A ternary soft-pack lithium-ion battery and its formation and aging processes

Abstract

The present invention relates to lithium-ion battery technology, and discloses a ternary soft-pack lithium-ion battery and its formation and aging process, including the following steps: S1. Shelve and age the battery filled with liquid under a temperature gradient; S2. At a preset temperature and pressure, charge the battery in S1 at a constant current to a preset voltage, evacuate air under negative pressure and seal it, and then age it under a temperature gradient; S3. Charge the battery in S2 at a constant current to a preset voltage, evacuate air under negative pressure and seal it, and then age it under a temperature gradient; S4. Charge the battery in S3 at a constant current to a preset voltage, evacuate air under negative pressure and seal it, and then age it, thus completing the entire formation process; and the charging rates during the formation in the three stages gradually increase. The beneficial effects of the present invention are as follows: Shelving and aging under a temperature gradient and three-stage stepped formation enable the side reactions inside the battery to occur sufficiently; evacuating air and aging promote the SEI film on the negative electrode surface to be denser, more uniform and stable, reduce the possibility of side reactions occurring again, and improve the shelving and cycling performance of the battery in a high-voltage system.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium - ion batteries, and in particular to a ternary soft - package lithium - ion battery and its formation and aging processes. Background Art

[0002] At present, lithium - ion secondary batteries have a certain strong share in both the 3C field and the electric vehicle field. With the continuous maturity of lithium - ion battery technology and the continuous reduction of costs, people have gradually realized that lithium - ion batteries should have a wider range of application fields. Formation is an important process in the production of lithium - ion batteries. During formation, a solid electrolyte membrane, that is, a solid polymer electrolyte membrane, is formed on the negative electrode surface. The uniformity and thickness of the solid polymer electrolyte membrane have a great influence on the capacity and cycle performance of the battery. Forming a uniform and stable solid polymer electrolyte membrane can well adapt to the volume expansion caused by the insertion and extraction of lithium ions.

[0003] In the traditional formation charging process of lithium - ion batteries, "pre - formation" is first carried out by charging with a small current to activate the battery cell. Then, after the SEI (solid electrolyte interface) membrane is stably formed, secondary air extraction and packaging are carried out, and then secondary charging is carried out. For example, a production method of a polymer battery disclosed in the Chinese invention patent document with the publication number CN103715448A. Although this method solves the problem of lithium deposition caused by gas bubbles in traditional ion batteries, the battery prepared by the formation process of this scheme has problems of poor high - temperature shelf life and cycle performance in a high - voltage system. Summary of the Invention

[0004] The technical problem to be solved by the present invention is how to provide a formation and aging process for a ternary soft - package lithium - ion battery to improve the high - temperature shelf life and cycle performance of the battery in a high - voltage system.

[0005] The present invention solves the above - mentioned technical problem by the following technical means:

[0006] The first aspect of the present invention provides a formation and aging process for a ternary soft - package lithium - ion battery, including the following steps:

[0007] S1. Pre - aging: The soft - package ion battery filled with electrolyte is subjected to temperature - gradient shelf aging.

[0008] S2. First - stage formation: At a preset temperature and pressure, the aged soft - package lithium - ion battery is charged at a first constant current to a first preset voltage for the first - step formation. After returning to room temperature, the first negative - pressure air extraction and sealing are carried out, and then the first temperature - gradient aging is carried out.

[0009] S3. Second-stage formation: The pouch lithium-ion battery formed in the first stage is charged at a second constant current to a second preset voltage for the second-step formation. After returning to room temperature, a second negative pressure evacuation and sealing are performed, and then a second temperature gradient aging is carried out;

[0010] S4. Third-stage formation: The pouch lithium-ion battery formed in the second stage is charged at a third constant current to a third preset voltage for the third-step formation. After returning to room temperature, a third negative pressure evacuation and sealing are performed, and then a third aging is carried out, thus completing the entire formation process; and the charging rates of the three-stage formation gradually increase.

