bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synergistic Suppression of Polysulfide Diffusion By Functional 2D Carbon Coating for Advanced Lithium-Sulfur Batteries
Authors: Jeong Yo Chan , Yang Seung Jae , Kim Jae Ho , Park Jisoo , Kim Yern Seung , Park Chong Rae 
Published: February 2020

Lithium-sulfur batteries have been significantly studied owing to a high theoretical specific capacity of 1672 mAh g-1. However, the fast capacity fading issue which mainly stems from both polysulfide dissolution into the bulk electrolyte followed by notorious ‘shuttle reaction’ and insulating nature of sulfur are hindering commercialization of lithium-sulfur batteries. Different types of porous materials were investigated to encapsulate the soluble polysulfide species into the pore by physically and/or chemically adsorption, thus the polysulfide species are able to stay in the cathode side. In addition, electrolyte additives such as lithium nitrate and separator coating with various materials were also attempted. Among them, separator coating strategies seemed to be very effective in inhibiting polysulfide diffusion when the effect is evaluated on the basis of the areal unit scale. Furthermore it can be easily scaled up. For example, roll-to-roll process can be utilized in fabricating polysulfide-trapping material-coated separators.
In the aspect of separator oriented strategy, diverse carbon materials such as carbon black [1], carbon nanotubes [2], reduced graphene oxides [3], and microporous carbons [4] were investigated as a polysulfide trapping layer. These attempts were based on the attractive interaction to anchor the polysulfide species in the cathode side. We realized that repulsive force might be also effective in restricting polysulfide species in the cathode side during the electrochemical reactions as illustrated in Figure 1.
Here, we report a facile and effective way to suppress the polysulfide diffusion by introducing a repulsion interaction rather than an attractive interaction on the cathode side of separator. Fluorine functionalized graphene layers were examined as a potential candidate for repulsing polysulfide species from the separator. In addition to the chemically repulsive interaction, 2D shapes of fluorinated graphene layers enhance the effect of polysulfide blocking layers by increasing the diffusion length through the separator. The synergistic effect of chemical and physical nature of the functionalized carbon material led to the improved electrochemical performance. To understand the improved performance, RAMAN, XPS, SEM, AFM and EIS characterizations were conducted.
[1] Adv. Funct. Mater. 2014, 24, 5299
[2] J. Phys. Chem. Lett. 2014, 5, 1978
[3] J. Power Sources 2013, 242, 65
[4] Adv. Mater. 2014, 26, 7352

Figure 1
Understanding Divalent Cation Intercalation into a Spinel-Type Mn2O4 Host Framework
Authors: Nolis Gene M , Adil Abdullah , Yoo Hyun Deog , Phillips Patrick J , Bayliss Ryan D , Klie Robert F , Cabana Jordi 
Published: February 2020

Li-ion batteries dominate the mobile device market due their high energy density; and their application is being extended to the automotive and grid storage industries. However, charge storage limitations limit the applicability of classic Li-ion technologies into these new markets, thus triggering interest in new energy storage concepts. Multivalent ion intercalation is an attractive alternative because, while conceptually similar to Li-ion, they store more charge per intercalated species and observe less dramatic structural rearrangement in the host. Recently, reversible electrochemical Mg intercalation into spinel-type Mn2O4 has been reported, where Mg2+ ions occupy vacant tetrahedral sites [1]. First principles calculations by Lui et al. argue that other multivalent ions (i.e. Ca2+, Zn2+, Al3+, Y3+) may be intercalated into spinel host framework to yield high voltage cathode materials for multivalent batteries [2].
In this work, cubic phase Mn2O4 was prepared electrochemically by delithiating commercially available spinel-type LiMn2O4 in a non-aqueous environment. Following, Mn2O4electrodes were reduced in concentrated aqueous solutions of Ca-, Mg- and Zn nitrate to -0.4 V/SCE. As-prepared electrodes were characterized using powder x-ray diffraction. As shown in the figure, the cubic structure is preserved upon delithiation and significant structural changes occurred upon reduction; indicating the formation of a tetragonal spinel (likely tetrahedral site occupation) in addition to the parent cubic phase. X-ray absorption spectroscopy and atomic resolution microscopic methods will also be used to help understand the structural changes as these divalent cations are intercalated into a spinel host framework.
References:

Kim, C., et al., Adv. Mater. 2015, 27, 3377

Miao, L., et al.,
Energy Environ. Sci. 2015, 8, 964

Figure 1
Degradation Mechanisms of Magnesium Metal Anodes in a (CF3SO2)2N- (TFSI)-Based Mg-Ion Electrolyte
Authors: Yoo Hyun Deog , Han Sang-Don , Nolis Gene M , Bayliss Ryan D , Burrell Anthony K. , Cabana Jordi 
Published: February 2020

