Abstract:
A power source element has a positive electrode case, a negative electrode case, and a pair of connecting terminals, each having a first end portion connected to a respective one of the positive and negative electrode cases, a second end portion for connection to a circuit board, and an intermediate portion disposed between the first and second end portions. The intermediate portion of each of the connecting terminals has a weakened region so that the first end portion is separated from the second end portion along a weakened line in the weakened region upon relative movement between the first and second end portions in a give direction.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a power source element, such as a battery or an electric double layer capacitor, having connecting terminals or terminal leads bonded to positive and negative electrode cases thereof. 
     As the development of electronic appliances advances, batteries or electric double layer capacitors with terminal leads welded to the positive and negative electrodes of the cases thereof are being broadly used in electronic circuit boards with the above terminal leads soldered thereon. Above all, button type lithium batteries, lithium ion secondary batteries and electric double layer capacitors have been widely utilized in applications such as memory backup. The terminal leads have had a thickness of from 0.1 mm to 0.3 mm to provide strength in order to satisfy the requirement for high reliability of battery function retention. 
     In recent years, as the concerns over environmental problem increase there have been increased demands on the designing stage to facilitate disassembling upon scrapping and reduce the materials to be separated. In the case where a battery or electric double layer capacitor is welded with terminal leads and thereafter soldered onto a board for usage, it is not easy to remove and separate the battery or electric double layer capacitor upon scrapping. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the present invention to provide a power source element, such as a battery or an electric double layer capacitor, with terminal leads which retains high reliability while reducing the burden of environmental considerations when being scrapped. 
     In accordance with the present invention, there is provided a power source element, such as a battery or an electric double layer capacitor, having terminal leads bonded to the positive electrode case and the negative electrode case thereof, and in which a mechanism (such as a cutting or breakable portion formed along a weakened line) is provided in each of the terminal leads to facilitate cutting, e.g., a thickness-reduced portion, a cut-out notch, perforation-like holes or the like. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side view of a flat type non-aqueous electrolytic lithium ion secondary battery to which the present invention is applied; 
     FIG. 2 is an overhead plane view of a flat type non-aqueous electrolytic lithium ion secondary battery of the invention; 
     FIG. 3 is a side view of a flat type electric double layer capacitor to which the invention is applied; 
     FIG. 4 is overhead plane view of the flat type electric double layer capacitor of the invention; and 
     FIG. 5 is a plane view as viewed from above of a flat type non-aqueous electrolytic lithium ion secondary battery to which the invention is applied. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     It has been a practice to use terminal leads with a strength having a thickness of 0.1 mm to 0.3 mm because of the requirement for high reliability in battery function retention. This however has resulted in the necessity to use some sort of tool for cutting leads when a battery with such leads is separated from the appliance on which it was used to be scrapped. 
     The invention accordingly provides a thickness-reduced portion, a cut-out notch portion, perforation-like holes or the like in one part of the terminal lead to facilitate cutting. When such means is provided on a strong terminal lead, if a bending, twist or the like is applied to the terminal lead when the battery with the terminal lead is separated from the board of the appliance, stresses are concentrated on this place. Thus, the terminal lead can be readily cut at that position. 
     Where a force is applied in the thickness direction of a terminal lead to be cut, it is preferred to provide it with a thickness-reduced portion or perforation-like holes in one part of the terminal lead. On the other head, where a force or twist is applied in the width direction of a terminal lead, it is advantageous to provide a cut-out notch in one part of the terminal lead. 
     The combined use of a thickness-reduced portion, a cut-out notch and perforation-like holes makes cutting easy. The thickness of the thickness-reduced portion or the degree of the cut-out notch portion may be determined by taking into account the easiness of cutting and reliability in battery function retention. 
     Also, although the explanation herein is only for a battery, the invention can be applied to an electric double layer capacitor or the like in the same shape. 
     The present invention will now be described with reference to the drawings. It should be noted that the examples shown hereunder are to embody the technical idea of the invention but not to limit the invention. 
     EXAMPLE 1 
     FIG. 1 is a side view wherein the invention is applied to a flat type non-aqueous electrolytic lithium ion secondary battery. FIG. 2 is a plane view of the same battery as viewed from above. 
