CN109540874B - Method for detecting content of inorganic elements in sample of lithium lanthanum zirconium oxygen type solid electrolyte - Google Patents
Method for detecting content of inorganic elements in sample of lithium lanthanum zirconium oxygen type solid electrolyte Download PDFInfo
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Abstract
The invention provides a method for detecting the content of inorganic elements in a sample of a lithium lanthanum zirconium oxygen type solid electrolyte, which comprises the following steps: (1) melting the sample, adding hydrofluoric acid, and filtering to obtain filtrate and filter residue; (2) carrying out alkali fusion treatment on the filter residue, and adding a hydrochloric acid solution to obtain a solution of the filter residue; (3) and (3) respectively measuring the contents of the inorganic elements in the solutions of the filtrate and the filter residue by using an inductively coupled plasma emission spectrometer. The detection method provided by the invention can detect the contents of lithium, lanthanum and zirconium in the lithium lanthanum zirconium oxygen type solid electrolyte sample by an inductively coupled plasma emission spectrometer, and has the advantages of higher data accuracy, simple and convenient operation, rapidness and high efficiency.
Description
Technical Field
The invention relates to the technical field of analytical chemistry, in particular to a method for detecting the content of inorganic elements in a sample of a lithium lanthanum zirconium oxygen type solid electrolyte.
Background
Lithium ion batteries have been considered as the most promising chemical energy storage devices since their commercialization in 1991. However, the safety problems caused by the flammability, leakage and easy dendrite crystallization of the organic liquid electrolyte hinder the lithium ion battery from having great advantages in large-scale energy storage. However, inorganic solid electrolytes have many advantages such as superior chemical, mechanical and thermal stability, and the possibility of miniaturization of batteries.
Among them, Li of garnet structure7La3Zr2O12(LLZO), due to its high overall ionic conductivity, excellent chemical and thermal stability, especially with respect to lithium metal, is an ideal solid electrolyte for lithium ion batteries. The garnet structure belongs to a mixed framework structure of a tetrahedron and an octahedron, so that the framework structure is adjusted by adopting a method of changing the composition of the compound, the bottleneck size of rapid migration of ions can be changed, the migration of lithium ions is enhanced, and a plurality of LLZO compounds with doped ions are derived, wherein Li7-xLa3Zr2-xTaxO12(LLZTO) is a typical representative of Zr site doping, has a garnet-type cubic structure, and has a room temperature conductivity as high as 6.1X 10-4S·cm-1。
However, at the present stage, there is no published literature report or test standard for testing the content of inorganic elements in a novel solid electrolyte material, i.e., an LLZO-type compound.
Disclosure of Invention
The present invention has been completed based on the following findings of the inventors:
in the research process, the inventor of the invention finds that the existing methods for measuring the content of inorganic elements in the LLZO type solid electrolyte mainly comprise a chemical analysis method, an atomic absorption method, an X fluorescence spectrometry method, an inductively coupled plasma emission spectrometry method and the like. The chemical analysis method is complex to operate, large in reagent consumption, long in analysis period and capable of influencing the accuracy of the test due to mutual interference among inorganic elements; the atomic absorption spectrometry is suitable for analyzing single elements, the testing conditions required by different elements are completely different, the testing process is complicated, and N used for testing high-temperature resistant elements zirconium (Zr) and tantalum (Ta)2O-C2H2In flame N2O has high risk, and the test effect of Zr and Ta is not ideal; in addition, although the X fluorescence spectrometry is suitable for testing the content of lanthanum (La), zirconium (Zr) and tantalum (Ta), it is not suitable for testing the content of light metal lithium (Li), and the equipment is expensive and has high maintenance cost, and the requirement of matching degree between the working curve and the matrix of the sample is very high when quantitative testing is performed.
The inventors of the present invention have conducted extensive studies and found that a cubic phase structure of a LLZO type solid electrolyte such as LLZTO is very stable and is hardly soluble in an inorganic acid such as hydrochloric acid, nitric acid, aqua regia, or hydrofluoric acid at normal temperature and pressure, and that a high content of zirconium and tantalum is very easily hydrolyzed in a non-hydrofluoric acid medium, and lanthanum (La) is stably present in a hydrofluoric acid medium, but is combined with hydrofluoric acid to form a lanthanum fluoride precipitate. Therefore, the above reasons have made it difficult to perform simultaneous measurement of lithium, lanthanum, zirconium and tantalum in the same medium for the LLZO type solid electrolyte. Therefore, the inventor adopts a sample of high-temperature molten LLZO type solid electrolyte, uses hydrofluoric acid to precipitate and separate lanthanum, then respectively tests the content of at least one of lithium, lanthanum, zirconium and tantalum in the filtrate and precipitate, and finally adds up to calculate the total content of each inorganic element.
