JP4581481B2 - Battery module manufacturing method - Google Patents

Description

  The present invention relates to a manufacturing method for manufacturing a battery module by combining a plurality of secondary batteries such as lithium batteries.

  Conventionally, secondary batteries such as lithium batteries are often used. For example, there is a secondary battery that is manufactured by winding a positive electrode plate and a negative electrode plate with a separator sheet between them, flattening them and enclosing them in a case, and injecting an electrolyte into the case. In such a secondary battery, since the electrolytic solution does not sufficiently permeate the separator sheet immediately after injection of the electrolytic solution, the battery performance is low. Therefore, in general, a predetermined leaving time is provided for the penetration and diffusion of the electrolytic solution. On the other hand, in order to shorten this standing time and to obtain a large capacity battery, it has been proposed to pressurize in the stacking direction of the electrode plates after injection of the electrolyte (see, for example, Patent Document 1).

  This secondary battery may be used alone, but a battery module in which a plurality of secondary batteries are combined is often used for automobiles that require high voltage and large current. For example, as shown in FIG. 1, there is a battery module 1 in which flat secondary batteries are stacked with their planar portions stacked and the outside is constrained. In this battery module 1, a plurality (six in this figure) of secondary batteries 10 are stacked in the same direction, and the top and bottom are sandwiched between end plates 11. Further, the end plates 11 are fixed to each other by a tension plate 12 and a rivet 13.

In general, when such a battery module 1 is manufactured, the secondary battery 10 stacked and sandwiched between the end plates 11 is restrained by applying a load in the stacking direction. In other words, the tension plate 12 is attached by the rivets 13 while being pressed with a press from the outside of the end plates 11 at both ends and a load is applied. This is performed for the purpose of helping the penetration and diffusion of the electrolyte solution and preventing the individual secondary batteries 10 from falling off due to the restraint by the tension plate 12 as described in the above document. Hereinafter, the load applied when the tension plate 12 is attached is referred to as a restraint load.
JP 2002-151156 A (page 4, FIG. 5)

  However, in the battery module manufactured by the above-described conventional manufacturing method, the load applied to the secondary battery 10 may gradually decrease with the passage of time after assembly, so-called “load loss” may occur. The reason for this is considered to be that plastic deformation elements in the battery cell, for example, a minute gap between the electrode plate and the separator sheet or a gap of the separator itself are gradually compressed and deformed. In particular, this plastic deformation is promoted by heat generated during charging and discharging. As a result, there is a problem that the surface condition of the electrode becomes non-uniform due to the load reduction, and the battery performance may become unstable.

  The present invention has been made to solve the problems of the conventional battery module manufacturing method described above. That is, an object of the present invention is to provide a battery module manufacturing method capable of manufacturing a battery module having a stable performance over a long period of time by preventing load loss due to passage of time or use.

  The battery module manufacturing method of the present invention made for the purpose of solving this problem is a battery module manufacturing method in which a flat battery is sandwiched between end plates, and the flat battery and end plate are laminated, A load is repeatedly applied to the laminated body in the thickness direction, and then the laminated body is restrained.

  Or the manufacturing method of the battery module of this invention is a manufacturing method of the battery module formed by laminating | stacking a flat battery, Comprising: A several flat battery is laminated | stacked, and load is repeatedly applied to the thickness direction with respect to the laminated body. And then the stack may be restrained.

  According to the battery module manufacturing method of the present invention, a flat battery and an end plate are laminated, or a plurality of flat batteries are laminated to form a battery module. At that time, since the load is repeatedly applied to the laminated body in the thickness direction, the plastic deformation element inside the flat battery is efficiently plastically deformed. Therefore, when the laminate is subsequently restrained, the plastic deformation that occurs after restraint is slight, and load loss due to passage of time or use is prevented. Thereby, it is a manufacturing method of the battery module which can manufacture the battery module which has the performance stable over a long period of time.

Furthermore, in the present invention, it is desirable to restrain the laminate by applying a load to the laminate and to change the load on the laminate between a smaller load and a larger load at the time of repeated loading. .
By doing so, the deformation of the plastic deformation element proceeds rapidly by a load larger than the load at the time of restraint, and the internal homogenization proceeds by changing to a smaller load. Therefore, a battery module with stable performance can be manufactured efficiently in a short time.

