Cylindrical lithium battery cell baking process

Abstract

The present application relates to the technical field of lithium battery, specifically to a cylindrical lithium battery cell baking process, comprising the following steps: S1, pre-drying; S2, pressure pulsation dehumidification; S3, sound wave resonance assistance; S4, gradient cold setting. The present application uses a four-stage synergistic process of pre-drying, pressure pulsation dehumidification, sound wave resonance assistance and gradient cold setting, combined with hot air spiral flushing, periodic pressure pulsation and sound wave resonance to strengthen mass transfer, which can deeply remove the residual moisture in the cylindrical lithium battery cell, stably control the water content of the cell at a very low level, has high process stability, and is suitable for large-scale production of 18650, 21700, 46800 and other specifications of cylindrical cells.

Description

Technical Field

[0001] This invention relates to the field of lithium battery technology, specifically a baking process for cylindrical lithium battery cells. Background Technology

[0002] Cylindrical lithium batteries are mainly classified into lithium iron phosphate, lithium cobalt oxide, lithium manganese oxide, and ternary materials, and are widely used in consumer electronics, power tools, and electric vehicles. The electrochemical performance and safety characteristics of lithium-ion batteries are highly dependent on the moisture content inside the cell. If the moisture content is too high, it will react with the lithium salt in the electrolyte to produce hydrofluoric acid, which not only corrodes the electrodes and damages the SEI film, but also causes cell swelling, increased internal resistance, and cycle degradation, and may even lead to serious safety hazards.

[0003] To address the need for water removal, CN105226318B discloses a lithium battery cell baking process, which achieves water removal through complex cyclic vacuuming, nitrogen filling, and vortex blowing. However, the process cycle is long and energy consumption is high. In addition, prolonged exposure of the cell to a high-temperature environment of 88-90℃ can easily cause problems such as thermal shrinkage of the separator, reduced porosity, and binder failure and powder shedding. This not only increases the risk of micro-short circuits but also leads to poor cell consistency and reduced cycle life. Summary of the Invention

[0004] The purpose of this invention is to provide a baking process for cylindrical lithium battery cells to solve the problems mentioned in the background art.

[0005] Unless otherwise stated, all pressure values ​​described in this invention are gauge pressures, based on standard atmospheric pressure. Negative values ​​indicate vacuum, and positive values ​​indicate overpressure.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a baking process for cylindrical lithium battery cells, comprising the following steps: S1. Pre-drying: Place the cylindrical lithium battery cell in an oven, control the temperature inside the oven to be 50-55℃ and the pressure to be -0.05--0.08 MPa, and control the airflow speed to be 5-15 m / s. Use hot air to spirally brush the surface and both ends of the cylindrical battery cell at an airflow angle of 20°-45° for 20-40 minutes. S2. Variable Pressure Pulsating Dehumidification: Raise the temperature inside the oven to 60-70℃ and perform periodic variable pressure pulsating operation: within 4-8 seconds, reduce the pressure inside the oven to a negative pressure peak of -0.095 to -0.099 MPa and maintain it for 3-6 seconds; then, within 6-15 seconds, introduce dry nitrogen to raise the pressure inside the oven back to a positive pressure peak of +0.010 to +0.020 MPa and maintain it for 2-5 seconds; repeat the above periodic variable pressure pulsating operation until the dew point temperature of the atmosphere inside the oven is below -55℃; S3. Acoustic Resonance Assistance: Raise the temperature inside the oven to 75–80℃ and the pressure to -0.060–-0.085 MPa. Turn on the acoustic wave generator and perform a frequency scan within the 200–2000 Hz frequency band. Lock onto and match the radial natural frequency of the cylindrical lithium battery cell, and control the acoustic power density to 0.05–0.20 W / cm². 2 The action time is 10–30 min; S4. Gradient cooling and shaping: Maintain the pressure inside the oven at +0.02 to +0.05 MPa, and uniformly spray dry nitrogen gas at a temperature of 15 to 25°C onto the side of the cylindrical lithium battery cell. Control the cooling rate inside the oven at 2 to 5°C / min. When the temperature drops to 50°C, control the cooling rate at 1 to 2°C / min until the temperature reaches room temperature.

