Method for determining liquid retention amount required by battery cell

Abstract

The invention relates to a method for determining the liquid retention amount required by a battery cell. The method comprises the following steps: acquiring the liquid and water removal quality of a battery cell; obtaining the storage and full absorption mass of the free electrolyte in the battery cell at multiple liquid level heights and the removal and full absorption mass of the battery cell, and calculating the storage and full absorption mass of the free electrolyte in the battery cell according to the multiple liquid level heights, the storage and full absorption mass at the multiple liquid level heights and the removal and full absorption mass at the multiple liquid level heights. Determining a mapping relation between the liquid level height of the free electrolyte in the battery cell and the mass of the free electrolyte in the battery cell; obtaining a safe liquid level height, and determining the safe dissociation quality of the dissociation electrolyte in the cell associated with the safe liquid level height according to the safe liquid level height and the mapping relation; and determining the liquid retention amount required by the battery cell according to the liquid and water removal quality, the travel removal and full absorption quality and the safe dissociation quality. The method for determining the liquid retention amount required by the battery cell provided by the invention has the advantages of short time consumption, low battery development cycle and progress, low battery cell research and development cost, no need of repeated verification, and high accuracy of obtaining the liquid retention amount required by the battery cell.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and in particular to a method for determining the amount of liquid required for a battery cell. Background Art

[0002] A lithium-ion battery cell primarily 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 soak the positive and negative electrodes, as well as the separator, forming a lithium ion conductive path between the two. Too little electrolyte in the cell will inevitably lead to insufficient wetting of some active material particles in the positive and negative electrodes, increased interfacial impedance, reduced capacity utilization, and a shortened cycle life. Too much electrolyte in the cell will increase manufacturing costs, while also causing corrosion to the cell's outer casing and potentially compromising battery safety. Therefore, determining the proper electrolyte level and maintaining the required electrolyte level within the cell has become a key concern.

[0003] Traditional methods for determining the required fluid volume for battery cells are cumbersome and time-consuming, severely impacting production schedules. Furthermore, traditional methods can increase the cycle and safety risks of the battery system. Summary of the Invention

[0004] Based on this, it is necessary to provide a new method for determining the amount of liquid required for a battery cell to address the above problem.

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

[0006] Obtaining the liquid- and water-removed mass of the battery cell; the liquid- and water-removed mass is the mass of the battery cell after the electrolyte is removed from the battery cell and the water is removed from its electrode assembly;

[0007] Obtaining the stored fully absorbed mass of the battery cell at multiple liquid level heights and the de-saturated fully absorbed mass of the battery cell for the free electrolyte in the battery cell, and determining a mapping relationship between the liquid level heights of the free electrolyte in the battery cell and the mass of the free electrolyte in the battery cell based on the multiple liquid level heights, the stored fully absorbed mass at the multiple liquid level heights, and the de-saturated fully absorbed mass; the stored fully absorbed mass is the mass of the battery cell after free electrolyte exists in the battery cell and the electrode assembly thereof is fully absorbed with electrolyte, and the de-saturated fully absorbed mass is the mass of the battery cell after the free electrolyte is removed from the battery cell and the electrode assembly thereof is fully absorbed with electrolyte;

[0008] Acquire a safe liquid level height, and determine a safe free mass of free electrolyte in the battery cell associated with the safe liquid level height according to the safe liquid level height and the mapping relationship;

[0009] The required liquid retention amount of the battery cell is determined according to the liquid and water removal mass, the free mass and the safe free mass.

[0010] In some embodiments, obtaining the liquid and water removal quality of the battery cell includes:

[0011] Obtaining an unfilled battery cell, wherein the unfilled battery cell is the battery cell before being filled with liquid;

[0012] baking the unfilled battery cell until the electrode assembly thereof is dried to obtain a first intermediate battery cell;

[0013] The first intermediate battery cell is weighed to obtain the liquid- and water-removed mass of the battery cell.

