An electrode tab, a method for manufacturing the same, and an application thereof

Abstract

This invention provides an electrode sheet, its preparation method, and its application. The preparation method includes the following steps: stirring and kneading an electrode active material, a first conductive agent, a portion of a first binder, and a second binder to obtain a kneaded material; mixing the remaining first binder, the second conductive agent, and the kneaded material to obtain an electrode slurry; coating the electrode slurry onto a current collector, and then drying and cold pressing to obtain the electrode sheet. This preparation method addresses the problems of easy cracking and powder shedding, excessive rebound, and low peel strength in electrode sheets prepared by traditional methods. By employing a multi-step approach and precise timing of component addition, it effectively prevents problems such as electrode sheet cracking, detachment, and excessive rebound, improving production yield and efficiency, and significantly reducing cell costs.

Description

Technical Field

[0001] This invention belongs to the field of battery technology and relates to an electrode sheet, its preparation method and application. Background Technology

[0002] With the promotion of new energy vehicles, lithium-ion batteries have become one of the current research hotspots. The popularization of new energy vehicles largely depends on their driving range, so lithium-ion batteries must have high energy density. In order to improve the energy density of the cell, existing technologies usually increase the energy density by increasing the thickness of the negative electrode coating, the coating surface density, and the cold pressing compaction density, such as using thick electrodes. However, the above methods can cause problems such as cracking of the negative electrode sheet, low peeling force, and large rebound, which seriously affect the production yield and efficiency, and increase the cost of the cell.

[0003] For example, CN 115939325A discloses a fast-charging negative electrode for lithium-ion batteries and its preparation method. The preparation method includes dispersing raw materials, conductive agents, and binders in a specific ratio into deionized water to obtain a uniform slurry, coating it onto the surface of copper foil, and then drying, rolling, and cutting to obtain a fast-charging negative electrode sheet. The preparation process still adopts the traditional negative electrode sheet preparation method. However, due to the increase in coating thickness and areal density, the traditional electrode sheet preparation method cannot make the thick electrode have the same excellent mechanical properties such as crack resistance. At the same time, it will also increase the defect rate and efficiency of electrode sheet preparation.

[0004] Based on the above research, there is a need to provide a method for preparing electrode sheets that can prevent electrode sheet cracking, detachment, and excessive rebound even when the coating thickness and areal density are increased, while improving production yield and efficiency. Summary of the Invention

[0005] The purpose of this invention is to provide an electrode sheet, its preparation method, and its application, particularly an electrode sheet for thick electrodes, its preparation method, and its application. The preparation method addresses the problems of cracking, powder shedding, excessive rebound, and low peel strength in the thick electrodes produced during the preparation of thick electrodes. By employing a multi-step approach and coordinating the timing of component addition, the method effectively prevents problems such as electrode sheet cracking, detachment, and excessive rebound, thereby improving production yield and efficiency and significantly reducing cell costs.

[0006] To achieve this objective, the present invention adopts the following technical solution:

[0007] In a first aspect, the present invention provides a method for preparing an electrode sheet, the method comprising the following steps:

[0008] (1) The electrode active material, the first conductive agent, a portion of the first binder and the second binder are stirred and kneaded to obtain a kneaded material;

[0009] (2) Mix the remaining first binder, second conductive agent and kneading material from step (1) to obtain electrode slurry;

[0010] (3) The electrode slurry described in step (2) is coated onto the current collector, and then dried and cold-pressed to obtain the electrode sheet.

[0011] This invention achieves thorough dispersion of multiple components and improves the peel strength and other properties of the resulting electrode by adding a first binder in steps (1), adding a first conductive agent and a second binder in step (2), and adding a second conductive agent in step (2). On the one hand, the mixing of the components in step (1) ensures that the first conductive agent, the first binder and the second binder are uniformly dispersed on the surface of the electrode active material, and the addition of the two binders improves the peel strength of the electrode. On the other hand, the addition of the first binder and the second conductive agent in step (2) further improves the dispersibility of the components and limits the rebound of the electrode. Therefore, this invention effectively prevents problems such as electrode cracking, detachment and excessive rebound by combining multiple steps and the timing of adding multiple components.

[0012] Preferably, the solid content of the kneading material in step (1) is above 70 wt%, for example, it can be 70 wt%, 70 wt%, 72.5 wt%, 75 wt%, 77.5 wt%, 80 wt%, 82.5 wt%, 85 wt%, 87.5 wt%, or 90 wt%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0013] The solid content of the kneading material described in this invention is above a certain solid content, which helps the first binder and the second binder to be uniformly dispersed on the surface of the electrode active material, reduces the proportion of free first binder, and improves the dispersion effect and electrode peeling force.

[0014] Preferably, in step (1), the first adhesive comprises CMC (carboxymethyl cellulose) adhesive.

[0015] Preferably, the solid content of the CMC adhesive is 1-8 wt%, for example, it can be 1 wt%, 5 wt% or 8 wt%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0016] Preferably, in step (1), the second adhesive comprises PAA (polyacrylic acid) and / or PAN (polyacrylonitrile).

