Testing method and device for moisture content in battery cells

Abstract

The present application provides a method and device for testing the moisture content of battery cells, the method comprising: before the battery cells are baked, the battery cells are divided into trays to obtain at least two groups of battery cells; the interlayer spacing and stagnation time of multiple battery cells in the same group of battery cells are obtained; the first battery cell and the second battery cell are determined according to the interlayer spacing and stagnation time of multiple battery cells, the interlayer spacing of the first battery cell is the smallest, and the stagnation time of the second battery cell is the longest; the target battery cell is determined according to the first battery cell and the second battery cell, the target battery cell is the most difficult battery cell to bake among the multiple battery cells; fake batteries are prepared according to the target batteries, the fake batteries are simulated batteries for moisture testing; and the fake batteries are tested for moisture. The method provided by the present application helps to solve the problem that there are individual differences and sampling position differences in battery cell moisture test samples, which lead to test fluctuations and affect the accuracy of test results.

Description

Technical Field

[0001] The present application relates to the field of energy storage cells, and in particular to a method and device for testing the moisture content of a cell. Background Art

[0002] In the process of battery cell production and manufacturing, water content is an important indicator for testing battery cell quality. The moisture test of battery cells is to test the moisture content of the electrodes and diaphragms inside the battery cells. The moisture test of battery cells usually adopts sampling detection. Defective or scrapped battery cells in the same batch of battery cells are selected, disassembled, and the electrodes at the specified position are extracted, and then placed in the Karl Fischer tester for testing. However, there are individual differences and sampling position differences in the battery cell moisture test samples, which lead to test fluctuations and affect the accuracy of the test results. Therefore, a method for testing the moisture content of battery cells is needed, so that the battery cells undergoing moisture testing need to be representative, so that the test results can be correct and can represent other battery cells. Summary of the invention

[0003] The present application provides a method and device for testing the moisture content of a battery cell, which helps to solve the problem that individual differences and sampling position differences exist in battery cell moisture test samples, leading to test fluctuations and affecting the accuracy of test results.

[0004] In a first aspect, the present application provides a method for testing the moisture content of a battery cell, comprising:

[0005] Before the battery cells are baked, the battery cells are divided into trays to obtain at least two groups of battery cells;

[0006] Get the interlayer spacing and idle time of multiple cells in the same group of cells;

[0007] Determine a first battery cell and a second battery cell according to the interlayer spacing and idle time of the plurality of battery cells, wherein the interlayer spacing of the first battery cell is the smallest and the idle time of the second battery cell is the longest;

[0008] Determine a target battery cell according to the first battery cell and the second battery cell, wherein the target battery cell is the most difficult battery cell to bake among the multiple battery cells;

[0009] Prepare a dummy battery cell according to the target battery cell, wherein the dummy battery cell is a simulated battery cell for moisture testing;

[0010] The fake battery cell is subjected to a moisture test.

[0011] In a second aspect, the present application provides a battery cell moisture testing device, comprising:

[0012] A tray separation module is used to separate the battery cells into trays before the battery cells are baked to obtain at least two groups of battery cells;

[0013] An acquisition module, used to acquire the interlayer spacing and idle time of multiple cells in the same group of cells;

[0014] Determine a target cell module, used to determine a first cell and a second cell according to the interlayer spacing and sluggish time of the multiple cells, wherein the interlayer spacing of the first cell is the smallest and the sluggish time of the second cell is the longest; determine a target cell according to the first cell and the second cell, wherein the target cell is the cell that is most difficult to bake among the multiple cells;

[0015] A preparation module, used for preparing a dummy battery cell according to the target battery cell, wherein the dummy battery cell is a simulated battery cell for moisture testing;

[0016] The moisture testing module is used to perform a moisture test on the fake battery cell.

[0017] Compared with the prior art, this application has at least the following technical effects:

