JP2013246953A - Electricity storage device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electricity storage device capable of reducing the flow of an electrolyte within an electrical cell.SOLUTION: An electricity storage device includes a plurality of electrical cells, a plurality of cooling plates and a binding member. Each electrical cell includes a wounded body serving as a power generation element, inside thereof. Each cooling plate is alternately disposed with each electrical cell, and has a plurality of projecting parts, the longitudinal direction of which is orthogonal to the winding axis of the wounded body, on the surface. The projecting parts are aligned in the winding axial direction on the surface of each cooling plate. The rigidity of a part of the projecting part of each cooling plate is lower than that of other parts of the projecting part.

Description

  The present invention relates to a technique for alleviating hindrance to electrolyte flow in a unit cell.

  There is a power storage device that forms a battery stack by arranging a plurality of single cells in one direction. In addition, there is one that applies a restraining load to a plurality of single cells by using a restraining mechanism. Here, the restraining load is a force that sandwiches the plurality of unit cells in the arrangement direction of the plurality of unit cells.

  Such a power storage device is provided with cooling plates that are alternately arranged between the single cells, secure a cooling air passage between the single cells, and apply a binding force to the single cells.

JP 2010-097693 A JP 2011-238457 A

  An example of the cooling plate is shown in FIG. A part of the structure of the power storage device is shown in FIG. 4 and shows a cooling plate sandwiched between single cells. In the cooling plate, a plurality of ribs for guiding the cooling air are formed in a convex shape in the outer direction of the cooling plate. Thereby, a plurality of concave grooves are formed between the ribs. A plurality of ribs of the cooling plate in FIG. 3 are arranged side by side in the longitudinal direction (Y-axis direction) of the cooling plate so that the longitudinal direction is the vertical axis direction (Z-axis direction).

  The cooling plate main body and the ribs of the cooling plate are made of a resin material having a rigidity high enough to secure a cooling flow path between the cells even when a high-pressure restraint load is applied. Since the rigidity is high, the restraining load applied from one surface of the cooling plate is propagated to the other surface, thereby restraining the unit cell (see FIG. 4). The restraint load and the propagation load from the cooling plate have a considerable influence on the case shape of the unit cell.

  The problem with the cooling plate as shown in FIG. 3 where the longitudinal direction of the rib is the vertical axis direction will be described with reference to FIG. FIG. 5 is a schematic view through the inside of the unit cell. The unit cell has a configuration in which a wound body having a winding axis in the Y-axis direction and an electrolytic solution are accommodated in a case. Both ends of the wound body in the winding axis direction become positive and negative electrodes, respectively.

  Since the surface of the cooling plate is uneven, the location of the cell case that abuts the rib (convex shape) of the cooling plate becomes convex toward the inside of the cell when it receives a load, and only that location is a cross section inside the case. (Cross section when viewed from the winding axis direction) becomes narrow. The structure in which the cross section in the case becomes narrow at intervals is a structure in which the areas between the rib contact points and the rib contact points are isolated from each other, and the flow of the electrolyte in the unit cell is hindered. This means that it takes a long time to relieve the unevenness of the internal electrolyte once it has occurred, and various problems such as an increase in resistance due to electrolyte withering and an accelerated deterioration due to uneven salt concentration inside the wound body. May cause.

  In order to solve the above problem, when using a cooling plate with ribs arranged in parallel with the winding axis, the obstruction factor of the electrolyte flow is certainly removed, but the cell shape is longer in the winding axis direction. As a result, the cooling efficiency decreases accordingly.

  Further, a method of providing spotted irregularities on the surface of the exterior resin of the electrode body composed of a stack of positive and negative electrodes and using this as a cooling path is also conceivable. However, in this case, the cooling efficiency decreases due to the turbulence of the airflow due to the unevenness. To compensate for this, it is possible to increase the difference in unevenness by reducing the diameter of the unevenness or increasing the convexity, but it becomes difficult to secure the necessary restraining pressure, or the overall size of the battery Becomes large.

  An object of the present invention is to reduce the obstruction of electrolyte flow inside a single cell when a plate having a rib whose longitudinal direction is perpendicular to the winding axis is adopted as a cooling plate of a power storage device.

  In order to solve the above problems, a power storage device according to the present invention includes (1) a plurality of single cells, a plurality of cooling plates, and a restraining member. The unit cell has a wound body that is a power generation element. The cooling plate is alternately arranged with the cells, and has a plurality of convex portions on the surface whose longitudinal direction is orthogonal to the winding axis of the wound body. This convex part is arranged along the winding axis direction on the surface of the cooling plate. The rigidity of a part of the convex part of the cooling plate is lower than that of other parts of the convex part.

