Detection Method of Battery Cell, Formation Equipment and Battery Production Line

Abstract

The present application discloses a detection method for battery cells, formation equipment and a battery production line. The detection method includes setting a battery cell on the formation equipment and connecting a negative pressure cup to the interior of the battery cell, performing an initial negative pressure test on the battery cell under a first test condition and screening out the battery cells that pass the initial test. The first test condition includes evacuating the battery cell to a first preset negative pressure, and the electrolyte in the battery cell does not enter the negative pressure cup under the first preset negative pressure. Under a second test condition, a recheck of the negative pressure is performed on the battery cells that pass the initial test, and the battery cells that pass the recheck are screened out. The second test condition includes evacuating the battery cell to a second preset negative pressure, and the absolute value of the second preset negative pressure is greater than the absolute value of the first preset negative pressure. The electrolyte in the battery cell enters the negative pressure cup under the second preset negative pressure. By respectively performing an initial test and a recheck on the battery cells, the battery cells with problems in airtightness can be screened out, and the situation of electrolyte leakage is reduced.

Description

Technical Field

[0001] The present application relates to the technical field of battery manufacturing, and particularly relates to a method for detecting a battery cell, a formation device, and a battery production line. Background Art

[0002] With the development of new energy, more and more fields use new energy as power. Due to advantages such as high energy density, rechargeability, safety, and environmental friendliness, battery devices are widely used in fields such as new energy vehicles, consumer electronics, and energy storage systems.

[0003] In related technologies, a battery device includes a plurality of battery cells. During the manufacturing process of the battery cells, formation operations need to be performed on them to activate the battery cells. Before performing the formation operations on the battery cells, the leakage rate of the battery cells needs to be detected. However, during the detection process, electrolyte leakage occurs in the battery cells with unqualified leakage rates, and the leaked electrolyte will contaminate other battery cells. Summary of the Invention

[0004] In view of the above problems, the present application provides a method for detecting a battery cell, a formation device, and a battery production line, which solves the problem of electrolyte leakage in battery cells with unqualified leakage rates.

[0005] A first aspect of the present application proposes a method for detecting a battery cell, and the detection method includes:

[0006] Setting the battery cell on the formation device;

[0007] Connecting the negative pressure cup of the formation device to the inside of the battery cell;

[0008] Under a first test condition, performing a preliminary negative pressure test on the battery cell, and screening out the battery cells that pass the preliminary test. Among them, the first test condition includes evacuating the battery cell to a first preset negative pressure, and under the first preset negative pressure, the electrolyte in the battery cell does not enter the negative pressure cup;

[0009] Under a second test condition, performing a retest of the negative pressure on the battery cells that pass the preliminary test, and screening out the battery cells that pass the retest. Among them, the second test condition includes evacuating the battery cell to a second preset negative pressure, the absolute value of the second preset negative pressure is greater than the absolute value of the first preset negative pressure, and under the second preset negative pressure, the electrolyte in the battery cell enters the negative pressure cup.

[0010] In this application, the battery cell is first preliminarily tested using a first preset negative pressure to screen whether the battery cell leaks on the premise that the electrolyte does not enter the negative pressure cup, and then the battery cells that pass the preliminary test are retested to screen whether the battery cell leaks on the premise that the electrolyte enters the negative pressure cup. By respectively performing the preliminary test and the retest on the battery cell, it is possible to screen out the battery cells with sealing problems, thereby reducing the leakage of the electrolyte of the battery cell during the test process.

[0011] In some embodiments of the present application, under the first test condition, the battery cell is subjected to a negative pressure preliminary test, and the battery cells that pass the preliminary test are screened out. Among them, the first test condition includes evacuating the battery cell to a first preset negative pressure. Under the first preset negative pressure, the steps for the electrolyte in the battery cell not to enter the negative pressure cup include:

[0012] Perform the first vacuum pumping operation on the battery cell;

[0013] End the first vacuum pumping operation according to the internal pressure of the battery cell reaching the first preset negative pressure;

[0014] Perform the first pressure holding operation on the battery cell and time the pressure holding process;

[0015] Calculate the preliminary test leakage rate of the battery cell according to the first pressure holding duration reaching the first preset duration;

[0016] Screen whether the preliminary test of the battery cell in the preliminary test is qualified according to the preliminary test leakage rate.

[0017] With such a setting, it is possible to first perform a preliminary test on the battery cell under the condition of a low preset negative pressure, so as to screen out the battery cells with sealing problems when the electrolyte does not enter the negative pressure cup, reducing the leakage of the electrolyte of the battery cell during the test process due to the sealing problem of the battery cell when the electrolyte enters the negative pressure cup under the condition of a high preset negative pressure.

[0018] In some embodiments of the present application, the step of screening whether the preliminary test of the battery cell in the preliminary test is qualified according to the preliminary test leakage rate includes:

[0019] Compare the preliminary test leakage rate with the first preset value;

[0020] When the preliminary test leakage rate is greater than or equal to the first preset value, determine that the battery cell is unqualified in the preliminary test;

[0021] When the preliminary test leakage rate is less than the first preset value, determine that the battery cell is qualified in the preliminary test.

[0022] By comparing the initial leakage rate of the battery cell with a preset first preset value and judging whether there is a problem with the sealing performance of the battery cell according to the comparison result, it is possible to achieve a preliminary screening of the battery cells with sealing problems, reducing the leakage of the electrolyte of the battery cell during the test process due to the sealing problem of the battery cell.

[0023] In some embodiments of the present application, in the step of comparing the initial leakage rate and the first preset value, the first preset value is in the range of 2 kPa / min to 5 kPa / min. With such a setting, during the initial measurement of the battery cell, the accuracy of screening the battery cells with sealing problems can be improved, and further reduce the leakage of the electrolyte of the battery cell during the test process.

[0024] In some embodiments of the present application, in the step of calculating the initial leakage rate of the battery cell according to the first pressure holding duration reaching the first preset duration, the first preset duration is in the range of 60 seconds to 180 seconds.

[0025] With such a setting, during the initial measurement, the battery cell can have a sufficient pressure holding duration, further improving the accuracy of screening the battery cells with sealing problems.

[0026] In some embodiments of the present application, the step of calculating the initial leakage rate of the battery cell according to the first pressure holding duration reaching the first preset duration includes:

[0027] Obtaining the first pressure value of the battery cell at the end of the first vacuum pumping;

[0028] Obtaining the second pressure value of the battery cell when the first pressure holding duration reaches the first preset duration;

[0029] Calculating the first difference between the first pressure value and the second pressure value, and taking the absolute value of the first difference as the first pressure difference;

[0030] Calculating the first ratio of the first pressure difference to the first preset duration, where the first ratio is the initial leakage rate.

[0031] With such a setting, during the initial measurement, the leakage situation of the battery cell can be quantified by data, and whether there is a problem with the sealing performance of the battery cell can be judged through data comparison, further improving the judgment accuracy of the battery cells with sealing problems.

[0032] In some embodiments of the present application, under the second test condition, the battery cells that passed the initial test are retested under negative pressure, and the battery cells that passed the retest are screened out. Among them, the second test condition includes evacuating the battery cell to a second preset negative pressure, and the absolute value of the second preset negative pressure is greater than the absolute value of the first preset negative pressure. And in the step of the electrolyte in the battery cell entering the negative pressure cup under the second preset negative pressure:

[0033] Perform a second evacuation operation on the battery cells that passed the initial test;

[0034] End the second evacuation operation according to the internal pressure of the battery cell reaching the second preset negative pressure;

[0035] Perform a second pressure holding operation on the battery cell and time the pressure holding process;

[0036] Calculate the retest leakage rate of the battery cell according to the second pressure holding duration reaching the second preset duration;

[0037] Screen whether the retest of the retested battery cells is qualified according to the retest leakage rate.

[0038] With such a setting, the battery cells can be retested under the condition of a high preset negative pressure, realizing further screening of the battery cells, thereby improving the detection rate of the battery cells with problems in sealing, and further reducing the failure rate of the battery cells.

[0039] In some embodiments of the present application, the step of screening whether the retest of the battery cells is qualified according to the retest leakage rate includes:

[0040] Compare the retest leakage rate with the second preset value;

[0041] When the retest leakage rate is greater than or equal to the second preset value, determine that the battery cell is unqualified in the retest;

[0042] When the retest leakage rate is less than the second preset value, determine that the battery cell is qualified in the retest.

[0043] By comparing the retest leakage rate of the battery cell with the preset second preset value and judging whether there is a problem with the sealing of the battery cell according to the comparison result, the battery cells with problems in sealing can be re-screened, improving the detection rate of the battery cells with problems in sealing, and reducing the situation of battery cell failures caused by problems in the sealing of the battery cells.

[0044] In some embodiments of the present application, in the step of comparing the retest leakage rate with the second preset value, the second preset value is in the range of 2 kPa / min to 5 kPa / min. With such a setting, during the retest of the battery cell, the accuracy of screening battery cells with sealing problems can be improved, and the occurrence of battery cell failures can be further reduced.

[0045] In some embodiments of the present application, in the step of calculating the retest leakage rate of the battery cell according to the second pressure holding duration reaching the second preset duration, the second preset duration is in the range of 60 seconds to 180 seconds.

[0046] With such a setting, during the retest, the battery cell can have a sufficient pressure holding duration, and the accuracy of screening battery cells with sealing problems is further improved.

[0047] In some embodiments of the present application, in the step of calculating the retest leakage rate of the battery cell according to the second pressure holding duration reaching the second preset duration, it includes:

[0048] Obtain the third pressure value of the battery cell at the end of the second evacuation;

[0049] Obtain the fourth pressure value of the battery cell when the second pressure holding duration reaches the second preset duration;

[0050] Calculate the second difference between the third pressure value and the fourth pressure value, and take the absolute value of the second difference as the second pressure difference;

[0051] Calculate the second ratio of the second pressure difference to the second preset duration, where the second ratio is the retest leakage rate.

[0052] With such a setting, during the retest, the leakage situation of the battery cell can be quantified, and whether there is a problem with the sealing of the battery cell can be judged through data comparison, further improving the judgment accuracy of battery cells with sealing problems.

