Formation method of lithium ion battery and lithium ion battery

Abstract

The invention relates to the technical field of lithium ion batteries, in particular to a formation method of a lithium ion battery and the lithium ion battery. The invention aims to solve the problem of how to reduce the impedance of the lithium ion battery so as to improve the energy density and the cycle life of the battery. In order to achieve the purpose, according to the formation method of the lithium ion battery, the lithium ion battery can be effectively activated by adopting a stepped current increasing charging mode, and the capacity climbing phenomenon in the initial period of circulation is avoided. Besides, a film-forming additive is added into the electrolyte of the battery cell in the charging mode, so that the SEI film formed by the negative electrode gradually becomes loose from compact from inside to outside, the SEI film structure can stabilize the electrode material and prevent irreversible chemical reaction between the electrolyte and the active substance, and the service life of the battery cell is prolonged. The impedance of a negative electrode SEI membrane can be reduced, so that the overall impedance of the battery is reduced, lithium ions can penetrate through the SEI membrane, and the energy density and the cycle life of the lithium ion battery are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium ion batteries, and in particular to a formation method of 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. More and more electrical devices are powered by lithium-ion batteries. In the production and manufacturing process of lithium-ion batteries, formation is an important process in the production process of lithium-ion batteries. Lithium-ion battery formation is the first charging process of the battery after the lithium-ion battery is filled with liquid. 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. The SEI film plays a vital role in stabilizing the electrode material and preventing the electrolyte from continuously and irreversibly reacting with the active substance. Therefore, the quality of the SEI film has a great influence on the cycle life and initial capacity loss of lithium-ion batteries.

[0003] The prior art lithium-ion battery formation method generally adopts a multi-stage pulse charging strategy with gradually increasing current. Specifically, the first stage is charged at 0.3C-0.5C to a SOC of 2-3%, the second stage is charged at 1C-1.2C to a SOC of 10-13%, the third stage is charged at 1.5C-1.8C to a SOC of 80-93%, and the fourth stage is charged at 1.5-1.8C to a SOC of 93-98%. The above-mentioned first small current charging is used for slow film formation to increase the firmness of the SEI film, and then the large current charging makes the SEI film dense, and accelerates side reactions and Brownian motion at high temperatures, improves the deposition of fluoride, and thus improves the thermal stability of the negative electrode. 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 the lithium-ion battery, thereby affecting the energy density and cycle life of the battery.

[0004] Accordingly, the art needs a new technical solution 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 a lithium-ion battery so as to improve the energy density and cycle life of the battery, the present application provides a lithium-ion battery formation method, comprising the following steps: 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%; Wherein, a film-forming additive is added to the electrolyte of the battery cell.

[0006] In the preferred technical solution of the above-mentioned chemical formation method, the film-forming additive includes one or more of vinylene carbonate, propylene sulfite, and fluoroethylene carbonate.

[0007] In the preferred technical solution of the above-mentioned chemical formation method, the added amount of the film-forming additive is 1-3% of the total mass of the electrolyte.

[0008] In the preferred technical solution of the above-mentioned chemical formation method, 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): Charge the battery cell with a current of 0.05-0.1C to a SOC of 15-40%.

[0009] In the preferred technical solution of the above-mentioned chemical formation method, between the step (1011) and the step (1012), the following steps are further included: Standing for a first preset time period; and / or The method further includes between step (1012) and step (1013): Allow to stand for a second preset period of time; and / or The step (1013) further includes: The device is left to stand for a third preset time period.

[0010] In a preferred technical solution of the above-mentioned chemical formation method, 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.

[0011] In the preferred technical solution of the above-mentioned formation method, the battery cell is charged under a vacuum degree of 45-80 KPa until the SOC is 80-100%.

[0012] In the preferred technical solution of the above chemical formation method, before step (101), the following steps are further included: Step (100): leaving the battery cell after injection to stand for a fourth preset time period.

[0013] In the preferred technical solution of the above-mentioned chemical formation method, the fourth preset time period is 12-36 hours.

[0014] The present application also provides a lithium-ion battery, which is obtained by the formation method described in any of the above preferred technical solutions.

[0015] It is understood by those skilled in the art that the formation method of the lithium-ion battery of the present application can effectively activate the lithium-ion battery by adopting a charging method with a step-by-step increasing current, avoid the capacity "climbing" phenomenon in the early stage of the cycle, and ensure that the capacity retention rate is high in the later stage of the cycle, and the cycle performance is excellent. In addition, by adding a film-forming additive to the electrolyte of the battery cell and charging the battery cell with a charging method with a step-by-step increasing current, the SEI film formed by the negative electrode gradually becomes loose from the inside to the outside, and this SEI film structure can not only stabilize the electrode material and prevent the electrolyte from having an irreversible chemical reaction with the active substance, but also reduce the impedance of the negative electrode SEI film, thereby reducing the overall impedance of the battery, which is conducive to lithium ions passing through the SEI film and improving the energy density and cycle life of the lithium-ion battery.

[0016] 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 changes from dense to loose from the inside to the outside when the battery cell is charged to a fixed amount of electricity using a step current method.

[0017] Furthermore, by dividing step (101) into three stages, i.e., charging the battery cell with a current of 0.01-0.03C to a SOC of 2-10%, charging the battery cell with a current of 0.03-0.05C to a SOC of 5-20%, and charging the battery cell with a current of 0.05-0.1C to a SOC of 15-40%, the stability of the SEI film can be improved while facilitating the SEI film to become loose from dense, thereby reducing the impedance of the negative electrode SEI film and thus reducing the overall impedance of the battery, facilitating lithium ions to pass through the SEI film, and improving the energy density and cycle life of the lithium ion battery.

