阅读说明：本技术 电池组 (Battery pack ) 是由 梅村幸司 于 2020-08-17 设计创作，主要内容包括：本发明涉及电池组,该电池组具备：多个单电池,每个单电池具备电极体和收容所述电极体的电池壳体,所述多个单电池在预定方向上排列；及1个或多个间隔件,配置于在所述预定方向上相邻的2个所述单电池之间。所述间隔件在与所述单电池相对的至少一方的面具有朝向所述单电池突出的凸部。所述凸部与所述单电池的电池壳体接触。所述电池壳体的与所述凸部接触的接触部向所述电池壳体的内部方向以能够将所述电极体向所述接触部的方向的移动卡定的方式突出。(The present invention relates to a battery pack including: a plurality of unit cells each having an electrode body and a cell case that houses the electrode body, the plurality of unit cells being arranged in a predetermined direction; and 1 or more spacers disposed between 2 of the unit cells adjacent in the predetermined direction. The spacer has a convex portion protruding toward the battery cell on at least one surface facing the battery cell. The protruding portion is in contact with a battery case of the single cell. The contact portion of the battery case, which is in contact with the projection, protrudes in the direction of the inside of the battery case so as to be capable of locking the movement of the electrode body in the direction of the contact portion.)

1. A battery pack is provided with:

a plurality of unit cells each having an electrode body and a cell case that houses the electrode body, the plurality of unit cells being arranged in a predetermined direction; and

1 or a plurality of spacers arranged between 2 of the unit cells adjacent in the predetermined direction,

wherein the spacer has a convex portion protruding toward the battery cell on at least one surface facing the battery cell,

the convex portion is in contact with the battery case of the single cell,

the contact portion of the battery case, which is in contact with the projection, protrudes in the direction of the inside of the battery case so as to be capable of locking the movement of the electrode body in the direction of the contact portion.

2. The battery pack according to claim 1, wherein the battery pack,

the contact portion is at a position opposite to an end portion of the electrode body.

3. The battery pack according to claim 2, wherein the battery pack,

an electrode terminal is attached to the battery case, and the contact portion is located at a position opposite to an end portion of the electrode body on the electrode terminal side.

4. The battery pack according to claim 3, wherein the battery pack,

the separator further includes a 2 nd convex portion protruding toward the cell on at least one surface facing the cell, a contact portion of the battery case contacting the 2 nd convex portion protrudes in an inner direction of the battery case so as to be capable of locking movement of the electrode body in a direction of the contact portion contacting the 2 nd convex portion, and the contact portion contacting the 2 nd convex portion is positioned to face an end portion of the electrode body opposite to the electrode terminal side.

5. The battery pack according to any one of claims 1 to 4,

the spacers have protrusions on both surfaces, and the contact portions of the battery case of the unit cell sandwiched by the spacers, which contact the protrusions, protrude in the direction of the inside of the battery case, and hold the electrode body by sandwiching it.

Technical Field

The present invention relates to a battery pack.

Background

Secondary batteries such as lithium ion secondary batteries and nickel metal hydride batteries used as vehicle-mounted power sources are generally used in the form of an assembled battery in which a plurality of single cells are connected in series in order to increase the output.

The battery pack typically has a structure in which a plurality of unit cells are arranged (stacked) in a predetermined direction with spacers interposed therebetween, and a restraining load is applied to the battery pack (see, for example, japanese patent laid-open publication No. 2015-. Japanese patent laid-open No. 2015-: according to the configuration in which the spacer is disposed at the center portion of the flat surface of the cell and the center portion of the flat surface of the cell is recessed into the contour of the spacer by a load, fatigue deterioration of the welded portion between the lid body and the main body of the battery case can be suppressed when the internal pressure of the battery case rises.

Disclosure of Invention

However, the inventors of the present application have made extensive studies and found that "in the conventional art represented by the above, when a vehicle on which an assembled battery is mounted passes over a protrusion on a road or the like and an external impact is applied to the vehicle, an electrode body in a cell may move to cause damage such as an internal short circuit or an internal disconnection of a terminal or the like", and that there is room for improvement in this point.

Accordingly, an object of the present invention is to provide a battery pack that is less likely to cause damage from external impact.

