In-situ detection method and system for lithium precipitation of battery and computer medium

Abstract

The embodiment of the invention discloses an in-situ detection method and system for lithium precipitation of a battery and a computer medium. The method comprises the following steps: acquiring a battery cell temperature correction coefficient through a calibration experiment; detecting the expansion force, the surface temperature of the battery cell and the voltage data of the battery cell in the in-situ charge-discharge test under different temperatures and different multiplying powers; generating a voltage-corrected expansive force change rate curve under different multiplying power values at each detection temperature based on the cell temperature correction coefficient, the expansive force, the cell surface temperature and the voltage data; and according to the voltage-corrected expansion force change rate curve, judging whether lithium precipitation occurs in the battery at the current test temperature and multiplying power. Charge and discharge, expansion force and temperature are obtained in an in-situ lossless manner, the expansion force is fitted by using a temperature correction coefficient, the influence of the temperature on the change of the expansion force is eliminated, misjudgment of lithium precipitation is avoided, the accuracy and reliability of detection are improved, and the lithium precipitation state of a battery cell at different temperatures and charging rates can be rapidly and accurately judged without preparing a three-electrode battery cell.

Description

Technical Field

[0001] This application relates to the field of lithium battery technology, and in particular to an in-situ detection method, system and computer medium for lithium plating in batteries. Background Technology

[0002] During actual use, lithium metal may deposit on the negative electrode surface of lithium-ion batteries (i.e., lithium plating). Lithium plating not only consumes the limited active lithium and accelerates capacity decay, but it can also cause serious safety hazards such as internal short circuits and thermal runaway, greatly affecting the safety and cycle life of the battery system. Therefore, developing a technology that can detect lithium plating online, in-situ, accurately, and reliably is of great significance for battery status monitoring, health management, and safety early warning.

[0003] Currently, existing technologies mainly employ monitoring changes in pressure or expansion signals during battery charging and discharging to detect lithium plating in situ, identifying the inflection point of lithium plating by analyzing the curve characteristics of the signal with respect to the state of charge (SOC). However, this method has significant limitations: on the one hand, it cannot effectively distinguish between the pressure signal caused by thermal expansion of the battery cell in scenarios such as fast charging and the signal caused by lithium plating, which is prone to misjudgment; on the other hand, its judgment logic is mainly designed for the expansion characteristics of specific cathode materials (such as NCM), making it difficult to apply to material systems with different expansion curve characteristics, such as lithium iron phosphate (LFP), resulting in poor universality and detection failure.

[0004] Therefore, there is an urgent need for an in-situ lithium plating detection method that can effectively eliminate or compensate for temperature interference and adapt to the differences in cell expansion characteristics of cathode material systems such as LFP, so as to improve the accuracy, reliability and universality of lithium plating detection. Summary of the Invention

[0005] This application aims to address at least one of the technical problems existing in the prior art. To this end, this application proposes an in-situ detection method, system, and computer medium for lithium plating in batteries, which can effectively eliminate or compensate for temperature interference and adapt to the differences in cell expansion characteristics of cathode material systems such as LFP, thereby improving the accuracy, reliability, and universality of lithium plating detection.

[0006] In a first aspect, this application provides an in-situ detection method for lithium plating in batteries, comprising: The cell temperature correction coefficient was obtained through calibration experiments. The expansion force data, cell surface temperature data, and voltage data of the battery cell were tested in situ charge-discharge tests at different temperatures and rates. Based on the cell temperature correction coefficient, the expansion force data, the cell surface temperature data, and the voltage data, a voltage-corrected expansion force change rate curve is generated at different magnification values ​​at each detection temperature. The voltage-corrected expansion force change rate curve is used to determine whether lithium plating occurs in the battery at the current test temperature and rate.

[0007] In some embodiments of the above-mentioned in-situ detection method for lithium plating in batteries, obtaining the cell temperature correction coefficient through calibration experiments includes: The measurement measures the change in cell expansion force with ambient temperature under different preset charging states. A cell temperature correction coefficient is generated based on the numerical curves of how the cell expansion force changes with the ambient temperature under different preset charging states.

[0008] In some embodiments of the above-mentioned in-situ detection method for lithium plating in batteries, the generation of a cell temperature correction coefficient based on the numerical curve of the cell expansion force changing with the ambient temperature under different preset charging states includes: Calculate the rate of increase of the cell expansion force value under each preset charged state with respect to the ambient temperature. The average value of the cell expansion force with respect to the rate of increase of the ambient temperature is calculated to obtain the cell temperature correction coefficient applicable to the current cell model and test system.

