Method and device for judging lithium precipitation of battery cell, electronic equipment and storage medium

Abstract

The invention relates to the technical field of lithium batteries, and discloses a method for judging lithium precipitation of a battery cell, which comprises the following steps: acquiring a first reactance modulus value sequence in the charging process of a reference battery cell and an electrochemical system of a target battery cell, the reference cell and the target cell have the same electrochemical system; taking the percentage of the preset state of charge as a step length, collecting a reactance modulus value at the end of each step length in the charging process of the target cell, and storing the reactance modulus value in a second reactance modulus value sequence; determining the lithium precipitation percentage of the target cell according to the first reactance modulus value sequence and the second reactance modulus value sequence; and according to the lithium precipitation percentage and the electrochemical system, judging whether the target cell precipitates lithium or not. Through the scheme, the problems of high cost and difficulty in adapting to different electrochemical systems in lithium separation judgment of the lithium battery in related technologies are solved, the cost of lithium separation judgment is reduced, and the lithium battery with different electrochemical systems is adapted.

Description

Technical Field

[0001] This application relates to the field of lithium battery technology, specifically to methods, apparatus, electronic devices, and storage media for determining lithium plating in battery cells. Background Technology

[0002] When lithium batteries are charged at high rates, at low temperatures, or overcharged, lithium ions can deposit on the surface of the negative electrode, forming metallic lithium. This phenomenon is called lithium plating. Lithium plating leads to the loss of active lithium in the cell, reducing battery capacity. In addition, the lithium dendrites that may form during lithium plating pose a risk of piercing the separator, causing short circuits or even thermal runaway, and also affect the cycle life of the lithium battery.

[0003] To confirm whether lithium plating exists in a lithium battery cell, related technologies include physically disassembling the cell casing and electrodes to observe the negative electrode of the cell to confirm whether lithium plating has occurred, or identifying it through ultrasonic or magnetic resonance imaging, which is extremely costly. At the same time, the methods for judging lithium plating vary greatly for different types of lithium batteries.

[0004] In other words, in related technologies, the lithium plating determination of lithium batteries suffers from high costs and difficulty in adapting to different electrochemical systems. Summary of the Invention

[0005] This application provides a method for determining lithium plating in battery cells, in order to solve the problems of high cost and difficulty in adapting to different electrochemical systems in the determination of lithium plating in lithium batteries in related technologies.

[0006] In the first aspect, this application provides a method for determining lithium plating in a battery cell, which obtains the first reactance modulus value sequence of the state of charge (SOC) of a reference battery cell from 0% to 100% and the electrochemical system of the target battery cell, wherein the number of cycle discharges of the reference battery cell is less than a preset discharge threshold, and the reference battery cell and the target battery cell have the same electrochemical system. Using a preset percentage of state of charge as the step size, the reactance modulus value is collected at the end of each step during the process of charging the target cell from 0% to 100% SOC, and saved to the second reactance modulus value sequence. The lithium plating percentage of the target cell is determined based on the first reactance modulus value sequence and the second reactance modulus value sequence. Based on the percentage of lithium plating and the electrochemical system, determine whether the target cell has undergone lithium plating.

[0007] In one optional implementation, determining whether a target cell has undergone lithium plating based on the lithium plating percentage and the electrochemical system includes: The target lithium plating threshold corresponding to the electrochemical system is determined from the mapping table between the system type of the target cell and the lithium plating threshold. The mapping table indicates that multiple electrochemical systems correspond one-to-one with multiple lithium plating thresholds. Based on the percentage of lithium plating and the target lithium plating threshold, determine whether the target cell has undergone lithium plating.

[0008] In one optional implementation, determining the lithium plating percentage of the target cell based on a first reactance modulus value sequence and a second reactance modulus value sequence includes: Traverse the second reactance modulus value sequence, and obtain the reactance modulus residual sequence by calculating the difference between each second reactance modulus value in the second reactance modulus value sequence and each first reactance modulus value in the first reactance modulus value sequence. The first reactance modulus value and the second reactance modulus value have the same SOC. The percentage of lithium plating is determined based on the residual sequence of reactance modulus and the sequence of first reactance modulus values.

[0009] In one optional implementation, determining the lithium plating percentage based on the reactance modulus residual sequence and the first reactance modulus value sequence includes: Traverse the reactance modulus residual sequence, and obtain the reactance modulus ratio sequence by quotienting the candidate reactance modulus residual values ​​in the reactance modulus residual sequence with the first reactance modulus value in the first reactance modulus value sequence; Calculate the sum of all elements in the reactance modulus ratio sequence to obtain the reactance modulus ratio sum; The percentage of lithium plating is determined based on the reactance modulus ratio and the length of the reactance modulus ratio sequence.

[0010] In one optional implementation, determining whether a target cell has undergone lithium plating based on the lithium plating percentage and a target lithium plating threshold includes: If the percentage of lithium plating is greater than or equal to the target lithium plating threshold, then the target cell has lithium plating; otherwise, the target cell does not have lithium plating.

[0011] In one alternative implementation, before acquiring the second reactance modulus value at the end of each step during the process of charging the target cell from 0% to 100% SOC, the method further includes: Obtain the target electrochemical impedance spectrum of the target cell at a preset percentage of state of charge; Determine the test frequency of electrochemical impedance spectroscopy based on the target electrochemical impedance spectrum; Electrochemical impedance spectroscopy (EIS) tests were performed on the target battery cell based on the test frequency.

