Preparation method of cylindrical battery and cylindrical battery

Abstract

In order to solve the problem that short-circuited cylindrical batteries cannot be effectively screened in the prior art, the invention provides a preparation method of a cylindrical battery and the cylindrical battery. The preparation method of the cylindrical battery comprises the following steps: forming a roll core by a positive plate, a diaphragm and a negative plate; the first internal resistance test equipment tests the internal resistance of the roll core, and the single roll core test time is less than or equal to the winding beat of the winding equipment; if the test internal resistance of the roll core is smaller than the first internal resistance, the roll core is short-circuited, and if the roll core internal resistance is larger than or equal to the first internal resistance, the roll core is qualified; putting the qualified roll core into a shell, and carrying out groove rolling on the shell to obtain a semi-finished battery; the second internal resistance test equipment tests the internal resistance of the semi-finished batteries, and the test time of a single semi-finished battery is less than or equal to the channeling beat of the channeling equipment; if the internal resistance of the semi-finished battery is smaller than the second internal resistance, the battery is short-circuited, and if the internal resistance of the semi-finished battery is larger than or equal to the second internal resistance, the battery is qualified. According to the preparation method provided by the invention, detection can be more accurately completed within limited time, and the detection efficiency and accuracy are improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of batteries, and in particular relates to a method for preparing a cylindrical battery and a cylindrical battery. Background Art

[0002] In the prior art, short-circuit detection of cylindrical batteries can be carried out in the winding process and the grooving process; in the winding process, a specific fixed voltage is applied to the positive and negative electrodes of the core, and then the core is charged and discharged, and the core leakage current is calculated by testing the internal resistance of the core; in the grooving process, one end is connected to the positive electrode ear and the other end is connected to the steel shell, and a fixed voltage is applied to charge and discharge first, and the core leakage current is calculated by testing the internal resistance of the core.

[0003] On the one hand, in the actual assembly process, affected by the production rhythm, the actual short-circuit test time of the battery is relatively short, and it is easy to miss or wrongly detect short circuits during the winding and grooving processes. On the other hand, after the battery is filled with liquid, the dust particles with short-circuit risks inside the battery become active due to the presence of liquid, which will cause short-circuit safety hazards during the use of the battery, and it is difficult to completely screen out micro-short-circuit batteries by monitoring the voltage during the formation process. Summary of the invention

[0004] Aiming at the problem that short-circuited cylindrical batteries cannot be effectively screened in the prior art, a method for preparing a cylindrical battery and a cylindrical battery are provided.

[0005] The technical solution adopted by the present invention to solve the above technical problems is as follows: A method for preparing a cylindrical battery, comprising the following operations: The positive electrode sheet, the separator and the negative electrode sheet are wound into a winding core by using a winding device; A first internal resistance testing device is used to connect the positive and negative tabs of the core to test the internal resistance of the core, and the test time of a single core is ≤ the winding cycle of the winding device; if the tested internal resistance of the core is < the first internal resistance, it is determined to be a short circuit; if the internal resistance of the core is ≥ the first internal resistance, it is determined to be a qualified core; The qualified winding core is placed into a shell, the negative electrode ear of the winding core is connected to the shell, and the shell is grooved by a groove rolling device to obtain a semi-finished battery; A second internal resistance testing device is used to connect the shell and the positive electrode ear of the winding core to test the internal resistance of the semi-finished battery, and the test time of a single semi-finished battery is ≤ the groove rolling cycle of the groove rolling device; if the internal resistance of the semi-finished battery is < the second internal resistance, it is judged to be a short circuit; if the internal resistance of the semi-finished battery is ≥ the second resistance, it is judged to be a qualified semi-finished battery.

[0006] Optionally, the first internal resistance testing device and the second internal resistance testing device are insulation internal resistance testers; The first internal resistance is the same as the second internal resistance.

[0007] Optionally, the first internal resistance and the second internal resistance are 200 MΩ.

