Formation process of battery

Abstract

The battery formation process provided by the embodiment of the invention comprises the following steps: a constant current-constant voltage charging process is carried out on a battery, the rate of constant current charging in the constant current-constant voltage charging process is 3C-5C, the cut-off voltage range of the constant current charging is 2.8 V-3. 0V, and the cut-off voltage range of the constant current charging in the constant current-constant voltage charging process is 2.8 V-3. 0V; the voltage of constant voltage charging in the constant current-constant voltage charging process is the cut-off voltage of constant current charging, and the cut-off rate of the constant voltage charging is 0.02-0.005 C; 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. According to the formation process of the battery provided by the invention, a constant current-constant voltage charging process of high-potential constant-voltage charging formation is adopted, and all additives are promoted to form a film at the same potential, so that an SEI film with sufficient mixing of organic and inorganic components, ionic conduction and mechanical properties is formed, and the fast charging performance of the battery is improved.

Description

Technical Field

[0001] The embodiments of the present application relate to the field of batteries, and in particular, to a battery formation process. Background Art

[0002] In the field of new energy, the development of batteries is becoming more and more important, and the requirements for battery performance are becoming higher and higher, especially for lithium-ion batteries. Studies have 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 usually refers to the process in which the lithium-ion battery is charged with a small current after the liquid is injected to form a dense SEI (solid electrolyte interface) on the surface of the negative electrode, and at the same time the battery voltage is increased to the operating voltage range. Furthermore, during 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 interfacial phase with ionic conductivity and electronic insulation. It plays a role in isolating the contact between the electrode and the electrolyte and protecting the electrolyte from being reduced by the negative electrode, which has a vital impact on the battery performance. The ideal SEI film needs to have good ionic conductivity, sufficient electronic insulation, good chemical stability and electrochemical stability, as well as good mechanical stability. For a given electrolyte and lithium-ion battery, since the formation of SEI depends on the external conditions imposed on the battery cell during the formation process, the formation process largely determines the "quality" of the SEI film, which has a significant impact on the performance of the battery cell.

[0003] As known in the art, the formation process generally includes multiple parameters such as temperature, voltage, rate, pressure, etc. Taking ternary battery as an example, the formation process commonly used in the industry at present is mostly at a certain pressure and temperature, with a certain rate (denoted as C1) charged to a certain cut-off voltage (denoted as V1), after standing for a period of time, then with a certain rate (denoted as C2) charged to a certain cut-off voltage (denoted as V2), after standing for a period of time, then with a certain rate (denoted as C3) charged to a certain cut-off voltage (denoted as V3)...... Repeat the above operation several times, until charged to the formation cut-off voltage, the formation stage ends. For the situation of charging three times, it is referred to as a three-stage formation process in the present invention, and the conventional three-stage formation process usually adopts the mode that C1, C2, and C3 are gradually increased, and a smaller current density (it is generally believed that a small current density can form a more compact SEI) is used in the additive film-forming stage, and the current is increased after SEI is formed, reducing the time cost of formation. Although this method takes into account the current control during the film formation stage, the film formation order of the additives is fixed, the film is often thicker, and the organic and inorganic components in the SEI cannot form a reasonable combination, resulting in poor ion conductivity. Summary of the invention

[0004] This application deeply analyzes the film-forming process of additives in the formation process, analyzes the relationship between film-forming quality and formation process, and proposes a new formation process to fully stimulate the film-forming reaction of additives to form a SEI film with fully mixed organic and inorganic properties and both ion conductivity and mechanical properties. Therefore, this formation process can significantly improve the fast charging performance of the battery.

