JP7194334B2 - Laminated secondary battery and assembled battery comprising said secondary battery - Google Patents

Description

TECHNICAL FIELD The present invention relates to a laminated secondary battery having a structure in which battery elements are housed in an outer package made of a laminated sheet, and more particularly to an assembled battery comprising a plurality of mutually electrically connected laminated secondary batteries.

Secondary batteries such as lithium-ion secondary batteries are lightweight and have high energy density. It is widely used as a power source for driving vehicles such as automobiles. As one form of a secondary battery used as a power source for driving a vehicle, a battery element (storage element) composed of an electrode assembly having positive and negative electrodes and an electrolyte is placed in an exterior body made of a bag-like laminate sheet (hereinafter simply referred to as (Also referred to as a "laminate outer package".).
Such a laminated exterior body is generally composed of a flexible material having a multi-layer structure including an outer layer composed of a heat-sealable plastic film such as polyolefin resin and an inner layer composed of a metal foil such as aluminum. It is an exterior body that is lightweight and has excellent airtightness (sealing property).
For example, Patent Literature 1 below describes a laminate-type secondary battery including this type of laminate outer package.

JP 2013-69696 A JP 2008-262804 A

By the way, the laminate sheet that constitutes the laminate outer package is lightweight and flexible, but it must be said that the strength against external impact is lower than that of a metal battery case. Therefore, it has been proposed to improve the physical strength against impacts such as dropping by making the laminated outer package into a double structure. For example, in Patent Document 2 above, a soft laminated exterior body (soft exterior material) that accommodates a battery element inside, and a hard laminate exterior body (hard exterior material) that accommodates the battery element and the soft exterior material inside is disclosed.

However, in a laminate type secondary battery having a double-layered laminated exterior body as described in Patent Document 2, while the physical strength is improved, the blockage inside the battery is increased, and in the event of an abnormality, Conversely, there is a risk that gas release from the inside of the battery and heat dissipation performance will be lower than in a normal laminated secondary battery having a single-layer laminated exterior body. In a relatively high-voltage, high-capacity secondary battery such as a lithium-ion secondary battery, it is preferable to quickly release heat or release gas generated inside the battery in the event of an abnormality such as an internal short circuit or overcharge. The situation is the same in a laminated secondary battery having a laminated exterior body with a double structure, and improvements in gas release characteristics and heat dissipation are required.

Therefore, the present invention was created to solve such problems in a laminate type secondary battery provided with a double structure laminate outer package, and a double structure laminate that achieves excellent gas release characteristics and heat dissipation. An object of the present invention is to provide a laminated secondary battery having an outer package. Another object of the present invention is to provide an assembled battery including a plurality of such laminated secondary batteries.

In order to achieve such an object, the laminated secondary battery disclosed herein includes a laminated electrode body having a structure in which a plurality of sheet-like positive and negative electrodes are laminated with a layer functioning as a separator interposed therebetween, and the laminated electrode body. From a soft laminate exterior body composed of a relatively soft laminate sheet to be accommodated inside, and a relatively hard laminate sheet to house the soft laminate exterior body with the laminated electrode body accommodated therein A laminate type secondary battery comprising:
In the laminate-type secondary battery disclosed herein, the soft laminate exterior body has a joint portion where the soft laminate sheets are joined together on the periphery facing the laminated side surface of the laminated electrode body housed inside. The hard laminate exterior body has an opening formed in a part of the circumference facing the laminated side surface of the laminated electrode body accommodated therein. Here, a part of the joint portion is characterized by protruding to the outside of the hard laminate exterior body through the opening.

