Method for determining chlorine content in ternary precursor

Abstract

The invention provides a method for determining chlorine content in a ternary precursor, which comprises the following steps: mixing a ternary precursor sample with an alcohol solvent to obtain a dispersion liquid, mixing the dispersion liquid with a buffer solution, and carrying out extraction treatment to obtain an extract liquid; heating the extract liquid, filtering to obtain a filtrate, mixing the filtrate with a citrate solution, and carrying out constant volume treatment to obtain a to-be-detected sample solution; and testing the to-be-tested sample solution by using an ion analyzer and adopting a standard curve method, and calculating the chlorine content in the ternary precursor. The method provided by the invention solves the problems of incomplete chloride ion extraction, serious metal ion interference, complex pretreatment, poor detection stability and the like in the existing method, realizes efficient, accurate and stable detection of the chlorine content, improves the operation safety, and is suitable for industrial detection requirements.

Description

Technical Field

[0001] This invention belongs to the field of chlorine content detection technology, and relates to a method for determining the chlorine content in ternary precursors. Background Technology

[0002] With the booming development of new energy vehicles and the energy storage industry, lithium-ion batteries, as core power and energy storage devices, face increasingly stringent performance and safety requirements. Ternary precursors, as the core raw materials for ternary lithium-ion battery cathode materials (NCM or NCA), have impurity elements whose type and content directly affect the battery's cycle performance, safety, and energy density. Chloride ions, a common impurity in lithium-ion battery cathode materials, can easily lead to material corrosion, electrolyte decomposition, and battery gas accumulation due to excessive residual chloride ions. This results in battery capacity decay and increased internal resistance, significantly negatively impacting the battery's electrochemical performance (such as cycle life, rate performance, and safety). Therefore, accurate detection of chloride content in ternary precursors is crucial for ensuring the quality and safety of lithium-ion battery materials.

[0003] Existing methods for detecting chlorine content in ternary precursors, such as ultrapure water leaching, can only detect chlorine on the surface of the ternary precursor and cannot detect chlorine inside the material, resulting in inaccurate test data.

[0004] CN120253720A discloses an analytical method for the chlorine content in ternary precursor battery materials. While the silver chloride turbidimetric-spectrophotometric method employed is highly sensitive and low-cost, it requires a complex distillation apparatus, is dangerous to operate, and suffers from incomplete extraction due to the volatility of chloride ions or their complexation with metal ions. Furthermore, the pretreatment process is time-consuming (up to 3 hours) and is susceptible to turbidity accuracy issues caused by the volatilization of metal ions and acetone. Although the nitric acid-hydrogen peroxide digestion method has high digestion efficiency, the use of strong oxidants in a closed container poses safety hazards, and the method's optimization range is limited to a chlorine mass percentage of 0.01% to 1%, resulting in insufficient detection accuracy in low concentration ranges.

[0005] CN117110387A discloses a method for determining water-soluble chloride ions in soil using an ion-selective electrode method. This method employs sodium nitrate TISAB to adjust the ion intensity, effectively stabilizing the ion intensity of the detection system and avoiding the influence of ion concentration fluctuations in the soil matrix on the electrode response. Potassium persulfate and copper sulfate are used as interference-removing reagents to achieve the determination of Br⁻, I⁻, CN⁻ and other anions, as well as S⁻. 2- The removal of chlorine optimizes the interference suppression effect of the soil system. However, its pretreatment method and interference suppression system are not suitable for ternary precursor materials. The surface coating of ternary precursors is complex, and directly using the soil treatment method will result in low chlorine extraction rate and severe metal ion interference, which cannot meet the requirements of high-precision detection.

[0006] The above-mentioned methods have problems such as high operational risks, poor detection accuracy, or poor anti-interference effect, which seriously affect the detection results. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the present invention aims to provide a method for determining the chlorine content in ternary precursors. This invention utilizes an alcohol solvent as a wetting agent, ultrasonic-assisted extraction coupled with an EDTA-ascorbic acid-citrate ternary buffer system to effectively mask Ni. 2+ / Co 2+ / Mn 2+ Plasma interference is eliminated by adjusting the solution pH and ionic strength, which solves the problems of incomplete chloride ion extraction, severe metal ion interference, complex pretreatment, and poor detection stability in existing methods. This enables efficient, accurate, and stable detection of chloride content, improves operational safety, and is suitable for industrial detection needs.

