Method for determining pole piece baking parameters and application

Abstract

This invention belongs to the field of secondary battery technology, specifically relating to a method and application for determining electrode baking parameters. The method for determining electrode baking parameters provided by this invention includes the following steps: adjusting the baking parameters of each oven section to control the average solvent evaporation rate of each oven section to be 0.6–0.9 g / m³. 2 •sec, the adjusted baking parameters are the determined baking parameters. This invention introduces the concept of average evaporation rate and provides a selection range for the optimal evaporation rate. Adjusting the baking parameters within this range achieves the best baking effect, improving the adhesion of the electrode and reducing its resistivity. This method does not rely on the operator's experience, eliminates the need for blindly setting parameters, ensures process stability, simplifies procedures, facilitates operation guidance, and is easy to promote and apply.

Description

Technical Field

[0001] This invention belongs to the field of secondary battery technology, specifically relating to a method for determining electrode baking parameters and its application. Background Technology

[0002] Many factors influence the performance of lithium batteries, such as the type of active material, the compaction density of the positive and negative electrodes, baking parameters, coating density, and electrolyte dosage. In the lithium-ion battery production process, electrode manufacturing is a crucial front-end process. The quality of the electrodes affects the progress of the mid-stage assembly process and also influences the electrochemical performance of the final lithium battery. Baking is a critical step in electrode production.

[0003] Currently, the lithium-ion battery industry lacks in-depth research on the principles and applications of electrode baking in the coating process, with most theories lacking practical application support. The industry primarily uses ovens to bake the electrodes. To ensure baking effectiveness and accelerate the baking process, a combination of high-temperature baking and circulating air vacuum is generally employed. The baking temperature is gradually increased, with the first 1-3 sections of the oven baked at low temperatures, the middle sections at high temperatures, and the last 1-3 sections at low temperatures. While this method is widely applicable and effective, and is adopted by most lithium battery companies, it lacks scientific characterization methods. Baking parameters are mostly adjusted fuzzily by technicians based on actual baking conditions, resulting in high yield losses, poor electrode adhesion, and process instability.

[0004] Since the settings of various parameters during baking affect the final baked electrode sheet, which in turn affects the performance of the secondary battery, there is an urgent need for a method to accurately determine the optimal baking parameters. Existing patent literature discloses some methods for determining the optimal coating and baking parameters for electrodes. Most of these methods rely on experience to provide a series of preset parameters for baking, then test the performance of the baked electrode sheet, and determine the optimal baking parameters based on the test results. However, the setting of preset parameters in these methods depends on the operator's experience, and different operators provide different preset parameters. The process is unstable, and the procedures are complex, requiring multiple batch comparison experiments to determine the optimal baking parameters, which is not conducive to widespread application. Summary of the Invention

[0005] Therefore, the technical problem to be solved by the present invention is to overcome the defects in the existing technology, such as the need for experience in setting the optimal baking parameters, unstable process, poor adhesion of the electrode after baking, complex process, and difficulty in promotion and application, so as to provide a method and application for determining electrode baking parameters.

[0006] Therefore, the present invention provides the following technical solution:

[0007] This invention provides a method for determining electrode baking parameters, comprising the following steps:

[0008] Adjust the baking parameters of each oven section to control the average solvent evaporation rate of each oven section to 0.6–0.9 g / m³. 2 •sec, the adjusted baking parameters are the determined baking parameters;

[0009] in,

[0010] W n ---Section n: Amount of solvent evaporated in the oven, in g / m³ 2 ;

[0011] V --- Coating speed, in m / sec;

[0012] L---Length of a single section of the oven, in meters.

[0013] In some alternative embodiments, the amount of solvent W evaporated from each oven section n The calculation method is as follows:

[0014]

[0015] Where E is the surface density, measured in g / m³. 2 ;

[0016] S n ---Solid content of the coating before entering the oven in section n, %;

[0017] S n+1 ---The solid content of the coating after drying in the nth section of the oven, %.

[0018] Currently, there are two methods for coating electrodes in this field:

[0019] (1) First coat one side (i.e., side A), then dry it in the oven, and then coat both sides (i.e., side B). Only one side is being baked in the oven, so E represents the surface density of one side.

[0020] (2) Coating is applied to both sides A and B simultaneously, and then the coating is applied to the oven. The surface density E here refers to the surface density of both sides.

[0021] In some alternative embodiments, the baking parameters include at least one of baking temperature, fan frequency, valve opening degree, and vacuum degree inside the oven.

[0022] In some alternative embodiments, when the electrode is a negative electrode, the baking temperature is adjusted to below 100°C; when the electrode is a positive electrode, the baking temperature is adjusted to below 120°C.

