Preparation method of cylindrical battery and a cylindrical battery

Abstract

To overcome the problem in the prior art that short-circuited cylindrical batteries cannot be effectively screened, the present invention provides a preparation method of a cylindrical battery and a cylindrical battery; the preparation method of the cylindrical battery includes the following operations: a positive electrode sheet, a separator, and a negative electrode sheet form a core; a first internal resistance testing device tests the internal resistance of the core, and the testing time for a single core ≤ the winding beat of the winding device; if the tested internal resistance of the core < the first internal resistance, it is short-circuited, and if the internal resistance of the core ≥ the first internal resistance, it is a qualified core; the qualified core is put into a housing, and the housing is grooved to obtain a semi-finished battery; a second internal resistance testing device tests the internal resistance of the semi-finished battery, and the testing time for a single semi-finished battery ≤ the grooving beat of the grooving device; if the internal resistance of the semi-finished battery < the second internal resistance, it is short-circuited, and if the internal resistance of the semi-finished battery ≥ the second resistance, it is a qualified semi-finished battery. The preparation method provided by the present invention can complete the detection more accurately within a limited time, improving the detection efficiency and accuracy.

Description

Technical Field

[0001] The present invention belongs to the technical field of batteries, and particularly relates to a preparation method of a cylindrical battery and a cylindrical battery. Background Art

[0002] In the prior art, short-circuit detection of a cylindrical battery can be carried out in the winding process and the grooving process; in the winding process stage, a specific fixed voltage is applied to the positive and negative electrodes of the core, then charged first and then discharged, and the leakage current of the core is calculated by testing the internal resistance value of the core; in the grooving process, one end is connected to the positive tab, and the other end is connected to the steel shell, and a fixed voltage is applied for charging first and then discharging, and the leakage current of the core is calculated by testing the internal resistance value 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 short, and when short-circuit detection is carried out in the winding process and the grooving process, it is easy to miss or misjudge; on the other hand, after the battery is filled with liquid, due to the presence of the liquid, the dust particles with short-circuit risk inside the battery become active, and short-circuit safety hazards will occur during the use of the battery, and it is also difficult to completely screen out micro-short-circuit batteries by monitoring the voltage in 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 preparation method of a cylindrical battery and a cylindrical battery are provided.

[0005] The technical solutions adopted by the present invention to solve the above technical problems are as follows:

[0006] A preparation method of a cylindrical battery includes the following operations:

[0007] Using a winding device to wind a positive electrode sheet, a separator and a negative electrode sheet to form a core;

[0008] Using a first internal resistance test device to connect the positive and negative tabs of the core, testing the internal resistance of the core, and the testing time of a single core ≤ the winding rhythm of the winding device; if the tested internal resistance of the core < the first internal resistance, it is determined to be short-circuited, and if the internal resistance of the core ≥ the first internal resistance, it is determined to be a qualified core;

[0009] Placing the qualified core into a shell, connecting the negative tab of the core to the shell, and using a grooving device to groove the shell to obtain a semi-finished battery;

[0010] Using a second internal resistance test device to connect the shell and the positive tab of the core, testing the internal resistance of the semi-finished battery, and the testing time of a single semi-finished battery ≤ the grooving rhythm of the grooving device; if the internal resistance of the semi-finished battery < the second internal resistance, it is determined to be short-circuited, and if the internal resistance of the semi-finished battery ≥ the second resistance, it is determined to be a qualified semi-finished battery.

[0011] Optionally, the first internal resistance testing device and the second internal resistance testing device are insulation internal resistance testers;

[0012] The first internal resistance and the second internal resistance are the same.

[0013] Optionally, the first internal resistance and the second internal resistance are 200 MΩ.

[0014] Optionally, the test voltage for testing the internal resistance of the core is 250 - 500 V; and / or,

[0015] The test voltage for testing the internal resistance of the semi-finished battery is 250 - 500 V.

[0016] Optionally, the diaphragm thickness 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,

[0017] The diaphragm thickness ≥ 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 500 V.

[0018] Optionally, the test time for a single core is 0.7 - 1.2 s.

[0019] Optionally, the test time for a single semi-finished battery is 0.1 - 0.3 s.