Efficiently using anodes based on the deposition of light metals would be a breakthrough that would produce leaps in energy density of rechargeable batteries. Magnesium is one of such metal electrodes that are not susceptible to dendrite formation. This unique property stems from (1) the thermodynamic stability in Grignard-based electrolytes and (2) the inherent preference to form three-dimensional deposits. However, the use of Grignard-based electrolytes results in severe chemical reactions between the nucleophilic electrolytes and electrophilic cathodes such as oxide materials. Accordingly, a lot of effort has been paid to find non-nucleophilic electrolyte solutions that deposit and dissolve Mg metal reversibly.
Among non-nucleophilic anions, bis(trifluoromethylsulfonyl)imide (CF3SO2)2N–, TFSI) anion has shown exceptional stability on Mg metal anode. And the ethereal solution of the magnesium salt (MgTFSI2) has shown quite reversible Mg metal deposition and dissolution with coulombic efficiency of ~90% and reasonable voltage stability window of about 3 V. The most important difference from the Grignard-based electrolytes is that the TFSI-based electrolyte solution is non-nucleophilic and possibly compatible with oxide cathodes, which can increase the voltage and energy density of Mg rechargeable batteries.
Herein, we report the mechanisms of degradation in the Mg metal anode and electrolyte after hundreds of cycles at high current density of 2 mA/cm2. Although the Mg metal anode operated without a significant problem at current densities lower than 0.1 mA/cm2, degradation was evident after long-term cycling at high current density. Overall, the Mg metal became mechanically brittle, with microscopy showing extremely porous structures (Fig. 1a). In addition, large hemispherical deposits up to several hundred micrometers were scattered or aggregated at the Mg surface (Fig. 1b). In turn, the color of the electrolyte turned to dark brown upon cycling, indicating a change in the chemical structure of the solvent. The macroscopic consequence was the short circuiting of the cells after several cycles at a high current density. These results suggest that the lemma of dendrite-free metal deposition is possible when the system meets several conditions such as absolute chemical stability of the metal in the electrolyte, adequate level of current density and charge density, and other engineering factors such as organic or inorganic additives that complexes with the metal ion and lead to more uniform metal deposition. Those understandings will serve as step stones to get to non-nucleophilic electrolytes, in which metal anodes operate without dendrite formation.

Figure 1
Replacement of Carbon with TiO2 Electrodes By Tuning Electronic Conductivity and Porosity for Stable Li-O2 Batteries
Authors: Nam Seunghoon , Kang Joonhyeon , Kim Chunjoong , Hyun Seungmin , Park Byungwoo 
Published: February 2020

Although carbon is ubiquitously used as the basis of the cathode, its use in Li-O2 battery is still problematic in that carbon decomposes on charge above 3 V vs. Li/Li+, and leads to electrolyte decomposition on both discharge and charge, rendering it unsuitable for aprotic Li-O2 cells. Meanwhile, a pioneering work from Bruce et al., [1] suggested that carbon be replaced with TiC which promoted reversible formation of Li2O2. By the way, it is open to debate that the stability of TiC originates from the TiO2 at the surface, and TiO2 itself can be an air cathode, provided that the electrical conductivity is guaranteed. For this reason, porous TiO2 [2] with some deliberate oxygen vacancies [3] was synthesized so that the electrode exhibited large surface area with moderate electronic and ionic conductivity. The porous black electrode showed a stable cycle-life performance, and the polarization during the decomposition of Li2O2 is greatly improved. Therefore, it is expected that the electronic conductivity- and porosity-tuned TiO2 can be a suitable substrate for Li-O2 chemistry. Finally, the origin of high stability of this porous black TiO2 as an air cathode is also investigated.
[1] M. M. Ottakam Thotiyl, S. A. Freunberger, Z. Peng, Y. Chen, Z. Liu, and P.G.Bruce, Nat. Mater. 12, 1050 (2013).
[2] J.-H. Shin, J.-H. Kang, W.-M. Jin, J. H. Park, Y.-S. Cho, and J. H. Moon, Langmuir, 27, 85 (2011).
[3] X. Chen, L. Liu, and F. Huang, Chem. Soc. Rev. 44, 1861 (2015).
Highly Stable Carbon-Free Ag/Co3O4 Cathodes for Li-Air Batteries with Aqueous Alkaline Electrolyte: Electrochemical and Structural Investigations
Authors: Wittmaier Dennis , Wagner Norbert , Friedrich K. Andreas 
Published: February 2020

