JP5105390B2 - Thin secondary battery and battery module for large current discharge - Google Patents

Description

  The present invention relates to a thin secondary battery and a battery module for discharging a large current, and in particular, a film-like container including an electrode group in which a positive electrode plate and a negative electrode plate are disposed via a separator and an electrolytic solution as an inner layer. The present invention relates to a sealed rectangular thin secondary battery for large current discharge and a battery module using a plurality of the thin secondary batteries for large current discharge.

  Conventionally, a power source of an electric vehicle or the like is a large current discharge in which a plurality of battery packs (battery modules) connected in series or in parallel with a plurality of so-called cylindrical sealed secondary batteries (unit cells) are further connected in series or in parallel. A power supply was used. In such a large current discharge power source, for example, 40 to 100 cylindrical sealed secondary batteries are generally used.

  A cylindrical container is used for the cylindrical sealed secondary battery, and an iron-based material is generally used for the cylindrical container for cost reduction. However, since iron has a large specific gravity, it has been a major limitation in reducing the weight of the battery. This problem is common to small sealed lead-acid batteries using injection-molded resin containers, and it is difficult to increase volumetric efficiency due to wall thickness as well as the weight is not so light. there were. For this reason, a technique using a laminate film as a battery container (film-like container) has been proposed for a long time (see, for example, Patent Document 1).

JP-A-60-230354

  However, since a battery using a laminate film as a battery container generally has a structure in which a terminal for taking out current from a laminated electrode group is taken out to the same one of four sides for both positive and negative electrodes, the terminal is attached to the electrode. Therefore, a rectangular lead-out portion (so-called “ear”) extending from the current collector is required. In lead batteries, the lattice is generally made by casting, so it is relatively easy to form the ears. However, in the case of lithium battery electrodes where the active material is thinly applied to a metal foil with a thickness of about several tens of microns, Ears must be formed by machining, and dust is unavoidable during processing. Since the electrode after coating is difficult to clean, the dust generated during ear formation cannot be completely removed. For this reason, there has been a problem that dust is likely to be mixed into the battery and easily cause a short circuit.

  In addition, as a result of taking out both poles on the same side, the active material in the part far from the ear is not used effectively, which causes deterioration of the characteristics at the time of high current discharge in particular, and the power source for hybrid vehicles where high current discharge is indispensable at the start It was not suitable as a battery structure.

  In addition, since the film-like container is lighter than the metal container and the outer periphery is sealed by heat welding, a certain amount of width is required, so there is a waste space in this part, and it is not necessarily in terms of volume efficiency. A big effect cannot be expected. Although the side where there is no terminal can considerably reduce the waste space by bending the laminate film, the side where the terminal is taken out has not been dealt with to increase the volume efficiency.

  Furthermore, in order to use the laminate film as a container, it is necessary to form a dent having substantially the same shape as the contents (electrode group). Such so-called cup molding is an aluminum foil provided to improve gas barrier properties. Because of the inner layer, it cannot be formed into a very deep shape. For this reason, it is difficult to make the capacity of a battery using a film-like container equal to that of a cylindrical sealed battery, and it has been difficult to apply to a use requiring a large output such as a hybrid vehicle. In addition, batteries using film-like containers have low dimensional accuracy and are difficult to hold. Therefore, for applications such as hybrid vehicles where a large number of single cells need to be integrated into a battery module, from the viewpoint of vibration resistance It was difficult to adopt.

  Regarding the material of the terminal, in general, lithium batteries preferably use aluminum or an aluminum alloy as a positive electrode terminal and copper or a copper alloy as a negative electrode terminal. However, welding of aluminum and copper is limited by a joining method such as ultrasonic bonding or electron beam welding. It has been. Ultrasonic bonding tends to be adversely affected by vibration inside the battery, and electron beam welding has disadvantages such as extremely high cost. In order to avoid this, nickel is also used as the negative electrode terminal, but it has the merit that it can be joined by resistance welding, but it has a larger electrical resistance than copper and is suitable for batteries for large current discharge applications. There was no problem.

  In view of the above circumstances, the present invention provides a thin secondary battery for large current discharge capable of obtaining a high output without being short-circuited by dust, and a battery module using a plurality of the thin secondary batteries for large current discharge. The issue is to provide.

