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Nanostructured carbon materials have been extensively used for encapsulating sulfur and improving cyclic stability of lithium-sulfur (Li-S) batteries, but high carbon content and low packing density greatly limit their volumetric energy density. Herein, we present MXene-based Ti3C2T x (T x stands for the surface terminations) nanodots-interspersed Ti3C2T x nanosheet (TCD-TCS) to accomplish spatial immobilization and conversion of high-loaded sulfur species. Rich surface polar sites in TCD-TCS enhance structural integrity of the resultant electrode, while the absence of the carbon-based materials and conductive additives results in high tap density of the cathode materials. The TCD-TCS/S electrode exhibits an almost theoretical discharge capacity at a medium sulfur loading of 1.8 mg cm-2. Notably, ultrahigh volumetric capacity (1957 mAh cm-3) and high areal capacity (13.7 mAh cm-2) are synchronously achieved at a high sulfur loading of 13.8 mg cm-2. The mechanism study of sulfur evolution during discharge process highlights the importance of the integration of MXene-based nanodots and nanosheets in Li-S batteries. This proposed methodology holds great promise for the development of various high-performance energy storage materials.

Lithium–sulfur (Li–S) batteries are one of the promising next-generation energy storage systems. Tremendous efforts have been devoted to developing conductive nanoarchitectures for improving sulfur utilization and cycling stability. MXenes, a family of 2D transition metal carbides, nitrides and carbonitrides, have recently captured considerable attention in energy storage and conversion. Herein, we have summarized recent advances of MXene-based materials in the cathodes, anodes and separators of Li–S batteries and highlighted the theoretical and experimental importance of high polarity and rich surface chemistry in polysulfide trapping. Their superiority for suppressing polysulfide shuttling and improving sulfur utilization has been demonstrated. We have also concluded the perspectives and challenges that need to be addressed for MXene-based Li–S batteries and some new strategies have been proposed to improve the electrochemical performance, which shed light on future development of MXene-based materials in high-energy-density Li–S batteries.

High gravimetric, areal and volumetric capacities together with long lifetime are key indexes for the applications of lithium-sulfur (Li-S) batteries in compact space. The sulfur host materials play pivotal roles in the practical deployment. Herein, one type of new heterostructure nanosheets composed of cobalt boride (CoB) on nitrogen, boron-codoped porous carbon (NBC), which is constructed through molten salt-assisted strategy using ZIF-67-encapsulated ZIF-8 as precursors is reported on. Benefiting from strong interfacial electronic interactions between binary sulfiphilic CoB and porous NBC, the CoB/NBC-S electrode exhibits the excellent cycling stability with low average capacity decay of 0.013% in ultralong 1500 cycles at high rate of 5 C. Remarkably, the electrode with high sulfur content of 82 wt% and high sulfur loading of 5.8 mg cm-2 delivers gravimetric capacity of 1309 mA h g-1 , areal capacity of 7.59 mA h cm-2 , and volumetric capacity of 1355 mA h cm-3 at 0.1 C. The favorable electrochemical performance can rival with the state-of-the-art of those in the reported nanosheets-based sulfur cathodes. This study provides new methodology for the design of heterostructure nanosheets of metal borides to achieve energy density and longevity of Li-S batteries.

Transition metal nitrides are promising mediators for improving the electrochemical performance of lithium–sulfur (Li–S) batteries, but the synthesis of ultrafine and durable nanoparticles in the absence of ammonia gas is still a great challenge. Herein, we reported a new method for the fabrication of ultrafine vanadium nitride (VN) nanoparticles uniformly embedded into N-doped porous carbon using a main-chain imidazolium-based ionic polymer (ImIP) containing metavanadate anions as a precursor. ImIP not only serves as sole carbon and nitrogen sources, but also effectively inhibits the aggregation and coalescence of VN nanoparticles during pyrolysis. Benefiting from the ultrafine particle size, high polarity and good electrocatalytic effects of VN, both redox kinetics of sulfur species and chemical adsorbability toward polysulfides are greatly expedited. The resultant electrode exhibits superior cycling stability with a low average capacity decay rate of 0.035% for 1200 cycles at a high rate of 5 C. This work develops a facile ammonia-free approach to fabricate ultrafine VN nanoparticles for improving electrochemical behaviors of Li–S batteries.

