bluuebunny/crossref_metadata_2025_split huggingface dataset:
Sulfur/Nitrogen Doped Carbon Nanotube Binder-Free Electrode for High Performance Li/S Batteries
Authors: Zhang Yongguang , Zhao Yan , Kurmanbayeva Indira , Bakenov Zhumabay 
Published: February 2020

Introduction

Due to low cost, environmental friendliness and high theoretical capacity of sulfur, rechargeable Li/S batteries are very promising power sources for various applications. However, the insulating nature of sulfur and solubility of polysulfides as discharge products restrict its practical application [1]. Among the approaches to overcome these problems, carbon nanotubes are widely used to obtain a flexible conductive matrix for S cathode [2]. Nitrogen doping of carbon nanotubes (N-CNTs) significantly improves its electronic conductivity because the nitrogen atoms provide additional free electrons for the conduction band [3].
In this work, we report for the first time on a high performance S/N-CNT cathode for Li/S battery. Exclusion of heat-treatment in the composite preparation avoided the sulfur loss; the composite contained 61 wt% of sulfur. Thanks to the self-weaving behavior of N-CNT, binders and current collectors are rendered unnecessary, thereby simplifying the electrode manufacturing process and increasing the sulfur content in the total electrode weight. The N-CNT core provides a highly conductive and mechanically flexible framework, enhancing the electronic conductivity and consequently the rate capability of the material. This resulting composite cathode sustains 833 mAh g-1 reversible specific discharge capacity after 100 cycles at 0.1 C, and 676 mAh g-1at 1 C with a coulombic efficiensy about 100%.

Experimental

The S/N-CNT composite preparation is schematically shown in Fig. 1. Nitrogen doped carbon nanotubes were dispersed in deionized water by sonication at room temperature. The obtained N-CNT suspension was mixed ultrasonically with the aqueous suspension of nano-sulfur. The resulting system was vacuum-filtered and thoroughly washed with deionized water and ethanol. The binder-free S/N-CNT composite was obtained by further drying in a vacuum oven at 60 °C overnight to remove the solvent.

Acknowledgments

This research was supported by a Research Grant from the Ministry of Education and Science of Kazakhstan and by a Subproject supported under the Technology Commercialization Project by the World Bank and the Government of Kazakhstan.

References

1. X. Ji, K.T. Lee, L.F. Nazar, Nat. Mater., 2009, 8, 500.
2. Y.S. Su, A. Manthiram, Chem. Commun., 2012, 48, 8817.
3. X.G.Sun, X. Wang, R.T. Mayes, S. Dai, ChemSusChem
,2012, 5, 2079.
Cycling Performances of Lithium-Air Batteries Assembled with Ionic Liquid-Based Electrolytes
Authors: Han Sang-Min , Kim Jae-Hong , Kim Dong-Won 
Published: February 2020

Li-air batteries have higher theoretical energy density than conventional rechargeable lithium batteries.[1,2] However, recent studies of Li-air batteries with conventional organic solvent-based electrolytes demonstrate that most of these solvents may not have long-term chemical stability in the presence of the superoxide radical.[3] Thus, improving the stability of electrolyte toward reduced oxygen species is the main key for developing the non-aqueous Li-air batteries with good capacity retention. In this work, we tried to investigate ionic liquid-based electrolytes for the Li-air batteries. They showed an oxidative stability higher than 5.3 V vs. Li/Li+, high ionic conductivity and good stability towards the superoxide radical. As a result, the Li-air batteries employing these electrolytes exhibited good cycling stability exceeding 100 cycles at a current density of 0.1 mA/cm². Good reversibility for oxygen reduction and evolution reaction was investigated by cycling voltammetry and ex-situ powder X-ray diffraction analysis.

References

[1] J. P. Zheng, R. Y. Liang, M. Hendricksonc, E. J. Plichta, J. Electrochem. Soc., 155(6), A432-A437(2008)
[2] Laoire, C. Ó., Mukerjee, S., Abraham, K. M., Plichta, E. J., Hendrickson, M. A. J. Phys. Chem. C, 114, 9178-9186(2010)
[3] F. Mizuno, S. Nakanishi, Y. Kotani, S. Yokoishi,. H.Iba, Electrochem, 78, 403- 405(2010)
Advanced Lithium-Sulfur Batteries with Carbon Nanotubes As Conductive Networks
Authors: Cheng Xin-Bing , Huang Jia-Qi , Peng Hong-Jie , Wei Fei , Zhang Qiang 
Published: February 2020

