JP6352640B2 - Battery module - Google Patents

Description

  The present invention relates to a battery module including a plurality of prismatic secondary batteries.

  Conventionally, in the field of rechargeable secondary batteries, aqueous batteries such as lead batteries, nickel-cadmium batteries, and nickel-hydrogen batteries have been mainstream. However, as electric devices become smaller and lighter, lithium ion secondary batteries having high energy density have attracted attention, and their research, development, and commercialization are rapidly progressing.

  In addition, electric vehicles (EV) and hybrid electric vehicles (HEV) that assist part of driving with electric motors have been developed by each automobile manufacturer due to global warming and depleted fuel problems. Secondary batteries have been demanded. As a power source that meets such requirements, high-voltage non-aqueous lithium ion secondary batteries have attracted attention. In particular, the prismatic lithium ion secondary battery is excellent in volumetric efficiency when a battery module (assembled battery) is constituted by a plurality of batteries, and therefore, the expectation for development as a power source for HEV or EV is increasing.

  In applications such as HEV or EV, secondary batteries are often used to repeatedly charge and discharge at a high current called high rate (see, for example, Patent Document 1). As described in Patent Document 1, particularly in a secondary battery having a wound electrode body, the inner pressure tends to be higher at the center in the winding axis direction than at the outside. In addition, if a restraining method that maintains the flat shape of the outer case is selected, the surface pressure cannot be maintained uniformly, and the secondary battery deteriorates.

  Therefore, in the secondary battery assembly described in Patent Document 1, the shape or arrangement of a plurality of discretely provided contact portions that are in contact with the pressed surface that is the side surface of the maximum area of the secondary battery is the compressed surface. The selection force is selected so that the pressing force is stronger in the offset region than in the central region. As a result, the internal pressure of the secondary battery can be made uniform so that the pressing force on the pressed surface is stronger than the central region in the offset region, and the surface pressure can be reduced even for a secondary battery used at a high rate. It is described that it can be kept uniform and the progress of deterioration of the secondary battery can be suppressed.

Japanese Patent No. 5187400

  In the secondary battery assembly described in Patent Document 1, the contact portion is formed to protrude from the connecting portion toward the pressed surface of the secondary battery. And the protrusion height of the contact part in both offset regions corresponding to the part deviated from the center in the winding axis direction in the wound electrode body is the contact part in the center region between the offset regions. It is higher than the protruding height. Thereby, the contact portion presses the pressed surface more strongly in both offset regions, and presses the pressed surface more weakly in the central region.

  The secondary battery assembly described in Patent Document 1 can equalize the surface pressure in the winding axis direction of the wound electrode body, but the surface in the direction perpendicular to the winding axis direction along the pressed surface. There is a possibility that the pressure becomes non-uniform. In this case, a difference occurs in the distance between the electrodes constituting the electrode body, and the secondary battery may be deteriorated.

  This invention is made | formed in view of the said subject, The place made into the objective can make more uniform the surface pressure which acts on the battery container of a secondary battery, and suppresses deterioration of a secondary battery. It is in providing the battery module which can be.

  In order to achieve the above object, the battery module of the present invention is configured by laminating a plurality of secondary batteries including a flat box type battery container that accommodates a flat wound electrode group via a spacer in the thickness direction of the battery container. The spacer includes a contact portion that contacts a wide flat surface of the battery container, and an elastic coefficient of the contact portion in a central region of the flat surface is the flat surface. It is characterized by being lower than the elastic coefficient of the contact portion in the end region.

  According to the battery module of the present invention, the elastic coefficient of the contact portion in the central region where the expansion amount of the flat surface of the battery container of the secondary battery is large is larger than the elastic coefficient of the contact portion in the end region where the expansion amount is small. Since it is low, deformation of the central region of the flat surface is allowed by elastic deformation of the contact portion, the surface pressure acting on the central region is reduced, and the surface pressure acting on the battery container in any direction along the flat surface is made uniform And deterioration of the secondary battery can be more effectively suppressed.

The perspective view which shows the battery module which concerns on embodiment of this invention. The perspective view of the secondary battery and cell holder which were removed from the battery module shown in FIG. The perspective view which shows the assembly state of the secondary battery and cell holder which are shown in FIG. The perspective view of the secondary battery shown in FIG. The exploded perspective view of the winding electrode group with which the secondary battery shown in FIG. 2 is provided. FIG. 4 is a schematic cross-sectional view of a secondary battery and a cell holder spacer taken along line AA in FIG. 3. FIG. 4 is a schematic cross-sectional view of a secondary battery and a cell holder spacer along line BB in FIG. 3. The front view of the secondary battery which shows arrangement | positioning of the contact part of the spacer shown in FIG. The top view of the expanded secondary battery and sectional drawing of the spacer corresponding to FIG. The side view of the expanded secondary battery and sectional drawing of the spacer corresponding to FIG. The front view of the secondary battery which shows the modification of arrangement | positioning of the contact part of the spacer shown in FIG. The front view of the secondary battery which shows the modification of arrangement | positioning of the contact part of the spacer shown in FIG.

  Hereinafter, embodiments of a battery module of the present invention will be described with reference to the drawings.

(Battery module)
FIG. 1 is a perspective view of a battery module M according to an embodiment of the present invention. 2 is a perspective view showing an exploded state of the secondary battery 100 and the cell holder 200 removed from the battery module M shown in FIG. 3 is a perspective view showing an assembled state of the secondary battery 100 and the cell holder 200 shown in FIG. 2 and 3, illustration of a contact portion described later is omitted.

