Measurement method for nickel, iron, copper and manganese in battery material

Abstract

The present invention relates to the technical field of analytical chemistry, and in particular to a measurement method for nickel, iron, copper and manganese in a battery material, comprising: first measuring the content of a manganese element, the content of an iron element, the content of a copper element, and the total amount of nickel, iron, copper and manganese elements, respectively, and then calculating the content of the nickel element on the basis of the total amount of nickel, iron, copper and manganese and the contents of the manganese element, the iron element and the copper element. During measurement of the content of the manganese element in the battery material, sodium pyrophosphate is used as a masking agent, such that Fe3+ can be masked while disproportionation of Mn3+ is inhibited, thereby achieving a double-masking effect, and ensuring the measurement accuracy of the manganese content. Therefore, the objective of accurately measuring the contents of four elements, i.e., nickel, iron, copper and manganese, in the battery material is achieved. In the measurement method, no expensive measurement device is required, and a constant analysis means is used; and by efficiently using the masking agent, the interference of coexistence elements on a specific element measurement method is effectively avoided, thereby achieving a stable and reliable measurement result.

Description

A method for detecting nickel, iron, copper and manganese in battery materials Technical Field

[0001] The present disclosure belongs to the technical field of analytical chemistry, and in particular relates to a method for detecting nickel, iron, copper and manganese in battery materials. Background Art

[0002] Nickel-iron-copper-manganese quaternary materials for sodium batteries offer advantages such as high specific capacity, a wide discharge voltage range, stable electrochemical performance, and good safety. Compared to nickel-cobalt-manganese ternary materials, they offer a higher cost-performance ratio and therefore hold broad market prospects. Accurately determining the nickel, iron, copper, and manganese contents in the nickel-iron-copper-manganese quaternary precursor is key to preparing the nickel-iron-copper-manganese quaternary material or its precursor.

[0003] Currently, the nickel, cobalt, and manganese content in ternary materials or precursors is typically determined using a combination of instrumental analysis, such as inductively coupled plasma atomic emission spectroscopy (ICP-AES) or atomic absorption spectroscopy (AAS), and chemical analysis. Quaternary precursors for sodium batteries also employ these methods, but these instrumental analyses are typically designed for trace elements, while the analysis of major elements can fluctuate significantly, affecting the accuracy of the test results. Furthermore, the instruments are expensive to purchase and require high operator skills, making them difficult to popularize.

[0004] Current technology is unable to accurately determine the nickel, iron, copper, and manganese content in sodium battery quaternary precursors through chemical analysis. Experimental studies have found that cross-interference exists among the four elements using chemical analysis, making accurate quantification difficult. For example, the complexometric titration conditions for iron, nickel, copper, and manganese are inconsistent, making it difficult to accurately titrate the combined amount of the four elements. Furthermore, there are no good masking agents or demasking agents that allow for step-by-step titration of the four elements. Currently, there is a gap in the field of methods for detecting the main content of nickel, iron, copper, and manganese quaternary materials for sodium batteries.

[0005] Therefore, there is an urgent need to develop a method that can accurately determine the nickel, iron, copper and manganese content in the quaternary precursors of sodium batteries.

[0006] In view of this, the present disclosure is proposed.

[0007] Summary of the Invention

[0008] The purpose of the present disclosure includes providing a method for detecting nickel, iron, copper and manganese in battery materials, aiming to accurately determine the content of the four elements nickel, iron, copper and manganese in battery materials.

[0009] In order to achieve the above-mentioned purpose of the present disclosure, the following technical solutions can be adopted:

[0010] The solution provided by the present disclosure includes a method for detecting nickel, iron, copper and manganese in battery materials, comprising:

[0011] The manganese content in battery materials was tested by redox potential titration using sodium pyrophosphate as a masking agent.

[0012] The iron content, copper content and the total amount of nickel, iron, copper and manganese elements were tested respectively;

[0013] The nickel content is calculated based on the total amount of nickel, iron, copper and manganese and the content of manganese, iron and copper.

[0014] In some embodiments of the present disclosure, the process of testing the manganese content includes: mixing and dissolving the battery material with an inorganic acid, and then diluting with water to obtain a battery material test solution; mixing the battery material test solution with excess hydrogen peroxide, heating the solution to remove excess hydrogen peroxide, and then mixing the solution with saturated sodium pyrophosphate, and titrating the solution with a standard potassium permanganate solution;

[0015] The manganese content in battery materials is obtained by the following calculation formula:

[0016] Where, is the molar concentration of potassium permanganate standard solution, in mol / L;

[0017] V KMnO4 is the titration volume of potassium permanganate standard solution, in mL;

[0018] m is the sample mass of the battery material, in g;

[0019] V is the volume of battery material solution pipetted during titration, in mL;

[0020] f is the ratio of the fixed volume to the volume of the sample removed.

[0021] In some embodiments of the present disclosure, the amount of saturated sodium pyrophosphate is calculated based on the theoretical total content of manganese and iron elements in the battery material test solution removed, and the molar ratio of the theoretical total content of manganese and iron elements to saturated sodium pyrophosphate is 1: (20-40).

[0022] In some embodiments of the present disclosure, before titration with potassium permanganate, the pH value of the solution is adjusted to 6.6-6.9, and the concentration of the potassium permanganate standard solution used in the titration is 0.01 mol / L-0.03 mol / L.

[0023] In some embodiments of the present disclosure, the inorganic acid is hydrochloric acid. After the battery material and the hydrochloric acid are mixed and dissolved, the volume is fixed with water to obtain a battery material test solution, wherein the battery material concentration in the battery material test solution is 5g / L-15g / L.

[0024] In some embodiments of the present disclosure, when preparing a solution of battery material to be tested, the battery material is first moistened with water, then mixed with hydrochloric acid and heated to dissolve.

[0025] In some embodiments of the present disclosure, the battery material is a nickel-iron-copper-manganese quaternary precursor or a sodium-electrolyte nickel-iron-copper-manganese quaternary positive electrode material.

[0026] In some embodiments of the present disclosure, the iodine titration method is used to test the contents of iron and copper respectively.

[0027] In some embodiments of the present disclosure, the process of testing the iron and copper content includes: taking two sets of battery material test solutions, labeled as sample A and sample B, wherein the battery material test solutions are prepared by mixing and dissolving the battery material with hydrochloric acid and then diluting the volume with water;

[0028] Treating sample A and sample B and reacting them with iodide to prepare titrable solution A and titrable solution B containing elemental iodine, wherein sodium fluoride is added as a masking agent during the preparation of titrable solution A;

[0029] Titrate solution A and solution B with sodium thiosulfate standard solution, wherein solution A and solution B consume volumes of sodium thiosulfate standard solution V1 and V3 respectively.

[0030] The content of iron and copper elements in battery materials is obtained by the following calculation formula:

[0031] Where, is the molar concentration of sodium thiosulfate standard solution, in mol / L;

[0032] V1 and V3 are the titration volumes of sodium thiosulfate standard solution, in mL;

[0033] m is the mass of the quaternary precursor, in g;

[0034] V2 is the pipetted volume of the quaternary precursor solution, in mL;

[0035] f is the ratio of the fixed volume to the volume of the sample removed.