[0007] Optionally, before S1, a loading step is also included: placing the cylindrical lithium battery cells vertically on a porous ventilated tray, and controlling the spacing between adjacent cylindrical lithium battery cells to be no less than 10 mm.

[0008] Optionally, the porous ventilation tray is placed on a rotating support inside the oven, and the rotating support is configured to rotate continuously or intermittently at a speed of 1 to 10 rpm.

[0009] Optionally, in step S1, the dew point temperature of the drying hot air is ≤-40℃; in S2, the dew point temperature of the injected drying nitrogen is ≤-70℃; and in S4, the dew point temperature of the injected drying nitrogen is ≤-70℃.

[0010] Optionally, in S3, the sound wave generating device includes several high-frequency loudspeakers or ultrasonic transducers evenly distributed around the inner wall of the oven, and the sound-emitting surface of the sound wave generating device faces the central area of ​​the oven to form a superimposed sound field.

[0011] Optionally, after S4, a post-processing step is also included: directly transferring the baked cylindrical lithium battery cell to a dry environment with a dew point ≤ -45°C, or performing a liquid injection process in the dry environment.

[0012] Optionally, the cylindrical lithium battery cell is a 18650, 21700, or 46800 model lithium battery cell that has completed the winding, casing, and sealing welding processes, or other cylindrical lithium battery cells with a diameter in the range of 18 to 50 mm.

[0013] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention employs a four-stage synergistic process of pre-drying, variable-voltage pulsed dehumidification, acoustic resonance assistance, and gradient cold-state shaping, combined with hot air spiral scouring, periodic variable-voltage pulses, and acoustic resonance to enhance mass transfer. This process can deeply remove residual moisture from the inside of cylindrical lithium battery cells, stably controlling the cell's moisture content at an extremely low level. The process exhibits high stability and is suitable for the large-scale production of cylindrical cells of various specifications, such as 18650, 21700, and 46800. 2. This invention employs acoustic resonance that matches the inherent radial frequency of the battery cell, significantly enhancing the removal of deep moisture from the electrodes, separators, and cores without damaging the internal microstructure of the battery cell. This solves the technical problem that traditional baking can only remove surface moisture, while internal moisture is difficult to remove completely, resulting in a significant improvement in both water removal efficiency and depth. 3. This invention achieves slow cooling of the battery cell through a gradient cold-state shaping process under controllable pressure and low-temperature dry nitrogen protection. This avoids electrode warping, core deformation, and secondary moisture absorption caused by sudden temperature changes, stabilizes the battery cell size and internal structure, and improves the consistency and reliability of the battery cell. Attached Figure Description

[0014] Figure 1 The results show the water content of cylindrical lithium-ion battery cells after different baking processes. Detailed Implementation

[0015] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0016] Example 1 This embodiment provides a baking process for cylindrical lithium battery cells, including the following steps: S1. Pre-drying: The cylindrical lithium battery cells (18650 lithium iron phosphate cells) are placed in an oven. The oven temperature is controlled at 52℃ and the pressure at -0.06 MPa. Hot air with an airflow velocity of 10 m / s and a dew point temperature of -45℃ is used to spirally spray the surface and both ends of the cylindrical cells at an airflow angle of 30° for 30 minutes. The cylindrical lithium battery cells are placed vertically on a porous ventilated tray, and the spacing between adjacent cylindrical lithium battery cells is controlled at 15 mm. The porous ventilated tray is placed on a rotating support in the oven, and the rotating support is set to rotate continuously at a speed of 5 rpm. S2, Pressure Variable Pulsating Dehumidification: Raise the temperature inside the oven to 65℃ and perform a periodic pressure variable pulsating operation: within 6.0 s, reduce the pressure inside the oven to a negative pressure peak of -0.097 MPa and maintain it for 4.0 s; then, within 10.0 s, introduce dry nitrogen gas with a dew point temperature of -76℃ to raise the pressure inside the oven back to a positive pressure peak of +0.015 MPa and maintain it for 3.0 s; repeat the above periodic pressure variable pulsating operation until the dew point temperature of the atmosphere inside the oven is below -55℃; S3. Acoustic Resonance Assistance: Raise the temperature inside the oven to 78℃ and the pressure to -0.070 MPa, turn on the acoustic wave generator, and perform a frequency scan in the 200–2000 Hz frequency band. Lock onto and match the radial natural frequency of the cylindrical lithium battery cell, and control the acoustic power density to 0.12 W / cm². 2 The action time is 20 minutes; S4. Gradient cold setting: Maintain the pressure inside the oven at +0.03 MPa, uniformly spray dry nitrogen gas with a temperature of 20℃ and a dew point temperature of -76℃ onto the side of the cylindrical lithium battery cell, control the cooling rate inside the oven at 3℃ / min, and when the temperature drops to 50℃, control the cooling rate at 1.5℃ / min until the temperature reaches room temperature.

