bluuebunny/crossref_metadata_2025 huggingface dataset:
Fabrication of Bi-Enzymatic Electrodes Base on Graphene Oxide-Modified ITO for Enzymatic Fuel Cell Utilizing Trehalose
Authors: Wang Xue , Seo Yang Gon , Kim Hyug-Han , Kim Chang-Joon
Published: February 2020

Graphene has been widely utilized in electronic devices and biosensors because it has large surface area, high electron conductivity, and stability. This paper describes a graphene as the platform substrate for enzyme immobilization as well as enhancing electron transfer in the fabrication of enzymatic biofuel cells utilizing trehalose. The graphene oxide (GO) film was formed over ITO surfaces by electrodeposition and it was reduced by applying electric potential ranging from -1.5 to -0.5 V (vs. Ag/AgCl). The electrodes were examined by using XPS, FESEM, and AFM and then their electrochemical performances were evaluated. The deposition time in deposition stage and pH of buffer solution in reduction stage, greatly influenced on GO loading and the extent of GO reduction. Glucose oxidase (GOD) or trehalase (Tre) was immobilized on the reduced graphene-modified ITO electrodes (r-GO-ITO) by physical adsorption. Electrodes with difference sequences of two enzymes were evaluated. The effects of GOD layers and units of Tre were investigated. Electrochemical impedance spectra and cyclic voltammograms showed that electrodes generated maximum peak currents with the lowest electron transfer resistance when electrode was covered with four-GOD layer and 2.6 U of Tre. Enzyme assay was performed to investigate whether increase in the unit of Tre influences on the mass transfer of substrate to GOD. Enzyme fuel cell was assembled in which anode was optimized GOD-Tre electrode while cathode was bilirubin oxidase immobilized r-GO-ITO. The fuel cell generated the power density of 0.42 μW/cm2 in 100 mM PBS buffer (pH, 7.0) containing 30 mM trehalose solution.
Infulence of Alkyl-Chain-Length of Quaternary Ammonium Cation on Zn Deposition Morphology in Alkaline-Based Electrolyte
Authors: Shimizu Masahiro , Hirahara Koichi , Arai Susumu
Published: February 2020

Zn-air batteries with a high energy density of 1350 Wh kg-1 is one of the breakthroughs required to achieve a low carbon society. However, morphology control of the Zn negative electrode during charge/discharge (Zn-deposition/stripping) is essential for practical application. Previously, we acheived smooth morphology of Zn deposit in alkaline-based electrolyte (0.25 ZnO\4M KOH) by adding cationic surfactant (quaternary ammonium cation). In the present study, we systematically investigated the effect of alkyl chain length in the quaternary ammonium cation on electrochemical Zn growth morphology. Completely smooth deposition morphology was achieved by changing from octyl to decyl group in the surfactant. Electrochemical impedance spectroscopic analysis revealed that charge transfer resistance associated with Zn deposition increased as alkyl chain length. The obtained results indicate that bulky ammonium cations suppress excess electrodeposition reactions by steric hindrance effect and thereby result in smooth morphology.

Figure 1
Investigations on the Aging-Related Lithium Loss in Lithium Ion Batteries by Using 6Li-Isotopically-Enriched Cathode Material and Post-Mortem Analysis by Means of Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry
Authors: Mense Maximilian , Siozios Vassilios , Winter Martin , Nowak Sascha
Published: February 2020

In the last decades, the lithium ion battery (LIB) became the technology of choice for a huge variety of power storage applications. Nevertheless, the loss of performance caused by complex aging phenomena remains challenging. In the first electrochemical cycles, the liquid organic electrolyte is decomposed at the electrodes surfaces leading to the formation of an electrically insulating passivation layer on the anode, the solid electrolyte interphase (SEI). Although the SEI formation involves an irreversible loss of electrolyte and active lithium, it is an essential process to provide sufficient cycling stability, as it prevents the remaining electrolyte from further decomposition. In order to improve the cycle performance of LIBs a deeper understanding of the aging processes is crucial.

Focusing on the SEI formation process, common techniques for lateral and/or depth resolved isotopic surface analysis are time of flight-secondary ion mass spectrometry (ToF-SIMS) and glow discharge-mass spectrometry (GD-MS), respectively. However, lateral and depth resolved isotopic imaging of whole electrodes at a reasonable time scale is only possible with laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS). This work features the post-mortem analysis of graphitic SEI formed in LIBs, including a 6Li-isotopically-enriched LiNi1/3Co1/3Mn1/3O2 (NMC111) cathode material, to investigate the SEI formation process and the lithium distribution in the first electrochemical cycles. Therefore, lithium isotope deposition pattern of aged anodes are investigated in lateral and depth dimension by means of LA-ICP-MS.
Composite Lithium Metal Anode Via a Simple Rolling-Cutting Method
Authors: Liang Zheng
Published: February 2020

Lithium metal–based batteries are attractive energy storage devices because of high energy density. However, uncontrolled dendrite growth and virtually infinite volume change, which cause performance fading and safety concerns, have limited their applications. Here, we demonstrate that a composite lithium metal electrode with an ion-conducting mesoscale skeleton can improve electrochemical performance by locally reducing the current density. In addition, the potential for short-circuiting is largely alleviated due to side deposition of mossy lithium on the three-dimensional electroactive surface of the composite electrode. Moreover, the electrode volume only slightly changes with the support of a rigid and stable scaffold. Therefore, this mesoscale composite electrode can cycle stably for 200 cycles with low polarization under a high areal current density up to 5 mA/cm2. Most attractively, the proposed fabrication process, which only involves simple mechanical deformation, is scalable and cost effective, providing a new strategy for developing high performance and long lifespan lithium anodes. It is worth noting that this composite electrode design holds great promise for metal electrodes coupled with solid electrolyte.

