Lithium secondary battery possessing stress relaxation layer

[0092] (1) Production of negative electrode current collectors for lithium secondary batteries

[0093] As the copper foil used as the metal support, a rolled copper foil with a thickness of 9 μm containing 0.01% by mass of tin was used. In order to clean the surface of the rolled copper foil, electrolytic degreasing and pickling were performed. Electrolytic degreasing treatment in the presence of sodium hydroxide 40g / dm 3 , sodium carbonate 20g / dm 3 In an aqueous solution at a temperature of 40°C and a current density of 5A / dm 2 Process for 10 seconds. Pickling treatment with sulfuric acid 150g / dm 3 in aqueous solution at 25°C for 5 seconds. Then, this copper foil was washed with running water.

[0094] Next, copper electroplating is performed on the surface of the copper foil. The copper plating solution contains copper sulfate pentahydrate 185g / dm 3 , Sulfuric acid 80g / dm 3 , Chloride ion 0.05g / dm 3 , Bis(3-sulfopropyl) disulfide 0.001g / dm 3 , polyethylene glycol...

[0105] (1) Production of negative electrode current collectors for lithium secondary batteries

[0106] On the basis of the fabrication of the lithium secondary battery negative electrode in Example 1, an electrolytic copper foil with a thickness of 12 μm was used as the copper foil, and the first stress relaxation layer with a thickness of 0.2 μm was produced in the same way as the second stress relaxation layer. layer, and a negative electrode current collector was produced in the same procedure as in Example 1 except that. The film thickness of nickel plating becomes thinner as the plating time becomes shorter. Through the above steps, a negative electrode current collector on which the stress relaxation layer is formed can be produced.

[0107] (2) Production of lithium secondary batteries

[0108] A wound battery was produced in the same procedure as in Example 1 except that the negative electrode current collector produced in (1) above was used.

[0110] (1) Production of negative electrode current collectors for lithium secondary batteries

[0111] On the basis of the fabrication of the lithium secondary battery negative electrode in Example 1, an electrolytic copper foil with a thickness of 12 μm was used as the copper foil, and a second stress relaxation layer with a thickness of 0.1 μm was produced in the same way as the first stress relaxation layer. layer, and a negative electrode current collector was produced in the same procedure as in Example 1. The film thickness of copper plating becomes thinner as the plating time becomes shorter. Through the above steps, a negative electrode current collector on which the stress relaxation layer is formed can be produced.

[0112] (2) Production of lithium secondary batteries

[0113] A wound battery was produced in the same procedure as in Example 1 except that the negative electrode current collector produced in (1) above was used.