[0053] In some embodiments of the present application, under the first test condition, the battery cell is subjected to a negative pressure initial test, and the battery cells that pass the initial test are screened out. Among them, the first test condition includes evacuating the battery cell to the first preset negative pressure. In the step that the electrolyte in the battery cell does not enter the negative pressure cup under the first preset negative pressure, it includes:

[0054] Obtain the type of the battery cell;

[0055] According to the type of the battery cell, match the test negative pressure in the negative pressure database and calibrate the test negative pressure as the first preset negative pressure.

[0056] With such a setting, it is possible to match the first preset negative pressure during the initial measurement of the battery cell according to the type of the battery cell, so that it is possible to perform the initial measurement on different types of battery cells and effectively improve the accuracy of the initial measurement.

[0057] In some embodiments of the present application, in the step of matching the test negative pressure in the negative pressure database according to the type of the battery cell and calibrating the test negative pressure as the first preset negative pressure, the establishment step of the negative pressure database includes:

[0058] Performing a vacuum pumping test on a plurality of different types of battery cells to obtain a plurality of test negative pressures;

[0059] Establishing a mapping relationship between the type of the battery cell and the test negative pressure to form a negative pressure database.

[0060] With such a setting, it is possible to perform data matching on different types of battery cells, thereby realizing the testing of different battery cells, and further being able to effectively detect the sealing performance of different types of battery cells.

[0061] In some embodiments of the present application, in the step of performing a vacuum pumping test on a plurality of different types of battery cells to obtain a plurality of test negative pressures, the vacuum pumping test includes:

[0062] Setting the battery cell on the formation device;

[0063] Performing a vacuum pumping operation on the battery cell to cause the electrolyte in the battery cell to enter the negative pressure cup of the formation device;

[0064] Stopping the vacuum pumping operation on the battery cell according to the pressure in the battery cell reaching the calibrated negative pressure, wherein the absolute value of the calibrated negative pressure is greater than the absolute value of the second preset negative pressure;

[0065] Increasing the internal pressure of the battery cell to cause the electrolyte in the negative pressure cup to flow back into the interior of the battery cell, and detecting the current liquid level of the electrolyte in the negative pressure cup and the current pressure value of the battery cell;

[0066] Recording the current pressure value as the test negative pressure when the current liquid level is zero.

[0067] With such a setting, it is possible to prevent the electrolyte in the battery cell from entering the negative pressure cup during the initial measurement of the battery cell, so as to perform the initial measurement of the battery cell on the premise that the electrolyte does not leave the battery cell, and reduce the situation of electrolyte leakage caused by the sealing problem of the battery cell.

[0068] A second aspect of the present application provides a formation device, which is used to implement the detection method of the battery cell as described above.

[0069] In this application, before the formation equipment forms a battery cell, it is necessary to first test the sealing performance of the battery cell. During the process of testing the sealing performance of the battery cell, the battery cell is first preliminarily tested using a first preset negative pressure to screen whether the battery cell leaks on the premise that the electrolyte does not enter the negative pressure cup. Then, the battery cells that pass the preliminary test are retested, and whether the battery cell leaks is screened on the premise that the electrolyte enters the negative pressure cup. By respectively conducting the preliminary test and the retest on the battery cell, battery cells with sealing problems can be screened out, thereby reducing the occurrence of electrolyte leakage of the battery cell during the testing process.

[0070] The third aspect of this application proposes a battery production line, including the above-mentioned formation equipment.

[0071] In this application, when processing a battery cell, it is necessary to form the battery cell. Before the formation equipment forms the battery cell, it is necessary to first test the sealing performance of the battery cell. During the process of testing the sealing performance of the battery cell, the battery cell is first preliminarily tested using a first preset negative pressure to screen whether the battery cell leaks on the premise that the electrolyte does not enter the negative pressure cup. Then, the battery cells that pass the preliminary test are retested, and whether the battery cell leaks is screened on the premise that the electrolyte enters the negative pressure cup. By respectively conducting the preliminary test and the retest on the battery cell, battery cells with sealing problems can be screened out, thereby reducing the occurrence of electrolyte leakage of the battery cell during the testing process.

[0072] The above description is only an overview of the technical solution of this application. In order to be able to more clearly understand the technical means of this application, it can be implemented according to the content of the specification. And in order to make the above and other purposes, features and advantages of this application more obvious and understandable, the following specifically illustrates the specific implementation manners of this application. Brief Description of the Drawings

[0073] Figure 1 Schematically shows a flowchart of a method for detecting a battery cell according to an embodiment of this application;

[0074] Figure 2 Schematically shows a partial structural diagram of a battery production line according to an embodiment of this application;

[0075] Figure 3 Schematically shows a partial structural schematic diagram of a formation equipment according to an embodiment of this application.

[0076] The reference numerals are as follows:

[0077] 1000, battery production line;

[0078] 100, formation equipment;

[0079] 10. Negative pressure cup

[0080] 200. Battery cell; 201. Electrolyte Detailed implementation manners

[0081] Hereinafter, embodiments of the technical solution of the present application will be described in detail with reference to the accompanying drawings. The following embodiments are only used to illustrate the technical solution of the present application more clearly, and therefore are only examples and cannot be used to limit the protection scope of the present application.

[0082] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in the specification and claims of this application and the above accompanying drawings are intended to cover non-exclusive inclusion.

[0083] In the description of the embodiments of the present application, technical terms such as "first" and "second" are only used to distinguish different objects and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity, specific order or primary-secondary relationship of the indicated technical features. In the description of the embodiments of the present application, "a plurality of" means two or more, unless otherwise specifically defined.

[0084] Referring to "embodiments" herein means that specific features, structures or characteristics described in connection with the embodiments can be included in at least one embodiment of the present application. The phrase appears in various places in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art explicitly and implicitly understand that the embodiments described herein can be combined with other embodiments.

[0085] In the description of the embodiments of the present application, the term "and / or" is only a description of the association relationship of associated objects, indicating that three relationships can exist. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " in this article generally represents an "or" relationship between the associated objects before and after.

[0086] In the description of the embodiments of the present application, the term "a plurality of" refers to two or more (including two). Similarly, "a plurality of groups" refers to two or more groups (including two groups), and "a plurality of sheets" refers to two or more sheets (including two sheets).

[0087] In the description of the embodiments of the present application, the orientation or positional relationship indicated by technical terms such as "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the embodiments of the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation to the embodiments of the present application.

[0088] In the description of the embodiments of the present application, unless otherwise clearly specified and limited, technical terms such as "installation", "connection", "connection", "fixation", etc. should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or integrated; it can also be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements or the interaction relationship between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the embodiments of the present application can be understood according to specific circumstances.

[0089] Currently, from the perspective of the development of the market situation, the application of battery devices is becoming more and more extensive. Battery devices are not only applied to energy storage power systems such as hydraulic, thermal, wind, and solar power stations, but also widely used in electric transportation such as electric bicycles, electric motorcycles, and electric vehicles, as well as in multiple fields such as military equipment and aerospace. With the continuous expansion of the application fields of battery devices, the market demand is also continuously increasing.

[0090] In the related art, a battery device includes a plurality of battery cells. During the manufacturing process of the battery cells, formation operations need to be performed on them to activate the battery cells. Before performing the formation operations on the battery cells, the leakage rate of the battery cells needs to be detected. However, during the detection process, the battery cells with unqualified leakage rates will have electrolyte leakage, and the leaked electrolyte will cause problems of contaminating other battery cells.

[0091] To solve the above problems, a detection method for battery cells is proposed in this application, which includes setting the battery cell on a formation device and connecting the negative pressure cup of the formation device to the inside of the battery cell. Under the first test condition, a preliminary negative pressure test is performed on the battery cell, and the battery cells that pass the preliminary test are screened out. Among them, the first test condition includes evacuating the battery cell to a first preset negative pressure, and under the first preset negative pressure, the electrolyte in the battery cell does not enter the negative pressure cup. Under the second test condition, a retest of the negative pressure is performed on the battery cells that pass the preliminary test, and the battery cells that pass the retest are screened out. Among them, the second test condition includes evacuating the battery cell to a second preset negative pressure, and the absolute value of the second preset negative pressure is greater than the absolute value of the first preset negative pressure, and under the second preset negative pressure, the electrolyte in the battery cell enters the negative pressure cup. First, a preliminary test is performed on the battery cell using the first preset negative pressure, and the battery cell is screened for leakage on the premise that the electrolyte does not enter the negative pressure cup. Then, the battery cells that pass the preliminary test are retested, and the battery cell is screened for leakage on the premise that the electrolyte enters the negative pressure cup. By performing a preliminary test and a retest on the battery cell respectively, the battery cells with problems in airtightness can be screened out, thereby reducing the situation of electrolyte leakage.

[0092] When the electrical equipment to which the battery device is applied is a vehicle, the vehicle can be a fuel vehicle, a gas vehicle or a new energy vehicle. The new energy vehicle can be a pure electric vehicle, a hybrid vehicle or an extended-range vehicle, etc. A motor, a controller and a battery device can be arranged inside the vehicle, and the controller is used to control the battery device to supply power to the motor. For example, the battery device can be arranged at the bottom, the front or the rear of the vehicle. The battery device can be used for power supply of the vehicle. For example, the battery device can be used as the operating power source of the vehicle and used for the circuit system of the vehicle, such as for the working power requirements during the start-up, navigation and operation of the vehicle. In another embodiment of this application, the battery device can not only be used as the operating power source of the vehicle, but also be used as the driving power source of the vehicle, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle.

[0093] The above-mentioned battery apparatus may include one or more battery cell assemblies for providing voltage and capacity. The battery cell assembly may include a plurality of battery cells, and the plurality of battery cells are connected in series, parallel or in a hybrid connection through a busbar component.

[0094] In some embodiments, the battery cell assembly is usually formed by arranging a plurality of battery cells.

[0095] As an example, the battery cell assembly can be a battery module, which is formed by arranging and fixing multiple battery cells to form an independent module. As an example, the battery module can be formed by bundling multiple battery cells with cable ties.

[0096] In some embodiments, the battery device can be a battery pack, which includes a box body and one or more battery cell assemblies, and the battery cell assemblies are accommodated in the box body.

