Formation method of lithium-supplemented battery cell, lithium ion battery and electric device

Abstract

The application provides a formation method of a lithium-supplemented battery cell, a lithium ion battery and an electric device, and solves the problem of gas generation and accumulation of a lithium ion battery due to a lithium supplementing agent in the prior art. The method comprises the following steps: pre-charging the lithium-supplemented battery cell at a first current for a first time length to obtain a first state battery cell; charging the first state battery cell to a first preset voltage at a second current to obtain a second state battery cell, the second current being greater than the first current; applying a first external pressure to the second state battery cell for a second time length to obtain a third state battery cell, the first external pressure being periodically changed within the second time length; applying a second external pressure to the third state battery cell for a third time length to obtain a fourth state battery cell, the internal pressure of the fourth state battery cell and the external pressure being dynamically balanced; and charging the fourth state battery cell to a second preset voltage at the second current to obtain a fifth state battery cell.

Description

Technical Field

[0001] This application relates to the field of lithium-ion battery technology, specifically to a method for forming a battery cell after lithium replenishment, a lithium-ion battery, and an electrical device thereof. Background Technology

[0002] During the initial charge and discharge of a lithium-ion battery, a solid electrolyte interphase (SEI) film forms on the surface of the negative electrode in response to the electrolyte. This process irreversibly consumes some active lithium, leading to a decrease in initial coulombic efficiency and potentially limiting the battery's energy density and cycle life. To compensate for this lithium loss, lithium replenishing agents, such as lithium-rich oxides, metallic lithium, or their complexes, are often introduced into the positive or negative electrode in industrial applications. By releasing additional lithium sources during the formation stage, initial efficiency can be effectively improved, and long-term cycle performance can be enhanced.

[0003] However, lithium supplements typically exhibit high chemical or electrochemical activity during formation, readily reacting with electrolyte components to generate gas, leading to a rapid increase in internal pressure. Excessive internal pressure can cause localized compression or deformation of the separator, disrupting the uniform contact at the electrode / separator interface. Simultaneously, the retention of gas bubbles on the electrode surface can interfere with the continuity and compactness of the SEI film, thereby affecting interfacial stability and ion transport kinetics. Furthermore, residual gas may expand further during subsequent high-temperature storage or cycling, posing a safety risk. Summary of the Invention

[0004] In view of this, the embodiments of this application aim to provide a method for the formation of a battery cell after lithium replenishment, a lithium-ion battery, and an electrical device, so as to solve the problem of gas generation and accumulation in lithium-ion batteries due to lithium replenishment agents in the prior art.

[0005] In a first aspect, embodiments of this application provide a method for forming a battery cell after lithium replenishment, comprising: The first state cell is obtained by pre-charging the lithium-replenished cell with the first current for a first time. The first state cell is charged to a first preset voltage using a second current to obtain a second state cell, wherein the second current is greater than the first current; A first external pressure of a second duration is applied to the second-state cell to obtain a third-state cell, wherein the first external pressure changes periodically within the second duration. A second external pressure of a third duration is applied to the third-state cell to obtain a fourth-state cell, wherein the internal pressure and external pressure of the fourth-state cell are dynamically balanced. The fourth-state cell is charged to a second preset voltage using the second current to obtain the fifth-state cell.

[0006] Optionally, the range of the first current is 0.01C to 0.03C; and / or, The range of the second current is C / 5 to C / 3.

[0007] Optionally, both the first preset voltage and the second preset voltage are in the range of 4V~4.3V, and the second preset voltage is greater than the first preset voltage.

[0008] Optionally, the step of applying a first external pressure for a second duration to the second-state cell to obtain a third-state cell, wherein the first external pressure changes periodically within the second duration, includes cyclically executing steps a and b at least once until the third-state cell is obtained, wherein steps a and b include: a. Apply a first pressure to the cell in the second state for a duration of a first sub-duration to obtain a cell in the first exhaust state; b. Apply a second pressure to the first venting state cell for a duration equal to the second sub-duration to obtain a cell in the second venting state.

