JP5169166B2 - Multilayer secondary battery - Google Patents

Description

  The present invention relates to a stacked secondary battery in which a plurality of electrode plates such as lithium ion secondary batteries are stacked.

  In recent years, lithium ion secondary batteries with high energy density and no memory effect have been studied as power sources for electric vehicles and hybrid vehicles. As a power source for mobile phones and mobile devices, a wound lithium ion secondary battery in which a strip electrode and a separator are wound is mainly used. However, when it is used for charging and discharging with a large capacity and a large current, it is necessary to increase the electrode area. Therefore, in a wound type battery, the electrode active material is bent at the portion where the radius of curvature is reduced. Problems such as an increase in thickness or occurrence of a portion where current concentrates become apparent. In order to use in applications that require high output such as a power source for automobiles, a stacked secondary battery in which a plurality of plate-like electrodes are stacked via separators is more suitable in terms of structure.

  As shown in a perspective view in FIG. 3, a conventional micro battery made of a polymer compound such as polyethylene or polypropylene is heat-welded around the electrodes in a stacked secondary battery in which a plurality of conventional flat electrodes are stacked. In some cases, the positive electrode 1 and the negative electrode 2 are each put in a bag and stacked using a separator processed into a bag shape. Moreover, in the bag-like separator in which the periphery of the electrode is thermally welded as shown in FIG. 3, since the wrinkle is generated in the separator due to heat, in Patent Document 1 and Patent Document 2, as shown in the plan views in FIGS. 4 and 5, respectively. A structure of the fusion bonded portion 5 that eliminates wrinkles has been proposed. In these drawings, 1 is a positive electrode, 2 is a negative electrode, 3 is a separator, 4 is a current collector, 56 is an electrode plate lead portion, and 57 is an electrode plate active portion.

  Furthermore, in Patent Document 3, as shown in a perspective view in FIG. 6, when the active material is peeled off from the current collector at the electrode end, the active material that has flowed out of the bag-shaped separator adheres to the counter electrode. In order to solve the problem that the self-discharge failure occurs, a structure in which the fusion sealing portion 9 is provided in addition to the fusion bonding portion 5 has been proposed.

  By the way, a laminated type secondary battery in which a plurality of electrode plates are stacked is a wound type secondary battery in which a belt-like electrode and a separator are wound. Since there is no structural problem such as an increase in thickness or a portion where current is concentrated, the present invention is excellent in applications that are used for charging and discharging with a large capacity and a large current. In addition, a stacked secondary battery in which electrodes covered with a bag-like separator are stacked is less likely to cause a short circuit between the positive and negative electrodes.

  However, in order to stack a laminated type secondary battery with a separator between a plurality of flat plate-like positive and negative electrodes, the stacked plates are stacked in a state where each electrode plate is positioned accurately so as not to be displaced. Need to be assembled. When misalignment occurs, a short circuit occurs between the electrode facing the terminal portion drawn from the electrode. In addition, there is a risk of depositing metallic lithium due to repeated charge and discharge. Therefore, it is extremely important to accurately position and stack the positive electrode and the negative electrode.

Japanese Patent Laid-Open No. 7-272761 JP-A-10-188938 JP 2003-17112 A

  In the above situation, the problem of the present invention is that it is possible to accurately position the positive electrode and the negative electrode facing each other through the separator, and excellent in reliability without causing a short circuit between the positive electrode and the negative electrode. The object is to provide a stacked secondary battery.

In order to solve the above-mentioned problems, the laminated secondary battery of the present invention is a rectangular plate-shaped laminated secondary battery in which a positive electrode and a negative electrode are opposed to each other via a separator, and two rectangular separator pieces are joined. One electrode of the positive electrode or the negative electrode is disposed inside the bag-shaped separator, and the electrode lead portion of the one electrode is drawn from the opening of the bag-shaped separator, and the opening of the bag-shaped separator A rectangular cut portion is formed in at least one of the corner portions located at both ends of the electrode, and one side of the cut rectangular shape at the cut portion is an electrode disposed outside the bag-shaped separator. The electrode lead portion is overlapped with one end of the drawn edge portion .

