Adhesion strength measurement system and method for wet electrode samples

Abstract

This invention relates to an adhesion measurement system for wet electrode samples capable of evaluating the adhesion of electrode samples immersed in an electrolyte, and a method for measuring the adhesion of wet electrode samples using the system.

Description

Technical Field

[0001] This application claims priority to Korean Patent Application No. 10-2021-0037134, filed on March 23, 2021, the entire contents of which are disclosed in which Korean Patent Application are incorporated herein by reference.

[0002] This invention relates to a system for measuring the adhesive strength of wet electrode samples and a method for measuring the adhesive strength of wet electrode samples using the system. Background Technology

[0003] With technological advancements and increasing demand for mobile devices, the need for rechargeable batteries as an energy source is rapidly growing. Among rechargeable batteries, lithium-ion batteries are widely used as the energy source for various mobile devices and electronic products due to their high energy density, high operating voltage, and excellent storage and lifespan characteristics.

[0004] Furthermore, secondary batteries are gaining attention as an energy source for electric or hybrid vehicles, and have been proposed as a solution to air pollution caused by conventional gasoline and diesel vehicles using fossil fuels. For secondary batteries to be used as an energy source for electric vehicles, they need to be high-output batteries.

[0005] These secondary batteries are being developed to achieve high voltage and high capacity models to meet consumer needs. To achieve high capacity, the four main components of the secondary battery—positive electrode material, negative electrode material, separator, and electrolyte solution—need to be optimized within a limited space.

[0006] Furthermore, electrodes for use in secondary batteries are prepared by coating an electrode slurry onto a current collector and drying it into a thin metal film. Because mechanical / environmental loads are applied to the electrodes during the preparation process, it is necessary to sample the electrode samples after specific processing steps or for each part, and to evaluate the physical properties of the samples.

[0007] During the evaluation of the physical properties of electrodes, the adhesive strength of the electrodes is a major factor affecting the fabrication processability or performance of secondary batteries. Therefore, during the fabrication process, it is necessary to measure the adhesive strength of the electrode mixture layer (hereinafter referred to as the electrode adhesive strength) during the adhesive coating of the electrode current collector with electrode slurry. Specifically, the method for measuring the electrode adhesive strength uses an apparatus that measures the peel strength by peeling the electrode mixture layer (active material) from the electrode current collector in order to measure the adhesive strength of the electrode mixture layer.

[0008] As mentioned above, in typical electrode adhesion strength measurement methods, the dried electrode is used to measure peel strength.

[0009] However, in actual secondary batteries, the electrodes are immersed in an electrolyte solution. Therefore, in order to more accurately evaluate the fabrication processability or performance of secondary batteries, techniques are needed that can simulate the actual state of the electrodes inside a secondary battery and measure the adhesion strength of the electrodes. Summary of the Invention

[0010] Technical issues

[0011] The present invention aims to solve the above problems and provides a system for measuring the adhesive strength of wet electrode samples and a method for measuring the adhesive strength of wet electrode samples using the system. The system is capable of evaluating the adhesive strength of electrode samples immersed in electrolyte solution.

[0012] Technical solution

[0013] The present invention provides a system for measuring the adhesive strength of a wet electrode sample. In one example, the system for measuring the adhesive strength of a wet electrode sample according to the present invention includes: a test substrate to which an electrode sample is attached; a fixing clamp configured to fix the test substrate such that the electrode sample attached to the test substrate is immersed in an electrolyte solution; and an adhesive strength measuring unit configured to measure the force of peeling off a mixture layer of the electrode sample by applying a tensile force to the clamped electrode sample, the adhesive strength measuring unit including a clamping portion configured to clamp a region of the electrode sample.

[0014] Specifically, the adhesion strength measurement system includes: a test substrate, wherein the surface of a mixture layer of an electrode sample is attached to the test plate; a fixing clamp configured to hold an electrolyte solution therein and to fix the test substrate such that the electrode sample attached to the test substrate is immersed in the electrolyte solution; and an adhesion strength measuring unit configured to measure the force that peels off the mixture layer of the electrode sample by applying a tensile force to the clamped electrode sample, the adhesion strength measuring unit including a clamping portion configured to clamp a region of the electrode sample. In this case, a recessed portion is formed on one surface of the fixing clamp to hold the electrolyte solution.

[0015] Furthermore, the present invention provides a method for measuring adhesive strength using the adhesive strength measurement system described above with wet electrode samples.

[0016] In one example, a method for measuring the adhesive strength of a wet electrode sample according to the present invention includes the following operations: impregnating a test substrate with the electrode sample attached thereto with an electrolyte solution, and measuring the adhesive strength of the electrode sample by applying a tensile force to the electrode sample impregnated with the electrolyte solution while fixing the test substrate to a fixing fixture.

[0017] Specifically, an adhesive strength measurement method includes the following operations: attaching an electrode sample to a test substrate such that a mixture layer of the electrode sample is in contact with the test substrate; impregnating the test substrate with the attached electrode sample in an electrolyte solution; and measuring the adhesive strength of the electrode sample by applying a tensile force to the electrode sample impregnated in the electrolyte solution, so as to measure the force required to peel the mixture layer of the electrode sample while fixing the test substrate to a fixture.

