JP2020170583A - Laminate type secondary cell and battery pack including secondary cell - Google Patents

Abstract

To provide a laminate type secondary cell including a laminate exterior of a double structure realizing excellent gas evolution characteristics and heat dissipation.SOLUTION: A laminate type secondary cell 100 includes a laminate electrode body 20, a soft laminate exterior 40 for internally housing the laminate electrode body, and a hard laminate exterior 50 for internally housing the soft laminate exterior in a state internally housing the laminate electrode body. The soft laminate exterior has a juncture where soft laminate sheets are joined in the surrounding facing the lamination side of the internally housed laminate electrode body, the hard laminate exterior has an opening 52 formed in a part of the surrounding facing the lamination side of the internally housed laminate electrode body, and a part of the juncture is projecting outward of the hard laminate exterior via the opening.SELECTED DRAWING: Figure 1

Description

The present invention relates to a laminated secondary battery having a structure in which a battery element is housed in an exterior body made of a laminated sheet, and further relates to an assembled battery including a plurality of the laminated secondary batteries electrically connected to each other.

Since secondary batteries such as lithium-ion secondary batteries are lightweight and can obtain high energy density, they can be used as portable power sources for personal computers and mobile terminals, EVs (electric vehicles), HVs (hybrid vehicles), and PHVs (plug-in hybrids). It is widely used as a power source for driving vehicles such as automobiles. As a form of a secondary battery used as such a power source for driving a vehicle, an exterior body (hereinafter, simply referred to as simply) in which a battery element (storage element) composed of an electrode body having positive and negative electrodes and an electrolyte is made of a bag-shaped laminated sheet. A so-called laminated battery having a structure surrounded by a “laminated exterior body”) can be mentioned.
Such a laminated exterior is generally made of a flexible material having a multi-layer structure including an outer layer made of a heat-bondable plastic film such as a polyolefin resin and an inner layer made of a metal foil such as aluminum. It is an exterior body that is lightweight and has excellent airtightness (sealing properties).
For example, Patent Document 1 below describes a laminated secondary battery including this type of laminated exterior body.

Japanese Unexamined Patent Publication No. 2013-69696 Japanese Unexamined Patent Publication No. 2008-262804

By the way, while the laminated sheet constituting the laminated exterior body is lightweight and flexible, it must be said that the strength against an impact received from the outside is lower than that of a metallic battery case. Therefore, it has been proposed to improve the physical strength against impacts such as dropping by making the laminated exterior body a double structure. For example, Patent Document 2 describes a soft laminated exterior body (soft exterior material) that houses a battery element inside, and a hard laminated exterior body (hard exterior material) that houses the battery element and the soft exterior material inside. A battery comprising the above is disclosed.

However, in a laminated secondary battery provided with a double-structured laminated exterior as described in Patent Document 2, while the physical strength is improved, the blockage inside the battery is also enhanced, and in an abnormal situation. Gas release and heat dissipation from the inside of the battery may be lower than those of a normal laminated secondary battery provided with a single-layer laminated exterior. In a relatively high-voltage, high-capacity secondary battery such as a lithium-ion secondary battery, it is preferable to quickly dissipate heat or release gas generated inside the battery in the event of an abnormality such as an internal short circuit or overcharging. The situation is the same for a laminated secondary battery equipped with a double-structured laminated exterior, and improvements in gas release characteristics and heat dissipation are required.

Therefore, the present invention was created to solve such a problem in a laminated secondary battery provided with a double-structured laminated exterior body, and is a double-structured laminate that realizes excellent outgassing characteristics and heat dissipation. An object of the present invention is to provide a laminated secondary battery having an exterior body. Another object of the present invention is to provide an assembled battery including a plurality of such laminated secondary batteries.

In order to realize such an object, the laminated secondary battery disclosed herein includes a laminated electrode body having a structure in which a plurality of sheet-shaped positive electrodes and negative electrodes are laminated while interposing a layer that functions as a separator, and the laminated electrode body. From a soft laminated exterior body composed of a relatively soft laminated sheet housed inside and a relatively hard laminated sheet containing the soft laminated outer body in a state where the laminated electrode body is housed inside. It is a laminated type secondary battery including a rigid laminated exterior body to be constructed.
Then, in the laminated secondary battery disclosed herein, the soft laminated exterior body has a joint portion in which the soft laminated sheets are joined to each other around the periphery facing the laminated side surface of the laminated electrode body housed therein. The rigid laminated exterior body has an opening formed in a part of the periphery facing the laminated side surface of the laminated electrode body housed therein. Here, a part of the joint portion is characterized in that it projects outward from the rigid laminated exterior body through the opening portion.

