Method and device for determining irreversible lithium precipitation amount of lithium ion battery

Abstract

The embodiment of the invention provides a method and device for determining the irreversible lithium precipitation amount of a lithium ion battery. The method comprises the steps that a pre-constructed linear relation is obtained, the linear relation is used for representing the relation between the irreversible pressure and the irreversible lithium precipitation amount of a sample battery in the charging process, and the irreversible pressure is used for representing the difference value of the pressure change amount of the sample battery in the charging process and the pressure change amount of the sample battery in the discharging process; obtaining a target irreversible pressure when the target battery is charged; and according to the target irreversible pressure and the linear relationship, determining the irreversible lithium precipitation amount of the target battery during charging. The method can realize rapid detection of irreversible lithium precipitation of the lithium battery.

Description

Technical Field

[0001] This application relates to the field of fault diagnosis technology for lithium-ion power batteries, and in particular to a method and apparatus for determining the amount of irreversible lithium deposition in lithium-ion batteries. Background Technology

[0002] Low-temperature charging or high-rate charging of lithium-ion batteries increases the risk of lithium plating and accelerates battery capacity degradation. Lithium dendrites formed during battery cycling, and even internal short circuits caused by lithium dendrites piercing the separator, can significantly impact the battery's cycle life and safety. Currently, research on in-situ lithium plating detection technology for large-capacity lithium iron phosphate batteries under complex operating conditions is scarce, thus necessitating rapid detection of lithium plating in lithium-ion batteries. Summary of the Invention

[0003] This application provides a method and apparatus for determining the amount of irreversible lithium plating in lithium-ion batteries, so as to achieve the effect of rapid detection of irreversible lithium plating in lithium batteries.

[0004] In a first aspect, embodiments of this application provide a method for determining the amount of irreversible lithium plating in a lithium-ion battery, including:

[0005] Obtain a pre-constructed linear relationship, which is used to characterize the relationship between irreversible pressure and irreversible lithium plating amount of the sample battery during charging. The irreversible pressure is used to characterize the difference between the pressure change during charging and the pressure change during discharging of the sample battery.

[0006] Obtain the target irreversible pressure of the target battery during charging;

[0007] Based on the target irreversible pressure and the linear relationship, the amount of irreversible lithium plating in the target battery during charging is determined.

[0008] Secondly, embodiments of this application provide a device for determining the amount of irreversible lithium plating in a lithium-ion battery, comprising:

[0009] The relationship acquisition module is used to acquire a pre-constructed linear relationship, which is used to characterize the relationship between the irreversible pressure and the amount of irreversible lithium plating of the sample battery during the charging process. The irreversible pressure is used to characterize the difference between the pressure change during the charging process and the pressure change during the discharging process of the sample battery.

[0010] The pressure acquisition module is used to acquire the target irreversible pressure of the target battery during charging.

[0011] The lithium deposition amount determination module is used to determine the amount of irreversible lithium deposition in the target battery during charging based on the target irreversible pressure and the linear relationship.

[0012] The method and apparatus for determining the amount of irreversible lithium plating in lithium-ion batteries provided in this application embodiment achieve the purpose of rapid detection of irreversible lithium plating in lithium-ion batteries by fitting the relationship between irreversible pressure and the amount of irreversible lithium plating in the battery and using pressure to quantitatively evaluate the irreversible lithium plating in the battery. Attached Figure Description

[0013] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0014] Figure 1 A schematic diagram of the method for determining the amount of irreversible lithium plating in lithium-ion batteries provided in this application;

[0015] Figure 2 The diagram shows the irreversible pressure and irreversible lithium plating loss of the battery under different discharge conditions provided in the embodiments of this application.

[0016] Figure 3 A graph showing the relationship between irreversible battery pressure and irreversible lithium deposition is provided for embodiments of this application.

[0017] Figure 4 A flowchart of in-situ lithium plating detection based on expansion force signal provided in this application embodiment;

[0018] Figure 5 A schematic diagram of the structure of the device for determining the irreversible lithium deposition amount of lithium-ion batteries provided in this application;

[0019] Figure 6 A schematic diagram of the structure of the electronic device provided in this application.

[0020] The accompanying drawings illustrate specific embodiments of this application, which will be described in more detail below. These drawings and descriptions are not intended to limit the scope of the concept in any way, but rather to illustrate the concept of this application to those skilled in the art through reference to particular embodiments. Detailed Implementation

[0021] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this application as detailed in the appended claims.

[0022] In recent years, lithium-ion batteries have been considered an effective way to reduce environmental pollution and energy consumption. However, low-temperature charging or high-rate charging increases the risk of lithium plating and accelerates battery capacity degradation. Lithium dendrites formed during battery cycling, and even internal short circuits caused by lithium dendrites piercing the separator, can significantly impact the battery's cycle life and safety. Achieving rapid in-situ detection of lithium plating in lithium-ion batteries is a key technology for their safe and efficient operation. Currently, most existing in-situ lithium plating detection methods are designed for single operating conditions and are time-consuming. Methods using impedance and relaxation voltage signals also have limitations. Furthermore, accurate in-situ lithium plating detection is difficult for large-capacity lithium iron phosphate batteries operating under complex conditions.