[0017] Example 2 This embodiment provides a baking process for cylindrical lithium battery cells, including the following steps: S1. Pre-drying: The cylindrical lithium battery cells (46800 lithium batteries) are placed in an oven. The oven temperature is controlled at 55℃ and the pressure at -0.08 MPa. Hot air with an airflow velocity of 15 m / s and a dew point temperature of -40℃ is used to spirally scour the surface and both ends of the cylindrical battery cells at an airflow angle of 45° for 40 minutes. The cylindrical lithium battery cells are placed vertically on a porous ventilated tray, and the spacing between adjacent cylindrical lithium battery cells is controlled at 20 mm. The porous ventilated tray is placed on a rotating support in the oven, and the rotating support is set to rotate continuously at a speed of 10 rpm. S2, Pressure Variable Pulsating Dehumidification: Raise the temperature inside the oven to 70℃ and perform a periodic pressure variable pulsating operation: within 4 seconds, reduce the pressure inside the oven to a negative pressure peak of -0.099 MPa and maintain it for 3 seconds; then, within 6 seconds, introduce dry nitrogen gas with a dew point temperature of -70℃ to raise the pressure inside the oven back to a positive pressure peak of +0.020 MPa and maintain it for 2 seconds; repeat the above periodic pressure variable pulsating operation until the dew point temperature of the atmosphere inside the oven is below -55℃; S3. Acoustic Resonance Assistance: Raise the temperature inside the oven to 80℃ and the pressure to -0.085 MPa, turn on the acoustic wave generator, and perform a frequency scan within the 200–2000 Hz frequency band. Lock onto and match the radial natural frequency of the cylindrical lithium battery cell, and control the acoustic power density to 0.20 W / cm². 2 The action time is 30 min; S4. Gradient cold setting: Maintain the pressure inside the oven at +0.05 MPa, uniformly spray dry nitrogen gas with a temperature of 15℃ and a dew point temperature of -70℃ onto the side of the cylindrical lithium battery cell, control the cooling rate inside the oven at 5℃ / min, and when the temperature drops to 50℃, control the cooling rate at 2℃ / min until the temperature reaches room temperature.

[0018] Example 3 This embodiment provides a baking process for cylindrical lithium battery cells, including the following steps: S1. Pre-drying: The cylindrical lithium battery cells (21700 lithium battery cells) are placed in an oven. The oven temperature is controlled at 50℃ and the pressure at -0.05 MPa. Hot air with an airflow velocity of 5 m / s and a dew point temperature of -50℃ is spirally sprayed onto the surface and both ends of the cylindrical battery cells at an airflow angle of 20° for 20 minutes. The cylindrical lithium battery cells are placed vertically on a porous ventilation tray, and the spacing between adjacent cylindrical lithium battery cells is controlled at 10 mm. The porous ventilation tray is placed on a rotating support in the oven. The rotating support is set to an intermittent mode of rotating for 30 s and stopping for 10 s, with an average rotation speed of 6 rpm. S2, Pressure Variable Pulsating Dehumidification: Raise the temperature inside the oven to 60℃ and perform a periodic pressure variable pulsating operation: within 8 seconds, reduce the pressure inside the oven to a negative pressure peak of -0.095 MPa and maintain it for 6 seconds; then, within 15 seconds, introduce dry nitrogen gas with a dew point temperature of -78℃ to raise the pressure inside the oven back to a positive pressure peak of +0.010 MPa and maintain it for 5 seconds; repeat the above periodic pressure variable pulsating operation until the dew point temperature of the atmosphere inside the oven is below -55℃; S3. Acoustic Resonance Assistance: Raise the temperature inside the oven to 75℃ and the pressure to -0.060 MPa, turn on the acoustic wave generator, and perform a frequency scan in the 200–2000 Hz frequency band. Lock onto and match the radial natural frequency of the cylindrical lithium battery cell, and control the acoustic power density to 0.05 W / cm². 2 The action time is 10 minutes; S4. Gradient cold setting: Maintain the pressure inside the oven at +0.02 MPa, uniformly spray dry nitrogen gas with a temperature of 15℃ and a dew point temperature of -78℃ onto the side of the cylindrical lithium battery cell, control the cooling rate inside the oven at 2℃ / min, and when the temperature drops to 50℃, control the cooling rate at 1℃ / min until the temperature reaches room temperature.

