A Polymer Network Layer Containing Dually Anchored Ionic Liquids for Stable Lithium-Sulfur Batteries.

Lithium-sulfur (Li-S) batteries with high sulfur utilization, long-cycle life, and dendrite-free features hold great promise for the development of next-generation energy storage devices of high energy density. Considerable efforts have been committed to solving the polysulfide shuttle problem toward highly stable Li-S batteries. Here, a unique polymer network containing dually anchored ionic liquids (DA-PIL) is devolped to improve the cycling performance and coulombic efficiency of Li-S batteries. This DA-PIL electrolyte incorporates the amphiphilicity of both the polysulfides anion and lithium cation, creating an ionic function layer on polypropylene separator. Noteworthily, the DA-PIL network is "clean" in the sense that no free ionic specifies are introduced to the electrolyte system. The DA-PIL layer not only enables strong supression against polysulfide shuttling but simultaneously allows fast lithium transportation owing to cooperate electrostatic interaction among anchored cations and anions. The DA-PIL layer functionalized on a polypropylene separator can boost excellent stability of Li-S battery with >1600 h cycling test at 0.25 mA cm-2 . The Li-S cell with DA-PIL layer delivers a higher discharge capacity of 827.4 mAh g-1 at 1C. A discharge capacity of 630.6 mAh g-1 is retained after 1000 cycles.

Emerging Ferroelectric Uniaxial Lamellar (Smectic AF) Fluids for Bistable In-Plane Polarization Memory.

The emerging matter category of liquid-matter ferroelectrics, i.e., ferroelectric nematics, demonstrates an unprecedented combination of fluidity and spontaneous polarization. However, unlike traditional ferroelectrics, the field-switched polarization at zero-field cannot be conserved, so the memory effect remains challenging. Here we report another new type of ferroelectric liquid crystal state, dubbed the ferroelectric smectic A phase, where the polarization is longitudinally coupled to the smectic quasi-layer order. With higher packing density, the phase exhibits higher values of refractive anisotropy and spontaneous polarization compared to the ferroelectric nematics. A delicate balance between the liquid crystal elasticity and flow viscosity enables both the switching and memory of the polarization field, thus opening the door toward realizing liquid-matter ferroelectric memory devices.

Development of emergent ferroelectric nematic liquid crystals with highly fluorinated and rigid mesogens.

The emerging ferroelectric nematic liquid crystals have been attracting broader interests in new liquid crystal physics and their unique material properties. One big challenge for the ferroelectric nematic research is to enrich the material choice, which is now limited to RM734 and DIO families as representatives, in sharp contrast to the enormously diverse variety of the traditional apolar nematic liquid crystals. Here, we report a design of novel ferroelectric nematic materials with highly fluorinated and rigid mesogens. Noteworthily, they show distinct chemical structural features compared with previous aromatic ester-based molecules. The ferroelectric nematic phase was identified and confirmed through rigorous experiments. The bulk polarization was found to become purely along the long axis director, creating giant dielectric anisotropy. This work demonstrates a great potential for expanding ferroelectric nematic material diversity and will accelerate the corresponding application research and technology innovation.