Battery and formation process thereof

Abstract

The invention provides a battery and a formation process thereof. The formation process of the battery comprises the following steps: standing a target battery cell after liquid injection; carrying out a preheating process and a pre-pressing process on the target battery cell; multi-stage charging is carried out on the target battery cell, so that the charge state of the target battery cell is charged to a cut-off charge state, and the cut-off charge state of the target battery cell is smaller than 100% SOC; and voltage screening is carried out on the charged target battery cell, so that the time required for formation is shortened, the production efficiency is improved, and meanwhile, the capacity, the first charge-discharge efficiency and the cycle performance of the battery are improved.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and in particular to a battery and its formation process. Background Art

[0002] Lithium-ion batteries have become the preferred energy carrier in consumer electronics, new energy vehicles, aerospace, defense and military fields due to their core advantages such as high energy density, no heavy metal pollution, on-demand charging, long cycle life and low self-discharge rate.

[0003] During the manufacturing process of lithium-ion batteries, the formation process forms a tight and uniform solid electrolyte membrane on the electrode surface by precisely controlling the current parameters to ensure the battery's cycle performance. Currently, the formation process lasts too long, reducing production efficiency and increasing production costs. Summary of the Invention

[0004] The embodiments of the present application provide a battery and a formation process thereof, which are used to solve or at least partially solve the deficiencies of the above-mentioned background technology.

[0005] In a first aspect, an embodiment of the present application provides a battery formation process, comprising:

[0006] Let the target battery cell stand still after injection;

[0007] Performing a preheating process and a pre-pressing process on the target battery cell;

[0008] Performing multi-stage charging on the target battery cell so that the state of charge of the target battery cell is charged to a cut-off state of charge, and the cut-off state of charge of the target battery cell is less than 100% SOC;

[0009] The charged target battery cell is subjected to voltage screening.

[0010] In one embodiment, the temperature of the preheating process is greater than or equal to 70° C. and less than or equal to 85° C.; the pressure of the pre-pressing process is greater than or equal to 1.0 MPa and less than or equal to 1.6 MPa.

[0011] In one embodiment, the time for the preheating process and the pre-pressing process is greater than or equal to 1 minute and less than or equal to 3 minutes.

[0012] In one embodiment, the step of performing multi-stage charging on the target battery cell includes:

[0013] Performing a first-stage charging on the target battery cell under a first charging rate condition;

[0014] Under the condition of the second charging rate, the target battery cell is charged in the second stage;

[0015] Wherein, the second charging rate is greater than the first charging rate.

[0016] In one embodiment, the first charging rate is greater than or equal to 0.02C and less than or equal to 0.1C; and the charging time of the target battery cell in the first stage is greater than or equal to 3 minutes and less than or equal to 10 minutes.

[0017] In one embodiment, the second charging rate is greater than or equal to 0.2C and less than or equal to 0.5C; and the charging time of the target battery cell in the second stage is greater than or equal to 2 minutes and less than or equal to 5 minutes.

[0018] In one embodiment, the step of performing multi-stage charging on the target battery cell further includes:

[0019] Under the condition of a third charging rate, the target battery cell is charged in a third stage;

[0020] Wherein, the third charging rate is greater than the second charging rate.

[0021] In one embodiment, the third charging rate is greater than or equal to 1C and less than or equal to 1.5C; and the charging time of the target battery cell in the third stage is greater than or equal to 40 minutes and less than or equal to 50 minutes.

[0022] In one embodiment, the cutoff state of charge of the target battery cell is greater than or equal to 80% SOC and less than or equal to 83% SOC.

[0023] In a second aspect, an embodiment of the present application provides a battery, which is obtained using the battery formation process described in the first aspect.

[0024] Beneficial effects of the embodiments of the present application: The embodiments of the present application provide a battery and a formation process thereof, wherein the formation process of the battery includes allowing the target battery cell to stand after liquid injection; performing a preheating process and a pre-pressing process on the target battery cell; performing multi-stage charging on the target battery cell so that the state of charge of the target battery cell is charged to a cut-off state of charge, and the cut-off state of charge of the target battery cell is less than 100% SOC; performing voltage screening on the charged target battery cell, thereby reducing the time required for formation, improving production efficiency, and at the same time improving the battery capacity, initial charge and discharge efficiency, and cycle performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solution in this embodiment, the following is a brief introduction to the drawings required for the description of the embodiment. Obviously, the drawings described below are only some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on these drawings without creative work.

