STTR Phase I: A Roll-to-Roll Process for Manufacturing Nanocellular Polymeric Thin Films

这个小型企业技术转移研究（STTR）第一阶段项目旨在开发一种卷对卷、固态、连续的工艺，用于制造纳米热塑性薄膜，这种薄膜具有10-100纳米的开放（相互连接）或封闭（不相互连接）电池，孔隙率高达50%。该项目的初步应用是一种改进型锂离子电池隔膜，该隔膜由10-25微米厚度的纳米多孔聚醚酰亚胺（PEI）薄膜和均匀分布的互连10-50纳米尺寸的电池组成。纳米多孔PEI分离器的耐热性明显高于目前的聚烯烃基分离器，解决了一个非常紧迫的安全问题，即由于分离器的热不稳定性导致电池爆炸和起火。此外，与目前制造电池隔膜的多步骤过程相比，这种连续过程的生产率更高，从而提高了韩国在电池制造方面的全球竞争力。到2020年，用于一次（一次性）和二次（可充电）锂电池的分离器的全球潜在市场总额预计将达到16.5亿美元，增长4.7%。这一创新的研究项目将为热塑性聚合物薄膜中的气体扩散和细胞成核领域提供新的知识，并使全新一类固态纳米细胞聚合物薄膜的开发、表征和应用成为可能。这个项目的智力价值在于开发一种制造工艺，将跨学科的知识结合起来，在各种工艺条件下合成和表征纳米结构。这一新知识将推动纳米制造领域的发展，并将用于优化实现商业化目标的过程。有两个技术挑战：(i)动态密封概念，该概念已在250微米厚的聚合物薄膜中得到验证，但在厚度低10-20倍的薄膜中则不适用；（ii）在细胞成核和生长过程中保持足够的气体浓度以产生纳米级细胞。该项目的目标是：(a)建立以1米/分钟的最低速度生产纳米细胞热塑性薄膜的卷对卷工艺的可行性；(b)开发100毫米宽、10-25微米厚的纳米多孔聚醚酰亚胺（PEI）薄膜，该薄膜具有锂离子电池隔膜应用所需的性能和纳米结构轮廓。通过实施动态密封技术，连续处理100毫米宽的薄膜，并立即加热薄膜以产生纳米电池，可以实现这两个目标。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

This Small Business Technology Transfer Research (STTR) Phase I project aims at developing a roll-to-roll, solid-state, continuous process for manufacturing nanocellular thermoplastic films with open (interconnected) or closed (not interconnected) cells of the order 10-100 nm and as much as 50% porosity. The initial application of this proposed project is an improved Lithium-ion battery separator comprising a nanoporous polyetherimide (PEI) film of 10-25-micron thickness with uniformly distributed interconnected 10-50 nm size cells. The nanoporous PEI separator, which has significantly higher heat resistance than current polyolefin-based separators, addresses a very urgent safety issue, i.e., batteries exploding and causing fire due to thermal instability of the separator. Moreover, compared to the current multi-step process for fabricating battery separators, this continuous process will have higher productivity thereby increasing the nation's global competitiveness in battery manufacturing. The total addressable global market for separators used in both primary (single-use) and secondary (rechargeable) lithium batteries is projected to be $1.65 billion by 2020 growing at 4.7%. This innovative research project will contribute to new knowledge in the areas of gas diffusion and cell nucleation in thermoplastic polymeric films and enable development, characterization and application of a whole new class of solid-state nanocellular polymer films.The intellectual merit of this project resides in the development of a manufacturing process that brings together interdisciplinary knowledge to synthesize and characterize nanostructures under various process conditions. This new knowledge will advance the field of nanomanufacturing and will be used to optimize processes towards commercialization targets. There are two technical challenges: (i) the dynamic seal concept, which has been proven in a 250-micron thick polymer film but not for a film 10-20 times lower in thickness; and (ii) maintaining enough gas concentration during the cell nucleation and growth to create nano-sized cells. The goals of this project are to: (a) establish the feasibility of a roll-to-roll process operating at a minimum speed of 1 meter/minute to produce nanocellular thermoplastic films and (b) develop a 100-mm wide, 10-25 micron thick nanoporous polyetherimide (PEI) film having the desired properties and nanostructure profile for a Li-ion battery separator application. These two goals will be achieved by implementing the dynamic seal technology to process a 100-mm wide film on a continuous basis and immediately heating the film to create nanocells.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.