  The battery module M of the present embodiment has a configuration in which a plurality of secondary batteries 100 including a flat box type battery container 1 are stacked via a cell holder 200 in the thickness direction of the battery container 1. In each figure, the thickness direction of the battery case 1 and the stacking direction of the secondary batteries 100 are the X-axis direction, the width direction of the battery case 1 is the Y-axis direction, and the height direction of the battery case 1 is the Z-axis direction. An orthogonal coordinate system is shown.

  The cell holder 200 includes a pair of end cell holders 210 disposed at both ends of the secondary battery 100 in the stacking direction, and a plurality of intermediate cell holders 220 disposed between the secondary batteries 100. In the following description, the end cell holder 210 and the intermediate cell holder 220 may be collectively referred to as the cell holder 200 in some cases.

  Although not shown, a pair of side plates are arranged outside the pair of end cell holders 210, and a pair of side frames extending in the stacking direction of the secondary battery 100 at both ends in the width direction of the pair of side plates. It is concluded. As a result, the periphery of the laminate composed of the end cell holder 210, the intermediate cell holder 220, and the secondary battery 100 is secured by the pair of side plates and the pair of side frames, and each secondary battery 100 is secured to the end cell holder 210. And the intermediate cell holder 220 or between the pair of intermediate cell holders 220, 220.

  The end cell holder 210 has a configuration in which the intermediate cell holder 220 is roughly divided into two along the flat surface 1 a along the width direction (Y-axis direction) of the battery container 1, and the secondary battery 100 is interposed between the end cell holder 210 and the intermediate cell holder 220. keeping. Therefore, in the following description, the configuration of the intermediate cell holder 220 will be described, and the description of the configuration of the end cell holder 210 will be omitted.

  The intermediate cell holder 220 extends in the width direction of the battery container 1 and faces the lower end surface 1d of the battery container 1 and a pair of rectangular side plates 221 arranged to face the side surfaces 1b on both sides of the battery container 1 in the width direction. And a rectangular plate-like bottom plate 222, and a spacer 230 facing the wide flat surface 1a along the width direction of the battery case 1. The plurality of secondary batteries 100 are stacked via spacers 230 in the thickness direction of the battery container 1.

  The pair of side plates 221 face each other in the width direction of the battery case 1, and have a width about half the thickness of the battery case 1 on both sides of the spacer 230 in the thickness direction (X-axis direction) of the battery case 1. doing. The width of the side plate 221 is such that when the pair of cell holders 200 are arranged on both sides in the thickness direction of the battery case 1, the end portions of the pair of side plates 221 adjacent in the thickness direction of the battery case 1 are the thicknesses of the battery case 1. It is set so that it abuts at a position about half the height, or faces with a slight gap. Openings 221 a, 221 b, and 221 c are formed at the center of the side plate 221. The openings 221 a, 221 b, and 221 c communicate with a space formed between the flat surfaces 1 a of the adjacent battery containers 1 through the spacer 230.

  The bottom plate 222 extends in the width direction of the battery case 1 and has a width about half the thickness of the battery case 1 on both sides of the spacer 230 in the same manner as the side plate 221, and connects the lower ends of the pair of side plates 221. Then, it faces the lower end surface 1d of the battery case 1. The width in the X-axis direction of the bottom plate 222 is similar to that of the side plate 221 when a pair of cell holders 200 are disposed on both sides in the thickness direction of the battery case 1, a pair of bottom plates 222 adjacent in the thickness direction of the battery case 1. These end portions are set to contact each other at about half the thickness of the battery container 1 or to face each other with a slight gap.

  The spacer 230 extends in the width direction of the battery case 1 and connects a pair of opposing side plates 221 to face the flat surface 1 a of the battery case 1. The spacer 230 includes an upper end spacer 231, an intermediate spacer 232, and a lower end spacer 233 that are arranged at intervals along the flat surface 1 a in the height direction (Z-axis direction) of the battery case 1. The upper end spacer 231, the intermediate spacer 232, and the lower end spacer 233 are disposed between the flat surfaces 1 a of the battery containers 1 of the two adjacent secondary batteries 100, and are disposed to face the flat surfaces 1 a.

  The upper end spacer 231 is wider in the Z-axis direction than the intermediate spacer 232 and the lower end spacer 233. The width of the upper end spacer 231 corresponds to a dimension (see FIG. 7) between a curved portion 40c of a wound electrode group 40 to be described later and the upper end surface 1c of the battery case 1. Between the upper end spacer 231 and the lower end spacer 233, a plurality of intermediate spacers 232 are arranged at intervals in the height direction of the battery container 1. The interval between the intermediate spacers 232 is wider than the interval between the intermediate spacer 232 and the upper end spacer 231 or the lower end spacer 233. Thereby, the dimension of the height direction of the some opening part 221b in between is made larger than the dimension of the height direction of opening part 221a, 221c of the side plate 221 in the height direction both ends of the battery container 1. FIG.

  The upper end spacer 231, the intermediate spacer 232, and the lower end spacer 233 are arranged at an interval from each other in the height direction (Z-axis direction) of the battery container 1, so that the battery container 1 of the rectangular secondary battery 100 can be provided. A plurality of slits S1, S2, and S3 extending in the width direction (Y-axis direction) are formed along the wide flat surface 1a. Corresponding to the interval between the spacers 231, 232, 233, the width in the Z-axis direction is between the upper end spacer 231 and the intermediate spacer 232 and between the intermediate spacer 232 and the lower end spacer 233. Relatively narrow slits S1 and S3 are formed. A slit S2 having a relatively wide width in the Z-axis direction is formed between the intermediate spacers 232.

