JP2015198024A - Method for manufacturing cell stack - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing cell stack, capable of more simply manufacturing a cell stack including a cell holder adhering to a battery cell.SOLUTION: A method for manufacturing a cell stack including a plurality of battery cells stacked therein includes the steps of: preparing a resin-made cell holder in a thermally expanded state, the cell holder including one or more housing spaces formed therein for housing each battery cell; housing the battery cells in each housing space; and cooling the cell holder to be shrunk, the cell holder housing the battery cells therein.

Description

  The present invention relates to a method for manufacturing a cell stack in which a plurality of battery cells are stacked.

  Conventionally, a cell stack configured by stacking a plurality of battery cells is known. In the cell stack, a plurality of holding frames 114 for holding a plurality of battery cells in a stacked state are used. FIG. 6 is a diagram illustrating an example of a conventional cell stack 110. As shown in FIG. 6, the conventional cell stack 110 includes a substantially flat holding frame 114 disposed between the battery cells 112 and a stacked body of the end plate 116, the holding frame 114, and the battery cells 112 in a stacked state. It was composed of a restraining band 120 or the like for restraining.

JP 2011-222490 A

  However, in such a conventional cell stack 110, it is necessary to prepare a large number of holding frames 114 in accordance with the number of battery cells 112, resulting in an increase in the number of parts. In addition, since the large number of holding frames 114 and battery cells 112 are all completely separate parts, there has been a problem such as an increase in work man-hours for stacking. Moreover, since all are separate parts, the battery cells are likely to be misaligned due to errors during assembly.

  Patent Document 1 discloses a battery holder that integrally includes a surface pressure member interposed between battery cells and a connecting member that connects adjacent surface pressure members. According to such a battery holder, the number of parts can be greatly reduced.

  However, in Patent Document 1, in order to facilitate the assembly of the battery holder, the gap between the surface pressure members is made larger than the thickness of the battery cell. As a result, there is a gap between the surface pressure member and the battery cell after assembly, and foreign matter such as dust may be mixed from the gap. Of course, in Patent Document 1, in order to eliminate this gap, the connecting member is configured to be elastically deformable, and when a compressive force in the stacking direction is applied to the battery holder, the gap between the surface pressure members becomes narrower, A device has been devised such that the pressure member and the battery cell are brought into close contact with each other. However, since special parts and processes are required to eliminate the gap between the surface pressure member and the battery cell, it is very troublesome.

  Accordingly, an object of the present invention is to provide a method for manufacturing a cell stack that can more easily manufacture a cell stack in which a cell holder is in close contact with a battery cell.

  The cell stack manufacturing method of the present invention is a cell stack manufacturing method in which a plurality of battery cells are stacked, and is a resin cell holder in which at least one storage space for storing each battery cell is formed, The step of preparing the cell holder in an expanded state, the step of storing the battery cell in each storage space, and the step of cooling and contracting the cell holder storing the battery cell are provided.

  In a preferred aspect, the storage space of the cell holder is designed to be larger than the battery cell during thermal expansion and to be the same as or slightly smaller than the battery cell when contracted by cooling. The wall surface to be formed is in close contact with the accommodated battery cell during cooling. In another preferred embodiment, a cell holder immediately after resin molding is prepared as the cell holder expanded by the heat.

  According to the present invention, since the battery cell is inserted into the thermally expanded cell holder and then the cell holder is contracted, a cell stack in which the cell holder is in close contact with the battery cell can be more easily manufactured.

It is a disassembled perspective view of the cell stack manufactured by embodiment of this invention. It is a flowchart which shows the flow of manufacture of a cell stack. (A) is a schematic cross-sectional view of the cell stack during heating, and (b) is a schematic cross-sectional view of the cell stack during cooling. (A) is a schematic longitudinal cross-sectional view of a cell stack when the internal pressure of a battery cell is normal, (b) is a schematic longitudinal cross-sectional view of a cell stack when the internal pressure of a battery cell rises. (A) is a schematic longitudinal cross-sectional view of the conventional cell stack when the internal pressure of the battery cell is normal, and (b) is a schematic vertical cross-sectional view of the conventional cell stack when the internal pressure of the battery cell is slightly increased. (C) is a schematic longitudinal cross-sectional view of the conventional cell stack when the internal pressure of a battery cell further rises. It is a perspective view of the conventional cell stack.

