A detection device and method for the ultimate compaction of a pole piece

Abstract

The present invention discloses a detection device and method for the ultimate compaction of a pole piece, comprising the following steps: arranging a plurality of pole piece assemblies made of different materials, wherein the pole piece assembly includes one or more pole piece strips made of the same material; respectively bending and connecting the pole piece strips and attaching the bent parts to the columnar shaft rod of an elastic tester, and connecting the end of the pole piece strip to the force measuring end of a force measuring mechanism; pulling the force measuring mechanism at a constant speed, and if the pulled pole piece strip is engraved by the columnar shaft rod, stop pulling the force measuring mechanism and record the reading N; record the readings N when one or more pole piece strips in the same pole piece assembly appear engraved on the columnar shaft rod, and take the average value of the readings N, and draw scatter plots and linear fitting curves of different materials according to the average values of different pole piece assemblies; substitute the preset limited fracture tensile force value into the linear fitting curve to calculate the ultimate compaction density of the pole piece strip; this detection method can simply, efficiently and quantitatively detect the ultimate compaction density of the pole piece.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium battery preparation, and particularly relates to a detection device and method for the ultimate compaction of electrode sheets. Background Art

[0002] Lithium-ion batteries are representatives of modern high-performance secondary batteries, which have many advantages such as high energy density, high average output voltage, small volume, long service life, safety and environmental protection. In recent years, with the increasing demand for new energy, the reduction of minerals and the major goal of carbon neutrality have promoted the development of the new energy industry. Lithium-ion batteries have now become the focus of new energy development. From mobile phone lithium-ion batteries to power batteries for electric vehicles and energy storage power stations, as people's requirements are getting higher and higher, developing lithium-ion batteries with high energy density, high safety and long service life has become the main focus.

[0003] Generally speaking, the higher the compaction density of the battery electrode sheet, the higher the energy density of the battery. Therefore, the compaction density of the electrode sheet is considered to be one of the important indicators for measuring the energy density of the battery. The compaction density of the electrode sheet is not only related to the size, shape, density and sphericity of the particles of the material itself, but also related to the raw material particle size and carbon layer coating in the manufacturing process. However, the higher the compaction of the electrode sheet is not necessarily better, because too high a compaction density of the electrode sheet will limit the diffusion and insertion / extraction of lithium ions, and at the same time reduce the porosity of the material, resulting in a decline in the rate performance of the battery. Moreover, during the production process, the electrode sheet may break due to overpressure, which will cause unnecessary losses. Therefore, it is crucial to develop a detection technology for the ultimate compaction of electrode sheets to maximize the energy density of the battery.

[0004] Most of the existing methods for testing the compaction limit of electrode sheets are to observe the crease state of the electrode sheet after folding or bending. However, this method has no quantitative data and is greatly affected by human factors, resulting in large differences in the results and deviating from actual production. Summary of the Invention

[0005] Based on the technical problems existing in the background art, the present invention proposes a detection device and method for the ultimate compaction of electrode sheets, with accurate, stable and reliable measurement results, realizing the quantitative calibration of the ultimate compaction of battery electrode sheets.

[0006] A detection device for the ultimate compaction of electrode sheets proposed by the present invention includes an electrode strip, a force measuring mechanism, an elastic tester and a columnar shaft rod. The columnar shaft rod is fixed on the elastic tester, the bent part after the electrode strip is bent is attached to the columnar shaft rod of the elastic tester, and the end of the electrode strip is connected to the force measuring end of the force measuring mechanism.

[0007] A detection device and method for the ultimate compaction of electrode sheets includes the following steps:

[0008] Set multiple pole piece components made of different materials, and each pole piece component includes one to multiple pole piece strips made of the same material;

[0009] After bending and connecting the pole piece strips respectively, attach the bent part to the columnar shaft rod of the elastic tester, and connect the end of the pole piece strip to the force measuring end of the force measuring mechanism;

[0010] Pull the force measuring mechanism at a constant speed. If the pulled pole piece strip is engraved by the columnar shaft rod, stop pulling the force measuring mechanism and record the reading N;

[0011] Record the reading N when one to multiple pole piece strips in the same pole piece component are engraved on the columnar shaft rod, and take the average value of the reading N

[0012] According to the average values of different pole piece components Draw scatter plots and linear fitting curves of different materials;

[0013] Substitute the preset limited fracture tensile force value into the linear fitting curve to calculate the ultimate compaction density of the pole piece strip.

