Manufacturing method for composite current collector electrode sheet, and evaluation method for composite current collector electrode sheet

Abstract

The present application relates to the technical field of batteries. Disclosed are a manufacturing method for a composite current collector electrode sheet and an evaluation method for a composite current collector electrode sheet. During the manufacturing of an electrode sheet, two negative-electrode metal foil current collector tabs are welded to two sides of a tab of a composite negative-electrode current collector body by means of ultrasonic waves, wherein the welding amplitude ranges between 90% and 100%, and the welding pressure is within 0.5 MPa-1 MPa; and two positive-electrode metal foil current collector tabs are welded to two sides of a tab of a composite positive-electrode current collector body by means of ultrasonic waves, so as to form a composite positive-electrode current collector electrode sheet, wherein the welding amplitude ranges between 30% and 35%, and the welding pressure is within 0.3 MPa-0.8 MPa. By controlling the welding amplitude and the welding pressure, the tensile strength of a welded composite current collector electrode sheet in a welding mark area can be ensured; in addition, the resistance of the welding mark area can be controlled to be within an appropriate range, so as to ensure that the composite current collector electrode sheet has good electrical conduction performance and current collection performance, thereby improving the cycle performance and rate performance of a battery.

Description

Method for manufacturing composite current collector electrode and method for evaluating composite current collector electrode

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to the Chinese patent application filed with the China Patent Office on April 3, 2024, with application number 202410399082.5 and invention name “Method for manufacturing composite current collector pole piece and method for evaluating composite current collector pole piece”, all contents of which are incorporated herein by reference. Technical Field

[0003] The present application relates to the field of battery technology, and in particular to a method for manufacturing a composite current collector electrode and a method for evaluating the composite current collector electrode. Background Art

[0004] Composite current collectors have thinner thickness and lighter weight, which is conducive to improving the energy density of lithium-ion batteries. The development of composite current collectors conforms to the development trend of cost reduction, thinning and weight reduction of current collectors, and is of great significance to improving battery safety, energy density and cycle performance.

[0005] The composite current collector includes an intermediate polymer layer and metal layers on either side of the polymer layer. Since the intermediate polymer layer is an insulating material, the metal layers on either side of it cannot conduct electricity during the charge and discharge process. This hinders the transmission of current from the battery cell to the electrode terminals. To solve the current transmission problem of the battery cell, the commonly used method is to use two layers of conventional metal foil current collector tabs to sandwich a layer of composite current collector tabs, and then weld the metal foil current collector tabs to the composite current collector tabs through ultrasonic welding or laser welding.

[0006] In the prior art, when manufacturing composite current collector electrodes, after welding the metal foil current collector electrode tab and the composite current collector electrode tab, the welding effect is difficult to ensure, which affects the electrochemical performance of the battery. Summary of the Invention

[0007] In view of this, the present application provides a method for manufacturing a composite current collector electrode and a method for evaluating a composite current collector electrode to solve the problem in the prior art that it is difficult to ensure the welding effect between the metal foil current collector electrode and the composite current collector electrode when manufacturing the composite current collector electrode, thereby affecting the electrochemical performance of the battery.

[0008] In a first aspect, the present application provides a method for manufacturing a composite current collector electrode sheet, wherein the composite current collector electrode sheet includes a composite current collector body and a metal foil current collector electrode ear, wherein the composite current collector body includes a composite negative electrode current collector body and a composite positive electrode current collector body; and the metal foil current collector electrode ear includes a negative electrode metal foil current collector electrode ear and a positive electrode metal foil current collector electrode ear. The method for manufacturing the composite current collector electrode sheet includes:

[0009] preparing a composite negative electrode current collector body;

[0010] The two negative electrode metal foil current collector tabs are ultrasonically welded to both sides of the tabs of the composite negative electrode current collector body to form a composite negative electrode current collector pole piece, with a welding amplitude of 90%-100% and a welding pressure of 0.5Mpa-1Mpa;

[0011] preparing a composite positive electrode current collector body;

[0012] The two positive electrode metal foil current collector tabs are ultrasonically welded on both sides of the tabs of the composite positive electrode current collector body to form a composite positive electrode current collector pole piece, with a welding amplitude of 30%-35% and a welding pressure of 0.3Mpa-0.8Mpa.