[0011] Beneficial effects: This application adopts a three-stage stepped formation. It performs temperature gradient shelving and aging before formation, and the charging rates of each stage of formation increase step by step, effectively prolonging the charging time and enabling sufficient side reactions to occur inside the battery; at the same time, gas extraction and aging operations are added in each stage of formation. On the one hand, formation and aging are interspersed, promoting the formation of a denser, more uniform and stable SEI film on the surface of the electrode particles at the negative electrode. On the other hand, it eliminates the possibility of side reactions occurring again during high-temperature shelving and charge-discharge cycling of the finished battery, thereby improving the high-temperature shelving and cycling performance of high-voltage system batteries.

[0012] Preferably, in the step S1, the first gradient temperature A of the aging temperature gradient 11 is 45 - 55 °C, and the aging time is 10 - 14 h; the second gradient temperature A 12 is 35 - 45 °C, and the aging time is 4 - 8 h; the third gradient temperature A 13 is 30 - 35 °C, and the aging time is 4 - 10 h.

[0013] Preferably, in the step S2, the preset temperature is 40 - 55 °C, and the preset pressure is 0.1 - 0.3 MPa.

[0014] Preferably, in the step S2, the first current is 0.01 - 0.04 C, the first preset voltage is 3.0 - 3.2 V, and the charging time is 4 - 6 h;

[0015] Preferably, in the step S2, the first gradient temperature A of the first temperature gradient aging 21 is 45 - 55 °C, and the aging time is 6 - 10 h; the second gradient temperature A 22 is 35 - 45 °C, and the aging time is 6 - 10 h.

[0016] Preferably, in the step S3, the second current is 0.05 - 0.1 C, the second preset voltage is 3.4 - 3.6 V, and the charging time is 4 - 6 h;

[0017] Preferably, in the step S3, the first gradient temperature A of the second temperature gradient aging31 is 45 to 55 °C, and the aging time is 8 to 10 h; the second gradient temperature A 32 is 35 to 45 °C, and the aging time is 6 to 10 h.

[0018] Preferably, the third current in the step S4 is 0.2 to 0.4 C, the third preset voltage is 3.9 to 4.1 V, and the charging time is 4 to 6 h; the temperature of the third aging in the step S4 is 40 to 55 °C, and the aging time is 4 to 8 h.

[0019] The second aspect of the present invention provides a ternary soft-pack lithium-ion battery prepared by using the above formation and aging process.

[0020] Preferably, the positive active material of the soft-pack ion battery is lithium nickel cobalt manganese oxide LiNi x Co y Mn Z O2, where 0.5 ≤ x ≤ 0.7; 0.02 ≤ y ≤ 0.2; 0.1 ≤ z ≤ 0.48, and x + y + z = 1; the negative active material is artificial graphite.

[0021] The advantages of the present invention are as follows:

[0022] This application adopts a three-stage stepped formation. Temperature gradient shelving aging is carried out before formation, and the charging rate of each stage of formation increases step by step, effectively extending the charging time and enabling sufficient side reactions to occur inside the battery. At the same time, gas extraction and aging operations are added in each stage of formation. On the one hand, formation and aging are interspersed, promoting the formation of a more dense, uniform and stable SEI film on the surface of the negative electrode by the electrode particles. On the other hand, it eliminates the possibility of side reactions occurring again during high-temperature shelving and charge-discharge cycling of the finished battery, thereby improving the high-temperature shelving and cycling performance of high-voltage system batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is the formation and aging process flow chart of the ternary soft-pack lithium-ion battery in Embodiment 1 of this application.

[0024] Figure 2 is the high-temperature shelving test result graph in Test Example 1 of this application.

[0025] Figure 3 is the high-temperature cycling test result graph in Test Example 1 of this application. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0026] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Apparently, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the scope of protection of the present invention.

[0027] The test materials, reagents, etc. used in the following embodiments can be obtained from commercial channels without special instructions.

[0028] For those not specifying specific technologies or conditions in the embodiments, they can all be carried out according to the technologies or conditions described in the literature in the field or according to the product specifications.

[0029] Example 1

[0030] On the one hand, this embodiment provides a formation and aging process for a ternary soft-pack lithium-ion battery, as Figure 1 shown, including the following steps:

[0031] S1. Pre-aging: Place the NCM523 type ternary soft-pack ion battery filled with liquid in a forced-air drying oven for temperature-gradient shelving and aging. First, age at 55 °C for 10 h, then at 40 °C for 8 h, and finally at 30 °C for 4 h.