[0017] Preferably, in step (1), the first conductive agent comprises a zero-dimensional conductive agent.

[0018] The first conductive agent added in this invention is a zero-dimensional conductive agent, which improves the dispersibility of the zero-dimensional conductive agent in the slurry and ensures a complete conductive network. If the first conductive agent is added later in step (2), its dispersibility cannot be guaranteed because it is a zero-dimensional conductive agent.

[0019] Preferably, the zero-dimensional conductive agent includes SP (conductive carbon black).

[0020] Preferably, the electrode active material in step (1) includes a negative electrode active material, preferably graphite.

[0021] Preferably, the revolution speed of the stirring and kneading in step (1) is 1-10 rpm, for example, 1 rpm, 5 rpm or 10 rpm, the rotation speed is 200-400 rpm, for example, 200 rpm, 300 rpm or 400 rpm, and the time is 70-110 min, for example, 70 min, 90 min or 110 min, but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0022] Preferably, in the process of mixing and kneading the electrode active material, the first conductive agent, the first binder, and the second binder, the electrode active material and the first conductive agent are first dry-mixed, and then mixed and kneaded with the first binder and the second binder.

[0023] Preferably, the revolution speed of the dry mixture is 5-25 rpm, for example, 5 rpm, 15 rpm or 25 rpm; the rotation speed is 500-700 rpm, for example, 500 rpm, 600 rpm or 700 rpm; the time is 15-45 min, for example, 15 min, 25 min, 35 min or 45 min; and the temperature is 25-40℃, for example, 25℃, 30℃ or 40℃, but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0024] Preferably, the first adhesive in step (1) is prepared by the following method:

[0025] After mixing CMC and deionized water, deionized water is added to the system again, and vacuum stirring, fast vacuum stirring and slow vacuum stirring are performed in sequence to obtain the first binder.

[0026] This invention improves the dispersibility of CMC adhesive during the pulping process and further enhances electrode performance by adding deionized water in stages and by combining vacuum stirring, fast vacuum stirring and slow vacuum stirring.

[0027] Preferably, the revolution speed of the stirring and mixing is 5-25 rpm, for example, 5 rpm, 15 rpm or 25 rpm; the rotation speed is 500-700 rpm, for example, 500 rpm, 600 rpm or 700 rpm; the time is 15-45 min, for example, 15 min, 25 min, 35 min or 45 min; and the temperature is 25-40℃, for example, 25℃, 30℃ or 40℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0028] Preferably, the vacuum degree of the vacuum stirring is -90 to -70 kPa, for example, -70 kPa, -80 kPa or -90 kPa; the revolution speed is 5-25 rpm, for example, 5 rpm, 15 rpm or 25 rpm; the rotation speed is 500-700 rpm, for example, 500 rpm, 600 rpm or 700 rpm; the time is 15-45 min, for example, 15 min, 25 min, 35 min or 45 min; and the temperature is 25-40℃, for example, 25℃, 30℃ or 40℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0029] Preferably, the vacuum degree of the vacuum rapid stirring is -90 to -70 kPa, for example, -70 kPa, -80 kPa or -90 kPa; the revolution speed is 15-35 rpm, for example, 15 rpm, 25 rpm or 35 rpm; the rotation speed is 1500-2500 rpm, for example, 1500 rpm, 2000 rpm or 2500 rpm; the stirring time is 4-6 h, for example, 4 h, 5 h or 6 h; and the stirring temperature is 40-50 °C, for example, 40 °C, 45 °C or 50 °C, but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0030] Preferably, the vacuum degree of the vacuum slow stirring is -90 to -70 kPa, for example, -70 kPa, -80 kPa or -90 kPa; the revolution speed is 5-10 rpm, for example, 5 rpm, 7 rpm or 10 rpm; the rotation speed is 100-500 rpm, for example, 100 rpm, 250 rpm or 500 rpm; the stirring time is 20-40 min, for example, 20 min, 30 min or 40 min; and the stirring temperature is 15-35℃, for example, 15℃, 25℃ or 35℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0031] Preferably, in step (2), the second conductive agent comprises a one-dimensional conductive agent.

[0032] Preferably, the one-dimensional conductive agent includes VGCF (vapor-grown carbon fiber).

[0033] In step (2), the present invention adds a one-dimensional conductive agent and uses a conductive agent with a large aspect ratio and high fiber hardness, which can effectively limit the electrode rebound. At the same time, VGCF and SP can construct a three-dimensional conductive network structure to improve electronic conductivity.