In the laminated secondary battery having such a configuration, among the double-structured laminated exterior bodies composed of the soft laminated exterior body and the hard laminated exterior body, in the hard laminated exterior body, the laminated side surface (that is, positive and negative electrodes) of the laminated electrode body is used. An opening is formed in a part of the periphery facing the side surface showing the laminated structure of the above. Further, a part of the joint portion of the soft laminated exterior body projects outward from the hard laminated exterior body through the opening. As a result, it is possible to effectively release gas and dissipate heat from the opening, particularly from a part of the joint projecting outward from the opening, in the event of an abnormality such as an internal short circuit or overcharging. ..
Therefore, according to the laminated secondary battery disclosed herein, it is possible to realize suitable outgassing characteristics and heat dissipation even if the laminated outer body has a double structure of soft and hard.

Further, the present invention is an assembled battery including a plurality of laminated secondary batteries disclosed herein, and is a set in which a plurality of laminated secondary batteries are laminated along the positive / negative electrode lamination direction of the laminated electrode body. Provide batteries. In the assembled battery having such a configuration, since each laminated secondary battery (also referred to as a single battery) constituting the assembled battery has suitable outgassing characteristics and heat dissipation as described above, any of the assembled batteries is included in the assembled battery. Even if a problem occurs in the cell, it is possible to prevent high heat from being conducted to another adjacent cell, and high stability can be realized.

It is a perspective view which shows typically the laminated type secondary battery which concerns on one Embodiment. It is a schematic diagram which shows the outline of the construction step of the laminated type secondary battery which concerns on one Embodiment. (A) shows a state before the laminated electrode body is housed inside the soft laminated exterior body. (B) shows the state after joining the entire circumference of the soft laminated exterior body. In (C), a state in which the soft laminated exterior body containing the laminated electrode body is housed inside the hard laminated exterior body is shown.

Hereinafter, an embodiment according to the present invention will be described with reference to the drawings. In each of the drawings described below, members and parts that perform the same action may be designated by the same reference numerals, and duplicate description may be omitted or simplified. Moreover, the dimensional relations (length, width, thickness, etc.) in each drawing do not reflect the actual dimensional relations. In addition, matters other than those specifically mentioned in the present specification and necessary for carrying out the present invention can be grasped as design matters of those skilled in the art based on the prior art in the art. Further, when the numerical range: A to B (where A and B are arbitrary numerical values having a relationship of A <B) is described in the present specification, it means A or more and B or less, and A. It is a numerical range that includes the case where it exceeds (when it is more than A without including it) and the case where it is less than B (when it is less than or without including B).

As used herein, the term "secondary battery" refers to a power storage device that can be charged and discharged and can repeatedly take out predetermined electrical energy. For example, a lithium ion secondary battery, a sodium ion secondary battery, and the like in which alkali metal ions in an electrolyte are responsible for charge transfer are typical examples included in the secondary battery referred to here. The "laminated secondary battery" refers to a secondary battery having a configuration in which an electrode body (for example, a laminated electrode body) and an electrolyte are housed inside an exterior body made of a laminated sheet.
Hereinafter, the present invention will be described in detail as an embodiment of the laminated secondary battery disclosed herein, by taking as an example a laminated secondary battery in which a flat rectangular laminated electrode body is housed in a laminated outer body. To do. It is not intended that the present invention be limited to those described in such embodiments.

<Overall structure of laminated secondary battery>
First, the rough overall structure of the laminated secondary battery disclosed here will be described with reference to FIG. FIG. 1 is a perspective view schematically showing the overall structure of the laminated secondary battery according to the embodiment.
As shown in FIG. 1, the laminated secondary battery 100 includes a laminated electrode body 20, a soft laminated outer body 40, and a hard laminated outer body 50.
As shown in the figure, the soft laminated exterior body 40 houses the laminated electrode body 20 inside. Further, the hard laminated outer body 50 houses the soft laminated outer body 40 in a state where the laminated electrode body 20 is housed inside. Then, a part of the sealed peripheral edge of the hard laminated exterior body 50 forms an opening 52 which is opened without being sealed, and a part of the soft laminated exterior body 40 is hard through the opening 52. It projects outward from the laminated exterior body 50. Further, a part of the positive electrode current collecting tab 12 and the negative electrode current collecting tab 14 attached to the laminated electrode body 20 near the tip is pulled out from both the soft laminated outer body 40 and the hard laminated outer body 50 and protrudes outward. ing.

