Rechargeable Lithium Sulfur Research Articles

A new approach to improve cycle performance of rechargeable lithium–sulfur batteries by inserting a free-standing MWCNT interlayer

A conductive multiwalled carbon nanotube (MWCNT) interlayer acting as a pseudo-upper current collector not only reduces the charge transfer resistance of sulfur cathodes significantly, but also localizes and retains the dissolved active material during cycling.

Improving the Performance of Lithium–Sulfur Batteries by Conductive Polymer Coating

Rechargeable lithium–sulfur (Li–S) batteries hold great potential for next-generation high-performance energy storage systems because of their high theoretical specific energy, low materials cost, and environmental safety. One of the major obstacles for its commercialization is the rapid capacity fading due to polysulfide dissolution and uncontrolled redeposition. Various porous carbon structures have been used to improve the performance of Li–S batteries, as polysulfides could be trapped inside the carbon matrix. However, polysulfides still diffuse out for a prolonged time if there is no effective capping layer surrounding the carbon/sulfur particles. Here we explore the application of conducting polymer to minimize the diffusion of polysulfides out of the mesoporous carbon matrix by coating poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonate) (PEDOT:PSS) onto mesoporous carbon/sulfur particles. After surface coating, coulomb efficiency of the sulfur electrode was improved from 93% to 97%, and capaci...

Graphene-Wrapped Sulfur Particles as a Rechargeable Lithium–Sulfur Battery Cathode Material with High Capacity and Cycling Stability

We report the synthesis of a graphene-sulfur composite material by wrapping poly(ethylene glycol) (PEG) coated submicrometer sulfur particles with mildly oxidized graphene oxide sheets decorated by carbon black nanoparticles. The PEG and graphene coating layers are important to accommodating volume expansion of the coated sulfur particles during discharge, trapping soluble polysulfide intermediates, and rendering the sulfur particles electrically conducting. The resulting graphene-sulfur composite showed high and stable specific capacities up to ∼600 mAh/g over more than 100 cycles, representing a promising cathode material for rechargeable lithium batteries with high energy density.

Ordered mesoporous carbon/sulfur nanocomposite of high performances as cathode for lithium–sulfur battery

Ordered mesoporous carbon/sulfur (OMC/S) nanocomposites with hierarchically structured sulfur loading, ranging from 50 to 75 wt%, were synthesized via a simple melt-diffusion strategy. The OMC with a BET surface area of 2102 m 2 g −1, a pore volume of 2.0 cm 3 g −1 and unique bimodal mesoporous (5.6/2.3 nm) structure, was prepared from a triconstituent co-assembly method. The resulting OMC/S nanocomposite material served as cathode of rechargeable lithium–sulfur (Li–S) battery. It has been tested that the novel OMC/S cathode can deliver a superior reversible capacity and cyclability. In particular, the nanocomposite with a loading of 60 wt% sulfur (OMC/S-60) presents the highest sulfur utilization ca. 70%, an excellent high rate capability ca. 6 C and a good cycling stability for up to 400 full charge–discharge cycles. The exceptional electrochemical performances are exclusively attributed to the large internal surface area and high porosity of the ordered mesoporous carbon, which favorites both electron and Li-ion transportations.

Carbon-Sulfur Nanocomposites and Electrolytes for Rechargeable Lithium Sulfur Batteries

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Effect of imidazolium cation on cycle life characteristics of secondary lithium–sulfur cells using liquid electrolytes

The cycle life performance of rechargeable lithium–sulfur (Li–S) cells was examined by using DME/DOX (4/1) solvent systems, where supporting electrolyte systems used were classified into the two groups: (1) conventional lithium salts and (2) mixed salts composed of lithium salt and imidazolium salt. To analyze the effect of the imidazolium cation on the cycle life characteristics of secondary Li–S cells, we applied the following three kinds of immidazolium salts, with the same anion, to the mixed-salt systems: 1-ethyl-3-methyl-imidazolium bis(trifluoromethylsulfonyl)imide (EMITFSI); 1-butyl-3-methyl-imidazolium bis(trifluoromethylsulfonyl)imide (BMITFSI); 1,2-dimethyl-3-propylimidazolium bis(trifluoromethylsulfony)imide (DMPITFSI). Even after 100 cycles, the EMI- and BMI-added Li–S cells showed much larger capacities, 721 and 642 mAh g −1-sulfur, respectively, when compared to that (534 mAh g −1-sulfur) of the LiTFSI-based Li–S cells. By contrast, the DMPI-added Li–S cells showed poor cycle life performance in that their capacity decreased to below 200 mAh g −1-sulfur even before 10 cycles. It is probable that this phenomenon is due mainly to the deactivation of the carbon cathode caused by coating of non-conductive and insoluble materials, which might result from side reactions between DMPI and lithium polysulfides.

