Secondary battery for internal short circuit experiments, and its manufacturing method and experimental method

Abstract

The present invention relates to a secondary battery for internal short circuit experiments, comprising: an electrode assembly; and a pouch accommodating the electrode assembly. The electrode assembly comprises: a first main electrode comprising a first main current collector and a first main coating layer coated on the remaining surface of the first main current collector except for a first plain surface defined by the first main current collector; a second electrode comprising a second coating layer coated on the surface of the second current collector; a main separator disposed between the first main electrode and the second electrode and having through holes formed at positions corresponding to the first plain surface; an auxiliary separator detachably attached to the main separator and closing or opening the through holes; and a first auxiliary electrode detachably attached to the first plain surface and connecting the first plain surface of the first main current collector to the second electrode via the through holes that are opened when removed so as to cause an internal short circuit.

Description

[Technical Field]

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2023-0033530, filed on March 14, 2023, the entire contents of which are incorporated herein by reference.

[0002] The present invention relates to a secondary battery for internal short circuit testing that can test for an internal short circuit between a positive electrode, a lithium deposit, and a negative electrode, or between a current collector provided on a positive electrode and a negative electrode, and a method for manufacturing the same and a testing method. [Background technology]

[0003] Generally, a secondary battery refers to a battery that can be charged and discharged, unlike a primary battery that cannot be charged. Such secondary batteries are widely used in mobile phones, laptops, video cameras, electric vehicles, etc.

[0004] Secondary batteries are classified into can-type secondary batteries, in which an electrode assembly is housed in a metal can, and pouch-type secondary batteries, in which an electrode assembly is housed in a pouch. Can-type secondary batteries include an electrode assembly, an electrolyte, a can containing the electrode assembly and the electrolyte, and a cap assembly mounted on the opening of the can. Pouch-type secondary batteries include an electrode assembly, an electrolyte, and a pouch containing the electrode assembly and the electrolyte.

[0005] Here, secondary batteries are subjected to internal short-circuit tests to improve safety. Internal short-circuits in secondary batteries can be broadly divided into two categories: first, an internal short-circuit between the positive electrode and negative electrode, and second, an internal short-circuit between the positive electrode, lithium deposits, and negative electrode.

[0006] The first internal short circuit is more dangerous than the second internal short circuit because the potential difference between the contacting materials is greater. Furthermore, when shorting the positive electrode current collector and the charged negative electrode in the second internal short circuit, if there is no positive electrode coating layer facing the negative electrode, the negative electrode will not be fully charged, making it difficult to conduct the experiment smoothly. Furthermore, when shorting the positive electrode current collector and the lithium deposits formed on the charged negative electrode in the second internal short circuit, if there is no positive electrode coating layer facing the negative electrode, the lithium deposits will only form partially, rather than over the entire desired area, making it difficult to conduct the experiment in the desired direction. Therefore, in order to conduct experiments on the internal short circuit of a secondary battery in a desired direction, a secondary battery for internal short circuit experiments is required. Summary of the Invention [Problem to be solved by the invention]

[0007] An object of the present invention is to provide a secondary battery for internal short circuit testing, which can smoothly and accurately test for an internal short circuit between a positive electrode, a lithium deposit, and a negative electrode, or between a current collector included in a positive electrode and a negative electrode, and a manufacturing method and testing method thereof. [Means for solving the problem]

[0008] The secondary battery for internal short circuit testing according to the present invention includes an electrode assembly and a pouch containing the electrode assembly, wherein the electrode assembly includes a first main electrode including a first main current collector and a first main coating layer coated on the remaining surface of the first main current collector except for a first plain surface defined by the first main current collector, a second electrode including a second coating layer coated on the surface of the second current collector, a main separator disposed between the first main electrode and the second electrode and having a through-hole formed at a position corresponding to the first plain surface, an auxiliary separator detachably attached to the main separator and closing or opening the through-hole, and a first auxiliary electrode detachably attached to the first plain surface and connecting the first plain surface of the first main current collector to the second electrode via the through-hole that opens when removed to cause an internal short circuit. This allows testing of an internal short circuit between the first main electrode and the second electrode in a desired direction.

[0009] The first auxiliary electrode may include a first auxiliary current collector having an attachment surface that is detachably attached to the first non-planar surface, and a first auxiliary coating layer that is coated on the attachment surface, thereby enabling the first auxiliary electrode to be stably and detachably attached to the first non-planar surface.

[0010] The first planar surface may be formed on an edge of the first main current collector, thereby allowing the first auxiliary electrode to be easily attached or detached from the first planar surface without damaging the first main coating layer.

[0011] The first auxiliary current collector may further include a second plane surface that is positioned outside the first main electrode when the attachment surface is attached to the first plane surface and that separates the first auxiliary current collector from the first plane surface, thereby allowing the first auxiliary electrode attached to the first plane surface to be easily removed.

[0012] The auxiliary separator may include a separation surface that is detachably attached to the main separator while covering the through-hole, and a gripping surface that is positioned outside the main separator when the separation surface is attached to the main separator and that separates the auxiliary separator from the main separator, thereby making it easy to remove the auxiliary separator attached to the main separator.

[0013] The first auxiliary electrode may have the same thickness as the first main coating layer, thereby preventing a step from occurring between the first auxiliary electrode and the first main coating layer.

[0014] The second coating layer may include a first coating surface coated on a surface of the second current collector corresponding to the through hole and a second coating surface coated on a surface of the second current collector not coated with the first coating surface, and the first coating surface may have a thickness smaller than that of the second coating surface. This allows lithium deposits to be smoothly generated on the first coating surface during charge and discharge, thereby preventing internal short circuits between the main first electrode, the lithium deposits, and the second electrode.

[0015] The main first electrode and the auxiliary first electrode may have the same polarity. The main first electrode and the auxiliary first electrode may be positive electrodes. The second electrode may be a negative electrode.

[0016] The first auxiliary electrode may be detachably attached to the first plain surface via an adhesive tape, thereby allowing the first auxiliary electrode to be stably and detachably attached to the first plain surface.

[0017] The auxiliary separator and the main separator can be detachably attached by heat sealing, which allows the main separator and the auxiliary separator to be stably attached, and the adhesive strength between the main separator and the auxiliary separator is weakened by impregnation with the electrolyte, allowing the main separator and the auxiliary separator to be easily separated.

