Boosting polysulfide redox conversion of Li-S batteries by one-step-synthesized Co-Mo bimetallic nitride

Lithium-sulfur(Li-S)batteries are considered as one of the most promising next generation energy storage systems due to the high theoretical specific capacity,low cost,and environmental benignity.However,the notorious shuttle effect of polysulfides hinders the practical application of Li-S batteries.Herein,we have rationally designed and synthesized sea urchin-like Co-Mo bimetallic nitride(Co_(3) MO_(3) N)in the absence of additional nitrogen sources with only one step,which was applied as the sulfur host materials for Li-S batteries.The results indicate that Co_(3) Mo_(3) N can efficiently anchor and catalyze the conversion of polysulfides,thus accelerating the electrochemical reaction kinetics and enabling prominent electrochemical properties.As a consequence,the S@Co_(3) Mo_(3) N cathode exhibits a high rate performance of 705 mAh g^(-1) at 3 C rate and an excellent cycling stability with a low capacity fading rate of 0.08%per cycle at 1 C over 600 cycles.Even at a high sulfur loading of 5.4 cmg cm^(-2),it delivers a high initial areal capacity of 4.50 mAh cm^(-2) which is still retained at 3.64 mAh cm^(-2) after 120 cycles.Furthermore,the catalytic mechanism and structural stability of Co_(3) Mo_(3) N during cycling were elucidated by a combination of X-ray photoelectron spectroscopy and X-ray absorption fine structure.This work highlights the strategy of structure-catalysis engineering of bimetallic nitride,which is expected to have a wide application in Li-S batteries.

Fe-Nx Sites enriched microporous carbon nanoflower planted with tangled bamboo-like carbon nanotube as a strong polysulfides anchor for lithium-sulfur batteries

Serious shuttle effect and sluggish conversion kinetics of lithium polysulfides(LiPSs)have a massive impact on obstructing the practical application of lithium-sulfur(Li-S)batteries.To address such issues,Fe-Nx sites enriched microporous nanoflowers planted with tangled bamboo-like carbon nanotubes(Fe-Nx-C/Fe_(3)C-CNTs NFs)are found to be effective catalytic mediators with strong anchoring capabilities for LiPSs.The bamboo-like carbon nanotubes catalyzed by Fe_(3)C/Fe entangled each other to form a conductive network,which encloses a flowerlike microporous carbon core with embedded well-dispersed Fe-Nx active sites.As expected,electrons smoothly transfer along the dense conductive bamboo-like carbon network while the flower-like carbon core consisting of micropores induces the homogeneous distribution of tiny sulfur and favors the lithium ions migration with all directions.Meanwhile,Fe-Nx sites strongly trap long-chain LiPSs with chemical anchoring,and catalyze the redox conversion of LiPSs.Due to the aforementioned synergistic effects,the S@Fe-Nx-C/Fe_(3)C-CNTs NFs cathode exhibited a remarkable specific capacity(635 mAh g_(s)^(-1))at 3 C and a favorable capacity decay with 0.04%per cycle even after 400 cycles at 1 C.

