Patent Publication Number: US-2009233169-A1

Title: Battery module and battery pack

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based upon and claims the benefit of priority from prior Japanese Patent Application No. 2008-068303, filed Mar. 17, 2008, the entire contents of which are incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to a battery module and a battery pack, and more particularly, to a battery module that contains a secondary battery (cell) such as a lithium-ion battery, which uses a non-aqueous electrolyte, and a battery pack in which a plurality of battery modules are electrically connected to one another. 
     2. Description of the Related Art 
     In recent years, non-aqueous secondary batteries, especially lithium-ion batteries, have been noted as energy sources for driving vehicles, such as electric vehicles, as well as ones for cordless, portable electronic devices. 
     If the internal pressure of a cell is increased by overcharge or the like, in these non-aqueous secondary batteries, a non-aqueous electrolyte and its gas component may leak out when the cell ruptures. According to a technique disclosed in Japanese Patent No. 3014293 (Patent Document 1), for example, a housing of a battery pack is provided with a partition wall, which divides a battery chamber and an electric circuit chamber that contain the cell and an electric circuit, respectively. The partition wall serves to isolate the electric circuit from an atmosphere on the cell side. According to this Patent Document 1, moreover, a technique is also disclosed such that the cell side of the housing is bored with at least one safety hole through which the non-aqueous electrolyte or its vapor leaked from the cell is released. 
     BRIEF SUMMARY OF THE INVENTION 
     The object of this invention is to provide a battery module and a battery pack configured to discharge an electrolyte and its gas component ejected from a cell to the outside. 
     A battery module according to an aspect of the invention comprises: a cell which contains an electrode group and a non-aqueous electrolyte; and a case including a cell containing portion which contains the cell and a hollow portion which communicates with the cell containing portion and configured so that an outlet is formed in each of a pair of sidewalls thereof which face each other with the hollow portion therebetween. 
     A battery pack according to another aspect of the invention comprises: a battery module including a cell which contains an electrode group and a non-aqueous electrolyte and a case including a cell containing portion which contains the cell and a hollow portion which communicates with the cell containing portion and configured so that an outlet is formed in each of a pair of sidewalls thereof which face each other with the hollow portion therebetween; and a tubular body fitted in the outlet formed in the case of the battery module, a plurality of the battery modules being connected to one another by the tubular body. 
     According to this invention, the case of which the cell containing portion contains the cell includes the hollow portion that communicates with the cell containing portion. Further, the outlet is formed in each of the pair of sidewalls of the case that face each other with the hollow portion therebetween. If the electrolyte and its gas component are ejected from the cell, therefore, they can be safely and securely discharged from the outlet to the outside of the battery module or the battery pack through the hollow portion. 
     Thus, corrosion or short-circuiting by the electrolyte and its gas component can be suppressed, and the reliability can be improved. 
     Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
       The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention, and together with the general description given above and the detailed description of the embodiments given below, serve to explain the principles of the invention. 
         FIG. 1  is a sectional view schematically showing a construction of a battery module according to one embodiment of the invention; 
         FIG. 2  is an enlarged perspective sectional view of a hollow portion of a case of the battery module shown in  FIG. 1 ; 
         FIG. 3  is an enlarged sectional view of the hollow portion of the battery module shown in  FIG. 1 ; 
         FIG. 4  is a perspective view schematically showing a construction of a battery module provided with a tubular body according to the one embodiment of the invention; 
         FIG. 5  is an enlarged sectional view of the respective hollow portions of the connected battery modules shown in  FIG. 4 ; 
         FIG. 6  is a perspective view schematically showing a construction of a battery module provided with a tubular body of another construction according to the one embodiment of the invention; 
         FIG. 7  is an enlarged sectional view of the respective hollow portions of the connected battery modules shown in  FIG. 6 ; 
         FIG. 8  is an enlarged sectional view of hollow portions of battery modules provided with a sealing member of another construction according to the one embodiment of the invention; and 
         FIG. 9  is an enlarged perspective sectional view of the hollow portions of the battery modules shown in  FIG. 8 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     A battery module and a battery pack according to one embodiment of this invention will now be described with reference to the accompanying drawings. 
     As shown in  FIGS. 1 to 3 , a battery module  1  is composed of a cell  10  and a case  20  that can contain the cell  10 . 
