Lithium-ion battery formation method

Abstract

The invention relates to the technical field of batteries, and discloses a lithium ion battery formation method, comprising the following steps: setting the initial thickness T0 of the battery, the first target thickness T1 of the battery, performing the first stage formation on the battery, setting the temperature C1, the current A1 and the time t1 of the first stage formation; performing the second stage formation on the obtained battery, setting the second target thickness T2 of the battery, raising the temperature of the second stage formation to C2, keeping the temperature for a time t2, and increasing the current of the second stage formation to A2; performing the third stage formation on the obtained battery, setting the third target thickness T3 of the battery, raising the temperature of the third stage formation to C3, keeping the temperature for a time t3, and increasing the current of the third stage formation to A3; performing the fourth stage formation on the obtained battery, setting the fourth target thickness T4 of the battery, lowering the temperature of the fourth stage formation to C4, keeping the temperature for a time t4, and reducing the current of the fourth stage formation to A4. The method can improve the thickness consistency, capacity consistency and cycle performance of the battery after formation.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and in particular to a lithium ion battery formation method. Background Art

[0002] Lithium batteries have the advantages of high voltage, high specific energy, long charge and discharge life, safety and environmental protection, etc. Therefore, they are widely used in various electronic products (such as mobile phones, digital cameras, laptops, power tools), portable small appliances, electric vehicles and energy storage systems.

[0003] The preparation process of lithium batteries is complicated, including stirring, coating, drying, bare cell preparation, packaging and formation. Among them, the formation process is an indispensable step in the lithium battery preparation process and plays a vital role in the performance of lithium batteries.

[0004] At present, the formation process of lithium batteries is to encapsulate the bare battery cell into a shell, then quantitatively inject electrolyte, and then form it after a period of standing. However, this formation process is complicated, and there are many factors that need to be controlled. The entire formation process requires a lot of time and operators, which wastes a lot of cost and process time. The interface of lithium-ion batteries treated by traditional constant temperature and constant current formation methods is not good, and many black spots and lithium precipitation are prone to occur. It is difficult to improve the capacity consistency, thickness consistency and electrical performance. In view of this, it is indeed necessary to provide a fast, simple and lithium battery formation method that can improve the performance of lithium batteries. Summary of the invention

[0005] The purpose of the present invention is to overcome the shortcomings of the prior art, on the one hand to provide a lithium ion battery formation method which is quick and easy to operate and can improve the performance of the lithium battery, and on the other hand to provide a lithium ion battery prepared by the method.

[0006] The objective of the present invention is achieved through the following technical solutions:

[0007] One aspect of the present invention provides a lithium ion battery formation method, comprising the following steps:

[0008] (1) setting the initial thickness of the battery to T0, setting the first target thickness of the battery to T1, performing a first stage of formation on the battery, and setting the temperature of the first stage of formation to C1, the current to A1, and the time to t1;

[0009] (2) performing a second stage formation on the battery obtained in step (1), setting a second target thickness of the battery to T2, raising the temperature of the second stage formation to C2, keeping the temperature for t2, and increasing the current of the second stage formation to A2;

[0010] (3) performing a third stage formation on the battery obtained in step (2), setting a third target thickness of the battery to T3, raising the temperature of the third stage formation to C3, keeping the temperature for t3, and increasing the current of the third stage formation to A3;

[0011] (4) Performing a fourth stage formation on the battery obtained in step (3), setting a fourth target thickness of the battery to T4, lowering the temperature of the fourth stage formation to C4, keeping the temperature for t4, and reducing the current of the fourth stage formation to A4.

[0012] In one embodiment, in steps (1) to (4), T0-T4=(0.8~1.2)mm.

[0013] In one embodiment, the temperature C1 of the first stage of step (1) is 45-55°C, the current A1 is 0.2-0.3°C, and the time t1 is 3-7 min; the temperature C2 of the second stage of step (2) is 60-70°C, the current A2 is 0.4-0.5°C, and the time t2 is 6-10 min; the temperature C3 of the third stage of step (3) is 75-85°C, the current A3 is 0.8-1.0°C, and the time t3 is 15-25 min; the temperature C4 of the fourth stage of step (4) is 45-55°C, the current A4 is 0.2-0.3°C, and the time t4 is 35-45 min.

