Gas collection method

Abstract

Provided is a collection method with which gas can easily be collected from a sealed body inside of which contents are sealed, without diluting the gas inside A gas collection method according to the present invention is a method for collecting gas in a laminated battery 1 comprising a cell structure 2 and a bag-shaped film 3 that houses the cell structure 2, and a space 10 that contains gas discharged from the cell structure 2 is present inside of the bag-shaped film 3. The gas collection method includes: an attachment step for attaching an elastic body 11 to the outer surface of the bag-shaped film 3; and a suction step for placing the tip end of a suction tube 17 into the space 10 so as to penetrate the elastic body 11, and sucking gas from the suction tube 17.

Description

Gas sampling method

[0001] The present invention relates to a method for sampling gas present inside a sealed body.

[0002] Lithium-ion batteries, with their high energy density and ability to be miniaturized and increase power output, are seeing growing demand for them in applications such as electric vehicles and home energy storage. Lithium-ion batteries can generate gas due to the decomposition of the electrolyte during charging and discharging, or due to internal reactions of moisture remaining during manufacturing. If a large amount of gas is generated and the internal pressure of the battery increases excessively, the battery may expand and become short-circuited. Therefore, analyzing the gas inside used batteries is important from the perspective of quality assessment. Gas analysis is typically performed using gas chromatography or gas chromatography-mass spectrometry. Gas components detected in batteries include inorganic gases such as hydrogen, carbon monoxide, and carbon dioxide, lower hydrocarbons such as methane, and electrolyte components. In addition, hydrogen fluoride may also be generated, so extreme care is required when sampling gas from batteries and feeding it into a measuring instrument.

[0003] One type of lithium-ion battery is a laminated type designed to be compact and lightweight (see, for example, Patent Document 1). A laminated lithium-ion battery has a structure in which a cell structure, consisting of multiple stacked rectangular thin cells, is laminated and sealed with an exterior film. In such a lithium battery, gas generated from the cell structure accumulates in the space inside the exterior film. If a gas chromatography syringe is directly pierced into the exterior film to aspirate the gas in order to collect and analyze it, the gas may leak out through the puncture hole. Furthermore, if contaminated ambient air enters the exterior film through the puncture hole, the surrounding air will be collected along with the gas, making accurate analysis of the gas difficult.

[0004] To prevent these problems, a method is used in which a large container (e.g., a Tedra bag) filled with inert gas is prepared, a laminated battery is placed inside the container, holes are made in the exterior film, the container is filled with the internal gas of the battery, and a mixture of the inert gas and the internal gas of the battery is collected and analyzed as a sample gas.

[0005] JP 2013-89311 A

[0006] However, this method may not be able to detect gas components in minute amounts because the gas to be analyzed is diluted with an inert gas. Also, it is not easy to perforate the exterior film and sample the gas from a battery placed inside a Tedra bag.

[0007] The present invention has been made in consideration of the above-mentioned situation, and aims to provide a method for easily collecting gas from a sealed body that seals the contents inside without diluting the gas inside.

[0008] A gas sampling method according to one aspect of the present invention is a method for sampling gas in a sealed body comprising a content and a sealed bag containing the content, wherein a space exists inside the sealed bag to contain gas discharged from the content. The gas sampling method includes a step of attaching an elastic body to the outer surface of the sealed bag, and a step of arranging a tip of a suction tube in the space so as to penetrate the elastic body and sucking the gas through the suction tube.

[0009] According to the aspects of the present invention, gas inside a sealed body can be easily collected without being diluted.

[0010] 1A is a schematic diagram showing a laminated battery used in one embodiment of the present invention, with FIG. 1A being a plan view, FIG. 1B being a front view, and FIG. 1C being a cross-sectional view taken along line A-A in FIG. 1A. The portion indicated by the dashed line shows the internal configuration of the laminated battery. This is an exploded view of the laminated battery of FIG. 1. This is a schematic diagram showing an elastic body attached to the laminated battery, with FIG. 3A being a plan view and FIG. 3B being a front view. This is a schematic diagram showing steps according to one embodiment of the present invention in the cross-sectional view taken along line B-B in FIG. 3A, with FIG. 4A being a step of preparing a laminated battery and an elastic body, FIG. 4B being a step of attaching the elastic body to the laminated battery, and FIG. 4C being a step of suctioning gas. This is a modified example of one embodiment of the present invention, showing a step of attaching an elastic body to a laminated battery, with FIG. 5A being a plan view and FIG. 5B being a front view. This is a diagram showing a modified example of FIG. 5, showing a step of suctioning gas in the cross-sectional view taken along line C-C in FIG. 5A.

