Abstract:
A battery includes an outer package including a laminated film including one or more resin layers, a terminal, and a melt-bonding assisting member including a thermoplastic resin and extending along the terminal. The outer package includes a melt-bonded region at which the terminal is sandwiched between the one or more resin layers. The terminal includes an inner part, a sandwiched part, and an outer part arranged in a first direction. The melt-bonding assisting member internally and externally extends in the first direction beyond contact with the outer package.

Description:
[0001]    The present application is a Continuation Application of U.S. patent application Ser. No. 13/564,817, filed on Aug. 2, 2012, which is based on and claims priority from Japanese Patent Application No. 2011-169563, filed on Aug. 2, 2011, the entire contents of which are incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    Field of the Invention 
         [0003]    This invention relates to a battery, in particular, a battery having an outer package made of a laminated film. 
         [0004]    Description of the Related Art 
         [0005]    JP-A-2006-324134 discloses a secondary battery having an outer package having a melt-bonded region formed by melt-bonding portions of a resin layer of a laminated film to each other, and a positive electrode terminal protruded outward from the outer package across the melt-bonded region. This positive electrode terminal has a laminated structure composed of a first region (first layer) made of aluminum, and a second region (second layer) made of Al alloy, copper, nickel or iron, thereby being heighten in mechanical strength. 
         [0006]    However, in the secondary battery of the publication, the second region, which is made of Al alloy, copper, nickel or iron, is high in thermal conductivity so that heat is easily conducted from the positive electrode terminal to localized sites of the resin layer of the laminated film, the heat being heat generated when the positive electrode terminal is welded to an external terminal, or Joule heat generated when a large quantity of electric current is caused to flow into the positive electrode terminal. As a result, the resin layer of the laminated film that contacts the positive electrode terminal is partially softened, so as to be declined in bonding strength. Thus, there is caused a problem that the sealing performance of the outer package is declined. 
       SUMMARY OF THE INVENTION 
       [0007]    This invention has been made to solve problems as described above, and an object of the invention is to provide a battery having an outer package restrained from being declined in sealing performance by heat. 
         [0008]    A first aspect of the present invention is a battery comprising an outer package comprising a laminated film having one or more resin layers, and a terminal having a plate-like first metal layer, and second metal layers arranged on both surfaces of the first metal layer, respectively, wherein the outer package is formed by bonding portions of the resin layer of the laminated film to each other, or by bonding the resin layers thereof to each other, the terminal is sandwiched between the portions of the resin layer or between the resin layers, and at its sandwiched region the second metal layers of the terminal contact the resin layer or the resin layers of the laminated film. 
         [0009]    This structure makes it possible to disperse heat from the first metal layer of the terminal to wide ranges through the second metal layers arranged on both the surfaces of the first metal layer, respectively. In this structure, it is possible to prevent a phenomenon that the heat from the first metal layer of the terminal is conducted to localized sites of the resin layer or the resin layers of the laminated film so that the resin layer or the resin layers of the laminated film is/are softened. As a result, the bonded region of the laminated film can be prevented from being lowered in bonding strength, so that the outer package can be restrained from being declined in sealing performance. In addition, since the second metal layers are arranged on both the surface of the first metal layer, the terminal can gain mechanical strength. 
         [0010]    In the battery of the present invention, it is preferred that thermal conductivity of the metal constituting the second metal layers is smaller than that of the metal constituting the first metal layer. This matter, i.e., a matter that thermal conductivity of the metal the second metal layers is smaller than that of the metal constituting the first metal layer, makes it possible to decrease a heat quantity transferred from the first metal layer to the resin layer or the resin layers of the laminated film. As a result, the bonded region of the laminated film can be restrained from being declined in bonding strength. The metal of the second metal layers is in particular preferably titanium or stainless steel. 