[0020] Optionally, the test time T = T1 + T2 + T3 + T4;

[0021] wherein, T1 is the time that the external trigger signal needs to be maintained;

[0022] T2 is the preparation time required from the external trigger signal to the start of the test;

[0023] T3 is the time required from the start of the test to the end of the test;

[0024] T4 is the test result signal sending time.

[0025] Optionally, the method for preparing the cylindrical battery further includes the following operations:

[0026] Inject electrolyte into the housing of the qualified semi-finished battery, weld the cap, seal, clean, and form to obtain a finished battery.

[0027] On the other hand, the present invention provides a cylindrical battery prepared by the described preparation method.

[0028] The beneficial effects of the present invention are as follows:

[0029] The preparation method of the cylindrical battery provided by the present invention conducts internal resistance testing during the specific preparation of the cylindrical battery, and screens out qualified cores through the screening conditions that the testing time of a single core ≤ the winding rhythm of the winding equipment and the internal resistance of the core ≥ the first internal resistance; meanwhile, in the shell grooving stage, for the obtained semi-finished battery, the screening condition that the testing time of a single semi-finished battery ≤ the grooving rhythm of the grooving equipment is set again to screen out qualified batteries. This application reasonably inserts inspection links in the preparation process of the cylindrical battery and restricts the testing time, which can detect the short-circuit situation of the core without adding too much additional production time; compared with the prior art, which has a complex detection process of first charging and then discharging specifically in the winding process and the grooving process, this method directly tests the internal resistance, and the detection method is more concise and efficient, reducing the situation of missed killing or wrong killing caused by the tight production rhythm; at the same time, due to the simplified detection process, the detection can be more accurately completed within a limited time, avoiding misjudgment caused by hasty time, and improving the detection efficiency and accuracy. Description of the Drawings

[0030] Figure 1 It is a voltage detection diagram during the battery storage process provided by the embodiments and comparative examples of the present invention;

[0031] Figure 2 It is the relevant testing time in the preparation method of the cylindrical battery of the present invention. Detailed Embodiments

[0032] In order to make the technical problems, technical solutions and beneficial effects solved by the present invention clearer, the present invention will be further described in detail below with reference to the 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.

[0033] The present invention provides a preparation method for a battery, including the following operations:

[0034] Use a winding device to wind a positive electrode sheet, a separator and a negative electrode sheet to form a core;

[0035] Connect the positive and negative electrode tabs of the core with a first internal resistance testing device to test the internal resistance of the core, and the testing time of a single core ≤ the winding rhythm of the winding device; if the tested internal resistance of the core < the first internal resistance, it is determined as short-circuited, and if the internal resistance of the core ≥ the first internal resistance, it is determined as a qualified core;

[0036] Place the qualified core into a shell, connect the negative electrode tab of the core with the shell, and use a grooving device to groove the shell to obtain a semi-finished battery;

[0037] Connect the second internal resistance testing device to the housing and the positive tab of the winding core to test the internal resistance of the semi-finished battery, and the testing time of a single semi-finished battery ≤ the grooving rhythm of the grooving device; if the internal resistance of the semi-finished battery < the second internal resistance, it is determined as a short circuit, and if the internal resistance of the semi-finished battery ≥ the second resistance, it is determined as a qualified semi-finished battery.

[0038] The preparation method of the cylindrical battery provided by the present invention performs internal resistance testing during the specific preparation of the cylindrical battery, and through the screening conditions that the testing time of a single winding core ≤ the winding rhythm of the winding device and the internal resistance of the winding core ≥ the first internal resistance, qualified winding cores are screened out; at the same time, during the housing grooving stage, for the obtained semi-finished battery, the screening condition that the testing time of a single semi-finished battery ≤ the grooving rhythm of the grooving device is set again to screen out qualified batteries. This application reasonably inserts the detection link in the preparation process of the cylindrical battery and restricts the testing time, which can detect the short-circuit situation of the winding core without adding too much additional production time; compared with the prior art, which specifically performs a complex detection process of charging first and then discharging in the winding process and the grooving process, this method directly tests the internal resistance, and the detection method is more concise and efficient, reducing the situation of missed or wrong killing caused by the tight production rhythm; at the same time, because the simplified detection process can complete the detection more accurately within a limited time, it avoids misjudgment caused by hasty time, improving the detection efficiency and accuracy.