[0012] Secondly, this application provides a device for determining lithium plating in battery cells, the device comprising: The acquisition module is used to acquire the first reactance modulus value sequence of the reference cell from 0% SOC to 100% and the electrochemical system of the target cell. The number of cycle discharges of the reference cell is less than a preset discharge threshold, and the reference cell and the target cell have the same electrochemical system. The acquisition module is used to acquire the reactance modulus value at the end of each step during the process of charging the target cell from 0% to 100% SOC, using a preset percentage of state of charge as the step size, and save it to the second reactance modulus value sequence. The determination module is used to determine the lithium plating percentage of the target cell based on the first reactance modulus value sequence and the second reactance modulus value sequence; The judgment module is used to determine whether the target cell has lithium plating based on the percentage of lithium plating and the electrochemical system.

[0013] Thirdly, this application provides an electronic device, including: a memory and a processor, which are interconnected. The memory stores computer instructions, and the processor executes the computer instructions to perform the cell lithium plating determination method of the first aspect or any corresponding embodiment described above.

[0014] Fourthly, this application provides a computer-readable storage medium storing computer instructions for causing a computer to execute the cell lithium plating determination method of the first aspect or any corresponding embodiment described above.

[0015] Fifthly, this application provides a computer program product, including computer instructions, which are used to cause a computer to execute the method for determining lithium plating in battery cells according to the first aspect or any corresponding embodiment described above.

[0016] According to the method for determining lithium plating in battery cells provided in this application, the following beneficial technical effects can be achieved compared to the prior art: The first reactance modulus value sequence of a reference cell charged from 0% to 100% SOC and the electrochemical system of the target cell were obtained. The reference cell had fewer cycle discharges than a preset discharge threshold, and the reference and target cells had the same electrochemical system, providing reference cell data for lithium plating determination of the target cell. Using a preset percentage of state of charge as the step size, the reactance modulus value at the end of each step during the charging process of the target cell from 0% to 100% SOC was collected and saved to the second reactance modulus value sequence, thus obtaining the reactance modulus value of the target cell during the charging process, which is used to determine the lithium plating of the target cell. Direct data was prepared for lithium plating detection; the percentage of lithium plating in the target cell was determined based on the first and second reactance modulus value sequences, enabling a comparison of the reactance modulus change of the target cell relative to the reference cell; based on the percentage of lithium plating and the electrochemical system, it was determined whether the target cell had lithium plating. By combining the electrochemical system of the target cell with the change in reactance modulus, the detection of lithium plating was adapted to different electrochemical systems. Compared with existing technologies that require expensive methods such as disassembling lithium batteries to observe lithium plating and using magnetic resonance imaging for lithium plating detection, this method significantly reduces the cost of lithium plating detection. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the specific embodiments of this application or the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram illustrating an application scenario according to an embodiment of this application; Figure 2 This is a flowchart of a method for determining lithium plating in battery cells according to an embodiment of this application; Figure 3 This is a flowchart of another method for determining lithium plating in battery cells according to an embodiment of this application; Figure 4 This is a comparison diagram of the total SOC reactance modulus according to an embodiment of this application; Figure 5 This is a Nyquist plot of an EIS of a battery cell according to an embodiment of this application; Figure 6 This is a schematic diagram showing the relationship between the frequency and the imaginary part of the impedance of a battery cell EIS according to an embodiment of this application; Figure 7 This is a structural block diagram of a lithium plating determination device for battery cells according to an embodiment of this application; Figure 8 This is a schematic diagram of the hardware structure of an electronic device according to an embodiment of this application. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0020] It is understood that before using the technical solutions disclosed in the various embodiments of this application, users should be informed of the types, scope of use, and usage scenarios of the personal information involved in this application in an appropriate manner in accordance with relevant laws and regulations, and user authorization should be obtained.

[0021] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0022] As an optional application scenario for the method of determining lithium plating in battery cells according to embodiments of this application, such as Figure 1 As shown, application 101 is installed in terminal device 110, and user 130 can interact with application 101 through terminal device 110 and / or access device of terminal device 110.

[0023] For example, application 101 can be any application that provides question-and-answer related services. For instance, application 101 could be a question-and-answer interactive application, such as a text-to-text application, an image-to-text application, etc. Figure 1 In the application scenario shown, if application 101 is active, the terminal device 110 can display the interface 102 of application 101. The interface 102 may include various pages that application 101 can provide, such as interactive pages, settings pages, query pages, etc.

[0024] In some embodiments, terminal device 110 is communicatively connected to server 120 to provide services to application 101. Terminal device 110 may be a mobile terminal, fixed terminal, or portable terminal, etc., including but not limited to mobile phones, desktop computers, laptop computers, multimedia tablets, e-book devices, gaming devices, or any combination thereof, including accessories and peripherals of these devices or any combination thereof. In some embodiments, terminal device 110 may also support any type of interface, and server 120 may be various types of computing systems or servers capable of providing computing power, including but not limited to mainframes, edge computing nodes, computing devices in cloud environments, etc.

[0025] It should be noted that, Figure 1 This is merely an example of an application scenario and does not limit the scope of protection of this application.

[0026] The embodiments of this application will be described below with reference to the accompanying drawings. It should be understood that the pages shown in the drawings are merely examples, and various page designs are possible in practice. The various graphic elements on the page may have different arrangements and different visual representations, one or more elements may be omitted or replaced, and one or more other elements may also be present; no limitations are imposed on the embodiments of this application. Furthermore, the embodiments are primarily described below with reference to terminal device 110. It should be understood that the actions described relative to terminal device 110 can be performed by application 101 on terminal device 110, or can be performed by application 101 in conjunction with its server (e.g., server 120).

