Prejudgment and solution method for internal resistance abnormity of lithium ion battery

Abstract

The pre-judging and solving method for the internal resistance abnormity of the lithium ion battery comprises the following steps: S1, selecting a machine to respectively obtain slurry samples from the upper position, the middle position and the lower position in a positive pole homogenizing process and a negative pole homogenizing process; s2, testing the resistivity of the three slurry samples by adopting a slurry resistance meter; s3, comparing the resistivity test results of the three slurry samples with a process standard, and if the test results are normal, continuing the next process procedure; and if the test result is abnormal, taking remedial measures until the test result is normal, and then carrying out the next process program. The method is completely adaptive to the existing lithium ion battery positive and negative plate production process, the operation method is simple, and the problem of abnormal internal resistance of the battery caused by abnormal homogenate can be effectively avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium-ion batteries, and in particular to a method for predicting and solving abnormal internal resistance of lithium-ion batteries. Background Art

[0002] The internal resistance of lithium-ion batteries directly affects the battery's charge and discharge efficiency, temperature changes, power characteristics, cycle life, and safety performance, and is one of the key indicators for measuring lithium-ion battery performance. The internal resistance of lithium-ion batteries is generally divided into ohmic internal resistance and polarization internal resistance. The ohmic internal resistance is closely related to the resistance between the components and assemblies of the battery, while the polarization internal resistance is mainly determined by the polarization of the electrochemical reaction of batteries with different material systems.

[0003] Inconsistent internal resistance of single cells will also lead to excessive voltage difference between cells in the back-end battery pack assembly, seriously affecting the service life and safety of the battery pack. Therefore, internal resistance is an important parameter for battery performance screening. By comparing the time required for the tested battery and the normal battery to be charged to the same voltage value at constant current or the voltage value corresponding to the same constant current charging time during the formation stage, batteries with good consistency can be quickly screened out during the formation stage, shortening the screening test cycle. However, it is impossible to avoid the problem of abnormal internal resistance of the entire batch of batteries due to abnormal production control. Relevant patents include CN108020788A "A method for rapid screening of internal resistance of lithium-ion batteries".

[0004] In the production process of lithium-ion batteries, the internal resistance of the lithium-ion battery can be estimated in advance by monitoring the resistivity or resistance value of the positive and negative electrode sheets, and it can be determined whether it can meet the subsequent production design requirements. This can avoid the problem of large-scale scrapping of lithium-ion batteries due to abnormal internal resistance of the electrode sheets. However, the electrode sheets with abnormal internal resistance can no longer be put into use, which still causes an increase in production costs. Relevant patents include CN108196123B "A method for judging abnormal internal resistance of lithium-ion battery cells".

[0005] Therefore, there is an urgent need for a method that can predict abnormal internal resistance of lithium-ion batteries during the preparation of positive and negative electrode slurries, and solve the problem of abnormal internal resistance by timely adjusting the homogenization process, avoiding the preparation of slurry with abnormal resistivity into electrode sheets, and completely solve the problem of abnormal internal resistance of batteries caused by abnormal homogenization from the source of production, significantly improve the production qualification rate, and reduce production costs. Summary of the invention

[0006] The purpose of the present invention is to provide a prediction and solution for abnormal internal resistance of a lithium-ion battery, which can effectively avoid the abnormal internal resistance of the battery caused by abnormal homogenization.

[0007] In order to achieve the above-mentioned purpose, the present invention provides a prediction and solution method for abnormal internal resistance of a lithium-ion battery, comprising: S1, in the process of positive electrode homogenization and negative electrode homogenization, selecting an opportunity to obtain slurry samples from the upper, middle and lower positions respectively; S2, using a slurry resistance meter to test the resistivity of the three slurry samples; S3, comparing the resistivity test results of the three slurry samples with the process standard, if the test result is normal, continuing to the next process procedure; if the test result is abnormal, taking remedial measures until the test result is normal before proceeding to the next process procedure.

