Abstract:
This invention relates to a method of manufacturing an electrode for a secondary battery, which enables cost savings and the manufacture of products having various sizes and shapes. The method includes (A) preparing an electrode plate, (B) cutting the electrode plate to conform to the width of the electrode, thus providing a unit electrode plate, and (C) removing at least one of the corner regions of the unit electrode plate.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a 371 of international application number PCT/KR2007/006753, filed on Dec. 21, 2007. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a method of manufacturing an electrode for a battery, and more particularly, to a method of manufacturing an electrode for a secondary battery, which enables cost savings and the manufacture of products having various sizes and shapes. 
         [0004]    2. Description of the Related Art 
         [0005]    Generally, a chemical battery refers to a battery composed of a positive electrode, a negative electrode, and an electrolyte to thus generate electrical energy using a chemical reaction, and is classified into a primary battery, which is disposable, and a secondary battery, which is chargeable and dischargeable, thus enabling repeated use. The use of such a secondary battery is gradually increasing due to the advantage of its chargeable and dischargeable characteristic. 
         [0006]    Among secondary batteries, a lithium secondary battery has high energy density per unit weight, and thus is widely used as a power source in electronic communication devices and in high-power hybrid vehicles. 
         [0007]    The lithium secondary battery includes an electrode group, composed of a positive electrode, a negative electrode, and a separator disposed between the positive and negative electrodes, and a positive electrode tab and a negative electrode tab respectively connected to the positive electrode and the negative electrode. In general, the electrodes such as the positive and negative electrodes are manufactured in such a way that an electrode plate is shaped into a predetermined electrode pattern using a metal die. 
         [0008]    When the electrodes are manufactured using a metal die, each of the electrodes defined in the electrode plate must be provided on four sides thereof with tolerances corresponding to more than 10% of the thickness of the electrode plate. In order to ensure providing such a tolerance, a portion of the electrode plate must be disposed of, thus causing the loss of raw material. Consequently, the cost of manufacturing electrodes may be increased and the productivity of electrodes may be greatly reduced. 
         [0009]    In this regard, after the electrodes are manufactured using a metal die, debris adhering to the metal die may fall on the electrode plate, and thus micro short-circuits may occur. This may cause the deterioration of reliability of a battery equipped with the electrodes. In order to avoid such defects, the electrode must have an additional resin layer or film and the like disposed thereunder, and thus manufacture of such electrodes is problematic. 
         [0010]    In addition, since the metal die has a fixed size and shape, it is possible to manufacture only one type of electrode having fixed size and shape using one metal die. Accordingly, when the size and shape of an electrode must be changed even slightly according to variation in the requirements of customers or market circumstances, all of the equipment for manufacturing the electrode must be replaced. 
       BRIEF SUMMARY OF THE INVENTION 
       [0011]    Accordingly, the present invention has been devised to solve the problems encountered in the related art, and provides a method of manufacturing an electrode for a battery, which minimizes raw material loss, prevents the occurrence of debris, and enables the manufacture of electrodes having various sizes and shapes. 
         [0012]    To overcome the above problems, the present invention provides a method of manufacturing an electrode for a battery, including the steps of: (A) preparing an electrode plate; (B) cutting the electrode plate to conform with a width of the electrode, thus providing a unit electrode plate; and (C) removing at least one of the corner regions of the unit electrode plate. 
         [0013]    The electrode plate may include a blank region at a side margin thereof, on which no active material is applied. 
         [0014]    The step (A) of preparing an electrode plate may include the steps of: (A1) preparing a preliminary electrode plate which includes blank regions at both sides thereof, and (A2) slitting the preliminary electrode plate, thus providing the electrode plate. 
         [0015]    The step (A2) of slitting the preliminary electrode plate may be conducted in such a way as to slit the preliminary electrode plate along a center line with respect to a width of the preliminary electrode plate. 
         [0016]    The step (B) of cutting the electrode plate may be conducted in a scissor manner. 
         [0017]    The step (C) of removing at least one of the corner regions may be conducted using a cutting tool having a planar shape corresponding to a shape of the corner region to be removed in a predetermined pattern. 
         [0018]    The unit electrode plate may include a blank region at a side margin thereof, on which no active material is applied, and the step (C) of removing at least one of the corner regions may be conducted in a such a way as to remove first and second corner regions positioned at opposite sides of the blank region. 
