Battery cell baking process and effectiveness determination method

Abstract

The present invention discloses a battery cell baking process and a method for determining baking effectiveness. The process comprises, in order, equipment vacuum leakage rate testing, baking pretreatment, staged preheating and heating, staged constant-temperature vacuum baking, staged nitrogen conversion baking, maintaining constant-temperature vacuum baking, and calculating the equipment vacuum leakage rate r1 during baking to determine whether to terminate baking. The process effectively shortens the initial preheating phase of battery cell baking, increases the proportion of high-vacuum baking time, and improves overall baking efficiency. It also automatically analyzes battery cell baking effectiveness online in real time. By monitoring the vacuum leakage rate, it analyzes the evaporation rate of moisture and alcohol additives and the baking effect, improving the consistency of moisture and alcohol additive control, eliminating the impact of sampling and testing moisture and alcohol additive content on baking equipment utilization, eliminating the problem of repeated baking and rework, and improving production line efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of battery cell baking and effectiveness determination, and in particular to a battery cell baking process and effectiveness determination method. Background Art

[0002] Lithium-ion batteries are electrochemical systems. Moisture and alcohol additives within the cells participate in a series of side reactions, impacting the quality, reliability, and safety of the cells. Therefore, baking is a crucial step in lithium-ion cell manufacturing to remove these internal moisture and alcohol additives. Monitoring the moisture and alcohol additive content after baking is also a crucial process for controlling semi-finished products.

[0003] The current conventional battery cell baking process adopts a vacuum baking method, including contact baking and thermal radiation baking. It is first preheated in a high-purity inert gas N2 environment for a certain period of time. After reaching the set temperature, it is then baked in a constant temperature vacuum for a certain period of time. After the baking process is completed, the battery cells are extracted and sent for testing of moisture and alcohol additive content. After the moisture and alcohol additive tests are qualified, the baked battery cells are cooled and circulated to complete the battery cell baking process. There are two main methods for determining the effectiveness of the battery cell baking process in the existing technical solutions. One is the commonly used post-baking sampling test of moisture and alcohol additive content, and the determination is made based on the moisture and alcohol additive content results, such as the drying method for lithium-ion batteries disclosed in patent CN2023101638574; the other is to make a determination with the help of the voltage-time curve of the first charging process of the battery cell (patent CN2015109793713, disclosed method for determining the effectiveness of the lithium-ion battery cell baking process).

[0004] The main shortcomings of existing technologies for determining the effectiveness of battery cell baking processes are as follows: during the initial preheating stage of battery cell baking, the battery cell temperature rises slowly and takes a long time; during the initial preheating stage of battery cell baking, the vacuum degree is low, and the boiling points of moisture and alcohol additives are high, which is not conducive to the vaporization of moisture and alcohol additives; after the battery cell baking process is completed, the process of taking moisture samples to test moisture and alcohol additives takes 30 to 60 minutes, and the battery cells occupy the baking equipment, resulting in low baking equipment utilization; battery cell baking is based on the test results of moisture and alcohol additives, and there is a certain proportion of re-baking and rework, which reduces equipment production capacity and production line efficiency; using the voltage-time curve of the battery cell's first charging process to determine the effectiveness of battery cell baking has serious hysteresis and can only evaluate the influence of moisture to a certain extent, but cannot evaluate the influence of alcohol additives; in addition, it usually takes at least two days from the end of baking to the first charge, and even if there is a problem with the baking effectiveness, it has become a fact and cannot be remedied. Therefore, this method can only be used in experimental research processes. Summary of the Invention

[0005] The present invention aims to overcome the shortcomings and defects of the prior art by providing a cell baking process and a method for determining baking effectiveness, which have high efficiency and good consistency. The process can effectively shorten the initial preheating phase of cell baking, increase the proportion of high-vacuum baking time, and improve overall baking efficiency. It can also automatically analyze cell baking effectiveness online in real time. By monitoring vacuum leakage rates, analyzing the evaporation rates of water and alcohol additives and baking effects, it can improve the consistency of water and alcohol additive control, eliminate the impact of sampling and testing water and alcohol additive content on baking equipment utilization, eliminate the problem of repeated baking and rework, and improve production line efficiency.

