bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Disulfite on the Solubility of Molybdate and Passivation of Iron in Concentrated LiBr Solution
Authors: Tezuka Hanami , Tsukazawa Shogo , Yashiro Hitoshi , Hirata Yoichi , Hishinuma Takashi
Published: February 2020

[Introduction]

Absorption refrigerator utilizes highly corrosive concentrated LiBr solution as an absorbent for water vaper. In order to inhibit corrosion of carbon steel, LiOH and key inhibitor of Li2MoO4 are added into the absorbent. LiNO3 is also used as a strong passivator in order to accelerate passivation of steel especially at a startup stage. Because of the limited solubility of Li2MoO4 in the absorbent, its concentration diminishes during long-term operation not only by consumption by the reaction with steel but also by precipitation at lower temperature part of refrigerator, i.e. in an absorber. In this research, concentration change of molybdate in the absorbent is studied at the absorber temperature (40ºC) and additives that inhibit the precipitation of Li2MoO4 are searched. The effect of precipitation inhibitor on the passivation of iron are also evaluated through electrochemical measurements. 

[Experimental]

The composition of the test solution is 17.3 mol kg-1 LiBr + 0.1 mol kg-1 LiOH with initial concentration of Li2MoO4 of 3.0×10-3 mol kg-1, where Li2MoO4 is supersaturated at 40ºC. The change in concentration of Li2MoO4 over time is measured at 40ºC. Several oxoacid salts are tested as a precipitation inhibitor for Li2MoO4. Electrochemical measurements are carried out for iron in the deaerated test solution at 155ºC in order to examine the effect of precipitation inhibitor (sodium disulfite) on the passivation of iron. 

[Results and discussion]

The concentration of molybdate in the test solution (initially 3.0×10-3 mol kg-1) reduced gradually at 40ºC and became almost constant around 5.0×10-4 mol kg-1. The addition of sodium carbonate, sodium nitrate, sodium borate, sodium phosphate was not effective at all, while sodium sulfate delayed the concentration decrease of molybdate. Sodium disulfite and sodium sulfite (1.0×10-2 mol kg-1) showed noticeable effect: sodium disulfite, in particular, kept the molybdate concentration above 2 × 10-3 mol kg-1 at 40ºC for long time. The effect of disulfite was kept even after the test solution experienced heating up to 155 ºC with additional passivator of lithium nitrate. The time variation of corrosion potential of iron in the test solution (17.3 mol kg-1 LiBr + 0.1 mol kg-1 LiOH+ 3.0×10-3 mol kg-1 Li2MoO4) at 155 ºC indicated that passivation of iron was delayed somehow by the addition of 1.0×10-2 mol kg-1 disulfite: it took about 10 h to reach passive region, while 5 h was needed in the absence of disulfite. But the delay was made up for by the further addition of nitrate passivator: the corrosion potential shifted into passive region soon after temperature reached 155 ºC irrespectively of the presence of disulfite. Polarization curves for iron also indicated harmlessness of disulfite against passivation behavior of iron. The results suggested usefulness of disufite salt as a precipitation inhibitor for Li2MoO4 with no harm in passivation of steel.
Electrochemical Lithium Recovery from Aqueous Sources
Authors: Chung Wook-Jin , Lawagon Chosel Pepito , Nisola Grace Masbate , Gebreegziabher Hana , Albarico Jed , Lee Seong Poong
Published: February 2020

Lithium shortage is inevitable, given the massive growth in its demand for use in transportation industry and various technologies. Consequently, recovery of lithium from seawater and brine is gaining attention to potentially alleviate the impending crisis. Two widely investigated methods for lithium recovery from seawater and brine deposits are adsorption using inorganic lithium ion sieves (LIS) and electrochemical processes. But the former has a drawback due to the use of toxic solvents which negatively affects the environment. Herein, an efficient type of lithium recovery approach is proposed by systematically designing an electrochemical system to sequester Li+ from aqueous sources.

An electrochemical cell was designed to selectively intercalate Li+ into the anode during charging phase. A microcell reactor was prepared and investigated for its feasibility to capture lithium ions (Li+). The reactor consists of a three-electrode assembly with an Li+-selective intercalating electrode, a chloride-capturing silver electrode, and Ag/AgCl reference electrode. Repetitive cyclic voltammetry and galvanostatic cycling showed highly selective and stable electrode system for aqueous Li+ uptake and release. The energy efficiency of the process was also investigated and compared with other electrochemical Li+ recovery methods. Overall, the results demonstrate the ability of the electrochemical system to selectively recover Li+ from aqueous sources. This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (2009-0093816) and Ministry of Science, ICT and future Planning (2015R1A2A1A15055407).
Facile Synthesis of Cobalt-Copper Layered Double Hydroxide Nanosheets As Cathode Catalysts for Rechargeable Lithium-Air Batteries
Authors: Shi Haohong , Liu Ying , Lu Zhouguang
Published: February 2020

Designing novel cost-effective catalyst is one of the greatest challenges in the development of high performance rechargeable Li-air battery. Here, we present a new type of bifunctional catalyst, the cobalt-copper layered double hydroxide (LDH) nanosheets. These Co-Cu LDH nanosheets are fabricated via a simple co-precipitation method under Ar gas. The Li-air batteries with Co-Cu LDH nanosheets exhibit superior electrochemical performance comparing with that using CoCu2O4 electrode. In simulated air environment, the Li-air batteries with Co-Cu LDH nanosheets exhibit higher discharge capacity of 4870 mAh g-1 at 200 mA g-1, lower charge overpotential and better cycling stability with controlling capacity of 1000 mAh g-1. The superior catalytic activity and enhanced electrochemical performance are associated with the unique layered structure of Co-Cu LDH nanosheets and the accumulation of active Co2+ and Co3+ ions in the layers, which provide more catalytic sites for the formation/decomposition of discharge products Li2O2, avoid severe aggregation during cycling and facilitate the O2
transportation among three-phase boundary.

