Preparation methods of battery cells, battery cells and energy storage devices

Abstract

This application relates to the field of energy storage technology, providing a method for preparing a battery cell, a battery cell, and an energy storage device. The preparation method includes: obtaining a cell assembly; performing hot-pressing treatment on the cell assembly and obtaining a first set of morphological parameters for the hot-pressed cell assembly; performing baking treatment on the hot-pressed cell assembly and obtaining a second set of morphological parameters for the baked cell assembly; determining whether the cell assembly has cell wrinkling abnormalities based on the first and second morphological parameter sets; and performing wrinkle repair treatment on the cell assembly with cell wrinkling abnormalities. The technical solution provided by this application can perform targeted monitoring of processes that may lead to cell wrinkling abnormalities during the preparation of battery cells, effectively repairing potential cell wrinkling abnormalities and improving the performance indicators of the prepared battery cells.

Description

Technical Field

[0001] This application relates to the field of energy storage technology, and in particular to a method for preparing a battery cell, the battery cell and the energy storage device. Background Technology

[0002] With the continuous development of new energy technologies, the demand for energy storage devices is also increasing. Energy storage devices can effectively store electrical energy and output it when needed. Energy storage devices use individual battery cells as energy storage units. These individual battery cells have good charge-discharge cycle characteristics, enabling the formation of electrochemical energy storage devices with a wide range of applications.

[0003] As the energy storage unit of an energy storage device, the performance of a single battery cell determines the amount of electrical energy that the device can store and its charge / discharge efficiency. During the manufacturing process of a battery cell, abnormal conditions such as cell wrinkles can easily occur, adversely affecting the cell's performance. Therefore, identifying and repairing these abnormalities during battery cell manufacturing is a crucial issue. Summary of the Invention

[0004] This application provides a method for preparing a battery cell, a battery cell, and an energy storage device, which helps to solve the problem of abnormal cell wrinkles that may occur during the preparation of battery cells.

[0005] The first aspect of this application provides a method for preparing a battery cell, which may specifically include the following steps: obtaining a cell assembly, wherein the cell assembly includes a negative electrode sheet, a separator, and a positive electrode sheet stacked together; performing a hot-pressing treatment on the cell assembly and obtaining a first set of morphological parameters of the hot-pressed cell assembly; performing a baking treatment on the hot-pressed cell assembly and obtaining a second set of morphological parameters of the baked cell assembly; determining whether the cell assembly has cell wrinkling abnormalities based on the first and second morphological parameter sets; performing wrinkle repair treatment on the cell assembly if cell wrinkling abnormalities are present; and placing the cell assembly without cell wrinkling abnormalities, and / or the cell assembly with wrinkle repair treatment to eliminate cell wrinkling abnormalities, into a housing to obtain a battery cell.

[0006] In one possible implementation of the first aspect above, the first set of morphological parameters includes the first cell perimeter of the hot-pressed cell assembly, the first cell perimeter being the perimeter of the first surface of the hot-pressed cell assembly; the second set of morphological parameters includes the second cell perimeter of the baked cell assembly, the second cell perimeter being the perimeter of the first surface of the baked cell assembly.

[0007] In one possible implementation of the first aspect described above, the first set of morphological parameters includes a first flatness parameter of the hot-pressed battery cell assembly, the first flatness parameter including the ratio of the minimum thickness to the maximum thickness of the first surface of the hot-pressed battery cell assembly in a first direction; the second set of morphological parameters includes a second flatness parameter of the baked battery cell assembly, the second flatness parameter including the ratio of the minimum thickness to the maximum thickness of the first surface of the hot-pressed battery cell assembly in a first direction.

[0008] In one possible implementation of the first aspect above, determining whether the battery cell assembly has a cell wrinkle abnormality includes: based on the first cell circumference and the second cell circumference, if the rate of change of the second cell circumference relative to the first cell circumference deviates from a first preset threshold, determining that the battery cell assembly has a cell wrinkle abnormality.

[0009] In one possible implementation of the first aspect above, determining whether the cell assembly has cell wrinkling abnormality includes: based on a first flatness parameter and a second flatness parameter, determining that the cell assembly has cell wrinkling abnormality when the first flatness parameter or the second flatness parameter deviates from a second preset threshold.

[0010] In one possible implementation of the first aspect above, the method for preparing a battery cell provided in this application may further include: performing a separator heat shrink marking treatment on the hot-pressed cell assembly, wherein the first set of morphological parameters includes the marking results corresponding to the separator heat shrink marking treatment; and the second set of morphological parameters includes the marking results after baking treatment.

[0011] In one possible implementation of the first aspect above, determining whether the cell assembly has cell wrinkling abnormality includes: determining the membrane heat shrinkage parameter of the cell assembly based on the difference in marking results before and after baking treatment; and determining that the cell assembly has cell wrinkling abnormality when the membrane heat shrinkage parameter deviates from a third preset threshold.