[0032] S2. First-stage formation: Move the aged soft-pack lithium-ion battery to a hot-press formation cabinet, set the preheating temperature to 45 °C, the extrusion pressure of the battery to 0.2 MPa, and charge at a constant current of 0.01C to 3.2 V, with the charging time being 6 h, to perform the first step of formation; after the first step of formation is completed, place it on a vacuum pumping and sealing device after returning to room temperature for the first vacuum pumping and sealing; then send the sealed battery to a forced-air drying oven, first age at 55 °C for 6 h, and then at 40 °C for 10 h to perform the first temperature-gradient aging, that is, complete the first-stage formation.

[0033] S3. Second-stage formation: Place the soft-pack lithium-ion battery formed in the first stage into a hot-press formation cabinet, charge at a constant current of 0.05C to 3.4 V, with the charging time being 6 h, to perform the second step of formation; after the second step of formation is completed, place it on a vacuum pumping and sealing device after returning to room temperature for the second vacuum pumping and sealing; then send the sealed battery to a forced-air drying oven, first age at 45 °C for 8 h, and then at 35 °C for 6 h to perform the second temperature-gradient aging, that is, complete the second-stage formation.

[0034] S4. Third-stage formation: Place the pouch-type lithium-ion battery after the second-stage formation into a hot-pressing formation cabinet, charge it at a constant current of 0.2C to 4.1V, with the charging time being 6h, thus performing the third-step formation; after the third-step formation is completed, after restoring to room temperature, place it on an air-extracting and sealing device, perform the third negative-pressure air extraction and sealing; then send the sealed battery to a blast drying oven, and age it at 40°C for 8h, thus performing the third aging, and the entire formation process is completed.

[0035] On the other hand, this embodiment provides a ternary pouch-type lithium-ion battery. The positive active material of this pouch-type ion battery is lithium nickel cobalt manganese oxide LiNi 0.5 Co 0.2 Mn 0.3 O2, and the negative active material is artificial graphite. After injecting the electrolyte into this ternary pouch-type ion battery, perform formation and aging according to the above process, and then obtain a ternary pouch-type lithium-ion battery.

[0036] Example 2

[0037] On the one hand, this embodiment provides a formation and aging process for a ternary pouch-type lithium-ion battery, including the following steps:

[0038] S1. Pre-aging: Place the NCM523-type ternary pouch-type ion battery after injecting the electrolyte in a blast drying oven for temperature-gradient shelf aging. First, age it at 50°C for 10h, then at 45°C for 8h, and finally at 30°C for 10h.

[0039] S2. First-stage formation: Move the aged pouch-type lithium-ion battery onto a hot-pressing formation cabinet, set the preheating temperature to 45°C, the extrusion pressure of the battery to 0.2MPa, charge it at a constant current of 0.02C to 3.0V, with the charging time being 6h, thus performing the first-step formation; after the first-step formation is completed, after restoring to room temperature, place it on an air-extracting and sealing device, perform the first negative-pressure air extraction and sealing; then send the sealed battery to a blast drying oven, first age it at 45°C for 8h, and then at 40°C for 10h, thus performing the first temperature-gradient aging, and the first-stage formation is completed.

[0040] S3. Second-stage formation: Place the pouch-type lithium-ion battery after the first-stage formation into a hot-pressing formation cabinet, charge it at a constant current of 0.08C to 3.4V, with the charging time being 6h, thus performing the second-step formation; after the second-step formation is completed, after restoring to room temperature, place it on an air-extracting and sealing device, perform the second negative-pressure air extraction and sealing; then send the sealed battery to a blast drying oven, first age it at 45°C for 8h, and then at 35°C for 6h, thus performing the second temperature-gradient aging, and the second-stage formation is completed.

[0041] S4. Third-stage formation: Place the pouch-type lithium-ion battery after the second-stage formation into a hot-press formation cabinet, charge it at a constant current of 0.3C to 3.9V, with a charging time of 6h, to conduct the third-step formation; after the third-step formation is completed, place it on a vacuum pumping and sealing device after restoring to room temperature, conduct the third-time negative-pressure pumping and sealing; then send the sealed battery to a blast drying oven and age it at 40°C for 8h to conduct the third-time aging, thus completing the entire formation process.