[0006] A battery cell baking process and effectiveness determination method, including

[0007] Step 1: Vacuum leakage rate r1 test: The battery cell baking equipment is in a sealed state, and the vacuum is evacuated to the set value P1. The vacuum is maintained for time t1, and the vacuum degree in the cavity is reduced from P1 to P1. t , the vacuum leakage rate r1 of the baking equipment is calculated: r1=(P1 t -P1)*V1 / t1;

[0008] The vacuum leakage rate r1 of the cell baking equipment in this step is tested regularly, and an alarm threshold C0 is set to detect the equipment's sealing, ensure sufficient vacuum holding capacity, and avoid insufficient baking capacity due to poor sealing of the baking equipment. When the vacuum leakage rate r1 exceeds the alarm threshold C0, the equipment automatically alarms and notifies the equipment personnel to perform sealing maintenance.

[0009] Step 2: Pre-baking treatment: Place the battery cell to be baked in the baking equipment, evacuate to the set value P2, and fill with high-purity inert gas N2 until the vacuum degree reaches the set value P3; before the baking starts and the temperature rises, the air in the equipment is evacuated and filled with inert gas N2 to avoid the problem of electrode oxidation during the temperature rise of the battery cell. At the same time, the inert gas N2 plays a role in protecting the heating metal plate and heat conduction during the baking process; the heating metal guides the electrical probe plate, which is used to connect the circuit to start heating. Nitrogen plays a role in heat conduction in the environment, and the temperature rise rate of the battery cell body is faster than that in a vacuum environment.

[0010] Step 3: Start preheating in stages, with the first stage temperature setting value T1 and duration t1; the second stage temperature setting value T2 and duration t2;

[0011] In the first preheating stage, since the battery cell is heated from room temperature, it is not limited to heating by heat radiation and contact heating. The temperature of the battery cell body is much lower than the normal baking temperature. The temperature setting T1 is 10-20°C higher than T2. ​​By increasing the temperature difference between the oven and the battery cell body, the heating speed of the battery cell from room temperature is increased and the heating time is shortened. This step three is used to quickly complete the preheating of the battery cell, shorten the preheating time, and stabilize the temperature in a constant temperature vacuum baking state.

[0012] Step 4: Start the staged constant temperature vacuum baking, the first stage temperature setting value is T3, the vacuum setting value is P L1 ~P U1 , duration t3; second stage temperature setting value T4, vacuum setting value P L2 ~P U2 , duration t4;

[0013] In each stage of baking, when the vacuum degree reaches P U1 / P U2 Continue to evacuate until P L1 / P L2 , vacuum degree in vacuum holding stage is from P L1 / P L2 Reduce to P U1 / P U2 The corresponding time t U1 / t U2 , and then calculate the vacuum leakage rate r of the current state t calculate;

[0014] In the first stage, due to the high moisture concentration in the oven environment, the moisture and alcohol additives inside the battery cell are quickly vaporized by heat, and the vacuum setting value P L1 ~P U1 Higher than P L2 ~P U2 , avoid the vacuuming time being too long, the temperature T3 being higher than or equal to T4, and promoting the shortening of the battery core temperature rise time; at the same time, in this stage, the water and alcohol additives inside the battery core are quickly vaporized in the high temperature and high vacuum environment and discharged through the vacuum pipeline, and no N2 filling operation is required; step four is the rapid evaporation stage of water and alcohol additives;

