聚酰亚胺纤维/溶解浆混合制备锂电池隔膜的研究

Preparation of Lithium Battery Separator with Mixed Polyimide Fiber/Dissolving Pulp

为制备一种耐高温、强度大的锂电池隔膜,本研究以聚酰亚胺(PI)短切纤维和溶解浆为基材,采用湿法造纸技术制备PI/溶解浆隔膜,并对隔膜的物理性能进行了测定。结果表明,单独使用PI纤维制备的隔膜的抗张指数、孔隙率、孔径、吸液率分别为16.7N·m/g、2.8%、82.7μm、440%;PI纤维和溶解浆混抄,溶解浆用量为25%时,制备的PI/溶解浆隔膜的抗张指数、孔隙率、孔径、吸液率分别为17.0N·m/g、4.3%、21.2μm、594%,性能指标均高于前者。与PI纤维隔膜相比,添加溶解浆后的PI纤维表面有松散的絮状物,纤维之间不存在明显的间隙,溶解浆的存在使得纤维交织成多孔结构。传统的聚烯烃(PP)隔膜在加热至200℃时已经完全熔融收缩,而PI隔膜和PI/溶解浆隔膜加热至200℃时,尺寸未发生任何变化,因此PI隔膜和PI/溶解浆隔膜的热尺寸稳定性远优于传统的PP隔膜。

Traditional lithium ion battery separator are polyolefin-based membranes which have low heat resistance. Battery explosion often occurs due to the exothermic reactions during charge-discharge processes. In order to improve the safety level of lithium ion batteries, it is of necessity to prepare separators with high heat resistance and high mechanical strength. In this paper, novel lithium ion battery separators were prepared via a wet-laid papermaking technology from polyimide (PI) fibers and dissolving wood pulp. Results showed that the tensile index, porosity, pore size and electrolyte absorption of polyimide separators were 16.7 N · m/g, 2.8%, 82.7 μm and 440%, respectively, while those of the separators prepared from mixing PI fibers and dissolving pulp (dissdving pulp dosage of 25%) were 17.0 N · m/g, 4.3%, 21.2 μm, 594%, respectively, which were better than those of the former. Dissolving pulp filled the gap between the polyimide fibers and reduced the pore size without affecting the porosity. Dissolving pulp also significantly improved the electrolyte absorption of separators due to its inherent porous and hydrophilic property. The polyolefin(PP) separator was completely melt-shrinked at 200℃ but the size of the PI separator and PI/dissolving pulp composite separator did not change.Therefore, the thermal dimensional stability of the PI separator and PI/dissolving pulp composite separator was much better than that of the conventional polyolefin separator.