[0012] In one possible implementation of the first aspect above, the wrinkle repair process for the battery cell assembly with abnormal cell wrinkles includes: performing a secondary hot-pressing shaping process on the battery cell assembly; and / or performing a preset current charge-discharge process on the battery cell assembly.

[0013] In one possible implementation of the first aspect above, the method for preparing a battery cell provided in this application may further include: obtaining a third set of morphological parameters of the cell assembly after wrinkle repair treatment; determining whether there are unrepaired cell wrinkle abnormalities in the cell assembly based on the first set of morphological parameters, the second set of morphological parameters and the third set of morphological parameters, and repeating the wrinkle repair treatment on the cell assembly with unrepaired cell wrinkle abnormalities.

[0014] The second aspect of this application provides a battery cell that is prepared by the method for preparing the battery cell provided in the first aspect.

[0015] A third aspect of this application provides an energy storage device comprising a plurality of battery cells provided in the second aspect.

[0016] The technical solution provided in this application has at least the following advantages: The technical solution provided in this application enables the acquisition and comparison of morphological parameters of the cell assembly before and after baking during the preparation of the battery cell, and allows for the identification and targeted repair of potential cell wrinkles in the cell assembly. The technical solution provided in this application can also perform targeted monitoring of the hot pressing and baking processes that may cause abnormal cell wrinkles during the preparation of the battery cell, effectively repairing potential abnormal cell wrinkles and helping to improve the performance indicators of the prepared battery cell. Attached Figure Description

[0017] One or more embodiments are illustrated by way of example with corresponding pictures in the accompanying drawings. These illustrations do not constitute a limitation on the embodiments. Unless otherwise stated, the pictures in the accompanying drawings do not constitute a limitation on scale. In order to more clearly illustrate the technical solutions in the embodiments of this application or in the conventional technology, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a schematic flowchart of a method for preparing a battery cell according to an embodiment of this application.

[0019] Figure 2 This is a schematic diagram of the wound side structure of a battery cell assembly after hot pressing, according to an embodiment of this application.

[0020] Figure 3 This is a schematic diagram of a process for determining whether there are abnormal cell wrinkles in a battery cell assembly, according to an embodiment of this application. Detailed Implementation

[0021] Based on the relevant descriptions in the background art, abnormal cell wrinkling can easily occur during the preparation of battery cells. To solve the above-mentioned technical problems, some embodiments of this application provide a method for preparing a battery cell, a battery cell, and an energy storage device. Targeted monitoring is performed on the hot-pressing and baking processes that may lead to abnormal cell wrinkling during battery cell preparation, effectively repairing potential abnormal cell wrinkling and helping to improve the performance indicators of the prepared battery cells.

[0022] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0023] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0024] In the description of the embodiments of this application, when a component "includes" another component, other components are not excluded unless otherwise stated, and other components may be further included. Furthermore, when a component such as a layer, film, region, or plate is referred to as being "on / located" on another component, it can be "directly on" the other component (i.e., located on the surface of the other component with no other components between them), or another component may be present therein. Moreover, when a component such as a layer, film, region, or plate is "directly located" on another component, or when a component such as a layer, film, region, or plate is located on the surface of another component, it indicates that no other components are located therein.

[0025] The terminology used in the description of the various embodiments herein is for the purpose of describing particular embodiments only and is not intended to be limiting. As used in the description of the various embodiments and the appended claims, the term "part" is also intended to include the plural form unless the context clearly indicates otherwise. Components include layers, films, regions, or plates, etc.

[0026] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the various embodiments of this application will be described in detail below with reference to the accompanying drawings. However, those skilled in the art will understand that many technical details have been provided in the various embodiments of this application to help readers better understand this application. However, the technical solutions claimed in this application can be implemented even without these technical details and various changes and modifications based on the following embodiments. The division of the various embodiments below is for the convenience of description and should not constitute any limitation on the specific implementation of this application. The various embodiments can be combined with and referenced by each other without contradiction.

[0027] In some embodiments of this application, Figure 1 A schematic flowchart of a method for preparing a battery cell is shown, such as... Figure 1 As shown, process 100 may specifically include the following steps: Step 110: Obtain the cell assembly. In some embodiments, the cell assembly may include a negative electrode, a separator, and a positive electrode stacked together; specifically, the negative electrode, separator, and positive electrode may be stacked sequentially, and the cell assembly may be obtained by winding or stacking, which is not limited here.

[0028] Step 120: Perform hot-pressing treatment on the cell assembly and obtain the first set of morphological parameters of the hot-pressed cell assembly. In some embodiments, taking the cell assembly obtained by sequentially stacking the negative electrode, separator, and positive electrode and winding them as an example, after the winding process, there may be certain local gaps, film wrinkles, and other defects between the negative electrode, separator, and positive electrode. These defects can easily lead to problems such as poor structural density, stability, and electrochemical performance of the cell assembly. These problems can be avoided by hot-pressing the cell assembly. Hot-pressing treatment refers to pressing the obtained cell assembly under preset temperature and pressure conditions, which can improve the contact state between the negative electrode, separator, and positive electrode, improve the overall density and stability of the cell assembly, and also help improve the electrolyte wetting effect in the subsequent preparation process of the battery cell, thereby improving the performance of the prepared battery cell. This is not limited here.

