Method for measuring chromium content of single side of copper foil

Abstract

The invention relates to a method for measuring the chromium content of a single side of a copper foil, which comprises the following steps of: obtaining the penetration rate of the copper foil to be measured based on the copper base material thickness of the copper foil to be measured and the relationship between the copper base material thickness and the penetration rate of a copper foil standard sample; and based on the penetration rate of the copper foil to be detected and the single-sided chromium content test value of the copper foil to be detected, obtaining a single-sided chromium content correction value of the chromium-plated surface to be detected of the copper foil to be detected. The chromium content measured by the method is high in accuracy, and the test process is simple and rapid.

Description

Technical Field

[0001] This application relates to the field of metal analysis and testing technology, and in particular to a method for determining the chromium content on one side of copper foil. Background Technology

[0002] Lithium-ion battery copper foil, as the preferred material for the negative electrode current collector in lithium-ion batteries, serves as both a carrier of the negative electrode active material and a collector and conductor of negative electrode electrons. It plays a crucial role in conducting and collecting current to generate maximum output current, significantly improving battery energy density and discharge performance. Chromium in lithium-ion battery copper foil enhances its corrosion resistance and high-temperature oxidation resistance, but at the cost of sacrificing some conductivity. Too low a chromium content reduces the peel strength between the copper foil and the active material, resulting in insufficient weather resistance; too high a chromium content increases the resistance of the copper foil, affecting battery cycle life. Therefore, accurately determining the chromium content in lithium-ion battery copper foil is one of the core challenges in manufacturing high-end lithium-ion battery copper foil. Currently, the commonly used X-ray fluorescence spectrometry method suffers from low accuracy in measuring the chromium content on one side of double-sided chromium-plated copper foil. Summary of the Invention

[0003] Therefore, it is necessary to provide a method for determining the chromium content on one side of copper foil to improve the accuracy of the test.

[0004] One aspect of this application provides a method for determining the chromium content on one side of copper foil, comprising the following steps:

[0005] Multiple copper foil standard samples with known chromium content are prepared. Each copper foil standard sample includes a copper substrate and a chromium plating layer on one surface of the copper substrate. The thickness of the copper substrate is different in the multiple copper foil standard samples.

[0006] Using the unplated chromium side of the copper foil standard sample as the test surface, the chromium content of the transmission effect of multiple copper foil standard samples was determined by X-ray fluorescence spectroscopy.

[0007] Based on the copper substrate thickness of multiple copper foil standard samples and the chromium content of the penetration effect and the chromium content, the relationship between the copper substrate thickness and the transmittance of the copper foil standard samples is obtained;

[0008] The chromium content of one side of the copper foil to be tested was determined by X-ray fluorescence spectroscopy to obtain the chromium content test value of the copper foil to be tested; the copper foil to be tested includes a copper substrate and chromium plating layers respectively disposed on two surfaces of the copper substrate.

[0009] The transmittance of the copper foil under test is obtained based on the relationship between the copper substrate thickness of the copper foil under test and the copper substrate thickness and transmittance of the copper foil standard sample.

[0010] Based on the transmittance of the copper foil under test and the single-sided chromium content test value of the copper foil under test, the single-sided chromium content correction value of the chromium-plated surface of the copper foil under test is obtained.

[0011] The above method explores the influence of the back-side transmission effect of copper substrates of different thicknesses on the single-sided chromium content of double-sided chromium-plated copper foil detected by X-ray fluorescence spectroscopy. It obtains the relationship between the thickness of the copper substrate and the transmittance of copper substrates of different thicknesses. Based on the X-ray fluorescence spectroscopy detection data, the transmittance can be used to correct the X-ray fluorescence spectroscopy detection data, and finally obtain more accurate single-sided chromium content data, controlling the deviation within 5%, which greatly improves the accuracy of the single-sided chromium content test of copper foil.

[0012] The above method eliminates the need to establish different standard curves for XRF quantitative analysis of copper substrates of different thicknesses, simplifies the testing steps for testing the chromium content of copper foils of different thicknesses, and is simple, convenient, and provides fast and accurate test results.

[0013] In some embodiments, the chromium content of the copper foil standard sample is 0~6 mg / m³. 2 .