[0026] Figure 1 A flow chart of the battery formation process provided in an embodiment of the present application;

[0027] Figure 2 Capacity data graph of the batteries in Example 1, Example 2, Example 3, Comparative Example 1, Comparative Example 2, and Comparative Example 3 provided in the embodiments of the present application;

[0028] Figure 3 This is a graph showing the initial charge and discharge efficiency data of the batteries in Example 1, Example 2, Example 3, Comparative Example 1, Comparative Example 2, and Comparative Example 3 provided in the embodiments of the present application;

[0029] Figure 4 A data graph showing the cycle capacity retention rates of the batteries in Example 1, Example 2, Example 3, Comparative Example 1, Comparative Example 2, and Comparative Example 3 provided in the embodiments of the present application;

[0030] Figure 5 This is a schematic diagram of the structure of the battery provided in an embodiment of the present application. DETAILED DESCRIPTION

[0031] The technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without making creative work are within the scope of protection of the present application. In addition, it should be understood that the specific implementation methods described herein are only used to illustrate and explain the present application, and are not used to limit the present application. In the present application, unless otherwise specified, the directional words used, such as "upper" and "lower", generally refer to the upper and lower parts of the device in actual use or working state, specifically the drawing direction in the accompanying drawings; and "inside" and "outside" refer to the outline of the device.

[0032] See also Figure 1 , which is a flow chart of the battery formation process provided in the embodiments of the present application.

[0033] This embodiment provides a battery formation process, comprising the following steps:

[0034] Step S10: leaving the target battery cell to rest after injection.

[0035] The target battery cell may be a soft-pack lithium-ion battery cell based on graphite, silicon-carbon or metal lithium negative electrode, or may be other battery cell structures suitable for hot pressing and forming processes. This embodiment does not impose any specific restrictions on the type of the target battery cell.

[0036] Specifically, step S10 includes the following steps:

[0037] Step S11: The target battery cell after injection is placed in a first temperature environment for 24 hours to allow the electrolyte to fully diffuse inside the target battery cell and evenly infiltrate the positive and negative electrode plates and diaphragm materials, while completing the preliminary activation process of the electrode surface to provide stable electrochemical interface conditions for subsequent formation processes.

[0038] Step S12: Transfer the target battery cell to a second temperature environment and let it stand for 24 hours to increase the wetting rate of the electrolyte on the electrode and the diaphragm, and promote the initial interfacial reaction between the surface of the active material inside the target battery cell and the electrolyte, thereby improving the consistency of the film forming reaction and the stability of the initial interface.

[0039] Specifically, the first temperature may be room temperature (25±5°C), and the second temperature may be a high temperature environment (40°C to 80°C);

[0040] It should be noted that the "film formation" proposed in this embodiment refers to the solid electrolyte interface film (SEI film) formed by the electrochemical reduction reaction between the negative electrode surface and the electrolyte during the first charge and discharge process of the target battery cell. The quality of this film layer has a key impact on the safety, cycle life and capacity retention rate of the battery cell.

[0041] Step S20: performing a preheating process and a pre-pressing process on the target battery cell, thereby improving the interface reaction stability and film formation uniformity at the initial stage of the formation process.

[0042] The preheating process is used to make the internal temperature of the target battery cell reach a predetermined temperature, thereby increasing the penetration and wetting speed of the electrolyte into the electrode and the diaphragm, promoting the initial interface reaction between the electrolyte and the electrode active material, and improving the reaction rate and film quality in the initial stage of film formation.

[0043] The preheating process can be completed in the formation fixture, the temperature of the preheating process is greater than or equal to 70°C and less than or equal to 85°C, and the time of the preheating process is greater than or equal to 1 minute and less than or equal to 3 minutes; wherein, the temperature of the preheating process and the time of the preheating process can be flexibly set according to the structural characteristics of the target battery cell, the electrolyte system and the product application requirements, so as to take into account both safety and formation quality.

[0044] The pre-pressing process is used to apply stable and uniform pressure to the target battery cell, so that the electrode and the diaphragm maintain a good fit, while avoiding gas accumulation during the formation process and swelling of the target battery cell, improving the stability of the morphology of the target battery cell in the subsequent formation process, and preventing abnormal deviation of the electrode structure.