[0005] Some embodiments of the present application provide a formation process of a battery, comprising: subjecting the battery to a constant current-constant voltage charging process, wherein the constant current charging ratio 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 constant voltage charging voltage in the constant current-constant voltage charging process is the cut-off voltage of the constant current charging, and the cut-off ratio of the constant voltage charging is 0.02C-0.005C; and subjecting the battery after the constant current-constant voltage charging process to a first constant current charging process and a second constant current charging process in sequence. In the present application, a high-potential constant-voltage formation method is used. At the beginning of the formation process, a large charging rate (for example, 3C-5C) is used to quickly reduce the negative electrode potential to below the reduction potential of all additives (for example, 2.8V-3.0V), so that all additives are forced to form films at the same potential (for example, 2.8V-3.0V), thereby realizing the process of simultaneous film formation of all additives, and obtaining an SEI film with fully mixed inorganic and organic components, ion conduction and mechanical properties, thereby improving the fast charging performance of the battery.

[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 a graphite material. In the present application, the above-mentioned formation process is applicable to a 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 a 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 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.

[0007] 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°C-50°C and the standing time is 25min-35min. In a further embodiment, 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 for 25min-35min, and after the first constant current charging process and before the second constant current charging process, the battery is allowed to stand for 25min-35min. In addition, after the second constant current charging process, the battery is allowed to stand for 25min-35min. Specifically, the purpose of standing is to eliminate polarization after charging and to evenly diffuse the lithium ions and additives in the electrolyte.

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

[0009] In summary, the battery formation process provided in the present application adopts a constant current-constant voltage charging process of high potential constant voltage charging formation, which prompts all additives to form a film at the same potential, thereby forming an SEI film with fully mixed organic and inorganic components, and taking into account both ion conduction and mechanical properties, thereby improving the battery fast charging performance. DETAILED DESCRIPTION

[0010] With the development of batteries in the field of new energy, the performance requirements for batteries are getting higher and higher. Studies have found that the composition and structure of the SEI film have an important influence on battery performance. The components of SEI include inorganic components and organic components. Generally speaking, when the inorganic components and organic components are evenly mixed, the SEI formed has good ion conductivity and mechanical properties. Since inorganic components and organic components are often formed by reduction of different additives, only when different additives undergo film-forming reactions at the same time can a SEI structure in which inorganic components and organic components are evenly mixed be formed. Considering the additive film-forming process of the formation process, according to the principle of electrochemical reaction, the reaction rate and reaction amount of the additive depend on the electrochemical reaction kinetics and diffusion mass transfer. For commonly used additives, the exchange current density of their electrochemical reactions is very large, and rapid reactions can be carried out at a small overpotential. Therefore, in order to achieve the effect of simultaneous reduction of multiple additives to form a film, a sufficiently high overpotential must be applied at the beginning of the formation process to reach the reduction potential of all additives so that they have the thermodynamic conditions for film formation. At this time, the film-forming reaction of the additives is controlled by the diffusion rate of the additives. Since the diffusion coefficients of each additive are similar, the effect of simultaneous reduction of multiple additives to form a film at the same potential can be achieved.

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

[0012] Some embodiments of the present application provide a formation process of a battery, comprising: subjecting the battery to a constant current-constant voltage charging process, wherein the constant current charging ratio 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 constant voltage charging voltage in the constant current-constant voltage charging process is the cut-off voltage of the constant current charging, and the cut-off ratio of the constant voltage charging is 0.02C-0.005C; and subjecting the battery after the constant current-constant voltage charging process to a first constant current charging process and a second constant current charging process in sequence. In the present application, a high-potential constant-voltage formation method is used. At the beginning of the formation process, a large charging rate (for example, 3C-5C) is used to quickly reduce the negative electrode potential to below the reduction potential of all additives (for example, 2.8V-3.0V), so that all additives are forced to form films at the same potential (for example, 2.8V-3.0V), thereby realizing the process of simultaneous film formation of all additives, and obtaining an SEI film with fully mixed inorganic and organic components, ion conduction and mechanical properties, thereby improving the fast charging performance of the battery.

[0013] 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 a graphite material. In the present application, the above-mentioned formation process is applicable to a 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 a graphite material. For this battery system, all additives can be caused to form a film at the same potential at the same time, thereby obtaining a SEI film in which inorganic components and organic components are fully mixed, and ion conduction and mechanical properties are taken into consideration.