[0036] In some embodiments of the present disclosure, the process of preparing solution A to be titrated and solution B to be titrated includes: mixing two groups of samples, sample A and sample B, with excess hydrogen peroxide for reaction, and then heating to remove excess hydrogen peroxide; mixing the two samples after the heating treatment with an ammonia solution until a brick-red precipitate appears, and then mixing with a hydrochloric acid solution until the precipitate dissolves, and adjusting the pH value to 0.8-1.2;

[0037] The pH-adjusted sample A is mixed with sodium fluoride, and then the two groups of samples are mixed with hydrochloric acid solution to adjust the pH value to less than 0.8, and then mixed with potassium iodide respectively for reaction, and the titration solution A and the titration solution B are obtained after constant volume.

[0038] In some embodiments of the present disclosure, during the preparation of solution A to be titrated and solution B to be titrated, the amount of sodium fluoride to be added is calculated based on the theoretical amount of iron in the sample, and the molar ratio of the amount of sodium fluoride to the theoretical amount of iron in the sample is controlled to be (20-50):1.

[0039] In some embodiments of the present disclosure, during the preparation of solution A to be titrated and solution B to be titrated, the amount of potassium iodide to be added is calculated based on the theoretical total amount of iron and copper elements in the sample, and the molar ratio of the amount of potassium iodide to the theoretical total amount of iron and copper elements in the sample is controlled to be (10-20):1.

[0040] In some embodiments of the present disclosure, after mixing with potassium iodide, the mixture is isolated from air and placed in a dark place to react for 5 minutes to 20 minutes.

[0041] In some embodiments of the present disclosure, in the process of preparing the solution A to be titrated and the solution B to be titrated, the mass fraction of the ammonia solution used is 12%-24%.

[0042] In some embodiments of the present disclosure, in the process of preparing the solution A to be titrated and the solution B to be titrated, the mass fraction of the hydrochloric acid solution used is 15%-20%.

[0043] In some embodiments of the present disclosure, the process of titrating solution A to be titrated and solution B to be titrated using a sodium thiosulfate standard solution includes: pipetting solution A to be titrated and solution B to be titrated, titrating with a sodium thiosulfate standard solution until they turn light yellow, then mixing with a starch solution, and continuing to titrate with a sodium thiosulfate standard solution until the sample changes from blue to a milky white turbid liquid, and recording the volume of the sodium thiosulfate standard solution consumed.

[0044] In some embodiments of the present disclosure, the concentration of the starch solution is 5 g / L-15 g / L.

[0045] In some embodiments of the present disclosure, the concentration of the sodium thiosulfate standard solution is 0.05 mol / L-0.15 mol / L.

[0046] In some embodiments of the present disclosure, the total amount of nickel, iron, copper, and manganese in the battery material is tested by a complexometric titration-back titration method.

[0047] In some embodiments of the present disclosure, the method includes taking a battery material test solution and an equal volume of water and labeling them as sample C and sample D; wherein the battery material test solution is obtained by mixing and dissolving the battery material with hydrochloric acid and then diluting the volume with water;

[0048] Samples C and D were mixed with hydroxylamine hydrochloride solution, and then mixed with EDTA standard solution and buffer solution with a pH value of 5.5-5.7. Xylenol orange reagent was added thereto and titrated with Zn standard solution. The end point was when the color of the sample changed from yellow to purple-red. The volume of Zn standard solution consumed was recorded. The total amount of the four elements nickel, iron, copper and manganese in the battery material was obtained by the following calculation formula:

[0049] Where n is the total amount of nickel, iron, copper and manganese;

[0050] C Zn is the molar concentration of Zn standard solution, in mol / L;

[0051] V0 is the volume of Zn standard solution consumed by the blank solution, in mL;

[0052] V1 is the volume of Zn standard solution consumed by the test solution, in mL;

[0053] V2 is the volume of the solution to be tested, in mL;

[0054] f is the ratio of the fixed volume to the volume of the sample removed.

[0055] In some embodiments of the present disclosure, the concentration of the hydroxylamine hydrochloride solution is 95 g / L-105 g / L, the volume of the hydroxylamine hydrochloride solution is calculated based on the total molar amount of iron and manganese, and the theoretical molar ratio of the amount of hydroxylamine hydrochloride to the iron and manganese elements in the sample is controlled to be (5-10):1.

[0056] In some embodiments of the present disclosure, the concentration of the EDTA standard solution is 0.01 mol / L-0.10 mol / L, and the volume of the EDTA standard solution added is calculated based on the theoretical total amount of nickel, iron, copper and manganese in the battery material test solution removed, so that the molar ratio of the molar amount of EDTA added to the theoretical total amount of nickel, iron, copper and manganese is (1.5-2.0):1.

[0057] In some embodiments of the present disclosure, the buffer solution is selected from any one of acetic acid-ammonium acetate buffer and hexamethyleneimine buffer.

[0058] In some embodiments of the present disclosure, the concentration of the Zn standard solution is 0.02 mol / L-0.03 mol / L.

[0059] In some embodiments of the present disclosure, the nickel content is obtained by the following calculation formula: Wt%(Ni)={n / m-{Wt%(Fe) / 55.845+Wt%(Mn) / 54.938+Wt%(Cu) / 63.55}*58.69;

[0060] Where n is the total amount of nickel, iron, copper and manganese in the battery material;

[0061] Wt%(Ni), Wt%(Fe), Wt%(Cu), and Wt%(Mn) are the percentage contents of nickel, iron, copper, and manganese in the quaternary precursor, respectively, in %.

[0062] m is the mass of the quaternary precursor, in g.

[0063] The present invention uses sodium pyrophosphate as a masking agent when testing the manganese content in battery materials to suppress the 3+ disproportionation reaction and can also mask Fe 3+ , achieving a double masking effect, ensuring the accuracy of manganese content testing; then, the iron content, copper content, and the total amount of nickel, iron, copper, and manganese are tested separately. The nickel content is calculated based on the total amount of nickel, iron, copper, and manganese and the contents of manganese, iron, and copper, achieving the goal of accurately detecting the contents of nickel, iron, copper, and manganese in battery materials. This detection method does not require the use of expensive testing equipment and is a conventional analysis method. Through the clever use of masking agents, it effectively avoids interference of coexisting elements on the specific element testing method, and the test results are stable and reliable. BRIEF DESCRIPTION OF THE DRAWINGS

[0064] In order to more clearly illustrate the technical solutions of the embodiments of the present disclosure, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present disclosure and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without creative work.

[0065] FIG1 is a flow chart of the detection of nickel, iron, copper and manganese in battery materials provided by an embodiment of the present disclosure. DETAILED DESCRIPTION

[0066] The embodiments of the present disclosure will be described in detail below with reference to the examples. However, those skilled in the art will appreciate that the following examples are intended only to illustrate the present disclosure and should not be construed as limiting the scope of the present disclosure. Where specific conditions are not specified in the examples, the experiments were performed under conventional conditions or the conditions recommended by the manufacturer. Where the manufacturer of the reagents or instruments is not specified, all are commercially available conventional products.

[0067] The endpoints of the ranges and any values ​​disclosed in this disclosure are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be considered to be specifically disclosed herein.

[0068] The solution provided in the embodiments of the present disclosure includes a method for detecting nickel, iron, copper and manganese in battery materials. The detection method provided in the embodiments of the present disclosure can accurately detect the content of the four elements nickel, iron, copper and manganese in battery materials, filling the gap in the main content testing method of sodium battery quaternary precursors.