[0042] On the other hand, this embodiment provides a ternary pouch-type lithium-ion battery. The positive active material of this pouch-type ion battery is lithium nickel cobalt manganese oxide LiNi 0.5 Co 0.2 Mn 0.3 O2, and the negative active material is artificial graphite. After injecting the electrolyte into this ternary pouch-type ion battery, conduct formation and aging according to the above process to obtain a ternary pouch-type lithium-ion battery.

[0043] Example 3

[0044] On the one hand, this embodiment provides a formation and aging process for a ternary pouch-type lithium-ion battery, including the following steps:

[0045] S1. Pre-aging: Place the NCM523-type ternary pouch-type ion battery after injecting the electrolyte in a blast drying oven for temperature-gradient shelf aging. First, age it at 50°C for 10h, then at 40°C for 8h, and finally at 30°C for 4h.

[0046] S2. First-stage formation: Move the pre-aged pouch-type lithium-ion battery to a hot-press formation cabinet, set the preheating temperature to 45°C, the extrusion pressure of the battery to 0.3MPa, charge it at a constant current of 0.03C to 3.2V, with a charging time of 6h, to conduct the first-step formation; after the first-step formation is completed, place it on a vacuum pumping and sealing device after restoring to room temperature, conduct the first-time negative-pressure pumping and sealing; then send the sealed battery to a blast drying oven, first age it at 55°C for 8h, and then at 38°C for 8h to conduct the first temperature-gradient aging, thus completing the first-stage formation.

[0047] S3. Second-stage formation: Place the pouch-type lithium-ion battery after the first-stage formation into a hot-press formation cabinet, charge it at a constant current of 0.05C to 3.6V, with a charging time of 6h, to conduct the second-step formation; after the second-step formation is completed, place it on a vacuum pumping and sealing device after restoring to room temperature, conduct the second-time negative-pressure pumping and sealing; then send the sealed battery to a blast drying oven, first age it at 50°C for 8h, and then at 45°C for 6h to conduct the second temperature-gradient aging, thus completing the second-stage formation.

[0048] S4. Third-stage formation: Place the pouch-type lithium-ion battery after the second-stage formation into a hot-press formation cabinet, charge it at a constant current of 0.4C to 3.9V, with a charging time of 6h, to conduct the third-step formation; after the third-step formation is completed, place it on a vacuum pumping and sealing device after restoring to room temperature, conduct the third-time negative-pressure pumping and sealing; then send the sealed battery to a blast drying oven, and age it at 40°C for 8h to conduct the third-time aging, thus completing the entire formation process.

[0049] On the other hand, this embodiment provides a ternary pouch-type lithium-ion battery. The positive active material of this pouch-type ion battery is lithium nickel cobalt manganese oxide LiNi 0.5 Co 0.2 Mn 0.3 O2, where x + y + z = 1; the negative active material is artificial graphite. After injecting the liquid into this ternary pouch-type ion battery, conduct formation and aging according to the above process to obtain a ternary pouch-type lithium-ion battery.

[0050] Example 4

[0051] On the one hand, this embodiment provides a formation and aging process for a ternary pouch-type lithium-ion battery, including the following steps:

[0052] S1. Pre-aging: Place the NCM523 type ternary pouch-type ion battery after injecting the liquid in a blast drying oven for temperature-gradient shelf aging. First, age it at 45°C for 14h, then at 35°C for 6h, and finally at 30°C for 10h.

[0053] S2. First-stage formation: Move the aged pouch-type lithium-ion battery to a hot-press formation cabinet, set the preheating temperature to 50°C, the extrusion pressure of the battery to 0.3MPa, charge it at a constant current of 0.04C to 3.0V, with a charging time of 5h, to conduct the first-step formation; after the first-step formation is completed, place it on a vacuum pumping and sealing device after restoring to room temperature, conduct the first-time negative-pressure pumping and sealing; then send the sealed battery to a blast drying oven, first age it at 50°C for 8h, and then at 35°C for 10h to conduct the first temperature-gradient aging, thus completing the first-stage formation.