[0019] Example 4 This embodiment provides a baking process for cylindrical lithium battery cells, including the following steps: S1. Pre-drying: The cylindrical lithium battery cells (32700 lithium iron phosphate cells) are placed in an oven. The oven temperature is controlled at 54℃ and the pressure at -0.075 MPa. Hot air with an airflow velocity of 12 m / s and a dew point temperature of -42℃ is used to spirally scour the surface and both ends of the cylindrical cells at a 35° airflow angle for 35 minutes. The cylindrical lithium battery cells are placed vertically on a porous ventilated tray, and the spacing between adjacent cylindrical lithium battery cells is controlled at 25 mm. The porous ventilated tray is placed on a rotating support in the oven, and the rotating support is set to rotate continuously at a speed of 1 rpm. S2, Pressure Variable Pulsating Dehumidification: Raise the temperature inside the oven to 68℃ and perform a periodic pressure variable pulsating operation: within 5 seconds, reduce the pressure inside the oven to a negative pressure peak of -0.098 MPa and maintain it for 5 seconds; then, within 8 seconds, introduce dry nitrogen gas with a dew point temperature of -74℃ to raise the pressure inside the oven back to a positive pressure peak of +0.018 MPa and maintain it for 4 seconds; repeat the above periodic pressure variable pulsating operation until the dew point temperature of the atmosphere inside the oven is below -55℃; S3. Acoustic Resonance Assistance: Raise the temperature inside the oven to 76℃ and the pressure to -0.070 MPa, turn on the acoustic wave generator, and perform a frequency scan within the 200–2000 Hz frequency band. Lock onto and match the radial natural frequency of the cylindrical lithium battery cell, and control the acoustic power density to 0.18 W / cm². 2 The action time is 25 min; S4. Gradient cold setting: Maintain the pressure inside the oven at +0.04 MPa, uniformly spray dry nitrogen gas with a temperature of 18℃ and a dew point temperature of -74℃ onto the side of the cylindrical lithium battery cell, control the cooling rate inside the oven at 2.5℃ / min, and when the temperature drops to 50℃, control the cooling rate at 1.2℃ / min until the temperature reaches room temperature.

[0020] In Examples 1 to 4, in S3, the sound wave generating device includes several high-frequency loudspeakers or ultrasonic transducers evenly distributed around the inner wall of the oven, and the sound-emitting surface of the sound wave generating device faces the central area of ​​the oven to form a superimposed sound field; after S4, a post-processing step is also included: the baked cylindrical lithium battery cells are directly transferred to a dry environment with a dew point ≤ -45°C, or a liquid injection process is performed in a dry environment.

[0021] Comparative Example 1 Compared with Example 1, the process of this comparative example skips S2, and the rest of the process is the same as that of Example 1.

[0022] Comparative Example 2 Compared with Example 1, the process of this comparative example skips S3, and the rest of the process is the same as that of Example 1.

[0023] Comparative Example 3 Compared with Example 1, during the periodic voltage pulsation operation of S2, the sound wave generator is simultaneously turned on to execute S3. When the dew point temperature of the atmosphere in the oven is detected to be below -55°C, the voltage pulsation operation and the sound wave action are stopped at the same time, and then S4 is executed. The rest of the process is the same as in Example 1.

[0024] Comparative Example 4 Compared with Example 1, this comparative example does not perform frequency scanning and frequency matching in step S3, but uses a fixed 28kHz sound wave for irradiation, and the rest of the process is the same as in Example 1.

