A method for forming a lithium-ion battery

Abstract

The present invention discloses a formation method for a lithium-ion battery, which comprises the following steps: S1. First, perform constant-power charging, and set the cut-off capacity to 1.2-1.4 times the rated capacity; S2. Then, perform constant-voltage charging for 3.5-4.5 hours; S3. Perform constant-power charge and discharge, and the rated discharge hour rate of the battery is 0.9-1.1; S4. Then, perform constant-voltage discharge for 3.5-4.5 hours; S5. Perform constant-power charging, and the rated charge hour rate of the battery is 0.9-1.1; S6. Perform constant-voltage charging for 3.5-4.5 hours, and the formation is completed. After the formation process of the battery is optimized, the quality of the battery is higher, the self-discharge rate is reduced by 20%, the capacity is increased by 3%, and the cycle life is normal, solving the problems in the prior art that long-time formation consumes a large amount of electric energy, and shortening the formation time reduces the production cost of the battery.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium-ion batteries, and particularly relates to a method for forming a lithium-ion battery. Background Art

[0002] Lithium-ion batteries made of different materials adopt different methods. Before forming, the battery already has all the required materials. The forming process is a process of activating the battery capacity. If an accident occurs during the forming process, all previous efforts will be wasted, resulting in obvious economic losses. The battery composed of a negative electrode sheet made of lithium titanate material as the active substance and a ternary material positive electrode sheet requires a longer time and a higher ambient temperature during the forming process. A large amount of electric energy is consumed during the forming process. Summary of the Invention

[0003] The purpose of the present invention is to provide a method for forming a lithium-ion battery to solve the problems in the background art.

[0004] To achieve the above purpose, the specific technical solution of a method for forming a lithium-ion battery of the present invention is as follows:

[0005] A method for forming a lithium-ion battery includes the following steps:

[0006] S1. After the temperature reaches 82 - 88 °C, first perform constant power charging. The rated charging hour rate of the battery is 0.9 - 1.1, the charging cut-off voltage is 1.1 - 1.3 times the rated voltage, and the cut-off capacity is set to 1.2 - 1.4 times the rated capacity;

[0007] S2. Then perform constant voltage charging for 3.5 - 4.5 hours, and then stand still for 8 - 12 minutes;

[0008] S3. Perform constant power charge and discharge. The rated discharge hour rate of the battery is 0.9 - 1.1, the discharge cut-off voltage is 0.7 - 0.9 times the minimum voltage, and the cut-off capacity is set to 1.1 - 1.3 times the rated capacity;

[0009] S4. Then perform constant voltage discharge for 3.5 - 4.5 hours, and then stand still for 8 - 12 minutes;

[0010] S5. Perform constant power charging. The rated charging hour rate of the battery is 0.9 - 1.1, the charging cut-off voltage is 1.1 - 1.3 times the rated voltage, and the cut-off capacity is set to 1.1 - 1.2 times the rated capacity;

[0011] S6. Perform constant voltage charging for 3.5 - 4.5 hours, and then stand still for 8 - 12 minutes, and the forming ends.

[0012] Further, before the step S1, the following steps are further included:

[0013] S01. Fabrication of the positive electrode sheet: Select ternary materials, use NMP as the solvent, and obtain the positive electrode slurry after stirring evenly. The final positive electrode sheet is prepared through steps such as coating, rolling, and slitting in sequence;

[0014] S02. Fabrication of the negative electrode sheet: Select lithium titanate materials, use NMP as the solvent, and obtain the negative electrode slurry after stirring evenly. The final negative electrode sheet is prepared through steps such as coating, rolling, and slitting in sequence;

[0015] S03. Baking: Place the positive electrode sheet and the negative electrode sheet obtained in steps S01 and S02 in an environment with a temperature of 117 - 123 °C, a relative humidity less than or equal to 25% RH, and a vacuum degree less than or equal to -0.098 MPa for baking for 24 hours;

