Patent Publication Number: US-2023145579-A1

Title: Foldable Pouch-Shaped Battery Cell and Method of Manufacturing the Same

Description:
TECHNICAL FIELD 
     This application claims the benefit of priority to Korean Patent Application No. 2020-0061358 filed on May 22, 2020, the disclosure of which is incorporated herein by reference in its entirety. 
     The present invention relates to a foldable pouch-shaped battery cell and a method of manufacturing the same, and more particularly to a foldable pouch-shaped battery cell configured such that an uncoated portion, which is a portion coated with no electrode mixture, is formed at a portion of the battery cell to be folded and a stepped structure having a recessed shape is formed at the portion of a pouch-shaped battery case corresponding to the uncoated portion, whereby it is possible to prevent movement of the electrode assembly, a method of manufacturing the same. 
     BACKGROUND ART 
     A lithium secondary battery, which is capable of being charged and discharged, has been widely used as an energy source for wireless mobile devices or wearable devices, and has also been used as an energy source for electric vehicles and hybrid electric vehicles presented as alternatives to existing gasoline and diesel vehicles, which cause air pollution. 
     In addition, with an increase in kinds of miniaturized multifunctional products and a trend of emphasizing design in electronic devices, the number of products based on new shapes, such as a shape including a curve or a geometrical shape, other than conventional simple structures, such as a planar structure and a prismatic structure, has increased. 
     Lithium secondary batteries having various shapes, such as a stepped shape and a polygonal shape, other than a rectangular shape, have been developed in order to apply the lithium secondary batteries to such products having various shapes. 
     For example, for a smartphone, the side thereof is curved in order to improve sensation of grip, and flexible display products capable of being bent or folded have come on the stage. 
     In the case in which a rectangular battery cell is used in a bendable or foldable device, there is a problem in that dead space is formed in large numbers. Therefore, it is necessary to develop a battery cell capable of securing capacity while reducing dead space even though the battery cell is mounted in a device having an atypical shape. 
     In connection therewith, Patent Document 1 discloses a secondary battery configured such that a positive electrode active material layer and a negative electrode active material layer are formed by coating so as to be spaced apart from each other by a predetermined distance and including a bending region configured to be bent at an uncoated portion, which is not coated with the positive electrode active material layer and the negative electrode active material layer. 
     The secondary battery disclosed in Patent Document 1 is suitably applied to a long device but has a problem in that a plurality of bending regions is formed, whereby the uncoated portion is widened, and therefore energy density is lowered. 
     Patent Document 2 relates to a battery cell including a current collector having at least one uncoated portion that partitions an electrode mixture, wherein the portion of a battery case at which the uncoated portion is located is bent, whereby the shape of the battery cell is changed. 
     In Patent Document 2, an electrode assembly is separated from the battery case, whereby there is a problem in that a bent portion of the battery case and a bent portion of the electrode assembly may be misaligned with each other when the battery cell is bent. 
     Patent Document 3 discloses a battery cell configured such that a recess is formed in a sealing portion in order to prevent occurrence of wrinkles at the sealed portion when the battery cell is bent. In this structure, however, an electrode mixture layer may be separated from an electrode assembly when the electrode assembly is bent. 
     Therefore, there is a high necessary for a battery cell applicable to devices having various shapes, such as a foldable or bendable battery cell, and technology capable of securing safety of the battery cell while preventing a decrease in capacity of the battery cell. 
     PRIOR ART DOCUMENTS 
     
         
         (Patent Document 1) Korean Patent Application Publication No. 2012-0022385 (2012.03.12) 
         (Patent Document 2) Korean Patent Application Publication No. 2017-0033513 (2017.03.27) 
         (Patent Document 3) Korean Patent Application Publication No. 2015-0096325 (2015.08.24) 
       
    
     DISCLOSURE 
     Technical Problem 
     The present invention has been made in view of the above problems, and it is an object of the present invention to provide a foldable pouch-shaped battery cell configured such that an uncoated portion, which is a portion coated with no electrode mixture, is formed at an electrode and a stepped structure having a recessed shape is formed at the portion of a pouch-shaped battery case corresponding to the uncoated portion, whereby it is possible to prevent dislocation of an electrode assembly, and therefore safety of the pouch-shaped battery cell is improved, and a method of manufacturing the same. 