[0014] In some embodiments, obtaining the stored fully absorbed mass of the battery cell and the de-ionized fully absorbed mass of the battery cell at multiple liquid level heights of the free electrolyte in the battery cell, and determining a mapping relationship between the liquid level heights of the free electrolyte in the battery cell and the mass of the free electrolyte in the battery cell according to the multiple liquid level heights, the stored fully absorbed mass, and the de-ionized fully absorbed mass at the multiple liquid level heights, includes:

[0015] Obtaining the first intermediate battery cell, and injecting electrolyte into the first intermediate battery cell to obtain a second intermediate battery cell;

[0016] After the electrode assembly of the second intermediate cell is fully filled with electrolyte and free electrolyte exists in the second intermediate cell, the free electrolyte in the second intermediate cell is removed multiple times until all the electrolyte is removed;

[0017] Weighing the second intermediate cell after each removal to obtain the stored fully-absorbed mass and the removed fully-absorbed mass at multiple liquid levels;

[0018] A mapping relationship between the liquid level height of the free electrolyte in the battery cell and the mass of the free electrolyte is determined according to multiple liquid level heights and the difference between the stored fully absorbed mass and the desorbed fully absorbed mass at the multiple liquid level heights.

[0019] In some embodiments, the electrode assembly of the second intermediate cell is fully filled with electrolyte, and free electrolyte exists in the second intermediate cell, including:

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

[0021] In some embodiments, after the electrode assembly of the second intermediate cell is fully filled with electrolyte and free electrolyte exists in the second intermediate cell, the free electrolyte in the second intermediate cell is removed multiple times until all the electrolyte is removed, comprising:

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

[0023] The free electrolyte in the battery cell is removed multiple times until all the free electrolyte is removed, in a manner that the free electrolyte in the battery cell drops by a preset number of liquid level lines each time.

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

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

[0026] In some embodiments, the liquid level of the free electrolyte in the battery cell is defined as x, the mass of the free electrolyte in the battery cell is defined as y, and the mapping relationship between the liquid level 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 housing 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 volume of the battery cell is defined as m 保 , the mass of liquid and water removed is m 始 The mass of the de-swimming full suction 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 above-mentioned method for determining the required liquid volume of the battery cell determines the 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 according to multiple liquid level heights, the full absorption mass of the storage at multiple liquid level heights, and the full absorption mass of the removal of the free electrolyte, and then determines the safe free mass of the free electrolyte according to the mapping relationship and the safe liquid level height. Finally, the method for determining the required liquid volume of the battery cell according to the liquid removal and water removal mass, the full absorption mass of the removal of the free electrolyte and the safe free mass, can determine the required liquid volume of the battery cell according to the mass and liquid level height. Compared with the traditional method of obtaining the required liquid volume of the battery cell, the present application can obtain the required liquid volume of the battery cell through simple operations and calculations, which is time-saving, effectively shortens the battery development cycle and progress, and reduces the battery cell R&D cost. Moreover, the method for obtaining the mass and liquid level height is simple and reliable, does not require repeated verification, and also helps to improve the accuracy of obtaining the required liquid volume of the battery cell. In addition, by adopting the method of determining the required liquid volume of the battery cell in the present application, the cycle risk and safety risk of the battery cell system are reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 Schematic diagram of a flow chart of a method for determining the required liquid retention amount of a battery cell in one embodiment of the present application;

[0032] Figure 2 This is a flow chart of a method for determining the required liquid retention amount of a battery cell in another embodiment of the present application;

[0033] Figure 3 This is a flow chart of a method for determining the required liquid retention amount of a battery cell in another embodiment of the present application;

[0034] Figure 4 This is a flow chart of a method for determining the required liquid retention amount of a battery cell in yet another embodiment of the present application;

[0035] Figure 5 Schematic diagram of the mapping relationship between the mass of free electrolyte and the liquid level in one embodiment of the present application. DETAILED DESCRIPTION

[0036] To make the above-mentioned objects, features, and advantages of the present application more clearly understood, the specific embodiments of the present application are described in detail below with reference to the accompanying drawings. The following description sets forth many specific details to facilitate a full understanding of the present application. However, the present application can be implemented in many other ways than those described herein, and those skilled in the art can make similar improvements without violating the scope of the present application. Therefore, the present application is not limited to the specific embodiments disclosed below.

[0037] In the description of the present application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present 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 the technical features being referred to. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of such features. Throughout the description of this application, "plurality" means at least two, for example, two, three, etc., unless otherwise specifically defined.

[0039] In this application, unless otherwise specified or limited, the terms "installed," "connected," "connect," "fixed," etc. should be understood in a broad sense. For example, they can refer to fixed connection, detachable connection, or integration; mechanical connection or electrical connection; direct connection or indirect connection through an intermediate medium; internal communication between two elements or interaction between two elements, unless otherwise specified. Those skilled in the art will understand the specific meanings of the above terms in this application based on specific circumstances.