[0034] Preferably, the mass ratio of the first adhesive in step (2) to the first adhesive in step (1) is (3-5):(5-7), for example, it can be 3:7, 4:6 or 5:5, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0035] Preferably, the revolution speed of the mixture in step (2) is 20-30 rpm, for example, 20 rpm, 25 rpm or 30 rpm, the rotation speed is 1500-2000 rpm, for example, 1500 rpm, 1800 rpm or 2000 rpm, the stirring time is 80-100 min, for example, 80 min, 90 min or 100 min, the stirring temperature is 30-40℃, for example, 30℃, 35℃ or 40℃, and the vacuum degree is -95 to -75 kPa, for example, -75 kPa, -80 kPa or -90 kPa, but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0036] Preferably, after mixing in step (2), a third binder is added and stirred to obtain the electrode slurry.

[0037] The third binder added at the end of this invention will have its molecular structure destroyed if it is added during the second addition of the adhesive solution, when stirred at high speed.

[0038] Preferably, the third adhesive comprises SBR (styrene-butadiene rubber).

[0039] Preferably, the revolution speed of the stirring is 5-25 rpm, for example, 5 rpm, 15 rpm or 25 rpm; the rotation speed is 100-350 rpm, for example, 100 rpm, 200 rpm, 300 rpm or 350 rpm; the stirring temperature is 15-35℃, for example, 15℃, 25℃ or 35℃; and the vacuum degree is -95 to -75 kPa, for example, -75 kPa, -85 kPa or -95 kPa, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0040] Preferably, in the electrode slurry described in step (2), the mass ratio of the electrode active material, the first conductive agent, the second conductive agent, the binder component in the first binder, the second binder, and the third binder is (94.5-97.6):(0.5-1):(0.5-1):(0.2-1):(0.2-1):(1-1.5), for example, it can be 94.5:1:1:1:1:1.5 or 97.6:0.5:0.5:0.2:0.2:1, but it is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0041] Preferably, before the drying in step (3), a solvent is sprayed onto the electrode slurry on the surface of the current collector.

[0042] In this invention, after coating the slurry and before drying, a solvent is sprayed onto the electrode slurry on the surface of the current collector. This can prevent the electrode from cracking and reduce the surface tension of the electrode, thus preventing the electrode from bulging.

[0043] Preferably, the solvent includes NMP (N-methylpyrrolidone).

[0044] Preferably, the drying method in step (3) includes three-stage drying.

[0045] Preferably, in the three-stage drying process, the temperature of the first stage drying and the temperature of the third stage drying are each independently greater than the temperature of the second stage drying.

[0046] This invention employs a three-stage drying process with a high-low-high drying trend, thereby suppressing the floatation of the binder and improving the peeling force of the electrode sheet.

[0047] Preferably, the drying temperature of the first stage is 110-120℃, for example, 110℃, 115℃ or 120℃; the drying temperature of the second stage is 90-100℃, for example, 90℃, 95℃ or 100℃; and the drying temperature of the third stage is 110-120℃, for example, 110℃, 115℃ or 120℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0048] Preferably, the cold pressing in step (3) includes three cold pressing operations performed sequentially.

[0049] Preferably, in the three cold presses, the pressure of the first cold press and the pressure of the second cold press are each independently greater than the pressure of the third cold press.

[0050] This invention, based on three cold pressing processes, makes the pressure of the first and second cold pressing processes greater than that of the third cold pressing process, which effectively prevents the electrode from cracking and improves the phenomenon of excessive rebound of the electrode.

[0051] Preferably, the ratio of the pressure of the first cold press, the pressure of the second cold press, and the pressure of the third cold press is (3-5):(3-5):(1-2), for example, it can be 3:3:1, 4:4:2 or 5:4:1, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0052] As a preferred embodiment of the preparation method of the present invention, the preparation method includes the following steps:

[0053] (1) CMC and deionized water are stirred and mixed at a revolution speed of 5-25 rpm, a rotation speed of 500-700 rpm, and a temperature of 25-40℃ for 15-45 min. Then, deionized water is added to the system again, and vacuum stirring, vacuum fast stirring and vacuum slow stirring are performed in sequence to obtain a first binder with a solid content of 1-8 wt%.

[0054] (2) First, the electrode active material and the first conductive agent are dry mixed at a revolution speed of 5-25 rpm, a rotation speed of 500-700 rpm and a temperature of 25-40°C for 15-45 min. Then, the mixture is stirred and kneaded with a portion of the first binder and the second binder. The revolution speed of the stirring and kneading is 1-10 rpm, the rotation speed is 200-400 rpm, and the time is 70-110 min, to obtain a kneaded material with a solid content of more than 70 wt%.

[0055] The first conductive agent includes a zero-dimensional conductive agent;

[0056] (3) Mix the remaining first binder, second conductive agent and the kneading material described in step (2) at a revolution speed of 20-30 rpm, a rotation speed of 1500-2000 rpm, a temperature of 30-40℃ and a vacuum of -95 to -75 kPa for 80-100 min. Then add the third binder and continue stirring at a revolution speed of 5-25 rpm, a rotation speed of 100-350 rpm, a stirring temperature of 15-35℃ and a vacuum of -95 to -75 kPa to obtain the electrode slurry.