In view of the above, an object of the present invention is to provide a method for detecting the content of lithium, lanthanum and zirconium in a LLZO-type solid electrolyte sample by ICP-OES, which has higher data accuracy and is simple and convenient to operate or more efficient.
In a first aspect of the invention, a method is provided for detecting the content of an inorganic element in a sample of a lithium lanthanum zirconium oxygen type solid electrolyte.
According to an embodiment of the invention, the inorganic element comprises at least one of lithium, lanthanum and zirconium, the method comprising: (1) melting the sample, adding hydrofluoric acid, and filtering to obtain filtrate and filter residue; (2) carrying out alkali fusion treatment on the filter residue, and adding a hydrochloric acid solution to obtain a solution of the filter residue; (3) and respectively carrying out content determination on the inorganic elements in the solutions of the filtrate and the filter residue by using an inductively coupled plasma emission spectrometer.
By adopting the detection method provided by the embodiment of the invention, after the sample of the lithium lanthanum zirconium oxide type solid electrolyte is melted and the precipitator hydrofluoric acid is added, lanthanum can be effectively separated, the precipitated filter residue is melted, and then the content of at least one of lithium, lanthanum and zirconium is respectively detected for the solution of the filtrate and the solution of the filter residue, so that the content of lithium lanthanum zirconium in the lithium lanthanum zirconium oxide type solid electrolyte sample is simultaneously detected by the inductively coupled plasma emission spectrometer, and the method is higher in data accuracy, simple and convenient to operate, quicker and more efficient.
In addition, the detection method according to the above embodiment of the present invention may further have the following additional technical features:
according to an embodiment of the present invention, the lithium lanthanum zirconium oxide type solid electrolyte is a lithium lanthanum zirconium tantalum oxide solid electrolyte, and the inorganic element includes at least one of lithium, lanthanum, zirconium, and tantalum.
According to an embodiment of the invention, the melting process comprises: (1-1) mixing the sample with anhydrous sodium carbonate and borax, heating to 900-1100 ℃, melting for 15-60 minutes, and cooling; (1-2) adding ultrapure water and hydrochloric acid into the cooled molten liquid, and extracting at 150-250 ℃.
According to the embodiment of the invention, the weight ratio of the sample to the anhydrous sodium carbonate and the borax is 3: (60-100): (30-50), wherein the weight ratio of the anhydrous sodium carbonate to the borax is 2: 1.
according to an embodiment of the invention, the step of adding hydrofluoric acid comprises: (1-3) adding the hydrofluoric acid into the melt after the melting treatment, heating and reacting for 10-30 minutes at 150-250 ℃, and standing for not less than 0.5 hour.
According to an embodiment of the invention, the step of filtering comprises: (1-4) filtering to obtain filtrate and filter residue; (1-5) transferring the filtrate to a 100mL volumetric flask to fix the volume and form a solution; (1-6) removing 10mL of the solution to a 50mL volumetric flask to obtain a first solution to be tested.
According to an embodiment of the present invention, the alkali fusion treatment includes: and (2-1) ashing the filter residue, adding sodium peroxide, and melting at 600-700 ℃ for 5-20 minutes.
According to an embodiment of the present invention, the step of adding a hydrochloric acid solution comprises: and (2-2) adding ultrapure water and hydrochloric acid into the melt subjected to alkali fusion treatment, extracting at 150-250 ℃, and transferring the extracted solution into a 500mL volumetric flask for constant volume to obtain a second solution to be measured.
According to an embodiment of the present invention, the step of determining the content of the inorganic element includes: (3-1) respectively carrying out inductively coupled plasma emission spectrum test on the first solution to be tested and the second solution to be tested under the detection wavelength corresponding to the inorganic element; and (3-2) calculating the sum of the contents of the inorganic elements corresponding to the result of the inductively coupled plasma spectrum test according to the standard curve of the inorganic elements.
According to the embodiment of the invention, when the inorganic element is lithium, the detection wavelength is 670 ± 1 nm; when the inorganic element is lanthanum, the detection wavelength is 379 +/-1 nm; when the inorganic element is zirconium, the detection wavelength is 339 +/-1 nm; and when the inorganic element is tantalum, the detection wavelength is 240 +/-1 nm.
