Method for testing content of zirconium oxide in positive electrode material

Abstract

The invention provides a method for testing the content of zirconium oxide in a positive electrode material. The test method comprises the following steps: S1, providing a to-be-tested positive electrode material; s2, carrying out first acid dissolution on the to-be-tested positive electrode material, and then testing to obtain a content ratio X1 of a main element to a doped zirconium element; s3, mixing the to-be-tested positive electrode material obtained in the S1 with an alkaline substance, carrying out a melting reaction, carrying out second acid dissolution on the substance after the melting reaction, and then testing to obtain a content ratio X2 of a main element to all zirconium elements; and S4, according to the mass ratio X1 of the main element to the zirconium element in the S2 and the mass ratio X2 of the main element to the zirconium element in the S3, obtaining the content ratio M of zirconium in the zirconium oxide coating layer, wherein M = (X2-X1). According to the test method provided by the invention, the sample is subjected to melting processing treatment, so that the harm caused by digesting by hydrofluoric acid is avoided, and the problem of relatively low melting processing test precision is solved, so that the content of the zirconium oxide coating layer can be accurately obtained.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of battery material detection, and relates to a method for testing the content of zirconium oxide in a positive electrode material. BACKGROUND

[0002] Lithium ion batteries are widely used due to their high energy density, high voltage and long cycle life, etc. However, further improvement of energy density and safety is needed for their application in commercial automobile industry. Nickel-cobalt-manganese ternary positive electrode materials are widely used in automobile power battery positive electrode materials due to their high specific energy, low cost, stable cycle performance, small toxicity and good safety, etc. However, the above-mentioned systems have the problem of very low electrical conductivity, which restricts the improvement of their electrochemical performance. Therefore, different modification methods (coating, element doping, etc.) are needed to improve the performance of the materials, such as coating zirconium oxide, which reduces the direct contact of active materials with electrolyte, prevents the corrosion of electrode active materials by HF in electrolyte, and thus improves the cycle performance of lithium ion battery ternary positive electrode materials. The addition amount of zirconium oxide coating has a great influence on the modification of nickel-cobalt-manganese ternary positive electrode materials. Therefore, the zirconium content in the coating modification production process of ternary positive electrode materials needs to be analyzed and tested at different time periods to control the consistency of the addition amount of zirconium oxide coating.

[0003] The conventional zirconium content testing methods mainly include ICP-OES and AAS. In order to ensure the appropriate coating amount, the surface-coated zirconium oxide needs to be accurately tested. The common method for accurate testing of elements is to dissolve the material and perform ICP testing. Zirconium oxide needs to be dissolved with hydrofluoric acid. However, hydrofluoric acid is dangerous, and improper use and handling can pose a risk to the tester and harm the environment. The detection solution containing hydrofluoric acid also causes corrosion of the ICP atomizer, greatly affecting the service life of the ICP. At the same time, some positive electrode materials also contain zirconium elements, which makes it difficult to calculate the content of Zr coating.

[0004] The use of the molten salt method can convert zirconium oxide into soluble zirconium salt, which is dissolved for ICP testing. Although this method is relatively safe and environmentally friendly compared to hydrofluoric acid, the reaction during the melting process is complex, the reaction is not easy to determine, the degree of reaction is not easy to calculate, and it is difficult to calculate the proportion of Zr in the initial system. At the same time, part of the material will stick to the crucible during the molten salt process, which will also affect the testing accuracy.

[0005] Therefore, how to obtain the content of the zirconium oxide coating layer in the positive electrode material, reduce the use of harmful dissolving substances, and improve the testing accuracy is a technical problem to be solved. SUMMARY

[0006] In view of the deficiencies of the prior art, the present application aims to provide a method for testing the content of zirconium oxide in a positive electrode material. The method provided by the present application avoids the harm caused by the use of hydrofluoric acid digestion by subjecting the sample to melt processing, and solves the problem of low test precision of melt processing, so that the content of the zirconium oxide coating layer can be accurately obtained.

