Formation process of battery

Abstract

Embodiments of the present application provide a formation process of a battery, comprising: performing a constant current-constant voltage charging process on the battery, wherein the rate of the constant current charging in the constant current-constant voltage charging process is 3C-5C, and the cut-off voltage range of the constant current charging is 2.8V-3.0V, and wherein the voltage of the constant voltage charging in the constant current-constant voltage charging process is the cut-off voltage of the constant current charging, and the cut-off rate of the constant voltage charging is 0.02C-0.005C; and sequentially performing a first constant current charging process and a second constant current charging process on the battery after the constant current-constant voltage charging process. The formation process of the battery provided by the present application adopts the constant current-constant voltage charging process of high potential constant voltage charging formation, which promotes all additives to form films at the same potential, thereby forming an SEI film in which organic and inorganic components are fully mixed, ion conduction and mechanical performance are taken into account, and the fast charging performance of the battery is improved.

Description

TECHNICAL FIELD

[0001] Embodiments of the present application relate to the field of batteries, in particular, to the formation process of batteries. BACKGROUND

[0002] In the field of new energy, the development of batteries is becoming more and more important, and the performance requirements of batteries are also getting higher and higher, especially for lithium ion batteries. It is found that in the preparation of lithium ion batteries, the formation process has a great influence on the performance of lithium ion batteries. It should be noted that the formation process generally refers to the process of charging the lithium ion battery with a small current after liquid injection to form a dense SEI (solid-state electrolyte interface) on the surface of the negative electrode, and at the same time, the battery voltage is raised to the working voltage interval. Further, in the formation process, the additives in the electrolyte of the lithium ion battery undergo an electrochemical reduction reaction on the surface of the negative electrode to form an SEI film. The SEI film is an interface phase with ion conductivity and electronic insulation, which plays a role in isolating the electrode and the electrolyte from contact and protecting the electrolyte from being reduced by the negative electrode, and has a crucial influence on the performance of the battery. An ideal SEI film needs to have good ion conductivity, sufficient electronic insulation, good chemical stability and electrochemical stability, and good mechanical stability. For a given electrolyte and lithium ion battery, since the formation of SEI depends on the external conditions applied to the battery during the formation process, the formation process largely determines the "quality" of the SEI film, thereby having a significant impact on the performance of the battery.

[0003] As known in the art, the formation process generally includes multiple parameters such as temperature, voltage, rate, pressure, etc. Taking a ternary battery as an example, the commonly used formation process in the industry is to charge to a certain cut-off voltage (denoted as V1) at a certain pressure and temperature with a certain rate (denoted as C1), stand for a period of time, then charge to a certain cut-off voltage (denoted as V2) at a certain rate (denoted as C2), stand for a period of time, then charge to a certain cut-off voltage (denoted as V3) at a certain rate (denoted as C3)...... repeat the above operation several times until the charge to the formation cut-off voltage, the formation stage ends. For the case of charging three times, it is called three-stage formation process in this application. The conventional three-stage formation process usually adopts the way of gradually increasing C1, C2, C3, using a smaller current density in the additive film formation stage (usually considered that a smaller current density can form a more dense SEI), and increasing the current after the formation of SEI to reduce the time cost of formation. Although this method considers the current control in the film formation stage, the additive film formation sequence is fixed, the film is often thick, and the organic and inorganic components in the SEI cannot form a reasonable collocation, resulting in poor ion conductivity. SUMMARY

[0004] The application analyzes the relationship between the film forming quality and the formation process by deeply analyzing the film forming process of the additive in the formation process, and proposes a new formation process, which fully stimulates the film forming reaction of the additive, forms an SEI film with sufficient mixing of organic and inorganic components, ion conductivity and mechanical performance, and therefore the formation process can significantly improve the battery fast charging performance.

