A method for estimating the lithium plating area of ​​a lithium-ion battery

Abstract

This invention relates to the field of battery testing technology, specifically to a method for estimating the lithium plating area of ​​a lithium-ion battery. The lithium-ion battery is a battery undergoing charge-discharge cycle testing. The method includes obtaining the mass of the negative electrode active material of the lithium-ion battery in the Nth charge-discharge cycle; calculating the negative electrode capacity per unit area of ​​the lithium-ion battery in the Nth charge-discharge cycle based on the mass of the negative electrode active material; and calculating the lithium plating area of ​​the lithium-ion battery in the Nth charge-discharge cycle based on the initial negative electrode capacity per unit area. This invention allows for obtaining the lithium plating area of ​​different charge-discharge cycles without disassembling the battery, achieving non-destructive testing and providing early warning for battery safety. Furthermore, it can directly reuse the negative electrode active material mass obtained from voltage differential curve fitting in existing tests, eliminating the need for complex testing procedures and additional testing equipment, thereby significantly improving R&D testing efficiency and reducing testing costs.

Description

Technical Field

[0001] This invention relates to the field of battery testing technology, and more specifically, to a method for estimating the lithium plating area of ​​a lithium-ion battery. In particular, it relates to the non-destructive measurement of lithium plating behavior in lithium-ion batteries. Background Technology

[0002] Lithium-ion batteries are widely used in new energy vehicles, electronic products, and energy storage industries due to their high energy density, low self-discharge rate, and long lifespan. However, during use, a series of side reactions occur inside the lithium battery, including electrolyte decomposition, SEI film growth, and lithium plating. Among these, lithium plating has a significant impact on battery life and safety. After lithium plating occurs, the usable capacity of the battery decreases; the larger the plating area, the faster the capacity decays. Simultaneously, an increased plating area means a higher risk of short circuits. Continuous lithium plating can form lithium dendrites, which can puncture the separator, leading to internal short circuits and safety risks. Therefore, early warning of lithium plating is essential.

[0003] Lithium plating causes lithium ions in the electrolyte to be reduced to metallic lithium, which then deposits on the negative electrode surface, forming irreversible dead lithium and directly resulting in a permanent reduction in the total amount of cyclic lithium ions inside the battery. Currently, methods for determining lithium plating behavior in lithium-ion batteries are mainly divided into two categories: non-destructive analysis and destructive analysis. Non-destructive analysis includes many methods, such as calorimetry, relaxation voltage curves, AC impedance testing, and three-electrode lithium plating potential measurement.

[0004] In a method for predicting the cycle life of a lithium-ion battery published in CN115236528A, the degradation trend of active lithium and active materials in the positive and negative electrodes during the cycle of the lithium-ion battery is obtained by performing voltage differential fitting on the capacity-voltage curve.

[0005] When lithium plating occurs in a battery, lithium metal covers the surface of the negative electrode, reducing the mass of usable negative electrode active material. However, current technology cannot calculate the lithium plating area by monitoring the mass of the negative electrode active material, making it impossible to estimate the area of ​​lithium metal covering the negative electrode surface, thus complicating the lithium plating calculation process. Summary of the Invention

[0006] The purpose of this invention is to provide a method for estimating the lithium plating area of ​​a lithium-ion battery, thereby solving the problem of complex lithium plating calculations. This method correlates the mass of the negative electrode active material with the lithium plating area, calculates the capacity per unit area of ​​the negative electrode during charge-discharge cycles, and further calculates the lithium plating area. This method is simple to operate and does not require disassembling the battery.

[0007] A method for estimating the lithium plating area of ​​a lithium-ion battery, wherein the lithium-ion battery is a battery undergoing charge-discharge cycle testing, the method comprising the following steps:

[0008] Obtain the mass of the negative electrode active material of the lithium-ion battery in the Nth charge-discharge cycle. ;

[0009] Based on the quality of the negative electrode active material Calculate the negative electrode capacity per unit area of ​​the lithium-ion battery in the Nth charge-discharge cycle. ;

[0010] Initial capacity per unit area of ​​the negative electrode Based on this, calculate the lithium plating area of ​​the lithium-ion battery in the Nth charge-discharge cycle. ;

[0011] in, It is a positive integer.

