Method for determining required liquid retention amount of battery cell

Abstract

The application relates to a method for determining the required liquid reserve amount of an electric core. The method comprises the following steps: obtaining the liquid-free and water-free mass of the electric core; obtaining the stored free electrolyte mass and the liquid-free and water-free mass of the electric core at multiple liquid level heights; determining the mapping relationship between the liquid level height of the free electrolyte in the electric core and the mass of the free electrolyte in the electric core according to the multiple liquid level heights, the stored free electrolyte mass at the multiple liquid level heights and the liquid-free and water-free mass; obtaining a safety liquid level height; determining the safety free electrolyte mass of the free electrolyte in the electric core associated with the safety liquid level height according to the safety liquid level height and the mapping relationship; and determining the required liquid reserve amount of the electric core according to the liquid-free and water-free mass, the liquid-free and water-free mass and the safety free electrolyte mass. The method provided by the application is short in time consumption, low in battery development cycle and progress, low in electric core research and development cost, does not need repeated verification, and is high in accuracy of the obtained required liquid reserve amount of the electric core.

Description

Technical Field

[0001] This application relates to the field of battery technology, specifically to a method for determining the required liquid retention capacity of a battery cell. Background Technology

[0002] A lithium-ion battery cell mainly consists of a positive electrode, a negative electrode, a separator, and an electrolyte. To ensure the full capacity of the active materials on the positive and negative electrodes, the electrolyte must completely wet the positive and negative electrodes and the separator to form a lithium-ion conductive path between them. Insufficient electrolyte in the cell will inevitably lead to inadequate wetting of some active material particles on the positive and negative electrodes, increased interfacial impedance, reduced capacity, and decreased cycle life. Excessive electrolyte will increase manufacturing costs and make the cell casing more susceptible to corrosion, potentially affecting battery safety. Therefore, determining the appropriate electrolyte level and retention capacity is crucial.

[0003] Traditional methods for determining the required liquid retention capacity of battery cells are cumbersome and time-consuming, severely impacting production schedules. Furthermore, these methods can increase the cyclic and safety risks associated with the battery cell system. Summary of the Invention

[0004] Therefore, it is necessary to provide a new method for determining the required liquid retention capacity of a battery cell to address the above-mentioned problems.

[0005] A method for determining the required liquid retention capacity of a battery cell, the method comprising:

[0006] Obtain the electrolyte and water removal mass of the battery cell; the electrolyte and water removal mass is the mass of the battery cell after removing the electrolyte and water from its electrode assembly;

[0007] The mass of the battery cell with free electrolyte and the mass of the battery cell without free electrolyte are obtained at multiple liquid level heights. Based on the multiple liquid level heights, the mass of the battery cell with free electrolyte and the mass of the battery cell without free electrolyte, a mapping relationship between the liquid level height of the battery cell and the mass of the free electrolyte in the battery cell is determined. The mass of the battery cell with free electrolyte is the mass of the battery cell after the presence of free electrolyte and the saturation of its electrode assembly. The mass of the battery cell without free electrolyte is the mass of the battery cell after the removal of free electrolyte and the saturation of its electrode assembly.

[0008] Obtain the safe liquid level height, and determine the safe free mass of the free electrolyte in the cell associated with the safe liquid level height based on the safe liquid level height and the mapping relationship;

[0009] The required liquid retention capacity of the battery cell is determined based on the liquid and water removal quality, the full absorption quality, and the safe free ionization quality.

[0010] In some embodiments, obtaining the dehydration and dewatering quality of the battery cell includes:

[0011] Obtain an unfilled battery cell, wherein the unfilled battery cell is the battery cell before it was in the liquid-filled state;

[0012] The unfilled battery cell is baked until its electrode assembly is dried to obtain a first intermediate battery cell.

[0013] Weigh the first intermediate cell to obtain the dehydration and dewatering mass of the cell.

