Formation Method of Lithium-Ion Battery and Lithium-Ion Battery

Abstract

The present invention relates to the technical field of lithium-ion batteries, and particularly to a formation method for a lithium-ion battery and a lithium-ion battery. This application aims to solve the problem of how to reduce the impedance of a lithium-ion battery so as to improve the energy density and cycle life of the battery. For this purpose, the formation method of the lithium-ion battery in this application can effectively activate the lithium-ion battery by adopting a charging method with a stepped increasing current, avoiding the phenomenon of capacity "ramp-up" in the initial stage of cycling. In addition, by adding a film-forming additive to the electrolyte of the battery cell under the above charging method, the SEI film formed on the negative electrode gradually becomes loose from the inside to the outside. This SEI film structure can not only stabilize the electrode material, prevent irreversible chemical reactions between the electrolyte and the active substance, but also reduce the impedance of the negative electrode SEI film, thereby reducing the overall impedance of the battery, facilitating the passage of lithium ions through the SEI film, and improving the energy density and cycle life of the lithium-ion battery.

Description

Technical Field

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

[0002] As a clean and convenient energy source, lithium-ion batteries play a very important role in people's daily lives, and more and more electrical devices use lithium-ion batteries for power supply. In the production and manufacturing process of lithium-ion batteries, formation is an important process in the production process of lithium-ion batteries. The formation of a lithium-ion battery is the first charging process of the battery after injection of electrolyte. This formation process can activate the active substances in the battery and generate a solid electrolyte interface film (SEI film) on the negative electrode side. This SEI film plays a crucial role in stabilizing the electrode material and preventing the electrolyte from continuously undergoing irreversible chemical reactions with the active substances. Therefore, the quality of the SEI film has a great impact on the cycle life, initial capacity loss, etc. of lithium-ion batteries.

[0003] The formation methods of lithium-ion batteries in the prior art usually adopt a pulsed charging strategy with gradually increasing multi-stage currents. Specifically, in the first stage of charging, it is charged at 0.3C - 0.5C until the state of charge (SOC) reaches 2 - 3%, in the second stage of charging, it is charged at 1C - 1.2C until the SOC reaches 10 - 13%, in the third stage of charging, it is charged at 1.5C - 1.8C until the SOC reaches 80 - 93%, and in the fourth stage of charging, it is charged at 1.5 - 1.8C until the SOC reaches 93 - 98%. By first using small current charging to slowly form a film and increase the firmness of the SEI film, then using large current charging to make the SEI film dense, and accelerating side reactions and Brownian motion at high temperature to improve the deposition of fluorides, thereby enhancing the thermal stability of the negative electrode sheet. However, the high density of the SEI film is not conducive to the transmission and diffusion of lithium ions, which will lead to an increase in the impedance of lithium-ion batteries, and further affect the energy density and cycle life of the batteries.

[0004] Correspondingly, a new technical solution is needed in this field to solve the above problems. Summary of the Invention

[0005] In order to solve at least one of the above problems in the prior art, that is, to solve the problem of how to reduce the impedance of lithium-ion batteries and thereby improve the energy density and cycle life of the batteries, the present application provides a formation method for a lithium-ion battery, including the following steps:

[0006] Step (101): Charge the battery cell with a current of 0.01 - 0.1C until the SOC reaches 2 - 40%;

[0007] Step (102): Charge the battery cell with a current of 0.1 - 1C until the SOC reaches 80 - 100%;

[0008] Among them, a film-forming additive is added to the electrolyte of the battery cell.

[0009] In a preferred technical solution of the above formation method, the film-forming additive includes one or more of vinylene carbonate, propylene sulfite, and fluoroethylene carbonate.

[0010] In a preferred technical solution of the above formation method, the addition amount of the film-forming additive is 1-3% of the total mass of the electrolyte.

[0011] In a preferred technical solution of the above formation method, the step (101) further includes:

[0012] Step (1011): Charge the battery cell at a current of 0.01-0.03C until the SOC reaches 2-10%;

[0013] Step (1012): Charge the battery cell at a current of 0.03-0.05C until the SOC reaches 5-20%;

[0014] Step (1013): Charge the battery cell at a current of 0.05-0.1C until the SOC reaches 15-40%.

[0015] In a preferred technical solution of the above formation method, between the step (1011) and the step (1012), it further includes:

[0016] Stand for a first preset time period; and / or

[0017] Between the step (1012) and the step (1013), it further includes:

[0018] Stand for a second preset time period; and / or

[0019] After the step (1013), it further includes:

[0020] Stand for a third preset time period.

[0021] In a preferred technical solution of the above formation method, the first preset time period, the second preset time period, and the third preset time period are each independently in the range of 5-10 minutes.

[0022] In a preferred technical solution of the above formation method, the battery cell is charged under a vacuum degree of 45-80 KPa until the SOC reaches 80-100%.

[0023] In a preferred technical solution of the above formation method, before the step (101), it further includes:

[0024] Step (100): Stand the battery cell after injecting the liquid for a fourth preset time period.

[0025] In the preferred technical solution of the above formation method, the fourth preset time period is 12 - 36h.

[0026] This application also provides a lithium-ion battery, which is obtained by the formation method described in any of the above preferred technical solutions.

[0027] Those skilled in the art can understand that the formation method of the lithium-ion battery of this application can effectively activate the lithium-ion battery by adopting a charging method with a stepwise increasing current, avoid the capacity "ramp-up" phenomenon in the initial stage of cycling, and at the same time ensure a high capacity retention rate in the later stage of cycling, with excellent cycling performance. In addition, by adding a film-forming additive to the electrolyte of the battery cell and charging the battery cell by adopting a stepwise increasing current charging method, the SEI film formed on the negative electrode gradually becomes loose from dense from the inside to the outside. This SEI film structure can not only stabilize the electrode material, prevent irreversible chemical reactions between the electrolyte and the active substance, but also reduce the impedance of the negative electrode SEI film, thereby reducing the overall impedance of the battery, facilitating the passage of lithium ions through the SEI film, and improving the energy density and cycle life of the lithium-ion battery.

[0028] Furthermore, by adding one or more of vinylene carbonate, propylene sulfite, and fluoroethylene carbonate to the electrolyte of the battery cell, the SEI film gradually becomes loose from dense from the inside to the outside when the battery cell is charged to a fixed charge amount by adopting a step current.