[0018] The present application provides a method for testing the moisture content of battery cells. Before the battery cells are baked, the battery cells are divided into discs to obtain at least two groups of battery cells. The battery cells with the smallest interlayer spacing and the battery cells with the longest stagnation time in the same group of battery cells are determined through characteristic values ​​of the battery cells, including interlayer spacing (determined by winding tension parameters and hot pressing pressure parameters) and stagnation time. The battery cells with the smallest interlayer spacing and the longest stagnation time in the same group of battery cells are determined. The battery cells that are most difficult to bake in the same group are determined. Fake batteries are made based on the batteries that are most difficult to bake, that is, simulated batteries for moisture testing are made, and the moisture test is performed on the fake batteries. On the one hand, fake batteries are made to replace real batteries for moisture testing to reduce the loss of real batteries. On the other hand, the most difficult battery to bake is found out according to the characteristic values ​​of the same group of batteries, and fake batteries are made based on the most difficult battery to bake for moisture testing. If the moisture test result of the fake battery is qualified, it means that the moisture test result of the group of batteries is qualified, which makes the moisture test result of the fake battery more representative, and helps to solve the problem that there are individual differences and sampling position differences in battery moisture test samples, which lead to test fluctuations and affect the accuracy of the test results. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 A schematic diagram of a flow chart of a method for testing moisture in a battery cell provided in an embodiment of the present application;

[0020] Figure 2 A schematic diagram of the structure of a fake battery cell provided in an embodiment of the present application;

[0021] Figure 3 A schematic diagram of the structure of the positive electrode sheet provided in an embodiment of the present application;

[0022] Figure 4 A schematic diagram of the structure of a battery cell moisture testing device provided in an embodiment of the present application. DETAILED DESCRIPTION

[0023] In the embodiments of the present application, unless otherwise specified, the character " / " indicates that the objects before and after the association are in an or relationship. For example, A / B can represent A or B. "And / or" describes the association relationship of the associated objects, indicating that three relationships can exist. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone.

[0024] It should be pointed out that the words "first", "second", etc. involved in the embodiments of the present application are only used to distinguish the description purpose, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated, nor can they be understood as indicating or implying order.

[0025] In the embodiments of the present application, "at least one" means one or more, and "more" means two or more. In addition, "at least one of the following" or similar expressions refers to any combination of these items, which may include any combination of single items or plural items. For example, at least one of A, B, or C can represent: A, B, C, A and B, A and C, B and C, or A, B and C. Among them, each of A, B, and C can be an element itself, or a set containing one or more elements.

[0026] In the embodiments of the present application, "exemplary", "in some embodiments", "in another embodiment", etc. are used to indicate examples, illustrations or descriptions. Any embodiment or design described as "exemplary" in the present application should not be interpreted as being more preferred or more advantageous than other embodiments or designs. Specifically, the use of the word "exemplary" is intended to present concepts in a concrete way.

[0027] In the embodiments of the present application, "of", "corresponding", and "corresponding" can sometimes be used interchangeably. It should be noted that when the distinction between them is not emphasized, the meanings to be expressed are consistent. In the embodiments of the present application, communication and transmission can sometimes be used interchangeably. It should be noted that when the distinction between them is not emphasized, the meanings to be expressed are consistent. For example, transmission can include sending and / or receiving, which can be a noun or a verb.

[0028] The equal to involved in the embodiments of the present application can be used in conjunction with greater than, and is applicable to the technical solution adopted when greater than, and can also be used in conjunction with less than, and is applicable to the technical solution adopted when less than. It should be noted that when equal to is used in conjunction with greater than, it cannot be used in conjunction with less than; when equal to is used in conjunction with less than, it cannot be used in conjunction with greater than.

[0029] At present, the moisture test of battery cells usually adopts sampling detection. The defective or scrapped battery cells in the same batch are selected, disassembled, and the pole pieces at the specified position are extracted, and then put into the Karl Fischer tester for testing. The current moisture test is an offline moisture test, which mainly uses the residual moisture value of the sample heated at 170°C by the moisture tester as the standard. The conventional standard is ≤400ppm for mixed samples. However, there are individual differences and sampling location differences in the battery cell moisture test samples, which leads to test fluctuations and affects the accuracy of the test results.

[0030] Based on the above problems, an embodiment of the present application proposes a method for testing the moisture content of a battery cell, which helps to solve the problem that individual differences and sampling position differences in battery cell moisture test samples lead to test fluctuations and affect the accuracy of the test results.

[0031] like Figure 1 As shown, Figure 1 The flowchart of the method for testing the moisture content of a battery cell provided in the embodiment of the present application specifically includes the following steps:

[0032] Step S11, before the battery cells are baked, the battery cells are divided into trays to obtain at least two groups of battery cells.