[0014] In some embodiments, the fully absorbed mass of the battery cell containing free electrolyte and the fully absorbed mass of the battery cell without free electrolyte are obtained at multiple liquid level heights. Based on the multiple liquid level heights, the fully absorbed mass of the battery cell containing free electrolyte at the multiple liquid level heights, and the fully absorbed mass of the battery cell without free electrolyte, a mapping relationship between the liquid level height of the free electrolyte in the battery cell and the mass of the free electrolyte in the battery cell is determined, including:

[0015] Obtain the first intermediate cell and inject electrolyte into the first intermediate cell to obtain the second intermediate cell;

[0016] After the electrode assembly of the second intermediate cell is filled with electrolyte and there is free electrolyte in the second intermediate cell, the free electrolyte in the second intermediate cell is removed multiple times until it is completely removed.

[0017] After each removal, the second intermediate cell is weighed to obtain the full adsorption mass of the current cell and the full adsorption mass of the cell after removal at multiple liquid level heights.

[0018] Based on multiple liquid level heights and the difference between the mass of the ionized electrolyte and the mass of the ionized electrolyte at the multiple liquid level heights, the mapping relationship between the liquid level height of the free electrolyte in the cell and the mass of the free electrolyte is determined.

[0019] In some embodiments, the electrode assembly of the second intermediate cell is saturated with electrolyte, and the second intermediate cell contains free electrolyte, including:

[0020] Electrolyte is injected into the second intermediate cell multiple times, and the cell is left to stand for a preset time after each injection until the electrode assembly of the second intermediate cell is fully saturated with electrolyte and free electrolyte is present in the second intermediate cell.

[0021] In some embodiments, after the electrode assembly of the second intermediate cell is saturated with electrolyte and free electrolyte remains in the second intermediate cell, the free electrolyte in the second intermediate cell is removed multiple times until it is completely removed, including:

[0022] After the electrode assembly of the second intermediate cell is filled with electrolyte and the housing of the second intermediate cell is filled with free electrolyte, multiple liquid level height lines are marked on the outside of the housing of the second intermediate cell along the height direction of the second intermediate cell.

[0023] The free electrolyte in the battery cell is removed multiple times until it is completely removed, by lowering the liquid level of the free electrolyte in the battery cell by a preset number of increments each time.

[0024] In some embodiments, the height difference between two adjacent liquid level height lines is H, where 1cm≤H≤5cm.

[0025] In some embodiments, a syringe or pipette is used to remove the free electrolyte from the battery cell.

[0026] In some embodiments, the liquid level height of the free electrolyte in the cell is defined as x, the mass of the free electrolyte in the cell is defined as y, and the mapping relationship between the liquid level height of the free electrolyte and the mass of the free electrolyte is: y = 11.46x + 1.3778.

[0027] In some embodiments, the height of the battery cell's casing is defined as H1, the safety liquid level height is defined as H2, and H1 / 3≤H2≤H1 / 2.

[0028] In some embodiments, the required liquid retention capacity of the battery cell is defined as m. 保 The amount of liquid and water removed is m 始 The mass of the swimmer is m. 终 The safe free mass is m 游 m 保 =m 终 -m 始 +m 游 .

[0029] Compared with the prior art, this application has the following beneficial effects:

[0030] The method for determining the required liquid retention of the aforementioned battery cell establishes a mapping relationship between the liquid level height and the mass of the free electrolyte within the cell, based on multiple liquid level heights, the mass of the fully absorbed electrolyte at these heights, and the mass of the fully absorbed electrolyte after removal. Then, based on this mapping relationship and a safe liquid level height, the safe free mass of the free electrolyte is determined. Finally, the required liquid retention of the cell is determined based on the mass of the removed electrolyte, the mass of the fully absorbed electrolyte after removal, and the safe free mass. Based on the mass and liquid level height, the required liquid retention of the battery cell can be determined. Compared to traditional methods for obtaining the required liquid retention of a battery cell, this application provides a simpler and more efficient method, significantly reducing the time required and effectively shortening the battery development cycle and schedule, thus lowering the battery cell R&D cost. Furthermore, the method for obtaining the mass and liquid level height is simple and reliable, requiring no repeated verification and contributing to improved accuracy in obtaining the required liquid retention of the battery cell. In addition, the method for determining the required liquid retention of the battery cell in this application reduces both the cycling risk and safety risk of the battery cell system. Attached Figure Description

[0031] Figure 1 This is a flowchart illustrating a method for determining the required liquid retention amount of a battery cell in one embodiment of this application.