According to an embodiment of the present invention, when the inorganic element is at least one selected from the group consisting of lithium, zirconium and tantalum, the standard curve of the inorganic element is determined by testing a series of mixed standard solutions of the inorganic element at different concentrations by an inductively coupled plasma emission spectrometer.
According to an embodiment of the present invention, when the inorganic element is lanthanum, the standard curve of the inorganic element is determined by testing a series of standard solutions of the inorganic element at different concentrations by an inductively coupled plasma emission spectrometer.
Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
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The foregoing aspects of the invention are explained in the description of the embodiments with reference to the following drawings, in which:
FIG. 1 is a schematic flow chart of a detection method according to an embodiment of the present invention;
fig. 2 is a schematic flow chart of a detection method according to another embodiment of the present invention.
Detailed Description
The following examples of the present invention are described in detail, and it will be understood by those skilled in the art that the following examples are intended to illustrate the present invention, but should not be construed as limiting the present invention. Unless otherwise indicated, specific techniques or conditions are not explicitly described in the following examples, and those skilled in the art may follow techniques or conditions commonly employed in the art or in accordance with the product specifications.
In one aspect of the invention, a method for detecting the content of an inorganic element in a sample of a lithium lanthanum zirconium oxygen type solid electrolyte is provided. It should be noted that the "Lithium Lanthanum Zirconium Oxide (LLZO) type solid electrolyte" herein specifically refers to a solid electrolyte having a garnet structure and containing elements such as lithium, lanthanum, zirconium, oxygen, and the like, and includes lithium lanthanum zirconium oxide compounds having other dopant ions, specifically, for example, Lithium Lanthanum Zirconium Tantalum Oxide (LLZTO), and the like.
According to the embodiment of the present invention, the detectable inorganic element includes at least one of lithium (Li), lanthanum (La) and zirconium (Zr), and the specific inorganic element species can be selected by those skilled in the art according to the specific species of the Li-La-Zr-o type solid electrolyte to be detected. In some embodiments of the present invention, the lithium lanthanum zirconium oxide type solid electrolyte may be a Lithium Lanthanum Zirconium Tantalum Oxide (LLZTO) solid electrolyte, and as such, the detectable inorganic elements include at least one of lithium (Li), lanthanum (La), zirconium (Zr), and tantalum (Ta), respectively.
According to an embodiment of the present invention, referring to fig. 1, the detection method includes:
s100: and melting the sample, adding hydrofluoric acid, and filtering to obtain filtrate and filter residue.
In the step, the sample is melted, hydrofluoric acid is added, and filtration treatment is performed to obtain filtrate and filter residue. Wherein Li and Ta in the Li-La-Zr-O type solid electrolyte are mainly distributed in the filtrate, and La and a part of Zr form precipitates in hydrofluoric acid, mainly as LaF3Form (A) and Na2ZrF6Is separated from the hydrofluoric acid.
According to an embodiment of the present invention, a specific method of the melting treatment in step S100 is not particularly limited, and those skilled in the art may select accordingly according to a specific kind of the lithium lanthanum zirconium oxide type solid electrolyte. In some embodiments of the present invention, referring to fig. 2, step S100 may include:
s110: mixing the sample with anhydrous sodium carbonate and borax, heating and melting, and cooling.
In the step, a sample of the lithium lanthanum zirconium oxide type solid electrolyte is mixed with anhydrous sodium carbonate and borax, and then the mixture is heated to 900-1100 ℃ to be melted for 15-60 minutes and then cooled, so that the Lithium Lanthanum Zirconium Oxide (LLZO) type compound can be decomposed at high temperature. In some embodiments of the present invention, for the Lithium Lanthanum Zirconium Tantalum Oxygen (LLZTO) sample, after mixing with anhydrous sodium carbonate and borax, the sample is heated to 1000 ℃ to melt for 30 minutes and then cooled, so that the melting treatment using the above conditions can effectively decompose the lithium lanthanum zirconium tantalum oxygen solid electrolyte.
According to the embodiment of the present invention, the specific ratio of the sample to the anhydrous sodium carbonate and the borax is not particularly limited, and those skilled in the art can adjust the ratio according to the specific kind of the lithium lanthanum zirconium oxide type solid electrolyte. In some embodiments of the invention, the weight ratio of the sample to the anhydrous sodium carbonate, borax may be 3: (60-100): (30-50), and the weight ratio of the anhydrous sodium carbonate to the borax can be 2:1, thus, the lithium lanthanum zirconium oxygen type solid electrolyte can be effectively decomposed at the temperature of 900-1100 ℃. In some specific examples, for a sample of Lithium Lanthanum Zirconium Tantalum Oxygen (LLZTO), the weight ratio of the sample to anhydrous sodium carbonate, borax may be 3: 80: 40, the weight ratio of the anhydrous sodium carbonate to the borax is 2:1, thus, the lithium lanthanum zirconium tantalum oxygen solid electrolyte can be effectively decomposed at 1000 ℃.
