JP7240611B2 - secondary battery - Google Patents

Description

The present invention relates to secondary batteries. More specifically, the present invention relates to a secondary battery comprising an electrode body, a battery case containing the electrode body, and an insulating film separating the electrode body and the inner wall of the battery case.

Non-aqueous electrolyte secondary batteries such as lithium ion secondary batteries (lithium secondary batteries) and sodium ion secondary batteries are lighter and have higher energy density than existing batteries. They are used as so-called portable power sources and batteries for driving vehicles. In particular, lithium-ion secondary batteries, which are lightweight and provide high energy density, are also preferably used as high-output power sources for driving vehicles such as electric vehicles (EV), hybrid vehicles (HV), and plug-in hybrid vehicles (PHV). ing.

Such batteries are generally constructed by separately manufacturing an electrode body and a battery case, and then housing the electrode body in the battery case. As the battery case, a metal package is often used from the viewpoint of high physical strength. In this case, in order to insulate the metal battery case and the electrode body, a method of isolating the electrode body from the inner wall of the battery case using an insulating film or the like is used. For example, Patent Document 1 describes a secondary battery composed of an electrode body having an insulating film arranged on the outer periphery and a battery case. A secondary battery composed of an electrode body having an insulating film disposed thereon and a battery case is described.

JP 2016-062645 A JP 2018-181435 A

By the way, in the process of inserting the electrode assembly with the insulating film disposed thereon into the battery case, not only the case where the insulating film is stuck to the bottom surface of the battery case, but also the case where the insulating film is not attached to the bottom surface (i.e. , in which the insulating film is floating from the bottom surface of the battery case) can also be manufactured. After being inserted into the battery case, the insulating film is held in its position only by the coefficient of friction of the insulating film with respect to the wall surface of the battery case and the binding load during assembly of the assembled battery.

Based on the above content, in a secondary battery in which the insulating film is floating from the bottom surface of the battery case, if the coefficient of friction between the insulating film and the battery case or the binding load during assembly of the assembled battery decreases (for example, , when a large impact is applied), the insulating film may slide down from the wall surface of the battery case. Such sliding down exposes a part of the surface of the electrode body and makes it impossible to maintain the insulation between the electrode body and the battery case, which may cause an internal short circuit.

The present invention has been made in view of such circumstances, and its object is to stably produce a highly reliable secondary battery without being influenced by the process of inserting an electrode body having an insulating film disposed thereon into a battery case. supply in a timely manner.

In order to achieve the above object, the present invention provides two batteries comprising: an electrode body having a flat rectangular wide surface; and a rectangular battery case having a rectangular wide surface in which the electrode body is housed. Provide the following batteries. In the secondary battery disclosed herein, an insulating film is disposed between the electrode body and the battery case to isolate the electrode body and the inner wall surface of the battery case, and the insulating film is the It is formed in a bag-like shape that encloses the periphery of the electrode body, and at least two projections are present on the bottom of the bag-shaped insulating film, and the projections make point-like contact with the bottom surface of the battery case. Alternatively, it is configured to linearly contact the bottom surface of the battery case along the long side direction and/or the short side direction.

In such a secondary battery, the electrode body is enclosed in a bag-like insulating film having at least two protrusions configured to make point-like or linear contact with the bottom surface of the battery case. . As a result, even when the coefficient of friction between the insulating film and the battery case or the restraining load during assembly of the assembled battery is reduced, the possibility of the insulating film slipping down from the wall surface of the battery case is reduced, so that an internal short circuit does not occur. less likely to occur. Therefore, it is possible to stably supply highly reliable secondary batteries.

