Method for improving black spot of lithium ion battery interface, formation and partial volume method and application

Abstract

The present application relates to a method for improving the interface black spot of a lithium ion battery, and a formation and capacity method and application, and belongs to the technical field of lithium ion batteries. The process method comprises the following steps: forming, aging, negative pressure discharging and capacity of the battery cell of the lithium ion battery. The method increases the negative pressure discharging process after the aging is completed in the existing formation and capacity process flow, so as to discharge the gas generated in the aging process, avoid the interface black spot caused by the residual gas, and realize the improvement of the interface black spot of the lithium ion battery, especially the high energy density system lithium ion battery. Moreover, the SoC of the battery is reduced during the discharging process, the pole piece spacing is increased, the gas is extracted under negative pressure at this time, the extraction effect is better, and the gas is more effectively avoided from being left in the pole piece.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery technology, specifically to a method for improving black spots at the interface of lithium-ion batteries, a method for forming and compatibility testing, and its application. Background Technology

[0002] Lithium-ion batteries are increasingly used in vehicle power systems, and market demands for them are also rising. A key requirement is the continuous improvement of battery energy density, as traditional graphite anode systems are no longer sufficient to meet the needs of next-generation high-energy-density lithium-ion batteries. Si materials have a theoretical capacity of up to 4200 mAh / g, more than ten times that of graphite, making them an ideal anode material. However, Si materials undergo significant volume expansion during lithium intercalation, leading not only to particle pulverization and breakage, causing damage to the electrode structure, but also to the damage to the SEI (Solid Electrolyte Interface) film on the anode surface. Adding FEC to the electrolyte to generate a LiF-rich SEI film on the anode surface can significantly improve the cycle stability of Si-containing anodes.

[0003] However, electrolytes containing FEC (fluoroethylene carbonate) often become unstable at high temperatures. Studies have shown that under high-temperature conditions, FEC easily undergoes a desulfurization reaction with Lewis acids (such as PF5) in the electrolyte, producing HF, as well as various other acids (such as H3OPF6, HPO2F2, H2PO3F, H3PO4). This HF then reacts with residual Li2CO3 on the surface of the ternary cathode material to produce a large amount of CO / CO2 gas. During the formation and aging stages of lithium-ion battery production, this large amount of gas can easily remain in the middle of the electrodes. Traditional formation and capacity testing methods involve capacity testing after aging, with the initial stage being full charging at atmospheric pressure. During charging, bubbles remaining in the electrodes can cause black spots at the interface, severely affecting battery performance and safety. Furthermore, the gas production during the aging process of cells with a Si-based anode + FEC-based electrolyte chemical system is significantly higher than that of conventional graphite anode + EC (ethylene carbonate)-based electrolyte chemical systems.

[0004] In existing battery cell manufacturing processes, for Si-based anodes and FEC-based electrolytes, there are two main methods to improve gas generation during the formation and capacity testing phase. The first is to add additives to the electrolyte to remove HF and other acids. By reducing the HF content in the electrolyte, the side reaction between HF and Li₂CO₃ on the surface of the ternary cathode material is reduced, thus lowering gas generation. The second is to increase negative pressure during the formation and aging stages to expel the generated gases. However, the first method undoubtedly increases the cost of the electrolyte, affecting the overall cost of the battery, and the added additives may also have other negative effects on the battery. The negative pressure formation method in the second approach is already widely used. However, compared to formation, aging takes longer, lasting 24-72 hours. Using negative pressure during aging results in significant energy consumption, and prolonged negative pressure leads to substantial electrolyte loss. Moreover, during the aging stage, the battery cell is generally above 70% SoC, with significant anode expansion and smaller electrode spacing, making gas extraction difficult and posing a risk of residual gas causing interface black spots. Summary of the Invention

[0005] Therefore, the technical problem to be solved by the present invention is to overcome the problem of interface black spots in the formation and capacity test of lithium-ion battery cells, thereby providing a method for improving interface black spots in lithium-ion batteries, a formation and capacity test method for improving interface black spots in lithium-ion batteries, and its application.

[0006] The technical solution of the present invention:

[0007] A method for improving black spots at the interface of a lithium-ion battery includes a formation and aging step, and a negative voltage discharge after the aging step is completed.