S120: adding ultrapure water and hydrochloric acid into the cooled molten liquid, and heating and extracting.
In this step, ultrapure water and hydrochloric acid are added to the cooled melt of step S110, and extraction is performed at 150 to 250 degrees Celsius, so that Li can be dissolved out from the excess hydrochloric acid solution+。
According to an embodiment of the present invention, the specific reaction mode after adding hydrofluoric acid in step S100 is not particularly limited, and those skilled in the art may select the reaction mode according to the specific kind of the lithium lanthanum zirconium oxide type solid electrolyte. In some embodiments of the present invention, referring to fig. 2, step S100 may further include:
s130: adding hydrofluoric acid into the molten liquid after the melting treatment, heating for reaction, and standing.
In this step, hydrofluoric acid may be further added to the hydrochloric acid solution obtained in step S120 to form lanthanum fluoride (LaF)3) Precipitating to separate out lanthanum, heating and reacting at 150-250 ℃ for 10-30 minutes, and standing for not less than 0.5 hour, so that lanthanum in the hydrochloric acid solution can fully react with excessive hydrofluoric acid. In some embodiments of the present invention, for the sample of Lithium Lanthanum Zirconium Tantalum Oxygen (LLZTO), hydrofluoric acid may be added after the melting process, and the sample is heated at 200 ℃ for 20 minutes, so that Li in the lithium lanthanum zirconium tantalum oxygen solid electrolyte can be effectively dissolved+、Ta5+。
According to an embodiment of the present invention, a specific method of the filtering treatment in step S100 is not particularly limited, and those skilled in the art may select accordingly according to a specific particle size of the precipitate in the hydrofluoric acid solution. In some embodiments of the present invention, referring to fig. 2, after the step of adding hydrofluoric acid, the step S100 may further include:
s140: filtering to obtain filtrate and residue.
In this step, the solution after the hydrofluoric acid is added in step S130 for reaction may be filtered, and thus, may contain Li+With the presence of LaF3And Na2ZrF6The filter residue is separated. In some embodiments of the invention, for the Lithium Lanthanum Zirconium Tantalum Oxygen (LLZTO) sample, the precipitate can be completely separated using medium speed filter paper, and thus Li can be obtained+、Ta5+With hydrochloric acid and hydrofluoric acid, and in the presence of LaF3And Na2ZrF6And (5) filtering the residue.
In some embodiments of the present invention, referring to fig. 2, in order to obtain more accurate ICP-OES test results, the filtrate after the filtration treatment of step S140 may be formulated as follows:
s150: the filtrate was transferred to a volumetric flask to prepare a solution.
In this step, the filtrate filtered in step S140 was transferred to a 100mL volumetric flask to be constant volume and to form a solution. Specifically, the filtrate after filtration can be directly collected in a 100mL plastic volumetric flask, and then ultrapure water is added, and the volume is determined and shaken up.
S160: and transferring part of the solution into a volumetric flask to prepare a first solution to be detected.
In this step, the volume is again measured from the solution obtained in step S150 in a 10mL to 50mL volumetric flask to obtain a first solution to be measured. Specifically, 10mL to 50mL of plastic volumetric flask can be removed from 100mL of solution with the first constant volume, and ultrapure water is added for second constant volume and shaking up, so that the obtained first solution to be tested is used for the subsequent ICP-OES test.
S200: and carrying out alkali fusion treatment on the filter residue, and adding a hydrochloric acid solution to obtain a solution of the filter residue.
In the step, the filter residue filtered in the step S100 is subjected to alkali fusion treatment, and then hydrochloric acid solution is added to obtain solution of the filter residue, so that LaF existing in the filter residue is treated3And Na2ZrF6Alkali fusion treatment is carried out again to obtain La dissolved in hydrochloric acid solution3+、Zr4+。
According to the embodiment of the present invention, the specific method of the alkali fusion treatment in step S200 is not particularly limited, and those skilled in the art can select the alkali fusion treatment according to the specific composition of the filter residue. In some embodiments of the present invention, referring to fig. 2, step S200 may include:
s210: ashing the filter residue, adding sodium peroxide, and melting.