[0045] The pre-pressing process can be completed in the formation fixture, the pressure of the pre-pressing process is greater than or equal to 1.0 MPa and less than or equal to 1.6 MPa, and the time of the pre-pressing process is greater than or equal to 1 minute and less than or equal to 3 minutes; wherein, the temperature of the pre-pressing process and the time of the pre-pressing process can be adaptively adjusted in combination with factors such as the packaging type, tab distribution and dimensional tolerance of the target battery cell.

[0046] It can be understood that by combining the preheating process and the pre-pressing process for the target battery cell, a stable initial thermal field and pressure field environment can be established, the uniformity of the internal reaction interface of the target battery cell can be improved, and the film formation integrity, density and stability of the solid electrolyte interface film can be improved, thereby improving the initial charge and discharge efficiency, capacity retention rate and long-term cycle stability of the target battery cell, providing key pre-processing support for the large-scale manufacturing of high-performance lithium-ion batteries.

[0047] Specifically, in step S20, the target battery cell may be placed in a formation fixture to undergo a preheating process and a pre-pressing process.

[0048] The formation fixture may be a hot press fixture, which is used to accommodate and clamp the target battery cell. The formation fixture may include an upper clamping plate, a lower clamping plate, and a temperature control and pressing mechanism.

[0049] The upper clamping plate and the lower clamping plate are arranged opposite to each other and are used to clamp the upper surface and the lower surface of the target battery cell; the temperature control mechanism is arranged inside or on the surface of the clamping plate, and is used to heat the formation fixture to maintain the clamping space within the set temperature range, thereby improving the film formation quality during the formation process of the target battery cell; wherein, the inner surfaces of the upper clamping plate and the lower clamping plate can be covered with an insulating protective layer to prevent the target battery cell from generating a short circuit risk due to the contact of the tab or the aluminum-plastic film with the metal surface of the clamp during the hot pressing process.

[0050] The pressing mechanism is used to apply a constant or adjustable pressure to the target battery cell during the formation process of the target battery cell, so as to control the thickness expansion of the target battery cell, improve the adhesion between battery cell layers, and ensure film formation uniformity.

[0051] Furthermore, the formation fixture also includes an electrode contact structure for electrically connecting to the positive and negative pole tabs of the target battery cell, and the electrode contact structure includes conductive contacts arranged on the upper clamping plate and / or the lower clamping plate, and the conductive contacts are used to form conductive contact with the positive tab and negative tab of the target battery cell respectively, and the conductive contacts are connected to a power supply through an external connecting wire to realize charging operation of the target battery cell.

[0052] It should be noted that this embodiment only takes placing the target battery cell in a formation fixture as an example for illustration. In actual applications, the formation process of the target battery cell can be processed using other types of fixtures or support structures according to different equipment configurations and production requirements.

[0053] Step S30: The target cell is charged in multiple stages so that the state of charge of the target cell is charged to a cut-off state of charge, and the cut-off state of charge of the target cell is less than 100% SOC, thereby improving the film formation quality and the interface reaction control capability while shortening the total formation time and improving production efficiency.

[0054] It should be noted that during the multi-stage charging of the target battery cell, the formation fixture continuously provides a constant temperature and constant pressure working environment for the battery cell, and improves the stability of the target battery cell structure and reaction interface through precise control of temperature and pressure.

[0055] Specifically, step S30 includes the following steps:

[0056] Step S31: performing a first-stage charging on the target battery cell at a first charging rate.

[0057] The first charging rate is greater than or equal to 0.02C and less than or equal to 0.1C, and the charging time of the target battery cell in the first stage is greater than or equal to 3 minutes and less than or equal to 10 minutes; by adopting a low rate and small current to charge the target battery cell in the first stage, the interface reaction rate between the internal electrode and the electrolyte of the target battery cell can be effectively controlled, avoiding the problems of local excessive deposition and structural unevenness of the solid electrolyte interface film due to excessive current input rate, thereby improving the integrity, density and stability of the initial solid electrolyte interface film on the entire electrode surface.

