Battery inspection method

Abstract

To provide a new battery inspection method that can be performed using a simple method.SOLUTION: A battery inspection method includes the steps of: placing an internal pressure inspection sheet containing an object whose deformation due to pressure can be visually confirmed on a sealing film that seals a liquid inlet of a battery; reducing the pressure around the battery; and determining a state of the internal pressure of the battery on the basis of a degree of deformation of the object after the pressure is reduced.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a method for testing a battery. [Background technology]

[0002] One example of a battery manufacturing method is to inject an electrolyte solution into an opening of a case containing battery cells and then seal the opening after the injection is complete.To ensure the quality of batteries manufactured using this method, an inspection is carried out to ensure that the sealing is performed properly after the injection is complete. For example, Patent Document 1 describes a method for leak testing of a sealed battery in which the battery is filled with helium and the concentration of helium leaking from the battery is detected by a helium leak detection device. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-117901 Summary of the Invention [Problem to be solved by the invention]

[0004] Some currently manufactured batteries have electrolyte inlets sealed with a resin sealing film. Because helium permeates resin, helium-based testing cannot be applied to batteries whose electrolyte inlets are sealed with a resin sealing film. Furthermore, the method described in Patent Document 1 requires a device to detect helium leaks, making it difficult to reduce testing costs. For this reason, it is desirable to be able to test the state of batteries using a simpler method. An object of one embodiment of the present disclosure is to provide a novel battery inspection method that can be carried out in a simple manner. [Means for solving the problem]

[0005] The means for solving the above problems include the following embodiments. a step of placing an internal pressure inspection sheet including an object that allows visible deformation due to pressure on a sealing film that seals a liquid filling port of the battery; reducing the pressure around the battery; and determining the state of the internal pressure of the battery based on the degree of deformation of the object after the pressure is reduced. [Effects of the Invention]

[0006] According to one embodiment of the present disclosure, a novel battery inspection method that can be performed in a simple manner is provided. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 2 is a cross-sectional view schematically illustrating an example of the configuration of an internal pressure inspection sheet. [Figure 2] 1 is a perspective view schematically illustrating an example of the configuration of a battery that is a target of a battery inspection method. [Figure 3] 1 is a perspective view schematically illustrating an example of the configuration of a battery that is a target of a battery inspection method. DETAILED DESCRIPTION OF THE INVENTION

[0008] The battery inspection method of the present disclosure includes: a step of placing an internal pressure inspection sheet including an object that allows visible deformation due to pressure on a sealing film that seals a liquid filling port of the battery; reducing the pressure around the battery; and determining the state of the internal pressure of the battery based on the degree of deformation of the object after the pressure is reduced. Hereinafter, the object included in the internal pressure inspection sheet that allows visible deformation due to pressure will also be referred to as a "display object."

[0009] The battery inspection method of the present disclosure is applied to a type of battery in which a liquid filling port for injecting an electrolyte into the battery is sealed with a film-like sealing member (that is, a sealing film). One method for inspecting batteries whose electrolyte inlet is sealed with a sealing film is to place the battery in a chamber connected to a pressure reducing device and observe the deformation of the sealing film when the pressure inside the chamber (i.e., around the battery) is reduced. More specifically, when the pressure inside the chamber is reduced, the sealing film deforms so that it protrudes toward the outside of the battery. The degree of deformation (displacement) of this sealing film is measured using a measuring device such as a laser displacement meter.

[0010] In the battery inspection method disclosed herein, the internal pressure of the battery being inspected is inspected by observing the degree of deformation of the display object included in the internal pressure inspection sheet placed on the sealing film. More specifically, when the pressure around the battery is reduced, the sealing film sealing the electrolyte inlet deforms so that it protrudes toward the outside of the battery. This deformation of the sealing film pressurizes the internal pressure test sheet, causing the display object to deform. Because the degree of deformation of the display object is visible, the internal pressure state of the battery being tested can be determined by visually observing the state of the deformed display object.

[0011] The internal pressure inspection sheet used in the method of the present disclosure is not particularly limited in form as long as it includes an object for display. From the viewpoint of ease of placement on the sealing film, the internal pressure inspection sheet is preferably in a state where the display object is sandwiched between the base sheet and the cover sheet. In the present disclosure, a "base sheet" is a component that is placed on the side of the internal pressure inspection sheet facing the sealing film, and a "cover sheet" is a component that is placed on the opposite side of the internal pressure inspection sheet facing the sealing film (i.e., the side on which the internal pressure inspection sheet is observed by an observer).

