Method for measuring density of circular coated pole piece of sodium ion battery

Abstract

The invention discloses a method for measuring the density of a circular coated pole piece of a sodium ion battery, and relates to the technical field of density measurement, and the method comprises the following steps: dividing the coated pole piece into a central region, a transition region and an edge region from the center to the edge in sequence according to the area weights of 40%, 30% and 30%; taking a plurality of points in each area for thickness measurement to obtain t center, t transition and t edge, wherein the weighted thickness taavg is equal to 0.4 t center + 0.3 t transition + 0.3 t edge; the area of the coated pole piece is measured and recorded as s, and the volume V of the coated pole piece is calculated according to the formula: V = s * tavg = s * (0.4 t center + 0.3 t transition + 0.3 t edge); the mass of the coated pole piece is measured and recorded as m, and the density rho of the coated pole piece is equal to m (1-0.015 * delta RH / 100) / (s * tavg) = m (1-0.015 * delta RH / 100) / [s * (0.4 t center + 0.3 t transition + 0.3 t edge)]; wherein delta RH is the difference value between the actual RH% and 50% RH; the thickness gradient caused by the edge effect of the thickness and the quality influence caused by the environment humidity can be eliminated through the thickness weighted measurement mode and the introduction of the humidity compensation factor k, so that the density measurement result is more accurate.

Description

Technical Field

[0001] The present invention relates to the technical field of density measurement, and particularly relates to a method for measuring the density of a circular coated electrode sheet of a sodium-ion battery. Background Art

[0002] The electrode sheet of a sodium-ion battery is a key component of the sodium-ion battery, which is made by coating a mixture of active material, conductive agent and binder on a current collector. The electrode sheet of a cylindrical sodium-ion battery usually exists in a circular shape, and its density is one of the important criteria for measuring the quality of the electrode sheet.

[0003] In the prior art, when measuring the density of a circular electrode sheet, the mass and volume are often measured first, and then the ratio of the two is calculated to obtain the density value; when measuring the volume, it is obtained by multiplying the measured area and thickness; however, the traditional measurement method only measures the thickness at the center point of the electrode sheet, ignoring the thickness gradient caused by the coating edge effect, so the obtained thickness value has an error. At the same time, when measuring its mass, and when manually measuring, the pressure of the measuring ruler on the electrode sheet is uneven, which may cause fluctuations in the thickness reading; at the same time, due to the humidity fluctuation (±10%RH) in the laboratory environment, the mass of the electrode sheet changes due to moisture absorption, and the calculation error of the mass can reach 2%-3%. Therefore, the density value finally obtained according to the ratio of mass to volume is not accurate enough, affecting the quality judgment. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for measuring the density of a circular coated electrode sheet of a sodium-ion battery, and solve the following technical problems:

[0005] How to improve the accuracy of measuring the density of a circular coated electrode sheet of a sodium-ion battery.

[0006] The purpose of the present invention can be achieved by the following technical solutions:

[0007] A method for measuring the density of a circular coated electrode sheet of a sodium-ion battery includes the following steps:

[0008] Step 1: Divide the coated electrode sheet into a central area, a transition area and an edge area in sequence from the center to the edge according to the area weights of 40%, 30% and 30%; take multiple points in each area for thickness measurement to obtain the average thickness, and denote the measured average thickness of the central area as t 中心 , denote the measured average thickness of the transition area as t 过渡 , denote the measured average thickness of the edge area as t 边缘 , then the weighted thickness t avg = 0.4t 中心 + 0.3t 过渡 + 0.3t 边缘 ;

[0009] Step 2: Measure the area of the coated electrode and denote it as s, and calculate the volume V of the coated electrode as V = s × t avg = s × (0.4t 中心 + 0.3t 过渡 + 0.3t 边缘 );

[0010] Step 3: Measure the mass of the coated electrode and denote it as m, then the density ρ of the coated electrode is ρ = m(1 - 0.015×ΔRH / 100) / (s × t avg ) = m(1 - 0.015×ΔRH / 100) / [s × (0.4t 中心 + 0.3t 过渡 + 0.3t 边缘 ); where ΔRH is the difference between the actual RH% and 50% RH.