  The slit S1 on the upper end surface 1c side of the battery case 1 communicates with the openings 221a and 221a of the opposing side plates 221 and 221. The slit S2 between the intermediate spacers 232 communicates with the openings 221b and 221b. The slit S3 on the lower end surface 1d side of the battery case 1 communicates with the openings 221c and 221c. Thereby, the cooling medium is allowed to pass through the slits S1, S2, and S3, and the flat surface 1a of the battery container 1 of the secondary battery 100 can be cooled.

  The end cell holder 210 and the intermediate cell holder 220 are, for example, glass epoxy resin, polypropylene, polybutylene terephthalate, polycarbonate, nylon resin and other resin materials, composite resin materials, aluminum, aluminum alloy, copper, copper alloy, magnesium alloy, stainless steel, etc. It can be composed of a metal material or a composite material of resin and metal. Moreover, when using a resin material, it is desirable to have a flame-retardant property.

(Secondary battery)
Next, an example of the configuration of the secondary battery 100 used in the battery module M of the present embodiment will be described in detail. 4 is a perspective view of the secondary battery 100 shown in FIG.

  The secondary battery 100 includes a flat rectangular box-shaped battery container 1. A flat wound electrode group 40 described later is accommodated in the battery container 1 (see FIGS. 6 and 7). The battery container 1 includes a flat rectangular parallelepiped battery can 10 having an upper opening and a battery lid 20 that seals and seals the upper opening of the battery can 10. As a material of the battery can 10 and the battery lid 20, for example, aluminum or an aluminum alloy can be used. The battery can 10 is formed, for example, by subjecting these materials to deep drawing.

  The battery container 1 has a flat box-shaped rectangular parallelepiped shape, and thus a pair of flat surfaces 1a having the maximum area on the side surface of the battery can 10 along the width direction (Y-axis direction) of the battery container 1, and the battery container The side surface 1b of the battery can 10 along the thickness direction (X-axis direction) 1 is smaller than the flat surface 1a, the upper end surface 1c that is the surface of the battery lid 20, and the bottom surface of the battery can 10. It has a certain lower end surface 1d.

  The battery lid 20 seals the upper opening of the battery can 10 by being joined to the entire periphery of the upper end portion of the battery can 10 by, for example, laser welding. The battery lid 20 is formed in a rectangular plate shape, and is provided with a positive electrode and a negative electrode terminal 2, 3 via an insulating member 21 at one end and the other end in the longitudinal direction, respectively, and the illustration inside the battery container 1 is omitted. A lid assembly is configured by being connected to the electric plate. The battery lid 20 is provided with a liquid injection port 22 and a gas discharge valve 23. The liquid injection port 22 is used for injecting the electrolytic solution into the battery container 1 after joining the battery lid 20 to the battery can 10, and the liquid injection plug 24 is welded and sealed after the injection of the electrolytic solution.

  The positive and negative terminals 2 and 3 include external terminals 2a and 3a disposed outside the battery lid 20, and connection terminals 2b and 3b that penetrate the battery lid 20 and have one end electrically connected to the external terminals 2a and 3a. Have. The other ends of the connection terminals 2b and 3b are connected to positive and negative current collectors disposed inside the battery lid 20 via an insulating member. The external terminal 2a, the connection terminal 2b, and the current collector on the positive electrode side are made of an aluminum alloy, and the external terminal 3a, the connection terminal 3b, and the current collector on the negative electrode side are made of a copper alloy. Bolts 2c and 3c for fastening the bus bar are projected from the external terminals 2a and 3a.

  The gas discharge valve 23 is formed, for example, by partially thinning the battery lid 20 by pressing. The gas discharge valve 23 may be formed by attaching a thin film member to the through hole of the battery lid 20 by, for example, laser welding. The gas discharge valve 23 is opened when the secondary battery 100 generates heat due to an abnormality such as overcharge and the like, and gas is generated inside the battery container 1 and the pressure in the battery container 1 rises to a predetermined pressure. By releasing the gas inside the container 1 to the outside, the pressure in the battery container 1 is reduced.

  FIG. 5 is an exploded perspective view showing a state where the wound electrode group 40 accommodated in the battery container 1 of the secondary battery 100 is developed.

  The wound electrode group 40 is formed by flatly winding an electrode laminate in which positive and negative electrodes 41 and 42 and separators 43 and 44 are alternately laminated and wound around a shaft core (not shown). Is provided. The wound electrode group 40 is formed in a flat shape so that a pair of flat portions 40b having a flat surface and a pair of curved portions 40c having curved surfaces continuous at both upper and lower ends of the flat portion 40b are provided. Have. The positive and negative electrodes 41 and 42 and the separators 43 and 44 are stacked in a flat state at the flat portion 40b, and are stacked in a curved state in a semicylindrical shape at the bending portion 40c.

  The positive electrode 41 includes a positive electrode metal foil 41a made of, for example, an aluminum foil, and has a positive electrode mixture layer 41b formed on both the front and back surfaces of the positive electrode metal foil 41a. One side in the width direction of the strip-shaped positive electrode metal foil 41a is a foil exposed portion 41c where the positive electrode mixture layer 41b is not coated and the positive electrode metal foil 41a is exposed.

