A method and apparatus for generating a solid electrolyte interfacial film.

Abstract

This application discloses a method and apparatus for generating a solid electrolyte interfacial film. When the voltage of a single battery cell reaches a first preset voltage, multiple charge-discharge operations are performed on the battery cell. The first preset voltage represents the voltage at which the film-forming reaction begins at the negative electrode interface of the battery cell. The charge-discharge operation includes charging and discharging operations. Each charge-discharge operation is performed based on the voltage and charge level of the previous operation. During each charging or discharging operation, the voltage of the battery cell is detected. When the voltage of the battery cell reaches a second preset voltage, a battery cell with a solid electrolyte interfacial film at the negative electrode interface is obtained. The second preset voltage represents the voltage at which the film-forming reaction ends. Based on the above scheme, the film-forming quality of the solid electrolyte interfacial film can be effectively improved, thereby enhancing battery performance.

Description

Technical Field

[0001] This application relates to the field of electrochemical energy storage technology, and in particular to a method and apparatus for generating a solid electrolyte interface film. Background Technology

[0002] Lithium-ion batteries are widely used in mobile electronic devices, electric vehicles, and energy storage systems due to their high energy density and long cycle life. During the manufacturing process of lithium-ion batteries, the formation of the solid electrolyte interface (SEI) film has a significant impact on battery performance, determining not only the initial coulombic efficiency but also directly affecting the battery's safety and lifespan.

[0003] Currently, the SEI film formation methods typically optimize the formation process by controlling the charging current or adding film-forming additives. However, these methods mostly remain at the level of parameter adjustment, limiting the film formation effect and making it difficult to significantly improve the overall performance of the battery. Summary of the Invention

[0004] This application provides a method and apparatus for generating a solid electrolyte interphase (SEI) film, which can effectively improve the film quality of the SEI film and thus improve battery performance.

[0005] The technical solution of this application embodiment is implemented as follows:

[0006] In a first aspect, embodiments of this application provide a method for generating a solid electrolyte interface film, the method comprising:

[0007] When the voltage of a single battery cell reaches a first preset voltage, multiple charge-discharge operations are performed on the single battery cell; wherein, the first preset voltage represents the voltage at which the film formation reaction begins at the negative electrode interface of the single battery cell; the charge-discharge operation includes charging operation and discharging operation; each charge-discharge operation in the multiple charge-discharge operations is performed based on the voltage and amount of charge in the previous charge-discharge operation.

[0008] The voltage of each battery cell is detected during each charging or discharging operation.

[0009] When the voltage of a single battery cell reaches a second preset voltage, a single battery cell with a solid electrolyte interfacial film at the negative electrode interface is obtained; wherein, the second preset voltage characterizes the voltage at which the film formation reaction ends.

[0010] In this embodiment, the focus is on the stage from the start of SEI film formation (i.e., when the battery cell voltage reaches the first preset voltage) to the end of SEI film formation (i.e., when the voltage reaches the second preset voltage). Multiple charge-discharge operations are performed, and each charge-discharge operation can be based on the voltage and charge of the previous charge-discharge operation. This allows for precise control of each charge-discharge operation, ensuring that the film-forming additives in the electrolyte can be evenly distributed on the negative electrode graphite surface and promoting the timely migration of by-products into the electrolyte phase. This improves the density and uniformity of the SEI layer, enhances the quality of SEI film formation, and ultimately extends the lifespan of the battery cell.

[0011] In some embodiments of this application, performing multiple charge-discharge operations on a single battery cell includes:

[0012] Based on the current discharge duration, the current charge and discharge operation is performed on the battery cell, and the current mapping relationship data of the battery cell in the current charge and discharge operation is obtained; wherein, the current mapping relationship data includes the data on the mapping relationship between voltage and capacity of the battery cell in the current charge and discharge operation.

[0013] The next charge / discharge operation is executed based on the current mapping data to complete multiple charge / discharge operations.

[0014] In this embodiment, by recording the mapping relationship between the voltage and charge of a single battery cell during each charge and discharge process, the subsequent charge and discharge process can be controlled more precisely, making the film formation reaction more stable and controllable, further optimizing the formation conditions of the SEI film, and improving the film formation consistency.

[0015] In some embodiments of this application, performing the next charge / discharge operation based on the current mapping relationship data includes:

[0016] The target voltage difference is determined based on the current mapping relationship data; whereby the target voltage difference represents the maximum value of the difference between the voltage corresponding to the charging operation and the voltage corresponding to the discharging operation in the current mapping relationship data.

[0017] The ratio between the current discharge duration and the target voltage difference is determined as the operation reference information, and the next charge and discharge operation is performed according to the operation reference information.

[0018] In this embodiment, by calculating the maximum voltage difference during charging and discharging, the degree of polarization during SEI film formation can be quantified. By combining the discharge duration with the determined operation reference information, the charging and discharging strategy can be dynamically adjusted to achieve closed-loop feedback control of the film formation process, thereby improving the efficiency and stability of SEI film formation.

[0019] In some embodiments of this application, performing the next charge / discharge operation according to the operating reference information includes:

[0020] During the discharge operation of the next charge / discharge operation, real-time voltage data and discharge duration data of the next charge / discharge operation are acquired.

[0021] The first operation information is determined based on real-time voltage data and discharge duration data. If the first operation information is equal to the operation reference information, the discharge operation is stopped to complete the next charge and discharge operation.

[0022] In this embodiment, by collecting and comparing the first operation information in real time, it can be ensured that the charging and discharging operation is performed according to the optimal film formation effect, thereby ensuring the repeatability and consistency of the film formation reaction and reducing the difference in SEI film quality caused by process fluctuations.

[0023] In some embodiments of this application, performing a current charge / discharge operation on a single battery cell based on the current discharge duration includes:

[0024] Perform the current charging operation on the battery cell based on the current charging duration and current charging rate;

[0025] The current discharge operation is performed on the battery cell based on the current discharge duration and the current discharge rate.

[0026] In this embodiment, by performing each charging operation according to a determined charging duration and charging rate, and each discharging operation according to a determined discharging duration and discharging rate, the kinetic conditions of the film-forming reaction can be adjusted more precisely, allowing the film-forming additives to fully participate in the reaction and reducing the accumulation of byproducts.