[0011] 1. First Embodiment An example of a first embodiment of the present invention is a gas collection method for a case where the contents are a cell structure, the sealed bag is a bag-shaped film, and the sealed body is a laminated battery. This will be explained using Figures 1 to 4.

[0012] 1-1. Structure of Laminated Battery The laminated battery 1 is, for example, a known or commercially available laminated lithium ion battery, and includes a cell structure 2, a bag-shaped film 3, and two terminals 4, as shown in FIG.

[0013] The cell structure 2 is a main element that functions as a lithium ion battery and has a rectangular flat plate shape. Although not shown, the cell structure 2 is formed by stacking a plurality of unit cells, each of which is composed of a thin film positive electrode, a separator, and a separator, in the thickness direction (first direction).

[0014] The bag-shaped film 3 is an exterior material that encases the cell structure 2 and has a substantially rectangular shape. The bag-shaped film 3 is composed of a single film. Specifically, as shown in FIG. 2 , a single film is folded along a centerline region (i.e., a folded portion 5) that divides the film into two equal parts, and the ends (ends of the three sides) other than the folded portion 5 are tightly attached and sealed by thermocompression or adhesive, thereby forming a bag shape. That is, the bag-shaped film 3 has a first sealed portion 6 extending in a second direction (a direction perpendicular to the first direction), two second sealed portions 7 extending in a third direction (an axis perpendicular to both the first and second directions) and facing each other with the cell structure 2 interposed therebetween, and a folded portion 5 extending in the second direction and facing the first sealed portion 6 with the cell structure 2 interposed therebetween. The cell structure 2 is contained by one side film 8, a folded portion 5 continuous with the one side film 8, and a second side film 9 continuous with the folded portion 5. The film constituting the bag-shaped film 3 is a barrier film that blocks air permeation, and is formed by alternately laminating inorganic films made of, for example, metal foil and organic films made of, for example, organic materials.

[0015] The two terminals 4 are composed of a positive terminal and a negative terminal. One end of each terminal 4 is electrically connected to the cell structure 2, and the other end of each terminal 4 is exposed from the bag-shaped film 3.

[0016] In the laminated battery 1, a space 10 exists inside the bag-like film 3, specifically in the area partitioned by the cell structure 2 and the one side film 8 and the other side film 9 of the bag-like film 3, and gas released from the laminated battery 1 is stored in the space 10. This space 10 may exist when the laminated battery 1 is manufactured, but it may be generated and expand due to gas released from the cell structure 2 when the laminated battery 1 is in use.

[0017] 1-2. Gas Sampling Method (Attachment Step) In this step, the elastic body 11 is attached to the outer surface of the bag-shaped film 3 as shown in FIG.

[0018] First, an elastic body 11 is prepared. The elastic body 11 has a flat plate shape with a predetermined thickness, specifically a rectangular flat plate shape. The elastic body 11 has adhesiveness on one surface in the thickness direction of the flat plate shape so that it can be attached. Specifically, one surface in the thickness direction of the elastic body 11 is an adhesive surface 14 on which an adhesive sheet is disposed, and the other surface in the thickness direction of the elastic body 11 is a non-adhesive surface 15. The elastic body 11 is formed from a rubber material such as nitrile rubber, acrylic rubber, natural rubber, silicone rubber, or urethane rubber. From the viewpoint of the restoring force when formed into a U-shape, the thickness of the elastic body 11 is preferably, for example, 0.5 mm or more and 10 mm or less.

[0019] Next, the adhesive surface 14 of the rubber elastic body 11 is brought into contact with the bag-shaped film 3. At this time, the rubber elastic body 11 is curved into a U-shape (see FIG. 4A ), and the U-shaped rubber elastic body 11 is thereby attached to the bag-shaped film 3 (see FIG. 4B ).

[0020] As shown in FIG. 3A , when the laminated battery 1 is observed from one side of the thickness direction toward the other side of the thickness direction (when observed in the thickness direction), the rubber elastic body 11 is positioned so that it does not overlap with the cell structure 2 and the sealing portions 6 and 7 of the bag-like film 3, but overlaps with the space 10 of the cell structure 2. In other words, the only components sandwiched by the U-shaped elastic body 11 are the bag-like film 3 and the space 10; the cell structure 2 and the sealing portions 6 and 7 are not sandwiched. On the adhesive surface 14 of the elastic body 11, the U-shaped curved portion 12 is positioned on the outer surface of the folded portion 5. The two straight portions 13 of the U-shape are positioned on the outer surface (first outer surface) of the one-side film 8 and the outer surface (second outer surface) of the other-side film 9, respectively. The positions of the straight portions 13 on the one-side film 8 and the other-side film 9 face each other. That is, when observed in the thickness direction, the attachment position of one film 8 overlaps with the attachment position of the other film 9. As a result, the elastic force of U-shaped elastic body 11 (the restoring force that returns it to a flat plate shape) pulls one film 8 and the other film 9 outward (in the direction of the arrow in FIG. 4B ), expanding space 10.

