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 a film-forming reaction begins at the negative electrode interface of a battery cell, a periodic processing procedure is performed on the battery cell until the film-forming reaction ends, resulting in a battery cell with a solid electrolyte interfacial film at the negative electrode interface. The periodic processing procedure includes multiple cycles, each cycle comprising a charging process and a resting process, with each resting process based on the previous resting process. Based on this approach, the quality and performance of the solid electrolyte interfacial film can be effectively improved.

Description

Technical Field

[0001] This application relates to the field of battery 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 methods for generating SEI films typically optimize the 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 quality of SEI films. Summary of the Invention

[0004] This application provides a method and apparatus for generating a solid electrolyte interface membrane, which can effectively improve the quality and performance of the solid electrolyte interface membrane.

[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 film-forming reaction begins at the negative electrode interface of the battery cell, a periodic processing procedure is performed on the battery cell until the film-forming reaction of the battery cell ends, resulting in a battery cell with a solid electrolyte interface film at the negative electrode interface.

[0008] The periodic processing flow includes multiple periodic processes. Each periodic process includes a charging process and a resting process. Each resting process is executed based on the previous resting process.

[0009] In this embodiment, a periodic processing flow is initiated when the film-forming reaction begins at the negative electrode interface of the battery cell. Alternating charging and resting processes are performed on the battery cell, and each resting process is based on the previous resting process. That is, the execution of the resting process in the next cycle can be determined based on the current resting process. This process continues until the film-forming reaction ends, thereby ensuring that the formation process of the solid electrolyte interface film is controllable and sufficient, improving the quality of the solid electrolyte interface film, and improving battery life.

[0010] In some embodiments of this application, a periodic processing procedure is performed on individual battery cells, including:

[0011] During the current cycle processing, the voltage change data of the battery cells during the current resting process is acquired; the voltage change data is used to determine the relationship between the voltage of the battery cells and time; the current resting process is the resting process in the current cycle processing.

[0012] The next resting process in the next cycle is executed based on the voltage change data;

[0013] Based on the voltage change data of the next resting process, the first resting process in the first cycle after the next cycle processing is executed until the cycle processing flow is completed.

[0014] In this embodiment, by collecting and analyzing the voltage change data of the resting process in each cycle, the resting process in the subsequent cycle is executed, realizing dynamic decision-making for the resting process in each cycle, so that each cycle process is conducive to the formation of solid electrolyte interfacial film, thereby improving the stability and efficiency of the film formation process, reducing the accumulation of by-reactants, and optimizing the structure of solid electrolyte interfacial film.

[0015] In some embodiments of this application, performing the next resting process in the next cycle processing based on voltage change data includes:

[0016] The time variable of the voltage change data is mathematically transformed to obtain the transformed voltage change data.

[0017] The converted voltage change data is linearly fitted to determine the current equilibrium voltage.

[0018] The first target information is determined based on the current equilibrium voltage, and the next settling process is executed according to the first target information.

[0019] In this embodiment, by mathematically transforming the time variable of the voltage change curve, the transformed voltage change data is obtained. The transformed voltage change data is then linearly fitted to extract the equilibrium voltage reflecting the internal state of the battery. Based on this, a reasonable settling strategy is determined to obtain the first target information. Subsequently, the settling process in the next cycle is executed according to the first target information, which can make the additives and by-products more evenly distributed, enhance the concentration driving effect, and further improve the density and uniformity of the solid electrolyte interface film.

[0020] In some embodiments of this application, determining the first target information based on the current equilibrium voltage includes:

[0021] Obtain the current initial voltage of a single battery cell at the start of the current resting process;

[0022] The current internal resistance information is determined based on the difference between the current initial voltage and the current equilibrium voltage, as well as the current charging current.

[0023] The ratio of the current settling time to the current internal resistance information is determined as the first target information; where the current settling time is the duration of the current settling process.

[0024] In this embodiment, the internal resistance information is calculated by combining the voltage difference between the current initial voltage and the current equilibrium voltage and the charging current, and then linked to the resting time. The ratio of the current resting time to the current internal resistance information is determined as the first target information to obtain a scientific resting reference basis, making each resting process more accurate, which helps to promote the stable formation of the solid electrolyte interface film and reduce the problem of uneven film layer caused by too short or too long resting.

[0025] In some embodiments of this application, performing the next settling process according to the first target information includes:

[0026] During the execution of the next settling process, the duration of the next settling process and real-time voltage data are obtained;

[0027] The second target information is determined based on real-time voltage data and duration.

[0028] If the second target information is equal to the first target information, stop the next settling process.

[0029] In this embodiment, by monitoring the voltage and duration of the resting process in real time, the second target information is calculated using the real-time voltage data and duration. The termination condition is dynamically determined based on the second target information, i.e., whether the second target information is equal to the first target information. This allows for precise control of the operation at each stage, avoiding adverse effects from excessive resting or premature termination, and ensuring that the optimal conditions for the formation of the solid electrolyte interface film are maintained.