Acknowledgments

This work was financially supported by the Shenzhen Peacock Plan (KQCX20140522150815065), the Natural Science Foundation of Shenzhen (JCYJ20150331101823677) and the Science and Technology Innovation Foundation for the Undergraduates of SUSTC (2015x19 and 2015x12).
Carbon Nanotube Composite Electrodes Toward All Solid Alkali Metal Ion Batteries
Authors: Sakamoto Yuki , Canghao Li , Ishii Yosuke , Kawasaki Shinji
Published: February 2020

Owing to the superior energy density, rechargeable Li-ion batteries (LIBs) have been used as a major power source of portable electric devices such as cell phones and lap-top computers. In addition to small-scale applications, LIBs are also installed in recently developed large scale systems such as electric vehicles (EVs), renewable energy storage systems, and smart grids. In commercially available LIBs, rare metal oxides, such as LiCoO2 and LiMnO4 are used for the cathode material. However, the capacity of LIB is not large enough for EV with long driving range. Furthermore, rare metals used in the present LIB such as Co, Ni and Li raise the cost of LIB. Therefore, we have to explore new electrode materials having high ion adsorption capacity and available at low cost so as to develop long driving range EV. Phosphorus is a candidate for such an electrode materials, because phosphorus is one of the ubiquitous elements and can adsorb much alkali metal ions. However, most of the polymorphs of phosphorus except for black phosphorus, which is prepared by high pressure and high temperature treatment, are electric insulators. We also take large volume change of phosphorus electrode with ion adsorption into account. Single-walled carbon nanotube (SWCNT) has good electric conductivity and huge hollow core space in which some molecules can be encapsulated. Therefore, if we input phosphorus molecules into the hollow core of SWCNT, the materials would work as a good electrode. In fact, it was found by our preliminary experiments that phosphorus encapsulated in SWCNT (P@SWCNT) can adsorb and desorb alkali metal ions such as Li and Na [1]. However, since the experiments were performed under limited conditions, we should perform more sophisticated experiments to examine the electrode properties of P@SWCNT more precisely. In this study, we discuss how the electrode property of P@SWCNT changes with different kinds of electrolytes. In the previous work, we used mixture of Ethylene Carbonate and Diethyl Carbonate (EC/DEC) as an electrolyte. In the present study, we prepared two different kinds of electrolytes: Propylene Carbonate (PC) and polyethyleneoxide based composite polymer electrolyte (PEO). The former has wide liquid temperature range and shows very good low temperature performance than EC/DEC solvent and high conductivity thus we can try to evaluate electrode material at low temperature. The latter is known for one of the solid electrolyte and show from 10-3 to 10-4 S/cm at over 60 degrees Celsius. In the symposium, we’ll discuss the electrode properties of P@SWCNT with different kinds of electrolyte and also talk about the possibility of all solid state battery using P@SWCNT.

References

[1] Y. Ishii, Y. Sakamoto, H. Song, K. Tashiro, Y. Nishiwaki, A. Al-zubaidi, S. Kawasaki, Alkali metal ion storage properties of sulphur and phosphorous molecules encapsulated in nanometer size carbon cylindrical pores, AIP Adv. 6, 035112 (2016).
Development of New Electrolytes for Electropolishing of Niobium
Authors: Kawamura Shoma , Yashiro Hitoshi , Ida Yoshiaki , Nii Keisuke , Monjushiro Hideaki , Kure-Chu Song-Zhu
Published: February 2020

1. Introduction

In an international linear collider (ILC) plan, superconducting radio frequency (SRF) cavities are essential components for acceleration of the charged particles beam. The cavities are made of high purity niobium (Nb) and the inner surfaces of these cavities are required to be smooth enough because they play a crucial role in the performance of cavities. Typically, in order to obtain a good surface finish, electropolishing is used for the SRF cavities made of Nb. Typical electropolishing process uses the electrolyte composed of hydrofluoric acid (HF, about 55 mass%) and sulfuric acid (H2SO4, about 98 mass%) in a volumetric ratio of 1:91). However, there is a strong demand to replace the electrolyte with less hazardous one. In this study, we made a preliminary search for less hazardous electrolyte that could change the traditional HF-H2SO4 electropolishing system.

2. Experimental

Following three types of electrolytes are tried for electropolishing of Nb: 3.7 M H2SO4, 10 M NaOH and 80 mass% CH3SO3H + 3 mass% NH4HF. A square of Nb (99% +, 20×20×0.5 mm3, Nilaco) is fixed on a Teflon holder (with exposed area of 1.13 cm2) and used as a working electrode. Before electropolishing, Nb samples is polished up to #6/0 SiC paper. A plate of aluminum is used as a counter electrode except in a NaOH solution where a nickel plate is used as a counter electrode. Electropolishing is carried out under constant voltage (5 – 10 V) for 30 min at temperatures of 30 - 80ºC. In each solution, I–V character and mass change are evaluated. The Nb surface after the electropolishing is characterized by a surface roughness meter and FE-SEM.

