Unlock the full potential of carbon cloth-based scaffolds towards magnesium metal storage via regulation on magnesiophilicity and surface geometric structure

The development of rechargeable magnesium(Mg) batteries is of practical significance to upgrade the electric energy storage devices due to exceptional capacity and abundant resources of Mg-metal anode.However,the reversible Mg electrochemistry suffers from unsatisfied rate capability and lifespan,mainly caused by non-uniform distribution of electrodeposits.In this work,a fresh design concept of threedimensional carbon cloths scaffolds is proposed to overcome the uncontrollable Mg growth via homogenizing electric field and improving magnesiophilicity.A microscopic smooth and nitrogen-containing defective carbonaceous layer is constructed through a facile pyrolysis of ZIF8 on carbon cloths.As revealed by finite element simulation and DFT calculation results,the smooth surface endows with uniform electric field distribution and simultaneously the nitrogen-doping species enable good magnesiophilicity of scaffolds.The fine and uniform Mg nucleus as well as the inner electrodeposit behavior are also disclosed.As a result,an exceptional cycle life of 500 cycles at 4.0 mA cm^(-2) and 4.0 mA h cm^(-2) is firstly realized to our best knowledge.Besides,the functional scaffolds can be cycled for over 2200 h at 2.0 mA cm^(-2) under a normalized capacity of 5.0 mA h cm^(-2),far exceeding previous results.This work offers an effective approach to enable the full potential of carbon cloths-based scaffolds towards metal storage for next generation battery applications.

教育改善贫困阶层代际传递的效果与机制——来自CLDS微观数据的证据

基于职业阶层流动视角,利用CLDS数据和Probit模型研究教育改善贫困阶层代际传递的效果与机制,并采用IV Probit模型进行检验。研究表明:(1)子代教育和父代教育显著促进了贫困群体实现代际阶层跨越,但对不同类型群体代际阶层跨越的影响存在显著差异。(2)贫困家庭子代通过自身教育实现阶层跨越的效应“70后”大于“60后”以及“80后”“90后”、城市地区大于农村地区、女性大于男性。(3)父代教育显著促进了“60后”以及“80后”“90后”个体、城市地区个体、女性个体实现代际阶层跨越;对“70后”个体、农村地区个体、男性个体的影响不显著。(4)父代教育和子代教育改善贫困阶层代际传递的机制与渠道表现出一定的差异性。增加就业稳定性、提升健康水平、积累社会资本、获得培训机会都是教育改善贫困阶层代际传递的重要机制与渠道。

High area-capacity Mg batteries enabled by sulfur/copper integrated cathode design

Rechargeable Mg batteries potentially display lower cost and competitive energy density compared with their Li-ion counterparts.However,the practical implementation of high area-capacity cathodes still remains a formidably challenging task.This work presents the sulfur/copper integrated cathodes fabricated by the conventional blade-coating process and slurry-dipping method.The sulfur/copper foil integrated cathodes deliver a high area-capacity of 2.6 mAh cm^(-2)after 40 cycles,while the sulfur/copperfoam integrated cathode exhibits an ultrahigh area-capacity of 35.4 mAh cm^(-2),corresponding to 743.1 Wh L^(-1)at the electrode level(1.5 times higher than the LiCoO_(2)-graphite system).The in-situ formed copper sulfide intermediates with sufficient cation defects can act as functional intermediates to regulate the sulfur electrochemistry during the first discharge process.The subsequent cycles are operated by the reversible displacement reaction between Mg-ions and copper sulfide active substances.In particular,the copper ions prefer to extrude along the[001]direction in copper sulfides lattice and simultaneously the rock-salt MgS crystals are generated.Besides,the nonuniform surface topography of the cycled Mgmetal anode,caused by the spatial inhomogeneity in current distribution,is demonstrated to lead to the battery performance degradation for high area-capacity Mg batteries.

