Patent ID: 10205135

Abstract:
A steel foil for a power storage device container includes a rolled steel foil, a nickel layer formed on a surface of the rolled steel foil, and a chromium-based surface treatment layer formed on a surface of the nickel layer. The nickel layer includes an upper layer portion which is in contact with the chromium-based surface treatment layer and contains Ni of 90 mass % or more among metal elements, and a lower layer portion which is in contact with the rolled steel foil and contains Ni of less than 90 mass % among the metal elements and Fe. <111> polar density in a reverse pole figure of the nickel layer in a rolling direction is 3.0 to 6.0. The nickel layer has a sub-boundary which is a boundary between two crystals having a relative orientation difference of 2° to 5°, and a large angle boundary which is a boundary between two crystals having the relative orientation difference of equal to or more than 15°. The average value of a ratio L5/L15 between a boundary length L5 which is the length of the sub-boundary, and a boundary length L15 which is the length of the large angle boundary, is equal to or more than 1.0.