In this step, the residue obtained in step S140 may be subjected to ashing treatment, and sodium peroxide (Na) may be further added2O2) And melting for 5-20 minutes at 600-700 ℃, thus, the precipitate in the filter residue can be decomposed by high-temperature alkali fusion. In some embodiments of the invention, for the Lithium Lanthanum Zirconium Tantalum Oxygen (LLZTO) sample, the filter paper with filter residue can be ashed to remove the filter paper and only retain the precipitate, and then an excess of Na can be added2O2And performing alkali fusion for 10 minutes at 650 ℃, thus effectively and fully performing alkali fusion decomposition on the filter residue after the lithium lanthanum zirconium tantalum oxygen solid electrolyte is melted.
According to an embodiment of the present invention, the specific manner of adding the hydrochloric acid solution in step S200 is not particularly limited, and those skilled in the art can select the hydrochloric acid solution according to the actual dissolution situation after adding the hydrochloric acid solution. In some embodiments of the present invention, referring to fig. 2, step S200 may further include:
s220: adding ultrapure water and hydrochloric acid into the melt subjected to alkali fusion treatment, extracting, and transferring the extracted solution into a volumetric flask to prepare a second solution to be detected.
In the step, ultrapure water and hydrochloric acid are added into the melt after the alkali fusion treatment in the step S210, then extraction is performed at 150-250 ℃, and the extracted solution is transferred into a 500mL glass volumetric flask for constant volume and shaking up to obtain a second solution to be measured.
S300: and (3) respectively measuring the contents of the inorganic elements in the solutions of the filtrate and the filter residue by using an inductively coupled plasma emission spectrometer.
In this step, the content of the inorganic element was measured by inductively coupled plasma emission spectrometry (ICP-OES) for each of the filtrate of step S100 and the solution of the residue of S200. In some embodiments of the present invention, referring to fig. 2, step S300 may include:
s310: and respectively carrying out inductively coupled plasma emission spectrum test on the first solution to be tested and the second solution to be tested under the detection wavelength corresponding to the inorganic element.
In the step, the first solution to be tested and the second solution to be tested are respectively subjected to ICP-OES test by selecting proper detection wavelength of inorganic elements. According to the embodiment of the present invention, a specific detection wavelength in the ICP-OES test process can be selected by a person skilled in the art according to a specific type of the inorganic element to be detected, specifically, for example, the detection wavelength corresponding to lithium is 670 ± 1nm, the detection wavelength corresponding to lanthanum is 379 ± 1nm, the detection wavelength corresponding to zirconium is 339 ± 1nm, the detection wavelength corresponding to tantalum is 240 ± 1nm, and the like, so that the spectral intensity of lithium, lanthanum, zirconium, or tantalum detected at a suitable detection wavelength is more accurate.
S320: and calculating the sum of the contents of the inorganic elements corresponding to the result of the inductively coupled plasma spectrum test according to the standard curve of the inorganic elements.
In this step, the sum of the contents of the inorganic elements corresponding to the ICP-OES test result of step S310 is calculated from the standard curve of the inorganic elements. Specifically, taking zirconium element as an example, a series of zirconium standard solutions can be prepared in advance, ICP-OES tests are sequentially performed on the zirconium standard solutions with different concentrations under the same detection wavelength, and a standard curve of the zirconium element can be drawn according to the spectral intensity on a spectrogram corresponding to each zirconium concentration; and respectively calculating corresponding zirconium concentration from the standard curve according to the ICP-OES spectral intensity of the first solution to be detected and the second solution to be detected under the same detection wavelength, and then summing the zirconium content in the filtrate and the filter residue to obtain the total zirconium content in the sample of the lithium lanthanum zirconium oxygen type solid electrolyte.
According to the embodiment of the present invention, the method for obtaining the standard curve of the inorganic element is not particularly limited, and the standard solution may be prepared by one inorganic element alone or by mixing a plurality of inorganic elements, and those skilled in the art may design the standard solution according to the types of the inorganic elements mainly existing in the filtrate and the residue during the actual test.
In some embodiments of the present invention, when the inorganic element is at least one selected from the group consisting of lithium, zirconium and tantalum, the standard curve of the inorganic element may be determined by ICP-OES testing a series of mixed standard solutions of the above inorganic elements at different concentrations (specifically, for example, 0, 5, 10, 15, 20 and 25 μ g/ml, etc.). Therefore, for the same standard solution, ICP-OES test can be carried out on different inorganic elements by only changing the detection wavelength, so that the time for obtaining the standard curve can be shortened.
