Patent Publication Number: US-2022223918-A1

Title: Secondary battery and battery module

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is a continuation application of PCT Patent Application Ser. No. PCT/CN2021/094549, filed on Mar. 19, 2021, which claims priority to Chinese Patent Application Ser. No. 202011052243.1, filed with the China National Intellectual Property Administration on Sep. 29, 2020, all of which are incorporated herein by reference in their entirety. 
    
    
     TECHNICAL FIELD 
     This application relates to a secondary battery and a battery module. 
     BACKGROUND 
     Existing rechargeable secondary batteries of conventional structures are commonly used in products such as mobile phones, notebooks, and electric vehicles. Such products are large in size whose extractable capacity requires a relatively high spatial occupancy. However, emergence of small portable electronic products imposes an increasingly high requirement on the battery size. If the internal structure of a conventional secondary battery is applied to a battery of a limit size, energy density needs to be further improved. 
     SUMMARY 
     This application provides a secondary battery, including a first electrode sheet and a second electrode sheet. The first electrode sheet includes a plurality of first conductive layers and a plurality of first bending portions, and two adjacent first conductive layers are connected through one of the first bending portions. The second electrode sheet includes a plurality of second conductive layers and a plurality of second bending portions, and two adjacent second conductive layers are connected through one of the second bending portions. The plurality of first conductive layers and the plurality of second conductive layers are alternately stacked. Viewed along the first direction perpendicular to a surface of the first conductive layer, each first bending portion includes a first edge, the first edge extends along a second direction perpendicular to the first direction; and each second bending portion includes a second edge, the second edge extends along a third direction perpendicular to the first direction. The second direction is different from the third direction. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a three-dimensional schematic diagram of a secondary battery according to a first embodiment of this application. 
         FIG. 2  is a schematic cross-sectional view of the secondary battery shown in  FIG. 1  along an A-A direction. 
         FIG. 3  is a schematic vertical view of a stacked first electrode sheet. 
         FIG. 4  is a schematic vertical view of an arc-shaped first side edge according to another embodiment of this application. 
         FIG. 5  is a schematic vertical view of a stacked first conductive layer according to another embodiment. 
         FIG. 6  is a schematic partial cross-sectional view of a secondary battery according to another embodiment. 
         FIG. 7  is a schematic cross-sectional view of the secondary battery shown in  FIG. 1  along a B-B direction. 
         FIG. 8  is a schematic vertical view of a stacked second electrode sheet. 
         FIG. 9  is a schematic vertical view of an arc-shaped second side edge according to another embodiment of this application. 
         FIG. 10  is a schematic vertical view of a stacked second conductive layer according to another embodiment. 
         FIG. 11  is a schematic partial cross-sectional view of a secondary battery according to another embodiment. 
         FIG. 12  shows a case in which there is a distance between a stacked first conductive layer and a second conductive layer according to another embodiment. 
         FIG. 13  shows a case in which there is a distance between a stacked second conductive layer and a first conductive layer according to another embodiment. 
         FIG. 14  is a schematic diagram of an unfolded first electrode sheet according to an embodiment of this application. 
         FIG. 15  is a schematic cross-sectional view of the first electrode sheet in  FIG. 14  along a C-C direction. 
         FIG. 16  is a schematic diagram of an unfolded second electrode sheet according to an embodiment of this application. 
         FIG. 17  is a schematic cross-sectional view of the second electrode sheet in  FIG. 16  along a D-D direction. 
         FIG. 18  is a three-dimensional schematic diagram of the stacked first electrode sheet and second electrode sheet according to the first embodiment of this application. 
         FIG. 19  is a schematic cross-sectional view of the first electrode sheet exposing a first metal layer according to the first embodiment of this application. 
         FIG. 20  is a schematic cross-sectional view of the first electrode sheet in  FIG. 19  along an E-E direction. 
         FIG. 21  is a schematic cross-sectional view of the second electrode sheet exposing a second metal layer according to the first embodiment of this application. 
         FIG. 22  is a schematic cross-sectional view of the second electrode sheet in  FIG. 21  along an F-F direction. 
         FIG. 23  is a schematic cross-sectional view showing that the first electrode sheet exposing the first metal layer and the second electrode sheet exposing the second metal layer are stacked. 
         FIG. 24  is a schematic vertical view of the unfolded first electrode sheet in  FIG. 15  with an active layer on a first bending portion removed. 
         FIG. 25  is a schematic cross-sectional view of the first electrode sheet in  FIG. 24  along an E-E direction. 
         FIG. 26  is a schematic cross-sectional view of the first electrode sheet in  FIG. 24  after being stacked. 
         FIG. 27  is a schematic cross-sectional view of the first electrode sheet in  FIG. 24  after being stacked in another embodiment. 
         FIG. 28  is a schematic cross-sectional view showing a first layer disposed at a position of a first bending portion of the first electrode sheet shown in  FIG. 25 . 
         FIG. 29  is a schematic cross-sectional view of the first electrode sheet in  FIG. 28  after being stacked. 
         FIG. 30  is a schematic vertical view of the unfolded second electrode sheet in  FIG. 17  with an active layer on a second bending portion removed. 
         FIG. 31  is a schematic cross-sectional view of the second electrode sheet in  FIG. 30  along an H-H direction. 
         FIG. 32  is a schematic cross-sectional view of the second electrode sheet in  FIG. 31  after being stacked. 
         FIG. 33  is a schematic cross-sectional view of the second electrode sheet in  FIG. 31  after being stacked in another embodiment. 
         FIG. 34  is a three-dimensional schematic diagram of a secondary battery provided with a conductive sheet according to the first embodiment of this application. 
         FIG. 35  is a three-dimensional schematic diagram of a secondary battery provided with a first conductive sheet and a second conductive sheet according to another embodiment. 
         FIG. 36  is a three-dimensional schematic diagram of a secondary battery provided with a first conductive sheet and a second conductive sheet according to another embodiment. 
         FIG. 37  is a three-dimensional schematic diagram of a secondary battery provided with a first conductive sheet and a second conductive sheet according to another embodiment. 
         FIG. 38  is a schematic partial cross-sectional view showing a first electrode sheet of the secondary battery shown in  FIG. 34  provided with a conductive sheet. 
         FIG. 39  is a schematic partial cross-sectional view showing a second electrode sheet of the secondary battery shown in  FIG. 34  provided with a conductive sheet. 
         FIG. 40  is a schematic partial cross-sectional view showing the first electrode sheet and the second electrode sheet with no specific-shaped separator provided in between according to the first embodiment of this application. 
         FIG. 41  is a three-dimensional schematic diagram of a battery module according to another embodiment of this application. 
         FIG. 42  is a schematic exploded view of the battery module shown in  FIG. 41 . 
         FIG. 43  is a schematic cross-sectional view of the battery module shown in  FIG. 41  along a J-J direction. 
         FIG. 44  is a schematic exploded view of a battery module provided with a connector according to another embodiment. 
         FIG. 45  is a schematic cross-sectional view of the battery module shown in  FIG. 44 . 
         FIG. 46  is a schematic exploded view of a battery module provided with a first connector and a second connector according to another embodiment. 