[0032] Figure 2 This is a flowchart illustrating a method for determining the required liquid retention amount of a battery cell in another embodiment of this application.

[0033] Figure 3 This is a flowchart illustrating a method for determining the required liquid retention amount of a battery cell in another embodiment of this application.

[0034] Figure 4 This is a flowchart illustrating a method for determining the required liquid retention amount of a battery cell in another embodiment of this application.

[0035] Figure 5 This is a schematic diagram illustrating the mapping relationship between the mass of the free electrolyte and the liquid level height in one embodiment of this application. Detailed Implementation

[0036] To make the above-mentioned objectives, features, and advantages of this application more apparent and understandable, the specific embodiments of this application are described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of this application. However, this application can be implemented in many other ways described herein, and those skilled in the art can make similar modifications without departing from the spirit of this application. Therefore, this application is not limited to the specific embodiments disclosed below.

[0037] In the description of this application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicating the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0038] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0039] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "joining," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise expressly limited. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0040] In this application, unless otherwise expressly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "on top of," and "over" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0041] It should be noted that when an element is referred to as being "fixed to" or "set on" another element, it can be directly on the other element or there may be an intervening element. When an element is considered to be "connected to" another element, it can be directly connected to the other element or there may be an intervening element. The terms "vertical," "horizontal," "upper," "lower," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only possible implementation.

[0042] A lithium-ion battery cell mainly consists of a positive electrode, a negative electrode, a separator, and an electrolyte. To ensure the full capacity of the active materials on the positive and negative electrodes, the electrolyte must completely wet the electrodes and separator to form a lithium-ion conductive path between them. Insufficient electrolyte in the cell will inevitably lead to inadequate wetting of some active material particles, increased interfacial impedance, reduced capacity, and decreased cycle life. Excessive electrolyte will increase manufacturing costs and make the cell casing more susceptible to corrosion, potentially affecting battery safety. Therefore, determining the appropriate electrolyte level and retention capacity is crucial.

[0043] In the existing technology, there are two main types of methods for determining the required liquid retention capacity of battery cells:

[0044] The first method involves calculating the porosity of the positive electrode, negative electrode, and separator, calculating the residual space within the cell casing, and then calculating the electrolyte usage using the electrolyte density. This calculation method is cumbersome and time-consuming, severely impacting production schedules. The second method involves injecting electrolyte into the cell according to multiple injection coefficients, then conducting performance tests on the required electrolyte retention gradient to determine the optimal electrolyte retention. However, this method requires significant testing resources for cyclic testing and is time-consuming. If the cell design is adjusted, retesting and verification are necessary, severely impacting battery development cycles and schedules. Furthermore, this method of determining the required electrolyte retention can easily increase the cyclic and safety risks of the cell system. To alleviate these problems, this application designs a method for determining the required electrolyte retention of a cell, comprising:

[0045] Please see Figure 1 Step S100: Obtain the electrolyte and water removal mass of the battery cell; the electrolyte and water removal mass is the mass of the battery cell after removing the electrolyte and water from its electrode assembly.

[0046] Step S200: Obtain the full-absorbed mass of the cell with free electrolyte at multiple liquid level heights and the full-absorbed mass of the cell without free electrolyte. Based on the multiple liquid level heights, the full-absorbed mass with free electrolyte at multiple liquid level heights, and the full-absorbed mass without free electrolyte, determine the mapping relationship between the liquid level height of the cell and the mass of the free electrolyte in the cell. The full-absorbed mass with free electrolyte is the mass of the cell after the free electrolyte is present and its electrode assembly is fully saturated with electrolyte. The full-absorbed mass without free electrolyte is the mass of the cell after the free electrolyte is removed and its electrode assembly is fully saturated with electrolyte.