Lithium-sulfur batteries, with the high theoretical capacity (1675 mAh g-1) and energy density (2600 Wh kg-1) as well as the easy access and non-toxic of raw materials, demonstrate a promising prospect among the high energy storage systems for electric vehicles (EVs) and portable electronic devices. However, there are also several issues to be handled before commercial application.
Firstly, different from traditional lithium-ion batteries, intermediate polysulfides generate and dissolve in the organic electrolyte during the discharge process of lithium-sulfur batteries. The dissolved polysulfides, shuttle between cathode and anode sides, lowering the utilization of sulfur and also react with the lithium anode without any electron transfer. However, the dissolution of polysulfide in a lithium-sulfur battery is highly dependent on the sulfur/electrolyte loading. Thus an appropriate dosage of electrolyte will build a concentration gradient, which will limit the dissolution of polysfulfides. In our work, A lithium-sulfur cell with a high initial discharge capacity of 1053 mAh g-1 at a high rate of 1 C and an ultralow decay rate of 0.049 %/per cycle during 1000 cycles was obtained by using CNT-sulfur cathode and suppressing polysulfide shuttle to a shuttle factor of 0.02 by matching the sulfur/electrolyte loading. Secondly, sulfur is with low electrical conductivity (5×10-30 S cm-1 at 25 oC) and extra conductive network is highly required. Generally, the addition of conductive materials will neutralize the advantage in high energy density of lithium-sulfur battery. Thus, the more sulfur content in the composite cathode, the larger energy density. Herein, we employed the carbon nanotubes (CNTs) to build the unblocked conductive skeleton and a room-temperature, one-step ball-milling treatment of aligned CNTs and sulfur was applied to obtain high sulfur content of 90 %. The 90 % sulfur loading cathode exhibited a superior density of 1.98 g cm-3 (2.07 g cm-3for sulfur), which will greatly increase the volumetric energy density of lithium-sulfur battery.

Reference:

[1] XB Cheng, et al. J. Power Sources, 2014, DOI: 10.1016/j.jpowsour.2013.12.031
[2] XB Cheng, et al. Nano Energy, 2014, accepted
Solvate Ionic Liquids for Lithium–Sulfur Batteries
Authors: Dokko Kaoru , Tachikawa Naoki , Ueno Kazuhide , Mandai Toshihiko , Watanabe Masayoshi 
Published: February 2020

Introduction

Glyme, which has a chemical structure of CH3–O–(CH2–CH2–O)
n
–CH3, can coordinate Li+ ions forming a 1 : 1 complex cation of [Li(glyme)]+ when n is either 3 or 4. The coordination number of Li+ is typically 4–5, thus, n = 3 or 4 is suitable for the equimolar complexation. Consequently, the equimolar mixture of glyme and certain Li salt with weakly Lewis basic anion can be regarded as a room temperature ionic liquid consisting of [Li(glyme)]+ complex cations and the anions. [1]-[3] Herein, we present the solvate ionic liquids as excellent electrolyte candidates for Li-S batteries; these electrolytes greatly suppress the dissolution of lithium polysulfides. [4] ,[5]

Experiments

Electrolytes were prepared by mixing tetraglyme (G4) with lithium bis(trifluoromethanesulfonyl)amide (Li[TFSA]) in an Ar-filled glove box. Sulfur was mixed with Ketjen black (KB, specific surface area: 1270 m2 g–1), and polyvinyl alcohol (PVA) for cathode preparation. The mass ratio of S/KB/PVA in the composite cathode was 60:30:10.

Results and discussion

Figure 1 shows charge–discharge stability of Li–S cells with [Li(G4)
x

][TFSA] electrolyte measured at low current densities. The initial discharge capacity of each Li–S cell was in the range 800–1000 mAh g–1, which corresponds to 50–60% of the theoretical capacity of elemental S (1672 mAh g–1). The coulombic efficiency of the cell with [Li(G4)4] [TFSA] rapidly decreased with each charge–discharge cycle. The lower coulombic efficiency is attributed to the occurrence of the redox shuttle mechanism of lithium polysulfides (Li2S
m
) within the cell during the charge and discharge processes. In contrast, the cell with [Li(G4)1][TFSA] can be cycled more than 50 times while maintaining a coulombic efficiency above 98%. This high efficiency can be attributed to the low solubility of Li2S
m
in [Li(G4)1][TFSA], indicating that the solid state Li2S
m
remains in the composite cathode and undergoes a reversible redox reaction. [5]

Acknowledgement

This study was supported in part by ALCA of Japan Science and Technology Agency (JST).

