JP6778393B2 - Sealed battery - Google Patents

Description

The present invention relates to a sealed battery in which an electrode body and an electrolytic solution are housed in a sealed case, and more particularly to a sealed battery provided with a gas discharge valve that is opened when the internal pressure of the case rises.

In recent years, secondary batteries such as lithium ion secondary batteries have become increasingly important as power sources for vehicles or as power sources for personal computers and mobile terminals. In particular, a lithium ion secondary battery that is lightweight and has a high energy density is preferably used as a high output power source for mounting on a vehicle. Such a secondary battery has, for example, a so-called closed battery structure in which an electrode body and an electrolytic solution, which are power generation elements, are housed in a closed case.

Generally, the case of such a sealed battery is provided with an internal pressure release mechanism for releasing the internal pressure when the gas pressure (internal pressure) in the case rises excessively due to overcharging or the like. As a specific example of such an internal pressure release mechanism, a gas discharge valve (opening valve) as described in Patent Document 1 can be mentioned. The gas discharge valve in Patent Document 1 is composed of a metal foil such as nickel foil whose cleavage pressure is adjusted to a predetermined pressure, and when the pressure inside the case (battery can) rises, the gas discharge valve is opened. It is configured to discharge the gas inside the case and reduce the internal pressure by opening it.

Japanese Unexamined Patent Publication No. 11-185820

However, in the sealed battery having the above-mentioned structure, when the gas discharge valve is opened to discharge the gas from the inside of the case, droplets of the electrolytic solution may be ejected from the gas discharge valve as the gas is discharged. .. In such a case, the droplets of the ejected electrolytic solution diffuse over a wide area and adhere to the case, which may deteriorate (corrosion) the case. Further, in a general sealed battery, an electrode terminal for connecting the battery and an external device is provided outside the case, and if droplets of electrolytic solution adhere to the electrode terminal for external connection, an external short circuit occurs. There is a risk of causing it.

The present invention has been made in view of the above problems, and an object of the present invention is to prevent the droplets of the electrolytic solution ejected from the gas discharge valve from spreading over a wide area when the gas discharge valve is opened. An object of the present invention is to provide a sealed battery capable of appropriately preventing deterioration of a case and occurrence of an external short circuit.

In order to realize the above object, the present invention provides a sealed battery having the following configuration.

In the sealed battery disclosed here, an electrode body having a positive electrode and a negative electrode and an electrolytic solution are housed in a square case, and the case is sealed.
In such a sealed battery, a recess recessed toward the inside of the case is formed on any surface of the outer surface of the square case, and at least one of the inner walls of the recess is directed toward the outside of the case. An opening is provided to open the battery, and a gas discharge valve that opens when the internal pressure of the case rises above a predetermined level is formed on the bottom surface of the recess.

In the sealed battery disclosed here, a recess recessed toward the inside of the case is formed on the outer surface of the case, and a gas discharge valve is provided on the bottom surface of the recess. An opening is provided on at least one of the inner walls of the recess so as to open toward the outside of the case.
According to the sealed battery having such a structure, when the gas discharge valve is opened due to an increase in the internal pressure of the case, the inner wall of the recess prevents the droplets of the electrolytic solution ejected from the gas discharge valve from spreading over a wide area. At the same time, the droplets of the electrolytic solution can be discharged from the opening opened toward the outside of the case. Therefore, it is possible to appropriately prevent the case from being deteriorated or an external short circuit from occurring due to the electrolytic solution ejected from the gas discharge valve.