[0039] On the one hand, the winding process on the battery production line is continuous, and the winding time of a single winding core determines the production rhythm of this link. In this application, the screening condition that the testing time of a single winding core ≤ the winding rhythm of the winding device is set to screen out qualified winding cores. Once an unqualified winding core is detected, it can be immediately removed from the production line to avoid short-circuited winding cores entering the subsequent processes, saving the subsequent processing time and cost.

[0040] On the other hand, the housing grooving is also an important link on the production line with a fixed operation time. The testing time of a single semi-finished battery ≤ the grooving rhythm of the grooving device enables the internal resistance of the semi-finished battery to be quickly tested after the grooving process, and at the same time, it can also detect abnormal internal connections or short circuits in the battery that may be caused by the grooving operation; if the internal structure of the battery is damaged during the grooving process, affecting the internal resistance, this test can determine it in time. The semi-finished batteries that meet the internal resistance testing requirements can enter the next process, while unqualified products are intercepted, avoiding further processing of semi-finished batteries with potential hazards into finished products, ensuring the stability of product quality.

[0041] The winding cycle is the time interval for the winding equipment to complete the winding action of a single battery cell during the specific production process of cylindrical batteries, measured in seconds per time or minutes per time; the grooving cycle refers to the time interval for the grooving equipment to perform grooving operations on the casing of cylindrical batteries during the production of cylindrical batteries, with the same unit of seconds per time or minutes per time.

[0042] In some embodiments, the first internal resistance testing device and the second internal resistance testing device are insulation internal resistance testers;

[0043] The first internal resistance and the second internal resistance are the same.

[0044] In some embodiments, the first internal resistance and the second internal resistance are 200 MΩ.

[0045] It should be noted that in the method for preparing cylindrical batteries of the present application, in order to strictly control the product quality and comprehensively consider the performance of the defective detection rate at different resistance values, the resistance value is finally selected to be set at 200 MΩ. In the inventor's previous verification, it was found that the defective detection rate of 200 MΩ is relatively higher. In the present application, 200 MΩ is selected as the screening basis because a lower resistance value setting means a stricter detection standard, which can detect the batteries that may have leakage current problems to the greatest extent on the basis of the same defective detection effect, so as to ensure that the products flowing into the market and subsequent application links meet higher quality requirements.

[0046] In some embodiments, the test voltage for testing the internal resistance of the wound core is 250 - 500 V; and / or,

[0047] The test voltage for testing the internal resistance of the semi-finished battery is 250 - 500 V.

[0048] When the applied voltage is relatively high, even if there is a relatively high internal resistance inside the wound core, sufficient current can be generated and thus captured by the internal resistance testing device. If the test is carried out at a lower voltage, for potential short-circuit parts with a relatively high internal resistance, the generated current may be too small to be accurately detected.

[0049] The range value of this test voltage is obtained based on a large number of previous experimental verifications, which can improve the accuracy of short-circuit detection on the premise of ensuring the safety of the internal resistance testing device and that the wound core is not damaged additionally.

[0050] In some embodiments, the thickness of the separator is 9 - 15 μm, and the steps of testing the internal resistance of the wound core and testing the internal resistance of the semi-finished battery both use a test voltage of 250 V; and / or,

[0051] The thickness of the separator ≥ 16 μm, and the steps of testing the internal resistance of the wound core and testing the internal resistance of the semi-finished battery both use a test voltage of 500 V.

[0052] Specifically, the separator separates the positive and negative electrodes of the battery in the wound core, preventing the direct contact between the positive and negative electrodes and short circuit, while allowing ions to pass through during charge and discharge to ensure the electrochemical working process of the battery.

[0053] When the battery voltage is too high, the electric field strength inside the battery will increase accordingly; for a thinner separator, its ability to withstand high electric field strength is relatively weak, and a larger electric field strength may break down the separator, destroying the isolation barrier between the positive and negative electrodes and easily causing battery short circuit.

