Hou Jian, Jang Wongi, Kim Sungyul, Kim Jun-Hyun, Byun Hongsik
Department of Chemical Engineering, Keimyung University Daegu 42601 South Korea
Department of Chemistry, Illinois State University Normal Illinois 61790-4160 USA.
RSC Adv. 2018 Apr 19;8(27):14958-14966. doi: 10.1039/c8ra01556b. eCollection 2018 Apr 18.
We describe a new strategy to prepare thermally- and electrochemically-stable polyimide (PI) nanofiber membranes by the hot-press treatment of polyamic acid (PAA) nanofiber sheets and examine their performance as Li-ion battery separators. Typical thermal imidization of PAA to PI membranes using sequential high temperature treatments in an oven takes a long time, but our method readily completes this conversion process at a mild temperature in 30 min while generating a high probability of inter-nanofiber imidization. Along with the improved electrolyte uptake capability and uniform distribution of the pore size and porosity caused by the dense and compact arrangements, the hot-press-induced PI membrane exhibits relatively thin sheets and a much greater mechanical strength than the membrane prepared by the thermal treatment. Subsequently, these PI-based membranes are installed in Li-ion full coin cells as battery separators whose C-rate (charging and discharging) performances are comparable to a commercial polyethylene (PE) separator. In addition, the highly improved thermal stabilities of these PI separators over PE separators are observed during thermal shrinkage and hot-box tests. Overall, our strategy can allow for the manufacture of diverse PI-based membranes with minimal preparation time and cost that can be utilized in high power portable devices requiring thermal and electrochemical stability.
我们描述了一种通过对聚酰胺酸（PAA）纳米纤维片进行热压处理来制备热稳定和电化学稳定的聚酰亚胺（PI）纳米纤维膜的新策略，并研究了它们作为锂离子电池隔膜的性能。使用烘箱中的连续高温处理将PAA典型地热亚胺化为PI膜需要很长时间，但我们的方法在温和温度下30分钟内即可轻松完成此转化过程，同时产生高概率的纳米纤维间亚胺化。由于致密和紧凑的排列导致电解质吸收能力提高以及孔径和孔隙率分布均匀，热压诱导的PI膜呈现出相对较薄的片材，并且比通过热处理制备的膜具有更大的机械强度。随后，这些基于PI的膜被安装在锂离子全硬币电池中作为电池隔膜，其C速率（充电和放电）性能与商用聚乙烯（PE）隔膜相当。此外，在热收缩和热箱测试中观察到这些PI隔膜相对于PE隔膜具有高度改善的热稳定性。总体而言，我们的策略可以在最短的制备时间和成本下制造出各种基于PI的膜，这些膜可用于需要热稳定性和电化学稳定性的高功率便携式设备。