In order to solve the above problems, the first aspect of the present invention is a rectangular shape in which a positive electrode plate and a negative electrode plate are sealed with a film-like container including an aluminum foil as an inner layer and an electrode group in which a positive electrode plate and a negative electrode plate are arranged via a separator A thin-type secondary battery for large current discharge, wherein a positive electrode terminal and a negative electrode terminal are respectively taken out via two strap portions on opposite sides of the film-like container, and the strap portions are respectively connected to the positive electrode terminal and the positive electrode terminal It is integral with the negative electrode terminal and is accommodated in the film-like container, and the positive electrode terminal is made of aluminum or aluminum alloy integral with the strap portion, and nickel is formed on at least one surface except a portion in contact with the electrolytic solution. It is characterized by being subjected to clad processing . The second aspect of the present invention is a rectangular thin film for large current discharge in which a positive electrode plate and a negative electrode plate are sealed with a film container containing an electrode group and an electrolytic solution with an aluminum foil as an inner layer. In the secondary battery, a positive electrode terminal and a negative electrode terminal are respectively taken out via two strap portions on opposite sides of the film-like container, and the strap portions are integrated with the positive electrode terminal and the negative electrode terminal, respectively. Yes, the negative electrode terminal is made of copper or a copper alloy integral with the strap portion, and at least one surface of the portion exposed to the outside of the battery is clad with nickel. It is characterized by.

In the first and second aspects, since the film container is used as the battery container, the battery can be reduced in weight, and the positive electrode terminal and the negative electrode terminal are respectively connected to the two opposite sides of the film container via strap portions. The strap portion is integrated with the positive electrode terminal and the negative electrode terminal, respectively, and is housed in a film-like container. After applying the active material to the current collector, the end face of the current collector is Since the processing for forming is not required, a highly reliable battery without a short circuit due to dust is obtained, and a high output can be obtained because the active material of the entire electrode is effectively used during large current discharge. In the first aspect, the positive electrode terminal is made of aluminum or an aluminum alloy integral with the strap portion, and at least one surface except for the portion that comes into contact with the electrolytic solution is clad with nickel. In the second aspect, the negative electrode terminal is made of copper or a copper alloy integral with the strap part, and at least one surface of the part exposed to the outside of the battery is clad with nickel so that the connection of the terminal is a resistance. It becomes possible by welding, and it is possible to avoid an adverse effect and cost increase due to ultrasonic vibrations, and it is possible to suppress an increase in the internal resistance of the battery to a practically satisfactory level. In the batteries of the first and second aspects, it is very easy to take out the terminals even when using not only a laminated type but also a wound type electrode group.

In the first aspect, if two or more of the positive electrode terminal and the negative electrode terminal are taken out to two opposite sides of the film-like container through a single strap portion, the internal resistance of the battery generated at the terminal is reduced. Can be made. Further, if the strap portion is bent in the shape of a “<” in the vicinity of the joint portion with the electrode group, the volume efficiency of the battery can be increased .

In order to solve the above-described problem, a third aspect of the present invention is a battery module using a plurality of secondary batteries according to the first or second aspect, and one positive electrode of two adjacent secondary batteries. A terminal and the other negative electrode terminal are joined together, and the one positive electrode terminal and the other negative electrode terminal are covered with the film-like container including a joint portion.

In the third aspect, one positive electrode terminal and the other negative electrode terminal of two adjacent secondary batteries are joined, and one positive electrode terminal and the other negative electrode terminal including the joint part are covered with a film container. Therefore, the waste space due to the sealing of the terminal portion can be reduced to about ½, and the two adjacent secondary batteries can be handled as an integral battery connected in series. It is possible to obtain a battery that is still light in weight while ensuring a capacity equivalent to that of a metal cylindrical battery by compensating for the small capacity that comes from the limit of the cup forming depth of the container.