[0008] The above prediction and solution of abnormal internal resistance of lithium-ion batteries, wherein in the step S1, the premise of obtaining the slurry sample is that the slurry already contains a solvent and at least one conductive agent and the slurry has a certain fluidity.

[0009] The prediction and solution of abnormal internal resistance of the above-mentioned lithium-ion battery, wherein, in the step S1, if the positive electrode or negative electrode homogenization process includes multiple additions, a slurry sample is obtained before the previous dispersion step is completed and before the next addition.

[0010] The above prediction and solution of abnormal internal resistance of lithium-ion batteries, wherein in step S1, the upper, middle and lower positions are any positions of the upper, middle and lower parts of the slurry body during sampling.

[0011] The above-mentioned prediction and solution of abnormal internal resistance of lithium-ion batteries, wherein in the step S1, the volume of the slurry sample obtained is 50mL to 150mL.

[0012] The above-mentioned prediction and solution of abnormal internal resistance of lithium-ion batteries, wherein, in step S2, the same test time, sampling time and data acquisition method are used for positive electrode slurry samples or negative electrode slurry samples of different batches of the same product.

[0013] The above-mentioned prediction and solution of abnormal internal resistance of lithium-ion batteries, wherein, in step S2, the test time of the slurry resistor meter is 5min to 20min, the sampling time is 10s to 30s, and the average value of the last ten data points is taken as the resistivity of the slurry sample.

[0014] The above-mentioned prediction and solution of abnormal internal resistance of lithium-ion batteries, wherein, in the step S3, the resistivity test results of the upper, middle and lower three slurry samples are compared with the process standards respectively. If the resistivity test results of the three slurry samples all meet the process standards, the test results are judged to be normal; if only one of the resistivity test results of the three slurry samples does not meet the process standards, the test results are judged to be abnormal.

[0015] The prediction and solution of the abnormal internal resistance of the above-mentioned lithium-ion battery, wherein, in the step S3, the remedial measures can be one or a combination of more than two of extending the slurry dispersion time, increasing the stirring revolution speed, increasing the stirring rotation speed, adjusting the cooling water flow rate, and adjusting the cooling water temperature.

[0016] Compared with the prior art, the beneficial technical effects of the present invention are:

[0017] (1) The present invention predicts and solves the abnormal internal resistance of lithium-ion batteries, and only requires adding sampling and testing steps to the existing production process, without introducing special processes and special processes. It is fully compatible with the existing production process of positive and negative electrodes of lithium-ion batteries, and the operation method is simple;

[0018] (2) The method for predicting and solving the abnormal internal resistance of lithium-ion batteries of the present invention can timely detect the uniformity of dispersion of materials such as conductive agents in the mixing stage, and predict the abnormal internal resistance of batteries caused by abnormal homogenization. Compared with evaluation methods such as battery internal resistance testing and electrode resistivity testing, the method has the advantages of being early, fast, and efficient, ensuring the efficient use of production resources and significantly reducing production costs.

[0019] (3) The prediction and solution of the abnormal internal resistance of the lithium-ion battery of the present invention can timely solve the abnormal internal resistance of the battery caused by abnormal homogenization in the mixing stage, prevent the quality problems from expanding, ensure the smoothness of the production process and product quality, avoid abnormal problems from the source of production, significantly improve the product qualification rate, and improve the economic benefits of the enterprise. DETAILED DESCRIPTION

[0020] The following is a further detailed description of the prediction and solution of abnormal internal resistance of the lithium-ion battery of the present invention.