The operation of a secondary lithium-air battery requires to run the battery in oxygen reduction reaction (ORR) as well as in oxygen evolution reaction (OER). OER represents the charge reaction and requires a sufficient catalyst for oxygen evolution. Currently carbon materials are widely used in cathodes of aqueous alkaline lithium-air batteries due to their high electronic conductivity, stability, relatively low costs and catalytic activity towards oxygen reduction reaction (ORR) [1, 2]. However, carbon-based cathode materials are non-stable in the potential range of OER as they start to corrode at potentials higher than open circuit voltage (OCV) [3, 4]. Corrosion leads to high degradation corresponding to successive capacity loss and ultimately destruction of the cathode. To improve long-term stability and reduce side reactions such as H2 and CO2 evolution carbon-free bifunctional cathodes for aqueous alkaline lithium-air batteries are of need [5, 6]. In this poster we present cathodes with a combination of Ag and Co3O4. Those were prepared with a dry-processed and solvent-free preparation method [7, 8]. Electrocatalytic activity regarding both ORR and OER was investigated by cyclic voltammetry (CV) for up to 300 cycles in half-cells. In addition structural and surface characteristics were investigated by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). These combined measurements give new insights in the materials’ oxidation states and the stability of Ag oxides in Ag/Co3O4 cathodes throughout a complete battery cycle [9]. Cathodes with the combination of Ag and Co3O4 show high activity for both reactions ORR and OER and a significant improvement in performance compared to both pure Ag and pure Co3O4 cathodes. Long-term tests show superior stability of the bimetal cathodes [6].
[1] H. Ohkuma, I. Uechi, M. Matsui, Y. Takeda, O. Yamamoto, N. Imanishi, J. Power Sources 245 (2014) 947.
[2] H. Arai, S. Müller, O. Haas, J. Electrochem. Soc. 147 (2000) 3584.
[3] P. N. Ross, M. Sattler, J. Electrochem. Soc. 135 (1988) 1464.
[4] P. N. Ross, H. Sokol, J. Electrochem. Soc. 131 (1984) 1742.
[5] D. Wittmaier, T. Danner, N. Wagner, K. A. Friedrich, J. App. Electrochem. 43 (2013) 73.
[6] D. Wittmaier, N. Wagner, K. A. Friedrich, H.A. Amin, H. Baltruschat, J. Power Sources 265 (2014) 299.
[7] D. Wittmaier, N. Wagner, H.A. Amin, H. Baltruschat, Patent App. PCT/EP2015/053586.
[8] D. Wittmaier, N. Wagner, H.A. Amin, H. Baltruschat, Patent App. DE 102014102304 A1.
[9] D. Wittmaier, Natalia A. Canas, I. Biswas, K. A. Friedrich, Adv. Energy Mater. 2015, doi: 10.1002/aenm.201500763.
Dynamic Modeling of the Reaction Mechanisms in a Li/O2 Battery Cell
Authors: Grübl Daniel , Mayur Manik , Bessler Wolfgang G. 
Published: February 2020

Extensive research efforts on metal-air batteries are being carried out due to their high theoretical energy density. Specifically, the lithium-oxygen (Li/O2) based batteries have drawn attention of the researchers as a promising alternative to Li-ion batteries for long range electric vehicles. However, this system suffers from high overpotentials during charge, indicating asymmetrical charge/discharge reaction mechanisms. High charge overpotentials lower the energy efficiency and can increase potential-driven side reactions (e.g., electrolyte decomposition). Furthermore, the discharge product forms as a new solid phase in the cathode by a nucleation and growth process, which is in general different from lithium-ion battery technologies. Thus, a detailed understanding of the reaction mechanism is crucial for enhancing battery performance and durability.
Our approach towards understanding the charge/discharge reaction mechanism is by development and exploitation of a continuum model of a lithium-oxygen cell [1]. The one-dimensional computational domain consists of a gas reservoir filled with oxygen, a porous carbon cathode flooded with an organic electrolyte, a porous separator, and a lithium metal anode. We present a multi-step reaction mechanism of the electrochemistry in the cathode, consisting of O2 dissolution, O2 reduction, LiO2 precipitation, LiO2 disproportionation during discharge (Figure 1, left), as well as Li2O2 electrostripping during charge. In particular, the mechanism is asymmetric with respect to discharge and charge. The model is parameterized by experimental Swagelok cells [2] and galvanostatic cycling simulations are compared to experimental data. Furthermore, possible reasons for the high charge overpotential are analyzed, options to reduce the charge overpotential (e.g. redox mediator) are discussed, and a charge reaction mechanism including a surface-mediated Li2O2 dissolution is proposed (Figure 1, right).
[1] D. Grübl, B. J. Bergner, J. Janek and W. G. Bessler, “Dynamic Modeling of the Reaction Mechanism in a Li/O2Cell: Influence of a Redox Mediator,” ECS Transactions 69(19), 11-21 (2015).
[2] B. J. Bergner, A. Schürmann, K. Peppler, A. Garsuch, and J. Janek, “TEMPO: A Mobile Catalyst for Rechargeable Li-O2 Batteries,” J. Am. Chem. Soc. 136, 15054–15064 (2014).