[0011] Further, in Step 1, the method for dividing the central region, transition region, and edge region is as follows: Draw two circles with the central dot of the coated electrode as the center, and divide the coated electrode into three regions from the inside out, namely the central region, transition region, and edge region; the areas of the central region, transition region, and edge region respectively account for 40%, 30%, and 30% of the total area of the coated electrode.

[0012] Further, in Step 1, the method for obtaining the average thickness by randomly taking points in each region for thickness measurement is: Make an equilateral triangle with the center as the center in the corresponding region, measure the thicknesses at the three vertices of the equilateral triangle, and calculate the average thickness at the three vertices.

[0013] Further, when performing thickness measurement, use a micrometer to measure with the same pressure of 9.5 - 10.5 N; preferably 10 N.

[0014] Further, in Step 2, the method for measuring the area of the coated electrode is: Cover the electrode with a transparent grid plate with an accuracy of 1 mm 2 and statistically calculate the effective coating area through image scanning.

[0015] Further, in Step 3, the method for measuring the mass of the coated electrode is: Use a precision weighing instrument with an accuracy of 0.1 mg for mass weighing, preferably an electronic analytical balance.

[0016] Advantages of the present invention:

[0017] 1. In the method for measuring the density of a circular coated electrode of a sodium-ion battery according to the present invention, by dividing the coated electrode into a central region, a transition region, and an edge region from the inside outwards, the areas of the central region, the transition region, and the edge region respectively account for 40%, 30%, and 30% of the total area of the coated electrode; an equilateral triangle is made with the center of the circle as the center in each region, and a micrometer is used to measure the thicknesses at the three vertices of the equilateral triangle with a constant pressure of 9.5 - 10.5 N, and the average thickness at the three vertices is calculated. Finally, the average thicknesses of the three regions are weighted and calculated to obtain the weighted thickness of the entire coated electrode, which can eliminate the influence caused by the thickness gradient due to the edge effect, make the volume calculation more accurate, and further improve the accuracy of the density calculation result.

[0018] 2. In the method for measuring the density of a circular coated electrode of a sodium-ion battery according to the present invention, by introducing a humidity compensation factor k, the influence of environmental humidity on the quality of the coated electrode can be eliminated, making the result of weighing the quality of the coated electrode more accurate, and further improving the accuracy of the density calculation result. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The present invention will be further described below with reference to the drawings.

[0020] Figure 1 It is a flowchart of the method for measuring the density of a circular coated electrode of a sodium-ion battery according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0021] The present invention discloses a method for measuring the density of a circular coated electrode of a sodium-ion battery. Please refer to Figure 1 , which includes the following steps:

[0022] Step 1: Draw two circles with the center dot of the coated electrode as the center of the circle, and divide the coated electrode into three regions from the inside outwards, namely a central region, a transition region, and an edge region; the areas of the central region, the transition region, and the edge region respectively account for 40%, 30%, and 30% of the total area of the coated electrode; an equilateral triangle is made with the center of the circle as the center in each region, and a micrometer is used to measure the thicknesses at the three vertices of the equilateral triangle with a pressure of 9.5 - 10.5 N, and the average thickness at the three vertices is calculated. Denote the measured average thickness of the central region as t 中心 , denote the measured average thickness of the transition region as t 过渡 , denote the measured average thickness of the edge region as t 边缘 , then the weighted thickness t avg = 0.4t 中心 + 0.3t 过渡 + 0.3t 边缘 ;

[0023] Step 2: Use a precision of 1 mm 2A transparent grid plate covers the coated electrode sheet. The effective coating area is statistically calculated by the image scanning method and denoted as s. The volume V of the coated electrode sheet is calculated as V = s × t avg = s × (0.4t 中心 + 0.3t 过渡 + 0.3t 边缘 );

[0024] Step 3: Use a precision weighing instrument with an accuracy of 0.1 mg to weigh the coated electrode sheet, and record the weighed mass result as m. Then, the density ρ of the coated electrode sheet is ρ = m(1 - 0.015 × ΔRH / 100) / (s × t avg ) = m(1 - 0.015 × ΔRH / 100) / [s × (0.4t 中心 + 0.3t 过渡 + 0.3t 边缘 ); where ΔRH is the difference between the actual RH% and 50% RH, and 0.015 is the humidity compensation factor k.

[0025] The mass measurement method of the coated electrode sheet is: use a precision weighing instrument with an accuracy of 0.1 mg to perform mass weighing.

[0026] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention.