[0027] The lithium plating phenomenon in lithium batteries can lead to the following hazards: Active lithium loss: reduces battery capacity and affects cell performance.

[0028] Safety risks: Lithium dendrites may puncture the separator, causing a short circuit or even thermal runaway.

[0029] Lifetime degradation: The irreversible lithium plating process reduces the battery's cycle life and shortens its service life.

[0030] To determine whether lithium plating has occurred in a lithium battery, related technologies use the following methods: 1. Traditional disassembly method: This involves physically removing the battery cell casing and peeling off each layer of the bare cell's electrodes. In a dehumidified environment, the presence of lithium plating can be determined by observing the negative electrode interface of the battery cell.

[0031] 2. Methods for determining whether lithium plating has occurred during the charging process of a battery cell: Common methods include the built-in three-electrode method, voltage change rate method, and impedance method. The three-electrode method involves embedding reference electrodes such as copper / aluminum wires between the electrodes during the cell manufacturing process. These electrodes are activated through lithium plating or activation to monitor the negative electrode potential. When the negative electrode potential is less than 0mV, the risk of lithium plating is considered high, serving as the boundary for lithium plating. The voltage change rate and impedance methods utilize changes in voltage or internal resistance; the appearance of abnormal peaks / value inflection points indicates the occurrence of lithium plating.

[0032] 3. Methods for determining whether existing battery cells have undergone lithium plating: After a period of use, it is necessary to determine whether lithium plating has occurred inside the battery cell without disassembling it, in order to infer its cycle life. Currently, there are two methods for determining whether lithium plating has occurred inside the battery cell: ① Ultrasonic method, which analyzes the scattering characteristics of sound waves at the lithium plating interface to identify the risk areas for lithium plating; ② Magnetic resonance imaging method, which uses the method of changing the local magnetic field distribution based on lithium metal deposition to achieve non-destructive observation of lithium plating in a laboratory environment.

[0033] The aforementioned disassembly methods, which rely on interface observation to determine lithium plating and its form, are simple and easy to implement, but their most significant drawback is their destructive nature. After disassembly, performance testing cannot continue, resulting in high costs and low efficiency. Furthermore, physical disassembly methods cannot monitor battery status in real time. For three-electrode cells, this method is only suitable for short-term testing, as the reference electrode cannot function effectively for extended periods. The voltage change rate method is relatively insensitive; verification shows that it only reveals lithium reintercalation peaks when lithium plating is severe, with lithium dendrites filling a large area of ​​the cell electrodes. Impedance methods perform well for layered systems such as lithium cobalt oxide and ternary materials, but for lithium iron phosphate cells, which have very long voltage plateaus, impedance methods cannot provide effective lithium plating signals. Ultrasonic and magnetic resonance imaging methods are not very accurate, and the cost of large-scale equipment is extremely high, limiting their widespread application. Therefore, for a typical battery cell, determining whether lithium plating has occurred after a period of use in a non-destructive, cost-effective manner, and adaptable to various electrochemical systems, is a pressing technical problem that needs to be solved.

[0034] As one optional application scenario in the embodiments of this application, such as Figure 1 As shown, the structural components of the product are introduced in conjunction with specific scenarios.

[0035] According to an embodiment of this application, an embodiment of a method for determining lithium plating in battery cells is provided. It should be noted that the steps shown in the flowchart in the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions. Furthermore, although a logical order is shown in the flowchart, in some cases, the steps shown or described may be executed in a different order than that shown here.

[0036] This embodiment provides a method for determining lithium plating in battery cells, which can be used in the aforementioned mobile terminals, such as mobile phones and tablets. Figure 2 This is a flowchart of a method for determining lithium plating in battery cells according to an embodiment of this application, as shown below. Figure 2 As shown, the process includes the following steps: Step S201: Obtain the first reactance modulus value sequence of the reference cell from 0% to 100% SOC and the electrochemical system of the target cell. The number of cycle discharges of the reference cell is less than a preset discharge threshold. The reference cell and the target cell have the same electrochemical system.

[0037] Specifically, the reference cell refers to a cell with a low number of discharge cycles, used to provide reference data for determining lithium plating in the target cell; that is, a cell that does not undergo lithium plating. SOC refers to the state of charge or remaining capacity of a lithium battery. The first reactance modulus value sequence refers to the sequence of reactance modulus values ​​collected during the charging process of the reference cell from 0% to 100% SOC. The target cell refers to the lithium battery cell for which lithium plating is currently being determined. The electrochemical system refers to the system within a lithium battery that achieves energy conversion through chemical reactions involving lithium, including different types such as lithium cobalt oxide batteries, lithium iron phosphate batteries, ternary lithium batteries, and lithium polymer batteries. The preset discharge threshold is a numerical value that measures the number of discharge cycles of a cell.

[0038] To determine whether the target cell has undergone lithium plating, a cell with fewer than a preset discharge threshold number of cycles is used as a reference cell. Optionally, the preset discharge threshold is 3. To ensure the accuracy of the determination of whether the target cell has undergone lithium plating, a reference cell with the same electrochemical system as the target cell is used. After obtaining a qualified reference cell, the reference cell's SOC is charged from 0% to 100%, and the reactance modulus value during this charging process is collected and saved to the first reactance modulus value sequence. Simultaneously, the electrochemical system of the target cell is obtained.