[0009] Optionally, the first pressure is less than the second pressure; and / or, The first pressure ranges from -10 kPa to 0 kPa, and the second pressure ranges from -85 kPa to -95 kPa; and / or, The first sub-duration ranges from 5 min to 15 min, and the second sub-duration ranges from 5 min to 15 min.

[0010] Optionally, the second external pressure P1 satisfies P1 = |P0 - P2|; Wherein, P0 refers to the atmospheric pressure of the environment in which the fourth-state battery cell is located, and P2 refers to the gas pressure inside the fourth-state battery cell.

[0011] Optionally, after the step of charging the fourth-state cell to a second preset voltage with the second current to obtain the fifth-state cell, the method further includes: The fifth-state cell is discharged to a preset SOC to obtain the sixth-state cell.

[0012] Optionally, after the step of discharging the fifth-state cell to a preset SOC to obtain the sixth-state cell, the method further includes: The sixth-state battery cell is placed in an environment with a first preset temperature and maintained for a first preset time to obtain a battery cell after formation and degassing.

[0013] Secondly, embodiments of this application provide a lithium-ion battery, comprising: a battery cell after formation degassing obtained using the formation method described in the first aspect.

[0014] Thirdly, embodiments of this application provide an electrical device including at least one lithium-ion battery as described in the second aspect.

[0015] The beneficial effects of the embodiments of this application are as follows: This application provides a method for the formation of a battery cell after lithium replenishment. This method, by combining staged current charging with periodic external pressure control, can actively intervene in gas behavior during the critical stage of lithium replenishment agent activity release. Specifically, the initial low-current pre-charging helps to moderate the reaction rate of the lithium replenishment agent and reduce the initial violent gas production; after the first current has been charged for a first duration, the method switches to a second current, i.e., a higher current, to accelerate the charging of the battery cell and accelerate gas production; when the battery cell is charged to a first preset voltage, it indicates that the current gas production is close to or has reached its peak. Applying a periodically varying first external pressure to the battery cell in this second state can promote the migration of the generated gas from the inside of the battery cell to the outside; after the generated gas has been basically discharged, the second external pressure is adjusted to make the internal and external pressures of the battery cell tend to be in dynamic equilibrium, avoiding continuous gas accumulation; finally, the battery cell is charged to a second preset voltage with a second current to further stabilize the formation of the SEI film and the consumption of the remaining active material. This method directly addresses the gas generation issue in battery cells after lithium replenishment by adjusting the formation process that is already required in battery production. It does not rely on special materials or equipment, nor does it require adding a separate process. It can effectively reduce the amount of gas trapped inside the cell during the formation process, thereby alleviating the membrane deformation caused by increased internal pressure, improving the uniformity and density of the SEI film, and enhancing the stability of the electrode / electrolyte interface, ultimately contributing to improved battery safety. Attached Figure Description

[0016] Figure 1 The diagram shown is a flowchart of a lithium-ion battery cell formation method provided in an embodiment of this application. Detailed Implementation

[0017] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0018] Please see Figure 1 This application provides a method for forming a battery cell after lithium replenishment, including steps S1 to S5. Specifically: S1. The lithium-recharged cell is pre-charged with the first current for a first duration to obtain the cell in the first state.

[0019] The lithium-filled and sealed battery cell is pre-charged with a first current for a first duration to bring the cell to its first state. A relatively low current density is used in this stage to slow down the initial reaction rate between the lithium-filling agent and the electrolyte, stabilize the activity of the lithium-filling agent, and avoid violent side reactions before the SEI film has stabilized. This gentle activation process helps to initially build a relatively uniform interfacial film on the negative electrode surface, providing a stable electrochemical environment for subsequent high-current formation.

[0020] S2. Charge the first state cell to the first preset voltage with the second current to obtain the second state cell, where the second current is greater than the first current.