[0005] Some embodiments of the application provide a formation process of a battery, including: performing a constant current-constant voltage charging process on the battery, wherein the rate of the constant current charging in the constant current-constant voltage charging process is 3C-5C, and the cutoff voltage range of the constant current charging is 2.8V-3.0V, and wherein the voltage of the constant voltage charging in the constant current-constant voltage charging process is the cutoff voltage of the constant current charging, and the cutoff rate of the constant voltage charging is 0.02C-0.005C; and sequentially performing a first constant current charging process and a second constant current charging process on the battery after the constant current-constant voltage charging process. In the application, the formation method of high potential constant voltage formation is used, the large charging rate (e.g. 3C-5C) is used at the beginning of the formation process to rapidly reduce the negative electrode potential below the reduction potential of all additives (e.g. 2.8V-3.0V), and all additives are caused to form films at the same potential (e.g. 2.8V-3.0V), thereby realizing the process of simultaneous film forming of all additives, obtaining an SEI film with sufficient mixing of inorganic and organic components, ion conductivity and mechanical performance, and improving the battery fast charging performance.

[0006] In some embodiments, the battery includes a positive electrode and a negative electrode, wherein the positive electrode active material of the positive electrode includes nickel-cobalt-manganese oxide, and the negative electrode active material of the negative electrode includes graphite material. In the application, the above-mentioned formation process is applicable to the battery system in which the positive electrode active material of the positive electrode includes nickel-cobalt-manganese oxide, and the negative electrode active material of the negative electrode includes graphite material. In some embodiments, the rate of the first constant current charging process and the second constant current charging process is 0.1C-0.4C, the cutoff voltage of the first constant current charging process and the second constant current charging process is 3.5V-3.8V, and the first rate and the first cutoff voltage of the first constant current charging process are respectively less than the second rate and the second cutoff voltage of the second constant current charging process.

[0007] In some embodiments, the battery is rested at a first temperature for 25-35 minutes before the constant current-constant voltage charging process, wherein the first temperature is 40-50℃. In further embodiments, the battery is rested for 25-35 minutes after the constant current-constant voltage charging process and before the first constant current charging process and the second constant current charging process, and the battery is rested for 25-35 minutes after the first constant current charging process and before the second constant current charging process. In addition, the battery is rested for 25-35 minutes after the second constant current charging process. Specifically, the purpose of the resting is to eliminate the polarization after charging, and make the lithium ions and additives in the electrolyte diffuse uniformly.

[0008] In some specific embodiments, the formation process of the battery of the present application comprises the following steps: charging the battery by a constant current-constant voltage charging process at a 4C rate to a cut-off voltage of 3.0V, and charging the battery by a constant voltage charging process at the cut-off voltage of 3.0V to a cut-off rate of 0.005C; charging the battery by a first constant current charging process at a 0.1C rate to a cut-off voltage of 3.5V; and charging the battery by a second constant current charging process at a 0.2C rate to a cut-off voltage of 3.8V.

[0009] In summary, the formation process of the battery provided by the present application adopts the constant current-constant voltage charging process of high-potential constant voltage charging formation, which promotes all additives to form films at the same potential, thereby forming SEI films with sufficient mixing of organic and inorganic components, ion conduction and mechanical performance, thereby improving the fast charging performance of the battery. DETAILED DESCRIPTION

[0010] With the development of batteries in the field of new energy, the performance requirements of batteries are also getting higher and higher. Research has found that the composition and structure of SEI film have an important influence on the performance of the battery. The composition of SEI includes inorganic components and organic components. Generally speaking, when the inorganic components and the organic components are uniformly mixed, the SEI formed has good ion conductivity and mechanical properties. Since the inorganic components and the organic components are often reduced by different additives, only when different additives simultaneously form a film reaction can the SEI structure with uniform mixing of inorganic components and organic components be formed. Considering the additive film forming process of the formation process, according to the principle of electrochemical reaction, the reaction rate and the reaction amount of the additive depend on the electrochemical reaction kinetics and diffusion mass transfer. For commonly used additives, the exchange current density of the electrochemical reaction is very large, and it can react quickly under a small overpotential. Therefore, in order to form the effect of simultaneous reduction and film formation of multiple additives, a high enough overpotential must be applied at the beginning of the formation process to reach the reduction potential of all additives, so that they all have the conditions for film formation in thermodynamics. At this time, the film forming reaction of the additive is controlled by the diffusion rate of the additive, and since the diffusion coefficients of the additives are similar, the effect of simultaneous reduction and film formation of multiple additives at the same potential can be achieved.

[0011] Based on the above, the present application proposes a formation process which can improve the fast charging performance of the battery. The three-stage constant current charging formation process of the traditional process is changed to high-potential constant voltage charging formation, which promotes the film formation of all additives at the same potential, thereby forming an SEI film with fully mixed organic and inorganic components, ion conduction and mechanical properties, and improving the fast charging performance of the battery.