[0007] To achieve the object of the present application, the present application adopts the following technical solutions:

[0008] In a first aspect, the present application provides a method for testing the content of zirconium oxide in a positive electrode material, which comprises the following steps:

[0009] S1: providing a positive electrode material to be tested, which comprises an inner core doped with zirconium elements and a zirconium oxide coating layer coated on the surface of the inner core, and the positive electrode material to be tested contains main elements in addition to the zirconium oxide coating and the zirconium element doping;

[0010] S2: subjecting the positive electrode material to be tested of S1 to first acid dissolution to obtain a dissolved solution, and then testing to obtain the content ratio X1 of the main elements and the doped zirconium elements;

[0011] S3: mixing the positive electrode material to be tested of S1 with an alkaline substance and subjecting it to melt reaction, subjecting the substance after melt reaction to second acid dissolution, and then testing to obtain the content ratio X2 of the main elements and all zirconium elements;

[0012] S4: calculating the content ratio M of zirconium in the zirconium oxide coating layer according to the mass ratio X1 of the main elements and the zirconium elements in S2 and the mass ratio X2 of the main elements and the zirconium elements in S3, wherein M = X2-X1, and then obtaining the content of the zirconium oxide from M.

[0013] It should be noted that the zirconium element doping in step S1 of the present application exists in the form of zirconate and can be dissolved in common acid solution without using hydrofluoric acid.

[0014] In addition, the main elements referred to in the present application refer to the core metal elements constituting the crystal structure framework of the material.

[0015] For example, when the positive electrode material to be tested is a nickel-cobalt-manganese system or a nickel-cobalt-aluminum positive electrode material, the main elements are nickel, cobalt and manganese or nickel, cobalt and aluminum; and when the positive electrode material to be tested is a nickel-manganese binary positive electrode material, the main elements are nickel and manganese.

[0016] The present application first dissolves other substances in the to-be-tested positive electrode material except the zirconium oxide coating layer through the first acid in step S2, so that the total content of the main elements and the content ratio of the doped zirconium elements in the entire to-be-tested positive electrode material can be accurately obtained. The to-be-tested positive electrode material is melted by the alkaline substance in step S3, so that the zirconium oxide coating layer can be converted into soluble zirconium salt. When the second acid is dissolved, all the zirconium elements in the to-be-tested positive electrode material can be dissolved, so that the content ratio of all the zirconium elements in the system can be obtained. Then, the content ratio of zirconium in the zirconium oxide coating layer can be accurately obtained from the content ratio of the doped zirconium in step S2 and the content ratio of the total zirconium elements in step S3. According to the ratio, the content of the corresponding zirconium oxide can be further calculated. The harm caused by the use of hydrofluoric acid is avoided, and the problem of low test precision in the melting process is solved.

[0017] The following is a preferred technical solution of the present application, but is not a limitation on the technical solutions provided by the present application. Through the following preferred technical solution, the technical purposes and beneficial effects of the present application can be better achieved and realized.

[0018] Preferably, the main elements in step S1 include nickel, cobalt and manganese.

[0019] Preferably, the acid solution used in the first acid dissolution includes a hydrochloric acid solution, and the concentration of the hydrochloric acid solution is 1 mol / L-10 mol / L, for example, 1 mol / , 2 mol / , 3 mol / , 4 mol / , 5 mol / , 6 mol / , 7 mol / , 8 mol / , 9 mol / or 10 mol / and the like, but is not limited to the listed values. Other values not listed in this range are also applicable.

[0020] In the first acid dissolution process in step S2, high-corrosive hydrofluoric acid is not required for element dissolution. A hydrochloric acid with a concentration of 1 mol / L-10 mol / L can be used for dissolution, which is more conducive to the dissolution of the doped zirconium elements in the core.

[0021] Preferably, in step S2, the usage amount of the to-be-tested positive electrode material is 0.2 g-1 g, for example, 0.2 g, 0.3 g, 0.4 g, 0.5 g, 0.6 g, 0.7 g, 0.8 g, 0.9 g or 1 g and the like, and the addition amount of the acid solution used in the first acid dissolution is 10 mL-20 mL, for example, 10 mL, 11 mL, 12 mL, 13 mL, 14 mL, 15 mL, 16 mL, 17 mL, 18 mL, 19 mL or 20 mL and the like, but is not limited to the listed values. Other values not listed in this range are also applicable.

[0022] In the first acid dissolution of step S2 of the present application, good dissolution effect can be achieved without using too much acid solution, the use amount of the to-be-tested positive electrode material is 0.2 g to 1 g, and the addition amount of the acid solution used in the first acid dissolution is 10 mL to 20 mL, which will not cause excessive use of acid and affect the subsequent test, and also ensures complete dissolution of the to-be-tested positive electrode material.