         [0019]    The step (C) of removing at least one of the corner regions may be conducted in such a way as to remove the first and second corner regions sequentially. 
         [0020]    The step (C) of removing at least one of the corner regions may include the steps of: disposing a cutting die over the first corner region; removing the first corner region of the unit electrode plate using the cutting tool; moving the unit electrode plate such that the cutting tool is positioned over the second corner region; and removing the second corner region of the unit electrode plate using the cutting tool. 
         [0021]    The step (B) of cutting the electrode plate and the step (C) of removing at least one of the corner regions may be conducted in a continuous process. 
         [0022]    The electrode may be adapted to be used in a lithium secondary battery. 
         [0023]    In the method of manufacturing an electrode for a battery according to the present invention, since a preliminary electrode plate or an electrode plate is sequentially cut into electrodes, the production cost of the electrodes can be reduced and the reliability of a battery equipped with the manufactured electrodes can be improved. 
         [0024]    More specifically, a preliminary electrode plate or an electrode plate is cut such that the cut electrode has a predetermined width and length, and thus the preliminary electrode plate or the electrode plate can be cut without entailing the loss of materials. Consequently, the loss of raw materials is minimized, and thus the production cost can be greatly reduced. 
         [0025]    Furthermore, since a preliminary electrode plate or an electrode plate is cut through slitting or shearing, it is possible to prevent the occurrence of debris. Consequently, micro short- circuits are prevented, and thus the reliability of a battery equipped with the manufactured electrode can be improved. In addition, there is no need to provide additional resin layers or films for preventing the occurrence of debris. 
         [0026]    According to the present invention, an electrode plate may be sheared using a cutting tool adapted to operate in a scissors manner, so that the shearing process is conducted in an automated facility. Further, a second step of shearing and a third step of removing the corner regions may be continuously conducted in an automated facility so as to enable the simplification of the process and the improvement of productivity. 
         [0027]    In the present invention, since it is possible to easily control a slitting location in a first step or a shearing location in a second step according to the predetermined width and length of an electrode, electrodes having a variety of sizes can be manufactured without restriction. In a third step, the corner regions of the electrode plate are sequentially removed using a cutting tool, and thus a tab junction having a desired size can be positioned at a desired location. 
         [0028]    In other words, according to this embodiment, electrodes having various shapes or sizes, which include tab junctions having various positions and sizes, can be manufactured without restriction. Accordingly, when the shape or size of an electrode must be changed, a predetermined electrode can be manufactured by adjusting the cutting position in an existing facility, without imposing the burden of constructing or purchasing a new facility. In this way, the method of manufacturing an electrode for a battery according to the present invention can properly respond to various demands of customers and market changes. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         [0029]      FIG. 1  is a perspective view showing a lithium secondary battery equipped with an electrode manufactured through a method according to an embodiment of the present invention; 
           [0030]      FIG. 2  is a top plan view showing an electrode manufactured through the method according to the embodiment of the present invention; 
           [0031]      FIG. 3  is a flowchart showing the method of manufacturing an electrode, according to an embodiment of the present invention; 
           [0032]      FIG. 4  is a perspective view showing a first step of the method of manufacturing an electrode, according to an embodiment of the present invention; 
           [0033]      FIG. 5  is a perspective view showing a second step of the method of manufacturing an electrode, according to the embodiment of the present invention; and 
           [0034]      FIGS. 6 to 10  are a perspective views showing a third step of the method of manufacturing an electrode, according to the embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0035]    The present invention is related to international application number PCT/KR2007/006753, filed on Dec. 21, 2007, which is incorporated herein by reference in its entirety. 
         [0036]    As described herein, with reference to  FIGS. 1-10 , various components are referred to by the following reference numerals.
     10  lithium secondary battery     20  electrode group     22  positive electrode     24  negative electrode     26  separator     32  positive electrode tab     34  negative electrode tab     40  case     42  adhesive region     50  electrode     50   a  current collector     50   b  active material     50   c  tab junction     52  preliminary electrode plate     56  electrode plate     58  unit electrode plate     58   c  first corner region     58   c ′ second corner region     60  slitting tool     62  shearing tool     64  cutting tool     110  preparation step     120  cutting blank plate step     130  cutting corner step     521  blank region     561  blank region     581  blank region.   
