Water based polyimide-powder coating composition and method for manufacturing composite separator for lithium secondary battery using same

A method for manufacturing a composite separator, the method comprising:

• (a) preparing a polyimide-powder by reacting a dianhydride with a diamine in water and further adding a compound represented by the following Chemical Formula 3:
• NH2—R3—Si(R4)3 [Chem. 3]
• wherein R3 is substituted or unsubstituted C1-10 alkylene or substituted or unsubstituted C1-10 heteroalkylene, wherein one or more hydrogen atoms are substituted with ═O, —OH, C1-3 alkyl or NH2 when substituted, and
• wherein each R4 is independently C1-3 alkoxy;
• (b) preparing a polyimide-binder solution by mixing the polyimide-powder prepared in step (a) with a binder;
• and
• (c) preparing a composite separator by coating a separator with the polyimide-binder solution prepared in step (b).