Multilayered PVDF-HFP Porous Separator via Phase Separation and Selective Solvent Etching for High Voltage Lithium-Ion Batteries.

The development of highly porous and thin separator is a great challenge for lithium-ion batteries (LIBs). However, the inevitable safety issues always caused by poor mechanical integrity and internal short circuits of the thin separator must be addressed before this type of separator can be applied to lithium-ion batteries. Here, we developed a novel multilayer poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) membrane with a highly porous and lamellar structure, through a combination of evaporation-induced phase separation and selective solvent etching methods. The developed membrane is capable of a greater amount of electrolyte uptake and excellent electrolyte retention resulting from its superior electrolyte wettability and highly porous structure, thereby offering better electrochemical performance compared to that of a commercial polyolefin separator (Celgard). Moreover, benefiting from the layered configuration, the tensile strength of the membrane can reach 13.5 MPa, which is close to the mechanical strength of the Celgard type along the transversal direction. The elaborate design of the multilayered structure allows the fabrication of a new class of thin separators with significant improvements in the mechanical and electrochemical performance. Given safer operation, the developed multilayer membrane may become a preferable separator required for high-power and high-energy storage devices.

Intertwined Nanosponge Solid-State Polymer Electrolyte for Rollable and Foldable Lithium-Ion Batteries.

Herein, we report a straigthforward procedure to prepare an excellent intertwined nanosponge solid-state polymer electrolyte (INSPE) for highly bendable, rollable, and foldable lithium-ion batteries (LIBs). The mechanically reliable and electrochemically superior INSPE is conjugated with intertwined nanosponge (IN) poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-co-HFP) and ion-conducting polymer electrolyte (PE) containing poly(ethylene glycol) diacrylate (PEGDA), succinonitrile (SCN) plasticizer, and lithium bis(trifluoromethanesilfonyl)imide (LiTFSI). The conjugated INSPE has both high strength with great flexibility (tensile strength of 2.1 MPa, elongation of 36.7%), and excellent ionic conductivity (1.04 × 10-3 S·cm-1, similar to the values of liquid electrolytes). As a result of such special combination, the as-prepared INSPE retains almost 100% of its ionic conductivity when subjected to many types of severe mechanical deformations. Therefore, the INSPE is successfully applied to bendable, rollable, and foldable LIBs that show excellent energy storage performance despite the intense mechanical deformations.

Au-Coated Honeycomb Structure as an Efficient TCO-Free Counter-Electrode for Quantum-Dot-Sensitized Solar Cells.

This study reports the fabrication of a Petri dish patterned with cylindrical micro-cavities that are produced using a one-step solvent-immersion phase-separation process. The developed 3D honeycomb Petri dish is coated with a Au film through a sputtering method to be an efficient Au-coated FTO-free electrode for quantum-dot-sensitized solar cells. Due to the high specific active surface area of the electrode with the Au-coated honeycomb structure, the energy conversion efficiency of devices that use this electrode is 5.2 % compared to 4.4 and 4.7 % by devices using an Au-coated flat Petri dish and an Au-coated FTO electrode, respectively. This design strategy offers excellent potential for the fabrication of highly efficient counter electrodes with FTO-free substrates of flexible photovoltaic devices.

Ordered cylindrical micropatterned Petri dishes used as scaffolds for cell growth.

Three-dimensional (3D) culture dish patterned with a microwell structure demonstrates a great application potential in biotechnology. This study reports on the easy fabrication of an ordered customizable honeycomb microwell array on the surface of polymer substrates including the commercial Petri dish to create a biological platform for cell culture. The fabrication method is based on a very simple solvent dip-coating technique and the methanol accumulation-induced phase separation in which a binary mixture of chloroform and methanol is used to induce a ternary solution and to guarantee the formation of the ordered pore array on the substrate. The surface topology of the honeycomb substrate is manipulated through varying the experimental conditions; notably, the obtained honeycomb structure is part of the substrate, which reveals an increase in the structure's stability for the practical applications. Honeycomb-structured Petri dish fabricated using this method is applied as a scaffold for cell growth to demonstrate its potential in biomedical applications.