[0054] S3. Second-stage formation: Place the pouch-type lithium-ion battery after the first-stage formation into a hot-press formation cabinet, charge it at a constant current of 0.1C to 3.6V, with a charging time of 4h, to conduct the second-step formation; after the second-step formation is completed, place it on a vacuum pumping and sealing device after restoring to room temperature, conduct the second-time negative-pressure pumping and sealing; then send the sealed battery to a blast drying oven, first age it at 55°C for 8h, and then at 40°C for 10h to conduct the second temperature-gradient aging, thus completing the second-stage formation.

[0055] S4. Third-stage formation: Place the pouch-type lithium-ion battery after the second-stage formation into a hot-pressing formation cabinet, charge it at a constant current of 0.3C to 4.0V, with a charging time of 4h, to conduct the third-step formation; after the third-step formation is completed, place it on a vacuum-pumping and sealing device after returning to room temperature, conduct the third negative-pressure vacuum pumping and sealing; then send the sealed battery to a blast drying oven, age it at 45°C for 6h, to conduct the third aging, thus completing the entire formation process.

[0056] On the other hand, this embodiment provides a ternary pouch-type lithium-ion battery. The positive active material of this pouch-type ion battery is lithium nickel cobalt manganese oxide LiNi 0.5 Co 0.2 Mn 0.3 O₂, and the negative active material is artificial graphite. After injecting the liquid into this ternary pouch-type ion battery, conduct formation and aging according to the above process, and then obtain a ternary pouch-type lithium-ion battery.

[0057] Example 5

[0058] On the one hand, this embodiment provides a formation and aging process for a ternary pouch-type lithium-ion battery, including the following steps:

[0059] S1. Pre-aging: Place the NCM523-type ternary pouch-type ion battery after injecting the liquid in a blast drying oven for temperature-gradient shelving aging. First, age it at 50°C for 10h, then at 45°C for 4h, and finally at 35°C for 8h.

[0060] S2. First-stage formation: Move the aged pouch-type lithium-ion battery to a hot-pressing formation cabinet, set the preheating temperature to 55°C, the extrusion pressure of the battery to 0.1MPa, charge it at a constant current of 0.02C to 3.1V, with a charging time of 4h, to conduct the first-step formation; after the first-step formation is completed, place it on a vacuum-pumping and sealing device after returning to room temperature, conduct the first negative-pressure vacuum pumping and sealing; then send the sealed battery to a blast drying oven, first age it at 45°C for 10h, and then at 38°C for 6h, to conduct the first temperature-gradient aging, thus completing the first-stage formation.

[0061] S3. Second-stage formation: Place the pouch-type lithium-ion battery after the first-stage formation into a hot-pressing formation cabinet, charge it at a constant current of 0.08C to 3.5V, with a charging time of 5h, to conduct the second-step formation; after the second-step formation is completed, place it on a vacuum-pumping and sealing device after returning to room temperature, conduct the second negative-pressure vacuum pumping and sealing; then send the sealed battery to a blast drying oven, first age it at 45°C for 10h, and then at 45°C for 8h, to conduct the second temperature-gradient aging, thus completing the second-stage formation.

[0062] S4. Third-stage formation: Place the pouch-type lithium-ion battery after the second-stage formation into a hot-press formation cabinet, charge it at a constant current of 0.3C to 3.9V, with a charging time of 5h, to perform the third-step formation; after the third-step formation is completed, place it on a vacuum pumping and sealing device after restoring to room temperature, perform the third-time negative-pressure pumping and sealing; then send the sealed battery to a blast drying oven and age it at 50°C for 4h to perform the third-time aging, thus completing the entire formation process.

[0063] On the other hand, this embodiment provides a ternary pouch-type lithium-ion battery. The positive active material of this pouch-type ion battery is lithium nickel cobalt manganese oxide LiNi 0.5 Co 0.2 Mn 0.3 O2, and the negative active material is artificial graphite. After injecting the electrolyte into this ternary pouch-type ion battery, perform formation and aging according to the above process to obtain a ternary pouch-type lithium-ion battery.

[0064] Comparative Example 1

[0065] This comparative example provides a formation and aging process for a ternary pouch-type lithium-ion battery, including the following steps:

[0066] S1. Pre-aging: Place the NCM523-type ternary pouch-type ion battery after injecting the electrolyte in a blast drying oven for temperature-gradient shelf aging. First, age it at 55°C for 10h, then at 40°C for 8h, and finally at 30°C for 4h.