[0023] And / or, the wind frequency adjustment range is 0 to 50 Hz; in this invention, wind frequency refers to the operating frequency of the equipment's air supply.

[0024] And / or, the valve opening adjustment range is 0 to 100%;

[0025] And / or, the vacuum degree can be adjusted within a range of -20 to 0 kPa.

[0026] In some alternative implementations, the average evaporation rate of the solvent in each oven section is controlled to be consistent.

[0027] In some alternative implementations, during the adjustment of baking parameters, the concentration of solvent in each oven section is controlled to not exceed an alarm value.

[0028] In this invention, the alarm value refers to the warning value at which the volume concentration of the solvent in the oven poses an explosion risk.

[0029] In some optional implementations, the alarm value is 40% when the solvent is N-methylpyrrolidone.

[0030] In some alternative implementations, during the adjustment of baking parameters, it is necessary to ensure that the electrode does not wrinkle in the oven;

[0031] And / or, the weight loss rate of the electrode sheet after baking is controlled to be ≤0.5%;

[0032] In this invention, the weight loss rate refers to the solvent (water) content of the electrode after drying. If the weight loss rate is 0.5%, the degree of drying of the electrode is 99.5%. 100% drying is the ideal situation, which is difficult to achieve in practice.

[0033] And / or, the number of sections in the oven is 3 to 25.

[0034] Based on the above method, in some specific embodiments, the method for determining the electrode baking parameters is as follows:

[0035] (1) Add the prepared slurry into the coating machine. To ensure the best coating effect, the solid content of the graphite system negative electrode slurry should be controlled at ≥45%, the solid content of the lithium iron phosphate system positive electrode slurry should be controlled at ≥55%, the solid content of the ternary material system positive electrode slurry should be controlled at ≥65%, and the solid content of the lithium cobalt oxide system positive electrode slurry should be controlled at ≥75%.

[0036] (2) According to the product design requirements, the slurry is coated onto the foil at the set surface density. The following explanation uses single-sided coating as an example, and the single-sided surface density is denoted as E. The solid content of the slurry before entering the first drying oven is known and denoted as S1. The electrode passes through the first drying oven at a certain speed. After exiting the first drying oven, the door of the second drying oven is opened, and 3-6g of the wet film slurry on the foil is quickly scraped off for solid content testing. The obtained solid content is denoted as S2. The weight of the solvent on the electrode before entering the drying oven is denoted as W.a Then W a =E / S1-E. The weight of the electrode solvent after exiting the first drying oven is recorded as W. b Then W b =E / S2-E. Therefore, the amount of wet film solvent evaporated from the electrode in the first drying oven, W1 = W a -W b =E / S1-E / S2.

[0037] (3) According to the method for determining baking parameters provided by the present invention, the average evaporation rate is controlled at 0.6 to 0.9 g / m³. 2 The optimal time is 1 second. The coating speed V and oven length L are known. W1 is calculated from the collected data, from which the average evaporation rate of the electrode after passing through the first section of the oven can be calculated. If the calculated average evaporation rate is not between 0.6 and 0.9 g / m... 2 If the result falls within the specified range (e.g., 0.6–0.9 g / m³), adjust the oven temperature and / or fan frequency, and re-acquire data until the result is within the range of 0.6–0.9 g / m³. 2 Within the sec interval.

[0038] (4) After fixing the temperature and airflow parameters of the first oven section, the second oven section is adjusted. The solid content of the wet film of the electrode before entering the second oven section is known as S2. Coating is started, and the electrode passes through the first and second oven sections at a certain speed V. After exiting the second oven section, the door of the third oven section is opened, and 3-6g of the wet film slurry on the foil is quickly scraped off for solid content testing. The obtained solid content is recorded as S3. The solvent weight on the electrode before entering the second oven section is W. b The weight of the electrode solvent after exiting the second drying oven is recorded as W. c Therefore, W3 = E / S3 - E. From this, we can deduce that the amount of wet film solvent evaporated from the electrode in the second drying oven is W2 = W b -W c =E / S2-E / S3.

[0039] (5) According to the method for determining baking parameters provided by the present invention, the average evaporation rate is controlled at 0.6 to 0.9 g / m³. 2 The optimal time is sec. The coating speed V and oven length L are known. W2 is calculated from the collected data, from which the average evaporation rate of the electrode after passing through the second section of the oven can be calculated. If the calculated average evaporation rate is not between 0.6 and 0.9 g / m... 2 If the result falls within the specified range (e.g., 0.6–0.9 g / m³), adjust the oven temperature and / or fan frequency, and re-acquire data until the result is within the range of 0.6–0.9 g / m³. 2 Within the sec interval.

