JP6696728B2 - Capacitor module manufacturing method - Google Patents

Description

  The present invention relates to a method for manufacturing a capacitor module in which a plurality of lithium-ion capacitors are arranged and restrained by a restraining member.

  2. Description of the Related Art Conventionally, there has been known an electricity storage module in which a plurality of electricity storage elements (secondary batteries and capacitors) are arranged side by side and sandwiched by restraining members. For example, in Patent Document 1, a plurality of power storage elements arranged side by side in a predetermined direction, a plurality of partition plates respectively disposed between adjacent power storage elements, and these power storage elements and partition plates on both sides in the predetermined direction. There is disclosed a power storage device including an end plate and a band for restraining the power storage device (see FIG. 1 of Patent Document 1).

JP, 2014-35985, A

By the way, a lithium ion capacitor (LiC: Lithium-ion capacitor) may be used as a storage element. Lithium-ion capacitors have low resistance compared to lithium-ion secondary batteries (LiB), and have a large capacity compared to electric double-layer capacitors (EDLC). Have.
A lithium ion capacitor (hereinafter, also simply referred to as “cell”) is in a state where no ions are adsorbed on the positive electrode active material (lithium ions or anions such as PF ₆ ⁻ are not adsorbed) (for example, cell voltage = 3.0 V). ) Is the most electrically stable. Therefore, if the cell voltage is left higher or lower than this voltage (hereinafter, also referred to as “stable voltage”), the cell voltage gradually approaches the stable voltage.

  Further, in the lithium-ion capacitor, when the cell voltage is higher than the stable voltage, anions are adsorbed on the positive electrode active material, the positive electrode active material layer becomes thicker, and the electrode body becomes thicker. In a lithium-ion capacitor, the ratio of the negative electrode capacity to the positive electrode capacity is very large. Therefore, at SOC 0% to 100%, the expansion / contraction amount of the negative electrode active material layer can be ignored compared to the expansion / contraction amount of the positive electrode active material layer. Because it is so small. Therefore, in the cell, the electrode body thickness and the cell thickness are the smallest when the cell voltage is the stable voltage, and the electrode body thickness and the cell thickness increase as the cell voltage becomes higher than the stable voltage.

  On the other hand, when the cell voltage is lower than the stable voltage, lithium ions are released from the negative electrode active material and the negative electrode active material layer becomes slightly thinner, but lithium ions are adsorbed to the positive electrode active material and the positive electrode active material layer becomes thicker. The electrode body becomes thicker. As described above, in the lithium ion capacitor, the expansion and contraction amount of the negative electrode active material layer is negligibly smaller than the expansion and contraction amount of the positive electrode active material layer at SOC 0% to 100%. Therefore, when the cell voltage is the stable voltage, the electrode body thickness and the cell thickness are the smallest, and the lower the cell voltage is below the stable voltage, the thicker the electrode body thickness and the cell thickness.

  As described above, the lithium-ion capacitor has a characteristic that the thickness of the electrode body changes depending on the cell voltage and the cell thickness changes accordingly. Therefore, when manufacturing a capacitor module in which a plurality of cells are constrained by a constraining member (hereinafter, also simply referred to as “module”), when constraining cells by using cells in a state in which the cell voltage is different from the stable voltage, Depending on the value of the cell voltage, such as when the cell voltage is stabilized after restraint, the cell thickness may be thinner than when restrained, and the restraint load may be lower than when restrained. Then, when the restraint load is much lower than that at the beginning of restraint, for example, when a large impact is applied to the module, the cells may be displaced or fall out, which is not preferable.

  The present invention has been made in view of the above circumstances, and a method for manufacturing a capacitor module that suppresses the occurrence of a state in which a restraining load for restraining a lithium ion capacitor becomes lower than the initial restraint regardless of the value of a cell voltage. The purpose is to provide.

One embodiment of the present invention for solving the above problems is a plurality of lithium batteries which are arranged side by side in the thickness direction and have a rectangular parallelepiped shape having an electrode body inside, in which the cell thickness changes due to a change in the electrode body thickness of the electrode body. A method of manufacturing a capacitor module, comprising: an ion capacitor ; and a restraining member that pushes and restrains these lithium ion capacitors in the thickness direction to push each of the electrode bodies. The thickness minimum voltage Vcmin (V) that minimizes the cell thickness is higher than the cell usage lower limit voltage Vce (V) and lower than the cell usage upper limit voltage Vcf (V), and the cell voltage Vc (V) A method of manufacturing a capacitor module, comprising: a restraining step of arranging the lithium ion capacitors adjusted to the minimum voltage Vcmin (V) in the thickness direction and pressing the restraint member in the thickness direction to restrain the lithium ion capacitors.