[0016] S04. Winding: Adopt the method of winding with the positive electrode sheet wrapping the negative electrode sheet. After winding is completed, shape the full tab and conduct an insulation withstand voltage test and weigh the battery cell simultaneously;

[0017] S05. Welding: Weld the positive electrode sheet and the negative electrode sheet at the corresponding positions of the battery in an environment with a temperature of 22 - 28 °C and a relative humidity less than or equal to 15% RH;

[0018] S06. Liquid injection: Conduct the first liquid injection in an environment with a temperature of 22 - 28 °C and a relative humidity less than or equal to 1% RH, with a liquid injection volume of 128 - 132 g. Let it stand for 12 hours at a temperature of 22 - 28 °C, then conduct the second liquid injection with a liquid injection volume of 78 - 82 g. The battery after liquid injection is left to stand for 48 hours in an environment with a temperature of 22 - 28 °C.

[0019] Furthermore, in step S01, the stirring temperature environment of the positive electrode sheet is 22 - 28 °C, and the relative humidity is less than or equal to 15% RH.

[0020] Furthermore, in step S02, the stirring temperature environment of the negative electrode sheet is 22 - 28 °C, and the relative humidity is less than or equal to 15% RH.

[0021] Furthermore, in step S04, the winding environmental temperature is 22 - 28 °C, and the relative humidity is less than or equal to 15% RH.

[0022] Furthermore, after step S6 formation is completed, the following steps are also included:

[0023] S7. Sealing: After formation is completed, seal the battery liquid injection port with a steel column in an environment with a temperature of 22 - 28 °C and a relative humidity less than or equal to 1% RH;

[0024] S8. Formation: After charging the sealed battery in a 1C charge-discharge cycle for 2 cycles, the battery is charged to a half-charged state for formation, which is carried out in an environment with a temperature of 20 - 30°C and a relative humidity less than or equal to 50%RH.

[0025] S9. Battery Aging: The formed battery is left standing for 5 days in an environment with a temperature of 42 - 48°C and a relative humidity less than or equal to 50%RH for aging test.

[0026] S10. OCV Test: Select battery products that have passed the aging test, test the batteries according to the national standard, and pack and store the batteries that meet the standards.

[0027] Compared with the prior art, the present invention has the following beneficial effects: The formation time is shortened, which can save a large amount of electric energy. After the formation process of the battery is optimized, the battery quality is higher, the self-discharge rate is reduced by 20%, the capacity is increased by 3%, and the cycle life is normal. It solves the problem that in the prior art, long-time formation requires a large amount of electric energy consumption, and shortening the formation time reduces the production cost of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a schematic block diagram of the process of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0029] In order to better understand the purpose, structure and function of the present invention, the following is combined with the attached Figure 1 , for the understanding of the present invention.

[0030] Embodiment 1

[0031] A method for forming a lithium-ion battery includes the following steps:

[0032] S1. When the temperature reaches 82°C, first perform constant-power charging. The rated charging hour rate of the battery is 0.9, the charging cut-off voltage is 1.1 times the rated voltage, and the cut-off capacity is set to 1.2 times the rated capacity.

[0033] S2. Then perform constant-voltage charging for 3.5 hours and then let it stand for 8 minutes.

[0034] S3. Perform constant-power charge and discharge. The rated discharge hour rate of the battery is 0.9, the discharge cut-off voltage is 0.7 times the minimum voltage, and the cut-off capacity is set to 1.1 times the rated capacity.

[0035] S4. Then perform constant-voltage discharge for 3.5 hours and then let it stand for 8 minutes.

[0036] S5. Perform constant-power charging. The rated charging hour rate of the battery is 0.9, the charging cut-off voltage is 1.1 times the rated voltage, and the cut-off capacity is set to 1.1 times the rated capacity.

[0037] S6. Adopt constant voltage charging for 3.5 hours, then stand still for 8 minutes to complete formation.