[0054] Combined with the specific technical problems solved by this application, the inventors found through previous research that when the separator thickness is in the range of 9 - 15 μm, using a 250V voltage can keep the electric field strength in a relatively safe and effective range, which can ensure the detection effect while avoiding breakdown of the separator due to too high electric field strength. When the separator thickness ≥ 16 μm, a thicker separator can withstand a higher electric field strength. Compared with a thinner separator, a thick separator can be tested at a higher voltage, that is, when the separator thickness ≥ 16 μm, a test voltage of 500V is used in both the steps of testing the internal resistance of the wound core and testing the internal resistance of the semi-finished battery; in addition, by adjusting the test voltage according to the separator thickness, it can ensure that separators of different thicknesses are detected under appropriate detection parameters, avoiding misjudgment caused by unreasonable detection conditions, and thus improving the quality of battery products.

[0055] In some embodiments, during the winding operation of the wound core, the test time for a single wound core is 0.7 - 1.2 s.

[0056] Specifically, during the winding operation of the wound core, the test time for a single wound core can be 0.7 s, 0.8 s, 0.9 s, 1.0 s, 1.1 s or 1.2 s.

[0057] In some embodiments, during the operation of the housing grooving, the test time for a single semi-finished battery is 0.1 - 0.3 s.

[0058] In some embodiments, during the operation of the housing grooving, the test time for a single semi-finished battery can be 0.1 s, 0.2 s or 0.3 s.

[0059] In some embodiments, the test time T = T1 + T2 + T3 + T4;

[0060] wherein, T1 is the holding time required for the external trigger signal;

[0061] T2 is the preparation time required from the external trigger signal to the start of the test;

[0062] T3 is the time required from the start of the test to the end of the test;

[0063] T4 is the signal sending time of the test result.

[0064] 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 preparatory work, such as initializing the measurement circuit, calibrating parameters, etc. T2 provides the necessary time for these preparatory works to ensure that the test equipment is in the best working state before starting to measure the internal resistance, thereby improving the measurement accuracy. 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 a 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 signals for subsequent production systems to make judgments and process. T4 ensures that the test results can be transmitted in a timely and accurate manner, avoiding affecting the production process due to the delay of result transmission. Refining the test time into T1, T2, T3, and T4 helps to comprehensively understand and optimize the test process, ensuring that all links cooperate closely within the total test time to achieve an efficient and accurate test process, and guaranteeing the production quality and production efficiency of cylindrical batteries (see Figure 2 ).

[0065] In some embodiments, the following operations are further included:

[0066] Inject electrolyte into the shell of the qualified semi-finished battery, weld the cap, seal, clean, and form to obtain a finished battery.

[0067] The preparation method of the battery includes the following specific operations:

[0068] Cut and dry the current collector to obtain a pole piece;

[0069] Wind the pole piece to obtain a wound core;

[0070] Place the wound core on the production line for transmission, connect the positive and negative pole tabs of the wound core with an insulation internal resistance tester (test parameters: diaphragm thickness is 9 - 15μm, voltage 250V, diaphragm thickness ≥ 16μm, voltage 250V), and the test time is 1s;

[0071] Judge the resistance value. If the resistance value < 200MΩ, it is NG and withdraw from the production line. If the resistance value > 200MΩ, it is qualified and proceed to the subsequent preparation process;

[0072] Take the qualified wound core into the shell, connect the negative pole tab of the wound core to the shell, and use a grooving device to groove the shell to obtain a semi-finished battery;

[0073] Test the resistance value again (test parameters: diaphragm thickness is 9 - 15μm, voltage 250V, diaphragm thickness ≥ 16μm, voltage 250V), and the test time is 0.3s;

[0074] Judge the resistance value. If the resistance value < 200 MΩ, it is NG and removed from the production line. If the resistance value > 200 MΩ, it is qualified;

[0075] Inject electrolyte into the shell of the qualified semi-finished battery and weld the cap;

[0076] After sealing and cleaning, it is formed to obtain the finished cylindrical battery.

[0077] The test time refers to the time calculated after 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 fully automatic winding machine equipment and the running time of the cam of the grooving machine.

[0078] Another embodiment of the present invention provides a cylindrical battery, and the cylindrical battery is obtained by using the above preparation method.

