Formation method of silicon-based negative electrode lithium ion battery cell, silicon-based negative electrode lithium ion battery cell and battery

Abstract

The invention provides a formation method of a silicon-based negative electrode lithium ion battery cell, the silicon-based negative electrode lithium ion battery cell and a battery, and belongs to the technical field of lithium ion batteries. According to the formation method, the number of turns of formation cycles is adjusted, the temperature, the pressure, the current density and the cut-off voltage in different formation cycles are regulated in a stepped manner, and meanwhile, a secondary liquid injection technology is combined, so that a compact and stable SEI film is formed on an electrode / electrolyte interface to the maximum extent; the volume expansion and shrinkage of the silicon-based negative electrode in the charging and discharging process are inhibited, meanwhile, the gas generation expansion in the formation process is reduced, and the liquid retention rate and the cycle performance of the battery cell are improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium-ion batteries, and particularly relates to a formation method for a silicon-based anode lithium-ion battery cell, a silicon-based anode lithium-ion battery cell, and a battery. Background Art

[0002] In lithium-ion batteries, the theoretical capacity of traditional graphite anodes is only 372 mAh / g. With the increasing demand for high-energy-density batteries in recent years, silicon-based anodes have received extensive attention due to their theoretical capacity nearly 10 times higher than that of graphite anodes. However, during charge and discharge, the volume of silicon-based anodes expands and contracts severely (about 300 - 400%), which will cause the pulverization and cracking of the anode active material, continue to react with the electrolyte side reaction, increase the interfacial impedance while generating gas, resulting in more severe swelling of the battery cell and performance degradation.

[0003] In order to alleviate the huge expansion and contraction problems of silicon-based anodes during cycling, a large number of studies have been carried out in all aspects of battery cell design. For example, from the aspect of improving the material system formula, modification can be carried out on silicon materials, cathode matching, conductive agents, binders, electrolytes, etc.; from the aspect of battery cell parameter design, modification can be carried out on the N / P ratio (the remaining capacity of the anode opposite the cathode exceeding the cathode under the same conditions in the same stage), compaction density, porosity, pore size, loading amount, etc.; from the aspect of battery cell process adjustment, optimization can be carried out on slurry mixing, coating, drying, rolling, formation, etc.

[0004] Modification from the aspect of material system formula adjustment or battery cell parameter design involves relatively complex technologies and processes, and it is difficult to balance battery cell performance, energy density, and cost reduction requirements in practical applications. Optimizing from the aspect of battery cell process adjustment is relatively simple. Among several improvement directions, optimizing formation conditions is the simplest and most effective, and has a relatively low impact on cost from the perspective of enterprise production. Summary of the Invention

[0005] The present invention aims to solve at least one of the technical problems in the prior art to some extent. For this purpose, an embodiment of the present invention provides a formation method for a silicon-based anode lithium-ion battery cell, a silicon-based anode lithium-ion battery cell, and a battery. The formation method can form a uniform and dense SEI film, effectively inhibit the expansion and contraction of the lithium-ion battery cell using this SEI film, thereby improving the performance of the battery.

[0006] A formation method for a silicon-based anode lithium-ion battery cell according to an embodiment of the present invention includes the following steps:

[0007] S1. Inject a first volume of electrolyte into the assembled battery cell to be filled with liquid, and then perform the first static placement;

[0008] S2. Perform at least three charge-discharge cycles on the battery cell obtained in step S1 under the conditions of temperature T and pressure P. First, charge at a constant current density I until the cut-off voltage V, and then discharge at the constant current density I until the lower limit voltage of the battery cell. The temperature T and pressure P of at least three charge-discharge cycles decrease sequentially, and the current density I and cut-off voltage V of at least three charge-discharge cycles increase sequentially; during the first charge-discharge cycle, the temperature T 首 is 50 - 80 °C; and / or, the pressure P 首 is 1 - 2 MPa; and / or, the current density I 首 is 0.02 - 0.12 C; and / or, the cut-off voltage V 首 is 3.3 - 3.6 V; during the first charge-discharge cycle, after the constant current charging process ends, perform a second static rest, and then discharge at a constant current until the lower limit voltage of the battery cell;

[0009] S3. Perform a third static rest and exhaust the gas on the battery cell obtained in step S2, and then inject the second volume of the electrolyte. The sum of the second volume and the first volume is equal to the designed amount of the electrolyte, and finally perform final sealing;

[0010] The advantages and technical effects brought by the formation method of the silicon-based anode lithium-ion battery cell in the embodiments of the present invention are as follows:

[0011] (1) In the formation method of the embodiments of the present invention, step S2 can effectively inhibit the gas generation during the initial film formation process at the interface in the formation stage of the battery cell, reduce the initial swelling. At the same time, in steps S1 and S3, the electrolyte is added in two times, which can reduce the large consumption of the electrolyte and improve the liquid retention rate, so as to inhibit the initial swelling and be beneficial to the long cycle performance of the battery cell;

[0012] (2) In the formation method of the embodiments of the present invention, a dense solid electrolyte interface film (abbreviated as SEI film) is formed at the electrode / electrolyte interface during the formation stage. During the repeated charge-discharge cycles, this SEI film can greatly resist the huge volume change caused by the expansion and contraction of the silicon-based anode, so that the battery cell will not break and reorganize, thereby inhibiting the continuous decomposition of the electrolyte and reducing the swelling of the battery cell, thus reducing the attenuation of battery performance;

[0013] (3) In the formation method of the embodiments of the present invention, step S2 performs at least three charge-discharge cycles, and the temperature T and pressure P of at least three charge-discharge cycles decrease sequentially, and the current density I and cut-off voltage V of at least three charge-discharge cycles increase sequentially, which can ensure a uniform and dense film formation effect.

[0014] (4) In the formation method of the embodiments of the present invention, the temperature T and pressure P of at least three charge-discharge cycles in step S2 decrease sequentially, which is to reduce the side reaction of battery materials when forming the SEI film at a high potential in the later stage.

[0015] (5) In the formation method of the embodiment of the present invention, in step S2, the current density I and the cut-off voltage V of at least three charge-discharge cycles increase sequentially. This is to ensure that the SEI film is slowly formed at a low potential in the early stage, so that the SEI film is uniform and dense, and the film formation speed is accelerated at a high potential in the later stage, thereby improving the production efficiency.

[0016] (6) In the formation method of the embodiment of the present invention, the temperature T of the first charge-discharge cycle 首 , the pressure P 首 , I 首 , V 首 are within the specified conditions, which is convenient to ensure a uniform and dense film formation effect.