[0029] In some embodiments, exemplarily, Figure 2 A schematic diagram of the wound side structure of a battery cell assembly after hot pressing is shown, as follows. Figure 2 As shown, the battery cell assembly 200 includes a wound and tightly fitted negative electrode 210, a separator 220, and a positive electrode 230, wherein the separator 220 is used to separate the negative electrode 210 and the positive electrode 230. In some embodiments, such as Figure 2The battery cell assembly 200 shown can be obtained by winding a negative electrode 210, a separator 220, and a positive electrode 230 stacked sequentially around a preset winding axis. The winding side refers to a side of the battery cell assembly perpendicular to the axial direction of the winding axis, and is not limited thereto. In some embodiments, such as... Figure 2 As shown, the wound side of the battery cell assembly after hot pressing is provided with a first direction x and a second direction y. The first direction x can be the direction of the preset pressure during the pressing process, i.e. the hot pressing direction during the hot pressing process. The second direction y can be the direction perpendicular to the first direction x in the plane of the wound side of the battery cell assembly, which is not limited here.

[0030] In some embodiments, specifically, the first set of morphological parameters can be used to characterize the appearance morphological features of the battery cell assembly after hot pressing; for example, with Figure 2 Taking the hot-pressed battery cell assembly 200 as an example, the first set of morphological parameters may specifically include the thickness value of the hot-pressed battery cell assembly 200 in the first direction x, the width value in the second direction y, and so on. Figure 2 The circumference of the wound side shown by the dashed line 240 is not limited here. It is understood that the first set of morphological parameters can determine the physical appearance of the battery cell assembly after hot pressing and provide necessary reference data for subsequent judgment of whether there are abnormal cell wrinkles. The specific composition and acquisition method of the first set of morphological parameters will be further explained in conjunction with the embodiments later, and will not be repeated here.

[0031] Step 130: The hot-pressed cell assembly is baked to obtain a second set of morphological parameters for the baked cell assembly. In some embodiments, during the preparation of the battery cell, the hot-pressed cell assembly can also be baked to remove environmental moisture that may have been adsorbed during the preparation process. This helps to improve the electrolyte wetting effect in subsequent battery cell preparation processes and improve the cell performance and reliability of the prepared battery cell. In some embodiments, specifically, the second set of morphological parameters can be used to characterize the appearance morphological features of the baked cell assembly, and the specific parameters included in the second set of morphological parameters can correspond to or be consistent with the specific parameters included in the aforementioned first set of morphological parameters, without limitation. Understandably, the second set of morphological parameters can determine the physical appearance of the battery cell assembly after baking. The high temperatures during baking cause secondary plasticization of components such as the negative electrode, separator, and positive electrode in the battery cell assembly. In particular, the thermal shrinkage of the tension separator can easily lead to abnormal appearance deformation of the battery cell assembly. By comparing the first and second sets of morphological parameters, it is possible to determine whether abnormal appearance deformation occurs in the battery cell assembly before and after baking, providing necessary reference data for subsequent determination of whether abnormal cell wrinkles exist. The specific composition and acquisition method of the second set of morphological parameters will be further explained later in conjunction with embodiments, and will not be elaborated here.

[0032] Step 140: Based on the first set of morphological parameters and the second set of morphological parameters, determine whether the cell assembly has cell wrinkling abnormalities, and perform wrinkle repair treatment on the cell assembly with cell wrinkling abnormalities. It is understood that during the hot pressing and baking process of the cell assembly, the cell assembly may undergo significant abnormal appearance deformation under heat and pressure, leading to defects such as cell wrinkling abnormalities. In the embodiments provided in this application, online detection and monitoring using the first and second sets of morphological parameters are supported in the early stages of the battery cell manufacturing process. This allows for targeted screening and timely repair of cell wrinkling abnormalities in the cell assembly, avoiding adverse effects of cell wrinkling abnormalities on the subsequent manufacturing process and performance of the battery cell. How to determine the presence of cell wrinkling abnormalities based on the first and second sets of morphological parameters will be further explained later in conjunction with embodiments, and will not be elaborated here.

[0033] In some embodiments, further, for cell assemblies with abnormal cell wrinkles, since the cell assembly is not yet placed in the corresponding casing of the individual battery cells, the abnormal cell wrinkles can be repaired specifically by means of hot-pressing and plastic adjustment. In some embodiments, other feasible means such as charging and discharging current can also be used to repair the abnormal cell wrinkles, which are not limited here. The specific content and implementation of the wrinkle repair treatment will be further explained later in conjunction with the embodiments, and will not be elaborated here.

