JP6680145B2 - Battery module - Google Patents

Description

  The present invention relates to a battery module in which a battery stack including a battery stack in which a plurality of rectangular batteries are stacked in the thickness direction and a pair of end plates arranged at both ends of the battery stack in the stacking direction is housed in a housing case. Regarding

  Non-aqueous electrolyte secondary batteries such as lithium-ion secondary batteries and sodium-ion secondary batteries are lighter in weight and have higher energy density than existing batteries, so they are the power source for driving electric vehicles and the power source for portable electronic devices. Is often used as. The battery module is a module formed by combining a plurality of battery cells each including such a non-aqueous electrolyte secondary battery.

  Here, among the battery cells formed of non-aqueous electrolyte secondary batteries, there is a prismatic battery in which an electrode body is housed in a flat rectangular parallelepiped cell case. In such a prismatic battery, it is desirable that the pressure be evenly applied to the entire surface of the substantially rectangular prismatic battery when housed in the housing case. If the applied pressure is biased, the reliability of the battery module will decrease due to unintended deterioration such as metal deposition, internal short circuit, gas generation, and eventually deformation of the battery case inside the prismatic battery. There is a risk.

  Therefore, in order to uniformly apply pressure to the entire surface of the prismatic battery, conventionally, a plurality of prismatic batteries (battery cells) and a resin separator are laminated in the thickness direction to form a battery laminate, It has been proposed to apply a compressive force (constraint load) to the battery stack. For example, Patent Document 1 discloses a technique of disposing a pair of end plates at both ends in the stacking direction of a battery stack and then fixing both ends of a metal restraining band to the pair of end plates by rivet fastening or the like. There is. At this time, if the length of the restraint band is adjusted so that the distance between the end plates is shorter than the length of the battery stack in the unloaded state in the stacking direction, the battery stack has a compressive force in the stacking direction, that is, , A constraint load can be applied.

JP, 2010-257651, A

  However, it is necessary to provide at least four restraint bands in order to uniformly apply a restraint load to the entire surface of each battery cell using the restraint bands. That is, in the prior art, it was necessary to prepare four restraint bands for one battery stack and further fix both ends of each of the four restraint bands to the end plates. In this case, the number of parts and the number of assembling steps increase.

  The restraint load applied to each battery cell is determined by the length of the restraint band (distance between the end plates) and the spring constant of the battery stack, but the spring constant of this battery stack has individual differences. As a result, even if the restraint bands have the same length, the restraint load varies depending on the battery stack. Therefore, in order to make the restraint load uniform in the prior art, it is necessary to change the length of the restraint band according to the spring constant of the battery stack, which causes an increase in the number of types of parts.

  Therefore, an object of the present invention is to provide a battery module that has a simple structure and can apply an appropriate restraining load to a battery stack.

  The battery module of the present invention is a battery stack including a battery stack in which a plurality of rectangular batteries are stacked in the thickness direction, and a pair of end plates arranged at both ends in the stacking direction of the battery stack, and an upper end is open. And a housing case having a housing space for housing the battery stack, wherein at least one of the pair of end plates has a dimension in the stacking direction of the battery stack as it approaches the lower end of the housing case. The stack space has a stack-side facing surface that is inclined to be small, the storage space faces the stack-side facing surface, and the dimension of the storage space in the stacking direction becomes smaller toward the lower end of the storage case. It is characterized in that it has a case-side facing surface that is inclined to.

  According to the present invention, since the stack-side facing surface and the case-side facing surface that face each other are respectively inclined, by pushing the battery stack into the accommodation space, a restraining load can be applied to the battery stack. In addition, since the restraint load at this time can be changed by changing the force pushing the battery stack, it is not necessary to change the dimensions of the parts according to the spring constant of the battery stack. As a result, according to the present invention, it is possible to provide a battery module that has a simple structure and can apply an appropriate restraining load to the battery stack.

It is a perspective view of a battery stack used for the battery module of the present invention. It is a schematic diagram of a battery module. It is a schematic diagram which shows the mode of assembly of a battery stack. It is a partially expanded view of a stack side facing surface and a case side facing surface. It is a figure which shows an example of the conventional battery stack.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view of a battery stack 12 mounted on a battery module 10 according to an embodiment of the present invention. In addition, FIG. 2 is a schematic diagram of the battery module 10. Note that the illustration of the separator 20 is omitted in FIG. 2.

