Battery module

Abstract

To provide a battery module having a simple and compact configuration, in which the in-plane surface pressure of each stacked battery cell is made uniform.SOLUTION: In a battery module 1 in which a stack 3 of a plurality of battery cells 2 is sandwiched and held by end plates (first end plate 4 and second end plate 5) from both ends in the stacking direction, the end plates 4 and 5 are battery modules having a convex surface S1 facing the stack 3. In this case, the end plates 4 and 5 may have a concave portion on the side opposite to the facing surface S1. Further, a support 6 may connect and support a high-voltage battery 4 and a low-voltage battery 5 in the stacking direction.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a battery module serving as a power source for an electric vehicle or the like.

Background Art

[0002] In order to properly function a battery module serving as a power source for an electric vehicle or the like, it is necessary to apply pressure in the stacking direction to the stacked battery cells to pressurize them. As a pressurizing method, there is a method of applying a surface pressure load to the battery cells by providing end fixing members (end plates) on both end faces of the stacked body of the battery cells and fastening them with a plurality of bolts or bolts and nuts. Generally, the end fixing member has a substantially uniform section modulus between bolts, and the pressurizing surface is a substantially flat surface. Then, when a predetermined bolt axial force is applied, the end fixing member is deformed in an arc shape, so that the pressurizing surface becomes concave when viewed from the pressurization target. For this reason, the surface pressure applied to the stacked battery cells becomes non-uniform within the plane of each battery cell, and a predetermined performance cannot be exhibited. On the other hand, a technique has been proposed in which the surface pressure of a stacked body with a high height is suppressed and the surface pressure between the stacked battery cells is equalized by imparting deflection to a flat plate-shaped end fixing member (for example, see Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the battery module of Patent Document 1, since a holding means having a screw mechanism or the like is used to adjust the deflection with respect to the end plate, the number of parts is large. In addition, the thickness of the end plate increases, and a space is formed between the stacked battery cells or between the end plate and the battery cells, so that the volume density of the battery becomes low.

[0005] The present invention has been made in view of the above circumstances, and an object thereof is to provide a battery module having a simple and compact configuration in which the in-plane surface pressure of each stacked battery cell is made uniform.

Means for Solving the Problems

[0006] (1) An end plate (for example, the first end plate 4 and the second end plate 5 described later) that sandwiches and holds a laminate (for example, the laminate 3 described later) of a plurality of battery cells (for example, the battery cell 2 described later) constituting a battery module (for example, the battery module 1 described later) from both ends in the stacking direction, wherein the opposing surface (for example, the opposing surface S1 described later) to the laminate has a convex portion.

[0007] (2) The end plate according to (1) above, wherein the surface on the side opposite to the opposing surface has a concave portion (for example, the surface S2 on the side opposite to the opposing surface described later).

[0008] (3) The end plate according to (1) or (2) above, which is interconnected by a plurality of connecting members (for example, the connecting bolt 6 described later) that connect between a plurality of pairs of pressure-receiving portions that are paired between the end plates on both ends, and the section modulus between two of its own pressure-receiving portions is small at an intermediate position between the pressure-receiving portions and large on the pressure-receiving portion side.

[0009] (4) An end plate (for example, the first end plate 4a and the second end plate 5a described later) that sandwiches and holds a laminate (for example, the laminate 3 described later) of a plurality of battery cells (for example, the battery cell 2 described later) that constitute a battery module (for example, the battery module 1a described later) from both ends in the stacking direction. The end plate is connected by a plurality of connecting members (for example, the connecting bolt 6 described later) that connect between a plurality of pairs of pressure-receiving portions (for example, the pressure-receiving portions 11 and 12 described later) that form pairs between the end plates on both ends. The opposing surface (for example, the opposing surface S1a described later) to the laminate has a convex portion and has a plurality of through holes (for example, H00, H11, …, H15, H16, (H00), H21, …, H25, H26) that penetrate its interior in the in-plane direction.

[0010] (5) The end plate according to (4) above, wherein the plurality of through holes are formed in a form such that the section modulus between two of the pressure-receiving portions in the one end plate is relatively large near the pressure-receiving portion and relatively low at a portion separated from the pressure-receiving portion.

[0011] (6) The end plate according to (5) above, wherein the plurality of through holes have a larger opening area for those closer to the central position between the pressure-receiving portions and a smaller opening area for those closer to the pressure-receiving portion.

[0012] (7) The end plate according to (5) above, wherein the plurality of through holes are formed in a truss shape in which the partition walls between adjacent ones are inclined with respect to the width direction of the end plate.

[0013] (8) A battery module (for example, the battery module 1 described later) in which a laminate of a plurality of battery cells is sandwiched and held by end plates (for example, the first end plate 4 and the second end plate 5 described later) from both ends in the stacking direction. The opposing surface (for example, the opposing surface S1 described later) of the end plate to the laminate has a convex portion.

[0014] (9) In the battery module of (8) above, the end plate has a concave portion on the surface opposite to the facing surface (for example, the surface S2 opposite to the facing surface described later).

[0015] (10) The battery module of (8) or (9) above includes a plurality of connecting members that connect between a plurality of pairs of pressure-receiving portions that are paired between the two end plates on both end sides, and the end plate has a sectional modulus between two of the pressure-receiving portions of itself that is small at an intermediate position between the pressure-receiving portions and large on the pressure-receiving portion side.

