Battery, battery separator and method for producing battery separator

A method for producing a battery separator, the method comprising the steps of:

• (i) feeding a substrate sheet into a nanofiber-forming space;
• (ii) in the nanofiber-forming space, forming nanofibers by electrostatic force from a raw material solution including a solvent and a resin raw material dissolved in the solvent, and depositing the formed nanofibers on a principal surface of the substrate sheet to form a porous sheet having a matrix structure of nanofibers;
• and
• (iii) joining a pair of the porous sheets to each other, with surfaces having been in contact with the principal surface of the substrate sheet facing each other, to form a battery separator having a first surface and a second surface opposite to the first surface, said first and second surfaces corresponding to surfaces of the pair of the porous sheets not having been in contact with the principal surface of the substrate sheet.

A method for producing a battery separator in which:

• long first and second substrate sheets are conveyed from upward toward downward of first and second lines, respectively, to form first and second porous sheets on principal surfaces of the first and second substrate sheets on the upstream side of the lines, respectively;
• and the first and second porous sheets are joined face to face on the downstream side of the lines, the method comprising the steps of:
• (i) conveying the first and second substrate sheets into nanofiber-forming spaces on the upstream side of the first and second lines, respectively;
• (ii) in the nanofiber-forming spaces, forming nanofibers by electrostatic force from a raw material solution including a solvent and a resin raw material dissolved in the solvent, and depositing the formed nanofibers on the principal surfaces of the conveyed first and second substrate sheets, respectively, to form first and second porous sheets each having a matrix structure of nanofibers;
• (iii) removing the first and second substrate sheets from the conveyed first and second porous sheets, on the downstream side of the first and second lines;
• and
• (iv) joining the conveyed first and second porous sheets to each other on the further downstream side of the first and second lines, with surfaces having been in contact with the principal surfaces of the first and second substrate sheets facing each other, to form a nanofiber sheet.