Battery module

Abstract

To provide a battery module which is advantageous in ensuring heat dissipation from a battery cell even when the battery cell expands, preventing a rise in temperature of the battery cell, and suppressing deterioration of the battery cell.SOLUTION: A battery module 10 includes a plurality of battery cells 12, a plurality of pads 14, a module case 16, a heat sink 18, and a plurality of capsules 20. A plurality of capsules 20 that burst to create voids in the pad 14 are arranged near a peripheral portion 14A of the pad 14, and thus the plurality of capsules 20 burst due to deformation of the battery cell 12 accompanying deterioration of the battery cell 12 to promote heat dissipation from a side surface 1202 of the battery cell through the voids 22 formed near the peripheral portion 14A of the pad 14.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a battery module.

Background Art

[0002] An electric vehicle having only a motor as a drive source, a hybrid vehicle, or an electric vehicle having a motor as a drive source such as a plug-in hybrid vehicle (PHEV) capable of external charging or external power supply is provided with a battery pack that supplies power to the motor. The battery pack is configured to include a plurality of battery modules. As such a battery module, one including a stacked battery cell (secondary battery such as a lithium ion battery) and a module case that houses these battery cells is known (see Patent Document 1). By the way, in addition to a rectangular battery cell having a metal cell case as shown in Patent Document 1, there is a laminate type for the battery cell (see Patent Document 2). A laminate type battery cell is one in which a positive electrode, a negative electrode, a separator, an electrolytic solution, etc. constituting a power generation element are sealed by being sandwiched between laminate films. By the way, in a battery module using a laminate type battery cell, in order to ensure the performance of the battery cell, it is necessary to pressurize the stacked battery cells in the stacking direction thereof. Therefore, in a battery module using a laminate type battery cell, a plurality of pads made of an elastic member such as urethane respectively arranged in the gaps between adjacent battery cells are provided, and a plurality of battery cells and a plurality of pads are constrained using a module case, whereby the plurality of battery cells are pressurized in the stacking direction of the battery cells via the plurality of pads.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

[0004] By the way, although a battery cell deteriorates by repeating charge and discharge, the battery cell expands in its thickness direction due to the gas generated inside the battery cell at that time. The amount of deformation in the thickness direction of the battery cell due to expansion generally becomes largest at the center of the battery cell, while decreasing toward the peripheral portion of the battery cell. Such deformation in the thickness direction of the battery cell is absorbed by the deformation of the pad. However, when the amount of deformation in the thickness direction of the battery cell gradually increases, eventually the pad at the center of the battery cell cannot absorb the deformation of the battery cell, and the centers of adjacent battery cells come into proximity through the crushed pad. In addition, since the internal resistance of the battery cell increases as the battery cell deteriorates, heat generation of the battery cell becomes prominent with charge and discharge. However, if the centers of the battery cells come close to each other, heat dissipation from the battery cells is inhibited, so there is a concern that the temperature of the battery cells will further increase and the deterioration of the battery cells will be accelerated. The present invention has been made in view of the above circumstances, and aims to provide a battery module that is advantageous in ensuring heat dissipation from the battery cell even when the battery cell expands, preventing an increase in the temperature of the battery cell, and suppressing deterioration of the battery cell. [Means for Solving the Problems]

[0005] In order to achieve the above object, an embodiment of the present invention provides a battery module including: a plurality of stacked battery cells; a plurality of pads made of an elastic material respectively disposed in gaps between adjacent battery cells; and a module case that restrains the plurality of battery cells and the plurality of pads, thereby pressing the plurality of battery cells in the stacking direction of the battery cells via the plurality of pads, wherein a plurality of capsules that create voids in the pads by rupturing are disposed near the peripheral portions of the pads. Also, an embodiment of the present invention is characterized in that the inside of the capsule is a cavity. Also, an embodiment of the present invention is characterized in that the inside of the capsule is filled with a solvent that dissolves the pad. Also, an embodiment of the present invention is characterized in that the pad has a thickness along the stacking direction, the pad has a pair of side surfaces located at both ends in the thickness direction and overlapped with the battery cells, and among the plurality of capsules disposed near the peripheral portion of the pad, the capsules disposed closer to the pair of side surfaces are more numerous than the capsules disposed at the center in the thickness direction of the pad. Also, an embodiment of the present invention is characterized in that among the plurality of capsules disposed near the peripheral portion of the pad, the capsules disposed at the peripheral portion are formed to rupture at a lower pressure than the capsules disposed at a location closer to the center of the pad.