[0030] In some embodiments of this application, the method further includes:

[0031] The charging time and the resting time are constrained in each cycle according to the preset duration constraint strategy.

[0032] The preset duration constraint strategy is used to constrain the charging duration to be greater than or equal to the first preset duration, the resting duration to be greater than or equal to the charging duration, and the product of the charging duration and the charging rate during the charging process to be less than or equal to the first preset capacity.

[0033] In this embodiment, by setting a preset duration constraint strategy, the charging time, resting time and charging rate in each cycle are constrained, so that the energy input of each operation is controllable, while ensuring sufficient time for the additive to diffuse to the graphite surface, which is conducive to the uniform growth of the solid electrolyte interface film and improves the film quality.

[0034] In some embodiments of this application, the method further includes:

[0035] Detect the voltage of individual battery cells;

[0036] The film formation reaction is initiated when the voltage of a single battery cell reaches the first voltage.

[0037] The film formation reaction is considered complete when the voltage of a single cell reaches the second voltage; the first voltage is less than the second voltage.

[0038] In this embodiment, the voltage of a single battery cell can be detected, and the initiation of the film-forming reaction can be determined by the real-time voltage of the battery cell, thereby achieving precise control of the solid electrolyte interface film formation process.

[0039] Secondly, embodiments of this application provide an apparatus for generating a solid electrolyte interface film, comprising:

[0040] The periodic processing module is used to perform a periodic processing on the battery cell when the film formation reaction begins at the negative electrode interface of the battery cell, until the film formation reaction of the battery cell ends, and obtain a battery cell with a solid electrolyte interface film at the negative electrode interface.

[0041] The periodic processing flow includes multiple periodic processes. Each periodic process includes a charging process and a resting process. Each resting process is executed based on the previous resting process.

[0042] In this embodiment, a periodic processing flow is initiated when the film-forming reaction begins at the negative electrode interface of the battery cell. Alternating charging and resting processes are performed on the battery cell, and each resting process is based on the previous resting process. That is, the execution of the resting process in the next cycle can be determined based on the current resting process. This process continues until the film-forming reaction ends, thereby ensuring that the formation process of the solid electrolyte interface film is controllable and sufficient, improving the quality of the solid electrolyte interface film, and improving battery life.

[0043] In some embodiments of this application, the periodic processing module is further configured to: acquire voltage change data of a battery cell during the current resting process during the execution of the current periodic processing; execute the next resting process in the next periodic processing based on the voltage change data; and execute the first resting process in the first periodic processing after the next periodic processing based on the voltage change data of the next resting process, until the periodic processing is completed; wherein, the voltage change data is used to determine the relationship between the voltage of the battery cell and time; and the current resting process is the resting process in the current periodic processing.

[0044] In this embodiment, by collecting and analyzing the voltage change data of the resting process in each cycle, the resting process in the subsequent cycle is executed, realizing dynamic decision-making for the resting process in each cycle, so that each cycle process is conducive to the formation of solid electrolyte interfacial film, thereby improving the stability and efficiency of the film formation process, reducing the accumulation of by-reactants, and optimizing the structure of solid electrolyte interfacial film.

[0045] In some embodiments of this application, the periodic processing module is further configured to perform mathematical transformation on the time variable of voltage change data to obtain transformed voltage change data; perform linear fitting processing on the transformed voltage change data to determine the current equilibrium voltage; and determine first target information based on the current equilibrium voltage, and execute the next resting process according to the first target information.

[0046] In this embodiment, by mathematically transforming the time variable of the voltage change curve, the transformed voltage change data is obtained. The transformed voltage change data is then linearly fitted to extract the equilibrium voltage reflecting the internal state of the battery. Based on this, a reasonable settling strategy is determined to obtain the first target information. Subsequently, the settling process in the next cycle is executed according to the first target information, which can make the additives and by-products more evenly distributed, enhance the concentration driving effect, and further improve the density and uniformity of the solid electrolyte interface film. Attached Figure Description

[0047] 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.

[0048] Figure 1 This is a schematic diagram of the film-forming reaction;

[0049] 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;

[0050] Figure 3This is a schematic diagram of voltage changes in the periodic processing flow proposed in the embodiments of this application;

[0051] Figure 4 This is a schematic diagram of voltage changes during the film formation process in the chemical formation process;

[0052] Figure 5 This is a schematic diagram of voltage changes during the film formation process as described in the embodiments of this application;

[0053] Figure 6 This is a schematic diagram of the differential capacitance curve proposed in the embodiments of this application;

[0054] Figure 7 This is a schematic diagram of the second-order differential capacitance curve proposed in the embodiments of this application;

[0055] Figure 8 This is a schematic diagram of the converted voltage change data proposed in the embodiments of this application;

[0056] Figure 9 This is a schematic diagram illustrating the linear fitting of the converted voltage change data according to an embodiment of this application;

[0057] Figure 10 This is a schematic diagram of the voltage difference change in the periodic processing flow proposed in the embodiments of this application;

[0058] Figure 11 This is a schematic diagram of the internal resistance change in the periodic processing flow proposed in the embodiments of this application;

[0059] Figure 12 This is a schematic diagram illustrating the test results of the charge-discharge cycle test proposed in the embodiments of this application;

[0060] Figure 13 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

[0061] 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.