References

[1] T. Tamura et al., Chem. Lett. 39 (2010) 753.
[2] K. Yoshida et al. J. Am. Chem. Soc. 133 (2011) 13121.
[3] K. Ueno et al., J. Phys. Chem. B 116 (2012) 11323.
[4] N. Tachikawa et al., Chem. Commun., 47 (2011) 8157.
[5] K. Dokko et al., J. Electrochem. Soc. 160 (2013) A1304.
Investigation of Lithium Solvated Ionic Liquid for High Performance Li-S Batteries
Authors: Seki Shiro , Serizawa Nobuyuki , Takei Katsuhito , Dokko Kaoru , Watanabe Masayoshi 
Published: February 2020

1:1 equimolar complex electrolytes composed of low-molecular-weight ether (glyme) and Li salt have been reported to exhibit high thermal and electrochemical stability due to strong interactions between the oxygen in the ether and the Li cation (Li salt glyme solvate ionic liquids) [1]. Favorable performances were achieved using 3V-class [LiFePO4 | Li metal] and 4V-class [LiNi1/3Mn1/3Co1/3O2 | Li metal] cells [2]. Moreover, Li salt glyme solvate ionic liquids have a weak coordinating ability, which allows for innovative Li-sulfur batteries with a long cycle life (over 400 cycles) by suppressing the dissolution of polysulfide and redox shuttle [3]. More specifically, it is becoming clear that Li salt glyme solvate ionic liquids have important performance benefits besides their safety. In previous research, we used electrochemical quartz crystal microbalance (EQCM) measurements to show that an observed decrease in local viscosity near the electrode-electrolyte interface is attributable to the concentration distribution of Li salt and the transitional liberation of glyme molecules during the deposition of Li metal [4]. Therefore, to improve the electrochemical stability and polysulfide solubility of Li salt glyme solvate ionic liquids, it is necessary to form long-lived robust complexes between oxygen in the ether electrolyte and Li cations. So, we propose Li salt glyme solvate ionic liquids that are non-equimolar and that are prepared by adding Li salts to achieve a higher Li salt concentration than that in the original 1:1 equimolar complex of glyme and Li salt. Moreover, we investigated relationships between sulfur positive electrode (composite material of elemental sulfur and high surface area carbon) and Li-S battery performances. In the presentation, we will report the relationships between Li-S battery performances and electrolyte / electrode materials.
This study was supported by ALCA project, from JST, Japan.
[1] K. Yoshida, M. Nakamura, Y. Kazue, N. Tachikawa, S. Tsuzuki, S. Seki, K. Dokko, M. Watanabe, J. Am. Chem. Soc., 133, 13121 (2001).
[2] S. Seki, N. Serizawa, K. Takei, K. Dokko, M. Watanabe, J. Power Sources, 243, 323 (2013).
[3] K. Dokko, N. Tachikawa, K. Yamauchi, M. Tsuchiya, A. Yamazaki, E. Takashima, J-W. Park, K. Ueno, S. Seki, N. Serizawa, M. Watanabe, J. Electrochem. Soc., 160, A1304 (2013).
[4] N. Serizawa, S. Seki, K. Takei, H. Miyashiro, K. Yoshida, K. Ueno, N. Tachikawa, K. Dokko, Y. Katayama, M. Watanabe, T. Miura, J. Electrochem. Soc., 160, A1529 (2013).
Inverse Opal Carbons As Li-O2 Cathodes with an Ionic Liquid-Based Electrolyte: Effect of Macropore Size on Capacity, Rate Capability and Reversibility
Authors: Olivares-Marín Mara , Palomino Pablo , Enciso Eduardo , Tonti Dino 
Published: February 2020

Inverse opals are beautiful macroporous materials prepared by template synthesis and presenting a well-defined arrangement of pores of tunable monodisperse size. Thus, they are ideal model systems for studying the effect of macropore size in lithium-oxygen electrodes.
In this work, inverse opal carbons were prepared by using poly(styrene-co-methacrylic acid) (PS-MAA) spheres of different size as templates via a resorcinol-formaldehyde sol-gel process. These were used in cathodes for Li-O2 batteries using different cell configurations and an ionic liquid electrolyte (LiTFSI in PYR14TFSI). The high porosity and open channels with low tortuosity allowed remarkable capacities of over 3000 mAh/g at 0.1 mA/cm2.
We could relate the carbon textural properties to the capacity, rate capability and reversibility. We observed better rate capability for discharge with the largest macropores (500 nm diameter), evidencing a mass transport limitation. However, charge profiles denoted a remarkable asymmetry respect to discharge, with low coulomb efficiency. Instead, when macropores were smaller than 100 nm we obtained a remarkable symmetry in time-limited discharge-charge profiles. This proves that confinement of discharge products in small pores effectively prevents the electrode passivation.

