JP6660569B2 - Manufacturing method of assembled battery - Google Patents

Description

  The present invention relates to a method of manufacturing an assembled battery in which a plurality of chargeable / dischargeable cells (rechargeable batteries) are arranged in a predetermined direction and are restrained while a load is applied in the arrangement direction.

  A lithium ion secondary battery, nickel hydride battery, other secondary battery, or a storage element such as a capacitor, which is lightweight and has a high energy density, is a unit cell, and an assembled battery formed by connecting a plurality of the unit cells in series can provide high output. The power source is preferably used as a power source for a vehicle or a power source for a personal computer and a portable terminal. For example, Patent Literature 1 discloses an example of an assembled battery for a vehicle, in which a plurality of cells of the same shape including a lithium ion secondary battery are arranged, and a positive electrode terminal and a negative electrode terminal provided on each cell are connected in series. Thus, an assembled battery configured as described above is disclosed.

JP 2014-137889 A

  By the way, in a battery pack mounted on a vehicle such as an automobile, the mounting space is limited, and it is assumed that the battery is used in a state where vibration is generated. Thus, an assembled battery in which a large number of cells are arranged and restrained (that is, each cell is fixed to each other) is constructed. At the time of such restraint, a considerable load is applied to the individual cells constituting the assembled battery.

According to the knowledge obtained by the present inventor, when a plurality of cells are arranged at the time of manufacturing an assembled battery and restrained by applying a load in the arrangement direction, the container of the cell (that is, the electrode body is housed inside) by the load. Distortion or deformation in the load direction occurs on the outer body that performs the load. Therefore, the thickness of each unit cell in the arrangement direction in a state where a load is applied in a predetermined arrangement direction and restrained depends on the thickness of the electrode body inside the container.
However, in general, the thickness of the electrode body has some variation (irregularity). When a large number of cells having the electrode bodies having a variation in thickness as described above are arranged and constrained in the stacking direction, the thickness of each cell in the constrained state varies in the arrangement direction, and the thickness of the cells varies. Is accumulated, the length of the obtained assembled battery in the arrangement direction varies. Such a variation in the length (outer size) of the battery pack in the arrangement direction is such that when the battery pack is mounted on a vehicle or the like, the battery pack cannot be accommodated in a prepared mounting space or is contained in the mounting space. In some cases, such a problem may occur that an extra gap remains. Alternatively, there may be a disadvantage in design such as increasing the tolerance of the external dimensions guarantee value of the assembled battery to allow variations in the external size (that is, providing an extra space around the assembled battery). Therefore, it is desirable to reduce the variation in the length in the arrangement direction when manufacturing the assembled battery.

  The present invention has been developed in order to solve the above-mentioned problems relating to the construction of a conventional battery pack. The purpose of the present invention is to reduce the unevenness of the shape of the electrode body housed inside each cell constituting the battery pack. Precise size as set in advance by suppressing variations in the length of the battery pack in the arrangement direction that may occur due to the cause (particularly, the length dimension of the battery pack in the arrangement direction of the cells constituting the battery pack) It is an object of the present invention to provide a method capable of manufacturing an assembled battery having the following.

  According to the present invention, there is provided a method for manufacturing an assembled battery in which a predetermined number of cells are arranged in a predetermined direction and restrained in a state where a load is applied in the arrangement direction. The method includes a step of preparing a plurality of unit cells each including an electrode body including a positive electrode and a negative electrode, and a container accommodating the electrode body. In addition, the method includes a step of classifying the plurality of unit cells into a plurality of thickness ranks according to the thickness in the arrangement direction of the electrode bodies housed in the unit cells. In addition, the method includes a step of arranging a predetermined number of the cells in the arrangement direction and constraining the cells in a state where a load is applied in the arrangement direction to form an assembled battery. Here, the step of constructing the assembled battery is performed by selecting and combining a predetermined number of cells used for constructing the assembled battery from two or more thickness ranks among the plurality of classified thickness ranks. Is performed so that the length in the arrangement direction conforms to a predetermined length set in advance.

  In the present specification, the term "unit cell" is a term indicating individual power storage elements that can be connected in series with each other to form a battery pack, and includes batteries and capacitors having various compositions unless otherwise limited. Further, the “secondary battery” generally refers to a battery that can be repeatedly charged, and includes a so-called storage battery such as a lithium ion secondary battery and a nickel hydride battery. The storage element constituting the lithium ion secondary battery is a typical example included in the “unit cell” here, and a lithium ion secondary battery module including a plurality of such unit cells is disclosed herein. This is one typical example of a "battery pack". According to the technology disclosed herein, a predetermined number of cells (for example, lithium ion secondary batteries) having a flat outer shape are arranged in a direction in which the flat surfaces are stacked (stacking direction), and electrode terminals of those cells are arranged. Can be particularly preferably applied to an assembled battery in which are connected in series or in parallel.