[0013] Beneficial effects: When the composite current collector electrode is manufactured by the present manufacturing method, the metal foil current collector electrode is welded to both sides of the electrode ear of the composite current collector body by ultrasonic welding. In the process of welding the negative metal foil current collector electrode and the positive metal foil current collector electrode, the negative metal foil current collector electrode and the positive metal foil current collector electrode can be effectively welded to the electrode ear of the composite current collector body by controlling the welding amplitude and welding pressure, thereby ensuring the tensile strength of the composite current collector electrode in the weld print area after welding and ensuring the firmness of the welding area; at the same time, by controlling the welding amplitude and welding pressure, the resistance of the weld print area can be controlled within an appropriate range, thereby ensuring that the composite current collector electrode has good conductivity and current collection performance, thereby improving the cycle and rate performance of the battery.

[0014] In an optional embodiment, when two negative electrode metal foil current collector tabs are ultrasonically welded to both sides of the tabs of the composite negative electrode current collector body, the welding amplitude is 100% and the welding pressure is 0.6 MPa.

[0015] In an optional embodiment, when two positive electrode metal foil current collector tabs are ultrasonically welded to both sides of the tabs of the composite positive electrode current collector body, the welding amplitude is 35% and the welding pressure is 0.4 MPa.

[0016] In an optional embodiment, the length of the composite current collector body on the side where the metal foil current collector tab is located is L1, the length of the weld mark area formed after welding the metal foil current collector tab is L2, and 25% L1≤L2≤L1.

[0017] Beneficial effect: The length of the welding area between the metal foil current collector tab and the composite current collector body can be guaranteed, thereby ensuring the welding firmness between the two, and further improving the tensile strength of the weld mark area after welding.

[0018] In an optional embodiment, the width W of the weld mark area formed after welding the metal foil current collector tab is 3 mm ≤ W ≤ 4.5 mm.

[0019] Beneficial effects: The width of the weld print area is controlled within an appropriate range to avoid the weld print area being too small to affect the welding strength. At the same time, the resistance can be increased due to the welding area being too small, thereby reducing the welding resistance. In addition, the width of the weld print area is moderate to avoid excessive weld prints that damage the metal foil current collector tabs and the tabs of the composite current collector body, thereby ensuring the welding quality and the stability of the welding resistance.

[0020] In an optional embodiment, preparing the composite negative electrode current collector body includes:

[0021] preparing a composite negative electrode current collector;

[0022] Graphite, conductive carbon black, sodium carboxymethyl cellulose, and styrene-butadiene rubber latex were mixed uniformly in deionized water at a mass ratio of 96.5:1.0:1.0:1.5 to form a negative electrode slurry;

[0023] Applying the negative electrode slurry on the composite negative electrode current collector and drying it to obtain the composite negative electrode current collector body;

[0024] And / or, manufacturing the composite positive electrode current collector body includes:

[0025] preparing a composite positive electrode current collector;

[0026] Nickel-rich ternary layered oxide, conductive carbon black, and polyvinylidene fluoride were mixed and stirred uniformly in an appropriate amount of N-methylpyrrolidone solvent at a mass ratio of 96.8:2:1.2 to form a positive electrode slurry;

[0027] The positive electrode slurry is coated on the composite positive electrode current collector, and the composite positive electrode current collector body is obtained after drying.

[0028] In an optional embodiment, when preparing a composite current collector, the process includes:

[0029] An insulating base film layer is prepared by using an insulating material, wherein the insulating material includes at least one of polyamide, polyterephthalate, polyimide, polypropylene, polybutylene terephthalate, and polycarbonate;

[0030] Metal conductive layers are respectively laid on the upper surface and the lower surface of the insulating base film layer.

[0031] In an optional embodiment, the thickness of the insulating base film layer is D0, 1 μm≤D0≤12 μm;

[0032] And / or, the thickness of the metal conductive layer is D1, 0.5 μm≤D1≤3 μm.

[0033] In an optional embodiment, the metal conductive layer is laid on the insulating base film layer by at least one method selected from the group consisting of hot pressing, mechanical rolling, bonding, vapor deposition, and chemical plating.