[0058] At the same time, using low-rate charging in the first stage can also reduce the polarization degree of active material particles and reduce the generation of interface by-products, which is conducive to establishing a stable electrode / electrolyte interface environment, providing a good reaction basis for the use of medium- and high-rate charging in subsequent stages, thereby improving the controllability of the film formation process and the overall film formation quality.

[0059] Step S32: performing a second-stage charging of the target battery cell under a second charging rate; wherein the second charging rate is greater than the first charging rate.

[0060] The second charging rate is greater than or equal to 0.2C and less than or equal to 0.5C, and the charging time of the target battery cell in the second stage is greater than or equal to 2 minutes and less than or equal to 5 minutes; it can be understood that, on the basis of forming an initial stable interface by charging in the first stage, the target battery cell is charged in the second stage, and the second charging rate is greater than the first charging rate, thereby improving the charging efficiency and reaction activity of the target battery cell, accelerating the growth and densification of the solid electrolyte interface film, and shortening the overall formation time, improving the formation efficiency, and meeting the process requirements of efficient mass production.

[0061] At the same time, the second-stage charging can activate the electrode material, increase the ion diffusion rate, and maintain the uniformity of the interface reaction, reducing the risks of film disintegration and lithium dendrite formation caused by high-rate direct charging, thereby improving the first charge and discharge consistency and safety of the target battery cell.

[0062] Furthermore, the step S30 further includes the following steps:

[0063] Step S33: performing a third stage charging on the target battery cell under a third charging rate; wherein the third charging rate is greater than the second charging rate.

[0064] The third charging rate is greater than or equal to 1C and less than or equal to 1.5C, and the charging time of the target battery cell in the third stage is greater than or equal to 40 minutes and less than or equal to 50 minutes, thereby improving the charging efficiency of the target battery cell and promoting the activity of the chemical reaction inside the target battery cell.

[0065] It can be understood that by performing the third stage charging on the target battery cell, and the third charging rate is greater than the second charging rate, the charging process of the target battery cell can be accelerated, the overall formation time can be shortened, and the formation efficiency can be improved; at the same time, the overall performance of the target battery cell can be maximized.

[0066] Specifically, in the step S33, the target battery cell is charged in the third stage under the condition of the third charging rate, so that the state of charge of the target battery cell is charged to the cut-off state of charge, and the cut-off state of charge of the target battery cell is less than 100% SOC; wherein, the cut-off state of charge of the target battery cell is greater than or equal to 80% SOC and less than or equal to 83% SOC, thereby avoiding the problem of overcharging of the target battery cell, reducing the thermal load of the formation equipment, and thereby extending the service life of the formation equipment.

[0067] It can be understood that this embodiment performs multi-stage charging on the target battery cell, so that the solid electrolyte interface film can be stably deposited in the first stage charging process to form a uniform and dense initial interface layer; in the second stage charging process, the growth rate and densification degree of the solid electrolyte interface film are improved by increasing the charging rate of the target battery cell; at the same time, in the third stage charging process, the charging rate of the target battery cell is further increased, thereby accelerating the charging process of the target battery cell, reducing the formation process cycle of the target battery cell, and then improving the formation efficiency to meet the process requirements of efficient mass production.

[0068] Step S40: performing voltage screening on the charged target battery cell.

[0069] Specifically, step S40 includes the following steps:

[0070] Step S41: placing the target battery cell after charging on hold; wherein, the time for placing the target battery cell on hold is greater than or equal to 3 minutes and less than or equal to 10 minutes. By placing the target battery cell on hold for a short period of time, the internal electrochemical reaction of the target battery cell is further stabilized, while avoiding the deviation of the voltage judgment result caused by the voltage fluctuation when charging is just completed, thereby improving the accuracy of screening.

[0071] Step S42: The target cell that has completed the formation process is removed from the formation fixture, and the target cell is subjected to voltage screening. By measuring the open circuit voltage value of the target cell, it is determined whether it is within the set voltage range, and then whether the formation effect of the target cell meets the standard.

[0072] Specifically, if the voltage value of the target battery cell does not meet the set standard, the charging rate, charging time, cut-off state of charge, temperature and pressure in the formation process can be reviewed to see whether there are deviations or abnormalities; and / or the target battery cell can be recharged and the voltage test can be performed again after recharging; and / or the target battery cell can be judged as a defective product and eliminated, and the cause of the defect can be analyzed in combination with its data and status to optimize the subsequent formation process parameters.