[0014] In some embodiments, the relationship between the copper substrate thickness and transmittance of the copper foil standard sample is: Y = 0.8051e -0.28x Where x is the thickness of the copper substrate of the copper foil standard sample, Y is the transmittance of the copper foil standard sample, and the transmittance is the ratio of the chromium content of the penetration effect to the chromium content.

[0015] Optionally, the step of obtaining the relationship between the copper substrate thickness and transmittance of the copper foil standard sample is as follows:

[0016] Based on the copper substrate thickness and the chromium content and penetration effect of multiple copper foil standard samples, regression curves of the copper substrate thickness and penetration rate of the copper foil standard samples were obtained.

[0017] The relationship between the copper substrate thickness and transmittance of the copper foil standard sample is obtained from the regression curve.

[0018] In some embodiments, the copper substrate of the copper foil to be tested includes a smooth surface and a rough surface, and obtaining the chromium content correction value of the rough surface of the copper foil to be tested includes the following steps:

[0019] Using the smooth chromium plating layer as the test surface, the chromium content A of the smooth surface was obtained by X-ray fluorescence spectroscopy.

[0020] Using the matte chromium plating layer as the test surface, the chromium content B of the matte surface was obtained by X-ray fluorescence spectroscopy.

[0021] The transmittance of the copper foil to be tested is used as the correction coefficient Y for the single-sided chromium content of the copper foil to be tested.

[0022] Based on the transmittance of the copper foil to be tested and the test values ​​A and B of the smooth chromium content of the copper foil to be tested, the correction value of the rough chromium content of the copper foil to be tested is obtained.

[0023] Optionally, the correction value B for the surface chromium content of the copper foil to be tested. 校 Formula B 校 =(Y*AB) / (Y 2 -1).

[0024] In some embodiments, the copper substrate of the copper foil to be tested includes a smooth surface and a rough surface. Obtaining the chromium content correction value of the smooth surface of the copper foil to be tested includes the following steps:

[0025] Using the smooth chromium plating layer as the test surface, the chromium content A of the smooth surface was obtained by X-ray fluorescence spectroscopy.

[0026] Using the matte chromium plating layer as the test surface, the chromium content B of the matte surface was obtained by X-ray fluorescence spectroscopy.

[0027] The transmittance of the copper foil to be tested is used as the correction coefficient Y for the single-sided chromium content of the copper foil to be tested.

[0028] Based on the transmittance of the copper foil under test, the test value A of the smooth chromium content, the test value B of the rough chromium content, and the correction value B of the rough chromium content. 校 The corrected value of the chromium content on the smooth surface of the copper foil to be tested is obtained;

[0029] Optionally, the correction value A for the smooth chromium content of the copper foil to be tested... 校 Formula A 校 =(A+B) / (1+Y)-B 校 .

[0030] In some embodiments, the step of using the unplated chromium surface of the copper foil standard sample as the test surface and measuring the chromium content of the transmission effect of multiple copper foil standard samples by X-ray fluorescence spectroscopy is as follows:

[0031] S1: The chromium content of the copper foil standard sample was measured by ICP-OES and used as the baseline chromium content;

[0032] S2: Using the chromium-plated surface of the copper foil standard sample as the test surface, the XRF intensity value of chromium on the chromium-plated surface is obtained by X-ray fluorescence spectroscopy, and the relationship between the reference chromium content and the XRF intensity value of chromium on the chromium-plated surface is established.

[0033] S3: Using the unplated chromium surface of the copper foil standard sample as the test surface, the XRF intensity value of chromium on the unplated chromium surface of the copper foil standard sample is measured by X-ray fluorescence spectroscopy. Based on the relationship between the reference chromium content and the XRF intensity value of chromium on the chromium-plated surface, the chromium content of the copper foil standard sample with penetration effect is obtained.

[0034] In some embodiments, in S1, the copper foil standard sample is dissolved in hydrochloric acid solution during the ICP-OES process, and the molar concentration of the hydrochloric acid solution is 0.1 mol / L to 3 mol / L.

[0035] Optionally, the dissolution temperature is 25°C to 60°C;

[0036] Optionally, the dissolution time is 30 min to 120 min.

[0037] In some embodiments, the copper substrate of the copper foil standard sample has a thickness of 3µm to 10µm; and / or,

[0038] The thickness of the copper substrate in the copper foil to be tested is 3µm to 10µm.

