JP2008243410A - Sealed secondary battery and battery module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sealed secondary battery capable of easily connecting in series or in series/parallel and to provide a battery module formed by connecting two or more sealed secondary batteries. <P>SOLUTION: The battery module 20 is formed by connecting eight laminated cells 10 in series. The laminated cell 10 uses two same-shaped films 1 as a battery container. A recess having a right-angled triangle cross section is formed in almost the central part of the film 1. Portions where the recess of the film 1 is formed are faced in the reverse directions. A rectangular parallelopiped-shaped housing part 2 is formed with the faced recesses. An electrode group is housed in the housing part 2. One of a positive terminal 3 and a negative terminal 4 is taken out of an optional one side and the other is taken out of the side of the diagonal to the optional side. Terminals to be joined of adjoined laminated cells 10 are directly joined in a joining part 7. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a sealed secondary battery and a battery module, and in particular, a sealed secondary battery using a flexible film having a rectangular parallelepiped housing portion that houses an electrode group as a battery container, and the sealed secondary battery. The present invention relates to a battery module in which a plurality of batteries are connected.

  Conventionally, a battery module in which a plurality of sealed secondary batteries are connected in series or in series-parallel has been used for a large current charging / discharging power source such as an electric vehicle or a hybrid vehicle. Generally, in such a large current charging / discharging power source, for example, 40 to 100 cylindrical secondary batteries are used.

  In order to reduce costs, an iron-based material is generally used for a cylindrical battery container used for a cylindrical secondary battery. However, since iron has a large specific gravity, it has been a major limitation in increasing the energy efficiency per unit weight of the battery (to reduce weight). For this reason, a technique of a film-type secondary battery (laminate cell) using a flexible film in which an aluminum foil or the like is incorporated as a gas barrier layer in the inner layer, a so-called laminate film as a battery container has been disclosed (for example, Patent Document 1). In such a film type secondary battery, an electrode group is housed in a film-like sealed container in which two (a pair of) laminated films are set as one set and the outer edges of the laminated films are thermally welded to each other. At this time, one of the two sheets is formed into a cup shape and the other is formed into a flat plate shape, or a so-called one cup shape in which both are formed into a cup shape with the same depth. Usually, the positive and negative external terminals led out from the electrode group are respectively arranged on the outer edge of the heat-welded laminate film. For this reason, even when a film type secondary battery is used singly or when a plurality of secondary batteries are connected and connected, when the thickness of the secondary battery is about 2 to 3 mm, there is a particular inconvenience in connecting external terminals. There is no.

JP-A-60-230354

  However, when a laminate cell is used for a large current charging / discharging power source for an electric vehicle or the like, there is a battery that has a thickness of 10 mm. Therefore, these batteries are arranged in a stacked state and connected in series or series-parallel. Various problems arise with modules. For example, as shown in FIG. 5, in the battery module 40 in which eight pieces of one-cup type laminate cells are connected in series, the negative electrode terminal 4a of the first laminate cell 30a on one side and the second laminate cell The positive terminal 3b of 30b is joined at the joint 7. On the other hand, since the positive electrode terminal 3a of the laminate cell 30a and the negative electrode terminal 4b of the laminate cell 30b are arranged close to each other, it is necessary to insert an insulator 35 between the terminals to prevent a short circuit due to contact. Further, since the negative electrode terminal 4b of the laminate cell 30b and the positive electrode terminal 3c of the third laminate cell 30c are arranged with an interval of about twice the thickness of the battery, they can be directly joined. Instead, both sides of the connector 36 are joined at the joint 7 respectively. For this reason, as the battery module 40, it is necessary to join by the 10 junction parts 7. FIG. Since extra parts such as the insulator 35 and the connector 36 are required, and if the terminals are directly joined to each other, only one place is required, but joining at two places on both ends of the connector 36 is required. The internal resistance increases and the output is reduced. Furthermore, since the number of the joint portions 7 is large, the risk of breakage of the joint portions is increased, and the reliability of the battery module is also lowered.