  Hereinafter, the manufacturing method of the cell stack 10 which is embodiment of this invention is demonstrated with reference to drawings. First, the cell stack 10 manufactured in the present embodiment will be briefly described with reference to FIG. FIG. 1 is an exploded perspective view of a cell stack 10 in the present embodiment.

  The cell stack 10 is formed by stacking a plurality of battery cells 12 in the thickness direction, and is used, for example, as a power source for an electric vehicle such as a hybrid car that runs with both an engine and a motor or an electric vehicle that runs with only a motor. .

  The cell stack 10 includes a plurality of battery cells 12 and a cell holder 14 that holds the battery cells 12. The battery cell 12 has a substantially flat plate shape and is stacked in the thickness direction so that its wide surfaces (hereinafter, this surface is referred to as “front surface or back surface”) face each other. As the battery cell 12, for example, a nickel hydrogen secondary battery, a lithium ion secondary battery, an organic radical battery, or the like is used. Each battery cell 12 is a flat rectangular parallelepiped whose outer peripheral surface is covered with an outer case of an electrically insulating resin. From the upper surface of each battery cell 12, the two terminal parts 18 which consist of a positive electrode terminal and a negative electrode terminal protrude. The stacked battery cells 12 are connected in series by a bus bar (not shown) connecting the terminal portions 18.

  The cell holder 14 is a member that holds the battery cells 12 in an insulated state while laminating the plurality of battery cells 12. The cell holder 14 used in the present embodiment is made of an insulating thermoplastic resin and is manufactured by a known technique such as injection molding. As shown in FIG. 1, the cell holder 14 has a substantially box shape in which a plurality of accommodation spaces 20 in which the battery cells 12 are accommodated are formed. In FIG. 1, only three accommodation spaces 20 are provided for ease of viewing, but the number of the accommodation spaces 20 is not particularly limited, and may be one or more. However, in order to facilitate the assembly of the battery cells 12, the number of the accommodation spaces 20 is desirably the same as the number of the battery cells 12.

  The upper surface of the cell holder 14 is completely open to accept insertion of the battery cell 12, and a wall that covers the battery cell 12 is formed on the other surface. On both sides of the accommodation space 20 in the stacking direction, partition plates 22 interposed between the battery cells 12 are formed. In FIG. 1, the partition plate 22 has a simple form in which a substantially rectangular convex portion is formed, but actually, the partition plate 22 has a cooling air passage on the front surface and the back surface. A plurality of grooves are formed.

  The cell holder 14 has a cross-sectional shape of the accommodation space 20 that is larger than the battery cell 12 when softened and expanded by heating, and is equal to or slightly more than the battery cell 12 when cured and reduced by cooling. It is designed to be large.

  Next, a flow of manufacturing the cell stack 10 will be described with reference to FIG. FIG. 2 is a flowchart showing a flow of manufacturing the cell stack 10. When manufacturing the cell stack 10, first, a thermoplastic resin as a material is injected into a mold for the cell holder 14 (S10).

  Subsequently, the injected thermoplastic resin is cooled together with the mold until the specified take-out temperature is reached (S12). This take-out temperature is the same as the take-out temperature applied during normal injection molding, and is a temperature before the thermoplastic resin is completely cured, although it is a temperature at which the thermoplastic resin can maintain its shape. The take-out temperature is desirably equal to or higher than the glass transition temperature of the thermoplastic resin, and may be, for example, about 50 ° C. to 60 ° C., depending on the type of thermoplastic resin.

  If it can be cooled to the specified removal temperature, the mold is opened and the cell holder 14 is removed (S14). At this time, the cell holder 14 is softened by molding heat, and the accommodation space 20 is larger than the battery cell 12 due to thermal expansion. In this state, the battery cell 12 is inserted into each accommodation space 20 of the cell holder 14 (S16). FIG. 3A is a schematic cross-sectional view of the cell stack 10 at this time. As shown in FIG. 3A, when the battery holder 14 is taken out of the mold, the accommodating portion of the cell holder 14 is slightly larger than the battery cell 12 due to thermal expansion. Therefore, each battery cell 12 can be easily inserted into the accommodation space 20.

  Subsequently, in this state, the cell holder 14 is cooled to room temperature, and the cell holder 14 is completely cured (S18). During this cooling process, the cell holder 14 gradually contracts. Finally, as shown in FIG. 3B, the battery cell 12 is in close contact with the battery cell 12 and cured in a shape along the outer shape of the battery cell 12. If complete cooling is possible, the manufacture of the cell stack 10 is completed. If necessary, end plates are arranged at both ends of the cell stack 10, or a restraining band or the like is attached to the cell stack 10 to apply a compressive force in the stacking direction, and a restraining load is applied to each battery stack. Also good.

