Battery case for secondary battery

Abstract

Disclosed herein is a battery case including a receiving part having an electrode assembly mounted therein, wherein the receiving part, which is formed by deforming a sheet type base material, is configured to have a stair-like structure in which at least one corner and/or surface forming a shape of the receiving part is deformed.

1 . A battery case comprising a receiving part having an electrode assembly mounted therein, wherein the receiving part, which is formed by deforming a sheet type base material, is configured to have a stair-like structure in which at least one corner and/or surface forming a shape of the receiving part is deformed. 
     
     
         2 . The battery case according to  claim 1 , wherein the base material is formed of a laminate sheet comprising a resin layer and a metal layer. 
     
     
         3 . The battery case according to  claim 2 , wherein the base material comprises an upper layer of a first polymer resin, an intermediate layer of a blocking metal, and a lower layer of a second polymer resin. 
     
     
         4 . The battery case according to  claim 1 , wherein the base material has a thickness of 0.3 mm to 6 mm. 
     
     
         5 . The battery case according to  claim 1 , wherein the receiving part has a side wall configured to have a stair-like structure comprising two or more steps, and the steps have heights gradually decreased in a depth direction of the receiving part. 
     
     
         6 . The battery case according to  claim 5 , wherein, in a case in which the stair-like structure comprises n steps, an n-th step is located at a lowermost end of the stair-like structure in the depth direction of the receiving part, an (n−1)-th step is located at a top of the n-th step, and the n-th step has a smaller height than the (n−1)-th step. 
     
     
         7 . The battery case according to  claim 6 , wherein the height of the n-th step is equivalent to 50 to 90% of that of the (n−1)-th step. 
     
     
         8 . The battery case according to  claim 6 , wherein a thickness of the side wall of the receiving part at the n-th step is equivalent to 90 to 99% of that of the side wall of the receiving part at the (n−1)-th step. 
     
     
         9 . A method of manufacturing a battery cell having an electrode assembly mounted in a battery case according to  claim 1 , the method comprising:
 (a) placing a sheet type base material on a die having a groove;   (b) pressing the sheet type base material into the groove of the die using a punch, an outside of which is configured to have an asymmetric structure, such that wrinkles and chlorosis do not occur at corners of a receiving part formed from the sheet type base material   (c) mounting an electrode assembly in the receiving part; and   (d) placing a cover on the receiving part to seal the receiving part, wherein   the groove of the die is formed in a shape corresponding to that of an outside of the punch such that the sheet type base material coincides with the shape of the outside of the punch when the sheet type base material contacts the punch and the groove of the die.   
     
     
         10 . The method according to  claim 9 , wherein a stair-like structure is formed at a bottom of the punch. 
     
     
         11 . The method according to  claim 10 , wherein the stair-like structure is formed at a middle, one side, or one corner of the bottom of the punch. 
     
     
         12 . The method according to  claim 9 , further comprising forming a vacuum in a space defined between the die and the sheet type base material such that the sheet type base material comes into tight contact with the groove of the die. 
     
     
         13 . The method according to  claim 9 , wherein
 the die is provided with a depressed part configured to have a stair-like structure comprising an upper step, a middle step, and a lower step, and   the punch comprises a first punch corresponding to a shape of the upper step of the die, a second punch corresponding to a shape of the middle step of the die, and a third punch corresponding to a shape of the lower step of the die.   
     
     
         14 . The method according to  claim 13 , wherein the second punch is formed in a shape corresponding to the shapes of the upper step and the middle step of the die, and the third punch is formed in a shape corresponding to the shapes of the upper step, the middle step, and the lower step of the die. 
     
     
         15 . The method according to  claim 14 , further comprising:
 (i) pressing the sheet type base material using the first punch to transfer the shape of the upper step of the die to the sheet type base material;   (ii) pressing the sheet type base material using the second punch to transfer the shapes of the upper step and the middle step of the die to the sheet type base material; and   (iii) pressing the sheet type base material using the third punch to transfer the shapes of the upper step, the middle step, and the lower step of the die to the sheet type base material.   
     
     
         16 . The method according to  claim 15 , further comprising forming a vacuum in a space defined between the die and the sheet type base material such that the sheet type base material comes into tight contact with the groove of the die. 
     
     
         17 . The method according to  claim 9 , wherein corners of an outside of the punch and corners of an inside of the die are rounded. 
     
     
         18 . The method according to  claim 9 , wherein the punch comprises two or more punches having different widths and heights, the die is provided at an inside thereof with a stair-like structure comprising steps formed in shapes corresponding to the respective punches, and the receiving part has a stair-like structure formed by the punch and the die. 
     
     
         19 . The method according to  claim 18 , wherein the stair-like structure of the receiving part is formed by pressing performed using one of the punches having largest width and then by pressing performed using the punches having next largest widths. 
     
     
         20 . The method according to  claim 19 , wherein the pressed depth of the sheet type base material is decreased as the sheet type base material is pressed using the punches in reverse order of width. 
     
     
         21 . The method according to  claim 20 , wherein, in a case in which the number of the punches is n, the pressed depth of the sheet type base material formed by the n-th punch is equivalent to 60 to 90% of that of the sheet type base material formed by the (n−1) th punch. 
     
     
         22 . The method according to  claim 21 , wherein corners of outsides of the punches and corners of an inside of the die are rounded. 
     
     
         23 . An apparatus for manufacturing a battery case according to  claim 1 , the apparatus comprising:
 a first die comprising a punching die having a punch to press a battery case sheet mounted at a bottom thereof and a stripper to fix the battery case sheet between the stripper and a stationary die during a drawing process; and   a second die comprising a block die having a block corresponding to the punch mounted at a top thereof, the stationary die to fix the battery case sheet between the stripper and the stationary die, and a mounting die having a depressed part, in which the block die is variably mounted.