[0039] Step S202: Using a preset percentage of state of charge as the step size, collect the reactance modulus value at the end of each step during the process of charging the target cell from 0% to 100% SOC, and save it to the second reactance modulus value sequence.

[0040] Specifically, the second reactance modulus value sequence refers to the process of charging the target cell from 0% to 100% SOC, using a preset percentage of the state of charge as the step size, collecting and saving the reactance modulus value of the target cell at the end of each step size until it is fully charged.

[0041] In one example, a step size of 0.5% of the State of Charge (SOC) is used. That is, during the process of charging from 0% to 100% SOC, the reactance modulus value of the target cell is collected every 0.5% of SOC. All reactance modulus values ​​collected during the entire charging process are saved to the second reactance modulus value sequence.

[0042] Step S203: Determine the lithium plating percentage of the target cell based on the first reactance modulus value sequence and the second reactance modulus value sequence.

[0043] Specifically, the lithium plating percentage refers to the difference in reactance modulus between the target cell and the reference cell throughout the charging process. A higher lithium plating percentage indicates a greater difference between the reactance modulus of the target cell and the reference cell at the same SOC during charging; conversely, a lower percentage indicates that the lithium plating data of the target cell is closer to that of the reference cell. This lithium plating data includes the SOC and reactance modulus of the lithium battery.

[0044] In one possible implementation, the lithium plating percentage is obtained by performing element-wise subtraction operations on the first reactance modulus value sequence and the second reactance modulus value sequence, and then quotienting the result with each element of the first reactance modulus and calculating the average value.

[0045] Step S204: Determine whether the target cell has lithium plating based on the lithium plating percentage and the electrochemical system.

[0046] Specifically, based on the electrochemical system of the target cell, the corresponding lithium plating threshold is determined. The relationship between the percentage of lithium plating and the lithium plating threshold is then used to determine whether lithium plating has occurred in the target cell.

[0047] The method for determining lithium plating in a battery cell provided in this embodiment obtains a first reactance modulus value sequence of a reference cell's State of Charge (SOC) from 0% to 100% and the electrochemical system of the target cell. The reference cell has fewer cycle discharges than a preset discharge threshold, and the reference and target cells have the same electrochemical system, providing reference cell data for comparison in determining lithium plating in the target cell. Using a preset percentage of state of charge as the step size, the reactance modulus value is collected at the end of each step during the charging process of the target cell from 0% to 100% SOC and saved to a second reactance modulus value sequence, thus obtaining the reactance modulus of the target cell during the charging process. The quantitative values ​​provide direct data for determining lithium plating in the target cell; based on the first and second reactance modulus value sequences, the percentage of lithium plating in the target cell is determined, enabling a comparison of the reactance modulus change of the target cell relative to the reference cell; based on the percentage of lithium plating and the electrochemical system, it is determined whether the target cell has undergone lithium plating. By combining the electrochemical system of the target cell with the change in reactance modulus, the determination is adapted to different electrochemical systems. Compared with existing technologies that require costly methods such as disassembling lithium batteries to observe lithium plating and using magnetic resonance imaging for lithium plating determination, this significantly reduces the cost of lithium plating determination.

[0048] This embodiment provides a method for determining lithium plating in battery cells, which can be used in the aforementioned mobile terminals, such as mobile phones and tablets. Figure 3 This is a flowchart of another method for determining lithium plating in battery cells according to an embodiment of this application, such as... Figure 3 As shown, the process includes the following steps: Step S301: Obtain the first reactance modulus value sequence of the reference cell from 0% to 100% SOC and the electrochemical system of the target cell. The number of cycle discharges of the reference cell is less than the preset discharge threshold. The reference cell and the target cell have the same electrochemical system.

[0049] Please see details Figure 2 Step S201 of the illustrated embodiment will not be described again here.

[0050] Step S302: Using a preset percentage of state of charge as the step size, collect the reactance modulus value at the end of each step during the process of charging the target cell from 0% to 100% SOC, and save it to the second reactance modulus value sequence.

[0051] Please see details Figure 2 Step S202 of the illustrated embodiment will not be described again here.

[0052] Step S303: Determine the lithium plating percentage of the target cell based on the first reactance modulus value sequence and the second reactance modulus value sequence.

[0053] Specifically, step S303 includes: Step S3031: Traverse the second reactance modulus value sequence, and obtain the reactance modulus residual sequence by calculating the difference between each second reactance modulus value in the second reactance modulus value sequence and each first reactance modulus value in the first reactance modulus value sequence, wherein the first reactance modulus value and the second reactance modulus value have the same SOC.

[0054] Specifically, the second reactance modulus value refers to an element in the second reactance modulus value sequence. The first reactance modulus value refers to an element in the first reactance modulus value sequence. The first and second reactance modulus values ​​have the same State of Charge (SOC), meaning that the SOC when collecting the first reactance modulus value of the reference cell is the same as the SOC when collecting the second reactance modulus value of the target cell. The reactance modulus residual sequence is the sequence obtained by subtracting corresponding elements from the second and first reactance modulus value sequences, reflecting the difference in reactance modulus between the target cell and the reference cell.

[0055] For example, if the first reactance modulus value sequence is A=[a,b,c,d,e] and the second reactance modulus value sequence is B=[u,v,w,x,y], then the reactance modulus residual sequence is C=BA=[ua,vb,wc,xd,ye].

[0056] Step S3032: Determine the percentage of lithium plating based on the reactance modulus residual sequence and the first reactance modulus value sequence.