[0039] In some embodiments, the thickness of the copper substrate in the copper foil to be tested is 5µm to 8µm.

[0040] In some embodiments, the deviation between the test value of the single-sided chromium content of the copper foil to be tested and the correction value of the single-sided chromium content of the copper foil to be tested is <5%. Detailed Implementation

[0041] To facilitate understanding of this application, a more complete description of the application will be provided below with reference to relevant embodiments. Preferred embodiments of the application are shown herein. However, the application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of this application.

[0042] 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. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0043] Low chromium content in lithium-ion battery copper foil reduces the peel strength between the foil and the active material, resulting in insufficient weather resistance. Conversely, excessive chromium content increases the resistance of the foil, affecting battery cycle life. Therefore, accurately determining the chromium content in lithium-ion battery copper foil is crucial for improving its quality. Currently, common methods for determining chromium content in lithium-ion battery copper foil include X-ray fluorescence spectrometry (XRF), inductively coupled plasma atomic absorption spectrometry (ICP), and atomic absorption spectrometry (AAS). However, AAS suffers from a narrow linear range and significant matrix interference. ICP involves complex pretreatment and cumbersome detection steps, requiring sample dissolution. Nitric acid dissolution is prone to penetration, leading to inaccurate test data, while hydrochloric acid dissolution is time-consuming and unsuitable for on-site production monitoring. XRF offers the advantages of rapid and non-destructive testing, but its accuracy is low for single-sided chromium content measurements on double-sided chromium-plated copper foil, failing to meet the demands of high-end lithium-ion battery copper foil manufacturing.

[0044] Based on this, one embodiment of this application provides a method for determining the chromium content on one side of copper foil, comprising the following steps:

[0045] Multiple copper foil standard samples with known chromium content are prepared. Each copper foil standard sample includes a copper substrate and a chromium plating layer on one surface of the copper substrate. The thickness of the copper substrate is different in the multiple copper foil standard samples.

[0046] Using the unplated chromium side of the copper foil standard sample as the test surface, the chromium content of the transmission effect of multiple copper foil standard samples was determined by X-ray fluorescence spectroscopy.

[0047] Based on the copper substrate thickness of multiple copper foil standard samples and the chromium content of the penetration effect and the chromium content, the relationship between the copper substrate thickness and the transmittance of the copper foil standard samples is obtained;

[0048] The chromium content of one side of the copper foil to be tested was determined by X-ray fluorescence spectroscopy to obtain the chromium content test value of the copper foil to be tested; the copper foil to be tested includes a copper substrate and chromium plating layers respectively disposed on two surfaces of the copper substrate.

[0049] The transmittance of the copper foil under test is obtained based on the relationship between the copper substrate thickness of the copper foil under test and the copper substrate thickness and transmittance of the copper foil standard sample.

[0050] Based on the transmittance of the copper foil under test and the single-sided chromium content test value of the copper foil under test, the single-sided chromium content correction value of the chromium-plated surface of the copper foil under test is obtained.

[0051] The above method explores the influence of the back-side transmission effect of copper substrates of different thicknesses on the single-sided chromium content of double-sided chromium-plated copper foil detected by X-ray fluorescence spectroscopy. It obtains the relationship between the thickness of the copper substrate and the transmittance of copper substrates of different thicknesses. Based on the X-ray fluorescence spectroscopy detection data, the transmittance can be used to correct the X-ray fluorescence spectroscopy detection data, and finally obtain more accurate single-sided chromium content data, controlling the deviation within 5%, which greatly improves the accuracy of the single-sided chromium content test of copper foil.

[0052] The above method eliminates the need to establish different standard curves for XRF quantitative analysis of copper substrates of different thicknesses, simplifies the testing steps for testing the chromium content of copper foils of different thicknesses, and is simple, convenient, and provides fast and accurate test results.

[0053] Understandably, the chromium content of the penetration effect of a copper foil standard sample refers to the XRF intensity value of chromium obtained when the unplated side of the copper foil standard sample is used as the test surface by X-ray fluorescence spectrometry. Because the incident X-rays can penetrate the thickness of the copper foil, the chromium on the chromium-plated side of the copper foil standard sample is excited. This unexpected fluorescence penetrates the copper foil and is captured. The chromium content corresponding to this XRF intensity value is the chromium content of the penetration effect.

