Method, device, storage medium and computer program product for determining battery lithium deposition

Abstract

The present application discloses a method, device, storage medium and computer program product for determining lithium deposition in a battery. The method comprises: obtaining the expansion force difference and capacity attenuation corresponding to the battery for each charge and discharge cycle in multiple charge and discharge cycles, wherein the expansion force difference is determined by the maximum expansion force of the battery during charge and the minimum expansion force of the battery during discharge; determining the amount of lithium deposition in the battery according to the expansion force difference and capacity attenuation corresponding to the battery during each charge and discharge cycle. The solution provided by the present application can realize non-destructive quantitative analysis of the lithium deposition behavior of the battery, and reduce the complexity of quantitative analysis of lithium deposition in the battery.

Description

Technical Field

[0001] The present application relates to the field of battery testing technology, and in particular to a method, device, storage medium and computer program product for determining battery lithium deposition. Background Art

[0002] During the battery aging process, the lithium deposition behavior of the battery will reduce the battery performance, causing the battery capacity to decay or even drop, shortening the battery life and reducing the battery safety. Therefore, how to monitor the lithium deposition behavior of the battery in real time during the aging process is of great significance. Summary of the invention

[0003] The present application provides a method, device, storage medium and computer program product for determining battery lithium deposition, which can realize non-destructive quantitative analysis of battery lithium deposition behavior and reduce the complexity of quantitative analysis of battery lithium deposition.

[0004] In a first aspect, the present application provides a method for determining lithium deposition in a battery, the method comprising: obtaining the expansion force difference and capacity attenuation corresponding to the battery for each charge and discharge cycle in multiple charge and discharge cycles, wherein the expansion force difference is determined by the maximum expansion force of charging and the minimum expansion force of discharging of the battery; determining the amount of lithium deposition in the battery according to the expansion force difference and capacity attenuation corresponding to the battery in each charge and discharge cycle.

[0005] In the embodiment of the present application, the expansion force difference and capacity attenuation in the battery charge and discharge cycle are collected in real time to realize real-time monitoring of the capacity attenuation change of the battery. Since in the embodiment of the present application, the lithium deposition of the battery will reduce the expansion force difference in the battery charge and discharge cycle, therefore, the capacity loss caused by the lithium deposition of the battery, that is, the amount of lithium deposition of the battery, can be determined by the change law of the expansion force difference with the battery capacity attenuation. Therefore, by monitoring the change of the expansion force difference and the capacity attenuation of the battery, the real-time monitoring of the amount of lithium deposition of the battery can be realized, and by analyzing the change of the expansion force difference with the change of the capacity attenuation of the battery, the quantitative analysis of irreversible lithium deposition during the battery aging process can be realized. In addition, in the process of monitoring the capacity attenuation of the battery, there is no need to disassemble the battery, and there is no need to perform complex calculations, thereby reducing the complexity of the quantitative analysis of battery lithium deposition.

[0006] In some embodiments, the expansion force difference and capacity attenuation of the battery in each charge and discharge cycle of multiple charge and discharge cycles are obtained, including: obtaining the initial discharge capacity corresponding to the first charge and discharge cycle of the multiple charge and discharge cycles; calculating the discharge capacity ratio of the discharge capacity in each charge and discharge cycle to the initial discharge capacity; and determining the capacity attenuation corresponding to each charge and discharge cycle according to the discharge capacity ratio in each charge and discharge cycle.

[0007] During the process of battery lithium deposition, the expansion force difference changes with the growth law of capacity attenuation. Therefore, by determining the phased change law of the expansion force difference curve and the capacity attenuation corresponding to the characteristic point and analyzing it, the quantitative analysis of battery lithium deposition can be realized; moreover, the capacity attenuation and expansion force difference of the battery can be determined only by charging and discharging the battery, without disassembling and reassembling the battery, thus reducing the complexity of the quantitative analysis of battery lithium deposition.

[0008] In some embodiments, the amount of lithium deposition of the battery is determined based on the expansion force difference and capacity attenuation of the battery in each charge and discharge cycle, including: performing data fitting based on the expansion force difference and capacity attenuation of the battery in each charge and discharge cycle to obtain a first curve, wherein the first curve is used to characterize the change pattern of the expansion force difference with the capacity attenuation; when there is an inflection point on the first curve, determining the target capacity attenuation change corresponding to the battery according to the first curve; and determining the amount of lithium deposition of the battery according to the target capacity attenuation change.

[0009] By determining the phased change law of the expansion force difference curve and the capacity attenuation corresponding to the characteristic points, and analyzing them, quantitative analysis of battery lithium plating can be achieved; moreover, the capacity attenuation and expansion force difference of the battery can be determined only by charging and discharging the battery, without disassembling and reassembling the battery, thereby reducing the complexity of quantitative analysis of battery lithium plating.

[0010] In some embodiments, before determining the target capacity attenuation change corresponding to the battery according to the first curve, it is detected whether there is an inflection point in the first curve; if there is no inflection point in the first curve, it is determined that the battery does not have lithium plating behavior; if there is an inflection point in the first curve, it is determined that the battery has lithium plating behavior.

[0011] By detecting whether there is an inflection point in the first curve, it is possible to quickly determine whether the battery has lithium deposition behavior. This method reduces the complexity of battery lithium deposition behavior detection and improves the efficiency and accuracy of battery lithium deposition behavior detection.

[0012] In some embodiments, when there is an inflection point on the first curve, determining a target capacity attenuation change corresponding to the battery based on the first curve includes: determining a linear segment corresponding to before the first inflection point from the first curve; and analyzing the first curve and the second curve where the linear segment is located to obtain the target capacity attenuation change corresponding to the battery.

[0013] After obtaining the second curve, the first curve is analyzed with reference to the second curve to determine the target capacity attenuation change corresponding to the battery. This process only requires simple curve analysis to achieve quantitative analysis of irreversible lithium deposition of battery capacity attenuation, without the need to disassemble and reassemble the battery, reducing the complexity of quantitative analysis of battery lithium deposition.