[0057] Specifically, based on the reactance modulus residual sequence reflecting the difference in reactance modulus values ​​between the target cell and the reference cell, and the first reactance modulus value sequence of the reference cell, a quotient sequence is obtained by dividing the corresponding elements. The average value of the quotient sequence can be used as the lithium plating percentage. Alternatively, the quotient of the sum of all elements in the reactance modulus residual sequence and the sum of all elements in the first reactance modulus value sequence can be used as the lithium plating percentage to reflect the degree of lithium plating of the target cell relative to the reference cell.

[0058] Step S304: Determine whether the target cell has lithium plating based on the lithium plating percentage and the electrochemical system.

[0059] Specifically, step S304 includes: Step S3041: Determine the target lithium plating threshold corresponding to the electrochemical system from the mapping table of system type and lithium plating threshold of the target cell, wherein the mapping table indicates that multiple electrochemical systems correspond one-to-one with multiple lithium plating thresholds.

[0060] Specifically, the mapping table between target cell system types and lithium plating thresholds refers to a form or database that stores multiple electrochemical systems and multiple lithium plating thresholds for target cells. In this mapping table, multiple electrochemical systems correspond one-to-one with multiple lithium plating thresholds. The target lithium plating threshold refers to the lithium plating threshold corresponding to the electrochemical system of the target cell; cells with different electrochemical systems have different lithium plating thresholds. By using the system type of the target cell, i.e., the electrochemical system, the target lithium plating threshold corresponding to that electrochemical system can be determined from this mapping table.

[0061] Step S3042: Determine whether the target cell has undergone lithium plating based on the lithium plating percentage and the target lithium plating threshold.

[0062] Specifically, based on the comparison between the percentage of lithium plating and the target lithium plating threshold, it can be determined whether the target cell has undergone lithium plating.

[0063] The lithium plating determination method for battery cells in this embodiment provides a reference battery cell for lithium plating of the target battery cell. Based on the same State of Charge (SOC) step size, the reactance modulus value of the target battery cell is recorded during the charging process from 0% to 100% SOC, and then compared with the reactance modulus value of the reference battery cell to obtain the percentage of lithium plating relative to the reference battery cell. Finally, the percentage of lithium plating is compared with the target lithium plating threshold corresponding to the electrochemical system of the target battery cell to determine whether the target battery cell has undergone lithium plating. This provides a low-cost lithium plating determination method applicable to batteries with various electrochemical systems. Furthermore, this method does not require physical disassembly of the battery cell or the use of equipment such as magnetic resonance imaging for lithium plating determination, greatly reducing the cost of lithium plating determination.

[0064] Figure 4 This is a comparison chart of the total SOC reactance modulus according to an embodiment of this application. For example... Figure 4As shown, the battery cell is divided into an initial fresh state reference cell and a target cell after lithium plating. During the charging process of the target cell from 0% to 100% SOC, the reactance modulus value of the target cell is collected in increments of 0.5%. This forms the full SOC reactance modulus curve of the target cell after lithium plating, as shown in the figure. Compared with the full SOC reactance modulus curve of the initial fresh state reference cell, the pre-recorded reactance modulus of the reference cell is larger and the rate of change of reactance modulus is greater during the SOC increase. As SOC increases, the reactance modulus value decreases more rapidly and tends to stabilize. Using the lithium plating determination method provided in this application, based on the first reactance modulus sequence of the reference cell, the second reactance modulus sequence of the target cell, and the electrochemical system of the target cell, it is possible to determine whether the cell has undergone lithium plating. In this figure, as the SOC increases, lithium ions in the target cell move from the positive electrode to the negative electrode and deposit lithium, resulting in an increase in the surface double layer capacitance of the positive and negative electrode materials of the battery.

[0065] In some optional implementations, step S3032 above includes: Step a1: Traverse the reactance modulus residual sequence, and obtain the reactance modulus ratio sequence by quotienting the candidate reactance modulus residual values ​​in the reactance modulus residual sequence with the first reactance modulus value in the first reactance modulus value sequence.

[0066] Specifically, the candidate reactance modulus residual value refers to the element in the reactance modulus residual sequence. The reactance modulus ratio sequence refers to the sequence that stores the quotients between the candidate reactance modulus residual values ​​and the first reactance modulus value. By traversing the reactance modulus residual sequence, the quotient of each element (candidate reactance modulus residual value) in the reactance modulus residual sequence and the corresponding element (first reactance modulus value) in the first reactance modulus value sequence is calculated, and all quotients are stored in the reactance modulus ratio sequence.

[0067] In one example, the first reactance modulus sequence is represented as A=[ The second reactance modulus sequence is represented as B=[ Then the reactance modulus residual sequence is C=[ The candidate reactance modulus residual is... , ∈[1,200]. The reactance modulus ratio sequence is: D=[ ].

[0068] Step a2: Calculate the sum of all elements in the reactance modulus ratio sequence to obtain the reactance modulus ratio sum.

[0069] Specifically, the reactance modulus ratio sum refers to the sum of all elements in the reactance modulus ratio sequence.

[0070] In one example, the reactance modulus ratio can be expressed as sumD= .

[0071] Step a3: Determine the percentage of lithium plating based on the reactance modulus ratio and the length of the sequence with respect to the reactance modulus ratio.

[0072] Specifically, the percentage of lithium plating in the target cell can be obtained by quotienting the reactance modulus ratio and the length of the reactance modulus ratio sequence.

[0073] In one example, the lithium plating percentage p1 can be expressed as: p1= =

[0074] The technical solution of this embodiment uses the first reactance modulus sequence and the second reactance modulus sequence to calculate the percentage of lithium plating, providing an important basis for judging whether the target cell has lithium plating.