[0027] In some embodiments of this application, the method further includes:

[0028] Differential capacitance curve data of individual battery cells are processed by differential operation to obtain second-order differential capacitance curve data; wherein, differential capacitance curve data is data characterizing the mapping relationship between differential capacitance and voltage of individual battery cells;

[0029] The first preset voltage and the second preset voltage are determined based on the positive and negative peak values ​​in the second differential capacitance curve data; wherein the first preset voltage is less than or equal to the voltage corresponding to the positive peak value, and the second preset voltage is greater than or equal to the voltage corresponding to the negative peak value.

[0030] In this embodiment, by analyzing the differential capacitance curve and its second derivative characteristics, the start and end voltages of the SEI film formation reaction can be accurately identified, thereby providing a reliable basis for charge and discharge operations and improving the controllability and accuracy of the film formation process.

[0031] In some embodiments of this application, the method further includes:

[0032] When the current charging rate is the same as the current discharging rate, it is determined that the current discharging time is less than the current charging time, and the current charging time is less than or equal to the first preset time.

[0033] When the current charging rate is different from the current discharging rate, it is determined that the product of the current discharging duration and the current discharging rate is less than the product of the current charging duration and the current charging rate, and the product of the current charging duration and the current charging rate is less than the first preset power level.

[0034] In this embodiment, by reasonably setting the relationship between the charge / discharge rate and the duration, the process of the film formation reaction can be effectively controlled, avoiding uneven film formation or increased side reactions caused by overcharging and discharging, thereby improving the overall performance of the SEI film.

[0035] Secondly, embodiments of this application provide an apparatus for generating a solid electrolyte interface film, comprising:

[0036] A charge / discharge operation module is used to perform multiple charge / discharge operations on a battery cell when the voltage of the battery cell reaches a first preset voltage; and to obtain a battery cell with a solid electrolyte interfacial film at the negative electrode interface when the voltage of the battery cell reaches a second preset voltage; wherein, the first preset voltage represents the voltage at which the film formation reaction begins at the negative electrode interface of the battery cell; the charge / discharge operation includes a charging operation and a discharging operation, and the second preset voltage represents the voltage at which the film formation reaction ends; each charge / discharge operation in the multiple charge / discharge operations is performed based on the voltage and charge level of the previous charge / discharge operation.

[0037] The voltage detection module is used to detect the voltage of individual battery cells during each charging or discharging operation.

[0038] In this embodiment, the solid electrolyte interphase (SEI) film generation device performs multiple charge-discharge operations from the start of SEI film formation (i.e., when the battery cell voltage reaches a first preset voltage) to the end of SEI film formation (i.e., when the voltage reaches a second preset voltage). This allows the film-forming additives in the electrolyte to be evenly distributed on the negative electrode graphite surface and promotes the timely migration of by-products into the electrolyte phase, thereby improving the density and uniformity of the SEI layer, enhancing the quality of SEI film formation, and ultimately increasing the service life of the battery cell.

[0039] In some embodiments of this application, the charge / discharge operation module is further configured to perform the current charge / discharge operation on a battery cell based on the current discharge duration, and obtain the current mapping relationship data of the battery cell in the current charge / discharge operation; wherein, the current mapping relationship data includes data on the mapping relationship between voltage and capacity of the battery cell in the current charge / discharge operation; and to perform the next charge / discharge operation based on the current mapping relationship data to complete multiple charge / discharge operations.

[0040] In this embodiment, the solid electrolyte interphase (SEI) film generation device can more accurately control the subsequent charging and discharging process by recording the mapping relationship between the voltage and charge of the battery cells during each charging and discharging process, making the film formation reaction more stable and controllable, further optimizing the formation conditions of the SEI film, and improving the film formation consistency.

[0041] In some embodiments of this application, the solid electrolyte interphase (SEI) membrane generation device can ensure that the charging and discharging operations are performed in accordance with the optimal film formation effect by collecting and comparing the first operation information in real time, thereby ensuring the repeatability and consistency of the film formation reaction and reducing the quality difference of the SEI membrane caused by process fluctuations. Attached Figure Description

[0042] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of this application.

[0043] Figure 1 This is a schematic diagram of the film-forming reaction;

[0044] Figure 2 This is a schematic diagram illustrating the implementation process of the method for generating a solid electrolyte interface film proposed in this application embodiment;

[0045] Figure 3 This is a schematic diagram of the voltage curve for the charge-discharge operation proposed in the embodiments of this application;

[0046] Figure 4 This is a schematic diagram of voltage changes during the film formation process in the chemical formation process;

[0047] Figure 5 This is a schematic diagram of voltage changes during the film formation process as described in the embodiments of this application;

[0048] Figure 6 This is a schematic diagram of the differential capacitance curve proposed in the embodiments of this application;

[0049] Figure 7 This is a schematic diagram of the second-order differential capacitance curve proposed in the embodiments of this application;

[0050] Figure 8 This is a schematic diagram illustrating the voltage change over time during the charging and discharging operation according to an embodiment of this application.

[0051] Figure 9 This is a schematic diagram of the voltage difference change during the charging and discharging operation proposed in the embodiments of this application;

[0052] Figure 10 This is a schematic diagram of the polarization impedance change during the charging and discharging operation proposed in the embodiments of this application;

[0053] Figure 11 This is a schematic diagram illustrating the test results of the charge-discharge cycle test proposed in the embodiments of this application;

[0054] Figure 12 This is a schematic diagram of the structure of the solid electrolyte interface film generation device proposed in the embodiments of this application. Detailed Implementation

[0055] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only for explaining the relevant application and not for limiting the application. Furthermore, it should be noted that, for ease of description, only the parts related to the relevant application are shown in the accompanying drawings.