  Further, a rectangular cut portion may be formed at a corner portion of the corner portion of the bag-shaped separator adjacent to the electrode lead portion drawn from the one electrode.

  According to the multilayer secondary battery of the present invention, one of the positive electrode and the negative electrode is covered with the bag-like separator bonded by the fusion bonded portion formed around the electrode, and is close to the positive electrode lead portion or the negative electrode lead portion. By providing a cut portion at the corner of the separator, it is possible to accurately position the positive electrode and the negative electrode facing each other through the separator, and it is excellent in reliability without causing a short circuit between the positive electrode and the negative electrode. A stacked secondary battery can be provided.

  The best mode for carrying out the present invention will be described with reference to the drawings.

  FIG. 1 shows a positive electrode coated with a bag-like separator of a laminated secondary battery of the present invention and an opposite negative electrode, FIG. 1 (a) is a front view of the negative electrode 2, and FIG. 1 (b) is covered with a bag-like separator. 2 is a front view of the positive electrode 1. FIG. 2 is a front view of the electrode laminate in the multilayer secondary battery of the present invention.

  1 and 2, reference numeral 3 denotes a bag-shaped separator having a hole closing portion and a fusion bonded portion. The separator 3 is a microporous film made of a polymer compound such as polyethylene or polypropylene. For this reason, by applying heat, it shrinks and melts easily, and pores can be reduced and lost, and fusion bonding between separators can be performed. Prior to the production of the bag-shaped separator, the hole was closed by heating the portion corresponding to the end of the electrode inserted in advance. Then, the bag-shaped separator was produced by melt-bonding two separators. In addition, when two separators are fusion-bonded, the occurrence of wrinkles can be prevented by intermittently welding. The opening of the bag-shaped separator, that is, the upper end of the separator 3 in FIG. The portion of the separator 3 thus prepared with the hole blocking portion and the fusion bonded portion formed thereon was displayed with dots.

  Next, the electrode is inserted into the bag-shaped separator. Alternatively, the electrode may be accommodated in the bag-shaped separator by fusion-bonding after arranging the electrode between the two separators. Thereafter, the rectangular cut portion (notch portion) 11 was formed by thermally fusing the corner portion (corner portion) of the separator to a position that coincided with the upper end side 12 of the opposing negative electrode 2 when they were overlapped.

  The positive electrode 1 covered with the bag-like separator 3 and the negative electrode 2 are alternately laminated while positioning the four corners of the bag-like separator 3 so as to face each other precisely at a predetermined position. can do. Further description will be given with reference to FIG. As shown in FIG. 1, the height h from the bottom side of the negative electrode 2 to the upper end side where the negative electrode lead portion 42 is drawn is from the bottom side of the bag-like separator 3 covering the positive electrode 1 to the upper left corner of the bag-like separator 3. It is equal to the height h up to the bottom side of the rectangular cut portion 11 formed in.

  By using the bag-shaped separator 3 having such a cut-out portion 11, it is opposed to one end in the cut-out portion 11 provided at a corner portion close to the positive electrode lead portion 41 in the separator 3 into which the positive electrode 1 is inserted. By aligning the upper ends of the corners of the negative electrode 2 so as to coincide with each other, the alignment becomes accurate and easy.

  For example, in order to overlap rectangular plates of the same size, positioning is possible by positioning two sides starting from one corner (corner), but the negative electrode in this embodiment is a bag-like shape. When we try to overlap the negative electrode with a bag-shaped separator that is slightly smaller than the separator and has no cut-out corners, the four corners of the negative electrode are inside the four corners of the separator. Alignment that can be set to be performed must be performed, which increases the process time. However, as in the present invention, if there is a matching edge between the bag-like separator and the negative electrode at the corner, the alignment is facilitated accordingly.