Background To avoid destructive sampling for conservation and genetic assessment, we isolated the DNA of clam Cyclina sinensis from their feces. DNA electrophoresis and PCR amplification were used to determine the quality of fecal DNA. And we analyzed the effects of different conditions on the degradation of feces and fecal DNA. Results The clear fecal DNA bands were detected by electrophoresis, and PCR amplification using clam fecal DNA as template was effective and reliable, suggesting that clam feces can be used as an ideal material for noninvasive DNA isolation. In addition, by analyzing the effects of different environmental temperatures and soaking times on the degradation of feces and fecal DNA, we found that the optimum temperature was 4 °C. In 15 days, the feces maintained good texture, and the quality of fecal DNA was good. At 28 °C, the feces degraded in 5 days, and the quality of fecal DNA was poor. Conclusions The clam feces can be used as an ideal material for noninvasive DNA isolation. Moreover, the quality of fecal DNA is negatively correlated with environmental temperature and soaking time.

It is of great significance to mediate the redox kinetics and shuttle effect of polysulfides in pursuit of high-energy-density and long-life lithium-sulfur (Li-S) batteries. Herein, a new strategy is proposed based on the electrostatic attraction and catalytic effect of polysulfides for the modification of the polypropylene (PP) separator. Guanidinium-based ionic-covalent organic nanosheets (iCON) on the surface of Ti3 C2 is presented as a coating layer for the PP separator. The synergetic effects of Ti3 C2 and iCON provide new platforms to suppress the shuttle effect of polysulfides, expedite the redox kinetics of sulfur species, and promote efficient conversion of the intercepted polysulfides. The functional separator endows carbon nanotube/sulfur cathodes with excellent electrochemical performance. The average capacity decay per cycle within 2000 cycles at 2 C is as low as 0.006%. The separator is even effective in the case of sulfur content of 90 wt% and sulfur loading of 7.6 mg cm-2 ; the reversible capacity, areal capacity, and volumetric capacity at 0.1 C are as high as 1186 mA h g-1 , 9.01 mA h cm-2 , and 1201 mA h cm-3 , respectively. This work provides a promising approach toward separator modification for the development of high-performance Li-S batteries.

Conductive porous carbons are promising sulfur host materials for improving mass and areal capacities in lithium-sulfur (Li–S) batteries, but they face a few congenital deficiencies, such as low tap density and weak entrapment ability toward lithium polysulfides (LiPS), resulting in poor volumetric performance. Herein, we report a self-supporting cathode based on electrochemical active graphene-like RuO2 (GRO) without the incorporation of any carbon hosts and additives to synchronously acquire high mass, areal and volumetric capacities. It has been certified that dynamic evolutions of both conductive GRO host and sulfur guest during cell operation expedite chemisorption/conversion of LiPS and regulate nucleation/growth of solid Li2S, which enables GRO-S with medium sulfur loading to achieve an almost theoretical capacity at 0.2 C. Remarkably, the electrode with higher sulfur loading of 8.4 mg cm−2 delivers mass, areal and volumetric capacities of 1225 mAh g−1, 10.3 mAh cm−2 and 1981 mAh cm−3 at 0.2 C, respectively. The volumetric capacity records the highest value in reported Li–S batteries. The cathode material reported in this work opens new avenues for the development of high-energy-density and long-life Li–S batteries.