Furthermore, in order to solve the above-mentioned problem, a fourth aspect of the present invention is a battery module using a plurality of secondary batteries according to the first or second aspect, wherein each of the secondary batteries is connected in series two by two. A tandem battery, and the tandem batteries have a connection structure in which two tandem batteries are connected in parallel to form a unit battery, and each of the tandem batteries is arranged in a stacked manner. Has a structure in which plate-shaped metal partition walls are arranged, and metal side plates are arranged on both side end surfaces of the unit battery in the stacking direction in which the tandem batteries are stacked. One side of the tandem battery is bonded with a double-sided adhesive tape, and the other side of the tandem battery has a fixing structure fixed to the partition wall or the side plate with a double-sided adhesive tape.

In the fourth aspect, the capacity can be increased because two tandem batteries are connected in parallel to form a unit battery, and the volume efficiency can be increased because each of the tandem batteries is stacked. Since the plate-shaped metal partition walls are arranged between the unit batteries, and the metal side plates are arranged on both end surfaces in the stacking direction where the tandem batteries of the unit batteries are stacked, each secondary battery is protected from external pressure. The heat accumulated in the stacked tandem batteries can be dissipated to ensure the battery performance of each secondary battery. Furthermore, one side of the tandem battery constituting the unit battery is bonded with a double-sided adhesive tape In addition, since the other surface of the tandem battery is fixed to the partition wall or the side plate with a double-sided adhesive tape, practically sufficient vibration resistance can be obtained even when mounted on a vehicle.

According to the present invention, it is possible to reduce the weight of the battery for using a film-like container in a battery container, takeout City the positive terminal and the negative terminal through respective strap portions opposite the two sides of the film-like container The strap portion is integrated with the positive electrode terminal and the negative electrode terminal, respectively, and is housed in a film-like container, so that an ear is formed on the end face of the current collector after application of the active material to the current collector. This eliminates the need for processing to obtain a highly reliable battery that is free from short circuits due to dust, and the active material of the entire electrode is effectively used during large current discharge, so that high output can be obtained. be able to.

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

1. First, a thin secondary battery for large current discharge (hereinafter referred to as a single battery) used in the battery module of this embodiment will be described.

(Preparation of positive electrode)
Lithium manganate having an average particle diameter of 10 μm, carbon powder having an average particle diameter of 3 μm, and polyvinylidene fluoride (trade name: KF # 120, manufactured by Kureha Chemical Industry Co., Ltd.) as a binder are used as solvents N -Disperse in methyl-2-pyrrolidone and mix to make slurry. This slurry is applied to both sides of an aluminum foil having a thickness of 20 μm as a current collector, dried, and then pressed to be integrated. Then, the width | variety was cut | disconnected to 94 mm and the strip-shaped positive electrode was produced. The height of the coating part was 86 mm, and the height of the plain part (reference numeral 7 in FIG. 1) was 10 mm.

(Preparation of negative electrode)
Carbon particles having an average particle diameter of 20 μm and polyvinylidene fluoride (trade name: KF # 120, manufactured by Kureha Chemical Industry Co., Ltd.) as a binder are put into a solvent N-methyl-2-pyrrolidone and mixed. To prepare a slurry-like solution. This slurry is applied to both sides of a copper foil having a thickness of 10 μm as a current collector, dried, and then pressed to be integrated. Then, the width | variety was cut | disconnected to 96 mm and the strip-shaped negative electrode was produced. The height of the coating part was 88 mm, and the height of the plain part (reference numeral 9 in FIG. 1) was 10 mm.

(Single cell assembly)
A positive electrode was sealed in a bag shape by thermal welding in a separator made of a polyethylene porous film having a thickness of 25 μm and a width of 100 mm. As shown in FIG. 1, 19 positive electrodes and 20 negative electrodes enclosed are alternately stacked such that the arrangement directions of the positive electrode terminal 2 and the negative electrode terminal 3 are up and down, and the positive electrode strap portion 6 integrated with the positive electrode terminal 2 respectively. The negative electrode strap 3 integrated with the negative electrode terminal 3 was ultrasonically welded to the positive electrode current collector and the negative electrode current collector, respectively, and the positive electrode terminal 2 and the negative electrode terminal 3 were derived from the electrode group 4.

  The positive electrode strap 6 is made of aluminum alloy A3003-H12 having a thickness of 0.3 mm, and only the portion of the positive electrode terminal 2 that is not in contact with the electrolyte (the portion exposed inside the battery) has a thickness of 0.1 mm on one side. The nickel was clad. On the other hand, a copper plate C1020-1 / 2H having a thickness of 0.3 mm was used for the negative electrode strap portion 8, and nickel having a thickness of 0.05 mm was clad on both surfaces of only the portion of the negative electrode terminal 3 exposed to the outside of the battery. The thickness of the electrode group 4 is approximately 4.8 mm.