         FIG. 47  is a schematic cross-sectional view of the battery module shown in  FIG. 46 . 
         FIG. 48  is a schematic exploded view of a battery module provided with a conductive sheet according to another embodiment. 
         FIG. 49  is a schematic cross-sectional view of the battery module shown in  FIG. 48 . 
         FIG. 50  is a schematic vertical view of an unfolded first electrode sheet according to a second embodiment of this application. 
         FIG. 51  is a schematic vertical view of an unfolded second electrode sheet according to the second embodiment of this application. 
         FIG. 52  is a schematic cross-sectional view of the first electrode sheet and the second electrode sheet after being stacked according to the second embodiment of this application; 
         FIG. 53  is a schematic vertical view of an unfolded first electrode sheet according to a third embodiment of this application. 
         FIG. 54  is a schematic vertical view of an unfolded second electrode sheet according to the third embodiment of this application. 
         FIG. 55  is a schematic cross-sectional view of the first electrode sheet and the second electrode sheet after being stacked according to the third embodiment of this application. 
         FIG. 56  is a schematic vertical view of an unfolded first electrode sheet according to a fourth embodiment of this application. 
         FIG. 57  is a schematic vertical view of an unfolded second electrode sheet according to the fourth embodiment of this application. 
         FIG. 58  is a schematic cross-sectional view of the first electrode sheet and the second electrode sheet after being stacked according to the fourth embodiment of this application. 
         FIG. 59  is a three-dimensional schematic diagram of an electronic device according to a fifth embodiment of this application. 
     
    
    
     REFERENCE SIGNS OF MAIN COMPONENTS 
     
         
         secondary battery  1   
         first electrode sheet  10   
         first conductive layer  11   
         first side  111   
         first region  112   
         second region  113 ,  116   
         second side  114   
         first side edge  115 ,  115 ′ 
         first distance H 1    
         first point O 1    
         second point O 2    
         second distance H 2    
         third point I 1    
         fourth point I 2    
         distance between the first side and the K 1    
         second conductive layer 
         distance between the second side and the K 2    
         second conductive layer 
         first distance L 1    
         second distance L 2    
         first bending portion  12   
         first edge  121 ,  121   a    
         first boundary M 
         first metal layer  13   
         first surface  131   
         second surface  132   
         fifth region A 
         first material layer  14   
         first end portion  15   
         first layer  16   
         first exposed portion  17   
         first opening  18   
         second electrode sheet  20   
         second conductive layer  21   
         third side  211   
         third region  212   
         fourth region  213 ,  216   
         fourth side  214   
         second side edge  215 ,  215 ′ 
         third distance H 3    
         fifth point O 3    
         sixth point O 4    
         fourth distance H 4    
         seventh point I 3    
         eighth point I 4    
         distance between the third side and the K 3    
         first conductive layer 
         distance between the fourth side and the K 4    
         first conductive layer 
         second bending portion  22   
         second edge  221 ,  221   a    
         second boundary N 
         second metal layer  23   
         third surface  231   
         fourth surface  232   
         sixth region B 
         second material layer  24   
         second end portion  25   
         second exposed portion  27   
         second opening  28   
         length D 1 , D 2 , D 3 , D 4 , D 5 , D 6   
         conductive sheet  30   
         first conductive sheet  31   
         second conductive sheet  32   
         separator  40   
         battery module  100   
         first package  50   
         first cover body  51   
         pole  52   
         first insulator  53   
         second package  60   
         second cover body  61   
         shell  62   
         second insulator  63   
         through hole  54   a ,  64   a ,  64   b    
         connector  70   
         first connector  71   
         second connector  72   
         first direction Z 
         second direction Y 
         third direction X 
         electronic apparatus  200   
         main body  80   
       
    
     DETAILED DESCRIPTION 
     The following describes the technical solutions in the embodiments of this application clearly and in detail. Apparently, the described embodiments are a part rather than all of the embodiments of this application. Unless otherwise defined, all technical and scientific terms used herein shall have the same meanings as commonly understood by those skilled in the art to which this application belongs. The terms used in the specification of this application are intended to describe specific embodiments but not intended to constitute any limitation on this application. 
     The following describes the embodiments of this application in detail. However, this application may be embodied in many different forms, and should not be construed as being limited to the example embodiments explained herein. Rather, these example embodiments are provided so that this application may be conveyed to those skilled in the art thoroughly and in detail. 
     In addition, for brevity and clarity, in the accompanying drawings, sizes or thicknesses of various components and layers may be enlarged. As used herein, the term “and/or” includes any and all combinations of one or more related listed items. In addition, it should be understood that when an element A is referred to as “connecting” an element B, the element A may be directly connected to the element B, or there may be an intermediate element C and the element A and the element B may be indirectly connected to each other. 
     Further, the use of “may” when describing the embodiments of this application refers to “one or more embodiments of this application”. 
     The terminology used herein is for the purpose of describing specific embodiments and is not intended to limit this application. As used herein, singular forms are intended to also include plural forms, unless the context clearly specifies otherwise. It should be further understood that the term “including”, when used in this specification, refers to the presence of the described features, values, steps, operations, elements, and/or components, but does not exclude the presence or addition of one or more other features, values, steps, operations, elements, components, and/or combinations thereof. 
     Spatial related terms such as “above” may be used herein for ease of description to describe the relationship between one element or feature and another element (a plurality of elements) or feature (a plurality of features) as illustrated in the figure. It should be understood that, in addition to the directions described in the figures, the spatial related terms are intended to include different directions in the use or operation of devices or apparatus. For example, if a device in the figure is turned over, an element described as “on” or “above” another element or feature should be oriented “below” or “under” the another element or feature. Therefore, the example term “above” may include directions of above and below. It should be understood that although the terms first, second, third, or the like may be used herein to describe various elements, components, regions, layers, and/or portions, these elements, components, regions, layers, and/or portions should not be limited by these terms. These terms are used to distinguish one element, component, region, layer, or portion from another element, component, region, layer, or portion. Therefore, the first element, component, region, layer, or portion discussed below may be referred to as the second element, component, region, layer, or portion without departing from the teachings of the example embodiments. 
     This application provides a secondary battery, including a first electrode sheet and a second electrode sheet. The first electrode sheet includes a plurality of first conductive layers and a plurality of first bending portions, and two adjacent first conductive layers are connected through one of the first bending portions. The second electrode sheet includes a plurality of second conductive layers and a plurality of second bending portions, and two adjacent second conductive layers are connected through one of the second bending portions. The plurality of first conductive layers and the plurality of second conductive layers are alternately stacked. Viewed along the first direction perpendicular to a surface of the first conductive layer, each first bending portion includes a first edge, the first edge extends along a second direction perpendicular to the first direction, and each second bending portion includes a second edge, the second edge extends along a third direction perpendicular to the first direction. The second direction is different from the third direction. 
     In the foregoing secondary battery, the first electrode sheet and the second electrode sheet are alternately bent in different directions, so that the first electrode sheet and the second electrode sheet are stacked in the first direction. Based on the secondary battery, more electrode sheets may be accommodated in limited space, thereby increasing energy density of the secondary battery. 