[0023] Preferably, in step S2, after the dissolved solution is filtered, the solution is made up to volume, a part of the solution made up to volume is taken out for testing of the total amount of main elements by standard titration method to obtain the total amount of main elements A, and the remaining part of the solution made up to volume is taken out for testing of the mass concentration of the doped zirconium element and the molar amount ratio of each element in the main elements.

[0024] In order to avoid the inaccuracy of directly testing the total amount of main elements from the solution made up to volume, the present application additionally performs standard titration on the total amount of main elements for further accurate correction of the content of main elements and improvement of the accuracy of the test.

[0025] Further, in the present application, the making up to volume can be performed in a volumetric flask, and the volume of the volumetric flask can be adaptively selected and adjusted according to actual requirements.

[0026] Specifically, the capacity of the volumetric flask can be 500 mL to 1000 mL, such as 500 mL, 600 mL, 700 mL, 800 mL, 900 mL or 1000 mL, but is not limited to the listed values, and other values not listed in the range are also applicable.

[0027] Preferably, the standard titration method comprises:

[0028] The solution made up to volume and the standard solution are mixed for titration test, and the total amount of main elements A is obtained according to the titration test result.

[0029] Preferably, the concentration of the standard solution is 0.01 mol / L to 0.05 mol / L, such as 0.01 mol / L, 0.02 mol / L, 0.03 mol / L, 0.04 mol / L or 0.05 mol / L, but is not limited to the listed values, and other values not listed in the range are also applicable.

[0030] Preferably, the standard solution comprises an EDTA standard solution.

[0031] Preferably, the total amount of main elements A is calculated according to the following formula:

[0032] Wherein, C 标准溶液 is the concentration of the standard solution, mol / L;

[0033] V标准溶液 The volume of standard solution consumed, in mL;

[0034] m1 is the amount of the positive electrode material to be tested in step S2, in grams;

[0035] V1 is the volume of the container to be filled to a constant volume, in mL;

[0036] V2 is the amount of mother liquor used to test the total mass content of the main element, in mL.

[0037] This invention is achieved through The main elements can be accurately obtained. Taking nickel-cobalt-manganese ternary cathode material as an example, it is the sum of the three main elements: nickel, cobalt, and manganese. Specifically, the unit of A is mol / kg.

[0038] Preferably, in step S2,

[0039] Among them, M represents the mass percentage of the main element obtained in step S2 in the cathode material under test.

[0040] C Zr1 The concentration of zirconium measured in step S2 is in mg / L;

[0041] n1 - The dilution factor of the solution during the volume adjustment in step S2;

[0042] m1 is the amount of the positive electrode material to be tested in step S2, in grams;

[0043] V1 is the volume of the container that was brought to volume in step S2, in mL.

[0044] Preferably, the principal element is obtained through the sum of the principal elements, A. The mass percentage of the main element in the cathode material to be tested obtained in step S2 is calculated based on the total number of moles, where N is the sum of the molar percentages of each element in the main element in the total molar amount of the main element.

[0045] In step S2 of this invention, apart from titration, the other elemental testing processes can be performed using conventional inductively coupled plasma (ICP) testing to obtain the corresponding results.

[0046] Furthermore, this invention further obtains M% by using the total amount of the main element A, taking nickel, cobalt, and manganese as examples, i.e., Ni% + Co% + Mn%. The specific process is as follows:

[0047]

[0048] Nimo1% - the molar percentage of nickel in the total nickel-cobalt-manganese metal determined by ICP in step S2;

[0049] Como 1% - the molar percentage of cobalt in the total metal of nickel, cobalt and manganese measured by ICP in step S2;

[0050] Mnmo 1% - the molar percentage of manganese in the total metal of nickel, cobalt and manganese measured by ICP in step S2;

[0051] The Ni% + Co% + Mn% can be further obtained from the total metal moles:

[0052] Ni% = (Nimol% x relative atomic mass of Ni x total metal moles) / m1,

[0053] Co% = (Comol% x relative atomic mass of Co x total metal moles) / m1,

[0054] Mn% = (Mnmol% x relative atomic mass of Mn x total metal moles) / m1.