[0016] (11) A battery module in which a laminate of a plurality of battery cells is sandwiched and held by end plates from both ends in the stacking direction, the battery module includes a plurality of connecting members that connect between a plurality of pairs of pressure-receiving portions that are paired between the two end plates on both end sides, and the end plate has a plurality of through holes that penetrate its interior in the in-plane direction.

[0017] (12) In the end plate of (11) above, the plurality of through holes are formed in a form in which the sectional modulus between two of the pressure-receiving portions in the one end plate is relatively large near the pressure-receiving portion and relatively low at a portion separated from the pressure-receiving portion.

[0018] (6) In the battery module of (12) above, the plurality of through holes have a larger opening area the closer they are to the central position between the pressure-receiving portions and a smaller opening area the closer they are to the pressure-receiving portion.

[0019] (14) In the battery module of (12) above, the plurality of through holes are formed in a truss shape in which the partition walls between adjacent ones are inclined with respect to the width direction of the end plate. [Effect of the Invention]

[0020] In the end plate of (1), since the surface facing the laminate has a convex portion, when the laminate of battery cells is sandwiched, the surface of the end plate on the battery cell side becomes substantially flat, and the surface pressure during sandwiching can be made uniform in the plane.

[0021] (2) In the end plate, the surface facing the laminate has a convex portion, and the surface opposite to the surface facing the laminate has a concave portion. For this reason, the section modulus of the end plate becomes relatively smaller at the central portion in the plane than at the peripheral portion, and the surface on the battery cell side is likely to become a substantially flat surface.

[0022] (3) In the end plate of (3), the end plates on both ends are interconnected by a plurality of connecting members that connect between a plurality of pairs of pressure-receiving portions that are paired between the end plates on both ends, and the section modulus between the two pressure-receiving portions of itself is small at the intermediate position between the pressure-receiving portions and large on the pressure-receiving portion side. For this reason, since it is easy to make the change in the section modulus in the end plate continuous, the surface on the battery cell side can be made more likely to become a substantially flat surface. That is, the uniformization of the surface pressure in the plane of the battery cell becomes even easier. Moreover, for this reason, it is not necessary to increase the number of parts, and therefore, the thickness of the end plate is not increased by those parts, so that downsizing can be achieved.

[0023] (4) The end plate of (4) has a plurality of through holes penetrating its interior in the in-plane direction. For this reason, the change in the section modulus can be made to change pseudo-continuously by the cutout by the through holes, and the surface on the battery cell side can be made likely to become a substantially flat surface. Also, weight reduction can be achieved by the cutout. Moreover, it is not necessary to increase the number of parts, and therefore, the thickness of the end plate is not increased by those parts, so that downsizing can be achieved. Furthermore, the side opposite to the surface on the battery cell side, which is the pressurized surface, can be made flat, and it is easy to handle when mounting other component parts.

[0024] In the end plate of (5), the plurality of through holes are formed in such a manner that the section modulus between the two pressure-receiving portions in the one end plate is relatively large in the vicinity of the pressure-receiving portion and relatively low in a portion separated from the pressure-receiving portion. Therefore, the surface on the battery cell side can be easily made substantially flat. That is, the surface pressure in the plane of the battery cell can be more easily made uniform. Moreover, for this reason, it is not necessary to increase the number of parts, and thus, the thickness of the end plate is not increased by those parts, so that downsizing can be achieved.

[0025] In the end plate of (6), the section modulus in the end plate can be made pseudo-continuously smaller as the position is closer to the central position between the pressure-receiving portions. Therefore, the surface pressure in the plane of the battery cell can be more easily made uniform.

[0026] In the end plate of (7), the section modulus in the end plate can be made pseudo-continuously smaller as the position is closer to the central position between the pressure-receiving portions. Therefore, the surface pressure in the plane of the battery cell can be more easily made uniform.

[0027] In the battery module of (8), since the surface of the end plate facing the laminate has a convex portion, when the laminate of the battery cells is clamped, the surface of the end plate on the battery cell side becomes substantially flat, and the surface pressure during clamping can be made uniform in the plane.

[0028] In the battery module of (9), the end plate has a convex portion on the surface facing the laminate and a concave portion on the surface opposite to the surface facing the laminate. For this reason, the section modulus of the end plate becomes relatively smaller at the central portion in the plane than at the peripheral portion, and the surface on the battery cell side can be easily made substantially flat.

[0029] In the battery module of (10), a plurality of connecting members are provided which connect between a plurality of pairs of pressure receiving portions that are paired between both end plates on both end sides of the laminate between the both end plates. The end plate has a sectional modulus between two of its own pressure receiving portions that is small at an intermediate position between the pressure receiving portions and large on the pressure receiving portion side. For this reason, since it is easy to make the change in the sectional modulus in the end plate continuous, it is possible to make the surface on the battery cell side even more likely to be a substantially flat surface. That is, it becomes even easier to equalize the surface pressure within the plane of the battery cell. Moreover, for this purpose, it is not necessary to increase the number of parts, and thus, since the thickness of the end plate is not increased by those parts, downsizing can be achieved.

[0030] In the battery module of (11), the end plate has a plurality of through holes that penetrate its interior in the in-plane direction. For this reason, by thinning due to the through holes, the change in the sectional modulus can be made to change pseudo-continuously, and the surface on the battery cell side can be made likely to be a substantially flat surface. Also, weight reduction can be achieved by thinning. Moreover, it is not necessary to increase the number of parts, and thus, since the thickness of the end plate is not increased by those parts, downsizing can be achieved. Furthermore, the side opposite to the surface on the battery cell side, which is the pressurized surface, can be made planar, making it easy to handle when mounting other component parts.