  The negative electrode 42 includes, for example, a negative electrode metal foil 42a made of copper foil or the like, and has a negative electrode mixture layer 42b formed on both front and back surfaces of the negative electrode metal foil 42a. One side in the width direction of the strip-shaped negative electrode metal foil 42a is a foil exposed portion 42c where the negative electrode mixture layer 42b is not applied and the negative electrode metal foil 42a is exposed.

The positive electrode mixture layer 41b can be manufactured, for example, as follows. First, the layered lithium nickel cobalt manganese oxide as a positive electrode active material (chemical formula _{Li (Ni x Co y Mn 1} -xy) O 2) relative to 100 parts by weight of scaly graphite and acetylene black and forming a total of 10 parts by weight as the conductive material 4 parts by weight of polyvinylidene fluoride (hereinafter referred to as PVDF) is added as an adhesive, N-methylpyrrolidone (hereinafter referred to as NMP) is added thereto as a dispersion solvent, and kneaded to produce a positive electrode slurry. Next, the positive electrode mixture layer 41b is formed by applying the positive electrode slurry, for example, on both surfaces of an aluminum foil having a thickness of 15 μm, leaving the exposed foil portions 41c. Thereafter, through each step of drying, pressing, and cutting, for example, a positive electrode 41 having a thickness of the positive electrode active material application portion that does not include an aluminum foil (total of both front and back surfaces) of 70 μm can be obtained.

  The negative electrode mixture layer 42b can be manufactured, for example, as follows. First, an aqueous solution of carboxymethyl cellulose (hereinafter referred to as CMC) as a thickener is added to 100 parts by weight of graphitic carbon powder as a negative electrode active material, and after mixing, 1 part by weight of styrene-butadiene rubber (as a binder) (Hereinafter referred to as SBR) is added, and the viscosity is adjusted after kneading to produce a negative electrode slurry. Next, the negative electrode mixture layer 42b is formed by applying the negative electrode slurry, for example, on both surfaces of a copper foil having a thickness of 10 μm, leaving the foil exposed portions 42c. Thereafter, through each step of drying, pressing, and cutting, for example, the negative electrode 42 having a negative electrode active material application portion that does not include a copper foil (total of both front and back surfaces) of 40 μm can be obtained.

  In order to produce the wound electrode group 40 by winding the positive electrode 41 and the negative electrode 42 with the separators 43 and 44 being overlapped, firstly, the tips of the separators 43 and 44 are welded to a shaft core (not shown), The separators 43 and 44 and the positive and negative electrodes 41 and 42 are alternately stacked and wound. At this time, the winding start side end of the positive electrode 41 is positioned so that the winding start side end of the positive electrode 41 is located inside the wound electrode group 40 after winding than the winding start side end of the negative electrode 42. Is wound around the axial center side of the winding start side end of the negative electrode 42.

  Here, a direction parallel to the axis of the wound electrode group 40, that is, a direction parallel to the width direction of the strip-like positive electrode 41 and the negative electrode 42 is defined as an axis D direction. In this case, the foil exposed portion 41 c of the positive electrode 41 and the foil exposed portion 42 c of the negative electrode 42 are arranged so as to be positioned at one end and the other end in the axis D direction of the wound electrode group 40. That is, the positive and negative electrodes 41 and 42 are laminated and wound so that the foil exposed portions 41c and 42c are positioned at both ends in the axis D direction.

  The width of the negative electrode mixture layer 42b, that is, the dimension in the axis D direction is made wider than the width of the positive electrode mixture layer 41b. The width of the separator 43 is such that the foil exposed portion 41 c of the positive electrode 41 is exposed from the separator 43 at one side edge of the wound electrode group 40. The width of the separator 44 is set such that the foil exposed portion 42 c of the negative electrode 42 is exposed from the separator 44 at the other side edge of the wound electrode group 40.

  A hollow portion 40a is formed on the winding start side of the wound electrode group 40, in other words, on the axial core side. Further, the winding electrode group 40 has a winding end side on which the outermost periphery is a separator 44 and the inner side is a negative electrode 42. Accordingly, the positive electrode mixture layer 41b is disposed between the negative electrode mixture layer 42b in the width direction from the winding start side to the winding end side.

  FIG. 6 is a schematic cross-sectional view of the secondary battery 100 and the intermediate cell holder 220 cut along a plane parallel to the XY plane along the line AA in FIG. FIG. 7 is a schematic cross-sectional view of the secondary battery 100 and the cell holder 200 cut along a plane parallel to the XZ plane along the line BB in FIG. In addition, in each figure, one illustration is abbreviate | omitted among the two cell holders 200 arrange | positioned at the thickness direction both sides of the battery container 1. FIG. Moreover, the illustration of the wound electrode group 40 is simplified, and a current collector plate, an insulating member, an insulating sheet, an electrolytic solution housed in the battery container 1, a positive electrode provided on the battery lid 20, a negative electrode terminal 2, 3, etc. Illustrations of components other than the battery container 1 and the wound electrode group 40 are omitted.

