锂电池用芳纶涂覆隔膜的制备及其性能

Preparation and properties of aramid coating separator for lithium battery

氮气气氛下,以对苯二胺、对苯二甲酰氯为单体,N-甲基吡咯烷酮为溶剂,氯化钙为助溶剂,合成了对位芳纶聚合物胶液。将芳纶胶液(固含量5%)和氧化铝(Al2O3)加入到N-甲基吡咯烷酮,进行高速分散,得到芳纶涂布液,将涂布液涂覆在聚乙烯多孔基材上,通过浸渍相反转的方法得到锂离子电池用芳纶涂覆隔膜。在芳纶基体中加入成核剂无机Al2O3后,能够促进异相成核,降低孔成核所需克服的自由能垒,增大相分离过程中成孔概率。结果表明,涂层中Al2O3的含量增大时,表面纤维致密性降低,孔尺寸增大,孔数量增多。当Al2O3与芳纶的质量比由1∶2变为5∶1时,单位涂层厚度Gurley值由33 (s/100 cm^(3))/μm减小至10 (s/100 cm^(3))/μm (减小了69.7%),透气度提升明显。当Al2O3与芳纶的质量比为1∶2时,热针刺面积由纯PE膜的6.22 mm^(2)减小至0.36 mm^(2),相较于PE膜减小了94.21%,与此同时,130℃下芳纶隔膜的热收缩率也相应减小,表明使用芳纶涂覆PE膜能够提升PE膜在锂电池中使用过程中的安全性能。

P-phenylenediamine and p-phenyldimethyl chloride were took as the monomers,N-methylpyrrolidone was employed as the solvent,while calcium chloride was served as a co-solvent,the para aramid polymer adhesive solution was synthetized under a nitrogen atmosphere.Aramid adhesive solution(solid content of 5%)and alumina(Al2O3)were added to Nmethylpyrrolidone to obtain aramid coating solution by high speed dispersion,then the coating liquid was coated on the polyethylene porous substrate and the aramid coating separator for lithium ion battery was prepared by a phase inversion method.The incorporation of inorganic Al2O3 as a nucleating agent into the aramid fiber matrix facilitates heterogeneous nucleation,and reduces the free energy barrier required for pore formation,and enhances the probability of pore generation during phase separation.The results show that with constantly increasing of alumina content in aramid coating,the fiber compactness on the surface decreases,the pore size and number of pores increases.When the mass ratio of Al2O3 to aramid changes from 1∶2 to 5∶1,the Gurley value per unit coating thickness also gradually decreases from 33(s/100 cm^(3))/μm to 10(s/100 cm^(3))/μm(decreases by 69.7%),air permeability is improved significantly.When the mass ratio of Al2O3 to aramid is 1∶2,the thermal nail penetration area of the aramid-coated separator decreases from 6.22 mm^(2) in the pure PE separator to 0.36 mm^(2),representing a reduction of 94.21%compared to that of the PE separator.Additionally,the thermal shrinkage rate of the aramid coating separator at 130℃is also minimized,further indicating that the use of aramid for coating PE separator can improve the safety performance of PE separator during use in lithium batteries.