3. Experimental results and discussion

In a 3.7 M H2SO4 solution at 30ºC, a blue oxide film was formed on Nb surface after applying 5 and 10 V. The results indicated that no polishing of Nb would proceed in this solution in a direct current mode. In a 10 M NaOH with constant voltages of 5 and 10 V, a gray-white oxide film was formed on Nb surface but no polishing proceeded either below 50ºC. At 80 ºC in a 10 M NaOH, a remarkable mass loss was observed at 10 V but the resultant surface was not very uniform. In a 80 mass% CH3SO3H + 3 mass% NH4HF at 30ºC, a gray-white oxide film formed on Nb surface at a constant voltage of 1 V. As the voltage is increased to 5 V, polishing proceeded most efficiently with mass loss of 4.3 mg cm-2 in 30 min. Further increase in voltage resulted in reduction in mass loss. The roughness of Nb surface was apparently improved in this solution.

References

1) P. V. Tyagi, M. Nishiwaki, T. Noguchi, M. Sawabe, T. Saeki, H. Hayano, S. Kato, Applied Surface Sci., 285P, 778 (2013).

2) Japan patent JP2008-95192A

Acknowledgment

The authors are grateful to Tohoku Business Federation for their financial support.
Numerical Analysis of Vanadium Ion Crossover Phenomena in All-Vanadium Redox Flow Batteries Based on the Concentrated Solution Theory
Authors: Moazzam Milad , Oh Kyeongmin , Ju Hyunchul
Published: February 2020

The crossover phenomena in all-vanadium redox flow batteries (VRFBs) are complicated due to the presence of a large number of crossover species in the membrane, including four oxidation states of vanadium species, protons, bisulfate, and water. The fact implies that the nature of crossover phenomena in VRFBs belongs to the concentrated solution regime. In this work, a new crossover model is developed based on concentration solution theory. The crossover model is then numerically incorporated in previously developed three-dimensional, transient, thermal VRFB model in which vanadium redox reactions, waste heat generation, resultant species and heat transport are all included. Using the comprehensive VRFB model, two types of VRFB simulation are conducted; one is based on diluted solution theory and the other on concentrated solution theory. The numerical comparison clearly elucidates the contribution of the multiple interactions of crossover species in the membrane to the overall crossover flux between the negative and positive electrodes at various charge and discharge stages.
Developing a Sensitive in-Situ Rotating Ring Disk Electrode (RRDE) Detection Method for Understanding the Deactivation of Cu Catalysts during CO2 Electroreduction
Authors: Zhang Fen , Coleman Eric J. , Co Anne C.
Published: February 2020

In response to the greenhouse effect and global energy crisis, reducing greenhouse gas emissions as well as developing alternative clean energy becomes one of the most important challenges our society is facing today. CO2 is one of the main components of greenhouse gas emitted into the atmosphere. The conversion of CO2 to more valuable products through an electrochemical pathway has the potential to efficiently utilize CO2. Among different types of metal catalysts, Cu has been considered as the best for the electrochemical reduction of CO2 to more complex hydrocarbons such as CH4, C2H4, C2H5OH and HCOO-. Although Cu-based catalysts demonstrate good catalytic activity towards the electrochemical reduction of CO2, the catalysts deactivate within hours and sometimes minutes, resulting in a drop in hydrocarbon production and a significant increase in H2evolved.

To date, the deactivation mechanism of the catalysts is not very well understood. Our goal is to develop a fast and sensitive method for detecting the intermediates and products generated from CO2 in-situ using a Rotating Ring Disk Electrode (RRDE), such that intermediate and product distribution due to the catalyst deactivation can be captured within a reasonable time frame.

The RRDE in this work uses a polycrystalline Cu disk electrode with a polycrystalline Pt ring electrode as the two working electrodes, a Pt mesh counter electrode and a reversible hydrogen electrode serves as the reference electrode. Under rotating conditions, the Pt ring electrode can be used to detect the in-situ formation of intermediate/product during the CO2 reduction reaction on the Cu disk. This work will discuss the changes in product selectivity and the deactivation behavior of Cu-based catalysts using RRDE.
Thin Layer Sonoelectrochemistry in Aqueous and Non-Aqueous Systems
Authors: Rathuwadu Nadeesha , Dey Patrick , Leddy Johna
Published: February 2020

In thin layer sonoelectrochemistry, ultrasonic sound waves introduced into an electrolyte layer increases the rates of heterogeneous processes [1, 2]. From previous studies of thin layer sonoelectrochemistry, the rates of heterogeneous electron transfer, oxygen reduction reaction (ORR), and methanol electrolysis were facilitated under sonication. In the thin layer of electrolyte, ultrasound energy is reected into the electrolyte at the electrolytejair meniscus to minimize the losses from attenuation found in bulk systems. This harvests the ultrasonic energy more e¢ ciently. The observed e/ects are on interfacial rates and not mass transport. No cavitation is thus far observed. These e/ects have been observed at platinum electrodes in aqueous electrolytes when the interfacial reactions are slow. The studies were done at a single frequency and varied intensity.

The fundamental mechanism of thin layer sonoelectrochemistry is not yet fully understood. Here, studies are undertaken to broaden inspection of experimental parameters. This identies critical parameters of the ultrasonic input (e.g., frequency, intensity, duty cycle) and the electrochemical system (e.g., solvent properties of viscosity and density, electrode materials). The data informs the models.

In this study, thin layer sonoelectrochemistry was undertaken on academically interesting reactions in aqueous and non aqueous electrolytes. Redox probes include tris(bipyridine)ruthenium(II) chloride (Ru(bpy)2+
3 ), iron ( III ) (Fe3+) and p-benzoquinone (p-BQ). These choices allow comparison of fast (Ru(bpy)2+
3 ) and slower (Fe3+) heterogeneous electron transfer rates as well as coupled proton electron (p-BQ) processes in different solvents. Cyclic voltammetry measurements were performed on a Pt wire working electrode against a shrouded Pt/PtO2 quasireference electrode (QRE). The ultrasonic transducer is placed in the cell but is electrically isolated from the electrochemical measurement circuit. The electrolytes are HNO3/H2SO4 in aqueous and tetrabutylammonium tetrauoroborate (TBABF4) in non-aqueous solvent DMF. The outcomes of these studies will support fundamental understanding of the thin layer sonoelectrochemical mechanisms.