     The following describes some embodiments of this application in detail. In absence of conflicts, the following embodiments and features in the embodiments may be combined. 
     First Embodiment 
     Referring to  FIG. 1 , a secondary battery  1  includes a first electrode sheet  10  and a second electrode sheet  20 . The first electrode sheet  10  includes a plurality of first conductive layers  11  and a plurality of first bending portions  12 , and two adjacent first conductive layers  11  are connected through one of the first bending portions  12 . There is a first boundary M between the first conductive layer  11  and the first bending portion  12 , and the first boundary M is a position at which the first conductive layer  11  and the first bending portion  12  are connected. The second electrode sheet  20  includes a plurality of second conductive layers  21  and a plurality of second bending portions  22 , and two adjacent second conductive layers  21  are connected through one of the second bending portions  22 . There is a second boundary N between the second conductive layer  21  and the second bending portion  22 , and the second boundary N is a position at which the second conductive layer  21  and the second bending portion  22  are connected. 
     The plurality of first conductive layers  11  and the plurality of second conductive layers  21  are alternately stacked. A direction perpendicular to the first conductive layer  11  and the second conductive layer  21  is defined as a first direction Z. Viewed along the first direction Z, each first bending portion  12  includes a first edge  121 , and the first edge  121  extends along a second direction Y Each second bending portion  22  includes a second edge  221 , and the second edge  221  extends along a third direction X. A predetermined angle is defined between the second direction Y and the third direction X. 
     The secondary battery  1  is further explained below. Referring to  FIG. 2 , the plurality of first conductive layers  11  included in the first electrode sheet  10  are stacked in the first direction Z. The first bending portions  12  are located on both sides of the first conductive layer  11  for connecting two adjacent first conductive layers  11 , and each of the first bending portions  12  is connected to the first conductive layer  11  at the position of the first boundary M. 
     In an embodiment, the first conductive layer  11  and the plurality of first bending portions  12  may be an integrally formed structure, so that the first electrode sheet  10  may be folded and stacked more conveniently. 
     Referring to  FIG. 3 , the first conductive layer  11  is viewed along the first direction Z. The first conductive layer  11  includes a first side  111  and a first region  112 . The first side  111  is an edge portion of the first conductive layer  11 ; Further, the first side  111  and the first boundary M refer to the same structure. The first side  111  is to better illustrate the structure and component of the first conductive layer  11 , and the first boundary M is to better distinguish between the first conductive layer  11  and the first bending portion  12 . The first region  112  is approximately located at the middle of the first conductive layer  11 . Specifically, the first region  112  is a region between two dotted lines in  FIG. 3 . 
     In the second direction Y, a length of the first region  112  is D 1 , a length of the first side  111  is D 2 , and D 1  is greater than D 2 . An area of the middle of the first conductive layer  11  is greater than an area of the edge, so that an overall area of the first conductive layer  11  is increased, thereby increasing energy density of the first conductive layer  11 . 
     Referring to  FIG. 3 , in an embodiment, the first conductive layer  11  further includes a second region  113 . The second region  113  is located between the first side  111  and the first region  112 , and connects the first side  111  and the first region  112 . Further, the second region  113  is a region between the first side  111  and a dotted line that is one of the two dotted lines used as boundaries of the first region  112  in  FIG. 3  and that is closer to the first side  111  than to a second side  114 . In the second direction Y, a length of the second region  113  is D 3 , and D 3  is between D 1  and D 2 , that is, the length of the second region  113  is greater than the length of the first side  111  and less than the length of a first region  112 . Therefore, when the length of the first conductive portion in the second direction X is extended from first side  111  to the first region  112 , an area of the first conductive layer  11  is gradually increased to further increase the overall energy density of the first conductive layer  11 . 
     In an embodiment, the first conductive layer  11  further includes a second side  114 . The second side  114  is an edge portion of the first conductive layer  11 , and the second side  114  and the first side  111  are disposed opposite to each other on both sides of the first conductive layer  11 . Further, the second side  114  and the first boundary M refer to the same structure. The second side  114  is also to better illustrate the component and structure of the first conductive layer  11 , and the first boundary M is to better distinguish between the first conductive layer  11  and the first bending portion  12 . 
     In an embodiment, the first conductive layer  11  further includes a second region  116 . The second region  116  is located between the second side  114  and the first region  112 , and connects the second side  114  and the first region  112 . Further, the second region  116  is a region between the second side  114  and a dotted line that is of the two dotted lines used as boundaries of the first region  112  in  FIG. 3  and that is closer to the second side  114  than to the first side  111 . A structure of the second region  116  is substantially the same as the structure of the second region  113 . Therein, “substantially the same” should be understood to mean that the main component and structure of the objects described are the same, but reasonable differences are also allowed. It may be understood that, in other embodiments, the second region  116  and the second region  113  may have different structures. 
     The first conductive layer  11  further includes first side edges  115  and  115 ′. In this embodiment, the first side edge  115  and the first side edge  115 ′ are approximately symmetrically arranged. Two ends of the first side edge  115 , as well as two ends of the first side edge  115 ′, are respectively connected to the first side  111  and the second side  114 , and the first side edges  115  and  115 ′ are edge portions of the first region  112  and the second regions  113  and  116 . Therein, “approximately symmetrically arranged” should be understood to include the case of symmetry as well as the case where there is a certain dimensional deviation between the first side edges  115  and  115 ′. For example, there is a deviation of ±5° between the first side edges  115  and  115 ′ along the third direction X. It may be understood that, in other embodiments, the first side edge  115  and the first side edge  115 ′ may alternatively be asymmetric structures, and an angle may be formed between them, so that the first conductive layer  11  has a different shape. 
     Further, the first side edges  115  and  115 ′ tend to be linear. 
     Referring to  FIG. 4 , in an embodiment, the first side edges  115  and  115 ′ may alternatively be arc-shaped. Along the third direction X, the first side edges  115  and  115 ′ gradually extend from an end of the first side  111  toward an end of the first region  112 , and then gradually extend from the first region  112  toward an end of the second side  114 . 
     Referring to  FIG. 3 , in an embodiment, when the first conductive layers  11  are stacked along the first direction Z, the first sides  111  of all the first conductive layers  11  may overlap. Then at least one portion of the plurality of first conductive layers  11  may overlap, so that the space utilization of the secondary battery  1  may be increased. The overlap described herein includes a case in which there is a deviation between first sides  111 . 
       FIG. 5  may be regarded as a state that two first conductive layers  11  are not completely overlapped. When the first conductive layers  11  are stacked along the first direction Z, some of the first sides  111  may overlap, so that some of the first side edges  115  and  115 ′ overlap. 
     The first side  111 , the first region  112 , the second region  113 , the second side  114 , and the first side edges  115  and  115 ′ are integrally formed. It may be understood that, in other embodiments, the first side edges  115  and  115 ′ are not limited to the linear and curved shapes described above. 