  The battery module 10 includes a module case 50 and a battery stack 12 housed in the module case 50. The number of the battery stacks 12 accommodated in one module case 50 may be one or more.

  The battery stack 12 includes a battery stack 14 and a pair of end plates 16 arranged on both sides of the battery stack 14 in the stacking direction. Further, the battery stack 14 is configured by stacking battery cells 18 and separators 20 made of resin alternately in the thickness direction.

  Here, the battery cell 18 is a chargeable / dischargeable secondary battery, such as a lithium ion secondary battery or a sodium ion secondary battery. The battery cell 18 of the present embodiment is a prismatic battery having an electrode body housed in a flat rectangular parallelepiped cell case. A positive electrode terminal 22p and a negative electrode terminal 22n project from the upper end surface of the battery cell 18. The positive electrode terminal 22p and the negative electrode terminal 22n are arranged at intervals in the width direction. Note that, in FIG. 1, the positive electrode terminal 22p and the negative electrode terminal 22n are illustrated as substantially cylindrical shapes, but the shapes of these terminals 22p and 22n may be appropriately changed.

  A gas release valve (not shown) is provided in the widthwise center of the upper end surface of the battery cell 18, that is, between the positive electrode terminal 22p and the negative electrode terminal 22n. The gas release valve is a valve that releases the gas generated inside the battery cell 18 when the battery cell 18 reacts abnormally. The gas release valve is closed when the internal pressure of the battery cell 18 is less than a certain value, but is opened when the internal pressure becomes a certain value or more to release the gas to the outside. This gas release valve is configured, for example, by forming a part of the case of the battery cell 18 into a thin wall so as to be broken when receiving a pressure of a certain level or more. However, the configuration of the gas release valve is not limited to this, and may be changed as appropriate.

  The plurality of battery cells 18 are stacked in the thickness direction. At this time, the plurality of battery cells 18 are arranged such that the positive electrode terminals 22p and the negative electrode terminals 22n are alternately arranged in the stacking direction so that the directions thereof are alternately changed. That is, when a certain battery cell 18 is arranged so that the positive electrode terminal 22p is located on the right side when facing, the next battery cell 18 is arranged so that the negative electrode terminal 22n is located on the right side facing. Then, the plurality of battery cells 18 are electrically connected in series by sequentially connecting the positive electrode terminal 22p and the negative electrode terminal 22n that are adjacent in the stacking direction with a bus bar (not shown).

  A separator 20 is arranged between the battery cells 18. In other words, the battery stack 14 is formed by alternately stacking the plurality of battery cells 18 and the plurality of separators 20. The separator 20 is made of an insulating material, and has a substantially flat base portion, a frame portion 26 protruding in the thickness direction from the peripheral edge of the base portion (not visible in FIG. 1), and a duct piece 28 protruding from the upper end of the base portion. And are equipped with. The base portion is a portion arranged between the battery cells 18, and a plurality of ribs for forming a coolant channel are formed on the surface of the base portion at intervals.

  The frame portion 26 has a shape along the peripheral surface of the battery cell 18, and restricts the movement of the battery cell 18 in the surface direction. A duct piece 28 is provided at the upper end of the separator 20 and at the center in the width direction. The duct piece 28 is formed so as to project from the upper end of the base portion of the separator 20, and has a substantially U-shape that opens toward the upper end surface of the battery cell 18. The upper surface of the duct piece 28 faces the gas release valve of the battery cell 18. Further, the duct piece 28 projects in the thickness direction from the base portion of the separator 20 and is in close contact with the duct piece 28 of another adjacent separator 20. When the plurality of duct pieces 28 are in close contact with each other, a tunnel extending in the stacking direction is formed in the battery stack 14. This tunnel serves as a smoke exhaust duct through which the gas released from the gas release valve flows.