[0014] In some embodiments, when there is an inflection point in the first curve, the first curve and the second curve where the linear segment is located are analyzed to obtain a target capacity decay change amount corresponding to the battery, including: obtaining a first expansion force difference corresponding to the first inflection point, and a second expansion force difference of the last charge and discharge cycle in multiple charge and discharge cycles; calculating the ratio of the first difference to the slope of the second curve to obtain a first capacity decay change amount, wherein the first difference is the difference between the second expansion force difference and the first expansion force difference, and the first capacity decay change amount is used to characterize the capacity decay caused by the generation of a fixed electrolyte interface SEI film; and determining the target capacity decay change amount according to the first capacity decay change amount.

[0015] In the process of determining the target capacity attenuation change caused by lithium deposition in the battery, the effect of SEI film formation on battery capacity attenuation is taken into account, thereby improving the accuracy of the capacity attenuation change caused by lithium deposition in the battery.

[0016] In some embodiments, when there are multiple inflection points in the first curve, the first curve and the second curve where the linear segment is located are analyzed to obtain a target capacity decay change corresponding to the battery, including: determining a first expansion force difference corresponding to the first inflection point and a third expansion force difference corresponding to the second inflection point from the first curve; determining a first capacity decay change caused by generating a fixed electrolyte interface SEI film according to the first expansion force difference, the third expansion force difference and the slope of the second curve; and determining a target capacity decay change according to the first capacity decay change.

[0017] In some embodiments, a first capacity decay change caused by generating a fixed electrolyte interface SEI film is determined based on the first expansion force difference, the third expansion force difference, and the slope of the second curve, including: calculating the difference between the first expansion force difference and the third expansion force difference to obtain a fourth expansion force difference; calculating the ratio of the fourth expansion force difference to the slope of the second curve to obtain the first capacity decay change.

[0018] By determining the impact of SEI film formation on battery capacity decay, the accuracy of capacity decay changes caused by battery lithium deposition can be improved.

[0019] In some embodiments, a target capacity attenuation change is determined based on the first capacity attenuation change, including: calculating the difference between the second capacity attenuation and the first capacity attenuation corresponding to the first inflection point to obtain the second capacity attenuation change, wherein the second capacity attenuation is the capacity attenuation of the last charge and discharge cycle in multiple charge and discharge cycles; calculating the difference between the second capacity attenuation change and the first capacity attenuation change to obtain the target capacity attenuation change.

[0020] The first capacity decay variation caused by the formation of SEI film is removed from the total capacity decay variation generated during the battery lithium deposition process to obtain the target capacity decay variation. This can not only realize the non-destructive quantitative analysis of the battery lithium deposition behavior and reduce the complexity of the quantitative analysis of the battery lithium deposition, but also improve the accuracy of the quantitative analysis of the battery lithium deposition.

[0021] In a second aspect, the present application also provides a device for determining lithium deposition in a battery, the device comprising: a data acquisition module for obtaining the expansion force difference and capacity attenuation corresponding to the battery in each charge and discharge cycle of multiple charge and discharge cycles, wherein the expansion force difference is determined by the maximum expansion force of charging and the minimum expansion force of discharging of the battery; a lithium deposition amount determination module for determining the lithium deposition amount of the battery based on the expansion force difference and capacity attenuation corresponding to the battery in each charge and discharge cycle.

[0022] In a fourth aspect, the present application provides a readable storage medium having computer program instructions stored thereon, and when the computer program instructions are executed by a processor, the method for determining battery lithium deposition as described in the first aspect is implemented.

[0023] In a fifth aspect, the present application provides a computer program product. When the instructions in the computer program product are executed by a processor of an electronic device, the electronic device executes the method for determining battery lithium deposition as described in the first aspect.

[0024] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The features, advantages and technical effects of exemplary embodiments of the present application will be described below with reference to the accompanying drawings.

[0026] Figure 1 A flow chart of a method for determining battery lithium deposition according to an embodiment of the present application;

[0027] Figure 2 This is a flow chart for determining the amount of lithium deposition in a battery according to one embodiment of the present application;

[0028] Figure 3 A graph showing the relationship between the expansion force difference and the capacity attenuation according to an embodiment of the present application;

[0029] Figure 4 A schematic diagram of a device for determining battery lithium deposition according to another embodiment of the present application.

[0030] In the drawings, the drawings are not necessarily drawn to scale. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0032] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by technicians in the technical field to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" in the specification and claims of this application and the above-mentioned figure descriptions and any variations thereof are intended to cover non-exclusive inclusions.

[0033] In the description of the embodiments of the present application, the technical terms "first", "second", etc. are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features. In the description of the embodiments of the present application, the meaning of "multiple" is more than two, unless otherwise clearly and specifically defined.

[0034] Mentioning "embodiment" in the embodiments of the present application means that the specific features, structures or characteristics described in conjunction with the embodiment may be included in at least one embodiment of the present application. The appearance of the phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiment described in the embodiments of the present application can be combined with other embodiments.

[0035] In the description of the embodiments of the present application, the term "and / or" is only a description of the association relationship of the associated objects, indicating that there may be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0036] In the description of the embodiments of the present application, the term "multiple" refers to more than two (including two). Similarly, "multiple groups" refers to more than two groups (including two groups), and "multiple pieces" refers to more than two pieces (including two pieces).

[0037] In the description of the embodiments of the present application, the technical terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, which are only for the convenience of describing the embodiments of the present application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the embodiments of the present application.

[0038] In the description of the embodiments of the present application, unless otherwise clearly specified and limited, technical terms such as "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, and it can be the internal connection of two elements or the interaction relationship between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the embodiments of the present application can be understood according to the specific circumstances.

[0039] Lithium deposition is a loss condition of lithium-ion batteries. It is a phenomenon in which lithium metal dissolves, migrates and deposits due to internal chemical reactions during the use or storage of lithium-ion batteries. This phenomenon can lead to a decrease in battery performance and cause safety issues. Therefore, it is of great significance to conduct quantitative analysis of lithium deposition in batteries.