[0023] To address the aforementioned issues, this application provides a method and apparatus for determining the amount of irreversible lithium plating in lithium-ion batteries. By fitting the relationship between irreversible pressure and the amount of irreversible lithium plating, it achieves a quantitative assessment of irreversible lithium plating using pressure, thus enabling rapid detection of irreversible lithium plating in lithium-ion batteries. Furthermore, it can also obtain the magnitude of the lithium plating boundary current at different temperatures, thereby providing strong support for battery developers to develop more cost-effective and competitive battery products.

[0024] The technical solution of this application and how the technical solution of this application solves the above-mentioned technical problems are described in detail below with specific embodiments. These specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described again in some embodiments. The embodiments of this application will now be described with reference to the accompanying drawings.

[0025] Figure 1 This is a schematic diagram of the method for determining the irreversible lithium deposition amount in lithium-ion batteries provided in this application, such as... Figure 1 As shown, the method includes the following steps:

[0026] S110, Obtain the pre-built linear relationship.

[0027] Among them, the linear relationship is used to characterize the relationship between the irreversible pressure and the amount of irreversible lithium plating during the charging process of the sample battery, and the irreversible pressure is used to characterize the difference between the pressure change during the charging process and the pressure change during the discharging process of the sample battery.

[0028] S120, Obtain the target irreversible pressure of the target battery during charging.

[0029] S130. Determine the amount of irreversible lithium plating in the target battery during charging based on the target irreversible pressure and linear relationship.

[0030] The method provided in this application embodiment achieves quantitative evaluation of irreversible lithium plating in batteries by fitting the relationship between irreversible pressure and irreversible lithium plating amount, thereby achieving the purpose of rapid detection of irreversible lithium plating in lithium-ion batteries.

[0031] Specifically, regarding step S210 above, when the sample battery undergoes a single charge-discharge cycle in a low-temperature environment, the irreversible pressure increase caused by the formation of the solid electrolyte interface (SEI) film during this single charge-discharge cycle can be ignored. That is, in the charging conditions of this embodiment, the main reason for the irreversible pressure increase is the irreversible increase in electrode thickness caused by irreversible lithium plating. Therefore, the capacity loss of the sample battery can be calculated using the capacity before and after a certain low-temperature charge-discharge cycle, thus determining the amount of irreversible lithium plating.

[0032] Specifically, by performing linear fitting on the irreversible pressure sequence and irreversible lithium deposition sequence of the sample batteries under constant current discharge conditions, the following relationship between irreversible pressure and irreversible lithium deposition was obtained:

[0033] F irr =k*Q irr

[0034] In the above formula, Firr represents the amount of irreversible lithium deposition, Qirr represents the irreversible pressure, and k is a set coefficient, which can be 1.0236.

[0035] Exemplary, in some embodiments, Figure 2 The following are diagrams showing the irreversible pressure and irreversible lithium plating loss of the battery under different discharge conditions provided in the embodiments of this application, such as... Figure 2 As shown, the irreversible pressure (corresponding to) of the sample battery under different charging conditions can be recorded. Figure 2 The vertical axis in the figure) and the amount of irreversible lithium plating (corresponding to) Figure 2 (The horizontal axis in the diagram). These charging conditions can refer to the charging rate, specifically any value between 0.2 and 1.5 times the rated capacity of the sample battery, i.e., between 0.2C and 1.5C. For example... Figure 2 The values ​​are 0.25C, 0.50C, 0.75C, 1.00C, 1.25C, and 1.50C.

[0036] Furthermore, Figure 3 The graph showing the relationship between irreversible battery pressure and irreversible lithium deposition amount provided in the embodiments of this application is as follows: Figure 3 As shown, after obtaining a series of irreversible battery pressures and irreversible lithium deposition amounts, the relationship curve between the obtained irreversible battery pressure and irreversible lithium deposition amount can be fitted. Figure 3In the figure, the horizontal axis represents the amount of irreversible lithium deposition, and the vertical axis represents the irreversible pressure.

[0037] For example, the sample battery can be a lithium-ion power battery with lithium iron phosphate as the positive electrode and graphite as the negative electrode.

[0038] Regarding step S220 above, for any lithium-ion battery, if it is necessary to determine the amount of irreversible lithium deposition during charging, a certain charging current can be used to charge the lithium-ion battery (i.e., the target battery) to obtain the irreversible pressure of the target battery.

[0039] Irreversible pressure can refer to the difference between the pressure change during the charging process and the pressure change rate during the discharging process of the target battery. Specifically, taking the target battery charging to a preset state of charge as an example, the pressure change during the charging process is A, and the pressure change during the discharging process of the target battery from the preset state of charge is B. The difference between A and B can be taken as the irreversible pressure.

[0040] Regarding step S230 above, after determining the irreversible pressure of the target battery, the irreversible lithium deposition amount of the target battery can be calculated based on the fitted curve of the relationship between the battery's irreversible pressure and the amount of irreversible lithium deposition.