[0040] In this application, unless otherwise expressly specified or limited, when a first feature is "above" or "below" a second feature, it may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Furthermore, when a first feature is "above," "above," or "above" a second feature, it may mean that the first feature is directly above or diagonally above the second feature, or simply means that the first feature is at a higher level than the second feature. When a first feature is "below," "below," or "below" a second feature, it may mean that the first feature is directly below or diagonally below the second feature, or simply means that the first feature is at a lower level than the second feature.

[0041] It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it may be directly on the other element or there may be an intermediate element. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be an intermediate 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 implementation methods.

[0042] A lithium-ion battery cell primarily 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 soak these, the negative electrode, and the separator, forming a lithium ion conductive path between the two. Too little electrolyte in the cell inevitably leads to insufficient wetting of some active material particles in the positive and negative electrodes, increased interfacial impedance, reduced capacity utilization, and a shortened cycle life. Too much electrolyte in the cell not only increases manufacturing costs but also easily corrodes the cell's casing, potentially compromising battery safety. Therefore, determining the proper electrolyte level and maintaining the required electrolyte level within the cell has become a key concern.

[0043] In the prior art, there are two main methods for determining the required liquid retention volume of a battery cell:

[0044] The first method: calculate the porosity of the positive electrode sheet, negative electrode sheet and diaphragm, calculate the residual space in the battery cell shell, and then use the electrolyte density to calculate the electrolyte usage. This calculation method is cumbersome and time-consuming, which seriously affects the production progress. The second method: inject the battery cell according to multiple injection coefficients, and then perform performance testing on the gradient of the required liquid retention of the battery cell to obtain the optimal liquid retention required for the battery cell. However, this method requires a large amount of testing resources for cycle testing and is time-consuming. If the battery cell design is adjusted, it needs to be retested and verified, which seriously affects the battery development cycle and progress. In addition, this method of determining the required liquid retention of the battery cell is also likely to increase the cycle risk and safety risk of the battery cell system. In order to alleviate the above problems, the present application designs a method for determining the required liquid retention of the battery cell, which includes:

[0045] See also Figure 1 Step S100: Obtain the mass of the battery cell after removing the liquid and water; the mass of the battery cell after removing the electrolyte and removing the water from its electrode assembly;

[0046] Step S200: Obtain the fully absorbed mass of the battery cell at multiple liquid level heights of the free electrolyte in the battery cell, and the fully absorbed mass of the battery cell after the free electrolyte is removed. Determine the mapping relationship between the liquid level heights of the free electrolyte in the battery cell and the mass of the free electrolyte in the battery cell according to the multiple liquid level heights, the fully absorbed mass at multiple liquid level heights, and the fully absorbed mass after removal. The fully absorbed mass is the mass of the battery cell after there is free electrolyte in the battery cell and its electrode assembly is fully absorbed with the electrolyte, and the fully absorbed mass after removal is the mass of the battery cell after the free electrolyte is removed from the battery cell and its electrode assembly is fully absorbed with the electrolyte.

[0047] Step S300: obtaining a safe liquid level height, and determining a safe free mass of free electrolyte in the battery cell associated with the safe liquid level height according to the safe liquid level height and a mapping relationship;

[0048] Step S400: Determine the required liquid retention amount of the battery cell according to the liquid and water removal quality, the free and full absorption quality, and the safe free quality.

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

[0050] The quality of the battery cell after liquid removal and water removal can be obtained before or after the battery cell is filled with liquid, and the specific quality can be determined according to actual conditions.

[0051] There is 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. Multiple liquid level heights of the free electrolyte in the battery cell are associated with multiple masses of the free electrolyte in the battery cell in a one-to-one correspondence.

[0052] The safe liquid level is the level of free electrolyte in the cell when the electrode assembly is fully absorbed by the electrolyte. For example, let's define the cell casing height as H1 and the safe liquid level as H2, where H1 / 3 ≤ H2 ≤ H1 / 2. Designing the safe liquid level within this range maintains battery safety and stability.