  According to this capacitor module manufacturing method, in the restraining step, the lithium ion capacitors whose cell voltage Vc is adjusted to the minimum thickness voltage Vcmin (for example, Vcmin = OCV3.0 (V)) are arranged in the thickness direction, and the restraining member is arranged. Restrain with. As a result, each cell is pressed and restrained in the state in which the cell thickness is the thinnest, so that the restraint load applied to each cell after restraint is the load at the time of restraint regardless of the cell voltage Vc of each cell. Or it will be larger. Therefore, in this module, even if the cell voltage Vc changes due to charging / discharging or leaving, the restraint load for restraining each cell can be suppressed from being lower than the initial restraint regardless of the value of the cell voltage Vc. In addition, it is preferable that the restraint by the restraint member is a fixed-size restraint in which the restraint is performed with a predetermined restraint size.

  Further, in the above-described method for manufacturing a capacitor module, when a float test for continuing to hold the cell voltage Vc at a predetermined holding voltage Vch (V) is performed, electrostatic capacitance after the test with respect to capacitance before the test is performed. When the voltage value that maximizes the capacitance retention rate (%) of the capacitance is the cell adjustment upper limit voltage Vcd (V), the cell voltage Vc of each lithium ion capacitor is set to Vcmin after the restraint step. It is preferable to use a method of manufacturing a capacitor module that includes a voltage adjusting step of adjusting the voltage within the range of <Vc ≦ Vcd.

  In this capacitor module manufacturing method, the cell voltage Vc of each cell is set to Vcmin <Vc ≦ Vcd (for example, Vcmin = OCV3.0 (V), Vcd = OCV3.8 (V)) in the voltage adjusting process after the restraining process. In the case of, it is adjusted within the range of 3.0 <Vc ≦ 3.8). As a result, it is possible to suppress a decrease in capacitance caused by keeping the cell voltage Vc at a value that is too low or a value that is too high.

Specifically, as a result of an investigation conducted by the present inventor, as will be described in detail later, when a lithium ion capacitor is subjected to a float test in which the cell voltage Vc is kept at a predetermined holding voltage Vch (V), the holding voltage Vch It was found that the capacitance significantly decreased with time when the value was too low or too high.
In particular, if the cell voltage Vc is kept kept at the low holding voltage Vch that is equal to or less than the minimum thickness voltage Vcmin, the electrostatic capacitance greatly decreases. Therefore, when it takes time before the module is used (charged and discharged), such as after the module is manufactured and before it is shipped, the cell voltage Vc is set higher than the minimum thickness voltage Vcmin (Vc> Vcmin). It is good to do it.
When the holding voltage Vch of the cell is low, the capacitance decreases with time because the holding voltage Vch is low and the negative electrode potential becomes lower than the reductive decomposition potential of the electrolytic solution, the electrolytic solution is reductively decomposed on the negative electrode plate. It is considered that the gas is generated along with this and a film is formed on the active material.

On the other hand, when the holding voltage Vch at which the capacitance retention rate (%) of the capacitance after the test with respect to the capacitance before the test of the float test is the largest, the cell adjustment upper limit voltage Vcd (V) If the holding voltage Vch, which is higher than the adjustment upper limit voltage Vcd, is kept held, the electrostatic capacitance greatly decreases. Therefore, when it takes time before the module is used (charged / discharged), such as after the module is manufactured until it is shipped, the cell voltage Vc is set to the cell adjustment upper limit voltage Vcd or less (Vc ≦ Vcd). It is good to do it.
When the holding voltage Vch of the cell is high, the capacitance decreases with time because the holding voltage Vch is high and the positive electrode potential becomes higher than the oxidative decomposition potential of the electrolytic solution, the electrolytic solution is oxidatively decomposed in the positive electrode plate. It is considered that the gas is generated along with this and a film is formed on the active material.