[0040] In related technologies, the following two methods are usually used to achieve quantitative analysis of battery lithium deposition:

[0041] Method 1: Disassemble the battery, take out the positive electrode, electrolyte and separator, and assemble them with the negative electrode embedded with lithium into a new battery. Then monitor the discharge capacity of the new battery to monitor the amount of lithium deposition in the negative electrode of the battery.

[0042] Method 2: Charge the lithium-ion battery using a constant voltage method, then discharge it using a constant current method, and record the curve of voltage change over time during the discharge process. Perform a second-order differential calculation on the curve, and then determine the amount of reversible lithium deposition during the battery charging process based on the inflection point and current obtained from the differential calculation.

[0043] The above-mentioned method 1 has a complex testing process, involving battery disassembly and reassembly, and cannot achieve real-time monitoring and quantification of lithium plating behavior during battery aging; the above-mentioned method 2 is computationally complex, and it only achieves quantitative analysis of reversible lithium plating during the energy-quantified charging process, but cannot quantify the irreversible lithium plating that causes battery capacity decay.

[0044] The applicant has found through research that during the charging and discharging process of the battery, there is a linear relationship between the difference between the maximum expansion force of the battery during charging and the minimum expansion force of the battery during discharging and the battery capacity attenuation. Moreover, after the battery undergoes lithium deposition, the difference between the charge and discharge expansion forces slows down along with the growth rate of the battery capacity attenuation. Based on this, the embodiments of the present application propose a method, device, storage medium, and computer program product for determining lithium deposition in a battery.

[0045] In an embodiment of the present application, a correlation relationship between the difference in charge and discharge expansion force of the battery and the battery capacity attenuation is constructed, and the correlation relationship is analyzed to monitor whether the battery has lithium deposition behavior. When it is determined that the battery has lithium deposition behavior, the amount of lithium deposition corresponding to the battery can be determined by further analyzing the correlation relationship.

[0046] Moreover, considering that the SEI (Solid Electrolyte Interface) film will also affect the battery capacity attenuation during the battery lithium deposition process, in the embodiment of the present application, the battery capacity attenuation caused by the formation of the SEI film after the battery lithium deposition and the battery capacity attenuation caused by the battery lithium deposition can also be calculated through the above-mentioned correlation relationship, which not only realizes the analysis of multiple factors causing battery capacity attenuation, but also improves the accuracy of quantitative analysis of battery lithium deposition.

[0047] It should be noted that after completing the quantitative analysis of lithium plating of a battery using the solution provided in the embodiment of the present application, the quantitative analysis results of lithium plating of the battery can be used to perform performance analysis on the battery or batteries of this type to detect whether batteries of this type meet the performance requirements of battery research and development, or to determine whether batteries of this type can be applied to specified application scenarios.

[0048] The following is an introduction to the method for determining battery lithium deposition provided in the embodiments of the present application.

[0049] It should be noted that the method provided in the embodiment of the present application can be applied to a battery analysis system, which includes at least a battery clamping component, a battery charging and discharging component, a data acquisition component, and a data analysis component. Among them, the battery clamping component is used to clamp the battery and collect the expansion force during the battery charging and discharging process; the data acquisition component can not only obtain the expansion force collected by the battery clamping component, but also collect the capacity decay data of the battery; the data analysis component is used to perform data analysis on the expansion force during the battery charging and discharging process and the battery capacity decay data, so as to realize the quantitative analysis of the lithium deposition of the battery.

[0050] In one embodiment, Figure 1 A flow chart showing a method for determining battery lithium deposition is shown, Figure 1As shown, the method may include the following steps S101 to S102:

[0051] Step S101, obtaining the expansion force difference and capacity attenuation corresponding to each charge and discharge cycle of the battery in multiple charge and discharge cycles.

[0052] In step S101, the battery is a lithium-ion battery, for example, a lithium iron phosphate battery. In the embodiment of the present application, a charge-discharge cycle includes a charging stage and a discharging stage of the battery, and each charge-discharge cycle obtains a set of data, each set of data includes an expansion force difference and a capacity attenuation amount; multiple sets of data can be obtained through multiple charge-discharge cycles, and the amount of lithium deposition of the battery can be determined by analyzing the multiple sets of data.

[0053] It should be noted that before testing the battery, it is necessary to deploy the test environment and set the test parameters corresponding to the test environment, where the test parameters include but are not limited to the test temperature, charge rate, and discharge rate. In multiple charge and discharge cycle tests of the same battery, the test environment for each charge and discharge cycle test is the same. In addition, the number of charge and discharge cycle tests can be set according to the test requirements of the battery, and is not specifically limited here.

[0054] In step S101, the expansion force difference corresponding to the battery is determined by the maximum expansion force of the battery during charging and the minimum expansion force of the battery during discharging, wherein the expansion force difference of the battery can be determined by formula (1):

[0055] (1)

[0056] In formula (1), is the expansion force difference of the battery; The maximum expansion force of the battery during charging. It is the minimum expansion force during discharge, that is, the minimum expansion force of the battery during discharge.

[0057] In addition, in step S101, the capacity decay of the battery can be determined by the discharge capacity of the battery. Specifically, the initial discharge capacity corresponding to the first charge and discharge cycle in multiple charge and discharge cycles is obtained by the data acquisition component; the data analysis component calculates the discharge capacity ratio of the discharge capacity in each charge and discharge cycle to the initial discharge capacity, and then determines the capacity decay corresponding to each charge and discharge cycle according to the discharge capacity ratio in each charge and discharge cycle.

[0058] As an example, the capacity decay corresponding to each charge and discharge cycle can be determined by formula (2):

[0059] (2)

[0060] In formula (2), is the capacity attenuation; is the initial discharge capacity corresponding to the first charge and discharge cycle; It is the discharge capacity corresponding to each charge and discharge cycle.

