Abstract:
A square shaped battery includes: an electrode plate group including a belt-like positive electrode plate, a belt-like negative electrode plate, and a belt-like separator, the belt-like positive electrode plate, the belt-like negative electrode plate, and the belt-like separator being laminated and rolled up to form the electrode plate group; and a pair of power collectors disposed on sides of the electrode plate group for collecting electric power from the electrode plate group.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to a square shaped battery, and specifically to a square shaped battery including an electrode plate group formed by rolling a belt-like positive electrode plate, a belt-like negative electrode plate, and a belt-like separator.  
           [0003]    2. Description of the Related Art  
           [0004]    In the case where a battery case is made of resin, electrode plates are laminated, and leads connected to end portions of respective electrode plates are gathered.  
           [0005]    In the case where a battery case is made of metal, a portion of a belt-like positive electrode plate and a sealing plate are both welded to a lead where the lead is connected between the portion of the belt-like positive electrode plate and the sealing plate, and a negative electrode plate is connected to the metal battery case through a lead or contacted directly with the metal battery for collecting electric power.  
           [0006]    A conventional square shaped battery  900  is now described with reference to FIG. 9.  
           [0007]    The square shaped battery  900  includes positive electrode plates  1  and negative electrode plates  2 . Each of the positive electrode plates  1  is formed of foamed nickel so as to have an unfilled portion having a 5 mm width at an end thereof. The unfilled portion is filled with a positive electrode material mainly composed of nickel hydroxide. A nickel lead is attached to the portion filled with the positive electrode material. The capacity of the positive electrode plate  1  is about 1 Ah (Ampere hour). Each negative electrode plate  2  is formed by punched metal which is coated with a negative electrode material mainly composed of hydrogen occlusion alloy so as to leave an uncoated portion having a 5 mm width at an end thereof. The capacity of the negative electrode plate  2  is about 1.25 Ah.  
           [0008]    The positive electrode plates  1  are each covered with a sack-like separator  3  formed of nonwoven polypropylene fabric. Seven positive electrode plates  1  and eight negative electrode plates  2  are alternately superposed thus forming an electrode plate group. Nickel leads  4  are provided to the electrode plates  1  and  2 . The nickel leads  4  are gathered at an upper end of the electrode plate group, and connected to external positive and negative terminals by resistance-welding. A resin case is used as a battery case for containing the square shaped battery  900 . The battery case containing the square shaped battery  900  is filled with electrolyte mainly composed of potassium hydroxide, and then, the square shaped battery  900  is charged and discharged at 0.1 C (Capacity) for activation. The capacity of the square shaped battery  900  is about 7 Ah.  
           [0009]    Another conventional square shaped battery  1000  is now described with reference to FIG. 10.  
           [0010]    The square shaped battery  1000  includes a belt-like positive electrode plate  5  and a belt-like negative electrode plate  6 . The positive electrode plate  5  is formed of foamed nickel so as to have an unfilled portion of 5 mm×5 mm at an end thereof. The unfilled portion is filled with a positive electrode material mainly composed of nickel hydroxide. A nickel lead is attached to the portion filled with the positive electrode material. The capacity of the positive electrode plate  5  is about 7 Ah. The negative electrode plate  6  is formed by punched metal which is coated with a negative electrode material mainly composed of hydrogen occlusion alloy so as to leave an uncoated portion of 5 mm×5 mm at an end thereof. The capacity of the negative electrode plate  6  is about 10 Ah.  
           [0011]    A separator  7  made of nonwoven polypropylene fabric is interposed between the positive electrode plate  5  and the negative electrode plate  6 , and a laminate of the positive electrode plate  5 , the separator  7 , and the negative electrode plate  6  is rolled to form an electrode plate group. For the purpose of connection with an external terminal (i.e., for the purpose of collecting electric power), a nickel lead  8  provided to the positive electrode plate  5  is welded to a sealing plate, and a negative electrode is connected to a battery case. The battery case is made of a metal. The battery case containing the square shaped battery  1000  is filled with electrolyte mainly composed of potassium hydroxide, and then, the square shaped battery  1000  is charged and discharged at 0.1 C for activation. The capacity of the square shaped battery  1000  is about 7 Ah.  
