Directing (110) Oriented Lithium Deposition through High-flux Solid Electrolyte Interphase for Dendrite-free Lithium Metal Batteries

Controlling lithium (Li) electrocrystallization with preferred orientation is a promising strategy to realize highly reversible Li metal batteries (LMBs) but lack of facile regulation methods. Herein, we report a high-flux solid electrolyte interphase (SEI) strategy to direct (110) preferred Li deposition even on (200)-orientated Li substrate. Bravais rule and Curie-Wulff principle are expanded in Li electrocrystallization process to decouple the relationship between SEI engineering and preferred crystal orientation. Multi-spectroscopic techniques combined with dynamics analysis reveal that the high-flux CF₃Si(CH₃)₃ (F₃) induced SEI (F₃-SEI) with high LiF and −Si(CH₃)₃ contents can ingeniously accelerate Li⁺ transport dynamics and ensure the sufficient Li⁺ concentration below SEI to direct Li (110) orientation. The induced Li (110) can in turn further promote the surface migration of Li atoms to avoid tip aggregation, resulting in a planar, dendrite-free morphology of Li. As a result, our F₃-SEI enables ultra-long stability of Li||Li symmetrical cells for more than 336 days. Furthermore, F₃-SEI modified Li can significantly enhance the cycle life of Li||LiFePO₄ and Li||NCM811 coin and pouch full cells in practical conditions. Our crystallographic strategy for Li dendrite suppression paves a path to achieve reliable LMBs and may provide guidance for the preferred orientation of other metal crystals.     

钙钛矿铁电纳米片诱导的P (VDF-TrFE)取向生长

Ferroelectric polymers are particularly attractive for applications in flexible electronic devices, and controlling its crystalline phase growth is crucial for obtaining optimized ferroelectric properties. Herein we report that a very low introduction (0.2% (w)) of single-domain ferroelectric PbTiO₃ nanoplates can effectively mediate the nucleation and subsequent growth of a crystalline phase within P (VDF-TrFE) (denoted by PVTF), forming highly oriented films and significantly improving the ferroelectric properties due to an alignment of the polarization directions of the polymer and the nanoplates.     

Spectroscopic analysis of post drawing relaxation in poly(lactic acid) with oriented mesophase

Uniaxial deformation of amorphous poly(lactic acid) (PLA) film was performed at 60 °C (around the glass transition temperature). The deformed samples revealed a strain-induced mesophase, and its fraction and thermal stability increased with draw strain. Further annealing was performed in situ at constant length, at the drawing temperature for the films drawn to strains of 100% and 230%. Interestingly, the orientation of amorphous phase relaxed more rapidly for the 100% sample compared with the 230% one. This could be ascribed to the constraint effect of mesophase on the amorphous chains. In addition, the chains of mesophase relaxed slightly for the 100% sample while it retained high orientation for the 230% sample. Meanwhile, the mesophase fraction decreased, and the trend was more significant for the sample drawn to 100%. These effects can be ascribed to the melting of mesophase and the different thermal stabilities of the mesophases.     

High-velocity stretching of polyolefin tapes

Stretched polyolefin films and tapes are used in many packaging applications, such as BigBags. Stretching is elongation of polymer tapes in one direction, resulting in improved mechanical properties. Both, amorphous and crystalline polymers are in principle stretchable but linear, unbranched macromolecules are highly stretchable. Hence, the stretchability of e.g. branched low density polyethylene (PE-LD) is lower than of high-density polyethylene (PE-HD). Basic requirements for stretching of thermoplastics are known, but correlations between material parameters and stretching behaviour are scarce. Moreover, stretching of polymers is usually studied with tensile tests at stretching velocities much lower (1–500 mm/min) than in industrial processes (400–1000 mm/s), while results from high-velocity stretching tests or on production machines have not been published as of yet. We investigated high-velocity (800 mm/s) stretching of PE-LD, PE-HD and isotactic polypropylene films and tapes and which stretching parameters resulted in maximum mechanical properties. It was found that sample geometry, temperature, and the degree of stretching have a significant influence on the properties of stretched tapes, e.g. higher stretching temperature resulted in higher mechanical properties and orientation of crystallites. Furthermore, about 80% of the maximum stretching degree resulted in maximum mechanical properties.     

Orientable edge colorings of graphs

An edge coloring of a graph is orientable if and only if it is possible to orient the edges of the graph so that the color of each edge is determined by the head of its corresponding oriented arc. The goals of this paper include finding a forbidden substructure characterization of orientable colorings and giving a linear time recognition algorithm for orientable colorings.An edge coloring is lexical if and only if it is possible to number the vertices of the graph so that the color of each edge is determined by its lower endpoint. Lexical colorings are, of course, the orientable colorings in which the underlying orientation is acyclic. Lexical colorings play an important role in Canonical Ramsey theory, and it is this standpoint that motivates the current study.     

