A review on electronically conducting polymers for lithium-sulfur battery and lithium-selenium battery:Progress and prospects

Lithium-sulfur(Li-S) batteries and lithium-selenium(Li-Se) batteries,as environmental protection energy storage systems with outstanding theoretical specific capacities and high energy densities,have become the hotspots of current researches.Besides,elemental S(Se) raw materials are widely sourced and their production costs are both low,which make them considered one of the new generations of high energy density electrochemical energy storage systems with the most potential for development.However,poor conductivity of elemental S/Se and the notorious "shuttle effect" of lithium polysulfides(polyselenides) severely hinder the commercialization of Li-S/Se batteries.Thanks to the excellent electrical conductivity and strong absorption of lithium polysulfide(polyselenide) about electronically conducting polymer,some of the above thorny problems have been effectively alleviated.The review presents the fundamental studies and current development trends of common electronically conducting polymers in various components of Li-S/Se batteries,which involves polyaniline(PANI) polypyrrole(PPy),and polythiophene(PTh) with its derivatives,e.g.polyethoxythiophene(PEDOT) and poly(3,4-ethylene dioxythiophene)-poly(styrenesulfonate)(PEDOT:PSS).Finally,the review not only summarizes the research directions and challenges facing the application of electronically conducting polymers,but also looks forward to the development prospects of them,which will provide a way for the practical use of electronically conducting polymers in Li-S/Se batteries with outstanding electrochemical properties in the short run.

A versatile nano-TiO_(2) decorated gel separator with derived multi-scale nanofibers towards dendrite-blocking and polysulfide-inhibiting lithium-metal batteries

In this study,a versatile fluorine-bearing gel membrane with multi-scale nanofibers was rationally designed and synthesized via facile one-step blend electrospinning of nano-titanium dioxide(TiO_(2))particles and fluorinated poly-m-phenyleneisophthalamide(PMIA)polymer solution.The prepared multiscale TiO_(2)-assisted gel separator presented relatively high porosity,small aperture,giving rise to superior affinity to electrolyte and sufficient active sites to accelerate lithium ions migration.Meanwhile,the asfabricated multifunctional GPE also rendered outstanding heat-resistance and well-distributed lithiumions flux,and the mutual overlaps between the coarse fibers and the fine fibers within the multi-scale nanofiber membrane provided a strong skeleton support,which in turn laid a solid footing stone for high-security and dendrite-proof batteries.Particularly,the nano-TiO_(2) particles within PMIA membrane acted as"gatekeepers",which can not only resist the growth of lithium dendrites,but also intercept the dissolved polysulfide on cathode side.Based on these merits,the gel PMIA-based lithium cobalt(LCO)/lithium battery obtained the remarkably improved rate capability and cycle performances on account of superior ionic conductivity,steady anodic stability window and weakened polarization behavior.Meanwhile,the resultant lithium-sulfur cell also delivered the outstanding cycling stability with the aid of the greatly prevented"shuttle effect"of dissolved lithium polysulfides based on the physical trapping and chemical binding of the prepared GPE to polysulfides species.This work proved that the addition of functional inorganic nanoparticles similar with TiO_(2) in multi-scale gel PMIA membrane can enhance the lithium ions transport capability,resist the growth of lithium dendrites as well as inhibit the shuttle effect of polysulfides,which would prompt a great development for dendrite-blocking and polysulfideinhibiting lithium-metal cells.

Characterization of CsWRKY29 and CsWRKY37 transcription factors and their functional roles in cold tolerance of tea plant

The WRKY gene family is most widely known as being the key plant transcription factor family involved in various stress responses and affecting plant growth and development.In this study,a total of 86 members of the CsWRKY genes were identified from the tea plant genome.Most of these genes contain several important Cis-regulatory elements in the promoter regions associated with multiple stress-responses.These genes were further classified into three groups,I,II,and III,each with 21,58,and 7 members,respectively.We showed evidence that tandem duplications,but not the whole genome duplication,are likely to drive the amplification of CsWRKY genes in tea plants.All the 86 CsWRKY genes showed differential expression patterns either in different tissues,or under exposure to diverse abiotic stresses such as drought,cold acclimation,and MeJA treatments.Additionally,the functional roles of two genes,CsWRKY29 and CsWRKY37,were examined under cold stress;and the silencing of these genes resulted in tea plant phenotypes susceptible to cold stress.Moreover,transgenic Arabidopsis lines overexpressing CsWRKY29 and CsWRKY37 genes showed higher survival rates and lower malondialdehyde levels under freezing treatment than the wild type plants.The core findings from this work provide valuable evolutionary pattern of WRKY gene family and underpinning the underlying regulatory roles of CsWRKY29 and CsWRKY37 from tea plants that conferred cold tolerance in transgenic Arabidopsis plants.