[0018] A method for manufacturing a secondary battery for internal short circuit experiments according to the present invention includes the steps of: (a) preparing a first main current collector having a first plain surface defined thereon, coating a first main coating layer on the surface of the first main current collector, and then removing the first main coating layer coated on the first plain surface to manufacture a first main electrode; (b) coating a second coating layer on the surface of a second current collector to manufacture a second electrode; (c) manufacturing a main separator having through holes formed therein by cutting a portion of the surface corresponding to the first plain surface when the main separator is disposed between the first main electrode and the second electrode; (d) manufacturing an auxiliary separator that closes or opens the through holes, and then detachably attaching the auxiliary separator to the main separator while covering the through holes; and (e) manufacturing an auxiliary electrode that connects or disconnects the first main current collector and the second electrode via the through holes to cause an internal short circuit, and then detachably attaching the auxiliary first electrode to the first plain surface. By using this method, a finished secondary battery for internal short-circuit testing can be easily manufactured.

[0019] In step (e), the first auxiliary electrode may include a first auxiliary current collector having an attachment surface that is detachably attached to the first plain surface, and a first auxiliary coating layer that is coated on the outer surface of the attachment surface.

[0020] In step (a), the first plain surface is defined at the edge of the main first current collector, and in step (e), the auxiliary first current collector may include a second plain surface that is located outside the main first electrode when the attachment surface is attached to the first plain surface and separates the auxiliary first current collector from the first plain surface.

[0021] The step (b) may further include a step of cutting a surface of the second coating layer corresponding to the through hole when the main separator is disposed between the main first electrode and the second electrode after coating the second coating layer, and the second coating layer may include a cut first coating surface and an uncut second coating surface, and the first coating surface may have a smaller thickness than the second coating surface.

[0022] After step (e), the method may further include the steps of: (f) manufacturing an electrode assembly by disposing the main separator, to which the auxiliary separator is attached, between the main first electrode, to which the auxiliary first electrode is attached, and the second electrode; and (g) housing the electrode assembly in a pouch and then sealing the pouch to manufacture the secondary battery for internal short circuit testing. The main first electrode and the auxiliary first electrode may have the same polarity.

[0023] The method for testing a secondary battery for internal short circuit testing according to the present invention can include the steps of: (A) applying a voltage to the secondary battery for internal short circuit testing according to any one of claims 1 to 12 and charging and discharging it; (B) cutting open the pouch of the secondary battery for internal short circuit testing; (C) removing the auxiliary first electrode attached to the main first electrode of the electrode assembly through the cutout of the pouch; (D) removing the auxiliary separator attached to the main separator of the electrode assembly through the cutout of the pouch to open the through-hole of the main separator; and (E) crimping the secondary battery for internal short circuit testing and contacting the first plain surface of the main first current collector with the second electrode through the through-hole to cause an internal short circuit. This allows testing of an internal short circuit between the main first electrode and the second electrode in a desired direction.

[0024] In step (A), the second coating layer of the second electrode is composed of a first coating surface and a second coating surface having a thickness greater than that of the first coating surface, and lithium deposits can be generated on the first coating surface corresponding to the auxiliary first electrode during charging and discharging, thereby allowing internal short circuits between the main first electrode, the lithium deposits, and the second electrode to be induced in a desired direction. [Effects of the Invention]

[0025] The secondary battery for internal short circuit testing of the present invention can test a short circuit between the first main electrode and the second electrode, or between the current collector included in the first main electrode and the second electrode, in a desired direction. [Brief explanation of the drawings]

[0026] [Figure 1] 1 is a perspective view showing an assembled state of a secondary battery for internal short circuit experiments according to a first embodiment of the present invention. [Figure 2] FIG. 2 is an exploded perspective view showing the electrode assembly of FIG. 1. [Figure 3] FIG. 3 is a cross-sectional view taken along line AA shown in FIG. 2. [Figure 4] FIG. 3 is a cross-sectional view taken along line BB shown in FIG. 2. [Figure 5] FIG. 3 is a cross-sectional view taken along line CC shown in FIG. 2. [Figure 6] FIG. 2 is a cross-sectional view showing the electrode assembly of FIG. [Figure 7] 7 is a cross-sectional view showing the electrode assembly from which an auxiliary first electrode and an auxiliary separator are removed from FIG. 6. FIG. [Figure 8] 8 is a cross-sectional view showing the electrode assembly in a crimped state from FIG. 7. FIG. [Figure 9] 3 is a flowchart showing a method for manufacturing an experimental secondary battery for internal short circuit according to the first embodiment of the present invention. [Figure 10] FIG. 1(a) is a perspective view showing a step of manufacturing a main first electrode. [Figure 11] FIG. 1(b) is a perspective view showing a step of manufacturing a second electrode. [Figure 12] FIG. 1(c) is a perspective view showing a step for manufacturing the main separator. [Figure 13] FIG. 10(d) is a perspective view showing the step of attaching the auxiliary separator to the main separator. [Figure 14] FIG. 10(e) is a perspective view showing a step of attaching the auxiliary first electrode to the main first electrode. [Figure 15] 3 is a flowchart showing an experimental method for an internal short-circuit test secondary battery according to the first embodiment of the present invention. [Figure 16] FIG. 10 is a plan view showing the charge and discharge steps. [Figure 17] FIG. 10 is a plan view showing the step of opening the pouch. [Figure 18] 10A and 10B are cross-sectional views showing a step of removing the auxiliary separator and the auxiliary first electrode. [Figure 19] 10 is a cross-sectional view showing a step of crimping a secondary battery for an internal short circuit experiment. FIG. [Figure 20] FIG. 6 is an exploded perspective view showing an electrode assembly according to a second embodiment of the present invention. [Figure 21] FIG. 21 is a cross-sectional view showing the electrode assembly of FIG. 20. [Figure 22] 22 is a cross-sectional view showing the electrode assembly from which an auxiliary first electrode and an auxiliary separator have been removed from FIG. 21. FIG. [Figure 23] 23 is a cross-sectional view showing the electrode assembly in a crimped state from FIG. 22. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0027] Hereinafter, with reference to the accompanying drawings, embodiments of the present invention will be described in detail so that those skilled in the art can easily carry out the present invention. However, the present invention may be realized in various different forms and is not limited to the embodiments described herein. In the drawings, parts that are not relevant to the description are omitted in order to clearly explain the present invention, and similar parts are designated by similar reference numerals throughout the specification.