[0012] Some embodiments of the present application provide a formation process of a battery, comprising: performing a constant current-constant voltage charging process on the battery, wherein the rate of the constant current charging in the constant current-constant voltage charging process is 3C-5C, and the cutoff voltage range of the constant current charging is 2.8V-3.0V, and wherein the voltage of the constant voltage charging in the constant current-constant voltage charging process is the cutoff voltage of the constant current charging, and the cutoff rate of the constant voltage charging is 0.02C-0.005C; and sequentially performing a first constant current charging process and a second constant current charging process on the battery after the constant current-constant voltage charging process. In the present application, the formation method of high-potential constant voltage formation is used, and a large charging rate (such as 3C-5C) is used at the beginning of the formation process to rapidly reduce the negative potential below the reduction potential of all additives (such as 2.8V-3.0V), which promotes the film formation of all additives at the same potential (such as 2.8V-3.0V), thereby realizing the process of simultaneous film formation of all additives, obtaining an SEI film with fully mixed inorganic components and organic components, ion conduction and mechanical properties, and improving the fast charging performance of the battery.

[0013] In some embodiments, the battery comprises a positive electrode and a negative electrode, wherein the positive active material of the positive electrode comprises nickel cobalt manganese oxide, and the negative active material of the negative electrode comprises graphite material. In the present application, the above formation process is applicable to the battery system in which the positive active material of the positive electrode comprises nickel cobalt manganese oxide, and the negative active material of the negative electrode comprises graphite material. For this battery system, all additives can be caused to form films simultaneously at the same potential, thereby obtaining an SEI film in which inorganic components and organic components are fully mixed, ion conduction and mechanical properties are taken into account.

[0014] In some embodiments, the rate of the first constant current charging process and the second constant current charging process is 0.1C-0.4C, the cut-off voltage of the first constant current charging process and the second constant current charging process is 3.5V-3.8V, and the first rate and the first cut-off voltage of the first constant current charging process are respectively less than the second rate and the second cut-off voltage of the second constant current charging process. In the present application, by the rate of the first constant current charging process and the second constant current charging process thereafter and by causing the rate of the second constant current charging process to be greater than the rate of the first constant current charging process, the cycle performance of the battery can be maintained. In addition, the first constant current charging process and the second constant current charging process can have the following beneficial effects: (1) causing the residual additives in the first-stage constant current-constant voltage charging process to continue to fully react; (2) simultaneously increasing the battery voltage, promoting the film-forming reaction of the positive electrode film-forming additive; (3) increasing the SOC (state of charge, reflecting the remaining capacity of the battery) of the battery, so that the negative electrode is in a semi-lithium intercalation state, and the SEI state of the negative electrode surface is stable. In addition, the first rate and the first cut-off voltage of the first constant current charging process are respectively less than the second rate and the second cut-off voltage of the second constant current charging process, because the current is gradually increased during the formation process, which is beneficial to the stability of the SEI film.

[0015] In some embodiments, before the constant current-constant voltage charging process, the battery is allowed to stand at a first temperature, wherein the first temperature is 40℃-50℃, and the standing time is 25min-35min. In further embodiments, after the constant current-constant voltage charging process and before the first constant current charging process and the second constant current charging process, the battery is allowed to stand, and the standing time is 25min-35min, and after the first constant current charging process and before the second constant current charging process, the battery is allowed to stand, and the standing time is 25min-35min. In addition, after the second constant current charging process, the battery is allowed to stand, and the standing time is 25min-35min. Specifically, the purpose of standing is to eliminate the polarization after charging, so that lithium ions and additives in the electrolyte diffuse uniformly.

[0016] In some embodiments, the formation process of the battery of the present application comprises the following steps: charging the battery by a constant current-constant voltage charging process at a 4C rate to a cut-off voltage of 3.0V, and charging the battery by a constant voltage charging process at the cut-off voltage of 3.0V to a cut-off rate of 0.005C; charging the battery by a first constant current charging process at a 0.1C rate to a cut-off voltage of 3.5V; and charging the battery by a second constant current charging process at a 0.2C rate to a cut-off voltage of 3.8V.