Figure 1
Structure and Dynamics Properties of Li-Ion Electrolytes in High Concentration Solution
Authors: Tong Jiahuan , Liang Xiaodong , Solms Nicolas von , Huo Feng , Zhang Suojiang
Published: February 2020

Electrolyte is an indispensable composition in energy storage since the positive and negative electrodes are interconnected by electrolytes that determines the charge transport during the charging/discharging process. Ideal electrolytes should satisfy the following requirements: i.e., excellent electrochemical stability, wide voltage window, high conductivity, environmental friendliness and easy availability with high purity.[
1
,2] In this work, molecular dynamics simulations have been carried out on two organic solvents (dimethyl carbonate, diethyl carbonate) and four imidazolium-based ionic liquids ([Cnmim][X], n=2,4, X=[BF4]- and [TFSI]-) doped with 2 mol/L LiTFSI salt at 298 K and 313 K. Physicochemical properties, including density, viscosity, self-diffusion coefficient and conductivity are investigated. The contribution and influence of independent conductivity type for uncorrelated and correlated ion on the total conductivity are explored. In parallel, the structure of all electrolytes were further analyzed by the radial distribution functions and the ion coordination numbers. Among them, the structures of solute (LiTFSI) were analyzed in details and the effects of different solvents as well as anion and cation of ionic liquids on the interaction of Li+ were explored. The results indicate that the organic solvents restrict the free motion of the ions, reducing the conductivity of the electrolytes, on the contrary, solute is more stable due to the ionic structure of ionic liquids, especially the [C4mim][BF4] with the highest conductivity among the ILs-based electrolytes. More interesting, two conformations of TFSI- (cis and trans) of solute coexist in all electrolytes. Meanwhile, it was found that the effect of Li+ coordination is mainly determined by anion of ionic liquids and the interaction between Li+ and anion of ionic liquids is directly proportional to the length of the side chain of cation for ionic liquids. In this study, the properties and structures of the electrolytes of organic solvents and ionic liquids were compared thoroughly. The advantages of ionic liquid electrolytes are explained in detail and it is helpful to design higher conductive and more stable ionic liquid electrolytes at molecular level.

Figure 1
Effective Pre-Electrochemical Treatment of Cu EQCM Electrode on Lithium Electrodeposition/Dissolution Processes
Authors: Niida Asako , Smaran Kumar Sai , Ohama Ayano , Uchino Yukina , Nishihara Kaho , Kondo Toshihiro
Published: February 2020

Lithium has been extensively expected as one of the most ideal anode materials of the next generation lithium-based batteries, because of its higher theoretical specific capacity (3860 mA h g-1) and its most negative redox potential (-3.04 V vs. SHE). On the lithium anode surface, however, it is well-known that the dendrite, which further leads to poor battery performance and short circuit, forms in charging. In addition, solid electrolyte interphase (SEI), which is generated by decomposition of electrolytes and/or solvents, also accumulates on the anode surface during the anode reaction. An ideal SEI layer is expected to be higher and lower conductive for lithium ion and electron, respectively, and it is flexible and has a relatively uniform flat surface with an appropriate thickness, in order to avoid dendrite formation [1].

During the electrochemical reaction, on the other hand, electrochemical quartz crystal microbalance (EQCM) technique gives us information not only of mass change on the electrode surface but also resonance resistance change, which shows surface area change of the electrode [2,3] and/or density and viscosity change at the electrode/electrolyte solution interface [4,5]. Using this technique, we found that the pre-electrochemical treatment of the Cu EQCM electrode strongly effects on the lithium electrodeposition/dissolution processes.

Acknowledgements: This work was totally supported by the Advanced Low Carbon Technology Research and Development Program (ALCA), specially promoted research for innovative next generation batteries (SPRING) from the Japan Science and Technology (JST).

References:

[1] X.-B. Cheng, R. Zhang, C.-Z. Zhao, F. Wei, J.-G. Zhang, Adv. Sci. 3 (2016) 1500213.

[2] K. Kanamura, S. Shiraishi, Z. Takehara, J. Electrochem. Soc. 147 (2000) 2070.

[3] D. Aurbach, M. Moshkovich, Y. Cohen, A. Schechter, Langmuir 15 (1999) 2947.

[4] K. Naoi, M. Mori, Y. Naruoka, W. M. Lamanna, R. Atanasoski, J. Electrochem. Soc. 146 (1999) 462.