           [0012]    In the case of a high power battery for use in hybrid energy vehicles (HEVs), etc., the electrochemical reaction resistance is reduced by increasing the area of the electrodes, whereby the power of the battery is increased. However, in the case where electric power is not sufficiently collected from an electrode plate group, desired high power cannot be obtained even if the electrochemical reaction resistance is reduced. Furthermore, when plate-shape electrodes are used, a large number of electrodes are required, and accordingly, the number of production steps increase.  
         SUMMARY OF THE INVENTION  
         [0013]    According to one embodiment of the present invention, a square shaped battery includes: an electrode plate group including a belt-like positive electrode plate, a belt-like negative electrode plate, and a belt-like separator, the belt-like positive electrode plate, the belt-like negative electrode plate, and the belt-like separator being laminated and rolled up to form the electrode plate group; and a pair of power collectors disposed on sides of the electrode plate group for collecting electric power from the electrode plate group.  
           [0014]    In one embodiment of the present invention, the pair of power collectors are welded to the sides of the electrode plate group.  
           [0015]    In another embodiment of the present invention, a welding interval of each of the power collectors is narrower in an upper portion than in a lower portion.  
           [0016]    In still another embodiment of the present invention, the pair of the power collectors have protrusions for obtaining a sufficient welding area through which the pair of the power collectors are welded to the electrode plate group.  
           [0017]    In still another embodiment of the present invention, each of the protrusions has a hollow portion.  
           [0018]    In still another embodiment of the present invention, each of the pair of the power collectors has a central portion in which a protrusion is not provided, and the central portion is pressed against the electrode plate group with the power collector being welded to the electrode plate group.  
           [0019]    In still another embodiment of the present invention, the pair of power collectors are disposed on both sides of the electrode plate group such that a width direction of the electrode plate group is substantially perpendicular to faces of the pair of power collectors.  
           [0020]    In still another embodiment of the present invention, one of the pair of power collectors collects electric power from the electrode plate group in a direction different from that of the other of the pair of power collectors.  
           [0021]    In still another embodiment of the present invention, each of the pair of power collectors has a “U”-shape which binds the electrode plate group so as to suppress expansion of the sides of the electrode plate group.  
           [0022]    According to one aspect of the present invention, belt-like electrode plates are rolled up to form an electrode plate group, and electric power is collected from the entire side faces of the rolled electrode plate group, whereby the resistance in power collectors can be reduced. With such a structure, increased electric power due to the increase in electrode plate area can be efficiently collected. Furthermore, the number of steps for forming the electrode plate group can be reduced.  
           [0023]    According to another aspect of the present invention, the facing area of electrode plates (i.e., the surface area between adjacent plates) can be increased while reducing the number of electrode plates.  
           [0024]    Thus, the invention described herein makes possible the advantages of (1) providing a high-power square shaped battery, (2) providing a square shaped battery in which electric power can be sufficiently collected, and (3) providing a square shaped battery in which an electrochemical reaction resistance can be reduced.  
           [0025]    These and other advantages of the present invention will become apparent to those skilled in the art upon reading and understanding the following detailed description with reference to the accompanying figures. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0026]    [0026]FIG. 1A is an exploded view of a square shaped battery  100  according to embodiment  1  of the present invention. FIG. 1B shows an assembled structure of the square shaped battery  100  according to embodiment  1 .  
         [0027]    [0027]FIG. 2 is an exploded view of a square shaped battery  100 A according to embodiment  2  of the present invention.  
         [0028]    [0028]FIG. 3 is an exploded view of a square shaped battery  100 B according to embodiment  3  of the present invention.  
         [0029]    [0029]FIG. 4 is an exploded view of a square shaped battery  100 C according to embodiment  4  of the present invention.  
         [0030]    [0030]FIG. 5 is an exploded view of a square shaped battery  100 D according to embodiment  5  of the present invention.  
         [0031]    [0031]FIG. 6 is an exploded view of a square shaped battery  100 E according to embodiment  6  of the present invention.  
         [0032]    [0032]FIG. 7 is an exploded view of a square shaped battery  100 F according to embodiment  7  of the present invention.  
         [0033]    [0033]FIG. 8 is an exploded view of a square shaped battery  100 G according to embodiment  8  of the present invention.  
         [0034]    [0034]FIG. 9 is a perspective view showing a conventional square shaped battery.  
         [0035]    [0035]FIG. 10 is a perspective view showing another conventional square shaped battery. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0036]    Hereinafter, embodiments of the present invention will be described with reference to the drawings.  