[0021] S3. Apply a first external pressure for a second duration to the second-state cell to obtain a third-state cell. The first external pressure changes periodically within the second duration.

[0022] The charging current is increased to a second current higher than the first current, and the first-state cell continues to be charged until its voltage reaches a first preset voltage, at which point the cell enters the second state. When the cell voltage rises to the range where the lithium supplement agent significantly participates in the reaction, the gas generation rate increases significantly. This first preset voltage is the voltage range where the lithium supplement agent significantly participates in the reaction, and this voltage range can be determined based on the material of the lithium supplement agent and experiments. Without intervention, gas will accumulate rapidly in the sealed cavity. Therefore, after the cell is in the second state, a first external pressure for a second duration is immediately applied to it, and this pressure changes periodically within the duration, thereby obtaining a third-state cell. This periodic pressure control simulates a "breathing" process. By alternately changing the external pressure environment of the cell, the internal trapped gas is driven by the pressure difference to migrate to the pressure relief structure and be discharged, effectively suppressing local bubble accumulation.

[0023] The pressure relief structure may include a microporous venting structure provided in the cell structure, and may also include a pressure relief hole provided on the top cover of the cell. As the specific pressure relief structure is not the focus of this application and belongs to the prior art, it will not be described in detail here.

[0024] S4. Apply a second external pressure for a third duration to the third-state cell to obtain the fourth-state cell. The internal pressure and external pressure of the fourth-state cell are dynamically balanced.

[0025] A second external pressure of a third duration is applied to the third-state cell, gradually bringing the internal gas pressure of the cell to a dynamic equilibrium with the external environment, thus forming the fourth-state cell. In other words, the external pressure is adjusted according to the actual venting situation inside the cell to avoid excessive suction that could lead to electrolyte loss or interface drying, while ensuring that residual gas is continuously and slowly released.

[0026] S5. Charge the fourth-state cell to the second preset voltage using the second current to obtain the fifth-state cell.

[0027] The fourth-state cell is charged to a higher second preset voltage using the second current, completing the main formation process and obtaining the fifth-state cell. At this point, the SEI film has been basically densified, the lithium replenishment reaction is basically complete, and due to the effective venting in the early stage, the internal pressure of the cell is within a controllable range, the separator generally does not undergo significant deformation, and the electrode interface maintains good contact.

[0028] The technical solution provided in this application mainly involves: First, a first current pre-charge is performed. The initial low current pre-charge helps to moderate the reaction rate of the lithium replenishment agent and reduce the initial violent gas production. After the first current has been charged for a first duration, the process switches to a second current, i.e., a higher current to accelerate the charging of the battery cell and accelerate the gas production of the battery cell. Then, when the battery cell is charged to a first preset voltage, it indicates that the current gas production is close to or has reached its peak. A periodically varying first external pressure is applied to the battery cell in this second state to promote the migration of the generated gas from the inside of the battery cell to the outside. After the generated gas has been basically discharged, the pressure inside and outside the battery cell is adjusted by controlling the second external pressure to make the pressure tend to be in dynamic equilibrium, so as to avoid the continuous accumulation of gas. Finally, the battery cell is charged to a second preset voltage with a second current to further stabilize the formation of the SEI film and the consumption of the remaining active material. This method directly addresses the gas generation issue in battery cells after lithium replenishment by adjusting the formation process that is already required in battery production. It does not rely on special materials or equipment, nor does it require adding a separate process. It can effectively reduce the amount of gas trapped inside the cell during the formation process, thereby alleviating the membrane deformation caused by increased internal pressure, improving the uniformity and density of the SEI film, and enhancing the stability of the electrode / electrolyte interface, ultimately contributing to improved battery safety.

[0029] It should be noted that the lithium replenishing agent can be lithium oxide, lithium peroxide, lithium ferrite, etc. In this embodiment, the lithium replenishing agent is lithium ferrite, and the subsequent settings for various currents, voltages, and times are all based on the material properties of lithium ferrite. Of course, in other embodiments, other lithium replenishing agents such as lithium oxide can also be used, and correspondingly, the settings for current, voltage, time, etc., can be adjusted according to the material characteristics of the lithium replenishing agent itself.

