A method for selecting a defective secondary battery

Abstract

The embodiment of the application discloses a secondary battery defective product selection method, which comprises the following steps: a side resistance measuring step, in which a battery with a primary battery structure is selected or self-made, the battery is provided with a first damage area, and the side resistance r1 of the first damage area is measured; a corrosion step, in which a corrosion experiment is conducted on the battery, the corrosion time t1 of the battery is measured, a first calculation formula of the electrochemical corrosion resistance life L1 of the battery is constructed, and the formula is L1 = AF * t1, wherein L1 is the electrochemical corrosion resistance life of the battery, and AF is an acceleration factor; a second calculation formula of the resistance r2 required to meet the electrochemical corrosion resistance life L2 is constructed, the resistance r2 is taken as the lower limit of the side resistance of the secondary battery to be measured, and if the measured side resistance of the secondary battery to be measured is less than the resistance r2, the secondary battery to be measured is determined as a defective product. According to the application, the judgment standard of the prior art secondary battery side resistance selection defective product is quantified.

Description

Technical Field

[0001] This invention relates to the field of batteries, and in particular to a method for selecting defective secondary batteries. Background Technology

[0002] Due to its advantages such as high energy density, long cycle life, and ease of assembly, pouch lithium batteries have become the main energy source for new energy vehicles and various mobile electronic devices.

[0003] Currently, defective batteries are selected by measuring the inter-side resistance between the aluminum casing and the negative or positive electrode through electrochemical corrosion risk testing. However, the industry currently only sets resistance value standards based on high, low, and production experience, resulting in the drawback of arbitrary setting of DC resistance standards for judging whether a battery is defective, lacking any theoretical basis.

[0004] In view of this, it is necessary to develop a method for selecting defective secondary batteries in order to solve the above problems. Summary of the Invention

[0005] The embodiments of the present invention provide a method for selecting defective secondary batteries. The method quantifies the judgment criteria for selecting defective secondary batteries based on the side resistance of existing secondary batteries, which can quickly distinguish defective secondary batteries from normal secondary batteries, thereby improving the quality control capability of secondary battery production.

[0006] To address the aforementioned technical problems, embodiments of the present invention disclose the following technical solutions:

[0007] On the one hand, a method for selecting defective secondary batteries is provided, comprising the following steps:

[0008] Steps for measuring edge resistance: Select or make a battery with a galvanic cell structure. The battery has a first damaged area. Measure the edge resistance r1 of the first damaged area.

[0009] Corrosion steps: Conduct a corrosion experiment on the battery, measure the corrosion time t1, and construct the first calculation formula for the battery's electrochemical corrosion resistance life: L1=AF×t1, where L1 is the battery's electrochemical corrosion resistance life and AF is the acceleration factor.

[0010] Construct a second formula for calculating the resistance r2 required to satisfy the electrochemical corrosion resistance lifetime L2: Using resistor r2 as the lower limit of the side resistance of the secondary battery under test, if the measured side resistance of the secondary battery under test is less than resistor r2, the secondary battery under test is determined to be defective.

[0011] In addition to one or more of the features disclosed above, or as an alternative, a heating device is obtained before the corrosion step; the battery is placed in the heating device until corrosion occurs, and the time from when the battery is placed in the heating device until corrosion occurs is recorded and set as corrosion time t1.

[0012] In addition to one or more of the features disclosed above, or alternatively, the heating temperature of the heating device is set to T. t , will T t Substituting into the Arrhenius formula, the acceleration factor AF is calculated:

[0013]

[0014] Among them, E a K is the empirical value of the activation energy, and K is the Boltzmann constant.

[0015] In addition to one or more features disclosed above, the battery includes a metal casing, a first insulating layer, and a second insulating layer, the first insulating layer and the second insulating layer respectively insulating the two side surfaces of the metal casing; prior to the edge resistance measurement step, it further includes:

[0016] Steps for constructing a galvanic cell structure:

[0017] A portion of the first insulating layer is damaged to obtain a first damaged area, and a portion of the second insulating layer is damaged to obtain a second damaged area, so as to expose the metal shell at the positions corresponding to the first and second damaged areas; a negative electrode material is arranged inside the metal shell, and a negative electrode tab is arranged outside the metal shell, so as to connect the metal shell, the negative electrode material and the negative electrode tab to form a conductive circuit.