[0021] The prediction and solution of abnormal internal resistance of lithium-ion batteries of the present invention include:

[0022] S1, during the homogenization of the positive electrode and the negative electrode, slurry samples are obtained from the upper, middle and lower positions respectively;

[0023] The prerequisite for obtaining a slurry sample is that there is a solvent and at least one conductive agent in the slurry and the slurry has a certain fluidity; the slurry sample must have a certain fluidity before the test probe of the slurry resistor meter can be placed in the sample for resistivity testing, and at least one conductive agent must be dispersed in the slurry sample so that the slurry sample has a certain conductivity, otherwise the resistivity obtained by the test is meaningless;

[0024] If the positive or negative electrode slurry preparation process includes multiple feedings, a slurry sample can be obtained after the previous dispersion step is completed and before the next feeding; taking the wet mixing method as an example, after the conductive agent 1 is dispersed according to the process requirements, the traditional method is to add the conductive agent 2 to continue the homogenization process, while in the present invention, the slurry can be sampled and the conductivity can be measured before the conductive agent 2 is added to monitor whether the dispersion process of the conductive agent 1 is abnormal. Similarly, after the conductive agent 2 is dispersed according to the process requirements, the slurry can be sampled and the conductivity can be measured before the next feeding to monitor whether the dispersion process of the conductive agent 2 is abnormal, so as to ensure the product quality at each stage of the homogenization process;

[0025] The upper, middle and lower positions can be any position of the upper, middle and lower part of the slurry body during sampling; by testing the samples at the upper, middle and lower positions, the consistency between the samples can be analyzed, which is helpful to judge whether the slurry has abnormal phenomena such as stratification and unevenness;

[0026] Preferably, the volume of the slurry sample obtained is 50mL to 150mL; if the slurry sample volume is less than 50mL, the slurry may not cover the slurry resistance meter test probe, affecting the accuracy of the test results; if the slurry sample volume is greater than 150mL, multiple sampling may change the final slurry ratio, affecting product performance;

[0027] S2, the resistivity of three slurry samples was tested using a slurry resistance meter;

[0028] For the positive electrode slurry samples or negative electrode slurry samples from different batches of the same product, the same test time, sampling time and data collection method shall be used;

[0029] Preferably, the test time of the slurry resistor meter is 5min to 20min, the sampling time is 10s to 30s, and the average value of the last ten data points is taken as the resistivity of the slurry sample; if the test time is less than 5min, the test value may not reach a steady state, affecting the judgment of the final result; if the test time is greater than 20min, the test time may be too long, prolonging the homogenization time and affecting the production efficiency;

[0030] S3, comparing the resistivity test results of the three slurry samples with the process standards, if the test results are normal, proceeding to the next process; if the test results are abnormal, taking remedial measures until the test results are normal before proceeding to the next process;

[0031] Assume that the resistivity test results of the upper, middle and lower slurry samples are ρ top , mid , bot , and ρ top , mid , botCompared with the process standards respectively, if ρ top , mid , bot If both meet the process standards, the test results are considered normal; ρ top , mid , bot If any one of them does not meet the process standard, the test result is considered abnormal;

[0032] The remedial measures may be one or a combination of two or more of extending the slurry dispersion time, increasing the stirring revolution speed, increasing the stirring rotation speed, adjusting the cooling water flow rate, and adjusting the cooling water temperature.

[0033] Example

[0034] The positive electrode of a lithium-ion battery is a high-nickel ternary material. The traditional wet mixing process is used in its preparation. The positive electrode formula is designed to be high-nickel ternary: binder: conductive agent 1: conductive agent 2 = 96:2:1:1. The mixing order is: ① making glue ② adding conductive agent 1 ③ adding conductive agent 2 ④ adding high-nickel ternary ⑤ adding NMP.

[0035] Before adding materials in processes ③, ④, and ⑤, 80 mL of slurry samples were obtained from the upper, middle, and lower parts of the slurry body, and the resistivity of the three slurry samples was tested using a slurry resistor. The test time was 8 minutes, the sampling time was 20 seconds, and the average of the last ten data points was taken as the resistivity of the slurry sample. The results are shown in Table 1. As can be seen from Table 1, the dispersion process of conductive agent 1 and conductive agent 2 is normal, but after the addition of high nickel ternary, the resistivity of the slurry is too large after the homogenization is completed according to the process requirements, which exceeds the process standard range. Therefore, the product preparation process was temporarily changed, and the dispersion time of high nickel ternary was increased by 30 minutes. The sample was tested again, and the resistivity obtained could meet the process standard. It was judged that the homogenization process returned to normal, and the subsequent electrode preparation and battery preparation could be carried out. The internal resistance of the lithium-ion battery finally prepared met the product performance index requirements.

