Abstract: A negative electrode collector using a copper-covered steel foil for carrying a negative electrode active material for lithium ion secondary batteries has a steel sheet as the core material thereof and has, on both surfaces thereof, a copper covering layer having a mean thickness tCu of from 0.02 to 5.0 ?m on each surface, and of which the total mean thickness, t, including the copper covering layer 7 is from 3 to 100 ?m with tCu/t of at most 0.3. The steel sheet can be common steel, austenitic stainless steel, or ferritic stainless steel. The copper covering layer can be a copper electroplating layer (including one rolled after plating). On the surface of the copper covering layer, for example, a carbon-based active material layer that has been densified through strong roll pressing is formed, and the copper-covered steel foil and the carbon-based active material layer constitute the negative electrode collector.

Abstract: A negative electrode collector using a copper-covered steel foil for carrying a negative electrode active material for lithium ion secondary batteries has a steel sheet as the core material thereof and has, on both surfaces thereof, a copper covering layer having a mean thickness tCu of from 0.02 to 5.0 ?m on each surface, and of which the total mean thickness, t, including the copper covering layer 7 is from 3 to 100 ?m with tCu/t of at most 0.3. The steel sheet can be common steel, austenitic stainless steel, or ferritic stainless steel. The copper covering layer can be a copper electroplating layer (including one rolled after plating). On the surface of the copper covering layer, for example, a carbon-based active material layer that has been densified through strong roll pressing is formed, and the copper-covered steel foil and the carbon-based active material layer constitute the negative electrode collector.

Abstract: [Problem] To provide a negative electrode collector for lithium ion secondary batteries, having a high strength and a large discharge capacity. [Means for Resolution] A negative electrode collector using a copper-covered steel foil 10 for carrying a negative electrode active material for lithium ion secondary batteries, which has a steel sheet 6 as the core material thereof and has, on both surfaces thereof, a copper covering layer 7 having a mean thickness tCu of from 0.02 to 5.0 ?m on each surface, and of which the total mean thickness, t, including the copper covering layer 7 is from 3 to 100 ?m with tCu/t of at most 0.3. To the steel sheet 6, for example, applicable is common steel, austenitic stainless steel or ferritic stainless steel. The copper covering layer 7 is, for example, a copper electroplating layer (including one rolled after plating).

Abstract: A negative electrode collector using a copper-covered steel foil for carrying a negative electrode active material for lithium ion secondary batteries has a steel sheet as the core material thereof and has, on both surfaces thereof, a copper covering layer having a mean thickness tCu of from 0.02 to 5.0 ?m on each surface, and of which the total mean thickness, t, including the copper covering layer 7 is from 3 to 100 ?m with tCu/t of at most 0.3. The steel sheet can be common steel, austenitic stainless steel, or ferritic stainless steel. The copper covering layer can be a copper electroplating layer (including one rolled after plating). On the surface of the copper covering layer, for example, a carbon-based active material layer that has been densified through strong roll pressing is formed, and the copper-covered steel foil and the carbon-based active material layer constitute the negative electrode collector.