Advantages of the Invention

[0006] According to an embodiment of the present invention, since a plurality of capsules that create voids in the pads by rupturing are disposed near the peripheral portions of the pads, heat dissipation from the side surfaces of the battery cells is promoted through the voids formed near the peripheral portions of the pads due to the rupture of the plurality of capsules caused by the deformation of the battery cells accompanying the deterioration of the battery cells. Therefore, as the battery cell deteriorates, deformation occurs. When the pad at the center of the battery cell can no longer absorb the deformation of the battery cell, even when the central parts of adjacent battery cells come close to each other through the crushed pad, heat dissipation from the side surface of the battery cell can be ensured through the voids formed near the peripheral edge of the pad. This is advantageous in preventing the temperature rise of the battery cell and suppressing the deterioration of the battery cell. Also, if the inside of the capsule is a cavity, when the capsule ruptures, the internal space thereof directly becomes voids. Thus, voids and gaps can be reliably formed near the peripheral edge of the pad where the capsule is disposed, which is more advantageous in promoting heat dissipation from the side surface of the battery cell through the gaps formed near the peripheral edge of the pad. Moreover, if the inside of the capsule is filled with a solvent that dissolves the pad, when the capsule disposed near the peripheral edge of the pad ruptures, the solvent inside the capsule dissolves the portion of the pad around the capsule, thereby forming voids with a large volume and thus forming gaps with a larger volume. Therefore, it is more advantageous in promoting heat dissipation from the side surface of the battery cell through the gaps with a larger volume formed near the peripheral edge of the pad. Also, among the plurality of capsules disposed near the peripheral edge of the pad, if the number of capsules disposed closer to a pair of pad side surfaces is made larger than the number of capsules disposed at the center in the thickness direction of the pad, when the capsules rupture, more voids and gaps are formed closer to the side surface of the battery cell. This is even more advantageous in promoting heat dissipation from the side surface of the battery cell through the gaps formed near the side surface of the battery cell. Also, among the capsules disposed near the peripheral edge of the pad, if the capsules disposed at the peripheral edge of the pad are formed to rupture at a lower pressure than the capsules disposed at a location closer to the center of the pad, it is advantageous in synchronizing the timing of rupture of the capsules disposed at the peripheral edge of the pad and the timing of rupture of the capsules disposed at a location closer to the center of the pad. The plurality of capsules disposed near the peripheral edge of the pad can be efficiently and reliably ruptured, and voids and gaps can be efficiently and reliably formed near the peripheral edge of the pad, which is more advantageous in promoting heat dissipation from the side surface of the battery cell through the gaps formed near the peripheral edge of the pad.

Brief Description of the Drawings

[0007]

Figure 1

Figure 2

Figure 3

Modes for Carrying Out the Invention

[0008] (First Embodiment) Hereinafter, embodiments of the present invention will be described with reference to the drawings. This embodiment is applied to a battery module that constitutes a battery pack mounted on an electric vehicle having only a motor as a drive source, such as an electric vehicle, a hybrid vehicle, or a plug-in hybrid vehicle capable of external charging or external power supply, and supplies power to the above-mentioned motor.

[0009] As shown in FIG. 1, the battery module 10 includes a plurality of battery cells 12, a plurality of pads 14, a module case 16, a heat sink 18, and a plurality of capsules 20. A plurality of battery modules 10 are connected to each other and housed in a case (not shown) to form a battery pack. For convenience of explanation, in FIG. 1, only the outline of the battery cell 12 is drawn, and the cross-sections of the module case 16, the pad 14, and the heat sink 18 are shown.

