A formation method for improving thermal shock performance of a soft package battery

Abstract

The application belongs to the technical field of battery formation, and particularly relates to a formation method for improving thermal shock performance of a soft package battery, which comprises the following steps: step one, first constant current charging is performed on the battery, and the battery is left after the charging is completed; step two, second constant current charging is performed on the battery, and the second constant current charging current is greater than the first constant current charging current, and the battery is left after the charging is completed; and step three, third constant current charging is performed on the battery, so that the charging current is charged to greater than or equal to 85% SOC, and the battery is left after the charging is completed, wherein the third constant current charging current is less than the second constant current charging current. The thermal shock performance of the battery cell is improved by increasing the charging cutoff voltage.

Description

Technical Field

[0001] This invention belongs to the technical field of battery formation, specifically relating to a formation method for improving the thermal shock performance of pouch batteries. Background Technology

[0002] Lithium-ion batteries, with their advantages of high energy density, long cycle life, low pollution, and recyclability, have become the core energy source for the vast majority of electronic products. With the rapid development of lithium-ion batteries, there is a growing demand for electronic products to withstand various harsh environments. Improving the safety performance of lithium-ion batteries under thermal shock has become a crucial obstacle that must be overcome for their widespread application.

[0003] However, existing batteries have poor thermal shock performance under abuse conditions. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of existing technologies by providing a formation method for improving the thermal shock performance of pouch batteries, which improves the thermal shock performance of the battery cell by increasing the charging cut-off voltage.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A formation method for improving the thermal shock performance of a pouch battery includes: Step 1, performing a first constant current charge on the battery and allowing it to stand after charging; Step 2, performing a second constant current charge on the battery, wherein the second constant current charge current is greater than the first constant current charge current, and allowing it to stand after charging; Step 3, performing a third constant current charge on the battery to charge it to ≥85% SOC, and allowing it to stand after charging, wherein the third constant current charge current is less than the second constant current charge current.

[0007] Preferably, in step one, the current of the first constant current charging is 0.2C, the charging time is 8.5min, the charging voltage is 4480mV, and the resting time is 0.1 to 1.0min.

[0008] Preferably, in step one, the formation temperature is 80°C and the formation pressure is 1.0 MPa.

[0009] Preferably, in step two, the current of the second constant current charging is 0.8 to 1.2C, the charging time is 4 to 10 minutes, the charging voltage is 4480mV, and the resting time is 0.1 to 1.0 minutes.

[0010] Preferably, in step two, the formation temperature is 80°C and the formation pressure is 1.0 MPa.

[0011] Preferably, in step three, the current of the third constant current charging is 0.3 to 0.7C, the charging time is 89 to 91 minutes, the charging voltage is 4480mV, and the resting time is 0.6 to 1.3 minutes.

[0012] Preferably, in step three, the formation temperature is 80°C and the formation pressure is 1.0 MPa.

[0013] Preferably, the current of the second constant current charging is 0.8C, 0.9C, 1.0C, 1.1C or 1.2C, and the current of the third constant current charging is 0.3C, 0.4C, 0.5C, 0.6C or 0.7C.

[0014] Preferably, step one further includes:

[0015] The battery was placed in an environment with a temperature of 80℃ and a pressure of 1.0MPa for 1 minute to allow the overall temperature of the battery to reach the set formation temperature.

[0016] Preferably, step three further includes:

[0017] The battery is subjected to evacuation, resealing, and capacity testing to obtain the finished secondary battery.

[0018] The beneficial effects of this invention are as follows: First, a small current is used for formation, which is conducive to forming a dense SEI film structure. Adjusting the short rest periods between charging currents facilitates the second constant-current charging. The second constant-current charging current is greater than the first. By increasing the second charging current, the formation time can be shortened, and as the formation process gradually stabilizes, increasing the formation current can still form a dense SEI film. Compared to the second charging current, reducing the third constant-current current while extending the charging time helps to increase the cell's charging cut-off voltage, thus generating a dense, thermally stable SEI film. Limiting the charge to greater than 85% SOC allows side reactions to proceed fully, generating a dense, thermally stable SEI film, while simultaneously eliminating internal battery polarization and improving cycle performance. The method of this invention is simple; simply increasing the charging cut-off voltage in the formation process can improve the cell's thermal shock performance and cycle performance. Attached Figure Description

[0019] The features, advantages, and technical effects of exemplary embodiments of the present invention will now be described with reference to the accompanying drawings.

[0020] Figure 1 This is a schematic diagram of the mechanism of the present invention.

[0021] Figure 2 This is a comparative diagram of the liquid retention capacity of the present invention.

[0022] Figure 3 This is a schematic diagram illustrating the data changes in the formation method of the present invention.

[0023] Figure 4 This is a schematic diagram illustrating the data changes in existing formation methods.

