Battery monomer adjusting method based on charging and discharging strategy and battery manufacturing method

Abstract

The invention relates to the technical field of battery manufacturing, and discloses a charging and discharging strategy-based single battery adjusting method and a battery manufacturing method. The single battery adjusting method based on the charging and discharging strategy comprises the following steps: charging single batteries subjected to capacity grading at a first rate to an over-charge SOC (State of Charge); standing for 1 to 10 minutes; discharging to a target SOC at a second rate; the target SOC is 2.3%-2.7% SOC, and the over-charge SOC is 1.05-1.4 times of the target SOC; the first multiplying power is 0.05 to 0.33 C, and the second multiplying power is 0.05 to 0.2 C. According to the method, polarization voltage (polarization dynamic compensation) is actively counteracted through charging and discharging circulation, the stabilization time is shortened by using the relaxation effect in the discharging stage (voltage convergence acceleration), the traditional SOC single-path limitation is broken through through charging and discharging bidirectional adjustment, and the effects of reducing the polarization effect of the single battery, reducing the voltage difference in the pack and shortening the shelving time are achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of battery manufacturing, and more specifically, to a method for adjusting a battery cell based on a charge-discharge strategy and a method for manufacturing a battery. Background Art

[0002] After adjusting the SOC of the existing battery cells, it is necessary to let them stand to naturally balance the SOC. The traditional method is to directly charge or discharge to the target SOC and then passively let them stand, which has two major defects: a) The polarization effect causes the voltage to be falsely high, and it is necessary to stand for a long time (>4 days) waiting for the voltage to drop, seriously delaying the production and testing rhythm; b) The initial characteristic differences of the battery cells in the group cause the SOC-voltage curve to deviate, resulting in a voltage difference >100 mV (for example, the difference reaches 136 mV when charging at 0.33C to 2.5% SOC), and the dispersion >0.7%.

[0003] In view of this, the present invention is specifically proposed. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for adjusting a battery cell based on a charge-discharge strategy and a method for manufacturing a battery.

[0005] The present invention is implemented as follows: In a first aspect, the present invention provides a method for adjusting a battery cell based on a charge-discharge strategy, including: Charging the battery cell after formation to an overcharge SOC at a first rate; Letting it stand for 1 to 10 minutes; Discharging to the target SOC at a second rate; The target SOC is 2.3 to 2.7% SOC, and the overcharge SOC is 1.05 to 1.4 times the target SOC; the first rate is 0.05 to 0.33C, and the second rate is 0.05 to 0.2C.

[0006] In an alternative embodiment, the second rate is less than the first rate.

[0007] In an alternative embodiment, the method of charging the battery cell after formation to an overcharge SOC at a first rate includes: Performing two charges. The first charge is at 0.15 to 0.25C for 6 to 8 minutes; the second charge is at 0.05C to 0.15C for 2 to 4 minutes.

[0008] In an alternative embodiment, the charging rate of the first charge in the two charges is greater than that of the second charge.

[0009] In an alternative embodiment, the standing time is 1 to 10 minutes.

[0010] In an alternative embodiment, the battery cell is LiFePO4 Battery

[0011] In an alternative embodiment, after grading the battery, discharge it completely and then charge it to the supercharge SOC at the first rate.

[0012] In an alternative embodiment, discharge it at a rate greater than 0 and ≤ 0.33C.

[0013] In a second aspect, the present invention provides a method for manufacturing a battery, including: Prepare battery cells; Grade the battery cells; Adjust the battery according to the adjustment method of any of the foregoing embodiments.

[0014] The present invention has the following beneficial effects: The method for adjusting the SOC of battery cells based on charge and discharge strategies provided by the embodiments of the present invention actively counteracts the polarization voltage through charge and discharge cycles (polarization dynamic compensation), uses the relaxation effect in the discharge stage to shorten the stabilization time (voltage convergence acceleration), and breaks through the traditional single-path limit of SOC through two-way charge and discharge adjustment (SOC-voltage decoupling optimization), achieving the effects of reducing the polarization effect of battery cells, narrowing the voltage difference within the group, and shortening the shelf time. Description of the Drawings

[0015] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as limiting the scope. For those of ordinary skill in the art, other related drawings can be obtained based on these drawings without creative efforts.