[0030] In some embodiments, the first current can be set to a range of 0.01C to 0.03C. This low current density effectively suppresses the rapid decomposition of the lithium replenishing agent during the initial charging stage, preventing localized gas concentration due to excessively vigorous reactions. Furthermore, when the first current is below 0.01C, the pre-charging time is significantly prolonged, affecting production efficiency; while if it is above 0.03C, it is difficult to adequately mitigate the initial activity of the lithium replenishing agent, resulting in some cells exhibiting micro-bulging in the early stages. Therefore, controlling the first current within the range of 0.01C to 0.03C achieves a better balance between interface stability and process efficiency.

[0031] Accordingly, the value range of the second current can be set to C / 5 to C / 3 (i.e., 0.2C to 0.33C). This current level is suitable for the later stages of SEI film growth and the main stage of lithium replenishment reaction, ensuring formation efficiency while avoiding excessive polarization or accelerated side reactions caused by excessive current. Especially after entering the active voltage range for gas production, using the second current within this range in conjunction with periodic pressure control helps maintain the match between the reaction rate and the exhaust capacity, preventing the gas generation rate from far exceeding the exhaust capacity and causing the internal pressure to rise too high.

[0032] It should be noted that the setting of this current parameter does not require any adjustment to the hardware configuration of the existing charging and discharging equipment; it can be achieved simply through program settings, making it easy to apply directly to conventional production lines, i.e., it can be directly applied to traditional formation processes.

[0033] In some embodiments, experimental verification has shown that most common lithium replenishing agents begin to significantly participate in the delithiation reaction when the charging voltage reaches approximately 4.0 V, accompanied by significant gas generation. If intervention is not timely at this stage, the gas will accumulate rapidly. Therefore, setting the first preset voltage in the range of 4 V to 4.3 V ensures that the external pressure control step is initiated in a timely manner after the lithium replenishing agent enters the main reaction region and before gas generation becomes uncontrollable. This voltage point avoids the initial SEI film formation stage (typically below 3.8 V) and does not excessively delay into the high-voltage side reaction intensification region, exhibiting good process window adaptability.

[0034] Correspondingly, the second preset voltage is also in the range of 4 V to 4.3 V, but it needs to be higher than the first preset voltage to ensure that the lithium replenishment reaction is fully completed and to promote further densification of the SEI film. For example, the first preset voltage can be set to 4.0 V to trigger the venting operation; the second preset voltage can be set to 4.2 V or 4.25 V as the formation termination point. This setting can ensure that the lithium replenishment agent releases enough active lithium, and can also avoid additional side reactions such as cathode material decomposition or electrolyte oxidation caused by overcharging to higher voltages (such as greater than 4.3 V), thereby reducing unnecessary gas generation sources.

[0035] It should be noted that the voltage range of 4 V to 4.3 V applies to current mainstream battery structures using cathode systems such as lithium cobalt oxide, lithium iron phosphate, and ternary lithium, paired with graphite or silicon-carbon anodes. This range can be fine-tuned for different cathode materials or types of lithium replenishing agents, but it generally falls within the potential window where the lithium replenishing agent is effectively activated and the electrolyte stability can be maintained.

[0036] In some embodiments, the step of applying a first external pressure for a second duration to the second-state cell to obtain a third-state cell, wherein the first external pressure changes periodically within the second duration, includes cyclically executing steps a and b at least once until a third-state cell is obtained. Steps a and b include: a. Apply a first pressure to the second-state cell for a duration of a first sub-duration to obtain a cell in the first exhaust state.

[0037] b. Apply a second pressure to the cell in the first exhaust state for a duration equal to the second sub-duration to obtain a cell in the second exhaust state.