[0054] Understandably, transmittance refers to the ratio of the chromium content affected by the penetration effect to the total chromium content, which can be the chromium content measured by the dissolution method. Transmittance is the proportion by which the single-sided chromium content test data is inflated due to the back-side penetration effect.

[0055] Understandably, the standard copper foil sample includes a copper substrate and a chromium plating on one surface of the copper substrate, while the other surface is not coated with any other plating.

[0056] Understandably, the single-sided chromium content refers to the mass content of the chromium plating layer on the chromium-plated side of the test in the copper foil to be tested.

[0057] In some of these embodiments, the copper substrate does not contain chromium.

[0058] In some of these embodiments, the surface of the copper substrate is chromium-free.

[0059] In some embodiments, before preparing a single-sided chromium-plated copper foil standard sample, copper substrates with different thicknesses that do not contain chromium are first prepared; then, the copper foil standard sample is prepared using the copper substrates that do not contain chromium.

[0060] In some embodiments, the chromium content of the copper foil standard sample is 0~6 mg / m³. 2 .

[0061] Understandably, the chromium content of copper foil standard samples can be adjusted by controlling electroplating process parameters. For example, the amount of chromium plating can be roughly controlled by adjusting the applied current, and the precise chromium content can be obtained by dissolution method. Different chromium contents are set to suggest standard curves.

[0062] In some embodiments, the chromium content of the copper foil standard sample is 0.1 mg / m³. 2 ~6mg / m 2 .

[0063] In some embodiments, the relationship between the copper substrate thickness and transmittance of the copper foil standard sample is: Y = 0.8051e -0.28x Where x is the copper substrate thickness of the copper foil standard sample in µm, Y is the transmittance of the copper foil standard sample, and the transmittance is the ratio of the chromium content of the transmittance effect to the chromium content in µm.

[0064] In some embodiments, the step of obtaining the relationship between the copper substrate thickness and transmittance of the copper foil standard sample is as follows:

[0065] Based on the copper substrate thickness and the chromium content and penetration effect of multiple copper foil standard samples, regression curves of the copper substrate thickness and penetration rate of the copper foil standard samples were obtained.

[0066] The relationship between the copper substrate thickness and transmittance of the copper foil standard sample is obtained from the regression curve.

[0067] Furthermore, the correlation coefficient of the regression curve, r, is ≥ 0.999.

[0068] In some embodiments, the copper substrate of the copper foil to be tested includes a smooth surface and a rough surface, and obtaining the chromium content correction value of the rough surface of the copper foil to be tested includes the following steps:

[0069] Using the smooth chromium plating layer as the test surface, the chromium content A of the smooth surface was obtained by X-ray fluorescence spectroscopy.

[0070] Using the matte chromium plating layer as the test surface, the chromium content B of the matte surface was obtained by X-ray fluorescence spectroscopy.

[0071] The transmittance of the copper foil to be tested is used as the correction coefficient Y for the single-sided chromium content of the copper foil to be tested.

[0072] Based on the transmittance of the copper foil under test and the test values ​​A and B of the smooth chromium content of the copper foil under test, the correction value of the rough chromium content of the copper foil under test is obtained.

[0073] Furthermore, the correction value B for the surface chromium content of the copper foil to be tested. 校 Formula B校 =(Y*AB) / (Y 2 -1).

[0074] Furthermore, A above can be the glossy chromium content data measured by an X-ray fluorescence spectrometer, and B can be the matte chromium content data measured by an X-ray fluorescence spectrometer.

[0075] Understandably, rough side refers to the side of the copper foil that faces away from the cathode roller during the copper foil (copper substrate) production process.

[0076] In some embodiments, the copper substrate of the copper foil to be tested includes a smooth surface and a rough surface. Obtaining the chromium content correction value of the smooth surface of the copper foil to be tested includes the following steps:

[0077] Using the smooth chromium plating layer as the test surface, the chromium content A of the smooth surface was obtained by X-ray fluorescence spectroscopy.

[0078] Using the matte chromium plating layer as the test surface, the chromium content B of the matte surface was obtained by X-ray fluorescence spectroscopy.

[0079] The transmittance of the copper foil to be tested is used as the correction coefficient Y for the single-sided chromium content of the copper foil to be tested.