[0018] Furthermore, by leaving the lithium-ion battery to rest after charging is completed in each charging stage, the stability of the lithium-ion battery performance can be ensured, and the consistency of the lithium-ion battery performance can be further improved.

[0019] Furthermore, by charging the battery cell with a step current under vacuum, the gas in the electrolyte is discharged, thereby improving the energy density and cycle life of the lithium-ion battery.

[0020] Furthermore, before charging the battery cell, the battery cell is injected with liquid and left to stand, which is conducive to full contact between the electrolyte and the electrode, so that the electrolyte can better infiltrate the electrode. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The preferred technical solution of the present application is described below with reference to the accompanying drawings. In the accompanying drawings: Figure 1 The present invention is a flow chart of a lithium-ion battery formation method. DETAILED DESCRIPTION

[0022] The technical solution 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 part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0023] Combination Figure 1 , the formation method of the lithium-ion battery of the present application is described.

[0024] In order to solve the problem of how to reduce the impedance of a lithium-ion battery and thereby improve the energy density and cycle life of the battery, the formation method of a lithium-ion battery of the present application comprises the following steps: 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 at a current of 0.1-1C to a SOC of 80-100%; Among them, film-forming additives are added to the electrolyte of the battery cell.

[0025] This application can effectively activate lithium-ion batteries by adopting a charging method with a step-by-step increasing current, avoid the capacity "climbing" phenomenon in the early stage of the cycle, and ensure a high capacity retention rate in the later stage of the cycle, and excellent cycle performance. In addition, by adding a film-forming additive to the electrolyte of the battery cell and charging the battery cell with a step-by-step increasing current charging method, the SEI film formed by the negative electrode gradually changes from dense to loose from the inside to the outside. This SEI film structure can not only stabilize the electrode material and prevent the electrolyte from having an irreversible chemical reaction with the active substance, but also reduce the impedance of the negative electrode SEI film, thereby reducing the overall impedance of the battery, which is beneficial for lithium ions to pass through the SEI film and improve the energy density and cycle life of the lithium-ion battery.

[0026] The preferred implementation of the formation method of the lithium-ion battery of the present application is introduced below.

[0027] Step (101): Charge the battery cell at a current of 0.01-0.1C to a SOC of 2-40%.

[0028] 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. By adding the above film-forming additive to the electrolyte, the SEI film can gradually change from dense to loose from the inside to the outside during the process of charging the battery cell with a step-by-step increasing current, thereby reducing the impedance of the negative electrode SEI film. Wherein, the amount of film-forming additive added is 1-3% of the total mass of the electrolyte.

[0029] Before step (101), the method further includes the following steps: Step (100): leaving the battery cell after injection to stand for a fourth preset time period.

[0030] By leaving the battery cell after injection to stand for a fourth preset time period, the electrolyte is fully in contact with the electrode, which is conducive to better infiltration of the electrode by the electrolyte. Among them, the fourth preset time period is 12-36 hours. If the standing time is less than 12 hours, the electrolyte infiltration is uneven, which will affect the subsequent SEI film formation and make film formation difficult. The SEI film forming effect will directly affect the performance of the lithium-ion battery. If the standing time is greater than 36 hours, the long standing time will reduce production efficiency and is not conducive to improving production benefits.

[0031] In other preferred embodiments, step (101) further comprises: Step (1011): charging the battery cell to a SOC of 2-10% at a current of 0.01-0.03C; Step (1012): charging the battery cell at a current of 0.03-0.05C to a SOC of 5-20%; Step (1013): Charge the battery cell at a current of 0.05-0.1C to a SOC of 15-40%.

[0032] By dividing step (101) into three charging operations, wherein the first charging operation is to charge the battery to a SOC of 2-10% using a current of 0.01-0.03C, the film is formed slowly, and the stability and firmness of the SEI film are improved. The second charging operation is to charge the battery to a SOC of 5-20% using a current of 0.03-0.05C, and the third charging operation is to charge the battery to a SOC of 15-40% using a current of 0.05-0.1C. The charging current is increased successively, and while the stability and firmness of the SEI film are ensured, the density of the SEI film is reduced, thereby reducing the impedance of the SEI film.

[0033] It should be noted that after each charging operation is completed and before the next charging is carried out, it is necessary to 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 also includes: standing for a first preset time period. Wherein, the first preset time period is in the range of 5-10 minutes. And / or, after the second charging operation is completed and before the third charging operation, it also includes: standing for a second preset time period. Wherein, the second preset time period is in the range of 5-10 minutes. And / or, after the third charging operation is completed, it also includes: standing for a third preset time period. Wherein, the third preset time period is in the range of 5-10 minutes. Standing time that is too short will affect the formation of the SEI film, thereby affecting the stability of the obtained SEI film structure, and standing time that is too long is not conducive to improving production efficiency.

[0034] Step (102): Charge the battery cell at a current of 0.1-1C to a SOC of 80-100%.

[0035] After step (101), the battery cell is charged to a SOC of 80-100% at a current of 0.1-1C. The SEI film obtained in this step has good stability and firmness, and has higher looseness than step (101). It can reduce the SEI film impedance, facilitate the passage of lithium ions, and improve the energy density and cycle life of the lithium-ion battery.

[0036] It should be noted that the entire formation process, i.e., step (101) and step (102), is carried out under a vacuum degree of 45-80 KPa, and the battery cell is charged to a SOC of 80-100% under the vacuum degree, so that gas can be removed. In addition, the entire formation process of the battery is carried out at room temperature.

[0037] It should also be noted that the present application has no limitation on the specific composition of the electrolyte, which can be a common electrolyte in the art.

[0038] The formation method of the lithium-ion battery of the present application is described in conjunction with the following embodiments.

