bluuebunny/crossref_metadata_2025 huggingface dataset:
Heterojunction Diodes Comprising Nitrogen-Doped Ultrananocrystalline Diamond/Hydrogentad Amorphous Carbon and p-Type Silicon
Authors: Zkria Abdelrahman , Yoshitake Tsuyoshi
Published: February 2020

Ultrananocrystalline diamond/hydrogenated amorphous carbon composite (UNCD/a-C:H) films, wherein diamond crystallites with diameters of less than 10 nm are embedded in an a-C:H matrix, have a large absorption coefficients of 105 - 106 cm-1 in the photon energy range between 3 and 6 eV  that make them applicable to optoelectronics devices. Moreover, the realizations of p-type and n-type diamonds are desirable for the applications of diamond-based electronic devices. In this work, the heterojunction diodes comprising nitrogen-doped UNCD/a-C:H and p-type Si were fabricated by coaxial arc plasma deposition (CAPD) and the heterojunction parameters were evaluated from the current–voltage (IV) and capacitance–voltage (CV) measurements carried out in dark at room temperature. Furthermore, the photodetection performance was studied.

Experimentally, n-type UNCD/a-C:H films were deposited on p-type silicon substrate at a substrate temperature of 550 ºC with ambient pressure of 53.3 Pa. the Pd electrode is deposited on both sides by using of Radio Frequency (RF) sputtering. The (I–V) characteristics of the diodes measured in the dark . I-V curve exhibited a rectiﬁcation ratio of more than 104, which evidently confirms that nitrogen-doped UNCD/a-C:H possesses n-type conduction and easily forms junction with p-type semiconductor.

C–V measurements of the diode confirm junction formation, in which capacitance non-linearly decreases with increasing reverse bias voltage. The built-in potential of the heterojunction was estimated to be 0.68 eV from the extended linear part of 1/C2 plot. From the slop of 1/C2, carrier concentration of the UNCD/a-C:H film was estimated to be 6×1015 cm-3. Here, carrier concentration of Si substrate was 1×1015 cm-3 for the ﬁtting analysis. The value of depletion region width 𝑊UNCD in the UNCD/a-C:H ﬁlm was estimated to be 200 nm at the reverse voltages of ±1 V, which is close to that value generally measured for heterojunctions with closed ranges of carrier concentrations. More details will be explained in presentation during the conference.
Enhanced Formation of Carbon Microcoils Having Different-Sized Ni Catalyst By Different Injection Gas Sequence
Authors: Kang Gi-Hwan , Kim Sung-Hoon , Park Sangmoon
Published: February 2020

Carbon microcoils were synthesized using C2H2 flow as a source gas along with an initial short time (5 min) SF6 flow as an incorporated additive gas under the thermal chemical vapor deposition (CVD) system. Different interruption/injection of C2H2 or SF6 flow and different injection sequences of the gas flow were applied while maintaining the identical overall injection time of C2H2 and/or SF6 flow. Indeed, the injection sequence of C2H2 or SF6 flow was manipulated according to the different-sized Ni catalysts, namely small (~ 0.1mm) or large (~100 mm) size in diameter. In the case of the small-sized Ni catalyst, the formation of the carbon microcoils could be well-developed under the injection sequence of SF6 flow → C2H2 flow. In the case of the large-sized Ni catalyst, on the other hand, the injection of C2H2 flow prior to the injection of SF6 flow promotes the formation of carbon microcoils. Based on these results we revealed the role of C2H2 flow injection or SF6 flow injection with the different-sized Ni catalyst for the enhanced formation of carbon microcoils. Finally, we suggest the growth mode of carbon microcoils with the different-sized Ni catalyst.
Mixing Vs Layering: Importance of Controlled Architecture in Bimetallic Multilayer Electrode Toward Efficient Electrocatalyst
Authors: Gu Minsu , Kim Byeong-Su
Published: February 2020

Even though traditional electrode fabrication methods such as simple mixing process have been used in various energy storage and conversion devices due to its handiness, however, these methods could not fully utilize and maximize the intrinsic properties of each active material. With the limited control over the internal structure of the electrode, it also often poses a significant challenge to elucidate the structure-property relationship between components within the electrode. Taking advantages of versatile layer-by-layer (LbL) assembly which can tailor nano-architecture of hybrid electrodes, here we report electrocatalytic thin films for methanol oxidation by adjusting the assembly sequence of LbL films based on the Au and Pd nanoparticles (NPs) and graphene oxide (GO) nanosheets. In case of co-assembled bimetallic LbL structure of (GO/Au/GO/Pd)
n
where respective Au and Pd NPs are supported with GO nanosheets, the electrocatalytic activity is significantly higher than that of respective monometallic LbL electrode (i.e. (GO/Au)
n
and (GO/Pd)
n
). To further investigate the architecture effect on the electrochemical behavior, Au and Pd NPs are assembled with GO in a different relative position of hybrid multilayer electrodes. It is proved that the electrocatalytic activity can be highly tunable by the position of metal NPs in the LbL structure, suggesting the structural dependence of charge and mass transfer between the electrolyte and the electrode, which is otherwise impossible to investigate in a simple conventional electrode fabrication method. Because of the highly tunable properties of LbL assembled electrodes coupled with electrocatalytic NPs, we anticipate that the general concept presented here will offer new insights in the nanoscale control over the architecture of the electrode toward development of novel electroactive catalysts.
Development of the Negative Electrode Using Coin-Stacked CNF for Li Ion Battery
Authors: Shimizu Akihiro , Oda Hirokazu , Nakagawa Kiyoharu
Published: February 2020

In general, graphite materials are used for the negative electrode material for lithium-ion batteries (LIBs). Charge/discharge mechanism of LIBs occurs by Li ion intercalation/deintercalation into/from graphite layers. More high-performance LIBs have been demanded for usage as a power source such as electric vehicles.

