JP2017135025A - Sealed battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sealed battery which makes possible to reduce the occurrence of a defective weld by suppressing the rise in battery internal pressure in welding a sealing member with a lid member.SOLUTION: A secondary battery 10 comprises: an electrode body 12; a battery case 18 containing the electrode body 12 and having an opening face; a lid member 19 closing the opening face of the battery case 18; a liquid inlet 25 extending through the lid member 19; and a sealing member 31 fixed to the lid member 19 by welding for sealing the liquid inlet 25. In the secondary battery, a mesh part 41 is formed in the liquid inlet 25. Supposing that the air permeability of the mesh part 41 measured according to JIS L 1096 Air permeability A method (Frazier Type method) is Q, the following relation is satisfied: Q≤Vaporization volume[cc] of Electrolyte/{Liquid inlet area [cm]×Welding time [sec]}.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a sealed battery in which an electrode body and an electrolytic solution are enclosed in a battery case. More specifically, the present invention relates to a sealed battery that is sealed by injecting an electrolyte from a liquid injection hole into a battery case and then sealing the liquid injection hole with a sealing member.

  Conventionally, there is a sealed battery in which an electrolytic solution is injected into a battery case containing an electrode body, and a liquid injection hole is sealed. For example, there is a secondary battery using a flat rectangular metal battery case in which a liquid injection hole is provided in a lid member that closes an opening surface of the battery case. And at the time of manufacture of a battery, the cover member in which the injection hole was formed is fixed to a battery case, and electrolyte solution is injected in a battery case from an injection hole. After the injection, the metal sealing member is placed over the injection hole, and the periphery of the sealing member and the lid member (the periphery of the injection hole) are welded without any gaps, so that the injection hole There is a sealed battery (see Patent Document 1).

JP 2014-026865 A

  However, in the above-described sealed battery, if the electrolyte is adhered to the back surface of the lid member after the electrolyte is injected into the battery case, the heat input during laser welding of the sealing member and the lid member There is a risk that the electrolyte attached to the lid member may evaporate. When the electrolytic solution evaporates, as shown in FIG. 7, the battery internal pressure increases and the electrolytic solution (gas) vaporized passes through the injection hole, and an excessive force is applied to the welded portion, and the welded portion is deformed. (Which was pushed up) could result in poor welding.

  Therefore, the present invention has been made to solve the above-described problems, and suppresses the application of excessive force to the welded portion when welding the sealing member and the lid member, thereby preventing poor welding. It aims at providing the sealed battery which can reduce generation | occurrence | production.

One aspect of the present invention made to solve the above problems includes an electrode body, a battery case that houses the electrode body and includes an opening surface, a lid member that closes the opening surface of the battery case, and the lid In a sealed battery having a liquid injection hole penetrating a member and a sealing member fixed to the lid member by welding to seal the liquid injection hole, a mesh portion is formed in the liquid injection hole The air permeability Q of the mesh part measured by JIS L 1096 air permeability A method (Fragile type method) is:
Q ≦ Vaporization volume of electrolytic solution [cc] / {Cross sectional area of injection hole [cm ² ] × welding time [sec]}
It is characterized by satisfying the following relationship.
Note that the vaporization volume of the electrolytic solution is the volume of the electrolytic solution vaporized when the sealing member is welded to the lid member, and the welding time is the time required to weld the sealing member to the lid member. .

  In this sealed battery, since the mesh portion is formed in the injection hole, and the air permeability Q of the mesh portion satisfies the above relationship, the electrolyte attached to the back surface of the lid member is separated from the sealing member. Even if it evaporates due to heat input during welding with the lid member, it is possible to prevent all of the evaporated electrolyte (gas) from passing through the mesh portion (liquid injection hole) until the end of welding. That is, a part of the gas derived from the electrolyte vaporized within the welding time can be kept in the battery container until the end of welding. As a result, even if the electrolytic solution evaporates due to heat input during welding between the sealing member and the lid member, it is difficult to apply an extra force to the welded portion, and the welded portion is prevented from being deformed (pushed up). Can do. Therefore, the sealing member and the lid member can be favorably welded, and the occurrence of poor welding can be reduced.