References

[1] C.G. Duda, Thin Layer Sonoelectrochemistry, Ph.D. 2012, University of Iowa

[2] J. Leddy, C. G. Duda, J. Lyon, and W. J. Leddy III, Thin Layer Sonoelectrochemistry and Sonoelectrochemistry Devices and Methods, U.S. Patent Application 20150147594 A1.
High-Rate Supercapacitors with Mesoporous Carbons for AC Line Filtering
Authors: Yoo Yongju , Kim Woong
Published: February 2020

In the electronic devices, aluminum electrolytic capacitors (AECs) have occupied the bulky volume. Using supercapacitors instead of the large AECs is expected to reduce size of electronic devices because they have more capacitance than AECs. However, the commercial supercapacitors with tortuous pore structure cannot be applied for AC line filtering because of their slow response at 120 Hz. In this study, we will present supercapacitors which have fast response, high voltage window and high areal capacitance using mesoporous carbon and organic electrolyte. From this, we proved that supercapacitors can replace with AECs up to 41 V.
Impact of Battery Size and Charge on the Thermal Runaway of Lithium Ion Batteries
Authors: Lamb Joshua , Steele Leigh Anna M , Orendorff Christopher J
Published: February 2020

Catastrophic battery failure is typically studied at or near full charge of the battery. This is generally assumed to be the worst-case scenario, and it is taken as conventional wisdom that the risk of thermal runaway is very low below 50% state of charge. Further, due to cost and safety issues, the bulk of laboratory scale battery abuse testing and careful calorimetry work is performed on relatively small cells (<5 AH). However, little has been reported on how data collected using these smaller cells scales to the large cells proposed for advanced energy storage applications, such as electric drive vehicles and grid scale energy storage. This work looks at how thermal failure of lithium ion batteries may scale as both the size of the battery and state of charge are changed. Different battery chemistries are observed using over temperature (thermal ramp) testing as well as large volume Accelerating Rate Calorimeters (ARC) to observe how the energy release and kinetics of thermal runaway scale as battery size increases, and through this discuss the benefits and limitations of smaller scale calorimetry.

ARC is used as well to observe the nature of thermally induced battery failure as the state of charge changes. As part of these results we explore the difference between the total heat released during battery failure, which has been observed to scale relatively linearly with state of charge, and the kinetics of battery failure, which has been observed in this work to scale exponentially at high states of charge (>80% SOC). A large format battery at a low state of charge may still have the potential for a significant amount of energy release even if a rapid thermal runaway is unlikely. This is of particular concern in large battery systems where well insulated cells in close contact with one another may see a propagating failure due to the significant amount of energy available to heat surrounding cells even if the thermal runaway of a single cell is unlikely.

Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.
Surface Functionalization and Capacitance Enhancement of Activated Carbon through Mechanical Activation
Authors: Li Ling , Liu Caihong , Shaw Leon
Published: February 2020

Lithium-ion capacitors (LICs) have the potential to combine the high energy density of lithium ion batteries and the high power density of supercapacitors into one device. In this study, we have investigated surface functionalization of activated carbon (AC) powder through mechanical activation for cathodes of LICs with non-aqueous electrolytes. Traditionally, surface functionalization is carried out via chemical activation or plasma treatment. Here, we show, for the first time, that surface functionalization can be achieved with mechanical activation using high-energy ball milling of AC powder in air at room temperature. It is found that mechanical activation is an effective way to create functional groups on the AC surface, thereby imparting pseudocapacitance and increasing the specific capacitance of the AC powder. The surface functionalization has led to an increase in the specific capacitance from 15.8 F/g for the as-received AC (AR-AC) to 33.5 F/g for the AC with 6-h high-energy ball milling (6h-AC). Note that although high-energy ball milling has resulted in significant reduction in the specific surface area of the AC powder, the surface functionalization induced by mechanical activation has drastically increased the areal specific capacitance from 2.3 μF/cm2 for the AR-AC to 68 μF/cm2 for the 6h-AC. As a result, the specific capacitance of AC has been increased through high-energy ball milling. The areal specific capacitance for the 6h-AC is 3 times the theorectical areal specific capacitance of the electrical double layer for graphene (21 μF/cm2), indicating the existence of the pseudocapacitance due to surface redox reactions in the 6h-AC powder. The presence of the pseudocapacitance due to surface redox reactions is also confirmed by cyclic voltammery (CV). The high specific capacitance achieved through mechanical activation is fairly stable over charge/discharge cycles, which is slightly better than the cyclic stability displayed by the AR-AC. X-ray photoelectron spectroscopy (XPS) analysis reveals that the pseudocapacitance displayed by the 6h-AC is mainly due to C=O functional groups introduced during mechanical activation. This work has opened up a new route to increase the specific capacitance of low cost and widely used AC powder for LICs.
Electric Double Layer Capacitor Properties of Pillared Carbons
Authors: Matsuo Yoshiaki , Fukuda Takuya , Kimizuka Osamu , Nishijima Motoaki , Kinoshita Hajime
Published: February 2020