We focused on the structure of carbon nanofilaments (CNF). The diameter of CNF is very small compared to graphite. CNF has a similar layered structure with graphite. Three distinct structure types of CNF has been identified based on the angle of graphene layers with respect to the filament axis, coin-stacked, cup-stacked, and tubular. CNF has remarkable electronic properties and many other unique characteristics. For this reason, CNF has received much attention. Therefore, in this study, we investigated that coin-stacked CNF (CSCNF) was synthesized by the chemical vapor deposition (CVD) method, and CSCNF negative electrode for LIBs was evaluated.

For CNF synthesis, nano metal particles loaded on oxidized diamond were used. Oxidized diamond has oxygen-containing functional groups arranged regularly. Therefore, nano metal particles is a highly dispersed on it. Pd metal was used for loaded metal. Pd metal could synthesized CNF having coin-stacked structures. Pd metal was loaded on oxidized diamond by metal nano-colloidal method. C2H4 as a feedstock for CSCNF was used.

Synthesized CSCNF was used for the negative electrode material. Electrochemical properties of the negative electrode were evaluated half-cell test. Half-cell was assembled in a glove box under an argon atmosphere. Oxidation-reduction reaction of the negative electrode was evaluated by cyclic voltammogram (CV) measurement. Capacity of the negative electrode was evaluated by a constant current charge and discharge (CC) measurement. CV and CC measurement were observed that CSCNF had a different discharge behavior as compared to graphite. Electrochemical measurements indicated that CSCNF negative electrode displayed discharged capacity (514 mAh/g) over the theoretical discharged capacity of graphite intercalation compounds (372 mAh/g). From the results, it seems that Li ion was intercalated into CNF layers and adsorbed on the surface of CNF. For this reason, adsorption of Li ion was gained high capacity of the negative electrode with CNF. The negative electrode with CNF was thus found to be appropriate materials for the use in LIBs.
Control of Galvanic Corrosion Behavior Between Tungsten and Titanium Nitride in CMP Application
Authors: Lee Kangchun , Seo Jihoon , Moon Jinok , Jung Yeongil , Paik Ungyu
Published: February 2020

Localized galvanic corrosion at the tungsten (W) and titanium nitride (TiN) interface causes fatal defects (e.g., corrosion and pitting issues) in chemical mechanical planarization (CMP) process. In this study, we control the corrosion potential difference between W and TiN via mixing of two corrosion inhibitors in order to decrease those defects. The roles of corrosion inhibitors in CMP slurry are analyzed by open circuit potential (OCP) measurements, linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS). Through these electrochemical approaches, we found that two mixed inhibitor system can decrease the galvanic potential and current density. CMP result with W/TiN patterned structure wafer shows that mixed inhibitor system prevents galvanic corrosion at the W/TiN interface during CMP, leading to decreasing the defects. We believe that the results investigated in this study will provide researchers with the importance of electrochemical approaches in W CMP.
Tribocorrosion of Type 316L Stainless Steel with Nanopore Arrays in Stimulated Body Fluid
Authors: Toji Chisato , Miyabe Sayaka , Tsuchiya Hiroaki , Fujimoto Shinji
Published: February 2020

Type 316L stainless steel is widely used as a biomaterial because of high corrosion resistance owing to the passive films that form spontaneously on the surface. However, if the passive films are broken by mechanical damages corrosion will be accelerated in the body, resulting in the failure of the integrity.

Wear causes the breakdown of passive films, which accelerates corrosion of metallic implant, as a result so-called tribocorrosion is induced. In order to suppress tribocorrosion, friction between materials should be well-controlled. For the control of friction, various surface treatments have been reported. Recently we reported the formation of nanopore arrays on Type 316L stainless steel by a simple anodization.In the present work, we examined tribocorrosion of Type 316L stainless steel with nanopore arrays in simulated body fluid.

The tribocorrosion of Type 316L stainless steel was examined in pin-on-disk wear test. UHMWPE (ultrahigh molecular weight polyethylene) and Type 316L stainless steel were used as a pin and disk materials, respectively. Two different surface morphologies were prepared for the disk of the stainless steel; mirror and nanopore arrays. The nanopore arrays were formed by anodization in an ethylene glycol containing sodium perchlorate. The pin-on-disk wear test was carried out in 0.9% NaCl solution or 30% FBS (fetal bovine serum) at 37 °C. During the test, the friction coefficient and the corrosion potential of the disk specimen were monitored simultaneously with time.