 
         [0064]    Hereinafter, a method of manufacturing an electrode for a battery according to an embodiment of the present invention will be described with reference to the appended drawings. 
         [0065]      FIG. 1  is a perspective view illustrating a lithium secondary battery equipped with an electrode that is manufactured according to an embodiment of the present invention. 
         [0066]    As illustrated in  FIG. 1 , the lithium secondary battery  10  according to the present invention includes an electrode group  20  including a first electrode  22  (cathode electrode; hereinafter, referred to as a “positive electrode”), a second electrode  24  (anode electrode; hereinafter, referred to as a “negative electrode”), and a separator  26  disposed between the positive electrode and the negative electrode, a first electrode tab  32  (hereinafter, referred to as a “positive electrode tab”) and a second electrode tab  34  (hereinafter, referred to as a “negative electrode tab”) respectively connected to the positive electrode  22  and the negative electrode  24 , and a battery case  40  for accommodating the electrode group  20 , the positive electrode tab  32 , and the negative electrode tab  34  therein while exposing the ends of the positive electrode tab  32  and the negative electrode tab  34 . 
         [0067]    Depending on the type of battery, an electrolyte in a liquid state may be injected in the battery case  40 , and the separator  26  may play a role as the electrolyte. Alternatively, after an electrolyte in a liquid state is injected in the battery case  40 , a polymerizable component may be added thereto, ultimately obtaining the electrolyte in a polymeric state. 
         [0068]    In the present embodiment, although the battery case  40  is shown as being comprised of a pouch that is sealed using adhesive regions  42 , the present invention is not limited thereto. In particular, a case made of metal or plastic material and having a circular shape or prismatic shape may be used as the battery case  40 , which also falls within the scope of the present invention. 
         [0069]    The positive electrode  22  and the negative electrode  24 , shown in  FIG. 1 , will now be described in more detail, with reference to  FIG. 2 . Since the positive electrode  22  and the negative electrode  24  are very similar to or identical to each other as to the basic structure, except for the position of a tab junction  50   c  (see  FIG. 2 ) and constituents of a current collector and an active material, the positive electrode  22  and the negative electrode  24  will be commonly referred to as an electrode  50  hereinafter. 
         [0070]      FIG. 2  is a plan view of the electrode  50  that is manufactured through the method according to an embodiment of the present invention. 
         [0071]    Referring to  FIG. 2 , the electrode  50  according to this embodiment comprises a current collector  50   a  and an active material  50   b  applied to at least one side of the current collector  50   a.    
         [0072]    In this regard, when the electrode  50  is a positive electrode, in an example, the current collector  50   a  may be made of aluminum while the active material  50   b  may be made of a lithium- based transition metal oxide. When the electrode  50  is a negative electrode, in an example, the current collector  50   a  may be made of copper while the active material  50   b  may be made of carbonaceous material. However, the present invention is not limited thereto, and the current collector  50   a  and the active material  50   b  of the electrode  50  may be made of material other than the materials stated above, which also falls within the scope of the present invention. 
         [0073]    The electrode  50  is provided with a tab junction  50   c  that protrudes outward from one side thereof. In alternative embodiments, the tab junction  50   c  may have various shapes and may be formed at various positions. The tab junction  50   c,  to which the positive electrode tab  32  (see  FIG. 1 ) or the negative electrode tab  34  (see  FIG. 1 ) is connected, is preferably comprised of a blank part, which does not contain the active material  50   b  thereon, so that the positive electrode tab  32  or the negative electrode tab  34  is efficiently connected to the electrode  50  through welding. 
         [0074]    The method of manufacturing the electrode  50  will now be described in more detail, with reference to  FIGS. 3 to 10 . 
         [0075]      FIG. 3  is a flowchart illustrating the method of manufacturing an electrode according to an embodiment of the present invention. 
         [0076]    Referring to  FIG. 3 , the method of manufacturing an electrode according to this embodiment of the invention comprises a first step  110  of preparing an electrode plate, a second step  120  of cutting the electrode plate into unit electrode plates, and a third step  130  of cutting away corner regions of the unit electrode plate. 
         [0077]    Hereinafter, the first step  110 , the second step  120 , and the third step  130  of the method according to this embodiment will be described in more detail, with reference to  FIGS. 4 to 10 . 
