Porous polyimide film, secondary battery separator, and secondary battery
A porous polyimide film has plural pores, in which an average flattening of the plural pores is within a range of 0.1 to 0.7, a coefficient of variation of a distance between adjacent pores is within a range of 0.10 to 0.40, and a front surface and aback surface communicate with each other through the plural pores.
1. A porous polyimide film comprising:
the porous polyimide film has a plurality of pores, an average flattening of the plurality of pores is within a range of 0.1 to 0.7, a coefficient of variation of a distance between adjacent pores is within a range of 0.10 to 0.40, and a front surface and a back surface communicate with each other through the plurality of pores.
2. The porous polyimide film according to claim 1 ,
wherein the average flattening is within a range of 0.2 to 0.7.
3. The porous polyimide film according to claim 1 ,
wherein a porosity of the porous polyimide film is within a range of 45% to 85%.
4. The porous polyimide film according to claim 1 ,
wherein an average major axis of the plurality of pores is within a range of 50 nm to 1,500 nm.
5. The porous polyimide film according to claim 1 ,
wherein a tensile breaking strength of the porous polyimide film is 20 MPa or more.
6. The porous polyimide film according to claim 1 ,
wherein an air permeability is 300 seconds/100 mL or less.
7. The porous polyimide film according to claim 6 ,
wherein the air permeability is 270 seconds/100 mL or less.
8. A secondary battery separator comprising the porous polyimide film according to claim 1 .
9. A secondary battery comprising the secondary battery separator according to claim 7 .