[0062] During the first charge, the negative electrode material of a lithium-ion battery undergoes a side reaction with the electrolyte, forming an SEI film. For example... Figure 1As 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 Layer) occurs. When the electrolyte contains film-forming additives, these additives preferentially participate in the film-forming reaction, forming the SEI layer and other byproducts. The quality of the SEI film directly affects the battery's cycle performance and lifespan. However, current constant-current formation strategies struggle to effectively control the uniformity and density of the SEI film, leading to uneven distribution of electrolyte additives and accumulation of byproducts, thereby reducing the overall stability of the SEI film.

[0063] To address the aforementioned issues, this application provides a method for generating a solid electrolyte interphase (SEI) film. The SEI film generation apparatus introduces a periodic processing step during the SEI film formation stage. Utilizing the concentration polarization driving principle, it promotes the uniform distribution of additives in the electrolyte on the graphite anode surface and accelerates the diffusion of byproducts into the electrolyte phase, reducing their interference with the SEI film structure. By detecting the voltage during each cycle and determining whether film formation is complete based on the voltage, precise control of the SEI film generation process is achieved. Ultimately, while ensuring film quality, this significantly improves the lifespan and electrochemical performance of the lithium-ion battery.

[0064] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings.

[0065] 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:

[0066] Step 101: When the film-forming reaction begins at the negative electrode interface of the battery cell, perform a periodic processing procedure on the battery cell until the film-forming reaction of the battery cell ends, and obtain a battery cell with a solid electrolyte interface film at the negative electrode interface; wherein, the periodic processing procedure includes multiple periodic processing, each periodic processing includes one charging process and one resting process, and each resting process is performed based on the previous resting process.

[0067] In the embodiments of this application, the solid electrolyte interface film generation device can perform a periodic processing procedure on the battery cell when the film formation reaction begins at the negative electrode interface of the battery cell, until the film formation reaction of the battery cell ends, to obtain a battery cell with a solid electrolyte interface film at the negative electrode interface; wherein, the periodic processing procedure includes multiple periodic processing, each periodic processing includes a charging process and a resting process, and each resting process is performed based on the previous resting process.

[0068] In the embodiments of this application, the charging process refers to applying a current of a certain rate to a battery cell, thereby causing an electrochemical reaction to occur inside the battery cell and continuing continuously. The charging process can be achieved through constant current charging (CC) or constant voltage charging (CV). The resting process refers to stopping the charging of the battery cell, thereby allowing the molecules inside the battery cell to tend to equilibrium and promoting the uniform distribution of additives on the surface of the negative electrode material. Compared with the constant current charging method of current formation technology, the periodic processing process can more effectively control the film formation process, prevent the accumulation of by-products due to local high concentration, and thus reduce the adverse effects of by-product accumulation on the quality of the solid electrolyte interface film.

[0069] 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.

[0070] 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.

[0071] In some embodiments of this application, when the battery cell enters the solid electrolyte interface film formation stage, the solid electrolyte interface film generation device can record and adjust the resting time in each cycle.

[0072] In some embodiments of this application, when the solid electrolyte interface film generation device performs a periodic processing flow on a battery cell, it can acquire voltage change data of the battery cell during the current resting process during the current periodic processing. The voltage change data is used to determine the relationship between the voltage of the battery cell and time. The current resting process is the resting process in the current periodic processing. The next resting process in the next periodic processing is executed based on the voltage change data. The first resting process in the first periodic processing after the next periodic processing is executed based on the voltage change data of the next resting process, until the periodic processing flow is completed.

[0073] In the embodiments of this application, voltage change data can reflect the dynamic response of the internal electrochemical reaction process of the battery, especially the polarization phenomenon when the solid electrolyte interface film is formed.

[0074] It is understandable that the first cycle processing refers to the next cycle processing after the next cycle processing is completed, and the first static process is the static process in the first cycle processing.

[0075] In some embodiments of this application, when the solid electrolyte interface membrane generation device performs the next settling process in the next cycle processing based on the voltage change data, it can perform mathematical transformation on the time variable of the voltage change data to obtain the transformed voltage change data; perform linear fitting processing on the transformed voltage change data to determine the current equilibrium voltage; determine the first target information based on the current equilibrium voltage, and perform the next settling process according to the first target information.

[0076] In some embodiments of this application, linear fitting is a mathematical method that removes noise interference by performing regression analysis on voltage change data and constructs a straight line or smooth curve that is as close as possible to the actual trend, thereby revealing the trend of voltage change more clearly.