[0034] Step 150: Place the cell assembly without cell wrinkling abnormalities, and / or the cell assembly with cell wrinkling abnormalities eliminated after wrinkle repair treatment, into the housing to obtain a battery cell. It is understood that the cell assembly without cell wrinkling abnormalities provided in Step 140, and / or the cell assembly with cell wrinkling abnormalities eliminated after wrinkle repair treatment, can be placed into the corresponding housing to form a battery cell, thus realizing the battery cell preparation process. In some embodiments, the cell assembly placed in the housing may undergo conventional battery cell preparation processes such as electrolyte injection, formation and capacity testing, and coating treatment before forming a usable battery cell; this is not limited here.

[0035] Based on the above process 100, the technical solution provided by this application can pre-judgment and adaptively repair the presence of cell wrinkles in the cell assembly before it is placed in the casing. This effectively detects and eliminates potential wrinkle abnormalities during the cell assembly manufacturing process, improving the adaptability of the battery cell manufacturing process and the quality of the resulting battery cells, overcoming the technical problem of easily occurring cell wrinkle abnormalities in battery cells. The specific implementation of each step in the above process 100 will be further explained and illustrated below with reference to specific embodiments.

[0036] In some embodiments of this application, in process 100 provided in the foregoing embodiments, the first set of morphological parameters may specifically include the first cell circumference of the hot-pressed cell assembly, wherein the first cell circumference is the circumference of the first surface of the hot-pressed cell assembly. In some embodiments, specifically, taking a cell assembly obtained by sequentially stacking a negative electrode, a separator, and a positive electrode and winding them around a preset winding axis as an example, the first surface of the cell assembly may be a side perpendicular to the axial direction of the winding axis, i.e., as shown in the figure. Figure 2 The wound side is shown; correspondingly, the circumference of the first cell can be the length of the outer contour line of the wound side of the cell assembly, i.e., as shown. Figure 2The dotted line 240 shown is not limited here; in some embodiments, taking the stacking of negative electrode, separator and positive electrode to obtain a cell assembly as an example, the first surface of the cell assembly can also be a side of the stack parallel to the stacking direction; in some embodiments, the first surface of the cell assembly can also be any cell assembly surface on the same plane (the cell assembly surface can be an absolutely flat surface in a strict sense; or it can be a non-absolutely flat surface with most areas on the same plane and a small part of the area having convex or concave surfaces relative to the plane, which is not limited here), the circumference of the first cell corresponds to the length of the outer contour line of the cell assembly surface, which is not limited here.

[0037] It is understood that the embodiments provided above are correct. Figure 2 It can be seen that if cell wrinkling abnormalities occur during the hot pressing and / or baking process of the cell assembly, the changes reflected in the physical morphology of the cell assembly may be abnormalities such as protrusions and depressions on the surface of the cell assembly. These abnormalities will cause changes in the outer perimeter of the cell assembly on the first surface (i.e., the first cell perimeter). Therefore, the first cell perimeter can be used as one of the indicators for evaluating cell wrinkling abnormalities, and can be included as a component of the first set of morphological parameters, without limitation. In some embodiments, in the process of obtaining the first cell perimeter, a camera with a charge-coupled device (CCD) can be used to scan and photograph the first surface of the cell assembly after hot pressing, and the scanned image can be analyzed and processed to obtain the specific length data of the required first cell perimeter. Users can also obtain the first cell perimeter using other available testing devices on the battery cell manufacturing production line, without limitation.

[0038] In some embodiments, correspondingly, in process 100 provided in the foregoing embodiments, the second morphological parameter set may specifically include the second cell perimeter of the baked cell assembly, wherein the second cell perimeter is the perimeter of the first surface of the baked cell assembly. The definition of the second cell perimeter can be found in the foregoing embodiments regarding the definition of the first cell perimeter, and will not be repeated here. In some embodiments, specifically, during the acquisition of the second morphological parameter set, a camera with a charge-coupled device (CCD) can also be used to scan and photograph the first surface of the baked cell assembly, and the scanned image can be analyzed and processed to obtain the specific length data of the required second cell perimeter; this is not limited here.

[0039] It is understood that, based on the relevant descriptions of the foregoing embodiments, the battery cell assembly may undergo significant abnormal appearance deformation before and after the baking process, leading to abnormal cell wrinkles. Therefore, in determining whether the battery cell assembly has abnormal cell wrinkles, the first cell circumference in the first set of morphological parameters and the second cell circumference in the second set of morphological parameters provided in the foregoing embodiments can be compared, and the abnormal cell wrinkles can be identified based on the comparison results. In some embodiments of this application, in determining whether the battery cell assembly has abnormal cell wrinkles, based on the first cell circumference and the second cell circumference, if the rate of change of the second cell circumference relative to the first cell circumference deviates from a first preset threshold, it can be determined that the battery cell assembly has abnormal cell wrinkles. In some embodiments, the rate of change of the second cell circumference relative to the first cell circumference can be determined by the ratio of the difference between the second cell circumference and the first cell circumference to the first cell circumference, and expressed as a percentage; specifically, the rate of change of the second cell circumference relative to the first cell circumference can be obtained by the following mathematical expression: ; in, The circumference of the second cell. The circumference of the first cell. It is the absolute value of the difference between the circumference of the second cell and the circumference of the first cell. The rate of change of the circumference of the second cell relative to the circumference of the first cell.