[0018] In addition to one or more of the features disclosed above, or alternatively, prior to forming the conductive circuit, the following features are also included:

[0019] Steps for obtaining the connection structure: One end of the connection structure is electrically connected to the negative electrode tab, and the other end is electrically connected to the metal shell through the second damaged area, forming an electronic path between the negative electrode tab and the metal shell.

[0020] In addition to one or more of the features disclosed above, or alternatively, prior to forming the conductive circuit, the following features are also included:

[0021] Electrolyte contact step: The electrolyte inside the metal shell comes into contact with the metal shell through the first damaged area, and an ion pathway is formed between the negative electrode material and the metal shell.

[0022] In addition to one or more of the features disclosed above, or as an alternative, the first damaged area is arranged on the side of the first insulating layer near the negative electrode material before the electrolyte contact step.

[0023] In addition to one or more of the features disclosed above, or as an alternative, the first damaged region and the second damaged region are arranged opposite each other before the conductive circuit is formed.

[0024] In addition to one or more of the features disclosed above, or alternatively, the side resistance r1 satisfies the first relationship:

[0025]

[0026] Where P is the resistivity of the conductive material, and L J Let S be the transmission path of the first damaged area, and let S be the cross-sectional area of ​​the transmission path of the first damaged area.

[0027] In addition to one or more of the features disclosed above, or alternatively, L1 also satisfies the second relation:

[0028]

[0029] Where Qi is the current of the battery, and E is the electromotive force of the battery reaction.

[0030] The above-mentioned technical solution provides a method for selecting defective secondary batteries with the following advantages or beneficial effects: By conducting corrosion experiments on batteries with a galvanic cell structure, the relationship between the battery's electrochemical corrosion life and corrosion time is established, and a first calculation formula is constructed. Based on the battery corrosion mechanism and internal resistance analysis of the ion transport process, the relationship between the battery's edge resistance and electrochemical corrosion life is established, and a second calculation formula is constructed. Finally, the minimum resistance of the battery that needs to meet a certain service life is calculated. By comparing the edge resistance of the secondary battery under test with the minimum resistance, it is determined whether the secondary battery under test is a defective product. This solves the problem that existing edge resistance measurement methods for identifying batteries with an electrochemical galvanic cell structure lack verifiable standards for edge resistance values. It quantifies the existing criteria for selecting defective secondary batteries based on edge resistance, providing a reasonable selection method that can quickly distinguish defective secondary batteries from normal secondary batteries, thereby improving the quality control capabilities of secondary battery production. Attached Figure Description

[0031] The technical solution and other beneficial effects of the present invention will become apparent from the following detailed description of the specific implementation methods of the present invention in conjunction with the accompanying drawings.

[0032] Figure 1 This is a flowchart illustrating the selection method provided according to an embodiment of the present invention;

[0033] Figure 2 This is a schematic diagram of a battery with a primary cell structure provided according to an embodiment of the present invention. Detailed Implementation

[0034] To make the objectives, technical solutions, and beneficial effects of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific implementation methods. It should be understood that the specific implementation methods described in this specification are merely for explaining the invention and are not intended to limit the invention.

[0035] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of the stated features. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0036] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection, a direct connection, or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0037] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is horizontally radially higher than the second feature. "Below," "below," and "under" the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is horizontally radially smaller than the second feature.