[0008] The lithium-ion battery is a high-energy-density lithium-ion battery with an energy density greater than 200Wh / kg; preferably, the chemical system of the high-energy-density lithium-ion battery is a Si anode, an FEC (fluoroethylene carbonate) based electrolyte and a ternary cathode; more preferably, the ternary cathode is an NCM (nickel, cobalt, manganese) ternary cathode.

[0009] The discharge voltage in the negative pressure discharge step is 3.6–2.5V, and the vacuum degree is no greater than -10 kPa; preferably, the vacuum degree is -10 to -80 kPa. The discharge and vacuuming process lasts for 10–30 minutes.

[0010] The formation process is a negative voltage formation process, which involves: evacuating the battery cell to -10 to -80 kPa, then applying a voltage of 3.8 to 2.5 V and a current of 0.1 C to 2 C for formation, with a formation time of 1 to 180 min.

[0011] The aging process is high-temperature aging, with an aging temperature of 45-60℃; preferably, the aging time is 24-72 hours.

[0012] The negative voltage discharge step includes placing the battery cell that has been aged at high temperature at room temperature; and performing negative voltage discharge on the battery cell that has been placed at room temperature.

[0013] The process includes liquid injection and high-temperature settling of the injected cells before the formation step; the settling temperature is 20-48°C, and preferably, the settling time is 14-48 hours.

[0014] A formation and capacity testing method for improving black spots at the interface of lithium-ion batteries includes the above-mentioned formation and aging method, and further includes capacity testing after the negative voltage discharge is completed.

[0015] After the capacity testing step, the cell is allowed to stand at room temperature at least once; the process also includes a step of testing the open-circuit voltage of the cell; preferably, the open-circuit voltage test is performed after the high-temperature standing step and after the room-temperature standing step. The process also includes a step of sealing the cell after the negative voltage discharge; and / or, a step of secondary electrolyte injection into the cell after the negative voltage discharge; and / or, secondary electrolyte injection into the cell after the negative voltage discharge, followed by sealing of the cell after secondary electrolyte injection; and capacity testing of the sealed cell.

[0016] The method for improving black spots at the interface of lithium-ion batteries, or the method for improving the formation and capacity of black spots at the interface of lithium-ion batteries, is used to prepare lithium-ion battery cells.

[0017] The technical solution of this invention has the following advantages:

[0018] The method of this invention adds a negative pressure discharge step after aging in the existing formation and capacity testing process to achieve the goal of completely removing the gas generated during aging, avoiding interface black spots caused by gas residue, thereby improving the interface black spot problem of lithium-ion batteries, especially high-energy-density lithium-ion batteries. Compared with existing commonly used improvement methods, it has the following advantages: First, it does not require the addition of cost-increasing additives to the electrolyte; second, compared with negative pressure gas extraction during aging, the negative pressure discharge time is much shorter than the aging time, avoiding increased energy consumption and electrolyte loss caused by prolonged negative pressure; third, during the discharge process, the battery SoC decreases and the electrode spacing increases, and negative pressure gas extraction at this time has a better extraction effect and more effectively avoids gas residue inside the electrodes. Attached Figure Description

[0019] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0020] Figure 1 This is a flowchart of a method for improving the formation and capacity of lithium-ion battery interfaces according to an embodiment of the present invention.

[0021] Figure 2 This is a flowchart of a lithium-ion battery cell formation and capacity testing method according to Comparative Example 1 of the present invention;

[0022] Figure 3 This is a flowchart of a lithium-ion battery cell formation and capacity testing method according to Comparative Example 2 of the present invention;

[0023] Figure 4 This is an explanation of the principle of the traditional fractionation and composting method in Example 1;

[0024] Figure 5 This is a description of the principle of the formation and capacity method after the addition of the negative pressure discharge step in Example 1;

[0025] Figure 6 This is a comparison diagram of the cell interfaces of Example 1 and Comparative Examples 1 and 2; Figure 6 (a) is a cell interface diagram of Example 1; Figure 6 (b) is a cell interface diagram of Comparative Example 1; Figure 6 (c) is a cell interface diagram of Comparative Example 2. Detailed Implementation

[0026] Example 1

[0027] like Figure 1 As shown, a formation and capacity testing method for improving interface black spots in high-energy-density lithium-ion batteries includes negative pressure formation, high-temperature aging, negative pressure discharge, and capacity testing steps. The chemical system of the high-energy-density lithium-ion battery is a Si anode, an FEC-based electrolyte, and an NCM ternary cathode, with an energy density of 260 Wh / kg.