[0008] To achieve this objective, the present invention adopts the following technical solution:

[0009] This invention provides a method for determining the chlorine content in a ternary precursor, the method comprising the following steps:

[0010] The ternary precursor sample was mixed with an alcohol solvent to obtain a dispersion, and the dispersion was mixed with a buffer solution for extraction to obtain an extract.

[0011] The extract was heated and then filtered to obtain the filtrate. The filtrate was mixed with citrate solution and then diluted to a final volume to obtain the sample solution to be tested.

[0012] The sample solution was tested using an ion analyzer with a standard curve method, according to the formula... Calculate the mass percentage of chloride ions in the ternary precursor sample, where W is the mass percentage of chloride ions in the ternary precursor sample, C is the concentration read by the instrument in mmol / L, V is the fixed volume of the sample in L, and m is the mass of the ternary precursor sample in g.

[0013] The solutes in the buffer solution include ethylenediaminetetraacetic acid (EDTA), acetic acid, acetate, and ascorbic acid.

[0014] The acetic acid and acetate in the buffer solution described in this invention exist in the form of a buffer pair, which serves as a buffer.

[0015] In the formula described in this invention, 35.5 is the molar mass of chlorine, expressed in g / mol.

[0016] This invention uses alcohol solvents as wetting agents. Alcohol solvents can disrupt hydrogen bond networks, enhancing material wettability. Utilizing the low surface tension of alcohol solvents, they penetrate into the surface micropores of the ternary precursor sample, disrupting the hydrophobic coating layer and creating efficient mass transfer channels for subsequent extraction. Samples wetted with alcohol solvents undergo extraction and peeling of the ternary precursor coating layer, releasing chloride ions from the intercrystalline lattice. The EDTA-ascorbic acid-citrate ternary buffer system can strongly chelate Ni. 2+ / Co 2+ / Mn 2+ Plasma (complexation constant > 10) 16 This blocks the competitive adsorption of chloride ions. Acetic acid-acetate buffer solution maintains a weakly acidic to neutral environment, inhibiting chloride ion volatilization. The reducing component of ascorbic acid inhibits the oxidation of metal ions and eliminates high-valence ions (such as Mn). 3+ The oxidation and corrosion of the electrode film (breaking the interference of metal ions) and the steric hindrance of citrate inhibit adsorption, thus achieving efficient complexation, reduction and steric shielding at the same time.

[0017] Preferably, the mass of the ternary precursor sample is 0.1g to 1g, for example: 0.1g, 0.2g, 0.5g, 0.8g or 1g, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0018] Preferably, the alcohol solvent includes ethanol.

[0019] Preferably, the mass-to-volume ratio of the ternary precursor sample to the alcohol solvent is 1g:(0.5~3)mL, for example: 1g:0.5mL, 1g:0.8mL, 1g:1mL, 1g:2mL or 1g:3mL, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0020] Preferably, the ternary precursor sample is mixed with an alcohol solvent and then subjected to vortex oscillation.

[0021] Preferably, the vortex oscillation time is 0.5 min to 5 min, for example: 0.5 min, 1 min, 2 min, 3 min, 4 min or 5 min, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0022] Preferably, the molar concentration of ethylenediaminetetraacetic acid salt in the buffer solution is 0.05 mol / L to 1 mol / L, for example: 0.05 mol / L, 0.1 mol / L, 0.2 mol / L, 0.5 mol / L or 1 mol / L, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0023] Preferably, the ethylenediaminetetraacetic acid salt includes disodium ethylenediaminetetraacetic acid.

[0024] Preferably, the volume fraction of acetic acid in the buffer solution is 0.5% to 1%, for example: 0.5%, 0.6%, 0.7%, 0.8%, 0.9% or 1%, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0025] Preferably, the mass concentration of acetate in the buffer solution is 5 g / L to 30 g / L, for example: 5 g / L, 8 g / L, 10 g / L, 20 g / L or 30 g / L, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0026] Preferably, the acetate comprises sodium acetate.

[0027] Preferably, the molar concentration of ascorbic acid in the buffer solution is 0.01 mol / L to 1 mol / L, for example: 0.01 mol / L, 0.05 mol / L, 0.1 mol / L, 0.5 mol / L or 1 mol / L, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0028] Preferably, the volume ratio of the dispersion to the buffer solution is (0.5~3):(10~80), for example: 0.5:10, 1:20, 2:50, 2.5:60 or 3:80, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0029] Preferably, the extraction process involves ultrasonic bath treatment.

[0030] This invention utilizes the mutual reinforcement of physical stress generated by vortex oscillation and ultrasonic cavitation effect to ensure the complete release of chloride ions, avoiding the problem of incomplete extraction caused by traditional methods and thus improving the extraction rate.