  A pair of end plates 16 are arranged on both sides in the stacking direction of the battery stack 14 including the battery cells 18 and the separator 20. The stack including the battery stack 14 and the pair of end plates 16 is the battery stack 12. The battery stack 12 is an expandable member having a spring constant in the stacking direction because it has the separator 20 made of resin and the like. The end plate 16 is a plate material made of a metal such as aluminum or a resin having sufficient rigidity. In this embodiment, the stack-side facing surface 17, which is the outer surface in the stacking direction, of the end plate 16 is an inclined surface whose thickness decreases as it approaches downward. In other words, the length of the battery stack 12 in the stacking direction becomes smaller toward the lower side. The reason for having such a configuration is to apply an appropriate restraining load Ft to the battery stack 14, which will be described later.

  The module case 50 is a box member made of metal such as aluminum, and has a housing space 56 for housing the battery stack 12. The module case 50 is roughly divided into a lower case 52 and an upper cover 54. The lower case 52 functions as a housing case that houses the battery stack 12. The number of battery stacks 12 accommodated in one lower case 52 is not limited and may be one or plural. In addition to the battery stack 12, the lower case 52 may further accommodate other members such as a cooling fan, a cooling duct, a heater, and a junction box (none of which are shown).

  An accommodation space 56 for accommodating the battery stack 12 is formed in the lower case 52. The accommodation space 56 is a space with an open top, and the battery stack 12 can be pushed in through this top opening. The case-side facing surface 58, which is both end surfaces in the stacking direction of the accommodation space 56, that is, the surface facing the stack-side facing surface 17, is an inclined surface such that the stacking direction length of the accommodation space 56 decreases as it approaches downward. Has become.

  Here, the inclination angle of the case-side facing surface 58 is substantially the same as the inclination angle of the stack-side facing surface 17. When the length in the stacking direction at the lower end of the battery stack 12 in the unloaded state is Ds and the length in the stacking direction at the lower end of the accommodation space 56 is Dd, Dd <Ds (see FIG. 3). When the length of the upper end of the accommodation space 56 in the stacking direction is Du, Ds <Du. With such a configuration, the restraining load Ft can be applied to the battery stack 12 that has been pushed into the storage space 56 and contracted, and this will be described later.

  The upper cover 54 covers the upper portion of the lower case 52. The upper cover 54 is arranged above the lower case 52 after the battery stack 12 and other necessary members (for example, a cooling fan) are housed in the lower case 52, and is fastened to the lower case 52.

  By the way, as is apparent from the above description, in the present embodiment, the end faces in the stacking direction of the battery stack 12 and the accommodation space 56 are inclined faces. The reason for adopting such a configuration will be described in comparison with the related art. In the prismatic battery (battery cell 18) in which the electrode body is housed in a prismatic cell case, it is desirable that pressure be uniformly applied to the entire surface thereof. If the applied pressure is biased, unintended deterioration such as metal (lithium) deposition, internal short-circuiting, gas generation, and deformation of the cell case will occur inside the battery cell 18, resulting in reliability of the battery module. May decrease.

  Therefore, conventionally, it has been proposed that after stacking a plurality of battery cells 18 in the thickness direction to form the battery stack 14, the stacking direction compression force, that is, the restraining load Ft is applied to the battery stack 14. ing. By applying the restraint load Ft, pressure is applied to the surfaces of the battery cells 18, and the movements of the plurality of battery cells 18 and the separators 20 constituting the battery stack 14 are restricted and restrained.

  In order to obtain this restraint load Ft, conventionally, a metal band called a restraint band 100 has been used. FIG. 5 is a diagram showing an example of a conventional battery stack 12. As shown in FIG. 5, conventionally, a pair of end plates 16 are arranged at both ends of the battery stack 14 in the stacking direction, and further, both ends of a restraining band 100 having a predetermined length are fixed to the pair of end plates 16. There is. Here, the length of the restraint band 100 is set so that the distance between the end plates 16 fixed to both ends of the restraint band 100 is shorter than the length of the battery stack 14 in the unloaded state. Therefore, by fixing the pair of end plates 16 to both ends of the restraint band 100, the battery stack 14 is sandwiched while being compressed by the pair of end plates 16. Then, as a result, the constraint load Ft is applied to the battery stack 14.

  However, in the conventional technique using such a restraint band 100, in order to apply the pressure evenly to the surface of each battery cell 18, a plurality of restraint bands 100 (for example, two on the upper side of the battery stack 14 and a lower one) are used. It is necessary to provide two on each side (total of four). Therefore, in the conventional technology, the number of parts is increased. Both ends of the plurality of restraint bands 100 are fixed to the end plate 16 by rivet fastening or the like. Therefore, if there are four restraint bands 100, it is necessary to rivet-fasten at least eight places, which also invites an increase in the number of steps for assembling the battery module 10.