[0033] Specifically, before the cells are baked, they can be randomly divided into trays according to the number of cells accommodated in the baking tray to obtain at least two groups of cells. Optionally, the cells can also be divided into trays according to the interlayer spacing or stagnation time of the cells to obtain at least two groups of cells, the interlayer spacing or stagnation time of the cells in the same group of cells are within the same range, and the interlayer spacing or stagnation time of the cells in different groups of cells are in different ranges. For example, the cells are grouped according to the interlayer spacing range of 20-50um, 50-100um, 100-150um, and 150-200um, to obtain the first group of cells (interlayer spacing range of 20-50um), the second group of cells (interlayer spacing range of 50-100um), the third group of cells (interlayer spacing range of 100-150um), and the fourth group of cells (interlayer spacing range of 150-200um); or the cells are grouped according to the idle time range of 0-6h, 6-12h, 12-18h, and 18-24h, to obtain the first group of cells (idle time range of 0-6h), the second group of cells (idle time range of 6-12h), the third group of cells (idle time range of 12-18h), and the fourth group of cells (idle time range of 18-24h). It is understandable that the number and basis of grouping can be set according to actual conditions, and this application does not limit this.

[0034] The present application divides the cells into trays according to the interlayer spacing or sluggish time of the cells, and can group cells with similar baking difficulty. The baking difficulty of cells in different groups is different, which helps to reduce the difference in moisture between the cells that are most difficult to bake (i.e., the target cells) and the cells in the same group. Then, fake cells are made according to the cells that are most difficult to bake for moisture testing. If the moisture test result of the fake cells is qualified, it means that the moisture test result of the group of cells is qualified, so that the moisture test result of the fake cells can better represent the moisture test result of the corresponding entire group of cells. In addition, if random grouping is adopted, due to the large difference in moisture between the cells in the same group, there are relatively more groups of cells with unqualified test results, and it is necessary to increase the baking time for more groups of cells. If the cells are grouped according to the difficulty of baking, the moisture test result of the group of cells that are easier to bake is qualified, and the moisture test of the group of cells that are less easy to bake is unqualified. Therefore, it is only necessary to increase the baking time for the group of cells that fail the moisture test, which helps to reduce power consumption compared with random grouping. Furthermore, if the moisture content of the same group of battery cells varies greatly, the moisture test results of the fake battery cells will not be significantly different from the moisture test results of the entire group of battery cells. After increasing the baking time, the battery cells with qualified moisture content will be easily over-baked, affecting the battery performance.

[0035] Step S12, obtaining the interlayer spacing and idle time of multiple battery cells in the same group of battery cells.

[0036] Specifically, the battery cell moisture testing system performs closed-loop collection of the interlayer spacing and sluggish duration of multiple battery cells in the same group of battery cells, thereby obtaining the interlayer spacing and sluggish duration of multiple battery cells. Among them, the interlayer spacing refers to the vertical distance between adjacent electrode layers or diaphragm layers in the battery cell, and the interlayer spacing can be calculated by the overall thickness of the battery cell and the number of film layers measured by the machine. For example, the battery cell includes multiple positive electrode sheets, negative electrode sheets, and diaphragms between the positive electrode sheets and the negative electrode sheets. The interlayer spacing of the battery cell is obtained by dividing the overall thickness of the battery cell by the number of film layers of the diaphragm. The preparation process of the battery cell includes winding, hot pressing, liquid injection, standing and baking. The preparation process parameters of the battery cell include winding parameters, hot pressing parameters, standing time, baking parameters, stagnation time, etc. The winding parameters include winding tension parameters and winding deviation parameters. The winding tension parameter is the tension value of the battery cell winding material during the winding process. The winding deviation parameter is the distance value of the battery cell winding material deviating from the reference position during the winding process; the hot pressing parameters include hot pressing temperature, hot pressing time and hot pressing pressure; the baking parameters include baking time and baking temperature; the stagnation time refers to the time when the battery cell is in the whole production and preparation process. The length of the waiting state and the sluggish time may occur in multiple links. For example, between different production processes, the battery cell may need to wait for the start of the next process, such as the electrode after coating may need to wait for the start of the rolling process; in some quality inspection links, the battery cell may need to wait for the test results to determine whether it has passed the test or needs to be reworked; in the maintenance or failure link, when the production equipment undergoes planned maintenance or unexpected failure, the battery cell may need to wait for the equipment to resume operation; in the material supply link, if the material supply of a certain production link is not available, the production of the battery cell may also be suspended until the material arrives. The extension of the sluggish time will increase production costs, reduce production efficiency, and may affect the performance of the battery cell.