  In the cell stack 10 formed in the above procedure, the cell holder 14 and the battery cell 12 are in close contact with each other so that the battery cell 12 does not fall even if it is turned upside down. Therefore, it is possible to effectively prevent foreign matters such as dust from entering through the gap between the cell holder 14 and the battery cell 12.

  Moreover, since the cell holder 14 of this embodiment is reduced and hardened according to the shape of the battery cell 12, the tolerance of the battery cell 12 can be easily absorbed. That is, it is desirable that the battery cell 12 is originally manufactured with a dimension as designed, but in reality, an error within a tolerance occurs. In order to absorb the error within the tolerance, the conventional cell stack 110 has a configuration as shown in FIG. In this conventional cell stack 110, the holding frames 114 arranged between the battery cells 112 are all configured separately. As a result, the holding frame 114 can be easily disposed between the battery cells 112 without any problem even if the thickness of the battery cells 112 varies. However, in such a conventional configuration, the number of parts is increased, and the work of assembling the battery cell 112 to the holding frame 114 is very complicated. Further, since all the holding frames 114 are separate, positional deviations in the plane direction perpendicular to the stacking direction between the holding frames 114 are likely to occur, and as a result, positional deviations in the plane direction perpendicular to the stacking direction between the battery cells 112 are caused. It was easy to occur.

  In order to prevent such positional deviation between the battery cells 112, it is effective to use a cell holder in which all the holding frames 114 are connected and the positional relationship is fixed. However, if the positional relationship of the holding frame 114 is fixed, there arises a problem that the tolerance of the battery cell 112 cannot be absorbed this time.

  In this embodiment, since the cell holder 14 in which the partition plates 22 arranged between the battery cells 12 are connected to each other is used, it is possible to effectively prevent the positional deviation between the battery cells 12. Moreover, since the cell holder 14 of this embodiment is reduced and hardened according to the shape of the battery cell 12, the tolerance of the battery cell 12 can be easily absorbed.

  In addition, if a plurality of battery cells 12 can be handled in an integrated state before inserting the battery cells 12 into the insertion space, the plurality of battery cells 12 can be inserted into the plurality of insertion spaces at once. It is also possible to do. As a result, the labor required for assembling the battery cell 12 can be greatly reduced as compared with the conventional technique. That is, in the conventional cell stack 110 (see FIG. 6), since the holding frames 114 are all configured separately, it is necessary to stack the battery cells 112 and the holding frames 114 one by one in order. There were many man-hours. On the other hand, in this embodiment, all the partition plates 22 are connected, and a plurality of insertion spaces into which the battery cells 12 are inserted are formed in advance. Therefore, it is possible to insert a plurality of battery cells 12 into a plurality of insertion spaces in one insertion operation, and the number of assembling operations can be greatly reduced. Moreover, in this embodiment, since the some partition plate 22 is connected and integrated, the number of parts can be reduced significantly compared with the conventional cell stack 110. FIG.

  Further, in the present embodiment, since the cell holder 14 is in close contact with all the battery cells 12 without gaps, it is possible to effectively suppress the rupture of the battery cell 12 when the internal pressure of the battery cell 12 increases. This will be described with reference to FIGS. FIG. 4 is a schematic longitudinal sectional view of the cell stack 10 of the present embodiment, where (a) shows a case where the internal pressure of the battery cell 12 is normal, and (b) shows a case where the internal pressure of the battery cell 12 has increased. Show. 5 is a schematic longitudinal sectional view of a conventional cell stack 110, where (a) shows a case where the internal pressure of the battery cell 112 is normal, and (b) shows a case where the internal pressure of the battery cell 112 slightly increases. (C) shows a case where the internal pressure of the battery cell 112 is further increased.

  Generally, the battery cell 12 which is a secondary battery may expand due to an increase in internal pressure due to the generation of gas when the internal temperature rises. If the expansion amount of the battery cell 12 is excessive, problems such as rupture of the battery cell 12 are caused. The conventional cell stack 110 has a problem that the battery cells are likely to expand.