         [0037]    Embodiment  1   
         [0038]    [0038]FIG. 1A is an exploded view of a square shaped battery  100  according to embodiment  1  of the present invention. FIG. 1B shows an assembled structure of the square shaped battery  100  according to embodiment  1 .  
         [0039]    As shown in FIGS. 1A and 1B, the square shaped battery  100  includes an electrode plate group  17  and a pair of power collectors  12  attached to both sides of the electrode plate group  17  for collecting electric power therefrom.  
         [0040]    The electrode plate group  17  includes a belt-like positive electrode plate  9 , a belt-like negative electrode plate  10 , and a belt-like separator  11 . The separator  11  is interposed between the positive electrode plate  9  and the negative electrode plate  10 . The electrode plate group  17  in formed by rolling up the positive electrode plate  9 , the negative electrode plate  10 , and the separator  11  interposed therebetween.  
         [0041]    The positive electrode plate  9  is formed of foamed nickel so as to have an unfilled portion having a 2 mm width at an end thereof. The unfilled portion is filled with a positive electrode material mainly composed of nickel hydroxide. A nickel lead is attached to the portion filled with the positive electrode material. The capacity of the positive electrode plate  9  is about 7 Ah.  
         [0042]    The negative electrode plate  10  is formed by punched metal which is coated with a negative electrode material mainly composed of hydrogen occlusion alloy so as to leave an uncoated portion having a 2 mm width at an end thereof. The capacity of the negative electrode plate  10  is about 10 Ah. The separator  11  is formed by nonwoven polypropylene fabric.  
         [0043]    The pair of power collectors  12  are provided on the both sides of the electrode plate group  17  such that the width direction of the electrode plate group  17  is perpendicular to faces of the pair of power collectors  12 . The pair of power collectors  12  are connected to both sides of the electrode plate group  17  by a laser weld at 20 mm intervals. The electrode plate group  17  is connected to external positive and negative terminals (not shown) through the pair of power collectors  12 .  
         [0044]    The pair of power collectors  12  are connected to the external positive and negative terminals at upper end portions  121  by resistance-welding. Nickel wax having a low melting temperature is applied to welding portions  122  of the pair of power collectors  12 .  
         [0045]    A case (not shown) for containing the square shaped battery  100  is made of resin. The case containing the square shaped battery  100  is filled with electrolyte, and the square shaped battery  100  is charged and discharged at 0.1 C for activation. The capacity of the square shaped battery  100  is about 7 Ah.  
         [0046]    The pair of power collectors  12 , which are provided on both sides of the electrode plate group  17  for collecting electric power from the electrode plate group  17 , results in the electrode plate group  17  being able to output high power.  
         [0047]    Embodiment  2   
         [0048]    [0048]FIG. 2 is an exploded view of a square shaped battery  100 A according to embodiment  2  of the present invention. In FIG. 2, like elements are indicated by like reference numerals used for the square shaped battery  100  of FIGS. 1A and 1B, and detailed descriptions thereof are omitted.  
         [0049]    A pair of power collectors  12  include a power collector  12 E and a power collector  12 F. The power collector  12 E is connected to an external positive terminal at an upper end  121  thereof by resistance-welding. The power collector  12 F is connected to an external negative terminal at a lower end  125  thereof by resistance-welding.  
         [0050]    In the square shaped battery  100 A according to embodiment  2 , the pair of power collectors  12  collect electric power in opposite directions (directions represented by arrows A and B), i.e., an electric current taken out from the electrode plate group  17  by the power collector  12 E flows in the power collector  12 E in a direction indicated by arrow A, and an electric current taken out from the electrode plate group  17  by the power collector  12 F flows in the power collector  12 F in a direction indicated by arrow B.  
         [0051]    Since the pair of power collectors  12  collect electric power in opposite directions, electric currents flow smoothly from the electrode plate group  17 .  
         [0052]    Embodiment  3   
         [0053]    [0053]FIG. 3 is an exploded view of a square shaped battery  100 B according to embodiment  3  of the present invention. In FIG. 3, like elements are indicated by like reference numerals used for the square shaped battery  100  of FIGS. 1A and 1B, and detailed descriptions thereof are omitted.  
         [0054]    In the square shaped battery  100 B according to embodiment  3 , the pair of power collectors  12  are connected to both sides of the electrode plate group  17  by a laser weld at intervals of D 1  (=10 mm). By increasing the number of power collection points (welding portions  122 ), power collection efficiency further increases.  
