Biomass walnut shell was used to prepare activated carbon (AC) through a carbonization treatment and an activation procedure with potassium hydroxide (KOH). AC showed hierarchical pores: 0.6 nm micropores, 2.7 nm mesopores and macropores with average diameter of 50 nm, providing a large specific surface area of 2318 m2 g−1. This highly porous AC was tested as a host material to encapsulate sulfur via a vapor phase infusion process. The developed AC-S electrode showed a high initial specific capacity of 1350 mAh g−1 and good capacity retention over 100 cycles at 0.1 C for lithium–sulfur battery. [Display omitted] •Porous carbon is fabricated by using biomass walnut shell.•An activation procedure using KOH-ethanol solution was conducted.•As-synthesized AC has an extremely large surface area of 2318 m2 g−1 with hierarchical pores.•The developed AC-S electrode shows a reversible capacity of 910 mAh g−1 after 100 cycles at 0.1 C.
Markets for energy storage that go beyond portable electronics have emerged rapidly this decade, including powering electric vehicles and "leveling the grid" fed by renewable sources such as solar energy, which are intermittent in supply. These new demands require a significant step-up in energy density that will probably not be met by Li-ion batteries; estimates suggest they are starting to approach their theoretical limits. But in the world of "beyond Li-ion," the options are limited. One of the most hopeful is the Li-S battery, for which greater energy storage can potentially be realized through phase-transformation chemistry using elemental sulfur as a positive electrode material, which converts to lithium sulfide. These future generation systems offer up to a five-fold increased specific energy and greatly reduced cost factors, but commercialization has been hindered owing to key challenges. Efforts over the last two years to better manipulate the cell chemistry and overcome these challenges are presented.
Display omitted] •3D porous GA/S nanocrystals are prepared by a one-step hydrothermal method.•The structure is affected by hydrothermal temperature and liquid sulfur’s viscosity.•The hybrid delivers a capacity of 716.2mAhg−1 after 50 cycles at 100mAg−1.•The nanosized S, strong adsorbability and intimate contact of GNS are main factors. Lithium–sulfur (Li–S) batteries are receiving significant attention as a new energy source because of its high theoretical capacity and specific energy. However, the low sulfur loading and large particles (usually in submicron dimension) in the cathode greatly offset its advantage in high energy density and lead to the instability of the cathode and rapid capacity decay. Herein, we introduce a one-step hydrothermal synthesis of three-dimensional porous graphene aerogels/sulfur nanocrystals to suppress the rapid fading of sulfur electrode. It is found that the hydrothermal temperature and viscosity of liquid sulfur have significant effects on particle size and loading mass of sulfur nanocrystals, graphitization degree of graphene and chemical bonding between sulfur and oxygen-containing groups of graphene. The hybrid could deliver a specific capacity of 716.2mAhg−1 after 50 cycles at a current density of 100mAg−1 and reversible capacity of 517.9mAhg−1 at 1Ag−1. The performance we demonstrate herein suggests that Li–S battery may provide an opportunity for development of rechargeable battery systems.
The fine structures of proteins, such as the positions of hydrogen atoms, distributions of valence electrons and orientations of bound waters, are critical factors for determining the dynamic and chemical properties of proteins. Such information cannot be obtained by conventional protein X-ray analyses at 3.0-1.5 Å resolution, in which amino acids are fitted into atomically unresolved electron-density maps and refinement calculations are performed under strong restraints. Therefore, we usually supplement the information on hydrogen atoms and valence electrons in proteins with pre-existing common knowledge obtained by chemistry in small molecules. However, even now, computational calculation of such information with quantum chemistry also tends to be difficult, especially for polynuclear metalloproteins. Here we report a charge-density analysis of the high-potential iron-sulfur protein from the thermophilic purple bacterium Thermochromatium tepidum using X-ray data at an ultra-high resolution of 0.48 Å. Residual electron densities in the conventional refinement are assigned as valence electrons in the multipolar refinement. Iron 3d and sulfur 3p electron densities of the Fe4S4 cluster are visualized around the atoms. Such information provides the most detailed view of the valence electrons of the metal complex in the protein. The asymmetry of the iron-sulfur cluster and the protein environment suggests the structural basis of charge storing on electron transfer. Our charge-density analysis reveals many fine features around the metal complex for the first time, and will enable further theoretical and experimental studies of metalloproteins.
