A method for testing the content of main substance elements of lithium sulfide
By oxidizing lithium sulfide at high temperature under an inert atmosphere and then digesting it, and then determining lithium and sulfur elements by spectrometry, the problems of large testing errors and operational hazards of lithium sulfide are solved, and the simultaneous determination of the lithium-sulfur molar ratio is realized, which is suitable for batch analysis and materials research and development.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- HEFEI INSEA NEW MATERIALS TECHNOLOGY CO LTD
- Filing Date
- 2026-03-20
- Publication Date
- 2026-06-12
AI Technical Summary
Existing technologies for testing lithium sulfide elements have large errors, are volatile, and are unsafe to operate. They also cannot simultaneously determine the lithium-sulfur molar ratio, thus failing to meet the precise control requirements of materials research and development.
A lithium sulfide sample was weighed and mixed with an alkaline substance under an inert atmosphere. The mixture was then oxidized at high temperature to produce lithium sulfate. After digestion, the lithium and sulfur content was determined by spectrometry. The concentrations of lithium and sulfur were determined by spectrometry, and the lithium-sulfur molar ratio was calculated.
It enables accurate determination of lithium sulfide, simplifies the operation process, improves safety and testing efficiency, and can simultaneously obtain the content and molar ratio of lithium and sulfur, supporting material quality control.
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Figure CN122192891A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of analytical chemistry, specifically to a method for testing the content of lithium sulfide as a main material element. Background Technology
[0002] Lithium sulfide is a substance that readily absorbs moisture from the air and is highly susceptible to hydrolysis. Therefore, it is unstable in air or water and will gradually decompose to produce hydrogen sulfide gas, which then volatilizes, leading to lower-than-expected sulfur content readings. Furthermore, the acids used in sample preparation for elemental analysis can also exacerbate the sulfur content degradation. 2- The volatilization of ions. These issues lead to significant errors in the testing of lithium sulfide's main constituent elements. The usual method involves adding an oxidizing agent, such as hydrogen peroxide, nitric acid, or perchloric acid, during sample dissolution to oxidize the lithium sulfide. After digestion and volume adjustment, emission spectroscopy is then used for testing. To avoid an overly vigorous oxidation reaction, lithium sulfide is first dissolved in water before adding the oxidizing agent. Lithium sulfide is highly hygroscopic and hydrolyzes readily, decomposing during routine sample preparation to produce hydrogen sulfide gas, which then volatilizes. This results in a systematically low sulfur content reading, endangering operator health and polluting the environment.
[0003] The method described in Chinese invention patent CN119354796A involves oxidizing a lithium sulfide sample at high temperature in an oxygen atmosphere, dissolving it in hot water and hydrochloric acid, reacting it with barium chloride to form barium sulfate precipitate, determining the mass of the barium sulfate precipitate by gravimetric analysis, and further calculating the sulfur content in the sample to infer the lithium sulfide content. While this method partially avoids initial hydrolysis, the process is complex (precipitation, filtration, ignition), inefficient, and prone to sample loss due to improper operation, leading to lower test results. Furthermore, it only measures sulfur content and cannot simultaneously obtain lithium content and the lithium-sulfur molar ratio, failing to meet the precise control requirements of stoichiometry in materials research.
[0004] Therefore, there is an urgent need to develop a test method that can quickly and safely determine the lithium and sulfur content in lithium sulfide. Summary of the Invention
[0005] Based on the above analysis, the present invention aims to provide a method for testing the main elemental content of lithium sulfide. This method employs high-temperature oxidation to react lithium sulfide with an oxidizing gas to generate lithium sulfate. The lithium sulfate is then digested and diluted to a fixed volume to obtain a sample test solution. Finally, a spectrometer is used to test the lithium and sulfur content in the sample solution. This method addresses the problems of sulfur volatility, inaccurate testing, hazardous operation, and the inability to simultaneously determine the lithium-sulfur molar ratio in existing lithium sulfide elemental analysis methods.
[0006] The objective of this invention is mainly achieved through the following technical solutions:
[0007] This invention provides a method for testing the main element content of lithium sulfide, comprising the following steps:
[0008] S1. Sample preparation and weighing: Under an inert atmosphere, weigh the lithium sulfide sample and alkaline substance and mix them; weigh using an analytical balance and place the mixture in a beaker after weighing.
