JP2018152164A - Sealed battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sealed battery which can inhibit increase of a case internal pressure caused by a gas occurring during charing/discharging without reducing the cubic volume of an electrode body relative to the internal capacity of a case.SOLUTION: In a sealed battery 100 disclosed herein, an electrode terminal 30 is provided at a case 10. The electrode terminal 30 of the sealed battery 100 includes: a collector member 32 in which a lower end 32a is electrically connected with an electrode body 20 in the case 10 and an upper end 32b is exposed to the outside of the case 10; and an insulative sealing member 38 which is disposed between the collector member 32 and the case 10 and seals the interior of the case 10. In the sealed battery 100 disclosed herein, the sealing member 38 is formed by a gas permeability resin. A gas conversion catalyst 40 which converts a non-permeable gas to a permeable gas is disposed in the case.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a sealed battery in which an electrode body and an electrolytic solution are accommodated in a case, and an electrode terminal is provided in the case.

  Secondary batteries such as lithium ion secondary batteries and nickel metal hydride batteries are becoming increasingly important as on-vehicle power supplies or personal computers and portable terminals. Such a secondary battery is constructed, for example, as a sealed battery in which an electrode body and an electrolytic solution are accommodated in a case, and electrode terminals are provided in the case.

  In this sealed battery, a part of the electrolytic solution is decomposed during charging and discharging, and an SEI film forming reaction in which gas is generated while an SEI film made of the decomposition product is formed on the surface of the negative electrode may occur. When such a SEI film forming reaction occurs, the generated gas may increase the internal pressure of the case and cause deformation or breakage of the case. For this reason, various techniques have been conventionally proposed that can prevent deformation and breakage of the case even when gas is generated in the case during charging and discharging.

  For example, Patent Document 1 discloses a technique in which a phosphonoacetate compound is included in an electrolytic solution, and a recess that is recessed inward is provided on the side surface of the case. In the technique described in Patent Document 1, the generation of gas can be suppressed by the phosphonoacetate compound, and the deformation of the case can be suppressed by the concave portion on the side surface of the case. Patent Document 2 discloses a technique in which a gas pocket is provided in a case, and gas generated by charging / discharging is sent to the gas pocket to suppress deformation of the case.

Patent 5913611 Japanese Patent Laid-Open No. 2006-9679

However, in the case of the technology for forming the recesses and gas pockets as described above, it is necessary to reduce the volume of the electrode body with respect to the internal capacity of the case, which causes a problem that battery performance such as energy density is lowered.
The present invention has been made in view of such points, and its main purpose is to suppress an increase in case internal pressure due to the generation of gas during charge and discharge without reducing the volume of the electrode body relative to the case internal capacity. It is an object of the present invention to provide a sealed battery that can be used.

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

The sealed battery disclosed here is a sealed battery in which an electrode body and an electrolytic solution are accommodated in a case, and electrode terminals connected to external devices are provided in the case.
The electrode terminal of the sealed battery has a current collecting member having one end electrically connected to the electrode body in the case and the other end exposed to the outside of the case, a current collecting member, And an insulating sealing member that is disposed between the case and seals the inside of the case.
Here, in the above-described sealed battery, the sealing member is made of a gas permeable resin, and a gas permeable to a non-permeable gas that hardly permeates the gas permeable resin out of the gas generated by charging and discharging. A conversion catalyst that converts the resin into a permeable gas that easily permeates is disposed in the case.

In contrast to the conventional technique, the present inventor, for the above-mentioned problems, can discharge the gas generated during charging / discharging without reducing the volume of the electrode body, as long as the gas generated by charging / discharging can be discharged to the outside of the case. We thought that deformation of the case could be prevented.
As a result of various studies on a structure that can appropriately discharge the gas in the case, the inventors have come to think that a gas permeable resin is used for the sealing member attached to the electrode terminal.
Specifically, a sealing member is attached to the electrode terminal of the sealed battery to insulate the current collecting member from the case and prevent the electrolyte in the case from leaking outside. If the inventor uses a gas permeable resin that allows gas to pass through the sealing member, the gas inside the case can be discharged to the outside through the sealing member. It was thought that the rise in

However, when a sealed battery having a sealing member made of a gas permeable resin was actually manufactured and tested, the gas in the case was not efficiently discharged, and the increase in the internal pressure of the case could not be sufficiently suppressed. The result was obtained.
As a result of further examination of the cause of the problem, the present inventor may include a gas (non-permeable gas) that is difficult to permeate the gas-permeable resin in the gas generated by charging / discharging. It has been found that when a large amount of reactive gas is generated, the gas in the case cannot be efficiently discharged even though the gas permeable resin is used for the sealing member.