[0015] Step 5: Start the staged N2 replacement baking, temperature setting value T4, vacuum setting value P L3 ~P U3 In the first stage, the following steps are repeated: fill the inert gas N2 to break the vacuum to the vacuum degree P4, the duration is t5, and continue to evacuate to the set value P L3 ~P U3, duration t6, repetition number n1; in the second stage, repeat the following steps: fill the inert gas N2 to break the vacuum to the vacuum degree P4, duration t5, continue to vacuum to the set value P L3 ~P U3 , duration t7, number of repetitions n2;

[0016] As the concentration of water and alcohol additives inside the battery cell decreases, the intermolecular forces between the water molecules and alcohol additive molecules and the active substances inside the electrode gaps significantly reduce the evaporation rate of water and alcohol additives. N2 needs to be filled in for displacement baking. N2 enters the electrode gaps, weakens the intermolecular forces between the water molecules and alcohol additive molecules and the active substances, and discharges trace amounts of water and alcohol additives through high vacuum. In the second stage of N2 displacement baking, the frequency of N2 replacement is significantly higher than that in the first stage, so that trace amounts of water and alcohol additive molecules are discharged to the greatest extent at the end of baking.

[0017] Step 6: After completing the N2 replacement baking in step 5, continue to maintain constant temperature vacuum baking for a duration of t8;

[0018] Step 7: Calculate the vacuum leakage rate r1 of the equipment during the baking process and determine whether to end the baking: The system automatically calculates the vacuum leakage rate r1 of the battery cell baking process from step 4 to step 6 above. t , and automatically generate the vacuum leakage rate r t -Time t curve based on vacuum leak rate r t -Time t curve to analyze and determine the vacuum leakage rate r for more than 3 consecutive times before the end of step 6 constant temperature vacuum baking t result:

[0019] When 3 consecutive r t If all of them are lower than the threshold C1, the baking is determined to be effective, the baking process ends normally, and the battery cell is taken out of the baking equipment and cooled automatically; otherwise, it will continue to automatically execute step 5, the second stage N2 replacement baking and step 6, constant temperature vacuum baking, for 3 consecutive r t When all the conditions are lower than the threshold C1, the baking is determined to be effective, the process ends, and the battery cell is removed from the baking equipment for cooling and automatic circulation; if it still does not meet the requirements, the effectiveness is determined by sampling and testing the moisture and alcohol additive content, and the vacuum leak rate r1 test in step 1 is repeated.

[0020] According to the vacuum leakage rate r t -Time t curve, when the baking process time is over, the vacuum leakage rate r t会 If the evaporation rate of the water in the battery cell is reduced to a certain level and meets a certain threshold range, it can be determined that the evaporation rate of the water in the current battery cell has reached an extremely low level and the baking process is ended; if the baking process time is over, the vacuum leakage rate of the last three times r tIf it is still relatively high and exceeds a certain threshold range, it is considered that the moisture content of the battery cell has not reached the baking effect.

[0021] Preferably, in step 1, P1 is 20-80 Pa, t1 is 10-60 min, V1 is the volume of the inner cavity of the device in an unloaded state, and the time accuracy of the device data collection is 1-5 s.

[0022] Preferably, in step 2, P2 is 20-100 Pa, and P3 is 50,000-90,000 Pa.

[0023] Preferably, in step three, T1 is 100-120° C., T2 is 90-105° C., t1 is 30-60 min, and t2 is 5-10 min.

[0024] Preferably, in step 4, T3 is 90-105°C, T4 is 90-100°C, t3 is 30-300min, t4 is 30-300min, P L1 50~80Pa, P U1 70~100Pa, P L2 30~50Pa, P U2 It is 60~80Pa.

[0025] Preferably, in step 4, the vacuum leakage rate r of the current state t Including the vacuum leakage rate r of the current state of the first stage t1， The vacuum leakage rate r of the current state in the second stage t2 , r t2 =(P U2 -P L2 )*V2 / t U2 , r t1 =(P U1 -P L1 )*V2 / t U1 , V2 is the volume of the inner cavity of the device in the loaded state.