[0037] Studies have shown that the winding tension parameters, hot pressing pressure parameters and sluggish time of the battery cell will affect the moisture content of the battery cell. Among them, the winding tension parameters and hot pressing pressure parameters of the battery cell affect the interlayer spacing of the battery cell, that is, the size of the interlayer spacing depends on the tightness of the winding and hot pressing. The larger the winding tension parameters and hot pressing pressure parameters, the smaller the interlayer spacing, the more difficult the battery cell is to bake, and the higher the moisture content of the battery cell. The longer the sluggish time of the battery cell, the longer the battery cell is in a waiting state, which will increase the risk of the battery cell being exposed to adverse environmental conditions (such as high humidity environments), thereby increasing the moisture content of the battery cell. In the present application, the winding tension parameter range can be 350kgf-800kgf, the hot pressing pressure parameter range can be 5t-10t, and the interlayer spacing range of the prepared battery cell can be 10um-200um.

[0038] Step S13, determining a first battery cell and a second battery cell according to the interlayer spacing and idle time of the plurality of battery cells, wherein the interlayer spacing of the first battery cell is the smallest, and the idle time of the second battery cell is the longest.

[0039] Specifically, according to the interlayer spacing and idle time of multiple battery cells in the same group of battery cells, the battery cell with the smallest interlayer spacing and the battery cell with the longest idle time in the group are determined, that is, the first battery cell and the second battery cell in the group are confirmed.

[0040] Step S14: determining a target battery cell according to the first battery cell and the second battery cell, wherein the target battery cell is the most difficult battery cell to bake among the plurality of battery cells.

[0041] In the actual moisture testing process, the moisture content must reach a certain level to be qualified. A qualified moisture value of the moisture test cell test represents that the entire furnace is qualified. However, it is possible that the moisture content of the moisture test cell is qualified, but due to the long stagnation time in the entire furnace, the moisture content of the incoming materials is high, or the winding and hot pressing processes fluctuate, the moisture content of some cells does not meet the standard after baking, that is, the moisture test cell is not representative. Therefore, the present application proposes to prepare fake cells based on the most difficult to bake cells for moisture testing, and the fake cells are tested for moisture. If the moisture test results of the fake cells are qualified, it means that the moisture test results of the entire furnace of cells are qualified, ensuring that the entire furnace of cells will not affect the true moisture value due to the long stagnation time of some cells (although the moisture test cells are qualified, the moisture content of some cells in the entire furnace is unqualified), making the moisture test results of the fake cells more representative.

[0042] Furthermore, the present application determines the target battery cell through the first battery cell and the second battery cell, that is, determines the battery cell that is most difficult to bake among multiple battery cells in the same group through the battery cell with the smallest interlayer spacing and the battery cell with the longest stagnation time. Because the battery cell that is most difficult to bake may be the battery cell with the smallest interlayer spacing or the battery cell with the longest stagnation time, the present application combines the influencing factors of the two to determine the target battery cell, so that the target battery cell is more representative and the moisture test results are more accurate.

[0043] Optionally, if the first battery cell and the second battery cell are the same battery cell, the target battery cell is the first battery cell; or if the first battery cell and the second battery cell are not the same battery cell, the interlayer spacing of the target battery cell is the interlayer spacing of the first battery cell, and the moisture value of the target battery cell before the moisture test is equal to the moisture value of the second battery cell before the moisture test. That is, if the battery cell with the smallest interlayer spacing also meets the condition of the longest stagnation time, then the battery cell is confirmed as the target battery cell; if the battery cell with the smallest interlayer spacing is not the battery cell with the longest stagnation time, for example, the battery cell with the smallest interlayer spacing is battery cell A, and the battery cell with the longest stagnation time is battery cell B, then the interlayer spacing of the target battery cell is determined to be the interlayer spacing of battery cell A, and the moisture value of the target battery cell before the moisture test is equal to the moisture value of battery cell B before the moisture test, so as to ensure that the target battery cell simultaneously meets the conditions of the smallest interlayer spacing and the longest stagnation time.

[0044] Step S15, preparing a dummy battery cell according to the target battery cell, wherein the dummy battery cell is a simulated battery cell for moisture testing.

