Steel foil for electricity storage device container, container for electricity storage device, and electricity storage device

Adopted is a steel foil for electricity storage device containers which comprises a steel foil, a chromium metal layer superposed on the steel foil, and a hydrated chromium oxide layer superposed on the chromium metal layer, wherein: the Fe concentration in the area ranging from the surface of the hydrated chromium oxide layer to a depth of 10 nm therefrom is less than 10 mass%; in the surface ofthe hydrated chromium oxide layer, the areal proportion of portions having an arithmetic average roughness Ra in a 1-um field of view of 10 nm or greater is less than 20%; and in the surface of the hydrated chromium oxide layer, the portions in which the arithmetic average roughness Ra in a 1-um field of view is less than 10 nm have an arithmetic average roughness Ra in a 1-um field of view of 3 nm or less. 本发明采用种蓄电设备容器用钢箔，其具备钢箔、层叠于钢箔上的金属铬层和层叠于金属铬层上的水合氧化铬层，从水合氧化铬层的表面到10nm为止的深度处的Fe浓度低于10质量％，在水合氧化铬层的表面中，1μm视野内的算术平均粗糙度Ra为10nm以上的部位所占的面积率低于20％，在水合氧化铬层的表面中，1μm视野内的算术平均粗糙度Ra低于10nm的部位的1μm视野内的算术平均粗糙度Ra为3nm以下。