  The electrode group 4 is placed on a laminate film 1 made of PP-aluminum foil-PET molded into a cup shape and having a thickness of about 120 μm, and a planar laminate film 1 ′ having the same configuration is placed thereon and sealed by thermal welding. did. At this time, after injecting a predetermined amount of the electrolytic solution using a syringe from the mating surface that was left without being partly welded, this part was again heat welded and sealed to obtain a single cell. The width | variety of the heat welding part 10 was about 10 mm over the perimeter. Two of the positive electrode terminal 2 and the negative electrode terminal 3 are taken out on two opposing sides of the film-like container via single strap portions 6 and 8, respectively. Note that the capacity of the single cell is about 3.2 Ah.

  As shown in FIG. 1, when the strap portions 6 and 8 are joined so as to be parallel to the laminate film of the battery, the space of the strap portions 6 and 8 impairs the volume efficiency of the battery. The positive electrode strap part 6 integrated with the terminal, the negative electrode strap part 8 integrated with the negative electrode terminal, and the positive electrode terminal 17 and the negative electrode terminal 18, which are bent into a “<” shape at a portion in the vicinity of the joint with the electrode group 4, It is preferable to use it.

2. Production of Tandem Battery Next, a tandem battery in which two (adjacent) unit cells were connected in series and integrated was produced. As shown in FIG. 3, a positive electrode terminal 20 made of aluminum alloy serving as a positive electrode of one unit cell and a negative electrode terminal 19 made of nickel serving as a negative electrode of the other unit cell are integrated in advance by laser welding at a joint 21. The positive electrode terminal 20 and the negative electrode terminal 19 including the joint portion 21 were covered by heat fusion of the laminate film 1 and the laminate film 1 ′ so that the joint portion 21 was substantially at the center. The width of the heat-welded portion was set to 10 mm as with the other sides.

3. Assembly of Battery Module Next, as shown in FIG. 4, four tandem batteries were stacked to produce a battery module. One side of the tandem battery is bonded with a double-sided adhesive tape 23, and one unit battery is constituted by two bonded tandem batteries. In order to improve volumetric efficiency, the heat-sealed portions 22 (see also FIG. 3) at the top and bottom in the longitudinal direction of the tandem battery are bent toward the laminated film 1 formed in a cup shape. The battery module of this embodiment is composed of two unit batteries.

(Connection structure)
Two tandem batteries laminated and laminated with the double-sided adhesive tape 23 are connected in parallel. Accordingly, in each unit battery, two unit cells are connected in series and two unit cells are connected in parallel. The two unit batteries (the positive terminal on one side and the negative terminal on the other side of the central partition wall 24) are connected in series by resistance welding of a bus bar 27 made of nickel. For this reason, the battery module of this embodiment has four unit cells connected in series and two unit cells connected in parallel. The capacity of the battery module is approximately 6.4 Ah because two cells are connected in parallel.

(Arrangement structure)
In addition, as described above, the battery module includes four tandem batteries stacked, and a central partition wall 24 made of an aluminum alloy having a thickness of 0.5 mm is disposed between the unit batteries. In addition, two side plates 25 and 26 made of aluminum alloy having the same thickness as the central partition wall 24 and 0.5 mm in thickness are disposed on both end faces in the stacking direction in which the tandem batteries of the unit batteries are stacked. In other words, the unit battery has an arrangement structure sandwiched between the side plate 25 or 26 and the central partition wall 24.

(Fixed structure)
As described above, one surface of each tandem battery is bonded with the double-sided adhesive tape 23, while the other surface is bonded and fixed to the central partition wall 24 or the side plates 25 and 26 with the double-sided adhesive tape 23. The side plates 25 and 26 and the central partition wall 24 are fixed by bolts 28 that are screwed into bolt holes formed therein.

  Next, the operation and effect of the battery module of this embodiment will be described.

