Resistance threshold determination method, determination device, electronic device and medium for performance anomaly of sodium battery positive electrode sheet

Abstract

The present application belongs to the field of sodium ion battery testing, and particularly relates to a method and device for determining the abnormal resistance threshold of a sodium battery cathode sheet, an electronic device and a medium. The method for determining the abnormal resistance threshold of a sodium battery cathode sheet compares the volume resistance Rv and surface resistance Rs of the sample to be tested with the first threshold and the second threshold, respectively, to determine the abnormal performance of the sodium battery cathode sheet. If Rv>the first threshold or Rs>the second threshold, the performance is determined to be abnormal. The present application first discloses a test method for the absolute resistance threshold of the abnormal performance of a sodium battery cathode sheet, and determines the specific values of the first threshold and the second threshold, filling the gap of quantitative criteria in this field. The threshold is statistically obtained based on a large amount of experimental data (≥50 samples), and is scientific and reproducible. At the same time, the first threshold and the second threshold can be directly used by process personnel as process optimization targets, shortening the process development cycle.

Description

Technical Field

[0001] This invention belongs to the field of sodium-ion battery testing, specifically relating to a method, device, electronic equipment, and medium for determining the resistance threshold of an abnormal performance of a sodium battery positive electrode. Background Technology

[0002] Sodium-ion batteries have broad application prospects in large-scale energy storage, low-speed electric vehicles, and two-wheeled vehicles due to their abundant resources, low cost, and excellent low-temperature performance. The positive electrode is the core component of a sodium battery, and its conductivity directly affects the battery's rate performance, cycle life, and safety performance.

[0003] Electrode resistance is a key parameter for measuring the conductivity of the positive electrode, and is generally divided into volume resistivity (unit: Ω·cm) and sheet resistance (unit: Ω·cm). 2 Bulk resistance reflects the conductivity of the electrode in the thickness direction and is related to the electron transport efficiency in the active material layer; surface resistance reflects the conductivity uniformity of the electrode surface layer and is related to the construction quality of the conductive network in the coating.

[0004] In the manufacturing process of sodium battery cathode sheets, process parameters such as coating and rolling (e.g., compaction density, rolling temperature, coating surface density) as well as material formulation (type and content of conductive agent, binder characteristics, etc.) all affect the bulk resistance and surface resistance of the electrode sheet. If the electrode sheet resistance is too high, it will lead to problems such as increased battery polarization, insufficient capacity utilization, poor rate performance, and shortened cycle life.

[0005] Currently, the industry's determination of the resistance of sodium battery positive electrode sheets largely relies on empirical values ​​or analogies with lithium-ion batteries. A quantitative and absolute threshold for abnormal resistance, validated through systematic experiments, has not yet been established. Some companies use a relative comparison method (comparing the resistance value of the electrode to be tested with that of a standard electrode; if the difference exceeds a preset range, it is deemed unqualified). This method depends on the selection and stability of the standard electrode, and carries the risk of benchmark drift. Other technologies assemble electrodes with different resistances into cells and then use the cell's internal resistance process standards to deduce the allowable boundaries of the electrode resistance. However, this method is indirect and requires numerous combined experiments, resulting in low efficiency. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method, device, electronic device and medium for determining the resistance threshold of abnormal performance of sodium battery positive electrode.

[0007] A method for determining the resistance threshold of a sodium battery positive electrode sheet with abnormal performance is provided. The method determines the abnormal performance of the sodium battery positive electrode sheet by comparing the volume resistance Rv and surface resistance Rs of the sample to be tested with a first threshold and a second threshold, respectively. If Rv > the first threshold or Rs > the second threshold, the performance is determined to be abnormal.

[0008] Preferably, the first threshold is 12 Ω·cm and the second threshold is 0.15 Ω·cm. 2 .