  In the wound electrode group 40, the foil exposed portions 41c and 42c at both ends in the direction of the axis D shown in FIG. 5 are bundled and joined at the flat portion 40b to form the joined portions 41d and 42d shown in FIG. Has been. The wound electrode group 40 is joined to the battery lid 20 via the positive electrode and the negative electrode current collector plate by joining the joint portions 41d and 42d to a positive electrode and a negative electrode current collector plate (not shown), for example, by ultrasonic welding. Fixed. Thus, the foil exposed portions 41c and 42c of the positive and negative electrodes 41 and 42 are electrically connected to the positive and negative terminals 2 and 3, respectively.

  Further, the wound electrode group 40 is arranged such that the direction of the axis D is along the flat surface 1a and the lower end surface 1d of the battery can 10 and preferably in parallel with the positive and negative current collectors (not shown). It is supported. Thereby, the axis D direction of the wound electrode group 40 is parallel to the width direction (Y-axis direction) of the battery case 1. In a state where the wound electrode group 40 is accommodated in the battery container 1, the flat part 40 b faces the flat surface 1 a of the battery container 1, and the pair of curved parts 40 c and 40 c are respectively connected to the upper end surface 1 c of the battery container 1. The lower end surface 1d faces the lower surface of the battery lid 20 and the bottom surface of the battery can 10. An insulating sheet (not shown) is disposed between the wound electrode group 40 and the battery container 1.

When the secondary battery 100 is assembled, first, a lid assembly including the battery lid 20, the insulating member 21, the positive electrode terminal 2, the negative electrode terminal 3, the insulating member, the current collector plate, the wound electrode group 40, and the like is configured. Next, the wound electrode group 40 fixed to the lid assembly is inserted from the upper opening of the battery can 10, and the battery lid 20 is sealed and welded to the upper opening of the battery can 10. Next, the secondary battery 100 is manufactured by injecting a nonaqueous electrolytic solution into the battery container 1 from the liquid injection port 22 and then sealingly welding the liquid injection plug 24 to the liquid injection port 22. As the non-aqueous electrolyte, for example, lithium hexafluorophosphate (LiPF ₆ ) was dissolved at a concentration of 1 mol / liter in a mixed solution in which ethylene carbonate and dimethyl carbonate were mixed at a volume ratio of 1: 2. Things can be used.

(Spacer)
Next, the spacer 230 provided in the cell holder 200 will be described in detail. FIG. 8 is a front view of the secondary battery 100 showing the arrangement of the contact portions 232a, 232b, 232c, and 232d included in the spacer 230. FIG.

  The battery module M shown in FIG. 1 has a plurality of secondary batteries 100 stacked in the thickness direction (X-axis direction) of the battery container 1 via the cell holder 200, so that the spacer 230 shown in FIGS. A plurality of secondary batteries 100 are stacked in the thickness direction. The spacer 230 has contact portions 232 a, 232 b, 232 c, and 232 d that contact the flat surface 1 a of the battery container 1. The contact portions 232a, 232b, 232c, and 232d are provided on the intermediate spacer 232 facing the flat surface 1a, and a plurality of contacts are formed along the flat surface 1a in the height direction (Z-axis direction) of the battery case 1. The parts 232a and 232c and a plurality of contact parts 232b and 232d are arranged.

  The contact portions 232a, 232b, 232c, and 232d can be made of an elastic resin material such as silicone resin, for example. In addition, for joining the contact portions 232a, 232b, 232c, 232d and the intermediate spacer 232, for example, adhesion or brazing can be appropriately selected according to the material of the contact portions 232a, 232b, 232c, 232d. it can.

  As shown in FIGS. 6 and 8, in the width direction (Y-axis direction) of the battery case 1, the elastic coefficient of the contact portion 232a provided in the central region Y1 of the flat surface 1a of the battery case 1 is the central region Y1. It is made lower than the elastic coefficient of the contact part 232b provided in the edge part area | region Y2 of both sides. Similarly, the elastic coefficient of the contact portion 232c provided in the central region Y1 is set lower than the elastic coefficient of the contact portion 232d provided in the end region Y2.

  Here, the central region Y1 in the width direction of the battery case 1 is, for example, a region in which the flat surface 1a of the battery case 1 faces the central part of the flat portion 40b of the wound electrode group 40. The end region Y2 is a region between the side surface 1b including the corner portion of the rectangular battery case 1 and the central region Y1, and is an outer region of the central region Y1 including the peripheral portion of the flat surface 1a. In the end region Y2, the flat surface 1a faces the joints 41d and 42d of the wound electrode group 40 and the vicinity thereof.

  As shown in FIGS. 7 and 8, in the height direction (Z-axis direction) of the battery case 1, the elastic coefficient of the contact portion 232a provided in the central region Z1 of the flat surface 1a of the battery case 1 is the central region. It is made lower than the elastic coefficient of the contact part 232c provided in the edge part area | region Z2 of the both sides of Z1. Similarly, the elastic coefficient of the contact part 232b provided in the central region Z1 is set lower than the elastic coefficient of the contact part 232d provided in the end region Z2. That is, the elastic coefficients of the contact portions 232a and 232b on the center side in the height direction are lower than the elastic coefficients of the contact portions 232c and 232d on the height direction end side, respectively.

  Here, the central region Z1 in the height direction of the battery case 1 is, for example, a region where the flat surface 1a of the battery case 1 faces the central portion of the flat portion 40b of the wound electrode group 40. The end region Z2 is a region between the upper end surface 1c and the lower end surface 1d including the corners of the rectangular battery case 1 and the central region Z1, and is a region above and below the central region Z1 including the peripheral portion of the flat surface 1a. It is. In the end region Z2, the flat surface 1a faces the curved portion 40c of the wound electrode group 40 and its vicinity.