The corrosion potential decreased immediately after the test was commenced and then recovered gradually with time. After the test wear debris with the size of several micrometers was observed on the surface. In the presentation, the effects of surface nanostuture and organic components included in FBS on the tribocorrosion behavior of Type 316L stainless steel will be discussed.
Corrosion Morphologies in Different Welding Zones of Friction-Stir Welded (FSW) Aluminum Alloy AA5086AA5086, AA6061AA6061, and Dissimilar AA5086AA6061 Joints Exposed in Various Atmospheric Environments
Authors: Wohner Natalie , Hihara Lloyd H.
Published: February 2020

Similar and dissimilar joints of AA6061-T6 and AA5086 have been exposed in mild and severe marine, volcanic (with acid rain), rainforest, and arid atmospheric environments in the Hawaiian islands. The severe marine environment on the Marine Corps Base Hawai'i (MCBH) shows high humidity and rainfall and high chloride ion concentrations; whereas, the mild marine site on Coconut Island is characterized by a significant lower chloride ion concentration. Samples near the Kilauea Volcano on the Big Island are under exposure of acid rain, variable humidity, and sulfur dioxide plume. The rainforest at the Lyon Arboretum in Manoa represents the wet climate with high rainfall, high humidity and time of wetness, and low chloride ion concentrations. In contrast, the dry climate in Waipahu shows low humidity and rainfall, low time of wetness, and low chloride ion concentrations. The impact of the atmospheric environment on the severity of the corrosion has been studied in different welding zones of each type of sample. The focus was to show the dissilimarities in morphology of the parent material, the weld nugget, the heat affected zone (HAZ), and the thermo-mechanically affected zone (TMAZ). The microstructure and chemical composition of the different welding zones before and after the exposure to the environment have been characterized using Scanning Electron Microscopy (SEM) and Energy-Dispersive X-ray Analysis (EDXA). In addition to the field tests, laboratory tests have been performed to study galvanic corrosion between the different welding zones using the zero-resistance ammeter (ZRA) technique.
Corrosion of Aluminum Alloy-Polymer Matrix Composite Interfaces in Diverse Natural Atmospheric Environments
Authors: Howard Brent Ernest , Hihara Lloyd H.
Published: February 2020

The environmental corrosion of carbon-fiber/epoxy and E-glass/epoxy composite laminated aluminum alloys [e.g., Al 1100-H14, Al 5456-H116 (non-sensitized), Al 5456-H116 (sensitized), and Al 7075-T6] was studied to characterize the interfacial corrosion between the composite and the aluminum substrate. Samples were exposed at 5 locations around the islands of Hawai’i that represented alpine, marine, severe marine, rainforest, and volcano environments over 1-month, 6-month, and 12-month time periods. After exposure, the samples were then adhesion strength tested by conducting pull test to remove the composite laminate from the aluminum substrate to determine the loss (if any) of the composite laminate adhesion to their respective aluminum substrates. The delaminated samples were then analyzed with a scanning electron microscope and energy dispersive X-ray analysis to determine the distribution of corrosion products and ionic species at the aluminum substrate - composite laminate interfaces. The decay in adhesion strength was correlated to the amount of corrosion at the interface that was dependent on the type of composite and type of aluminum alloy.
Investigation of Anticorrosion Coatings for Iron Using Polyaniline By Electrochemical Impedance Method
Authors: Fujimatsu Ai , Aoki Atsushi
Published: February 2020

The most efficient corrosion inhibitors are based on heavy metal such as Cr. However, the use of them has now been widely restricted by law due to environmental and toxicological issues. So recently, anticorrosion method with conducting polymer has attracted attention because of free heavy metal. The conducting polymer, polyaniline is known to have a number of molecular configurations by redox status and pH. Two half oxidized forms, protonated emerardine salt(ES) and deprotonated emerardine base(EB) change reversibly by acid-base processing. In order to investigate the anticorrosion mechanism of the iron plate coated by deprotonated polyaniline film, we investigate electrochemical characteristics by AC impedance technique in the different anion solutions. Moreover, native oxidation layer of bare iron is also investigated. The three models of the equivalent circuits are proposed to explain the anticorrosion mechanism of the iron plate coated by deprotonated polyaniline film.

 

The metallic samples used in this study were bare iron JISG3141, rolled steel plate. All metallic samples were degreasing with acetone. EB was dissolved in N-methyl-2-pyrrolidinone and that 5.0 mg/mL polyaniline(EB) solution was prepared. This solution was casted to iron plate on the hot plate at 60 °
C. This state was maintaining for 6 hours to get EB coating plate. All AC impedance measurements were conducted using three-electrode system. Working electrode is iron electrode, reference electrode is saturated calomel electrode and counter electrode is Pt coil electrode. Also, two electrolysis solutions, 1.0 M NaCl solution and 0.1 M Na2B4O7 solution were used to compare corrosion behavior by anion species.

 

[1] D. W. DeBerry, J.Electrochem.Soc., 132, 1022-1026(1985).
Electrochemical Conversion of CoSb3 in Various Acidic Electrolytes
Authors: Veys-Renaux Delphine , Drevet Richard , Petitjean Carine , Aranda Lionel , David Nicolas , Berthod Patrice
Published: February 2020

CoSb3-based skutterudite compounds are promising thermoelectric materials thanks to a high figure of merit ZT. However their sensitivity to thermal degradation under oxidation mechanisms is a significant problem regarding their high operating temperature. A protective coating is therefore necessary. In this framework, the formation of an oxide conversion layer by surface anodizing represents an interesting alternative to PVD coatings usually considered.

