Laminated body, separator, and nonaqueous secondary battery
A first laminated body includes: a porous film containing a polyolefin as a main component; and a porous layer on at least one surface of the porous film, the porous layer containing a resin. A second laminated body includes: a porous film containing a polyolefin as a main component; and a porous layer containing a resin. The laminated body is usable as a secondary battery separator having a higher dielectric strength. A third laminated body is provided in which occurrence of a curl is prevented. A nonaqueous secondary battery separator is provided disposed between a cathode and an anode, the separator including: a porous base material containing a polyolefin as a main component; and a porous layer on at least one surface of the porous base material, the porous layer containing a polyvinylidene fluoride-based resin.
1. A separator, comprising:
a laminated body comprising:
a stack of (i) a first porous layer containing a polyolefin-based resin and (ii) a second porous layer containing a polyvinylidene fluoride-based resin,
a difference between (A) a water content rate of the laminated body in an atmosphere having a dew point of 20° C. and (B) a water content rate of the laminated body in an atmosphere having a dew point of −30° C. is 100 ppm or more and 1000 ppm or less,
a difference between (C) a water content of the first porous layer and (D) a water content of the second porous layer both in an atmosphere having a dew point of 20° C. is 1 mg/m 2 or more and 10 mg/m 2 or less, and
respective openings of pores each having an area of 0.5 μm 2 or more occupying 0.001% to 30% of a surface of the second porous layer.
2. The separator according to claim 1 ,
wherein
the respective openings occupy 5% or less of the surface of the second porous layer.
3. The separator according to claim 1 ,
wherein
the second porous layer either (i) has a structure in which skeletons each having a diameter of 1 μm or less are connected to each other to form a three-dimensional network or (ii) contains a fine resin particle.
4. The separator according to claim 3 ,
wherein
the fine resin particle is of a resin having a structure unit derived from α-olefin having 2 to 4 carbon atoms.
5. A nonaqueous secondary battery, comprising the separator according to claim 1 .