  Preferably, the elastic coefficient of the contact portion 232a disposed in the central regions Y1 and Z1 in the Y-axis direction and the Z-axis direction of the flat surface 1a is the lowest, and the Y-axis direction and Z-axis direction end portions of the flat surface 1a The elastic coefficient of the contact portion 232d arranged in the regions Y2 and Z2 is the highest. In this case, 232b is disposed in the end region Y2 in the Y-axis direction of the flat surface 1a and is disposed in the central region Z1 in the Z-axis direction, and is disposed in the central region Y1 in the Y-axis direction of the flat surface 1a. The magnitude relationship of the elastic coefficients with the 232c arranged in the end region Z2 in the Z-axis direction is determined according to the magnitude relationship of the expansion amount of the flat surface 1a in each region described later.

  Next, the operation of the battery module M of this embodiment will be described.

  FIG. 9 is a plan view of the secondary battery 100 shown in FIG. 3 in an expanded state and a cross-sectional view of the intermediate spacer 232 along the line AA. FIG. 10 is a side view of the secondary battery 100 shown in FIG. 3 in an expanded state and a cross-sectional view of the intermediate spacer 232 along the line BB. In each drawing, the expansion of the battery container 1 is exaggerated for easy understanding of the present embodiment. In FIG. 10, the upper end spacer 231, the lower end spacer 233, the bottom plate 222, and the like are not shown.

  The battery module M according to the present embodiment is configured such that the power charged in the wound electrode group 40 of each secondary battery 100 is supplied to an external device such as a motor via the positive and negative terminals 2 and 3 of the plurality of secondary batteries 100. The wound electrode group 40 is charged via the positive and negative terminals 2 and 3 of each secondary battery 100 with the power supplied from an external power source such as a generator. The wound electrode group 40 expands and contracts as the secondary battery 100 is charged and discharged. In the wound electrode group 40, the central portion of the flat portion 40b is likely to expand, and the surrounding joint portions 41d and 42d and the curved portion 40c are unlikely to expand. Therefore, if the wound electrode group 40 is freely expanded, the wound electrode group 40 expands into a convex curved surface having the central portion of the flat portion 40b as a vertex.

  More specifically, the flat portion 40b that is relatively easily expanded when the wound electrode group 40 is expanded has a quadrangular outer shape when viewed from the front. A curved portion 40c that hardly expands is adjacent to an upper side portion and a lower side portion of the rectangular outer shape, and joint portions 41d and 42d that are difficult to expand are formed on the left side portion and the right side portion of the rectangular outer shape. For this reason, if the wound electrode group 40 is freely expanded, the peripheral portion closer to each side of the rectangular outer shape in the front view of the flat portion 40b is less likely to expand, and the central portion farther from each side is more likely to expand. . Thereby, the flat part 40b expand | swells to a quadrangular pyramid convex curved surface shape.

  Therefore, the expansion amount of the flat surface 1a of the battery container 1 is the largest in the central regions Y1 and Z1 facing the central portion of the flat portion 40b of the wound electrode group 40, and the end regions around the central regions Y1 and Z1. It gradually decreases toward Y2 and Z2. That is, the expansion amount of the flat surface 1a of the battery container 1 is such that the expansion amount of the central region Y1 of the flat surface 1a is the end region Y2 in the width direction (Y-axis direction) parallel to the axis D direction of the wound electrode group 40. In addition to the expansion amount of the wound electrode group 40, the expansion amount of the central region Z1 of the flat surface 1a is also expanded in the end region Z2 in the height direction (Z-axis direction) perpendicular to the axis D direction of the wound electrode group 40. More than the amount. Therefore, for example, when the contact portion included in the conventional secondary battery assembly described in Patent Document 1 is used, the surface pressure in the height direction along the flat surface 1a of the battery container 1 perpendicular to the axis D direction is not uniform. There is a risk of becoming.

  On the other hand, in the battery module M of the present embodiment, the elastic coefficient of the contact part 232a in the central regions Y1, Z1 is made lower than the elastic coefficient of the contact parts 232b, 232c, 232d in the end regions Y2, Z2. ing. That is, the center region Y1, which is a region where the amount of expansion of the flat surface 1a is relatively large, the end region Y2, which is a region where the elastic coefficient of the contact portion 232a in the Z1 is relatively small, It is made lower than the elastic coefficient of the contact parts 232b, 232c, 232d in Z2.

  As shown in FIG. 9, the expansion amount of the flat surface 1a in the thickness direction (X direction) of the battery case 1 in the width direction (Y-axis direction) of the battery case 1 is larger in the central region Y1 than in the end region Y2. Is also big. However, the elastic coefficients of the contact portions 232a and 232c that contact the central region Y1 are lower than the elastic coefficients of the contact portions 232b and 232d that contact the end region Y2, respectively. Therefore, compared with the case where the contact portions 232b and 232d of the end region Y2 are also disposed in the central region Y1, the contact portions 232a and 232c of the central region Y1 are moved from the contact portions 232a and 232c of the central region Y1 to the central region Y1. The acting elastic force can be reduced and the central region Y1 can be easily allowed to expand.