  According to the assembled battery manufacturing method having the above-described configuration, the predetermined number of cells used for constructing the assembled battery offset the variation in the thickness of the electrode body in each of the cells (and the variation in the thickness of each of the cells in the restrained state). Since the length of the battery pack in the arrangement direction is selected and combined so as to conform to the specified length, the correct size (particularly, the length of the battery pack relative to the arrangement direction of the cells constituting the battery pack) (Size). Therefore, according to the manufacturing method of the present invention, it is possible to provide an assembled battery for vehicle use and other uses with good external dimensions (length in the arrangement direction) and excellent mountability.

In a preferred embodiment of the battery pack manufacturing method disclosed herein, the electrode body includes a positive electrode sheet having a positive electrode active material layer on a long positive electrode current collector, and a negative electrode active on a long negative electrode current collector. It is a flat wound electrode body formed by winding a negative electrode sheet having a material layer.
The thickness of the wound electrode body tends to be uneven depending on the degree and state of winding. Therefore, in a unit cell including such a wound electrode body, the thickness of the unit cell is likely to be non-uniform at the time of restraint, but in the manufacturing method of the above configuration, the length in the arrangement direction of the assembled battery conforms to the reference length. By selecting and combining cells having different thickness ranks, it is possible to manufacture an assembled battery in which the length in the arrangement direction of the assembled battery accurately matches the specified value (specified length). For this reason, according to the manufacturing method of this aspect, it is possible to manufacture an assembled battery including a plurality of unit cells each including the wound electrode body as a component and having excellent mountability.

  In a preferred aspect of the assembled battery manufacturing method disclosed herein, in the step of preparing a plurality of cells, a positive electrode active material layer having a length corresponding to a plurality of cells is provided on the positive electrode current collector. A positive electrode sheet base material continuously formed in the longitudinal direction, and a negative electrode sheet in which a negative electrode active material layer having a length corresponding to a plurality of unit cells is continuously formed in the longitudinal direction on the negative electrode current collector. A process of forming a plurality of wound electrode bodies by cutting the base material at predetermined lengths while overlapping and winding the base material is included. According to such a configuration, while a plurality of wound electrode bodies can be efficiently formed, the shape of the obtained wound electrode body tends to be irregular. However, according to the manufacturing method of the above configuration, the wound electrode body has an exact size as set in advance by suppressing the variation in the length in the arrangement direction of the battery pack which may be caused due to the irregular shape of the wound electrode body. An assembled battery can be manufactured. For this reason, according to the manufacturing method of this aspect, an assembled battery having a good external size and good mountability can be efficiently manufactured.

  In a preferred embodiment of the battery pack manufacturing method disclosed herein, the number of cells constituting the battery pack is 30 or more (preferably 50 or more). As the number of cells increases, it is more advantageous to increase the capacity of the assembled battery, but the unevenness of the shape of the electrode body tends to cause a variation in the length of the assembled battery in the arrangement direction. However, according to the manufacturing method of the above configuration, despite the variation in the thickness of the electrode bodies in a large number of cells, the variation in the thickness of the electrode bodies in each of the cells is offset to set the length in the arrangement direction to the specified value. It is possible to manufacture an assembled battery that precisely matches the (specified length). For this reason, according to the manufacturing method of this aspect, it is possible to manufacture an assembled battery having high capacity and good mountability.

It is a perspective view showing typically the composition of the battery pack concerning one embodiment. It is a side view showing typically composition of an assembled battery concerning one embodiment. It is a front view showing typically the wound electrode body concerning one embodiment. It is a figure showing typically the state in the container of the unit cell concerning one embodiment. It is explanatory drawing which shows typically the manufacturing method of the wound electrode body which concerns on one Embodiment. It is explanatory drawing which shows typically the manufacturing method of the wound electrode body which concerns on one Embodiment. 4 is a graph showing the relationship between the thickness of an electrode body and the thickness of a unit cell in a constrained state.

Hereinafter, preferred embodiments of the present invention will be described. It should be noted that matters other than matters specifically mentioned in this specification (for example, the structure of a unit cell as a component of a battery pack) and matters necessary for carrying out the present invention (for example, the structure of a positive electrode, a negative electrode, and a separator) And the manufacturing method, the method of restraining the unit cells, and the method of mounting the assembled battery on the vehicle) can be grasped as design matters of those skilled in the art based on the conventional technology in the field. The present invention can be implemented based on the contents disclosed in this specification and common technical knowledge in the field.
The assembled battery according to the present invention can be suitably used as a power source for a motor (electric motor) mounted on a vehicle such as an automobile. Accordingly, the present invention provides a vehicle (typically, a vehicle, particularly a vehicle including an electric motor such as a hybrid vehicle, an electric vehicle, or a fuel cell vehicle) including the battery pack as a power supply.