         [0078]      FIG. 4  is a perspective view showing the first step  110  of the method according to this embodiment of the invention, and  FIG. 5  is a perspective view showing the second step  120  of the method according to this embodiment of the invention. Further,  FIGS. 6 to 10  are perspective views showing the third step  130  of the method according to this embodiment of the invention. 
         [0079]    As shown in  FIG. 4 , in the first step  110 , a preliminary electrode plate  52  is slit so as to prepare an electrode plate  56  (see  FIG. 5 ). 
         [0080]    Specifically, a preliminary electrode plate  52 , which is provided at both side margin regions with a blank part  521 , which is not coated with an active material, is first prepared, and the preliminary electrode plate  52  is slit using a tool such as a slitting blade  60 . In this slitting, the preliminary electrode plate  52  is slit such that the resulting electrode  50  (see  FIG. 2 ) has a predetermined width (T 1 ), as shown in  FIG. 4 . 
         [0081]    In an example, the preliminary electrode plate  52  may be prepared such that a current collector  50   a  (see  FIG. 2 ) having a width twice the predetermined width (T 1 ) of the electrode is coated with the active material  50   b  (see  FIG. 2 ) except for both side margin regions thereof, that is, both blank regions  521 , as shown in  FIG. 4 , and then the preliminary electrode plate  52  may be slit along the longitudinal center line, which is plotted on the center axis with respect to the lateral direction (the y direction in  FIG. 4 ). 
         [0082]    However, the present invention is not limited to the above-described manner, and the preliminary electrode plate  52  may be slit into electrode plates  56  which have widths (T 1 ) that are different from each other, which also falls within the scope of the present invention. 
         [0083]    According to this embodiment, since the preliminary electrode plate  52  is slit into the electrode plates  56  to match a predetermined width (T 1 ) of the electrode  50 , all of the preliminary electrode plate  52  can be utilized without any discarded material, thus minimizing the waste of material for the preliminary electrode plate  52 . 
         [0084]    Subsequently, as shown in  FIG. 5 , in the second step  120 , the electrode plate  56 , which has blank regions  561  at one side margin region thereof, is cut, or more specifically, sheared into unit electrode plates  58  using a shearing tool  62 . In this regard, the electrode plate  56  is sheared to match a predetermined length (T 2 ) of the electrode  50 . 
         [0085]    In this embodiment, since the electrode plate  56  is sheared to match a predetermined length (T 2 ) of the electrode  50 , all of the electrode plate  56  can be used without wasting materials, thus minimizing the waste of material for the electrode plate  56 . 
         [0086]    The shearing tool  62  may be operated in a manner in which scissors are employed. By performing such a scissor operation, the electrode plate  56  may be cut using the shearing tool  62  at a certain interval while the electrode plate  56  is transferred by the transfer conveyor on which the electrode plate  56  is placed. In this embodiment, the electrode plate  56  is sheared in a scissor manner, so that the electrode plate  56  can be efficiently sheared using automated equipment. However, the present invention is not limited thereto, and the shearing tool may be operated in any manner other than the scissor manner, which also falls within the scope of the present invention. 
         [0087]    Subsequently, as shown in  FIGS. 6 to 10 , in the third step  130 , the unit electrode plate  58  is cut using a cutting tool  64 , such that both corner regions  58   c,    58   c ′ thereof are removed, thus providing a tab junction  50   c  on the blank region  581 . 
         [0088]    In this embodiment, both corner regions  58   c,    58   c ′, which are positioned at the opposite ends of the blank region  581  formed at a side of the unit electrode plate  58 , are removed. However, the present invention is not limited thereto, and the present invention may be applied to any case in which at least one corner of the unit electrode plate  58  is removed. 
         [0089]    In  FIGS. 6-9 , there is shown only the cutting tool  64  for clarity of explanation. The cutting tool  64  may be formed to have a shape corresponding to the corner regions  58   c,    58   c ′. The term “shape corresponding to the corner regions” denotes a shape in which the corner regions  58   c,    58   c ′ are cut away according to a previously defined pattern. In this embodiment, the cutting tool  64  has a planar rectangular shape in which the corner regions  58   c,    58   c ′ are cut away in rectangular shapes. 
         [0090]    The cutting tool  64  may include cutting knifes therein so as to remove the corner regions  58   c,    58   c ′. However, the present invention is not limited thereto, and the cutting tool  64  may be comprised of various configurations, such as a metal die. 