[0041] The following examples describe in detail how to construct the above linear relationship.

[0042] Taking a lithium-ion power battery with lithium iron phosphate as the positive electrode and graphite as the negative electrode as an example, and charging three sample batteries at different temperatures and charging rates (i.e., charging conditions), in some embodiments, the irreversible pressure of the sample batteries at different charging rates can be obtained through the following steps:

[0043] Step a: Under the condition that the sample battery is charged under different charging conditions and irreversible lithium plating occurs, obtain the irreversible pressure of the sample battery under each charging condition, as well as the difference in battery capacity before and after charging.

[0044] Step b: Construct an irreversible pressure sequence based on the irreversible pressure of the sample batteries under various charging conditions;

[0045] Step c: Construct an irreversible lithium deposition sequence based on the battery capacity difference of the sample batteries under various charging conditions;

[0046] Step d: Construct a linear relationship based on the irreversible pressure sequence and the irreversible lithium deposition sequence.

[0047] In this embodiment, for step a, firstly, the sample battery can be charged with a preset current so that the sample battery reaches a preset state of charge.

[0048] The preset current is determined by the charging rate of the sample battery, which can be any value within the range of 1 / 5C to 1.5C. The preset state of charge (SOC) is 60%-99% of the remaining capacity; for example, the preset SOC is 95%. For instance, the sample battery can be charged with a constant current at a charging rate of 1C to achieve 95% SOC (i.e., the preset SOC).

[0049] The difference between the pressure change during charging and the pressure change during discharging of the sample battery at different charging rates is calculated to obtain the irreversible pressure of the sample battery at different charging rates, thus forming an irreversible pressure sequence (which includes multiple irreversible pressures), as shown in Table 1.

[0050] Table 1

[0051]

[0052] Secondly, during charging, lithium ions are extracted from the positive electrode and inserted into the graphite intercalation layer of the negative electrode. The decrease in reaction rate constant and diffusion coefficient under low-temperature charging conditions causes the lithium ion insertion rate in the negative electrode to be lower than the lithium extraction rate in the positive electrode at high SOC. Both of these factors cause lithium ions that are not intercalated in the negative electrode particles to gain electrons on the negative electrode surface to form lithium metal, which adheres to the negative electrode surface. This process is called lithium deposition.

[0053] In this process, reversible lithium deposition releases electrons during discharge to form lithium ions, which are then re-intercalated into the cathode particles. However, some of the deposited lithium undergoes side reactions with solvents in the electrolyte (such as carbonates), generating an unstable SEI film that covers the deposited lithium surface, causing it to lose electrical contact with the electrode and forming "dead lithium." The accumulation of "dead lithium" further forms dendrites, which in turn further distort the local electric field, leading to a tip effect (electric field concentration at high curvature), accelerating dendrite growth, and creating a positive feedback effect of dendrite growth and increased irreversible expansion force of the battery.

[0054] In this embodiment, the capacity loss of the sample battery can be obtained based on the capacity difference before and after charging at a certain current where irreversible lithium plating occurs, and this loss can be determined as the amount of irreversible lithium plating. This allows for the determination of a sequence of irreversible lithium plating capacities (including multiple amounts of irreversible lithium plating).

[0055] Furthermore, linear fitting was performed on the obtained irreversible pressure sequence and irreversible lithium deposition sequence to obtain the linear relationship between the battery's irreversible pressure and irreversible lithium deposition (see above for details). Figure 3 If irreversible lithium plating occurs in the battery, there is irreversible pressure. The greater the amount of irreversible lithium plating, the greater the irreversible pressure. Therefore, the irreversible lithium plating in the battery can be detected and quantified by the increase of the battery's irreversible pressure.

[0056] In addition, in some embodiments, the previous embodiment mentioned that the sample battery can be charged by a preset current to make the sample battery reach a preset state of charge. This scenario is equivalent to charging the sample battery to the preset state of charge under different charging conditions. In this scenario, the change in charging pressure during the charging process of the sample battery and the change in discharging pressure during the discharging process of the sample battery can be obtained. Then, based on the difference between the change in charging pressure and the change in discharging pressure, the irreversible pressure of the sample battery under each charging condition can be obtained.

[0057] In this embodiment, the pressure change refers to the change in internal pressure of the sample battery during charging and discharging. Specifically, the pressure change can be collected using an integrated testing fixture. This integrated testing fixture may include a three-plate constant displacement device, a charge / discharge testing equipment, a high / low temperature chamber, and a multi-channel temperature acquisition device.

[0058] During charging, lithium ions are embedded in the negative electrode material, causing the negative electrode to expand in volume and increasing the internal stress of the battery, resulting in a rise in pressure. During discharging, lithium ions are released from the negative electrode, the spacing between the graphite layers decreases, the negative electrode shrinks in volume, resulting in a drop in pressure.

[0059] In some embodiments, the change in discharge pressure during the discharge process of a sample battery can be obtained by combining the following two steps:

[0060] Step 1: During the constant current test or dynamic discharge test of the sample battery until the remaining charge inside the sample battery is lower than the preset lower limit, obtain the first pressure change of the sample battery.