[0014] In one embodiment, the temperatures C1, C2, C3, and C4 of the first, second, third, and fourth stages of formation are 45 to 85° C., the currents A1, A2, A3, and A4 of the first, second, third, and fourth stages of formation are 0.2 to 1.0° C., and the times t1, t2, t3, and t4 of the first, second, third, and fourth stages of formation are 3 to 45 min; wherein C2=C1+15, C3=C2+15, C4=C1, A2=A1+0.2, A3=2A2, A4=A1, t2=2t1, t3=2.5t2,

[0015] In one embodiment, while the first stage of formation is being carried out in step (1), transverse and longitudinal vibrations are also carried out, with a vibration frequency of 15 to 25 Hz and a vibration time of 1 / 2t1.

[0016] In one embodiment, the temperature increase in step (2) is to pass dry high-temperature gas to increase the temperature of the second stage of formation to C2, while controlling the dew point to td1; the temperature increase in step (3) is to pass dry high-temperature gas to increase the temperature of the third stage of formation to C3, while continuing to control the dew point to td2; the temperature reduction in step (4) is to pass dry room-temperature gas to reduce the temperature of the fourth stage of formation to C4; wherein td1=td2=(-42 to -48)°C.

[0017] In one embodiment, steps (1) to (4) are performed in a formation cabinet, which includes a cabinet shell, a carrying device, a formation charge and discharge system, a time control system, a temperature control system, a humidity control system, a circulation ventilation system, and a transverse and longitudinal vibration system. The carrying device is arranged in the cabinet shell, and the carrying device is used to accommodate and install batteries. The formation charge and discharge system is electrically connected to the carrying device, and is used to charge and discharge the battery and control the current of charging and discharging. The time control system and the temperature control system are both electrically connected to the formation charge and discharge system, and are used to control the temperature and time of charging and discharging. The transverse and longitudinal vibration system is connected to the carrying device, and is used to subject the battery to transverse and longitudinal vibration. The circulation ventilation system is connected to the cabinet shell, and is used to introduce external dry gas and discharge internal humid gas. The temperature control system and the humidity control system are both connected to the circulation ventilation system, and are used to control the temperature and dew point temperature inside the cabinet shell.

[0018] Another aspect of the present invention provides a lithium ion battery prepared by any of the above-mentioned lithium ion battery formation methods.

[0019] Compared with the prior art, the present invention has at least the following advantages:

[0020] 1. The formation method of the present invention performs segmented charging on the lithium ion battery, adopts charging formation in four stages of variable temperature, variable current and decreasing thickness limit, wherein the temperature variation rule is heating, heating again and cooling down in sequence, and the current variation rule is current increase, current increase again and current reduction in sequence. Experimental verification shows that under substantially the same or similar parameters, compared with the traditional constant temperature and constant current formation method, the lithium ion battery finally obtained after such treatment has no black spots and lithium precipitation, has a good interface, and can improve capacity consistency, thickness consistency and cycle performance.

[0021] 2. The traditional constant temperature and constant current formation method is mature, and even if the parameters such as temperature, current and time are adjusted many times, the performance of the battery after formation cannot be further improved. The four-stage formation of the present invention uses specific temperature, current, time and battery target thickness in each stage of formation. This is a breakthrough made by the inventor through creative labor. The inventor found that according to the algorithmic relationship between the battery target thickness of the first stage formation, the second stage formation, the third stage formation and the fourth stage formation specified in the present invention, the battery target thickness of each stage formation is calculated; on this basis, the algorithmic relationship between the temperature, current and time of the first stage formation, the second stage formation, the third stage formation and the fourth stage formation specified in the present invention is used, and the temperature, current and time of each stage formation are calculated. The prepared lithium ion battery has improved in capacity consistency, thickness consistency and cycle performance. This is valuable in the current lithium ion battery formation method is mature, and it is difficult to further improve the material performance by optimizing the parameters in the preparation step.

[0022] 3. The formation method of the present invention, in step (1), starts the transverse and longitudinal vibration system, so that the lithium ion battery is subjected to transverse and longitudinal vibration during the charging and forming process, and the transverse and longitudinal vibrations are used to assist the charging and forming, thereby increasing the wetting angle between the electrolyte and the material, allowing the electrolyte to more fully infiltrate the pores of the battery cell electrode, thereby increasing the charging and forming speed of the battery and significantly shortening the time of the first stage of formation.