[0018] Beneficial effects

[0019] The adhesive strength measurement system for wet electrode samples according to the present invention and the method for determining the adhesive strength of wet electrode samples using the system can simulate electrodes in a secondary battery, thereby facilitating the measurement of the adhesive strength of the electrodes. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of an adhesive strength measurement system according to an embodiment of the present invention.

[0021] Figure 2 This is a schematic diagram of the fixing fixture in the adhesive strength measurement system according to the present invention.

[0022] Figure 3 This is a side view of a fixing clamp according to an embodiment of the present invention.

[0023] Figure 4 This is a plan view of a fixing clamp according to an embodiment of the present invention.

[0024] Figure 5 This is a schematic diagram of an adhesive strength measurement system according to another embodiment of the present invention.

[0025] Figure 6 This is a flowchart illustrating a method for measuring the adhesive strength of a wet electrode sample in one example of the present invention. Detailed Implementation

[0026] This invention provides a system for measuring the adhesive strength of a wet electrode sample. In one example, the system for measuring the adhesive strength of a wet electrode sample according to the invention includes: a test substrate to which an electrode sample is attached; a fixing clamp configured to fix the test substrate such that the electrode sample attached to the test substrate is immersed in an electrolyte solution; and an adhesive strength measuring unit configured to measure the force required to peel off a mixture layer of the electrode sample by applying a tensile force to the clamped electrode sample, the adhesive strength measuring unit including a clamping portion configured to clamp a region of the electrode sample.

[0027] The electrodes in a secondary battery are immersed in an electrolyte solution. The adhesion strength of the electrodes varies depending on whether the electrodes are wet or dry. According to the present invention, the state of the electrodes disposed in a secondary battery can be simulated, and then the adhesion strength of the electrodes can be measured.

[0028] In one embodiment, an electrode sample is attached to a test substrate such that the surface of the mixture layer of the electrode sample contacts the test substrate, and a retaining fixture holds the electrolyte solution therein and fixes the test substrate such that the electrode sample attached to the test substrate is immersed in the electrolyte solution.

[0029] In a specific embodiment, the fixing clamp has a surface in which a recessed portion is formed to hold the electrolyte solution. The electrolyte solution is held in the recessed portion.

[0030] In one example, the fixing fixture includes a first fixing part and a second fixing part, which are arranged in the form of strips to fix one side and the other side of the test substrate, respectively. Furthermore, one side of the second fixing part can be pivotally engaged by a hinge pin, and the other side of the second fixing part may have a connecting groove formed thereon.

[0031] In a specific example, the retaining clamp includes a connecting protrusion, to which the connecting groove of the second retaining part engages. Alternatively, the connecting protrusion may be located in the area facing the hinge pin.

[0032] In addition, the first fixing part and the second fixing part may include fastening members for applying pressure to the test substrate.

[0033] In another example, the clamping portion of the adhesive strength measuring unit includes a metal jaw plate surface having a surface in which an engraved or embossed grid is formed. In a particular example, the recess depth or protrusion height of the engraved or embossed grid formed on the surface of the metal jaw plate can range from an average of 0.001 mm to 1 mm.

[0034] In yet another example, the adhesive strength measuring unit according to the invention further includes an output unit configured to output the force of the mixture layer that peels off the electrode sample.

[0035] Furthermore, the present invention provides a method for measuring adhesive strength using the adhesive strength measurement system described above with wet electrode samples.

[0036] In one example, a method for measuring the adhesive strength of a wet electrode sample according to the present invention includes the following operations: impregnating a test substrate with the electrode sample attached thereto with an electrolyte solution, and measuring the adhesive strength of the electrode sample by applying a tensile force to the electrode sample impregnated with the electrolyte solution while fixing the test substrate to a fixing fixture.

[0037] In a specific example, attaching the electrode sample to the test substrate involves attaching the electrode sample to the test substrate such that the mixture layer of the electrode sample contacts the test substrate. Additionally, measuring the adhesion strength of the electrode sample involves measuring the force required to peel off the mixture layer of the electrode sample by applying a tensile force to the electrode sample immersed in the electrolyte solution.

[0038] Specifically, the method for measuring the adhesive strength of a wet electrode sample according to the present invention includes the following operations: attaching an electrode sample to a test substrate such that the mixture layer of the electrode sample is in contact with the test substrate; impregnating the test substrate to which the electrode sample is attached with an electrolyte solution; and measuring the adhesive strength of the electrode sample by applying a tensile force to the electrode sample impregnated with the electrolyte solution while fixing the test substrate to a fixing fixture to measure the force that peels off the mixture layer of the electrode sample.

[0039] In one example, attaching an electrode sample to a test substrate includes a process of attaching double-sided adhesive tape to one surface of the test substrate; and a process of attaching the electrode sample to the test substrate with the double-sided adhesive tape attached such that the surface of the mixture layer of the electrode sample contacts the test substrate. In this case, the process of attaching the electrode sample may include attaching the electrode sample, excluding the freestanding areas of the electrode sample, to the test substrate.

[0040] In one example, the operation of immersing a test substrate with attached electrode samples in an electrolyte solution may include immersing the electrode samples, excluding the self-standing regions, in an electrolyte solution.

[0041] In another example, the operation of measuring the adhesive strength of an electrode sample includes a process of stretching the self-standing region of the electrode sample in a direction perpendicular to the test substrate.