[0010] In this embodiment, a case where a plurality of battery cells 12 are of the laminate type will be described. However, the plurality of battery cells 12 may be rectangular with a metal cell case, and the present invention is applicable to various conventionally known battery cells. In addition, in the present embodiment, the case where each battery cell 12 is configured by a lithium ion battery will be described, but various conventionally known secondary batteries can be used as the battery cell 12. Although not shown in the drawings, each battery cell 12 is configured by sandwiching with a laminate film a stacked structure including a positive electrode, a negative electrode, a separator, an electrolytic solution, etc., which constitute a power generation element, and sealing them. Each battery cell 12 has a rectangular plate shape with the same shape and size, and has a thickness, a height with a dimension larger than the thickness, and a width with a dimension larger than the thickness. A pair of battery cell side surfaces 1202 are located facing each other at both ends in the thickness direction of the battery cell 12, a battery cell upper end surface 1204 and a battery cell lower end surface 1206 are located at both ends in the height direction of the battery cell 12, and a battery cell front end surface 1208 and a battery cell rear end surface (not shown) are located at both ends in the width direction of the battery cell 12. In the present embodiment, the plurality of battery cells 12 are stacked with their battery cell side surfaces 1202 facing each other and the height direction oriented in the vertical direction. Therefore, the stacking direction of the battery cells 12 coincides with the thickness direction of the battery cells 12.

[0011] As shown in FIGS. 1 and 2, each pad 14 has a rectangular plate shape with the same shape and size and a contour slightly smaller than that of the battery cell 12. Their thicknesses are formed to be smaller than the thickness of the battery cell 12, and they are respectively arranged in the gaps between adjacent battery cells 12, in other words, in the gaps between the opposing battery cell side surfaces 1202. A pair of pad side surfaces 1402 are located at both ends in the thickness direction of the pad 14, in other words, at both ends in the stacking direction of the battery cells 12. A pad upper end surface 1404 and a pad lower end surface 1406 are located at both ends in the height direction of the pad 14, and a pad front end surface 1408 and a pad rear end surface 1410 (see FIG. 2) are located at both ends in the width direction of the pad 14. Each pad 14 is formed of an elastically deformable elastic material, and various conventionally known highly elastic foams such as urethane foam, and various conventionally known rubbers and elastomers can be used as such an elastic material.

[0012] The module case 16 houses and constrains a plurality of stacked battery cells 12 and a plurality of pads 14, thereby evenly pressing the plurality of battery cells 12 in the stacking direction thereof via the plurality of pads 14. By evenly pressing the electrodes inside the battery cells 12 from the outside in this way, the performance of the battery cells 12 is ensured. In the present embodiment, the module case 16 includes an upper wall 1602 facing the upper end surface 1204 of the battery cell, a bottom wall 1604 facing the lower end surface 1206 of the battery cell, both ends of the upper wall 1602 and both ends of the bottom wall 1604 in the stacking direction of the battery cells 12 are connected, and a pair of side walls 1606 that are overlapped with the battery cell side surfaces 1202 located at both ends in the stacking direction of the battery cells 12, and front walls and rear walls (not shown in the figure) that connect both ends in the width direction orthogonal to the height direction of the pair of side walls 1606. Note that it is optional to form heat dissipation openings communicating with the internal space of the battery pack in at least a part of the upper wall 1602, the pair of side walls 1606, the front wall, and the rear wall, and to cool each battery cell 12 by bringing it into contact with the air inside the battery pack through the openings.

[0013] The front end surface 1208 and the rear end surface of the battery cells 12 of the plurality of battery cells 12 are sandwiched by the front wall and the rear wall of the module case 16, thereby being fixed so as not to move in the width direction. Further, among the plurality of battery cells 12, the respective battery cell side surfaces 1202 of the battery cells 12 located at both ends in the stacking direction of the battery cells 12 are sandwiched by the pair of side walls 1606 of the module case 16, whereby the plurality of battery cells 12 and the plurality of pads 14 are fixed so as not to move in the stacking direction. Also, the lower end surface 1206 of the battery cell is placed on the bottom wall 1604 of the module case 16 via the heat sink 18. Also, although a certain gap is formed between the upper end surface 1204 of the battery cell and the upper wall 1602 of the module case 16, the upper end surface 1204 of the battery cell is fixed so as not to move upward by, for example, a fitting (not shown) provided on the upper wall 1602. In other words, the module case 16 restrains a plurality of stacked battery cells 12 and a plurality of pads 14 by a pair of side walls 1606, a front wall, a rear wall, and an upper wall 1602.