[0045] Specifically, Figure 2 As shown, Figure 2 The structure diagram of the fake battery cell provided in the embodiment of the present application, the structure of the fake battery cell 1 includes an acrylic plate 14, a negative electrode sheet 13, a diaphragm 12, a positive electrode sheet 11, a diaphragm 12, a negative electrode sheet 13 and an acrylic plate 14, that is, the positive electrode sheet 14 is in the middle, the negative electrode sheets 13 are arranged at both ends of the positive electrode sheet, the diaphragm 12 is arranged between the positive electrode sheet 14 and the negative electrode sheet 13, and the acrylic plate 14 is arranged at the outermost sides of both ends. Among them, the acrylic plates 14 on both sides can be clamped by clips to clamp the positive electrode sheet 11, the negative electrode sheet 13 and the diaphragm 12, and the acrylic plates 14 can also be fixed and clamped with torque screws. Specifically, an acrylic plate hook is set under the cover plate of the battery cell, and a torque screw is provided on the edge of the acrylic plate, and the acrylic plates are fixed and clamped with torque screws. Negative electrode sheet-diaphragm-positive electrode sheet-diaphragm-negative electrode sheet is the minimum structure of the battery cell for testing moisture. This application sets the structure of the dummy battery cell as the minimum test unit, so that it can be used for moisture testing while also helping to reduce material loss. The size of the positive electrode sheet of the dummy battery cell is set to be the same as the size of the positive electrode sheet in the target battery cell without the arc area. Figure 3 As shown, Figure 3 A schematic diagram of the structure of the positive electrode sheet provided in the embodiment of the present application, Figure 3 The Y area in the figure is the area without the arc area, and the two sides of the Y area are arc areas. The present application sets the size of the positive electrode sheet of the fake battery cell to be the same as the size of the positive electrode sheet in the target battery cell without the arc area, because the interlayer spacing in the non-arc area is small, and usually unqualified moisture is manifested as unqualified moisture in the positive electrode. Therefore, the size of the positive electrode sheet of the fake battery cell is set to be the size of the positive electrode sheet of the target battery cell without the arc area, thereby forming a moisture test sample, making the test sample more representative, and further improving the accuracy of the moisture test result.

[0046] Adjust the torque screws between the acrylic plates to adjust the interlayer spacing of the dummy cells to the interlayer spacing of the target cells. That is, the interlayer spacing of the dummy cells can be adjusted to the interlayer spacing corresponding to the target cells using the torque screws. After the dummy cells are made, put them into the aluminum shell, cover them with the cover plate, and seal the gap between the cover plate and the shell with tape.

[0047] The present application utilizes torque screws between acrylic plates to flexibly adjust the interlayer spacing of dummy cells, so that the interlayer spacing of the manufactured dummy cells is consistent with that of the target cells.

[0048] In some optional embodiments, the method provided by the present application further includes: judging whether to perform moisture compensation on the fake cell according to the sluggish time of the target cell. Too long an sluggish time will increase the moisture content of the cell and affect the accuracy of the moisture test result. If the sluggish time of the target cell is too long, the fake cell needs to be compensated for moisture before the moisture test, so that the fake cell is closer to the actual moisture of the target cell and the accuracy of the moisture test is improved.

[0049] Based on this, the present application proposes to determine whether to compensate for moisture in the fake battery cell according to the sluggish time of the target battery cell. Optionally, the judgment condition is that moisture compensation is required when the sluggish time is greater than 36 hours (it can also be 24, 48 hours, etc., which can be set according to actual needs).

[0050] Specifically, moisture compensation includes introducing an inert gas with moisture into the injection port of the dummy battery cell for moisture compensation, mainly to compensate for the moisture absorption during long stagnation time. Optionally, the moisture compensation time (i.e., the time for introducing the gas) is greater than 1 minute and less than or equal to 3 minutes. If the moisture compensation time is too short, moisture compensation cannot be achieved, and if it is too long, it is easy to over-supplement moisture, affecting the moisture test results. In addition to using an inert gas with moisture to compensate for the battery cell, the storage conditions of the battery cell can also be controlled, such as storing it in a high humidity environment, which can prompt the battery cell to absorb moisture, thereby compensating the battery cell for moisture.

[0051] Step S16, performing a moisture test on the fake battery cell.

[0052] Specifically, after the fake battery cell is prepared and baked together with the battery cells in the same group, it is sent to the moisture testing station for heating at a temperature of 170°C for 1 minute. There is a gas path interface above the injection hole of the fake battery cell, through which the moisture gas is discharged, the moisture gas discharged after heating is collected, and the dew point temperature of the moisture gas discharged after heating is detected using a dew point meter to obtain a first dew point temperature.

[0053] The method provided in the present application also includes: obtaining the second dew point temperature of the fake battery cell before the moisture test; determining whether the moisture content of the target battery cell is qualified based on the relationship between the difference between the first dew point temperature and the second dew point temperature and a preset value.