  A battery assembly manufactured by applying the technology disclosed herein is a battery assembly in which cells (typically cells having a flat outer shape) are arranged and constrained in the arrangement direction (stacking direction). A battery may be used, and the configuration of each cell is not particularly limited. Examples of single cells suitable for application of the present invention include secondary batteries such as nickel-metal hydride batteries and electric double layer capacitors. In particular, the present invention can be preferably employed as a method for manufacturing a battery pack using a lithium ion secondary battery as a unit cell. Since a lithium ion secondary battery is a secondary battery capable of realizing high output with high energy density, a high-performance assembled battery, particularly an assembled battery (battery module) for mounting on a vehicle can be constructed. Further, the present invention is suitable as a method of manufacturing a battery pack in which a plurality of the arranged cells are connected in series or in parallel (typically in series).

  Although not intended to limit the present invention in particular, the following description is made by way of example of a case where a flat lithium ion secondary battery is used as a unit cell and a plurality of the unit cells are connected in series to manufacture an assembled battery. The invention will be described in detail. Further, in the drawings below, members / parts having the same function are denoted by the same reference numerals, and redundant description may be omitted or simplified.

  A cell used as a constituent element of the battery pack manufactured in the embodiment described below is typically a predetermined battery constituent material (the active material of each of the positive and negative electrodes, similar to the cell provided in the conventional battery pack). , A current collector for each of the positive and negative electrodes, a separator, etc.), and a container for accommodating the electrode body and an appropriate electrolyte.

  As an example, as shown in FIGS. 1 and 2, a plurality of battery packs 10 disclosed herein (typically 10 or more (eg, 10 to 100), preferably 30 or more, more preferably 50 or more) (More preferably, 60 or more). The unit cell 12 includes a container 14 having a shape (a box shape in the present embodiment) capable of accommodating a flat wound electrode body described later.

The container 14 is provided with a positive electrode terminal 15 electrically connected to the positive electrode of the wound electrode body and a negative electrode terminal 16 electrically connected to the negative electrode of the electrode body. As shown in the drawing, one positive electrode terminal 15 and the other negative electrode terminal 16 are electrically connected by a connector 17 between adjacent unit cells 12. By thus connecting the cells 12 in series, the assembled battery 10 having a desired voltage is constructed.
Note that a safety valve or the like for releasing gas generated inside the container may be provided in these containers 14 in the same manner as in a conventional cell container. Since the configuration of the container 14 itself does not characterize the present invention, a detailed description is omitted.

  The material of the container 14 is not particularly limited as long as it is the same as that used in a conventional unit cell. From the viewpoint of being suitable for mounting on a vehicle or the like, a material that is relatively lightweight is preferable as the material for implementing the present invention. For example, a container made of a metal (for example, aluminum or steel), a container made of a synthetic resin (for example, a polyolefin resin such as polyethylene or polypropylene, or a high melting point resin such as polyethylene terephthalate, polytetrafluoroethylene, or a polyamide resin) is preferably used. Can be used. Alternatively, a container made of a resin film conventionally used as an outer package of a battery, for example, an outer (protective) layer composed of a high melting point resin (eg, a high melting point resin such as polyethylene terephthalate, polytetrafluoroethylene, or a polyamide resin); A barrier layer (that is, a layer capable of blocking gas and moisture) composed of a metal foil (for example, aluminum or steel) and a heat-fusible resin (a resin having a relatively low melting point, for example, ethylene vinyl acetate or polyethylene, A container made of a laminated film having a three-layer structure with an adhesive layer made of a polyolefin resin such as polypropylene) may be used. The container 14 according to the present embodiment is made of, for example, aluminum.

  As shown in FIGS. 1 and 2, the plurality of single cells 12 are turned one by one so that the positive terminals 15 and the negative terminals 16 are alternately arranged at a constant interval, and the wide surface of the container 14 is turned over. 14A (that is, a surface corresponding to a flat surface of a later-described wound electrode body 30 accommodated in the container 14) are arranged in a direction facing each other. Further, between the unit cells 12 to be arranged and on both outsides in the unit cell arrangement direction, cooling plates 11 of a predetermined shape are arranged in close contact with the wide surface 14A of the container 14. The cooling plate 11 functions as a heat radiating member for efficiently dissipating heat generated in each unit cell during use, and introduces a cooling fluid (typically air) between the unit cells 12. It has a possible frame shape (e.g., an uneven shape as viewed from the side like a comb shown in the figure). A cooling plate 11 made of metal having good thermal conductivity or made of lightweight and hard polypropylene or other synthetic resin is preferable.