[0061] Step 2: During the process of conducting a small current discharge test on the sample battery until the remaining charge inside the sample battery is lower than the preset lower limit, the second pressure change of the sample battery is obtained.

[0062] The total pressure change of the sample battery during the two-step discharge can be recorded based on the first pressure change and the second pressure change.

[0063] In this embodiment, a two-step discharge test is performed on the sample battery. The first step is a constant current test or a dynamic discharge condition test, and the second step is a small current discharge test, which discharges all the remaining charge inside the sample battery. The total pressure change of the sample battery during the two-step discharge is recorded as the discharge pressure change during the discharge process of the sample battery.

[0064] Furthermore, in some embodiments, the following steps can be used to determine whether lithium plating occurs in the sample battery under different charging conditions:

[0065] Step (1) Based on the irreversible pressure of the sample battery under each charging condition, determine the minimum and maximum charging current for irreversible lithium plating of the battery.

[0066] Step (2) Determine the critical charging current range for irreversible lithium plating of the sample battery based on the minimum and maximum charging current values.

[0067] Step (3) Obtain the irreversible pressure range corresponding to the sample battery when it is charged within the critical charging current range;

[0068] Step (4) Determine the irreversible pressure threshold based on the irreversible pressure range;

[0069] Step (5) Determine whether irreversible lithium plating has occurred in the sample battery based on the irreversible pressure threshold.

[0070] In this embodiment, different charging conditions refer to charging the sample battery with different charging currents. Under different charging currents, the sample battery may or may not undergo lithium plating. For example, the sample battery may not undergo lithium plating at charging current A1, but lithium plating will occur when the charging current is increased to A2. Then, the charging current is sequentially increased to A3, A4, and A5, and lithium plating still occurs until the charging current is increased to A6, at which point lithium plating ceases. Therefore, the minimum charging current for irreversible lithium plating of the sample battery is determined to be A2, and the maximum charging current for irreversible lithium plating is determined to be A5.

[0071] In addition, when charging the sample battery with different charging currents, the corresponding irreversible pressure can be obtained. That is, the minimum charging current corresponds to an irreversible pressure Y1, and the maximum charging current corresponds to an irreversible pressure Y2. Thus, the range of irreversible pressure is [Y1, Y2].

[0072] In the embodiments of this application, by obtaining the magnitude of the lithium plating boundary current of the battery at different temperatures, it can provide strong support for battery developers to develop more cost-effective and competitive battery products.

[0073] Furthermore, in some embodiments, in relation to step (1) above, the irreversible pressure of the sample battery under different charging conditions can be clustered according to the mean clustering method to obtain irreversible lithium plating clusters and non-irreversible lithium plating clusters; then, based on the irreversible lithium plating clusters and non-irreversible lithium plating clusters, the minimum and maximum charging current values ​​of the sample battery for irreversible lithium plating are determined.

[0074] In this embodiment, specifically, the fuzzy c-means clustering method can be used to cluster the irreversible pressure of the battery at different charging rates to obtain "irreversible lithium plating clusters" and "irreversible lithium plating clusters".

[0075] Among them, the sample points in "irreversible lithium clusters occurred" are those in which irreversible lithium plating occurred in the sample battery at the corresponding charging rate, while the sample points in "no irreversible lithium clusters occurred" are those in which irreversible lithium plating did not occur in the sample battery at the corresponding charging rate.

[0076] Specifically, the minimum charging rate in the "irreversible lithium cluster formation" can be determined as the minimum value of the critical charging current range for irreversible lithium plating of the battery, and the maximum charging rate in the "non-irreversible lithium cluster formation" can be determined as the minimum value of the critical charging current range for irreversible lithium plating of the battery, thus obtaining the critical charging current range for irreversible lithium plating of the battery.

[0077] In addition, an irreversible pressure threshold can be set based on the irreversible pressure range corresponding to the charging critical current range of irreversible lithium plating.

[0078] For example, Table 2 below shows the clustering results of irreversible pressure under two discharge conditions. Clustering divides the irreversible pressure into two clusters: "Clusters where irreversible lithium plating occurs" (labeled Y) and "Clusters where irreversible lithium plating does not occur" (labeled N). The membership degree is the probability that a given charging rate belongs to either the "Clusters where irreversible lithium plating occurs" or the "Clusters where irreversible lithium plating does not occur". In this embodiment, clusters with a membership degree greater than 0.5 are determined as the final cluster to which a given charging rate belongs.

[0079] Table 2

[0080]

[0081] Based on the clustering results in Table 2 above, it can be determined that under constant current discharge and dynamic discharge conditions, when the charging rate is ≥1C, the sample batteries exhibit irreversible lithium plating. The critical charging current range for irreversible lithium plating in the sample batteries can be determined to be between 0.75C and 1C.

[0082] The critical value of irreversible pressure under constant current discharge conditions is between 0.19 kN and 0.91 kN, while the critical value of irreversible pressure under FUDS discharge conditions is between 0.41 kN and 0.81 kN. For example, to improve the accuracy of lithium plating detection and reduce the false alarm rate, this embodiment selects the average of the maximum lower limit of the irreversible pressure critical range (0.41 kN) and the minimum upper limit (0.81 kN), which is 0.61 kN, as the threshold value of irreversible pressure.