[0039] Example 1 A method for preparing an unformed lithium-ion battery comprises the following steps:

[0040] Step (a) Preparation of positive electrode sheet: Lithium iron phosphate positive electrode active material, conductive carbon black and polyvinylidene fluoride are weighed in a weight ratio of 95.5:2.1:2.4, stirred and coated on a 12 μm carbon-coated aluminum foil, with a coating surface density of 380 g / cm 2 , compacted density 2.3g / cm 3 , and the positive electrode sheet is obtained through rolling and die-cutting.

[0041] Step (b) Preparation of negative electrode sheet: Graphite, conductive carbon black, sodium carboxymethyl cellulose and styrene-butadiene rubber were weighed in a weight ratio of 96.3:1:1.3:1.4, and the mixture was homogenized and coated on 8 μm copper foil with a coating surface density of 154 g / cm 2 , compaction 1.6g / cm 3 , after rolling and die-cutting, the negative electrode sheet is obtained.

[0042] Step (c) battery assembly, the pole pieces obtained in steps (a) and (b) are stacked in a Z-shape, with 28 positive pole pieces and 29 negative pole pieces, and a polyethylene film with a thickness of 9 μm is used as a separator. The battery cell is encapsulated in an aluminum-plastic film, and after baking and injection, an unformed lithium-ion battery is obtained; wherein the electrolyte used for injection includes LiPF6, propylene carbonate, ethylene carbonate and dimethyl carbonate in a mass ratio of 13:35:20:32.

[0043] Example 2

[0044] A formation method for a lithium-ion battery, comprising: Step (100): After the battery cell of Example 1 is filled with electrolyte, it is left to stand for 24 hours; wherein 2% vinylene carbonate is added to the electrolyte; Step (1011): charging the battery cell to a SOC of 5% at a current of 0.01C in a negative pressure environment of 80 kPa, and leaving it to stand for 10 minutes; Step (1012): charging the battery cell to a SOC of 10% at a current of 0.03C in a negative pressure environment of 80 kPa, and leaving it for 10 minutes; Step (1013): charging the battery cell to a SOC of 30% at a current of 0.05C in a negative pressure environment of 80 kPa, and leaving it for 10 minutes; Step (102): charging the battery cell at a current of 0.5C to a SOC of 100% in a negative pressure environment of 80 kPa, thereby obtaining a lithium-ion battery that has been formed.

[0045] Example 3 A formation method for a lithium-ion battery, comprising: Step (100): After the battery cell of Example 1 is filled with electrolyte, it is left to stand for 24 hours; wherein 2% vinylene carbonate is added to the electrolyte; Step (1011): charging the battery cell to a SOC of 5% at a current of 0.02C in a negative pressure environment of 80 kPa, and leaving it to stand for 10 minutes; Step (1012): charging the battery cell to a SOC of 10% at a current of 0.03C in a negative pressure environment of 80 kPa, and leaving it for 10 minutes; Step (1013): charging the battery cell to a SOC of 30% at a current of 0.05C in a negative pressure environment of 80 kPa, and leaving it for 10 minutes; Step (102): charging the battery cell at a current of 0.5C to a SOC of 100% in a negative pressure environment of 80 kPa, thereby obtaining a lithium-ion battery that has been formed.

[0046] Example 4 A formation method for a lithium-ion battery, comprising: Step (100): After the battery cell of Example 1 is filled with electrolyte, it is left to stand for 24 hours; wherein 2% vinylene carbonate is added to the electrolyte; Step (1011): charging the battery cell to a SOC of 5% at a current of 0.02C in a negative pressure environment of 80 kPa, and leaving it to stand for 10 minutes; Step (1012): charging the battery cell to a SOC of 10% at a current of 0.04C in a negative pressure environment of 80 kPa, and leaving it for 10 minutes; Step (1013): charging the battery cell to a SOC of 30% at a current of 0.05C in a negative pressure environment of 80 kPa, and leaving it for 10 minutes; Step (102): charging the battery cell at a current of 0.5C to a SOC of 100% in a negative pressure environment of 80 kPa, thereby obtaining a lithium-ion battery that has been formed.

[0047] Example 5 A formation method for a lithium-ion battery, comprising: Step (100): After the battery cell of Example 1 is filled with electrolyte, it is left to stand for 24 hours; wherein 2% vinylene carbonate is added to the electrolyte; Step (1011): charging the battery cell to a SOC of 5% at a current of 0.02C in a negative pressure environment of 80 kPa, and leaving it to stand for 10 minutes; Step (1012): charging the battery cell to a SOC of 10% at a current of 0.03C in a negative pressure environment of 80 kPa, and leaving it for 10 minutes; Step (1013): charging the battery cell to a SOC of 30% at a current of 0.1C in a negative pressure environment of 80 kPa, and leaving it for 10 minutes; Step (102): charging the battery cell at a current of 0.5C to a SOC of 100% in a negative pressure environment of 80 kPa, thereby obtaining a lithium-ion battery that has been formed.

[0048] Example 6 A formation method for a lithium-ion battery, comprising: Step (100): After the battery cell of Example 1 is filled with electrolyte, it is left to stand for 24 hours; wherein 2% vinylene carbonate is added to the electrolyte; Step (1011): charging the battery cell to a SOC of 5% at a current of 0.02C in a negative pressure environment of 80 kPa, and leaving it to stand for 10 minutes; Step (1012): charging the battery cell to a SOC of 10% at a current of 0.03C in a negative pressure environment of 80 kPa, and leaving it for 10 minutes; Step (1013): charging the battery cell to a SOC of 30% at a current of 0.05C in a negative pressure environment of 80 kPa, and leaving it for 10 minutes; Step (102): charging the battery cell at a current of 1C in a negative pressure environment of 80 kPa until the SOC is 100%, thereby obtaining a fully formed lithium-ion battery.