[0031] Preferably, the power of the water bath ultrasound is 200W~400W, for example: 200W, 250W, 300W, 350W or 400W, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0032] Preferably, the extraction temperature is 40℃~60℃, for example: 40℃, 45℃, 50℃, 55℃ or 60℃, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0033] Preferably, the extraction time is 3 min to 10 min, for example: 3 min, 5 min, 6 min, 8 min or 10 min, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0034] Preferably, the heating rate of the heating treatment is 3℃ / min to 8℃ / min, for example: 3℃ / min, 5℃ / min, 6℃ / min, 7℃ / min or 8℃ / min, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0035] Preferably, the temperature of the heat treatment is 70℃~80℃, for example: 70℃, 72℃, 75℃, 78℃ or 80℃, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0036] Preferably, the heat treatment holding time is 15 min to 30 min, for example: 15 min, 18 min, 20 min, 25 min or 30 min, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0037] Preferably, the filter paper used for filtration has a pore size of 3μm to 30μm, such as 3μm, 5μm, 10μm, 20μm or 30μm, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0038] Preferably, the molar concentration of the citrate solution is 0.05 mol / L to 1 mol / L, for example: 0.05 mol / L, 0.1 mol / L, 0.5 mol / L, 0.8 mol / L or 1 mol / L, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0039] Preferably, the citrate comprises sodium citrate.

[0040] Preferably, the volume ratio of the filtrate to the citrate solution is (2~4):1, for example: 2:1, 2.5:1, 3:1, 3.5:1 or 4:1, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0041] Preferably, the volume of the volume adjustment process is 50mL to 200mL, for example: 50mL, 80mL, 100mL, 150mL or 200mL, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0042] The use of an ion analyzer to test the sample solution using the standard curve method includes:

[0043] Prepare chloride standard solutions with gradient concentrations, perform multi-point slope calibration on the ion analyzer, place the sample solution to be tested on the calibrated ion analyzer, and use the standard electrode method to test the chloride ion concentration in the prepared sample.

[0044] Preferably, the concentration of chloride ions in the chloride standard solution is 0.01 mmol / L to 10 mmol / L, for example: 0.01 mmol / L, 0.05 mmol / L, 0.1 mmol / L, 0.2 mmol / L, 0.5 mmol / L, 1 mmol / L, 2 mmol / L, 5 mmol / L, 8 mmol / L or 10 mmol / L, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0045] Preferably, the chloride standard solution also includes citrate.

[0046] Preferably, the concentration of citrate in the chloride standard solution is the same as the concentration of citrate in the sample solution to be tested.

[0047] Preferably, the determination coefficient R of the multi-point slope calibration 2 ≥0.999.

[0048] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0049] Compared with the prior art, the present invention has the following beneficial effects:

[0050] (1) This invention introduces alcohol solvents as wetting agents and uses an EDTA-ascorbic acid-citrate ternary buffer system in conjunction with ultrasonic-assisted extraction to effectively mask Ni. 2+ / Co 2+ / Mn 2+ Plasma interference is eliminated by adjusting the solution pH and ionic strength, which solves the problems of incomplete chloride ion extraction, severe metal ion interference, complex pretreatment, and poor detection stability in existing methods. This enables efficient, accurate, and stable detection of chloride content, improves operational safety, and is suitable for industrial detection needs.

[0051] (2) This invention employs an EDTA-ascorbic acid-citrate complex buffer system. EDTA complexes metal ions, and ascorbic acid reduces Mn. 3+Citrate acts as an ionic strength modifier, preventing the adsorption or oxidation of metal ions on the electrode surface through steric hindrance. Its dual shielding effect reduces interference from coexisting ions, controls pH, inhibits chlorine volatilization, and avoids metal ion precipitation. This shortens single-sample processing time, reduces equipment investment costs, and improves detection efficiency, making it suitable for batch analysis on production lines.

