Method for forming SEI film in battery

Abstract

The invention relates to the technical field of batteries, and discloses a method for forming an SEI film in a battery, and the method comprises the following steps: step 1, surface pretreatment; step 2, initial linear scanning; step 3, SEI membrane reforming; 4, performing final linear scanning; 5, real-time monitoring is carried out; and step 6, real-time regulation and control. In the process of forming the SEI film in the battery, the SEI film is ensured to be uniformly formed on the surface of an electrode through a series of fine steps and technical measures, initial linear scanning is carried out by adopting a multi-section scanning strategy, voltage is gradually increased, and scanning is carried out for multiple times, so that the initial formation and uniformity of the SEI film are effectively controlled; quality detection is carried out through a scanning electron microscope (SEM), feedback adjustment is carried out according to a detection result, uniform formation and high performance of the SEI film are further ensured, and the beneficial effects that the uniformity of the SEI film is improved, and the SEI film is uniformly formed in different areas are achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and in particular to a method for forming a SEI film in a battery. Background Art

[0002] The solid electrolyte interface (SEI) is extremely important in lithium-ion batteries. On the one hand, the SEI membrane can be stably present in solvents, effectively inhibiting the dissolution of materials and the co-intercalation of solvent molecules, protecting the electrode materials and thus significantly improving the cycling stability and service life of the electrodes. On the other hand, the SEI membrane allows the passage of ions while inhibiting the passage of electrons, thus ensuring the generation of side reactions and the continuous charge and discharge of the "rocking chair battery" while suppressing excessive consumption of lithium ions and improving battery life.

[0003] In order to solve the above-mentioned technical problems, a battery formation method for forming a stable SEI film was found through search with publication number CN 110034336 A. The method comprises: (1) applying a voltage to the electrode of the battery to be formed and performing a linear scan to obtain a battery with a pre-constructed SEI film; (2) reforming the SEI film of the battery with the pre-constructed SEI film in step (1) to obtain a battery with a reformed SEI film; and (3) applying a voltage to the electrode of the battery with the reformed SEI film in step (2) and performing a linear scan to obtain a formed battery. The battery formation method for forming a stable SEI film provided by the present invention can construct a very stable SEI film on the negative electrode surface, reduce the irreversible capacity loss of the battery, and improve the wettability inside the battery, thereby reducing the time cost of the battery preparation process.

[0004] However, the aforementioned technical solution of applying voltage to the electrode for linear scanning will not form the SEI film uniformly in all areas, resulting in poor uniformity of the SEI film. At the same time, multiple processing steps will also affect the consistency of the SEI film. Especially in large-scale production, it is difficult to ensure that each battery can obtain the same quality SEI film. Summary of the Invention

[0005] Technical issues solved:

[0006] In response to the shortcomings of the existing technology, the present invention provides a method for forming an SEI film in a battery, which has the advantages of improving the uniformity of the SEI film and ensuring that the SEI film is formed evenly in different areas; and real-time monitoring and adjustment of parameters of each step in large-scale production to ensure the consistency of the SEI film, thereby solving the problems of the above-mentioned technology.

[0007] Technical solution:

[0008] To achieve the above object, the present invention provides the following technical solution: a method for forming an SEI film in a battery, comprising the following steps:

[0009] Step 1: Surface pretreatment: Mechanical polishing is used to pretreat the surface of the electrode to be formed into a battery, and metal nanoparticles are coated on the pretreated electrode surface to improve the conductivity and surface properties of the electrode;

[0010] Step 2: Initial linear scan: Apply voltage to the pretreated electrode for initial linear scan. Use a multi-segment scan strategy to gradually increase the voltage. Adjust the scan speed to 5-50 mV / s, gradually increasing from 0 V to 1.0-1.5 V according to the characteristics of the electrode material and electrolyte, to ensure the initial formation of the SEI film. Perform 3-5 scans to ensure the uniformity of the SEI film.

[0011] Step 3: SEI film reformation: Use a constant current charge-discharge method to reform the SEI film to improve its structure and stability. Depending on the battery capacity, select a current density in the range of 0.1-1C and perform 3-5 charge-discharge cycles;

[0012] Step 4: Final linear scan: Apply voltage to the electrodes of the reformed SEI film battery for a final linear scan. According to the characteristics of the reformed SEI film, adjust the scan speed within the range of 10-100mV / s, gradually increase from 0V to 1.0-1.5V, and perform 2-3 scans to ensure the uniformity and stability of the SEI film.

