A method and system for evaluating stability of SEI film formation in lithium battery formation

Abstract

The application provides a lithium battery formation SEI film stability evaluation method and system, wherein the method comprises the following steps: obtaining a curve of voltage differential capacity of the lithium battery in a formation process varying with voltage as a first curve; obtaining a voltage corresponding to an SEI film formation peak in the first curve as a film formation voltage; after a first target number of charge and discharge cycles of the lithium battery after formation, discharging the lithium battery to a voltage less than the film formation voltage as a first discharging process; charging the lithium battery after the first discharging process to a voltage greater than the film formation voltage as a first charging process; obtaining a curve of voltage differential capacity of the lithium battery in the first charging process varying with voltage as a second curve; and evaluating the lithium battery formation SEI film stability according to whether there is a film formation peak in the second curve. The application can detect whether the SEI film is stable during the battery cycle use process, is simple to operate, does not need to invest in new equipment, and is easy to implement.

Description

Technical Field

[0001] This invention belongs to the field of battery testing technology, and in particular relates to a method and system for evaluating the stability of the SEI film formed in lithium batteries. Background Technology

[0002] The SEI (Solid Electrolyte Interface) film is a solid electrolyte film that forms on the surface of the negative electrode during the first discharge of a battery. It effectively prevents solvent molecules from embedding into the negative electrode material while allowing lithium ions to pass through freely. The volume changes of the negative electrode material during charge and discharge can cause the SEI film to rupture, and a new SEI film will form on the surface of the active material exposed in the electrolyte. This process, repeated with cycling, can lead to excessive growth of the SEI film, increasing the battery's internal resistance.

[0003] Patent application number 2020111399256 discloses a method for detecting the SEI film on the surface of lithium-ion battery electrodes. The method analyzes the relationship between the SEI film mass and its heat release using differential scanning calorimetry (DSC). The main steps are as follows: First, the battery to be tested is disassembled, washed, and dried. Then, the obtained electrode sheets are assembled into a coin cell and discharged. The fully discharged electrode sheets are subjected to DSC testing. Finally, the DSC spectrum is analyzed, and the heat release of the SEI film is obtained by integrating the heat release peaks in the range of 100℃ to 150℃. This heat release is proportional to its content, thus the heat release of the SEI film is used as a semi-quantitative data of its content.

[0004] However, the above method requires disassembling the battery, causing irreversible damage. Once the damage is detected, the battery cannot be used again, meaning that it is impossible to detect whether the SEI film is stable during battery cycling. Summary of the Invention

[0005] This invention provides a method and system for evaluating the stability of the SEI film formed in lithium batteries. It eliminates the need to disassemble the battery, thus avoiding irreversible damage to the battery. In other words, it can detect the stability of the SEI film during battery cycling.

[0006] In a first aspect, this embodiment provides a method for evaluating the stability of the SEI film formed in a lithium battery, including:

[0007] The curve of the differential capacity of the lithium battery as a function of voltage during the formation process is obtained and used as the first curve;

[0008] Obtain the voltage corresponding to the SEI film formation peak in the first curve, and use it as the film formation voltage;

[0009] The formed lithium battery is subjected to the first target number of charge-discharge cycles; one full charge and one full discharge constitute one charge-discharge cycle.

[0010] The lithium battery that has completed the first target number of charge-discharge cycles is discharged until the voltage is lower than the film formation voltage, which is taken as the first discharge process;

[0011] The lithium battery that has completed the first discharge process is charged at a constant current until the voltage is greater than the film formation voltage, which is used as the first charging process;

[0012] Obtain the curve of the differential capacity of the lithium battery as a function of voltage during the first charging process, and use it as the second curve;

[0013] The stability of the SEI film formed in lithium batteries can be assessed based on the presence or absence of a film-forming peak in the second curve.

[0014] Optionally, the first aspect also includes:

[0015] If a film-forming peak is found in the second curve, the lithium battery that has completed the first charging process is subjected to a second target number of charge-discharge cycles.