[0027] The experimental methods in the following embodiments are all conventional methods unless otherwise specified, and are carried out according to the techniques or conditions described in the literature in the field or according to the product instructions.

[0028] Example 1

[0029] Select a circular coated electrode sheet of a sodium-ion battery as Sample 1 and perform density measurement. The measurement method is as follows:

[0030] Step 1: Draw two circles with the center dot of Sample 1 as the center of the circle. Divide Sample 1 into three regions from the inside out, namely the central region, the transition region, and the edge region; the areas of the central region, the transition region, and the edge region respectively account for 40%, 30%, and 30% of the total area of the coated electrode sheet; make an equilateral triangle with the center of the circle as the center in the corresponding region, and use a micrometer to measure the thickness at the three vertices of the equilateral triangle with the same pressure of 10 N, and calculate the average thickness at the three vertices. Record the measured average thickness of the central region as t 中心 、Record the measured average thickness of the transition region as t 过渡 、Record the measured average thickness of the edge region as t边缘 , the weighted thickness t avg = 0.4t 中心 + 0.3t 过渡 + 0.3t 边缘 ;

[0031] Step 2: Cover the sample 1 with a transparent grid plate with a precision of 1 mm 2 . Statistically calculate the effective coating area by the image scanning method and record it as s, and calculate the volume V of the sample 1 = s × t avg = s × (0.4t 中心 + 0.3t 过渡 + 0.3t 边缘 );

[0032] Step 3: Weigh the sample 1 with a precision weighing instrument with a precision of 0.1 mg and record the weighed mass result as m. Then, the density ρ of the sample 1 = m(1 - 0.015 × ΔRH / 100) / (s × t avg ) = m(1 - 0.015 × ΔRH / 100) / [s × (0.4t 中心 + 0.3t 过渡 + 0.3t 边缘 ); where ΔRH is the difference between the actual RH% and 50% RH.

[0033] Example 2

[0034] Select a circular coated electrode of a sodium-ion battery as the sample 2 and perform density measurement. The measurement method is as follows:

[0035] Step 1: Draw two circles with the center dot of the sample 2 as the center of the circle, and divide the coated electrode into three regions from the inside out, namely the central region, the transition region, and the edge region; the areas of the central region, the transition region, and the edge region account for 40%, 30%, and 30% of the total area of the coated electrode respectively; make equilateral triangles with the center of the circle as the center in the corresponding regions, and use a micrometer to measure the thicknesses at the three vertices of the equilateral triangle with the same pressure of 1*N, and calculate the average thickness at the three vertices. Record the measured average thickness of the central region as t 中心 , record the measured average thickness of the transition region as t 过渡 , record the measured average thickness of the edge region as t 边缘 , then the weighted thickness t avg = 0.4t 中心 + 0.3t 过渡 + 0.3t 边缘 ;

[0036] Step 2: Cover the coated electrode with a transparent grid plate with a precision of 1 mm 2 . Statistically calculate the effective coating area by the image scanning method and record it as s, and calculate the volume V of the coated electrode = s × tavg = s × (0.4t 中心 + 0.3t 过渡 + 0.3t 边缘 );

[0037] Step 3: Weigh the coated electrode sheet using a precision weighing instrument with an accuracy of 0.1 mg, and record the weighed mass result as m. Then, the density ρ of the coated electrode sheet is ρ = m(1 - 0.015 × ΔRH / 100) / (s × t avg ) = m(1 - 0.015 × ΔRH / 100) / [s × (0.4t 中心 + 0.3t 过渡 + 0.3t 边缘 ); where ΔRH is the difference between the actual RH% and 50% RH.

[0038] Example 3

[0039] Select a circular coated electrode sheet of a sodium-ion battery as Sample 3 for density measurement. The measurement method is as follows:

[0040] Step 1: Draw two circles with the center dot of Sample 3 as the center, and divide the coated electrode sheet into three regions from the inside out, namely the central region, the transition region, and the edge region. The areas of the central region, the transition region, and the edge region account for 40%, 30%, and 30% of the total area of the coated electrode sheet, respectively. Make an equilateral triangle with the center as the center within the corresponding region, and use a micrometer to measure the thicknesses at the three vertices of the equilateral triangle with the same pressure of 10 N, and calculate the average thickness at the three vertices. Record the measured average thickness of the central region as t 中心 , record the measured average thickness of the transition region as t 过渡 , record the measured average thickness of the edge region as t 边缘 , then the weighted thickness t avg = 0.4t 中心 + 0.3t 过渡 + 0.3t 边缘 ;