[0031] In the battery module of (12), the plurality of through holes are formed in such a form that the sectional modulus between two of the pressure receiving portions in the one end plate is relatively large in the vicinity of the pressure receiving portion and relatively low at a portion separated from the pressure receiving portion. For this reason, the surface on the battery cell side can be made likely to be a substantially flat surface. That is, it becomes even easier to equalize the surface pressure within the plane of the battery cell. Moreover, for this purpose, it is not necessary to increase the number of parts, and thus, since the thickness of the end plate is not increased by those parts, downsizing can be achieved.

[0032] In the battery module of (13), the section modulus in the end plate can be made pseudo-continuously smaller as the position gets closer to the central position between the pressure-receiving parts. Therefore, it becomes even easier to equalize the surface pressure within the plane of the battery cell.

[0033] In the battery module of (14), the section modulus in the end plate can be made pseudo-continuously smaller as the position gets closer to the central position between the pressure-receiving parts. Therefore, it becomes even easier to equalize the surface pressure within the plane of the battery cell.

Brief Description of the Drawings

[0034]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Modes for Carrying Out the Invention

[0035] (First Embodiment) Hereinafter, the first embodiment of the present invention will be described with reference to the drawings. In the drawings shown below, the same parts or corresponding parts are denoted by the same reference numerals. FIG. 1 is a plan view showing a battery module as the first embodiment of the present invention, FIG. 2 is a side view showing the battery module of FIG. 1, FIG. 3 is a view of the battery module of FIG. 1 seen from one end plate side, and FIG. 4 is a view of the battery module of FIG. 1 seen from the other end plate side.

[0036] The battery module 1 of the first embodiment is configured by sandwiching and holding a laminate 3 of a plurality of flat-shaped battery cells 2, which are laminates such as laminated lithium-ion battery cells, for example, between a first end plate 4 and a second end plate 5 from both ends in the stacking direction. Each battery cell 2 is configured such that a laminated electrode LE is packed with a laminate sheet, and a positive electrode terminal (positive electrode tab) TP and a negative electrode terminal (negative electrode tab) TN are led out through a predetermined in-cell connection. The battery cells 2 are alternately stacked such that those of a type in which the terminal pair of the positive electrode tab TP and the negative electrode tab TN is arranged closer to the right end side and those of a type in which they are arranged in reverse and closer to the left end side to form the laminate 3. The first end plate 4 and the second end plate 5 are tightened by connection bolts 6, which are four connecting members, in a direction to narrow the distance between both end plates 4 and 5. For the first end plate 4 and the second end plate 5, the surface facing the laminate 3 is referred to as S1, and the surface on the side opposite to the facing surface S1 is referred to as S2. As will be described later, the facing surface S1 to the laminate 3 has a convex portion, and the surface S2 on the side opposite to the facing surface S1 has a concave portion.

[0037] The connecting bolt 6 has a shaft portion 7 forming the main body, a head portion 8 formed at one end side of the shaft portion 7, and a male thread portion 9 formed at the other end side of the shaft portion 7, and a nut 10 is screwed onto the male thread portion 9. On the other hand, the nut 10 is in surface contact with the first end plate 4, and a pressure receiving portion 11 for receiving the pressing force from the nut 10 is formed. Further, on the second end plate 5, a pressure receiving portion 12 for receiving the pressing force from the nut 10 is formed by surface contact with the head portion 8 of the connecting bolt 6. The pressure receiving portion 11 of the first end plate 4 and the pressure receiving portion 12 of the second end plate 5 are located on both end sides of one connecting bolt 6 and form a pair. Corresponding to the four connecting bolts 6, there are four pairs of the pressure receiving portion 11 and the pressure receiving portion 12. That is, the four connecting bolts 6 connect between a plurality of pairs (four pairs) of the pressure receiving portions 11 and 12 that form pairs between the first end plate 4 and the second end plate 5.

[0038] Specifically, as shown in FIGS. 1 to 4, the four connecting bolts 6 are a first connecting bolt 61, a second connecting bolt 62, a third connecting bolt 63, and a fourth connecting bolt 64. Here, when paying attention around the first connecting bolt 61, the pressing force from the nut 10 screwed onto the male thread portion 9 acts on the pressure receiving portion 11 of the first end plate 4. Each nut 10 fits into recesses 41 formed in the thickness direction at the four corners of the surface S2 on the side opposite to the facing surface S1 of the laminate 3 of the first end plate 4 in the tightened state.

[0039] Also, the pressing force from the head portion 8 acts on the pressure receiving portion 12 of the second end plate 5. The first end plate 4 and the second end plate 5 are each provided with four insertion holes 13 for inserting the four connecting bolts 6. In the vicinity of the position where the nut 10 is screwed onto the male thread portion 9 of the connecting bolt 6 and at the portion inserted into the insertion hole 13, a nut-side large diameter portion 14 having a larger diameter than the male thread portion 9 and the shaft portion 7 is coaxially formed. The nut-side large diameter portion 14 fits tightly with a nut-side inlay portion 15 formed in the insertion hole 13, and the connecting bolt 6 is centered on the nut 10 side.

[0040] Further, a large-diameter portion 16 on the head portion side with a diameter larger than that of the shaft portion 7 is coaxially formed at a portion inserted into an insertion hole 13 continuous with the head portion 8 of the connecting bolt 6. The large-diameter portion 16 on the head portion side is closely fitted with an inlay portion 17 on the head portion side formed in the insertion hole 13, and the connecting bolt 6 is centered on the head portion 8 side.