[0075] In one possible implementation, in conjunction with the above embodiments, step S3032 can also obtain the lithium plating percentage p2 through the first reactance modulus sequence A and the reactance modulus residual sequence C using the following calculation method: p2=

[0076] It should be noted that the target lithium plating threshold for this lithium plating percentage p2 is different from the target lithium plating threshold for the lithium plating percentage p1 in the example above. A mapping table between the corresponding system type and the lithium plating threshold can be constructed according to the electrochemical system and calculation method of the target cell.

[0077] In some optional implementations, step S3042 above includes: If the percentage of lithium plating is greater than or equal to the target lithium plating threshold, then the target cell has lithium plating; otherwise, the target cell does not have lithium plating.

[0078] Specifically, if the lithium plating percentage is greater than or equal to the target lithium plating threshold, it indicates that the target cell has a high lithium plating percentage, and therefore lithium plating has occurred in the target cell. Otherwise, it indicates that the lithium plating percentage is low, and lithium plating is not present in the target cell.

[0079] The technical solution of this embodiment provides a judgment result for whether the target cell has lithium plating, and realizes the lithium plating judgment of lithium batteries that are low-cost and adaptable to multiple electrochemical systems.

[0080] In some optional implementations, before collecting the reactance modulus value at the end of each step during the charging process of the target cell from 0% to 100% SOC in step S302 above, the following step is further included: Step b1: Obtain the target electrochemical impedance spectrum of the target cell at a preset percentage of state of charge.

[0081] Specifically, electrochemical impedance spectroscopy (EIS) is an analytical method that uses a small high- to low-frequency sinusoidal electrical signal as a "probe" to measure the voltage or current response of a target battery cell, thereby non-destructively analyzing the complex internal structure and operating state of the target battery cell. The target battery cell can be "scanned" with electrical signals of different frequencies to measure the "response" signal. Before acquiring the reactance modulus value of the target battery cell's SOC during charging, the target electrochemical impedance spectrum of the target battery cell at a preset state of charge percentage is read; preferably, the preset state of charge percentage is 50%.

[0082] Step b2: Determine the test frequency of the electrochemical impedance spectroscopy test based on the target electrochemical impedance spectrum.

[0083] Specifically, the test frequency refers to the fundamental frequency of the target battery cell. In the Nyquist plot of the target electrochemical impedance spectroscopy, the semicircular vertex of the electrochemical reaction resistance is found. Considering that the frequency at the vertex position may shift slightly during use, the frequency to the right of the vertex is taken as the test frequency.

[0084] In one example, Figure 5 This is a Nyquist plot of the EIS of a battery cell according to an embodiment of this application. The horizontal axis represents the real part of the impedance, and the vertical axis represents the imaginary part of the impedance. The arrow points to the sample point to the right of the semicircular vertex of the electrochemical reaction resistance; the test frequency can be determined based on this sample point.

[0085] Step b3: Perform electrochemical impedance spectroscopy (EIS) testing on the target cell based on the test frequency.

[0086] Specifically, the test frequency is used as the frequency for electrochemical impedance spectroscopy (EIS) testing of the target battery cell. The reactance modulus value is recorded during the EIS test.

[0087] In one possible implementation, for unplated lithium-ion cells, the electrolyte and anode material form a surface double-layer capacitance, resulting in a small electrochemically active surface area and therefore a small capacitance. For lithium-plated cells, lithium dendrites grow, causing a rapid expansion of the active surface area and leading to a larger capacitance. Single-frequency electrochemical impedance spectroscopy can detect changes in the double-layer capacitance and reactance of the graphite anode during charging.

[0088] For the surface active capacitance of the electric double layer, the relationship with the angular frequency and reactance modulus of the impedance test is as follows:

[0089] Where Cs is the double-layer capacitance, ω is the angular frequency of the impedance test, and Z'' is the imaginary part of the impedance, i.e., reactance. In the electrochemical impedance of lithium batteries, Z'' is negative, and the modulus of reactance |Z''| is taken for easy processing.

[0090] For continuous testing at a fixed single frequency (test frequency f), since ω=2πf remains constant, the change in reactance modulus can be used directly to determine whether lithium plating has occurred.

[0091] In one example, Figure 6 This is a schematic diagram illustrating the relationship between the frequency and the imaginary part of the impedance of a battery cell EIS according to an embodiment of this application. Figure 6 As shown, the horizontal axis represents frequency, the vertical axis represents the reactance modulus of impedance, and the position indicated by the arrow is the reactance modulus value corresponding to the test frequency.

[0092] This embodiment also provides a device for determining lithium plating in battery cells. This device is used to implement the above embodiments and preferred embodiments, and will not be repeated as already described. As used below, the term "module" can be a combination of software and / or hardware that implements a predetermined function. Although the device described in the following embodiments is preferably implemented in software, hardware implementation, or a combination of software and hardware, is also possible and contemplated.