[0040] (6) Repeat steps (2) to (3) to collect the evaporation rate of the subsequent oven in sequence, and adjust the corresponding temperature, wind frequency, valve opening and / or vacuum degree in the oven to determine the parameters of the subsequent oven in sequence.

[0041] In this invention, the temperature parameters of the oven can only be set section by section. Once the parameters of the preceding ovens are finalized, they remain unchanged. During normal coating, the process proceeds through the preceding ovens and then to the oven where the number of sections to be verified is reached to collect relevant data. The parameters are then finalized according to the method described above.

[0042] In some alternative implementations, after locking the evaporation rate of the first oven section, the controlled evaporation rate of each subsequent oven section must be consistent with that of the first section, such as the evaporation rate of the first oven section being 0.7 g / m³. 2 If the concentration is 0.7 g / m, then the subsequent ovens will all be set at 0.7 g / m. 2 The evaporation rate is used to regulate the corresponding temperature, fan frequency, valve opening, and / or vacuum level inside the oven.

[0043] During parameter setting, ensure that the electrode does not wrinkle in the oven. If wrinkling occurs, the evaporation rate value needs to be readjusted for verification.

[0044] This invention also provides a method for preparing an electrode sheet, wherein the electrode sheet baking parameters are determined using the method described above. In this invention, other steps and parameters in the electrode sheet preparation process are conventional in the field and are not specifically limited herein.

[0045] Typically, and not specifically, the positive electrode current collector can be aluminum foil, carbon-coated aluminum foil, or composite aluminum foil, with a thickness of 8μm to 15μm; the negative electrode current collector can be copper foil or composite copper foil, with a thickness of 3μm to 10μm; the active materials commonly used in the positive electrode slurry of lithium-ion battery systems are one or a mixture of lithium iron phosphate, lithium nickel cobalt manganese oxide, lithium cobalt oxide, lithium manganese oxide, and lithium manganese iron phosphate; the active materials commonly used in the positive electrode slurry of sodium-ion battery systems are one or a mixture of layered oxides, polyanions, and Prussian blue, and the positive electrode slurry also includes conventional amounts of binders and conductive agents; the active materials commonly used in the negative electrode slurry of lithium-ion battery systems are graphite or a mixture of graphite-doped silicon-carbon or graphite-doped silicon-oxygen; the active materials commonly used in the negative electrode slurry of sodium-ion battery systems are one or a mixture of hard carbon and soft carbon, and the negative electrode slurry also includes conventional amounts of binders and conductive agents. The solvent content in the slurry is within the solid content range mentioned above. The areal density of the positive electrode sheet ranges from 50 to 250 g / m². 2 The areal density of the negative electrode sheet ranges from 40 to 150 g / m². 2 The solvent typically used in positive electrode slurry is NMP, while the solvent typically used in negative electrode slurry is either NMP or deionized water.

[0046] The present invention also provides a secondary battery comprising an electrode sheet prepared by the above-described preparation method.

[0047] In this invention, the electrode can be either a positive or negative electrode; the secondary battery can be a lithium-ion battery or a sodium-ion battery, etc. The composition and preparation method of the secondary battery are conventional in the field and are not specifically limited here. For example, the battery preparation steps may include homogenization, coating, rolling (roll pressing and cutting), assembly, baking, electrolyte injection, and formation and capacity testing.

[0048] The technical solution of this invention has the following advantages:

[0049] The method for determining electrode baking parameters provided by this invention includes the following steps: adjusting the baking parameters of each oven section to control the average evaporation rate of the solvent in each oven section to be 0.6–0.9 g / m³. 2 •sec, the adjusted baking parameters are the determined baking parameters. This invention introduces the concept of average evaporation rate and provides a selection range for the optimal evaporation rate. Adjusting the baking parameters within this range achieves the best baking effect, improving the adhesion of the electrode and reducing its resistivity. This method does not rely on the operator's experience, eliminates the need for blindly setting parameters, ensures process stability, simplifies procedures, facilitates operation guidance, and is easy to promote and apply.

[0050] The method for determining electrode baking parameters provided by this invention controls the average evaporation rate of the solvent in each oven section to be consistent, which can further improve the peeling force of the electrode and reduce the resistivity of the electrode.

[0051] The method for determining electrode baking parameters provided by this invention controls the concentration of solvent in each oven section to not exceed the alarm value, thereby ensuring the safety of the production process and avoiding fire hazards. Detailed Implementation

[0052] The following embodiments are provided to better understand the present invention and are not limited to the preferred embodiments described. They do not constitute a limitation on the content and scope of protection of the present invention. Any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the protection scope of the present invention.