[0029] Furthermore, by dividing step (101) into three stages, that is, charging the battery cell to an SOC of 2 - 10% with a current of 0.01 - 0.03C, charging the battery cell to an SOC of 5 - 20% with a current of 0.03 - 0.05C, and charging the battery cell to an SOC of 15 - 40% with a current of 0.05 - 0.1C, it is possible to improve the stability of the SEI film while facilitating the change of the SEI film from dense to loose, reducing the impedance of the negative electrode SEI film, thereby reducing the overall impedance of the battery, facilitating the passage of lithium ions through the SEI film, and improving the energy density and cycle life of the lithium-ion battery.

[0030] Furthermore, by standing the lithium-ion battery after each charging stage is completed, the stability of the performance of the lithium-ion battery can be guaranteed, and the consistency of the performance of the lithium-ion battery can be further improved.

[0031] Furthermore, by charging the battery cell with a step current under vacuum, it is beneficial to discharge the gas in the electrolyte, and improve the energy density and cycle life of the lithium-ion battery.

[0032] Furthermore, injecting liquid into the battery cell and standing it before charging the battery cell is beneficial to make the electrolyte fully contact with the electrode and make the electrolyte better infiltrate the electrode. Brief Description of the Drawings

[0033] The preferred technical solutions of the present application will be described below with reference to the accompanying drawings. In the drawings:

[0034] Figure 1 is a flowchart of the formation method of the lithium-ion battery of the present application. Detailed Embodiments

[0035] The technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without making creative efforts shall fall within the protection scope of the present invention.

[0036] In conjunction with Figure 1 , the formation method of the lithium-ion battery of the present application will be described.

[0037] In order to solve the problem of how to reduce the impedance of the lithium-ion battery and thereby improve the energy density and cycle life of the battery, the formation method of the lithium-ion battery of the present application includes the following steps:

[0038] Step (101): Charge the battery cell to an SOC of 2-40% at a current of 0.01-0.1C;

[0039] Step (102): Charge the battery cell to an SOC of 80-100% at a current of 0.1-1C;

[0040] Among them, a film-forming additive is added to the electrolyte of the battery cell.

[0041] By adopting a charging method with a stepwise increasing current, the present application can effectively activate the lithium-ion battery, avoid the capacity "ramp-up" phenomenon at the initial stage of cycling, and ensure a high capacity retention rate in the later stage of cycling, with excellent cycling performance. In addition, by adding a film-forming additive to the electrolyte of the battery cell and charging the battery cell by adopting a charging method with a stepwise increasing current, the SEI film formed on the negative electrode gradually becomes loose from inside to outside. This SEI film structure can not only stabilize the electrode material, prevent irreversible chemical reactions between the electrolyte and the active substance, but also reduce the impedance of the negative electrode SEI film, thereby reducing the overall impedance of the battery, facilitating the passage of lithium ions through the SEI film, and improving the energy density and cycle life of the lithium-ion battery.

[0042] The preferred embodiments of the formation method of the lithium-ion battery of the present application will be introduced below.

[0043] Step (101): Charge the battery cell to an SOC of 2-40% at a current of 0.01-0.1C.

[0044] Among them, a film-forming additive is added to the electrolyte of the battery cell. The film-forming additive includes one or more of vinylene carbonate, propylene sulfite, and fluoroethylene carbonate. By adding the above film-forming additive to the electrolyte, during the process of charging the battery cell with a stepwise increasing current, the SEI film gradually becomes loose from the inside to the outside, thereby reducing the impedance of the negative electrode SEI film. Among them, the addition amount of the film-forming additive is 1-3% of the total mass of the electrolyte.

[0045] Before step (101), the following steps are further included:

[0046] Step (100): Let the battery cell after liquid injection stand for a fourth preset time period.

[0047] By letting the battery cell after liquid injection stand for a fourth preset time period, the electrolyte is in full contact with the electrode, which is beneficial for the electrolyte to better infiltrate the electrode. Among them, the fourth preset time period is 12-36h. If the standing time is less than 12h, the electrolyte infiltration is uneven, which will affect the subsequent formation of the SEI film and lead to difficult film formation, and the forming effect of the SEI film will directly affect the performance of the lithium-ion battery. If the standing time is greater than 36h, the longer standing time will reduce the production efficiency and is not conducive to improving the production benefit.

[0048] In other preferred embodiments, step (101) further includes:

[0049] Step (1011): Charge the battery cell to an SOC of 2-10% with a current of 0.01-0.03C;

[0050] Step (1012): Charge the battery cell to an SOC of 5-20% with a current of 0.03-0.05C;

[0051] Step (1013): Charge the battery cell to an SOC of 15-40% with a current of 0.05-0.1C.

[0052] By dividing step (101) into three charging operations, where the first charging operation is to charge with a current of 0.01-0.03C to an SOC of 2-10%, the film formation is slow, which is beneficial for improving the stability and firmness of the SEI film. The second charging operation is to charge with a current of 0.03-0.05C to an SOC of 5-20%, and the second charging operation is to charge with a current of 0.05-0.1C to an SOC of 15-40%. The charging current increases successively. While ensuring the stability and firmness of the SEI film, the density of the SEI film decreases, thereby reducing the impedance of the SEI film.

[0053] It should be noted that before each charging operation is completed and before the next charging, it is necessary to let it stand still to ensure the stability of the performance of the lithium-ion battery and further improve the consistency of the performance of the lithium-ion battery. Specifically, after the first charging operation is completed and before the second charging operation, it further includes: letting it stand still for a first preset time period. Among them, the first preset time period is within the range of 5 - 10 minutes. And / or, after the second charging operation is completed and before the third charging operation, it further includes: letting it stand still for a second preset time period. Among them, the second preset time period is within the range of 5 - 10 minutes. And / or, after the third charging operation is completed, it further includes: letting it stand still for a third preset time period. Among them, the third preset time period is within the range of 5 - 10 minutes. If the standing time is too short, it will affect the formation of the SEI film, thereby affecting the stability of the structure of the obtained SEI film. If the standing time is too long, it is not conducive to improving production efficiency.

[0054] Step (102): Charge the battery cell to an SOC of 80 - 100% at a current of 0.1 - 1C.

[0055] After step (101), charge the battery cell to an SOC of 80 - 100% at a current of 0.1 - 1C. The SEI film obtained in this step has good stability and firmness, and its porosity performance is higher than that of step (101). It can reduce the impedance of the SEI film, facilitate the passage of lithium ions, and improve the energy density and cycle life of the lithium-ion battery.

[0056] It should be noted that the entire formation process, that is, step (101) and step (102), is carried out under a vacuum degree of 45 - 80 KPa. The battery cell is charged to an SOC of 80 - 100% under this vacuum degree, which can remove gases. In addition, the entire formation process of the battery is carried out at room temperature.