[0014] The heat sink 18 is provided between the bottom wall 1604 of the module case 16 and the lower end surface 1206 of the stacked battery cells 12, and cools each battery cell 12 by placing the lower end surface 1206 of each battery cell 12 thereon. As such a heat sink 18, various conventionally known heat sinks such as a liquid-cooled heat sink that cools the battery cells 12 by allowing a refrigerant such as a coolant to flow therein and an air-cooled heat sink that cools the battery cells 12 by allowing air to flow therein can be used.

[0015] As shown in FIG. 2, a plurality of capsules 20 are arranged near the peripheral edge 14A of the pad 14 and create holes in the pad 14 by rupturing. In the present embodiment, the peripheral edge 14A of the pad 14 is a location near the upper end surface 1404 of the pad, a location near the lower end surface 1406 of the pad, a location near the front end surface 1408 of the pad, and a location near the rear end surface 1410 of the pad. In the present embodiment, the inside of the capsule 20 is hollow. As the material of the capsule 20, in addition to synthetic resin and glass, gelatin, plant fiber, starch, etc. can be used. In the present embodiment, among the plurality of capsules 20 arranged near the peripheral edge 14A of the pad 14, the capsules 20 arranged closer to the pair of pad side surfaces 1402 are more numerous than the capsules 20 arranged at the center in the thickness direction of the pad 14. In other words, among the plurality of capsules 20 arranged near the peripheral edge 14A of the pad 14, the capsules 20 arranged closer to the pair of battery cell side surfaces 1202 are more numerous than the capsules 20 arranged at the center in the thickness direction of the pad 14. Further, in the present embodiment, among the plurality of capsules 20 arranged near the peripheral portion 14A of the pad 14, the capsules 20 arranged on the peripheral portion 14A of the pad 14 are formed to rupture at a lower pressure than the capsules 20 arranged at a location closer to the center of the pad 14. For example, among the plurality of capsules 20 arranged near the peripheral portion 14A of the pad 14, the capsules 20 arranged on the peripheral portion 14A of the pad 14 are formed to be thinner than the capsules 20 arranged at a location closer to the center of the pad 14. Alternatively, among the plurality of capsules 20 arranged near the peripheral portion 14A of the pad 14, the capsules 20 arranged on the peripheral portion 14A of the pad 14 are formed of a material having a lower strength than the capsules 20 arranged at a location closer to the center of the pad 14.

[0016] Next, the operation and effect of the battery module 10 of the present embodiment will be described with reference to FIG. 3. For convenience of explanation, in FIG. 3, only the outline of the battery cell 12 is drawn for the battery cell 12, and a cross section is shown for the pad 14. As described above, in the battery module 10, the plurality of battery cells 12 and the plurality of pads 14 are constrained by the module case 16, so that the plurality of battery cells 12 are used in a state of being pressurized in the stacking direction of the battery cells 12 via the plurality of pads 14.

[0017] As shown in FIG. 3(A), in the initial state where the number of charge and discharge cycles of the battery cell 12 is small and the battery cell 12 is not deteriorated, the amount of deformation in the thickness direction at the center of the battery cell 12 is zero. Therefore, the thickness of the pad 14 is uniform throughout its entire area. As the number of charge and discharge cycles of the battery cell 12 increases and the battery cell 12 deteriorates, the pair of battery cell side surfaces 1202 of the battery cell 12 gradually expand. At this time, since the center of the adjacent battery cell side surfaces 1202 expands more than the peripheral portion of the battery cell side surfaces 1202, the center of the adjacent battery cell side surfaces 1202 deforms more greatly in a direction closer to each other than the peripheral portion of the battery cell side surfaces 1202. Here, due to the restraint of the module case 16, a plurality of battery cells 12 are pressed in the stacking direction of the battery cells 12 via a plurality of pads 14. Therefore, as the adjacent battery cell side surfaces 1202 are deformed, a compressive force in the compression direction is applied to the pads 14, and the compressive force also acts on the plurality of capsules 20 arranged near the peripheral edge 14A of the pads 14 via the pads 14.