[0034] In a second aspect, the present application further provides a method for evaluating a composite current collector electrode, wherein the composite current collector electrode is manufactured using any of the above-described methods for manufacturing a composite current collector electrode. The method for evaluating the composite current collector electrode comprises:

[0035] Obtaining a test sample of the composite current collector electrode;

[0036] The test sample is placed in a testing machine, wherein one clamp of the testing machine clamps the composite current collector body of the test sample, and another clamp of the testing machine clamps the metal foil current collector tab of the test sample;

[0037] Perform a tensile test on the test sample until the weld mark area of ​​the metal foil current collector tab breaks, and record the maximum tensile force F that the test sample withstands when it breaks;

[0038] Measure the welding resistance of the composite current collector electrode weld mark area to obtain the welding resistance R;

[0039] The evaluation coefficient S=F / R is calculated. The larger the S value is, the better the welding effect between the composite current collector body and the metal foil current collector tab is.

[0040] Beneficial effect: When the maximum welding tensile force F that the composite current collector electrode can withstand is greater and the welding resistance S is smaller, the larger the S value is, the more ideal the welding effect of the composite current collector electrode is. The welding effect between the composite current collector body and the metal foil current collector electrode can be intuitively evaluated by the size of the evaluation coefficient S value, and the optimal welding amplitude and welding pressure can be screened according to the evaluation coefficient S value, and a composite current collector electrode with better performance can be prepared accordingly, while improving the electrochemical performance of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In order to more clearly illustrate the specific implementation methods of the present application or the technical solutions in the prior art, the following is a brief introduction to the drawings required for use in the specific implementation methods or the description of the prior art. Obviously, the drawings described below are some implementation methods of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0042] FIG1 is a schematic diagram of a composite current collector electrode piece manufactured using a method for manufacturing a composite current collector electrode piece according to an embodiment of the present application;

[0043] FIG2 is a schematic diagram of a composite current collector electrode piece manufactured using a method for manufacturing a composite current collector electrode piece according to an embodiment of the present application during a tensile test;

[0044] FIG3 is a schematic diagram of a resistance test of a composite current collector electrode piece manufactured using a method for manufacturing a composite current collector electrode piece according to an embodiment of the present application.

[0045] Explanation of reference numerals: 1. composite current collector electrode; 11. composite current collector body; 12. metal foil current collector tab; 13. weld mark area. DETAILED DESCRIPTION

[0046] To make the purpose, technical solutions, and advantages of the embodiments of the present application more clear, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without making creative efforts shall fall within the scope of protection of this application.

[0047] The following describes an embodiment of the present application in conjunction with Figures 1 to 3.

[0048] According to an embodiment of the present application, on the one hand, a method for manufacturing a composite current collector electrode sheet 1 is provided, wherein the composite current collector electrode sheet 1 includes a composite current collector body 11 and a metal foil current collector electrode tab 12, wherein the composite current collector body 11 includes a composite negative electrode current collector body and a composite positive electrode current collector body; the metal foil current collector electrode tab 12 includes a negative electrode metal foil current collector electrode tab and a positive electrode metal foil current collector electrode tab; the method for manufacturing the composite current collector electrode sheet 1 includes:

[0049] preparing a composite negative electrode current collector body;

[0050] The two negative electrode metal foil current collector tabs are ultrasonically welded to both sides of the tabs of the composite negative electrode current collector body to form a composite negative electrode current collector pole piece, with a welding amplitude of 90%-100% and a welding pressure of 0.5Mpa-1Mpa;

[0051] preparing a composite positive electrode current collector body;

[0052] The two positive electrode metal foil current collector tabs are ultrasonically welded on both sides of the tabs of the composite positive electrode current collector body to form a composite positive electrode current collector pole piece, with a welding amplitude of 30%-35% and a welding pressure of 0.3Mpa-0.8Mpa.

