Patent Publication Number: US-2022238908-A1

Title: Rectangular secondary battery

Description:
TECHNICAL FIELD 
     The present invention relates to a rectangular secondary battery. 
     BACKGROUND ART 
     With a higher output of an on-vehicle secondary battery, a current flowing through the battery increases. As a result, an increasing amount of heat is generated in the battery, whereby the temperature of the entire battery rises. An excessive rise in the temperature of the entire battery may deteriorate resin parts such as a gasket and/or alter an electrolyte, for example. 
     Patent Document 1 discloses a sealed battery (e.g., a secondary battery) obtained by fastening a current collecting terminal (i.e., a current collector) to an external terminal by crimping a rivet. The current collecting terminal is connected to each of positive and negative electrodes of an electrode body. 
     CITATION LIST 
     Patent Document 
     Patent Document 1: Japanese Unexamined Patent Publication No. 2013-105538 
     SUMMARY OF THE INVENTION 
     In the secondary battery with the structure disclosed in Patent Document 1, the rivet needs to have a thickness reduced to some extent so as to be crimped. The rivet cannot have thus a large cross-sectional area. A large current flowing through the rivet may increase the Joule heat and cause an excessive temperature rise inside the battery. 
     In a lithium ion battery with a high energy density, a positive electrode current collector is typically made of aluminum or an aluminum alloy, and a negative electrode current collector is typically made of copper or a copper alloy. The rivet connected to each current collector is made of the same material as the current collector. That is, the rivet (e.g., aluminum) used for the positive electrode has a higher electrical resistance than the rivet (e.g., copper) used for the negative electrode. Accordingly, a large current flowing through the rivet for the positive electrode may increase the Joule heat and cause excessive temperature rise inside the battery. 
     The present invention was made in view of the foregoing. It is a main objective of the present invention to provide a secondary battery causing less Joule heat and less temperature rise inside. 
     A rectangular secondary battery according to the present invention includes: an electrode body including a positive electrode plate and a negative electrode plate; a rectangular battery case having an opening and housing the electrode body; a sealing plate sealing the opening; a current collector connected to an edge of the positive electrode plate or the negative electrode plate at a longitudinal end of the sealing plate; and an external terminal located outside the sealing plate and connected to the current collector, the current collector having a hole at an end closer to the sealing plate, and the current collector being connected to the external terminal with a connector interposed therebetween which is inserted into the hole. 
     The present invention provides a secondary battery causing less Joule heat and less temperature rise inside. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  and  FIG. 1B  schematically show a configuration of a rectangular secondary battery according to an embodiment of the present invention.  FIG. 1A  is a top view, while  FIG. 1B  is a cross-sectional view taken along line Ib-Ib of  FIG. 1A . 
         FIG. 2A  and  FIG. 2B  illustrate a procedure of assembling the rectangular secondary battery according to the embodiment. 
         FIG. 3  illustrates the procedure of assembling the rectangular secondary battery according to the embodiment. 
         FIG. 4  illustrates the procedure of assembling the rectangular secondary battery according to the embodiment. 
         FIG. 5A  and  FIG. 5B  illustrate the procedure of assembling the rectangular secondary battery according to the embodiment. 
         FIG. 6  illustrates the procedure of assembling the rectangular secondary battery according to the embodiment. 
         FIG. 7A  and  FIG. 7B  illustrate a procedure of assembling a rectangular secondary battery according to another embodiment. 
         FIG. 8A  and  FIG. 8B  illustrate the procedure of assembling the rectangular secondary battery according to the other embodiment. 
         FIG. 9  is a partial schematic perspective view of a structure of the current collector for electrode bodies with a wound structure. 
         FIG. 10  is a partial schematic perspective view of another structure of the current collector for electrode bodies with a wound structure. 
         FIG. 11  is a partial cross-sectional view of a structure of the current collector for a single electrode body. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Embodiments of the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the following embodiments. Modifications may be made as appropriate without departing from the scope of the advantages of the present invention. 