Chromopeptide A, a highly cytotoxic depsipeptide from the marine sediment-derived bacterium Chromobacterium sp. HS-13-94

A bicyclic depsipeptide, chromopeptide A(1), was isolated from a deep-sea-derived bacterium Chromobacterium sp. HS-13-94. Its structure was determined by extensive spectroscopic analysis and by comparison with a related known compound. The absolute configuration of chromopeptide A was established by X-ray diffraction analysis employing graphite monochromated Mo K_α radiation(λ ? 0.71073 ?) with small Flack parameter 0.03. Chromopeptide A suppressed the proliferation of HL-60, K-562, and Ramos cells with average IC_(50) values of 7.7, 7.0, and 16.5 nmol/L, respectively.

Terminal sulfur atoms formation via defect engineering strategy to promote the conversion of lithium polysulfides

The defect engineering shows great potential in boosting the conversion of lithium polysulfides intermediates for high energy density lithium-sulfur batteries(LSBs),yet the catalytic mechanisms remain unclear.Herein,the oxygen-defective Li_(4)Ti_(5)O_(12)-xhollow microspheres uniformly encapsulated by N-doped carbon layer(OD-LTO@NC)is delicately designed as an intrinsically polar inorganic sulfur host for the research on the catalytic mechanism.Theoretical simulations have demonstrated that the existence of oxygen deficiencies enhances the adsorption capability of spinel Li_(4)Ti_(5)O_(12)towards soluble lithium polysulfides.Some-S-S-bonds of the Li2S6on the defective Li_(4)Ti_(5)O_(12)surface are fractured by the strong adsorption force,which allows the inert bridging sulfur atoms to be converted into the susceptible terminal sulfur atoms,and reduces the activation energy of the polysulfide conversion in some degree.In addition,with the N-doped carbon layer,secondary hollow microspheres architecture built with primary ultrathin nanosheets provide a large amount of void space and active sites for sulfur storage,adsorption and conversion.The as-designed sulfur host exhibits a remarkable rate capability of 547 m Ah g^(-1)at 4C(1 C=1675 m A g^(-1))and an outstanding long-term cyclability(519 m Ah g^(-1)after 1000 cycles at 3 C).Besides,a high specific capacity of 832 m Ah g^(-1)is delivered even after 100 cycles under a high sulfur mass loading of 3.2 mg cm^(-2),indicating its superior electrochemical performances.This work not only provides a strong proof for the application of oxygen defect in the adsorption and catalytic conversion of lithium polysulfides,but offers a promising avenue to achieve high performance LSBs with the material design concept of incorporating oxygen-deficient spinel structure with hierarchical hollow frameworks.

Selenium vacancies enable efficient immobilization and bidirectional conversion acceleration of lithium polysulfides for advanced Li-S batteries

Heterostructures composed of oxides and sulfides(nitrides or carbides)show great potential as sulfur host additives because of the strong adoptability of oxides and catalytic capability of sulfides towards the notorious lithium polysulfides(LiPSs).However,the migration and conversion pathway of LiPSs is seriously confined at a localized interface with inadequate active sites.In this work,the introduction of selenium vacancies into VSe_(2−x)has been demonstrated to successfully synergize the adsorbability and catalytic reactions of LiPSs at an integrated functional surface.The N-doped carbon nanosheets-assembled flower architectures embedded with selenium vacancy-rich VSe_(2−x)and partial vanadium oxides have been controllably synthesized and employed as the cathode additives for lithium-sulfur(Li-S)batteries.Both the experiments and first-principle calculations reveal their strong adsorption to LiPSs and their bidirectional catalytic functionality towards the conversion between S8 and Li_(2)S.As expected,the charge and discharge kinetics of VSe_(2−x)containing sulfur cathodes is fundamentally improved(an outstanding rate capabilitiy with 693.7 mAh·g^(−1)at 2 C,a remarkable long-term cyclability within 1,000 cycles at 2 C with S loading 2.27 mg·cm^(−2),and an excellent areal capacity with 3.44 mAh·cm^(−2)within 100 cycles at 0.5 C).This work presents an effective resolution to couple the adsorbability and catalytic reactions of LiPSs at the material design perspective,and the insights on bidirectional catalytic functionality are of vital to develop functional materials for advanced Li-S batteries.