[0073] The technical solutions of the embodiments of the present application are now described in conjunction with specific embodiments.

[0074] Example 1

[0075] A battery formation process comprises the following steps:

[0076] S1: Place the injected battery cell at room temperature (25±5°C) for 24 hours, then transfer it to a high temperature (45±2°C) environment and place it at room temperature for 24 hours.

[0077] S2: placing the battery cell in a formation fixture for a preheating process and a pre-pressing process; wherein the temperature of the preheating process is 70° C.; the pressure of the pre-pressing process is 1.0 MPa; and the time of the preheating process and the pre-pressing process is 1 minute.

[0078] S3: performing a first-stage charging of the battery cell at a first charging rate; wherein the first charging rate is 0.02C; and the charging time of the battery cell in the first stage is 3 minutes.

[0079] S4: performing a second-stage charging of the battery cell at a second charging rate; wherein the second charging rate is 0.2C; and the charging time of the battery cell in the second stage is 2 minutes.

[0080] S5: Under the condition of a third charging rate, the battery cell is charged in the third stage so that the state of charge of the battery cell is charged to a cut-off state of charge; wherein, the third charging rate is 1C; the charging time of the battery cell in the third stage is 48 minutes; and the cut-off state of charge of the battery cell is 80% SOC.

[0081] S6: putting the battery cells that have completed charging aside; wherein, the battery cells are put aside for 3 minutes.

[0082] S7: taking out the battery cell from the formation fixture to complete the entire formation process.

[0083] Example 2

[0084] A battery formation process comprises the following steps:

[0085] S1: Place the injected battery cell at room temperature (25±5°C) for 24 hours, then transfer it to a high temperature (45±2°C) environment and place it at room temperature for 24 hours.

[0086] S2: placing the battery cell in a formation fixture for a preheating process and a pre-pressing process; wherein the temperature of the preheating process is 85° C.; the pressure of the pre-pressing process is 1.6 MPa; and the time of the preheating process and the pre-pressing process is 3 minutes.

[0087] S3: performing a first-stage charging of the battery cell at a first charging rate; wherein the first charging rate is 0.1C; and the charging time of the battery cell in the first stage is 10 minutes.

[0088] S4: performing a second-stage charging of the battery cell at a second charging rate; wherein the second charging rate is 0.5C; and the charging time of the battery cell in the second stage is 5 minutes.

[0089] S5: Under the condition of a third charging rate, the battery cell is charged in the third stage so that the state of charge of the battery cell is charged to a cut-off state of charge; wherein, the third charging rate is 1.5C; the charging time of the battery cell in the third stage is 40 minutes; and the cut-off state of charge of the battery cell is 83% SOC.

[0090] S6: putting the battery cells that have completed charging aside; wherein, the battery cells are put aside for 10 minutes.

[0091] S7: taking out the battery cell from the formation fixture to complete the entire formation process.

[0092] Example 3

[0093] A battery formation process comprises the following steps:

[0094] S1: Place the injected battery cell at room temperature (25±5°C) for 24 hours, then transfer it to a high temperature (45±2°C) environment and place it at room temperature for 24 hours.

[0095] S2: placing the battery cell in a formation fixture for a preheating process and a pre-pressing process; wherein the temperature of the preheating process is 80° C.; the pressure of the pre-pressing process is 1.2 MPa; and the time of the preheating process and the pre-pressing process is 2 minutes.

[0096] S3: performing a first-stage charging of the battery cell at a first charging rate; wherein the first charging rate is 0.05C; and the charging time of the battery cell in the first stage is 5 minutes.

[0097] S4: performing a second-stage charging of the battery cell at a second charging rate; wherein the second charging rate is 0.5C; and the charging time of the battery cell in the second stage is 3 minutes.

[0098] S5: Under the condition of a third charging rate, the battery cell is charged in the third stage so that the state of charge of the battery cell is charged to a cut-off state of charge; wherein, the third charging rate is 1.2C; the charging time of the battery cell in the third stage is 45 minutes; and the cut-off state of charge of the battery cell is 82% SOC.

[0099] S6: putting the battery cells that have completed charging aside; wherein, the battery cells are put aside for 6 minutes.

[0100] S7: taking out the battery cell from the formation fixture to complete the entire formation process.