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

[0054] According to the 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, and 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 the present application, the 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 based on multiple liquid level heights, the full absorption mass of the storage at multiple liquid level heights, and the full absorption mass of the desorption, and then the safe free mass of the free electrolyte is determined based on the mapping relationship and the safe liquid level height. Finally, the required liquid retention amount of the battery cell is determined based on the desorption and dewatering mass, the full absorption mass of the desorption, and the safe free mass. According to the mass and liquid level height, the required liquid retention amount of the battery cell can be determined. Compared with the traditional method of obtaining the required liquid retention amount of the battery cell, the present application can obtain the required liquid retention amount of the battery cell through simple operations and calculations, which is time-saving, effectively shortens the battery development cycle and progress, and reduces the battery cell R&D cost. Moreover, the method of obtaining the mass and liquid level height is simple and reliable, does not require repeated verification, and also helps to improve the accuracy of obtaining the required liquid retention amount of the battery cell. In addition, by adopting the method of determining the required liquid retention amount of the battery cell in the present application, the cycle risk and safety risk of the battery cell system are reduced.

[0056] See also 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: obtaining an unfilled battery cell, where the unfilled battery cell is a battery cell before being filled with liquid;

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

[0059] Step S130: weighing the first intermediate cell to obtain the mass of the cell after removing liquid and water.

[0060] Obtaining an unfilled cell eliminates the need for de-liquidation (i.e., electrolyte removal), improving testing efficiency. De-liquidation is achieved by baking the unfilled cell, which is simple, convenient, and reliable. The cell after de-liquidation and de-watering is considered the first intermediate cell.

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

[0062] See also Figure 1 、 Figure 3 and Figure 5In some embodiments, step S200 of obtaining the stored fully charged mass of the battery cell and the discharged fully charged mass of the battery cell at multiple liquid levels of the free electrolyte in the battery cell, and determining a mapping relationship between the liquid level of the free electrolyte in the battery cell and the mass of the free electrolyte in the battery cell based on the multiple liquid levels, the stored fully charged mass, and the discharged fully charged mass at the multiple liquid levels, includes:

[0063] Step S210: obtaining a first intermediate cell and injecting an electrolyte into the first intermediate cell to obtain a second intermediate cell;

[0064] Step S220: After the electrode assembly of the second intermediate cell is fully filled with electrolyte and free electrolyte exists in the second intermediate cell, the free electrolyte in the second intermediate cell is removed multiple times until all the electrolyte is removed;

[0065] Step S230: weighing the second middle cell after each removal to obtain the fully charged mass at multiple liquid levels and the fully charged mass at multiple liquid levels;

[0066] Step S240: determining a mapping relationship between the liquid level heights of the free electrolyte in the battery cell and the mass of the free electrolyte according to the multiple liquid level heights and the difference between the fully charged mass and the fully charged mass at the multiple liquid level heights.

[0067] The first intermediate battery cell in the liquid-filled state is the second intermediate battery cell.

[0068] For example, after the electrode assembly of the second intermediate cell is fully filled with electrolyte and free electrolyte remains 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, and highly accurate, improving test efficiency and accuracy.

[0069] After each removal of the free electrolyte prior to the final removal, the liquid level of the free electrolyte in the second intermediate cell needs to be measured or read. As an example, multiple liquid level lines can be marked on the outer shell of the second intermediate cell. By reading the liquid level line that is flush with the liquid surface of the free electrolyte, the liquid level of the free electrolyte in the second intermediate cell after the transfer can be determined. Alternatively, the liquid level of the free electrolyte in the second intermediate cell after the transfer can be measured using an intelligent level finder, ruler, etc.

[0070] After each removal of the free electrolyte, the second intermediate cell needs to be weighed. The mass of the cell obtained by each weighing before the last removal is the fully absorbed mass of the cell. It can be understood that after each removal of the free electrolyte before the last removal, the liquid level of the free electrolyte in the cell and the fully absorbed mass will change, and different liquid level heights correspond to different fully absorbed masses of the cell. The mass of the cell obtained by weighing after the last removal of the free electrolyte is the fully absorbed mass of the cell.

[0071] The difference between the fully charged mass of the cell and the fully de-charged mass of the cell is the mass of the free electrolyte in the cell. The difference between the fully charged mass and the fully de-charged mass varies at different liquid levels, so different free electrolyte masses can be obtained based on different liquid levels.

