Patent Publication Number: US-2022223897-A1

Title: Method and apparatus for manufacturing electrode assembly of secondary battery

Description:
CROSS-REFERENCE OF RELATED APPLICATIONS 
     The present application is a continuation of International Application No. PCT/CN2020/114503, filed on Sep. 10, 2020, which claims priority to Chinese Patent Application No. 201910957293.5, filed on Oct. 10, 2019, both of which are hereby incorporated by reference in their entireties. 
    
    
     TECHNICAL FIELD 
     The present application relates to the field of battery technology, in particular to a method and apparatus for manufacturing an electrode assembly of a secondary battery. 
     BACKGROUND 
     With the development of society, human beings pay more and more attention to the importance of protecting the environment. Therefore, new energy vehicles are widely used as a transportation means with good environmental friendliness. The main source of power for new energy vehicles is power batteries. In the power battery processing equipment, the electrode assembly forming the power battery is wound by a winding machine, making the winding machine become an important apparatus for the production of power batteries. However, the currently equipped winding machine basically adopts a process in which the positive electrode plate, the separator, the negative electrode plate, and the separator are simultaneously wound around the winding needle and then cut. This type of winding machine is prone to problems such as the folding of the pole piece and the entraining of dust in winding during the production process, which in turn affects the yield and production efficiency of the electrode assembly. In addition, the current winding manner requires a roll-in auxiliary mechanism, such as a merging film roller group or a rolling feeding component, to be disposed in the upstream close to the winding needle to assist the positive electrode plate, the separator and the negative electrode plate to smoothly enter the winding needle separately, which causes the structure of the winding machine is complicated, and the efficiency of feeding and winding is low. 
     SUMMARY 
     Embodiments of the present application provide a method and apparatus for manufacturing an electrode assembly of a secondary battery. The method for manufacturing the electrode assembly of the secondary battery can improve the yield of the electrode assembly, simplify the structure of the winding apparatus, and improve the efficiency of the winding operation. 
     Embodiments of the present application proposes a method for manufacturing an electrode assembly of a secondary battery, which includes: 
     joining a positive electrode plate and a first separator to form a positive electrode composite plate body; 
     joining a negative electrode plate and a second separator to form a negative electrode composite plate body; 
     winding the positive electrode composite plate body and the negative electrode composite plate body together to form an electrode assembly, and the positive electrode plate and the negative electrode plate are disposed to isolate from each other by a first separator and a second separator. 
     According to an embodiment of the present application, before completing the joining of the positive electrode plate and the first separator, a cutting off process is performed for the positive electrode plate in the upstream of the joining position of the positive electrode plate and the first separator; and/or 
     Before completing the joining of the negative electrode plate and the second separator, a cutting off process is performed for the negative electrode plate in the upstream of the joining position of the negative electrode plate and the second separator. 
     According to an embodiment of the present application, in the upstream of the joining position of the positive electrode plate and the first separator, a dust removal process is performed for the positive electrode plate and/or the first separator before joined; and/or 
     In the upstream of the joining position of the negative electrode plate and the second separator, a dust removal process is performed for the negative electrode plate and/or the second separator before joined. 
     According to an embodiment of the present application, in the step of joining the positive electrode plate and the first separator to form a positive electrode composite plate body, the composite starting end and/or the composite ending end of the positive electrode plate is adhesively connected to the first separator; and/or 
     In the step of joining the negative electrode plate and the second separator to a negative electrode composite plate body, the composite starting end and/or the composite ending end of the negative electrode plate is adhesively connected to the second separator. 
     According to an embodiment of the present application, in the step of winding the positive electrode composite plate body and the negative electrode composite plate body together to form an electrode assembly, the positive electrode composite plate body and/or the negative electrode composite plate body is transported from bottom to top to winding station and a winding process is performed. 
     According to an embodiment of the present application, the joining of the positive electrode plate and the first separator may be completed in composite manner such as electrostatic adsorption, hot pressing joining, or glue pasting joining; and/or the joining of the negative electrode plate and the second separator may be completed in a composite manner such as electrostatically adsorption, plasma adsorption, hot pressing joining or glue pasting joining. 
     According to an embodiment of the present application, before the winding process is performed, the positive electrode plate and the first separator are joined in advance, and the negative electrode plate and the second separator are joined, so that the positive electrode plate and the first separator are connected to each other to form a whole, and the negative electrode plate and the second separator are connected to each other to form a whole. Then, the positive electrode composite plate body and the negative electrode composite plate body are separately transported to the winding station. The positive electrode plate and the negative electrode plate are separately driven by the first separator and the second separator to enter the winding process. In this way, in contrast to the processing manner that the positive electrode plate, the negative electrode plate, and the separator enter the winding process independently, the method for manufacturing the electrode assembly of the secondary battery in the embodiments of the present application, on the one hand, can effectively reduce the total number of plate bodies entering the winding process. Therefore it is beneficial to reducing the difficulty of aligning the positive electrode plate, the negative electrode plate and the separator, reducing the possibility that the positive electrode plate and the negative electrode plate are not aligned with each other, and improving the winding alignment accuracy. Here, alignment means that the positive electrode plate, the negative electrode plate and the separator are aligned with each other in their respective width directions. On the other hand, it can reduce the possibility that the positive electrode plate and the negative electrode plate may be folded or wrinkled when entering the winding process, and effectively improve the yield of the electrode assembly; moreover, the positive electrode plate, the negative electrode plate and the separator may not be provided with a roll-in auxiliary mechanism, such as a merging film roller group or a rolling feeding component, for guiding the positive electrode plate and the negative electrode plate to be rolled in, in the upstream close to the winding station, which is beneficial to reducing the number of parts used, simplifying the overall structure of the corresponding winding apparatus, and at the same time improving the efficiency of the winding operation. 