[0047] Step S300: Obtain the safe liquid level height, and determine the safe free mass of the free electrolyte in the cell associated with the safe liquid level height based on the safe liquid level height and the mapping relationship;

[0048] Step S400: Determine the required liquid retention amount of the cell based on the liquid and water removal quality, the full absorption quality, and the safe ionization quality.

[0049] Specifically, cell electrolyte retention refers to the amount of electrolyte held inside the cell. Maintaining an appropriate electrolyte retention is crucial for the stability and safety of the battery. The appropriate electrolyte retention within the cell is the required electrolyte retention, which consists of the electrolyte adsorbed by the cell's electrode components and the electrolyte free between the cell's outer shell and the electrode components. The electrolyte free between the cell's outer shell and the electrode components is called free electrolyte.

[0050] The quality of the dehydration of the battery cell can be obtained before or after the cell is injected with electrolyte, depending on the specific circumstances.

[0051] There is a mapping relationship between the liquid level of the free electrolyte in the cell and the mass of the free electrolyte in the cell. Multiple liquid levels of the free electrolyte in the cell are correspondingly associated with multiple masses of the free electrolyte in the cell.

[0052] The safe electrolyte level is the height of the free electrolyte within the battery cell when the electrode assembly is fully saturated with electrolyte. As an example, let the height of the battery cell casing be H1, and the safe electrolyte level be H2, where H1 / 3 ≤ H2 ≤ H1 / 2. Designing the safe electrolyte level within this range maintains the safety and stability of the battery operation.

[0053] When injecting the required amount of electrolyte into the battery cell, the height of the free electrolyte level inside the cell is the safe electrolyte level, which can be obtained through experience or testing.

[0054] Based on the mapping relationship between the liquid level height of the free electrolyte in the cell and the mass of the free electrolyte in the cell, as well as the safe liquid level height, the safe free mass of the free electrolyte associated with the safe liquid level height can be determined.

[0055] In this application, a mapping relationship between the liquid level height and the mass of the free electrolyte within the cell is determined based on multiple liquid level heights, the mass of the fully absorbed electrolyte at these heights, and the mass of the fully absorbed electrolyte after removal. Then, based on this mapping relationship and a safe liquid level height, the safe free mass of the free electrolyte is determined. Finally, the required liquid retention capacity of the cell is determined based on the mass of the removed electrolyte, the mass of the fully absorbed electrolyte after removal, and the safe free mass. Based on the mass and liquid level height, the required liquid retention capacity of the cell can be determined. Compared to traditional methods of obtaining the required liquid retention capacity of a cell, this application provides a simpler and more efficient method, significantly reducing the time required and effectively shortening the battery development cycle and schedule, thus lowering cell R&D costs. Furthermore, the method for obtaining the mass and liquid level height is simple and reliable, requiring no repeated verification, and also helps improve the accuracy of obtaining the required liquid retention capacity. In addition, the method for determining the required liquid retention capacity of a cell using this application reduces both the cycling risk and safety risk of the cell system.

[0056] Please see Figure 1 and Figure 2 In some embodiments, step S100, obtaining the liquid and water removal quality of the battery cell, includes:

[0057] Step S110: Obtain unfilled battery cells, which are the cells before they were filled with electrolyte;

[0058] Step S120: Bake the unfilled battery cell until its electrode assembly is dried to obtain the first intermediate battery cell;

[0059] Step S130: Weigh the first intermediate cell to obtain the cell's liquid and water removal quality.

[0060] Obtaining unfilled battery cells eliminates the need for electrolyte removal, thus improving testing efficiency. The dehydration process is achieved by baking the unfilled cells, a simple, convenient, and reliable method. The cell after dehydration can be considered the first intermediate cell.

[0061] By removing electrolyte and water from the battery cells, the interference of the original electrolyte and moisture inside the cells on the testing process can be reduced, thus improving the accuracy of the test.