[0057] In step (3), the mass ratio of the first adhesive to the first adhesive in step (2) is (3-5):(5-7), and the second conductive agent includes a one-dimensional conductive agent;

[0058] (4) The electrode slurry described in step (3) is coated on the current collector, and then a solvent is sprayed onto the electrode slurry on the surface of the current collector. Then, three-stage drying and three cold pressing are performed in sequence to obtain the electrode sheet.

[0059] In the three-stage drying process, the temperatures of the first and third stages of drying are independently greater than the temperature of the second stage of drying. In the three-stage cold pressing process, the pressures of the first and second cold pressings are independently greater than the pressures of the third cold pressing.

[0060] In a second aspect, the present invention provides an electrode sheet, which is obtained by the preparation method described in the first aspect.

[0061] Preferably, the thickness of the electrode sheet is not less than 100 μm, for example, it can be 100 μm, 200 μm, 300 μm or 400 μm, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0062] Thirdly, the present invention provides a battery comprising electrode plates as described in the second aspect.

[0063] Compared with the prior art, the present invention has the following beneficial effects:

[0064] This invention effectively prevents problems such as electrode cracking, detachment, and excessive rebound by adjusting the timing of each component addition and the coordination between each step. Specifically, the second binder added in step (1) increases the kneading solids content, which helps the first and second binders to be evenly dispersed on the surface of the electrode active material, reduces the proportion of free first binder, and improves the dispersion effect and electrode peeling force. At the same time, this invention further prevents electrode cracking by spraying solvent on the slurry surface before coating, reduces the surface tension of the electrode, and prevents the electrode from bulging. The subsequent three-stage drying, combined with high and low temperature settings, suppresses the floatation of the binder and improves the electrode peeling force. The three-stage cold pressing process effectively prevents electrode cracking and improves the problem of excessive electrode rebound. Detailed Implementation

[0065] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0066] Example 1

[0067] This embodiment provides a method for preparing an electrode sheet, wherein the electrode sheet is a negative electrode sheet, and the preparation method includes the following steps:

[0068] (1) CMC and deionized water were stirred and mixed at a revolution speed of 15 rpm, a rotation speed of 600 rpm, and a temperature of 35°C for 15 min. Then, deionized water was added to the system again, and vacuum stirring, fast vacuum stirring, and slow vacuum stirring were performed in sequence to obtain the first binder with a solid content of 5 wt%. The vacuum stirring was performed at a vacuum degree of -85 kPa, a revolution speed of 15 rpm, a rotation speed of 600 rpm, a time of 15 min, and a temperature of 35°C. The fast vacuum stirring was performed at a vacuum degree of -85 kPa, a revolution speed of 25 rpm, a rotation speed of 2000 rpm, a stirring time of 5 h, and a stirring temperature of 45°C. The slow vacuum stirring was performed at a vacuum degree of -85 kPa, a revolution speed of 10 rpm, a rotation speed of 300 rpm, a stirring time of 30 min, and a stirring temperature of 25°C.

[0069] (2) First, the electrode active material and the first conductive agent are dry mixed at a revolution speed of 15 rpm, a rotation speed of 600 rpm and a temperature of 35°C for 30 min. Then, they are stirred and kneaded with a portion of the first binder and the second binder. The revolution speed of the stirring and kneading is 5 rpm, the rotation speed is 300 rpm and the time is 90 min, to obtain a kneaded material with a solid content of 85 wt%.

[0070] The first conductive agent is SP, the electrode active material is graphite, and the second binder is PAA;

[0071] (3) The remaining first binder, second conductive agent and the kneaded material in step (2) are mixed at a revolution speed of 25 rpm, a rotation speed of 1800 rpm, a temperature of 35°C and a vacuum of -85 kPa for 90 min. Then the third binder is added and the mixture is stirred at a revolution speed of 15 rpm, a rotation speed of 250 rpm, a stirring temperature of 25°C and a vacuum of -85 kPa to obtain an electrode slurry. In the electrode slurry, the mass ratio of electrode active material, first conductive agent, second conductive agent, binder component in the first binder, second binder and third binder is 96.5:0.9:0.7:0.4:0.3:1.2.

[0072] In step (3), the mass ratio of the first adhesive to the first adhesive in step (2) is 4:6, the second conductive agent is VGCF, and the third adhesive is SBR;

[0073] (4) The electrode slurry described in step (3) is coated on the current collector, and then NMP is sprayed on the electrode slurry on the surface of the current collector. Then, three-stage drying and three cold pressing are performed in sequence to obtain the electrode sheet with a thickness of 120 μm.

[0074] The current collector is a 12μm copper foil. In the three-stage drying process, the temperatures of the first and third stages of drying are independently higher than the temperature of the second stage of drying. The temperature of the first stage of drying is 115℃, the temperature of the second stage of drying is 95℃, and the temperature of the third stage of drying is 115℃. In the three-stage cold pressing process, the pressures of the first and second cold pressings are independently higher than the pressure of the third cold pressing. The ratio of the pressures of the first, second, and third cold pressings is 4:4:2.