[0097] As an example, the battery cell assembly can be a battery module, and the battery cell assembly can be accommodated in the box body by fixing the battery module in the box body.

[0098] As an example, the battery cell assembly can also be accommodated in the box body by directly fixing multiple battery cells to the box body.

[0099] As an example, the box body can include a first box body and a second box body. The first box body and the second box body are snapped together so that a closed space is formed inside the box body to accommodate the battery cell assembly. Here, "closed" means covered or closed, which can be sealed or non-sealed. The first box body can be a top cover or a bottom plate.

[0100] As an example, the box body can include a top cover, a frame, and a bottom plate. The top cover and the bottom plate are respectively connected to the frame so that a closed space is formed inside the box body to accommodate the battery cell assembly.

[0101] In some embodiments, the box body can be a part of the chassis structure of a vehicle. For example, a part of the box body can become at least a part of the floor of the vehicle, or a part of the box body can become at least a part of the cross beam and longitudinal beam of the vehicle.

[0102] The technical solutions described in the embodiments of the present application are applicable to various electrical devices using battery cells, such as mobile phones, portable devices, laptop computers, battery cars, electric toys, electric tools, vehicles, ships, and spacecrafts, etc. For example, spacecrafts include airplanes, rockets, space shuttles, and spaceships, etc.

[0103] In some embodiments of the present application, the battery cell can be a secondary battery, which refers to a battery cell that can be activated by charging after discharging so as to continue to be used.

[0104] The battery cell can be a lithium-ion battery, a sodium-ion battery, a sodium-lithium-ion battery, a lithium-metal battery, a sodium-metal battery, a lithium-sulfur battery, a magnesium-ion battery, a nickel-metal hydride battery, a nickel-cadmium battery, a lead-acid battery, etc., and the embodiments of the present application do not limit this.

[0105] In some embodiments of the present application, the battery cell includes a housing, a pressure relief mechanism, an electrode assembly, and an insulating member. The housing includes a plurality of side walls, among which there is a first side wall, and the pressure relief mechanism is provided on the first side wall. The pressure relief mechanism is configured to open or close according to whether the internal pressure of the housing reaches a pressure threshold. The electrode assembly is disposed inside the housing, and the insulating member is provided inside the housing and between the housing and the electrode assembly for insulating and isolating the housing and the electrode assembly, and the insulating member abuts against the electrode assembly.

[0106] As an example, the battery cell can be a cylindrical battery cell, a prismatic battery cell, a pouch battery cell, or a battery cell of other shapes. The prismatic battery cell includes a square shell battery cell, a blade-shaped battery cell, a multi-prismatic battery, and the multi-prismatic battery is, for example, a hexagonal prism battery, etc., and there is no particular limitation in the present application.

[0107] The electrode assembly includes a positive electrode, a negative electrode, and a separator. The separator is disposed between the negative electrode and the positive electrode. During the charge and discharge process of the battery cell, active ions (such as lithium ions) are embedded and extracted back and forth between the positive electrode and the negative electrode. The separator is disposed between the positive electrode and the negative electrode, which can play a role in preventing short circuit between the positive and negative electrodes, and at the same time can allow active ions to pass through.

[0108] In some embodiments, the positive electrode can be a positive electrode sheet, and the positive electrode sheet can include a positive electrode current collector and a positive electrode active material provided on at least one surface of the positive electrode current collector.

[0109] As an example, the positive electrode current collector has two surfaces opposite to each other in its own thickness direction, and the positive electrode active material is provided on any one or both of the two opposite surfaces of the positive electrode current collector.

[0110] As an example, the positive electrode current collector can be made of a metal foil, a conductive polymer material, a carbon material, or a composite current collector. For example, as the metal foil, pure metal, alloy, or metal with surface treatment can be used, including but not limited to stainless steel, copper, aluminum, nickel, titanium, or silver, etc. The composite current collector can include a polymer material base layer and a metal layer. The composite current collector can be formed by forming a metal material (such as aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.).

[0111] As an example, the positive electrode active material may include at least one of the following materials: lithium-containing phosphates, lithium transition metal oxides, and their respective modified compounds. However, the present application is not limited to these materials, and other conventional materials that can be used as the positive electrode active material of the battery can also be used. These positive electrode active materials can be used alone or in combination of two or more. Among them, examples of lithium-containing phosphates may include, but are not limited to, lithium iron phosphate (such as LiFePO4 (which can also be abbreviated as LFP)), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO4), a composite material of lithium manganese phosphate and carbon, lithium manganese iron phosphate, and at least one of a composite material of lithium manganese iron phosphate and carbon. Examples of lithium transition metal oxides may include, but are not limited to, lithium cobalt oxide (such as LiCoO2), lithium nickel oxide (such as LiNiO2), lithium manganese oxide (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (which can also be abbreviated as NCM 333 ), LiNi 0.5 Co 0.2 Mn 0.3 O2 (which can also be abbreviated as NCM 523 ), LiNi 0.5 Co 0.25 Mn 0.25 O2 (which can also be abbreviated as NCM 211 ), LiNi 0.6 Co 0.2 Mn 0.2 O2 (which can also be abbreviated as NCM 622 ), LiNi 0.8 Co 0.1 Mn 0.1 O2 (which can also be abbreviated as NCM 811 ), lithium nickel cobalt aluminum oxide (such as LiNi 0.8 Co 0.15 Al 0.05 O2) and their modified compounds, etc. The modified compound refers to a substance obtained by modification means such as doping or coating on the basis of the above substances.

[0112] In some embodiments, the positive electrode may adopt a foam metal. The foam metal can be nickel foam, copper foam, aluminum foam, foam alloy, or foam carbon, etc. When the foam metal is used as the positive electrode, the positive electrode active material may not be provided on the surface of the foam metal, and of course, the positive electrode active material may also be provided. As an example, the positive electrode active material is filled and / or deposited in the foam metal.

[0113] In some embodiments, the negative electrode may be a negative electrode sheet, and the negative electrode sheet may include a negative electrode current collector.

[0114] As an example, the negative electrode current collector may be made of a metal foil, a conductive polymer material, a carbon material, or a composite current collector. For example, as the metal foil, pure metals, alloys, and metals with surface treatment can be used, including but not limited to stainless steel, copper, aluminum, nickel, titanium, or silver, etc. The composite current collector may include a polymer material base layer and a metal layer. The composite current collector can be formed by forming a metal material (such as copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer material substrate (such as substrates of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.).

[0115] As an example, the negative electrode sheet may include a negative electrode current collector and a negative electrode active material provided on at least one surface of the negative electrode current collector.

[0116] As an example, the negative electrode current collector has two surfaces opposite to each other in its own thickness direction, and the negative electrode active material is provided on either one or both of the two opposite surfaces of the negative electrode current collector.

[0117] As an example, the negative electrode active material may be a negative electrode active material for a battery cell known in the art. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc. The silicon-based materials may be selected from at least one of elemental silicon, silicon oxides, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based materials may be selected from at least one of elemental tin, tin oxides, and tin alloys. However, the present application is not limited to these materials, and other conventional materials that can be used as the negative electrode active material of a battery cell can also be used. These negative electrode active materials can be used alone or in combination of two or more.

[0118] In some embodiments, the negative electrode may be made of a foam metal. The foam metal may be foam nickel, foam copper, foam aluminum, foam alloy, or foam carbon, etc. When the foam metal is used as the negative electrode sheet, the negative electrode active material may not be provided on the surface of the foam metal, and of course, the negative electrode active material may also be provided.

[0119] As an example, the negative electrode active material may be filled or / and deposited in the negative electrode current collector.

[0120] In some embodiments, the material of the positive electrode current collector may be aluminum, and the material of the negative electrode current collector may be copper.

[0121] In some embodiments, the electrode assembly further includes a separator, and the separator is disposed between the positive electrode and the negative electrode.

[0122] In some embodiments, the separator is a separator membrane. The present application does not particularly limit the type of the separator membrane, and any well-known porous structure separator membrane with good chemical stability and mechanical stability can be selected.

[0123] As an example, the main material of the separator membrane can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, polyvinylidene fluoride, and ceramics. The separator membrane can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator membrane is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation. The separator can be a single component located between the positive and negative electrodes, or can be attached to the surfaces of the positive and negative electrodes. An inorganic particle coating, an organic particle coating, or an organic / inorganic composite coating can also be coated on the surface of the separator membrane.

[0124] In some embodiments, the separator is a solid electrolyte. The solid electrolyte is disposed between the positive electrode and the negative electrode, and simultaneously functions to transport ions and isolate the positive and negative electrodes.

[0125] The electrode assembly can be a wound structure, a stacked structure, or a mixed structure of winding and stacking.

[0126] In some embodiments, the electrode assembly is a wound structure. The positive electrode sheet and the negative electrode sheet are wound into a wound structure.

[0127] In some embodiments, the electrode assembly is a stacked structure.

[0128] As an example, multiple positive electrode sheets and multiple negative electrode sheets can be respectively provided, and the multiple positive electrode sheets and the multiple negative electrode sheets are alternately stacked.

[0129] As an example, multiple positive electrode sheets can be provided, and the negative electrode sheet is folded to form multiple stacked folding segments, and a positive electrode sheet is clamped between adjacent folding segments.

[0130] As an example, both the positive electrode sheet and the negative electrode sheet are folded to form multiple stacked folding segments.

[0131] As an example, multiple separators can be provided and are respectively disposed between any adjacent positive electrode sheets or negative electrode sheets.

[0132] As an example, the separators can be continuously provided and are disposed between any adjacent positive electrode sheets or negative electrode sheets by folding or winding.

[0133] In some embodiments, the shape of the electrode assembly can be cylindrical, flat, or multi-prismatic, etc.

[0134] In some embodiments, the electrode sheet of the electrode assembly is provided with electrode tabs, and the electrode tabs can lead the current out of the electrode assembly. The electrode tabs include a positive electrode tab and a negative electrode tab.

[0135] In some embodiments, a pressure relief mechanism is provided on the outer casing. The pressure relief mechanism is used to discharge the internal gas of the battery cell.

