Preparation and properties of aramid coating separator for lithium battery
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 synthe-tized under a nitrogen atmosphere.Aramid adhesive solution(solid content of 5%)and alumina(Al2O3)were added to N-methylpyrrolidone to obtain aramid coating solution by high speed dispersion,then the coating liquid was coated on the polyethyl-ene porous substrate and the aramid coating separator for lithium ion battery was prepared by a phase inversion method.The incorpo-ration 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 cm3)/µm to 10(s/100 cm3)/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 separa-tor decreases from 6.22 mm2 in the pure PE separator to 0.36 mm2,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.
lithium batteryseparatoraramidpore structurethermal nail penetration area
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