[0009] In some embodiments of the above-mentioned in-situ detection method for lithium plating in batteries, the data on expansion force, cell surface temperature, and voltage during in-situ charge-discharge tests of the battery cell at different temperatures and rates include: In-situ charge-discharge tests of the battery cells were conducted at different temperatures and rates. The system acquires voltage data of the battery cell during in-situ charge-discharge testing, obtains surface temperature data of the battery cell based on a temperature sensor attached to the surface of the battery cell, and obtains expansion force data in the thickness direction of the battery cell based on a force sensor in contact with the side of the battery cell with a larger area.

[0010] In some embodiments of the above-mentioned in-situ detection method for lithium plating in batteries, the generation of voltage-corrected expansion force change rate curves at different rate values ​​at each detection temperature based on the cell temperature correction coefficient, the expansion force data, the cell surface temperature data, and the voltage data includes: Based on the cell temperature correction coefficient, the expansion force data, the cell surface temperature data, and the voltage data, generate voltage-corrected expansion force variation curves for the cell during charging at different rates at each detection temperature; The rate of change of expansion force with respect to voltage is calculated based on the voltage-corrected expansion force change curve during the charging of the battery cell, thereby obtaining the voltage-corrected expansion force change rate curve at different multipliers at each detection temperature.

[0011] In some embodiments of the above-mentioned in-situ detection method for lithium plating in batteries, the step of generating voltage-corrected expansion force change curves for the battery cell at different charging rates under each detection temperature based on the cell temperature correction coefficient, the expansion force data, the cell surface temperature data, and the voltage data includes: The expansion force data is obtained by correcting the expansion force data according to the cell temperature correction coefficient; Based on the corrected expansion force data and the voltage data, a voltage-corrected expansion force variation curve is generated when the battery cell is charged at different rates at each detection temperature.

[0012] In some embodiments of the above-described in-situ detection method for lithium plating in batteries, determining whether lithium plating has occurred in the battery at the current test temperature and rate based on the voltage-corrected expansion force change rate curve includes: By querying the voltage-corrected expansion force change rate curves at different rate values ​​under each detection temperature, the typical voltage range of the battery can be obtained, along with the corresponding corrected expansion force change rate at different rate values ​​under each detection temperature. Based on the corrected rate of change of expansion force corresponding to different rate values ​​at each detection temperature within the typical voltage range of the battery, it is determined whether lithium plating occurs in the cell at the current detection temperature and rate value.

[0013] In some embodiments of the above-mentioned in-situ detection method for lithium plating in batteries, the step of determining whether lithium plating has occurred in the battery cell at the current detection temperature and rate value based on the corrected rate of change of expansion force corresponding to different rate values ​​at each detection temperature within the typical voltage range of the battery includes: Determine whether the corrected rate of change of expansion force corresponding to different rate values ​​at each detection temperature within the typical voltage range of the battery is greater than a preset threshold. If so, it is determined that lithium plating has occurred in the cell under the current test temperature and test rate.

[0014] Secondly, this application provides an in-situ detection system for lithium plating in batteries, comprising: The acquisition module is used to obtain the cell temperature correction coefficient through calibration experiments; The inspection module is used to detect the expansion force data, cell surface temperature data, and voltage data of the battery cell during in-situ charge-discharge tests at different temperatures and rates. The generation module is used to generate voltage-corrected expansion force change rate curves at different magnification values ​​at each detection temperature based on the cell temperature correction coefficient, the expansion force data, the cell surface temperature data, and the voltage data. The judgment module is used to determine whether lithium plating occurs in the battery at the current test temperature and rate based on the voltage-corrected expansion force change rate curve.

[0015] Thirdly, this application also provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of the in-situ detection method for lithium plating in batteries as described in any one of the first aspects.

[0016] The above-described one or more embodiments of this application have at least one or more of the following beneficial effects: The in-situ lithium plating detection method provided in this application does not require disassembly or damage to the battery cell. It obtains the electrical, mechanical, and thermal coupling data of the battery cell in situ without damage, namely charge and discharge data, expansion force data, and temperature data. The expansion force is fitted using a temperature correction coefficient k to eliminate the influence of temperature on the expansion force change, which can avoid misjudgment of lithium plating and greatly improve the accuracy and reliability of detection. It can quickly and accurately determine the lithium plating state of the battery cell at different temperatures and charging rates without the need to prepare a three-electrode battery cell.

