JP2010080370A - Battery pack device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a battery pack device for preventing the application of excessive stress onto single cells. <P>SOLUTION: In the battery pack device, the plurality of rectangular solid shaped single cells 1 and a plurality of plate shaped spacers 2 are alternately laminated, and pressed and constrained at both ends in the laminating direction. The spacers 2 each consist of a binder 21 having a positive linear expansion coefficient and a filler having a negative linear expansion coefficient. Preferably, the filler is a fibrous body 22 oriented along the laminating direction of the single cells 1 and the spacers 2. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an assembled battery device in which a plurality of unit cells are stacked with a spacer interposed therebetween.

Conventionally, as an assembled battery device, as shown in FIG. 2 of Patent Document 1, spacers (420) are arranged between single battery cells (410), so that the distance between columns arranged in parallel does not increase. A technique is disclosed in which a row is constrained by constraining spacers (430) and constraining rods (440) disposed at both ends. In this technique, adjacent spacer protrusions (422A, 422B) are arranged at positions that do not face each other in order to prevent stress concentration on the single battery cells during thermal expansion of the single battery cells or spacers. Since the spacer expands and contracts at high temperatures and low temperatures, the spacers restrain the single cells at the low temperature with the restraining rods so that the constraining rods are not detached from the rows of the single cells at low temperatures.
Japanese Patent Laying-Open No. 2008-4289 (FIG. 2)

  However, if the restraint spacer and the restraining rod are restrained so as not to disengage the single battery cells at low temperatures, the spacers and single battery cells expand at high temperatures, and excessive stress is applied to the single battery cells. Therefore, the influence on the battery performance of the single battery cell is still a concern.

  This invention is made | formed in view of this situation, and makes it a subject to provide the assembled battery apparatus which can prevent that an excessive stress is added to a single battery cell.

  The present invention is an assembled battery device in which a plurality of unit cells each having a rectangular parallelepiped shape and plate-like insulating spacers are alternately stacked, and are pressure-constrained from both ends in the stacking direction, The spacer includes a binder having a positive linear expansion coefficient in the stacking direction and a filler having a negative linear expansion coefficient in the stacking direction (Claim 1).

  The filler is preferably a fibrous body oriented along the laminating direction (Claim 2).

  The filler is preferably composed of one or more selected from PBO fibers, para-aramid fibers, and high-strength polyethylene fibers.

  According to the present invention, the battery cells and the spacers are alternately stacked. The spacer includes a binder having a positive linear expansion coefficient in the stacking direction and a filler having a negative linear expansion coefficient in the stacking direction. For this reason, the linear expansion coefficient in the stacking direction of the spacers is smaller than the linear expansion coefficient of the spacer made of only the binder. Therefore, the spacer is prevented from expanding in the stacking direction at a high temperature, and the stress applied to the single battery cell can be reduced.

  When the filler is a fibrous body oriented along the stacking direction of the single battery cells, the thermal expansion / contraction of the spacer in the stacking direction can be effectively suppressed.

  When the filler is selected from PBO fibers, para-aramid fibers, and high-strength polyethylene fibers, the xylon fibers and high-strength polyethylene fibers are oriented in the fiber length direction. For this reason, the filler has a negative linear expansion coefficient, and can effectively suppress an increase in the linear expansion coefficient of the spacer.

  The assembled battery device of the present invention is suitably used as a power supply device for electric vehicles, hybrid vehicles, and the like.

  In the assembled battery device of the present invention, a general so-called prismatic battery cell can be used as the single battery cell. You may use one with a resin casing, or one with an insulating coating on the surface, but use a single battery cell that exposes a metal casing such as iron or aluminum with high thermal conductivity. It is preferable. In general, a pair of electrodes project from the upper part of the unit cell. Usually, a plurality of unit cells are stacked so that the sides having the electrodes are all the same side.

  A plate-like spacer is interposed between the unit cells. The spacer includes a binder having a positive linear expansion coefficient in the stacking direction and a filler having a negative linear expansion coefficient in the stacking direction.

  Conventionally, the spacer interposed between the single battery cells is composed of a binder having a positive linear expansion coefficient. In this case, the temperature rises due to the heat generated from the single battery cells, and the spacers are greatly expanded in the stacking direction, causing excessive stress to the single battery cells. Therefore, the present invention reduces the linear expansion coefficient of the spacer composed of the binder and the filler by adding a filler having a negative linear expansion coefficient to a binder having a positive linear expansion coefficient. .

  A binder having a positive linear expansion coefficient in the stacking direction is poor in molecular orientation, and when molecular motion becomes active due to a temperature rise, each molecule tends to stretch and extends in the stacking direction. The binder is preferably an insulating material, and for example, silicone rubber or the like can be used. The linear expansion coefficient of silicone rubber is about 200 ppm / ° C.