     Embodiments of the present application further provide an apparatus for manufacturing an electrode assembly of a secondary battery, which includes: 
     a positive electrode feeding device for outputting a positive electrode plate; 
     a first separator feeding device for outputting a first separator; 
     a first joining device arranged in the downstream of the positive electrode feeding device and the first separator feeding device, wherein the first joining device can join the positive electrode plate and the first separator to form a positive electrode composite plate body; 
     a negative electrode feeding device for outputting a negative electrode plate; 
     a second separator feeding device for outputting a second separator; 
     a second joining device arranged in the downstream of the negative electrode feeding device and the second separator feeding device, wherein the second joining device can join the negative electrode plate and the second separator to form a negative electrode composite plate body; 
     a winding device arranged in the downstream of the first joining device and the second joining device, wherein the winding device can wind the positive electrode composite plate body and the negative electrode composite plate body to form an electrode assembly. 
     According to an embodiment of the present application, the apparatus further includes a positive electrode plate cutter, the positive electrode plate cutter is arranged in the upstream of the first joining device, and the positive electrode plate cutter is configured for cutting off the positive electrode plate in the upstream the joining position of the positive electrode plate and the first separator; and/or 
     The apparatus further includes a negative electrode plate cutter, the negative electrode plate cutter is arranged in the upstream of the second joining device, and the negative electrode plate cutter is configured for cutting off the negative electrode plate in the upstream of the joining position of the negative electrode plate and the second separator. 
     According to an embodiment of the present application, the apparatus further includes a first dust removal device, the first dust removal device is arranged in the upstream of the first joining device, and the first dust removal device is configured for performing dust removal process for the positive electrode plate and/or the first separator before joined; and/or 
     The apparatus further includes a second dust removal device, the second dust removal device is arranged in the upstream of the second joining device, and the second dust removal device is configured for performing a dust removal process for the negative electrode plate and/or the second separator before joined. 
     According to an embodiment of the present application, the winding device includes a winding needle, a positive electrode roll-in guide roller group and a negative electrode roll-in guide roller group, and the positive electrode roll-in guide roller group and the negative electrode roll-in guide roller group are both arranged in the upstream of the winding needle, the positive electrode roll-in guide roller group and the negative winding roller group are disposed below the winding needle, the positive electrode roll-in guide roller group transports the positive electrode composite plate body directly to the winding needle from bottom to top, and the negative electrode roll-in guide roller group transports the negative composite plate body directly to the winding needle from bottom to top. 
     According to an embodiment of the present application, the winding device further includes a rotating base and two or more winding needles, and the two or more winding needles are arranged on the rotating base at intervals around a rotation axis of the rotating base. 
     According to an embodiment of the present application, the apparatus further includes a first glue pasting device, the first glue pasting device is arranged in the downstream of the first joining device, and the first glue pasting device is configured for adhesively connecting the composite starting end and/or the composite ending end of the positive electrode plate to the first separator; and/or 
     The apparatus further includes a second glue pasting device, the second glue pasting device is arranged in the downstream of the second joining device, and the second glue pasting device is configured for adhesively connecting the composite starting end and/or composite ending end of the negative electrode plate to the second separator. 
     According to an embodiment of the present application, the apparatus further includes a first detection device, the first detection device is arranged in the downstream of the first joining device, and the first detection device is configured for detecting the composite alignment degree of the positive electrode plate and the first separator; and/or 
     The apparatus further includes a second detection device, the second detection device is provided in the downstream of the second joining device, the second detection device is configured for detecting the composite alignment degree of the negative electrode plate and the second separator. 
     According to an embodiment of the present application, the apparatus further includes a first correcting device, the first correcting device is arranged in the upstream of the first joining device, the first correcting device is configured for adjusting the relative position of the positive electrode plate and the first separator; and/or 
     The apparatus further includes a second correcting device, the second correcting device is arranged in the upstream of the second joining device, the second correcting device is configured for adjusting the relative position of the negative electrode plate and the second separator. 
     According to an embodiment of the present application, the apparatus further includes a tension adjusting device, the tension adjusting device is arranged in the upstream of the winding device, and is configured for adjusting the tension of the positive electrode composite plate body or the negative electrode composite plate body. 
     According to the equipment for manufacturing the electrode assembly of the secondary battery according to the embodiment of the present application, the positive electrode plate and the first separator are joined in advance by the first joining device, and the negative electrode plate and the second separator are joined in advance by the second joining device, so that the positive electrode plate and the first separator are connected to each other to form a whole, and the negative electrode plate and the second separator are connected to each other to form a whole. Then, the positive electrode composite plate body and the negative electrode composite plate body are separately transported to the winding station of the winding device to complete the winding operation. The positive electrode plate and the negative electrode plate are respectively driven by the first separator and the second separator to enter the winding process. In this way, in contrast to the processing manner that the positive electrode plate, the negative electrode plate, and the separator enter the winding process independently, the apparatus for manufacturing the electrode assembly of the secondary battery in the embodiment of the present application can effectively reduce the total number of plate bodies entering the winding process, which is beneficial to reducing the difficulty of aligning the positive electrode plate, the negative electrode plate and the separator, reducing the possibility that the positive electrode plate and the negative electrode plate are not aligned with each other, and improving the winding alignment accuracy. On the other hand, it can reduce the possibility that the positive electrode plate and the negative electrode plate may be folded or wrinkled when entering the winding process, which is beneficial to improving the yield of the electrode assembly; moreover, the positive electrode plate, the negative electrode plate and the separator may not be provided with a roll-in auxiliary mechanism for guiding the positive electrode plate and the negative electrode plate to be rolled in in the upstream close to the winding device, which is beneficial to reducing the number of parts used, simplifying the overall structure of the apparatus, and at the same time improving the efficiency of winding operation. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In order to explain the technical solutions of embodiments of the present application more clearly, the drawings needed in the embodiments will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application. For the skilled person in the art, without inventive work, other drawings can be obtained from these drawings. 
         FIG. 1  is a schematic diagram of an exploded structure of a secondary battery according to an embodiment of the present application; 
         FIG. 2  is a schematic cross-sectional structure diagram of an electrode assembly according to an embodiment of the present application; 
         FIG. 3  is a flowchart of manufacturing an electrode assembly of a secondary battery according to an embodiment of the present application; 
         FIG. 4  is a schematic structural diagram of an apparatus for manufacturing an electrode assembly of a secondary battery according to an embodiment of the present application. 
     
    
    
     In the drawings, the drawings are not drawn according to actual scale. 