[0016] The lithium battery that has completed the second target number of charge-discharge cycles is discharged until the voltage is lower than the film formation voltage, which is the second discharge process;

[0017] The lithium battery that has completed the second discharge process is charged at a constant current until the voltage is greater than the film formation voltage, which is used as the second charging process;

[0018] Obtain the curve of the differential capacity of the lithium battery voltage as a function of voltage during the second charging process, and use it as the third curve;

[0019] Determine whether the area of ​​the film-forming peak under the third curve is smaller than the preset area and the area of ​​the film-forming peak under the second curve;

[0020] If the area is smaller than the preset area and the area of ​​the film formation peak under the second curve, then the stability of the SEI film formed by the lithium battery is determined to meet the requirements.

[0021] If the area is not less than the preset area and / or the area of ​​the film formation peak under the second curve, then the stability of the SEI film formed by the lithium battery is determined to be unsatisfactory.

[0022] Optionally, the step of constantly charging the lithium battery after the first discharge process until the voltage is greater than the film formation voltage, as the first charging process, includes:

[0023] The lithium battery that has completed the first discharge process is charged at a constant current rate of 0.02C-0.05C until the voltage is greater than the film formation voltage, which is the first charging process.

[0024] Optionally, the step of constantly charging the lithium battery after the second discharge process until the voltage is greater than the film formation voltage, as the second charging process, includes:

[0025] The lithium battery that has completed the second discharge process is charged at a constant current rate of 0.02C-0.05C until the voltage is greater than the film formation voltage, which is the second charging process.

[0026] Secondly, the present invention provides a system for evaluating the stability of the SEI film during lithium battery formation, comprising:

[0027] The first acquisition module is used to acquire the curve of the differential capacity of the lithium battery voltage changing with voltage during the formation process, as the first curve;

[0028] The second acquisition module is used to acquire the voltage corresponding to the SEI film formation peak in the first curve, as the film formation voltage;

[0029] The charge-discharge cycle module is used to perform the first target number of charge-discharge cycles on the formed lithium battery; one full charge and one full discharge constitute one charge-discharge cycle.

[0030] The discharge module is used to discharge the lithium battery that has completed the first target number of charge-discharge cycles until the voltage is lower than the film formation voltage, as the first discharge process;

[0031] The charging module is used to charge the lithium battery that has completed the first discharge process with a constant current until the voltage is greater than the film formation voltage, so as to perform the first charging process.

[0032] The third acquisition module is used to acquire the curve of the differential capacity of the lithium battery as a function of voltage during the first charging process, so as to serve as the second curve.

[0033] The evaluation module is used to assess the stability of the SEI film formed in lithium batteries based on the presence of a film-forming peak in the second curve.

[0034] Optionally, the charge-discharge cycle module is further configured to perform a second target number of charge-discharge cycles on the lithium battery that has completed the first charging process if a film-forming peak is determined to exist in the second curve.

[0035] The discharge module is also used to discharge the lithium battery that has completed the second target number of charge-discharge cycles until the voltage is lower than the film formation voltage, as a second discharge process.

[0036] The charging module is also used to charge the lithium battery that has completed the second discharge process with a constant current until the voltage is greater than the film formation voltage, so as to perform the second charging process.

[0037] The third acquisition module is also used to acquire the curve of the differential capacity of the lithium battery as a function of voltage during the second charging process, as the third curve.

[0038] Optionally, the second aspect also includes:

[0039] The judgment module is used to determine whether the area of ​​the film-forming peak under the third curve is less than the preset area and the area of ​​the film-forming peak under the second curve.

[0040] The first determining module is used to determine that the stability of the SEI film formed by the lithium battery meets the requirements when the determining module determines that the area is smaller than the preset area and the area of ​​the film formation peak under the second curve.

[0041] The second determining module is used to determine that the stability of the SEI film formed by lithium battery does not meet the requirements if the determining module determines that the area is not less than the preset area and / or the area of ​​the film formation peak under the second curve.

[0042] Optionally, the charging module includes:

[0043] The charging unit is used to charge the lithium battery that has completed the first discharge process at a constant current rate of 0.02C-0.05C until the voltage is greater than the film formation voltage, which is the first charging process.

[0044] Optionally, the charging unit is further configured to charge the lithium battery that has completed the second discharge process at a constant current rate of 0.02C-0.05C until the voltage is greater than the film formation voltage, as a second charging process.

[0045] Thirdly, the present invention provides a computer-readable storage medium for storing a computer program; when the computer program is executed by a processor, it implements the steps of the lithium battery formation SEI film stability evaluation method described in the first aspect.