[0061] It should be noted that during the process of battery lithium deposition, the expansion force difference changes with the growth law of capacity attenuation. Therefore, by determining the phased change law of the expansion force difference curve and the capacity attenuation corresponding to the characteristic point and analyzing it, the quantitative analysis of battery lithium deposition can be realized; moreover, the capacity attenuation and expansion force difference of the battery can be determined only by charging and discharging the battery, without disassembling and reassembling the battery, thereby reducing the complexity of the quantitative analysis of battery lithium deposition.

[0062] Step S102, determining the amount of lithium deposition in the battery according to the difference in expansion force and capacity attenuation of the battery in each charge and discharge cycle.

[0063] In step S102, multiple sets of data can be obtained by acquiring the expansion force difference and capacity attenuation of the battery in multiple charge and discharge cycles. By performing data fitting on the multiple sets of data, a correlation relationship between the expansion force difference and the capacity attenuation that characterizes the battery can be obtained. By analyzing the correlation relationship, the amount of lithium plating in the battery can be determined.

[0064] Based on the scheme defined by the above steps S101 to S102, it can be known that in the embodiment of the present application, the expansion force difference and the capacity decay amount in the battery charge and discharge cycle are collected in real time to realize real-time monitoring of the capacity decay change of the battery. Since in the embodiment of the present application, the lithium deposition of the battery will reduce the expansion force difference in the battery charge and discharge cycle, therefore, the capacity loss caused by the lithium deposition of the battery, that is, the lithium deposition amount of the battery, can be determined by the change law of the expansion force difference with the battery capacity decay. Therefore, by monitoring the change of the expansion force difference and the capacity decay of the battery, the real-time monitoring of the lithium deposition amount of the battery can be realized, and by analyzing the change of the expansion force difference with the capacity decay change of the battery, the quantitative analysis of irreversible lithium deposition during the battery aging process can be realized. In addition, in the process of monitoring the capacity decay of the battery, there is no need to disassemble the battery, and there is no need to perform complex calculations, thereby reducing the complexity of the quantitative analysis of the lithium deposition of the battery.

[0065] The following is an introduction to the implementation process of the method provided in the embodiment of the present application.

[0066] After obtaining the capacity attenuation and expansion force difference of the battery in each charge and discharge cycle, such as Figure 2 As shown, the data analysis component determines the amount of lithium deposition in the battery through the following steps S1021 to S1023:

[0067] Step S1021, according to the expansion force difference and capacity attenuation corresponding to the battery in each charge and discharge cycle, the relationship between the expansion force difference and the capacity attenuation is fitted to obtain a first curve.

[0068] In step S1021, multiple sets of data can be obtained through multiple charge and discharge cycles, and the difference in expansion force can be obtained by fitting the multiple sets of data. Capacity attenuation The first curve of the relationship between .

[0069] As an example, a lithium iron phosphate battery with a nominal capacity of 172Ah is used as a test object, and the test environment is configured to obtain a test environment with a test temperature of 45°C, a charge rate of 1P, and a discharge rate of 1P. The discharge capacity, the maximum charge expansion force, and the minimum discharge expansion force of each charge and discharge cycle are recorded during the charge and discharge cycle. The expansion force difference and the capacity attenuation of each charge and discharge cycle are calculated, and then data fitting is performed. For example, using the existing data fitting method, the following can be obtained: Figure 3 The difference in the indicated expansion force is shown Capacity attenuation The first curve L1 of the relationship between .

[0070] Step S1022: when there is an inflection point on the first curve, determine a target capacity attenuation change amount corresponding to the battery according to the first curve.

[0071] Combination Figure 3 From the first curve L1 in the figure, we can see that the battery tops the shell near Qloss=5%, and then ∆F grows steadily; after point A (17.14%, 918.46), the growth trend of ∆F slows down; after point C (20.89%, 1030.71), ∆F remains basically unchanged. It can be inferred that point A is the initial point of lithium precipitation, and the slow growth trend of ∆F in the AC interval is the result of the combined effect of lithium precipitation and SEI film formation; the SEI film formation behavior basically ends at point C, and the CD segment is mainly lithium precipitation behavior.

[0072] Based on the above analysis, as long as there is an inflection point in the first curve L1, it can be determined that the battery has lithium deposition behavior in multiple charge and discharge cycles, and the first inflection point of the first curve L1 is the initial point of lithium deposition. If no new SEI film is generated in the future, the first curve L1 will go straight after the inflection point, and the change in Qloss corresponding to the straight section (i.e., the change in capacity attenuation) is the capacity loss caused by lithium deposition; if SEI film is generated during the lithium deposition process, the growth rate of the first curve L1 will slow down after the inflection point, and the change in Qloss corresponding to the force value of the slow-down interval (i.e., Figure 3 Q1 in the figure is the capacity loss caused by lithium plating, and this capacity loss is the target capacity attenuation change Q2.

[0073] Step S1023, determining the lithium deposition amount of the battery according to the target capacity attenuation change.

[0074] In step S1023, the target capacity decay variation is used to characterize the battery capacity loss caused by the lithium deposition of the battery, which can reflect the amount of lithium deposition of the battery during the entire test process. For example, the correlation between the capacity decay variation caused by the lithium deposition of the battery and the amount of lithium deposition of the battery can be pre-established. After determining the target capacity decay variation caused by the lithium deposition of the battery, the amount of lithium deposition of the battery can be determined through the above correlation, thereby realizing non-destructive quantitative analysis of the lithium deposition behavior of the battery and reducing the complexity of the quantitative analysis of the lithium deposition of the battery.

[0075] After obtaining the expansion force difference and capacity attenuation of the battery in multiple charge and discharge cycles, and fitting the relationship between the expansion force difference and capacity attenuation according to the expansion force difference and capacity attenuation corresponding to the battery in each charge and discharge cycle, and obtaining the first curve, the data analysis component can detect whether there is an inflection point in the first curve, and determine whether the battery has lithium deposition behavior based on the detection result. Specifically, if there is no inflection point in the first curve, the data analysis component can determine that the battery does not have lithium deposition behavior; if there is an inflection point in the first curve, the data analysis component determines that the battery has lithium deposition behavior.

