采用原位成孔法制备热闭孔特性的高强度聚酰亚胺多孔薄膜

Preparation of High-Strength Polyimide Porous Films with Thermally Closed Pore Property by In Situ Pore Formation Method

提高电池隔膜的热稳定性、化学稳定性和力学强度,可以避免电池发生热失控等安全事故,对于提高电池的安全性能具有至关重要的作用。聚酰亚胺(Polyimide,PI)热稳定性优异、化学稳定性好、力学强度高,是电池隔膜材料的理想选择之一。本文研究了一种具有高温自闭孔性质的热塑性PI多孔薄膜的制备方法,通过将聚酰胺酸与有机碱三乙胺(Triethylamine,TEA)成盐,经热酰亚胺化后释放出TEA,原位成孔制备出具有高强度的PI多孔薄膜。通过红外,扫描电镜,力学性能表征等手段研究了PI多孔薄膜的成孔机理,微观形貌及影响因素,受热自闭孔历程,构效关系。研究结果表明:PI薄膜在热酰亚胺化过程中TEA脱除原位形成孔洞结构,孔洞的尺寸可以通过TEA的含量进行调控。该PI多孔薄膜具有热闭孔特性,且在闭孔前、后均呈现出优异的力学强度(~120 MPa)。本文采用原位成孔法构筑了具有优异热稳定性、高力学强度的PI多孔薄膜,该PI多孔薄膜在高温时可自闭孔,隔绝物质、热量的传输,有望为电池提供更有力的安全保障。

Improving the thermal stability,chemical stability,and mechanical strength of battery separators is crucial to prevent safety incidents like thermal runaway in batteries.This significantly enhances the overall safety performance of batteries.Among various options,polyimide(PI)stands out as an ideal choice due to its outstanding thermal stability,excellent chemical stability,and high mechanical strength.However,existing preparation methods of PI separators,such as non-solvent induced phase separation(NIPS),template method,and electrospinning,often suffer from issues like inadequate mechanical strength.Therefore,this study focused on investigating a novel method to prepare thermoplastic PI porous films with thermally closed pores and enhanced mechanical strength.Several characterization techniques,including scanning electron microscopy(SEM),in situ Fourier transform infrared spectroscopy(FTIR),and thermal gravimetric analyzer(TGA)-FTIR coupling,were employed to understand the pore-forming mechanism of PI porous films.The findings revealed that the temperature range of triethylamine(TEA)removal was consistent with the main stage of the imidization reaction and pore formation.This indicated that the pore structure was formed in situ during the thermal imidization process when TEA was stripped out of the PI film.PI films with varying TEA contents were prepared to investigate the impact on pore structure,showing that pore size could be regulated by TEA content.A more regular reticulated small pore structure on the macroporous pore wall was observed when TEA content was≥100%.SEM analysis showed that the films were thermally self-closed at a heat treatment temperature of 300℃.Additionally,TGA indicated that the thermal decomposition temperature of PI porous film reached 580℃.The mechanical strength of the PI films before and after pore closure was investigated,demonstrating excellent mechanical strength of approximately 120 MPa.The novel in situ pore formation method for PI porous films through the salt-formation method of poly(amic acid)(PAA)with the organic base TEA,followed by TEA release during thermal imidization,resulted in PI porous films with outstanding thermal stability and high mechanical strength.The self-closure of the PI porous film at high temperatures effectively isolates material and heat transport,providing robust safety assurance for batteries.This advancement has the potential to significantly improve battery safety and performance.