[0038] Specifically, after the battery cell is charged to the first preset voltage and enters the second state, step a is executed first: a first pressure is applied to the battery cell for a first duration, putting the battery cell into a first venting state. This stage typically uses an environment close to atmospheric pressure or a slight negative pressure to stabilize the gas phase distribution inside the battery cell and avoid disturbances at the electrolyte interface due to sudden vacuuming. Then, step b is executed: a lower second pressure (i.e., a stronger negative pressure) is switched to for a second duration, forming a second venting state. Under this negative pressure condition, the gas accumulated inside the battery cell migrates outward and is discharged through the pressure relief structure driven by the pressure difference.

[0039] Steps a and b above constitute a complete "pressure cycle," which can be repeated once or multiple times depending on the actual gas production. For example, in a system with more vigorous gas production, it can be cycled 2 to 3 times to ensure that the gas is released in batches and smoothly, rather than causing structural impact due to a one-time violent exhaust. Compared with continuous vacuuming, this intermittent negative pressure strategy is more conducive to maintaining the electrolyte wetting state, while avoiding failure of the sealing structure due to long-term negative pressure fatigue.

[0040] It should be noted that steps a and b above only require program adjustments to the existing gas path control logic of the formation fixture or cavity, without the need for additional complex hardware. Effective management of the exhaust rhythm can be achieved simply by switching pressure levels and using timing control.

[0041] Furthermore, the first pressure can be set within the range of -10 kPa to 0 kPa. This pressure is close to atmospheric pressure or only a slight negative pressure is applied, and its main function is to provide a buffer stage before entering the strong negative pressure exhaust phase. On the one hand, this avoids drastic disturbance of the gas phase inside the cell due to sudden pressure difference changes; on the other hand, it helps stabilize the electrolyte interface and prevent local drying during subsequent evacuation. In this embodiment, the first pressure is 0 kPa.

[0042] Accordingly, the second pressure can be set within the range of -85 kPa to -95 kPa. This negative pressure level is sufficient to create an effective pressure difference between the inside and outside of the cell, driving the trapped gas to be discharged through the pressure relief structure, while not being too low to cause electrolyte to be drawn away and lost.

[0043] Regarding the duration of action, both the first and second sub-durations can be set within the range of 5 to 15 minutes. In this embodiment, both the first and second sub-durations are set to 10 minutes to avoid insufficient gas migration to the pressure relief channel and incomplete venting if the time is too short (e.g., less than 5 minutes); or excessive time (e.g., more than 15 minutes), which would lengthen the formation cycle and reduce production line efficiency. In practice, the duration can be adjusted within this range based on factors such as cell size, type of lithium replenishing agent, and amount of electrolyte injected. For example, 10 to 15 minutes can be used for larger capacity pouch cells, while 5 to 8 minutes can be used for small cylindrical cells.

[0044] In the aforementioned formation process, after the periodic pressure control is completed, the cell enters the third state. At this time, a small amount of residual gas may still exist inside, and its pressure is not yet fully balanced with the external environment. If the cell directly enters the subsequent high-voltage charging stage, these gases may expand due to temperature or exothermic reactions, causing the internal pressure to rise again. Therefore, in some embodiments, a dynamic balancing stage can be applied after the third state, that is, a second external pressure of a third duration is applied to the cell in the third state, and this pressure is adjusted according to the actual gas pressure inside the cell.

[0045] In detail, the second external pressure P1 satisfies: P1 = |P0 - P2|; Wherein, P0 refers to the atmospheric pressure of the environment in which the fourth-state battery cell is located, which is usually the standard atmospheric pressure or the pressure set in the production line cavity; P2 refers to the gas pressure inside the fourth-state battery cell. From the above relationship with P1, it can be seen that the technical solution of this embodiment can dynamically adjust the externally applied pressure by monitoring the internal pressure of the battery cell in real time or in stages, so that the pressure difference between the external and internal pressures is maintained within a small and controllable range.