     Technical Solution 
     A pouch-shaped battery cell according to the present invention to accomplish the above object is a pouch-shaped battery cell having an electrode assembly received in a pouch-shaped battery case, wherein the electrode assembly includes positive electrodes and negative electrodes, each of the positive electrodes and the negative electrodes being configured to have a structure in which the length of the electrode in an overall width direction is less than the length of the electrode in an overall length direction, each of the positive electrodes and the negative electrodes has an uncoated portion, which is a portion coated with no electrode mixture, formed parallel to outer peripheries of the electrode in the overall width direction or outer peripheries of the electrode in the overall length direction and a coated portion, which is coated with an electrode mixture, formed at the remaining portion of the electrode excluding the uncoated portion, and a stepped structure is formed at the part of the pouch-shaped battery case corresponding to the uncoated portion so as to be recessed inwards. 
     In the pouch-shaped battery cell according to the present invention, positive electrode tabs and negative electrode tabs may protrude from one of the outer peripheries of the electrode assembly in the overall width direction. 
     In the pouch-shaped battery cell according to the present invention, each of the positive electrodes and the negative electrodes may have a first coated portion and a second coated portion formed symmetrical or asymmetrical with respect to the uncoated portion, and each of the positive electrodes and the negative electrodes may be folded at the uncoated portion. 
     In addition, a positive electrode tab or a negative electrode tab may be formed so as to protrude from one of the first coated portion and the second coated portion. 
     In the pouch-shaped battery cell according to the present invention, an insulating member may be added to outer surfaces of a part of the uncoated portion and a portion of the coated portion as a border portion between the uncoated portion and the coated portion. 
     In addition, the insulating member may be an insulation tape or an insulating solution. 
     In the pouch-shaped battery cell according to the present invention, a wrinkled folding line may be formed at the uncoated portion. 
     In the pouch-shaped battery cell according to the present invention, the pouch-shaped battery case may include a first battery case and a second battery case, and a stepped portion may be formed at a portion of at least one of the first battery case and the second battery case corresponding to the uncoated portion so as to be recessed inwards. 
     In addition, the recessed stepped portion of the pouch-shaped battery case may be attached to each of the uppermost electrode and the lowermost electrode of the electrode assembly. 
     In the pouch-shaped battery cell according to the present invention, the pouch-shaped battery case may be folded as a result of the electrode assembly being folded, and a notch may be formed in a sealed portion located at the portion of the pouch-shaped battery case that is folded. 
     In addition, the present invention provides a method of manufacturing the pouch-shaped battery cell. Specifically, the method includes (a) coating an electrode sheet to form a coated portion, which is a portion coated with an electrode mixture, and an uncoated portion, which is a portion coated with no electrode mixture; (b) adding an insulating member to outer surfaces of a part of the coated portion and a part of the uncoated portion as a border portion between the coated portion and the uncoated portion; (c) rolling the electrode sheet; and (d) slitting the electrode sheet of step (c). 
     In the method according to the present invention, an insulating tape may be attached or an insulation solution may be applied in step (b). 
     The method according to the present invention may include a process of manufacturing an electrode assembly by stacking a positive electrode and a negative electrode manufactured by cutting the electrode sheet slit in step (d) in the state in which a separator is interposed therebetween, receiving the electrode assembly in a pouch-shaped battery case having a stepped portion formed thereat, and hermetically sealing the pouch-shaped battery case. 
     In addition, the method according to the present invention may further include a process of receiving the electrode assembly in a pouch-shaped battery case having stepped portions formed thereat and attaching each of the uppermost electrode and the lowermost electrode of the electrode assembly to a corresponding one of the stepped portions of the pouch-shaped battery case. 
     Advantageous Effects 
     As is apparent from the above description, a pouch-shaped battery cell according to the present invention is configured to have a structure in which an uncoated portion, which is a portion coated with no electrode mixture, is formed at each of a positive electrode and a negative electrode, and an electrode assembly is folded at the uncoated portion, whereby it is possible to prevent separation of an electrode mixture layer from an electrode current collector as a result of folding. 
     In addition, a stepped portion having a recessed shape is formed at the portion of a pouch-shaped battery case corresponding to the uncoated portion of the electrode assembly, whereby it is possible to seat and fix a coated portion of the electrode assembly onto a protruding portion of the pouch-shaped battery case, which relatively protrudes. 
