Method for preparing dry electrode sheet for secondary battery, calendering device for preparing dry electrode sheet for secondary battery, dry electrode sheet for secondary battery, electrode for secondary battery and secondary battery

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

• preparing a dry electrode sheet by allowing a composition for preparing a dry electrode sheet, including an electrode active material and a binder, to pass through a calendering device,
• wherein the calendering device includes a plurality of rolls,
• wherein the calendering device has two or more inter-roll gaps (G) provided by two rolls (Ra and Rb) adjacent to each other among the rolls, through which the composition passes sequentially,
• wherein the two rolls (Rna and Rnb) adjacent to each other and providing the nth inter-roll gap (Gn) have a velocity (V) ratio of 10% or more to less than 50%, represented by Equation (1):
• Velocity
• ⁢
• ratio
• =
• [
• V
• ⁡
• (
• R
• ⁢
• n
• ⁢
• a
• )
• -
• V
• ⁡
• (
• R
• ⁢
• n
• ⁢
• b
• )
• ]
• ×
• 100
• /
• V
• ⁡
• (
• R
• ⁢
• n
• ⁢
• b
• )
• [
• Equation
• ⁢
• (
• 1
• )
• ]
• where Rna indicates a roll further from a point at which the composition is injected, and Rnb indicates a roll closer to a point at which the composition is injected, wherein, as for the nth inter-roll gap (Gn) and the n+1th inter-roll gap (Gn+1), a reduction ratio between Gn and Gn+1 represented by Equation (2) as below is more than 10% to less than 50%:
• Reduction
• ⁢
• ratio
• ⁢
• between
• ⁢
• Gn
• ⁢
• and
• ⁢
• Gn
• +
• 1
• =
• [
• (
• G
• ⁢
• n
• )
• -
• (
• G
• ⁢
• n
• +
• 1
• )
• ]
• ×
• 100
• /
• Gn
• [
• Equation
• ⁢
• (
• 2
• )
• ]
• where Gn indicates an inter-roll gap provided on a side closer to a point at which the composition is injected, and Gn+1 indicates an inter-roll gap provided on a side farther from a point at which the composition is injected.