[0028] The negative pressure formation step is as follows: after the cell has been injected with electrolyte and allowed to stand, it is evacuated to -80 kPa, and then a voltage of 3.2V and a current of 0.1C are applied for formation. The standing temperature is 45℃ and the standing time is 24h.

[0029] After negative voltage formation, an open-circuit voltage test is performed to obtain OCV1 (open-circuit voltage 1), followed by aging. The high-temperature aging step is as follows: the negative voltage formed cell is aged at 50°C for 48 hours.

[0030] The negative pressure discharge step is as follows: After the high-temperature aging process (when the SoC is above 70%), the battery cell is left to stand at room temperature for 1 hour. Then, while discharging the battery cell, a vacuum is simultaneously drawn into the battery cell for negative pressure evacuation. The discharge voltage is 2.5V, the discharge current is set to 1C, the negative pressure is -80Kpa, and the negative pressure discharge time is 30 minutes. After the negative pressure discharge, the battery cell SoC is 0%. After standing at room temperature for 1 hour, an open-circuit voltage test can be performed to obtain OCV2 (open-circuit voltage 2) before proceeding with the negative pressure discharge.

[0031] The capacity grading step is as follows: the cells after negative pressure discharge are grading. After the negative pressure discharge, the steps of secondary liquid injection, sealing, and helium testing are also included. Specifically, the cells after negative pressure discharge are injected with liquid a second time until the liquid injection coefficient is 2.5g / Ah; the cells after secondary liquid injection are laser sealed; the sealed cells are subjected to a second helium test; the cells that pass the helium test are grading; the cells after capacity grading are subjected to room temperature standing for 2 and 3 times in sequence, followed by coating and capacity grouping, and open circuit voltage tests are performed after room temperature standing for 2 and 3 times respectively to obtain OCV3 (open circuit voltage 3) and OCV4 (open circuit voltage 4).

[0032] Example 2

[0033] like Figure 1 As shown, a formation and capacity testing method for improving interface black spots in high-energy-density lithium-ion batteries includes negative pressure formation, high-temperature aging, negative pressure discharge, and capacity testing steps. The chemical system of the high-energy-density lithium-ion battery is a Si anode, an FEC-based electrolyte, and an NCM ternary cathode, with an energy density of 260 Wh / kg.

[0034] The negative pressure formation step is as follows: after the cell has been injected with electrolyte and allowed to stand, it is evacuated to -80 kPa, and then a voltage of 3.2V and a current of 0.1C are applied for formation. The standing temperature is 45℃ and the standing time is 24h.

[0035] After negative voltage formation, an open-circuit voltage test is performed to obtain OCV1 (open-circuit voltage 1), followed by aging. The high-temperature aging step is as follows: the negative voltage formed cell is aged at 50°C for 48 hours.

[0036] The negative pressure discharge step is as follows: After the high-temperature aging process (when the SoC is above 70%), the battery cell is left to stand at room temperature for 1 minute. Then, while discharging the battery cell, a vacuum is simultaneously drawn into the battery cell for negative pressure evacuation. The discharge voltage is 3.6V, the discharge current is set to 2C, the negative pressure is -10Kpa, and the negative pressure discharge time is 10 minutes. After the negative pressure discharge, the SoC of the battery cell is 40%. After standing at room temperature for 1 minute, an open-circuit voltage test can be performed to obtain OCV2 (open-circuit voltage 2) before performing the negative pressure discharge.

[0037] The capacity grading step is as follows: the cells after negative pressure discharge are grading. After the negative pressure discharge, the steps also include secondary electrolyte injection, sealing, and helium testing. Specifically, the cells after negative pressure discharge are injected with electrolyte to 2.5 g / Ah; the cells after secondary electrolyte injection are laser sealed; the sealed cells are subjected to a second helium test; the cells that pass the helium test are grading; the cells after capacity grading are sequentially subjected to room temperature resting for 2 and 3 days, followed by coating and capacity grouping, and open circuit voltage tests are performed after room temperature resting for 2 and 3 days respectively to obtain OCV3 (open circuit voltage 3) and OCV4 (open circuit voltage 4).