[0055] After the above calculation process, the mass percentage of the total mass of the main elements of Ni+Co+Mn in the measured positive electrode material can be obtained, and the mass ratio of the doped zirconium element to the main elements can be obtained.

[0056] Preferably, the alkaline substance in step S3 comprises sodium carbonate and / or sodium hydroxide.

[0057] Preferably, in step S3, the mass ratio of the alkaline substance to the measured positive electrode material is (0.25-0.5):1, for example 0.25:1, 0.3:1, 0.35:1, 0.4:1, 0.45:1 or 0.5:1, etc., but not limited to the listed values, other values not listed in this range are also applicable.

[0058] In step S3 of the present application, the mass ratio of the alkaline substance to the measured positive electrode material is controlled to be (0.25-0.5):1, which can better play a melting role and convert zirconium oxide into a soluble salt.

[0059] Preferably, the amount of the measured positive electrode material used in step S3 is consistent with the amount of the measured positive electrode material used in step S2.

[0060] In the present application, the amount of the measured positive electrode material used in the testing process in steps S2 and S3 is consistent, which can ensure that the combined amount of the main elements and the mass percentage of the main elements do not need to be tested again, and the relative simplicity of the variables is ensured.

[0061] Preferably, the temperature of the melting reaction in step S3 is 500-800℃, for example 500℃, 550℃, 600℃, 650℃, 700℃, 750℃ or 800℃, etc., but not limited to the listed values, other values not listed in the range are also applicable.

[0062] Preferably, the time of the melting reaction in step S3 is 2-6h, for example 2h, 3h, 4h, 5h or 6h, etc., but not limited to the listed values, other values not listed in the range are also applicable.

[0063] Preferably, the acid solution used in the second acid solution in step S3 includes a hydrochloric acid solution, and the concentration of the hydrochloric acid solution is 1-10mol / L, for example 1mol / , 2mol / , 3mol / , 4mol / , 5mol / , 6mol / , 7mol / , 8mol / , 9mol / or 10mol / , etc., but not limited to the listed values, other values not listed in the range are also applicable.

[0064] Preferably, in step S3, the amount of the positive electrode material to be tested is 0.2-1g, for example 0.2g, 0.3g, 0.4g, 0.5g, 0.6g, 0.7g, 0.8g, 0.9g or 1g, etc., and the amount of the acid solution used in the second acid solution is 10-20mL, for example 10mL, 11mL, 12mL, 13mL, 14mL, 15mL, 16mL, 17mL, 18mL, 19mL or 20mL, etc., but not limited to the listed values, other values not listed in the range are also applicable.

[0065] Preferably, the testing process in step S3 includes:

[0066] In step S3, after the dissolved solution is filtered, it is made to a constant volume, and the solution after constant volume is tested for the mass concentration of all zirconium elements.

[0067] Preferably, in step S3,

[0068] Wherein, Mmain% is the mass percentage of the main element in the positive electrode material to be tested, which is obtained by testing in step S2,

[0069] C Zr2 C is the concentration of zirconium measured in step S3, mg / L;

[0070] n2 is the dilution multiple of the solution when constant volume is performed in step S3;

[0071] m2 is the amount of the positive electrode material to be tested in step S3, g;

[0072] V3 is the volume of the container in step S3, mL.

[0073] In the second acid dissolution process of step S3, the specific volume and test process of step S2 can be referred to, and there is no need to test M again, because the same selected positive electrode material to be tested has the same content of main elements in the system; at the same time, for the calculation process of total zirconium elements in the system, the test process of Zr1% can be referred to.

[0074] Compared with the prior art, the present application has the following beneficial effects:

[0075] The present application first dissolves other substances in the positive electrode material to be tested except the zirconium oxide coating layer through the first acid dissolution of step S2, so that the total content of main elements and the content ratio of doped zirconium elements in the whole positive electrode material to be tested can be accurately obtained; and the positive electrode material to be tested is melted by the alkaline substance of step S3, so that the zirconium oxide coating layer can be converted into soluble zirconium salt, and all zirconium elements in the positive electrode material to be tested can be dissolved in the second acid dissolution, so that the content ratio of all zirconium elements in the system is obtained; and then the content ratio of zirconium in the zirconium oxide coating layer can be accurately obtained from the content ratio of doped zirconium of step S2 and the content ratio of total zirconium elements of step S3, and the corresponding content of zirconium oxide can be further calculated according to the ratio, which avoids the harm caused by the use of hydrofluoric acid digestion and solves the problem of low test precision of melting processing. DETAILED DESCRIPTION

[0076] The technical solutions of the present application will be further described through specific embodiments. Those skilled in the art should understand that the embodiments are only used to help understand the present application, and should not be regarded as specific limitations on the present application.