In some embodiments of the invention, where the inorganic element is lanthanum, the standard curve for the inorganic element can be determined by ICP-OES testing a series of standard solutions of the inorganic element at different concentrations (specifically, e.g., 0, 10, 20, 30, 40, and 50 micrograms/ml, etc.). Therefore, for lanthanum element, ICP-OES test is carried out on standard solutions with different concentrations under the same detection wavelength, and a standard curve of lanthanum can be accurately obtained.
According to the embodiment of the invention, in order to more accurately detect the content of the inorganic element in the sample of the lithium lanthanum zirconium oxide type solid electrolyte, the content of the substrate in the prepared standard solution can be consistent with that of the solution to be detected, and specifically, the weight ratio of the inorganic element to the anhydrous sodium carbonate and the borax can be 3: (60-100): (30-50), and the weight ratio of the anhydrous sodium carbonate to the borax can be 2:1, and the like, so that the content of the substrate in the standard solution is similar to that of the solution to be detected, for example, the content of the substrate in the mixed standard solution of lithium, zirconium and tantalum is similar to that of the first solution to be detected, and the content of the substrate in the lanthanum standard solution is similar to that of the second solution to be detected, and therefore, the calculated contents of the inorganic elements in the filtrate and the filter residue can be more accurate.
In summary, according to the embodiments of the present invention, the present invention provides a detection method, in which after a sample of a lithium lanthanum zirconium oxide type solid electrolyte is melted and added with a precipitant hydrofluoric acid, lanthanum can be effectively separated, then a precipitated filter residue is melted, and then the contents of at least one of lithium, lanthanum and zirconium in a filtrate and a solution of the filter residue are respectively detected, so that the contents of lithium, lanthanum and zirconium in the lithium lanthanum zirconium oxide type solid electrolyte sample can be detected by an inductively coupled plasma emission spectrometer, which has higher data accuracy, is simple and convenient to operate, and is faster and more efficient.
The invention will now be described with reference to specific examples, which are intended to be illustrative only and not to be limiting in any way.
Apparatus and materials
The instrument comprises the following steps: iCAP 7400 inductively coupled plasma emission spectrometer, available from Thermo Scientific, usa; smart Plus-N ultra pure water machine, purchased from shanghai likang; muffle furnace, available from Beijing west nit.
Raw materials: the standard solution of the single elements of Li, La, Zr and Ta with the concentration of 1000ug/mL is purchased from the national iron and steel materials testing center iron and steel research institute; anhydrous sodium carbonate-borax mixed flux with high grade purity, wherein the mass ratio of sodium carbonate to borax is 2: 1; sodium peroxide, analytically pure; HCl and HF which are both MOS grade; the water used in the experiment was ultrapure water, and the resistivity was 18.2 M.OMEGA.cm.
Example 1
In this example, Li was detected7-xLa3Zr2-xTaxO12(LLZTO) Li, La, Zr and Ta contents in the samples of solid electrolyte. The specific method comprises the following steps:
(a) weighing 0.1000g of sample in a platinum crucible, adding 3g of anhydrous sodium carbonate-borax (mass ratio of 2:1) mixed flux, uniformly stirring, covering 1g, then putting the platinum crucible in a muffle furnace heated to 900 ℃, and heating to 1000 ℃ for melting for 30 min;
(b) after the platinum crucible in the step (a) is slightly cooled, taking out the platinum crucible from the muffle furnace, putting the platinum crucible into a 50mL polytetrafluoroethylene beaker, adding 25mL of ultrapure water and 10mL of hydrochloric acid, and then putting the mixture on a heating plate at 200 ℃ for extraction;
(c) taking out the platinum crucible, adding 10mL of hydrofluoric acid, continuously heating for 20min, taking out, and standing for 2 hours;
(d) filtering the solution after standing through medium-speed filter paper to a 100mL plastic volumetric flask, and performing constant volume and shaking up;
(e) transferring 10mL of the solution from a 100mL plastic volumetric flask to another clean 50mL plastic volumetric flask, and performing constant volume and shaking up to obtain a first solution to be detected;