[0038] Example 3

[0039] like Figure 1 As shown, a formation and capacity testing method for improving interface black spots in high-energy-density lithium-ion batteries includes negative pressure formation, high-temperature aging, negative pressure discharge, and capacity testing steps. The chemical system of the high-energy-density lithium-ion battery is a Si anode, an FEC-based electrolyte, and an NCM ternary cathode, with an energy density of 260 Wh / kg.

[0040] The negative pressure formation step is as follows: after the cell has been injected with electrolyte and allowed to stand, it is evacuated to -80 kPa, and then a voltage of 3.2V and a current of 0.1C are applied for formation. The standing temperature is 45℃ and the standing time is 24h.

[0041] After negative voltage formation, an open-circuit voltage test is performed to obtain OCV1 (open-circuit voltage 1), followed by aging. The high-temperature aging step is as follows: the negative voltage formed cell is aged at 50°C for 48 hours.

[0042] The negative pressure discharge step is as follows: After the high-temperature aging process (when the SoC is above 70%), the battery cell is left to stand at room temperature for 1 minute. Then, while discharging the cell, a vacuum is simultaneously drawn into the cell for negative pressure evacuation. The discharge voltage is 2.9V, the discharge current is 1.5C, the negative pressure is -50Kpa, and the negative pressure discharge time is 20 minutes. After the negative pressure discharge, the SoC of the battery cell is 20%. After standing at room temperature for 1 minute, an open-circuit voltage test can be performed to obtain OCV2 (open-circuit voltage 2) before proceeding with the negative pressure discharge.

[0043] The capacity grading step is as follows: the cells after negative pressure discharge are grading. After the negative pressure discharge, the steps also include secondary electrolyte injection, sealing, and helium testing. Specifically, the cells after negative pressure discharge are injected with electrolyte to 2.5 g / Ah; the cells after secondary electrolyte injection are laser sealed; the sealed cells are subjected to a second helium test; the cells that pass the helium test are grading; the cells after capacity grading are sequentially subjected to room temperature resting for 2 and 3 days, followed by coating and capacity grouping, and open circuit voltage tests are performed after room temperature resting for 2 and 3 days respectively to obtain OCV3 (open circuit voltage 3) and OCV4 (open circuit voltage 4).

[0044] Example 4

[0045] like Figure 1 As shown, a formation and capacity testing method for improving interface black spots in high-energy-density lithium-ion batteries includes negative pressure formation, high-temperature aging, negative pressure discharge, and capacity testing steps. The chemical system of the high-energy-density lithium-ion battery is a Si anode, an FEC-based electrolyte, and an NCM ternary cathode, with an energy density of 260 Wh / kg.

[0046] The negative pressure formation step is as follows: after the cell has been injected with electrolyte and allowed to stand, it is evacuated to -80 kPa, and then a voltage of 3.2V and a current of 0.1C are applied for formation. The standing temperature is 45℃ and the standing time is 24h.

[0047] After negative voltage formation, an open-circuit voltage test is performed to obtain OCV1 (open-circuit voltage 1), followed by aging. The high-temperature aging step is as follows: the cells after negative voltage formation are aged at 45°C for 70 hours.

[0048] The negative pressure discharge step is as follows: After the high-temperature aging process (when the SoC is above 70%), the battery cell is left to stand at room temperature for 1 minute. Then, while discharging the battery cell, a vacuum is simultaneously drawn into the battery cell for negative pressure evacuation. The discharge voltage is 3.3V, the discharge current is 1.7C, the negative pressure is -30Kpa, and the negative pressure discharge time is 15 minutes. After the negative pressure discharge, the SoC of the battery cell is 10%. After standing at room temperature for 1 minute, an open-circuit voltage test can be performed to obtain OCV2 (open-circuit voltage 2) before proceeding with the negative pressure discharge.

[0049] The capacity grading step is as follows: the cells after negative pressure discharge are grading. After the negative pressure discharge, the steps also include secondary electrolyte injection, sealing, and helium testing. Specifically, the cells after negative pressure discharge are injected with electrolyte to 2.5 g / Ah; the cells after secondary electrolyte injection are laser sealed; the sealed cells are subjected to a second helium test; the cells that pass the helium test are grading; the cells after capacity grading are sequentially subjected to room temperature resting for 2 and 3 days, followed by coating and capacity grouping, and open circuit voltage tests are performed after room temperature resting for 2 and 3 days respectively to obtain OCV3 (open circuit voltage 3) and OCV4 (open circuit voltage 4).

