Method for measuring chromium content in lithium battery copper foil

Abstract

The invention belongs to the technical field of analysis and detection, and particularly relates to a method for determining the chromium content in a lithium battery copper foil. According to the method, the atomic absorption spectrometer is adopted to measure the sample, the measurement accuracy is improved, and the method is simple, rapid, economical and efficient in operation method, steps and measurement process. By adopting the method disclosed by the invention, measurement can be directly carried out without separating a matrix solution, the problems of complicated operation procedures and complicated steps of traditional methods such as extraction separation are solved, and the measurement accuracy is improved. In addition, nitric acid and hydrogen peroxide are adopted to further oxidize chromium (III) in the sample into chromium VI, so that the measurement precision and accuracy are improved; by adopting the sensibilization effect of the ammonium chloride solution and hydrochloric acid on chromium, the sensitivity is improved, the operation is simple and convenient, the analysis process is short, the analysis speed is greatly improved, the operation labor intensity is greatly reduced, batch operation is easy to realize, a reliable guarantee is provided for uniform, continuous and stable production of the lithium battery copper foil, and the benefit is remarkable.

Description

Technical Field

[0001] The invention belongs to the technical field of analysis and detection, and specifically relates to a method for determining the chromium content in a lithium battery copper foil. Background Art

[0002] Electrolytic copper foil has become an irreplaceable functional key basic raw material in the electronics industry. Copper foil products are widely used in terminal application fields such as copper clad laminates (CCLs) and printed circuit boards (PCBs), new energy vehicles, 3C digital products, energy storage systems, communication equipment, automotive electronics, etc. In today's rapid development of the electronic information industry, electrolytic copper foil is called the "neural network" for signal and power transmission and communication of electronic products.

[0003] In recent years, with the rapid development of the electric vehicle industry, the demand for lithium battery copper foil as a special material for the negative electrode of new energy power lithium batteries has been increasing, and the requirements for its quality have been continuously improved. Ultra-thin electrolytic copper foil is widely used because of its high energy density, good charge and discharge cycle characteristics and light weight.

[0004] Lithium battery copper foil is the core material of the negative electrode of lithium-ion batteries. The quality of copper foil has an important influence on the negative electrode manufacturing process and the performance of lithium batteries. Lithium battery copper foil is generally prepared by electrolysis. After being rolled off the foil machine, if the copper foil is stored for a long time, its surface will oxidize. High temperature, moisture, etc. will accelerate the oxidation of the copper foil. Therefore, it is necessary to perform anti-oxidation treatment on the surface of lithium battery copper foil. The prior art generally plates an anti-oxidation film mainly composed of chromium on both sides of the copper foil by chemical or electrolytic methods to isolate the copper foil from the air to achieve the purpose of anti-oxidation. Among them, the chromium-containing anti-oxidation process is simple, the raw materials are cheap, and the generated chromium-containing anti-oxidation film has good air isolation effect and strong high temperature resistance. Therefore, the most common method at present is to use hexavalent chromium (chromic (VI) acid or its salt) to perform anti-oxidation treatment on the surface of copper foil.

[0005] The chromium content in electrolytic copper foil is crucial to the anti-oxidation of copper foil. The chromium content is an important analytical indicator that needs to be controlled in the production of electrolytic copper foil. There is currently no established detection method for the determination of chromium content in lithium battery copper foil. Based on the technical problems existing in the chromium content detection and analysis methods, there is an urgent need for a method that can accurately and quickly analyze the chromium content. Summary of the invention

[0006] In view of the problems existing in the prior art, the present invention provides a method for determining the chromium content in lithium battery copper foil, and the present invention specifically includes the following contents:

[0007] A method for determining the chromium content in a lithium battery copper foil comprises the following steps:

[0008] S1, prepare the sample: add nitric acid solution to the copper foil sample to dissolve the copper foil to obtain a solution; heat the solution under reflux for a period of time; then add nitric acid solution to the solution, continue to heat under reflux until no brown smoke is generated; after the reaction solution is cooled, add hydrogen peroxide to it, react at 90-98°C until no large bubbles are generated; then continue to add hydrogen peroxide solution until only small bubbles are generated; then evaporate and concentrate the reaction solution, transfer it to a volumetric flask after cooling, add ammonium chloride solution and hydrochloric acid solution, and then add pure water to dilute it to obtain a sample;