In the laminate-type secondary battery having such a configuration, in the double structure laminate outer package composed of the soft laminate outer package and the hard laminate outer package, in the hard laminate outer package, the laminated side surface of the laminated electrode body (that is, the positive and negative electrodes) An opening is formed in a part of the periphery facing the side surface where the laminated structure of ) is exposed. Further, a part of the joining portion of the soft laminate exterior body protrudes outward from the hard laminate exterior body through the opening. As a result, it is possible to effectively release gas and radiate heat from the opening, particularly from a portion of the joint projecting outward from the opening, in the event of an internal short circuit, overcharge, or other abnormality. .
For this reason, according to the laminated secondary battery disclosed herein, even if it has a soft and hard double-layer laminated exterior body, it is possible to achieve suitable gas release characteristics and heat dissipation properties.

Further, the present invention provides an assembled battery comprising a plurality of the laminated secondary batteries disclosed herein, wherein the assembled battery has a configuration in which the plurality of laminated secondary batteries are laminated along the positive and negative electrode lamination direction of the laminated electrode body. Provide batteries. In the assembled battery with such a configuration, each laminated secondary battery (also referred to as a single cell) constituting the assembled battery has suitable gas release characteristics and heat dissipation properties as described above. Even if a problem occurs in one unit cell, it is possible to prevent high heat from being conducted to other adjacent unit cells, and high stability can be achieved.

1 is a perspective view schematically showing a laminated secondary battery according to one embodiment; FIG. FIG. 2 is a schematic diagram showing an outline of steps for constructing a laminate type secondary battery according to one embodiment. (A) shows the state before the laminated electrode body is housed inside the soft laminated outer package. (B) shows the state after bonding the entire periphery of the soft laminate exterior body. (C) shows a state in which a soft laminate housing housing a laminated electrode body is housed inside a hard laminate housing.

An embodiment according to the present invention will be described below with reference to the drawings. In each drawing described 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 reflect the actual dimensional relationships. Matters other than those specifically mentioned in this specification, which are necessary for carrying out the present invention, can be grasped as design matters by those skilled in the art based on the prior art in the field. Furthermore, in the present specification, when the numerical range is described as A to B (where A and B are arbitrary numerical values in a relationship of A<B), it means A or more and B or less, and A (not including A) and below B (not including B).

As used herein, the term “secondary battery” refers to a chargeable/dischargeable power storage device from which predetermined electrical energy can be repeatedly extracted. For example, lithium-ion secondary batteries, sodium-ion secondary batteries, and the like in which alkali metal ions in the electrolyte are responsible for charge transfer are typical examples included in the secondary battery referred to here. A “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 laminate sheet.
Hereinafter, as an embodiment of the laminated secondary battery disclosed herein, the present invention will be described in detail by taking as an example a laminated secondary battery in which a flat rectangular laminated electrode body is housed in a laminated outer package. do. However, it is not intended to limit the present invention to those described in such embodiments.

<Overall Structure of Laminated Secondary Battery>
First, the rough overall structure of the laminated secondary battery disclosed herein will be described with reference to FIG. FIG. 1 is a perspective view schematically showing the overall structure of a laminated secondary battery according to one embodiment.
As shown in FIG. 1 , the laminated secondary battery 100 includes a laminated electrode body 20 , a soft laminated outer casing 40 and a hard laminated outer casing 50 .
As shown in the figure, the flexible laminated outer body 40 accommodates the laminated electrode body 20 inside. In addition, the hard laminate exterior body 50 accommodates therein the soft laminate exterior body 40 in which the laminated electrode body 20 is accommodated. A portion of the sealed peripheral edge of the hard laminate exterior body 50 forms an opening 52 that is open without being sealed, and a portion of the soft laminate exterior body 40 is hard through the opening 52 . It protrudes outward from the laminated exterior body 50 . Parts 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 end are pulled out from both the soft laminated outer package 40 and the hard laminated outer package 50 and protrude outward. ing.