[0040] In some embodiments, further, if the rate of change of the circumference of the second cell relative to the circumference of the first cell deviates from a first preset threshold, it indicates that the change in the circumference of the second cell relative to the circumference of the first cell exceeds a preset allowable deformation range, and the cell assembly is identified as having cell wrinkling abnormality. In some embodiments, specifically, the first preset threshold can be set to 1%. When the rate of change of the circumference of the second cell relative to the circumference of the first cell is greater than or equal to 1%, the cell assembly can be identified as having cell wrinkling abnormality. In other embodiments, the first preset threshold can also be dynamically adjusted according to the actual process requirements of the battery cell manufacturing process, for example, it can be set to 0.5%, 1.5%, or the range [0%, 1.2%], etc., without limitation. In other embodiments, further considering that the theoretical data of the cell assembly of the same batch of battery cells are the same in appearance during the preparation of battery cells on a single production line, the rate of change of the circumference of the second cell relative to the circumference of the first cell can also be directly characterized by the difference between the circumference of the second cell and the circumference of the first cell. When the difference deviates from the preset first threshold (for example, the first preset threshold can be 1% of the design processing value corresponding to the circumference of the first cell of the cell assembly), it is determined that the cell assembly has abnormal cell wrinkles, which is not limited here.

[0041] In some embodiments of this application, in process 100 provided in the foregoing embodiments, the first set of morphological parameters may further include a first flatness parameter of the hot-pressed cell assembly, wherein the first flatness parameter includes the ratio of the minimum thickness to the maximum thickness of the first surface of the hot-pressed cell assembly in a first direction. In some embodiments, specifically, taking a cell assembly obtained by sequentially stacking a negative electrode, a separator, and a positive electrode and winding them around a preset winding shaft as an example, the first surface of the cell assembly may be a side perpendicular to the axial direction of the winding shaft, i.e., as shown in the figure. Figure 2 The first direction of the wound side shown can be the direction of the preset pressure applied during the pressing process in hot pressing, i.e., the hot pressing direction. It can be understood that the first flatness parameter of the battery cell assembly after hot pressing can reflect the flatness of the battery cell assembly, such as... Figure 2 Taking the battery cell assembly 200 as an example, under ideal conditions, the maximum thickness of the first surface of the battery cell assembly in the first direction after hot pressing is shown as length 250 in the figure, and the minimum thickness of the first surface of the battery cell assembly in the first direction after hot pressing is shown as length 260 in the figure. The ratio of the minimum thickness to the maximum thickness can be used to obtain the degree of thickness difference at different positions of the battery cell assembly in the first direction (i.e., the hot pressing direction). The closer the ratio of the minimum thickness to the maximum thickness is to 1, the closer the minimum thickness and the maximum thickness are numerically, and the better the flatness of the battery cell assembly in the first direction. In some embodiments, the first flatness parameter can be obtained by the following mathematical expression: ; in, The minimum thickness of the battery cell assembly in the first direction. The maximum thickness of the battery cell assembly in the first direction. This refers to the first flatness parameter of the battery cell assembly after hot pressing. In some embodiments, based on the above mathematical expression, it can be seen that the first flatness parameter of the battery cell assembly is negatively correlated with the flatness of the battery cell assembly in the first direction. The larger the value of the first flatness parameter, the worse the flatness of the battery cell assembly in the first direction. The first flatness parameter can also be obtained based on other mathematical expressions related to the ratio of the minimum thickness to the maximum thickness of the first surface of the battery cell assembly in the first direction, which is not limited here.

[0042] In some embodiments, the first flatness parameter may further include other parameters that can characterize the surface flatness of the battery cell assembly, such as the difference between the maximum and minimum thickness of the first surface of the hot-pressed battery cell assembly in the first direction, the number of surface protrusions on the first surface of the hot-pressed battery cell assembly in the first direction, etc., which are not limited here.

[0043] In some embodiments, correspondingly, in the process 100 provided in the foregoing embodiments, the second morphology parameter set specifically includes a second flatness parameter of the baked battery cell assembly, wherein the second flatness parameter includes the ratio of the minimum thickness to the maximum thickness of the first surface of the baked battery cell assembly in a first direction. The specific references to the first surface and the first direction can be found in the relevant descriptions in the foregoing embodiments, and will not be repeated here. In some embodiments, the second flatness parameter and the first flatness parameter provided in the foregoing embodiments can be determined using the same definition and acquisition method, and will not be limited here. In some embodiments, specifically, in the process of acquiring the second morphology parameter set, a camera with a charge-coupled device (CCD) can also be used to scan and photograph the first surface of the baked battery cell assembly, and the scanned image can be analyzed and processed to obtain the values ​​of the minimum and maximum thickness of the first surface of the baked battery cell assembly in the first direction, and then the second flatness parameter can be determined by calculation, and will not be limited here.

