A pretreatment process for detecting main elements of sodium ferrite-based ternary positive electrode material

Abstract

The application relates to the field of element detection, in particular to a pretreatment process for detecting main elements of a sodium ferrite-based ternary positive electrode material, which comprises the following steps: S1, ball milling: sodium ferrite-based ternary positive electrode material is subjected to ball milling in a wet ball mill until the mass of powder with a pore diameter of -100 mesh accounts for more than 50% of the sodium ferrite-based ternary positive electrode material, and the powder is taken; S2, sampling: the powder obtained in the step S1 is taken into a colorimetric tube, and a mixed solution of deionized water, hydrochloric acid and an additive is added; S3, dissolving: the colorimetric tube in the step S2 is subjected to water bath heating at 70-80 DEG C until the powder is completely dissolved; S4, dilution: deionized water is added to the colorimetric tube in the step S3 to constant volume, and a dilute solution of the sodium ferrite-based ternary positive electrode material is obtained. The application has the effects of reducing the use amount of raw materials when the sodium ferrite-based ternary positive electrode material is pretreated and reducing the error of the detection result.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of element detection, and in particular to a pretreatment process for detecting main elements of sodium ferrite-based ternary positive electrode materials. BACKGROUND

[0002] The main elements of sodium ferrite-based ternary positive electrode materials for sodium-ion batteries are sodium, nickel, iron and manganese, and the content of a single element is as high as 20%. The existing detection technology is based on YS / T 928.4-2013, and the pretreatment scheme is to take 0.2g of sample in a polytetrafluoroethylene beaker, add 20mL of hydrochloric acid, and slightly heat to dissolve. After complete dissolution, transfer to a 200mL volumetric flask and make up to volume.

[0003] The existing technology has many disadvantages. The existing pretreatment method takes a sample of 0.2g, which is too large, resulting in a high dilution factor when analyzing in liquid phase, which increases the error and the consumption of hydrochloric acid. When dissolving the positive electrode material with hydrochloric acid, the electric heating plate is generally used to heat the beaker. The electric heating plate is not uniform in digestion and heating, and the digestion speed is different when multiple samples are digested, which is time-consuming and labor-intensive. When diluting the sample and making up to volume, the solution needs to be transferred from the beaker to the volumetric flask, and there is loss in transferring the digestion solution from the beaker. SUMMARY

[0004] In order to reduce the amount of raw materials when pretreating sodium ferrite-based ternary positive electrode materials and reduce the error of the detection results, the present application provides a pretreatment process for detecting main elements of sodium ferrite-based ternary positive electrode materials.

[0005] The pretreatment process for detecting main elements of sodium ferrite-based ternary positive electrode materials provided by the present application adopts the following technical scheme:

[0006] A pretreatment process for detecting main elements of sodium ferrite-based ternary positive electrode materials, comprising the following steps:

[0007] S1, ball milling: ball milling the sodium ferrite-based ternary positive electrode material in a wet ball mill, using a 100 mesh sieve to screen, and continuously feeding the remaining particles into the wet ball mill for ball milling until the mass of the powder with a pore size of-100 mesh accounts for more than 50% of the sodium ferrite-based ternary positive electrode material, and taking the powder;

[0008] S2, sampling: taking the powder obtained in step S1 and adding a mixed solution of deionized water, hydrochloric acid and additives into a colorimetric tube;

[0009] S3, dissolving: heating the colorimetric tube in step S2 in a water bath at 70-80℃ until the powder is completely dissolved;

[0010] S4, dilution: adding deionized water to the colorimetric tube in step S3 to make up to volume, to obtain a dilution solution of the sodium ferrite-based ternary positive electrode material;

[0011] The additive in the step S2 is one or a combination of nitric acid and telluric acid, the additive in the step S2 is one or a combination of nitric acid and telluric acid, the additive in the step S2 is one or a combination of nitric acid and telluric acid, the concentration of hydrochloric acid is 36-38wt%, the concentration of nitric acid is 65-70wt%, and the concentration of telluric acid is 25-30wt%.