[0093] This embodiment provides a device for determining lithium plating in battery cells, such as... Figure 7 As shown, it includes: The acquisition module 701 is used to acquire the first reactance modulus value sequence of the SOC of the reference cell from 0% to 100% and the electrochemical system of the target cell. The number of cycle discharges of the reference cell is less than a preset discharge threshold, and the reference cell and the target cell have the same electrochemical system. The acquisition module 702 is used to acquire the reactance modulus value at the end of each step during the process of charging the target cell from 0% to 100% SOC, with a preset percentage of state of charge as the step size, and save it to the second reactance modulus value sequence. The determining module 703 is used to determine the lithium plating percentage of the target cell based on the first reactance modulus value sequence and the second reactance modulus value sequence; The judgment module 704 is used to determine whether the target cell has lithium plating based on the lithium plating percentage and the electrochemical system. In some optional implementations, the determination module 704 includes: The threshold determination unit is used to determine the target lithium plating threshold corresponding to the electrochemical system from the mapping table between the system type of the target cell and the lithium plating threshold, wherein the mapping table indicates that multiple electrochemical systems correspond one-to-one with multiple lithium plating thresholds; The judgment unit is used to determine whether the target cell has undergone lithium plating based on the lithium plating percentage and the target lithium plating threshold.

[0094] In some alternative implementations, the determining module 703 includes: A reactance modulus residual unit is determined to traverse the second reactance modulus value sequence. The reactance modulus residual sequence is obtained by calculating the difference between each second reactance modulus value in the second reactance modulus value sequence and each first reactance modulus value in the first reactance modulus value sequence. The first reactance modulus value and the second reactance modulus value have the same SOC. A lithium plating percentage determination unit is used to determine the lithium plating percentage based on the reactance modulus residual sequence and the first reactance modulus value sequence.

[0095] In some alternative implementations, determining the lithium plating percentage unit includes: Determine candidate sequence sub-units for traversing the reactance modulus residual sequence. Obtain the reactance modulus ratio sequence by quoting the candidate reactance modulus residual values ​​in the reactance modulus residual sequence with the first reactance modulus values ​​in the first reactance modulus value sequence. The calculation sub-unit is used to calculate the sum of all elements in the reactance modulus ratio sequence to obtain the reactance modulus ratio sum; A lithium plating percentage determination subunit is used to determine the lithium plating percentage based on the reactance modulus ratio and the length of the sequence with respect to the reactance modulus ratio.

[0096] In some optional implementations, the determination unit includes: The lithium plating determination subunit is used to determine whether lithium plating exists in the target cell if the percentage of lithium plating is greater than or equal to the target lithium plating threshold; otherwise, lithium plating does not exist in the target cell.

[0097] In some alternative implementations, the acquisition module 702 further includes: An electrochemical impedance spectroscopy acquisition unit is used to acquire the target electrochemical impedance spectrum of the target cell at a preset percentage of state of charge. The test frequency determination unit is used to determine the test frequency of the electrochemical impedance spectroscopy test based on the target electrochemical impedance spectrum. The test unit is used to perform electrochemical impedance spectroscopy tests on the target cell based on the test frequency.

[0098] The lithium plating detection device for battery cells provided in this application can execute the lithium plating detection method for battery cells provided in any embodiment of this application, and has the corresponding functional modules and beneficial effects for executing the method. Further functional descriptions of the above modules and units are the same as those in the corresponding embodiments described above, and will not be repeated here.

[0099] Figure 8 This is a schematic diagram of the structure of an electronic device provided in an embodiment of this application.

[0100] The following is a detailed reference. Figure 8 The diagram illustrates a structural schematic suitable for implementing the electronic device described in the embodiments of this application. The electronic device may include a processor (e.g., a central processing unit, graphics processor, etc.) 801, which can perform various appropriate actions and processes according to a program stored in read-only memory (ROM) 802 or a program loaded from memory 808 into random access memory (RAM) 803. The RAM 803 also stores various programs and data required for the operation of the electronic device. The processor 801, ROM 802, and RAM 803 are interconnected via a bus 804. An input / output (I / O) interface 805 is also connected to the bus 804.

[0101] Typically, the following devices can be connected to I / O interface 805: input devices 806 including, for example, touchscreens, touchpads, keyboards, mice, cameras, microphones, accelerometers, gyroscopes, etc.; output devices 807 including, for example, liquid crystal displays (LCDs), speakers, vibrators, etc.; memory devices 808 including, for example, magnetic tapes, hard disks, etc.; and communication devices 809. Communication device 809 allows electronic devices to communicate wirelessly or wiredly with other devices to exchange data. Although Figure 8 Electronic devices with various devices are shown, but it should be understood that it is not required to implement or have all of the devices shown, and more or fewer devices may be implemented or have instead.

[0102] Specifically, according to embodiments of this application, the processes described above with reference to the flowcharts can be implemented as computer software programs. For example, embodiments of this application include a computer program product comprising a computer program carried on a non-transitory computer-readable medium, the computer program containing program code for performing the methods shown in the flowcharts. In such embodiments, the computer program can be downloaded and installed from a network via a communication device 809, or installed from a memory 808, or installed from a ROM 802. When the computer program is executed by the processor 801, it performs the functions defined in the lithium plating determination method for battery cells according to embodiments of this application.

[0103] Figure 8 The electronic device shown is merely an example and should not impose any limitation on the functionality and scope of use of the embodiments of this application.

[0104] This application also provides a computer-readable storage medium. The methods described in this application can be implemented in hardware or firmware, or implemented as recordable on a storage medium, or implemented as computer code downloaded via a network and originally stored on a remote storage medium or a non-transitory machine-readable storage medium and then stored on a local storage medium. Thus, the methods described herein can be processed by software stored on a storage medium using a general-purpose computer, a dedicated processor, or programmable or dedicated hardware. The storage medium can be a magnetic disk, optical disk, read-only memory, random access memory, flash memory, hard disk, or solid-state drive, etc.; further, the storage medium can also include combinations of the above types of memory. It is understood that computers, processors, microprocessor controllers, or programmable hardware include storage components capable of storing or receiving software or computer code. When the software or computer code is accessed and executed by the computer, processor, or hardware, the method for determining lithium plating in battery cells shown in the above embodiments is implemented.