[0023] 4. Ordinary formation cabinets use heating devices such as electric heating wires to heat up the internal environment of the cabinet. Generally speaking, the closer the object is to the heating device, the greater the heat it receives, and the farther the object is from the heating device, the less heat it receives. There are common problems of uneven heating and high humidity in the internal environment, which leads to battery polarization. The formation method of the present invention, during the second stage formation and the third stage formation, introduces dry high-temperature gas to uniformly heat the battery, and during the fourth stage formation, introduces dry room-temperature gas to uniformly cool the battery, ensuring that the internal temperature of the battery is consistent with the ambient temperature, and taking away the internal environmental water vapor through the circulating flow, so that the internal environmental humidity is reduced, and the battery polarization is significantly reduced from these two aspects, thereby improving the cycle performance of the lithium ion battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0025] Figure 1The present invention is a flowchart of a lithium-ion battery formation method according to one embodiment of the present invention. DETAILED DESCRIPTION

[0026] The following describes the embodiments of the present invention through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention.

[0027] Unless otherwise specified, the following examples and comparative examples are parallel tests, using the same processing steps, processing equipment and condition parameters.

[0028] Example 1

[0029] The lithium ion battery formation method comprises the following steps:

[0030] (1) setting the initial thickness of the battery to T0, setting the first target thickness of the battery to T1, performing a first stage of formation on the battery, and setting the temperature of the first stage of formation to C1, the current to A1, and the time to t1;

[0031] (2) performing a second stage formation on the battery obtained in step (1), setting a second target thickness of the battery to T2, raising the temperature of the second stage formation to C2, keeping the temperature for t2, and increasing the current of the second stage formation to A2;

[0032] (3) performing a third stage formation on the battery obtained in step (2), setting a third target thickness of the battery to T3, raising the temperature of the third stage formation to C3, keeping the temperature for t3, and increasing the current of the third stage formation to A3;

[0033] (4) Performing a fourth stage formation on the battery obtained in step (3), setting a fourth target thickness of the battery to T4, lowering the temperature of the fourth stage formation to C4, keeping the temperature for t4, and reducing the current of the fourth stage formation to A4.

[0034] (5) After charging is completed, the battery obtained in step (4) is evacuated, sealed and capacity divided.

[0035] While the first stage of formation is being carried out in step (1), transverse and longitudinal vibrations are also carried out, with a vibration frequency of 15 to 25 Hz and a vibration time of 1 / 2t1 = 1.5 min.

[0036] In steps (1) to (4), T0-T4=(0.8-1.2) mm. In this embodiment, T0=6 mm, T4=5.2 mm, and the calculated values ​​are T1=5.8 mm, T2=5.6 mm, and T3=5.4 mm.

[0037] The temperatures C1, C2, C3, and C4 of the first, second, third, and fourth stages of formation are 45 to 85° C., the currents A1, A2, A3, and A4 of the first, second, third, and fourth stages of formation are 0.2 to 1.0° C., and the times t1, t2, t3, and t4 of the first, second, third, and fourth stages of formation are 3 to 45 minutes; wherein C2=C1+15, C3=C2+15, C4=C1, A2=A1+0.2, A3=2A2, A4=A1, t2=2t1, t3=2.5t2, In this embodiment, the temperature C1 of the first stage is 45°C, the current A1 is 0.2C, and the time t1 is 3min. The temperature C2 of the second stage is 60°C, the current A2 is 0.4C, and the time t2 is 6min. The temperature C3 of the third stage is 75°C, the current A3 is 0.8C, and the time t3 is 15min. The temperature C4 of the fourth stage is 45°C, the current A4 is 0.2C, and the time t4 is 30min.