[0017] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0018] The disclosure of this application will become more readily understood with reference to the accompanying drawings. It will be readily understood by those skilled in the art that these drawings are for illustrative purposes only and are not intended to limit the scope of protection of this application. Furthermore, similar numbers in the drawings are used to denote similar components, wherein: Figure 1 This is a flowchart of an in-situ detection method for lithium plating in batteries provided in one embodiment of this application; Figure 2 This is a graph showing the relationship between expansion force and temperature under different charging states in the calibration experiment of the in-situ detection method for lithium plating in batteries provided in one embodiment of this application; Figure 3 This is a schematic diagram illustrating the growth rate of cell expansion force with temperature during the calibration experiment in the in-situ detection method for lithium plating in batteries provided in one embodiment of this application. Figure 4 This is a schematic diagram of the tooling fixture and charge / discharge test used in the in-situ detection method for lithium plating in batteries provided in one embodiment of this application; Figure 5 This is a schematic diagram of the voltage-corrected expansion force change curves generated during cell charging at different rates at 5°C in the in-situ detection method for lithium plating of batteries provided in one embodiment of this application. Figure 6 This is a schematic diagram of the voltage-corrected expansion force change curves generated during cell charging at different rates at 15°C in one embodiment of the battery lithium plating detection method provided in this application.

[0019] Figure 7 This is a schematic diagram of the voltage-corrected expansion force change rate curves generated in the in-situ detection method for lithium plating in batteries provided in one embodiment of this application during cell charging at different rates at 5°C. Figure 8 This is a schematic diagram of the voltage-corrected expansion force change rate curve generated in the in-situ detection method for lithium plating in batteries at different rates at 15°C, generated in one embodiment of this application. Figure 9 This is a schematic diagram showing the measurement results of the negative electrode potential at 5℃ using a three-electrode method; Figure 10 This is a schematic diagram showing the measurement results of the negative electrode potential at 15℃ using a three-electrode method. Figure 11 This is an architecture diagram of an in-situ detection system for lithium plating in batteries provided in one embodiment of this application. Detailed Implementation

[0020] Some embodiments of this application are described below with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are merely illustrative of the technical principles of this application and are not intended to limit the scope of protection of this application.

[0021] As described in the background section, current methods mainly rely on monitoring changes in pressure or expansion signals during battery charging and discharging to detect lithium plating in situ. The inflection point of lithium plating is identified by analyzing the curve characteristics of the signal with the state of charge. However, this method cannot effectively distinguish between the pressure signal caused by thermal expansion of the battery cell and the signal caused by lithium plating in scenarios such as fast charging, which is prone to misjudgment. Furthermore, the judgment logic of this method is mainly designed for the expansion characteristics of specific cathode materials (such as NCM), which is difficult to apply to material systems with different expansion curve characteristics, such as lithium iron phosphate (LFP), resulting in poor universality and detection failure.

[0022] To address the aforementioned issues, this application creatively proposes an in-situ detection method, system, and computer medium for lithium plating in batteries. This method acquires charge / discharge data, expansion force data, and temperature data of the battery cell in situ without disassembling or damaging the cell. A temperature correction coefficient k is used to fit the expansion force, eliminating the influence of temperature on expansion force changes. This avoids misjudgments of lithium plating, significantly improving the accuracy and reliability of the detection. Furthermore, it eliminates the need for preparing a three-electrode battery cell, enabling rapid and accurate determination of the lithium plating state of the cell at different temperatures and charging rates.

[0023] The present application will be described in detail below through specific embodiments.

[0024] Specifically, this application provides an in-situ detection method for lithium plating in batteries, referring to... Figure 1 As shown, it includes: S110. Obtain the cell temperature correction coefficient through calibration experiments.

[0025] The cell temperature correction factor k can quantify the law of cell expansion force changing with temperature. The specific value of the cell temperature correction factor k is not a universal constant, but is related to the characteristics of the cell itself and the test system conditions.

[0026] Because different types, batches, and specifications of battery cells have variations in the coefficient of thermal expansion of electrode materials, electrolyte characteristics, electrode compaction density, and diaphragm elasticity, the correlation between cell expansion force and temperature varies. Furthermore, the tooling fixtures, force sensor accuracy, and temperature sensor installation location of the in-situ testing device can also affect the accuracy of expansion force and temperature data acquisition, thus impacting the correlation between cell expansion force and temperature. Additionally, under different states of charge, the crystal structure of the electrode materials and the degree of lithium-ion insertion / extraction differ, leading to variations in thermal expansion characteristics. Therefore, it is impossible to pre-determine a uniform value for the cell temperature correction coefficient k. Calibration is needed to compensate for errors based on the specific cell and the hardware conditions of the testing system. The value of the cell temperature correction coefficient k obtained through calibration experiments should best match the actual characteristics of the cell and the testing system, ensuring the effectiveness of temperature correction.

[0027] In some embodiments, the cell temperature correction coefficient k is obtained by collecting a large amount of cell expansion force and temperature data at different temperatures, SOC (State of Charge), and cycle counts using machine learning fitting methods. A multi-dimensional model of "expansion force-temperature-SOC" is fitted using machine learning algorithms such as linear regression and random forest, and the cell temperature correction coefficient k value is automatically output. This method can cover more complex nonlinear relationships and has high accuracy, but it requires the collection of massive amounts of data, resulting in high initial data accumulation costs and high algorithm complexity.