[0017] In summary, the formation process of the present application comprises a constant current-constant voltage charging process and two constant current charging processes (first and second constant current charging processes). In the constant current-constant voltage charging process, the constant current charging rate is 3C-5C, the cut-off voltage range is 2.8V-3.0V, the constant voltage charging voltage is the cut-off voltage of the constant current charging, and the cut-off rate is 0.02C-0.005C. By controlling the constant current-constant voltage charging process, the formation process of the present application uses a large charging rate at the beginning to rapidly reduce the negative electrode potential below the reduction potential of all additives, which promotes the film formation of all additives at the same potential, thereby achieving a process for simultaneous film formation of all additives, obtaining an SEI film with sufficient mixing of inorganic components and organic components, ion conduction, and mechanical properties, and improving the fast charging performance of the battery.

[0018] In some embodiments, the battery is a lithium ion battery. The lithium ion battery comprises a positive electrode, a negative electrode, a separator, an electrolyte, etc. The positive electrode comprises a positive electrode active material and a positive electrode current collector, and the positive electrode active material comprises nickel-cobalt-manganese oxide, which can have a chemical formula of: Li y Ni d Mn e O 2-f, y, d, e and f values are in the following ranges: 0.8≤y≤1.2, 0.3≤d≤0.98, 0.02≤e≤0.7, -0.1≤f≤0.2. In some embodiments, the positive current collector can include an aluminum foil. The negative electrode includes a negative active material and a negative current collector, the negative active material including a graphite material, specifically, can include one or more of low graphitized carbon, easily graphitized carbon, artificial graphite, natural graphite, etc. In some embodiments, the negative current collector can include a copper foil. The separator film includes at least one selected from polyethylene, polypropylene, polyethylene terephthalate, polyimide, and aramid. The electrolyte can include any commonly used electrolyte in the art, in some embodiments, the electrolyte includes a lithium salt and a non-aqueous solvent. The lithium salt can be LiPF6. The non-aqueous solvent can be a carbonate compound, a carboxylic ester compound, an ether compound, other organic solvents, or a combination thereof. The carbonate compound can be a chain carbonate compound, a cyclic carbonate compound, a fluorinated carbonate compound, or a combination thereof. Examples of the chain carbonate compound are diethyl carbonate (DEC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), methyl ethyl carbonate (MEC), and a combination thereof. Examples of the cyclic carbonate compound are ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), vinyl ethylene carbonate (VEC), and a combination thereof. An example of the fluorinated carbonate compound is fluoroethylene carbonate (FEC). Examples of the carboxylic ester compound are methyl acetate, ethyl acetate, n-propyl acetate, t-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, γ-butyrolactone, decanolactone, valerolactone, caprolactone, methyl formate, and a combination thereof, etc.

[0019] The positive electrode, the separator film, and the negative electrode are wound or folded or stacked in order to form an electrode assembly, which is then packaged in, for example, an aluminum plastic film, electrolyte is injected, formation, packaging, i.e., a lithium ion battery is prepared.

[0020] Those skilled in the art will understand that the above-described method for preparing a lithium ion battery is only an embodiment. Other methods commonly used in the art can be employed without departing from the content disclosed in the present application.

[0021] Some specific examples and comparative examples are listed below to better illustrate the present application.

[0022] In the following examples, the specific preparation method of the positive and negative electrodes of the lithium ion battery is as follows:

[0023] The positive active material ternary NMC (LiNi 0.9 Co 0.05 Mn 0.05The positive electrode slurry is obtained by mixing artificial graphite as the positive electrode active material, polyvinylidene fluoride as the binder and Super P as the conductive agent in a weight ratio of 98:1:1, adding N-methyl pyrrolidone (NMP), and stirring under the action of a vacuum stirrer until the system is homogeneous and transparent. The positive electrode slurry is uniformly coated on the positive electrode current collector aluminum foil. Then, the aluminum foil is dried in an oven after being air-dried at room temperature, and then subjected to cold pressing and slitting to obtain the positive electrode. The negative electrode slurry is obtained by mixing artificial graphite as the negative electrode active material, Super P as the conductive agent, carboxymethyl cellulose sodium (CMC-Na) as the thickening agent, and styrene-butadiene rubber (SBR) as the binder in a mass ratio of 96:1:1:2, adding deionized water, and stirring under the action of a vacuum stirrer. The negative electrode slurry is uniformly coated on the negative electrode current collector copper foil. Then, the copper foil is dried in an oven after being air-dried at room temperature, and then subjected to cold pressing and slitting to obtain the negative electrode. A porous polyethylene (PE) film is used as the separator. The electrolyte is a commonly used electrolyte in the art, including ethylene carbonate (EC), propylene carbonate (PC), fluoroethylene carbonate (FEC), methyl ethyl carbonate (EMC), dimethyl carbonate (DMC), etc. The positive electrode, the separator and the negative electrode are sequentially wound or folded or stacked into an electrode assembly, which is then packaged in, for example, an aluminum plastic film, and the electrolyte is injected to obtain a lithium ion battery without a formation process. The formation process of the lithium ion battery will be described in detail below.

