
Tuning of Lithium Storage Properties of MLi2Ti6O14 (M=2 Na, Sr)
Authors: Yoo Young Geun , Bae Seongjun , Nam Inho , Park Soomin , Park Jongseok , Lee Jong Min , Han Jeong Woo , Yi Jongheop
Published: February 2020

Supplying precise power is a significant factor in many electric devices to secure optimized performance, energy efficiency and device protection. For example, in OLEDs, the energy efficiency is highly dependent on the applied potential. However, most of electrode materials for batteries have its unique thermodynamic value, which is almost impossible to be adjusted. Therefore, tunability of the electrochemical property of materials is highly desirable for improving the performance of electric devices.

MLi2Ti6O14 (MLTO, M = 2 Na, Sr, Pb, Ca, Ba etc.) have been paid attention for the next-generation anode material for lithium-ion batteries (LIB) because of its lower working voltage than that of Li4Ti5O12 (LTO). Also, they shows flat potential plateau as well as LTO. Their operating potential and equivalent amount of intercalatible lithium ions varies depend on the M species. However, all of their crystal structures are analogous, except minor differences. Based on these observations, we achieved precise tuning of the electrochemical properties of MLTO with two coexisting M species by modulating stoichiometry of M species.

In this research, we used Na, Sr-coexisting MLTO (Na2-2xSrxLi2Ti6O14, NaSrLTO). Na2Li2Ti6O14 (NaLTO) has the lowest working potential (1.25 V) as well as the lowest reversibly intercalatible Li+ (2.0 equiv.-1) among the MLTOs, and SrLi2Ti6O14 (SrLTO) is diametrical of NaLTO (1.4 V and 2.5 equiv.-1). In NaSrLTO, operating potential gradually rises and equivalent inserted Li+ increases as higher ratio of Sr exists. Ab initio calculations revealed that the gradual potential change is originated from the gradual change of electron density of Ti3+/Ti4+ redox center. Also, Because SrLTO has half-vacant 8f Wyckoff position, SrLTO is able to store more Li+ than NaLTO, which all of Na atoms fully occupy the 8f Wyckoff position.
Copper Nanowire Network: A Promising Current Collector for High Performance Li Secondary Batteries
Authors: Ha Yoon-Cheol
Published: February 2020

Copper nanowire network has recently been considered as a promising current collector which can replace the conventional copper foil commercially used in lithium secondary batteries. Using this new kind of current collector and silicon as the active material, two different Cu-Si nanostructured electrodes were fabricated, i.e., Cu-Si core-shell nanostructure by vapor deposition of Si onto Cu nanowire network and Si nanoparticle decorated Cu nanowire network by solution mixing and co-settling. The former showed excellent rate and cycle performance, i.e., the specific capacity over 1,000 mAh/g @ 4 A/g with no capacity decay during 100 cycles, while the latter showed higher capacity (~2,400 mAh/g @ 0.1 A/g) with poor rate performance. The contact resistance between Cu nanowires and Si active materials played crucial role in the electrochemical performance of Cu-Si nanostructured anodes. With these preliminary results and the full mechanistic understanding of Cu nanowire growth in solution, the practical applications of the copper nanowire network current collector are discussed.
Designing Microstructure with Voids of Si-Based Anode Materials for Li-Ion Batteries
Authors: Kang Inyeong , Jang Juyoung , Kim Moon-Soo , Kim Jae-Hun , Park Jin-Woo , Cho Young Whan
Published: February 2020

Silicon has been regarded as one of the most promising anode materials for Li-ion batteries because of its higher specific capacity than carbon anodes. However, there is a fatal problem that Si undergoes massive volumetric change (about 400%) during lithiation/delithiation process. This large volume change results in the following sequential processes; pulverization, breakage of solid electrolyte interface (SEI), creation of new surface for SEI formation, continuous exhaustion of electrolyte, and finally sudden capacity fade. Among many attempts to solve these problems, the microstructure control with voids showed notable progress in improving the cycle performance. But the synthetic methods adopted so far were too complicate to apply to large scale commercial processes.

