JP5569482B2 - Secondary battery cell case - Google Patents

Description

  The present invention relates to a secondary battery, and more particularly to a cell case of a secondary battery.

  In recent years, the demand for secondary batteries has increased due to an increase in environmental awareness. The secondary battery is modularized, for example, for use in a hybrid vehicle. One module is, for example, an electrode bundle in which a thin film-like positive electrode, negative electrode, and separator are overlapped and wound in a cell case and sealed together with an electrolytic solution. Thus, one battery cell is formed and a plurality of battery cells are bundled.

In such secondary batteries, a metal case is generally used as a cell case.
However, when a metal case is used, there is a problem that the weight of the secondary battery increases. In such a case, since the weight ratio of the cell case to the secondary battery weight increases, the weight energy density decreases.
In addition, the metal case has a problem that the temperature inside the cell is easily affected by the outside air temperature. It is known that when the temperature inside the cell becomes high due to the influence of the outside air temperature, the material constituting the electrode melts and the battery performance deteriorates. In addition, when the temperature inside the cell becomes low due to the influence of the outside air temperature, the reaction balance in the battery is lost, and the battery performance may be deteriorated.

  On the other hand, due to the demand for higher performance, smaller size, and lighter weight of secondary batteries, it is expected that the trend toward higher capacity and higher output of batteries will increase in the future. Therefore, in addition to solving the problems caused by the metal case described above, the use of a resin case has been studied as a means for realizing the above-described increase in capacity and output.

  For example, in Patent Document 1, as a battery case of a nickel-metal hydride battery, hydrogen molecules and water vapor are contained on a part of the outer surface of a side part of a resin battery case via a first resin layer serving as a binder. A second resin layer that serves as a gas barrier for preventing leakage is integrally formed, and a third resin layer that serves to protect the surface of the resin layer from corrosion is further formed thereon. It is disclosed.

Japanese Patent Laid-Open No. 2004-22455

  However, the resin cases currently under study have a problem that moisture tends to permeate from the outside if priority is given to the resistance to electrolyte. If water permeates, the non-aqueous electrolyte solution may react with water and storage stability may decrease, especially when the temperature rises, the amount of water permeation is large. Not in.

  Even in the invention disclosed in Patent Document 1, although a resin layer for preventing leakage of hydrogen molecules and water vapor is formed on a part of the outer surface of the case side portion, in a place other than the part where the resin layer is formed Has a problem that moisture permeation may occur.

  Furthermore, it is well known that in a secondary battery, the internal pressure rises as it is used, and the pressure is locally concentrated inside the case. There has been a problem that the structure may be deteriorated, for example, the substance may be detached, and the performance may be locally lowered.

  For this reason, the present invention can suppress the influence of the outside air temperature, prevent the permeation of moisture from the outside to the inside of the cell case, and can distribute the locally concentrated pressure inside the cell case. It aims at providing the cell case of a secondary battery.

The cell case of the secondary battery according to the first invention for solving the above-mentioned problems includes an outer layer made of resin and constituting the outer surface side, an inner layer made of resin and constituting the inner surface side, the outer layer and the inner layer, and an air-containing layer having a hollow portion provided between the hollow portion, the dispersion density of the air-containing layer in accordance with the temperature rise region of the battery is characterized by different of Rukoto.

  A cell case of a secondary battery according to a second invention for solving the above problem is characterized in that in the cell case of the secondary battery according to the first invention, the air-containing layer is made of resin or metal. And

The cell case of the secondary battery according to the third invention for solving the above-mentioned problem is the cell case of the secondary battery according to the first or second invention, wherein the outer layer is made of polystyrene, polyolefin, acrylic, polycarbonate It is a moisture permeation preventing layer made of methacryl, vinyl chloride, epoxy, polyester, or amorphous polyolefin.

A cell case of a secondary battery according to a fourth invention for solving the above-described problem is the cell case of the secondary battery according to any one of the first to third inventions, wherein the inner layer is made of polyolefin, polyimide, It is an electrolyte solution layer made of polyamideimide or polyetherimide.