[0026] Preferably, in step 5, the nitrogen filled is high purity ≥ 99.9%, P4 is 80000-90000Pa, t5 is 2-5min, t6 is 30-60min, t7 is 20-40min, P L 30~50Pa, P U The pressure is 60 to 80 Pa, and the number of replacements n is 2 to 10 times.

[0027] Preferably, in step six, t8 is 20 to 60 minutes.

[0028] Preferably, in the first cell baking process in step seven, the water and alcohol additive sampling test results are used as the basis for effectiveness judgment, and the vacuum leakage rate r t Only record and upload the vacuum leak rate r t Average value, starting from the second battery cell baking process, the device is automatically determined by the program based on the threshold value for effectiveness.

[0029] The threshold C1 is the vacuum leakage rate r of the last three consecutive times in each battery cell baking process. t The weighted average of the average value*coefficient K, K is 1.01~1.10, and the coefficient K needs to be dynamically updated according to the test results of moisture and alcohol additive content.

[0030] For each baking process, there will be three consecutive vacuum leakage rates rt, and an average value will be calculated; for each additional baking process thereafter, an average value will be added, and the average value of the last three vacuum leakage rates rt of each baking process will be used as the data source for continuing to calculate the average value, and will be updated in a rolling manner.

[0031] The method of the present invention increases the temperature rise rate of the battery cell, shortens the baking preheating time, increases the high vacuum baking time ratio, improves the overall baking efficiency, and shortens the baking time.

[0032] The method of the present invention improves the effect of removing moisture and alcohol additives inside the battery cell and improves the ability to control the content of moisture and alcohol additives after baking.

[0033] The method of the present invention can view and analyze the evaporation rate of water and alcohol additives inside the battery cell in real time through the vacuum leakage rate time curve, which is more convenient for comparing the effects of different baking process designs.

[0034] According to the method of the present invention, after the cell baking process is completed, online judgment is performed through vacuum leakage rate data, thereby avoiding the waiting time for sampling and testing the moisture and butanediol content, and greatly improving production efficiency and equipment utilization. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a flow chart of a battery cell baking process and effectiveness determination method of the present invention.

[0036] Figure 2 It is a vacuum leakage rate-time curve diagram obtained in the baking process of the present invention. DETAILED DESCRIPTION

[0037] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0038] See also Figure 1 As shown in the embodiment of the present application, the cell baking process and effectiveness determination method include the following steps:

[0039] Step 1: Vacuum leakage rate r1 test: When the battery cell baking equipment is sealed, vacuum is drawn to the set value P1, and the vacuum is maintained for time t1. The vacuum degree in the cavity is reduced from P1 to P1. t , calculate the vacuum leakage rate r1 of the battery baking equipment, r1=(P1 t -P1)*V1 / t1, V1 is the volume of the inner cavity of the equipment in the no-load state. When the vacuum leakage rate r1 exceeds the threshold C0, the equipment alarms;

[0040] Step 2: Pre-baking treatment: Place the battery cell to be baked in the battery cell baking equipment, evacuate to the set value P2, and fill with high-purity inert gas N2 until the vacuum reaches the set value P3, where P3 is greater than P2; before the baking temperature rises, evacuate the air in the battery cell baking equipment and fill it with inert gas N2;

[0041] Step 3: Start staged preheating: the first stage temperature setting value is T1, the duration is t1; the second stage temperature setting value is T2, the duration is t2; t1 is greater than t2, T1 is higher than T2;

[0042] Step 4: Start the staged constant temperature vacuum baking: the first stage temperature setting value is T3, the first vacuum setting value is P L1 ~P U1 , duration t3; second stage temperature setting value T4, second vacuum setting value P L2 ~P U2 , duration t4; in the staged baking, when the vacuum degree reaches P U1 / P U2 Continue to evacuate until P L1 / P L2 , vacuum degree in vacuum holding stage is from P L1 / P L2 Reduce to P U1 / P U2 The corresponding time t U1 / t U2 , the vacuum leakage rate r of the current state t Calculation: First vacuum setting value P L1 ~P U1 Higher than the second vacuum setting value P L2 ~P U2 , temperature T3 is higher than / equal to T4;