[5] N. Serizawa, S. Seki, K. Takei, H. Miyamoto, K. Yoshida, K. Ueno, N. Tachikawa, K. Dokko, Y. Katayama, M. Watanabe, T. Miura, J. Electrochem. Soc. 160 (2013) A1529.
Symmetric Redox Flow Batteries with Bifunctional Molecules
Authors: Cording Faye , Friedl Jochen , Stimming Ulrich
Published: February 2020

The continued integration of renewable energy sources into the power grid, as well as the development of decentralised energy systems, requires energy storage in order to capture and store the energy produced intermittently from renewable sources. One energy storage option is the Redox Flow Battery (RFB) which has several advantages over other secondary batteries. As the active species of an RFB remain in solution during charge and discharge, degradation of the electrodes is minimised. Further, due to external storage of the electrolytes, the energy and power of an RFB can be adjusted independently by varying the volume of stored electrolyte or size of the cell stack. The most mature RFB is the all-vanadium RFB but this also has drawbacks, such as slow electron transfer kinetics of the vanadium ions1 and a requirement for the use of acidic electrolytes.

Polyoxometalates (POMs) are anionic metal-oxygen clusters of early transition metals, commonly vanadium, molybdenum and tungsten, which can undergo redox reactions in which multiple electrons are transferred. The electrochemical properties of POMs prompted their investigation by our group and the development of a POM RFB which was based on the reactions of [PV14O42]9- at the cathode and [SiW12O40]4- at the anode.2 This work demonstrated that an RFB cell with multi-electron redox reactions occurring in each half-cell could be created by using POMs and that the charge transfer reactions of POMs are relatively fast.2 The [PV14O42]9-/[SiW12O40]4- RFB was classified as an asymmetric RFB due to the use of different POM active species in each half-cell. Alternatively, symmetric RFBs can be designed which utilise the same active material in both half-cells.

Our group has also investigated the approach of using bifunctional molecules, which can undergo redox reactions at positive and negative potentials, as the active species in symmetric RFBs. This includes the use of fullerene species functionalised with ferrocene units.3 POMs can also be bifunctional species when composed of two different redox-active metals. In this poster, we outline the results of work in our group on the use of bifunctional species in symmetric RFBs, including the study of a POM for a symmetric RFB which has shown good stability in charge-discharge testing so far in conditions that are only mildly acidic.

References

J. Friedl and U. Stimming, Electrochimica Acta, 2017, 227, 235–245.

J. Friedl, M. V. Holland-Cunz, F. Cording, F. L. Pfanschilling, C. Wills, W. McFarlane, B. Schricker, R. Fleck, H. Wolfschmidt and U. Stimming, Energy Environ. Sci., 2018, 11, 3010–3018.

J. Friedl, M. A. Lebedeva, K. Porfyrakis, U. Stimming and T. W. Chamberlain, J. Am. Chem. Soc., 2018, 140, 401–405.
Studying Aging of Lithium Ion Batteries – Observing Gas Evolution with in-Operando Mass Spectrometry
Authors: Mattinen Ulriika , Lindbergh Göran , Lindström Rakel Wreland , Klett Matilda
Published: February 2020

Increasing our understanding on different aging processes and mechanisms linked to the lifetime and safety of lithium ion batteries is crucial for extending their usability in e.g. hybrid and electric vehicles followed by potential 2nd life applications. Coupling a mass spectrometer (MS) to a special on-line electrochemical cell hosting battery components enables time resolved detection of gases that are evolving during cycling and other aging. Gas evolving processes are for example decomposition of the electrolyte, formation of the SEI (solid electrolyte interphase) and other side reactions [1-3].

In this work, an in-house made adjustable electrochemical in-operando cell with a connection to the MS is used to study aging-related gas evolution at two types of cells: laboratory-scale lithium ion batteries and larger commercial cylindrical batteries. The design of the in-operando cell is flexible for different battery chemistries and to some extent different sizes.

The commercial cylindrical cells used in this study are NMC-based Li-ion batteries. The battery can is pierced to allow gas diffusion inside the leak-tight housing connected to the MS. Aging of the large batteries can be inhomogeneous [4] and therefore it is highly interesting to measure the gas evaluation also from large cells and compare these to small laboratory-scale cells aged at more defined conditions. For the commercial batteries, the possibility to perform long term aging experiments is desirable. The cell construction used in this work allows replacing the gas sampled from the cell head-space, ensuring constant pressure in the measurement chamber and enabling prolonged measurements. A safety valve is installed to release overpressure in case of an extensive gas evolution.

The goal of the presented work is to quantify gaseous products evolving upon battery aging with different operating parameters such as rate of charging [5], temperature, state of charge and voltage window to gain more insight to the aging phenomena.

[1] S. Meini, M. Piana, N. Tsiouvaras, A. Garsuch, H.A. Gasteiger, Electrochemical and Solid-State Letters 15(4) (2012) A45-A48.

[2] B.B. Berkes, A. Jozwiuk, M. Vracar, H. Sommer, T. Brezesinski, J. Janek, Analytical Chemistry 87(12) (2015) 5878-5883.

[3] D. Streich, A. Gueguen, M. Mendez, F. Chesneau, P. Novak, E.J. Berg, Journal of the Electrochemical Society 163(6) (2016) A964-A970.

[4] M. Klett, P. Svens, C. Tengstedt, A. Seyeux, J. Swiatowska, G. Lindbergh, R. Wreland Lindstroem, J. Phys. Chem. C 119(1) (2015) 90-100.