[0014] Further, in the step of after bending and connecting the pole piece strips respectively, attaching the bent part to the columnar shaft rod of the elastic tester, and connecting the end of the pole piece strip to the force measuring end of the force measuring mechanism, it specifically includes:

[0015] Fix the elastic tester;

[0016] After bending and connecting the pole piece strips, attach the bent part to the columnar shaft rod of the elastic tester;

[0017] Clamp the head and tail ends of the bent pole piece strip with a clip;

[0018] Fix the clip to the force measuring end of the spring dynamometer, and zero the spring dynamometer before use.

[0019] Further, the multiple pole piece components made of different materials are roll-pressed by the same rolling mechanism to obtain pole piece components with different compaction densities.

[0020] Further, in the case where the pole piece component includes one to multiple pole piece strips made of the same material, the pole piece strips are obtained by cutting the pole piece component, specifically as follows:

[0021] Lay the pole piece components made of different materials and with different compaction densities on the cutting scissors;

[0022] Cut off the pole lugs and wrinkled parts around the pole piece component, and cut the pole piece component into one to multiple rectangular pole piece strips;

[0023] Further, in the case where the pulled pole piece strip is engraved by the columnar shaft rod, the engraving includes reticulation, cracking or spalling.

[0024] Further, in the process of uniformly pulling the force measuring mechanism, the force measuring direction of the force measuring mechanism is parallel to the length direction of the pulled pole piece strip.

[0025] Further, in accordance with the average value of different pole piece assemblies When plotting the scatter diagrams and linear fitting curves of different materials, it specifically includes:

[0026] The average value of different pole piece assemblies Plot the scatter diagrams of different materials;

[0027] Calculate the linear fitting curve for the scatter diagram through the linear regression equation.

[0028] Further, when recording the indication N when one or more pole piece strips in the same pole piece assembly appear with markings on the columnar shaft rod, at least record the indication N when three pole piece strips appear with markings on the columnar shaft rod.

[0029] Further, in accordance with the average value of different pole piece assemblies Among them, at least calculate the average values of five pole piece assemblies

[0030] The advantages of a pole piece ultimate compaction detection device and method provided by the present invention are as follows: The pole piece ultimate compaction detection device and method provided in the structure of the present invention can simply, efficiently and quantitatively detect the ultimate compaction density of the pole piece, that is, the measurement result is accurate, stable and reliable, realizing the quantitative calibration of the ultimate compaction of the battery pole piece, and solving the problem that the existing pole piece ultimate compaction density test method is divorced from actual production. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a schematic structural diagram of the detection device of the present invention;

[0032] Figure 2 It is a schematic flow diagram of realizing the detection method of the present invention;

[0033] Figure 3 It is a schematic diagram of the fracture tensile force values of pole pieces with different materials and different compaction densities;

[0034] Figure 4 It is a schematic diagram of the scatter diagrams and linear fitting curves of Examples 1, 2 and 3;

[0035] Wherein, 1 - pole piece strip, 2 - force measuring mechanism, 3 - elastic tester, 4 - columnar shaft rod. DETAILED DESCRIPTION OF THE INVENTION

[0036] Next, the technical solution of the present invention will be described in detail through specific embodiments. Many specific details are set forth in the following description in order to fully understand the present invention. However, the present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without departing from the connotation of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed below.

[0037] As Figures 1 to 4 shown, a detection device for the ultimate compaction of a pole piece according to the present invention includes a pole piece strip 1, a force measuring mechanism 2, an elastic tester 3, and a columnar shaft rod 4. The columnar shaft rod 4 is fixed on the elastic tester 3. The bent part after the pole piece strip 1 is bent is attached to the columnar shaft rod 4 of the elastic tester 3, and the end of the pole piece strip 1 is connected to the force measuring end of the force measuring mechanism 2.