  The convex portion may be a convex protrusion provided on the surface of the cooling plate, or may be a convex portion formed by forming a groove on the surface of the cooling plate.

  In the configuration of (1) above, (2) the convex portion having low rigidity is recessed in the cooling plate inner direction.

  In the configuration of (1) or (2) above, (3) the convex portion having low rigidity is made of a resin different from the cooling plate body by two-color molding.

  According to the present invention, it is possible to reduce the hindrance to the flow of the electrolyte in the unit cell.

It is a perspective view of the electrical storage apparatus of an embodiment. It is a figure which shows the cooling plate with which the electrical storage apparatus of embodiment is equipped. It is a figure which shows a cooling plate. It is a schematic diagram which shows the cooling plate arrange | positioned between a cell and a cell. It is a figure explaining the problem in the case of using the cooling plate shown in FIG.

  FIG. 1 is a perspective view of a power storage device according to the present embodiment, FIG. 2 is a diagram showing a cooling plate incorporated in the power storage device, and a portion indicated by a dotted line is a portion of a single cell. . In these drawings, an X axis, a Y axis, and a Z axis indicate three mutually orthogonal orthogonal axes. The power storage device 100 includes a battery group 1 in which the cells 11 and the cooling plate 20 are alternately stacked, a pair of end plates 3, and first to fourth restraining bands (corresponding to restraining members) 4a to 4d. The power storage device 100 stores power supplied to a motor that drives the vehicle. The vehicle may be an electric vehicle that drives wheels only by the power of the motor, or a hybrid vehicle that uses both the power of the motor and the power of the engine as power sources. The hybrid vehicle may be a plug-in hybrid vehicle that can be charged by a commercial power source provided outside the vehicle.

  The battery group 1 includes a plurality of single cells 11 that are electrically connected in series with each other. These unit cells 11 are stacked in the X-axis direction. The unit cell 11 is a so-called square cell having a pair of outer surfaces facing in the stacking direction of the unit cells 11, a pair of outer surfaces facing in the Y-axis direction, and a pair of outer surfaces facing in the Z-axis direction. The unit cell 11 may be a secondary battery such as a lithium ion battery or a nickel metal hydride battery, or may be a capacitor. A projecting positive electrode terminal 11a and a negative electrode terminal 11b are formed side by side in the Y-axis direction on one of the pair of outer surfaces facing in the Z-axis direction.

  As shown in FIG. 2, the positive electrode terminal 11 a is one end of a winding body (for example, the winding body shown in FIG. 5) that is a power generation element and is located inside the unit cell 11 via the positive electrode connection terminal 11 c. It is connected to the. The negative electrode terminal 11b is connected to the other end portion of the wound body (for example, the wound body shown in FIG. 5) located inside the unit cell 11 through the negative electrode connection terminal 11d. Each of the first to fourth restraint bands 4 a to 4 d extends in the stacking direction of the unit cells 11 and is covered with an insulating protective frame 12. The protective frame 12 may be a resin.

  The pair of end plates 3 are arranged at positions sandwiching the battery group 1. A pair of sandwiching plates 33a and 33b that sandwich and hold the first restraining band 4a and the third restraining band 4c are formed on the end surfaces of the pair of end plates 3 in the X-axis direction. These sandwiching plates 33 a and 33 b are riveted via rivets 6. Thereby, the 1st restraint band 4a and the 3rd restraint band 4c are fixed firmly.

  A pair of clamping plates 32a and 32b are formed on the end surfaces in the X-axis direction of the pair of end plates 3 at positions aligned with the clamping plates 33a and 33b in the Y-axis direction. The pair of sandwiching plates 32a and 32b sandwich and hold the second restraining band 4b and the fourth restraining band 4d. These sandwiching plates 32 a and 32 b are riveted via a rivet 6. Thereby, the 2nd restraint band 4b and the 4th restraint band 4d are fixed firmly.

  A pair of end plate 3 is provided with the flange part 34 extended along an XY plane direction (refer FIG. 1). The flange portion 34 includes a through hole portion 34a. By fastening a fastening member (not shown) to the through hole portion 34a, the power storage device 100 can be fixed to the fixed portion of the vehicle. Here, the fixed portion of the vehicle may be a floor panel located under the vehicle seat or the inside of the luggage room.

  Among the unit cells 11 adjacent to each other in the stacking direction, the positive electrode terminal 11a of one unit cell 11 and the negative electrode terminal 11b of the other unit cell 11 face each other in the stacking direction. The positive terminal 11a and the negative terminal 11b are electrically and mechanically connected via a bus bar 51 illustrated in FIG.