[0083] Furthermore, in some embodiments, after determining the irreversible pressure threshold, the first irreversible pressure of the sample battery when it is charged to the first state of charge under the first charging condition can be obtained; if the first irreversible pressure is greater than the irreversible pressure threshold, it is determined that irreversible lithium plating exists in the sample battery under the first charging condition.

[0084] In this embodiment, the irreversible lithium plating status of the sample battery during the charging process is determined based on the irreversible pressure threshold, as follows:

[0085] ① If irreversible pressure exceeds the threshold when the charging current is charged to a specific state of charge range, it is determined that the sample battery has irreversible lithium plating at the charging rate.

[0086] ② If the irreversible pressure does not exceed the threshold when the charging current is charged to a specific state of charge range, it is determined that the sample battery does not have irreversible lithium plating at the charging rate.

[0087] Specifically, the sample battery was charged at a constant current rate of 1.25C to reach 95% SOC. The irreversible pressure of the sample battery was then calculated, which was 1.84 kN (constant current discharge condition) or 1.47 kN (dynamic discharge condition). The irreversible pressure value exceeded the threshold of 0.61 kN under both conditions, indicating that lithium plating occurred in the sample battery during 1.25C charging and that irreversible lithium plating was present.

[0088] Furthermore, under constant current discharge conditions, the irreversible pressure values ​​at charging rates of 1C, 1.25C, and 1.5C all exceeded the threshold, indicating that lithium plating occurred in the sample battery at these three charging rates, and irreversible lithium plating was present. Under dynamic discharge conditions, the irreversible pressure values ​​at charging rates of 1C, 1.25C, and 1.5C all exceeded the threshold, indicating that lithium plating occurred in the sample battery at these three charging rates, and irreversible lithium plating was present.

[0089] Figure 4 A flowchart of in-situ lithium plating detection based on expansion force signal provided in this application embodiment is shown below. Figure 4 As shown, it includes the following steps:

[0090] S410, based on an integrated testing fixture, performs charge and discharge tests on batteries at different rates;

[0091] S420, record the pressure change during charging and the pressure change during discharging;

[0092] S430. Calculate the difference between the pressure change during charging and the pressure change during discharging to obtain the irreversible pressure of the battery.

[0093] S440. Clustering the irreversible stress of the battery to obtain the critical charging current range for irreversible lithium plating of the battery.

[0094] S450, Set the battery irreversible pressure threshold;

[0095] S460. Determine the lithium plating status of the battery during current charging based on the battery's irreversible pressure threshold.

[0096] In this embodiment, the battery is charged at different rates using an integrated testing fixture to achieve the expected state of charge, and the pressure change during charging is recorded. Then, a two-step discharge test is performed on the battery: the first step is a constant current test or a dynamic discharge test, and the second step is a low current discharge test to release all the remaining charge inside the battery. The total pressure change during the two discharge steps is recorded. Finally, the difference between the battery charging pressure change and the total discharge pressure change is calculated to obtain the irreversible pressure value of the battery.

[0097] In addition, the irreversible pressure value of the battery is clustered using the fuzzy c-means clustering method to obtain the critical charging current range in which the battery exhibits irreversible lithium plating. Based on the irreversible pressure range corresponding to this range, the irreversible pressure threshold of the battery is set to realize the detection and quantitative evaluation of irreversible lithium plating in the battery.

[0098] If the irreversible pressure of the battery exceeds the threshold after charging and discharging at the preset current, it is considered that irreversible lithium plating occurs when the battery is charged at the preset current. If the irreversible pressure of the battery does not exceed the threshold after a certain charge and discharge, it is determined that irreversible lithium plating does not occur when the battery is charged at the preset current.

[0099] Finally, by fitting the relationship between irreversible pressure and irreversible lithium deposition in the battery, a quantitative assessment of irreversible lithium deposition in the battery using pressure is achieved.

[0100] This embodiment enables rapid detection of irreversible lithium plating in lithium-ion batteries and provides insights into the lithium plating boundary current at different temperatures. This provides strong support for battery developers to create more cost-effective and competitive battery products.

[0101] Taking a lithium-ion power battery with lithium iron phosphate as the positive electrode and graphite as the negative electrode as an example, the correctness of this embodiment is verified by conducting charging experiments at different rates and temperatures using three batteries. The integrated testing fixture includes: a three-plate constant displacement device, a charge-discharge testing device, a high-low temperature chamber, and a multi-channel temperature acquisition device. This embodiment may specifically include the following steps:

[0102] Step 1: Conduct charging experiments on the battery at different rates to bring the battery to the preset state of charge, and record the pressure changes during the charging and discharging processes.

[0103] The preset current is determined by the battery's charging rate, which can be any value within the range of 1 / 5C to 1.5C. The preset state of charge (SOC) is 60%-99%. Preferably, the preset SOC is 95%.