[0024] Figure 5 This is a comparative schematic diagram of the cyclic capacity decay diagram of the present invention. Detailed Implementation

[0025] If certain terms are used in the specification and claims to refer to specific components, those skilled in the art will understand that hardware manufacturers may use different names to refer to the same component. This specification and claims do not distinguish components based on differences in name, but rather on differences in function. The term "comprising" as used throughout the specification and claims is an open-ended term and should be interpreted as "comprising but not limited to." "Approximately" means that within an acceptable margin of error, those skilled in the art can solve the technical problem and substantially achieve the technical effect within a certain margin of error.

[0026] Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be interpreted as indicating or implying relative importance.

[0027] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0028] The following is in conjunction with the appendix Figures 1-5 The present invention will be described in further detail, but this is not intended to limit the invention.

[0029] A formation method for improving the thermal shock performance of pouch batteries includes: Step 1, performing a first constant current charge on the battery and allowing it to stand after charging; Step 2, performing a second constant current charge on the battery, wherein the second constant current charge current is greater than the first constant current charge current, and allowing it to stand after charging; Step 3, performing a third constant current charge on the battery to charge it to ≥85% SOC, and allowing it to stand after charging, wherein the third constant current charge current is less than the second constant current charge current.

[0030] It should be noted that: using a small current for initial formation is beneficial for forming a dense SEI film structure; adjusting the short rest periods between charging currents is beneficial for the second constant current charging; the second constant current charging current is greater than the first constant current charging current. By increasing the current of the second charging, the formation time can be shortened, and as the formation process gradually begins to stabilize, increasing the formation current can also form a dense SEI film; compared to the second charging current, reducing the third constant current current while extending the charging time helps to increase the cell charging cutoff voltage, thereby generating a dense SEI film with good thermal stability; limiting the charge to more than 85% SOC allows side reactions to proceed fully, generating a dense SEI film with good thermal stability, while eliminating internal polarization of the battery and improving cycle performance.

[0031] In the formation method for improving the thermal shock performance of pouch batteries according to the present invention, in step one, the current of the first constant current charge is 0.2C, the charging time is 8.5min, the charging voltage is 4480mV, and the resting time is 0.1 to 1.0min, preferably 0.5min.

[0032] In the formation method for improving the thermal shock performance of pouch batteries according to the present invention, in step one, the formation temperature is 80°C and the formation pressure is 1.0 MPa.

[0033] In the formation method for improving the thermal shock performance of pouch batteries according to the present invention, in step two, the current of the second constant current charge is 0.8–1.2C, preferably 1C; the charging time is 4–10 min, preferably 5 min; the charging voltage is 4480 mV; and the resting time is 0.1–1.0 min, preferably 0.5 min. Compared to the initial charging current, gradually increasing the current of the second charge can shorten the formation time. Furthermore, as the formation process gradually stabilizes, increasing the formation current can also form a dense SEI film. In some embodiments, the formation temperature is 80°C, and the formation pressure is 1.0 MPa.

[0034] In the formation method for improving the thermal shock performance of pouch batteries according to the present invention, in step three, the current of the third constant current charge is 0.3–0.7C, preferably 0.5C, the charging time is 89–91 min, preferably 89 min, the charging voltage is 4480 mV, and the resting time is 0.6–1.3 min, preferably 1 min. Compared to the current of the second charge, the constant current of the third charge is reduced, while the charging time is extended, increasing the cell charging cutoff voltage to generate a dense SEI film with good thermal stability, while eliminating internal polarization of the battery and improving cycle performance. In some embodiments, the formation temperature is 80°C, and the formation pressure is 1.0 MPa.

[0035] In the formation method for improving the thermal shock performance of pouch batteries according to the present invention, the current of the second constant current charge is 0.8C, 0.9C, 1.0C, 1.1C, or 1.2C, preferably 1C; and the current of the third constant current charge is 0.3C, 0.4C, 0.5C, 0.6C, or 0.7C, preferably 0.5C.

[0036] In the formation method for improving the thermal shock performance of pouch batteries according to the present invention, step one further includes:

[0037] The battery is preheated and placed in an environment with a temperature of 80℃ and a pressure of 1.0MPa for 1 minute to allow the overall temperature of the battery to reach the set formation temperature. Preheating pressure is then applied to ensure good contact between the electrode and the separator.

[0038] In the formation method for improving the thermal shock performance of pouch batteries according to the present invention, step three further includes:

[0039] The battery undergoes processes such as degassing, resealing, and capacity testing to obtain the finished secondary battery.

[0040] Example 1

[0041] S1. First, let it stand for 1 minute at a temperature of 80℃ and a pressure of 1.0MPa. Preheat the pressure to make the overall temperature of the battery reach the set formation temperature, and ensure good contact between the electrode and the separator.

[0042] S2. Perform the first constant current charge at 80℃ and 1.0MPa, with a charging current of 0.2C, a charging time of 8.5min, and a charging voltage of 4480mV; after charging, let it stand for 0.5min.

[0043] S3. Perform a second constant current charge at 80℃ and 1.0MPa pressure, with a charging current of 1C, a charging time of 5min, and a charging voltage of 4480mV; after charging, let it stand for 0.5min.