[0062] Please see Figure 1 , Figure 3 and Figure 5In some embodiments, step S200 involves obtaining the fully absorbed mass of the battery cell containing free electrolyte at multiple liquid level heights and the fully absorbed mass of the battery cell without free electrolyte. Based on the multiple liquid level heights, the fully absorbed mass of the battery cell containing free electrolyte at the multiple liquid level heights, and the fully absorbed mass of the battery cell without free electrolyte, a mapping relationship between the liquid level height of the battery cell and the mass of the free electrolyte in the battery cell is determined, including:

[0063] Step S210: Obtain the first intermediate cell and inject electrolyte into the first intermediate cell to obtain the second intermediate cell;

[0064] Step S220: After the electrode assembly of the second intermediate cell is filled with electrolyte and there is free electrolyte in the second intermediate cell, the free electrolyte in the second intermediate cell is removed multiple times until it is completely removed.

[0065] Step S230: Weigh the second intermediate cell after each removal to obtain the full adsorption mass of the current cell and the full adsorption mass of the current cell at multiple liquid level heights;

[0066] Step S240: Based on multiple liquid level heights and the difference between the mass of the ionized electrolyte and the mass of the ionized electrolyte at multiple liquid level heights, determine the mapping relationship between the liquid level height of the free electrolyte in the cell and the mass of the free electrolyte.

[0067] The first intermediate cell after being filled with electrolyte becomes the second intermediate cell.

[0068] As an example, once the electrode assembly of the second intermediate cell is saturated with electrolyte and there is free electrolyte within the second intermediate cell, the free electrolyte can be removed using a syringe or pipette. Removing the free electrolyte using a syringe or pipette is simple, easy to operate, and highly accurate, thus improving testing efficiency and accuracy.

[0069] After each removal of the free electrolyte before the final removal, the liquid level of the free electrolyte in the second intermediate cell needs to be measured or read. For example, multiple liquid level lines can be marked on the outer casing of the second intermediate cell. The liquid level of the free electrolyte after transfer can be determined by reading the line that is level with the free electrolyte surface. Alternatively, the liquid level of the free electrolyte in the second intermediate cell after transfer can also be measured using a smart leveling device, ruler, etc.

[0070] After each removal of the free electrolyte, the second intermediate cell needs to be weighed. The mass of the cell obtained from each weighing before the final removal is the cell's fully absorbed mass with free electrolyte remaining. It can be understood that after each removal of the free electrolyte before the final removal, the liquid level and the fully absorbed mass of the free electrolyte inside the cell will change, with different liquid levels corresponding to different fully absorbed masses. The mass of the cell obtained after the final removal of the free electrolyte is the cell's fully absorbed mass without free electrolyte remaining.

[0071] The difference between the fully absorbed mass of the battery cell and the fully absorbed mass of the battery cell without the electrolyte is the mass of the ionized electrolyte inside the cell. At different electrolyte levels, the difference between the fully absorbed mass of the battery cell and the fully absorbed mass of the battery cell without the electrolyte is different; therefore, different masses of ionized electrolyte can be obtained based on different electrolyte levels.

[0072] Specifically, taking the example that the liquid level of the free electrolyte in the second intermediate cell drops by 2 cm after each removal of the free electrolyte, the mass of the free electrolyte at multiple liquid level heights can be obtained through steps S220, S230, and 240, as follows:

[0073]

[0074] Table 1

[0075] Based on multiple liquid level heights and the difference between the current and remaining fully absorbed mass at these heights, the mapping relationship between the liquid level height and the mass of the free electrolyte within the cell is determined. The specific process is as follows: A planar coordinate system is established, defining the liquid level height of the free electrolyte within the cell as x, and the mass of the free electrolyte as y. The liquid level height is used as the abscissa, and the mass of the free electrolyte is used as the ordinate. Coordinate points are established within the planar coordinate system. Based on multiple liquid level heights and the corresponding masses of the free electrolyte, multiple coordinate points can be established within the planar coordinate system. The mapping relationship between the liquid level height and the mass of the free electrolyte is then obtained by plotting these points and drawing lines.

[0076] Specifically, with Figure 5 For example, according to Table 1 above, the mapping relationship between the free electrolyte level and the free electrolyte mass, obtained by plotting points and drawing lines, is: y = 11.46x + 1.3778. Based on this mapping relationship, the safe liquid level is used as the x-value, and substituting it into the mapping relationship, the safe free electrolyte mass associated with the safe liquid level can be obtained. In this embodiment, the mapping relationship between the free electrolyte level and the free electrolyte mass can be obtained through simple liquid transfer, weighing, and plotting points and drawing lines. This method of obtaining the mapping relationship is simple, convenient, and highly accurate.