[0077] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the present application; the terms "include" and "have" and any variations thereof in the present application are intended to cover non-exclusive inclusion.

[0078] In the description of the present application, the technical terms "first", "second", etc. are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features. In the description of the embodiments of the present application, the meaning of "a plurality of" is two or more, unless otherwise specifically limited.

[0079] In one specific embodiment, the present application provides a positive electrode material to be tested:

[0080] The to-be-tested positive electrode material comprises a zirconium element doped inner core and a zirconia coating layer coated on the surface of the inner core, and the to-be-tested positive electrode material contains nickel, cobalt and manganese main elements in addition to the zirconia coating and zirconium element doping; that is, the inner core is a zirconium doped nickel-cobalt-manganese ternary positive electrode material, and the inner core surface is coated with a zirconia coating layer.

[0081] The following examples and comparative examples all use the to-be-tested positive electrode material of the above specific embodiment as the to-be-tested sample.

[0082] Example 1

[0083] The present embodiment provides a method for testing the content of zirconia in a positive electrode material, which comprises the following steps:

[0084] S1: selecting the positive electrode material provided in the above specific embodiment as the to-be-tested sample;

[0085] S2: Zr doping amount and main element total amount test: take 0.5g of the to-be-tested sample, add 15mL of hydrochloric acid solution with a concentration of 10mol / L, dissolve at a temperature of 180℃ for 1h, filter the dissolved solution and rinse the residues on the filter paper with water, after the solution is cooled to room temperature, transfer the solution to a 500mL volumetric flask, add water to constant volume, shake well to form a mother liquor; dilute a part of the mother liquor by several times respectively, then use ICP to test the ratio of main elements and zirconium elements, and use a standard EDTA solution with a concentration of 0.03mol / L to titrate and test the total amount of main elements;

[0086] ①Main element total amount A;

[0087]

[0088] In the formula:

[0089] A—main element total amount, mol / kg;

[0090] C EDTA —EDTA standard solution concentration in step S2, mol / L;

[0091] V EDTA —volume of consumed EDTA in step S2, mL;

[0092] m1—mass of the to-be-tested sample in step S2, g;

[0093] V1—volume of the volumetric flask in step S2, mL;

[0094] V2—volume of the mother liquor removed for titration in step S2, mL.

[0095] ②Ratio X1 of main element content and zirconium content before treatment:

[0096]

[0097] Ni% = Nimol% × 58.69 × total metal moles / m1

[0098] Co% = Comol% × 58.93 × total metal moles / m1

[0099] Mn% = Mnmol% × 54.94 × total metal moles / m1

[0100]

[0101] In the formula:

[0102] Nimo1% - The molar percentage of nickel in the total nickel-cobalt-manganese metal determined by ICP in step S2;

[0103] Como1% - The molar percentage of cobalt in the total nickel-cobalt-manganese metal determined by ICP in step S2;

[0104] Cumo1% - The molar percentage of manganese in the total nickel-cobalt-manganese metal determined by ICP in step S2;

[0105] CZr1—The concentration of zirconium in the solution determined by ICP in step S2, in mg / L;

[0106] n1—the dilution factor of the solution in step S2;

[0107] V1—The volume of the volumetric flask in step S2, mL;

[0108] m1 — Mass of the solid sample in step S2, in g.

[0109] S3: Take 0.5g of the sample to be tested and mix it thoroughly with 2.0g of Na2CO3. Place it in a muffle furnace and react at 700℃ for 4h to obtain the treated sample. Take the treated sample and add 15mL of 10mol / L hydrochloric acid solution to dissolve it at 180℃ for 1h. After the solution cools to room temperature, transfer the solution to a 500mL volumetric flask, add water to make up to volume, dilute it several times, and then test the mass percentage of all zirconium elements.