[0050] Comparative Example 1

[0051] like Figure 2 As shown, a formation and capacity testing process for a high-energy-density lithium-ion battery cell includes negative pressure formation, high-temperature aging, and capacity testing steps. The chemical system of the high-energy-density lithium-ion battery is a Si anode, an FEC-based electrolyte, and an NCM ternary cathode, with an energy density of 260 Wh / kg.

[0052] The negative pressure formation step is as follows: after the cell has been injected with electrolyte and allowed to stand, it is evacuated to -80 kPa, and then a voltage of 3.2V and a current of 0.1C are applied for formation. The standing temperature is 45℃ and the standing time is 24h.

[0053] The high-temperature aging step is as follows: the battery cell after negative voltage formation is aged at 50°C for 48 hours. After negative voltage formation, an open-circuit voltage test can be performed to obtain OCV1 (open-circuit voltage 1) before aging.

[0054] The capacity grading process involves grading the cells after high-temperature aging and a 1-day resting period at room temperature. Following the 1-day resting period at room temperature after high-temperature aging, the process includes secondary electrolyte injection, sealing, and helium testing. Specifically, the cells after the 1-day resting period at room temperature are injected with electrolyte to a concentration of 2.5 g / Ah; the cells after the secondary electrolyte injection are laser-sealed; the sealed cells undergo a secondary helium test; the cells that pass the helium test are then graded; the graded cells are then subjected to a 2-day resting period at room temperature and a 3-day resting period at room temperature, followed by coating and capacity grouping. Open-circuit voltage tests are then performed after the 2-day and 3-day resting periods at room temperature, yielding OCV3 (open-circuit voltage 3) and OCV4 (open-circuit voltage 4).

[0055] Comparative Example 2

[0056] like Figure 3 As shown, a formation and capacity testing method for improving black spots at the interface of a high-energy-density lithium-ion battery cell includes negative pressure formation, high-temperature aging, negative pressure venting, and capacity testing steps. The chemical system of the high-energy-density lithium-ion battery is a Si anode, an FEC-based electrolyte, and an NCM ternary cathode, with an energy density of 260 Wh / kg.

[0057] The negative pressure formation step is as follows: after the cell has been injected with electrolyte and allowed to stand, it is evacuated to -80 kPa, and then a voltage of 3.2V and a current of 0.1C are applied for formation. The standing temperature is 45℃ and the standing time is 24h.

[0058] After negative voltage formation, an open-circuit voltage test is performed to obtain OCV1 (open-circuit voltage 1), followed by aging. The high-temperature aging step is as follows: the negative voltage formed cell is aged at 50°C for 48 hours.

[0059] The negative pressure exhaust step is as follows: After the high-temperature aging process is completed (the SoC is above 70%), the battery cell is left to stand at room temperature for 1 hour. Then, the battery cell left to stand at room temperature for 1 hour is evacuated to -80 kPa for negative pressure exhaust. The negative pressure exhaust time is 30 minutes. After standing at room temperature for 1 hour, an open circuit voltage test can be performed to obtain OCV2 (open circuit voltage 2) before negative pressure exhaust.

[0060] The capacity grading step is as follows: the cells after negative pressure venting are grading. After the negative pressure venting is completed, the steps of secondary electrolyte injection, sealing, and helium testing are also included. Specifically, the cells after negative pressure venting are injected with electrolyte a second time to 2.5 g / Ah; the cells after secondary electrolyte injection are laser sealed; the sealed cells are subjected to a second helium test; the cells that pass the helium test are grading; the cells after capacity grading are subjected to room temperature standing for 2 and 3 times in sequence, followed by coating and capacity grouping, and open circuit voltage tests are performed after room temperature standing for 2 and 3 times respectively to obtain OCV3 (open circuit voltage 3) and OCV4 (open circuit voltage 4).

