Battery pole piece for performance testing and method of making the same

Abstract

This application belongs to the field of electrode testing, and particularly relates to a battery electrode for performance testing and its preparation method. This battery electrode and its preparation method use the battery electrode compaction rate instead of the traditional compaction density testing method to roll-press the electrode. Specifically, the target compaction rate (58% ± 1%) is first calculated based on the target compaction density of the active material, and the target roll-pressed thickness d of the electrode is then calculated based on the target compaction rate. 目标 During the subsequent rolling process, it is only necessary to compare the thickness of the rolled electrode with the target rolling thickness d. 目标 The comparison method can quickly determine whether the electrode sheet is qualified, effectively improving the rolling efficiency. This method has the advantages of being easy to operate, having good stability, and being fast and efficient.

Description

Technical Field

[0001] This application relates to the field of electrode testing technology, and in particular to a battery electrode for performance testing and its preparation method. Background Technology

[0002] As a crucial component in battery production, the performance of electrodes directly impacts the stability of subsequent processes, as well as the performance and safety of the battery cell. Therefore, evaluating electrode performance is of paramount importance. Among these, electrode resistivity and peel strength are key indicators for evaluating electrode performance and hold an irreplaceable position in battery research and development and production.

[0003] Before resistivity and peel strength tests, the rolled positive / negative electrode sheets need to be taken and cut using a custom die. Currently, to ensure the electrode sheets reach the required compaction density during the rolling process, a battery negative electrode material electrode sheet compaction density test method disclosed in patent CN 107655791 A is typically used. This test method requires weighing the cut electrode sheet and current collector, measuring the thickness of the electrode sheet at three different locations after rolling under different pressures, and calculating using electrode sheet areal density and compaction density formulas. This method is difficult to operate, cumbersome, and has low rolling efficiency, affecting the preparation efficiency of battery electrode sheets. Summary of the Invention

[0004] This application provides a battery electrode for performance testing and a method for preparing the same, aiming to improve the preparation efficiency of battery electrodes.

[0005] Therefore, according to one aspect of this application, a method for preparing battery electrode sheets for performance testing is provided, comprising the following steps:

[0006] S1. Cut the coated and dried original electrode sheet into 30mm×300mm electrode sheets using a utility knife. Measure the thickness of each cut electrode sheet at five different locations. Select the electrode sheet with a thickness error <2μm and record the average thickness of the five different locations as the initial electrode sheet thickness d0. Calculate the target roll forming thickness d using the following formula. 目标 :

[0007] d1≤d 目标 ≤d2

[0008] d1=(d0-d cf )·(100-(58-1))%+d cf

[0009] d2=(d0-d cf )·(100-(58+1))%+d cf

[0010] Among them, d0 is the initial thickness of the electrode sheet, d cf is the thickness of the current collector, and the target rolling thickness d 目标 is an integer;

[0011] S2. Set the double-roller linear speed of the electric double-roller machine to 2.0 m / min, take 2 Mpa as the starting value of the rolling pressure. After the pressure is stabilized, place the electrode sheet selected in step S1 into the electric double-roller machine for rolling. Gradually increase the rolling pressure by an increment of 0.5 Mpa until the two sides of the electrode sheet become wavy and vertical stripes appear in the middle of the electrode sheet;

[0012] S3. Use a micrometer to measure the thicknesses of five different positions of the rolled electrode sheet. The electrode sheet that meets the target rolling thickness d 目标 and the thickness difference between any two of them is less than 2 μm is a qualified electrode sheet.

[0013] Optionally, after step S3, the following steps are further included:

[0014] S4. Record the average value d 实 of the thicknesses of five different positions on the qualified electrode sheet, and calculate the actual compaction rate R 实 according to the following formula:

[0015] R 实 = 1 – {(d 实 - d cf ) ÷ (d0 - d cf )} · 100%

[0016] Judge whether R 实 is within the range of 58% ± 1%. If so, it is qualified; otherwise, it is unqualified.

[0017] Optionally, in step S1, the drying condition is: place it in an oven at 110°C - 130°C for 3 to 5 hours.

[0018] Optionally, in step S1, the drying condition is: place it in an oven at 120°C for 4 hours.

[0019] Optionally, except for the drying in step S1, the rest of the battery electrode sheet preparation method is carried out under the conditions of 25 ± 1°C and humidity ≤ 60% RH.

[0020] According to another aspect of the present application, a battery electrode sheet for performance testing is provided. The battery electrode sheet is prepared by the battery electrode sheet preparation method described above.