         [0055]    Embodiment  4   
         [0056]    [0056]FIG. 4 is an exploded view of a square shaped battery  100 C according to embodiment  4  of the present invention. In FIG. 4, like elements are indicated by like reference numerals used for the square shaped battery  100  of FIGS. 1A and 1B, and detailed descriptions thereof are omitted.  
         [0057]    In the square shaped battery  100 C according to embodiment  4 , for each of the pair of power collectors  12 , a welding interval D 2  in an upper portion is narrower than a welding interval D 3  in a lower portion.  
         [0058]    The upper portion of the power collector  12  is connected to a side of the electrode plate group  17  by a laser weld at intervals of D 2 =10 mm. The lower portion of the power collector  12  is connected to a side of the electrode plate group  17  by a laser weld at intervals of D 3 =20 mm.  
         [0059]    A welding point (welding portion  122 ) in the lower portion of the electrode plate group  17  does not greatly contribute to power collection. Accordingly, it is preferable that welding points are concentrated in the upper portion of the power collector  12 .  
         [0060]    Embodiment  5   
         [0061]    [0061]FIG. 5 is an exploded view of a square shaped battery  100 D according to embodiment  5  of the present invention. In FIG. 5, like elements are indicated by like reference numerals used for the square shaped battery  100 C of FIG. 4, and detailed descriptions thereof are omitted.  
         [0062]    In the square shaped battery  100 D according to embodiment  5 , a pair of power collectors  12 A each have bent portions  123 . The bent portions  123  suppress expansion of the sides of the electrode plate group  17 . As shown in FIG. 5, each of the pair of power collectors  12 A has a “U”-shape so as to bind the electrode plate group  17 .  
         [0063]    Since each of the pair of power collectors  12 A has bent portions  123 , i.e., each of the pair of power collectors  12 A has a “U”-shape which binds the electrode plate group  17 , expansion of the sides of the electrode plate group  17  can be suppressed. With such a structure, reliability of power collection is improved.  
         [0064]    Embodiment  6   
         [0065]    [0065]FIG. 6 is an exploded view of a square shaped battery  100 E according to embodiment  6  of the present invention. In FIG. 6, like elements are indicated by like reference numerals used for the square shaped battery  100 D of FIG. 5, and detailed descriptions thereof are omitted.  
         [0066]    In the square shaped battery  100 E according to embodiment  6 , a pair of power collectors  12 B each have protrusions  124  at welding points thereof so as to secure a larger area for welding than that of Embodiments  1  through  5 .  
         [0067]    With the protrusions  124  at the welding points, nickel wax is effectively applied to the welding points. Thus, welding efficiency improves since a larger welding area is secured.  
         [0068]    Embodiment  7   
         [0069]    [0069]FIG. 7 Is an exploded view of a square shaped battery  100 F according to embodiment  7  of the present invention. In FIG. 7, like elements are indicated by like reference numerals used for the square shaped battery  100 E of FIG. 6, and detailed descriptions thereof are omitted.  
         [0070]    In the square shaped battery  100 F according to embodiment  7 , a pair of power collectors  12 C each have protrusions  124  at welding points thereof so as to secure a larger area for welding. Each protrusion  124  has a hollow portion  124 A.  
         [0071]    With the hollow portions  124 A of the protrusions  124  located at the welding points, a larger area again to that of Embodiment  6  can be secured for welding, and accordingly, welding efficiency further improves. Furthermore, nickel wax is more effectively applied to the welding points.  
         [0072]    Embodiment  8   
         [0073]    [0073]FIG. 8 is an exploded view of a square shaped battery  100 G according to embodiment  8  of the present invention. In FIG. 8, like elements are indicated by like reference numerals used for the square shaped battery  100  of FIGS. 1A and 1B, and detailed descriptions thereof are omitted.  
         [0074]    In the square shaped battery  100 G according to embodiment  8 , a pair of power collectors  12 D each have a central portion  126  in which a rib (protrusion) is not provided. While the pair of power collectors  12 D are welded to the electrode plate group  17 , the central portions  126  are pressed against the electrode plate group  17 . With such a structure, even when the electrode plate group  17  is not tightly rolled up, unevenness of welding can be suppressed. As a result, welding efficiency improves.  