[0013] Step 5. Real-time monitoring: In each step, monitor voltage, current, and temperature parameters;

[0014] Step 6. Real-time control: Using an automated control system, dynamically adjust the parameters of each step based on real-time monitoring data to ensure the consistency of the SEI film. Perform quality inspections after each step, using a scanning electron microscope (SEM) to check the uniformity and thickness of the SEI film, and make feedback adjustments based on the test results.

[0015] Preferably, the step 1 further includes the following detailed steps:

[0016] S1.1. Electrode surface cleaning: Use acetone and ethanol to ultrasonically clean the electrode surface in sequence to remove organic pollutants and moisture on the surface, and dry the electrode to ensure that there is no residual solvent on the surface;

[0017] S1.2 Mechanical polishing: Fix the electrode on the polishing machine and use a coarse-grained polishing cloth (400 mesh) for preliminary polishing to remove surface unevenness and impurities. Then switch to a fine-grained polishing cloth (1000-2000 mesh) and continue polishing. During the polishing process, rinse the electrode with deionized water every 3-5 minutes to remove particles and impurities generated by polishing.

[0018] S1.3. Surface roughness test: Use a surface roughness tester to test the surface roughness of the polished electrode to ensure that it meets the required flatness standard: Ra < 0.1 μm;

[0019] S1.4. Metal nanoparticle coating: Prepare a metal nanoparticle solution with a concentration determined according to experimental needs, usually 0.1-1 mg / mL. Immerse the polished electrode in the metal nanoparticle solution for coating. Place the coated electrode in a vacuum drying oven at 60°C and dry for 30 minutes to allow the metal nanoparticles to adhere to the electrode surface.

[0020] Preferably, the single-segment scanning time in step 2 is calculated as:

[0021]

[0022] Where: t i is the scanning time of the i-th segment, in seconds; v i is the scanning speed of the i-th segment, in millivolts per second.

[0023] Preferably, the total scanning time in step 2 is calculated as:

[0024]

[0025] Where: T is the total scan time in seconds; t i is the scanning time of the i-th segment, in seconds;

[0026] The first section: the voltage is from 0V to 0.5V, the voltage increment ΔV1 = 0.5V, the scanning speed v1 = 10mV / s, and the calculation time is:

[0027]

[0028] Second segment: voltage from 0.5V to 1.0V, voltage increment ΔV2 = 0.5V; scanning speed v2 = 20mV / s; calculation time is:

[0029] Preferably, the constant current charge-discharge calculation in step 3 is:

[0030] Assume the battery capacity is C and the current density is selected between 0.1C and 1C;

[0031] The constant current charge calculation is:

[0032]

[0033] Where: t charge is the charging time in hours; I is the charging current in milliamperes;

[0034] Discharge time t discharge Also use the above formula to calculate:

[0035] Preferably, the time for each cycle in step 3 is calculated as:

[0036] t cycle =t charge +t discharge

[0037] Where: t cycle is the time of each charge and discharge cycle in hours; t charge is the charging time; t discharge is the discharge time;

[0038] The total charge and discharge time T in step 3 total The total time of all cycles is:

[0039] T total =n×t cycle

[0040] Where: n is the total number of charge and discharge cycles, the number of charge and discharge cycles performed; t cycle The time for each charge and discharge cycle indicates the length of time required for a complete charge and discharge process.

[0041] Preferably, the scanning time in step 4 is calculated as:

[0042]

[0043] Where: t scan is the time of each scan in seconds; v is the scan speed in millivolts per second.

[0044] Preferably, the total scanning time Ttotal in step 4 is the total time of all scans:

[0045] T total =m×t scan

[0046] Where: T total is the total scan time in seconds; m is the number of scans performed.

[0047] Preferably, the SEI film thickness distribution in step 6 is calculated as:

[0048] Assume that the SEI film thickness t detected at multiple points i , calculate the average thickness

[0049]

[0050] Where: SEI film thickness is t i The average thickness is

[0051] Preferably, the standard deviation σ calculated in step 6 is:

[0052]

[0053] Where: the standard deviation is σ and the number of detection points is n.