The sealed battery disclosed here is based on the above-described knowledge, and converts a non-permeable gas that does not easily pass through the gas-permeable resin into a permeable gas that easily passes through the gas-permeable resin. A gas conversion catalyst is mounted in the battery case.
Thereby, even when non-permeable gas is generated by charging / discharging, the non-permeable gas is converted to permeable gas, and the gas in the case is efficiently discharged to the outside through the sealing member. Can increase the internal pressure of the case due to the generation of gas during charging and discharging.

For example, in a sealed battery in which carbon dioxide (CO ₂ ) and carbon monoxide (CO) are generated during charging and discharging, polyethylene, perfluoroalkoxyalkane, or the like is used as a gas-permeable resin that allows CO ₂ gas to permeate. . Pt / SnO ₂ or the like is used as a gas conversion catalyst that converts CO gas into CO ₂ gas.

It is a figure which shows typically the sealed battery which concerns on one Embodiment of this invention. It is sectional drawing of the electrode terminal vicinity of the sealed battery shown in FIG. 6 is a graph showing measurement results of case internal pressure in Test Example 1; 6 is a graph showing a measurement result of a case internal pressure in Test Example 2. 10 is a graph showing measurement results of case internal pressure in Test Example 3.

  Hereinafter, a lithium ion secondary battery will be described as an example of a sealed battery according to an embodiment of the present invention. In the drawings referred to in the following description, the same reference numerals are given to members / parts having the same action. In addition, the dimensional relationship (length, width, thickness, etc.) in each drawing does not reflect the actual dimensional relationship. Further, matters other than the matters specifically mentioned in the present specification and necessary for the implementation of the present invention (for example, the configuration of the electrode body and the electrolytic solution) can be obtained by those skilled in the art based on the prior art in this field. It can be grasped as a design matter.

1. Overall Configuration FIG. 1 is a diagram schematically showing a sealed battery according to this embodiment. As shown in FIG. 1, in the sealed battery 100 according to this embodiment, an electrode body 20 and an electrolytic solution (not shown) are accommodated in a rectangular case 10. The case 10 of the sealed battery 100 includes a flat rectangular case main body 12 having an open upper surface and a plate-like lid body 14 that closes the opening on the upper surface of the case main body 12. In addition, the lid body 14 is provided with a liquid injection port 15 for injecting an electrolytic solution into the case 10. In addition, it is preferable that the case 10 is mainly composed of a metal material that is lightweight and has good thermal conductivity, such as aluminum.

  Although not specifically illustrated, the electrode body 20 in the present embodiment includes a long sheet-like positive electrode in which a positive electrode mixture layer is provided on the surface of a foil-like positive electrode current collector, and a foil-like negative electrode current collector. Formed by laminating the sheet-like positive electrode and the negative electrode through a separator, and winding the laminate. Has been. In addition, a wound core portion 20A is formed in the center portion of the electrode body 20 in the width direction X so that the positive electrode and negative electrode mixture layers face each other, and no mixture layer is provided on both side edges. A terminal connection portion 20B around which the current collector is wound is formed.

  In the sealed battery 100 according to the present embodiment, the material of each member (for example, the positive electrode, the negative electrode, and the separator) constituting the electrode body 20 is the same as that used for a conventional general lithium ion secondary battery. The present invention can be used without limitation, and does not characterize the present invention. Similarly, with respect to the solvent and supporting salt used in the electrolytic solution, since a general material can be used without any particular limitation, detailed description thereof is omitted.