[0012] The materials for the base sheet and cover sheet are not particularly limited as long as they do not prevent the display object from deforming due to pressure. For example, they may be sheets containing a resin such as a thermoplastic resin. Thermoplastic resins that can be used include, without limitation, polyolefins such as polypropylene and polyethylene, polystyrene, polyvinyl chloride, polyvinylidene chloride, ABS (acrylonitrile butadiene styrene) resin, AS (acrylonitrile styrene) resin, acrylic resin, polyamide, polyester, polycarbonate, polyimide, etc. The materials of the base sheet and the cover sheet are preferably hydrophobic.

[0013] The cover sheet is preferably transparent so that deformation of the display object due to pressure can be visually recognized. In order to make the deformation of the display object due to pressure visible, it is preferable that the color of the base sheet is different from that of the display object.

[0014] There are no particular limitations on the thickness of the cover sheet and the base sheet, as long as they do not prevent the display object from being deformed by pressure. The thickness of each of the cover sheet and the substrate sheet may be selected, for example, from the range of 10 μm to 1000 μm.

[0015] The material of the display object is not particularly limited as long as it can be deformed by the pressure applied to the display object due to the deformation of the sealing film. A method for making the deformation of the display object visible is to impart a visible color to the display object, which may be achieved by using a pigment, dye, or the like.

[0016] An example of the configuration of an internal pressure inspection sheet in which an indication object is sandwiched between a base sheet and a cover sheet will be described with reference to the drawings. In the present disclosure, the sizes of components shown in the drawings are conceptual, and the relative relationships between the sizes of the components are not limited to these.

[0017] The internal pressure inspection sheet 100 shown in FIG. 1(A) comprises a base sheet 1, a cover sheet 2, and an indication object 3. The display object 3 is disposed between the base sheet 1 and the cover sheet 2, and is housed inside a space partitioned by partial joining of the base sheet 1 and the cover sheet 2. The size or shape of the space housing the display object 3 is set to a size or shape that allows the display object 3 to be deformed.

[0018] The method for partially joining the base sheet 1 and the cover sheet 2 is not particularly limited and can be selected depending on their materials, shapes, etc. Specific joining methods include adhesion using an adhesive, welding by heating, etc.

[0019] The position where the base sheet 1 and the cover sheet 2 are joined in the internal pressure inspection sheet 100 may correspond to a portion where no pressure is applied to the internal pressure inspection sheet 100. An example of a portion where no pressure is applied to the internal pressure inspection sheet 100 is the area around the injection port used to inject electrolyte into the battery, where the sealing film is fixed.

[0020] Fig. 1(B) shows the state of the display object 3 included in the internal pressure test sheet shown in Fig. 1(A) when it is deformed. The state of deformation of the display object 3 can be confirmed as a change in size or shape of the display object 3 observed from the cover sheet 2 side. The size or shape of the display object 3 observed from the cover sheet 2 side before and after deformation is not particularly limited as long as it is a size or shape that can be used for visually inspecting the battery.

[0021] In the method of the present disclosure, the method for placing the internal pressure inspection sheet on the sealing film is not particularly limited. From the viewpoint of accurately grasping the degree of deformation of the display object included in the internal pressure inspection sheet, it is preferable that the internal pressure inspection sheet is fixed to the sealing film. The fixing method is not particularly limited, and may be adhesion using an adhesive, welding by heat, etc. The internal pressure inspection sheet may or may not be removed from the sealing film after the battery inspection is completed.

[0022] In the method of the present disclosure, the method for reducing the pressure around the battery is not particularly limited. For example, a method may be used in which the battery is housed in a chamber connected to a pressure reducing device, and the pressure inside the chamber is reduced.

[0023] The step of reducing the pressure around the battery may be carried out in a state where a member having a flat surface facing the internal pressure inspection sheet is placed on top of the internal pressure inspection sheet placed on the sealing film. A member having a flat surface facing the internal pressure inspection sheet, for example, prevents the internal pressure inspection sheet from moving in the thickness direction following the deformation of the sealing film, making it easier for deformation of the display object to occur.

[0024] The method for determining the state of the internal pressure of the battery based on the degree of deformation of the display object after the pressure is reduced is not particularly limited, and may be performed visually or using an image analyzer, etc. From the viewpoint of reducing inspection costs, visual inspection is preferred.

[0025] The battery to be inspected by the method of the present disclosure has an electrolyte inlet sealed with a sealing film. The method for sealing the inlet with the sealing film is not particularly limited and can be selected depending on the material, shape, etc. of the inlet. Specific sealing methods include adhesion using an adhesive, welding, etc.