Here, we introduce a microstructure of Si-based anode materials with voids using water-soluble compounds. The role of water-soluble compounds is to create enough spaces within the anode agglomerate particles, so that they can expand without generating excessive crack on the surface during the electrochemical reaction. We synthesized active anode materials using ball-milled ferrosilicon alloy and fine water-soluble compound mixtures as starting materials. After coating with carbon precursor followed by carbonization heat treatment, they were washed with distilled water to remove the water-soluble compounds which create void structure in anode particles. The evidences of the removal of the water-soluble compounds were provided by X-ray diffraction, FIB cross-section/EDS analysis, and BET analysis. From the electrochemical cell test, significant improvement of battery performance including coulombic efficiency, irreversible capacity were observed, especially at the beginning of the cycles, compared to that of anode materials without void structure. The present study shows the simple and practical approach to realize an ideal microstructure of Si-based anode for rechargeable Li-ion batteries.
EU R&D Project "inside" - in-Situ Diagnostics in Water Electrolysers
Authors: Biswas Indro , Schulze Mathias
Published: February 2020

In this joint R&D project supported by the EU Fuel Cell and Hydrogen Joint Undertaking, an electrochemical in-situ diagnostics tool for the monitoring of locally resolved current densities in polymer electrolyte membrane fuel cells, is adapted to three different water electrolysis technologies. The developed tools allow correlating performance issues and ageing processes with local anomalies. The corresponding mechanisms are investigated with ex-situ analytics.

Partners

– Deutsches Zentrum für Luft- und Raumfahrt e.V., Stuttgart, Germany (Coordination)

– NEL Hydrogen AS, Notodden, Norway (Alkaline water electrolysis)

– Heliocentris Italy S.r.l., Crespina, Italy (Anion exchange membrane based water electrolysis)

– Centre National de la Recherche Scientifique, France (Ex-situ analytics)

– Université de Strasbourg, Strasbourg, France (Ex-situ analytics)

– Hochschule Esslingen, Esslingen, Germany (Ex-situ analytics)

 The patented segmented printed circuit board (PCB) for the monitoring of current density distributions in PEM based fuel cells is used and continuously improved at DLR. Applications are e.g. the investigation of specific degradation mechanisms, or systematic optimisation of operation parameters.

 The embedding of an in-situ diagnostics tool in water electrolysis system enables:

– monitoring of performance and local anomalies during operation

– revealing systematical deficiencies not detectable with off-line diagnostics

– correlating degradation mechanisms and system parameters

– identifying and preventing critical operation

– systematically improving the efficiency of water electrolysis

Acknowledgements

The research leading to these results has received funding from the European Union's Seventh Framework Programme (FP7/2007-2013) for Fuel Cell and Hydrogen Joint Technology Initiative under Grant No. 621237 (INSIDE).
Organosilane Coatings for Ni-Rich High-Voltage Lithium Ion Batteries
Authors: Peebles Cameron , Dogan Fulya , Hubaud Aude A. , Vaughey John T. , Liao Chen
Published: February 2020

One of the more promising cathode materials for high-energy high-voltage lithium ion batteries (LIBs) are Ni-rich layered cathode materials such as LiNixMnyCozO2 (where x + y + z = 1). Although these cathode materials are attractive from a high capacity standpoint, they commonly suffer from poor structural stability at highly delithiated (charged) states leading to poor electrochemical performance.1-3 While incorporation of additives into the electrolyte provides one way to improve cycling performance in LIBs, surface coatings are becoming a widely adopted method to improve the cycling performance of high-voltage cathode materials. More widely investigated coating materials include oxide coatings (Al2O3, TiO2, etc.)4 while comparatively fewer studies have investigated organic monomer or polymer coatings (PEDOT, polyimide, etc.).5 Additionally, the mechanism of the coating interaction with the material is intriguing due to its importance in creating a performance-enhancing coating.

In this work, the surface of LiNi0.5Mn0.3Co0.2O2 cathode materials were coated with organosilane reagents to investigate their effect on cell electrochemical performance. The impact of the cathode pretreatment, the weight percentage of organosilane used and the functionality of the organosilane used will be presented. Characterization of the organosilane coating using SEM shows a slight morphological change in the cathode surface while EDX and FTIR confirm the presence of a Si-containing coating. Half cells (Li/ LiNi0.5Mn0.3Co0.2O2) using the organosilane coated cathodes operating in the voltage window of 3.0 - 4.4 V showed similar cycling behavior to that of non-coated material. In conclusion, a new type of organic coating was utilized on Ni-rich cathode materials and this research explores a new type of coating for high voltage cathodes.

References

1)      Son, I. H.; Park, J. H.; Kwon, S.; Mun, J. and Choi, J. W. Chem. Mat.
2015, 27, 7370-7379.

2)      Bak, S.-M.; Hu, E.; Zhou, Y.; Yu, X.; Senanayake, S. D.; Cho, S.-J.; Kim, K.-B.; Chung, K. Y.; Yang, X.-Q. and Nam, K.-W. ACS Appl. Mater. Interfaces
2014, 6, 22594-22601.

3)      Lin, F.; Markus, I. M.; Doeff, M. M.; Xin, H. L. Sci. Rep., 2014, 4, 5694.