  That is, as shown in FIG. 5A, in the conventional cell stack 110, the holding frame 114 is interposed between the battery cells 112. A compressive force in the stacking direction is applied to the cell stack 110 by a restraining band 120 or the like so that each holding frame 114 is in close contact with the battery cell 112. However, it is difficult to completely eliminate the gap between the battery cell 112 and the holding frame 114 only with such a mechanical force, and a minute gap is generated between the battery cell 112 and the holding frame 114.

  As shown in FIG. 5 (b), when the internal pressure of the battery cell 112 rises and the battery cell 112 tries to expand, there is nothing that hinders the expansion of the battery cell 112 in the range of this gap. The battery cell 112 easily expands and deforms.

  When the internal pressure of the battery cell 112 further increases and the battery cell 112 expands further, the holding frames 114 on both sides of the battery cell 112 receive the expansion pressure from the battery cell 12 as shown in FIG. Become. At this time, if there is no gap between the holding frame 114 and the adjacent battery cell 112, the holding frame 114 exhibits a reaction force to inhibit the expansion of the battery cell 112. However, if there is a gap between the holding frame 114 and the adjacent battery cell 112, the holding frame 114 that has received the expansion pressure moves in a direction to reduce the gap, and the expansion of the battery cell 112 further proceeds. Will do.

  As described above, if even a small gap is generated between each battery cell 112 and the holding frame 114, the expansion of one battery cell 112 proceeds relatively easily, and the battery cell 112 easily expands. In some cases, it will burst.

  On the other hand, according to the manufacturing method of this embodiment, as described above, the battery cell 12 and the cell holder 14 are completely in close contact with each other. Therefore, as shown in FIG. 4, even if the internal pressure of the battery cell 12 rises and tries to expand, the expansion of the battery cell 12 is inhibited by the partition plate 22. As a result, the deformation amount of the battery cell 12 can be greatly suppressed as compared with the prior art, and as a result, the battery cell 12 can be effectively prevented from bursting.

  In the present embodiment, the battery cell 12 is inserted immediately after the cell holder 14 is molded. However, if the insertion space of the cell holder 14 is thermally expanded to a size larger than that of the battery cell 12, the battery cell is at another timing. 12 may be inserted. For example, the battery cell 12 may be inserted after the cell holder 14 that has been completely cooled and completely cured after injection molding is heated to a temperature at which it expands and softens. With this configuration, the manufacturing site of the cell holder 14 and the insertion site of the battery cell 12 can be separated.

  In the present embodiment, the number of the accommodation spaces 20 of the cell holder 14 is the number of the battery cells 12, but the number of the accommodation spaces 20 is not particularly limited as long as it is 1 or more. When the storage space 20 uses a single cell holder 14, cell holders 14 are prepared for the number of battery cells 12, and a plurality of cell holders 14 may be connected by a restraining band or the like. Even in this case, after inserting the battery cell 12 into the cell holder 14 that has been heated and expanded in the same manner as in the present embodiment, if the cell holder 14 is cooled and contracted, each battery cell 12 comes into close contact with the corresponding cell holder 14. . As a result, it is possible to obtain effects such as preventing foreign matter from entering the gap between the cell holder 14 and the battery cell 12 and absorbing the tolerance of the battery cell 12.

  Moreover, in this embodiment, although the cell holder 14 is made into the box shape which completely covers the five surfaces of the battery cell 12, it is good also as a different shape suitably according to the capability calculated | required by the cell stack 10. FIG. For example, a vent hole or the like may be formed on the side surface of the cell holder 14.

  10, 110 cell stack, 12, 112 battery cell, 14 cell holder, 18 terminal part, 20 accommodating space, 22 partition plate, 114 holding frame, 116 end plate, 120 restraining band.

Claims (3)

A method of manufacturing a cell stack in which a plurality of battery cells are stacked,
A step of preparing a cell holder made of resin in which one or more accommodation spaces for accommodating each battery cell are formed, the cell holder being expanded by heat;
Accommodating the battery cell in each accommodation space;
Cooling and shrinking the cell holder containing the battery cells;
A cell stack manufacturing method comprising: A method of manufacturing a cell stack according to claim 1,
The storage space of the cell holder is larger than the battery cell at the time of thermal expansion, and is designed to be the same or slightly smaller than the battery cell when contracted by cooling,
The wall surface forming the accommodation space is in close contact with the accommodated battery cell during cooling.
A method of manufacturing a cell stack. A method for manufacturing a cell stack according to claim 1 or 2,
A method of manufacturing a cell stack, comprising preparing a cell holder immediately after resin molding as a cell holder in a state of being expanded by heat.