[0104] Step 2: Calculate the difference between the pressure change during the charging process and the pressure change during the discharging process at the charging rate, to obtain the irreversible pressure of the battery at the charging rate. See Table 1 above for details.

[0105] Step 3: (1) Use the fuzzy c-means clustering method to cluster the irreversible pressure of the battery at different charging rates to obtain "irreversible lithium plating clusters" and "non-irreversible lithium plating clusters". (2) Determine the minimum value of the charging critical current range for irreversible lithium plating in the "irreversible lithium plating clusters" with the minimum charging rate, and determine the minimum value of the charging critical current range for irreversible lithium plating in the "non-irreversible lithium plating clusters" with the maximum charging rate, and finally obtain the charging critical current range for irreversible lithium plating. (3) Set the irreversible pressure threshold of the battery according to the irreversible pressure range corresponding to the charging critical current range for irreversible lithium plating. See Table 2 above for details.

[0106] Step 4: Based on the battery's irreversible pressure threshold, determine the irreversible lithium plating situation during the charging process:

[0107] If the irreversible pressure of the battery exceeds the threshold when the charging current is charged to a specific state of charge range, it is determined that the battery has irreversible lithium plating at the charging rate.

[0108] If the irreversible pressure of the battery does not exceed the threshold when the charging current is charged to a specific state of charge range, it is determined that there is no irreversible lithium plating in the battery at the charging rate.

[0109] Specifically, the battery can be charged at a constant current rate of 1.25C to reach 95% SOC. The irreversible pressure of the battery can then be calculated, which is 1.84 kN (constant current discharge condition) or 1.47 kN (dynamic discharge condition). The irreversible pressure values ​​exceed the threshold of 0.61 kN under both conditions, indicating that lithium plating occurred during 1.25C charging and that irreversible lithium plating exists.

[0110] Furthermore, under constant current discharge conditions, the irreversible pressure values ​​at charging rates of 1C, 1.25C, and 1.5C all exceeded the threshold, indicating that lithium plating occurred in the battery at these three charging rates, and irreversible lithium plating was present. Under dynamic discharge conditions, the irreversible pressure values ​​at charging rates of 1C, 1.25C, and 1.5C all exceeded the threshold, indicating that lithium plating occurred in the battery at these three charging rates, and irreversible lithium plating was present.

[0111] Step 5: Obtain the irreversible pressure sequence of the battery from all charging conditions where irreversible lithium plating occurs, as obtained in Step 4. Then, based on the capacity difference before and after charging at a certain current where irreversible lithium plating occurs, obtain the battery capacity loss and determine the irreversible lithium plating capacity, thus obtaining the battery irreversible lithium plating capacity sequence. Finally, perform linear fitting on the obtained irreversible pressure sequence and irreversible lithium plating amount sequence to obtain the linear relationship between battery irreversible pressure and irreversible lithium plating amount.

[0112] Step 6: Obtain the irreversible pressure of the battery when charging with any charging current, and calculate the amount of irreversible lithium plating based on the fitted relationship between the irreversible pressure and the amount of irreversible lithium plating.

[0113] This embodiment innovatively calculates the irreversible pressure of the battery by analyzing pressure changes during charging and discharging. By clustering the irreversible pressures, it determines the critical charging current range for irreversible lithium plating, thereby establishing a threshold for irreversible lithium plating and enabling detection. Furthermore, by fitting a formula relating irreversible pressure to the amount of irreversible lithium plating, a quantitative assessment of irreversible lithium plating is achieved.

[0114] Figure 5 This is a schematic diagram of the device for determining the irreversible lithium deposition content of a lithium-ion battery provided in this application, as shown below. Figure 5 As shown, the lithium-ion battery irreversible lithium deposition determination device 50 provided in this embodiment includes:

[0115] The relationship acquisition module 510 is used to acquire pre-built linear relationships.

[0116] Among them, the linear relationship is used to characterize the relationship between the irreversible pressure and the amount of irreversible lithium plating during the charging process of the sample battery, and the irreversible pressure is used to characterize the difference between the pressure change during the charging process and the pressure change during the discharging process of the sample battery.

[0117] The pressure acquisition module 520 is used to acquire the target irreversible pressure of the target battery during charging.

[0118] The lithium deposition amount determination module 530 is used to determine the amount of irreversible lithium deposition in the target battery during charging based on the target irreversible pressure and linear relationship.

[0119] In one possible implementation, a relationship building module is also included, used for:

[0120] When the sample battery is charged under different charging conditions and irreversible lithium plating occurs, the irreversible pressure of the sample battery under each charging condition and the difference in battery capacity before and after charging are obtained.

[0121] Based on the irreversible pressure of the sample batteries under various charging conditions, an irreversible pressure sequence is constructed.

[0122] Based on the battery capacity difference of the sample batteries under various charging conditions, an irreversible lithium deposition sequence was constructed.

[0123] A linear relationship was constructed based on the irreversible pressure sequence and the irreversible lithium deposition sequence.

[0124] In one possible implementation, the relationship building module can also be used for:

[0125] Under different charging conditions, the changes in charging pressure during the charging process and the changes in discharge pressure during the discharging process of the sample battery are obtained.