Acknowledgement

The research leading to these results has received funding from the European Union’s Seventh Framework Programme under EC-GA No. 265971 ‘LABOHR’, and from the Spanish Government under contract MAT2012-39199-C02-01. M.O. acknowledges CSIC for a JAE-DOC research contract.
Stability Enhancement of Nasicon Solid Electrolytes As Protective Layer for Li-Air Systems
Authors: Ni Chung-Ta , Tsai Shu-Yi , Fung Kuan-Zong 
Published: February 2020

The development of Li-air battery has received great attention recently. However, using metallic lithium directly as as an anode has been challenging due to the high reactivity of Li. Protective coatings with ionic conduction on metallic Li has be proposed to solve this problem.Inorganic Li ion conductors may be suitable for using as the protection layer.
NASCION-type LiTi2(PO4)3 and perovsikte-La0.50Li0.50TiO3 are known to be inorganic solid electrolytes with adequate conductivity in a range of 10-3 S/cm after required modification. However, Li tends to react with La0.56Li0.33TiO3
due to the incorporation of the released electrons with Ti+4 ions. Simultaneously, Li+ ions will migrate into the vacant sites in the cation sublattice. As a result, La0.50Li0.50TiO3 perovsikte becomes a mixed ionic/electronic conductor after reacting with Li. On the other hand, limited reaction was observed on the Li1+xAlxTi2-x(PO4)3
electrolyte when the metallic Li was used as the anode.
In order to improve the stability of Li1+xAlxTi2-x (PO4)3, a concept of composite electrolyte based on NASCION-type LiTi2(PO4)3 and perovsikte-La0.50Li0.50TiO3 is proposed. With proper mixing and distribution of these two electrolytes, a better stabiltiy from the composite electrolyte is expected.
Thus, the objective of this work is (1) to develop a composite electrolyte based on the mixture of Li1+xAlxTi2-x (PO4)3, and La0.50Li0.50TiO3, (2) to analyze the interface reaction between two components of composite cathode, (3) to investigate the electrical conduction/stability of composite as a function of volume fraction, grain size, and thickness, (4) to evaluate the feasibility of using composite electrolyte for Li-Air battery. The stability of composite electrolyte will be determined based on the measurement of the induced electronic conductivity and the open circuit voltage after a Li-air cell is assembled.
Adsorption of Polysulfides from Electrolyte Using Porous Carbons
Authors: Hippauf Felix , Nickel Winfried , Oschatz Martin , Borchardt Lars , Doerfler Susanne , Kaskel Stefan 
Published: February 2020

Due to their high theoretical specific energy density and the low costs of sulfur, Lithium-sulfur (Li-S) batteries are of high interest as the storage of electric energy becomes more and more important. After several year of investigation, they still lack of a high cycling stability, which can be mainly ascribed to the formation of dendrites and particularly, to the so-called polysulfide (PS) shuttle mechanism. Therefore, the understanding of the latter and its possible inhibition is the aim of current research. Adding traces of LiNO3 to the electrolyte or using composite cathodes with additional polysulfide reservoirs seems to prolong the battery life.1,2 Other publications report on carbon host materials with specially designed porosity in order to avoid the polysulfide diffusion. Up to now, the detailed mechanism of the shuttle and the effect of PS reservoirs is not fully understood as previous studies concentrated more on electrochemical characterization of half-cells including other components, such as separator and anode.3

This study is focused on the liquid phase adsorption of stoichiometric and ex-situ synthesized polysulfides from a Li-S battery electrolyte on porous carbons to simulate a simplified Li-S cell environment. Several micro and meso and hierarchically structured porous carbons were investigated - both industrial reference materials and specially designed carbons. The latter are already electrochemically tested as carbon-sulfur cathode composite in Li-S cells. Li2Sx(x=4,6,8) were synthesized by stirring stoichiometric amounts of Lithium and sulfur in DOL/DME (1:1) at 70°C under Argon until the solution reached equilibrium condition. Subsequently, the porous carbons were added and the PS adsorption was monitored by UV/Vis spectroscopy. The influence of different carbon porosities on the adsorption properties of the polysulfides species was investigated.
(1) Ji, X.; Evers, S.; Black, R.; Nazar, L. F. Nat. Commun.
2011, 2, 325.
(2) Aurbach, D.; Pollak, E.; Elazari, R.; Salitra, G.; Kelley, C. S.; Affinito, J. J. Electrochem. Soc.
2009, 156, A694.
(3) Evers, S.; Yim, T.; Nazar, L. F. J. Phys.
Chem. C
2012, 116, 19653–19658.
Charge Transfer and Transport Properties of Lithium Polysfulfide Solutions
Authors: Woodford William , Fan Frank , Baram Nir , Helal Ahmed , Carter W. Craig , Chiang Yet-Ming , McKinley Gareth 
Published: February 2020