[0028] [Secondary battery for internal short circuit experiments according to the first embodiment of the present invention] FIG. 1 is a perspective view showing an assembled state of a secondary battery for internal short circuit experiments according to the first embodiment of the present invention, FIG. 2 is an exploded perspective view showing the electrode assembly of FIG. 1, FIG. 3 is a cross-sectional view taken along line AA of FIG. 2, FIG. 4 is a cross-sectional view taken along line BB of FIG. 2, FIG. 5 is a cross-sectional view taken along line CC of FIG. 2, FIG. 6 is a cross-sectional view showing the electrode assembly of FIG. 1, FIG. 7 is a cross-sectional view showing the electrode assembly of FIG. 6 from which the auxiliary first electrode and auxiliary separator have been removed, and FIG. 8 is a cross-sectional view showing the electrode assembly of FIG. 7 in a crimped state.

[0029] The secondary battery for internal short circuit experiment according to the first embodiment of the present invention is used to experiment on internal short circuit between the positive electrode, lithium precipitate (Li), and negative electrode. That is, as shown in FIG. 1, the secondary battery 1 for internal short circuit experiments according to the first embodiment of the present invention includes an electrode assembly 10, a pouch 20 that houses the electrode assembly 10, and an electrode lead 30 that is connected to the electrode assembly 10 and has a tip that is extended outside the pouch 20.

[0030] electrode assembly 2, the electrode assembly 10 includes a main first electrode 11, a second electrode 12, a main separator 13, an auxiliary separator 14, and an auxiliary first electrode 15. Here, the auxiliary separator 14 is attached to the main separator 13, and the auxiliary first electrode 15 is attached to the main first electrode 11.

[0031] On the other hand, the main first electrode 11 is a positive electrode, and the second electrode 12 is a negative electrode. The auxiliary first electrode 15 has the same polarity as the main first electrode 11. That is, the auxiliary first electrode 15 is a positive electrode.

[0032] 3, the first main electrode 11 includes a first main current collector 111 and a first main coating layer 112 coated on the remaining surface of the first main current collector 111 except for a first plain surface 1111. That is, the first main electrode 11 includes the first main coating layer 112 coated with a first electrode active material and the first plain surface 1111 where no first electrode active material is present. An electrode tab connected to an electrode lead 30 is formed on the first main current collector 111.

[0033] Meanwhile, in a method for manufacturing the first main electrode 11, the first main coating layer 112 is coated on both surfaces of the first main current collector 111. Then, the first main coating layer 112 coated on the first plain surface 1111 defined on one side of the first main current collector 111 is removed. Then, the first main electrode 11 consisting of the first plain surface 1111 and the first main coating layer 112 can be manufactured.

[0034] On the other hand, the main first electrode 11 may be a positive electrode, and the main first coating layer 112 may be a positive electrode coating layer made of a positive electrode active material.

[0035] Meanwhile, the first main current collector 111 may be provided as a metal plate, and preferably may be made of aluminum (Al) material.

[0036] 2, the first unfilled surface 1111 may be formed on any part of the edge of the first main current collector 111. Preferably, the first unfilled surface 1111 may be formed on an edge surface of the first main current collector 111 where no electrode tab is present. This allows the first auxiliary electrode 15 to be attached or removed from the first unfilled surface 1111 without damaging the first main coating layer 112.

[0037] 5, the second electrode 12 includes a second current collector 121 and a second coating layer 122 coated on the surface of the second current collector 121. That is, the second electrode 12 is manufactured by coating the surface of the second current collector 121 with the second coating layer 122. An electrode tab for connection to the electrode lead 30 is formed on the second current collector 121.

[0038] On the other hand, the second electrode 12 may be a negative electrode. The second current collector 121 is provided as a metal plate, and preferably, the second current collector 121 is made of a copper material.

[0039] Meanwhile, the second electrode 12 has a structure that allows lithium deposits (Li) to be generated at the set portions on the surface of the second coating layer 122 during charge and discharge. That is, the second coating layer 122 includes a first coating surface 1221 coated on the surface of the second current collector 121 corresponding to the through-holes 131 of the main separator 13, and a second coating surface 1222 coated on the surface of the second current collector 121 that is not coated with the first coating surface 1221. Here, the first coating surface 1221 has a thickness smaller than that of the second coating surface 1222. As a result, lithium deposits (Li) are generated on the surface of the second coating layer 122 during charge and discharge, and at this time, large lithium deposits are generated on the first coating surface 1221 where the interaction between the main first coating layer 112 and the first coating surface 1221 of the second coating layer 122 is not smooth, resulting in the growth of dendrites.

[0040] Meanwhile, the thickness of the first coating surface 1221 can be formed so that the NP ratio of the thickness of the second coating surface 1222 is 100 or less. That is, the thickness of the first coating surface 1221 can be formed to be 5 to 80% of the thickness of the second coating surface 1222, and preferably 40 to 75% of the thickness of the second coating surface 1222. In particular, the first coating surface 1221 can be formed by cutting a portion of the surface of the second coating surface 1222.

[0041] 2, the main separator 13 is intended to prevent contact between the first main electrode 11 and the second electrode 12. That is, the main separator 13 is disposed between the first main electrode 11 and the second electrode 12.

[0042] In particular, the main separator 13 has a through hole 131 formed at a position corresponding to the first unfilled surface 1111, and the first unfilled surface 1111 and the second electrode 12 come into contact with each other through the through hole 131, causing an internal short circuit. Meanwhile, the through hole 131 is formed inside the edge of the main separator 13 by a set distance in order to reinforce the strength of the main separator 13.

[0043] 4, the auxiliary separator 14 is intended to close the through-hole 131 formed in the main separator 13. That is, the auxiliary separator 14 is large enough to cover the through-hole 131, and is detachably attached to the main separator 13 in a state where it covers the through-hole 131. In this way, the auxiliary separator 14 can close or open the through-hole 131.

[0044] Here, the adhesive strength between the main separator 13 and the auxiliary separator 14 is weaker than the adhesive strength between the main separator 13 and the first electrode, which prevents separation between the main separator 13 and the first electrode when the auxiliary separator 14 is removed from the main separator 13.

[0045] Meanwhile, the auxiliary separator 14 may be made of the same material as the main separator 13. However, the auxiliary separator 14 has a thinner thickness than the main separator 13. This is because, as shown in FIG. 2, the auxiliary separator 14 is disposed on the upper surface of the main separator 13, which may cause a step between the main separator 13 and the first main electrode 11. Therefore, by minimizing the thickness of the auxiliary separator 14, the step between the main separator 13 and the first main electrode 11 can be minimized.