Nowadays, energy storage systems have been considered as an effective way to meet the urgent demand for portable electronic products and electric vehicle industry, which requires the development of power sources that can provide high capacity as well as high safety, resulting in an increase on secondary batteries with excellent performances and non-pollution. Lithium-sulfur (Li-S) battery is considered as one of the most promising candidate batteries due to its high theoretical energy density, low cost and non-toxicity. Despite many advantages associated with Li–S battery, it is hard to be applied to commercial-scale production owing to its shuttle effect, insulating nature, agglomeration of sulfur, polysulfide dissolution and fast capacity decay during charge–discharge process. To meet these challenges, numerous characteristics of sulfur electrode have been designed, such as sufficient space to accommodate sulfur volume expansion, small dimensions of active material to avoid pulverization, and appropriate electrolyte additives to minimize the shuttle effect. According to previous studies, morphology of sulfur carriers has an important effect on electrochemical performances of Li–S battery. This review mainly aims at present status of different morphological sulfur carriers including carbon, metallic oxide, organic polymer and their composites, then summarizes their advantages, unresolved problems and common synthesis methods, respectively. At last, development and future prospects of Li–S battery are also presented. •The relationships between sulfur carriers and their electrochemical performances were summarized.•The state-of-art research on sulfur carriers was presented.•The advantages, unresolved problems and common synthesis on sulfur carriers were reviews.
Breaking through low sulfur loading and shuttle effect are the key to achieve high performance lithium-sulfur battery. It is necessary to prepare an ultralight sulfur host with strong polysulfide adsorption/blocking ability. Herein, the polydopamine coated ochroma lagopus carbon (A-PDA@OLC) with super-high specific surface area is exploited as sulfur host for high-performance lithium-sulfur batteries. The cathode with 60.13 wt % sulfur content (2 mg cm−2 sulfur loading) delivered the higher initial capacity of 1294.27 mA h g−1 and excellent reversible capacity (959.13 mA h g−1 at 0.1C after 200 cycles). Moreover, when the sulfur content was increased to 82.30 wt% (4 mg cm−2 sulfur loading), the A-PDA@OLC@S cathode exhibits the higher reversible capacity of 1258 mA h g−1 at 0.1C and a prolonged cycle life (723 mA h g−1 after 250 cycles). The prepared PDA coated natural ultralight biochar are proven to be an effective strategy for the encapsulation and adsorption of lithium polysulfides(LiPSs), which demonstrates enhanced electrochemical performance for high-sulfur-loading Li–S batteries. •A novel biochar from Ochroma lagopus has been introduced into Li-S batteries for the first time.•The novel dopamine wrapped biomass-derived porous carbon endows the Li-S batteries with excellent electrical conductivity.•The novel materials have a strong chemical affinity with lithium polysulfides.•The double high sulfur cathode with the higher initial capacity and outstanding cycling stability was obtained.
Display omitted] This review is focused on the state-of-the-art of lithium-sulfur batteries. The great advantage of these energy storage devices in view of their theoretical specific capacity (2500Whkg−1, 2800WhL−1, assuming complete reaction to Li2S) has been the motivation for a huge amount of works. However, these batteries suffer of disadvantages that have restricted their applications such as high electrical resistance, capacity fading, self-discharge, mainly due to the so-called shuttle effect. Strategies have been developed with the recent modifications that have been proposed as a remedy to the shuttle effect, and the insulating nature of the polysulfides. All the elements of the battery are concerned and the solution, as we present herewith, is a combination of modification of the cathode, of the separator, of the electrolyte, including the choice of binder, even though few binder-free architectures have now been proposed.