[0038] Example 2

[0039] The lithium ion battery formation method comprises the following steps:

[0040] (1) setting the initial thickness of the battery to T0, setting the first target thickness of the battery to T1, performing a first stage of formation on the battery, and setting the temperature of the first stage of formation to C1, the current to A1, and the time to t1;

[0041] (2) performing a second stage formation on the battery obtained in step (1), setting a second target thickness of the battery to T2, raising the temperature of the second stage formation to C2, keeping the temperature for t2, and increasing the current of the second stage formation to A2;

[0042] (3) performing a third stage formation on the battery obtained in step (2), setting a third target thickness of the battery to T3, raising the temperature of the third stage formation to C3, keeping the temperature for t3, and increasing the current of the third stage formation to A3;

[0043] (4) Performing a fourth stage formation on the battery obtained in step (3), setting a fourth target thickness of the battery to T4, lowering the temperature of the fourth stage formation to C4, keeping the temperature for t4, and reducing the current of the fourth stage formation to A4.

[0044] (5) After charging is completed, the battery obtained in step (4) is evacuated, sealed and capacity divided.

[0045] While the first stage of formation is being carried out in step (1), transverse and longitudinal vibrations are also carried out, with a vibration frequency of 15 to 25 Hz and a vibration time of 1 / 2t1 = 2.5 min.

[0046] In steps (1) to (4), T0-T4=(0.8-1.2) mm. In this embodiment, T0=6 mm, T4=4.8 mm, and the calculated values ​​are T1=5.7 mm, T2=5.4 mm, and T3=5.1 mm.

[0047] The temperatures C1, C2, C3, and C4 of the first, second, third, and fourth stages of formation are 45 to 85° C., the currents A1, A2, A3, and A4 of the first, second, third, and fourth stages of formation are 0.2 to 1.0° C., and the times t1, t2, t3, and t4 of the first, second, third, and fourth stages of formation are 3 to 45 minutes; wherein C2=C1+15, C3=C2+15, C4=C1, A2=A1+0.2, A3=2A2, A4=A1, t2=2t1, t3=2.5t2, In this embodiment, the temperature C1 of the first stage is 55°C, the current A1 is 0.3C, and the time t1 is 5min. The temperature C2 of the second stage is 70°C, the current A2 is 0.5C, and the time t2 is 10min. The temperature C3 of the third stage is 85°C, the current A3 is 1.0C, and the time t3 is 25min. The temperature C4 of the fourth stage is 55°C, the current A4 is 0.3C, and the time t4 is 50min.

[0048] Example 3

[0049] The lithium ion battery formation method comprises the following steps:

[0050] (1) setting the initial thickness of the battery to T0, setting the first target thickness of the battery to T1, performing a first stage of formation on the battery, and setting the temperature of the first stage of formation to C1, the current to A1, and the time to t1;

[0051] (2) performing a second stage formation on the battery obtained in step (1), setting a second target thickness of the battery to T2, raising the temperature of the second stage formation to C2, keeping the temperature for t2, and increasing the current of the second stage formation to A2;

[0052] (3) performing a third stage formation on the battery obtained in step (2), setting a third target thickness of the battery to T3, raising the temperature of the third stage formation to C3, keeping the temperature for t3, and increasing the current of the third stage formation to A3;

[0053] (4) Performing a fourth stage formation on the battery obtained in step (3), setting a fourth target thickness of the battery to T4, lowering the temperature of the fourth stage formation to C4, keeping the temperature for t4, and reducing the current of the fourth stage formation to A4.

[0054] (5) After charging is completed, the battery obtained in step (4) is evacuated, sealed and capacity divided.

[0055] While the first stage of formation is being carried out in step (1), transverse and longitudinal vibrations are also carried out, with a vibration frequency of 15 to 25 Hz and a vibration time of 1 / 2t1 = 2 min.

[0056] In steps (1) to (4), T0-T4=(0.8-1.2) mm. In this embodiment, T0=6 mm, T4=5 mm, and the calculated values ​​are T1=5.75 mm, T2=5.5 mm, and T3=5.25 mm.

[0057] The temperatures C1, C2, C3, and C4 of the first, second, third, and fourth stages of formation are 45 to 85° C., the currents A1, A2, A3, and A4 of the first, second, third, and fourth stages of formation are 0.2 to 1.0° C., and the times t1, t2, t3, and t4 of the first, second, third, and fourth stages of formation are 3 to 45 minutes; wherein C2=C1+15, C3=C2+15, C4=C1, A2=A1+0.2, A3=2A2, A4=A1, t2=2t1, t3=2.5t2, In this embodiment, the temperature C1 of the first stage is 50°C, the current A1 is 0.25C, and the time t1 is 4min. The temperature C2 of the second stage is 65°C, the current A2 is 0.45C, and the time t2 is 8min. The temperature C3 of the third stage is 80°C, the current A3 is 0.9C, and the time t3 is 20min. The temperature C4 of the fourth stage is 50°C, the current A4 is 0.25C, and the time t4 is 40min.