[0069] The detection method provided in the embodiments of the present disclosure is for battery materials, which can be a nickel-iron-copper-manganese quaternary precursor or a sodium-electrolyte nickel-iron-copper-manganese quaternary cathode material. Before testing the content of each element, the battery material is first dissolved and the volume is constant to obtain a battery material solution to be tested.

[0070] In some embodiments of the present disclosure, the preparation process of the battery material test solution is as follows: after the battery material and the inorganic acid are mixed and dissolved, the solution is diluted with water to a fixed volume and set aside. The inorganic acid can be concentrated hydrochloric acid. If other inorganic acids are used, the valence state of the iron ion may be affected, affecting the accuracy of the detection. In actual operation, the battery material can also be first moistened with water and then mixed with concentrated hydrochloric acid and heated to dissolve. The battery material concentration in the battery material test solution is a solution of 5g / L-15g / L, such as 5g / L, 10g / L, 15g / L, etc.

[0071] As shown in Figure 1, after preparing the battery material test solution, perform the following steps:

[0072] S1. Test the content of manganese

[0073] The manganese content in the battery material is tested by redox potential titration using sodium pyrophosphate as a masking agent. The titration can be performed using the commonly used potassium permanganate standard solution titration method.

[0074] It should be noted that in conventional potentiometric titration, there is no iron ion in the solution, so the test process is relatively simple. Sodium electrolyte materials (such as sodium electrolyte quaternary precursors) contain iron. When testing manganese content, whether it is Fe 2+ Or Fe 3+ All of these will have a significant impact on the test process and affect the accuracy of the results. 3+ Masking agents such as fluoride and citrate are not suitable for the detection method provided by the present disclosure. Fluoride and Fe 3+ A large amount of precipitation will be produced; citrate will react with Fe3+ Produces a yellow complex and can react with Mn 2+ Forming a stable complex, commonly used Fe 3+ Masking agents have a certain impact on the test process. Sodium pyrophosphate has a certain impact on Fe 3+ It has strong complexing ability, sodium pyrophosphate and Fe 3+ It can generate colorless soluble complex and can react with Mn 3+ Form a stable complex and inhibit the titration product Mn 3+ Thus, the method provided by the present disclosure is to firstly disproportionate Fe 2+ Completely oxidized to Fe 3+ , using sodium pyrophosphate to inhibit Mn 3+ disproportionation reaction and can also mask Fe 3+ , with a double masking effect, ensuring the accuracy of manganese content testing.

[0075] In some embodiments of the present disclosure, the process of testing the manganese content includes: mixing the battery material solution to be tested with excess hydrogen peroxide to react, and reducing the Fe 2+ All oxidized to Fe 3+ The sample is then heated to remove excess hydrogen peroxide, mixed with saturated sodium pyrophosphate, and titrated using a standard potassium permanganate solution. The manganese content in the battery material is calculated using the following formula:

[0076] Where, is the molar concentration of potassium permanganate standard solution, in mol / L;

[0077] V KMnO4 is the titration volume of potassium permanganate standard solution, in mL;

[0078] m is the sample mass of the battery material, in g;

[0079] V is the volume of battery material solution pipetted during titration, in mL;

[0080] f is the ratio of the fixed volume to the volume of the sample removed;

[0081] 4 is the ratio of the number of electron transfers in the reaction between potassium permanganate and divalent manganese;

[0082] 54.938 is the relative atomic mass of the element Mn.

[0083] Specifically, the hydrogen peroxide can be commercially available analytical grade hydrogen peroxide with a mass fraction of 26.5%.

[0084] In some embodiments of the present disclosure, before titrating with potassium permanganate, the pH of the solution is adjusted to 6.6-6.9. Titration is performed under weakly acidic conditions to achieve higher test accuracy. The concentration of the potassium permanganate standard solution used in the titration is 0.01mol / L-0.03mol / L, such as 0.01mol / L, 0.02mol / L, 0.03mol / L, etc.

[0085] Furthermore, the amount of saturated sodium pyrophosphate is calculated based on the theoretical total content of manganese and iron in the battery material test solution. The molar ratio of the theoretical total content of manganese and iron to saturated sodium pyrophosphate is 1:(20-40). The amount of saturated sodium pyrophosphate is preferably controlled within the above range. Too little amount will not provide a good masking effect. Specifically, the molar ratio of the theoretical total content of manganese and iron to saturated sodium pyrophosphate can be 1:20, 1:25, 1:30, 1:35, 1:40, etc.

[0086] S2. Test the content of iron and copper elements

[0087] The iron and copper contents are tested separately. Existing analytical methods can be used to detect the contents of iron and copper, such as iodine titration.

[0088] In some embodiments of the present disclosure, the process of testing the content of iron and copper elements includes: taking two groups of battery material test solutions, marked as sample A and sample B, treating sample A and sample B and reacting them with iodide to prepare titrable solution A and titrable solution B containing elemental iodine, wherein sodium fluoride is added as a masking agent during the preparation of solution A to be titrated; using sodium thiosulfate standard solution to titrate solution A and solution B to be titrated, the volume of sodium thiosulfate standard solution consumed by solution A to be titrated and solution B to be titrated are V1 and V3 respectively; the content of iron and copper elements in the battery material is obtained by the following calculation formula:

[0089] Where, is the molar concentration of sodium thiosulfate standard solution, in mol / L;

[0090] V1 and V3 are the titration volumes of sodium thiosulfate standard solutions, in mL;

[0091] m is the mass of the quaternary precursor, in g;

[0092] V2 is the pipetted volume of the quaternary precursor solution, in mL;

[0093] f is the ratio of the fixed volume to the volume of the sample removed;

[0094] 63.55 and 55.845 are the relative atomic masses of Cu and Fe respectively.

[0095] Specifically, the elemental iodine content in solution A to be titrated and solution B to be titrated is titrated using a standard sodium thiosulfate solution. Sodium fluoride is added as a masking agent during the preparation of solution A to be titrated to mask iron ions. V1 is the amount of elemental iodine obtained after the reaction of copper ions, and V3 is the amount of elemental iodine obtained after the reaction of the total amount of copper and iron. Therefore, V3 minus V1 is the amount of elemental iodine obtained after the reaction of iron ions.

[0096] It should be noted that the conventional iodine titration method for copper and iron is to use step-by-step titration, first adding ammonium bifluoride to Fe 3+ Mask, then add aluminum chloride to Fe 3+ After the release, Fe 3+ This method has serious color interference, as follows: (1) During the titration of copper, a large amount of white precipitate Cu(SCN)2 is generated, and the excess potassium thiocyanate can react with Fe 3+ The generated blood-red complex seriously interferes with the next test; (2) the added aluminum chloride reacts with Fe[F6] 3- The formation of aluminum fluoride precipitates also seriously interferes with color determination in subsequent tests, making accuracy unreliable. The disclosed method first uses sodium fluoride to mask iron before testing copper, then resamples and titrates the combined amount of copper and iron. This eliminates any color interference during the test, further improving detection accuracy.