[0046] Beneficial effects:

[0047] This invention provides a method and system for evaluating the stability of the SEI film formed in lithium batteries. The method involves subjecting the lithium battery to different numbers of charge-discharge cycles, then charging it with a small current to obtain a curve showing the voltage-differential capacity versus voltage. The stability of the SEI film is evaluated based on the presence and size of the film formation peaks on the curve. This invention eliminates the need to disassemble the lithium battery, avoiding irreversible damage. It allows for the detection of SEI film stability during lithium battery cyclic use, is simple to operate, requires no new equipment, and is easy to implement. Attached Figure Description

[0048] To more clearly illustrate the technical solution of the present invention, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0049] Figure 1A schematic flowchart of a method for evaluating the stability of a lithium battery SEI film provided in an embodiment of the present invention;

[0050] Figure 2 A schematic diagram of the curve of differential capacity of lithium battery formation voltage versus voltage provided in an embodiment of the present invention;

[0051] Figure 3 A schematic diagram of the voltage differential capacity versus voltage under low-current constant-current charging provided in an embodiment of the present invention;

[0052] Figure 4 This is a schematic diagram of the structure of the lithium battery formation SEI film stability evaluation system provided in an embodiment of the present invention. Detailed Implementation

[0053] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0054] Example 1

[0055] like Figure 1 As shown, this embodiment of the invention provides a method for evaluating the stability of the SEI film formed in a lithium battery, including:

[0056] Step 101: Obtain the curve of the differential capacity of the lithium battery as a function of voltage during the formation process, and use it as the first curve.

[0057] In this step, the electrolyte-impregnated battery is formed according to a specific formation process, and then manufactured into a battery according to normal manufacturing procedures, such as... Figure 2 As shown, the voltage differential capacity is plotted as a function of voltage (dQ / dV-V) on the conversion data, and this is used as the first curve.

[0058] Step 102: Obtain the voltage corresponding to the SEI film formation peak in the first curve, and use it as the film formation voltage.

[0059] In this step, the voltage corresponding to the SEI film formation peak has a range, that is, a range voltage. In this embodiment, the minimum voltage value of the range voltage is taken as the film formation voltage.

[0060] Step 103: Perform the first target number of charge-discharge cycles on the formed lithium battery; one full charge and one full discharge constitute one charge-discharge cycle.

[0061] In this step, the first target number of cycles ranges from 1 to 5. After the lithium battery is formed, it undergoes charge-discharge cycles sequentially, for example, 5 times. Discharging to zero means the lithium battery is discharged until its charge level is 0, i.e., the state of charge (SOC) = 0; fully charging means the lithium battery is charged to its full charge level, i.e., the state of charge (SOC) = 1.

[0062] Step 104: Discharge the lithium battery that has completed the first target number of charge-discharge cycles until the voltage is lower than the film formation voltage, as the first discharge process.

[0063] Step 105: The lithium battery that has completed the first discharge process is charged at a constant current until the voltage is greater than the film formation voltage, which is the first charging process.

[0064] In this step, the lithium battery that has completed the first discharge process is charged at a constant current rate of 0.02C-0.05C until the voltage is greater than the film formation voltage, which is the first charging process.

[0065] Step 106: Obtain the curve of the differential capacity of the lithium battery voltage as a function of voltage during the first charging process, and use it as the second curve.

[0066] Step 107: Determine the stability of the SEI film formed in the lithium battery based on whether there is a film formation peak in the second curve.

[0067] In this step, if there is no film-forming peak in the second curve, such as Figure 3 As shown, if the stability of the SEI film formed by the lithium battery meets the requirements, then the lithium battery needs to be subjected to a second target number of charge-discharge cycles to re-evaluate the stability of the SEI film.

[0068] For example, the lithium battery formation SEI film stability evaluation method provided in this embodiment further includes:

[0069] If a film-forming peak is found in the second curve, the lithium battery that has completed the first charging process is subjected to a second target number of charge-discharge cycles (10-20 times in this embodiment).

[0070] The lithium battery that has completed the second target number of charge-discharge cycles is discharged until the voltage is lower than the film formation voltage, which is called the second discharge process.