[0009] S2, prepare a blank sample: add an ammonium chloride solution and a hydrochloric acid solution equal to that of S1 to a volumetric flask of the same specifications, and then add pure water to dilute to obtain a blank sample;

[0010] S3, prepare standard solution: add chromium solution to a volumetric flask of the same specification, add ammonium chloride solution and hydrochloric acid solution in the same amount as S1, and dilute with pure water to obtain chromium standard solutions of different concentrations;

[0011] S4, drawing a standard working curve for determination: using an atomic absorption spectrometer to measure the absorbance of chromium standard solutions with different concentrations, and drawing a standard working curve for determination with the chromium content as the abscissa and the absorbance value as the ordinate;

[0012] S5, measuring the absorbance of the sample: using an atomic absorption spectrometer to measure the absorbance of the sample;

[0013] S6, calculate the chromium content in the sample:

[0014] M(Cr)=(C1-C0)×2.50×f×51.996 / 100m,

[0015] in,

[0016] M(Cr) represents the chromium content, in %;

[0017] C1 represents the absorbance of the sample;

[0018] C0 represents the absorbance of the blank sample;

[0019] f represents the dilution factor of the sample;

[0020] m represents the mass of the copper foil sample, in g.

[0021] Furthermore, the concentration of the nitric acid solution in step S1 is 1.4-1.5 g / mL.

[0022] Furthermore, the volume concentration of the hydrogen peroxide solution in step S1 is 25%-35%.

[0023] Furthermore, in step S1: the mass concentration of the ammonium chloride solution is 95-105 g / L; and / or the density of the hydrochloric acid solution is 1.4-1.5 g / mL.

[0024] Furthermore, the concentrations of the ammonium chloride solution and the hydrochloric acid solution in steps S2-S3 are the same as those in step S1.

[0025] Further, in step S1: the first heating reflux time is 8-12 min; and / or, the mass of the copper foil sample is 2-3 g; and / or, the volume of the nitric acid solution added for the first time is 4-6 mL; and / or, the volume of the nitric acid solution added for the second time is 4-6 mL; and / or, the volume of hydrogen peroxide added for the first time is 2-4 mL; and / or, the volume of hydrogen peroxide added for the second time is 0.5-1.5 mL; and / or, the reaction solution is evaporated and concentrated to 4-6 mL; and / or, the amount of ammonium chloride solution added is 4-6 mL; and / or, the amount of hydrochloric acid solution added is 2-4 mL.

[0026] Furthermore, the concentrations of the chromium standard solutions of different concentrations in step S3 are: 0.00 mg / L, 1.00 mg / L, 3.00 mg / L, and 5.00 mg / L, respectively.

[0027] Furthermore, the method for measuring absorbance in step S4 and step S5 is: measuring at an atomic absorption spectrometer wavelength of 357.9 nm, a spectral passband width of 0.2 nm, and a burner height of 10 mm.

[0028] Beneficial effects of the present invention:

[0029] The method for determining the chromium content in lithium battery copper foil disclosed in the present invention adopts an atomic absorption spectrometer to measure the sample, thereby improving the measurement accuracy. Moreover, the operation method and steps of the method are simple, fast, economical and efficient in the measurement process. The method described in the present invention can be used to directly measure without separating the matrix solution, thereby overcoming the problems of complicated operation procedures and complicated steps of traditional methods such as extraction and separation, thereby improving the measurement accuracy. In addition, the present invention adopts nitric acid and hydrogen peroxide to further oxidize the chromium (III) in the sample to chromium (VI), thereby improving the measurement precision and accuracy; the sensitization effect of ammonium chloride solution and hydrochloric acid on chromium is adopted to improve the sensitivity, and the operation is simple, the analysis process is short, the analysis speed is greatly improved, the labor intensity of the operation is greatly reduced, and batch operation is easy to realize, thereby providing a reliable guarantee for the uniform, continuous and stable production of lithium battery copper foil, and the benefits are remarkable. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a schematic diagram of the operation flow of the method disclosed in the present invention;

[0031] Figure 2This is a standard working curve diagram for measuring the embodiment 1 of the present invention;

[0032] Figure 3 The standard working curve diagram of Example 2 of the present invention is measured;

[0033] Figure 4 This is a standard working curve diagram for measuring Example 3 of the present invention. DETAILED DESCRIPTION

[0034] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. The embodiments shown below do not limit the invention content described in the claims. In addition, the entire contents of the structures represented by the following embodiments are not limited to those necessary as solutions to the invention described in the claims.