[0057] It should also be noted that the present application does not limit the specific composition of the electrolyte, and it can be a common electrolyte in the art.

[0058] The formation method of the lithium-ion battery of the present application will be described in conjunction with the following embodiments.

[0059] Example 1

[0060] The preparation method of the unformed lithium-ion battery includes the following steps:

[0061] Step (a) Preparation of the positive electrode sheet: Weigh lithium iron phosphate positive electrode active material, conductive carbon black, and polyvinylidene fluoride according to a weight ratio of 95.5:2.1:2.4, stir and then coat it on a 12 μm carbon-coated aluminum foil, with a coating surface density of 380 g / cm 2 , and a compaction density of 2.3 g / cm 3 , and obtain the positive electrode sheet through rolling and die-cutting.

[0062] Step (b) Preparation of the negative electrode sheet: Weigh graphite, conductive carbon black, sodium carboxymethyl cellulose, and styrene-butadiene rubber according to a weight ratio of 96.3:1:1.3:1.4, homogenize them, and coat them on an 8-μm copper foil with a coating areal density of 154 g / cm 2 , and compact it to 1.6 g / cm 3 . After rolling and die-cutting, obtain the negative electrode sheet.

[0063] Step (c) Battery assembly: Stack the electrode sheets obtained in steps (a) and (b) in a zigzag pattern. The number of positive electrode sheet layers is 28, and the number of negative electrode sheet layers is 29. Use a 9-μm-thick polyethylene film as the separator, encapsulate the battery cell in an aluminum-plastic film, and after baking and injecting electrolyte, obtain an unformed lithium-ion battery; the electrolyte used for injecting includes LiPF6, propylene carbonate, ethylene carbonate, and dimethyl carbonate with a mass ratio of 13:35:20:32.

[0064] Example 2

[0065] Method for forming a lithium-ion battery, including:

[0066] Step (100): After the battery cell in Example 1 is filled with electrolyte, let it stand for 24 h; among them, 2% vinylene carbonate is added to the electrolyte;

[0067] Step (1011): Charge the battery cell to an SOC of 5% at a current of 0.01C in a negative pressure environment of 80 kPa, and let it stand for 10 min;

[0068] Step (1012): Charge the battery cell to an SOC of 10% at a current of 0.03C in a negative pressure environment of 80 kPa, and let it stand for 10 min;

[0069] Step (1013): Charge the battery cell to an SOC of 30% at a current of 0.05C in a negative pressure environment of 80 kPa, and let it stand for 10 min;

[0070] Step (102): Charge the battery cell to an SOC of 100% at a current of 0.5C in a negative pressure environment of 80 kPa to obtain a formed lithium-ion battery.

[0071] Example 3

[0072] Method for forming a lithium-ion battery, including:

[0073] Step (100): After the battery cell in Example 1 is filled with electrolyte, let it stand for 24 h; among them, 2% vinylene carbonate is added to the electrolyte;

[0074] Step (1011): Charge the battery cell to an SOC of 5% at a current of 0.02C in a negative pressure environment of 80 kPa, and let it stand for 10 min;

[0075] Step (1012): Charge the battery cell at a current of 0.03C to an SOC of 10% in a negative pressure environment of 80 kPa, and let it stand for 10 min;

[0076] Step (1013): Charge the battery cell at a current of 0.05C to an SOC of 30% in a negative pressure environment of 80 kPa, and let it stand for 10 min;

[0077] Step (102): Charge the battery cell at a current of 0.5C to an SOC of 100% in a negative pressure environment of 80 kPa to obtain a formed lithium-ion battery.

[0078] Example 4

[0079] The formation method of a lithium-ion battery includes:

[0080] Step (100): After the battery cell in Example 1 is filled with electrolyte, let it stand for 24 h; wherein, 2% vinylene carbonate is added to the electrolyte;

[0081] Step (1011): Charge the battery cell at a current of 0.02C to an SOC of 5% in a negative pressure environment of 80 kPa, and let it stand for 10 min;

[0082] Step (1012): Charge the battery cell at a current of 0.04C to an SOC of 10% in a negative pressure environment of 80 kPa, and let it stand for 10 min;

[0083] Step (1013): Charge the battery cell at a current of 0.05C to an SOC of 30% in a negative pressure environment of 80 kPa, and let it stand for 10 min;

[0084] Step (102): Charge the battery cell at a current of 0.5C to an SOC of 100% in a negative pressure environment of 80 kPa to obtain a formed lithium-ion battery.

[0085] Example 5

[0086] The formation method of a lithium-ion battery includes:

[0087] Step (100): After the battery cell in Example 1 is filled with electrolyte, let it stand for 24 h; wherein, 2% vinylene carbonate is added to the electrolyte;

[0088] Step (1011): Charge the battery cell at a current of 0.02C to an SOC of 5% in a negative pressure environment of 80 kPa, and let it stand for 10 min;

[0089] Step (1012): Charge the battery cell at a current of 0.03C to an SOC of 10% in a negative pressure environment of 80 kPa, and let it stand for 10 min;

[0090] Step (1013): Charge the battery cell at a current of 0.1C to an SOC of 30% in a negative pressure environment of 80 kPa, and let it stand for 10 min;

[0091] Step (102): Charge the battery cell at a current of 0.5C to an SOC of 100% in a negative pressure environment of 80 kPa to obtain a formed lithium-ion battery.

[0092] Example 6

[0093] A method for forming a lithium-ion battery, comprising:

[0094] Step (100): After the battery cell in Example 1 is filled with electrolyte, let it stand for 24 h; wherein, 2% vinylene carbonate is added to the electrolyte;

[0095] Step (1011): Charge the battery cell at a current of 0.02C to an SOC of 5% in a negative pressure environment of 80 kPa, and let it stand for 10 min;

[0096] Step (1012): Charge the battery cell at a current of 0.03C to an SOC of 10% in a negative pressure environment of 80 kPa, and let it stand for 10 min;

[0097] Step (1013): Charge the battery cell at a current of 0.05C to an SOC of 30% in a negative pressure environment of 80 kPa, and let it stand for 10 min;

[0098] Step (102): Charge the battery cell at a current of 1C to an SOC of 100% in a negative pressure environment of 80 kPa to obtain a formed lithium-ion battery.