[0126] The irreversible pressure of the sample battery under each charging condition is obtained by measuring the difference between the change in charging pressure and the change in discharging pressure.

[0127] In one possible implementation, a lithium plating determination module is also included, for:

[0128] Based on the irreversible pressure of the sample battery under each charging condition, determine the minimum and maximum charging current values ​​for irreversible lithium plating in the sample battery.

[0129] Based on the minimum and maximum charging current values, determine the critical charging current range for irreversible lithium plating to occur in the sample battery.

[0130] Obtain the irreversible pressure range corresponding to the sample battery when it is charged within the critical charging current range;

[0131] Determine the irreversible pressure threshold based on the irreversible pressure range;

[0132] Based on the irreversible pressure threshold, determine whether irreversible lithium plating has occurred in the sample battery.

[0133] In one possible implementation, the relationship building module can also be used for:

[0134] The first irreversible pressure of the sample battery is obtained when the sample battery is charged to the first state of charge under the first charging condition.

[0135] When the first irreversible pressure is greater than the irreversible pressure threshold, it is determined that irreversible lithium plating exists in the sample battery under the first charging condition.

[0136] In one possible implementation, the relationship building module can also be used for:

[0137] Based on the mean clustering method, the irreversible pressure of the sample batteries under different charging conditions is clustered to obtain clusters that have undergone irreversible lithium plating and clusters that have not undergone irreversible lithium plating.

[0138] Based on whether irreversible lithium clusters have occurred or not, determine the minimum and maximum charging current values ​​for the sample battery when irreversible lithium plating occurs.

[0139] In one possible implementation, the relationship building module can also be used for:

[0140] During the constant current test or dynamic discharge test of the sample battery until the remaining charge inside the sample battery is lower than the preset lower limit, the first pressure change of the sample battery is obtained.

[0141] During the process of conducting a small-current discharge test on the sample battery until the remaining charge inside the sample battery is lower than a preset lower limit, the second pressure change of the sample battery is obtained.

[0142] Based on the first pressure change and the first pressure change, the discharge pressure change during the discharge process of the sample battery is determined.

[0143] In one possible implementation, the preset state of charge is any value between 60% and 99% of the battery capacity.

[0144] In one possible implementation, the charging condition is a charging rate, which is any value between 0.2 and 1.5 times the rated capacity of the sample battery.

[0145] The lithium-ion battery irreversible lithium deposition determination device provided in this embodiment can execute the method provided in the above method embodiment. Its implementation principle and technical effect are similar, and will not be described in detail here.

[0146] Figure 6 A schematic diagram of the structure of the electronic device provided in this application. Figure 6 As shown, the electronic device 60 provided in this embodiment includes at least one processor 601 and a memory 602. Optionally, the device 60 further includes a communication component 603. The processor 601, memory 602, and communication component 603 are connected via a bus.

[0147] In a specific implementation, at least one processor 601 executes computer execution instructions stored in memory 602, causing at least one processor 601 to perform the above-described method.

[0148] The specific implementation process of processor 601 can be found in the above method embodiments, and its implementation principle and technical effect are similar. It will not be repeated here.

[0149] In the above embodiments, it should be understood that the processor can be a Central Processing Unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), etc. The general-purpose processor can be a microprocessor or any conventional processor. The steps of the method disclosed in this invention can be directly implemented by a hardware processor, or implemented by a combination of hardware and software modules within the processor.

[0150] The memory may include random access memory (RAM) and may also include non-volatile memory (NVM), such as at least one disk storage device.

[0151] The bus can be an Industry Standard Architecture (ISA) bus, a Peripheral Component Interconnect (PCI) bus, or an Extended Industry Standard Architecture (EISA) bus, etc. Buses can be categorized as address buses, data buses, control buses, etc. For ease of illustration, the buses shown in the accompanying drawings are not limited to a single bus or a single type of bus.

[0152] This application also provides a computer program product, including a computer program that, when executed by a processor, implements the above-described method.

[0153] This application also provides a computer-readable storage medium storing computer-executable instructions, which, when executed by a processor, implement the above-described method.

[0154] The aforementioned readable storage medium can be implemented by any type of volatile or non-volatile storage device or a combination thereof, such as static random access memory (SRAM), electrically erasable programmable read-only memory (EEPROM), erasable programmable read-only memory (EPROM), programmable read-only memory (PROM), read-only memory (ROM), magnetic storage, flash memory, magnetic disk, or optical disk. The readable storage medium can be any available medium accessible to a general-purpose or special-purpose computer.

[0155] An exemplary readable storage medium is coupled to a processor, enabling the processor to read information from and write information to the readable storage medium. Of course, the readable storage medium can also be a component of the processor. The processor and the readable storage medium can reside in an Application Specific Integrated Circuit (ASIC). Alternatively, the processor and the readable storage medium can exist as discrete components in the device.

[0156] The division of units is merely a logical functional division; in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be indirect coupling or communication connection through some interfaces, devices, or units, and may be electrical, mechanical, or other forms.

[0157] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0158] In addition, the functional units in the various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit.