[0018] Then, as shown in FIG. 3(B), at the center of the battery cell 12, the pad 14 is no longer able to absorb the deformation of the battery cell 12, and the centers of the adjacent battery cells 12 come close to each other via the crushed pads 14. When the compressive force applied from the pad 14 exceeds the strength of each capsule 20 near the peripheral edge 14A of the pad 14, each capsule 20 ruptures, and thus a number of voids corresponding to the plurality of capsules 20 are respectively formed near the peripheral edge 14A of the pad 14. Then, the adjacent voids communicate with each other, so that a gap 22 is formed near the peripheral edge 14A of the pad 14. A part of the gap 22 is opened outward from the upper pad surface 1404, the lower pad surface 1406, the front pad surface 1408, and the rear pad surface 1410. Heat dissipation from the battery cell side surface 1202 is promoted through the gap 22 formed in this way. Specifically, the heat at a location near the upper end surface 1204 of the battery cell on the battery cell side surface 1202 is dissipated to the gap between the upper end surface 1204 of the battery cell and the upper wall 1602 of the module case 16 through the gap 22 opened to the upper pad surface 1404. The heat at a location near the lower end surface 1206 of the battery cell on the battery cell side surface 1202 is dissipated from the lower end surface 1206 of the battery cell to the heat sink 18 through the gap 22 opened to the lower pad surface 1406. The heat at a location near the front end surface 1208 of the battery cell on the battery cell side surface 1202 and at a location near the rear end surface of the battery cell 12 is dissipated to the front wall and the rear wall of the module case 16.

[0019] According to this embodiment, since a plurality of capsules 20 that create holes in the pad 14 by rupturing are arranged near the peripheral portion 14A of the pad 14, the deformation of the battery cell 12 accompanying the deterioration of the battery cell 12 causes the plurality of capsules 20 to rupture, thereby promoting heat dissipation from the battery cell side surface 1202 through the void 22 formed near the peripheral portion 14A of the pad 14. Therefore, when deformation occurs due to the deterioration of the battery cell 12 and the pad 14 at the center of the battery cell 12 can no longer absorb the deformation of the battery cell 12, and even when the centers of adjacent battery cells 12 are in proximity through the crushed pad 14, heat dissipation from the battery cell side surface 1202 can be ensured through the void 22 formed near the peripheral portion 14A of the pad 14. This is advantageous in preventing the temperature rise of the battery cell 12 and suppressing the deterioration of the battery cell 12.

[0020] Further, in this embodiment, since the inside of the capsule 20 is a cavity, when the capsule 20 ruptures, the internal space directly becomes a hole. Thus, holes and voids 22 can be reliably formed near the peripheral portion 14A of the pad 14 where the capsules 20 are arranged. Therefore, it is more advantageous in promoting heat dissipation from the battery cell side surface 1202 through the void 22 formed near the peripheral portion 14A of the pad 14, ensuring heat dissipation from the battery cell 12, preventing the temperature rise of the battery cell 12, and suppressing the deterioration of the battery cell 12.

[0021] Moreover, in this embodiment, among the plurality of capsules 20 arranged near the peripheral portion 14A of the pad 14, the capsules 20 arranged closer to the pair of pad side surfaces 1402 are more numerous than the capsules 20 arranged at the center in the thickness direction of the pad 14. Therefore, when the capsules 20 rupture, more holes and voids 22 are formed closer to the battery cell side surface 1202. Therefore, it is even more advantageous in promoting heat dissipation from the battery cell side surface 1202 through the void 22 formed closer to the battery cell side surface 1202, ensuring heat dissipation from the battery cell 12, preventing the temperature rise of the battery cell 12, and suppressing the deterioration of the battery cell 12.

[0022] Also, when the side surface 1202 of the battery cell 12 expands as the battery cell 12 deteriorates, the central portion of the side surface 1202 of the battery cell deforms more greatly than the peripheral portion of the side surface 1202 of the battery cell. Therefore, the compressive force applied to the pad 14 from the expanding side surface 1202 of the battery cell gradually decreases from the peripheral portion 14A to the central portion of the pad 14. Therefore, in the present embodiment, among the capsules 20 arranged near the peripheral portion 14A of the pad 14, the capsules 20 arranged at the peripheral portion 14A of the pad 14 are formed to rupture at a lower pressure than the capsules 20 arranged at a location closer to the central portion of the pad 14. Therefore, it is advantageous in matching the timing at which the capsules 20 arranged at the peripheral portion 14A of the pad 14 rupture and the timing at which the capsules 20 arranged at a location closer to the central portion of the pad 14 rupture. In other words, it becomes possible to rupture a plurality of capsules 20 arranged near the peripheral portion 14A of the pad 14 simultaneously. Therefore, a plurality of capsules 20 arranged near the peripheral portion 14A of the pad 14 can be efficiently and reliably ruptured, and pores and voids 22 can be efficiently and reliably formed near the peripheral portion 14A of the pad 14. Therefore, it is more advantageous in promoting heat dissipation from the side surface 1202 of the battery cell through the voids 22 formed near the peripheral portion 14A of the pad 14, ensuring heat dissipation from the battery cell 12, preventing a temperature rise of the battery cell 12, and suppressing deterioration of the battery cell 12.

