A capacity division method for improving voltage stability of special-shaped lithium-ion batteries

Abstract

The present application proposes a capacity division method for improving the voltage stability of special-shaped lithium-ion batteries. The capacity division method includes the following steps: S1, under constant current and constant voltage conditions, charging and discharging the battery for at least one cycle, and then charging; S2, discharging the battery at a low current of 0.01C to 0.03C for 10 seconds to 30 seconds; S3, under constant current and constant voltage conditions, charging the battery; S4, discharging the battery at a low current of 0.005C to 0.02 for 10 seconds to 30 seconds. The battery capacity division process steps of the present application are simple, and the step of discharging with a low current for several seconds can reduce the high voltage condition after the capacity division, stabilize the battery voltage, shorten the aging and static time of the battery after the capacity division, thereby improving battery production efficiency, reducing production costs, and improving product competitiveness.

Description

Technical Field

[0001] The present invention relates to the field of battery capacity division, and in particular to a capacity division method for improving the voltage stability of special-shaped lithium-ion batteries. Background Art

[0002] Currently, lithium-ion batteries are known as green batteries due to their high energy density, long cycle life, lack of memory effect, and environmental friendliness. They are widely used in mobile phones, laptops, electric vehicles, and other fields. With the rapid development of the industry, the demand for lithium-ion batteries is increasing day by day, and therefore, lithium-ion batteries have a broad market potential.

[0003] In the production of lithium-ion batteries, capacity separation is an important step in battery production. After capacity separation, the battery cell voltage is in an unstable state, especially at full charge SOC, where the voltage is "falsely high", that is, the battery voltage is too high. In addition, the battery after capacity separation needs to be left standing for a period of time to eliminate the polarized voltage before the next production step can be carried out. This standing process will consume a certain amount of time, thereby reducing the battery production efficiency.

[0004] Therefore, it is necessary to provide a technical solution to reduce the voltage overload after capacity division, improve the stability of battery voltage after capacity division, reduce the standing time of capacity division and improve production efficiency. Summary of the Invention

[0005] The present invention proposes a capacity division method for improving the voltage stability of special-shaped lithium-ion batteries. The purpose is to provide a lithium-ion battery capacity division method that reduces the voltage overshoot after capacity division, improves the stability of the battery voltage after capacity division, reduces the capacity division standby time and improves production efficiency.

[0006] The technical solution adopted by the present invention is as follows: a capacity division method for improving the voltage stability of special-shaped lithium-ion batteries, the capacity division method comprising the following steps:

[0007] S1. Under constant current and constant voltage conditions, charge and discharge the battery for at least one cycle, then charge;

[0008] S2. Discharge the battery at a low current of 0.01C to 0.03C for 10 to 30 seconds;

[0009] S3, charge the battery under constant current and constant voltage conditions;

[0010] S4. Discharge the battery at a low current of 0.005C to 0.02 for 10 seconds to 30 seconds.

[0011] Furthermore, the method further includes the following steps:

[0012] S5. After the capacity-separated battery is left to stand at room temperature for 24 hours, a voltage K value test is performed.

[0013] Furthermore, the constant current and constant voltage condition is specifically that the current is set to 0.1 to 1.5C.

[0014] Furthermore, the upper limit voltage of the charging step in S1 is 4.0V to 4.5V, and the cut-off current is 0.01C to 0.07C.

[0015] Furthermore, the lower limit voltage of the discharge step in S1 is 2.0V to 4.0V.

[0016] Furthermore, the upper limit voltage of the charging step in S3 is 4.0V to 4.5V, and the cut-off current is 0.01C to 0.03C.

[0017] Furthermore, the battery is left for 2 to 8 minutes before the discharge step in S1.

[0018] Furthermore, the battery is a lithium-ion battery whose positive electrode material is lithium cobalt oxide and whose negative electrode material is artificial graphite.

[0019] Furthermore, the standard capacity of the battery is 1000 mAh.

[0020] The beneficial effects of the present invention are:

[0021] The battery capacity division process of the present application is simple, wherein the step of discharging with a small current for a few seconds can reduce the high voltage condition after the capacity division, stabilize the battery voltage, and shorten the polarization standing time after the battery capacity division, thereby improving the battery production efficiency, reducing production costs, and improving product competitiveness. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the following detailed description, they are used to explain the present invention but should not be construed as limiting the present invention. In the accompanying drawings:

[0023] Figure 1 The figure is a flow chart of a method for improving the voltage stability of special-shaped lithium-ion batteries according to an embodiment of the present invention. DETAILED DESCRIPTION

[0024] The following describes the specific embodiments of the present invention in detail with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention and are not intended to limit the present invention.