[5] A.S. Mussa, M. Klett, M. Behm, G. Lindbergh, R.W. Lindström, Journal of Energy Storage 13 (2017) 325-333.
Utilization of Carbon Nanotube Based Catalyst for the Performance Enhancement of Aqueous Organic Redox Flow Battery
Authors: Lee Wonmi , Ji Jungyeon , Kwon Yongchai
Published: February 2020

Alloxazine and ferrocyanide were introduced as redox couple for aqueous organic redox flow battery (AORFB). Alloxazine was further modified by carboxylic acid (COOH) (COOH-alloxazine) to increase the aqueous solubility. For improving the performance of AORFB, the redox reactivity of the rate determining reaction (RDR) should be enhanced. Carboxylic acid group doped carbon nanotube (CA-CNT) catalyst was used for increasing the redox reactivity of RDR. The CA-CNT induced a better redox reactivity of COOH-alloxazine that was RDR because of the function of COOH as a proton donor. The strengthened hydrophilic property of COOH-alloxazine and the increased number of active sites were another reasons for causing the better redox reactivity. Regarding AORFB full cell testing, when the CA-CNT was adopted as the catalyst for the negative electrode, the performance of AORFB increased. According to the detailed results, charge/discharge overpotential and IR drop potential were enhanced, coulombic and energy efficiencies also increased, and discharging capacity reached to the similar level to that of vanadium redox flow battery.

Reference

[1] "Effect of carboxylic acid doped carbon nanotube catalyst on the performance of aqueous organic redox flow battery using the modified alloxazine and ferrocyanide redox couple", W. Lee, B.W. Kwon and Y. Kwon, ACS Applied Materials & Interfaces, 10, 36882-36891, 2018
Ultra-Thin Composite Electrolytes for Energy Conversion Devices
Authors: Lim Seohee , Park Jong-Hyeok , Park Jin-Soo
Published: February 2020

Most of electrochemically driven energy conversion devices consist of anodic reaction, ion movement and cathodic reaction to complete full electrochemical cells. Ions move from anode to cathode or vice versa for electron exchanges. Pathway for ions is normally in an aqueous phase. Regardless, the introduction of any aqueous phase in energy conversion devices causes many problems during fabrication, operation, maintenance, and so on. Thus, much efforts have been devoted to develop quasi-solid electrolytes such as gel polymer, ion exchangeable polymers, impregnation of ions in porous matrix and so on. One of major disadvantages to use polymeric electrolytes is significant Ohmic voltage decay due to high areal resistance compared to aqueous phases. An approach to minimize areal resistance of film-type polymeric electrolytes is to make film thickness as thin as possible. Free standing polymeric electrolytes, however, show low mechanical properties. Thus, composite membranes could be used by impregnating polymeric electrolytes into thin porous substrates. In this study, three-layered (electrolyte-skeleton/electrolyte-electrolyte) composite membranes with the thickness of 12-18 μm were prepared. A technique to impregnate polymeric electrolytes into hydrophilic or hydrophobic porous substrates were intensively developed so as to prepare void-free composite membranes. Characterization in terms of ion conductivity, ion exchange capacity, water uptake, dimensional stability, mechanical strength was carried out.
Heterogeneous Electron Transport at PEDOT-PSS Electrode-Electrolyte Interfaces
Authors: Wijeratne Kosala , Ail Ujwala , Brooke Robert , Vagin Mikhail , Liu Xianjie , Fahlman Mats , Crispin Xavier
Published: February 2020

Heterogeneous electron transport (HET) is important in many technologies, including batteries, fuel cells, medical sensors, organic electrochemical synthesis, food analysis, corrosion protection, and thermogalvanic cell. HET takes place at the interface between a solid electrode and a reactant in a liquid electrolyte, and it depends on the type of reactants, electrodes, solvents, and electrolyte. HET has been well studied for metal, semiconductor, metal oxide, carbon electrode. The current passing at the electrode/electrolyte interface is related to the density of electronic states of the electrode, the concentration of reactant and the rate of electron transfer and the electronic level of the reactant in the solution

Here, we study the HET between a conducting polymer electrode and a redox electrolyte, and we found that a new phenomenon is observed. Conducting polymers possess a unique combination of properties compared with most of the inorganic electrodes: acid resistance, the absence of surface-insulating oxide, low temperature and solution processability, a high natural abundance of their elements, molecular porosity. Conducting polymers are in-homogeneous conductors composed of ordered and disordered regions through which electronic transport takes place via percolation paths.

We studied the heterogeneous electron transport between the conducting polymer poly(3,4-ethylenedioxythiophene) (PEDOT) and redox electrolyte ferro/ferricyanide in an aqueous electrolyte. We discovered that the density of percolation paths in the bulk of the material dictates the rate of electron transfer at the electrolyte–polymer electrode interface. This reveals one of the key parameters of designs to achieve efficient electrochemical technologies based on polymer electrodes.

We use this finding to optimize the electrical power generated by a thermogalvanic cell (TGC), which is an electrochemical device that converts heat energy into electricity. The power produced by the TGC increased by four orders of magnitude upon changing the morphology and electrical conductivity of the PEDOT electrode.

References:

Wijeratne K, Vagin M, Brooke R, & Crispin X (2017) Poly(3,4-ethylenedioxythiophene)-tosylate (PEDOT-Tos) electrodes in thermogalvanic J. Mater. Chem. A 5:19619 –19625.