[0076] In one example, if Figure 3 As shown, when there is no lithium deposition in the battery, the expansion force difference Capacity attenuation Steady growth, such as Figure 3 The line segment before point A of the first curve L1 in the figure; when lithium deposition occurs in the battery, the expansion force difference Capacity attenuation The growth trend slowed down, such as Figure 3 It can be seen that point A is the inflection point of the first curve L1, that is, when there is an inflection point in the first curve L1, it can be determined that the battery has lithium deposition behavior, and the initial point of lithium deposition is the first inflection point.

[0077] By detecting whether there is an inflection point in the first curve, it is possible to quickly determine whether the battery has lithium deposition behavior. This method reduces the complexity of battery lithium deposition behavior detection and improves the efficiency and accuracy of battery lithium deposition behavior detection.

[0078] When there is an inflection point in the first curve, it can be determined that the battery has lithium deposition behavior. In this scenario, the data analysis component determines the linear segment corresponding to the first inflection point from the first curve, and analyzes the first curve and the second curve where the linear segment is located to obtain the target capacity attenuation change corresponding to the battery.

[0079] by Figure 3 For example, when the first curve L1 has an inflection point, the first curve L1 is divided into two curve segments with the first inflection point A as the boundary, wherein the first curve segment, that is, the line segment before the first inflection point A, is a linear segment. By fitting the linear segment, the second curve L2 can be obtained. That is, the curve where the linear segment of the first curve L1 is located is the second curve L2. L2 can be expressed by formula (3):

[0080] (3)

[0081] In formula (3), k is the slope of the second curve L2, and b is the intercept of the second curve L2. Figure 3 middle, , .

[0082] When no lithium plating occurs in the battery, the expansion force difference ∆F will increase steadily along with the capacity attenuation Qloss according to the trend of formula (3).

[0083] After obtaining the second curve L2, the first curve is analyzed with reference to the second curve L2 to determine the target capacity attenuation change corresponding to the battery. This process only requires simple curve analysis to achieve quantitative analysis of irreversible lithium deposition of battery capacity attenuation, without the need to disassemble and reassemble the battery, reducing the complexity of quantitative analysis of battery lithium deposition.

[0084] The following describes how to analyze the first curve and the second curve where the linear segment is located, respectively, with respect to the number of inflection points included in the first curve, so as to obtain the target capacity attenuation change corresponding to the battery.

[0085] When there is an inflection point in the first curve, the data analysis component obtains a first expansion force difference corresponding to the first inflection point and a second expansion force difference of the last charge and discharge cycle in multiple charge and discharge cycles; calculates the ratio of the first difference to the slope of the second curve to obtain a first capacity decay change; and then determines a target capacity decay change based on the first capacity decay change.

[0086] In the above embodiment, the first difference is the difference between the second expansion force difference and the first expansion force difference, and the first capacity decay variation is used to characterize the capacity decay caused by the generation of the fixed electrolyte interface SEI film.

[0087] by Figure 3 For example, when the first curve L1 has only one inflection point, the linear segment before the first inflection point A indicates that the battery has not undergone lithium deposition; after the first inflection point, the battery undergoes lithium deposition, but the capacity decay of the capacitor at this time is not entirely caused by lithium deposition of the battery, but also includes capacity decay caused by the formation of SEI film.

[0088] In this scenario, Q1 is the capacity attenuation change caused by the generation of SEI film. The capacity attenuation change corresponding to the AE segment is calculated, and then the capacity attenuation change corresponding to the AE segment is subtracted from the capacity attenuation change caused by the generation of SEI film to obtain the target capacity attenuation change caused by lithium deposition in the battery.

[0089] In this embodiment, the first capacity decay variation, that is, the capacity decay variation caused by the formation of the SEI film, can be determined by formula (4):

[0090] (4)

[0091] In formula (4), Q1 is the first capacity attenuation change; is the second expansion force difference corresponding to the last charge and discharge cycle; is the first expansion force difference corresponding to the first inflection point; is the slope of the second curve.

[0092] After the first capacity decay variation Q1 is obtained by formula (4), the target capacity decay variation caused by battery lithium deposition can be obtained by calculating the difference between the second capacity decay variation and the first capacity decay variation between AE.

[0093] In the process of determining the target capacity attenuation change caused by lithium deposition in the battery, the effect of SEI film formation on battery capacity attenuation is taken into account, thereby improving the accuracy of the capacity attenuation change caused by lithium deposition in the battery.

[0094] When there are multiple inflection points in the first curve, the data analysis component determines the first expansion force difference corresponding to the first inflection point and the third expansion force difference corresponding to the second inflection point from the first curve; then, based on the first expansion force difference, the third expansion force difference and the slope of the second curve, the first capacity attenuation change caused by the generation of the fixed electrolyte interface SEI film is determined; and based on the first capacity attenuation change, the target capacity attenuation change is determined.

[0095] by Figure 3 For example, when the first curve L1 has only two inflection points, the linear segment before the first inflection point A indicates that the battery has not undergone lithium deposition; the first inflection point A and the second inflection point C indicate that the battery has undergone lithium deposition, and at the same time, an SEI film is generated, that is, the AC interval characterizes that the battery capacity decay is caused by both battery lithium deposition and SEI film formation; the interval after the second inflection point C indicates that the SEI film formation ends, and at this time, the battery capacity decay is caused by battery lithium deposition.

[0096] In this scenario, Q1 is the capacity attenuation change caused by the generation of SEI film. The capacity attenuation change corresponding to the AC segment is calculated, and then the capacity attenuation change corresponding to the AD segment is subtracted from the capacity attenuation change caused by the generation of SEI film to obtain the target capacity attenuation change caused by lithium deposition in the battery.

[0097] In the process of determining the target capacity attenuation change caused by lithium deposition in the battery, the effect of SEI film formation on battery capacity attenuation is taken into account, thereby improving the accuracy of the capacity attenuation change caused by lithium deposition in the battery.

[0098] In a scenario where the first curve L1 has multiple inflection points, the first capacity attenuation change caused by the formation of the SEI film can be determined by the expansion force difference corresponding to the first inflection point and the expansion force difference corresponding to the second inflection point.