  The filler having a negative linear expansion coefficient in the stacking direction may be, for example, a polymer material having molecular orientation. When the polymer chain of the polymer material is stretched and oriented, the final ideal structure becomes a trans zigzag structure as shown in FIG. Since this structure cannot be stretched any more, if each atom moves vigorously due to the temperature rise, as shown in FIG. 4 (b), it contracts in the molecular chain axis direction and is orthogonal to the molecular chain axis direction. It expands in the direction. Therefore, many polymer materials having molecular orientation have many negative linear expansion coefficients in the molecular chain axis direction.

  Examples of the polymer material having such molecular orientation include high-strength polyethylene fibers (trade name “Dyneema”), PBO fibers (trade name “Zyron”), para-aramid fibers (trade name “Kevlar 29”, "Kevlar 49", "Technora", etc.). The high-strength polyethylene fiber has a linear expansion coefficient of −12 ppm / ° C., a crystallinity of 95% or more, and a molecular weight of about 4 million. The PBO fiber is a fiber obtained by liquid crystal spinning of polyparaphenylene benzobisoxazole (PBO). The linear expansion coefficient of the xylon fiber is −6 ppm / ° C., and the crystallinity (for example) is 95% or more. Kevlar 29 (trade name) has a linear expansion coefficient of −4.0 ppm / ° C., and Kevlar 49 (trade name) has a linear expansion coefficient of −4.9 ppm / ° C. Technora (trade name) is copolyparaphenylene-3,4'oxydiphenylene-terephthalamide and has a linear expansion coefficient of -6 ppm / ° C.

  The filler having a negative linear expansion coefficient may be a fibrous body. The fibrous body may be a short fiber or a long fiber, but is preferably a short fiber so as to be arranged in the thickness direction of the spacer.

  It is desirable that the polymer material constituting the fibrous body is molecularly oriented in the fiber direction. Moreover, it is desirable for the fibrous body to have its fiber direction oriented parallel to the stacking direction of the unit cells. Thereby, the linear expansion coefficient in the stacking direction of the spacers can be effectively suppressed.

  When the spacer is sandwiched between the battery cells in the thickness direction, the fibrous body is preferably oriented in the thickness direction of the spacer. In this case, the thermal expansion / contraction of the spacer in the stacking direction can be effectively suppressed.

  In order to orient the fibrous body in a predetermined direction of the spacer, for example, a mixed material in which the fibrous body is mixed with a binder is formed. When the mixed material is molded, the mixed material in the mold is melted and a magnetic field is applied in the thickness direction of the mixed material. Thereby, the fibrous body is oriented so that the fiber length direction is parallel to the magnetic field direction. And the spacer in which the fibrous body orientated in the thickness direction can be produced.

  The mixing ratio (volume ratio) of the filler having a negative linear expansion coefficient to the binder having a positive linear expansion coefficient is preferably 1 to 40% by volume. In this case, the linear expansion coefficient of the spacer can be kept low while maintaining the shape of the spacer.

Example 1
FIG. 1 is a front view of the assembled battery device according to the present embodiment. In this assembled battery device, a single battery cell 1 having a rectangular parallelepiped shape and plate-like spacers 2 made of an electrically insulating resin are alternately laminated in the thickness direction to form a laminate 3. Yes. Resin constraining plates 4 are disposed at both ends of the laminate 3, and are constrained in a state in which the unit cells 1 and the spacers 2 are pressed by the constraining rods 5 so as to be in close contact with each other.

  As shown in FIG. 2, the single battery cell 1 is a lithium ion secondary battery, and battery elements such as an electrode plate, a separator, and an electrolytic solution are housed in an aluminum casing 10. A pair of positive and negative electrodes 11 and 12 protrude from the upper portion of the housing 10. The casing 10 and the spacer 2 of the single battery cell 1 have six surfaces. Two surfaces 14 and 15 which face each other in the stacking direction of the surface of the housing 10 face the surfaces 24 and 25 of the spacer 2, respectively. The thickness of the single battery cell 1 is 14 mm.

  As shown in FIG. 3, the spacer 2 is formed of a binder 21 made of silicone rubber and a fibrous body 22. Silicone rubber has a linear expansion coefficient of 200 ppm / ° C. and a thermal conductivity of 5 W / mK. The fibrous body 22 is a short single fiber having a length of 0.2 mm, and uses a high-strength polyethylene fiber (“Dyneema” manufactured by Toyobo). The fibrous body 22 is uniformly dispersed in the binder 21 and is oriented in the thickness direction of the spacer 2. The linear expansion coefficient of the high-strength polyethylene fiber is −12 ppm / ° C. (−12E−6 mm / mm / ° C.), and the crystallinity is 95% or more. The compounding ratio (volume ratio) of the high-strength polyethylene fiber to the silicone rubber is 15% by volume.