Effects of imidazolium salts on discharge performance of rechargeable lithium–sulfur cells containing organic solvent electrolytes

In this study, lithium–sulfur (Li–S) cells using mixed imidazolium salts and lithium salts for the electrolytes are investigated as a means to improve discharge performance and cycle-life characteristics. By introducing 5 or 10 vol.% of imidazolium salt into the electrolytes containing lithium salts, the Li–S cells give a greatly enhanced discharge capacity of >600 mAh g −1 up to the 100th charge–discharge cycle. Furthermore, both the discharge capacity and the average discharge voltage at a high discharge rate, as well as the low-temperature performance, are all dramatically improved when compared with those of conventional cells using organic electrolyte solvents and lithium salts.

Rechargeable Lithium Sulfur Battery : I. Structural Change of Sulfur Cathode During Discharge and Charge

In this paper, the structural change of the sulfur cathode during the electrochemical reaction of a lithium sulfur battery employing 0.5 M -tetra(ethylene glycol) dimethyl ether (TEGDME) was studied by means of scanning electron microscopy (SEM), X-ray diffraction (XRD), and wave dispersive spectroscopy (WDS). The discharge process of the lithium sulfur cell could be divided in the first discharge region (2.4-2.1 V) where the reduction of elemental sulfur to form soluble polysulfides and further reduction of the soluble polysulfide occur, and the second discharge region (2.1-1.5 V) where the soluble polysulfides are reduced to form a nonuniform solid film covered over the carbon matrix. It was also found that the charge of lithium sulfur cell leads to the conversion from to the soluble polysulfide, resulting in the removal of layer formed on carbon matrix. However, the oxidization of the soluble polysulfide to solid sulfur hardly occurs and few are left on carbon matrix even at 100% depth of charge. © 2003 The Electrochemical Society. All rights reserved.

Rechargeable Lithium Sulfur Battery : II. Rate Capability and Cycle Characteristics

This paper reports on the investigation of rate capability and cycle characteristics of a lithium sulfur battery. The second discharge region where solid is formed on the surface of the carbon matrix in the cathode was highly sensitive to cathode thickness and discharge rate. The scanning electron microscope (SEM) observation suggests that thick layer formed at the surface of the cathode causes the diminution of the second discharge region at high discharge rate. Upon repeated cycle, the delocalization of the surface layer happened, however, the irreversible gradually increased with cycle as evidence by (SEM) and wave dispersive spectroscopy measurements, causing capacity fade. The formation of the irreversible was more significant for higher rates of discharge. It is believed that the destruction of the carbon matrix by stress generated during the localized deposition of is responsible for the formation of irreversible © 2003 The Electrochemical Society. All rights reserved.

Structural Factors of Sulfur Cathodes with Poly(ethylene oxide) Binder for Performance of Rechargeable Lithium Sulfur Batteries

The structure and the room temperature performances of sulfur cathodes composed of sulfur, carbon, and poly(ethylene oxide) (PEO) binder were studied with varying preparation method and binder content. Two different methods, ball mixing and mechanical stirring, were employed for preparation of slurry to obtain morphologically different cathodes. The cathodes prepared with mechanical stirring (SC cathodes) revealed more porous structure than those with ball mixing (BC cathodes). Scanning electron microscopy observations showed that sulfur particles were covered with dense and thick PEO film in the BC cathodes, whereas sulfur particles were bonded with porous PEO film in the SC cathodes. The SC-based cells exhibited much higher discharge capacity yielding 75% of sulfur utilization than the BC-based cells. The difference of discharge behaviors with different mixing methods indicates that the porosity of the cathode and the morphology of PEO binder are highly important factors for favorable electrochemical performance of lithium sulfur batteries. The cycle life of the SC-based cell was improved with the increase of binder content and with the roll pressing due to the increase of adhesiveness and cohesiveness of the sulfur cathode. © 2002 The Electrochemical Society. All rights reserved.

Rechargeable lithiumsulfur battery (extended abstract)

Rechargeable lithiumsulfur battery (extended abstract)