  According to the method for manufacturing a battery module of the present invention, it is possible to manufacture a battery module having a stable performance over a long period of time by preventing load loss due to passage of time or use.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the best mode for embodying the present invention will be described in detail with reference to the accompanying drawings. The present embodiment is a manufacturing method for manufacturing a battery module configured by stacking a plurality of secondary batteries.

  As shown in FIG. 1, the battery module 1 manufactured by the manufacturing method of this embodiment is formed by stacking a plurality of flat secondary batteries 10 and restraining them by an end plate 11, a tension plate 12, and a rivet 13. . Here, the secondary battery 10 to be used may have a can structure enclosed in a can case or a laminate structure enclosed in a laminate film outer package. The end plate 11 is made of a highly rigid material such as cast iron. The tension plate 12 is formed of a thin steel plate or the like, and the rivet 13 is attached to the side surface of the end plate 11. Further, instead of the rivet 13, it may be bolted.

  Here, in the case of the battery module 1 using the secondary battery 10 having a can structure, the corner portions of the can case are pressed against each other when a restraining load is applied by stacking them, and there is a possibility that a sufficient load is not applied to the central portion. . In order to avoid this point and to cool the heat at the time of charging / discharging of the secondary battery 10, the cooling plate 14 is inserted as shown in FIG. Each cooling plate 14 is formed slightly smaller than the planar shape of the secondary battery 10. In the battery module 1 shown in this figure, a plurality of cooling plates 14 are inserted between the secondary batteries 10 and between the secondary battery 10 and the end plates 11 on both sides.

  Next, a method for manufacturing the battery module 1 of the present embodiment will be described. First, each single secondary battery 10 is manufactured by a general manufacturing method. Here, it is assumed that the battery module 1 uses a can-structure secondary battery 10. Next, the required number of secondary batteries 10 are stacked with the cooling plate 14 interposed therebetween, and the end plates 11 are arranged on both sides thereof. Next, the stacked secondary battery 10 and the entire end plate 11 are pressed in the stacking direction by a press machine. Since there is the cooling plate 14, each secondary battery 10 is deformed as shown in FIG. 2, and a sufficient load is applied to the central portion of the secondary battery 10. In this figure, for ease of understanding, the deformation amount of the secondary battery 10 is shown large, but the actual deformation amount is small. For example, the deformation amount of the secondary battery 10 having an original thickness of 15 to 20 mm is about several mm from the plane including the corners of the can case.

  Further, before attaching the tension plate 12, a repeated load is applied as shown in FIG. Here, a load approximately twice the restraining load is repeated five times. That is, firstly, a load twice as large as the restraining load is applied, and then the load is set to zero four times. Then, after applying the load about twice the restraint load for the fifth time, the load is lowered to the restraint load and held, and the tension plate 12 is attached with the rivet 13 in this state. This completes the battery module 1. It is advisable to perform the repeated loading once in about 10 seconds each.

  Next, the restraint load will be described. The restraining load has an appropriate range to optimize the battery characteristics. An example of this relationship is shown in the graph of FIG. In this figure, the relationship between the restraining load and the battery characteristics (in this case, the internal resistance) is shown for the battery module 1 in which six secondary batteries 10 having a can structure with a plane of about 10 cm square are stacked. As shown in this figure, in order for the internal resistance to be less than or equal to a predetermined value, the restraining load needs to be within a predetermined range. If the load is too small, the electrode surface becomes non-uniform due to insufficient pressing and the internal resistance increases, which is not preferable. On the other hand, if the load is too large, the battery reaction is hindered by excessive pressing and the internal resistance increases, which is not preferable. In the battery module 1 shown in this example, an appropriate restraining load is in the range of 1 to 9 kN.

  Next, the effectiveness of repeated loads will be described. The inventor repeatedly applied a load to one of the laminate-type secondary batteries and examined the change in thickness. For example, when a load of up to 10 kN was repeatedly applied to a secondary battery called a 308 type cell, the thickness changed as shown in FIG. The thickness before applying the load was about 16 mm, and the first load was compressed to about 14.2 mm as shown in the graph d1. Thereafter, when the load was returned to 0, it returned to about 15.1 mm, which is the starting point of the second graph d2. At this time, it is considered that the elastic element of the secondary battery is restored and the plastic deformation element undergoes some plastic deformation.