The battery pack disclosed herein includes: a plurality of unit cells each having an electrode body and a cell case that houses the electrode body, the plurality of unit cells being arranged in a predetermined direction; and 1 or more spacers disposed between 2 of the unit cells adjacent in the predetermined direction. The spacer has a convex portion protruding toward the battery cell on at least one surface facing the battery cell. The protruding portion is in contact with a battery case of the single cell. The contact portion of the battery case, which is in contact with the projection, protrudes in the direction of the inside of the battery case so as to be capable of locking the movement of the electrode body in the direction of the contact portion.

With this structure, it is possible to provide a battery pack that is less likely to be damaged by external impact.

In one aspect of the battery pack disclosed herein, the contact portion is at a position opposite to an end portion of the electrode body.

According to such a structure, damage of the battery pack against external impact is less likely to occur.

In another aspect of the battery pack disclosed herein, an electrode terminal is mounted to the battery case, and the contact portion is located at a position opposite to an end of the electrode body on the electrode terminal side.

With such a configuration, the battery pack is further less likely to be damaged by external impact.

In still another aspect of the assembled battery disclosed herein, the spacer further includes a 2 nd convex portion protruding toward the unit cell on at least one surface facing the unit cell, a contact portion of the battery case contacting the 2 nd convex portion protrudes in an inner direction of the battery case so as to be capable of locking movement of the electrode body in a direction of the contact portion contacting the 2 nd convex portion, and the contact portion contacting the 2 nd convex portion is located at a position facing an end portion of the electrode body on a side opposite to the electrode terminal side.

With such a structure, the battery pack is further less likely to be damaged by external impact.

In one aspect of the assembled battery disclosed herein, the spacers have protrusions on both surfaces, and the contact portions of the battery case of the unit cells sandwiched by the spacers, which contact the protrusions, protrude in the direction of the inside of the battery case, and sandwich and hold the electrode body.

According to such a structure, damage of the battery pack against external impact is less likely to occur.

Drawings

The features, advantages and technical and industrial significance of exemplary embodiments of the present invention will be described below with reference to the accompanying drawings, in which like reference numerals represent like elements, and in which:

fig. 1 is a perspective view schematically showing an example of the battery pack according to the present embodiment.

Fig. 2 is a plan view schematically showing the single cell shown in fig. 1.

Fig. 3 is a longitudinal sectional view schematically showing the unit cell shown in fig. 1.

Fig. 4 is an exploded view schematically showing the electrode body shown in fig. 3.

Fig. 5 is a partial sectional view schematically showing the rear of the battery pack of the present embodiment.

Fig. 6 is a plan view schematically showing a single cell in a preferred mode.

Fig. 7 is a schematic diagram partially showing the structure of the test piece of test example 1.

Fig. 8 is a schematic diagram partially showing the structure of the test piece of test example 3.

Fig. 9 is a graph showing the evaluation results of the fatigue deterioration resistance test of the welded portion in each test example.

Detailed Description

Hereinafter, preferred embodiments of the battery pack disclosed herein will be described with reference to the drawings as appropriate. Note that the embodiments described herein are not intended to limit the present invention. The battery pack disclosed herein can be implemented based on the disclosure of the present specification and the technical common knowledge in the art.

In the following drawings, members and portions having the same function are denoted by the same reference numerals, and redundant description may be omitted or simplified. The reference numerals U, D, F, Rr, L, R in the drawings mean up, down, front, rear, left, right, respectively. Reference numeral X, Y, Z in the drawing denotes the arrangement direction of the cells, the width direction of the long side walls of the cells, and the vertical direction of the long side walls of the cells, respectively. However, these are merely directions for convenience of explanation, and the arrangement of the battery pack is not limited at all. The dimensional relationships (length, width, thickness, etc.) in the drawings do not reflect actual dimensional relationships.