[0080] Based on the transmittance of the copper foil under test, the test value A of the smooth chromium content, the test value B of the rough chromium content, and the correction value B of the rough chromium content. 校 The corrected value of the chromium content on the smooth surface of the copper foil to be tested is obtained.

[0081] Furthermore, the correction value A for the smooth chromium content of the copper foil to be tested... 校 Formula A 校 =(A+B) / (1+Y)-B 校 .

[0082] Furthermore, A above can be the glossy chromium content data measured by an X-ray fluorescence spectrometer, and B can be the matte chromium content data measured by an X-ray fluorescence spectrometer.

[0083] Understandably, the smooth side refers to the side of the copper foil that comes into contact with the cathode roller during the copper foil (copper substrate) production process.

[0084] In some embodiments, the step of using the unplated chromium surface of the copper foil standard sample as the test surface and measuring the chromium content of the transmission effect of multiple copper foil standard samples by X-ray fluorescence spectroscopy is as follows:

[0085] S1: The chromium content of the copper foil standard sample was measured by ICP-OES and used as the baseline chromium content;

[0086] S2: Using the chromium-plated surface of the copper foil standard sample as the test surface, the XRF intensity value of chromium on the chromium-plated surface is obtained by X-ray fluorescence spectroscopy, and the relationship between the reference chromium content and the XRF intensity value of chromium on the chromium-plated surface is established.

[0087] S3: Using the unplated chromium surface of the copper foil standard sample as the test surface, the XRF intensity value of chromium on the unplated chromium surface of the copper foil standard sample is measured by X-ray fluorescence spectroscopy. Based on the relationship between the reference chromium content and the XRF intensity value of chromium on the chromium-plated surface, the chromium content of the copper foil standard sample with penetration effect is obtained.

[0088] In some embodiments, in S1, before immersing the copper foil standard sample in hydrochloric acid solution, a 10cm*10cm sampler is used to cut it into square samples with a side length of 10cm.

[0089] In some embodiments, in S1, the copper foil standard sample is dissolved in hydrochloric acid solution, wherein the molar concentration of the hydrochloric acid solution is 0.1 mol / L to 3 mol / L.

[0090] As an example, the molar concentrations of hydrochloric acid solutions are 0.1 mol / L, 0.5 mol / L, 1.0 mol / L, 1.5 mol / L, 2.0 mol / L, 2.5 mol / L, and 3.0 mol / L, or any two of the above values ​​can be used as endpoints within the range.

[0091] Furthermore, the molar concentration of the hydrochloric acid solution is 1.5 mol / L to 2.5 mol / L.

[0092] Furthermore, the melting temperature is 25℃~60℃.

[0093] Furthermore, the dissolution temperature is 45℃~55℃.

[0094] Furthermore, the dissolution time is 30 min to 120 min.

[0095] Furthermore, the dissolution time is 90 min to 120 min.

[0096] In some embodiments, in S2, an X-ray fluorescence spectrometer is used to measure the chromium-plated surface of the copper foil standard sample to obtain its XRF intensity value, and the reference chromium content information is input to establish a detection standard curve with a correlation coefficient r≥0.999.

[0097] In some implementations, in S2, the correlation coefficient of determination r of the standard curve is ≥0.999.

[0098] In some embodiments, the thickness of the copper substrate of the plurality of copper foil standard samples is 3µm to 10µm.

[0099] In some embodiments, the thickness of the copper substrate in the copper foil to be tested is 3µm to 10µm.

[0100] As an example, the thickness of the copper substrate in the copper foil to be tested can be 3µm, 4µm, 5µm, 6µm, 7µm, 8µm, 9µm and 10µm, or it can be within the range formed by any two of the above point values ​​as end values.

[0101] Furthermore, the thickness of the copper substrate in the copper foil to be tested is 5µm to 8µm. Within this thickness range, the accuracy of single-sided chromium content testing of the copper foil to be tested is better, and the deviation of chromium content testing can be controlled within 3%.

[0102] In some embodiments, the deviation between the test value of the single-sided chromium content of the copper foil to be tested and the correction value of the single-sided chromium content of the copper foil to be tested is <5%.

[0103] In some embodiments, the copper foil to be tested is a lithium-ion battery copper foil with double-sided chromium plating.