[0038] Before the step S1, the following steps are further included:

[0039] S01. Production of the positive electrode sheet: Select ternary materials, use NMP as the solvent, and obtain the positive electrode slurry after stirring evenly. Then, through steps such as coating, rolling, and slitting, the final positive electrode sheet is obtained. The stirring temperature environment of the positive electrode sheet is 22°C, and the relative humidity is less than or equal to 15%RH;

[0040] S02. Production of the negative electrode sheet: Select lithium titanate materials, use NMP as the solvent, and obtain the negative electrode slurry after stirring evenly. Then, through steps such as coating, rolling, and slitting, the final negative electrode sheet is obtained. The stirring temperature environment of the negative electrode sheet is 22°C, and the relative humidity is less than or equal to 15%RH;

[0041] S03. Baking: Place the positive electrode sheet and the negative electrode sheet obtained in steps S01 and S02 in an environment with a temperature of 117°C, a relative humidity less than or equal to 25%RH, and a vacuum degree less than or equal to -0.098MPa for baking for 24 hours;

[0042] S04. Winding: Adopt the method of wrapping the negative electrode sheet with the positive electrode sheet for winding. After winding is completed, shape the full pole ear, and at the same time, conduct an insulation withstand voltage test and weigh the battery cell. The winding environment temperature is 22°C, and the relative humidity is less than or equal to 15%RH;

[0043] S05. Welding: In an environment with a temperature of 22°C and a relative humidity less than or equal to 15%RH, weld the positive electrode sheet and the negative electrode sheet at the corresponding positions of the battery;

[0044] S06. Liquid injection: For the first liquid injection, in an environment with a temperature of 22°C and a relative humidity less than or equal to 1%RH, the liquid injection amount is 128g. Stand still for 12 hours at 22°C, then conduct the second liquid injection, and the liquid injection amount is 78g. The battery after liquid injection stands still for 48 hours in an environment with a temperature of 22°C.

[0045] After the step S6 formation is completed, the following steps are further included:

[0046] S7. Sealing: After the formation is completed, use a steel column to seal the battery liquid injection port in an environment with a temperature of 22°C and a relative humidity less than or equal to 1%RH;

[0047] S8. Capacity grading: After charging the sealed battery for 2 cycles of 1C charge and discharge, charge the battery to half charge state for capacity grading, which is carried out in an environment with a temperature of 20°C and a relative humidity less than or equal to 50%RH;

[0048] S9. Battery Aging: The batteries after capacitance grading are left standing for 5 days in an environment with a temperature of 42 °C and a relative humidity less than or equal to 50% RH for aging test;

[0049] S10. OCV Test: Select the battery products that pass the aging test, test the batteries according to the national standard, and pack and store the batteries that meet the standards in the warehouse.

[0050] Example 2

[0051] A lithium-ion battery formation method includes the following steps:

[0052] S1. After the temperature reaches 85 °C, constant power charging is first carried out. The rated charging hour rate of the battery is 1, the charging cut-off voltage is 1.2 times the rated voltage, and the cut-off capacity is set to 1.3 times the rated capacity;

[0053] S2. Then constant voltage charging is carried out for 4 hours, and then left standing for 10 minutes;

[0054] S3. Constant power charge and discharge are carried out. The rated discharge hour rate of the battery is 1, the discharge cut-off voltage is 0.8 times the minimum voltage, and the cut-off capacity is set to 1.2 times the rated capacity;

[0055] S4. Then constant voltage discharge is carried out for 4 hours, and then left standing for 10 minutes;

[0056] S5. Constant power charging is carried out. The rated charging hour rate of the battery is 1, the charging cut-off voltage is 1.2 times the rated voltage, and the cut-off capacity is set to 1.15 times the rated capacity;

[0057] S6. Constant voltage charging is carried out for 4 hours, and then left standing for 10 minutes, and the formation is completed.