Next, the configuration and each component of the laminate type secondary battery 100 will be described in detail.
<Laminated electrode body>
As the laminated electrode body 20, a laminated electrode body used in this type of laminated secondary battery can be used without particular limitation. Specifically, for example, the laminated electrode body 20 is formed by laminating a plurality of rectangular sheet-shaped positive electrodes and rectangular sheet-shaped negative electrodes in a mutually insulated state with a layer functioning as a separator (not shown) interposed therebetween. there is

－Positive electrode－
The positive electrode typically includes a rectangular sheet-like positive electrode current collector and a positive electrode active material layer formed on a 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 intercalating and deintercalating lithium ions (for example, lithium transition metal composite oxide such as lithium nickel cobalt manganese composite oxide). As the positive electrode current collector, for example, a positive electrode current collector made of aluminum 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－
A negative electrode typically includes a rectangular sheet-shaped negative electrode current collector and a negative electrode active material layer formed on a surface (one side or both sides) of the negative electrode current collector. The negative electrode active material layer contains a negative electrode active material capable of intercalating and deintercalating lithium ions (for example, a carbonaceous material such as graphite). As the negative electrode current collector, for example, a negative electrode current collector made of copper is used. As shown in the figure, the negative electrode current collector is provided with a negative electrode current collecting tab 14 and 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. Roughly speaking, the type of layer that functions as a separator differs depending on the electrolyte provided in the laminate secondary battery 100 . Specifically, for example, when the laminated secondary battery 100 is a so-called all-solid 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 a sulfide-based solid electrolyte and an oxide-based solid electrolyte. Further, when the laminate type secondary battery 100 is a type of secondary battery that includes an electrolytic solution, the separator sheet corresponds to a layer functioning as a separator. Examples of separator sheets include sheets made of resin such as polyethylene or polypropylene.

<Laminate exterior body>
The soft laminate exterior body 40 has a laminated structure of a resin film layer made of insulating polyolefin, polyethylene terephthalate, polyamide, etc., which constitutes the surface layer, and a metal layer made of aluminum, stainless steel, etc. which constitutes the inner layer, for example, a polyamide layer and , a metal layer, and a polyolefin layer are laminated in this order to form a laminate sheet having a three-layer structure. Although the thickness of each layer is not particularly limited, for example, the polyamide layer may have a thickness of 10 to 100 μm, the aluminum layer may have a thickness of 30 to 150 μm (preferably 100 μm, more preferably 50 μm or less), and the polyolefin layer may have a thickness of 10 to 100 μm.
As with the soft laminate exterior body 40, the hard laminate exterior body 50 may typically have a laminated structure of a resin film layer and a metal layer. For example, it is composed of a laminate sheet having a structure in which a polyamide layer, a metal layer, and a polyolefin layer are laminated in this order. The thickness of each layer may be, for example, 10 to 100 μm for the polyamide layer, 100 to 500 μm (preferably 200 to 400 μm, more preferably 250 to 350 μm) for the metal layer, and 10 to 100 μm for the polyolefin layer.
By having the laminate sheets, which are the constituent materials of the soft laminated outer body 40 and the hard laminated outer body 50, configured as described above, that is, by giving different thicknesses to the metal layers such as aluminum constituting the laminated sheets. , the bending properties and mechanical hardness of the laminate sheath can be adjusted. The soft laminate outer covering 40 is composed of a relatively soft laminate sheet compared to the hard laminate outer covering 50 . On the other hand, the hard laminate outer covering 50 is composed of a laminate sheet that is relatively hard compared to the soft laminate outer covering 40 .