[0043] Step 5: Start the staged N2 replacement baking: temperature setting value T4, vacuum setting value P L3 ~P U3The first stage of N2 replacement baking repeats the following steps: filling the inert gas N2 to break the vacuum to the vacuum degree P4, duration t5, continue to vacuum to the set value P L3 ~P U3 , duration t6, repetition number n1; the second stage N2 replacement baking repeats the following steps: fill the inert gas N2 to break the vacuum to the vacuum degree P4, duration t5, continue to vacuum to the set value P L3 ~P U3 , duration t7, number of repetitions n2;

[0044] Step 6: Continue to maintain constant temperature vacuum baking for a duration of t8;

[0045] Step 7: Calculate the vacuum leakage rate r1 of the equipment during the baking process and determine whether to end the baking: Automatically calculate the vacuum leakage rate r1 of the battery cell during the above steps 4 to 6. t , and automatically generate the vacuum leakage rate r t r with time t t- t curve, through r t- t curve analysis and judgment step 6: vacuum leakage rate r for at least 3 times in a row before the end of constant temperature vacuum baking t result;

[0046] At least 3 consecutive vacuum leak rates r t If both meet the requirements below the threshold C1, it is determined to be valid and the baking process ends normally; otherwise, the second stage N2 replacement baking of step 5 and the constant temperature vacuum baking of step 6 are automatically executed once, and then the vacuum leakage rate r t If both conditions are lower than the threshold C1, it is determined to be effective and the process ends. If it is still not satisfied, the effectiveness is determined by sampling and testing the moisture and alcohol additive content, and the vacuum leakage rate r1 test in step 1 is repeated.

[0047] Example 1

[0048] A battery cell baking process and effectiveness determination method comprises the following steps:

[0049] Step 1: The battery cell baking equipment is in a sealed state, and the vacuum is evacuated to a set value of 50Pa, and the vacuum is maintained for 30 minutes. The vacuum degree in the cavity is reduced from P1 to P1 t , the vacuum leakage rate r1 of the baking equipment is calculated: r1=(P1 t -50)*V1 / 30;

[0050] Step 2: Place the battery cell to be baked in the baking equipment, evacuate to the set value of 50Pa, and fill with high-purity inert gas N2 until the vacuum reaches the set value of 80000Pa;

[0051] Step 3: Start preheating in stages. The first stage temperature setting value is 110℃ and the duration is 60 minutes. The second stage temperature setting value is 100℃ and the duration is 5 minutes.

[0052] Step 4: Start the staged constant temperature vacuum baking. The first stage temperature setting value is 100°C, the vacuum setting value is 50Pa~100Pa, and the duration is 60min; the second stage temperature setting value is 100°C, the vacuum setting value is 30Pa~80Pa, and the duration is 180min.

[0053] Step 5: Start phased N2 replacement baking, set the temperature to 100°C, and the vacuum setting to 30Pa-80Pa. In the first phase, repeat the following steps: fill with inert gas N2 to break the vacuum to 90,000Pa for 3 minutes, continue to vacuum to the set value of 30Pa-80Pa for 60 minutes, and repeat twice. In the second phase, repeat the following steps: fill with inert gas N2 to break the vacuum to 90,000Pa for 3 minutes, continue to vacuum to the set value of 30Pa-80Pa for 30 minutes, and repeat five times.

[0054] Step 6: After completing the N2 replacement baking in step 5, continue to maintain constant temperature vacuum baking for 30 minutes.