[0021] The beneficial effects of the battery electrode sheet and its preparation method for performance testing provided in this application are as follows: Compared with the prior art, the battery electrode sheet and its preparation method for performance testing in this application use the battery electrode sheet compaction rate instead of the traditional compaction density testing method to roll the electrode sheet. That is, the target compaction rate of 58% ± 1% is first calculated based on the target compaction density of the active material, and the target roll thickness d of the electrode sheet is calculated based on the target compaction rate. 目标 During the subsequent rolling process, it is only necessary to compare the thickness of the rolled electrode with the target rolling thickness d. 目标 The comparison method can quickly determine whether the electrode sheet is qualified, effectively improving the rolling efficiency. This method has the advantages of being easy to operate, having good stability, and being fast and efficient. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] in:

[0024] Figure 1 This is a schematic flowchart illustrating a method for preparing battery electrode sheets for performance testing, as shown in one embodiment of this application.

[0025] Figure 2 It is the average resistivity curve of the battery electrode used for performance testing provided in an embodiment of this application during resistivity testing.

[0026] Figure 3 It is a graph of the average peel force of the battery electrode used for performance testing provided in an embodiment of this application during the peel strength test. Detailed Implementation

[0027] The following are preferred embodiments of the present invention. It should be noted that those skilled in the art can make several improvements and modifications without departing from the principle of the present invention, and these improvements and modifications are also considered to be within the protection scope of the present invention.

[0028] It should be noted that when a component is referred to as being "fixed to" or "set on" another component, it can be directly on or indirectly on that other component. When a component is referred to as being "connected to" another component, it can be directly connected to or indirectly connected to that other component.

[0029] It should be understood that the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0030] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0031] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0032] According to one aspect of this application, embodiments of this application provide a method for preparing battery electrode sheets for performance testing, such as... Figure 1 As shown, the method for preparing the battery electrode includes the following steps:

[0033] S1. Cut the coated and dried original electrode sheet into 30mm×300mm electrode sheets using a utility knife. Measure the thickness of each cut electrode sheet at five different locations. Select the electrode sheet with a thickness error <2μm and record the average thickness of the five different locations as the initial electrode sheet thickness d0. Calculate the target roll forming thickness d using the following formula. 目标 :

[0034] d1≤d 目标 ≤d2

[0035] d1=(d0-d cf )·(100-(58-1))%+d cf

[0036] d2=(d0-d cf )·(100-(58+1))%+d cf

[0037] Where d0 is the initial electrode thickness, d cf For the current collector thickness, the target roll forming thickness is d. 目标 Take the integer part;

[0038] S2. Set the linear speed of the double rollers of the electric double roller machine to 2.0 m / min, and use 2 MPa as the initial value of the roller pressing pressure. After the pressure stabilizes, put the electrode sheet selected in step S1 into the electric double roller machine for roller pressing. The roller pressing pressure is added up in increments of 0.5 MPa until the electrode sheet reaches the point where the two sides are wavy and vertical lines appear in the middle of the electrode sheet.

[0039] S3. Use a micrometer to measure the thickness of the electrode sheet at five different locations after roll forming to ensure it meets the target roll forming thickness d. 目标 Furthermore, any electrode with a thickness difference of less than 2 μm between any two of its thickness values ​​is considered a qualified electrode.

[0040] Note: To ensure the accuracy of thickness measurement and the consistency of electrode preparation, except for drying in step S1, all other battery electrode preparation methods are carried out at 25±1℃ and humidity ≤60%RH.

[0041] Formula explanation:

[0042] Density calculation formula: ρ = m / V = m / πr 2 h = m / πr 2 d, due to the mass m and area πr at the same location 2 Since they are the same, the density ρ is only related to the thickness d.

[0043] Material Tap density / g / cm3 Compacted density / g / cm3 <![CDATA[True density / g / cm 3 > Natural graphite ≥0.9 ≥1.45 2.20-2.26 Mesophase carbon microspheres artificial graphite ≥1.1 ≥1.40 2.20-2.26 Needle-shaped coke artificial graphite ≥0.8 ≥1.40 2.20-2.26 Petroleum coke artificial graphite ≥1.0 ≥1.3 2.20-2.26 Composite Graphite ≥0.8 ≥1.3 2.20-2.26

[0044] The table above summarizes that the compacted density of various types of graphite ranges from 1.45 to 2.26 g / cm³. 3 Within the specified range, the present invention uses 2.20 g / cm³. 3 To achieve the target compaction density, use a slicer to cut out qualified circular electrode sheets with a diameter of r, and weigh their mass m1 and the mass m of the current collector after removing the active material. cf The formula ρ=m / πr 2 The thickness of the target active material is calculated by d. 目标 -d cf =(m1-m cf ) / πr 2 ρ, from which the target compaction rate R0 = [1 - (d 目标 -d cf ) / (d0-d cf Substituting 100% into the measurement, R0 is 58% for each thickness, and the target compaction rate is taken as 58% ± 1%.