<Construction of laminated secondary battery>
Next, construction of the laminated secondary battery 100 will be described with reference to FIG. FIG. 2 schematically shows an outline of steps for constructing a laminated secondary battery according to one embodiment. (A) shows a state before the laminated electrode body 20 is accommodated inside the soft laminated outer package 40 . (B) shows the state after the entire circumference of the soft laminate exterior body 40 has been bonded. (C) shows a state in which the soft laminate exterior body 40 containing the laminated electrode assembly 20 is housed inside the hard laminate exterior body 50 .
-Construction of the electrode body and accommodation in the soft laminate exterior body-
First, the laminated electrode body 20 is constructed using the materials described above. Next, as shown in FIG. 2(A), the laminated electrode body 20 is formed into two rectangular sheet-like soft laminate sheets 40 (in FIG. 2(A), the laminated outer body 40 is (indicated by the symbol ). Then, as shown in FIG. 2(B), the soft laminate sheets are joined together, for example, by thermal welding, in the periphery facing the laminated side surface of the laminated electrode body 20 housed inside. As illustrated, the flexible laminate exterior body 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 a hard laminated exterior body－
Next, the flexible laminated outer package 40 (FIG. 2B) in which the laminated electrode body 20 is accommodated is placed between, for example, two rectangular sheet-shaped rigid laminated outer packages 50, which are formed by rigid laminate sheets. It is sandwiched and accommodated (not shown). Then, the periphery of the laminated electrode body 20 accommodated inside facing the laminated side surface is joined by thermal welding, but a part is left unjoined to form an opening. Specifically, for example, as shown in FIG. 2(C), in the hard laminate exterior body 50, the portions facing the joints 40a, 40b, and 40d are joined. However, since the portion facing the joint portion 40c, which is the above portion, is not joined, an opening portion 52 is formed. As the site where the opening 52 is formed, for example, it is preferable to use the short side portion of the rectangular laminate sheet as the site where the opening 52 is formed. part. Here, as illustrated, it is preferable that a portion of the joint portion 40c protrude outward from the hard laminate exterior body 50 through the opening 52 (see also FIG. 1). As a result, the opening 52, particularly the part of the joint 40c protruding outward from the opening 52, can effectively release gas and heat in the event of an internal short circuit, overcharging, or other abnormality. can.
The positive electrode current collecting tab 12 and the negative electrode current collecting tab 14 protrude outward from the joint portion of the hard laminate exterior body 50 facing the joint portion 40a, and are externally connectable.

The laminate-type secondary battery 100 constructed as described above has a double-layered laminated outer package composed of a soft laminated outer package and a hard laminated outer package 50 . Among them, in the hard laminate exterior body 50, an opening 52 is formed in a part of the periphery facing the lamination side surface of the laminated electrode body 20, and a part of the joint portion 40c of the soft laminate exterior body 40 is formed through the opening 52. It protrudes outward from the exterior body 50 . From this, it is possible to effectively release gas and heat in the event of an abnormality such as an internal short circuit or overcharging. be able to.

<Battery pack>
An assembled battery can be produced by using the laminated secondary battery 100 as a single cell. Although detailed illustration is omitted, specifically, for example, a plurality (approximately 2 to 50 pieces) of laminated secondary batteries 100 are laminated along the positive and negative electrode lamination direction of the laminated electrode body 20 . For example, when connecting a plurality of laminated secondary batteries 100 as single cells in parallel, the laminated secondary batteries 100 are stacked such that the positive electrode current collecting tabs 12 and the negative electrode current collecting tabs 14 are overlapped.
As described above, since the laminated secondary battery 100 as the unit cell of the assembled battery has good gas release characteristics and heat dissipation properties, even if a problem occurs in any of the unit cells included in the assembled battery, However, it is possible to prevent high heat from being conducted to other adjacent cells, and high stability can be achieved.

<Modification 1>
If the laminate type secondary battery 100 is a type of secondary battery that contains an electrolytic solution, the electrolytic solution is accommodated inside before the flexible laminate exterior body 40 is completely sealed. Specifically, for example, after bonding the soft laminate sheets to form the bonding portions 40a, 40b, and 40d, the electrolytic solution is accommodated inside the laminate outer body 40. FIG. Thereafter, the openings of the remaining soft laminate sheets are joined together to form joints 40c.