In the present work, the electrochemical behavior of CoSb3 is studied over a large anodic voltage range (0 to 50 V) in three acids, i.e. phosphoric acid, oxalic acid and sulfuric acid at different concentrations (0.01 M to 1 M). Potentiodynamic polarizations performed on CoSb3 plates, in comparison with pure Co and pure Sb, reveal the possible formation of a passive layer between 1V and 3V, on a passivation plateau. Actually, below 3V, the electrochemical behavior of CoSb3 is similar to the behavior of pure Sb, whatever the electrolyte and the concentration. Beyond this potential, the current density rises on CoSb3 and stabilizes one order of magnitude higher. Regarding pure Co, it obviously undergoes dissolution as shown by the very high current densities reached.

The oxidation of CoSb3 at 2V in sulfuric and oxalic acids results in the growth of a conversion layer. According to SEM-EDS and DRX experiments, this coating is mainly made of amorphous antimony oxides (due to the high selective dissolution rate of cobalt in these media), constituting a porous (exfoliated) matrix. In the specific case of oxalic acid, sticks of crystallized oxalates (mostly antimony oxalate hydroxide but also cobalt oxalate hydroxide) are tangled between the oxide sheets.

Figure 1
Study of Micro-Scale Experimental Teaching Materials of Corrosion and Corrosion Protection for Maintenance Engineers
Authors: Ito Daisuke , Yokoyama Takashi , Okazaki Shinji
Published: February 2020

In this study, micro-scale experimental teaching materials corrosion and corrosion protection has been developed, it was investigated the educational effect and its usefulness. Experimental program is shown below.　

A. Basic experiment of Corrosion

1) Corrosion Observation

2) Confirmation of reaction on the iron surface

3) Observation of current caused by corrosion

B. Types of corrosion

4) Heterologous metal contact 　

5) Local corrosion under the sediments of rust　

6) Influence of chloride ions on the corrosion of stainless steel

C. Mechanism of corrosion protection

7) Cathodic protection by galvanic anode system

8) Cathodic protection by the external power supply system

Figure 1
Nonflammable, Fast Charging & Superb Cycle Life Battery Technology For Automotive Applications
Authors: Liu Wenjuan
Published: February 2020

Li-ion batteries are one of the most potential candidates as the energy storage devices mainly due to their high energy densities with fairly good rate capabilities and a fairly long cycle life.  Currently, Lithium-ion batteries are nearing their theoretical energy density limit and battery manufacturers are beginning to focus on improving manufacturing methods and increasing safety. In this presentation, I will introduce Microvast’s non-flammable battery technology for lithium-ion batteries resolves battery safety issues through a multi-level approach from materials to the system level. The new technology takes both active and passive protection measures in order to enhance product safety, including improvements to the battery's electrolyte, separator and protection system.  Meanwhile, the fast charging and superb cycle life are maintained for the automotive application. The nonflammable, fast charging & superb cycle life battery technology can solve the current key constraints in electric vehicle development and to redesign electric vehicle power systems to the mass adoption of electric vehicles.
Advanced Materials for Future Generations of Automotive Batteries: Potential and Limits
Authors: Lamp Peter
Published: February 2020

New mobility concepts are required to balance the individual need for mobility and the sustainable utilization of natural resources as well as the protection of the environment. Technology improvements are necessary that allow the transition towards mobility concepts based on renewable energies. Today the electrification of drive trains, ranging from hybrid vehicles to plug-in hybrids, and finally to pure electric vehicles, is the commonly accepted next step in this direction. BMW is strongly committed to this path.

The electric energy storage is the key technology for electrification. Energy and/or power density of the storage system define the fuel reduction potential as well as the customer acceptance. To make it a success story, care has to be taken to fulfill the present and future customer expectations, in particular with regard to safety and reliability, performance and costs. One of the major factors for a high market penetration of electric vehicles is the ratio between driving range and costs. More than 90% of the world wide vehicle market falls in the price range below 50.000$; on the other hand, a driving range above 400 km is needed. That requires energy density targets above 250 Wh/kg or 400 Wh/l for a battery pack, with costs as low as 150 $/kWh.

Different strategies are nowadays considered which enable a considerable increase in the electric range. These include the optimization of cell and electrode design. But the largest impact on the energy density is the introduction of novel cathode and anode materials for Li-ion cells. There are a number of materials in development which may give an improvement in energy density. But only a few seem to have the potential to meet automotive requirements in particular regarding lifetime and safety. For most of the material developments considerable improvements are needed before a possible industrialization of the new generations of batteries for automotive application can be envisaged.

This presentation will outline the potential and limits of present material concepts from a car manufacturer point of view. In particular it will address open issues to be solved in the future development of electric energy storage technologies for automotive applications.
Conversion-Alloying Anode Materials for Lithium-Ion Batteries
Authors: Mueller Franziska , Bresser Dominic , Passerini Stefano
Published: February 2020

Lithium-ion batteries, the most succesful power source for portable electronic devices, are emerging as the most promising energy storage devices for hybrid and, most likely, full electric vehicles. In our continuous efforts to develop high capacity, conversion-alloying anode materials for lithium-ion batteries,[1-4] we developed a new active material, Fe-doped SnO2 (Sn0.9Fe0.1O2, SFO), ideally characterized by low (de-)lithiation potential, high coulombic efficiency and long-term cycling stability. To the best of our knowledge, this is the first report on iron-doped tin oxide as active material for lithium-ion batteries. For battery applications, however, only one manuscript dealing with the utilization of molybdenum-doped SnO2 as active material for lithium-ion batteries was reported in 1999[5], i.e., prior to the first report on transition metal oxides as conversion materials by Poizot et al. in 2000.[6]

Within this study it is shown as doping SnO2 with Fe leads to significantly enhanced specific capacity, cycling stability, and coulombic efficiency. SFO-C offers, after ten cycles, a reversible specific capacity of 1519 mAh g-1, i.e., about twice that of pure SnO2, due to the presence of the dopant (Fe) favoring the reversible formation of lithium oxide and, thus, enabling the beneficial combination of lithium storage by alloying and conversion.