[0028] In some embodiments, the cell temperature correction coefficient k is obtained by referring to literature data. This involves consulting publicly available research literature and industry standards for cells with the same cathode material and similar capacity, and referencing reported cell temperature correction coefficient k values ​​or cell expansion force-temperature slope data. This saves time and effort and eliminates the need for calibration experiments. However, the k values ​​in the platform literature are derived based on specific cells and testing systems, resulting in low matching with the user's own cells / equipment. Furthermore, the differences in detection temperature and SOC point selection between different studies are significant, leading to poor data comparability and potential correction failure.

[0029] S120: Detects the expansion force data, cell surface temperature data, and voltage data of the battery cell during in-situ charge-discharge tests at different temperatures and rates.

[0030] The expansion force data of the battery cell reflects the mechanical stress generated during charging and discharging due to lattice changes in the active material and side reactions caused by lithium-ion insertion / extraction. The cell surface temperature reflects the heat generation and heat exchange with the environment during charging and discharging. Voltage reflects the potential difference between the positive and negative electrodes and is strongly correlated with the state of charge and the phase transition process of the electrode materials. Voltage data can map the expansion force curves obtained at different temperatures and rates onto a unified "voltage-expansion force" coordinate system, facilitating subsequent curve analysis.

[0031] S130 generates voltage-corrected expansion force change rate curves at different magnification values ​​at each detection temperature based on cell temperature correction coefficient, expansion force data, cell surface temperature data, and voltage data.

[0032] Specifically, the expansion force data P, cell surface temperature data T, and voltage data V obtained from in-situ charge-discharge tests of the battery cell at different temperatures and charging rates are grouped in two dimensions according to the test temperature and charging rate. For example: For the 5℃ temperature group: filter out the (V, P, T) data groups corresponding to the charging rates of 0.1C, 0.2C, 0.5C, 0.8C, and 1C; For the 15℃ testing temperature group: filter out the (V, P, T) data groups corresponding to the charging rates of 0.2C, 0.5C, 0.9C, and 1.2C; Each set of data corresponds one-to-one; under the same voltage V, only one set of P and T values ​​is retained. The corrected expansion force is calculated point-by-point for each set of data: (1); Where: P is the cell expansion force measured in real time, and T is the real-time temperature (°C) obtained in step S120. The initial temperature for this test group is k, which is the cell temperature correction factor, for example: k = 1.556 kg / ℃; For each set of data, the expansion force P and cell surface temperature T corresponding to each voltage V are substituted into the formula to obtain the corrected expansion force. This ultimately forms the voltage-corrected expansion force (V) for each group. The data pairs are then used to calculate the voltage-corrected rate of change of expansion force curve.

[0033] S140. Determine whether lithium plating occurs in the battery at the current test temperature and rate based on the voltage-corrected expansion force change rate curve.

[0034] Specifically, the voltage-corrected expansion force change rate curve is analyzed within the high-voltage range of the charging process. If abnormal characteristics of the voltage-corrected expansion force change rate appear within the high-voltage range of the charging process, it indicates that the expansion force increases abnormally with increasing voltage within this voltage range. In this case, it is determined that lithium plating has occurred in the cell at the current test temperature and rate. The high-voltage range of the charging process is a range near the full charge voltage Vmax of the cell.

[0035] In some embodiments, step S110 includes: The changes in cell expansion force with ambient temperature under different preset charging states are measured; a cell temperature correction coefficient is generated based on the curves showing the changes in cell expansion force with ambient temperature under the different preset charging states.

[0036] In one embodiment, the battery cell is charged to several different preset states of charge: 20%, 40%, 60%, 80%, and 100%. The ambient temperature is varied at each fixed state of charge point, for example, referring to... Figure 2 As shown, the temperature is varied stepwise from 5℃ to 35℃. The change of cell expansion force with temperature is measured and recorded to generate a numerical curve of cell expansion force changing with ambient temperature. Based on the numerical curve of cell expansion force changing with ambient temperature, a cell temperature correction coefficient k is generated.

[0037] In some embodiments, generating a cell temperature correction coefficient based on the numerical curves of cell expansion force changing with ambient temperature under different preset charging states includes: Calculate the rate of increase of the cell expansion force value with respect to the ambient temperature under each preset charging state; calculate the average value of the rate of increase of the cell expansion force value with respect to the ambient temperature to obtain the cell temperature correction coefficient applicable to the current cell model and test system.