[0012] In this technical solution, the target object for estimating the lithium plating area is a lithium-ion battery undergoing charge-discharge cycle testing. In existing technologies, the battery under test is placed in a constant temperature chamber for charge-discharge cycle testing. Every set number of charge-discharge cycles E (E is a positive integer), two consecutive low-rate charge-discharge cycles are performed. The voltage-capacity curve corresponding to the second low-rate charge-discharge cycle is differentially processed to obtain a voltage differential curve. The least squares method is then used to fit this voltage differential curve to obtain the decay trend of active lithium and active materials at the positive and negative electrodes during the charge-discharge cycle of the lithium-ion battery. From this, the mass of the negative electrode active material is calculated. The second charge or discharge curve is used for voltage differential curve fitting analysis because the first cycle is unstable due to the influence of the intermediate high-rate charge-discharge cycle. In this solution, the mass of the negative electrode active material obtained during the charge-discharge cycle test is used to estimate the lithium plating area. This eliminates the need for additional detection methods such as calorimetry, AC impedance analysis, and relaxation voltage curves, as well as the need for dedicated testing equipment or battery disassembly. The core advantage of this solution is that it can directly reuse the negative electrode active material quality obtained from existing tests based on voltage differential curve fitting (this quality is a relative characteristic value, and its changing trend directly characterizes the degree of failure of the negative electrode active material caused by lithium plating), without the need for additional testing procedures, thereby greatly improving R&D testing efficiency and reducing testing costs.

[0013] Specifically, the implementation of this solution does not require changing the original testing process. Lithium plating area estimation can be completed simply by obtaining the mass of the negative electrode active material. Firstly, during the life prediction process, voltage differential curve fitting is continuously performed. Typically, the interval between two adjacent voltage differential curve fittings is E cycles, where E ≥ 50, and E is a positive integer. The number of cycles in this interval does not include two cycles of low-rate charge-discharge cycling tests. Alternatively, the interval between two adjacent calculations of the negative electrode active material mass is D days. Thus, the mass of the negative electrode active material is calculated each time the voltage differential curve is fitted. When the trigger condition is met, the method is executed. That is, it is determined that lithium plating occurs in the lithium battery during the Nth cycle of the charge-discharge cycle. At this time, the lithium plating area calculation process is initiated, thereby avoiding errors caused by premature detection and timely capturing of the lithium plating signal. Here, N is the actual number of charge-discharge cycles (including the number of cycles of low-rate charge-discharge cycling tests). Therefore, the Nth cycle must be the second cycle of low-rate charge-discharge cycling tests.

[0014] In acquiring Then, by combining the specific capacity of the negative electrode active material and the total effective area of ​​the lithium battery negative electrode, the unit area capacity of the lithium-ion battery negative electrode after the Nth charge-discharge cycle can be calculated. Wherein, the negative electrode unit area capacity The calculation formula is:

[0015] ;

[0016] In the formula, The specific capacity of the negative electrode active material of the lithium-ion battery; The total area of ​​the negative electrode of the lithium-ion battery is denoted as .

[0017] Subsequently, the initial unit area capacity of the negative electrode was used. Based on the benchmark, through comparison and The degree of degradation was determined, and the lithium deposition area of ​​the lithium-ion battery in the Nth charge-discharge cycle was finally calculated. The lithium plating area of ​​the battery The calculation formula is: It needs to be made clear that, This method measures the effective area of ​​the negative electrode active material that cannot perform its electrochemical functions due to lithium plating, rather than quantifying the amount of lithium plating itself. It only characterizes the area of ​​the negative electrode region that has failed due to lithium plating. This overcomes the limitation of existing technologies that can only qualitatively detect whether lithium plating has occurred and cannot quantitatively characterize the degree of lithium plating. At the same time, it solves the defect of existing non-destructive testing that can only detect lithium plating during the process of lithium plating and cannot identify historical lithium plating that has occurred in the battery. This is because this method is based on the cumulative change trend of the mass of the negative electrode active material. Regardless of whether lithium plating is ongoing, as long as there is a loss of mass of the negative electrode active material due to lithium plating, the lithium plating area can be calculated by trend extrapolation, thus achieving an effective determination of the lithium plating area throughout the entire cycle of the lithium battery.