[0053] When the composite current collector electrode 1 is manufactured using the present manufacturing method, the metal foil current collector electrode 12 is welded to both sides of the electrode ears of the composite current collector body 11 by ultrasonic welding. In the process of welding the negative metal foil current collector electrode ear and the positive metal foil current collector electrode ear, the negative metal foil current collector electrode ear and the positive metal foil current collector electrode ear can be effectively welded to the electrode ears of the composite current collector body 11 by controlling the welding amplitude and welding pressure, thereby ensuring the tensile strength of the composite current collector electrode 1 in the weld mark area 13 after welding and ensuring the firmness of the welding area; at the same time, by controlling the welding amplitude and welding pressure, the resistance of the weld mark area 13 can be controlled within an appropriate range, ensuring that the composite current collector electrode 1 has good conductivity and current collecting performance, thereby improving the cycle and rate performance of the battery.

[0054] As shown in Table 1, the composite current collector electrode sheet 1 produced using this application can withstand a maximum welding tensile force F during a tensile test that satisfies the following conditions: 5N ≤ F ≤ 30N. The welding resistance R satisfies the following conditions: 0.01mΩ ≤ R ≤ 5mΩ. The welding resistance R can be selected within a range of 0.2mΩ ≤ R ≤ 1.1mΩ. Batteries produced using this composite current collector electrode sheet 1 have low internal resistance, stable electrochemical performance, and can extend the battery's service life.

[0055] Optionally, in one embodiment, when ultrasonically welding the two negative electrode metal foil current collector tabs to the tabs on either side of the composite negative electrode current collector body, the welding amplitude is 100% and the welding pressure is 0.6 MPa. By further optimizing the welding amplitude and welding pressure during welding of the negative electrode metal foil current collector tabs, the tensile strength of the composite negative electrode current collector electrode sheet in the weld mark area 13 is further improved; at the same time, the welding resistance in the weld mark area 13 is further reduced, further improving the conductivity and current collection performance of the composite negative electrode current collector electrode sheet.

[0056] Optionally, in one embodiment, when ultrasonically welding the two positive electrode metal foil current collector tabs to the tabs on both sides of the composite positive electrode current collector body, the welding amplitude is 35% and the welding pressure is 0.4 MPa. By further optimizing the welding amplitude and welding pressure during welding of the positive electrode metal foil current collector tabs, the tensile strength of the composite positive electrode current collector electrode sheet in the weld mark area 13 is further improved; at the same time, the welding resistance in the weld mark area 13 can be further reduced, further improving the conductivity and current collection performance of the composite positive electrode current collector electrode sheet.

[0057] As shown in Figure 1, optionally, in one embodiment, the length of the composite current collector body 11 on the side where the metal foil current collector tab 12 is located is L1, and the length of the weld mark area 13 formed after the metal foil current collector tab 12 is welded is L2, and 25% L1≤L2≤L1 can ensure the length of the welding area between the metal foil current collector tab 12 and the composite current collector body 11, thereby ensuring the welding firmness between the two, and further improving the tensile strength of the weld mark area 13 after welding.

[0058] Optionally, in one embodiment, as shown in FIG. 1, the width of the welding mark area 13 is W, and 3 mm ≤ W ≤ 4.5 mm. By controlling the width of the welding mark area 13 within a suitable range, it is possible to avoid the welding mark area 13 being too small and affecting the welding strength. At the same time, if the welding area is too small, the resistance will increase, and the welding resistance can be reduced. In addition, the width of the welding mark area 13 is appropriate, avoiding excessive welding marks from damaging the tab of the metal foil current collector 12 and the tab of the composite current collector body 11, thus ensuring the welding quality and the stability of the welding resistance.

[0059] The composite current collector body 11 includes a composite current collector and an active material layer. The composite negative current collector body includes a composite negative current collector and a negative active material layer; the composite positive current collector body includes a composite positive current collector and a positive active material layer.

[0060] In one embodiment, fabricating the composite negative current collector body includes:

[0061] Preparing a composite negative current collector;

[0062] Mixing graphite, conductive carbon black, sodium carboxymethyl cellulose, and styrene-butadiene rubber latex in a mass ratio of 96.5:1.0:1.0:1.5 in deionized water and stirring evenly to form a negative electrode slurry;

[0063] Coating the negative electrode slurry on the composite negative current collector and drying to obtain the composite negative current collector body;

[0064] Fabricating the composite positive current collector body includes:

[0065] Preparing a composite positive current collector;

[0066] Mixing nickel-rich layered ternary oxide, conductive carbon black, and polyvinylidene fluoride in a mass ratio of 96.8:2:1.2 in an appropriate amount of N-methylpyrrolidone solvent and stirring evenly to form a positive electrode slurry;

[0067] Coating the positive electrode slurry on the composite positive current collector and drying to obtain the composite positive current collector body.