[0072] Specifically, taking the example that the liquid level of the free electrolyte in the second intermediate cell drops by 2 cm each time the free electrolyte is removed, the mass of the free electrolyte at multiple liquid levels can be obtained through steps S220, S230, and S240, as follows:

[0073] Free electrolyte level (cm) Mass of free electrolyte (g) 18 205.3 16 185.2 14 163.9 12 141.5 10 114.9 8 92.8 6 67.9 4 46.9 2 25.4

[0074] Table 1

[0075] Based on multiple liquid level heights and the difference between the fully absorbed mass and the fully absorbed mass at the multiple liquid level heights, the mapping relationship between the liquid level height of the free electrolyte in the battery cell and the mass of the free electrolyte is determined. The specific process is as follows: establish a plane coordinate system, define the liquid level height of the free electrolyte in the battery cell as x, and the mass of the free electrolyte in the battery cell as y, use the liquid level height of the free electrolyte in the battery cell as the horizontal coordinate, and the mass of the free electrolyte in the battery cell as the vertical coordinate, and set coordinate points in the plane coordinate system. Based on the multiple liquid level heights and the mass of the free electrolyte corresponding to the multiple liquid level heights, multiple coordinate points can be set in the plane coordinate system, and then the mapping relationship between the liquid level height of the free electrolyte and the mass of the free electrolyte can be obtained by tracing points and lines.

[0076] Specifically, Figure 5 For example, according to Table 1 above, the mapping relationship between the liquid level height of the free electrolyte and the mass of the free electrolyte is obtained by drawing a dotted line: y = 11.46x + 1.3778. According to the above mapping relationship, the safe liquid level height is used as the x value and substituted into the above mapping relationship to obtain the safe free mass of the free electrolyte associated with the safe liquid level height. In this embodiment, the mapping relationship between the liquid level height of the free electrolyte and the mass of the free electrolyte can be obtained by simple pipetting, weighing and drawing a dotted line. This method of obtaining the mapping relationship is simple, convenient and highly accurate.

[0077] See also Figure 3 and Figure 4 In some embodiments, step S220: until the electrode assembly of the second intermediate cell is fully filled with electrolyte and free electrolyte exists in the second intermediate cell, includes:

[0078] Step S221: injecting electrolyte into the second intermediate cell multiple times, and letting it stand for a preset time after each injection of electrolyte until the electrode assembly of the second intermediate cell is fully absorbed by the electrolyte and free electrolyte exists in the second intermediate cell.

[0079] Among them, the preset time length can be set to 5 minutes, 10 minutes, etc. according to production needs, and is not limited here.

[0080] By repeatedly injecting liquid into the second intermediate cell and letting it sit for a preset period of time after each injection, it can be ensured that the electrode assembly can be fully absorbed by the electrolyte, which is beneficial to improving the accuracy of the test.

[0081] In some embodiments, step S220: after the electrode assembly of the second intermediate cell is fully filled with electrolyte and free electrolyte exists in the second intermediate cell, removing the free electrolyte in the second intermediate cell multiple times until all the electrolyte is removed, further includes:

[0082] Step S222: After the electrode assembly of the second intermediate cell is fully filled with electrolyte and the housing of the second intermediate cell is filled with free electrolyte, a plurality of liquid level lines are marked on the outside of the housing of the second intermediate cell and along the height direction of the second intermediate cell;

[0083] Step S223 : removing the free electrolyte in the battery cell multiple times until all the free electrolyte is removed, in a manner such that the free electrolyte in the battery cell drops by a preset number of liquid level lines each time.

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

[0085] When the electrode assembly of the second intermediate battery cell is full of electrolyte and the outer shell of the second intermediate battery cell is full of free electrolyte, multiple liquid level height lines are marked outside the outer shell of the second intermediate battery cell and along the height direction of the second intermediate battery cell, and the outer shell height of the second intermediate battery cell is equally divided. Each time, the liquid level height of the free electrolyte is lowered by a preset number of liquid level height lines (for example, one or more grids). After each removal, the liquid level height of the free electrolyte can be read through the liquid level height line 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 battery cell after each removal, thereby improving test efficiency.

[0086] As an example, the height difference between two adjacent liquid level lines is H, 1 cm ≤ H ≤ 5 cm. In this way, the height of the housing can be evenly divided into multiple grids, so as to facilitate multiple removals of the free electrolyte and to read the liquid level of the free electrolyte after each removal.