[0075] Example 2

[0076] This embodiment provides a method for preparing an electrode sheet, wherein the electrode sheet is a negative electrode sheet, and the preparation method includes the following steps:

[0077] (1) CMC and deionized water were stirred and mixed at a revolution speed of 5 rpm, a rotation speed of 500 rpm, and a temperature of 25°C for 45 min. Then, deionized water was added to the system again, and vacuum stirring, fast vacuum stirring, and slow vacuum stirring were performed in sequence to obtain the first binder with a solid content of 1 wt%. The vacuum stirring was performed at a vacuum degree of -90 kPa, a revolution speed of 25 rpm, a rotation speed of 700 rpm, a time of 15 min, and a temperature of 25°C. The fast vacuum stirring was performed at a vacuum degree of -70 kPa, a revolution speed of 35 rpm, a rotation speed of 2500 rpm, a stirring time of 4 h, and a stirring temperature of 40°C. The slow vacuum stirring was performed at a vacuum degree of -70 kPa, a revolution speed of 10 rpm, a rotation speed of 500 rpm, a stirring time of 20 min, and a stirring temperature of 15°C.

[0078] (2) First, the electrode active material and the first conductive agent are dry mixed at a revolution speed of 25 rpm, a rotation speed of 700 rpm and a temperature of 25°C for 15 min. Then, they are stirred and kneaded with the first binder and the second binder. The revolution speed of the stirring and kneading is 1 rpm, the rotation speed is 200 rpm and the time is 110 min to obtain a kneaded material with a solid content of 70 wt%.

[0079] The first conductive agent is SP, the electrode active material is graphite, and the second binder is PAA;

[0080] (3) The first binder, the second conductive agent and the kneading material described in step (2) are mixed at a revolution speed of 20 rpm, a rotation speed of 1500 rpm, a temperature of 40°C and a vacuum of -75 kPa for 80 min. Then the third binder is added and the mixture is stirred at a revolution speed of 5 rpm, a rotation speed of 100 rpm, a stirring temperature of 35°C and a vacuum of -95 kPa to obtain an electrode slurry. In the electrode slurry, the mass ratio of the electrode active material, the first conductive agent, the second conductive agent, the binder component in the first binder, the second binder and the third binder is 94.5:1:1:1:1:1.5.

[0081] In step (3), the mass ratio of the first adhesive to the first adhesive in step (2) is 3:7, the second conductive agent is VGCF, and the third adhesive is SBR;

[0082] (4) The electrode slurry described in step (3) is coated on the current collector, and then NMP is sprayed on the electrode slurry on the surface of the current collector. Then, three-stage drying and three cold pressing are performed in sequence to obtain the electrode sheet with a thickness of 120 μm.

[0083] The current collector is a 12μm copper foil. In the three-stage drying process, the temperatures of the first and third stages of drying are independently higher than the temperature of the second stage of drying. The temperature of the first stage of drying is 120℃, the temperature of the second stage of drying is 100℃, and the temperature of the third stage of drying is 120℃. In the three-stage cold pressing process, the pressure of the first and second cold pressing is independently higher than the pressure of the third cold pressing. The ratio of the pressure of the first, second, and third cold pressing is 3:3:1.

[0084] Example 3

[0085] This embodiment provides a method for preparing an electrode sheet, wherein the electrode sheet is a negative electrode sheet, and the preparation method includes the following steps:

[0086] (1) CMC and deionized water were stirred and mixed at a revolution speed of 25 rpm, a rotation speed of 700 rpm, and a temperature of 40°C for 15 min. Then, deionized water was added to the system again, and vacuum stirring, fast vacuum stirring, and slow vacuum stirring were performed in sequence to obtain the first binder with a solid content of 8 wt%. The vacuum stirring was performed at a vacuum degree of -70 kPa, a revolution speed of 5 rpm, a rotation speed of 500 rpm, a time of 45 min, and a temperature of 40°C. The fast vacuum stirring was performed at a vacuum degree of -90 kPa, a revolution speed of 15 rpm, a rotation speed of 1500 rpm, a stirring time of 6 h, and a stirring temperature of 50°C. The slow vacuum stirring was performed at a vacuum degree of -90 kPa, a revolution speed of 5 rpm, a rotation speed of 100 rpm, a stirring time of 40 min, and a stirring temperature of 35°C.

[0087] (2) First, the electrode active material and the first conductive agent are dry mixed at a revolution speed of 5 rpm, a rotation speed of 500 rpm and a temperature of 40°C for 45 min. Then, the first binder and the second binder are stirred and kneaded. The revolution speed of the stirring and kneading is 10 rpm, the rotation speed is 400 rpm and the time is 70 min, to obtain a kneaded material with a solid content of 80 wt%.