[0009] S2, High-temperature oxidation: The mixture obtained in step S1 is transferred to an atmosphere furnace and subjected to a high-temperature oxidation reaction under an oxidizing atmosphere to convert lithium sulfide into lithium sulfate.
[0010] S3. Digestion and volume adjustment: After wetting the product oxidized in step S2 with water, acid is added for digestion to obtain a clear solution. Then, the solution is adjusted to volume and diluted to prepare a test solution.
[0011] S4. Spectroscopic Testing and Calculation: The concentrations of lithium and sulfur in the test solution obtained in step S3 are determined by spectroscopic method. Based on the sample weight, the final volume, and the dilution factor, the lithium content, sulfur content, main substance content, and lithium-sulfur molar ratio in the lithium sulfide sample are calculated.
[0012] Further, in step S1, the inert atmosphere is one or more of nitrogen, argon, helium, and neon; the water content and oxygen content in the inert atmosphere are both ≤500.0 ppm, preferably both ≤100.0 ppm, and most preferably both ≤10.0 ppm. The lower water and oxygen content can maintain the stability of lithium sulfide solid and prevent lithium sulfide from hydrolyzing or volatilizing.
[0013] Further, in step S1, the alkaline substance is a metal hydroxide, selected from one or more of sodium hydroxide, potassium hydroxide, magnesium hydroxide, iron hydroxide, and cerium hydroxide; the purpose of adding the alkaline substance is to prevent the sulfur dioxide produced by the oxidation of lithium sulfide from volatilizing and causing loss; since sulfur dioxide gas may be produced during the oxidation of lithium sulfide sample by oxygen, adding the alkaline substance can convert the produced sulfur dioxide gas into sulfite, and then into sulfate without volatilization, thus avoiding errors in sulfur content testing.
[0014] Further, in step S1, the molar ratio of the alkaline substance to the lithium sulfide sample is 1.0 to 10.0:1.0, and the content of impurity elements (lithium + calcium + magnesium + sodium + potassium + iron + manganese + copper + zinc) in the alkaline substance is ≤200 ppm.
[0015] Further, in step S2, the oxidizing atmosphere is one or more of oxygen or ozone, and the water content in the oxidizing atmosphere is ≤10 ppm; the reaction temperature of the high-temperature oxidation reaction is 150℃~550℃, and the reaction time is 1.0~8.0h.
[0016] Further, in step S3, the acid is one or more of hydrochloric acid, nitric acid, or perchloric acid, and its solute mass fraction is 5.0% to 40.0%. The content of impurity elements (lithium + calcium + magnesium + sodium + potassium + iron + manganese + copper + zinc) in the acid is ≤200ppm.
[0017] Further, in step S4, the spectroscopic method is one or more of inductively coupled plasma atomic absorption spectrometry (ICP-AES) and flame atomic absorption spectrometry (FAAS). The advantages of ICP-AES are high atomic excitation energy and the ability to simultaneously and quickly detect the content of multiple elements, but it is easily affected by background interference and thus produces errors. Flame atomic absorption spectrometry has lower excitation energy and requires the use of hollow cathode lamps with absorption wavelengths corresponding to the elements. Therefore, only one element can be measured at a time, and the number of detectable elements is relatively small. However, precisely because the detection wavelength is single, the background interference is small, and the test results are more accurate. The wavelength for testing lithium can be 670.78 nm and the wavelength for sulfur can be 180.73 nm using the ICP-AES.
[0018] Furthermore, in step S3, the digestion method is selected from one or more of thermal digestion and microwave digestion.
[0019] Furthermore, in step S3, the concentration range of lithium and sulfur in the test solution is 1.0 ppm to 50.0 ppm. The upper limit of this content depends on the detection limit of the testing instrument; the lower limit is to prevent excessive detection error by considering that the content of lithium and sulfur in the solution is too low.
[0020] Furthermore, in step S1, the sample weight of the lithium sulfide sample is 0.0010 g to 2.000 g, preferably 0.0100 g to 1.000 g, and most preferably 0.1000 g to 0.5000 g. If the sample weight is too small, the weighing error of the analytical balance will be large; if the sample weight is too large, the dilution factor in the later stage will be too large, which will also easily lead to errors.
