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Pole piece resistance method to evaluate the stability of pole piece batch

Author:INITIAL ENERGY SCIENCE&TECHNOLOGY Co.,Ltd(IEST) Click: Time:2021-04-14 09:00:00

Pole pieces are an important part of lithium-ion batteries. The batch stability and uniformity of pole pieces affect the uniformity of lithium deintercalation and the uniformity of interface expansion thickness during charging and discharging of the battery on the one hand, and on the other hand, it will also affect the consistency of the mass production core. At present, two commonly used methods for monitoring the stability of the pole piece process are: using in-situ online laser thickness measurement or non-in-situ height gauge to monitor the uniformity of the pole piece thickness and using the pole piece post-punching weighing method to calculate the uniformity of the compaction density However, these two parameters cannot accurately represent the electrical performance of the pole piece, nor can they be related to the positive and negative electrode materials, formula, porosity and other parameters. As an important electrical performance of the pole piece, the pole piece resistance is affected by the pole piece. Thickness, pole piece formula, pole piece porosity, etc., so the difference in pole piece resistance of different batches can fully characterize the batch stability of the pole piece. Choosing the pole piece resistance method to evaluate the stability of pole piece batches has the following important meanings:

1) Quickly evaluate the process stability of lithium-ion batteries and identify defective products in advance;

2) Optimize active materials, pole piece formulas, and process parameters;

3) Assist R&D personnel to perform failure analysis of lithium-ion batteries and quickly locate key failure points;

This paper uses the pole piece resistance test method to evaluate the resistance stability of the positive and negative pole pieces of different batches, and monitors the stability of the stirring, coating, and rolling processes by formulating the resistance specification range of qualified batches to speed up the production and R&D progress .

    1.Experimental equipment and test methods

1.1 Experimental equipment: Pole piece resistance meter, model BER1300 (IEST Yuanneng Technology), electrode diameter 14mm, can apply pressure 5~60MPa. The equipment is shown in Figure 1(a) and 1(b).

 

1.2 Test methods: Cut the pole piece sample to be tested into a rectangular size of about 5cm×10cm and place it on the sample stage. After setting the test pressure and pressure holding time on the MRMS software, start the test. The software will automatically read the pole piece thickness, resistance, resistivity, conductivity and other data.

2. Data analysis

Select 10 batches of rolled positive and negative pole pieces for pole piece resistance test, the data results are shown in Figure 2 (a) and 3 (b). Comparing the resistance data of the positive pole piece, if the resistance specification range of this sample is 26~28mΩ through a large number of tests before, and the test results of the 10 batches this time are all within this range, indicating that the data is qualified, it can be considered that there is no abnormality in the uniformity of the pole piece, and the process control is relatively stable. Comparing the negative pole piece resistance data, if the resistance specification range of this sample is 2~4mΩ through a large number of tests before, and 9 of the 10 batches of test results this time were within the pass range. the result of 1 batch is greater than 4 mΩ, it can intercept abnormal batches, further combine SEM topography analysis, pole piece density and other methods to investigate the cause of the high resistance, which may be caused by factors such as uneven mixing of the slurry, uneven coating, or poor parallelism between the rolls of the roll press.

 

 

Figure 2. (a) Positive pole piece resistance after rolling 10 batches; (b) Negative pole piece resistance after rolling 10 batches

3. Summarize

Using the pole piece resistance test method to evaluate the resistance stability of the positive and negative pole pieces of different batches can be monitored. In addition, the stability of the stirring, coating, and rolling processes can be monitored by formulating the resistance specification range of qualified batches to speed up production and research and development progress.


 Initial Energy Science&Technology Co.,Ltd(IEST)

Address: Unit 426-430, 4th floor, Hamanni Plaza, No.2 Huli Avenue, Huli District, Xiamen City  Tel: (86) 592-5367060 Mobile Email: info@iesttech.com

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@copyrigth 2020 INITAL ENERGY SCIENCE&TECHNOLOGYCo.,Ltd(IEST)  technical support:zacnet

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