[0009] The method for confirming the first threshold and the second threshold includes the following steps: 1) preparing at least 50 positive electrode sheets with different resistance levels; 2) testing the resistance value of each positive electrode sheet; the resistance value includes volume resistance and surface resistance; 3) assembling each positive electrode sheet with the same batch of qualified negative electrode sheets into a battery; 4) performing performance tests on the battery, recording the number of cycles and capacity retention rate when the capacity decays to 80% of the initial value; 5) plotting scatter plots of Rv versus cycle life and Rs versus capacity retention rate; determining the first threshold based on the inflection point of the scatter plot of Rv versus cycle life, and determining the second threshold based on the inflection point of the scatter plot of Rs versus capacity retention rate.

[0010] By adjusting the residual alkali content, conductive agent content, rolling pressure, and coating density, 50 positive electrode sheets with different resistance levels were prepared.

[0011] Step 2) The volume resistance and surface resistance are measured using the online four-probe method. Five equidistant points are taken along the length of each positive electrode. The volume resistance and surface resistance are measured at each point, and the average value is taken as the Rv and Rs of that electrode.

[0012] Step 4) The cycle life test method is as follows: constant current charge and discharge at 1C rate and 25℃, voltage range 1.5-4.0V, record the number of cycles when the capacity decays to 80% of the initial value; the rate performance test method is as follows: discharge at 0.2C, 1C and 5C respectively, and calculate the 5C / 0.2C capacity retention rate.

[0013] The method for determining the resistance threshold of the sodium battery positive electrode sheet performance abnormality includes the following steps: 1) Obtain the positive electrode sheet to be tested; 2) Measure the volume resistance Rv and the surface resistance Rs; 3) Determine if Rv > the first threshold or Rs > the second threshold; 4) If the result is otherwise, determine that it is qualified; if the result is yes, determine that it is abnormal; 5) If it is qualified, output a qualified signal; if it is abnormal, output an abnormal signal.

[0014] The present invention also includes a determination device for performing the determination method described above; including a testing module for testing the volume resistance Rv and surface resistance Rs of the sample to be tested; Judgment module: Used to compare the results of the test module with the first threshold and the second threshold; and to make a judgment based on the comparison results.

[0015] The present invention also includes an electronic device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that the processor implements the determination method when executing the program.

[0016] The present invention also includes a storage medium having a computer program stored thereon, which, when executed by a processor, implements the determination method described above.

[0017] Compared with the prior art, the beneficial effects of the present invention are: This invention discloses for the first time a test method for the absolute resistance threshold of sodium battery positive electrode performance abnormalities, and simultaneously determines the specific values ​​of the first and second thresholds, filling a gap in quantitative criteria in this field. These thresholds are statistically derived from a large amount of experimental data (≥50 samples), possessing scientific validity and repeatability. Applying this method to the testing of samples allows for rapid determination during the electrode manufacturing stage: a single measurement time is less than 10 seconds, allowing integration into online testing equipment for immediate determination after coating or rolling, preventing defective electrodes from flowing into subsequent assembly processes. Calculations show that this can reduce cell assembly waste by approximately 15%-25%. Furthermore, process engineers can directly use the first and second thresholds as process optimization targets, shortening the process development cycle. Attached Figure Description

[0018] Figure 1 This is a flowchart of the method for determining the resistance threshold of abnormal performance of sodium battery positive electrode sheet according to the present invention; Figure 2 This is a scatter plot of Rv versus cycle life in this invention; Figure 3 This is a scatter plot of the Rs and 5C retention rates of this invention. Detailed Implementation

[0019] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and preferred embodiments.

[0020] Example 1: Threshold determination, including the following steps: 1) Prepare at least 50 positive electrode sheets with different resistance levels; Cathode material: Sodium transition metal oxide; Conductive agent: SuperP+CNT; Binder: PVDF.

[0021] By adjusting the residual alkali content of the positive electrode (0.03-1.0wt%), the conductive agent content (0.5%-5%), the rolling pressure (20, 40, 60, 80, 100MPa), and the coating surface density (20-50g / m²), the optimal coating method can be achieved. 2 Fifty positive electrode sheets with different resistance levels were prepared. After being slit, each sheet was independently numbered.