[0008] Optionally, the test voltage for testing the internal resistance of the winding core is 250-500V; and / or, The test voltage for testing the internal resistance of the semi-finished battery is 250-500V.

[0009] Optionally, the thickness of the diaphragm is 9-15 μm, and the steps of testing the internal resistance of the core and testing the internal resistance of the semi-finished battery both use a test voltage of 250 V; and / or, The thickness of the diaphragm is ≥16 μm, and the steps of testing the internal resistance of the core and testing the internal resistance of the semi-finished battery both use a test voltage of 500V.

[0010] Optionally, the test time of a single winding core is 0.7-1.2 s.

[0011] Optionally, the test time of a single semi-finished battery is 0.1-0.3s.

[0012] Optionally, the test time T=T1+T2+T3+T4; Among them, T1 is the time the external trigger signal needs to be maintained; T2 is the preparation time required from the external trigger signal to the start of the test; T3 is the time required from the start of the test to the end of the test; T4 is the time when the test result signal is sent.

[0013] Optionally, the method for preparing the cylindrical battery further includes the following operations: The electrolyte is injected into the shell of the qualified semi-finished battery, and the cap is welded, sealed, cleaned and formed to obtain a finished battery.

[0014] On the other hand, the present invention provides a cylindrical battery, which is prepared by the preparation method.

[0015] The beneficial effects of the present invention are: The preparation method of cylindrical batteries provided by the present invention performs an internal resistance test in the specific preparation of cylindrical batteries, and screens out qualified cores through screening conditions that the test time of a single core is ≤ the winding rhythm of the winding device and the core internal resistance is ≥ the first internal resistance; at the same time, in the shell groove rolling stage, the semi-finished battery obtained is again set with the screening condition that the test time of a single semi-finished battery is ≤ the groove rolling rhythm of the groove rolling device to screen out qualified batteries. The present application reasonably inserts detection links in the preparation process of cylindrical batteries and limits the test time, so that the short circuit of the core can be detected without adding too much production time; compared with the complex detection process of the prior art that specifically performs charging first and then discharging in the winding process and the groove rolling process, this method directly tests the internal resistance, and the detection method is simpler and more efficient, reducing the omission or wrong killing caused by the tight production rhythm; at the same time, due to the simplified detection process, the detection can be completed more accurately within a limited time, avoiding misjudgment caused by time rush, and improving the detection efficiency and accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a voltage detection diagram of a battery storage process provided by an embodiment of the present invention and a comparative example; Figure 2 It is the relevant test time in the preparation method of the cylindrical battery of the present invention. DETAILED DESCRIPTION

[0017] In order to make the technical problems, technical solutions and beneficial effects solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0018] The present invention provides a method for preparing a battery, comprising the following operations: The positive electrode sheet, the separator and the negative electrode sheet are wound into a winding core by using a winding device; A first internal resistance testing device is used to connect the positive and negative tabs of the core to test the internal resistance of the core, and the test time of a single core is ≤ the winding cycle of the winding device; if the tested internal resistance of the core is < the first internal resistance, it is determined to be a short circuit; if the internal resistance of the core is ≥ the first internal resistance, it is determined to be a qualified core; The qualified winding core is placed into a shell, the negative electrode ear of the winding core is connected to the shell, and the shell is grooved by a groove rolling device to obtain a semi-finished battery; A second internal resistance testing device is used to connect the shell and the positive electrode ear of the winding core to test the internal resistance of the semi-finished battery, and the test time of a single semi-finished battery is ≤ the groove rolling cycle of the groove rolling device; if the internal resistance of the semi-finished battery is < the second internal resistance, it is judged to be a short circuit; if the internal resistance of the semi-finished battery is ≥ the second resistance, it is judged to be a qualified semi-finished battery.