[0101] Comparative Example 1

[0102] A battery formation process comprises the following steps:

[0103] S1: Place the target cell after injection at room temperature (25℃±5) for 24 hours, then transfer it to a high temperature (45℃±2) and place it for 24 hours.

[0104] S2: performing a first-stage charging of the battery cell at a first charging rate; wherein the first charging rate is 0.02C; and the charging time of the battery cell in the first stage is 3 minutes.

[0105] S3: performing a second-stage charging of the battery cell at a second charging rate; wherein the second charging rate is 0.2C; and the charging time of the battery cell in the second stage is 2 minutes.

[0106] S4: Under the condition of a third charging rate, the battery cell is charged in the third stage so that the state of charge of the battery cell is charged to a cut-off state of charge; wherein, the third charging rate is 1C; the charging time of the battery cell in the third stage is 48 minutes; and the cut-off state of charge of the battery cell is 80% SOC.

[0107] S5: putting the battery cells that have completed charging aside; wherein, the battery cells are put aside for 3 minutes.

[0108] S6: taking out the battery cell from the formation fixture to complete the entire formation process.

[0109] Comparative Example 2

[0110] A battery formation process comprises the following steps:

[0111] S1: Place the injected battery cell at room temperature (25±5°C) for 24 hours, then transfer it to a high temperature (45±2°C) environment and place it at room temperature for 24 hours.

[0112] S2: placing the battery cell in a formation fixture for a preheating process and a pre-pressing process; wherein the temperature of the preheating process is 70° C.; the pressure of the pre-pressing process is 1.0 MPa; and the time of the preheating process and the pre-pressing process is 1 minute.

[0113] S3: performing a first-stage charging of the battery cell at a first charging rate; wherein the first charging rate is 0.2C; and the charging time of the battery cell in the first stage is 2 minutes.

[0114] S4: performing a second-stage charging of the battery cell at a second charging rate; wherein the second charging rate is 0.8C; and the charging time of the battery cell in the second stage is 6 minutes.

[0115] S5: Under the condition of a third charging rate, the battery cell is charged in the third stage so that the state of charge of the battery cell is charged to a cut-off state of charge; wherein, the third charging rate is 1.5C; the charging time of the battery cell in the third stage is 36 minutes; and the cut-off state of charge of the battery cell is 80% SOC.

[0116] S6: putting the battery cells that have completed charging aside; wherein, the battery cells are put aside for 3 minutes.

[0117] S7: taking out the battery cell from the formation fixture to complete the entire formation process.

[0118] Comparative Example 3

[0119] A battery formation process comprises the following steps:

[0120] S1: Place the injected battery cell at room temperature (25±5°C) for 24 hours, then transfer it to a high temperature (45±2°C) environment and place it at room temperature for 24 hours.

[0121] S2: placing the battery cell in a formation fixture for a preheating process and a pre-pressing process; wherein the temperature of the preheating process is 70° C.; the pressure of the pre-pressing process is 1.0 MPa; and the time of the preheating process and the pre-pressing process is 1 minute.

[0122] S3: performing a first-stage charging of the battery cell at a first charging rate; wherein the first charging rate is 0.02C; and the charging time of the battery cell in the first stage is 3 minutes.

[0123] S4: performing a second-stage charging of the battery cell at a second charging rate; wherein the second charging rate is 0.2C; and the charging time of the battery cell in the second stage is 2 minutes.

[0124] S5: Under the condition of a third charging rate, the battery cell is charged in the third stage so that the state of charge of the battery cell is charged to a cut-off state of charge; wherein, the third charging rate is 1C; the charging time of the battery cell in the third stage is 48 minutes; and the cut-off state of charge of the battery cell is 100% SOC.

[0125] S6: putting the battery cells that have completed charging aside; wherein, the battery cells are put aside for 3 minutes.

[0126] S7: taking out the battery cell from the formation fixture to complete the entire formation process.

[0127] Test methods include:

[0128] 1. Battery capacity test

[0129] The batteries in the above embodiments (Example 1, Example 2 and Example 3) and comparative examples (Comparative Example 1, Comparative Example 2 and Comparative Example 3) were subjected to capacity tests. The steps for the battery capacity test are as follows:

[0130] ① Under room temperature conditions, the battery cell that has completed the formation process is left to stand for a certain period of time, and then charged and discharged four times at a rate of 0.5C in the voltage range of 3.0V to 4.4V. The average of the last three discharge capacities is taken as its actual capacity value. The results are recorded in Table 1.