[0038] The specific detection method of the above device is as follows:

[0039] As Figure 2 shown, a detection method for the ultimate compaction of a pole piece includes the following steps:

[0040] S1: Set a plurality of pole piece assemblies made of different materials. The pole piece assemblies include one or more pole piece strips made of the same material;

[0041] The plurality of pole piece assemblies made of different materials are roll-pressed by the same roll-pressing mechanism to obtain pole piece assemblies with different compaction densities. Therefore, there are differences in different materials and different compaction densities among the pole piece assemblies in this embodiment.

[0042] Cut the same pole piece assembly to obtain pole piece strips. Specifically: lay the pole piece assemblies made of different materials and different compaction densities on the cutting scissors, cut off the pole ears and wrinkled parts around the pole piece assemblies, and cut the pole piece assemblies into one or more rectangular pole piece strips. The surfaces of the pole piece strips are smooth and flat, without wrinkles or damages. Since the pole piece strips of the same material are cut from the same material and the same compaction density, the pole piece strips of the same material can be subjected to tensile tests simultaneously and can be superimposed on each other to take the average value, so as to obtain the fracture tensile value of the pole piece strips of the same material more accurately.

[0043] S2: Bend and connect the pole piece strips respectively, and attach the bent part to the columnar shaft rod of the elastic tester. The end of the pole piece strip is connected to the force measuring end of the force measuring mechanism;

[0044] Among them, a spring dynamometer can be used as the force measuring mechanism. Fix the elastic tester, bend and connect the pole piece strips, attach the bent part to the columnar shaft rod of the elastic tester, clamp the head and tail ends of the bent pole piece strip with a clip, fix the clip to the force measuring end of the spring dynamometer, and zero the spring dynamometer before use.

[0045] The clip can be a windproof clip to avoid the defect that inaccurate final test results are caused after a certain force is exerted on the clip by the wind in the environment.

[0046] The specification of the elasticity tester is the QTX elasticity tester, such as the paint film elasticity tester.

[0047] S3: Uniformly pull the force measuring mechanism. If the pulled pole piece strip is engraved by the columnar shaft rod, stop pulling the force measuring mechanism and record the reading N.

[0048] The engraving includes reticulation, cracks or peeling. The engraving can be observed through a magnifying glass. In addition, by using a columnar shaft rod, the engraving can be more clearly displayed to obtain a more accurate reading.

[0049] S4: Record the readings N when one or more pole piece strips in the same pole piece assembly are engraved on the columnar shaft rod, and take the average value of the readings N.

[0050] In this embodiment, at least record the readings N when three pole piece strips are engraved on the columnar shaft rod, and take the average value of the readings N of these three pole piece strips to obtain the average value. Adopt the average value It represents the fracture tensile force value of the pole piece, and the final scatter plot is more accurate.

[0051] S5: According to the average values of different pole piece assemblies Draw scatter plots and linear fitting curves of different materials;

[0052] The linear fitting curve is calculated from the scatter plot through a linear regression equation. The linear regression equation is prior art and will not be elaborated here.

[0053] In this embodiment, at least calculate the average values of five pole piece assemblies To increase the number of points corresponding to the scatter plot and further improve the fitting accuracy of the linear fitting curve.

[0054] S6: Substitute the preset limited fracture tensile force value into the linear fitting curve to calculate the ultimate compaction density of the pole piece strip.

[0055] The preset limited fracture tensile force value can be obtained based on long-term tests and records during use.

[0056] Through steps S1 to S6, the ultimate compaction density of the pole piece can be simply, efficiently and quantitatively detected. The measurement results are accurate, stable and reliable, realizing the quantitative calibration of the ultimate compaction of the battery pole piece and solving the problem that the existing test method for the ultimate compaction density of the pole piece is divorced from actual production.

[0057] Example 1

[0058] Lay the electrode sheet assemblies of Material 1 with compaction densities of 2.35, 2.40, 2.44, 2.53, 2.58, and 2.63 g / cc flat on a paper cutter. Cut off the tabs and wrinkles around the electrode sheet assemblies, and cut the electrode sheet assemblies into rectangular electrode strips of 10 cm × 2 cm. Fix the QTX elasticity tester on the edge of the table to prevent it from shaking or displacing, zero the spring dynamometer, and hook the spring of the clip with the hook.