  A pair of end plates 18 and 19 are further arranged outside the cooling plates 11 arranged on both outsides of the unit cells 12 and the cooling plates 11 arranged as described above. Then, the entire unit cell group and the end plates 18 and 19 are stacked by a plurality of tightening restraint bands 21 attached so as to bridge (connect) the both end plates 18 and 19 in the stacking direction of the restrained body 24. It is restrained in a state where a load is applied in the (array direction).

Then, the entire unit cell group, the cooling plate 11 and the end plates 18 and 19 (hereinafter also referred to as a “constrained body”) arranged in the stacking direction of the unit cells 12 form both end plates 18 and 19. The constrained body is constrained by a prescribed constraining pressure P in the stacking direction of the constrained body by a tightening constraining band 21 attached so as to be cross-linked. More specifically, as shown in FIG. 2, by tightening and fixing the end of the restraining band 21 to the end plate 18 with a screw 22, the restrained body 24 is moved to a predetermined restraining pressure P (for example, a container). 14 is applied so that the surface pressure applied to the wall surface 14 is about 2 × 10 ^{6 to} 5 × 10 ⁶ Pa). The length (in the example shown in FIGS. 1 and 2, the length between the outer ends of the end plates 18 and 19) of the battery pack 10 restrained by the specified restraint pressure P is the specified length LT. Here, in the present specification, the “specified length LT” refers to the length of the battery pack along a direction in which a predetermined number of cells constituting the battery pack are arranged, and is typically allowed including a tolerance. It can be understood as a range of length. For example, when the specified length LT is Xcm, it can be grasped as a range of X ± α including the tolerance ± α.

In the manufacturing method according to the present example, the assembled battery 10 having the above configuration is efficiently manufactured so that the specified length LT is stably realized as follows. Hereinafter, the manufacturing method will be described with reference to the schematic diagrams shown in FIGS.
First, a process of preparing a plurality of cells 12 used for constructing the assembled battery 10 will be described. The cell 12 includes an electrode body 30 including a positive electrode and a negative electrode. In this embodiment, the electrode body 30 includes a positive electrode sheet 32 having a positive electrode active material layer on a long positive electrode current collector, a negative electrode sheet 34 having a negative electrode active material layer on a long negative electrode current collector, and a separator. 36 is a flat wound electrode body 30 formed by winding.

The materials and members constituting the wound electrode body 30 may be the same as those of a conventional lithium ion battery, and are not particularly limited. For example, the positive electrode sheet 32 can be formed by providing a positive electrode active material layer for a lithium ion battery on a long positive electrode current collector. As the positive electrode current collector, an aluminum foil (this embodiment) or another metal foil suitable for the positive electrode is preferably used. As the positive electrode active material, one kind or two or more kinds of substances conventionally used for lithium ion batteries can be used without particular limitation. Preferred examples include lithium transition metal oxides such as LiMn ₂ O ₄ , LiCoO ₂ , and LiNiO ₂ . For example, an aluminum foil having a length of about 2 m to 4 m (for example, 2.7 m), a width of about 8 cm to 12 cm (for example, 10 cm), and a thickness of about 5 μm to 20 μm (for example, 15 μm) is used as a current collector, and a positive electrode is formed in a predetermined region on the surface thereof. By forming the active material layer, a suitable positive electrode sheet 32 can be obtained.

  On the other hand, the negative electrode sheet 34 can be formed by providing a negative electrode active material layer for a lithium ion battery on a long negative electrode current collector. As the negative electrode current collector, a copper foil (this embodiment) or another metal foil suitable for the negative electrode is preferably used. As the negative electrode active material, one or more types of materials conventionally used in lithium ion batteries can be used without any particular limitation. Preferable examples include carbon-based materials such as graphite carbon and amorphous carbon, and lithium transition metal oxides and transition metal nitrides. For example, a copper foil having a length of about 2 m to 4 m (for example, 2.9 m), a width of about 8 cm to 12 cm (for example, 10 cm), and a thickness of about 5 μm to 20 μm (for example, 10 μm) is used, and a negative electrode active material layer is formed in a predetermined region on the surface. By forming, a suitable negative electrode sheet 34 is obtained.

  Further, as a suitable separator sheet 36 used between the positive and negative electrode sheets 32 and 34, a sheet made of a porous polyolefin resin is exemplified. For example, a porous separator sheet made of synthetic resin (for example, made of polyolefin such as polyethylene) having a length of about 2 m to 4 m (for example, 3.1 m), a width of about 8 cm to 12 cm (for example, 11 cm), and a thickness of about 5 μm to 30 μm (for example, 25 μm) can be obtained. It can be suitably used.

