Analysis test method for chlorine content in ternary precursor battery material

Abstract

The present application relates to a kind of analysis test methods of the chlorine content in ternary precursor battery material, belong to ternary material chemical analysis technical field.The method of the present application includes sample distillation, partial solution, adding nitric acid, acetone, silver nitrate solution and preparation test solution by diluting with water, draw standard working curve, determine the content of chlorine element and the like steps.The analysis test method of the present application uses silver chloride turbidimetric spectrophotometry to test, with the advantages of high sensitivity, strong anti-interference ability, good selectivity, high accuracy, wide applicable concentration range, low analysis cost, simple and fast operation, can be used as the routine method of the chlorine content analysis test in ternary precursor battery material.The sample applicable to the present method includes NCM series, NCA series, NCM90, NCMA series and the like ternary precursor battery material product.

Description

TECHNICAL FIELD

[0001] The present application relates to a method for analyzing and testing the chlorine content in ternary precursor battery materials, in particular to a method for analyzing and testing the chlorine content in ternary precursor battery materials using silver chloride turbidimetric spectrophotometry, and belongs to the technical field of ternary material chemical analysis. BACKGROUND

[0002] Ternary precursor materials are an important component of lithium-ion battery cathode materials, and their performance directly affects key indicators such as energy density, cycle life, and safety of the battery. With the growing demand for new energy vehicles and renewable energy storage, the demand for high-performance lithium-ion batteries is also rapidly rising, thereby driving the research and development of ternary precursor materials.

[0003] Ternary precursor materials such as NCM and NCA materials are widely used in lithium-ion batteries, and their performance directly affects the energy density, cycle life, and safety of the battery. During the preparation of these materials, chloride ions as a common impurity element may have a negative impact on the electrochemical performance of the materials. Therefore, accurately determining the chlorine content in ternary precursor materials has important technical background and practical significance.

[0004] The presence of chloride ions in ternary precursor materials may cause the following problems: chloride ions may react with lithium ions to form undesirable compounds, reducing the conductivity and ion migration ability of the material. The presence of chloride ions may cause the crystal structure of the material to be unstable, affecting its cycle performance during charging and discharging. In the case of high temperature or battery overcharging, chloride ions may trigger unsafe reactions, increasing the risk of the battery.

[0005] With the widespread application of ternary precursor materials, related testing standards and specifications are also constantly improving. For example, the requirements for measuring chloride ion content are gradually increasing in national standards and industry standards to ensure the quality and safety of the materials. SUMMARY

[0006] To solve the technical problem of measuring the chlorine content in ternary precursor battery materials, the present application uses silver chloride turbidimetry to accurately measure the chlorine content in ternary precursor materials. This method dissolves the sample and reacts with silver nitrate to form a silver chloride suspension, and then uses a spectrophotometer to measure the absorbance of the suspension to calculate the concentration of chloride ions. This method has the advantages of simple operation, low cost, and high sensitivity.

[0007] The present application uses silver chloride turbidimetric spectrophotometry for determination, which has the characteristics of short process, accurate results, and easy operation.

[0008] The present application adopts the following technical solutions to solve the above technical problems:

[0009] The application discloses a method for analyzing and testing the content of chlorine in a ternary precursor battery material, and the content of chlorine is determined by adopting a silver chloride turbidimetric spectrophotometry method.

[0010] (1) Sample distillation: when the temperature of pre-distilled sulfuric acid is reduced to 25-70 DEG C, a ternary precursor battery material sample (mass m0) is weighed and added into a distillation flask, a distillation device is connected for distillation; the solution in the distillation flask is heated to be warmed, the water vapor flow and the heating power are adjusted, the temperature is controlled to be 100-200 DEG C, after receiving, the receiving bottle is removed, the solution in the receiving bottle is transferred into a volumetric flask, water is used for dilution to the scale (total volume of the test solution V0), and the solution is shaken and evenly distributed, and is ready for use; a blank sample is prepared at the same time;

[0011] (2) A part of the solution (V1) is taken into a glass volumetric flask;

[0012] (3) Water is added to a certain volume, nitric acid is added, the solution is mixed, acetone is added, the solution is mixed, finally, silver nitrate solution is added, the solution is diluted to the scale with water, and the solution is mixed; the volumetric flask is placed in a water bath for heating, the volumetric flask is removed, and the solution is cooled to room temperature by flowing water, the solution is transferred into a dark room, and the solution is mixed;

[0013] (4) A part of the solution is transferred into a cuvette, the blank solution of the test sample is used as a reference, the absorbance of the solution is measured at a wavelength of 410-460 nm in a spectrophotometer, and the mass of chlorine (m1) is calculated from a corresponding working curve.

