Abstract:
A battery unit having at least two pouch type secondary battery cells and a single safety device serving each cell in the battery unit. Each individual battery or cell body fits into a space within a casing. The battery unit may use one or more casings. The battery cells are arranged such that the terminals of different battery cells are located near the terminals of other battery cells within the unit. These terminals are connected to the safety device. The safety device may be a safety circuit board that is positioned in a space within the battery unit so that the battery unit does not consume any more space than when no safety circuit board is used.

Description:
CLAIM OF PRIORITY  
         [0001]    This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C. §119 from an application entitled “POUCH TYPE SECONDARY BATTERY” earlier filed in the Korean Intellectual Property Office on 18 Dec. 2002 and thereby duly assigned Serial No. 2002-81072.  
         BACKGROUND OF THE INVENTION  
         [0002]    1. Technical Field  
           [0003]    The present invention relates to a secondary battery unit, and more particularly, to a secondary battery unit having two or more interconnected individual pouch type secondary battery cells, the battery unit having a single safety circuit board for all of the individual battery cells in the battery unit, the single safety circuit board not adding size, volume or bulk of the battery unit.  
           [0004]    2. Related Art  
           [0005]    Conventionally, secondary batteries have a small size and a high storage capacity, in addition to being rechargeable. Representative examples of such secondary batteries include nickel-hydrogen (Ni-MH) batteries and lithium (Li) secondary batteries.  
           [0006]    According to the shapes of a case for accommodating a battery body, secondary batteries are classified as cylindrical batteries using cylindrical aluminum cans, prismatic batteries using prismatic aluminum cans, and pouch-type batteries using thin pouch-type cases.  
           [0007]    Among them, the pouch-type secondary batteries has a battery body for generating a predetermined electric current and a pouch-type case for enclosing the battery body. The battery body further has a lead, which is connected to an electrode tab extended from a side of the battery body, to provide an electrical passage to the outside. Some parts of the lead are installed to be exposed from the pouch-type case.  
           [0008]    The pouch-type case has a case body having a space for accommodating the battery body, and a case cover extending from an end of the case body and forming an integral structure with the case body. The edges of the case body are formed with flanges to seal the case body by coupling the case body with the case cover.  
           [0009]    The pouch-type case of a pouch-type secondary battery with the above-described structure is made up of a mixed sheet of a metal foil and resin layers. By way of example, a pouch-type case is with aluminum foil may be formed by pressing together aluminum foil, a thermal adhesive layer and a resin layer. The thermal adhesive layer is formed at an inner surface of the aluminum foil. The thermal adhesive layer and the resin layer are sequentially formed at an outer surface of the aluminum foil. The thermal adhesive layer is made up of a polymer resin including modified polypropylene such as casted polypropylene (CPP). The resin layer is made up of nylon and polyethylene terephthalate. There exist pouch-type cases with various shapes including those as disclosed in U.S. Pat. Nos. 6,042,966 and 6,106,973.  
           [0010]    Generally, the pouch-type secondary batteries with the above-described structure have a small storage capacity, and thus, are interconnected in parallel or series when used in electronic devices with a relatively high consumption of electric power such as notebook computers.  
           [0011]    Meanwhile, the pouch-type secondary batteries further have a safety device for preventing explosion of the batteries due to a gas generated by an overcharge or an interelectrode short when charged or discharged. The safety device may be a safety circuit board with a positive temperature coefficient (PTC) device, and a safety vent, which is installed at a side of the case to change its structure according to the internal pressure of the case. The safety circuit board may be installed in each battery. Alternatively, in a case where multiple battery cells are interconnected in parallel or series, a single safety circuit board may be employed, the single circuit board being electrically connected to the terminals of each individual battery cell in a battery unit, which connects with electrode terminals of individual battery cells.  
           [0012]    In this case, however, lead wires are required for connecting the safety circuit board with the electrode terminals of individual battery cells, and the installation of the safety circuit board produces many limitations. In particular, in the case where secondary battery cells are used in portable electric devices, the volume of the battery unit increases as a result of the area occupied by the safety circuit board. Therefore, it is difficult to limit the size of a secondary battery unit having multiple secondary battery cells interconnected in series or parallel via the safety circuit board.  
           [0013]    One example of a battery unit comprising multiple secondary battery cells interconnected in parallel or series is disclosed in Korean Patent Laid-Open Publication No. 1999-54989. The battery unit comprises multiple individual battery cells are interconnected in parallel or series, each individual battery cell having alternately laminated multiple positive electrodes and multiple negative electrodes, which are separated by separators. The battery unit has a positive electrode connecting means for connecting the multiple positive electrodes to each other and negative electrode connecting means for connecting the multiple negative electrodes to each other.  