     REFERENCE DESCRIPTION 
       10 . secondary battery;  11 . case;  12 . electrode assembly;  121 . positive electrode plate;  122 . first separator;  123 . negative electrode plate;  124 . second separator;  20 . positive electrode composite plate body;  30 . negative electrode composite plate body;  99 . joining position;  100 . apparatus;  101 . positive electrode feeding device;  102 . first separator feeding device;  103 . first joining device;  104 . negative electrode feeding device;  105 . second separator feeding device;  106 . second joining device;  107 . winding device;  107   a . winding needle;  107   b , rotating base;  107   c . positive electrode roll-in guide roller group;  107   d . negative electrode roll-in guide roller group;  108 . tension adjustment device;  109 . positive electrode plate cutter;  110 . negative electrode plate cutter;  111 . first dust removal device;  112 , second dust removal device;  113 . separator cutter;  114 . first glue pasting device;  115 . second glue pasting device;  116 . first detection device;  117 . second detection device;  118 . first correction device;  119 . second correction device. 
     DETAILED DESCRIPTION 
     The following describes the implementation of the present application in further detail with reference to the accompanying drawings and examples. The detailed description and drawings of the following embodiments are used to exemplarily illustrate the principle of the present application, but in no way to limit the scope of the present application, that is, the present application is not limited to the described embodiments. 
     In the description of the present application, it should be noted that, unless otherwise specified, “plurality” means more than two; the orientation or positional relationship indicated by the terms “upper”, “lower”, “left”, “right”, “inner”, “outside”, etc. is only for the convenience of describing the present application and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, and must be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation to the present application. In addition, the terms “first”, “second”, “third”, etc. are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance. The term “vertical” does not require “vertical” strictly, but within the allowable error range. The term “parallel” does not require “parallel” strictly, but within the allowable error range. 
     The orientation words appearing in the following description are all directions shown in the figures, and do not limit the specific structure of the present application. In the description of the present application, it should also be noted that, unless otherwise clearly defined and limited, the terms “mounting”, “to be connected with”, and “connecting” should be understood in a broad sense and for example, may be a fixed connection or a detachable connection, or integral connection; may be directly connected or indirectly connected through an intermediate medium. For the skilled person in the art, the specific meaning of the above-mentioned terms in the present application can be understood according to specific circumstances. 
     In order to better understand the present application, the following describes embodiments of the present application in conjunction with  FIGS. 1 to 4 . 
     Referring to  FIG. 1 , embodiments of the present application provide a secondary battery  10 . The secondary battery  10  includes a case  11 , an electrode assembly  12  provided in the case  11 , and a top cover assembly that is hermetically connected to the case  11 . The case  11  in the embodiment of the present application has a square structure or other shapes. The case  11  has an internal space for accommodating the electrode assembly  12  and the electrolyte, and an opening communicating with the internal space. The case  11  may be made of materials such as aluminum, aluminum alloy, or plastic. 
     As shown in  FIG. 2 , the electrode assembly  12  of the embodiment of the present application includes a positive electrode plate  121 , a negative electrode plate  123  and a separator, wherein the separator is an insulator between the positive electrode plate  121  and the negative electrode plate  123 . The electrode assembly  12  has a main body and tabs. The main body of the present embodiment has a flat structure as a whole, which has a predetermined thickness, height, and width. The active material of the positive electrode plate  121  is coated on the coated area of the positive electrode plate  121 , and the active material of the negative electrode plate  123  is coated on the coated area of the negative electrode plate  123 . The uncoated area extending from the coated area of the main body is used as a tab. The electrode assembly  12  includes two tabs, namely a positive electrode tab and a negative electrode tab. The positive electrode tab extends from the coated area of the positive electrode plate  121 , and the negative electrode tab extends from the coated area of the negative electrode plate  123 . 
     Referring to  FIG. 3 , embodiments of the present application provide a method for manufacturing an electrode assembly  12  of a secondary battery  10 , which includes the following steps: 
     the positive electrode plate  121  and the first separator  122  are joined to form a positive electrode composite plate body  20 ; 
     the negative electrode plate  123  and the second separator  124  are joined to form a negative electrode composite plate body  30 ; 
     the positive electrode composite plate body  20  and the negative electrode composite plate body  30  are wound together to form the electrode assembly  12 . The positive electrode plate  121  and the negative electrode plate  123  included by the wound electrode assembly  12  are disposed to isolate from each other through the first separator  122  and the second separator  124 . 
     In an embodiment, the positive electrode plate  121  and the first separator  122  may complete the joining in a composite manner such as electrostatic adsorption, hot pressing joining or glue pasting joining. The positive electrode plate  121  and the first separator  122  are laminated on each other along the thickness direction of the positive electrode plate  121 . The negative electrode plate  123  and the second separator  124  can complete the joining in a composite manner such as electrostatic adsorption, plasma adsorption, hot pressing joining or glue pasting joining. The negative electrode plate  123  and the second separator  124  are laminated on each other in the thickness direction of the negative electrode plate  123 . 
     In the embodiment of the present application, before the winding process is performed, the positive electrode plate  121  and the first separator  122  are joined in advance, and the negative electrode plate  123  and the second separator  124  are joined, so that the positive electrode plate  121  and the first separator  122  are connected to each other to form a whole, and the negative electrode plate  123  and the second separator  124  are connected to each other to form a whole. Then, the positive electrode composite plate body  20  and the negative electrode composite plate body  30  are separately transported to the winding station. The positive electrode plate  121  and the negative electrode plate  123  are respectively driven by the first separator  122  and the second separator  124  to enter the winding process. In this way, in contrast to the processing manner that the positive electrode plate  121 , the negative electrode plate  123 , and the separator enter the winding process independently, the method for manufacturing the electrode assembly  12  of the secondary battery  10  according to the embodiment of the present application, on the one hand, can effectively reduce the total number of plate body entering into the winding process. Thus it is beneficial to reducing the difficulty in alignment of the positive electrode plate  121 , the negative electrode plate  123  and the separator, reducing the possibility of the positive electrode plate  121  and the negative electrode plate  123  being misaligned with each other, and improving the winding alignment accuracy. Here, alignment means that the positive electrode plate  121 , the negative electrode plate  123 , and the separator are aligned with each other in their respective width directions. On the other hand, it can reduce the possibility of that the positive electrode plate  121  and the negative electrode plate  123  may be folded or wrinkled when entering into the winding process, which effective improves the yield of the electrode assembly  12 ; moreover, the positive electrode plate  121 , the negative electrode plate  123  and the separator may not be provided with a roll-in auxiliary mechanism, such as a merging film roller group or a rolling feeding component, for guiding the positive electrode plate  121  and the negative electrode plate  123  to be rolled in in the upstream close to the winding station, which is beneficial to reducing the number of parts used, simplifying the overall structure of the corresponding winding apparatus, and at the same time improving the efficiency of winding operation. 