[0044] S4. The third constant current charging was performed at 80℃ and 1.0MPa, with a charging current of 0.5C, a charging time of 89min, and a charging voltage of 4800mV. After charging, the device was left to stand for 1min.

[0045] The battery obtained by this formation method is then further processed into the next step, including degassing, secondary sealing, and capacity testing, to obtain the finished secondary battery.

[0046] Comparative Example 1

[0047] S1. First, let it stand for 1 minute at a temperature of 80℃ and a pressure of 1.0MPa;

[0048] S2. Perform the first constant current charge at 80℃ and 1.0MPa, with a charging current of 0.2C, a charging time of 8.5min, and a charging voltage of 4480mV; after charging, let it stand for 0.5min.

[0049] S3. Perform a second constant current charge at 80℃ and 1.0MPa pressure, with a charging current of 1C, a charging time of 5min, and a charging voltage of 4480mV; after charging, let it stand for 0.5min.

[0050] S4. The third constant current charging was performed at 80℃ and 1.0MPa, with a charging current of 1.4C, a charging time of 29min, and a charging voltage of 4800mV. After charging, the device was left to stand for 1min.

[0051] The battery obtained by this formation method is then further processed into the next step, including degassing, secondary sealing, and capacity testing, to obtain the finished secondary battery.

[0052] Table 1. Thermal shock suspension test results of the battery in Example 1 and the comparative example battery.

[0053] 130℃ / 4.48V 6 / 6 pass 6 / 6 pass 132℃ / 4.48V 6 / 6 pass 6 / 6 pass 135℃ / 4.48V 6 / 6 pass fail

[0054] From the table above and Figure 2It can be seen that the battery prepared in Example 1 has better thermal shock performance, cycle capacity retention, and liquid retention than Comparative Example 1 at 130℃ / 4.48V, 132℃ / 4.48V, and 135℃ / 4.48V. This indicates that the formation method of the present invention can improve the thermal stability of the SEI film by increasing the charging cut-off voltage to ≥4.37V in the early stage of SEI film formation by increasing the SOC to ≥85%, thereby improving the thermal shock performance of the cell, increasing the liquid retention, eliminating polarization, and improving cycle performance.

[0055] Based on the disclosure and teachings of the foregoing specification, those skilled in the art can make changes and modifications to the above embodiments. Therefore, the present invention is not limited to the specific embodiments described above, and any obvious improvements, substitutions, or modifications made by those skilled in the art based on the present invention are within the scope of protection of the present invention. Furthermore, although some specific terms are used in this specification, these terms are only for convenience of explanation and do not constitute any limitation on the present invention.

Claims

1. A formation method for improving the thermal shock performance of pouch batteries, characterized in that, include: Step 1: Perform the first constant current charge on the battery, and let it stand after charging is complete; Step 2: Perform a second constant current charge on the battery, with the second constant current charging current being greater than the first constant current charging current. After charging is complete, let the battery rest. Step 3: Perform a third constant current charge on the battery to charge it to ≥85% SOC. After charging is complete, let it rest. The third constant current charge current is less than the second constant current charge current. The second constant current charging current is 0.8C, 0.9C, 1.0C, 1.1C or 1.2C, and the third constant current charging current is 0.3C, 0.4C, 0.5C, 0.6C or 0.7C.

2. The formation method for improving the thermal shock performance of pouch batteries as described in claim 1, characterized in that: In step one, the current of the first constant current charging is 0.2C, the charging time is 8.5min, the charging voltage is 4480mV, and the resting time is 0.1 to 1.0min.

3. The formation method for improving the thermal shock performance of pouch batteries as described in claim 1, characterized in that: In step one, the formation temperature is 80℃ and the formation pressure is 1.0MPa.

4. The formation method for improving the thermal shock performance of pouch batteries as described in claim 1, characterized in that: In step two, the charging time is 4 to 10 minutes, the charging voltage is 4480mV, and the resting time is 0.1 to 1.0 minutes.

5. The formation method for improving the thermal shock performance of pouch batteries as described in claim 1, characterized in that: In step two, the formation temperature is 80℃ and the formation pressure is 1.0MPa.

6. The formation method for improving the thermal shock performance of pouch batteries as described in claim 1, characterized in that: In step three, the charging time is 89-91 minutes, the charging voltage is 4480mV, and the resting time is 0.6-1.3 minutes.

7. The formation method for improving the thermal shock performance of a pouch battery as described in claim 1, characterized in that: In step three, the formation temperature is 80℃ and the formation pressure is 1.0MPa.

8. The formation method for improving the thermal shock performance of a pouch battery as described in claim 1, characterized in that: Step one also includes: The battery was placed in an environment with a temperature of 80℃ and a pressure of 1.0MPa for 1 minute to allow the overall temperature of the battery to reach the set formation temperature.

9. The formation method for improving the thermal shock performance of a pouch battery as described in claim 1, characterized in that, Step three also includes: The battery is subjected to evacuation, resealing, and capacity testing to obtain the finished secondary battery.

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