[0052] (3) Through the verification of implementation examples, the method of the present invention has high precision and accuracy in the analysis of chlorine content in ternary precursors, with an extraction rate of over 99.3%. The ternary buffer system can withstand interference from high concentrations of metal ions. Moreover, the total time is significantly reduced compared to the prior art, the equipment cost is low, and the efficiency is improved by 40%-60% compared to the existing methods. It is suitable for batch testing in production lines, and achieves the technical effect of efficient chlorine content testing, with a total time of less than 1.5 hours, a detection accuracy of >98%, and stable detection of chlorine content in ternary precursors. It improves operational safety and meets the needs of industrial testing. Attached Figure Description

[0053] Figure 1 This is a schematic diagram of the process flow for determining the chlorine content in a ternary precursor according to an embodiment of the present invention. Detailed Implementation

[0054] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0055] The "range" disclosed in this invention can be defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of the specific range. This type of range definition can include or exclude endpoints; any endpoint can be independently included or excluded, and they can be arbitrarily combined, meaning any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60~120 and 80~110 are listed for specific parameters, it is understood that ranges of 60~110 and 80~120 are also expected. Furthermore, if minimum range values ​​1 and 2 are listed, and maximum range values ​​3, 4, and 5 are also listed, then the following ranges are all expected: 1~3, 1~4, 1~5, 2~3, 2~4, and 2~5. In this invention, unless otherwise stated, the numerical range "a~b" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0~5" indicates that all real numbers between "0" and "5" have been listed in this article; "0~5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is described as an integer ≥2, it is equivalent to listing integers such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc. For instance, when a parameter is described as an integer selected from "2~10", it is equivalent to listing the integers 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0056] In this invention, "a combination of at least two" refers to a quantity greater than or equal to two, unless otherwise specified. For example, "any combination of one or at least two" means one or more or more items. It can be understood that when referring to "a combination of at least two," it refers to any suitable combination of multiple items, that is, a combination of "at least two" items carried out in a manner that does not conflict with and enables the implementation of this invention.

[0057] Unless otherwise specified, all embodiments and optional embodiments of the present invention can be combined with each other to form new technical solutions.

[0058] The term "embodiment" as used in this invention means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment or implementation of the invention. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a mutually exclusive, independent, or alternative embodiment. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described in this invention can be combined with other embodiments.

[0059] Those skilled in the art will understand that the order in which the steps are written in the methods of the various embodiments does not imply a strict execution order. The detailed execution order of each step should be determined by its function and possible internal logic. Unless otherwise specified, all steps of the present invention may be performed sequentially or randomly, but are preferably performed sequentially. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the method may also include step (c), meaning that step (c) can be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0060] In this invention, open-ended technical features or solutions described using terms such as "comprising" do not exclude additional members beyond those listed unless otherwise specified. They can be considered as providing both closed-ended features or solutions comprised of the listed members and open-ended features or solutions that include additional members beyond the listed members. For example, A includes a1, a2, and a3. Unless otherwise specified, it may also include other members or exclude additional members. This can be considered as providing both technical features or solutions where "A is composed of a1, a2, and a3" or "A is selected from a1, a2, and a3," and technical features or solutions where "A includes not only a1, a2, and a3, but also other members."

[0061] In this invention, unless otherwise specified, the features or solutions corresponding to "and / or" include any one of two or more of the related listed items, as well as any and all combinations of the related listed items. These arbitrary and all combinations include any two related listed items, any more related listed items, or a combination of all related listed items. For example, "A and / or B" represents a group consisting of A, B, and "a combination of A and B". "Containing A and / or B" can mean "containing A, containing B, and containing A and B", or "containing A, containing B, or containing A and B", and can be appropriately understood according to the context.

[0062] In this invention, the terms "first aspect," "second aspect," "third aspect," "fourth aspect," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or quantity, nor should they be construed as implicitly indicating the importance or quantity of the indicated technical features. Moreover, "first," "second," "third," "fourth," etc., serve only as a non-exhaustive enumeration and should be understood not to constitute a closed limitation on the quantity.

[0063] In this invention, "optional" means that something is optional, that is, it refers to any one of the two parallel solutions of "having" or "not having". If there are multiple "optional" options in a technical solution, unless otherwise specified, and there are no contradictions or mutual constraints, then each "optional" option is independent.

[0064] In this invention, "room temperature" generally refers to 4℃~35℃, and can refer to 20℃±5℃. In some embodiments of this invention, room temperature refers to 20℃~30℃.

[0065] The known chlorine mass percentage content in the NCM613 sample used in the embodiments and comparative examples of this invention is 0.0085%, and the known chlorine mass percentage content in the NCA sample is 0.0152%.

[0066] Example 1

[0067] This embodiment provides a method for determining the chlorine content in a ternary precursor, the method comprising the following steps:

[0068] Weigh 0.5g of NCM613 sample and place it in a glass beaker. Add 0.5mL of ethanol and vortex for 1min until the sample is completely dispersed to obtain a dispersion. Add 30mL of buffer solution to the glass beaker. The buffer solution contains 0.8% acetic acid, 20g / L sodium acetate, 0.2mol / L EDTA-2Na, and 0.05mol / L ascorbic acid. After sealing, place the beaker in a 50℃ water bath and sonicate at 300W power and 40kHz frequency for 5min to obtain an extract.

