Functionalized Carbon Nanotube Sponge as Sulfur Reservoir for Lithium Sulfur Battery

Lithium sulfur batteries offer many advantages such as high specific capacity, environmental friendliness and low cost. However, several problems limit their commercialization, like low sulfur utilization because of the insulating nature of sulfur, and capacity degradation caused by dissolution of the intermediate product, polysulfide. Herein, we proposed that unzipping the carbon nanotube electrode to increase its surface area can enhance sulfur utilization due to the larger contact area. Furthermore, graphene oxide was chosen as a polysulfide immobilizer due to the electrostatic interaction between graphene oxide and polysulfide. Our results show much better battery cycle performance after the treatments just mentioned before, which are reliable supports for the hypothesis

Polyisoprene Captured Sulfur Nanocomposite Materials for High-Areal-Capacity Lithium Sulfur Battery

A polyisoprene-sulfur (PIPS) copolymer and nano sulfur composite material (90 wt % sulfur) is synthesized through inverse vulcanization of PIP polymer with micrometer-sized sulfur particles for high-areal-capacity lithium sulfur batteries. The polycrystalline structure and nanodomain nature of the copolymer are revealed through high-resolution transmission electron microscopy (HRTEM). PIP polymer is also used as binders for the electrode to further capture the dissovlved polysulfides. A high areal capacity of ca. 7.0 mAh/cm2 and stable cycling are achieved based on the PIPS nanosulfur composite with a PIP binder, crucial to commercialization of lithium sulfur batteries. The chemical confinement both at material and electrode level alleviates the diffusion of polysulfides and the shuttle effect. The sulfur electrodes, both fresh and cycled, are analyzed through scanning electron microscopy (SEM). This approach enables scalable material production and high sulfur utilization at the cell level

Evolutionary cell biology: Functional insight from “Endless forms most beautiful”

In animal and fungal model organisms, the complexities of cell biology have been analyzed in exquisite detail and much is known about how these organisms function at the cellular level. However, the model organisms cell biologists generally use include only a tiny fraction of the true diversity of eukaryotic cellular forms. The divergent cellular processes observed in these more distant lineages are still largely unknown in the general scientific community. Despite the relative obscurity of these organisms, comparative studies of them across eukaryotic diversity have had profound implications for our understanding of fundamental cell biology in all species and have revealed the evolution and origins of previously observed cellular processes. In this Perspective, we will discuss the complexity of cell biology found across the eukaryotic tree, and three specific examples of where studies of divergent cell biology have altered our understanding of key functional aspects of mitochondria, plastids, and membrane trafficking

Free-standing compact cathodes for high volumetric and gravimetric capacity Li–S batteries

Free-standing high performance Li–S battery cathodes are currently attracting significant research efforts. Loose macroporous structures have been proposed by many to improve sulfur utilization and areal capacity. However, their low cathode sulfur densities and high electrolyte fractions lead to low cell volumetric and gravimetric capacities. We report here a compact free-standing Li–S cathode structure that delivers areal, volumetric and gravimetric capacities all exceeding those of typical Li-ion batteries. The cathodes, formed by pressure filtration of the constituents, are composed of highly micro/mesoporous nitrogen-doped carbon nanospheres (NCNSs) embedded in the macropores of a multi-walled carbon nanotube (MWCNT) network to form a dense structure. The MWCNT network facilitates low cathode impedance. The NCNSs maximize sulfur utilization and immobilization. These collectively result in high cathode volumetric capacity (1106 mA h cm−3) and low electrolyte requirement (6 μL mg−1 of sulfur), which together lead to high cell-level gravimetric capacity. Stable long-term cycling at 0.3C (2.5 mA cm−2 for 5 mg cm−2 areal sulfur-loading) has also been achieved, with the areal and volumetric capacities of the best remaining above typical Li-ion values over 270 cycles and the per-cycle capacity fading being only 0.1%. The facile preparation means significant potential for large scale use.CH acknowledges a Postdoctoral Fellowship provided by Loughborough University