[0038] Specifically, the rate of increase in temperature due to expansion force is calculated at each state of charge point. Finally, the average rate of change is taken for all state of charge points to obtain the temperature correction factor k applicable to this type of cell and testing system. This is merely an example. Figure 2 As shown, the relationship between expansion force and temperature under different states of charge (20%, 40%, 60%, 80%, and 100% SOC) was obtained. Figure 3 The growth rate of the cell expansion force with temperature is shown, and the calculated value is k = 1.556 kg / ℃.

[0039] In some embodiments, step S120 includes: In-situ charge-discharge tests of the battery cells were conducted at different temperatures and rates. Voltage data of the battery cells during the in-situ charge-discharge tests were obtained, and surface temperature data of the battery cells was obtained based on a temperature sensor attached to the surface of the battery cells, as well as expansion force data in the thickness direction of the battery cells were obtained based on a force sensor in contact with the side of the battery cells with a larger area.

[0040] Reference Figure 4 As shown, during in-situ charge-discharge testing, the battery cell is fixed in a fixture. A temperature sensor is attached to the surface of the battery cell. A pair of clamping plates in the fixture apply clamping force to the two parallel outer surfaces of the battery cell with larger areas. A force sensor is positioned between one of the larger outer surfaces of the battery cell and the adjacent clamping plate, ensuring good contact between the force sensor and the larger surface of the battery cell to measure the expansion force in the thickness direction. The thickness direction of the battery cell is the direction of the clamping force applied by the fixture, perpendicular to the surface with the larger area of ​​the battery cell.

[0041] Connect the battery cell to the charge / discharge testing equipment and perform in-situ charge / discharge tests at different temperatures (5℃, 15℃) and different rates (0.1C-1C or 0.2-1.2C). Simultaneously detect the cell's expansion force P, cell surface temperature T, and voltage V. The expansion force P, cell surface temperature T, and voltage V are collected synchronously to avoid data misalignment caused by time differences. The voltage range throughout the charging process covers the high-risk range of lithium plating in the battery cell, and the data sampling interval is ≤0.01V to ensure continuous and smooth curves.

[0042] In some embodiments, step S130 includes: Based on the cell temperature correction coefficient, the expansion force data, the cell surface temperature data, and the voltage data, a voltage-corrected expansion force variation curve is generated for the cell charging at different rates under each detection temperature. Based on the voltage-corrected expansion force variation curve during cell charging, the rate of change of expansion force with respect to voltage is calculated to obtain the voltage-corrected expansion force variation rate curve for different rates under each detection temperature.

[0043] The generation of voltage-corrected expansion force variation curves for charging the battery cell at different rates under each detection temperature, based on the cell temperature correction coefficient, the expansion force data, the cell surface temperature data, and the voltage data, includes: The expansion force data is corrected according to the cell temperature correction coefficient to obtain the corrected expansion force data; based on the corrected expansion force data and the voltage data, a voltage-corrected expansion force change curve is generated when the cell is charged at different rates at each detection temperature.

[0044] For example, the cell temperature correction coefficient k = 1.556 kg / ℃ was obtained through calibration experiments. In-situ charge-discharge tests were conducted on the cell at different temperatures (5℃, 15℃) and different rates (0.1C-1C or 0.2-1.2C). Simultaneously, the cell expansion force P, cell surface temperature T, and voltage V were detected. The obtained test data were then grouped in two dimensions according to the test temperature and charging rate, with each group of data forming an independent curve. The corrected expansion force P was calculated point-by-point for each group of test temperature-charging rate data using formula (1) to obtain the corrected expansion force. For each group of voltages, the corrected expansion force (V) is used. Based on the data pairs, voltage-corrected expansion force variation curves are generated for each cell at different charging rates under each detection temperature.

[0045] For each group of voltage-corrected expansion forces (V, The data is arranged in ascending order of voltage, and the differential operation is performed using the difference between adjacent points. (2); in: For indexing data points, and It is the corrected expansion force between two adjacent data points. and These are the corresponding adjacent voltages. After point-by-point calculation, each group is formed ( ) data pairs, in each group ( Based on the data pairs, voltage-corrected expansion force variation curves are generated for each cell at different charging rates under each detection temperature.

[0046] like Figure 5 and Figure 6 As shown, the voltage V-corrected for expansion force during cell charging at different rates (0.1C, 0.2C, 0.5C, 0.8C, 1C) at 5℃ was obtained. The variation curve, and the voltage V-corrected expansion force of the battery cell at different charging rates (0.2C, 0.5C, 0.9C, 1.2C) at 15℃. The change curve, i.e., V- Curve. Further calculation of expansion force. rate of change of voltage V , obtain Figure 7 and Figure 8 The voltage-corrected rate of change of expansion force V- is shown. curve.