[0068] Optionally, in other embodiments, the active material in the negative electrode slurry may also be at least one of materials such as carbon, silicon, silicon oxide, silicon carbide, etc. The active material in the positive electrode slurry may be at least one of LiMPO4 (M may be at least one of Fe, Mn, Co), ternary LiMn 1-x-y Ni x Co y O2 (0 < x < 1, 0 < y < 1, 0 < x + y < 1), LiMn2O4, etc.

[0069] In one embodiment, when preparing the composite current collector, it includes:

[0070] The insulating base film layer is prepared by using an insulating material, wherein the insulating material includes at least one of polyamide, polyterephthalate, polyimide, polypropylene, polybutylene terephthalate, and polycarbonate;

[0071] Metal conductive layers are laid on the upper and lower surfaces of the insulating base film layer. The composite current collector can significantly reduce the material cost, weight and thickness of the current collector by replacing part of the metal material with a polymer insulating material.

[0072] Optionally, in one embodiment, the thickness of the insulating base film layer is D0, 1 μm≤D0≤12 μm;

[0073] The thickness of the metal conductive layer is D1, 0.5 μm≤D1≤3 μm.

[0074] In one embodiment, the metal conductive layer can be laid on the insulating base film layer by at least one method selected from the group consisting of hot pressing, mechanical rolling, bonding, vapor deposition, and chemical plating.

[0075] According to an embodiment of the present application, on the other hand, a method for evaluating a composite current collector electrode piece 1 is provided. The composite current collector electrode piece 1 is manufactured using the above-mentioned method for manufacturing the composite current collector electrode piece 1. The method for evaluating the composite current collector electrode piece 1 includes:

[0076] Obtaining a test sample of the composite current collector electrode 1;

[0077] The test sample is placed in a testing machine, with one clamp of the testing machine clamping the composite current collector body 11 of the test sample, and another clamp of the testing machine clamping the metal foil current collector tab 12 of the test sample;

[0078] Perform a tensile test on the test sample until the weld mark area 13 of the metal foil current collector tab 12 breaks, and record the maximum tensile force F that the test sample withstands when it breaks;

[0079] Measuring the welding resistance of the weld print area 13 of the composite current collector electrode 1 to obtain the welding resistance R;

[0080] The evaluation coefficient S=F / R is calculated. The larger the S value is, the better the welding effect between the composite current collector body 11 and the metal foil current collector tab 12 is.

[0081] When the maximum welding tensile force F that the composite current collector electrode 1 can withstand is greater and the welding resistance S is smaller, the larger the S value is, the more ideal the welding effect of the composite current collector electrode 1 is. The welding effect between the composite current collector body 11 and the metal foil current collector electrode 12 can be intuitively evaluated by the size of the evaluation coefficient S value, and the optimal welding amplitude and welding pressure can be screened out according to the evaluation coefficient S value, and a composite current collector electrode 1 with better performance can be prepared accordingly, while improving the electrochemical performance of the battery.

[0082] Specifically, in one embodiment of the present invention, when performing a tensile test on the composite current collector electrode 1, the welded composite current collector electrode 1 is punched into a test sample with a width of 15 mm and a length of 100 mm. The test sample is then installed in the upper and lower clamps of an electronic universal testing machine, and the initial length is set to 50 mm. The tensile test is performed at a tensile rate of 10 mm / min until the weld mark area 13 of the test sample breaks, and the tensile force F that the test sample withstands when it is broken is recorded.

[0083] In one embodiment, when performing a welding resistance test, a DC resistance meter is used to measure the welding resistance, and the composite current collector electrode 1 is cut to form a test sample with a width of 15 mm and a weld mark width of 3 mm. The test sample is placed horizontally on the test bench, and the test chuck of the DC resistance meter is fixed on both sides of the weld mark, and the welding resistance R is recorded under different currents.