4)      Xu, S.; Jacobs, R. M.; Nguyen, H. M.; Hao, S.; Mahanthappa, M.; Wolverton, C.; Morgan, D. J. Mater. Chem. A, 2015, 3, 17248.

5)      Zhang, J.; Lu, Q.; Fang, J.; Wang, J.; Yang, J. and NuLi, Y. ACS Appl. Mater. Interfaces
2014, 6, 17965-17973.
Improved Catalysts for Direct Methanol Fuel Cells
Authors: Fang Dan , Yang Bo , Narayanan S. R.
Published: February 2020

Direct methanol fuel cells (DMFCs) are attractive among advanced energy conversion technologies due to the high energy density of methanol, the overall simplicity of system and easy refueling.[1] Although they made an early market entry but did not achieve large-scale commercialization mainly because of the cost, performance and durability issues. The state-of-art DMFC systems are based on the use of Pt-Ru catalyst at the anode, Pt catalyst at the cathode, and a polymer electrolyte membrane separating the two electrodes.[2] Our present study is focused on the anode catalyst, specifically to improve its performance and durability and reduce its cost. To this end, we have examined the use of titanium oxide-ruthenium oxide solid solutions as co-catalyst supports. 

We have prepared Pt/Ti0.7Ru0.3O2 for use as an anode catalyst. Ti0.7Ru0.3O2 as a co-catalyst support was synthesized in a one-step hydrothermal process and then platinum was deposited using polyol method. The structure of the synthesized catalyst was investigated by XRD, SEM and EDX. Results of steady-state voltammetry suggest that the electrocatalytic activity and stability of the newly synthesized catalysts compare well with the commercially available carbon-supported Pt-Ru catalyst. The Tafel slopes suggested that the well-known bifunctional mechanism for methanol oxidation was operative on the new catalyst as well. With further optimization of this type of catalyst we expect to be able to lower the noble metal content further to enable practical use of these materials in fuel cells. 

References [1] S. Surampudi, S. R. Narayanan, E. Vamos, H. Frank, G. Halpert, A. LaConti, J. Kosek, G. K. Surya Prakash and GA Olah, "Advances in Direct Oxidation Methanol Fuel Cells," Journal of Power Sources, 47, 377-385 (1994) [2] Handbook of Fuel Cells, “Portable Direct Methanol Fuel Cell Systems”, S. R. Narayanan, T. I.Valdez, in Vol IV Part 1, (Eds. H. Gasteiger, A. Lamm and  W. Veilstich), Wiley Interscience ( March 2003)
Effect of Metal Ions Doping on the Structural and Electrochemical Properties of Olivine LiFePO4
Authors: Nieto Ramos Santander M , Mosquera Vargas Edgar E , Morel Mauricio
Published: February 2020

Li ion rechargeable batteries have better performance over the other competitive rechargeable batteries due to their higher operative voltage (around 3-4 v range), high-energy storage capacity, low self-discharge, and high cycleability. For the application in high power devices (various consumer electronic products such as laptop, camcorder, etc.) the discharge capacity of Li ion batteries at higher current rate required is to be improved. As diffusion of lithium ions inside the active material particles is the rate-limiting step of intercalation process, faster Li+ diffusion in the electrode materials could improve the rate capabilities of Li ion batteries. Olive LiFePO4 is a very promising cathode material used in lithium ion batteries, due to its environmental friendliness, high theoretical capacity (170 mAhg-1), low cost of precursors, high reversibility of Li+ insertion/extraction, good thermal stability, and lack of toxicity. In spite of these attractive features, LiFePO4 requires further modifications to overcome limitations such as poor electronic conductivity  and  slow  lithium  ion  diffusion.  In  this  work  we  have  synthesized  olivine  LiFe1-xMxPO4 (M = Nb, Yb, Sb, Mg)(LFMPO) powders by chemical synthesis and co-precipitation method. The synthesized powders were used to prepare cathodes for Li ion coin cells. The structural and electrochemical properties were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared, Raman spectroscopy, cyclic voltammetry and charge-discharge studies, respectively. The phase pure and crystalline quality of the materials was studied from XRD peaks and their line widths respectively. 7Li magic angle spinning nuclear magnetic resonance were used to compare the cation arrangement in the undoped and doped powders. The cyclic voltammetry of both the cathodes revealed the reversible nature of Li-ion intercalation in the cell. The dopant induced structural and stoichiometric modifications were correlated with the voltage cycling and charge discharge characteristics of these cathode materials.
Synthesis and Electrochemical Characterization of LiMn2-xFeXO4 Cathode Materials for LI Ion Rechargeable Batteries
Authors: Singhal Rahul , Katiyar Rajesh K. , Katiyar Ram , Chiovoloni Sam , Lemaire Peter
Published: February 2020