[0017] (7) In the formation method of the embodiment of the present invention, first, in step S1, a first volume of electrolyte is injected into the assembled battery cell to be filled with electrolyte, and then in step S3, after the battery cell stands and exhausts, a second volume of electrolyte is injected. This is beneficial to ensure a certain electrolyte filling amount and sufficient infiltration of the battery cell, while preventing excessive film formation interface reactions.

[0018] In some embodiments, in step S1, the first volume is 40-70% of the designed amount of the electrolyte.

[0019] In some embodiments, in step S2, 3-6 times of the charge-discharge cycles are performed.

[0020] In some embodiments, in step S2, during the first charge-discharge cycle, constant current charging is carried out in two stages. The current density I of the first stage 首I is 0.02-0.05Co, and the cut-off voltage V 首I is 3.3-3.5V; the current density I of the second stage 首II is 0.08-0.12Co, and the cut-off voltage V 首II is 3.5-3.6V, and V 首I < V 首II .

[0021] In some embodiments, in step S2, at the last charge-discharge cycle, the temperature T 末 is 20-50°C; and / or, the pressure P 末 is 0.3-1MPa; and / or, the current density I 末 is 0.2-0.3Co; and / or, the cut-off voltage V 末 is 3.9-4.2V.

[0022] In some embodiments, in step S2, the temperature difference between two adjacent charge-discharge cycles is 5 - 20 °C, and / or the pressure difference between two adjacent charge-discharge cycles is 0.15 - 0.6 MPa, and / or the current density difference between two adjacent charge-discharge cycles is 0.01 - 0.1 C, and / or the cut-off voltage difference between two adjacent charge-discharge cycles is 0.05 - 0.3 V.

[0023] In some embodiments, in step S3, between injecting the second volume of the electrolyte and performing the final sealing, there is also a supplementary formation step: the battery cell after injecting the second volume of the electrolyte is charged at a constant current density I' to a cut-off voltage V' at a temperature T' and a pressure P'; then the fourth static state and gas exhaust are performed; the pressure P' in step S3 is the same as the pressure P during the first charge-discharge cycle in step S2; 首 the current density I' in step S3 is the same as the current density I during the first charge-discharge cycle in step S2, 首 the cut-off voltage V' in step S3 is the same as the cut-off voltage V during the last charge-discharge cycle in step S2; 末 the temperature T' in step S3 is greater than or equal to room temperature.

[0024] In some embodiments, the time of the first static state is 20 - 30 h; and / or the time of the second static state is 20 - 30 h; and / or the time of the third static state is 10 - 15 h, and / or the time of the fourth static state is 10 - 15 h.

[0025] In addition, an embodiment of the present invention also provides a silicon-based anode lithium-ion battery cell obtained by the formation method of the silicon-based anode battery cell of the embodiment of the present invention.

[0026] The advantages and technical effects brought by the silicon-based anode lithium-ion battery cell of the embodiment of the present invention are as follows:

[0027] Compared with the silicon-based anode lithium-ion battery cell obtained by the formation method in the prior art, in the silicon-based anode lithium-ion battery cell of the embodiment of the present invention, during the repeated charge-discharge cycle process, the volume change of the silicon-based anode is smaller, the retention rate of the electrolyte is higher, and the cycle performance of the battery cell is good.

[0028] In addition, an embodiment of the present invention also provides a silicon-based anode lithium-ion battery, including the silicon-based anode lithium-ion battery cell of the embodiment of the present invention.

[0029] The advantages and technical effects brought by the silicon-based anode lithium-ion battery of the embodiment of the present invention are as follows:

[0030] The silicon-based anode lithium-ion battery according to the embodiment of the present invention uses a silicon-based anode lithium-ion battery cell obtained by the formation method of the embodiment of the present invention. Therefore, during the repeated charge and discharge cycles, the volume change of the silicon-based anode is small, the retention rate of the electrolyte is high, and the battery cycle performance is good. Description of the Drawings

[0031] Figure 1 The flowcharts of the formation methods of Examples 1-3 are shown;

[0032] Figure 2 The electrolyte retention quality of the silicon-based anode lithium-ion battery cells obtained by the formation methods of Example 1 and Comparative Example 1 is shown;

[0033] Figure 3 The thickness increase of the silicon-based anode lithium-ion battery cells obtained by the formation methods of Example 1 and Comparative Example 1 is shown;

[0034] Figure 4 The discharge capacity retention rate of the silicon-based anode lithium-ion battery cells obtained by the formation methods of Example 1 and Comparative Example 1 is shown;

[0035] Figure 5 The DC internal resistance of the silicon-based anode lithium-ion battery cells obtained by the formation methods of Example 1 and Comparative Example 1 is shown; Detailed Embodiments

[0036] The embodiments of the present invention are described in detail below. The examples of the embodiments are shown in the drawings. The embodiments described below by referring to the drawings are exemplary and are intended to explain the present invention and should not be construed as limiting the present invention.

[0037] The embodiment of the present invention provides a formation method for a silicon-based anode lithium-ion battery cell, including the following steps:

[0038] S1. Inject a first volume of electrolyte into the assembled cell to be filled with electrolyte, and then perform the first static placement;

[0039] S2. Perform at least three charge and discharge cycles on the cell obtained by processing in step S1 under the conditions of temperature T and pressure P. First, charge at a constant current density I to the cut-off voltage V, and then discharge at the constant current density I to the lower limit voltage of the cell. The temperature T and pressure P of at least three charge and discharge cycles decrease in sequence, and the current density I and cut-off voltage V of at least three charge and discharge cycles increase in sequence; during the first charge and discharge cycle, the temperature T 首 is 50-80 °C; and / or, the pressure P 首 is 1-2 MPa; and / or, the current density I 首 is 0.02-0.12 Co; and / or, the cut-off voltage V 首is 3.3 - 3.6V; during the first charge-discharge cycle, after the constant-current charging process ends, a second static rest is performed, and then constant-current discharging is carried out until the lower limit voltage of the battery cell.

[0040] S3. The battery cell obtained by processing in step S2 is subjected to a third static rest and degassing, and then a second volume of the electrolyte is injected. The sum of the second volume and the first volume is equal to the designed amount of the electrolyte. Finally, terminal sealing is performed.

[0041] Specifically, the formation method of the embodiments of the present invention adjusts the number of charge-discharge cycles during the formation process, and performs stepped control on the temperature, pressure, current density, and cut-off voltage during at least three charge-discharge cycles. At the same time, combined with the secondary liquid injection technology, it maximally realizes the formation of a dense and stable SEI film at the electrode / electrolyte interface, inhibits the expansion and contraction of the battery cell during subsequent charge-discharge cycles, reduces the gas generation and expansion during the formation process, and improves the liquid retention rate and cycle performance of the battery cell.