[0014] In step (1), the receiving time is 10-40 min. The mass of the ternary precursor battery material sample is 0.05-1.00 g. The mass-volume ratio of the mass of the ternary precursor battery material sample to the mass of the total volume of the test solution diluted to the scale with water is (0.05-1.00) g:100 ml.

[0015] The ternary precursor battery material sample includes NCM (lithium nickel cobalt manganese oxide) series, NCA (lithium nickel cobalt aluminum oxide) series, NCM90 (high-nickel lithium cobalt manganese oxide) and / or NCMA (lithium nickel cobalt manganese aluminum oxide) series and other ternary precursor battery material products.

[0016] The method for pre-distillation purification of sulfuric acid comprises the following steps: 150-300 parts by volume of water is placed in a distillation flask of a water vapor distillation device and heated to boiling, ready for use; 5-20 parts by volume of water is placed in a 50-200 parts by volume receiving flask as an absorption liquid, ready for use; 20-100 parts by volume of sulfuric acid is added to the distillation flask, the mouth of the flask is cleaned with water, and zeolite is added, and the distillation device is connected; the solution in the distillation flask is heated, the water vapor flow and the heating power are adjusted to maintain the temperature at 100-200 DEG C, heating is stopped after 10-40 minutes of distillation, and the receiving liquid is discarded. The concentration of the sulfuric acid is concentrated sulfuric acid with a mass fraction of 95-98%.

[0017] In step (3), after dilution to the scale with water, the amount of nitric acid added is 1vol.%-5vol.%, the amount of acetone added is 1vol.%-5vol.%, and the amount of silver nitrate solution added is 1vol.%-5vol.%; the nitric acid is concentrated nitric acid with a mass fraction of 65%-70%, and the mass concentration of the silver nitrate solution is 5-15 g / L. The temperature of heating in the water bath is 70 DEG C±1 DEG C, and the time is 5-15 minutes. The room temperature is 25 DEG C±3 DEG C, and the solution is moved into a dark room for 5-15 minutes.

[0018] In step (4), the diameter of the cuvette is 1-3 cm, and the volume of the solution moved into the cuvette is 1-3 mL.

[0019] The method for drawing the working curve comprises the following steps:

[0020] (I) applicable to Cl amount of 0.005%-0.010% (mass%, containing 0.010%)

[0021] (1) 0, 0.50, 1.00, 2.00, 3.00, 4.00 mL of chlorine standard solution is moved into a group of 100 mL volumetric flasks, 1:1 nitric acid is added, water is added for dilution to a certain volume, and mixing is performed; then acetone is added, mixing is performed, finally silver nitrate solution is added, water is added for dilution to the scale, and mixing is performed; the volumetric flasks are placed in a water bath for heating, taken out, cooled to room temperature under running water, moved into a dark room for placement, and mixed; the concentration of the chlorine standard solution is 10 μg / ml;

[0022] (2) part of the chromogenic solution is moved into a cuvette, the absorbance is measured at a wavelength of 430 nm in a spectrophotometer, and a working curve is drawn with the mass of chlorine as the abscissa and the absorbance as the ordinate.

[0023] (II) applicable to Cl amount of 0.010%-0.20% (mass%, not containing 0.010%)

[0024] (1) Take 0 mL, 0.20 mL, 0.60 mL, 0.80 mL, 1.00 mL, 1.20 mL, 1.60 mL chlorine standard solution into a set of 100 mL volumetric flasks, add 1:1 nitric acid, dilute to a certain volume with water, mix well; then add acetone, mix well, finally add silver nitrate solution, dilute to the mark with water, mix well; place the volumetric flask in a water bath, take it out, cool to room temperature under running water, move into a dark room, mix well; the concentration of chlorine standard solution is 50 μg / ml;

[0025] (2) Move part of the color developing solution into a cuvette, measure its absorbance at 410-460 nm on a spectrophotometer; plot a working curve with the mass of chlorine as the abscissa and the absorbance as the ordinate.