  Further, in the technique using the restraint band 100, the restraint load Ft applied to the battery stack 14 is determined by the length of the restraint band 100 (distance between the end plates 16) and the spring constant K of the battery stack 14. However, there are individual differences in the spring constant K of the battery stack 14. As a result, even if the restraint band 100 has the same length, the restraint load Ft applied differs depending on the battery stack 14. Therefore, in order to make the restraint load Ft uniform in the prior art, it is necessary to change the length of the restraint band 100 according to the spring constant K of the battery stack 14, which causes an increase in the number of types of parts.

  On the other hand, in this embodiment, the end faces in the stacking direction of the battery stack 12 and the accommodation space 56 (the stack-side facing surface 17 and the case-side facing surface 58) are inclined surfaces. With such a configuration, an appropriate restraint load Ft can be applied to the battery stack 14 without using the restraint band 100. This will be described with reference to FIG.

When the battery stack 12 is assembled to the lower case 52, the battery stack 12 is pushed into the accommodation space 56 through the upper opening of the accommodation space 56, as shown in FIG. Here, as described above, the lower end length Ds of the battery stack 12 in the unloaded state is smaller than the upper end length Du of the accommodation space 56 and larger than the lower end length Dd of the accommodation space 56. Therefore, the battery stack 12 can enter the accommodation space 56 without hitting the case-side facing surface 58 up to the middle, but when the battery stack 12 enters a certain amount or more, the stack-side facing surface 17 of the battery stack 12 becomes the case-side facing surface 58. Will be hit. When the battery stack 12 is pushed further downward with the stack-side facing surface 17 hitting the case-side facing surface 58, the case-side facing surface 58 receives the downward force F1 by the stack-side facing surface 17. The downward force F1 is decomposed into a force F2 parallel to the case-side facing surface 58 and a vertical component force F3 perpendicular to the case-side facing surface 58. At the same time, a vertical reaction force F4 of the vertical component force F3 is generated on the stack side facing surface 17. Then, the battery stack 12 receives a force having the magnitude of the horizontal component force F5 of the vertical reaction force F4 from both sides in the stacking direction. That is, the battery stack 12 receives the constraint load Ft of F5 × 2. When the angle formed by the case-side facing surface 58 and the horizontal is α, the magnitudes of the vertical component force F3 and the vertical drag force F4 are F1 · sinα, and the magnitude of the horizontal component force F5 of the vertical drag force F4 is , F4 · sin α = F1 · sin ² α. The constraint load Ft is Ft = 2 · F1 · sin ² α.

  Upon receiving such a restraining load Ft, the battery stack 12 contracts and deforms in the stacking direction. For example, when the battery stack 12 is pushed to the bottom of the accommodation space 56, the length of the battery stack 12 in the stacking direction becomes smaller by ε = Ds−Dd than in the unloaded state. At this time, the battery stack 12 receives a constraint load Ft = K × ε having a magnitude obtained by multiplying the deformation amount ε by the spring constant K. Then, at this time, the plurality of battery cells 18 forming the battery stack 12 are evenly applied to the entire surfaces thereof.

  That is, according to the present embodiment, by merely pushing the battery stack 12 downward in the accommodation space 56, a restraining load, which is a compressive force in the stacking direction, can be applied to the battery stack 12. At this time, since the restraint band is unnecessary, the number of parts and the number of assembling steps can be significantly reduced as compared with the conventional technique.

  The size of the restraint load Ft applied to the battery stack 12 is determined by the force of pushing the battery stack 12 downward, that is, the size of the assembly load F1 and the inclination angles of the facing surfaces 17 and 58. Since the inclination angles of the opposing surfaces 17 and 58 are substantially fixed, the restraint load Ft can be freely adjusted by adjusting only the assembly load F1. Alternatively, as described above, since the restraint load Ft is a product of the deformation amount ε of the battery stack 12 and the spring constant K, the deformation amount ε of the battery stack 12, and thus the pushing amount of the battery stack 12, is adjusted. The restraint load Ft may be adjusted. In any case, according to the present embodiment, it is not necessary to individually adjust the dimensions of the constraining component according to the variation in the spring constant of each battery stack 12. As a result, an appropriate restraining load Ft can be applied to the battery stack 12 while reducing the number of types of parts.