[0136] As an example, it is actuated to release the internal pressure or temperature when the internal pressure or temperature of the battery cell reaches a predetermined threshold. When the internal pressure or temperature of the battery cell reaches a predetermined threshold, the pressure relief mechanism performs an action or a weak structure provided in the pressure relief mechanism is damaged, thereby forming an opening or a channel for discharging the internal pressure or temperature. This threshold design varies according to different design requirements. The threshold may depend on one or several materials among the positive electrode sheet, negative electrode sheet, electrolyte, and separator in the battery cell.

[0137] As an example, the pressure relief mechanism can be integrally formed with the outer casing.

[0138] As an example, the pressure relief mechanism can also be separately provided and connected to the outer casing.

[0139] As used in this application, "actuation" means that the pressure relief mechanism generates an action or is activated to a certain state, so that the internal pressure and temperature of the battery cell can be discharged. The actions generated by the pressure relief mechanism may include, but are not limited to: the components in the pressure relief mechanism move to form an exhaust channel, at least a part of the pressure relief mechanism breaks, shatters, is torn, or opens, etc. When the pressure relief mechanism is actuated, the high-temperature and high-pressure substances inside the battery cell will be discharged outward from the actuated part as emissions. In this way, the battery cell can be depressurized and cooled under a controllable pressure or temperature, thereby reducing the occurrence of potential more serious accidents.

[0140] In some embodiments, when the outer casing is a non-sealed structure, the pressure relief mechanism can be set as a through hole for discharging the internal gas of the battery cell.

[0141] The emissions from the battery cell mentioned in this application include, but are not limited to: electrolyte, dissolved or split positive and negative electrode sheets, fragments of the separator, high-temperature and high-pressure gases generated by the reaction, flames, etc.

[0142] The positive electrode tab and the negative electrode tab can be led out from the same end of the electrode sheet, or can be respectively led out from the opposite ends of the electrode sheet.

[0143] The structures of the positive electrode tab and the negative electrode tab can be the same or different. Taking the positive electrode tab as an example, the positive electrode tab can include multiple positive electrode tab layers, and the multiple positive electrode tab layers are stacked together to form the positive electrode tab. The positive electrode tab can include at least two parts, one part is located between the main body of the electrode sheet and the insulating member, and the other part is located between the insulating member and the electrode lead-out member.

[0144] The insulating member can insulate at least part of the tab from the end face of the main body portion, so as to reduce the risk of the tab being inserted into the main body portion when the battery cell is affected by external impacts, vibrations, etc., thereby reducing the risk of short circuit of the battery cell and being beneficial to improving the reliability of the battery cell.

[0145] The insulating member can be of an integral structure or a split structure. As an example, the insulating member is formed by connecting a plurality of independently formed parts. As another example, the insulating member is integrally formed by stamping.

[0146] For example, the insulating member is a plastic part, and the insulating member that is a plastic part is integrally formed by injection molding. The plastic part is convenient to process and has a low manufacturing cost.

[0147] In some embodiments of the present application, the housing includes a housing body and an end cover. The housing body has an opening, the end cover is connected to the housing body and closes the opening, the end cover forms a first side wall, and the pressure relief mechanism is arranged on the end cover.

[0148] In some embodiments of the present application, the housing can be a steel shell, an aluminum shell, a plastic shell (such as polypropylene), a composite metal shell (such as a copper-aluminum composite housing), or an aluminum-plastic film, etc. In some embodiments, the housing can be a sealed structure or a non-sealed structure. As an example, when the housing is a non-sealed structure, the housing plays a role in protecting the electrode assembly, and a sealing bag is further included between the housing and the electrode assembly. The sealing bag is used to encapsulate the electrode assembly and the electrolyte. Specifically, the sealing bag can be a bag-shaped insulating member or an aluminum-plastic film. When the housing is a sealed structure, it is used to encapsulate components such as the electrode assembly and the electrolyte. The housing body can be provided with one or more openings. The end cover can also be provided with one or more.

[0149] In addition, the connection manner between the end cover and the housing body includes but is not limited to snap connection, bonding, welding, or connection through a connecting member.

[0150] In some embodiments of the present application, the battery cell further includes an electrode terminal, and the electrode terminal is arranged on the end cover and electrically connected to the electrode assembly. The electrode terminal is electrically connected to the tab of the electrode assembly. The electrode terminal can be directly connected to the tab or indirectly connected to the tab through a current collecting member. The electrode terminal can be arranged on the end cover or on the housing body. In the embodiment shown in the present application, the electrode terminal is arranged on the end cover.

[0151] In order for the battery cell to work properly, formation needs to be performed on the battery cell, and the battery cell completes the formation operation on a formation device.

[0152] After the battery cell is filled with electrolyte, it needs to be initially charged to activate the battery cell and form a dense SEI film (solid electrolyte interphase) on the anode to ensure the cycle life of the battery cell, thereby completing the formation operation of the battery cell.

[0153] During the initial charging process of the battery cell, the electrolyte inside the battery cell participates in redox reactions to generate a relatively large amount of gas. To effectively discharge the generated gas in a timely manner during the manufacturing process, it is necessary to perform a leak rate test on the battery cell before the process starts, that is, the formation leak detection process.

[0154] During the test, the nozzle of the negative pressure cup of the formation equipment presses against the liquid injection hole, the pipeline connected to the negative pressure cup opens the negative pressure valve, evacuates to the set value and holds the pressure. After holding the pressure for a certain period of time, it is determined whether the leak rate of the battery cell is qualified. If the leak rate is qualified, the next process is continued; if the leak rate is unqualified, the formation press directly disengages and alarms.

[0155] However, since the maximum negative pressure used in the formation process is generally relatively large, the electrolyte will be drawn into the negative pressure cup under high negative pressure. When there are problems with the sealing of the battery cell, air will enter the negative pressure cup. After the pressure holding test is completed, the electrolyte in the negative pressure cup cannot all be "sucked" back into the interior of the battery cell. At the same time, due to the unqualified leak rate, the formation press disengages, and when the nozzle disengages, the residual electrolyte in the negative pressure cup will spray onto the top cover of the battery cell, resulting in the scrapping of the battery cell and increasing the defective rate of the battery cell.

[0156] As Figures 1 to 3 shown, some embodiments of the present application propose a detection method for a battery cell 200, and the detection method includes:

[0157] S10: Set the battery cell 200 on the formation equipment 100.

[0158] Specifically, before performing the formation operation on the battery cell 200, it is necessary to test the sealing performance of the battery cell 200. When performing the sealing performance test, the battery cell 200 is set on the formation equipment 100, and the formation press fixes the battery cell 200 on the formation equipment 100, thereby fixing the position of the battery cell 200 to facilitate the test of the sealing performance of the battery cell 200.

[0159] S20: Connect the interior of the negative pressure cup 10 of the formation equipment 100 to the interior of the battery cell 200.

[0160] Specifically, after the battery cell 200 is fixed on the formation device 100, the airtightness of the battery cell 200 needs to be tested before the formation operation of the battery cell 200. The negative pressure cup 10 of the vacuum pumping device of the formation device 100 cooperates with the battery cell 200, and the inside of the battery cell 200 is communicated with the negative pressure cup 10, so that the vacuum pumping device can perform a vacuum pumping operation on the battery cell 200, thereby completing the test of the airtightness of the battery cell 200.

[0161] Further, the negative pressure cup 10 includes a nozzle, the nozzle abuts against the end cover of the battery cell 200, and the nozzle is communicated with the liquid injection hole on the end cover. The vacuum pumping device performs a vacuum pumping operation on the battery cell 200 through the nozzle on the negative pressure cup 10, so as to detect the airtightness of the battery cell 200 under the condition of vacuum pumping.

[0162] S30: Under the first test condition, a negative pressure preliminary test is performed on the battery cell 200, and the battery cells 200 that pass the preliminary test are screened out. Among them, the first test condition includes evacuating the battery cell 200 to a first preset negative pressure, and under the first preset negative pressure, the electrolyte 201 in the battery cell 200 does not enter the negative pressure cup 10.

[0163] Specifically, under the first test condition, a negative pressure preliminary test is performed on the battery cell 200. During the test, the vacuum pumping device performs a vacuum pumping operation on the battery cell 200. When the pressure inside the battery cell 200 reaches the first preset negative pressure, the vacuum pumping operation on the battery cell 200 stops. At this time, the electrolyte 201 inside the battery cell 200 does not reach the situation of leaving the inside of the battery cell 200 and entering the negative pressure cup 10.

[0164] In the present application, when the internal pressure of the battery cell 200 reaches the first preset negative pressure, the electrolyte 201 in the battery cell 200 does not flow out from the liquid injection hole on the end cover.

[0165] Under the first test condition, since the electrolyte 201 inside the battery cell 200 does not enter the negative pressure cup 10, testing the battery cell 200 under this test condition can screen out the battery cells 200 with poor airtightness, and reduce the situation that the electrolyte 201 of the battery cells 200 with poor airtightness enters the negative pressure cup 10 and causes electrolyte 201 leakage.

[0166] It should be understood that during the negative pressure test, the vacuum pumping device performs a vacuum pumping operation on the inside of the battery cell 200, and the internal pressure of the battery cell 200 is less than zero. When the internal pressure of the battery cell 200 reaches the first preset negative pressure, the vacuum pumping device stops running, and at this time the first preset negative pressure is also less than zero.

[0167] In some embodiments of the present application, under the first test condition, the battery cell 200 is initially tested under negative pressure, and the battery cells 200 that pass the initial test are screened out. Among them, the first test condition includes evacuating the battery cell 200 to a first preset negative pressure. Under the first preset negative pressure, the step that the electrolyte 201 in the battery cell 200 does not enter the negative pressure cup 10 specifically includes the following steps:

[0168] S31: Obtain the type of the battery cell 200.

[0169] Specifically, different types of battery cells 200 need to be tested under different test parameters to improve the test accuracy. Based on this, it is necessary to obtain the type of the battery cell 200 to match the corresponding test parameters according to the type of the battery cell 200.

[0170] S32: According to the type of the battery cell 200, match the test negative pressure in the negative pressure database and calibrate the test negative pressure as the first preset negative pressure.