     Referring to  FIG. 2  and  FIG. 3  again, viewed along the first direction Z, the first edge  121  of the first bending portion  12  is parallel to the first side  111 . Therein, “parallel” should be understood to include the case where there is no angle or a small angle between the first edge  121  and the first side  111 . For example, there is a deviation of 5° between the first edge  121  and the first side  111 . The first bending portion  12  is bent toward the third direction X, and the first bending portion  12  is located outside the two first conductive layers  11 . 
     Referring to  FIG. 5  and  FIG. 6 , along the third direction X, a distance L 1  is generated between the non-overlapped first edge  121  and the first edge  121  at the overlapped position, so that some of the first sides  111 , as well as some of the first side edges  115  and  115 ′, are not overlapped. L 1  is less than or equal to 3 mm, which may, for example, enable the secondary battery  1  to decrease a possibility of increasing in size. Further, for example, when there is L 1 , a connection position of the first bending portion  12  and the first conductive layer  11  connected to the first bending portion  12  and a connection position of the adjacent first bending portion  12  and the first conductive layer  11  connected to the adjacent first bending portion  12  are staggered, thereby reducing an overall height of the secondary battery  1 , which is conducive to the increase of the energy density of the secondary battery  1 . 
     Referring to  FIG. 6 , viewed along the first direction Z, the first bending portion  12  has a length greater than a distance between two adjacent first sides  111 . Specifically, in the first direction Z, the first bending portion  12  has a first distance H 1 , which is the distance between the two ends of the inner bending portion of the first bending portion  12 , i.e., the distance of the first point O 1  and the second point O 2 . The distance between the two adjacent first sides  111  is a second distance H 2 , which is the distance between the third point I 1  and the fourth point I 2 . The first distance H 1  is greater than the second distance H 2 . Based on this arrangement, the first bending portion  12  is easier to be bent, and an electrolyte may be filled in the inner side of the first bending portion  12 , which may enhance strength of the first bending portion  12  while supporting the first bending portion  12 . 
     It may be understood that, in an embodiment, to increase space utilization at the edge of the secondary battery  1 , the first distance H 1  may be the maximum distance of the first bending portion  12  in the first direction Z. A larger distance between edges of the secondary battery  1  may be avoided when viewed along the first direction Z by making the first distance H 1  equal to the second distance H 2 . 
     Referring to  FIG. 6 , in an embodiment, viewed along the first direction Z, some of the first bending portions  12  overlap. If the first distance H 1  is greater than the second distance H 2 , the non-overlapped first bending portions  12  and the overlapped first bending portions  12  may be complementary along the first direction Z, to increase space utilization of the secondary battery  1  along the first direction Z. 
     Referring to  FIG. 7 , the plurality of second conductive layers  21  included in the second electrode sheet  20  are stacked along the first direction Z. The second bending portions  22  are located on both sides of the second conductive layer  21  for connecting two adjacent second conductive layers  21 , and each of the second bending portions  22  is connected to the second conductive layer  21  at the position of the second boundary N. 
     In an embodiment, the second conductive layers  21  and the plurality of second bending portions  22  may be an integrally formed structure, so that the second electrode sheet  20  may be bent and stacked more conveniently. 
     Referring to  FIG. 8 , the second conductive layer  21  is viewed along the first direction Z. The second conductive layer  21  includes a third side  211  and a third region  212 . The third side  211  is an edge portion of the second conductive layer  21 . Further, the third side  211  and the second boundary N refer to the same structure. The third side  211  is to better illustrate the component and structure of the second conductive layer  21 , and the second boundary N is to better distinguish between the second conductive layer  21  and the second bending portion  22 . The third region  212  is approximately located at the middle of the second conductive layer  21 . Specifically, the third region  212  is a region between two dotted lines in  FIG. 8 . 
     In the third direction X, a length of the third region  212  is D 4 , a length of the third side  211  is D 5 , and D 4  is greater than D 5 . In other words, an area of the middle of the second conductive layer  21  is increased compared to an area of the edge, and an overall area of the second conductive layer  21  is increased, so that energy density of the second conductive layer  21  is increased. 
     Referring to  FIG. 8 , in an embodiment, the second conductive layer  21  further includes a fourth region  213 . The fourth region  213  is located between the third side  211  and the third region  212 , and connects the third side  211  and the third region  212 . Further, the fourth region  213  is a region between the third side  211  and a dotted line that is of the two dotted lines used as boundaries of the third region  212  in  FIG. 8  and that is closer to the third side  211  than to a fourth side  214 . In the third direction X, a length of the fourth region  213  is D 6 , and D 6  is between D 4  and D 5 , that is, the length of the fourth region  213  is greater than the length of the third side  211  and less than the length of a third region  212 . 
     In an embodiment, the second conductive layer  21  further includes a fourth side  214 . The fourth side  214  is an edge portion of the second conductive layer  21 , and the fourth side  214  and the third side  211  are disposed opposite to each other on both sides of the second conductive layer  21 . Further, the fourth side  214  and the second boundary N refer to the same structure. The fourth side  214  is also to better illustrate the structure and component of the second conductive layer  21 , and the second boundary N is to better distinguish between the second conductive layer  21  and the second bending portion  22 . 
     In an embodiment, the second conductive layer  21  further includes a fourth region  216 . The fourth region  216  is located between the fourth side  214  and the third region  212 , and connects the fourth side  214  and the third region  212 . Further, the fourth region  216  is a region between the fourth side  214  and a dotted line that is of the two dotted lines used as boundaries of the third region  212  in  FIG. 8  and that is close to the fourth side  214  than to the third side  211 . A structure of the fourth region  216  is substantially the same as the structure of the fourth region  213 . It may be understood that, in other embodiments, the fourth region  216  and the fourth region  213  may have different structures. 
     The second conductive layer  21  further includes second side edges  215  and  215 ′. In this embodiment, the second side edge  215  and the second side edge  215 ′ are approximately symmetrically arranged. Two ends of the second side edge  215 , as well as two ends of the second side edge  215 ′, are respectively connected to the third side  211  and the fourth side  214 , and the second side edges  215  and  215 ′ are edge portions of the third region  212  and the fourth regions  213  and  216 . It can be understood that, in other embodiments, the second side edge  215  and the second side edge  215 ′ may alternatively be asymmetric structures, and an angle may be formed between them, so that the second conductive layer  21  has a different shape. 
     Further, the second side edges  215  and  215 ′ tend to be linear. 
     Referring to  FIG. 9 , in an embodiment, the second side edges  215  and  215 ′ may alternatively be arc-shaped. Along the second direction Y, a distance between the second side edges  215  and  215 ′ gradually increase from an end of the third side  211  toward an end of the third region  212 , and then gradually decrease from the third region  212  toward an end of the fourth side  214 . 
     Referring to  FIG. 8 , in an embodiment, when the second conductive layers  21  are stacked along the first direction Z, the third sides  211  of all the second conductive layers  21  may overlap, and then the plurality of second conductive layers  21  may have at least one portion overlapped with each other. The overlap described herein includes a case in which there is a deviation between third sides  211 . 
       FIG. 10  may be regarded as a state that the two second conductive layers  21  may be not completely overlapped. When the second conductive layers  21  are stacked along the first direction Z, some of the third sides  211  overlap, so that some of the second side edges  215  and  215 ′ may overlap. 