[0053] For experiments not specifically described in the examples, the procedures or conditions should be followed according to the conventional experimental procedures described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available conventional reagent products.

[0054] Example 1

[0055] This embodiment provides a method for determining electrode baking parameters, and the specific steps and operating parameters are as follows:

[0056] (1) The prepared positive electrode slurry is added to the coating machine. The composition of the positive electrode slurry is: lithium iron phosphate: PVDF: SP: carbon nanotubes (CNTs) = 96wt%: 2.2wt%: 1wt%: 0.8wt%; the solid content of the slurry is 60wt%, and the solvent is NMP.

[0057] (2) According to the product design requirements, the slurry is coated onto the foil (aluminum foil with a thickness of 12μm in this embodiment) at a set surface density. The coating method is single-sided coating, and the single-sided surface density is denoted as E(180g / m²). 2 The solid content of the slurry before entering the first drying oven is known and denoted as S1 (60wt%). The electrode passes through the first drying oven at a speed of 12m / min. The oven length is 5m, the valve opening is 70%, the vacuum degree is -5kPa, the baking temperature is 100℃, and the air frequency is 30Hz. After exiting the first drying oven, the door of the second drying oven is opened, and 5g of the wet film slurry on the foil is quickly scraped for solid content testing. The obtained solid content is denoted as S2 (64.3%). According to the formula W1 = W a -W b =E / S1-E / S2 Calculation yields 20g / m² of wet film solvent evaporated from the electrode after passing through the first drying oven. 2 The average evaporation rate is calculated using the following formula: The calculated average evaporation rate is 0.8 g / m³. 2 •sec, falling within 0.6–0.9 g / m 2 Within the range of 0.6–0.9 g / m³. 2 If the result falls within the specified range (e.g., 0.6–0.9 g / m³), adjust the oven temperature and / or fan frequency, and re-acquire data until the result is within the range of 0.6–0.9 g / m³. 2 Within the sec interval.

[0058] (3) After fixing the temperature and air frequency parameters of the first oven section, proceed with the debugging of the second oven section. Repeat step (2) to collect the evaporation rate of the subsequent oven sections in sequence, adjust the corresponding temperature and / or air frequency, and keep the valve opening and vacuum level unchanged so that the average evaporation rate of each oven section is 0.8 g / m³. 2• The parameters of the subsequent ovens are determined sequentially. Oven temperature parameters can only be set section by section. Once the parameters of the preceding ovens are determined, they remain unchanged. Normal coating proceeds through the preceding ovens, and relevant data is collected at the oven requiring verification. Parameters are determined using the method described above. Following this method, the temperatures of the second, third, fourth, fifth, and sixth ovens are determined as follows: baking temperature 100℃, airflow frequency 30Hz. During the adjustment of baking parameters, the solvent concentration in each oven section must be controlled to not exceed the alarm value. It is also crucial to ensure that the electrode sheets do not wrinkle in the oven; if wrinkling occurs, the evaporation rate must be readjusted for verification.

[0059] (4) Prepare the electrode according to the baking parameters determined above, prepare the slurry with the same composition as in step (1), prepare the slurry according to the method in step (2), coat the slurry onto the foil according to the set surface density, and bake according to the parameters determined in steps (2) and (3) to obtain the electrode.

[0060] Example 2

[0061] This embodiment provides a method for determining electrode baking parameters, and the specific steps and operating parameters are as follows:

[0062] (1) Add the prepared slurry to the coating machine. The composition of the slurry is the same as in Example 1.

[0063] (2) According to the product design requirements, the slurry is coated onto the foil (aluminum foil with a thickness of 12μm in this embodiment) at a set surface density. The coating method is single-sided coating, and the single-sided surface density is denoted as E (same as in Example 1). The solid content of the slurry before entering the first drying oven is known and denoted as S1 (same as in Example 1). The electrode passes through the first drying oven at a speed of 15m / min. The drying oven is 5m long, the valve opening is 70%, the vacuum degree is -5kPa, the baking temperature is 100℃, and the air frequency is 25Hz. After exiting the first drying oven, the door of the second drying oven is opened and 5g of wet film slurry on the foil is quickly scraped off for solid content testing. The obtained solid content is denoted as S2 (63.6%). According to the formula W1 = W a -W b =E / S1-E / S2 Calculation shows that the amount of wet film solvent evaporated from the electrode in the first oven section is 17g / m 2 The average evaporation rate is calculated using the following formula: The calculated average evaporation rate is 0.85 g / m³. 2 •sec, falling within 0.6–0.9 g / m 2Within the range of 0.6–0.9 g / m³. 2 If the result falls within the specified range (e.g., 0.6–0.9 g / m³), adjust the oven temperature and / or fan frequency, and re-acquire data until the result is within the range of 0.6–0.9 g / m³. 2 Within the sec interval.