     Specifically, the cell  10  is a secondary battery such as a lithium-ion battery, which uses a non-aqueous electrolyte LQ, and is designed so that an electrode group EL and the non-aqueous electrolyte LQ are hermetically sealed in an armor case AC. The external shape of the cell  10  (i.e., that of the armor case AC) is substantially rectangular parallelepipedic. 
     The electrode group EL includes a positive electrode and a negative electrode that are coiled with a separator between them and has a radially compressed, flat rectangular shape. A positive terminal  11  and a negative terminal  12  are connected to the positive and negative electrodes, respectively, of the electrode group EL. The positive and negative terminals  11  and  12  both protrude outward from one surface (upper surface) of the armor case AC. 
     Further, the cell  10  is provided with a rupture plate  13  on the upper surface of the armor case from which the positive and negative terminals  11  and  12  protrude. The rupture plate  13  is configured to rupture, thereby allowing the electrolyte or its gas component to escape from the cell  10 , if the internal pressure of the cell increases. 
     The case  20  includes a cell containing portion  21  and a hollow portion  22  that communicate with each other. The case  20  is formed of a resin, such as polycarbonate (PC) or polyphenylene sulfide (PPS) resin, or ceramics. 
     The cell containing portion  21  is formed as a rectangular parallelepipedic space larger than the contour of the cell  10 . The cell containing portion  21  is defined by six wall plates  21 A to  21 F that surround the cell  10 . These six wall plates  21 A to  21 F may be formed integrally with one another, or alternatively, at least one wall plate may be joined to another one by screwing or some other method. The one wall plate  21 A that defines the cell containing portion  21  faces the upper surface of the cell  10  and is formed with two insertion holes  21 H into which the positive and negative terminals  11  and  12  of the cell  10  can be inserted. 
     When the cell  10  is contained in the cell containing portion  21 , a small gap for the passage of a coolant (e.g., cold blast) is formed between the cell  10  and the case  20 . Further, the positive and negative terminals  11  and  12  that are inserted individually into the insertion holes  21 H project outward from the wall plate  21 A, so that they can be easily connected to leads. 
     The hollow portion  22  is formed as a projection that protrudes outward (i.e., oppositely from the cell containing portion  21 ) from the wall plate  21 A. The hollow portion  22  communicates with the cell containing portion  21  through a substantially rectangular opening  22 AP formed in the wall plate  21 A. In this embodiment, the hollow portion  22  is formed as a substantially rectangular parallelepipedic space, which is surrounded by four sidewalls  22 A to  22 D that rise outward from the wall plate  21 A and a top wall  22 E that faces the opening  22 AP across the hollow portion  22 . The hollow portion  22  is not limited to this illustrated shape but may be of another shape. 
     The sidewall  22 A extends substantially at right angles to the wall plate  21 A from which the positive terminal  11  projects and is formed, for example, integrally with the wall plate  21 A. The sidewall  22 B extends substantially at right angles to the wall plate  21 A from which the negative terminal  12  projects and is formed, for example, integrally with the wall plate  21 A. 
     The sidewall  22 C is a flat plate that extends parallel to the wall plate  21 C so as to be, for example, integral with the plate  21 C. The sidewall  22 D is a flat plate that extends parallel to the wall plate  21 D so as to be, for example, integral with the plate  21 D. The top wall  22 E is substantially rectangular and formed, for example, integrally with the four sidewalls  22 A to  22 D. 
     The opening  22 AP is formed so as to face the rupture plate  13  of the cell  10  in the cell containing portion  21 . Thus, the hollow portion  22  faces the rupture plate  13  across the opening  22 AP within the case  20 . 
     Of the four sidewalls  22 A to  22 D, the pair of sidewalls  22 C and  22 D that are opposed to each other across the hollow portion  22  are formed with outlets  22 H, individually. These outlets  22 H penetrate the sidewalls  22 C and  22 D from the hollow portion  22  to the outside (so that the inside and outside of the case  20  communicate with each other). Each of the outlets  22 H is cylindrical, for example. 
     According to the battery module  1  constructed in this manner, the hollow portion  22  faces the rupture plate  13  of the cell  10  that is contained in the cell containing portion  21 . If the rupture plate  13  ruptures, thereby allowing the electrolyte in the cell and its gas component to be ejected, therefore, the electrolyte and the gas component are discharged into the hollow portion  22 . The internal pressure of the cell  10  can be reduced especially when the gas component that causes its increase is discharged into the hollow portion  22 . 