[0056] During the first charge of a lithium-ion battery, an irreversible side reaction occurs on the surface of the negative electrode, forming a solid intermediate phase, commonly known in the industry as the SEI layer; for example... Figure 1 As shown, the left side represents the positive electrode material of a lithium-ion battery, and the right side represents the negative electrode material. During the first charge, a film-forming side reaction of the SEI (Sediment Injection) occurs. When the electrolyte contains film-forming additives, the additives preferentially participate in the film-forming reaction, forming the SEI layer and other byproducts. Currently, the commonly used formation strategy in the industry is the constant current charging strategy. However, the constant current formation strategy will have the following problems during SEI film formation: The electrolyte additives react on the graphite surface, generating both the main components of the SEI layer and byproducts that accumulate on the graphite surface. These byproducts continuously accumulate on the graphite surface and further participate in the SEI film-forming reaction, reducing the quality of the SEI film. At the same time, because the additives participate in the reaction, the additives in the electrolyte phase need a certain amount of time, and the concentration of film-forming additives on the graphite surface decreases, resulting in the SEI film quality not reaching the optimal level. The quality of the SEI layer directly affects the lifespan of lithium-ion batteries during subsequent use. A poor SEI layer is prone to damage and repair during use, resulting in significant active lithium consumption and deteriorating battery life. To improve the quality of the SEI layer, common methods include adding film-forming additives to the electrolyte, such as ethylene carbonate, fluoroethylene carbonate, and vinyl ethylene carbonate. These additives react preferentially with the solvent during SEI layer formation, promoting a better SEI layer structure. However, using constant current charging for SEI film formation can lead to uneven additive distribution and by-reactant accumulation, resulting in high SEI film impedance and structural instability, which negatively impacts battery cycle life.

[0057] To address the aforementioned issues, this application provides a method for generating a solid electrolyte interphase (SEI) film. This method involves performing multiple charge-discharge operations when the voltage of a single battery cell reaches a first preset voltage, detecting voltage changes during each operation, and finally determining that SEI film formation is complete when the voltage reaches a second preset voltage. This method optimizes the charge-discharge strategy, ensuring that film-forming additives in the electrolyte fully participate in the reaction, reducing the impact of byproducts, thereby forming a dense and stable SEI film, significantly improving the lifespan and performance of lithium-ion batteries.

[0058] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings.

[0059] One embodiment of this application provides a method for generating a solid electrolyte interface film, such as... Figure 2 As shown, the method for generating a solid electrolyte interface film may include the following steps:

[0060] Step 101: When the voltage of a single battery cell reaches a first preset voltage, perform multiple charge-discharge operations on the single battery cell; wherein, the first preset voltage represents the voltage at which the negative electrode interface of the single battery cell begins to form a film reaction; the charge-discharge operation includes a charging operation and a discharging operation; each charge-discharge operation in the multiple charge-discharge operations is performed based on the voltage and amount of charge in the previous charge-discharge operation.

[0061] In the embodiments of this application, the solid electrolyte interface film generation device can perform multiple charge-discharge operations on a battery cell when the voltage of the battery cell reaches a first preset voltage; wherein, the first preset voltage represents the voltage at which the negative electrode interface of the battery cell begins the film formation reaction; the charge-discharge operation includes a charging operation and a discharging operation; each charge-discharge operation in the multiple charge-discharge operations is performed based on the voltage and amount of charge in the previous charge-discharge operation.

[0062] In the embodiments of this application, the preset voltage is a specific voltage value set according to the electrochemical behavior of the battery cell during the SEI film formation process, used to determine the start and end stages of the film formation reaction; wherein, the preset voltage may include a first preset voltage and a second preset voltage, the first preset voltage characterizing the voltage at which the film formation reaction begins at the negative electrode interface, and the second preset voltage characterizing the voltage at which the film formation reaction ends.

[0063] In some embodiments of this application, the first preset voltage can be 2V. When the voltage of a single battery cell reaches 2V, it usually marks the beginning of the formation of a solid electrolyte interface film. The film-forming additives in the electrolyte begin to participate in the reaction and preferentially react on the graphite surface of the negative electrode, thereby promoting the initial formation of the solid electrolyte interface film.

[0064] In the embodiments of this application, the charging operation can be implemented by constant current charging (CC), and the discharging operation can be implemented by constant current discharging (DC).

[0065] In the embodiments of this application, performing multiple charge-discharge operations on a battery cell when the voltage of the battery cell reaches a first preset voltage means starting to perform multiple charge-discharge operations on the battery cell after the voltage of the battery cell reaches the first preset voltage.

[0066] In some embodiments of this application, a battery cell refers to a basic unit capable of converting chemical energy into electrical energy, which can be used to manufacture battery modules or battery packs for supplying power to electrical devices.

[0067] For example, two bare cells, i.e. unencapsulated wound or stacked electrode assemblies, are placed in parallel inside the battery casing. The top cover is sealed by laser welding, and after vacuum baking to remove moisture, electrolyte is injected to form a battery cell to be formed. Then, in the subsequent formation process, the solid electrolyte interface film (SEI film) generation method provided in the embodiments of this application is used to generate a solid electrolyte interface film (SEI film) on the negative electrode surface of each bare cell, thereby activating the electrochemical performance of the battery cell. In other words, the battery cell can be an independent electrochemical unit with a complete structure including bare cells, casing, electrolyte, etc.

[0068] In some embodiments of this application, performing multiple charge-discharge operations on a single battery cell includes performing a current charge-discharge operation on the single battery cell based on the current discharge duration, and obtaining the current mapping relationship data of the single battery cell in the current charge-discharge operation; wherein, the current mapping relationship data includes data on the mapping relationship between voltage and capacity of the single battery cell in the current charge-discharge operation; and then performing the next charge-discharge operation based on the current mapping relationship data to complete multiple charge-discharge operations.

[0069] In the embodiments of this application, the current discharge duration refers to the duration of each discharge operation.

[0070] In some embodiments of this application, performing a current charge / discharge operation on a battery cell based on the current discharge duration includes performing a current charge operation on the battery cell based on the current charging duration and the current charging rate; and performing a current discharge operation on the battery cell based on the current discharge duration and the current discharge rate.

[0071] In some embodiments of this application, the current charging rate refers to the ratio of the current used during the current charging operation to the battery's rated capacity (Ah). For example, performing a charging operation at a current charging rate of 0.05C means performing a charging operation at 5% of the battery's rated capacity; the current charging duration refers to the length of time a charging operation is continuously performed at a specific charging rate.

[0072] In some embodiments of this application, the current discharge rate refers to the ratio of the current used during the discharge operation of the current charge-discharge operation to the rated capacity of the battery; for example, performing a discharge operation at a current discharge rate of 0.05C is equivalent to performing a discharge operation at 5% of the rated capacity of the battery; the current discharge duration refers to the length of time that the discharge operation is continuously performed at a specific charge rate.

[0073] In some embodiments of this application, the order in which the charging or discharging operation is performed is not limited. For example, the charging operation may be performed first, followed by the discharging operation, or the discharging operation may be performed first, followed by the charging operation.