[0018] Preferably, the number of cycles between two consecutive calculations of the mass of the negative electrode active material is E, where E≥50 and E is a positive integer; the counting of the number of cycles does not include two cycles of low-rate charge-discharge cycle testing.

[0019] Alternatively, the number of days between two consecutive calculations of the mass of the negative electrode active material is D.

[0020] In one embodiment, the voltage-capacity curve is acquired during the charging phase of a charge-discharge cycle.

[0021] In another embodiment, the voltage-capacity curve is acquired during the discharge phase of a charge-discharge cycle.

[0022] It is evident that the voltage-capacity curve acquisition stage must remain singular; either all curves from the charging stage or all curves from the discharging stage should be selected, and curves from different stages should not be mixed. This is because the electrochemical reaction mechanisms and voltage-capacity change patterns of lithium batteries differ fundamentally between the charging and discharging stages, resulting in different characteristics of the corresponding voltage differential curves and varying degrees of participation of the negative electrode active material in the reaction. Essentially, this requires comparing charging curves with charging curves and discharging curves with discharging curves. For example, when fitting curves from 1, 100, 200…1000 charge-discharge cycles, all curves from each cycle must be used, or all curves from each cycle must be used. This ensures a unified benchmark for comparing capacity loss and negative electrode active material degradation across different cycle numbers, guaranteeing the accuracy and reliability of lithium plating area estimation.

[0023] As an improvement, a trigger condition is set, and the method is executed only when the trigger condition is met. This eliminates the need to perform calculations in every charge-discharge cycle or at every data acquisition interval. This significantly improves the execution efficiency of the solution, reduces unnecessary calculations and data processing steps, and avoids resource waste.

[0024] Preferably, the triggering condition is that the mass of the negative electrode active material continuously decreases more than a preset number A;

[0025] Where A ≥ 3, and A is a positive integer. During charge-discharge cycles, lithium batteries are affected by accidental factors such as minor fluctuations in the testing environment, instrument detection errors, and fluctuations in the microscopic reactions of active materials. There may be 1-2 brief drops. These drops are not due to continuous degradation caused by lithium plating, but rather normal test deviations or occasional fluctuations, and are not representative. If A < 3 (i.e., A = 1 or A = 2), these occasional fluctuations are easily misjudged as continuous degradation caused by lithium plating, leading to false triggering of the trigger condition and the initiation of an invalid process. The calculation and subsequent lithium plating area estimation process not only increases the workload of processing invalid data and reduces testing efficiency, but may also lead to lifetime prediction errors due to misjudgment. However, when A≥3, the interference of random fluctuations can be effectively eliminated, and only when... Only after three or more consecutive decreases can the decay trend be determined to be a continuous and accelerated decay caused by lithium plating, ensuring the accurate timing of the calculation and providing reliable data support for subsequent lithium plating area estimation, while avoiding missing real lithium plating signals.

[0026] As another preferred embodiment, the triggering condition is:

[0027] The current calculated mass of the negative electrode active material is lower than the previously calculated mass, and the previously calculated mass of the negative electrode active material... Quality of initial active material for the negative electrode.

[0028] The aforementioned preset threshold B% is preferably set to 5%. Considering that the decline in the quality of the negative electrode active material caused by lithium plating is difficult to predict accurately, setting a relatively wide range of 5% can avoid missing the lithium plating signal due to an overly narrow range setting. At the same time, even if the previously calculated quality of the negative electrode active material is... If the initial active material quality of the negative electrode decreases by more than the preset threshold B%, the current sampling point should also be observed to prevent a single large decrease caused by test anomalies, such as the cell temperature rising to the upper limit during battery charging and discharging, causing the test to stop, or data recording jumping point (directly jumping to the cutoff voltage, causing data anomalies), from being misjudged as continuous degradation caused by lithium plating, so as to ensure the accuracy of the trigger calculation.