Figure 1
Solvation Structure of Zinc-Based Electrolytes from X-Ray Absorption Spectroscopy
Authors: Kim Soojeong , Han Sang-Don , Balasubramanian Mahalingam , Fister Timothy T 
Published: February 2020

Multivalent (e.g., Mg2+, Ca2+ and Zn2+) metal cells using a nonaqeous electrolyte are potential candidates for post-lithium-ion batteries. However, the development of multivalent electrolytes is challenging due to its poor compatibility with both the metal anode and higher voltage cathode chemistries, leading to poor coulombic efficiency, formation of passivation layer on the metal anode, etc. Defining the connection between the electrochemical properties of a multivalent electrolyte system with its molecular scale structure is a crucial step for developing these new chemistries. Here we use X-ray absorption fine structure (XAFS) spectroscopy to determine the solvation structure of zinc-based electrolytes with varying solvent species and concentrations. To explore the role of ion-pairing, the results are compared to first principle simulations of the electrolyte and electrochemical data.
Novel Cathode Materials for Rechargeable Magnesium Ion Batteries
Authors: Wang Lu , Vullum-Bruer Fride 
Published: February 2020

Over the past few years, considerable effort has been devoted to the development of new energy storage devices with high power and energy density to substitute Lithium-based batteries, because the predicted high demand associated with many large-scale applications has generated serious concerns regarding the safety and sustainability of metallic Li.[1] In particular, Mg ion battery (MIB) has been regarded as the most promising candidate because of its ‘green’ character, high natural abundance in the Earth’s crust (13.9% as compared to 7*10-4 % for Li), and chemical stability.[2] In comparison with Li, Mg is inherently much safer due to its stability in air and lack of dendritic formation during electrochemical cycling.[3] Also, compared to Li, Mg has a theoretical volumetric capacity of 3833 mAh cm-3, nearly twice that of Li (2061 mAh cm-3), indicating that MIB has a good potential for reaching a high volumetric energy density.[4,5] However, it is still in high demand to find the electrode materials that unites with metallic Mg and fulfil requirements such as high specific capacity, power density, rate performance and good cyclability.[2,6,7]
Here, we report several novel cathode materials, Mn3O4 nanoparticles, Mn3O4/graphene nanocomposite, Fe3O4 nanoparticles and microwave exfoliated graphite oxide (MEGO). The studies of Mg-battery performances were carried out in a standard coin cell which the synthesized materials as cathode, magnesium ribbon as anode, glass fibre as separator and (PhMgCl)2-AlCl3/THF as electrolyte. The electrochemical performance was evaluated by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and galvanostatic charge-discharge techniques.

References:

[1] L. G. Lu, X. B. Han, J. Q. Li, J. F. Hua and M. G. Ouyang, J. Power Sources, 2013, 226, 272.

[2] E. Levi, Y .Gofer and D. Aurbach, Chem. Mater., 2010, 22, 860.

[3] J. O. Besenhard and M. Winter, ChemPhysChem, 2002, 3, 155.

[4] M. Matsui, J. Power Sources, 2011, 196, 7048.

[5] C. Ling, D. Banerjee and M. Matsui, Electrochim. Acta, 2012, 76, 270.

[6] H. D. Yoo, I. Shterenberg, Y. Gofer, G. Gershinsky, N. Pour and D. Aurbach, Energy Environ. Sci., 2013, 6, 2265.