[0099] Example 7

[0100] A method for forming a lithium-ion battery, comprising:

[0101] Step (100): After the battery cell in Example 1 is filled with electrolyte, let it stand for 24 h; wherein, 1% vinylene carbonate and 1% fluoroethylene carbonate are added to the electrolyte;

[0102] Step (1011): Charge the battery cell at a current of 0.02C to an SOC of 5% in a negative pressure environment of 80 kPa, and let it stand for 10 min;

[0103] Step (1012): Charge the battery cell at a current of 0.03C to an SOC of 10% in a negative pressure environment of 80 kPa, and let it stand for 10 min;

[0104] Step (1013): Charge the battery cell at a current of 0.05C to an SOC of 30% in a negative pressure environment of 80 kPa, and let it stand for 10 min;

[0105] Step (102): Charge the battery cell at a current of 0.5C in a negative pressure environment of 80 kPa until the state of charge (SOC) reaches 100% to obtain a formed lithium-ion battery.

[0106] Example 8

[0107] A method for forming a lithium-ion battery, comprising:

[0108] Step (100): After the battery cell in Example 1 is filled with electrolyte, let it stand for 24 h; wherein, 2% of fluoroethylene carbonate is added to the electrolyte.

[0109] Step (1011): Charge the battery cell at a current of 0.02C in a negative pressure environment of 80 kPa until the SOC reaches 5%, and let it stand for 10 min.

[0110] Step (1012): Charge the battery cell at a current of 0.03C in a negative pressure environment of 80 kPa until the SOC reaches 10%, and let it stand for 10 min.

[0111] Step (1013): Charge the battery cell at a current of 0.05C in a negative pressure environment of 80 kPa until the SOC reaches 30%, and let it stand for 10 min.

[0112] Step (102): Charge the battery cell at a current of 0.5C in a negative pressure environment of 80 kPa until the SOC reaches 100% to obtain a formed lithium-ion battery.

[0113] Example 9

[0114] A method for forming a lithium-ion battery, comprising:

[0115] Step (100): After the battery cell in Example 1 is filled with electrolyte, let it stand for 24 h; wherein, 2% of propylene sulfite is added to the electrolyte.

[0116] Step (1011): Charge the battery cell at a current of 0.02C in a negative pressure environment of 80 kPa until the SOC reaches 5%, and let it stand for 10 min.

[0117] Step (1012): Charge the battery cell at a current of 0.03C in a negative pressure environment of 80 kPa until the SOC reaches 10%, and let it stand for 10 min.

[0118] Step (1013): Charge the battery cell at a current of 0.05C in a negative pressure environment of 80 kPa until the SOC reaches 30%, and let it stand for 10 min.

[0119] Step (102): Charge the battery cell at a current of 0.5C in a negative pressure environment of 80 kPa until the SOC reaches 100% to obtain a formed lithium-ion battery.

[0120] Example 10

[0121] A formation method for a lithium-ion battery, comprising:

[0122] Step (100): After the injection of electrolyte into the battery cell of Example 1 is completed, leave it standing for 24 h; wherein, 2% vinylene carbonate is added to the electrolyte;

[0123] Step (1011): Charge the battery cell at a current of 0.01C to an SOC of 7% in a negative pressure environment of 80 kPa, and leave it standing for 10 min;

[0124] Step (1012): Charge the battery cell at a current of 0.03C to an SOC of 10% in a negative pressure environment of 80 kPa, and leave it standing for 10 min;

[0125] Step (1013): Charge the battery cell at a current of 0.05C to an SOC of 30% in a negative pressure environment of 80 kPa, and leave it standing for 10 min;

[0126] Step (102): Charge the battery cell at a current of 0.5C to an SOC of 100% in a negative pressure environment of 80 kPa to obtain a lithium-ion battery with formation completed.

[0127] Example 11

[0128] A formation method for a lithium-ion battery, comprising:

[0129] Step (100): After the injection of electrolyte into the battery cell of Example 1 is completed, leave it standing for 24 h; wherein, 2% vinylene carbonate is added to the electrolyte;

[0130] Step (1011): Charge the battery cell at a current of 0.01C to an SOC of 5% in a negative pressure environment of 80 kPa, and leave it standing for 10 min;

[0131] Step (1012): Charge the battery cell at a current of 0.03C to an SOC of 20% in a negative pressure environment of 80 kPa, and leave it standing for 10 min;

[0132] Step (1013): Charge the battery cell at a current of 0.05C to an SOC of 30% in a negative pressure environment of 80 kPa, and leave it standing for 10 min;

[0133] Step (102): Charge the battery cell at a current of 0.5C to an SOC of 100% in a negative pressure environment of 80 kPa to obtain a lithium-ion battery with formation completed.

[0134] Example 12

[0135] A formation method for a lithium-ion battery, comprising:

[0136] Step (100): After the electrolyte injection of the battery cell in Example 1 is completed, let it stand for 24 h; wherein, 2% vinylene carbonate is added to the electrolyte solution.

[0137] Step (1011): Charge the battery cell at a current of 0.01C to an SOC of 5% in a negative pressure environment of 80 kPa, and let it stand for 10 min.

[0138] Step (1012): Charge the battery cell at a current of 0.03C to an SOC of 10% in a negative pressure environment of 80 kPa, and let it stand for 10 min.

[0139] Step (1013): Charge the battery cell at a current of 0.05C to an SOC of 30% in a negative pressure environment of 80 kPa, and let it stand for 10 min.

[0140] Step (102): Charge the battery cell at a current of 0.5C to an SOC of 80% in a negative pressure environment of 80 kPa to obtain a lithium-ion battery with formation completed.

[0141] Example 13

[0142] A method for forming a lithium-ion battery, comprising:

[0143] Step (100): After the electrolyte injection of the battery cell in Example 1 is completed, let it stand for 24 h; wherein, 2% vinylene carbonate is added to the electrolyte solution.

[0144] Step (1011): Charge the battery cell at a current of 0.02C to an SOC of 8% in a negative pressure environment of 80 kPa, and let it stand for 10 min.

[0145] Step (1012): Charge the battery cell at a current of 0.03C to an SOC of 15% in a negative pressure environment of 80 kPa, and let it stand for 10 min.

[0146] Step (1013): Charge the battery cell at a current of 0.05C to an SOC of 35% in a negative pressure environment of 80 kPa, and let it stand for 10 min.

[0147] Step (102): Charge the battery cell at a current of 0.5C to an SOC of 100% in a negative pressure environment of 80 kPa to obtain a lithium-ion battery with formation completed.

[0148] Example 14

[0149] A method for forming a lithium-ion battery, comprising:

[0150] Step (100): After the electrolyte injection of the battery cell in Example 1 is completed, let it stand for 30 h; wherein, 1.5% vinylene carbonate is added to the electrolyte solution.