[0025] The present invention provides a capacity division method for improving the voltage stability of special-shaped lithium-ion batteries. The purpose is to provide a lithium-ion battery capacity division method that reduces the voltage overshoot after capacity division, improves the stability of the battery voltage after cell capacity division, reduces the capacity division standstill time and improves production efficiency.

[0026] See also Figure 1 To achieve this purpose, the present invention provides a capacity division method for improving the voltage stability of special-shaped lithium-ion batteries, the capacity division method comprising the following steps:

[0027] S1. Under constant current and constant voltage conditions, charge and discharge the battery for at least one cycle, then charge;

[0028] S2. Discharge the battery at a low current of 0.01C to 0.03C for 10 to 30 seconds;

[0029] S3, charge the battery under constant current and constant voltage conditions;

[0030] S4. Discharge the battery at a low current of 0.005C to 0.02 for 10 seconds to 30 seconds.

[0031] Wherein, each step is carried out at room temperature.

[0032] Furthermore, the method further includes the following steps:

[0033] S5. After the capacity-separated battery is left to stand at room temperature for 24 hours, a voltage K value test is performed.

[0034] Furthermore, the constant current and constant voltage condition is specifically that the current is set to 0.1 to 1.5C.

[0035] Furthermore, the upper limit voltage of the charging step in S1 is 4.0V to 4.5V, and the cut-off current is 0.01C to 0.07C.

[0036] Furthermore, the lower limit voltage of the discharge step in S1 is 2.0V to 4.0V.

[0037] Furthermore, the upper limit voltage of the charging step in S3 is 4.0V to 4.5V, and the cut-off current is 0.01C to 0.03C.

[0038] Furthermore, the battery is left for 2 to 8 minutes before the discharge step in S1.

[0039] Furthermore, the battery is a lithium-ion battery whose positive electrode material is lithium cobalt oxide and whose negative electrode material is artificial graphite. It is manufactured according to the conventional production process of lithium-ion batteries and then divided into different capacities, wherein the battery cells are selected from the same batch; the standard capacity of the battery is 1000mAh.

[0040] The battery capacity division process of the present application is simple, wherein the step of discharging with a small current for a few seconds can reduce the high voltage condition after the capacity division, stabilize the battery voltage, and shorten the polarization standing time after the battery capacity division, thereby improving the battery production efficiency, reducing production costs, and improving product competitiveness.

[0041] Example 1

[0042] The battery to be divided is divided at room temperature, specifically comprising the following steps:

[0043] S1, charge the battery at a constant current and constant voltage of 1000mA, with an upper voltage of 4.2V and a cut-off current of 20mA;

[0044] Leave the battery for 5 minutes;

[0045] S2, discharge the battery at a constant current of 1200mA, with a lower limit voltage of 3.0V;

[0046] S3, charge the battery at a constant current and constant voltage of 1000mA, with an upper voltage of 4.20V and a cut-off current of 50mA;

[0047] S4, discharge the battery at 20mA for 20 seconds;

[0048] S5. Charge the battery at a constant current and constant voltage of 500mA, with an upper voltage of 4.20V and a cutoff current of 20mA.

[0049] S6. Discharge the battery at 10 mA for 20 seconds.

[0050] After the capacity division is completed, the battery is left to stand at room temperature for 24 hours and then the K value test is performed. The obtained K value is 0.100mV / h.

[0051] Comparative Example 1

[0052] The cells to be divided are divided at room temperature. The specific steps are as follows:

[0053] S1, charge the battery at a constant current and constant voltage of 1000mA, with an upper voltage of 4.2V and a cut-off current of 20mA;

[0054] S2. Leave the battery for 5 minutes;

[0055] S3, discharge the battery at a constant current of 1200mA, with a lower voltage limit of 3.0V;

[0056] S4, charge the battery at a constant current and constant voltage of 1000mA, with an upper voltage of 4.2V and a cut-off current of 50mA;

[0057] S5. Charge the battery at a constant current and constant voltage of 500mA, with an upper voltage of 4.2V and a cutoff current of 20mA.

[0058] After the capacity division is completed, the battery is left to stand at room temperature for 24 hours and then the K value test is performed. The obtained K value is 0.185mV / h.

[0059] Comparative Example 2

[0060] The cells to be divided are divided at room temperature. The specific steps are as follows:

[0061] S1, charge the battery at a constant current and constant voltage of 1000mA, with an upper voltage of 4.2V and a cut-off current of 20mA;

[0062] S2. Leave the battery for 5 minutes;

[0063] S3, discharge the battery at a constant current of 1200mA, with a lower voltage limit of 3.0V;

[0064] S4, charge the battery at a constant current and constant voltage of 1000mA, with an upper voltage of 4.2V and a cut-off current of 50mA;

[0065] S5. Charge the battery at a constant current and constant voltage of 500mA, with an upper voltage of 4.2V and a cutoff current of 20mA.