  As shown in FIG. 2, one surface 24 in the thickness direction of the spacer 2 is a flat surface, and the other surface 25 has a large number of grooves 20 for air circulation. The thickness T of the spacer 2 is 3 mm, and the depth D of the groove 20 is 2 mm.

  In manufacturing the spacer 2, silicone rubber and high-strength polyethylene fiber are mixed to form a composite material, and heated to melt the silicone rubber. This composite material is put into a mold, and a magnetic field is applied in the thickness direction at room temperature for 1 hour. The strength of the magnetic field is 8T (Tesla). After the fibrous body is oriented in the thickness direction, the composite material is cooled. Thereby, the spacer 2 in which high-strength polyethylene fibers are oriented in the thickness direction is obtained.

(Example 2)
The assembled battery device of this example is different from Example 1 in that the fibrous body contained in the spacer is not oriented. In the spacer, the fibrous bodies are arranged in random directions and uniformly dispersed. When manufacturing the spacer, a composite material composed of silicone rubber and high-strength polyethylene is molded without applying a magnetic field. Others are the same as in the first embodiment.

(Comparative Example 1)
The assembled battery device of this comparative example is different from the example 1 in that the spacer does not include a fibrous body. That is, the spacer is formed only from silicone rubber. Others are the same as in the first embodiment.

<Experiment>
The linear expansion coefficients of the spacers of Examples 1 and 2 and Comparative Example 1 were measured. The size of the spacer used for measurement was 130 mm long × 130 mm wide × 1 mm thick. In the spacer of Example 1, the fibrous body was oriented in the longitudinal direction. A standard line was marked in the vertical direction on the spacer when the standard temperature was 25 ° C., and it was put in a constant temperature bath at a predetermined temperature for several hours. The temperature of the thermostatic bath is −40 ° C. and 90 ° C. Then, the length of the marked line was measured with a scale. The difference (elongation amount ΔL) between the length of the marked line at 25 ° C. and the length of the marked line at a predetermined temperature was determined. The linear expansion coefficient was calculated by dividing this difference by the temperature difference (ΔT) from 25 ° C. The equation for calculating the linear expansion coefficient is expressed as elongation amount ΔL / (length of marked line at 25 ° C. × temperature difference ΔT).

  The measured linear expansion coefficient of the spacer is shown in Table 1, and FIG. 5 shows the amount of extension ΔL of the spacer.

  From the measurement results, the spacer of Example 1 had the smallest linear expansion coefficient (elongation amount), and Comparative Example 1 had the largest linear expansion coefficient (elongation amount). The reason why the linear expansion coefficients of the spacers of Examples 1 and 2 are small is that the fibrous material 22 having a negative linear expansion coefficient is contained in the binder 21 as shown in FIG.

  Further, the spacer of Example 1 had a smaller linear expansion coefficient than the spacer of Example 2. The reason why the linear expansion coefficient of Example 1 is smaller than that of Example 2 is that the fibrous body 22 of Example 1 is oriented in the stacking direction, and the spacer 2 is less likely to extend in the orientation direction of the fibrous body 22. is there.

1 is a front view of an assembled battery device of Example 1. FIG. FIG. 3 is an explanatory view showing a single battery cell and a spacer of Example 1. It is explanatory drawing which shows the expansion-contraction direction of a plate of Example 1. FIG. Explanatory drawing (a) which shows the trans zigzag structure of a molecular chain, and explanatory drawing (b) which shows the molecular chain which carried out heat contraction. It is a diagram which shows the relationship between the extension amount of the spacer of Example 1, 2, and the comparative example 1, and temperature.

Explanation of symbols

1: single battery cell, 2: spacer, 3: laminate, 4: constraining plate, 5: constraining rod, 20: groove, 21: binder, 22: fibrous body.

Claims (3)

A battery pack device in which a plurality of unit cells each having a rectangular parallelepiped shape and plate-like insulating spacers are alternately stacked, and are pressure-constrained from both ends in the stacking direction,
The assembled battery device, wherein the spacer includes a binder having a positive linear expansion coefficient in the stacking direction and a filler having a negative linear expansion coefficient in the stacking direction.   The assembled battery device according to claim 1, wherein the filler is a fibrous body oriented along the stacking direction.   3. The filler according to claim 1 or 2, wherein the filler comprises one or more selected from polyparaphenylene benzobisoxazole fibers (hereinafter referred to as "PBO fibers"), para-type aramid fibers, and high-strength polyethylene fibers. The assembled battery device described.

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