[0041] Step 2: Cover the coated electrode sheet with a transparent grid plate with an accuracy of 1 mm 2 , and statistically count the effective coating area by the image scanning method and record it as s. Calculate the volume V of the coated electrode sheet as V = s × t avg = s × (0.4t 中心 + 0.3t 过渡 + 0.3t 边缘 );

[0042] Step 3: Weigh the coated electrode sheet using a precision weighing instrument with an accuracy of 0.1 mg, and record the weighed mass result as m. Then, the density ρ of the coated electrode sheet is ρ = m(1 - 0.015 × ΔRH / 100) / (s × tavg ) = m(1 - 0.015×ΔRH / 100) / [s×(0.4t 中心 + 0.3t 过渡 + 0.3t 边缘 )]; where ΔRH is the difference between the actual RH% and 50% RH.

[0043] Comparative Example 1

[0044] The density of Sample 1 was measured as follows:

[0045] Step 1: Use a micrometer to measure the thickness at the center point of Sample 1 with a pressure of 10 N, denoted as t;

[0046] Step 2: Cover Sample 1 with a transparent grid plate with an accuracy of 1 mm 2 and statistically calculate the effective coating area by image scanning method and denote it as s. Calculate the volume V of Sample 1 = s×t;

[0047] Step 3: Use a precision weighing instrument with an accuracy of 0.1 mg to weigh the mass of Sample 1 and record the weighed mass result as m. Then the density ρ of Sample 1 = m(1 - 0.015×ΔRH / 100) / V; where ΔRH is the difference between the actual RH% and 50% RH.

[0048] Comparative Example 2

[0049] The density of Sample 2 was measured as follows:

[0050] Step 1: Use a micrometer to measure the thickness at the center point of Sample 2 with a pressure of 10 N, denoted as t;

[0051] Step 2: Cover Sample 2 with a transparent grid plate with an accuracy of 1 mm 2 and statistically calculate the effective coating area by image scanning method and denote it as s. Calculate the volume V of Sample 2 = s×t;

[0052] Step 3: Use a precision weighing instrument with an accuracy of 0.1 mg to weigh the mass of Sample 2 and record the weighed mass result as m. Then the density ρ of Sample 2 = m(1 - 0.015×ΔRH / 100) / V; where ΔRH is the difference between the actual RH% and 50% RH.

[0053] Comparative Example 3

[0054] The density of Sample 3 was measured as follows:

[0055] Step 1: Use a micrometer to measure the thickness at the center point of Sample 3 with a pressure of 10 N, denoted as t;

[0056] Step 2: Cover Sample 3 with a transparent grid plate with an accuracy of 1 mm 2The transparent grid plate covers the sample 3, and the effective coating area is statistically counted by the image scanning method and denoted as s. Calculate the volume V of the sample 3 = s×t;

[0057] Step 3: Weigh the sample 3 using a precision weighing instrument with an accuracy of 0.1 mg, and record the weighed mass result as m. Then the density ρ of the sample 3 = m(1 - 0.015×ΔRH / 100) / V; where ΔRH is the difference between the actual RH% and 50% RH.

[0058] Comparative Example 4

[0059] Measure the density of sample 1, and the measurement method is as follows:

[0060] Step 1: Draw two circles with the center dot of sample 1 as the center, and divide sample 1 into three regions from the inside out, namely the central region, the transition region, and the edge region; the areas of the central region, the transition region, and the edge region respectively account for 40%, 30%, and 30% of the total area of the coated electrode; make equilateral triangles with the center as the center in the corresponding regions, use a micrometer to measure the thickness at the three vertices of the equilateral triangle with the same pressure of 10 N, and calculate the average thickness at the three vertices. Record the measured average thickness of the central region as t 中心 , record the measured average thickness of the transition region as t 过渡 , record the measured average thickness of the edge region as t 边缘 , then the weighted thickness t avg = 0.4t 中心 + 0.3t 过渡 + 0.3t 边缘 ;

[0061] Step 2: Use a transparent grid plate with an accuracy of 1 mm 2 to cover sample 1, statistically count the effective coating area by the image scanning method and denote it as s, and calculate the volume V of sample 1 = (s×t avg ) = s×(0.4t 中心 + 0.3t 过渡 + 0.3t 边缘 );

[0062] Step 3: Weigh the sample 1 using a precision weighing instrument with an accuracy of 0.1 mg, and record the weighed mass result as m. Then the density ρ of the sample 1 = m / (s×t avg ) = m / [s×(0.4t 中心 + 0.3t 过渡 + 0.3t 边缘 )].