[0038] Aluminum-plastic film soft-pack lithium-ion batteries are widely used in HEV vehicles due to their high energy density, variable size, and ease of assembly. However, compared to prismatic or cylindrical batteries, aluminum-plastic film soft-pack batteries are relatively fragile and more prone to corrosion and leakage. In the aluminum-plastic film structure, a polypropylene (PP) layer is wrapped on the inner side, which prevents the electrolyte from contacting the aluminum layer during use. However, if the PP layer is damaged during the manufacturing process, such as by heat-sealing dissolution or scratches, the aluminum layer will directly contact the electrolyte. Simultaneously, the exposed edges of the aluminum layer, cut away from the battery, are connected to the negative electrode tab by metal wires, or a salt bridge structure forms on the outside in high-humidity environments. This creates a primary discharge circuit, causing an alloy reaction between the aluminum layer and lithium, gradually destroying the dense alumina structure of the aluminum layer, resulting in corrosion, pitting, and leakage, directly ending the lifespan of the soft-pack lithium-ion battery. Therefore, the identification and testing of the electrochemical resistance of the aluminum-plastic film primary battery structure is a crucial step in the production process. The commonly used method for determining whether a battery possesses an electrochemical galvanic cell structure is to measure the resistance between the aluminum casing and the positive or negative electrode. Specifically, this involves measuring the resistance between the aluminum metal in the middle layer of the aluminum-plastic film and the negative or positive electrode. If the resistance is low, the battery is considered defective. The principle behind this method is that if the PP layer inside the aluminum-plastic film is damaged, allowing the aluminum metal to come into contact with the electrolyte, the aluminum metal will exhibit electrode characteristics in the electrolyte. Therefore, measuring the resistance between the aluminum metal and the negative or positive electrode can identify whether the PP layer is damaged.

[0039] However, the industry currently only sets resistance value standards based on high, low and production experience, which leads to the drawback that the DC resistance value standards for judging whether a battery is defective are set arbitrarily and have no theoretical basis.

[0040] Figure 1 This is a flowchart illustrating the selection method provided according to an embodiment of the present invention, with reference to... Figure 1 A method for selecting defective secondary batteries, the method comprising the following steps:

[0041] Steps for measuring edge resistance: Select or make a battery with a galvanic cell structure. The battery has a first damaged area 6. Measure the edge resistance r1 of the first damaged area 6.

[0042] Corrosion steps: Conduct a corrosion experiment on the battery and measure the corrosion time t1. Construct the first calculation formula for the battery's electrochemical corrosion resistance life: L1=AF×t1, where L1 is the battery's electrochemical corrosion resistance life and AF is the acceleration factor. Substitute the corrosion time t1 and the acceleration factor AF into the first calculation formula to calculate the battery's electrochemical corrosion resistance life L1.

[0043] Construct a second formula for calculating the resistance r2 required to satisfy the electrochemical corrosion resistance lifetime L2: An electrochemical corrosion resistance lifetime L2 can be set according to requirements, for example, the electrochemical corrosion resistance lifetime L2 equals 10.

[0044] In 2010, L2, r1 and L1 were substituted into the second calculation formula to calculate the resistance r2 required to meet the electrochemical corrosion resistance life L2.

[0045] Using resistor r2 as the lower limit of the side resistance of the secondary battery under test, if the measured side resistance of the secondary battery under test is less than resistor r2, the secondary battery under test is determined to be defective. That is, after selecting a secondary battery, if the measured side resistance r1 of the secondary battery under test is less than resistor r2, the secondary battery under test is determined to be defective. A secondary battery determined to be defective means that the secondary battery has a short electrochemical corrosion resistance life, that is, the secondary battery under test is prone to dangerous conditions such as punctures and leakage.

[0046] Corrosion experiments were conducted on batteries with a galvanic cell structure to establish the relationship between the battery's electrochemical corrosion life and corrosion time, thus constructing a first calculation formula. Based on the battery corrosion mechanism and internal resistance analysis of the ion transport process, the relationship between the battery's edge resistance and electrochemical corrosion life was established, constructing a second calculation formula. Finally, the minimum resistance required for a battery to meet a certain lifespan was calculated. By comparing the edge resistance of the tested secondary battery with the minimum resistance, it was determined whether the tested secondary battery was defective. This solves the problem that existing edge resistance measurement methods for identifying batteries with an electrochemical galvanic cell structure lack verifiable standards for edge resistance values. It quantifies the criteria for selecting defective secondary batteries based on edge resistance, providing a reasonable selection method that can quickly distinguish defective secondary batteries from normal ones, thereby improving the quality control capabilities of secondary battery production.

[0047] In this embodiment, before performing the corrosion step, a heating device is first obtained, and the battery is placed in the heating device until corrosion occurs. The time from when the battery is placed in the heating device until corrosion occurs is recorded and set as corrosion time t1.