     In an embodiment, before the joining between the positive electrode plate  121  and the first separator  122  is completed, a cutting off process is performed for the positive electrode plate  121  in the upstream of the joining position of the positive electrode plate  121  and the first separator  122 . The joining position  99  of the positive electrode plate  121  and the first separator  122  is far away from the winding station. Therefore, the cutting off process is performed for the positive electrode plate  121  in the upstream of the joining position  99 , which can further effectively reduce the possibility of a short circuit between the positive electrode plate  121  and the negative electrode plate  123  caused by the dust piercing the separator due to the dust generated during the cutting off process to be rolled in. After the cutting off process is performed for the positive electrode plate  121 , the positive electrode plate  121  forms a composite ending end close to the joining position  99  and a composite starting end far away from the joining position  99  and for winding the next electrode assembly  12  on two sides of the cutting off position, respectively. In an exemplary embodiment, the cutting off process may be performed by a mechanical cutter or a laser cutter. 
     In an embodiment, before the joining of the negative electrode plate  123  and the second separator  124  is completed, a cutting off process is performed for the negative electrode plate  123  in the upstream of the joining position  99  of the negative electrode plate  123  and the second separator  124 . The joining position  99  of the negative electrode plate  123  and the second separator  124  is far away from the winding station. Therefore, the cutting off process is performed for the negative electrode plate  123  in the upstream of the joining position  99 , which can further effectively reduce the possibility of a short circuit between the positive electrode plate  121  and the negative electrode plate  123  caused by the dust piercing the separator due to the dust generated during the cutting off process to be rolled in. After the cutting off process is performed for the negative electrode plate  123 , the negative electrode plate  123  forms a composite ending end close to the joining position  99  and a composite starting end far away from the joining position  99  and for winding the next electrode assembly  12  on two sides of the cutting off place, respectively. In an exemplary embodiment, the cutting off process may be performed by a mechanical cutter or a laser cutter. 
     In an exemplary embodiment, before the joining of the positive electrode plate  121  and the first separator  122  is completed, a cutting off process is performed for the positive electrode plate  121  in the upstream of the joining position  99  of the positive electrode plate  121  and the first separator  122 , and at the same time before the joining of the negative electrode plate  123  and the second separator  124  is completed, a cutting off process is performed for the negative electrode plate  123  in the upstream of the joining position  99  of the negative electrode plate  123  and the second separator  124 . 
     In an embodiment, in the upstream of the joining position  99  of the positive electrode plate  121  and the first separator  122 , a dust removal process is performed for the positive electrode plate  121  before joined, so as to remove dust generated during the cutting off process of the positive electrode plate  121  or remove the dust that enters the area of the positive electrode plate  121  close to the joining position  99  from the external environment, and reduce the possibility that the dust will follow the positive electrode plate  121 , remain in the positive electrode composite plate body  20  formed after the joining is completed and follow the positive electrode composite plate body  20  to be rolled in. In another embodiment, in the upstream of the joining position  99  of the positive electrode plate  121  and the first separator  122 , the dust removal process is performed for the first separator  122  before joined to remove the dust that enters the area of the first separator  122  close to the joining position  99  from the external environment and reduce the possibility that the dust will follow the first separator  122 , remain in the positive electrode composite plate body  20  formed after the joining is completed and follow the positive electrode composite plate body  20  to be rolled in. In an exemplary embodiment, in the upstream of the joining position  99  of the positive electrode plate  121  and the first separator  122 , a dust removal process is simultaneously performed for the positive electrode plate  121  and the first separator  122  before joined. 
     In an embodiment, in the upstream of the joining position  99  of the negative electrode plate  123  and the second separator  124 , a dust removal process is performed for the negative electrode plate  123  before joined, so as to remove dust generated during the cutting off process of the negative electrode plate  123  or remove the dust that enters the area of the negative electrode plate  123  close to the joining position  99  from the external environment, and reduce the possibility that the dust will follow the negative electrode plate  123 , remain in the negative electrode composite plate body  30  formed after the joining is completed and follow the negative electrode composite plate body  30  to be rolled in. In another embodiment, in the upstream of the joining position  99  of the negative electrode plate  123  and the second separator  124 , a dust removal process is performed for the second separator  124  before joined to remove the dust that enters the area of the second separator  124  close to the joining position  99  from the external environment, and reduce the possibility that the dust will follow the second separator  124 , remain in the negative electrode composite plate body  30  formed after the joining is completed and follow the negative electrode composite plate body  30  to be rolled in. In an exemplary embodiment, in the upstream of the joining position  99  of the negative electrode plate  123  and the second separator  124 , the dust removal process is simultaneously performed for the negative electrode plate  123  and the second separator  124  before joined. 
     The positive electrode plate  121  to be joined has a composite starting end. After the positive electrode plate  121  is cut off after one winding process is completed, a composite ending end and a composite starting end for the next winding process are formed. In the step that the positive electrode plate  121  and the first separator  122  are joined to form the positive electrode composite plate body  20 : the composite starting end or the composite ending end of the positive electrode plate  121  is adhesively connected to the first separator  122 , thereby effectively reducing the possibility that during the composite process, the conveying process or the winding process, the composite starting end or the composite ending end of the positive electrode plate  121  joined to the first separator  122  may be folded or wrinkled. In an example, the composite starting end or composite ending end of the positive electrode plate  121  is adhesively connected to the first separator  122  by an adhesive tape. In an exemplary embodiment, the composite starting end and the composite ending end of the positive electrode plate  121  are adhesively connected to the first separator  122 . 