  Since the unit cell of the present embodiment uses a film-like container composed of the laminate films 1 and 1 ′, the battery can be reduced in weight. In addition, since the positive electrode terminal 2 (17) and the negative electrode terminal 3 (18) are taken out from the two opposite sides of the battery container via the strap portions 6 and 8, respectively, the active material is applied to the current collector. Later, processing for forming an ear on the end face of the current collector becomes unnecessary. Therefore, a short circuit generated by dust generated by ear processing does not occur, and a highly reliable battery can be obtained. Furthermore, since the active material of the entire electrode is effectively used during large current discharge, a high output can be obtained.

  Moreover, in the cell of this embodiment, two or more positive electrode terminals 2 (17) and negative electrode terminals 3 (18) are taken out to two opposite sides of the battery container via single strap portions 6 and 8, respectively. Since it did in this way, the internal resistance of the battery produced at a terminal can be reduced. Further, the positive electrode terminal 2 (17) is made of an aluminum alloy that is integral with the positive electrode strap portion 6, and is clad with nickel on at least one surface except a portion that comes into contact with the electrolytic solution. The negative electrode terminal 3 (18) is Because it is made of a copper plate integrated with the negative electrode strap portion 8 and only the portion exposed to the outside of the battery is clad with nickel on both sides, the terminals can be connected by resistance welding, and adverse effects and costs due to ultrasonic vibration can be reduced. While an increase can be avoided, an increase in the internal resistance of the battery can be suppressed to the extent that there is no practical problem.

  Further, in the unit cell of this embodiment, the strap portions 6 and 8 are bent in the shape of “<” in the vicinity of the boundary of the joint portion with the electrode group 4 (a portion in FIG. 2). Efficiency can be increased.

  In the tandem battery of this embodiment, one positive electrode terminal 20 and the other negative electrode terminal 21 of two unit cells are joined, and the one positive electrode terminal 20 and the other negative electrode terminal 21 including the joint portion 21 are laminated. Covered with films 1, 1 '. For this reason, the waste space by sealing of the terminal part can be reduced to about 1/2. In addition, since two unit cells can be handled as an integral tandem battery connected in series, the capacity of the laminate film 1 is compensated for the small capacity due to the limit of the cup molding depth, and the capacity equivalent to that of a metal cylindrical battery is provided. A battery that is still light in weight while being secured can be obtained.

  In the battery module of this embodiment, since the unit battery is configured by connecting two tandem batteries in parallel as described above, the capacity can be increased. Further, since each of the tandem batteries is stacked and arranged, the volume efficiency can be increased, and a central partition wall 24 made of aluminum alloy is arranged between the unit batteries, and both sides of the stacking direction in which the tandem batteries of the unit batteries are stacked. Since the side plates 25 and 26 made of aluminum alloy are arranged on the end face, each unit cell can be protected from external pressure, and heat accumulated in the stacked tandem cells can be radiated to ensure the cell performance of each unit cell. Can do. Furthermore, one side of the tandem battery constituting the unit battery is bonded with a double-sided adhesive tape 23, and the other side of the tandem battery is fixed to the central partition wall 24 or the side plates 25, 26 with the double-sided adhesive tape 23. Vibration resistance sufficient for practical use can be obtained.

(Comparison with conventional technology)
For comparison, each of the unit cells of the present embodiment and a unit cell of a conventional structure (for example, the uncoated portion of the electrode processed into an ear shape) were manufactured and the performance was compared.

  When the DC resistance was compared by discharging at 50 to 200 A corresponding to the current at the start of the electric vehicle, the average cell of this embodiment was 1.91 mΩ, whereas the single cell of the conventional structure was 2.24 mΩ. Thus, it was confirmed that the unit cell of this embodiment clearly has a higher current discharge performance than the unit cell of the conventional structure.

  In addition, in the battery of the conventional structure, 7 out of 100 batteries have micro short-circuits caused by the generation of dust, whereas the single battery of this embodiment does not need to process the ears on the end face of the electrode after coating. There was no short circuit failure.

  Furthermore, the tandem battery according to the present embodiment has a battery module with a conventional structure having a dimension in the longitudinal direction of the battery module by bending the terminal into a "<" shape and integrally forming the terminal of the adjacent battery. Compared to the case where it was used, it could be reduced by about 30 mm, and the volumetric efficiency was improved by about 12%.