[0046] Meanwhile, the auxiliary separator 14 has a structure that allows it to be easily removed from the main separator 13. That is, the auxiliary separator 14 includes a separation surface 141 that is detachably attached to the main separator 13 while covering the through-hole 131, and a gripping surface 142 that is located outside the main separator 13 when the separation surface 141 is attached to the main separator 13 and that separates the auxiliary separator 14 from the main separator 13. As a result, by pulling the gripping surface 142 exposed outside the main separator 13, the separation surface 141 attached to the main separator 13 can be easily removed.

[0047] On the other hand, the length of the gripping surface exposed to the outside of the main separator 13 can be formed to be 5 mm to 50 mm, preferably 10 to 20 mm. The auxiliary separator 14 and the main separator 13 can be bonded to each other by heat fusion. That is, the auxiliary separator 14 and the main separator 13 can be bonded to each other using heat and pressure. The auxiliary separator 14 and the main separator 13 can be easily separated from each other when the electrolyte is impregnated because the bonding strength between the auxiliary separator 14 and the main separator 13 weakens.

[0048] Meanwhile, in another embodiment, the auxiliary separator 14 may be detachably attached to the main separator 13 via an adhesive, thereby maintaining stable adhesion between the auxiliary separator 14 and the main separator 13.

[0049] The auxiliary first electrode 15 is intended to fill the surface of the second electrode 12 facing the first unfinished surface 1111 in order to test an internal short circuit between the first unfinished surface 1111 and the second electrode 12.

[0050] That is, the auxiliary first electrode 15 is detachably attached to the first plain surface 1111, and when removed, the first plain surface 1111 of the main first current collector 111 is connected to the second electrode 12 through the opened through-hole 131 so as to cause an internal short circuit.

[0051] As an example, the first auxiliary electrode 15 includes a first auxiliary current collector 151 having an attachment surface 1511 that is detachably attached to the first plain surface 1111, and a first auxiliary coating layer 152 that is coated on the attachment surface 1511.

[0052] Here, the attachment surface 1511 has the same area as the first plain surface 1111. This can prevent gaps from occurring between the attachment surface 1511 and the first coating layer. Meanwhile, the attachment surface 1511 may be formed 1 to 2 mm larger per unit area than the first plain surface 1111, which can significantly prevent gaps from occurring between the attachment surface 1511 and the first coating layer.

[0053] Meanwhile, the first auxiliary electrode 15 may have the same polarity as the first main electrode 11. That is, the first auxiliary electrode 15 may be formed as a positive electrode, and accordingly, the first auxiliary coating layer 152 may be a positive electrode coating layer made of a positive electrode active material.

[0054] Meanwhile, the adhesive strength between the first auxiliary electrode 15 and the first plain surface 1111 is smaller than the adhesive strength between the first main electrode 11 and the main separator 13. This prevents separation between the first main electrode 11 and the main separator 13 when the first auxiliary electrode 15 is removed from the first plain surface 1111.

[0055] Meanwhile, the first auxiliary electrode 15 can be detachably attached to the first plain surface 1111 via adhesive tape. This allows for stable attachment between the first auxiliary electrode 15 and the first plain surface 1111, and the adhesive strength of the adhesive tape weakens when the electrolyte is impregnated, allowing the first auxiliary electrode 15 and the first plain surface 1111 to be easily separated.

[0056] Meanwhile, in another embodiment, the auxiliary first electrode 15 can be detachably attached to the first plain surface 1111 via an adhesive, thereby maintaining a stable adhesive force between the auxiliary first electrode 15 and the first plain surface 1111. Alternatively, the auxiliary first electrode and the first plain surface may be attached by heat and pressure.

[0057] Meanwhile, the first auxiliary current collector 151 may further include a second plain surface 1512 that is located outside the first main electrode 11 when the attachment surface 1511 is attached to the first plain surface 1111 and separates the first auxiliary current collector 151 from the first plain surface 1111. That is, the second plain surface 1512 is formed as a surface that is not coated with the first auxiliary coating layer 152. As a result, the first auxiliary electrode 151 can be easily removed from the first plain surface 1111 using the second plain surface 1512.

[0058] Meanwhile, the first auxiliary electrode 15 may have the same thickness as the first coating layer, thereby preventing a step from occurring between the first auxiliary electrode 15 and the first main electrode 11.

[0059] The electrode assembly 10 having this structure has a structure in which first main electrodes 11 and second electrodes 12, each having a first auxiliary electrode 15 attached thereto, are alternately arranged with a main separator 13 having an auxiliary separator 14 attached thereto interposed therebetween. Here, when the auxiliary separator 14 attached to the main separator 13 is removed and the first auxiliary electrode 15 attached to the first main electrode 11 is removed from the electrode assembly 10, the first unfinished surface 1111 of the first main electrode 11 can come into contact with the second electrode 12 and lithium deposits formed on the second electrode 12 during charge and discharge, thereby generating an internal short circuit between the first main electrode 11, the lithium deposits, and the second electrode 12.

[0060] Pouch The pouch 20 is for containing the electrode assembly 10 and the electrolyte solution. That is, the pouch 20 includes an upper pouch and a lower pouch for containing the electrode assembly 10 and the electrolyte solution.

[0061] Electrode Lead The electrode leads 30 are coupled to electrode tabs formed on the first main electrode 11 and the second electrode 12 of the electrode assembly 10, respectively, and have a structure in which their ends are drawn out of the pouch 20. That is, the electrode leads 30 include a first electrode lead 31 coupled to the electrode tab of the first main electrode 11 and a second electrode lead 32 coupled to the electrode tab of the second electrode 12.

[0062] Therefore, the secondary battery 1 for internal short circuit testing according to the first embodiment of the present invention can be used to test internal short circuits between the main first electrode 11, the lithium precipitate, and the second electrode 12. Hereinafter, a method for manufacturing an experimental secondary battery for internal short circuit according to the first embodiment of the present invention will be described.

[0063] [Method of manufacturing an experimental secondary battery for internal short circuit according to the first embodiment of the present invention] FIG. 9 is a flowchart showing a method for manufacturing a secondary battery for internal short circuit experiments according to the first embodiment of the present invention, FIG. 10 is (a) an oblique view showing the step of manufacturing a main first electrode, FIG. 11 is (b) an oblique view showing the step of manufacturing a second electrode 12, FIG. 12 is (c) an oblique view showing the step of manufacturing a main separator, FIG. 13 is (d) an oblique view showing the step of attaching an auxiliary separator to the main separator, and FIG. 14 is (e) an oblique view showing the step of attaching an auxiliary first electrode to the main first electrode.

