Shedding Light on the Oxygen Reduction Reaction Mechanism in Ether-Based Electrolyte Solutions: A Study Using Operando UV-Vis Spectroscopy

Hirshberg, Daniel,Sharon, Daniel,Afri, Michal,Lavi, Ronit,Frimer, Aryeh A.,Metoki, Noa,Eliaz, Noam,Kwak, Won-jin,Sun, Yang-Kook,Aurbach, Doron American Chemical Society 2018 ACS APPLIED MATERIALS & INTERFACES Vol.10 No.13

<P>Using UV-vis spectroscopy in conjunction with various electrochemical techniques, we have developed a new effective operando methodology for investigating the oxygen reduction reactions (ORRs) and their mechanisms in nonaqueous solutions. We can follow the in situ formation and presence of superoxide moieties during ORR as a function of solvent, cations, anions, and additives in the solution. Thus, using operando UV-vis spectroscopy, we found evidence for the formation of superoxide radical anions during oxygen reduction in LiTFSI/diglyme electrolyte solutions. Nitro blue tetrazolium (NBT) was used to indicate the presence of superoxide moieties based on its unique spectral response. Indeed, the spectral response of NBT containing solutions undergoing ORR could provide a direct indication for the level of association of the Li cations with the electrolyte anions.</P> [FIG OMISSION]</BR>

High-Performance Cells Containing Lithium Metal Anodes, LiNi_0.6Co_0.2Mn_0.2O₂ (NCM 622) Cathodes, and Fluoroethylene Carbonate-Based Electrolyte Solution with Practical Loading

Salitra, Gregory,Markevich, Elena,Afri, Michal,Talyosef, Yosef,Hartmann, Pascal,Kulisch, Joern,Sun, Yang-Kook,Aurbach, Doron American Chemical Society 2018 ACS APPLIED MATERIALS & INTERFACES Vol.10 No.23

<P>We report on the highly stable lithium metal|LiNi<SUB>0.6</SUB>Co<SUB>0.2</SUB>Mn<SUB>0.2</SUB>O<SUB>2</SUB> (NCM 622) cells with practical electrodes’ loading of 3.3 mA h g<SUP>-1</SUP>, which can undergo many hundreds of stable cycles, demonstrating high rate capability. A key issue was the use of fluoroethylene carbonate (FEC)-based electrolyte solutions (1 M LiPF<SUB>6</SUB> in FEC/dimethyl carbonate). Li|NCM 622 cells can be cycled at 1.5 mA cm<SUP>-2</SUP> for more than 600 cycles, whereas symmetric Li|Li cells demonstrate stable performance for more than 1000 cycles even at higher areal capacity and current density. We attribute the excellent performance of both Li|NCM and Li|Li cells to the formation of a stable and efficient solid electrolyte interphase (SEI) on the surface of the Li metal electrodes cycled in FEC-based electrolyte solutions. The composition of the SEI on the Li and the NCM electrodes is analyzed by X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy. A drastic capacity fading of Li|NCM cells is observed, followed by spontaneous capacity recovery during prolonged cycling. This phenomenon depends on the current density and the amount of the electrolyte solution and relates to kinetic limitations because of SEI formation on the Li anodes in the FEC-based electrolyte solution.</P> [FIG OMISSION]</BR>

Mechanistic Role of Li⁺ Dissociation Level in Aprotic Li–O₂ Battery

Sharon, Daniel,Hirsberg, Daniel,Salama, Michael,Afri, Michal,Frimer, Aryeh A.,Noked, Malachi,Kwak, Wonjin,Sun, Yang-Kook,Aurbach, Doron American Chemical Society 2016 ACS APPLIED MATERIALS & INTERFACES Vol.8 No.8

<P>The kinetics and thermodynamics of oxygen reduction reactions (ORR) in aprotic Li electrolyte were shown to be highly dependent on the surrounding chemical environment and electrochemical conditions. Numerous reports have demonstrated the importance of high donor number (DN) solvents for enhanced ORR, and attributed this phenomenon to the stabilizing interactions between the reduced oxygen species and the solvent molecules. We focus herein on the often overlooked effect of the Li salt used in the electrolyte solution. We show that the level of dissociation of the salt used plays a significant role in the ORR, even as important as the effect of the solvent DN. We clearly show that the salt used dictates the kinetics and thermodynamic of the ORR, and also enables control of the reduced Li2O2 morphology. By optimizing the salt composition, we have managed to demonstrate a superior ORR behavior in diglyme solutions, even when compared to the high DN DMSO solutions. Our work paves the way for optimization of various solvents with reasonable anodic and cathodic stabilities, which have so far been overlooked due to their relatively low DN.</P>

The Effect of Income and Earnings Management on Firm Value: Empirical Evidence from Indonesia