[0105] A portion of this application can be applied as a computer program product, such as computer program instructions, which, when executed by a computer, can invoke or provide the methods and / or technical solutions according to this application through the operation of the computer. Those skilled in the art will understand that the forms in which computer program instructions exist in a computer-readable medium include, but are not limited to, source files, executable files, installation package files, etc. Correspondingly, the ways in which computer program instructions are executed by a computer include, but are not limited to: the computer directly executing the instructions, or the computer compiling the instructions and then executing the corresponding compiled program, or the computer reading and executing the instructions, or the computer reading and installing the instructions and then executing the corresponding installed program. Here, the computer-readable medium can be any available computer-readable storage medium or communication medium accessible to a computer.

[0106] Although embodiments of this application have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of this application, and all such modifications and variations fall within the scope defined by the appended claims.

Claims

1. A method for determining lithium plating in battery cells, characterized in that, The method includes: Obtain the first reactance modulus value sequence of the reference cell's SOC from 0% to 100% and the electrochemical system of the target cell. The reference cell's cycle discharge number is less than a preset discharge threshold, and the reference cell and the target cell have the same electrochemical system. Using a preset percentage of state of charge as the step size, the reactance modulus value is collected at the end of each step during the process of charging the target cell from 0% to 100% SOC, and saved to the second reactance modulus value sequence. The lithium plating percentage of the target cell is determined based on the first reactance modulus value sequence and the second reactance modulus value sequence. Based on the lithium plating percentage and the electrochemical system, it is determined whether the target cell has undergone lithium plating.

2. The method according to claim 1, characterized in that, The step of determining whether the target cell has undergone lithium plating based on the lithium plating percentage and the electrochemical system includes: The target lithium plating threshold corresponding to the electrochemical system is determined from the mapping table between the system type of the target cell and the lithium plating threshold, wherein the mapping table indicates that multiple electrochemical systems correspond one-to-one with multiple lithium plating thresholds; Based on the lithium plating percentage and the target lithium plating threshold, it is determined whether the target cell has undergone lithium plating.

3. The method according to claim 1, characterized in that, Determining the lithium plating percentage of the target cell based on the first reactance modulus value sequence and the second reactance modulus value sequence includes: Traverse the second reactance modulus value sequence, and obtain the reactance modulus residual sequence by calculating the difference between each second reactance modulus value in the second reactance modulus value sequence and each first reactance modulus value in the first reactance modulus value sequence, wherein the first reactance modulus value and the second reactance modulus value have the same SOC; The percentage of lithium plating is determined based on the residual sequence of reactance modulus and the sequence of the first reactance modulus value.

4. The method according to claim 3, characterized in that, Determining the lithium plating percentage based on the reactance modulus residual sequence and the first reactance modulus value sequence includes: Traverse the reactance modulus residual sequence, and obtain the reactance modulus ratio sequence by quotienting the candidate reactance modulus residual values ​​in the reactance modulus residual sequence with the first reactance modulus values ​​in the first reactance modulus value sequence; Calculate the sum of all elements in the reactance modulus ratio sequence to obtain the reactance modulus ratio sum; The percentage of lithium plating is determined based on the reactance modulus ratio and the length of the reactance modulus ratio sequence.

5. The method according to claim 2, characterized in that, The step of determining whether the target cell has undergone lithium plating based on the lithium plating percentage and the target lithium plating threshold includes: If the percentage of lithium plating is greater than or equal to the target lithium plating threshold, then the target cell has lithium plating; otherwise, the target cell does not have lithium plating.

6. The method according to claim 1, characterized in that, Before acquiring the reactance modulus value at the end of each step during the process of charging the target cell from 0% to 100% SOC, the method further includes: Obtain the target electrochemical impedance spectrum of the target cell at a preset percentage of state of charge; Based on the target electrochemical impedance spectrum, determine the test frequency of the electrochemical impedance spectroscopy test; Based on the test frequency, the target battery cell is subjected to electrochemical impedance spectroscopy testing.

7. A device for determining lithium plating in battery cells, characterized in that, The device includes: The acquisition module is used to acquire the first reactance modulus value sequence of the SOC of the reference cell from 0% to 100% and the electrochemical system of the target cell. The number of cycle discharges of the reference cell is less than a preset discharge threshold, and the reference cell and the target cell have the same electrochemical system. The acquisition module is used to acquire the reactance modulus value at the end of each step during the process of charging the target cell from 0% to 100% SOC, with a preset percentage of state of charge as the step size, and save it to the second reactance modulus value sequence. The determining module is used to determine the lithium plating percentage of the target cell based on the first reactance modulus value sequence and the second reactance modulus value sequence; The judgment module is used to determine whether the target cell has lithium plating based on the lithium plating percentage and the electrochemical system.

8. An electronic device, characterized in that, include: The device includes a memory and a processor, which are interconnected. The memory stores computer instructions, and the processor executes the computer instructions to perform the method for determining lithium plating in battery cells as described in any one of claims 1 to 6.

9. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores computer instructions for causing the computer to execute the method for determining lithium plating in battery cells as described in any one of claims 1 to 6.

10. A computer program product, characterized in that, Includes computer instructions, which are used to cause a computer to execute the method for determining lithium plating in battery cells as described in any one of claims 1 to 6.

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