     Also, in the case in which the uncoated portion of the electrode assembly is attached to the stepped portion of the pouch-shaped battery case, it is possible to more securely fix the position of the electrode assembly. Consequently, it is possible to prevent separation of the electrode assembly, and therefore it is possible to prevent damage to electrode tabs and an electrode lead. 
    
    
     
       DESCRIPTION OF DRAWINGS 
         FIG.  1    is a plan view showing the state in which electrodes according to the present invention are stacked. 
         FIG.  2    is a side view of an electrode according to the present invention. 
         FIG.  3    is a side view of an electrode having a folding line formed thereat. 
         FIG.  4    is a side view of pouch-shaped battery cells according to the present invention. 
         FIG.  5    is a partial enlarged view of a vertical section of a pouch-shaped battery cell according to the present invention. 
         FIG.  6    is a perspective view of a pouch-shaped battery cell having a notch formed in a sealed portion thereof. 
         FIG.  7    is a perspective view showing a process of upwardly bending a pouch-shaped battery cell according to the present invention based on an x axis. 
         FIG.  8    is a perspective view showing a process of downwardly bending the pouch-shaped battery cell according to the present invention based on the x axis. 
         FIG.  9    is a perspective view showing a process of upwardly bending a pouch-shaped battery cell according to the present invention based on a y axis. 
     
    
    
     BEST MODE 
     Now, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings such that the preferred embodiments of the present invention can be easily implemented by a person having ordinary skill in the art to which the present invention pertains. In describing the principle of operation of the preferred embodiments of the present invention in detail, however, a detailed description of known functions and configurations incorporated herein will be omitted when the same may obscure the subject matter of the present invention. 
     In addition, the same reference numbers will be used throughout the drawings to refer to parts that perform similar functions or operations. In the case in which one part is said to be connected to another part throughout the specification, not only may the one part be directly connected to the other part, but also, the one part may be indirectly connected to the other part via a further part. In addition, that a certain element is included does not mean that other elements are excluded, but means that such elements may be further included unless mentioned otherwise. 
     In addition, a description to embody elements through limitation or addition may be applied to all inventions, unless particularly restricted, and does not limit a specific invention. 
     Also, in the description of the invention and the claims of the present application, singular forms are intended to include plural forms unless mentioned otherwise. 
     Also, in the description of the invention and the claims of the present application, “or” includes “and” unless mentioned otherwise. Therefore, “including A or B” means three cases, namely, the case including A, the case including B, and the case including A and B. 
     In addition, all numeric ranges include the lowest value, the highest value, and all intermediate values therebetween unless the context clearly indicates otherwise. 
     Embodiments of the present invention will be described in detail with reference to the accompanying drawings. 
     A pouch-shaped battery cell according to the present invention is configured to have a structure in which an electrode assembly is received in a pouch-shaped battery case made of a laminate sheet including an outer resin layer, a barrier layer, and an inner adhesive layer in a hermetically sealed state. The electrode assembly may be a stacked type electrode assembly, which is configured to have a structure in which a positive electrode and a negative electrode are stacked in the state in which a separator is interposed therebetween, or a laminated and stacked type electrode assembly, which is configured to have a structure in which two or more bicells, each of which positive electrodes and negative electrodes are disposed in the state in which two separators are interposed respectively therebetween, are laminated in a state of being stacked. 
     Each of the positive electrode and the negative electrode is configured to have a rectangular planar shape of a structure in which the length of the electrode in an overall width direction is less than the length of the electrode in an overall length direction, and has a structure in which an uncoated portion, which is a portion coated with no electrode mixture, is formed parallel to the outer peripheries of the electrode in the overall width direction or the outer peripheries of the electrode in the overall length direction and a coated portion, which is coated with an electrode mixture, is formed at the remaining portion of the electrode excluding the uncoated portion. 
     The pouch-shaped battery cell according to the present invention is foldable, wherein the uncoated portion is folded, whereby the pouch-shaped battery cell is folded. 
     In connection therewith, an electrode mixture formed on an electrode current collector by coating may be separated from the folding portion of the electrode current collector when the pouch-shaped battery cell is folded. In order to prevent this, in the present invention, the uncoated portion is formed, and the pouch-shaped battery cell is folded at the uncoated portion, whereby it is possible to prevent the above problem. 
       FIG.  1    is a plan view showing the state in which electrodes according to the present invention are stacked, and  FIG.  2    is a side view of an electrode according to the present invention. 