[0012] By adopting the above technical scheme, the current detection of the metal element content in the sodium ferrite-based ternary positive electrode material for sodium ion batteries is based on YS / T 928.4-2013. The standard pretreatment scheme for the positive electrode material is to take 0.2g of sample in a polytetrafluoroethylene beaker, add 20mL of hydrochloric acid, and heat to dissolve. After complete dissolution, transfer to a 200mL volumetric flask and dilute to volume. However, this scheme has many problems in actual operation:

[0013] First, in the prior art, hydrochloric acid is used to dissolve metal elements. Hydrochloric acid mainly relies on its acidity to dissolve metal materials, so that when dissolving metal materials, the amount of hydrochloric acid used is large, and the dissolution efficiency is low. In the present application, by adding nitric acid or telluric acid to hydrochloric acid, the oxidizing property of the acid solution is greatly improved, so that the same concentration of acid solution can dissolve more metal materials, reducing the amount of acid used.

[0014] Second, in the prior art, the beaker is heated by a heating plate. This heating method heats the solution in the beaker unevenly, so that it takes a long time for the acid solution to completely dissolve the metal material. In the present application, the water bath heating method is used to heat the entire cuvette, which is more uniform and shortens the time for the acid solution to dissolve the metal material.

[0015] Third, in the prior art, when configuring the sample for injection, the solution in the beaker needs to be transferred to a volumetric flask for dilution to volume. However, during the transfer of the solution, the solution is easily lost or even contaminated, resulting in an increase in the error of the test results. In the present application, the dilution step is directly performed in the cuvette, reducing the steps of solution transfer and reducing the loss of solution during transfer, thereby reducing the error of the final test results.

[0016] Optionally, before heating the cuvette to 70-80℃ in the step S3, the following steps are further performed:

[0017] S31, open the upper end cap of the cuvette, and heat in a water bath at 30-50℃ for 4-6 minutes.

[0018] By adopting the technical scheme, when the nitric acid solution is directly heated to a high temperature, the nitric acid is easy to decompose, so that the concentration of the acid solution decreases, and more acid needs to be added to dissolve the metal material. In the application, the colorimetric tube is preheated at a lower temperature, and then heated to the target temperature for dissolution, effectively reducing the decomposition of nitric acid and reducing the amount of nitric acid.

[0019] Optionally, before the step S4 of adding deionized water to the colorimetric tube to constant volume, the following steps are further performed:

[0020] S41, placing the colorimetric tube in step S3 in the fume hood to cool to room temperature;

[0021] S42, observing whether the colorimetric tube is completely dissolved, if not, continue to add the mixed solution of deionized water, hydrochloric acid and nitric acid, and repeat steps S31, S3 and S41.

[0022] By adopting the technical scheme, in the application, the temperature is first lowered and then the sample is prepared, which reduces the error caused by temperature change. Since the temperature drop may cause the solute to precipitate, the repeated acid dissolution method is used to make the metal material not precipitate at room temperature.

[0023] Optionally, the amount of powder in step S2 is 0.1-0.2g.

[0024] By adopting the technical scheme, in the prior art, the amount of metal material is generally 0.2g. In the application, the experimental error is reduced by improving the process, so that the amount of raw material is less when preparing the sample.

[0025] Optionally, the additive in step S2 is telluric acid.

[0026] By adopting the technical scheme, in the application, the chloride ion of hydrochloric acid forms a complex ion with the metal element, thereby reducing the difficulty of dissolving the metal element with an oxidizing acid. Through repeated experiments by the operator, it is found that using telluric acid instead of nitric acid still has good dissolution effect.

[0027] Optionally, the volume ratio of deionized water, hydrochloric acid and additive in step S2 is 2:(0.5-1):(1.5-3).

[0028] By adopting the technical scheme, through repeated experiments by the operator, it is found that when the volume ratio of deionized water, hydrochloric acid and additive is 2:(0.5-1):(1.5-3), the dissolution effect on the metal element is better.

[0029] Optionally, the solid-liquid ratio of the powder and the mixed solution in step S2 is 1 gram:(50-100) milliliters.

[0030] By adopting the technical scheme, the acid dosage is significantly reduced by improving the acid solution formula.

[0031] Optionally, the solid-liquid ratio of the powder in step S2 and the solution after constant volume in step S4 is 1 gram:(250-1000) milliliters.

[0032] By adopting the technical scheme, the sample solution with different concentrations can be conveniently configured by using the colorimetric tube as the constant volume container, and the operation is more convenient.