Ionic Liquid-Based Polymer Electrolytes via Surfactant-Assisted Polymerization at the Plasma-Liquid Interface.

We first report an innovative method, which we refer to as interfacial liquid plasma polymerization, to chemically cross-link ionic liquids (ILs). By this method, a series of all-solid state, free-standing polymer electrolytes is successfully fabricated where ILs are used as building blocks and ethylene oxide-based surfactants are employed as an assisted-cross-linking agent. The thickness of the films is controlled by the plasma exposure time or the ratio of surfactant to ILs. The chemical structure and properties of the polymer electrolyte are characterized by scanning electron microscopy (SEM), Fourier transformation infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR) spectroscopy, X-ray photoelectron spectroscopy (XPS), differential scanning calorimetry (DSC), and electrochemical impedance spectroscopy (EIS). Importantly, the underlying polymerization mechanism of the cross-linked IL-based polymer electrolyte is studied to show that fluoroborate or halide anions of ILs together with the aid of a small amount of surfactants having ethylene oxide groups are necessary to form cross-linked network structures of the polymer electrolyte. The ionic conductivity of the obtained polymer electrolyte is 2.28 × 10(-3) S·cm(-1), which is a relatively high value for solid polymer electrolytes synthesized at room temperature. This study can serve as a cornerstone for developing all-solid state polymer electrolytes with promising properties for next-generation electrochemical devices.

Super-amphiphilic surface of nano silica/polyurethane hybrid coated PET film via a plasma treatment.

This study first reports the fabrication of a super-amphiphilic surface using PET films with a silica-polyurethane hybrid top-coat layer through a non-thermal, one-atmospheric-pressure plasma treatment. This surface displays contact angle close to zero with both aqueous and oily liquids, which has attracted enormous attention for a wide-range of practical applications. We systematically investigated the influence of the plasma treatment time on the wetting behavior of the silica-polyurethane coated PET surface. The changes in morphology and chemical composition of PET surfaces before and after a plasma treatment were analyzed. In order to gain an insight into the formation of a super-amphiphilic PET surface and optimize the conditions under which super-amphiphilicity can be realized, we used a hemi-wicking action as a theoretical model and experimentally verified it through determining the critical angle. We also proposed a guide for designing a nano-sphere patterned PDMS surface which can generate super-wetting properties after a plasma treatment.

Large-scale fabrication of commercially available, nonpolar linear polymer film with a highly ordered honeycomb pattern.

Highly ordered, hexagonally patterned poly(methyl methacrylate) (PMMA) thin film is successfully fabricated using an improved phase separation method. A mixture of chloroform and methanol, which is used as a volatile solvent/nonsolvent pair, effectively controls the surface morphology and sensitively determines the ordered pattern. In particular, the methanol accumulation, which induces the formation of a gel-like protective layer and enhances the lateral capillary force, is crucial in the formation of the highly ordered hexagonal pattern even when using a nonpolar polymer such as PMMA. The convergence of cost-effective and large-scale production of highly ordered micropatterned film has wide potential for application, and it can enable new prospects for the commercialization of future high-tech devices that require specific multifunctionality.

Data from crosslinked PS honeycomb thin film by deep UV irradiation.

Thin polystyrene (PS) films with highly ordered honeycomb pattern were successfully fabricated by an improved phase separation method. The PS film was successfully crosslinked after applying a deep UV irradiation. This work presents a proof of crosslinking PS by characterizing ATR-FTIR, TGA and the wetting property of the honeycomb films, which were prepared using a solvent/non-solvent ratio of 90/10, before and after 6 h of UV irradiation.

A surfactant-free bio-compatible film with a highly ordered honeycomb pattern fabricated via an improved phase separation method.

Thin films of bio-compatible poly(lactic acid) with highly ordered hexagonal patterns were successfully fabricated under normal ambient conditions without using any surfactant via an improved phase separation method. The patterned surface was successfully applied to fabricate silicon/copper dome-patterned electrodes for high-performance hybrid capacitors.