Digestion method of titanium oxide in sodium battery positive electrode material and titanium content detection method

Abstract

The present invention provides a method for digesting titanium oxides in sodium cathode materials and a method for detecting titanium content, which comprises the following steps: uniformly mixing the sodium cathode material with barium carbonate to obtain a pre-sintered material; sintering the pre-sintered material in a heating box to obtain a digestion sample 1; dissolving the digestion sample 1 with an acid solution to obtain a digestion sample 2; sintering at a temperature of 500 to 800° C. and for a sintering time of 1 to 2 hours; diluting and fixing the digestion sample 2, and detecting the titanium content therein using an ICP technique and a standard curve method. In the present invention, barium carbonate is mixed with the titanium oxides in the sodium cathode material and sintered to perform a melting reaction, which not only achieves effective conversion of the titanium oxides, but also facilitates subsequent digestion and titanium extraction, thereby increasing the yield of the titanium element; and by avoiding the use of sulfuric acid and a strong sodium-containing base, the efficiency and accuracy of detecting the titanium content using the ICP technique are improved; compared with traditional technologies, the present method significantly reduces the requirements for experimental containers, thereby improving the economic efficiency and safety of the experiment.

Description

Technical Field

[0001] The invention relates to the technical field of sodium battery positive electrode material detection and analysis, in particular to a method for digesting titanium oxides in sodium battery positive electrode materials and a method for detecting the titanium content. Background Art

[0002] As a new energy storage technology, sodium-ion batteries have attracted much attention in recent years due to their abundant resources, low cost and excellent performance. In sodium-ion batteries, the performance of the cathode material has a significant impact on the overall performance of the battery. Titanium is commonly used in the industry to inhibit the migration of Fe and Cr, thereby increasing the charging voltage and improving the performance of sodium-based cathode materials. Therefore, doping and coating titanium are key means to improve the electrochemical performance, cycle stability and energy storage efficiency of sodium-based cathode materials. Furthermore, the addition and coating method of titanium and the precise control of the ratio are crucial to ensure the performance of sodium-ion batteries. This has led to the accurate detection of the titanium content in sodium-based cathode materials becoming an urgent problem to be solved.

[0003] Titanium dioxide, a common titanium source, possesses unique advantages in the preparation of sodium battery cathode materials due to its unique crystal structure and chemical properties. However, the extraction and detection of titanium in sodium battery cathode materials currently face significant challenges, such as cumbersome procedures, long analysis cycles, high workload, and poor precision.

[0004] Since titanium dioxide is soluble in concentrated sulfuric acid and hydrofluoric acid, technicians have tried to use this method to extract titanium from sodium battery positive electrode materials. However, the iron oxide in the sodium battery positive electrode material will react with sulfuric acid to form iron sulfate, which is insoluble in acid. A large amount of solid suspended matter is instantly generated in the reaction solution, making it difficult to remove impurities and use ICP technology to detect the titanium content.

[0005] In some literature, some technicians have tried to use alkaline substances such as sodium hydroxide or sodium borate as co-solvents to extract titanium from sodium cathode materials through high-temperature digestion to improve the yield. However, sodium hydroxide or sodium borate will introduce sodium elements, and in ICP (inductively coupled plasma technology) detection, easily ionized elements such as sodium will interfere with the content detection of the analyte and reduce the accuracy of the results. At the same time, substances such as sodium hydroxide and sodium borate are highly alkaline and have a strong corrosive effect on equipment and containers. Generally, expensive platinum crucibles are required, and the digestion temperature is high (above 800°C), which increases laboratory testing costs and experimental safety risks.

[0006] In summary, although existing measurement methods can, to a certain extent, measure the titanium content in sodium-ion battery cathode materials, some problems and challenges still exist. Therefore, it is necessary to explore more efficient, accurate, and low-cost measurement methods to promote the further development of sodium-ion battery technology. Summary of the Invention

[0007] The purpose of the present invention is to provide a method for digesting titanium oxides in sodium battery positive electrode materials and a method for detecting the titanium content, so as to extract the titanium element in the sodium battery positive electrode materials and detect its content more efficiently, accurately and at low cost.