[0041] On the other hand, the head portions 8 of the first connecting bolt 61, the second connecting bolt 62, the third connecting bolt 63, and the fourth connecting bolt 64 are substantially disk-shaped, and a notch portion 81 for preventing rotation, as visible in FIG. 4, is formed in a part of the outer periphery thereof. Each notch portion 81 abuts against a contact surface 52 of a recess 51 formed in the thickness direction at the four corners of a surface S2 opposite to the surface S1 facing the laminate 3 of the second end plate 5, and displacement around the axis is restricted.

[0042] FIG. 5 is a view showing the first end plate 4 of the battery module 1 in FIG. 1 alone. In FIG. 5, the first end plate 4 alone is shown enlarged in the same viewing angle as in FIG. 1. Insertion holes 13, nut-side inlay portions 15, recesses 41, and pressure-receiving portions 11 described with reference to FIG. 1 are provided on both end sides in the width direction of the first end plate 4. As shown in the figure, the center of the pressure-receiving portion 11 coincides with the axis of the connecting bolt 6 passing through the insertion hole 13. Let the central position from the right end side (the lower pressure-receiving portion 11 side in FIG. 5) to the left end side (the upper pressure-receiving portion 11 side in FIG. 5) in the width direction of the first end plate 4 be w5, and let them be w4, w3, w2, w1 at equal intervals from there toward the right end side (the lower side in FIG. 5). Similarly, let them be w6, w7, w8, w9 at equal intervals from w5 toward the left end side (the upper side in FIG. 5).

[0043] The first end plate 4 has a convex surface portion on the opposing surface S1 to the laminate 3. In the example of FIG. 5, substantially the entire opposing surface S1 is convex in the contact direction with the laminate 3. That is, with respect to the virtual plane VP passing through both ends of the opposing surface S1 to the laminate 3, the opposing surface S1 has the maximum separation width at the central position w5 with a separation of w5. Specifically, the opposing surface S1 of the first end plate 4 gradually separates from the virtual plane VP from the position w1 to w2, w3, w4, w5 in the contact direction with the laminate 3, has the maximum separation width from the virtual plane VP at the central position w5, and exhibits a curved surface in which the separation width gradually decreases from the central position w5 to the positions w6, w7, w8, w9.

[0044] On the other hand, the surface S2 on the side opposite to the opposing surface S1 of the first end plate 4 to the laminate 3 has a concave surface portion. In the example of FIG. 5, substantially the entire surface S2 on the side opposite to the opposing surface S1 is concave in the contact direction with the laminate 3. Specifically, the surface S2 of the first end plate 4 gradually depresses from the position w1 to w2, w3, w4, w5 in the contact direction with the laminate 3, has the maximum depth of depression at the central position w5, and exhibits a curved surface in which the depth of depression gradually decreases from the central position w5 to the positions w6, w7, w8, w9.

[0045] The characteristics of the first end plate 4 having the above-described shape will be described from the viewpoint of the section modulus (bending rigidity). The section modulus of the first end plate 4 gradually decreases from the position w1 to w2, w3, w4, w5, becomes minimum at the central position w5, gradually increases from the central position w5 to the positions w6, w7, w8, w9, and tends to be substantially equal to the section modulus at the position w1 at the position w9. That is, in the first end plate 4, the section modulus between the two pressure receiving portions 11, 11 on the left and right is small at the position w5 which is the intermediate position between the two pressure receiving portions 11, 11 and large on the sides of the two pressure receiving portions 11, 11 (the positions w1, w9 side).

[0046] FIG. 6 is a diagram showing the distribution of surface pressure during pressurization of the first end plate 4 described with reference to FIG. 5. In the figure, the direction of the arrow represents the direction in which the surface pressure acts from the laminate 3 toward the opposing surface S1, and the length represents the magnitude of the surface pressure at the position of the arrow. The value obtained by integrating the surface pressure Ptr at each position (infinitesimal unit area) of the opposing surface S1 over the entire area of the opposing surface S1 is the total pressure on the opposing surface S1. This phenomenon is the same for the second end plate 5. That is, the first end plate 4 and the second end plate 5 sandwich and hold the laminate 3 with four connecting bolts 6, and this total pressure is generated. Therefore, if the axial force of one connecting bolt 6 is Ftr, a force several times (four times) that amount opposes the above total pressure. At the stage during pressurization as shown in FIG. 6, the surface pressure at each part within the plane of the opposing surface S1 shows the following tendency when focusing on each position assumed in FIG. 5. That is, starting from position w1, it gradually increases to positions w2, w3, w4, w5, and the surface pressure of the infinitesimal unit area becomes maximum at the central position w5. From the central position w5, it gradually decreases to positions w6, w7, w8, w9, and the surface pressure of the infinitesimal unit area at position w9 tends to be approximately equal to the value at position w1. That is, the surface pressure at each part within the plane of the opposing surface S1 shows a distribution that varies depending on the position, being large at the center of the convex opposing surface S1 and small at the periphery, and does not become uniform over the entire surface. For this reason, in the state of FIG. 6, each battery cell 2 constituting the laminate 3 cannot exhibit sufficient performance. From this state, each nut 10 of the four connecting bolts 6 is further tightened to increase the axial force of the connecting bolts 6. Then, initially, the opposing surface S1, which was convex, gradually bends toward the central position w5 according to the distribution of the section modulus described with reference to FIG. 5 and approaches a flat surface.