High energy density batteries are essential for portable electronic devices e.g. Laptops, mobile phones, iPads, toy etc. Besides this, high energy density batteries are also required for power tools and hybrid electric vehicles. Commercially available lead-acid batteries are toxic and have low energy density and not suitable for electronic devices. Advanced Li-ion batteries possess high specific energy as compared to existing rechargeable battery technologies. Commercially available Li ion rechargeable batteries having LiCoO2 as cathode materials are toxic and expensive due to the presence of cobalt. Additional disadvantage of LiCoO2 based batteries is their low operating voltage (3 V), which restricts their application for hybrid electric vehicles and power tools. It has already been reported that the charge-discharge characteristics and cycleability of LiMn2O4 can be improved by substituting the Mn3+ ion with transition metals e.g. Cr, Co, Ni, Cu  etc. To increase the energy density of the Li ion rechargeable batteries we will be exploring the cathode materials, working in higher operating voltage (~5V) range.

We have synthesized LiMn2-xFexO4 cathode materials for Li ion rechargeable batteries. The concentration of Fe varies from 0.1 to 0.5 with an increment of 0.1. The cathode materials were synthesized by sol-gel method and calcined at various temperature in the range of 800 oC to 950 oC. The synthesized materials were physically characterized by X-ray diffraction (XRD), differential thermal scanning calorimetry (DSC), micro-Raman spectroscopy and scanning electron microscopy.  We obtained phase pure Fd3m structure in all synthesized compounds. The electrochemical characterization were carried out in a coin cell configuration using cyclic voltammetry, charge-discharge characteristics, impedance spectroscopy and cycleability. Cyclic voltametric studies reveal the reversible electrochemical properties of LiMn2-xFexO4 cathode materials. The detailed results and discussion on physical and electrochemical properties of LiMn2-xFexO4 cathode materials will be presented in the ECS 229th meeting.
Synthesis and Conductivity of Directly Cross-Linked Poly(vinyl alcohol)/ Bis (2 chloroethyl) Ether-1,3-Bis[3-(Dime- thylamino) Propyl]Urea Copolymer Composite
Authors: Qiao Jinli
Published: February 2020

The alkaline membrane fuel cells (AMFCs), which use the anion-exchange membranes to display the proton-exchange membranes with OH- anions instead of H+ ions, have aroused new interest due to their faster electrokinetics, lower fuel crossover, reduced CO poisoning, and use of non-precious metal catalysts 1,2.In the development of AEMFCs, the conductivity of  alkaline anion-exchange membranes (AEMs) is considered to be the most challenge, since the mobility of OH- is only 1/4 of that of the H+ transportation (membranes that conduct H+ cations), the membranes that can have high OH- conductivity are highly desired for making a breakthrough in AEMFCs performances3,4. However, these polymers were generally of high price and their quaternization is complex process.

In this work, we report a novel alkaline anion-exchange membrane prepared from poly(vinyl alcohol)/Bis(2-chloroethyl)ether-1,3-bis[3-(dimethylamino)propyl]urea copolymer (PUB) composite on the basis of direct chemical cross-linking method5 .By incorporation of PUB, the OH- conductivity of the PVA/PUB membrane was found to be greatly improved and reached high up to 5.56×10-
3S cm-1 .

The membranes were prepared by a simple solution-casting method, where PVA (99% hydrolyzed, average molecular weight Mw=86,000-89,000; Aldrich) was fully dissolved in water to make a 10% solution at 70oC. PUB (62% as active ingredients in H2O; Aldrich) and glutaraldehyde (GA) solution(25% mass) was directly added by addition of a drop of HCl to get a homogeneous appearance at room temperature, and stir for 30 min. The anion conductivity of PVA/PUB/GA composite membrane is studied using AC impedance technique.

Figure 1 composite membrane picture of PVA/PUB. It is obvious that the membrane is standing and flexible. 

Figure 2 shows the ionic conductivity of the membrane (PVA:PUB:GA=1:0.25:0.05 and PVA:PUB:GA=1:0.25:0.1 by mass) as a function of content of GA. The sOH
- values increased with increasing GA contents and reached 5.56×10-3 S cm-1 when polymer composition is PVA:PUB:GA=1:0.5:0.1 by mass.

References

1. J. Zhou, M. Ünlü, I. Anestis-Richard, P.A. Kohl, J. Membrane Science, 350 (2010)286.

2.J. L. Qiao, J. Fu, R. Lin, J. X. Ma, J. S. Liu, “Alkaline solid polymer electrolyte membranes based on structurally modified PVA/PVP with improved alkali stability,”Polymer, Vol. 51, pp. 4850-4859(2010).