[0049] Example 7 A formation method for a lithium-ion battery, comprising: Step (100): After the battery cell of Example 1 is filled with electrolyte, it is left to stand for 24 hours; wherein 1% vinylene carbonate and 1% fluoroethylene carbonate are added to the electrolyte; Step (1011): charging the battery cell to a SOC of 5% at a current of 0.02C in a negative pressure environment of 80 kPa, and leaving it to stand for 10 minutes; Step (1012): charging the battery cell to a SOC of 10% at a current of 0.03C in a negative pressure environment of 80 kPa, and leaving it for 10 minutes; Step (1013): charging the battery cell to a SOC of 30% at a current of 0.05C in a negative pressure environment of 80 kPa, and leaving it for 10 minutes; Step (102): charging the battery cell at a current of 0.5C to a SOC of 100% in a negative pressure environment of 80 kPa, thereby obtaining a lithium-ion battery that has been formed.

[0050] Example 8 A formation method for a lithium-ion battery, comprising: Step (100): After the battery cell of Example 1 is filled with electrolyte, it is left to stand for 24 hours; wherein 2% fluoroethylene carbonate is added to the electrolyte; Step (1011): charging the battery cell to a SOC of 5% at a current of 0.02C in a negative pressure environment of 80 kPa, and leaving it to stand for 10 minutes; Step (1012): charging the battery cell to a SOC of 10% at a current of 0.03C in a negative pressure environment of 80 kPa, and leaving it for 10 minutes; Step (1013): charging the battery cell to a SOC of 30% at a current of 0.05C in a negative pressure environment of 80 kPa, and leaving it for 10 minutes; Step (102): charging the battery cell at a current of 0.5C to a SOC of 100% in a negative pressure environment of 80 kPa, thereby obtaining a lithium-ion battery that has been formed.

[0051] Example 9 A formation method for a lithium-ion battery, comprising: Step (100): After the battery cell of Example 1 is filled with electrolyte, it is left to stand for 24 hours; wherein 2% propylene sulfite is added to the electrolyte; Step (1011): charging the battery cell to a SOC of 5% at a current of 0.02C in a negative pressure environment of 80 kPa, and leaving it to stand for 10 minutes; Step (1012): charging the battery cell to a SOC of 10% at a current of 0.03C in a negative pressure environment of 80 kPa, and leaving it for 10 minutes; Step (1013): charging the battery cell to a SOC of 30% at a current of 0.05C in a negative pressure environment of 80 kPa, and leaving it for 10 minutes; Step (102): charging the battery cell at a current of 0.5C to a SOC of 100% in a negative pressure environment of 80 kPa, thereby obtaining a lithium-ion battery that has been formed.

[0052] Example 10 A formation method for a lithium-ion battery, comprising: Step (100): After the battery cell of Example 1 is filled with electrolyte, it is left to stand for 24 hours; wherein 2% vinylene carbonate is added to the electrolyte; Step (1011): charging the battery cell to a SOC of 7% at a current of 0.01C in a negative pressure environment of 80 kPa, and leaving it to stand for 10 minutes; Step (1012): charging the battery cell to a SOC of 10% at a current of 0.03C in a negative pressure environment of 80 kPa, and leaving it for 10 minutes; Step (1013): charging the battery cell to a SOC of 30% at a current of 0.05C in a negative pressure environment of 80 kPa, and leaving it for 10 minutes; Step (102): charging the battery cell at a current of 0.5C to a SOC of 100% in a negative pressure environment of 80 kPa, thereby obtaining a lithium-ion battery that has been formed.

[0053] Embodiment 11 A formation method for a lithium-ion battery, comprising: Step (100): After the battery cell of Example 1 is filled with electrolyte, it is left to stand for 24 hours; wherein 2% vinylene carbonate is added to the electrolyte; Step (1011): charging the battery cell to a SOC of 5% at a current of 0.01C in a negative pressure environment of 80 kPa, and leaving it to stand for 10 minutes; Step (1012): charging the battery cell to a SOC of 20% at a current of 0.03C in a negative pressure environment of 80 kPa, and leaving it to stand for 10 minutes; Step (1013): charging the battery cell to a SOC of 30% at a current of 0.05C in a negative pressure environment of 80 kPa, and leaving it for 10 minutes; Step (102): charging the battery cell at a current of 0.5C to a SOC of 100% in a negative pressure environment of 80 kPa, thereby obtaining a lithium-ion battery that has been formed.

[0054] Example 12 A formation method for a lithium-ion battery, comprising: Step (100): After the battery cell of Example 1 is filled with electrolyte, it is left to stand for 24 hours; wherein 2% vinylene carbonate is added to the electrolyte; Step (1011): charging the battery cell to a SOC of 5% at a current of 0.01C in a negative pressure environment of 80 kPa, and leaving it to stand for 10 minutes; Step (1012): charging the battery cell to a SOC of 10% at a current of 0.03C in a negative pressure environment of 80 kPa, and leaving it for 10 minutes; Step (1013): charging the battery cell to a SOC of 30% at a current of 0.05C in a negative pressure environment of 80 kPa, and leaving it for 10 minutes; Step (102): charging the battery cell at a current of 0.5C to a SOC of 80% in a negative pressure environment of 80 kPa, thereby obtaining a fully formed lithium-ion battery.