Wijeratne K, Ail U, Brooke R, Vagin M, Liu X, Fahlman M, & Crispin X (2018) Bulk electronic transport impacts on electron transfer at conducting polymer electrode-electrolyte interfaces. PNAS, 115:11899 - 11904.
Redox Fuel Cells: The Fusion of Redox Flow Batteries and Fuel Cells
Authors: An Liang
Published: February 2020

In conventional fuel cells that use hydrogen peroxide as oxidant, the cathode potential is created by the reduction reaction of hydrogen peroxide. In this work, we propose to create the cathode potential by introducing a redox couple to the cathode while using hydrogen peroxide to chemically charge the redox ions. The idea not only completely eliminates the mixed-potential issue associated with the direct reduction of hydrogen peroxide, but also enables faster cathodic electrochemical kinetics with no catalysts. It is demonstrated that the ethanol-hydrogen peroxide fuel cell with a redox couple of V4/V5 yields a peak power density of 450 mW cm-2, which is much higher than that of the conventional cell with direct reduction of hydrogen peroxide.
Synthesis and Characterization of a Composite Cathode Material (Li2S@rGO) for Li-S Batteries Made By in Situ Electrochemical Conversion of MoS2@rGO
Authors: Balach Juan , Zensich Maximiliano , Jaumann Tony , Morales Gustavo Marcelo , Giebeler Lars , Barbero Cesar Alfredo
Published: February 2020

Lithium disulfide (Li2S) could be used as cathode material for high-energy-density lithium–sulfur (Li–S) batteries, having a large theoretical specific capacity (1166 mAh g–1). However, the material has low conductivity. Additionally, soluble lithium polysulfide species can be formed during cell operation in carbonate-based electrolytes resulting in a poor cycling stability. In this work, Li2S particles are wrapped in reduced graphene oxide (Li2S@rGO) to produce cathode materials for Li–S batteries in carbonate-based electrolytes. First GO is produced by a modified Hummers method. Then, rGO is reduced hydrothermally on MoS2 particles. The composite is then fully lithiated and irreversible decomposed at 0.01 V vs. Li/Li+ to produce a Li2S@rGO with a high Li2S (loading of ≈5 mg cm–2). The material is characterized by SEM, TEM, EDXS, N2 isotherm and XRD (before and after cell cycling). The material is then used as cathode with Li foil as counter electrode. The system is mounted as coin cells (CR2025) in an Ar filled glove box, filled with 1 M LiPF6 in ethylene carbonate/dimethyl carbonate (EC/DMC; 1:1 v/v). The cells are sealed and then cycled in air (constant temperature and humidity). The electrochemical properties are investigated using galvanostatoc charge/discharge cycles, cyclic voltammetry and electrochemical impedance spectroscopy measurements. The cathode material exhibits a high initial capacity: 1401 mAh g–1 (based on S weight) at 0.1 C. Besides, it shows a good capacity retention (411 mAh g–1 at 2 C after 150 cycles) and excellent Coulombic efficiency (≈99.5%). The material could be used in high-loading Li2S cathodes for high-performance Li–S batteries without the disadvantage of polysulfide formation.
Novel Perceptions of Lithium Ion Batteries: Isotopic Labeling for Insights into Lithium Losses and Solid Electrolyte Interphase Formation By Means of Plasma-Based Techniques
Authors: Nowak Sascha , Evertz Marco , Diehl Marcel , Kenkel Alexander , Winter Martin
Published: February 2020

Since their introduction in the early 90’s, the lithium ion battery (LIB) has to face challenging demands for mobile and stationary applications, respectively. In state-of-the-art LIBs, carbonaceous negative electrodes and lithium transition metal oxide (e.g. LiNi1/3Co1/3Mn1/3O2 (NCM111)) positive electrodes are used delivering outstanding energy densities. However, the cell suffers from performance losses - especially at elevated charging cut-off voltages exceeding 4.4 V - which cause is still a matter of discussion in literature.1,2

One postulated degradation mechanism is assigned to the passivation layer on the carbonaceous negative electrode, which is called the solid electrolyte interphase (SEI). It is formed during the first cycle due to the high reductive potential affecting the electrolyte and consuming active lithium. Nonetheless, it is still unknown which lithium source, either electrolytic or cathodic lithium, is electrochemically lost during this SEI formation. In order to quantify the lithium loss in both positive and negative electrodes, plasma-based analytical techniques are well suited for these investigations.

In this work, inductively coupled plasma-optical emission spectroscopy (ICP-OES) is used to investigate the lithium loss in charge/discharge aged layered NCM-based cathode materials as well as the lithium loss in carbonaceous anodes using glow discharge-sector field-mass spectrometry (GD-SF-MS). Additionally, investigations of 6Li-enriched cathode material or electrolyte solutions (6LiPF6) were conducted using inductively coupled plasma-mass spectrometry (ICP-MS) and GD-SF-MS for bulk and depth-resolved quantification of lithium losses in charge/discharge aged LIBs. Therefore, a NCM111 material is synthesized using 6Li-enriched components as source material as well as an isotope labelled conducting salt and cycled in a full-cell set-up to elucidate the origin of lithium losses. With this approach, it is possible to distinguish between lithium losses either from the conducting salt or the cathode material.