[0071] The lithium battery that has completed the second discharge process is charged at a constant current (e.g., at a rate of 0.02C-0.05C) until the voltage is greater than the film formation voltage, which is the second charging process.

[0072] Obtain the curve of the differential capacity of the lithium battery voltage as a function of voltage during the second charging process, and use it as the third curve.

[0073] Determine whether the area of ​​the film-forming peak under the third curve is less than the preset area and the area of ​​the film-forming peak under the second curve.

[0074] If the area is less than the preset area and the area of ​​the film formation peak under the second curve, then the stability of the SEI film formed by the lithium battery is determined to meet the requirements.

[0075] If the area is not less than the preset area and / or the area of ​​the film formation peak under the second curve, then the stability of the SEI film formed by the lithium battery is determined to be unsatisfactory.

[0076] In summary, this embodiment provides a method for evaluating the stability of the SEI film formed in a lithium battery. After subjecting the lithium battery to different numbers of charge-discharge cycles, a voltage-differential capacity curve is obtained by charging with a small current. The stability of the SEI film is evaluated based on the presence and size of the film formation peak in the curve. This embodiment eliminates the need to disassemble the lithium battery, avoiding irreversible damage. It allows for testing the stability of the SEI film during the cyclic use of the lithium battery. This embodiment is simple to operate, requires no new equipment, and is easy to implement.

[0077] Example 2

[0078] Based on the same inventive concept as Example 1, this embodiment provides a lithium battery formation SEI film stability evaluation system. Since the principle of this system in solving the problem is similar to the aforementioned lithium battery formation SEI film stability evaluation method, the implementation of this system can refer to the implementation of the lithium battery formation SEI film stability evaluation method.

[0079] like Figure 4 As shown, the lithium battery formation SEI film stability evaluation system includes:

[0080] The first acquisition module is used to acquire the curve of the differential capacity of the lithium battery voltage changing with voltage during the formation process, as the first curve;

[0081] The second acquisition module is used to acquire the voltage corresponding to the SEI film formation peak in the first curve, as the film formation voltage;

[0082] The charge-discharge cycle module is used to perform the first target number of charge-discharge cycles on the formed lithium battery; one full charge and one full discharge constitute one charge-discharge cycle.

[0083] The discharge module is used to discharge the lithium battery that has completed the first target number of charge-discharge cycles until the voltage is lower than the film formation voltage, as the first discharge process;

[0084] The charging module is used to charge the lithium battery that has completed the first discharge process with a constant current until the voltage is greater than the film formation voltage, so as to perform the first charging process.

[0085] The third acquisition module is used to acquire the curve of the differential capacity of the lithium battery as a function of voltage during the first charging process, so as to serve as the second curve.

[0086] The evaluation module is used to assess the stability of the SEI film formed in lithium batteries based on the presence of a film-forming peak in the second curve.

[0087] For example, the charge-discharge cycle module is further configured to perform a second target number of charge-discharge cycles on the lithium battery that has completed the first charging process when it is determined that there is a film formation peak in the second curve;

[0088] The discharge module is also used to discharge the lithium battery that has completed the second target number of charge-discharge cycles until the voltage is lower than the film formation voltage, as a second discharge process.

[0089] The charging module is also used to charge the lithium battery that has completed the second discharge process with a constant current until the voltage is greater than the film formation voltage, so as to perform the second charging process.

[0090] The third acquisition module is also used to acquire the curve of the differential capacity of the lithium battery as a function of voltage during the second charging process, as the third curve.

[0091] For example, the lithium battery formation SEI film stability evaluation system provided in this embodiment further includes:

[0092] The judgment module is used to determine whether the area of ​​the film-forming peak under the third curve is less than the preset area and the area of ​​the film-forming peak under the second curve.

[0093] The first determining module is used to determine that the stability of the SEI film formed by the lithium battery meets the requirements when the determining module determines that the area is smaller than the preset area and the area of ​​the film formation peak under the second curve.

[0094] The second determining module is used to determine that the stability of the SEI film formed by lithium battery does not meet the requirements if the determining module determines that the area is not less than the preset area and / or the area of ​​the film formation peak under the second curve.

[0095] For example, the charging module includes:

[0096] The charging unit is used to charge the lithium battery that has completed the first discharge process at a constant current rate of 0.02C-0.05C until the voltage is greater than the film formation voltage, which is the first charging process.