[0029] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0030] This method for estimating the lithium plating area of ​​lithium-ion batteries correlates the mass loss of the negative electrode active material with the lithium plating area to calculate the lithium plating area. It can obtain the lithium plating area under different charge-discharge cycles without disassembling the battery, achieving the effect of non-destructive testing and providing early warning for battery safety.

[0031] Moreover, this method can directly reuse the negative electrode active material quality obtained from existing tests based on voltage differential curve fitting, without the need for complex testing procedures or additional testing equipment, thereby significantly improving R&D testing efficiency and reducing testing costs. Attached Figure Description

[0032] Figure 1 This is a schematic diagram illustrating the steps of the method for estimating the lithium plating area of ​​a lithium-ion battery according to the present invention;

[0033] Figure 2 This is a schematic diagram illustrating the steps for calculating the mass of the negative electrode active material of the present invention;

[0034] Figure 3 This is a graph showing the change in the mass of the negative electrode active material in the lithium iron phosphate single-layer soft-pack battery of the present invention under different cycles.

[0035] Figure 4 This is a graph showing the change in the unit area capacity of the negative electrode of the lithium iron phosphate single-layer soft-pack battery of the present invention with the number of charge-discharge cycles.

[0036] Figure 5 This is a graph showing the change in lithium plating area of ​​the lithium iron phosphate single-layer soft-pack battery of the present invention with the number of charge-discharge cycles;

[0037] Figure 6 This is a schematic diagram of the negative electrode sheet of a disassembled lithium iron phosphate battery analyzed using image analysis software according to the present invention.

[0038] Figure 7 This is a graph showing the mass change of the negative electrode active material in the lithium nickel cobalt manganese oxide single-layer soft-pack battery of the present invention under different cycles;

[0039] Figure 8 This is a graph showing the variation of the negative electrode capacity per unit area of ​​the lithium nickel cobalt manganese oxide single-layer soft-pack battery of the present invention with the number of charge-discharge cycles.

[0040] Figure 9 This is a graph showing the change in lithium plating area of ​​the nickel-cobalt-manganese lithium monolayer soft-pack battery of the present invention with the number of charge-discharge cycles;

[0041] Figure 10 This is a schematic diagram of the negative electrode of a lithium nickel cobalt manganese oxide battery analyzed and disassembled using image analysis software according to the present invention. Detailed Implementation

[0042] It should be understood that the specific embodiments described herein are merely illustrative of the technical solutions of this application and are not intended to limit this application.

[0043] Figure 1 The steps of a method for estimating the lithium plating area of ​​a lithium-ion battery are shown. In this step, the lithium-ion battery is a battery undergoing charge-discharge cycle testing. Exemplary application scenarios include, but are not limited to:

[0044] While conducting charge-discharge cycle tests to verify the battery's core performance such as charge-discharge cycle capacity retention rate and charge-discharge cycle impedance changes, lithium plating area estimation was carried out simultaneously.

[0045] Sampling charge-discharge cycle tests were conducted on mass-produced lithium-ion batteries. Combined with the lithium plating area estimation results, the consistency of the production process and the differences in lithium plating risk among batteries of the same batch were determined.

[0046] Long-cycle charge-discharge aging tests were conducted on lithium-ion batteries. The lithium deposition area was estimated through continuous or intermittent tests throughout the entire process, and the correlation between the lithium behavior development law and the battery charge-discharge cycle life was analyzed.

[0047] Special environmental adaptability testing scenarios for lithium batteries, such as charge-discharge cycle testing under extreme environments like low temperature (≤0℃), ultra-low temperature (≤-20℃), and high altitude, are conducted simultaneously to estimate the lithium plating area in order to quantify the impact of extreme environments on lithium plating in batteries.

[0048] Cyclic tests were conducted on customized charge and discharge regimes with different charging rates, different cutoff voltages, and different pulse charge and discharge strategies. The charge and discharge regimes were optimized based on the lithium plating area estimation results to suppress lithium plating.

[0049] Charge-discharge cycle tests are conducted on retired power batteries, and the lithium plating state of the retired batteries is determined by estimating the lithium plating area, providing a basis for sorting and reuse.