[0058] Before the step S1, the following steps are further included:

[0059] S01. Production of the positive electrode sheet: Select ternary materials, use NMP as the solvent, stir evenly to obtain the positive electrode slurry, and finally obtain the positive electrode sheet through steps such as coating, rolling, and slitting. The stirring temperature environment of the positive electrode sheet is 25 °C, and the relative humidity is less than or equal to 15% RH;

[0060] S02. Production of the negative electrode sheet: Select lithium titanate materials, use NMP as the solvent, stir evenly to obtain the negative electrode slurry, and finally obtain the negative electrode sheet through steps such as coating, rolling, and slitting. The stirring temperature environment of the negative electrode sheet is 25 °C, and the relative humidity is less than or equal to 15% RH;

[0061] S03. Baking: Place the positive electrode sheet and the negative electrode sheet obtained in steps S01 and S02 in an environment with a temperature of 120 °C, a relative humidity less than or equal to 25% RH, and a vacuum degree less than or equal to -0.098 MPa and bake for 24 hours;

[0062] S04. Winding: Adopt the method of winding with the positive electrode sheet wrapping the negative electrode sheet. After winding is completed, shape the full tab, and at the same time conduct an insulation withstand voltage test and weigh the battery cell. The ambient temperature for winding is 25 °C, and the relative humidity is less than or equal to 15% RH;

[0063] S05. Welding: Weld the positive electrode sheet and the negative electrode sheet at the corresponding positions of the battery in an environment with a temperature of 25 °C and a relative humidity less than or equal to 15% RH;

[0064] S06. Liquid injection: Conduct the first liquid injection in an environment with a temperature of 25 °C and a relative humidity less than or equal to 1% RH. The liquid injection volume is 130 g. Let it stand for 12 hours at 25 °C, and then conduct the second liquid injection. The liquid injection volume is 80 g. The battery after liquid injection is left standing for 48 hours at 25 °C.

[0065] After step S6 formation is completed, the following steps are further included:

[0066] S7. Sealing: After formation is completed, use a steel column to seal the liquid injection port of the battery in an environment with a temperature of 25 °C and a relative humidity less than or equal to 1% RH;

[0067] S8. Capacity grading: After the battery is sealed, charge it with a charging process of 1C charge and discharge for 2 cycles, and then charge the battery to a half-charged state for capacity grading, which is carried out in an environment with a temperature of 25 °C and a relative humidity less than or equal to 50% RH;

[0068] S9. Battery aging: Let the battery after capacity grading stand for 5 days at a temperature of 45 °C and a relative humidity less than or equal to 50% RH for aging test;

[0069] S10. OCV test: Select the battery products that have passed the aging test, test the batteries according to the national standard, and pack and store the batteries that meet the standards in boxes.

[0070] Example 3

[0071] A lithium-ion battery formation method includes the following steps:

[0072] S1. When the temperature reaches 88 °C, first conduct constant-power charging. The rated charging hour rate of the battery is 1.1, the charging cut-off voltage is 1.3 times the rated voltage, and the cut-off capacity is set to 1.4 times the rated capacity;

[0073] S2. Then conduct constant-voltage charging for 4.5 hours and then let it stand for 12 minutes;

[0074] S3. Adopt constant power charge and discharge. The rated discharge hour rate of the battery is 1.1. The discharge cut-off voltage is 0.9 times the minimum voltage, and the cut-off capacity is set to 1.3 times the rated capacity.

[0075] S4. Then adopt constant voltage discharge for 4.5 hours and then stand still for 12 minutes.

[0076] S5. Conduct constant power charge. The rated charge hour rate of the battery is 1.1. The charge cut-off voltage is 1.3 times the rated voltage, and the cut-off capacity is set to 1.2 times the rated capacity.

[0077] S6. Adopt constant voltage charge for 4.5 hours and then stand still for 12 minutes to complete formation.