[0054] Optionally, if the difference between the first dew point temperature and the second dew point temperature is less than or equal to the preset value, the moisture content of the target battery cell is qualified; or if the difference between the first dew point temperature and the second dew point temperature is greater than the preset value, the moisture content of the target battery cell is unqualified.

[0055] For example, the preset value is 20, the first dew point temperature is -30, the second dew point temperature is -45, the difference between the first dew point temperature and the second dew point temperature is -30-(-45)=15, and the difference between the first dew point temperature and the second dew point temperature is less than the preset value, then the moisture content of the target battery cell is qualified.

[0056] The battery cell moisture testing method in the related art requires the defective battery cells to be dismantled, and the samples are selected and then placed in a Karl Fischer tester for offline testing. The samples are also required to be heated at 170°C for more than ten minutes to measure the residual moisture value. The present application performs online moisture testing on the entire fake battery cell, and determines whether the moisture content of the target battery cell is qualified through the dew point difference. The test time is short and the operation is convenient.

[0057] This application determines whether the moisture content of the target battery cell is qualified by the dew point difference. Furthermore, if the moisture content of the target battery cell is unqualified, the baking time of the entire group of battery cells corresponding to the target battery cell can be adjusted. By adjusting the baking time, the moisture content of the target battery cell is guaranteed to be qualified. If the moisture content of the target battery cell is qualified, it means that the moisture content of the entire group of battery cells is qualified. For example, according to the moisture test results of the fake battery cell, the moisture content of the corresponding target battery cell is unqualified, then it is necessary to increase the baking time of the entire group of battery cells corresponding to the target battery cell by 2h, that is, bake the entire group of battery cells (including the fake battery cell) again, and test the moisture content of the fake battery cell again after baking until the moisture content of the fake battery cell is qualified.

[0058] In other optional embodiments, machine learning and deep learning algorithms can be used to build a model, with the characteristic values ​​of the battery cell (including winding parameters, hot pressing parameters, interlayer spacing, stagnation time, static time, baking time, etc.) as input, and whether the moisture content of the battery cell is qualified as output. If the moisture content of the battery cell is unqualified, the baking time is automatically adjusted until the moisture content of the battery cell is qualified. Based on this model, the moisture content of the battery cell is monitored in real time in units of furnaces, and the baking time is adjusted in a closed loop to achieve qualified moisture and automatic configuration of the baking time.

[0059] Optionally, the winding parameters and / or hot pressing parameters of other prepared battery cells can be adjusted according to the moisture test results of the battery cells. For example, if the moisture test results of the prepared battery cells are unqualified, the winding tension and / or hot pressing pressure can be reduced, and the interlayer spacing of the battery cells can be increased, so that the battery cells are easier to bake, and the moisture content of the battery cells after baking meets the standards. By reducing the winding tension and / or hot pressing pressure of the battery cells, the moisture content of the battery cells can be qualified without adjusting the baking time (specifically increasing the baking time), thereby reducing the energy consumption generated by the baking process.

[0060] Before the battery cells are baked, the present application divides the battery cells into discs to obtain at least two groups of battery cells; through the characteristic values ​​of the battery cells, including the interlayer spacing (determined by the winding tension parameter and the hot pressing pressure parameter) and the stagnation time, the battery cell with the smallest interlayer spacing and the battery cell with the longest stagnation time in the same group of battery cells are determined, and the battery cell that is most difficult to bake in the same group of battery cells is determined based on the battery cell with the smallest interlayer spacing and the battery cell with the longest stagnation time, and a dummy battery cell is made based on the battery cell that is most difficult to bake, that is, a simulated battery cell for moisture testing is made, and the moisture test is performed on the dummy battery cell. On the one hand, fake batteries are made to replace real batteries for moisture testing to reduce the loss of real batteries. On the other hand, the most difficult battery to bake is found out according to the characteristic values ​​of the same group of battery cells, and fake batteries are made based on the most difficult battery to bake for moisture testing. If the moisture test result of the fake battery is qualified, it means that the moisture test result of the group of battery cells is qualified, which makes the moisture test result of the fake battery more representative, and helps to solve the problem that there are individual differences and sampling position differences in battery moisture test samples, which lead to test fluctuations and affect the accuracy of the test results.