[0077] For example, such as Figure 3 As shown, in a certain cycle, the charging process is executed first, followed by the resting process. As the charging process is executed, the voltage gradually increases, and then the voltage gradually decreases during the resting process.

[0078] In some embodiments of this application, when performing mathematical transformation on the time variable of voltage change data, specifically, mathematical transformation can be performed on the time variable of the voltage change curve corresponding to the resting process in the voltage change data.

[0079] For example, the voltage change curve during the resting process in a certain cycle is a curve showing the mapping relationship between voltage (V) and time (T). By mathematically transforming the time variable T, time is converted into... The resulting converted voltage change data is voltage versus time. The curve between; and then by analyzing the relationship between voltage and time A linear fit is performed on the curve between the two values, and the intercept of this curve is the final equilibrium voltage, which is also the current equilibrium voltage.

[0080] In some embodiments of this application, the next settling process is executed according to the first target information, which mainly determines the timing of the end of the next settling process based on the first target information.

[0081] In some embodiments of this application, when the solid electrolyte interface film generation device determines the first target information based on the current equilibrium voltage, it can obtain the current initial voltage of the battery cell at the start of the current resting process; determine the current internal resistance information based on the difference between the current initial voltage and the current equilibrium voltage, and the current charging current; and then determine the ratio of the current resting time to the current internal resistance information as the first target information; wherein, the current resting time is the duration of the current resting process.

[0082] In some embodiments of this application, the current initial voltage refers to the voltage of a single cell measured at the start of the current resting process in the current cycle processing. This voltage reflects the initial conditions of the internal electrochemical state of the single cell at the start of the resting process.

[0083] In some embodiments of this application, the current charging current refers to the charging current corresponding to the charging process in the current periodic processing flow.

[0084] In some embodiments of this application, when determining the current internal resistance information based on the difference between the current initial voltage and the current equilibrium voltage, and the current charging current, the ratio of the difference between the current initial voltage and the current equilibrium voltage to the current charging current can be used to determine the current internal resistance information.

[0085] For example, assuming the current process is the nth cycle, the current initial voltage is expressed as: The current equilibrium voltage is expressed as The current charging current is The difference between the current initial voltage and the current equilibrium voltage can then be expressed as: The current internal resistance information can be expressed as .

[0086] In some embodiments of this application, when the solid electrolyte interface membrane generation device performs the next settling process according to the first target information, it can acquire the duration and real-time voltage data of the next settling process during the execution of the next settling process; then determine the second target information based on the real-time voltage data and the duration, and stop the next settling process when the second target information is equal to the first target information.

[0087] In some embodiments of this application, the real-time voltage data includes the initial voltage value of a single battery cell measured at the start of the resting process in the next cycle processing, and also includes the voltage value at each time point during the continuous real-time process of the subsequent resting process.

[0088] Understandably, the duration of the next settling process represents the total duration of the settling process up to now during the execution of the next settling process.

[0089] For example, assuming the current process is the (n-1)th periodic processing flow, the first target information can be represented as: Therefore, when executing the next cycle, i.e., the nth cycle, assuming the nth charging process is executed first and then the nth resting process begins, the real-time voltage data and duration of the nth resting process can be obtained. Then, using the real-time voltage data and the charging current during the nth charging process, the internal resistance value of the battery cell corresponding to the nth cycle can be calculated. This allows us to utilize the internal resistance value and the duration of the current record. Real-time calculation of second target information ,when When the time is up, stop the settling process, thus completing the nth cycle of processing.

[0090] In some embodiments of this application, when determining the first target information based on the current equilibrium voltage, the first target information can also be determined based on the difference between the current initial voltage and the current equilibrium voltage, and the current resting time.

[0091] For example, in the current n-1th periodic processing flow, the voltage difference between the current initial voltage and the current equilibrium voltage can be expressed as: The current resting time is expressed as If the ratio between the current resting time and the voltage difference is determined as the first target information, then the first target information can be expressed as: .

[0092] In some embodiments of this application, when performing the next settling process, when determining the second target information based on real-time voltage data and duration, the initial voltage value in the real-time voltage data and the voltage value at each time point during the real-time process of the settling process can be directly used to calculate the real-time voltage difference, and the second target information can be calculated using the duration and the real-time voltage difference.

[0093] For example, assuming the current process is the (n-1)th periodic processing flow, the first target information can be represented as: Therefore, when executing the next periodic processing flow, i.e., the nth periodic processing flow, assuming the nth charging process is executed first and then the nth resting process begins, the real-time voltage data of the nth resting process can be obtained, and the real-time voltage difference can be determined using the real-time voltage data. Simultaneously record duration Thus, the information of the second target can be calculated in real time. ,when When the time is up, stop the settling process, thus completing the nth cycle of processing.