[0077] Please see Figure 3 and Figure 4 In some embodiments, step S220: until the electrode assembly of the second intermediate cell is saturated with electrolyte, and free electrolyte is present within the second intermediate cell, includes:

[0078] Step S221: Inject electrolyte into the second intermediate cell multiple times, and let it stand for a preset time after each injection of electrolyte until the electrode assembly of the second intermediate cell is fully saturated with electrolyte and there is free electrolyte in the second intermediate cell.

[0079] The preset duration can be set to 5 minutes, 10 minutes, etc., according to production needs, and is not limited here.

[0080] By repeatedly injecting electrolyte into the second intermediate cell and allowing it to stand for a preset time after each injection, the electrode assembly can be fully saturated with electrolyte, which helps improve the accuracy of the test.

[0081] In some embodiments, step S220: after the electrode assembly of the second intermediate cell is saturated with electrolyte and free electrolyte remains in the second intermediate cell, the free electrolyte in the second intermediate cell is repeatedly removed until it is completely removed, further includes:

[0082] Step S222: After the electrode assembly of the second intermediate cell is filled with electrolyte and the outer shell of the second intermediate cell is filled with free electrolyte, mark multiple liquid level height lines on the outer shell of the second intermediate cell along the height direction of the second intermediate cell.

[0083] Step S223: Remove the free electrolyte from the battery cell multiple times until it is completely removed, following the pattern of the free electrolyte level in the battery cell decreasing by a preset number of increments each time.

[0084] When the casing of the second intermediate battery cell is filled with free electrolyte, the height of the free electrolyte level is the height of the casing of the second intermediate battery cell. In this embodiment, the height of the casing of the second intermediate battery cell is greater than the length and width of the casing of the second intermediate battery cell.

[0085] When the electrode assembly of the second intermediate cell is filled with electrolyte and the casing of the second intermediate cell is filled with free electrolyte, multiple liquid level height lines are marked on the outside of the casing of the second intermediate cell along the height direction of the second intermediate cell. The height of the casing of the second intermediate cell is divided equally. Each time, the cell is removed by lowering the liquid level height by a preset number of divisions (e.g., one or more divisions) of the liquid level height lines. After each removal, the liquid level height of the free electrolyte can be read by reading the liquid level height line that is flush with the liquid level height. This design makes it easy to know and record the liquid level height of the free electrolyte in the cell after each removal, thus improving the testing efficiency.

[0086] As an example, the height difference between two adjacent liquid level lines is H, where 1cm ≤ H ≤ 5cm. In this way, the height of the casing can be divided into multiple equal sections to facilitate the removal of free electrolyte multiple times, and the liquid level height of the free electrolyte can be read after each removal.

[0087] In some embodiments, the required liquid retention capacity of the battery cell is defined as m. 保 The mass of liquid and water removed is m 始 The mass of the swimmer is m 终 The safe free mass is m 游 m 保 =m 终 -m 始 +m 游 .

[0088] Understandable, m 终 -m 始 The mass of electrolyte absorbed by the electrode assembly when it is fully saturated with electrolyte is obtained. The sum of this electrolyte mass and the safe free mass is the required electrolyte retention capacity of the battery cell. This method of calculating the required electrolyte retention capacity of the battery cell is simple, convenient, and highly accurate.

[0089] The following is a detailed explanation of how to determine the required liquid retention capacity of the battery cell.