[0019] The preparation method of cylindrical batteries provided by the present invention performs an internal resistance test in the specific preparation of cylindrical batteries, and screens out qualified cores through screening conditions that the test time of a single core is ≤ the winding rhythm of the winding device and the core internal resistance is ≥ the first internal resistance; at the same time, in the shell groove rolling stage, the semi-finished battery obtained is again set with the screening condition that the test time of a single semi-finished battery is ≤ the groove rolling rhythm of the groove rolling device to screen out qualified batteries. The present application reasonably inserts detection links in the preparation process of cylindrical batteries and limits the test time, so that the short circuit of the core can be detected without adding too much production time; compared with the complex detection process of the prior art that specifically performs charging first and then discharging in the winding process and the groove rolling process, this method directly tests the internal resistance, and the detection method is simpler and more efficient, reducing the omission or wrong killing caused by the tight production rhythm; at the same time, due to the simplified detection process, the detection can be completed more accurately within a limited time, avoiding misjudgment caused by time rush, and improving the detection efficiency and accuracy.

[0020] On the one hand, the winding process on the battery production line is carried out continuously, and the winding time of a single core determines the production rhythm of this link. In this application, the test time of a single core is set to ≤ the winding rhythm of the winding equipment to screen qualified cores. Once unqualified cores are detected, they can be immediately removed from the production line to avoid short-circuit cores from entering subsequent processes, saving subsequent processing time and costs.

[0021] On the other hand, shell grooving is also an important link in the production line, with a set operation time. The test time of a single semi-finished battery is ≤ the grooving rhythm of the grooving equipment, so that after the grooving process is completed, the internal resistance test of the semi-finished battery can be quickly carried out, and at the same time, abnormal internal connection or short circuit problems of the battery caused by the grooving operation can be discovered; if the internal structure of the battery is damaged during the grooving process, affecting the internal resistance, the test can make a timely judgment, and the semi-finished batteries that meet the test internal resistance requirements can enter the next process, while unqualified products are intercepted, avoiding the further processing of semi-finished batteries with hidden dangers into finished products, thereby ensuring the stability of product quality.

[0022] The winding cycle refers to the time interval for the winding equipment to complete the winding action of a single battery cell in the specific production process of cylindrical batteries, and is measured in seconds / time or minutes / time; the groove rolling cycle refers to the time interval for the groove rolling equipment to perform groove rolling operations on the shell of the cylindrical battery in the production of cylindrical batteries, and is also measured in seconds / time or minutes / time.

[0023] In some embodiments, the first internal resistance test device and the second internal resistance test device are insulation internal resistance testers; The first internal resistance is the same as the second internal resistance.

[0024] In some embodiments, the first internal resistance and the second internal resistance are 200 MΩ.

[0025] It should be noted that in the cylindrical battery preparation method of the present application, in order to strictly control the product quality, the performance of the defective detection rate under different resistance values ​​was comprehensively considered, and the resistance value was finally set at 200 MΩ. The inventor found in the preliminary verification that the defective detection rate of 200 MΩ was relatively higher. 200 MΩ was selected as the screening basis in this application. The reason is that a lower resistance setting means that the detection standard is more stringent, and on the basis of the same defective detection effect, batteries that may have leakage current problems can be detected to the greatest extent, thereby ensuring that the products flowing into the market and subsequent application links can meet higher quality requirements.

[0026] In some embodiments, the test voltage for testing the internal resistance of the winding core is 250-500V; and / or, The test voltage for testing the internal resistance of the semi-finished battery is 250-500V.

[0027] When the applied voltage is high, even if there is a high internal resistance inside the winding core, sufficient current can be generated to be captured by the internal resistance test equipment. If the test is performed at a lower voltage, the potential short-circuit parts with high internal resistance may not be accurately detected because the current generated is too small.

[0028] The range of the test voltage is based on a large number of previous experimental verifications, and can improve the accuracy of short-circuit detection while ensuring the safety of the internal resistance test equipment and preventing the core from additional damage.