     Referring to  FIG.  1   , electrodes (a) and electrodes (b) are shown. Referring to  FIG.  2   , a side view of the positive electrode (a) of  FIG.  1    is shown. In  FIG.  1   , a separator interposed between a positive electrode and a negative electrode is omitted for convenience of description. 
     The electrodes (a) and the electrodes (b) are stacks of positive electrodes  110  and  210  and negative electrodes  120  and  220  configured to have a structure in which the length of the electrode in the overall width direction, i.e. an x-axis direction, is less than the length of the electrode in the overall length direction, i.e. a y-axis direction. Each of positive electrode tabs  112  and  212  and negative electrode tabs  122  and  222  protrudes from one of the outer peripheries of a corresponding one of the electrodes in the overall width direction. 
     Each of the electrodes (a) has a structure in which an uncoated portion, which is a portion coated with no electrode mixture, is formed parallel to the outer peripheries of the electrode in the overall width direction. The positive electrode  110  has coated portions  111  formed symmetrical with respect to an uncoated portion  115  formed parallel to the outer peripheries of the electrode in the overall width direction, and the negative electrode  120  has coated portions  121  formed symmetrical with respect to an uncoated portion  125  formed parallel to the outer peripheries of the electrode in the overall width direction. 
     For the positive electrode  110 , an insulating member  113  is added to outer surfaces of a part of the uncoated portion  115  and a part of each coated portion  111  as a border portion between the uncoated portion  115  and the coated portion  111 . For the negative electrode  120 , an insulating member  123  is added to outer surfaces of a part of the uncoated portion  125  and a part of each coated portion  121  as a border portion between the uncoated portion  125  and the coated portion  121 . 
     Each of the electrodes (b) has a structure in which an uncoated portion, which is a portion coated with no electrode mixture, is formed parallel to the outer peripheries of the electrode in the overall length direction. The positive electrode  210  has coated portions  211  formed symmetrical with respect to an uncoated portion  215  formed parallel to the outer peripheries of the electrode in the overall length direction, and the negative electrode  220  has coated portions  221  formed symmetrical with respect to an uncoated portion  225  formed parallel to the outer peripheries of the electrode in the overall length direction. 
     For the positive electrode  210 , an insulating member  213  is added to outer surfaces of a part of the uncoated portion  215  and a part of each coated portion  211  as a border portion between the uncoated portion  215  and the coated portion  211 . For the negative electrode  220 , an insulating member  223  is added to outer surfaces of a part of the uncoated portion  225  and a part of each coated portion  221  as a border portion between the uncoated portion  225  and the coated portion  221 . 
     Meanwhile, the present invention relates to a pouch-shaped battery cell that is folded based on an uncoated portion, and therefore coated portions may be formed asymmetrical with respect to the uncoated portion, unlike what is shown in  FIGS.  1  and  2   . 
     Although the present invention relates to a foldable pouch-shaped battery cell, it is preferable to understand that the pouch-shaped battery cell does not always remain folded when in use and may be folded or unfolded as needed. 
     Consequently, it is preferable for the electrode tabs to protrude in one direction in the state in which the pouch-shaped battery cell according to the present invention is not folded. The electrode tabs protrude from one of the outer peripheries of the electrode in the overall width direction. 
     In addition, on the assumption that, for the electrodes (a), the coated portions  111  and  121  located above the uncoated portions  115  and  125  are first coated portions and the coated portions  111  and  121  located under the uncoated portions  115  and  125  are second coated portions, the positive electrode tab  112  and the negative electrode tab  122  protrude from the first coated portions. On the assumption that, for the electrodes (b), the coated portions  211  and  221  located on the left sides of the uncoated portions  215  and  225  are first coated portions and the coated portions  211  and  221  located on the right sides of the uncoated portions  215  and  225  are second coated portions, the positive electrode tab  212  and the negative electrode tab  222  protrude from the first coated portions. Since the positive electrode tab or the negative electrode tab is formed at any one coated portion, as described above, the positions of a positive electrode terminal and a negative electrode terminal may be uniformly fixed irrespective of whether the pouch-shaped battery cell is folded or unfolded. 
     Each of the insulating members  113  and  213  may be a member configured to have a structure in which an insulating layer is attached to an adhesive layer as a substrate, such as an insulating tape. Consequently, the insulating tape may be added to the border portion between the coated portion and the uncoated portion by attachment, or an insulating solution obtained by dissolving an insulating material in a solvent may be added to the border portion between the coated portion and the uncoated portion by coating. 