[0035] Reference Figure 1 A method for determining the chromium content in a lithium battery copper foil comprises the following steps:

[0036] S1, prepare the sample: add 4-6mL of 1.4-1.5g / mL nitric acid solution to 2-3g copper foil sample to dissolve the copper foil and obtain a solution; heat the solution to reflux for 8-12min; then add 4-6mL of 1.4-1.5g / mL nitric acid solution to the solution, continue heating and reflux until no brown smoke is generated; after the reaction solution is cooled, add 2-4mL of 25%-35% hydrogen peroxide to it, react at 90-98℃ until no large bubbles are generated; then continue to add 0.5-1.5mL of hydrogen peroxide solution until only small bubbles are generated; then evaporate and concentrate the reaction solution to 4-6mL, transfer it to a volumetric flask after cooling, add 4-6mL of 95-105g / L ammonium chloride solution and 2-4mL of 1.4-1.5g / mL hydrochloric acid solution, and then add pure water to dilute and fix the volume to obtain a sample;

[0037] S2, prepare a blank sample: add an equal amount of ammonium chloride solution and hydrochloric acid solution of the same concentration as S1 to a volumetric flask of the same specifications, and then add pure water to dilute to volume to obtain a blank sample;

[0038] S3, prepare standard solution: add chromium solution to a volumetric flask of the same specification, add ammonium chloride solution and hydrochloric acid solution of the same amount and concentration as S1, dilute with pure water to obtain chromium standard solutions of different concentrations; the concentrations of the chromium standard solutions of different concentrations are: 0.00 mg / L, 1.00 mg / L, 3.00 mg / L, 5.00 mg / L;

[0039] S4, drawing a standard working curve for determination: using an air-acetylene flame at an atomic absorption spectrometer wavelength of 357.9 nm, a spectral passband width of 0.2 nm, and a burner height of 10 mm, measuring the absorbance of chromium standard solutions of different concentrations, and drawing a standard working curve for determination with the chromium content as the abscissa and the absorbance value as the ordinate;

[0040] S5, measuring the absorbance of the sample: using an air-acetylene flame at an atomic absorption spectrometer wavelength of 357.9 nm, a spectral passband width of 0.2 nm, and a burner height of 10 mm, measuring the absorbance of the sample;

[0041] S6, calculate the chromium content in the sample:

[0042] M(Cr)=(C1-C0)×2.50×f×51.996 / 100m,

[0043] in,

[0044] M(Cr) represents the chromium content, in %;

[0045] C1 represents the absorbance of the sample;

[0046] C0 represents the absorbance of the blank sample;

[0047] f represents the dilution factor of the sample;

[0048] m represents the mass of the copper foil sample, in g.

[0049] Example 1

[0050] A method for determining the chromium content in a lithium battery copper foil comprises the following steps:

[0051] S1, using anti-static gloves, carefully cut 2 copper foil samples of 10×10cm and 6-10μm in thickness, weigh 2.4654g on the analytical balance, place in a 250ml beaker, carefully add 5ml nitric acid solution, place on a temperature-controlled electric hot plate, cover with a watch glass, and keep the sample dissolved at low temperature. Heat and reflux for 10min without boiling, add 5ml nitric acid solution, cover with a watch glass, and continue to heat and reflux until no brown smoke is generated. After the above solution cools down, slowly add 3ml hydrogen peroxide, continue to cover with a watch glass, and keep the temperature at 95℃, heat until no large bubbles are generated, continue to add 1ml hydrogen peroxide solution, until only fine bubbles are generated, and then evaporate to 5ml. After the solution cools down, wash the inner wall with an appropriate amount of water 3 times, transfer to a 250ml volumetric flask, add 5ml ammonium chloride solution and 3ml hydrochloric acid solution, and dilute with water to the mark.

[0052] S3, add ammonium chloride solution and hydrochloric acid solution of the same concentration as S1 to a volumetric flask of the same specifications, and then add pure water to dilute to volume to obtain a blank sample.

[0053] S2. Prepare 0.00, 1.00, 3.00, and 5.00 mg / L chromium standard solutions in four 100 ml volumetric flasks, respectively. Add 5 ml of ammonium chloride solution and 3 ml of hydrochloric acid solution to the standard series, dilute to the scale, shake well, and set aside.