  In addition, since the cup-shaped laminate cell has a limit in the depth at which cup molding is possible, it is difficult to increase the capacity (increase the thickness of the electrode group). However, in the case of an electric vehicle or the like, there is a demand for extending the distance that can be traveled, and in order to increase the capacity as much as possible, there is a strong demand for connecting secondary batteries not only in series but also in parallel. Even when used in such a parallel series connection, it is desirable in terms of cost and reliability that the terminals can be directly joined without using any special parts.

  An object of the present invention is to provide a sealed secondary battery that can be easily connected in series or series-parallel and a battery module in which a plurality of the sealed secondary batteries are connected.

  In order to solve the above-described problem, a first aspect of the present invention is a sealed secondary battery using a flexible film having a rectangular parallelepiped housing portion that houses an electrode group as a battery container. Either one of the terminals is derived from an arbitrary side of the accommodating portion, and either one of the terminals is derived from a side diagonal to the arbitrary one side.

  In the first aspect, since either one of the positive electrode terminal and the negative electrode terminal is derived from an arbitrary side of the battery container housing portion, and the other is derived from a side diagonal to the arbitrary one side. Since the terminals of the adjacent sealed secondary batteries are opposed to each other by juxtaposing a plurality of sealed secondary batteries so that the positive electrode terminals and the negative electrode terminals are staggered with the accommodating portions facing each other, A plurality of sealed secondary batteries can be easily connected in series.

  In the first aspect, the positive electrode terminal and the negative electrode terminal may be led out from two opposite sides of the accommodating portion, respectively. The accommodating part may be formed by a pair of flexible films having triangular prism-shaped depressions, with the depressions facing each other in opposite directions. Further, if the leading end of the positive electrode terminal and the negative electrode terminal is formed with an arm portion having a length larger than the length of the outer edge corresponding to the side from which the positive electrode terminal and the negative electrode terminal of the flexible film are derived, respectively, By arranging a plurality of sealed secondary batteries so that the arms of the positive terminals of the matching sealed secondary batteries overlap each other, the arms can be directly joined and easily connected in parallel.

  According to a second aspect of the present invention, in the battery module in which the plurality of sealed secondary batteries of the first aspect are connected, the sealed secondary batteries are arranged in parallel with the housing portions facing each other. Are directly joined and connected in series. According to a third aspect of the present invention, there is provided a battery module in which a plurality of sealed secondary batteries having arms formed at the leading ends of the positive electrode terminal and the negative electrode terminal in the first aspect are connected. The secondary battery is placed side by side with the housing portions facing each other, adjacent terminals are directly joined, and the arms of the positive electrode terminal and the negative electrode terminal are arranged to overlap each other, and the overlapping arm portions are directly connected to each other. It is joined and connected in parallel.

  According to the present invention, one of the positive electrode terminal and the negative electrode terminal is derived from any one side of the battery container housing portion, and either one is derived from the side diagonal to the arbitrary one side. Since the terminals of the adjacent sealed secondary batteries are opposed to each other by juxtaposing a plurality of sealed secondary batteries so that the positive electrode terminals and the negative electrode terminals are staggered with the accommodating portions facing each other, It is possible to obtain an effect that a plurality of sealed secondary batteries can be easily connected in series.

  Hereinafter, embodiments of a battery module to which the present invention is applied will be described with reference to the drawings.

(Constitution)
As shown in FIG. 1, the battery module 20 of the present embodiment includes a film-type lithium ion secondary battery (hereinafter referred to as a laminate cell) as a sealed secondary battery in which a laminate film (flexible film) is used for a battery container. It has 8).

  The eight laminated cells 10 are arranged such that the positive electrode terminals 3 and the negative electrode terminals 4 are staggered. Adjacent laminate cells 10 are bonded with a double-sided tape. That is, the eight laminated cells 10 are arranged in a stacked state. The terminals to be joined of the adjacent laminate cells 10 are directly joined at the joint 7 (white circle portion in FIG. 1) by resistance welding, and the eight laminate cells 10 are connected in series.