[0151] Step (1011): Charge the battery cell at a current of 0.02C in a negative pressure environment of 80 kPa until the state of charge (SOC) reaches 3%, and then let it stand for 10 minutes.

[0152] Step (1012): Charge the battery cell at a current of 0.03C in a negative pressure environment of 80 kPa until the SOC reaches 7%, and then let it stand for 10 minutes.

[0153] Step (1013): Charge the battery cell at a current of 0.05C in a negative pressure environment of 80 kPa until the SOC reaches 20%, and then let it stand for 10 minutes.

[0154] Step (102): Charge the battery cell at a current of 0.5C in a negative pressure environment of 80 kPa until the SOC reaches 100%, obtaining a formed lithium-ion battery.

[0155] Example 15

[0156] The forming method of a lithium-ion battery includes:

[0157] Step (100): After the battery cell in Example 1 is filled with electrolyte, let it stand for 12 hours; wherein, 1% of vinylene carbonate is added to the electrolyte.

[0158] Step (1011): Charge the battery cell at a current of 0.03C in a negative pressure environment of 45 kPa until the SOC reaches 10%, and then let it stand for 8 minutes.

[0159] Step (1012): Charge the battery cell at a current of 0.05C in a negative pressure environment of 45 kPa until the SOC reaches 20%, and then let it stand for 8 minutes.

[0160] Step (1013): Charge the battery cell at a current of 0.1C in a negative pressure environment of 45 kPa until the SOC reaches 40%, and then let it stand for 8 minutes.

[0161] Step (102): Charge the battery cell at a current of 1C in a negative pressure environment of 45 kPa until the SOC reaches 100%, obtaining a formed lithium-ion battery.

[0162] Example 16

[0163] The forming method of a lithium-ion battery includes:

[0164] Step (100): After the battery cell in Example 1 is filled with electrolyte, let it stand for 36 hours; wherein, 3% of vinylene carbonate is added to the electrolyte.

[0165] Step (1011): Charge the battery cell at a current of 0.01C in a negative pressure environment of 60 kPa until the SOC reaches 2%, and then let it stand for 5 minutes.

[0166] Step (1012): Charge the battery cell at a current of 0.03C in a negative pressure environment of 60 kPa until the SOC reaches 5%, and then let it stand for 10 min;

[0167] Step (1013): Charge the battery cell at a current of 0.05C in a negative pressure environment of 60 kPa until the SOC reaches 15%, and then let it stand for 5 min;

[0168] Step (102): Charge the battery cell at a current of 0.1C in a negative pressure environment of 60 kPa until the SOC reaches 80% to obtain a formed lithium-ion battery.

[0169] Comparative Example 1

[0170] The formation method of a lithium-ion battery includes:

[0171] Step (100): After the battery cell in Example 1 is filled with electrolyte, let it stand for 24 h; wherein, 2% vinylene carbonate is added to the electrolyte;

[0172] Step (1011): Charge the battery cell at a current of 0.01C in a negative pressure environment of 80 kPa until the SOC reaches 5%, and then let it stand for 10 min;

[0173] Step (1012): Charge the battery cell at a current of 0.01C in a negative pressure environment of 80 kPa until the SOC reaches 10%, and then let it stand for 10 min;

[0174] Step (1013): Charge the battery cell at a current of 0.01C in a negative pressure environment of 80 kPa until the SOC reaches 30%, and then let it stand for 10 min;

[0175] Step (102): Charge the battery cell at a current of 0.01C in a negative pressure environment of 80 kPa until the SOC reaches 100% to obtain a formed lithium-ion battery.

[0176] Comparative Example 2

[0177] The formation method of a lithium-ion battery includes:

[0178] Step (100): After the battery cell in Example 1 is filled with electrolyte, let it stand for 24 h; wherein, 2% vinylene carbonate is added to the electrolyte;

[0179] Step (1011): Charge the battery cell at a current of 0.5C in a negative pressure environment of 80 kPa until the SOC reaches 5%, and then let it stand for 10 min;

[0180] Step (1012): Charge the battery cell at a current of 0.5C in a negative pressure environment of 80 kPa until the SOC reaches 10%, and then let it stand for 10 min;

[0181] Step (1013): Charge the battery cell at a current of 0.5C in a negative pressure environment of 80 kPa until the SOC reaches 30%, and then let it stand for 10 min;

[0182] Step (102): Charge the battery cell at a current of 0.5C in a negative pressure environment of 80 kPa until the SOC reaches 100%, obtaining a formed lithium-ion battery.

[0183] Comparative Example 3

[0184] A method for forming a lithium-ion battery, comprising:

[0185] Step (100): After the battery cell in Example 1 is filled with electrolyte, let it stand for 24 h;

[0186] Step (1011): Charge the battery cell at a current of 0.01C in a negative pressure environment of 80 kPa until the SOC reaches 5%, and then let it stand for 10 min;

[0187] Step (1012): Charge the battery cell at a current of 0.03C in a negative pressure environment of 80 kPa until the SOC reaches 10%, and then let it stand for 10 min;

[0188] Step (1013): Charge the battery cell at a current of 0.05C in a negative pressure environment of 80 kPa until the SOC reaches 30%, and then let it stand for 10 min;

[0189] Step (102): Charge the battery cell at a current of 0.5C in a negative pressure environment of 80 kPa until the SOC reaches 100%, obtaining a formed lithium-ion battery.

[0190] Comparative Example 4

[0191] A method for forming a lithium-ion battery, comprising:

[0192] Step (100): After the battery cell in Example 1 is filled with electrolyte, let it stand for 36 h; wherein, 2% vinylene carbonate is added to the electrolyte;

[0193] Step (1011): Charge the battery cell at a current of 0.04C in a negative pressure environment of 80 kPa until the SOC reaches 5%, and then let it stand for 10 min;

[0194] Step (1012): Charge the battery cell at a current of 0.03C in a negative pressure environment of 80 kPa until the SOC reaches 10%, and then let it stand for 10 min;

[0195] Step (1013): Charge the battery cell at a current of 0.05C in a negative pressure environment of 80 kPa until the SOC reaches 30%, and then let it stand for 10 min;

[0196] Step (102): Charge the battery cell at a current of 0.5C in a negative pressure environment of 80 kPa until the SOC reaches 100%, obtaining a formed lithium-ion battery.

[0197] Comparative Example 5

[0198] The forming method of a lithium-ion battery includes:

[0199] Step (100): After the battery cell in Example 1 is filled with electrolyte, let it stand for 36 h; wherein, 2% vinylene carbonate is added to the electrolyte.