[0110] ③ The ratio of the main element content to the zirconium content after treatment is X2;

[0111]

[0112] In the formula:

[0113] C Zr2 —The concentration of zirconium in the sample was determined by ICP in step S3, in mg / L;

[0114] n2—the dilution factor of the solution in step S3;

[0115] V3 - volume of the volumetric flask in step S3, mL;

[0116] m2 - mass of the sample to be tested in step (2), g.

[0117] S4: obtaining the total content of major elements A, the ratio X1 of the content of major elements and the content of zirconium before treatment, the ratio X2 of the content of major elements and the content of zirconium after treatment, obtaining the doping Zr content, and the coated Zr content M = X2 - X1.

[0118] The same sample was selected to perform three tests (1#, 2# and 3#) by using the test process of Example 1, and the test results are shown in Table 1.

[0119] Table 1

[0120]

[0121] Example 2

[0122] The difference between this example and Example 1 is that in step S2 of this example, the concentration of hydrochloric acid is 1 mol / L, and the concentration of the standard solution is 0.05 mol / L.

[0123] In step S3, the mass of Na2CO3 used is 1 g, and the melting reaction is melting at 500°C for 6 h; the concentration of hydrochloric acid is 1 mol / L.

[0124] The rest of the test conditions and parameters remain the same as those of Example 1.

[0125] Example 3

[0126] The difference between this example and Example 1 is that in step S2 of this example, the concentration of hydrochloric acid is 5 mol / L, and the concentration of the standard solution is 0.01 mol / L.

[0127] In step S3, the mass of Na2CO3 used is 0.8 g, and the melting reaction is melting at 800°C for 2 h; the concentration of hydrochloric acid is 5 mol / L.

[0128] The rest of the test conditions and parameters remain the same as those of Example 1.

[0129] Comparative Example 1

[0130] The difference between this comparative example and Example 1 is that in this comparative example, hydrofluoric acid is directly used for the dissolution of the sample to be tested, and the solution obtained after dissolution is used for zirconium content testing.

[0131] The same sample was selected to perform three tests (1#, 2# and 3#) by using the test processes of Examples 2-3 and Comparative Example 1, and the test results are shown in Table 2.

[0132] Table 2

[0133]

[0134] From Table 1 to Table 2, it can be concluded that:

[0135] By using the test method of the present application, the content of zirconium doping elements and the content of coated zirconium elements can be accurately obtained at the same time, and the operator and the instrument will not be damaged, and the problems of undistinguishable doping and coating zirconium and irreversible loss caused by using hydrofluoric acid are avoided.

[0136] To sum up, the present application first dissolves other substances in the measured positive electrode material except the zirconium oxide coating layer by the first acid in step S2, so that the total content of the main elements and the content ratio of the doped zirconium elements in the whole measured positive electrode material can be accurately obtained; and the measured positive electrode material is melted by the alkaline substance in step S3, so that the zirconium oxide coating layer can be converted into soluble zirconium salt, and when the second acid is dissolved, all the zirconium elements in the measured positive electrode material can be dissolved, so that the content ratio of all the zirconium elements in the system is obtained; and then the content ratio of the doped zirconium in step S2 and the content ratio of the total zirconium elements in step S3 can accurately obtain the content ratio of zirconium in the zirconium oxide coating layer, and according to the ratio, the corresponding content of zirconium oxide can be further calculated; the harm caused by using hydrofluoric acid is avoided, and the problem of low test precision of melting processing is solved.

[0137] The applicant declares that the above is only a specific embodiment of the present application, but the protection scope of the present application is not limited thereto, and those skilled in the art should understand that any changes or replacements within the technical scope disclosed by the present application can be easily thought by any person skilled in the art, and all fall within the protection scope and disclosure scope of the present application.

Claims

1. A method for testing the content of zirconium oxide in a positive electrode material, characterized in that, The test method comprises the following steps: S1: providing a to-be-tested positive electrode material, the to-be-tested positive electrode material comprising a zirconium element doped inner core and a zirconia coating layer coated on the surface of the inner core, the to-be-tested positive electrode material containing main elements in addition to the zirconia coating and the zirconium element doping; S2: performing first acid dissolution on the to-be-tested positive electrode material of S1 to obtain a dissolved solution, and then performing testing to obtain a content ratio X1 of the main elements and the doped zirconium elements; S3: mixing the to-be-tested positive electrode material of S1 with an alkaline substance to perform a melting reaction, performing second acid dissolution on the substance after the melting reaction, and then performing testing to obtain a content ratio X2 of the main elements and all zirconium elements; S4: calculating a content ratio M of zirconium in the zirconia coating layer according to the mass ratio X1 of the main elements and the zirconium elements in S2 and the mass ratio X2 of the main elements and the zirconium elements in S3, wherein the M = X2-X1, and obtaining the content of the zirconia from the M.