[0094] In some embodiments of this application, the solid electrolyte interface film generation device can also constrain the charging time of the charging process and the resting time of the resting process in each cycle processing according to a preset duration constraint strategy; wherein, the preset duration constraint strategy is used to constrain the charging time to be greater than or equal to a first preset duration, the resting time to be greater than or equal to the charging time, and the product of the charging time and the charging rate of the charging process to be less than or equal to a first preset amount of electricity.

[0095] In some embodiments of this application, when the solid electrolyte interface film generation device performs the current cycle processing on a battery cell based on the current resting time, it can perform the current charging process on the battery cell based on the current charging time and the current charging rate; and then perform the current resting process on the battery cell based on the current resting time.

[0096] In some embodiments of this application, the current charging rate refers to the ratio of the current used during the current charging cycle to the battery's rated capacity (Ah). For example, performing a charging process at a current charging rate of 0.05C means charging at 5% of the battery's rated capacity; the current charging duration refers to the length of time the charging process continues at a specific charging rate.

[0097] For example, the first preset duration is 1 second, the first preset charge can be 0.04% SOC, and assuming the current charging duration is represented by T1, the current resting duration is represented by T2, and the current charging rate is represented by C1, then the relationship that the current charging duration and the current resting duration need to satisfy can be expressed as: T2≥T1≥1s, and T1×C1≤0.04%SOC.

[0098] In some embodiments of this application, the number of cycles included in the periodic processing flow can be determined based on the current charging time, the current charging rate, and the second preset power level.

[0099] For example, the second preset battery level is 8% SOC. Assuming the current charging time is represented as T1, the current charging rate is represented as C1, and the number of times the periodic processing flow is executed is N, then the method of determining the number of times the periodic processing flow is executed based on the current charging time, the current charging rate, and the second preset battery level can be expressed as T1×C1×N≥8%SOC.

[0100] In some embodiments of this application, the method for generating a solid electrolyte interface film may further include the following steps:

[0101] Step 102: Detect the voltage of the individual battery cells.

[0102] In the embodiments of this application, the apparatus for generating a solid electrolyte interface film can detect the voltage of a single battery cell.

[0103] 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.

[0104] In the embodiments of this application, the voltage of the battery cell needs to be monitored in real time during each cycle 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.

[0105] Step 103: In response to the voltage of the battery cell reaching the first voltage, the film formation reaction is initiated.

[0106] Step 104: In response to the voltage of the battery cell reaching the second voltage, the film formation reaction is determined to be complete.

[0107] In embodiments of this application, the first voltage may be less than the second voltage.

[0108] In the embodiments of this application, the first voltage and the second voltage are specific voltage values ​​set according to the electrochemical behavior of the battery cell during the SEI film formation process, and are used to determine the start and end stages of the film formation reaction; wherein, the first voltage characterizes the voltage at which the film formation reaction begins at the negative electrode interface, and the second voltage characterizes the voltage at which the film formation reaction ends.

[0109] In some embodiments of this application, the first 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.

[0110] In the embodiments of this application, the solid electrolyte interface film generation device determines that the film formation reaction has ended when the voltage of the battery cell reaches a second voltage during the process of detecting the voltage of the battery cell, and a battery cell with a solid electrolyte interface film on the negative electrode interface can be obtained; wherein, the second voltage characterizes the voltage corresponding to the end of the film formation reaction.

[0111] In some embodiments of this application, the second voltage may be 2.7V.

[0112] 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 4As 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.

[0113] In some embodiments of this application, the solid electrolyte interface film generation device can also 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 differential capacitance and electrode potential; then, a first voltage and a second voltage are determined based on the positive peak and negative peak in the secondary differential capacitance curve relationship data; wherein, the first voltage is less than or equal to the potential corresponding to the positive peak, and the second voltage is greater than or equal to the potential corresponding to the negative peak.

[0114] 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 7 As shown, two peak potentials can be obtained from the data of the second differential capacitance curve, including the voltage corresponding to the positive peak and the voltage corresponding to the negative peak. Then, the first voltage V1 can be less than or equal to the voltage corresponding to the positive peak, and the second voltage V2 can be greater than or equal to the voltage corresponding to the negative peak.

[0115] In some embodiments of this application, before the cell begins the film-forming reaction, that is, before the cell voltage reaches the first voltage, the cell can be charged to bring the cell voltage to the first voltage. This application does not limit the charging method of this charging process. For example, the cell voltage can be charged to the first voltage by constant current charging.

[0116] In some embodiments of this application, after the voltage of a single battery cell reaches a second voltage through multiple cycles of processing, that is, 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, that is, the battery SOC, and has a low impact on the solid electrolyte interface film.