[0021] Furthermore, in step S4, the lithium content W Li Or sulfur content W S The calculation formula is as follows:
[0022]
[0023]
[0024] Among them, C Li Indicates the lithium content in the sample, in ppm; C S This indicates the sulfur content in the sample to be tested, in ppm. The dilution factor after the solution is brought to volume has no unit; V represents the volume after the solution is brought to volume in mL; M represents the sample weight in g.
[0025] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:
[0026] (1) First, the weighing and mixing of the sample are completed under an inert atmosphere to avoid hydrolysis and hydrogen sulfide volatilization of lithium sulfide when it comes into contact with air or water in the early stage of sample preparation. Second, since lithium sulfide generally contains a small amount of impurities such as lithium polysulfides and thiosulfates, direct high-temperature treatment will cause this part of the sulfur to volatilize in the form of sulfur dioxide, which will bring test errors. In the subsequent high-temperature oxidation process, an alkaline substance is added. This alkaline substance can effectively absorb and fix the sulfur dioxide gas generated by impurities such as water, lithium polysulfides, and thiosulfates that may exist in the sample at high temperature, and convert it into non-volatile sulfite, and then into more stable sulfate, thereby avoiding test errors caused by sulfur escaping in the gas phase and improving the accuracy of the analysis results.
[0027] (2) The method of using spectroscopic analysis to analyze the lithium and sulfur content in lithium sulfide samples can achieve simultaneous and rapid determination of lithium and sulfur. Compared with the cumbersome and time-consuming gravimetric method (such as barium sulfate precipitation method) in the background technology, the method of the present invention simplifies the operation and is more suitable for batch analysis. At the same time, the method can obtain the lithium content and sulfur content at the same time, so as to accurately calculate the main substance content of the sample and the key lithium-sulfur molar ratio, providing data support for the quality control and performance research of materials. The method uses standard solutions of lithium and sulfur, whose composition is close to that of the sample solution to be tested, reducing the influence of background error.
[0028] (3) The present invention uses high-temperature oxidation to convert lithium sulfide into air-stable lithium sulfate, which solves the problem of easy hydrolysis and volatilization, and allows subsequent processing to be carried out in a normal environment. The equipment scheme of directly connecting the glove box to the atmosphere furnace means that the sample pretreatment process does not need to come into contact with air, which not only completely avoids lithium sulfide from contacting moisture in the atmosphere, but also effectively isolates the operators from hydrogen sulfide gas, improves the safety of the experimental process, and reduces environmental pollution.
[0029] In this invention, the above-mentioned technical solutions can be combined with each other to achieve more preferred combinations. Other features and advantages of this invention will be set forth in the following description, and some advantages may become apparent from the description or be learned by practicing the invention. The objectives and other advantages of this invention can be realized and obtained through the specific details pointed out in the embodiments of the description. Attached Figure Description
[0030] Figure 1 This is a process flow diagram of Embodiment 1 of the present invention. Detailed Implementation
[0031] The present application will now be described in further detail with reference to the accompanying drawings. It should be noted that the following specific embodiments are only used to further illustrate the present application and should not be construed as limiting the scope of protection of the present application. Those skilled in the art can make some non-essential improvements and adjustments to the present application based on the above application content.
[0032] Example 1
[0033] a. In a glove box with an oxygen content ≤10.0ppm, weigh 0.2000g±0.0010g of commercially available lithium sulfide sample (labeled lithium sulfide mass fraction ≥99.9%) into a 100mL beaker using an analytical balance (accuracy 0.0001g) and then weigh 0.9800g±0.0010g of potassium hydroxide into the same beaker according to a molar ratio of alkaline substance to lithium sulfide of 4:1.
[0034] b. The glove box transition chamber is connected to an atmosphere furnace pre-purified with inert protective gas. The weighed sample is transferred directly into the atmosphere furnace without passing through the atmospheric environment, and the chamber door is closed. Oxygen (99.999% purity, water content ≤10ppm after dehydration) that has been dehydrated by molecular sieves is introduced into the atmosphere furnace at a flow rate of 30.0L / h. The high-temperature reaction temperature is 400℃, and the reaction time is 4.0h. After the reaction is completed and cooled to room temperature, the sample is removed from the atmosphere furnace for later use.