  Further, by repeating the load, the graph d3 changed for the third time, the graph d4 for the fourth time, and the graph d5 for the fifth time changed. As can be seen from the results, the difference from the pre-load was remarkable after the first 2 or 3 loads, and the difference gradually disappeared. This seems to be because the plastic deformation of the plastic deformation element was almost completed by only five loads, and only the elastic element was obtained. From this result, it was found that with this secondary battery, the number of repetitions of the load was insufficient at 3 times, and the effect was hardly improved even when it was repeated more than 5 times. Therefore, the number of repetitions is 4 times or more, preferably 5 times. In this respect, the secondary battery 10 having a can structure is almost the same.

  From the above, it was found that in the battery module 1 in which six secondary batteries 10 having a can of about 10 cm square are stacked, the appropriate repeated load is as follows. First, the load is increased to about 10 kN and held for 7 to 8 seconds, and then the load is returned to 0 kN. Repeat this 4 times. After raising the load to about 10 kN for the fifth time, the load is returned to about 5 kN and held, and the tension plate 12 is attached with the rivet 13 in this state. As a result of carrying out a predetermined environmental test on the battery module 1 manufactured in this way, the load loss was 10% or less, and good restraint characteristics were obtained.

  Thus, by repeatedly applying a load, for example, plastic deformation proceeds more effectively in a shorter time than when a load of 10 kN is continuously applied for a long time. Thereby, the internal state of the secondary battery 10 is made more uniform. In addition, by doing so, it is not necessary to apply a large load such as 20 kN or 30 kN, it is possible to implement with simple equipment, and there is no possibility of damaging the secondary battery itself.

  As described in detail above, according to the manufacturing method of the battery module 1 of the present embodiment, since the load is repeatedly applied, the plastic deformation element in the secondary battery 10 is almost completely canceled, and the subsequent occurrence of creep occurs. Absent. Accordingly, the battery module 1 has a stable performance over a long period of time by preventing load loss due to passage of time or use.

In addition, this form is only a mere illustration and does not limit this invention at all. Therefore, the present invention can naturally be improved and modified in various ways without departing from the gist thereof.
For example, the magnitude of the repeated load, the number of repetitions, the restraint load, and the like are not limited to the above numerical values, and may be selected appropriately according to the size and configuration of each battery module 1.
Further, for example, the configuration of the battery module 1 shown in the above embodiment is one example, and the size and case material of the single secondary battery 10 to be used, and the number of the secondary batteries 10 incorporated in the battery module 1. Etc. are not limited to this. In the case of a battery module using a secondary battery having a laminated structure instead of a can structure, the cooling plate may not be provided.
Moreover, in said form, the secondary battery 10 by which the electrode body was press-fitted in the inside of the can case in the manufacture stage is used. For this reason, the electrode body receives a slight load from the can case only by being mounted on the case, but is not limited to such a secondary battery 10.

It is a perspective view which shows the outline of the battery module of this form. It is sectional drawing which shows the outline of the battery module of a can structure. It is a graph which shows a repeated load. It is a graph which shows the relationship between a restraint load and a battery characteristic. It is a graph which shows the relationship between a repeated load and the thickness of a secondary battery.

Explanation of symbols

1 Battery module 10 Secondary battery (flat battery)
11 End plate

Claims (3)

In a battery module manufacturing method in which a flat battery is sandwiched between end plates,
Laminating a flat battery and end plate,
A load is repeatedly applied to the laminate in the thickness direction,
Thereafter, the laminated body is restrained. In a method for manufacturing a battery module in which flat batteries are stacked,
Laminating multiple flat batteries,
A load is repeatedly applied to the laminate in the thickness direction,
Thereafter, the laminated body is restrained. In the manufacturing method of the battery module according to claim 1 or 2,
The stack is restrained by applying a load to the stack,
A battery module manufacturing method characterized by changing a load on a laminate between a smaller load and a larger load at the time of repetitive loading.

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