[0064] 9, the method for manufacturing a secondary battery for internal short-circuit experiments according to the first embodiment of the present invention includes the steps of (a) manufacturing a main first electrode 11, (b) manufacturing a second electrode, (c) manufacturing a main separator, (d) manufacturing an auxiliary separator and attaching it to the main separator, (e) manufacturing an auxiliary first electrode and attaching it to the main first electrode 11, (f) manufacturing an electrode assembly, and (g) manufacturing a secondary battery for internal short-circuit experiments. Meanwhile, the steps of (c) manufacturing the main separator and (d) manufacturing the auxiliary separator and attaching it to the main separator may be performed simultaneously, or the step of (d) manufacturing the auxiliary separator and attaching it to the main separator may be performed before the step of (c) manufacturing the main separator.

[0065] (a) Manufacturing a main first electrode (a) In the step of manufacturing the first main electrode, as shown in Fig. 10, a first main current collector 111 having a first unformed surface 1111 defined therein is prepared. Next, a first main coating layer 112 is coated on the surface of the first main current collector 111. Next, the first main coating layer 112 coated on the first unformed surface 1111 is removed. Then, the first main electrode 11 can be manufactured.

[0066] Meanwhile, the main first coating layer 112 coated on the first plain surface 1111 can be removed by cutting it with a cutting device (not shown) or by wiping it off with NMP (N-Methyl-2-pyrrolidone: a binder solvent for the first electrode material) and then drying it (to evaporate the NMP).

[0067] Here, the first plain surface 1111 is defined on the edge of the main first current collector 111, and this is for easily attaching or removing the first auxiliary electrode 15 attached to the first plain surface 1111. In particular, the first plain surface 1111 may be formed in a rectangular shape.

[0068] The first coating layer is coated to the same thickness on the entire surface of the first main current collector 111, including the first plain surface 1111. The cutting device cuts and removes the first coating layer coated on the first plain surface 1111 so that the first plain surface 1111 is exposed to the outside. On the other hand, the main first electrode 11 is a positive electrode, and the first coating layer is a positive electrode coating layer.

[0069] (b) Fabricating a second electrode (b) In the step of manufacturing the second electrode, as shown in Fig. 11, a second current collector 121 is prepared. Next, a second coating layer 122 is coated on the surface of the second current collector 121. Then, the second electrode 12 can be manufactured.

[0070] Here, after coating the surface of the second current collector 121 with the second coating layer 122, a removal process is further included in which a portion of the surface of the second coating layer 122 corresponding to the first plain surface 1111 is removed. That is, the removal process removes the portion of the surface of the second coating layer 122 corresponding to the through-hole 131 of the main separator 13 when the main separator 13 is disposed between the first main electrode 11 and the second electrode 12. In particular, the removal process removes only a portion of the entire thickness of the second coating layer 122 so that the second current collector 121 is not exposed to the outside.

[0071] Meanwhile, the surface of the second coating layer 122 corresponding to the through-holes 131 may be removed by cutting, or by repeatedly applying and peeling off adhesive tape.

[0072] Accordingly, the second coating layer 122 includes a first coating surface 1221 and a second coating surface 1222, and the first coating surface 1221 has a smaller thickness than the second coating surface 1222. As a result, lithium deposits can be induced to occur on the first coating surface 1221 during charge and discharge.

[0073] (c) manufacturing the main separator (c) In the step of manufacturing the main separator, as shown in Fig. 12, a main separator 13 is prepared. Then, when the main separator 13 is disposed between the first main electrode 11 and the second electrode 12, a portion of the surface of the main separator 13 corresponding to the first unfinished surface 1111 is cut to form a through-hole 131. Then, the main separator 13 having the through-hole 131 formed therein can be manufactured.

[0074] (d) Fabricating an auxiliary separator and attaching it to the main separator (d) The step of manufacturing an auxiliary separator and attaching it to the main separator involves manufacturing an auxiliary separator 14 to close or open the through-hole 131 formed in the main separator 13, as shown in FIG. 13 . Here, the auxiliary separator 14 has an area larger than the area of ​​the through-hole. Next, the auxiliary separator 14 is attached to the main separator 13 while covering the through-hole 131. At this time, the auxiliary separator 14 is detachably attached to the main separator 13. That is, when the auxiliary separator 14 is attached to the main separator 13, the through-hole 131 can be closed, and when the auxiliary separator 14 is removed from the main separator 13, the through-hole 131 can be opened.

[0075] Here, the auxiliary separator 14 includes a separation surface 141 that is detachably attached to the main separator 13 while covering the through hole 131, and a gripping surface 142 that is positioned outside the main separator 13 when the separation surface 141 is attached to the main separator 13 and is used to separate the auxiliary separator 14 from the main separator 13. Here, the auxiliary separator 14 and the main separator 13 can be attached using heat fusion (heat and pressure).

[0076] On the other hand, the adhesive strength between the auxiliary separator 14 and the main separator 13 is smaller than the adhesive strength between the main first electrode 11 and the main separator 13 .

[0077] Meanwhile, the auxiliary separator 14 may be made of the same material as the main separator 13. However, in order to minimize the occurrence of steps, the thickness of the auxiliary separator 14 is smaller than the thickness of the main separator 13. Meanwhile, in another embodiment, the auxiliary separator and the main separator may be made of different materials.

[0078] (e) Fabricating an auxiliary first electrode and attaching it to the main first electrode (e) The step of manufacturing the auxiliary first electrode and attaching it to the main first electrode involves manufacturing the auxiliary first electrode 15, which connects or cuts off the connection between the main first current collector 111 and the second electrode 12 so as to cause an internal short circuit through the through-hole 131 of the main separator 13, as shown in FIG. 14.

[0079] That is, the first auxiliary electrode 15 includes a first auxiliary current collector 151 having an attachment surface 1511 that is detachably attached to the first plain surface 1111, and a first auxiliary coating layer 152 that is coated on the outer surface of the attachment surface 1511. The attachment surface 1511 may have the same area as the first plain surface 1111.

[0080] In particular, the auxiliary first electrode 15 has the same polarity as the main first electrode 11. That is, the auxiliary first electrode 15 and the main first electrode 11 may be positive electrodes, and the second electrode 12 may be negative electrodes.