[0035] c. After soaking the sample in 10.0 mL of pure water, add 25.0 mL of nitric acid aqueous solution with a solute mass fraction of 30%; heat to 90℃ for 2.0 h for high-temperature digestion; after cooling, transfer to a 100 mL volumetric flask and dilute to volume with water; use a 1.0 mL pipette to take 1.0 mL of the diluted sample and add it to a 100 mL volumetric flask, then dilute to volume again with water to obtain a 100-fold diluted sample for later use; in addition, during the digestion of the sample, use a hydrogen sulfide detector to measure the volatile gas composition at 20 cm directly above the beaker. No hydrogen sulfide gas was detected, indicating that the sample after high-temperature treatment contains sulfur dioxide (S). 2- There are very few ions; it has been completely converted into high-valence sulfur.
[0036] Further, repeat steps a and b of the sample preparation process. Add 10 mL of a 10% hydrochloric acid aqueous solution to the treated sample, dissolve it in 50 mL of water, and then use 0.005 mol·L⁻¹ water. -1 Titration with potassium permanganate aqueous solution resulted in the consumption of only 0.25 mL of potassium permanganate solution at the titration endpoint. This indicates that very little of the oxidizable substance remained in the sample after high-temperature treatment, suggesting that S... 2- The ions are almost completely converted into sulfate ions, or in other words, only a very small amount of sulfite and thiosulfate ions are present.
[0037] d. Using the standard curve method, lithium and sulfur standard solutions were mixed to prepare five mixed standard solutions of different concentrations. The concentrations of lithium and sulfur in the five mixed standard solutions are shown in the table below. Using an inductively coupled plasma spectrometer, the response values of lithium and sulfur in the mixed standard solutions were first tested at 670.78 nm and 180.73 nm, respectively, and a standard curve (the relationship between the concentration of the measured element and the instrument response value) was plotted. Then, the sample to be tested was tested, and the content of lithium and sulfur in the sample was calculated based on the standard curve. Finally, the lithium content and sulfur content of the lithium sulfide sample could be calculated according to the formula for calculating lithium and sulfur content, and then the lithium-sulfur molar ratio of the sample could be calculated.
[0038] Mixed Standard 1 Mixed Standard 2 Mixed Standard 3 Mixed Standard 4 Mixed Standard 5 Lithium content / ppm 2 4 6 8 10 Sulfur content / ppm 5 10 15 20 25
[0039] Example 2
[0040] Example 2 follows the same steps as Example 1, except that sodium hydroxide is used as an alkaline additive instead of potassium hydroxide.
[0041] Example 3
[0042] Example 3 follows the same steps as Example 1, except that magnesium hydroxide is used as an alkaline additive instead of potassium hydroxide.
[0043] Example 4
[0044] Example 4 follows the same steps as Example 1, except that cerium hydroxide is used as an alkaline additive instead of potassium hydroxide.
[0045] Comparing Examples 1-4, sodium hydroxide is slightly less alkaline than potassium hydroxide, but the molar ratio of alkaline substances added is sufficient to inhibit sulfur volatilization. Magnesium hydroxide and cerium hydroxide are weak bases, and the effect is slightly worse with the same amount added.
[0046] Example 5
[0047] Example 5 follows the same steps as Example 1, except that the molar ratio of potassium hydroxide added is changed to 1:1.
[0048] Example 6
[0049] Example 6 follows the same steps as Example 1, except that the molar ratio of potassium hydroxide added is changed to 1:6.
[0050] Example 7
[0051] Example 7 follows the same steps as Example 1, except that the molar ratio of potassium hydroxide added is changed to 1:10.
[0052] Comparative Example 1
[0053] Comparative Example 1 follows the same steps as Example 1, except that no alkaline substance was added in step a.
[0054] Comparative Example 2
[0055] Comparative Example 2 followed the same steps as Example 1, except that the molar ratio of potassium hydroxide added was changed to 0.2:1.
[0056] Comparative Example 3
[0057] Comparative Example 3 followed the same steps as Example 1, except that the molar ratio of potassium hydroxide added was changed to 15:1.
[0058] Comparing Examples 1 and 5-7 with Comparative Examples 1-3, it can be found that the sulfur content test results are low when no alkaline substance is added. As the amount of alkaline substance added increases, the relative recovery rate of sulfur also increases. In particular, when the molar ratio of alkaline substance added reaches 1:1 or higher, it has a significant effect on inhibiting sulfur volatilization. However, the higher the molar ratio added, the more the mass of alkaline substance added is compared with the sample amount, which also requires an increase in the amount of acid used for subsequent digestion, thus increasing the reagent consumption.