[0029] In some embodiments, the thickness of the separator is 9-15 μm, and the steps of testing the internal resistance of the core and testing the internal resistance of the semi-finished battery both use a test voltage of 250 V; and / or, The thickness of the diaphragm is ≥16 μm, and the steps of testing the internal resistance of the core and testing the internal resistance of the semi-finished battery both use a test voltage of 500V.

[0030] Specifically, the separator separates the positive and negative electrodes of the battery in the winding core to prevent the positive and negative electrodes from directly contacting and short-circuiting, while allowing ions to pass through during the charging and discharging process to ensure the electrochemical working process of the battery.

[0031] When the battery voltage is too high, the electric field strength inside the battery will increase accordingly; for a thinner diaphragm, its ability to withstand high electric field strength is relatively weak, and a larger electric field strength may break through the diaphragm, destroying the isolation barrier between the positive and negative electrodes, and easily causing a battery short circuit.

[0032] In combination with the specific technical problems solved by the present application, the inventors have discovered through preliminary research that when the thickness of the diaphragm is in the range of 9-15μm, the use of a voltage of 250V can keep the electric field strength in a relatively safe and effective range, which can ensure the detection effect while avoiding the breakdown of the diaphragm due to excessive electric field strength. The diaphragm thickness is ≥16μm, and thicker diaphragms can withstand higher electric field strengths. Compared with thinner diaphragms, thick diaphragms can be tested at a higher voltage, that is, when the diaphragm thickness is ≥16μm, a test voltage of 500V is used in both the steps of testing the internal resistance of the core and testing the internal resistance of the semi-finished battery; in addition, by adjusting the test voltage through the diaphragm thickness, it can ensure that diaphragms of different thicknesses are detected within appropriate detection parameters, avoiding misjudgment due to unreasonable detection conditions, and thereby improving the quality of battery products.

[0033] In some embodiments, during the winding operation of the core, the test time of a single core is 0.7-1.2 s.

[0034] Specifically, in the winding operation of the core, the test time of a single core may be 0.7 s, 0.8 s, 0.9 s, 1.0 s, 1.1 s or 1.2 s.

[0035] In some embodiments, during the shell rolling operation, the testing time of a single semi-finished battery is 0.1-0.3 s.

[0036] In some embodiments, during the shell rolling operation, the test time of a single semi-finished battery may be 0.1 s, 0.2 s or 0.3 s.

[0037] In some embodiments, the test time T=T1+T2+T3+T4; Among them, T1 is the maintenance time required by the external trigger signal; T2 is the preparation time required from the external trigger signal to the start of the test; T3 is the time required from the start of the test to the end of the test; T4 is the time when the test result signal is sent.

[0038] Specifically, T1 is the maintenance time required for the external trigger signal. The existence of T1 ensures the stability and effectiveness of the trigger signal in the cylindrical battery preparation method. After receiving the trigger signal, the test equipment needs to perform a series of preparations, such as initializing the measurement circuit, calibrating parameters, etc. T2 provides the necessary time for these preparations, ensuring that the test equipment is in the best working state before starting to measure the internal resistance, thereby improving the accuracy of the measurement. T3 is the core time part directly used to measure the internal resistance of the semi-finished battery. During the T3 time period, the test equipment applies the test voltage to the battery, measures the current and calculates the internal resistance. After the test is completed, the test results need to be sent out in the form of a signal so that the subsequent production system can judge and process it. T4 ensures that the test results can be transmitted in a timely and accurate manner to avoid affecting the production process due to delays in the transmission of results. The test time is refined into T1, T2, T3 and T4, which helps to fully understand and optimize the test process, ensure that each link is closely coordinated within the total test time, realize an efficient and accurate test process, and ensure the production quality and production efficiency of cylindrical batteries (see Figure 2 ).

[0039] In some embodiments, the following operations are also included: The electrolyte is injected into the shell of the qualified semi-finished battery, and the cap is welded, sealed, cleaned and formed to obtain a finished battery.