       FIG. 1A  and  FIG. 1B  schematically show a configuration of a rectangular secondary battery according to an embodiment of the present invention.  FIG. 1A  is a top view, while  FIG. 1B  is a cross-sectional view taken along line Ib-Ib of  FIG. 1A . 
     As shown in  FIG. 1A  and  FIG. 1B , in a rectangular secondary battery  1  according to this embodiment, an electrode body  10 , which is a power generation element, is housed together with an electrolyte in a rectangular battery case  11 . The structure of the electrode body  10  is obtained by stacking a positive electrode plate and a negative electrode plate with a separator (none of them are shown) interposed therebetween. The positive electrode plate includes a positive electrode active material layer on the surface of a positive electrode core, while the negative electrode plate includes a negative electrode active material layer on the surface of a negative electrode core. The battery case  11  has an opening sealed with a sealing plate  12 . 
     Each of the positive and negative electrode plates has exposures  10   a  and  10   b,  in which the active material layer is not formed, at the longitudinal ends of the sealing plate  12 . The exposures  10   a  and  10   b  extend oppositely along the longitudinal direction of the sealing plate  12  and are connected to positive and negative current collectors  20 A and  20 B, respectively. Specifically, the plurality of exposures  10   a  and  10   b  are jointed to the current collectors  20 A and  20 B, respectively, while being bundled. The joining may be laser welding, for example. 
     The materials of the current collectors  20 A and  20 B are not particularly limited as long as being free from the influence of positive and negative electrode potentials in the electrolyte. The materials may be the same as the materials of the exposures  10   a  and  10   b  of the positive and negative electrode plates, respectively, in one preferred embodiment. For example, in the case of a lithium ion secondary battery, the (positive) current collector  20 A connected to the exposure  10   a  of the positive electrode plate is made of aluminum or an aluminum alloy in one preferred embodiment. The (negative) current collector  20 B connected to the exposure  10   b  of the negative electrode plate is made of copper or a copper alloy in one preferred embodiment. 
     The positive and negative current collectors  20 A and  20 B are block bodies with a thickness along the width of the sealing plate  12 , and holes  23 A and  23 B at their ends closer to the sealing plate  12 . Connectors  22 A and  22 B are respectively inserted into the holes  23 A and  23 B in the current collectors  20 A and  20 B. 
     The connectors  22 A and  22 B are formed of tubular bodies (e.g., cylindrical bodies) with flanges which are joined to external terminals  21 A and  21 B, respectively. Accordingly, the current collectors  20 A and  20 B are respectively connected to the positive and negative external terminals  21 A and  21 B with the connectors  22 A and  22 B interposed therebetween which are inserted into the holes  23 A and  23 B. 
     The connectors  22 A and  22 B are insulated from the sealing plate  12  by insulating members (i.e., gaskets)  30 A and  30 B, respectively. The external terminals  21 A and  21 B are insulated from the sealing plate  12  by insulating members  31 A and  31 B, respectively. 
     The electrode body  10  and the current collectors  20 A and  20 B are wrapped in an insulating holder  40  and housed in the battery case  11 . The insulating holder  40  is in the shape of a bag open toward the sealing plate  12 . The material of the insulating holder  40  is not particularly limited, and examples thereof include resin sheets such as polypropylene (PP) and polyethylene (PET). 
     Now, a procedure of assembling the rectangular secondary battery  1  according to this embodiment will be described with reference to  FIGS. 2 to 6 . 
     First, as shown in  FIG. 2A  and  FIG. 2B , the electrode body  10  and the current collector  20 A (or  20 B) are prepared. As shown in  FIG. 2A , the electrode body  10  has positive and negative exposures  10   a  and  10   b  at both the longitudinal ends of the sealing plate  12 . As shown in  FIG. 2B , the current collector  20 A is a block body with a hole  23 A, into which the connector  22 A is inserted, at the end closer the sealing plate  12 . The negative electrode current collector  20 B has the same configuration. In the following description, the description of the current collector  20 B will be omitted. 
     Next, as shown in  FIG. 3  and  FIG. 4 , the two electrode bodies  10 A and  10 B with the same structure are arranged side by side along the width of the sealing plate  12 . The exposures  10   a  and  10   a  of the electrode bodies  10 A and  10 B sandwich the current collector  20 A. The exposures  10   a  and  10   a  and the current collector  20 A are joined by laser welding, for example, in a joint area  24 . 