[0024] Example 1

[0025] Formation process of the lithium ion battery

[0026] The lithium ion battery is placed in a formation cabinet (a commonly used formation cabinet in the art) to perform the formation process, which includes the following steps:

[0027] S1: adjusting the temperature of the formation cabinet to 45°C and resting for 30 min;

[0028] S2: charging the battery by a constant current-constant voltage charging process at a 4C rate to a cut-off voltage of 3.0V;

[0029] S3: charging the battery by a constant voltage charging process (CV) at a cut-off voltage of 3.0V to a cut-off rate of 0.005C;

[0030] S4: resting for 30 min;

[0031] S5: charging the battery by a first constant current charging process at a 0.1C rate to a cut-off voltage of 3.5V;

[0032] S6: resting for 30 min;

[0033] S7: constant current charging (CC) the battery to the cut-off voltage 3.8V by second constant current charging process at 0.2C rate;

[0034] S8: standing for 30min; and

[0035] S9: the end of the formation stage, then, packaging, obtaining a lithium ion battery, further, the specific process of the formation process is shown in Table 1 as follows:

[0036] Table 1 Formation process flow in Example 1

[0037] Step No. Formation process flow S1 Adjust formation tank temperature 45°C, rest 30 min S2 4C CC to 3.0V S3 3.0V CV to 0.005C S4 Rest 30 min S5 0.1C CC to 3.5V S6 Rest 30 min S7 0.2C CC to 3.8V S8 Rest 30 min S9 End of formation stage

[0038] Example 2

[0039] Consistent with the preparation method of Example 1, except that the specific process of the formation process in Example 2 is shown in Table 2 as follows:

[0040] Table 2 Formation process flow in Example 2

[0041] Step No. Formation process flow S1 Adjust formation tank temperature 40°C, rest 35 min S2 3C CC to 2.8V S3 2.8V CV to 0.02C S4 Rest 35 min S5 0.2C CC to 3.5V S6 Rest 30 min S7 0.4C CC to 3.7V S8 Rest 35 min S9 End of formation stage

[0042] Example 3

[0043] Consistent with the preparation method of Example 1, except that the specific process of the formation process in Example 3 is shown in Table 3 as follows:

[0044] Table 3 Formation process flow in Example 3

[0045]

[0046]

[0047] Comparative Example 1

[0048] Consistent with the preparation method of Example 1, except that the formation process in Comparative Example 1 has no constant current-constant voltage charging process, and the specific process of the formation process in this Comparative Example 1 is shown in Table 4 as follows:

[0049] Table 4 Formation process flow in Comparative Example 1

[0050] Step No. Formation process flow S1 Adjust formation tank temperature 45°C, rest 30 min S2 0.05C CC to 3V S3 Rest 30 min S4 0.1C CC to 3.5V S5 Rest 30 min S6 0.33C CC to 3.8V S7 Rest 30 min S8 End of formation process

[0051] Lithium ion battery performance test method:

[0052] (1) Direct current resistance (DCR) test

[0053] At a specified temperature, the lithium ion batteries in Examples 1-3 and Comparative Example 1 were discharged at 1C current to 50% SOC (state of charge, reflecting the remaining capacity of the battery), then the current was increased to 4C and maintained for 30s, the difference between the updated stable voltage (i.e., the voltage at the end of discharging) and the original plateau voltage (i.e., the voltage at the beginning of discharging) was detected, and the ratio of the value to the 4C current value was the DCR of the lithium ion battery. The DCR test result after the first full charge of the lithium ion battery was the initial DCR of the lithium ion battery.