[0067] S2. First-stage formation: Move the aged pouch-type lithium-ion battery to a hot-press formation cabinet, set the preheating temperature to 45°C, the extrusion pressure of the battery to 0.2MPa, charge it at a constant current of 0.01C to 3.2V, with a charging time of 6h, to perform the first-step formation; after the first-step formation is completed, perform the first-time negative-pressure pumping and sealing after restoring to room temperature.

[0068] S3. Second-stage formation: Place the pouch-type lithium-ion battery after the first-stage formation into a hot-press formation cabinet, charge it at a constant current of 0.05C to 3.4V, with a charging time of 6h, to perform the second-step formation; after the second-step formation is completed, perform the second-time negative-pressure pumping and sealing after restoring to room temperature.

[0069] S4. Third-stage formation: Place the pouch-type lithium-ion battery after the second-stage formation into a hot-press formation cabinet, charge it at a constant current of 0.2C to 4.1V, with a charging time of 6h, to perform the third-step formation.

[0070] S5. Aging: After the third-step formation is completed, perform the third-time negative-pressure pumping and sealing after restoring to room temperature; then send the sealed battery to a blast drying oven and age it at 40°C for 8h, thus completing the entire formation process.

[0071] On the other hand, this comparative example provides a ternary soft-pack lithium-ion battery. The positive active material of this soft-pack ion battery is lithium nickel cobalt manganese oxide LiNi 0.5 Co 0.2 Mn 0.3 O2, and the negative active material is artificial graphite. After the ternary soft-pack ion battery is filled with electrolyte, formation and aging are carried out according to the above process to obtain a ternary soft-pack lithium-ion battery.

[0072] Comparative Example 2

[0073] This comparative example provides a formation and aging process for a ternary soft-pack lithium-ion battery, including the following steps:

[0074] S1. Pre-aging: The NCM523 type ternary soft-pack ion battery filled with electrolyte is aged at 50 °C for 24 h in a forced-air drying oven.

[0075] S2. First-stage formation: The aged soft-pack lithium-ion battery is transferred to a hot pressing formation cabinet. The preheating temperature is set at 45 °C, the extrusion pressure of the battery is 0.2 MPa, and it is charged at a constant current of 0.02C to 3.0 V for 6 h to carry out the first step of formation; after the first step of formation is completed, it is returned to room temperature and then the first negative pressure evacuation and sealing are carried out; then the sealed battery is sent to a forced-air drying oven, aged at 55 °C for 6 h first, and then aged at 40 °C for 10 h to carry out the first temperature gradient aging, that is, the first-stage formation is completed.

[0076] S3. Second-stage formation: The soft-pack lithium-ion battery formed in the first stage is placed in a hot pressing formation cabinet and charged at a constant current of 0.08C to 3.4 V for 6 h to carry out the second step of formation; after the second step of formation is completed, it is returned to room temperature, and then the second negative pressure evacuation and sealing are carried out; then the sealed battery is sent to a forced-air drying oven, aged at 45 °C for 8 h first, and then aged at 35 °C for 6 h to carry out the second temperature gradient aging, that is, the second-stage formation is completed.

[0077] S4. Third-stage formation: The soft-pack lithium-ion battery formed in the second stage is placed in a hot pressing formation cabinet and charged at a constant current of 0.3C to 3.9 V for 6 h to carry out the third step of formation; after the third step of formation is completed, it is returned to room temperature, and then the third negative pressure evacuation and sealing are carried out; then the sealed battery is sent to a forced-air drying oven and aged at 40 °C for 8 h to carry out the third aging, that is, the entire formation process is completed.

[0078] On the other hand, this comparative example provides a ternary soft-pack lithium-ion battery. The positive active material of this soft-pack ion battery is lithium nickel cobalt manganese oxide LiNi 0.5 Co 0.2 Mn 0.3The cathode active material is LiNiCoMnO₂ and the anode active material is artificial graphite. After the ternary soft-pack lithium-ion battery is filled with electrolyte, it is formed and aged according to the above process to obtain a ternary soft-pack lithium-ion battery.