     The third side  211 , the third region  212 , the fourth region  213 , the fourth side  214 , and the second side edges  215  and  215 ′ are also an integrally formed structure. It may be understood that, in other embodiments, the second side edges  215  and  215 ′ are not limited to the linear and curved shapes described above. 
     Referring to  FIG. 7  and  FIG. 8  again, viewed along the first direction Z, the second edge  221  of the second bending portion  22  is parallel to the third side  211 . The second bending portion  22  is bent toward the second direction Y, and the second bending portion  22  is located outside the two second conductive layers  21 . 
     Referring to  FIG. 10  and  FIG. 11 , in the second direction Y, a distance L 2  is generated between the non-overlapped second edge  221  and the second edge  221  at the overlapped position, so that some of the third sides  211  and some of the third side edges  215  and  215 ′ are not overlapped. For example, L 2  is less than or equal to 3 mm, which may enable the secondary battery  1  to decrease a possibility of increasing in size. Further, for example, when there is L 2 , a connection position of the second bending portion  22  and the second conductive layer  21  connected to the second bending portion  22  and a connection position of the adjacent second bending portion  22  and the second conductive layer  21  connected to the adjacent second bending portion  22  are staggered. Thereby reducing an overall height of the secondary battery  1 , which is conducive to increase of the energy density of the secondary battery  1 . 
     Referring to  FIG. 11 , viewed along the first direction Z, the second bending portion  22  has a length greater than a distance between two adjacent third sides  211 . Specifically, the second bending portion  22  has a third distance H 3 , which is the distance between the two ends of the inner bending portion of the second bending portion  22 , i.e., the distance of the fifth point O 3  and the sixth point O 4 . The distance between the two adjacent third sides  211  is a fourth distance H 4 , which is the distance between the seventh point I 3  and the eighth point I 4 . The third distance H 3  is greater than the fourth distance H 4 . Based on this arrangement, the first bending portion  12  is easier to be bent, and an electrolyte may be filled in the inner side of the first bending portion  12 , which may enhance strength of the first bending portion  12  while supporting the first bending portion  12 . 
     It may be understood that, in an embodiment, to increase space utilization at the edge of the secondary battery  1 , the third distance H 3  may be the maximum distance of the second bending portion  22  in the first direction Z. A larger distance between edges of the secondary battery  1  may be avoided when viewed along the first direction Z by making the third distance H 3  equal to the fourth distance H 4 . 
     Referring to  FIG. 11 , in an embodiment, viewed along the first direction Z, some of the second bending portions  22  overlap. If the third distance H 3  is greater than the fourth distance H 4 , the non-overlapped second bending portion  22  and the overlapped second bending portion  22  may be complementary along the first direction Z, to increase space utilization of the secondary battery  1  along the first direction Z. 
       FIG. 12  shows a distance between the first conductive layer  11  and the second conductive layer  21 . A distance between the first edge  121  closer to the first side  111  than to the second side  114  and the second conductive layer  21  is K 1 , and a distance between the first edge  121   a  closer to the second side  114  than to the first side  111  and the second conductive layer  21  is K 2 , and K 1  may be different from K 2 . K 1  is the distance between the first edge  121  and the second side edge  215  of the second conductive layer  21  in the third direction X, and K 2  is the distance between the first edge  121   a  and the second side edge  215 ′ of the second conductive layer  21  in the third direction X. When another structure is provided on the first conductive layer  11 , if K 1  is greater than K 2 , the other structure may be disposed on one side of the second side  114  of the first conductive layer  11 . So that during stacking, the other structure may be more fixed when the second conductive layer  21  is disposed on the first conductive layer  11 . 
     For example, a sum of K 1  and K 2  may be less than or equal to 3 mm. Setting the sum of K 1  and K 2  to be less than or equal to 3 mm may decrease a possibility tahn the first sides  111  or second sides  114  of the two adjacent first conductive layers  11  may contact each other and cause short-circuit. Further, the secondary battery  1  may be enabled to decrease a possibility of increasing in size. In an embodiment, the sum of K 1  and K 2  is 0.5 mm, 1 mm, 1.5 mm, 2 mm, or 2.5 mm. It may be understood that, in other embodiments, the sum of K 1  and K 2  is not limited thereto. 
       FIG. 13  shows a state that there is a distance between the second conductive layer  21  and the first conductive layer  11 . A distance between the second edge  221  closer to the third side  211  than to the fourth side  214  and the first conductive layer  11  is K 3 , and a distance between the second edge  221   a  closer to the fourth side  214  than to the third side  211  and the first conductive layer  11  is K 4 , and K 3  is different from K 4 . K 3  is the distance between the second edge  221  and the first side edge  115  of the first conductive layer  11 , and K 4  is the distance between the second edge  221   a  and the first edge  115 ′ of the first conductive layer  11 . For example, a sum of K 3  and K 4  is less than or equal to 3 mm. Setting the sum of K 3  and K 4  to be less than or equal to 3 mm may decrease a possibility that the third sides  211  or fourth sides  214  of the two adjacent second conductive layers  21  may contact each other and cause short-circuit. Further, the secondary battery  1  may be enabled to decrease a possibility of increasing in size. In an embodiment, the sum of K 3  and K 4  is 0.5 mm, 1 mm, 1.5 mm, 2 mm, or 2.5 mm. It may be understood that, in other embodiments, the sum of K 3  and K 4  is not limited thereto. 
     Referring to  FIG. 14  and  FIG. 15 , the first electrode sheet  10  includes a first metal layer  13  and a first material layer  14 .  FIG. 14  and  FIG. 15  schematically show the structure of the first electrode sheet  10  in its unfolded state. The first metal layer  13  includes a first surface  131  and a second surface  132 . The first material layers  14  are disposed on the first surface  131  and the second surface  132 , and the first conductive layer  11  and the first bending portion  12  are formed by bending the first metal layer  13 . The first conductive layer  11  and the first bending portion  12  are finally formed structures included in the first electrode sheet  10  when the first electrode sheet  10  has been formed, and the first metal layer  13  and the first material layer  14  are the structures forming the first electrode sheet  10 . 
     Referring to  FIG. 16  and  FIG. 17 , the second electrode sheet  20  includes a second metal layer  23  and a second material layer  24 .  FIG. 16  and  FIG. 17  schematically show the structure of the second electrode sheet  20  in its unfolded state. The second metal layer  23  includes a third surface  231  and a fourth surface  232 . The second material layers  24  are disposed on the third surface  231  and the fourth surface  232 , and the plurality of second conductive layers  21  and the plurality of second bending portions  22  are formed by bending the second metal layer  23 . Same as the first electrode sheet  10 , the plurality of second conductive layers  21  and the plurality of second bending portions  22  are finally formed structures included in the second electrode sheet  20  when the second electrode sheet  20  has been formed, and the second metal layer  23  and the second material layer  24  are the structures forming the second electrode sheet  20 . 
     Referring to  FIG. 15 ,  FIG. 17 , and  FIG. 18 . In this embodiment, ends of the first metal layer  13  provided with the first material layer  14  and ends of the second metal layer  23  provided with the second material layer  24  are stacked along the first direction Z. Then the first metal layer  13  is bent back and forth along the third direction X, the second metal layer  23  is bent back and forth along the second direction Y The first metal layer  13  and the second metal layer  23  are alternately stacked, to form the secondary battery  1  finally. 