[0064] (3) After fixing the temperature and air frequency parameters of the first oven section, debug the second oven section. Repeat step (2) to collect the evaporation rate of the subsequent ovens in sequence, adjust the corresponding temperature and / or air frequency, keep the valve opening and vacuum level unchanged, so that the average evaporation rate of the first 6 oven sections is 0.85 g / m³. 2 The average evaporation rate of the oven in Section 7 is 0.9 g / m³. 2 • sec, sequentially finalize the parameters of the subsequent ovens. Oven temperature parameters can only be set section by section. Once the parameters of the preceding ovens are finalized, they remain unchanged. Normal coating proceeds through the preceding ovens, collecting relevant data at the oven requiring verification, and finalizing parameters according to the above method. Following this method, the temperatures for the second, third, and fourth ovens are determined as follows: baking temperature 100℃, airflow frequency 25Hz; baking temperature 100℃, airflow frequency 25Hz; baking temperature 100℃, airflow frequency 25Hz; baking temperature 100℃, airflow frequency 25Hz; baking temperature 100℃, airflow frequency 25Hz; baking temperature 100℃, airflow frequency 25Hz; baking temperature 100℃, airflow frequency 25Hz; and baking temperature 115℃, airflow frequency 45Hz. During the adjustment of baking parameters, the solvent concentration in each oven section must be controlled to not exceed the alarm value. During parameter adjustment, it is also necessary to ensure that the electrode does not wrinkle in the oven; if wrinkling occurs, the evaporation rate value must be readjusted for verification.

[0065] (4) Prepare the electrode according to the baking parameters determined above, prepare the slurry with the same composition as in step (1), prepare the slurry according to the method in step (2), coat the slurry onto the foil according to the set surface density, and bake according to the parameters determined in steps (2) and (3) to obtain the electrode.

[0066] Example 3

[0067] This embodiment provides a method for determining electrode baking parameters, and the specific steps and operating parameters are as follows:

[0068] (1) Add the prepared slurry to the coating machine. The composition of the slurry is the same as in Example 1.

[0069] (2) According to the product design requirements, the slurry is coated onto the foil (aluminum foil with a thickness of 12μm in this embodiment) at a set surface density. The coating method is single-sided coating, and the single-sided surface density is denoted as E (same as in Example 1). The solid content of the slurry before entering the first drying oven is known and denoted as S1 (same as in Example 1). The electrode passes through the first drying oven at a speed of 15m / min. The drying oven is 5m long, the valve opening is 70%, the vacuum degree is -5kPa, the baking temperature is 80℃, and the air frequency is 25Hz. After exiting the first drying oven, the door of the second drying oven is opened and 5g of wet film slurry on the foil is quickly scraped off for solid content testing. The obtained solid content is denoted as S2 (62.5%). According to the formula W1 = W a -W b =E / S1-E / S2 Calculation yields 12g / m² of wet film solvent evaporated from the electrode after passing through the first oven section. 2 The average evaporation rate is calculated using the following formula: The calculated average evaporation rate is 0.6, falling within the range of 0.6–0.9 g / m³. 2 Within the range of 0.6–0.9 g / m³. 2 If the result falls within the specified range (e.g., 0.6–0.9 g / m³), adjust the oven temperature and / or fan frequency, and re-acquire data until the result is within the range of 0.6–0.9 g / m³. 2 Within the sec interval.

[0070] (3) After fixing the temperature and air frequency parameters of the first oven section, adjust the second oven section. Repeat step (2) to collect the evaporation rate of the subsequent ovens, adjust the corresponding temperature and / or air frequency, keep the valve opening and vacuum level unchanged, and set the average evaporation rate of each oven section to 0.6-0.9 g / m³. 2 Within the range of sec, the second oven section has a concentration of 0.65 g / m. 2 •sec, the third oven section has a concentration of 0.8g / m 2 •sec, the fourth oven section has a concentration of 0.9g / m 2 •sec, the fifth oven section has a concentration of 0.85g / m 2 •sec, the sixth oven is 0.85g / m 2 •sec, the seventh oven section has a concentration of 0.75g / m 2 •sec, the eighth oven is 0.6g / m 2• sec, sequentially finalize the parameters of the subsequent ovens. Oven temperature parameters can only be set section by section. Once the parameters of the preceding ovens are finalized, they remain unchanged. Normal coating proceeds through the preceding ovens, collecting relevant data at the oven requiring verification, and finalizing parameters according to the above method. Following this method, the temperatures for the second oven section are determined as follows: baking temperature 85℃, airflow frequency 30Hz; the third oven section: baking temperature 95℃, airflow frequency 35Hz; the fourth oven section: baking temperature 115℃, airflow frequency 45Hz; the fifth oven section: baking temperature 110℃, airflow frequency 40Hz; the sixth oven section: baking temperature 110℃, airflow frequency 40Hz; the seventh oven section: baking temperature 90℃, airflow frequency 35Hz; and the eighth oven section: baking temperature 80℃, airflow frequency 25Hz. During the adjustment of baking parameters, the solvent concentration in each oven section is controlled to not exceed the alarm value. During parameter adjustment, it is also necessary to ensure that the electrode does not wrinkle in the oven. If wrinkling occurs, the evaporation rate value needs to be readjusted for verification.