[0059] Connect the rectangular electrode strips slowly end to end to form a certain arc, attach the bent area of the electrode strip to a cylindrical shaft rod with a diameter of 3 ± 0.05 mm, and clamp the end with a clip. Keep the spring dynamometer parallel to the tabletop and slowly pull it at a constant speed of 0.01 m / s. Observe the electrode strip with the aid of a magnifying glass. If it is observed that the electrode strip is engraved with reticulations, cracks, and peeling by the shaft rod, stop pulling the spring dynamometer and record the reading N. Repeat 3 times to obtain 3 breaking tensile forces N. 1-3 And take the average value

[0060] According to the average breaking tensile force As Figure 3 shown, make a scatter plot and a linear fitting curve of different compactions of Material 1. As Figure 4 shown, then substitute the ultimate breaking tensile force value of 2.5 N into the linear fitting curve to calculate the ultimate compaction density of the electrode of Material 1 as 2.56 g / cc.

[0061] Example 2

[0062] Lay the electrode sheet assemblies of Material 2 with compaction densities of 2.35, 2.38, 2.43, 2.52, 2.59, and 2.68 g / cc flat on a paper cutter. Cut off the tabs and wrinkles around the electrode sheet assemblies, and cut the electrode sheet assemblies into rectangular electrode strips of 10 cm × 2 cm. Fix the QTX elasticity tester on the edge of the table to prevent it from shaking or displacing, zero the spring dynamometer, and hook the spring of the clip with the hook.

[0063] Connect the rectangular electrode strips slowly end to end to form a certain arc, attach the bent area of the electrode strip to a cylindrical shaft rod with a diameter of 3 ± 0.05 mm, and clamp the end with a clip. Keep the spring dynamometer parallel to the tabletop and slowly pull it at a constant speed of 0.01 m / s. Observe the electrode strip with the aid of a magnifying glass. If it is observed that the electrode strip is engraved with reticulations, cracks, and peeling by the shaft rod, stop pulling the spring dynamometer and record the reading N. Repeat 3 times to obtain 3 breaking tensile forces N. 1-3 And take the average value

[0064] According to the average breaking tensile force As Figure 3As shown, make the scatter plot and linear fitting curve of different compactions of Material 2, as Figure 4 shown. Then substitute the ultimate fracture tensile force value of 2.5 N into the linear fitting curve to calculate the ultimate compaction density of the Material 2 electrode sheet as 2.66 g / cc.

[0065] Example 3

[0066] Lay the electrode sheet assemblies of Material 3 with compaction densities of 2.40, 2.45, 2.50, 2.56, 2.62, 2.70, 2.72, and 2.74 g / cc flat on a paper cutter, cut off the tab and wrinkled parts around the electrode sheet assemblies, and cut the electrode sheet assemblies into rectangular electrode strips of 10 cm × 2 cm. Fix the QTX elastic tester on the table edge to prevent it from shaking or displacing, and zero the spring dynamometer. Hook the spring of the clip with the hook.

[0067] Connect the rectangular electrode strips slowly end to end to form a certain arc, attach the bent area of the electrode strip to a cylindrical shaft rod with a diameter of 3 ± 0.05 mm, and clamp the end with a clip. Keep the spring dynamometer parallel to the tabletop and slowly pull it at a constant speed of 0.01 m / s. Use a magnifying glass to assist in observing the electrode strip. If it is observed that the electrode strip is engraved with reticulations, cracks, and peeling by the shaft rod, stop pulling the spring dynamometer and record the reading N. Repeat 3 times to obtain 3 fracture tensile forces N 1-3 and take the average value

[0068] According to the average value of the fracture tensile force as Figure 3 shown, make the scatter plot and linear fitting curve of different compactions of Material 3, as Figure 4 shown. Then substitute the ultimate fracture tensile force value of 2.5 N into the linear fitting curve to calculate the ultimate compaction density of the Material 3 electrode sheet as 2.71 g / cc.