(f) transferring the filter residue filtered in the step (d) and medium-speed filter paper to a high-aluminum crucible, gradually heating for ashing, adding 1g of sodium peroxide, uniformly stirring, and melting at 650 ℃ for 10 min;
(g) taking out the high-alumina crucible in the step (f), cooling the high-alumina crucible slightly, putting the high-alumina crucible into a 50mL polytetrafluoroethylene beaker, adding 25mL of ultrapure water and 10mL of hydrochloric acid, slightly heating the high-alumina crucible to extract after the violent reaction stops, transferring the extracted solution into a 500mL glass volumetric flask, and performing constant volume and shaking uniformly to obtain a second solution to be detected;
(h) weighing 6 parts of anhydrous sodium carbonate-borax (weight ratio is 2:1) mixed solvent, adding 0.8g of each part into a polytetrafluoroethylene beaker, adding a small amount of water for dissolution, adding 5mL of hydrochloric acid, transferring into a 100mL plastic volumetric flask, and transferring 0mL, 0.5mL, 1.0mL, 1.5mL, 2.0mL and 2.5mL of lithium, zirconium and tantalum standard solutions into the plastic volumetric flask respectively to prepare 0, 5, 10, 15, 20 and 25ug/mL of lithium, zirconium and tantalum mixed standard solution; sequentially carrying out ICP-OES test on a series of mixed standard solutions, wherein the detection wavelength is 670.784nm when testing lithium, 339.198nm when testing zirconium and 240.063nm when testing tantalum, and respective standard curves of lithium, zirconium and tantalum can be respectively obtained;
(i) weighing 6 parts of sodium peroxide solvent, putting 0.2g of each part into a polytetrafluoroethylene beaker, adding a small amount of water for dissolution, adding 2mL of hydrochloric acid, transferring into a 100mL glass volumetric flask, and then respectively transferring 0mL, 1mL, 2mL, 3mL, 4mL and 5mL of lanthanum standard solution into the glass volumetric flask to prepare 0, 10, 20, 30, 40 and 50ug/mL of lanthanum standard solution; sequentially carrying out ICP-OES test on a series of standard solutions, selecting 379.478nm as the detection wavelength when testing lanthanum, and obtaining a standard curve of lanthanum;
(j) respectively carrying out ICP-OES test on the first solution to be tested and the second solution to be tested obtained in the steps (e) and (g), wherein the detection wavelength is 670.784nm when testing lithium, 379.478nm when testing lanthanum, 339.198nm when testing zirconium and 240.063nm when testing tantalum, and ICP-OES spectral information of lithium, lanthanum, zirconium and tantalum in filtrate and filter residue can be obtained;
(k) and (e) calculating the respective contents of lithium, lanthanum, zirconium and tantalum in the filtrate and the filter residue according to the standard curves of lithium, lanthanum, zirconium and tantalum in the steps (h) and (i), and finally adding the contents of the filtrate and the filter residue to obtain the contents of Li, La, Zr and Ta in the sample of the LLZTO solid electrolyte.
The operating parameters when an ICP-OES instrument was used in the steps (h), (i), and (j) are shown in Table 1.
TABLE 1
| Operating parameters | Numerical value | Operating parameters | Numerical value |
| Plasma powerratio/W | 1150 | Height/mm of vertical observation | 12 |
| Atomizer flow/(L/min) | 0.5 | Auxiliary air flow/(L/min) | 0.5 |
| Number of readings/times | 3 | Analysis of Pump speed/rpm | 50 |
The calculation results of the four inorganic elements of this example are shown in Table 2, and from Table 2, it can be seen that Li and Ta are mainly distributed in the filtrate, while La is substantially present in the precipitate, and only Zr is largely distributed in both the filtrate and the precipitate, so that the content of each inorganic element in LLZTO is based on the total content of the filtrate and the precipitate.
TABLE 2
| Element(s) | Wavelength nm | Regression coefficient R2 | The filtrate% | RSD％ | Filter residue% | RSD％ | The total amount of the measurement is w/w% |
| Li | 670.784 | 0.999889 | 5.23 | 0.36 | 0.05 | 1.79 | 5.28 |
| La | 379.478 | 0.999893 | 0.24 | 0.52 | 39.27 | 1.23 | 39.51 |
| Zr | 339.198 | 0.999809 | 7.37 | 0.40 | 4.36 | 0.25 | 11.73 |
| Ta | 240.063 | 0.999946 | 10.99 | 0.68 | 0.12 | 0.68 | 11.11 |
In addition, as can be seen from table 2, the test Relative Standard Deviation (RSD) of the filtrate and the residue was less than 2%, indicating that the stability of the ICP-OES test results was high; and the molar ratio of Li, La, Zr and Ta is substantially in accordance with Li7-xLa3Zr2-xTaxO12The molar ratio of the inorganic elements in the alloy is only slightly higher than that of Li, which is related to Li7-xLa3Zr2-xTaxO12The excess amount is 5-20% in order to compensate for high-temperature volatilization of Li in the preparation process.