[0033] In summary, the present application has at least one of the following beneficial technical effects:

[0034] 1. By adding nitric acid or telluric acid to hydrochloric acid, the oxidizing property of the acid solution is greatly improved, so that the same concentration of acid solution can dissolve more metal materials, and the acid dosage is reduced;

[0035] 2. In the present application, the colorimetric tube is heated by water bath, the whole colorimetric tube can be heated, the heating effect is more uniform, and the time for the acid solution to dissolve the metal material is shortened;

[0036] 3. In the present application, the constant volume step is directly performed in the colorimetric tube, the solution transfer steps are reduced, the solution transfer loss is reduced, and the final test result error is reduced. DETAILED DESCRIPTION

[0037] The present application will be further described by specific embodiments, but the protection scope of the present application is not limited thereto.

[0038] Preparation of positive material powder: take 10g of iron-based sodium ternary positive material (prepared by using existing process, the theoretical calculation of the manganese content in the positive material is 16.43%, the iron content is 16.70%, and the nickel content is 17.55%), ball mill in a wet ball mill, screen with a 100 mesh sieve, continue to put the remaining particles into the wet ball mill for ball milling until the mass of the powder with a pore size of-100 mesh accounts for more than 50% of the sodium ferrite-based ternary positive material.

[0039] Example 1: take 0.1g powder into the colorimetric tube, add 2ml deionized water, 1ml hydrochloric acid and 3ml mixed solution of nitric acid, first heat in water bath at 30-50℃ for 5 minutes, then heat in water bath at 70-80℃ until the powder is completely dissolved, place the colorimetric tube in the fume hood and cool to room temperature, no precipitation is precipitated, add deionized water to constant volume to 50ml.

[0040] Comparative Example 1 differs from Example 1 in that the pre-treatment of the positive electrode material in Comparative Example 1 is carried out using a prior art method, as shown in the following steps:

[0041] Take 0.2 g of powder into a polytetrafluoroethylene beaker, add 20 mL of hydrochloric acid, and dissolve it by heating. After complete dissolution, transfer it to a 200 mL volumetric flask and dilute to volume.

[0042] Example 2 differs from Example 1 in that the additive used in Example 2 is telluric acid.

[0043] Example 3: Take 0.2 g of powder into a cuvette, add 2 ml of deionized water, 1 ml of hydrochloric acid, and 3 ml of a mixed solution of telluric acid, and first heat in a water bath at 30-50°C for 5 minutes, and then heat in a water bath at 70-80°C until the powder is completely dissolved. Place the cuvette in a fume hood and cool to room temperature without precipitation. Add deionized water to dilute to 50 ml.

[0044] Example 4: Take 0.2 g of powder into a cuvette, add 2 ml of deionized water, 1 ml of hydrochloric acid, and 3 ml of a mixed solution of nitric acid, and first heat in a water bath at 30-50°C for 5 minutes, and then heat in a water bath at 70-80°C until the powder is completely dissolved. Add 1 ml of a mixed solution of deionized water, hydrochloric acid, and nitric acid in a ratio of 2:1:3, and first heat in a water bath at 30-50°C for 5 minutes, and then heat in a water bath at 70-80°C until the powder is completely dissolved. Place the cuvette in a fume hood and cool to room temperature without precipitation. Add deionized water to dilute to 50 ml.

[0045] Examples 5 and 6 differ from Example 2 in that the volume after dilution in step S4 is different, as shown in the following table:

[0046] Example 2 Example 5 Example 6 Volume (ml) 50 20 100

[0047] Example 7: Take 0.1 g of powder into a cuvette, add 6 ml of a mixed solution (deionized water, hydrochloric acid, and telluric acid in a volume ratio of 4:1:3), and first heat in a water bath at 30-50°C for 5 minutes, and then heat in a water bath at 70-80°C until the powder is completely dissolved. Add 2 ml of a mixed solution of deionized water, hydrochloric acid, and nitric acid in a ratio of 4:1:3, and first heat in a water bath at 30-50°C for 5 minutes, and then heat in a water bath at 70-80°C until the powder is completely dissolved. Place the cuvette in a fume hood and cool to room temperature without precipitation. Add deionized water to dilute to 50 ml.