[0046] In practice, this can be achieved through a closed-loop control system: when the internal pressure of the cell is detected to be slightly higher than the ambient pressure, a moderate negative pressure is applied; if the internal pressure is close to or lower than the ambient pressure, the negative pressure is reduced or stopped to prevent reverse air intake or structural collapse. This process continues for a third duration, allowing the internal and external pressures of the cell to gradually reach dynamic equilibrium, forming the fourth-state cell.

[0047] It should be noted that the third duration can range from 5 minutes to 15 minutes. In this embodiment, the third duration is 10 minutes.

[0048] Please see Figure 1 In some embodiments, after step S5, which involves charging the fourth-state cell to a second preset voltage with a second current to obtain the fifth-state cell, the method further includes: S6. Discharge the fifth-state cell to the preset SOC to obtain the sixth-state cell.

[0049] Specifically, the fifth-state battery cell is discharged to a preset state of charge (SOC) using a constant current or constant power method, for example, 30%–70% SOC, to obtain a sixth-state battery cell. The main reasons for discharging the fifth-state battery cell are as follows: On the one hand, at the end of formation, the cell is usually in a high SOC state (such as close to 100%). At this time, the positive electrode is in a high delithiation state, the interface activity is high, and the residual side reaction may still proceed slowly. On the other hand, trace amounts of gas that are not completely discharged have low solubility at high potentials and tend to aggregate to form microbubbles. By discharging appropriately, the electrode potential can be reduced, thereby enhancing the electrolyte's ability to dissolve residual gas and reducing the driving force of interfacial side reactions. This helps the gas to dissolve further or escape slowly through the pressure relief structure.

[0050] Please see Figure 1 In some embodiments, after step S6 of discharging the fifth-state cell to a preset SOC to obtain the sixth-state cell, the method further includes: S7. Place the sixth-state battery cell in an environment with a first preset temperature and maintain it for a first preset time to obtain the battery cell after formation and degassing.

[0051] Specifically, the first preset temperature can be selected from 45℃ to 50℃. In this embodiment, the first preset temperature is set to 45℃. The first preset time can range from 12 hours to 36 hours. In this embodiment, the first preset time is set to 24 hours. This step S7 is usually performed in an atmospheric pressure or slightly negative pressure environment without the need for additional electrical excitation. Under these conditions, the diffusion rate of the trace gas remaining inside the cell increases due to the temperature rise, making it easier to slowly discharge through the pressure relief structure; at the same time, the SEI film undergoes a certain degree of "self-repair" or reorganization under the gentle thermal effect, improving its density and ion conductivity.

[0052] It should also be noted that during steps S1 to S6, the temperature is set to a second preset temperature, which ranges from 20°C to 30°C. In this embodiment, the second preset temperature can be selected as 25°C to avoid high temperatures accelerating side reactions. In addition, a dynamic temperature control mechanism is introduced throughout the entire formation process, dynamically adjusting the temperature based on real-time monitoring data. This dynamic temperature control mechanism can be directly implemented through the temperature control program built into the formation cabinet, which is an existing temperature control technology and will not be elaborated upon here.

[0053] In summary, the lithium-added cell formation method provided in this application first uses a lower current for pre-charging to mitigate the activity of the lithium-adding agent, then switches to a higher current for charging to the active gas-generating voltage range. Subsequently, periodically varying external pressures (such as alternating atmospheric and negative pressures) are applied to promote gas expulsion. Then, the external pressure is dynamically adjusted to bring the internal and external pressures of the cell to equilibrium before final charging. Furthermore, the cell can be further discharged to a moderate state of charge (SOC) and subjected to temperature-controlled resting to promote residual gas release and interface stability. The entire solution requires no special materials or production line modifications; by simply optimizing the charge / discharge program and pressure control logic, it can significantly reduce internal pressure buildup within the cell, improve separator deformation and SEI film quality, and enhance battery consistency, cycle performance, and safety.