[0066] After the capacity division was completed, the sample was left to stand at room temperature for 48 hours and then the K value was tested. The K value obtained was 0.142 mV / h.

[0067] Comparative Example 3

[0068] The cells to be divided are divided at room temperature. The specific steps are as follows:

[0069] S1, charge the battery at a constant current and constant voltage of 1000mA, with an upper voltage of 4.2V and a cut-off current of 20mA;

[0070] S2. Leave the battery for 5 minutes;

[0071] S3, discharge the battery at a constant current of 1200mA, with a lower voltage limit of 3.0V;

[0072] S4, charge the battery at a constant current and constant voltage of 1000mA, with an upper voltage of 4.2V and a cut-off current of 50mA;

[0073] S5. Charge the battery at a constant current and constant voltage of 500mA, with an upper voltage of 4.2V and a cutoff current of 20mA.

[0074] After the capacity division was completed, the sample was left to stand at room temperature for 72 hours and then the K value was tested. The K value obtained was 0.105 mV / h.

[0075] According to the above data, the K values ​​measured in Example 1, Comparative Example 1, Comparative Example 2 and Comparative Example 3 are as follows:

[0076] Example Voltage K value / mV / h Example 1 (24h) 0.100 Comparative Example 1 (24h) 0.185 Comparative Example 2 (48h) 0.142 Comparative Example 3 (72h) 0.105

[0077] From the comparison of the K values ​​of the various embodiments, it can be seen that in terms of the standing time, for example, Example 1 and Comparative Example 1 have the same standing time, but the voltage K value of Example 1 is smaller. Therefore, it can be seen that within the same standing time, after the small current discharge in Example 1, the battery voltage after capacity division can be lowered, and the battery voltage stability is higher. Therefore, the capacity division method in Example 1 can reduce the "falsely high" voltage condition and improve the stability of the battery voltage after capacity division.

[0078] In terms of K value comparison, in Example 1, only 24 hours of standing are required to make the K value reach 0.100, while in the three comparative examples, it takes 72 hours of standing to reach 0.105. Therefore, it takes more time for the comparative examples to reach the same or similar K value as that of Example 1. Therefore, it can be seen that after the small current discharge in Example 1, the battery voltage after capacity division can be kept in a stable state, thereby shortening the polarization standing time of the battery after capacity division, thereby improving battery production efficiency, reducing production costs, and improving product competitiveness.

[0079] As long as it does not violate the creative ideas of the present invention, any combination of various different embodiments of the present invention should be regarded as the content disclosed by the present invention; within the technical concept of the present invention, any simple modifications of the technical solution and any combination of different embodiments that do not violate the creative ideas of the present invention should be within the protection scope of the present invention.

Claims

1. A method for improving the voltage stability of special-shaped lithium-ion batteries, characterized in that: The capacity division method comprises the following steps: S1. Under constant current and constant voltage conditions, charge and discharge the battery for at least one cycle, then charge; S2. Discharge the battery at a low current of 0.01C to 0.03C for 10 to 30 seconds; S3, charge the battery under constant current and constant voltage conditions; S4. Discharge the battery at a low current of 0.005C to 0.02 for 10 seconds to 30 seconds.

2. The method for improving the voltage stability of special-shaped lithium-ion batteries according to claim 1, characterized in that: The following steps are also included: S5. After the capacity-separated battery is left to stand at room temperature for 24 hours, a voltage K value test is performed.

3. The method for improving the voltage stability of special-shaped lithium-ion batteries according to claim 1, wherein: The specific condition of constant current and constant voltage is that the current is set to 0.1~1.5C.

4. The method for improving the voltage stability of special-shaped lithium-ion batteries according to claim 1, wherein: The upper limit voltage of the charging step in S1 is 4.0V to 4.5V, and the cut-off current is 0.01C to 0.07C.

5. The method for improving the voltage stability of special-shaped lithium-ion batteries according to claim 1, wherein: The lower limit voltage of the discharge step in S1 is 2.0V to 4.0V.

6. The method for improving the voltage stability of special-shaped lithium-ion batteries according to claim 1, wherein: The upper limit voltage of the charging step in S3 is 4.0V to 4.5V, and the cut-off current is 0.01C to 0.03C.

7. The method for improving the voltage stability of special-shaped lithium-ion batteries according to claim 1, characterized in that: Before the discharge step in S1, the battery is left alone for 2 to 8 minutes.

8. The method for improving voltage stability of special-shaped lithium-ion batteries according to claim 1, wherein: The battery is a lithium-ion battery whose positive electrode material is lithium cobalt oxide and whose negative electrode material is artificial graphite.

9. The method for improving voltage stability of special-shaped lithium-ion batteries according to claim 1, wherein: The standard capacity of the battery is 1000 mAh.

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