  In the present embodiment, the stacked electrode group 4 is exemplified, but the present invention is not limited to this, and the strap portion can be easily formed even when the wound electrode group 12 is used as shown in FIG. Can be welded to assemble the unit cell. In FIG. 5, reference numerals 13 and 14 are a positive electrode uncoated region and a negative electrode uncoated region, respectively.

  Moreover, in this embodiment, although the example which laminates | stacks the tandem battery which connected two unit cells in series was shown, this invention is applicable not only to this but the battery which connected three or more unit cells in series. There is no reason to wait.

  The present invention provides a thin secondary battery for large current discharge capable of obtaining a light output and high output without a short circuit due to dust, and a battery module using a plurality of the thin secondary batteries for large current discharge. Therefore, it contributes to the manufacture or sale of a thin secondary battery for large current discharge, and thus has industrial applicability.

It is the top view and side sectional view which show an example of the thin secondary battery for large current discharge used for the battery module of embodiment which can apply this invention. It is the top view and side sectional view which show the other example of the thin secondary battery for large current discharge used for the battery module of embodiment which can apply this invention. It is a top view of the terminal junction part vicinity of the tandem battery used for the battery module of embodiment. It is a disassembled perspective view of the battery module of an embodiment. It is the top view, side sectional view, and front sectional view showing other examples of the thin secondary battery for large current discharge to which the present invention can be applied.

Explanation of symbols

1 Laminate film (part of film container)
1 'Laminate film (part of film container)
2, 17, 20 Positive terminal 3, 18, 19 Negative terminal 4, 12 Electrode group 6 Positive strap part (strap part)
8 Negative strap (strap)
10, 22 Welding part 21 Joint part 23 Double-sided adhesive tape 24 Central partition (partition)
25, 26 Side plate

Claims (6)

A rectangular secondary battery for large current discharge sealed with a film container containing an electrode group in which a positive electrode plate and a negative electrode plate are disposed via a separator and an electrolytic solution as an inner layer, and a positive electrode terminal negative terminal and is withdrawn through a respective strap portions opposite the two sides of the film-like container, wherein the strap portion is integral with each said positive terminal and said negative terminal, it is accommodated in the film-like container The positive electrode terminal is made of aluminum or an aluminum alloy integral with the strap portion, and at least one surface excluding a portion in contact with the electrolytic solution is clad with nickel . A rectangular secondary battery for large current discharge sealed with a film container containing an electrode group in which a positive electrode plate and a negative electrode plate are disposed via a separator and an electrolytic solution as an inner layer, and a positive electrode terminal A negative electrode terminal is taken out through two strap sides facing each other of the film-like container, and the strap part is integral with the positive electrode terminal and the negative electrode terminal, respectively, and is accommodated in the film-like container. And the negative electrode terminal is made of copper or a copper alloy integral with the strap portion, and at least one surface of a portion exposed to the outside of the battery is clad with nickel. Said positive terminal and said negative terminal, respectively according to claim 1 or claim 2, characterized in that taken out two or more two opposing sides of the film-like container through a single of the strap portion Secondary battery.   3. The secondary battery according to claim 1, wherein the strap portion is bent into a “<” shape near a joint portion with the electrode group. 4. In the battery module using a plurality of secondary battery according to any one of claims 1 to 4, and one of the positive terminal of the two secondary batteries adjacent the other of the negative terminal is joined The battery module is characterized in that the one positive electrode terminal and the other negative electrode terminal are covered with the film-like container including a joint portion. In the battery module using a plurality of secondary battery according to any one of claims 1 to 4, wherein the secondary battery is composed tandem cell are respectively series connected two by two, the tandem cell It has a connection structure in which two unit batteries are connected in parallel to each other, each of the tandem batteries is arranged in a stack, and a plate-shaped metal partition is arranged between the unit batteries, The unit battery has an arrangement structure in which metal side plates are arranged on both end faces in the stacking direction where the tandem batteries are stacked, and one side of the tandem battery constituting the unit battery is bonded with a double-sided adhesive tape The battery module is characterized in that the other surface of the tandem battery has a fixing structure fixed to the partition wall or the side plate with a double-sided adhesive tape.

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