[0159] If a function is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this invention, or the part that contributes to the prior art, or a part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods of the various embodiments of this invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0160] Those skilled in the art will understand that all or part of the steps of the above-described method embodiments can be implemented by hardware related to program instructions. The aforementioned program can be stored in a computer-readable storage medium. When executed, the program performs the steps of the above-described method embodiments; and the aforementioned storage medium includes various media capable of storing program code, such as ROM, RAM, magnetic disks, or optical disks.

[0161] Finally, it should be noted that other embodiments of the invention will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This invention is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein, and is not limited to the precise structures described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of the invention is limited only by the appended claims.

Claims

1. A method for determining the amount of irreversible lithium plating in a lithium-ion battery, characterized in that, include: Obtain a pre-constructed linear relationship, which is used to characterize the relationship between irreversible pressure and irreversible lithium plating amount of the sample battery during charging. The irreversible pressure is used to characterize the difference between the pressure change during charging and the pressure change during discharging of the sample battery. Obtain the target irreversible pressure of the target battery during charging; Based on the target irreversible pressure and the linear relationship, the amount of irreversible lithium plating in the target battery during charging is determined.

2. The method according to claim 1, characterized in that, The linear relationship is constructed through the following steps: When the sample battery is charged under different charging conditions and irreversible lithium plating occurs, the irreversible pressure of the sample battery under each charging condition and the difference in battery capacity before and after charging are obtained. Based on the irreversible pressure of the sample battery under each of the charging conditions, an irreversible pressure sequence is constructed. Based on the battery capacity difference of the sample batteries under each of the charging conditions, an irreversible lithium deposition sequence is constructed. The linear relationship is constructed based on the irreversible pressure sequence and the irreversible lithium deposition sequence.

3. The method according to claim 2, characterized in that, The process of obtaining the irreversible pressure of the sample battery under each of the charging conditions includes: Under different charging conditions, the change in charging pressure during the charging process and the change in discharge pressure during the discharging process of the sample battery are obtained. The irreversible pressure of the sample battery under each charging condition is obtained based on the difference between the change in charging pressure and the change in discharging pressure.

4. The method according to claim 3, characterized in that, Determining that irreversible lithium plating has occurred in the sample battery includes the following steps: Based on the irreversible pressure of the sample battery under each charging condition, determine the minimum and maximum charging current values ​​for the sample battery to undergo irreversible lithium plating. Based on the minimum and maximum charging current values, the critical charging current range for irreversible lithium plating in the sample battery is determined. Obtain the irreversible pressure range corresponding to the sample battery when it is charged within the charging critical current range; Based on the aforementioned irreversible pressure range, determine the irreversible pressure threshold; Based on the irreversible pressure threshold, it is determined whether the sample battery has undergone irreversible lithium plating.

5. The method according to claim 4, characterized in that, The step of determining whether irreversible lithium plating has occurred in the sample battery based on the irreversible pressure threshold includes: The first irreversible pressure of the sample battery is obtained when the sample battery is charged to the first state of charge under the first charging condition. If the first irreversible pressure is greater than the irreversible pressure threshold, it is determined that the sample battery has irreversible lithium plating under the first charging condition.

6. The method according to claim 4, characterized in that, The step of determining the minimum and maximum charging current values ​​for irreversible lithium plating in the sample battery based on the irreversible pressure of the sample battery under each charging condition includes: Based on the mean clustering method, the irreversible pressure of the sample batteries under different charging conditions is clustered to obtain irreversible lithium plating clusters and non-irreversible lithium plating clusters. Based on the occurrence and non-occurrence of irreversible lithium clusters, the minimum and maximum charging current values ​​for irreversible lithium plating in the sample battery are determined.

7. The method according to claim 3, characterized in that, Obtaining the change in discharge pressure during the discharge process of the sample battery includes: During the constant current test or dynamic discharge test of the sample battery until the remaining charge inside the sample battery is lower than a preset lower limit, the first pressure change of the sample battery is obtained. During the process of performing a low-current discharge test on the sample battery until the remaining charge inside the sample battery is lower than the preset lower limit, the second pressure change of the sample battery is obtained. Based on the first pressure change and the first pressure change, the discharge pressure change during the discharge process of the sample battery is determined.

8. The method according to claim 3, characterized in that, The preset state of charge is any value between 60% and 99% of the sample battery's charge.

9. The method according to any one of claims 2-8, characterized in that, The charging condition is the charging rate, which is any value between 0.2 and 1.5 times the rated capacity of the sample battery.

10. A device for determining the amount of irreversible lithium plating in a lithium-ion battery, characterized in that, include: The relationship acquisition module is used to acquire a pre-constructed linear relationship, which is used to characterize the relationship between the irreversible pressure and the amount of irreversible lithium plating of the sample battery during the charging process. The irreversible pressure is used to characterize the difference between the pressure change during the charging process and the pressure change during the discharging process of the sample battery. The pressure acquisition module is used to acquire the target irreversible pressure of the target battery during charging. The lithium deposition amount determination module is used to determine the amount of irreversible lithium deposition in the target battery during charging based on the target irreversible pressure and the linear relationship.

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