  Of the four corners of the bag-shaped separator, if a rectangular cut-out is provided in the corner close to the positive electrode lead portion pulled out from the positive electrode inserted in the bag, alignment is performed near the positive electrode lead portion. Therefore, the position of the positive electrode lead can be determined more accurately in the electrode stacking process.

  Next, an example produced based on this embodiment will be described. At this time, the overall size of the bag-like separator 3 is 120 × width 220 mm, and the size of the rectangular cut portion 11 is 9 × width 4 mm. In the step of laminating the four positive electrodes and the five negative electrodes inserted into the bag-shaped separator while aligning them, the process time is reduced by 30% compared to the conventional example using the bag-shaped separator having no cut portion. I was able to. Further, the outer dimensions of the laminated secondary battery obtained by covering the electrode laminate impregnated with the electrolytic solution with an aluminum laminate were 140 × 250 × 4 mm excluding the electrode terminal portion.

  As described above, in the multilayer secondary battery of the present invention, one of the positive electrode and the negative electrode is covered with the bag-shaped separator whose both surfaces are joined by the fusion-bonded portion formed around the electrode, and the positive electrode lead portion or the negative electrode. By providing a cut-out portion at the corner of the separator adjacent to the lead portion, it is possible to accurately position the positive and negative electrodes facing each other through the separator, and a short circuit occurs due to misalignment between the positive and negative electrodes. Thus, it is possible to provide a stacked secondary battery that is excellent in reliability and free from defects.

  By the way, in the laminated type secondary battery using insertion / removal of lithium ions to / from the electrode, the positive electrode is inserted into the bag-shaped separator, but the bag-shaped separator having cut portions at the corners as used in the present invention is used. The use can contribute to shortening of the process time in the electrode stacking process in the rectangular plate-type stacked secondary battery in which the positive electrode and the negative electrode are opposed to each other with a separator interposed therebetween.

  Moreover, you may form a square-shaped cutting part in both the corner | angular parts located in the both ends of the opening part of a bag-shaped separator, and also the opening in the separator 3 upper end in drawing of FIG.1 (b). A square cut portion may be formed only at the corner on the right side of the portion, and in any case, alignment in the electrode stacking step is facilitated.

1 shows a positive electrode coated with a bag-like separator and an opposing negative electrode in the laminated secondary battery of the present invention, FIG. 1 (a) is a front view of the negative electrode, and FIG. 1 (b) is a negative electrode covered with a bag-like separator. Front view. The front view of the electrode laminated body in the laminated type secondary battery of this invention. The perspective view which shows an example of the laminated | stacked electrode of the conventional laminated type secondary battery. The top view which shows the other example of the electrode coat | covered with the separator in the conventional laminated type secondary battery. The top view which shows the further another example of the electrode coat | covered with the separator in the conventional laminated type secondary battery. The perspective view which shows the other example of the laminated | stacked electrode in the conventional laminated secondary battery.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Positive electrode 2 Negative electrode 3 Separator 4 Current collector 5 Fusion joint part 11 Cutting part 12 Upper end side 41 Positive electrode lead part 42 Negative electrode lead part

Claims (2)

In a rectangular plate laminated secondary battery in which a positive electrode and a negative electrode are opposed to each other with a separator interposed therebetween, one of the positive electrode and the negative electrode is placed inside a bag-like separator formed by joining two rectangular separator pieces. An electrode is disposed, an electrode lead portion of the one electrode is drawn out from the opening of the bag-shaped separator, and a rectangular cut is formed in at least one of the corners located at both ends of the opening of the bag-shaped separator. Part is formed ,
One side of the rectangular shape cut out at the cut-out portion is overlaid on one end of the edge portion where the electrode lead portion of the electrode disposed outside the bag-like separator is drawn out. Secondary battery.   2. The stacked secondary battery according to claim 1, wherein a rectangular cut portion is formed in a corner portion adjacent to an electrode lead portion drawn out from the one electrode among corner portions of the bag-shaped separator. .

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