[0023] (Second Embodiment) Next, a second embodiment will be described. In the following embodiments, the same parts and members as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted, and the different parts will be mainly described. Referring to FIGS. 1 - 3 for explanation, in the second embodiment, the difference from the first embodiment is that the inside of the capsule 20 is not a cavity, but is filled with a solvent (not shown) that dissolves the pad 14 inside the capsule 20. When the pad 14 is formed of urethane foam, for example, various conventionally known organic solvents such as ethanol and acetone can be used as such a solvent. Also, when the pad 14 is formed of rubber or elastomer, various conventionally known organic solvents such as toluene can be used.

[0024] According to the second embodiment, of course, the same effects as those of the first embodiment are achieved, and the following effects are achieved. That is, as shown in FIG. 3(B), when the capsule 20 disposed at the peripheral edge portion 14A of the pad 14 ruptures, the solvent inside the capsule 20 dissolves the portion of the pad 14 around the capsule 20, so that a larger volume of pores is formed compared to the case of using the capsule 20 having a hollow inside, and thus a larger volume of voids 22 is formed. Therefore, it is more advantageous in promoting heat dissipation from the battery cell side surface 1202 through the larger volume of voids 22 formed near the peripheral edge portion 14A of the pad 14, ensuring heat dissipation from the battery cell 12, preventing the temperature rise of the battery cell 12, and suppressing the deterioration of the battery cell 12.

[0025] In the embodiment, the case where the battery cell 12 has a rectangular plate shape has been described. However, the shape of the battery cell 12 is not limited, and it goes without saying that the shape of the battery cell 12 in plan view may be various conventionally known shapes such as other polygonal shapes such as triangles and pentagons, or circular shapes.

Description of Reference Numerals

[0026] 10 Battery module 12 Battery cell 1202 Battery cell side surface 1204 Battery cell upper end surface 1206 Battery cell lower end surface 1208 Battery cell front end surface 14 Pad 1402 Pad side surface 1404 Pad upper end surface 1406 Pad lower end surface 1408 Front end surface of the pad 1410 Rear end surface of the pad 14A Peripheral part of the pad 16 Module case 1602 Upper wall 1604 Bottom wall 1606 Side wall 18 Heat sink 20 Capsule 22 Gap

Claims

1. A plurality of stacked battery cells, A plurality of pads made of an elastic material respectively disposed in gaps between adjacent ones of the battery cells, A battery module comprising: a module case that pressurizes the plurality of battery cells in a stacking direction of the battery cells via the plurality of pads by restraining the plurality of battery cells and the plurality of pads, A plurality of capsules that create voids in the pads by rupturing are disposed near a peripheral portion of the pads. A battery module characterized by the above.

2. The interior of the capsules is hollow. The battery module according to Claim 1, characterized by the above.

3. The interior of the capsules is filled with a solvent that dissolves the pads. The battery module according to Claim 1, characterized by the above.

4. The pads have a thickness along the stacking direction, The pads have a pair of side surfaces that are located at both ends in the thickness direction and are overlapped with the battery cells, Among the plurality of capsules disposed near the peripheral portion of the pads, the capsules disposed closer to the pair of side surfaces are more numerous than the capsules disposed at the center in the thickness direction of the pads. The battery module according to any one of Claims 1 to 3, characterized by the above.

5. Among the plurality of capsules disposed near the peripheral portion of the pads, the capsules disposed at the peripheral portion are formed to rupture at a lower pressure than the capsules disposed at a location closer to the center portion of the pads. The battery module according to any one of Claims 1 to 3, characterized by the above.

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