[0042] In addition, the electrode sample may have a structure with a metal current collector and an electrode mixture layer formed on one or both sides of the metal current collector.

[0043] Detailed description of preferred embodiments

[0044] The present invention will now be described in detail. Before the description, the terms or words used in this specification and claims should not be construed as limited to their conventional or dictionary meanings, but should be interpreted based on the inventor's ability to appropriately define the concepts of the terms in order to best describe the principles of his invention in a meaning and concept consistent with the technical spirit of the invention.

[0045] This invention relates to a system for measuring the adhesive strength of wet electrode samples and a method for measuring the adhesive strength of wet electrode samples using the system.

[0046] Typically, methods for measuring electrode adhesion strength involve peeling the electrode mixture layer from the electrode current collector and measuring the peel strength to assess the adhesion strength of the electrode mixture layer. Specifically, double-sided adhesive tape is attached to a glass slide, and the electrode sample is attached to one side of the slide, such that the mixture layer of the electrode sample to be evaluated is in contact with the slide surface. Additionally, a UTM instrument is used to measure the force required to pull one side of the electrode sample and peel it from the glass slide. That is, in related technologies, the peel strength of the dried electrode is measured to measure the adhesion strength of the electrode.

[0047] However, in reality, the electrodes in secondary batteries are immersed in an electrolyte solution. Therefore, in order to more accurately evaluate the fabrication processability or performance of secondary batteries, techniques are needed that can simulate the actual state of the electrodes inside a secondary battery and measure the adhesion strength of the electrodes.

[0048] Therefore, the present invention provides a system for measuring the adhesive strength of wet electrode samples and a method for measuring the adhesive strength of wet electrode samples using the system, the system being capable of evaluating the adhesive strength of electrode samples immersed in electrolyte solution.

[0049] In this invention, the term "electrode sample" refers to an object to be measured using the adhesive strength measurement system for wet electrode samples according to the invention, and can be an electrode having a metal current collector and an electrode mixture layer formed on one or both sides of the metal current collector. For example, an electrode sample can be a sample obtained by stamping an electrode to a predetermined width and predetermined length.

[0050] The adhesive strength measurement system for wet electrode samples according to the present invention and the method for measuring the adhesive strength of wet electrode samples using the system will be described in detail with reference to the accompanying drawings.

[0051] Figure 1 This is a schematic diagram of an adhesive strength measurement system according to an embodiment of the present invention. Figure 2 This is a schematic diagram of the fixing clamp in the adhesive strength measurement system according to the present invention. Figure 3 This is a side view of a fixing clamp according to an embodiment of the present invention, and Figure 4 This is a plan view of a fixing clamp according to an embodiment of the present invention.

[0052] Reference Figure 1 and Figure 2The adhesive strength measurement system 100 for wet electrode samples according to the present invention is configured to include a test substrate 110 to which an electrode sample 111 is attached, a fixing clamp 120 for fixing the test substrate 110, and an adhesive strength measurement unit 130 configured to measure the force of peeling off a mixture layer of the electrode sample 111 by applying a tensile force to a region of the electrode sample 111. Furthermore, the fixing clamp 120 may include a recessed portion 121 having a recessed structure for holding an electrolyte solution.

[0053] As an example, the adhesive strength measurement system 100 according to the present invention includes a test substrate 110 for fixing an electrode sample 111. The test substrate 110, to which the electrode sample 111 is attached to fix the electrode sample 111, may be a metal block or a glass substrate (glass slide).

[0054] Furthermore, the electrode sample 111 can be attached to the surface of the test substrate 110 using an adhesive member. As a specific example, the mixture layer of the electrode sample 111 can be attached to the surface of the test substrate 110, and can be attached to areas other than the self-standing region 1111 of the electrode sample 111. Here, the "self-standing region" refers to the area of ​​the electrode sample 111 held by the clamping portion 131 of the adhesive strength measuring unit 130, which will be described below, and the area of ​​the electrode sample 111 that is not impregnated by the electrolyte solution. The self-standing region 1111 of the electrode sample 111 can be held by the clamping portion 131 of the adhesive strength measuring unit 130 to receive tensile force in a direction perpendicular to the test substrate 110.

[0055] The adhesive component can be a robust adhesive with strong adhesive strength that does not deform during adhesive strength measurement and thus does not affect the mixture layer of electrode sample 111. Furthermore, since this invention is used to measure the adhesive strength of electrode sample 111 in a wet state, the adhesive component can be an adhesive that does not deform or swell when exposed to an electrolyte solution. The adhesive component can be an epoxy resin adhesive or double-sided tape, such as polyimide double-sided tape.

[0056] In one example, the adhesive strength measurement system 100 according to the invention includes a clamping fixture 120 for fixing a test substrate 110. In a particular example, the clamping fixture 120 holds an electrolyte solution therein and fixes the test substrate 110 such that an electrode sample 111 attached to the test substrate 110 is immersed in the electrolyte solution. In particular, a recessed portion 121 for holding the electrolyte solution is included in a surface of the clamping fixture 120.

[0057] Specifically, preferably, a space is provided in the fixture 120 to accommodate the test substrate 110 to which the electrode sample 111 to be evaluated is attached. Additionally, the recessed portion 121 can be formed to a predetermined depth to retain the electrolyte solution therein, allowing the electrode sample 111 to be easily immersed in the electrolyte solution. Furthermore, a space for placing the test substrate 110 can be provided inside the recessed portion 121 of the fixture 120.