[0048] In this embodiment, the heating temperature of the heating device is set to T. t , will Tt Substituting into the Arrhenius formula, the acceleration factor AF is calculated: Among them, E a The activation energy is an empirical value, and K is the Boltzmann constant. In this embodiment, E... a =0.56, K = 8.6 × 10 -5 eV / K. It is worth noting that E a The specific values ​​of K and E are given only as examples. a Any value of K is within the scope of protection of this application.

[0049] Preferably, an oven is selected as the heating device, and the battery is placed in the oven for corrosion testing. The heating temperature of the oven is adjusted according to the requirements of the battery corrosion test.

[0050] In this embodiment, Figure 2 This is a schematic diagram of a battery with a primary cell structure according to an embodiment of the present invention, with reference to... Figure 2 The battery includes a metal casing 1, a positive electrode material 21, a positive electrode tab 2, a negative electrode material 31, a negative electrode tab 3, and a separator 4. A first insulating layer 11 is disposed on the inner surface of the metal casing 1, isolating the metal casing 1 from the electrolyte. The positive electrode material 21 is disposed inside the metal casing 1. One end of the positive electrode tab 2 is electrically connected to the positive electrode material 21, and the other end passes through the first insulating layer 11, the metal casing 1, and the second insulating layer 12 to the outside of the metal casing 1. A second insulating layer 12 is disposed on the outer surface of the metal casing 1. The negative electrode material 31 is disposed inside the metal casing 1. One end of the negative electrode tab 3 is electrically connected to the negative electrode material 31, and the other end passes through the first insulating layer 11, the metal casing 1, and the second insulating layer 12 to the outside of the metal casing 1. The separator 4 is disposed inside the metal casing 1 and located between the positive electrode material 21 and the negative electrode material 31. The metal casing 1 is made of aluminum, while the positive electrode tab 2 and the negative electrode tab 3 are made of graphite. The first insulating layer 11 is made of polypropylene, and the second insulating layer 12 is made of nylon.

[0051] In this embodiment, the first insulating layer 11 and the second insulating layer 12 respectively insulate the two side surfaces of the metal housing 1; before performing the edge resistance measurement step, the method further includes:

[0052] Steps for constructing a galvanic cell structure:

[0053] A portion of the first insulating layer 11 is damaged to obtain a first damaged area 6, and a portion of the second insulating layer 12 is damaged to obtain a second damaged area 7, so as to expose the metal shell 1 at the positions corresponding to the first damaged area 6 and the second damaged area 7; a negative electrode material 31 is arranged inside the metal shell 1, and a negative electrode tab 3 is arranged outside the metal shell 1, so as to connect the metal shell 1, the negative electrode material 31 and the negative electrode tab 3 to form a conductive circuit.

[0054] A battery with a galvanic cell structure can be selected through testing. Alternatively, a good battery can be selected, and the first insulating layer 11 of the battery can be cut to create the first damaged area 6, and the second insulating layer 12 can be cut to create the second damaged area 7. Then, a conductive circuit can be formed between the negative electrode material 31, the negative electrode tab 3, and the metal casing 1 to complete the self-made battery with a galvanic cell structure.

[0055] In other words, the battery with the galvanic cell structure has a first damaged area 6 and a second damaged area 7, and the metal casing 1, the negative electrode material 31 and the negative electrode tab 3 are connected to each other, establishing a galvanic cell structure that allows the metal casing 1 to corrode. The galvanic cell structure causes lithium ions to gradually migrate to the metal casing 1 and undergo a lithium-aluminum combination reaction, which erodes the dense aluminum oxide layer on the surface of the metal casing 1, forming a loose and porous structure in the metal casing 1. It also gradually reacts chemically with the electrolyte, causing corrosion of the metal casing 1, until corrosion holes and leakage occur, directly leading to the termination of the battery life.

[0056] In this embodiment, before forming a conductive circuit, the method further includes: obtaining a connection structure step: one end of the connection structure is electrically connected to the negative electrode tab 3, and the other end is electrically connected to the metal casing 1 through the second damaged area 7, and an electronic path is formed between the negative electrode tab 3 and the metal casing 1.

[0057] The connection structure is a metal wire. The metal wire connects the negative electrode tab 3 and the metal housing 1, thus forming an electronic path between them. In other embodiments, the negative electrode tab 3 and the metal housing 1 can also be stapled together to achieve electrical connection.

