Single-walled carbon nanotube conductive paste four-probe resistivity test method

Abstract

The present application belongs to the technical field of lithium ion batteries, and particularly relates to a single-walled carbon nanotube conductive paste four-probe resistivity testing method. Pure Si powder is used as an active substance, single-walled carbon nanotube conductive paste is used as a conductive agent, CMC and SBR are used as binders, and a certain formula proportion is mixed and stirred to prepare a uniform paste, which is coated on a preservative film, cut into pieces after drying at 60 DEG C for 30 min, pressed into tablets, and finally tested by using a four-probe tester. The method is more stable and accurate in testing data, low in cost, and simple in process.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery technology, specifically relating to a four-probe resistivity testing method for single-walled carbon nanotube conductive paste. Background Technology

[0002] Single-walled carbon nanotube (SUV) conductive pastes possess excellent conductivity, as well as high strength, high flexibility, and a high aspect ratio. Currently, SUV conductive pastes have been applied in nanoelectronic devices, energy storage devices, and structural and functional composite materials. Resistivity is one of the important performance indicators for SUV conductive pastes.

[0003] Current methods for detecting the resistivity of single-walled carbon nanotube conductive paste involve directly stirring the paste with a glass rod or a stirring paddle, coating it directly onto a PET film, cutting it into 15mm diameter sheets, holding it under 10t pressure for 3-5 minutes, measuring the thickness with a micrometer, and then testing it using a four-probe resistivity meter. This method suffers from limited sample preparation, lacks background comparison with active materials, resulting in unstable data, no reference material for comparison, and fluctuations in resistivity data when the state of the conductive paste changes. Summary of the Invention

[0004] To address the problems existing in the prior art, this invention aims to propose a four-probe resistivity testing method for single-walled carbon nanotube conductive paste. This invention uses pure Si powder as the active material, single-walled carbon nanotube conductive paste as the conductive agent, and CMC and SBR as binders. These are mixed and stirred in a specific ratio to prepare a uniform paste, which is then coated onto plastic wrap, dried at 60°C for 30 minutes, cut into sheets, pressed, and finally tested using a four-probe resistivity tester.

[0005] The present invention adopts the following technical solution.

[0006] A four-probe resistivity testing method for single-walled carbon nanotube conductive paste includes the following specific steps: Step 1: Mix deionized water and aqueous conductive slurry containing single-walled carbon nanotubes with a timer stirrer and a dispersion plate. Stir at 1000 rpm for 5-10 minutes. Step 2: Add Si powder and continue stirring for 5-10 minutes; Step 3: Add CMC and continue stirring for 1-2 hours; Step 4: Add SBR and continue stirring for 10-20 minutes; Step 5: Using a four-sided coating apparatus with a coating thickness of 400 μm, coat the glass panel with plastic wrap and no wrinkles, and use an infrared vacuum coating machine for automatic coating. Step 6: Take out the dried sample, separate it from the plastic wrap, use a manual slicer to cut the sample into thin round slices with a diameter of 12mm, and use a powder tablet press to compress them into tablets. Step 7: Use a micrometer screw gauge to measure the thickness of the sheet using the 5-point method, and use an RTS-8 digital four-probe tester to obtain the resistivity value.

[0007] Furthermore, the mass percentage ratios of each component are as follows: single-walled carbon nanotube conductive paste = 0.25%, CMC = 2.193%, Si powder = 93.4485%, SBR = 4.108%; solid content = 0.43-0.45%.

[0008] Furthermore, the timed mixer in step 1 is a timed mixer.

[0009] Furthermore, in step 5, the heating conditions of the infrared vacuum coating machine are 60°C for 30 minutes.

[0010] Furthermore, the tableting conditions in step 6 are 10 MPa and 15 s.

[0011] Compared with the prior art, the beneficial effects of the present invention are as follows.

[0012] This invention uses pure Si powder as the active material to demonstrate the resistivity performance of single-walled conductive paste; it employs vacuum stirring to remove the influence of air bubbles and impurities in the paste; and its preparation method makes the test data more stable and accurate, with low cost and simple process.

[0013] The dispersion of single-walled carbon nanotubes in the slurry was tested, and the resistivity of the same batch of single-walled carbon nanotubes in the conductive slurry was tested multiple times using this method to demonstrate stability and the accuracy of the production process. Detailed Implementation

[0014] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0015] A four-probe resistivity testing method for single-walled carbon nanotube conductive paste includes the following specific steps: Step 1: Mix deionized water and aqueous conductive slurry containing single-walled carbon nanotubes with a timer stirrer and a dispersion plate. Stir at 1000 rpm for 5-10 minutes. Step 2: Add Si powder and continue stirring for 5-10 minutes; Step 3: Add CMC and continue stirring for 1-2 hours; Step 4: Add SBR and continue stirring for 10-20 minutes; Step 5: Using a four-sided coating apparatus with a coating thickness of 400 μm, coat the glass panel with plastic wrap and no wrinkles. Use an infrared vacuum coating machine for automatic coating, with heating conditions of 60℃ for 30 min. Step 6: Take out the dried sample, separate it from the plastic wrap, use a manual slicer to cut the sample into thin round slices with a diameter of 12mm, and use a powder tablet press to compress the sample into tablets at 10MPa for 15s. Step 7: Use a micrometer screw gauge to measure the thickness of the sheet using the 5-point method, and use an RTS-8 digital four-probe tester to obtain the resistivity value.