[0047] In some embodiments, step S140 includes: By querying the voltage-corrected expansion force change rate curves at different rate values ​​under each detection temperature, the corrected expansion force change rate corresponding to the typical voltage range of the battery at different rate values ​​under each detection temperature is obtained. Based on the corrected expansion force change rate corresponding to the typical voltage range of the battery at different rate values ​​under each detection temperature, it is determined whether lithium plating occurs in the cell at the current detection temperature and rate value.

[0048] Specifically, it is determined whether the corrected rate of change of expansion force corresponding to different rate values ​​at each detection temperature in the typical voltage range of the battery is greater than a preset threshold; if so, it is determined that lithium plating has occurred in the cell at the current test temperature and test rate.

[0049] For example, the battery cell is a lithium iron phosphate battery cell. For lithium iron phosphate battery cells, Typically, the voltage is 3.6V, therefore the typical voltage range for lithium iron phosphate cells is 3.57V to 3.63V. Within this range, a large number of lithium ions have already been released from the positive electrode. If the negative electrode cannot receive them in time due to kinetic limitations, the risk of lithium plating is highest. The voltage-corrected rate of change of expansion force V- is obtained. Following the curve, pay attention to the typical voltage range of 3.57V to 3.63V, specifically the area highlighted in the box. If this area... This indicates that lithium plating occurred in the battery cell at the current test temperature and test rate. The results show that lithium plating occurred at 0.5C, 0.8C, and 1C at 5℃; and at 0.9C and 1.2C at 15℃.

[0050] Verification: such as Figure 9 , 10 As shown, the accuracy of the lithium plating determination method of this application is verified by using a three-electrode method to obtain the negative electrode potential. The three-electrode test results show that at 5℃, the negative electrode potential of the cell is less than 0V at 0.5C, 0.8C, and 1C rates, indicating lithium plating in the cell; at 15℃, the negative electrode potential of the cell is less than 0V at 0.9C and 1.2C rates, indicating lithium plating in the cell. This is consistent with the determination results of the in-situ detection method for lithium plating in batteries provided in this application.

[0051] This application also provides an in-situ detection system for lithium plating in batteries, referring to... Figure 11 As shown, it includes: The acquisition module 111 is used to obtain the cell temperature correction coefficient through calibration experiments; Inspection module 112 is used to detect the expansion force data, cell surface temperature data and voltage data of the battery cell in the in-situ charge and discharge test at different temperatures and different rates; The generation module 113 is used to generate voltage-corrected expansion force change rate curves at different magnification values ​​at each detection temperature based on the cell temperature correction coefficient, the expansion force data, the cell surface temperature data, and the voltage data. The judgment module 114 is used to determine whether lithium plating occurs in the battery at the current test temperature and rate based on the voltage-corrected expansion force change rate curve.

[0052] In some embodiments, the acquisition module 111 includes: The measurement unit is used to measure the change in the cell expansion force with ambient temperature under different preset charging states. The first generation unit is used to generate a cell temperature correction coefficient based on the numerical curve of the cell expansion force changing with the ambient temperature under different preset charging states.

[0053] In some embodiments, the first generation unit includes: The first calculation subunit is used to calculate the rate of increase of the cell expansion force value under each preset charged state with respect to the ambient temperature. The second subunit is used to calculate the average value of the cell expansion force value with respect to the rate of increase of the ambient temperature to obtain a cell temperature correction coefficient applicable to the current cell model and test system.

[0054] In some embodiments, the inspection module 112 includes: The test unit is used to perform in-situ charge and discharge tests on the battery cells at different temperatures and rates. The acquisition unit is used to acquire voltage data of the battery cell during in-situ charge and discharge testing, obtain surface temperature data of the battery cell based on a temperature sensor attached to the surface of the battery cell, and obtain expansion force data in the thickness direction of the battery cell based on a force sensor in contact with the side of the battery cell with a larger area.

[0055] In some embodiments, the generation module 113 includes: The second generation unit is used to generate voltage-corrected expansion force change curves of the battery cell at different charging rates under each detection temperature, based on the battery cell temperature correction coefficient, the expansion force data, the battery cell surface temperature data, and the voltage data. The calculation unit is used to calculate the rate of change of expansion force with respect to voltage based on the voltage-corrected expansion force change curve during the charging of the battery cell, so as to obtain the voltage-corrected expansion force change rate curve at different multiplier values ​​at each detection temperature.

[0056] In some embodiments, the second generation unit includes: The acquisition sub-unit is used to correct the expansion force data according to the cell temperature correction coefficient to obtain the corrected expansion force data. A generation subunit is used to generate a voltage-corrected expansion force variation curve of the battery cell at different charging rates under each detection temperature, based on the corrected expansion force data and the voltage data.