Next, the configuration of the laminated secondary battery 100 and each component will be described in detail.
<Stacked electrode body>
As the laminated electrode body 20, the laminated electrode body used in this type of laminated secondary battery can be used without particular limitation. Specifically, for example, in the laminated electrode body 20, a plurality of rectangular sheet-shaped positive electrodes and a rectangular sheet-shaped negative electrode are laminated in a state of being insulated from each other while interposing a layer that functions as a separator (not shown). There is.

-Positive electrode-
The positive electrode typically includes a rectangular sheet-shaped positive electrode current collector and a positive electrode active material layer formed on the surface (one side or both sides) of the positive electrode current collector. The positive electrode active material layer contains a positive electrode active material capable of occluding and releasing lithium ions (for example, a lithium transition metal composite oxide such as a lithium nickel cobalt manganese composite oxide). Further, as the positive electrode current collector, for example, an aluminum positive electrode current collector is used. A positive electrode current collector tab 12 is attached to the positive electrode current collector, and functions as a positive electrode terminal for external connection.

− Negative electrode −
The negative electrode typically includes a rectangular sheet-shaped negative electrode current collector and a negative electrode active material layer formed on the surface (one side or both sides) of the negative electrode current collector. The negative electrode active material layer contains a negative electrode active material (for example, a carbon-based material such as graphite) capable of occluding and releasing lithium ions. Further, as the negative electrode current collector, for example, a copper negative electrode current collector is used. As shown in the figure, the negative electrode current collector is provided with a negative electrode current collector tab 14, which functions as a negative electrode terminal for external connection.

− Separator −
As described above, the laminated electrode body 20 includes a layer that functions as a separator that insulates between the positive electrode and the negative electrode. The type of layer that functions as a separator roughly depends on the electrolyte contained in the laminated secondary battery 100. Specifically, for example, when the laminated secondary battery 100 is a so-called all-solid-state battery including a solid electrolyte, the solid electrolyte layer corresponds to a layer that functions as a separator. Examples of the solid electrolyte contained in the solid electrolyte layer include sulfide-based solid electrolytes and oxide-based solid electrolytes. Further, when the laminated secondary battery 100 is a type of secondary battery including an electrolytic solution, the separator sheet corresponds to a layer that functions as a separator. Examples of the separator sheet include a resin sheet such as polyethylene or polypropylene.

<Laminate exterior>
The soft laminated exterior 40 has a laminated structure of a resin film layer made of insulating polyolefin, polyethylene terephthalate, polyamide or the like constituting the surface layer and a metal layer made of aluminum, stainless steel or the like constituting the inner layer, for example, a polyamide layer. , The metal layer and the polyolefin layer may be composed of a three-layer structure laminated sheet laminated in this order. The thickness of each layer is not particularly limited, but can be, for example, a polyamide layer of 10 to 100 μm, an aluminum layer of 30 to 150 μm (preferably 100 μm, more preferably 50 μm or less), and a polyolefin layer of 10 to 100 μm.
Like the soft laminated exterior body 40, the hard laminated exterior body 50 may typically have a laminated structure of a resin film layer and a metal layer. For example, the polyamide layer, the metal layer, and the polyolefin layer are composed of a laminated sheet having a structure in which they are laminated in this order. Regarding the thickness of each layer, for example, the polyamide layer may be 10 to 100 μm, the metal layer may be 100 to 500 μm (preferably 200 to 400 μm, more preferably 250 to 350 μm), and the polyolefin layer may be 10 to 100 μm.
By having the above-mentioned structure of the laminated sheet which is a constituent material of the soft laminated exterior body 40 and the hard laminated exterior body 50, that is, by making the thickness of the metal layer such as aluminum constituting the laminated sheet different. , The bending characteristics and mechanical hardness of the laminated exterior can be adjusted. The soft laminated exterior body 40 is composed of a laminated sheet that is relatively soft as compared with the hard laminated exterior body 50. On the other hand, the hard laminated exterior body 50 is composed of a laminated sheet that is relatively hard as compared with the soft laminated exterior body 40.