[0200] Step (1011): Charge the battery cell at a current of 0.005C in a negative pressure environment of 80 kPa until the SOC reaches 5%, and let it stand for 10 min.

[0201] Step (1012): Charge the battery cell at a current of 0.03C in a negative pressure environment of 80 kPa until the SOC reaches 10%, and let it stand for 10 min.

[0202] Step (1013): Charge the battery cell at a current of 0.05C in a negative pressure environment of 80 kPa until the SOC reaches 30%, and let it stand for 10 min.

[0203] Step (102): Charge the battery cell at a current of 0.5C in a negative pressure environment of 80 kPa until the SOC reaches 100%, obtaining a formed lithium-ion battery.

[0204] Comparative Example 6

[0205] The forming method of a lithium-ion battery includes:

[0206] Step (100): After the battery cell in Example 1 is filled with electrolyte, let it stand for 24 h; wherein, 2% vinylene carbonate is added to the electrolyte.

[0207] Step (1011): Charge the battery cell at a current of 0.01C in a negative pressure environment of 80 kPa until the SOC reaches 5%, and let it stand for 10 min.

[0208] Step (1012): Charge the battery cell at a current of 0.02C in a negative pressure environment of 80 kPa until the SOC reaches 10%, and let it stand for 10 min.

[0209] Step (1013): Charge the battery cell at a current of 0.05C in a negative pressure environment of 80 kPa until the SOC reaches 30%, and let it stand for 10 min.

[0210] Step (102): Charge the battery cell at a current of 0.5C in a negative pressure environment of 80 kPa until the SOC reaches 100%, obtaining a formed lithium-ion battery.

[0211] Comparative Example 7

[0212] The formation method of a lithium-ion battery includes:

[0213] Step (100): After the injection of electrolyte into the battery cell in Example 1, let it stand for 24 h; wherein, 2% vinylene carbonate is added to the electrolyte;

[0214] Step (1011): Charge the battery cell to an SOC of 5% at a current of 0.01C in a negative pressure environment of 80 kPa, and let it stand for 10 min;

[0215] Step (1012): Charge the battery cell to an SOC of 10% at a current of 0.06C in a negative pressure environment of 80 kPa, and let it stand for 10 min;

[0216] Step (1013): Charge the battery cell to an SOC of 30% at a current of 0.05C in a negative pressure environment of 80 kPa, and let it stand for 10 min;

[0217] Step (102): Charge the battery cell to an SOC of 100% at a current of 0.5C in a negative pressure environment of 80 kPa to obtain a lithium-ion battery with formation completed.

[0218] Comparative Example 8

[0219] The formation method of a lithium-ion battery includes:

[0220] Step (100): After the injection of electrolyte into the battery cell in Example 1, let it stand for 36 h; wherein, 2% vinylene carbonate is added to the electrolyte;

[0221] Step (1011): Charge the battery cell to an SOC of 15% at a current of 0.03C in a negative pressure environment of 80 kPa, and let it stand for 10 min;

[0222] Step (1012): Charge the battery cell to an SOC of 25% at a current of 0.05C in a negative pressure environment of 80 kPa, and let it stand for 10 min;

[0223] Step (1013): Charge the battery cell to an SOC of 50% at a current of 0.2C in a negative pressure environment of 80 kPa, and let it stand for 10 min;

[0224] Step (102): Charge the battery cell to an SOC of 100% at a current of 1C in a negative pressure environment of 80 kPa to obtain a lithium-ion battery with formation completed.

[0225] Comparative Example 9

[0226] The formation method of a lithium-ion battery includes:

[0227] Step (100): After the electrolyte injection of the battery cell in Example 1 is completed, let it stand for 24 h; wherein, 2% vinylene carbonate is added to the electrolyte solution.

[0228] Step (1011): Charge the battery cell at a current of 0.01C to an SOC of 5% in a negative pressure environment of 80 kPa, and let it stand for 10 min.

[0229] Step (1012): Charge the battery cell at a current of 0.03C to an SOC of 10% in a negative pressure environment of 80 kPa, and let it stand for 10 min.

[0230] Step (1013): Charge the battery cell at a current of 0.03C to an SOC of 30% in a negative pressure environment of 80 kPa, and let it stand for 10 min.

[0231] Step (102): Charge the battery cell at a current of 0.5C to an SOC of 100% in a negative pressure environment of 80 kPa to obtain a lithium-ion battery with formation completed.

[0232] Comparative Example 10

[0233] The formation method of a lithium-ion battery includes:

[0234] Step (100): After the electrolyte injection of the battery cell in Example 1 is completed, let it stand for 24 h; wherein, 2% vinylene carbonate is added to the electrolyte solution.

[0235] Step (1011): Charge the battery cell at a current of 0.01C to an SOC of 5% in a negative pressure environment of 80 kPa, and let it stand for 10 min.

[0236] Step (1012): Charge the battery cell at a current of 0.03C to an SOC of 10% in a negative pressure environment of 80 kPa, and let it stand for 10 min.

[0237] Step (1013): Charge the battery cell at a current of 0.05C to an SOC of 30% in a negative pressure environment of 80 kPa, and let it stand for 10 min.

[0238] Step (102): Charge the battery cell at a current of 2C to an SOC of 100% in a negative pressure environment of 80 kPa to obtain a lithium-ion battery with formation completed.

[0239] Comparative Example 11

[0240] The formation method of a lithium-ion battery includes:

[0241] Step (100): After the electrolyte injection of the battery cell in Example 1 is completed, let it stand for 24 h; wherein, 2% vinylene carbonate is added to the electrolyte solution.

[0242] Step (1011): Charge the battery cell at a current of 0.01C in a negative pressure environment of 80 kPa until the SOC reaches 5%, and then let it stand for 10 min;

[0243] Step (1012): Charge the battery cell at a current of 0.03C in a negative pressure environment of 80 kPa until the SOC reaches 10%, and then let it stand for 10 min;

[0244] Step (1013): Charge the battery cell at a current of 0.05C in a negative pressure environment of 80 kPa until the SOC reaches 30%, and then let it stand for 10 min;

[0245] Step (102): Charge the battery cell at a current of 0.08C in a negative pressure environment of 80 kPa until the SOC reaches 100% to obtain a formed lithium-ion battery.