[0058] Additionally, the fixing clamp 120 includes a fixing portion for fixing the test substrate 110. In a particular example, the fixing clamp 120 may include a first fixing portion 122 and a second fixing portion 123 in the form of a strip. The first fixing portion 122 can fix one side of the test substrate 110, and the second fixing portion 123 can fix the other side of the test substrate 110.

[0059] The first fixing portion 122 and the second fixing portion 123 are in the form of strips, and the test substrate 110 fixed to the fixing clamp 120 is disposed between the upper surface of the recess 121 and the fixing portion 122, and between the upper surface of the recess 121 and the fixing portion 123. Additionally, the first fixing portion 122 and the second fixing portion 123 may also include fastening members 1221 and 1231. Fastening members 1221 and 1231 are used to fix the test substrate 110 inserted between the recess 121 and the first fixing portion 122 of the fixing clamp 120, and between the recess 121 and the second fixing portion 123 of the fixing clamp 120. For example, fastening members 1221 and 1231 may be fastening bolts. Furthermore, the first fixing portion 122 and the second fixing portion 123 may include threaded holes with a structure corresponding to the threads formed on the outer peripheral surface of the fastening bolts, and the fastening bolts can fix the test substrate 110 while engaging with the holes of the first fixing portion 122 and the second fixing portion 123.

[0060] like Figure 3 As shown, the first fixing part 122 can be fixed to the interior of the recessed portion 121 of the fixing clamp 120, and can be disposed on a side of the space in which the test substrate 110 is placed. As described above, the first fixing part 122 can be in the form of a strip, and both ends of the strip-shaped first fixing part 122 can be fixed to the upper surface of the fixing clamp 120. Furthermore, the first fixing part 122 can be installed in a direction intersecting the length direction of the test substrate 110, and the middle region, except for the two ends of the first fixing part 122, can be bent upward, so that the test substrate 110 can be disposed between the first fixing part 122 and the upper surface of the fixing clamp 120. In addition, a fastening member 1221 can be installed in the middle region of the first fixing part 122, and the fastening member 1221 can fix one side of the test substrate 110.

[0061] like Figure 4 As shown, the second fixing part 123 can be disposed inside the recessed portion 121 of the fixing clamp 120, and on the other side of the space in which the test substrate 110 is placed. However, the second fixing part 123 can be in the form of a strip, like the first fixing part 122, but one side of the second fixing part 123 can be pivotally engaged by a hinge pin (not shown), and the other side of the second fixing part 123 can have a connecting groove 1232 formed thereon. For reference, the connecting groove 1232 can be connected to a connecting protrusion described below. One side of the second fixing part 123 is fixed, and the pivotable other side can easily fix the test substrate 110.

[0062] Furthermore, the fixing clamp 120 may include a connecting protrusion 1233 to which the connecting groove 1212 of the second fixing portion 123 is to be connected. In a particular example, the connecting protrusion 1233 may be located in the area opposite to the hinge pin (not shown). That is, when the connecting groove 1232 of the second fixing portion 123 is connected to the connecting protrusion 1233, the first fixing portion 122 and the second fixing portion 123 may be parallel to each other.

[0063] Furthermore, similar to the first fixing part, the middle region excluding both ends of the second fixing part 123 can be bent upwards, allowing the test substrate 110 to be disposed between the upper surface of the second fixing part 123 and the fixing clamp 120. Additionally, the fastening member 1231 can be installed in the middle region of the second fixing part 123.

[0064] To secure the test substrate 110 with the electrode sample 111 attached to it to the fixing fixture 120, the test substrate 110 is first placed in the recess 121 of the fixing fixture 120. In this case, the connecting groove 1212 on the other side of the second fixing part 123 disengages from the connecting protrusion 1233. In addition, the fastening member 1221 of the first fixing part 122 is pressed to fix one side of the test substrate 110.

[0065] Subsequently, by pivoting the other side of the second fixing part 123, the connecting groove 1212 connects to the connecting protrusion 1233. Additionally, the fastening member 1231 of the second fixing part 123 is pressed to secure the other side of the test substrate 110. Furthermore, when the electrode sample 111 is attached to the test substrate 110, the self-standing region 1111 is excluded. The fastening member 1231 of the second fixing part 123 can secure the test substrate 110 except for the self-standing region 1111 of the electrode sample 111.

[0066] In one example, the adhesive strength measurement system 100 for wet electrode samples according to the invention includes an adhesive strength measurement unit 130. In a particular example, the adhesive strength measurement unit 130 may include a clamping portion 131 for clamping a region of an electrode sample 111, and measures the force (hereinafter referred to as adhesive strength) that peels off the mixture layer of the electrode sample 111 by applying a tensile force to the clamped electrode sample 111.

[0067] The adhesive strength measuring unit 130 can be a conventional peel tester. As a specific example, the adhesive strength measuring unit 130 can fix the self-standing region 1111 of the electrode sample 111 to the clamping part 131 of the adhesive strength measuring unit 130 in order to measure the adhesive strength of the electrode sample 111 and the force required to peel the mixture layer at a 90° angle.