[0022] 2) Test the resistance of each positive electrode. Using the online four-probe method, take five equidistant points (head, 1 / 4, 1 / 2, 3 / 4, and tail) along the length of each electrode. Measure the volume resistance and surface resistance at each point, and take the average value as the Rv and Rs of that electrode. Measurement results: Rv range 1-50 Ω·cm, Rs range 0-0.35 Ω·cm 2 .

[0023] 3. Full Cell Assembly: The positive electrode sheet of each design is combined with the same batch of hard carbon negative electrode sheet (with confirmed resistance) and separator (PE / PP composite film) to form a cell according to the 21700 standard winding process. After standard processes such as casing, spot welding, electrolyte injection (1M NaPF6 / EC+DEC), sealing, formation, and aging, 50 21700 cylindrical full cells are produced.

[0024] 4. Performance testing; Cycle life test: Constant current charge and discharge at 1C rate and 25℃, voltage range 1.5~4.0V, record the number of cycles when the capacity decays to 80% of the initial value.

[0025] Rate performance test: Discharge at 0.2C, 1C and 5C respectively, and calculate the 5C / 0.2C capacity retention rate.

[0026] 5. Data Analysis and Threshold Determination Plot a scatter plot of Rv versus cycle lifetime. Figure 2 It was found that when Rv>12Ω·cm, the cycle life dropped sharply from an average of 1800 cycles to 1150 cycles, a decrease of 36.1%. The statistical inflection point was 12.1Ω·cm, rounded to 12Ω·cm.

[0027] Plot a scatter plot of Rs versus 5C retention rate ( Figure 3 When Rs>0.15Ω·cm 2 At that time, the 5C retention rate dropped from an average of 94.1% to 90.1%, a decrease of 4.3%.

[0028] Determine the threshold: Volume resistance > first threshold 12 Ω·cm or surface resistance > second threshold 0.15 Ω·cm 2 It has been determined to be abnormal.

[0029] Example 2: Independent sample testing, and verification of the threshold of Example 1.

[0030] Take another 20 electrode pieces that were not involved in the threshold determination and measure their resistance using the same method. Meanwhile, 21700 batteries were assembled and their performance was tested.

[0031] The criteria were determined using a threshold of 12 / 0.15: 11 pieces were acceptable (Rv≤12 and Rs≤0.15), and 9 pieces were unacceptable (Rv>12 or Rs>0.15).

[0032] Actual test results: The average cycle life of the qualified group was 1810 cycles, and the average cycle life of the abnormal group was 1165 cycles.

[0033] With a cycle life of ≥1500 cycles as the qualification standard, this method has an accuracy of 95% (19 / 20), a sensitivity (true positive rate) of 100%, and a specificity (true negative rate) of 90%, indicating that this threshold determination method has high reliability.

[0034] Table 1. Threshold Validation Experimental Data

[0035] Example 3: A method for determining the resistance threshold of a sodium battery positive electrode sheet with abnormal performance. The method involves measuring the bulk resistance Rv and surface resistance Rs of the sample; comparing Rv with a first threshold and Rs with a second threshold; if Rv > the first threshold or Rs > the second threshold, the performance is determined to be abnormal. The specific process is as follows: Figure 1 The following steps are shown: 1) Obtain the positive electrode of the sample to be tested; 2) Measure the bulk resistance Rv and the surface resistance Rs; 3) Determine if Rv > the first threshold or Rs > the second threshold; 4) If the result is otherwise, determine that it is qualified; if the result is yes, determine that it is abnormal; 5) If it is qualified, output a qualified signal; if it is abnormal, output an abnormal signal.

[0036] Example 4: A determination device for performing the determination method described above; including a testing module for testing the volume resistance Rv and surface resistance Rs of the sample to be tested; Judgment module: Used to compare the results of the test module with the first threshold and the second threshold; and to make a judgment based on the comparison results.

[0037] The present invention also includes an electronic device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that the processor implements the determination method when executing the program.

[0038] The present invention also includes a storage medium having a computer program stored thereon, which, when executed by a processor, implements the determination method described above.