  Furthermore, in the method for manufacturing the capacitor module described above, when the lower limit voltage of the cell voltage Vc in actual use is a cell use lower limit voltage Vce (V) and the upper limit voltage is a cell use upper limit voltage Vcf (V), The voltage adjusting step is preferably a method of manufacturing a capacitor module, which is a step of adjusting the cell voltage Vc within a range of Vcd− (Vcf−Vce) × 0.2 ≦ Vc ≦ Vcd.

  In this method for manufacturing a capacitor module, the cell voltage Vc (V) is slightly lower than the cell adjustment upper limit voltage Vcd in the voltage adjustment step based on the cell use lower limit voltage Vce (V) and the cell use upper limit voltage Vcf (V). , Vcd− (Vcf−Vce) × 0.2 ≦ Vc ≦ Vcd (for example, Vcmin = OCV3.0 (V), Vcd = OCV3.8 (V), Vce = OCV2.2 (V), Vcf = OCV3.8. In the case of (V), it is adjusted within the range of 3.5 ≦ Vc ≦ 3.8. As described above, by adjusting the cell voltage Vc to a high value within the range equal to or lower than the cell adjustment upper limit voltage Vcd, it is possible to more effectively reduce the capacitance by keeping the cell voltage Vc at a low value. Can be suppressed.

It is a side view of the capacitor module concerning an embodiment. It is a perspective view of the lithium ion capacitor which concerns on embodiment. It is explanatory drawing which shows a mode that the lithium ion capacitor etc. were restrained in the restraint process regarding the manufacturing method of the capacitor module which concerns on embodiment. It is a graph which shows the relationship between cell voltage Vc and the restraint load applied to a lithium ion capacitor. It is a graph which shows the relationship between the holding voltage Vch of a cell, and the electrostatic capacitance maintenance rate after a float test.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a capacitor module 1 (hereinafter, also simply referred to as “module 1”) according to the present embodiment, and FIG. 2 shows a lithium ion capacitor 10 (hereinafter, also simply referred to as “cell 10”) that constitutes this module 1. ) Is shown. In the description below, the thickness direction BH, the horizontal direction CH, and the vertical direction DH of the cell 10 are defined as the directions shown in FIGS. 2 and 1.
The module 1 of this embodiment is mounted in a vehicle such as a hybrid vehicle. This module 1 includes a plurality of rectangular parallelepiped cells 10 arranged side by side in the thickness direction BH, a plurality of spacers 20 interposed between adjacent cells 10, and the cells 10 and the spacers 20 in the thickness direction. The restraint member 30 restrains the BH while pressing it.

The cell 10 has a form in which the cell thickness changes due to a change in the electrode body thickness of the electrode body 13 inside the cell 10. Specifically, the cell 10 includes a battery case 11, a flat electrode body 13 and an electrolytic solution 15 housed inside the battery case 11, a positive electrode terminal 17 and a negative electrode terminal 18 supported by the battery case 11, and the like. It In the cell 10 of the present embodiment, the cell use lower limit voltage Vce (V) of the cell voltage Vc in actual use is Vce = OCV2.2 (V), and the cell use upper limit voltage Vcf (V) is Vcf = OCV3. It is set to 8 (V).
Of these, the battery case 11 has a rectangular parallelepiped shape and is made of metal (specifically, aluminum). A positive electrode terminal 17 made of aluminum and a negative electrode terminal 18 made of copper are fixed to the upper wall 11a of the battery case 11 via an insulating member 19 made of resin.

The electrode body 13 is formed by stacking a strip-shaped positive electrode plate and a strip-shaped negative electrode plate on top of each other with a pair of separators made of resin interposed therebetween and winding them into a flat shape. The positive electrode plate is formed by providing a positive electrode active material layer containing activated carbon on a positive electrode current collector foil made of aluminum. The negative electrode plate is formed by providing a negative electrode active material layer containing carbon on a negative electrode current collector foil made of copper. The positive electrode terminal 17 is electrically connected to the positive electrode plate of the electrode body 13 inside the battery case 11. Further, the negative electrode terminal 18 is connected to the negative electrode plate of the electrode body 13 inside the battery case 11 and is electrically connected.
The electrolyte of the electrolyte solution 15 is lithium hexafluorophosphate (LiPF ₆ ), and the non-aqueous solvent is a mixture of ethylene carbonate (EC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC) and diethyl carbonate (DEC). It is a mixed organic solvent.