     Next, as shown in  FIG. 5A  and  FIG. 5B , the current collector  20 A is fixed to the sealing plate  12  and the external terminal  21 A. Here,  FIG. 5A  is an enlarged partial perspective view of portion around the sealing plate  12  of the current collector  20 A.  FIG. 5B  is a partial cross-sectional view taken along line Vb-Vb of  FIG. 5A . 
     As shown in  FIG. 5A  and  FIG. 5B , the insulating member (i.e., the gasket)  30 A, the sealing plate  12 , the insulating member  31 A, and the external terminal  21 A are placed in this order on the current collector  20 A. Each of the insulating member  30 A, the sealing plate  12 , the insulating member  31 A, and the external terminal  21 A has a through-hole in a corresponding position to the hole  23 A of the current collector  20 A. In addition, the insulating member  30 A has an outer periphery abutting on the inner peripheral surface of a through-hole  12   a  in the sealing plate  12 . 
     Then, the connector  22 A passes through the through-holes in the insulating member  30 A, the sealing plate  12 , the insulating member  31 A, and the external terminal  21 A, and press-fitted into the hole  23 A of the current collector  20 A. Accordingly, the current collector  20 A is fixed to the connector  22 A more firmly. At this time, a compressed insulating member (i.e., gasket)  30 A is interposed between the inner peripheral surface of the through-hole  12   a  in the sealing plate  12  and the outer peripheral surface of the connector  22 A, and between the bottom surface of the sealing plate  12  and the upper surface of the current collector  20 A. 
     After that, the flange of the connector  22 A and the external terminal  21 A are welded with laser, for example, to melt-bond the connector  22 A and the external terminal  21 A, which further reduces the electrical resistance. 
     When the connector  22 A is press-fitted into the hole  23 A, the space inside the hole  23 A is gradually compressed. That is, the connector  22 A gradually has difficulty in being press-fitted and may not reach a predetermined depth. In order to solve this problem, as shown in  FIG. 5B , the connector  22 A has a continuous hole  26 A causing the hole  23 A to communicate with the outside in one preferred embodiment. Accordingly, the connector  22 A can be press-fitted to a predetermined depth of the hole  23 A, while releasing the air inside the hole  23 A through the continuous hole  26 A to the outside. 
     Next, as shown in  FIG. 6 , the sealing plate  12 , to which the current collector  20 A, the connector  22 A, and the external terminal  21 A are integrally fixed, is inserted into the insulating holder  40 . The electrode body  10  and the current collector  20 A wrapped in the insulating holder  40  are then housed in the battery case  11 . After that, the end of the battery case  11  closer to the opening and the outer periphery of the sealing plate  12  are welded with laser, for example, to seal the battery case  11 . At the end, an electrolyte is poured into the battery case  11  through a liquid inlet (not shown) in the sealing plate  12 , and then the liquid inlet is closed with a plug  50  (see  FIG. 1 ). 
     According to this embodiment, the connector  22 A connecting the current collector  20 A and the external terminal  21 A is a tubular body, which provides a larger cross-sectional area for flowing a current than in typical fastening by crimping a rivet. Accordingly, the electrical resistance decreases at the connector  22 A, which generates less Joule heat even when a large current flows through the connector  22 A. This results in less temperature rise inside the battery. 
     In this embodiment, the two electrode bodies  10 A and  10 B are arranged side by side along the width of the sealing plate  12 . As shown in  FIG. 4 , the exposures  10   a  and  10   a  of the electrode bodies  10 A and  10 B sandwich the current collector  20 A to be jointed to the current collector  20 A. The block body of the current collector  20 A has thus a greater thickness along the width of the sealing plate  12 . This increases the cross-sectional area of the current collector  20 A and eventually the inner diameter of the hole  23 A. As a result, the outer diameter of the connector  22 A increases, which reduces temperature rise inside the battery more advantageously. 