[0042] Performing gradient adjustment on the temperature, pressure, current density, and cut-off voltage can not only ensure the film formation effect but also ensure the production efficiency. The film formation reaction is intense at high temperatures, and most film formation reactions occur at relatively low potentials. Therefore, at the initial stage of the reaction, it is desired that more film formation reactions occur, the reaction is slower, and the SEI film is more uniform. As the potential rises, a larger current can be set, so the film formation reaction efficiency will be higher and the formation time can be shortened. Therefore, considering comprehensively, the formation method of the embodiments of the present invention is proposed. In step S2, at least three charge-discharge cycles are performed, which can not only improve the film formation effect but also take into account a relatively high formation efficiency.

[0043] In the formation method of the embodiments of the present invention, the temperature T and pressure P of at least three of the charge-discharge cycles in step S2 both decrease in sequence, and the current density I and cut-off voltage V of at least three of the charge-discharge cycles both increase in sequence. The cut-off voltage and current density both increase in sequence to ensure that the SEI film is slowly formed at a low potential in the early stage, so that the SEI film has high uniformity and density, and the SEI film is formed at a high potential at a faster speed in the later stage to improve the production efficiency. If the cut-off voltage or current density during these charge-discharge cycles does not meet the above conditions, it is difficult to form a uniform film and it will affect the production efficiency.

[0044] In the formation method of the embodiments of the present invention, the temperature T and pressure P of at least three of the charge-discharge cycles in step S2 both decrease in sequence, and the current density I and cut-off voltage V of at least three of the charge-discharge cycles both increase in sequence. The pressure of at least three of the charge-discharge cycles decreases in sequence to reduce the pressure when forming the SEI film at a high potential in the later stage and reduce the side reactions of battery materials. The temperature of at least three of the charge-discharge cycles also decreases in sequence to reduce the temperature when forming the SEI film at a high potential in the later stage and slow down the intensity of the reaction, thereby reducing the side reactions of battery materials.

[0045] In the formation method of the embodiment of the present invention, first, in step (1), an electrolyte of a first volume is injected into the assembled battery cell to be filled with electrolyte, and then, in step S3, after the battery cell stands and vents, an electrolyte of a second volume is injected. This is beneficial for the battery cell to ensure a certain amount of electrolyte injection and full infiltration, while preventing excessive film-forming interface reactions. If all the designed amount of electrolyte is injected into the assembled battery cell to be filled with electrolyte at one time in step S1, it is easy to make the SEI film too thick, resulting in an increase in interface impedance.

[0046] In the formation method of the embodiment of the present invention, in step S1, a part of the electrolyte is first added. After completing at least three charge-discharge cycles in step S2, the remaining electrolyte is added in step S3 for formation. By adopting this design of adding electrolyte in steps, the film-forming reaction in step S2 can be controlled to avoid forming an overly thick SEI film. If all the designed amount of electrolyte is added in step S1 and then step S2 is carried out, an overly thick SEI film will be formed due to continuous growth of the SEI film, resulting in an increase in the battery interface impedance and a decrease in the kinetic level.

[0047] In some embodiments, in step S1, the first volume is 40-70% of the designed amount of the electrolyte, such as 40%, 45%, 50%, 55%, 60%, 65%, 70%, etc. When the proportion of the first volume is too small, insufficient film formation will occur, which is not conducive to the SEI film playing the role of conducting ions. When the proportion of the first volume is too large, excessive film formation will occur, resulting in an increase in interface impedance. Preferably, the first volume is 45-55% of the designed amount of the electrolyte.

[0048] In some embodiments, in step S1, the time of the first standing is 20-30h, such as 20h, 21h, 22h, 23h, 24h, 25h, 26h, 27h, 28h, 29h, 30h, etc. When the time of the first standing is too short, it is not conducive to the full progress of the reaction; when the time of the first standing is too long, it is not conducive to improving production efficiency. It is desired to form a uniform and dense film at a low potential, so the time of the first standing is longer than the standing time in the subsequent step S3.

[0049] In some embodiments, in step S2, 3-6 charge-discharge cycles are carried out, such as 3 times, 4 times, 5 times, 6 times, etc. Since the film-forming reaction is not the more the better, and long-term standing of the battery cell at high temperature will trigger side reactions at other material levels, it is not recommended to set the number of charge-discharge cycles too many. Preferably, 3-5 charge-discharge cycles are carried out; more preferably, 4 charge-discharge cycles are carried out.

[0050] The formation method according to the embodiment of the present invention. In step S2, the specific operation of the first charge-discharge cycle is as follows: The battery cell obtained by processing in step S1 is subjected to a charge-discharge cycle at a temperature T 首 and a pressure P 首 . First, it is constantly charged at a current density I 首 to a cut-off voltage V 首 , and then it is constantly discharged at a current density I 首 to the lower limit voltage of the battery cell. During the first charge-discharge cycle, the temperature T 首 is 50 - 80°C, such as 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, etc.; and / or, the pressure P 首 is 1 - 2 MPa, such as 1 MPa, 1.2 MPa, 1.4 MPa, 1.6 MPa, 1.8 MPa, 2 MPa, etc.; and / or, the current density I 首 is 0.02 - 0.12 Co (Co represents the current density required to discharge the theoretical initial capacity of the battery cell within 1 hour), such as 0.02 Co, 0.04 Co, 0.06 Co, 0.08 Co, 0.10 Co, 0.12 Co, etc.; and / or, the cut-off voltage V 首 is 3.3 - 3.6 V, such as 3.3 V, 3.35 V, 3.4 V, 3.45 V, 3.5 V, 3.6 V, etc. When the temperature, pressure, current density, and cut-off voltage of the first charge-discharge cycle meet the above conditions, the compactness and uniformity of the SEI film can be effectively improved, thereby improving the charge-discharge cycle performance of the battery cell. When the temperature, pressure, current density, and cut-off voltage of the first charge-discharge cycle do not meet the above conditions, the compactness and uniformity of the SEI film are both poor, resulting in poor charge-discharge cycle performance of the battery cell.