  In the sealed battery 100 according to this embodiment, the electrode terminal 30 that is electrically connected to an external device such as a motor is provided on the lid body 14 that forms the upper surface of the case 10. Hereinafter, a specific structure of the electrode terminal 30 in the present embodiment will be described.

2. Electrode Terminal FIG. 2 is a cross-sectional view of the vicinity of the electrode terminal of the sealed battery shown in FIG. As shown in FIGS. 1 and 2, the electrode terminal 30 of the sealed battery 100 according to the present embodiment includes a current collecting member 32, a bolt 34, an external connection member 36, and a sealing member 38. Yes. Hereinafter, each member which comprises the electrode terminal 30 is demonstrated.

(1) Current Collection Member The current collection member 32 is a long conductive member that extends in the height direction Z of the sealed battery 100. The lower end 32 a of the current collecting member 32 is electrically connected to the terminal connection portion 20 </ b> B of the electrode body 20 in the case 10, and the upper end 32 b is exposed to the outside of the case 10. Specifically, as shown in FIG. 2, the upper end 32 b of the current collecting member 32 penetrates each of the lid body 14, the sealing member 38, and the external connection member 36 and is exposed to the outside of the case 10. The sealing member 38 and the external connection member 36 are fixed to the lid 14 of the case 10 by caulking the upper end 32 b of the current collecting member 32. Examples of the conductive material used for the current collecting member 32 include aluminum.

(2) Bolt As shown in FIG. 1, the bolt 34 is a columnar conductive member erected in the height direction Z of the sealed battery 100 outside the case 10. A thread groove (not shown) is formed on the outer peripheral surface of the columnar bolt 34 so that it can be connected to an external device. The bolt 34 can be preferably made of the same material as that of the current collecting member 32 described above.

(3) External Connection Member The external connection member 36 is a plate-like conductive member that electrically connects the current collecting member 32 and the bolt 34 outside the case 10. Specifically, the external connection member 36 extends along the width direction X (see FIG. 1) of the sealed battery so as to electrically connect the current collecting member 32 and the bolt 34. For the external connection member 36, the same kind of conductive material as that of the current collecting member 32 can be used.

(4) Sealing member As shown in FIG. 2, the sealing member 38 is an insulating member that is disposed between the current collecting member 32 and the case 10 (lid 14) and seals the inside of the case 10. is there. The sealing member 38 in the present embodiment includes an insulating holder 37 and an internal sealing material 39.
Specifically, the insulating holder 37 is disposed on the upper surface of the lid body 14, and each of the conductive members (the current collecting member 32, the bolt 34, and the external connection member 36) described above is connected to the lid body 14 of the case 10. Preventing energization. The insulating holder 37 is formed with a first insertion hole 37a through which the upper end 32b of the current collecting member 32 is inserted.
On the other hand, the inner sealing material 39 is disposed between the lid body 14 and the current collecting member 32 inside the case 10 (below the lid body 14). The inner sealing material 39 is formed with a second insertion hole 39a through which the upper end 32b of the current collecting member 32 is inserted, and a cylindrical protrusion 39b is provided around the second insertion hole 39a. The protrusion 39 b of the inner seal material 39 is inserted into the third insertion hole 14 a of the lid body 14 and is crimped to the bottom surface of the insulating holder 38. Thus, a sealing member 38 that insulates the current collecting member 32 and the lid body 14 and seals the inside of the case 10 is formed.

And in the sealed battery 100 which concerns on this embodiment, the sealing member 38 (the insulation holder 37 and the internal sealing material 39) is comprised with the gas-permeable resin.
Such a gas permeable resin can be appropriately selected according to the type of gas mainly generated in the case 10 during charging and discharging. For example, in the case of a lithium ion secondary battery, carbon dioxide (CO ₂ ) is mainly generated by the SEI film formation reaction during charging / discharging, and therefore the gas permeable resin suitably transmits the CO ₂ gas. A resin material that can be used is used. Examples of the gas permeable resin that suitably transmits CO ₂ gas include polyolefin resins such as polyethylene and polypropylene, and fluorine resins such as perfluoroalkoxyalkane (PFA) and polytetrafluoroethylene (PTFE).