[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, the cycle performance of the battery can be maintained by the rate of the first constant current charging process and the second constant current charging process and by making the rate of the second constant current charging process greater than the rate of the first constant current charging process. In addition, the first constant current charging process and the second constant current charging process can have the following beneficial effects: (1) Prompt the residual additives in the first stage of the constant current-constant voltage charging process to continue to fully react; (2) At the same time, the battery voltage is increased to promote the film-forming reaction of the positive electrode film-forming additive; (3) Improve 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 embedded state, and stabilize the SEI state on the negative electrode surface. In addition, the first rate and the first cutoff voltage of the first constant current charging process are respectively smaller than the second rate and the second cutoff voltage of the second constant current charging process. The reason is that gradually increasing the current during the formation process 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°C-50°C and the standing time is 25min-35min. In a further embodiment, 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 for 25min-35min, and after the first constant current charging process and before the second constant current charging process, the battery is allowed to stand for 25min-35min. In addition, after the second constant current charging process, the battery is allowed to stand for 25min-35min. Specifically, the purpose of standing is to eliminate polarization after charging and to evenly diffuse the lithium ions and additives in the electrolyte.

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

[0017] In summary, the formation process of the present application includes 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 voltage of the constant voltage charging 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 is started with a large charging rate to quickly reduce the negative electrode potential to below the reduction potential of all additives, so that all additives are forced to form a film at the same potential, thereby realizing the process of simultaneous film formation of all additives, and obtaining an SEI film with full mixing of inorganic 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 includes a positive electrode, a negative electrode, a separator, and an electrolyte. The positive electrode includes a positive electrode active material and a positive electrode current collector. The positive electrode active material includes nickel cobalt manganese oxide. The chemical formula of nickel cobalt manganese oxide can be: Li y Ni d Mn e O 2-f, y, d, e and f values ​​are respectively 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 electrode collector may include aluminum foil. The negative electrode includes a negative electrode active material and a negative electrode collector, and the negative electrode active material includes a graphite material, specifically, it may include one or more of low-graphitized carbon, easily graphitized carbon, artificial graphite, natural graphite, etc. In some embodiments, the negative electrode collector may include copper foil. The isolation film includes at least one selected from polyethylene, polypropylene, polyethylene terephthalate, polyimide and aramid. The electrolyte may include any commonly used electrolyte in the art, and in some embodiments, the electrolyte includes a lithium salt and a non-aqueous solvent. The lithium salt may be selected from LiPF6. The non-aqueous solvent may be a carbonate compound, a carboxylate compound, an ether compound, other organic solvents or a combination thereof. The carbonate compound may be a chain carbonate compound, a cyclic carbonate compound, a fluorinated carbonate compound or a combination thereof. Examples of linear carbonate compounds are diethyl carbonate (DEC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), ethyl methyl carbonate (MEC) and combinations thereof. Examples of cyclic carbonate compounds are ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), vinyl ethylene carbonate (VEC) and combinations thereof. Examples of fluorocarbonate compounds are fluoroethylene carbonate (FEC). Examples of carboxylic acid ester compounds are methyl acetate, ethyl acetate, n-propyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, γ-butyrolactone, decalactone, valerolactone, caprolactone, methyl formate and combinations thereof, etc.

[0019] The positive electrode, separator, and negative electrode are wound, folded, or stacked in sequence to form an electrode assembly, and then packaged in, for example, an aluminum-plastic film, injected with electrolyte, formed, and packaged to produce a lithium-ion battery.

[0020] Those skilled in the art will understand that the above-described method for preparing a lithium-ion battery is only an example, and other commonly used methods in the art may be used without departing from the contents disclosed in the present application.