  Here, the connection state of the laminate cell 10 will be described focusing on three laminate cells 10a, 10b, and 10c arranged in order from one side of the battery module 20 (left side in FIG. 1). The positive electrode terminal 3 a of the laminate cell 10 a is connected to a positive electrode external terminal (not shown) of the battery module 20. The negative electrode terminal 4a of the laminate cell 10a and the positive electrode terminal 3b of the laminate cell 10b are joined at the joint portion 7, and the negative electrode terminal 4b of the laminate cell 10b and the positive electrode terminal 3c of the laminate cell 10c are joined at the joint portion 7. Yes. Similarly, the remaining five laminate cells 10 are sequentially connected from the negative electrode terminal 4c of the laminate cell 10c to the positive electrode terminal 3 of the laminate cell 10 disposed on the other side of the battery module 20 (right side in FIG. 1). . The negative electrode terminal 4 of the laminate cell 10 disposed on the other side of the battery module 20 is connected to a negative electrode external terminal (not shown) of the battery module 20.

  As shown in FIG. 2, the laminate cell 10 used in the battery module 20 uses two (a pair) rectangular laminate films (hereinafter simply referred to as films) 1 for the battery container. The film 1 has an aluminum foil serving as a gas barrier layer as an inner layer. A heat-welding polypropylene (hereinafter abbreviated as PP) film is bonded to one surface of the aluminum foil, and a polyethylene terephthalate (hereinafter abbreviated as PET) film is bonded to the other surface. Yes. That is, PP film-aluminum foil-PET film is overlaid on film 1, and in this example, the thickness is set to about 120 μm.

  As shown in FIG. 3, a triangular columnar depression having a right-angled apex at the bottom side and a right-angled apex is formed in a substantially central portion of the film 1. Two sides sandwiching the right angle are composed of a long side and a short side. Two films 1 having the same shape are faced to each other so that the perpendicular vertices of the recesses are opposite to each other. A rectangular parallelepiped accommodating portion 2 is formed by the recesses facing each other. For this reason, the direction of the short side of the two sides sandwiching the right angle of the right triangle of the film 1 is the thickness direction of the electrode group.

  As shown in FIG. 2, an electrode group (not shown) is accommodated in the accommodating portion 2 of the laminate cell 10. One of the positive electrode terminal 3 and the negative electrode terminal 4 connected to the electrode group is led out from any one side of the housing portion 2. The other of the positive electrode terminal 3 and the negative electrode terminal 4 is derived from a side diagonal to an arbitrary side. In other words, the positive electrode terminal 3 and the negative electrode terminal 4 are led out from two sides of the accommodating portion 2 that face each other and are not the same surface (non-identical surfaces). The two films 1 are sealed with a heat-welded portion 8 in which PP films at the outer edge portions are heat-welded, and the laminate cell 10 has a sealed structure. The positive electrode terminal 3 and the negative electrode terminal 4 are sandwiched between the heat welding parts 8 and are led out with their leading ends protruding outward in opposite directions. For this reason, the heat welding part 8 is located in the diagonal position of the accommodating part 2 seeing from the side surface of the laminate cell 10, and the positive electrode terminal 3 and the negative electrode terminal 4 are led out to one side of the diagonal line, respectively. (See also FIG. 1).

  In the electrode group housed in the housing portion 2, 19 rectangular positive plates and 20 rectangular negative plates are alternately stacked. For this reason, the electrode group is formed in a rectangular parallelepiped shape. Each positive electrode plate is inserted into a separator formed into a bag shape by heat welding. For example, a polyethylene porous film having a thickness of 25 μm and a width of 100 mm is used as the separator. The plain part of the positive electrode plate and the plain part of the negative electrode plate are joined to the positive electrode terminal 3 and the negative electrode terminal 4 by ultrasonic welding, respectively. The positive electrode plate and the negative electrode plate are overlapped so that the positive electrode terminal 3 and the negative electrode terminal 4 are led out in directions opposite to each other. The thickness of the electrode group is set to about 4.8 mm.

  When the laminate cell 10 is assembled, the electrode group is placed in the depression of one film 1 and the other film 1 is placed on the upper side of the electrode group. Four sides of the film 1 are heat-welded to form a heat-welded portion 8. At this time, the mating surface of the film 1 that is not thermally welded is left on a part of the side where the positive electrode terminal 3 and the negative electrode terminal 4 are not led out. A predetermined amount of non-aqueous electrolyte is injected from the mating surface of the film 1 using a syringe. By heat welding the mating surfaces, the four sides of the film 1 were sealed by heat welding, and the assembly of the laminate cell 10 was completed. In this example, the welding width of the heat welding portion 8 is set to about 10 mm over the entire circumference. The laminate cell 10 is set to a capacity of about 3.2 Ah.