[0131] 2. Test of the battery's first charge and discharge efficiency

[0132] The batteries in the above embodiments (Example 1, Example 2, and Example 3) and comparative examples (Comparative Example 1, Comparative Example 2, and Comparative Example 3) were tested for initial charge and discharge efficiency. The test steps for the initial charge and discharge efficiency of the batteries are as follows:

[0133] ① Under room temperature conditions, perform constant current and constant voltage charging at a current of 0.2C, charge to a cut-off voltage of 4.4V, and after the cut-off current is 0.02C~0.05C, record the charge capacity Q1 and let it sit for 10 minutes; ② Perform constant current discharge at a current of 0.5C, discharge to a cut-off voltage of 3.0V, record the discharge capacity Q2, ③ Calculate the first charge and discharge efficiency; where the first charge and discharge efficiency = discharge capacity (Q2) / charge capacity (Q1) × 100%, and the results are recorded in Table 1.

[0134] 3. Battery cycle capacity retention test

[0135] The batteries in the above embodiments (Example 1, Example 2 and Example 3) and comparative examples (Comparative Example 1, Comparative Example 2 and Comparative Example 3) were subjected to cycle performance tests. The cycle performance test steps of the batteries are as follows:

[0136] ① Under room temperature conditions, perform constant current and constant voltage charging at a current of 1.2C to a cut-off voltage of 4.4V. After the cut-off current is 0.02C to 0.05C, record the charging capacity Q1 and let it sit for 10 minutes; ② Perform constant current discharge at a current of 5C to a cut-off voltage of 3.0V and let it sit for 5 minutes; ③ After cycling steps ① and ② for 260 cycles, record the discharge capacity as Q3; ④ Calculate the 260-cycle capacity retention rate; where 260-cycle capacity retention rate = discharge capacity (Q3) / charge capacity (Q1) × 100%. The results are recorded in Table 1.

[0137] Table 1

[0138] project Battery capacity (mAh) First charge and discharge efficiency (%) Cycle capacity retention rate (%) Example 1 1966.4 89.5％ 95％ Example 2 1965.3 89.2％ 89.8％ Example 3 1976.3 91.2％ 95％ Comparative Example 1 1950.2 89.8％ 86.5％ Comparative Example 2 1952.1 89.2％ 88.3％ Comparative Example 3 1961.1 87.5％ 89.5％

[0139] Combined with Example 1, Example 2, Example 3, Comparative Example 1, Comparative Example 2, Comparative Example 3, Table 1, Figure 2 、 Figure 3 and Figure 4 It can be seen that by placing the battery cell after injection in the formation fixture; performing a preheating process and a pre-pressing process on the battery cell; and performing multi-stage charging on the battery cell, the battery cell's state of charge is charged to the cut-off state of charge, and the battery cell's cut-off state of charge is less than 100% SOC; after charging is completed, setting a shelf time and performing voltage screening, so that the electrochemical state of the battery cell before entering the subsequent process is stable and reliable, thereby improving the film formation quality of the solid electrolyte interface film and the consistency of the interface reaction, shortening the entire formation process cycle, increasing the number of battery cells processed per unit time, and improving production efficiency; at the same time, improving the battery cell's first charge and discharge efficiency, capacity retention rate and long-term cycle performance.

[0140] Specifically, in combination with Example 1, Example 2, Example 3, Comparative Example 1, Table 1 and Figure 3 It can be seen that the first charge and discharge efficiency of the battery provided in Example 1, the first charge and discharge efficiency of the battery provided in Example 2, and the first charge and discharge efficiency of the battery provided in Example 3 are all greater than the first charge and discharge efficiency of the battery provided in Comparative Example 1, indicating that by performing a combined preheating process and a pre-pressing process on the battery cell, a stable initial thermal field and pressure field environment for formation can be established, the uniformity of the reaction interface inside the battery cell can be improved, and the film formation integrity, density and stability of the solid electrolyte interface film can be improved, thereby improving the first charge and discharge efficiency of the battery cell.