When the gas permeable resin described above is used for the sealing member 38, as shown in FIG. 2, a gas discharge path A is formed in the sealing member 38, and the CO ₂ gas in the case 10 passes through the gas discharge path A. Is discharged out of the case 10. The gas permeation speed in the sealing member 38 can be calculated based on the following equation. The “gas permeability coefficient” in the following formula can be calculated based on a differential pressure method based on JIS K 7126.
Permeation speed = gas permeation coefficient x pressure difference x (cross-sectional area of sealing member / length of gas discharge path)

(5) Gas Conversion Catalyst Furthermore, as shown in FIG. 1, in the sealed battery 100 according to the present embodiment, a gas conversion catalyst 40 is disposed in the case 10. Since the gas conversion catalyst 40 includes a metal catalyst that converts a non-permeable gas into a permeable gas among the gases generated by charging and discharging, the gas generated by charging and discharging is passed through the sealing member 38. It can be suitably discharged out of the case 10. For this reason, it can prevent suitably that case 10 internal pressure rises during charging / discharging, and the said case 10 deform | transforms and breaks.

The catalytic metal used for the gas conversion catalyst 40 described above can be appropriately selected according to the type of the non-permeable gas generated in the case 10 during charging and discharging. For example, in charging / discharging of a lithium ion secondary battery, carbon monoxide (CO) may be generated in addition to the above-described carbon dioxide (CO ₂ ), and this CO gas may be a polyolefin resin or a fluorine resin. Hard to permeate gas permeable resin. In such a case, a metal catalyst that can convert CO gas, which is a non-permeable gas, into CO ₂ gas, which is a permeable gas, is used for the gas conversion catalyst 40. Examples of the metal catalyst for converting the CO gas into CO ₂ gas include, for example, a composite material (Pt / SnO ₂ , Pd / CeO _2, etc.) of a noble metal and an easily reducible metal oxide, a gold nanoparticle catalyst (Au / _{TiO 2, Au / Fe 2 O} 3 , etc.) and the like.

  Note that contact between the electrolytic solution (not shown) accommodated in the case 10 and the gas conversion catalyst 40 may cause problems such as reduction in gas conversion efficiency, and thus the gas conversion catalyst 40 and the electrolytic solution are in contact with each other. It is preferable to provide various structures that do not. For example, the gas conversion catalyst 40 is preferably attached to the lid 14 on the upper surface of the case 10 as shown in FIG.

  Moreover, in order to prevent the contact between the gas conversion catalyst 40 and the electrolytic solution, the gas conversion catalyst 40 may be covered with a resin film. As such a resin film, a film is used that is configured to block the electrolytic solution and allow the permeable gas and the non-permeable gas to permeate. For such a resin film, for example, a resin material such as polyethylene or polypropylene is used. In addition, it is preferable to set the thickness of a resin film in the range of 10 micrometers-200 micrometers.

3. Other Embodiments Although one embodiment of the sealed battery disclosed herein has been described, the present invention is not limited to the above-described embodiment, and various structures can be changed.

  For example, in the above-described embodiment, the lithium ion secondary battery has been described as an example of the sealed battery disclosed herein. However, the sealed battery disclosed herein is not limited to the lithium ion secondary battery. A nickel metal hydride battery may be used. When the present invention is applied to a battery other than a lithium ion secondary battery, the gas permeable resin constituting the sealing member 38 and the gas conversion catalyst 40 are used according to the type of gas generated during charging and discharging. It is preferable to variously change the metal catalyst.

[Test example]
Hereinafter, tests related to the present invention will be described. However, the following description is not intended to limit the present invention.

1. Each test example (1) Test example 1
In Test Example 1, an electrode terminal using perfluoroalkoxyalkane (PFA) as a sealing member for the electrode terminal was produced, and the produced electrode terminal was attached to an empty case in which the electrode body and the electrolytic solution were not accommodated. A test pack was prepared. Then, the case of the test pack was connected to a gas supply device, and CO gas was introduced into the case at a predetermined flow rate from the gas supply device for 6 months. Note that the gas flow rate here was set to a flow rate at which the internal pressure of the case was 250% six months after the start of gas introduction, as shown in FIG.