[0071] (4) Prepare the electrode according to the baking parameters determined above, prepare the slurry with the same composition as in step (1), prepare the slurry according to the method in step (2), coat the slurry onto the foil according to the set surface density, and bake according to the parameters determined in steps (2) and (3) to obtain the electrode.

[0072] Example 4

[0073] This embodiment provides a method for determining electrode baking parameters, and the specific steps and operating parameters are as follows:

[0074] (1) The prepared negative electrode slurry is added to the coating machine. The composition of the negative electrode slurry is: graphite: conductive agent: CMC: SBR = 96wt%: 1wt%: 1.2wt%: 1.8wt%, the slurry solid content is 50wt%, and the solvent is deionized water.

[0075] (2) According to the product design requirements, the slurry is coated onto the foil (in this embodiment, a copper foil with a thickness of 6 μm) at a set surface density. The coating method is single-sided coating, and the single-sided surface density is denoted as E(80 g / m²). 2 The solid content of the slurry before entering the first drying oven is known and denoted as S1 (50wt%). The electrode passes through the first drying oven at a speed of 18m / min. The oven length is 5m, the valve opening is 70%, the vacuum degree is -5kPa, the baking temperature is 60℃, and the air frequency is 25Hz. After exiting the first drying oven, the door of the second drying oven is opened, and 5g of the wet film slurry on the foil is quickly scraped for solid content testing. The obtained solid content is denoted as S2 (54.5%). According to the formula W1 = W a -W b=E / S1-E / S2 Calculation yields 13.3 g / m² of wet film solvent evaporated from the electrode after passing through the first drying oven. 2 The average evaporation rate is calculated using the following formula: The calculated average evaporation rate is 0.8 g / m³. 2 •sec, falling within 0.6–0.9 g / m 2 Within the range of 0.6–0.9 g / m³. 2 If the result falls within the specified range (e.g., 0.6–0.9 g / m³), adjust the oven temperature and / or fan frequency, and re-acquire data until the result is within the range of 0.6–0.9 g / m³. 2 Within the sec interval.

[0076] (3) After fixing the temperature and air frequency parameters of the first oven section, proceed with the debugging of the second oven section. Repeat step (2) to collect the evaporation rate of the subsequent ovens, adjust the corresponding temperature and / or air frequency, keep the valve opening and vacuum level unchanged, and the average evaporation rate is 0.8 g / m³. 2 • sec, sequentially finalize the parameters of the subsequent ovens. Oven temperature parameters can only be set section by section. Once the parameters of the preceding ovens are finalized, they remain unchanged. Normal coating proceeds through the preceding ovens, collecting relevant data at the oven requiring verification, and finalizing parameters according to the above method. Following this method, the temperatures for the second, third, fourth, fifth, and sixth ovens are determined as follows: baking temperature 60℃, airflow frequency 25Hz. During the adjustment of baking parameters, the solvent concentration in each oven section must be controlled to not exceed the alarm value. It is also crucial to ensure that the electrode sheets do not wrinkle in the oven; if wrinkling occurs, the evaporation rate must be readjusted for verification.

[0077] (4) Prepare the electrode according to the baking parameters determined above, prepare the slurry with the same composition as in step (1), prepare the slurry according to the method in step (2), coat the slurry onto the foil according to the set surface density, and bake according to the parameters determined in steps (2) and (3) to obtain the electrode.

[0078] Comparative Example 1

[0079] This comparative example provides a method for preparing an electrode sheet. The specific steps and operating parameters are as follows: Prepare a slurry according to the method of Example 1 and coat it onto a foil; pass the electrode sheet through 6 drying ovens at a speed of 12 m / min. Each drying oven is 5 m long. Set the temperatures of the 1st to 6th drying ovens to be 80℃, 90℃, 110℃, 110℃, 100℃, and 80℃, respectively, and set the air frequencies to be 25 Hz, 28 Hz, 35 Hz, 35 Hz, 30 Hz, and 28 Hz, respectively, to obtain the electrode sheet.