1 is a perspective view schematically showing the outer shape of a secondary battery according to one embodiment; FIG. FIG. 2 is a perspective view schematically showing a manner in which a wound electrode body enclosed by a bag-shaped insulating film according to one embodiment is housed in a battery case. In addition, the white arrow in the figure indicates the direction perpendicular to the winding axial direction of the wound electrode assembly. 3 is a developed view showing a developed structure of the bag-shaped insulating film in FIG. 2; FIG. FIG. 2 is a perspective view schematically showing a manner in which a wound electrode body enclosed by a bag-shaped insulating film according to one embodiment is housed in a battery case. In addition, the white arrow in the figure indicates the direction perpendicular to the winding axial direction of the wound electrode assembly. 5 is a developed view showing a developed structure of the bag-like insulating film in FIG. 4; FIG. FIG. 2 is a perspective view schematically showing a manner in which a wound electrode body enclosed by a bag-shaped insulating film according to one embodiment is housed in a battery case. In addition, the white arrow in the figure indicates the direction perpendicular to the winding axial direction of the wound electrode assembly. FIG. 7 is a developed view showing a developed structure of the bag-shaped insulating film in FIG. 6;

A preferred embodiment (first embodiment) of the present invention will be described below with reference to the drawings as appropriate. Matters other than those specifically mentioned in this specification that are necessary for carrying out the present invention (for example, a general manufacturing process for a battery that does not characterize the present invention) are conventional methods in the relevant field. It can be grasped as a design matter of a person skilled in the art based on technology. The present invention can be implemented based on the contents disclosed in this specification and common general technical knowledge in the field. In the drawings below, members and portions having the same function are denoted by the same reference numerals, and redundant description may be omitted or simplified. Also, the dimensional relationships (length, width, thickness, etc.) in each drawing do not necessarily reflect the actual dimensional relationships.

The secondary battery according to the present invention can be suitably applied to a secondary battery having a structure comprising an electrode body composed of a positive electrode sheet, a negative electrode sheet and a separator, and a collector terminal joined to the electrode body. Examples of such secondary batteries include storage batteries such as lithium ion secondary batteries and nickel-hydrogen batteries, and batteries including storage battery elements such as electric double layer capacitors. Further, in the following embodiments, a lithium ion secondary battery including a wound electrode body will be described in detail as an example, but the present invention is not intended to be limited to such embodiments. For example, a laminated electrode body having a laminated structure in which a plurality of positive electrode sheets and negative electrode sheets are mutually overlapped with separators interposed therebetween is also preferably applied.

FIG. 1 is a perspective view schematically showing the outer shape of a prismatic lithium-ion secondary battery according to this embodiment. Lithium ion secondary battery 100 shown in FIG. It is configured by being housed in a flat rectangular battery case (that is, outer container) 10 . The battery case 10 according to the present embodiment includes a box-shaped (that is, bottomed rectangular parallelepiped) square case body 20 having an opening at one end (corresponding to the upper end in normal use of the battery); It is composed of a rectangular lid body 32 that seals the opening of the case body 20 . An insulating film (not shown) and an electrode body (not shown) can be housed in the battery case 10 through this opening. The battery case 10 (battery case main body 20) has a flat box-like shape (square shape) corresponding to the shape of the flat electrode body in the space (internal space) surrounded by the inner wall surface. The inner wall surface of the battery case 10 (battery case main body 20) includes a substantially rectangular bottom surface, two wide surfaces standing upright from both ends along the long side of the bottom surface, and two wide surfaces facing each other. It is composed of two narrow surfaces facing each other and standing upright from both ends along the edge. In addition, the cover 32 has a positive terminal 40 and a negative terminal 42 for external connection. A thin safety valve 34 set to release the internal pressure and an injection port (not shown) for injecting the non-aqueous electrolyte are provided. The configurations of the positive and negative electrode active materials, the electrolyte, the non-aqueous electrolyte, and the like according to the present embodiment are not particularly limited, and those that can be used in conventionally known lithium ion secondary batteries can be suitably used. Since the present invention relates to an insulating film, detailed description is omitted.

Next, the insulating film according to this embodiment will be described with reference to the drawings as appropriate. In addition, the "insulating film" in the present specification is not limited to a film-like one, and may include a sheet-like insulating sheet. Moreover, as the material of the insulating film according to the present embodiment, a resin material or the like that functions as an insulating material can be used. Specifically, it contains at least one polymer material selected from the group consisting of polypropylene, thermoplastic polyester, polyvinyl alcohol, polyethylene, polyamide, polyethylene terephthalate, polyvinyl chloride, polycarbonate, and ethylene-vinyl acetate copolymer. A resin material or the like can be used. Furthermore, conventionally known methods can be employed without limitation as the method for producing the insulating film according to the present embodiment. As the insulating film, a commercially available one may be appropriately purchased and used.