3. Jinli Qiao, Jing Zhang, Jiujun Zhang, Journal of Power Sources 237 (2013) 1e4.

4.Y. Wan, B. Peppley, K A.M Creber, V. Tam Bui, J. Power Sources. Soc. 195, 3785 (2010).

5.J. L. Qiao, J. Fu, L. L. Liu, L. Xu, Y. Y. Liu, J. W. Sheng, Int. J. Hydrogen Energy 37, 4580 (2012).

Figure 1
Marker Pen Lithography for Flexible and Curvilinear on-Chip Energy Storage
Authors: Kurra Narendra , Jiang Qiu , Alshareef Husam
Published: February 2020

On-Chip energy storage is currently on high demand as its potentiality for compatible integration with flexible and miniaturized functional electronic devices. Conventional microfabrication has been the widely employed technique in fabricating interdigitated microsupercapacitor devices in a reliable manner. However, developing unconventional lithography techniques can be attractive interms of simplicity with minimal sophistication while not compromising the performance. Here, we propose a simple and versatile strategy to fabricate on-chip microsupercapacitors (MSCs) employing hand-written sacrificial marker ink patterns, both in lift-off and etching modes. As a prototype, this technique is demonstrated for the fabrication of conducting polymer MSCs involving poly(3,4-ethylenedioxythiophene), polyaniline and metal oxide electrode materials. Typical values of energy density in the range of 5-11 mWh/cm3 at power densities of 1-6 W/cm3 are achieved, that are comparable to thin film batteries and superior to the carbon and metal oxide based microsupercapacitors reported in the literature. Fabrication of microsupercapacitor devices on curved surfaces and multi-stack designs are additional assets of this technique. This innovative strategy may be broadened for scalable fabrication of a wide variety of on-chip energy storage devices.
Li Salt Rich Separator for Li-Ion Batteries
Authors: Mourzagh Djamel
Published: February 2020

In order to reduce the duration of the electrolyte filling step, Solvay proposes a new concept of separator embedding itself Li salt thanks to a Li salt rich film coated on (Patent Solvay).

The objective of the present study was to quantify the impact (benefits and drawbacks) of a Li salt containing PVdF based film deposited by coating onto a conventional polyolefin based separator. The thin coated layer is composed of Solef® PVdF containing LiTFSI salt in appropriate amount. The separator selected for the study was the Celgard® 2320.

After having developed the method for manufacturing such a coated separator, electrical evaluations were conducted in representative intermediate capacity-level Li-ion cells, trials with pilot coating machines were also performed to demonstrate the feasibility of coating a separator at industrial level and the impact of the storage were also studied.
Evaluation of Silicon-Based Full Cells and the Importance of Scale-up
Authors: Karulkar Mohan , Wen Hao , Blaser Rachel , Kudla Robert
Published: February 2020

USABC long-term EV targets highlight the need for higher energy density in automotive batteries [1].  Many promising high energy materials have been demonstrated in academia, but there is a gap between academic and industrial research.  This is partly due to the incompatibility of automotive targets with academic research metrics.  Some common metrics are shared between the two arenas, but there remain others that do not translate due to scale.  Bench-top experiments are helpful for identifying promising materials, but key automotive metrics like volume change are impractical to measure in bench-scale cells.  Thus, scale-up of benchtop research is critical to fully addressing automotive needs.

This talk will detail various metrics that lend themselves to scale-up.  Specifically, we will discuss Ford’s efforts to quantify volume change in Silicon-based anodes.  Previously, Ford has reported on electrochemical performance of silicon-based cells [2], and here we will tie those results in with volume expansion for different cell configurations.  We will also combine the results with our ongoing Automotive Target Modelling efforts [3].  Finally, this talk will provide an overview of the user-based battery fabrication facilities available at the University of Michigan Battery Lab.

[1] “USABC Goals for Advanced Batteries for EVs - CY 2020 Commercialization,”  http://www.uscar.org/commands/files_download.php?files_id=364 (2014)

[2] M. Karulkar, R. Blaser, R. Kudla, J. Power Sources, 273, 1194-1201 (2015).

[3] M. Karulkar, “Battery Metrics and Real World Automotive Target Modelling,” 227th Electrochemical Society Meeting, Paper MA2015-01 33, Chicago, IL (2015).
Macroscale Vs. Microscale Simulation of Porous Battery Electrodes
Authors: Higa Kenneth , Wu Shao-Ling , Parkinson Dilworth Y. , Fu Yanbao , Battaglia Vince , Srinivasan Venkat
Published: February 2020

Typical porous composite electrodes are enormously complicated, disordered arrangements of active material, binder, conductive material, and pore space. In spite of this complexity, battery simulations based on the porous electrode model pioneered by John Newman have provided a wealth of insight into battery operation at low computational cost. This is made possible by the use of spatial averaging to produce vastly simplified spatial domains on which averaged governing equations can be rapidly solved. With these simplifications, the porous electrode model can provide information about the average spatial variation of quantities such as lithium ion concentration and electrochemical potential.