References:

1. D. Bresser, E. Paillard, R. Kloepsch, S. Krueger, M. Fiedler, R. Schmitz, D. Baither, M. Winter, S. Passerini, Adv. Energy Mater.
2013, 3, 513.

2. F. Mueller, D. Bresser, E. Paillard, M. Winter, S. Passerini, J. Power Sources
2013, 236, 87.

3. D. Bresser, F. Mueller, M. Fiedler, S. Krueger, R. Kloepsch, D. Baither, M. Winter, E. Paillard, S. Passerini, Chem. Mater.
2013, 25, 4977.

4. A. Varzi, D. Bresser, J. von Zamory, F. Mueller, S. Passerini, Adv. Energy Mater.
2014, 4, 1400054.

5. J. Morales, L. Sánchez, J. Electrochem. Soc.
1999, 146, 1640.

6. P. Poizot, S. Laruelle, S. Grugeon, L. Dupont, J.-M. Tarascon, Nature
2000, 407, 496.
Correlation Study Between 3D Three-Phase Electrode Morphology and Li-Ion Battery Performance: A Case for LiFePO4
Authors: Wang Hongqian , Liu Zhao , Verhallen Tomas , Singh Deepak , Wagemaker Marnix , Barnett Scott A
Published: February 2020

It is well known that the microstructure of the Li-ion battery (LIB) electrode can largely impact performance of LIBs. One approach to improve the performance of the LIBs is to gain insight in the correlations between the complex heterogeneous microstructure existing of active material, conductive additive and electrolyte, providing the required electronic and ionic transport. In a recent study we successfully demonstrated a simple and cost effective templating technique utilizing hydrogen carbonate salts to enhance the power density of LiFePO4electrodes without compromising the electrode density [1]. The applied templating method improves the capacity retention at high rates significantly. More importantly, the template only results in a slight increase in the porosity, leading to a combination of large tap density (high volumetric energy density) and large power density. The electrochemical data analysis indicates the better performance of templated electrodes may due to better interconnectivity and tortuosity within electrolyte induced by the template. However, direct evidence to correlate the microstructure of the templating electrode with LIBs performance is still needed.

In this work, by combining focused ion beam-scanning electron microscopy (FIB-SEM) and neutron depth profiling (NDP), we have obtained three-phase 3D electrode microstructure and Li-ion concentration profiles to better understand the improved rate performance of the templated LiFePO4 electrodes. Although it is proposed that the hierarchical interconnected porosity in the templated sample can enhance the electrode rate performance, no significant electrolyte tortuosity differences were found between the conventional and carbonate templated LiFePO4 electrodes. Surprisingly, although the same amount of CB was used in the two electrodes, a better electronic conductive CB network was observed for the templated sample (Figure 1 a, b), enhancing the activity of LiFePO4 at near the electrolyte-electrode interface as directly observed with NDP. Moreover, the CB structure in the templated electrode possesses a less tortuous pathway for electron transport, and the tortuosity distribution is less heterogeneous than in the conventional electrode, as shown in Figure 1 c-f. This results from 3D microstructure analysis is consistent with the NDP result where the templated electrodes show enhancing charging/discharging activity near the electrolyte-electrode interface than conventional LiFePO4electrode. The results demonstrate that the templated electrode has better charge transport network, which result in improved performance.  

[1] Singh, D. P.; Mulder, F. M.; Abdelkader, A. M.; Wagemaker, M. Advanced Energy Materials
2013, 3, 572.

Figure 1
A New Thermally Stable and Conducting Electrolyte Based on Litdi As Lithium Salt for Li-Ion Batteries
Authors: Berhaut Christopher Logan , Schmidt Gregory , Timperman Laure , Lemordant Daniel , Anouti Mérièm
Published: February 2020

Most of the LiBs used in electrical devices currently available contain lithium hexafluorophosphate (LiPF6) dissolved in a mixture of alkylcarbonates as the electrolyte. The main reasons for this [1] are the high conductivity of LiPF6 solutions, the formation of a protective SEI layer on graphite and its ability to passivate aluminum, a low-cost metal which can be used as a current collector. Other advantageous properties, which should also be observed by all LiB electrolytes, include low viscosity and a large life-span without safety risks, especially when damaged. However, the thermodynamic instability and moisture sensitivity of LiPF6 induce high risks of releasing HF and/or PF5 via its thermal decomposition or hydrolysis in the presence of traces of water. These drawbacks have been highly criticized justifying the importance in finding a replacement. Owing to (i) its high thermal stability, (ii) low sensitivity to the presence of water and (iii) its electrochemical stability [2], the lithium 4,5-dicyano-2-trifluoromethyl-imidazole (LiTDI) is seen as a promising substitute for LiPF6in LiBs.