[0057] In some embodiments, the determining module 114 includes: The query unit is used to query the voltage-corrected expansion force change rate curve at different rate values ​​under each detection temperature to obtain the typical voltage range of the battery and the corresponding corrected expansion force change rate at different rate values ​​under each detection temperature. The judgment unit is used to determine whether lithium plating occurs in the battery cell at the current detection temperature and rate value, based on the corrected rate of change of expansion force corresponding to different rate values ​​at each detection temperature within the typical voltage range of the battery.

[0058] In some embodiments, the determining unit includes: The first judgment subunit is used to determine whether the corrected rate of change of expansion force corresponding to different rate values ​​at each detection temperature in the typical voltage range of the battery is greater than a preset threshold. The second judgment subunit is used to determine whether lithium plating has occurred in the battery cell under the current test temperature and test rate after the judgment result of the first judgment subunit is yes.

[0059] This application also provides a computer-readable storage medium storing a computer program thereon, which, when executed by a processor, performs the following steps: The cell temperature correction coefficient was obtained through calibration experiments. The expansion force data, cell surface temperature data, and voltage data of the battery cell were tested in situ charge-discharge tests at different temperatures and rates. Based on the cell temperature correction coefficient, the expansion force data, the cell surface temperature data, and the voltage data, a voltage-corrected expansion force change rate curve is generated at different magnification values ​​at each detection temperature. The voltage-corrected expansion force change rate curve is used to determine whether lithium plating occurs in the battery at the current test temperature and rate.

[0060] When the computer program is executed by the processor, it also performs the following steps: The measurement measures the change in cell expansion force with ambient temperature under different preset charging states. A cell temperature correction coefficient is generated based on the numerical curves of how the cell expansion force changes with the ambient temperature under different preset charging states.

[0061] When the computer program is executed by the processor, it also performs the following steps: Calculate the rate of increase of the cell expansion force value under each preset charged state with respect to the ambient temperature. The average value of the cell expansion force with respect to the rate of increase of the ambient temperature is calculated to obtain the cell temperature correction coefficient applicable to the current cell model and test system.

[0062] When the computer program is executed by the processor, it also performs the following steps: the expansion force data, cell surface temperature data, and voltage data detected in the in-situ charge-discharge test of the battery cell at different temperatures and different rates include: In-situ charge-discharge tests of the battery cells were conducted at different temperatures and rates. The system acquires voltage data of the battery cell during in-situ charge-discharge testing, obtains surface temperature data of the battery cell based on a temperature sensor attached to the surface of the battery cell, and obtains expansion force data in the thickness direction of the battery cell based on a force sensor in contact with the side of the battery cell with a larger area.

[0063] When the computer program is executed by the processor, it also performs the following steps: Based on the cell temperature correction coefficient, the expansion force data, the cell surface temperature data, and the voltage data, generate voltage-corrected expansion force variation curves for the cell during charging at different rates at each detection temperature; The rate of change of expansion force with respect to voltage is calculated based on the voltage-corrected expansion force change curve during the charging of the battery cell, thereby obtaining the voltage-corrected expansion force change rate curve at different multipliers at each detection temperature.

[0064] When the computer program is executed by the processor, it also performs the following steps: The expansion force data is obtained by correcting the expansion force data according to the cell temperature correction coefficient; Based on the corrected expansion force data and the voltage data, a voltage-corrected expansion force variation curve is generated when the battery cell is charged at different rates at each detection temperature.

[0065] When the computer program is executed by the processor, it also performs the following steps: By querying the voltage-corrected expansion force change rate curves at different rate values ​​under each detection temperature, the typical voltage range of the battery can be obtained, along with the corresponding corrected expansion force change rate at different rate values ​​under each detection temperature. Based on the corrected rate of change of expansion force corresponding to different rate values ​​at each detection temperature within the typical voltage range of the battery, it is determined whether lithium plating occurs in the cell at the current detection temperature and rate value.

[0066] When the computer program is executed by the processor, it also performs the following steps: Determine whether the corrected rate of change of expansion force corresponding to different rate values ​​at each detection temperature within the typical voltage range of the battery is greater than a preset threshold. If so, it is determined that lithium plating has occurred in the cell under the current test temperature and test rate.

[0067] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0068] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0069] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.

Claims

1. An in-situ detection method for lithium plating in batteries, characterized in that, include: The cell temperature correction coefficient was obtained through calibration experiments. The expansion force data, cell surface temperature data, and voltage data of the battery cell were tested in situ charge-discharge tests at different temperatures and rates. Based on the cell temperature correction coefficient, the expansion force data, the cell surface temperature data, and the voltage data, a voltage-corrected expansion force change rate curve is generated at different magnification values ​​at each detection temperature. The voltage-corrected expansion force change rate curve is used to determine whether lithium plating occurs in the battery at the current test temperature and rate.