[0099] Specifically, the data analysis component calculates the difference between the first expansion force difference and the third expansion force difference to obtain a fourth expansion force difference; calculates the ratio of the fourth expansion force difference to the slope of the second curve to obtain a first capacity attenuation change.

[0100] In this embodiment, the first capacity decay variation, that is, the capacity decay variation caused by the formation of the SEI film, can be determined by formula (5):

[0101] (5)

[0102] In formula (5), Q1 is the first capacity attenuation change; is the third expansion force difference corresponding to the second inflection point; is the first expansion force difference corresponding to the first inflection point; is the slope of the second curve.

[0103] After the first capacity decay variation Q1 is obtained by formula (5), the target capacity decay variation caused by battery lithium deposition can be obtained by calculating the difference between the second capacity decay variation and the first capacity decay variation between AD.

[0104] By determining the impact of SEI film formation on battery capacity decay, the accuracy of capacity decay changes caused by battery lithium deposition can be improved.

[0105] Through the above introduction, after determining the battery capacity attenuation change caused by the formation of the SEI film, the target capacity attenuation change can be determined according to the first capacity attenuation change. In the embodiment of the present application, the target capacity attenuation change can be determined by any of the following two methods.

[0106] In the first method, the target capacity attenuation change is obtained by calculating the difference between the total capacity attenuation change during the lithium precipitation process and the first capacity attenuation change caused by the formation of the SEI film. Specifically, the difference between the second capacity attenuation and the first capacity attenuation corresponding to the first inflection point is calculated to obtain the second capacity attenuation change; then, the difference between the second capacity attenuation change and the first capacity attenuation change is calculated to obtain the target capacity attenuation change. Among them, the second capacity attenuation is the capacity attenuation of the last charge and discharge cycle in multiple charge and discharge cycles.

[0107] by Figure 3 Taking point D as an example, the difference between the second capacity attenuation corresponding to point D and the first capacity attenuation corresponding to point A is calculated to obtain the total capacity attenuation change (i.e., the second capacity attenuation change) generated during the battery lithium deposition process. The first capacity attenuation change Q1 caused by the formation of the SEI film is removed from the total capacity attenuation change to obtain the target capacity attenuation change Q2.

[0108] The first capacity decay variation caused by the formation of SEI film is removed from the total capacity decay variation generated during the battery lithium deposition process to obtain the target capacity decay variation. This can not only realize the non-destructive quantitative analysis of the battery lithium deposition behavior and reduce the complexity of the quantitative analysis of the battery lithium deposition, but also improve the accuracy of the quantitative analysis of the battery lithium deposition.

[0109] In the second method, the target point is determined by performing equivalent processing on the capacity attenuation corresponding to the second inflection point, and the target capacity attenuation change is determined based on the target point.

[0110] Specifically, the data analysis component determines the target point from the second curve based on the capacity attenuation corresponding to the first inflection point and the first capacity attenuation change; then, determines the fourth capacity attenuation corresponding to the target point from the second curve; and then calculates the second capacity attenuation of the last charge and discharge cycle in multiple charge and discharge cycles, and the difference between the second capacity attenuation and the fourth capacity attenuation, to obtain the target capacity attenuation change.

[0111] Still Figure 3 For example, after calculating the first capacity attenuation change Q1 (Q1=2.38%), determine the target point of Q1 on the second curve L2, that is, point B. The horizontal coordinate of point B can be determined through the second curve L2, that is, the capacity attenuation corresponding to point B (the fourth capacity attenuation) is 19.52%. After determining point B, calculate the capacity attenuation change corresponding to the BD interval to obtain the target capacity attenuation change, Q2 is 4.79%.

[0112] Through the above method, the first capacity attenuation change caused by the formation of the SEI film is removed to obtain the target capacity attenuation change, which can not only realize the non-destructive quantitative analysis of the battery lithium deposition behavior, reduce the complexity of the battery lithium deposition quantitative analysis, but also improve the accuracy of the battery lithium deposition quantitative analysis.

[0113] This completes the explanation of the method provided in the embodiments of the present application.

[0114] By adopting the method provided in the embodiment of the present application, a non-destructive quantitative analysis of the lithium deposition behavior is performed on any battery that exhibits lithium deposition behavior during the aging process and monitors the capacity and expansion force data of the cycle process. This reduces the complexity of the lithium deposition quantitative analysis while improving the accuracy of the lithium deposition quantitative analysis.

[0115] It should be understood that, although the various steps in the flowcharts involved in the above-mentioned embodiments are displayed in sequence according to the indication of the arrows, these steps are not necessarily executed in sequence according to the order indicated by the arrows. Unless there is a clear explanation in this article, the execution of these steps does not have a strict order restriction, and these steps can be executed in other orders. Moreover, at least a part of the steps in the flowcharts involved in the above-mentioned embodiments can include multiple steps or multiple stages, and these steps or stages are not necessarily executed at the same time, but can be executed at different times, and the execution order of these steps or stages is not necessarily to be carried out in sequence, but can be executed in turn or alternately with other steps or at least a part of the steps or stages in other steps.

[0116] In one embodiment, Figure 4 A schematic diagram of a device for determining battery lithium deposition is given. Figure 4 It can be seen that the device 400 includes: a data acquisition module 401 and a lithium deposition amount determination module 402.

[0117] The data acquisition module 401 is used to obtain the expansion force difference and capacity attenuation corresponding to each charge and discharge cycle of the battery in multiple charge and discharge cycles, wherein the expansion force difference is determined by the maximum expansion force of charging and the minimum expansion force of discharging of the battery;

[0118] The lithium deposition amount determination module 402 is used to determine the lithium deposition amount of the battery according to the expansion force difference and capacity attenuation corresponding to the battery in each charge and discharge cycle.

[0119] In one embodiment, the data acquisition module is specifically used to obtain the initial discharge capacity corresponding to the first charge and discharge cycle in multiple charge and discharge cycles; calculate the discharge capacity ratio of the discharge capacity in each charge and discharge process to the initial discharge capacity; and determine the capacity attenuation corresponding to each charge and discharge cycle based on the discharge capacity ratio in each charge and discharge cycle.

