Lithium ion battery self-discharging quick screening method and screening method based on DC impedance

A lithium-ion battery and DC impedance technology, which is applied in the direction of measuring devices, measuring electricity, and measuring electrical variables, can solve the problems of misjudgment of measurement accuracy, low recognition rate of slightly self-discharging cells, and time-consuming problems. Achieve the effects of improving accuracy, saving manpower and equipment investment, and improving production efficiency

Active Publication Date: 2019-08-30
天津普兰能源科技有限公司
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AI-Extracted Technical Summary

Problems solved by technology

[0004] However, the method based on standing still requires a period of stagnation, and at the same time requires a second retest of the cell data to calculate the difference, that is, the first test data is used, and due to the influence of measurement accuracy, misjudgment often occurs and the corresponding situation of production ; and the screening of charging time or capacity in the constant voltage charging stage can only screen out the batteries with serious abno...
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Method used

According to the analysis to self-discharge, and utilize the principle of shunting between parallel resistor branches, a plurality of monomer electric cores are clamped in parallel with tooling form, carry out DC impedance test to the battery system of parallel connection, promptly give in a short time Generate a current wave, read the distribution of the current in different branches after the short-time pulse, and read the current value in different branches in the last second of the short time, so as to screen out the single cells with discrete data, So as to achieve the purpose of rapid screening of sin...
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Abstract

The invention relates to a lithium ion battery self-discharging quick screening method and screening method based on DC impedance. Multiple monomer cells are connected in parallel to form a parallel battery system, thereby constructing a screening device, the DC impedance testing is performed on the parallel batter system to screened the data-discrete mono cells; the DC impedance testing specifically is to give a current wave within short time, and then read the distribution of the current in different branches after short-time pulse. The screening device disclosed by the invention has the advantages that a high-efficiency, low-input and easily-realized self-discharging screening scheme is provided; compared with the standing method, the detection time is greatly shortened, the manpower equipment input is saved, the production period is shortened, and the production efficiency is improved; and meanwhile, the distinguishing between the cells in slight short-circuit and non-short-circuitcan be enlarged by controlling the input current, the mono cell with short-circuit potential can be induced as the short-circuited cell to identify, and the detection accuracy rate is improved.

Application Domain

Electrical testing

Technology Topic

Lithium electrodePower flow +12

Image

  • Lithium ion battery self-discharging quick screening method and screening method based on DC impedance
  • Lithium ion battery self-discharging quick screening method and screening method based on DC impedance
  • Lithium ion battery self-discharging quick screening method and screening method based on DC impedance

Examples

  • Experimental program(2)

Example Embodiment

[0021] Example 1:
[0022] The battery cell is selected as 20ah ternary/lithium titanate cylindrical battery cell, and the shipping state is 50% SOC. At the end of the formation, the battery cell is charged or discharged to the shipping state, and then this test is performed. Install the above-mentioned cells in the lower bus bar cell filling position, connect the upper and lower bus bars to the high-current charging and discharging equipment charging and discharging machine, use the charging and discharging machine to charge the screening device with a current of 2C×7 for 5s, and read Take the current at 5s, the specific values ​​are shown in Table 1;
[0023] Table 1
[0024]
[0025]
[0026] According to the data in Table 1, it can be seen that the current value of the No. 5 cell is significantly higher than the other 6 groups, which is a defective cell. For further verification, the above-mentioned cell is fully charged and allowed to stand at room temperature for 1 month to test its capacity retention rate. As shown in table 2.
[0027] Table 2
[0028] Serial number 1 2 3 4 5 6 7 Capacity retention rate 98.6% 99.1% 98.4% 99.0% 96.2% 99.1% 99.2%
[0029] It can be seen from the data in Table 2 that the capacity retention rate of the No. 5 cell is lower than the other six groups. The No. 5 cell is disassembled and found that there are 7 black spots with a diameter of less than 1 mm in the diaphragm, which are self-discharge points. Confirmed the accuracy of the detection scheme.

Example Embodiment

[0030] Example 2:
[0031] Choose the battery cell to be 20ah ternary/lithium titanate cylindrical cell, and the shipping state is 50% SOC. At the end of the formation, charge or discharge the cell to the shipping state to perform this test. This test expands the number of samples to 28 single cells.
[0032] First test the 28 cells by the static method, and then test their OCV difference after 3 days of high temperature standing. The test data is shown in Table 3, and the unit is V;
[0033] table 3
[0034]
[0035]
[0036] According to the data in Table 3, the test results are normal, and these 28 single cells have no defective cells. Then divide the 28 cells into 4 groups, install them in the lower bus bar, connect to the upper bus bar in turn, charge the screening device with a charging and discharging machine with a current of 5C×7 for 5 seconds, and read the current at the 5th second. The specific values ​​are as follows Table 4;
[0037] Table 4
[0038] Serial number 1 2 3 4 5 6 7 Current value/A 19.4 18.9 24.9 19.0 19.2 19.5 19.2 Serial number 8 9 10 11 12 13 14 Current value/A 18.8 25.7 18.7 18.6 19.6 19.1 19.3 Serial number 15 16 17 18 19 20 21 Current value/A 19.9 19.4 19.6 20.5 19.7 20.3 20.5 Serial number 22 23 24 25 26 27 28 Current value/A 20.1 20.9 20.2 19.8 19.7 20.3 19.3
[0039] According to Table 4, it can be seen that the data of No. 3 and No. 9 batteries are significantly different from other batteries. Dismantling the No. 3 and No. 9 batteries, it is found that there are 5 to 7 black spots with a diameter of less than 1mm in the diaphragm. It is the short-circuit point. Compared with the traditional static method, this solution can expand the difference between light short-circuit and non-short-circuit cells, induce single cells with short-circuit hazards as short-circuit cells and identify them, and this method is real-time The comparison of data eliminates the influence of initial data due to measurement accuracy, and the screening results are more accurate.

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