Hollow nanostructures with intricate interior and catalytic effects hold great promise for the construction of advanced lithium-sulfur batteries. Herein, a double-shelled hollow polyhedron with inlaid cobalt nanoparticles encapsulated by nitrogen-doped carbon (Co/NC) nanodots (Co-NC@Co9 S8 /NPC) is reported, which is acquired by using imidazolium-based ionic-polymer-encapsulated zeolitic imidazolate framework-67 as a core-shelled precursor. The Co/NC nanodots promote redox kinetics and chemical adsorbability toward polysulfides, while the interconnected double shells serve as a nanoscale electrochemical reaction chamber, which effectively suppresses the polysulfide shuttling and accelerates ion/electron transport. Benefiting from structural engineering and reaction kinetics modulation, the Co-NC@Co9 S8 /NPC-S electrode exhibits high cycling stability with a low capacity decay of 0.011% per cycle within 2000 cycles at 2 C. The electrode still shows high rate performance and cyclability over 500 cycles even in the case of high sulfur loading of 4.5 mg cm-2 and 75 wt% sulfur content. This work provides one type of new hollow nanoarchitecture for the development of advanced Li-S batteries and other energy storage systems.

Mactra veneriformis (Bivalvia: Mactridae) is one commonly cultured bivalve species in the western Pacific Ocean. In the current study, the complete mitrochondrial DNA (mtDNA) of the clam M. veneriformis was determined. The M. veneriformis mt genome is 16,854 bp in length and encodes 34 genes on the same strand, including 12 protein-coding genes (PCGs), 2 ribosomal RNA genes and 20 transfer RNA genes. The length of 12 PCGs is 11,358 bp, which accounts for 67.4% in whole mt genome. The proportion is similar to other clams' mt genomes and within those of bivalves mt genomes. Gene order (which is the same as that of RZ C. antiquata) of M. veneriformis mt genome is compared with that of other veneroids. Compared with the typical gene content of animal mt genomes, atp8 and two tRNA(Ser) genes are missing in the mt genome. All non-coding regions are 1978 bp in length, among them the longest one is speculated as the control region, which is located between the tRNA(His) and tRNA(Arg). The secondary largest non-coding region (NCR(664)) between the tRNA(Gln) and tRNA(Thr) in the M. veneriformis mt genome contains one section of tandem repeats (125 nt × 5.2 or 249 nt × 2.6). The tandem repeats account for 97.89% (650/664) of the NCR(664), which is a unique characteristic of the M. veneriformis mt non-coding regions compared with those of other veneroids.

A full-length cDNA coding lipoprotein lipase (LPL) was cloned from liver of adult common carp (Cyprinus carpio Var. Jian) by RT-PCR and rapid amplification of cDNA ends (RACE) approaches. The cDNA obtained was 2,411 bp long with a 1,524 bp open reading frame (ORF) encoding 507 amino acids. This amino acid sequence contains two structural regions: N-terminus (24-354 residues) and C-terminus (355-507 residues). Before N-terminus, 1-23 residues is signal peptide, 6-23 residues is transmembrance helix. At N-terminus, some conversed functional sites were found, including two N-linked glycosylation sites Asn(41) and Asn(88); one catalytic triad Ser(174), Asp(198) and His(283); one conserved heparin-binding site Arg(321) to Arg(324) (RKNR); eight cysteines residues Cys(69) and Cys(82), Cys(258) and Cys(281), Cys(306) and Cys(325), Cys(317) and Cys(320) which are involved in four disulfide bridges; one polypeptide "lid" that participates in substrate specificity. At C-terminus, Asn(401) is another N-linked glycosylation site, and Trp(434) and Trp(435) (WW) is lipid-binding site. The amino acid sequence has a high similarity, and shows similar structural features to LPL of other species. Tissue distribution of LPL mRNA in liver, head kidney, mesenteric adipose tissue, heart and white muscle of common carp was analyzed by semi-quantitative RT-PCR method using beta-actin gene as internal control. The result showed that the expressions of LPL mRNA were detected in all examined tissues of common carp. The expression levels of LPL in the mesenteric adipose tissue was highest among these tissues, following in liver and head kidney, and the lowest expression was found in heart and white muscle.