Recently, carbon materials with controlled pores such as mesoporous carbons, template carbons, carbon nanotubes, etc are attracting much attention for the electrode materials of electric double layer capacitor (EDLC). In this context, we have prepared pillared carbons in which adjacent graphene layers are connected with each other by silsesquioxane pillars and they possess micro or mesopores between their graphene layers and pillars [1,2]. Though the width of the space between pillars available for the entrance of foreign molecules was less than 0.4 nm, BF4
- ions can be intercalated into the pillared carbon [3]. The capacity per surface area was larger than that of activated carbon, indicating that the surface of pillared carbon was more effectively utilized for energy storage [3]. In this study, we have prepared pillared carbons with various surface area and the EDLC properties of them were investigated. Pillared carbons were prepared from the thermal reduction of silyalted graphite oxide. By using graphite oxide with different oxygen contents and various siylating reagents, pillared carbons with the surface area between 380 and 650 m2/g were obtained. The constant current charge-discharge measurement at 80 mA/g was performed by using two-electrode symmetric cell. The upper limit voltage was changed every 5 cycles from 2.0 to 3.5 V. The capacity of the resulting pillared carbons increased as the increase in the upper limit voltage and the pillared carbons were gradually activated. The capacity almost linearly increased and reached 19.6 F/g. The X-ray diffraction measurement of the charged negative electrode indicated that larger cations were also intercalated into pillared carbons.

References

1) Y. Matsuo, et al, Chem. Lett., 36, (2007) 1050-1051.

2) Y. Matsuo, et al, Chem.Commun., 47 (2011) 4409-4411.

3) Y. Matsuo, et al, Carbon, submitted.
Simplified Lithium-Ion Capacitors with Irreversible Lithiated Materials in the Positive Electrode
Authors: Jezowski Pawel , Crosnier Olivier , Poizot Philippe , Brousse Thierry , Béguin François
Published: February 2020

The lithium-ion capacitor (LIC) is a high energy hybrid system which combines an electrical double-layer (EDL) positive electrode made from nanoporous carbon with a negative intercalation electrode made from graphite or hard carbon [1,2]. The electrolyte is a lithium salt (LiPF6) which is generally dissolved in ethylene carbonate:dimethyl carbonate (EC:DMC) mixture. The most common concept of LIC uses an auxiliary metallic lithium electrode for graphite pre-lithiation [1,2]. Since this additional lithium electrode complicates the cell construction and might be the cause of thermal runaway during LIC operation, alternative strategies have been considered. Pre-lithiation has been proposed directly from the electrolyte [3], but it leads to a decrease of electrolyte concentration and conductivity, which might have a negative impact on the LIC power. A better strategy to lithiate the negative electrode consists in irreversible lithium de-intercalation from lithium metal oxide (Li2MoO3, Li5FeO6, Li0.65Ni1.35O2) incorporated together with activated carbon in the positive electrode [4,5]. However, for some of these oxides, the extraction potential of lithium ions exceeds 4.5 V vs. ref. Li/Li+, which causes detrimental electrochemical oxidation of the electrolyte.

The first objective of this presentation is to design new materials from which high amounts of lithium can be irreversibly de-intercalated at potential lower than 4.2 V vs. Li/Li+. For example, we demonstrated that lithium can be irreversibly extracted at 3.3 V vs. Li/Li+ with a capacity of ca. 350 mAh/g during galvanostatic oxidation of the renewable organic derivative C6H3CN(OLi)2; the LIC cell based on the use of this material demonstrates an excellent cycle life in the potential range from 2.2 ~ 4.0 V. The second objective is to investigate materials with the lowest residual mass after the delithiation step. We will show that this can be achieved by selecting materials which liberate neutral gases simultaneously to lithium deintercalation. Hence, after this step, the positive electrode contains only activated carbon, leading the system to display much higher energy density.

[1] N. Ando, S. Takasi, H. Taguchi, Y. Hato, Organic electrolyte capacitor, EP1400996A1 (2002)

[2] T. Aida, K. Yamada and M. Morita, Electrochem. Solid-State Lett. 9 (2006) A534.

[3] V. Khomenko, E. Raymundo-Piñero, F. Béguin, J. Power Sources 177 (2008) 643.

[4] M.-S. Park, Y.-G. Lim, J.-H. Kim, Y.-J. Kim, J. Cho and J.-S. Kim, Adv. Energy Mater. 1 (2011) 1002.

[5] P. Jeżowski, K. Fic, O. Crosnier, T. Brousse, F. Béguin, Electrochim. Acta (2016) http://dx.doi.org/10.1016/j.electacta.2015.12.034.
Vanadium Nitride Electrodes: Limitations and Practical Use in Electrochemical Capacitors
Authors: Brousse Thierry , Morel Alban , Bélanger Daniel , Borjon-Piron Yann
Published: February 2020

Vanadium nitride has displayed many interesting characteristics for its use as a pseudocapacitive [1] electrode in an electrochemical capacitor, such as good electronic conductivity, good thermal stability, high density and high specific capacitance. Thin films of VN were prepared by D.C. reactive magnetron sputtering. The electrochemical stability of the films as well as the influence of dissolved oxygen in 1 M KOH electrolyte were investigated. In order to avoid material as well as electrolyte degradation, it was concluded that vanadium nitride should only be cycled between -0.4 and -1.0 V vs. Hg/HgO. After a 24 hours stabilization period, the prepared VN thin film showed an initial capacitance of 19 mF.cm-2 and a capacity retention of 96% after 10000 cycles. Furthermore, dissolved oxygen in the electrolyte was demonstrated to cause self-discharge up to a potential above -0.4 V vs. Hg/HgO, where VN was shown to be unstable. Additionally, the presence of oxygen was shown to shift the open circuit potential of a VN electrode to about 0 V through self-discharge processes [2].