[0097] In some embodiments of the present disclosure, the process of preparing solution A to be titrated and solution B to be titrated includes: mixing two groups of samples, sample A and sample B, with excess hydrogen peroxide, respectively, and then heating them to completely decompose the excess hydrogen peroxide to achieve the purpose of removing the excess hydrogen peroxide; taking the two samples after the heat treatment and mixing them with an ammonia solution, controlling the amount of ammonia to just form a brick-red precipitate in the system to better remove the hydrogen peroxide, and then mixing them with a hydrochloric acid solution until the precipitate dissolves, adjusting the pH to 0.8-1.2, so that the precipitate dissolves and facilitates titration. The pH-adjusted sample A is mixed with sodium fluoride (sample B is not added), and then the two groups of samples are mixed with a hydrochloric acid solution to adjust the pH to less than 0.8, and then they are mixed and reacted with potassium iodide, and the volumes are fixed to obtain solution A to be titrated and solution B to be titrated.

[0098] In some embodiments of the present disclosure, during the preparation of solution A and solution B to be titrated, the amount of sodium fluoride to be added is calculated based on the theoretical amount of iron in the sample, and the molar ratio of the amount of sodium fluoride to the theoretical amount of iron in the sample is controlled to be (20-50):1 to fully mask the iron ions. Specifically, the molar ratio of the amount of sodium fluoride to the theoretical amount of iron in the sample can be 20:1, 30:1, 40:1, 50:1, etc.

[0099] In some embodiments of the present disclosure, during the preparation of titrable solution A and titrable solution B, the amount of potassium iodide to be added is calculated based on the theoretical total amount of iron and copper in the sample, and the molar ratio of potassium iodide to the theoretical total amount of iron and copper in the sample is controlled to be (10-20):1 to ensure sufficient reaction of the iron and copper. Specifically, the molar ratio of potassium iodide to the theoretical total amount of iron and copper in the sample can be 10:1, 15:1, 20:1, etc.

[0100] Furthermore, after mixing with potassium iodide, the mixture is isolated from air and placed in a dark place to react for 5-20 minutes to prevent the influence of light and oxygen on the reaction. Specifically, the reaction time in the dark can be 5 minutes, 10 minutes, 15 minutes, 20 minutes, etc.

[0101] In some embodiments of the present disclosure, in the process of preparing solution A to be titrated and solution B to be titrated, the mass fraction of the ammonia solution used is 12%-24%, which can be obtained by mixing commercially available concentrated ammonia water and water in a volume ratio of 1:1, that is, a (1+1) ammonia solution.

[0102] In some embodiments of the present disclosure, in the process of preparing the solution A to be titrated and the solution B to be titrated, the mass fraction of the hydrochloric acid solution used is 15%-20%, and commercially available concentrated hydrochloric acid (about 36% by mass) can be mixed with water in a volume ratio of 1:1, that is, a (1+1) hydrochloric acid solution.

[0103] Furthermore, the process of titrating solution A to be titrated and solution B to be titrated using sodium thiosulfate standard solution includes: pipetting solution A to be titrated and solution B to be titrated, titrating with sodium thiosulfate standard solution until they turn light yellow, then mixing with starch solution, and continuing to titrate with sodium thiosulfate standard solution until the sample changes from blue to a milky white turbid liquid, and recording the volume of sodium thiosulfate standard solution consumed. First, most of the iodine is titrated with sodium thiosulfate standard solution, where iodine is a strong oxidizing agent and sodium thiosulfate is a reducing agent, and the two react quantitatively; after most of the iodine is reacted, starch solution is added, the solution turns blue, and titration is continued with sodium thiosulfate standard solution until the color gradually weakens until the blue disappears, which is the volume of sodium thiosulfate standard solution consumed.

[0104] In some embodiments of the present disclosure, the concentration of the starch solution is 5 g / L-15 g / L. The addition of starch does not need to be quantitative, and 3 to 4 drops are generally sufficient. Excessive starch will wrap the iodine element, resulting in a low test result.

[0105] In some embodiments of the present disclosure, the concentration of the sodium thiosulfate standard solution is 0.05 mol / L-0.15 mol / L. Within this concentration range, the amount of sodium thiosulfate used can be better controlled, thereby improving detection accuracy. Specifically, the concentration of the sodium thiosulfate standard solution can be 0.05 mol / L, 0.10 mol / L, 0.15 mol / L, etc.

[0106] S3, testing the total amount of nickel, iron, copper and manganese elements;

[0107] The total amount of nickel, iron, copper and manganese in the battery material is tested by the complexometric titration-back titration method, that is, the four metal elements are combined with EDTA, and then the total amount of nickel, iron, copper and manganese is tested by titration with Zn standard solution.

[0108] In some embodiments of the present disclosure, the process of testing the total amount of four elements, nickel, iron, copper, and manganese, includes: taking a battery material solution to be tested and the same volume of water as sample C and sample D (i.e., a blank control sample), mixing sample C and sample D with a hydroxylamine hydrochloride solution, and then mixing with an EDTA standard solution and a buffer solution with a pH value of 5.5-5.7, adding a xylenol orange reagent thereto, and titrating with a Zn standard solution. The end point is when the sample changes from yellow to purple-red, and the volume of the consumed Zn standard solution is recorded. The total amount of the four elements, nickel, iron, copper, and manganese, in the battery material is obtained by the following calculation formula:

[0109] Where n is the total amount of nickel, iron, copper and manganese;

[0110] C Zn is the molar concentration of Zn standard solution, in mol / L;

[0111] V0 is the volume of Zn standard solution consumed by the blank solution, in mL;

[0112] V1 is the volume of Zn standard solution consumed by the test solution, in mL;

[0113] V2 is the volume of the solution to be tested, in mL;

[0114] f is the ratio of the fixed volume to the volume of the sample removed.

[0115] Specifically, sample D does not contain any metal elements and is a blank control. The volume difference of the Zn standard solution consumed by the two samples is the corresponding consumption of the four metal elements of nickel, iron, copper and manganese.

[0116] It should be noted that since trivalent iron can be hydrolyzed to form a precipitate under pH 1-2, and the titration of metal ions is usually carried out under alkaline conditions, Fe 3+Fe(OH)3 precipitation will be generated, which will interfere with the test. If the back titration method is used, Fe 2+ The EDTA complex itself is colored, interfering with endpoint color determination. Introducing hydroxylamine hydrochloride can avoid this and allow the titration to proceed sequentially. Hydroxylamine hydrochloride acts as a reducing agent, reducing ferric iron to ferrous iron while preventing the conversion of divalent manganese to trivalent and tetravalent manganese, stabilizing the valence of the metal elements at divalent. By controlling the titration pH to around 5, the four metal ions will not hydrolyze, effectively solving the problem of total element testing.

[0117] Furthermore, the concentration of the hydroxylamine hydrochloride solution is 95g / L-105g / L. The volume of the hydroxylamine hydrochloride solution is calculated based on the total molar amount of iron and manganese, and the theoretical molar ratio of the hydroxylamine hydrochloride to the iron and manganese elements in the sample is controlled to be (5-10):1. By controlling the amount of hydroxylamine hydrochloride added, the metal elements are better stabilized at a divalent state, thereby improving the accuracy of the titration. Specifically, the molar ratio of the hydroxylamine hydrochloride to the theoretical iron and manganese elements in the sample can be 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, etc.

[0118] Furthermore, the concentration of the EDTA standard solution is 0.01 mol / L-0.10 mol / L, and the volume of the EDTA standard solution added is calculated based on the theoretical total amount of nickel, iron, copper, and manganese in the battery material test solution removed, so that the molar ratio of the molar amount of EDTA added to the theoretical total amount of nickel, iron, copper, and manganese is (1.5-2.0):1, so that the four metal elements and EDTA are fully combined. Specifically, the molar ratio of the molar amount of EDTA added to the theoretical total amount of nickel, iron, copper, and manganese can be 1.5:1, 1.6:1, 1.7:1, 1.8:1, 1.9:1, 2.0:1, etc.