[0016] Figure 1 OCV distribution diagrams for adjusting to 2.5% SOC in different embodiments and comparative examples. Detailed Embodiments

[0017] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. For those conditions not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. For reagents or instruments not specified by the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0018] The features and performance of the present invention will be further described in detail below in conjunction with the embodiments.

[0019] The method for adjusting battery cells based on charge and discharge strategies and the method for manufacturing a battery provided by the embodiments of the present invention are described below.

[0020] An embodiment of the present invention provides a method for regulating a battery cell based on a charge-discharge strategy, including: Charging the sorted battery cell at a first rate to an overcharge SOC; Letting it stand for 1 to 10 minutes; Discharging at a second rate to a target SOC; The target SOC is 2.3 to 2.7% SOC (such as 2.3% SOC, 2.5% SOC, or 2.7% SOC), and the overcharge SOC is 1.05 to 1.4 times the target SOC (such as 1.05 times, 1.1 times, 1.2 times, 1.3 times, or 1.4 times); the first rate is 0.05 to 0.33C (such as 0.05C, 0.1C, 0.2C, or 0.33C), and the second rate is 0.05 to 0.2C (such as 0.05C, 0.1C, 0.15C, or 0.2C).

[0021] The method for regulating a battery cell based on a charge-discharge strategy provided by the embodiment of the present invention first charges the sorted battery cell at a low rate to a value slightly higher than the target SOC to trigger the polarization voltage but control it in the non-saturated region; then lets it stand for an appropriate time to rapidly decay the polarization; and then compensates and regulates it to the target SOC at a low rate, using the depolarization effect of the reverse current to cancel the residual polarization. The regulation method provided by the present invention actively cancels the polarization voltage (polarization dynamic compensation) through charge-discharge cycles, uses the relaxation effect in the discharge stage to shorten the stabilization time (voltage convergence acceleration), and breaks through the traditional single-path limit of SOC (SOC-voltage decoupling optimization) through two-way charge-discharge regulation, achieving the effects of reducing the polarization effect of the battery cell, narrowing the voltage difference within the group, and shortening the shelving time.

[0022] Preferably, to further reduce polarization, the second rate is less than the first rate.

[0023] Preferably, to better reduce polarization, the way of charging the sorted battery cell at a first rate to an overcharge SOC includes: Performing two charges. The first charge is at 0.15 to 0.25C (such as 0.15C, 0.2C, or 0.25C) for 6 to 8 minutes (such as 6 minutes, 7 minutes, or 8 minutes); the second charge is at 0.05C to 0.15C (such as 0.05C, 0.1C, or 0.15C) for 2 to 4 minutes (such as 2 minutes, 3 minutes, or 4 minutes).

[0024] Preferably, to better reduce polarization, the charging rate of the first charge in the two charges is greater than that of the second charge.

[0025] Optionally, the battery cell is a LiFePO 4 battery. Specifically, for example, it is LiFePO 4Soft-pack battery.

[0026] Preferably, after the battery is formation-tested, it is discharged completely and then charged at the first rate to the supercharge SOC.

[0027] Specifically, taking a soft-pack battery with a capacity of 20 Ah and a charge-discharge voltage range of 2.5~3.65 V as an example, the operation method after the battery monomers are assembled is as follows: 4 Soft-pack battery, capacity 20 Ah, charge-discharge voltage range 2.5~3.65 V. For example, the operation method after the battery monomers are assembled is as follows: S1. Alignment at the end of discharge: The battery monomers are formation-tested at 25±2°C with a charge-discharge rate of 0.5C, and then discharged at a current of ≤0.33C to the lower limit voltage of 2.3V to completely discharge the battery monomers. S2. SOC adjustment: At 25±2°C, charge at the first rate to the supercharge SOC, stand for 1~10 min (such as 1 min, 5 min or 10 min), and then discharge at the second rate to the target SOC. Preferably, the standing time is 3~7 min, such as 5 min.

[0028] The present invention provides a method for manufacturing a battery, including: Preparing battery monomers; Performing formation on the battery monomers; Adjusting the battery according to the adjustment method provided in the embodiments of the present invention.