     Preferably, in this embodiment, the first direction Z, the second direction Y, and the third direction X are perpendicular to each other. It may be understood that, in other embodiments, the second direction Y and the third direction X may be at another angle, and the angle may be 80°, 81°, 82°, 83°, 84°, 85°, 86°, 87°, 88°, 89°, 91°, 92°, 93°, 94°, 95°, 96°, 97°, 98°, 99°, or 100°. 
     Referring to  FIG. 19  and  FIG. 20 , the first electrode sheet  10  includes a first metal layer  13  and a first material layer  14 .  FIG. 19  and  FIG. 20  schematically show the structure of the first electrode sheet  10  in its unfolded state. In this embodiment, the first electrode sheet  10  enable the secondary battery  1  to be directly electrically connected to a package structure packaging the secondary battery  1 . In an embodiment, the first electrode sheet  10  includes a first end portion  15 , the first surface  131  includes a fifth region A extending from the first end portion  15 , and the fifth region A exposes at least one portion of the first surface  131  of the first metal layer  13 . Referring to  FIG. 21  and  FIG. 22 , the second electrode sheet  20  includes a second metal layer  23  and a second material layer  24 .  FIG. 21  and  FIG. 22  schematically show the structure of the second electrode sheet  20  in its unfolded state. In this embodiment, the second electrode sheet  20  includes a second end portion  25 . The second end portion  25  is located on a side of the second electrode sheet  20  farther away from the first end portion  15 , the third surface  231  includes a sixth region B extending from the second end portion  25 , and the sixth region B exposes at least one portion of the surface of the second metal layer  23 . This exposure is only relative to other positions of the fifth region A or the sixth region B. Because the metal layer at other positions is covered by the material layer, the metal layer at the position of the fifth region A and the sixth region B is exposed relative to the covered metal layer. 
     Referring to  FIG. 23 , after the secondary battery  1  is formed through folding, the fifth region A and the sixth region B are located at two opposite ends of the secondary battery  1  in the first direction Z, respectively. 
     Referring to  FIG. 24  and  FIG. 25 , which schematically show the structure of the first electrode sheet  10  in its unfolded state. The first metal layer  13  includes the first surface  131  and the second surface  132 , and a plurality of the first material layers  14  are arranged on the first surface  131  and the second surface  132 . In this embodiment, the exposed surface between the first material layers  14  is defined as a first exposed portion  17 . The term “exposed” described here means that a portion of the first metal layer  13  is exposed from the first material layer  14 , and does not negate the fact that the first exposed portion  17  is covered by the electrolyte and the package. Referring  FIG. 26 , the first exposed portion is located at each the first bending portion  12 . For example, at the position of the first bending portion  12 , the first material layer  14  on a surface of the first metal layer  13  may be removed through intermittent coating, laser cleaning, scraping, or the like. Removing the first material layer  14  at the position of the first bending portion  12  may ensure that, for example, occurrence of lithium precipitation may be suppressed when the secondary battery  1  is used in a high-power charging scenario. Moreover, the bent first material layer  14  may also be enabled to decrease a possibility of easily falling off from the first metal layer  13 , and other effects of this phenomenon on the secondary battery  1  may also be suppressed. 
     Referring to  FIG. 27 , the first exposed portion  17  has different opening distances. And further, a distance of the first metal layer  13  exposed on the first bending portion  12  ranges from 0.2 mm to 5 mm. That is, the opening distance of the first exposed portion  17  is 0.2 mm to 5 mm. Specifically, the distance of the first exposed portion  17  may be 0.5 mm, 1 mm, 1.5 mm, 2 mm, 2.52 mm, 3.2 mm, 3.52 mm, 4.2 mm, or 4.5 mm. For example, disposing the first exposed portion  17  may reduce an overall height of the secondary battery  1  along the first direction Z, thereby increasing the energy density. 
     Referring to  FIG. 28  and  FIG. 29 , in an embodiment, the first bending portion  12  is provided with a first layer  16  including an insulation material at a position of the first exposed portion  17 . The first layer  16  covers the first surface  131  of the first metal layer  13  at the position of the first exposed portion  17 . For example, to suppress a short circuit caused when the first electrode sheet  10  comes into contact with the second electrode sheet  20  due to damage and failure occurring at the position of the first bending portion  12  in the case of mechanical abuse of the secondary battery  1 . 
     Referring to  FIG. 30  and  FIG. 31 , which schematically show the structure of the second electrode sheet  20  in its unfolded state. The second metal layer  23  includes the third surface  231  and the fourth surface  232 , and a plurality of the second material layers  24  are arranged on the third surface  231  and the fourth surface  232 . In this embodiment, the exposed surface between the second material layers  24  is defined as a second exposed portion  27 . The term “exposed” described here means that a portion of the second metal layer  23  is exposed from the second material layer  24 , and does not negate the fact that the second exposed portion  27  is covered by the electrolyte and the package. Referring  FIG. 32 , to reduce a risk of getting off of the second material layer  24  at the position of the second bending portion  22 , the second bending portion  22  is provided with the second exposed portion  27 . The third surface  231  and the fourth surface  232  of the second metal layer  23  are exposed at a position of the second exposed portion  27 , and the second material layer  24  may be removed through intermittent coating, laser cleaning, scraping, or the like. 
     Referring to  FIG. 33 , the second exposed portion  27  has different opening distances. And further, a distance of the second metal layer  23  exposed on the second bending portion  22  ranges from 0.1 mm to 5 mm. That is, the opening distance of the second exposed portion  27  is 0.1 mm to 5 mm. Specifically, the distance of the second exposed portion  27  may be 0.5 mm, 1 mm, 1.5 mm, 2 mm, 2.52 mm, 3.2 mm, 3.52 mm, 4.2 mm, or 4.5 mm. For example, disposing the second exposed portion  27  may reduce an overall height of the secondary battery  1  along the first direction Z, thereby increasing the energy density. 
     Referring to  FIG. 15  and  FIG. 17 , in an embodiment, the first direction Z is a thickness direction of the first material layer  14  and the second material layer  24 . A thickness of the first material layer  14  arranged on the first surface  131  is different form a thickness of the first material layer  14  arranged on the second surface  132 , and a thickness of the second material layer  24  arranged on the third surface  231  is different from the second material layer  24  arranged on the fourth surface  232 . 
     Specifically, a thickness of the first material layer  14  arranged on the first surface  131  is greater than a thickness of the first material layer  14  arranged on the second surface  132 . A thickness of the second material layer  24  arranged on the third surface  231  is greater than a thickness of the second material layer  24  arranged on the fourth surface  232 . Setting different thicknesses for the first material layer  14  and the second material layer  24  may further increase overall space utilization of the secondary battery  1 . 
