二氧化硅/聚乙烯醇多孔层对锂离子电池用聚丙烯隔膜性能的影响

Effect of Silica/Polyvinyl Alcohol Porous Layers on Performance of Polypropylene Separators for Lithium-ion Batteries

以二氧化硅(Si O2)为陶瓷颗粒,以聚乙烯醇(PVA)为粘结剂,以水为分散介质,制备出一种水性Si O2分散液.采用浸涂法将Si O2陶瓷层涂覆到聚丙烯(PP)隔膜表面.对Si O2/PVA涂覆层的表面及断面形貌进行了表征,对原隔膜及复合隔膜的孔结构进行了分析,对水及水性Si O2分散液在隔膜表面的接触角进行了测试,并研究了陶瓷涂覆层对隔膜热稳定性、润湿性、吸液量、离子电导率、倍率性能及循环性能的影响.测试结果表明,涂覆层具有多孔网络结构,其厚度仅为800 nm.涂覆层的引入,使复合隔膜的孔隙率增大到62.9%,而其Gurley数则降低到515 s.与原隔膜相比,复合隔膜的热收缩率降低,液体电解液对复合隔膜的润湿性明显改善,复合隔膜的吸液量和离子电导率增大,电池倍率性能和循环性能提高.

A water-based silica （SiO2） dispersion was prepared with SiO2 as ceramic particle and polyvinyl alcohol （PVA） as binder, and the composite separator for lithium-ion batteries was prepared by the introduction of SiO2 layer on both sides of polypropylene （PP） separator surface through a dip-coating process. The surface and cross-section morphology of SiOJPVA layer were investigated, and the porous structure of pristine and composite separators was quantitatively analyzed by the porosity and the Gurley value. The contact angles of water and water-based SiO2 dispersion with and without the surfactant on PP surface were measured, and the influence of the coated layers on thermal stability, wettability, electrolyte uptake,ionic conductivity, C- rate capability and cyclability was researched. The test results showed that the coated layer had porous network structure and its thickness was only 800 nm. Owing to the introduction of the porous thin layer on PP separator surface, the porosity of the composite separator increased to 62.9% and the Gurley value of composite separator decreased to 515 s. Compared to the pristine separator, the composite separator showed not only lower thermal shrinkage but also better wettability with liquid electrolyte and higher electrolyte uptake. Furthermore, the composite separator exhibited higher ionic conductivity and better cell performance such as C-rate capability and cycle performance.