The Role of Sulfur Metabolism in Effective Plant-Microbe Interactions

Bradyrhizobium japonicum USDA110 and Sinorhizobium meliloti RM1021 are nitrogen fixing rhizobia that fix nitrogen when in a symbiotic relationship with legumes. For effective nitrogen-fixing symbiosis to occur these rhizobia must differentiate into nitrogen-fixing bacteroids. This involves the production of high levels of sulfur rich nitrogenase as well as other sulfur containing compounds, creating a large demand for sulfur. This work examined the role of organic sulfur in the establishment of symbiosis and viability of rhizobia in plant nodules. Disruption of the sulfonate sulfur utilization gene ssuD in both Bradyrhizobium japonicum USDA110 and Sinorhizobium meliloti RM1021 resulted in a strong nitrogen deficient phenotype in the host plants. This phenotype was linked to a reduced ability to invade host plants as a result of increased sensitivity to oxidative stress. Additionally, once inside the plant nodules, the ssuD mutants were slow to grow with no observable nitrogen fixation occurring. However, the ability of ssuD mutants to continue to grow at slow rates in nodules resulted in the discovery that sulfate esters are another important sulfur source during symbiosis. Dickeya dadantii 3937 is a phytopathogen, which causes disease in potato, maize, banana, and pineapple as well as ornamental house plants and a wide range of subtropical and tropical plants. D. dadantii has been used as a model organism for the study of secretion systems and virulence factors in phytopathogens. This work examined the regulation, induction, and role of organic and inorganic sulfur utilization genes during the infection of potato by D. dadantii. The regulation of sulfur metabolism in D. dadantii was determined to be similar to the model organism Escherichia coli. However, disruption of the arylsulfatase operon slowed the spread of maceration in potato infections despite D. dadantii being unable to grow on arylsulfonates. Examination of the arylsulfatase operon resulted in the discovery of a phenol dependent sulfotransferase that was able to sulfonate salicylic acid and is hypothesized to play a role in subverting salicylic acid induced immunity in host plants

Carbonyl‐ β ‐Cyclodextrin as a Novel Binder for Sulfur Composite Cathodes in Rechargeable Lithium Batteries

As one of the essential components in electrodes, the binder affects the performance of a rechargeable battery. By modifying β ‐cyclodextrin ( β ‐CD), an appropriate binder for sulfur composite cathodes is identified. Through a partial oxidation reaction in H 2 O 2 solution, β ‐CD is successfully modified to carbonyl‐ β ‐cyclodextrin (C‐ β ‐CD), which exhibits a water solubility ca. 100 times that of β ‐CD at room temperature. C‐ β ‐CD possesses the typical properties of an aqueous binder: strong bonding strength, high solubility in water, moderate viscosity, and wide electrochemical windows. Sulfur composite cathodes with C‐ β ‐CD as the binder demonstrate a high reversible capacity of 694.2 mA h g (composite) −1 and 1542.7 mA h g (sulfur) −1 , with a sulfur utilization approaching 92.2%. The discharge capacity remains at 1456 mA h g (sulfur) −1 after 50 cycles, which is much higher than that of the cathode with unmodified β ‐CD as binder. Combined with its low cost and environmental benignity, C‐ β ‐CD is a promising binder for sulfur cathodes in rechargeable lithium batteries with high electrochemical performance. The sulfur utilization and cycling stability of composite cathodes in rechargeable lithium batteries are enhanced by carbonyl‐ β ‐cyclodextrin (C‐ β ‐CD) as the binder in sulfur composite cathodes. This is made possible by the fact that C‐ β ‐CD is highly soluble in water, ca. 100 times more soluble than β ‐CD at room temperature, and because it exhibits strong bonding strength.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/96706/1/adfm_201201847_sm_suppl.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/96706/2/1194_ftp.pd

Functionalized Carbon Nanotube Sponge as Sulfur Reservoir for Lithium Sulfur Battery

Lithium sulfur batteries offer many advantages such as high specific capacity, environmental friendliness and low cost. However, several problems limit their commercialization, like low sulfur utilization because of the insulating nature of sulfur, and capacity degradation caused by dissolution of the intermediate product, polysulfide. Herein, we proposed that unzipping the carbon nanotube electrode to increase its surface area can enhance sulfur utilization due to the larger contact area. Furthermore, graphene oxide was chosen as a polysulfide immobilizer due to the electrostatic interaction between graphene oxide and polysulfide. Our results show much better battery cycle performance after the treatments just mentioned before, which are reliable supports for the hypothesis