[0246] Comparative Example 12

[0247] The formation method of a lithium-ion battery includes:

[0248] Step (100): After the battery cell in Example 1 is filled with electrolyte, let it stand for 24 h; wherein, 2% vinylene carbonate is added to the electrolyte;

[0249] Step (1011): Charge the battery cell at a current of 0.01C in a negative pressure environment of 80 kPa until the SOC reaches 5%, and then let it stand for 10 min;

[0250] Step (1012): Charge the battery cell at a current of 0.03C in a negative pressure environment of 80 kPa until the SOC reaches 10%, and then let it stand for 10 min;

[0251] Step (1013): Charge the battery cell at a current of 0.05C in a negative pressure environment of 80 kPa until the SOC reaches 30%, and then let it stand for 10 min;

[0252] Step (102): Charge the battery cell at a current of 0.5C in a negative pressure environment of 80 kPa until the SOC reaches 50% to obtain a formed lithium-ion battery.

[0253] Comparative Example 13

[0254] The formation method of a lithium-ion battery includes:

[0255] Step (100): After the battery cell in Example 1 is filled with electrolyte, let it stand for 24 h; wherein, 2% vinylene carbonate is added to the electrolyte;

[0256] Step (1011): Charge the battery cell at a current of 0.02C in a negative pressure environment of 80 kPa until the SOC reaches 12%, and then let it stand for 10 min;

[0257] Step (1012): Charge the battery cell at a current of 0.03C to an SOC of 15% in a negative pressure environment of 80 kPa, and let it stand for 10 min;

[0258] Step (1013): Charge the battery cell at a current of 0.05C to an SOC of 35% in a negative pressure environment of 80 kPa, and let it stand for 10 min;

[0259] Step (102): Charge the battery cell at a current of 0.5C to an SOC of 100% in a negative pressure environment of 80 kPa to obtain a formed lithium-ion battery.

[0260] Comparative Example 14

[0261] The formation method of a lithium-ion battery includes:

[0262] Step (100): After the battery cell in Example 1 is filled with electrolyte, let it stand for 30 h; wherein, 1.5% vinylene carbonate is added to the electrolyte;

[0263] Step (1011): Charge the battery cell at a current of 0.02C to an SOC of 1% in a negative pressure environment of 80 kPa, and let it stand for 10 min;

[0264] Step (1012): Charge the battery cell at a current of 0.03C to an SOC of 15% in a negative pressure environment of 80 kPa, and let it stand for 10 min;

[0265] Step (1013): Charge the battery cell at a current of 0.05C to an SOC of 20% in a negative pressure environment of 80 kPa, and let it stand for 10 min;

[0266] Step (102): Charge the battery cell at a current of 0.5C to an SOC of 100% in a negative pressure environment of 80 kPa to obtain a formed lithium-ion battery.

[0267] Comparative Example 15

[0268] The formation method of a lithium-ion battery includes:

[0269] Step (100): After the battery cell in Example 1 is filled with electrolyte, let it stand for 24 h; wherein, 2% vinylene carbonate is added to the electrolyte;

[0270] Step (1011): Charge the battery cell at a current of 0.02C to an SOC of 8% in a negative pressure environment of 80 kPa, and let it stand for 10 min;

[0271] Step (1012): Charge the battery cell at a current of 0.03C to an SOC of 25% in a negative pressure environment of 80 kPa, and let it stand for 10 min;

[0272] Step (1013): Charge the battery cell at a current of 0.05C to an SOC of 35% in a negative pressure environment of 80 kPa, and let it stand for 10 min;

[0273] Step (102): Charge the battery cell at a current of 0.5C to an SOC of 100% in a negative pressure environment of 80 kPa to obtain a formed lithium-ion battery.

[0274] Comparative Example 16

[0275] The formation method of a lithium-ion battery includes:

[0276] Step (100): After the battery cell in Example 1 is filled with electrolyte, let it stand for 30 h; wherein, 1.5% vinylene carbonate is added to the electrolyte;

[0277] Step (1011): Charge the battery cell at a current of 0.02C to an SOC of 3% in a negative pressure environment of 80 kPa, and let it stand for 10 min;

[0278] Step (1012): Charge the battery cell at a current of 0.03C to an SOC of 4% in a negative pressure environment of 80 kPa, and let it stand for 10 min;

[0279] Step (1013): Charge the battery cell at a current of 0.05C to an SOC of 20% in a negative pressure environment of 80 kPa, and let it stand for 10 min;

[0280] Step (102): Charge the battery cell at a current of 0.5C to an SOC of 100% in a negative pressure environment of 80 kPa to obtain a formed lithium-ion battery.

[0281] Comparative Example 17

[0282] The formation method of a lithium-ion battery includes:

[0283] Step (100): After the battery cell in Example 1 is filled with electrolyte, let it stand for 24 h; wherein, 2% vinylene carbonate is added to the electrolyte;

[0284] Step (1011): Charge the battery cell at a current of 0.02C to an SOC of 8% in a negative pressure environment of 80 kPa, and let it stand for 10 min;

[0285] Step (1012): Charge the battery cell at a current of 0.03C to an SOC of 15% in a negative pressure environment of 80 kPa, and let it stand for 10 min;

[0286] Step (1013): Charge the battery cell at a current of 0.05C to an SOC of 50% in a negative pressure environment of 80 kPa, and let it stand for 10 min;

[0287] Step (102): Charge the battery cell at a current of 0.5C in a negative pressure environment of 80 kPa until the SOC reaches 100%, obtaining a formed lithium-ion battery.

[0288] Comparative Example 18

[0289] The formation method of a lithium-ion battery includes:

[0290] Step (100): After the battery cell in Example 1 is filled with electrolyte, let it stand for 30 h; wherein, 1.5% vinylene carbonate is added to the electrolyte.

[0291] Step (1011): Charge the battery cell at a current of 0.02C in a negative pressure environment of 80 kPa until the SOC reaches 3%, and let it stand for 10 min.

[0292] Step (1012): Charge the battery cell at a current of 0.03C in a negative pressure environment of 80 kPa until the SOC reaches 7%, and let it stand for 10 min.

[0293] Step (1013): Charge the battery cell at a current of 0.05C in a negative pressure environment of 80 kPa until the SOC reaches 12%, and let it stand for 10 min.

[0294] Step (102): Charge the battery cell at a current of 0.5C in a negative pressure environment of 80 kPa until the SOC reaches 100%, obtaining a formed lithium-ion battery.

[0295] Comparative Example 19

[0296] The formation method of a lithium-ion battery includes:

[0297] Step (100): After the battery cell in Example 1 is filled with electrolyte, let it stand for 24 h; wherein, 2% vinylene carbonate is added to the electrolyte.

[0298] Step (1011): Charge the battery cell at a current of 0.02C in a negative pressure environment of 80 kPa until the SOC reaches 8%, and let it stand for 10 min.