  Here, the bus bar 51 is formed with a pair of through-hole portions penetrating in the plate thickness direction (Z-axis direction), and one through-hole portion has a positive electrode terminal in one unit cell 11 adjacent in the stacking direction. 11a is inserted, and the negative terminal 11b of the other unit cell 11 is inserted through the other through hole. Screw grooves are formed on the outer surfaces of the positive electrode terminal 11a and the negative electrode terminal 11b, and the bus bar 51 is fixed by fastening a fastening nut 61 in these screw grooves. However, the unit cells 11 adjacent in the stacking direction may be electrically connected in parallel. In order to simplify the drawing, the bus bar 51 and the fastening nut 61 are not shown in FIG.

  The cooling plate 20 is located between the adjacent unit cells 11 in the stacking direction (X-axis direction). Here, the cooling plate 20 will be described with reference to FIG. In FIG. 2, an enlarged view of the region indicated by the alternate long and short dash line is shown on the right side of FIG.

  On the YZ plane of the cooling plate 20, a plurality of ribs 21 (corresponding to convex portions) that are convex in the outward X-axis direction of the cooling plate 20 are provided. The rib 21 has a longitudinal direction (Z-axis direction) perpendicular to the winding axis direction of the winding body in the unit cell 11, and the winding axis direction (Y-axis direction) of the winding body in the unit cell 11. Are arranged side by side. Each of the ribs 21 includes a rigid portion 21A and a flexible portion 21B (see an enlarged view). The rigid portion 21A and the flexible portion 21B are alternately arranged in the longitudinal direction of the rib 21, and the material of the rigid portion 21A is the same resin as the main body portion of the cooling plate 20 in this embodiment. The soft portion 21B is manufactured from a resin different from the rigid portion 21A by two-color molding, and a soft material that is easier to deform than the rigid portion 21A is used. Resin may be sufficient as the raw material of the flexible part 21B.

Further, in the surface shape of the rib 21 in the YZ plane, the surface of the rigid portion 21A is flat (the displacement in the X-axis direction does not change in the YZ plane), but the surface of the flexible portion 21B is the cooling plate. 20 is a hollow shape recessed inwardly in the X-axis direction.

  As described above, since the flexible portion 21B is a material that is easily deformed, even if a high-pressure restraint load is applied from the first to fourth restraint bands 4a to 4d, the portion of the unit cell 11 that contacts the soft portion 21B. The amount of deformation can be reduced. Moreover, the contact shape of the rib 21 and the unit cell 11 can be alleviated by making the surface shape of the flexible portion 21B a concave shape recessed in the cooling plate inner side direction.

Here, the dimension regarding the rib 21 is demonstrated. First, the width W1 of the rib 21 is about 2 mm in the present embodiment, and the interval length W2 of the rib 21 (the width of the portion that becomes the groove) is about 3 mm in the present embodiment. The length L1 of the rigid portion 21A is calculated based on the area required for restraint. When the required area is S, the width of the rib 21 is W1, and the number of the ribs 21 is N, the length L1 is calculated by, for example, the following equation.
L1 = S / (W1 × N)
In the present embodiment, the length L1 of the rigid portion 21A is about 5 mm. The length L2 of the flexible portion 21B only needs to be approximately the same as the length L1 of the rigid portion 21A, and is approximately 5 mm in this embodiment.

  In this way, for each of the ribs arranged on the cooling plate, a material that is easily deformed is used as a part, and the rigidity of that part is made lower than that of other parts, thereby inhibiting the flow of electrolyte in the unit cell. Can be reduced. Thereby, while being able to maintain a high restraint load, cooling property and electrolyte solution fluidity are securable.

DESCRIPTION OF SYMBOLS 1 Battery group 3 End plate 4a-4d 1st-4th restraint band 6 Rivet 11 Cell 11a Positive electrode terminal 11b Negative electrode terminal 12 Protective frame 20 Cooling plate 21 Rib 21A Rigid part 21B Soft part 32a, 32b, 33a, 33b Plate 34 Flange 34a Through hole 100 Power storage device

Claims (1)

A plurality of single cells each having a wound body, which is a power generation element,
Alternating with the unit cell, the longitudinal direction is a convex part orthogonal to the winding axis of the winding body, and each has a plurality of convex parts arranged on the surface in the winding axis direction A plurality of cooling plates arranged in the
A restraining member for restraining the plurality of single cells and the plurality of cooling plates in the stacking direction;
A power storage device having
The power storage device, wherein a rigidity of a part of the convex portion of the cooling plate is lower than that of another part of the convex portion.

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