According to the cell case of the secondary battery according to the first aspect described above, a hollow is provided between the outer layer made of resin and constituting the outer surface side, the inner layer made of resin and constituting the inner surface side, and the outer layer and the inner layer. Since the air-containing layer having the portion is provided, it is possible to suppress the influence of the outside air temperature, prevent the permeation of moisture from the outside, and disperse the locally concentrated pressure inside the case. In addition, by providing an air-containing layer, it is possible to prevent the permeation of moisture from the outside of the cell case, making it possible to use a resin for the outer layer and the inner layer, which is lighter than when using a metal case. Can be realized. In addition, since the hollow portion has a different dispersion density in the air-containing layer according to the temperature rise region of the battery, the influence of the outside air temperature can be efficiently reduced.

  According to the cell case of the secondary battery according to the second invention, since the air-containing layer is made of resin or metal, the air-containing layer can be easily formed.

According to the cell case of the secondary battery according to the third invention, the outer layer is a moisture permeation preventive layer made of polystyrene, polyolefin, acrylic, polycarbonate, methacryl, vinyl chloride, epoxy, polyester, or amorphous polyolefin. Permeation of moisture into the case can be more reliably prevented.

According to the cell case of the secondary battery according to the fourth invention, since the inner layer is an electrolyte-resistant layer made of polyolefin, polyimide, polyamideimide, or polyetherimide, the electrolyte layer leaks from the inside of the cell case. This can be prevented more reliably.

It is a perspective view which shows the cell case of the secondary battery which concerns on the Example of this invention. It is II-II sectional drawing of FIG. It is the III section enlarged view of FIG. It is the IV section enlarged view of FIG. It is a perspective view which shows an example of the positional relationship of the hollow part of the air content layer of the cell case of the secondary battery which concerns on the Example of this invention, and an electrode bundle.

  Hereinafter, the details of the cell case of the secondary battery according to the present invention will be described with reference to the drawings.

An embodiment of a cell case of a secondary battery according to the present invention will be described with reference to FIGS.
As shown in FIGS. 1 and 2, a cell (hereinafter referred to as a battery cell) 1 of a secondary battery according to the present embodiment is configured by putting an electrode bundle 2 in a cell case 3 and sealing with an electrolyte 4. Yes. At both upper ends of the battery cell 1, a positive electrode terminal 5 extending from the positive electrode and a negative electrode terminal 6 extending from the negative electrode are provided.

  As shown in FIG. 3, the electrode bundle 2 includes a thin-film positive electrode 21, a negative electrode 22, and a separator 23 sandwiched between the positive electrode 21 and the negative electrode 22 so as to insulate the positive electrode 21 and the negative electrode 22. It is made by wrapping things. The positive electrode 21 includes a positive electrode current collector 21a and a positive electrode active material 21b applied to both surfaces of the positive electrode current collector 21a, and the negative electrode 22 is applied to both surfaces of the negative electrode current collector 22a and the negative electrode current collector 22a. It is comprised from the negative electrode active material 22b.

  As shown in FIG. 4, the cell case 3 includes a first layer 31 as an outer layer constituting the outer surface side of the cell case 3, a second layer 32 as an air-containing layer positioned inside the first layer 31, And it has the three-layer structure which consists of the 3rd layer 33 as an inner layer which is located inside the 2nd layer 32 and comprises the inner surface side of the cell case 3. FIG. In other words, the second layer 32 is provided between the first layer 31 provided on the outer surface side of the cell case 3 and the third layer 33 provided on the inner surface side of the cell case 3.

  The first layer 31 is made of resin and is a moisture permeation preventing layer made of polyolefin so as not to permeate moisture, for example. The second layer 32 is made of, for example, a resin and is made of polyolefin so as not to transmit moisture, and has a large number of hollow portions 32a in the layer, like the first layer 31. The hollow portion 32a can be configured, for example, by forming bubbles by dispersing a large number of microcapsules in the layer. The third layer 33 is made of resin and is an electrolyte solution layer made of polystyrene so as to have an electrolyte solution resistance, for example.

  In the present embodiment, for the sake of convenience, the description has been given with the side on which the positive electrode terminal 5 and the negative electrode terminal 6 are provided as the upper side, but in actual use, which is positioned as the upper side is arbitrary.