[0061] Based on the same idea, the present application also provides a battery cell moisture testing device, such as Figure 4 This is a schematic diagram of a battery cell moisture testing device provided in an embodiment of this specification. The battery cell moisture testing device 40 mainly includes:

[0062] A tray dividing module 41, which divides the battery cells into trays before the battery cells are baked to obtain at least two groups of battery cells;

[0063] An acquisition module 42 is used to acquire winding tension parameters, hot pressing pressure parameters and stagnation time of multiple battery cells;

[0064] A target cell module 43 is used to determine a first cell according to the winding tension parameters and hot pressing pressure parameters of the multiple cells, wherein the interlayer spacing of the first cell is the smallest, and the interlayer spacing corresponds to the winding tension parameters and the hot pressing pressure parameters one by one; determine a second cell according to the idle time of the multiple cells, wherein the idle time of the second cell is the longest; determine a target cell according to the first cell and the second cell, wherein the target cell is the cell that is the most difficult to bake among the multiple cells;

[0065] A preparation module 44 is used to prepare a dummy battery cell according to the target battery cell, wherein the dummy battery cell is a simulated battery cell for moisture testing;

[0066] The moisture testing module 45 is used to perform a moisture test on the fake battery cell.

[0067] In one possible implementation, the disk partitioning module 41 is further used for:

[0068] The battery cells are divided into plates according to the interlayer spacing or idle time of the battery cells to obtain at least two groups of battery cells, the interlayer spacing or idle time of the battery cells in the same group of battery cells are within the same range, and the interlayer spacing or idle time of the battery cells in different groups of battery cells are in different ranges.

[0069] In one possible implementation, determining the target battery cell module 43 is further used for:

[0070] If the first battery cell and the second battery cell are the same battery cell, the target battery cell is the first battery cell; or

[0071] If the first battery cell and the second battery cell are not the same battery cell, the interlayer spacing of the target battery cell is the interlayer spacing of the first battery cell, and the moisture value of the target battery cell before the moisture test is equal to the moisture value of the second battery cell before the moisture test.

[0072] In one possible implementation, the preparation module 44 is further used for:

[0073] The structure of the dummy battery cell includes an acrylic plate, a negative electrode sheet, a separator, a positive electrode sheet, a separator, a negative electrode sheet and an acrylic plate. The size of the positive electrode sheet of the dummy battery cell is the same as the size of the positive electrode sheet of the target battery cell without the arc-shaped area. The acrylic plates are fixed with torque screws.

[0074] The torque screw is adjusted to adjust the interlayer spacing of the dummy battery cell to the interlayer spacing of the target battery cell.

[0075] In one possible implementation, the battery cell moisture testing device 40 further includes:

[0076] The moisture compensation module is used to determine whether to perform moisture compensation on the dummy battery cell according to the idle time of the target battery cell; and is also used to introduce an inert gas containing moisture into the injection port of the dummy battery cell for moisture compensation.

[0077] In one possible implementation, the moisture compensation time is greater than 1 minute and less than or equal to 3 minutes.

[0078] In one possible implementation, the moisture testing module 45 is also used to: place the fake battery cell in a moisture testing station for heating at a heating temperature of 170°C for a heating time of 1 minute, collect the moisture gas discharged after heating, and use a dew point meter to detect the dew point temperature of the moisture gas discharged after heating to obtain a first dew point temperature.

[0079] In one possible implementation, the battery cell moisture testing device 40 further includes:

[0080] A judgment module is used to obtain the second dew point temperature of the dummy battery cell before the moisture test; and determine whether the moisture of the target battery cell is qualified according to the relationship between the difference between the first dew point temperature and the second dew point temperature and a preset value, including:

[0081] If the difference between the first dew point temperature and the second dew point temperature is less than or equal to the preset value, the moisture content of the target battery cell is qualified; or

[0082] If the difference between the first dew point temperature and the second dew point temperature is greater than the preset value, the moisture content of the target battery cell is unqualified.

[0083] Figure 4 The battery cell moisture testing device 40 provided in the illustrated embodiment can be used to implement the technical solution of the method embodiment shown in the present application. Its implementation principle and technical effects can be further referred to the relevant description in the method embodiment.