[0044] It is understood that, based on the descriptions in the foregoing embodiments, the battery cell assembly may undergo significant abnormal deformation due to pressure and heat during hot pressing and baking processes, leading to abnormal cell wrinkles. Therefore, in determining whether a battery cell assembly exhibits abnormal cell wrinkles, the first flatness parameter and the second flatness parameter from the first morphology parameter set provided in the foregoing embodiments can be used to identify abnormal cell wrinkles that may exist during the battery cell manufacturing process. In some embodiments of this application, in determining whether a battery cell assembly exhibits abnormal cell wrinkles, the first flatness parameter and the second flatness parameter can be used as a basis. If either the first flatness parameter or the second flatness parameter deviates from a second preset threshold, it can be determined that the battery cell assembly exhibits abnormal cell wrinkles. In some embodiments, the first flatness parameter and the second flatness parameter of the battery cell assembly can be obtained based on the mathematical expressions provided in the foregoing embodiments and represented as percentages, without limitation. Further, if the first flatness parameter or the second flatness parameter deviates from the second preset threshold, it indicates that the flatness of the battery cell assembly exceeds the preset allowable deviation range during the hot pressing and / or baking process, and it is determined that the battery cell assembly has abnormal cell wrinkles. In some embodiments, specifically, the second preset threshold can be set to 1%. When the first flatness parameter or the second flatness parameter is greater than or equal to 1%, it can be determined that the battery cell assembly has abnormal cell wrinkles. In other embodiments, the second preset threshold can also be dynamically adjusted according to the actual process requirements of the battery cell preparation process, for example, it can be set to 0.4%, 1.4%, or the range [0%, 1.1%], without limitation. In other embodiments, the flatness parameter and the second flatness parameter of the battery cell assembly can also be determined based on the number of surface protrusions in the first direction on the first surface of the battery cell assembly. When the number of surface protrusions in the first direction on the first surface of the battery cell assembly after hot pressing or baking exceeds a predetermined number of the second preset threshold, it is determined that the battery cell assembly has abnormal cell wrinkles, which is not limited here.

[0045] In some embodiments of this application, the first set of morphological parameters may simultaneously include the first cell perimeter and the first flatness parameter provided in the foregoing embodiments; correspondingly, the second set of morphological parameters may simultaneously include the second cell perimeter and the second flatness parameter provided in the foregoing embodiments; in the process of determining whether there is a cell wrinkle abnormality in the cell assembly, it is possible to synchronously or asynchronously determine whether the rate of change of the second cell perimeter relative to the first cell perimeter deviates from the first preset threshold, and whether the first flatness parameter or the second flatness parameter deviates from the second preset threshold. If the result of any one of the determinations is a deviation, it is determined that there is a cell wrinkle abnormality in the cell assembly, which is not limited here.

[0046] Based on the descriptions of the foregoing embodiments, it is possible to determine whether there are abnormal cell wrinkles after hot pressing and baking based on the overall morphological changes of the cell assembly. In some embodiments of this application, considering that abnormal cell wrinkles are usually caused by the thermal shrinkage of the tension diaphragm in the cell assembly, the tension diaphragm in the cell assembly can also be independently identified and judged during the identification of abnormal cell wrinkles. In some embodiments, the specific implementation of step 120 provided in the foregoing embodiments may include the following steps: performing diaphragm thermal shrinkage marking processing on the hot-pressed cell assembly; correspondingly, the first morphological parameter set may include the marking result corresponding to the diaphragm thermal shrinkage marking processing, and the second morphological parameter set includes the marking result after baking. The marking result can be obtained by taking pictures of the cell assembly with a camera equipped with a charge-coupled device (CCD), which is not limited here. In some embodiments, specifically during the process of heat shrink marking the diaphragm, a preset imprint mark can be applied to the corresponding position on each tab side of the battery cell assembly using a stamp at the end of the diaphragm. This imprint mark is the marking result corresponding to the heat shrink marking process of the diaphragm. In some embodiments, the imprint mark can specifically be a square mark of 10 cm by 10 cm, formed by a colored coating that does not affect the performance of the battery cell assembly after liquid injection, and is not limited here.

[0047] In some embodiments of this application, further, Figure 3 This diagram illustrates a process for determining whether a battery cell assembly exhibits abnormal cell wrinkling. Figure 3 As shown, process 300 may specifically include the following steps: Step 310: Based on the difference in marking results before and after baking, determine the membrane heat shrinkage parameters of the battery cell assembly.