[0104] To make the objectives, technical solutions, and advantages of this application clearer and more concise, the following specific embodiments are used for illustration, but this application is by no means limited to these embodiments. The embodiments described below are merely preferred embodiments of this application and can be used to describe this application, but should not be construed as limiting the scope of this application. It should be noted that any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

[0105] To better illustrate this application, the following description, in conjunction with specific embodiments, further explains its content. The following are specific embodiments.

[0106] Examples 1-7

[0107] 1) Take a series of lithium-ion battery copper substrates with thicknesses of 3.0μm, 4.0μm, 4.5μm, 5.0μm, 6.0μm and 8.0μm, respectively, with chromium-free surfaces;

[0108] 2) The lithium-ion battery copper substrate from step 1) is chromium-plated on one side to prepare multiple single-sided chromium-plated copper foil standard samples with different surface chromium contents and thicknesses. That is, the copper foil standard sample includes a copper substrate and a chromium plating layer on one surface of the copper substrate. The thickness of the copper substrate and the chromium content are different in the multiple copper foil standard samples, so as to form a copper substrate thickness gradient and chromium content gradient for establishing a standard curve in the standard samples. The surface chromium content of the standard sample is controlled to be approximately within the range of 0~6 mg / m2 by controlling the electroplating current (the chromium content will be accurately determined by ICP-OES in subsequent steps). At the same time, copper foils with a surface chromium content of 0 and thicknesses of 3.0 μm, 4.0 μm, 4.5 μm, 5.0 μm, 6.0 μm and 8.0 μm are prepared.

[0109] 3) Cut the single-sided chromium-plated copper foil standard sample prepared in step 2) into a square single-sided chromium-plated copper foil standard sample using a 10cm*10cm sampler.

[0110] 4) The single-sided chromium-plated copper foil standard sample obtained in step 3) was soaked in 2 mol / L hydrochloric acid solution at 50°C for 120 min and then transferred to a volumetric flask. After being diluted to volume with pure water, it was tested by ICP-OES to obtain the chromium content of the single-sided chromium-plated copper foil standard sample, as shown in Table 1. This chromium content is used as the baseline chromium content data.

[0111] 5) Cut the single-sided chromium-plated copper foil standard sample prepared in step 2) into a circular sample with a diameter of 40 mm, place it in a sample cup, use the chromium-plated side of the standard sample as the test surface, and use an X-ray fluorescence spectrometer to test the chromium element intensity of the sample. Input the reference chromium content data information from step 4) into the instrument to generate a standard curve with a relevant determination coefficient r2≥0.999.

[0112] 6) Take out the standard sample from the sample cup in step 5), and use its unplated back side as the test surface. Use an X-ray fluorescence spectrometer to test the chromium intensity of the sample (unplated, the test signal is generated by the back penetration effect). Use the standard curve in step 5) to detect chromium. As shown in Table 1, the penetration effect chromium content data of multiple copper foil standard samples are obtained.

[0113] 7) Based on the thickness data, chromium content data, and chromium content data of the standard samples in step 6), the regression curves of the back-side penetration effect of chromium for copper foils of different thicknesses were obtained: Y=0.8051e -0.28x x represents the thickness of the copper substrate of the copper foil standard sample, and Y represents the transmittance; thus, the relationship between the thickness of the copper substrate and the transmittance of the copper foil standard sample is obtained; where, transmittance = transmittance effect chromium content / chromium content (%).

[0114] 8) When testing the single-sided chromium content of the copper foil using X-ray fluorescence spectroscopy, the single-sided chromium content data obtained by X-ray fluorescence spectroscopy was corrected using the aforementioned regression curve, Y=0.8051e -0.28x In this context, x represents the thickness of the copper foil to be tested, and Y represents the correction coefficient for the chromium content on one side of the copper foil (using the transmittance of the copper foil as the correction coefficient for the chromium content on one side); the correction formula for the chromium content on the rough surface of the copper foil to be tested is: B 校 =(Y*AB) / (Y 2 -1); The correction formula for the chromium content G on the smooth surface of the copper foil to be tested is: A 校 =(A+B) / (1+Y)-B, where A is the measured value of chromium content on the smooth surface obtained by X-ray fluorescence spectrometry, and B is the measured value of chromium content on the rough surface obtained by X-ray fluorescence spectrometry.