[0055] Embodiment 13 A formation method for a lithium-ion battery, comprising: Step (100): After the battery cell of Example 1 is filled with electrolyte, it is left to stand for 24 hours; wherein 2% vinylene carbonate is added to the electrolyte; Step (1011): charging the battery cell to a SOC of 8% at a current of 0.02C in a negative pressure environment of 80 kPa, and leaving it for 10 minutes; Step (1012): charging the battery cell to a SOC of 15% at a current of 0.03C in a negative pressure environment of 80 kPa, and leaving it at rest for 10 minutes; Step (1013): charging the battery cell to a SOC of 35% at a current of 0.05C in a negative pressure environment of 80 kPa, and leaving it for 10 minutes; Step (102): charging the battery cell at a current of 0.5C to a SOC of 100% in a negative pressure environment of 80 kPa, thereby obtaining a lithium-ion battery that has been formed.

[0056] Embodiment 14 A formation method for a lithium-ion battery, comprising: Step (100): After the battery cell of Example 1 is filled with electrolyte, it is left to stand for 30 hours; wherein 1.5% vinylene carbonate is added to the electrolyte; Step (1011): charging the battery cell to a SOC of 3% at a current of 0.02C in a negative pressure environment of 80 kPa, and leaving it to stand for 10 minutes; Step (1012): charging the battery cell to a SOC of 7% at a current of 0.03C in a negative pressure environment of 80 kPa, and leaving it for 10 minutes; Step (1013): charging the battery cell to a SOC of 20% at a current of 0.05C in a negative pressure environment of 80 kPa, and leaving it for 10 minutes; Step (102): charging the battery cell at a current of 0.5C to a SOC of 100% in a negative pressure environment of 80 kPa, thereby obtaining a lithium-ion battery that has been formed.

[0057] Embodiment 15 A formation method for a lithium-ion battery, comprising: Step (100): After the battery cell of Example 1 is filled with electrolyte, it is left to stand for 12 hours; wherein 1% vinylene carbonate is added to the electrolyte; Step (1011): charging the battery cell to a SOC of 10% at a current of 0.03C in a negative pressure environment of 45 kPa, and standing for 8 minutes; Step (1012): charging the battery cell to a SOC of 20% at a current of 0.05C in a negative pressure environment of 45 kPa, and standing for 8 minutes; Step (1013): charging the battery cell to a SOC of 40% at a current of 0.1C in a negative pressure environment of 45 kPa, and leaving it for 8 minutes; Step (102): charging the battery cell at a current of 1C to a SOC of 100% in a negative pressure environment of 45 kPa, thereby obtaining a fully formed lithium-ion battery.

[0058] Example 16 A formation method for a lithium-ion battery, comprising: Step (100): After the battery cell of Example 1 is filled with electrolyte, it is left to stand for 36 hours; wherein 3% vinylene carbonate is added to the electrolyte; Step (1011): charging the battery cell to a SOC of 2% at a current of 0.01C in a negative pressure environment of 60 kPa, and standing for 5 minutes; Step (1012): charging the battery cell to a SOC of 5% at a current of 0.03C in a negative pressure environment of 60 kPa, and leaving it at rest for 10 minutes; Step (1013): charging the battery cell to a SOC of 15% at a current of 0.05C in a negative pressure environment of 60 kPa, and leaving it for 5 minutes; Step (102): charging the battery cell at a current of 0.1C to a SOC of 80% in a negative pressure environment of 60 kPa, thereby obtaining a lithium-ion battery that has been formed.

[0059] Comparative Example 1 A formation method for a lithium-ion battery, comprising: Step (100): After the battery cell of Example 1 is filled with electrolyte, it is left to stand for 24 hours; wherein 2% vinylene carbonate is added to the electrolyte; Step (1011): charging the battery cell to a SOC of 5% at a current of 0.01C in a negative pressure environment of 80 kPa, and leaving it at rest for 10 minutes; Step (1012): charging the battery cell to a SOC of 10% at a current of 0.01C in a negative pressure environment of 80 kPa, and leaving it for 10 minutes; Step (1013): charging the battery cell to a SOC of 30% at a current of 0.01C in a negative pressure environment of 80 kPa, and leaving it for 10 minutes; Step (102): charging the battery cell at a current of 0.01C to a SOC of 100% in a negative pressure environment of 80 kPa, thereby obtaining a fully formed lithium-ion battery.

[0060] Comparative Example 2 A formation method for a lithium-ion battery, comprising: Step (100): After the battery cell of Example 1 is filled with electrolyte, it is left to stand for 24 hours; wherein 2% vinylene carbonate is added to the electrolyte; Step (1011): charging the battery cell to a SOC of 5% at a current of 0.5C in a negative pressure environment of 80 kPa, and leaving it to stand for 10 minutes; Step (1012): charging the battery cell to a SOC of 10% at a current of 0.5C in a negative pressure environment of 80 kPa, and leaving it at rest for 10 minutes; Step (1013): charging the battery cell to a SOC of 30% at a current of 0.5C in a negative pressure environment of 80 kPa, and leaving it for 10 minutes; Step (102): charging the battery cell at a current of 0.5C to a SOC of 100% in a negative pressure environment of 80 kPa, thereby obtaining a lithium-ion battery that has been formed.

[0061] Comparative Example 3 A formation method for a lithium-ion battery, comprising: Step (100): After the battery cell of Example 1 is filled with liquid, it is left to stand for 24 hours; Step (1011): charging the battery cell to a SOC of 5% at a current of 0.01C in a negative pressure environment of 80 kPa, and leaving it to stand for 10 minutes; Step (1012): charging the battery cell to a SOC of 10% at a current of 0.03C in a negative pressure environment of 80 kPa, and leaving it for 10 minutes; Step (1013): charging the battery cell to a SOC of 30% at a current of 0.05C in a negative pressure environment of 80 kPa, and leaving it for 10 minutes; Step (102): charging the battery cell at a current of 0.5C to a SOC of 100% in a negative pressure environment of 80 kPa, thereby obtaining a lithium-ion battery that has been formed.