It is a figure which shows typically the cross-sectional structure of the lithium ion secondary battery which concerns on one Embodiment of this invention. It is a perspective view which shows typically the vicinity of the gas discharge valve of the lithium ion secondary battery which concerns on one Embodiment of this invention.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The dimensional relationships (length, width, thickness, etc.) in each figure do not reflect the actual dimensional relationships. In addition, members and parts that perform the same action are designated by the same reference numerals, and duplicate explanations are omitted or simplified. In addition, matters other than those specifically mentioned in the present specification and necessary for carrying out the present invention (for example, a method for producing an electrode body and various materials used for the electrode body) are in the art. It can be grasped as a design matter of a person skilled in the art based on the prior art. The present invention can be carried out based on the contents disclosed in the present specification and common general technical knowledge in the art.

In the following, a lithium ion secondary battery will be described as an embodiment of the sealed battery disclosed here, but such description is not intended to limit the application of the present invention. That is, the sealed battery disclosed here may be a sealed battery (for example, a nickel hydrogen battery) other than the lithium ion secondary battery.

FIG. 1 is a diagram schematically showing a cross-sectional structure of a lithium ion secondary battery according to the present embodiment. As shown in FIG. 1, in the lithium ion secondary battery 10 according to the present embodiment, an electrode body 30 having a positive electrode 32 and a negative electrode 34 and an electrolytic solution (not shown) are housed in a square case 20. It is configured by sealing the case 20.

(1) Case The case 20 in the present embodiment is a flat square container. The case 20 includes a box-shaped case body 21 having an opening on one side and a sealing plate 22 that closes the opening of the case body 21.
The material of the case 20 (case body 21 and sealing plate 22) may be the same as that used in the conventional sealed battery, and an appropriate material can be appropriately selected in consideration of strength. Examples of the material of the case 20 include aluminum, stainless steel, nickel-plated steel and the like.

Further, the lithium ion secondary battery 10 according to the present embodiment has a structure called a so-called thin cell. In the lithium ion secondary battery 10 having such a thin cell structure, in order to easily accommodate the electrode body 30 inside the thin case 20, the opening for accommodating the electrode body 30 is a flat surface of the case body 21. (That is, the surface having the largest area among the surfaces constituting the flat square case 20) is provided. Then, in such a thin cell, the electrode body 30 is housed inside the case 20 so that the flat surface of the case body 21 (upper surface 20a of the case 20) and the flat surface 30a of the electrode body 30 face each other.
The specific thickness of the case 20 of the thin cell (dimensions of the electrode body 30 in the stacking direction X) is set to about 0.5 mm to 15 mm.

Although not shown, electrode terminals (positive electrode terminal and negative electrode terminal) for connecting the lithium ion secondary battery 10 and an external device are provided on the upper surface 20a of the case 20, and each electrode terminal is provided. , The positive electrode 32 and the negative electrode 34 constituting the electrode body 30 housed inside the case 20 are electrically connected.

Although the specific structure will be described later, as shown in FIGS. 1 and 2, in the lithium ion secondary battery 10 according to the present embodiment, the recess 23 is formed in the upper surface 20a (flat surface of the case body 21) of the case 20. Is formed, and a gas discharge valve 40 is provided on the bottom surface 23a of the recess 23.

(2) Electrode body In the lithium ion secondary battery 10 according to the present embodiment, a laminated electrode body is used as the electrode body 30. The laminated electrode body 30 is formed by laminating a plurality of sheet-shaped positive electrode 32 and negative electrode 34 via a separator 36. As described above, in the present embodiment, the laminated electrode body 30 is formed in a substantially flat shape, and the flat surface 30a of the laminated electrode body 30 faces the upper surface 20a of the case 20 (in other words,). The laminated electrode body 30 is housed in the case 20 (so that the stacking direction X of the laminated electrode body 30 and the upper surface 20a of the case 20 are substantially perpendicular to each other).

In the lithium ion secondary battery 10 according to the present embodiment, the structure of each member constituting the laminated electrode body 30 and the material of the member shall be the same as those of the electrode body of a general lithium ion secondary battery. Can be done. Hereinafter, each member constituting the laminated electrode body 30 will be briefly described.