[0084] The following describes the manufacturing process of the composite current collector electrode 1 in conjunction with a specific embodiment:

[0085] Example 1

[0086] Preparation of composite negative electrode current collector:

[0087] An insulating base film layer is selected, and a copper conductive layer is laid on the upper and lower surfaces of the insulating base film layer by a magnetron sputtering process to obtain a composite copper current collector body used as the negative electrode of the battery.

[0088] The preparation process of the composite negative electrode current collector electrode is as follows:

[0089] Graphite, conductive carbon black, sodium carboxymethyl cellulose (CMC), and styrene-butadiene rubber emulsion (SBR) were uniformly stirred in deionized water at a mass ratio of 96.5:1.0:1.0:1.5 to form a negative electrode slurry; the negative electrode slurry was then coated on a composite copper current collector body, and dried to obtain a composite negative electrode current collector electrode sheet.

[0090] The preparation process of the composite positive electrode current collector is as follows:

[0091] An insulating base film layer is selected and placed in a vacuum coating chamber. An aluminum metal layer is deposited on the upper and lower surfaces of the insulating base film layer by high-temperature evaporation to form a composite aluminum current collector body used as the positive electrode of the battery.

[0092] The preparation process of the composite positive electrode current collector electrode is as follows:

[0093] The positive electrode active material nickel-rich ternary layered oxide (LiNi0.8Co0.1Mn0.1O2 (NCM811)), conductive carbon black, and polyvinylidene fluoride (PVDF) are mixed and stirred uniformly in an appropriate amount of N-methylpyrrolidone (NMP) solvent at a mass ratio of 96.8:2:1.2 to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode collector and dried to obtain a composite positive electrode current collector body.

[0094] The welding steps of the composite negative electrode current collector and the composite positive electrode current collector are as follows:

[0095] Under the action of the ultrasonic welding head, the welding amplitude is selected to be 95% and the welding pressure is 0.55Mpa, and the copper metal foil current collector tabs are welded on the upper and lower surfaces of the electrode sheet of the composite negative electrode collector body; under the action of the ultrasonic welding head, the welding amplitude is selected to be 35% and the welding pressure is 0.3Mpa, and the aluminum metal foil current collector tabs are welded on the upper and lower surfaces of the electrode sheet of the composite positive electrode collector.

[0096] Example 2

[0097] The difference between this embodiment and embodiment 1 is that:

[0098] Select a welding amplitude of 100% and a welding pressure of 0.55 MPa to weld the copper metal foil current collector tabs on the upper and lower surfaces of the electrode sheet of the composite negative electrode current collector body; under the action of the ultrasonic welding head, select a welding amplitude of 35% and a welding pressure of 0.3 MPa to weld the aluminum metal foil current collector tabs on the upper and lower surfaces of the electrode sheet of the composite positive electrode current collector.

[0099] Example 3

[0100] The difference between this embodiment and embodiment 1 is that:

[0101] Select a welding amplitude of 100% and a welding pressure of 0.6 MPa to weld the copper metal foil current collector tabs on the upper and lower surfaces of the composite negative electrode current collector body; under the action of the ultrasonic welding head, select a welding amplitude of 35% and a welding pressure of 0.3 MPa to weld the aluminum metal foil current collector tabs on the upper and lower surfaces of the tabs of the composite positive electrode current collector tab.

[0102] Example 4

[0103] The difference between this embodiment and embodiment 1 is that:

[0104] Select a welding amplitude of 100% and a welding pressure of 0.6 MPa to weld the copper metal foil current collector tabs on the upper and lower surfaces of the electrode sheet of the composite negative electrode current collector body; under the action of the ultrasonic welding head, select a welding amplitude of 35% and a welding pressure of 0.4 MPa to weld the aluminum metal foil current collector tabs on the upper and lower surfaces of the electrode sheet of the composite positive electrode current collector.

[0105] Example 5

[0106] The difference between this embodiment and embodiment 1 is that:

[0107] Select a welding amplitude of 100% and a welding pressure of 0.6 MPa to weld the copper metal foil current collector tabs on the upper and lower surfaces of the composite negative electrode current collector body; under the action of the ultrasonic welding head, select a welding amplitude of 30% and a welding pressure of 0.4 MPa to weld the aluminum metal foil current collector tabs on the upper and lower surfaces of the tabs of the composite positive electrode current collector tab.