[0008] One of the technical solutions of the present invention is: a method for digesting titanium oxide in a sodium cathode material, comprising the steps of:

[0009] Mixing the sodium cathode material and barium carbonate to obtain a material before sintering;

[0010] The material before sintering is placed in a heating box for sintering to obtain digestion sample 1;

[0011] Dissolve digestion sample 1 with acid to obtain digestion sample 2.

[0012] Furthermore, the mass ratio of barium carbonate to titanium dioxide in the sodium battery positive electrode material is greater than 2.5:1.

[0013] Furthermore, the sintering temperature is 500-800° C., and the sintering time is 1 h-2 h.

[0014] Furthermore, the acid solution is hydrochloric acid or aqua regia.

[0015] Another technical solution of the present invention is: a method for detecting titanium content in a sodium battery positive electrode material, comprising the steps of:

[0016] Take the digestion sample 2 obtained by the digestion method of the titanium oxide in the sodium cathode material described above, dilute it with pure water or ultrapure water, and make up the volume to obtain a solution to be tested;

[0017] Establishing a standard curve: preparing a series of gradient standard solutions containing titanium, measuring the spectral line intensity of the titanium element in the series of gradient standard solutions under the set working conditions of the inductively coupled plasma atomic emission spectrometer, using the solution concentration of the titanium element in each standard solution as the abscissa and the spectral line intensity of the titanium element in each standard solution as the ordinate, and fitting a standard curve of the titanium element solution concentration-spectral line intensity using the standard curve method;

[0018] Under the same inductively coupled plasma atomic emission spectrometer working conditions as those for establishing the standard curve, the spectral line intensity of the solution to be tested is measured, and the solution concentration of titanium element in the solution to be tested is calculated using the standard curve of titanium element solution concentration-spectral line intensity. Then, based on the solution concentration of titanium element in the solution to be tested, the mass proportion of titanium element in the sodium battery positive electrode material is calculated.

[0019] Furthermore, when establishing the standard curve, the wavelength of the optimal sensitive analysis line of titanium was 336.121 nm.

[0020] Furthermore, when establishing the standard curve, the working conditions of the inductively coupled plasma atomic emission spectrometer were set as follows: RF generator power of 1150 W, pump speed of 50 r / min, and integration time of 30 s.

[0021] Furthermore, the mass proportion of titanium element in the sodium battery positive electrode material = the mass proportion of titanium element in the material before sintering / the mass proportion of sodium battery positive electrode material in the material before sintering, and the mass proportion of titanium element in the material before sintering w = c * a;

[0022] Wherein: c is the mass ratio of titanium element in digestion sample 1, and a is the sintering mass ratio of sodium battery positive electrode material and barium carbonate.

[0023] Furthermore, c = (solution concentration of titanium element in digestion sample 2 × volume of digestion sample 2) / mass of digestion sample 1; solution concentration of titanium element in digestion sample 2 = solution concentration of titanium element in the test solution × dilution factor of digestion sample 2.

[0024] Further, a = (M3 - M1) / (M2 - M1);

[0025] Wherein: M1 is the mass of the sintering container, M2 is the total mass of the sodium cathode material, barium carbonate and sintering container before sintering; M3 is the total mass of the digestion sample and sintering container after sintering.

[0026] The present invention has the beneficial effects of mixing barium carbonate with titanium-containing oxide in a sodium cathode material, sintering the mixture, and performing a melting reaction to convert the titanium-containing oxide into a substance easily soluble in hydrochloric acid, thereby achieving effective conversion of the titanium-containing oxide and facilitating subsequent digestion and titanium extraction, thereby improving the yield of the titanium element; and by avoiding the use of sulfuric acid and a strong sodium-containing base, improving the efficiency and accuracy of detecting the titanium content using the ICP technology; compared with traditional technologies, the present method significantly reduces the requirements for experimental containers, thereby improving the economic efficiency and safety of the experiment. DETAILED DESCRIPTION

[0027] The present invention will be further described below in conjunction with embodiment:

[0028] Unless otherwise defined, all technical terms used hereinafter have the same meanings as those commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing specific embodiments and comparative examples only and are not intended to limit the scope of protection of the present invention. It should be noted that the same organic structure may have multiple names; as long as the structure falls within the scope of this patent, all of them are protected by this patent.