In the description of the present invention, it is to be understood that the terms "first", "second" and the like are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implying any number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present invention, "a plurality" means at least two, e.g., two, three, etc., unless specifically limited otherwise.
In the description herein, references to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, various embodiments or examples and features of different embodiments or examples described in this specification can be combined and combined by one skilled in the art without contradiction.
Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, modifications, substitutions and alterations can be made to the above embodiments by those of ordinary skill in the art within the scope of the present invention.
Claims (10)
1. A method of detecting the content of an inorganic element in a sample of a lithium lanthanum zirconium oxygen type solid state electrolyte, wherein the inorganic element comprises at least one of lithium, lanthanum, zirconium and tantalum, the method comprising:
(1) melting the sample, adding hydrofluoric acid, and filtering to obtain filtrate and filter residue, wherein the melting treatment comprises:
(1-1) mixing the sample with anhydrous sodium carbonate and borax, heating to 900-1100 ℃, melting for 15-60 minutes, and cooling;
(1-2) adding ultrapure water and hydrochloric acid into the cooled molten liquid, and extracting at 150-250 ℃;
(2) and carrying out alkali fusion treatment on the filter residue, and adding a hydrochloric acid solution to obtain a solution of the filter residue, wherein the alkali fusion treatment comprises the following steps:
(2-1) ashing the filter residue, adding sodium peroxide, and melting at 600-700 ℃ for 5-20 minutes;
(3) utilizing an inductively coupled plasma emission spectrometer to respectively carry out the content measurement of the inorganic elements on the filtrate and the solution of the filter residue, wherein the content measurement of the inorganic elements comprises the following steps:
and respectively testing the content of the inorganic element in the filtrate and the filter residue, and adding the content of the inorganic element in the filtrate and the filter residue to obtain the content of the inorganic element in the sample of the lithium lanthanum zirconium oxide type solid electrolyte.
2. The method of claim 1, wherein the lithium lanthanum zirconium oxide type solid electrolyte is a lithium lanthanum zirconium tantalum oxide solid electrolyte and the inorganic element comprises at least one of lithium, lanthanum, zirconium, and tantalum.
3. The method of claim 1, wherein the weight ratio of the sample to the anhydrous sodium carbonate and the borax is 3: (60-100): (30-50), wherein the weight ratio of the anhydrous sodium carbonate to the borax is 2: 1.
4. the method according to claim 1 or 2, wherein the step of adding hydrofluoric acid comprises:
(1-3) adding the hydrofluoric acid into the melt after the melting treatment, heating and reacting for 10-30 minutes at 150-250 ℃, and standing for not less than 0.5 hour.
5. The method according to claim 1 or 2, wherein the step of filtering comprises:
(1-4) filtering to obtain filtrate and filter residue;
(1-5) transferring the filtrate to a 100mL volumetric flask to fix the volume and form a solution;
(1-6) removing 10mL of the solution to a 50mL volumetric flask to obtain a first solution to be tested.
6. The method of claim 5, wherein the step of adding a hydrochloric acid solution comprises:
and (2-2) adding ultrapure water and hydrochloric acid into the melt subjected to alkali fusion treatment, extracting at 150-250 ℃, and transferring the extracted solution into a 500mL volumetric flask for constant volume to obtain a second solution to be measured.
7. The method according to claim 6, wherein the step of determining the content of the inorganic element comprises:
(3-1) respectively carrying out inductively coupled plasma emission spectrum test on the first solution to be tested and the second solution to be tested under the detection wavelength corresponding to the inorganic element;
and (3-2) calculating the sum of the contents of the inorganic elements corresponding to the result of the inductively coupled plasma spectrum test according to the standard curve of the inorganic elements.
8. The method of claim 7,
when the inorganic element is lithium, the detection wavelength is 670 +/-1 nm;
when the inorganic element is lanthanum, the detection wavelength is 379 +/-1 nm;
when the inorganic element is zirconium, the detection wavelength is 339 +/-1 nm;
and when the inorganic element is tantalum, the detection wavelength is 240 +/-1 nm.
9. The method according to claim 7, wherein when the inorganic element is at least one selected from the group consisting of lithium, zirconium and tantalum, the standard curve of the inorganic element is determined by testing a series of mixed standard solutions of the inorganic element at different concentrations by an inductively coupled plasma emission spectrometer.
10. The method of claim 7, wherein the standard curve for the inorganic element is determined by inductively coupled plasma emission spectroscopy testing a series of standard solutions of the inorganic element at different concentrations when the inorganic element is lanthanum.
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