(2) Test example 2
In Test Example 2, as in Test Example 1, a test pack in which PFA was used as the electrode terminal sealing member was produced. In the test pack of Test Example 2, a mixed gas in which CO and CO ₂ were mixed at a ratio of 1: 1 was introduced into the case for 6 months at the same flow rate as in Test Example 1.

(3) Test example 3
In Test Example 3, the gas conversion catalyst (Au / Fe ₂ O ₃ ) that converts CO gas into CO ₂ gas was placed in the case, and the test was performed under the same conditions as Test Example 1 and Test Example 2. A pack was made. Then, as in Test Example 2, a mixed gas in which CO and CO ₂ were mixed at a ratio of 1: 1 was introduced into the case.

2. Evaluation Test During the above-described gas introduction period (6 months), the case internal pressure of each test pack was measured daily to examine the rate of increase in internal pressure of the case. FIG. 3 shows the internal pressure increase rate of the case internal pressure in Test Example 1, FIG. 4 shows the measurement result of the internal pressure increase rate in Test Example 2, and FIG. 5 shows the measurement result of the internal pressure increase rate in Test Example 3. In addition, the numerical value of the vertical axis | shaft of FIGS. 3-5 has shown the ratio at the time of setting the case internal pressure of the test pack of the test example 1 of the test example 1 month after a test start to 100%.

As shown in FIG. 3 and FIG. 4, comparing Test Example 1 and Test Example 2, the case internal pressure of Test Example 2 was slightly lower. However, the case internal pressure in Test Example 2 is also a value that may cause deformation or breakage in the case, and it is difficult to say that the increase in internal pressure is sufficiently suppressed. And as a result of examining the gas partial pressure in the case of Test Example 2, in Test Example 2, the pressure of CO ₂ gas was increased while the pressure of CO ₂ gas was decreased. From these results, it was confirmed that when PFA is used for the electrode terminal sealing member, the CO ₂ gas in the case can be discharged to the outside, but the CO gas cannot be discharged.

On the other hand, as shown in FIG. 5, in Test Example 3, the increase in the case internal pressure was appropriately suppressed, and deformation and breakage due to the increase in the internal pressure were suitably prevented. As a result of examining the partial pressure of the gas in Test Example 3, no CO gas was present in the case of Test Example 3, and the CO gas was converted to CO ₂ gas. Therefore, the CO gas is converted to CO ₂ gas by placing the Au / _Fe 2 _{O 3} is a gas conversion catalyst into the case, since the CO ₂ gas can be appropriately discharged from the sealing member made of PFA It has been found that deformation and breakage of the case due to an increase in the internal pressure of the case can be suitably prevented.

  As mentioned above, although the specific example of this invention was demonstrated in detail, these are only illustrations and do not limit a claim. The technology described in the claims includes various modifications and changes of the specific examples illustrated above.

DESCRIPTION OF SYMBOLS 10 Case 12 Case main body 14 Cover body 14a 3rd insertion hole 15 Injection hole 20 Electrode body 20A Winding core part 20B Terminal connection part 30 Electrode terminal 32 Current collecting member 32a Lower end of current collecting member 32b Upper end of current collecting member 34 Bolt 36 External Connection Member 37 Insulating Holder 37a First Insertion Hole 38 Sealing Member 39 Internal Seal Material 39a Second Insertion Hole 39b Protrusion 40 Gas Conversion Catalyst 100 Sealed Battery A Gas Discharge Path X Width Direction Z Height Direction

Claims (1)

An electrode body and an electrolytic solution are accommodated in the case, and an electrode terminal connected to an external device is a sealed battery provided in the case,
The electrode terminal is
A current collecting member having one end electrically connected to the electrode body in the case and the other end exposed to the outside of the case;
An insulating sealing member disposed between the current collecting member and the case and sealing the inside of the case;
Here, the sealing member is made of a gas permeable resin, and a non-permeable gas that hardly permeates the gas permeable resin out of the gas generated by charging and discharging is transmitted through the gas permeable resin. A sealed battery in which a gas conversion catalyst that converts easily into a permeable gas is disposed in the case.

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