     In this embodiment, portion of the (positive electrode) connector  22 A connected to the positive electrode current collector  20 A is located in the battery case  11  below the sealing plate  12 . However, as shown in  FIG. 5B , the compressed insulating member (i.e., gasket)  30 A is interposed between the inner peripheral surface of the through-hole  12   a  in the sealing plate  12  and the outer peripheral surface of the connector  22 A, and between the bottom surface of the sealing plate  12  and the upper surface of the current collector  20 A. That is, the connector  22 A press-fitted into the hole  23 A of the current collector  20 A is isolated from the space inside the battery case  11  by the insulating member (i.e., the gasket)  30 A and the current collector  20 A. The connector  22 A does not come into contact with the electrolyte in the battery case  11  and is thus free from the influence of the electrolyte, even if the positive electrode connector  22 A is made of copper or a copper alloy. 
     Accordingly, the positive electrode connector  22 A is made of copper or a copper alloy instead of typically used aluminum or an aluminum alloy to further reduce the electrical resistance at the connector  22 A. As a result, less Joule heat is generated even when a large current flows through the connector  22 A, which further reduces temperature rise inside the battery. If the positive electrode connector  22 A is made of copper or a copper alloy, the external terminal for the positive electrode (i.e., the positive electrode external terminal)  21 A may also be made of copper or a copper alloy. 
     In this embodiment, the connector  22 A is press-fitted into the hole  23 A of the current collector  20 A to fix the current collector  20 A. This causes less contact resistance between the connector  22 A and the current collector  20 A than in typical fastening by crimping a rivet. Accordingly, less Joule heat is generated at the connector  22 A, which further reduces temperature rise inside the battery. 
     While the present invention has been described with reference to a preferred embodiment, such description is not limiting, and various modifications may be made. 
     For example, while the connector  22 A is the tubular body with the flange in the embodiment described above, the configuration is not limited thereto. The connector  22 A may be a bolt, for example. 
       FIGS. 7A, 7B, 8A, and 8B  illustrate an assembly procedure where the connector  22 A is a bolt. Here,  FIG. 7A  is an enlarged partial perspective view of portion around the sealing plate  12  of the current collector  20 A, while  FIG. 7B  is a partial cross-sectional view taken along line VIIb-VIIb of  FIG. 7A . Here,  FIG. 8A  is an enlarged partial perspective view of portion around the sealing plate  12  of the current collector  20 A, while  FIG. 8B  is a partial cross-sectional view taken along line VIIIb-VIIIb of  FIG. 8A . 
     As shown in  FIG. 7A  and  FIG. 7B , the insulating member (i.e., the gasket)  30 A, the sealing plate  12 , and an insulating member  32 A are placed in this order on the current collector  20 A. Each of the insulating member  30 A, the sealing plate  12 , and the insulating member  32 A has a through-hole in a corresponding position to the hole  23 A (with an internal thread) of the current collector  20 A. In addition, the insulating member  30 A has an outer periphery abutting on the inner peripheral surface of the through-hole in the sealing plate  12 . 
     Next, the connector  22 A passes through the through-holes in the sealing plate  12  and the insulating member  32 A, and fastened with a bolt to the hole  23 A (with the internal thread) of the current collector  20 A. Accordingly, the current collector  20 A and the insulating member  30 A are fixed to the sealing plate  12  by the connector  22 A. Note that the connector  22 A may have a continuous hole  26 A causing the space inside the hole  23 A (with an internal thread) to communicate with the outside. 
     Next, as shown in  FIG. 8A  and  FIG. 8B , the insulating member  31 A and the external terminal  21 A are placed on the sealing plate  12 , and the flange of the connector  22 A and the external terminal  21 A are welded with laser, for example. Accordingly, the connector  22 A and the external terminal  21 A are melt-bonded, which further reduces the electrical resistance. 
     Even the connector  22 A, which is a bolt, secures a larger cross-sectional area, through which a current flows, than in typical fastening by crimping with a rivet, which reduces the electrical resistance at the connector  22 A. Accordingly, less Joule heat is generated even when a large current flows through the connector  22 A, which reduces temperature rise inside the battery. 