         [0011]    It is preferred that each of the second metal layers of the terminal contacts the resin layer of the laminated film with a second resin layer which is different from the resin layer of the laminated film interposed therebetween. When joining strength is not easily obtained between each of the second metal layers of the terminal and the resin layer of the laminated film, the second resin layer is arranged on the surface of the second metal layer of the terminal, whereby the second resin layer can be joined to the resin layer of the laminated film. The laying of the second resin layer makes it possible to decrease a heat quantity transferred from the first metal layer to the resin layer of the laminated film. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    The forgoing and other features of the invention will become apparent to one skilled in the art to which the invention relates upon consideration of the invention with reference to the accompanying drawings, wherein: 
           [0013]      FIG. 1  is a perspective view illustrating an entire structure of a battery according to an embodiment of the present invention; 
           [0014]      FIG. 2  is a sectional view of the battery taken along a line  200 - 200  in  FIG. 1 ; 
           [0015]      FIG. 3  is a sectional view illustrating a layer structure of an outer package of the battery of the embodiment of the present invention; 
           [0016]      FIG. 4  is an enlarged sectional view illustrating a positive electrode terminal of the battery according to the embodiment of the present invention; 
           [0017]      FIG. 5  is a sectional view of the terminal taken along a line  300 - 300  in  FIG. 4 ; and 
           [0018]      FIG. 6  is a sectional view of a battery according to another embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0019]    Hereinafter, preferred embodiments of the present invention will be described with reference to the attached drawings. First, with reference to  FIGS. 1 to 5 , a description will be made about the structure of a battery  100  according to one embodiment of the present invention. 
         [0020]    The battery  100  of one embodiment of the present invention is a lithium ion battery having a discharge capacity of 10 Ah or more. As illustrated in  FIGS. 1 and 2 , the battery  100  has an outer package  1  made of a laminated film, and a positive electrode terminal  2  and a negative electrode terminal  3  that are protruded outward, respectively, from both ends in Y direction of the battery  100 . As illustrated in  FIG. 2 , the outer package  1  holds therein a power generating element  4 , and an electrolyte solution. The positive electrode terminal  2  and the negative electrode terminal  3  are each an example of the “terminals” referred to in the present invention. 
         [0021]    The outer package  1  is formed into a cylindrical form by melt-bonding both edges of a sheet made of the laminated film to each other. As illustrated in  FIGS. 1 and 2 , the outer package  1  has, at each of both end portions in Y direction of the battery  100 , a melt-bonded region  1   a  formed by melt-bonding faced portions of the inside surface of the laminated film to each other. About the melt-bonded regions  1   a  at both the end portions of the battery  100 , the melt-bonding is attached in the state that the positive electrode terminal  2  and the negative electrode terminal  3  are sandwiched. As illustrated in  FIG. 3 , the laminated film constituting the outer package  1  has a laminated structure in which a polyethylene (PE) melt-bonding layer  11 , a polyethylene terephthalate (PET) layer  12 , an aluminum layer  13 , a PET layer  14  and a PE melt-bonding layer  15  are laminated in this order from the inside of the battery toward the outside. The thickness (total thickness) t 1  of the laminated film is made into the range of 150 μm or more and 500 μm or less. Between the aluminum layer  13  and each of the PET layers  12  and  14 , an adhesive layer is laid for bonding the aluminum layer  13  to the PET layer. 
         [0022]    The PE melt-bonding layers  11  and  15  are each made of polyethylene, which is a thermoplastic resin, and has a melting point of about 130° C. The thickness of each of the PE melt-bonding layers  11  and  15  ranges from about 40 μm or more and about 200 μm or less, preferably from about 80 μm or more and about 150 μm or less. The aluminum layer  13  is a piece of aluminum foil that has a thickness of about 4 μm or more and about 100 μm or less, and the piece is laid in the form of one of the laminated layers inside the outer package  1  made of the laminated film. 
         [0023]    In the present embodiment, the positive electrode terminal  2  is a flat plate form. As illustrated in  FIGS. 1 and 2 , the terminal  2  is arranged to be protruded outward from the outer package  1  across one of the melt-bonded regions  1   a  in Y direction of the outer package  1 . The positive electrode terminal  2  is connected to a positive electrode of the power generating element  4  inside the outer package  1 . As illustrated in  FIGS. 4 and 5 , the positive electrode terminal  2  is a laminated body formed by rolling a first metal layer  21  made of aluminum, and second metal layers  22  made of titanium in such a manner that the layer  21  can be joined with each of the layers  22 . 