The regulatory pathways of distinct flowering characteristics in Chinese jujube

Flowering is the most important event in higher plants.Compared to most fruit tree species,Chinese jujube(Ziziphus jujuba Mill.),the most important member of the large,diverse Rhamnaceae family and a leading dry fruit-producing species,has unique characteristics that include a short juvenile phase and extremely fast flower bud differentiation.However,the distinct mechanism of flowering regulation in Chinese jujube is still unclear.The morphological and cytological development period of jujube flowering was first investigated,and the crucial developmental stages were defined.Flower bud differentiation in Chinese jujube took only approximately 11–13 days,which is a distinct characteristic of perennial fruit trees.Afterward,44 genes related to six flowering pathways were identified in the jujube genome and were found to be randomly distributed among 11 of the 12 chromosomes.Tissue-specific and spatiotemporal expression patterns showed that all these genes were expressed in the flowers.Overall,photoperiodrelated genes were highly expressed during flower bud differentiation.These genes were also positively responsive to photoperiod regulation and phase change processes,indicating that photoperiod-related genes play crucial roles in jujube flower bud differentiation.Under protected cultivation,ZjPIF4,a temperature-related gene,was expressed in the early stages of flowering and responded to increasing temperatures.Moreover,STRING analysis and yeast two-hybrid screening indicated that photoperiod-related(ZjCO)and temperature-related(ZjPIF4)proteins could interact with ZjFT,the key protein involved in the determination of flowering time,indicating crosstalk between photoperiodrelated pathways and ambient temperature-related pathways in jujube.This study is the first report to comprehensively analyze the flowering pathways in Chinese jujube and revealed that photoperiod-related and ambient temperature-related pathways are the main mechanisms regulating the distinct flowering process and that members of the ZjPHY family(ZjPIF4,ZjFT,and ZjCO5)are the key factors involved in the regulatory network.These results will increase our understanding of the molecular and genetic mechanisms of flowering in Chinese jujube and provide meaningful clues for the flowering regulation of other fruit tree species.

Field-assisted electrocatalysts spark sulfur redox kinetics:From fundamentals to applications

The chief culprit impeding the commercialization of lithium–sulfur(Li–S)batteries is the parasitic shuttle effect and restricted redox kinetics of lithium polysulfides(LiPSs).To circumvent these key stumbling blocks,incorporating electrocatalysts with rational electronic structure modulation into sulfur cathode plays a decisive role in vitalizing the higher electrocatalytic activity to promote sulfur utilization efficiency.Breaking the stereotype of contemporary electrocatalyst design kept on pretreatment,field-assisted electrocatalysts offer strategic advantages in dynamically controllable electrochemical reactions that might be thorny to regulate in conventional electrochemical processes.However,the highly interdisciplinary fieldassisted electrochemistry puzzles researchers for a fundamental understanding of the ambiguous correlations among electronic structure,surface adsorption properties,and catalytic performance.In this review,the mechanisms,functionality explorations,and advantages of field-assisted electrocatalysts including electric,magnetic,light,thermal,and strain fields in Li–S batteries have been summarized.By demonstrating pioneering work for customized geometric configuration,energy band engineering,and optimal microenvironment arrangement in response to decreased activation energy and enriched reactant concentration for accelerated sulfur redox kinetics,cutting-edge insights into the holistic periscope of chargespin-orbital-lattice interplay between LiPSs and electrocatalysts are scrutinized,which aspires to advance the comprehensive understanding of the complex electrochemistry of Li–S batteries.Finally,future perspectives are provided to inspire innovations capable of defeating existing restrictions.

Designing principles of advanced sulfur cathodes toward practical lithium-sulfur batteries

As one of the most promising candidates for next-generation energy storage systems,lithium-sulfur(Li-S)batteries have gained wide attention owing to their ultrahigh theoretical energy density and low cost.Nevertheless,their road to commercial application is still full of thorns due to the inherent sluggish redox kinetics and severe polysulfides shuttle.Incorporating sulfur cathodes with adsorbents/catalysts has been proposed to be an effective strategy to address the foregoing challenges,whereas the complexity of sulfur cathodes resulting from the intricate design parameters greatly influences the corresponding energy density,which has been frequently ignored.In this review,the recent progress in design strategies of advanced sulfur cathodes is summarized and the significance of compatible regulation among sulfur active materials,tailored hosts,and elaborate cathode configuration is clarified,aiming to bridge the gap between fundamental research and practical application of Li-S batteries.The representative strategies classified by sulfur encapsulation,host architecture,and cathode configuration are first highlighted to illustrate their synergetic contribution to the electrochemical performance improvement.Feasible integration principles are also proposed to guide the practical design of advanced sulfur cathodes.Finally,prospects and future directions are provided to realize high energy density and long-life Li-S batteries.