[0117] This application provides a method for generating a solid electrolyte interfacial film. The solid electrolyte interfacial film generation apparatus performs a periodic processing procedure on the battery cell when the film-forming reaction begins at the negative electrode interface, until the film-forming reaction ends, resulting in a battery cell with a solid electrolyte interfacial film at the negative electrode interface. The periodic processing procedure includes multiple cycles, each cycle comprising a charging process and a resting process, with each resting process based on the previous one. Therefore, by initiating the periodic processing procedure when the film-forming reaction begins at the negative electrode interface of the battery cell, alternating charging and resting processes are performed on the battery cell, and each resting process is based on the previous one. This means the execution of the resting process in the next cycle can be determined based on the current resting process, and this process continues until the film-forming reaction ends, thereby ensuring that the formation process of the solid electrolyte interfacial film is controllable and sufficient, improving the quality of the solid electrolyte interfacial film, and extending battery life.

[0118] Based on the above embodiments, in another embodiment of this application, for example, in the SEI film formation stage, by performing multiple cycle processes, 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.

[0119] 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 cycle processing is performed for the film formation stage to generate a good solid electrolyte interface film on the negative electrode interface of the battery cell.

[0120] 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 of time, they can be rested again or charged to reach the shipment capacity. During this process, the SEI film of the battery cells has already formed. The formation process of this application can include: first, after resting the battery cells for 30 seconds, charging the battery cells 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 short resting time of 30 seconds, multiple cycles can be started. The process involves a charging process and a resting process in each cycle. The charging process is carried out at a charging rate of 0.05C for T1s, and the resting time is T2s. Multiple cycles are performed alternately and repeatedly, until the voltage reaches V2, which is the voltage corresponding to the end of the film formation reaction, and the formation of the SEI film is confirmed. 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.

[0121] 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.

[0122] 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.

[0123] In some embodiments of this application, for the setting of some parameters in the periodic processing flow, assuming the current charging time is represented as T1, the current resting time as T2, and the current charging rate as C1, the relationship that the current charging time and the current resting time need to satisfy can be expressed as: T2≥T1≥1s, and T1×C1≤0.04%SOC; in addition, assuming that the number of times the periodic processing is executed in the periodic processing flow is N, then N needs to satisfy T1×C1×N≥8%SOC.

[0124] 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 scheme focuses on the film formation stage, using an alternating charging and resting strategy to make the additives more evenly distributed on the graphite surface of the negative electrode; due to the alternating charging and resting strategy, the voltage exhibits a spiral increasing trend, as shown... Figure 5As shown, this can help to better form the SEI layer.

[0125] In some embodiments of this application, during the film-forming stage, the planned impedance gradually increases with the increase in the degree of SEI film formation, thus requiring a longer settling time to allow the additive to be evenly distributed on the graphite surface. Therefore, to more accurately determine the settling time in each cycle, a valid voltage data point can be recorded every second during the execution of each cycle, as described above. Figure 3 As shown, during a certain cycle, the voltage gradually increases as the charging process proceeds and gradually decreases as the resting process proceeds. The voltage curve during the resting phase in each cycle, i.e., the time variable T of the voltage versus time curve during each resting phase, can be mathematically transformed to convert time T into... ,like Figure 8 As shown, voltage and time are obtained. The curve between, time is And by analyzing voltage and time Linear fitting is performed on the curves between them, such as... Figure 9 As shown, the intercept of the curve is the final equilibrium voltage Vt, which is the current equilibrium voltage.

[0126] For example, assuming the current processing cycle is n, the current initial voltage is expressed as: The current equilibrium voltage is expressed as The current charging current is The difference between the current initial voltage and the current equilibrium voltage can then be expressed as: The current internal resistance information can be expressed as .

[0127] For example, such as Figure 10 As shown, the voltage difference changes with the increase of the number of pulses (i.e., the number of times the cycle is processed). Meanwhile, as... Figure 11 As shown, the internal resistance changes with the increase of the number of pulses; the higher the internal resistance, the longer the resting time required for each process, and vice versa; the resting time needs to meet the following requirements. or ,in, This represents the internal resistance value corresponding to the nth cycle processing. Let be the duration of the resting process in the nth cycle. This represents the internal resistance value of the corresponding process in the n-1th cycle. This represents the duration of the resting process in the n-1th cycle.

[0128] For example, for mass-produced battery cells, a fixed shipment capacity is generally required. Therefore, after film formation, 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 cycle processing can be performed to charge the battery cell to the required shipment capacity or voltage.

[0129] Table 1

[0130]

[0131] 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 process 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.

[0132] For example, considering the timeliness of the solution, in actual production, the lithium-ion battery cells after electrolyte injection can be subjected to high-temperature immersion at 45℃~55℃ for 20~30 hours. After the electrolyte has fully immersed the positive and negative electrode plates in the battery cells, the first charging formation of the lithium-ion battery cells is carried out at a formation temperature of 45~55℃. By evacuating the lithium-ion battery cells and maintaining a negative pressure state throughout the process, the gas generated by the SEI film formation side reaction is promoted to be discharged in a timely manner. Table 2 below shows the formation process in a practical application scenario:

[0133] Table 2

[0134]

[0135] In some embodiments of this application, as described above Figure 5 As shown, due to multiple cycle processing, when the voltage reaches the second voltage, for example 2.5V, the concentration of additives and by-reactants diffuses during the SEI film formation process, resulting in a significant decrease in the voltage relaxation process. Therefore, it can be seen that the present application can achieve the same formation improvement effect as stopping formation when the voltage reaches the second voltage by stopping the operation when the voltage reaches 3.0V.