First, the bag-shaped insulating film according to this embodiment will be described with reference to FIGS. 2 and 3. FIG. FIG. 2 is a perspective view schematically showing a manner in which a wound electrode assembly enclosed in a bag-shaped insulating film according to the present embodiment is accommodated in a battery case, and FIG. 3 is a perspective view of the bag-shaped insulating film in FIG. 1 is an exploded view showing an exploded structure of the . In the present description, external elements such as terminals of the wound electrode body are not necessary, so illustration thereof is omitted.
First, as shown in FIG. 2, the wound electrode body 110 having the bag-like insulating film 120 disposed therearound is arranged in the direction of the long side of the wide surface of the battery case 10 and the winding of the electrode body 110. It is inserted into the battery case 10 so that the axial direction matches. Since the insulating film 120 prevents contact between the electrode body 110, which is a power generation element, and the battery case 10 (battery case main body 20), the insulation between the electrode body 110 and the battery case 10 is preferably maintained. . Bag-shaped insulating film 120 also has projections 121 configured to linearly contact along the short side of the bottom surface of battery case 10 . As a result, even when the coefficient of friction between the bag-shaped insulating film 120 and the battery case 10 or the restraining load during assembly of the assembled battery is reduced (for example, when a large impact is applied), the insulating film 120 does not interfere with the battery case 10 . Since the possibility of slipping down from the wall surface of the battery case 10 is reduced, the insulation inside the battery case 10 can be preferably maintained.

FIG. 3 is a developed view showing the developed structure of the bag-shaped insulating film 120. As shown in FIG. The procedure for producing the bag-shaped insulating film 120 will be described below using such a developed view. It should be noted that folding toward the front side of the drawing along the folding lines is referred to as "valley fold", and folding toward the back side of the drawing is referred to as "mountain fold".
First, while paying attention to the bending points a (there are four points), creases are made along the folding lines 131 so as to form valley folds, and then they are put back. Next, a crease is made along the fold line 132 so as to form a valley fold, and then it is put back. Subsequently, after folding along the folding line 133 to form a mountain fold, it is folded along the folding line 134 to form a valley fold. Finally, the outer shape of the bag-like insulating film 120 is constructed by overlapping the ends A while following the creases made so far. Further, when fixing the shape of the insulating film 120, for example, welding means such as ultrasonic welding, laser welding, or the like can be appropriately used in addition to spot fusion or heat fusion. Alternatively, it may be fixed using a tape, an adhesive, or the like, as long as it can be sufficiently fixed and does not adversely affect the battery performance (internal short circuit, change in electrolyte composition, etc.). Then, as shown in FIG. 2, the electrode body 110 is covered with a bag-shaped insulating film 120 constructed through such a process, and the winding axis of the electrode body 110 is aligned with the long side direction of the wide surface of the battery case 10 . By inserting into the battery case 10 so as to match the direction, the insulation inside the battery case 10 is preferably maintained.

Next, another preferred embodiment (second embodiment) will be described with reference to FIGS. 4 and 5. FIG. FIG. 4 is a perspective view schematically showing a manner in which a wound electrode body enclosed in a bag-shaped insulating film according to the present embodiment is accommodated in a battery case, and FIG. 5 is a perspective view of the bag-shaped insulating film in FIG. 1 is an exploded view showing an exploded structure of the . In the present description, external elements such as terminals of the wound electrode body are not necessary, so illustration thereof is omitted.
First, as shown in FIG. 4, the wound electrode assembly 110 in which the bag-like insulating film 220 is arranged so as to enclose the periphery is arranged in the long side direction of the wide surface of the battery case 10 and the winding of the electrode assembly 110. It is inserted into the battery case 10 so that the axial direction matches. Since the insulating film 220 prevents contact between the electrode assembly 110, which is a power generation element, and the battery case 10 (battery case main body 20), the insulation between the electrode assembly 110 and the battery case 10 is preferably maintained. . The bag-shaped insulating film 220 also has a protrusion 221 configured to linearly contact the bottom surface of the battery case 10 along the long side direction. As a result, even when the coefficient of friction between the bag-shaped insulating film 220 and the battery case 10 or the restraining load during assembly of the assembled battery is reduced (for example, when a large impact is applied), the insulating film 220 does not interfere with the battery case 10 . Since the possibility of slipping down from the wall surface of the battery case 10 is reduced, the insulation inside the battery case 10 can be preferably maintained.