     To explain the application of the invention to a battery, a one-element battery will be used. The battery is a non-aqueous electrolytic lithium ion secondary battery including a negative electrode lithium ion secondary battery including a negative electrode having silicon oxide as an active material and a positive electrode having lithium manganese oxide as an active material. The battery has a size of 6.8 mm in diameter and 2.0 mm in height. The negative electrode case  111  is made of stainless steel (SUS304) while the positive electrode case  110  is of stainless steel (SUS444). Each case is laser-welded with a negative electrode terminal lead  103  and positive electrode terminal lead  102  that are made of stainless steel (SUS304) with a thickness of 0.15 mm. As shown in FIG. 1, each terminal is provided with respective first end portions  102   a ,  103   a  and thickness-reduced portions  104  and  114  having a thickness of about 0.1 mm. The battery  101  with its terminal leads was fixed onto a circuit board  106  by soldering second end portion  105 ,  115 . When a force was applied to the battery in the force applying direction A as shown FIG. 1, it was confirmed that bending easily occurred at the thickness-reduced portion  104  and  114 , and several such vertical movements easily accomplished cutting off of the battery portion. Thus the thickness-reduced portions  104 ,  114  define weakened lines along which the battery portion can be separated from the soldering portions. 
     EXAMPLE 2 
     FIG. 3 is a side view where the invention is applied to a flat type electric double layer capacitor. FIG. 4 is a plan view of the capacitor as viewed from above. 
     Explained is an electric double layer capacitor to which the invention is applied. This capacitor is an electric double layer capacitor including activated carbon as a polarizing active material and a non-aqueous solvent as an electrolytic solution. The capacitor has a size of 6.8 mm in diameter and 2.1 mm in height, the same as that of Example 1. A negative electrode case  211  is made of stainless steel (SUS304) while a positive electrode case  210  is of stainless steel (SUS444). Each case is laser-welded with a negative electrode terminal lead  203  and positive electrode terminal lead  202  that are made of stainless steel (SUS304) with a thickness of 0.15 mm. As shown in FIG. 3 and 4, each terminal is provided with respective first end portions  202   a ,  203   a  and cut-out notch portions  204  and  214 . This electric double layer capacitor  201  with its terminal leads was fixed onto a circuit board  206  by soldering second end portions  205 ,  215 . A force applied to this electric double layer capacitor in the force applying direction A as shown FIG. 3, it could be confirmed that cracking easily occurred by the cut-out notch portion  204  and  214 , and cutting off of the capacitor was easily done by several such vertical movements. 
     EXAMPLE 3 
     FIG. 5 is a plane view, as viewed from above, where the invention is applied to a flat type non-aqueous electrolytic lithium ion secondary battery. 
     The same battery as in Example 1 is used, a one-element battery  301 , to which the invention is applied. The case is laser-welded with a negative electrode terminal lead  303  and a positive electrode terminal lead  302  that are made of stainless steel (SUS304) with a thickness of 0.15 mm. As shown in FIG. 5, each terminal is provided with respective first end portions  302   a ,  303   a , perforation-like holes  304  and  314  and notch portions  320 ,  322 . While not shown in the embodiment of FIG. 5, it will be appreciated-by those skilled in the art that the first end portion  303   a  corresponds to the negative electrode terminal lead  303  and is disposed on a surface of the battery  301  opposite a surface thereof on which the first end portion  302   a  is disposed. The battery  301  with its terminal leads was fixed onto a circuit board  106  by soldering second end portions  305 ,  315 . A force was applied to the battery so as to cause twisting in the area of the perforation-like holes  304  and  314  and notch portions  320 ,  322 . The terminal lead could be torn off by repeating such movements several times. The shape and number of holes and notches are not particularly limited. The shape may be, besides circular, oval, square, rhombic or the like. The number and size of the holes and notches may be determined by taking into account the force to be applied for cutting. 
     The invention is therefore directed to a power source element with terminal leads wherein the terminal leads are bonded to positive and negative electrode terminals, and in which a mechanism is provided in each of the terminal leads to facilitate cutting, e.g. a thickness-reduced portion, a cut-out notch, perforation-like holes or the like. Due to this, the power source element, such as a battery or an electric double layer capacitor, is easily cut away when scrapping the appliance within which the power source element is incorporated, thereby facilitating scrapping that includes separation by category of material and hence reducing environmental burden cause by scrapping.