[0040] The method for preparing the battery comprises the following specific operations: The current collector is cut and dried to obtain a pole piece; The pole piece is wound to obtain a winding core; The wound core is placed on the production line for transmission, and the positive and negative ears of the core are connected using an insulation internal resistance tester (test parameters: diaphragm thickness 9-15μm, voltage 250V, diaphragm thickness ≥16μm, voltage 250V), and the test time is 1s; Determine the resistance value. If the resistance value is less than 200MΩ, it is NG and the product is removed from the production line. If the resistance value is greater than 200MΩ, it is qualified and the product is ready for subsequent preparation processes. Put the qualified core into the shell, connect the negative electrode ear of the core with the shell, and roll the shell with a groove rolling device to obtain a semi-finished battery; Test the resistance again (test parameters: diaphragm thickness 9-15μm, voltage 250V, diaphragm thickness ≥16μm, voltage 250V), test time 0.3s; Determine the resistance value, if the resistance value is less than 200MΩ, it is NG and withdrawn from the production line; if the resistance value is greater than 200MΩ, it is qualified; Inject electrolyte into the shell of qualified semi-finished batteries and weld the caps; After sealing and cleaning, the finished cylindrical battery is obtained.

[0041] The test time refers to the time when the test equipment reaches the set test voltage. The longer the test time, the more stable the leakage current. In actual operation, the test time is set according to the production rhythm of the full-automatic winding machine equipment and the running time of the groove rolling machine cam.

[0042] Another embodiment of the present invention provides a cylindrical battery, which is manufactured using the above-mentioned manufacturing method.

[0043] The cylindrical battery of the present invention may be a lithium ion cylindrical battery.

[0044] The cylindrical battery of the present invention can be applied to energy storage devices, automobiles, mobile phones, etc. The present invention does not impose any special restrictions on the application field of the provided cylindrical battery.

[0045] The present invention is further described below by way of examples.

[0046] It should be noted that the inventors previously conducted DOE tests using an insulation internal resistance tester, setting the voltage at 25V, 50V, 100V, 125V, 250V, 500V and 1000V for testing. However, it was found that if the voltage was too low, the defect detection capability was insufficient, and if the voltage was too high, additional damage would be caused to the diaphragm. Therefore, in the preliminary experiments, the voltage levels were set to 125V, 250V, and 500V, and the resistance values ​​were set to 50MΩ, 200MΩ, and 1000MΩ, respectively. The defect rate (ppm) of the battery was tested through DOE testing, and the following test results were obtained: Table 1

[0047] During the verification, it was found that the defective detection rate of 200MΩ was relatively higher. 200MΩ was selected as the screening basis because a lower resistance setting means stricter detection standards, and batteries with possible leakage current problems will be inspected to the greatest extent, thereby ensuring that products entering the market and subsequent application links meet higher quality requirements.

[0048] Example 1 This embodiment is used to illustrate a method for preparing a battery disclosed in the present invention, which includes the following steps: Winding the positive electrode sheet, the separator and the negative electrode sheet to form a winding core; The wound core is placed on the production line for transmission, and the insulation internal resistance tester is used to connect the positive and negative tabs of the core to test the internal resistance of the core (test parameters: diaphragm thickness 9μm, voltage 250V), and the test is 0.7s; If the internal resistance of the winding core is less than 200MΩ, it is NG and the product is removed from the production line. If the internal resistance of the winding core is greater than or equal to 200MΩ, it is qualified and the subsequent preparation process is carried out. The qualified winding core is put into the shell, the negative electrode ear is welded to the bottom of the shell, and the shell is grooved to obtain a semi-finished battery; An insulation internal resistance tester was used to connect the shell of the semi-finished battery and the positive electrode ear of the winding core to test the internal resistance of the semi-finished battery (test parameters: diaphragm thickness of 9 μm, voltage of 200 V), and the test lasted for 0.1 s. Determine the internal resistance of semi-finished batteries. If the internal resistance of semi-finished batteries is less than 200MΩ, they are NG and withdrawn from the production line. If the internal resistance of semi-finished batteries is ≥200MΩ, they are qualified. Inject electrolyte into the shell of qualified semi-finished batteries and weld the caps; After sealing and cleaning, the battery is formed into a finished product.