[0051] The formation method according to the embodiment of the present invention. In step S2, the specific operation of the first charge-discharge cycle is as follows: The battery cell obtained by processing in step S1 is subjected to a charge-discharge cycle at a temperature T 首 and a pressure P 首 . First, it is constantly charged at a current density I 首 to a cut-off voltage V 首 , and then it is constantly discharged at a current density I 首 to the lower limit voltage of the battery cell. In some embodiments, the constant current charging process of the first charge-discharge cycle can be carried out in two stages. In the first stage, the battery cell obtained by processing in step S1 is at a temperature T 首I and a pressure P 首I . First, it is constantly charged at a current density I 首I to a cut-off voltage V 首I . In the second stage, the battery cell obtained by processing in the first stage is at a temperature T 首I and a pressure P 首I . At a current density I首II Constant current charge to the cut-off voltage V 首II and I 首I < I 首II、 V 首I < V 首II . The constant current charging process of the first charge-discharge cycle is carried out in two stages, and the current density in the first stage is less than that in the second stage, in order to control the small current density at the initial stage of film formation and facilitate the formation of a dense SEI film. In some embodiments, the current density I 首I in the first stage is 0.02 - 0.05 Co, and the cut-off voltage V 首I is 3.3 - 3.5 V; the current density I 首II in the second stage is 0.08 - 0.12 Co, and the cut-off voltage V 首II is 3.5 - 3.6 V, and V 首I < V 首II .

[0052] In the formation method of the embodiment of the present invention, in step S2, the time of the second static state is 20 - 30 h, such as 20 h, 21 h, 22 h, 23 h, 24 h, 25 h, 26 h, 27 h, 28 h, 29 h, 30 h, etc. When the time of the second static state is too short, it is not conducive to the full progress of the reaction; when the time of the second static state is too long, it is not conducive to improving the production efficiency. It is hoped to form a film uniformly and densely at a low potential, so the time of the second static state is longer than the static time in the subsequent step S3.

[0053] In some embodiments, in step S2, at the last charge-discharge cycle, the temperature T 末 is 20 - 50 °C, such as 20 °C, 25 °C, 30 °C, 35 °C, 40 °C, 45 °C, 50 °C, etc.; and / or, the pressure P 末 is 0.3 - 1 MPa, such as 0.3 MPa, 0.4 MPa, 0.5 MPa, 0.6 MPa, 0.7 MPa, 0.8 MPa, 0.9 MPa, 1 MPa, etc.; and / or, the current density I 末 is 0.2 - 0.3 Co, such as 0.2 Co, 0.22 Co, 0.24 Co, 0.26 Co, 0.28 Co, 0.3 Co, etc.; and / or, the cut-off voltage V 末 is 3.9 - 4.2 V, such as 3.9 V, 3.95 V, 4 V, 4.05 V, 4.1 V, 4.15 V, 4.2 V, etc. Under the above conditions, the formation speed of the SEI film can be accelerated and the production efficiency can be improved.

[0054] In some embodiments, in step S2, the temperature difference between two adjacent charge-discharge cycles is 5 - 20 °C, and / or the pressure difference between two adjacent charge-discharge cycles is 0.15 - 0.6 MPa, and / or the current density difference between two adjacent charge-discharge cycles is 0.01 - 0.1 C, and / or the cut-off voltage difference between two adjacent charge-discharge cycles is 0.05 - 0.3 V. When the above conditions are met, it helps to guide the formation of a dense interfacial solid electrolyte membrane (abbreviated as SEI membrane) at the electrode / electrolyte interface during the formation stage. When the temperature difference and / or pressure difference is too small, it is not conducive to the full progress of the film-forming reaction; when the temperature difference or pressure difference is too large, side reactions will be aggravated. When the current density difference or cut-off voltage difference is too small, it is not conducive to improving production efficiency; when the current density difference or cut-off voltage difference is too large, the reaction is too fast, which is not conducive to improving the uniformity and density of the SEI membrane.

[0055] In some embodiments, in step S3, between injecting the second volume of the electrolyte and performing the final sealing, there is also a supplementary formation step: the battery cell after injecting the second volume of the electrolyte is charged at a constant current density I' to a cut-off voltage V' under the conditions of temperature T' and pressure P'; then the fourth static state and gas exhaust are performed. When the film-forming property of the electrolyte used itself is not good enough, the remaining electrolyte injected in step S3 can also undergo a charging reaction through the above steps, avoiding the risk of insufficient growth of the SEI membrane in step S2.

[0056] There are no special restrictions on the formation conditions temperature T', pressure P', current density I', and cut-off voltage V' of the supplementary formation step in step S3 of the formation method according to the embodiments of the present invention. Preferably, the pressure P' is the same as the pressure P during the first charge-discharge cycle in step S2 首 ; the current density I' is the same as the current density I during the first charge-discharge cycle in step S2 首 ; the cut-off voltage V' is the same as the cut-off voltage V during the last charge-discharge cycle in step S2 末 . Since the remaining electrolyte is supplemented and injected in step S3, this step is preferably carried out with a relatively small current for film formation, and at the same time, a relatively large pressure is adopted, so that the pressure acting on film formation is relatively uniform, improving the film formation uniformity.

[0057] In some embodiments, in the supplementary formation step of step S3, the temperature T' is greater than or equal to room temperature, such as 25 - 80 °C, such as 25 °C, 30 °C, 40 °C, 50 °C, 60 °C, 70 °C, 80 °C, etc. Under the above temperature conditions, the remaining electrolyte injected in step S3 can also undergo a charging reaction, avoiding the risk of insufficient growth of the SEI membrane in step S2. Preferably, in the supplementary formation step of step S3, the temperature T' is room temperature 25 °C, because the film-forming reaction will be very intense at high temperatures, and an overly thick SEI membrane will increase the interfacial impedance.

[0058] In some embodiments, in step S3, the time for the third standing is 10 - 15 h, such as 10 h, 11 h, 12 h, 13 h, 14 h, 15 h, etc. To improve production efficiency, the time for the third standing can be shorter than the time for the first standing in step S1 and the second standing in step S2.

[0059] In some embodiments, in step S3, the time for the fourth standing is 10 - 15 h, such as 10 h, 11 h, 12 h, 13 h, 14 h, 15 h, etc. To improve production efficiency, the time for the fourth standing can be shorter than the time for the first standing in step S1 and the second standing in step S2.

[0060] Classically, the formation method of the silicon-based anode lithium-ion battery cell includes the following steps:

[0061] S1. Inject a first volume of electrolyte into the assembled cell to be filled with electrolyte, and then perform the first standing.

[0062] S2-1. Perform charge and discharge cycles on the cell obtained by processing in step S1 under the conditions of temperature T1 and pressure P1. First, charge at a constant current density I1 to the cut-off voltage V1, then charge at a constant current density I2 to the cut-off voltage V2, then perform the second standing, and then discharge at a constant current density I2 to the lower limit voltage in the cell design.