[0016] Furthermore, the mass percentage ratios of each component are as follows: single-walled carbon nanotube conductive paste = 0.25, CMC = 2.193, Si powder = 93.448, SBR = 4.108; solid content = 0.43-0.45.

[0017] Example 1.

[0018] A four-probe resistivity testing method for single-walled carbon nanotube conductive paste includes the following specific steps: Step 1: Mix deionized water and aqueous conductive slurry containing single-walled carbon nanotubes using a planetary vacuum mixer with a dispersion disc. Stir at 1000 rpm for 5-10 minutes. Step 2: Add Si powder and continue stirring for 5-10 minutes; Step 3: Add CMC and continue stirring for 1-2 hours; Step 4: Add SBR and continue stirring for 10-20 minutes; Step 5: Using a four-sided coating apparatus with a coating thickness of 400 μm, coat the glass panel with plastic wrap and no wrinkles. Use an infrared vacuum coating machine for automatic coating, with heating conditions of 60℃ for 30 min. Step 6: Take out the dried sample, separate it from the plastic wrap, use a manual slicer to cut the sample into thin round slices with a diameter of 12mm, and use a powder tablet press to compress the sample into tablets at 10MPa for 15s. Step 7: Use a micrometer screw gauge to measure the thickness of the sheet using the 5-point method, and use an RTS-8 digital four-probe tester to obtain the resistivity value.

[0019] The same batch of single-walled carbon nanotube conductive paste was mixed according to the following mass percentages: single-walled carbon nanotube conductive paste = 0.25%, CMC = 2.193%, Si powder = 93.448%, SBR = 4.108%; solid content = 0.45%. The resistivity of the wafers was then tested using the method described above. The resistivity result was 23 Ω·cm. Repeated verification experiments: The experiment was repeated according to the test procedure in Example 1, and the data are as follows: Table 1. Data table repeated ten times.

[0020] Data dispersion: 1.06.

[0021] Comparative Example 1.

[0022] The existing resistivity testing methods are as follows: Step 1: Mix deionized water and aqueous conductive slurry containing single-walled carbon nanotubes using a planetary vacuum mixer with a dispersion disc. Stir at 1000 rpm for 5-10 minutes. Step 2: Add SiO powder and continue stirring for 5-10 minutes; Step 3: Add CMC and continue stirring for 1-2 hours; Step 4: Add SBR and continue stirring for 10-20 minutes; Step 5: Using a four-sided coating apparatus with a coating thickness of 400 μm, coat the glass panel with plastic wrap and no wrinkles. Use an infrared vacuum coating machine for automatic coating, with heating conditions of 60℃ for 30 min. Step 6: Take out the dried sample, separate it from the plastic wrap, use a manual slicer to cut the sample into thin round slices with a diameter of 12mm, and use a powder tablet press to compress the sample into tablets at 10MPa for 15s. Step 7: Use a micrometer screw gauge to measure the thickness of the sheet using the 5-point method, and use an RTS-8 digital four-probe tester to obtain the resistivity value.

[0023] The same batch of single-walled carbon nanotube conductive paste was mixed according to the following mass percentages: single-walled carbon nanotube conductive paste = 0.25%, CMC = 2.193%, SiO powder = 93.448%, SBR = 4.108%; solid content = 0.45%. The resistivity of the wafers was then tested using the method described above. The resistivity result was 102 Ω·cm.

[0024] Repeated verification experiments: Table 2. Data table repeated ten times.

[0025] Data dispersion: 11.275.

[0026] The dispersion of the repeated experimental data in Example 1 is lower than that in Comparative Example 1. The representativeness of the central tendency measure values ​​in the Example 1 data is stronger than that in Comparative Example 1.

Claims

1. A four-probe resistivity testing method for single-walled carbon nanotube conductive paste, characterized in that, The specific steps include the following: Step 1: Mix deionized water and aqueous conductive slurry containing single-walled carbon nanotubes with a timer stirrer and a dispersion plate. Stir at 1000 rpm for 5-10 minutes. Step 2: Add Si powder and continue stirring for 5-10 minutes; Step 3: Add CMC and continue stirring for 1-2 hours; Step 4: Add SBR and continue stirring for 10-20 minutes; Step 5: Using a four-sided coating apparatus, coat the glass panel covered with plastic wrap and free of wrinkles. Use an infrared vacuum coating machine for automatic coating. The heating conditions of the infrared vacuum coating machine are 60℃ for 30 min. The coating thickness of the four-sided coating apparatus is 400 μm. The pressing conditions are 10 MPa and 15 s. Step 6: Take out the dried sample, separate it from the plastic wrap, use a manual slicer to cut the sample into thin round slices with a diameter of 12mm, and use a powder tablet press to compress them into tablets. Step 7: Use a micrometer screw gauge to measure the thickness of the thin sheet using the 5-point method, and use a four-probe tester to test and obtain the resistivity value; The mass percentage ratio of each component is as follows: single-walled carbon nanotube conductive paste = 0.25%, CMC = 2.193%, Si powder = 93.4485%, SBR = 4.108%; solid content = 0.43-0.45%.

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