[0054] Compared with the prior art, the present invention provides a method for forming an SEI film in a battery, which has the following beneficial effects:

[0055] 1. The present invention ensures that the SEI film is uniformly formed on the electrode surface through a series of sophisticated steps and technical measures during the formation of the SEI film in the battery. First, the surface pretreatment includes electrode surface cleaning, mechanical polishing and metal nanoparticle coating. These measures improve the flatness and activity of the electrode surface, laying the foundation for the uniform formation of the SEI film. Then, a multi-segment scanning strategy is used to perform an initial linear scan, gradually increasing the voltage and performing multiple scans to effectively control the initial formation and uniformity of the SEI film. Subsequently, the SEI film is reformed by a constant current charge-discharge method to further improve its structure and stability, and the SEI film is ensured to be uniformly distributed by dynamically adjusting the current density. In the final linear scan, the scanning speed is adjusted and multiple scans are performed to ensure the final uniformity and stability of the SEI film. At the same time, throughout the process, the voltage, current and temperature parameters are monitored in real time, and the automatic control system is used to dynamically adjust the process parameters to ensure the consistency of the SEI film. Finally, quality inspection is carried out by scanning electron microscope SEM, and feedback adjustment is made according to the inspection results to further ensure the uniform formation and high performance of the SEI film. Through these comprehensive measures, the uniformity of the SEI film in different areas is effectively improved, thereby improving the overall performance and life of the battery, and achieving the beneficial effect of improving the uniformity of the SEI film and making the SEI film uniformly formed in different areas.

[0056] 2. This invention achieves real-time monitoring and adjustment of parameters at each step during large-scale production, ensuring SEI film consistency, by integrating automated control systems and high-precision monitoring equipment, combined with advanced data analysis and feedback mechanisms. Specific measures include: using a highly integrated automated control system to collect key parameters such as voltage, current, and temperature in real time, and monitoring the electrode surface state and SEI film formation process using high-precision sensors and real-time imaging technology; establishing a big data platform to analyze production data using machine learning and artificial intelligence algorithms, predict problems, and optimize process parameters; after each step, automated quality inspection equipment conducts real-time inspections, and the results are fed back to the control system for dynamic adjustment of subsequent process parameters; Operators are trained to ensure proficiency in equipment operation, and monitoring equipment is regularly maintained and calibrated to ensure its accuracy and reliability. Through these comprehensive measures, the beneficial effect of real-time monitoring and adjustment of parameters at each step during large-scale production is achieved, ensuring SEI film consistency. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Figure 1 Schematic diagram of the process flow of the present invention; DETAILED DESCRIPTION

[0058] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0059] See also Figure 1 , a method for forming an SEI film in a battery, comprising the following steps:

[0060] Step 1: Surface pretreatment: Mechanical polishing is used to pretreat the surface of the electrode to be formed into a battery, and metal nanoparticles are coated on the pretreated electrode surface to improve the conductivity and surface properties of the electrode;

[0061] Step 2: Initial linear scan: Apply voltage to the pretreated electrode for initial linear scan. Use a multi-segment scan strategy to gradually increase the voltage. Adjust the scan speed to 5-50 mV / s, gradually increasing from 0 V to 1.0-1.5 V according to the characteristics of the electrode material and electrolyte, to ensure the initial formation of the SEI film. Perform 3-5 scans to ensure the uniformity of the SEI film.

[0062] Step 3: SEI film reformation: Use a constant current charge-discharge method to reform the SEI film to improve its structure and stability. Depending on the battery capacity, select a current density in the range of 0.1-1C and perform 3-5 charge-discharge cycles;

[0063] Step 4: Final linear scan: Apply voltage to the electrodes of the reformed SEI film battery for a final linear scan. According to the characteristics of the reformed SEI film, adjust the scan speed within the range of 10-100mV / s, gradually increase from 0V to 1.0-1.5V, and perform 2-3 scans to ensure the uniformity and stability of the SEI film.