<Construction of laminated secondary battery>
Next, the construction of the laminated secondary battery 100 will be described with reference to FIG. FIG. 2 schematically shows an outline of a step of constructing a laminated secondary battery according to an embodiment. (A) shows a state before the laminated electrode body 20 is housed inside the soft laminated exterior body 40. (B) shows the state after joining the entire periphery of the soft laminated exterior body 40. FIG. (C) shows a state in which the soft laminated outer body 40 containing the laminated electrode body 20 is housed inside the hard laminated outer body 50.
-Construction of electrode body and accommodation in soft laminated exterior body-
First, the laminated electrode body 20 is constructed using the above-mentioned materials. Next, as shown in FIG. 2 (A), the laminated electrode body 20 constitutes the two rectangular sheet-shaped soft laminated exterior bodies 40 (in FIG. 2 (A), the laminated exterior body 40 It is sandwiched between (indicated by the code of) and accommodated. Then, as shown in FIG. 2 (B), the soft laminated sheets are joined to each other by, for example, heat welding, in the periphery facing the laminated side surface of the laminated electrode body 20 housed inside. As shown, the soft laminated exterior 40 has joints 40a, 40b, 40c, and 40d. Here, the soft laminated exterior body 40 accommodates a part of the positive electrode current collecting tab 12 and the negative electrode current collecting tab 14 inside, but does not accommodate the other part, and they protrude outward from the joint portion 40a. There is.

-Accommodation in hard laminated exterior-
Next, the soft laminated outer body 40 (FIG. 2 (B)) in which the laminated electrode body 20 is housed is placed between the hard laminated sheets forming, for example, two rectangular sheet-shaped hard laminated outer bodies 50. It is sandwiched and accommodated (not shown). Then, the periphery facing the laminated side surface of the laminated electrode body 20 housed inside is joined by heat welding, but an opening is formed without joining a part of the laminated electrode body 20. Specifically, for example, as shown in FIG. 2C, in the rigid laminated exterior body 50, the joint portions 40a, 40b, and the portions facing 40d are joined. However, since the portion facing the joint portion 40c, which is a part of the above, is not joined, the opening 52 is formed. As the portion where the opening 52 is formed, for example, in a rectangular laminated sheet, the short side portion is preferably the forming portion of the opening 52, and typically faces the positive electrode / negative electrode current collecting tab forming portion. The part is mentioned. Here, as shown in the drawing, it is preferable that a part of the joint portion 40c projects outward of the rigid laminated exterior body 50 through the opening 52 (see also FIG. 1). As a result, it is possible to effectively release gas and dissipate heat from the opening 52, particularly from a part of the joint 40c protruding outward from the opening 52, in the event of an abnormality such as an internal short circuit or overcharging. it can.
The positive electrode current collecting tab 12 and the negative electrode current collecting tab 14 project outward from the joint portion of the hard laminated exterior body 50 facing the joint portion 40a, and can be externally connected.

The laminated secondary battery 100 constructed as described above includes a double-structured laminated exterior body including a soft laminated exterior body and a hard laminated exterior body 50. Among them, in the hard laminated exterior body 50, an opening 52 is formed in a part of the periphery facing the laminated side surface of the laminated electrode body 20, and a part of the joint portion 40c of the soft laminated exterior body 40 is hard laminated through the opening 52. It projects outward from the exterior body 50. From here, it is possible to effectively release gas and dissipate heat in the event of an abnormality such as an internal short circuit or overcharge, and even if a laminated exterior body with a double structure is provided, suitable gas release characteristics and heat dissipation are realized. be able to.

<Assembled battery>
An assembled battery can be manufactured by using the laminated secondary battery 100 as a single battery. Although detailed illustration is omitted, specifically, for example, a plurality of (about 2 to 50) laminated secondary batteries 100 are laminated along the positive and negative electrode stacking directions of the laminated electrode body 20. For example, when a plurality of laminated secondary batteries 100 as a single battery are connected in parallel, the laminated secondary batteries 100 are laminated so that the positive electrode current collecting tabs 12 and the negative electrode current collecting tabs 14 are overlapped with each other.
As described above, since the laminated secondary battery 100 as a cell of the assembled battery has good outgassing characteristics and heat dissipation, there is a case where a problem occurs in any of the cells included in the assembled battery. However, it is possible to prevent high heat from being conducted to other adjacent cells, and it is possible to realize high stability.