[0084] The above is only a specific implementation of the present application. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application. The protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A method for testing the moisture content of a battery cell, characterized in that: The method comprises: Before the battery cells are baked, the battery cells are divided into trays to obtain at least two groups of battery cells; Get the interlayer spacing and idle time of multiple cells in the same group of cells; Determine a first battery cell and a second battery cell according to the interlayer spacing and idle time of the plurality of battery cells, wherein the interlayer spacing of the first battery cell is the smallest and the idle time of the second battery cell is the longest; Determine a target battery cell according to the first battery cell and the second battery cell, wherein the target battery cell is the most difficult battery cell to bake among the multiple battery cells; Prepare a dummy battery cell according to the target battery cell, wherein the dummy battery cell is a simulated battery cell for moisture testing; Conducting a moisture test on the fake battery cell; The determining the target battery cell according to the first battery cell and the second battery cell includes: If the first battery cell and the second battery cell are the same battery cell, the target battery cell is the first battery cell; or If the first battery cell and the second battery cell are not the same battery cell, the interlayer spacing of the target battery cell is the interlayer spacing of the first battery cell, and the moisture value of the target battery cell before the moisture test is equal to the moisture value of the second battery cell before the moisture test; The step of preparing a dummy battery cell according to the target battery cell comprises: The structure of the dummy battery cell includes an acrylic plate, a negative electrode sheet, a separator, a positive electrode sheet, a separator, a negative electrode sheet and an acrylic plate. The size of the positive electrode sheet of the dummy battery cell is the same as the size of the positive electrode sheet of the target battery cell without the arc-shaped area. The acrylic plates are fixed with torque screws. The torque screw is adjusted to adjust the interlayer spacing of the dummy battery cell to the interlayer spacing of the target battery cell.

2. The method according to claim 1, characterized in that: The step of dividing the battery cells into discs to obtain at least two groups of battery cells comprises: The battery cells are divided into plates according to the interlayer spacing or idle time of the battery cells to obtain at least two groups of battery cells, the interlayer spacing or idle time of the battery cells in the same group of battery cells are within the same range, and the interlayer spacing or idle time of the battery cells in different groups of battery cells are in different ranges.

3. The method according to claim 1, characterized in that The method further comprises, Whether to perform moisture compensation on the dummy battery cell is determined according to the idle time of the target battery cell.

4. The method according to claim 3, characterized in that The moisture compensation includes: Inert gas containing moisture is introduced into the liquid injection port of the dummy battery cell to compensate for moisture.

5. The method according to claim 4, characterized in that The moisture compensation time is greater than 1 minute and less than or equal to 3 minutes.

6. The method according to claim 1, characterized in that The step of testing the moisture content of the fake battery cell comprises: The dummy battery cell is placed in a moisture testing station for heating at a temperature of 170° C. for a heating time of 1 minute, the moisture gas discharged after heating is collected, and the dew point temperature of the moisture gas discharged after heating is detected using a dew point meter to obtain a first dew point temperature.

7. The method according to claim 6, characterized in that The method further comprises: Obtaining a second dew point temperature of the dummy battery cell before the moisture test; Determining whether the moisture content of the target battery cell is qualified according to the relationship between the difference between the first dew point temperature and the second dew point temperature and a preset value, including: if the difference between the first dew point temperature and the second dew point temperature is less than or equal to the preset value, the moisture content of the target battery cell is qualified; or If the difference between the first dew point temperature and the second dew point temperature is greater than the preset value, the moisture content of the target battery cell is unqualified.

8. A battery cell moisture testing device, characterized in that: The device comprises: A tray separation module is used to separate the battery cells into trays before the battery cells are baked to obtain at least two groups of battery cells; An acquisition module, used to acquire the interlayer spacing and idle time of multiple cells in the same group of cells; Determine a target cell module, used to determine a first cell and a second cell according to the interlayer spacing and sluggish time of the multiple cells, wherein the interlayer spacing of the first cell is the smallest and the sluggish time of the second cell is the longest; determine a target cell according to the first cell and the second cell, wherein the target cell is the cell that is most difficult to bake among the multiple cells; A preparation module, used for preparing a dummy battery cell according to the target battery cell, wherein the dummy battery cell is a simulated battery cell for moisture testing; A moisture testing module, used for performing a moisture test on the fake battery cell; The target cell module is also used to: If the first battery cell and the second battery cell are the same battery cell, the target battery cell is the first battery cell; or If the first battery cell and the second battery cell are not the same battery cell, the interlayer spacing of the target battery cell is the interlayer spacing of the first battery cell, and the moisture value of the target battery cell before the moisture test is equal to the moisture value of the second battery cell before the moisture test; The preparation module is also used for: The structure of the dummy battery cell includes an acrylic plate, a negative electrode sheet, a separator, a positive electrode sheet, a separator, a negative electrode sheet and an acrylic plate. The size of the positive electrode sheet of the dummy battery cell is the same as the size of the positive electrode sheet of the target battery cell without the arc-shaped area. The acrylic plates are fixed with torque screws. The torque screw is adjusted to adjust the interlayer spacing of the dummy battery cell to the interlayer spacing of the target battery cell.

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