[0299] Step (1012): Charge the battery cell at a current of 0.03C in a negative pressure environment of 80 kPa until the SOC reaches 15%, and let it stand for 10 min.

[0300] Step (1013): Charge the battery cell at a current of 0.05C in a negative pressure environment of 80 kPa until the SOC reaches 35%, and let it stand for 10 min.

[0301] Step (102): Charge the battery cell at a current of 0.5C in a negative pressure environment of 80 kPa until the SOC reaches 70%, obtaining a formed lithium-ion battery.

[0302] Comparative Example 20

[0303] The formation method of a lithium-ion battery includes:

[0304] Step (100): After the injection of electrolyte in the battery cell of Example 1 is completed, stand still for 30 h; wherein, 1.5% vinylene carbonate is added to the electrolyte;

[0305] Step (1011): Charge the battery cell to an SOC of 3% at a current of 0.02C in a negative pressure environment of 80 kPa, and stand still for 10 min;

[0306] Step (1012): Charge the battery cell to an SOC of 7% at a current of 0.03C in a negative pressure environment of 80 kPa, and stand still for 10 min;

[0307] Step (1013): Charge the battery cell to an SOC of 20% at a current of 0.05C in a negative pressure environment of 80 kPa, and stand still for 10 min;

[0308] Step (102): Charge the battery cell to an SOC of 50% at a current of 0.5C in a negative pressure environment of 80 kPa to obtain a lithium-ion battery with the formation completed.

[0309] Perform performance tests on the lithium-ion batteries with the formation completed obtained in the above Examples 2-16 and Comparative Examples 1-20. The test results are shown in Table 1 below.

[0310] Table 1

[0311] DCR (mΩ) Discharge specific capacity at 0.5C (mAh / g) Capacity retention rate after 1000 cycles at room temperature (%) Example 2 4.02 145 95.4 Example 3 4.05 145 95.2 Example 4 4.06 145 95.1 Example 5 4.08 145 94.9 Example 6 4.12 145 93.8 Example 7 4.12 145 93.1 Example 8 4.11 145 94.9 Example 9 4.21 144 93.8 Example 10 4.22 144 92.4 Example 11 4.28 144 91.5 Example 12 4.36 145 92.7 Example 13 4.31 144 91.1 Example 14 4.27 145 91.8 Example 15 4.37 144 90.7 Example 16 4.35 144 91.3 Comparative Example 1 4.45 143 92.1 Comparative Example 2 4.01 141 90.5 Comparative Example 3 4.41 143 88.6 Comparative Example 4 4.32 144 91.4 Comparative Example 5 4.10 144 91.5 Comparative Example 6 4.08 144 90.7 Comparative Example 7 4.15 143 89.7 Comparative Example 8 4.07 144 86.6 Comparative Example 9 4.05 143 88.5 Comparative Example 10 4.11 143 86.9 Comparative Example 11 4.15 143 88.3 Comparative Example 12 4.45 145 89.2 Comparative Example 13 4.45 144 88.7 Comparative Example 14 4.42 143 87.4 Comparative Example 15 4.52 144 86.4 Comparative Example 16 4.51 143 85.3 Comparative Example 17 4.49 144 86.1 Comparative Example 18 4.52 143 85.6 Comparative Example 19 4.57 142 86.8 Comparative Example 20 4.62 140 83.7

[0312] As can be seen from Table 1, compared with Comparative Examples 1-20, the lithium-ion battery obtained by using the formation method of the present application has a large discharge specific capacity of 0.5C, all being 144 mAh / g, a small DC resistance (DCR), and a high capacity retention rate after 1000 cycles at room temperature. It shows that by using the formation method of the present application, an SEI film with a gradient change from dense to loose can be obtained from the inside to the outside. This structure of the SEI film not only helps to inhibit the ramp phenomenon of the lithium-ion battery, but also significantly improves the room temperature cycle performance of the battery.

[0313] Those skilled in the art can understand that although some of the embodiments described herein include certain features included in other embodiments rather than other features, the combination of features of different embodiments means that it is within the scope of the present application and forms different embodiments. For example, in the claims of the present application, any one of the claimed embodiments can be used in any combination.

[0314] It should be noted that although the detailed steps of the method of the present application are described in detail above, those skilled in the art can combine, split, and change the order of the above steps on the premise of not deviating from the basic principle of the present application. The technical solutions modified in this way do not change the basic concept of the present application, and thus also fall within the protection scope of the present application.

[0315] So far, the technical solutions of the present application have been described in combination with the preferred embodiments shown in the drawings. However, it is easy for those skilled in the art to understand that the protection scope of the present application is obviously not limited to these specific embodiments. On the premise of not deviating from the principle of the present application, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will all fall within the protection scope of the present application.

Claims

1. A formation method for a lithium ion battery, characterized in that: The following steps are involved: Step (101): charging the battery cell at a current of 0.01-0.1C to a SOC of 2-40%; Step (102): charging the battery cell with a current of 0.1-1C to a SOC of 80-100%; The step (101) further comprises: Step (1011): charging the battery cell with a current of 0.01-0.03C to a SOC of 2-10%; Step (1012): charging the battery cell at a current of 0.03-0.05C to a SOC of 5-20%; Step (1013): charging the battery cell with a current of 0.05-0.1C to a SOC of 15-40%; Wherein, a film-forming additive is added to the electrolyte of the battery cell, and the film-forming additive includes one or more of vinylene carbonate, propylene sulfite, and fluoroethylene carbonate.

2. The chemical formation method according to claim 1, characterized in that: The added amount of the film-forming additive is 1-3% of the total mass of the electrolyte.

3. The chemical formation method according to claim 1, characterized in that: The method further includes between step (1011) and step (1012): Allow to stand for a first preset period of time; and / or The method further includes between step (1012) and step (1013): Allow to stand for a second preset period of time; and / or After step (1013), the method further includes: The device is left to stand for a third preset time period.

4. The chemical formation method according to claim 3, characterized in that: The first preset time period, the second preset time period and the third preset time period are independently within the range of 5-10 minutes.

5. The chemical formation method according to claim 1, characterized in that: The battery cell is charged under a vacuum condition of 45-80KPa until the SOC is 80-100%.

6. The chemical formation method according to claim 1, characterized in that: Before step (101), the method further includes: Step (100): leaving the battery cell after injection to stand for a fourth preset time period.

7. The chemical formation method according to claim 6, characterized in that: The fourth preset time period is 12-36 hours.

8. A lithium ion battery, characterized in that: The lithium-ion battery is obtained by the formation method according to any one of claims 1 to 7.

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