[0079] The cylindrical battery of the present invention can be a lithium-ion cylindrical battery.

[0080] The cylindrical battery of the present invention can be applied to energy storage devices, automobiles, mobile phones, etc. The present invention does not impose special restrictions on the application fields of the provided cylindrical battery.

[0081] The present invention will be further described below through embodiments.

[0082] It should be noted that the inventor previously conducted DOE experiments through an insulation resistance tester, and detected by setting the voltage at 25V, 50V, 100V, 125V, 250V, 500V, and 1000V. However, it was found that if the voltage was too low, the ability to detect defects was insufficient, and if the voltage was too high, it would cause additional damage to the diaphragm. Therefore, in the preliminary pre-experiment, the voltage levels were set at 125V, 250V, 500V, and the resistance values were respectively set at 50 MΩ, 200 MΩ, 1000 MΩ. Through DOE testing, the defect rate (ppm) of the battery was detected, and the following test results were obtained:

[0083] Table 1

[0084]

[0085] It was found during verification that the defect detection rate of 200 MΩ was relatively higher. 200 MΩ was selected as the screening basis. The reason is that a lower resistance value setting means a more stringent detection standard, and batteries that may have leakage current problems are inspected to the greatest extent, so as to ensure that the products flowing into the market and subsequent application links can meet higher quality requirements.

[0086] Example 1

[0087] This example is used to illustrate a preparation method of a battery disclosed by the present invention, including the following operating steps:

[0088] Wind the positive electrode sheet, separator, and negative electrode sheet to form a core;

[0089] Place the wound core on the production line for transmission, and use an insulation internal resistance tester to connect the positive and negative electrode tabs of the core to test the internal resistance of the core (test parameters: separator thickness is 9 μm, voltage is 250 V), and test for 0.7 s;

[0090] If the internal resistance of the core < 200 MΩ, NG, remove it from the production line; if the internal resistance of the core ≥ 200 MΩ, it is qualified and proceed to the subsequent preparation process;

[0091] Put the qualified core into the shell, weld the negative electrode tab to the bottom of the shell, and perform grooving operation on the shell to obtain a semi-finished battery;

[0092] Use an insulation internal resistance tester to connect the shell of the semi-finished battery and the positive electrode tab of the core to test the internal resistance of the semi-finished battery (test parameters: separator thickness is 9 μm, voltage is 200 V), and test for 0.1 s;

[0093] Judge the internal resistance of the semi-finished battery. If the internal resistance of the semi-finished battery < 200 MΩ, NG, remove it from the production line; if the internal resistance of the semi-finished battery ≥ 200 MΩ, it is qualified;

[0094] Inject electrolyte into the shell of the qualified semi-finished battery and weld the cap;

[0095] After sealing and cleaning, carry out formation to obtain a finished battery.

[0096] Example 2

[0097] This example is used to illustrate a method for preparing a battery disclosed in the present invention, including most of the operations in Example 1, and the difference is that:

[0098] In the test parameters, the separator thickness is 13 μm.

[0099] Example 3

[0100] This example is used to illustrate a method for preparing a battery disclosed in the present invention, including most of the operations in Example 1, and the difference is that:

[0101] In the test parameters, the separator thickness is 15 μm.

[0102] Example 4

[0103] This example is used to illustrate a method for preparing a battery disclosed in the present invention, including most of the operations in Example 1, and the difference is that:

[0104] The test voltage is 500 V, and the separator thickness is 16 μm.

[0105] Example 5

[0106] This example is used to illustrate a method for preparing a battery disclosed by the present invention, including most of the operations in Example 1, and the differences are as follows:

[0107] The test voltage is 500V, and the diaphragm thickness is 18μm.

[0108] Example 6

[0109] This example is used to illustrate a method for preparing a battery disclosed by the present invention, including most of the operations in Example 1, and the differences are as follows:

[0110] The test time for a single core is 0.9s, and the test time for a single semi-finished battery is 0.2s.

[0111] Example 7

[0112] This example is used to illustrate a method for preparing a battery disclosed by the present invention, including most of the operations in Example 1, and the differences are as follows:

[0113] The test time for a single core is 1.1s, and the test time for a single semi-finished battery is 0.3s.