[0088] The first conductive agent is SP, the electrode active material is graphite, and the second binder is PAA;

[0089] (3) The first binder, the second conductive agent and the kneading material described in step (2) are mixed at a revolution speed of 30 rpm, a rotation speed of 2000 rpm, a temperature of 30°C and a vacuum of -95 kPa for 100 min. Then the third binder is added and the mixture is stirred at a revolution speed of 25 rpm, a rotation speed of 350 rpm, a stirring temperature of 15°C and a vacuum of -95 kPa to obtain an electrode slurry. In the electrode slurry, the mass ratio of the electrode active material, the first conductive agent, the second conductive agent, the binder component in the first binder, the second binder and the third binder is 97.6:0.5:0.5:0.2:0.2:1.

[0090] In step (3), the mass ratio of the first adhesive to the first adhesive in step (2) is 4.5:5.5, the second conductive agent is VGCF, and the third adhesive is SBR;

[0091] (4) The electrode slurry described in step (3) is coated on the current collector, and then NMP is sprayed on the electrode slurry on the surface of the current collector. Then, three-stage drying and three cold pressing are performed in sequence to obtain the electrode sheet with a thickness of 120 μm.

[0092] The current collector is a 12μm copper foil. In the three-stage drying process, the temperatures of the first and third stages of drying are independently higher than the temperature of the second stage of drying. The temperature of the first stage of drying is 110℃, the temperature of the second stage of drying is 90℃, and the temperature of the third stage of drying is 110℃. In the three-stage cold pressing process, the pressures of the first and second cold pressings are independently higher than the pressure of the third cold pressing. The ratio of the pressures of the first, second, and third cold pressings is 5:4:2.

[0093] Example 4

[0094] This embodiment provides a method for preparing an electrode sheet. Except for the solid content of the kneading material in step (2) being 60 wt%, the preparation method is the same as in Example 1.

[0095] Example 5

[0096] This embodiment provides a method for preparing an electrode sheet. Except for step (3), in which the second conductive agent is conductive graphite KS-6, the preparation method is the same as in embodiment 1.

[0097] Example 6

[0098] This embodiment provides a method for preparing an electrode sheet. The preparation method is the same as that in Embodiment 1 except that a third binder is not added in step (3).

[0099] Example 7

[0100] This embodiment provides a method for preparing an electrode sheet. Except for step (4), in which NMP is not sprayed before the three-stage drying process, the preparation method is the same as in embodiment 1.

[0101] Example 8

[0102] This embodiment provides a method for preparing an electrode sheet. Except for the three-stage drying in step (4), where the temperature of the first stage drying is 95°C, the temperature of the second stage drying is 115°C, and the temperature of the third stage drying is 95°C, so that the temperature of the second stage drying is greater than the temperature of the first stage drying and the temperature of the third stage drying, the rest of the preparation method is the same as that in embodiment 1.

[0103] Example 9

[0104] This embodiment provides a method for preparing an electrode sheet. Except for the three-stage drying in step (4), where the temperature of the first stage drying is 115°C, the temperature of the second stage drying is 120°C, and the temperature of the third stage drying is 95°C, so that the temperature of the first stage drying and the temperature of the second stage drying are independently greater than the temperature of the third stage drying, the rest of the preparation method is the same as in embodiment 1.

[0105] Example 10

[0106] This embodiment provides a method for preparing an electrode sheet. Except for step (4), which involves drying at 115°C in one step, the preparation method is the same as in Embodiment 1.

[0107] Example 11

[0108] This embodiment provides a method for preparing an electrode sheet. Except for step (4), which involves only the first cold pressing, the preparation method is the same as that in embodiment 1.

[0109] Example 12

[0110] This embodiment provides a method for preparing an electrode sheet. Except for the fact that the pressure of the third cold pressing in step (4) is the same as that of the first and second cold pressing, the preparation method is the same as that in Embodiment 1.

[0111] Comparative Example 1

[0112] This comparative example provides a method for preparing an electrode sheet. The preparation method is the same as in Example 1, except that the first binder in step (3) is added all at once in the stirring and kneading step in step (2), that is, the first binder is not added in steps.

[0113] Comparative Example 2

[0114] This comparative example provides a method for preparing an electrode sheet. The preparation method is the same as that in Example 1, except that the second conductive agent in step (3) is added in the stirring and kneading step in step (2).

[0115] Comparative Example 3

[0116] This comparative example provides a method for preparing an electrode sheet. The preparation method is the same as in Example 1, except that a second conductive agent is added in step (2) and a first conductive agent is added in step (3), that is, the order of adding the first conductive agent and the second conductive agent is reversed.

[0117] Comparative Example 4

[0118] This comparative example provides a method for preparing an electrode sheet. The preparation method is the same as in Example 1, except that a second binder is not added in step (2) to change the solid content of the kneading material.

[0119] For the electrode sheets obtained in the above embodiments and comparative examples, their cracking, peel force, and rebound performance were tested. Cracking was determined using SEM. The peel force was tested using a tensile testing machine. The stainless steel plate and current collector were fixed on the two clamps of the tensile testing machine, and then a 180-degree peel test was performed at a speed of 10 mm / min and a load of 30 N. The force detected when the current collector was completely peeled off was the peel force. The rebound performance was tested using a thickness gauge to measure the thickness H1 of the cold-pressed electrode sheet and the thickness H of the foil. 箔材 After standing for 24 hours, the electrode thickness H2, the rebound rate = (H2-H1) / (H1-H 箔材 ).