[0078] Before the step S1, the following steps are further included:

[0079] S01. Fabrication of the positive electrode sheet: Select ternary materials, use NMP as the solvent, and obtain the positive electrode slurry after stirring evenly. The final positive electrode sheet is obtained through steps such as coating, rolling, and slitting. The stirring temperature environment of the positive electrode sheet is 28°C, and the relative humidity is less than or equal to 15%RH.

[0080] S02. Fabrication of the negative electrode sheet: Select lithium titanate materials, use NMP as the solvent, and obtain the negative electrode slurry after stirring evenly. The final negative electrode sheet is obtained through steps such as coating, rolling, and slitting. The stirring temperature environment of the negative electrode sheet is 28°C, and the relative humidity is less than or equal to 15%RH.

[0081] S03. Baking: Place the positive electrode sheet and negative electrode sheet obtained in steps S01 and S02 in an environment with a temperature of 123°C, a relative humidity less than or equal to 25%RH, and a vacuum degree less than or equal to -0.098MPa for baking for 24 hours.

[0082] S04. Winding: Adopt the method of winding the positive electrode sheet around the negative electrode sheet. After winding, shape the full pole ear, and at the same time conduct insulation withstand voltage test and weigh the battery cell. The winding environment temperature is 28°C, and the relative humidity is less than or equal to 15%RH.

[0083] S05. Welding: Weld the positive electrode sheet and negative electrode sheet at the corresponding positions of the battery in an environment with a temperature of 28°C and a relative humidity less than or equal to 15%RH.

[0084] S06. Liquid injection: Conduct the first liquid injection in an environment with a temperature of 28°C and a relative humidity less than or equal to 1%RH. The liquid injection amount is 132g. Stand still for 12 hours at 28°C, and then conduct the second liquid injection. The liquid injection amount is 82g. The battery after liquid injection stands still for 48 hours at 28°C.

[0085] After the conversion in step S6 is completed, the following steps are further included:

[0086] S7. Sealing: After the conversion is completed, use a steel column to seal the battery liquid injection port in an environment with a temperature of 28°C and a relative humidity less than or equal to 1%RH;

[0087] S8. Formation: After the battery is sealed, charge the battery for 2 cycles with a charge and discharge rate of 1C, and then charge the battery to a half-charged state for formation, which is carried out in an environment with a temperature of 30°C and a relative humidity less than or equal to 50%RH;

[0088] S9. Battery aging: Let the formed battery stand for 5 days in an environment with a temperature of 48°C and a relative humidity less than or equal to 50%RH for aging test;

[0089] S10. OCV test: Select the battery products that pass the aging test, test the batteries according to the national standard, and pack and store the batteries that meet the standards.

[0090] This lithium-ion battery conversion method shortens the conversion time, can save a large amount of electric energy, and the battery conversion process is optimized, so that the battery has higher quality, the self-discharge rate is reduced by 20%, the capacity is increased by 3%, and the cycle life is normal, solving the problem that in the prior art, long-time conversion consumes a large amount of electric energy, and shortening the conversion time reduces the production cost of the battery.

[0091] It can be understood that the present invention is described through some embodiments. Those skilled in the art know that without departing from the spirit and scope of the present invention, various changes or equivalent replacements can be made to these features and embodiments. In addition, under the teaching of the present invention, these features and embodiments can be modified to adapt to specific situations and materials without departing from the spirit and scope of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application belong to the scope protected by the present invention.