[0087] In some embodiments, the required liquid volume of the battery cell is defined as m 保 , the mass of liquid and water removed is m 始 , the mass of the full suction 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 absorbed is obtained. The sum of this mass of electrolyte and the safe free mass is the required electrolyte retention volume of the battery cell. This method of calculating the required electrolyte retention volume of the battery cell is simple, convenient, and highly accurate.

[0089] The following describes in detail how to determine the required liquid retention volume for a battery cell.

[0090] First, bake the unfilled cell until the electrode assembly is dry, producing the first intermediate cell. Next, weigh the first intermediate cell to determine its mass after removing liquid and water. Then, inject electrolyte into the first intermediate cell to produce the second intermediate cell. This injection process requires multiple injections, and each injection is followed by a predetermined period of rest until no further electrolyte can be injected into the second intermediate cell. At this point, the electrode assembly in the second intermediate cell is fully filled with electrolyte, and the space between the electrode assembly and the outer casing is filled with electrolyte. Next, mark the liquid level on the outer casing of the second intermediate cell. Use a syringe or pipette to remove the free electrolyte in multiple times until all the free electrolyte in the second intermediate cell is removed. Record the free electrolyte level in the second intermediate cell after each removal until the final removal, and weigh the second intermediate cell after each removal. After the last removal, the desorbed mass of the cell is weighed, and the mass of the second intermediate cell weighed before the last removal is the stored fully absorbed mass of the cell. Subtract the stored fully absorbed mass of each cell from the desorbed fully absorbed mass to obtain the mass of the free electrolyte in the cell at each liquid level. In the corresponding liquid level height and the mass of the free electrolyte, the liquid level height is used as the x-coordinate, the mass of the free electrolyte is used as the y-coordinate, and the coordinate points are drawn in the plane coordinate system. Each liquid level height has a different corresponding coordinate point. According to the relationship between the coordinate points, the mapping relationship between the liquid level height of the free electrolyte and the mass of the free electrolyte is determined by tracing points and lines: y = 11.46x + 1.3778. Then, the safe liquid level height is used as the x-coordinate, and the mapping relationship between the liquid level height of the free electrolyte and the mass of the free electrolyte is substituted into the mapping relationship between the free electrolyte and the mass of the free electrolyte to obtain the safe free mass of the free electrolyte associated with the safe liquid level height. Finally, according to the formula m 保 =m 终 -m 始 +m 游 , calculate the required liquid retention volume of the battery cell.

[0091] The above-mentioned method for determining the required liquid volume of the battery cell determines the 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 according to multiple liquid level heights, the full absorption mass of the storage at multiple liquid level heights, and the full absorption mass of the removal of the free electrolyte, and then determines the safe free mass of the free electrolyte according to the mapping relationship and the safe liquid level height. Finally, the method for determining the required liquid volume of the battery cell according to the liquid removal and water removal mass, the full absorption mass of the removal of the free electrolyte and the safe free mass, can determine the required liquid volume of the battery cell according to the mass and liquid level height. Compared with the traditional method of obtaining the required liquid volume of the battery cell, the present application can obtain the required liquid volume of the battery cell through simple operations and calculations, which is time-saving, effectively shortens the battery development cycle and progress, and reduces the battery cell R&D cost. Moreover, the method for obtaining the mass and liquid level height is simple and reliable, does not require repeated verification, and also helps to improve the accuracy of obtaining the required liquid volume of the battery cell. In addition, by adopting the method of determining the required liquid volume of the battery cell in the present application, the cycle risk and safety risk of the battery cell system are reduced.

[0092] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned 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 above-described embodiments merely represent several implementation methods of the present application. 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 a person of ordinary skill in the art may make various modifications and improvements without departing from the spirit of the present application, and these modifications and improvements fall within the scope of protection of the present application. Therefore, the scope of protection of the present patent application shall be determined by the appended claims.