  According to the secondary battery according to the above-described embodiment, a large number of hollow portions are formed between the first layer 31 constituting the outer surface side of the cell case 3 and the third layer 33 constituting the inner surface side of the cell case 3. By providing the second layer 32 having 32a, the permeation of moisture from the outside of the cell case 3 and the influence of the outside air temperature can be blocked in the second layer 32, and the internal pressure is absorbed by the hollow portion 32a. Localization of pressure can be prevented.

  Furthermore, if the first layer 31 and the second layer 32 are made of polyolefin that does not transmit moisture, and the third layer 33 is made of polystyrene having resistance to electrolyte, it is possible to more reliably transmit moisture from the outside of the cell case 3. In addition, it is possible to reliably prevent the electrolyte from leaking from the inside of the cell case 3. Moreover, it becomes possible to reduce the weight of the battery cell 1 by comprising the 1st layer 31 and the 3rd layer 33 with resin compared with the case where a metal case is used.

  4 shows an example in which the hollow portions 32a are uniformly dispersed in the second layer 32, the distribution of the hollow portions 32a is not limited to the example shown in FIG. The influence of pressure may be more efficiently reduced by dispersing a large amount of the hollow portion 32a in a portion having a relatively low rigidity. Further, since it is well known that the temperature of the central portion of the electrode bundle is likely to rise, as shown in FIG. 5, the central portion of the side surface of the cell case 3 corresponding to the central portion of the electrode bundle 2 corresponding to the temperature rising region ( A large amount of the hollow portions 32a may be dispersed in a portion surrounded by a one-dot chain line in FIG. Thus, the hollow part 32a can change a dispersion density according to the objective.

  Moreover, although the example which comprises the 2nd layer 32 from resin was shown in the Example mentioned above, the material which comprises the 2nd layer 32 is not limited to resin, For example, foil-like metal is formed in a waveform A second layer having a hollow portion between the first layer 31 and the third layer 33, such as by giving a hollow portion like corrugated paper by using a natural material such as wood or pumice containing air Any material can be used as long as it can be provided, and various modifications can be made without departing from the spirit of the present invention.

  Moreover, although the example which uses polyolefin as the material of the 1st layer 31 was shown, the material of the 1st layer 31 is not restricted to polyolefin, For example, acrylic, polycarbonate, methacryl, polystyrene, vinyl chloride, epoxy, polyester, amorphous polyolefin Etc. In addition, as a material of the first layer 31, it is more preferable to use a material that hardly transmits moisture.

  Moreover, although the example which uses a polystyrene as a material of the 3rd layer 33 was shown, the material of the 3rd layer 33 is not restricted to a polystyrene, For example, polyolefin, a polyimide, a polyamideimide, a polyetherimide, etc. may be sufficient. . In addition, as a material of the 3rd layer 33, it is more suitable if the material which has electrolyte solution resistance is used.

  The present invention is suitable for application to a cell case of a secondary battery.

DESCRIPTION OF SYMBOLS 1 Battery cell 2 Electrode bundle 3 Cell case 4 Electrolyte solution 5 Positive electrode terminal 6 Negative electrode terminal 21 Positive electrode 21a Positive electrode collector 21b Positive electrode active material 22 Negative electrode 22a Negative electrode collector 22b Negative electrode active material 23 Separator 31 1st layer (outer layer)
32 Second layer (air-containing layer)
32a Hollow part 33 3rd layer (inner layer)

Claims (4)

An outer layer made of resin and constituting the outer surface side;
An inner layer made of resin and constituting the inner surface side;
An air-containing layer provided between the outer layer and the inner layer and having a hollow portion ;
The hollow portion, the cell case of a secondary battery dispersion density in the air-containing layer in accordance with the temperature rise region of the battery is characterized by different of Rukoto. The cell case of the secondary battery according to claim 1, wherein the air-containing layer is made of resin or metal. The secondary battery according to claim 1 or 2 , wherein the outer layer is a moisture permeation preventive layer made of polystyrene, polyolefin, acrylic, polycarbonate, methacryl, vinyl chloride, epoxy, polyester, or amorphous polyolefin. Cell case. The cell case of the secondary battery according to any one of claims 1 to 3 , wherein the inner layer is an electrolyte solution layer made of polyolefin, polyimide, polyamideimide, or polyetherimide.

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