Method and apparatus for preparing dry electrode sheet for secondary battery, dry electrode sheet for secondary battery, electrode for secondary battery and secondary battery

A method of manufacturing a dry electrode sheet for a secondary battery, the method comprising:

• providing a dry electrode composition comprising an electrode active material and a binder;
• and
• feeding the dry electrode composition directly to a calendering operation wherein the calendering operation includes:
• injecting the dry electrode composition between two adjacent rolls spaced apart from each other by a first interval W1 to provide a first electrode sheet,
• inserting the first electrode sheet between two adjacent rolls spaced apart from each other by a second interval W2 to provide the dry electrode sheet, and
• wherein the first interval W1 and the second interval W2 have a compression ratio expressed by the following equation (1) of 0.10 or more and 0.27 or less,
• Compression Ratio=(W1−W2)/W1 (equation (1)),
• wherein the two adjacent rolls in the injecting step includes a first roll and a second roll, and the two adjacent rolls in the inserting step includes the second roll, a third roll and a fourth roll, the dry electrode composition is introduced between the first roll and the second roll to prepare the first electrode sheet, and the first electrode sheet is introduced between the third roll and the fourth roll to manufacture the dry electrode sheet,
• wherein a rotational speed V1 of the first roll, a rotational speed V2 of the second roll, a rotational speed V3 of the third roll, and a rotational speed V4 of the fourth roll satisfy the following relationship,
• V1>V2≤V3>V4 (4)
• where in formula (4), V1<V4
• wherein a rotation speed ratio V1:V2:V3:V4 of the first roll, the second roll, the third roll, and the fourth roll is 10:11 to 20:11 to 20:12 to 40.