[0136] 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 testing. The improvement group is the periodic processing strategy of this application, and the base group is the current constant current discharge formation process. The cycle strategy can be shown in Table 3 below:

[0137] Table 3

[0138]

[0139] For example, such as Figure 12 As shown, a 1C charge-discharge cycle test was conducted at 45°C. It was determined that, compared to the current constant-current charging benchmark cells, the cells obtained by using the alternating charge-discharge strategy of this application (i.e., the improved group) exhibit a higher quality SEI layer. This results in more stable SEI film performance during cycling, leading to slower capacity decay. At the 50th cycle, the benchmark group maintained a capacity retention rate of 95.9%, while the improved group maintained 96.2%, representing a 0.3% improvement. Compared to current methods that improve SEI film quality through graphite enhancement (e.g., low-lithium-consumption graphite) or additive enhancement (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 benchmark and improved group batteries were identical; the only difference was that this application employed a periodic processing procedure during the film formation stage, resulting in a significant improvement in battery life.

[0140] This application provides a method for generating a solid electrolyte interfacial film. The solid electrolyte interfacial film generation apparatus performs a periodic processing procedure on the battery cell when the film-forming reaction begins at the negative electrode interface, until the film-forming reaction ends, resulting in a battery cell with a solid electrolyte interfacial film at the negative electrode interface. The periodic processing procedure includes multiple cycles, each cycle comprising a charging process and a resting process. Therefore, by initiating the periodic processing procedure when the film-forming reaction begins at the negative electrode interface of the battery cell, alternating charging and resting processes are performed on the battery cell. Each resting process is based on the previous resting process, meaning the execution of the resting process in the next cycle can be determined based on the current resting process. This process continues until the film-forming reaction ends, ensuring that the formation process of the solid electrolyte interfacial film is controllable and sufficient, improving the quality of the solid electrolyte interfacial film, and extending battery life.

[0141] 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 13 As shown, the solid electrolyte interface film generation device 1 may include a periodic processing module 11 and a voltage detection module 12.

[0142] The periodic processing module 11 is used to perform a periodic processing on the battery cell when the film formation reaction begins at the negative electrode interface of the battery cell, until the film formation reaction of the battery cell ends, to obtain a battery cell with a solid electrolyte interface film at the negative electrode interface; wherein, the periodic processing includes multiple periodic processing, each periodic processing includes a charging process and a resting process, and each resting process is performed based on the previous resting process.

[0143] In some embodiments of this application, the periodic processing module 11 is further configured to acquire voltage change data of a battery cell during the current resting process while performing the current periodic processing; wherein the voltage change data is used to determine the relationship between the voltage of the battery cell and time; the current resting process is the resting process in the current periodic processing; the next resting process in the next periodic processing is executed based on the voltage change data; the first resting process in the first periodic processing after the next periodic processing is executed based on the voltage change data of the next resting process, until the periodic processing is completed.

[0144] In some embodiments of this application, the periodic processing module 11 is further used to perform mathematical transformation on the time variable of voltage change data to obtain transformed voltage change data; perform linear fitting processing on the transformed voltage change data to determine the current equilibrium voltage; determine the first target information based on the current equilibrium voltage, and execute the next resting process according to the first target information.

[0145] In some embodiments of this application, the periodic processing module 11 is further configured to obtain the current initial voltage of the battery cell at the start of the current resting process; determine the current internal resistance information based on the difference between the current initial voltage and the current equilibrium voltage, and the current charging current; and determine the ratio of the current resting duration to the current internal resistance information as the first target information; wherein the current resting duration is the duration of the current resting process.

[0146] In some embodiments of this application, the periodic processing module 11 is further configured to, during the execution of the next resting process, acquire the duration and real-time voltage data of the next resting process; determine second target information based on the real-time voltage data and duration; and stop the next resting process if the second target information is equal to the first target information.

[0147] In some embodiments of this application, the periodic processing module 11 is further configured to constrain the charging duration of the charging process and the resting duration of the resting process in each periodic processing according to a preset duration constraint strategy; wherein, the preset duration constraint strategy is configured to constrain the charging duration to be greater than or equal to a first preset duration, the resting duration to be greater than or equal to the charging duration, and the product of the charging duration and the charging rate of the charging process to be less than or equal to a first preset power.

[0148] The voltage detection module 12 is used to detect the voltage of the battery cell during each charging process or resting process, and to determine the start of the film formation reaction when the voltage of the battery cell reaches a first voltage; and to determine the end of the film formation reaction when the voltage of the battery cell reaches a second voltage; and the first voltage is less than the second voltage.