[0047] FIG. 7 is a diagram showing the surface pressure distribution at the completion of pressurization of the first end plate 4 described with reference to FIG. 5. Similar to FIG. 6, the direction of the arrow indicates the direction in which the surface pressure acts from the laminate 3 to the opposing surface S1, and the length represents the magnitude of the surface pressure at the position of the arrow. At the stage of pressurization in FIG. 6, the surface pressure at each part in the plane of the opposing surface S1 exhibits a distribution that varies depending on the position, being large at the center of the convex opposing surface S1 and small at the periphery, and is not uniform across the entire surface. When each nut 10 of the four connecting bolts 6 is further tightened from this stage to increase the axial force of the connecting bolts 6, the opposing surface S1 of the first end plate 4 bends more easily at the central position w5 according to the distribution of the section modulus described with reference to FIG. 5 and becomes a substantially perfect plane as shown in FIG. 7. In this case, the axial force of each of the four connecting bolts 6 becomes an axial force Ftarget that is larger than Ftr at the stage of FIG. 5. Also, the surface pressure at each position (infinitesimal unit area) in the plane of the opposing surface S1 becomes a uniform design target value Ptarget across the entire surface of the opposing surface S1 that has become a substantially perfect plane. Therefore, the value obtained by simply multiplying this value Ptarget by the area of the opposing surface S1 is the total pressure. This total pressure counteracts several times (4 times) the axial force F of one connecting bolt 6. In the state of FIG. 7, the surface pressure in the plane of the opposing surface S1 becomes a uniform target value Ptarget across the entire surface. For this reason, the surface pressure in the plane of each battery cell 2 constituting the laminate 3 is equalized, and the battery module can exhibit sufficient performance.

[0048] With reference to FIGS. 5 to 7, the structure and mechanical characteristics of the first end plate 4 have been described. The structure and mechanical characteristics of the second end plate 5 are also in a form similar to that described above for the first end plate 4.

[0049] (Second Embodiment) Next, a second embodiment of the present invention will be described with reference to the drawings. In the following figures, the same parts or corresponding parts are denoted by the same reference numerals. FIG. 8 is a plan view showing a battery module as a second embodiment of the present invention, FIG. 9 is a side view showing the battery module of FIG. 8, FIG. 10 is a view of the battery module of FIG. 8 seen from one end plate side, and FIG. 11 is a view of the battery module of FIG. 8 seen from the other end plate side.

[0050] The battery module 1a of the second embodiment is configured by sandwiching and holding a laminate 3 of a plurality of battery cells 2, which are laminates such as laminated pack lithium ion battery cells, between a first end plate 4a and a second end plate 5a from both ends in the lamination direction. Each battery cell 2 is configured such that a laminated electrode LE is packed with a laminate sheet, and a positive electrode terminal (positive electrode tab) TP and a negative electrode terminal (negative electrode tab) TN are led out through a predetermined in-cell connection. The battery cells 2 are alternately laminated with those having a terminal pair of the positive electrode tab TP and the negative electrode tab TN arranged closer to the right end side and those arranged closer to the left end side to form the laminate 3. The first end plate 4a and the second end plate 5a are tightened by connection bolts 6, which are four connecting members, in a direction to narrow the distance between both end plates 4a and 5a. For the first end plate 4a and the second end plate 5a, the surfaces facing the laminate 3 are referred to as S1a, and the surfaces opposite to the facing surfaces S1a are referred to as S2a.

[0051] The connecting bolt 6 has a shaft portion 7 forming the main body, a head portion 8 formed on one end side of the shaft portion 7, and a male screw portion 9 formed on the other end side of the shaft portion 7, and a nut 10 is screwed onto the male screw portion 9. On the other hand, a pressure receiving portion 11 that is in surface contact with the nut 10 and receives the pressing force from the nut 10 is formed on the first end plate 4a. Further, on the second end plate 5a, a pressure receiving portion 12 that is in surface contact with the head portion 8 of the connecting bolt 6 and receives the pressing force from the nut 10 is formed. The pressure receiving portion 11 of the first end plate 4a and the pressure receiving portion 12 of the second end plate 5a are located on both end sides of one connecting bolt 6 and form a pair. Corresponding to the four connecting bolts 6, there are four pairs of the pressure receiving portion 11 and the pressure receiving portion 12. That is, the four connecting bolts 6 connect between a plurality of pairs (four pairs) of the pressure receiving portions 11 and 12 that form a pair between the first end plate 4a and the second end plate 5a.

[0052] Specifically, as shown in FIGS. 8 to 11, the four connecting bolts 6 are a first connecting bolt 61, a second connecting bolt 62, a third connecting bolt 63, and a fourth connecting bolt 64. Here, when paying attention around the first connecting bolt 61, the pressing force from the nut 10 screwed onto the male screw portion 9 acts on the pressure receiving portion 11 of the first end plate 4a. Each nut 10 fits into recesses 41 formed in the thickness direction at the four corners of the surface S2 on the side opposite to the facing surface S1 of the first end plate 4a to the laminate 3 in the tightened state.

[0053] Further, the pressing force from the head portion 8 acts on the pressure receiving portion 12 of the second end plate 5a. The first end plate 4a and the second end plate 5a are each provided with four insertion holes 13 through which the four connecting bolts 6 are inserted. In the vicinity of the position where the nut 10 is screwed onto the male screw portion 9 of the connecting bolt 6 and at the portion inserted through the insertion hole 13, a nut-side large-diameter portion 14 having a larger diameter than the male screw portion 9 and the shaft portion 7 is coaxially formed. The nut-side large-diameter portion 14 fits tightly with a nut-side inlay portion 15 formed in the insertion hole 13, and the connecting bolt 6 is centered on the nut 10 side.