However, results from simulations based on the porous electrode model are known to diverge from experimental results under relatively demanding operating conditions (see, for instance, [1]) that can arise during typical electric vehicle use. This might be the consequence of the spatial averaging approach of the porous electrode method, as electrode microstructure might have a significant influence on transport processes and cell performance. In order to explore this possibility, we have performed traditional porous electrode model simulations and corresponding electrochemical simulations based on the microscale electrode structure.

Nickel manganese cobalt oxide (NMC) electrodes were fabricated and incorporated into half-cells, from which discharge curves were obtained. Electrode parameters were used to construct simulations based on the porous electrode model, and an optimization scheme was used to minimize discrepancies between simulation and experimental results.

Samples of the same uncycled NMC electrode material were then imaged at the X-ray microtomography beamline of the Advanced Light Source (ALS). Three-dimensional reconstructions were transformed into spatial domains, on which direct numerical simulations were performed to obtain discharge curves. These simulations preserved spatial detail but involved much higher computational costs than those based on the porous electrode model.

We will present results from these microscale and macroscale simulations, exploring reasons for discrepancies between the two models and discussing present shortcomings with respect to experimental results.

[1] M. Doyle, J. Newman, A. S. Gozdz, C. N. Schmutz, and J.-M. Tarascon, J. Electrochem. Soc. 1996, vol. 143, issue 6, pp. 1890-1903
An Innovative Polymer Design for Polysulphides Shuttle Effect in Lithium-Sulphur Batteries
Authors: Ling Min , Yang Changan , Zhao Hui , Jia Zhe , Wang Huali , Fang Shan , Liu Gao
Published: February 2020

Lithium sulphur batteries hold great potential due to its around 5 fold energy density promotion compare to conventional lithium ion batteries. However, wide-scale has been impeded by rapid capacity fading mainly caused by shuttle effect in consequence of intermediate polysulphides diffusion. Herein, we propose a scalable bottom-up polymer approach to immobilize intermediate polysulphides.  The evolution of the chemical bonding was studied in detail. The electrochemical results show a high initial capacity of ca. 1500 mAh/g and 900 mAh/g after 100 cycles specifically at 0.05 C to magnify the shuttle effect. Moreover, a high areal capacity of ca. 6 mAh/cm2 is achieved, which demonstrate the excellent capability to trap soluble polysulphide intermediates.
In Situ Measurement of the Surface Lithiation of Metal Oxide Thin Films at Elevated Potentials
Authors: Fister Timothy T , Kim Jae Jin , Evmenenko Guennady , Buchholz Donald Bruce , Chen Xiao , Bedzyk Michael J. , Castro Fernando , Wu Jinsong , Dravid Vinayak , Esbenshade Jennifer , Lundberg Kimberly E. , Gewirth Andrew A. , Yildirim Handan , Greeley Jeff , Fenter Paul
Published: February 2020

The capacity of most battery insertion reactions is limited by the number of open lithium sites in electrode’s crystal structure, usually reaching one per metal atom. Conversion reactions, where the metal oxygen bond is broken to form clusters of Li2O and metal particles, can achieve far higher lithium stoichiometry. However, this process is much less reversible than intercalation and occurs at significantly lower potentials than theoretically expected, which has limited their commercial appeal. To pinpoint the underlying connection between structural changes and the observed overpotentials for lithiation, we have studied conversion reactions in MOx (M = Ni, Fe, and Cr) thin films using the sub-nm interfacial sensitivity of in situ x-ray reflectivity. These studies show that conversion begins at elevated potentials (near 2 V) at the surface before propagating into the bulk. Heterostructures incorporating metal interlayers can also help define the direction and extent of the phase separation. We will discuss the possible origins of this effect and strategies to improve the kinetics and scalability of these model electrodes. This work was supported as part of the Center for Electrochemical Energy Science, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science.