           [0014]    Korean Patent Laid-Open Publication No. 1999-5862 discloses a secondary battery with an improved energy density by interconnecting in parallel electrodes with an integral structure of a current collector and an electrode terminal.  
           [0015]    In the above-described secondary battery units, a separate safety circuit board must be installed at the side or front part of each battery cell, and thus, it is difficult to decrease the size of the battery unit.  
         SUMMARY OF THE INVENTION  
         [0016]    It is therefore an object of the present invention to provide a design for a battery unit made up of more than one pouch type battery cell, the entire battery unit having a single safety device.  
           [0017]    It is also an object of the present invention to provide a battery unit made up of more than one pouch type battery cell, the battery unit having a single safety device for the entire battery unit, the safety device not adding to the total volume of the battery unit.  
           [0018]    It is still an object of the present invention to provide a better design for a battery unit having more than one pouch type battery cell where a single safety circuit board is used to protect the entire battery unit, the safety circuit board being connected to the terminals of the cells in the battery unit.  
           [0019]    It is further an object of the present invention to provide a safety circuit board for a battery unit having more than one individual battery cell, each individual battery cell being disposed in its own casing, the single safety circuit board being connected to the terminals of the individual battery cells, the single safety circuit board not adding any volume to the battery unit.  
           [0020]    It is further an object of the present invention to provide a safety circuit board for a battery unit having more than one individual battery cell, the entire battery unit having a single casing where each individual battery cell is disposed therein, the single safety circuit board being connected to the terminals of the individual battery cells, the single safety circuit board not adding any volume to the battery unit.  
           [0021]    These and other objects may be achieved by a battery unit having at least two individual secondary pouch-type battery cells encased in a casing. The battery unit has a single safety circuit board or device that is used for all of the individual battery cells in the battery unit. The safety unit is disposed within the casing in such a way as not to add volume to the battery unit. The electrode terminals of the individual battery cells are interconnected with each other and with the safety circuit board. The casing for the battery unit may be a single casing for the entire battery unit, the single casing accommodating each of the individual batteries. Alternatively, each individual battery cell has its own casing. In either case, the casing has a body portion and a cover portion connected to the body portion, the body portion having a flanged portion.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0022]    A more complete appreciation of the invention, and many of the attendant advantages thereof, will be readily apparent as the same becomes better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings in which like reference symbols indicate the same or similar components, wherein:  
         [0023]    [0023]FIG. 1 is a partial cut-away perspective view of a battery body of stacked electrode plates unwounded, the battery body of FIG. 1 being a first variation of a battery body that can be used in the embodiments of the present invention;  
         [0024]    [0024]FIG. 2 is a perspective view of a battery body of electrode plates being helically wound, the battery body of FIG. 2 being a second variation of a battery body that can be used in the embodiments of the present invention;  
         [0025]    [0025]FIG. 3A is an exploded perspective view of a pouch-type secondary battery unit according to a first embodiment of the present invention, wherein the individual cells of the battery unit are in separate cases, FIG. 3A illustrating the first embodiment according to the first variation of battery bodies of FIG. 1;  
         [0026]    [0026]FIG. 3B is a side view when assembled of the pouch-type secondary battery unit of FIG. 3A;  
         [0027]    [0027]FIG. 4 is a perspective view of a pouch-type secondary battery unit according to a second embodiment of the present invention;  
         [0028]    [0028]FIG. 5A is a perspective view of a pouch-type secondary battery unit according to a third embodiment of the present invention using the helically wound type battery body of FIG. 2;  
         [0029]    [0029]FIG. 5B is a perspective view illustrating folding of the pouch-type secondary battery unit of FIG. 5A; and  
         [0030]    [0030]FIG. 6 is a perspective view of a pouch-type secondary battery unit according to a fourth embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0031]    Before discussing the embodiments of the present invention, the different types of battery bodies that can be used in the embodiments of the present invention will now be discussed. Turning to FIG. 1, FIG. 1 illustrates a first variation for a battery body which is a stacked electrode plate battery body  25  ( 35 ) that can be used in the embodiments of the present invention. The reason why two reference numerals are illustrated for each part in FIG. 1 is that if an embodiment to be described later has two individual battery cells using battery bodies according to FIG. 1, the first reference numeral is used for the first cell and the second reference numeral is used for the second cell, even though the two cells may be identical. As illustrated in FIG. 1, the stacked electrode plates are not wound. The first and second battery bodies  25  and  35  respectively of FIG. 1 each have positive electrode plates  27  and  37 , which are formed by coating positive electrode current collectors with positive electrode active materials and are formed with the positive electrode terminals  26  and  36 , negative electrode plates  29  and  39 , which are formed by coating negative electrode current collectors with negative electrode active materials and are formed with the negative electrode terminals  28  and  38 , and separators  210  and  310  interposed therebetween, as illustrated in FIG. 1. Alternately, the battery bodies used in the embodiments that follow can be the battery body  55  ( 56 ) illustrated in FIG. 2. In this second variation, battery body  55  ( 56 ) are stacked electrode layers helically wound. The first and second battery bodies  55  and  56  may be formed by helically winding strip-shaped positive and negative electrode plates, as illustrated in FIG. 2. In this present invention, the term “battery unit” means a group of individual batteries (or cells) interconnected in parallel or in series.  