[0064] Step 5. Real-time monitoring: In each step, monitor voltage, current, and temperature parameters;

[0065] Step 6. Real-time control: Using an automated control system, dynamically adjust the parameters of each step based on real-time monitoring data to ensure the consistency of the SEI film. Perform quality inspections after each step, using a scanning electron microscope (SEM) to check the uniformity and thickness of the SEI film, and make feedback adjustments based on the test results.

[0066] In the process of forming the SEI film in the battery, a series of sophisticated steps and technical measures are taken to ensure that the SEI film is uniformly formed on the electrode surface. First, surface pretreatment includes electrode surface cleaning, mechanical polishing and metal nanoparticle coating. These measures improve the flatness and activity of the electrode surface, laying the foundation for the uniform formation of the SEI film. Next, a multi-segment scanning strategy is used for the initial linear scan, gradually increasing the voltage and performing multiple scans to effectively control the initial formation and uniformity of the SEI film. Subsequently, the SEI film is reformed by a constant current charge-discharge method to further improve its structure and stability, and the SEI film is uniformly distributed by dynamically adjusting the current density. In the final linear scan, the scan speed is adjusted and multiple scans are performed to ensure the final uniformity and stability of the SEI film.

[0067] Throughout the entire process, voltage, current, and temperature parameters are monitored in real time, and an automated control system dynamically adjusts process parameters to ensure the consistency of the SEI film. Finally, quality inspection is performed using a scanning electron microscope (SEM), and feedback adjustments are made based on the test results to further ensure the uniform formation and high performance of the SEI film.

[0068] Specifically, step one also includes the following detailed steps:

[0069] S1.1. Electrode surface cleaning: Use acetone and ethanol to ultrasonically clean the electrode surface in sequence to remove organic pollutants and moisture on the surface, and dry the electrode to ensure that there is no residual solvent on the surface;

[0070] S1.2 Mechanical polishing: Fix the electrode on the polishing machine and use a coarse-grained polishing cloth (400 mesh) for preliminary polishing to remove surface unevenness and impurities. Then switch to a fine-grained polishing cloth (1000-2000 mesh) and continue polishing. During the polishing process, rinse the electrode with deionized water every 3-5 minutes to remove particles and impurities generated by polishing.

[0071] S1.3. Surface roughness test: Use a surface roughness tester to test the surface roughness of the polished electrode to ensure that it meets the required flatness standard: Ra < 0.1 μm;

[0072] S1.4. Metal nanoparticle coating: Prepare a metal nanoparticle solution with a concentration determined according to experimental needs, usually 0.1-1 mg / mL. Immerse the polished electrode in the metal nanoparticle solution for coating. Place the coated electrode in a vacuum drying oven at 60°C and dry for 30 minutes to allow the metal nanoparticles to adhere to the electrode surface.

[0073] Automation control system

[0074] Integrated control platform: Use a highly integrated control system that can collect and process data from various steps in real time. These systems typically include PLCs (programmable logic controllers), SCADA (supervisory control and data acquisition systems), and MES (manufacturing execution systems).

[0075] Sensors and monitoring equipment are installed at each step to collect real-time data on key parameters such as voltage, current, temperature, and electrode surface roughness. This data is transmitted to the central control platform via wired or wireless networks.

[0076] The control system analyzes real-time data and automatically adjusts process parameters. For example, during the electrode surface pretreatment stage, the system can automatically adjust the polishing time and the particle size of the polishing cloth based on feedback from the surface roughness meter.

[0077] Use high-precision sensors to monitor the electrode surface cleanliness, polishing effect, metal nanoparticle distribution on the electrode surface, etc. For example, use optical sensors or electrochemical sensors to monitor the state of the electrode surface.

[0078] During the SEI film formation process, real-time imaging techniques (such as infrared imaging and electrochemical impedance spectroscopy (EIS)) are used to monitor the formation process and uniformity of the SEI film. These techniques can provide detailed information about the SEI film formation process.

[0079] Establish a big data platform to store and analyze various data from the production process. Use machine learning and artificial intelligence algorithms to analyze data trends and patterns, predict potential problems, and provide optimization suggestions.

[0080] After each step, real-time monitoring data is compared with pre-set standards to identify deviations and adjust process parameters in a timely manner. For example, after the SEI film reformation step, the uniformity and thickness of the SEI film are tested by SEM. The test results are fed back to the control system to dynamically adjust the constant current charge and discharge parameters.