Since the performances reached on thin film electrodes are difficult to translate to VN powder, the use of VN thin films in hybrid microdevices has been investigated [3]. Microdevices were designed using VN thin films as negative electrode and electrodeposited Co3O4 as positive electrode in order to combine the high capacity of the Faradaic type cobalt based electrode and the high capacitance and good cycling ability of VN electrode when used in an optimized electrochemical window. The performance of such devices will be reported and discussed with regards to existing literature on the field.

References

[1] Brousse, T.; Belanger, D.; Long, J. W. J. Electrochem. Soc. 2015, 162, A5185–A5189.

[2] Morel, A.; Borjon-Piron, Y.; Lucio Porto, R.; Brousse, T.; Bélanger, D.; J. Electrochem. Soc. 2016, 163, A1077-A1082.

[3] Eustache, E.; Frappier, R.; Porto, R. L.; Bouhtiyya, S.; Pierson, J.-F.; Brousse, T. Electrochem. Commun. 2013, 28, 104–106.
Solid-State Microsupercapacitors Assembled Using Ionic Liquids for Wide Temperature-Range Applications
Authors: Teng Hsisheng , Chang Pei Yi , Huang Hsin-Chieh
Published: February 2020

Microsupercapacitors (MSCs) have the potential to serve as power sources or energy storage units in microelectronic devices.1 We have reported a laser micromachining technique to produce in-plane interdigitated microelectrodes for microsupercapacitors, in which the electrode fingers were fabricated using high-porosity activated mesophase pitch.2 The use of an ionogel, comprising an ionic liquid and fumed silica, enables the MSC to reach stack capacitance of 12 F cm-3, stack energy of 16 mWh cm-3, and stack power of 160 W cm-3. These energy and power values are unprecedented for MSCs. The developed laser machining technique is highly scalable, enabling lithography-free fabrication and on-chip integration of MSCs into microelectronic units. We obtained results demonstrating that the laser-patterned interdigitated design substantially reduces the resistance for electrode-electrolyte interfacial diffusion and drift transport through the carbon films. The challenge of solid-state MSCs in versatile applications is the operation temperature range and high thermal stability.

In this report, we present the use of an ether-bridged dication ionic liquid as an additive to commercially available ionic liquids to enable operation of MSCs at temperatures ranging from -20 to +60 ºC. The proposed fabrication strategy, using a laser for the micromachining in conjunction with a wide temperature range ionogel, provides an opportunity for the development of robust solid-state MSCs applicable a variety of micro/nano-sized energy devices.

 

References

1. M. Beidaghi, Y. Gogotsi, Energy Environ. Sci. 7 (2014) 867.

2. H.C. Huang, C.J. Chung, C.T. Hsieh, P.L. Kuo, H. Teng, Nano Energy 21 (2016), 90

Acknowledgments: This research was supported by the Ministry of Science and Technology, Taiwan (104-2221-E-006-231-MY3, 104-2221-E-006-234-MY3, 105-3113-E-006-005, and 104-3113-E-006-011-CC2), and by the Ministry of Education, Taiwan, The Aim for the Top University Project to the National Cheng Kung University.
Facile Synthesis of Nickel Cobalt Layered Double Hydroxides Microspheres with High Pseudocapacitive Performance
Authors: Zha Daosong , Han Qiaofeng , Wang Xin
Published: February 2020

To meet the ever-growing demand for peak-power assistance in portable electronics and electric vehicles,considerable efforts have been devoted to the development of pseudocapacitorelectrode materials with superiorspecific capacitance and excellent rate performance. Transition metal hydroxides such as Ni(OH)2 possesses hightheoretical specific capacitance, butits unsatisfactory ratecapability is confinedby the inferior intrinsic conductivity [1]. Encouragingly, theintegration of more conductive Co(OH)2 can significantly improvespecific capacitanceand rate capability [2].

In the present work, a facile one-step and cost-effective solvent thermal strategy was adopted to obtain Nickel–cobalt layered double hydroxides microspheres (LDHMs) with hierarchical architecture.Methanol without any other solvent was selected as reaction menstruumduring the whole reaction process, along with urea as alkaline source.Meanwhile, neither surfactant nor template was introduced.All electrochemical tests of all as-prepared microspheres with different Ni/Co atomic ratio (NixCo1-xLDHMs) were performed using 2M KOH aqueous electrolyte. This unique architecture was assembled by numerous ultrathin nanoflakes with an average thickness of about 30 nm randomly and tightly.

Particularly, Ni0.6Co0.4LDHMs exhibitedthe most outstandingelectrochemical performance and rate performance, including an ultrahigh specific capacitance of 1624F/g at 0.5A/g,while even at a high current density of 10A/g,the specific capacitance still maintained as high as 1531F/g (~94.27% capacitance retention). Otherwise, the Ni0.6Co0.4LDHMs also exhibited an excellent long-term cycling stability. An ultrahigh retention about 89.94%of specific capacitance was acquired after 8000 cycles of continuousgalvanostaticcharge-discharge processes at 4A/g.

The remarkable elecrochemical performance may arise from both the unique morphorlogy and the synergistic effect between the binary hydroxides components [3]. All these results demonstrate that our research can provide a novel way to easily fabricate the structure tunable materials with improved capacitance behavior for energy storage/conversion devices.

References:

[1] Shang C, Dong S, Wang S, et al. [J]. ACS nano, 2013, 7(6): 5430-5436.

[2] Qu L, Zhao Y, Khan A M, et al. [J]. Nano letters, 2015, 15(3): 2037-2044

[3] Trang N T H, Van Ngoc H, Lingappan N, et al. [J]. Nanoscale, 2014, 6(4): 2434-2439
Electrochemical Characteristics of Large Area Thin Film Supercapacitors for Flexible Electronic Applications
Authors: Yoo Jung-Joon , Kim Young Il , Kim Jong-Huy
Published: February 2020

Electronic products have been asked to be small, light, safe, eco-friendly and even flexible. Supercapacitors are one of the great candidates of the next generation rechargeable energy storage devices for the portable electronic devices.