[0048] Comparative Example 2: 0.1 g of powder was taken into a colorimetric tube, 6 ml of mixed solution (deionized water, hydrochloric acid and telluric acid in a volume ratio of 8:1:3) was added, and the colorimetric tube was heated in a water bath at 30-50°C for 5 minutes, then heated in a water bath at 70-80°C until the powder was completely dissolved. 2 ml of mixed solution (deionized water, hydrochloric acid and nitric acid in a volume ratio of 8:1:3) was added, and the colorimetric tube was heated in a water bath at 30-50°C for 5 minutes, then heated in a water bath at 70-80°C until the powder was completely dissolved. The process was repeated several times until the powder was completely dissolved. Compared with Example 2, the volume of the mixed solution finally added was 6 ml. The colorimetric tube was placed in a fume hood and cooled to room temperature, and no precipitate was precipitated. Deionized water was added to make up to 50 ml.

[0049] Comparative Examples 3 and 4 are repeated tests of Example 1.

[0050] Comparative Examples 5 and 6 are repeated tests of Example 2.

[0051] Comparative Examples 7 and 8 are repeated tests of Comparative Example 1.

[0052] In the above examples and comparative examples, the concentration of hydrochloric acid is 37 wt%, the concentration of nitric acid is 65 wt%, and the concentration of telluric acid is 25 wt%

[0053] Detection method:

[0054] A nickel chloride solution was prepared according to the concentration gradient of 0.1, 0.2, 0.3, 0.4 and 0.5 g / l, and liquid phase analysis was performed to obtain a nickel chloride standard curve.

[0055] A ferric chloride solution was prepared according to the concentration gradient of 0.1, 0.2, 0.3, 0.4 and 0.5 g / l, and liquid phase analysis was performed to obtain a ferric chloride standard curve.

[0056] A manganese chloride solution was prepared according to the concentration gradient of 0.1, 0.2, 0.3, 0.4 and 0.5 g / l, and liquid phase analysis was performed to obtain a manganese chloride standard curve.

[0057] The final solution of each example and comparative example was sampled and subjected to liquid phase analysis, and the peak area of each metal element in each example and comparative example was compared with the standard curve to obtain the content of nickel, iron and manganese elements.

[0058] The detection results are as follows:

[0059] Conclusion: According to the experimental process of Example 1 and Comparative Example 1, it can be seen that when the metal material is pretreated, only 6 ml of acid solution is needed to treat 0.1 g of metal sample, which is significantly lower than the 20 ml of acid solution in the prior art.

[0060] Heating duration (min) Example 1 15 Comparative Example 1 25

[0061] Conclusion: From the heating time of Example 1 and Comparative Example 1 in the above table, it can be seen that, compared with the prior art, the time for heating and dissolving the metal material is significantly shortened, the efficiency is improved, and the energy consumption is reduced. This is because, compared with the heating mode of using an electric heating plate, the water bath heating mode can heat the entire cuvette uniformly, thereby shortening the time for dissolving the metal material in the acid solution.

[0062] Example 1 Comparative Example 1 Iron element content (g / l) 0.3320 0.3318 Iron element error (%) 0.599 0.659 Nickel element content (g / l) 0.3489 0.3487 Nickel element error (%) 0.598 0.655 Manganese element content (g / l) 0.3266 0.3264 Manganese element error (%) 0.609 0.67

[0063] Conclusion: From the data of Example 1 and Comparative Example 1 in the above table (the element error is calculated compared with the theoretical concentration of the sample solution), it can be seen that the sample content of the positive electrode material prepared by the present application is higher than that of the positive electrode material prepared by the prior art. At the same time, the content of each metal element in the sample of the positive electrode material prepared by the present application is smaller in error and closer to the theoretical data than that of the positive electrode material prepared by the prior art. This is because, in the present application, the constant volume step is directly performed in the cuvette, which reduces the steps of solution transfer, reduces the loss of solution during transfer, and reduces the error of the final test results.

[0064] Example 1 Example 2 Example 3 Iron element content (g / l) 0.3320 0.3322 0.6643 Iron element error (%) 0.599 0.539 0.554 Nickel element content (g / l) 0.3489 0.3491 0.6982 Nickel element error (%) 0.598 0.541 0.541 Manganese element content (g / l) 0.3266 0.3268 0.6537 Manganese element error (%) 0.609 0.548 0.533

[0065] Conclusion: From the data of Example 1, Example 2 and Example 3 in the above table (the element error is calculated compared with the theoretical concentration of the sample solution), it can be seen that, in the present application, the addition of nitric acid and telluric acid both have good pretreatment effects. However, the oxidation product of nitric acid is a gas, while the oxidation product of telluric acid is a solute remaining in the sample, which reduces the generation of toxic and harmful gases and is more suitable for the current requirements of green production.