[0063] S2-2. Perform charge and discharge cycles on the cell obtained by processing in step S2-1 under the conditions of temperature T2 and pressure P2. First, charge at a constant current density I3 to the cut-off voltage V3, and then discharge at a constant current density I3 to the lower limit voltage in the cell design.

[0064] S2-3. Perform charge and discharge cycles on the cell obtained by processing in step S2-2 under the conditions of temperature T3 and pressure P3. First, charge at a constant current density I4 to the cut-off voltage V4, and then discharge at a constant current density I4 to the lower limit voltage in the cell design.

[0065] S2-4. Perform charge and discharge cycles on the cell obtained by processing in step S2-3 under the conditions of temperature T4 and pressure P4. First, charge at a constant current density I5 to the cut-off voltage V5, and then discharge at a constant current density I5 to the lower limit voltage in the cell design.

[0066] S3-1. Perform the third standing on the cell obtained by processing in step S2-4, exhaust the gas, and then inject a second volume of the electrolyte. The sum of the second volume and the first volume is equal to the designed amount of the electrolyte.

[0067] S3-2. Under the condition of pressure P1, the battery cell obtained in step S3-1 is charged at a constant current density I2 until the cut-off voltage V5; then it is left standing for the fourth time, exhausted, and finally sealed.

[0068] Among them, T1 > T2 > T3 > T4, P1 > P2 > P3 > P4, I1 < I2 < I3 < I4 < I5, V1 < V2 < V3 < V4 < V5.

[0069] Among them, in step S2-1, the temperature T1 is 50-80 °C, such as 50 °C, 55 °C, 60 °C, 65 °C, 70 °C, 75 °C, 80 °C, etc.; and / or, the pressure P1 is 1-2 MPa, such as 1 MPa, 1.2 MPa, 1.4 MPa, 1.6 MPa, 1.8 MPa, 2 MPa, etc.; and / or, the current density I1 is 0.02-0.05 Co, such as 0.02 Co, 0.03 Co, 0.04 Co, 0.05 Co, etc.; and / or, the cut-off voltage V1 is 3.3-3.5 V, such as 3.3 V, 3.35 V, 3.4 V, 3.45 V, 3.5 V, etc.; and / or, the current density I2 is 0.08-0.12 Co, such as 0.08 Co, 0.09 Co, 0.1 Co, 0.11 Co, 0.12 Co, etc.; and / or, the cut-off voltage V2 is 3.5-3.6 V, such as 3.5 V, 3.52 V, 3.54 V, 3.56 V, 3.58 V, 3.6 V, etc. In this step, the constant current charging process is carried out in two stages, and I1 is less than I2. At the same time, standing is also required. It is hoped that the current density is small at the initial stage of film formation, combined with standing for a certain period of time, so as to obtain a dense SEI film. And the subsequent charge and discharge cycles can be appropriately accelerated to improve production efficiency.

[0070] When the temperature T1 and pressure P1 are too small, it will have an adverse effect of insufficient film formation reaction at low voltage. When the temperature T1 and pressure P1 are too large, the side reaction will be aggravated. When the current density I1 and cut-off voltage V1 are too small, it is not conducive to shortening the formation time and improving production efficiency. When the current density I1 and cut-off voltage V1 are too large, it is not conducive to improving the film formation uniformity. When the current density I2 and cut-off voltage V2 are too small, it is not conducive to shortening the formation time and improving production efficiency. When the current density I2 and cut-off voltage V2 are too large, it is not conducive to improving the film formation uniformity. It should be noted that in the charge and discharge cycle of step S2-1, the charging process is divided into two stages. In the first stage, it is charged at a constant current density I1 until the cut-off voltage V1, and in the second stage, it is charged at a constant current density I2 until the cut-off voltage V2, which is conducive to forming a dense and uniform SEI film.

[0071] Among them, in step S2-2, the temperature T2 is 40-70 °C, such as 40 °C, 45 °C, 50 °C, 55 °C, 60 °C, 65 °C, 70 °C, etc.; and / or, the pressure P2 is 0.8-1.5 MPa, such as 0.8 MPa, 0.9 MPa, 1.0 MPa, 1.1 MPa, 1.2 MPa, 1.3 MPa, 1.4 MPa, 1.5 MPa, etc.; and / or, the current density I3 is 0.1-0.2 Co, such as 0.1 Co, 0.12 Co, 0.14 Co, 0.16 Co, 0.18 Co, 0.2 Co, etc.; and / or, the cut-off voltage V3 is 3.5-3.7 V, such as 3.5 V, 3.55 V, 3.6 V, 3.65 V, 3.7 V, etc. When the temperature T2 and the pressure P2 are too small, it is not conducive to the full progress of the film-forming reaction. When the temperature T2 and the pressure P2 are too large, side reactions will be aggravated. When the current density I3 and the cut-off voltage V3 are too small, it is not conducive to shortening the formation time and improving production efficiency. When the current density I3 and the cut-off voltage V3 are too large, it is not conducive to improving the film-forming uniformity.

[0072] Among them, in step S2-3, the temperature T3 is 30-60 °C, such as 30 °C, 35 °C, 40 °C, 45 °C, 50 °C, 55 °C, 60 °C, etc.; and / or, the pressure P3 is 0.6-1.2 MPa, such as 0.6 MPa, 0.7 MPa, 0.8 MPa, 0.9 MPa, 1.0 MPa, 1.1 MPa, 1.2 MPa, etc.; and / or, the current density I4 is 0.15-0.25 Co, such as 0.15 Co, 0.16 Co, 0.18 Co, 0.2 Co, 0.22 Co, 0.24 Co, 0.25 Co, etc.; and / or, the cut-off voltage V4 is 3.7-3.9 V, such as 3.7 V, 3.75 V, 3.8 V, 3.85 V, 3.9 V, etc. When the temperature T3 and the pressure P3 are too small, it is not conducive to the full progress of the film-forming reaction. When the temperature T3 and the pressure P3 are too large, side reactions will be aggravated. When the current density I4 and the cut-off voltage V4 are too small, it is not conducive to shortening the formation time and improving production efficiency. When the current density I4 and the cut-off voltage V4 are too large, it is not conducive to improving the film-forming uniformity.