[0063] Comparative Example 5

[0064] Measure the density of sample 2, and the measurement method is as follows:

[0065] Step 1: Draw two circles with the central dot of Sample 2 as the center, and divide Sample 2 into three regions from the inside out, namely the central region, the transition region, and the edge region; the areas of the central region, the transition region, and the edge region respectively account for 40%, 30%, and 30% of the total area of the coated electrode; make equilateral triangles with the center as the center in the corresponding regions, use a micrometer to measure the thicknesses at the three vertices of the equilateral triangle with the same pressure of 10 N, and calculate the average thickness at the three vertices. Denote the measured average thickness of the central region as t 中心 , denote the measured average thickness of the transition region as t 过渡 , denote the measured average thickness of the edge region as t 边缘 , then the weighted thickness t avg = 0.4t 中心 + 0.3t 过渡 + 0.3t 边缘 ;

[0066] Step 2: Cover Sample 2 with a transparent grid plate with a precision of 1 mm 2 , statistically count the effective coating area by the image scanning method and denote it as s, calculate the volume V of Sample 2 = (s × t avg ) = s × (0.4t 中心 + 0.3t 过渡 + 0.3t 边缘 );

[0067] Step 3: Use a precision weighing instrument with a precision of 0.1 mg to weigh Sample 2 and denote the weighed mass result as m. Then the density ρ of Sample 2 = m / (s × t avg ) = m / [s × (0.4t 中心 + 0.3t 过渡 + 0.3t 边缘 )].

[0068] Comparative Example 6

[0069] Measure the density of Sample 3, and the measurement method is as follows:

[0070] Step 1: Draw two circles with the central dot of Sample 3 as the center, and divide Sample 3 into three regions from the inside out, namely the central region, the transition region, and the edge region; the areas of the central region, the transition region, and the edge region respectively account for 40%, 30%, and 30% of the total area of the coated electrode; make equilateral triangles with the center as the center in the corresponding regions, use a micrometer to measure the thicknesses at the three vertices of the equilateral triangle with the same pressure of 10 N, and calculate the average thickness at the three vertices. Denote the measured average thickness of the central region as t 中心 , denote the measured average thickness of the transition region as t 过渡 , denote the measured average thickness of the edge region as t 边缘 , then the weighted thickness tavg =0.4t 中心 +0.3t 过渡 +0.3t 边缘 ;

[0071] Step 2: Use an accuracy of 1mm 2 The transparent grid plate is used to cover the sample 3. The effective coating area is counted by image scanning method and recorded as s. The volume of the sample 3 is calculated as V = (s × t avg )=s×(0.4t 中心 +0.3t 过渡 +0.3t 边缘 );

[0072] Step 3: Use a precision weighing instrument with an accuracy of 0.1 mg to weigh the mass of sample 3 and record the mass result as m. Then the density of sample 3 is ρ = m / (s×t avg )=m / [s×(0.4t 中心 +0.3t 过渡 +0.3t 边缘 )].

[0073] Next, perform standard density tests on Sample 1, Sample 2, and Sample 3 respectively. The test methods are as follows:

[0074] Step 1: Using a three-dimensional laser scanning method to measure the volume of the sample by laser scanning, denoted as v;

[0075] Step 2: Use a precision weighing instrument with an accuracy of 0.1 mg to weigh the mass of sample 1 and record the weighed mass result as m. The standard density of the sample is ρ = m / v.

[0076] The density measurement results (ρ x ) and the standard density (ρ) of the corresponding sample to calculate the error rate. The error rate calculation formula is: Error rate (%) = |ρ-ρ x | / ρ x .