[0036] Table 1 Resistivity test results of positive electrode slurry

[0037]

[0038]

[0039] The prediction and solution of abnormal internal resistance of the lithium-ion battery in this embodiment is simple to operate and is fully compatible with the existing production process of positive and negative electrode sheets of lithium-ion batteries, and can effectively avoid the problem of abnormal internal resistance of the battery caused by abnormal slurry.

[0040] Although the content of the present invention has been specifically described by the above embodiments, it should be appreciated that the above description should not be considered as a limitation of the present invention. After reading the above content, it will be apparent to those skilled in the art that various modifications and substitutions of the present invention will occur. Therefore, the protection scope of the present invention should be limited by the appended claims.

Claims

1. Prediction and solution of abnormal internal resistance of lithium-ion batteries, characterized in that: include: S1, during the homogenization of the positive electrode and the negative electrode, slurry samples are obtained from the upper, middle and lower positions respectively; S2, the resistivity of three slurry samples was tested using a slurry resistance meter; S3, comparing the resistivity test results of the three slurry samples with the process standards, if the test results are normal, proceed to the next process procedure; If the test result is abnormal, remedial measures are taken until the test result is normal before proceeding to the next process.

2. The method for predicting and solving abnormal internal resistance of a lithium-ion battery according to claim 1, characterized in that: In the step S1, the premise for obtaining the slurry sample is that the slurry already contains a solvent and at least one conductive agent and the slurry has a certain fluidity.

3. The method for predicting and solving abnormal internal resistance of a lithium-ion battery according to claim 2, characterized in that: In step S1, if the homogenization process of the positive electrode or the negative electrode includes multiple additions, a slurry sample is obtained after the previous dispersion step is completed and before the next addition.

4. The method for predicting and solving abnormal internal resistance of a lithium-ion battery according to claim 1, characterized in that: In step S1, the three positions of upper, middle and lower are any positions of the upper, middle and lower part of the slurry body during sampling.

5. The method for predicting and solving abnormal internal resistance of a lithium-ion battery according to claim 1, characterized in that: In the step S1, the volume of the slurry sample obtained is 50 mL to 150 mL.

6. The method for predicting and solving abnormal internal resistance of a lithium-ion battery according to claim 1, characterized in that: In step S2, the same test time, sampling time and data acquisition method are used for positive electrode slurry samples or negative electrode slurry samples of different batches of the same product.

7. The method for predicting and solving abnormal internal resistance of a lithium-ion battery according to claim 6, characterized in that: In step S2, the test time of the slurry resistor meter is 5 minutes to 20 minutes, the sampling time is 10 seconds to 30 seconds, and the average value of the last ten data points is taken as the resistivity of the slurry sample.

8. The method for predicting and solving abnormal internal resistance of a lithium-ion battery according to claim 1, characterized in that: In the step S3, the resistivity test results of the upper, middle and lower slurry samples are compared with the process standards respectively. If the resistivity test results of the three slurry samples all meet the process standards, the test results are judged to be normal; If any one of the resistivity test results of the three slurry samples does not meet the process standard, the test result is considered abnormal.

9. The method for predicting and solving abnormal internal resistance of a lithium-ion battery according to claim 1, characterized in that: In step S3, the remedial measures may be one or a combination of two or more of extending the slurry dispersion time, increasing the stirring revolution speed, increasing the stirring rotation speed, adjusting the cooling water flow rate, and adjusting the cooling water temperature.

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