The Reference Genome of Tea Plant and Resequencing of 81 Diverse Accessions Provide Insights into Its Genome Evolution and Adaptation

Tea plant is an important economic crop,which is used to produce the world's oldest and most widely consumed tea beverages.Here,we present a high-quality reference genome assembly of the tea plant(Camellia sinensis var.sinensis)consisting of 15 pseudo-chromosomes.LTR retrotransposons(LTR-RTs)account for 70.38%of the genome,and we present evidence that LTR-RTS play critical roles in genome size expansion and the transcriptional diversification of tea plant genes through preferential insertion in promoter regions and introns.Genes,particularly those coding for terpene biosynthesis pro-teins,associated with tea aroma and stress resistance were significantly amplified through recent tandem duplications and exist as gene clusters in tea plant genome.Phylogenetic analysis of the sequences of 81 tea plant accessions with diverse origins revealed three well-differentiated tea plant populations,support-ing the proposition for the southwest origin of the Chinese cultivated tea plant and its later spread to western Asia through introduction.Domestication and modern breeding left significant signatures on hundreds of genes in the tea plant genome,particularly those associated with tea quality and stress resis-tance.The genomic sequences of the reported reference and resequenced tea plant accessions provide valuable resources for future functional genomics study and molecular breeding of improved cul-tivars of tea plants.

Theoretical investigations of electrical transport properties in CoSb3 skutterudites under hydrostatic loadings

CoSb3-based mark mid-temperature skutterudites have been a benchthermoelectric material under intensive experimental and theoretical studies for decades. Doping and filling, to the first order, alter the crystal lattice constant of CoSb3 in the context of ＂chemical pressure.＂ In this work, we employed ab initio density functional theory in conjunction with semiclassical Boltzmann transport theory to investigate the mechanical properties and especially how hydrostatic loadings, i.e., ＂physical pressure,＂ impact the electronic band structure, Seebeck coefficient, and power factor of pristine CoSb3. It is found that hydrostatic pressure enlarges the band gap, suppresses the density of states （DOS） near the valence band edge, and fosters the band convergence between the valley bands and the conduction band minimum （CBM）. By contrast, hydrostatic tensile reduces the band gap, increases the DOS near the valence band edge, and diminishes the valley bands near the CBM. Therefore, applying hydrostatic pressure provides an alternative avenue for achieving band convergence to improve thermoelectric properties of N-type CoSb3, which is further supported by our carrier concentration studies. These results provide valuable insight into the further improvement of thermoelectric performance of CoSb3-based skutterudites via a synergy of physical and chemical pressures.

Mapping the elastic properties of two-dimensional MoS_(2) via bimodal atomic force microscopy and finite element simulation

Elasticity is a fundamental mechanical property of two-dimensional(2D)materials,and is critical for their application as well as for strain engineering.However,accurate measurement of the elastic modulus of 2D materials remains a challenge,and the conventional suspension method suffers from a number of drawbacks.In this work,we demonstrate a method to map the in-plane Young’s modulus of mono-and bi-layer MoS_(2) on a substrate with high spatial resolution.Bimodal atomic force microscopy is used to accurately map the effective spring constant between the microscope tip and sample,and a finite element method is developed to quantitatively account for the effect of substrate stiffness on deformation.Using these methods,the in-plane Young’s modulus of monolayer MoS_(2) can be decoupled from the substrate and determined as 265±13 GPa,broadly consistent with previous reports though with substantially smaller uncertainty.It is also found that the elasticity of mono-and bi-layer MoS_(2) cannot be differentiated,which is confirmed by the first principles calculations.This method provides a convenient,robust and accurate means to map the in-plane Young’s modulus of 2D materials on a substrate.

Bi-material strip based temperature sensor design and optimization through thermo-mechanical multi-physics modeling

With the capability of additive manufacturing,complex structures are easily fabricated to achieve various design purposes.In this work,a bi-material strip temperature sensor with complex periodic pattern design is purposed and investigated through both the analytical modeling and multi-physics finite element analysis.Three design patterns are considered:standard,E-shape and S-shape.In the standard solid strip design,the curvature of the bi-material strip under temperature variation is in a linear relationship with the coefficient of thermal expansion(CTE)difference,but in a reciprocal relationship with the strip thickness.The curvature of the bi-material strip depends on the Young’s modulus ratio and layer thickness ratio of the two materials,but is independent of the magnitude of the materials’Young’s modulus.Based on analytical derivation and numerical validation,the optimized design parameters can be provided.Compared to S-shape pattern design,E-shape pattern design can significantly increase the temperature sensitivity of the bi-material strip.An analytical prediction of the E-shape pattern’s temperature sensitivity is introduced and discussed.This work proves the concept that new design space becomes available with the capability of additive manufacturing,and provides the general design guideline for a bi-material strip based temperature sensor with possible design patterns.

薄壁零件残余应力演化机理及变形控制方法

变形是难加工材料薄壁零件切削加工所面临的最主要挑战之一,整个工艺过程,零件残余应力随材料去除不断演化,导致最终零件的精度很难保证。针对薄壁零件切削加工变形问题,提出一种考虑工艺过程残余应力演化的薄壁零件变形控制方法。首先,通过微元切片法建立了薄壁零件工艺过程简化模型,分析了零件夹紧点的载荷分布,建立了零件夹紧点等效载荷平衡方程;并基于变形叠加原理和微小变形理论,建立了零件夹紧点变形几何平衡方程;分析了工艺过程不同时刻的零件载荷分布情况,揭示了薄壁零件残余应力及其等效载荷演化机理。在此基础上,建立了工序间零件变形精确调控模型,实现了薄壁零件残余应力演化与最终变形控制。最后,设计了3组切削加工实验,分别采用不同加工工艺加工相同的薄板零件,实验结果表明,采用所提出的变形控制方法最大可降低加工变形82.2%。