Fig. 1 is a perspective view schematically showing an example of the battery pack 1 according to the embodiment of the present invention. The assembled battery 1 includes a plurality of single cells 10 and a plurality of spacers 40. The battery pack 1 further includes a binding mechanism. Specifically, for example, as shown in the drawing, the battery pack 1 includes a pair of end plates 50A and 50B, a plurality of tie-down bands 52, and a plurality of screws 54. The pair of end plates 50A, 50B are disposed at both ends of the battery pack 1 in a predetermined arrangement direction X (the front-rear direction in fig. 1). A plurality of straps 52 are mounted across the pair of end plates 50A, 50B. The plurality of cells 10 are arranged in the arrangement direction X. The plurality of spacers 40 are disposed between the 2 adjacent single cells 10 in the arrangement direction X. Further, 2 end spacers 60 are disposed between the single cell 10 and the end plate 50A and between the single cell 10 and the end plate 50B, respectively. The number of the cells 10 is not particularly limited as long as it is 2 or more. When the assembled battery 1 includes 2 single cells 10, the number of the spacers 40 is 1.

The end plates 50A, 50B sandwich the plurality of single cells 10, the plurality of spacers 40, and the 2 end spacers 60 in the arrangement direction X. A plurality of straps 52 are secured to the end plates 50A, 50B by a plurality of screws 54. The plurality of straps 52 are attached to each other so as to apply a predetermined restraining pressure in the arrangement direction X. The plurality of tie-down bands 52 are formed such that the surface pressure in the region pressed by the spacers 40 of the single cells 10 is substantially 90 to 600kgf/cm²(e.g., 200 to 500 kgf/cm)²Left and right). Thereby, a load is applied to the plurality of single cells 10, the plurality of spacers 40, and the 2 end spacers 60 from the arrangement direction X, and the assembled battery 1 is integrally held. In the illustrated example, the end plates 50A and 50B, the plurality of straps 52, and the plurality of screws 54 constitute a binding mechanism, but the binding mechanism is not limited thereto.

Fig. 2 is a plan view schematically showing the single cell 10. Fig. 3 is a longitudinal sectional view schematically showing the single cell 10. The cell 10 is typically a secondary battery (for example, a lithium ion secondary battery, a nickel metal hydride battery, an electric double layer capacitor, or the like) that can be repeatedly charged and discharged. The cell 10 includes an electrode body 20, an electrolyte (not shown), and a battery case 30.

The battery case 30 is an outer case that houses the electrode body 20 and the electrolyte. The battery case 30 is made of metal such as aluminum or steel, for example. The battery case 30 illustrated in the drawing has a bottomed square (rectangular parallelepiped) outer shape. The battery case 30 is composed of a lid body and a case main body. The lid body and the case body are joined by welding such as laser welding.

The battery case 30 has an upper wall 30u, a bottom wall 30b opposed to the upper wall 30u, and a pair of short side walls 30n and a pair of long side walls 30w as side walls continuous from the bottom wall 30 b. The lid of the battery case 30 is formed by an upper wall 30u, and the case body is formed by a bottom wall 30b, a pair of short side walls 30n, and a pair of long side walls 30 w. The case body is formed by drawing, for example, 1 metal plate. The pair of short sidewalls 30n and the pair of long sidewalls 30w have flat portions, respectively. The thickness (plate thickness) of the bottom wall 30b, the pair of short side walls 30n, and the pair of long side walls 30w is generally 1mm or less, typically 0.5mm or less, for example, 0.3 to 0.4 mm. The pair of long side walls 30w of the battery case 30 are respectively opposed to the spacers 40 except for the end portions of the battery pack 1. At the end of the battery pack 1, a pair of long side walls 30w of the battery case 30 are opposed to the spacer 40 and the end spacer 60, respectively.

A thin safety valve 32 is provided on the upper wall 30u of the battery case 30 so as to release the internal pressure of the battery case 30 when the internal pressure rises to a predetermined level or more. The upper wall 30u of the battery case 30 is provided with a liquid inlet (not shown) for injecting an electrolyte. A positive electrode terminal 12T and a negative electrode terminal 14T for external connection are attached to an upper wall 30u of the battery case 30. The positive electrode terminal 12T and the negative electrode terminal 14T of the adjacent single cells 10 are electrically connected by a bus bar 18. Thereby, the single cells 10 are electrically connected in series. However, the shape, size, number, arrangement, connection method, and the like of the cells 10 constituting the battery assembly 1 are not limited to those disclosed herein, and can be appropriately modified. For example, in the assembled battery 1, a part or all of the single cells 10 may be electrically connected in parallel.