[0108] The composite current collector electrode sheets 1 prepared in Examples 1 to 5 were used to prepare secondary batteries and perform performance tests according to the following steps:

[0109] The composite positive electrode current collector electrode sheet, separator, and composite negative electrode current collector electrode sheet are stacked in sequence to form an electrode group, which is then installed in a battery casing. The electrolyte is then injected into the casing and sealed to obtain a lithium-ion secondary battery.

[0110] The test steps for the battery's cycle performance are:

[0111] 1. Charge at a constant current rate of 1 / 3C to a voltage of 4.2V, then charge at a constant voltage rate to a current ≤ 0.05C;

[0112] 2. Discharge at a constant current rate of 1 / 3C to a voltage of 2.5V;

[0113] 3. Record the first discharge capacity C0;

[0114] 4. Repeat steps 1 to 3 1000 times and record the discharge capacity C1 after 1000 cycles.

[0115] 5. Calculate the discharge capacity retention rate (%) after 1000 cycles = C1 / C0×100%.

[0116] The battery rate performance test steps are as follows:

[0117] 1. Charge at a constant current rate of 1 / 3C to a voltage of 4.2V, then charge at a constant voltage rate to a current ≤ 0.05C;

[0118] 2. Discharge at a constant current rate of 1 / 3C to a voltage of 2.5V;

[0119] 3. Record the discharge capacity C2 at 1 / 3C rate;

[0120] 4. Charge at a constant current rate of 1 / 3C to a voltage of 4.2V, then charge at a constant voltage rate to a current ≤ 0.05C;

[0121] 5. Discharge at a constant current of 3C to a voltage of 2.5V;

[0122] 6. Record the discharge capacity C3 at 3C rate;

[0123] 7. Calculate the battery 3C rate capacity retention rate (%) = C3 / C2×100%.

[0124] The test results of the welding tensile force F and welding resistance R of the composite current collector electrode 1, as well as the battery's capacity retention rate after 1000 cycles and 3C rate capacity retention rate are shown in Table 1.

[0125] Table 1

[0126] It can be seen from Table 1 that when welding the negative electrode metal foil current collector tab, the welding amplitude is 100% and the welding pressure is 0.6 MPa. When welding the positive electrode metal foil current collector tab, the welding amplitude is 35% and the welding pressure is 0.4 MPa. That is, the evaluation coefficient S value of the composite current collector electrode piece 1 prepared in Example 4 is the largest, and its welding effect is the best; the battery prepared by the composite current collector electrode piece 1 in Example 4 has the best cycle 1000 capacity retention rate and 3C rate capacity retention rate.

[0127] As shown in Table 1, the maximum welding tensile force F that the composite current collector electrode 1 produced by the present application can withstand during the tensile test satisfies: 5N≤F≤30N. The welding resistance R satisfies: 0.01mΩ≤R≤5mΩ. The welding tensile force and welding resistance of the composite current collector satisfy: S=F / R, 1N / mΩ≤S≤3000N / mΩ. The greater the welding tensile force, the smaller the welding resistance, and the larger the S value, the more ideal the welding effect of the composite current collector electrode 1. The excellent welding effect can ensure that the composite current collector electrode 1 has good conductivity and current collection performance, thereby improving the cycle and rate performance of the battery.

[0128] Although the embodiments of the present application have been described with reference to the accompanying drawings, those skilled in the art may make various modifications and variations without departing from the spirit and scope of the present application, and such modifications and variations shall fall within the scope defined by the appended claims.