[0171] With such a setting, the first preset negative pressure in the initial test process of the battery cell 200 can be matched according to the type of the battery cell 200, so that the initial test of different types of battery cells 200 can be realized, and the test accuracy can be effectively improved.

[0172] Furthermore, the negative pressure database is stored in the control device of the formation device 100. By inputting the type of the corresponding battery cell 200, the control device matches the type of the battery cell 200 with the data in the negative pressure database, so that the battery cell 200 matches the best first preset negative pressure.

[0173] Among them, the negative pressure database is established through the following steps:

[0174] S01: Conduct vacuum tests on multiple different types of battery cells 200 to obtain multiple test negative pressures.

[0175] Specifically, on the formation device 100, when the liquid level of the electrolyte 201 in the battery cell 200 reaches the highest liquid level of the battery cell 200 (i.e., the critical position where the electrolyte 201 is about to flow out of the battery cell 200), record the internal pressure of the current type of battery cell 200. This internal pressure is the test negative pressure (the first preset negative pressure). By replacing different types of battery cells 200, multiple test negative pressures are obtained.

[0176] S02: Establish a mapping relationship between the type of the battery cell 200 and the test negative pressure to form a negative pressure database.

[0177] Specifically, a mapping relationship is formed between the type of each battery cell 200 and its corresponding test negative pressure, thereby forming a negative pressure database.

[0178] With such a setting, data matching for different types of battery cells 200 can be achieved, thereby enabling the testing of different battery cells 200, and further enabling effective detection of the sealing performance of different types of battery cells 200.

[0179] In some embodiments of the present application, in the step of performing a vacuum pumping test on multiple different types of battery cells 200 to obtain multiple test negative pressures, the vacuum pumping test includes:

[0180] S011: Set the battery cell 200 on the formation device 100.

[0181] Specifically, the battery cell 200 is fixed on the formation device 100, and the vacuum pumping device of the formation device 100 is connected to the interior of the battery through the liquid injection hole on the end cover of the battery cell 200, so that the vacuum pumping device can perform a vacuum pumping operation on the battery cell 200.

[0182] S012: Perform a vacuum pumping operation on the battery cell 200 to cause the electrolyte 201 in the battery cell 200 to enter the negative pressure cup 10 of the formation device 100.

[0183] S013: Stop the vacuum pumping operation on the battery cell 200 according to the pressure in the battery cell 200 reaching the calibrated negative pressure, where the absolute value of the calibrated negative pressure is greater than the absolute value of the second preset negative pressure.

[0184] S014: Increase the internal pressure of the battery cell 200 to cause the electrolyte 201 in the negative pressure cup 10 to flow back into the interior of the battery cell 200, and detect the current liquid level of the electrolyte 201 in the negative pressure cup 10 and the current pressure value of the battery cell 200.

[0185] S015: Record the current pressure value as the test negative pressure when the current liquid level is zero.

[0186] With such a setting, it can be ensured that the electrolyte 201 in the battery cell 200 does not enter the negative pressure cup 10 during the initial test of the battery cell 200, so as to achieve the initial test of the battery cell 200 on the premise that the electrolyte 201 does not leave the battery cell 200, and reduce the situation of electrolyte 201 leakage caused by the sealing problem of the battery cell 200.

[0187] S33: Perform a first vacuum pumping operation on the battery cell 200.

[0188] Specifically, the battery cell 200 is fixed on the formation device 100. The vacuum pumping device of the formation device 100 is connected to the inside of the battery cell 200. The battery cell 200 is preliminarily tested under the first test condition. The vacuum pumping device operates to pump the battery cell 200 to make the inside of the battery cell 200 in a negative pressure state, so as to detect the sealing performance of the battery cell 200.

[0189] It should be understood that under the first test condition, when the vacuum pumping device pumps the battery cell 200, the outer shell of the battery cell 200 may deform or may not deform.

[0190] S34: End the first vacuum pumping operation according to the internal pressure of the battery cell 200 reaching the first preset negative pressure.

[0191] Specifically, the battery cell 200 is preliminarily tested under the first test condition. The vacuum pumping device pumps the battery cell 200. During the vacuum pumping process, the internal pressure of the battery cell 200 is detected. When the internal pressure of the battery cell 200 reaches the first preset negative pressure, the vacuum pumping device is stopped, so that the vacuum pumping operation stops, in order to test the sealing performance of the battery cell 200.

[0192] S35: Perform the first pressure holding operation on the battery cell 200 and time the pressure holding process.

[0193] Specifically, the battery cell 200 is preliminarily tested under the first test condition. The vacuum pumping device pumps the battery cell 200. When the internal pressure of the battery cell 200 reaches the first preset negative pressure, the vacuum pumping device is stopped, so that the battery cell 200 enters the first pressure holding state, and timing starts from when the vacuum pumping device stops operating, in order to time the first pressure holding duration of the battery cell 200, calculate the leakage rate of the battery cell 200 using the first pressure holding duration, and judge the sealing performance of the battery cell 200 according to the calculated leakage rate, so as to screen out the battery cells 200 with sealing problems.

[0194] S36: Calculate the preliminary test leakage rate of the battery cell 200 according to the first pressure holding duration reaching the first preset duration.

[0195] Specifically, the battery cell 200 is preliminarily tested under the first test condition. After the vacuum pumping device finishes pumping the battery cell 200, the battery cell 200 enters the pressure holding state, and timing starts from when the vacuum pumping device stops. When the first pressure holding duration reaches the first preset duration, the preliminary test leakage rate of the battery cell 200 is calculated.

[0196] In some embodiments of the present application, the first preset duration ranges from 60 seconds to 180 seconds.

[0197] By setting the first preset duration within the range of 60 seconds to 180 seconds, it is possible to ensure sufficient pressure holding duration for the battery cell 200 during the initial measurement, further improving the accuracy of screening for battery cells 200 with sealing problems.

[0198] It should be noted that the first preset duration can be 60 seconds, 70 seconds, 80 seconds, 90 seconds, 100 seconds, 110 seconds, 120 seconds, 130 seconds, 140 seconds, 150 seconds, 160 seconds, 170 seconds, or 180 seconds.

[0199] In the step of calculating the initial measurement leakage rate of the battery cell 200 based on the first pressure holding duration reaching the first preset duration, the following specific steps are included:

[0200] S361: Obtain the first pressure value of the battery cell 200 at the end of the first vacuum pumping.

[0201] Specifically, during the initial measurement of the battery cell 200 under the first test conditions, after the vacuum pumping device finishes the vacuum pumping operation on the battery cell 200, the battery cell 200 enters the pressure holding state, and timing starts from when the vacuum pumping device stops. Obtain the internal pressure of the battery cell 200 at the start of timing and record this pressure as the first pressure value.

[0202] It should be understood that the first pressure value is the maximum pressure value of the battery cell 200 in the pressure holding state. During the pressure holding period, the internal pressure of the battery cell 200 may decrease. The sealing performance of the battery cell 200 is judged based on the internal pressure change of the battery cell 200, thereby improving the accuracy of the judgment.

[0203] S362: Obtain the second pressure value of the battery cell 200 when the first pressure holding duration reaches the first preset duration.

[0204] Specifically, during the initial measurement of the battery cell 200 under the first test conditions, after the vacuum pumping device finishes the vacuum pumping operation on the battery cell 200, the battery cell 200 enters the pressure holding state, and timing starts from when the vacuum pumping device stops. Obtain the internal pressure of the battery cell 200 at the start of timing and record this pressure as the first pressure value. When the pressure holding state of the battery cell 200 reaches the first pressure holding duration, obtain the internal pressure of the battery cell 200 at this moment and record this pressure as the second pressure value.

[0205] It should be understood that the second pressure value is the minimum pressure value of the battery cell 200 in the pressure holding state within the first pressure holding duration.

[0206] S363: Calculate the first difference between the first pressure value and the second pressure value, and take the absolute value of the first difference as the first pressure difference.

[0207] Specifically, when the absolute value of the first pressure value is greater than or equal to the absolute value of the second pressure value, during the calculation, subtract the second pressure value from the first pressure value to obtain the first difference. This first difference is negative. After taking the absolute value of the first difference, the first pressure difference is obtained, and the first pressure difference is used to determine whether there is a problem with the seal of the battery cell 200.

[0208] S364: Calculate the first ratio of the first pressure difference to the first preset duration, where the first ratio is the initial leak rate.

[0209] Specifically, during the calculation, subtract the second pressure value from the first pressure value to obtain the first difference, take the absolute value of the first difference to obtain the first pressure difference, and then divide the first pressure difference by the first preset duration to obtain the pressure change rate of the battery cell 200 during the pressure holding period under the first test condition. This pressure change rate is the initial leak rate of the battery cell 200. The seal of the battery cell 200 is judged according to the initial leak rate, so as to screen out the battery cells 200 with seal problems.

[0210] In the step of calculating the initial leak rate of the battery cell 200 when the first pressure holding duration reaches the first preset duration, by setting steps S361 to S364, the leakage situation of the battery cell 200 can be quantified during the initial measurement, and whether there is a problem with the seal of the battery cell 200 can be judged by data comparison, further improving the judgment accuracy of the battery cells 200 with seal problems.

[0211] S37: Screen whether the initial measurement of the battery cell 200 in the initial measurement is qualified according to the initial leak rate.

[0212] In some embodiments of the present application, in the step of screening whether the initial measurement of the battery cell 200 in the initial measurement is qualified according to the initial leak rate, the following steps are specifically included:

[0213] S371: Compare the initial leak rate with the first preset value.

[0214] Specifically, the initial test is performed on the battery cell 200 under the first test condition. After the evacuation device finishes the evacuation operation on the battery cell 200, the battery cell 200 enters the pressure-holding state, and timing starts from when the evacuation device stops. The internal pressure of the battery cell 200 at the start of timing is obtained and recorded as the first pressure value. When the pressure-holding state of the battery cell 200 reaches the first pressure-holding duration, the second pressure value of the battery cell 200 is recorded. The first pressure difference of the battery cell 200 is calculated based on the first pressure value and the second pressure value, and the initial leakage rate is obtained by the ratio of the first pressure difference and the first preset duration.