(A) Positive electrode The positive electrode 32 includes a sheet-shaped positive electrode current collector (for example, an aluminum foil) and a positive electrode active material layer applied to the surface of the positive electrode current collector, and the positive electrode active material layer contains lithium ions. Contains a positive electrode active material, which is a substance that can store and release. As such a positive electrode active material, one kind or two or more kinds of substances conventionally used for lithium ion secondary batteries can be used without particular limitation.
Further, in addition to the above-mentioned positive electrode active material, an additive such as a conductive material or a binder may be added to the positive electrode active material layer of the positive electrode 32, if necessary.

(B) Negative electrode On the other hand, the negative electrode 34 includes a sheet-shaped negative electrode current collector (for example, copper foil) and a negative electrode active material layer applied to the surface of the negative electrode current collector. Similarly, as the negative electrode active material contained in the negative electrode active material layer, one kind or two or more kinds of substances conventionally used for lithium ion secondary batteries can be used without particular limitation.
Further, as in the case of the positive electrode active material layer, an additive such as a binder may be added to the negative electrode active material layer of the negative electrode 34.

(C) Separator The separator 36 is arranged between the positive electrode 32 and the negative electrode 34, and is a charge carrier (for example, lithium) that insulates the positive electrode 32 and the negative electrode 34 and moves between the positive electrode 32 and the negative electrode 34. It has a plurality of minute holes through which ions) can pass.

(3) Electrolyte As described above, the electrolytic solution (not shown) is housed inside the case 20. As such an electrolytic solution, the same electrolytic solution as that conventionally used for a lithium ion secondary battery can be used without particular limitation.

(4) Gas Discharge Valve FIG. 2 is a perspective view schematically showing the vicinity of the gas exhaust valve of the lithium ion secondary battery according to the present embodiment.
The gas discharge valve 40 in the present embodiment is configured to open (split) when the internal pressure of the case 20 rises above a predetermined level. Specifically, the gas discharge valve 40 is formed so as to be thinner than the wall thickness of the case 20 as shown in FIG. For example, when the thickness of the wall surface of the case is 0.3 mm to 1.5 mm (for example, 0.5 mm), the thickness of the gas discharge valve 40 is set to a wall thickness of 0.05 mm to 0.5 mm. Then, as shown in FIG. 2, a breaking groove 42 is formed on the upper surface of the gas discharge valve 40 in the present embodiment. By providing the gas discharge valve 40 having such a structure in the case 20, when the internal pressure of the case 20 rises to a predetermined level or higher (for example, 0.3 MPa or higher) due to gas generation or the like, the gas discharge valve 40 is provided. The internal pressure of the case 20 can be reduced by cleaving along the fracture groove 42.
The gas discharge valve 40 may have a structure that is opened when the internal pressure of the case 20 rises above a predetermined level, and is not limited to the above-mentioned structure.

In the lithium ion secondary battery 10 according to the present embodiment, a recess 23 recessed toward the inside of the case 20 is formed in the vicinity of the outer edge 20b of the upper surface 20a of the case 20, and the bottom surface 23a of the recess 23 is formed. A gas discharge valve 40 is provided. Further, an opening 23c opened toward the outside of the case 20 is provided on one surface of the inner wall 23b of the recess 23.

According to the lithium ion secondary battery 10 according to the present embodiment, when the gas discharge valve 40 is opened by providing the gas discharge valve 40 on the bottom surface 23a of the recess 23 having the opening 23c as described above. It is possible to appropriately prevent the electrolytic solution ejected from the inside of the case 20 from diffusing over a wide range and causing deterioration of the case 20 and an external short circuit.
Specifically, in the lithium ion secondary battery 10 according to the present embodiment, since the gas discharge valve 40 is surrounded by the inner wall 23b of the recess 23, the electrolytic solution is ejected from the gas discharge valve 40. It is possible to suppress the diffusion of the electrolytic solution over a wide area. Further, in the present embodiment, since the opening 23c opened toward the outside of the case 20 is provided on one surface of the inner wall 23b of the recess 23, as shown by the arrow A in FIG. 2, the gas discharge valve The electrolytic solution ejected from 40 passes through the opening 23c and is discharged toward the outside of the case 20. As described above, in the lithium ion secondary battery 10 according to the present embodiment, the electrolytic solution ejected from the gas discharge valve 40 is suppressed from diffusing over a wide range, and then the electrolytic solution is discharged toward the outside of the case 20. Therefore, deterioration of the case 20 and occurrence of an external short circuit due to the electrolytic solution can be appropriately prevented.