Claims

1. A method for manufacturing a composite current collector electrode, characterized in that: The composite current collector electrode sheet includes a composite current collector body and a metal foil current collector tab. The composite current collector body includes a composite negative electrode current collector body and a composite positive electrode current collector body. The metal foil current collector tab includes a negative electrode metal foil current collector tab and a positive electrode metal foil current collector tab. The method for manufacturing the composite current collector electrode includes: preparing a composite negative electrode current collector body; The two negative electrode metal foil current collector tabs are ultrasonically welded to both sides of the tabs of the composite negative electrode current collector body to form a composite negative electrode current collector pole piece, with a welding amplitude of 90%-100% and a welding pressure of 0.5Mpa-1Mpa; preparing a composite positive electrode current collector body; The two positive electrode metal foil current collector tabs are ultrasonically welded to the two sides of the tabs of the composite positive electrode current collector body to form a composite positive electrode current collector pole piece, with a welding amplitude of 30%-35% and a welding pressure of 0.3Mpa-0.8Mpa; The width of the weld mark area formed after welding the metal foil current collector tab is W, 3mm≤W≤4.5mm.

2. The method for manufacturing a composite current collector electrode according to claim 1, wherein: When two negative electrode metal foil current collector tabs are ultrasonically welded to both sides of the tabs of the composite negative electrode current collector body, the welding amplitude is 100% and the welding pressure is 0.6 MPa.

3. The method for manufacturing a composite current collector electrode according to claim 1 or 2, characterized in that: When two positive electrode metal foil current collector tabs are ultrasonically welded to both sides of the tabs of the composite positive electrode current collector body, the welding amplitude is 35% and the welding pressure is 0.4 MPa.

4. The method for manufacturing a composite current collector electrode according to claim 1 or 2, characterized in that: The length of the composite current collector body on the side where the metal foil current collector tab is located is L1, and the length of the weld mark area formed after the metal foil current collector tab is welded is L2, and 25% of L1≤L2≤L1.

5. The method for manufacturing a composite current collector electrode according to claim 1 or 2, characterized in that: The production of the composite negative electrode current collector body includes: preparing a composite negative electrode current collector; Graphite, conductive carbon black, sodium carboxymethyl cellulose, and styrene-butadiene rubber latex were mixed uniformly in deionized water at a mass ratio of 96.5:1.0:1.0:1.5 to form a negative electrode slurry; Applying the negative electrode slurry on the composite negative electrode current collector and drying it to obtain the composite negative electrode current collector body; The production of the composite positive electrode current collector body includes: preparing a composite positive electrode current collector; Nickel-rich ternary layered oxide, conductive carbon black, and polyvinylidene fluoride were mixed and stirred uniformly in an appropriate amount of N-methylpyrrolidone solvent at a mass ratio of 96.8:2:1.2 to form a positive electrode slurry; The positive electrode slurry is coated on the composite positive electrode current collector, and the composite positive electrode current collector body is obtained after drying.

6. The method for manufacturing a composite current collector electrode according to claim 1 or 2, characterized in that: When preparing the composite current collector, the steps include: An insulating base film layer is prepared by using an insulating material, wherein the insulating material includes at least one of polyamide, polyterephthalate, polyimide, polypropylene, polybutylene terephthalate, and polycarbonate; Metal conductive layers are respectively laid on the upper surface and the lower surface of the insulating base film layer.

7. The method for manufacturing a composite current collector electrode according to claim 6, characterized in that: The thickness of the insulating base film layer is D0, 1 μm≤D0≤12 μm; And / or, the thickness of the metal conductive layer is D1, 0.5 μm≤D1≤3 μm.

8. The method for manufacturing a composite current collector electrode according to claim 6, wherein: The metal conductive layer is laid on the insulating base film layer by at least one method selected from the group consisting of hot pressing, mechanical rolling, bonding, vapor deposition, and chemical plating.

9. A method for evaluating a composite current collector electrode, characterized in that: The composite current collector electrode is manufactured using the manufacturing method of the composite current collector electrode according to any one of claims 1 to 8. The evaluation method of the composite current collector electrode comprises: Obtaining a test sample of the composite current collector electrode; The test sample is placed in a testing machine, wherein one clamp of the testing machine clamps the composite current collector body of the test sample, and another clamp of the testing machine clamps the metal foil current collector tab of the test sample; Perform a tensile test on the test sample until the weld mark area of ​​the metal foil current collector tab breaks, and record the maximum tensile force F that the test sample withstands when it breaks; Measure the welding resistance of the composite current collector electrode weld mark area to obtain the welding resistance R; The evaluation coefficient S=F / R is calculated. The larger the S value is, the better the welding effect between the composite current collector body and the metal foil current collector tab is.

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