  At the time of producing the positive electrode plate constituting the electrode group, a lithium transition metal double oxide such as lithium manganate as the positive electrode active material, carbon powder as the conductive material, and polyvinylidene fluoride as the binder are N— A slurry is prepared by dispersing and mixing in methyl-2-pyrrolidone. This slurry is applied to both sides of a rectangular aluminum foil having a thickness of 20 μm which is a positive electrode current collector, dried, pressed and integrated. At this time, a plain portion to which slurry is not applied is formed on one side of the aluminum foil. Thereafter, it is cut into a width (length of one side not coated with slurry) of 94 mm to produce a strip-like positive electrode plate. The height of the coating part (the length in the direction intersecting the width direction) is set to 86 mm, and the height of the plain part is set to 10 mm.

  On the other hand, at the time of producing the negative electrode plate, carbon particles as a negative electrode active material and polyvinylidene fluoride as a binder are charged and mixed in N-methyl-2-pyrrolidone as a solvent to produce a slurry solution. . This slurry is applied to both sides of a rectangular copper foil having a thickness of 10 μm which is a negative electrode current collector, dried, pressed and integrated. At this time, a plain portion to which the slurry is not applied is formed on one side of the copper foil. Then, it cut | disconnects to width 96mm and a strip-shaped negative electrode plate is produced. The height of the coated part is set to 88 mm, and the height of the plain part is set to 10 mm.

  Next, the operation and the like of the battery module 20 of the present embodiment will be described.

  In the battery module 20 of the present embodiment, the laminate cells 10 are juxtaposed so that the housing portions 2 in which the electrode groups are housed face each other and the positive terminal 3 and the negative terminal 4 are staggered. In this laminate cell 10, one of the positive electrode terminal 3 and the negative electrode terminal 4 is derived from any one side of the housing portion 2, and the other is derived from a side diagonal to the arbitrary one side. . For this reason, in the two adjacent laminate cells 10, the positive electrode terminal 3 of one laminate cell 10 and the negative electrode terminal 4 of the other laminate cell 10 face each other at close positions. The terminal 4 can be directly joined to the joint 7. Thereby, the laminate cells 10 can be easily connected in series without using a connection member, and the battery module 20 can be manufactured.

  Moreover, in the battery module 20 of this embodiment, since the terminal which should adjoin the adjacent laminate cell 10 is directly joined, compared with the case where a connection member is used, the increase in an internal resistance and an output fall are suppressed. be able to. Furthermore, when the connecting member is used, it is necessary to join two places on both sides, but by joining directly, only one place can be joined. Therefore, the number of joint portions 7 can be reduced. As a result, the assembling work of the battery module 20 can be simplified, so that the cost can be reduced and the possibility of the joint breakage is reduced by the small number of the joints 7. Reliability degradation can be suppressed.

  Furthermore, in this embodiment, the laminate cell 10 constituting the battery module 20 is formed by thermally welding the outer edge portions of the two films 1. The rectangular parallelepiped-shaped accommodation part 2 is formed by facing the recesses of the triangular prism shape (triangular right-angled triangle shape) formed in the film 1 in opposite directions. For this reason, the depth which can be shape | molded can be enlarged compared with the case of the cup shaping | molding which forms a rectangular parallelepiped hollow (accommodating part) in one film. Thereby, since the depth of the accommodating part 2 can be enlarged (the length of the short side of the two sides sandwiching the right angle) can be increased, the number of the positive and negative electrode plates constituting the electrode group can be increased. It is possible to increase the output and capacity of the laminate cell 10 and thus the battery module 20.

  In addition, in this embodiment, although the battery module 20 which connected the eight laminated cells 10 in series was illustrated, this invention is not limited to this. For example, the number of laminate cells 10 connected in series may be increased or decreased, and the laminate cells 10 may be configured in series and parallel connection in combination with parallel connection. Even when the laminate cells 10 are connected in parallel, it is preferable to directly join the terminals without using a connection member. This can be realized by changing the shapes of the positive electrode terminal 3 and the negative electrode terminal 4.