[0058] Example 4

[0059] The lithium ion battery formation method comprises the following steps:

[0060] (1) setting the initial thickness of the battery to T0, setting the first target thickness of the battery to T1, performing a first stage of formation on the battery, and setting the temperature of the first stage of formation to C1, the current to A1, and the time to t1;

[0061] (2) performing a second stage formation on the battery obtained in step (1), setting a second target thickness of the battery to T2, raising the temperature of the second stage formation to C2, keeping the temperature for t2, and increasing the current of the second stage formation to A2;

[0062] (3) performing a third stage formation on the battery obtained in step (2), setting a third target thickness of the battery to T3, raising the temperature of the third stage formation to C3, keeping the temperature for t3, and increasing the current of the third stage formation to A3;

[0063] (4) Performing a fourth stage formation on the battery obtained in step (3), setting a fourth target thickness of the battery to T4, lowering the temperature of the fourth stage formation to C4, keeping the temperature for t4, and reducing the current of the fourth stage formation to A4.

[0064] (5) After charging is completed, the battery obtained in step (4) is evacuated, sealed and capacity divided.

[0065] In steps (1) to (4), T0-T4=(0.8-1.2) mm. In this embodiment, T0=6 mm, T4=5 mm, and the calculated values ​​are T1=5.75 mm, T2=5.5 mm, and T3=5.25 mm.

[0066] The temperature C1 of the first stage of step (1) is 45-55°C, the current A1 is 0.2-0.3°C, and the time t1 is 3-7min; the temperature C2 of the second stage of step (2) is 60-70°C, the current A2 is 0.4-0.5°C, and the time t2 is 6-10min; the temperature C3 of the third stage of step (3) is 75-85°C, the current A3 is 0.8-1.0°C, and the time t3 is 15-25min; the temperature C3 of the fourth stage of step (4) is 45-55°C, the current A4 is 0.2-0.3°C, and the time t4 is 35-45min. In this embodiment, the temperature C1 of the first stage is 50°C, the current A1 is 0.25C, and the time t1 is 6min. The temperature C2 of the second stage is 65°C, the current A2 is 0.45C, and the time t2 is 8min. The temperature C3 of the third stage is 80°C, the current A3 is 0.9C, and the time t3 is 20min. The temperature C4 of the fourth stage is 50°C, the current A4 is 0.25C, and the time t4 is 40min.

[0067] Example 5

[0068] The lithium ion battery formation method comprises the following steps:

[0069] (1) setting the initial thickness of the battery to T0, setting the first target thickness of the battery to T1, performing a first stage of formation on the battery, and setting the temperature of the first stage of formation to C1, the current to A1, and the time to t1;

[0070] (2) performing a second stage formation on the battery obtained in step (1), setting a second target thickness of the battery to T2, raising the temperature of the second stage formation to C2, keeping the temperature for t2, and increasing the current of the second stage formation to A2;

[0071] (3) performing a third stage formation on the battery obtained in step (2), setting a third target thickness of the battery to T3, raising the temperature of the third stage formation to C3, keeping the temperature for t3, and increasing the current of the third stage formation to A3;

[0072] (4) Performing a fourth stage formation on the battery obtained in step (3), setting a fourth target thickness of the battery to T4, lowering the temperature of the fourth stage formation to C4, keeping the temperature for t4, and reducing the current of the fourth stage formation to A4.

[0073] (5) After charging is completed, the battery obtained in step (4) is evacuated, sealed and capacity divided.

[0074] While the first stage of formation is being carried out in step (1), transverse and longitudinal vibrations are also carried out, with a vibration frequency of 15 to 25 Hz and a vibration time of 1 / 2t1 = 2 min.