Figure 1
Atomic Layer Deposited Fluoride Coatings for Li-Ion Battery Cathodes
Authors: Jackson David H. K. , Laskar Masihhur , Fang Shuyu , Xu Shenzhen , Ellis Ryan G. , Li Xiaoqing , Dreibelbis Mark , Babcock Susan E. , Mahanthappa Mahesh K. , Morgan Dane , Hamers Robert J. , Kuech Thomas F.
Published: February 2020

Atomic layer deposition (ALD)1, 2 of AlF3 coatings for the Li-ion battery cathode LiNi0.5Mn0.3Co0.2O2  (NMC)3, 4 was investigated using a combination of trimethylaluminum and TaF5 precursors. ALD growth mode was dictated by a competition between temperature-limited desorption of Ta reaction byproducts and temperature-driven conversion of these byproducts into nonvolatile TaC. At T ≥ 200°C, decomposition to TaC occurred, leading to continuous deposition and high concentrations of TaC in the resulting films. A self-limited ALD growth mode was found to occur when deposition temperature was reduced to 125 °C, and the TaF5 exposures were followed by an extended purge. During ALD growth, vapor-surface ligand exchange reactions lead to formation of Ta(CH3)xF5-x and AlF3. Ta(CH3)xF5-x desorbs from the surface or it decomposes via an intermolecular α-hydrogen abstraction,5,6 eventually forming TaC. The extended purge times and lower temperatures reduce decomposition, while also allowing more time for Ta(CH3)xF5-x desorption. NMC cathode powders were coated using these optimized conditions, and coin cells employing these coated cathode particles were characterized using electrochemical impedance spectroscopy and by cycle performance testing, which demonstrated significant improvements in charge capacity fade at high discharge rates as compared to uncoated materials (Figure 1). These improvements at high C-rates are attributed to the reduction of undesirable electrode-electrolyte reactions by protection of the cathode surface with the ALD coating through which fast Li-ion transport occurs.7-9

Figure 1: Averaged gravimetric capacity of coin cells versus discharge cycle number during a rate test. Black squares (■) fluoride ALD coated, red circles (●) uncoated.

References

1.             R. L. Puurunen, Journal of Applied Physics, 2005, 97, 52.

2.             S. M. George, Chemical Reviews, 2010, 110, 111-131.

3.             Z. H. Lu, D. D. MacNeil and J. R. Dahn, Electrochemical and Solid State Letters, 2001, 4, A200-A203.

4.             N. Yabuuchi and T. Ohzuku, Journal of Power Sources, 2003, 119, 171-174.

5.             R. R. Schrock, Journal of Organometallic Chemistry, 1976, 122, 209-225.

6.             Y. D. Wu, K. W. K. Chan and Z. Xue, Journal of the American Chemical Society, 1995, 117, 9259-9264.

7.             K. S. Lee, S. T. Myung, D. W. Kim and Y. K. Sun, Journal of Power Sources, 2011, 196, 6974-6977.

8.             S. Q. Hao and C. Wolverton, Journal of Physical Chemistry C, 2013, 117, 8009-8013.

9.             S. Z. Xu, R. M. Jacobs, H. M. Nguyen, S. Q. Hao, M. Mahanthappa, C. Wolverton and D. Morgan, Journal of Materials Chemistry A, 2015, 3, 17248-17272.

Figure 1
Solid Electrolyte Interphase Formation Mechanism on Silicon Revealed By in-Situ Attenuated Total Reflection-Infrared
Authors: Shi Feifei , Ross Philip N
Published: February 2020

Si has been widely recognized as one of the most promising anode materials for its high energy density; however, critical drawbacks such as large irreversible capacity decay and poor reliability/durability over extended cycles have significantly constrained its commercialization in many long duration, heavy duty applications. Aforementioned drawbacks are partially due to loss of electrolyte by reduction at electrode surface (formation of Solid Electrolyte Interphase (SEI)) and the chemical/mechanical instability of SEI through cycling. For a better understanding on the mechanism of Si electrode failure during battery cycling, we design and develop a novel in-situ ATR-FTIR spectra-electrochemical cell, and study the SEI chemistry using this in-situ ATR-FTIR technique.

In this work, we investigate the chemical composition of SEI on single crystal silicon electrode (100), which was selected as an ideal model surface. By tuning the probing depth in vibrational spectra of molecules near the electrode surface, we specifically address the dependence of SEI chemical composition on applied potential and penetration depth from interface to bulk. The experimental observation indicates that soluble species like DEDOHC is formed at silicon surface covered by native oxide, which is related to the chemical instability of SEI and contributes to the early failures of Si anode. In contrast, the main component of SEI on Li15Si4 is LiEDC, which is responsible for the passivation of freshly cracked surface during the long-term cycling. Si-F species are visible at inner interphase, while the organic product mainly locates at the outer portion of SEI. These clues pave the SEI formation paths on silicon anode, showing how the chemical side reactions couples with mechanical degradation. These failure modes understanding would also benefit other alloy host electrodes, which suffer from multiple fold degradation.