[0074] In the embodiments of this application, when the current charging rate and the current discharging rate are the same, the current discharging duration is less than the current charging duration, the current charging duration is less than or equal to the first preset duration, and the current discharging duration is less than or equal to the difference between the current charging duration and the second preset duration.

[0075] For example, the current charging rate is represented by C1, the current discharging rate by D1, the current discharging duration by T2, and the current charging duration by T1; when C1 = D1, T2 < T1 ≤ 30s must be satisfied, where the first preset duration is 30s; and T2 ≤ T1 - 10 must also be satisfied, where the second preset duration is 10s.

[0076] In the embodiments of this application, when the current charging rate and the current discharging rate are different, the product of the current discharging duration and the current discharging rate is less than the product of the current charging duration and the current charging rate, the product of the current charging duration and the current charging rate is less than the first preset energy level, and the product of the current discharging duration and the current discharging rate is less than or equal to the second preset energy level.

[0077] For example, when C1≠D1, it is necessary to satisfy T2×D1<T1×C1≤0.04%SOC, where the first preset power is 0.04%SOC; and it is also necessary to satisfy T2×D1≤0.014%SOC, where the second preset power is 0.014%SOC.

[0078] In the embodiments of this application, multiple alternating charging and discharging operations are performed to promote the uniform distribution of electrolyte additives on the negative electrode surface, thereby improving the quality of the SEI film. This alternating charging and discharging method differs from the traditional one-time constant current charging strategy. Instead, it utilizes the principle of electromigration to allow the additives to diffuse to the graphite phase surface in a timely manner and to allow the generated byproducts to diffuse into the electrolyte liquid phase in a timely manner, thereby reducing the impact of byproducts on the SEI film structure and improving the stability and density of the SEI film.

[0079] In some embodiments of this application, when a battery cell enters the solid electrolyte interface film formation stage, the solid electrolyte interface film generation device can record and adjust the time of each charge and discharge.

[0080] In some embodiments of this application, the current mapping relationship data can be understood as the mapping relationship between the voltage of a battery cell and its corresponding charge change during each specific charge and discharge operation. The current mapping relationship data can be represented in the form of tables, curves, or functions.

[0081] In some embodiments of this application, the current mapping relationship data under different charge and discharge cycles can be used to determine whether the solid electrolyte interface film is in a state of gradual improvement. For example, after a battery cell has undergone multiple charge and discharge operations, if the correspondence between voltage and charge tends to be stable, it indicates that the solid electrolyte interface film has gradually reached the optimal state. This state helps to improve the overall performance of the battery cell and extend its service life.

[0082] In the embodiments of this application, the next charge / discharge operation is performed based on the current mapping relationship data, which mainly involves determining the timing of the end of the discharge operation in the next charge / discharge operation based on the current mapping relationship data.

[0083] In some embodiments of this application, performing the next charge / discharge operation based on the current mapping relationship data includes determining a target voltage difference based on the current mapping relationship data; wherein, the target voltage difference represents the maximum value of the difference between the voltage corresponding to the charging operation and the voltage corresponding to the discharging operation in the current mapping relationship data; then, the ratio between the current discharging duration and the target voltage difference is determined as operation reference information, and the next charge / discharge operation is performed according to the operation reference information.

[0084] For example, such as Figure 3 As shown, based on the voltage curves of the charging and discharging processes in a certain charge-discharge operation, with voltage on the vertical axis and energy on the horizontal axis, the voltage values ​​corresponding to the same energy level during the charging and discharging processes can be selected. Then, the voltage difference between the voltage values ​​during the charging and discharging processes is obtained. By analogy, the voltage difference corresponding to each energy level during each charge-discharge operation can be obtained. Finally, the maximum value among these voltage differences is selected as the target voltage difference.

[0085] In the embodiments of this application, the target voltage difference reflects the degree of polarization of the internal chemical reaction process of a battery cell during a certain charge and discharge operation, that is, the portion of the voltage corresponding to the charging operation that is higher than the voltage corresponding to the discharging operation. The larger the target voltage difference, the greater the energy loss and polarization phenomenon in the battery during the charge and discharge process. Therefore, by determining the operation reference information based on the target voltage difference and executing the next charge and discharge operation according to the operation reference information, the subsequent charge and discharge strategy can be optimized according to the polarization degree of the battery cell, thereby improving the quality and stability of the SEI film at the negative electrode interface of the battery cell, and thus improving the cycle life and efficiency of the battery.

[0086] In the embodiments of this application, the operation reference information is a parameter obtained by mathematically calculating the difference between the current discharge duration and the target voltage, which is used to guide the execution method of the next charge and discharge operation.

[0087] For example, the current operation is the (n-1)th charge / discharge cycle, and the target voltage difference determined based on the current mapping data is... The current discharge duration is Then the operation reference information can be .

[0088] In some embodiments of this application, performing the next charge / discharge operation according to the operation reference information includes, during the discharge operation of the next charge / discharge operation, acquiring real-time voltage data and discharge duration data during the next charge / discharge operation; then determining first operation information based on the real-time voltage data and discharge duration data; and stopping the discharge operation to complete the next charge / discharge operation if the first operation information is equal to the operation reference information.

[0089] In the embodiments of this application, the real-time voltage data is the data obtained by real-time voltage acquisition of the battery cell during the charging and discharging operation of the battery cell; the real-time voltage data may include the real-time voltage value of the charging operation and the real-time voltage value of the discharging operation during the charging and discharging operation.

[0090] In the embodiments of this application, the discharge duration data represents the discharge duration up to the present during the discharge operation of performing the next charge-discharge operation.

[0091] In the embodiments of this application, the specific calculation method for determining the first operation information based on real-time voltage data and discharge duration data is similar to the calculation method for determining operation reference information. It uses the real-time voltage value of the charging operation and the real-time voltage value of the discharging operation in the real-time voltage data to determine the first voltage difference. The first voltage difference is obtained by subtracting the real-time voltage value of the charging operation and the real-time voltage value of the discharging operation corresponding to the same amount of electricity. That is, when acquiring real-time voltage data, the corresponding amount of electricity can be recorded; then the ratio of the discharge duration data to the first voltage difference is calculated, and this ratio is the first operation information.