In the module 1, the plurality of cells 10 are arranged in a row in the thickness direction BH via the spacers 20, and the cells 10 are electrically connected by the bus bar 40.
The spacer 20 has a rectangular plate shape and is made of resin. Then, the cells 10 and the spacers 20 that are alternately arranged are constrained by the constraining member 30 while being pressed in the thickness direction BH. Thereby, the electrode body 13 inside each cell 10 is also pressed in its thickness direction EH (same as the thickness direction BH of the cell 10).

  The restraint member 30 has a pair of end plates 31 and four restraint rods 33. The end plates 31 have a rectangular plate shape, and are arranged on both sides of the cells 10 and the spacers 20 arranged in a row in the thickness direction BH. The restraint rods 33 are arranged between the pair of end plates 31 and fixed to the end plates 31 by fastening bolts 35.

  In the module 1 of this embodiment, as shown in FIG. 4, the constraint load applied to each cell 10 changes depending on the magnitude of the cell voltage Vc of each cell 10. As is clear from FIG. 4, when the cell voltage Vc of each cell 10 is OCV = 3.0 (V), the restraint load is the smallest, and the restraint load increases as the cell voltage Vc becomes higher than 3.0V. Further, the binding load increases as the cell voltage Vc becomes lower than 3.0V.

  The reason is considered to be as follows. The cell 10 has the minimum electrode body thickness and cell thickness when the cell voltage Vc = OCV 3.0 (V). That is, the minimum thickness voltage Vcmin = OCV3.0 (V). When the cell voltage Vc is higher than the minimum thickness voltage Vcmin = 3.0 (V), anions are adsorbed to the positive electrode active material to increase the thickness of the positive electrode active material layer, and lithium ions are occluded in the negative electrode active material to cause negative electrode activity. The material layer also becomes thicker. Therefore, as the cell voltage Vc becomes higher than the minimum thickness voltage Vcmin = 3.0 (V), the electrode body thickness and the cell thickness increase. In the module 1, since each cell 10 is constrained in the thickness direction BH, it is considered that the constraining load increases as the cell voltage Vc becomes higher than the minimum thickness voltage Vcmin = 3.0 (V).

  On the other hand, when the cell voltage Vc is lower than the minimum thickness voltage Vcmin = 3.0 (V), lithium ions are released from the negative electrode active material and the negative electrode active material layer becomes slightly thin, but the positive electrode active material contains lithium ions. The positive electrode active material layer is thickened by being adsorbed. As described above, in the lithium ion capacitor, the ratio of the negative electrode capacity to the positive electrode capacity is very large, so the expansion / shrinkage amount of the negative electrode active material layer is negligibly small compared to the expansion / shrinkage amount of the positive electrode active material layer. Therefore, as the cell voltage Vc becomes lower than the minimum thickness voltage Vcmin = 3.0 (V), the electrode body thickness and the cell thickness increase. In the module 1, since each cell 10 is constrained in the thickness direction BH, it is considered that the constraining load increases as the cell voltage Vc becomes lower than the minimum thickness voltage Vcmin = 3.0 (V).

  Next, a method of manufacturing the module 1 will be described. First, a plurality of cells 10 are prepared, and the cell voltage Vc (V) of each cell 10 is adjusted to the minimum thickness voltage Vcmin (V) that minimizes the cell thickness. Specifically, as described above, since the minimum thickness voltage Vcmin = OCV3.0 (V), the cell voltage Vc = OCV3.0 (V) is adjusted for each cell 10. Separately, a plurality of spacers 20 are prepared.

  Next, in the restraint step, as shown in FIG. 3, the cells 10 are arranged in the thickness direction BH with the spacers 20 interposed therebetween. Then, the constraining member 30 presses in the thickness direction BH to constrain it to a fixed size with a predetermined constraining dimension. Specifically, the end plates 31 of the restraint member 30 are arranged on both sides of the cells 10 and the spacers 20 arranged in a row in the thickness direction BH, and the restraint rod 33 is arranged between the pair of end plates 31. The fastening bolt 35 fixes the end plate 31. As a result, each cell 10 is pressed in the thickness direction BH, and the electrode bodies 13 inside thereof are also pressed in the thickness direction EH.