Furthermore, the origin of the lithium, which forms the SEI, can be traced via this approach. The electrode-near SEI consists of lithium originating from the electrolyte, while a mixed interlayer of lithium from both electrolyte and electrode is formed afterwards. Eventually, lithium in the electrolyte-near SEI originates from the cathode material (see Figure).

1 J. Vetter, P. Novák, M.R. Wagner, C. Veit, K.-C. Möller, J.O. Besenhard, M. Winter, M. Wohlfahrt-Mehrens, C. Vogler, A. Hammouche, J. Power Sources, 2005
, 147, 269-281.

2 J. Kasnatscheew, M. Evertz, B. Streipert, R. Wagner, R. Klöpsch, B. Vortmann, H. Hahn, S. Nowak, M. Amereller, A. C. Gentschev, P. Lamp and M. Winter, Phys. Chem. Chem. Phys., 2016, 18 , 3956-3965.

Figure 1
Redox Mechanisms and Film Formation at Interfaces in Lithium-sulfur Battery System
Authors: Drvarič Talian Sara , Moskon Joze , Adamič Michel , Dominko Robert , Gaberscek Miran
Published: February 2020

The lithium-sulfur battery is widely considered as one of the most perspective post lithium-ion systems. However, the high theoretical capacity of 1672 mAh g-1 is difficult to attain in practice. Also, the typical power capability lags behind that of the Li-ion rivals. We will present extensive experimental work using many different types of electrochemical cells and different measuring techniques with the aim to elucidate the main processes taking place at two interfaces: lithium/electrolyte and electrolyte/carbon cathode. We will identify the main electrochemical reaction show how they directly or indirectly limited the performance of state-of-the-art Li-S systems. Selected typical results will be interpreted based on modeling using the transmission line approach. New insights into well known mechanisms such as deposition of solid film, depletion of polysulfides in bulk electrolyte, the shuttle effect etc. will be presented and discussed.
Online Characterization of Porous Separators for Disproportionation Redox Flow Batteries
Authors: Smith Kirk P , Ascencio Pedro , Howey David Alastair , Monroe Charles W
Published: February 2020

Disproportionation redox flow batteries (DRFBs) employ active species whose oxidation states in both electrolytes are identical in the fully discharged condition, as seen in Figure 1. This feature allows for the use of simple porous materials for separators instead of more expensive, less robust ion-exchange membranes. DRFBs with porous separators tolerate crossover, because recombination of reduced and oxidized active species through the separator only affects round-trip efficiency, and does not permanently degrade the battery’s capacity. This advantage presents challenges when attempting to characterize DRFB performance, however, because crossover is always present, and substantial voltage relaxation occurs when performing open-circuit holds. A new characterization method is used to estimate the relationship between system state-of-charge and open-circuit potential (Nernst-equation parameterization, Figure 2) simultaneously with the instantaneous rate of crossover inside the reactor. This method, based on a simplified reactor model for DRFBs, consists of an adaptive observer which uses transient current and voltage data from the battery to quantify these interrelated phenomena.

The online characterization method was used to perform a parameter study probing the effects of liquid flowrates, active-species concentration, separator thickness/porosity, and solvent choice on the performance of porous separators in DRFBs by evaluating crossover rates, Nernst curves, and efficiencies. The DRFB used in this study consisted of vanadium acetylacetonate in various organic solvents, with tetraethylammonium tetrafluoroborate as a supporting salt. Various polypropylene separators (originally designed for lithium ion batteries) were used in the DRFBs.

This adaptive observer method is shown to be straightforward to implement and useful for characterizing the performance of different porous separators in DRFBs. Additionally, the overall parameter study allows for a greater understanding of the tradeoffs involved in operating DRFBs, independent of separator.

Figure 1
Spray-Drying As a Versatile Synthesis Method for Fluorophosphate-Based Compounds As Cathodes Material for Na-Ion Batteries
Authors: Bodart Jérôme , Eshraghi Nicolas , Mahmoud Abdelfattah , Vertruyen Bénédicte , Cloots Rudi , Boschini Frederic
Published: February 2020

Fluorophosphate compounds attract much attention as cathode materials for Na-ion batteries. Indeed, thanks to the inductive effect of the fluoride and phosphate groups, such compounds exhibit a relatively high working potential and good theoretical capacity [1]. In this work, we focus on the iron (Na2FePO4F (NFPF)) and vanadium (Na3V2(PO4)3F3(NVPF)) based fluorophosphate materials which are characterized by a high theoretical capacity of 124 mAh/g and 128 mAh/g, respectively. In addition, the iron-based phase is also more environmental friendly due to the low toxicity of the iron.

The preparation of such complex phases using conventional solid-state route requires at least two steps with long heat treatment durations. Here, we report a facile aqueous synthesis using the spray-drying method that can be used for both NFPF and NVPF materials and that can be tuned in order to optimize the composition and the morphology of the desired materials.

The major limitation of phosphate-based electrodes is their low intrinsic electronic conductivity. The synthesis of composites with carbon is an effective strategy for the enhancement of the electronic conductivity of these compounds. Spray-drying is a suitable method to incorporate carbon in composite compounds due to the high homogeneity of the obtained particle [2]. It is also a cost effective and up-scalable technique which can produce large quantities of the desired material.