[0068] In one example, the adhesive strength measurement unit 130 also includes an output unit 133 configured to output the force that peels the mixture layer of the electrode sample 111. The output unit 133 can use a numerical value to represent the adhesive strength of the electrode sample 111.

[0069] As another example, the adhesion strength measurement unit 130 may also include a storage unit (not shown). When the adhesion strength measurement of the electrode sample 111 is completed, the storage unit receives and stores the adhesion strength measurement results. The storage unit can store the measurement results of the electrode samples to establish a database of measurement results. Specifically, the type of electrode sample 111 is classified according to the type and thickness of the metal thin film, the type of active material forming the mixed layer, etc., and accordingly, the adhesion strength measurement results of the electrode sample 111 can be summarized in a table or graph. When the measurement data are combined in different ways, the adhesion strength of the electrode sample 111 can be predicted, and it is also possible to predict whether the electrode will detach after the battery cell is fabricated.

[0070] Figure 5 This is a schematic diagram of an adhesive strength measuring system according to another embodiment of the present invention. (Refer to...) Figure 5 The adhesive strength measurement unit 130 of the adhesive strength measurement system 100 may include a clamping part 131 for clamping a self-standing region that is a region of the electrode sample 111.

[0071] In this case, the clamping part 131 may include a metal jaw plate surface 1311 having a grid-forming surface. During the measurement of the physical properties of the electrode sample 111, it is possible for the electrode sample to detach from its composite layer or for the electrode sample to slide while the clamping part 131 applies pressure. According to the present invention, by forming a grid on the surface of the jaw plate facing the electrode sample 111, the fixing force of the clamping part 131 on the electrode sample 111 can be increased. The metal jaw plate surface 1311 can be formed of various types of metal (e.g., carbon steel, stainless steel, aluminum, or alloys thereof).

[0072] In one example, the metal jaw plate surface 1311 mentioned in this invention has a surface on which an engraved or embossed grid is formed. By forming a grid pattern on the surface of the metal jaw plate surface 1311, the holding force on the electrode sample 111 can be increased. In this invention, the term "grid" refers to a pattern in the form of a grid or checkerboard, and is collectively referred to as a form in which two or more parallel patterns intersect each other. In a particular example, the recess depth or protrusion height of the engraved or embossed grid formed on the surface of the metal jaw plate surface 1311 ranges from an average of 0.001 mm to 1 mm. For example, the recess depth or protrusion height of the grid ranges from an average of 0.001 mm to 0.1 mm, from 0.001 mm to 0.01 mm, from 0.01 mm to 0.1 mm, or from 0.01 mm to 0.05 mm. According to the invention, by forming a pattern with a very low level of recess or protrusion, the holding force on the electrode sample 111 can be increased without deteriorating the mechanical properties of the electrode sample 111.

[0073] In addition, the present invention provides a method for measuring the adhesive strength of wet electrode samples using the adhesive strength measurement system described above.

[0074] Figure 6 This is a flowchart illustrating a method for measuring the adhesive strength of a wet electrode sample in one example of the present invention. (Refer to...) Figure 6 The method for measuring the adhesive strength of a wet electrode sample according to the present invention includes the following operations: attaching an electrode sample to a test substrate such that the mixture layer of the electrode sample is in contact with the test substrate (S10); impregnating the test substrate to which the electrode sample is attached with an electrolyte solution (S20); and measuring the adhesive strength of the electrode sample by measuring the force that peels off the mixture layer of the electrode sample while applying a tensile force to the electrode sample impregnated with the electrolyte solution while fixing the test substrate to a fixing fixture (S30).

[0075] First, the operation of attaching the electrode sample to the test substrate (S10) includes a process of attaching double-sided adhesive tape to one surface of the test substrate; and a process of attaching the electrode sample to the test substrate with the double-sided adhesive tape attached, such that the surface of the mixture layer of the electrode sample contacts the test substrate. In this case, the process of attaching the electrode sample may include attaching the electrode sample to the test substrate except for the self-standing area of ​​the electrode sample. The "self-standing area" that is a region of the electrode sample may be held by the clamping part of the adhesive strength measuring unit, and may be the area of ​​the electrode sample that is not immersed in the electrolyte solution.

[0076] As a specific example, the operation of attaching the electrode sample to the test substrate (S10) includes attaching the electrode sample to be evaluated to the glass substrate, which serves as the test substrate, using double-sided adhesive tape. In this case, the surface of the mixture layer of the electrode sample can contact the glass substrate. Furthermore, after attaching the electrode sample to the glass substrate, it can be rolled approximately 10 times. Additionally, after placing the test substrate with the attached electrode sample at a temperature range of 40°C to 80°C, 50°C to 70°C, or approximately 60°C for 6 to 16 hours, 10 to 14 hours, or approximately 12 hours, the degree of transformation of the electrode sample can be confirmed.

[0077] Next, the present invention includes an operation (S20) of immersing a test substrate with attached electrode samples in an electrolyte solution. In this case, the operation (S20) of immersing the test substrate with attached electrode samples in an electrolyte solution may include a process of immersing the electrode samples, excluding the self-standing regions, in the electrolyte solution. The self-standing regions are the regions held by the clamping part of the adhesive strength measuring unit and are regions that are not affected by the electrolyte solution during the adhesive strength measurement test. In a specific example, the operation (S20) of immersing the test substrate with attached electrode samples in an electrolyte solution may include: confirming that the electrode samples are attached to the test substrate, placing the test substrate on a tray, injecting the electrolyte solution, covering the tray with a lid, and then performing the immersion.