     The insulating layer of the insulating tape may be made of cast polypropylene (CPP) or polyethylene terephthalate (PET). 
     The insulating solution may be manufactured, for example, by mixing styrene butadiene rubber (SBR), alumina (Al 2 O 3 ), and carboxymethyl cellulose (CMC) in a weight ratio of 80:20:0.008 to prepare a mixture and adding 40 weight % of distilled water to the mixture. 
     A method of manufacturing a pouch-shaped battery cell according to the present invention may include (a) a step of coating an electrode sheet to form a coated portion, which is a portion coated with an electrode mixture, and an uncoated portion, which is a portion coated with no electrode mixture; (b) a step of adding an insulating member to outer surfaces of a part of the coated portion and a part of the uncoated portion as a border portion between the coated portion and the uncoated portion; (c) a step of rolling the electrode sheet; and (d) a step of slitting the electrode sheet of step (c). 
     The insulating member may be formed on the coated portion by coating so as to have a size of at least 0.1 mm. Preferably, the insulating member is formed on the coated portion by coating so as to overlap the coated portion by less than 0.4 mm. In order to prevent an increase in overall thickness of the electrode due to addition of the insulating member, however, it is preferable for the thickness of the insulating member not to be greater than the thickness of the coated portion based on the insulating member formed on the uncoated portion by coating. 
     Since the insulation member is added to the border portion between the uncoated portion and the coated portion, as in the present invention, it is possible to prevent occurrence of short circuit due to contact between the positive electrode and the negative electrode even though the separator interposed between the positive electrode and the negative electrode shrinks. 
     In connection therewith, since the area of the coated portion of the negative electrode is generally designed so as to be greater than the area of the coated portion of the positive electrode, the coated portion of the negative electrode is disposed in contact with the coated portion of the positive electrode in the stacking direction. In the case in which the separator shrinks due to overheating of the electrode assembly, therefore, short circuit may occur due to contact between the coated portion of the negative electrode and the coated portion of the positive electrode. 
     In the present invention, since the insulating member is added to the border between the coated portion and the uncoated portion, it is possible to prevent contact between the coated portion of the negative electrode and the coated portion of the positive electrode even though the separator shrinks. 
     In the electrode according to the present invention, it is preferable for the height of the uncoated portion, which corresponds to the distance between the first coated portion and the second coated portion, to be uniformly formed in a lateral direction of the uncoated portion perpendicular thereto. In order to prevent the coated portion from being separated from the electrode current collector even though the electrode assembly is folded 180 degrees, the height of the uncoated portion may be set in consideration of the thickness of the electrode current collector and the thickness of the coated portion formed on one surface or opposite surfaces of the electrode current collector by coating. 
       FIG.  3    is a side view of an electrode having a folding line formed thereat. 
     Referring to  FIG.  3   , the electrode of  FIG.  3    is similar to the electrode of  FIG.  2    but is different from the electrode of  FIG.  2    in that a wrinkled folding line  318  is formed at an uncoated portion  315 . 
     In the case in which the folding line  318  is formed, as described above, stress concentrated on a bent portion when the electrode is folded is dispersed, whereby it is possible to prevent damage to the bent portion. 
     The above description of the electrode of  FIG.  2    may be equally applied to an electrode tab, coated portion, uncoated portion, and insulating member of the electrode of  FIG.  3   . 
     Meanwhile, the method of manufacturing the pouch-shaped battery cell according to the present invention may include a process of manufacturing an electrode assembly by stacking a positive electrode and a negative electrode manufactured by cutting the electrode sheet slit in step (d) in the state in which a separator is interposed therebetween, receiving the electrode assembly in a pouch-shaped battery case having a stepped portion formed thereat, and hermetically sealing the pouch-shaped battery case. 
       FIG.  4    is a side view of pouch-shaped battery cells according to the present invention. 
     Referring to  FIG.  4   , a pouch-shaped battery cell (a) and a pouch-shaped battery cell (b) include first battery cases  431  and  531  and second battery cases  432  and  532 , respectively. The first battery case  431  of the pouch-shaped battery cell (a) has formed therein a receiving portion  433  configured to receive an electrode assembly, and a stepped portion  436  is formed at the receiving portion  433  so as to be recessed inwards. The stepped portion  436  is formed at a portion corresponding to the portion of the electrode assembly at which an uncoated portion is located. The second battery case  432  has a flat shape having no receiving portion formed therein. 