[0119] Furthermore, the buffer solution is selected from any one of acetic acid-ammonium acetate buffer and hexamethyleneimine buffer, and both of the above buffer solutions can meet the pH value requirements.

[0120] Furthermore, the concentration of the Zn standard solution is 0.02mol / L-0.03mol / L. A smaller concentration of the Zn standard solution is preferred to better control the amount of instillation and improve the accuracy of the titration. Specifically, the concentration of the Zn standard solution can be 0.020mol / L, 0.025mol / L, 0.030mol / L, etc.

[0121] S4. Calculate nickel content

[0122] The nickel content is calculated based on the total amount of nickel, iron, copper and manganese and the contents of manganese, iron and copper. The nickel content is calculated by subtracting the contents of manganese, iron and copper from the total amount of nickel, iron, copper and manganese.

[0123] In some embodiments of the present disclosure, since the contents of manganese, iron, and copper are expressed as mass fractions, the nickel content can be calculated using the following formula: Wt%(Ni)={n / m-{Wt%(Fe) / 55.845+Wt%(Mn) / 54.938+Wt%(Cu) / 63.55}*58.69 (Formula 5);

[0124] Where n is the total amount of nickel, iron, copper and manganese in the battery material;

[0125] Wt%(Ni), Wt%(Fe), Wt%(Cu), and Wt%(Mn) are the percentage contents of nickel, iron, copper, and manganese in the quaternary precursor, respectively, in %.

[0126] m is the mass of the quaternary precursor, in g;

[0127] 58.69, 55.845, 63.55 and 54.938 are the relative atomic masses of nickel, iron, copper and manganese respectively.

[0128] The features and performance of the present disclosure are further described in detail below with reference to the embodiments.

[0129] The test object of the following embodiments is a sodium quaternary precursor. Theoretically, 1 gram of the sodium quaternary precursor contains 1.0 mmol of Cu, 1.9 mmol of Ni, 2.9 mmol of Fe, and 2.9 mmol of Mn.

[0130] The reagents used in the following examples are:

[0131] The potassium permanganate titration solution was prepared with analytical grade potassium permanganate at a concentration of 0.0237 mol / L and was calibrated with the national standard manganese solution at a concentration of 1000 mg / L.

[0132] Saturated sodium pyrophosphate solution was prepared with analytical grade sodium pyrophosphate and was a saturated solution at 25°C;

[0133] 0.1% bromothymol blue indicator is prepared from high-grade pure bromothymol blue;

[0134] The hydrogen peroxide was analytical grade with a mass fraction of 25.6%;

[0135] Concentrated hydrochloric acid is analytical grade with a mass fraction of 36%;

[0136] (1+1) Hydrochloric acid: Mix concentrated hydrochloric acid (36%) and water in a volume ratio of 1:1 to obtain;

[0137] The ammonia water is (1+1) analytical grade, i.e., commercially available concentrated ammonia water is mixed with water in a volume ratio of 1:1, and the ammonia mass fraction in the (1+1) ammonia water is 12-14%;

[0138] Sodium thiosulfate solution was 0.097 mol / L analytical grade solution;

[0139] The starch solution was 10 g / L analytical grade solution;

[0140] Potassium iodide was solid analytical grade;

[0141] EDTA standard solution is 0.05560 mol / L analytical grade solution;

[0142] The Zn standard solution is a 0.02492 mol / L reference reagent solution;

[0143] Xylenol orange is a 0.5% aqueous solution;

[0144] Sodium fluoride was solid analytical grade;

[0145] Acetic acid-sodium acetate is a buffer solution with a pH of approximately 5.6.

[0146] Example 1

[0147] This embodiment provides a method for detecting nickel, iron, copper and manganese in battery materials, which is as follows:

[0148] (1) Preparation of test solution

[0149] Accurately weigh 2.0±0.005g of quaternary precursor powder into a 250mL beaker, moisten with 10mL of ultrapure water, add 15mL of concentrated hydrochloric acid, heat until completely dissolved, cool, dilute to a 200mL volumetric flask, shake well and set aside.

[0150] (2) Sample testing

[0151] Determine the mass percentage of manganese: Accurately pipette 5 mL of the solution to be tested, after dissolving and adjusting to volume, into a 500 mL beaker. Add 30 mL of ultrapure water and 2 mL of hydrogen peroxide. Heat on a graphite hotplate to decompose the hydrogen peroxide. After the heated solution stops bubbling, add 1 mL of ammonia to ensure complete decomposition of the hydrogen peroxide. Then, add 2 mL of concentrated hydrochloric acid to dissolve the ferric hydroxide precipitate and the manganese dioxide produced by the reduction. After dissolution is complete, remove the beaker and cool in a fume hood. After cooling, add a magnetic stir bar, 120 mL of saturated sodium pyrophosphate solution, approximately 250 mL of ultrapure water, and 2 to 3 drops of bromothymol blue. Adjust the solution to sky blue with concentrated ammonia to a pH of approximately 6.8. Test on a potentiometric titrator in dynamic titration mode, pre-adding 5 mL of potassium permanganate standard solution. The potentiometric titrator was a Leici ZDJ-4A potentiometric titrator, with a platinum working electrode and a calomel reference electrode. The initial potential was 272 mV, and the titration endpoint was 423 mV. The volume of potassium permanganate standard solution consumed was recorded. The mass percentage of manganese was calculated according to formula (1).

[0152] Determine the mass percentage of copper and iron: Accurately pipette 5 mL of the dissolved and fixed solution into two 250 mL conical flasks A and B, respectively. Add 2 mL of hydrogen peroxide to flasks A and B, and heat on a graphite hot plate to decompose the hydrogen peroxide. After ensuring that the hydrogen peroxide is completely decomposed, add (1+1) ammonia solution dropwise to flasks A and B where the hydrogen peroxide is completely decomposed until a brick-red precipitate appears. Then, add (1+1) hydrochloric acid dropwise until the precipitate is completely dissolved. Adjust the solution pH to approximately 1. Continue to add approximately 2g of solid sodium fluoride to bottle A (not to bottle B), shake well, add 1mL of (1+1) hydrochloric acid, and then add approximately 2g of solid potassium iodide. After isolating from air, place in a dark place for 10 minutes. Add pure water to bottles A and B respectively to the 100mL mark and titrate with sodium thiosulfate standard solution until the sample turns light yellow. Then add 4-5 drops of starch solution to the sample and continue titrating with sodium thiosulfate solution until the sample changes from blue to milky white turbidity. This is the endpoint. Record the titrated volume of sodium thiosulfate solution. Calculate the copper and iron contents according to formulas (2) and (3), respectively.

[0153] Determine the total amount of substance of the four elements nickel, iron, copper, and manganese: Accurately transfer 2 mL of the solution to be tested after dissolution and dilution to a 250 mL conical flask, record it as C, and at the same time transfer the same volume of pure water to another 250 mL conical flask, record it as D. Add 10 mL of hydroxylamine hydrochloride solution to the C and D conical flasks, shake well, and accurately add 20 mL of EDTA standard solution and 15 mL of acetic acid-ammonium acetate buffer. Continue to shake well and add a few drops of xylenol orange reagent. Titrate with Zn standard solution. The end point is when the sample solution changes from yellow to purple-red. Record the titration volume of Zn standard solution. Calculate the total amount of substance of the four elements nickel, iron, copper, and manganese according to formula (4).