[0025] Experimental Example 1: Moisture Content Test Experimental Procedure: Cylindrical lithium-ion battery cells baked using the processes described in Examples 1-4 and Comparative Examples 1-4 were used as test samples. Fifty cells were randomly selected from each cell group corresponding to each example and comparative example. The cells were disassembled and the cores removed in a dry environment with a dew point temperature ≤ -45℃. Electrode samples of equal mass were cut from the center, middle, and edge regions of each cell core and mixed. The total moisture content of the samples was immediately measured using a Karl Fischer moisture analyzer, with results expressed in ppm. The average moisture content results for each group are shown in Table 1 and [Table data missing]. Figure 1 As shown.

[0026] Table 1

[0027] Please refer to Table 1 and Figure 1Cylindrical lithium-ion battery cells processed using the processes in Examples 1-4 showed stable water content control between 82.8 and 85.2 ppm, far below the required upper limit of 100 ppm before electrolyte injection, and the standard deviation of each group did not exceed 1.5 ppm, indicating that the process has excellent repeatability and controllability. In contrast, Comparative Example 1, lacking a core step, had a water content as high as 115.6 ppm, completely failing to meet the requirements; Comparative Examples 2 and 4 reached 103.8 ppm and 102.5 ppm respectively, both exceeding the limit; Comparative Example 3 measured 97.5 ppm, which is numerically acceptable, but its value is extremely close to the critical point, and the standard deviation is 2.9 ppm, which could easily lead to batch defects due to environmental fluctuations or equipment accuracy deviations in actual mass production.

[0028] Therefore, this invention not only ensures that the battery cells pass the baking test, but also provides a sufficient process safety window.

[0029] Experimental Example 2: Electrochemical Performance Test Test Procedure: Cylindrical lithium-ion battery cells baked using the processes described in Examples 1-4 were selected. Fifty cells were randomly chosen from the cell sets corresponding to each example as test samples. All samples were subjected to subsequent liquid injection, settling, formation, and capacity testing in a dry environment with a dew point ≤ -45℃, strictly following the standard industrial production process corresponding to each cell specification. The following tests were then conducted (all tests were performed at an ambient temperature of 25℃): First charge-discharge efficiency (ICE) test: Charged at 0.2 C constant current and constant voltage to a cutoff voltage of 4.2 V, allowed to stand for 10 min, and then discharged at 0.2 C constant current to a cutoff voltage of 2.5 V. The first charge capacity and the first discharge capacity were recorded, and the first coulombic efficiency was calculated. Storage self-discharge rate (K-value) test: Charge the cell at a 1C rate to the 50% SOC voltage (3.65 V). Measure the initial voltage after a 2-hour rest period before storage. Store at 25℃ for 7 days, and measure the termination voltage after a 2-hour rest period following storage. Calculate the K-value: K-value (mV / d) = (initial voltage) / (mV / d) Termination voltage) / 7 days; 3C rate retention test: Based on the 0.2C discharge capacity, discharge at 0.2C, 0.5C, 1C, 2C and 3C respectively to the 2.5V cutoff voltage. Let stand for 30 minutes between each rate test. Before each test, charge at 1C constant current and constant voltage to 4.2V. 1000-cycle retention: Cyclic tests were performed using a 1 C constant current constant voltage charging to 4.2 V and a 1 C constant current discharging to 2.5 V rate. A 0.2 C capacity test was performed every 50 weeks, and the retention rate of the discharge capacity at week 1000 relative to the average capacity of weeks 3 to 5 was recorded.

[0030] The average values ​​of all test data are summarized in Table 2.

[0031] Table 2

[0032] Please refer to Table 2, which shows that: 1. The ICE of the cells in each embodiment is as high as 91.5% or more, indicating that under standard electrolyte injection, formation and capacity testing, the present invention can effectively remove residual moisture inside the cell, reduce the consumption of active lithium caused by moisture decomposition during the formation process, and form a high-quality SEI film.

[0033] 2. The K value of the cells in each embodiment was controlled below 0.45 mV / d, which proves that the internal moisture of the cells is well controlled and the interfacial side reactions are weak, which can effectively avoid voltage drop during long-term storage.