     A receiving portion  533  configured to receive an electrode assembly is formed in each of the first battery case  531  and the second battery case  532  of the pouch-shaped battery cell (b), and a stepped portion  536  is formed at the receiving portion  533  so as to be recessed inwards. The stepped portion  536  is formed at a portion corresponding to the portion of the electrode assembly at which an uncoated portion is located. 
     Since the pouch-shaped battery cell (a) and the pouch-shaped battery cell (b) are configured respectively such that the stepped portions  436  and  536  are formed so as to correspond to the portions of the electrode assemblies at which the uncoated portions are located, as described above, coated portions of the electrode assemblies are received respectively in protruding portions  437  and  537 , which relatively protrude, whereby fixation in position of the electrode assemblies in the battery cases may be achieved. 
     In addition, the method of manufacturing the pouch-shaped battery cell according to the present invention may further include a process of receiving the electrode assembly in a pouch-shaped battery case having a stepped portion formed thereat and attaching the uppermost electrode and the lowermost electrode of the electrode assembly to the stepped portion of the pouch-shaped battery case. 
     In connection therewith,  FIG.  5    is a partial enlarged view of a vertical section of a pouch-shaped battery cell according to the present invention. 
     Referring to  FIG.  5   , an electrode assembly is the electrode assembly (a) of  FIG.  1   , and the separator is omitted for convenience of description. A battery case is the battery case of the pouch-shaped battery cell (b) shown in  FIG.  4   . 
     The electrode assembly is a stacked type electrode assembly, which is configured to have a structure in which positive electrodes  110  and negative electrodes  120  are alternately stacked in the state in which separators are interposed respectively between the positive electrodes and the negative electrodes. Each of the positive electrodes  110  and the negative electrodes  120  is provided with a coated portion and an uncoated portion. A stepped portion of a first battery case  531  is attached to the uncoated portion of the negative electrode  120  located at the uppermost end of the electrode assembly, and a second battery case  532  is attached to the uncoated portion of the positive electrode  110  located at the lowermost end of the electrode assembly. 
     Since the electrode assembly is coupled to the pouch-shaped battery case, as described above, it is possible to prevent movement of the electrode assembly in the battery case due to external impact. Consequently, it is possible to prevent damage to electrode tabs and an electrode lead due to movement of the electrode assembly. 
     Pouch-shaped battery cells manufactured using the method of manufacturing the pouch-shaped battery cell described above are shown in  FIGS.  6  to  9   . 
       FIG.  6    is a perspective view of a pouch-shaped battery cell having a notch formed in a sealed portion thereof. 
     In the pouch-shaped battery cell according to the present invention, a notch may be formed in a battery case in order to prevent damage to the battery case due to tensile force generated at a folding portion of the battery case at the time of folding. 
     Referring to  FIG.  6   , a stepped portion  636  and receiving portions  633  are formed at each of a first battery case  631  and a second battery case  632 . In the case in which the pouch-shaped battery case is folded upwards based on the stepped portion  636 , as shown in  FIG.  6   , a sealed portion of the pouch-shaped battery case may be extended by the two receiving portions  633 , which protrude. Consequently, a notch  660  is formed in the sealed portion of the portion of the pouch-shaped battery case that is folded, as in the pouch-shaped battery case of  FIG.  6   , whereby it is possible to prevent damage to the pouch-shaped battery case or to prevent release of sealing of the sealed portion. 
       FIG.  7    is a perspective view showing a process of upwardly bending a pouch-shaped battery cell according to the present invention based on an x axis, and  FIG.  8    is a perspective view showing a process of downwardly bending the pouch-shaped battery cell according to the present invention based on the x axis. 
     Referring to  FIGS.  7  and  8   , the pouch-shaped battery cell has a structure in which a stepped portion  736  is formed at a pouch-shaped battery case so as to be parallel to the x axis, i.e. a structure in which a stepped portion is formed at only a first battery case, which is an upper battery case, as in the pouch-shaped battery cell (a) of  FIG.  4   . 
     Consequently, in the case in which the pouch-shaped battery cell is bent upwards, as shown in  FIG.  7   , the height of an uncoated portion of an electrode assembly and the distance between protruding portions  737  must be set in consideration of the height of the protruding portions. 