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

[0022] In the following examples, the specific preparation methods of the positive and negative electrodes of lithium-ion batteries are as follows:

[0023] The positive electrode active material is ternary NMC (LiNi 0.9 Co 0.05 Mn 0.05O2), polyvinylidene fluoride as a binder and Super P as a conductive agent are mixed in a weight ratio of 98:1:1, N-methylpyrrolidone (NMP) is added, and the system is stirred under the action of a vacuum mixer until it is uniform and transparent to obtain a positive electrode slurry, and the positive electrode slurry is evenly coated on the positive electrode current collector aluminum foil, and then the aluminum foil is dried at room temperature and transferred to an oven for drying, and then cold pressed and cut to obtain a positive electrode. Artificial graphite is used as a negative electrode active material, Super P is used as a conductive agent, sodium carboxymethyl cellulose (CMC-Na) is used as a thickener, and styrene-butadiene rubber (SBR) is used as a binder, and mixed in a mass ratio of 96:1:1:2, deionized water is added, and a negative electrode slurry is obtained under the action of a vacuum mixer, and the negative electrode slurry is evenly coated on the negative electrode current collector copper foil, and then the copper foil is dried at room temperature and transferred to an oven for drying, and then cold pressed and cut to obtain a negative electrode. A polyethylene (PE) porous polymer film is used as a diaphragm. The electrolyte is a commonly used electrolyte in the art, including ethylene carbonate (EC), propylene carbonate (PC), fluoroethylene carbonate (FEC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), etc. The positive electrode, the separator, and the negative electrode are wound or folded or stacked in sequence to form an electrode assembly, and 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] Lithium-ion battery formation process

[0026] The lithium-ion battery is placed in a formation cabinet (commonly used in the art) and subjected to a formation process, specifically the following steps:

[0027] S1: Adjust the temperature of the formation cabinet to 45°C and let it rest for 30 minutes;

[0028] S2: The battery is charged at a constant current (CC) rate of 4C to a cut-off voltage of 3.0V through a constant current-constant voltage charging process;

[0029] S3: charging the battery at a constant voltage (CV) to a cutoff rate of 0.005C at a cutoff voltage of 3.0V;

[0030] S4: let stand for 30 minutes;

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

[0032] S6: let stand for 30 minutes;

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

[0034] S8: let stand for 30 minutes; and

[0035] S9: After the formation stage is completed, the lithium-ion battery is packaged and obtained. Furthermore, the specific process of the formation process is shown in Table 1 below:

[0036] Table 1 Chemical formation process flow in Example 1

[0037] Step No. Chemical Process S1 Adjust the temperature of the forming cabinet to 45°C and let it rest for 30 minutes. S2 4C CC to 3.0V S3 3.0V CV to 0.005C S4 Let stand for 30 minutes S5 0.1C CC to 3.5V S6 Let stand for 30 minutes S7 0.2C CC to 3.8V S8 Let stand for 30 minutes S9 End of the formation phase

[0038] Example 2

[0039] The preparation method is consistent with that of Example 1, except that the specific process of the chemical formation process in Example 2 is shown in Table 2 below:

[0040] Table 2 Formation process flow in Example 2

[0041] Step No. Chemical Process S1 Adjust the temperature of the forming cabinet to 40°C and let it rest for 35 minutes. S2 3C CC to 2.8V S3 2.8V CV to 0.02C S4 Let stand for 35 minutes S5 0.2C CC to 3.5V S6 Let stand for 30 minutes S7 0.4C CC to 3.7V S8 Let stand for 35 minutes S9 End of the formation phase

[0042] Example 3

[0043] The preparation method is consistent with that in Example 1, except that the specific process of the chemical formation process in Example 3 is shown in Table 3 below:

[0044] Table 3 Formation process flow in Example 3

[0045]

[0046]

[0047] Comparative Example 1

[0048] The preparation method is consistent with that of Example 1, except that the formation process in Comparative Example 1 does not have a constant current-constant voltage charging process. The specific process of the formation process in Comparative Example 1 is shown in Table 4 below:

[0049] Table 4 Chemical Process Flow in Comparative Example 1

[0050] Step No. Formation process S1 Adjust the temperature of the forming cabinet to 45°C and let it rest for 30 minutes. S2 0.05C CC to 3V S3 Let stand for 30 minutes S4 0.1C CC to 3.5V S5 Let stand for 30 minutes S6 0.33C CC to 3.8V S7 Let stand for 30 minutes S8 The process is finished