  Next, in the inspection step, the cell 10 constrained by the constraining member 30 is left at room temperature (20 ° C. ± 15 ° C.), and the voltage drop of each cell 10 is measured. Then, the cell 10 in which the cell voltage Vc drops compared to the other cells 10 is excluded as a defective product. This is because it is considered that a minute short circuit has occurred in the cell 10 having a large voltage drop due to the inclusion of foreign matter or the like.

Next, in the voltage adjusting step, the cell voltage Vc of each cell 10 is adjusted within the range of Vcmin <Vc ≦ Vcd, more specifically, Vcd− (Vcf−Vce) × 0.2 ≦ Vc ≦ Vcd. It should be noted that the cell adjustment upper limit voltage Vcd (V) is, as will be described later, obtained when a float test in which the cell voltage Vc is continuously held at a predetermined holding voltage Vch (V) is performed, after the test with respect to the capacitance before the test. Is the voltage value at which the electrostatic capacity maintenance rate (%) of the electrostatic capacity is maximum, and in the present embodiment, the cell adjustment upper limit voltage Vcd = OCV 3.8 (V). Further, as described above, the minimum thickness voltage Vcmin = OCV3.0 (V), the cell use lower limit voltage Vce = OCV2.2 (V), and the cell use upper limit voltage Vcf = OCV3.8 (V). Therefore, in this voltage adjustment step, the cell voltage Vc of each cell 10 is adjusted within the range of 3.5 ≦ Vc ≦ 3.8, for example, the cell voltage Vc = OCV 3.7 (V).
The cell voltage Vc is preferably adjusted independently for each cell 10. This is because when the cells 10 are electrically connected and the cell voltage Vc is adjusted all at once, the cell voltage Vc may also vary due to variations in the capacitance and internal resistance of each cell 10.

  Next, in the connecting step, each cell 10 constrained by the constraining member 30 is electrically connected using the bus bar 40 (see FIG. 1). Thus, the module 1 is completed.

  Next, the results of tests conducted on the relationship between the cell voltage Vc of the cell 10 and the durability of the cell 10 will be described. First, the “float test” was performed in which the cell 10 was placed in a constant temperature bath, slightly charged from the outside, and the cell voltage Vc was constantly kept at a predetermined holding voltage Vch (V) for 4000 hours. Then, the capacitance of the cell 10 was measured before and after the test, and the capacitance retention rate (%) was calculated from the capacitance after the test with respect to the capacitance before the test. The holding voltage Vch was changed in the range of about 2.2 to about 4.0V. The result is shown in the graph of FIG.

  The capacitance was measured by the following method. That is, after being charged to the rated cell voltage Vc3 (Vc3 = 3.8V in this embodiment) with 40 times the discharge current of the cell 10 (nominal capacitance × voltage operation width / 3600: 17.8A in this embodiment), The cells are discharged to the lowest operating cell voltage Vc1 (Vc1 = 2.2V in this embodiment) with the same current value. At that time, the discharge time It from the cell voltage Vc2 corresponding to 80% of the rated cell voltage Vc3 to the minimum operating cell voltage Vc1 is measured. Then, the electrostatic capacitance is obtained from the formula of electrostatic capacitance (F) = It / (V2-V1). This measurement is repeated 3 times, and the average value is taken as the capacitance.

  As is clear from FIG. 5, in the range where the cell voltage Vc is lower than 3.8V, that is, in the range lower than the cell adjustment upper limit voltage Vcd, when the cell voltage Vc is kept held at the low holding voltage Vch, the holding voltage Vch becomes It can be seen that the lower the capacitance, the lower the capacitance. In particular, if the cell voltage Vc is kept kept at the holding voltage Vch of the minimum thickness voltage Vcmin = 3.0V or less, the electrostatic capacitance greatly decreases. As described above, when the holding voltage Vch of the cell 10 is low, the electrostatic capacity is decreased. As described above, when the holding voltage Vch is low and the negative electrode potential is lower than the reductive decomposition potential of the electrolytic solution, electrolysis occurs on the negative electrode plate. It is considered that the liquid 15 is reductively decomposed, gas is generated with this, and a film is formed on the active material.