         [0024]    Detailedly, the second metal layers  22  are laid on both surfaces of the first metal layer  21 , which is in a plate form, respectively; the surfaces are specifically the front side surface (Z 1  direction surface) of the layer  21 , and the rear side surface (Z 2  direction surface) thereof. As illustrated in  FIG. 5 , the first metal layer  21  has a thickness t 2  of 0.1 mm or more and 1.0 mm or less. The second metal layers  22  each have a thickness t 3  of 50 μm or more and 500 μm or less. The second metal layers  22  made of titanium are small in thermal conductivity than the first metal layer  21  made of aluminum The thermal conductivity of the first metal layer  21  is about 241 W/(m·K) while that of the second metal layers  22  is about 22 W/(m·K) 
         [0025]    As illustrated in  FIGS. 4 and 5 , a melt-bonding assisting member  5  is set to cover the outer circumference of the positive electrode terminal  2 . The melt-bonding assisting member  5  is made of a thermoplastic resin such as polypropylene. When the melt-bonding of one of the melt-bonded regions  1   a  of the outer package  1  is thermally attained, the melt-bonding assisting member  5  is melt-bonded together with the PE melt-bonding layer  11 . In this way, the melt-bonded region  1   a  of the outer package  1  can be certainly melt-bonded in the state that the positive electrode terminal  2  is sandwiched. Since the melt-bonding assisting member  5  is interposed between each of the second metal layer  22  of the positive electrode terminal  2  and the PE melt-bonding layer  11  of the laminated film, it is possible to decrease a heat quantity conducted from the positive electrode terminal  2  to the PE melt-bonding layer  11  of the laminated film. The melt-bonding assisting member  5  is an example of the “second resin layer” referred to in the present invention. 
         [0026]    In the present embodiment, the negative electrode terminal  3  is a flat plate form. As illustrated in  FIGS. 1 and 2 , the terminal  3  is arranged to be protruded outward from the outer package  1  across the other of the melt-bonded regions  1   a  in Y direction of the outer package  1 . The negative electrode terminal  3  is connected to a negative electrode of the power generating element  4  inside the outer package  1 . The negative electrode terminal  3  has a first metal layer  31  made of copper, and second metal layers  32  laid on both surfaces of the first metal layer  31 , respectively. In the same manner as in the positive electrode terminal  2 , the second metal layers  32  are made of titanium. The first metal layer  31  made of copper has a thermal conductivity of about 420 W/(m·K) 
         [0027]    In the embodiment, the positive electrode terminal  2  is formed as a laminated body having the first metal layer  21  made of aluminum, and the second metal layers  22  made of titanium and laid on both the surfaces of the first metal layer  21 , respectively. The structure of the positive electrode terminal  2  makes the following possible: in a case where heat is generated when the positive electrode terminal  2  is welded to an external terminal or Joule heat is generated when a large quantity of electric current flows into the positive electrode terminal  2 , the heat diffuses from the first metal layer  21  of the positive electrode terminal  2  through the second metal layers  22  into wide ranges to prevent the heat from being conducted to localized sites of the PE resin layer  11  of the laminated film. 
         [0028]    This matter makes it possible to restrain a phenomenon that the PE resin layer  11  of the laminated film is softened by heat so that the sealing performance of the outer package  1  is declined. Furthermore, the second metal layers  22  made of titanium are smaller in thermal conductivity than the first metal layer  21  made of aluminum; this matter makes it possible to make small a heat quantity transferred from the first metal layer  21  of the positive electrode terminal  2  to the PE resin layer  11  of the laminated film. The negative electrode terminal  3  can also gain the same advantageous effects since the terminal has the same structure. 
         [0029]    Moreover, the second metal layers  22  are made of titanium, which is larger in mechanical strength than aluminum; thus, the second metal layers  22  can heighten the mechanical strength of the positive electrode terminal  2 . This matter makes it possible that when the positive electrode terminal  2  is inserted into an inside hollow  110  in a connector  110 , the positive electrode terminal  2  is restrained from being deformed. 
         [0030]    In the embodiment, each of the second metal layers  22  of the positive electrode terminal  2  is made into a thickness of 50 μm or more and 500 μm or less. When the thickness of the second layer  22  is set to 50 μm or more, the mechanical strength of the positive electrode terminal  2  can be effectively heightened. When the thickness of the second metal layer  22  is set to 500 μm or less, the thickness of the positive electrode terminal  2  is restrained from being excessively increased so that the melt-bonding of the melt-bonded region  1   a  can be attained with a good precision. The negative electrode terminal  3  can also gain the same advantageous effects since the terminal has the same structure. 