     The negative electrode plate  123  to be joined has a composite starting end. After the negative electrode plate  123  is cut off after one winding process is completed, a composite ending end and a composite starting end for the next winding process are formed. In the step that the negative electrode plate  123  and the second separator  124  are joined to form the negative electrode composite plate body  30 : the composite starting end or the composite ending end of the negative electrode plate  123  is adhesively connected to the second separator  124 , thereby effectively reducing the possibility that during the composite process, the conveying process or the winding process, the composite starting end or the composite ending end of the negative electrode plate  123  joined to the second separator  124  may be folded or wrinkled. In an example, the composite starting end or composite ending end of the negative electrode plate  123  is adhesively connected to the second separator  124  by an adhesive tape. In an exemplary embodiment, the composite starting end and the composite ending end of the negative electrode plate  123  are adhesively connected to the second separator  124 . 
     In the step of winding the positive electrode composite plate body  20  and the negative electrode composite plate body  30  together to form the electrode assembly  12 , the positive electrode composite plate body  20  or the negative electrode composite plate body  30  is transported from bottom to top to the winding station and the winding process is performed. Here, “from bottom to top” refers to the vertical direction as the reference direction. Since the positive electrode plate  121  and the negative electrode plate  123  of the embodiment of the present application are joined with the first separator  122  and the second separator  124  respectively, the positive electrode plate  121  and the negative electrode plate  123  follow the first separator  122  and the second separator  124  respectively to go through the winding process directly. Therefore, the positive electrode composite plate body  20  or the negative electrode composite plate body  30  of the embodiment of the present application can adopt the manner of conveying from bottom to top, and meanwhile the composite starting end and the composite ending end of the positive electrode plate  121  or the negative electrode plate  123  will not be put in a hanging down state under its own gravity, which otherwise results in fold or wrinkle. In addition, it can further make that during the conveying process of the positive electrode composite plate body  20  or the negative electrode composite plate body  30 , the dust carried will be separated and fall under the action of its own gravity, thereby reducing the possibility that the dust will follow the positive electrode composite plate body  20  or the negative electrode composite plate body  30  to enter into the electrode assembly  12  resulting from winding and affect the use safety of the electrode assembly  12 . In an exemplary embodiment, the positive electrode composite plate body  20  and the negative electrode composite plate body  30  are conveyed from bottom to top to the winding station and the winding process is performed. 
     The method for manufacturing the electrode assembly  12  of the secondary battery  10  in the embodiment of the present application adopts the manner that the positive electrode plate  121  and the first separator  122  are joined and the negative electrode plate  123  and the second separator  124  are joined in advance, and then the composite plate body  20  and the negative electrode composite plate body  30  are wound. Therefore, compared with the manner that the positive electrode plate  121 , the negative electrode plate  123 , and the two separators are wound independently, the method in the embodiment of the present application is no longer necessary to provide a roll-in auxiliary mechanism for guiding the positive electrode plate  121 , the negative electrode plate  123  and the two separators to be rolled in, thereby reducing the number of parts used, at the same time more easily ensuring the accuracy of alignment of the positive electrode plate  121 , the negative electrode plate  123 , the first separator  122  and the second separator  124 , and reducing the possibility of affecting the electrical performance of the electrode assembly  12  due to misalignment of the positive electrode plate  121 , the negative electrode plate  123 , and the separator. 
     Referring to  FIG. 4 , embodiments of the present application provide an apparatus  100  for manufacturing the electrode assembly  12  of the secondary battery  10 , which can be used to implement the method for manufacturing the electrode assembly  12  of the secondary battery  10  in the foregoing embodiments. The apparatus  100  of the present embodiment includes a positive electrode feeding device  101 , a first separator feeding device  102 , a first joining device  103 , a negative electrode feeding device  104 , a second separator feeding device  105 , a second joining device  106 , and a winding device  107 . 
     The positive electrode feeding device  101  is used to mount and fix the positive electrode plate  121  material roll, and then output the positive electrode plate  121  through the unwinding machine. The positive electrode plate  121  is driven by the transfer roller group to move toward the joining position  99 . The first separator feeding device  102  is used to mount and fix the separator material roll, and then output the first separator  122  through the unwinding machine. The first separator  122  moves toward the joining position  99  under the driving of the conveying roller group. The first joining device  103  is arranged in the downstream of the positive electrode feeding device  101  and the first separator feeding device  102 . Both the positive electrode plate  121  and the first separator  122  are transported to the first joining device  103 , and then the first joining device  103  joins the positive electrode plate  121  and the first separator  122  to form the positive electrode composite plate body  20 . In an example, the first joining device  103  includes a hot pressing mechanism. The positive electrode plate  121  and the first separator  122  are joined through hot pressing by a hot pressing mechanism. In another example, the first joining device  103  includes an electrostatic generator. The positive electrode plate  121  and the first separator  122  are joined through electrostatic adsorption. In yet another example, the first joining device  103  includes a glue pasting mechanism. The positive electrode plate  121  and the first separator  122  are joined via pasting glue. The positive electrode plate  121  and the first separator  122  are laminated and joined on each other in the thickness direction. 
     The negative electrode feeding device  104  is used to mount and fix the negative electrode plate  123  material roll, and then output the negative electrode plate  123  through the unwinding machine. The negative electrode plate  123  moves toward the joining position  99  under the driving of the transfer roller group. The second separator feeding device  105  is used to mount and fix the separator material roll, and then output the second separator  124  through the unwinding machine. The second separator  124  moves toward the joining position  99  under the driving of the conveying roller group. The second joining device  106  is arranged downstream of the negative electrode feeding device  104  and the second separator feeding device  105 . Both the negative electrode plate  123  and the second separator  124  are transported to the second joining device  106 , and then the second joining device  106  joins the negative electrode plate  123  and the second separator  124  to form a negative composite plate body  30 . In an example, the second joining device  106  includes a hot pressing mechanism. The negative electrode plate  123  and the second separator  124  are joined through hot pressing by a hot pressing mechanism. In another example, the second joining device  106  includes an electrostatic generator. The negative electrode plate  123  and the second separator  124  are joined through electrostatic adsorption. In yet another example, the second joining device  106  includes a glue pasting mechanism. The negative electrode plate  123  and the second separator  124  are joined via pasting glue. The negative electrode plate  123  and the second separator  124  are superimposed and joined on each other in the thickness direction. 