[0073] Among them, in step S2-4, the temperature T4 is 20-50°C, such as 20°C, 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, etc.; and / or, the pressure P4 is 0.3-1 MPa, such as 0.3 MPa, 0.4 MPa, 0.5 MPa, 0.6 MPa, 0.7 MPa, 0.8 MPa, 0.9 MPa, 1 MPa, etc.; and / or, the current density I5 is 0.2-0.3 Co, such as 0.2 Co, 0.22 Co, 0.24 Co, 0.26 Co, 0.28 Co, 0.3 Co, etc.; and / or, the cut-off voltage V5 is 3.9-4.2 V, such as 3.9 V, 3.95 V, 4 V, 4.05 V, 4.1 V, 4.15 V, 4.2 V, etc. When the temperature T4 and the pressure P4 are too small, it is not conducive to the full progress of the film-forming reaction. When the temperature T4 and the pressure P4 are too large, the side reactions will be aggravated. When the current density I5 and the cut-off voltage V5 are too small, it is not conducive to shortening the formation time and improving the production efficiency. When the current density I5 and the cut-off voltage V5 are too large, it is not conducive to improving the film-forming uniformity.

[0074] In addition, the embodiment of the present invention also provides a silicon-based negative electrode lithium-ion cell, which is obtained by the formation method of the silicon-based negative electrode cell of the embodiment of the present invention.

[0075] Compared with the silicon-based negative electrode lithium-ion cell obtained by the formation method in the prior art, the silicon-based negative electrode lithium-ion cell of the embodiment of the present invention has a smaller volume change of the silicon-based negative electrode and a higher retention rate of the electrolyte during the later repeated charge and discharge cycles, and the cycle performance of the cell is good.

[0076] In addition, the embodiment of the present invention also provides a silicon-based negative electrode lithium-ion cell, which is obtained by the formation method of the silicon-based negative electrode cell of the embodiment of the present invention.

[0077] In addition, the embodiment of the present invention also provides a silicon-based negative electrode lithium-ion battery, including the silicon-based negative electrode lithium-ion cell of the embodiment of the present invention.

[0078] The silicon-based negative electrode lithium-ion battery of the embodiment of the present invention, due to adopting the silicon-based negative electrode lithium-ion cell obtained by the formation method of the embodiment of the present invention, has a smaller volume change of the silicon-based negative electrode and a higher retention rate of the electrolyte during the repeated charge and discharge cycles, and the cycle performance of the battery is good.

[0079] The present invention will be described in detail below with reference to the embodiments and the drawings.

[0080] Embodiment 1

[0081] A formation method of a silicon-based negative electrode lithium-ion cell, as Figure 1 shown, includes the following steps:

[0082] (1) Inject half of the designed amount of electrolyte into the assembled battery cell to be filled with electrolyte, and let it stand for 24 h at normal temperature and pressure.

[0083] (2) Perform charge-discharge cycles on the battery cell obtained from step (1) under the conditions of temperature T1 = 55 °C and pressure P1 = 1.5 MPa. First, charge at a constant current density I1 = 0.02 Co to the cut-off voltage V1 = 3.3 V, then charge at a constant current density I2 = 0.08 Co to the cut-off voltage V2 = 3.5 V. After standing for 24 h, discharge at a constant current density I2 = 0.08 Co to the lower limit voltage V0 = 2.5 V of the battery cell design.

[0084] (3) Perform charge-discharge cycles on the battery cell obtained from step (2) under the conditions of temperature T2 = 45 °C and pressure P2 = 1.0 MPa. First, charge at a constant current density I3 = 0.1 Co to the cut-off voltage V3 = 3.6 V, then discharge at a constant current density I3 = 0.1 Co to the lower limit voltage V0 = 2.5 V of the battery cell design.

[0085] (4) Perform charge-discharge cycles on the battery cell obtained from step (3) under the conditions of temperature T3 = 35 °C and pressure P3 = 0.8 MPa. First, charge at a constant current density I4 = 0.15 Co to the cut-off voltage V4 = 3.7 V, then discharge at a constant current density I4 = 0.15 Co to the lower limit voltage V0 = 2.5 V of the battery cell design.

[0086] (5) Perform charge-discharge cycles on the battery cell obtained from step (4) under the conditions of temperature T4 = 25 °C and pressure P4 = 0.5 MPa. First, charge at a constant current density I5 = 0.2 Co to the cut-off voltage V5 = 3.9 V, then discharge at a constant current density I5 = 0.2 Co to the lower limit voltage V0 = 2.5 V of the battery cell design.

[0087] (6) Let the battery cell obtained from step (5) stand for 12 h at temperature T4 = 25 °C and pressure P4 = 0.5 MPa. After exhausting the gas, inject the remaining part of the electrolyte, that is, half of the designed amount of electrolyte.

[0088] (7) Under the conditions of normal temperature and pressure P1 = 1.5 MPa, charge the battery cell obtained from step (6) at a constant current density I2 = 0.08 Co to the cut-off voltage V5 = 3.95 V.

[0089] (8) Let the battery cell obtained from step (7) stand for 12 h at normal temperature and pressure. After exhausting the gas, perform final sealing to complete the formation process.

[0090] Among them, T1 > T2 > T3 > T4, P1 > P2 > P3 > P4, I1 < I2 < I3 < I4 < I5, V1 < V2 < V3 < V4 < V5.

[0091] Example 2

[0092] A formation method for a silicon-based anode battery cell, as Figure 1 shown, includes the following steps:

[0093] (1) Inject half of the designed amount of electrolyte into the assembled battery cell to be filled with electrolyte, and let it stand at normal temperature and pressure for 24 h.

[0094] (2) Perform the first charge-discharge cycle on the battery cell obtained in step (1) under the conditions of temperature T1 = 75 °C and pressure P1 = 1.8 MPa. First, charge at a constant current density I1 = 0.02 Co to the cut-off voltage V1 = 3.3 V, then charge at a constant current density I2 = 0.08 Co to the cut-off voltage V2 = 3.5 V. After standing for 24 h, discharge at a constant current density I2 = 0.08 Co to the lower limit voltage V0 = 2.5 V of the battery cell design.

[0095] (3) Perform the second charge-discharge cycle on the battery cell obtained in step (2) under the conditions of temperature T2 = 65 °C and pressure P2 = 1.4 MPa. First, charge at a constant current density I3 = 0.1 Co to the cut-off voltage V3 = 3.5 V, then discharge at a constant current density I3 = 0.1 Co to the lower limit voltage V0 = 2.5 V of the battery cell design.

[0096] (4) Perform the third charge-discharge cycle on the battery cell obtained in step (3) under the conditions of temperature T3 = 55 °C and pressure P3 = 1 MPa. First, charge at a constant current density I4 = 0.15 Co to the cut-off voltage V4 = 3.7 V, then discharge at a constant current density I4 = 0.15 Co to the lower limit voltage V0 = 2.5 V of the battery cell design.