[0092] For example, when performing the nth charge / discharge operation, assuming the nth charging operation is performed first, the real-time voltage value during the nth charging operation can be collected first. Then, when performing the nth discharging operation, the real-time voltage value during the nth discharging operation can be collected. A first voltage difference is determined based on the real-time voltage values ​​during the nth charging and nth discharging operations. During the nth discharging operation, the first operation information and operation reference information obtained by comparing the ratio of the discharge duration data and the first voltage difference are compared in real time. Assuming that the first operation information and operation reference information are equal at time t1, the discharge is stopped, and the current charge / discharge operation is determined to be completed. The discharge duration of this operation is recorded based on t1. The discharge duration of this operation can also be used to determine the execution duration of the discharge operation in the next charge / discharge operation.

[0093] Step 102: Detect the voltage of each battery cell during each charging or discharging operation.

[0094] In the embodiments of this application, the solid electrolyte interface film generation device can detect the voltage of the battery cell during each charging or discharging operation while performing multiple charge and discharge operations on the battery cell.

[0095] In the embodiments of this application, the voltage of a single battery cell can be the voltage between the positive and negative terminals of the battery cell.

[0096] In the embodiments of this application, the voltage of the battery cell needs to be monitored in real time during each charge and discharge operation in order to accurately determine the formation state of the SEI film; the solid electrolyte interface film generation device can use the voltage detection results to identify the start and end points of the film formation reaction.

[0097] Step 103: When the voltage of the battery cell reaches the second preset voltage, a battery cell with a solid electrolyte interface film at the negative electrode interface is obtained; wherein, the second preset voltage characterizes the voltage at which the film formation reaction ends.

[0098] In the embodiments of this application, the solid electrolyte interface film generation device can determine that a battery cell with a solid electrolyte interface film on the negative electrode interface is obtained when the voltage of the battery cell is detected to reach a second preset voltage.

[0099] In some embodiments of this application, the second preset voltage can be 2.7V.

[0100] It should be noted that current formation processes all employ a one-step film formation method, which involves using a constant current to initially charge the battery, directly charging it to a target capacity. This operation begins before the film formation reaction and extends to a considerable period after the reaction concludes; for example, such as Figure 4 As shown, related formation processes use a constant current to directly charge the battery to a voltage of 3V, at which point the battery capacity is typically 15% SOC; other methods directly charge the battery to its shipping capacity, such as 50% SOC, which typically corresponds to a voltage of 3.3V; or directly charge the battery to 70% SOC, which typically corresponds to a voltage of 3.5V; this application, however, precisely identifies the voltage at which the film formation reaction begins and ends, and then performs multiple alternating charging and discharging operations throughout the entire process, such as... Figure 5 As shown, due to the alternating charging and discharging, and the fact that the charging amount is greater than the discharging amount, the voltage exhibits a spiral increasing trend, which can help to better form the SEI layer.

[0101] In the embodiments of this application, the differential capacitance curve data of a battery cell can be processed by differential operation to obtain secondary differential capacitance curve data; wherein, the differential capacitance curve data is data characterizing the mapping relationship between the differential capacitance and voltage of a battery cell; then, a first preset voltage and a second preset voltage are determined based on the positive peak and negative peak in the secondary differential capacitance curve data; wherein, the first preset voltage is less than or equal to the voltage corresponding to the positive peak, and the second preset voltage is greater than or equal to the voltage corresponding to the negative peak.

[0102] In embodiments of this application, the differential capacitance curve data can be a curve plotted by measuring the change in electrode potential and charge during battery charging or discharging. The differential capacitance curve can reflect the electrochemical reaction process occurring inside the battery; for example, such as Figure 6 As shown, in the differential capacitance curve, the vertical axis can be the differential capacitance dQ / dV, which reflects the relationship between the rate of change of charge and the rate of change of voltage. The horizontal axis can be the voltage. It can be seen that a reaction peak involving the additive in film formation occurs between 2V and 2.5V. After performing differential operations on the differential capacitance curve data, the second-order differential capacitance curve data can be obtained, for example, as shown... Figure 7As shown, two peak potentials can be obtained from the second differential capacitance curve data, including the voltage corresponding to the positive peak and the voltage corresponding to the negative peak. Then, the first preset voltage V1 can be less than or equal to the voltage corresponding to the positive peak, and the second preset voltage V2 can be greater than or equal to the voltage corresponding to the negative peak.

[0103] In some embodiments of this application, the battery cell can be charged before its voltage reaches the first preset voltage, so that its voltage reaches the first preset voltage. The charging method is not limited in this application. For example, the voltage of the battery cell can be charged to the first preset voltage by constant current charging.

[0104] In some embodiments of this application, after the voltage of a single battery cell reaches a second preset voltage through multiple charge-discharge operations, i.e., after the single battery cell has completed the formation of a solid electrolyte interface film, the single battery cell can continue to be charged. This application does not limit the charging method of this charging process. For example, this process can be completed by charging and resting. This process can be used to adjust the lithium intercalation degree of the negative electrode graphite, i.e., the battery SOC, and has a low impact on the solid electrolyte interface film.

[0105] This application provides a method for generating a solid electrolyte interfacial film. The apparatus for generating the solid electrolyte interfacial film can perform multiple charge-discharge operations on a battery cell when the voltage of the battery cell reaches a first preset voltage. The first preset voltage represents the voltage at which the film-forming reaction begins at the negative electrode interface of the battery cell. The charge-discharge operation includes a charging operation and a discharging operation. Each charge-discharge operation in the multiple charge-discharge operations is performed based on the voltage and charge in the previous charge-discharge operation. In each charging or discharging operation, the voltage of the battery cell is detected. When the voltage of the battery cell reaches a second preset voltage, a battery cell with a solid electrolyte interfacial film on the negative electrode interface is obtained. The second preset voltage represents the voltage at which the film-forming reaction ends. Therefore, this embodiment mainly targets the stage from the beginning of SEI film formation, i.e., when the battery cell voltage reaches the first preset voltage, to the end of SEI film formation, i.e., when the voltage reaches the second preset voltage, multiple charge and discharge operations are performed. Each charge and discharge operation can be performed based on the voltage and charge in the previous charge and discharge operation. This allows for precise control of each charge and discharge operation, enabling the film-forming additives in the electrolyte to be evenly distributed on the negative electrode graphite surface and promoting the timely migration of by-products into the electrolyte phase. This improves the density and uniformity of the SEI layer, enhances the quality of SEI film formation, and ultimately extends the service life of the battery cell.