[0048] Step 320: If the membrane heat shrinkage parameter deviates from the third preset threshold, it is determined that the cell assembly has abnormal cell wrinkling. In some embodiments, taking a square marking of 10 cm by 10 cm as an example, the membrane heat shrinkage parameter of the cell assembly can be obtained based on the following mathematical expression: ; in, The area occupied by the marking results before baking. This represents the area occupied by the marking results after baking. This is the absolute value of the difference between the area occupied by the marking result after baking and the area occupied by the marking result before baking. This refers to the thermal shrinkage parameter of the separator in the battery cell assembly. Based on the above mathematical expression, it can be seen that the larger the thermal shrinkage parameter of the separator in the battery cell assembly, the more obvious the thermal shrinkage of the separator, and the higher the probability of abnormal cell wrinkling in the battery cell assembly. In some embodiments, specifically, the third preset threshold can be set to 0.5%. When the thermal shrinkage parameter of the separator in the battery cell assembly is greater than 0.5%, it can be considered that the battery cell assembly has abnormal cell wrinkling. In other embodiments, the third preset threshold can also be dynamically adjusted according to the actual process requirements of the battery cell manufacturing process, for example, it can be set to 0.2%, 0.3%, or the range [0%, 0.4%], etc., without limitation here.

[0049] In some embodiments of this application, during the process of repairing a cell assembly with abnormal cell wrinkles in the aforementioned embodiment, the process may specifically include: performing a secondary hot-pressing shaping process on the cell assembly, and / or performing a preset current charge-discharge process on the cell assembly. It is understood that when abnormal cell wrinkles are identified in the cell assembly, the cell assembly can be re-hot-pressed to enhance the bonding density between the various layers of the cell assembly, reducing or even eliminating the existing cell wrinkles. For example, the hot-pressing parameters for the secondary hot-pressing shaping process can be set to a hot-pressing load of 4t and a duration of 30 seconds, etc., without limitation. In some embodiments, in addition to using a secondary hot-pressing shaping process to repair abnormal cell wrinkles, a preset current charge-discharge process can also be used to repair abnormal cell wrinkles: it is understood that by controlling the preset small charge-discharge current of the cell assembly, the various layers of the cell assembly can expand relatively uniformly and slowly during charging, using the expansion force to eliminate abnormal cell wrinkles, without limitation.

[0050] Based on the descriptions of the foregoing embodiments, it is possible to perform wrinkle repair processing on battery cell components with cell wrinkling abnormalities. However, whether the battery cell component after wrinkle repair still has unresolved cell wrinkling abnormalities requires further identification and evaluation. In some embodiments of this application, further, in the process 100 provided in the foregoing embodiments, after step 140 is executed, a third set of morphological parameters of the battery cell component after wrinkle repair processing can be obtained; then, based on the first set of morphological parameters, the second set of morphological parameters, and the third set of morphological parameters, it is determined whether the battery cell component has unrepaired cell wrinkling abnormalities, and the wrinkle repair processing is repeated on the battery cell components with unrepaired cell wrinkling abnormalities. In some embodiments, the parameter items included in the third set of morphological parameters may correspond to the parameter items included in the first and second sets of morphological parameters provided in the foregoing embodiments, and are not limited here. In some embodiments, the cell assembly may still have cell wrinkle abnormalities after a single wrinkle repair treatment. The solution provided in this application supports continuous cyclic wrinkle repair treatment of the cell assembly after wrinkle repair treatment, which can continuously reduce the existing battery wrinkle abnormalities, thereby achieving zero wrinkle abnormalities in the cell assembly. In other embodiments, if the cell assembly still has cell wrinkle abnormalities that are difficult to eliminate after a preset number of wrinkle repair treatments, it can be considered that the wrinkle abnormalities of the cell assembly are difficult to repair through wrinkle repair treatment and need to be scrapped. This is not limited here.

[0051] In some embodiments of this application, the battery cell preparation method can not only eliminate abnormal cell wrinkles in the battery cell assembly, but also establish a cell wrinkle database based on the various process data collected during the preparation process. This database can be used to provide reverse guidance for preparation process windows such as electrode winding and cell hot pressing, which helps to reduce the difficulty of exploring various process windows and / or the difficulty of troubleshooting preparation equipment failures during the preparation of battery cells. This is not limited here.

[0052] In some embodiments of this application, a battery cell is also provided, which can be prepared by the preparation method of the battery cell provided in the foregoing embodiments. In some embodiments, the battery cell provided in this application can be widely used in battery fields requiring high energy density and long cycle life, including high-end electric vehicle battery systems, portable electronic devices, and large-scale energy storage power stations. The battery cell provided in this application can achieve large-capacity energy storage, achieving a comprehensive improvement in energy density, cycle life, and safety performance, and can meet the needs of long-term energy storage, achieving long-term energy storage of 4 hours or more, for example, it can be applied to energy storage scenarios such as 5 hours, 6 hours, and 8 hours. Herein, long-term energy storage means being able to continuously discharge for 4 hours or even longer at rated power, or achieving large-scale low-cost energy storage for several days or months.

