Pretreatment method for wet digestion assisted LLZTO powder element content detection

Abstract

According to the pretreatment method for wet digestion assisted LLZTO powder element content detection, hydrochloric acid and nitric acid are used for pretreatment of an LLZTO sample, the ratio of the hydrochloric acid to the nitric acid is limited, and meanwhile hydrofluoric acid is omitted; the method solves the problems that LLZTO powder cannot be completely dissolved during pretreatment, and element composition and content cannot be accurately and quantitatively analyzed subsequently, and meanwhile, the cost is also saved; on the other hand, the parameters of the inductively coupled plasma emission spectrometer and the concentration of the standard solution are optimized, so that the test result of sample elements is more accurate.

Description

Technical Field

[0001] The present invention belongs to the technical field of solid-state battery detection, and specifically relates to a pretreatment method for detecting the element content of LLZTO powder assisted by wet digestion. Background Art

[0002] In recent years, inorganic solid electrolytes have received extensive attention. As the core component of solid-state batteries, solid electrolytes largely determine various performance parameters of solid-state batteries, such as power density, safety performance, high and low temperature performance, and service life. However, there is currently no unified national standard for the performance requirements and testing methods of solid electrolytes. Oxide solid electrolytes usually contain a large amount of elements such as lithium (Li), lanthanum (La), zirconium (Zr), tantalum (Ta), etc. The lithium content has a significant impact on the ionic conductivity of oxide solid electrolytes. Generally, a higher lithium content helps to improve the ionic conductivity, but an excessive lithium content may lead to an unstable structure of the electrolyte; in NASICON-type solid electrolytes, the substitution of different content elements may generate impurity phases, thereby reducing the ionic conductivity of the overall electrolyte and affecting the electrochemical performance such as the rate and cycle of the battery. Therefore, it is necessary to accurately determine the major elements in the electrolyte to monitor the proportion of major elements and thus improve the battery structure and performance. Traditional digestion methods can only partially dissolve LLZTO, resulting in a large deviation in the measured element content and having no reference value. Therefore, it is necessary to develop an accurate testing method to accurately control the element content of LLZTO in order to improve and enhance the product quality. Summary of the Invention

[0003] The purpose of the present invention is to provide a pretreatment method for detecting the element content of LLZTO powder assisted by wet digestion to solve the problems mentioned in the background art.

[0004] To achieve the above purpose, the present invention provides the following technical solutions:

[0005] A pretreatment method for detecting the element content of LLZTO powder assisted by wet digestion, comprising the following steps:

[0006] The first step: Adjust and optimize the parameters of the inductively coupled plasma emission spectrometer;

[0007] The second step: Prepare standard solutions of Li, La, Zr, and Ta with acids, and calibrate the inductively coupled plasma emission spectrometer using the prepared standard solutions;

[0008] Step 3: Pretreat the sample by wet digestion, that is, weigh the LLZTO solid powder into a 50 mL centrifuge tube with a lid, add hydrochloric acid and nitric acid, and the volume ratio of hydrochloric acid to nitric acid is 2.7 - 3.6:0.9 - 1.2. Digest it on a graphite digester until completely dissolved, take it down and let it cool slightly, and make up the volume to 500 mL with deionized water in a volumetric flask and shake well for measurement.

[0009] In one embodiment, the parameters of the inductively coupled plasma optical emission spectrometer in the first step are set as follows: the sample lift delay is 25 - 35 s, the power is 1200 - 1400 W, the plasma flow rate is 13 - 16 L / min, the sample flow rate is 1.3 - 1.7 mL / min, the nebulizer gas flow rate is 0.6 - 0.8 L / min, the auxiliary gas flow rate is 0.3 - 0.5 L / min, and the observation mode is radial.

[0010] In one embodiment, the concentration of the acid in the standard solution prepared in the second step is 0.5 - 2.0% electronic grade HNO 3 .

[0011] In one embodiment, the standard solutions in the second step are as follows: four standard solutions containing Li with concentrations of 5, 10, 15, and 20 mg / L; four standard solutions containing La with concentrations of 50, 100, 150, and 200 mg / L; four standard solutions containing Zr with concentrations of 15, 30, 45, and 60 mg / L; four standard solutions containing Ta with concentrations of 10, 20, 30, and 40 mg / L.

[0012] In one embodiment, the mass of the LLZTO solid powder weighed in the wet digestion in the third step is 0.05 - 0.2 g.

[0013] In one embodiment, both the hydrochloric acid and nitric acid in the third step are electronic grade, and the volume ratio of hydrochloric acid to nitric acid is 3:1.

[0014] In one embodiment, the temperature of the graphite digester in the third step is 110 - 150 °C.

[0015] Compared with the prior art, the present invention has the following advantages or beneficial effects:

[0016] (1) The present invention optimizes the parameters of the inductively coupled plasma optical emission spectrometer and the concentration of the standard solution, making the test results of sample elements more accurate;

[0017] (2) The present invention limits the acid used for the pretreatment of the LLZTO sample and the ratio of its components, enabling complete dissolution during the pretreatment of the LLZTO powder, and solving the problem that the LLZTO powder cannot be completely dissolved during pretreatment and subsequent accurate quantitative analysis of the element composition and content cannot be carried out.