[0081] After each step, automated equipment is used for quality inspection. For example, after electrode surface pretreatment, an automated surface roughness meter is used to test surface flatness. After SEI film formation, an automated SEM instrument is used to test the thickness and uniformity of the SEI film.

[0082] Based on the quality inspection results, the control system adjusts the process parameters of the subsequent steps in real time. If the SEI film thickness is found to be uneven in the final linear scan, the control system can adjust the scanning speed or number of scans to ensure the uniformity of the SEI film.

[0083] Specifically, the single-segment scan time in step 2 is calculated as:

[0084]

[0085] Where: t i is the scanning time of the i-th segment, in seconds; v i is the scanning speed of the i-th segment, in millivolts per second.

[0086] Specifically, the total scan time in step 2 is calculated as:

[0087]

[0088] Where: T is the total scan time in seconds; t i is the scanning time of the i-th segment, in seconds;

[0089] The first section: the voltage is from 0V to 0.5V, the voltage increment ΔV1 = 0.5V, the scanning speed v1 = 10mV / s, and the calculation time is:

[0090]

[0091] Second segment: voltage from 0.5V to 1.0V, voltage increment ΔV2 = 0.5V; scanning speed v2 = 20mV / s; calculation time is:

[0092] Specifically, the constant current charge-discharge calculation in step 3 is:

[0093] Assume the battery capacity is C and the current density is selected between 0.1C and 1C;

[0094] The constant current charge calculation is:

[0095]

[0096] Where: t charge is the charging time in hours; I is the charging current in milliamperes;

[0097] Discharge time t discharge Also use the above formula to calculate:

[0098] Specifically, the time for each cycle in step 3 is calculated as:

[0099] t cycle =t charge +t discharge

[0100] Where: t cycle is the time of each charge and discharge cycle in hours; t charge is the charging time; t discharge is the discharge time;

[0101] Total charge and discharge time T in step 3 total The total time of all cycles is:

[0102] T total =n×t cycle

[0103] Where: n is the total number of charge and discharge cycles, the number of charge and discharge cycles performed; t cycle The time for each charge and discharge cycle indicates the length of time required for a complete charge and discharge process.

[0104] Specifically, the scanning time in step 4 is calculated as:

[0105]

[0106] Where: t scan is the time of each scan in seconds; v is the scan speed in millivolts per second.

[0107] Specifically, the total scan time Ttotal in step 4 is the total time of all scans:

[0108] T total =m×t scan

[0109] Where: T total is the total scan time in seconds; m is the number of scans performed.

[0110] Specifically, the SEI film thickness distribution in step 6 is calculated as:

[0111] Assume that the SEI film thickness t detected at multiple pointsi , calculate the average thickness

[0112]

[0113] Where: SEI film thickness is t i The average thickness is

[0114] Specifically, the standard deviation σ calculated in step 6 is:

[0115]

[0116] Where: the standard deviation is σ and the number of detection points is n.

[0117] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A method for forming a SEI film in a battery, characterized in that: The following steps are involved: Step 1: Surface pretreatment: Use mechanical polishing to perform surface pretreatment on the electrode to be formed into a battery, and coat the pretreated electrode surface with metal nanoparticles to improve the conductivity and surface properties of the electrode; Step 2, initial linear scan: Apply voltage to the pretreated electrode for initial linear scan, use a multi-segment scan strategy, gradually increase the voltage, and adjust the scan speed to 5-50mV / s, gradually increase from 0V to 1.0-1.5V according to the characteristics of the electrode material and the electrolyte, to ensure the initial formation of the SEI film, and perform 3-5 scans to ensure the uniformity of the SEI film; Step 3: SEI film reformation: Use constant current charge-discharge method to reform the SEI film to improve its structure and stability. According to the battery capacity, select the current density in the range of 0.1-1C and perform 3-5 charge-discharge cycles; Step 4, final linear scan: Apply voltage to the electrodes of the reformed SEI membrane battery for final linear scan. According to the characteristics of the reformed SEI membrane, adjust the scan speed within the range of 10-100mV / s, gradually increase from 0V to 1.0-1.5V, and perform 2-3 scans to ensure the uniformity and stability of the SEI membrane; Step 5. Real-time monitoring: In each step, monitor the voltage, current, and temperature parameters; Step 6. Real-time control: Use an automated control system to dynamically adjust the parameters of each step based on real-time monitoring data to ensure the consistency of the SEI film. Perform quality inspection after each step and use a scanning electron microscope (SEM) to check the uniformity and thickness of the SEI film, and make feedback adjustments based on the test results.