[0054] In some embodiments, this application provides a lithium-ion battery, which includes at least one battery cell after formation and degassing obtained by the formation method of the lithium-added battery cell described in any of the foregoing embodiments, so that the internal state of the formed battery cell reaches the same and stable electrochemical state, which is beneficial to improving the overall cycle life, fast charging performance and safety of the lithium-ion battery.

[0055] In practical applications, multiple cells after formation can be divided for capacity testing to assemble cells with the same electrochemical characteristics into the same cell group, thereby improving the consistency of the same cell group in lithium-ion batteries, which is beneficial to improving the battery performance of lithium-ion batteries and reducing the failure rate.

[0056] In some embodiments, this application provides an electrical device including at least one lithium-ion battery as described in the foregoing embodiments. In this embodiment, the electrical device is an electric vehicle, but this should not be construed as a limitation of this application. In other embodiments, the electrical device may also be a mobile phone, a laptop computer, a mobile charging station, or other similar device. This electrical device has the same beneficial effects as the lithium-ion battery described in the foregoing embodiments, which will not be repeated here.

[0057] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications or equivalent substitutions made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for forming a battery cell after lithium replenishment, characterized in that, include: The first state cell is obtained by pre-charging the lithium-replenished cell with the first current for a first time. The first state cell is charged to a first preset voltage using a second current to obtain a second state cell, wherein the second current is greater than the first current; A first external pressure of a second duration is applied to the second-state cell to obtain a third-state cell, wherein the first external pressure changes periodically within the second duration. A second external pressure of a third duration is applied to the third-state cell to obtain a fourth-state cell, wherein the internal pressure and external pressure of the fourth-state cell are dynamically balanced. The fourth-state cell is charged to a second preset voltage using the second current to obtain the fifth-state cell.

2. The method according to claim 1, characterized in that, The first current ranges from 0.01C to 0.03C; and / or, The range of the second current is C / 5 to C / 3.

3. The method according to claim 1, characterized in that, The first preset voltage and the second preset voltage are both in the range of 4V~4.3V, and the second preset voltage is greater than the first preset voltage.

4. The method according to claim 1, characterized in that, The step of applying a first external pressure for a second duration to the second-state battery cell to obtain a third-state battery cell, wherein the first external pressure changes periodically within the second duration, includes cyclically executing steps a and b at least once until the third-state battery cell is obtained. Steps a and b include: a. Apply a first pressure to the cell in the second state for a duration of a first sub-duration to obtain a cell in the first exhaust state; b. Apply a second pressure to the first venting state cell for a duration equal to the second sub-duration to obtain a cell in the second venting state.

5. The method according to claim 4, characterized in that, The first pressure is less than the second pressure; and / or, The first pressure ranges from -10 kPa to 0 kPa, and the second pressure ranges from -85 kPa to -95 kPa; and / or, The first sub-duration ranges from 5 min to 15 min, and the second sub-duration ranges from 5 min to 15 min.

6. The method according to claim 1, characterized in that, The second external pressure P1 satisfies: P1 = |P0 - P2|; Wherein, P0 refers to the atmospheric pressure of the environment in which the fourth-state battery cell is located, and P2 refers to the gas pressure inside the fourth-state battery cell.

7. The method according to claim 1, characterized in that, After the step of charging the fourth-state cell to a second preset voltage with the second current to obtain the fifth-state cell, the method further includes: The fifth-state cell is discharged to a preset SOC to obtain the sixth-state cell.

8. The method according to claim 7, characterized in that, After the step of discharging the fifth-state cell to a preset SOC to obtain the sixth-state cell, the method further includes: The sixth-state battery cell is placed in an environment with a first preset temperature and maintained for a first preset time to obtain a battery cell after formation and degassing.

9. A lithium-ion battery, characterized in that, include: The battery cell after formation and degassing obtained by the formation method according to any one of claims 1 to 8.

10. An electrical appliance, characterized in that, It includes at least one lithium-ion battery as described in claim 9.

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