The configurations of the electrode body 20 and the electrolyte solution housed inside the battery case 30 may be the same as in the related art, and are not particularly limited. The electrolytic solution is, for example, a nonaqueous electrolytic solution including a nonaqueous solvent and a supporting salt. Examples of the nonaqueous solvent include carbonates such as Ethylene Carbonate (EC), diethyl carbonate (DMC) and Ethyl Methyl Carbonate (EMC). The supporting salt is, for example, LiPF₆、LiBF₄And the like lithium salts.

Fig. 4 is an exploded view schematically showing the electrode body 20. In the illustrated example, the electrode body 20 is a wound electrode body. The electrode body 20 is configured by laminating a strip-shaped positive electrode 12 and a strip-shaped negative electrode 14 in an insulated state with a strip-shaped separator 16 interposed therebetween and winding the laminated layers around a winding axis WL.

The positive electrode 12 includes a positive electrode current collector and a positive electrode active material layer 12a fixed to the surface thereof. The positive electrode active material layer 12a includes a positive electrode active material (for example, a lithium-transition metal composite oxide) capable of reversibly storing and releasing charge carriers. The negative electrode 14 includes a negative electrode current collector and a negative electrode active material layer 14a fixed to the surface thereof. The negative electrode active material layer 14a includes a negative electrode active material (for example, a carbon material) capable of reversibly storing and releasing charge carriers. The separator 16 is a porous member that allows charge carriers to permeate therethrough and insulates the positive electrode active material layer 12a and the negative electrode active material layer 14 a.

The width W3 of the separator 16 is wider than the width W1 of the cathode active material layer 12a and the width W2 of the anode active material layer 14a in the width direction Y of the electrode body 20. The width W2 of the negative electrode active material layer 14a is wider than the width W1 of the positive electrode active material layer 12 a. That is, W1, W2, and W3 satisfy W1< W2< W3. In the range of the width W1 of the cathode active material layer 12a, the cathode active material layer 12a and the anode active material layer 14a face each other in an insulated state.

A positive electrode collector exposed portion 12n is provided at the right end of the electrode body 20 in the width direction Y. A positive current collector plate 12c for a current collector foil is attached to the positive current collector exposed portion 12 n. The positive electrode 12 of the electrode assembly 20 is electrically connected to the positive electrode terminal 12T via the positive electrode current collector plate 12 c. Further, a negative electrode collector exposed portion 14n is provided at the left end portion in the width direction Y of the electrode body 20. A negative electrode current collector plate 14c for a current collector foil is attached to the negative electrode current collector exposed portion 14 n. The negative electrode 14 of the electrode assembly 20 is electrically connected to the negative electrode terminal 14T via the negative electrode current collector plate 14 c.

The appearance of the electrode body 20 is a flat shape. The electrode body 20 has a pair of winding flat portions 20f and a pair of winding R portions 20R interposed between the pair of winding flat portions 20f in a cross section orthogonal to the winding axis WL. A pair of end portions in the width direction Y of the electrode body 20 is open, and the inside and the outside of the electrode body 20 communicate at the end portions in the width direction Y.

In the unit cell 10, one of the pair of wound R portions 20R of the electrode body 20 is disposed on the bottom wall 30b side of the battery case 30, and the other is disposed on the upper wall 30u side of the battery case 30. In other words, the pair of wound R portions 20R of the electrode body 20 is disposed vertically above and below the vertical direction Z. A pair of end portions of the electrode body 20 in the width direction Y are arranged so as to face a pair of short side walls 30n of the battery case 30. The pair of winding flat portions 20f of the electrode body 20 is disposed so as to face the pair of long side walls 30w of the battery case 30. In other words, the pair of winding flat portions 20f of the electrode body 20 is arranged along the arrangement direction X.

In the illustrated example, the electrode body 20 is a wound electrode body, but the form of the electrode body 20 is not limited to this. The electrode assembly 20 may be a laminated electrode assembly in which a plurality of sheet-shaped positive electrodes and a plurality of sheet-shaped negative electrodes are alternately laminated.

Fig. 5 is a schematic partial sectional view of the rear portion of the battery pack 1 along the stacking direction and the vertical direction. The spacers 40 are interposed between the adjacent 2 single cells 10. The spacer 40 is made of a resin material such as polypropylene (PP) or Polyphenylene Sulfide (PPs) or a metal material having high thermal conductivity.