FIG. 5 is a developed view showing the developed structure of the bag-shaped insulating film 220. As shown in FIG. The procedure for producing the bag-shaped insulating film 220 will be described below using such a developed view. It should be noted that folding toward the front side of the drawing along the folding lines is referred to as "valley fold", and folding toward the back side of the drawing is referred to as "mountain fold".
First, a crease is made along the folding line 230 so as to form a mountain fold, and then it is put back. Next, a crease is made along the folding line 231 so as to form a valley fold, and then it is put back. Subsequently, cuts are made along cut lines 232 (there are eight cut lines). Next, it is folded along the folding line 233 toward the front side of the drawing so as to form a triangle. Finally, after each end is folded toward the front side of the drawing along the folding lines 234 to 236, the ends B are overlapped along the creases made so far, thereby constructing the outer shape of the bag-shaped insulating film 220. be done. Further, when fixing the shape of the insulating film 220, for example, in addition to spot fusion bonding and heat fusion bonding, welding means such as ultrasonic welding and laser welding can be appropriately used. Alternatively, it may be fixed using a tape, an adhesive, or the like, as long as it can be sufficiently fixed and does not adversely affect the battery performance (internal short circuit, change in electrolyte composition, etc.). Then, as shown in FIG. 4, the electrode body 110 is covered with a bag-shaped insulating film 220 constructed through such a process, and the winding axis of the electrode body 110 is aligned with the long side direction of the wide surface of the battery case 10 . By inserting into the battery case 10 so as to match the direction, the insulation inside the battery case 10 is preferably maintained.

Next, another preferred embodiment (third embodiment) will be described with reference to FIGS. 6 and 7. FIG. FIG. 6 is a perspective view schematically showing a manner in which the wound electrode body enclosed in the bag-shaped insulating film according to the present embodiment is accommodated in the battery case, and FIG. 7 is a perspective view of the bag-shaped insulating film in FIG. 1 is an exploded view showing an exploded structure of the . In the present description, external elements such as terminals of the wound electrode body are not necessary, so illustration thereof is omitted.
First, as shown in FIG. 6, the wound electrode body 110 in which the bag-shaped insulating film 320 is arranged so as to enclose the periphery is disposed in the long side direction of the wide surface of the battery case 10 and the winding of the electrode body 110. It is inserted into the battery case 10 so that the axial direction matches. Since the insulating film 320 prevents contact between the electrode body 110, which is a power generation element, and the battery case 10 (battery case main body 20), the insulation between the electrode body 110 and the battery case 10 is preferably maintained. . In addition, bag-shaped insulating film 320 has projections 321 configured to linearly contact the bottom surface of battery case 10 along the long-side direction and the short-side direction. As a result, even when the coefficient of friction between the bag-shaped insulating film 320 and the battery case 10 or the restraining load during assembly of the assembled battery is reduced (for example, when a large impact is applied), the insulating film 320 does not interfere with the battery case 10 . Since the possibility of slipping down from the wall surface of the battery case 10 is reduced, the insulation inside the battery case 10 can be preferably maintained.

FIG. 7 is a developed view showing a developed structure of the bag-shaped insulating film 120. As shown in FIG. The procedure for producing the bag-shaped insulating film 120 will be described below using such a developed view. It should be noted that folding toward the front side of the drawing along the folding lines is referred to as "valley fold", and folding toward the back side of the drawing is referred to as "mountain fold".
First, a crease is made along the folding line 330 so as to form a mountain fold, and then it is put back. Next, a crease is made along the folding line 331 so as to form a valley fold, and then it is put back. Subsequently, cuts are made along the cut lines 332 (four places exist). Next, after each end portion is folded toward the front side of the drawing along the folding lines 333 and 334, the end portions C are overlapped along the creases made so far, thereby constructing the outer shape of the bag-shaped insulating film 320. be done. In addition, when fixing the shape of the insulating film 320, for example, in addition to spot fusion and heat fusion, welding means such as ultrasonic welding and laser welding can be appropriately used. Alternatively, it may be fixed using a tape, an adhesive, or the like, as long as it can be sufficiently fixed and does not adversely affect the battery performance (internal short circuit, change in electrolyte composition, etc.). Then, as shown in FIG. 6, the electrode body 110 is covered with a bag-shaped insulating film 320 constructed through such a process, and the winding axis of the electrode body 110 is aligned with the long side direction of the wide surface of the battery case 10 . By inserting into the battery case 10 so as to match the direction, the insulation inside the battery case 10 is preferably maintained.