[0062] Comparative Example 4 A formation method for a lithium-ion battery, comprising: Step (100): After the battery cell of Example 1 is filled with electrolyte, it is left to stand for 36 hours; wherein 2% vinylene carbonate is added to the electrolyte; Step (1011): charging the battery cell to a SOC of 5% at a current of 0.04C in a negative pressure environment of 80 kPa, and leaving it to stand for 10 minutes; Step (1012): charging the battery cell to a SOC of 10% at a current of 0.03C in a negative pressure environment of 80 kPa, and leaving it for 10 minutes; Step (1013): charging the battery cell to a SOC of 30% at a current of 0.05C in a negative pressure environment of 80 kPa, and leaving it for 10 minutes; Step (102): charging the battery cell at a current of 0.5C to a SOC of 100% in a negative pressure environment of 80 kPa, thereby obtaining a lithium-ion battery that has been formed.

[0063] Comparative Example 5 A formation method for a lithium-ion battery, comprising: Step (100): After the battery cell of Example 1 is filled with electrolyte, it is left to stand for 36 hours; wherein 2% vinylene carbonate is added to the electrolyte; Step (1011): charging the battery cell to a SOC of 5% at a current of 0.005C in a negative pressure environment of 80 kPa, and leaving it to stand for 10 minutes; Step (1012): charging the battery cell to a SOC of 10% at a current of 0.03C in a negative pressure environment of 80 kPa, and leaving it for 10 minutes; Step (1013): charging the battery cell to a SOC of 30% at a current of 0.05C in a negative pressure environment of 80 kPa, and leaving it for 10 minutes; Step (102): charging the battery cell at a current of 0.5C to a SOC of 100% in a negative pressure environment of 80 kPa, thereby obtaining a lithium-ion battery that has been formed.

[0064] Comparative Example 6 A formation method for a lithium-ion battery, comprising: Step (100): After the battery cell of Example 1 is filled with electrolyte, it is left to stand for 24 hours; wherein 2% vinylene carbonate is added to the electrolyte; Step (1011): charging the battery cell to a SOC of 5% at a current of 0.01C in a negative pressure environment of 80 kPa, and leaving it to stand for 10 minutes; Step (1012): charging the battery cell to a SOC of 10% at a current of 0.02C in a negative pressure environment of 80 kPa, and leaving it for 10 minutes; Step (1013): charging the battery cell to a SOC of 30% at a current of 0.05C in a negative pressure environment of 80 kPa, and leaving it for 10 minutes; Step (102): charging the battery cell at a current of 0.5C to a SOC of 100% in a negative pressure environment of 80 kPa, thereby obtaining a lithium-ion battery that has been formed.

[0065] Comparative Example 7 A formation method for a lithium-ion battery, comprising: Step (100): After the battery cell of Example 1 is filled with electrolyte, it is left to stand for 24 hours; wherein 2% vinylene carbonate is added to the electrolyte; Step (1011): charging the battery cell to a SOC of 5% at a current of 0.01C in a negative pressure environment of 80 kPa, and leaving it to stand for 10 minutes; Step (1012): charging the battery cell to a SOC of 10% at a current of 0.06C in a negative pressure environment of 80 kPa, and leaving it for 10 minutes; Step (1013): charging the battery cell to a SOC of 30% at a current of 0.05C in a negative pressure environment of 80 kPa, and leaving it for 10 minutes; Step (102): charging the battery cell at a current of 0.5C to a SOC of 100% in a negative pressure environment of 80 kPa, thereby obtaining a lithium-ion battery that has been formed.

[0066] Comparative Example 8 A formation method for a lithium-ion battery, comprising: Step (100): After the battery cell of Example 1 is filled with electrolyte, it is left to stand for 36 hours; wherein 2% vinylene carbonate is added to the electrolyte; Step (1011): charging the battery cell to a SOC of 15% at a current of 0.03C in a negative pressure environment of 80 kPa, and leaving it to stand for 10 minutes; Step (1012): charging the battery cell to a SOC of 25% at a current of 0.05C in a negative pressure environment of 80 kPa, and leaving it to stand for 10 minutes; Step (1013): charging the battery cell to a SOC of 50% at a current of 0.2C in a negative pressure environment of 80 kPa, and leaving it to stand for 10 minutes; Step (102): charging the battery cell at a current of 1C in a negative pressure environment of 80 kPa until the SOC is 100%, thereby obtaining a fully formed lithium-ion battery.

[0067] Comparative Example 9 A formation method for a lithium-ion battery, comprising: Step (100): After the battery cell of Example 1 is filled with electrolyte, it is left to stand for 24 hours; wherein 2% vinylene carbonate is added to the electrolyte; Step (1011): charging the battery cell to a SOC of 5% at a current of 0.01C in a negative pressure environment of 80 kPa, and leaving it to stand for 10 minutes; Step (1012): charging the battery cell to a SOC of 10% at a current of 0.03C in a negative pressure environment of 80 kPa, and leaving it for 10 minutes; Step (1013): charging the battery cell to a SOC of 30% at a current of 0.03C in a negative pressure environment of 80 kPa, and leaving it to stand for 10 minutes; Step (102): charging the battery cell at a current of 0.5C to a SOC of 100% in a negative pressure environment of 80 kPa, thereby obtaining a lithium-ion battery that has been formed.