[0149] This application provides an apparatus for generating a solid electrolyte interfacial film, including a periodic processing module. This module performs a periodic processing procedure on the battery cell when a film-forming reaction begins at the negative electrode interface, continuing until the film-forming reaction ends, resulting in a battery cell with a solid electrolyte interfacial film at the negative electrode interface. The periodic processing procedure includes multiple cycles, each cycle comprising a charging process and a resting process, with each resting process based on the previous one. Therefore, by initiating the periodic processing procedure when the film-forming reaction begins at the negative electrode interface of the battery cell, alternating charging and resting processes are performed on the battery cell. Each resting process is based on the previous one, meaning the execution of the resting process in the next cycle can be determined based on the current resting process. This process continues until the film-forming reaction ends, ensuring that the formation of the solid electrolyte interfacial film is controllable and sufficient, improving the quality of the solid electrolyte interfacial film, and extending battery life.

[0150] Furthermore, in this embodiment, the functional modules can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional module.

[0151] If the integrated unit is implemented as a software functional module and is not sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this embodiment, in essence, or the part that contributes to the prior art, or all or part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) or processor to execute all or part of the steps of the method of this embodiment. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0152] 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.

[0153] 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.

[0154] 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.

[0155] 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.

[0156] 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 a film-forming reaction begins at the negative electrode interface of a battery cell, a periodic processing procedure is performed on the battery cell until the film-forming reaction of the battery cell ends, resulting in a battery cell with a solid electrolyte interface film at the negative electrode interface; wherein, the periodic processing procedure includes multiple periodic processes, each of which includes one charging process and one resting process. Regarding the current static process in the current cycle of the multiple cycle processes: The time variable of the voltage change data during the current resting process is mathematically transformed to obtain the transformed voltage change data; the voltage change data is used to determine the relationship between the voltage of the battery cell and time. The current equilibrium voltage is determined by performing linear fitting on the converted voltage change data; Obtain the current initial voltage of the battery cell at the start of the current resting process; The ratio of the difference between the current initial voltage and the current equilibrium voltage to the current charging current is used as the current internal resistance information; The ratio of the current resting time to the current internal resistance information is used as the first target information; wherein, the current resting time is the duration of the current resting process; During the next settling process, the second target information is determined based on the real-time voltage data of the next settling process and the duration of the next settling process. The next settling process is stopped if the second target information is equal to the first target information.

2. The method for generating a solid electrolyte interface film according to claim 1, characterized in that, The periodic processing procedure for the battery cell includes: Based on the voltage change data of the next resting process, the first resting process in the first cycle after the next cycle processing is executed until the cycle processing flow is completed.

3. The method for generating a solid electrolyte interface film according to claim 1 or 2, characterized in that, The method further includes: According to the preset duration constraint strategy, the charging duration of the charging process and the resting duration of the resting process are constrained in each cycle of processing. The preset duration constraint strategy is used to constrain the charging duration to be greater than or equal to a first preset duration, the resting duration to be greater than or equal to the charging duration, and the product of the charging duration and the charging rate of the charging process to be less than or equal to a first preset power.

4. The method for generating a solid electrolyte interface film according to claim 1 or 2, characterized in that, The method further includes: Detect the voltage of the individual battery cells; In response to the voltage of the battery cell reaching a first voltage, the film formation reaction is determined to begin; The film-forming reaction is determined to be complete when the voltage of the battery cell reaches the second voltage; the first voltage is less than the second voltage.

5. An apparatus for generating a solid electrolyte interfacial film, characterized in that, include: A periodic processing module is used to perform a periodic processing procedure on a battery cell when a film-forming reaction begins at the negative electrode interface of the battery cell, until the film-forming reaction of the battery cell ends, to obtain a battery cell with a solid electrolyte interface film at the negative electrode interface; wherein, the periodic processing procedure includes multiple periodic processes, and each periodic process includes one charging process and one resting process. Regarding the current static process in the current cycle of the multiple cycle processes: The periodic processing module is further used to perform mathematical transformation on the time variable of the voltage change data during the current resting process to obtain the transformed voltage change data; perform linear fitting processing on the transformed voltage change data to determine the current equilibrium voltage; obtain the current initial voltage of the battery cell at the start of the current resting process; use the ratio of the difference between the current initial voltage and the current equilibrium voltage to the current charging current as the current internal resistance information; use the ratio of the current resting duration to the current internal resistance information as the first target information; in the next resting process, determine the second target information based on the real-time voltage data and the duration of the next resting process; stop the next resting process if the second target information is equal to the first target information; wherein, the voltage change data is used to determine the relationship between the voltage of the battery cell and time; the current resting duration is the duration of the current resting process.

6. The apparatus for generating a solid electrolyte interface film according to claim 5, characterized in that, The periodic processing module is also used to execute the first resting process in the first periodic processing after the next periodic processing based on the voltage change data of the next resting process, until the periodic processing is completed.

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