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

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

[Test Example 1: Production 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, housed inside a soft laminate outer package having an aluminum layer of 40 μm thickness, and the entire circumference of the laminated outer package was joined by heat welding. Next, this was housed inside a hard laminate exterior body with an aluminum layer having a thickness of 300 μm, and the periphery of the hard laminate exterior body was joined by heat welding. Here, the short sides, which are part of the periphery of the exterior body and from which the positive and negative electrode current collecting tabs do not protrude, are not joined, and the joints in the portion of the soft laminate exterior body inside the hard laminate exterior body are not joined. Made to protrude from the body. Then, an assembled battery according to an example was produced by stacking three laminated secondary batteries produced in this way.
- Comparative example -
In the laminated secondary battery, the same procedure as in the example was carried out, except that the entire circumference of the hard laminate outer casing was joined so that all joints of the soft laminate outer casing were housed inside the hard laminate outer casing. , an assembled battery according to a comparative example was produced.

[Test Example 2: Overcharge Test]
Appropriate conditioning treatment was performed on one laminated secondary battery constituting the assembled battery according to the example and the comparative example produced above. Next, constant current charging was performed at room temperature (25° C.). Furthermore, constant-current charging was continued even after the charging of the laminate type secondary battery was completed, and the laminate type secondary battery was forced into an overcharged state. Then, it was observed whether smoke emission (that is, chain smoke emission due to high heat conduction) occurred in other adjacent laminate type secondary batteries.
Table 1 shows the results.

As shown in Table 1, a laminated secondary battery having a structure in which a part of the hard laminate outer casing has an opening and a part of the joint portion of the soft laminate outer casing protrudes outward has improved heat dissipation. Therefore, chain emission of smoke due to overcharging did not occur in the assembled battery according to the example having this as the single cell. On the other hand, a laminate-type secondary battery in which the entire circumference of the hard laminate exterior body is joined and which does not have an opening has low heat dissipation. Chain fumes occurred.

Although the present invention has been described in detail above, the above-described embodiments are merely examples, and the invention disclosed herein includes various modifications and alterations of the above-described specific examples.
For example, the laminated secondary battery 100 may be a secondary battery other than a lithium ion secondary battery, such as a sodium ion secondary battery. Also in this case, the present invention can obtain the same effect as described above.

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

Claims (1)

A laminated electrode body having a structure in which a plurality of rectangular sheet-shaped positive and negative electrodes are laminated with a layer functioning as a separator interposed therebetween;
a planar rectangular soft laminate exterior body composed of a relatively soft laminate sheet for accommodating the laminated electrode body therein;
a planar rectangular hard laminate outer package composed of a relatively hard laminate sheet inside which accommodates the soft laminate outer package in which the laminated electrode body is accommodated;
a positive electrode current collecting tab and a negative electrode current collecting tab attached to the laminated electrode body and protruding outward from the soft laminate exterior body and the hard laminate exterior body;
A laminated secondary battery comprising
The flexible laminate exterior body has a joint portion where the flexible laminate sheets are joined together in a periphery facing the laminated side surface of the laminated electrode body housed inside,
The hard laminate exterior body has an opening and a portion where the hard laminate exterior bodies are joined together in a periphery facing the laminated side surface of the laminated electrode body accommodated therein,
The soft laminate exterior body has an aluminum layer with a thickness of 30 to 150 μm, and the hard laminate exterior body has an aluminum layer with a thickness of 200 to 400 μm,
The positive electrode current collecting tab and the negative electrode current collecting tab are attached to the same stacked side surface of the stacked electrode body,
Here, in the hard laminate exterior body,
The hard laminate exterior bodies are bonded to each other at a portion facing the laminated side surface of the laminated electrode body to which the positive electrode current collecting tab and the negative electrode current collecting tab are attached,
The opening is formed at a portion opposite to the portion where the hard laminate exterior bodies are joined together,
A laminate type secondary battery, wherein a part of the joint portion in the soft laminate outer package protrudes to the outside of the hard laminate outer package through the opening.

Images