Here, we report the influence of the carbon addition of the structural, morphological and electrochemical properties of NFPF and NVPF compounds. The prepared composite materials were investigated by combining several characterisation techniques such as XRD, SEM and TEM. The electrochemical properties were evaluated by galvanostatic cycling and electrochemical impedance spectroscopy in Na-ion batteries.

[1] Eshraghi, N., Caes, S., Mahmoud, A., Cloots, R., Vertruyen, B., & Boschini, F. (2017). Sodium vanadium (III) fluorophosphate/carbon nanotubes composite (NVPF/CNT) prepared by spray-drying: good electrochemical performance thanks to well-dispersed CNT network within NVPF particles. Electrochimica Acta, 228, 319-324.

[2]Vertruyen, B., Eshraghi, N., Piffet, C., Bodart, J., Mahmoud, A., & Boschini, F. (2018). Spray-Drying of Electrode Materials for Lithium-and Sodium-Ion Batteries. Materials, 11(7), 1076.
Studies on Full Na-Ion Batteries with a Hard Carbon Anode and Oxide Cathode Materials
Authors: Mikhailova Daria , Maletti Sebastian , Leones Rita , Pampel Jonas , Dörfler Susanne , Giebeler Lars
Published: February 2020

The limited abundance of lithium on the Earth forces the search of alternative battery systems for mobile and stationary applications. Sodium-ion batteries could be a reasonable replacement for lithium-ion ones if a compromise between electrochemical performance and cost can be found.

Since the ionic radius of Na+ is larger than of Li+, the choice for electrode materials is more restricted compared to Li-ion batteries, despite the similar chemistry of Na- and Li-compounds in many cases. The reason for that is a lower stability of crystalline phases with Na in fully charged or discharged states because of a larger volume change upon sodiation/desodiation.

Anode materials like metallic alloys on the basis of Sn, Sb or Ge represent the most crucial point in Na-ion batteries because of a huge volume difference between sodiated and desodiated states, resulting in fast capacity fading due to reducing the particle size and contact loss. Hence, nowadays solely hard carbons (HC) can exhibit electrochemical performance suitable for a potential application. The structure of hard carbon consists of amorphous areas (sp
3-hybridization of carbon) embedding and partially crosslinking layered graphitic segments of low dimensional graphene layers (sp
2-hybridization of carbon). Electrochemical insertion of sodium into hard carbon involves two steps: a slope potential region resulting from very stable intercalation of Na-ions between graphitic layers, and a plateau in potentials from adsorption of ions in micropores. Upon desodiation, a large irreversible capacity up to 70 % of the total first discharging capacity is usually observed, which includes the solid-electrolyte interface (SEI) formation, and Na-ions being stably trapped between graphitic layers [1].

In our present work, we studied electrochemical performance of full Na-ion batteries with olivine-like NaFePO4 or layered-type NaNi0.5Ti0.5O2 cathodes, and HC anode materials. In order to overcome the problem with irreversible capacity loss, hard carbon materials were partially or fully sodiated (discharged) prior to electrochemical tests. A NaPF6-containing electrolyte modified with 1-butyl-1-methylpyrrolidinium hexafluorophosphate was used. The observed specific capacities of about 150 mAh g-1 for NaFePO4/HC batteries after 20 cycles are comparable with half NaFePO4/Na cells [2], while NaNi0.5Ti0.5O2/HC batteries show about 75 mAh g-1 (Fig. 1). The reason for a lower capacity retention of NaNi0.5Ti0.5O2 upon cycling is discussed.

Figure 1. Specific capacity of full Na-ion batteries with NaFePO4 (NFPO) and NaNi0.5Ti0.5O2 (NNTO) cathodes and hard carbon (HC) anodes, normalized on the cathode weight, at C/10 rate meaning 1Na intercalated during 10 h.

References

[1] E. Irisarri et al., J. Electrochem. Soc., 162 (2015) A2476-A2482.

[2] G. Ali et al., ACS Appl. Mater. Interfaces, 8 (2016) 15422−15429.

Figure 1
Carbon Hybrids As Versatile Electrocatalysts for Energy Related Reactions
Authors: Fernandes Diana Mesquita , Freire Cristina
Published: February 2020

Since their discovery, carbon nanomaterials (CMs) have been attracting considerable experimental and theoretical interest because of their exceptional structures and properties. Due to their unique structural diversity and the ease of tuning their chemical, electronic and crystalline properties, CMs are attractive for a wide range of electrochemical applications, such as electrocatalysis, fuel cells, batteries and supercapacitors. Also, their properties, such as fast electron transportation, excellent mechanical strength and high surface area, suggest their ability to detect analytes and to promote a fast electron transfer between the electrode and the analyte, which make them promising ECs. CMs have also been presented as effective electrocatalysts that fulfill the requirements for several electrochemical reactions of massive importance in energy conversion systems. Additionally, the possibility of chemical modification and/or functionalization broadens their utility and gives rise to favourable electrocatalytic properties with regard to several electrochemical processes.