[0054] On one hand, the head portions 8 of the first connecting bolt 61, the second connecting bolt 62, the third connecting bolt 63, and the fourth connecting bolt 64 are generally disk-shaped, and a notch portion 81 for anti-rotation as visually recognized in FIG. 11 is formed in a part of their outer peripheries. Each notch portion 81 abuts against the contact surface 52 of the recess 51 formed in the thickness direction at the four corners of the surface S2a on the side opposite to the facing surface S1a of the laminate 3 of the second end plate 5a, and the displacement around the axis is restricted.

[0055] In the second embodiment of the present invention shown in FIGS. 8 to 11, the forms of the first end plate 4a and the second end plate 5a are different from those of the first embodiment. The first end plate 4a and the second end plate 5a have a plurality of through holes H penetrating in the in-plane direction inside them. The longitudinal direction of each through hole H is in the in-plane direction and is the vertical direction of the first end plate 4a and the second end plate 5a (the direction connecting the side where the electrodes TP and TN of each battery cell 2 are provided and the opposite side). That is, the longitudinal direction of each through hole H is the direction intersecting perpendicularly to the paper surface in FIG. 8, the vertical direction in FIG. 9, and the left-right direction in FIGS. 10 and 11.

[0056] As shown in the figure, among the plurality of through holes H, the through hole H00 at the central position in the vertical direction of the first end plate 4a and the second end plate 5a has the largest opening area. The sequential through holes H11,..., H15, H16 at positions going from the central through hole H00 to the right side (the lower side in FIG. 8) take a form in which the opening area gradually decreases sequentially. Also, the sequential through holes H21,..., H25, H26 at positions going from the central through hole H00 to the left side (the upper side in FIG. 8) take a form in which the opening area gradually decreases sequentially. Alternatively, ribs between the through holes may not be provided parallel to each other, but may be set in a diagonal truss shape or the like so that the section modulus (section rigidity) gradually decreases toward the central portion.

[0057] The first end plate 4a and the second end plate 5a are provided with through holes H00, H11, …, H15, H16, (H00), H21, …, H25, H26 as described above. For this reason, the section modulus of the first end plate 4a between the two left and right pressure-receiving portions 11, 11 is small at the location where the through hole H00 is provided at the intermediate position between the two pressure-receiving portions 11, 11 and large on the sides of the two pressure-receiving portions 11, 11 (the sides where the through holes H16 and H26 are provided). Similarly, the section modulus of the second end plate 5a between the two left and right pressure-receiving portions 12, 12 is small at the location where the through hole H00 is provided at the intermediate position between the two pressure-receiving portions 12, 12 and large on the sides of the two pressure-receiving portions 12, 12 (the sides where the through holes H16 and H26 are provided). The section moduli of the first end plate 4a and the second end plate 5a change discontinuously and stepwise between the two left and right pressure-receiving portions. By adopting a structure in which the stepwise change in the opening area of the through hole gradually changes in a large number of steps, it is also possible to obtain an end plate in a form in which the section modulus shows a pseudo-continuous change. Since the first end plate 4a and the second end plate 5a have a structure in which the section modulus changes stepwise or pseudo-continuously as described above, as described with reference to FIGS. 6 and 7, the in-plane surface pressure when sandwiching and holding the laminate 3 of the plurality of battery cells 2 becomes a uniform value over the entire surface. For this reason, the in-plane surface pressure of each battery cell 2 constituting the laminate 3 is equalized, and the battery module 1a can exhibit sufficient performance.

[0058] According to the end plate and the battery module of the embodiment of the present invention, the following effects are obtained.

[0059] (1) In the first end plate 4 and the second end plate 5, since the facing surface S1 to the laminate 3 has a convex portion, when sandwiching the laminate 3 of the battery cells 2, the surfaces of the first end plate 4 and the second end plate 5 on the battery cell 2 side become substantially flat, and the surface pressure during sandwiching can be equalized in the plane.

[0060] (2) The facing surface S1 to the laminate 3 has a convex portion, and the surface S2 on the side opposite to the facing surface S1 to the laminate 3 has a concave portion. For this reason, the section modulus of the first end plate 4 and the second end plate 5 becomes relatively smaller at the central portion in the plane than at the peripheral portion, and the surface on the battery cell 2 side is likely to become substantially flat.

[0061] (3) The first end plate 4 and the second end plate 5 are interconnected by a plurality of connecting bolts 6 that connect between a plurality of pairs of pressure-receiving portions 11 and 12 that are paired between the first end plate 4 and the second end plate 5, and the section modulus between two of its own pressure-receiving portions 11, 11; 12, 12 is small at the intermediate position between the pressure-receiving portions and large on the pressure-receiving portion side. For this reason, since it is easy to make the change in the section modulus in the first end plate 4 and the second end plate 5 continuous, it is possible to make the surface on the battery cell 2 side even more likely to become substantially flat. That is, the surface pressure in the plane of the battery cell 2 can be made even more uniform. Moreover, for this reason, it is not necessary to increase the number of parts, and therefore, the thickness of the first end plate 4 and the second end plate 5 is not increased by those parts, so that downsizing can be achieved.