     However, in the case in which the pouch-shaped battery cell is bent downwards, as shown in  FIG.  8   , the height of the uncoated portion of the electrode assembly and the distance between the protruding portions may be set to be less than the height of the uncoated portion of the electrode assembly of  FIG.  7    and the distance between the protruding portions, since no protruding portions are formed on a second battery case, which is a lower battery case. 
     Unlike what is shown in  FIG.  8   , the pouch-shaped battery cell may have a structure in which a stepped portion and protruding portions are formed at each of the first battery case and the second battery case, as in the pouch-shaped battery cell (b) of  FIG.  4   . 
       FIG.  9    is a perspective view showing a process of upwardly bending a pouch-shaped battery cell according to the present invention based on a y axis. 
     Referring to  FIG.  9   , a pouch-shaped battery cell that has a narrow and long shape may be applied depending on the shape of a device. As shown in  FIG.  9   , it is possible to manufacture the pouch-shaped battery cell so as to be bent based on the y axis, which is parallel to the overall length direction of the pouch-shaped battery cell. 
     The pouch-shaped battery cell of  FIG.  9    has a structure in which a stepped portion  836  is formed at a pouch-shaped battery case so as to be parallel to the y axis, i.e. a structure in which a stepped portion is formed at only a first battery case, which is an upper battery case, as in the pouch-shaped battery cell (a) of  FIG.  4   . 
     Consequently, the height of an uncoated portion of an electrode assembly and the distance between protruding portions  837  must be set in consideration of the height of the protruding portions. 
     Although  FIG.  9    shows the case in which the pouch-shaped battery cell is bent upwards, the pouch-shaped battery cell may be bent downwards, as shown in  FIG.  8   . 
     In addition, unlike what is shown in  FIG.  9   , the pouch-shaped battery cell may have a structure in which a stepped portion and protruding portions are formed at each of the first battery case and the second battery case, as in the pouch-shaped battery cell (b) of  FIG.  4   . 
     As described above, the pouch-shaped battery cell according to the present invention is configured such that the uncoated portion is formed at the electrode assembly and the stepped portion is formed at the pouch-shaped battery case so as to correspond to the uncoated portion, whereby it is possible for a user to fold or unfold the pouch-shaped battery cell when in use. 
     In addition, since the electrode assembly and the inner surface of the pouch-shaped battery case are partially coupled to each other, it is possible to prevent movement of the electrode assembly in the pouch-shaped battery case, and therefore it is possible to improve safety of the pouch-shaped battery cell. 
     Those skilled in the art to which the present invention pertains will appreciate that various applications and modifications are possible within the category of the present invention based on the above description. 
     DESCRIPTION OF REFERENCE NUMERALS 
     
         
           110 ,  310 : Positive electrodes 
           111 ,  121 ,  211 ,  221 ,  311 : Coated portions 
           112 ,  212 ,  312 : Positive electrode tabs 
           113 ,  123 ,  213 ,  223 ,  313 : Insulating members 
           115 ,  125 ,  215 ,  225 ,  315 : Uncoated portions 
           120 ,  220 : Negative electrodes 
           122 ,  222 : Negative electrode tabs 
           431 ,  531 ,  631 : First battery cases 
           432 ,  532 ,  632 : Second battery cases 
           433 ,  533 ,  633 : Receiving portions 
           436 ,  536 ,  636 ,  736 ,  836 : Stepped portions 
           437 ,  537 ,  737 ,  837 : Protruding portions 
           660 : Notch 
       
    
     INDUSTRIAL APPLICABILITY 
     As is apparent from the above description, a pouch-shaped battery cell according to the present invention is configured to have a structure in which an uncoated portion, which is a portion coated with no electrode mixture, is formed at each of a positive electrode and a negative electrode, and an electrode assembly is folded at the uncoated portion, whereby it is possible to prevent separation of an electrode mixture layer from an electrode current collector as a result of folding. 
     In addition, a stepped portion having a recessed shape is formed at the portion of a pouch-shaped battery case corresponding to the uncoated portion of the electrode assembly, whereby it is possible to seat and fix a coated portion of the electrode assembly onto a protruding portion of the pouch-shaped battery case, which relatively protrudes. 
     Also, in the case in which the uncoated portion of the electrode assembly is attached to the stepped portion of the pouch-shaped battery case, it is possible to more securely fix the position of the electrode assembly. Consequently, it is possible to prevent separation of the electrode assembly, and therefore it is possible to prevent damage to electrode tabs and an electrode lead.