[0058] In this embodiment, before forming a conductive circuit, the electrolyte comes into contact with the metal casing 1 through the first damaged area 6, and an ion pathway is formed between the negative electrode material 31 and the metal casing 1.

[0059] By electrically connecting the negative electrode tab 3 and the metal casing 1, the electrolyte comes into contact with the metal casing 1 through the first damaged area 6, thereby establishing a galvanic cell structure between the metal casing 1, the negative electrode material 31, and the negative electrode tab 3 to allow the metal casing 1 to corrode.

[0060] In this embodiment, see continue to refer to Figure 2 Preferably, before the electrolyte contact step, the first damaged area 6 is arranged on the side close to the first insulating layer 11 of the negative electrode material 31. The first damaged area 6 and the second damaged area 7 are arranged opposite to each other. The first damaged area 6 and the second damaged area 7 correspond to the same location of the metal casing 1.

[0061] Based on the calculation of the battery's internal resistance, the electrolyte region inside the battery can be divided into two sections. Region one is the portion of the first insulating layer 11 located between the negative electrode and the metal casing 1, containing the electrolyte region between the first insulating layer 11 and the metal casing 1. Region two is the electrolyte region contained within the first damaged region 6 caused by damage to the first insulating layer 11. According to the porous electrode theory, liquid phase current transmission also obeys Ohm's law, and the relationship between Ohm's resistance and the transmission path dimensions is as follows:

[0062] In this embodiment, r1 satisfies the first relation: P is the resistivity of the conductive material, that is, P is the resistivity of the electrolyte, L J Let S be the transmission path of the first damaged area 6, and let S be the cross-sectional area of ​​the transmission path of the first damaged area 6.

[0063] Assuming the battery dimensions are 300mm × 100mm, and the defect area of ​​the first damaged area 6 is calculated to be 0.1mm × 0.1mm, the thickness of area one is approximately 0.03mm, and the cross-sectional area of ​​the transmission path in area one is approximately 15000mm². 2 The cross-sectional area of ​​the transmission path in region two is approximately 0.01 mm². 2 The resistivity is taken as the reciprocal of the electrolyte ionic conductivity, which is 1 Ω·m. The calculated resistance value R of region one is 0.002 Ω, and the calculated resistance value of region two, i.e., the edge resistance r1 of the battery, is 8 kΩ. Although the impedance caused by concentration polarization under DC conditions is not considered, a comparison of the values ​​of R and r12 shows that the difference between R and r12 is extremely large. It can still be determined that the internal resistance of the galvanic cell depends on the size of the first damaged region 6.

[0064] According to electrochemical principles, the circuit current I equals the electromotive force E divided by the sum of the external load R and the battery's internal resistance r. That is, under the same external load, the battery discharge current depends on its internal resistance. The corrosion amount Q at the end of the battery's life is equivalent to the current QI, which can be used to directly measure the electrochemical corrosion resistance of the metal casing 1, and the following formula can be obtained:

[0065] If we set R to be much smaller than r1, we can obtain the second relation:

[0066] QI is the current of the battery, and E is the electromotive force of the battery reaction. L1 also satisfies the second relationship.

[0067] Specifically, by implementing the above selection method, three batteries were artificially made as standard samples for testing. The oven temperature was set to 65℃. First, the corresponding acceleration factor AF was calculated to be 13.2. The corrosion time t1 of the metal casing 1 was recorded. The corrosion time t1 and the acceleration factor AF were substituted into the first calculation formula to calculate the electrochemical corrosion resistance life L1 of the battery.

[0068] The electrochemical corrosion resistance life L2 is set to 10 years. Finally, the electrochemical corrosion resistance life L1, electrochemical corrosion resistance life L2, and the different edge resistances r1 of the three batteries are substituted into the second calculation formula to obtain the three resistances r2. The edge resistance values ​​of the aluminum-plastic film are then calculated according to the above formula to implement the standard. Referring to the table below, the edge resistance r1 of sample number 1 is 0.685 MΩ, the edge resistance r1 of sample number 2 is 0.536 MΩ, and the edge resistance r1 of sample number 3 is 0.705 MΩ.