[0026] Among them, after diluting to the mark with water, the addition amount of 1:1 nitric acid is 1vol.%-5vol.%, the addition amount of acetone is 1vol.%-5vol.%, and the addition amount of silver nitrate solution is 1vol.%-5vol.%; 1:1 nitric acid is a mixture of nitric acid (65%-70% by mass) and water in a volume ratio of 1:1, and the mass concentration of silver nitrate solution is 5g / L-15 g / L. The temperature in the water bath is 70℃±1℃, and the time is 5 min-15 min. The room temperature is 25℃±3℃, and the time in the dark room is 5 min-15 min.

[0027] Among them, the diameter of the cuvette is 1-3 cm, and the volume of the moved part of the solution is 1 mL-3 mL.

[0028] Calculation of analysis results:

[0029] The mass fraction of chlorine is denoted by w, and the value is expressed in %, which is calculated according to formula (1):

[0030] •••••••• (1)

[0031] In the formula:

[0032] m1 ——the mass of chlorine calculated from the working curve, in micrograms (μg);

[0033] V0 ——the total volume of the test solution, in milliliters (mL);

[0034] m0 ——the mass of the test material, in grams (g);

[0035] V1 ——the volume of the test solution, in milliliters (mL).

[0036] The analysis results are expressed to four decimal places.

[0037] The water is double-distilled water and above.

[0038] The analysis test method of the present application adopts silver chloride turbidimetric spectrophotometry for testing, and has the advantages of high sensitivity, strong anti-interference ability, good selectivity, high accuracy, wide applicable concentration range, low analysis cost, simple and rapid operation, and can be used as a conventional method for analyzing and testing the chlorine content in ternary precursor battery material.

[0039] The samples applicable to the method include NCM series, NCA series, NCM90, NCMA series and other ternary precursor battery material products. BRIEF DESCRIPTION OF DRAWINGS

[0040] Figure 1 The chlorine working curve diagram of Example 1 of the present application;

[0041] Figure 2 The chlorine working curve diagram of Example 2 of the present application. DETAILED DESCRIPTION

[0042] The present application will be described in detail below with reference to examples.

[0043] The analysis test method of the chlorine content in ternary precursor battery material of the present application adopts silver chloride turbidimetric spectrophotometry for determination, and includes the steps of sample distillation, partial solution collection, addition of nitric acid, acetone and silver nitrate solution and preparation of test solution by dilution with water, drawing of standard working curve, determination of chlorine element content and the like.

[0044] Sample determination:

[0045] 1.1 Sulfuric acid pre-distillation purification: 150 mL-300 mL of water is placed in the distillation flask of the water vapor distillation device, heated to boiling, and ready for use. 5 mL-20 mL of water is placed in a 50 mL-200 mL receiving flask as an absorption liquid, ready for use. 20 mL-100 mL of sulfuric acid is added to the distillation flask, the mouth of the flask is cleaned with water, and zeolite is added, and the distillation device is connected. The solution in the distillation flask is heated, the water vapor flow and heating power are adjusted to maintain the temperature at 100℃-200℃, and after 10 min-40 min of distillation, the heating is stopped and the receiving liquid is discarded.

[0046] 1.2 Sample distillation: when the temperature of the pre-distilled sulfuric acid in the distillation flask drops to 25℃-70℃, the test material is added to the distillation flask, and the distillation device is connected for distillation. The solution in the distillation flask is heated, the water vapor flow and heating power are adjusted to maintain the temperature at 100℃-200℃, and after 10 min-40 min of distillation, the receiving flask is removed, and the solution in the receiving flask is transferred to a 100 mL volumetric flask, diluted to the mark with water, shaken well, and ready for use.

[0047] 2.1 Transfer a portion of the solution into a 100 mL glass volumetric flask.

[0048] 3.1 Add water to about 30 mL, 3 mL nitric acid, mix, add 2 mL acetone, mix, add 2 mL silver nitrate solution, dilute to the mark with water, mix. Place the flask in a water bath at 70 °C (± 1 °C) for 8 min, remove, cool to room temperature under running water, transfer to a dark room and let stand for 10 min, mix.