[0097] (5) Perform the fourth charge-discharge cycle on the battery cell obtained in step (4) under the conditions of temperature T4 = 45 °C and pressure P4 = 0.8 MPa. First, charge at a constant current density I5 = 0.2 Co to the cut-off voltage V5 = 3.9 V, then discharge at a constant current density I5 = 0.2 Co to the lower limit voltage V0 = 2.5 V of the battery cell design.

[0098] (6) Let the battery cell obtained in step (5) stand at temperature T4 = 25 °C and pressure P4 = 0.5 MPa for 12 h. After exhausting the gas, inject the remaining part of the electrolyte, that is, half of the designed amount of electrolyte.

[0099] (7) Charge the battery cell obtained in step (6) at a constant current density I2 = 0.08 Co to the cut-off voltage V5 = 3.9 V under normal temperature and pressure P1 = 1.8 MPa.

[0100] (8) Leave the battery cells obtained in step (7) to stand at normal temperature and pressure for 12 h. After exhausting the gas, perform final sealing to complete the formation process.

[0101] Among them, T1 > T2 > T3 > T4, P1 > P2 > P3 > P4, I1 < I2 < I3 < I4 < I5, V1 < V2 < V3 < V4 < V5.

[0102] Example 3

[0103] A method for forming a silicon-based anode battery cell, as Figure 1 shown, includes the following steps:

[0104] (1) Inject half of the designed amount of electrolyte into the assembled battery cell to be filled with electrolyte, and leave it to stand at normal temperature and pressure for 24 h.

[0105] (2) Perform the first charge-discharge cycle on the battery cell obtained in step (1) under the conditions of temperature T1 = 55 °C and pressure P1 = 1.5 MPa. First, charge at a constant current density I1 = 0.05 Co until the cut-off voltage V1 = 3.5 V, then charge at a constant current density I2 = 0.12 Co until the cut-off voltage V2 = 3.55 V. After standing for 24 h, discharge at a constant current density I2 = 0.12 Co until the lower limit voltage V0 = 2.5 V of the battery cell design.

[0106] (3) Perform the second charge-discharge cycle on the battery cell obtained in step (2) under the conditions of temperature T2 = 45 °C and pressure P2 = 1.0 MPa. First, charge at a constant current density I3 = 0.2 Co until the cut-off voltage V3 = 3.7 V, then discharge at a constant current density I3 = 0.2 Co until the lower limit voltage V0 = 2.5 V of the battery cell design.

[0107] (4) Perform the third charge-discharge cycle on the battery cell obtained in step (3) under the conditions of temperature T3 = 35 °C and pressure P3 = 0.8 MPa. First, charge at a constant current density I4 = 0.25 Co until the cut-off voltage V4 = 3.9 V, then discharge at a constant current density I4 = 0.25 Co until the lower limit voltage V0 = 2.5 V of the battery cell design.

[0108] (5) Perform the fourth charge-discharge cycle on the battery cell obtained in step (4) under the conditions of temperature T4 = 25 °C and pressure P4 = 0.5 MPa. First, charge at a constant current density I5 = 0.3 Co until the cut-off voltage V5 = 4.2 V, then discharge at a constant current density I5 = 0.3 Co until the lower limit voltage V0 = 2.5 V of the battery cell design.

[0109] (6) The battery cells obtained from the treatment in step (5) are left standing for 12 h under the conditions of temperature T4 = 25°C and pressure P4 = 0.5 MPa. After exhausting the gas, the remaining part of the electrolyte, i.e., half of the designed amount of electrolyte, is injected.

[0110] (7) The battery cells obtained from the treatment in step (6) are charged at a constant current density of I2 = 0.12 C0 to the cut-off voltage V5 = 4.2 V under normal temperature and pressure P1 = 1.5 MPa.

[0111] (8) The battery cells obtained from the treatment in step (7) are left standing for 12 h under normal temperature and pressure. After exhausting the gas, they are finally sealed to complete the formation process.

[0112] Among them, T1 > T2 > T3 > T4, P1 > P2 > P3 > P4, I1 < I2 < I3 < I4 < I5, V1 < V2 < V3 < V4 < V5.

[0113] Comparative Example 1

[0114] A formation method for a silicon-based anode battery cell includes the following steps:

[0115] (1) Inject all of the designed amount of electrolyte into the assembled battery cell to be filled with electrolyte, and leave it standing for 24 hours under normal temperature and pressure.

[0116] (2) The battery cells obtained from step (1) are subjected to a charging and formation process at a temperature of 45°C, a pressure of 0.8 MPa, and are charged at a constant current density of 0.05 C0 to 3.5 V; then charged at a constant current density of 0.1 C0 to 3.9 V; after leaving it standing for 24 h under normal temperature and pressure, the gas is exhausted and finally sealed to complete the formation process.

[0117] Comparative Example 2

[0118] The formation method for the silicon-based anode battery cell in this comparative example is the same as that in Example 1, except that step (2) is omitted.

[0119] Comparative Example 3

[0120] The formation method for the silicon-based anode battery cell in this comparative example is the same as that in Example 1, except that steps (3) and (4) are omitted.

[0121] Perform performance tests on the battery cells obtained from the formation methods of Example 1 and Comparative Examples 1 - 4:

[0122] (1) Respectively perform weight detection on the battery cell before injecting electrolyte and the battery cell after formation. The difference between the two is the mass of the electrolyte retained in the battery cell after the formation process. The test results are as Figure 2 shown.

[0123] (2) Detect the average thickness of the battery cell before liquid injection and the battery cell before final sealing and exhaust during formation. The difference between the two is the volume of gas generated in the battery cell during the formation process. The test results are as Figure 3 shown.

[0124] (3) Perform grading treatment on the battery cells that have completed the formation process, and continue to carry out capacity calibration and fast charge cycles. The conditions for the fast charge cycle are charging at 4C and discharging at 1C. The test results of the cycle are as Figure 4 shown. The test results of the DC resistance (DCR) of the battery cells tested every 100 cycles are as Figure 5 shown.

[0125] Analysis of performance test results: Since the battery cell designs in Example 1 and Comparative Example 1 are the same, the amount of electrolyte injected is the same. Therefore, the degree of side reaction of the electrolyte can be reflected by the mass of the electrolyte remaining in the battery cell after the formation process. As Figure 2 shown, the mass of the electrolyte remaining in Example 1 is significantly higher than that in Comparative Example 1, proving that compared with the formation method of Comparative Example 1 that undergoes two charging and formation processes, the formation method of Example 1 has a significant effect on suppressing the excessive decomposition reaction of the electrolyte during the formation process. Similarly, Figure 2 it also shows that when the first charge-discharge conditions in step S2 do not meet the conditions within the scope defined in the present invention (Comparative Example 2), or when only two charge-discharge cycles are performed in step S2 (Comparative Example 3), or when the charge-discharge cycle conditions in step S2 are not gradient changes (Comparative Example 4), the corresponding formation method has a poor effect on suppressing the excessive decomposition reaction of the electrolyte.