[0029] Unless otherwise defined, the raw materials, reagents, etc. in the following examples can be purchased from the market or prepared according to reported methods.

[0030] This embodiment provides a method for digesting titanium oxides in sodium battery cathode materials and a method for detecting titanium content, which specifically includes: a stage of extracting titanium from the sodium battery cathode material and a stage of detecting the content of the extracted titanium.

[0031] In the extraction stage of titanium element in the sodium battery cathode material, the above-mentioned digestion method is used to digest the sodium battery cathode material, and the specific steps include:

[0032] (A1) Mixing a sodium cathode material and barium carbonate to obtain a pre-sintered material.

[0033] (A2) The pre-sintered material is placed in a heating box and sintered to obtain digestion sample 1.

[0034] In this step, the titanium dioxide in the sodium cathode material undergoes the following chemical reaction with barium carbonate: TiO2 + BaCO3 == BaTiO3 + CO2↑. As a result, the resulting digestion sample 1 contains BaTiO3 generated by the reaction, as well as other substances in the sodium cathode material besides titanium dioxide. The BaTiO3 in digestion sample 1 is soluble in hydrochloric acid. This reaction not only effectively converts titanium dioxide but also facilitates subsequent digestion and titanium extraction.

[0035] The selected barium carbonate will not introduce easily ionized sodium elements, which can improve the accuracy of the ICP detection results of titanium elements; barium carbonate has weak alkalinity and is non-corrosive, and can be contained in ordinary infrared carbon-sulfur crucibles, reducing experimental costs; the temperature required for the reaction of titanium dioxide and barium carbonate is relatively low. Generally speaking, sintering at a temperature of 500-800℃ for 1h-2h can make the two fully react, reducing experimental costs and safety risks.

[0036] In this step, the temperature and time of the sintering treatment are more critical. When the sintering temperature is 650°C and the sintering time is 1 hour, the reactants can fully melt and react, and the reaction proceeds fully to obtain the ideal product and titanium element yield.

[0037] In order to improve the accuracy of detecting the content of titanium in sodium battery positive electrode materials, the barium carbonate to be added should be able to fully react with the titanium dioxide in the sodium battery positive electrode materials. Generally, during the preparation stage of sodium battery positive electrode materials, the titanium doping amount has a known range of values, and the amount of barium carbonate added can be calculated based on this range of values, and the mass ratio of barium carbonate to titanium dioxide in the sodium battery positive electrode materials can be controlled to be greater than 2.5:1.

[0038] (A3) After the digestion sample 1 is cooled, the digestion sample 1 is dissolved with acid to obtain the digestion sample 2.

[0039] In this step, the BaTiO in the digestion sample 1 and other substances except titanium dioxide in the sodium positive electrode material react with acid solution to generate soluble substances, and then the titanium element is converted into a solution state, so that quantitative detection, for avoiding the iron oxides etc. in the sodium positive electrode material and acid reaction to generate suspended solids, impact detection, acid solution is preferably hydrochloric acid or aqua regia, avoids generating the ferric sulfate that is insoluble in acid. And this method can avoid the use of hydrofluoric acid, avoids its corrosion to the glass apparatus used in this experiment, improves experimental safety.

[0040] If the dissolution rate is too slow, appropriate heating can be used to increase the dissolution rate, but the sample must be cooled before proceeding to the subsequent content detection step. To avoid sampling close to or in contact with the crucible wall, which may introduce impurities and affect the test results, the sampling point of the digestion sample can be controlled at the center of the material in the crucible. The general sampling amount is 0.1g-0.5g.

[0041] After adding the positive electrode material to be tested to 5mL of hydrochloric acid solution and heating it for 10 to 15 minutes, the appropriate hydrochloric acid concentration helps to accelerate the dissolution of the positive electrode material to be tested. In some embodiments, the mass percentage concentration of the hydrochloric acid solution is 5 to 20%; for example, it can be 5%, 15%, 20%, etc., and is not specifically limited. The mass volume ratio of the positive electrode material to be tested and the hydrochloric acid solution is 0.1g: (5 to 10)mL; for example, it can be 0.1g: 5mL, 0.1g: 6mL, 0.1g: 7mL, 0.1g: 8mL, 0.1g: 9mL or 0.1g: 11mL, etc., and is not specifically limited.