[0106] Based on the above embodiments, in another embodiment of this application, for the SEI film formation stage, by performing multiple charging and discharging operations, the additives are uniformly distributed on the graphite surface, and the by-reactants are transferred to the electrolytic liquid phase in a timely manner, thereby avoiding the by-reactants from participating in the formation of the SEI film. This not only effectively improves the quality of the SEI film, but also significantly extends the service life of the lithium-ion battery.

[0107] In some embodiments of this application, as described above Figure 6 As shown, in the differential capacitance curve plotted under the current constant current charging formation strategy, a reaction peak of additive participation in film formation occurs between 2V and 2.5V. Based on this, the embodiments of this application provide the following formation method that can be directly mass-produced. In the formation process, multiple charge and discharge operations are performed for the film formation stage to generate a good solid electrolyte interface film on the negative electrode interface of the battery cell.

[0108] For example, in current related formation strategies, after a certain resting time, the battery cells can be charged at a certain charging rate. After charging for a certain period, they can be rested again or charged to reach the shipment capacity. At this point, the SEI film of the battery cell has already formed. The formation process of this application may include: first, after resting the battery cell for 30 seconds, charging the battery cell at a charging rate of 0.05C until the voltage reaches V1, which is the voltage at which the film formation reaction begins; then, after a brief resting time of 30 seconds, the process can be... The process begins with multiple charge-discharge operations. The charging operation is performed at a charging rate of 0.05C for T1s, and the discharging operation is performed at a discharging rate of 0.05C for T2s. These charging and discharging operations are repeated until the voltage reaches V2, which is the voltage corresponding to the end of the film formation reaction, thus confirming the formation of the SEI film. Then, the degree of lithium intercalation in the graphite can be selectively adjusted. For example, after resting for 30s, the graphite can be charged at a charging rate of 0.1C for 2 minutes, then rested for 30s, then charged at a charging rate of 0.33C for 3 minutes, and then rested for 30 seconds.

[0109] For example, to accurately identify V1 and V2, the differential capacitance curve can be recalculated to obtain a second differential capacitance curve. Then, the positive and negative peak values ​​in the second differential capacitance curve can be used to determine V1 and V2, where V1 ≤ the voltage corresponding to the positive peak value and V2 ≥ the voltage corresponding to the negative peak value.

[0110] In some embodiments of this application, the discharge rate D1 ≤ charge rate C1 ≤ 0.1C; in this embodiment, the charge rate and discharge rate can be 0.05C.

[0111] In some embodiments of this application, the execution duration T1 of the charging operation and the execution duration T2 of the discharging operation can be set accordingly based on whether D1 is equal to C1; when C1 = D1, T2 < T1 ≤ 30s and T2 ≤ T1 - 10 must be satisfied; when C1 ≠ D1, T2 × D1 < T1 × C1 ≤ 0.04% SOC and T2 × D1 ≤ 0.014% SOC must be satisfied.

[0112] It should be noted that all current formation processes are one-step film formation methods, that is, the film formation process is completed in one step using a constant current, and the voltage curve is as described above. Figure 4 As shown, the voltage increases linearly; however, this solution focuses on the film formation stage, using an alternating charge and discharge strategy to make the additives more evenly distributed on the graphite surface of the negative electrode. Because of the alternating charge and discharge strategy, and the fact that the charging capacity is greater than the discharging capacity, the voltage exhibits a spiral increasing trend, as described above. Figure 5 As shown, this can help to better form the SEI layer.

[0113] For example, in a charge / discharge operation, such as performing a charging operation first and then a discharging operation, the change in voltage over time can be as follows: Figure 8 As shown; to more accurately determine the discharge duration T2, assume D1=C1 and T1 is fixed. Since the contribution of SEI to polarization impedance gradually increases with the increase of SEI formation degree during the film formation stage, a longer discharge time is required to ensure uniform distribution of the additive; as mentioned above. Figure 3 As shown, the duration of the discharge operation in the next charge / discharge operation can be constrained by determining the maximum value of the difference between the voltage corresponding to the charging operation and the voltage corresponding to the discharging operation in the current charge / discharge operation.

[0114] For example, the voltage corresponding to the charging operation is denoted as Vxn, and the voltage corresponding to the discharging operation is denoted as Vyn, where n represents the nth charging / discharging operation, and the voltage difference is denoted as Vn = Vxn - Vyn; where the voltage difference Vn can be understood as twice the polarization voltage, thus the voltage difference can reflect the degree of polarization; for example Figure 9 and Figure 10 As shown, with the increase of the number of charge-discharge operations, the SEI film formation degree increases. Simultaneously, the voltage difference and polarization resistance also gradually increase. The polarization resistance can be obtained through Vn / C1 or Vn / D1. When the polarization voltage decreases, it indicates that the SEI film formation process is nearing completion. To improve the SEI film formation quality, the first operation information corresponding to each charge-discharge operation can be made the same. For example, the first operation information corresponding to the nth charge-discharge operation is the same as the first operation information corresponding to the n-1th charge-discharge operation, which can be expressed as: ,in, , This indicates the charging duration of the charging operation in the first charge / discharge operation.

[0115] For example, during the next charge / discharge operation, such as the nth charge / discharge operation, relevant data can be collected in real time and the first operation information can be calculated. When the first operation information is equal to the operation reference information, the current discharge operation is stopped.

[0116] For example, for mass-produced battery cells, a fixed shipment capacity is generally required. Therefore, after the SEI film is formed, there are high-rate charging steps such as 0.1C and 0.33C. On the one hand, this can repair the SEI film to some extent, although the repair effect is weak. On the other hand, it also adjusts the capacity of the lithium battery for shipment. For example, as shown in Table 1 below, after obtaining a battery cell with an SEI film, multiple charge and discharge operations can be performed to charge the battery cell to the required shipment capacity or voltage.

[0117] Table 1

[0118]

[0119] In some embodiments of this application, in order to better form the SEI layer, slow charging can be performed directly after formation. For example, the voltage required for shipment is set to the maximum voltage Vmax. The Vmax of lithium iron phosphate (LFP) is 3.65V, and the Vmax of nickel cobalt manganese oxide (NCM) is 4.4V. The voltage of the battery cell can be directly charged to the above-mentioned maximum voltage through the charging operation during the formation stage. Alternatively, after charging to 100% SOC, 50% of the capacity can be released at a rate of 0.05~0.33C to achieve the 50% capacity required for shipment. Generally, the shipment capacity is between 30% and 80% SOC.