[0054] S3, use atomic absorption spectrometer to make chromium working curve. The curve correction coefficient is 0.9992, and the linear relationship is very good. The working curve is as follows Figure 2 shown.

[0055] S4, detecting the absorbance of the sample prepared in S1 and the blank sample in S2 according to the method in S3.

[0056] S5, the chromium content in the sample is calculated according to the working curve, and the measured result is 0.0055%.

[0057] Example 2

[0058] A method for determining the chromium content in a lithium battery copper foil comprises the following steps:

[0059] Using anti-static gloves, carefully cut 2 copper foil samples with a thickness of 10×10cm and a thickness of 6-10μm, weigh 2.5732g on the analytical balance, place in a 250ml beaker, carefully add 5ml nitric acid solution, place on a temperature-controlled electric hot plate, cover with a watch glass, and keep the sample dissolved at low temperature. Heat and reflux for 10min without boiling, add 5ml nitric acid solution, cover with a watch glass, and continue to heat and reflux until no brown smoke is generated. After the above solution cools down, slowly add 3ml hydrogen peroxide, continue to cover with a watch glass, and keep the temperature at 95℃, heat until no large bubbles are generated, continue to add 1ml hydrogen peroxide solution, until only fine bubbles are generated, and then evaporate to 5ml. After the solution cools down, wash the inner wall with an appropriate amount of water 3 times, transfer to a 250ml volumetric flask, add 5ml ammonium chloride solution and 3ml hydrochloric acid solution, and dilute with water to the mark.

[0060] In four 100ml volumetric flasks, prepare 0.00, 1.00, 3.00, 5.00mg / L chromium standard solutions respectively. Add 5ml ammonium chloride solution and 3ml hydrochloric acid solution to the standard series respectively, dilute to the scale, shake well, and set aside. In four 100ml volumetric flasks, prepare 0.00, 1.00, 3.00, 5.00mg / L chromium standard solutions respectively. Add 5ml ammonium chloride solution and 3ml hydrochloric acid solution to the standard series respectively, dilute to the scale, shake well, and set aside. Use atomic absorption spectrometer to make chromium working curve. The curve correction coefficient is 0.9989, and the linear relationship is very good. The working curve is as follows: Figure 3 According to the curve, the sample was tested and the result was 0.0063%.

[0061] Example 3

[0062] A method for determining the chromium content in a lithium battery copper foil comprises the following steps:

[0063] Using anti-static gloves, carefully cut 2 10×10 copper foil samples with a thickness of 6-10, weigh them on the analytical balance to 2.6012g, place them in a 250ml beaker, carefully add 5ml nitric acid solution, place them on a temperature-controlled electric hot plate, cover them with a watch glass, and keep the sample dissolved at a low temperature. Heat and reflux for 10min without boiling, then add 5ml nitric acid solution, cover them with a watch glass, and continue to heat and reflux until no brown smoke is generated. After the above solution cools down, slowly add 3ml hydrogen peroxide, continue to cover them with a watch glass, and keep the temperature at 95℃, heat until no large bubbles are generated, continue to add 1ml hydrogen peroxide solution, until only fine bubbles are generated, and then evaporate the volume to 5ml. After the solution cools down, wash the inner wall with an appropriate amount of water 3 times, transfer it into a 250ml volumetric flask, add 5ml ammonium chloride solution and 3ml hydrochloric acid solution, and dilute with water to the mark.

[0064] In four 100ml volumetric flasks, prepare 0.00, 1.00, 3.00, 5.00mg / L chromium standard solutions, add 5ml ammonium chloride solution and 3ml hydrochloric acid solution to the standard series, dilute to the scale, shake well, and set aside. In four 100ml volumetric flasks, prepare 0.00, 1.00, 3.00, 5.00mg / L chromium standard solutions, add 5ml ammonium chloride solution and 3ml hydrochloric acid solution to the standard series, dilute to the scale, shake well, and set aside. Use atomic absorption spectrometer to make chromium working curve. The curve correction coefficient is 0.9995, and the linear relationship is very good. The working curve is as follows: Figure 4 According to the curve, the sample was tested and the result was 0.0072%.

[0065] Precision test:

[0066] Using the method of the present invention, the same sample was measured 11 times, and the measurement results are shown in Table 1:

[0067] Table 1 Chromium measurement precision

[0068]

[0069] It can be seen from Table 2 that the method disclosed in the present invention has very good precision, RSD≤0.1%, which fully meets the requirements of the analytical method.