[0079] Comparative Example 3

[0080] This comparative example provides a formation and aging process for a ternary soft-pack lithium-ion battery, including the following steps:

[0081] S1. Pre-aging: The NCM523 type ternary soft-pack lithium-ion battery filled with electrolyte is placed in a forced-draft drying oven for temperature-gradient shelving and aging. First, it is aged at 55 °C for 10 h, then at 40 °C for 8 h, and finally at 30 °C for 4 h.

[0082] S2. First-stage formation: The aged soft-pack lithium-ion battery is transferred to a hot-pressing formation cabinet. The preheating temperature is set at 45 °C, the extrusion pressure of the battery is 0.2 MPa, and it is charged at a constant current of 0.01C to 3.2 V for 6 h to perform the first step of formation; after the first step of formation is completed, it is cooled to room temperature and then sealed for the first time. Then, the sealed battery is sent to a forced-draft drying oven and aged at 55 °C for 6 h and then at 40 °C for 10 h to perform the first temperature-gradient aging, thus completing the first-stage formation.

[0083] S3. Second-stage formation: The soft-pack lithium-ion battery after the first-stage formation is placed in a hot-pressing formation cabinet and charged at a constant current of 0.05C to 3.4 V for 6 h to perform the second step of formation; after the second step of formation is completed, it is cooled to room temperature and then sealed for the second time. Then, the sealed battery is sent to a forced-draft drying oven and aged at 45 °C for 8 h and then at 35 °C for 6 h to perform the second temperature-gradient aging, thus completing the second-stage formation.

[0084] S4. Third-stage formation: The soft-pack lithium-ion battery after the second-stage formation is placed in a hot-pressing formation cabinet and charged at a constant current of 0.2C to 4.1 V for 6 h to perform the third step of formation; after the third step of formation is completed, it is cooled to room temperature and then sealed for the third time. Then, the sealed battery is sent to a forced-draft drying oven and aged at 40 °C for 8 h to perform the third aging, thus completing the entire formation process.

[0085] On the other hand, this comparative example provides a ternary soft-pack lithium-ion battery. The cathode active material of this soft-pack lithium-ion battery is LiNi 0.5 Co 0.2 Mn 0.3 O₂, and the anode active material is artificial graphite. After the ternary soft-pack lithium-ion battery is filled with electrolyte, it is formed and aged according to the above process to obtain a ternary soft-pack lithium-ion battery.

[0086] Test Example

[0087] The ternary soft-pack lithium-ion batteries prepared in Examples 1-5 and Comparative Examples 1-3 were subjected to formation, and then charged under constant current and constant voltage conditions on a Neware battery test cabinet to conduct high-temperature storage and high-temperature cycling tests.

[0088] Among them, the high-temperature storage conditions were: charging current: 1C, charging cut-off current: 0.05C, charging cut-off voltage: 4.35V, and high-temperature storage at 60°C for 7 days. The high-temperature cycling conditions were: cycling test temperature: 45°C, charging current: 1C, charging cut-off current: 0.05C, charging cut-off voltage: 4.35V, and discharging current: 1C.

[0089] The above high-temperature storage test results are as Figure 2 shown, and the high-temperature cycling test results are as Figure 3 shown. Combining Figure 2 、 Figure 3 It can be seen that compared with Comparative Examples 1-3, the ternary soft-pack lithium-ion batteries prepared in Examples 1-5 showed higher retention rates and recovery rates under high-temperature storage conditions. The retention rate could reach 98% and above, and the recovery rate could reach 100% and above, indicating that the SEI film on the surface of the electrode sheet was denser and more stable; at the same time, the ternary soft-pack lithium-ion batteries prepared in Examples 1-5 also showed good high-temperature cycling performance. At 45°C, the capacity retention rate was still maintained at 95% and above after 400 cycles.