     Further, the outlets  22 H that individually open to the outside are formed individually in the sidewalls  22 C and  22 D that define the hollow portion  22 . Thus, the ejected electrolyte and gas component are discharged to the outside of the case  20 , that is, the outside of the battery module  1 , through the outlets  22 H. 
     Accordingly, corrosion or short-circuiting of the cell  10  by the ejected electrolyte and gas component can be suppressed, and the reliability can be improved. 
     As shown in  FIGS. 1 to 3 , moreover, the battery module  1  is provided with a sealing member  30  for sealing the hollow portion  22  to the cell containing portion  21  within the case  20 . The sealing member  30  is formed of rubber or some other material that is resistant to corrosion by the electrolyte and has elasticity and a sealing function. The sealing member  30  is in close contact with the cell  10  that is contained in the cell containing portion  21 . Further, the sealing member  30  is formed in a ring shape that ensures communication between the rupture plate  13  and the hollow portion  22 . 
     In the example described herein, the sealing member  30  has a substantially L-shaped cross section. Thus, the sealing member  30  is located so as to seal the gap between the cell  10  and the case  20  (between the cell  10  and the wall plate  21 A, in particular) and is in close contact with the four sidewalls  22 A to  22 D that define the hollow portion  22 . 
     The sealing member  30  constructed in this manner may be previously adhesively bonded to the cell  10 . Further, the sealing member  30  may be previously fitted into the hollow portion  22  so that it can be deformed and brought into close contact with the cell  10  and the case  20  under a sufficient surface pressure when the cell  10  is contained in the cell containing portion  21 . 
     According to the battery module  1  using this sealing member  30 , the electrolyte and its gas component ejected from the cell  10  can be prevented from infiltrating into a space (within the cell containing portion  21 ) between the cell  10  and the case  20 . Further, the electrolyte and its gas component can be prevented from being mixed into the coolant. 
     In an example shown in  FIGS. 4 and 5 , a battery module  1  is provided with a tubular body  40  that is fitted in at least one of the pair of outlets  22 H in the case  20 . The tubular body  40  is formed of rubber or some other material that is resistant to corrosion by the electrolyte and has elasticity and a sealing function. 
     In the example described above, the tubular body  40  includes a tube portion  41  and a pair of rings  42  and  43  that are formed integrally with the tube portion  41 . 
     The tube portion  41  has an outside diameter equal to the inside diameter of each outlet  22 H. Thus, the tube portion  41  is in close contact with the inner surface of each outlet  22 H. Further, the tube portion  41  has a length greater than that of each outlet  22 H, that is, a thickness T of each of the sidewalls  22 C and  22 D of case  20 , or substantially twice as great as the thickness T of each sidewall. The rings  42  and  43  are connected individually to the opposite ends of the tube portion  41  and have an outside diameter greater than the inside diameter of the outlets  22 H. When the tubular body  40  is fitted in each outlet  22 H, the rings  42  and  43  are located in the hollow portion  22 . This tubular body  40  may be adhesively bonded to each outlet  22 H or need not be specially fixed to the case  20 . 
     According to the battery module  1  using this tubular body  40 , the electrolyte and its gas component discharged into the hollow portion  22  can be discharged from the module  1  through the tubular body  40 . 
     Further, a plurality of battery modules  1  can be connected to one another by using the tubular body  40 . In the case shown in  FIG. 5 , the tubular body  40  is fitted in the outlets  22 H in the sidewalls of the respective cases  20  of two adjacent battery modules  1 A and  1 B. 
     Specifically, the ring  42  of the tubular body  40  is situated in the hollow portion  22  of the one battery module  1 A and in close contact with the inner surface of the sidewall  22 D. Further, the tube portion  41  is in close contact with the outlet  22 H of the sidewall  22 D. 
     The other battery module  1 B is configured so that the sidewall  22 D of its case  20  is opposed to and in close contact with the sidewall  22 C of the battery module  1 A. The ring  43  of the tubular body  40  is situated in the hollow portion  22  of this battery module  1 B and in close contact with the inner surface of the sidewall  22 C. Further, the tube portion  41  is in close contact with the outlet  22 H of the sidewall  22 C. 