[0049] Example 2 This example is used to illustrate a method for preparing a battery disclosed in the present invention, and includes most of the operations in Example 1, except that: In the test parameters, the thickness of the diaphragm is 13μm.

[0050] Example 3 This example is used to illustrate a method for preparing a battery disclosed in the present invention, and includes most of the operations in Example 1, except that: In the test parameters, the thickness of the diaphragm is 15 μm.

[0051] Example 4 This example is used to illustrate a method for preparing a battery disclosed in the present invention, and includes most of the operations in Example 1, except that: The test voltage was 500 V and the diaphragm thickness was 16 μm.

[0052] Example 5 This example is used to illustrate a method for preparing a battery disclosed in the present invention, and includes most of the operations in Example 1, except that: The test voltage was 500 V and the diaphragm thickness was 18 μm.

[0053] Example 6

[0054] This example is used to illustrate a method for preparing a battery disclosed in the present invention, and includes most of the operations in Example 1, except that: The test time of a single winding core is 0.9 s, and the test time of a single semi-finished battery is 0.2 s.

[0055] Example 7 This example is used to illustrate a method for preparing a battery disclosed in the present invention, and includes most of the operations in Example 1, except that: The test time of a single winding core is 1.1 s, and the test time of a single semi-finished battery is 0.3 s.

[0056] Comparative Example 1 This comparative example is used to compare and illustrate a method for preparing a battery disclosed in the present invention, and includes most of the operations in Example 1, except that: The test time of a single winding core> the winding cycle of the winding device (1.5s), The test time of a single semi-finished battery is greater than the groove rolling cycle of the groove rolling device (0.5s).

[0057] Comparative Example 2 This comparative example is used to compare and illustrate a method for preparing a battery disclosed in the present invention, and includes most of the operations in Example 1, except that: The test time of a single winding core> the winding cycle of the winding device; (1.3s), The test time of a single semi-finished battery is greater than the groove rolling cycle of the groove rolling device (0.4s).

[0058] Comparative Example 3 This comparative example is used to compare and illustrate a method for preparing a battery disclosed in the present invention, and includes most of the operations in Example 1, except that: Use conventional short-circuit detection methods to screen short-circuited batteries.

[0059] The qualified batteries selected from Implementation 1 and Comparative Example 3 were placed in a room temperature environment for 30 days and then tested for consistency. Figure 1 .

[0060] like Figure 1 As described, the average voltage drop of the batteries selected in Example 1 after being placed for 30 days is significantly lower than that of the batteries selected in Comparative Example 3, and thus the batteries in Example 1 have relatively good consistency, and thus can more effectively utilize the battery capacity, extend the battery life, and improve its reliability and stability.

[0061] Fill in Table 2 with the defective rate test results of the batteries prepared in Examples 1-7 and Comparative Examples 1-3.