[0215] The initial leakage rate is compared with the first preset value, and the sealing performance of the battery cell is judged according to the comparison result.

[0216] It should be understood that during the comparison between the initial leakage rate and the first preset value, it is a numerical comparison between the two.

[0217] In some embodiments of the present application, the first preset value is in the range of 2 kPa / min to 5 kPa / min. With such a setting, during the initial test of the battery cell 200, the accuracy of screening the battery cell 200 with sealing problems can be improved, and further the situation of leakage of the electrolyte 201 of the battery cell 200 during the test can be reduced.

[0218] It should be noted that the first preset value can specifically be 2 kPa / min, 2.5 kPa / min, 3 kPa / min, 3.5 kPa / min, 4 kPa / min, 4.5 kPa / min, 5 kPa / min.

[0219] S372: When the initial leakage rate is greater than or equal to the first preset value, it is determined that the battery cell 200 fails the initial test.

[0220] Specifically, when the initial leakage rate is greater than or equal to the first preset value, it is determined that the battery cell 200 fails the initial test, and the battery cell 200 that fails the initial test is separated from the formation device 100 to discharge the battery cell 200 with sealing problems.

[0221] S373: When the initial leakage rate is less than the first preset value, it is determined that the battery cell 200 passes the initial test.

[0222] Specifically, when the initial leakage rate is less than the first preset value, it is determined that the battery cell 200 passes the initial test, and the battery cell 200 that passes the initial test is kept on the formation device 100 for retesting the battery cell 200 that passes the initial test.

[0223] In the step of screening whether the initial measurement of the battery cell 200 is qualified according to the initial measurement leakage rate, steps S371 to S373 are set. By comparing the initial measurement leakage rate of the battery cell 200 with a preset first preset value and judging whether there is a problem with the sealing performance of the battery cell 200 according to the comparison result, the initial screening of the battery cell 200 with a problem in sealing performance can be realized, reducing the situation that the electrolyte 201 of the battery cell 200 leaks during the test due to the problem in the sealing performance of the battery cell 200.

[0224] Under the first test condition, the battery cell 200 is subjected to a negative pressure initial measurement, and the battery cells 200 with qualified initial measurement are screened out. Among them, the first test condition includes the step of evacuating the battery cell 200 to a first preset negative pressure, and under the first preset negative pressure, the electrolyte 201 in the battery cell 200 does not enter the negative pressure cup 10. By setting steps S31 to S37, the battery cell 200 can be initially measured under the condition of a low preset negative pressure, so as to screen out the battery cells 200 with a problem in sealing performance when the electrolyte 201 does not enter the negative pressure cup 10, reducing the situation that the electrolyte 201 of the battery cell 200 leaks during the test due to the problem in the sealing performance of the battery cell 200 after the electrolyte 201 enters the negative pressure cup 10 under the condition of a high preset negative pressure.

[0225] S40: Under the second test condition, the battery cells 200 with qualified initial measurement are subjected to a negative pressure retest, and the battery cells 200 with qualified retest are screened out. Among them, the second test condition includes evacuating the battery cell 200 to a second preset negative pressure, the absolute value of the second preset negative pressure is greater than the absolute value of the first preset negative pressure, and under the second preset negative pressure, the electrolyte 201 in the battery cell 200 enters the negative pressure cup 10.

[0226] Specifically, in this application, the battery cell 200 is initially measured with the first preset negative pressure, and whether the battery cell 200 leaks is screened out on the premise that the electrolyte 201 does not enter the negative pressure cup 10. Then, the battery cells 200 with qualified initial measurement are retested, and whether the battery cell 200 leaks is screened out on the premise that the electrolyte 201 enters the negative pressure cup 10. By respectively performing the initial measurement and retest on the battery cell 200, the battery cells 200 with a problem in sealing performance can be screened out, thereby reducing the situation that the electrolyte 201 of the battery cell 200 leaks during the test.

[0227] In the present application, when the internal pressure of the battery cell 200 reaches the second preset negative pressure, the electrolyte 201 inside the battery cell 200 will flow out from the liquid injection hole on the end cap and enter the negative pressure cup 10. After the retest is completed, the pressure inside the battery cell 200 returns to normal. At this time, the electrolyte 201 in the negative pressure cup 10 flows back into the battery cell 200, thereby reducing the situation of electrolyte 201 overflowing.

[0228] Under the second test condition, since the electrolyte 201 inside the battery cell 200 enters the negative pressure cup 10, testing the battery cell 200 under this test condition can further screen out the battery cells 200 with poor sealing performance, reducing the problem of battery cell 200 failure caused by unqualified sealing of the battery cell 200.

[0229] It should be understood that during the negative pressure test, the vacuum pumping device performs a vacuum pumping operation on the inside of the battery cell 200, and the internal pressure of the battery cell 200 is less than zero. When the internal pressure of the battery cell 200 reaches the second preset negative pressure, the vacuum pumping device stops operating, and at this time, the second preset negative pressure is also less than zero.

[0230] In some embodiments of the present application, under the second test condition, the battery cells 200 that passed the initial test are subjected to a negative pressure retest, and the battery cells 200 that passed the retest are screened out. Among them, the second test condition includes evacuating the battery cell 200 to the second preset negative pressure. The absolute value of the second preset negative pressure is greater than the absolute value of the first preset negative pressure, and in the step where the electrolyte 201 inside the battery cell 200 enters the negative pressure cup 10 under the second preset negative pressure, it specifically includes the following steps:

[0231] S41: Perform a second vacuum pumping operation on the battery cells 200 that passed the initial test.

[0232] Specifically, the battery cells 200 are fixed on the formation equipment 100. The vacuum pumping device of the formation equipment 100 is connected to the inside of the battery cells 200. Under the first test condition, the battery cells 200 are initially tested. The vacuum pumping device operates to perform a vacuum pumping operation on the battery cells 200 to make the inside of the battery cells 200 in a negative pressure state for detecting the sealing performance of the battery cells 200. When the battery cells 200 pass the initial test, the vacuum pumping device performs a second vacuum pumping operation on the battery cells 200 that passed the initial test.

[0233] It should be understood that under the second test condition, when the vacuum pumping device performs a vacuum pumping operation on the battery cells 200, the outer shell of the battery cells 200 may deform.

[0234] S42: End the second vacuum pumping operation according to the internal pressure of the battery cell 200 reaching the second preset negative pressure.

[0235] Specifically, under the second test condition, the battery cell 200 is retested. The vacuum pumping device performs a vacuum pumping operation on the battery cell 200, and the internal pressure of the battery cell 200 is detected during the vacuum pumping process. When the internal pressure of the battery cell 200 reaches the second preset negative pressure, the vacuum pumping device is stopped, so that the vacuum pumping operation stops, in order to test the sealing performance of the battery cell 200.

[0236] It should be noted that the second preset negative pressure is greater than or equal to the maximum negative pressure capacity of the vacuum pumping device, and at the same time, the second preset negative pressure is less than or equal to the maximum negative pressure used in the formation process.

[0237] S43: Perform a second pressure holding operation on the battery cell 200 and time the pressure holding process.

[0238] Specifically, under the second test condition, the battery cell 200 is retested. The vacuum pumping device performs a vacuum pumping operation on the battery cell 200. When the internal pressure of the battery cell 200 reaches the second preset negative pressure, the vacuum pumping device is stopped, so that the battery cell 200 enters the second pressure holding state, and timing starts from when the vacuum pumping device stops operating, in order to time the second pressure holding duration of the battery cell 200, calculate the leakage rate of the battery cell 200 using the second pressure holding duration, and judge the sealing performance of the battery cell 200 based on the calculated leakage rate, so as to screen out the battery cells 200 with sealing problems.

[0239] S44: Calculate the retest leakage rate of the battery cell 200 according to the second pressure holding duration reaching the second preset duration.

[0240] Specifically, under the second test condition, the battery cell 200 is retested. After the vacuum pumping device finishes the vacuum pumping operation on the battery cell 200, the battery cell 200 enters the pressure holding state, and timing starts from when the vacuum pumping device stops. When the second pressure holding duration reaches the second preset duration, the retest leakage rate of the battery cell 200 is calculated.

[0241] In some embodiments of the present application, the second preset duration is in the range of 60 seconds to 180 seconds.

[0242] By setting the second preset duration in the range of 60 seconds to 180 seconds, the battery cell 200 can have a sufficient pressure holding duration during the retest, further improving the accuracy of screening the battery cells 200 with sealing problems.

[0243] It should be noted that the second preset duration can be 60 seconds, 70 seconds, 80 seconds, 90 seconds, 100 seconds, 110 seconds, 120 seconds, 130 seconds, 140 seconds, 150 seconds, 160 seconds, 170 seconds, 180 seconds.

[0244] In the step of calculating the retest leakage rate of the battery cell 200 according to the second pressure holding duration reaching the second preset duration, the following steps are specifically included:

[0245] S441: Obtain the third pressure value of the battery cell 200 at the end of the second vacuum pumping.

[0246] Specifically, under the second test condition, the battery cell 200 is retested. After the vacuum pumping device finishes the vacuum pumping operation on the battery cell 200, the battery cell 200 enters the pressure holding state, and timing starts from when the vacuum pumping device stops. Obtain the internal pressure of the battery cell 200 at the start of timing and record this pressure as the third pressure value.

[0247] It should be understood that the third pressure value is the maximum pressure value of the battery cell 200 in the pressure holding state. During the pressure holding period, the internal pressure of the battery cell 200 may decrease. The tightness of the battery cell 200 is judged according to the change of the internal pressure of the battery cell 200, thereby improving the accuracy of the judgment.

[0248] S442: Obtain the fourth pressure value of the battery cell 200 when the second pressure holding duration reaches the second preset duration;

[0249] Specifically, under the second test condition, the battery cell 200 is retested. After the vacuum pumping device finishes the vacuum pumping operation on the battery cell 200, the battery cell 200 enters the pressure holding state, and timing starts from when the vacuum pumping device stops. Obtain the internal pressure of the battery cell 200 at the start of timing and record this pressure as the third pressure value. When the pressure holding state of the battery cell 200 reaches the second pressure holding duration, obtain the internal pressure of the battery cell 200 at this moment and record this pressure as the fourth pressure value.