[0120] For example, in practical applications, lithium-ion battery cells after electrolyte injection can be subjected to high-temperature immersion at 45°C to 55°C for 20 to 30 hours. After the electrolyte has fully immersed the positive and negative electrode plates in the battery cell, the first charging formation of the lithium-ion battery cell is performed at a formation temperature of 45 to 55°C. By evacuating the lithium-ion battery cell and maintaining a negative pressure state throughout the process, the gas generated by the SEI film formation side reaction is promptly discharged. Table 2 below shows a formation process in a practical application scenario:

[0121] Table 2

[0122]

[0123] For example, to verify the SEI film between the solid electrolyte interphase (SEI) film generated by the method of this application embodiment and the currently related formation process, the battery cells obtained by the two methods can be subjected to cycle tests. The cycle strategy can be shown in Table 3 below:

[0124] Table 3

[0125]

[0126] For example, such as Figure 11 As shown, a 1C charge-discharge cycle test was conducted at 45°C. It was determined that compared to the current constant-current charging baseline cells, the cells obtained using the alternating charge-discharge strategy of this application (i.e., the improved group) exhibited a higher quality SEI layer. This resulted in more stable SEI film performance during cycling, leading to slower capacity decay. At the 50th cycle, the baseline group maintained a capacity retention of 95.9%, while the improved group maintained 96.3%, representing a 0.4% increase in capacity retention. Compared to current methods that improve SEI film quality through graphite improvements (e.g., low-lithium-consumption graphite) or additive improvements (e.g., high-film-quality additives), this application is the first in the industry to address the issue of uneven additive and by-reactant concentrations during formation and proposes an effective, low-cost improvement measure. In the effect verification experiment, the design, electrolyte, and additives of the baseline and improved group batteries were identical; the only difference was that this application employed an alternating charge-discharge method during the film formation stage, resulting in a significant improvement in battery life.

[0127] In summary, the formation technology that alternates between multiple charge and discharge operations solves the problem of poor SEI film quality in the relevant formation stages, providing a low-cost and high-efficiency solution for improving the performance of lithium-ion batteries. It also has good practicality and broad application prospects in the field of battery manufacturing.

[0128] Based on the above embodiments, in another embodiment of this application, a device for generating a solid electrolyte interface film is provided, such as... Figure 12 As shown, the solid electrolyte interface film generation device 1 may include a charge / discharge operation module 11 and a voltage detection module 12.

[0129] The charge / discharge operation module 11 is used to perform multiple charge / discharge operations on a battery cell when the voltage of the battery cell reaches a first preset voltage; and to obtain a battery cell with a solid electrolyte interface film at the negative electrode interface when the voltage of the battery cell reaches a second preset voltage; wherein, the first preset voltage represents the voltage at which the film formation reaction begins at the negative electrode interface of the battery cell; the charge / discharge operation includes a charging operation and a discharging operation, and the second preset voltage represents the voltage at which the film formation reaction ends; each charge / discharge operation in the multiple charge / discharge operations is performed based on the voltage and charge during the previous charge / discharge operation.

[0130] The voltage detection module 12 is used to detect the voltage of a single battery cell during each charging or discharging operation.

[0131] In some embodiments of this application, the charge / discharge operation module 11 is further configured to perform the current charge / discharge operation on the battery cell based on the current discharge duration, and obtain the current mapping relationship data of the battery cell in the current charge / discharge operation; wherein, the current mapping relationship data includes data on the mapping relationship between voltage and capacity of the battery cell in the current charge / discharge operation; and to perform the next charge / discharge operation based on the current mapping relationship data to complete multiple charge / discharge operations.

[0132] In some embodiments of this application, the charge / discharge operation module 11 is further configured to determine a target voltage difference based on the current mapping relationship data; and to determine the ratio between the current discharge duration and the target voltage difference as operation reference information, and to perform the next charge / discharge operation according to the operation reference information; wherein, the target voltage difference represents the maximum value of the difference between the voltage corresponding to the charging operation and the voltage corresponding to the discharging operation in the current mapping relationship data.

[0133] In some embodiments of this application, the charge / discharge operation module 11 is further configured to acquire real-time voltage data and discharge duration data during the discharge operation of the next charge / discharge operation; and to determine first operation information based on the real-time voltage data and discharge duration data, and to stop the discharge operation when the first operation information is equal to the operation reference information, so as to complete the next charge / discharge operation.

[0134] In some embodiments of this application, the charge / discharge operation module 11 is further configured to perform a current charging operation on a battery cell based on the current charging duration and the current charging rate; and to perform a current discharging operation on a battery cell based on the current discharging duration and the current discharging rate.

[0135] In some embodiments of this application, the charge / discharge operation module 11 is further configured to perform differential operation processing on the differential capacitance curve data of the battery cell to obtain secondary differential capacitance curve data; wherein, the differential capacitance curve data is data characterizing the mapping relationship between the differential capacitance and voltage of the battery cell; and to determine a first preset voltage and a second preset voltage based on the positive peak and negative peak in the secondary differential capacitance curve data; wherein, the first preset voltage is less than or equal to the voltage corresponding to the positive peak, and the second preset voltage is greater than or equal to the voltage corresponding to the negative peak.

[0136] In some embodiments of this application, the charging and discharging operation module 11 is further configured to determine, when the current charging rate and the current discharging rate are the same, that the current discharging duration is less than the current charging duration, and the current charging duration is less than or equal to a first preset duration; and when the current charging rate and the current discharging rate are different, that the product of the current discharging duration and the current discharging rate is less than the product of the current charging duration and the current charging rate, and the product of the current charging duration and the current charging rate is less than a first preset charge.