[0021] (Suction Step) In this step, the tip of the suction tube 17 is placed in the space 10 so as to penetrate the elastic body 11 (see FIG. 4C ), and then gas is sucked from the suction tube 17 .

[0022] First, an aspirator 16 (e.g., a gas body and an injector such as a syringe) for aspirating gas is prepared. Examples of the aspirator 16 include an injector such as a gas-tight syringe used in gas chromatography. The tip of an aspirator tube 17 provided in the aspirator 16 is sharp, e.g., a syringe needle.

[0023] Next, the suction tube 17 is inserted into the U-shaped curved portion 12 of the elastic body 11, penetrates the elastic body 11 and the folded portion 5 of the bag-shaped film 3, and reaches the space 10. The insertion direction of the suction tube 17 is the third direction, i.e., a direction perpendicular to the thickness direction. The tip of the suction tube 17 is positioned in the space 10 sandwiched between the U-shaped elastic bodies 11. At this position, the restoring force of the elastic bodies 11 expands the space 10 in the thickness direction, making it difficult for the tip of the suction tube 17 to come into contact with the inner surface of the bag-shaped film 3, thereby suppressing contamination due to adhesion of components other than gas components.

[0024] Next, the suction tool 16 is operated to collect the gas in the space 10 into the suction tool 16 via the suction tube 17. Thereafter, the suction tube 17 is pulled out from the elastic body 11 and the laminated battery 1.

[0025] (Analysis Step) After the suction step, the collected gas is analyzed. Specifically, the gas collected in the suction tool 16 is introduced into an analysis device such as a gas chromatograph or a gas chromatograph mass spectrometer. The analysis device is then operated in a known or conventional manner to analyze the gas components.

[0026] According to the sampling method of the first embodiment, gas leakage to the outside through the through-hole in the bag-shaped film 3 when the suction tube 17 is inserted or removed or when suctioning is performed can be suppressed. Furthermore, gas can be sampled easily by simply attaching the elastic body 11 to the bag-shaped film 3. Internal gas can be sampled at its original concentration without dilution, allowing even minute amounts of gas to be analyzed with high accuracy. Furthermore, because the elastic body 11 is attached to the one-side film 8 and the other-side film 9, even if the suction tube 17 is pierced from the one-side film 8 and reaches the other-side film 9 on the opposite side, leaking gas to the outside of the laminated battery 1 can be suppressed. Because the elastic body 11 is attached to the folded portion 5, when the suction tube 17 is pierced from the folded portion 5 in the third direction, the tip of the suction tube 17 is less likely to come into contact with the inner surface of the bag-shaped film 3, thereby suppressing contamination of the suction tube 17. Since the flat elastic body 11 is attached in a U-shape, the one side film 8 and the other side film 9 are pulled outward, widening the space 11, thereby preventing the tip of the suction tube 17 from coming into contact with the inner surface of the bag-shaped film 3.

[0027] 1-3. Modification of the First Embodiment In the above embodiment, the elastic body 11 is curved into a U-shape and attached to the bag-shaped film 3, but this is not a limitation. For example, as shown in FIG. 5 , two elastic bodies 11 may be prepared, with one elastic body 11 attached to the outer surface of one film 8 of the bag-shaped film 3 and the other elastic body 11 attached to the outer surface of the other film 9. In this case, it is preferable that the position of the outer surface attached to one film 8 faces the position of the outer surface attached to the other film 9. In this embodiment, as shown in FIG. 6 , a suction tube 17 is inserted in the thickness direction so as to penetrate one elastic body 11. Then, the tip of the suction tube 17 is placed in the space 10 so as not to contact the other film 9. Thereafter, the suction tool 16 is operated to collect gas in the space 10.

[0028] 2. Other Embodiments In the first embodiment, the sealed body was a laminated film, but the present invention is not limited to this. For example, although not shown, gas discharged from a sealed body such as a bagged centrifuge tube can also be collected. In a bagged centrifuge tube, the contents are a centrifuge tube filled with a gas-generating substance such as a microorganism, and the sealed bag is a resealable bag. In such a bagged centrifuge tube, gas generated within the centrifuge tube may accumulate in the space within the sealed bag. In this case, an elastic body 11 is attached to the outer surface of the resealable bag, and the tip of a suction tube 17 is placed in the space within the resealable bag so as to penetrate the elastic body 11 and the outer surface, and the gas is sucked through the suction tube 17.