[0051] Lithium-ion battery performance test method:

[0052] (1) DC resistance (DCR) test

[0053] At a specified temperature, when the lithium-ion batteries in Examples 1-3 and Comparative Example 1 are discharged to 50% SOC (state of charge, reflecting the remaining capacity of the battery) at a current of 1C, the current is increased to 4C and maintained for 30 seconds, and the difference between the updated stable voltage (i.e., the voltage at the end of discharge) and the original platform voltage (i.e., the voltage at the start of discharge) is detected. The ratio of its value to the 4C current value is the DCR of the lithium-ion battery. The DCR test result after the lithium-ion battery is fully charged for the first time is the initial DCR of the lithium-ion battery.

[0054] (2) Fast charging performance test

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

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

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

[0058] Table 5. Lithium ion battery performance test results of Examples 1 to 3 and Comparative Example 1

[0059]

[0060] From the above results, it can be seen that the lithium ion batteries in the embodiments 1-3 using the improved formation process of the present invention (with constant current-constant voltage charging process) are compared with the lithium ion batteries in comparative example 1 using the traditional formation process (without constant current-constant voltage charging process). The DCR of the lithium ion battery with the improved formation process is smaller and the fast charging capability is stronger, highlighting the effectiveness of the improved formation process of the present application. This is because the present application uses a high-potential constant-voltage formation formation method, and a large charging rate (e.g., 3C-5C) is used at the beginning of the formation process to rapidly reduce the negative electrode potential to below the reduction potential of all additives (e.g., 2.8V-3.0V), prompting all additives to form films at the same potential (e.g., 2.8V-3.0V), thereby realizing the process of simultaneous film formation of all additives, obtaining an SEI film with full mixing of inorganic and organic components, ion conduction and mechanical properties, and improving the fast charging performance of the battery.

[0061] The features of several embodiments are summarized above so that those skilled in the art can better understand aspects of the present invention. Those skilled in the art should understand that they can easily use the present invention as a basis to design or modify other processes and structures for implementing the same purpose and / or achieving the same advantages as the embodiments introduced herein. Those skilled in the art should also appreciate that this equivalent construction does not deviate from the spirit and scope of the present invention, and that they can make multiple changes, substitutions and changes herein without departing from the spirit and scope of the present invention.

Claims

1. A battery formation process, characterized in that: include: The battery is subjected to a constant current-constant voltage charging process, wherein the constant current charging rate 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 constant voltage charging voltage 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 The battery after the constant current-constant voltage charging process is sequentially subjected to a first constant current charging process and a second constant current charging process.

2. The battery formation process according to claim 1, characterized in that: 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.

3. The battery formation process according to claim 1, characterized in that: The ratio of the first constant current charging process and the second constant current charging process is 0.1C-0.4C.

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

5. The battery formation process according to claim 1, characterized in that: The first rate and the first cut-off voltage of the first constant current charging process are respectively smaller than the second rate and the second cut-off voltage of the second constant current charging process.

6. The battery formation process according to claim 1, characterized in that: Before the constant current-constant voltage charging process, the battery is allowed to stand at a first temperature. Wherein, the first temperature is 40°C-50°C, and the standing time is 25min-35min.

7. 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 minutes to 35 minutes.

8. 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 stand for 25 minutes to 35 minutes.

9. 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 minutes to 35 minutes.

10. The battery formation process according to claim 1, characterized in that: The following steps are involved: The battery is charged at a constant current to a cut-off voltage of 3.0V at a rate of 4C by the constant current-constant voltage charging process, and the battery is charged at a constant voltage to a cut-off rate of 0.005C at a cut-off voltage of 3.0V; The battery is charged at a constant current to a cut-off voltage of 3.5V by the first constant current charging process at a rate of 0.1C; as well as The battery is charged at a constant current to a cut-off voltage of 3.8V through the second constant current charging process at a rate of 0.2C.

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

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