[0137] This application provides an apparatus for generating a solid electrolyte interface film, including a charge-discharge operation module for performing multiple charge-discharge operations on a battery cell when the voltage of the battery cell reaches a first preset voltage; and for obtaining a battery cell with a solid electrolyte interface film on the negative electrode interface when the voltage of the battery cell reaches a second preset voltage; wherein, the first preset voltage represents the voltage at which the film-forming reaction begins at the negative electrode interface of the battery cell; the charge-discharge operation includes a charging operation and a discharging operation, and the second preset voltage represents the voltage at which the film-forming reaction ends; each charge-discharge operation in the multiple charge-discharge operations is performed based on the voltage and charge in the previous charge-discharge operation; and a voltage detection module is used to detect the voltage of the battery cell in each charging or discharging operation. Therefore, the solid electrolyte interphase (SEI) film generation device mainly targets the stage from the beginning of SEI film formation (when the battery cell voltage reaches the first preset voltage) to the end of SEI film formation (when the voltage reaches the second preset voltage). Multiple charge-discharge operations are performed, and each operation can be based on the voltage and charge level of the previous operation. This allows for precise control of each operation, ensuring uniform distribution of film-forming additives in the electrolyte on the negative electrode graphite surface and promoting the timely migration of byproducts into the electrolyte phase. This improves the density and uniformity of the SEI layer, enhances the quality of the SEI film, and ultimately extends the lifespan of the battery cell.

[0138] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of hardware embodiments, software embodiments, or embodiments combining software and hardware aspects. Furthermore, this application can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage and optical storage) containing computer-usable program code.

[0139] This application is described with reference to schematic and / or block diagrams of implementations of methods, apparatus (systems), and computer program products according to embodiments of this application. It should be understood that each block of the schematic and / or block diagrams can be implemented by computer program instructions, and combinations of blocks in the schematic and / or block diagrams can be implemented. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create a machine for implementing the schematic and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0140] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in the implementation flow diagram. Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0141] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0142] The above embodiments are merely preferred embodiments provided to fully illustrate the present invention, and the scope of protection of the present invention is not limited thereto. Equivalent substitutions or modifications made by those skilled in the art based on the present invention are all within the scope of protection of the present invention.

Claims

1. A method for generating a solid electrolyte interfacial film, characterized in that, The method includes: When the voltage of a single battery cell reaches a first preset voltage, multiple charge-discharge operations are performed on the single battery cell; wherein, the first preset voltage represents the voltage at which the film-forming reaction begins at the negative electrode interface of the single battery cell; the charge-discharge operation includes a charging operation and a discharging operation. During each of the charging or discharging operations, the voltage of the individual battery cells is detected. When the voltage of the battery cell reaches a second preset voltage, the battery cell with a solid electrolyte interface film at the negative electrode interface is obtained; wherein, the second preset voltage characterizes the voltage at which the film formation reaction ends. The step of performing multiple charge-discharge operations on the battery cell includes: Based on the current discharge duration of the battery cell, a current charge / discharge operation is performed on the battery cell, and the current mapping relationship data of the battery cell in the current charge / discharge operation is obtained; wherein, the current mapping relationship data includes data on the mapping relationship between voltage and capacity of the battery cell in the current charge / discharge operation; The maximum value of the difference between the voltage corresponding to the charging operation and the voltage corresponding to the discharging operation in the current mapping relationship data is determined as the target voltage difference. The ratio of the current discharge duration to the target voltage difference is determined as the operation reference information; During the discharge operation in the next charge / discharge operation, a first voltage difference is determined based on the real-time voltage value of the next charge operation and the real-time voltage value of the next discharge operation. The ratio of the discharge duration data of the battery cell in the next discharge operation to the first voltage difference is used as the first operation information. If the first operation information is equal to the operation reference information, the next discharge operation is stopped to complete the next charge and discharge operation, until the multiple charge and discharge operations are completed.

2. The method for generating a solid electrolyte interface film according to claim 1, characterized in that, The step of performing a current charge / discharge operation on the battery cell based on the current discharge duration of the battery cell includes: The current charging operation is performed on the battery cell based on the current charging duration and the current charging rate. The current discharge operation is performed on the battery cell based on the current discharge duration and the current discharge rate.

3. The method for generating a solid electrolyte interface film according to claim 1 or 2, characterized in that, The method further includes: The differential capacitance curve data of the battery cell is processed by differential operation to obtain the second differential capacitance curve data; wherein, the differential capacitance curve data is data characterizing the mapping relationship between the differential capacitance and voltage of the battery cell; The first preset voltage and the second preset voltage are determined based on the positive and negative peak values ​​in the second differential capacitance curve data; wherein the first preset voltage is less than or equal to the voltage corresponding to the positive peak value, and the second preset voltage is greater than or equal to the voltage corresponding to the negative peak value.

4. The method for generating a solid electrolyte interface film according to claim 2, characterized in that, The method further includes: When the current charging rate is the same as the current discharging rate, it is determined that the current discharging duration is less than the current charging duration, the current charging duration is less than or equal to a first preset duration, and the current discharging duration is less than or equal to the difference between the current charging duration and a second preset duration. If the current charging rate is different from the current discharging rate, it is determined that the product of the current discharging duration and the current discharging rate is less than the product of the current charging duration and the current charging rate, and the product of the current charging duration and the current charging rate is less than the first preset power level.

5. An apparatus for generating a solid electrolyte interfacial film, characterized in that, include: A charge / discharge operation module is used to perform multiple charge / discharge operations on a battery cell when the voltage of the battery cell reaches a first preset voltage. And when the voltage of the battery cell reaches a second preset voltage, a battery cell with a solid electrolyte interface film at the negative electrode interface is obtained; wherein, the first preset voltage characterizes the voltage at which the film-forming reaction begins at the negative electrode interface of the battery cell; the charge-discharge operation includes a charging operation and a discharging operation, and the second preset voltage characterizes the voltage at which the film-forming reaction ends; A voltage detection module is used to detect the voltage of the battery cell during each charging or discharging operation. The charging and discharging operation module is further configured to perform a current charging and discharging operation on the battery cell based on the current discharge duration of the battery cell, and obtain the current mapping relationship data of the battery cell in the current charging and discharging operation; wherein, the current mapping relationship data includes data on the mapping relationship between voltage and capacity of the battery cell in the current charging and discharging operation; the maximum value of the difference between the voltage corresponding to the charging operation and the voltage corresponding to the discharging operation in the current mapping relationship data is determined as the target voltage difference; the ratio between the current discharge duration and the target voltage difference is determined as operation reference information; during the discharge operation in the next charging and discharging operation, a first voltage difference is determined based on the real-time voltage value of the next charging operation and the real-time voltage value of the next discharging operation; the ratio of the discharge duration data of the battery cell in the next discharge operation to the first voltage difference is used as first operation information, and when the first operation information is equal to the operation reference information, the next discharge operation is stopped to complete the next charging and discharging operation, until the multiple charging and discharging operations are completed.

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