“Structure and mechanical properties of blown films of ionomer-compatibilized LDPE nanocomposites”

Blown films based on low density polyethylene (LDPE) organoclay nanocomposites (NCs) were obtained by melt extrusion followed by film blowing, using a zinc ionomer of poly(ethylene-co-methacrylic acid) (Pema-Zn) as a compatibilizer. The parameters studied were the compatibilizer and the montmorillonite (MMT) contents that ranged from 0 to 20% and from 0 to 5%, respectively. The presence of clay hindered Pema-Zn crystallization indicating the existence of interaction between the Pema-Zn and the clay. Analysis of the nanostructure showed that the MMT was found inside microscopic domains of Pema-Zn distributed throughout the LDPE matrix. The addition of Pema-Zn improved the dispersion of the clay in LDPE films resulting in synergistic improvements in the mechanical properties. These improvements occur both in the machine and transverse directions. Thus, the presence of Pema-Zn is a determining factor in biaxiality and can clearly be attributed to the bidimensional laminar structure of clays such as MMT.     

高分子量级分含量对熔体挤出拉伸法制备聚丙烯微孔膜的影响

通过熔体挤出拉伸法以两种聚丙烯为原料制备微孔膜.通过考察原料分子量数据发现高分子量聚丙烯(PPH)在高分子量级分(重均分子量>106)含量上大于低分子量聚丙烯(F401).PPH的弛豫时间在相同条件下也远大于F401.红外二向光法结果表明,PPH在相同熔体牵伸比下片晶取向度较F401高.相同加工条件下PPH微孔膜片较F401成孔分布更均匀,孔径尺寸也更均匀.2种微孔膜孔隙率都随熔体牵伸比的增加而提高,微孔分布随着熔体牵伸比的提高和片晶取向度的增加而趋于均匀,孔尺寸也随之区域均匀.研究表明,聚合物树脂中高分子量级分含量是影响预制膜中片晶取向度、冷热拉伸成孔分布和尺寸均匀度的重要影响因素.     

Effect of Draw Ratio on the Morphologies and Properties of BPDA/PMDA/ODA Polyimide Fibers

3,3,4,4-Biphenyltetracarboxylic dianhydride/pyromellitic dianhydride/4,4-oxydianiline（BPDA/PMDA/ODA） polyimide copolymer fibers with different draw ratios were prepared from the imidization of polyacrylic acid（PAA） fibers via a dry-jet wet-spinning process.Their morphologies,microcrystal orientations,thermal stabilities,and mechanical properties were investigated via scanning electron microscopy（SEM）,wide angle X-ray diffraction（WAXD）,thermogravimetric analysis（TGA）,and tensile experiments.In order to acquire fibers with better mechanical performance,we aimed at obtaining the optimal draw ratio.Drawing during thermal imidization resulted in a decreased diameter of fiber from 25.8 μm to 16.9 μm corresponding to draw ratio from 1 to 3.5.WAXD results show that the degree of the orientation of the undrawn sample is 64.1％,whereas that of the drawn sample is up to 82％.The as-spun fiber and those with different draw ratios all exhibit high thermal stabilities,i.e.,the temperature at a mass loss of 5％ can reach as high as 570 ℃.The tensile strengths and tensile modulus of the fibers increase with the draw ratios,and the maximum tensile strength and modulus are 0.90 and 12.61 GPa,respectively.     

DC与CC 5052铝合金冷轧后沿厚度方向织构分布状态对比的X射线衍射分析

采用X射线衍射测试极图、使用专用软件计算织构取向分布函数(ODF), 研究了热轧后454℃×4h再结晶退火的直接铸造5052铝合金板(DC 5052)和双履带连续冷却铸造5052铝合金板(CC 5052)冷轧制到不同压下量的试样,自表层至心部层的冷轧织构分布差别,为工业上生产及应用DC 5052与CC 5052铝合金冷轧板提供依据。结果显示：同样的大压下量时CC 5052的β织构强度及体积分数高于DC 5052的。冷轧前CC 5052的再结晶织构Cube的体积分数小于DC 5052的,剩余位向的体积分数多于DC 5052的,导致CC 5052表层的β织构强度及体积分数达到与1/4层、中心层接近所需要的冷轧压下量比DC 5052试样需要的小。CC 5052冷轧板冲压加工方面的性能优于DC 5052冷轧板。     

Control of morphology orientation in thin films of PS-b-PEO diblock copolymers and PS-b-PEO/resorcinol molecular complexes

One of the main limits in the use of block copolymers for nanotechnological applications lies in the poor control over the alignment of the nanoscopic domains. The self-assembling behavior of polystyrene-block-poly(ethylene oxide) (PS-b-PEO) has been modified by stoichiometric complexation of the ethylene oxide units with resorcinol and a simple procedure to prepare nanostructured films with normally oriented cylinders is reported. By direct spin coating of a series of complexated PS-b-PEO samples with different molecular weight and composition, films with the same morphology and orientation (i.e., normally oriented packed cylinders) have been obtained, also when different nanostructures and alignments were expected on the basis of the volume fraction composition and self-assembling behavior of pure copolymers. Tuning of the cylinder diameters in the range from 20 to 50 nm was possible by varying the length of the PEO block. The effects of resorcinol complexation have been studied by differential scanning calorimetry and X-ray diffraction and the morphologies of PS-b-PEO and PS-b-PEO/resorcinol films have been monitored by atomic force microscopy and electron microscopies. DSC and XRD analyses demonstrate that resorcinol significantly influences the crystallization behavior of the PEO block. The varied interfacial and surface energies of the PEO domains and the overall reduction of the crystalline phase in PS-b-PEO/resorcinol films appear to be strictly related to the morphological changes occurring by complexation.