[0059] Example 8
[0060] Example 8 is the same as Example 1 in terms of steps, except that in step b, the temperature of the high-temperature treatment is adjusted from 400°C to 150°C.
[0061] Example 9
[0062] Example 9 is the same as Example 1 in terms of steps, except that in step b, the temperature of the high-temperature treatment is adjusted from 400°C to 250°C.
[0063] Example 10
[0064] Example 10 follows the same steps as Example 1, except that in step b, the high-temperature treatment temperature is adjusted from 400°C to 350°C.
[0065] Example 11
[0066] Example 11 is the same as Example 1 in terms of steps, except that in step b, the high-temperature treatment temperature is adjusted from 400°C to 550°C.
[0067] Comparative Example 4
[0068] Comparative Example 4 follows the same steps as Example 1, except that in step b, the high-temperature treatment temperature is adjusted from 400°C to 100°C.
[0069] Comparative Example 5
[0070] Comparative Example 5 follows the same steps as Example 1, except that in step b, the high-temperature treatment temperature is adjusted from 400°C to 650°C.
[0071] Comparative Example 6
[0072] Comparative Example 6 did not subject the lithium sulfide sample to high-temperature oxidation treatment, but instead directly used the traditional method of dissolving and acidifying it with water.
[0073] Comparing Examples 1, 8-11, and Comparative Examples 4-6, it can be observed that as the high-temperature treatment temperature increases, the measured values of lithium and sulfur first increase and then decrease; when the high-temperature treatment temperature is too low, the reaction temperature between the sample and oxygen is insufficient to dissolve sulfur. 2- The sulfur is oxidized to sulfate. Titration with acidic potassium permanganate solution revealed that Comparative Example 4 and Comparative Example 6 samples contained more reducing substances. However, no hydrogen sulfide gas was detected during the digestion process, indicating that sulfite, thiosulfate, and other sulfides were generated after high-temperature treatment. These substances decompose and volatilize during acid digestion, resulting in the loss of sulfur. When the high-temperature treatment temperature is too high, the measured values of lithium and sulfur also decrease. This is because at high temperatures, the volatility of lithium increases, and the decomposition tendency of sulfate and sulfite increases, weakening the effect of alkaline substances in inhibiting sulfur volatilization.
[0074] Comparative Example 7
[0075] Comparative Example 7 follows the same steps as Example 1, but the water content in the inert gas used for high-temperature treatment is 40 ppm to 60 ppm.
[0076] Comparative Example 8
[0077] Comparative Example 8 follows the same steps as Example 1, but the water content in the inert gas used for high-temperature treatment is 100ppm~120ppm.
[0078] Comparative Example 9
[0079] Comparative Example 9 follows the same steps as Example 1, but the water content in the inert gas used for high-temperature treatment is 450ppm~550ppm.
[0080] Comparing Example 1 with Comparative Examples 6-9, it can be observed that as the water content in the inert gas increases, the measured value of sulfur gradually decreases. This is because S... 2- It is extremely easy to hydrolyze when it comes into contact with water, and in addition, the high temperature environment causes a large amount of hydrogen sulfide gas to volatilize, resulting in a significant loss of sulfur.
[0081] Comparative Example 10
[0082] Comparative Example 10: Under normal atmospheric conditions, lithium sulfide samples were treated with water and hydrogen peroxide, and hydrogen peroxide was added for oxidation.
[0083] In a fume hood, weigh 0.2000 g ± 0.0100 g of commercially available lithium sulfide sample (labeled lithium sulfide mass fraction of 99.9%) into a 100 mL beaker using an analytical balance (accuracy 0.0001 g).
[0084] In a fume hood, after soaking the sample in 10.0 mL of pure water, 25 mL of 28% hydrogen peroxide was gradually added dropwise. After the reaction continued until no more bubbles were generated, 25 mL of 30% nitric acid solution was added, and the mixture was heated to 90°C for 2.0 h for high-temperature digestion. After the sample cooled, it was transferred to a 100 mL volumetric flask and diluted to volume with water. Using a 1.0 mL pipette, 1.0 mL of the diluted sample was added to a 100 mL volumetric flask and diluted to volume with water to obtain a 100-fold diluted sample for testing. The method described in Example 1 was used to measure the volatile gases, and it was found that the generated hydrogen sulfide gas exceeded the instrument's detection limit, and the operator needed to wear a gas mask to operate the device.