[0090] First, the unfilled battery cells are baked until the electrode assemblies are dried, resulting in a first intermediate battery cell. Next, the first intermediate battery cell is weighed to obtain its dehydrated mass. Then, electrolyte is injected into the first intermediate battery cell to obtain a second intermediate battery cell. During electrolyte injection, multiple injections are required, with a preset set time allowed after each injection, until no more electrolyte can be injected into the second intermediate battery cell. At this point, the electrode assemblies in the second intermediate battery cell are saturated with electrolyte, and the space between the electrode assemblies and the outer casing is filled with electrolyte. Next, a liquid level mark is marked on the outer casing of the second intermediate battery cell. Then, using a syringe or pipette, the free electrolyte is removed in multiple batches until all the free electrolyte is removed from the second intermediate battery cell. After each removal of free electrolyte before the final removal, the liquid level of the free electrolyte in the second intermediate battery cell must be recorded, and the second intermediate battery cell must be weighed after each removal of free electrolyte. After the final removal, the mass of the battery cell after the last full absorption was measured. The mass of the second intermediate battery cell measured before the last removal was the mass of the battery cell with remaining full absorption. The difference between the mass of each battery cell with remaining full absorption and the mass after the last full absorption was calculated to obtain the mass of the ionized electrolyte in the battery cell at each liquid level. Using the corresponding liquid level and the mass of the ionized electrolyte, coordinate points were plotted in a plane coordinate system with the liquid level as the x-coordinate and the mass of the ionized electrolyte as the y-coordinate. Each liquid level had a different corresponding coordinate point. Based on the relationship between these coordinate points, the mapping relationship between the liquid level and the mass of the ionized electrolyte was determined by plotting points and drawing lines: y = 11.46x + 1.3778. Then, using the safe liquid level as the x-coordinate, the mapping relationship between the liquid level and the mass of the ionized electrolyte was substituted to obtain the safe free mass of the ionized electrolyte associated with the safe liquid level. Finally, according to formula m... 保 = m 终 -m 始 +m 游 The required liquid retention amount for the battery cell is calculated.

[0091] The method for determining the required liquid retention of the aforementioned battery cell establishes a mapping relationship between the liquid level height and the mass of the free electrolyte within the cell, based on multiple liquid level heights, the mass of the fully absorbed electrolyte at these heights, and the mass of the fully absorbed electrolyte after removal. Then, based on this mapping relationship and a safe liquid level height, the safe free mass of the free electrolyte is determined. Finally, the required liquid retention of the cell is determined based on the mass of the removed electrolyte, the mass of the fully absorbed electrolyte after removal, and the safe free mass. Based on the mass and liquid level height, the required liquid retention of the battery cell can be determined. Compared to traditional methods for obtaining the required liquid retention of a battery cell, this application provides a simpler and more efficient method, significantly reducing the time required and effectively shortening the battery development cycle and schedule, thus lowering the battery cell R&D cost. Furthermore, the method for obtaining the mass and liquid level height is simple and reliable, requiring no repeated verification and contributing to improved accuracy in obtaining the required liquid retention of the battery cell. In addition, the method for determining the required liquid retention of the battery cell in this application reduces both the cycling risk and safety risk of the battery cell system.

[0092] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0093] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A method for determining the required liquid retention capacity of a battery cell, characterized in that, The method for determining the required liquid retention capacity of the battery cell includes: Obtain the electrolyte and water removal mass of the battery cell; the electrolyte and water removal mass is the mass of the battery cell after removing the electrolyte and water from its electrode assembly; The mass of the battery cell with free electrolyte and the mass of the battery cell without free electrolyte are obtained at multiple liquid level heights. Based on the multiple liquid level heights and the difference between the mass of the battery cell with free electrolyte and the mass of the battery cell without free electrolyte at the multiple liquid level heights, a mapping relationship between the liquid level height of the battery cell and the mass of the battery cell with free electrolyte is determined. The mass of the battery cell with free electrolyte is the mass of the battery cell after the presence of free electrolyte and the electrode assembly of the battery cell are fully saturated with electrolyte. The mass of the battery cell without free electrolyte is the mass of the battery cell after the removal of free electrolyte and the saturation of the electrode assembly of the battery cell. Obtain the safe liquid level height, and determine the safe free mass of the free electrolyte in the cell associated with the safe liquid level height based on the safe liquid level height and the mapping relationship; The required liquid retention amount of the battery cell is determined based on the liquid and water removal quality, the full absorption quality, and the safe free ionization quality. The required liquid retention capacity of the battery cell is defined as m. 保 The amount of liquid and water removed is m 始 The mass of the swimmer is m. 终 The safe free mass is m 游 m 保 =m 终 -m 始 +m 游 .