[0078] Furthermore, the present invention includes an operation (S30) for measuring the adhesion strength using an electrode sample impregnated with an electrolyte solution. The operation (S30) for measuring the adhesion strength of the electrode sample includes, according to the present invention, fixing a test substrate with the attached electrode sample to a fixing fixture and a process for transporting the electrolyte solution in a transport tray. Additionally, by applying a tensile force to the electrolyte-impregnated electrode sample while fixing the test substrate to the fixing fixture, the force required to peel off the mixture layer of the electrode sample can be measured.

[0079] In a specific example, the operation (S30) of measuring the adhesive strength of the electrode sample includes a process of stretching the self-standing region of the electrode sample in a direction perpendicular to the test substrate. That is, the operation (S30) of measuring the adhesive strength of the electrode sample may include performing the measurement using a 90° peel test. For example, the adhesive strength of the electrode sample can be measured by setting the load of the UTM instrument to zero and then setting the load speed in the range of 10 to 200 mm / min. For example, the adhesive strength of the electrode sample can be measured using a UTM instrument (TA Corporation).

[0080] The operation (S30) for measuring the adhesive strength of the electrode sample includes measuring the adhesive strength of the wet electrode sample. In this case, the adhesive strength of the electrode can be easily measured while simulating the internal state of the secondary battery.

[0081] Furthermore, the electrode sample may have a structure comprising: a metal current collector; and an electrode mixture layer formed on one or both surfaces of the metal current collector, and the electrode sample may also have a structure in which a mixture layer comprising active material is formed on the positive or negative current collector.

[0082] Furthermore, the electrolyte solution may include organic solvents and electrolyte salts, with the electrolyte salt being a lithium salt. Those commonly used in non-aqueous electrolyte solutions for lithium secondary batteries can be used as lithium salts without limitation. For example, the negative ions of the lithium salt may include those selected from F… - Cl - ,Br - I - NO3 - N(CN)2 - BF4 - ClO4 - PF6 - (CF3)2PF4 - (CF3)3PF3 - (CF3)4PF2 - (CF3)5PF - (CF3)6P - CF3SO3 - CF3CF2SO3 - (CF3SO2)2N - (FSO2)2N - CF3CF2(CF3)2CO - (CF3SO2)2CH - (SF5)3C - CF3(CF2)7SO3 - CF3CO2 - CH3CO2- SCN - and (CF3CF2SO2)2N - A mixture of one, two, or more of the constituent groups.

[0083] Organic solvents commonly used in electrolyte solutions for lithium secondary batteries can be used as organic solvents contained in the aforementioned electrolyte solutions without limitation. For example, ethers, esters, amides, straight-chain carbonates, or cyclic carbonates can be used alone or in mixtures of two or more types. Typically, organic solvents can include cyclic carbonates, straight-chain carbonates, or mixtures thereof as carbonate compounds.

[0084] Specific examples of cyclic carbonate compounds include one or more mixtures of two or more selected from the group consisting of ethylene carbonate (EC), propylene carbonate (PC), 1,2-butenyl carbonate, 2,3-butenyl carbonate, 1,2-pentadiene carbonate, 2,3-pentadiene carbonate, vinylene carbonate, butadiene carbonate, and their halides.

[0085] Examples of these halides include, but are not limited to, fluoroethylene carbonate (FEC).

[0086] In addition, one or more mixtures selected from the group consisting of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate, methyl ethyl carbonate (EMC), methyl propyl carbonate and ethyl propyl carbonate can be generally used as specific examples of straight-chain carbonate compounds, but the invention is not limited thereto.

[0087] In particular, among carbonate-based organic solvents, ethylene carbonate and propylene carbonate, as cyclic carbonates, are high-viscosity organic solvents with high dielectric constants, thus carbonates can better separate lithium salts in electrolytes. When cyclic carbonates are mixed with linear carbonates such as dimethyl carbonate or diethyl carbonate, which have low viscosity and low dielectric constant, in appropriate proportions, electrolyte solutions with higher conductivity can be prepared.

[0088] In addition, ethers selected from one or more of the group consisting of dimethyl ether, diethyl ether, dipropyl ether, methyl ethyl ether, methyl propyl ether and ethyl propyl ether can be used as organic solvents, but the present invention is not limited thereto.

[0089] In addition, esters selected from one or more of methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, γ-butyrolactone, γ-valerolactone, γ-caprolactone, α-valerolactone and ε-caprolactone can be used as organic solvents, but the present invention is not limited thereto.

[0090] The present invention will be described in detail below with reference to embodiments and the like. However, the configurations described in the embodiments herein are merely examples of the present invention and do not represent all the technical spirit of the present invention. Therefore, it should be understood that various equivalents and modifications may be used instead of this configuration when submitting this application.

[0091] <Preparation Example>

[0092] Preparation Example 1

[0093] Using slot die coating, a copper (Cu) thin film serving as the negative electrode current collector was coated with a negative electrode paste containing 48% solids to form a mixture layer on the surface of the copper thin film. The mixture layer was then rolled to prepare an electrode in which the mixture layer was formed. At this time, the coating speed was 32 m / min and the rolling pressure was 1.05 ton / cm². 2 Then, the electrodes are stamped to a size of 20mm × 125mm to prepare electrode samples.