[0042] During the titanium content detection phase after extraction, ICP technology is used to detect the titanium content. The specific steps include:

[0043] (B1) preparing a series of standard solutions with a gradient: preparing a series of standard solutions with a gradient, wherein the standard solutions contain the element titanium, measuring the spectral line intensity of the element titanium in the series of standard solutions with a gradient under the set working conditions of an inductively coupled plasma atomic emission spectrometer, and fitting a standard curve of the solution concentration of the element titanium - the spectral line intensity of the element titanium in each standard solution using the standard curve method, with the solution concentration of the element titanium in each standard solution as the abscissa and the spectral line intensity of the element titanium in each standard solution as the ordinate.

[0044] In this step, the working conditions of the inductively coupled plasma atomic emission spectrometer were set as follows: RF generator power of 1150 W, pump speed of 50 r / min, integration time of 30 s, and the wavelength of the optimal sensitive analysis line of titanium element was 336.121 nm.

[0045] In this step, the concentrations of titanium in the prepared series of gradient standard solutions are 0.5 mg / L, 1 mg / L, 2 mg / L, 5 mg / L and 10 mg / L, respectively. The blank solution (titanium concentration is 0 mg / L) and the titanium concentration in the standard solution are injected and tested in order from low to high to prepare a standard curve of titanium solution concentration-spectral line intensity.

[0046] (B2) Under the same operating conditions of the inductively coupled plasma atomic emission spectrometer as those used to establish the standard curve, the spectral line intensity of the solution to be tested is measured, and the solution concentration of the titanium element in the solution to be tested is calculated using the standard curve of the solution concentration of the titanium element - the spectral line intensity. Then, based on the solution concentration of the titanium element in the solution to be tested, the mass percentage of the titanium element in the sodium cathode material is calculated.

[0047] In this step, the mass proportion of titanium in the sodium cathode material = the mass proportion of titanium in the material before sintering / the mass proportion of the sodium cathode material in the material before sintering, and the mass proportion of titanium in the material before sintering w = c * a;

[0048] The above-mentioned c is the mass proportion of titanium element in digestion sample one, and its calculation method is: c = (solution concentration of titanium element in digestion sample two × volume of digestion sample two) / mass of digestion sample one; solution concentration of titanium element in digestion sample two = solution concentration of titanium element in the test solution × dilution multiple of digestion sample two; the mass of digestion sample one mentioned here is the actual amount of digestion sample one taken when digestion sample one is dissolved in acid solution.

[0049] The above-mentioned a is the sintering mass ratio of the sodium cathode material and barium carbonate, and its calculation method is: a = (M3-M1) / (M2-M1), where M1 is the mass of the sintering container, M2 is the total mass of the sodium cathode material, barium carbonate and sintering container before sintering; M3 is the total mass of the digestion sample and the sintering container after sintering.

[0050] Some specific examples are listed below. It should be pointed out that in these specific examples, a mixture of nickel, iron, manganese sodium oxide and titanium dioxide with a known accurate ratio is selected to simulate the sodium positive electrode material for titanium digestion and content detection, so as to calculate the titanium element yield and verify the technical effects of the digestion method and content detection method provided in this application.

[0051] Example 1:

[0052] (1) using a high-speed mixer to uniformly mix barium carbonate, nickel iron manganese sodium oxide and titanium dioxide to obtain a pre-sintering material, wherein the mass fractions of the substances are 26%, 64% and 10% respectively;

[0053] Use a carbon-sulfur crucible as the sintering container and weigh the mass M1 = 16.5546 g;

[0054] The above-mentioned material before sintering was placed in a carbon-sulfur crucible and weighed to a mass of M2 = 23.0541 g;

[0055] The carbon-sulfur crucible and the pre-sintered material were placed in a muffle furnace and sintered at 650°C for 1 hour to perform a melting reaction to obtain digestion sample 1;

[0056] After cooling, weigh the mass of digestion sample 1 and carbon-sulfur crucible M3 = 22.8915 g;

[0057] The sintering mass ratio a was calculated to be (M3-M1) / (M2-M1)=97.498%.