[0055] Step 7: The system automatically calculates the vacuum leakage rate r during the above steps 4 to 6 of the cell baking process t , according to the vacuum leakage data during vacuum baking, the vacuum leakage rate r is obtained t -Time t curve, and through the last three consecutive vacuum leakage rate data before the end of constant temperature vacuum baking in step 6, determine whether the baking process is effective and whether the baking test bench is ended. That is, the vacuum leakage rate data is used to characterize the evaporation rate of moisture and alcohol additives inside the battery cell, which is used to determine the moisture and alcohol additive content levels after the battery cell baking is completed, so as to determine the effectiveness of the process, and then conduct benchmark analysis in combination with the offline sampling test results.

[0056] Example 2

[0057] A battery cell baking process and effectiveness determination method comprises the following steps:

[0058] Step 1: The battery cell baking equipment is in a sealed state, and the vacuum is evacuated to a set value of 50Pa, and the vacuum is maintained for 30 minutes. The vacuum degree in the cavity is reduced from P1 to P1 t , the vacuum leakage rate r1 of the baking equipment is calculated: r1=(P1 t -50)*V1 / 30;

[0059] Step 2: Place the battery cell to be baked in the baking equipment, evacuate to the set value of 50Pa, and fill with high-purity inert gas N2 until the vacuum reaches the set value of 80000Pa;

[0060] Step 3: Start preheating in stages. The first stage temperature setting value is 110℃ and the duration is 60 minutes. The second stage temperature setting value is 108℃ and the duration is 5 minutes.

[0061] Step 4: Start the staged constant temperature vacuum baking. The first stage temperature setting value is 105℃, the vacuum setting value is 50Pa~100Pa, and the duration is 30min; the second stage temperature setting value is 100℃, the vacuum setting value is 30Pa~80Pa, and the duration is 210min.

[0062] Step 5: Start the phased N2 replacement bake, set the temperature to 100°C, and the vacuum setting to 30Pa-80Pa. In the first phase, repeat the following steps: fill the vacuum with inert gas N2 to break the vacuum to 90,000Pa for 3 minutes, continue to vacuum to the set value of 30Pa-80Pa for 60 minutes, and repeat twice. In the second phase, repeat the following steps: fill the vacuum with inert gas N2 to break the vacuum to 90,000Pa for 3 minutes, continue to vacuum to the set value of 30Pa-80Pa for 30 minutes, and repeat five times.

[0063] Step 6: After completing the N2 replacement baking in step 5, continue to maintain constant temperature vacuum baking for 30 minutes.

[0064] Step 7: The system automatically calculates the vacuum leakage rate r during the above steps 4 to 6 of the cell baking process t , according to the vacuum leakage data during vacuum baking, the vacuum leakage rate r is obtained t -Time t curve, and use the last three consecutive vacuum leakage rate data to determine whether the baking process is effective and whether the baking is completed. That is, the vacuum leakage rate data is used to characterize the evaporation rate of moisture and alcohol additives inside the battery cell, which is used to determine the moisture and alcohol additive content levels after the battery cell baking is completed, so as to determine the effectiveness of the process, and then combine it with the offline sampling test results for benchmark analysis.

[0065] The following is a comparison of the baking effects of the same product using the baking process of Example 1 and the traditional baking process:

[0066] Note: The traditional baking process is: preheating at 100℃ for 120min, baking at 30Pa vacuum for 700min, replacing N2 once every 1h for 5min.

[0067]

[0068] The method of the present invention collects vacuum leakage rate data of the oven in no-load and loaded states, timely identifies the sealing state of the oven, and improves the reliability of the vacuum leakage rate analysis of the oven in loaded state.

[0069] The method of the present invention adopts staged preheating. The temperature setting value in the initial stage is 10 to 20°C higher than the normal baking temperature, thereby increasing the temperature gradient, improving the temperature rise rate of the battery cell, shortening the preheating time of the battery cell, and gradually restoring the temperature to the normal baking temperature through the second stage preheating, thereby preventing the temperature of the battery cell body from exceeding the controllable range of the constant temperature baking temperature.