Further, the lithium ion secondary battery 10 according to the present embodiment can be particularly preferably used as a unit battery constituting the assembled battery. A general assembled battery is constructed by arranging a plurality of flat square cell cells so that the flat surfaces face each other and restraining the arranged cell group. If the gas discharge valve is formed on the flat surface of each cell in the assembled battery having such a structure, the gas discharge valve may be blocked by another adjacent cell.
On the other hand, in the lithium ion secondary battery 10 according to the present embodiment, the recess 23 is formed on the upper surface (flat surface) 20a of the case 20, and the gas discharge valve 40 is provided on the bottom surface 23a of the recess 23. Therefore, even when a plurality of batteries are arranged so that the flat surfaces face each other to construct an assembled battery, it is appropriately prevented that the gas discharge valve 40 is blocked by another adjacent battery. be able to.

As described above, when the recess is formed on the upper surface of the case, the thickness of the case in the portion where the recess is formed becomes thinner than the other portions. Therefore, when the electrode body is arranged below the recess, The gas discharge valve may be blocked by the electrode body. In particular, in the case of a thin cell, there is a higher possibility that the gas discharge valve will be blocked by the laminated electrode body.
Therefore, in the lithium ion secondary battery 10 according to the present embodiment, the dimensions of the laminated electrode body 30 are set so that the gas discharge region 50 in which the laminated electrode body 30 is not arranged is formed below the recess 23 in the case 20. The accommodation position is adjusted. As a result, it is possible to reliably prevent the gas discharge valve 40 from being blocked from the inside by the laminated electrode body 30.

Although the present invention has been described above with respect to preferred embodiments, the above-described embodiments do not limit the present invention, and of course, various modifications can be made.
For example, in the above-described embodiment, the laminated electrode body 30 in which a plurality of sheet-shaped positive electrode 32, negative electrode 34, and separator 36 are laminated is used as the electrode body, but the structure of the electrode body is not particularly limited. As the electrode body, for example, a wound electrode body formed by winding a laminated body in which a long positive electrode, a negative electrode, and a separator are superposed in the longitudinal direction can also be used.
Further, in the above-described embodiment, the recess 23 is formed on the upper surface 20a of the case 20, but the position where the recess is formed may be any surface of the outer surface of the square case. Not particularly limited. For example, a recess for providing a gas discharge valve may be provided in the sealing plate.

10 Lithium-ion secondary battery 20 Case 20a Top surface of case (flat surface)
20b Outer edge of case 21 Case body 22 Sealing plate 23 Recess 23a Bottom surface of recess 23b Inner wall of recess 23c Opening 30 Electrode body (laminated electrode body)
30a Flat surface of electrode body 32 Positive electrode 34 Negative electrode 36 Separator 40 Gas discharge valve 42 Breaking groove 50 Gas discharge area X Lamination direction

Claims (1)

A sealed battery in which an electrode body having a positive electrode and a negative electrode and an electrolytic solution are housed in a square case, and the case is sealed.
A recess recessed toward the inside of the case is formed on any surface of the outer surface of the square case, and an opening is opened only on one surface of the inner wall of the recess toward the outside of the case. Along with the part
A sealed battery in which a gas discharge valve that opens when the internal pressure of the case rises above a predetermined level is formed on the bottom surface of the recess.

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