Comparison of the Structural Evolution of β Polypropylene during the Sequential and Simultaneous Biaxial Stretching Process

Engineering Polymer-Based Porous Membrane for Sustainable Lithium-Ion Battery Separators

Due to the growing demand for eco-friendly products, lithium-ion batteries (LIBs) have gained widespread attention as an energy storage solution. With the global demand for clean and sustainable energy, the social, economic, and environmental significance of LIBs is becoming more widely recognized. LIBs are composed of cathode and anode electrodes, electrolytes, and separators. Notably, the separator, a pivotal and indispensable component in LIBs that primarily consists of a porous membrane material, warrants significant research attention. Researchers have thus endeavored to develop innovative systems that enhance separator performance, fortify security measures, and address prevailing limitations. Herein, this review aims to furnish researchers with comprehensive content on battery separator membranes, encompassing performance requirements, functional parameters, manufacturing protocols, scientific progress, and overall performance evaluations. Specifically, it investigates the latest breakthroughs in porous membrane design, fabrication, modification, and optimization that employ various commonly used or emerging polymeric materials. Furthermore, the article offers insights into the future trajectory of polymer-based composite membranes for LIB applications and prospective challenges awaiting scientific exploration. The robust and durable membranes developed have shown superior efficacy across diverse applications. Consequently, these proposed concepts pave the way for a circular economy that curtails waste materials, lowers process costs, and mitigates the environmental footprint.

β-Nucleated Polypropylene: Preparation, Nucleating Efficiency, Composite, and Future Prospects

The β-crystals of polypropylene have a metastable crystal form. The formation of β-crystals can improve the toughness and heat resistance of a material. The introduction of a β-nucleating agent, over many other methods, is undoubtedly the most reliable method through which to obtain β-PP. Furthermore, in this study, certain newly developed β-nucleating agents and their compounds in recent years are listed in detail, including the less-mentioned polymer β-nucleating agents and their nucleation characteristics. In addition, the various influencing factors of β-nucleation efficiency, including the polymer matrix and processing conditions, are analyzed in detail and the corresponding improvement measures are summarized. Finally, the composites and synergistic toughening effects are discussed, and three potential future research directions are speculated upon based on previous research.

Low-Cost Mass Manufacturing Technique for the Shutdown-Functionalized Lithium-Ion Battery Separator Based on Al2O3 Coating Online Construction during the β-iPP Cavitation Process

A shutdown-functionalized lithium-ion battery separator plays a pivotal role in preventing thermal runaway as cells experience electrical abuse, overcharge, and external short circuit. In this article, the trilayer separator endowed with shutdown function was fabricated by ingenious co-extrusion and bidirectional drawing based on the nano-Al₂O₃ coating online construction during the β-iPP cavitation process. The middle layer composed of nano-Al₂O₃, polyethylene, and polypropylene offers a shutdown temperature of 130 °C, and skin polypropylene layers with nano-Al₂O₃ coating hold optimized dimensional stability below the meltdown temperature. Crystal structure measurement and pore structure diagnosis disclose that nano-Al₂O₃ thins coarse fibrils and makes the porous structure uniform. De-bonding of nano-Al₂O₃/β-iPP interfaces retains nano-Al₂O₃ not only on the top surface of the separator but also on the pore intine to realize nano-Al₂O₃ coating online construction, consequently strengthening tensile capacity, dimensional stability to heating, and electrolyte affinity. Electrochemical tests further disclose that nano-Al₂O₃ coating stabilizes solid electrolyte interphase germination and heightens lithium-ion migration numbers, confining cell resistances and granting optimal high-rate performance and cycling ability. The proposed approach features simple technics, environment-friendly, continuous fabrication, and coating online construction, which can offer new ideas for the mass fabricating of the high-end separator.