In a previous study [3] the poor dissociation of ion pairs (IP) of LiTDI in electrolyte solutions was discussed and the IP dissociation coefficient was found to be around 30 % in an ethylene carbonate/dimethyl carbonate (EC/DMC) mixture. The power capability of LiTDI in EC/DMC with an added 2% FEC in half-cells, using either a NMC or a graphite electrode, and in full NMC/graphite systems was investigated and compared to that of LiPF6 in the same solvent mixture.  It was noticed that both lithium salts performed equally within graphite half-cells but not in the NMC half-cells where a greater capacity loss was observed in the case of the LiTDI based electrolyte when increasing the NMC lithiation speed. The reason was attributed to the lower IP dissociation of LiTDI; LiPF6 being 85% dissociated in EC/DMC. Taking into account this observation a new solvent mixtures is proposed. We present here the results obtained using this new solvent mixture allowing a better dissociation of LiTDI (37 %), a higher conductivity (8.5 mS.cm-1 instead of 6.1 mS.cm-1in EC/DMC at 25°C) and a lower viscosity (2.4 mPa.s instead of 2.8 mPa.s in EC/DMC at 25°C). In addition a better power capability is achieved at higher current rates.

1.            Eshetu, G.G., et al., LiFSI vs. LiPF6 electrolytes in contact with lithiated graphite: Comparing thermal stabilities and identification of specific SEI-reinforcing additives. Electrochimica Acta, 2013. 102(0): p. 133-141.

2.            Niedzicki, L., et al., New covalent salts of the 4V class for Li batteries. Journal of Power Sources, 2011. 196(20): p. 8696-8700.

3.            Berhaut, C.L., et al., LiTDI as electrolyte salt for Li-ion batteries: transport properties in EC/DMC. Electrochimica Acta, 2015. 180: p. 778-787.
Rational Design of 5V Electrolytes
Authors: Flamme Benjamin , Haddad Mansour , Phansavath Phannarath , Vidal Virginie , Chagnes Alexandre
Published: February 2020

The development of new technologies for electrochemical energy storage is one of the main challenges of the next decades. Many hopes now rely on lithium-ion batteries (LiBs) that have invaded the market of laptops and which appear to be the best choice with the short time for electric vehicles, and perhaps for network applications (electricity storage from wind turbines or solar cells for example). Many works concern the search for cathodes with high-energy density but only few studies focus their research on the synthesis of new dipolar aprotic organic solvents for LiBs electrolytes. Thus, there is a need to deviate from traditional approaches for identifying new electrolytes stable to high voltage that are based on "Trial and Errors" approaches. To alleviate this issue, a collaborative project funded by the French Research Agency (ANR) and reuniting multidisciplinary research groups that combines highly and specific complementary skills in organic chemistry, electrochemistry, solution chemistry, thermodynamics and theoretical chemistry was launched in October 2014. The present paper aims at presenting recent advances from this group on the design of new electrolytes for high-voltage batteries.

First, a critical review of the physicochemical and electrochemical properties of the electrolytes will be presented in this talk (boiling and melting points, viscosity, ionic conductivity in the presence of lithium salts, oxidation potential, etc.). This critical review highlights the lack of homogeneity in the literature data for performing rational design of electrolytes by means of quantitative structure-property relationship calculations (QSPR). Therefore, these data were completed and homogenized by performing new experiments. In particular, a set of 20 new dipolar aprotic organic solvents were synthesized and characterized.

Second, the physicochemical properties of these new dipolar aprotic organic solvents including viscosity, ionic conductivity and their electrochemical behaviors on graphite, LiCoO2, NMC and Lithium rich electrodes as well as platinum and glassy carbon electrodes will be presented and discussed. In particular, their anodic stability will be discussed based on DFT calculations giving interesting information at the molecular level.

Finally, this talk will give the main drawbacks and the next challenges in the design of new electrolytes for 5V lithium-ion batteries.
Ionic Liquid - Alkyl Carbonate Hybrid Electrolytes: Understanding Their Interfacial Electrochemistry in Lithium Batteries
Authors: Theivaprakasam Sowmiya , MacFarlane Douglas R , Mitra Sagar
Published: February 2020

The electrolytes for lithium batteries, are an important area of research as it is believed that small changes in either the composition or the concentration  is expected impact performance. Current electrolytes are limited in terms of their thermal stability, operation temperature window, metal dissolution and high potential operation. Room temperature Ionic liquids (RTILs) are potential electrolyte ingredients as they can exhibit better electrochemistry in a wider potential window and high thermal stability1. However their use is hampered by the interfacial issues with graphite electrodes and also their viscosity2. The current study is focused towards electrolytes being a mixture of ionic liquids in conventional electrolyte components3. The studies were carried out with an optimized amount of ~40%   N-Methyl-N-Propyl Pyrrolidinium bis (trifluoromethanesulfonyl) imide[C3mpyr][TFSI] in a mixture of LiPF6and the alkyl carbonates, also known as Hybrid Electrolytes(HE), and was focussed towards understanding the synergistic benefits evolved at the interface upon ionic liquid addition. The viscous effects of ionic liquids were alleviated by the alkyl carbonates in the solution.

As the ionic liquids, are known for their thermal stability, their addition produces a positive impact on the thermal stability of the hybrid electrolytes. Lithium symmetric cell studies were carried out in the conventional electrolyte (LP30), pure ionic liquid and the hybrid combination to look into the synergy brought by this combination. The combination lowers the overpotential in the symmetric cells as shown in Figure 1a. The combination also widens the temperature of operation of these batteries both on the low and high temperature scales. Further studies were carried out of the electrochemical performance of hybrid electrolytes with commercial battery cathodes where the performance of these combination gives better performance than the conventional system. The effect of metal dissolution on LiFePO4cathodes on these electrolytes were compared upon storage, and a clear distinction was observed on the separators from the aged cells dismantled after 30 days as shown in the Figure 1b & 1c inset. The EDAX analysis of such separators also confirms the traces of iron as shown in Figure 1b&1c.