[0114] Comparative Example 1

[0115] This comparative example is used to comparatively illustrate a method for preparing a battery disclosed by the present invention, including most of the operations in Example 1, and the differences are as follows:

[0116] The test time for a single core > the winding beat of the winding device (1.5s),

[0117] The test time for a single semi-finished battery > the grooving beat of the grooving device (0.5s).

[0118] Comparative Example 2

[0119] This comparative example is used to comparatively illustrate a method for preparing a battery disclosed by the present invention, including most of the operations in Example 1, and the differences are as follows:

[0120] The test time for a single core > the winding beat of the winding device; (1.3s),

[0121] The test time for a single semi-finished battery > the grooving beat of the grooving device (0.4s).

[0122] Comparative Example 3

[0123] This comparative example is used to comparatively illustrate a method for preparing a battery disclosed by the present invention, including most of the operations in Example 1, and the differences are as follows:

[0124] Screen short - circuited batteries using a conventional short - circuit detection method.

[0125] After uniformly placing the qualified batteries selected in Example 1 and Comparative Example 3 in a normal - temperature environment for 30 days, the consistency was detected to obtain Figure 1 .

[0126] As Figure 1 described, the average voltage drop of the batteries selected in Example 1 decreased significantly less than that of the batteries selected in Comparative Example 3 after being stored for 30 days. Furthermore, the consistency of the batteries in Example 1 is relatively better, and thus the battery capacity can be utilized more effectively, the battery service life can be extended, and its reliability and stability can be improved.

[0127] Fill the defective - rate detection results of the batteries prepared in Examples 1 - 7 and Comparative Examples 1 - 3 into Table 2.

[0128] Table 2

[0129]

[0130] It can be seen from the test results in Table 2 that Examples 1 - 6 can all detect unqualified batteries well; among them, in Examples 1 - 3, batteries with separator thicknesses of 9μm, 13μm, and 15μm were detected using a voltage of 250V respectively. 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 thicker separator was used, and when detecting with a voltage of 250V, there may be a situation of reduced detection force.

[0131] In Examples 4 - 5, batteries with separator thicknesses of 16μm and 18μm were detected using a voltage of 500V respectively. Compared with Example 4, the detected defective rate of Example 5 is relatively lower. Similarly, because a thicker separator was used in Example 5, there may be a situation of reduced detection force.

[0132] Compared with Example 1, in Examples 6 - 7, the detection time of the wound core or semi - finished batteries is relatively too long. Correspondingly, the detection of the defective rate or the detection intensity is improved compared with Example 1.

[0133] In Comparative Example 1, a detection time outside the scope defined in this application was used and the detection time was relatively too long, and it is easy to have the problem of missed detection during detection. Therefore, the detected defective rate is relatively low. Compared with Comparative Example 2, the detection time of Comparative Example 1 is greater than that of Comparative Example 2. Therefore, the missed - detection situation in Comparative Example 1 will also be relatively serious, that is, the defective rate of Comparative Example 1 in Table 2 is lower than that of Comparative Example 2.

[0134] In Comparative Example 3, a conventional short-circuit detection method was used to screen short-circuited batteries, and the defective rate detected was nearly halved compared to that of Example 1, indicating that the missed detection situation was serious in the screening by the conventional method.

[0135] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included within 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 beat of the groove rolling device; if the internal resistance of the semi-finished battery is less than the second internal resistance, it is determined to be a short circuit; if the internal resistance of the semi-finished battery is ≥ the second resistance, it is determined to be a qualified semi-finished battery; The test time of a single core is 0.7-1.2s; The test time of a single semi-finished battery is 0.1-0.3s; The first internal resistance and the second internal resistance are both 200 MΩ; The voltage for testing the internal resistance of the winding core is 250-500V; The test voltage for testing the internal resistance of the semi-finished battery is 250-500V; 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.

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

3. The method for preparing a cylindrical battery according to claim 1, 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; 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.

4. The method for preparing a cylindrical battery according to claim 1, characterized in that: 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.

5. 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.

6. A cylindrical battery, characterized in that: The cylindrical battery is prepared by the preparation method described in any one of claims 1 to 5.

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