  When constructing the wound electrode body 30, similarly to the wound electrode body of a normal lithium ion secondary battery, the positive electrode sheet 32, the first separator 36, the negative electrode sheet 34, and the second separator 36 Are laminated in this order, and the positive electrode sheet 32 and the negative electrode sheet 34 are wound while being slightly shifted. Then, the flattened wound electrode body 30 is manufactured by crushing the obtained wound body from the side direction and crushing it.

In a preferred embodiment, when manufacturing the wound electrode body 30, a positive electrode sheet is manufactured by forming a positive electrode active material layer on a long positive electrode current collector. For example, as shown in FIG. 5, a composition obtained by dispersing a material for forming a positive electrode active material containing a positive electrode active material as a main component in an appropriate dispersion medium is applied to one end of the positive electrode current collector in the longitudinal direction (application start point). Is applied to the other end (application end point) and dried, and is pressed between rollers 68, so as to correspond to a plurality (for example, 100 to 500) of unit cells 12 on the positive electrode current collector. A positive electrode sheet base material 32a in which a positive electrode active material layer having a predetermined length is formed continuously in the longitudinal direction is produced.
Similarly, a composition obtained by dispersing a material for forming a negative electrode active material containing a negative electrode active material as a main component in an appropriate dispersion medium is applied from one end (application start point) to the other end (application start point) in the longitudinal direction of the negative electrode current collector. After coating and drying at the coating end point, and pressing it between rollers, a length corresponding to a plurality (for example, 100 to 500) of the unit cells 12 is formed on the long negative electrode current collector. The negative electrode active material layer is continuously formed in the longitudinal direction to produce a negative electrode sheet base material 34a.

  Then, as shown in FIG. 6, a positive electrode roll 33 obtained by winding the positive electrode sheet base material 32a into a roll, a negative electrode roll 35 obtained by winding the negative electrode sheet base material 34a into a roll, and a separator roll (of the unit cell 12) A separator sheet preform 36a having a length corresponding to a plurality of pieces is wound into a roll) 37), and the positive electrode sheet preform 32a, the negative electrode sheet preform 32a are taken from each of the rolls 33, 35, 37. The material 34a and the two separator sheet base materials 36a are pulled out. Then, a positive electrode sheet base material 32a, a first separator sheet base material 36a, a negative electrode sheet base material 34a, and a second separator sheet base material 36a are stacked in this order and wound up by a predetermined amount, and each is wound up at the end of winding up. The wound electrode body 30 is manufactured by cutting at a terminal position so as to have a predetermined length (length of one unit cell), and winding the wound end portion cut at the terminal position. By repeating this process, a plurality of (for example, 100 to 500) wound electrode bodies 30 can be continuously formed from one roll 33, 35, 37.

As shown in FIG. 3, the obtained flat wound electrode body 30 was wound with a slight shift in the lateral direction with respect to the winding direction of the wound electrode body 30, resulting in a positive electrode sheet 32 and a negative electrode sheet. Part of the ends of the sheet 34 are wound core portions 31 (that is, portions where the positive electrode active material layer forming portion of the positive electrode sheet 32, the negative electrode active material layer forming portion of the negative electrode sheet 34, and the separator sheet 36 are densely wound). ) Protrudes outward. A positive electrode lead terminal 32B and a negative electrode lead terminal 34B are attached to the positive electrode side protruding portion (that is, a portion where the positive electrode active material layer is not formed) 32A and the negative electrode side protruding portion (that is, a portion where the negative electrode active material layer is not formed) 34A. The lead terminals 32B and 34B are electrically connected to the above-described positive terminal 15 and negative terminal 16, respectively. Then, the wound electrode body 30 is accommodated in the container 14 with the wound axis turned sideways as shown in FIG. 4, and a suitable supporting salt (for example, a lithium salt such as LiPF ₆ ) is put in an appropriate amount. The unit cell 12 is constructed by injecting and sealing a non-aqueous electrolyte (electrolyte solution) such as a mixed solvent (for example, a mass ratio of 1: 1) of diethyl carbonate and ethylene carbonate (for example, having a concentration of 1 M). Thereafter, by repeating charging or discharging of each unit cell 12 once or a plurality of times, the assembled unit cell can be activated and brought into a practically usable state.