  As shown in FIG. 4, the leading end portions of the positive electrode terminal 3 and the negative electrode terminal 4 of the laminate cell 10 are larger than the length of the outer edge side corresponding to the side from which the positive electrode terminal 3 and the negative electrode terminal 4 of the film 1 are derived. A widened portion (arm portion) 22 having a length is formed. That is, the positive electrode terminal 3 and the negative electrode terminal 4 in a portion protruding from the film 1 are formed in a T shape. A plurality of laminate cells 10 are arranged so that the widened portions 22 of the positive electrode terminal 3 and the widened portions 22 of the negative electrode terminal 4 overlap each other. If it does in this way, the positive electrode terminals 3 of the adjacent laminate cells 10 and the negative electrode terminals 4 are directly joined at the joint portion 9 (black circle portion in FIG. 4), thereby easily connecting in parallel without requiring a connection member. can do. Therefore, if a plurality of, for example, m laminate cells 10 are connected in parallel, and a plurality of, for example, n, are connected in series, an arbitrary m parallel / n series battery module 20 can be easily manufactured. be able to. The battery module 20 is configured by connecting the m laminated cells 10 in parallel and n in series to form a battery module 20. The battery module used for a large current charge / discharge power source that requires high output and high capacity, in particular, can run. It can be suitably used as a battery module for an electric vehicle power source that requires a large capacity as much as possible to extend the distance.

  Furthermore, in this embodiment, although the film comprised by three layers of PP film-aluminum foil-PET film was illustrated as the film 1, this invention is not restrict | limited in particular to the structure of a film, It uses as a battery container. Any configuration of flexible film can be used. Moreover, although the example which uses the rectangular film 1 was shown in this embodiment, this invention is not limited to this. It is only necessary that the accommodating portion 2 for accommodating the electrode group can be formed, and for example, it may be circular. Furthermore, in this embodiment, although the example which comprises a sealed container by using two films 1 and heat-welding four sides was shown, two depressions are formed in one film, and the center part is turned up. You may do it. In this case, the hermetic container can be configured by thermally welding the three sides.

  Furthermore, in the present embodiment, an example in which one positive electrode terminal 3 and one negative electrode terminal 4 are led out has been shown. However, the present invention is not limited to this, and may be, for example, two or more. In consideration of large current charging / discharging, it is preferable to arrange a plurality of currents in order to secure a current-carrying area. Further, in the present embodiment, the electrode group in which the positive electrode plates and the negative electrode plates formed in a strip shape are alternately laminated is illustrated, but the present invention is not limited to this, for example, a positive electrode plate formed in a strip shape, The negative electrode plate may be wound in a flat shape.

  Furthermore, in the present embodiment, a lithium ion secondary battery is illustrated as the laminate cell 10 constituting the battery module 20, but the present invention is not limited to this, and a flexible film is used for the battery container. It can be applied to a sealed secondary battery. Of course, there is no limitation on materials such as positive and negative electrode active materials used in the lithium ion secondary battery.

  Next, examples of the battery module 20 of the present embodiment will be described. The conventional battery module 40 produced for comparison is also shown. Although the conventional battery module 40 is configured as follows, the same members as those of the battery module 20 described above are denoted by the same reference numerals, and only different points will be described.

  As shown in FIG. 5, in the battery module 40, eight single-cup type laminate cells 30 are connected in series. The connection state of the laminate cell 30 will be described focusing on three laminate cells 30a, 30b, and 30c arranged in order from one side of the battery module 40. The negative electrode terminal 4 a of the laminate cell 30 a and the positive electrode terminal 3 b of the laminate cell 30 b are directly joined at the joint 7. Since the positive electrode terminal 3a of the laminate cell 30a and the negative electrode terminal 4b of the laminate cell 30b are arranged close to each other, it is necessary to prevent a short circuit due to contact. For this reason, an insulator 35 made of a PP flat plate having a thickness of 0.3 mm is inserted between the terminals. The insulator 35 is a double-sided adhesive tape and is fixed to the laminate cells 30a and 30b. The negative electrode terminal 4b of the laminate cell 30b and the positive electrode terminal 3c of the laminate cell 30c are arranged with an interval of about twice the thickness of the laminate cell 30. Both sides of the character-shaped connector 36 are joined at the joint 7 respectively.