[0085] The sample was tested using an inductively coupled plasma spectrometer, and the testing process was the same as in Example 1. Finally, the lithium content and sulfur content of the lithium sulfide sample were calculated according to the formula for calculating lithium content and sulfur content, and then the lithium-sulfur molar ratio of the sample was calculated.
[0086] The method in Comparative Example 10 not only leads to sulfur volatilization, but also requires high levels of personnel safety protection during the testing process and causes significant environmental pollution.
[0087] Comparative Example 11
[0088] In a glove box with a water oxygen content ≤10.0ppm, weigh 0.2000g±0.0100g of commercially available lithium sulfide sample (labeled lithium sulfide mass fraction of 99.9%) into a 100mL beaker using an analytical balance (accuracy 0.0001g).
[0089] The glove box transition chamber is connected to an atmosphere furnace pre-purified with inert protective gas. The weighed sample is transferred directly into the atmosphere furnace without passing through the atmospheric environment, and the chamber door is closed. Oxygen (99.999% purity, water content ≤10ppm after dehydration) that has been dehydrated by molecular sieves is introduced into the atmosphere furnace at a flow rate of 30.0 L / h. The high-temperature reaction temperature is 400℃, and the reaction time is 4.0 h. After the reaction is completed and cooled to room temperature, the sample is removed from the atmosphere furnace for later use.
[0090] Dissolve the sample in 300 mL of hot water until clear; add 2-3 drops of methyl orange indicator (2 g / L) to the solution, neutralize with 6 mol / L hydrochloric acid solution in excess, so that the pH of the solution is less than 3.1; heat the solution to boiling, and slowly add 10 mL of barium chloride solution (100 g / L) while stirring constantly, and maintain a gentle boil for about 1 hour, so that the final volume of the solution is 100 mL.
[0091] After cooling and standing overnight, the solution was filtered through dense, ashless, quantitative, slow-speed filter paper and washed with hot water until no chloride ions were found (tested with 10 g / L silver nitrate solution to ensure no turbidity). The filter paper with precipitate was transferred to a porcelain crucible of known mass, ashed at low temperature, and then ignited in a high-temperature furnace at 800°C for 20 minutes. The crucible was then removed, slightly cooled in air, and placed in a desiccator to cool to room temperature before weighing the barium sulfate. Based on the mass of barium sulfate, the sulfur content in the lithium sulfide sample was calculated.
[0092] The gravimetric method described in CN119354796A for testing the sulfur content of lithium sulfide samples is complex, inefficient, and improper operation may result in sample loss, leading to lower test results.
[0093] The test results from Examples 1-11 and Comparative Examples 1-11 are summarized in Table 1 below.
[0094] Example Lithium content / % Sulfur content / % Lithium sulfide content / % Lithium / Sulfur Ratio Lithium relative recovery rate / % Relative sulfur recovery rate / % Potassium permanganate titration volume / mL Peak hydrogen sulfide release concentration / ppm Example 1 30.20% 69.76% 99.96 1.9996 100.00 100.00 0.25 Not detected Example 2 30.19% 69.74% 99.93 1.9995 99.97 99.97 0.45 Not detected Example 3 30.15% 69.62% 99.77 2.0003 99.83 99.80 0.85 Not detected Example 4 30.14% 69.60% 99.74 2.0002 99.80 99.77 0.60 Not detected Example 5 30.12% 69.58% 99.70 1.9995 99.74 99.74 0.30 Not detected Example 6 30.19% 69.74% 99.93 1.9995 99.97 99.97 0.25 Not detected Example 7 30.19% 69.73% 99.92 1.9998 99.97 99.96 0.25 Not detected Comparative Example 1 30.10% 40.63% 70.73 3.4219 99.67 58.24 1.00 Not detected Comparative Example 2 30.11% 52.63% 82.74 2.6425 99.70 75.44 0.90 Not detected Comparative Example 3 30.19% 69.73% 99.92 1.9998 99.97 99.96 0.25 Not detected Example 8 30.13% 68.20% 98.33 2.0406 99.77 97.76 3.24 Not detected Example 9 30.13% 69.39% 99.52 2.0056 99.77 99.47 1.25 Not detected Example 10 30.16% 69.70% 99.86 1.9987 99.87 99.91 0.60 Not detected Example 11 30.04% 69.68% 99.72 1.9913 99.47 99.89 0.25 Not detected Comparative Example 4 30.18% 60.17% 90.35 2.3168 99.93 86.25 10.91 Not detected Comparative Example 5 29.81% 68.36% 98.17 2.0142 98.71 97.99 0.25 Not detected Comparative Example 6 30.11% 58.33% 88.44 2.3843 99.70 83.62 15.53 Not detected Comparative Example 7 30.16% 63.39% 93.55 2.1976 99.87 90.87 0.55 Not detected Comparative Example 8 30.15% 56.87% 87.02 2.4488 99.83 81.52 0.60 Not detected Comparative Example 9 30.15% 39.46% 69.61 3.5292 99.83 56.57 0.85 Not detected Comparative Example 10 30.10% 43.11% 73.21 3.2250 99.67 61.80 —— ≥100 (overrange) Comparative Example 11 —— 69.44% 99.50% —— —— 99.54% 3.24 39 Table 1
