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.

An electrochemical cell, preferably a secondary, rechargeable cell, including a casing comprised of a main body portion having opposed lower and upper open ends closed by respective lower and upper lids is described. The main body portion is composed of titanium Grades 5 or 23 having a relatively high electrical resistivity material while the lower and upper lids are composed of titanium Grades 1 or 2. The lids are preferably joined to the main body portion using laser welding. The combination of these differing titanium alloys provides a cell casing that effectively retards eddy current induced heating during cell recharging.

A nickel-plated heat-treated steel sheet for a battery can, having a nickel layer with a nickel amount of 4.4 to 26.7 g/m.sup.2 on a steel sheet. When the Fe intensity and the Ni intensity are continuously measured along the depth direction from the surface of the nickel-plated heat-treated steel sheet for a battery can, by using a high frequency glow discharge optical emission spectrometric analyzer, the difference between the depth at which the Fe intensity exhibits a first predetermined value and the depth at which the Ni intensity exhibits a second predetermined value is less than 0.04 m.

A surface-treated steel sheet for a battery container, including a steel sheet, an iron-nickel diffusion layer formed on the steel sheet, and a nickel layer formed on the iron-nickel diffusion layer and constituting the outermost layer, wherein when the Fe intensity and the Ni intensity are continuously measured from the surface of the surface-treated steel sheet for a battery container along the depth direction with a high frequency glow discharge optical emission spectrometric analyzer, the thickness of the iron-nickel diffusion layer being the difference between the depth at which the Fe intensity exhibits a first predetermined value and the depth at which the Ni intensity exhibits a second predetermined value is 0.04 to 0.31 m; and the total amount of the nickel contained in the iron-nickel diffusion layer and the nickel contained in the nickel layer is 10.8 to 26.7 g/m.sup.2.

A surface-treated steel sheet for a battery container, including a steel sheet, an iron-nickel diffusion layer formed on the steel sheet, and a nickel layer formed on the iron-nickel diffusion layer and constituting the outermost layer, wherein when the Fe intensity and the Ni intensity are continuously measured from the surface of the surface-treated steel sheet for a battery container along the depth direction with a high frequency glow discharge optical emission spectrometric analyzer, the thickness of the iron-nickel diffusion layer being the difference between the depth at which the Fe intensity exhibits a first predetermined value and the depth at which the Ni intensity exhibits a second predetermined value is 0.04 to 0.31 m; and the total amount of the nickel contained in the iron-nickel diffusion layer and the nickel contained in the nickel layer is 4.4 g/m.sup.2 or more and less than 10.8 g/m.sup.2.

A battery cell housing of a round battery cell includes a cylindrical housing shell with an outer diameter of more than 15 mm, preferably more than 20 mm, particularly preferably more than 22 mm, and to the use of an aluminium alloy for manufacturing a battery cell housing. The object of providing a high-strength battery cell housing of a round battery cell, having a cylindrical housing shell with a diameter of more than 15 mm, preferably more than 20 mm, in particular more than 22 mm, which allows improved properties regarding heat management and weight of the round battery cell without excessively limiting the capacity of the round battery cell, is achieved in that the housing shell consists at least partially of an aluminium alloy, and the yield strength R.sub.p0.2 of the housing shell is at least 183 MPa, preferably at least 220 MPa, particularly preferably at least 250 MPa.

A battery cell housing of a round battery cell includes a cylindrical housing shell with an outer diameter of more than 15 mm, preferably more than 20 mm, particularly preferably more than 22 mm, and to the use of an aluminium alloy for manufacturing a battery cell housing. The object of providing a high-strength battery cell housing of a round battery cell, having a cylindrical housing shell with a diameter of more than 15 mm, preferably more than 20 mm, in particular more than 22 mm, which allows improved properties regarding heat management and weight of the round battery cell without excessively limiting the capacity of the round battery cell, is achieved in that the housing shell consists at least partially of an aluminium alloy, and the yield strength R.sub.p0.2 of the housing shell is at least 183 MPa, preferably at least 220 MPa, particularly preferably at least 250 MPa.

A solid-state battery package including: a substrate; a solid-state battery on the substrate; a covering portion covering the solid-state battery; and a shape-maintaining layer in contact with the covering portion.

A surface-treated steel sheet for a battery container, including a steel sheet, an iron-nickel diffusion layer formed on the steel sheet, and a nickel layer formed on the iron-nickel diffusion layer (and constituting the outermost layer, wherein when the Fe intensity and the Ni intensity are continuously measured from the surface of the surface-treated steel sheet for a battery container along the depth direction with a high frequency glow discharge optical emission spectrometric analyzer, the thickness of the iron-nickel diffusion layer being the difference between the depth at which the Fe intensity exhibits a first predetermined value and the depth at which the Ni intensity exhibits a second predetermined value is 0.04 to 0.31 m; and the total amount of the nickel contained in the iron-nickel diffusion layer and the nickel contained in the nickel layer is 4.4 g/m2 or more and less than 10.8 g/m2.

A surface-treated steel sheet for a battery container, including a steel sheet, an iron-nickel diffusion layer formed on the steel sheet, and a nickel layer formed on the iron-nickel diffusion layer (and constituting the outermost layer, wherein when the Fe intensity and the Ni intensity are continuously measured from the surface of the surface-treated steel sheet for a battery container along the depth direction with a high frequency glow discharge optical emission spectrometric analyzer, the thickness of the iron-nickel diffusion layer being the difference between the depth at which the Fe intensity exhibits a first predetermined value and the depth at which the Ni intensity exhibits a second predetermined value is 0.04 to 0.31 m; and the total amount of the nickel contained in the iron-nickel diffusion layer and the nickel contained in the nickel layer is 4.4 g/m2 or more and less than 10.8 g/m2.