  As shown in FIG. 6, in the laminated cell 30 constituting the battery module 40, a cup-shaped film 31 a having a rectangular parallelepiped recess capable of accommodating an electrode group formed in a substantially central portion, and a flat film 31 b are battery containers. Is used. The outer edge part of the films 31a and 31b is thermally welded, whereby the accommodating part 32 is formed. The accommodating part 32 accommodates an electrode group, and the positive electrode terminal 3 and the negative electrode terminal 4 are led out from two opposite sides of the battery container, respectively. In other words, in the battery module 40, the positive electrode terminal 3 and the negative electrode terminal 4 are led out from two sides of the same surface that face each other of the housing portion 32.

  Table 1 below shows the results of a comparison of the number of parts 36 and the number of connection locations (joint portions 7) of the connector 36 and the insulator 35 necessary for connecting the laminated cells for the battery module 20 of the example and the battery module 40 of the comparative example. Show.

  As shown in Table 1, in the battery module 40 of the comparative example, three connectors 36 and four insulators 35 were required, and the number of connection points was also ten. This is because, if the terminals to be connected are arranged close to each other, only one joint is required, but since the connector 36 is used, two joints on both sides are required. On the other hand, in the battery module 20 of the example, it is clear that no connector or insulator parts are required, and the number of connection points is seven (about 2/3 of the comparative example).

  The present invention provides a sealed secondary battery that can be easily connected in series or series-parallel and a battery module in which a plurality of sealed secondary batteries are connected. Since it contributes, it has industrial applicability.

It is sectional drawing which shows the connection state of the lamination cell in the battery module of embodiment to which this invention is applied. It is a perspective view which shows the laminate cell which comprises the battery module of embodiment. It is a perspective view which shows a pair of laminate film used for the battery container of the laminate cell. It is a perspective view which shows the state which connected in parallel the laminate cell by which the wide part was formed in the positive electrode terminal and the negative electrode terminal. It is sectional drawing which shows the connection state of the lamination cell in the conventional battery module. It is a perspective view which shows a pair of laminate film used for the battery container of the laminate cell which comprises the conventional battery module.

Explanation of symbols

1 Laminate film (flexible film)
2 Housing 3 Positive Electrode Terminal 4 Negative Electrode 7 Joint 10 Laminate Cell (Sealed Secondary Battery)
20 Battery module

Claims (6)

  In a sealed secondary battery using a flexible film having a rectangular parallelepiped housing portion that houses an electrode group as a battery container, either the positive electrode terminal or the negative electrode terminal is led out from any one side of the housing portion. One of the other is led out from a side diagonal to the one side, and the sealed secondary battery.   2. The sealed secondary battery according to claim 1, wherein the positive electrode terminal and the negative electrode terminal are led out from two opposite sides of the housing portion that are opposite to each other.   The said accommodating part is formed so that the part in which the said hollow was formed faced mutually in the reverse direction with a pair of flexible film in which the triangular prism-shaped hollow was formed. Sealed secondary battery.   The leading end portion of the positive electrode terminal and the negative electrode terminal is formed with an arm portion having a length larger than the length of the outer edge corresponding to the side from which the positive electrode terminal and the negative electrode terminal of the flexible film are respectively led out. The sealed secondary battery according to any one of claims 1 to 3, wherein:   2. The battery module in which a plurality of sealed secondary batteries according to claim 1 are connected, wherein the sealed secondary batteries are arranged in parallel with the housing portions facing each other, and adjacent terminals are directly joined to each other and connected in series. A battery module characterized by being made.   5. The battery module in which a plurality of sealed secondary batteries according to claim 4 are connected, wherein the sealed secondary batteries are juxtaposed with the housing portions facing each other and adjacent terminals are directly joined to each other, and A battery module, wherein the arms of the positive electrode terminal and the negative electrode terminal are arranged to overlap each other, and the overlapping arm portions are directly joined and connected in parallel.

Images