[0050] It should be noted that the above examples of lithium-ion battery charge-discharge cycle testing are merely illustrative of the technical application background of this embodiment and do not constitute a limitation on the scope of protection of this invention. The method for estimating the lithium plating area of ​​a lithium-ion battery according to this invention is applicable to all application scenarios of charge-discharge cycle testing of liquid electrolyte lithium-ion batteries. Any technical solution that implements lithium plating area estimation during lithium-ion battery charge-discharge cycle testing falls within the scope of protection of this invention.

[0051] Figure 1 The steps of the method shown for estimating the lithium plating area of ​​a lithium-ion battery include:

[0052] S100. Obtain the mass of the negative electrode active material of the lithium-ion battery during the Nth charge-discharge cycle. ;in, It is a positive integer.

[0053] Figure 2 The steps for calculating the mass of the negative electrode active material are shown, including:

[0054] S101. Perform two consecutive low-rate charge-discharge cycle tests; wherein, the voltage-capacity curve corresponding to the second low-rate charge-discharge cycle test is subjected to voltage differentiation processing to obtain the voltage differentiation curve;

[0055] S102. Fit the voltage differential curve using the least squares method to calculate the mass of the negative electrode active material.

[0057] S200, based on the quality of the negative electrode active material Calculate the negative electrode capacity per unit area of ​​the lithium-ion battery in the Nth charge-discharge cycle. ;

[0058] negative electrode capacity per unit area The calculation formula is:

[0059] ;

[0060] In the formula, The specific capacity of the negative electrode active material in lithium-ion batteries; This represents the total area of ​​the negative electrode in a lithium-ion battery.

[0061] S300, initial unit area capacity of the negative electrode Based on this, calculate the lithium plating area of ​​the lithium-ion battery in the Nth charge-discharge cycle. ;

[0062] Battery lithium plating area The calculation formula is: .

[0063] In some embodiments, the voltage-capacity curve is acquired during the charging phase of a charge-discharge cycle.

[0064] In some embodiments, the voltage-capacity curve is acquired during the discharge phase of a charge-discharge cycle.

[0065] In some embodiments, a trigger condition is set, and the method is executed when the trigger condition is met. The trigger condition is that the mass of the negative electrode active material continuously decreases more than a preset number A.

[0066] Where A ≥ 3, and A is a positive integer. Alternatively, the triggering condition is:

[0067] The current calculated mass of the negative electrode active material is lower than the previously calculated mass, and the previously calculated mass of the negative electrode active material... The initial active material quality of the negative electrode decreased by more than the preset threshold B%.

[0068] Preferably, in this embodiment, the lithium-ion battery is placed in a constant temperature chamber and connected to a test cabinet for charge-discharge cycle testing.

[0069] Preferably, the temperature range of the constant temperature chamber should be -20℃ to 55℃.

[0070] For example, during the life prediction process, continuous low-rate charge-discharge cycle tests are performed, with E=100. This means that after each low-rate charge-discharge cycle test, a second low-rate charge-discharge cycle test is performed after a 100-cycle interval. Specifically, after 100 cycles, two low-rate charge-discharge cycle tests are performed, and the voltage-capacity curve corresponding to the second low-rate charge-discharge cycle test is used for voltage differentiation to calculate the mass of the negative electrode active material. After 202 cycles, two more low-rate charge-discharge cycle tests were performed. The voltage-capacity curve corresponding to the second low-rate charge-discharge cycle test was then processed by voltage differentiation to calculate the mass of the negative electrode active material. ... and so on, until the test ends. If accelerated loss of negative electrode active material occurs before the test ends, the lithium plating area is calculated. The specific calculation process has been disclosed above and will not be repeated here.

[0071] Preferably, the normal charge-discharge cycle test rate is 1C, and the low-rate charge-discharge cycle test rate is 0.1C.