Here, we have proposed a new fabrication approach for making a large area thin film supercapacitor that achieved moderate areal capacitance and robust mechanical and thermal strength. The total thickness of a packaged device was ~0.3 mm. The fabricated devices had the electrode dimension of 10x10 cm2. They showed good mechanical flexibility with no change in the capacitance of the device after 1000 bending cycles with the bending radius of 20 mm and superior long-term thermal stability for for 2,000 hours at 60℃. It indicated that the unique film-type energy storage device for commercial small electronic applications has been developed.
High Performance Supercapacitors Electrode Based on N-Doped Carbon Nanofibers
Authors: Liu Rong , Zhang Fangping , Li Enyuan , Xu Jun , Yuan Guohui
Published: February 2020

Supercapacitors (also known as electrochemical capacitors) are considered to be the most promising devices to meet the urgent and pressing requirements of energy storage. Supercapacitive electrode materials, which are strongly related to the high-efficiency storage of energy, have provoked more attentions and interests. Heteroatom doping (nitrogen, oxygen, phosphorus, boron et.al) has been conceived as a promising approach to increase the special surface area, tune pore size distribution, and incorporate pseudo-capacitance. Recently, nitrogen-doped three-dimensional (3D) nanostructured carbon electrode materials have attracted immense interest due to their great potential merits, including enhance the electrical conductivity, surface polarity, wettability and electro-active surface area, provide an additional pseudo-capacitance and achieve high rate performance and good cycling stability.

Herein, a simple, eco-friendly, novel, and effective way to fabricate N-doped carbon nanofiber networks (N-CNFs) is studied. The N-CNFs are successfully fabricated through in situ polymerization using pyrrole and ammonium persulfate as the monomer and oxidant, respectively, then followed by pyrolyzed in a nitrogen atmosphere. The fabricated electrode exhibits an excellent reversible specific capacitance of 233.5 F g-1 at the current density of 0.5 A g-1, and a high rate performance of 80.2 % retention at 5 A g−1 in 6.0 mol L-1 KOH electrolyte. The exceptional properties mostly stem from robust redox reactions of N-doping in the CNFs, which providing enhanced pseudo-capacitance. Furthermore, this kind of hybrid doped material could be easily scaled up and represents an alternative promising candidate for an efficient electrode material for supercapacitors.
Thermal Energy Harvesting Using Carbon Nanotube and Polymer Aqueous Electrolyte Composite
Authors: Kazim Ali Hussain , Cola Baratunde
Published: February 2020

Thermo-electrochemical cells (thermocells) convert temperature difference to electricity with no moving parts and is an inexpensive technology to harvest waste heat. However, low power conversion efficiency and power output has limited its use from being a commercial application. In a thermocell, when a temperature difference is applied at the electrodes, oxidation and reduction takes place at the hot and cold electrodes respectively. The electron released at the hot electrode (anode) due to oxidation of ion passes through the external circuit, while the oxidized ion moves towards the cold electrode (cathode) where it is reduced and the cycle repeats. To minimize the over potentials at the electrode/electrolyte interface (interfacial charge transfer resistance) due to electronic transport, concentration polarization near the electrode interface (mass transfer resistance) due to ions, transport of ions in the bulk fluid (ohmic resistance) are the primary requirements for high energy conversion efficiency.1 Increasing the flux of charge carriers to flux of heat flowing between the electrodes is also needed. In this work, the effect of mixing carbon nanotubes (CNT) and poly (3,4-ethylenedioxythiophene)−poly(styrenesulfonate) (PEDOT:PSS) composite in aqueous potassium ferri/ferrocyanide electrolyte is characterized using electrochemical impedance spectroscopy. Here we report a 10% decrease in ohmic resistance and 5-fold decrease in interfacial charge transfer resistance. The decrease is ohmic resistance is attributed to increase in PEDOT:PSS ions and interfacial polarization2 due to CNT present in the electrolyte. While the decrease in interfacial charge transfer resistance is attributed to composite increasing the contact area at the electrode/electrolyte interface.3, 4 The composite electrolyte improved the power performance of the standard electrolyte by about 30% and gave a stable output over a 30 day period suggesting that it can be used for long term operation.

1. T. Quickenden and C. Vernon, Solar Energy, 1986, 36, 63-72.

2. P. F. Salazar, S. T. Stephens, A. H. Kazim, J. M. Pringle and B. A. Cola, Journal of Materials Chemistry A, 2014, 2, 20676-20682.

3. T. Kato, T. Kado, S. Tanaka, A. Okazaki and S. Hayase, Journal of the Electrochemical Society, 2006, 153, A626-A630.

4. C. P. Lee, K. M. Lee, P. Y. Chen and K. C. Ho, Solar Energy Materials and Solar Cells, 2009, 93, 1411-1416.
The Effect of pH on the Reduction of Graphene Oxide in Regards to the Structure and ORR Capabilities in Alkaline Media
Authors: Glass Dean , Prakash G. K. Surya , Olah George A.
Published: February 2020