Platinum nanoparticles supported on carbon materials (Pt/C) are the most effective known ORR/HER catalysts, leading to low ORR/HER overpotential, large current densities, and selectivity toward a direct 4-electron pathway in the case of ORR. Nevertheless, the required high Pt loading associated with its high cost, scarcity, declining activity and possible Pt-deactivation by methanol crossover for ORR, have limited the large-scale application of Pt-based ECs. Therefore, research efforts have been devoted to developing alternative ECs, with a competitive activity with the Pt/C but more stable and cost-effective. In this context, we have developed several ECs (POM@CMs, metal oxides@CMs and biomass-derived CMs) with good electrocatalytic activity towards ORR and/or HER.

Figure 1. ORR by Co4(PW9)2@Carbon material in alkaline medium

Figure 1
(Invited) Magnesium Organic Batteries
Authors: Bitenc Jan , Pirnat Klemen , Randon-Vitanova Anna , Dominko Robert
Published: February 2020

Magnesium insertion cathodes are predominantly based on chalcogenide materials and possess low energy density due to high molecular weight and low operational voltage. Redox active organic material can be considered as an alternative material, which due to open structure caused by relatively weak intermolecular forces possess much higher gravimetrical energy density. Although, their drawback can be low volumetric energy density since polymers have low density, latter can be compensated with high volumetric density of Mg metal. Redox active organic molecules were considered as a cathode for rechargeable Mg batteries more than decades ago, however their practical application in two electrode cell has been demonstrated with discovery of non-nucleophilic electrolytes which enable reversible stripping and deposition of metallic magnesium. Several different redox active organic materials show potential application, but the most promising direction is use of conjugated carbonyls since predicted theoretical energy density can exceed 700 Wh/kg and batteries show working potential of 2V. Reduction of conjugated carbonyl compounds occurs through the reversible reduction of carbonyl bond as it has been demonstrated by ATR-IR operando measurements.

In this presentation, an overview of recent achievements on the field of magnesium organic batteries will be discussed with a focus on remaining problems that has to be solved in the future.

Acknowledgement: This work is supported HONDA R&D Europe and by the Slovenian Research Agency (research core funding No. P2-0393 and research project J2-8167).

References:

1) J. Bitenc, K. Pirnat, T. Bančič, M. Gaberšček, B. Genorio, A. Randon-Vitanova and R. Dominko, Anthraquinone-Based Polymer as Cathode in Rechargeable Magnesium Batteries, ChemSusChem, 2015, 8, 4128–4132.

2) A. Vizintin, J. Bitenc, A. Kopač Lautar, K. Pirnat, J. Grdadolnik, J. Stare, A. Radon-Vitanova and R. Dominko, Probing electrochemical reactions in organic cathode materials via in operando infrared spectroscopy, Nat. Commun., 2018, 9, 661.

3) J. Bitenc, K. Pirnat, G. Mali, B. Novosel, A. Randon Vitanova and R. Dominko, Poly(hydroquinoyl-benzoquinonyl sulfide) as an active material in Mg and Li organic batteries, Electrochem. commun., 2016, 69, 1–5.

4) T. Bančič, J. Bitenc, K. Pirnat, A. Kopač Lautar, J. Grdadolnik, A. Randon Vitanova and R. Dominko, Electrochemical performance and redox mechanism of naphthalene-hydrazine diimide polymer as a cathode in magnesium battery, J. Power Sources, 2018, 395, 25–30.

5) K. Pirnat, J. Bitenc, A. Vizintin, A. Krajnc and E. Tchernychova, Indirect Synthesis Route toward Cross-Coupled Polymers for High Voltage Organic Positive Electrodes, Chem. Mater., 2018, 30, 5726–5732.
Electrodeposition of Lithium in LiPF6-Based Electrolyte with Trace-Amount of Water
Authors: Yoshii Kazuki , Taguchi Noboru , Kiuchi Hisao , Sakaebe Hikari , Matsubara Eiichiro
Published: February 2020

Lithium metal has been considered as an attractive candidate of the anode material for the next-generation secondary batteries because of its high theoretical capacity and low redox potential. Among a lot of strategies in order to suppress the inhomogeneous or dendritic growth of lithium during deposition have been proposed so far, some reports suggested that the trace-amount of water leads to smooth the morphology of deposited lithium metal. (1, 2) However, the relationship between the morphology of deposited lithium metal and the content of the electrolyte which changes with the time after addition of the water is not clear. In the present study, we investigated the electrodeposition of lithium in LiPF6-based electrolyte with trace-amount of water. Especially, we focused on the change of the morphology and surface state of the deposited lithium metal with the content of the electrolyte.

100 ppm of water was added into 1.0 mol dm–3 LiPF6 in propylene carbonate (PC) in the Ar-filled glove box and temporal change of its water content was checked by Karl-Fischer titration method. The water content was gradually decreased with time due to the reaction of LiPF6 and water. (3) When the electrodeposition of lithium was conducted on the copper electrode in the electrolyte, the morphology of the deposited lithium changed from inhomogeneous to granular and smooth as time passes after addition of water. This result proposed that the decomposed product in the electrolyte was strongly affected to the morphology of the deposit. (4) We also checked the surface state of the deposits by auger electron spectroscopy, X-ray and hard X-ray photoelectron spectroscopy, suggesting that the component of the film greatly influences the morphology of the deposit.

Acknowledgement

This work was supported by the New Energy and Industrial Technology Development Organization (NEDO) under the “Research and Development Initiative for Scientific Innovation of New Generation Batteries 2 (RISING2)”

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