[0018] (3) Compared with the prior art, the present invention removes the originally used expensive hydrofluoric acid, which helps to reduce the cost of testing and cut down on expenses.

[0019] (4) Compared with the prior art, the present invention requires a lower temperature during digestion, so it is more energy-efficient. Description of the Drawings

[0020] Figure 1 It is the calibration curve of four elements in the present invention;

[0021] Figure 2 It is the test result and precision of the major elements of the LLZTO sample in the present invention;

[0022] Figure 3 It is the repeatability RSD of the major elements in the LLZTO sample. Detailed Embodiments

[0023] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of them. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without any creative work belong to the scope of protection of the present invention.

[0024] Embodiment:

[0025] First, set the parameters of the inductively coupled plasma optical emission spectrometer as follows: sample lift delay 30 s, power 1400 W, plasma gas flow rate 15 L / min, sample flow rate 1.5 mL / min, nebulizer gas flow rate 0.7 L / min, auxiliary gas flow rate 0.4 L / min, and the observation mode is radial. Use 1% HNO 3 (electronic grade) to prepare the standard solution. The standard solution is: four standard solutions containing Li with concentrations of 5, 10, 15, and 20 mg / L; four standard solutions containing La with concentrations of 50, 100, 150, and 200 mg / L; four standard solutions containing Zr with concentrations of 15, 30, 45, and 60 mg / L; four standard solutions containing Ta with concentrations of 10, 20, 30, and 40 mg / L, and use the standard solution to calibrate the inductively coupled plasma optical emission spectrometer. Weigh 0.1 ± 0.0001 g of LLZTO solid powder into a 50 mL capped centrifuge tube, add 3 mL of a mixed acid of hydrochloric acid + 1 mL of nitric acid (both are electronic grade), digest at 125 °C on a graphite digester until completely dissolved, take it down and let it cool slightly, and make up the volume to 500 mL with deionized water in a volumetric flask and shake well for testing.

[0026] Comparative Example 1:

[0027] First, set the parameters of the inductively coupled plasma emission spectrometer as follows: sample lift delay 30 s, power 1400 W, plasma flow rate 15 L / min, sample flow rate 1.5 mL / min, nebulizer gas flow rate 0.7 L / min, auxiliary gas flow rate 0.4 L / min, and the observation mode is radial. Use 1% HNO 3 (electronic grade) to prepare the standard solutions. The standard solutions are: four standard solutions containing Li at concentrations of 5, 10, 15, and 20 mg / L; four standard solutions containing La at concentrations of 50, 100, 150, and 200 mg / L; four standard solutions containing Zr at concentrations of 15, 30, 45, and 60 mg / L; four standard solutions containing Ta at concentrations of 10, 20, 30, and 40 mg / L. Then, calibrate the inductively coupled plasma emission spectrometer using the standard solutions. Weigh 0.1 ± 0.0001 g of LLZTO solid powder into a 50 mL capped centrifuge tube, add a mixed acid of 3 mL of hydrochloric acid + 1 mL of nitric acid + 2 mL of hydrofluoric acid (all electronic grade), digest at 125 °C on a graphite digester until completely dissolved, remove and cool slightly, and make up the volume to 500 mL with deionized water in a volumetric flask, shake well and wait for measurement.

[0028] Comparative Example 2:

[0029] First, set the parameters of the inductively coupled plasma emission spectrometer as follows: sample lift delay 30 s, power 1400 W, plasma flow rate 15 L / min, sample flow rate 1.5 mL / min, nebulizer gas flow rate 0.7 L / min, auxiliary gas flow rate 0.4 L / min, and the observation mode is radial. Use 1% HNO 3 (electronic grade) to prepare the standard solutions. The standard solutions are four standard solutions containing Li at concentrations of 5, 10, 15, and 20 mg / L; four standard solutions containing La at concentrations of 50, 100, 150, and 200 mg / L; four standard solutions containing Zr at concentrations of 15, 30, 45, and 60 mg / L; four standard solutions containing Ta at concentrations of 10, 20, 30, and 40 mg / L. Then, calibrate the inductively coupled plasma emission spectrometer using the standard solutions. Weigh 0.1 ± 0.0001 g of LLZTO solid powder into a 50 mL capped centrifuge tube, add a mixed acid of 2 mL of hydrochloric acid + 1 mL of nitric acid (all electronic grade), digest at 125 °C on a graphite digester for the same time as in the example, remove and cool slightly, and make up the volume to 500 mL with deionized water in a volumetric flask, shake well and wait for measurement.