[0081] The auxiliary first current collector 151 includes a second blank surface 1512 positioned outside the main first electrode 11 when the attachment surface 1511 is attached to the first blank surface 1111, and the second blank surface 1512 serves as a handle for separating the attachment surface 1511 of the auxiliary first current collector 151 from the first blank surface 1111.

[0082] Meanwhile, the first auxiliary electrode 15 may have the same thickness as the first main coating layer 112. This can increase the adhesion between the first main electrode 11 and the main separator, and prevent the occurrence of steps.

[0083] Meanwhile, the adhesive strength between the first auxiliary electrode 15 and the first plain surface 1111 is smaller than the adhesive strength between the first main electrode 11 and the main separator 13 .

[0084] Meanwhile, the first auxiliary electrode 15 may be attached to the first plain surface 1111 using adhesive tape. On the other hand, steps (d) and (e) may be performed simultaneously, or step (e) may be performed before step (d).

[0085] (f) manufacturing the electrode assembly (f) In the step of manufacturing an electrode assembly, as shown in FIG. 2, a main separator 13 having an auxiliary separator 14 attached thereto is disposed between the main first electrode 11 having the auxiliary first electrode 15 attached thereto and the second electrode 12 to manufacture an electrode assembly 10.

[0086] In this case, the electrode assembly 10 has the gripping surface 142 of the auxiliary separator 14 and the second plain surface 1512 of the auxiliary first electrode 15 exposed to the outside, and the auxiliary separator 14 and the auxiliary first electrode 15 can be removed from the electrode assembly 10 using the gripping surface 142 and the second plain surface 1512.

[0087] (g) Step of manufacturing a secondary battery for internal short circuit experiments (g) In the step of manufacturing a secondary battery for internal short-circuit testing, as shown in FIG. 1, electrode leads 30 are connected to the electrode tabs of electrode assembly 10, and then electrode assembly 10 and an electrolyte (not shown) are housed in pouch 20. At this time, the tip of electrode lead 30 is pulled out of pouch 20. Next, pouch 20 is sealed to hermetically seal it. This completes the manufacturing of secondary battery 1 for internal short-circuit testing. Hereinafter, an experimental method using the secondary battery for internal short-circuit experiments according to the first embodiment of the present invention will be described.

[0088] [Experimental Method for Secondary Battery for Internal Short-Circuit Experiments According to the First Embodiment of the Present Invention] FIG. 15 is a flowchart showing an experimental method for the secondary battery 1 for internal short-circuit experiments according to the first embodiment of the present invention, FIG. 16 is a plan view showing the charge / discharge steps, FIG. 17 is a plan view showing the step of cutting open the pouch 20, FIG. 18 is a cross-sectional view showing the step of removing the auxiliary separator and auxiliary first electrode 15, and FIG. 19 is a cross-sectional view showing the step of crimping the secondary battery for internal short-circuit experiments.

[0089] As shown in FIG. 15, the experimental method for the secondary battery for internal short-circuit experiments according to the first embodiment of the present invention includes (A) a charge / discharge step, (B) a pouch cutting step, (C) an auxiliary first electrode removal step, (D) an auxiliary separator removal step, (E) a crimping step for the secondary battery for internal short-circuit experiments, and (F) an internal short-circuit experiment step.

[0090] (A) Charge / discharge steps (A) In the charge / discharge step, as shown in FIG. 16, a charge / discharge device 2 is connected to the electrode lead 30 of the secondary battery 1 for the internal short-circuit experiment, and then power is applied to the secondary battery 1 for the internal short-circuit experiment to repeatedly charge or discharge it. At this time, lithium deposits are generated on the first coating surface 1221 provided on the second coating layer 122 of the second electrode 12.

[0091] (B) Pouch incision step 17, when charging and discharging of the secondary battery 1 for internal short-circuit experiments is completed, the pouch 20 of the secondary battery 1 for internal short-circuit experiments is cut open using a cutting device 3. At this time, the surface of the pouch 20 adjacent to the second plain surface 1512 and the gripping surface 142 of the auxiliary separator 14 is cut open.

[0092] (C) Removal step of the first auxiliary electrode (C) In the step of removing the auxiliary first electrode, as shown in Fig. 18, the auxiliary first electrode 15 attached to the main first electrode 11 of the electrode assembly 10 is removed through the cutout 21 of the pouch 20. Here, the auxiliary first electrode and the main first electrode are attached with adhesive tape, and the adhesive strength of the adhesive tape is weakened by the electrolyte, thereby making it possible to easily remove the auxiliary first electrode from the main first electrode.

[0093] In other words, when the second plain surface 1512 of the auxiliary first electrode 15 exposed to the outside of the electrode assembly 10 is pulled, the attachment surface 1511 of the auxiliary first electrode 15 attached to the first plain surface 1111 of the main first electrode 11 is separated and can be removed.

[0094] (D) Auxiliary separator removal step (D) In ​​the auxiliary separator removal step, as shown in Figure 18, the auxiliary separator 14 attached to the main separator 13 of the electrode assembly 10 is removed through the cutout 21 of the pouch 20. Here, the adhesive strength between the auxiliary separator and the main separator is weakened by the impregnation with the electrolyte, so that the auxiliary separator can be easily removed from the main separator.

[0095] That is, when the gripping surface 142 of the auxiliary separator 14 exposed to the outside of the electrode assembly 10 is pulled, the separation surface 141 of the auxiliary separator 14 attached to the main separator 13 separates, allowing the auxiliary separator 14 to be easily removed. This opens the through-hole 131 of the main separator 13.

[0096] (E) Crimping step of secondary battery for internal short circuit experiment (E) In the step of crimping the secondary battery for internal short circuit experiments, the secondary battery for internal short circuit experiments 1 is crimped for 3 minutes to 1 hour, preferably 15 minutes to 30 minutes, using a crimping device 4, as shown in Fig. 19. This brings the first unpainted surface 1111 of the first main current collector 111, the lithium deposit, and the first coated surface 1221 of the second electrode 12 into contact with each other via the through-holes 131 of the main separator 13, resulting in an internal short circuit. That is, an internal short circuit can occur between the main first electrode 11, the lithium deposit, and the second electrode 12.

[0097] (F) Internal short circuit experiment steps In the (F) internal short circuit experiment step, an internal short circuit experiment device (not shown) is used to measure the voltage, resistance, and temperature of the secondary battery 1 for internal short circuit experiment in which an internal short circuit has occurred. That is, by measuring and recording the voltage flowing through the electrode lead 30 of the secondary battery 1 for internal short circuit experiment in which an internal short circuit has occurred, it is possible to experiment whether an internal short circuit has occurred due to pressure, time, and voltage difference.