Here, according to the knowledge obtained by the present inventor, as described above, when a plurality of cells 12 are arranged in the manufacture of the assembled battery 10 and constrained in the arrangement direction, the container 14 is flexible. The container 14 may be distorted or deformed in the load direction. Therefore, the thickness of each of the cells 12 in the arrangement direction in a state where a load is applied in a predetermined arrangement direction and constrained is more dependent on the thickness of the electrode body 30 inside the container 14 than the outer shape of the container 14 when not constrained. I do.
However, in general, the thickness of the electrode body 30 has some variation (irregularity) due to a variation in conditions during manufacturing.
As described above, when a large number of cells 12 each having the electrode body 30 having a variation in thickness are arranged and constrained in the stacking direction, as shown in FIG. Variations occur in the thickness of the unit cells 12 in the arrangement direction, and as a result of accumulating the dispersion in the thicknesses of the unit cells 12, the length of the obtained assembled battery 10 in the arrangement direction varies. FIG. 7 is a graph showing a relationship between the thickness of the electrode body and the thickness (when restrained) of a cell including the electrode body.

  In the manufacturing method disclosed herein, in order to converge the variation in the length in the arrangement direction of the assembled batteries 10 which may be caused due to the irregular shape of the electrode body 30, the electrode in each cell 12 is converged. The assembled battery 10 is constructed by combining a plurality of unit cells 12 in which variations in the thickness of the body 30 are offset.

That is, the step of preparing a plurality of the cells 12 described above includes measuring the thickness T in the arrangement direction of the electrode bodies 30 housed in each of the cells 12.
Then, according to the thickness (measured value) T of the electrode body 30 in the arrangement direction, each of the plurality of unit cells 12 is classified into a plurality of thickness ranks having different thickness ranges (ranges) (classification step). For example, based on the graph of FIG. 7, the electrode body 30 in which the thickness T of the electrode body 30 in the arrangement direction is in the range of the target electrode body thickness A ± 0.2 mm (A−0.2 mm ≦ T ≦ A + 0.2 mm) , The thickness T of the electrode body 30 in the arrangement direction of the electrode body 30 in the range of A + 0.2 mm <T ≦ A + 0.6 mm in the thickness rank 2 whose representative value is “A” is represented by “A + 0.4 mm”. The thickness T of the electrode body 30 in the arrangement direction of the electrode body 30 in the range of A−0.6 mm ≦ T <A−0.2 mm is “A−0.4 mm” as a representative value. To the thickness rank 3. A predetermined number of the unit cells 12 used for constructing the assembled battery 10 are defined by a predetermined length in which the length in the arrangement direction of the assembled battery 10 is set in advance from two or more thickness ranks among the thickness ranks 1 to 3. Select a combination that matches LT.

  In a preferred embodiment, a predetermined number of the cells 12 used in the construction of the assembled battery 10 are combined from the thickness ranks 1 to 3 such that the sum of the representative values of the thickness ranks to which the respective cells belong becomes the specified electrode body length RT. To select. Specifically, when selecting and combining X cells of thickness rank 1, Y cells of thickness rank 2, and Z cells of thickness rank 3, “A + 0.4 mm” × X + A × Y + The combination is selected such that the total value of “A−0.4 mm” × Z matches the specified electrode body length RT. The specified electrode body length RT is typically calculated from “target electrode body thickness A × predetermined number”, and is defined as a restricted electrode body having a total thickness of the specified electrode body length RT and other components constituting the assembled battery. It is set such that a battery pack having a specified length LT in the arrangement direction is configured by constraining the body 24 with a specified constraining pressure P.

  The predetermined number of the cells 12 selected above are alternately arranged with the cooling plates 11 and end plates 18 and 19 are arranged at both ends to construct a constrained body. Then, as shown in FIG. 2, the ends of the restraining band 21 are tightened and fixed to the end plates 18 and 19 with screws 22 so that the restrained body 24 is restrained so that a predetermined restraining pressure P is applied in the arrangement direction. To construct the assembled battery 10 (construction step of the assembled battery).

Here, according to the manufacturing method of the present embodiment, the predetermined number of the cells 12 to be used are not changed by the electrode bodies 30 in each of the cells 12, regardless of the variation in the thickness of the electrode bodies 30 in each of the cells 12. Of two or more thickness ranks 1 to 3 so that the length in the arrangement direction of the battery pack 10 conforms to the specified length LT by offsetting the variation in the thickness of the battery pack (and the variation in the thickness of each cell in the constrained state). 3 are selected and combined. As a result, variations in the thickness of the individual electrode bodies are offset, and the assembled battery 10 having a length in the arrangement direction satisfying the specified length LT can be manufactured.
Therefore, as in the case of a conventional assembled battery, when the length in the arrangement direction of the assembled batteries is varied due to the irregular shape of the electrode body in each unit cell, the mounting space prepared in advance is used. It is possible to avoid inconveniences such as that the assembled battery cannot be accommodated or that an extra gap remains when the assembled battery is accommodated in the mounting space. In addition, since it is not necessary to increase the tolerance of the guaranteed outer dimensions of the assembled battery to allow variation in the outer size of the assembled battery (that is, to provide an extra space around the assembled battery), the mounting space of the assembled battery 10 is reduced. It can be designed smaller than before. Further, for example, a method of using only the unit cells 12 corresponding to the thickness rank 2 for manufacturing the assembled battery 10 and excluding the unit cells 12 corresponding to the thickness rank 1 (thick) or the thickness rank 3 (thin) as defective products. In contrast, according to the manufacturing method of the present embodiment, the defective rate of the unit cell 12 can be reduced, and the manufacturing cost of the assembled battery 10 can be reduced.