[0068] Comparative Example 10 A formation method for a lithium-ion battery, comprising: Step (100): After the battery cell of Example 1 is filled with electrolyte, it is left to stand for 24 hours; wherein 2% vinylene carbonate is added to the electrolyte; Step (1011): charging the battery cell to a SOC of 5% at a current of 0.01C in a negative pressure environment of 80 kPa, and leaving it to stand for 10 minutes; Step (1012): charging the battery cell to a SOC of 10% at a current of 0.03C in a negative pressure environment of 80 kPa, and leaving it for 10 minutes; Step (1013): charging the battery cell to a SOC of 30% at a current of 0.05C in a negative pressure environment of 80 kPa, and leaving it for 10 minutes; Step (102): charging the battery cell at a current of 2C to a SOC of 100% in a negative pressure environment of 80 kPa, thereby obtaining a fully formed lithium-ion battery.

[0069] Comparative Example 11 A formation method for a lithium-ion battery, comprising: Step (100): After the battery cell of Example 1 is filled with electrolyte, it is left to stand for 24 hours; wherein 2% vinylene carbonate is added to the electrolyte; Step (1011): charging the battery cell to a SOC of 5% at a current of 0.01C in a negative pressure environment of 80 kPa, and leaving it to stand for 10 minutes; Step (1012): charging the battery cell to a SOC of 10% at a current of 0.03C in a negative pressure environment of 80 kPa, and leaving it for 10 minutes; Step (1013): charging the battery cell to a SOC of 30% at a current of 0.05C in a negative pressure environment of 80 kPa, and leaving it for 10 minutes; Step (102): charging the battery cell at a current of 0.08C to a SOC of 100% in a negative pressure environment of 80 kPa, thereby obtaining a lithium-ion battery that has been formed.

[0070] Comparative Example 12 A formation method for a lithium-ion battery, comprising: Step (100): After the battery cell of Example 1 is filled with electrolyte, it is left to stand for 24 hours; wherein 2% vinylene carbonate is added to the electrolyte; Step (1011): charging the battery cell to a SOC of 5% at a current of 0.01C in a negative pressure environment of 80 kPa, and leaving it to stand for 10 minutes; Step (1012): charging the battery cell to a SOC of 10% at a current of 0.03C in a negative pressure environment of 80 kPa, and leaving it for 10 minutes; Step (1013): charging the battery cell to a SOC of 30% at a current of 0.05C in a negative pressure environment of 80 kPa, and leaving it for 10 minutes; Step (102): charging the battery cell at a current of 0.5C to a SOC of 50% in a negative pressure environment of 80 kPa, thereby obtaining a lithium-ion battery that has been formed.

[0071] Comparative Example 13 A formation method for a lithium-ion battery, comprising: Step (100): After the battery cell of Example 1 is filled with electrolyte, it is left to stand for 24 hours; wherein 2% vinylene carbonate is added to the electrolyte; Step (1011): charging the battery cell to a SOC of 12% at a current of 0.02C in a negative pressure environment of 80 kPa, and leaving it to stand for 10 minutes; Step (1012): charging the battery cell to a SOC of 15% at a current of 0.03C in a negative pressure environment of 80 kPa, and leaving it at rest for 10 minutes; Step (1013): charging the battery cell to a SOC of 35% at a current of 0.05C in a negative pressure environment of 80 kPa, and leaving it for 10 minutes; Step (102): charging the battery cell at a current of 0.5C to a SOC of 100% in a negative pressure environment of 80 kPa, thereby obtaining a lithium-ion battery that has been formed.

[0072] Comparative Example 14 A formation method for a lithium-ion battery, comprising: Step (100): After the battery cell of Example 1 is filled with electrolyte, it is left to stand for 30 hours; wherein 1.5% vinylene carbonate is added to the electrolyte; Step (1011): charging the battery cell to a SOC of 1% at a current of 0.02C in a negative pressure environment of 80 kPa, and leaving it to stand for 10 minutes; Step (1012): charging the battery cell to a SOC of 15% at a current of 0.03C in a negative pressure environment of 80 kPa, and leaving it at rest for 10 minutes; Step (1013): charging the battery cell to a SOC of 20% at a current of 0.05C in a negative pressure environment of 80 kPa, and leaving it for 10 minutes; Step (102): charging the battery cell at a current of 0.5C to a SOC of 100% in a negative pressure environment of 80 kPa, thereby obtaining a lithium-ion battery that has been formed.

[0073] Comparative Example 15 A formation method for a lithium-ion battery, comprising: Step (100): After the battery cell of Example 1 is filled with electrolyte, it is left to stand for 24 hours; wherein 2% vinylene carbonate is added to the electrolyte; Step (1011): charging the battery cell to a SOC of 8% at a current of 0.02C in a negative pressure environment of 80 kPa, and leaving it for 10 minutes; Step (1012): charging the battery cell to a SOC of 25% at a current of 0.03C in a negative pressure environment of 80 kPa, and leaving it for 10 minutes; Step (1013): charging the battery cell to a SOC of 35% at a current of 0.05C in a negative pressure environment of 80 kPa, and leaving it for 10 minutes; Step (102): charging the battery cell at a current of 0.5C to a SOC of 100% in a negative pressure environment of 80 kPa, thereby obtaining a lithium-ion battery that has been formed.

[0074] Comparative Example 16 A formation method for a lithium-ion battery, comprising: Step (100): After the battery cell of Example 1 is filled with electrolyte, it is left to stand for 30 hours; wherein 1.5% vinylene carbonate is added to the electrolyte; Step (1011): charging the battery cell to a SOC of 3% at a current of 0.02C in a negative pressure environment of 80 kPa, and leaving it to stand for 10 minutes; Step (1012): charging the battery cell to a SOC of 4% at a current of 0.03C in a negative pressure environment of 80 kPa, and leaving it to stand for 10 minutes; Step (1013): charging the battery cell to a SOC of 20% at a current of 0.05C in a negative pressure environment of 80 kPa, and leaving it for 10 minutes; Step (102): charging the battery cell at a current of 0.5C to a SOC of 100% in a negative pressure environment of 80 kPa, thereby obtaining a lithium-ion battery that has been formed.