In addition, the bag-shaped insulating films 120, 220 and 320 are expected to have the following effects. Here, the bag-shaped insulating film 120 will be described as an example. For example, the protruding portion 121 of the bag-shaped insulating film 120 can play the role of an electrolytic solution retaining portion. As a result, as shown in FIG. 2, even when the electrode assembly 110 is dried up due to repeated charge/discharge, the excess electrolyte injected into the bag-shaped insulating film 120 can be prevented. A liquid (not shown) rises in the direction of the white arrow due to capillary action and reaches the inside of the electrode body 110 , whereby the electrode body 110 can be replenished with the electrolytic solution. Moreover, the support of the projecting portion 121 reduces the possibility of the bag-shaped insulating film 120 slipping down from the wall surface of the battery case 10, so that the binding load during assembly of the assembled battery can be reduced. This can solve the conventional problem that the electrolytic solution contained in the electrode body leaks to the outside due to the binding load applied when constructing the assembled battery. Furthermore, conventionally, it was necessary to consider the coefficient of friction of the insulating film against the wall surface of the battery case as a management item for managing the quality of the battery. can. This makes it possible to reduce the time and cost required for quality inspection. These effects are also expected for the bag-shaped insulating films 220 and 320 as well.

Since it is difficult to construct the bag-shaped insulating film having protrusions that are configured to make point-like contact with the bottom surface of the battery case 10 using the developed view as described above, Not listed. For example, it is preferably formed by an injection molding method or the like.

Although the present invention has been described with some preferred embodiments, such description is not intended to be limiting, and various modifications are of course possible. For example, the type of battery is not limited to the above-mentioned lithium ion secondary battery, but batteries with various contents with different electrode body constituent materials and electrolytes, such as nickel hydrogen batteries, nickel cadmium batteries, or so-called physical batteries such as electric double layer capacitors. It may be a battery. Also, the type of electrolyte is not limited to the non-aqueous electrolyte described above, and may be an aqueous electrolyte, a solid or gel electrolyte, or the like.

According to the battery disclosed herein, as described above, a highly reliable battery (for example, a lithium ion secondary battery) can be provided. Therefore, the battery disclosed herein can be suitably used, for example, as a driving power source mounted on a vehicle such as an automobile. In particular, it is suitable as a power source for driving plug-in hybrid vehicles (PHV), hybrid vehicles (HV), electric vehicles (EV), and the like. Further, according to the present invention, the battery disclosed herein (for example, a lithium-ion secondary battery) is preferably used as a power source (typically, a set of mutually electrically connected plural secondary batteries). A vehicle equipped as a battery) is provided.

10 Battery Case 20 Battery Case Main Body 32 Lid 34 Safety Valve 40 Positive Electrode Terminal 42 Negative Electrode Terminal 100 Lithium Ion Secondary Battery 110 Wound Electrode Body 120, 220, 320 Bag-shaped Insulating Film 121, 221, 321 Protrusions 131, 132, 133 , 134 bending lines 230, 231, 233, 234, 235, 236 bending lines 330, 331, 333, 334 bending lines 232, 332 cut lines a bending points A, B, C ends

Claims (1)

A secondary battery comprising an electrode body having a flat rectangular wide surface and a rectangular battery case having a rectangular wide surface for housing the electrode body,
An insulating film is disposed between the electrode body and the battery case to separate the electrode body and the inner wall surface of the battery case,
The insulating film is formed in a bag shape that encloses the periphery of the electrode body,
At the bottom of the bag-shaped insulating film, there are two linear projections,
The two protrusions are configured to linearly contact the bottom surface of the battery case along only the long side thereof , or linearly contact the bottom surface of the battery case only along the short side thereof. A secondary battery .

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