<Modification example 1>
When the laminated secondary battery 100 is a type of secondary battery including an electrolytic solution, the electrolytic solution is housed inside before the soft laminated outer body 40 is completely sealed. Specifically, for example, after joining soft laminate sheets to form the joint portions 40a, 40b, and 40d, the electrolytic solution is housed inside the laminate exterior body 40. Then, the openings of the remaining soft laminate sheets are joined to form the joint 40c.

<Modification 2>
In the above embodiment, two laminated sheets are used (FIG. 2A), but even if the soft laminated outer body 40 and the hard laminated outer body 50 are both composed of only one laminated sheet. Good. In this case, the one laminated sheet can be folded back and used as a laminated exterior body by joining the peripheral edges of the folded back portion.

Hereinafter, test examples of the laminated secondary battery disclosed herein will be described, but the present invention is not intended to be limited to those shown in such test examples.

[Test Example 1: Fabrication of laminated secondary battery and assembled battery]
Laminated secondary batteries in Examples and Comparative Examples were produced by the process described below.
-Example-
A laminated electrode body was produced by a conventionally known method, an aluminum layer was housed inside a soft laminated outer body having a thickness of 40 μm, and the entire periphery of the laminated outer body was joined by heat welding. Next, this was housed inside a hard laminated exterior body having an aluminum layer having a thickness of 300 μm, and the periphery of the hard laminated exterior body was joined by heat welding. Here, the short side that is a part of the periphery of the exterior body and the positive and negative electrode current collecting tabs do not protrude is not joined, and the joint portion of the internal soft laminated exterior body at the portion is the hard laminated exterior. I made it stick out from my body. Then, three laminated secondary batteries produced in this manner were stacked to produce the assembled battery according to the embodiment.
-Comparative example-
In the laminated secondary battery, the same as in the embodiment except that the entire circumference of the hard laminated exterior body is joined so that all the joints of the soft laminated exterior body are accommodated inside the hard laminated exterior body. , The assembled battery according to the comparative example was produced.

[Test Example 2: Overcharge test]
Appropriate conditioning treatment was performed on one laminated type secondary battery constituting the assembled battery according to the examples and comparative examples produced above. Next, constant current charging was performed under the condition of room temperature (25 ° C.). Further, the constant current charging was continued even after the charging of the laminated type secondary battery was completed, and the laminated type secondary battery was forcibly put into an overcharged state. Then, it was observed whether or not smoke generation (that is, chain smoke generation due to high heat conduction) occurs in another adjacent laminated type secondary battery.
The results are shown in Table 1.

As shown in Table 1, a laminated secondary battery having a structure in which a part of the hard laminated exterior has an opening and a part of the joint of the soft laminated exterior protrudes outward has improved heat dissipation. Therefore, in the assembled battery according to the embodiment having this as a single battery, chain smoke generation due to overcharging did not occur. On the other hand, a laminated secondary battery in which the entire circumference of a hard laminated exterior body is joined and has no opening has low heat dissipation, and the assembled battery according to the comparative example having such a battery as a single battery is due to overcharging. Chain smoke occurred.

Although the present invention has been described in detail above, the above-described embodiment is merely an example, and the invention disclosed here includes various modifications and modifications of the above-mentioned specific examples.
For example, the laminated secondary battery 100 may be a secondary battery other than the lithium ion secondary battery, for example, a sodium ion secondary battery. Even in this case, the same effect as described above can be obtained in the present invention.

12 Positive electrode current collecting tab 14 Negative electrode current collecting tab 20 Laminated electrode body 40 Soft laminated exterior body 40a Joint part 40b Joint part 40c Joint part 40d Joint part 50 Hard laminated exterior body 52 Opening 100 Laminated secondary battery

Claims (1)

A laminated electrode body having a structure in which a plurality of sheet-shaped positive electrodes and negative electrodes are laminated while interposing a layer that functions as a separator.
A soft laminated exterior body composed of a relatively soft laminated sheet accommodating the laminated electrode body inside, and
A hard laminated exterior body composed of a relatively hard laminated sheet that houses the soft laminated outer body in a state where the laminated electrode body is housed inside, and
It is a laminated type secondary battery equipped with
The soft laminated exterior body has a joint portion in which the soft laminated sheets are joined to each other around the periphery facing the laminated side surface of the laminated electrode body housed therein.
The hard laminated exterior body has an opening formed in a part of the periphery facing the laminated side surface of the laminated electrode body housed therein.
Here, a laminated secondary battery, characterized in that a part of the joint portion projects outward of the rigid laminated exterior body through the opening.

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