[0098] More specifically, depending on the magnitude of the resistance during an internal short circuit, the following modes appear in the behavior of voltage and temperature. First mode: The voltage gradually decreases, the temperature rises slightly, and then decreases gradually until the experiment ends without ignition. Second: A sudden drop in voltage and a sudden rise in temperature can lead to a fire. Third: A mode in which the voltage drops and temperature rises suddenly, but the critical point for ignition is not reached, so the temperature then drops gradually and ignition does not occur.

[0099] Therefore, in the (E) step of crimping the secondary battery for internal short circuit experiment, an internal short circuit experiment can be carried out using the secondary battery for internal short circuit experiment 1. In the following description of other embodiments of the present invention, the same reference numerals will be used for components having the same functions as those in the above-described embodiment, and duplicated descriptions will be omitted.

[0100] [Second embodiment of the present invention, a secondary battery for internal short circuit experiments] FIG. 20 is an exploded perspective view showing an electrode assembly according to a second embodiment of the present invention, FIG. 21 is a cross-sectional view showing the electrode assembly of FIG. 20, FIG. 22 is a cross-sectional view showing the electrode assembly from FIG. 21 with the auxiliary first electrode 15 and auxiliary separator 14 removed, and FIG. 23 is a cross-sectional view showing the electrode assembly from FIG. 22 in a pressurized state. In describing the secondary battery for internal short-circuit experiments according to the second embodiment of the present invention, the same components will be designated by the same reference numerals, and duplicated descriptions will be omitted.

[0101] As shown in FIG. 20, the secondary battery for internal short circuit experiments according to the second embodiment of the present invention includes an electrode assembly 10′, a pouch (not shown) that houses the electrode assembly 10′, and an electrode lead 30 that is connected to the electrode assembly 10 and has a tip that extends outside the pouch.

[0102] Here, the secondary battery for internal short-circuit experiments according to the second embodiment of the present invention has the same configuration as that of the secondary battery for internal short-circuit experiments according to the first embodiment of the present invention described above, except for the second electrode 12, and therefore, redundant explanations will be omitted.

[0103] 21, the second electrode 12 includes a second current collector 121 and a second coating layer 122 coated on the surface of the second current collector 121. That is, referring to FIG. 21, the second coating layer 122 is coated on both surfaces of the second current collector 121. The second current collector 121 includes electrode tabs for connection to the electrode lead 30.

[0104] Here, unlike the second electrode 12 included in the secondary battery for internal short circuit experiments according to the first embodiment, the second electrode 12 does not have a first coating surface 1221 formed thereon, and therefore, lithium deposits do not occur on the surface of the second coating layer 122 of the second electrode 12 during charging and discharging.

[0105] In the secondary battery for internal short circuit testing according to the second embodiment of the present invention having such a structure, when the auxiliary first electrode 15 and the auxiliary separator 14 are removed from the electrode assembly 10′ as shown in FIG. 22, the first plain surface 1111 of the main first electrode 11 and the second coating layer 122 of the second electrode 12 can be connected to face each other through the through hole 131 of the main separator 13.

[0106] Furthermore, when the secondary battery for internal short circuit experiments according to the second embodiment of the present invention is crimped as shown in FIG. 23, the first plain surface 1111 of the main first electrode 11 and the second coating layer 122 of the second electrode 12 come into contact with each other through the through-hole 131 of the main separator 13, thereby causing an internal short circuit. Therefore, the secondary battery for internal short circuit testing according to the second embodiment of the present invention can be used to test internal short circuit between the main first electrode 11 and the second electrode 12.

[0107] [Experimental Example] Experimental preparation The purpose of the experiment is to derive the influence of lithium deposits and the critical point at which fire occurs when an internal short circuit (in dangerous and non-dangerous areas) occurs due to lithium deposits.

[0108] In the experimental method, a secondary battery for internal short-circuit testing (positive electrode current collector-lithium deposit-charged negative electrode) (hereinafter referred to as Experimental Object 1) according to the first embodiment of the present invention and a secondary battery for internal short-circuit testing (positive electrode current collector-charged negative electrode) (hereinafter referred to as Experimental Object 2) according to the second embodiment were prepared. Then, the unit area (mm 2 ) of Experimental Object 1 and Experimental Object 2 was measured. 2 ) and apply unit pressures (MPa) of 0.3, 0.5, and 1.0 to the pressures of 1.76 (1.5Φ), 7.06 (3.0Φ), and 79.62 (5.0Φ).

[0109] Experimental results for Experiment 1 As shown in Table 1 below, in Experiment 1, an internal short circuit occurred due to lithium deposits, and the critical point for ignition could not be identified due to the high resistance of the lithium deposits. In other words, it can be confirmed that no ignition occurred in Experiment 1.

[0110] [Table 1]

[0111] <Experimental Table 1> As shown in Experimental Table 2 below, in Experimental Material 2, as the pressure per unit area increases, a critical point for ignition due to an internal short circuit can be confirmed. In other words, in Experimental Material 2, it can be confirmed that as the pressure increases, ignition occurs when the short circuit area increases.

[0112] [Table 2]

[0113] <Experimental Table 2> Therefore, Experimental Table 3 shown in Table 3 below can be prepared by referring to Experimental Table 1 and Experimental Table 2. In this manner, an internal short circuit can be tested using the secondary batteries for internal short circuit tests according to the first and second embodiments of the present invention.