[0075] In steps (1) to (4), T0-T4=(0.8-1.2) mm. In this embodiment, T0=6 mm, T4=5 mm, and the calculated values ​​are T1=5.75 mm, T2=5.5 mm, and T3=5.25 mm.

[0076] The temperatures C1, C2, C3, and C4 of the first, second, third, and fourth stages of formation are 45 to 85° C., the currents A1, A2, A3, and A4 of the first, second, third, and fourth stages of formation are 0.2 to 1.0° C., and the times t1, t2, t3, and t4 of the first, second, third, and fourth stages of formation are 3 to 45 minutes; wherein C2=C1+15, C3=C2+15, C4=C1, A2=A1+0.2, A3=2A2, A4=A1, t2=2t1, t3=2.5t2, In this embodiment, the temperature C1 of the first stage is 50°C, the current A1 is 0.25C, and the time t1 is 4min. The temperature C2 of the second stage is 65°C, the current A2 is 0.45C, and the time t2 is 8min. The temperature C3 of the third stage is 80°C, the current A3 is 0.9C, and the time t3 is 20min. The temperature C4 of the fourth stage is 50°C, the current A4 is 0.25C, and the time t4 is 40min.

[0077] The heating in step (2) is to introduce dry high-temperature gas to raise the temperature of the second stage of formation to C2, while controlling the dew point to td1; the heating in step (3) is to introduce dry high-temperature gas to raise the temperature of the third stage of formation to C3, while continuing to control the dew point to td2; the cooling in step (4) is to introduce dry normal-temperature gas to lower the temperature of the fourth stage of formation to C4; wherein td1=td2=(-42 to -48)°C.

[0078] Example 6

[0079] The lithium ion battery formation method comprises the following steps:

[0080] (1) setting the initial thickness of the battery to T0, setting the first target thickness of the battery to T1, performing a first stage of formation on the battery, and setting the temperature of the first stage of formation to C1, the current to A1, and the time to t1;

[0081] (2) performing a second stage formation on the battery obtained in step (1), setting a second target thickness of the battery to T2, raising the temperature of the second stage formation to C2, keeping the temperature for t2, and increasing the current of the second stage formation to A2;

[0082] (3) performing a third stage formation on the battery obtained in step (2), setting a third target thickness of the battery to T3, raising the temperature of the third stage formation to C3, keeping the temperature for t3, and increasing the current of the third stage formation to A3;

[0083] (4) Performing a fourth stage formation on the battery obtained in step (3), setting a fourth target thickness of the battery to T4, lowering the temperature of the fourth stage formation to C4, keeping the temperature for t4, and reducing the current of the fourth stage formation to A4.

[0084] (5) After charging is completed, the battery obtained in step (4) is evacuated, sealed and capacity divided.

[0085] While the first stage of formation is being carried out in step (1), transverse and longitudinal vibrations are also carried out, with a vibration frequency of 15 to 25 Hz and a vibration time of 1 / 2t1 = 2 min.

[0086] Step (1) to step (4), T0-T4=(0.8-1.2) mm. In this embodiment, T0=6 mm, T4=5 mm, and the calculated values ​​are T1=5.75 mm, T2=5.5 mm, and T3=5.25 mm.

[0087] The temperatures C1, C2, C3, and C4 of the first, second, third, and fourth formations are 45 to 85° C., the currents A1, A2, A3, and A4 of the first, second, third, and fourth formations are 0.2 to 1.0° C., and the times t1, t2, t3, and t4 of the first, second, third, and fourth formations are 3 to 45 minutes. In this embodiment, the temperature C1 of the first stage is 50°C, the current A1 is 0.25C, and the time t1 is 4min. The temperature C2 of the second stage is 62°C, the current A2 is 0.42C, and the time t2 is 7min. The temperature C3 of the third stage is 76°C, the current A3 is 0.85C, and the time t3 is 18min. The temperature C4 of the fourth stage is 48°C, the current A4 is 0.23C, and the time t4 is 37min.