Further morphological studies were also carried out on delithiated cathodes and it appears that the ionic liquid forms a protective layer on the cathode which helps in achieving a better cyclic stability of the electrodes. On the whole, addition of ionic liquid in the alkyl carbonate system helps in the thermal stability, interfacial kinetics and better cyclic stability.

References

1.    MacFarlane, D. R. et al,Acc. Chem. Res. 40, 1165–1173 (2007).

2.    Navarra, M. A., MRS Bull. 38, 548–553 (2013).

3.    Theivaprakasam, S., MacFarlane, D. R. & Mitra, S.,Electrochim. Acta 180, 737–745 (2015).

Figure 1
Atomic Layer Deposition of HfO2 at Anode/Electrolyte Interface for Stable Anodes in Li and Na Ion Battery Applications
Authors: Ahmed Bilal , Alshareef Husam
Published: February 2020

Recently, atomic layer deposition (ALD) has emerged as a promising and powerful technique to fabricate nanostructured electrodes and improve electrode/electrolyte interface in energy storage devices such as Li and Na ion batteries. In this project, we have deposited an electrochemically inert oxide material, hafnium oxide (HfO2), on different anode materials. We demonstrate that a nanoscale layer of HfO2 on zero dimensional (0D) SnO2 nanospheres, one dimensional (1D) MoO3 nanorods and two dimensional (2D) MoS2 nanosheets significantly improves the cyclic stability, when these materials were applied as anode in Li ion batteries. Moreover, HfO2 coated MoS2 nanosheets were tested as anode material in Na ion batteries and, after 50 charge/discharge cycles, HfO2 coated MoS2 electrodes retained 91% of the initial capacity and bare MoS2 electrodes retained only 63%.

Most importantly, the mechanism of capacity retention was explained by ex situ high resolution transmission electron microscopy (HRTEM), electrical impedance spectroscopy (EIS), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy and X-ray diffraction. We showed that capacity retention is directly related to the degree of crystallinity retention after charge/discharge process. For instance, in case of MoO3, ex-situ HRTEM analysis showed that after 50 charge/discharge cycles, the crystal structure of bare MoO3 electrodes degrades severely while HfO2 preserves the crystal structure during charge/discharge process. Furthermore, it was found that thickness and amorphous nature of HfO2 layer plays critical role because Li+ ions has to diffuse through this layer. In summary, a mechanistic insight into capacity retention after HfO2 coating has been provided by post – electrochemical ex-situ analysis.
Solid Electrolytes: Bulk and Grain Boundary Li Ion Conductivity of Li1.5Al0.5Ti1.5(PO4)3
Authors: Breuer Stefan , Prutsch Denise , Ma Qianli , Epp Viktor , Preishuber-Pflügl Florian , Tietz Frank , Wilkening Martin
Published: February 2020

Lithium aluminium titanium phosphate (LATP) belongs to the class of materials exhibiting very high Li+ ionic conductivities. While many impedance studies can be found in literature that report on overall ion conductivities, a discrimination of bulk and grain boundary electrical responses via conductivity spectroscopy has rarely been reported so far. Here, we took advantage of impedance measurements that were carried out at low temperatures to separate bulk contributions from the grain boundary response. It turned out that bulk ion conductivity is by at least three orders of magnitude higher than ion transport across the grain boundary regions. At temperatures well below ambient long-range Li ion dynamics is governed by activation energies ranging from 0.26 to 0.29 eV, depending on the sintering conditions. As an example, at temperatures as low as 173 K, the bulk ion conductivity, measured in N2 inert gas atmosphere, is in the order of 8.1 x 10−6 S cm−1. Extrapolating this value to room temperature yields ca. 3.4 x 10−3 S cm−1 at 293 K. Interestingly, exposing the dense impedance pellets to air atmosphere over a long period of time causes a significant decrease of bulk ion transport. The effect can be reversed if the phosphate is calcined at elevated temperatures again.
Understanding Electrode-Electrolyte Solution Interactions Between TiO2 Nanotube Electrode and Nonaqueous Electrolytes for Sodium-Ion Batteries
Authors: Smith Kassiopeia , Karsann Devan , Parrish Riley , Hunt Riley , Dufek Eric J. , Kamath Ganesh , Sankaranarayanan Subramanian , Xiong Hui (Claire)
Published: February 2020

Sodium-ion battery technology presents a promising sustainable alternative to the current dominating lithium-ion battery technology due to its low cost associated with its high earth abundance. It has been shown that the interfacial chemistry between anodes and sodium-based or lithium-based electrolytes have markedly different effect even when using the same solvent. It is important to investigate sodium-based electrolytes and to elucidate the mechanisms of electrode and electrolyte interactions. The design and development of next generation electrolytes for sodium-ion batteries is catered towards the improved performance based on evaluation of thermodynamic /transport properties, chemical and electrochemical stability, thermal stability and interfacial chemistry. In this work, we have investigated the electrochemical properties of TiO2 nanotube electrode in various electrolytes containing different solvent mixtures (cyclic, acyclic carbonates) with NaClO4
1 salt and NaPF6 salt and have found that the interaction between the TiO2NT electrode and the nonaqueous electrolytes plays a critical role in the charging/discharging processes. In addition, we have conducted fundamental studies of the chosen sodium-based electrolytes on their chemical stability, thermal stability and electrochemical stability.