     The connector  22 A fastened to the hole  23 A (with the internal thread) of the current collector  20 A with the bolt is isolated from the space inside the battery case  11  by the insulating member (i.e., the gasket)  30 A and the current collector  20 A. The connector  22 A does not come into contact with the electrolyte in the battery case  11  and is thus free from the influence of the electrolyte, even if the positive electrode connector  22 A is made of copper or a copper alloy. Accordingly, the connector  22 A is made of copper or a copper alloy to further reduce the electrical resistance at the connector  22 A. As a result, less Joule heat is generated even when a large current flows through the connector  22 A, which further reduces temperature rise inside the battery. 
     In the embodiment described above, the connector  22 A and the external terminal  21 A are separate components. Alternatively, the connector  22 A and the external terminal  21 A may be integrally formed into a single member. In addition, the connector  22 A has a solid structure in one preferred embodiment, but may have a partially hollow structure. 
     In addition, in the embodiment described above, each electrode body is obtained by stacking the positive and negative electrode plates with the separator interposed therebetween. Alternatively, the positive and negative electrode plates may be wound with a separator interposed therebetween. 
       FIG. 9  is a partial perspective view schematically showing a structure of the current collector  20 A for the electrode body  10 A with the wound structure. 
     As shown in  FIG. 9 , the electrode bodies  10 A and  10 B have a plurality of exposures  10   a  at the longitudinal ends of the sealing plate  12  of wound electrode plates. Each of the exposures  10   a  is compressed at a middle area P in the height direction of the battery case  11 , while being bundled. 
     On the other hand, the current collector  20 A is placed while being sandwiched between the exposures  10   a  and  10   a  of the electrode bodies  10 A and  10 B. At this time, in a middle area Q in the height direction of the battery case  11 , the current collector  20 A has, along the width of the sealing plate  12 , a width increasing toward the exposures  10   a  and  10   a  to come into contact with the exposures  10   a  and  10   a.  Accordingly, in the areas P and Q, the current collector  20 A and the exposures  10   a  and  10   a  are joined by laser welding, for example. 
     The current collector  20 A has a solid structure in  FIG. 9 , but may have a hollow structure as shown in  FIG. 10 . In this case, the hole  23 A, into which the connector  22 A ( 22 B) is inserted, may be made as follows. The current collector  20 A may have, at the end closer to the sealing plate  12 , a cylindrical part  23   a  with the hole  23 A. 
     In the embodiment described above, the two electrode bodies  10 A and  10 B with the same structure are arranged in the battery case  11 . Alternatively, a single electrode body may be placed. In this case, as shown in  FIG. 11 , the electrode body  10  has, at the longitudinal ends of the sealing plate  12 , a plurality of exposures  10   a  which are bundled at the transverse ends of the sealing plate  12 . Then, the exposures  10   a  and the current collector  20  may be joined by laser welding, for example, with the current collector  20  abutting on the exposures  10   a.    
     In the embodiment described above, the current collectors  20 A and  20 B are connected to the exposures  10   a  and  10   b  at both edges of the positive and negative electrode plates, respectively. Alternatively, the current collector  20  may be connected to the exposures  10   a  and  10   b  of only one of the positive or negative electrode plate. 
     The type of the rectangular secondary battery according to this embodiment is not particularly limited. For example, the rectangular secondary battery is applicable to a lithium ion secondary battery, a nickel hydrogen secondary battery, or other batteries. 
     DESCRIPTION OF REFERENCE CHARACTERS 
     
         
           1  Rectangular Secondary Battery 
           10 ,  10 A,  10 B Electrode Body 
           10   a,    10   b  Exposure 
           11  Battery Case 
           12  Sealing Plate 
           12   a  Through-hole 
           20 ,  20 A,  20 B Current Collector 
           21 A,  21 B External Terminal 
           22 A,  22 B Connector 
           23 A,  23 B Hole 
           23   a  Cylindrical Part 
           24  Joint Area 
           26 A,  26 B Continuous Hole 
           30 A,  30 B Insulating Member (Gasket) 
           31 A,  31 B Insulating Member 
           32 A Insulating Member 
           40  Insulating Holder 
           50  Plug