2. The method for determining the required liquid retention capacity of the battery cell according to claim 1, characterized in that, Obtaining the dehydration and dewatering quality of the battery cell includes: Obtain an unfilled battery cell, wherein the unfilled battery cell is the battery cell before it was in the liquid-filled state; The unfilled battery cell is baked until its electrode assembly is dried to obtain a first intermediate battery cell. Weigh the first intermediate cell to obtain the dehydration and dewatering mass of the cell.

3. The method for determining the required liquid retention capacity of the battery cell according to claim 2, characterized in that, The process involves obtaining the fully absorbed mass of the battery cell containing free electrolyte at multiple liquid level heights and the fully absorbed mass of the battery cell without free electrolyte. Based on the multiple liquid level heights and the difference between the fully absorbed mass of the battery cell containing free electrolyte and the fully absorbed mass of the battery cell without free electrolyte at the multiple liquid level heights, a mapping relationship between the liquid level height of the battery cell and the mass of the free electrolyte in the battery cell is determined, including: Obtain the first intermediate cell and inject electrolyte into the first intermediate cell to obtain the second intermediate cell; After the electrode assembly of the second intermediate cell is filled with electrolyte and there is free electrolyte in the second intermediate cell, the free electrolyte in the second intermediate cell is removed multiple times until it is completely removed. After each removal, the second intermediate cell is weighed to obtain the full adsorption mass of the remaining electrolyte and the full adsorption mass of the removed electrolyte at multiple liquid level heights. The mass of the cell after the last removal of the free electrolyte is the full adsorption mass of the cell. Based on the multiple liquid level heights and the difference between the full adsorption mass of the remaining electrolyte and the full adsorption mass of the removed electrolyte at the multiple liquid level heights, the mapping relationship between the liquid level height of the free electrolyte in the cell and the mass of the free electrolyte is determined.

4. The method for determining the required liquid retention capacity of the battery cell according to claim 3, characterized in that, The electrode assembly of the second intermediate cell is saturated with electrolyte, and free electrolyte is present within the second intermediate cell, including: Electrolyte is injected into the second intermediate cell multiple times, and the cell is left to stand for a preset time after each injection until the electrode assembly of the second intermediate cell is fully saturated with electrolyte and free electrolyte is present in the second intermediate cell.

5. The method for determining the required liquid retention capacity of the battery cell according to claim 3, characterized in that, After the electrode assembly of the second intermediate cell is saturated with electrolyte and free electrolyte remains in the second intermediate cell, the free electrolyte in the second intermediate cell is repeatedly removed until it is completely removed, including: After the electrode assembly of the second intermediate cell is filled with electrolyte and the housing of the second intermediate cell is filled with free electrolyte, multiple liquid level height lines are marked on the outside of the housing of the second intermediate cell along the height direction of the second intermediate cell. The free electrolyte in the battery cell is removed multiple times until it is completely removed, by lowering the liquid level of the free electrolyte in the battery cell by a preset number of increments each time.

6. The method for determining the required liquid retention capacity of a battery cell according to claim 5, characterized in that, The height difference between two adjacent liquid level height lines is H, where 1cm ≤ H ≤ 5cm.

7. The method for determining the required liquid retention capacity of the battery cell according to claim 3, characterized in that, The free electrolyte in the battery cell is removed using a syringe or pipette.

8. The method for determining the required liquid retention capacity of a battery cell according to claim 1, characterized in that, Let x be the height of the free electrolyte in the cell, and y be the mass of the free electrolyte in the cell. The mapping relationship between the height of the free electrolyte and the mass of the free electrolyte is: y = 11.46x + 1.3778.

9. The method for determining the required liquid retention capacity of a battery cell according to claim 1, characterized in that, The height of the battery cell's casing is defined as H1, and the safety liquid level height is defined as H2, where H1 / 3 ≤ H2 ≤ H1 / 2.

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