Acknowledgement:

This work was supported by the Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Freedom CAR and Vehicle Technologies of the U.S. Department of Energy under contract No. DE-AC02-OSCH11231.
Coupling of Electrochemical Charging with Mechanical Expansion and Degradation in Nanostructured MnO2 Cathodes
Authors: Ignatova Tetyana , Rajapakse Arith J. , Collins Philip G.
Published: February 2020

The faster kinetics of nanostructured charge-storage materials are often accompanied by accelerated degradation and failure, compromising the potential advantages of nanostructure and nanoporosity.  Understanding and controlling the exact mechanisms of this degradation is a complex materials characterization challenge.  The recent availability of in situ and in operando techniques allows new fundamental studies of these issues, including the failure of nanoscale porosity to fully accommodate the mechanical strains of charge insertion.

Here, we use atomic force microscopy in liquid electrolytes to experimentally measure the mechanical expansion of porous, nanostructured Li-ion cathodes during charge cycling.  Using thin films of LixMnO2 on Pt collectors, we analyze expansion as a function of scan rate, voltage window, and porosity.  Comparative measurements in aqueous and nonaqueous electrolytes confirm the role of Li-ion species in the results.  The rate dependent measurements of expansion can be separated into diffusion-limited, bulk components driven by Mn3+/4+ charging and faster, surface processes, in the same way that these contributions to capacitance are normally separated.  Consequently, we have extracted the electrochemical-mechanical coupling coefficients ∂V/∂Q for surface and bulk processes separately.  While the bulk coupling coefficient provides an excellent match to values predicted from first-principles theory, the surface coupling is surprisingly large.  In fact, surface capacitance is responsible for a majority of the mechanical expansion at high rates, even when most of this capacitance would normally be attributed to double-layer charging mechanisms.  The result demonstrates the importance of Mn3+/4+ species at the electrolyte interface and the inability of these species to take advantage of the film’s nanoporosity for accommodating expansion.  In other words, fast surface charging processes do not involve mechanical relaxation of the material into adjacent pores, but rather drive expansion of the solid matrix.
High Temperature Alkaline Electrolysis - Status and Potential
Authors: Chatzichristodoulou Christodoulos , Mogensen Mogens Bjerg
Published: February 2020

Alkaline electrolysis is a proven technology with several large scale facilities for hydrogen production realized and operated reliably for decades. Nevertheless, its broader deployment is hindered by the relatively high cost for hydrogen production. To overcome this obstacle, it is necessary to improve cell efficiency, increase the production rate, and decrease capital cost. Since conventional alkaline electrolysis technology has reached maturation, only small incremental improvements can be expected. To achieve a drastic step forward, we have developed a new generation of alkaline electrolysis cells that can operate at elevated temperature and pressure, producing pressurized hydrogen at high rate (m3 H2/hm2 cell area) and high electrical efficiency.

The concept relies on the development of corrosion resistant high temperature diaphragms, based on mesoporous ceramic membranes where aqueous KOH is immobilized by capillary forces, in combination with gas diffusion electrodes that overcome mass transport limitations at large production rates. Raising the operating temperature offers a means to drastically improve performance, as both ionic transport and reaction kinetics are exponentially activated with temperature. Indeed, we have demonstrated alkaline electrolysis cells operating at 200-250 °C and 20-50 bar at very high efficiencies and power densities. This enables high production rates near the thermoneutral voltage, thereby overcoming the need for cooling.

This work will provide an overview of the exploratory technical studies undertaken so far. Two electrochemical test stations have been established to carry our experiments at elevated pressures (up to 99 bar) and temperatures (up to 300 °C). The conductivity of aqueous KOH was investigated at elevated temperatures to establish the optimum concentration at 200-250 °C. An optimum value of 0.84 S cm-1 was established at 200 °C for 45 wt% aqueous KOH immobilized in mesoporous SrTiO3. Gas diffusion electrodes were developed using metal foams loaded with different non-precious metal electrocatalysts in order to reduce the overpotentials for oxygen and hydrogen evolution. Small cells have been fabricated and operated at current densities of up to 1.75 A cm-2 and 3.75 A cm-2 at cell voltages of 1.5 V and 1.75 V at 200 °C at 20 bar, corresponding to electrical efficiencies of almost 99 % and 85 %, respectively. Long-term operation at 200 °C was successfully demonstrated for 400 h, suggesting relatively stable cell performance. Finally, low-cost production methods have been utilized for a first scale-up of the cell size from 1 cm2 to 25 cm2. Efforts are currently directed towards the investigation of the intrinsic activity of mixed oxides for the oxygen evolution reaction at elevated temperatures and pressures, and towards establishing the required infrastructure for testing of 25 cm2 cells.