In the example shown, the spacer 40 has a plurality of ribs 42 on both sides. The spacer 40 may not have the rib 42. The ribs 42 may have the same structure as those of a spacer of a known battery pack. In the illustrated example, these ribs 42 face the electrode body 20 (particularly, the winding flat portion 20 f). Since a restraining load is applied to the battery pack 1, the ribs 42 press the battery case 30 by the restraining load. By pressing the battery case 30, expansion and the like of the electrode body 20 can be suppressed.

In the illustrated example, the ribs 42 are arranged in a comb-like shape so that a cooling fluid (for example, air) can pass between the spacer 40 and the battery case 30. Thus, the spacer 40 has a function as a heat sink for dissipating heat generated inside the single cell 10 by the ribs 42. The arrangement of the ribs 42 is not limited to this.

The spacer 40 has a convex portion 44R protruding toward the cell 10 on a surface facing the cell 10 on the right side. The spacer 40 has a convex portion 44L protruding toward the cell 10 on the surface facing the cell 10 on the left side.

The spacer 40 and the cell 10 on the right side thereof will be described in detail below. The convex portion 44R contacts the battery case 30 of the single cell 10. The contact portion 34 of the battery case 30 that contacts the convex portion 44R protrudes toward the inside of the battery case 30. Thereby, the contact portion 34 serves as a stopper when the electrode body 20 moves in the direction of the contact portion 34 (i.e., the upward direction U in the drawing). That is, the contact portion 34 protrudes in the internal direction of the battery case 30 so as to be able to lock the movement of the electrode body 20 in the direction of the contact portion 34.

In the illustrated example, the long side walls 30w are deformed into a shape corresponding to the convex portions 44R of the spacer 40 by the restraining load, and thereby the contact portions 34 protrude toward the inside of the battery case 30. That is, the contact portion 34 is recessed when viewed from the outer surface side of the cell 10, and protrudes when viewed from the inner surface side of the cell 10. Thus, the contact portion 34 can be projected toward the inside of the battery case 30 by the deformation of the battery case 30 due to the restraining load, and therefore, the long side walls 30w of the battery case 30 of the single cell 10 before the assembly of the battery pack 1 can be flat. Alternatively, before the battery pack 1 is assembled, the portions of the long side walls 30w of the battery case 30 that are to be in contact with the convex portions 44R of the spacer 40 may be deformed in advance so as to be recessed when viewed from the outer surface side of the single cell 10, so that the convex portions 44R of the spacer 40 can be easily aligned with the battery case 30. In this case, the deformation may be in a shape corresponding to the convex portion 44R of the spacer 40, but the amount of deformation is preferably smaller than this so as not to interfere with the insertion operation of the electrode body 20 into the battery case 30.

The contact portion 34 has a protruding portion protruding in the inner direction of the battery case 30, but the size of the protruding portion may be appropriately determined according to the design of the single cell 10 and the electrode body 20. The dimension of the protruding portion in the protruding direction (i.e., the height of the protruding portion; specifically, the dimension from the inner surface of the battery case 30 to the apex of the protruding portion in the arrangement direction X) is preferably 0.5% or more and 15% or less, more preferably 2% or more and 10% or less of the thickness of the electrode body 20.

In the illustrated example, the contact portion 34 is located opposite to the end portion of the electrode body 20. In this case, the movement of the electrode body 20 can be effectively locked, and damage to the external impact is less likely to occur. However, the position of the contact portion 34 is not limited to this, and can be appropriately set according to the outer shape of the electrode body 20. For example, when the electrode body 20 has a recessed outer shape in the central portion, the contact portion 34 may be provided at a position of the battery case 30 facing the recess in the central portion of the electrode body 20.

As shown in the drawing, the contact portion 34 is advantageous to be opposed to the end portion on the electrode terminal (i.e., the positive electrode terminal 12T and the negative electrode terminal 14T) side among the end portions of the electrode body 20. When the electrode body 20 is moved in the direction of the electrode terminal, the internal disconnection of the terminal is more easily caused. With this configuration, movement of the electrode body 20 in the direction of the electrode terminal can be suppressed, and damage to the external impact is less likely to occur. In the illustrated example, the positive electrode terminal 12T and the negative electrode terminal 14T are attached to the lid body, and the lid body and the case main body are welded. With this configuration, fatigue deterioration of the welded portion between the lid body and the case main body can be further suppressed.

A more preferred embodiment of the cell is schematically shown in fig. 6. In a more preferred embodiment, the spacer 40 further has a 2 nd convex portion protruding toward the cell 10 on at least one surface facing the cell 10, a contact portion (2 nd contact portion) 34 ' of the battery case 30 contacting the 2 nd convex portion protrudes in an inner direction of the battery case 30 so as to be able to lock the movement of the electrode body 20 in a direction of the 2 nd contact portion 34 ', and the 2 nd contact portion 34 ' is located opposite to an end portion of the electrode body 20 opposite to the electrode terminal side. As shown in fig. 6, by providing the 1 st contact portion 34 and the 2 nd contact portion 34' at both ends of the electrode body 20, the movement of the electrode body 20 can be further suppressed, and damage to the external impact is less likely to occur.

In the illustrated example, the contact portion 34 protruding toward the inside of the battery case 30 is in contact with the electrode body 20. However, the contact portion 34 may not be in contact with the electrode body 20. The smaller the distance between contact portion 34 and electrode body 20, the more the movement of electrode body 20 can be suppressed, and in particular, it is advantageous that contact portion 34 is in contact with electrode body 20. The contact portion 34 may be in direct contact with the electrode body 20, or may be in indirect contact with the electrode body 20 through an insulating film when the electrode body 20 is covered with the insulating film.

The spacer 40 also has a convex portion 44L protruding toward the cell 10 on the surface facing the cell 10 on the left side. The surface of the spacer 40 facing the left single cell 10 and the left single cell 10 have the same configuration as described above. That is, the convex portion 44L contacts the battery case of the left cell 10, and similarly, the contact portion of the battery case that contacts the convex portion 44L protrudes in the internal direction of the battery case so as to be able to lock the movement of the electrode body in the direction of the contact portion. However, the spacer 40 may have the above-described convex portion on only one surface.

As shown in the drawing, it is advantageous that the spacer 40 has the convex portions 44R and 44L on both surfaces, and the contact portions of the battery case 30 of the single cell 10 sandwiched by the spacer 40, which contact the convex portions, protrude toward the inside of the battery case 30 of the single cell 10, and sandwich and hold the electrode body 20. With such a configuration, the electrode body 20 can be firmly fixed, and thus movement of the electrode body 20 can be further suppressed, and thus damage to external impact is more unlikely to occur. In particular, when the electrode body 20 is a wound electrode body as in the illustrated example, the electrode body 20 has the wound R portion 20R at the end portion, and therefore, the end portion of the electrode body 20 is easily sandwiched and held, which is more advantageous.

The face of the end spacer 60 opposite the end plate 50B is flat. On the other hand, the end spacer 60 has a rib 62 on a surface facing the single cell 10. The ribs 62 are arranged in a comb-like shape, similarly to the ribs 42 of the spacer 40. The end spacers 60 may have the same configuration as known end spacers disposed between the end plates and the cells. However, it is advantageous that the end spacer 60 also has a convex portion 64 on the face opposing the single cell 10, as in the illustrated example. The convex portions 64 are in contact with the battery case 30 of the single cell 10 similarly to the convex portions 44R of the spacer 40, and the contact portions 36 of the battery case 30 that are in contact with the convex portions 64 protrude in the direction of the inside of the battery case 30 so as to be able to lock the movement of the electrode body in the direction of the contact portions 36. With such a configuration, the single cells 10 located at the end of the battery assembly 1 are less likely to be damaged by external impact. The end spacer 60 may have a structure without the projection 64.

The assembled battery 1 configured as described above is less likely to cause damage such as internal short-circuiting due to external impact, or internal disconnection of terminals. In addition, fatigue deterioration of the welded portion between the lid body and the case main body of the battery case is less likely to occur. The battery pack 1 can be used for various purposes. The battery pack 1 can be used favorably as a power source (driving power source) for a motor mounted on a vehicle, for example. The type of vehicle is not particularly limited, but typically includes an automobile (e.g., a plug-in hybrid vehicle (PHV), a Hybrid Vehicle (HV), an Electric Vehicle (EV), etc.). In addition, the battery pack 1 can be used as an industrial or household power storage device.

The inventors of the present application have actually performed a simple test using a single cell and a pair of spacers in order to verify the effects of the assembled battery disclosed herein. The present invention is not limited to the above-described embodiments.

[ preparation of test body ]

A unit cell 110 in which a wound electrode body 120 is housed in a battery case 130 as shown in fig. 7 is prepared. The structure of the wound electrode assembly 120 of the unit cell 110 is similar to that of a general lithium ion secondary battery. The battery case 130 is composed of a case body and a lid body, which are joined by laser welding. Terminals (not shown) are also attached to the battery cells 110 in the same manner as in fig. 2 and 3.

Further, as shown in fig. 7, a pair of spacers 140 having ribs 142 and protrusions 144 on one surface are prepared. The spacer 140 is made of PP. The battery cell 110 is sandwiched by the pair of spacers 140 so that the surface having the convex portions 144 and the ribs 142 faces the battery cell 110. Then, the sheet was sandwiched by a pair of SUS-made binding plates, and a binding load was applied. The contact area between the binding plate and the spacer 140 is set to 13cm²The applied load was set to 50N. Thus, a test piece of test example 1 was produced. In the test body of test example 1, the contact portion of the battery case 130 contacting the convex portion was deformed by the restraining load and protruded inward, and the dimension h (h in fig. 7) in the protruding direction was 0.2 cm.

As test example 2, a test piece was prepared in which the dimension h (h in fig. 7) of the contact portion in the protruding direction was 0.4cm, while changing the dimension of the convex portion 144.

In addition, a pair of spacers 240 having ribs 242 without projections as shown in fig. 8 were prepared. The spacer 240 is also made of PP. In betweenIn the spacer 240, the portion of the spacer 140 having the convex portion 144 also has a rib 242. The cell 110 is sandwiched by a pair of spacers 240 so that the surface having the ribs 242 faces the cell 110. Then, the sheet was sandwiched by a pair of SUS-made binding plates, and a binding load was applied. The contact area between the binding plate and the spacer 240 is set to 13cm²The applied load was set to 50N. Thus, a test piece of test example 3 was produced. The dimension h (h in fig. 7) of the test piece in the protruding direction in test example 3 corresponds to 0 cm.

[ impact resistance test ]

The test bodies of test examples 1 to 3 were subjected to an upward impact (in the direction of U in the drawing). X-ray transmission observation was performed on the test piece after the impact was applied, and the movement of the electrode body 120 and the presence or absence of internal disconnection were examined. In the impact resistance test, the strength of the impact was varied within a range of 10G to 100G. The results are shown in table 1.

[ TABLE 1 ]

TABLE 1

O: no electrode moving and no internal wire break

X: with moving electrode bodies and without internal breakage

X: with moving electrode bodies and with internal breaks

As is clear from the results in table 1, by providing the spacer with the convex portion and projecting the contact portion of the battery case that contacts the convex portion toward the inside of the battery case, the movement of the electrode body and the internal disconnection can be suppressed.

[ fatigue deterioration resistance test of weld part of Battery case ]

Air was introduced from the side surface of the cell of the test bodies of test examples 1 to 3 to change the internal pressure of the cell. The initial battery internal pressure was set to 0.25MPa, and the internal pressure fluctuation within the range of ± 0.20MPa was set to 1 cycle. The internal pressure was repeatedly varied, and the number of cycles in which air leakage occurred from the welded portion between the lid body and the main body of the battery case 130 was determined. Further, the number of cycles in which air leakage from the welded portion occurred when the internal pressure fluctuation within the range of ± 0.15MPa was set to 1 cycle and the number of cycles in which air leakage from the welded portion occurred when the internal pressure fluctuation within the range of ± 0.10MPa was set to 1 cycle were also determined. The results are shown in FIG. 9.

As is clear from the results of fig. 9, by providing the protruding portions on the spacers and projecting the contact portions of the battery case that contact the protruding portions into the battery case, fatigue deterioration of the welded portions between the lid body and the main body of the battery case can be suppressed.

Although specific examples of the present invention have been described in detail above, these are merely examples and do not limit the claims. The techniques described in the claims include those obtained by variously changing or modifying the specific examples illustrated above.