[0045] In an embodiment of the present application, the battery electrode sheet for performance testing and its preparation method roll the electrode sheet by using the compaction rate of the battery electrode sheet instead of the traditional compaction density test method. That is, first, the target compaction rate is calculated to be 58% ± 1% based on the target compaction density of the active material. According to the target compaction rate, the target rolling thickness d of the electrode sheet is calculated by the formula in step S1. 目标 , during the subsequent rolling process, it is only necessary to compare the thickness of the rolled electrode sheet with the target rolling thickness d 目标 to quickly determine whether the electrode sheet is qualified, effectively improving the rolling efficiency. This method has the advantages of strong operability, good stability, and being fast and efficient.

[0046] In one embodiment, after step S3, the following steps are further included:

[0047] S4. Record the average value d of the thicknesses at five different positions on the qualified electrode sheet 实 , and calculate the actual compaction rate R according to the following formula 实 :

[0048] R 实 = 1 – {(d 实 - d cf ) ÷ (d0 - d cf )} · 100%

[0049] Judge whether R 实 is within the range of 58% ± 1%. If so, it is qualified; otherwise, it is unqualified.

[0050] By step S4, it is further verified whether the electrode sheet is qualified, improving the accuracy.

[0051] In one embodiment, in step S1, the drying conditions are: placing in an oven at 110°C - 130°C for 3 to 5 hours. Preferably, the drying conditions are: placing in an oven at 120°C for 4 hours.

[0052] In one embodiment, the comparison table of the battery electrode sheets prepared by using the battery electrode sheet preparation method provided in the present application and the compaction density test method mentioned in the background technology and the subsequent test data is as follows:

[0053]

[0054] Data summary: Combining Figure 2 and Figure 3The average peel force and average resistivity data from Experiment 2 to Experiment 2 remained stable, while the average resistance data from Experiment 1 to Experiment 2 decreased, and the average peel force data from Experiment 1 to Experiment 2 increased. Experimental findings: 1. The electrode compaction rate reached 58% ± 1%, and the compaction density was also within the maximum compaction density range. 2. When the compaction rate was 56%, the compaction density decreased significantly. 3. This confirms that the method of using the electrode compaction rate test method instead of the compaction density test method for rolling the electrode in the battery electrode preparation method described in this application is stable and effective.

[0055] According to another aspect of this application, embodiments of this application also provide a battery electrode for performance testing, wherein the battery electrode is prepared by the battery electrode preparation method in any of the above embodiments.

[0056] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0057] The above embodiments are merely illustrative of several implementation methods of this application, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims.

Claims

1. A method for preparing battery electrodes for performance testing, characterized in that, Includes the following steps: S1. Cut the coated and dried original electrode sheet into 30mm×300mm electrode sheets using a utility knife. Measure the thickness of each cut electrode sheet at five different locations. Select the electrode sheet with a thickness error <2μm and record the average thickness of the five different locations as the initial electrode sheet thickness d0. Calculate the target roll forming thickness d using the following formula. 目标 : d1≤d 目标 ≤d2 d1=(d0- d cf )•(100-(58-1))%+d cf； d2=(d0- d cf )•(100-(58+1))%+d cf； Where d0 is the initial electrode thickness, d cf For the current collector thickness, the target roll forming thickness is d. 目标 Take the integer part; S2. Set the linear speed of the double rollers of the electric double roller machine to 2.0 m / min, and use 2 MPa as the initial value of the roller pressing pressure. After the pressure stabilizes, put the electrode sheet selected in step S1 into the electric double roller machine for roller pressing. The roller pressing pressure is added up in increments of 0.5 MPa until the electrode sheet reaches the point where the two sides are wavy and vertical lines appear in the middle of the electrode sheet. S3. Use a micrometer to measure the thickness of the electrode sheet at five different locations after roll forming to ensure it meets the target roll forming thickness d. 目标 Furthermore, any electrode with a thickness difference of less than 2 μm between any two of its thickness values ​​is considered a qualified electrode. S4. Record the average thickness d at five different locations on the qualified electrode sheet. 实 The actual compaction rate R is calculated using the following formula. 实 : R 实 =1–{(d 实 - d cf )÷(d0- d cf )}•100% ； Determine R 实 Whether it is within the range of 58% ± 1%. If so, it is qualified; otherwise, it is unqualified.

2. The method for preparing battery electrodes according to claim 1, characterized in that, In step S1, the drying conditions are: place in an oven at 110℃-130℃ for 3 to 5 hours.

3. The method for preparing battery electrodes according to claim 2, characterized in that, In step S1, the drying conditions are: place in an oven at 120°C for 4 hours.

4. The method for preparing battery electrode sheets according to claim 1, characterized in that, Except for drying in step S1, the battery electrode preparation method is carried out at 25±1℃ and RH ≤60%.

5. A battery electrode for performance testing, characterized in that, The battery electrode is prepared by the battery electrode preparation method as described in any one of claims 1-4.

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