[0154] Combining the mass percentages of manganese, copper, and iron and the total amount of the four elements nickel, iron, copper, and manganese, the Ni content was calculated using formula (5). The test results of each element in the quaternary precursor are shown in Table 1.

[0155] Table 1 Test results of each element in the quaternary precursor

[0156] As can be seen from Table 1, the RSD (relative standard deviation) of the nickel, iron, copper and manganese contents of the quaternary precursors measured by the method provided in the present disclosure are all less than 1.0%, indicating that the inventive method is very suitable for the main content detection of the quaternary sodium electrode precursor, and the detection results are stable and reliable.

[0157] The process of the embodiment was repeated, except that a certain amount of nickel, iron, copper and manganese national standard substances were added during the sample volume determination process in (1) to perform spiked recovery verification. The results are shown in Table 2 below.

[0158] Table 2 Verification results of spike recovery

[0159] As can be seen from Table 2, the recovery rates of nickel, iron, copper and manganese content obtained by the method provided by the present disclosure are between 95% and 105%, indicating that the present invention meets the requirements of nickel, iron, copper and manganese quaternary sodium precursors for the accuracy of detection results.

[0160] Example 2

[0161] This embodiment provides a method for detecting nickel, iron, copper and manganese in battery materials, which is as follows:

[0162] (1) Preparation of test solution

[0163] Accurately weigh 1.0±0.005g of quaternary precursor powder into a 250mL beaker, moisten with 10mL of ultrapure water, add 15mL of concentrated hydrochloric acid, heat until completely dissolved, cool and dilute to a 200mL volumetric flask, shake well and set aside.

[0164] (2) Sample testing

[0165] Determine the mass percentage of manganese: Accurately pipette 5 mL of the solution to be tested, after dissolving and adjusting to volume, into a 500 mL beaker. Add 30 mL of ultrapure water and 2 mL of hydrogen peroxide. Heat on a graphite hotplate to decompose the hydrogen peroxide. After the heated solution stops bubbling, add 1 mL of ammonia to ensure complete decomposition of the hydrogen peroxide. Then, add 2 mL of concentrated hydrochloric acid to dissolve the ferric hydroxide precipitate and the manganese dioxide produced by the reduction. After dissolution is complete, remove the beaker and cool in a fume hood. After cooling, add a magnetic stir bar, 120 mL of saturated sodium pyrophosphate solution, approximately 250 mL of ultrapure water, and 2 to 3 drops of bromothymol blue. Adjust the solution to sky blue with concentrated ammonia to a pH of approximately 6.6. Test on a potentiometric titrator in dynamic titration mode, pre-adding 2.5 mL of potassium permanganate standard solution. The potentiometric titrator was a Leici ZDJ-4A potentiometric titrator, with a platinum working electrode and a calomel reference electrode. The initial potential was 269 mV, and the titration endpoint was 425 mV. The volume of potassium permanganate standard solution consumed was recorded. The mass percentage of manganese was calculated according to formula (1).

[0166] Determine the mass percentage of copper and iron: Accurately pipette 5 mL of the solution to be tested after dissolution and volume adjustment into two 250 mL conical flasks A and B, respectively. Add 2 mL of hydrogen peroxide to flasks A and B, heat on a graphite hot plate to decompose the hydrogen peroxide. After ensuring that the hydrogen peroxide is completely decomposed, add (1+1) ammonia solution dropwise to flasks A and B where the hydrogen peroxide is completely decomposed until a brick-red precipitate appears. Then, add (1+1) hydrochloric acid dropwise until the precipitate is completely dissolved. Adjust the solution pH to about 0.8. Continue to add about 1g of solid sodium fluoride to bottle A (not to bottle B), shake well, add 1mL of (1+1) hydrochloric acid, then add about 1g of solid potassium iodide. After isolating from air, place in a dark place for 5 minutes. Add pure water to bottles A and B respectively to the 100mL mark, titrate with sodium thiosulfate standard solution until the sample turns light yellow, then add 4-5 drops of starch solution to the sample, and continue titrating with sodium thiosulfate solution until the sample changes from blue to milky white turbidity. This is the end point, and record the titrated volume of sodium thiosulfate solution. Calculate the copper and iron contents according to formula (2) and formula (3), respectively.

[0167] Determine the total amount of substance of the four elements nickel, iron, copper, and manganese: Accurately transfer 2 mL of the solution to be tested after dissolution and dilution to a 250 mL conical flask, record it as C, and at the same time transfer the same volume of pure water to another 250 mL conical flask, record it as D. Add 10 mL of hydroxylamine hydrochloride solution to the C and D conical flasks, shake well, and accurately add 10 mL of EDTA standard solution and 15 mL of acetic acid-ammonium acetate buffer. Continue to shake well and add a few drops of xylenol orange reagent. Titrate with Zn standard solution. The end point is when the sample solution changes from yellow to purple-red. Record the titration volume of Zn standard solution. Calculate the total amount of substance of the four elements nickel, iron, copper, and manganese according to formula (4).

[0168] Combining the mass percentages of manganese, copper, and iron and the total amount of the four elements nickel, iron, copper, and manganese, the Ni content is calculated using formula (5).

[0169] Example 3

[0170] This embodiment provides a method for detecting nickel, iron, copper and manganese in battery materials, which is as follows:

[0171] (1) Preparation of test solution

[0172] Accurately weigh 3.0±0.005g of quaternary precursor powder into a 250mL beaker, moisten with 15mL of ultrapure water, add 15mL of concentrated hydrochloric acid, heat until completely dissolved, cool and dilute to a 200mL volumetric flask, shake well and set aside.

[0173] (2) Sample testing

[0174] Determine the mass percentage of manganese: Accurately pipette 5 mL of the solution to be tested, after dissolving and adjusting to volume, into a 500 mL beaker. Add 30 mL of ultrapure water and 2 mL of hydrogen peroxide. Heat on a graphite hotplate to decompose the hydrogen peroxide. After the heated solution stops bubbling, add 1 mL of ammonia to ensure complete decomposition of the hydrogen peroxide. Then add 2 mL of concentrated hydrochloric acid to dissolve the ferric hydroxide precipitate and the manganese dioxide produced by the reduction. After dissolution is complete, remove the beaker and cool in a fume hood. After cooling, add a magnetic stir bar, 120 mL of saturated sodium pyrophosphate solution, approximately 250 mL of ultrapure water, and 2-3 drops of bromothymol blue. Adjust the solution to sky blue with concentrated ammonia to a pH of approximately 6.9. Test on a potentiometric titrator in dynamic titration mode, pre-adding 8 mL of potassium permanganate standard solution. The potentiometric titrator was a Leici ZDJ-4A potentiometric titrator, with a platinum working electrode and a calomel reference electrode. The initial potential was 275 mV, and the titration endpoint was 420 mV. The volume of potassium permanganate standard solution consumed was recorded. The mass percentage of manganese was calculated according to formula (1).