[0141] Combined with Example 1, Example 2, Example 3, Comparative Example 2, Comparative Example 3, Table 1 and Figure 4 , it can be seen that the cycle capacity retention rate of the battery provided by Example 1, the cycle capacity retention rate of the battery provided by Example 2, and the cycle capacity retention rate of the battery provided by Example 3 are all greater than the cycle capacity retention rate of the battery provided by Comparative Example 2, indicating that by performing multi-stage charging on the battery cell, wherein, in the first stage charging, the first charging rate is greater than or equal to 0.02C and less than or equal to 0.1C, and the charging time of the first stage is greater than or equal to 3 minutes and less than or equal to 10 minutes; in the second stage charging, the second charging rate is greater than or equal to 0.2C and less than The battery cell is designed to have a charge rate of 0.5C or higher, a charging time of 2 minutes or higher, and 5 minutes or lower. In the third stage of charging, the third charging rate is 1C or higher, and 1.5C or lower, a charging time of 40 minutes or higher, and 50 minutes or lower. The cutoff state of charge of the battery cell is 80% SOC or higher, and 83% SOC or lower, thereby improving the long-term cycle performance of the battery cell. At the same time, the charging process of the battery cell is accelerated, the formation process cycle of the battery cell is reduced, and the formation efficiency is improved to meet the process requirements of efficient mass production.

[0142] See also Figure 5 , is a schematic structural diagram of the battery provided in an embodiment of the present application.

[0143] This embodiment further provides a battery 1, which is obtained by using the battery formation process described in any of the above embodiments.

[0144] It is understandable that the formation process of the battery has been described in detail in the above embodiments and will not be repeated here.

[0145] In the above embodiments, the description of each embodiment has its own focus. For parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0146] The above is a detailed introduction to a battery and its formation process provided in this embodiment. Specific examples are used herein to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only used to help understand the method and core idea of ​​the present application. At the same time, for those skilled in the art, based on the ideas of the present application, there may be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present application.

Claims

1. A battery formation process, characterized in that: include: Let the target battery cell stand still after injection; Performing a preheating process and a pre-pressing process on the target battery cell; Performing multi-stage charging on the target battery cell so that the state of charge of the target battery cell is charged to a cut-off state of charge, and the cut-off state of charge of the target battery cell is less than 100% SOC; The charged target battery cell is subjected to voltage screening.

2. The battery formation process according to claim 1, characterized in that: The temperature of the preheating process is greater than or equal to 70° C. and less than or equal to 85° C.; the pressure of the pre-pressing process is greater than or equal to 1.0 MPa and less than or equal to 1.6 MPa.

3. The battery formation process according to claim 2, characterized in that: The time for the preheating process and the pre-pressing process is greater than or equal to 1 minute and less than or equal to 3 minutes.

4. The battery formation process according to any one of claims 1 to 3, characterized in that: The step of performing multi-stage charging on the target battery cell comprises: Performing a first-stage charging on the target battery cell under a first charging rate condition; Under the condition of the second charging rate, the target battery cell is charged in the second stage; Wherein, the second charging rate is greater than the first charging rate.

5. The battery formation process according to claim 4, characterized in that: The first charging rate is greater than or equal to 0.02C and less than or equal to 0.1C; the charging time of the target battery cell in the first stage is greater than or equal to 3 minutes and less than or equal to 10 minutes.

6. The battery formation process according to claim 4, characterized in that: The second charging rate is greater than or equal to 0.2C and less than or equal to 0.5C; the charging time of the target battery cell in the second stage is greater than or equal to 2 minutes and less than or equal to 5 minutes.

7. The battery formation process according to claim 4, characterized in that: The step of performing multi-stage charging on the target battery cell further includes: Under the condition of a third charging rate, the target battery cell is charged in a third stage; Wherein, the third charging rate is greater than the second charging rate.

8. The battery formation process according to claim 7, characterized in that: The third charging rate is greater than or equal to 1C and less than or equal to 1.5C; the charging time of the target battery cell in the third stage is greater than or equal to 40 minutes and less than or equal to 50 minutes.

9. The battery formation process according to any one of claims 1 to 3, characterized in that: The cutoff state of charge of the target battery cell is greater than or equal to 80% SOC and less than or equal to 83% SOC.

10. A battery, characterized in that: The battery is obtained by using the battery formation process according to any one of claims 1 to 9.

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