         [0091]    More specifically, as shown again in  FIG. 6 , the first corner region  58   c  of the unit electrode plate  58  is first disposed under the cutting tool  64 . Subsequently, as shown in  FIG. 7 , the first corner region  58   c  is removed using the cutting member  64 . Then, as shown in  FIG. 8 , the unit electrode plate  58  is moved such that the second corner region  58   c ′ is positioned under the cutting tool  64 . Thereafter, as shown in  FIG. 9 , the second corner region  58   c ′ of the unit electrode plate  58  is cut away using the cutting tool  64 . Consequently, the manufacture of an electrode  50  including a tab junction  50   c  is completed, as shown in  FIG. 10 . 
         [0092]    According to this embodiment, the first corner region  58   c  and the second corner region  58   c ′ are sequentially cut away using only one cutting tool  64 , so that the tab junction  50   c  is created between the cut regions corresponding to the first and second corner regions  58   c,    58   c ′. In other words, in a conventional art, which includes cutting tools  64  designed to remove both first and second corner regions concurrently, the size of the tab junction  50   c  is fixed. Meanwhile, in this embodiment of the present invention, in which first and second corner regions  58   c,    58   c ′ are sequentially removed using only one cutting tool  64 , the tab junction may be configured to have a desired position and size according to the relative position between the cutting tool  64  and the unit electrode plate  58 . 
         [0093]    Alternatively, the second step  120  and the third step  130  in this embodiment as described above may be continuously conducted through an automated facility which is equipped with the shearing tool  62  in the second step  120  and the cutting tool  64  in the third step  130 , which are adapted to be sequentially operated. According to this alternative embodiment, the process of manufacturing an electrode may be further simplified, and thus the productivity of the process may be more improved. 
         [0094]    As described above, in the method of manufacturing an electrode for a battery according to this embodiment, the first step  110 , the second step  120  and the third step  130  are sequentially conducted so as to provide a predetermined electrode  50 . 
         [0095]    In the first step  110  and the second step  120 , the preliminary electrode plate  52  and the electrode plate  56  are cut to match the predetermined width (T 1 ) and length (T 2 ) of the electrode  50 , thus enabling the preliminary electrode plate  52  and the electrode plate  56  to be cut without wasting materials. Therefore, it is possible to minimize the waste of the preliminary electrode plate  52  and the electrode plate  56 . 
         [0096]    Furthermore, since a cutting operation, such as the slitting or the shearing, is conducted in the first step  110  and the second step  120 , it is possible to prevent debris that is generated in these steps from falling on the electrode plate, thus preventing micro short-circuits. In addition, there is no need to provide an additional resin layer or film, which otherwise must be used under the electrode. 
         [0097]    In addition, according to this embodiment, since the location at which the electrode plate is to be slit or sheared can be controlled without difficulty, in conformity with the predetermined width (T 1 ) and length (T 2 ) of the electrode  50 , electrodes  50  having a variety of sizes can be freely manufactured. Further, in the third step  130 , since the first corner region  58   c  and the second corner region  58   c ′ are sequentially removed using the cutting tool  64 , it is possible to provide a tab junction  50   c  having a desired size at a desired location. 
         [0098]    In this manner, this embodiment of the present invention is able to manufacture electrodes that can be incorporated in electrodes having a variety of shapes and sizes. 
         [0099]    In the embodiment mentioned above, although there has been described a process of manufacturing an electrode of a stacked type electrode, which contains a plurality of positive electrodes and negative electrodes, the present invention is not limited thereto. Accordingly, a winding type battery, in which a positive electrode and a negative electrode are rolled one on the other with a separator disposed therebetween and the positive and negative electrodes have respective protruding tab junctions, can also be manufactured according to the present invention, which also falls within the scope of the invention. 
         [0100]    Furthermore, although the electrode manufactured according to the embodiment has been described as being used in a lithium secondary battery, the present invention is not limited thereto, but can be applied to a process of manufacturing a variety of types of electrodes for batteries, which also falls within the scope of the present invention. 
         [0101]    Although the preferred embodiment of the present invention has been disclosed for illustrative purposes, the present invention is not limited thereto, and those skilled in the art will appreciate that various modifications, additions and substitutions are possible within the technical spirit and scope of the invention, which is defined by the detailed description and the accompanying drawings.