[0062] Table 2

[0063] It can be seen from the test results in Table 2 that Examples 1-6 can detect unqualified batteries well; among them, in Examples 1-3, a voltage of 250V is used to detect batteries with a diaphragm thickness of 9μm, 13μm and 15μm, respectively, and the defective rate of Example 3 is slightly lower than that of Example 1 and Example 2. The reason is that when preparing cylindrical batteries in Example 3, a relatively thick diaphragm is used, and the detection force may be reduced by using a voltage of 250V for detection; In Examples 4-5, a voltage of 500 V was used to detect batteries with a diaphragm thickness of 16 μm and 18 μm, respectively. Compared with Example 4, the defective rate detected in Example 5 was relatively low. Similarly, since a thicker diaphragm was used in Example 5, there may be a situation where the detection force is reduced; Compared with Example 1, in Example 6-7, the detection time of the core or semi-finished battery in Example 6-7 is relatively too long, and correspondingly, the detection or detection intensity of the defective rate is improved compared with Example 1; In Comparative Example 1, a detection time outside the limit of the present application is used and the detection time is relatively long, which easily leads to missed detection during detection, and thus the detection failure rate is low. Compared with Comparative Example 2, the detection time of Comparative Example 1 is longer than that of Comparative Example 2. Therefore, the missed detection in Comparative Example 1 is also relatively serious, that is, the failure rate of Comparative Example 1 in Table 2 is lower than that of Comparative Example 2. Comparative Example 3 uses a conventional short-circuit detection method to screen short-circuited batteries, and the defective rate detected is nearly half that of Example 1, indicating that the problem of missed detection in the conventional screening method is serious.

[0064] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a cylindrical battery, characterized in that: The following operations are included: The positive electrode sheet, the separator and the negative electrode sheet are wound into a winding core by using a winding device; A first internal resistance testing device is used to connect the positive and negative tabs of the core to test the internal resistance of the core, and the test time of a single core is ≤ the winding cycle of the winding device; if the tested internal resistance of the core is < the first internal resistance, it is determined to be a short circuit; if the internal resistance of the core is ≥ the first internal resistance, it is determined to be a qualified core; The qualified winding core is placed into a shell, the negative electrode ear of the winding core is connected to the shell, and the shell is grooved by a groove rolling device to obtain a semi-finished battery; A second internal resistance testing device is used to connect the shell of the semi-finished battery and the positive electrode ear of the winding core to test the internal resistance of the semi-finished battery, and the test time of a single semi-finished battery is ≤ the groove rolling rhythm of the groove rolling device; if the internal resistance of the semi-finished battery is < the second internal resistance, it is judged as a short circuit; if the internal resistance of the semi-finished battery is ≥ the second resistance, it is judged as a qualified semi-finished battery.

2. The method for preparing a cylindrical battery according to claim 1, characterized in that: The first internal resistance test device and the second internal resistance test device are insulation internal resistance testers; The first internal resistance is the same as the second internal resistance.

3. The method for preparing a cylindrical battery according to claim 1, characterized in that: The first internal resistance and the second internal resistance are 200 MΩ.

4. The method for preparing a cylindrical battery according to claim 1, characterized in that: The voltage for testing the internal resistance of the winding core is 250-500V; and / or, The test voltage for testing the internal resistance of the semi-finished battery is 250-500V.

5. The method for preparing a cylindrical battery according to claim 4, characterized in that: The thickness of the diaphragm is 9-15 μm, and the steps of testing the internal resistance of the core and testing the internal resistance of the semi-finished battery both use a test voltage of 250V; and / or, The thickness of the diaphragm is ≥16 μm, and the steps of testing the internal resistance of the core and testing the internal resistance of the semi-finished battery both use a test voltage of 500V.

6. The method for preparing a cylindrical battery according to claim 1, characterized in that: The test time of a single winding core is 0.7-1.2 s.

7. The method for preparing a cylindrical battery according to claim 1, characterized in that: The test time of a single semi-finished battery is 0.1-0.3s.

8. The method for preparing a cylindrical battery according to claim 4, characterized in that: The test time T=T1+T2+T3+T4; Among them, T1 is the time the external trigger signal needs to be maintained; T2 is the preparation time required from the external trigger signal to the start of the test; T3 is the time required from the start of the test to the end of the test; T4 is the time when the test result signal is sent.

9. The method for preparing a cylindrical battery according to claim 1, characterized in that: The following operations are also included: The electrolyte is injected into the shell of the qualified semi-finished battery, and the cap is welded, sealed, cleaned and formed to obtain a finished battery.

10. A cylindrical battery, characterized in that: The cylindrical battery is prepared by the preparation method described in any one of claims 1 to 9.

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