From this result, when it takes time to use (charge and discharge) the module 1 after manufacturing the module 1 to shipping it, the cell voltage Vc is set higher than the minimum thickness voltage Vcmin ( It is understood that it is better to keep Vc> Vcmin).
In particular, by adjusting the cell voltage Vc within a range of 3.5 to 3.8V, which is slightly lower than 3.8V, that is, Vcd− (Vcf−Vce) × 0.2 ≦ Vc ≦ Vcd, the cell voltage is adjusted. It is possible to effectively suppress a decrease in electrostatic capacitance caused by keeping Vc at a low value.

  On the other hand, if the cell voltage Vc is set higher than 3.8V, that is, in the range where the cell adjustment upper limit voltage Vcd is exceeded, if the cell voltage Vc is kept held at the high holding voltage Vch, the higher the holding voltage Vch is, the higher the capacitance becomes. It can be seen that it drops significantly. As described above, the electrostatic capacitance decreases when the holding voltage Vch of the cell 10 is high, as described above, when the holding voltage Vch is high and the positive electrode potential is higher than the oxidative decomposition potential of the electrolytic solution, the positive electrode plate is electrolyzed. It is considered that the liquid 15 is oxidatively decomposed, gas is generated with this, and a film is formed on the active material.

From this result, when it takes time before the module 1 is used (charged and discharged) after the module 1 is manufactured and before shipment, the cell voltage Vc is set to the cell adjustment upper limit voltage Vcd or less ( It is understood that it is better to keep Vc ≦ Vcd).
From the above, by adjusting the cell voltage Vc to Vcmin <Vc ≦ Vcd, more preferably Vcd− (Vcf−Vce) × 0.2 ≦ Vc ≦ Vcd, the cell voltage Vc is too low or too high. It is possible to suppress a decrease in electrostatic capacitance caused by continuing to hold the value.

  As described above, according to the method for manufacturing the module 1 of the present embodiment, the cell voltage Vc is adjusted to the minimum thickness voltage Vcmin (specifically, Vcmin = OCV3.0 (V)) in the constraint step. The cells 10 are arranged in the thickness direction BH and restrained by the restraining member 30. As a result, since each cell 10 is pressed and constrained in the state where the cell thickness is thinnest, the constraining load applied to each cell 10 after constraining is constrained regardless of the value of the cell voltage Vc of each cell 10. The load will be equal to or greater than the actual load (see Fig. 4). Therefore, in this module 1, even if the cell voltage Vc changes due to charging / discharging or leaving, the restraint load for restraining each cell 10 is suppressed from being lower than the restraint load regardless of the value of the cell voltage Vc. it can.

  Further, in the present embodiment, in the voltage adjusting step after the restraining step, the cell voltage Vc (V) of each cell 10 is Vcmin <Vc ≦ Vcd (specifically, 3.0 <Vc ≦ 3.8). Within the range, more specifically, within the range of Vcd− (Vcf−Vce) × 0.2 ≦ Vc ≦ Vcd (specifically, 3.5 ≦ Vc ≦ 3.8). As a result, it is possible to effectively suppress a decrease in electrostatic capacitance caused by keeping the cell voltage Vc at a value that is too low or too high.

  Although the present invention has been described above according to the embodiments, it goes without saying that the present invention is not limited to the above-described embodiments and can be appropriately modified and applied without departing from the scope of the invention.

1 Capacitor Module 10 Lithium Ion Capacitor 13 Electrode Body 20 Spacer 30 Restraining Member 40 Bus Bar BH (Cell's) Thickness Direction CH (Cell's) Lateral DH (Cell's) Vertical Direction EH (Electrode's) Thickness Direction

Claims (1)

A plurality of lithium ion capacitors that are arranged side by side in the thickness direction and have a rectangular parallelepiped shape having an electrode body inside, in which the cell thickness changes due to a change in the electrode body thickness of the electrode body,
A method of manufacturing a capacitor module, comprising: a constraint member that presses and constrains these lithium ion capacitors in the thickness direction to press each of the electrode bodies,
The lithium ion capacitor is
The thickness minimum voltage Vcmin (V) that minimizes the cell thickness is higher than the cell use lower limit voltage Vce (V) and lower than the cell use upper limit voltage Vcf (V),
The lithium ion capacitor cell voltage Vc (V) is adjusted respectively to the minimum voltage Vcmin (V), arranged in the thickness direction, of the capacitor module with constraints step of restraining by pressing by the restraining member in the thickness direction Production method.

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