[0095] Based on Table 1 above, as well as the various embodiments and comparative examples, the following conclusions can be drawn:
[0096] The test results show that the method described in this invention can simultaneously determine the lithium and sulfur content in lithium sulfide samples and further calculate the lithium-sulfur molar ratio in the samples. By adding alkaline substances and oxidizing the samples at high temperatures, the accuracy of sulfur element testing can be improved compared with traditional water-soluble and acid-treated methods. Compared with existing methods, it is simpler and more efficient, the test results are more accurate, and it can determine the content of both lithium and sulfur elements.
[0097] The embodiments described above are merely examples of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention.
Claims
1. A method for testing the content of lithium sulfide main element, characterized in that, Includes the following steps: S1. Processing and weighing: Under an inert atmosphere, weigh the lithium sulfide sample and the alkaline substance and mix them. S2, High-temperature oxidation: The mixture obtained in step S1 is transferred to an atmosphere furnace and subjected to a high-temperature oxidation reaction under an oxidizing atmosphere to convert lithium sulfide into lithium sulfate. S3. Digestion and volume adjustment: After wetting the product oxidized in step S2 with water, acid is added for digestion to obtain a clear solution. Then, the solution is adjusted to volume and diluted to prepare a test solution. S4. Spectroscopic Testing and Calculation: The concentrations of lithium and sulfur in the test solution obtained in step S3 are determined by spectroscopic method. Based on the sample weight, the final volume, and the dilution factor, the lithium content, sulfur content, main substance content, and lithium-sulfur molar ratio in the lithium sulfide sample are calculated.
2. The test method according to claim 1, characterized in that, In step S1, the inert atmosphere is one or more of nitrogen, argon, helium, and neon; the water content and oxygen content in the inert atmosphere are both ≤500.0 ppm.
3. The test method according to claim 1, characterized in that, In step S1, the alkaline substance is a metal hydroxide, selected from one or more of sodium hydroxide, potassium hydroxide, magnesium hydroxide, iron hydroxide, and cerium hydroxide.
4. The test method according to claim 1, characterized in that, In step S1, the molar ratio of the alkaline substance to the lithium sulfide sample is 1.0 to 10.0:1.0, and the content of impurity elements in the alkaline substance is ≤200 ppm.
5. The test method according to claim 1, characterized in that, In step S2, the oxidizing atmosphere is oxygen or ozone, and the water content in the oxidizing atmosphere is ≤10 ppm; the reaction temperature of the high-temperature oxidation reaction is 150℃~550℃, and the reaction time is 1.0~8.0 h.
6. The test method according to claim 1, characterized in that, In step S3, the acid is one or more of hydrochloric acid, nitric acid, or perchloric acid, and its solute mass fraction is 5.0% to 40.0%. The content of impurity elements in the acid is ≤200ppm.
7. The test method according to claim 1, characterized in that, In step S4, the spectroscopic method is one or more of inductively coupled plasma atomic absorption spectrometry and flame atomic absorption spectrometry.
8. The test method according to claim 1, characterized in that, In step S3, the digestion method is selected from one or more of thermal digestion and microwave digestion.
9. The test method according to claim 1, characterized in that, In step S3, the concentration range of lithium and sulfur in the test solution is 1.0 ppm to 50.0 ppm.
10. The test method according to claim 1, characterized in that, In step S1, the weight of the lithium sulfide sample is 0.0010 g to 2.000 g.