         [0031]    As illustrated in  FIG. 6 , in another embodiment of the present invention, a Ni plating layer  23  can be formed on the outside surface of each second metal layer  22  of a positive electrode terminal  2 . The Ni plating layer  23  makes it possible to improve the positive electrode terminal  2  in corrosion resistance. Moreover, the Ni plating layer  23  makes it possible to make the surface roughness of the positive electrode terminal  2  small to decrease the contact resistance of the positive electrode terminal  2 . When the positive electrode terminal  2  is inserted into an inside hollow  110   a  in a connector  110 , this decrease makes small the contact resistance between the positive electrode terminal  2  and the inside hollow  110   a.  Therefore, the positive electrode terminal  2  can easily be inserted into the inside hollow  110   a  in the connector  110 . The Ni plating layer may be unfavorably melted at a side thereof near the positive electrode terminal  2 . Thus, no Ni plating layer is formed on an inside region A 2  of an outer package  1  of the positive electrode terminal  2 . 
         [0032]    The embodiments disclosed herein should be interpreted to be merely exemplificative in every point, and not to be restrictive. The scope of the present invention is not specified by the above-mentioned description of the embodiments but specified by the claims. Modified embodiments each having a meaning and a scope equivalent to those based on the claims are wholly included in the scope of the present invention. 
         [0033]    In the above-mentioned embodiments, for the first metal layer of its positive electrode terminal, and that of its negative electrode terminal, aluminum and copper are used, respectively. However, the present invention is not limited into this manner. In the present invention, for a first metal layer of its positive electrode terminal, and one of its negative electrode terminal, an aluminum alloy and a copper alloy may be used, respectively. 
         [0034]    In the embodiments, as its second metal layers, layers made of titanium have been described. However, the present invention is not limited into this manner. In the present invention, second metal layers made of stainless steel may be used. In this case, SUS 316, which is not easily soluble in an electrolyte solution, is preferred. For reference, stainless steel has a thermal conductivity of about 12 W/(m·K). In the present invention, its second metal layers may contain a component other than titanium or stainless steel. 
         [0035]    In the embodiments, as the structure thereof, a structure has been described wherein second metal layers made of titanium are laid on both surfaces of a first metal layer, respectively. However, the present invention is not limited into this structure. The second metal layer laid on one of the surfaces of the first metal layer may be different in metal as a raw material from the second metal layer laid on the other surface of the first metal layer. For example, it is allowable to lay a second metal layer made of titanium on one of the surfaces of a first metal layer, and lay a second metal layer made of stainless steel on the other surface of the first metal layer. 
         [0036]    In the embodiments, as the structure of each of its positive and negative electrode terminals, a structure has been described wherein a first layer is jointed to second layers by rolling. However, the present invention is not limited into this structure. In the present invention, its terminals may each have, for example, a laminated structure wherein a first layer is jointed to second layers through an adhesive. 
         [0037]    In another embodiment illustrated in  FIG. 6 , as the metal plating layer in the present invention, a Ni plating layer has been described. However, the present invention is not limited into this manner. In the present invention, it is allowable to use a metal plating layer other than the Ni plating layer, for example, a metal plating layer made of gold, silver, tin or lead. 
         [0038]    In the embodiments, in each of its positive and negative electrode terminals, a laminated body composed of a first metal layer and second metal layers is used. However, the present invention is not limited to this manner. In the present invention, it is allowable to render only one of its positive and negative electrode terminals a laminated body composed of a first metal layer and second metal layers. It is also allowable in the present invention that the material of second metal layers of the positive electrode terminal is different from that of second metal layers of the negative electrode terminal thereof. 
         [0039]    In the embodiments, examples have been described wherein the battery of the present invention is applied to a lithium ion battery. However, the present invention is not limited into this manner. The battery of the present invention may be applied to a nonaqueous electrolyte battery other than lithium ion batteries, and may be applied to an aqueous electrolyte battery such as a nickel hydrogen battery.