  Accordingly, the deformation amounts of the contact portions 232a and 232c in the central region Y1 are larger than the deformation amounts of the contact portions 232b and 232d in the end region Y2, respectively. However, the elastic coefficients of the contact portions 232a and 232c in the central region Y1 are lower than the elastic coefficients of the contact portions 232b and 232d in the end region Y2, respectively. Therefore, the difference between the elastic force acting on the flat surface 1a from the contact portion 232a and the elastic force acting on the flat surface 1a from the contact portion 232b, and the elastic force acting on the flat surface 1a from the contact portion 232c. The difference from the elastic force acting on the flat surface 1a from the contact portion 232d can be reduced. Therefore, in the width direction of the battery case 1 parallel to the axis D direction of the wound electrode group 40, the surface pressure at the center of the flat portion 40b of the wound electrode group 40 that tends to increase the amount of expansion and increase the surface pressure is reduced. The surface pressure acting on the wound electrode group 40 can be made uniform.

  Furthermore, as shown in FIG. 10, the expansion amount of the flat surface 1a in the thickness direction (X direction) of the battery case 1 in the height direction (Z-axis direction) of the battery case 1 is the end portion in the central region Z1. It is larger than the region Z2. However, the elastic coefficients of the contact portions 232a and 232b that contact the central region Z1 are lower than the elastic coefficients of the contact portions 232c and 232d that contact the end region Z2, respectively. Therefore, compared with the case where the contact portions 232c and 232d of the end region Z2 are also arranged in the central region Z1, the contact portions 232a and 232b of the central region Z1 are moved from the contact portions 232a and 232b of the central region Z1 to the central region Z1. The acting elastic force can be reduced, and the expansion of the central region Z1 can be easily allowed.

  Accordingly, the deformation amounts of the contact portions 232a and 232b in the central region Z1 are larger than the deformation amounts of the contact portions 232c and 232d in the end region Z2, respectively. However, the elastic coefficients of the contact portions 232a and 232b in the central region Z1 are lower than the elastic coefficients of the contact portions 232c and 232d in the end region Z2, respectively. Therefore, the difference between the elastic force that acts on the flat surface 1a from the contact portion 232a and the elastic force that acts on the flat surface 1a from the contact portion 232c, and the elastic force that acts on the flat surface 1a from the contact portion 232b. The difference from the elastic force acting on the flat surface 1a from the contact portion 232d can be reduced. Therefore, in the height direction of the battery case 1 perpendicular to the axis D direction of the wound electrode group 40, the surface pressure at the central portion of the flat portion 40b of the wound electrode group 40 that tends to increase the amount of swelling and increase the surface pressure is reduced. The surface pressure acting on the wound electrode group 40 can be made uniform.

  As described above, according to the battery module M of the present embodiment, not only the width direction of the battery container 1 parallel to the axis D direction of the wound electrode group 40 but also the height of the battery container 1 perpendicular to the axis D direction. Also in the vertical direction, the surface pressure acting on the flat surface 1a and the wound electrode group 40 can be made more uniform. Therefore, according to the battery module M of the present embodiment, the deterioration of the secondary battery 100 can be more effectively suppressed.

  Further, as shown in FIG. 7, in the height direction of the battery container 1, the thicknesses of the contact portions 232 a and 232 b that contact the central region Z <b> 1 of the flat surface 1 a of the battery container 1 respectively You may make it thicker than the thickness of contact part 232c, 232d contact | abutted to partial area Z2. Similarly, in the width direction of the battery case 1, the thicknesses of the contact portions 232a and 232c that come into contact with the central region Y1 of the flat surface 1a of the battery case 1 are respectively set to contact with the end region Y2 of the flat surface 1a. You may make it thicker than the thickness of contact part 232b, 232d. Thereby, the deformation of the central regions Y1 and Z1 of the flat surface 1a can be more easily allowed, and the surface pressure acting on the wound electrode group 40 in the central regions Y1 and Z1 of the flat surface 1a can be further reduced. It becomes possible.

  Further, the upper end spacer 231 and the lower end spacer 233 of the spacer 230 are respectively a portion between the upper end of the flat portion 40b and the battery lid 20, and between the lower end of the flat portion 40b and the lower end surface 1d of the battery case 1. It is provided so as to face the part. These portions are relatively less susceptible to the expansion of the wound electrode group 40. Therefore, regardless of the expansion and contraction of the battery container 1, the battery container 1 is securely held by the pair of upper end spacers 231 and the pair of lower end spacers 233 on both sides in the thickness direction of the battery container 1. The secondary battery 100 can be reliably held between the intermediate cell holders 220 and between the intermediate cell holders 220.

  In addition, an opening 221b communicating with the slit S2 between the contact portions 232a and 232b and the contact portions 232c and 232d is formed in the pair of side plates 221 facing the width direction of the battery case 1 of the cell holder 200. . Therefore, it is possible to improve the performance of the secondary battery 100 by allowing a cooling medium to flow into the slit S2 from the opening 221b of the one side plate 221 and effectively cooling the flat surface 1a of the battery container 1 with the cooling medium. it can. Similarly, the cooling medium is caused to flow into the slits S1 and S3 from the upper and lower openings 221a and 221c of the side plate 221, and the flat surface 1a of the battery case 1 is effectively cooled by the cooling medium, thereby improving the performance of the secondary battery 100. Can be improved.

  In addition, arrangement | positioning of contact part 232a, 232b, 232c, 232d is not limited to the arrangement | positioning shown in FIG. Modification examples of the arrangement of the contact portions 232a, 232b, 232c, and 232d are shown in FIGS.