[0039] In summary, this invention discloses for the first time a test method for the absolute resistance threshold of sodium battery positive electrode performance abnormalities, and simultaneously determines the specific values ​​of the first and second thresholds, filling a gap in quantitative criteria in this field. These thresholds are derived statistically from a large amount of experimental data (≥50 samples), possessing scientific validity and repeatability. Applying this method to the testing of samples allows for rapid determination during the electrode manufacturing stage: a single measurement time is less than 10 seconds, allowing integration into online testing equipment for immediate determination after coating or rolling, preventing defective electrodes from flowing into subsequent assembly processes. Calculations show that this can reduce cell assembly waste by approximately 15%-25%. Furthermore, process engineers can directly use the first and second thresholds as process optimization targets, shortening the process development cycle.

[0040] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for determining the resistance threshold of abnormal performance of a sodium battery positive electrode, characterized in that, The performance of the sodium battery cathode is determined by comparing the volume resistance Rv and surface resistance Rs of the sample to the first threshold and the second threshold, respectively; if Rv > the first threshold or Rs > the second threshold, the performance is determined to be abnormal.

2. The method for determining the resistance threshold of abnormal performance of sodium battery positive electrode sheet according to claim 1, characterized in that, The first threshold is 12 Ω·cm, and the second threshold is 0.15 Ω·cm. 2 .

3. The method for determining the resistance threshold of abnormal performance of sodium battery positive electrode sheet according to claim 1, characterized in that, The method for confirming the first and second thresholds includes the following steps: 1) preparing at least 50 positive electrode sheets with different resistance levels; 2) testing the resistance value of each positive electrode sheet, wherein the resistance value includes volume resistance and surface resistance; 3) assembling each positive electrode sheet with the same batch of qualified negative electrode sheets into a battery; 4) performing performance tests on the battery, recording the number of cycles and capacity retention rate when the capacity decays to 80% of the initial value; 5) plotting scatter plots of Rv versus cycle life and Rs versus capacity retention rate, respectively; and determining the first and second thresholds based on the inflection points of the scatter plots.

4. The method for determining the resistance threshold of abnormal performance of sodium battery positive electrode sheet according to claim 3, characterized in that, By adjusting the residual alkali content, conductive agent content, rolling pressure, and coating density, 50 positive electrode sheets with different resistance levels were prepared.

5. The method for determining the resistance threshold of abnormal performance of sodium battery positive electrode sheet according to claim 3, characterized in that, Step 2) The volume resistance and surface resistance are measured using the online four-probe method. Five equidistant points are taken along the length of each positive electrode. The volume resistance and surface resistance are measured at each point, and the average value is taken as the Rv and Rs of that electrode.

6. The method for determining the resistance threshold of abnormal performance of sodium battery positive electrode sheet according to claim 3, characterized in that, Step 4) The method for cycle life testing is as follows: constant current charge and discharge at 1C rate and 25℃, voltage range 1.5-4.0V, record the number of cycles when the capacity decays to 80% of the initial value; preferably, the rate performance testing method is as follows: discharge at 0.2C, 1C and 5C respectively, and calculate the 5C / 0.2C capacity retention rate.

7. The method for determining the resistance threshold of abnormal performance of sodium battery positive electrode sheet according to claim 1, characterized in that, Specifically, the steps are as follows: 1) Obtain the positive electrode of the sample to be tested; 2) Measure the volume resistance Rv and the surface resistance Rs; 3) Determine if Rv > the first threshold or Rs > the second threshold; 4) If the result is otherwise, determine that it is qualified; if the result is yes, determine that it is abnormal; 5) If it is qualified, output a qualified signal; if it is abnormal, output an abnormal signal.

8. A determining device, characterized in that, Used to perform the determination method described in any one of claims 1-7; Includes a test module for testing the volume resistance Rv and surface resistance Rs of the sample under test; Judgment module: Used to compare the results of the test module with the first threshold and the second threshold; and to make a judgment based on the comparison results.

9. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the program, it implements the determination method according to any one of claims 1-7.

10. A storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the determination method according to any one of claims 1-7.

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