[0070] Spike recovery test:

[0071] Using the method of the present invention, different amounts of chromium ion standard solution were added to the same sample in batches, and the measurement results are shown in Table 2:

[0072] Table 2 Chromium determination spike recovery test

[0073]

[0074] It can be seen from Table 2 that, using the method disclosed in the present invention, the recovery rate of chromium is between 98.3% and 102.8%, which can meet the requirements of the analytical method.

[0075] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for determining the chromium content in lithium battery copper foil, characterized in that: The following steps are involved: S1, preparing a sample: adding a nitric acid solution to a copper foil sample to dissolve the copper foil to obtain a solution; heating the solution under reflux for a period of time; Then add nitric acid solution to the dissolved solution, continue heating and reflux until no brown smoke is generated; after the reaction solution is cooled, add hydrogen peroxide thereto, react at 90-98°C until no large bubbles are generated; then continue to add hydrogen peroxide solution until only small bubbles are generated; then evaporate and concentrate the reaction solution, transfer it to a volumetric flask after cooling, add ammonium chloride solution and hydrochloric acid solution, and then add pure water to dilute it to obtain a sample; S2, prepare a blank sample: add an ammonium chloride solution and a hydrochloric acid solution equal to that of S1 to a volumetric flask of the same specifications, and then add pure water to dilute to obtain a blank sample; S3, prepare standard solution: add chromium solution to a volumetric flask of the same specification, add ammonium chloride solution and hydrochloric acid solution in the same amount as S1, and dilute with pure water to obtain chromium standard solutions of different concentrations; S4, drawing a standard working curve for determination: using an atomic absorption spectrometer to measure the absorbance of chromium standard solutions with different concentrations, and drawing a standard working curve for determination with the chromium content as the abscissa and the absorbance value as the ordinate; S5, measuring the absorbance of the sample: using an atomic absorption spectrometer to measure the absorbance of the sample and the blank sample; S6, calculate the chromium content in the sample: M(Cr)=(C1-C0)×2.50×f×51.996 / 100m, in, M(Cr) represents the chromium content, in %; C1 represents the absorbance of the sample; C0 represents the absorbance of the blank sample; f represents the dilution factor of the sample; m represents the mass of the copper foil sample, in g.

2. The method for determining the chromium content in a lithium battery copper foil according to claim 1, characterized in that: The concentration of the nitric acid solution in step S1 is 1.4-1.5 g / mL.

3. The method for determining the chromium content in a lithium battery copper foil according to claim 2, characterized in that: The volume concentration of the hydrogen peroxide solution in step S1 is 25%-35%.

4. The method for determining the chromium content in a lithium battery copper foil according to claim 3, characterized in that: In step S1: the mass concentration of the ammonium chloride solution is 95-105 g / L; and / or the density of the hydrochloric acid solution is 1.4-1.5 g / mL.

5. The method for determining the chromium content in a lithium battery copper foil according to claim 4, characterized in that: The concentrations of the ammonium chloride solution and the hydrochloric acid solution in steps S2-S3 are the same as those in step S1.

6. The method for determining the chromium content in a lithium battery copper foil according to claim 5, characterized in that: In step S1: the first heating reflux time is 8-12min; and / or, the mass of the copper foil sample is 2-3g; and / or, the volume of the nitric acid solution added for the first time is 4-6mL; and / or, the volume of the nitric acid solution added for the second time is 4-6mL; and / or, the volume of hydrogen peroxide added for the first time is 2-4mL; and / or, the volume of hydrogen peroxide added for the second time is 0.5-1.5mL; and / or, the reaction solution is evaporated and concentrated to 4-6mL; and / or, the amount of ammonium chloride solution added is 4-6mL; and / or, the amount of hydrochloric acid solution added is 2-4mL.

7. The method for determining the chromium content in a lithium battery copper foil according to claim 1, characterized in that: The concentrations of the chromium standard solutions of different concentrations in step S3 are: 0.00 mg / L, 1.00 mg / L, 3.00 mg / L, and 5.00 mg / L, respectively.

8. The method for determining the chromium content in lithium battery copper foil according to any one of claims 1 to 7, characterized in that: The method for measuring the absorbance in step S4 and step S5 is: measuring at an atomic absorption spectrometer wavelength of 357.9 nm, a spectral passband width of 0.2 nm, and a burner height of 10 mm.

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