[0069] The extract was heated to 80℃ at a rate of 5℃ / min and held at that temperature for 20min to destroy the core-shell structure of the material and release the embedded chloride ions. After cooling to room temperature, it was filtered through medium-speed quantitative filter paper (pore size 8μm) and 30mL of filtrate was collected. 10mL of sodium citrate solution with a molar concentration of 0.05mol / L was added to the filtrate and the volume was adjusted to 100mL to obtain the sample solution to be tested.

[0070] Sodium chloride standard solutions with chloride ion concentrations of 0.01 mmol / L, 0.1 mmol / L, 1 mmol / L, and 10 mmol / L were prepared, each containing sodium citrate. The molar concentration of sodium citrate in the sodium chloride standard solutions was the same as that in the sample solutions. Multi-point slope calibration of the ion analyzer was performed using the sodium chloride standard solutions. The coefficient of determination R for multi-point slope calibration was... 2 The value was 0.9995. The sample solution was placed on an ion analyzer with a calibrated slope. The chloride ion concentration in the sample was measured in six parallel experiments using the standard electrode method. The concentration was then calculated according to the formula. The chlorine content is calculated, where W is the mass percentage of chloride ions in the ternary precursor sample, C is the concentration read by the instrument in mmol / L, V is the final volume of the sample in L, and m is the mass of the ternary precursor sample in g.

[0071] Example 2

[0072] This embodiment provides a method for determining the chlorine content in a ternary precursor, the method comprising the following steps:

[0073] Weigh 0.5g of NCA sample and place it in a glass beaker. Add 1.5mL of ethanol and vortex for 0.5min until the sample is completely dispersed to obtain a dispersion. Add 30mL of buffer solution to the glass beaker. The buffer solution contains 0.5% acetic acid, 5g / L sodium acetate, 0.05mol / L EDTA-2Na, and 0.01mol / L ascorbic acid. After sealing, place the beaker in a 60℃ water bath and sonicate at 200W power and 40kHz frequency for 3min to obtain an extract.

[0074] The extract was heated to 70°C at a rate of 3°C / min and held at that temperature for 30 min to destroy the core-shell structure of the material and release the embedded chloride ions. After cooling to room temperature, it was filtered through medium-speed quantitative filter paper (pore size 3μm) and 40 mL of filtrate was collected. 10 mL of sodium citrate solution with a molar concentration of 1 mol / L was added to the filtrate and the volume was adjusted to 100 mL to obtain the sample solution to be tested.

[0075] Sodium chloride standard solutions with chloride ion concentrations of 0.01 mmol / L, 0.1 mmol / L, 1 mmol / L, and 10 mmol / L were prepared, each containing sodium citrate. The molar concentration of sodium citrate in the sodium chloride standard solutions was the same as that in the sample solutions. Multi-point slope calibration of the ion analyzer was performed using the sodium chloride standard solutions. The coefficient of determination R for multi-point slope calibration was... 2 The value was 0.9995. The sample solution was placed on an ion analyzer with a calibrated slope. The chloride ion concentration in the sample was measured in six parallel experiments using the standard electrode method. The concentration was then calculated according to the formula. The chlorine content is calculated, where W is the mass percentage of chloride ions in the ternary precursor sample, C is the concentration read by the instrument in mmol / L, V is the final volume of the sample in L, and m is the mass of the ternary precursor sample in g.

[0076] Example 3

[0077] This embodiment provides a method for determining the chlorine content in a ternary precursor, the method comprising the following steps:

[0078] Weigh 0.5g of NCM613 sample and place it in a glass beaker. Add 0.25mL of ethanol and vortex for 5min until the sample is completely dispersed to obtain a dispersion. Add 20mL of buffer solution to the glass beaker. The buffer solution contains 1% acetic acid, 30g / L sodium acetate, 1mol / L EDTA-2Na, and 1mol / L ascorbic acid. After sealing, place the beaker in a 40℃ water bath and sonicate at 400W power and 40kHz frequency for 10min to obtain an extract.

[0079] The extract was heated to 80℃ at a rate of 8℃ / min and held at that temperature for 15min to destroy the core-shell structure of the material and release the embedded chloride ions. After cooling to room temperature, it was filtered through medium-speed quantitative filter paper (pore size 30μm) and 20mL of filtrate was collected. 10mL of sodium citrate solution with a molar concentration of 0.1mol / L was added to the filtrate and the volume was adjusted to 100mL to obtain the sample solution to be tested.