[0120] In one embodiment, the lithium deposition amount determination module includes: a fitting module, a data analysis module and a determination module. The fitting module is used to perform data fitting according to the expansion force difference and capacity attenuation of the battery in each charge and discharge cycle to obtain a first curve, wherein the first curve is used to characterize the change law of the expansion force difference with the capacity attenuation; the data analysis module is used to determine the target capacity attenuation change corresponding to the battery according to the first curve when there is an inflection point in the first curve; the determination module is used to determine the lithium deposition amount of the battery according to the target capacity attenuation change.

[0121] In one embodiment, the device for determining battery lithium deposition also includes: a lithium deposition behavior detection module, which is used to fit the relationship between the expansion force difference and the capacity attenuation according to the expansion force difference and the capacity attenuation corresponding to the battery during each charge and discharge cycle, and after obtaining the first curve, detect whether there is an inflection point in the first curve; if there is no inflection point in the first curve, determine that the battery does not have lithium deposition behavior; if there is an inflection point in the first curve, determine that the battery has lithium deposition behavior.

[0122] In one embodiment, the data analysis module includes: a linear segment determination module and a first analysis module. The linear segment determination module is used to determine the linear segment corresponding to the first inflection point from the first curve; the first analysis module is used to analyze the first curve and the second curve where the linear segment is located to obtain the target capacity attenuation change corresponding to the battery.

[0123] In one embodiment, the first analysis module includes: a second analysis module, which is used to obtain a first expansion force difference corresponding to a first inflection point and a second expansion force difference of a last charge and discharge cycle in multiple charge and discharge cycles when there is an inflection point in the first curve; calculate the ratio of the first difference to the slope of the second curve to obtain a first capacity decay change, wherein the first difference is the difference between the second expansion force difference and the first expansion force difference, and the first capacity decay change is used to characterize the capacity decay caused by the generation of a fixed electrolyte interface SEI film; and determine a target capacity decay change based on the first capacity decay change.

[0124] In one embodiment, the first analysis module further includes: an expansion force determination module, an attenuation amount determination module and a third analysis module. The expansion force determination module is used to determine the first expansion force difference corresponding to the first inflection point and the third expansion force difference corresponding to the second inflection point from the first curve when there are multiple inflection points in the first curve; the attenuation amount determination module is used to determine the first capacity attenuation change caused by the generation of the fixed electrolyte interface SEI film according to the first expansion force difference, the third expansion force difference and the slope of the second curve; the third analysis module is used to determine the target capacity attenuation change according to the first capacity attenuation change.

[0125] In one embodiment, the attenuation amount determination module is specifically used to calculate the difference between the first expansion force difference and the third expansion force difference to obtain a fourth expansion force difference; calculate the ratio of the fourth expansion force difference to the slope of the second curve to obtain the first capacity attenuation change.

[0126] In one embodiment, the second analysis module or the third analysis module is specifically used to calculate the difference between the second capacity attenuation and the first capacity attenuation corresponding to the first inflection point to obtain a second capacity attenuation change, wherein the second capacity attenuation is the capacity attenuation of the last charge and discharge cycle in multiple charge and discharge cycles; and calculate the difference between the second capacity attenuation change and the first capacity attenuation change to obtain a target capacity attenuation change.

[0127] In one embodiment, the present application further provides a readable storage medium having computer program instructions stored thereon. When the computer program instructions are executed by a processor, the above-mentioned method for determining battery lithium deposition is implemented.

[0128] In one embodiment, the present application further provides a computer program product. When the instructions in the computer program product are executed by a processor of an electronic device, the electronic device executes the above-mentioned method for determining battery lithium deposition.

[0129] It should be clear that the present application is not limited to the specific configuration and processing described above and shown in the figures. For the sake of simplicity, a detailed description of the known method is omitted here. In the above embodiments, several specific steps are described and shown as examples. However, the method process of the present application is not limited to the specific steps described and shown, and those skilled in the art can make various changes, modifications and additions, or change the order between the steps after understanding the spirit of the present application.

[0130] The functional blocks shown in the above structural block diagram can be implemented as hardware, software, firmware or a combination thereof. When implemented in hardware, it can be, for example, an electronic circuit, an application-specific integrated circuit (ASIC), appropriate firmware, a plug-in, a function card, etc. When implemented in software, the elements of the present application are programs or code segments used to perform the required tasks. The program or code segment can be stored in a machine-readable medium, or transmitted on a transmission medium or a communication link via a data signal carried in a carrier. "Machine-readable medium" may include any medium capable of storing or transmitting information. Examples of machine-readable media include electronic circuits, semiconductor memory devices, ROMs, flash memory, erasable ROMs (EROMs), floppy disks, CD-ROMs, optical disks, hard disks, optical fiber media, radio frequency (RF) links, etc. The code segment can be downloaded via a computer network such as the Internet, an intranet, etc.

[0131] It should also be noted that the exemplary embodiments mentioned in this application describe some methods or systems based on a series of steps or devices. However, this application is not limited to the order of the above steps, that is, the steps can be performed in the order mentioned in the embodiment, or in a different order from the embodiment, or several steps can be performed simultaneously.

[0132] The above describes various aspects of the present application with reference to the flowchart and / or block diagram of the determination method, device, storage medium and computer program product of the battery lithium analysis according to the embodiment of the present application. It should be understood that each box in the flowchart and / or block diagram and the combination of each box in the flowchart and / or block diagram can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general-purpose computer, a special-purpose computer, or other programmable data processing device to produce a machine so that these instructions executed by the processor of the computer or other programmable data processing device enable the implementation of the function / action specified in one or more boxes of the flowchart and / or block diagram. Such a processor may be, but is not limited to, a general-purpose processor, a special-purpose processor, a special application processor or a field programmable logic circuit. It is also understood that each box in the block diagram and / or flowchart and the combination of boxes in the block diagram and / or flowchart may also be implemented by dedicated hardware that performs a specified function or action, or may be implemented by a combination of dedicated hardware and computer instructions.