A preferable application target of the technology disclosed herein is an assembled battery including a wound electrode body 30 formed using the above-described positive electrode sheet base material 32a and negative electrode sheet base material 34a. While such a wound electrode body 30 can be formed efficiently, its shape tends to be irregular. More specifically, in the positive electrode sheet base material 32a (FIG. 5) in which a positive electrode active material layer having a length corresponding to a plurality of unit cells is continuously formed on the positive electrode current collector, the positive electrode current collector The thickness of the positive electrode active material layer tends to gradually decrease from one end (application start point) to the other end (application end point) in the longitudinal direction. Similarly, in a negative electrode sheet base material 34a in which a negative electrode active material layer having a length corresponding to a plurality of unit cells 12 is continuously formed on the negative electrode current collector, one end in the longitudinal direction of the negative electrode current collector The thickness of the negative electrode active material layer tends to gradually decrease from the part (application start point) to the other end (application end point). Therefore, as shown in FIG. 6, when a plurality of wound electrode bodies 30 are continuously formed using the positive electrode sheet base material 32a and the negative electrode sheet base material 34a, the positive electrode sheet base material 32a and the negative electrode sheet base material 34a become Since there is the same thickness variation, both thick portions (or thin portions) are combined with each other, and the difference in thickness of the wound electrode body 30 tends to increase. In the initial stage of winding, the relatively thick wound electrode body 30 tends to solidify, and in the late stage of winding, the relatively thin wound electrode body 30 tends to solidify.
Then, when an assembled battery is constructed by combining the unit cells having the relatively thick wound electrode body 30 (or the relatively thin wound electrode body 30) solidified in such a forming order, the length of the assembled battery in the arrangement direction is increased. In particular, the variation in the length tends to be large.
However, according to this aspect, an assembled battery having an exact size as set in advance by suppressing variations in the length of the assembled battery in the arrangement direction, which can be caused by the irregular shape of the wound electrode body. Can be manufactured. For this reason, according to the manufacturing method of this aspect, an assembled battery having a good external size and good mountability can be efficiently manufactured.

  In the above-described embodiment, the case where the plurality of unit cells 12 are classified into three thickness ranks 1 to 3 according to the thickness of the electrode body 30 is illustrated, but the number of classified thickness ranks is not limited thereto. For example, the number of thickness ranks may be two or more, three or more, or five or more. The upper limit of the number of thickness ranks is not particularly limited as long as the above-described effects can be obtained, but may be, for example, 10 or less.

  In the above-described embodiment, the thickness of the electrode body 30 in the arrangement direction is measured, and the thickness is classified into a plurality of thickness ranks based on the measured value. However, the criterion for classification is not limited to the actually measured value. For example, the thickness of the positive electrode sheet 32 and the negative electrode sheet 34 used for manufacturing the electrode body 30 may be measured, and the thickness of the electrode body 30 may be estimated from the sheet thickness. Since the thickness of the electrode body 30 depends on the thicknesses of the positive electrode sheet 32 and the negative electrode sheet 34, the thickness of the electrode body 30 may be estimated from the sheet thickness, and may be classified into a plurality of thickness ranks based on the estimated value. However, as in the above-described embodiment, when the thickness is classified into a plurality of thickness ranks based on the actually measured values of the thickness of the electrode body 30, the above classification can be performed accurately, and the specified length LT in the arrangement direction is satisfied. The assembled battery 10 can be manufactured with high accuracy.