     It may be understood that, in other embodiments, the thickness of the first material layer  14  arranged on the second surface  132  may be greater than the thickness of the first material layer  14  arranged on the first surface  131 , and the thickness of the second material layer  24  arranged on the fourth surface  232  may be greater than the thickness of the material layer arranged on the third surface  231 ; or the thicknesses of the first material layer  14  arranged on the first surface  131  and the second surface  132  may be the same, and the thicknesses of the second material layer  24  arranged on the third surface  231  and the fourth surface  232  may be the same. 
     In this embodiment, the first electrode sheet  10  is a positive electrode sheet, and the second electrode sheet  20  is a negative electrode sheet. The first metal layer  13  and the second metal layer  23  are current collector layers, and the first material layer  14  and the second material layer  24  are active material layers. In the battery field, current collector layers and active material layers of a positive electrode sheet and a negative electrode sheet are relatively common. For example, aluminum foil is used as the current collector layer of the positive electrode sheet, copper foil is used as the current collector layer of the negative electrode sheet, and the active material layer is coated on the current collector layer to form an electrode sheet. 
     Referring to  FIG. 34 , the first electrode sheet  10  or the second electrode sheet  20  is provided with a conductive sheet  30 . The first electrode sheet  10  or the second electrode sheet  20  may be electrically connected to a package packaging the first electrode sheet  10  or the second electrode sheet  20  through the conductive sheet  30 . Further, the conductive sheet  30  is a tab. 
     Referring to  FIG. 35 ,  FIG. 36 , and  FIG. 37 , in an embodiment, the first electrode sheet  10  is provided with a first conductive sheet  31 , and the second electrode sheet  20  is provided with a second conductive sheet  32 . Viewed along the first direction Z, a range of an angle θ between the first conductive sheet  31  and the second conductive sheet  32  is 0°≤θ≤180°. 
     Specifically, referring to  FIG. 35 , the first conductive sheet  31  and the second conductive sheet  32  overlap when being viewed along the first direction Z. 
     Referring to  FIG. 36 , the angle θ between the first conductive sheet  31  and the second conductive sheet  32  is 90° when being viewed along the first direction Z. 
     Referring to  FIG. 35 , the angle θ between the first conductive sheet  31  and the second conductive sheet  32  is 180° when being viewed along the first direction Z. 
     It may be understood that, in other embodiments, the angle θ may alternatively be other degrees, which may be set depending on specific conditions. Each of the first electrode sheets  10  may be provided with the first conductive sheet  31 , and each of the second electrode sheets  20  may be provided with the second conductive sheet  32 . The plurality of first conductive sheets  31  are connected, the plurality of second conductive sheets  32  are connected, and all of them are then connected to the package. 
     Referring to  FIG. 38 , when the first conductive sheet  31  is disposed on the first electrode sheet  10  or the second conductive sheet  32  is disposed on the second electrode sheet  20 , a part of the first material layer  14  is removed from the first surface  131  or the second surface  132  of the first metal layer  13  to form an first opening  18 , and then the first conductive sheet  31  is disposed at a position of the first opening  18  and electrically connected to the first metal layer  13 . Referring to  FIG. 39 , a part of the second material layer  24  is removed from the third surface  231  or the fourth surface  232  of the second metal layer  23  to form an second opening  28 , the second conductive sheet  32  is disposed at a position of the second opening  28 , and the second conductive sheet  32  is electrically connected to the second metal layer  23 . 
     In this embodiment, the first opening  18  and the second opening  28  are enclosed by a surface of the first metal layer  13  and a side surface of the first material layer  14 , or are enclosed by a surface of the second metal layer  23  and a side surface of the second material layer  24 . 
     The first electrode sheet  10  and the second electrode sheet  20  are electrically connected to the package through the first conductive sheet  31  and the second conductive sheet  32 , respectively. 
     Referring to  FIG. 2  again, in an embodiment, the secondary battery  1  further includes a separator  40 . The separator  40  is disposed between the first electrode sheet  10  and the second electrode sheet  20  for separating the first electrode sheet  10  from the second electrode sheet  20 . 
     The separator  40  may be made of a material that at least includes, but is not limited to, one or more of polyethylene and polypropylene. 
     Referring to  FIG. 40 , in an embodiment, the separator  40  may be in a solid form. In other words, an electrolyte membrane may be used to replace the separator  40  to separate the first electrode sheet  10  and the second electrode sheet  20 , and the electrolyte membrane may also ensure transmission of lithium ions during charge and discharge. The method of using the electrolyte membrane as the separator  40  is the prior art, and is not described herein. 
     Referring to  FIG. 41 , this application further provides a battery module  100 . The battery module  100  includes a first package  50  and a second package  60  matching the first package  50 , and the battery module  100  further includes the secondary battery  1  according to any one of the foregoing embodiments. The secondary battery  1  is accommodated in the first package  50  and the second package  60 , and is connected to the first package  50  and the second package  60 . The battery module  100  uses the secondary battery  1  according to any one of the foregoing embodiments, and therefore has all the beneficial effects of the secondary battery  1 . Details are not repeated herein. 
     Referring to  FIG. 42  and  FIG. 43 , the first package  50  includes a first cover body  51 , a pole  52 , and a first insulator  53 . The pole  52  and the first insulator  53  are disposed on a side of the first cover body  51  facing the second package  60 , and the pole  52  is configured to connect the secondary battery  1 . When the first cover body  51  is disposed on the second package  60 , the first insulator  53  is located between the first cover body  51  and the second package  60 . The first insulator  53  is configured to insulate the first cover body  51  and the second package  60 , and may also be configured to seal the first cover body  51  and the second package  60 . 
     The first insulator  53  is provided with a through hole  54   a , and the pole  52  passes through the through hole  54   a.    
     The second package  60  includes a second cover body  61 , the shell  62 , and a second insulator  63 . The secondary cover body  61  is disposed on an end of the shell  62 , and the secondary battery  1  is accommodated in the shell  62  and wrapped with an insulation layer (not shown in the figure), to insulate the secondary battery  1  and the shell  62 . The second insulator  63  is disposed between the secondary battery  1  and the second cover body  61 , and is configured to insulate the second cover body  61  and the secondary battery  1 . 
     The second cover body  61  is provided with a through hole  64   a , the second insulator  63  is provided with a through hole  64   b , the through hole  64   a  corresponds to the through hole  64   b , and the pole  52  passes through the through hole  64   a  and the through hole  64   b  to be connected to the secondary battery  1 . 
     The first package  50  may be directly buckled on the second package  60  to connect the first package  50  and the second package  60 . It may be understood that the connection manner of the first package  50  and the second package  60  is not limited thereto. 
     In this embodiment, the first insulator  53  and the second insulator  63  are insulation spacers. The first package  50  is a positive electrode package, and the second package  60  is a negative electrode package. It may be understood that, in other embodiments, the first insulator  53  and the second insulator  63  may be replaced by other structures with equivalent functions or roles. Polarities of the first package  50  and the second package  60  may be exchanged. 
     In an embodiment, the first package  50  and the second package  60  may at least be, but are not limited to, made of at least one or more of aluminum plastic film, polyethylene, polypropylene, and polyethylene glycol terephthalate. 
     In another embodiment, the first package  50  and the second package  60  may at least be, but are not limited to, made of at least one or more of phenolic plastic, polyurethane plastic, epoxy plastic, unsaturated polyester plastic, furan plastic, silicone resin, and propylene-based resin. 