[0029] 3. Aspects It will be appreciated by those skilled in the art that the exemplary embodiments described above are examples of the following aspects.

[0030] (Item 1) A gas collection method according to one embodiment is a method for collecting gas in a sealed body comprising contents and a sealed bag containing the contents, wherein a space exists inside the sealed bag to contain gas discharged from the contents, and the method may include an attachment step of attaching an elastic body to the outer surface of the sealed bag, and a suction step of positioning the tip of a suction tube in the space so as to penetrate the elastic body, and suctioning the gas from the suction tube.

[0031] According to the gas sampling method described in paragraph 1, an elastic body is attached to the surface of a sealed bag, and the tip of a suction tube is placed in the space of the sealed bag so that it penetrates the elastic body, and then suction is performed. Therefore, since the through-hole of the sealed bag is covered with the elastic body, gas leakage from the through-hole can be suppressed when inserting or removing the suction tube or during suction. Furthermore, since it is only necessary to attach the elastic body, the method is easy. Furthermore, since it is not necessary to place the sealed bag in a large container filled with inert gas, the gas inside is not diluted, and even minute amounts of gas can be analyzed accurately.

[0032] (2) In the collection method described in 1, the attaching step may involve attaching the elastic body to a first outer surface of the sealed bag and a second outer surface of the sealed bag opposite the first outer surface.

[0033] According to the collection method of paragraph 2, an elastic body is attached to the first outer surface and the opposing second outer surface. Therefore, even if the suction tube is pierced through the first outer surface and reaches the opposite second outer surface, creating a hole, the elastic body on the outside of the second outer surface can close the hole in the second side surface. This prevents gas from leaking out of the sealed body.

[0034] (Clause 3) In the collection method described in paragraph 1 or 2, the sealed bag is a sealed film in which the folded portion of the film is folded back and the edges of the film are sealed, and in the attachment process, the elastic body may be attached to the folded portion, the first outer surface continuous with the folded portion, and the second outer surface continuous with the folded portion.

[0035] According to the collection method of paragraph 3, an elastic body is attached to the folded portion, the first outer surface, and the second outer surface. Therefore, by inserting the suction tube through the folded portion and guiding the tip of the suction tube so that it is positioned between the first outer surface and the second outer surface, the possibility of the tip of the suction tube coming into contact with the inner surface of the sealed bag can be reduced. As a result, contamination of the suction tube by components other than gas can be prevented.

[0036] (Item 4) In the collection method described in any one of Items 1 to 3, in the pasting step, the flat elastic body may be pasted so that it is curved in a U-shape.

[0037] According to the collection method of paragraph 4, the flat elastic body is arranged in a U-shape, so that the first outer surface and the second outer surface are pulled outward by the restoring force of the elastic body 11, widening the space between them, thereby more reliably preventing the tip of the suction tube from coming into contact with the inner surface of the bag-shaped film 3.

[0038] (Item 5) In the collection method described in any one of items 1 to 4, the contents may be a cell structure, and the sealed body may be a laminated battery.

[0039] According to the sampling method of the fifth aspect, the gas generated from the cell structure of the laminated battery can be easily sampled without dilution.

[0040] REFERENCE SIGNS LIST 1 Laminated battery 2 Cell structure 3 Bag-shaped film 5 Folded portion 8 One side film 9 Other side film 10 Space 11 Elastic body 16 Suction tool

Claims

1. A method for collecting gas from a sealed body comprising a content and a sealed bag containing the content, wherein a space exists inside the sealed bag to contain gas discharged from the content, the method comprising: an attachment step of attaching an elastic body to the outer surface of the sealed bag; and a suction step of positioning the tip of a suction tube in the space so that the tip penetrates the elastic body, and suctioning the gas from the suction tube.

2. The collection method according to claim 1, wherein in the attaching step, the elastic body is attached to a first outer surface of the sealed bag and a second outer surface of the sealed bag opposite the first outer surface.

3. The collection method according to claim 2, wherein the sealed bag is a sealed film in which the folded portion of the film is folded back and the edges of the film are sealed together, and in the attaching step, the elastic body is attached to the folded portion, the first outer surface continuous with the folded portion, and the second outer surface continuous with the folded portion.

4. The collection method according to claim 3, wherein in the attaching step, the flat elastic body is attached so that it is curved in a U-shape.

5. The collection method according to claim 1, wherein the contents are a cell structure and the sealed body is a laminated battery.

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