[0133] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them; although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application, and they should all be included in the scope of the claims and specification of the present application. In particular, as long as there is no structural conflict, the various technical features mentioned in the various embodiments can be combined in any way. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions that fall within the scope of the claims.

Claims

1. A method for determining battery lithium deposition, characterized in that: include: Obtaining the expansion force difference and capacity attenuation corresponding to each charge and discharge cycle of the battery in multiple charge and discharge cycles, wherein the expansion force difference is determined by the maximum charge expansion force and the minimum discharge expansion force of the battery; Determining the amount of lithium deposition of the battery according to the difference in expansion force and capacity attenuation of the battery in each charge and discharge cycle; The method of determining the amount of lithium deposition of the battery according to the expansion force difference and the capacity attenuation of the battery in each charge and discharge cycle comprises: performing data fitting according to the expansion force difference and the capacity attenuation of the battery in each charge and discharge cycle to obtain a first curve, wherein the first curve is used to characterize the change law of the expansion force difference with the capacity attenuation; when there is an inflection point on the first curve, determining the target capacity attenuation change corresponding to the battery according to the first curve; and determining the amount of lithium deposition of the battery according to the target capacity attenuation change.

2. The method according to claim 1, characterized in that The obtaining of the capacity attenuation amount of the battery corresponding to each charge and discharge cycle of the battery in multiple charge and discharge cycles includes: Obtaining an initial discharge capacity corresponding to a first charge and discharge cycle in the plurality of charge and discharge cycles; Calculating the discharge capacity ratio of the discharge capacity in each charge and discharge cycle to the initial discharge capacity; The capacity attenuation corresponding to each charge and discharge cycle is determined according to the discharge capacity ratio in each charge and discharge cycle.

3. The method according to claim 2, characterized in that Before determining the target capacity attenuation change amount corresponding to the battery according to the first curve, the method further includes: Detecting whether the inflection point exists in the first curve; When the first curve does not have the inflection point, determining that the battery does not have lithium deposition behavior; When the first curve has the inflection point, it is determined that the battery has lithium plating behavior.

4. The method according to claim 3, characterized in that In the case where the first curve has an inflection point, determining a target capacity attenuation change amount corresponding to the battery according to the first curve includes: Determine a linear segment corresponding to a first inflection point from the first curve; The first curve and the second curve where the linear segment is located are analyzed to obtain a target capacity attenuation change amount corresponding to the battery.

5. The method according to claim 4, characterized in that In the case where the first curve has an inflection point, analyzing the first curve and the second curve where the linear segment is located to obtain a target capacity attenuation change corresponding to the battery includes: Obtaining a first expansion force difference corresponding to the first inflection point and a second expansion force difference of a last charge-discharge cycle in the multiple charge-discharge cycles; Calculating a ratio of the first difference to the slope of the second curve to obtain a first capacity decay variation, wherein the first difference is a difference between the second expansion force difference and the first expansion force difference, and the first capacity decay variation is used to characterize the capacity decay caused by the generation of a fixed electrolyte interface SEI film; The target capacity decay variation is determined according to the first capacity decay variation.

6. The method according to claim 4, characterized in that In the case where the first curve has a plurality of inflection points, analyzing the first curve and the second curve where the linear segment is located to obtain a target capacity attenuation change amount corresponding to the battery includes: Determine, from the first curve, a first expansion force difference corresponding to a first inflection point, and a third expansion force difference corresponding to a second inflection point; Determining a first capacity decay variation caused by generating a fixed electrolyte interface SEI film according to the first expansion force difference, the third expansion force difference, and the slope of the second curve; The target capacity decay variation is determined according to the first capacity decay variation.

7. The method according to claim 6, characterized in that The determining, according to the first expansion force difference, the third expansion force difference and the slope of the second curve, a first capacity decay variation caused by generating a fixed electrolyte interface SEI film comprises: Calculating a difference between the first expansion force difference and the third expansion force difference to obtain a fourth expansion force difference; The first capacity decay variation is obtained by calculating a ratio of the fourth expansion force difference to the slope of the second curve.

8. The method according to claim 5 or 6, characterized in that: The determining the target capacity attenuation change amount according to the first capacity attenuation change amount includes: Calculating a difference between a second capacity attenuation amount and a first capacity attenuation amount corresponding to the first inflection point to obtain a second capacity attenuation change amount, wherein the second capacity attenuation amount is a capacity attenuation amount of a last charge and discharge cycle in the multiple charge and discharge cycles; The difference between the second capacity decay variation and the first capacity decay variation is calculated to obtain the target capacity decay variation.

9. A device for determining battery lithium deposition, characterized in that: include: A data acquisition module, used to acquire the expansion force difference and capacity attenuation corresponding to each charge and discharge cycle of the battery in multiple charge and discharge cycles, wherein the expansion force difference is determined by the maximum expansion force of charging and the minimum expansion force of discharging of the battery; A lithium deposition amount determination module, used to determine the lithium deposition amount of the battery according to the expansion force difference and capacity attenuation corresponding to the battery in each charge and discharge cycle; The lithium deposition amount determination module includes: a fitting module, which is used to perform data fitting according to the expansion force difference and the capacity attenuation of the battery in each charge and discharge cycle to obtain a first curve, wherein the first curve is used to characterize the change law of the expansion force difference with the capacity attenuation; a data analysis module, which is used to determine the target capacity attenuation change corresponding to the battery according to the first curve when there is an inflection point in the first curve; and a determination module, which is used to determine the lithium deposition amount of the battery according to the target capacity attenuation change.

10. A readable storage medium, characterized in that: Computer program instructions are stored on the readable storage medium, and when the computer program instructions are executed by the processor, the method for determining battery lithium deposition as described in any one of claims 1-8 is implemented.

11. A computer program product, characterized in that When the instructions in the computer program product are executed by a processor of an electronic device, the electronic device executes the method for determining battery lithium deposition as described in any one of claims 1 to 8.

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