     Since the length of the tube portion  41  is equal to the sum of the respective thicknesses of the sidewalls  22 C and  22 D, the two battery modules  1 A and  1 B can be connected to each other with the sidewalls  22 C and  22 D in close contact with each other. In this case, the tubular body  40  may be adhesively bonded to the two battery modules  1 A and  1 B. 
     If the rupture plate  13  in the one battery module  1 A ruptures, according to this arrangement, the electrolyte and its gas component can be guided from the hollow portion  22  to that of the other battery module  1 B that is connected to the battery module  1 A by the tubular body  40 . Thus, the capacity of a space that accommodates the ejected electrolyte and gas component can be increased, so that a buffer function to reduce the pressure can be improved. Even in the case of a battery pack that is composed of a plurality of battery modules connected to one another, moreover, the electrolyte and its gas component can be safely and securely discharged from the battery pack. 
     In a modification of the tubular body  40 , as shown in  FIGS. 6 and 7 , for example, the tube portion  41  may be configured so that its length is equal to the thickness T of each sidewall. This tubular body  40  is fitted in the outlet  22 H in such a manner that its rings  42  and  43  are in close contact with the inner and outer surfaces, respectively, of the sidewall. In this modification, the respective rings  43  of two tubular bodies  40  that are in close contact with the respective outer surfaces of the sidewalls of two battery modules are brought into close contact with each other, whereby the tube portions  41  communicate with each other. 
     If the rupture plate  13  in the one battery module  1 A ruptures, according to this arrangement, the electrolyte and its gas component can be guided from the hollow portion  22  to that of the other battery module  1 B through the two tubular bodies  40 . Thus, the capacity of a space that accommodates the ejected electrolyte and gas component can be increased, as in the case shown in  FIGS. 4 and 5 . Even in the case of a battery pack that is provided with a plurality of battery modules, moreover, the electrolyte and its gas component can be safely and securely discharged from the battery pack. 
     In an example shown in  FIGS. 8 and 9 , each battery module  1  is provided with a sealing member  50  for sealing the hollow portion  22  to the cell containing portion  21  within the case  20 . Further, the sealing member  50  includes a tubular body  60  that extends outward from one of the pair of outlets  22 H. The sealing member  50  is formed of rubber or some other material that is resistant to corrosion by the electrolyte and has elasticity and a sealing function. 
     The sealing member  50  is in close contact with the cell  10  that is contained in the cell containing portion  21 . Further, the sealing member  50  is provided with an opening that faces the rupture plate  13  and ensures communication with the hollow portion  22 . Thus, the sealing member  50  seals the hollow portion  22  to the cell containing portion  21 . In this illustrated example, the sealing member  50  has an external shape that is congruous to the internal shape of the hollow portion  22  and is in close contact with all the sidewalls and the top wall that define the hollow portion  22 . 
     The tubular body  60  is fitted in the outlet  22 H that is formed in one of the sidewalls that define the hollow portion  22 . Specifically, the tubular body  60  includes a tube portion  61  and a ring  62  that is formed integrally with the tube portion  61 . The tube portion  61  has an outside diameter equal to the inside diameter of each outlet  22 H. Thus, the tube portion  61  is in close contact with the inner surface of each outlet  22 H. Further, the tube portion  61  is longer than each outlet  22 H. The ring  62  is connected to one end of the tube portion  61  that projects form the sidewall and has an outside diameter greater than the inside diameter of each outlet  22 H. 
     The sealing member  50  constructed in this manner may be previously adhesively bonded to the cell  10  or the case  20 . Further, the sealing member  50  may be previously fitted into the hollow portion  22  so that it can be deformed and brought into close contact with the cell  10  and the case  20  under a sufficient surface pressure when the cell  10  is contained in the cell containing portion  21 . 
     According to the battery module  1  using this sealing member  50 , the aforementioned sealing member  30  and the tubular body  40  are formed integrally with each other, so that the number of parts can be reduced, and a reduction in the number of assembly processes can be expected. It is to be understood, moreover, that the aforementioned effect of provision of the sealing member  30  can be obtained jointly with the effect of provision of the tubular body  40 . 
     This invention is not limited directly to the embodiment described above, and in carrying out the invention, its components may be embodied in modified forms without departing from the scope or spirit of the invention. Further, various inventions may be made by suitably combining a plurality of components described in connection with the foregoing embodiment. For example, some of the components according to the foregoing embodiment may be omitted. Furthermore, components according to different embodiments may be combined as required.