[0070] The method of the present invention uses a staged constant temperature baking process. In the initial baking phase, water and alcohol additives evaporate rapidly, and the vacuum setting is slightly higher to avoid baking timeouts caused by continuous vacuum failure. In the second phase, the vacuum setting is further reduced to lower the boiling points of water and alcohol additives, promoting vaporization and evaporation.

[0071] The method of the present invention adopts staged N2 replacement baking and designs an N2 replacement frequency gradient. In the baking process where the evaporation rate of moisture and alcohol additives decreases, the N2 replacement frequency is low in the initial stage, and in the process where the evaporation rate of moisture and alcohol additives further decreases, the N2 replacement frequency is increased to promote the replacement of N2 with moisture and alcohol additives, which helps to improve the removal effect of moisture and alcohol additives in the later stage of the baking process.

[0072] The method of the present invention adopts online collection and calculation of vacuum leakage rate, and establishes a characterization relationship between the vacuum leakage rate and the evaporation rate of moisture and alcohol additives inside the battery cell. It can be used to compare the baking effects of different baking processes, and can also determine the levels of moisture and alcohol additive content in the battery cell online, assist in determining the baking results, and compare them with offline measurement results, eliminating the waiting time for sampling and testing the moisture and alcohol additive content, and helping to improve the utilization rate of baking equipment.

[0073] The basic principles, main features and advantages of the present invention are shown and described above. It is obvious to those skilled in the art that the present invention is not limited to the details of the above exemplary embodiments and that the present invention can be implemented in other specific forms without departing from the spirit or basic features of the present invention.

[0074] The embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being defined by the appended claims rather than the foregoing description, and all changes that come within the meaning and range of equivalents of the claims are therefore intended to be embraced therein.

[0075] In addition, it should be understood that although this specification is described in terms of implementation methods, not every implementation method contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

Claims

1. The battery cell baking process and effectiveness determination method are characterized by: The following steps are involved: Step 1: Vacuum leakage rate r1 test: When the battery cell baking equipment is sealed, vacuum is drawn to the set value P1, and the vacuum is maintained for time t1. The vacuum degree in the cavity is reduced from P1 to P1. t , calculate the vacuum leakage rate r1 of the battery baking equipment, r1=(P1 t -P1)*V1 / t1, V1 is the volume of the inner cavity of the equipment in the no-load state. When the vacuum leakage rate r1 exceeds the threshold C0, the equipment alarms; Step 2: Pre-baking treatment: Place the battery cell to be baked in the battery cell baking equipment, evacuate to the set value P2, and fill with high-purity inert gas N2 until the vacuum reaches the set value P3, where P3 is greater than P2; before the baking temperature rises, evacuate the air in the battery cell baking equipment and fill it with inert gas N2; Step 3: Start staged preheating: the first stage temperature setting value is T1, the duration is t1; The second stage temperature setting value is T2, duration is t2; t1 is greater than t2, T1 is higher than T2; Step 4: Start the staged constant temperature vacuum baking: the first stage temperature setting value is T3, the first vacuum setting value is P L1 ~P U1 , duration t3; The second stage temperature setting value T4, the second vacuum setting value P L2 ~P U2 , duration t4; in the staged baking, when the vacuum degree reaches P U1 / P U2 Continue to vacuum until P L1 / P L2 , vacuum degree in vacuum holding stage is from P L1 / P L2 Reduce to P U1 / P U2 The corresponding time t U1 / t U2 , the vacuum leakage rate r of the current state t Calculation: First vacuum setting value P L1 ~P U1 Higher than the second vacuum setting value P L2 ~P U2 , temperature T3 is higher than / equal to T4; Step 5: Start the staged N2 replacement baking: temperature setting value T4, vacuum setting value P L3 ~P U3 The first stage of N2 replacement baking repeats the following steps: filling the inert gas N2 to break the vacuum to the vacuum degree P4, duration t5, continue to vacuum to the set value P L3 ~P U3 , duration t6, repetition number n1; the second stage N2 replacement baking repeats the following steps: fill the inert gas N2 to break the vacuum to the vacuum degree P4, duration t5, continue to vacuum to the set value P L3 ~P U3 , duration t7, number of repetitions n2; Step 6: Continue to maintain constant temperature vacuum baking for a duration of t8; Step 7: Calculate the vacuum leakage rate r1 of the equipment during the baking process and determine whether to end the baking: Automatically calculate the vacuum leakage rate r1 of the battery cell during the above steps 4 to 6. t , and automatically generate the vacuum leakage rate r t r with time t t- t curve, through r t- t curve analysis and judgment step 6: vacuum leakage rate r for at least 3 times in a row before the end of constant temperature vacuum baking t result; At least 3 consecutive vacuum leak rates r t If both meet the requirements below the threshold C1, it is determined to be valid and the baking process ends normally; otherwise, the second stage N2 replacement baking of step 5 and the constant temperature vacuum baking of step 6 are automatically executed once, and then the vacuum leakage rate r t If both conditions are lower than the threshold C1, it is determined to be effective and the process ends. If it is still not satisfied, the effectiveness is determined by sampling and testing the moisture and alcohol additive content, and the vacuum leakage rate r1 test in step 1 is repeated.