[0250] It should be understood that the fourth pressure value is the minimum pressure value of the battery cell 200 in the second pressure holding duration in the pressure holding state.

[0251] S443: Calculate the second difference between the third pressure value and the fourth pressure value, and take the absolute value of the second difference as the second pressure difference.

[0252] Specifically, the absolute value of the third pressure value is greater than or equal to the absolute value of the fourth pressure value. During the calculation, the third pressure value is subtracted from the fourth pressure value to obtain a second difference value, which is a negative value. After taking the absolute value of the second difference value, a second pressure difference is obtained, and the second pressure difference is used to determine whether there is a problem with the sealing performance of the battery cell 200.

[0253] S444: Calculate a second ratio of the second pressure difference to a second preset duration, where the second ratio is the retest leakage rate.

[0254] Specifically, during the calculation, the third pressure value is subtracted from the fourth pressure value to obtain a second difference value, and after taking the absolute value of the second difference value, a second pressure difference is obtained. Then, the second pressure difference is divided by the second preset duration to obtain the pressure change rate of the battery cell 200 during the pressure holding period under the second test condition. This pressure change rate is the retest leakage rate of the battery cell 200. Based on the retest leakage rate, the sealing performance of the battery cell 200 is judged, so as to screen out the battery cells 200 with sealing problems.

[0255] In the step of calculating the retest leakage rate of the battery cell 200 according to the second pressure holding duration reaching the second preset duration, by setting steps S441 to S444, the leakage situation of the battery cell 200 can be quantified during the retest, and whether there is a problem with the sealing performance of the battery cell 200 can be judged through data comparison, further improving the judgment accuracy of the battery cells 200 with sealing problems.

[0256] S45: Screen whether the retest of the battery cell 200 is qualified according to the retest leakage rate.

[0257] In some embodiments of the present application, in the step of screening whether the initial test of the battery cell 200 is qualified according to the retest leakage rate, the following steps are specifically included:

[0258] S451: Compare the retest leakage rate with a second preset value.

[0259] Specifically, during the retest of the battery cell 200 under the second test condition, after the vacuum pumping device finishes the vacuum pumping operation on the battery cell 200, the battery cell 200 enters the pressure holding state, and timing starts from when the vacuum pumping device stops. The internal pressure of the battery cell 200 at the start of timing is obtained and recorded as the third pressure value. When the pressure holding state of the battery cell 200 reaches the second pressure holding duration, the fourth pressure value of the battery cell 200 is recorded. The second pressure difference of the battery cell 200 is calculated based on the third pressure value and the fourth pressure value, and the retest leakage rate is obtained through the ratio of the second pressure difference to the second preset duration.

[0260] Compare the re - tested leakage rate with the second preset value, and judge the tightness of the battery cell according to the comparison result.

[0261] It should be understood that during the comparison between the re - tested leakage rate and the second preset value, it is a comparison of the numerical values of the two.

[0262] In some embodiments of the present application, the second preset value is in the range of 2 kPa / min to 5 kPa / min. With such a setting, during the re - testing of the battery cell 200, the accuracy of screening the battery cell 200 with tightness problems can be improved, and further, the leakage of the electrolyte 201 of the battery cell 200 during the test can be reduced.

[0263] It should be noted that the second preset value can specifically be 2 kPa / min, 2.5 kPa / min, 3 kPa / min, 3.5 kPa / min, 4 kPa / min, 4.5 kPa / min, 5 kPa / min.

[0264] S452: When the re - tested leakage rate is greater than or equal to the second preset value, it is determined that the re - test of the battery cell 200 is unqualified.

[0265] Specifically, when the re - tested leakage rate is greater than or equal to the second preset value, it is determined that the initial test of the battery cell 200 is unqualified, and the battery cell 200 with an unqualified initial test is separated from the formation device 100 to discharge the battery cell 200 with tightness problems.

[0266] S453: When the re - tested leakage rate is less than the second preset value, it is determined that the re - test of the battery cell 200 is qualified.

[0267] Specifically, when the re - tested leakage rate is less than the second preset value, it is determined that the initial test of the battery cell 200 is qualified, and the battery cell 200 with a qualified initial test is kept on the formation device 100 for the formation operation of the battery cell 200 with a qualified re - test.

[0268] In the step of screening whether the re - test of the battery cell 200 is qualified according to the re - tested leakage rate under the second test condition, steps S451 to S453 are set. By comparing the re - tested leakage rate of the battery cell 200 with the preset second preset value and judging whether there is a problem with the tightness of the battery cell 200 according to the comparison result, the re - screening of the battery cell 200 with tightness problems can be realized, the detection rate of the battery cell 200 with tightness problems is improved, and the situation of battery cell 200 failure caused by the tightness problem of the battery cell 200 is reduced.

[0269] Under the second test condition, the battery cell 200 that passed the initial test is retested under negative pressure, and the battery cell 200 that passed the retest is screened out. Among them, the second test condition includes evacuating the battery cell 200 to a second preset negative pressure. The absolute value of the second preset negative pressure is greater than the absolute value of the first preset negative pressure. And in the step of the electrolyte 201 in the battery cell 200 entering the negative pressure cup 10 under the second preset negative pressure, by setting steps S41 to S45, the battery cell 200 can be retested under the condition of a high preset negative pressure, realizing further screening of the battery cell 200, so as to improve the detection rate of the battery cell 200 with sealing problems, and further reduce the failure rate of the battery cell 200.

[0270] When detecting the sealing performance of the battery cell 200, first set the battery cell 200 on the formation device 100 and connect the negative pressure cup 10 of the vacuum pumping device of the formation device 100 to the inside of the battery cell 200. Conduct the first vacuum pumping operation on the battery cell 200. End the first vacuum pumping operation according to the internal pressure of the battery cell 200 reaching -45 ± 5 kPa. Conduct the first pressure holding operation on the battery cell 200 and time the pressure holding process. Obtain the first pressure value of the battery cell 200 at the end of the first vacuum pumping according to the first pressure holding duration reaching 60 seconds. Obtain the second pressure value of the battery cell 200 when the first pressure holding duration reaches the first preset duration. Calculate the first difference between the first pressure value and the second pressure value, and take the absolute value of the first difference to obtain the first pressure difference. Calculate the first ratio of the first pressure difference to the first preset duration. Among them, the first ratio is the initial test leakage rate. Compare the initial test leakage rate with the first preset value. The first preset value is 3 kPa / min. When the initial test leakage rate is greater than or equal to the first preset value, determine that the battery cell 200 fails the initial test. When the initial test leakage rate is less than the first preset value, determine that the battery cell 200 passes the initial test.

[0271] Under the second test condition, a second vacuum pumping operation is performed on the battery cell 200 that passed the initial test. When the internal pressure of the battery cell 200 reaches -80 ± 5 kPa, the second vacuum pumping operation ends. A second pressure holding operation is performed on the battery cell 200 and the pressure holding process is timed. When the second pressure holding duration reaches 60 seconds, a third pressure value of the battery cell 200 at the end of the second vacuum pumping is obtained, and a fourth pressure value of the battery cell 200 when the second pressure holding duration reaches the second preset duration is obtained. A second difference between the third pressure value and the fourth pressure value is calculated, and the absolute value of the second difference is taken to obtain a second pressure difference. A second ratio of the second pressure difference to the second preset duration is calculated. Here, the second ratio is the retest leakage rate. The retest leakage rate is compared with a second preset value, and the second preset value is 3 kPa / min. When the retest leakage rate is greater than or equal to the second preset value, the battery cell 200 is determined to be unqualified in the retest. When the retest leakage rate is less than the second preset value, the battery cell 200 is determined to be qualified in the retest.

[0272] A second aspect of the present application proposes a formation device 100, which is used to implement the detection method of the battery cell 200 as described above.

[0273] In the present application, before the formation device 100 forms the battery cell 200, the sealing performance of the battery cell 200 needs to be tested first. During the process of testing the sealing performance of the battery cell 200, the battery cell 200 is initially tested with a first preset negative pressure, and whether the battery cell 200 leaks is screened on the premise that the electrolyte 201 does not enter the negative pressure cup 10. Then, the battery cells 200 that passed the initial test are retested, and whether the battery cell 200 leaks is screened on the premise that the electrolyte 201 enters the negative pressure cup 10. By respectively performing the initial test and the retest on the battery cell 200, the battery cells 200 with sealing problems can be screened out, thereby reducing the leakage of the electrolyte 201 of the battery cell 200 during the test process.

[0274] A third aspect of the present application proposes a battery production line 1000, including the formation device 100 as described above.

[0275] In this application, when the battery cell 200 is being processed, formation of the battery cell 200 is required. Before the formation equipment 100 forms the battery cell 200, it is necessary to first test the sealing performance of the battery cell 200. During the process of testing the sealing performance of the battery cell 200, the battery cell 200 is first preliminarily tested using a first preset negative pressure, and whether the battery cell 200 leaks is screened on the premise that the electrolyte 201 does not enter the negative pressure cup 10. Then, the battery cells 200 that pass the preliminary test are retested, and whether the battery cell 200 leaks is screened on the premise that the electrolyte 201 enters the negative pressure cup 10. By respectively performing the preliminary test and the retest on the battery cell 200, battery cells 200 with sealing problems can be screened out, thereby reducing the leakage of the electrolyte 201 of the battery cell 200 during the testing process.

[0276] The above description is only an overview of the technical solution of this application. In order to be able to more clearly understand the technical means of this application, it can be implemented in accordance with the content of the specification. And in order to make the above and other purposes, features and advantages of this application more obvious and understandable, the specific embodiments of this application are specifically given below.

[0277] In the embodiment of this application, as Figures 1 to 3 shown, this application proposes a detection method for a battery cell 200, and the detection method includes the following steps:

[0278] The battery cell 200 is set on the formation equipment 100, and the negative pressure cup 10 of the vacuum pumping device of the formation equipment 100 is communicated with the inside of the battery cell 200.