References:

Kamath, G.; Cutler, R.; Deshmukh, S. A.; Shakourian-Fard, M.; Parrish, R.; Huether, J.; Butt, D.; Xiong, H.; Sankaranarayanan, S. K. R. S., In Silico Based Rank-Order Determination and Experiments on Non-Aqueous Electrolytes for Sodium Ion Battery Applications. J. Phys. Chem. C 2014, 118, 13406−13416
How Crystallographic Evolution of Sodium within Electrodes during Sodium-Ion Battery Function Can be Used to Make Better Electrodes?
Authors: Sharma Neeraj
Published: February 2020

A large proportion of the function of batteries arises from the electrodes, and these are in turn mediated by the atomic-scale perturbations or changes in the crystal structure during an electrochemical process (e.g. battery use). Sodium insertion and extraction into/from electrodes during charge/discharge can lead to dramatic changes in the crystal structure and these are typically detrimental to performance. By understanding how and when large structural changes occur, electrochemical limits and solid state chemistry can be invoked to provide solutions. Therefore, to understand battery function and improve performance it is critical to probe the crystal structure evolution in situ or operando - while an electrochemical process is occurring inside a battery.

This presentation will showcase some of our recent work on tracking the structural evolution of electrodes during battery operation with a particular emphasis on the sodium location and distribution. Examples will include studies on the Na3V2O2x(PO4)2F3-2x system, Fe[Fe(CN)6]1-x.yH2O framework materials, layered P2 and O3 polymorphs of Na2/3Fe2/3Mn1/3O2 at varying current rates and layered P2 Na2/3Mn0.8Ti0.1Fe0.1O2 and Na2/3Mn0.8Mg0.2O2materials. The relationship between electrochemical parameters such as current rate, number of cycles and battery history will be tied with phase transitions and sodium site occupancy evolution. Such detailed relationships will help to build an atomic scale picture of electrode functionality.

The message in the presentation will be the ability to literally “see” how sodium behaves in such electrodes and thus build a sodium-centred picture of battery function. For room temperature sodium-ion batteries based on intercalation chemistry to become a reality the insertion/extraction process needs to be understood and manipulated.
Development of MnCo2O4 Microspheres Based Air Electrode for Rechargeable Sodium - Air Batteries
Authors: Shang Mengshi , Liu Yu
Published: February 2020

Rechargeable metal-air batteries have been gained much attention because of their high energy densities. As a newly developed member of metal-air batteries,great efforts have been devoted to sodium-air batteries(SABs). SABs are still in an infant stage and many problems needs to be solved.As well-known, cathode is the key of oxygen reduction reaction (ORR) and oxygen evolution reduction(OER). In this work, MnCo2O4  microspheres have been synthesized and demonstrated as a highly efficient electrocatalyst for the air cathode of sodium-air cell. The cell shows an initial discharge capacity of 7709.4 mAh/g(based on the carbon mass vs. Na). The crystal structure and phase purity of MnCo2O4 are confirmed from powder XRD patterns shown in Fig.1. The diameter of MnCo2O4 varies from 1 to 2 μm and the morphology has a high dependence on the synthesis temperature, as shown in Fig. 2. The electrochemcial performance of the MnCo2O4@ carbon black was compared with the carbon black as air electrode in oxygen evolution reduction(OER) and oxygen reduction reaction (ORR). For the first discharge profiles shown in Fig.3a, the discharge capacity of the MnCo2O4 microspheres is 4882.6 mAh/g, nearly about 10 times over carbon black. By the modification of the morphology, MnCo2O4 microspheres exhibited much greater discharge and charge abilities, as shown in Fig. 3b. The cycling stability of the as-proposed MnCo2O4 electrode was shown in Fig.3c.

Figure 1
Low Cost Nanocomposite Catalysts for Lithium-Air Batteries
Authors: Sun Chunwen
Published: February 2020

Among various metal/air batteries, lithium-air batteries possess the highest theoretical gravimetric energy density. However, for the rechargeable Li-air battery, besides the challenges of cost, another issue that has to be addressed in the current technology is the limitations of oxygen reduction reaction (ORR) during discharging process and oxygen evolution reaction (OER) during charging process. The sluggish kinetics of the ORR and OER in Li-air batteries is ascribed to the low efficiency of catalysts. Therefore, the design of a low-cost and stable bifunctional electrocatalyst is a major challenge to the construction of efficient Li-air batteries. Several nanocomposite bifunctional catalysts with low cost have been developed in our lab and studied for lithium-air battery applications. In particular, the ORR/OER properties of graphene-Co3O4 nanocomposite catalyst have been systematically studied. It demonstrates an excellent catalytic activity toward oxygen reduction reaction including a much more positive half-wave potential (-0.23V) than the pristine graphene (-0.39V) as well as higher cathodic currents. Importantly, this catalyst shows a better long-term durability than the commercial Pt/C catalyst in an alkaline solution. The preliminary results indicate that the graphene-Co3O4 nanocomposite is an efficient and stable bifunctional catalyst for a Li-air battery. It may be as an alternative to the high-cost commercial Pt/C catalyst for the ORR/OER in alkaline solutions.