[0029] Since the method for manufacturing a battery provided by the present invention includes the adjustment method provided in the embodiments of the present invention, this manufacturing method does not require long-term shelving compared with the existing manufacturing methods, and greatly shortens the production time of the battery.

[0030] Examples and comparative examples 1. Monomer type: LiFePO 4 Soft-pack battery, capacity 20 Ah, charge-discharge voltage range 2.5~3.65 V; divided into 4 groups, with 250 pcs in each group; 2. Alignment at the end of discharge: The battery monomers are formation-tested at 25°C with a charge-discharge rate of 0.5C, and then discharged at a current of 0.2C to the lower limit voltage of 2.3V to completely discharge the battery monomers. 3. SOC adjustment: At 25°C, adjust the SOC to 2.5% in the manner shown in Table 1. Table 1 SOC adjustment strategies for each example and comparative example

[0031] 4. Shelf test and data collection: At 25±3°C, the OCV and ACR of the battery monomers are measured every 12 h, as Figure 1 shown, and the voltage distribution is compared with the stabilization time, and the comparison results are recorded in Table 2.

[0032] Table 2 Comparison of Voltage Distribution and Stabilization Time

[0033] 5. Test result: Passed Figure 1 It can be seen from the data in Table 2 that for each embodiment, compared with the comparative example (the existing adjustment method), the voltage range is reduced by 30% - 90%, the dispersion is reduced by 10% - 90%, and the storage time is shortened by 10% - 45%, significantly improving the consistency and production efficiency of the battery pack. In particular, for Embodiment 4, the within-group range ≤ 15 mV, the dispersion is 0.09%, and the voltage fluctuation < ±2 mV after 2.5 days of storage; compared with the comparative example of the traditional SOC adjustment method, the within-group range, dispersion, and voltage stabilization time are reduced by 90%, 88.3%, and 44.4% respectively. Although the within-group range, dispersion, and voltage stabilization time of Embodiment 6 are small, the process time is relatively long.

[0034] In summary, the battery cell adjustment method based on charge and discharge strategies provided by the embodiments of the present invention actively counteracts the polarization voltage through charge and discharge cycles (polarization dynamic compensation), uses the relaxation effect during the discharge stage to shorten the stabilization time (voltage convergence acceleration), and breaks through the traditional SOC single-path limitation through two-way charge and discharge adjustment (SOC-voltage decoupling optimization), achieving the effects of reducing the polarization effect of battery cells, narrowing the within-group voltage difference, and shortening the storage time.

[0035] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various modifications and changes. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A battery cell adjustment method based on a charge and discharge strategy, characterized in that: include: Charging the divided battery cells at a first rate to a supercharge SOC; Let stand for 1 to 10 minutes; Discharging at a second rate to a target SOC; The target SOC is 2.3~2.7%SOC, and the supercharge SOC is 1.05~1.4 times the target SOC; the first ratio is 0.05~0.33C, and the second ratio is 0.05~0.2C.

2. The adjustment method according to claim 1, characterized in that: The second magnification is smaller than the first magnification.

3. The adjustment method according to claim 1, characterized in that: The method of charging the divided battery cells at the first rate to the supercharge SOC includes: Charge twice, the first time at 0.15~0.25C for 6~8min; the second time at 0.05C~0.15C for 2~4min.

4. The adjustment method according to claim 3, characterized in that: The charging rate of the first of the two charges is greater than the charging rate of the second charge.

5. The adjustment method according to claim 1, characterized in that: The standing time is 1~10min.

6. The adjustment method according to claim 1, characterized in that: The battery cell is a LiFePO4 battery.

7. The adjustment method according to claim 1, characterized in that: After the battery is divided into different capacities, it is discharged and then charged at the first rate to a supercharge SOC.

8. The adjustment method according to claim 7, characterized in that: Discharge the battery at a rate greater than 0 and ≤ 0.33C.

9. A method for manufacturing a battery, characterized in that: include: A battery monomer is prepared; Scaling the capacity of the battery cells; The battery is regulated according to the regulation method as described in any one of claims 1 to 8.

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