[0094] Preparation Examples 2 to 6

[0095] Electrode samples were prepared in the same manner as in Preparation Example 1, except that the coating speed, solid content and pressure during the rolling process of the negative electrode slurry were changed.

[0096] In each preparation example, the coating rate of the negative electrode slurry, the solid content, and the rolling pressure of the mixture layer during electrode preparation are shown in Table 1 below.

[0097] [Table 1]

[0098]

[0099] <Experimental Example>

[0100] Experimental Example 1. Measuring the Adhesion Strength of Dry Electrodes

[0101] The adhesion strength of the electrode samples prepared in each preparation example was measured by a 90° peel test.

[0102] Specifically, imide double-sided adhesive tape was attached to a glass slide, and the electrodes prepared in each preparation example were set and bonded by rolling them ten times with a load of 2 kg. Furthermore, an electrode sample was attached to one surface of the glass slide such that the mixture layer of the electrode sample was in contact with the surface of the glass slide.

[0103] Then, the glass slide with the attached electrode sample was placed in an oven at 60°C for about 12 hours, and the degree of adhesion between the electrode sample and the double-sided tape was checked using the torn portion of the electrode sample.

[0104] Next, the force required to peel one side of the electrode sample from the slide at a speed of 100 mm / min was measured using a UTM instrument (TA Instruments). At this point, the measurement angle between the slide and the electrode was 90°.

[0105] At this point, three electrode samples were prepared, and the adhesion strength of each electrode sample was measured by the 90° peel test described above, and the average value was found. The results are shown in Table 2 below.

[0106] Experimental Example 2. Measuring the adhesive strength of electrodes impregnated with electrolyte solution.

[0107] After impregnating the electrode samples prepared in each preparation example with an electrolyte solution, the adhesive strength of the electrode samples was measured using a 90° peel test.

[0108] Specifically, imide double-sided adhesive tape is attached to a glass slide, and the electrodes prepared in each preparation example are set and bonded by rolling them ten times with a load of 2 kg. In this case, the electrode sample, except for the free-standing area of ​​the electrode sample, is attached to the glass slide, such that the mixture layer of the electrode sample is in contact with the surface of the glass slide.

[0109] Then, the glass slide with the attached electrode sample was placed in an oven at 60°C for about 12 hours, and the degree of adhesion between the electrode sample and the double-sided tape was checked using the torn portion of the electrode sample.

[0110] Next, a glass slide with the attached electrode sample was placed on a tray, wherein an electrolyte solution of 1M LiPF6 dissolved in a mixed solvent of dimethyl carbonate (DEC) and ethylene carbonate (EC) (DEC:EC = 1:1) was prepared such that the electrode sample was immersed in the electrolyte solution. In this case, the free-standing areas of the electrode sample were not immersed in the electrolyte solution. Furthermore, the electrolyte solution and the electrode sample were transferred to the adhesive strength measuring fixture of the present invention, and the adhesive strength of the electrode sample was measured in the same manner as in Experimental Example 1. Three electrode samples were prepared, and the adhesive strength of each electrode sample was measured by the 90° peel test described above, and the average value was found. The results are shown in Table 2 below.

[0111] Experimental Example 3. Checking electrode detachment after electrode cell fabrication

[0112] After preparing a single cell using the negative electrode according to each preparation example, check whether the negative electrode active material has been extracted.

[0113] In a single cell, lithium metal is used as the positive electrode, and a separator is inserted between the negative and positive electrodes. The single cells are then stacked to fabricate an electrode assembly. Subsequently, an electrolyte solution containing 1 M LiPF6 dissolved in a mixed solvent of dimethyl carbonate (DEC) and ethylene carbonate (EC) (DEC:EC = 1:1) is injected into the electrode assembly to fabricate a lithium secondary battery.

[0114] The lithium secondary battery prepared as described above was charged and discharged 50 times at 25°C, and the cross-section of the negative electrode was observed after disassembly. Furthermore, the results regarding whether the active material was extracted are shown in Table 2 below.

[0115] [Table 2]

[0116]

[0117] Referring to Table 2, after the battery cell was prepared, no electrode active material was extracted in Preparation Example 1, but the electrode active material was extracted in Preparation Example 2.

[0118] Additionally, the difference in adhesion strength between the dry electrode and the electrode immersed in the electrolyte solution can be examined. Specifically, comparing Preparation Example 3 and Preparation Example 6, the adhesion strengths of the dry electrode are 21.4 gf / 20 mm and 21.7 gf / 20 mm, respectively, which are similar. However, the adhesion strengths (wet adhesion strengths) of the electrodes immersed in the electrolyte solution are different. Specifically, the wet adhesion strength in Preparation Example 3 is 9.5 gf / 10 mm, while the wet adhesion strength in Preparation Example 6 is 7.1 gf / 10 mm. The wet adhesion strength in Preparation Example 3 is higher than that in Preparation Example 6.

[0119] Furthermore, in the results of whether the active material was extracted in Preparation Example 3 and Preparation Example 6, the active material was extracted from the electrode of Preparation Example 6, which had low wet adhesion strength.