[0097] For example, the charging unit is further configured to charge the lithium battery that has completed the second discharge process at a constant current rate of 0.02C-0.05C until the voltage is greater than the film formation voltage, as a second charging process.

[0098] Example 3

[0099] This embodiment provides a computer device, including a processor and a memory; wherein, when the processor executes the computer program stored in the memory, it implements the steps of the lithium battery formation SEI film stability evaluation method described in Embodiment 1.

[0100] For a more detailed explanation of the above method, please refer to the relevant content disclosed in Example 1, which will not be repeated here.

[0101] Example 4

[0102] This embodiment provides a computer-readable storage medium for storing a computer program; when the computer program is executed by a processor, it implements the steps of the lithium battery formation SEI film stability evaluation method described in Embodiment 1.

[0103] For a more detailed explanation of the above method, please refer to the relevant content disclosed in Example 1, which will not be repeated here.

[0104] Example 5

[0105] This embodiment provides a computer program product, including computer-executable instructions or a computer program. When the computer-executable instructions or the computer program are executed by a processor, they implement the steps of the lithium battery formation SEI film stability evaluation method described in Embodiment 1.

[0106] For a more detailed explanation of the above method, please refer to the relevant content disclosed in Example 1, which will not be repeated here.

[0107] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the systems, devices, storage media, and computer program products disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the descriptions are relatively simple, and relevant parts can be referred to the method section.

[0108] Those skilled in the art will clearly understand that the techniques in the embodiments of the present invention can be implemented using software plus necessary general-purpose hardware platforms. Based on this understanding, the technical solutions in the embodiments of the present invention, or the parts that contribute to the prior art, can be embodied in the form of a software product. This computer software product can be stored in a storage medium, such as ROM / RAM, magnetic disk, optical disk, etc., and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute the methods described in various embodiments or certain parts of the embodiments of the present invention.

[0109] In some embodiments, computer-executable instructions may take the form of programs, software, software modules, scripts, or code, written in any form of programming language (including compiled or interpreted languages, or declarative or procedural languages), and may be deployed in any form, including as stand-alone programs or as modules, components, subroutines, or other units suitable for use in a computing environment.

[0110] As an example, computer-executable instructions may, but do not necessarily, correspond to files in a file system. They may be stored as part of a file that holds other programs or data, for example, in one or more scripts in a Hyper Text Markup Language (HTML) document, in a single file dedicated to the program in question, or in multiple co-located files (e.g., files that store one or more modules, subroutines, or code sections).

[0111] As an example, computer-executable instructions can be deployed to execute on a single electronic device, or on multiple electronic devices located at one location, or on multiple electronic devices distributed across multiple locations and interconnected via a communication network.

[0112] The present invention has been described in detail above with reference to specific embodiments and exemplary examples; however, these descriptions should not be construed as limiting the present invention. Those skilled in the art will understand that various equivalent substitutions, modifications, or improvements can be made to the technical solutions and embodiments of the present invention without departing from the spirit and scope of the invention, and all such modifications and improvements fall within the scope of the present invention. The scope of protection of the present invention is defined by the appended claims.

Claims

1. A method for evaluating the stability of the SEI film during lithium battery formation, characterized in that, include: The curve of the differential capacity of the lithium battery as a function of voltage during the formation process is obtained and used as the first curve; Obtain the voltage corresponding to the SEI film formation peak in the first curve, and use it as the film formation voltage; The formed lithium battery is subjected to the first target number of charge-discharge cycles; one full charge and one full discharge constitute one charge-discharge cycle. The lithium battery that has completed the first target number of charge-discharge cycles is discharged until the voltage is lower than the film formation voltage, which is taken as the first discharge process; The lithium battery that has completed the first discharge process is charged at a constant current until the voltage is greater than the film formation voltage, which is used as the first charging process; Obtain the curve of the differential capacity of the lithium battery as a function of voltage during the first charging process, and use it as the second curve; If a film-forming peak is found in the second curve, the lithium battery that has completed the first charging process is subjected to a second target number of charge-discharge cycles. The lithium battery that has completed the second target number of charge-discharge cycles is discharged until the voltage is lower than the film formation voltage, which is the second discharge process; The lithium battery that has completed the second discharge process is charged at a constant current until the voltage is greater than the film formation voltage, which is used as the second charging process; Obtain the curve of the differential capacity of the lithium battery as a function of voltage during the second charging process, and use it as the third curve; Determine whether the area of ​​the film-forming peak under the third curve is smaller than the preset area and the area of ​​the film-forming peak under the second curve; If the area is smaller than the preset area and the area of ​​the film formation peak under the second curve, then the stability of the SEI film formed by the lithium battery is determined to meet the requirements. If the area is not less than the preset area and / or the area of ​​the film formation peak under the second curve, then the stability of the SEI film formed by the lithium battery is determined to be unsatisfactory.