[0080] Comparative Example 2

[0081] This comparative example provides a method for determining electrode baking parameters. The specific steps and operating parameters are as follows:

[0082] (1) Add the prepared slurry to the coating machine. The composition of the slurry is the same as in Example 1.

[0083] (2) According to the product design requirements, the slurry is coated onto the foil at a set surface density. The coating method is single-sided coating, and the single-sided surface density is denoted as E (same as in Example 1). The solid content of the slurry before entering the first drying oven is known and denoted as S1 (same as in Example 1). The electrode passes through the first drying oven at a speed of 12 m / min. The drying oven is 5 m long, the baking temperature is 60℃, and the air frequency is 20 Hz. After exiting the first drying oven, the door of the second drying oven is opened, and 5 g of wet film slurry on the foil is quickly scraped off for solid content testing. The obtained solid content is denoted as S2 (62.6%). According to the formula W1 = W a -W b =E / S1-E / S2 Calculation yields 12.5 g / m² of wet film solvent evaporated from the electrode after passing through the first drying oven. 2 The average evaporation rate is calculated using the following formula: The calculated average evaporation rate is 0.5 g / m³. 2 ·sec.

[0084] (3) After fixing the temperature and air frequency parameters of the first oven section, adjust the second oven section. Repeat step (2) to collect the evaporation rate of the subsequent ovens in sequence. Adjust the corresponding temperature and / or air frequency, keeping the valve opening and vacuum level unchanged, so that the second oven section is 0.55 g / m³. 2 •sec, the third oven section has a concentration of 0.65g / m 2 •sec, the fourth oven section has a concentration of 0.8g / m 2 •sec, the fifth oven section has a concentration of 0.9g / m 2 •sec, the sixth oven is 0.8g / m 2 •sec, the sixth oven is 0.6g / m 2• sec, sequentially determine the parameters of the subsequent ovens. Following the above method, determine the following oven temperatures: Second oven: 70℃, fan frequency 30Hz; Third oven: 80℃, fan frequency 35Hz; Fourth oven: 100℃, fan frequency 40Hz; Fifth oven: 110℃, fan frequency 45Hz; Sixth oven: 100℃, fan frequency 40Hz; Sixth oven: 80℃, fan frequency 35Hz. During parameter adjustment, ensure the solvent concentration in each oven does not exceed the alarm value. Also, ensure the electrode sheets do not wrinkle in the oven; if wrinkling occurs, readjust the evaporation rate value for verification.

[0085] (4) Prepare the electrode according to the baking parameters determined above, prepare the slurry with the same composition as in step (1), prepare the slurry according to the method in step (2), coat the slurry onto the foil according to the set surface density, and bake according to the parameters determined in steps (2) and (3) to obtain the electrode.

[0086] Comparative Example 3

[0087] This comparative example provides a method for determining electrode baking parameters. The specific steps and operating parameters are as follows:

[0088] (1) Add the prepared slurry to the coating machine. The composition of the slurry is the same as in Example 1.

[0089] (2) According to the product design requirements, the slurry is coated onto the foil at a set surface density. The coating method is single-sided coating, and the single-sided surface density is denoted as E (same as in Example 1). The solid content of the slurry before entering the first drying oven is known and denoted as S1 (same as in Example 1). The electrode passes through the first drying oven at a speed of 12 m / min. The drying oven is 5 m long, the valve opening is 70%, the vacuum degree is -5 kPa, the baking temperature is 80℃, and the air frequency is 25 Hz. After exiting the first drying oven, the door of the second drying oven is opened, and 5 g of wet film slurry on the foil is quickly scraped off for solid content testing. The obtained solid content is denoted as S2 (63.2%). According to the formula W1 = W a -W b =E / S1-E / S2 Calculation yields 15g / m² of wet film solvent evaporated from the electrode after passing through the first drying oven. 2 The average evaporation rate is calculated using the following formula: The calculated average evaporation rate is 0.6.

[0090] (3) After fixing the temperature and air frequency parameters of the first oven section, adjust the second oven section. Repeat step (2) to collect the evaporation rate of the subsequent ovens. Adjust the corresponding temperature and / or air frequency, keeping the valve opening and vacuum level constant, so that the second oven section is 0.7 g / m³.2 •sec, the third oven section has a concentration of 0.8g / m 2 •sec, the fourth oven section has a concentration of 0.9g / m 2 •sec, the fifth oven section is 1.0g / m 2 •sec, the sixth oven is 0.8g / m 2 • sec, determine the parameters of the subsequent ovens sequentially. Following the above method, determine the following oven temperatures: Second oven: 90℃, fan frequency 30Hz; Third oven: 100℃, fan frequency 35Hz; Fourth oven: 110℃, fan frequency 40Hz; Fifth oven: 120℃, fan frequency 45Hz; Sixth oven: 100℃, fan frequency 35Hz. During parameter adjustment, ensure the solvent concentration in each oven does not exceed the alarm value. Also, ensure the electrode sheets do not wrinkle in the oven; if wrinkling occurs, readjust the evaporation rate value for verification.