Retno Indah HERNAWATI,Imam GHOZALI,Etna Nur Afri YUYETTA,Andri PRASTIWI 한국유통과학회 2021 The Journal of Asian Finance, Economics and Busine Vol.8 No.4

This study aims to find empirical evidence of the effect of increasing income on the potential transfer of wealth from manufacturing companies that go public to stakeholders. Earnings management with an accrual approach with the Modified Jones model is an identifier of the availability of earnings management practices, without paying attention to both positive and negative symbols. The interpretation of the results of the discretionary accrual measurement between positive and negative symbols has different meanings. Positive discretionary accruals indicate that management uses income-increasing techniques. Meanwhile, negative discretionary accruals indicate that management uses income-reducing techniques. Income-increasing techniques tend to be viewed as opportunistic behavior of managers. This study used 111 data from manufacturing companies listed on the IDX (Indonesia Stock Exchange) from 2015–2018. Path analysis is used to test the hypothesis. The results of this study are in line with the point of view of management strategy, increasing income is used as a way to transfer potential welfare from the company to stakeholders. Social welfare (tax) and managerial remuneration are proven to be mediators in increasing the effect of increasing income on future company value. Further research can complete the potential welfare transfer against the shareholders related to income-increasing strategy

Whistleblowing Intention: Theory of Planned Behavior Perspectives

Lili WAHYUNI,Anis CHARIRI,Etna Afri YUYETTA 한국유통과학회 2021 The Journal of Asian Finance, Economics and Busine Vol.8 No.1

This study aims to document empirically the individual factors that influence the intention to do whistleblowing. This study uses several variables, including internal locus of control, external locus of control, and whistleblowing intention. The use of the theory of Planned Behavior in this study is to explain and analyze the perception of behavior control as a determinant of whistleblowing intention. A quantitative research approach is used. The type of data in this study is primary data in the form of a questionnaire. The data collection method in this research is using the survey method. The sampling technique used a nonprobability sampling method, namely, the census method. The census method is the entire population sampled. The population in this study was all employees of the Pratama tax office in West Semarang. The research was conducted by distributing 111 questionnaires. Ninety-one valid questionnaires were returned appropriate for analysis. The data were processed using Partial Least SquareStructural Equation Modeling ((PLS-SEM) using the Warp PLS 7.0 program. WarpPLS 7.0 was used to test hypotheses and the relationship between variables. The study results showed that both internal locus of control and external locus of control affect whistleblowing intention.

Li–O₂ cells with LiBr as an electrolyte and a redox mediator

Kwak, Won-Jin,Hirshberg, Daniel,Sharon, Daniel,Afri, Michal,Frimer, Aryeh A.,Jung, Hun-Gi,Aurbach, Doron,Sun, Yang-Kook Royal Society of Chemistry 2016 ENERGY AND ENVIRONMENTAL SCIENCE Vol.9 No.7

<P>After many years of successful and disappointing results, the field of Li-O-2 research seems to have reached an equilibrium state. The extensive knowledge that has accrued through advanced analytical studies enables us to delineate the weaknesses of the Li-O-2 battery. It is now clear that the instability of the cell components toward extreme conditions existing during cell operation leads to early cell failure as well. One serious challenge is the high oxidation potential applied during the charge process. Redox-mediators may reduce the over-potential and, therefore, improve the efficiency and cyclability of Li-O-2 cells. Their use in Li-O-2 cells is mandatory. We have previously shown that LiI can indeed behave in such a manner; however, it also promotes the formation of side products during cell operation. We have, therefore, embarked on a comprehensive study of lithium halide salts as electrolytes for use in Li-O-2 cells. We examine herein the effect of other components in the cell, such as solvents and contaminants, on the lithium halide salt activity. Based on the electrochemical behavior and the identity of the final cell products under various conditions, we can glean substantial information regarding the detailed operation mechanisms for each specific case. We have concluded that low concentration of LiBr in diglyme solution can improve the cell performance with fewer side effects than LiI. With LiBr, only the desired Li2O2 is formed during discharge. During charge, the bromine redox couple (Br-/Br-3(-)) can reduce the oxidation potential to only 3.5 V. Higher efficiency and better cyclability of cells containing LiBr demonstrate that the electrolyte solution is the key to a successful Li-O-2 battery.</P>

Understanding the behavior of Li–oxygen cells containing LiI

Kwak, Won-Jin,Hirshberg, Daniel,Sharon, Daniel,Shin, Hyeon-Ji,Afri, Michal,Park, Jin-Bum,Garsuch, Arnd,Chesneau, Frederick Francois,Frimer, Aryeh A.,Aurbach, Doron,Sun, Yang-Kook The Royal Society of Chemistry 2015 Journal of Materials Chemistry A Vol.3 No.16