[0120] The test results are shown in the table below:

[0121] Table 1

[0122]

[0123]

[0124] As can be seen from the table above:

[0125] (1) The preparation method described in this invention can effectively prevent problems such as electrode shedding and excessive rebound of thick electrode sheets; As can be seen from Examples 1 and 4, if the solid content in the kneaded material is too low, the dispersibility of the first binder and the second binder will decrease, and the free first binder component will increase, which is not conducive to improving the electrode sheet peeling force; As can be seen from Examples 1 and 5, the second conductive agent of this invention is preferably a one-dimensional conductive agent, which is beneficial to limiting the rebound of the electrode sheet; As can be seen from Examples 1 and 6, the addition of the third binder can further improve the electrode sheet peeling force; As can be seen from Examples 1 and 7, spraying solvent before drying can prevent the electrode sheet from cracking, reduce the surface tension of the electrode sheet, and is beneficial to improving the mechanical strength of the electrode sheet; As can be seen from Examples 1 and 8-10, the electrode sheet performance obtained by setting high, low, and high temperatures in the three-stage drying process of this invention is optimal; As can be seen from Examples 1 and 11-12, the three cold pressing and specific pressure trend of this invention can prevent the electrode sheet from cracking and improve the problem of excessive rebound of the electrode sheet.

[0126] (2) As can be seen from Example 1 and Comparative Examples 1-2, the timing of adding the first binder is beneficial to improving the dispersibility of the components, and the timing of adding the second conductive agent, combined with its intrinsic characteristics, is beneficial to limiting the rebound of the electrode. As can be seen from Example 1 and Comparative Example 3, the first and second conductive agents of different dimensions need to be added at specific times in order to help them play their respective roles and improve the performance of the electrode. As can be seen from Example 1 and Comparative Example 4, the addition of the second binder helps to improve the kneading solids content and improve the dispersibility, thereby improving the performance of the electrode.

[0127] In summary, this invention provides an electrode sheet, its preparation method, and its application. The preparation method addresses the problems of cracking, powder shedding, excessive rebound, and low peel strength in the preparation of thick electrodes. By employing a multi-step approach and coordinating the timing of component addition, the method effectively prevents problems such as electrode sheet cracking, detachment, and excessive rebound, thereby improving production yield and efficiency and significantly reducing cell costs.

[0128] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method of making an electrode tab, characterized by, The preparation method includes the following steps: (1) The electrode active material, the first conductive agent, part of the first binder and the second binder are stirred and kneaded to obtain a kneaded material; (2) Mix the remaining first binder, second conductive agent and the kneading material from step (1) to obtain electrode slurry; (3) The electrode slurry described in step (2) is coated onto the current collector, and then dried and cold-pressed to obtain the electrode sheet; The drying method described in step (3) includes three-stage drying; in the three-stage drying, the temperature of the first stage drying and the temperature of the third stage drying are independently greater than the temperature of the second stage drying. The cold pressing in step (3) includes three cold pressing operations performed sequentially; in the three cold pressing operations, the pressure of the first cold pressing and the pressure of the second cold pressing are each independently greater than the pressure of the third cold pressing.

2. The production method according to claim 1, characterized by, The solid content of the kneading material in step (1) is above 70 wt%.

3. The preparation method according to claim 1, characterized in that, Step (1) The first adhesive comprises CMC adhesive liquid.

4. The preparation method according to claim 3, characterized in that, The solid content of the CMC adhesive is 1-8 wt%.

5. The preparation method according to claim 1, characterized in that, Step (1) The second adhesive comprises PAA and / or PAN.

6. The preparation method according to claim 1, characterized in that, Step (1) The first conductive agent includes a zero-dimensional conductive agent.

7. The preparation method according to claim 6, characterized in that, The zero-dimensional conductive agent includes SP.

8. The preparation method according to claim 1 or 2, characterized in that, The revolution speed of the stirring and kneading in step (1) is 1-10 rpm, the rotation speed is 200-400 rpm, and the time is 70-110 min.

9. The preparation method according to claim 1, characterized in that, In step (1), during the process of mixing and kneading the electrode active material, the first conductive agent, a portion of the first binder and the second binder, the electrode active material and the first conductive agent are first dry-mixed, and then mixed and kneaded with a portion of the first binder and the second binder.

10. The preparation method according to claim 9, characterized in that, The dry mixture has a revolution speed of 5-25 rpm, a rotation speed of 500-700 rpm, a time of 15-45 min, and a temperature of 25-40℃.

11. The preparation method according to claim 1, characterized in that, Step (1) The first adhesive is prepared by the following method: After mixing CMC and deionized water, deionized water is added to the system again, and vacuum stirring, fast vacuum stirring and slow vacuum stirring are performed in sequence to obtain the first binder.