Claims

1. A method for forming a lithium-ion battery, characterized in that, It includes the following steps: S1. After the temperature reaches 82 - 88 °C, first perform constant - power charging. The rated charging hour rate of the battery is 0.9 - 1.1, the charging cut - off voltage is 1.1 - 1.3 times the rated voltage, and the cut - off capacity is set to 1.2 - 1.4 times the rated capacity; S2. Then perform constant - voltage charging for 3.5 - 4.5 hours, and then let it stand for 8 - 12 minutes; S3. Perform constant - power discharging. The rated discharging hour rate of the battery is 0.9 - 1.1, the discharging cut - off voltage is 0.7 - 0.9 times the minimum voltage, and the cut - off capacity is set to 1.1 - 1.3 times the rated capacity; S4. Then perform constant - voltage discharging for 3.5 - 4.5 hours, and then let it stand for 8 - 12 minutes; S5. Perform constant - power charging. The rated charging hour rate of the battery is 0.9 - 1.1, the charging cut - off voltage is 1.1 - 1.3 times the rated voltage, and the cut - off capacity is set to 1.1 - 1.2 times the rated capacity; S6. Perform constant - voltage charging for 3.5 - 4.5 hours, and then let it stand for 8 - 12 minutes, and the formation is completed.

2. The formation method of the lithium-ion battery according to claim 1, wherein Before the step S1, there are also the following steps; S01. Fabrication of the positive electrode sheet: Select ternary materials, use NMP as the solvent, and obtain the positive electrode slurry after stirring evenly. The final positive electrode sheet is obtained through the steps of coating, rolling, and slitting in sequence; S02. Fabrication of the negative electrode sheet: Select lithium titanate materials, use NMP as the solvent, and obtain the negative electrode slurry after stirring evenly. The final negative electrode sheet is obtained through the steps of coating, rolling, and slitting in sequence; S03. Baking: Place the positive electrode sheet and negative electrode sheet obtained in steps S01 and S02 in an environment with a temperature of 117 - 123 °C, a relative humidity less than or equal to 25%RH, and a vacuum degree less than or equal to - 0.098 MPa for baking for 24 hours; S04. Winding: Adopt the method of winding the positive electrode sheet around the negative electrode sheet. After winding is completed, shape the full - pole ear, and at the same time perform an insulation withstand voltage test and weigh the battery cell; S05. Welding: In an environment with a temperature of 22 - 28 °C and a relative humidity less than or equal to 15%RH, weld the positive electrode sheet and the negative electrode sheet at the corresponding positions of the battery; S06. Liquid injection: In an environment with a temperature of 22 - 28 °C and a relative humidity less than or equal to 1%RH, perform the first liquid injection with a liquid injection volume of 128 - 132 g, let it stand for 12 hours at a temperature of 22 - 28 °C, then perform the second liquid injection with a liquid injection volume of 78 - 82 g, and the battery after liquid injection is left to stand for 48 hours in an environment with a temperature of 22 - 28 °C.

3. The formation method of the lithium-ion battery according to claim 2, wherein, In the step S01, the stirring temperature environment of the positive electrode sheet is 22 - 28 °C, and the relative humidity is less than or equal to 15%RH.

4. The formation method of the lithium-ion battery according to claim 2, wherein, In the step S02, the stirring temperature environment of the negative electrode sheet is 22 - 28 °C, and the relative humidity is less than or equal to 15%RH.

5. The formation method of the lithium-ion battery according to claim 2, wherein In the step S04, the winding environment temperature is 22 - 28 °C, and the relative humidity is less than or equal to 15%RH.

6. The formation method of the lithium-ion battery according to claim 1, wherein After the step S6 formation is completed, there are also the following steps: S7. Sealing: After formation is completed, the liquid injection port of the battery is sealed using a steel column in an environment with a temperature of 22 - 28°C and a relative humidity less than or equal to 1% RH; S8. Capacity grading: After the battery is sealed, it is charged with a 1C charge and discharge for 2 cycles, and then the battery is charged to half charge state for capacity grading, which is carried out in an environment with a temperature of 20 - 30°C and a relative humidity less than or equal to 50% RH; S9. Battery aging: The capacity - graded battery is left standing for 5 days in an environment with a temperature of 42 - 48°C and a relative humidity less than or equal to 50% RH for aging test; S10. OCV test: Select the battery products that pass the aging test, test the batteries according to the national standard, and pack and store the qualified batteries in the warehouse.

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