[0049] 4.1 Transfer a portion of the solution into a 1-3 cm cuvette, use the blank solution of the test material as the reference, measure the absorbance at 410-460 nm on the spectrophotometer, calculate the mass of chlorine from the corresponding working curve.

[0050] Preparation of the working curve:

[0051] For Cl amounts of 0.005 % - 0.010 %

[0052] Transfer 0, 0.50, 1.00, 2.00, 3.00, 4.00 mL of the chlorine standard solution (10 μg / ml) into a set of 100 mL volumetric flasks, add 3 mL of 1:1 nitric acid, dilute to 30 mL with water, mix. Follow step 3.1.

[0053] Transfer a portion of the coloured solution into a 3 cm cuvette, measure the absorbance at 430 nm on the spectrophotometer. Plot the working curve with the mass of chlorine as the abscissa and the absorbance as the ordinate.

[0054] For Cl amounts of 0.010 % - 0.20 %

[0055] 1. Transfer 0 mL, 0.20 mL, 0.60 mL, 0.80 mL, 1.00 mL, 1.20 mL, 1.60 mL of the chlorine standard solution (50 μg / ml) into a set of 100 mL volumetric flasks, add 3 mL of 1:1 nitric acid, dilute to 30 mL with water, mix. Follow step 3.1.

[0056] 2. Transfer a portion of the coloured solution into a 1-3 cm cuvette, measure the absorbance at 410-460 nm on the spectrophotometer. Plot the working curve with the mass of chlorine as the abscissa and the absorbance as the ordinate.

[0057] Calculation of the analytical results:

[0058] The mass fraction of chlorine is denoted by w and the value is expressed in %, calculated according to formula (1):

[0059] •••••••• (1)

[0060] In the formula:

[0061] m1 - the mass of chlorine calculated from the working curve, in micrograms (μg);

[0062] V0 - the total volume of the test solution, in milliliters (mL);

[0063] m0 - the mass of the test material, in grams (g);

[0064] V1 - the volume of the test solution taken, in milliliters (mL).

[0065] The analysis results are expressed to four decimal places.

[0066] The water is double-distilled water and above purity.

[0067] Example 1:

[0068] The analysis and testing method for determining the chlorine content in the ternary precursor battery material in Example 1 of the present application adopts the silver chloride turbidimetric spectrophotometric method, and the reagents used are as follows:

[0069] Nitric acid (ρ = 1.42 g / mL);

[0070] 1:1 nitric acid is a mixture of nitric acid (ρ = 1.42 g / mL) and water in a volume ratio of 1:1;

[0071] Sulfuric acid (ρ = 1.84 g / mL);

[0072] Acetone;

[0073] Silver nitrate solution (10 g / L);

[0074] Chlorine standard solution (10 μg / ml);

[0075] The water is double-distilled water and above purity, at least double-distilled water is used, and the water is chlorine ion-free water: take 50 mL of deionized water, add 2 drops of HNO3, 1 mL of silver nitrate solution, and observe in the dark, which should have no chlorine ion reaction; wherever reagent preparation, dilution water, etc. are involved in this method, the water referred to is this kind of water.

[0076] This example determines the chlorine content with NCM series as the test sample, which specifically includes the following steps:

[0077] (I) Preparation of working curve: applicable to Cl amount of 0.0050%~0.010%

[0078] 1. Pipette 0, 0.50, 1.00, 2.00, 3.00, 4.00 mL of chlorine standard solution (10 μg / mL) into a set of 100 mL volumetric flasks, add 3 mL of 1:1 nitric acid, dilute to 30 mL with water, mix. Add 2 mL of acetone, mix, add 2 mL of silver nitrate solution, dilute to the mark with water, mix. Place the flasks in a water bath at 70°C for 8 min, remove, cool to room temperature under running water, transfer to a dark room for 10 min, mix.

[0079] 2. Pipette a portion of the developed solution (3 mL) into a 3 cm cuvette, measure its absorbance at 440 nm on a spectrophotometer. Plot the working curve as shown in Fig. 1. Figure 1

[0080] (B) Distillation and testing of samples

[0081] 3. Distillation of sample: After the temperature of the pre-distilled sulfuric acid in the distillation flask drops to 50°C, weigh 1.00 g of the ternary precursor battery material sample into the distillation flask, connect the distillation apparatus for distillation. Heat the solution in the distillation flask to adjust the water vapor flow and heating power to control the temperature at 100°C. After 40 min of liquid reception, remove the receiving flask, and transfer the solution in the receiving flask to a 100 mL volumetric flask, dilute to the mark with water, shake well, and reserve for use. A blank sample is also prepared.