2. The battery cell baking process and effectiveness determination method according to claim 1, characterized in that: In the step 1, P1 is 20-80 Pa, t1 is 10-60 min, and the equipment collects data with a time accuracy of 1-5 s.

3. The battery cell baking process and effectiveness determination method according to claim 1, characterized in that: In the step 2, P2 is 20-100 Pa, and P3 is 50,000-90,000 Pa.

4. The battery cell baking process and effectiveness determination method according to claim 1, characterized in that: In the step 3, T1 is 100-120° C., T2 is 90-105° C., t1 is 30-60 min, and t2 is 5-10 min.

5. The battery cell baking process and effectiveness determination method according to claim 1, characterized in that: In the step 4, T3 is 90-105°C, T4 is 90-100°C, t3 is 30-300min, t4 is 30-300min, P L1 50~80Pa, P U1 70~100Pa, P L2 30~50Pa, P U2 It is 60~80Pa.

6. The battery cell baking process and effectiveness determination method according to claim 1, characterized in that: In step 4, the vacuum leakage rate r of the current state t Including the current vacuum leakage rate r of the first stage t1， The vacuum leakage rate r of the current state in the second stage t2 , r t2 =(P U2 -P L2 )*V2 / t U2 , r t1 =(P U1 -P L1 )*V2 / t U1 , V2 is the volume of the inner cavity of the device in the loaded state.

7. The battery cell baking process and effectiveness determination method according to claim 1, characterized in that: In the step 5, the nitrogen is filled with a purity of ≥99.9%, P4 is 80000-90000 Pa, t5 is 2-5 min, t6 is 30-60 min, t7 is 20-40 min, P L3 / P L4 30~50Pa, P U3 / P U4 It is 60~80Pa, and the number of replacements n1 / n2 is 2~10 times.

8. The battery cell baking process and effectiveness determination method according to claim 6, characterized in that: In the step 6, t8 is 20 to 60 minutes.

9. The battery cell baking process and effectiveness determination method according to claim 7, characterized in that: In the step 7, during the first cell baking process, the water and alcohol additive sampling test results are used as the basis for effectiveness judgment. Finally, the vacuum leakage rate r t Only record and upload the vacuum leak rate r t Average value, starting from the second battery cell baking process, the device program automatically determines the effectiveness according to the threshold.

10. The battery cell baking process and effectiveness determination method according to claim 1, characterized in that: In step 7, the threshold value C1 is the vacuum leakage rate r of at least three consecutive times in each battery cell baking process. t The average value is obtained by adding the weighted average value * coefficient K, where K is 1.01 to 1.

10. The coefficient K is dynamically updated according to the test results of moisture and alcohol additive content.

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