Pouch for a secondary battery including a bridge and accommodation grooves
A method for manufacturing a secondary battery includes a forming step of pressing a pouch sheet by using a press die so that left and right accommodation grooves, which are bilaterally symmetrical to each other and are opened upward, and a bridge connecting the left and right accommodation grooves to each other are formed in the pouch sheet, wherein the bridge protrudes upward with respect to bottom surfaces of the left and right accommodation grooves, and a curved portion having a rounded shape is formed on an upper end of the bridge, a seating step of seating an electrode assembly in one of the left and right accommodation grooves, and a folding step of folding the pouch sheet so that the left and right accommodation grooves face each other.
1. A pouch for a secondary battery, the pouch comprising:
a pouch sheet, wherein in an unfolded form, the pouch sheet includes:
a pair of accommodation grooves for accommodating an electrode assembly when the pouch sheet is in a folded form and which are bilaterally symmetrical to each other and are opened upward; and
a bridge connecting the pair of accommodation grooves to each other,
wherein the bridge protrudes upward with respect to bottom surfaces of the pair of accommodation grooves, and a curved portion having a rounded shape is formed on an upper end of the bridge,
wherein, when a length along the pouch sheet between a portion, which is configured to contact a lower edge of the electrode assembly adjacent to the bridge, and the bridge is d 1 , a length along the pouch sheet between a portion, which is configured to contact an upper edge of the electrode assembly adjacent to the bridge, and the bridge is d 2 , a length along the pouch sheet of the bridge is d 3 , and a height of the electrode assembly seated on the pouch sheet is h,
the pouch sheet is formed to satisfy the following conditional expression: h≤d 1 +d 2 +d 3 .
2. The pouch of claim 1 , wherein, when a protruding height of the bridge with respect to the bottom surfaces of the pair of accommodation grooves is a,
the pouch sheet is formed to satisfy the following conditional expression: h/2≥a.
3. The pouch of claim 1 , wherein, in the pouch sheet, in its unfolded form, the bridge has a width of 4 mm or less.
4. The pouch of claim 3 , wherein the width of the bridge is defined by a width of a protrusion protruding between the pair of accommodation grooves, and
end points of the width of the protrusion are defined by inflection points between bending parts adjacent the bottom surfaces of the pair of accommodation grooves and side surfaces of the protrusion.
5. The pouch of claim 1 , wherein, in the pouch sheet, in its unfolded form, the bridge has a width of 1 mm to 2 mm.
6. The pouch of claim 5 , wherein the width of the bridge is defined by a width of a protrusion protruding between the pair of accommodation grooves, and
end points of the width of the protrusion are defined by inflection points between bending parts adjacent the bottom surfaces of the pair of accommodation grooves and side surfaces of the protrusion.
7. The pouch of claim 1 , wherein, in the pouch sheet, in its unfolded form, the bottom surfaces of the pair of accommodation grooves are inclined to be bilaterally symmetrical to each other,
wherein the bottom surfaces of the pair of accommodation grooves have inclinations decreasing in a direction that is away from the bridge.
8. The pouch of claim 7 , wherein, in the pouch sheet, in its unfolded form, the inclination of each of the bottom surfaces of the pair of accommodation grooves decreases at an angle of 1.5° to 3°.
9. The pouch of claim 1 , wherein, in the pouch sheet, in its unfolded form, the upper end of the bridge has a semicircular shape.