[0026] An example of the configuration of a battery that is a target of the inspection method of the present disclosure will be described with reference to the drawings. Fig. 2 is a perspective view showing an example of a battery configuration, and Fig. 3 is a perspective view showing an exploded state of the battery shown in Fig. 2. Arrows UP, FR, and LH in each drawing indicate the upper side in the up-down direction, the front side in the front-rear direction, and the left side in the left-right direction, respectively. LD in each drawing indicates the stacking direction of the battery cells.

[0027] The battery 10 shown in Figures 2 and 3 includes a stack 15 of battery cells 12, a resin structure 20 arranged on the outer periphery of the stack 15, and a sealing film 30 arranged in a portion of the resin structure 20 having a liquid injection port 27.

[0028] The stack 15 is a stack of multiple battery cells 12. The configuration of each battery cell 12 is not particularly limited and can be selected from known configurations. Each battery cell 12 includes, for example, at least one of a positive electrode or a negative electrode, and a separator.

[0029] Resin structure 20 is composed of a main body 22 arranged on the outer periphery of laminate 15 and a liquid pouring frame 25 provided on the side of main body 22. A slit-shaped opening 23 is provided in the side of the main body 22. The liquid filling frame 25 is provided in the side of the main body 22 at a location where the slit-shaped opening 23 exists. The liquid filling frame 25 is provided with a liquid filling port 27 for filling the electrolyte into the battery cells 12 that make up the stack 15. That is, the electrolyte filled from the liquid filling port 27 passes through the opening 23 of the main body 22 and reaches the battery cells 12 that make up the stack 15.

[0030] The main body 22 and the liquid filling frame 25 of the resin structure 20 may be a combination of parts manufactured in different manufacturing processes, or may be a single part manufactured in the same manufacturing process.

[0031] The main body 22 and the liquid filling frame 25 of the resin structure 20 each contain a resin. The type of resin is not particularly limited. For example, the resin may be selected from thermoplastic resins such as polyolefins such as polypropylene and polyethylene, polystyrene, polyvinyl chloride, polyvinylidene chloride, ABS (acrylonitrile butadiene styrene) resin, AS (acrylonitrile styrene) resin, acrylic resin, polyamide, polyester, polycarbonate, and polyimide.

[0032] After the electrolyte injection operation is completed, a sealing film 30 is attached to the surface of the injection frame 25 having the injection port 27 to seal the injection port 27. The sealing film 30 includes, for example, a resin. The resin may be selected from the resins that can be included in the resin structure 20 described above. The method for attaching the sealing film 30 to the surface of the liquid filling frame 25 on which the liquid filling port 27 is formed is not particularly limited, and can be selected from adhesion using an adhesive, welding by heat, etc. From the viewpoint of ensuring the tightness of the liquid filling port 27 of the battery, it is preferable to attach the sealing film 30 by welding.

[0033] After the filling port 27 of the filling frame 25 is sealed with the sealing film 30, the battery 10 is inspected according to the inspection method of the present disclosure described above. That is, the internal pressure inspection sheet used in the inspection method of the present disclosure is placed on the sealing film 30.

[0034] The sealing film 30 has a portion bonded to the liquid filling frame 25 and a portion not bonded to the liquid filling frame 25 (a portion corresponding to the liquid filling port 27). When the pressure around the battery is reduced, the deformation of the sealing film 30 occurs in the portion where the sealing film 30 is not bonded to the liquid filling frame 25. Therefore, it is preferable to arrange the internal pressure inspection sheet so that the display object included in the internal pressure inspection sheet is arranged in the portion of the sealing film 30 not bonded to the liquid filling frame 25.

[0035] The type of battery that can be subjected to the inspection method of the present disclosure is not particularly limited as long as the inlet for injecting the electrolyte is sealed with a sealing film, and can be selected from rechargeable batteries such as lithium-ion secondary batteries, lead-acid batteries, nickel-metal hydride batteries, nickel-cadmium batteries, nickel-iron batteries, nickel-zinc batteries, silver oxide-zinc batteries, and cobalt-titanium lithium secondary batteries. In an embodiment, the battery to be inspected by the inspection method of the present disclosure may be a lithium-ion secondary battery for an automobile. In an embodiment, the battery to be inspected by the inspection method of the present disclosure may be a bipolar lithium ion secondary battery. [Explanation of symbols]

[0036] 1 Base sheet 2 Cover Sheet 3. Objects whose deformation due to pressure can be seen (display objects) 100 Internal pressure test sheet

Claims

[Claim 1] a step of placing an internal pressure inspection sheet including an object that allows visible deformation due to pressure on a sealing film that seals a liquid filling port of the battery; reducing the pressure around the battery; and determining the state of the internal pressure of the battery based on the degree of deformation of the object after the pressure is reduced.

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