[0120] Furthermore, referring to Table 2, it can be seen that the adhesive strength of wet electrode samples is difficult to estimate solely by measuring the adhesive strength of dry electrode samples. That is, under equivalent conditions, dry adhesive strength can exhibit completely different performance from wet adhesive strength. In this invention, by evaluating the adhesive strength of electrode samples immersed in electrolyte solution, electrodes in secondary batteries can be simulated. Additionally, through evaluation, this invention can improve the reliability of predictive evaluation of electrode active material release.

[0121] The above description is merely an illustration of the technical spirit of the present invention, and those skilled in the art can make various modifications and variations without departing from the basic characteristics of the invention. Therefore, the embodiments disclosed herein are not intended to limit but rather describe the technical spirit of the invention, and the scope of the invention is not limited by these embodiments. The scope of the invention should be understood through the appended claims, and all technical spirit within its equivalents should be understood to be included within the scope of the invention.

[0122] [Description of reference numerals in the accompanying drawings]

[0123] 100: Adhesion Strength Measurement System

[0124] 110: Test substrate

[0125] 111: Electrode

[0126] 1111: Independent Region

[0127] 120: Fixture

[0128] 121: Recessed portion

[0129] 122: First fixed part

[0130] 1221: Fastening components

[0131] 123: Second fixed part

[0132] 1231: Fastening components

[0133] 1232: Connecting slot

[0134] 1233: Connecting protrusion

[0135] 130: Adhesion strength measurement unit

[0136] 131: Clamping part

[0137] 1311: Metal jaw plate face

Claims

1. A system for measuring the adhesive strength of a wet electrode sample, the system comprising: Test substrate; An electrode sample comprising a freestanding region and a region other than the freestanding region, the region other than the freestanding region having a metal current collector and an electrode mixture layer on at least one side of the metal current collector, and the surface of the electrode mixture layer being attached to the test substrate; A fixing clamp having a surface defining the recess for holding an electrolyte solution in a recess, the fixing clamp being configured to fix the test substrate such that the area of ​​the electrode sample attached to the test substrate, except for the self-standing region, is immersed in the electrolyte solution, while the self-standing region of the electrode sample is not immersed in the electrolyte solution. as well as An adhesive strength measuring unit includes a clamping portion configured to clamp the self-standing region of the electrode sample and apply a tensile force to the self-standing region in a direction perpendicular to the surface of the electrode mixture layer attached to the test substrate. The adhesive strength measuring unit is configured to measure the force applied to the electrode mixture layer of the electrode sample by the tensile force as it is peeled from the test substrate.

2. The adhesive strength measuring system according to claim 1, wherein, The fixing clamp includes a first fixing part and a second fixing part, which are arranged in the form of strips to fix one side and the other side of the test substrate, respectively. One side of the second fixing part is pivotally engaged by a hinge pin, and a connecting groove is formed on the other side of the second fixing part.

3. The adhesive strength measuring system according to claim 2, wherein, Both ends of the first fixing part are fixed to the upper surface of the fixing clamp.

4. The adhesive strength measuring system according to claim 2, wherein, The fixing clamp includes a connecting protrusion, the connecting groove of the second fixing part is connected to the connecting protrusion, and the connecting protrusion is disposed in the area facing the hinge pin.

5. The adhesive strength measuring system according to claim 2, wherein, Each of the first fixing part and the second fixing part includes a fastening member for applying pressure to the test substrate.

6. The adhesive strength measuring system according to claim 1, wherein, The clamping part of the adhesive strength measuring unit includes a metal jaw plate surface having a surface with an engraved or embossed grid.

7. The adhesive strength measuring system according to claim 6, wherein, The depth of the recess or the height of the engraved or relief grid formed on the surface of the metal jaw plate ranges from an average of 0.001 mm to 1 mm.

8. The adhesive strength measuring system according to claim 1, wherein, The adhesive strength measuring unit further includes an output unit configured to output the force that peels the mixture layer off the electrode sample.

9. A method for measuring the adhesive strength of a wet electrode sample, the method comprising the following operations: Electrode samples are attached to the test substrate, wherein... The electrode sample includes a freestanding region and a region other than the freestanding region, the region other than the freestanding region having a metal current collector and an electrode mixture layer on at least one side of the metal current collector, and wherein the surface of the electrode mixture layer is attached to the test substrate; The test substrate with the attached electrode sample is fixed to the fixing fixture; The test substrate with the attached electrode sample is immersed in an electrolyte solution, wherein the test substrate and the regions of the electrode sample other than the freestanding region are immersed in the electrolyte solution, while the freestanding region of the electrode sample is not immersed in the electrolyte solution; and The adhesive strength of the electrode sample is measured by applying a tensile force to the self-standing region of the electrode sample while the test substrate is immersed in the electrolyte solution and fixed to the fixing fixture, wherein the tensile force is applied in a direction perpendicular to the surface of the test substrate to determine the force applied to peel the electrode mixture layer of the electrode sample from the test substrate.

10. The method for measuring adhesive strength according to claim 9, wherein, The operation of attaching the electrode sample to the test substrate includes: The process of attaching double-sided tape to one surface of the test substrate; and The process of attaching the electrode sample to the test substrate such that the surface of the test substrate with the double-sided tape attached comes into contact with the surface of the mixture layer of the electrode sample.

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