[0115] Table 1

[0116]

[0117] In Examples 1-7, double-sided chromium-plated lithium battery copper foils with copper substrate thicknesses of 3μm, 5μm, and 6μm were prepared as copper foils to be tested, according to step 2) above.

[0118] The chromium content of the copper foil on the smooth surface was measured as A using an X-ray fluorescence spectrometer, and the chromium content of the copper foil on the rough surface was measured as B using an X-ray fluorescence spectrometer.

[0119] The regression curve Y=0.8051e -0.28x The thickness data of the copper foil to be tested (copper substrate thickness, excluding chromium plating) is used as the single-sided chromium content correction coefficient of the copper foil to be tested, and the single-sided chromium content correction coefficient Y of each copper foil to be tested is calculated.

[0120] Through B 校 =(Y*AB) / (Y 2 -1) and A 校 =(A+B) / (1+Y)-B 校 The corrected chromium content of the copper foil under test (corrected value of bright chromium content) and the corrected chromium content of the copper foil under test (corrected value of rough chromium content) are obtained.

[0121] Deviation: (Correction value of single-sided chromium content of copper foil under test - single-sided ICP-OES chromium content of copper foil under test) / single-sided ICP-OES chromium content of copper foil under test, then take the absolute value.

[0122] The accuracy of the corrected values ​​for the smooth chromium content measured in Examples 1-7 was verified as follows: The non-test surfaces of the copper foil under test were passivated with silane, and after applying adhesive tape, the copper foil was cut into 10cm x 10cm samples. The samples were then soaked in 3mol / L hydrochloric acid solution for 120 minutes to dissolve the chromium content. The solution was transferred to a volumetric flask, diluted to volume with pure water, and the chromium content on one side was determined using ICP-OES. The results are as follows:

[0123] Table 2

[0124]

[0125] As shown in Table 2 above, Examples 1-7 have high accuracy in testing the chromium content on one side of copper foil, and the deviation can be controlled within 5%.

[0126] 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.

[0127] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. 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 patent application should be determined by the appended claims.

Claims

1. A method for determining the chromium content on one side of copper foil, characterized in that, Includes the following steps: Multiple copper foil standard samples with known chromium content are prepared. Each copper foil standard sample includes a copper substrate and a chromium plating layer on one surface of the copper substrate. The thickness of the copper substrate is different in the multiple copper foil standard samples. Using the unplated chromium side of the copper foil standard sample as the test surface, the chromium content of the transmission effect of multiple copper foil standard samples was determined by X-ray fluorescence spectroscopy. Based on the copper substrate thickness of multiple copper foil standard samples and the chromium content of the penetration effect and the chromium content, the relationship between the copper substrate thickness and the transmittance of the copper foil standard samples is obtained; The chromium content of one side of the copper foil to be tested was determined by X-ray fluorescence spectroscopy to obtain the chromium content test value of the copper foil to be tested; the copper foil to be tested includes a copper substrate and chromium plating layers respectively disposed on two surfaces of the copper substrate. The transmittance of the copper foil under test is obtained based on the relationship between the copper substrate thickness of the copper foil under test and the copper substrate thickness and transmittance of the copper foil standard sample. Based on the transmittance of the copper foil under test and the single-sided chromium content test value of the copper foil under test, the single-sided chromium content correction value of the chromium-plated surface of the copper foil under test is obtained.

2. The method for determining the chromium content on one side of copper foil as described in claim 1, characterized in that, The chromium content of the copper foil standard sample is 0~6 mg / m³. 2 .

3. The method for determining the chromium content on one side of copper foil as described in claim 1, characterized in that, The relationship between the copper substrate thickness and transmittance of the copper foil standard sample is: Y = 0.8051e -0.28x Where x is the thickness of the copper substrate of the copper foil standard sample, Y is the transmittance of the copper foil standard sample in µm, and the transmittance is the ratio of the chromium content to the chromium content in the transmission effect in µm; Optionally, the step of obtaining the relationship between the copper substrate thickness and transmittance of the copper foil standard sample is as follows: Based on the copper substrate thickness and the chromium content and penetration effect of multiple copper foil standard samples, regression curves of the copper substrate thickness and penetration rate of the copper foil standard samples were obtained. The relationship between the copper substrate thickness and transmittance of the copper foil standard sample is obtained from the regression curve.