[0088] Example 7

[0089] The lithium ion battery formation method comprises the following steps:

[0090] (1) setting the initial thickness of the battery to T0, setting the first target thickness of the battery to T1, performing a first stage of formation on the battery, and setting the temperature of the first stage of formation to C1, the current to A1, and the time to t1;

[0091] (2) performing a second stage formation on the battery obtained in step (1), setting a second target thickness of the battery to T2, raising the temperature of the second stage formation to C2, keeping the temperature for t2, and increasing the current of the second stage formation to A2;

[0092] (3) performing a third stage formation on the battery obtained in step (2), setting a third target thickness of the battery to T3, raising the temperature of the third stage formation to C3, keeping the temperature for t3, and increasing the current of the third stage formation to A3;

[0093] (4) Performing a fourth stage formation on the battery obtained in step (3), setting a fourth target thickness of the battery to T4, lowering the temperature of the fourth stage formation to C4, keeping the temperature for t4, and reducing the current of the fourth stage formation to A4.

[0094] (5) After charging is completed, the battery obtained in step (4) is evacuated, sealed and capacity divided.

[0095] While the first stage of formation is being carried out in step (1), transverse and longitudinal vibrations are also carried out, with a vibration frequency of 15 to 25 Hz and a vibration time of 1 / 2t1 = 2 min.

[0096] Step (1) to step (4), T0-T4=(0.8-1.2) mm. In this embodiment, T0=6 mm, T4=5 mm, and the calculated values ​​are T1=5.75 mm, T2=5.5 mm, and T3=5.25 mm.

[0097] The temperatures C1, C2, C3, and C4 of the first, second, third, and fourth formations are 45 to 85° C., the currents A1, A2, A3, and A4 of the first, second, third, and fourth formations are 0.2 to 1.0° C., and the times t1, t2, t3, and t4 of the first, second, third, and fourth formations are 3 to 45 minutes. In this embodiment, the temperature C1 of the first stage is 50°C, the current A1 is 0.25C, and the time t1 is 4min. The temperature C2 of the second stage is 68°C, the current A2 is 0.48C, and the time t2 is 9min. The temperature C3 of the third stage is 84°C, the current A3 is 0.95C, and the time t3 is 22min. The temperature C4 of the fourth stage is 52°C, the current A4 is 0.27C, and the time t4 is 43min.

[0098] Performance test: Due to space constraints, the present invention only selects the above 7 embodiments, each of which uses three groups of batteries, the battery is a 4.45V lithium-ion battery, model 411525, and the marked capacity is 180mAh. However, the present invention is not limited to this battery. Experiments have proved that the formation method of the present invention can be applied to other lithium-ion batteries and can also achieve corresponding similar effects, which will not be repeated here.

[0099] The following table shows the test results of the capacity retention rate of the lithium-ion batteries obtained in various embodiments after 300 cycles at different rates and temperatures.

[0100] Table 1 Electrical properties of the batteries after formation in various embodiments

[0101]

[0102]

[0103] In terms of data comparison: (1) The cycle performance of the batteries of Examples 1 to 7 is better than that of the traditional constant temperature and constant current formation method. The cycle performance difference of the batteries of Examples 1 to 4 is not significant. The cycle performance of the battery of Example 5 is better than that of Example 3. The cycle performance of the battery of Example 3 is better than that of Examples 6 and 7. (2) It can be seen from the performance parameters of Example 4 and Example 3 that the cycle performance of the battery of Example 4 is similar to that of the battery of Example 3, but the time of the first stage of formation needs to be increased from 4 minutes to 6 minutes. It can be seen that the use of the horizontal and vertical vibration-assisted charging formation specified in the present invention can increase the battery charging formation speed and significantly shorten the time of the first stage of formation. (3) It can be seen from the performance parameters of Example 5 and Example 3 that the present invention introduces dry high-temperature gas during the second and third stages of formation, and introduces dry room temperature gas during the fourth stage of formation to uniformly cool the battery, which can reduce battery polarization and improve the cycle performance of the battery. (4) From the comparison of the performance parameters of Examples 5, 6, and 7, it can be seen that if the formation temperature, current, and time of each stage do not adopt the corresponding relationship specified by the algorithm provided by the present invention, even if the formation temperature, current, and time are within the range specified by the present invention, the technical effect of Example 3 cannot be achieved.