[0061] Results Analysis

[0062] like Figure 6 As shown in (a), through optimized process methods, the aging and capacity testing method of Example 1 can effectively improve the problem of interface black spots in high energy density systems, while avoiding the risks of cell performance degradation and safety caused by interface black spots. This is because the aging and capacity testing process in Example 1 adds a negative pressure discharge step after aging, reducing the cell's SoC state while adding negative pressure venting. Since the SoC state decreases to 0% after discharge, the negative electrode begins to shrink, and the spacing between the electrodes increases. Implementing negative pressure at this time facilitates the complete and thorough discharge of gas, preventing it from remaining inside the cell. Figure 5 As shown.

[0063] like Figure 6 As shown in (b), compared to the conventional process in Example 1, the cell interface shows obvious black spots. This is because the gas formed during the aging process is not expelled. In the initial stage of capacity testing, the cell is fully charged at atmospheric pressure. Air bubbles remaining in the electrodes during charging cause black spots to form at the interface. Figure 4 As shown.

[0064] like Figure 6 As shown in (c), the improved process method of Comparative Example 2 did not exhaust gas thoroughly enough, and black spots still remained at the cell interface. This is because Comparative Example 2 only performed negative pressure venting after aging. At this time, the SoC state of the cell is generally 70% to 100%, the negative electrode expands significantly, and the venting space inside the cell is small, making it difficult for gas to escape. Gas remains inside the cell, and the air bubbles remaining in the electrode during the capacity grading charging process will still cause black spots to form at the interface.

[0065] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for improving black spot of lithium ion battery interface, comprising formation and aging steps, characterized in that, The negative pressure discharge is performed after the aging step ends; The negative pressure discharge step includes: static storage of the high-temperature aged battery cell at room temperature; negative pressure discharge of the battery cell after the static storage at room temperature; and the negative pressure discharge is performed by vacuumizing the battery cell while discharging. The discharge voltage in the negative pressure discharge step is 3.6-2.5V, and the vacuum degree is not more than -10Kpa. The chemical conversion is negative pressure chemical conversion, which includes: vacuumizing the battery cell to -10 to -80Kpa, and then applying a voltage of 3.8-2.5V and a current of 0.1C-2C for chemical conversion, and the chemical conversion time is 1-180min.

2. The method of claim 1, wherein, The lithium ion battery is a high-energy-density-system lithium ion battery with an energy density greater than 200Wh / kg.

3. The method of claim 2, wherein, The chemical system of the high-energy-density-system lithium ion battery is Si-based negative electrode, FEC-based electrolyte and ternary positive electrode.

4. The method of claim 3, wherein, The ternary positive electrode is NCM ternary positive electrode.

5. The method of claim 1, wherein, The vacuum degree in the negative pressure discharge step is -10 to -80Kpa.

6. The method of claim 1, wherein, The aging is high-temperature aging, and the aging temperature is 45-60℃.

7. The method of claim 6, wherein, The aging time is 24-72h.

8. The method according to any one of claims 1 to 7, characterized in that, The method further includes a step of injecting electrolyte and high-temperature static storage of the battery cell after the injection before the chemical conversion step, and the static storage temperature is 20-48℃.

9. A formation and capacity method for improving the black spot of the lithium ion battery interface, characterized in that, The method of any one of claims 1-8 further includes a step of performing capacity test after the negative pressure discharge ends.

10. The chemical formation and dispensing method of claim 9, wherein, At least one static storage at room temperature is performed after the capacity test ends. The method further includes a step of open-circuit voltage test of the battery cell. And / or, the method further includes a step of sealing the battery cell after the negative pressure discharge ends. And / or, the method further includes a step of secondary injection of the battery cell after the negative pressure discharge ends.

11. The chemical formation and dispensing method of claim 10, wherein, The open-circuit voltage test is performed after the high-temperature static storage step and the static storage at room temperature.

12. The chemical formation and batching method of claim 10, wherein, The battery cell after the negative pressure discharge is subjected to secondary injection, the battery cell after the secondary injection is sealed, and the sealed battery cell is subjected to capacity test.

13. The use of the method for improving the black spot of the interface of lithium ion battery according to any one of claims 1-8 or the formation and partial charge method for improving the black spot of the interface of lithium ion battery according to any one of claims 9-12, characterized in that The method is used for preparing a lithium ion battery cell. The method is used for preparing a lithium ion battery cell.

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