[0114] [Table 3]

[0115] <Experimental Table 3> The scope of the present invention is defined by the claims below rather than the above detailed description, and various embodiments are possible within the meaning and scope of the claims and their equivalent concepts. [Explanation of symbols]

[0116] 1: Secondary battery for internal short circuit experiments 10: Electrode assembly 11: Main 1st electrode 111: Main 1st current collector 1111: 1st plain ground 112: Main first coating layer 12:Second electrode 121: Second current collector 122: Second coating layer 1221: First coated surface 1222: Second coated surface 13: Main separator 131: Through hole 14: Auxiliary separator 141: Separation surface 142: Gripping surface 15: Auxiliary 1st electrode 151: Auxiliary first current collector 1511: Adhesion surface 1512: 2nd plain ground 152: Auxiliary first coating layer 20: Pouch 21: Incision 30: Electrode lead 31: First electrode lead 32: Second electrode lead 2: Charge / discharge device 3: Incision device 4: Crimping device

Claims

1. an electrode assembly; a pouch that accommodates the electrode assembly; Including, The electrode assembly is a first main electrode including a first main current collector and a first main coating layer coated on the remaining surface of the first main current collector except for a first unfilled surface defined thereon; a second electrode including a second current collector and a second coating layer coated on the surface of the second current collector; a main separator disposed between the first main electrode and the second main electrode, the main separator having a through hole formed at a position corresponding to the first plain surface; an auxiliary separator that is detachably attached to the main separator and closes or opens the through-hole; an auxiliary first electrode that is detachably attached to the first plain surface and that connects the first plain surface of the main first current collector and the second electrode through the through hole that is opened when the main first current collector is removed so as to cause an internal short circuit; A secondary battery for internal short circuit experiments.

2. The auxiliary first electrode is a first auxiliary current collector having an attachment surface that is detachably attached to the first plain surface; 2. The secondary battery for internal short circuit experiments according to claim 1, further comprising: an auxiliary first coating layer coated on the attachment surface.

3. 3. The secondary battery for internal short-circuit experiments according to claim 2, wherein the first unfinished surface is formed on an edge of the main first current collector.

4. The auxiliary first current collector is 4. The secondary battery for internal short-circuit experiments according to claim 3, further comprising a second plain surface located outside the main first electrode when the attachment surface is attached to the first plain surface, for separating the auxiliary first current collector from the first plain surface.

5. The auxiliary separator is a separation surface that is detachably attached to the main separator while covering the through-hole; 2. The secondary battery for internal short-circuit experiments according to claim 1, further comprising: a gripping surface located outside the main separator when the separation surface is attached to the main separator, for separating the auxiliary separator from the main separator.

6. The secondary battery for internal short-circuit experiments according to claim 1 , wherein the first auxiliary electrode has the same thickness as the first main coating layer.

7. The second coating layer is a first coating surface coated on a surface of the second current collector corresponding to the through-hole; and a second coating surface coated on a surface of the second current collector that is not coated with the first coating surface, 2. The secondary battery for internal short circuit experiments according to claim 1, wherein the first coating surface has a thickness smaller than that of the second coating surface.

8. 3. The secondary battery for internal short-circuit experiments according to claim 2, wherein the main first electrode and the auxiliary first electrode have the same polarity.

9. 9. The secondary battery for internal short-circuit experiments according to claim 8, wherein the main first electrode and the auxiliary first electrode are positive electrodes.

10. 2. The secondary battery for internal short-circuit experiments according to claim 1, wherein the second electrode is a negative electrode.

11. 2. The secondary battery for internal short circuit experiments according to claim 1, wherein the first auxiliary electrode is detachably attached to the first plain surface via an adhesive tape.

12. 2. The secondary battery for internal short circuit experiments according to claim 1, wherein the auxiliary separator and the main separator are detachably attached by heat fusion.

13. (a) preparing a first main current collector having a first unformed surface defined thereon, coating a first main coating layer on a surface of the first main current collector, and then removing the first main coating layer coated on the first unformed surface to manufacture a first main electrode; (b) coating a second coating layer on a surface of a second current collector to produce a second electrode; (c) manufacturing a main separator having through-holes formed by cutting a portion of the surface corresponding to the first plain surface when the main separator is disposed between the first electrode and the second electrode; (d) manufacturing an auxiliary separator that closes or opens the through-hole, and then detachably attaching the auxiliary separator to the main separator in a state where the auxiliary separator covers the through-hole; (e) fabricating an auxiliary first electrode that connects or disconnects the main first current collector and the second electrode through the through hole so as to cause an internal short circuit, and then detachably attaching the auxiliary first electrode to the first plain surface; A method for manufacturing a secondary battery for internal short circuit experiments, comprising:

14. In the step (e), the first auxiliary electrode is 14. The method for manufacturing a secondary battery for internal short circuit experiments according to claim 13, comprising: a first auxiliary current collector having an attachment surface formed thereon that is detachably attached to the first plain surface; and a first auxiliary coating layer coated on an outer surface of the attachment surface.

15. In the step (a), the first unfilled area is defined on an edge of the main first current collector, 15. The method for manufacturing a secondary battery for internal short circuit experiments according to claim 14, wherein in step (e), the first auxiliary current collector includes a second plain surface that is located outside the first main electrode when the attachment surface is attached to the first plain surface and that separates the first auxiliary current collector from the first plain surface.

16. the step (b) further includes a step of cutting a surface of the second coating layer corresponding to the through-hole when the main separator is disposed between the main first electrode and the second electrode after coating the second coating layer; 14. The method for manufacturing an internal short-circuit experimental secondary battery according to claim 13, wherein the second coating layer includes a cut first coating surface and an uncut second coating surface, and the first coating surface has a thickness smaller than that of the second coating surface.

17. After step (e), (f) manufacturing an electrode assembly by disposing the main separator, to which the auxiliary separator is attached, between the main first electrode, to which the auxiliary first electrode is attached, and the second electrode; 14. The method for manufacturing a secondary battery for internal short circuit experiments according to claim 13, further comprising: (g) housing the electrode assembly in a pouch and then sealing the pouch to manufacture the secondary battery for internal short circuit experiments.

18. The method for manufacturing an internal short-circuit experimental secondary battery according to claim 13 , wherein the main first electrode and the auxiliary first electrode have the same polarity.

19. (A) applying a voltage to the secondary battery for internal short-circuit experiments according to any one of claims 1 to 12 to charge and discharge the battery; (B) cutting open the pouch of the secondary battery for internal short circuit experiment; (C) removing the auxiliary first electrode attached to the main first electrode of the electrode assembly through the incision in the pouch; (D) removing the auxiliary separator attached to the main separator of the electrode assembly through the cut portion of the pouch to open the through-hole of the main separator; (E) crimping the secondary battery for internal short circuit experiment to bring the first plain surface of the main first current collector into contact with the second electrode through the through-hole to cause an internal short circuit; An experimental method for a secondary battery for internal short circuit experiments, including:

20. 20. The method for testing a secondary battery for internal short circuit testing according to claim 19, wherein in step (A), the second coating layer of the second electrode is composed of a first coating surface and a second coating surface having a thickness greater than that of the first coating surface, and lithium deposits are generated on the first coating surface corresponding to the first auxiliary electrode during charging and discharging.

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