  As shown in FIG. 11, an abutting portion 232a that abuts the central region Z1 in the height direction (Z-axis direction) of the flat surface 1a and abuts the central region Y1a in the width direction (Y-axis direction) of the flat surface 1a. The length in the Y-axis direction of the abutting portion 232c that abuts the end region Z2 in the Z-axis direction of the flat surface 1a and the central region Y1b in the Y-axis direction of the flat surface 1a Instead, it may be longer. In this case, the central regions Y1a and Y1b in the Y-axis direction of the flat surface 1a are wider in the Y-axis direction toward the center side in the Z-axis direction of the flat surface 1a.

  In this way, in the Z-axis direction of the flat surface 1a, the length of the central regions Y1a and Y1b in the Y-axis direction is made different, for example, when the flat surface 1a expands into a spherical shape with the central portion at the apex. Also, corresponding to the expansion shape of the flat surface 1a, the elastic coefficients of the contact portions 232a and 232c in the region where the flat surface 1a has a large expansion amount are set as the elastic coefficients of the contact portions 232b and 232d in the region where the flat surface 1a has a small expansion amount. It can be made lower than the elastic modulus. Accordingly, the surface pressure acting on the flat surface 1a and the wound electrode group 40 can be equalized more accurately corresponding to the expanded shape of the flat surface 1a.

  Further, as shown in FIG. 12, the elastic coefficients of the contact portions 232a and 232c in the Y-axis direction of the flat surface 1a are not changed, and the elastic coefficients of the contact portions 232a of the central region Z1 in the Z-axis direction of the flat surface 1a. May be lower than the elastic coefficient of the contact portion 232c of the end region Z2. For example, if the configuration and arrangement of the wound electrode group 40 accommodated in the battery container 1 of the secondary battery 100 are different, there is almost no difference in the amount of expansion in the Y-axis direction of the flat surface 1a, and the central region only in the Z-axis direction. It is possible that the expansion amount of Z1 becomes larger than the end region Z2.

  In such a case, the elastic coefficients of the contact portions 232a and 232c in the Y-axis direction of the flat surface 1a are not changed, and the elastic coefficients of the contact portions 232a of the central region Z1 in the Z-axis direction of the flat surface 1a are end. By making it lower than the elastic coefficient of the contact part 232c of the partial region Z2, the same effect as the above-mentioned contact parts 232a, 232b, 232c, 232d can be obtained.

  The embodiment of the present invention has been described in detail with reference to the drawings, but the specific configuration is not limited to this embodiment, and there are design changes and the like without departing from the gist of the present invention. They are also included in the present invention. For example, the number of intermediate spacers is not limited to four, and may be three or five or more, for example.

DESCRIPTION OF SYMBOLS 1 ... Battery container 1a ... Flat surface 1b ... Side surface 1c ... Upper end surface 1d ... Lower end surface 40 ... Winding electrode group 40b ... Flat part 40c ... Curved part 41c, 42c ... Foil exposed part 41d, 42d ... Joint part 100 ... Secondary Battery 200 ... cell holder 210 ... end cell holder (cell holder)
220 ... Intermediate cell holder (cell holder)
221 ... Side plate 221b ... Opening 222 ... Bottom plate 230 ... Spacer 232 ... Intermediate spacer (spacer)
232a-232d ... contact part D ... axis M ... battery module S2 ... slit (space between contact parts)
Y1, Y1a, Y1b, Z1 ... central region Y2, Z2 ... end region

Claims (3)

A battery module in which a plurality of secondary batteries including a flat box type battery container that accommodates a flat wound electrode group are stacked via a spacer in the thickness direction of the battery container,
The spacer has a contact portion that contacts the wide flat surface of the battery container,
Elastic modulus of the abutting portion abutting the central region of the flat surface, rather lower than the elastic coefficient of the abutment portion abuts against the end region of the flat surface,
The wound electrode group is arranged such that the axial direction is parallel to the flat surface and the lower end surface of the battery container,
A plurality of the contact portions are arranged in a height direction of the battery container perpendicular to the lower end surface, and an elastic coefficient of the contact portion that contacts the central region in the height direction is the height direction of the battery container. the abuts against the end regions rather lower than the elastic coefficient of the abutment portion,
The elastic coefficient of the contact portion that contacts the central region in the width direction of the battery container parallel to the axial direction of the wound electrode group is that of the contact portion that contacts the end region in the width direction. rather than lower than the elastic coefficient,
The wound electrode group includes a pair of curved portions opposed to the lower end surface and the upper end surface of the battery container, a pair of flat portions opposed to the flat surface, and foils at both ends in the axial direction in the flat portion. And having a joint part obtained by bundling and exposing the exposed part,
The amount of expansion of the flat surface is the largest in the central region facing the central portion of the flat portion, and gradually decreases toward the end region around the central region ,
A length in the width direction of the abutting portion that abuts on the central region in the height direction and abuts on the central region in the width direction abuts on the end region in the height direction; and the width direction the said abutment portion and the widthwise direction of that batteries module to said longer than the length of which abuts the central region of. A cell holder for clamping the battery container in the thickness direction;
The cell holder includes a pair of side plates facing a pair of side surfaces along the thickness method of the battery container, and a bottom plate facing the lower end surface of the battery container and extending in the width direction to connect the pair of side plates. And the spacer facing the flat surface,
The battery module according to claim 1, wherein the side plate has an opening communicating with a space between the contact portions. The abutment, battery module according to claim 1 or claim 2, characterized in that it is constituted by a resin material having elasticity.

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