[0090] Under the same high-temperature storage and high-temperature cycling test conditions as above, when the charging cut-off voltage was 4.3V, compared with Comparative Examples 1-3, the retention rate of the ternary soft-pack lithium-ion batteries prepared in Examples 1-5 could reach 98.3% and above under high-temperature storage conditions, the recovery rate could reach 100% and above, and the capacity retention rate was still maintained at 96.8% and above after 400 cycles; when the charging cut-off voltage was 4.4V, compared with Comparative Examples 1-3, the retention rate of the ternary soft-pack lithium-ion batteries prepared in Examples 1-5 could reach 97.5% and above under high-temperature storage conditions, the recovery rate could reach 100% and above, and the capacity retention rate was still maintained at 93.5% and above after 400 cycles. The above results show that at a high voltage state of 4.3-4.4V, in terms of high-temperature storage and high-temperature cycling, increasing the aging at different temperature gradients before cycle formation, the aging during formation, and the negative pressure evacuation can significantly improve the capacity retention rate and recovery rate.

[0091] The implementation principle of this application is as follows: This application adopts a three-stage stepped formation process. It conducts temperature gradient shelving and aging before formation, and the charging rate of each stage of formation increases in a stepped manner, effectively extending the charging time and enabling sufficient side reactions to occur inside the battery. At the same time, gas extraction and aging operations are added during each stage of formation. On the one hand, formation and aging are interspersed, promoting the formation of a more dense, uniform, and stable SEI film on the surface of the negative electrode by the electrode particles. On the other hand, it eliminates the possibility of side reactions occurring again during high-temperature shelving and charge-discharge cycling of the finished battery, thereby improving the high-temperature shelving and cycling performance of high-voltage system batteries.

[0092] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments or perform equivalent replacements for some of the technical features. However, such modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A formation and aging process for a ternary soft-pack lithium-ion battery, characterized in that: Including the following steps: S1. Pre-aging: The soft-packaged lithium-ion battery filled with liquid is placed for aging with a temperature gradient; the first gradient temperature A in the pre-aging step 11 is 45 - 55 °C, and the aging time is 10 - 14 h; the second gradient temperature A 12 is 35 - 45 °C, and the aging time is 4 - 8 h; the third gradient temperature A 13 is 30 - 35 °C, and the aging time is 4 - 10 h; S2. First-stage formation: At a preset temperature and pressure, the aged soft-pack lithium-ion battery is charged at a constant current of a first current to a first preset voltage for the first-step formation. After returning to room temperature, the first negative pressure evacuation and sealing are carried out, and then the first temperature gradient aging is carried out; the preset temperature is 40-55 °C, and the preset pressure is 0.1-0.3 MPa; the first current is 0.01-0.04 C, the first preset voltage is 3.0-3.2 V, and the charging time is 4-6 h; the first gradient temperature A of the first temperature gradient aging 21 is 45-55 °C, and the aging time is 6-10 h; the second gradient temperature A 22 is 35-45 °C, and the aging time is 6-10 h; S3. Second-stage formation: The soft-pack lithium-ion battery formed in the first stage is charged at a second constant current to a second preset voltage for the second-step formation. After returning to room temperature, a second negative-pressure air extraction and sealing are carried out, and then a second temperature-gradient aging is performed. The second current is 0.05 - 0.1C, the second preset voltage is 3.4 - 3.6V, and the charging time is 4 - 6h. The first gradient temperature A of the second temperature-gradient aging 31 is 45 - 55°C, and the aging time is 8 - 10h; the second gradient temperature A 32 is 35 - 45°C, and the aging time is 6 - 10h; S4. Third-stage formation: The soft-pack lithium-ion battery formed in the second stage is charged at a third constant current to a third preset voltage for the third-step formation. After returning to room temperature, the third negative-pressure air extraction and sealing are carried out, and then the third aging is carried out, thus completing the entire formation process; and the charging rates of the three-stage formation gradually increase; the third current is 0.2-0.4C, the third preset voltage is 3.9-4.1V, and the charging time is 4-6h; the temperature of the third aging is 40-55°C, and the aging time is 4-8h.

2. A ternary soft-pack lithium-ion battery prepared by using the formation and aging process as described in claim 1.

3. A ternary soft-pack lithium-ion battery according to claim 2, characterized in that: The positive electrode active material of the soft-packaged ion battery is lithium nickel cobalt manganese oxide LiNi x Co y Mn Z O2, where 0.5 ≤ x ≤ 0.7; 0.02 ≤ y ≤ 0.2; 0.1 ≤ z ≤ 0.48, and x + y + z = 1; the negative electrode active material is artificial graphite.

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