Separator for Power Storage Devices, and Power Storage Device Comprising Same
AssigneeAsahi Kasei Battery Separator Corporation
InventorKazushi Misawa
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Abstract
Provided is a separator for a power storage device, the separator including: a substrate 10 that is a polyolefin microporous membrane containing a polyolefin as a main component; and a coating layer 20 that is arranged on at least one surface of the substrate 10. In this separator, the coating layer 20 contains an inorganic filler 1 and a thermoplastic polymer, the thermoplastic polymer contains a particulate polymer 2 protruding from the surface of an inorganic filler portion L1, and, in the surface observation of the coating layer 20, a coefficient of variation (cv) of the areas (si) of Voronoi polygons obtained by Voronoi tessellation using the protruding particulate polymer 2 as a generator is 0.10 to 0.60.
Claims11
1:
- A separator for a power storage device, comprising:
- a substrate that is a polyolefin microporous membrane containing a polyolefin as a main component;
- and
- a coating layer that is arranged on at least one surface of the substrate,
- wherein
- the coating layer contains an inorganic filler and a particulate polymer of a thermoplastic polymer,
- the particulate polymer includes a particulate polymer protruding from the surface of the inorganic filler portion, and
- in the surface observation of the coating layer, a coefficient of variation (cv) of the areas (si) of Voronoi polygons obtained by Voronoi tessellation using the protruding particulate polymer as a generator is 0.10 to 0.60.
2:
- The separator for a power storage device according to claim 1, wherein
- the coating layer is formed in an inclined manner such that it increases in thickness toward the protruding particulate polymer, and
- when the thickness of the inorganic filler portion is defined as L1 and a maximum distance from a substrate-coating layer boundary to the outer surface of the inorganic filler formed in the inclined manner is defined as L2, an average value of the gradient L2/L1 of the coating layer is 1.2 or more.
3:
- The separator for a power storage device according to claim 1, wherein
- the coating layer is formed in an inclined manner such that it increases in thickness toward the protruding particulate polymer, and
- when the thickness of the inorganic filler portion is defined as L1, a maximum distance from a substrate-coating layer boundary to the outer surface of the inorganic filler formed in the inclined manner is defined as L2, and a maximum distance from the substrate-coating layer boundary to the outline of the protruding particulate polymer is defined as L3, an average value of the coverage ratio (L2−L1)/(L3−L1) of the protruding particulate polymer is 0.4 or more.
4:
- The separator for a power storage device according to claim 1, wherein 20% or more of the protruding particulate polymer is in contact with the surface of the substrate.
5:
- The separator for a power storage device according to claim 1, wherein the coating layer has a 180° peel strength from the substrate of 200 gf/cm or more.
6:
- The separator for a power storage device according to claim 1, wherein the number of particles of the protruding particulate polymer is 50% or more of a total number of particles of the particulate polymer contained in the coating layer.
7:
- The separator for a power storage device according to claim 1, wherein the protruding particulate polymer is in the form of primary particles.
8:
- The separator for a power storage device according to claim 7, wherein the primary particles have an average particle size of 1 μm to 10 μm.
9:
- The separator for a power storage device according to claim 1, having a TD heat shrinkage rate at 130° C. in 1 hour of 5% or less.
10:
- The separator for a power storage device according to claim 1, having a TD heat shrinkage rate at 150° C. in 1 hour of 5% or less.
11:
- A power storage device, comprising the separator for a power storage device according to claim 1.