[0091] (4) Prepare the electrode according to the baking parameters determined above, prepare the slurry with the same composition as in step (1), prepare the slurry according to the method in step (2), coat the slurry onto the foil according to the set surface density, and bake according to the parameters determined in steps (2) and (3) to obtain the electrode.

[0092] Comparative Example 4

[0093] This comparative example provides a method for preparing an electrode sheet. The specific steps and operating parameters are as follows: Prepare a slurry according to the method of Example 4 and coat it onto a foil; pass the electrode sheet through 6 drying ovens at a speed of 12 m / min. Each drying oven is 5 m long. Set the temperatures of the 1st to 6th drying ovens to 65℃, 75℃, 90℃, 90℃, 85℃, and 80℃, respectively, and set the air frequencies to 25Hz, 28Hz, 35Hz, 35Hz, 30Hz, and 28Hz, respectively, to obtain the electrode sheet.

[0094] Test case

[0095] The peel force and film resistance of the electrodes prepared in each embodiment and comparative example were tested. Specific testing methods followed the national standard GB / T 25256 (180° peel force test method). Film resistance was tested using the two-probe method, a commonly used industry testing method. Electrodes were selected, and the test parameters were first set on the software of the internal resistance tester: pressure of 25 MPa and holding time of 15 s. The electrodes were then placed in the tester, and the test was started. The resistivity data was automatically read upon completion. Specific test results are shown in the table below:

[0096] Table 1

[0097]

[0098]

[0099] As can be seen from the test results of the examples and comparative examples in the table above, determining the electrode baking parameters according to the method provided by the present invention can achieve better baking results, improve the peeling force of the electrode, and reduce the resistivity of the electrode. Specifically, a comparison of the data between Example 1 and Example 3 shows that controlling the average evaporation rate of the solvent in each oven section to be consistent can further improve the peeling force of the electrode and also achieve a lower electrode resistivity.

[0100] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for determining electrode baking parameters, characterized in that, Includes the following steps: Adjust the baking parameters of each oven section to control the average evaporation rate of the solvent in each oven section to 0.6~0.9 g / m²·sec. The adjusted baking parameters are the determined baking parameters. wherein , W n --- the amount of solvent evaporated by the n-th oven, in g / m2; V --- Coating speed, in m / sec; L---Length of a single section of the oven, in meters; The amount W of solvent evaporated by each oven section n The calculation is as follows: ， Where E is the surface density, in g / m². S n --- solid content of the film coating before entering the nth oven, % S n+1 --- Solid content of the coating film after the n-th oven, %.

2. The method of determining pole piece bake parameters according to claim 1, wherein, The baking parameters include at least one of baking temperature, fan frequency, valve opening degree, and vacuum degree inside the oven.

3. The method of determining pole piece bake parameters according to claim 2, wherein, When the electrode is a negative electrode, the baking temperature should be adjusted below 100℃; when the electrode is a positive electrode, the baking temperature should be adjusted below 120℃. And / or, the wind frequency adjustment range is 0~50Hz; And / or, the valve opening adjustment range is 0~100%; And / or, the vacuum degree can be adjusted within a range of -20 to 0 kPa.

4. The method of determining baking parameters for a pole piece according to any one of claims 1 to 3, characterized in that, The average evaporation rate of the solvent in each oven section is kept consistent.

5. The method of determining pole piece bake parameters of claim 1, wherein, During the adjustment of baking parameters, the concentration of solvent in each oven section should be controlled to not exceed the alarm value.

6. The method of determining pole piece bake parameters according to claim 5, wherein, When the solvent is N-methylpyrrolidone, the alarm value is 40%.

7. The method of determining pole piece bake parameters of claim 1, wherein, During the process of adjusting the baking parameters, it is necessary to ensure that the electrode sheets do not wrinkle in the oven; And / or, the weight loss rate of the electrode sheet after baking is controlled to be ≤0.5%; And / or, the number of sections in the oven is 3 to 25.

8. A method of manufacturing a pole piece, characterized by, The electrode baking parameters are determined by the method described in any one of claims 1-7.

9. A secondary battery characterized by comprising: Including the electrode sheet prepared by the preparation method of claim 8.

Images