[0080] Sodium chloride standard solutions with chloride ion concentrations of 0.01 mmol / L, 0.1 mmol / L, 1 mmol / L, and 10 mmol / L were prepared, each containing sodium citrate. The molar concentration of sodium citrate in the sodium chloride standard solutions was the same as that in the sample solutions. Multi-point slope calibration of the ion analyzer was performed using the sodium chloride standard solutions. The coefficient of determination R for multi-point slope calibration was... 2 The value was 0.9995. The sample solution was placed on an ion analyzer with a calibrated slope. The chloride ion concentration in the sample was measured in six parallel experiments using the standard electrode method. The concentration was then calculated according to the formula. The chlorine content is calculated, where W is the mass percentage of chloride ions in the ternary precursor sample, C is the concentration read by the instrument in mmol / L, V is the final volume of the sample in L, and m is the mass of the ternary precursor sample in g.

[0081] Example 4

[0082] The only difference between this embodiment and Example 1 is that interfering ions (Ni) are added to the dispersion. 2+ =500 mg / L, Co 2+ =100mg / L, Mn 2+ =100mg / L), other conditions and parameters are exactly the same as in Example 1.

[0083] Example 5

[0084] The only difference between this embodiment and Example 1 is that interfering ions (Ni) are added to the dispersion. 2+ =1000mg / L, Co 2+ =200mg / L, Mn 2+=200mg / L), other conditions and parameters are exactly the same as in Example 1.

[0085] Example 6

[0086] The only difference between this embodiment and Example 1 is that the molar concentration of EDTA-2Na in the buffer solution is 0.01 mol / L. All other conditions and parameters are exactly the same as in Example 1.

[0087] Example 7

[0088] The only difference between this embodiment and Example 1 is that the molar concentration of EDTA-2Na in the buffer solution is 2 mol / L. All other conditions and parameters are exactly the same as in Example 1.

[0089] Example 8

[0090] The only difference between this embodiment and Example 1 is that the molar concentration of ascorbic acid in the buffer solution is 0.001 mol / L. All other conditions and parameters are exactly the same as in Example 1.

[0091] Example 9

[0092] The only difference between this embodiment and Example 1 is that the molar concentration of ascorbic acid in the buffer solution is 2 mol / L, while the other conditions and parameters are exactly the same as in Example 1.

[0093] Example 10

[0094] The only difference between this embodiment and Example 1 is that the molar concentration of the sodium citrate solution is 0.01 mol / L; all other conditions and parameters are exactly the same as in Example 1.

[0095] Example 11

[0096] The only difference between this embodiment and Example 1 is that the molar concentration of the sodium citrate solution is 2 mol / L; all other conditions and parameters are exactly the same as in Example 1.

[0097] Comparative Example 1

[0098] The only difference between this comparative example and Example 2 is that ethanol is replaced with pure water; all other conditions and parameters are exactly the same as in Example 1.

[0099] Comparative Example 2

[0100] The only difference between this comparative example and Example 1 is that the buffer solution does not contain ascorbic acid; all other conditions and parameters are exactly the same as in Example 1.

[0101] Comparative Example 3

[0102] The only difference between this comparative example and Example 1 is that the buffer solution does not contain EDTA-2Na; all other conditions and parameters are exactly the same as in Example 1.

[0103] Comparative Example 4

[0104] The only difference between this comparative example and Example 1 is that sodium citrate solution is not added; all other conditions and parameters are exactly the same as in Example 1.

[0105] Comparative Example 5

[0106] The only difference between this comparative example and Example 2 is that the silver chloride turbidimetric-spectrophotometric method described in CN120253720A was used to detect the chlorine content in the dispersion. All other conditions and parameters are exactly the same as in Example 2.

[0107] Comparative Example 6

[0108] The only difference between this comparative example and Example 2 is that the chlorine-hydrogen peroxide digestion method described in CN120213838A was used to detect the chlorine content in the dispersion. All other conditions and parameters are exactly the same as in Example 2.

[0109] Comparative Example 7

[0110] The only difference between this comparative example and Example 2 is that the soil ion-selective electrode method described in CN117110387A was used to detect the chlorine content in the dispersion. All other conditions and parameters are exactly the same as in Example 2.