[7] I. Shterenberg, M. Salama, Y. Gofer, E. Levi and D. Aurbach, MRS Bull., 2014, 39, 453.
Impact of the Water Content in Glyme-Based Electrolyte to Rechargeable Magnesium-Organic Battery
Authors: Senoh Hiroshi , Shimizu Ryo , Uchida Makoto , Sano Hikaru , Sakaebe Hikari , Yao Masaru , Takeichi Nobuhiko , Kiyobayashi Tetsu 
Published: February 2020

Rechargeable magnesium battery can be a candidate of the next-generation batteries because magnesium has a higher volumetric capacity, is more abundant in terms of the resources, and is less reactive in air than lithium. We previously found that a redox-active organic compound, 2,5-di­methoxy-1,4-benzo­quinone (DMBQ), has the potential to serve as the positive electrode material for the Mg system1. Recently, we have investigated two kinds of electrolytes, sulfone-based and glyme-based electrolytes2-3, for the rechargeable magnesium-organic batteries. In the case of monoglyme-based electrolyte, the discharge voltage of the Mg-DMBQ cell significantly increases, not decreases, after a few cycles, for which, we found, a decrease in the overpotential for the Mg dissolution upon cycling is responsible3. However, what caused the decrease in the overpotential on the Mg negative electrode is not clear. In the present study, we report the impact of the water content in the monoglyme-based electrolyte to the rechargeable Mg-organic battery.
Magnesium bis(trifluoromethane sulfonyl)amide (Mg(TFSA)2) and monoglyme were purchased from Kishida Chemical and used without further purification. The electrolyte was prepared by dissolving 0.5 mol L-1 of Mg(TFSA)2 in monoglyme. The water content of the as-prepared electrolyte was 40 ppm. Two other electrolyte solutions were prepared in which pure water was deliberately added to 100 and 1000 ppm. The electrochemical cells were set up and tested based on our previous study3.
The specific conductivities of water-added 0.5 mol L-1 Mg(TFSA)2/monoglyme did not shift from that of the as-prepared. The discharge and charge curves of the cells in the electrolytes at various water contents showed that in all three cases the first discharge curve has two potential plateaus below 0.7 V. In the case of the water-added electrolytes, the discharge voltage during the second cycle significantly increased, while in the as-prepared electrolyte the discharge voltage remained below 0.7 V even after several cycles. The drastic dissolution of Mg from the surface of the negative electrode was observed by SEM only in the water-added electrolytes. A certain amount of water plays an important role in preparing the surface of the electrode to let Mg dissolve in the electrolyte.
1. H. Sano et al., Chem. Lett., 41, 1594 (2012).
2. H. Senoh et al., J. Electrochem. Soc., 161, A1 (2014).
3. H. Senoh et al., ECS Transactions, in press.
Metal Hybrid Supercapacitors Based on a Rocking-Chair Mechanism
Authors: Yoo Hyun Deog , Han Sang-Don , Bayliss Ryan D , Gewirth Andrew A , Burrell Anthony K. , Cabana Jordi 
Published: February 2020

Supercapacitors can provide high rate capability and long-term cycleability, thanks to their simple mechanism based on the adsorption and desorption of ions on the surface of electrodes. It is possible to charge or discharge supercapacitor cells in a minute for 10,000 cycles without notable degradation. Based on the high power characteristics, supercapacitors can augment the batteries or fuel cells for electric vehicles or heavy equipment. So far, most of supercapacitors have symmetric configuration with activated carbon electrodes as the positive and negative electrodes (Fig. 1a). And they follow a Daniell-type mechanism, where the electrolyte is depleted of and replenished with ions upon charging and discharging, respectively (Fig. 1b). In this mechanism, electrolyte serves as an ionic reservoir, from which cations and anions are separated to negative and positive electrodes, respectively. As a result, sufficient volume of electrolyte is indispensable for the operation of supercapacitors. This leads to a limitation in energy density and an increase in the internal resistance as the starvation of the concentration of salts in the electrolyte decreases during operation.
Herein, we introduce a hybrid supercapacitor that follows a ‘rocking-chair’ mechanism for the first time. This hybrid supercapacitor is composed of metal anodes and activated carbon as the negative and positive electrodes, respectively (Fig. 1c). Metal (M, e.g. Mg or Zn) ions are replenished at the negative electrode while they are adsorbed into the pores of the positive electrode upon the discharging of the cell (Fig. 1d). On the other hand, metal ions are released from the positive electrode while metal is deposited on the negative electrode upon the charging of the cell. As a result, only a minimum amount of electrolyte is needed to operate the cell since the electrolyte serves exclusively as a medium of metal ion transport. The use of metal electrodes can increase the energy density of the cell significantly by virtue of the large volumetric capacity. Therefore, ‘rocking-chair’ metal hybrid supercapacitors can double the energy density of a supercapacitor, and the internal resistance can be kept constant during the operation of the cell. The electrochemical results show highly reversible reactions at the positive and negative electrodes thanks to newly-developed Mg-ion and Zn-ion electrolytes. Charge-discharge cycles at rates up to 5 mA/cm2 were possible, whereas cycling tests showed 64% retention of the capacity after 400 cycles. Detailed studies of the mechanisms of degradation and evidences of the ‘rocking-chair’-type mechanism will be presented.

Figure 1