     The winding device  107  is provided in the downstream of the first joining device  103  and the second joining device  106 . The positive electrode composite plate body  20  and the negative electrode composite plate body  30  are conveyed to the winding device  107 . The winding device  107  winds the positive electrode composite plate body  20  and the negative electrode composite plate body  30  to produce the electrode assembly  12 . 
     In an embodiment, the first joining device  103  and the second joining device  106  are symmetrically arranged on both sides of the winding device  107 , so as to ensure the consistency of the positions of the respective joining position  99  of the positive electrode plate  121  and the negative electrode plate  123  and the consistency of the roll-in positions of the positive electrode composite plate body  20  and the negative electrode composite plate body  30  formed after joined, which is beneficial to improving the alignment accuracy of the wound positive electrode plate  121  and the negative electrode plate  123 . 
     In an embodiment, the apparatus  100  further includes a tension adjustment device  108 . The tension adjusting device  108  is arranged in the upstream of the winding device  107  and is used to adjust the tension degree of the positive electrode composite plate body  20  or the negative electrode composite plate body  30 . 
     In the apparatus  100  for manufacturing the electrode assembly  12  of the secondary battery  10  in the embodiment of the present application, the positive electrode plate  121  and the first separator  122  are joined in advance by the first joining device  103 , and the negative electrode plate  123  and the second separator  122  are joined in advance by the second joining device  106 , so that the positive electrode plate  121  and the first separator  122  are connected to each other to form a whole, and the negative electrode plate  123  and the second separator  124  are connected to each other to form a whole. Then, the positive electrode composite plate body  20  and the negative electrode composite plate body  30  are separately conveyed to the winding station of the winding device  107  to complete the winding operation. The positive electrode plate  121  and the negative electrode plate  123  are respectively driven by the first separator  122  and the second separator  124  to enter the winding process. In this way, in contrast to the processing manner that the positive electrode plate  121 , the negative electrode plate  123 , and the separator enter the winding process independently, the apparatus  100  for manufacturing the electrode assembly  12  of the secondary battery  10  of the embodiment of the present application, on the one hand, can effectively reduce the total number of the plate bodies entering into the winding process, which is beneficial to reducing the difficulty in alignment of the positive electrode plate  121 , the negative electrode plate  123  and the separator, reducing the possibility of misalignment of the positive electrode plate  121  and the negative electrode plate  123 , and improving the accuracy of winding alignment. On the other hand, it can reduce the possibility that the positive electrode plate and the negative electrode plate  123  may be folded or wrinkled when entering the winding process, which is beneficial to improving the yield of the electrode assembly  12 ; moreover, the positive electrode plate  121 , the negative electrode plate  123  and the separator may not be provided with a roll-in auxiliary mechanism for guiding the positive electrode plate  121  and the negative electrode plate  123  to be rolled in in the upstream close to the winding device  107 , which is beneficial to reducing the number of parts used, simplifying the overall structure of the apparatus  100 , and improving the efficiency of winding operation at the same time. 
     In an embodiment, the apparatus  100  further includes a positive electrode plate cutter  109  for cutting off the positive electrode plate  121 . The positive electrode plate cutter  109  is arranged in the upstream of the first joining device  103 . The positive electrode plate cutter  109  is used to cut off the positive electrode plate  121  in the upstream of the joining position  99  of the positive electrode plate  121  and the first separator  122 . In an example, the positive electrode plate cutter  109  includes a cutter and a cutter seat. The positive electrode plate  121  passes between the cutter and the cutter holder. When it is necessary to cut off the positive electrode plate  121 , the cutter and the cuter seat come close to each other to cut off the positive electrode plate  121 . In an example, the positive electrode plate cutter  109  may be a laser cutter, and the positive electrode plate  121  is cut by laser. Before the joining of the positive electrode plate  121  and the first separator  122  is completed, a cutting off process is performed for the positive electrode plate  121  in the upstream of the joining position  99  of the positive electrode plate  121  and the first separator  122 . The joining position  99  between the positive electrode plate  121  and the first separator  122  is far away from the winding station. Therefore, the cutting off process is performed for the positive electrode plate  121  in the upstream of the joining position  99 , which can further effectively reduce the possibility of a short circuit between the positive electrode plate  121  and the negative electrode plate  123  caused by the dust piercing the separator due to the dust generated during the cutting off process to be rolled in. In an embodiment, the apparatus  100  further includes a negative electrode plate cutter  110  for cutting the negative electrode plate  123 . The negative electrode plate cutter  110  is arranged in the upstream of the second joining device  106 . The negative electrode plate cutter  110  is used to cut off the negative electrode plate  123  in the upstream of the joining position  99  of the negative electrode plate  123  and the second separator  124 . In an example, the negative electrode plate cutter  110  includes a cutter and a cutter seat. The negative electrode plate  123  passes between the cutter and the cutter seat. When it is necessary to cut off the negative electrode plate  123 , the cutter and the cutter seat come close to each other to cut off the negative electrode plate  123 . In an example, the negative electrode plate cutter  110  may be a laser cutter, and the negative electrode plate  123  is cut by laser. Before the joining of the negative electrode plate  123  and the second separator  124  is completed, a cutting off process is performed for the negative electrode plate  123  in the upstream of the joining position  99  of the negative electrode plate  123  and the second separator  124 . The joining position  99  of the negative electrode plate  123  and the second separator  124  is far away from the winding station. Therefore, the cutting off process is performed for the negative electrode plate  123  in the upstream of the joining position  99 , which can further effectively reduce the possibility of a short circuit between the positive electrode plate  121  and the negative electrode plate  123  caused by the dust piercing the separator due to the dust generated during the cutting off process to be rolled in. In an exemplary embodiment, the apparatus  100  includes a positive electrode plate cutter  109  for cutting off the positive electrode plate  121  and a negative electrode plate cutter  110  for cutting off the negative electrode plate  123 . 