[0072] In the first embodiment, a method for calculating the number of charge-discharge cycles is proposed. Specifically, a lithium iron phosphate single-layer pouch battery is placed in a 25°C constant temperature chamber, connected to a test cabinet, and subjected to charge-discharge cycle testing. Based on voltage differential fitting, the mass of the negative electrode active material is analyzed at 200-cycle intervals under different numbers of charge-discharge cycles. The results are as follows: Figure 3 As shown.

[0073] Using the mass of negative electrode active material under different number of turns ( ), capacity ( ) and total area of ​​negative electrode ( ), calculate the capacity per unit area of ​​the negative electrode ( The results are as follows, depending on the number of charge-discharge cycles: Figure 4 As shown.

[0074] Where S = negative electrode length * negative electrode width, specifically:

[0075] (100*10-3)*(43*10-3)=0.0043m²;

[0076] ;in, It is 352.958 Ah / kg.

[0077] With the initial unit area capacity of the negative electrode ( Based on the baseline, and combined with the total area of ​​the negative electrode, the lithium plating area of ​​the battery is calculated. The change in lithium plating area during charge-discharge cycles was obtained, such as... Figure 5 As shown.

[0078] in, .

[0079] Finally, the battery is disassembled, and image processing and analysis software is used. Preferably, this software includes, but is not limited to, ImageJ, Fiji, CellProfiler, and other software capable of analyzing the area of ​​irregular shapes. Using the electrode width of 43mm as a standard scale, the total area of ​​the negative electrode and the lithium plating area are selected separately. Figure 6 As shown in the figure, 1 is the total area of ​​the negative electrode, and 2-4 are the areas of the lithium plating region of the negative electrode. Calculation error, error (%) = ( (Calculate area) - (Image analysis software) *100 / (The area was calculated), and the results are listed in Table 1.

[0080] Table 1 shows the comparison results of lithium iron phosphate batteries at 25℃ based on the quality of the negative electrode active material and the lithium plating area calculated by image analysis software.

[0081] Calculation method Image analysis software / mm² Calculate area / mm² error / % Total area of ​​negative electrode 4354.8 4300 -1.27 lithium plating area 397.5 413.3 3.82

[0082] Table 1

[0083] As shown in Table 1, the final lithium plating area calculated using the mass of the negative electrode active material is: The lithium plating area calculated by image analysis software The result is largely consistent, with an error of 3.82%. The result calculated using the mass of the negative electrode active material is slightly overestimated, possibly because the mass loss of another portion of active material due to the formation of the SEI film on the negative electrode is also included in the calculation of the lithium plating area. This method for estimating the negative electrode lithium plating area is simple to operate and does not require disassembling the battery; it can be achieved by analyzing the changes in the mass of the negative electrode active material during charge-discharge cycles.

[0084] The second embodiment proposes a calculation method after a certain number of charge-discharge cycles. Specifically, a lithium nickel cobalt manganese oxide single-layer soft-pack battery is placed in a 35°C constant temperature chamber and connected to a test cabinet for charge-discharge cycle testing. The mass of the negative electrode active material is analyzed based on the active lithium loss-active material loss model at 1 / 586 / 1182 / 1285 / 1936 / 2087 charge-discharge cycles, and the results are as follows. Figure 7 As shown.

[0085] Using the mass of negative electrode active material under different number of turns ( ), capacity ( ) and total area of ​​negative electrode ( ), calculate the capacity per unit area of ​​the negative electrode ( The results are as follows, depending on the number of charge-discharge cycles: Figure 8 As shown.

[0086] Where S = negative electrode length * negative electrode width, specifically:

[0087] (121*10-3)*(52*10-3)=0.006292m²;

[0088] ;in, It is 337.272 Ah / kg.

[0089] With the initial unit area capacity of the negative electrode ( Based on the baseline, and combined with the total area of ​​the negative electrode, the lithium plating area of ​​the battery is calculated. The change in lithium plating area during charge-discharge cycles was obtained, such as... Figure 9 As shown.

[0090] in, .

[0091] Finally, the battery is disassembled, and image processing and analysis software is used. Preferably, this software includes, but is not limited to, ImageJ, Fiji, CellProfiler, and other software capable of analyzing the area of ​​irregular shapes. Using the electrode width of 52mm as a standard scale, the total area of ​​the negative electrode and the lithium plating area are selected separately. Figure 10 As shown in the figure, 1 is the total area of ​​the negative electrode and 2 is the area of ​​the lithium deposition region of the negative electrode. The calculation error and the results are listed in Table 2.