The hydrothermal reduction of many compounds including graphene oxide usually takes place in a basic aqueous environment when using many reducing agents. In this study, graphene oxide was reduced by sodium borohydride in aqueous solutions among a wide spectrum of pH values ranging from 1 to 13. X-ray powder diffraction (XRD), thermogravimetric analysis, and infrared spectroscopy (FTIR) confirmed the reduction of the graphene oxide at each respective pH value. With increasing pH values, Raman and X-Ray photoelectron spectroscopy (XPS) spectra of the resultant graphenes showed an increase in the repair in the carbon sp2 lattice while XRD showed a larger overall particle size. Electrochemical testing in basic media showed higher oxygen reduction capabilities in the catalysts that were reduced at higher pH values. The onset potential of the oxygen reduction reaction (ORR) as well as the electron transfer number also increased as the pH of the solution increased overall. The graphene oxide catalyst reduced at pH 1, however, showed superior limiting current densities in the linear sweep voltammetries even though the onset potential was the lowest. This increased ORR activity is most likely due to the better repaired graphitic domain of the catalysts reduced at higher pH values even though the overall particle size is bigger.
Catalytic Activity of Gold Nanoparticle Functionalized Carbon Nanotubes for a Hydrogen Evolution Reaction
Authors: Abdel-Fattah Tarek M , Huff Clay , Dushatinski Thomas
Published: February 2020

Hydrogen gas is an attractive alternative to carbon-based fuels because of its green byproducts of combustion, and its renewable nature [1]. Dihydrogen can be evolved from water, but the energy produced from burning will only match the energy expended to produce the gas. Further, the inability to reach 100% efficiency in fuel cells or combustion engines further reduces the usable energy produced. These limitations require better means of producing hydrogen gas. Solid storage materials are being researched as a possible solution to the problems presented not only by the energy costs of evolving hydrogen gas, but also the pressurized storage a gaseous fuel requires. Metal hydrides are known for their hydrogen releasing capacities, content of readily available chemical compounds. Sodium borohydride (NaBH4) has the highest hydrogen content by weight and is the most produced in the largest quantities of metal hydride materials. The oxidation of aqueous NaBH4 is a slow process, but ultimately liberates 4 moles of dihydrogen per mole of NaBH4. Many catalysts have been implemented in this reaction such as Ni materials, but these catalysts suffer from oxidation degradation [2-3]. Despite their cost, they also offer significantly higher surface area than bulk films and can be functionalized with many different species, often offering stability to the absorbed species.

Catalytic activity of the produced Au-MWCNT composites was tested in an aqueous NaBH4 hydrogen evolution reaction. The evolved gas was measured through the use of a water-displacement system, Ohaus microbalance, and mass logging software. The Au-MWCNT composite greatly outperformed the original MWCNT, but only when precursor solution of suspended MWCNTs and Au-nanoparticles was stirred. When the precursor was sonicated, the films showed a much lower catalytic activated, worse than the original MWCNTs. It can be inferred that the sonication caused damage to the MWCNTs, and thus that stirring is a better preparatory technique for the composites.

Catalytic Surface

Rate Constant (10-3 min-1)

Au-MWCNT stirred
8

Au-MWCNT sonicated
5.5

MWCNT
5.8

References:

Schlesinger, H.; Brown, H.; Finholt, A.; Gilbreath, J.; Hoekstra, H.; Hyde, E. Sodium Borohydride, Its Hydrolysis and its Use as a Reducing Agent and in the Generation of Hydrogen. 1952,
J. Am. Chem. Soc. 75(1) 215-219

Chinnappan, A.; Kang, H.; Kim, H. Preparation of PVDF nanofiber composites for hydrogen generationfrom sodium borohydride. 2011,
Energy 36(2) 755-759
Scalable Conversion of Carbon Dioxide into Graphene for Electrochemical Energy Storage
Authors: Li Chen , Zhang Xiong , Ma Yanwei
Published: February 2020

Graphene materials are regarded as one promising candidate for next-generation electrochemical energy storage devices due to its unique properties, such as high specific surface area and electrical conductivity. However, most of the up-to-date methodologies for producing graphene, such as chemical vapor deposition, mechanical exfoliation and reduction of graphite oxide, involve several severe drawbacks including heavy ion pollution, low yield and labor-intensive processes, which raise the cost and limit the scalability of graphene production. Therefore, a facile and cost-saving pathway for high-quality graphene synthesis is urgently needed.

Combustion of fossil oil still represents a major energy source for electricity generation around the world, which releases a tremendous amount of CO2 to cause detrimental global warming. As a result, a prospective method for graphene production is to use the available CO2 as feedstock gas. But due to the inherent chemical stability of C=O bond, it is a great challenge to reduce CO2 into carbon materials by conventional techniques. It is well-established that magnesiothermic reaction is capable of dissociating strong chemical bonds, which offers a potential way for effective utilization of CO2.

Herein, we present an ultra-fast magnesiothermic reaction to fabricate few-layer graphene with highly developed mesoporosity from CO2 and magnesium/magnesium oxide mixture. It is demonstrated that magnesium oxide acts as the crucial template to guide graphene formation and provide mesopores after acid rising. The ordered mesoporous graphene exhibits a high specific surface area of 709 m2 g-1 and a narrow pore size distribution around 4 nm.

We further confirm its excellent electrochemical performance as supercapacitor electrodes. In IL electrolyte, the specific capacitance of MSG is as high as 260 F g-1 at 2 A g-1, corresponding to an energy density of 135.6 Wh kg-1, and can still maintain 173 F g-1 at an ultra-high rate of 100 A g-1. This excellent rate capability performance gives birth to an unprecedented power density of 7684 kW kg-1. Moreover, the electrochemical stability is demonstrated by a high capacitance retention of 90% after 1 million cycles of rapid charge/discharge at 100 A g-1. We believe our present work will give a new insight into the production of high-quality graphene materials.

Fig. 1 Ordered mesoporous graphene prepared by ultra-fast magnesiothermic reaction

Figure 1