  If the desired binding load can be applied to the battery stack 12 by pushing down the battery stack 12 in the accommodation space 56 with a predetermined assembly load, the battery stack 12 is fixed. There are various conceivable methods for fixing the battery stack 12. In the present embodiment, in order to fix the battery stack 12 at a desired pushing position, the sawtooth-shaped irregularities 60 and 62 are formed on the surfaces of the stack-side facing surface 17 and the case-side facing surface 58, respectively. This will be described with reference to FIG.

  As shown in FIG. 4, in the present embodiment, on the stack-side facing surface 17, the horizontal plane 60a and the inclined surface 60b approaching the inner side as approaching downward are provided with saw-toothed concavities and convexities 60 which are alternately arranged at a predetermined pitch in the vertical direction. Is forming. Similarly, on the case-side facing surface 58, a horizontal surface 62a and an inclined surface 62b that approaches the inside (battery stack 12 side) toward the lower side form saw-tooth-like irregularities 62 that are alternately arranged in the vertical direction at a predetermined pitch. are doing. The arrangement pitch of the sawtooth-shaped irregularities 60 on the stack side facing surface 17 and the sawtooth-shaped irregularities 62 on the case side facing surface 58 and the inclination angles of the inclined surfaces 60b and 62b are substantially the same. The crests of the concavo-convex shape can be engaged with the troughs of the other serrated concavity and convexity.

  When the battery stack 12 having such a configuration is pushed downward in the accommodation space 56, the inclined surfaces 60b and 62b of the saw-toothed concavities and convexities 60 and 62 of the opposing surfaces 17 and 58 come into contact with each other, so that the battery stack 12 moves downward. Is acceptable. On the other hand, when the pushed-in battery stack 12 tries to move upward, the horizontal planes 60a and 62a of the sawtooth-shaped irregularities 60 and 62 of the opposite surfaces 17 and 58 are locked to each other, so that the battery stack 12 The upward movement is hindered. As a result, the battery stack 12 is fixed in the pushed position.

  The fixing method described here is an example, and another fixing method may be used as long as it can prevent the battery stack 12 pushed into a desired depth from moving upward. For example, the battery stack 12 may be fixed by pressing the upper surface of the battery stack 12 with the upper cover 54. The battery stack 12 may be fixed by fixing means such as screwing or welding.

  Further, the configuration described so far is an example, and at least the one end surface in the stacking direction of the battery stack 12 and the surface facing the one end surface of the accommodation space 56 are inclined, other configurations are , May be changed. For example, in the above description, both end faces in the stacking direction of the battery stack 12 and both end faces in the stacking direction of the accommodation space 56 are inclined faces, but only one of them may be an inclined face and the other may be a vertical face. . Moreover, the shapes and the numbers of the battery cells 18 and the separators 20 illustrated in the present embodiment are all examples, and other configurations may be appropriately changed as long as the battery cells 18 are rectangular. Further, in the present embodiment, the plurality of battery cells 18 are connected in series, but the plurality of battery cells 18 may be connected in parallel.

10 battery modules, 12 battery stacks, 14 battery stacks, 16 end plates, 17 stack side facing surfaces, 18 battery cells, 20 separators, 22n negative electrode terminals, 22p positive electrode terminals, 26 frame portions, 28 duct pieces, 50 module cases, 52 lower case, 54 upper cover, 56 accommodation space, 58 case-side facing surface, 60, 62 serrated irregularities, 100 restraining band.

Claims (1)

A battery stack including a battery stack in which a plurality of prismatic batteries are stacked in the thickness direction, and a pair of end plates arranged at both ends of the battery stack in the stacking direction,
A storage case having a storage space in which the upper end is opened and the battery stack is stored,
Equipped with
At least one of the pair of end plates has a stack-side facing surface that is inclined so that the dimension in the stacking direction of the battery stack becomes smaller toward the lower end of the housing case,
The accommodating space has a case-side opposing surface that opposes the stack-side opposing surface and that is inclined so that the dimension of the accommodating space in the stacking direction becomes smaller toward the lower end of the accommodating case.
A battery module characterized by the above.

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