[0279] Under the first test condition, a first vacuum pumping operation is performed on the battery cell 200. When the internal pressure of the battery cell 200 reaches the first preset negative pressure, the first vacuum pumping operation ends. A first pressure maintaining operation is performed on the battery cell 200 and the pressure maintaining process is timed. When the first pressure maintaining duration reaches the first preset duration (the first preset duration is in the range of 60 seconds to 180 seconds), the first pressure value of the battery cell 200 at the end of the first vacuum pumping is obtained. The second pressure value of the battery cell 200 when the first pressure maintaining duration reaches the first preset duration is obtained. The first difference between the first pressure value and the second pressure value is calculated, and the absolute value of the first difference is taken to obtain the first pressure difference. The first ratio of the first pressure difference to the first preset duration is calculated. Among them, the first ratio is the preliminary test leakage rate. The preliminary test leakage rate is compared with the first preset value (the first preset value is in the range of 2 kPa / min to 5 kPa / min). When the preliminary test leakage rate is greater than or equal to the first preset value, it is determined that the battery cell 200 is unqualified in the preliminary test. When the preliminary test leakage rate is less than the first preset value, it is determined that the battery cell 200 is qualified in the preliminary test.

[0280] Under the second test condition, a second vacuum pumping operation is performed on the battery cell 200 that passed the initial test. When the internal pressure of the battery cell 200 reaches the second preset negative pressure, the second vacuum pumping operation ends. A second pressure holding operation is performed on the battery cell 200 and the pressure holding process is timed. When the second pressure holding duration reaches the second preset duration (the second preset duration is in the range of 60 seconds to 180 seconds), the third pressure value of the battery cell 200 at the end of the second vacuum pumping is obtained, and the fourth pressure value of the battery cell 200 when the second pressure holding duration reaches the second preset duration is obtained. The second difference between the third pressure value and the fourth pressure value is calculated, and the absolute value of the second difference is taken to obtain the second pressure difference. The second ratio of the second pressure difference to the second preset duration is calculated. Herein, the second ratio is the retest leakage rate. The retest leakage rate is compared with the second preset value (the second preset value is in the range of 2 kPa / min to 5 kPa / min). When the retest leakage rate is greater than or equal to the second preset value, it is determined that the battery cell 200 fails the retest. When the retest leakage rate is less than the second preset value, it is determined that the battery cell 200 passes the retest.

[0281] In this application, during the process of testing the sealing performance of the battery cell 200, the battery cell 200 is initially tested with the first preset negative pressure, and whether the battery cell 200 leaks is screened on the premise that the electrolyte 201 does not enter the negative pressure cup 10. Then, the battery cells 200 that passed the initial test are retested, and whether the battery cell 200 leaks is screened on the premise that the electrolyte 201 enters the negative pressure cup 10. By respectively performing the initial test and the retest on the battery cell 200, the battery cells 200 with sealing problems can be screened out, thereby reducing the leakage of the electrolyte 201 of the battery cell 200 during the test process.

[0282] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, and are not intended to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application, and they should all be covered within the scope of the claims and the description of the present application. In particular, as long as there is no structural conflict, the technical features mentioned in each embodiment can be combined in any way. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A method for detecting a battery cell, characterized in that, The detection method includes: Setting a battery cell on formation equipment; Connecting the negative pressure cup of the formation equipment to the interior of the battery cell; Under a first test condition, performing a negative pressure preliminary test on the battery cell and screening out the battery cells that pass the preliminary test. Among them, the first test condition includes evacuating the battery cell to a first preset negative pressure, and under the first preset negative pressure, the electrolyte in the battery cell does not enter the negative pressure cup; Under a second test condition, performing a negative pressure retest on the battery cells that pass the preliminary test and screening out the battery cells that pass the retest. Among them, the second test condition includes evacuating the battery cell to a second preset negative pressure, the absolute value of the second preset negative pressure is greater than the absolute value of the first preset negative pressure, and under the second preset negative pressure, the electrolyte in the battery cell enters the negative pressure cup.

2. The detection method of the battery cell according to claim 1, characterized in that, Under a first test condition, performing a negative pressure preliminary test on the battery cell and screening out the battery cells that pass the preliminary test. Among them, the first test condition includes evacuating the battery cell to a first preset negative pressure, and the steps that under the first preset negative pressure, the electrolyte in the battery cell does not enter the negative pressure cup include: Performing a first vacuum pumping operation on the battery cell; Ending the first vacuum pumping operation according to the internal pressure of the battery cell reaching the first preset negative pressure; Performing a first pressure holding operation on the battery cell and timing the pressure holding process; Calculating the preliminary test leakage rate of the battery cell according to the first pressure holding duration reaching a first preset duration; Screening whether the battery cells in the preliminary test are qualified according to the preliminary test leakage rate.

3. The detection method of the battery cell according to claim 2, wherein The steps of screening whether the battery cells in the preliminary test are qualified according to the preliminary test leakage rate include: Comparing the preliminary test leakage rate with a first preset value; When the preliminary test leakage rate is greater than or equal to the first preset value, determining that the battery cell fails the preliminary test; When the preliminary test leakage rate is less than the first preset value, determining that the battery cell passes the preliminary test.

4. The detection method of the battery cell according to claim 3, wherein, In the step of comparing the preliminary test leakage rate with the first preset value, the first preset value is in the range of 2 kPa / min to 5 kPa / min.

5. The detection method of the battery cell according to claim 2, characterized in that, In the step of calculating the preliminary test leakage rate of the battery cell according to the first pressure holding duration reaching a first preset duration, the first preset duration is in the range of 60 seconds to 180 seconds.

6. The detection method of the battery cell according to claim 2, wherein, In the step of calculating the preliminary test leakage rate of the battery cell according to the first pressure holding duration reaching a first preset duration, it includes: Obtaining a first pressure value of the battery cell at the end of the first vacuum pumping; Obtaining a second pressure value of the battery cell when the first pressure holding duration reaches the first preset duration; Calculating a first difference between the first pressure value and the second pressure value, and taking the absolute value of the first difference as the first pressure difference; Calculating a first ratio of the first pressure difference to the first preset duration, where the first ratio is the preliminary test leakage rate.

7. The detection method of the battery cell according to claim 1, wherein, Under a second test condition, performing a negative pressure retest on the battery cells that pass the preliminary test and screening out the battery cells that pass the retest. Among them, the second test condition includes evacuating the battery cell to a second preset negative pressure, the absolute value of the second preset negative pressure is greater than the absolute value of the first preset negative pressure, and the steps that under the second preset negative pressure, the electrolyte in the battery cell enters the negative pressure cup include: Performing a second vacuum pumping operation on the battery cells that pass the preliminary test; Ending the second vacuum pumping operation according to the internal pressure of the battery cell reaching the second preset negative pressure; Perform a second pressure holding operation on the battery cell and time the pressure holding process; Calculate the re - leak rate of the battery cell according to the second pressure holding duration reaching the second preset duration; Screen whether the re - tested battery cells are qualified according to the re - leak rate.

8. The detection method of the battery cell according to claim 7, characterized in that, The step of screening whether the re - test of the battery cell is qualified according to the re - leak rate includes: Compare the re - leak rate with the second preset value; When the re - leak rate is greater than or equal to the second preset value, determine that the battery cell is unqualified in the re - test; When the re - leak rate is less than the second preset value, determine that the battery cell is qualified in the re - test.

9. The detection method of the battery cell according to claim 8, wherein, In the step of comparing the re - leak rate with the second preset value, the second preset value is in the range of 2 kPa / min to 5 kPa / min.

10. The detection method of the battery cell according to claim 6, characterized in that, In the step of calculating the re - leak rate of the battery cell according to the second pressure holding duration reaching the second preset duration, the second preset duration is in the range of 60 seconds to 180 seconds.

11. The detection method of the battery cell according to claim 7, wherein, In the step of calculating the re - leak rate of the battery cell according to the second pressure holding duration reaching the second preset duration, it includes: Obtain the third pressure value of the battery cell at the end of the second vacuum pumping; Obtain the fourth pressure value of the battery cell when the second pressure holding duration reaches the second preset duration; Calculate the second difference between the third pressure value and the fourth pressure value, and take the absolute value of the second difference as the second pressure difference; Calculate the second ratio of the second pressure difference to the second preset duration, where the second ratio is the re - leak rate.

12. The detection method of the battery cell according to any one of claims 1 to 11, characterized in that, Under the first test condition, perform a negative pressure initial test on the battery cell and screen out the battery cells that are qualified in the initial test. Among them, the first test condition includes the steps of pumping the battery cell to the first preset negative pressure, and under the first preset negative pressure, the electrolyte in the battery cell does not enter the negative pressure cup, including: Obtain the type of the battery cell; Match the test negative pressure in the negative pressure database according to the type of the battery cell, and calibrate the test negative pressure as the first preset negative pressure.

13. The detection method of the battery cell according to claim 12, characterized in that, In the step of matching the test negative pressure in the negative pressure database according to the type of the battery cell and calibrating the test negative pressure as the first preset negative pressure, the establishment step of the negative pressure database includes: Perform vacuum pumping tests on multiple different types of battery cells to obtain multiple test negative pressures; Establish a mapping relationship between the type of the battery cell and the test negative pressure to form a negative pressure database.

14. The detection method of the battery cell according to claim 13, characterized in that, In the step of performing vacuum pumping tests on multiple different types of battery cells to obtain multiple test negative pressures, the vacuum pumping test includes: Set the battery cell on the formation equipment; Perform a vacuum pumping operation on the battery cell to make the electrolyte in the battery cell enter the negative pressure cup of the formation equipment; Stop the vacuum pumping operation on the battery cell according to the pressure in the battery cell reaching the calibrated negative pressure, where the absolute value of the calibrated negative pressure is greater than the absolute value of the second preset negative pressure; Increase the internal pressure of the battery cell to make the electrolyte in the negative pressure cup flow back into the interior of the battery cell, and detect the current liquid level in the negative pressure cup and the current pressure value of the battery cell; When the current liquid level is zero, record the current pressure value as the test negative pressure.

15. A formation device, characterized in that, The formation equipment is used to implement the detection method of the battery cell according to any one of claims 1 to 14.

16. A battery production line, characterized in that, Including the formation equipment according to claim 15.

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