  Note that the air permeability of the mesh portion is desirably set as high as possible while satisfying the above relationship. Thus, by setting the air permeability of the mesh part, liquid injection property (liquid injection efficiency) can also be ensured.

  According to the sealed battery according to the present invention, as described above, it is possible to prevent an excessive force from being applied to the welded portion when welding the sealing member and the lid member, thereby reducing the occurrence of poor welding. Can do.

It is sectional drawing which shows schematic structure of the secondary battery which concerns on embodiment. It is a perspective view which shows a cover member. It is an expanded sectional view around a liquid injection hole. It is a top view of a mesh member. It is a figure which shows the modification of a mesh member. It is a figure which shows another modification of a mesh member. It is an expanded sectional view around the injection hole in the conventional sealed battery.

  DESCRIPTION OF EMBODIMENTS Hereinafter, an embodiment embodying a sealed battery of the present invention will be described in detail with reference to the drawings. In this embodiment, a case where the present invention is applied to a sealed lithium ion secondary battery in which an electrode body and an electrolytic solution are sealed in a rectangular metal case will be described. Then, the lithium ion secondary battery which concerns on this embodiment is demonstrated, referring FIGS. 1-4.

  As shown in FIG. 1, the secondary battery 10 according to the present embodiment is a sealed battery in which an electrode body 12 and an electrolytic solution 13 are enclosed in a battery container 11. The battery container 11 is made of metal and has a flat rectangular box shape.

  The electrode body 12 of this embodiment is a wound body in which a belt-like positive electrode plate and a belt-like negative electrode plate are wound with a belt-like separator interposed therebetween. The positive electrode plate of this embodiment has a positive electrode active material layer formed on both sides of an aluminum foil. The positive electrode active material layer includes a positive electrode mixture of a positive electrode active material capable of inserting and extracting lithium ions. For example, a lithium-containing metal oxide kneaded with a binder and a dispersion solvent is used. be able to. In the present embodiment, the negative electrode plate is obtained by forming a negative electrode active material layer on both surfaces of a copper foil. The negative electrode active material layer includes a carbon material and the like.

  The secondary battery 10 has a positive electrode terminal 15 and a negative electrode terminal 16 which are provided so as to protrude outside the battery container 11. The positive electrode terminal 15 is connected to the positive electrode plate of the electrode body 12 inside the battery container 11. The negative electrode terminal 16 is connected to the negative electrode plate of the electrode body 12 inside the battery container 11. The electrolytic solution 13 is obtained by dissolving an electrolyte in an organic solvent. In this embodiment, ethyl methyl carbonate (EMC) and dimethyl carbonate (DMC) are used as the organic solvent.

  As shown in FIG. 1, the battery container 11 includes a substantially rectangular parallelepiped battery case 18 whose one surface is open and a lid member 19 that closes the opening surface. The battery case 18 and the lid member 19 are fixed to each other by being welded around the entire circumference of the lid member 19 without a gap.

  And the cover member 19 before attachment is an elongate plate-shaped member in which several holes etc. were formed, as shown in FIG. The lid member 19 is made of, for example, an aluminum plate having a thickness of about 1 mm. Through holes 21 and 22 are formed at both ends of the lid member 19 in the longitudinal direction. The through hole 21 is for penetrating the positive electrode terminal 15 (see FIG. 1). The through hole 22 is for penetrating the negative electrode terminal 16 (see FIG. 1).

An oval safety valve 23 is formed near the center of the lid member 19. The safety valve 23 is not penetrating but is a portion formed thinner than other portions. When the internal pressure of the battery container 11 becomes higher than the opening pressure of the safety valve 23, the safety valve 23 is broken and opened, and the gas or the like increasing the internal pressure is released to the outside. A liquid injection hole 25 is formed next to the safety valve 23 through the lid member 19. The liquid injection hole 25 is a hole for injecting the electrolytic solution 13 into the assembled battery container 11. In the present embodiment, for example, the diameter of the liquid injection hole 25 is 4.0 mm, and the cross-sectional area S is S = 0.04π [cm ² ].