12. The preparation method according to claim 11, characterized in that, The stirring and mixing process involves a revolution speed of 5-25 rpm, a rotation speed of 500-700 rpm, a time of 15-45 min, and a temperature of 25-40℃.

13. The preparation method according to claim 11, characterized in that, The vacuum stirring is performed at a vacuum level of -90 to -70 kPa, a revolution speed of 5 to 25 rpm, a rotation speed of 500 to 700 rpm, a time of 15 to 45 minutes, and a temperature of 25 to 40°C.

14. The preparation method according to claim 11, characterized in that, The vacuum speed mixer has a vacuum degree of -90~-70Kpa, a revolution speed of 15-35rpm, a rotation speed of 1500-2500rpm, a mixing time of 4-6h, and a mixing temperature of 40-50℃.

15. The preparation method according to claim 11, characterized in that, The vacuum degree of the vacuum slow stirring is -90~-70Kpa, the revolution speed is 5-10rpm, the rotation speed is 100-500rpm, the stirring time is 20-40min, and the stirring temperature is 15-35℃.

16. The preparation method according to claim 1, characterized in that, Step (2) The second conductive agent includes a one-dimensional conductive agent.

17. The preparation method according to claim 16, characterized in that, The one-dimensional conductive agent includes VGCF.

18. The preparation method according to claim 1, characterized in that, In step (2), the mass ratio of the first adhesive to the first adhesive in step (1) is (3-5):(5-7).

19. The preparation method according to claim 1, characterized in that, The mixing process in step (2) involves a revolution speed of 20-30 rpm, a rotation speed of 1500-2000 rpm, a stirring time of 80-100 min, a stirring temperature of 30-40℃, and a vacuum degree of -95~-75 kPa.

20. The preparation method according to claim 1, characterized in that, After mixing in step (2), a third binder is added and stirred to obtain the electrode slurry.

21. The preparation method according to claim 20, characterized in that, The stirring speed is 5-25 rpm, the rotation speed is 100-350 rpm, the stirring temperature is 15-35℃, and the vacuum degree is -95~-75Kpa.

22. The preparation method according to claim 1, characterized in that, Before drying in step (3), a solvent is sprayed onto the electrode slurry on the surface of the current collector.

23. The preparation method according to claim 1, characterized in that, The drying temperature for the first stage is 110-120℃, the drying temperature for the second stage is 90-100℃, and the drying temperature for the third stage is 110-120℃.

24. The preparation method according to claim 1, characterized in that, The ratio of the pressure of the first cold press, the pressure of the second cold press, and the pressure of the third cold press is (3-5):(3-5):(1-2).

25. The preparation method according to claim 1, characterized in that, The preparation method includes the following steps: (1) CMC and deionized water are stirred and mixed at a revolution speed of 5-25 rpm, a rotation speed of 500-700 rpm, and a temperature of 25-40℃ for 15-45 min. Then, deionized water is added to the system again, and vacuum stirring, vacuum fast stirring and vacuum slow stirring are performed in sequence to obtain the first binder with a solid content of 1-8 wt%. (2) First, the electrode active material and the first conductive agent are dry mixed at a revolution speed of 5-25 rpm, a rotation speed of 500-700 rpm and a temperature of 25-40°C for 15-45 min. Then, they are stirred and kneaded with a portion of the first binder and the second binder. The revolution speed of the stirring and kneading is 1-10 rpm, the rotation speed is 200-400 rpm, and the time is 70-110 min, to obtain a kneaded material with a solid content of more than 70 wt%. The first conductive agent includes a zero-dimensional conductive agent; (3) Mix the remaining first binder, second conductive agent and the kneading material described in step (2) at a revolution speed of 20-30 rpm, a rotation speed of 1500-2000 rpm, a temperature of 30-40℃ and a vacuum of -95~-75Kpa for 80-100 min. Then add the third binder and continue stirring at a revolution speed of 5-25 rpm, a rotation speed of 100-350 rpm, a stirring temperature of 15-35℃ and a vacuum of -95~-75Kpa to obtain the electrode slurry. In step (3), the mass ratio of the first adhesive to the first adhesive in step (2) is (3-5):(5-7), and the second conductive agent includes a one-dimensional conductive agent; (4) The electrode slurry described in step (3) is coated on the current collector, and then a solvent is sprayed onto the electrode slurry on the surface of the current collector. Then, three-stage drying and three cold pressing are performed in sequence to obtain the electrode sheet. In the three-stage drying process, the temperatures of the first and third stages of drying are independently greater than the temperature of the second stage of drying. In the three-stage cold pressing process, the pressures of the first and second cold pressings are independently greater than the pressures of the third cold pressing.

26. An electrode sheet, characterized in that, The electrode sheet is obtained by the preparation method described in any one of claims 1-25.

27. A battery, characterized in that, The battery includes the electrode plates as described in claim 26.

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