2. A method for forming a SEI film in a battery according to claim 1, characterized in that: The step 1 also includes the following detailed steps: S1.

1. Electrode surface cleaning: Use acetone and ethanol to ultrasonically clean the electrode surface in sequence to remove organic pollutants and moisture on the surface, dry the electrode, and ensure that there is no residual solvent on the surface; S1.2, Mechanical polishing: Fix the electrode on the polishing machine, select a coarse-grained polishing cloth: 400 mesh, perform preliminary polishing to remove surface unevenness and impurities, switch to a fine-grained polishing cloth: 1000 mesh-2000 mesh, and continue polishing. During the polishing process, clean the electrode with deionized water every 3-5 minutes to remove particles and impurities generated by polishing; S1.3, Surface roughness test: Use a surface roughness meter to test the surface roughness of the polished electrode to ensure that the required flatness standard is met: Ra < 0.1 μm; S1.4, Metal nanoparticle coating: Prepare a metal nanoparticle solution with a concentration determined according to experimental needs, usually 0.1-1 mg / mL, immerse the polished electrode in the metal nanoparticle solution for coating, place the coated electrode in a vacuum drying oven, set at 60°C and dry for 30 minutes, so that the metal nanoparticles adhere to the electrode surface.

3. A method for forming a SEI film in a battery according to claim 1, characterized in that: The single-segment scanning time in step 2 is calculated as: Where: t i is the scanning time of the i-th segment, in seconds; v i is the scanning speed of the ith segment, in millivolts per second.

4. A method for forming a SEI film in a battery according to claim 1, characterized in that: The total scan time in step 2 is calculated as: Where: T is the total scan time in seconds; t i is the scanning time of the i-th segment, in seconds; The first stage: the voltage is from 0V to 0.5V, the voltage increment ΔV1 = 0.5V, the scanning speed v1 = 10mV / s, and the calculation time is: The second stage: the voltage is from 0.5V to 1.0V, the voltage increment ΔV2 = 0.5V; the scanning speed v2 = 20mV / s; the calculation time is:

5. A method for forming a SEI film in a battery according to claim 1, characterized in that: The constant current charge-discharge calculation in step 3 is: Assume the battery capacity is C, and the current density is selected between 0.1C and 1C; The constant current charge calculation is: Where: t charge is the charging time in hours; I is the charging current in milliamperes; Discharge time t discharge Also use the above formula to calculate:

6. A method for forming a SEI film in a battery according to claim 5, characterized in that: In step 3, each cycle time is calculated as: t cycle =t charge +t discharge Where: t cycle is the time of each charge and discharge cycle, in hours; t charge is the charging time; t discharge is the discharge time; The total charge and discharge time T in step 3 total The total time for all cycles is: T total =n×t cycle Where: n is the total number of charge and discharge cycles, the number of charge and discharge cycles performed; t cycle The time for each charge and discharge cycle indicates the length of time required for a complete charge and discharge process.

7. A method for forming a SEI film in a battery according to claim 1, characterized in that: The scanning time in step 4 is calculated as: Where: t scan is the time of each scan in seconds; v is the scan speed in millivolts per second.

8. A method for forming a SEI film in a battery according to claim 7, characterized in that: The total scanning time Ttotal in step 4 is the total time of all scans: T total =m×t scan Where: T total is the total scan time in seconds; m is the number of scans performed.

9. A method for forming a SEI film in a battery according to claim 1, characterized in that: The SEI film thickness distribution in step 6 is calculated as: Assume that the SEI film thickness t detected at multiple points i , calculate the average thickness t: Where: SEI film thickness is t i The average thickness is 10. A method for forming a SEI film in a battery according to claim 9, characterized in that: The standard deviation σ calculated in step 6 is: Among them: the standard deviation is σ and the number of detection points is n.

Images