[0075] Comparative Example 17 A formation method for a lithium-ion battery, comprising: Step (100): After the battery cell of Example 1 is filled with electrolyte, it is left to stand for 24 hours; wherein 2% vinylene carbonate is added to the electrolyte; Step (1011): charging the battery cell to a SOC of 8% at a current of 0.02C in a negative pressure environment of 80 kPa, and leaving it for 10 minutes; Step (1012): charging the battery cell to a SOC of 15% at a current of 0.03C in a negative pressure environment of 80 kPa, and leaving it at rest for 10 minutes; Step (1013): charging the battery cell to a SOC of 50% at a current of 0.05C in a negative pressure environment of 80 kPa, and leaving it for 10 minutes; Step (102): charging the battery cell at a current of 0.5C to a SOC of 100% in a negative pressure environment of 80 kPa, thereby obtaining a lithium-ion battery that has been formed.

[0076] Comparative Example 18 A formation method for a lithium-ion battery, comprising: Step (100): After the battery cell of Example 1 is filled with electrolyte, it is left to stand for 30 hours; wherein 1.5% vinylene carbonate is added to the electrolyte; Step (1011): charging the battery cell to a SOC of 3% at a current of 0.02C in a negative pressure environment of 80 kPa, and leaving it to stand for 10 minutes; Step (1012): charging the battery cell to a SOC of 7% at a current of 0.03C in a negative pressure environment of 80 kPa, and leaving it for 10 minutes; Step (1013): charging the battery cell to a SOC of 12% at a current of 0.05C in a negative pressure environment of 80 kPa, and leaving it for 10 minutes; Step (102): charging the battery cell at a current of 0.5C to a SOC of 100% in a negative pressure environment of 80 kPa, thereby obtaining a lithium-ion battery that has been formed.

[0077] Comparative Example 19 A formation method for a lithium-ion battery, comprising: Step (100): After the battery cell of Example 1 is filled with electrolyte, it is left to stand for 24 hours; wherein 2% vinylene carbonate is added to the electrolyte; Step (1011): charging the battery cell to a SOC of 8% at a current of 0.02C in a negative pressure environment of 80 kPa, and leaving it for 10 minutes; Step (1012): charging the battery cell to a SOC of 15% at a current of 0.03C in a negative pressure environment of 80 kPa, and leaving it at rest for 10 minutes; Step (1013): charging the battery cell to a SOC of 35% at a current of 0.05C in a negative pressure environment of 80 kPa, and leaving it for 10 minutes; Step (102): charging the battery cell at a current of 0.5C to a SOC of 70% in a negative pressure environment of 80 kPa, thereby obtaining a fully formed lithium-ion battery.

[0078] Comparative Example 20 A formation method for a lithium-ion battery, comprising: Step (100): After the battery cell of Example 1 is filled with electrolyte, it is left to stand for 30 hours; wherein 1.5% vinylene carbonate is added to the electrolyte; Step (1011): charging the battery cell to a SOC of 3% at a current of 0.02C in a negative pressure environment of 80 kPa, and leaving it to stand for 10 minutes; Step (1012): charging the battery cell to a SOC of 7% at a current of 0.03C in a negative pressure environment of 80 kPa, and leaving it for 10 minutes; Step (1013): charging the battery cell to a SOC of 20% at a current of 0.05C in a negative pressure environment of 80 kPa, and leaving it for 10 minutes; Step (102): charging the battery cell at a current of 0.5C to a SOC of 50% in a negative pressure environment of 80 kPa, thereby obtaining a lithium-ion battery that has been formed.

[0079] The performance of the lithium-ion batteries obtained in the above-mentioned Examples 2-16 and Comparative Examples 1-20 was tested. The test results are shown in Table 1 below.

[0080] Table 1 DCR (mΩ) 0.5C discharge capacity (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 Embodiment 11 4.28 144 91.5 Example 12 4.36 145 92.7 Embodiment 13 4.31 144 91.1 Embodiment 14 4.27 145 91.8 Embodiment 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 As can be seen from Table 1, compared with Comparative Examples 1-20, the lithium-ion battery obtained by the formation method of the present application has a large 0.5C discharge gram capacity of 144 mAh / g, a small direct current resistance (DCR), and a high capacity retention rate after 1000 cycles at room temperature. This shows that by adopting the formation method of the present application, an SEI film showing a gradient change from dense to loose from the inside to the outside can be obtained. This structure of the SEI film not only helps to suppress the climbing phenomenon of the lithium-ion battery, but also significantly improves the room temperature cycle performance of the battery.

[0081] Those skilled in the art will appreciate that, although some embodiments described herein include certain features included in other embodiments but not other features, the combination of features of different embodiments is meant to be within the scope of the present application and form different embodiments. For example, in the claims of the present application, any one of the claimed embodiments may be used in any combination.

[0082] It should be noted that although the detailed steps of the method of the present application are described in detail above, without departing from the basic principles of the present application, technical personnel in this field can combine, split and change the order of the above steps. The modified technical solution does not change the basic concept of the present application and therefore falls within the scope of protection of the present application.

[0083] So far, the technical solutions of the present application have been described in conjunction with the preferred embodiments shown in the accompanying 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. Without departing from the principles 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 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.

2. The chemical formation method according to claim 1, characterized in that: The film-forming additive includes one or more of vinylene carbonate, propylene sulfite, and fluoroethylene carbonate.

3. 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.

4. 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 following steps are further included: The device is left to stand for a third preset time period.

5. The chemical formation method according to claim 4, 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.

6. 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%.

7. 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.

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

9. 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 8.

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