•Metal organic framework @ reduced graphene oxide was applied for sulfur cathode.•MIL-101(Cr)@rGO/S composites are synthesized by a facile two-step liquid method.•Cycling stability of MIL-101(Cr)@rGO/S sulfur cathode was improved. Mesoporous metal organic framework @ reduced graphene oxide (MIL-101(Cr)@rGO) materials have been used as a host material to prepare the multi-composite sulfur cathode through a facile and effective two-step liquid phase method successfully, which is different from the simple MIL-101(Cr)/S mixed preparation method. The successful reduced graphene oxide coating in the MIL-101(Cr)@rGO improve the electronic conductivity of meso-MOFs effectively. The discharge capacity and capacity retention rate of MIL-101(Cr)@rGO/S composite sulfur cathode are as high as 650mAhg−1 and 66.6% at the 50th cycle at the current density of 335mAg−1. While the discharge capacity and capacity retention rate of MIL-101(Cr)/S mixed sulfur cathode is 458mAhg−1 and 37.3%. Test results indicate that the MIL-101(Cr)@rGO is a promising host material for the sulfur cathode in the lithium–sulfur battery applications.
Sulfur storage and transport between different reservoirs such as core, mantle, crust and atmosphere of Mars are tied to igneous processes. Martian meteorites carry a record of mantle melting and subsequent differentiation history of Martian magmas. Investigation of S geochemistry of Martian meteorites can thus provide an understanding of how S is transferred from the Martian interior to the exosphere. In this study we measured bulk S concentration of 7 Martian meteorites and modeled the behavior of S during both isobaric crystallization of primary Martian magmas and isentropic partial melting of Martian mantle. Comparisons between measured data and modeled results suggest that (1) sulfides may become exhausted at the source during decompression melting of the mantle and mantle-derived basalts may only become sulfide-saturated after cooling and crystallization at shallow depths and (2) in addition to degassing induced S loss, mixing between these differentiated sulfide-saturated basaltic melts and cumulus minerals with/without cumulate sulfides could also be responsible for the bulk sulfur contents in some Martian meteorites. In this case, a significant quantity of S could remain in Martian crust as cumulate sulfides or in trapped interstitial liquid varying from 2 to 95 percent by weight. Our modeling also suggests that generation of sulfide-undersaturated parental magmas requires that the mantle source of Martian meteorites contain <700–1000 ppm S if melting degree estimation of 2–17 wt.% based on compositions of shergottites is relevant. •We measured bulk S concentration of 7 Martian meteorites.•We modeled the fate of S during isobaric crystallization and decompression melting.•Sulfides may get exhausted during decompression melting in the Martian mantle.•Cumulate-melt mixing may explain the S contents in some Martian meteorites.•Mantle source of Martian meteorites contain <700–1000 ppm S.
Seven members of the homologous series of the liquid crystal dimers, the bis(ω-(cholesteryloxycarbonyl)alkyl)disulfides, which contain a sulfur−sulfur link in the flexible spacer have been synthesised and their liquid crystal properties characterised. The dimers are referred to using the acronym Chol-n-SS-n-Chol in which n denotes the number of carbon atoms linking the cholesteryl-based groups and the sulfur atoms, and was varied between 3, 5, 6, 8, 10, 11 and 12. All seven homologues exhibit a chiral nematic phase and for the longest three members a smectic A phase was also observed. An odd−even effect is apparent in both the transition temperatures and the values of the entropy change associated with the chiral nematic−isotropic transition, ΔS N*I /R, in which dimers with even values of n show the higher values. This is interpreted in terms of the average molecular shapes in which the C−S−S−C dihedral angle is around 90°. The values of ΔS N*I /R shown by these dimers are very small for liquid crystal dimers and this is attributed to the increased molecular biaxiality arising from the C−S−S−C dihedral angle. The smectic A phase exhibited by the homologues with n = 10, 11 and 12 is proposed to consist of an intercalated arrangement of the dimers which is driven by the mismatch in cross-sectional areas of the cholesteryl-based groups and alkyl chains.