       EXAMPLE  
       [0075]    Table 1 shows measurement results of an output characteristic for the square shaped batteries  100 ,  100 A to  100 G (Embodiments  1 - 8 ), the conventional square shaped battery  900  described with reference to FIG. 9 (Conventional  1 ), and the conventional square shaped battery  1000  described with reference to FIG. 10 (Conventional  2 ). For each battery, after SOC had been adjusted to 60%, the battery was subjected to a large current discharge. Based on the result of the large current discharge, a current value with which 10 seconds or more can be secured before a voltage value reaches 1 V was selected, and the selected current value was multiplied by 1 V. The result of the multiplication was obtained as an output characteristic. The unit of the output characteristic is “W”. Each value of the output characteristic is an average of 10 samples.  
                                     TABLE 1                                   Output characteristic (W)                                        Conventional 1    95           Conventional 2   100           Embodiment 1   120           Embodiment 2   140           Embodiment 3   130           Embodiment 4   130           Embodiment 5   135           Embodiment 6   140           Embodiment 7   145           Embodiment 8   150                      
 
         [0076]    As shown in Table 1, the square shaped battery  100  according to embodiment  1  of the present invention can produce electrical power about 20% higher than the conventional square shaped battery  1000  (Conventional  2 ). This is because the pair of power collectors  12  efficiently collect electric power from the electrode plate group  17  which can produce high electric power.  
         [0077]    The square shaped battery  100 A according to embodiment  2  of the present invention can produce still higher electrical power. This is because the pair of power collectors collect electric power in opposite directions, and accordingly, electric currents flow smoothly. In the square shaped battery  100 A, the pair of power collectors  12  can more efficiently collect electric power from the electrode plate group  17  which can produce high electric power.  
         [0078]    The square shaped battery  100 B according to embodiment  3  of the present invention can produce electrical power about 10% higher than the square shaped battery  100  according to embodiment  1 . This means that power collection efficiency is further increased by increasing the number of power collection points.  
         [0079]    The square shaped battery  100 C according to embodiment  4  of the present invention can produce electrical power comparable to that produced by the square shaped battery  100 B according to embodiment  3 . This means that a welding point in the lower portion of the electrode plate group  17  does not greatly contribute to power collection. Accordingly, it is preferable that welding points are concentrated in the upper portions of the power collectors  12 .  
         [0080]    The output characteristic of the square shaped battery  100 D according to embodiment  5  of the present invention is higher than that of the square shaped battery  100 C according to embodiment  4  by about 4%. This is because the power collector  12 A has bent portions  123  so as to have a “U”-shape which binds the electrode plate group  17 . With such a structure, expansion of the sides of the electrode plate group  17  can be suppressed, whereby reliability of power collection is improved.  
         [0081]    The output characteristic of the square shaped battery  100 E according to embodiment  6  of the present invention is higher than that of the square shaped battery  100 D according to embodiment  5  by about 4%. This is because each power collector  12 B has protrusions  124  at welding points thereof, and accordingly, nickel wax is effectively applied to the welding points. With such a structure, welding efficiency improves while a larger welding area is secured.  
         [0082]    The output characteristic of the square shaped battery  100 F according to embodiment  7  of the present invention is higher than that of the square shaped battery  100 E according to embodiment  6  by about 4%. This is because each protrusion  124  at a welding point of the power collectors  12  has a hollow portion  124 A so that a larger area can be secured for welding, such that welding efficiency is further improved. Furthermore, with the hollow portions  124 A, nickel wax can be more effectively applied to the welding points.  
         [0083]    The output characteristic of the square shaped battery  100 G according to embodiment  8  of the present invention is higher than that of the square shaped battery  100 F according to embodiment  7  by about 4%. This is because unevenness of welding can be suppressed even when the electrode plate group  17  is not tightly rolled up, and accordingly, welding efficiency improves.  
         [0084]    As described hereinabove, the present invention can provide a high-power square shaped battery.  
         [0085]    Further, the present invention can provide a square shaped battery from which electric power can be sufficiently collected.  
         [0086]    Furthermore, the present invention can provide a square shaped battery in which an electrochemical reaction resistance can be reduced.  
         [0087]    With a structure of a square shaped battery according to the present invention, the facing area of electrode plates can be increased while reducing the number of electrode plates. The higher amount of power produced by the larger facing area can also be efficiently utilized. As a result, a high power battery can be provided.  
         [0088]    Various other modifications will be apparent to and can be readily made by those skilled in the art without departing from the scope and spirit of this invention. Accordingly, it is not intended that the scope of the claims appended hereto be limited to the description as set forth herein, but rather that the claims be broadly construed.