[0077] The above calculation results are listed in Table 1, which is as follows:

[0078] Table 1

[0079]

[0080]

[0081] By analyzing the data in Table 1, it can be known that for Sample 1, the error rate of the density measurement results in Example 1 is significantly higher than that in Comparative Example 1 and Comparative Example 4; for Sample 2, the error rate of the density measurement results in Example 2 is significantly higher than that in Comparative Example 2 and Comparative Example 5; for Sample 3, the error rate of the density measurement results in Example 3 is significantly higher than that in Comparative Example 3 and Comparative Example 6; this shows that the method for measuring the density of the circular coated electrode of the sodium-ion battery of the present invention has higher accuracy.

[0082] In the description of the present invention, it should be understood that the terms "upper", "lower", "left", "right", etc. indicating the orientation or position relationship are based on the orientation or position relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation and specific orientation structure and operation. Therefore, it cannot be understood as a limitation to the present invention. In addition, "first" and "second" are only for the purpose of description, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present invention, unless otherwise specified, the meaning of "a plurality" is two or more.

[0083] The above has described a detailed description of an embodiment of the present invention, but the content described is only a preferred embodiment of the present invention and cannot be considered as limiting the scope of implementation of the present invention. All equivalent changes and improvements made according to the scope of the application of the present invention should still fall within the scope covered by the patent of the present invention.

Claims

1. A method for measuring the density of a circular coated electrode of a sodium-ion battery, characterized in that, It includes the following steps: Step 1: Divide the coated electrode into a central region, a transition region, and an edge region in sequence from the center to the edge according to the area weights of 40%, 30%, and 30%; take multiple points in each region for thickness measurement to obtain the average thickness, and denote the measured average thickness of the central region as t 中心 , denote the measured average thickness of the transition region as t 过渡 , denote the measured average thickness of the edge region as t 边缘 , then the weighted thickness t avg = 0.4t 中心 + 0.3t 过渡 + 0.3t 边缘 ; Step 2: Measure the area of the coated electrode and denote it as s, and calculate the volume of the coated electrode V = s × t avg = s × (0.4t 中心 + 0.3t 过渡 + 0.3t 边缘 ); Step 3: Measure the mass of the coated electrode and record it as m. Then, the density ρ of the coated electrode is ρ = m(1 - 0.015×ΔRH / 100) / (s×t avg ) = m(1 - 0.015×ΔRH / 100) / [s×(0.4t 中心 + 0.3t 过渡 + 0.3t 边缘 )]; where ΔRH is the difference between the actual RH% and 50% RH.

2. The method for measuring the density of the circular coated anode plate of a sodium ion battery according to claim 1, wherein In step one, the method for dividing the central area, transition area, and edge area is as follows: draw two circles with the central dot of the coated electrode as the center of the circle, and divide the coated electrode into three areas from the inside out, namely the central area, transition area, and edge area.

3. The method for measuring the density of the circular coated anode plate of a sodium-ion battery according to claim 2, characterized in that, The areas of the central area, transition area, and edge area respectively account for 40%, 30%, and 30% of the total area of the coated electrode.

4. The method for measuring the density of the circular coated electrode of the sodium-ion battery according to claim 1, wherein In step one, the method for obtaining the average thickness by randomly taking points in each area for thickness measurement is as follows: make an equilateral triangle with the center of the circle as the center in the corresponding area, measure the thickness at the three vertices of the equilateral triangle, and calculate the average thickness at the three vertices.

5. The method for measuring the density of the circular coated anode plate of a sodium-ion battery according to claim 4, wherein When measuring the thickness, a micrometer is used for measurement with the same pressure.

6. The method for measuring the density of the circular coated anode plate of a sodium-ion battery according to claim 5, wherein The same pressure is 9.5 - 10.5 N.

7. The method for measuring the density of the circular coated anode plate of a sodium-ion battery according to claim 5, wherein The same pressure is 10 N.

8. The method for measuring the density of the circular coated electrode of the sodium ion battery according to claim 1, characterized in that, In step two, the area of the coated electrode is measured as follows: a transparent grid plate with a precision of 1 mm 2 is used to cover the electrode, and the effective coating area is counted by the image scanning method.

9. The method for measuring the density of the circular coated anode of the sodium-ion battery according to claim 1, characterized in that, In step three, the method for measuring the mass of the coated electrode is as follows: a precision weighing instrument with an accuracy of 0.1 mg is used for mass weighing.

10. The method for measuring the density of the circular coated electrode of the sodium-ion battery according to claim 1, wherein, The precision weighing instrument is an electronic analytical balance.

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