[0175] Determine the mass percentage of copper and iron: Accurately pipette 5 mL of the dissolved and fixed solution to be tested into two 250 mL conical flasks A and B, respectively. Add 2 mL of hydrogen peroxide to flasks A and B, and heat on a graphite hot plate to decompose the hydrogen peroxide. After ensuring that the hydrogen peroxide is completely decomposed, add (1+1) ammonia solution dropwise to flasks A and B where the hydrogen peroxide is completely decomposed until a brick-red precipitate appears. Then, add (1+1) hydrochloric acid dropwise until the precipitate is completely dissolved. Adjust the solution pH to approximately 1.2. Continue to add approximately 2g of solid sodium fluoride to bottle A (not to bottle B), shake well, add 1mL of (1+1) hydrochloric acid, and then add approximately 2g of solid potassium iodide. After isolating from air, place in a dark place for 20 minutes. Add pure water to bottles A and B respectively to the 100mL mark and titrate with sodium thiosulfate standard solution until the sample turns light yellow. Then add 4-5 drops of starch solution to the sample and continue titrating with sodium thiosulfate solution until the sample changes from blue to milky white turbidity. This is the endpoint. Record the titrated volume of sodium thiosulfate solution. Calculate the copper and iron contents according to formulas (2) and (3), respectively.

[0176] Determine the total amount of substance of the four elements nickel, iron, copper, and manganese: Accurately transfer 2 mL of the solution to be tested after dissolution and dilution to a 250 mL conical flask, record it as C, and at the same time transfer the same volume of pure water to another 250 mL conical flask, record it as D. Add 10 mL of hydroxylamine hydrochloride solution to the C and D conical flasks, shake well, and accurately add 30 mL of EDTA standard solution and 15 mL of acetic acid-ammonium acetate buffer. Continue to shake well and add a few drops of xylenol orange reagent. Titrate with Zn standard solution. The end point is when the sample solution changes from yellow to purple-red. Record the titration volume of Zn standard solution. Calculate the total amount of substance of the four elements nickel, iron, copper, and manganese according to formula (4).

[0177] Combining the mass percentages of manganese, copper, and iron and the total amount of the four elements nickel, iron, copper, and manganese, the Ni content is calculated using formula (5).

[0178] It should be noted that the test results of Examples 2 and 3 are similar to those of Example 1.

[0179] Comparative Example 1

[0180] The principle of the method of Comparative Example 1 is the same as that of Example 1, with the only difference being the selection of the masking agent, in which saturated sodium pyrophosphate is replaced with sodium fluoride + sodium pyrophosphate. The specific steps are as follows:

[0181] (1) Preparation of test solution

[0182] Same as Example 1.

[0183] (2) Sample testing

[0184] Accurately transfer 5 mL of the dissolved, fixed-volume solution to a 500 mL beaker. Add 30 mL of ultrapure water and 2 mL of hydrogen peroxide. Heat on a graphite hotplate to decompose the hydrogen peroxide. Once the heated solution is fully bubbling, add 1 mL of ammonia to ensure complete decomposition of the hydrogen peroxide. Then, add 2 mL of concentrated hydrochloric acid to dissolve the precipitated iron hydroxide and the resulting manganese dioxide. After dissolution is complete, remove the beaker and cool in a fume hood. After cooling, add a magnetic stir bar, 100 mL of saturated sodium pyrophosphate, 0.5 g of solid sodium fluoride, and approximately 250 mL of ultrapure water. Add 2-3 drops of bromothymol blue. Adjust the solution to sky blue with concentrated ammonia to a pH of approximately 6.8. Test on a potentiometric titrator in dynamic titration mode, pre-adding 5 mL of potassium permanganate standard solution for titration.

[0185] The other steps of Example 1 were repeated respectively to detect the mass percentages of manganese, copper, and iron and the total amount of the four elements of nickel, iron, copper, and manganese. The Ni content was calculated using formula (5). The test results of each element in the quaternary precursor are shown in Table 3.

[0186] Table 3 Comparison of test results of Example 1 and Comparative Example 1

[0187] It can be seen from Table 3 that compared with conventional masking agents, the masking agent used in the embodiment of the present disclosure has a smaller impact on the test results and has better test result stability. The method of the embodiment of the present invention can achieve Fe 3+ The shielding can also prevent Mn 3+ A disproportionation reaction occurs.

[0188] Comparative Example 2

[0189] The method principle of Comparative Example 2 is consistent with that of Example 1, except that the masking agent is selected by replacing saturated sodium pyrophosphate with sodium citrate + sodium pyrophosphate, the molar ratio of sodium citrate to sodium pyrophosphate is 1:1, and the total amount of the two is consistent with the amount of saturated sodium pyrophosphate in Example 1.

[0190] The results showed that sodium citrate can react with Mn 2+ The formation of stable complexes has a serious impact on the test results. Therefore, the use of sodium citrate and sodium pyrophosphate as mixed masking agents will affect the accuracy of the test results. Industrial Applicability

[0191] The improved detection method disclosed in the present invention adopts a constant analysis method, with the help of sodium pyrophosphate as a masking agent, while suppressing the Mn 3+ disproportionation reaction and can also mask Fe 3+ , playing a double masking effect, ensuring the accuracy of manganese content testing. The entire detection process does not require the use of expensive testing equipment, and the test results are stable and reliable, with low detection costs, and has very good industrial application prospects.

Claims

1. A detection method for nickel, iron, copper and manganese in battery materials, characterized in that, Including: Using sodium pyrophosphate as a masking agent, the content of manganese element in the battery material is tested by redox potential titration method; The contents of iron element, copper element and the total amount of nickel, iron, copper and manganese elements are tested respectively; According to the total amount of nickel, iron, copper and manganese and the contents of manganese element, iron element and copper element, the content of nickel element is calculated.

2. The detection method according to claim 1, wherein The process of testing the content of manganese element includes: after mixing and dissolving the battery material with inorganic acid, diluting it with water to obtain a battery material solution to be tested; after mixing and reacting the battery material solution to be tested with excessive hydrogen peroxide, heating to remove the excessive hydrogen peroxide, then mixing with saturated sodium pyrophosphate, and titrating with potassium permanganate standard solution; The content of manganese element in the battery material is obtained through the following calculation formula: Wherein, $c$ is the molar concentration of the potassium permanganate standard solution, with the unit of mol / L; V KMnO4 is the titration volume of the potassium permanganate standard solution, in mL; $m$ is the weighed sample mass of the battery material, with the unit of g; $V$ is the pipetted volume of the battery material solution during titration, with the unit of mL; $f$ is the ratio of the constant volume to the pipetted sample volume.

3. The detection method according to claim 2, wherein According to the theoretical total content of manganese and iron elements in the pipetted battery material solution to be tested, the dosage of the saturated sodium pyrophosphate is calculated, and the molar ratio of the theoretical total content of manganese and iron elements to the saturated sodium pyrophosphate is 1:(20 - 40).

4. The detection method according to claim 2 or 3, characterized in that, Before titrating with potassium permanganate, adjust the pH value of the solution to 6.6 - 6.9, and the concentration of the potassium permanganate standard solution used during titration is 0.01 mol / L - 0.03 mol / L.

5. The detection method according to claim 2 or 3, characterized in that, The inorganic acid is hydrochloric acid. After mixing and dissolving the battery material with hydrochloric acid, it is fixed in volume with water to obtain a battery material solution to be tested, and the concentration of the battery material in the battery material solution to be tested is a solution of 5 g / L - 15 g / L.

6. The detection method according to claim 5, wherein When preparing the battery material solution to be tested, first moisten the battery material with water, and then mix it with hydrochloric acid and heat to dissolve.