[0058] (2) Remove solution sample 1 from the part that does not contact the wall of the carbon-sulfur crucible, weigh 0.1 g and add it to a beaker, add 5 mL of hydrochloric acid to the beaker and place it on a heating furnace at 600 ° C for digestion to obtain digestion sample 2, transfer digestion sample 2 to a 100 mL volumetric flask, dilute to volume, and obtain the solution to be tested;

[0059] (3) Based on the concentration of the sample to be tested, the concentrations of titanium in the prepared series of gradient standard solutions were 0.5 mg / L, 1 mg / L, 2 mg / L, 5 mg / L and 10 mg / L, respectively. The blank solution (titanium concentration was 0 mg / L) and the titanium concentration in the standard solution were injected and tested in the order from low to high, and a standard curve of titanium solution concentration-spectral line intensity was prepared.

[0060] (4) Under the same inductively coupled plasma atomic emission spectrometer operating conditions as those used to establish the standard curve, the spectral line intensity of the test solution was measured, and the solution concentration of titanium in the test solution was calculated using the titanium solution concentration-spectral line intensity standard curve. The set operating conditions of the inductively coupled plasma atomic emission spectrometer were: RF generator power of 1150 W, pump speed of 50 r / min, integration time of 30 s, and the optimal sensitive analytical line wavelength of titanium was 336.121 nm.

[0061] According to the above formula, the mass proportion of titanium element in the digested sample 1 is calculated to be c=6.133%, and the mass proportion of titanium element in the material before sintering is further calculated to be w=5.9796%.

[0062] Based on the fact that the mass proportion of titanium dioxide in the material before sintering is 10%, the mass proportion of titanium in the material before sintering is 5.993%, and the yield of titanium in this digestion method is calculated to be 99.77%.

[0063] Example 2:

[0064] (1) using a high-speed mixer to uniformly mix barium carbonate, nickel iron manganese sodium oxide and titanium dioxide to obtain a pre-sintering material, wherein the mass fractions of the respective substances are 36%, 60% and 4% respectively;

[0065] Use a carbon-sulfur crucible as the sintering container and weigh the mass M1 = 15.0786 g;

[0066] The above-mentioned material before sintering was placed in a carbon-sulfur crucible and weighed to a mass of M2 = 21.6861 g;

[0067] The carbon-sulfur crucible and the pre-sintered material were placed in a muffle furnace and sintered at 650°C for 1 hour to perform a melting reaction to obtain digestion sample 1;

[0068] After cooling, weigh the mass of digestion sample 1 and carbon-sulfur crucible M3 = 21.5434 g;

[0069] The sintering mass ratio a=(M3-M1) / (M2-M1)=97.840% was calculated.

[0070] (2) Remove sample 1 from the part that does not contact the wall of the carbon-sulfur crucible, weigh 0.1 g and add it to a beaker, add 5 mL of hydrochloric acid to the beaker and place it on a heating furnace at 600 ° C for digestion to obtain digestion sample 2, transfer digestion sample 2 to a 100 mL volumetric flask, dilute to volume, and obtain the solution to be tested;

[0071] (3) Based on the concentration of the sample to be tested, the concentrations of titanium in the prepared series of gradient standard solutions were 0.5 mg / L, 1 mg / L, 2 mg / L, 5 mg / L and 10 mg / L, respectively. The blank solution (titanium concentration was 0 mg / L) and the titanium concentration in the standard solution were injected and tested in the order from low to high, and a standard curve of titanium solution concentration-spectral line intensity was prepared.

[0072] (4) Under the same working conditions of the inductively coupled plasma atomic emission spectrometer as those for establishing the standard curve, the spectral line intensity of the solution to be tested was measured, and the solution concentration of the titanium element in the solution to be tested was calculated using the standard curve of the solution concentration of the titanium element-the spectral line intensity. Then, according to the above formula, the mass proportion of the titanium element in the digested sample 1 was calculated to be c = 2.430%, and the mass proportion of the titanium element in the material before sintering was further calculated to be w = 2.3775%.

[0073] According to the mass proportion of titanium dioxide in the material before sintering being 4%, the mass proportion of titanium in the material before sintering is 2.397%, and the yield of titanium in this digestion method is calculated to be 99.17%.