[0082] Pre-distillation purification of sulfuric acid: Place 150 mL of water in the distillation flask of the water vapor distillation apparatus, heat to boiling, and reserve for use. Take 15 mL of water and place it in a 200 mL receiving flask as the absorption liquid, and reserve for use. Add 100 mL of sulfuric acid to the distillation flask, rinse the mouth of the flask with water, and add zeolite, connect the distillation apparatus. Heat the solution in the distillation flask to adjust the water vapor flow and heating power to maintain the temperature at 180°C. After 30 min of distillation, stop heating and discard the receiving liquid.

[0083] 4. Pipette a portion of the solution into a 100 mL glass volumetric flask.

[0084] 5. Add water to a volume of about 30 mL, 3 mL of nitric acid, mix, add 2 mL of acetone, mix, add 2 mL of silver nitrate solution, dilute to the mark with water, mix. Place the flask in a water bath at 70°C (±1°C) for 8 min, remove, cool to room temperature under running water, transfer to a dark room for 10 min, mix.

[0085] 6. Pipette a portion of the solution (3 mL) into a 3 cm cuvette, with the blank solution of the test material as the reference, measure its absorbance at 440 nm on a spectrophotometer, and calculate the mass of chlorine from the corresponding working curve. ​

[0086] The test was repeated 11 times according to the same process, and the results calculated according to formula (1) are shown in Table 1. It was determined that the content of chlorine in the measured sample was 0.0064wt.%.

[0087] Example 2:

[0088] This example is basically the same as Example 1, except that:

[0089] This example uses NCA series as a sample for chlorine content determination

[0090] The reagents used are as follows:

[0091] Nitric acid (p = 1.42 g / mL);

[0092] 1:1 nitric acid is a mixture of nitric acid (p = 1.42 g / mL) and water in a volume ratio of 1:1;

[0093] Sulfuric acid (p = 1.84 g / mL);

[0094] Acetone;

[0095] Silver nitrate solution (10 g / L);

[0096] Chlorine standard solution (50 μg / ml);

[0097] Water is twice distilled water and above purity, at least twice distilled water, and the water is chlorine ion free water: take 50 mL of deionized water, add 2 drops of HNO3, 1 mL of silver nitrate solution, observe in the dark, there should be no chlorine ion reaction; This method refers to the water used for reagent preparation, dilution, etc.

[0098] Specifically includes the following steps:

[0099] (I) Preparation of working curve: applicable to Cl amount of >0.010 % ~ 0.20 %

[0100] 1. Transfer 0 mL, 0.20 mL, 0.60 mL, 0.80 mL, 1.00 mL, 1.20 mL, 1.60 mL of chlorine standard solution (50 μg / ml) to a group of 100 mL volumetric flasks, add 3 mL of 1:1 nitric acid, dilute with water to 30 mL, mix well. Add 2 mL of acetone, mix well, add 2 mL of silver nitrate solution, dilute with water to the mark, mix well. Place the volumetric flask in a water bath at 70°C for 8 min, take it out, cool to room temperature with running water, transfer to a dark room for 10 min, mix well.

[0101] 2. Move part of the color developing solution (2 mL) into a 1 cm cuvette, and measure its absorbance at 440 nm on the spectrophotometer. Plot the working curve as shown in Figure 1, with the mass of chlorine as the abscissa and the absorbance as the ordinate. Figure 2

[0102] (II) Distillation and testing of the sample

[0103] 3. Sample distillation: After the temperature of the pre-distilled sulfuric acid in the distillation flask drops to 25°C, weigh 0.50 g of the ternary precursor battery material sample into the distillation flask, and connect the distillation device for distillation. Heat the solution in the distillation flask to adjust the water vapor flow and heating power, and control the temperature at 200°C. After 10 min of liquid reception, remove the receiving flask, and transfer the solution in the receiving flask to a 100 mL volumetric flask, dilute to the calibration mark with water, shake well, and reserve for use. A blank sample is also prepared.