[0092] Table 2 shows the comparison results of lithium nickel cobalt manganese oxide batteries at 35℃ based on the quality of the negative electrode active material and the lithium plating area calculated by image analysis software.

[0093] Calculation method Image analysis software / mm² Calculate area / mm² error / % Total area of ​​negative electrode 6442 6292 -2.38 lithium plating area 2075 2163 4.07

[0094] Table 2

[0095] As shown in Table 2, the final lithium plating area calculated using the mass of the negative electrode active material is: The lithium plating area calculated by image analysis software It is fairly consistent, with an error of approximately 4.068%, which is relatively small.

[0096] The above are merely preferred embodiments of this application and do not limit the patent scope of this application. Any equivalent structural or procedural transformations made using the content of this application's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent scope of this application.

Claims

1. A method for estimating the lithium plating area of ​​a lithium-ion battery, wherein the lithium-ion battery is a battery undergoing charge-discharge cycle testing, characterized in that... The method includes the following steps: Obtain the mass of the negative electrode active material of the lithium-ion battery in the Nth charge-discharge cycle. ; Based on the quality of the negative electrode active material Calculate the negative electrode capacity per unit area of ​​the lithium-ion battery in the Nth charge-discharge cycle. ; Initial capacity per unit area of ​​the negative electrode Based on this, calculate the lithium plating area of ​​the lithium-ion battery in the Nth charge-discharge cycle. ; in, It is a positive integer.

2. The method for estimating the lithium plating area of ​​a lithium-ion battery according to claim 1, characterized in that, The steps for calculating the mass of the negative electrode active material include: Two consecutive low-rate charge-discharge cycle tests were performed; the voltage-capacity curve corresponding to the second low-rate charge-discharge cycle test was differentially processed to obtain the voltage differential curve. The voltage differential curve was fitted using the least squares method to calculate the mass of the negative electrode active material.

3. The method for estimating the lithium plating area of ​​a lithium-ion battery according to claim 1, characterized in that, The negative electrode unit area capacity The calculation formula is: ； In the formula, The specific capacity of the negative electrode active material of the lithium-ion battery; The total area of ​​the negative electrode of the lithium-ion battery is denoted as .

4. The method for estimating the lithium plating area of ​​a lithium-ion battery according to claim 3, characterized in that, The lithium plating area of ​​the battery The calculation formula is: .

5. The method for estimating the lithium plating area of ​​a lithium-ion battery according to claim 2, characterized in that, The number of cycles between two consecutive calculations of the mass of the negative electrode active material is E, where E≥50 and E is a positive integer; the counting of the interval cycles does not include two cycles of low-rate charge-discharge cycle testing. Alternatively, the number of days between two consecutive calculations of the mass of the negative electrode active material is D.

6. The method for estimating the lithium plating area of ​​a lithium-ion battery according to claim 2, characterized in that, The voltage-capacity curves were collected during the charging phase of a charge-discharge cycle.

7. The method for estimating the lithium plating area of ​​a lithium-ion battery according to claim 2, characterized in that, The voltage-capacity curves were collected during the discharge phase of a charge-discharge cycle.

8. The method for estimating the lithium plating area of ​​a lithium-ion battery according to claim 2, characterized in that, Set a trigger condition, and execute the method when the trigger condition is met.

9. The method for estimating the lithium plating area of ​​a lithium-ion battery according to claim 8, characterized in that, The triggering condition is that the mass of the negative electrode active material continuously decreases more than a preset number A; Where A≥3, and A is a positive integer.

10. The method for estimating the lithium plating area of ​​a lithium-ion battery according to claim 8, characterized in that, The triggering condition is: The current calculated mass of the negative electrode active material is lower than the previously calculated mass, and the decrease in the previously calculated mass of the negative electrode active material compared to the initial mass of the negative electrode active material exceeds a preset threshold B.

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