<▼1><P>This work deals with core issues of Li–oxygen battery systems; intrinsic stability of polyether electrolyte solutions and the role of important redox mediators such as LiI/I2.</P></▼1><▼2><P>Mankind has been in an unending search for efficient sources of energy. The coupling of lithium and oxygen in aprotic solvents would seem to be a most promising direction for electrochemistry. Indeed, if successful, this system could compete with technologies such as the internal combustion engine and provide an energy density that would accommodate the demands of electric vehicles. All this promise has not yet reached fruition because of a plethora of practical barriers and challenges. These include solvent and electrode stability, pronounced overvoltage for oxygen evolution reactions, limited cycle life and rate capability. One of the approaches suggested to facilitate the oxygen evolution reactions and improve rate capability is the use of redox mediators such as iodine for the fast oxidation of lithium peroxide. In this paper we have examined LiI as an electrolyte and additive in Li oxygen cells with ethereal electrolyte solutions. At high concentrations of LiI, the presence of the salt promotes a side reaction that forms LiOH as a major product. In turn, the presence of oxygen facilitates the reduction of I3<SUP>−</SUP> to 3I<SUP>−</SUP> in these systems. At very low concentrations of LiI, oxygen is reduced to Li2O2. The iodine formed in the anodic reaction serves as a redox mediator for Li2O2 oxidation.</P></▼2>

Feasibility of Full (Li-Ion)–O₂ Cells Comprised of Hard Carbon Anodes

Hirshberg, Daniel,Sharon, Daniel,De La Llave, Ezequiel,Afri, Michal,Frimer, Aryeh A.,Kwak, Won-Jin,Sun, Yang-Kook,Aurbach, Doron American Chemical Society 2017 ACS APPLIED MATERIALS & INTERFACES Vol.9 No.5

<P>Aprotic Li-O-2 battery is an exciting concept. The enormous theoretical energy density and cell assembly simplicity make this technology very appealing. Nevertheless, the instability of the cell components, such as cathode, anode, and electrolyte solution during cycling, does not allow this technology to be fully commercialized. One of the intrinsic challenges facing researchers is the use of lithium metal as an anode in Li-O-2 cells. The high activity toward chemical moieties and lack of control of the dissolution/deposition processes of lithium metal makes this anode material unreliable. The safety issues accompanied by these processes intimidate battery manufacturers. The need for a reliable anode is crucial. In this work we have examined the replacement of metallic lithium anode in Li-O-2 cells with lithiated hard carbon (HC) electrodes. HC anodes have many benefits that are suitable for oxygen reduction in the presence of solvated lithium cations. In contrast to lithium metal, the insertion of lithium cations into the carbon host is much more systematic and safe. In addition, with HC anodes we can use aprotic solvents such as glymes that are suitable for oxygen reduction applications. By contrast, lithium cations fail to intercalate reversibly into ordered carbon such as graphite and soft carbons using ethereal electrolyte solutions, due to detrimental co-intercalation of solvent molecules with Li ions into ordered carbon structures. The hard carbon electrodes were prelithiated prior to being used as anodes in the Li-O-2 rechargeable battery systems. Full cells containing diglyme based solutions and a monolithic carbon cathode were measured by various electrochemical methods. To identify the products and surface films that were formed during cells operation, both the cathodes and anodes were examined ex situ by XRD, FTIR, and electron microscopy. The HC anodes were found to be a suitable material for (Li-ion) O-2 cell. Although there are still many challenges to tackle, this study offers a more practical direction for this promising battery technology and sets up a platform for further systematic optimization of its various components.</P>

2,4-Dimethoxy-2,4-dimethylpentan-3-one: An Aprotic Solvent Designed for Stability in Li–O₂ Cells

Sharon, Daniel,Sharon, Pessia,Hirshberg, Daniel,Salama, Michael,Afri, Michal,Shimon, Linda J. W.,Kwak, Won-Jin,Sun, Yang-Kook,Frimer, Aryeh A.,Aurbach, Doron American Chemical Society 2017 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.139 No.34

<P>In this study, we present a new aprotic solvent, 2,4-dimethoxy-2,4-dimethylpentan-3-one (DMDMP), which is designed to resist nucleophilic attack and hydrogen abstraction by reduced oxygen species. Li-O-2 cells using DMDMP solutions were successfully cycled. By various analytical measurements, we showed that even after prolonged cycling only a negligible amount of DMDMP was degraded. We suggest that the observed capacity fading of the Li-O-2 DMDMP-based cells was due to instability of the lithium anode during cycling. The stability toward oxygen species makes DMDMP an excellent solvent candidate for many kinds of electrochemical systems which involve oxygen reduction and assorted evaluation reactions.</P>