         [0032]    Turning now to the embodiments of the present invention, FIGS. 3A and 3B illustrate a battery unit  10  according to the first embodiment of the present invention. Referring to FIGS. 3A and 3B, the battery unit  10  has a first and second pouch-type secondary battery cells  20  and  30 , and a safety circuit board  40 , which is installed in a space between the first and second secondary battery cells  20  and  30 . Safety circuit board  40  electrically connects first and second positive electrode terminals  26  and  36  and first and second negative electrode terminals  28  and  38  of cells  20  and  30  together.  
         [0033]    The first and second secondary battery cells  20  and  30  are made up of first and second cases  24  and  34 , respectively. The first and second cases  24  and  34  respectively are made up of first and second case bodies  22  and  32 , which are formed with first and second spaces  21  and  31  with a predetermined depth, and first and second case covers  23  and  33 , which are coupled with the first and second case bodies  22  and  32  to seal the first and second spaces  21  and  31 . Here, the first and second cases  24  and  34  have a flexible structure by coating a metal foil, for example, an aluminum foil, with a composite resin material, but is not limited thereto. As illustrated in FIGS. 3A and 3B, battery unit  10  has two battery (or cell) bodies  25  and  35 , and two cases  24  and  34 , respectively, one case for each battery body.  
         [0034]    In the case of a lithium secondary battery, generally, aluminum foils are used as the positive electrode current collectors and copper foils are used as the negative electrode current collectors. The positive electrode active materials are mixtures including lithium-based oxides and the negative electrode active materials are mixtures including carbonaceous materials.  
         [0035]    When the first battery body  25  is inserted in the first space  21  and when the first case body  22  and the first case cover  23  are coupled with each other, the first positive and negative electrode terminals  26  and  28  are exposed from a side of the coupled first case body  22  and cover  23 . On the other hand, when the second battery body  35  is inserted in the second space  31  and when the second case body  32  and the second case cover  33  are coupled with each other, the second positive and negative electrode terminals  36  and  38  are protruded from a side of the coupled second case body  32  and cover  33 . The two battery cells  20  and  30  are aligned so that the first positive electrode terminal  26  is adjacent to the second positive electrode terminal  36  and the first negative electrode terminals  28  is adjacent to the second negative electrode terminal  38 . That is, the first and second secondary battery cells  20  and  30  are installed in such a manner that the same polarity terminals of the two secondary battery cells face each other.  
         [0036]    Meanwhile, the safety circuit board  40  is positioned between the interconnected first and second battery cells  20  and  30  and connects with the first and second positive electrode terminals  26  and  36  and the first and second negative electrode terminals  28  and  38 . Preferably, the safety circuit board  40  is installed between a flange portion  22   a  of the first case body, from which the first positive and negative electrode terminals extend outward, and a flange portion  32   a  of the second case body, from which the second positive and negative electrode terminals extend outward. This way, the inclusion of safety circuit board  40  does not add to the overall size or volume of the battery unit  10 .  
         [0037]    Preferably, the first and second secondary battery cells  20  and  30  are arrayed in such a manner that protruded outer surfaces of the first and second spaces  21  and  31  come in contact with each other, so that the flange portions  22   a  and  32   a  are separated from each other with safety circuit board  40  disposed therebetween flanges  22   a  and  32   a , thus not resulting in an increased volume of the battery unit  10 . This external void  49  is between flanges (or flanged portions)  22   a  and  32   a . External void  49  is really a space that is external to the cases and is between the cases when the cases are stacked onto each other as in FIG. 3B. External void  49  is external to any of the cases but is located between two adjoining cases. Safety circuit board  40  is disposed within external void  49 . Because safety circuit board  40  is within external void  49 , safety circuit board  40  does not add any volume or bulk to battery unit  10 .  
         [0038]    The first embodiment thus far has been described in terms of using the stacked electrode plates of FIG. 1 as the battery bodies  25  and  35  in battery unit  10 . However, this invention is not limited thereto. Alternatively, the helically wound battery bodies  55  and  56  of FIG. 2 can be used in the first embodiment instead of the stacked electrode battery bodies  25  and  35  of FIG. 1. Also, one battery body may be stacked and the other may be helically wound. Thus, the arrangement of FIGS. 3A and 3B may mix or match stacked or helically wound batteries.  