[0104] Sulfuric acid pre-distillation purification: Place 150 mL of water in the distillation flask of the water vapor distillation device, and heat to boiling. Take 15 mL of water and place it in a 200 mL receiving flask as the absorption liquid. Add 100 mL of sulfuric acid to the distillation flask, rinse the mouth of the flask with water, and add zeolite, and connect the distillation device. Heat the solution in the distillation flask, adjust the water vapor flow and heating power, and maintain the temperature at 180°C. After 30 min of distillation, stop heating, and discard the receiving liquid.

[0105] 4. Move part of the solution to a 100 mL glass volumetric flask.

[0106] 5. Add water to a volume of about 30 mL, 3 mL of nitric acid, mix well, add 2 mL of acetone, mix well, add 2 mL of silver nitrate solution, dilute to the calibration mark with water, mix well, and place the volumetric flask in a water bath at 70°C (±1°C) for heating for 8 min. Remove, cool to room temperature under running water, and move to a dark room for 10 min, mix well.

[0107] 6. Move part of the solution (2 mL) into a 1 cm cuvette, and measure its absorbance at 440 nm on the spectrophotometer with the blank solution of the sample as the reference. Calculate the mass of chlorine from the corresponding working curve.

[0108] The test is repeated 11 times according to the same process, and the results are calculated according to formula (1) and shown in Table 1. It is determined that the content of chlorine in the measured sample is 0.0160 wt.%.

[0109] ​The above chemical reaction mainly decomposes the sample by sulfuric acid. The chlorine in the sample is separated from the sample by escaping with water vapor and is absorbed by water. The mass concentration of chlorine ions is determined by spectrophotometry. Silver nitrate is added to form a suspension, and the absorbance is measured at 440 nm. The absorbance is proportional to the chlorine content within a certain concentration range.

[0110] Table 1 Precision test results

[0111]

[0112] As can be seen from the results in Table 1, the RSD of the chlorine content is 2.93% to 3.70%, indicating that the method has good precision and can meet the analysis requirements.

[0113] Table 2 Standard addition recovery test

[0114]

[0115] As can be seen from the results in Table 2, the standard addition recovery rate of the chlorine content in the ternary precursor battery material measured according to the experimental method is 95.4% to 101.2%, which has high accuracy and can meet the analysis requirements.

Claims

1. An analytical method for determining the chlorine content in ternary precursor battery materials, using the silver chloride turbidimetric spectrophotometric method, comprising the following steps: (1) Sample distillation: When the temperature of the pre-distilled sulfuric acid is reduced to 25℃-70℃, weigh the ternary precursor battery material sample and add it to the distillation flask. Connect the distillation apparatus for distillation. Heat the solution in the distillation flask to raise the temperature. Adjust the steam flow rate and heating power to control the temperature at 100℃~200℃. After receiving the liquid, remove the receiving flask and transfer the solution in the receiving flask to a volumetric flask. Dilute with water to the mark, shake well, and set aside. Prepare blank samples at the same time. (2) Transfer a portion of the solution into a glass volumetric flask; (3) Add water to a certain volume, add nitric acid, mix well, then add acetone, mix well, and finally add silver nitrate solution, dilute with water to the mark, mix well; place the volumetric flask in a water bath and heat, remove it, cool it to room temperature with running water, place it in a dark room and mix well. (4) Transfer a portion of the solution into a cuvette, and use the blank solution of the sample as a reference. Measure its absorbance at a wavelength of 410~460 nm using a spectrophotometer, and calculate the mass of chlorine from the corresponding working curve.

2. The method for analyzing and testing the chlorine content in ternary precursor battery materials according to claim 1, characterized in that: The mass-to-volume ratio of the ternary precursor battery material sample to the total volume of the test solution diluted to the mark with water is 0.05 g: 100 ml to 1.00 g: 100 ml.

3. The method for analyzing and testing the chlorine content in ternary precursor battery materials according to claim 1, characterized in that: The contact time is 10-40 minutes.