[0074] Example 3:

[0075] The difference from Example 1 and Example 2 is that the nickel iron manganese sodium oxide and titanium dioxide are mixed in a mass ratio of 96:4, 0.1 g is weighed and 5 mL of hydrochloric acid is added thereto for dissolution and then filtered, the filtrate is transferred to a 100 mL volumetric flask, the volume is constant, and the test solution is obtained. The solution concentration of titanium element in the test solution is detected by the same method as in Example 1 and Example 2, and the mass proportion of titanium element in the material before dissolution with hydrochloric acid is calculated to be 1.44%, and it is further calculated that the yield of titanium element in this embodiment is only 60%.

[0076] The above is a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for digesting titanium oxides in sodium cathode materials, and a method for detecting titanium content in sodium cathode materials using an inductively coupled plasma atomic emission spectrometer, characterized in that: Including steps: Mixing the sodium cathode material and barium carbonate to obtain a pre-sintered material; The material before sintering is placed in a heating box for sintering to obtain digestion sample 1; Dissolve digestion sample 1 with acid to obtain digestion sample 2; The mass ratio of barium carbonate to titanium dioxide in the sodium cathode material is greater than 2.5:1; The sintering temperature is 500~800℃ and the sintering time is 1h~2h; The acid solution is hydrochloric acid or aqua regia.

2. A method for detecting titanium content in sodium battery cathode materials, characterized in that: Including steps: Take the digestion sample 2 obtained by the digestion method of titanium oxide in the sodium cathode material according to claim 1, dilute it with pure water or ultrapure water, and make it up to volume to obtain a solution to be tested; Establishing a standard curve: Prepare a series of gradient standard solutions containing titanium. Under the set working conditions of the inductively coupled plasma atomic emission spectrometer, measure the spectral line intensity of the titanium element in the series of gradient standard solutions. Use the solution concentration of the titanium element in each standard solution as the abscissa and the spectral line intensity of the titanium element in each standard solution as the ordinate to fit a standard curve of the solution concentration of the titanium element - the spectral line intensity of the titanium element using the standard curve method; Under the same inductively coupled plasma atomic emission spectrometer working conditions as those for establishing the standard curve, the spectral line intensity of the solution to be tested is measured, and the solution concentration of titanium element in the solution to be tested is calculated using the standard curve of titanium element solution concentration-spectral line intensity. Then, based on the solution concentration of titanium element in the solution to be tested, the mass proportion of titanium element in the sodium battery positive electrode material is calculated.

3. The method for detecting titanium content in sodium battery cathode materials according to claim 2, characterized in that: When establishing the standard curve, the wavelength of the most sensitive analytical line for titanium was 336.121 nm.

4. The method for detecting titanium content in sodium battery cathode materials according to claim 2, characterized in that: When establishing the standard curve, the working conditions of the inductively coupled plasma atomic emission spectrometer were set as follows: RF generator power of 1150 W, pump speed of 50 r / min, and integration time of 30 s.

5. The method for detecting titanium content in sodium battery cathode materials according to any one of claims 2 to 4, characterized in that: The mass proportion of titanium in the sodium battery positive electrode material = the mass proportion of titanium in the material before sintering / the mass proportion of sodium battery positive electrode material in the material before sintering. The mass proportion of titanium in the material before sintering is w = c * a; Wherein: c is the mass ratio of titanium element in digestion sample 1, and a is the sintering mass ratio of sodium battery positive electrode material and barium carbonate.

6. The method for detecting titanium content in sodium battery cathode materials according to claim 5, characterized in that: c = (concentration of titanium solution in digestion sample 2 × volume of digestion sample 2) / mass of digestion sample 1; concentration of titanium solution in digestion sample 2 = concentration of titanium solution in the test solution × dilution multiple of digestion sample 2.

7. The method for detecting titanium content in sodium battery cathode materials according to claim 5, characterized in that: a=(M3-M1) / (M2-M1); Wherein: M1 is the mass of the sintering container, M2 is the total mass of the sodium cathode material, barium carbonate and sintering container before sintering; M3 is the total mass of the digestion sample and sintering container after sintering.