         [0039]    Turning to FIG. 4, FIG. 4 illustrates a battery unit  11  according to the second embodiment of the present invention. FIG. 4 is similar to the embodiment of FIGS. 3A and 3B except that first and second spaces  21  and  31  are arrayed in the same directions in FIG. 4 as opposed to opposite directions in FIGS. 3A and 3B. As with the first embodiment, in the second embodiment of FIG. 4, it is preferable to install the first and second battery cells  20  and  30  in such a manner that the first and second positive electrode terminals face each other and the first and second negative electrode terminals face each other. As with the first embodiment, the second embodiment may mix or match either the stacked electrode battery bodies  25  and  35  of FIG. 1 or the helically wound battery (or cell) bodies  55  and  56  as illustrated in FIG. 2.  
         [0040]    Turning to FIGS. 5A and 5B, FIGS. 5A and 5B illustrate a pouch-type secondary battery unit  50  according to a third embodiment of the present invention. Referring to FIGS. 5A and 5B, the pouch-type secondary battery unit  50  has only a single case  51  and first and second battery bodies  55  and  56 . In FIGS. 5A and 5B, helically wound batteries  55  and  56  are illustrated, but stacked type batteries of FIG. 1 may instead be used. In addition, one of the battery bodies may be helically wound and the other may be stacked.  
         [0041]    The case  51  has a case cover  57  and a case body  52 , which is formed with two spaces  53  and  54  (FIG. 5A), which are spaced apart from each other by a predetermined distance. The first battery body  55  has first positive and negative electrode terminals  55   a  and  55   b  and the second battery body  56  has second positive and negative electrode terminals  56   a  and  56   b . The battery bodies  55  and  56  are inserted into the respective spaces  53  and  54  of the case  51 .  
         [0042]    The case body  52  is coupled with the case cover  57  to seal the spaces  53  and  54 . The case body  52  and the case cover  57  maybe formed to have an integral structure. The secondary battery unit  50  is folded (FIG. 5B) in such a manner that protruded outer surfaces of the spaces  53  and  54  of the case body  52  come in contact with each other and form a external void  59  between the electrode terminals  55   a ,  55   b ,  56   a ,  56   b  and between the opposite portions of the folded cover  57 . Unlike spaces  53  and  54 , external void  59  is not sealed within case  51 . Instead, external void  59  is formed between separate folded sections of case  51 , each section containing a separate pouch type battery cell. External void  59  is really a space that is external to the case and is disposed between adjoining sections of the case when the case is folded onto itself as in FIG. 5B. In this external void  59 , a safety circuit board  40  can be positioned as illustrated in FIG. 5B. As illustrated in FIG. 5B, because safety circuit board  40  is within external void  59  of battery unit  50 , safety circuit board  40  does not add any volume or bulk to battery unit  50 . In this case, the first and second positive electrode terminals  55   a  and  56   a  and the first and second negative electrode terminals  55   b  and  56   b  are connected to a signal line of the safety circuit board  40 . Preferably, the first and second positive electrode terminals  55   a  and  56   a  face each other and the first and second negative electrode terminals  55   b  and  56   b  face each other. The battery bodies  55  and  56  may be the same as battery bodies  55  and  56  in FIG. 2 or may be instead like battery bodies  25  and  35  in FIG. 1.  
         [0043]    [0043]FIG. 6 illustrates a pouch-type secondary battery unit  80  according to the fourth embodiment of the present invention. Referring to FIG. 6, a case  70  is made up of a case body  71  and a case cover  72 . The case body  71  is formed with in-line multiple spaces  73 . Battery bodies (not illustrated) with exposed electrode terminals  74  are disposed within respective spaces  73 . The case  70  is folded in such a manner that the battery bodies overlap each other forming voids therebetween. A safety circuit board  40  is installed in a void defined among the spaces  73  containing battery bodies. As with the other embodiments, the battery bodies may be helically wound as in FIG. 2 or stacked as in FIG. 1 or a combination thereof.  
         [0044]    As apparent from the above description, in a pouch-type secondary battery unit according to the present invention, a safety circuit board is installed in an extra void or space defined between individual secondary battery cells, and thus, the volume of the battery unit is not increased by the inclusion of the safety circuit board. In particular, at least two secondary battery cells use a single or common safety circuit board protecting each cell within the battery unit, and thus, the number of the constitutional elements of the secondary battery unit can be reduced.  
         [0045]    While the present invention has been particularly illustrated and described with reference to exemplary embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims.