JP2017027900A - Power storage device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power storage device in which a short circuit due to a metallic foreign matter never takes place, even if a metallic foreign matter is adhering to a gap filling member placed in the battery case of a power storage device.SOLUTION: In a power storage device including an electrode assembly 20 laminating a plurality of sheet-like electrodes, and a battery case 11 housing the electrode assembly 20, where the battery case 11 has a pair of side faces 25, 26 facing a pair of outermost layer electrodes 23, 24 in the lamination direction of the electrode, a gap filling member is placed in a gap existing between the outermost layer electrode 24 and the side face 26, and the gap filling member has stretchability.SELECTED DRAWING: Figure 6

Description

  The present invention relates to a power storage device.

In recent years, lithium ion secondary batteries have been adopted not only as power sources for electronic devices but also as power sources for hybrid vehicles and electric vehicles.
Usually, a battery case of a lithium ion secondary battery contains an electrode assembly and an electrolytic solution as power generation elements. The electrode assembly includes a positive electrode as an electrode obtained by applying a positive electrode active material to a metal foil, a negative electrode as an electrode obtained by applying a negative electrode active material to a metal foil, and a separator as an insulating member interposed between the positive electrode and the negative electrode With. Examples of the electrode assembly include a wound type and a laminated type.

  As a related art of the power storage device, an assembled battery disclosed in Patent Document 1 is known. This assembled battery is configured by arranging a plurality of wound type cells. A gap filling member that closes a gap existing between the pair of side walls of the container and the electrode assembly is inserted in the container of each unit cell, and the assembled battery is configured while ensuring the heat dissipation of the assembled battery. The thickness in the arrangement direction of each unit cell to be made uniform.

JP 2009-212055 A

  By the way, when manufacturing the gap filling member of the assembled battery disclosed in Patent Document 1, a metal foreign matter may be generated and adhered to the gap filling member. For this reason, when the power storage device is assembled with the metal foreign matter attached to the gap filling member, the gap filling member may be pierced by the metal foreign matter. Furthermore, there is a possibility that the electrode, the separator, and the insulating sheet covering the battery case may be pierced by a metallic foreign matter. If the electrode and the separator are broken, the electrode may be short-circuited, and if the insulating sheet is broken, the electrode and the battery case may be short-circuited.

  The present invention has been made in view of the above problems, and an object of the present invention is to use a metal foreign object even if a metal foreign object adheres to a gap filling member disposed in a battery case of a power storage device. An object of the present invention is to provide a power storage device that does not cause a short circuit.

  In order to solve the above problems, the present invention includes an electrode assembly in which a plurality of sheet-like electrodes are stacked, and a battery case that houses the electrode assembly, and the battery case includes the electrode assembly. A power storage device having a pair of side surfaces facing a pair of outermost layer electrodes in the stacking direction, wherein a gap filling member is disposed in a gap existing between the outermost layer electrode and the side surfaces, and the gap filling member is stretched It has the property.

  According to the present invention, even if a metal foreign matter adheres to the gap filling member, the gap filling member is stretched without being broken by the metal foreign matter.

  In the above power storage device, the gap filling member may be a multilayer film including a plurality of films each formed of a stretchable material. According to the above configuration, the gap filling member is further hardly broken by the metal foreign matter and is easily extended.

  The plurality of films may be a film formed of polyethylene terephthalate, a film formed of nylon, and a film formed of polypropylene. According to the above configuration, the gap filling member can be realized at low cost.

  The present invention can provide a power storage device that does not cause a short circuit due to a metal foreign matter even if a metal foreign matter adheres to a gap filling member disposed in the battery case of the power storage device.

1 is an exploded perspective view of a secondary battery according to an embodiment of the present invention. 1 is a longitudinal sectional view in a longitudinal direction of a secondary battery according to an embodiment of the present invention. It is a disassembled perspective view which shows a part of electrode assembly of the secondary battery which concerns on embodiment of this invention. It is a longitudinal cross-sectional view of the secondary direction of the secondary battery which concerns on embodiment of this invention. (A) is a schematic diagram which shows the reference | standard space when the reference | standard electrode assembly is accommodated in the reference | standard space, (b) shows the empty space at the time of arranging the electrode assembly with comparatively small thickness in a battery case. It is a schematic diagram. (A) is a schematic diagram which shows the metal foreign material which exists between filling films, (b) is a schematic diagram which shows the metal foreign material which exists between a filling film and an electrode assembly.

Hereinafter, a power storage device according to an embodiment of the present invention will be described with reference to the drawings.
In the present embodiment, a secondary battery as a power storage device is illustrated, and the secondary battery of the present embodiment is specifically a lithium ion secondary battery.

  As shown in FIG.1 and FIG.2, the battery 10 of this embodiment is a square secondary battery. An electrode assembly 20 is accommodated in the battery case 11 of the battery 10. The battery case 11 has a bottomed rectangular parallelepiped case main body 12 and a rectangular flat plate-like lid body 14 that closes an opening 13 of the case main body 12. The case body 12 and the lid body 14 are made of a metal material (for example, aluminum). The battery 10 of this embodiment is a power storage device of the present invention.

  The case main body 12 includes a rectangular bottom portion 19, a pair of side wall portions 15 and 16 along the longitudinal direction of the bottom portion 19 standing from the bottom portion 19, and a pair along the short direction of the bottom portion 19 standing from the bottom portion 19. Side wall portions 17 and 18. The inner side surfaces of the case body 12 of the pair of side wall portions 15 and 16 along the longitudinal direction are the pair of side surfaces 25 and 26. The side surface 25 faces the side surface 26. An insulating sheet (not shown) as an insulating member is attached to the inner surface of the case main body 12 as an insulating member for insulation from the electrode assembly 20 accommodated in the battery case 11. Further, an insulating sheet (not shown) as an insulating member for insulating the electrode assembly 20 housed in the battery case 11 is attached to the inner surface of the lid body 14. A pair of through holes 47 are formed in the lid body 14.

The electrode assembly 20 is a power generation element that generates battery functions such as charging and discharging.
As shown in FIG. 3, the electrode assembly 20 is formed by alternately laminating a plurality of sheet-like positive electrodes 21 and a plurality of sheet-like negative electrodes 22 so as to face each other. The electrode stacking direction A is defined as the electrode stacking direction of the electrode assembly 20. A separator 29 that insulates the positive electrode 21 from the negative electrode 22 is disposed between the positive electrode 21 and the negative electrode 22. The separator 29 is an insulating member formed by, for example, a porous resin sheet. The positive electrode 21 and the negative electrode 22 of this embodiment are the electrodes of the present invention.

  As shown in FIG. 3, the plurality of positive electrodes 21 are formed to have the same shape. The positive electrode 21 includes a positive electrode sheet 30 having a rectangular sheet surface and a belt-like positive electrode tab portion 31 formed at the edge of the positive electrode sheet 30. The positive electrode sheet 30 includes a positive electrode metal foil 32 and a positive electrode active material layer 33 formed of a positive electrode active material coated on both surfaces of the positive electrode metal foil 32. The positive electrode active material is, for example, a lithium compound. The positive electrode tab portion 31 is formed of a positive electrode metal foil, and the positive electrode tab portion 31 is not coated with a positive electrode active material. In addition, the positive electrode metal foil 32 of this embodiment is an aluminum foil.

  As shown in FIG. 3, the plurality of negative electrodes 22 are formed to have the same shape. The negative electrode 22 includes a negative electrode sheet 34 having a rectangular sheet surface and a strip-shaped negative electrode tab portion 35 formed at the edge of the negative electrode sheet 34. The negative electrode sheet 34 includes a negative electrode metal foil 36 and a negative electrode active material layer 37 formed of a negative electrode active material coated on both surfaces of the negative electrode metal foil 36. The negative electrode active material is, for example, a carbon compound. The negative electrode tab portion 35 is formed of a negative electrode metal foil, and the negative electrode tab portion 35 is not coated with a negative electrode active material. In addition, the negative electrode metal foil 36 of this embodiment is a copper foil.

  As shown in FIG. 3, the positive electrode tab portions 31 are arranged in a row along the electrode stacking direction A. The negative electrode tab portions 35 are arranged in a row along the electrode stacking direction A in the same manner as the positive electrode tab portion 31 so as not to overlap the positive electrode tab portion 31 in the electrode stacking direction A. In this embodiment, each positive electrode tab part 31 is formed in the mutually same dimension, and the negative electrode tab part 35 is also formed in the mutually same dimension. As shown in FIG. 1, the positive electrode tab portions 31 of the plurality of positive electrodes 21 are collected on one end side in the electrode stacking direction A to form a positive electrode current collecting group 38, and the negative electrode tab portions 35 of the plurality of negative electrodes 22 are Collected on the same side as the current collecting group 38 to form a negative electrode current collecting group 39.

  As shown in FIGS. 1 and 2, a positive current collector plate 40 is joined to the positive current collector group 38, and a negative current collector plate 41 is joined to the negative current collector group 39. The positive electrode current collector plate 40 is provided with a positive electrode terminal 43 that is electrically connected via an overcurrent interrupt device 42. In addition, the negative electrode current collector plate 41 is provided with a negative electrode terminal 45 that is electrically connected via an overcurrent interrupt device 44. In a state where the electrode assembly 20 is accommodated in the battery case 11, the positive electrode terminal 43 and the negative electrode terminal 45 are exposed to the outside of the battery case 11 through the pair of through holes 47 of the lid body 14. A cylindrical insulating ring 46 made of resin for insulating the positive electrode terminal 43 and the negative electrode terminal 45 from the lid body 14 is attached to the positive electrode terminal 43 and the negative electrode terminal 45, respectively.

  As shown in FIG. 4, the thickness of the electrode assembly 20 is defined as a thickness T1. The electrode assembly 20 includes a pair of electrodes (hereinafter referred to as “outermost layer electrodes”) 23 and 24 that are outermost layers in the electrode stacking direction A. In a state where the electrode assembly 20 is accommodated in the battery case 11, the sheet surface 27 of the outermost layer electrode 23 faces the side surface 25 of the battery case 11, and the sheet surface 28 of the outermost layer electrode 24 faces the side surface 26.

  An electrode assembly 20 is accommodated in the space inside the battery case 11. Due to tolerances at the time of manufacturing the electrode assembly 20, the thicknesses of the positive electrode 21, the negative electrode 22, and the separator 29 vary, and the thickness T1 of the electrode assembly 20 varies. For this reason, variations occur in the size of the space occupied by the electrode assembly 20 in the battery case 11. The reference electrode assembly 20 is accommodated in the battery case 11 and is restrained by the side surfaces 25 and 26. When the positive electrode sheets 30 of the plurality of positive electrodes 21 and the negative electrode sheets 34 of the plurality of negative electrodes 22 receive loads from the side surfaces 25 and 26 of the battery case 11, the reference electrode assembly 20 has the side surface 25 in the electrode stacking direction A. , 26 are in contact with each other. The reference electrode assembly 20 is used as a reference electrode assembly. As shown in FIG. 5A, the space occupied by the reference electrode assembly in the space inside the battery case 11 is defined as a reference space S1. The distance in the electrode stacking direction A of the reference space S1 is the same distance D1 as the length of the battery case 11 in the short direction.

  When the thickness T1 of the electrode assembly 20 is relatively small, when the electrode assembly 20 is accommodated in the battery case 11 so that the outermost electrode 23 is in contact with the side surface 25 of the battery case 11, as shown in FIG. In the reference space S1, there are a space occupied by the electrode assembly 20 and an empty space S2. The empty space S <b> 2 is a gap that exists between the outermost electrode 24 of the electrode assembly 20 and the side surface 26 of the battery case 11. The distance in the electrode stacking direction A of the empty space S2 is the distance D2.

  In this embodiment, when empty space S2 exists, as shown in FIG. 4, the filling film 50 is arrange | positioned in empty space S2. The filling film 50 is a gap filling member of the present invention. The filling film 50 has stretchability. In the present embodiment, a multilayer film that is a resin film is used as the filling film 50. The multilayer film includes a plurality of films each formed of a stretchable material. For example, the multilayer film includes a film 50A formed of polyethylene terephthalate (PET) shown in FIG. 4, a film 50B formed of stretched nylon (ON), and a film 50C formed of unstretched polypropylene (CPP). The thickness of the multilayer film is about 20 to 250 μm (micrometer).

  As shown in FIG. 4, one filling film 50 has a thickness T2. As shown in FIG. 1, the filling film 50 has a rectangular sheet surface 52. The size of the sheet surface 52 of the filling film 50 is a size that can cover the sheet surface 28 of the outermost layer electrode 24, and is accommodated in the battery case 11 and indirectly through the filling film 50. It is preferable that the size be such that a load can be uniformly applied to the entire 24 sheet surfaces 28.

  In the present embodiment, as shown in FIG. 4, the three filling films 50 are arranged to overlap in the empty space S2. The number of the filling films 50 is determined based on the size of the distance D2 of the empty space S2. In this embodiment, when three filling films 50 having a thickness T2 are stacked and the thickness of the three filling films 50 is defined as a thickness T3 (T2 × 3), the distance D2 of the empty space S2 is substantially equal to the thickness T3. To do. The number of the filling films 50 is determined by the thickness T2 of the filling film and the distance D2 of the empty space so that the thickness T3 of the three filling films 50 of the thickness T2 is smaller than the distance D2 and maximum. Incidentally, when the distance D2 of the empty space S2 is large, the number of sheets of the filling film 50 having the thickness T2 increases. On the contrary, when the distance D2 of the empty space S2 is small, the number of sheets used of the filling film 50 having the thickness T2 decreases.

Hereinafter, the effect | action of the filling film 50 used for the battery 10 which concerns on this embodiment is demonstrated.
A battery 10 in which three filling films 50 are stacked in the empty space S2 will be described as an example.

  Inside the battery case 11 of the battery 10, an electrode assembly 20 having a thickness T1 and three filling films 50 having a thickness T2 are accommodated. The electrode assembly 20 is disposed such that the sheet surface 27 of the outermost layer electrode 23 is in contact with the side surface 25 of the battery case 11, and the filling film 50 is formed between the side surface 26 of the battery case 11 and the outermost layer electrode 24 of the electrode assembly 20. It arrange | positions so that the sheet | seat surface 28 may be contact | connected.

  In the manufacturing process of the filling film 50, when cutting the filling film 50, metal foreign matter such as a cutting piece of a cutting machine blade may adhere to the filling film 50. When a metal foreign matter having a dimension (for example, a length of 500 μm [micrometer]) that cannot be visually confirmed adheres to the filling film 50, the battery 10 is assembled on the sheet surface 52 of the filling film 50. In some cases, metal foreign matter may be attached to the inside of the battery case 11 while attached.

  For example, as shown to Fig.6 (a), the metal foreign material B may exist between the sheet | seat surfaces 52 of the filling film 50 which adjoins. In assembling the battery 10, after the electrode assembly 20 is inserted into the battery case 11, the three filling films 50 are inserted into the empty space S <b> 2 of the battery case 11. When the metal foreign matter B adheres to the sheet surface 52 of the filling film 50, the metal foreign matter B is sandwiched between the sheet surfaces 52 of the adjacent filling films 50. The three filling films 50 are disposed so as to contact the side surface 26 of the battery case 11 and the sheet surface 28 of the outermost layer electrode 24 of the electrode assembly 20, and the side surface 26 of the battery case 11 and the outermost layer of the electrode assembly 20. It is pressed from the sheet surface 28 of the electrode 24. By pressing the sheet surface 52 of the filling film 50 with the relatively hard metal foreign matter B existing between the sheet surfaces 52 of the adjacent filling films 50 by pressing, the filling film 50 having stretchability is not torn. Has been extended.

  Further, for example, as shown in FIG. 6B, a metal foreign matter B may exist between the filling film 50 and the outermost layer electrode 24. In assembling the battery 10, after the electrode assembly 20 is inserted into the battery case 11, the three filling films 50 are inserted into the empty space S <b> 2 of the battery case 11. When the metallic foreign matter B adheres to the sheet surface 52 of the filling film 50 in contact with the sheet surface 28 of the outermost layer electrode 24, the metallic foreign matter B is sandwiched between the filling film 50 and the outermost layer electrode 24. Exist. The three filling films 50 are disposed so as to contact the side surface 26 of the battery case 11 and the sheet surface 28 of the outermost layer electrode 24 of the electrode assembly 20, and the side surface 26 of the battery case 11 and the outermost layer electrode of the electrode assembly 20. 24 sheet surfaces 28 are pressed. By pressing the filling film 50 with a relatively hard metal foreign matter B existing between the filling film 50 and the outermost layer electrode 24 by pressing, the filling film 50 having stretchability is stretched without being broken. ing. Note that the metallic foreign matter B in the drawing is exaggerated for convenience of explanation.

The battery 10 according to this embodiment has the following effects.
(1) The filling film 50 is a multilayer film having stretchability. Therefore, in the manufacturing process of the filling film 50, even if a metallic foreign matter adheres to the filling film 50, the filling film 50 is stretched by the metallic foreign matter and does not break through the filling film 50. Therefore, the positive electrode sheet 30 or the negative electrode sheet 34 and the separator 29 are further broken by the metal foreign matter, and the positive electrode 21 and the negative electrode 22 are short-circuited, or the insulating sheet covering the battery case 11 is broken and the outermost layer electrode 24 is broken. And the battery case 11 can be prevented from being short-circuited.

The above embodiment shows an embodiment of the present invention, and the present invention is not limited to the above embodiment, and various modifications can be made within the scope of the invention as described below. Is possible.
In the above embodiment, a multilayer film is used as the filling film 50, but this is not the case. The filling film may be a member having solvent resistance and stretchability with respect to the electrolytic solution, and may be a single layer film.

In the above embodiment, the three filling films 50 are arranged so as to overlap the empty space S2, but the size of the empty space S2 and the number of the filling films 50 are not particularly limited. Moreover, the thickness of the filling film may be changed according to the material of the film.

In the above embodiment, a multilayer film is used as the filling film 50, and the multilayer film is formed by CPP between a film 50A formed by PET and a film 50B formed by ON as shown in FIG. It is a layered shape with the film 50C formed therebetween, but is not limited thereto. The multilayer film only needs to be layered, and may be a layered structure in which a film formed by PET is sandwiched between a film formed by ON and a film formed by CPP, and a film formed by PET It is good also as a layer form which pinched | interposed the film formed by ON between the films formed by CPP.

10 Battery (as a power storage device)
11 Battery case 20 Electrode assembly 21 Positive electrode (as an electrode)
22 Negative electrode (as electrode)
23, 24 Outermost layer electrode 25, 26 Side surface 50 Filling film (as gap filling member)

Claims (3)

An electrode assembly in which a plurality of sheet-like electrodes are laminated, and a battery case that houses the electrode assembly,
The battery case is a power storage device having a pair of side surfaces facing a pair of outermost layer electrodes in the stacking direction of the electrodes,
A gap filling member is disposed in a gap existing between the outermost layer electrode and the side surface;
The power storage device, wherein the gap filling member has stretchability.   The power storage device according to claim 1, wherein the gap filling member is a multilayer film including a plurality of films each formed of a stretchable material.   The power storage device according to claim 2, wherein the plurality of films are a film formed of polyethylene terephthalate, a film formed of nylon, and a film formed of polypropylene.

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