[0069] According to the appendix Figure 3 it can be obtained that under the same surface density (the same material), the greater the compaction density, the smaller the fracture tensile force value, where the compaction density is equal to the quotient of the surface density and the electrode sheet thickness.

[0070] Generally speaking, the greater the ultimate compaction density, the greater the energy density that the material can provide, the better the flexibility of the material, it is not easy to break, and the yield rate of the final electrode sheet also tends to increase. According to the appendix Figure 3 it can be obtained that the ultimate compaction density obtained in Example 3 is the largest, and the surface density corresponding to Example 3 is greater than that of Example 2 and less than that of Example 1, indicating that the higher the compaction of the electrode sheet is not necessarily better, and the ultimate compaction density of the electrode sheet needs to be obtained through experimental calculation.

[0071] The above are only the preferred specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, making equivalent substitutions or changes should be covered within the protection scope of the present invention.

Claims

1. A detection method for the ultimate compaction of a pole piece, characterized in that The method includes the following steps: Set a plurality of pole piece assemblies made of different materials, and each pole piece assembly includes one to multiple pole piece strips made of the same material; Bend each pole piece strip and connect the head and tail to form the end of the pole piece strip. Attach the bent part to the columnar shaft rod of the elastic tester, and connect the end of the pole piece strip to the force measuring end of the force measuring mechanism; Pull the force measuring mechanism at a constant speed. If the pulled pole piece strip is engraved by the columnar shaft rod, stop pulling the force measuring mechanism and record the reading N. The engraving includes reticulation, cracks or spalling; Record the indication N when one or more electrode strips in the same electrode assembly are engraved on the columnar shaft rod, and take the average value of the indication N ; Based on the average values of different electrode assemblies , scatter plots and linear fitting curves of different materials are plotted; Substitute the preset limited fracture tensile force value into the linear fitting curve to calculate the ultimate compaction density of the pole piece strip.

2. The detection method for the ultimate compaction of the electrode sheet according to claim 1, wherein In the step of attaching the bent part to the columnar shaft rod of the elastic tester and connecting the end of the pole piece strip to the force measuring end of the force measuring mechanism after bending and connecting each pole piece strip respectively, it specifically includes: Fix the elastic tester; Attach the bent part to the columnar shaft rod of the elastic tester after bending and connecting the pole piece strips; Clamp the head and tail ends of the bent pole piece strip with a clip; Fix the clip to the force measuring end of the spring dynamometer, and zero the spring dynamometer before use.

3. The detection method for the ultimate compaction of the electrode sheet according to claim 1, characterized in that The plurality of pole piece assemblies made of different materials are roll-pressed by the same rolling mechanism to obtain pole piece assemblies with different compaction densities.

4. The detection method for the ultimate compaction of the electrode sheet according to claim 3, characterized in that, In the case that the pole piece assembly includes one to multiple pole piece strips made of the same material, the pole piece strips are obtained by cutting the pole piece assembly, specifically as follows: Lay the pole piece assemblies made of different materials and with different compaction densities flat on the cutting scissors; Cut off the tabs and wrinkled parts around the pole piece assembly, and cut the pole piece assembly into one to multiple rectangular pole piece strips.

5. The detection method for the ultimate compaction of the electrode sheet according to claim 1, characterized in that, When pulling the force measuring mechanism at a constant speed, the force measuring direction of the force measuring mechanism is parallel to the length direction of the pulled pole piece strip.

6. The detection method for the ultimate compaction of the electrode sheet according to claim 1, wherein Based on the average value of different electrode components , in the process of plotting the scatter diagrams and linear fitting curves of different materials, it specifically includes: Average value of different pole piece components , draw a scatter plot of different materials; Calculate the linear fitting curve for the scatter plot through the linear regression equation.

7. The detection method for the ultimate compaction of the electrode tab according to claim 1, characterized in that When recording the readings N when one to multiple pole piece strips in the same pole piece assembly are engraved on the columnar shaft rod, at least record the readings N when three pole piece strips are engraved on the columnar shaft rod; Based on the average value of different electrode tab components calculate the average value of at least five electrode tab components .

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