[0066] Conclusion: From the test processes of Example 1 and Example 2, and Example 3 and Example 4, it is found that, after using telluric acid instead of nitric acid, the acid solution has a stronger dissolving effect on the metal positive electrode material. Therefore, in the present application, the additive of the acid solution is preferably telluric acid.

[0067] Conclusion: From the test processes of Example 2, 7 and Comparative Example 2, it can be seen that, in the present application, the volume ratio of deionized water, hydrochloric acid and additive in step S2 is preferably 2:(0.5-1):(1.5-3). When the ratio of water is too high, the acid concentration is low, and the volume of acid solution required for dissolving the metal material is large, which is more troublesome to operate.

[0068] Example 2 Example 5 Example 6 Iron element content (g / l) 0.3322 0.8304 0.1661 Iron element error (%) 0.539 0.551 0.539 Nickel element content (g / l) 0.3491 0.8728 0.1745 Nickel element error (%) 0.541 0.536 0.57 Manganese element content (g / l) 0.3268 0.8169 0.1634 Manganese element error (%) 0.548 0.56 0.548

[0069] Conclusion: From the data of example 2, 5, 6 in the above table (the element error in the table is calculated compared with the theoretical concentration of sample solution), it can be seen that the concentration values of the metal sample solution prepared in the application at different concentrations are close to the theoretical values, and the error is small, which shows that using a colorimetric tube as a constant volume container can conveniently configure sample solutions with different concentrations, and the operation is more convenient.

[0070]

[0071]

[0072] Conclusion: From the data in the above table, compared with the traditional process, the addition of nitric acid or tellurium acid in hydrochloric acid in the application significantly reduces the detection result error, and the test result is more stable under multiple repeated tests.

[0073] The above are preferred embodiments of the application, and do not limit the protection scope of the application, so: any equivalent changes made according to the structure, shape, principle of the application should be covered within the protection scope of the application.

Claims

1. A pretreatment process for detecting major elements in sodium ferrite-based ternary cathode materials, characterized in that: It comprises the following steps: S1, ball milling: ball milling sodium ferrite-based ternary positive electrode material in a wet ball mill, using a 100 mesh screen for screening, and continuously feeding the remaining particles into the wet ball mill for ball milling until the mass of the powder with a pore size of 100 mesh accounts for more than 50% of the sodium ferrite-based ternary positive electrode material, and then taking the powder; S2, sampling: taking the powder obtained in step S1 and adding it into a colorimetric tube, adding a mixed solution of deionized water, hydrochloric acid and additives; The amount of powder used in step S2 is 0.1-0.2g, and the volume ratio of deionized water, hydrochloric acid and additives is 2:(0.5-1):(1.5-3); The additive in step S2 is telluric acid, the concentration of hydrochloric acid is 36-38wt%, and the concentration of telluric acid is 25-30wt%; The solid-liquid ratio of the powder and the mixed solution in step S2 is 1g:(50-100)ml; S3, dissolution: heating the colorimetric tube in step S2 in a water bath at 70-80℃ until the powder is completely dissolved; Before heating the colorimetric tube to 70-80℃ in step S3, the following step is also performed: S31, opening the upper end cap of the colorimetric tube, and heating in a water bath at 30-50℃ for 4-6 minutes; S4, dilution: adding deionized water to the colorimetric tube in step S3 to obtain a dilute solution of sodium ferrite-based ternary positive electrode material.

2. The pretreatment process for detecting main elements of a sodium ferrite-based ternary positive electrode material according to claim 1, characterized in that: Before adding deionized water to the colorimetric tube to constant volume in step S4, the following steps are also performed: S41, placing the colorimetric tube in step S3 in a fume hood and cooling to room temperature; S42, observing whether the colorimetric tube is completely dissolved, if not, continue to add a mixed solution of deionized water, hydrochloric acid and nitric acid, and repeat steps S31, S3 and S41.

3. The pretreatment process for detecting main elements of a sodium ferrite-based ternary positive electrode material according to claim 1, characterized in that: The solid-liquid ratio of the powder in step S2 to the solution after constant volume in step S4 is 1g:(250-1000)ml.

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