[0062] (4) The first end plate 4a and the second end plate 5a whose facing surface S1a to the laminate 3 has a convex portion have a plurality of through holes H00, H11, H15, H16, H21, H25, H26 that penetrate the inside in the plane direction. For this reason, the change in the section modulus can be made to change pseudo-continuously by the cutouts by the through holes H00, H11, H15, H16, H21, H25, H26, and the surface S1a on the battery cell 2 side can be made likely to become substantially flat. Also, weight reduction can be achieved by the cutouts. Moreover, it is not necessary to increase the number of parts, and therefore, the thickness of the first end plate 4a and the second end plate 5a is not increased by those parts, so that downsizing can be achieved. Furthermore, the side opposite to the surface on the battery cell 2 side, which is the pressurized surface, can be made flat, and it is easy to handle when attaching other component parts.

[0063] (5) The first end plate 4a and the second end plate 5a have a plurality of through holes H00, H11, H15, H16, H21, H25, H26 formed in such a manner that the section modulus between two pressure receiving portions 11, 11; 12, 12 in the one end plate, the first end plate 4a (the second end plate 5a), is relatively large near the pressure receiving portion and relatively low at a portion separated from the pressure receiving portion. For this reason, the surface on the battery cell 2 side can be easily made substantially flat. That is, the surface pressure can be more easily equalized within the plane of the battery cell 2. Moreover, for this purpose, it is not necessary to increase the number of parts, and thus, since the thickness of the end plate is not increased by those parts, downsizing can be achieved.

[0064] (6) Among the plurality of through holes H00, H11, H15, H16, H21, H25, H26 of the first end plate 4a and the second end plate 5a, those closer to the central position between the pressure receiving portions 11, 11; 12, 12 have a larger opening area, and those closer to the pressure receiving portions 11; 12 have a smaller opening area. For this reason, the section modulus in the first end plate 4a and the second end plate 5a can be made pseudo - continuously smaller at positions closer to the central position between the pressure receiving portions 11, 11; 12, 12. Therefore, the surface pressure can be more easily equalized within the plane of the battery cell 2.

[0065] (7) The plurality of through holes of the first end plate and the second end plate are formed in a truss shape in which the partition walls between adjacent ones are inclined with respect to the width direction of the end plate. For this reason, the section modulus in the end plate can be made pseudo - continuously smaller at positions closer to the central position between the pressure receiving portions. Therefore, the surface pressure can be more easily equalized within the plane of the battery cell.

[0066] (8) The battery module 1 includes a first end plate 4 and a second end plate 5 that sandwich and hold a stack 3 of a plurality of battery cells 2 from both ends in the stacking direction. The opposing surfaces S1 of the first end plate 4 and the second end plate 5 to the stack 3 have convex portions. Therefore, when the stack 3 of the battery cells 2 is clamped, the surfaces S1 on the battery cell 2 side of the first end plate 4 and the second end plate 5 become substantially flat, and the surface pressure during clamping can be made uniform in the plane.

[0067] (9) The battery module 1 has concave portions on the surfaces S2 of the first end plate 4 and the second end plate 5 on the side opposite to the opposing surfaces S1 to the stack 3. For this reason, the section modulus of the first end plate 4 and the second end plate 5 tends to be smaller on the central side than on the end side of the end plate. Therefore, the first end plate 4 and the second end plate 5 are more easily bent toward the central position w5 of the opposing surface S1 to the stack 3 according to the distribution of the section modulus, and become substantially a complete plane in a state where the stack 3 is sandwiched and held from both ends in the stacking direction. As a result, the surface pressure of the opposing surface S1 to the stack 3 becomes uniform in the plane. For this reason, each battery cell 2 constituting the stack 3 can exhibit sufficient performance.

[0068] (10) The battery module 1 includes connection bolts 6 (61, 62, 63, 64) which are a plurality of connection members that connect between a plurality of pairs of pressure receiving portions 11-12 that are paired between the first end plate 4 and the second end plate 5. The first end plate 4 and the second end plate 5 have a section modulus that is small at the intermediate position between the two pressure receiving portions 11, 11 and 12, 12 of themselves and large on the pressure receiving portion side. For this reason, according to the distribution of the section modulus, it is more easily bent toward the central position w5 of the opposing surface S1 to the stack 3, and becomes substantially a complete plane in a state where the stack 3 is sandwiched and held from both ends in the stacking direction. As a result, the surface pressure of the opposing surface S1 to the stack 3 becomes uniform in the plane. As a result, each battery cell 2 constituting the stack 3 can exhibit sufficient performance.

[0069] (11) The battery module 1a includes connection bolts 6 (61, 62, 63, 64) which are a plurality of connection members connecting between a plurality of pairs of pressure receiving parts 11-12 that form pairs between the first end plate 4 and the second end plate 5 that sandwich and hold the laminate 3 of the plurality of battery cells 2 from both ends in the stacking direction. The first end plate 4 and the second end plate 5 have a convex surface part on the facing surface S1a to the laminate 3, and have a plurality of through holes H00, H11, …, H15, H16, (H00), H21, …, H25, H26 that penetrate their own interiors in the in-plane direction and sequentially change in size. For this reason, the first end plate 4 and the second end plate 5 can be configured such that the section modulus is smaller on the central part side than on the end part side. Therefore, the in-plane surface pressure when sandwiching and holding the laminate 3 of the plurality of battery cells 2 can be made uniform over the entire surface, and thereby, each battery cell 2 constituting the laminate 3 can exhibit sufficient performance.