[0126] Since the battery cell designs in Example 1 and Comparative Example 1 are the same, the amount of electrolyte injected is the same. Therefore, the degree of expansion and gas generation of the battery cell during the formation process can be reflected by comparing the thickness difference of the battery cell before liquid injection and after formation (before final exhaust sealing). As Figure 3 shown, compared with Comparative Example 1, the increase in the thickness of the battery cell in Example 1 is greatly reduced, indicating that the formation method of Example 1 can effectively alleviate the expansion effect caused by gas generation due to the electrolyte decomposition reaction during the initial film formation process of the battery cell. Similarly, Figure 3 it also shows that when the first charge-discharge conditions in step S2 do not meet the conditions within the scope defined in the present invention (Comparative Example 2), or when only two charge-discharge cycles are performed in step S2 (Comparative Example 3), or when the charge-discharge cycle conditions in step S2 are not gradient changes (Comparative Example 4), the corresponding formation method has a poor effect on alleviating the gas expansion during the formation process.

[0127] As Figure 4 shown, compared with the battery cells obtained by the formation method of Comparative Example 1, the battery cells obtained by the formation method of Example 1 obviously have a higher capacity retention rate during the cycle. Similarly,Figure 4 It also shows that when the first charge-discharge conditions in step S2 do not meet the conditions defined in the present invention (Comparative Example 2), or when only two charge-discharge cycles are performed in step S2 (Comparative Example 3), or when the charge-discharge cycle conditions in step S2 are not gradient-changing (Comparative Example 4), the capacity retention rate of the battery cells obtained by the corresponding formation methods is relatively poor. At the same time, as Figure 5 shown, the DCR increase of the battery cells obtained by the formation method of Example 1 during the cycling process is significantly smaller than that of Comparative Examples 1-4. The above two points can both prove that the formation method of Example 1 can effectively form a dense and stable interfacial SEI film, thereby suppressing the side reaction gas generation and performance degradation caused by volume expansion and contraction at the interface between the silicon-based negative electrode and the electrolyte during the cyclic charge and discharge process.

[0128] In the present invention, the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples", etc. mean that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0129] Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention.

Claims

1. A formation method for a silicon-based anode lithium-ion battery cell, characterized in that, It includes the following steps: S1. Inject an electrolyte of a first volume into the assembled battery cell to be filled with electrolyte, and then perform a first static placement; S2. Perform at least three charge-discharge cycles on the battery cell obtained in step S1 under the conditions of temperature T and pressure P. First, charge at a constant current density I to the cut-off voltage V, and then discharge at the constant current density I to the lower limit voltage of the battery cell. The temperature T and pressure P of at least three charge-discharge cycles decrease sequentially, and the current density I and cut-off voltage V of at least three charge-discharge cycles increase sequentially; during the first charge-discharge cycle, the temperature T 首 is 50 - 80 °C; and / or, the pressure P 首 is 1 - 2 MPa; and / or, the current density I 首 is 0.02 - 0.12 C; and / or, the cut-off voltage V 首 is 3.3 - 3.6 V; during the first charge-discharge cycle, after the constant current charging process ends, perform a second rest, and then discharge at a constant current to the lower limit voltage of the battery cell; S3. After performing a third static placement and exhausting air on the battery cell obtained by processing in step S2, inject a second volume of the electrolyte. The sum of the second volume and the first volume is equal to the designed amount of the electrolyte, and finally perform final sealing.

2. The formation method according to claim 1, wherein In step S1, the first volume is 40-70% of the designed amount of the electrolyte.

3. The forming method according to claim 1, wherein In step S2, perform 3-6 of the charge and discharge cycles.

4. The formation method according to claim 1, characterized in that, In step S2, during the first charge-discharge cycle, constant current charging is carried out in two stages. The current density I in the first stage 首I is 0.02 - 0.05 Co, and the cut-off voltage V 首I is 3.3 - 3.5 V; the current density I in the second stage 首II is 0.08 - 0.12 Co, and the cut-off voltage V 首II is 3.5 - 3.6 V, and V 首I < V 首II .

5. The formation method according to claim 1, wherein In step S2, during the last charge-discharge cycle, the temperature T 末 is 20 - 50 °C; and / or, the pressure P 末 is 0.3 - 1 MPa; and / or, the current density I 末 is 0.2 - 0.3 Co; and / or, the cut-off voltage V 末 is 3.9 - 4.2 V.

6. The formation method according to claim 1, wherein In step S2, the temperature difference between adjacent charge and discharge cycles is 5-20 °C, and / or the pressure difference between adjacent charge and discharge cycles is 0.15-0.6 MPa, and / or the current density difference between adjacent charge and discharge cycles is 0.01-0.1 Co, and / or the cut-off voltage difference between adjacent charge and discharge cycles is 0.05-0.3 V.

7. The formation method according to claim 1, characterized in that In step S3, between injecting the second volume of the electrolyte and performing the final sealing, there is also a supplementary formation step: the battery cell after injecting the second volume of the electrolyte is charged at a constant current density I' to a cut-off voltage V' under the conditions of temperature T' and pressure P'; then, the fourth static rest and gas exhaust are carried out; the pressure P' in step S3 is the same as the pressure P during the first charge-discharge cycle in step S2; the current density I' in step S3 is the same as the current density I during the first charge-discharge cycle in step S2; the cut-off voltage V' in step S3 is the same as the cut-off voltage V during the last charge-discharge cycle in step S2; the temperature T' in step S3 is greater than or equal to room temperature. 首 are the same; the current density I' in step S3 and the current density I during the first charge-discharge cycle in step S2 首 are the same, the cut-off voltage V' in step S3 and the cut-off voltage V during the last charge-discharge cycle in step S2 末 are the same; the temperature T' in step S3 is greater than or equal to room temperature.

8. The formation method according to claim 7, characterized in that, The time of the first static placement is 20-30 h; and / or the time of the second static placement is 20-30 h; and / or the time of the third static placement is 10-15 h, and / or the time of the fourth static placement is 10-15 h.

9. A silicon-based anode lithium-ion battery cell, characterized in that, Obtained by the formation method according to any one of claims 1-8.

10. A silicon-based anode lithium-ion battery, characterized in that, It includes the silicon-based anode lithium-ion battery cell according to claim 9.

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