[0104] The experiment proves that the battery surface obtained after the treatment of the conventional constant temperature and constant current formation method (condition parameters: the temperature of formation is 65±5℃, the current is 0.55±0.5C, and the time is 96±10min) has a small amount of black spots and lithium precipitation, the actual thickness difference (the coefficient of variation = standard deviation / mean value) is 2.3-3.3%, the actual capacity difference (the coefficient of variation = standard deviation / mean value) is 4.2-6.2%, and the capacity retention rate after 300 cycles is 73-75%. The battery surface obtained after the treatment of the formation method of the present invention has no black spots and lithium precipitation, the interface is good, the actual thickness difference is 1.5-2.5%, the actual capacity difference is 3.5-4.5%, and the capacity retention rate after 300 cycles is 83-85%. Therefore, the battery obtained after the treatment of the formation method of the present invention has no black spots and lithium precipitation, the interface is good, and the thickness consistency can be improved by 35-45%, the capacity consistency by 25-35%, and the cycle performance by 11-16%.

[0105] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A lithium ion battery formation method, characterized in that: The following steps are involved: (1) setting the initial thickness of the battery to T0, setting the first target thickness of the battery to T1, performing a first stage of formation on the battery, and setting the temperature of the first stage of formation to C1, the current to A1, and the time to t1; (2) performing a second stage formation on the battery obtained in step (1), setting a second target thickness of the battery to T2, raising the temperature of the second stage formation to C2, keeping the temperature for t2, and increasing the current of the second stage formation to A2; (3) performing a third stage formation on the battery obtained in step (2), setting a third target thickness of the battery to T3, raising the temperature of the third stage formation to C3, keeping the temperature for t3, and increasing the current of the third stage formation to A3; (4) performing a fourth stage formation on the battery obtained in step (3), setting a fourth target thickness of the battery to T4, lowering the temperature of the fourth stage formation to C4, keeping the temperature for t4, and reducing the current of the fourth stage formation to A4; In steps (1) to (4), T1 = T0-(T0- T4) / 4, T2 = T1- (T0- T4) / 4, T3 = T2- (T0- T4) / 4, T4 = T3- (T0- T4) / 4, T0-T4 = 0.8-1.2 mm; The temperature C1 of the first stage of the step (1) is 45-55°C, the current A1 is 0.2-0.3°C, and the time t1 is 3-7 min; the temperature C2 of the second stage of the step (2) is 60-70°C, the current A2 is 0.4-0.5°C, and the time t2 is 6-10 min; the temperature C3 of the third stage of the step (3) is 75-85°C, the current A3 is 0.8-1.0°C, and the time t3 is 15-25 min; (4) the temperature C4 of the fourth stage of the step is 45-55°C, the current A4 is 0.2-0.3°C, and the time t4 is 35-45 min; Among them, C2=C1+15℃, C3=C2+15℃, C4=C1, =A1+0.2℃, A3=2A2, A4=A1, t2=2t1, t3=2.5t2, t4=t2·t3 / t1; While the first stage of formation is being carried out in step (1), transverse and longitudinal vibration is also carried out, the vibration frequency is 15 to 25 Hz, and the vibration time is 1 / 2t1; The heating in step (2) is to introduce dry high-temperature gas to raise the temperature of the second stage of formation to C2, while controlling the dew point to td1; the heating in step (3) is to introduce dry high-temperature gas to raise the temperature of the third stage of formation to C3, while continuing to control the dew point to td2; the cooling in step (4) is to introduce dry normal-temperature gas to lower the temperature of the fourth stage of formation to C4; wherein td1=td2=-42 to -48°C.

2. The lithium ion battery formation method according to claim 1, characterized in that: Steps (1) to (4) are carried out in a formation cabinet, which comprises a cabinet shell, a carrying device, a formation charge and discharge system, a time control system, a temperature control system, a humidity control system, a circulation ventilation system and a transverse and longitudinal vibration system. The carrying device is arranged in the cabinet shell, the formation charge and discharge system is electrically connected to the carrying device, the time control system and the temperature control system are both electrically connected to the formation charge and discharge system, the transverse and longitudinal vibration system is connected to the carrying device, the circulation ventilation system is communicated with the cabinet shell, and the temperature control system and the humidity control system are both connected to the circulation ventilation system.

3. A lithium ion battery, characterized in that: The lithium ion battery is prepared by the lithium ion battery formation method according to any one of claims 1 to 2.

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