[0030] Comparative Example 3:

[0031] First, set the parameters of the inductively coupled plasma optical emission spectrometer as follows: sample lift delay 30 s, power 1400 W, plasma gas flow rate 15 L / min, sample flow rate 1.5 mL / min, nebulizer gas flow rate 0.7 L / min, auxiliary gas flow rate 0.4 L / min, and the observation mode is radial. Use 1% HNO 3 (electronic grade) to prepare standard solutions. The standard solutions are four standard solutions containing Li at concentrations of 5, 10, 15, and 20 mg / L; four standard solutions containing La at concentrations of 50, 100, 150, and 200 mg / L; four standard solutions containing Zr at concentrations of 15, 30, 45, and 60 mg / L; and four standard solutions containing Ta at concentrations of 10, 20, 30, and 40 mg / L. Then, use the standard solutions to calibrate the inductively coupled plasma optical emission spectrometer. Weigh 0.1 ± 0.0001 g of LLZTO solid powder into a 50 mL capped centrifuge tube, add 3 mL of a mixed acid of hydrochloric acid + 1 m nitric acid (both are electronic grade), heat it to 125 °C for digestion in a normal way, which is the same as the time in the example. Take it down and let it cool slightly, and then dilute it to 500 mL with deionized water in a volumetric flask and shake well for measurement.

[0032] The following table shows the detection data of the examples and comparative examples:

[0033]

[0034] From the comparison of the experimental data between the example and Comparative Example 1, it can be known that when treating LLZTO powder, comparing the experimental data without adding hydrofluoric acid with the experimental data with adding hydrofluoric acid, all the sample powders can be completely dissolved, and the test results are almost the same, which proves that without adding hydrofluoric acid, the same technical effect can also be achieved only by adding hydrochloric acid and nitric acid;

[0035] And by comparing the experimental data of the example and Comparative Example 2, it can be seen that when reducing the amount of hydrochloric acid during sample pretreatment, partial dissolution of the LLZTO powder will occur, and the test results deviate greatly from the theoretical design values, making it impossible to effectively evaluate the product;

[0036] Finally, by comparing the experimental data of the example and Comparative Example 3, it can be known that without using a graphite digestion instrument in Comparative Example 3, even if the acid ratio is the same as that in the example, the purpose of complete digestion of the sample cannot be achieved;

[0037] As Figures 1-3 shown: By comparing the test results of the element contents for many times, it can be seen that the four elements are tested in parallel 5 times, and the results are all close, and the precision is less than 0.3%, which can ensure the accuracy of the test.

[0038] The foregoing has shown and described the basic principles, main features and advantages of the present invention. For a person skilled in the art, it is obvious that the present invention is not limited to the details of the above-mentioned exemplary embodiments, and without departing from the spirit or basic features of the present invention, the present invention can be implemented in other specific forms. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, it is intended to embrace all changes falling within the meaning and scope of the equivalent elements of the claims in the present invention.

[0039] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A pretreatment method for detecting the element content of LLZTO powder assisted by wet digestion, characterized in that: The following steps are involved: Step 1: Adjust and optimize the parameters of the inductively coupled plasma optical emission spectrometer; Step 2: Prepare Li, La, Zr, and Ta standard solutions with acid, and calibrate the inductively coupled plasma emission spectrometer using the prepared standard solutions; Step 3: Pre-treat the sample by wet digestion, i.e. weigh LLZTO solid powder into a 50mL centrifuge tube with a cap, add hydrochloric acid and nitric acid, and the volume ratio of hydrochloric acid to nitric acid is 2.7-3.6:0.9-1.2, digest on a graphite digester until it is completely dissolved, remove and cool slightly, dilute to 500mL volumetric flask with deionized water and shake well for testing.

2. The pre-treatment method for detecting the element content of LLZTO powder by wet digestion according to claim 1, characterized in that: In the first step, the parameters of the inductively coupled plasma emission spectrometer are set as follows: sample lifting delay is 25-35s, power is 1200-1400W, plasma flow rate is 13-16L / min, sample flow rate is 1.3-1.7mL / min, nebulizer gas flow rate is 0.6-0.8L / min, auxiliary gas flow rate is 0.3-0.5L / min, and the observation mode is radial.

3. The pre-treatment method for detecting the element content of LLZTO powder by wet digestion according to claim 1, characterized in that: In the second step, the acid concentration in the standard solution is 0.5-2.0% electronic grade HNO3.

4. The pre-treatment method for detecting the element content of LLZTO powder by wet digestion according to claim 1, characterized in that: The standard solutions in the second step are: four standard solutions containing Li at concentrations of 5, 10, 15 and 20 mg / L; four standard solutions containing La at concentrations of 50, 100, 150 and 200 mg / L; four standard solutions containing Zr at concentrations of 15, 30, 45 and 60 mg / L; and four standard solutions containing Ta at concentrations of 10, 20, 30 and 40 mg / L.

5. The pre-treatment method for detecting the element content of LLZTO powder by wet digestion according to claim 1, characterized in that: In the wet digestion in the third step, the mass of the LLZTO solid powder weighed is 0.05-0.2 g.

6. The pre-treatment method for detecting the element content of LLZTO powder by wet digestion according to claim 1, characterized in that: The hydrochloric acid and nitric acid in the third step are both electronic grade, and the volume ratio of hydrochloric acid to nitric acid is 3:

1.

7. The pre-treatment method for detecting the element content of LLZTO powder by wet digestion according to claim 1, characterized in that: The temperature of the graphite digester in the third step is 110-150°C.

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