Metal-sulfur couples are of interest due to the high energy density and potentially low cost of these chemistries. However, the existence of soluble polysulfide intermediates—which exist in all known polar electrolyte systems—has challenged the cycle life and efficiency of these systems. Recently, interest in catholyte cells based on dissolved polysulfide solutions has renewed, in part due to the possible use of these catholytes as flow electrodes with low cost.1-3To realize the potential advantages of dissolved polysulfide catholytes, highly concentrated solutions are needed to obtain high charge storage capacities, which simultaneously retaining adequate rate capability. To achieve this, the rate limiting mechanisms in polysulfide solutions must be understood as a function of concentration and solution composition.
Here, we present experimental measurements of the exchange current density and ionic conductivity and of lithium polysulfide solutions of varying concentration in non-aqueous solvents. Exchange current densities are measured by three different methods: steady-state voltammetry at a C-fiber microelectrode, electrochemical impedance spectroscopy at a glassy carbon macroelectrode, and galvanostatic polarization measurements at a glassy carbon macroelectrode. Solvents of interest include tetraethylene glycol dimethyl ether (TEGDME), 1,2-dimethoxyethane (DME), 1,3-dioxolane (DOL), and mixtures thereof. Ionic conductivies are measured with and without supporting LiTFSI salt, as shown for several selected solvent systems in Figure 1(A). The measured ionic conductivities are correlated with measured solution viscosities, as shown for the TEDGME system in Figure 1(B). Lithium polysulfide solutions with sulfur concentrations of 1-8 M in these solvents have measured exchange current densities on the order of 0.01 – 1 mA cm-2 and ionic conductivities are on the order of 1 – 10 mS cm-1.
This work represents the first report of systematic measurements of these fundamental charge transfer and transport properties for polysulfide solutions. These results enable rational interpretation of the limiting processes in conventional solid sulfur cells as well as the catholyte systems and provide a quantitative basis for selection of electrolyte solvents.

References

1. Demir-Cakan, R. et al. Li–S batteries: simple approaches for superior performance. Energy & Environmental Science
6,176 (2012).
2. Yang, Y., Zheng, G. & Cui, Y. A membrane-free lithium/polysulfide semi-liquid battery for large-scale energy storage. Energy & Environmental Science
6,1552 (2013).
3. Manthiram, A., Fu, Y. & Su, Y.-S. Challenges and Prospects of Lithium–Sulfur Batteries. Acc. Chem. Res.
46,1125–1134 (2013).

Acknowledgements

This work was supported as part of the Joint Center for Energy Storage Research, an Energy Innovation Hub funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences.
Nanoscale Operando and 3D In Situ Imaging of Micron-Sized Ge Anode Particles in Li Batteries
Authors: Weker Johanna Nelson , Liu Nian , Andrews Joy C , Toney Michael , Cui Yi 
Published: February 2020

Ge anodes have very high theoretical lithium capacity (1600 mAhg-1) and are promising anodes for Li batteries. Ge is more electronically conductive than Si and has a higher room temperature Li-ion diffusivity. However, because of their high capacity, Ge anodes suffer from large volume changes (up to 400%; similar to Si, at 4200 mAhg-1) during electrochemical cycling. Repeated expansion and contraction of these materials lead to fracturing and eventual pulverization resulting in the loss of electrical contact with the current collector and ultimately battery failure.
In order to better understand these failures we have conducted the first 3D nanoscale in situ study of a Li battery system. We imaged Ge anodes with hard X-rays (11.2 keV, above the Ge K-edge) with transmission X-ray microscopy at 30 nm resolution. 2D images in operando were collected at several regions within the particles, and 3D tomography data was also collected at different time points within the fully operating battery (in situ) to further examine the crack formation and density changes that occur with cycling. We found that volume expansion during lithiation is particle size dependent, but the subsequent volume contraction is not. Moreover, we found that only the largest particles actively participate in the second (de)lithiation cycle. From the in situ tomographic information we quantified the volume change in particles and measured the changes in porosity or density as particles (de)lithiate. Our results demonstrate the significant value of high resolution 3D imaging of batteries under operating conditions.