[0069] Among them, the only difference between sample 1 and sample 2 is the resistance value of the side resistor r1; their parameters are identical. Therefore, it can be determined that the resistance r2 required to meet the 10-year electrochemical corrosion resistance life of the secondary battery is 21.05 MΩ. If the resistance r2 of the secondary battery is lower than 21.05 MΩ, the above-mentioned secondary battery is judged as a defective product.

[0070]

[0071] The above steps are provided only to help understand the method, structure, and core ideas of this invention. Those skilled in the art can make various improvements and modifications to this invention without departing from its principles, and these improvements and modifications also fall within the scope of protection of the claims.

Claims

1. A method for selecting defective secondary batteries, characterized in that, The selection method includes the following steps: Steps for measuring edge resistance: Select or make a battery with a primary cell structure. The battery has a first damaged area (6). Measure the edge resistance r1 of the first damaged area (6). Corrosion steps: Conduct a corrosion experiment on the battery, measure the corrosion time t1, and construct the first calculation formula for the battery's electrochemical corrosion resistance life: L1=AF×t1, where L1 is the battery's electrochemical corrosion resistance life and AF is the acceleration factor. Construct a second formula for calculating the resistance r2 required to satisfy the electrochemical corrosion resistance lifetime L2: Using resistor r2 as the lower limit of the side resistance of the secondary battery under test, if the measured side resistance of the secondary battery under test is less than resistor r2, the secondary battery under test is determined to be defective.

2. The selection method as described in claim 1, characterized in that, Before the corrosion step, a heating device is obtained; the battery is placed in the heating device until corrosion occurs, and the time from when the battery is placed in the heating device until corrosion occurs is recorded and set as corrosion time t1.

3. The selection method as described in claim 2, characterized in that, The heating temperature of the heating device is set to T. t , will T t Substituting into the Arrhenius formula, the acceleration factor AF is calculated: Among them, E a K is the empirical value of the activation energy, and K is the Boltzmann constant.

4. The selection method as described in claim 1, characterized in that, The battery includes a metal casing (1), a first insulating layer (11), and a second insulating layer (12), wherein the first insulating layer (11) and the second insulating layer (12) respectively insulate the two side surfaces of the metal casing (1); before the side resistance measurement step, the battery further includes: Steps for constructing a galvanic cell structure: A portion of the first insulating layer (11) is damaged to obtain a first damaged area (6), and a portion of the second insulating layer (12) is damaged to obtain a second damaged area (7), so as to expose the metal shell (1) at the positions corresponding to the first damaged area (6) and the second damaged area (7); a negative electrode material (31) is arranged inside the metal shell (1), and a negative electrode tab (3) is arranged outside the metal shell (1), so as to connect the metal shell (1), the negative electrode material (31) and the negative electrode tab (3) to form a conductive circuit.

5. The selection method as described in claim 4, characterized in that, Before forming a conductive circuit, the following is also included: Steps for obtaining the connection structure: One end of the connection structure is electrically connected to the negative electrode (3), and the other end is electrically connected to the metal shell (1) through the second damaged area (7). An electronic path is formed between the negative electrode (3) and the metal shell (1).

6. The selection method as described in claim 4, characterized in that, Before forming a conductive circuit, the following is also included: Electrolyte contact step: The electrolyte inside the metal shell (1) comes into contact with the metal shell (1) through the first damaged area (6), and an ion pathway is formed between the negative electrode material (31) and the metal shell (1).

7. The selection method as described in claim 6, characterized in that, Prior to the electrolyte contact step, the first damaged area (6) is arranged on the side of the first insulating layer (11) near the negative electrode material (31).

8. The selection method as described in claim 4, characterized in that, Before forming a conductive circuit, the first damaged area (6) and the second damaged area (7) are arranged opposite to each other.

9. The selection method as described in claim 1, characterized in that, The side resistance r1 satisfies the first relationship: Where P is the resistivity of the conductive material, and L J S is the transmission path of the first damaged area (6), and S is the cross-sectional area of ​​the transmission path of the first damaged area (6).

10. The selection method as described in claim 1, characterized in that, L1 also satisfies the second relation: Where Qi is the current of the battery, and E is the electromotive force of the battery reaction.

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