  In the secondary battery 10 of the present embodiment, a sealing member 31 is attached to the liquid injection hole 25 as shown in FIG. Specifically, as shown in FIG. 3, the sealing member 31 is disposed so as to cover the liquid injection hole 25 from the outside, and the periphery of the sealing member 31 and the lid member 19 (the periphery of the liquid injection hole 25) are arranged. The welded portion 35 is welded without a gap. Thereby, the injection hole 25 is sealed by the sealing member 31.

  The welding may be performed by continuous spot welding or seamless welding using, for example, a YAG laser, a fiber laser, or an electron beam. From the viewpoint of ease of welding, the sealing member 31 is preferably made of the same material as the lid member 19.

The battery container 11 is sealed by welding the sealing member 31 and the lid member 19 and by welding the battery case 18 and the lid member 19 described above. Therefore, if the welding between the sealing member 31 and the lid member 19 is poor, there is a possibility that liquid leakage occurs.
Here, when the electrolytic solution 13 is adhered to the back surface of the lid member 19 after the electrolytic solution 13 is injected into the battery container 11, due to heat input when welding the sealing member 31 and the lid member 19, The electrolytic solution 13 attached to the lid member 19 evaporates. When the electrolytic solution 13 is vaporized, the internal pressure of the battery container 11 is increased, an extra force is applied to the welded portion 35, and the welded portion 35 is deformed (pushed up) to cause poor welding ( (See FIG. 7).

  Therefore, in the secondary battery 10 of the present embodiment, as shown in FIG. 3, the mesh member 40 is provided in the liquid injection hole 25. As shown in FIGS. 3 and 4, the mesh member 40 has a disk shape, and the mesh portion 41 is fixed to the lid member 19 so as to cover the opening of the liquid injection hole 25.

  Here, the mesh member 40 is not limited to the one shown in FIGS. 3 and 4. For example, as shown in FIG. 5, the mesh member 40 a fixed to the outer wall side of the lid member 19 (the liquid injection hole 25). It may be. Moreover, the mesh part 41 may be distorted like the mesh member 40a. Further, as shown in FIG. 6, the mesh portion 41 may be formed integrally with the lid member 19.

And the air permeability Q of the mesh part 41 measured by JIS L 1096 air permeability A method (fragile type method) satisfies the following relationship.
Q ≦ Volume of electrolytic solution [cc] / {area of injection hole [cm ² ] × welding time [sec]}

  By setting the air permeability Q of the mesh portion 41 in this way, even if the electrolyte solution 13 evaporates due to heat input during welding of the sealing member 31 and the lid member 19, as shown in FIG. Thus, all of the evaporated electrolyte (gas) does not pass through the mesh portion 41 (the liquid injection hole 25) by the end of welding. That is, a part of the gas derived from the electrolyte vaporized within the welding time can be kept in the battery container 11 (inside the liquid injection hole 25) until the end of welding. Thereby, since the raise of the internal pressure in the welding part 35 can be suppressed, it becomes difficult to apply excessive force to the welding part 35, and it can suppress that the welding part 35 deform | transforms (pushes up). Therefore, the sealing member 31 and the lid member 19 can be favorably welded, and the occurrence of poor welding can be reduced. Thereby, generation | occurrence | production of the liquid leakage from the liquid injection hole 25 can be prevented.

  And it is desirable for the air permeability Q of the mesh part 41 to be set as high as possible while satisfying the above relationship. This is because when the air permeability Q of the mesh portion 41 is set in this way, it is possible to ensure the liquid injection property (liquid injection efficiency) when the electrolyte solution 13 is injected into the battery container 11.

Here, the vaporization volume V of the electrolytic solution 13 is based on the state equation of gas,
Vaporization volume V = (evaporation amount w × gas constant R × temperature T) / (pressure P × molecular weight M)
Can be calculated.
Note that the evaporation amount w [g] is the amount of the electrolyte solution 13 evaporated and vaporized when the sealing member 31 is welded out of the electrolyte solution 13 attached to the lid member 19.