     In an embodiment, the apparatus  100  further includes a first dust removal device  111 . The first dust removal device  111  is arranged in the upstream of the first joining device  103  and is used to perform a dust removal process for the positive electrode plate  121  and/or the first separator  122  before joined. The first dust removal device  111  is close to the positive electrode plate cutter  109 . In the upstream of the joining position  99  of the positive electrode plate  121  and the first separator  122 , the first dust removal device  111  performs a dust removal process for the positive electrode plate  121  and/or the first separator  122  before joined, so as to remove the dust generated during the cutting off process of the positive electrode plate  121  or remove the dust entering the area near the joining position  99  from the external environment, thus reducing the possibility that the dust will remain in the positive composite plate body  20  formed after the joining is completed and follow the positive composite plate body  20  to be rolled in. In an example, the first dust removal device  111  includes a dust suction tube and a negative pressure generator connected to the dust suction tube. In an embodiment, the apparatus  100  further includes a second dust removal device  112 . The second dust removal device  112  is arranged in the upstream of the second joining device  106  and is used to perform a dust removal process for the negative electrode plate  123  and/or the second separator  124  before joined. The second dust removal device  112  is close to the negative electrode plate cutter  110 . In the upstream of the joining position  99  of the negative electrode plate  123  and the second separator  124 , the second dust removal device  112  performs a dust removal process for the negative electrode plate  123  and/or the second separator  124  before joined, so as to remove the dust generated during the cutting off process of the negative electrode plate  123  or remove the dust entering the area near the joining position  99  from the external environment, thus reducing the possibility that the dust will remain in the negative electrode composite plate body  30  formed after the joining is completed and follow the negative composite plate body  30  to be rolled in. In an example, the second dust removal device  112  includes a dust suction tube and a negative pressure generator connected to the dust suction tube. 
     In an embodiment, the winding device  107  includes a winding needle  107   a , a positive electrode roll-in guide roller group  107   c , and a negative electrode roll-in guide roller group  107   d . Both the positive electrode roll-in guide roller group  107   c  and the negative electrode roll-in guide roller group  107   d  are arranged in the upstream of the winding needle  107   a . In an example, both the positive electrode roll-in guide roller group  107   c  and the negative electrode roll-in guide roller group  107   d  are arranged below the winding needle  107   a . The positive electrode roll-in guide roller group  107   c  directly conveys the positive electrode composite plate body  20  from bottom to top to the winding needle  107   a . The negative electrode roll-in guide roller group  107   d  directly conveys the negative electrode composite plate body  30  from bottom to top to the winding needle  107   a . In an example, the winding needle  107   a  includes two half shafts that can be close to or away from each other. The starting ends of the first separator  122  and the second separator  124  are pre-clamped between the two half shafts, and then the winding needle  107   a  is rotated by a predetermined number of turns to wind the first separator  122  and the second separator  124  with a predetermined length. Then, the positive electrode plate  121  and the negative electrode plate  123  are respectively driven by the first separator  122  and the second separator  124  to enter into the winding needle  107   a  for winding. After a predetermined length of the positive electrode plate  121  and the negative electrode plate  123  are wound, the positive electrode plate  121  and the negative electrode plate  123  are cut off. After the positive electrode plate  121  and the negative electrode plate  123  are wound, the winding needle  107   a  continues to rotate by a predetermined number of turns to continue winding the first separator  122  and the second separator  124 . After the first separator  122  and the second separator  124  of a predetermined length are wound, the first separator  122  and the second separator  124  are cut off, and the winding operation is finally completed. The two half shafts are opened, and the electrode assembly  12  is removed from the winding needle  107   a  to complete the feeding. In an example, the winding device  107  includes a rotating base  107   b  and two winding needles  107   a  arranged on the rotating base  107   b  at intervals. After the first winding needle  107   a  completes the winding operation, the rotating base  107   b  rotates, so that the first winding needle  107   a  rotates to the feeding station, and the second winding needle  107   a  rotates to the winding station. The second coiling needle  107   a  clamps the first separator  122  and the second separator  124 , and then the first separator  122  and the second separator  124  are cut off between the two winding needles  107   a  by the separator cutter  113 . The two winding needles  107   a  are used in cycle to perform winding operation, so that in the process of winding a plurality of electrode assemblies  12  using the apparatus  100  for manufacturing the electrode assembly  12  of the secondary battery  10 , the roll-in operation is required to perform on the first separator  122  and the second separator  124  only once in the initial stage, and then the two winding needles  107   a  alternately clamp the first separator  122  and the second separator  124  to continuously perform the winding operation. The roll-in operation is no longer required to perform on the first separator  122  and the second separator  124 , thereby effectively improving the efficiency of the winding operation. The number of winding needles  107   a  is not limited to the above-mentioned two, and may be three or more. Each winding needle  107   a  can be switched between the unloading station and the winding station under the driving of the rotating base  107   b . In an example, the positive electrode roll-in guide roller group  107   c  and the negative electrode roll-in guide roller group  107   d  are symmetrically arranged on both sides of the winding needle  107   a  in the winding station, so as to ensure the consistency of the roll-in positions of the positive electrode composite plate body  20  and the negative electrode composite plate body  30 , which is beneficial to improving the alignment accuracy of the positive electrode plate  121  and the negative electrode plate  123  after the winding. 