[0070] (12) In the battery module 1a, the through holes H00, H11, …, H15, H16, (H00), H21, …, H25, H26 that sequentially change in size are formed in a form such that the section modulus between two pressure receiving parts 11, 11 (12, 12) in the one end plate, the first end plate 4a (the second end plate 5a) is relatively large near the pressure receiving part and relatively low at a site separated from the pressure receiving part. For this reason, the surface S1 on the battery cell 2 side can be easily made substantially flat. That is, the uniformization of the in-plane surface pressure of the battery cell 2 becomes even easier. Moreover, for this reason, it is not necessary to increase the number of parts, and therefore, since the thickness of the end plate is not increased by those parts, downsizing can be achieved.

[0071] (13) In the battery module 1a, among the plurality of through holes H00, H11, …, H15, H16, (H00), H21, …, H25, H26 of the first end plate 4 and the second end plate 5, those closer to the central position between the plurality of pairs of pressure receiving parts 11-12 have a larger opening area, and those closer to the pressure receiving parts 11, 12 have a smaller opening area. Therefore, the uniformization of the in-plane surface pressure of the battery cell becomes even easier.

[0072] (14) The battery module 1a has a plurality of through holes H00, H11, …, H15, H16, (H00), H21, …, H25, H26. Since the partition walls between adjacent ones are formed in a truss shape inclined with respect to the width direction of the end plate first end plate 4a (second end plate 5a), the section modulus in the end plate first end plate 4a (second end plate 5a) can be made pseudo-continuously smaller as the position is closer to the central position between the pressure-receiving parts. Therefore, it becomes even easier to equalize the in-plane surface pressure of the battery cell 2.

[0073] As described above, the embodiments of the present invention have been described, but the present invention is not limited thereto. Within the scope of the gist of the present invention, the detailed configuration may be appropriately changed. For example, in the above-described first embodiment example and second embodiment, in order to sandwich and hold the laminate of a plurality of battery cells between end plates from both ends in the stacking direction, a configuration is adopted in which both end plates are connected using connection bolts as connection members. However, the connection member is not limited to connection bolts, and a configuration using a plate-shaped long member can also be adopted.

[0074] Also, in the second embodiment, as both end plates, those having a plurality of through holes penetrating their own interiors in the in-plane direction are applied. However, instead of this, an extruded material or a drawn material or a member formed by stacking members made of different materials may be applied, as long as the section modulus thereof changes as in the end plate in the above-described aspect. Also in that case, the change in the section modulus may be made to change discontinuously step by step, or may be made to change pseudo-continuously.

Explanation of reference numerals

[0075] 1, 1a… Battery module 2… Battery cell 3… Laminate 4… First end plate 5… Second end plate 6… Connection bolt 7… Shaft portion 8… Head portion 9…Male thread part 10…Nut 11, 12…Pressure receiving part 13…Insertion hole 14…Large diameter part on nut side 15…Inlet part on nut side 16…Large diameter part on head part side 17…Inlet part on head part side 41…Recessed part 51…Recessed part 52…Contact surface 61…First connecting bolt 62…Second connecting bolt 63…Third connecting bolt 64…Fourth connecting bolt 81…Notch part H00, H11, H15, H16, H21, H25, H26…Through hole S1, S1a…Opposing surface to laminate S2, S2a…Surface opposite to opposing surface to laminate

Claims

1. An end plate that sandwiches and holds a laminate of a plurality of battery cells constituting a battery module from both end sides in the stacking direction, Connected by a plurality of connecting members that connect between a plurality of pairs of pressure-receiving portions that form pairs between the end plates on both end sides, the facing surface to the laminate has a convex portion, and has a plurality of through holes that penetrate its interior in the in-plane direction, Fastened by the connecting member in a direction to narrow the distance between the end plates on both end sides, and as the facing surface becomes flat, both end plates on both end sides are deformed so that the in-plane surface pressure of the plurality of battery cells is made uniform, The plurality of through holes are formed in a form in which the section modulus between two of the pressure-receiving portions in the one end plate is relatively large near the pressure-receiving portion and relatively low at a portion separated from the pressure-receiving portion. End plate.

2. The end plate according to claim 1, wherein the plurality of through holes have a larger opening area the closer they are to the central position between the pressure-receiving portions and a smaller opening area the closer they are to the pressure-receiving portions.

3. The end plate according to claim 1, wherein the plurality of through holes are formed in a truss shape in which the partition walls between adjacent ones are inclined with respect to the width direction of the end plate.

4. A battery module in which a laminate of a plurality of battery cells is sandwiched and held by end plates from both end sides in the stacking direction, Comprising a plurality of connecting members that connect between a plurality of pairs of pressure-receiving portions that form pairs between both end plates on both end sides with respect to both end plates on both end sides, The end plate has a convex portion on the facing surface to the laminate, and has a plurality of through holes that penetrate its interior in the in-plane direction, Fastened by the connecting member in a direction to narrow the distance between the end plates on both end sides, and as the facing surface becomes flat, both end plates on both end sides are deformed so that the in-plane surface pressure of the plurality of battery cells is made uniform, The plurality of through holes are formed in a form in which the section modulus between two of the pressure-receiving portions in the one end plate is relatively large near the pressure-receiving portion and relatively low at a portion separated from the pressure-receiving portion. Battery module.

5. The battery module according to claim 4, wherein the plurality of through holes have a larger opening area the closer they are to the central position between the pressure-receiving portions and a smaller opening area the closer they are to the pressure-receiving portions.

6. The battery module according to claim 4, wherein the plurality of through holes are formed in a truss shape in which partition walls between adjacent ones are inclined with respect to the width direction of the end plate.

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