[0054] (2) Fast charging performance test

[0055] The fast charging capability of the lithium ion batteries in Examples 1-3 and Comparative Example 1 above was measured using a three-electrode battery. In an oven at a specified temperature (room temperature 25°C), charging was carried out at a current of 4C in a specified potential range (i.e., the range of the charge and discharge cut-off voltage of the battery 2.5-4.25V), and the cell capacity of the lithium ion battery when the negative electrode potential reached -20mV was recorded and converted to SOC.

[0056] It should be noted that the charge and discharge cut-off voltage of the lithium ion battery is: 2.5-4.25V

[0057] The test results are shown in Table 5 below.

[0058] Table 5. Test results of lithium ion battery performance of Examples 1-3 and Comparative Example 1

[0059]

[0060] From the above results, it can be seen that the lithium ion batteries of Examples 1-3 using the improved formation process (with constant current-constant voltage charging process) of the application and the lithium ion batteries of Comparative Example 1 using the conventional formation process (without constant current-constant voltage charging process) have smaller DCR and stronger fast charging capability, highlighting the effectiveness of the improved formation process of the application. This is because the formation method using high potential constant voltage formation in the application uses a large charge rate (e.g., 3C-5C) at the beginning of the formation process to rapidly reduce the negative electrode potential below the reduction potential of all additives (e.g., 2.8V-3.0V), which promotes the formation of all additives at the same potential (e.g., 2.8V-3.0V), thereby achieving a process in which all additives are formed simultaneously, resulting in a SEI film with sufficient mixing of inorganic and organic components, ion conduction and mechanical properties, and improving the fast charging performance of the battery.

[0061] The foregoing summary of some embodiments has been presented with sufficient particularity by way of example to convey the spirit and scope of the application to persons skilled in the art. It is clear that other embodiments can be drawn from the foregoing description that are not specifically described herein, but would be obvious to those skilled in the art. Accordingly, the patentable scope of the application is not to be determined from the foregoing description, but rather from claims that follow.

Claims

1. A battery formation process, characterized in that, include: The battery undergoes a constant current-constant voltage charging process, wherein the constant current charging rate is 3C-5C, and the cutoff voltage range of the constant current charging is 2.8V-3.0V; wherein the constant voltage charging voltage is the cutoff voltage of the constant current charging process, and the cutoff rate of the constant voltage charging is 0.02C-0.005C; and The battery, after the constant current-constant voltage charging process, is then subjected to a first constant current charging process and a second constant current charging process in sequence. The battery includes a positive electrode and a negative electrode, wherein the positive electrode active material includes nickel cobalt manganese oxide, and the negative electrode active material includes graphite material.

2. The battery formation process according to claim 1, characterized in that, The rate of change for the first constant current charging process and the second constant current charging process is 0.1C-0.4C.

3. The battery formation process according to claim 2, characterized in that, The cutoff voltage of the first constant current charging process and the second constant current charging process is 3.5V - 3.8V.

4. The battery formation process according to claim 1, characterized in that, The first rate and the first cutoff voltage of the first constant current charging process are respectively less than the second rate and the second cutoff voltage of the second constant current charging process.

5. The battery formation process according to claim 1, characterized in that, Before the constant current-constant voltage charging process, the battery is placed at a first temperature. The first temperature is 40℃-50℃, and the standing time is 25min-35min.

6. The battery formation process according to claim 1, characterized in that, After the constant current-constant voltage charging process and before the first constant current charging process and the second constant current charging process, the battery is left to stand for 25-35 minutes.

7. The battery formation process according to claim 1, characterized in that, After the first constant current charging process and before the second constant current charging process, the battery is left to rest for 25-35 minutes.

8. The battery formation process according to claim 1, characterized in that, After the second constant current charging process, the battery is left to stand for 25-35 minutes.

9. The battery formation process according to claim 1, characterized in that, Includes the following steps: The battery is charged at a constant current rate to a cutoff voltage of 3.0V using the constant current-constant voltage charging process, and then charged at a constant voltage rate to a cutoff rate of 0.005C using the cutoff voltage of 3.0V. The battery is charged to a cutoff voltage of 3.5V using the first constant current charging process at a 0.1C rate. as well as The battery is charged to the cutoff voltage of 3.8V using the second constant current charging process at a 0.2C rate.

10. The battery formation process according to any one of claims 1-9, characterized in that, The battery is a lithium-ion battery.

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