  Further, in the above-described embodiment, in the step of preparing a plurality of single cells 12, the case where all the thicknesses (the total number) of the individual electrode bodies 30 are measured is exemplified. However, the number of the electrode bodies 30 for measuring the thickness is as follows. It is not limited to this. For example, the thickness of each electrode body 30 may be grasped by sampling extraction for each lot. For example, when a plurality of wound electrode bodies 30 are continuously formed using one positive electrode sheet base material 32a and one negative electrode sheet base material 34a as described above, the distribution of the thickness of the wound electrode body 30 is irregular ( In other words, the relatively thick wound electrode body 30 tends to solidify in the early stage of winding, and the relatively thin wound electrode body 30 tends to solidify in the late winding stage. Therefore, in the step of preparing a plurality of single cells 12, even if the thickness of each of the individual electrode bodies 30 is not entirely measured, sampling and extraction of each of the plurality of wound electrode bodies in the order of formation can be performed by sampling each of the lots. The approximate thickness can be grasped, and the lot can be classified into a plurality of thickness ranks. Such an embodiment may be included in the battery pack manufacturing method disclosed herein.

As described above, the preferred embodiment of the battery pack manufacturing method of the present invention has been described in detail, but the present invention is not intended to be limited to the specific embodiment.
For example, in the above-described embodiment, the electrode body 30 is housed in the container 14 in a direction in which the winding axis of the wound electrode body 30 is in the width direction of the unit cell 12 (the thickness direction in FIG. 2). The electrode body 30 may be arranged so that the axis of rotation is in the height direction of the cell 12 (vertical direction in FIG. 2). Instead of the wound electrode body 30, a laminated electrode body formed by alternately laminating a plurality of positive electrode sheets and a plurality of negative electrode sheets together with a separator sheet may be used. Even in a laminated electrode body, there may be variations (unevenness) in thickness due to fluctuations in conditions during manufacturing and the like. The invention disclosed herein relates to a unit cell (particularly, a wound type or a stacked type electrode unit, in which the electrode unit having various configurations is accommodated in a container, This can be preferably applied to an assembled battery in which a plurality of cells (unit cells housed in a container overlapping in the direction) are arranged in the stacking direction.

In addition, the type of unit cell that constitutes the assembled battery is not limited to the above-described lithium ion secondary battery, and batteries of various contents having different electrode body constituent materials and electrolytes, for example, a lithium secondary battery using lithium metal or a lithium alloy as a negative electrode It may be a battery, a nickel hydride battery, a nickel cadmium battery, or an electric double layer capacitor.
Although the assembled battery 10 shown in FIG. 1 has a simple configuration for the purpose of explaining the present invention, various modifications and additions of equipment can be made as long as the configuration and effects of the present invention are not impaired. It is clear to the trader. For example, when the battery pack is mounted on a vehicle such as an automobile, an exterior cover for protecting a main part (a unit cell group or the like) of the battery pack, a component for fixing the battery pack to a predetermined portion of the vehicle, a plurality of battery packs ( Components for interconnecting the battery modules may be provided, but the presence or absence of such a device does not affect the technical scope of the present invention.

Reference Signs List 10 Battery pack 11 Cooling plate 12 Single cell 14 Container 15 Positive electrode terminal 16 Negative terminal 17 Connector 18, 19 End plate 21 Restricted band 30 Wound electrode body 32 Positive sheet 34 Negative sheet 36 Separator

Claims (3)

A method for manufacturing an assembled battery in which a predetermined number of cells are arranged in a predetermined direction and restrained in a state where a load is applied in the arrangement direction,
An electrode body including a positive electrode and a negative electrode, and a step of preparing a plurality of single cells including a container that accommodates the electrode body and a flexible container that can be strained or deformed in a direction in which the load is applied ,
A step of classifying the plurality of cells into a plurality of thickness ranks according to the thickness in the arrangement direction of the electrode bodies housed in the cells;
Constructing a battery pack by arranging a predetermined number of the cells in the arrangement direction and restraining the cells in a state where a load is applied in the arrangement direction;
,
The step of constructing the assembled battery is performed by selecting and combining a predetermined number of cells used for constructing the assembled battery from two or more thickness ranks of the classified plurality of thickness ranks, thereby forming the arrangement of the assembled batteries. A method for manufacturing an assembled battery, wherein the length in the direction is adjusted to conform to a predetermined length set in advance.   The electrode body has a flat shape formed by winding a positive electrode sheet having a positive electrode active material layer on a long positive electrode current collector and a negative electrode sheet having a negative electrode active material layer on a long negative electrode current collector. The production method according to claim 1, wherein the electrode is a wound electrode body. In the step of preparing a plurality of the single cells, a positive electrode sheet base material in which a positive electrode active material layer having a length corresponding to a plurality of the single cells is continuously formed in the longitudinal direction on the positive electrode current collector, On the negative electrode current collector, a negative electrode active material layer having a length corresponding to a plurality of unit cells is superposed and wound on a negative electrode sheet base material formed continuously in the longitudinal direction. The method according to claim 2, further comprising a step of forming a plurality of wound electrode bodies by cutting into pieces.