7. The detection method according to any one of claims 1-6, characterized in that The battery material is a nickel, iron, copper and manganese quaternary precursor or a sodium - based nickel, iron, copper and manganese cathode material.

8. The detection method according to any one of claims 1-7, characterized in that, The contents of iron element and copper element are tested respectively by iodometry.

9. The detection method according to claim 8, wherein The process of testing the contents of iron element and copper element includes: taking two groups of battery material solutions to be tested and marking them as sample A and sample B. Among them, the battery material solution to be tested is obtained by mixing and dissolving the battery material with hydrochloric acid and then fixing it in volume with water; Treating sample A and sample B and reacting with iodide to prepare titration solutions A and B containing elementary iodine. Among them, sodium fluoride is added as a masking agent during the preparation process of titration solution A; Titrating titration solution A and titration solution B with sodium thiosulfate standard solution. The volumes of the sodium thiosulfate standard solution consumed by titration solution A and titration solution B are $V_1$ and $V_3$ respectively; The content of iron and copper elements in the battery material is obtained through the following calculation formula: Wherein, $c_1$ is the molar concentration of the sodium thiosulfate standard solution, with the unit of mol / L; $V_1$, $V_3$ are the titration volumes of the sodium thiosulfate standard solution, with the unit of mL; $m$ is the weighed sample mass of the quaternary precursor, with the unit of g; $V_2$ is the pipetted volume of the quaternary precursor solution, with the unit of mL; $f$ is the ratio of the constant volume to the pipetted sample volume.

10. The detection method according to claim 9, wherein, The process of preparing the solution A to be titrated and the solution B to be titrated includes: mixing two groups of samples, namely sample A and sample B, with excessive hydrogen peroxide respectively for reaction, and then performing heat treatment to remove the excessive hydrogen peroxide; taking the two samples after the heat treatment and mixing them with an ammonia water solution until a brick-red precipitate appears, and then mixing them with a hydrochloric acid solution until the precipitate dissolves, and adjusting the pH value to 0.8 - 1.2; Mixing the sample A after adjusting the pH value with sodium fluoride, then mixing the two groups of samples with a hydrochloric acid solution to adjust the pH value to less than 0.8, and then mixing them with potassium iodide respectively for reaction, and making up the volume to obtain the solution A to be titrated and the solution B to be titrated.

11. The detection method according to claim 10, characterized in that During the process of preparing the solution A to be titrated and the solution B to be titrated, calculate the dosage of sodium fluoride according to the theoretical amount of iron element in the sample, and control the molar ratio of the dosage of sodium fluoride to the theoretical amount of iron element in the sample to be (20 - 50):

1.

12. The detection method according to claim 10 or 11, characterized in that, During the process of preparing the solution A to be titrated and the solution B to be titrated, calculate the dosage of potassium iodide according to the total theoretical amount of iron and copper elements in the sample, and control the molar ratio of the dosage of potassium iodide to the total theoretical amount of iron and copper elements in the sample to be (10 - 20):

1.

13. The detection method according to any one of claims 10-12, characterized in that After mixing with potassium iodide, isolate from air and react in the dark for 5 min - 20 min.

14. The detection method according to any one of claims 10-13, characterized in that, During the process of preparing the solution A to be titrated and the solution B to be titrated, the mass fraction of the ammonia water solution used is 12% - 24%.

15. The detection method according to any one of claims 10-14, characterized in that, During the process of preparing the solution A to be titrated and the solution B to be titrated, the mass fraction of the hydrochloric acid solution used is 15% - 20%.

16. The detection method according to any one of claims 9-15, characterized in that, The process of titrating the solution A to be titrated and the solution B to be titrated with the sodium thiosulfate standard solution includes: pipetting the solution A to be titrated and the solution B to be titrated, titrating with the sodium thiosulfate standard solution until it turns light yellow, then mixing with a starch solution, and continuing to titrate with the sodium thiosulfate standard solution until the sample changes from blue to a milky white turbid solution, and record the volume of the sodium thiosulfate standard solution consumed.

17. The detection method according to claim 16, wherein The concentration of the starch solution is 5 g / L - 15 g / L.

18. The detection method according to claim 16 or 17, characterized in that, The concentration of the sodium thiosulfate standard solution is 0.05 mol / L - 0.15 mol / L.

19. The detection method according to any one of claims 1-18, characterized in that, Test the total amount of nickel, iron, copper, and manganese in the battery material by the method of complexometric titration - back titration.

20. The detection method according to claim 19, wherein Including: Taking the battery material test solution and the same volume of water and marking them as sample C and sample D; wherein, the battery material test solution is obtained by mixing and dissolving the battery material with hydrochloric acid and making up the volume with water. Mix the sample C and the sample D with hydroxylamine hydrochloride solution respectively, then mix them with EDTA standard solution and a buffer solution with a pH value of 5.5 - 5.

7. Add xylenol orange reagent thereto and titrate with Zn standard solution. The end point is when the sample changes from yellow to purple-red. Record the volume of the consumed Zn standard solution. The total amount of substance of the four elements nickel, iron, copper, and manganese in the battery material is obtained through the following calculation formula: In the formula, n is the total amount of substance of nickel, iron, copper, and manganese; C Zn is the molar concentration of the Zn standard solution, with the unit of mol / L; V0 is the volume of the Zn standard solution consumed by the blank solution, with the unit of mL; V1 is the volume of the Zn standard solution consumed by the test solution, with the unit of mL; V2 is the volume of the test solution pipetted, with the unit of mL; f is the ratio of the volume made up to the volume of the sample pipetted.

21. The detection method according to claim 20, characterized in that, The concentration of the hydroxylamine hydrochloride solution is 95 g / L - 105 g / L. Calculate the volume of the hydroxylamine hydrochloride solution according to the total molar amount of iron and manganese, and control the molar ratio of the dosage of hydroxylamine hydrochloride to the theoretical molar ratio of iron and manganese elements in the sample to be (5 - 10):

1.

22. The detection method according to claim 20 or 21, characterized in that, The concentration of the EDTA standard solution is 0.01 mol / L - 0.10 mol / L. The volume of the EDTA standard solution added is calculated according to the theoretical total amount of nickel, iron, copper and manganese in the battery material test solution to be taken, so that the molar ratio of the amount of EDTA added to the theoretical total amount of nickel, iron, copper and manganese is (1.5 - 2.0):

1.

23. The detection method according to any one of claims 20-22, characterized in that, The buffer solution is selected from any one of acetic acid - ammonium acetate buffer solution and hexamethylenimine buffer solution.

24. The detection method according to any one of claims 20-23, characterized in that, The concentration of the Zn standard solution is 0.02 mol / L - 0.03 mol / L.

25. The detection method according to any one of claims 1-24, characterized in that, The nickel element content is obtained through the following calculation formula: Wt%(Ni)={n / m - {Wt%(Fe) / 55.845 + Wt%(Mn) / 54.938 + Wt%(Cu) / 63.55}*58.69; In the formula, n is the total amount of the four elements of nickel, iron, copper and manganese in the battery material; Wt%(Ni), Wt%(Fe), Wt%(Cu), and Wt%(Mn) are the percentage contents of nickel, iron, copper and manganese elements in the quaternary precursor respectively, and the unit is %; m is the weighed mass of the quaternary precursor, and the unit is g.

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