[0034] 3. The cells in each embodiment still maintained more than 93.5% of their capacity under 3C high-rate discharge, showing good ion transport channels and low polarization characteristics. After 1000 cycles, the capacity retention rate was close to or exceeded 89%, indicating that the baking process significantly delayed the capacity decay throughout the battery's life cycle.

[0035] Therefore, the cell baking process provided by this invention, combined with standard downstream processes, can effectively remove moisture from the inside of the cell, significantly improve the first charge and discharge efficiency of cylindrical lithium batteries, suppress self-discharge, and maintain excellent rate performance and long cycle life. It is suitable for the mass production of cylindrical cells of various specifications such as 18650, 21700, and 46800. At the same time, it has been proven that this invention does not damage the internal microstructure of the cell while deeply removing water.

[0036] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A baking process for cylindrical lithium battery cells, characterized in that, Includes the following steps: S1. Pre-drying: Place the cylindrical lithium battery cell in an oven, control the temperature inside the oven to be 50-55℃ and the pressure to be -0.05--0.08 MPa, and control the airflow speed to be 5-15 m / s. Use hot air to spirally brush the surface and both ends of the cylindrical battery cell at an airflow angle of 20°-45° for 20-40 minutes. S2. Variable Pressure Pulsating Dehumidification: Raise the temperature inside the oven to 60-70℃ and perform periodic variable pressure pulsating operation: within 4-8 seconds, reduce the pressure inside the oven to a negative pressure peak of -0.095 to -0.099 MPa and maintain it for 3-6 seconds; then, within 6-15 seconds, introduce dry nitrogen to raise the pressure inside the oven back to a positive pressure peak of +0.010 to +0.020 MPa and maintain it for 2-5 seconds; repeat the above periodic variable pressure pulsating operation until the dew point temperature of the atmosphere inside the oven is below -55℃; S3. Acoustic Resonance Assistance: Raise the temperature inside the oven to 75–80℃ and the pressure to -0.060–-0.085 MPa. Turn on the acoustic wave generator and perform a frequency scan within the 200–2000 Hz frequency band. Lock onto and match the radial natural frequency of the cylindrical lithium battery cell, and control the acoustic power density to 0.05–0.20 W / cm². 2 The action time is 10–30 min; S4. Gradient cooling and shaping: Maintain the pressure inside the oven at +0.02 to +0.05 MPa, and uniformly spray dry nitrogen gas at a temperature of 15 to 25°C onto the side of the cylindrical lithium battery cell. Control the cooling rate inside the oven at 2 to 5°C / min. When the temperature drops to 50°C, control the cooling rate at 1 to 2°C / min until the temperature reaches room temperature.

2. The cylindrical lithium battery cell baking process according to claim 1, characterized in that, Before S1, there is also a loading step: placing the cylindrical lithium battery cells vertically on a porous ventilated tray, and controlling the spacing between adjacent cylindrical lithium battery cells to be no less than 10 mm.

3. The cylindrical lithium battery cell baking process according to claim 2, characterized in that, The porous, breathable tray is placed on a rotating support inside the oven, and the rotating support is configured to rotate continuously or intermittently at a speed of 1 to 10 rpm.

4. The baking process for cylindrical lithium battery cells according to claim 1, characterized in that, In step S1, the dew point temperature of the drying hot air is ≤-40℃; in S2, the dew point temperature of the injected drying nitrogen is ≤-70℃; in S4, the dew point temperature of the injected drying nitrogen is ≤-70℃.

5. The baking process for cylindrical lithium battery cells according to claim 1, characterized in that, In S3, the sound wave generating device includes several high-frequency loudspeakers or ultrasonic transducers evenly distributed around the inner wall of the oven, and the sound-emitting surface of the sound wave generating device faces the central area of ​​the oven to form a superimposed sound field.

6. The cylindrical lithium battery cell baking process according to claim 1, characterized in that, Following S4, a post-processing step is also included: directly transferring the baked cylindrical lithium battery cell to a dry environment with a dew point ≤ -45°C, or performing a liquid injection process in the dry environment.

7. The cylindrical lithium battery cell baking process according to claim 1, characterized in that, The cylindrical lithium battery cell is a 18650, 21700, or 46800 model lithium battery cell that has completed the winding, casing, and sealing welding processes, or other cylindrical lithium battery cells with a diameter in the range of 18 to 50 mm.

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