  The evaporation amount w [g] can be calculated by subtracting the weight of the lid member 19 in the battery container 11 immediately after welding from the weight of the lid member 19 in the battery container 11 immediately after welding after the injection. . Since the amount of evaporation is considered to be substantially constant for batteries of the same specification, the amount of evaporation w [g] may be obtained in advance using a test battery container. In this embodiment, the evaporation amount w [g] is set to w = 0.03 [g] as an example.

  In this embodiment, as an example, ethylmethyl carbonate (EMC) and dimethyl carbonate (DMC) are used as the organic solvent of the electrolytic solution 13. Therefore, the molecular weight M [g / mol] is set to M = 100 [g / mol] using the average molecular weight.

As conditions for welding the sealing member 31 to the lid member 19, if the temperature T is 100 ° C. and T = 373 [K] and the pressure P is atmospheric pressure and P = 101300 [Pa], then the sealing member The vaporization volume V [cc] of the electrolytic solution 13 that evaporates when 31 is welded to the lid member 19 is calculated as follows.
V = (0.03 [g] × 8.31 [Pa · m ³ / mol · K] × 373 [K])
/ (101300 [Pa] × 100 [g / mol])
= 9.17956 [cc]

Therefore, in the secondary battery 10 of the present embodiment, since the welding time of the sealing member 31 is 0.2 sec, the air permeability Q of the mesh portion 41 is
Q = (9.17956 [cc] / (0.04π [cm ² ] × 0.2 [sec])
= 365.429 [cc / cm ² / sec]
It becomes. Therefore, in the secondary battery 10, the air permeability Q of the mesh portion 41 in the mesh member 40 provided in the liquid injection hole 25 may be 365 [cc / cm ² / sec] or less.

In the secondary battery 10, the air permeability Q of the mesh portion 41 is, for example, Q = 365 [cc / cm ² / sec] in order to ensure the liquid injection property. Thereby, in the secondary battery 10, the entire evaporation amount w of the electrolytic solution 13 does not pass through the mesh portion 41. Therefore, according to the secondary battery 10, it is possible to prevent an extra force from being applied to the sealing member 31 during welding of the sealing member 31 while ensuring the liquid injection property, thereby reducing the occurrence of poor welding. can do.

  As described above, according to the secondary battery 10 according to the present embodiment, the mesh portion 41 is formed in the liquid injection hole 25, and measurement was performed by the JIS L 1096 breathability A method (Fragile method). Since the air permeability Q of the mesh portion 41 satisfies the above predetermined relationship, the electrolytic solution 13 attached to the back surface of the lid member 19 evaporates due to heat input during welding of the sealing member 31 and the lid member 19. Even so, it is possible to prevent all of the evaporated electrolyte (gas) from passing through the mesh portion 41 (the liquid injection hole 25) until the end of welding. Therefore, even if the electrolyte solution 13 evaporates due to heat input during welding between the sealing member 31 and the lid member 19, no excessive force is applied to the welded portion 35, and the welded portion 35 is deformed (pushed up). Can be suppressed. Therefore, the sealing member 31 and the lid member 19 can be favorably welded, and the occurrence of poor welding can be reduced.

  It should be noted that the above-described embodiment is merely an example and does not limit the present invention in any way, and various improvements and modifications can be made without departing from the scope of the invention.

DESCRIPTION OF SYMBOLS 10 Secondary battery 11 Battery container 12 Electrode body 13 Electrolyte 18 Battery case 19 Lid member 25 Injection hole 31 Sealing member 35 Welding part 40 Mesh member 41 Mesh part

Claims (1)

An electrode body, a battery case that houses the electrode body and includes an opening surface, a lid member that closes the opening surface of the battery case, a liquid injection hole that penetrates the lid member, and a seal for sealing the liquid injection hole In a sealed battery having a sealing member fixed to the lid member by welding to
A mesh portion is formed in the liquid injection hole,
When the air permeability of the mesh portion measured by JIS L 1096 air permeability A method (fragile type method) is Q,
Q ≦ Volume of electrolytic solution [cc] / {area of injection hole [cm ² ] × welding time [sec]}
A sealed battery characterized by satisfying the following relationship.

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