2. The test method of claim 1, wherein, The main elements in step S1 include nickel, cobalt and manganese.

3. The test method of claim 1, wherein, The acid solution used in the first acid dissolution comprises a hydrochloric acid solution, and the concentration of the hydrochloric acid solution is 1 mol / L-10 mol / L; Preferably, in step S2, the usage amount of the to-be-tested positive electrode material is 0.2 g-1 g, and the added amount of the acid solution used in the first acid dissolution is 10 mL-20 mL.

4. The test method of claim 1, wherein, In step S2, after filtering the dissolved solution, the solution is made constant volume, a part of the constant volume solution is taken to perform testing of the total mass content of the main elements by a standard titration method to obtain the total mass content A of the main elements, and the remaining part of the constant volume solution is taken to perform testing of the mass concentration of the doped zirconium elements and the molar amount ratio of each element in the main elements in the main elements.

5. The test method of claim 4, wherein, The standard titration method comprises: mixing the constant volume solution and a standard solution to perform titration testing, and obtaining the total mass content A of the main elements according to the titration testing result; Preferably, the concentration of the standard solution is 0.01 mol / L-0.05 mol / L, and the standard solution comprises an EDTA standard solution; Preferably, the main element combination wherein C 标准溶液 is the concentration of the standard solution, mol / L; V 标准溶液 V for the volume of the standard solution consumed, mL; m1 is the usage amount of the to-be-tested positive electrode material in step S2, g; V1 is the volume of the constant volume container, mL; V2 is the usage amount of the mother liquor for testing the total mass content of the main elements, mL.

6. The test method of claim 5, wherein, In step S2, Mmain% - the mass percentage of the main element in the positive electrode material to be tested, which is obtained by testing in step S2, C Zr1 C for the concentration of zirconium measured in step S2, mg / L; n1 is the dilution multiple of the solution when constant volume is performed in step S2; m1 is the usage amount of the to-be-tested positive electrode material in step S2, g; V1 is the volume of the constant volume container in step S2, mL.

7. The test method of claim 6, wherein, The dominant element is obtained from the sum of the dominant elements, A. The mass percentage of the main element in the cathode material to be tested obtained in step S2 is calculated based on the total number of moles, where N is the sum of the molar percentages of each element in the main element in the total molar amount of the main element.

8. The test method of claim 1, wherein, The alkaline substance in step S3 comprises sodium carbonate and / or sodium hydroxide; Preferably, in step S3, the mass ratio of the alkaline substance to the to-be-tested positive electrode material is (0.25-0.5):1; Preferably, the usage amount of the to-be-tested positive electrode material in step S3 is consistent with the usage amount of the to-be-tested positive electrode material in step S2; Preferably, the temperature of the melting reaction in step S3 is 500°C-800°C, and the time of the melting reaction is 2 h-6 h.

9. The test method according to claim 1 or 8, characterized in that, The acid solution used in the second acid solution in step S3 comprises a hydrochloric acid solution, and the concentration of the hydrochloric acid solution is 1 mol / L-10 mol / L; Preferably, in step S3, the usage amount of the positive electrode material to be tested is 0.2g-1g, and the adding amount of the acid solution used in the second acid dissolution is 10mL-20mL.

10. The test method of claim 1 or 7, wherein, The testing process in step S3 includes: In step S3, after the dissolved solution is filtered, the solution is made up to volume, and the solution after being made up to volume is tested for the mass concentration of all zirconium elements; Preferably, in step S3, Mmain% - the mass percentage of the main element in the positive electrode material to be tested, which is obtained by testing in step S2, C Zr2 for the concentration of zirconium measured in step S3, mg / L; n2 is the dilution multiple of the solution when being made up to volume in step S3; m2 is the usage amount of the positive electrode material to be tested in step S3, g; V3 is the volume of the container when being made up to volume in step S3, mL.

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