[0053] In some embodiments of this application, an energy storage device is also provided, which includes multiple battery cells provided in the foregoing embodiments. In some embodiments, the energy storage device provided in this application includes, but is not limited to, residential energy storage cabinets, commercial energy storage cabinets, energy storage containers, energy storage racks, energy storage power stations, energy storage battery packs, or portable energy storage devices. The energy storage device may also include an energy management system (EMS), a battery management system (BMS), and a power conversion system (PCS).

[0054] Those skilled in the art will understand that the above embodiments are specific examples of implementing this application, and in practical applications, various changes in form and detail can be made without departing from the spirit and scope of this application. Any person skilled in the art can make various alterations and modifications without departing from the spirit and scope of this application; therefore, the scope of protection of this application should be determined by the scope defined in the claims.

Claims

1. A method for producing a battery cell, characterized by, include: A battery cell assembly is obtained, the battery cell assembly comprising a negative electrode, a separator, and a positive electrode stacked together; The battery cell assembly is subjected to hot pressing treatment, and a first set of morphological parameters of the battery cell assembly after hot pressing treatment is obtained; The hot-pressed battery cell assembly is then baked to obtain a second set of morphological parameters for the baked battery cell assembly. Based on the first set of morphological parameters and the second set of morphological parameters, it is determined whether the cell assembly has cell wrinkle abnormalities. If the battery cell assembly has the abnormality of cell wrinkles, the battery cell assembly is subjected to wrinkle repair treatment; The cell assembly without the cell wrinkle abnormality, and / or the cell assembly with the cell wrinkle abnormality eliminated after the wrinkle repair treatment, are placed in the housing to obtain the battery cell. Wherein, the first set of morphological parameters includes the first cell perimeter of the battery cell assembly after hot pressing, the first cell perimeter being the perimeter of the first surface of the battery cell assembly after hot pressing; the second set of morphological parameters includes the second cell perimeter of the battery cell assembly after baking, the second cell perimeter being the perimeter of the first surface of the battery cell assembly after baking; and / or The first set of morphological parameters includes a first flatness parameter of the battery cell assembly after hot pressing, wherein the first flatness parameter includes the ratio of the minimum thickness to the maximum thickness of the first surface of the battery cell assembly after hot pressing in a first direction; the second set of morphological parameters includes a second flatness parameter of the battery cell assembly after baking, wherein the second flatness parameter includes the ratio of the minimum thickness to the maximum thickness of the first surface of the battery cell assembly after baking in a first direction.

2. The method of claim 1, wherein the method further comprises: The determination of whether the battery cell assembly has abnormal cell wrinkles includes: Based on the first cell circumference and the second cell circumference, if the rate of change of the second cell circumference relative to the first cell circumference deviates from a first preset threshold, it is determined that the cell assembly has the cell wrinkling abnormality.

3. The method for preparing a single battery cell according to claim 1, characterized in that, The determination of whether the battery cell assembly has abnormal cell wrinkles includes: Based on the first flatness parameter and the second flatness parameter, if the first flatness parameter or the second flatness parameter deviates from the second preset threshold, it is determined that the cell assembly has cell wrinkling abnormality.

4. The method for preparing a single battery cell according to claim 1, characterized in that, Also includes: The cell assembly after hot pressing is subjected to diaphragm heat shrink marking treatment, and the first set of morphology parameters includes the marking results corresponding to the diaphragm heat shrink marking treatment; The second set of morphological parameters includes the marking results after the baking process.

5. The method for preparing a single battery cell according to claim 4, characterized in that, The determination of whether the battery cell assembly has abnormal cell wrinkles includes: Based on the difference in the marking results before and after the baking process, the thermal shrinkage parameters of the separator in the battery cell assembly are determined. If the diaphragm heat shrinkage parameter deviates from the third preset threshold, it is determined that the cell assembly has cell wrinkling abnormality.

6. The method for preparing a single battery cell according to claim 1, characterized in that, The process of repairing the cell assembly with the cell wrinkling abnormality includes: The battery cell assembly undergoes a secondary hot-pressing molding process; and / or The battery cell assembly is subjected to a preset current charge / discharge process.

7. The method for preparing a single battery cell according to claim 1, characterized in that, Also includes: Obtain the third set of morphological parameters of the battery cell assembly after the wrinkle repair treatment; Based on the first set of morphological parameters, the second set of morphological parameters, and the third set of morphological parameters, it is determined whether there are unrepaired cell wrinkles in the cell assembly, and the wrinkle repair process is repeated for the cell assembly with unrepaired cell wrinkles.

8. A single battery cell, characterized in that, The battery cell is prepared by the method for preparing a battery cell according to any one of claims 1 to 7.

9. An energy storage device, characterized in that, include: Multiple battery cells as described in claim 8.

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