[0111] Performance testing:

[0112] (1) The detection results of Examples 1-11 and Comparative Examples 1-4 are shown in Table 1, where the extraction rate = measured chlorine content / actual chlorine content of the sample × 100%

[0113] Table 1

[0114]

[0115] Spiking recovery experiments were conducted on samples from Examples 1-11 and Comparative Examples 1-4. The spiking amount was based on the sample background value, and three levels of spiking were performed: low (0.002), medium (0.008), and high (0.015). The recovery rates are shown in Table 2.

[0116] Table 2

[0117]

[0118] As shown in Tables 1-2, and as demonstrated in Examples 1-11, the method described in this invention, within the parameter range specified in this invention, exhibits high extraction rate (92.9%~100%) and high accuracy (RSD≤3.56%) for the determination of chlorine content in ternary precursors. By adjusting the test parameters and conditions, the chlorine extraction rate can reach 98.8%-100%, and within the preferred parameter range, the recovery rate is 97.9%-103.2%, indicating that the method has wide applicability, stability, and good anti-interference ability, meeting the needs of industrial detection.

[0119] A comparison of Examples 1 and 4-5 shows that, in the method for determining the chlorine content in the ternary precursor described in this invention, even with the addition of high concentrations of nickel, cobalt, and manganese ions, the relative standard deviation of the test is still ≤ ±2.31%, proving that the synergistic effect of EDTA chelation + ascorbic acid reduction + sodium citrate steric hindrance can effectively block metal ion interference and solve the problem of severe interference from transition metal ions in existing methods.

[0120] A comparison of Examples 1 and 6-7 shows that, in the method for determining the chlorine content in ternary precursors described in this invention, the molar concentration of EDTA salt in the buffer solution affects the detection effect. Controlling the molar concentration of EDTA salt in the buffer solution between 0.05 mol / L and 1 mol / L yields better detection results. If the molar concentration of EDTA salt in the buffer solution is too high, it may lead to excessive ionic strength in the solution, affecting the electrode response sensitivity and thus slightly reducing the extraction rate. If the molar concentration of EDTA salt in the buffer solution is too low, the chelating ability is insufficient, failing to effectively mask metal ion interference, resulting in a decrease in extraction rate and accuracy.

[0121] A comparison of Examples 1 and 8-9 shows that, in the method for determining the chloride content in a ternary precursor described in this invention, the molar concentration of ascorbic acid in the buffer solution affects the detection effect. Controlling the molar concentration of ascorbic acid in the buffer solution between 0.01 mol / L and 1 mol / L yields better detection results. If the molar concentration of ascorbic acid in the buffer solution is too high, excessive reducing substances may be introduced, altering the redox potential of the solution, affecting electrode stability, and leading to a decrease in extraction rate. If the molar concentration of ascorbic acid in the buffer solution is too low, the reducing power is insufficient, and it cannot effectively inhibit high-valence metal ions (such as Mn). 3+ Oxidation interference from ) leads to a decrease in extraction rate and recovery rate.

[0122] A comparison of Examples 1 and 10-11 shows that in the method for determining the chloride content in the ternary precursor described in this invention, the molar concentration of the sodium citrate solution affects the detection effect. Controlling the molar concentration of the sodium citrate solution between 0.01 mol / L and 1 mol / L yields better detection results. If the molar concentration of the sodium citrate solution is too high, the electrode response to chloride ions may be shielded due to excessively high ionic strength, reducing detection sensitivity and leading to a decrease in extraction rate. If the molar concentration of the sodium citrate solution is too low, the ionic strength adjustment is insufficient, the adsorption inhibition effect is weakened, resulting in a significant decrease in extraction rate and poor stability.

[0123] Comparing Example 1 and Comparative Examples 1-4, it can be seen that the present invention uses alcohol solvents as wetting agents. Alcohol solvents can disrupt hydrogen bond networks, enhancing material wettability. Utilizing the low surface tension of alcohol solvents, they penetrate into the surface micropores of the ternary precursor sample, disrupting the hydrophobic coating layer and creating efficient mass transfer channels for subsequent extraction. Samples wetted with alcohol solvents undergo extraction and peeling of the ternary precursor coating layer, releasing chloride ions from the intercrystalline lattice. The EDTA-ascorbic acid-citrate ternary buffer system can strongly chelate Ni. 2+ / Co 2+ / Mn 2+ Plasma (complexation constant > 10) 16 This blocks the competitive adsorption of chloride ions. Acetic acid-acetate buffer solution maintains a weakly acidic to neutral environment, inhibiting chloride ion volatilization. The reducing component of ascorbic acid inhibits the oxidation of metal ions and eliminates high-valence ions (such as Mn). 3+ The oxidation and corrosion of the electrode film (breaking the interference of metal ions) and the steric hindrance of citrate inhibit adsorption, thus achieving efficient complexation, reduction and steric shielding at the same time.