Claims

1. A method for determining the amount of liquid required for a battery cell, characterized in that: The method for determining the required liquid retention amount of the battery cell includes: Obtaining the liquid- and water-removed mass of the battery cell; the liquid- and water-removed mass is the mass of the battery cell after the electrolyte is removed from the battery cell and the water is removed from its electrode assembly; Obtaining the stored fully absorbed mass of the battery cell at multiple liquid level heights and the de-saturated fully absorbed mass of the battery cell for the free electrolyte in the battery cell, and determining a mapping relationship between the liquid level heights of the free electrolyte in the battery cell and the mass of the free electrolyte in the battery cell based on the multiple liquid level heights, the stored fully absorbed mass at the multiple liquid level heights, and the de-saturated fully absorbed mass; the stored fully absorbed mass is the mass of the battery cell after free electrolyte exists in the battery cell and the electrode assembly thereof is fully absorbed with electrolyte, and the de-saturated fully absorbed mass is the mass of the battery cell after the free electrolyte is removed from the battery cell and the electrode assembly thereof is fully absorbed with electrolyte; Acquire a safe liquid level height, and determine a safe free mass of free electrolyte in the battery cell associated with the safe liquid level height according to the safe liquid level height and the mapping relationship; The required liquid retention amount of the battery cell is determined according to the liquid and water removal mass, the free mass and the safe free mass.

2. The method for determining the required liquid retention amount of a battery cell according to claim 1, wherein: Obtaining the liquid and water removal quality of the battery cell includes: Obtaining an unfilled battery cell, wherein the unfilled battery cell is the battery cell before being filled with liquid; baking the unfilled battery cell until the electrode assembly thereof is dried to obtain a first intermediate battery cell; The first intermediate battery cell is weighed to obtain the liquid- and water-removed mass of the battery cell.

3. The method for determining the required liquid retention amount of the battery cell according to claim 2, characterized in that: Obtaining the stored fully absorbed mass of the battery cell and the de-ionized fully absorbed mass of the battery cell at multiple liquid level heights of the free electrolyte in the battery cell, and determining a mapping relationship between the liquid level heights of the free electrolyte in the battery cell and the mass of the free electrolyte in the battery cell according to the multiple liquid level heights, the stored fully absorbed mass, and the de-ionized fully absorbed mass at the multiple liquid level heights, including: Obtaining the first intermediate battery cell, and injecting electrolyte into the first intermediate battery cell to obtain a second intermediate battery cell; After the electrode assembly of the second intermediate cell is fully filled with electrolyte and free electrolyte exists in the second intermediate cell, the free electrolyte in the second intermediate cell is removed multiple times until all the electrolyte is removed; Weighing the second intermediate cell after each removal to obtain the stored fully-absorbed mass and the removed fully-absorbed mass at multiple liquid levels; A mapping relationship between the liquid level height of the free electrolyte in the battery cell and the mass of the free electrolyte is determined according to multiple liquid level heights and the difference between the stored fully absorbed mass and the desorbed fully absorbed mass at the multiple liquid level heights.

4. The method for determining the required liquid retention amount of a battery cell according to claim 3, wherein: The method of step (a) absorbing electrolyte to the electrode assembly of the second intermediate cell and (b) allowing free electrolyte to exist in the second intermediate cell, comprises: The electrolyte is injected into the second intermediate cell multiple times, and the cell is left to stand for a preset time after each injection of the electrolyte until the electrode assembly of the second intermediate cell is fully filled with the electrolyte and free electrolyte exists in the second intermediate cell.

5. The method for determining the required liquid retention amount of the battery cell according to claim 3, characterized in that: After the electrode assembly of the second intermediate cell is fully filled with electrolyte and free electrolyte exists in the second intermediate cell, the free electrolyte in the second intermediate cell is removed multiple times until all the electrolyte is removed, comprising: After the electrode assembly of the second intermediate cell is fully filled with electrolyte and the housing of the second intermediate cell is filled with free electrolyte, a plurality of liquid level lines are marked on the outside of the housing of the second intermediate cell and along the height direction of the second intermediate cell; The free electrolyte in the battery cell is removed multiple times until all the free electrolyte is removed, in a manner that the free electrolyte in the battery cell drops by a preset number of liquid level lines each time.

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

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

8. The method for determining the required liquid retention amount of a battery cell according to claim 1, wherein: The liquid level of the free electrolyte in the battery cell is defined as x, the mass of the free electrolyte in the battery cell is defined as y, and the mapping relationship between the liquid level 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 amount of a battery cell according to claim 1, wherein: The height of the battery cell shell is defined as H1, the safety liquid level height is defined as H2, and H1 / 3≤H2≤H1 / 2.

10. The method for determining the required liquid retention amount of a battery cell according to claim 1, wherein: Define the required liquid volume of the battery cell as m 保 , the mass of liquid and water removed is m 始 The mass of the de-swimming full suction is m 终 , the safe free mass is m 游 , m 保 =m 终 -m 始 +m 游 .

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