     In an embodiment, the apparatus  100  includes a first glue pasting device  114 . The first glue pasting device  114  is arranged in the downstream of the first joining device  103 . The composite starting end or the composite ending end of the positive electrode plate  121  is adhesively connected to the first separator  122  through the first glue pasting device  114 , thereby further effectively reducing the possibility that the composite starting end or the composite ending end of the positive electrode plate  121  joined to the first separator  122  may be folded or wrinkled during the composite process, conveying process or winding process. In an exemplary embodiment, the composite starting end and the composite ending end of the positive electrode plate  121  are adhesively connected to the first separator  122 . In an example, the first glue pasting device  114  includes an adhesive tape output mechanism, an adhesive tape sticking mechanism, and an adhesive tape cutting-off mechanism. At least one of the composite starting end and the composite ending end of the positive electrode plate  121  is adhesively connected to the first separator  122  by an adhesive tape. In an embodiment, the apparatus  100  includes a second glue pasting device  115 . The second glue pasting device  115  is arranged in the downstream of the second joining device  106 . The composite starting end or the composite ending end of the negative electrode plate  123  is adhesively connected to the second separator  124  by the second glue pasting device  115 , thereby further effectively reducing the possibility that the composite starting end or the composite ending end of the negative electrode plate  123  joined to the second separator  124  may be folded or wrinkled during the composite process, conveying process or winding process. In an exemplary embodiment, the composite starting end and the composite ending end of the negative electrode plate  123  are adhesively connected to the second separator  124 . In an example, the second glue pasting device  115  includes an adhesive tape output mechanism, an adhesive tape sticking mechanism, and an adhesive tape cutting-off mechanism. The composite starting end or composite ending end of the negative electrode plate  123  is adhesively connected to the second separator  124  by an adhesive tape. In an exemplary embodiment, the apparatus  100  includes a first glue pasting device  114  and a second glue pasting device  115 . 
     In an embodiment, the apparatus  100  further includes a first detection device  116  for detecting the composite alignment degree of the positive electrode plate  121  and the first separator  122 . The first detection device  116  is arranged in the downstream of the first joining device  103  and can detect in real time the alignment degree of the positive electrode plate  121  and the first separator  122  after being joined. When the alignment degree of the positive electrode plate  121  and the first separator  122  meets the accuracy requirements, the positive electrode composite plate body  20  can be transported to the winding device  107  for winding, which is beneficial to ensuring the yield and quality of the wound electrode assembly  12 . In an example, the first detection device  116  includes an industrial camera or a photoelectric sensor for detecting the degree of alignment. In an embodiment, the apparatus  100  further includes a second detection device  117  for detecting the composite alignment degree of the negative electrode plate  123  and the second separator  124 . The second detection device  117  is disposed in the downstream of the second joining device  106 , and can detect in real time the alignment degree of the negative electrode plate  123  and the second separator  124  after being joined. When the alignment degree of the negative electrode plate  123  and the second separator  124  meets the accuracy requirements, the negative electrode composite plate body  30  can be transported to the winding device  107  for winding, which is beneficial to ensuring the yield and quality of the wound electrode assembly  12 . In an example, the second detection device  117  includes an industrial camera or a photoelectric sensor for detecting the degree of alignment. In an exemplary embodiment, the apparatus  100  further includes a first detection device  116  and a second detection device  117 . 
     In an embodiment, the apparatus  100  further includes a first correction device  118  for adjusting the alignment degree of the positive electrode plate  121  and the first separator  122 . Before the positive electrode plate  121  and the first separator  122  are joined, the first correcting device  118  adjusts the relative position of the positive electrode plate  121  and the first separator  122  along the width direction of the positive electrode plate  121 , so that the positive electrode plate  121  and the first separator  122  are aligned with each other so as to satisfy product requirements, which is beneficial to improving the yield of the wound electrode assembly  12 . In an example, the apparatus  100  includes a first detection device  116 . The first correction device  118  is in communication with the first detection device  116 . When the first detection device  116  detects that the alignment degree between the positive electrode plate  121  and the first separator  122  does not meet the requirements, it sends a signal to the first correction device  118 , and then the first correction device  118  performs a correction action to adjust the alignment degree of the positive electrode plate  121  and the first separator  122 . In an embodiment, the apparatus  100  further includes a second correction device  119  for adjusting the alignment degree of the negative electrode plate  123  and the second separator  124 . Before the negative electrode plate  123  and the second separator  124  are joined, the second correcting device  119  adjusts the relative position of the negative electrode plate  123  and the second separator  124  along the width direction of the negative electrode plate  123 , so that the negative electrode plate  123  and the second separator  124  are aligned with each other so as to satisfy the product requirements, which is beneficial to improving the yield of the wound electrode assembly  12 . In an example, the apparatus  100  includes a second detection device  117 . The second correction device  119  is in communication with the second detection device  117 . When the second detection device  117  detects that the alignment degree between the negative electrode plate  123  and the second separator  124  does not meet the requirements, it sends a signal to the second correcting device  119 , and then the second correcting device  119  performs a correcting action to adjust the alignment degree of the negative electrode plate  123  and the second separator  124 . In an exemplary embodiment, the apparatus  100  further includes a first correction device  118  and a second correction device  119 . 
     According to the apparatus  100  for manufacturing the electrode assembly  12  of the secondary battery  10  of the embodiment of the present application, the positive electrode plate  121  and the first separator  122 , and the negative electrode plate  123  and the second separator  124  are joined to form the positive electrode composite plate body  20  and the negative electrode composite plate body  30  in advance, so that the positive electrode plate  121  and the first separator  122  are connected as a whole, the negative electrode plate  123  and the second separator  124  are connected as a whole, and then the positive electrode composite plate body  20  and the negative electrode composite plate body  30  are wound to form the electrode assembly  12 . In this way, on the one hand, the apparatus  100  of the embodiment of the present application does not require that the positive electrode plate  121 , the negative electrode plate  123  and the separator to be rolled in for winding separately, which can reduce the possibility that the positive electrode plate  121  and the negative electrode plate  123  may be folded or wrinkled when they enter the winding process separately, and that the positive electrode plate  121  and the negative electrode plate  123  are not aligned with each other, and thus improve the yield of the electrode assembly  12  effectively. On the other hand, the positive electrode plate  121 , the negative electrode plate  123  and the separator may not be provided with a roll-in auxiliary mechanism for guiding the positive electrode plate  121  and the negative electrode plate  123  to be rolled in in the upstream of the winding device  107 , which is beneficial to reducing the number of parts used, simplifying the overall structure of the apparatus  100 , and at the same time improving the efficiency of winding operation. 
     Although the present application has been described with reference to the preferred embodiments, without departing from the scope of the present application, various improvements can be made to it and the components therein can be replaced with equivalents. In particular, as long as there is no structural conflict, the various technical features mentioned in the various embodiments can be combined in any manner. The present application is not limited to the specific embodiments disclosed in the text, but includes all technical solutions falling within the scope of the claims.