2. The method for evaluating the stability of the SEI film in lithium battery formation according to claim 1, characterized in that, The process of charging the lithium battery, after completing the second discharge process, at a constant current until the voltage is greater than the film formation voltage, as the second charging process, includes: The lithium battery that has completed the second discharge process is charged at a constant current rate of 0.02C-0.05C until the voltage is greater than the film formation voltage, which is the second charging process.

3. The method for evaluating the stability of the SEI film in lithium battery formation according to claim 1, characterized in that, The process of charging the lithium battery, after completing the first discharge process, at a constant current until the voltage is greater than the film formation voltage, as the first charging process, includes: The lithium battery that has completed the first discharge process is charged at a constant current rate of 0.02C-0.05C until the voltage is greater than the film formation voltage, which is the first charging process.

4. A system for evaluating the stability of the SEI film during lithium battery formation, characterized in that, include: The first acquisition module is used to acquire the curve of the differential capacity of the lithium battery as a function of voltage during the formation process, and use it as the first curve. The second acquisition module is used to acquire the voltage corresponding to the SEI film formation peak in the first curve, as the film formation voltage; The charge-discharge cycle module is used to perform the first target number of charge-discharge cycles on the formed lithium battery; one full charge and one full discharge constitute one charge-discharge cycle. The discharge module is used to discharge the lithium battery that has completed the first target number of charge-discharge cycles until the voltage is lower than the film formation voltage, as the first discharge process; The charging module is used to charge the lithium battery that has completed the first discharge process with a constant current until the voltage is greater than the film formation voltage, so as to perform the first charging process. The third acquisition module is used to acquire the curve of the differential capacity of the lithium battery as a function of voltage during the first charging process, so as to serve as the second curve. The charge-discharge cycle module is also used to perform a second target number of charge-discharge cycles on the lithium battery that has completed the first charging process when it is determined that there is a film formation peak in the second curve. The discharge module is also used to discharge the lithium battery that has completed the second target number of charge-discharge cycles until the voltage is lower than the film formation voltage, as a second discharge process; The charging module is also used to charge the lithium battery that has completed the second discharge process with a constant current until the voltage is greater than the film formation voltage, so as to perform the second charging process. The third acquisition module is also used to acquire the curve of the differential capacity of the lithium battery voltage changing with voltage during the second charging process, as the third curve. The judgment module is used to determine whether the area of ​​the film-forming peak under the third curve is less than the preset area and the area of ​​the film-forming peak under the second curve. The first determining module is used to determine that the stability of the SEI film formed by the lithium battery meets the requirements when the determining module determines that the area is smaller than the preset area and the area of ​​the film formation peak under the second curve. The second determining module is used to determine that the stability of the SEI film formed by lithium battery does not meet the requirements if the determining module determines that the area is not less than the preset area and / or the area of ​​the film formation peak under the second curve.

5. The lithium battery formation SEI film stability evaluation system according to claim 4, characterized in that, The charging module includes: The charging unit is used to charge the lithium battery that has completed the first discharge process at a constant current rate of 0.02C-0.05C until the voltage is greater than the film formation voltage, which is the first charging process.

6. The lithium battery formation SEI film stability evaluation system according to claim 5, characterized in that, The charging unit is also used to charge the lithium battery that has completed the second discharge process at a constant current rate of 0.02C-0.05C until the voltage is greater than the film formation voltage, as a second charging process.

7. A computer-readable storage medium, characterized in that, Used to store computer programs; when executed by a processor, the computer programs implement the steps of the lithium battery formation SEI film stability evaluation method according to any one of claims 1-3.

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