4. The method for analyzing and testing the chlorine content in ternary precursor battery materials according to claim 1, characterized in that: A method for pre-distilling and purifying sulfuric acid includes the following steps: 150-300 parts by volume of water are placed in a distillation flask of a steam distillation apparatus and heated to boiling; 5-20 parts by volume of water are placed in a receiving flask containing 50-200 parts by volume as the absorption liquid; 20-100 parts by volume of sulfuric acid are added to the distillation flask, the mouth of the flask is rinsed with water, boiling chips are added, and the distillation apparatus is connected; the solution in the distillation flask is heated, the steam flow rate and heating power are adjusted to maintain the temperature at 100℃~200℃, and heating is stopped after distillation for 10 min-40 min, and the receiving liquid is discarded.

5. The method for analyzing and testing the chlorine content in ternary precursor battery materials according to claim 1, characterized in that: After diluting with water to the mark, the amount of nitric acid added is 1 vol.%-5 vol.%, the amount of acetone added is 1 vol.%-5 vol.%, and the amount of silver nitrate solution added is 1 vol.%-5 vol.%. The temperature in the water bath is 70℃±1℃, and the time is 5 min-15 min. Then, it is placed in a dark room for 5 min-15 min.

6. The method for analyzing and testing the chlorine content in ternary precursor battery materials according to claim 5, characterized in that: The nitric acid is concentrated nitric acid with a mass fraction of 65%-70%, and the silver nitrate solution has a mass concentration of 5 g / L-15 g / L.

7. The method for analyzing and testing the chlorine content in ternary precursor battery materials according to claim 1, characterized in that: The cuvette has a diameter of 1-3 cm, and the volume of the solution transferred into it is 1 mL-3 mL.

8. The method for analyzing and testing the chlorine content in ternary precursor battery materials according to claim 1, characterized in that: The method for plotting the working curve includes the following steps: (a) Applicable to Cl concentrations of 0.005 wt.% ~ 0.010 wt.% (1) Transfer 0, 0.50, 1.00, 2.00, 3.00, and 4.00 mL of chlorine standard solution into a set of 100 mL volumetric flasks, add 1:1 nitric acid, dilute with water to a certain volume, and mix well; then add acetone, mix well, and finally add silver nitrate solution, dilute with water to the mark, and mix well; place the volumetric flasks in a water bath for heating, remove them, cool them to room temperature under running water, place them in a dark room, and mix well; the concentration of the chlorine standard solution is 10 μg / mL; (2) Transfer a portion of the colorimetric solution into a cuvette and measure its absorbance at a wavelength of 430 nm using a spectrophotometer; plot the working curve with the mass of chlorine as the abscissa and the absorbance as the ordinate. (ii) Applicable to Cl concentrations greater than 0.010 wt.% and less than or equal to 0.20 wt.%. (1) Transfer 0 mL, 0.20 mL, 0.60 mL, 0.80 mL, 1.00 mL, 1.20 mL, and 1.60 mL of chlorine standard solution into a set of 100 mL volumetric flasks, add 1:1 nitric acid, dilute with water to a certain volume, and mix well; then add acetone, mix well, and finally add silver nitrate solution, dilute with water to the mark, and mix well; place the volumetric flasks in a water bath for heating, remove them, cool them to room temperature under running water, place them in a dark room, and mix well; the concentration of the chlorine standard solution is 50 μg / mL; (2) Transfer a portion of the colorimetric solution into a cuvette and measure its absorbance at a wavelength of 410~460 nm using a spectrophotometer; plot the working curve with the mass of chlorine as the abscissa and the absorbance as the ordinate.

9. The method for analyzing and testing the chlorine content in ternary precursor battery materials according to claim 8, characterized in that: After diluting with water to the mark, the amount of nitric acid added is 1 vol.%-5 vol.%, the amount of acetone added is 1 vol.%-5 vol.%, and the amount of silver nitrate solution added is 1 vol.%-5 vol.%; the mass concentration of the silver nitrate solution is 5 g / L-15 g / L; the heating temperature in the water bath is 70℃±1℃, and the time is 5 min-15 min; then it is placed in a dark room for 5 min-15 min.

10. The method for analyzing and testing the chlorine content in ternary precursor battery materials according to claim 1, characterized in that: The mass fraction of chlorine in the analytical results is expressed as w, and the value is expressed as % according to formula (1): •••••••• (1) In the formula: m1 — The mass of chlorine calculated from the working curve, in micrograms; V0 — Total volume of the test solution, in milliliters; m0 — Mass of the sample, in grams; V1 — Volume of test solution taken, in milliliters.

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