     In another embodiment, the first package  50  and the second package  60  may at least be, but are not limited to, made of at least one or more of a steel material, an aluminum alloy material, a magnesium alloy material, a copper alloy material, a nickel alloy material, and a titanium alloy material. 
     In different usage scenarios, different materials may be used to make the first package  50  and the second package  60  according to an actual need. If the shell  62  is required to have a great overall strength, the first package  50  and the second package  60  may be made of steel materials. Both the first package  50  and the second package  60  include conductive materials, so that electrical conduction may be achieved when the battery module  100  is connected to an external structure. Further, a lower part of the first cover body  51  and a lower part of the shell  62  are made of conductive materials. 
     In this embodiment, the secondary battery  1  may be directly connected to the first package  50  and the second package  60  through the exposed first metal layer  13  and the exposed second metal layer  23 . So that in limited space of the first package  50  and the secondary package  60 , there is no need to connect the first package  50 , the second package  60 , and the secondary battery  1  through other structures. This improves space utilization rate of the battery module  100 , so that a bigger secondary battery  1  may be accommodated, and energy density of the secondary battery  1  is improved. 
     Referring to  FIG. 44  and  FIG. 45 , in an embodiment, the battery module  100  further includes a connector  70 , where the connector  70  is disposed between the secondary battery  1  and the first package  50 , or the connector  70  is disposed between the secondary battery  1  and the second package  60 , and the connector  70  is connected to the secondary battery  1 , the first package  50 , or the second package  60 . 
     Referring to  FIG. 46  and  FIG. 47 , in an embodiment, the battery module  100  may include two connectors  70 , and the two connectors  70  are classified into a first connector  71  and a second connector  72 . The first connector  71  is connected to the secondary battery  1  and the first package  50 , and the second connector  72  is connected to the secondary battery  1  and the second package  60 . 
     The first connector  71  and the second connector  72  are metal domes. Using the metal domes to connect the packages and the secondary battery  1  may improve reliability of a battery cell, and may avoid poor contact, poor deformation of the secondary battery  1 , and the like by preventing the exposed metal layer from being directly connected to the shell  62 . 
     It may be understood that, in other embodiments, the first connector  71  and the second connector  72  may be replaced by other structures with equivalent functions or roles. 
     Referring to  FIGS. 48 and 49 , in an embodiment, a conductive sheet  30  is provided on the secondary battery  1 , and the secondary battery  1  may be connected to the first package  50  or the second package  60  through the conductive sheet  30 . Further, if the first conductive sheet  31  and the second conductive sheet  32  are provided on the secondary battery  1 , the secondary battery  1  may be connected to the first package  50  and the second package  60  through the first conductive sheet  31  and the second conductive sheet  32 . 
     It may be understood that, in other embodiments, the secondary battery  1  may be combined with the connector  70  and the conductive sheet  30  through the exposed metal layer, and connected to the first package  50  and the second package  60 . 
     In this application, there are cases where the numerical signs of certain structures or parts are omitted in order to avoid the drawings becoming too complicated. For example, the first electrode sheet  10 , the first conductive layer  11 , the first side  111 , the second side  114 , the first side edge  115 , the first bending portion  12 , the first edge  121 , the first boundary M, the first material layer  14 , the first layer  16 , the second electrode sheet  20 , the second conductive layer  21 , the third side  211 , the fourth side  214 , the second side edge  215 , the second bending portion  22 , the second side edge  221 , the second boundary N, the second material layer  24 , and other structures will be omitted from the related numerical signs in some of the drawings. 
     Second Embodiment 
     Referring to  FIG. 50 ,  FIG. 51 , and  FIG. 52 , the secondary battery  1  and the battery module  100  in the second embodiment are substantially the same as those in the first embodiment. A difference lies in that the unfolded first electrode sheet  10  is arranged along the second direction Y Viewed along the first direction Z, distances of the plurality of first conductive layers  11  extending along the second direction Y are the same, and the distances of the plurality of first conductive layers  11  extending along the third direction X gradually decrease. The unfolded second electrode sheet  20  is arranged along the third direction X, distances of the plurality of second conductive layers  21  extending along the second direction Y are the same, and the distances of the plurality of second conductive layers  21  extending along the third direction X gradually decrease. 
     Third Embodiment 
     Referring to  FIG. 53 ,  FIG. 54 , and  FIG. 55 , the secondary battery  1  and the battery module  100  in the third embodiment are substantially the same as those in the second embodiment. A difference lies in that the unfolded first electrode sheet  10  is arranged along the third direction X. Viewed along the first direction Z, distances of the plurality of first conductive layers  11  extending along the second direction Y are the same, and the distances of the plurality of first conductive layers  11  extending along the third direction X gradually decrease. The unfolded second electrode sheet  20  is arranged along the third direction Y, and viewed along the first direction Z, distances of the plurality of second conductive layers  21  extending along the second direction Y are the same, and the distances of the plurality of second conductive layers  21  extending along the third direction X gradually decrease. 
     Fourth Embodiment 
     Referring to  FIG. 56 ,  FIG. 57 , and  FIG. 58 , the secondary battery  1  and the battery module  100  in the fourth embodiment are substantially the same as those in the first embodiment. A difference lies in that the unfolded first electrode sheet  10  is arranged along the second direction Y Distances of the plurality of first conductive layers  11  extending along the second direction Y gradually decrease, and the distances of the plurality of first conductive layers  11  extending along the third direction X gradually decrease. The unfolded second electrode sheet  20  is arranged along the third direction X, distances of the plurality of second conductive layers  21  extending along the second direction Y gradually decrease, and the distances of the plurality of second conductive layers  21  extending along the third direction X gradually decrease. 
     Fifth Embodiment 
     Referring to  FIG. 59 , this application also provides an electronic apparatus  200 . The electronic apparatus  200  includes a main body  80  and a battery module  100  disposed in the main body  80  for supplying power to the main body  80 . The battery module  100  is the battery module  100  according to any one of the foregoing embodiments, and therefore has all the beneficial effects of the battery module  100 . Details are not repeated herein. 
     The electronic apparatus  200  may be a Bluetooth headset, a Bluetooth speaker, a smart flashlight, a smart wearable device, or the like. 
     In conclusion, in the embodiments of this application, the secondary battery  1  and the battery module  100  are provided. The first electrode sheet  10  and the second electrode sheet  20  are alternately stacked in different directions. So that more volumes of the first electrode sheet  10  and the second electrode sheet  20  may be accommodated, in space of the shell  62  of a normal size or a specially required size that packages the secondary battery  1 , and the secondary battery  1  has higher capacity. 
     Based on the foregoing secondary battery and the battery module, the first electrode sheet and the second electrode sheet in the secondary battery are bent back and forth in different directions and stacked. So that along a stacking direction, the first electrode sheet and the second electrode sheet of more sizes can be accommodated, thereby increasing energy density of the secondary battery. 
     In addition, those of ordinary skill in the art should realize that the foregoing embodiments are merely used to illustrate this application, and not construed as a limitation to this application.