4. The method for determining the chromium content on one side of copper foil as described in claim 1, characterized in that, The copper substrate of the copper foil to be tested includes a smooth surface and a rough surface. Obtaining the chromium content correction value of the rough surface of the copper foil to be tested includes the following steps: Using the smooth chromium plating layer as the test surface, the chromium content A of the smooth surface was obtained by X-ray fluorescence spectroscopy. Using the matte chromium plating layer as the test surface, the chromium content B of the matte surface was obtained by X-ray fluorescence spectroscopy. The transmittance of the copper foil to be tested is used as the correction coefficient Y for the single-sided chromium content of the copper foil to be tested. Based on the transmittance of the copper foil to be tested and the test values ​​A and B of the smooth chromium content of the copper foil to be tested, the correction value of the rough chromium content of the copper foil to be tested is obtained. Optionally, the correction value B for the surface chromium content of the copper foil to be tested. 校 Formula B 校 =(Y*AB) / (Y 2 -1).

5. The method for determining the chromium content on one side of copper foil as described in claim 4, characterized in that, The copper substrate of the copper foil to be tested includes a smooth surface and a rough surface. Obtaining the chromium content correction value of the smooth surface of the copper foil to be tested includes the following steps: Using the smooth chromium plating layer as the test surface, the chromium content A of the smooth surface was obtained by X-ray fluorescence spectroscopy. Using the matte chromium plating layer as the test surface, the chromium content B of the matte surface was obtained by X-ray fluorescence spectroscopy. The transmittance of the copper foil to be tested is used as the correction coefficient Y for the single-sided chromium content of the copper foil to be tested. Based on the transmittance of the copper foil under test, the test value A of the smooth chromium content, the test value B of the rough chromium content, and the correction value B of the rough chromium content. 校 The corrected value of the chromium content on the smooth surface of the copper foil to be tested is obtained; Optionally, the correction value A for the smooth chromium content of the copper foil to be tested... 校 Formula A 校 =(A+B) / (1+Y)-B 校 .

6. The method for determining the chromium content on one side of copper foil as described in any one of claims 1 to 5, characterized in that, The steps for determining the chromium content of multiple copper foil standard samples by X-ray fluorescence spectroscopy using the unplated surface of the copper foil standard sample as the test surface are as follows: S1: The chromium content of the copper foil standard sample was measured by ICP-OES and used as the baseline chromium content; S2: Using the chromium-plated surface of the copper foil standard sample as the test surface, the XRF intensity value of chromium on the chromium-plated surface is obtained by X-ray fluorescence spectroscopy, and the relationship between the reference chromium content and the XRF intensity value of chromium on the chromium-plated surface is established. S3: Using the unplated chromium surface of the copper foil standard sample as the test surface, the XRF intensity value of chromium on the unplated chromium surface of the copper foil standard sample is measured by X-ray fluorescence spectroscopy. Based on the relationship between the reference chromium content and the XRF intensity value of chromium on the chromium-plated surface, the chromium content of the copper foil standard sample with penetration effect is obtained.

7. The method for determining the chromium content on one side of copper foil as described in claim 6, characterized in that, In step S1, during the ICP-OES process, the copper foil standard sample is dissolved using a hydrochloric acid solution, wherein the molar concentration of the hydrochloric acid solution is 0.1 mol / L to 3 mol / L. Optionally, the dissolution temperature is 25°C to 60°C; Optionally, the dissolution time is 30 min to 120 min.

8. The method for determining the chromium content on one side of copper foil as described in any one of claims 1 to 5, characterized in that, The copper substrate of the copper foil standard sample has a thickness of 3µm to 10µm; and / or, The thickness of the copper substrate in the copper foil to be tested is 3µm to 10µm.

9. The method for determining the chromium content on one side of copper foil as described in any one of claims 1 to 5, characterized in that, The thickness of the copper substrate in the copper foil to be tested is 5µm~8µm.

10. The method for determining the chromium content on one side of copper foil as described in any one of claims 1 to 5, characterized in that, The deviation between the single-sided chromium content test value and the single-sided chromium content correction value of the copper foil to be tested is <5%.

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