[0124] The key test indicators of Example 2 and Comparative Examples 5-7 were analyzed (the test standard for RSD here is n=3, i.e., 3 parallel tests), and the analysis results are shown in Table 3:

[0125] Table 3

[0126]

[0127] As shown in Table 3, the total time of the method described in this invention is only 1.5h, which is much shorter than CN120253720A (3.5h) and CN120213838A (2.5h); the RSD (0.85%) is significantly better than the existing methods (1.7%-5.8%); the applicable range covers 0.0050%-0.30%, and the equipment cost is low, which fully meets the industrial demand for "rapid and accurate detection of large-scale samples".

[0128] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method of determining the chlorine content in a ternary precursor, characterized in that, The method comprises the following steps: The ternary precursor sample is mixed with an alcohol solvent to obtain a dispersion liquid, and the dispersion liquid is mixed with a buffer solution for leaching treatment to obtain a leaching liquid; After the leaching liquid is subjected to heating treatment and filtration, a filtrate is obtained, and the filtrate is mixed with a citrate solution, and then subjected to constant volume treatment to obtain a to-be-tested sample solution; The ion analyzer is used to test the sample solution by using the standard curve method, and the mass percentage content of the chloride ion in the ternary precursor sample is calculated according to the formula The mass percentage content of the chloride ion in the ternary precursor sample is calculated, W is the mass percentage content of the chloride ion in the ternary precursor sample, C is the concentration read by the instrument, V is the constant volume of the sample, and m is the mass of the ternary precursor sample. The solute of the buffer solution comprises ethylenediaminetetraacetate, acetic acid, acetate and ascorbic acid.

2. The method of claim 1, wherein, The mass of the ternary precursor sample is 0.1g-1g; Preferably, the alcohol solvent comprises ethanol; Preferably, the mass-volume ratio of the ternary precursor sample to the alcohol solvent is 1g:(0.5-3)mL.

3. The method of claim 1 or 2, wherein, The ternary precursor sample is mixed with an alcohol solvent and then subjected to vortex oscillation; Preferably, the vortex oscillation time is 0.5min-5min.

4. The method according to any one of claims 1 to 3, characterized in that, The molar concentration of ethylenediaminetetraacetate in the buffer solution is 0.05mol / L-1mol / L; Preferably, the volume fraction of acetic acid in the buffer solution is 0.5%-1%; Preferably, the mass concentration of acetate in the buffer solution is 5g / L-30g / L; Preferably, the molar concentration of ascorbic acid in the buffer solution is 0.01mol / L-1mol / L; Preferably, the volume ratio of the dispersion liquid to the buffer solution is (0.5-3):(10-80).

5. The method according to any one of claims 1 to 4, wherein Water bath ultrasonic treatment is performed during the leaching treatment; Preferably, the power of the water bath ultrasonic treatment is 200W-400W; Preferably, the leaching treatment temperature is 40℃-60℃; Preferably, the leaching treatment time is 3min-10min.

6. The method according to any one of claims 1 to 5, wherein, The heating treatment has a temperature rising speed of 3℃ / min-8℃ / min; Preferably, the heating treatment temperature is 70℃-80℃; Preferably, the heating treatment has a holding time of 15min-30min.

7. The method according to any one of claims 1 to 6, wherein The filter paper used for the filtration has a pore size of 3um-30um.

8. The method according to any one of claims 1 to 7, wherein, The molar concentration of the citrate solution is 0.05mol / L-1mol / L; Preferably, the volume ratio of the filtrate to the citrate solution is (2-4):1; Preferably, the constant volume treatment has a volume of 50mL-200mL.

9. The method according to any one of claims 1 to 8, wherein, The use of the ion analyzer to test the to-be-tested sample solution by the standard curve method comprises: A gradient concentration chloride standard solution is prepared, the ion analyzer is subjected to multi-point slope calibration, the to-be-tested sample solution is placed on the ion analyzer with calibrated slope, and the standard electrode method is used to test the chloride ion concentration in the prepared to-be-tested sample.

10. The method of claim 9, wherein, The concentration of chloride ions in the chloride standard solution is 0.01mmol / L-10mmol / L; Preferably, the chloride standard solution further comprises citrate; Preferably, the concentration of citrate in the chloride standard solution is the same as that of citrate in the to-be-tested sample solution; Preferably, the determination coefficient R of the multi-point slope calibration is 2 ≥ 0.999.

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