2. The in-situ detection method for lithium plating in batteries according to claim 1, characterized in that, The cell temperature correction coefficient obtained through calibration experiments includes: The measurement measures the change in cell expansion force with ambient temperature under different preset charging states. A cell temperature correction coefficient is generated based on the numerical curves of how the cell expansion force changes with the ambient temperature under different preset charging states.

3. The in-situ detection method for lithium plating in batteries according to claim 2, characterized in that, The cell temperature correction coefficient generated based on the numerical curves of cell expansion force changing with ambient temperature under different preset charging states includes: Calculate the rate of increase of the cell expansion force value under each preset charged state with respect to the ambient temperature. The average value of the cell expansion force with respect to the rate of increase of the ambient temperature is calculated to obtain the cell temperature correction coefficient applicable to the current cell model and test system.

4. The in-situ detection method for lithium plating in batteries according to claim 1, characterized in that, The data on expansion force, cell surface temperature, and voltage during in-situ charge-discharge tests of the battery cell at different temperatures and rates include: In-situ charge-discharge tests of the battery cells were conducted at different temperatures and rates. The system acquires voltage data of the battery cell during in-situ charge-discharge testing, obtains surface temperature data of the battery cell based on a temperature sensor attached to the surface of the battery cell, and obtains expansion force data in the thickness direction of the battery cell based on a force sensor in contact with the side of the battery cell with a larger area.

5. The in-situ detection method for lithium plating in batteries according to claim 1, characterized in that, The generation of voltage-corrected expansion force change rate curves at different magnification values ​​at each detection temperature, based on the cell temperature correction coefficient, the expansion force data, the cell surface temperature data, and the voltage data, includes: Based on the cell temperature correction coefficient, the expansion force data, the cell surface temperature data, and the voltage data, generate voltage-corrected expansion force variation curves for the cell during charging at different rates at each detection temperature; The rate of change of expansion force with respect to voltage is calculated based on the voltage-corrected expansion force change curve during the charging of the battery cell, thereby obtaining the voltage-corrected expansion force change rate curve at different multipliers at each detection temperature.

6. The in-situ detection method for lithium plating in batteries according to claim 5, characterized in that, The step of generating voltage-corrected expansion force variation curves for the battery cell at different charging rates under each detection temperature, based on the cell temperature correction coefficient, the expansion force data, the cell surface temperature data, and the voltage data, includes: The expansion force data is obtained by correcting the expansion force data according to the cell temperature correction coefficient; Based on the corrected expansion force data and the voltage data, a voltage-corrected expansion force variation curve is generated when the battery cell is charged at different rates at each detection temperature.

7. The in-situ detection method for lithium plating in batteries according to claim 1, characterized in that, The step of determining whether lithium plating has occurred in the battery at the current test temperature and rate based on the voltage-corrected expansion force change rate curve includes: By querying the voltage-corrected expansion force change rate curves at different rate values ​​under each detection temperature, the typical voltage range of the battery can be obtained, along with the corresponding corrected expansion force change rate at different rate values ​​under each detection temperature. Based on the corrected rate of change of expansion force corresponding to different rate values ​​at each detection temperature within the typical voltage range of the battery, it is determined whether lithium plating occurs in the cell at the current detection temperature and rate value.

8. The in-situ detection method for lithium plating in batteries according to claim 7, characterized in that, The determination of whether lithium plating occurs in the battery cell at the current detection temperature and rate value, based on the corrected rate of change of expansion force corresponding to different rate values ​​at each detection temperature within the typical voltage range of the battery, includes: Determine whether the corrected rate of change of expansion force corresponding to different rate values ​​at each detection temperature within the typical voltage range of the battery is greater than a preset threshold. If so, it is determined that lithium plating has occurred in the cell under the current test temperature and test rate.

9. An in-situ detection system for lithium plating in batteries, characterized in that, include: The acquisition module is used to obtain the cell temperature correction coefficient through calibration experiments; The inspection module is used to detect the expansion force data, cell surface temperature data, and voltage data of the battery cell during in-situ charge-discharge tests at different temperatures and rates. The generation module is used to generate voltage-corrected expansion force change rate curves at different magnification values ​​at each detection temperature based on the cell temperature correction coefficient, the expansion force data, the cell surface temperature data, and the voltage data. The judgment module is used to determine whether lithium plating occurs in the battery at the current test temperature and rate based on the voltage-corrected expansion force change rate curve.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the steps of the in-situ detection method for lithium plating in batteries as described in any one of claims 1-8.

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